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June 7
spinal meningitis: asprin? or not?
My roommate was exposed to a woman who had taken care of her mother who was diagnosed with spinal meningitis... she has since fell ill and in complaining of a stiff neck, she has a high fever and is sleepy a lot more than usual fatigue... she took some asprin today and i am concerned that that was not a good idea. Is taking asprin a problem for suffers of spinal meningitis? I know she should seek medical treatment as soon as possible but I want to know of extreme dangers with taking asprin. Thank you! -- Joann
I have turned your question into one that follows the guidelines listed at the top of the page, and all your phone numbers and email addresses have been removed for privacy. I encourage you to read about them at meningitis, and asprin. Asprin is probably good for her! The symptoms sound a lot like meningitis. I hope she gets well soon! — TheMac Davis] ⌇☢ ญƛ.02:52, 7 June 2006 (UTC)[reply]
The problem would seem to be that she has reason to believe she has meningitis and has not immediately gone to an emergency room. That choice means that she might die. Prompt diagnosis - a matter of hours - makes the difference between survival and death. The aspirin will certainly be a problem if she's substituting it for prompt diagnosis and treatment of what may be a fatal illness. - Nunh-huh03:20, 7 June 2006 (UTC)[reply]
If the sun was to be extinguished how long would it take for the landmass of the earth to be too frozen for human life
Just a few days, I would think. After all, the temps drop by something like 2 degrees an hour on average at night. That would be 48 degrees a day, or close to 200 degrees lower than the starting temp in 4 days. That would be enough for you to feel Jack Frost nipping at your... StuRat02:50, 7 June 2006 (UTC)[reply]
It's eight and a half minutes, but that's irrelevant, or we would all die every time there's an eclipse, LOL. StuRat03:01, 7 June 2006 (UTC)[reply]
You're assuming a linear time dependence, when it would probably be closer to exponential decay (see Newton's law of cooling). We could use the data you give about the cooling rate at night though to figure out the relaxation time of the exponential. I expect the rate would be higher with no sun than it would at night, for obvious reasons. -lethetalk+03:39, 7 June 2006 (UTC)[reply]
You mean me? All I said was the time it takes from light from the sun to get to the Earth. What what do you mean Stu about dying everytime there is an eclipse? I didn't say anything like that either. — TheMac Davis] ⌇☢ ญƛ.03:52, 7 June 2006 (UTC)[reply]
Nope, I mean StuRat. StuRat is assuming a linear fit. And what StuRat means about dying every time there's an eclipse is this: you mention that it takes 8 minutes for light from the sun to reach the Earth. The implication of your statement is that when the light stops is when the heat will stop. If that were true, we would freeze every night and every eclipse. Of course, it is true to some extent. Temperature does fall every night and every eclipse. It's true that if the Sun disappeared, we would not start cooling off until 8 minutes later. Nevertheless, those 8 minutes are fairly negligible next to the time the cooling takes, which is on the order of a couple days. -lethetalk+04:02, 7 June 2006 (UTC)[reply]
As for StuRat's 48 degrees a day, I would assume quite a bit higher. Sunlight has a considerable effect on the temperature of the dark side, basically because the atmosphere permits circulation of the warm air. If the sun turned off, the only thing heating the earth would be the core, but I don't think that would do much to slow down freezing, and even the core wouldn't last too long, without all the electric activity coming from the sun. freshofftheufoΓΛĿЌ 04:50, 7 June 2006 (UTC)[reply]
I would think circulation of water would continue until the surface of the oceans froze solid (circulation would continue beneath the surface until the oceans froze solid, if ever, but this would not have much effect on the atmospheric temp). The atmosphere would also continue to circulate until the temps were equal everywhere. However, this circulation would provide no net warming of the Earth's surface, but would only equalize the temps. I suspect the temp drop would start out a bit higher than 48 degrees a day, but then reduce as the temps approached the equilibrium surface temp, which would still be considerably above absolute zero due to nuclear radiation from the Earth's core and gravitational tides from the Moon and Sun (if it still exists even though no longer putting out any light). StuRat17:59, 7 June 2006 (UTC)[reply]
Right, well I guess it depends what temperature you assume the planet would achieve equilibrium at. Without any figures or evidence to back me up, I have a hunch that the temperature drop wouldn't slow down very much until after reaching freezing. I'm so bold! freshofftheufoΓΛĿЌ 06:41, 8 June 2006 (UTC)[reply]
I agree, and this is why the simple version of my answer was that it will drop approximately linearly, at around 50 degrees a day, for the first few days, by which time we would all be dead and no longer care if the rate is linear or not. StuRat19:39, 8 June 2006 (UTC)[reply]
Are you suggesting that the Earth's core is powered by electricity from the Sun? That sounds preposterous for a number of reasons. -lethetalk+06:17, 7 June 2006 (UTC)[reply]
I didn't mean to imply just that, though I admit I might be mistaken. I was under the impression that the electromagnetic radiation from the sun had some effect on the earth's magnetic field, which then in turn influenced the motions of the metals in the earth's core. freshofftheufoΓΛĿЌ 06:59, 7 June 2006 (UTC)[reply]
I don't think that's true. The only thing I can say about the Sun and the Earth's magnetic field is that the Aurora Borealis comprises matter from the Sun (and other cosmic radiation) caught in the Earth's magnetic field. But the field arises from the rotation of the iron core, which is just leftover angular momentum from when the planet formed. -lethetalk+07:03, 7 June 2006 (UTC)[reply]
However, wouldn't most (all) of the energy (heat) loss be through electromagnetic radiation, so the Earth would cool down at something proportionate to its temperature to the 4th? --Borbrav06:48, 7 June 2006 (UTC)[reply]
I suspect lack of solar radiation would cool the core. Without sunlight the atmosphere & surface would cool increasing the heat loss from the core. But I suspect humans would improvize and survive without much dificulty. XM16:15, 7 June 2006 (UTC)[reply]
Well, not if the temps dropped worldwide to hundreds of degrees below zero in under a week, there would be no time to adjust. Even if there were years to prepare, only a few wealthy nations could set up the nuclear reactors needed to provide the heat necessary for survival. StuRat17:59, 7 June 2006 (UTC)[reply]
As for the Earth's core cooling due to a lack of sunlight, I would expect it to cool somewhat, but when this caused the layer of solid crust to become much thicker, say 3000 miles thick, this would prevent cooling by convection, volcanoes, plate tectonics, geysers, etc., and the small amount of heat produced by the nuclear radiation and tidal forces would then be retained in the Earth's core. However, for the same reason, very little of this heat would reach the surface. StuRat18:52, 7 June 2006 (UTC)[reply]
An eclipse would not have the same effect as the sun extinguishing, an eclipse only completely covers a very small area, and there are large areas that are not even marginally covered. PhilcTECI18:00, 7 June 2006 (UTC)[reply]
Well, that's true, but even if the Sun completely stopped shining on the Earth entirely for the duration of an eclipse, the effect would still be minimal. So, in that way, both have the same effect (very little) on the Earth's temp. StuRat18:52, 7 June 2006 (UTC)[reply]
Fair enough, what temperature would the earth drop to, considering its nice warm molten core, and if the surface became uninhabitable could we just dig down and live underground closer to the mantle. PhilcTECI21:04, 7 June 2006 (UTC)[reply]
I would think the surface temp would eventually drop to maybe tens of degrees above absolute zero, although this would take millions or even billions of years, as it would depend on the Earth's mantle cooling first, leaving only the core molten. Since the mantle is a huge temperature sink, and is somewhat well insulated by the current thin crust, and will eventually be well insulated by an extremely thick crust, this will take a while. Moving down to where it's warm would require digging holes thousands of miles deep, no easy task. I would think we would want to move underground, but just far enough to benefit from the insulation effect, perhaps a few hundred feet. Thus, our heating needs could be met by a modest energy source, say a nuclear reactor. The food supply would need to be grown hydroponically, using the same energy source. We would need to recycle all our water and air or get frozen water and liquid air from the surface. I suppose any unrecycleable waste would just be piled up on the surface, where it would stay frozen forever. It would be really ugly, but nobody would be on the surface to complain. StuRat19:39, 8 June 2006 (UTC)[reply]
Why would the core cool so dramarically, considering only a tiny amount of the energy the keeps it warm is provided by the sun. PhilcTECI15:30, 13 June 2006 (UTC)[reply]
Well, only a tiny amount of the heat is produced by radiation and tidal forces, too. There is very little heating of the Earth's core going on, it's just very well insulated so that any small amount accumulates over time. Remove the Sun and it would start to dissipate over time, until it got to a considerably lower temp. StuRat04:25, 14 June 2006 (UTC)[reply]
I have serious doubts about whether the human race would survive such an event. Well, it's obvious that the 6 billion of us wouldn't all survive. But would a couple thousand survive at least? I am dubious, but I guess it's possible. -lethetalk+04:50, 8 June 2006 (UTC)[reply]
Given enough time, I would think preparations could be made for many people, perhaps millions, to survive. However, I doubt if any current underground location exists with a water supply, food supply, air supply, energy supply, and sewage system which aren't at least partially dependent on the surface, in the long run. Given only a few days, there wouldn't be time to build such a system, either. People might hide out in deep mines and bomb shelters for a while, but once the supplies expired, so would they. StuRat19:56, 8 June 2006 (UTC)[reply]
How is the Sun being extinguished? If you simply stop the nuclear reactions, the Sun will still be very hot and still radiating black body radiation. The Sun will start to cool, but it could be a long time before Earth is actually affected. Peter Grey04:05, 9 June 2006 (UTC)[reply]
Okay let me revamp, if for a reason unknown to us the Sun suddenly became completely extinguished giving off no radiation in any shape or form, how long would it take for the surface of the earth to becone too could to support human life as it is now, as a starting point I understand (and dont hesitate to correct me if I am wrong)it takes eight minutes for radiation in the form of light to reach Earth from the Sun. Sorry for not signing my name originally60.234.132.13003:21, 14 June 2006 (UTC) Hatch[reply]
As I said, a few days. Specifically, I would expect the majority of the human race to be dead by the end of a week. StuRat04:25, 14 June 2006 (UTC)[reply]
Chemistry - crystallisation
hello..
i'm Dianne and I just want to know what would happen if the crystals are dried over the bunsen flame?
250 degrees Celsius
CuSo4.5H20 -------------> CuSo4 copper (II) sulphate
blue crystals white powder
Since the temperature of the bunsen flame is higher , what would happen?
Hello, I am Mac! When heated in an open flame copper sulfate crystals are dehydrated and turn grayish-white. If you burn them, the copper ions are responsible for a blue tint. Fireworks that are blue have copper in them. Check the Copper(II) sulfate article first next time. This is an encyclopedia after all. — TheMac Davis] ⌇☢ ญƛ.04:03, 7 June 2006 (UTC)[reply]
Hydrogen supplement devices for gasoline engines
I've found a couple interesting links to devices that are installed on automobiles, and make use of electricity from the auto's electrical system to separate water into gaseous oxygen and hydrogen, which is then introduced into the intake manifold. Claims of better fuel efficiency and decreased pollution are made for vehicles which have these devices. Are these claims sensible, or are these devices like the infamous "200 mpg carburetor" that the auto industry is supposedly keeping secret?
I don't know anything about cars, but based on what I know about physics, it sure sounds possible, and it would be an award winning science fair project on the order of the Intel Science and Engineering Fair. The separation of water into oxygen and hydrogen theoretically used is through the process of electrolysis, and it indeed uses electricity. There would probably be less pollution if burning hydrogen and oxygen worked along with gasoline well, because hydrogen and oxygen are totally clean burners. However, more pollution is created this way most likely, because of the production, use, and dispensing of the car's lead acid batteries. — TheMac Davis] ⌇☢ ญƛ.04:09, 7 June 2006 (UTC)[reply]
Uh? So you'd be burning some gasoline to power the electrolytic apparatus, which will then produce some hydrogen, which is added to the air intake to be combusted, thus reducing overall gasoline consumption? Sounds rather perpetual-energyish to me, unless you can actually get more energy by using X amount of gasoline to electrolyse water and then burning the H2, as opposed to just burning the gasoline?--inksT04:16, 7 June 2006 (UTC)[reply]
No, silly! You're using the car battery to power the electrolytic apparatus, which produces hydrogen which is added to the air intake to be combusted, thus reducing overall gasoline consumption. — TheMac Davis] ⌇☢ ญƛ.04:37, 7 June 2006 (UTC)[reply]
Nothing, like I said in my first response to the questioner, however, more pollution is created this way most likely, because of the production, use, and dispensing of the car's lead acid batteries — TheMac Davis] ⌇☢ ญƛ.04:50, 7 June 2006 (UTC)[reply]
There's a problem here. The alternator is constantly recharging the car's battery; the engine, of course, burns fuel in order to power the alternator via a spinning belt. Bloodshedder17:28, 7 June 2006 (UTC)[reply]
The hydrogen-oxygen mix is supposed to make the petrol-oxygen mix burn with higher efficiency, enough to more than compensate for the energy used in electrolysis. (I think it works because hydrogen will burn in anything, taking the petrol with it; this allows the burn to be leaner, so the expansion phase is more efficient. Also, it produces water in the exhaust, giving the expansion phase more power.) Obviously, the fuel ratio and timing settings need adjusting. Any gain is going to be pretty marginal. -- EdC
Yes, Brown's Gas was mentioned on a couple of the websites I found when looking up hydrogen supplement devices (I posted the original question). I would agree that the whole concept sounds too "perpetual-motion"-ish to be believable, coupled with the near irresistible lure of better gas mileage now that gas out here is about $3.20/gallon.
What I can't reason out is if there's any net energy gain, or if the various losses in the systems involved negate the increased combustion energy. I was told by one of the proponents of this idea that "it takes very little energy to liberate the hydrogen and oxygen from water". That being said, aren't chemical reactions reversible and wouldn't the energy change be equal? So the energy released in (added to) the combustion chamber would be about equal to the energy it took to generate the Brown's gas. Which means the auto's engine had to drive the alternator a little harder to create the power to make the hydrogen, which would negate any net benefit...? Right?
The energy created by burning hydrogen in oxygen is exactly equal to the energy required to separate the two, assuming 100% efficiency. However, there will always be some inefficiency, such as excess heat given off into the atmosphere. So, in reality, performing any type of reversible chemical reaction both ways will cost energy. Now, if hydrogen gas is really a wonderful catalysts for gasoline combustion, then that might offset this energy loss. However, I am skeptical regarding this part of the claim. StuRat20:05, 8 June 2006 (UTC)[reply]
Home-made infrared filters
According to the Wikipedia infrared filter article: "There have been several reports that using exposed and developed film works as an infrared filter. The theory is that the film goes jet-black thus blocking visible light but allowing infrared to pass."
Oh come on! Only "several reports"? Shouldn't it be easy to test this sort of thing?
Anyways, I decided to take out 3 film negatives, and use them as a filter for my digital camera. They seem to work. For example, here is a photo of a tree (and here is the full-sized version).
CCDs in the digital camera only see red, green, and blue light, don't they? A few days ago somebody asked a question regarding the night vision goggles article's external link showing that being done. They asked if it was possible, and why. — TheMac Davis] ⌇☢ ญƛ.04:19, 7 June 2006 (UTC)[reply]
Actually, most CCDs are sensitive to infrared light. (See Charge-coupled device#Applications.) Digital cameras have a mirror that reflects the IR but lets visible light through, but no mirror is perfect.
To show that my Canon Powershot A620's CCD is sensitive to IR, here is a picture of a remote control, clearly showing the two infrared bulbs. (Here is the full-sized version.) --Bowlhover04:44, 7 June 2006 (UTC)[reply]
More expensive cameras like yours have night settings that use IR and produce green pictures, but most cheap cameras do not feature this. — TheMac Davis] ⌇☢ ญƛ.05:31, 7 June 2006 (UTC)[reply]
The "weasel words" were probably used because either a) it hasn't been universally accepted that the result actually shows infrared imaging or b) it's a simple case of weakly disguised original research. Judging by the images you provided, they don't seem to help much in filtering out infrared light, though the properties of the pigment in the grass and the leaves seem to make them stand out considerably. I'd expect the cars to show some evidence of infrared, though as they are it simply looks like an oddly contrasted B&W photo.
The original quote says "exposed and developed film", so I assume there's some way to prepare the film so that it completely blocks out all light apart from infrared, and even then, as Mac said, a normal camera (using normal film) probably wouldn't show any difference even with the filter in place, for the simple reason that commercial cameras aren't sensitive to infrared light. It seems to me that using a film that has been completely blacked out (to visible light) as a filter in a camera sensitive to infrared light frequencies should work, assuming you have such a camera. The filter would just serve to cut out the un-needed visible frequencies of light. freshofftheufoΓΛĿЌ 04:35, 7 June 2006 (UTC)[reply]
I'll take your word on those new prints. I don't know much (or anything) about CCDs : (. I can't really think why the lights would appear purple though... freshofftheufoΓΛĿЌ 04:54, 7 June 2006 (UTC)[reply]
Well, infrared rays don't have any colour (because we can't see them), so the purple colour is entirely because of the white balance. If, after I put the filter over the lens, I set the white balance to "manual" and let the camera assess what it should be, I will get a black-and-white photo (like the photo of the tree that I posted).
Anyways, to show that film negatives do work as an infrared filter, here are three photos of my remote control:
All 3 photos were taken within 2 minutes of each other. They were taken using the same camera and with the exact same camera settings (I set my camera's shooting mode to "manual"). My 3 film negatives were only used as an IR filter in the second photo.
Actually I made the comment about the cars. I expected the most likely source of infrared light from the first picture would be the trees and the cars (assuming they were somewhat warm), and possibly the windows from the house. I'm still confused about the purple though... even if the camera white-balanced the color settings, purple is on the opposite end of the light spectrum. I would expect the camera to shift the infrared light into the visible red spectrum, unless it got really confused. freshofftheufoΓΛĿЌ 06:53, 7 June 2006 (UTC)[reply]
The wavelengths of infrared rays spans a million nanometres, from 700 nm to 1 million nm. (For comparison, all the colours of the rainbow are cramped into 300 nm). The infrared emitted by warm objects is black body radiation. The wavelength at which black body radiation has the strongest intensity (we'll call it the peak wavelength) depends on the temperature of the object: as the temperature increases, the peak wavelength gets shorter, and vice versa.
Thermal imaging is done with infrared rays which have a wavelength of 900 nm to 14 000 nm. This corresponds to a black body temperature of 2950 degrees Celsius (for 900 nm) to -66 degrees Celsius (for 14 000 nm). Black body radiation emitted by a human has a peak wavelength of 9343 nm. However, according to our infrared filter article, exposed & developed film starts transmission at 710-730 nm. 730 nm corresponds to a temperature of 3696 degrees Celsius--far hotter than any cars or houses. Even if my camera's CCD sensor can detect wavelengths as long as 9300 nm (which I doubt), IR emitted by the Sun completely overwhelms what little black body radiation houses/cars/trees emit. As with normal photography, the IR photography I do mostly involves reflected radiation, not emitted radiation.
As for why the infrared bulb on my remote control appears violet, I admit I don't really know. But according to the graph halfway down the page at [1] (also read the paragraph before it), the red, green, and blue filters in the Bayer filter mosiac will begin allowing more infrared to pass at longer wavelengths. At around 840 nm, all three filters will admit approximately the same amount of infrared. Mixing red, green, and blue produces white, so the camera will get confused and think that 840-nm radiation is the colour white. If the camera thinks that an object is white, then the colour of the object in the final image depends entirely on the white balance. --Bowlhover04:35, 8 June 2006 (UTC)[reply]
The top of this image [2] shows the spectral response of an unmodified digital camera, below is the response of the IR modified camera. This image was taken using a CD as a diffraction grating and a tungsten bulb as the light source. Thought the method was not very scientific and the accuracy may be suspect, it gives some indication of the efficency of film as an IR filter. From [3] — TheMac Davis] ⌇☢ ญƛ.07:42, 7 June 2006 (UTC)[reply]
Appreciate the explanations. Now I must admit that that's pretty damn cool. Infrared webcam! And as for the original question: why several reports? Someone being too cautious I guess. Find one good source and it should be easy to make that statement more concrete. freshofftheufoΓΛĿЌ 06:28, 8 June 2006 (UTC)[reply]
Nuclear weapon question
OK, I'm writing a science fiction story. It takes place after an apocalypse level event, so most of the human population is gone, and it's in Australia.
My characters need a nuke to destroy a rival settlement. I figured I could just have them retrieve one from an American warship that was in the country at the time. The crew would be dead, and I'm pretty sure American fighter jets and even the ship itself would have nuclear missiles in them with tasty retrievable warheads.
However, I also need for them to have a codebook of some kind to set off the nuke (or an access key, or something. It's a MacGuffin. I just need something small that is neccesary to use the nuke). And I'm fairly certain nuclear warheads in fighter jet missiles don't have codebooks, they just get shot out at high speed and go off from the impact.
So if there was no codebook, and they just cut a nuclear warhead out of a missile and lugged it away... how would they set it off? Drop it out of a plan? Take the Glen Bateman (The Stand) way and just pack dynamite around it?
Help me out here! This kind of stuff is very hard to research because it's generally classified as a military secret.
I bet your characters (describe them?) would probably just set a timed explosion, with C4 and blaster caps. Find an interesting way they could make a makeshift fuse for timed detonation. — TheMac Davis] ⌇☢ ญƛ.04:54, 7 June 2006 (UTC)[reply]
Well, the arming and triggering device depends on what type of nuclear weapon it is! :D You can't just drop it from a height and expect it to go off, nor can you just randomly pack explosives around it. Have you read Tom Clancy's Sum of All Fears?--inksT04:57, 7 June 2006 (UTC)[reply]
Edit: It would me much simpler if they were to find a classified "suitcase nuke" that had been armed and left in that state until your characters discovered it (military hardware = overbuilt and very durable). Then detonation could be with a simple timer.--inksT05:03, 7 June 2006 (UTC)[reply]
Some (many? most?) nukes were detonated in the air shortly before hitting anything to cause damage over a wide area. That means they either use a timer or were remotely detonated by some sort of electronic signal. It would be easy to make plot twists on this, seeing as how it's in the future, and you could probably think of a lot of "traps" that could have been set up in the programming. E.g. calling on the remote "foob()" function detonates the bomb instantly, wheras "executeBomb()" causes it to malfunction or go on some kind of rampage sub-sequence. Then again, I always think it's best when you don't try to explain such things in stories, because the cooler you try to make it, the lamer it becomes. The mere fact that most people can't imagine how bombs actually work and detonate makes them believable. freshofftheufoΓΛĿЌ 05:14, 7 June 2006 (UTC)[reply]
Yeah! Most people know nothing about nuclear physics and engineering. In your story, you gotta have one of your characters display a great knowledge about nuclear weapons design, then have him rig it up. Many to most nuclear weapons were detonated after being dropped out of a plane—the rest were set a top 20-40 m steel towers. — TheMac Davis] ⌇☢ ญƛ.05:43, 7 June 2006 (UTC)[reply]
Warheads are designed to be very difficult to set off accidentally. While some nuclear warheads have been fitted with contact or proximity fuses, there is always an additional arming step before the fuses become 'live'. If you check out the List of military nuclear accidents, you'll find a number of instances where aircraft or missiles carrying nuclear warheads have crashed or been destroyed by fire. While in some cases radioactive contamination of the immediate area and detonation of the conventional high explosives have occurred, there has never been an accidental nuclear explosion.
The device or scheme that you're looking for is the Permissive Action Link (PAL). Interestingly, you probably are really looking for a codebook. If you read through some of the external links from that article, you can get a pretty good idea of what might make a plausible plot device. :D
I'll note in reply to Freshgavin's comment that airburst nukes don't employ a timer, and are never remotely detonated. (As suggested, there would be too much opportunity for mischief or failure.) Airbursts are triggered using a combination of air pressure sensors and radar altimeters. TenOfAllTrades(talk) 05:46, 7 June 2006 (UTC)[reply]
A PAL device! Of course, why didn't I think of that! (And I call myself a Metal Gear Solid fan...) Thanks TenOfAllTrades. Can anyone confirm that American warships (even aircraft carriers) carry nuclear missiles? Or will one have to be removed from a fighter jet onboard the ship?
Well, on US Navy ships you might find nuclear-versions of the anti-submarine ASROC or TLAM/A nuclear land attack version of the BGM-109 Tomahawk. Whether they actually carry them regularly I don't know, but you might as well assume they do. No one's going to know any better! Sum010:16, 7 June 2006 (UTC)[reply]
Nuclear weapons have multiple safeguards against detonation. Not only the Permissive Action Link mentioned above, but a set of environmental sensors that check the expected physical conditions the weapon will undergo. For example, a ballistic missile will undergo acceleration (at liftoff), then free fall (the ballistic portion of flight) combined with low temperature and pressure, then increasing pressure as it returns to earth. If these conditions are not experienced (or experienced in the wrong order) the weapon won't denotate.
While responsible countries likely do all of these things to prevent accidentally detonation, I doubt if countries like North Korea do. However, getting hold of one of their nukes in the story could be trickier. Perhaps it could be in the process of being shipped from North Korea to terrorists, hidden in a freight ship, when everyone died and the ship went adrift ? StuRat17:31, 7 June 2006 (UTC)[reply]
The main reason for putting in place these safeguards is to protect your own personnel against accidents and sabotage. The more paranoid the regime, the more worried about the latter, surely. Certainly the Soviet nuclear weapons programme used a wide array of environmental sensors. Gdr15:41, 13 June 2006 (UTC)[reply]
Everyone died? Seeing as it's in the future, how about North and South Korea go to war, and then North Korea sneaks a nuke into a bunker to attack South Korea, however they are pushed back and lose the bunker which is very well hidden (in some mountain range {I don't know), and then are afraid to reclaim it or claim ownership for fear of international reaction...and over time, the documents for it are lost (as it was a secret mission)...Well it's amazingly stupid but it's something
Anti Magnetic Metal/Substance
Which metal or substance doesnt allow magnetic effect to pass through that metal/substance.
Good question. If you can think back to high school biology (if you ever took it I'm assuming), you may have learned the basics of Mendelian Genetics which says that for every trait, there is a dominant allele and a recessive allele. In other words, the trait eye color has dominant and recessive colors. Blue eyes happen to be recesive; in that they, when paired up with say Brown eyes, are not expressed. For example: Let B = the allele for brown eyes, and b = the allele for blue eyes. Say your father has the heterozygousgenotype Bb (brown eyes), and your mother has the homozygous genotype BB (brown eyes). When you were concieved, you recieved either a (B) or a (b) from your fathers sperm, and a (B) from your mothers egg. No matter what, though, the (B)-brown eye allele you recieved from your mother overrides the (b)-blue eye allele you -may- have recieved from your father. Hopefully I didn't confuse you more with the genetic-speak -- but if I did, read about Mendelian Genetics. If you're still with me then read on... Since it's a recessive trait -- it is generally not going to be as prevalent as a dominant eye color like brown would be. But as Benbread said, in certain areas, it may be common simply because many people that have blue eyes mate with other blue-eyed individuals; preserving the (bb) recessive genotype to the next generation. That's why Scandinavian countries and perhaps Germany and the UK have more blue-eyed individuals whereas places like the United States where there is a more diverse gene pool, do not. Hopefully that answered your question.
As for why they're desireable. Well that's more of a matter of opinion to be perfectly honest. Sure many will say that blonde-haired/blue-eyed individuals look better which is probably where you get the notion they're more desireable but again... a BH-BE person is no better than a brown-haired/brown-eyed individual. It's simply a matter of opinion. -Novaprospekt02:29, 14 June 2006 (UTC)[reply]
Computer power-off
I checked an old hard disk for any important files it might contain, and to my dismay the computer booted Windows 95, contained by the disk. It was buggy as usual, but I noticed one neat feature I haven't seen on my regular OS (Debian GNU/Linux): it switched the computer's power off after system shutdown. Is there a way this could be enabled in Linux, too? –Mysid(t)06:56, 7 June 2006 (UTC)[reply]
Every version of Linux I've run for many years has powered off the computer when I tell it to shutdown. There should be a /etc/init.d/halt script, which should call poweroff after doing what ever is appropriate with raid drives, UPS power supplies, etc. I suspect that Debian sets up fewer of these conveniences than the distros with fancy install programs, such as (K)Ubuntu (which is based on Debian).-gadfium07:49, 7 June 2006 (UTC)[reply]
If you don't see a "poweroff" command, then you should take a look at what your copy of "shutdown" does. See shutdown. If I'm not running X11, I normally turn off the computer by typing (as root) "shutdown -h now", where the -h turns off the power.-gadfium07:56, 7 June 2006 (UTC)[reply]
Shutdown, shutdown -h now, and poweroff do the same thing – shut down the system and print "Power down." on the screen. –Mysid(t)09:55, 7 June 2006 (UTC)[reply]
Linux's "least common denominator" behavior on shutdown is to simply put the processor into an idle state and halt execution. To actually turn off the power, it needs a driver to be able to talk to your motherboard's power management system. This is normally done using ACPI or, on older computers, APM. Try enabling both of those options in your kernel (I believe they're under the "device drivers" menu), and see if that helps. —David Wahler(talk)04:16, 8 June 2006 (UTC)[reply]
Manufacturers make the hardware of commercially sold computers in a way that allows Windows to easily talk to it at a low level, allowing Windows to switch it off easily, but doesn't mean that manufacturers have made it easy for other platforms to do it. The point of ACPI was to have an industry standard for this kind of thing, and although Linux's support for it is technically incomplete, it still generally works in terms of turning the power off. The last thing I see on the screen of my Linux system before the machine turns off is "acpi_power_off called". ACPI support in Linux has gotten a lot better recently; try looking for the packages "acpi" and "acpid" on Debian. -- Daverocks (talk) 07:45, 10 June 2006 (UTC)[reply]
Way forward for Struts/Stxx application.
We have a large web application based on Apache Struts and STXX. This gives us a nice separation of business logic and presentation. We are now being asked to give an improved user experience with AJAX-like client side verification and dynamic form changes (e.g. displaying an optional question if you select "yes" in a Yes/no button group.
Is it possible to do this with an XSLT based framework. Can you maintain separation of presentation and business logic with AJAX? What open source solutions should we look for if migration is needed? -- Chris Q08:30, 7 June 2006 (UTC)[reply]
Visual "chemical noise" in the brain
Close you eyes (this is important). Wait a while, in a dark room and you might see patterns. I've noticed these patterns, usually light areas that move around inside your brain, somewhere between your eyes and that projector screen called the imagination. First, what are these called? I assume they are chemical "noise". Ok, now I can 'will' these to move around, not with much accuracy mind you. Is there a name for what I am doing? I'd like to read up on it. Thanks. Mjm196409:36, 7 June 2006 (UTC)[reply]
I have noticed the ability to move them, too. I've experimented with it and came to the conclusion that it's because I move my eyes while they're closed. If you keep your eyes pointed at the same direction, the patterns won't move. –Mysid(t)10:00, 7 June 2006 (UTC)[reply]
Ah!! I have the answer! I learned this a few weeks ago, because I have the same weird thing. I'll talk to you about it, because I've asked a few times and no body has told me anything worth... anything. They are not phosphenes, or floaters, both of which come from the eye itself, but they are known as closed-eye hallucinations. I see level 1 through level 4. You? You described it much better than I had. :) The patterns are like little dancing phantasmagoric sugar plum fairies. Usually for me they're green if I'm in a dark room, and red and yellow if it is bright light. — TheMac Davis] ⌇☢ ญƛ.21:53, 7 June 2006 (UTC)[reply]
Ah hah! When I was young I used to see Level 3 quite frequently, but not so much now that I am an adult. Perhaps if I indulged with Ms. Jane they would come back. --Ginkgo100talk ʘ contribs03:13, 8 June 2006 (UTC)[reply]
Most interesting. I get level 1 when my eyes are open as well as closed (I thought of it as static and didn't see the link) and used to get level 3 a lot. Maybe I don't do enough involved maths anymore. When very relaxed (not quite sleeping) I can get level 4, and used to play with that when I was little. Odd, I never really thought about them before. Skittle11:08, 8 June 2006 (UTC)[reply]
When surgeons want to amputate a person, they immerse the knife and other cutting tools in a liquid to prevent infecting the human with some disease and germs in order to avoid killing the patient.
It could be ethanol, but it's quite possible - and in my opinion more likely - it's another specially created chemical entirely. - Mgm|(talk)11:47, 7 June 2006 (UTC)[reply]
Now a disinfectant is only used when instruments can not be sterilized by autoclaving. Historically, commmon disinfectants have included phenol (carbolic acid) and ethanol. During 18th and 19th century battlefields and naval warfare, liquor with a high alcohol content or even hot tar or red-hot iron cautery was used. alteripse12:00, 7 June 2006 (UTC)[reply]
6% hydrogen peroxide is an effective high-level disinfectant [4], as long as the instrument to be sterilized is properly cleaned first (no gunk left behind to shelter pathogens) and sufficient exposure time is allowed (for objects with narrow crevices and channels, up to 20 minutes). There are reports that acidifying the solution somewhat increases efficacy, as does the addition of a small amount of surfactant. As noted above, autoclaving is definitely the preferred method, however. Single use items are often gamma irradiated by the manufacturer. TenOfAllTrades(talk) 15:03, 7 June 2006 (UTC)[reply]
How do they keep the instruments sterile between their removal from the autoclave and use in surgery ? StuRat17:18, 7 June 2006 (UTC)[reply]
Instruments (or, for smaller tools, instrument trays) are wrapped before autoclaving. The covering isn't removed until just before use. TenOfAllTrades(talk) 18:29, 7 June 2006 (UTC)[reply]
Hydrogen peroxide does have the disadvantage of turning into water and oxygen over time, so alcohol may be safer, since it won't do that. I suspect that hydrogen peroxide is more likely to cause the instruments to rust, too, although not to the extent that bleach would. On the other hand, alcohol is both volatile and flammable. StuRat17:18, 7 June 2006 (UTC)[reply]
A few notes: ethanol requires long contact times to be an effective disinfectant, and some viruses and bacterial spores are somewhat resistant even after long exposure. (The tuberculosis bacterium and the hepatitis B virus are a couple of examples that come to mind.) Bleach too loses effectiveness with time, as the chlorine is volatile. Bleach is also inactivated if there is a large amount of organic matter. TenOfAllTrades(talk) 18:29, 7 June 2006 (UTC)[reply]
I had never heard of an autoclave before. The article was informative. Are there specially trained people who work with autoclaves, or do the doctors just handle their own instruments, or have nurses do it, or what? Is there school for autoclave operators? moink18:11, 7 June 2006 (UTC)[reply]
Hospitals and research institutes that are of any reasonable size will have individuals who carry out sterilization services full time. While autoclaves aren't usually particularly difficult to use, a certain amount of care must be taken because they do operate at high heat and pressure. Autoclave operators must also be familiar with good quality control practices—there are various tests that are performed regularly to verify that appropriate (pathogen-killing) temperatures are reached throughout the autoclave volume. TenOfAllTrades(talk) 18:29, 7 June 2006 (UTC)[reply]
I think of an autoclave as a medical pressure cooker. Is that a reasonable analogy?
Yes. By the way, the term "disinfection" refers to a level of microbial kill that is generally considered inadequate for surgical-level asepsis. The most commonly used room-temperature chemical "sterilant" is glutaraldehyde. This is the agent used on surgical intruments that cannot be heat-sterilized, such as flexible endoscopes, that have parts that would be damaged by heat.
I don't know about computer programming. Nonetheless, I have become curious about the source code of the Windows XP Professional operating system that governs all the interactivity between Windows and applications software, utility programs, and so forth. I want to scroll through the entire code to see it.
However, the Windows source code was partially leaked in early 2004. You can read an article here about it. Perhaps the code is still floating around somewhere. --Chris14:20, 7 June 2006 (UTC)[reply]
Do you think every board member of Microsoft has seen the complete source code for Windows?
I doubt any one person, even Bill Gates, has seen the complete source code for Windows, assuming we take "seen" to mean something beyond superficial overview. However, the project management types should all be familiar with whatever document structure is used to formally define that particular Windows version.
It's also worth noting that the source code for operating systems is quite complex. It's not the same as a program source code that you would find running within the OS. --Chris15:07, 7 June 2006 (UTC)[reply]
And a lot of what you probably consider intuitively to be "Windows source code" is likely only a component of the operating system (that is, a lot of it is no doubt bound up in drivers and DLLs). Frankly, if you aren't someone trained in computer programming, what do you plan to make of it? It will likely be as equally incomprehensive to you as the code for the Linux kernal. --Fastfission12:31, 9 June 2006 (UTC)[reply]
Hello, I was wondering what species of wood is displayed on the attached photo of a wood veneer on a door. Thank you very much for any help that you can provide!
--PrincepsLupus
Hmmm... that pic narrows it down to about a dozen. We need to see the grain up close before making a determination (although if it truly is a veneer then that narrows it down a bit more). Could you post a closeup?--Anchoress17:48, 7 June 2006 (UTC)[reply]
Here is a closer up look at the actual grain. --PrincepsLupus
The wide spacing of the grain suggests a softwood such as pine or cedar, rather than a hardwood such as oak or cherry. The color is irrelevant; many softwoods are stained to resemble cherry wood.
--Mark Bornfeld DDS19:33, 7 June 2006 (UTC)[reply]
Hmmm, weird, my edit to this page just disappeared lol. Anyways, I agree with you Mark, my first thoughts were pine, fir or cedar (in that order), but the issue is whether or not it's actually a veneer. Because why would anyone bother veneering with a cheap wood, unless the door is made of coreplast or styrofoam? If it is veneer, I'd guess rosewood or mahogany.--Anchoress06:14, 8 June 2006 (UTC)[reply]
It also depends where the door is - a lot of countries have native timbers that might appear like that (if the door were in New Zealand, for instance, I'd hazard a guess at rimu. Mind you, that is itself a kind of pine). Grutness...wha?09:23, 8 June 2006 (UTC)[reply]
Thank you all for your help - my father is building a bunch of desks for a company whose doors and wooden trim are that wood, and they want the desks to match that, yet are unable to tell what kind of wood it is, and he wasn't sure either. I really appreciate the answers. --PrincepsLupus
Atomic radii exception
In a book, I found that atomic radii of oxygen(73 Ă) is greater than that of nitrogen(70 Ă). But no reason for this exception was given. For chromium, the case is of half stable configuration. But I was not able to find any reason for it. Even all my classmates (I am a student) are not able to find anything. But I have confirmed that this is true.
I shall be very grateful to anyone who is able to give a reason of this exception.
I must have this fear, as eyeball surgery makes me ill, especially when they start sewing on the eyeball. If they pull out a staple gun, I'm gonna toss my cookies for sure. :-) StuRat20:45, 7 June 2006 (UTC)[reply]
I don't think you have a fear, but more like me, I just have to turn around, and turn up my music really loud to block out any surgeon commentary. Gives me the creeps. I can watch any other surgery (well, birth is pretty disgusting), but the eye surgery takes the cake. How could they show that!??? On TLC?? — TheMac Davis] ⌇☢ ญƛ.22:05, 7 June 2006 (UTC)[reply]
Perhaps a more interesting question is, why would that be? Why are people (including myself) so squeamish about eyes? I can handle images of, say, brain surgery, but just the thought of eye surgery makes me cringe. Zagalejo01:13, 8 June 2006 (UTC)[reply]
Because the eye is one of the "raw" parts of the body? No skin... Just speculating, though. -- МиборовскийU|T|C|M|E|66601:36, 8 June 2006 (UTC)[reply]
Also just speculating, but I think it is a result of the fact that the eyes are both very sensitive and very important sensory organs to humans. Fear of eye injury would be adaptive, and that fear could easily be expressed in a fear of seeing eye injury. --Ginkgo100talk ʘ contribs03:18, 8 June 2006 (UTC)[reply]
Capital 'N' is most likely referring to nitrogen. Italicized lowercase n probably refers to the conformation of a particular molecule. In naming alkyl chains like #2, n-heptyl refers to the straight-chain seven-carbon alkyl substituent. Isopropyl20:43, 7 June 2006 (UTC)[reply]
(edit conflict, wahoo) It's important to realise in science captilising of a letter ususally completely changings it meaning. Eg. for a simple chemistry example (i dont know if these chemicals are stable but thats irrelavant to the point) ClRbH = one chlorine, one rubidium, and one hydrogen atom CLrBh = one carbon, one lawrencium, and one bohrium aton But this extends far beyond chemistry and atomic equations. PhilcTECI20:57, 7 June 2006 (UTC)[reply]
Benign Prostatic Hyperplasia
What are the possible causes of Benign Prostatic Hyperplasia in young males age 20 to 25?
Please include any possible risk factor(s) attributed to a paticular segment of the community be in race, lifestyle, or truma.
The article we have does not really answer the question though. The vast majority of people affected by BPH are over 50. Getting BPH at 20-25 would be almost unheard of (and a PubMed search seems to vindicate this). I'd venture to suggest that although there are no international standards of diagnosis for BPH, a benign enlargement of the prostate in a male under 25 would probably not be diagnosed as BPH, simply due to the fact that BPH is a condition primarily associated with ageing and long term presence of testosterone. If you get prostate enlargment at 25, those key criteria are not met, and so it's probably caused by some pathology unrealated to the normal BPH mechanism.--inksT22:19, 7 June 2006 (UTC)[reply]
Product that creates a rubber coating on metal
I need the name of product I have heard of before. You dip something like a pair of metal plyers in this product and the object comes out covered with a thin coat of rubbery stuff. You might use it on metal parts to prevent rust, or to provide electrical insulation. Know what this stuff is called? ike989821:10, 7 June 2006 (UTC)[reply]
You could just drop by your local hardware store and they should have it. It's often used to coat the handles of tools. Dismas|(talk)01:50, 8 June 2006 (UTC)[reply]
Warning: this product is not intended for use as a contraceptive. Any such usage may be injurious to health and will void the manufacturer's warranty.
Vegetable People
If you lost all of you brain apart from the parts associated with Homeostasis and controlling basic functions (if there any any recquired other than homestasis), could an animal or human survive as a complete vegetable. And out of interest, what are all of the organs that we can live without, eg. we dont need a stomach providing our food is sterilised, in a paste or liquid, and emulsified (or do we), and others. PhilcTECI21:19, 7 June 2006 (UTC)[reply]
Do you want to elaborate on the question? Because the answer to "Could an X survive as a vegetable if it still had organs and brains to run basic functions?" is of course "Yes", because "Basic Functions" could certainly mean "Enough functions to enable a vegetative state of existence".--inksT21:39, 7 June 2006 (UTC)[reply]
The notorious Terry Schiavo case is a well-known example of a person in a vegetative state who had no trouble surviving, with the critical exception that she could not feed herself, so nutrition had to be provided via a feeding tube. When the tube was removed, she died. So I suppose that if you wanted to be pedantic (and oh, don't all we Wikipedians want to be pedantic?), you could say that in a vegetative state, one could not survive because one could not feed oneself. As for organs, I know people can survive with partial bowels and partial kidneys, and without any gall bladder or spleen. I'm not a physician, so that's about as much as I can say on that subject. --Ginkgo100talk ʘ contribs03:24, 8 June 2006 (UTC)[reply]
Theoretically, you could keep subtracting parts from a human (legs, arms, skin, etc.) providing there was a welcoming enough enviroment to protect it, and you would be left with (in a way) nothing but a vegetable. If you just keep on taking out non-essential systems of the body, eventually you'd be left with nothing more than a single cell... theoretically speaking! freshofftheufoΓΛĿЌ 05:13, 8 June 2006 (UTC)[reply]
I specified homeostasis, the quetion was meant to mean (among other things), can you survive with no parts of the brain apart from homeostasis, and if not, what do you need. PhilcTECI17:45, 8 June 2006 (UTC)[reply]
Sodium methoxide
I would like to know the process for manufacturing sodium methoxide and all the physical data for the reagents and the products. Data such as
density, viscosity, surface tension, heats of reaction, heats of fusion all thermodynamic properties, reaction rates of formation, ideal conditions for the reaction, etc.
You obviously haven't done much research yet. Sodium methoxide is a solid until 150 C, therefore you can ignore viscosity and surface tension. You should probably say how toxic it is in addition to all those. Why don't you do a google search for each permutation. "sodium methoxide density" "sodium methoxide viscocity." — TheMac Davis] ⌇☢ ญƛ.22:23, 7 June 2006 (UTC)[reply]
Wood is not entirely cellulose. I believe there are small amounts of simple sugars, and other organic molecules that a human could technically utilize. The major problems is that these are in low concentration, and that our digestive system is poorly adapted to with deal with something that is so hard, and highly insoluble. ike989813:53, 8 June 2006 (UTC)[reply]
In Norway during periods of hunger in the middle ages, bread was made from a mixture of barley flour and bark from elm or pine trees. I suppose the bark was added mainly to make the flour last longer, but I wouldn't exclude the possiblity that it had some nutritional value (carbohydrates other than cellulose?). Anyway, here are some pictures of a lady baking "bark bread", the text is in Norwegian only. --21:29, 8 June 2006 (UTC)
Cellulose (ie, sawdust) is commonly added to powdered or ground dry foods, especially dry cheeses, to keep it from clumping together if it gets damp. --Serie18:19, 9 June 2006 (UTC)[reply]
Some mammals digest cellulose : bovines and other ruminating ones. Others don't, which causes horse or elephant dung to be used for specially decorated papers. Now you know to what kind of animals we are related. --DLL21:41, 8 June 2006 (UTC)[reply]
Penicllin
Allergic reactions to any β-lactam antibiotic may occur in up to 10% of patients receiving that agent. Anaphylaxis will occur in approximately 0.01% of patients. (Rossi, 2004) There is perhaps a 5-10% cross-sensitivity between penicillin-derivatives, cephalosporins and carbapenems; but this figure has been challenged by various investigators.
About 10% will exhibit some sort of allergic reaction. About 0.01% will have a life-threatening reaction. --Serie23:21, 7 June 2006 (UTC)[reply]
The usual effect that gets a person labeled as pcn allergic is simply a rash. Because there are other antibiotics, the label is rarely challenged and when it is, is often not provable.
Anaphylaxis is a severe and potentially deadly allergic reaction usually involved swelling of the windpipe (laryngeal edema) and/or a drop in blood pressure, leading to asphyxia or cardiac arrest. A risk of 0.01% means 1 in 10,000 patients.
There have been rare cases where a person with a severe pcn allergy also reacted severely to one of a different class of antibiotics. The event is too rare to yield reliable statistics but the 5-10% risk is often cited and hard to disprove. The risk of cross-reaction when the pcn allergy is nothing but a vague rash history is probably much lower. alteripse23:35, 7 June 2006 (UTC)[reply]
Do desperate junkies who've used up all their veins actually do this? I've often heard this story repeated but it sounds like an urban myth to me. --Kurt Shaped Box22:34, 7 June 2006 (UTC)[reply]
After years of addiction, they can certainly collapse all the surface veins large enough to accept a needle. Sometimes they have to resort to injecting into the cock vein (ouch!). This is where the 'eyeball story' usually comes in... --Kurt Shaped Box22:49, 7 June 2006 (UTC)[reply]
Well, looking at my cock, there's certainly one long, thick vein. The smaller ones would probably rupture if I was to try injecting anything into them... --Kurt Shaped Box22:53, 7 June 2006 (UTC)[reply]
I'm no doctor, but that "thick vein" you're thinking about may be your urethra. Injections there would probably not give the desired effect (as it would probably all leak out that hole at the end of your penis that you might have noticed). 65.96.221.10700:57, 8 June 2006 (UTC)[reply]
(I can't believe I'm entering into this discussion). In any case, the "cock vein" being referred to is most likely NOT the urethra (which is far less visible and on the underside of the penis), but an actual vein carrying blood. Don't ask me why I know this, just trust me. (No, I've never injected anything into it!) ;)Loomis5101:50, 8 June 2006 (UTC)[reply]
I can't believe I'm getting involved here, either. There are a number of veins in the penis; the most obvious is the superficial dorsal vein (pic). If you accidentally stick the needle in too deep, I suppose you would end up just below that, in the aptly-named deep dorsal vein. (I have no comment regarding my opinion of people who a) stick needles into their penis, and b) are incautious enough to stick it in too deeply when so doing.) There are a number of smaller veins that are often visible over the entire surface of the penis (save for the glans); they're almost always smaller than the dorsal veins, and probably (even) worse targets for injection. Let me just say, ouch. TenOfAllTrades(talk) 02:14, 8 June 2006 (UTC)[reply]
For what it's worth, the metabolic exchange and equilibration between systemic circulation and vitreous humor is so slow that vitreous humor is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted, or metabolized from the general circulation. I vote for false urban legend as well. alteripse11:28, 8 June 2006 (UTC)[reply]
Why is it that when I stick my head in the freezer and take a big gulp of air I end up coughing it out and having to breath room temp air? — TheMac Davis] ⌇☢ ญƛ.22:51, 7 June 2006 (UTC)[reply]
At a guess, I'd say that your lungs don't particularly like the ice crystals in the frozen air. As a matter of interest, why have you been sticking your head in the freezer and taking deep breaths? :) --Kurt Shaped Box22:55, 7 June 2006 (UTC)[reply]
Sticking your head in the freezer is a great way to cool down after exercising hard. As a side benefit, there's a refrigerator full of cold drinks within easy reach. --Serie23:25, 7 June 2006 (UTC)[reply]
Sadly, i know exactly what you're talking about. And, i suspect it's the humidity in your lungs dropping below freezing and condensing on your alveoli (cells that let oxygen and co2 in and out of your blood). At least, thats what the strange freezing and burning sensation feels like to *me*. I second the suggestion that you not do that if it bothers you. Instead, try drinking cold water or pressing large pieces of ice against your face.
This happens to me also. I don't stick my head in the freezer, but I do occasionally have to inhale during the winter when it's -10º F (-25º C), and whenever I take a deep breath, it always hurts my lungs and makes me cough. Shallow breaths are usually OK. -lethetalk+04:53, 8 June 2006 (UTC)[reply]
Are you inhaling through your mouth? It might not be so bad if you inhale through your nose, so the nasal structures can warm the air a bit before it hits your lungs. --Ginkgo100talk · contribs19:39, 8 June 2006 (UTC)[reply]
Careful with the comparison...breathing vapor off of dry ice also brings you acidity in addition to "very cold". DMacks06:43, 9 June 2006 (UTC)[reply]
Absolutely. Resulting in your CO2 sensing olfactory neurons going haywire, which is not a GOOD THING. Don't anyone try it at home, btw, as it really isn't very clever. I'm a professional ;) Rockpocket07:03, 9 June 2006 (UTC)[reply]
I'm a long-time question answerer at these reference desks, but I think this is the first time I've asked a question.
Boranes with a formula of BnHn2- are in the shape of a regular polyhedra with triangular faces, where the number of points on the polyhedron is the same as the number of boron atoms. This is the closo configuration, and from that I can work out the nido and arachno configurations for different ratios of B to H.
We were told in class to memorise the names, and to be able to draw the simpler ones. Somehow, I've ended up with a picture of the 11-pointed polyhedron in my notes but no name for it. I've looked through our articles on polyhedron but not recognised it, and I'm not a mathematician so I know know how to describe it in mathemetical terms such as by Wythoff formula.
What ingredient is it that makes fake tan smell so bad? My friend and I tried to compare ingredients of 3 but werent sure (its sad but its summer and we got bored)
Further my question on Sata Drives, windows will not accept them as a boot drive, if I wanted to have duel boot, would Linux be able to use them.-User talk:erniehatt Ernie
I've moved this question from the original location at #Windows as it's largely unrelated to the original question, and it will get more attention at the bottom of the page.-gadfium01:24, 8 June 2006 (UTC)[reply]
My current system boots both Windows XP and Kubuntu amd64 from the SATA drive. I did have problems installing both operating systems, because the machine also has an IDE drive, and both OSs put their boot loader on the IDE drive even though the system gives the SATA drive priority. I had to disconnect the IDE drive to install them correctly. In the case of Windows XP, this may be because I was installing from an original XP CD, not one which had Service Pack 2 already applied. XP was unable to see more than the first 140 (approx) GB of the disk until I added SP2. I note that Kubuntu calls the SATA disk /dev/sda, which is a name I would normally associate with a SCSI disk under Linux. Kubuntu calls my IDE disk /dev/hda as expected.
In short, I don't see why both Windows and Linux can't boot from a SATA drive, unless there is another drive in the system confusing them, or your BIOS is set up to not include the SATA drive as a boot device.-gadfium01:41, 8 June 2006 (UTC)[reply]
When sata drives first came out, I was caught in a situation with my new Linux machine, in that you couldn't directly install to sata. But you could always boot from it, once you figured out how to install. --Zeizmic12:02, 8 June 2006 (UTC)[reply]
THanks for that, but what I would like to be able to do is leave Windows on the IDE, and put Linux on the sata, is that possible.-Ernie
As far as I know, yes. Once you're in GRUB you can boot from different hard drives. To get to GRUB, the BIOS needs to boot from the hard drive which has GRUB in its MBR. Setting up a dual boot like this depends on which hard drive the BIOS boots from first -- you can check that in the BIOS. Say you have the BIOS booting the SATA hard drive first, then you would put GRUB on the MBR of the SATA hard drive. But the lines in GRUB which boot to Windows would have to refer to, say, hd1 instead of hd0, to boot from the other IDE drive. Your numbers will probably be different because I don't know the exact setup of your drives, but it's definitely possible to do. -- Daverocks (talk) 08:05, 10 June 2006 (UTC)[reply]
Thankyou very much.-[[user:erniehatt|Ernie
medical question on horses
Hi thank you for taking the time to help me with a question its a test question that i find very tricky on my test and just cant make up my mind on which one it would be, i have been all over the internet trying to determain it, so here it goes; a long tubelike isterument called a rhionoscope is used to examine the nasal cavity of a horse with nasal discharge and obstructed airflow, the instrument may pass through "spaces in the nasal cavity called?
1. conchae
2. nasal septum
well thats what i have it narrowed down to but im just not sure :(
thank you again for your time and your help would be appreciated...
Greek for nose is rhino, for look is scopos, so you are of course describing a rhinoscope. It goes into a nostril so the doc can look around in the nose. A septum is always a dividing wall between anatomic cavities, and does not refer to a cavity itself. Conchae are shell-shaped anatomic structures, including partially enclosed spaces. I have no idea what a horse nose is like inside but suspect your answer is conchae. A sinus is an anatomic term for a more fully enclosed space. There are usually sinuses connecting into the upper reaches of mammalial noses, but you didn't list that as a choice and perhaps even horse sinuses do not have passages large enough to stick a rhinoscope into. Your teacher can flunk me if I'm wrong. alteripse02:43, 8 June 2006 (UTC)[reply]
Water absorption in loose bowel movements
I have been wondering about this for a while. I know that most water absorption from a fecal bolus takes place in the large intestine, and that a good amount of that water is absorbed in the decending colon. I am also aware that when one is suffering from diarrhea (and at other times), most of the loose stool collects in the sigmoid colon before release. However, is it possible (perhaps with coniderable concentration and sphincter strength) to "hold in" diarrhea so long that it solidifies? That is, can one still absorb water from a fecal bolus that is on the verge of "coming out"?Tuckerekcut03:03, 8 June 2006 (UTC)[reply]
So the question is along the lines of "Does significant water resorption take place in the sigmoid colon"?--inksT03:11, 8 June 2006 (UTC)[reply]
Really, the question is: "Can one hold in a loose stool so long that it becomes a normal one," and all the rest of this babbling is me thinking out-loud.Tuckerekcut03:19, 8 June 2006 (UTC)[reply]
IIRC, water absorption (sp?) in the large intestine is driven by osmosis and accounts for roughly 10% of total water absorption in the digestive tract (the small intestine accounts for the remaining 90%). Since diarrhea is generally caused by increased motility and decreased time spent in the intestines (and vice versa for constipation), I would venture that the answer to your question is yes (assuming the characterisitics of the sigmoid colon are roughly comparable to the large intestine in general).--inksT03:29, 8 June 2006 (UTC)[reply]
I guess this begs a new question, then: Are the sigmoid colon and rectum comparable to the rest of the intestines with respect to water absorption? The answer to the first question, too, does not necessarily follow from the phenomenon of constipation with bowel retention because whereas an already firm stool might have enough volume and bulk to remain partially in an absorptive section of the colon, a watery stool may slip completely into the rectum.Tuckerekcut04:06, 8 June 2006 (UTC)[reply]
Really, this is Wikipedia. What we need is a peer-reviewed study, published in a reputable, scholarly journal where people had to hold it in for, say, a few hours to a day...(shudder)--inksT08:19, 8 June 2006 (UTC)[reply]
What we need is some common sense. Experience (ahem) says that it's not possible to "hold" diarrhea, so it's a moot question. To support my observation, I quote from Diarrhea: "...[T]he [excessive] water dilutes toxins as well as triggers contractions of the intestine due to increase in intestinal distension. These contractions push the contents of the lower GI tract towards and out of the anal canal." So physiologically, one's gut is working to prevent one from "holding it." --Ginkgo100talk · contribs03:41, 9 June 2006 (UTC)[reply]
Physics problem
A cyclist intends to cycle up a 14.0 degree hilll whose vertical height is 120 m. Assume the mass of bicycle plus person is 75.0 kg. If each conmplete revolution of the pedals moves the bikes 5.10m along its path, calculate the average force that must be exerted on the pedals tangent to the circular path. Neglect work done by friction and other forces. The pedals turn in a circle of diameter 36.0 cm. Answer: 802 N
I'm just overwhelmed with all the information given here. How would I start off with this problem and then proceed to the next steps? It gives way too much numerical data for me to make sense of.....Any help would be appreciated. Thanks. C-c-c-c04:12, 8 June 2006 (UTC)[reply]
It's not that bad. First find the force of gravity the cyclist has to overcome. Then figure out the mechanical advantage of the whole system, including the gears and the inclined plane, in other words, the ratio between the distance the pedals move and the vertical distance the bike travels. You can split that into multiple steps: remember, mechanical advantage is multiplicative, so the advantage of the whole system is the advantage of the inclined plane (= the sine of the angle) times the advantage of the gear system (= the distance the pedals move over the distance the bike moves). —Keenan Pepper04:26, 8 June 2006 (UTC)[reply]
Oh, and usually when there are suspiciously many pieces of information, you should look for red herring that don't have any effect on the answer, but in this case there are none. —Keenan Pepper04:28, 8 June 2006 (UTC)[reply]
1) Don't let yourself become overwhelmed! I bet you can answer this problem if you can see it as a few smaller questions: First, find out how much force will be needed to move the biker (you can think of him and the bike together as a frictionless block on an inclined plane) up the plane. Since no time is involved, we can assume that the biker is not going to be accelerating horizontally, and thus we only need to take into account the force of gravity. Thus, enough force must me used to counteract the force of gravity. So draw a free diagram of the box on the inclined plane, and find out what gravity's component force is parallel to the downward slope of the inclined plane. The biker must create a force equal to this component force in order to avoid deceleration. ( You will use the slope and biker's mass in this section
2) Now that you know how much force will be needed to keep the biker from slipping down the inclined plane, find out how much force is needed on the pedals to create this forward force. First, use torque = r x F (with r = the radius of the circle with the circumference 5.1m) to find the torque needed by the wheels to produce the forward force, then use the same equation in reverse (this time with the radius of the pedals) to find the linear force needed to create the same amount of torque on the pedals. (This section takes into account the distance traveled over one rotation, the radius of the pedals, and the answer from part one.)
Notice that this is a question about work and energy, so thinking in terms of forces and accelerations is an unnecessary complication. During one revolution of the pedals the rider exerts an average tangential force F on the pedals over a distance πd (where d is the diameter of the pedals) so the work done by the rider is Fπd. Make the simplifying assumption that the speed of the bike is constant and the wheels do not slip, so the kinetic energy of the bike and rider is constant. No work is wasted overcoming friction, so all of the work done by the rider goes into increasing the potential energy of the bike and rider. The increase in potential energy is mgh where m is the combined mass of bike and rider, g is acc. due to gravity, and h is the vertical distance travelled during one revolution of the pedals. Trigonometry gives you h, then you can find F from F = (mgh) / (πd). Gandalf6109:56, 8 June 2006 (UTC)[reply]
Theoretical question on time
Hi, my girlfriend is writing a story and she asked me the following question, but while I can make guesses, I was wondering if anyone could answer it with reference to actual theories. Her question is: What would happen if time collided with a differently moving time?
Is there any way in which this would be possible? Or if not, could you point me in the direction of the reason why? Thanks! Phileas04:38, 8 June 2006 (UTC)[reply]
She is obviously thinking of time as something like a piece of matter—a physical, concrete, thing; an object. This is not the case as far as we know. Time is a dimension, a measurement of that dimension, a property of the system. Can you say "what if width hit another width" or "what if one piece of direction hit another direction?" — TheMac Davis] ⌇☢ ญƛ.07:28, 8 June 2006 (UTC)[reply]
But that's quite right, because, as we all know, time flies like an arrow, and an arrow could collide with another arrow flying in a different direction even if such a collision is quite rare. – b_jonas09:05, 8 June 2006 (UTC)[reply]
Is it possible to construct a bomb in such a way so as to use some sort of filler(as only 3%-5% of the material gets fissioned)to make an efficient device without unfissioned material after explosion?
It's hard to say, as nuclear weapon design details are secret and much of the public domain information is merely intelligent guesswork. According to our article on nuclear weapon design, fusion-boosted weapons can have an efficiency of about 40%, so 60% of the material remains unfissioned.
Why do you want to know about maximising efficiency? If you want to minimise fallout, what you need to do is maximise the proportion of the total yield which comes from fusion rather than fission, as fission is essentially fallout-free. If your point is "bang for buck", use a fission-fusion-fission weapon with an outer case of cheap and readily obtainable natural or depleted uranium. --Robert Merkel05:29, 8 June 2006 (UTC)[reply]
Is it possible to speculate that if it is possible to compute the portion of the supercritical mass that undergoes fission,then let only that portion be fissionable,the rest be some sort of filler material,so as to make the entire fissionable material to undergo fission.
By 'fissioned' and 'unfissioned' I assume you DO NOT mean 'fissile' and 'unfissile'. Fissile and unfissile mean they can be 'fissioned' and 'unfissioned,' but not necessarily are. This question is incoherent—the amount and kind of fissile material, the material that gets fissioned, is what matters, not what percent of the material in the bomb, because that percent IS the bomb. — TheMac Davis] ⌇☢ ญƛ.07:32, 8 June 2006 (UTC)[reply]
I think the questioner is asking is it possible to arrange things so that all, or nearly all the fissile material in the bomb (ie the U-235 or Pu-239) actually fissions, by careful bomb design. The answer to their question appears, from the open literature, to be "no". --Robert Merkel12:27, 8 June 2006 (UTC)[reply]
Why isnt it possible to make a smaller fissile core(Pu or Ur) and suround it with another metal that produces neutrons(say lithium)and expect the entire solid fissile core to undergo fission with full efficiency and no unfissioned material?
The quick answer is no. The reason you need the other 95-97% of the fissile material is because of the low neutron cross-section of it. i.e. Most of the neutrons go straight through undeflected and unabsorbed. If you have a 1000g core, of which only 40g of material are fissioned, why can't you only start with 40g instead of wasting a kilo of enriched uranium? The answer is because the 40g doesn't capture 100% of the incoming neutrons, in fact, it hardly captures any. So you need all the fissile material to capture just a fraction of the neutrons. -- Eh-Steve09:24, 9 June 2006 (UTC)[reply]
Lightning Rod
What happens to be the concept of using a lower amperage fuse for a large current for a short duration , Is there any mathematical explaination about it?
I'm not sure I understand the question, but I'll take a shot at it. A fuse is designed that if a large amount of current attempts to pass through it (typically the result of a short, like a toddler sticking a fork in a socket, for example), it will burn out, breaking the circuit.
The mathematical explination is simple enough - Ohm's law, Voltage = Current * Resistance. For the time scales we are considering, the voltage is effectively constant (120 volts in the US), and if someone shorts the line, the resistance is very close to 0. Therefore, the current will be very high - suffecient to kill someone. Raul65405:09, 8 June 2006 (UTC)[reply]
Actually I was wondering how does a lightning rod survive a lightning strike..
What's to survive? It doesn't have any biological or electronic parts to be damaged, it can't catch fire. If it's low enough resistance it won't melt. I guess the worst thing that could happen is along the way to ground connections could short out.--Anchoress06:31, 8 June 2006 (UTC)[reply]
Who would want to put a fuse into a lightning rod ? Well, turns out such devices are actually used for testing lightning rods - see here. Gandalf6109:26, 8 June 2006 (UTC)[reply]
Right. If they made it able to burn DVDs, it would have to be more expensive, because it would need a more powerful and accurate laser, among other things. —Keenan Pepper05:51, 8 June 2006 (UTC)[reply]
And I looked thru the diffs but I can't figure out when or how. I posted this and didn't notice until almost an hour and half later that it was gone. Looked thru every diff, didn't see it go. Reposted it (paraphrased) here.--Anchoress06:24, 8 June 2006 (UTC)[reply]
Thanks for the replies. Knowledge Seeker, thanks for spotting that. Jondel, I know about edit conflicts, and this wasn't one. It saved fine without any errors, and I saw my post on the page after saving. Then the next time I looked it was gone. This had nothing to do with edit conflicts or problems saving, the post saved and was clearly compiled to the page. But thanx for the comment anyways, if I'm making a large addition I *do* edit elsewhere and add, it's a good idea.--Anchoress08:01, 8 June 2006 (UTC)[reply]
Anchoress, before an edit conflict can occur, the first edit must be saved to the page. It will show up on the page. Then the second user gets the conflict, and accidentally kills the first edit. What you've described is consistent with what happens in an edit conflict. -lethetalk+08:38, 8 June 2006 (UTC)[reply]
Well, aren't 'cha gonna put it back?
Lethe, can you explain that more clearly? How would that explain what happened to my edit (as per Knowledge Seeker's link above)? I've seen lots of edit conflict windows, and they never resulted in lost data, either mine or that of the editor before me.--Anchoress09:24, 8 June 2006 (UTC)[reply]
Well first of all, my point was that it was not you, but rather Tuckereckut who had the edit conflict. So the fact that you yourself never saw the edit conflict window means nothing at all. If anyone saw the edit conflict dialogue, it would have been him. As for the fact that you've never seen an edit conflict result in loss of data, let me suggest that you revise your position: never before today have you seen it occur. Today you did see it occur. I have seen it occur in the past, so I don't know what else to tell you except "welcome to the suckiness that is MediaWiki". Looking at the edits, it appears that Tuckerekcut made two edits in rapid succession, the second revising the first. Probably he used the back button after submitting. This often allows to bypass the edit conflict mechanism. This sort of thing happens a lot on high traffic pages. Is it clear now? -lethetalk+09:56, 8 June 2006 (UTC)[reply]
Does mental calculation improve concentration, memory and other mental capabilities unrelated to calculation? I need conclusive , authoritve proofs from Doctors, psychologist and am searching the web. I believe it does, it's just that a cite source is demanded at the mental calculation page. --Jondel07:37, 8 June 2006 (UTC)[reply]
You're may be using Google Scholar, which is ok. You could also try PubMed ([5]) with some keywords. I did have a quick try on PubMed but didn't find anything immediately relevant.--inksT08:02, 8 June 2006 (UTC)[reply]
Could you define 'mental calculation'? Do you mean doing math in your head, thinking four moves ahead in chess, doing the word puzzles in the paper without writing anything down, or...?--Anchoress08:04, 8 June 2006 (UTC)[reply]
4 moves ahead in chess and word puzzles also improves concentration, memory and other mental capabilities, I believe. But that's aside the topic of mental calculation.--Jondel09:21, 8 June 2006 (UTC)[reply]
Yes it does, but if you want authoritive proof, asking a doctor or psychologist directly is going to help you much more than searching the web. Mental excersize (calculation, puzzles, riddles and the like) improve the neuron connections in your brain which is good when it comes to memory and other things you use your brain for. It's been proven that people who do puzzles on a regular basis are less likely to suffer dementia and other brain problems in the long run. As for concentration, the more you practice it, the easier it gets. - Mgm|(talk)08:52, 8 June 2006 (UTC)[reply]
Mgm, are you sure about this statement: "It's been proven that people who do puzzles on a regular basis are less likely to suffer dementia and other brain problems in the long run."? How have the studies you refer to been able to separate cause and effect? People with a latent or beginning dementia might be less likely to want to do puzzles on a regular basis than those who have no latent brain disease.
I searched PubMed for (cognitive[All Fields] AND (("aptitude"[TIAB] NOT Medline[SB]) OR "aptitude"[MeSH Terms] OR abilities[Text Word])) AND ("training"[All Fields] OR "excercise"[All Fields]), and for (cognitive[All Fields] AND (("aptitude"[TIAB] NOT Medline[SB]) OR "aptitude"[MeSH Terms] OR abilities[Text Word])) AND mental[All Fields] AND (calculation[All Fields] OR computation[All Fields] OR arithmetic[All Fields]), with very few relevant hits.
A 1992 review paper, Nolan KA, Blass JP, Preventing cognitive decline. Clin Geriatr Med. 1992 Feb;8(1):19-34. (Abstract) states, rather disappointingly that "Although they are rapidly becoming more numerous, the efficacy of cognitive training programs in preventing or slowing cognitive decline has not yet been demonstrated."
This paper: Martini L, Domahs F, Benke T, Delazer M. Everyday numerical abilities in Alzheimer's disease. J Int Neuropsychol Soc. 2003 Sep;9(6):871-8. (Abstract) did not appear to be relevant in itself, but if you could get a copy from the library, it might have some relevant references.
The abstract of this paper: ACTIVE: a cognitive intervention trial to promote independence in older adults. Jobe JB, Smith DM, Ball K, Tennstedt SL, Marsiske M, Willis SL, Rebok GW, Morris JN, Helmers KF, Leveck MD, Kleinman K. Control Clin Trials. 2001 Aug;22(4):453-79. (Abstract) states that cognitive training interventions (memory, reasoning, and speed of information processing), have previously been found to be successful at improving mental abilities under laboratory or small-scale field conditions. Maybe there is something in the references of that paper which may be relevant.
This paper, Dehaene S. Varieties of numerical abilities. Cognition. 1992 Aug;44(1-2):1-42. (Abstract) might also have relevant references.
If any reliable data exists, I would expect it to be either from training regimens for the elderly, or perhaps some early work in experimental psychology. The results of the search suggest that there simply is no experimental data to support the claim. It may, of course, still be true. My guess is that this assumption has never been tested rigorously. When you think about the study design that would be needed, and the amount of work that would be involved, that is perhaps not so surprising. --vibo56talk17:49, 8 June 2006 (UTC)[reply]
MGM's statement is correct, I believe, and it doesn't make any assumptions as to cause-and-effect. I had to read numerous articles on this in neuroscience classes back in college, and it's been shown both for people who do crosswords on a regular basis, and for people who were more verbose and descriptive in their writings during young adulthood (I could possibly dig up the references). What has been shown, as you rightly note, is a correlation, not a causation. However, cognitive reserve has been possibly shown in a number of cases, which seems to show that people who use their brains more show fewer signs of dementia, even after onset of pathologies such as Alzheimer's. So the reserve doesn't prevent the neural damage, but it does seem to prevent, or at least delay, their effects. A moment of searching finds this as a pretty good recent review article. — Asbestos | Talk (RFC)18:27, 8 June 2006 (UTC)[reply]
In the context that MGM presented it, I read this as an argument of a causal relationship, but you are right in pointing out that the statement, in itself, does not imply causality. As for the mental reserve argument, the attraction towards intellectually stimulating activities and the slower progression of dementia may have a common cause (the mental reserve), or the mental training may lead to a greater mental reserve, and therefore be the cause of slower onset of dementia. The original question was whether data exists to support the hypothesis that doing mental calculation has other, positive effects on cognitive function. I doubt that the such data exists, but would be delighted in being proven wrong. --vibo56talk19:25, 8 June 2006 (UTC)[reply]
[Unindenting] Well I guess it probably wouldn't be any use, but a couple of years ago I saw a piece on Animal Planet or something where geriatric beagles who were put through mazes and given memory exercises and taught new tricks retained their faculties better and longer than the 'control beagle' group.--Anchoress19:31, 8 June 2006 (UTC)[reply]
Animal studies could certainly be the way to go to prove causality, if the study was well designed. If mental training can be shown to delay dementia in animal studies, I would find it reasonable to assume that the association observed in humans is indeed causal. --vibo56talk20:01, 8 June 2006 (UTC)[reply]
Well if you think it's any use, here is an article on the beagle study.--Anchoress 20:23, 8 June 2006 (UTC) ADDENDUM Actually it looks like there may be some interesting data on humans on the same page. Check it out.--Anchoress20:25, 8 June 2006 (UTC)[reply]
If you want a citation, I read this in A User's Guide to the Brain by Dr. John Ratey, a psychiatrist. It's a very approachable book for laypeople. --Ginkgo100talk · contribs20:10, 8 June 2006 (UTC)[reply]
Thank you very much for your discussion and inputs. This is a big help. I'll try to research the above to add sources on the article.--Jondel01:46, 9 June 2006 (UTC)[reply]
low vs. high pressure
IN our physics book we learned an equation P=F/A,
where p is pressure , f for force and A for area.
it means if force is constant than pressure is inversly proportional to area. but in fluid mechanics book i read that when water at high pressure passes thrigh a nozzle or a notch(which obviously have area reducing), the pressure reduces and velocity increases, isn't it against the above mentioned equation, according to which by reducing area pressure should increase! kindly solve my problem!
Your physics book is correct, the equation is , meaning that the pressure on an object will be equal to the force being applied to that object, divided by its area. This explains why it is more painful when your foot is trodden on by a high-heeled shoe as opposed to a trainer (sneaker): the high-heeled shoe has a lower surface area, and thus applies more pressure with the same amount of force. I suppose water will come out of a nozzle at high velocity because it was originally under high pressure, but is moving into a low pressure environment. An analogy could be when you shake a can of Coke and then open it; the cola will spill everywhere at quite a high speed, as it goes from a high pressure environment inside the can to the low pressure environment outside. Andrew10:14, 8 June 2006 (UTC)[reply]
(1) There actually is less force because the force is not being applied only against the cross-section of the fluid, but also against the nozzle. (2) By definition a fluid has no resistance to shear forces. A fluid does not transmit a linear force - generally you want energy density Energy/Volumne = Force/Area = Pressure. The increase in velocity leads to a decrease in pressure. Peter Grey15:21, 8 June 2006 (UTC)[reply]
Games where the rules change
I've read a number of studies that show that playing "games where the rules keep changing" is good for the brain, warding off dementia and generally keeping you in tune. My question: Are there any pencil-and-paper one-player games that would be something like that? I know of games like nomic, and thhe card-based versions like fluxx, but is there any thing remotely similar in a one-player game? — Asbestos | Talk (RFC)15:18, 8 June 2006 (UTC)[reply]
I was mostly kidding. But if you come up with a new theory, you will be effectively changing the rules of the game. Conscious10:51, 9 June 2006 (UTC)[reply]
Play with cards : Eleusis. Each one puts a card in turn and one of the players says if it is OK or not with the rule he devised at the beginning. The one who guesses that rule takes h[er|is] place and a new game starts with a new rule. --DLL21:24, 8 June 2006 (UTC)[reply]
At university we would occasionally play Calvinchess, a variation of Calvinball using a chessboard and chessmen. Very entertaining, but still generally requiring at least two players. --Ginkgo100talk · contribs03:35, 9 June 2006 (UTC)[reply]
If you were asking about computer games, I would have recommended ADOM. You can choose a random character class and a random race, and gameplay will be very different for each session. --KJ08:15, 9 June 2006 (UTC)[reply]
Hmmm... Doesn't sound like we're finding any one-player games. I feel like it must be possible, but I can't quite see what it would be like. One thing I'm thinking is that the rule-changing can happen in one of two (or more?) ways: Either the player consciously makes new rules, trying to put them together in some way that guarantees his victory (obviously with some limitations on what kind of rules can be made), or the rules change automatically as a result of his previous move — e.g. if the board lookis like this, then only these kinds of moves are allowed. Hmmm, I'm seeing potential here. — Asbestos | Talk (RFC)11:59, 9 June 2006 (UTC)[reply]
Much of the fun of games where the rules change is pitting one intelligence against another, and the entertainment afforded by watching another person's creativity at work. If you were the kind of person that was entertained by your own brilliance, you would know it by now. Other than that, you could adapt the idea of one of the card games to your own purposes: Create a deck of cards with rules (or aspects of rules) on them, then at intervals during a normal one-player game, draw one (or a set) and follow its (or their) instructions. In the case of a set-based game, you could have a relatively small number of cards and, through the magic of combination, quite a few rule changes. And, you can simulate the challenge of playing against someone (somewhat) by including "goal" cards, with changes in the conditions by which you win the game. Draw them at more-or-less random, preset intervals, and follow the instructions. It would be just like a turn-based game where the opponent keeps setting you back in some way, in that anything you'd just done would probably wind up being counterproductive. Hey, this has some serious potential. Black Carrot22:54, 9 June 2006 (UTC)[reply]
Correction: Since you say pencil-and-paper, you could write up a small handbook with the same info in it, then use dice (or a random number calculator if you know any easy ones) to do the random drawing for you. Black Carrot22:56, 9 June 2006 (UTC)[reply]
Has anyone being able to develop a complete theory for the cognitive neurosciece and neurons (linking,learning,etc...)? If so, I'd like to know where to find it.
What exactly do you mean by a "complete theory"? What kind of answer were you hoping for? The mechanics of learning in the brain fills several very large textbooks currently on my shelf. How memory works fills several more textbooks. Neuroanatomy, alongside neurogenesis and cell death, is another huge topic. What would a "complete theory" look like? The category you're looking for, by the way, is probably Category:Neuroscience and maybeCategory:Cognitive science. It's much easier to have a complete theory on something with a fixed set of rules, like a neural network. — Asbestos | Talk (RFC)18:05, 8 June 2006 (UTC)[reply]
I agree with Asbestos. Aside from the question being a bit ill-defined, there's a huge mass of information that you'd need to know before you could go about trying to make a "complete theory." Parts of such a theory do exist though. Temporal Difference Learning is a fair approximation to operant conditioning (augmenting the more abstract and problematic Rescorla-Wagner model of classical conditioning). Kohonen's SOM can broadly reproduce aspects of early sensory areas. More abstract models also exist for, e.g., planning behavior. All of these approaches are, however, abstract and generally quite divorced from the reality of the biological neural networks that support such computation in the brain. This is all to say: the brain is complicated and such a theory as you're after is probably a long way's off. I'm a computational neuroscientist and I have done a fair bit of modelling many parts of the brain and aspects of cognition, and from that it's clear that: 1. we currently lack enough computing power to make detailed, quantitative models/theories that are widely applicable in the brain, and 2. the tiny details of neuronal functioning have a significant effect on the population/network activity and those details vary as you move around the brain, so any theory that attempts to subsume everything will likely be a very complicated one. Of course, if you can prove me wrong, I'd be very happy to see such a theory. 128.197.81.18123:08, 8 June 2006 (UTC)[reply]
Why is a kilogram no longer a part of the difinition of a liter? I use it all of the time to measure the volume of a container simply by filling the container (liquid) with water and then subtracting the empty container's weight and just like magic I get the volume in liters. What's goin' one here? ...IMHO (Talk) 15:38, 8 June 2006 (UTC)[reply]
You have it the wrong way round. The liter was defined as a volume, based on a pre-existing measure, the meter. The gram was then defined as the weight of 1 cm3 of water at 4 deg, and from the gram we get the kilogram. However, the weight of 1 cubic cm of water is not standard, and so a standard kilogram measure was created using independant units. The last article linked has the explanations. — Asbestos | Talk (RFC)15:51, 8 June 2006 (UTC)[reply]
Actually, the kilogram isn't defined using independent units; it's defined to be the mass of a lump of platinum-iridium kept in a vault in Paris. Somewhat embarrasingly, the lump has lost 50 billionths of its mass since it was made, which means that anything that had a mass of 1 kilogram 100 years ago, and hasn't changed since, now has a mass of 1.000000050 kg. They're trying to sort this problem out by redefining it as the mass of a particular number of atoms, but haven't worked out the details yet. EdC04:51, 9 June 2006 (UTC)[reply]
The liter is a derived unit, equal to one cubic decimeter (one one-thousandth of a cubic meter). Currently, the meter is defined as the length of the path travelled by light in absolute vacuum during a time interval of 1/299,792,458 of a second. This is an extraordinarily precise defined value that we can measure to an arbitrarily high degree of precision, at least as long as you have good enough instruments.
Practically speaking, nobody outside a lab actually measures out meters (or decimeters, or liters) with a light and stopwatch. Rather, we use various approximations to go about our business. The density of liquid water is fairly close to 1 kilogram per liter, so in practice we can use a liter of water as a stand-in for a kilogram mass, and vice versa. Note that since water does change a bit in volume (and therefore density) depending on its temperature, you shouldn't rely on this volume to mass conversion for more than rough approximation. TenOfAllTrades(talk) 16:18, 8 June 2006 (UTC)[reply]
Great this was the answer I was hoping to find since in many instances it is sufficient to have only a rough approximation such as when you want to know if the scale at the grocery store is off by a whole lot. With a rough kilogram/liter equivalent you can quickly check the store scale with a 2 liter bottle of pop which equals about 4.4 lbs. Scale says 5 lbs shop somewhere else. ...IMHO (Talk) 17:02, 8 June 2006 (UTC)[reply]
Well sure. I thought you were asking why the kg was no longer part of the definition of liter. Obviously the weight is almost exactly the same as it's always been, and certainly neither the weight nor the definition has changed in any of our lifetimes. — Asbestos | Talk (RFC)17:58, 8 June 2006 (UTC)[reply]
Electrical resistance
Hi, physics AS tomorrow and im stuck on this. State the effect on the ammeter reading and the voltmeter reading (of a circuit) as the temp of resistor is increased. Obviously with increased enthalpy the resistance of the circuit will increase, thus the current will decrease. My problem is that what happens to the voltage if the resistance increases and the current decreases (due to IR=V)?
Hi, you're right to say that the resistance will increase as its temperature increases. But what happens to the voltage across it will depend on the circuit that it's in. For example, if it's connected directly across a battery (that is of comparatively low internal resistance) then the voltage across it isn't going to change significantly, but if it's connected across a battery in series with another resistor, then the voltage across it will increase. But in any case, in any simple circuit you'd be reasonably likely to be considering, the current through it would decrease. If you get a chance, then please clarify the question by describing the circuit you have. If not -- well, all the best in your exam! Arbitrary username16:17, 8 June 2006 (UTC)[reply]
Hi, yeh circuit with emf of 3v (negligable internal resistance) attached to a 'bundle' of thin insulated copper wire, an ammeter in series with this and a voltmetre in parallel around the copper wire. thanks chemaddict16:27, 8 June 2006 (UTC)[reply]
Active X controls and other internet security considerations
I have several questions
1. I am soliciting an opinion about Javacool's Spyware Blaster which prevents the installation of ActiveX spyware. Spybot recommended it, I don't know much about it. Does it eat up a lot of memory to run? Would it significantly benefit someone like me whose surfing habits wouldn't upset a parental control module set to neurotic?
2. Anyone know any useful security extensions for Firefox? I have the NoScripts, but that's it.
3. Should I use OSCP to validate certificates in Mozilla Firefox? I really have no idea what that is.
4. How do you prevent CDs from automatically running programs upon insertion? I have heard all this junk about music CDs running and installing stuff surreptitiously and frankly I don't want to wonder when I play a CD or DVD. Can you disable it so that it won't run its contents upon insertion without first letting me see what is on the blasted thing?
Sorry that I can't answer all your questions, but to address number four, the default key in Windows for disabling run-on-load software on removable media like CDs or DVDs is to hold down the shift key when putting in the media. --Kuzaar-T-C-18:48, 8 June 2006 (UTC)[reply]
In Windows XP, for a more permanent solution: go to My Computer, right-click on your CD drive, select Properties, then select the AutoPlay tab at the top. For each "content type", you can choose from a list of predefined actions, or select Prompt me each time to choose an action. --LarryMac20:44, 8 June 2006 (UTC)[reply]
Question number 1: If you're using Firefox, no ActiveX can run, so you wouldn't need the "Spyware Blaster" program. (unless you're using a special ActiveX-enabled version of Firefox or have a Firefox ActiveX extension, but don't use those.) Question number 2: Firefox is inherently quite secure, and you shouldn't need too many extensions to make it more secure. Still, there are still are some good security extensions which you can search for here. Question number 3: I don't know much about validating certificates, but from my experience Firefox is quite picky about validating certificates, so you should be fine. Question number 4: A good solution was suggested above, but I'll add to it. If for some reason, you keep AutoPlay enabled, you can still hold the Shift key while you're putting the CD in the drive to stop AutoPlay. I hope this has helped. :) -- Daverocks (talk) 08:16, 10 June 2006 (UTC)[reply]
humming in my head
When I am very quiet I can hear humming in my head. I don't think it's Tinnitus, and it is high rather than low pitched (which is how The Hum is described). I've wondered if it could be caused by the electrical activity in the brain. The lower limit of hearing in humans is cited as about 20 Hz, which is only slightly above the that of Alpha waves. However, if that were the case one would expect a low-pitched sound. Any ideas? --Halcatalyst17:57, 8 June 2006 (UTC)[reply]
Do you have any dental work ? People do sometimes pick up radio signals there which are transformed into an audio signal. They aren't very loud, but seem so since they are inside your own head. In rare cases, people can even make out words or music being broadcast. Another possibility is that it's just a malfunctioning nerve in your ear. This happens all the time, but would be temporary and in only one ear. StuRat18:21, 8 June 2006 (UTC)[reply]
I strongly suspect it's tinnitus. I get the same thing (in fact, I have it right now) and it seems to match the description in the article. Nice theory for The Hum though. Skittle18:23, 8 June 2006 (UTC)[reply]
You can't hear your brain. That's just silly. Even if you could, you would go through adaptation to accept it as something to be ignored. — TheMac Davis] ⌇☢ ญƛ.02:47, 9 June 2006 (UTC)[reply]
Assuming that Halcatalyst is correct in thinking that it's not tinnitus, then I think I know what it is.... I have the same thing.
IANAMD, I don't have the knowledge of biology or physics to define it properly, and I'm only sharing what I've heard, from someone who really should know what he's talking about (I asked an ear specialist.... I saw him about an unrelated matter, but asked about this because I take my hearing very seriously) and this was about twenty years ago, so please don't jump all over me if it's totally wrong.
It's like a reference tone.... a sort of continuously generated frequency against which the brain evaluates other sounds. Most people are not conciously aware of it, (precisely because of adaption, I should think) and it's not clear why any of us are able to hear it. TheMadBaron03:45, 9 June 2006 (UTC)[reply]
In an oft-quoted passage of John Cage's book Silence he describes entering a soundproof room, and he hears
... two sounds, one high and one low. When I described them to the engineer in charge he informed me that the high one was my nervous system in operation and the low one was my blood in circulation.
Well, the articles on Cage and the work those sounds inspired (4'33") suggest that it's probably not true. Interestingly enough there may be another explanation - your ears are generating the sound. The ear actually has a feedback mechanism that as well as hearing sounds will, under the right conditions, produce them (it's supposed to help you hear very quiet noises), and while these sounds are usually not independently audible, there have been cases where other people have heard the noises someone's ears make. I may be able to WP:CITE a source or two in a few days' time. Confusing Manifestation12:54, 9 June 2006 (UTC)[reply]
This happens to me too. Sometimes when I'm in bed I swallow and all of a sudden there a high-pitched noise in my ear. I always thought it was just background noise but I guess it's more than that. But it only happens in the middle of the night for me (could that mean something?) --Jonathantalk21:45, 9 June 2006 (UTC)[reply]
If Mars is terraformed, where would the best place to live be? Considering climate, mountains, water supply and others I might not be thinking of. It would be a great help if someone could help me with this.
It would probably be difficult to predict the climate and water supply of a particular place on Mars before it is terraformed. Terraforming is a rather intensive undertaking, and it would change a whole lot about the planet's surface. —Bkell (talk) 18:17, 8 June 2006 (UTC)[reply]
But it wouldn't change how the planet is shaped (mountains), would it?
~Cathy~
Here are some pictures I've modified with water... sorry that you have to kinda download it... I just uploaded them real quick.
http://www.esnips.com/web/harry-potter-here
~Cathy~
Terraforming probably wouldn't change where mountain ranges are (although maybe it would, if it were done by creating volcanoes or something). But there are many factors besides mountains that make somewhere a good place to live. You will want to know about the climate, nearby water, natural hazards (like storms), vegetation, and so on. Think of what the Earth would be like if it were "unterraformed". As an example, the coast of Norway is about the same latitude as northern continental Canada, but their temperatures in January differ by about 30°C because of the Gulf Stream. This effect would be very difficult to predict if Earth had no oceans and very little atmosphere. How can you even predict what sea level would be on a terraformed Mars? —Bkell (talk) 18:54, 8 June 2006 (UTC)[reply]
While I agree with your point about the Gulf Stream, a Martian sea level is easy to predict -- just pick a contour line and color everything below it blue. — LomnTalk19:01, 8 June 2006 (UTC)[reply]
At second thought, you're probably also pointing out the uncertainty of the quantity of water, not the shape an arbitrary quantity would take. Anyway, to go back a bit: the original poster might want to check out Kim Stanley Robinson's Mars trilogy, which (among other topics) discusses terraforming. As a quick guideline, though, you would probably aim for an equatorial low-elevation region to maximize temperature and air pressure. If a society is capable of terraforming a planet, they're also presumably capable of building water pipelines, so I wouldn't worry overmuch about proximity to potential oceans. — LomnTalk19:08, 8 June 2006 (UTC)[reply]
Written before your last comment: That would be a Martian coastline you're predicting, not the Martian sea level. How do you figure out which contour line to choose? You would choose the one corresponding to the predicted sea level. Now how do you predict the sea level? You will have to know how much water is currently on Mars, how much would be in liquid form after terraforming, how much would be above ground, whether water would be imported or created during the process of terraforming, and so on. —Bkell (talk) 19:10, 8 June 2006 (UTC)[reply]
I was interpreting the question as asking for the most aesthetically pleasing or the most comfortable place to live on Mars, assuming that the planet had been "Earthified", hence my comment about nearby bodies of water. Your recommendation of an equatorial low-elevation region seems to be mostly an engineering recommendation, since it would be easiest to convert such a location to a habitable environment. Of course, one can actually make reasonable engineering recommendations. ;-) —Bkell (talk) 19:16, 8 June 2006 (UTC)[reply]
You can't just color everything blue below a certain contour line, can you? Because Mars is spinning, sea level will not remain exactly at the same level around the globe. Isn't that why the sea level on one side of the Panama canal is different than the sea level on the other side? --Kainaw(talk)20:31, 8 June 2006 (UTC)[reply]
Some of my first response was also based on the aforementioned sci-fi stuff, which postulates that terraformers could exercise some control over the amount of water released, thus predicting an approximate coastline. As for the Panama Canal question, that's not an issue of centripedal force bur rather of lunar tides and America impeding the free flow of water. Mars doesn't have moons capable of causing significant tides. However, centripedal force does cause planetary deformation (sea level at the equator on earth is a few miles farther from the center than sea level at the poles). Depending on whether/how a contour line is drawn on a martian map, this might/might not matter -- I presume it would be readily predictable in advance, though, and it would still provide a good rough approximation — LomnTalk20:35, 8 June 2006 (UTC)[reply]
This is off the subject, but what do you mean by "America impeding the free flow of water"? Surely the sea level was different on either side of Panama before the canal was built, or even before the United States existed. —Bkell (talk) 22:07, 8 June 2006 (UTC)[reply]
America the continents, not the country. Landmasses delay the tides and so the coastlines of the Atlantic and Pacific, though close as the crow flies, are incredibly distant with respect to sea level fluxuations. — LomnTalk03:22, 9 June 2006 (UTC)[reply]
I just need a small section around 220,000 km² big with water nearby, not a lot of mountains (but some), and good climate. Just make a good guess... you'd be closer than what I would guess. Plus, I have no idea how much space 220,000 km² would take up on Mars!
~Cathy~
Well, obviously, unless huge mirrors were used to provide additional illumination to polar and mid-latitude regions the tropics will, in general, be the warmest place. One possibility that occurs to me is the bottom of Valles Marineris. ---Robert Merkel23:54, 8 June 2006 (UTC)[reply]
Why the bottom? (BTW, I've just started to learn about Mars (about two weeks or so)
~Cathy~
Generally, you'd want the bottom to maximize air pressure. As is, the lowest elevations on Mars are (with respect to air pressure) comparable to or lower than that found atop Everest. — LomnTalk03:23, 9 June 2006 (UTC)[reply]
Not only is the air going to be thicker, it's going to be warmer. Additionally, water flows downhill, so you'd expect there to be water at the bottom of the largest canyon in the solar system if liquid water was indeed flowing on your terraformed Mars. --Robert Merkel07:13, 9 June 2006 (UTC)[reply]
Acetyl-CoA synthesis
How is acetyl-CoA synthesized? The article on CoA says that "Coenzyme A (CoA, CoASH, or HSCoA) is adapted from β-mercaptoethylamine, panthothenate and adenosine triphosphate" and also "The conversion of pyruvate into Acetyl-CoA..." Not sure if these mean that CoA can be synthesized from either. Does it? Jack Daw18:17, 8 June 2006 (UTC)[reply]
Coenzyme A is the universal carrier of acyl groups, a special case of these are acetyl groups. The acetyl groups may be derived from glycolysis, such as in your example (pyruvate), and they may also be derived from the breakdown of fatty acids and certain amino acids. The statement "The conversion of pyruvate into Acetyl-CoA..." is a slightly misleading, the reaction is
according to my 1975 copy of Lubert Stryer, Biochemistry (yes, I'm considering buying a newer copy :-) ).
CoA is recycled, it is neither synthesised nor consumed in this reaction.
According to the same source, the biosynthesis of CoA starts with pantothenate (vitamin B5), which is first is linked to cysteine, a carboxyl group is lost, AMP is added (from ATP), and finally the product is phosphorylated. I'm not sure about where the β-mercaptoethylamine enters, maybe it's an alternative pathway for synthesising CoA. --vibo56talk18:55, 8 June 2006 (UTC)[reply]
The word enzyme is reserved for biological catalysts, and coenzymes are simply the active sections of binary enzymes. Thus "coenzyme" is mostly a fancy word for a type of catalyst. Since catalysts by definition are not altered by the chemical reactions they catalyze, Coenzyme A is not used up in acylation. (This is less of an answer and more clarification / support for the addition immediately preceding this one).Tuckerekcut20:09, 8 June 2006 (UTC)[reply]
No. You're confusing two things, one is the synthesis of brand new (Acetyl-)CoA, which occurs from Adenosine, etc. The other is the synthesis of Acetyl-CoA from CoA which occurs in the Citric acid cycle. Once synthesised, Coenzyme A serves to pick up an acetyl group (forming Acetyl-CoA) which it later loses, forming CoA again, but the base CoA stays the same. --BluePlatypus16:31, 9 June 2006 (UTC)[reply]
Virtual Machine Screensaver
On Mepis Live (linux) there is a screensaver called 'virtual machine' that appears to display a load of random coloured letters and numbers across the screen, kind of matrix stylee. Are these randomly calculated or are they actually displaying some sort of information like what the processor is up to? --Username132 (talk) 19:55, 8 June 2006 (UTC)[reply]
From the program's description: "a virtual machine that can be used to make a simulation of automata construction under randomly changing conditions." I don't really know exactly what that means. --Kainaw(talk)20:29, 8 June 2006 (UTC)[reply]
It means nothing. Well technically it means "a fake machine that can be used to simulate an automatically interacting device with random input", but simplified to non-bullshit English that basically means "a program that runs on random numbers", which answers the first user's question. freshofftheufoΓΛĿЌ 03:42, 9 June 2006 (UTC)[reply]
How does this edit conflict thing work?
So I just added a (small) contribution to the Acetyl CoA question, and ran into an editing conflict. I simply accepted without changing (as I seem to have screwed this up earlier today...) and the contribution is not recorded. Is the newer edit always just erased in these situations? The edit conflict wasn't even in the same section as the other additions (they did not overlap). Needless to say this is very frustrating, as it is the second time in 14 hours.Tuckerekcut20:07, 8 June 2006 (UTC)[reply]
I have redrafted my contribution to the CoA question, but the frustration remains, why would the newer article be automatically removed in an editing conflict?Tuckerekcut20:13, 8 June 2006 (UTC)[reply]
The Wikipedia:Help desk is a better place for these kinds of questions, but yes, basically the newer version is discarded if you let it do so. The edit conflict screen shows you two text boxes and clearly states that the one on the top is the one that will be saved. Your edits are shown in the one on the bottom. What you need to do is to copy-and-paste your edits into the one on the top, making any adjustments as necessary to account for the fact that the article you meant to change has now already been changed. This is necessary, as how else would wikipedia understand what to do with two potentially conflicting edits? It also alerts you to the fact that something new has happened between the time you started editing and when you pressed "save". — Asbestos | Talk (RFC)20:16, 8 June 2006 (UTC)[reply]
I never realised how complicated the edit conflict issue was, cuz I just thought everyone did what I do, which is select and copy my new unsaved text, exit the edit window without saving, go into a fresh edit window, and add my text to the newest version. I also try to edit small sections when they exist rather than editing from the top edit tab all the time. You know I didn't even know until just now that it was possible to deliberately overwrite previous changes from the edit conflict window; that's why I didn't understand lethe's explanation above. LOL There was an edit conflict while I was replying.--Anchoress20:16, 8 June 2006 (UTC)[reply]
I know I'm pointing out something you most probably know very well, but just to be on the safe side: When you want to edit a section, you do click on the small [edit] link on the right hand side just above the horizontal line that defines the section, and not the "edit this page" tab at the top of the page, right? --vibo56talk20:29, 8 June 2006 (UTC)[reply]
Yeah, I have just been editing with the little link accross from the section header, but that has apparently not eliminated editing conflicts when other sections are changed. It does seem like the software could just add in all information contributed after a conflict, rather than discarding the most recent. I suppose the "edit conflict" warning window is still neccesary, to allow users to reformat, but I don't see any reason why wikipedia shouldn't be able to add all the edits together. Judging from the comparison section of the conflict screen, it "knows" where to put the new information, and simply "chooses" to make the user do the copying and pasting.Tuckerekcut20:48, 8 June 2006 (UTC)[reply]
That's largely a function of the page in question. For a large talk page like this, where users are editing only their own paragraphs, sure, automated conflict resolution is viable. What about an article edit, though, where two people are altering the same paragraph at once? Computer systems aren't capable of intelligently resolving that situation on a consistent basis, so merges are left to the human users in question. — LomnTalk21:26, 8 June 2006 (UTC)[reply]
There do appear to be three problems that could be addressed, however:
1) There is no way to edit the top "introduction" section of an article without editing the entire article. This makes edit conflicts more likely.
2) When two people do edit the same section at once, rather than giving a section-level edit conflict, this causes an article-level edit conflict. This means that anyone saving from that point is saving the entire article, and more likely to encounter additional conflicts with unrelated edits in other sections.
3) Self-edit conflicts are possible, usually as a result of errors and/or using the back button on the browser. If both edits were made by the same user, it should just ignore the earlier one and accept the final edit. StuRat21:51, 9 June 2006 (UTC)[reply]
Unless two editors are trying to edit the same line (or append text after a given line), MediaWiki does resolve edit conflicts automatically. That includes introduction edit conflicts. Titoxd(?!?)04:56, 12 June 2006 (UTC)[reply]
That's not true. Try finding a random section in this page, clicking edit, then waiting ten minutes or so before saving. You'll get an edit conflict, whether or not the conflict was on the line you were editing. I just proved myself wrong. Um, ok, my mistake. — Asbestos | Talk (RFC)13:47, 12 June 2006 (UTC)[reply]
Answer to 1) - not true, you can edit the introduction with a small URL hack. Copy the URL for the "edit section" link (for instance, http://en.wikipedia.org/enwiki/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit§ion=79), and replace the section=79 with section=0. Enter the new URL into your browser's address bar and voilà! — QuantumEleven10:47, 13 June 2006 (UTC)[reply]
Distance Light Travels
Last night I took my flashlight and some dog food to my backyard to feed my dog. While walking back inside I was throwing my flashlight (while turned on) up in the air and catching it. It occured to me that the light has tyo go somewhere as there aren't any trees above it or anything. How far does the light go? If an airplane were to fly above, would the light shine in the passengers eyes? Just FYI I have
It'll keep going until it hits something, but it'll spread out so much that the airplane passengers, for instance, probably won't be able to make it out as brighter than the background. Some of the individual photons, though, will surely make it far into space to be absorbed by interstellar hydrogen atoms. —Keenan Pepper21:58, 8 June 2006 (UTC)[reply]
The thing is, it goes in a cone rather than a cylinder, which you can verify because the spot gets larger as you shine it on more distant surfaces. As the same amount of light spreads over a larger area, it gets dimmer. —Keenan Pepper22:03, 8 June 2006 (UTC)[reply]
Light which "stays together" more (say, in a laser) keeps on going pretty high (that is, is identifiable as coming from a single source and is very visible). Hence there have been a number of people who have gone to jail for shining laser pointers at airplanes and things like that and actually making it into the cockpit with them. (see this story about it, for example). --Fastfission00:19, 9 June 2006 (UTC)[reply]
I don't mean to detract too much from the discussion at hand, but I couldn't help but wonder - why do you consider the Pioneer plaque to be foolish, alterelipse? — QuantumEleven10:51, 13 June 2006 (UTC)[reply]
He doesn't - he was quoting someone else (whose name escapes me at the moment) who said that about the Pioneer plaque. The reason is that any hostile aliens could use the pioneer plaque to find mankind and destroy/enslave us (ala Battlefield Earth). Raul65410:53, 13 June 2006 (UTC)[reply]
An interesting thing to try is going out on a country road at night. Point the flashlight at a reflective roadsign some distance away. Even a small household torch will cause a reflective sign of good highway quality to reflect from a distance of up to 1/4 of a mile (400m). Grutness...wha?03:01, 9 June 2006 (UTC)[reply]
Also, "hits something" also applies to particles in the air, most of which are probably water, which would deflect or possibly absorb much of the light. On a super clear day it may be possible to see a speck of light from a rather powerful flashlight, but on a foggy/rainy day you might not even be able to see the light from a giant light house, many hundreds of times stronger than your average flashlight. freshofftheufoΓΛĿЌ 03:37, 9 June 2006 (UTC)[reply]
Note that the spotlights used for advertising new stores (and sometimes used to spot airplanes at night during wars) can light up objects thousands of feet up, even though they aren't lasers. They make up for their higher light scattering rate (than lasers) by using more photons to start with. You can tell if a lot of scattering happens by whether the beam itself is visible. On a foggy night, it will be quite visible, but won't go very far, while on a clear night it will be almost invisible and will go quite far. Stars can even send light through billions of light years of almost completely empty space to reach us. StuRat21:32, 9 June 2006 (UTC)[reply]
Compare it to a 1mW laser pointer. If we knew at what distance a laser pointer is barely visible at night, then we'd know that a flashlight would only be barely visible at a much closer distance. Most google hits only mention at what distance the spot is visible on a surface. One says that a 95mW green laser beam is visible at 45 miles distance. --Wjbeaty05:26, 11 June 2006 (UTC)[reply]
June 9
One server, multiple domain names
Let's say I sign up for a web hosting service, and create two websites in separate directories (say, /~myusername/public_html/greathats/ and /~myusername/public_html/shoes4sale/). Let's say I then register two domain names (greathats.com and shoes4sale.com). What do I need in order to make it so that greathats.com and shoes4sale.com associate themselves with those particular directories in a nonobvious way (that is, the site will not make it clear that there are any higher levels to it than those particular directories they are hosted in)? Put another way (I apologize for my inarticulateness with this -- if I knew what to call it, I'm sure I could figure it out myself!), I don't want it to be clear that either of the URLs are at all connected in the same server in any obvious fashion (someone could run a WHOIS of course and find out, but I don't care about that -- I just want them to superficially look like two different websites, but hosted on the same server).
What should I look for in a web host if I plan to have this sort of arrangement? I've seen some which say things like they offer "5 primary and secondary DNS" services, but I don't really know what that means (though I suspect it might be relevant) and "4 domain forwarding" and "virtual hosting" (but I don't want virtual hosting of the sort where you get subdomains, like bowlers.greathats.com; the two URLs will look nothing like each other). If I got a plan that had both of those, would it allow me to do what I wanted? I'm confused. :-( Can someone make this easy for me? Many thanks. --Fastfission00:26, 9 June 2006 (UTC)[reply]
I am a Linux/Unix and Apache person. I don't do Windows. In Apache, you just edit your config file (most likely httpd.conf) and tell it which directory each domain name goes to. Then, point all the domain names to your server. You can also point each domain to a different set of logs (and set different permissions for each domain). As for what to look for, it depends on what you need. If you are going to hosting a lot of sites and you want a highly dependable service, then spend the money and lease a server. I spend $300/month on my network services - which makes some webhosting people cringe. However, I bring in just over $2,000/month. I could make a lot more, but I don't want the extra work. --Kainaw(talk)00:53, 9 June 2006 (UTC)[reply]
(edit conflict) The service you are looking for is usually described as "Add-on domains" or "Host X domains in 1". It is accomplished at the webhost level and is becoming fairly common, but not universal. I operate websites with two different webhosts (one is professional level, one is more basic). The more basic host that I use is Bluehost and they offer the service you are looking for and are likely to meet your other needs unless your planned sites will be quite busy or need unusual features (such as direct control of mail services). Dragons flight00:56, 9 June 2006 (UTC)[reply]
The secret is that $7/mo is with a 2 year contract. It's $8/month for 1 year, and their pricing structure is such that it is basically noncompetitive to consider periods shorter than that. See also my talk page reply. Dragons flight03:27, 9 June 2006 (UTC)[reply]
Better question: According to the operation plumbbob article, there is an urban legend of a manhole cover being propelled upward by an underground blast and exceeding Escape Velocity thus leaving the earth's orbit and eventually the solar system. This seems quite far-fetched... Anyone care to postulate if it's physically possible?
There is some discussion of it on Sublette's Plumbbob page and specifically this page. If you scroll down to the Pascal-B shot info, Sublette has a number of equations and other mumbo jumbo describing why it didn't happen, but doesn't say anything definitive about whether it could feasibly happen if you wanted it to. --Fastfission17:16, 9 June 2006 (UTC)[reply]
I've had moderate pain in my lower abdomen after moving around some while using an anal vibrator for the first time. The pain seems to have continued for 12 hours or so. It feels a lot like a muscle pain, and seems to be in the front, but I was nervous, because I've heard stories about people suffering from internal bleeding and things. As long as I'm not in severe pain, and I don't have any blood in the stool, am I all right to wait and see what happens? -- LazerTruck66604:23, 9 June 2006 (UTC)[reply]
We're not qualified to answer that. Your best option is to see a doctor. You don't want to find out you waited to long when it's already too late. - 131.211.210.1007:43, 9 June 2006 (UTC)[reply]
i regulary use anal vibrators and (less regularly) have anal sex and have never had a long lasting pain -is it possible thats its just a coincidence and in fact has been caused by somethine else? 195.93.21.813:24, 9 June 2006 (UTC)[reply]
Of course it's possible. And it's possible it's not. That's why he should see a doctor, because neither he nor we have the information or expertise to know which is actually the case. Black Carrot23:02, 9 June 2006 (UTC)[reply]
Special relativity
I heard my teacher saying to another student that "...therefore empty space loses its meaning in special relativity"
Why does empty space loses its meaning? Thanks!
Because special relativity basically boils down to "there is no absolute space or absolute time, only space and time relative to other frames of reference" and in empty space, all frames of reference are indistinguishable. Confusing Manifestation12:48, 9 June 2006 (UTC)[reply]
ConMan's explanation for what your teacher may have meant is very plausible. I'd like to add that this statement is probably far too strong: just because there is no such thing as an absolute reference frame does not imply that there is no such thing as space or that it cannot be empty. Indeed, there is such a thing as empty space in relativity. -lethetalk+15:03, 9 June 2006 (UTC)[reply]
ConMan is full of beans. There is spacetime objectively. Certain properties are subjective, but you could talk about a region of empty space over a time interval objectively. (Cj6701:38, 11 June 2006 (UTC))[reply]
If HIV has no "proof-reading" mechanisms, hence the immense genetic variability and recombinant effects producing many subtypes, how come the genes for gp120, gp41, and gp 160 are so stable, hence no glycoprotein mutations? HIV doesn't have half a proof-reading mechanism, just for the envelope. What's going on? -- Eh-Steve09:40, 9 June 2006 (UTC)[reply]
Usually where proteins show little change over time, it is because their functions are extremely sensitive to mutation. gp120 and gp41 are the proteins that allow HIV to recognize, bind, and insert itself into cells; mutations to these proteins are likely to produce a virus that cannot bind to T-cells and therefore cannot infect them and reproduce.
So there are probably lots of mutated variants of gp160 being cranked out—however, they are unable to infect T-cells and so they don't get reproduced. TenOfAllTrades(talk) 14:30, 9 June 2006 (UTC)[reply]
Microkinesitherapy
Hello -- I would like to find out more about microkinesitherapy - a therapeutic treatment used in France to unblock energy in one's body that was blocked by past trauma. Thank you.
hi,
yesterday, i was sitting in my garden with my (brand new) red linen trousers (h&m's finest) when a sea gull deficated on me. i washed them but they havent come out AT ALL - its as though i havent washed then at all. firstly, why is sea gull poo so tough? and secondly, does anyone know how to get it out? thanks! 195.93.21.813:27, 9 June 2006 (UTC)[reply]
I suggest you immediately remove any such clothes, scrape off as much poo as possible, soak the area with stain remover, then wash it. It sounds like it might be too late for many of these steps, so you may not have much luck removing the stain. How about making them into a nice pair of summer cut-offs ? :-) StuRat21:05, 9 June 2006 (UTC)[reply]
where can you get more info about insect hair? (or spider hair). it must be a lot smaller than mammal hair. Is it made from the same protien? is there a wikipedia article about it? Jonathantalk15:40, 9 June 2006 (UTC)[reply]
Yes, I see the hair article does not clearly state the fact: hair is found only on mammals, and all mammals have hair. The hairlike protruberances on other animals are different in structure --Seejyb22:41, 9 June 2006 (UTC)[reply]
This is simply not true. Hair is found on other animals (such as insects) and not all mammals have hair (e.g. dolphins and whales are completely hairless). Hair is made of keratin, but I can't confirm how different it is on insects. (that pubmed article may help). —Pengo15:16, 11 June 2006 (UTC)[reply]
Pengo, all mammals do have hair; it is one of their defining features. Dolphins and whales and elephants are only hairless in the sense that a bald human is hairless; they still have hair, just streamlined. Skittle21:29, 11 June 2006 (UTC)[reply]
Is there any eyeglasses out there which could be used while viewing a computer screen? My doctor said I have no distant vision or near vision. He also said there are no eyeglasses such as to be used while reading a computer.
Do you know any eyeglasses such? Please tell me.
You should be able to wear the same glasses to look at a computer screen as you use to look at a piece of paper the same distance away. It doesn't matter what you're looking at, only how far away it is. What does "no distant vision or near vision" mean? You're blind? You have astigmatism? —Keenan Pepper17:44, 9 June 2006 (UTC)[reply]
Perhaps you mean nearsighted or farsighted? Regardless, as Keenan pointed out there is nothing special about a computer screen that eyeglasses can help. What is special is that when you work at a computer for long periods, your eyes naturally 'trance' (not sure if there is a technical term for this) and the rate of blinking slows down greatly. This leads to dry eyes, and irritation. If you are suffering from eye fatigue and you have no other vision problems (and you're sitting far enough back from the screen), then that's probably it.
I think you should either trust what your doctor says or go to another doctor or optometrist. They should be able to give you better and more personal advice than us here. If you can see the display perfectly at first but you have problems after watching it for a longer time (such as tired or irritated or dry eyes, blurry vision etc) there might be other fixes than glasses. For example, you may need to take breaks every hour; fiddle with the brightness and contrast controls of the monitor; make it sure that no direct sunlight falls on the monitor but the computer is not in a very dark environment either; there are no annoying reflections on the monitor (the most common ones being sun rays reflected from an open window or the reflections of a lamp); make sure you're not watching the monitor from too close; or use approperiate eye drops. – b_jonas11:21, 11 June 2006 (UTC)[reply]
You know how if you click on the little "hand" tool in Adobe Reader, you can click-and-drag to scroll around the page image? Is there any way to easily implement a similar function on a webpage — so that if the user clicks and drags, the page will scroll within the browser window? It's not worth tearing one's hair out over, but for some little thing I am doing it would be a neat effect. It seemed like the sort of thing that wouldbe implemented with some sort of CSS tagging or Javascript using a "onmousedown" attribute or something like that. Is such a thing easily implementable? I suspect not, but thought I would ask. --Fastfission16:38, 9 June 2006 (UTC)[reply]
The article on trams asserts Saint Petersburg's tramway network still is the largest in the world. You may want to do some googling to verify that. Weregerbil20:49, 9 June 2006 (UTC)[reply]
Low TSH-levels and hyperthyroidism
The TSH article says this: "Higher than normal levels of TSH may indicate congenital hypothyroidism (cretinism), hypothyroidism or thyroid hormone resistance. Lower than normal (suppressed) levels of TSH may indicate hyperthyroidism."
Is this true? I was thinking since hyperthyroidism is overactivity of the thyroid doesn't that mean TSH levels should be elevated? And vice versa. Jack Daw20:35, 9 June 2006 (UTC)[reply]
It's counterintuitive. The high levels of TSH are because the thyroid won't respond to normal levels, so the anterior pituitary gland, sensing a lack of T3 and T4, keeps making TSH. When too much T3 and T4 are made, the pituitary gland is inhibited, so no more TSH is made, so levels are low. The malfunction is all due to the thyroid. Hope that helped. --Eh-Steve21:31, 9 June 2006 (UTC)[reply]
Shouldn't the article also be stating the obvious that low TSH can be due to hypopituitarism and high TSH to an excess production by a pituitary tumor (adenoma)? --Seejyb22:59, 9 June 2006 (UTC)[reply]
There is a further detail that is even more counterintuitive than the above: in hypopituitary hypothyroidism ("central" or "secondary" hypothyroidism) the TSH is often borderline high (typically 6-8) because of a complex dual feedback system at the hypothalamic level.alteripse02:35, 13 June 2006 (UTC)[reply]
Ok, so what should I do? I previously downloaded the.. uhm.. thing that you can run the system off a cd. I burned it on a cd, but I couldn't figure out how to get it to work. Should I do that? Should I do it the other way? — TheMac Davis] ⌇☢ ญƛ.05:22, 6 June 2006 (UTC)[reply]
Presumably, you're talking about a Live CD, which can boot the operating system without modifying the hard drive.
To get it to work, you need to restart the computer with the CD in the drive. Depending on how your computer is configured, (1) it might say that it has detected a bootable CD and you need to press a key to boot it, or (2) it might go straight to your already-installed operating system (which means you probably need to change the bios - done by pressing delete/F8/etc when the computer starts - to try to boot the CD drive before it tries to boot the hard drive). Raul65405:29, 6 June 2006 (UTC)[reply]
It tells you to press a particular key to access your BIOS settings. Usually, its one of - Del, F1, F2, F4, F8, F10, F11, or F12. It depends on your motherboard. Then look around (probably in the "boot-up settings" if there is one) without changing any settings until you find a boot sequence option. Change it from - "Floppy - HDD - CD ROM" to "CD ROM - Floppy - HDD", then save your settings (often F10) and restart your computer with the CD in the drive... It should now boot from CD. If that doesn't work, tell us the model of the motherboard, and it'll be easy. --Eh-Steve01:57, 10 June 2006 (UTC)[reply]
The Ubuntu Desktop CD includes some Windows programs as well. So to tell if you burned the CD correctly, stick it in a Windows system, and browse the CD-ROM device. If you see the Windows programs (and some documentation) in there, then you've burned the CD correctly, and should be able to boot into Ubuntu if you can convince the BIOS. If you can only see 1 file on the CD, then you burned it incorrectly, and you need to record it as an ISO image, not by copying the ISO file to the CD. This will depend on your CD burning software, but look for something like "record disc from image". --Booch21:43, 12 June 2006 (UTC)[reply]
With the water as a solvent, the ions, Na+, Cl-, and K+ will pretty much just float around, and would form salts if the H20 was removed (NaCl and KCl). I'm not sure what the CHO is doing there, needs clearer notation. Is that an aldehyde carbonyl (a positively charged carbon double bonded to oxygen with a hydrogen connected, which would form Cl-CH=O, an acyl chloride) or an alcohol (COH, where the C would be doubly positively charged, or bonded to 2 other atoms not written)? Essentially, since it seems you are indicating a bunch of ions are floating around in your "seawater", which is istelf an ionic solvent, not much is gonna happen; your ions are mostly just gonna float around as such.Tuckerekcut02:53, 10 June 2006 (UTC)[reply]
Well, I have absolutely no idea what you responded to me with (well, kind of, but not really). I made all C's in chemistry. But it was an extra credit question on my final last week and I had no idea. Thank you though. schyler02:59, 10 June 2006 (UTC)[reply]
It looks kinda like one of those cutsey rearrange-the-letters things... would "Water Nacho Clock" mean anything to you? --AySz88^-^05:37, 10 June 2006 (UTC)[reply]
I don't think so :). I think it's actually some kind of food though, because that was the last section we did and we had to do a project that had like 10 compounds we recognized and break it down and tell what made it that and whatnot. I think I got a 47/100 on that one. Thanks. schyler13:12, 10 June 2006 (UTC)[reply]
H2O is water, and NaCl is table salt. Perhaps by "CHO" you meant C12H22O11, which is sugar (sucrose). I'm not sure what food you should get from K, which is potassium, a very reactive silvery white metal. You wouldn't want to eat pure potassium. There's KCl, potassium chloride, which can be used as a substitute for table salt by people who want to reduce their sodium intake. Bananas have lots of potassium, but of course there are many, many other things in bananas besides K. Are you sure you gave us the question correctly? —Bkell (talk) 13:31, 10 June 2006 (UTC)[reply]
Yah. Pretty sure. My (chemistry-savy) friend said it sounds like what would be in Gatorade. I don't know how she came up with that though. schyler00:48, 11 June 2006 (UTC)[reply]
Sounds right (except it would be mighty unpleasant without flavoring). Gatorade is essentially sugar-water with electrolytes (KCl, NaCl) added, meant to replace fluids and electrolytes lost by sweating. - Nunh-huh01:00, 11 June 2006 (UTC)[reply]
Incidentally, the reason sugars (and starch and other sugar-based compounds) are called carbohydrates is that their (empirical) chemical formulas can be written as (CH2O)n, where n is some whole number. That of course tells nothing about how the atoms are bonded together, but back in the days before such details were known, it made sense to refer to them as "hydrates of carbon".
In fact, it turns out that the simple formula is in some ways quite close to the truth: sugars are mainly composed of chained CH2O groups, though not entirely — and it's the "not entirely" that makes sugars behave chemically the way they do. I do hope, by the way, that your Gatorade does not contain plain CH2O — that's formaldehyde. —Ilmari Karonen (talk) 11:52, 11 June 2006 (UTC)[reply]
First Springtime Flowers
I have noticed that the the color of the very first flowering bushes in springtime (after winter in colder regions) are almost exclusively yellow. What is the reason for that? --03:04, 10 June 2006 (UTC)~~
Yellow flowers usually attract bees, as opposed to red, which usually attract birds. I'm not sure exactly how that fits in with springtime. Do bees come out before birds? —Pengo15:10, 11 June 2006 (UTC)[reply]
The Ultimate Speed Limit
The Special Theory of Relativity says no matter or material objects can travel faster that light.But what about things that don't involve the movement of matter, such as gravitational influences?How can it apply and how does it apply to immaterial things?
Perhaps even more important than matter, special relativity implies that no information can travel faster than light, because that would be equivalent to sending the information back in time. Things can certainly appear to move faster than light though. For example, take a big laser and shine it on the moon. Now turn the laser quickly so it sweeps across the moon. The spot will travel across the surface of the moon faster than the speed of light, but that's okay because the spot that moves isn't made of matter (it's caused by different photons reflecting off the moon at different times), and because it doesn't carry information from one side of the moon to the other. Of course, because it's going faster than the speed of light, a different observer could see the spot moving in the opposite direction, or a whole swath of the moon illuminated at once. —Keenan Pepper05:59, 10 June 2006 (UTC)[reply]
But what if you formed the laser beam spot into a word and repeated the same experiment ? Then information would indeed move faster than the speed of light, wouldn't it ? Quantum tunneling also seems to violate that restriction, so something about the restriction must be wrong. StuRat15:24, 10 June 2006 (UTC)[reply]
Suppose you formed the laser beam into a word. Two people on opposite sides of the moon couldn't use your laser to transmit information between them faster than the speed of light, because for one thing they can't control what the laser says. So when you wave the laser across the moon, you're not transmitting information from one side of the moon to the other; you're transmitting information from Earth to different points on the moon. That information is encoded as a laser beam, so of course it travels at the speed of light, from the Earth to the moon. —Bkell (talk) 19:37, 10 June 2006 (UTC)[reply]
Skewed logic. You could construct the laser so that it drew out the word instantly across the entire surface of the moon, but that doesn't mean that the information is travelling instantly. The information doesn't travel from the point at where you start drawing the word to the point where you finish, but from the laser source to the target area. freshofftheufoΓΛĿЌ 06:01, 12 June 2006 (UTC)[reply]
But I'm asking about how can it apply to anything that exists, not just matter.
Gravitational influence involves a transfer of energy, and therefore cannot travel faster than light. Some effects can exhibit superluminal velocities though, like the point of contact of a pair of scissors, or a shadow moving across the face of a moon, or the correlation of measurement of entangled particles. These effects convey no energy or information at superluminal speeds. StuRat is mistaken when he claims that quantum tunneling allows superluminal movement. -lethetalk+05:12, 12 June 2006 (UTC)[reply]
According to Albert Einstein, gravity curves space. Is this true? If ti is how does this happen.
Try General relativity which Curved Space redirects to. Albert Einstein doesn't say gravity curves space, he says that the phenomenon that's known as gravity is caused by inertial motion in a warped spacetime, like a marble rolling around a trampoline with a bowling ball placed in the centre. --ColourBurst05:01, 10 June 2006 (UTC)[reply]
Although, it's worth pointing out that using a gravity-based metaphor to describe something that replaces traditional gravity is a bit circular. Black Carrot16:58, 10 June 2006 (UTC)[reply]
I'm allergic to shrimp, which I understand is a common allergen. The only reaction I have ever had is contact dermatitis, whether in my mouth and throat (if I eat it) or on my skin (if I touch it). After reading allergy and other relevant articles, I'm not completely clear what this means, technically. The reaction is fast, within minutes or less, so I think it's Type I (true allergy), but as I mentioned, the only symptom is contact dermatitis (local swelling, hives, itching) -- no runny nose, no anaphylaxis, etc. Rest assured I stopped eating shrimp years ago -- but if I were to eat some, is it reasonable to assume there's a likelihood of anaphylaxis? Or is it some other kind of hypersensitivity? Is there any treatment I could ask my doctor about, or can I never eat shrimp again? --Ginkgo100talk · contribs04:15, 10 June 2006 (UTC)[reply]
Anaphylaxis is a possibility in the future. I too am allergic to crustaceans and prawns (prawn is what shrimp is called in Australia). The reaction I had was an irritated hand, a swollen lip and a swollen eye. After that, I saw an allergist and got an allergy test, which confirmed I was allergic. The only real "treatment"s are things like adrenalin to open up the throat in the case of anaphylaxis, or a steroid like Prednisone to bring down swollen areas quicker. However, these aren't really considered treatment, because they do not "cure" the allergy. The problem is that allergies are a reaction from the Immune system, so treatment of allergies would have to involve suppressing the immune system, but if this was done all the time, you would catch all sorts of diseases pretty quickly due to an inability to fight against them. The quick answer to your question is that no, you should never eat shrimp again. Personally, I don't care about that, since I never really liked shrimp that much, but I still have to watch out for products that contain prawn in them. If you had a nut allergy, I might say different, because it is not uncommon to "grow out" of nut allergies (at the expense of nut allergies in general being more severe). However, crustacean allergies are usually lifelong. Yeah, it might suck, but really, don't ever eat shrimp again. If you are still curious, it would be a good idea to go to your doctor and take his/her advice rather than people on Wikipedia who know no specific details about your condition. -- Daverocks (talk) 08:50, 10 June 2006 (UTC)[reply]
There are, apparently, six clinics in the UK (e.g. this one) that can "desensitise" you to these conditions. They seem to use conventional medicine. Here is a UK Parliament report describing how difficult it is to find this treatment in the UK. I have also read that the treatment is much more easily available in France. Sorry, but I don't know how it works. --Heron14:45, 10 June 2006 (UTC)[reply]
Allergies come about when our bodies, or more precisely our immunoglobulin, finds a chemical marker that it thinks represents a threat, and mobilizes the immune system's offensive units, most importantly the histamine releasing mast cells. Your Ig cells see a protein specific to shellfish as a major alien threat, but if you were somehow able to sensitize (i use this word ironically, since it is usually used to describe the development of an allergy) your Ig cells to accept that this protein is not a threat, then the allergy would go away. There are clinics that claim to be able to accellerate this resensitization process (it happens naturally over several, usually 7-10, years) and cause patients to lose their allergies. I should note, however, that this might be very dangerous if done outside of strict medical supervision, so don't try it on your own. However, under normal conditions, you can expect your allergic reaction to shellfish to become more severe with each exposure to the causative agent. It is reasonable to assume that a future exposure to shellfish will result in an anaphylactic reaction. By the way, if you are from the US, stay away from both freshwater prawn and saltwater shrimp.Tuckerekcut16:59, 10 June 2006 (UTC)[reply]
Science -Mostly Already Discovered?
Now that we've reached the 21st century, and science and technology has become very advanced, is it true that most of the things and phenomena in science and nature, and all the facts about them, have already been discovered?I mean, is it true that we're reaching an age when there's not much more to discover in science, and not much more to invent?
If there is much more to discover in science, then is there as much to discover in science as to lead to the invention of things such as the time machine,gravity-making machine,teleporter, and warp drive?
At the beginning of the 20th century, physicists were pretty content - with Maxwell's equations, and Newton's laws, they thought they had pretty much all of the physical universe figured out. One even went so far as to predict that 'physics as we know it will be over in 6 months'. Then came the ultraviolet catastrophe, which Einstein's and Plank 's work solved, but in the process, they totally demonlished Newton. (The laws based on Einstien's work reduce to Newton's laws at low speeds and low gravity; this is called the corrospondence principle). The laws we have now - relavity (for very large things) and quantum mechanics (for very small things) to a great job of explaining their stuff, but unfortuately the two are provably incompatible - one of them must be wrong. Raul65408:02, 10 June 2006 (UTC)[reply]
Raul's claim that at the beginning of the 20th century most physicists thought physics was almost "done" is a commonly repeated and incorrect myth. -lethetalk+05:08, 12 June 2006 (UTC)[reply]
It depends what you mean by "discover". It is true that, by some parameters, the rate of technological "invention" has slowed down from the middle to end of the last century (though it doesn't seem that way when i consider that when i went to University just 11 years ago we didn't even have email!). But in terms of scientific understanding, i would argue from a personal perspective, that we are ever advancing in how much we understand and the further we go, they more there is yet to realise. Ask any scientist worth their salt, they will tell you every answer poses 10 more questions. Empirically speaking, that would suggest knowledge space is exponentially large (or at least that we have yet to reach the zenith of knowledge aquisition).
In the field of molecular biology, for example, there were some who believed the discovery of the structure of DNA in the 1950s was the key step in understanding "life". It was certainly important as a milestone, but it revealed further levels of complexity that we set out to understand. The sequencing the entire human genome about 50 years later led some to believe this would be the key step in understanding "life". Instead what happened was the the scientists realised a further level of complexity (alternative splicing) must be understood before we can claim to fully understand the basis of "life". I expect, at some point in the next 10 years or so, we will have a handle on the entire transcriptosome only to find yet another mechanism through which complexity is generated, and so on... So will we ever reach a level where there is nothing left to learn? Perhaps, but i doubt it. If only on a philosophical level, will anyone ever really be able to answer the question: Who am i and why am i here?. Though it seems to me that we will never know the answer to your question, as the rate of self destruction may well be advancing faster that of human knowledge, so i expect our extinction will beat us to any definative answer. Rockpocket08:37, 10 June 2006 (UTC)[reply]
To wonder how close we are to discovering all there is to know is to assume a finite amount of knowledge, but there's no evidence to support that assumption. Humans have been discovering new things since Neanderthal times. They have a funny way of asking tricky questions that nobody else ever thought of, and these lead to further enquiries, that lead on to further discoveries. If anything, the pattern suggests we will just go on forever, questioning and discovering. History is replete with examples of people who considered that the level of knowledge at their time was pretty much all there was to know, and anything else was just unimportant trivia. How wrong they were. One of my favourite anti-quotes is by Max Beerbohm: "Anything that is worth doing has been done frequently. Things hitherto undone should be given, I suspect, a wide berth" - I think this can be applied to discovery of things hitherto unsuspected. JackofOz09:04, 10 June 2006 (UTC)[reply]
Ah of course the iHole, Apple's ultra-stylish solution to 21st Century consumer apathy. 10,000 parallel universes in your pocket (battery life 4 hours). --The Gold Miner12:36, 10 June 2006 (UTC)[reply]
I don't know about you, but I just subscribe to several popular Holecasts. Of course, you can always download collections of alternate universes from The Pirate Bay, since they've relocated their servers to the Tannhauser Gate, and the MPAA/RIAA attack fleet won't be there for another three parsecs. --ByeByeBaby17:16, 10 June 2006 (UTC)[reply]
I agree that knowledge is infinite (although perhaps finite in life sciences, since I doubt if anything biological happens below the atomic level). However, we do indeed appear to have reached a plateau, where everything "new" is just a slight tweak on old technologies (cell phones from land lines, Internet from DARPA-net, laptop computers from mainframes, etc.). I suspect a new scientific discovery, equivalent to Relativity or Quantum Mechanics, is needed to spur on a round of truly new inventions. StuRat15:16, 10 June 2006 (UTC)[reply]
Think you so? I would have thought there were more than enough natural laws to keep us inventing for quite some time. And no, we probably aren't anywhere near understanding everything there is to understand. And there's no way to predict, at this point, whether things like time travel will ever be possible or not. Black Carrot16:56, 10 June 2006 (UTC)[reply]
Amazing that you consider cell phones a "slight tweak" from landlines and laptops a "slight tweak" from mainframes. I think it goes to show how entirely subjective something like technological change is. I consider both of those examples to be evidence of how radically technology can change in a brief period of time. Sure, the basic concepts are related, but the implementation required major jumps in a wide variety of technological and scientific areas. I imagine you also think that rDNA technology is just a "slight tweak" on classical breeding. ;-) --Fastfission19:39, 10 June 2006 (UTC)[reply]
Compare the changes taking place around 1900 with those around 2000... Don't you consider the change from horses and buggies to automobiles a greater change than from land lines to cell phones, for example ? Or from hot air balloons to airplanes versus from mainframes to laptops ? And don't you consider the change from photographs to movies a greater change than from analog TV to digital TV ? How about the change from gas lights to electric lights versus from incandescent lights to high intensity LEDs ? StuRat05:04, 14 June 2006 (UTC)[reply]
I'd say about 90% of modern day science is accepted theory and not proven, therefore, is a way, we haven't "discovered" much yet, we have only guessed what it is. So really, we have just about everything to discover. PhilcTECI16:59, 10 June 2006 (UTC)[reply]
Be careful that you don't fall into the trap of thinking "scientific theory" means "guess that hasn't been proven". The word theory in science does not mean a guess or a hypothesis, as the word is often used in casual conversation. —Bkell (talk) 19:34, 10 June 2006 (UTC)[reply]
Oh, I know it's much more than a guess, and there is lots of evidence for these theories, but for example tectonic plates, all the evidence points to it being true, and their is no feasible alternative explanation, but it still can't be categorically proven, so it may be wrong. Though, admittadly it is unlikely. PhilcTECI19:52, 10 June 2006 (UTC)[reply]
Out of curiosity, what's the 10% of science that you think has been "proven", and how is this different from the other 90%, other than just having more evidence? —Bkell (talk) 20:25, 10 June 2006 (UTC)[reply]
The proven things are generally the things that recquire a short timescale (i.e. shorter than a human lifetime) to enact. Like a lot of biology and some chemistry, but almost no physics (if any). For example, alot the organ systems are well understood, and chemical reactions, the conservation of mass in chemical reactions, and things like that. PhilcTECI22:46, 11 June 2006 (UTC)[reply]
Two things sit at the bottom of your question: 1. is it possible to have a perfect description of reality?, and 2. is it possible to know how close our current descriptions are to that? The first case is not just a question of "is reality out there?" but a more complicated and nuanced question about what it means to describe reality (a big, long-standing philosophical question). The second case is not just a case of knowing "what is true?" but being able to take into account our current state of knowledge in comparison with the potentiality of perfect knowledge. Since we don't know the latter, though, it's hard to judge the former. I'm personally of the persuasion that judging scientific knowledge as a state of completeness (i.e., "we are 50% to perfect knowledge") is a misleading and ultimately useless metaphor. --Fastfission19:39, 10 June 2006 (UTC)[reply]
"Sometimes I really regret that I did not live in those times when there was still so much that was new; to be sure enough much is yet unknown, but I do not think that it will be possible to discover anything easily nowadays that would lead us to revise our entire outlook as radically as was possible in the days when telescopes and microscopes were still new." - Heinrich Hertz as a physics student, 1875. A bit more here: |The End of Science?
Also, there are several places in science history where the Next Big Thing had already been discovered, but it was being disbelieved and ridiculed by the science community at the time. This isn't common, but it's also not that rare. The seeds of the Next Big Thing may already be sitting around ignored. But only someone from fifty years in the future could tell us which "crazy worthless" new ideas are important, and which ones are genuinely worthless. --Wjbeaty05:14, 11 June 2006 (UTC)[reply]
Huh? Of course we have. Just because there are some lunatics out there with conspiracy theories to the contrary doesn't mean that mainstream science hasn't figured it out. Ditto for evolution, only the dissenters aren't conspiracy theorists, they're religious loons ... still with no more understanding of science, though. --Cyde↔Weys15:50, 11 June 2006 (UTC)[reply]
From a practical point of view (not a philoscophical one), science is progressing more rapidly now on more fronts, than ever before. I don't know how many scientific journals are published a month, but it is a lot (>10,000). Certain specific areas seem to get exhausted and people lose interest in them, on balance, more new areas of inquiry open up than shut down.
Also, I think sometimes in this conversation 'technology' and 'science' have been used as if they are interchangable. I don't believe they are. I think that the development of a technology can reach a practicle endpoint. The nail is an important piece of technology, but now, new developments in nails are pretty far between. I suppose 20 years from now, cell phones will be much the same. ike989817:13, 12 June 2006 (UTC)[reply]
You say that 20 years from now cell phones will be much the same as they are now? I'll take you up on that bet. —Bkell (talk) 21:03, 12 June 2006 (UTC)[reply]
Oh, that's not actually what I meant. I meant to say that in 20 years cells phones will reach a point in their development where they aren't changing much anymore. I realize they are rapidly changing right now. ike989818:08, 13 June 2006 (UTC)[reply]
Neural Networks and Parallel-Processing Computers
In computer science, what's the difference between a neural network and a parallel-processing computer?
A parallel computer is a computer capable of working on two or more problems (or parts of the same problem) at the same time. A neural network is a mathematical construct - a way of associating data (much like a graph, or a venn diagram, or an excel spread sheet). They are two very different things. Raul65409:44, 10 June 2006 (UTC)[reply]
However, there is a link in that a parallel processing computer might be the best way to simulate a neural network. StuRat15:03, 10 June 2006 (UTC)[reply]
By what definition would that be "best"? Parallel computation and serial computation are both Turing-equivalent, so the only real difference is speed. It should be mentioned that a neural network embodied in, e.g., a silicon substrate is basically a parallel computer. It has been shown that neural networks are also Turing-equivalent (well, for specific sorts of neural networks). 128.197.81.18123:26, 10 June 2006 (UTC)[reply]
So, given that all such computers are operationally equivalent, how would the fastest one not be the "best"? What, specifically, are you nitpicking at? Black Carrot16:53, 11 June 2006 (UTC)[reply]
"Best" is a relative term. It really depends on the work you're having the computer do.
For example, a neural network is very fast at pattern recognition, but slow at mathematics. A traditional digital logic computer is very fast at mathematics, but slow at pattern recognition. A massively-parallel supercomputer is fast at numerical simulation, but slow at logic-based computing. Each of these computers can do all of the same tasks, but at different speeds. --Serie21:30, 12 June 2006 (UTC)[reply]
The Reaction Between Silver Chloride and Concentrated Hydrochloric Acid
Background: My chemisty teacher and I saw a question on a practice test in which AgCl was added to HCl(conc), and a reaction was supposed to occur. We debated on what could possibly happen, or if the test made a typo. I looked on the page Silver Chloride and found out that a complex was supposed to form, AgCl2-. When my teacher and I performed the experiment, we were not too surprised to see no reaction had occurred. When we wafted the test tube we found that Chlorine gas was being released. After we added NaCl, the solution turned a pale green, the color of chlorine gas. The experiment was cut short, but we still noticed that the AgCl had disolved and the NaCl was left behind.
My Question: What accounts for the reactions we witnessed? Any help would be appreciated, it has us both somewhat confused. M@$+@Ju ~ ♠13:40, 10 June 2006 (UTC)[reply]
Was silver metal formed? If so, the was apparently oxidised by , which makes even less sense because the E std. value for this redox reaction is (0.8 - 1.36 = -0.56V), so the reaction is not feasible, and should never happen... but thats seems like the most likely way that is formed. Unless it was just HCl fumes...--Eh-Steve15:07, 10 June 2006 (UTC)[reply]
Well Silver metal was not formed in any significant amount (if at all). My teacher said that it smelled like Chlorine gas and not just the fumes of Hydrochloric Acid. As for waiting around for the gas to be released, that didn't happen because we were involved in an experiment that lasted 2 minutes at most. When the whole mixture turned pale green, was that dissolved Chlorine gas? M@$+@Ju ~ ♠21:17, 12 June 2006 (UTC)[reply]
Probably not — a bit of googling confirms my recollection that Cl2(aq) is pretty much colorless. I'll try to find my inorganic chemistry lab notes and see if I can figure out what was going on. However, I can't really think of any way to get a green tint from a solution of Ag+, Na+ and Cl- in pure water, so I suspect some impurities were involved. —Ilmari Karonen (talk) 11:40, 13 June 2006 (UTC)[reply]
Strange that there would be impurities in a stock solution of HCl and distilled water, but my teacher had to make the AgCl from the reaction of AgNO3 and NaCl, or some similar mixture, so it is possible. M@$+@Ju ~ ♠20:57, 13 June 2006 (UTC)[reply]
Revision IDs
I realise that this is a question about Wikipedia, but it didn't seem right for the helpdesk, as it is more about trivia. Are the revision ids (like this one: -) just given out at random? The lowest one I can find is 5, which is an edit to User:Magnus Manske, but it doesn't appear to be the oldest. What do the numbers mean? smurrayinchester(User), (Talk)16:02, 10 June 2006 (UTC)[reply]
There was this time that i chew gum for a short while until it mysterously dissloved in my mouth. Can anyone find an explaination for that?
High Acidic content from bacteria in your mouth respiring using sugars left from eating. Do you brush your teeth more now that you can't do it? PhilcTECI16:54, 10 June 2006 (UTC)[reply]
What also sometimes happens after a few years of marriage is that the partners experience diss-love for each other, so they decide to dissolve the marriage. :--) JackofOz22:37, 10 June 2006 (UTC)[reply]
Say that you have a concrete wall. Gamma rays, X-rays, radio waves can all pass though it. But why does it block visible light?Yanwen02:52, 11 June 2006 (UTC)[reply]
When electromagnetic radiation (in the form of photons) passes through a material, its intensity decreases exponentially (attenuation). The decrease in intensity depends on the energy of the photons, the thickness of the material and the absorption coefficient of the material. A dense material like concrete will have a high absorption coefficient. The energy of the photons varies with frequency according to Planck's law. Gamma rays and x-rays have a high frequency (and therefore higher energy) in comparison with visible light, and are hence more likely to pass through the concrete wall. However, their intensity will still decrease. Radio waves have a lower energy than visible light and would not pass through the concrete wall - notice how you lose reception on a car radio if you go through a tunnel. Oldelpaso18:29, 10 June 2006 (UTC)[reply]
Yes, concrete has a high absorption coefficient, but that does not answer the question. The bit about high-energy photons passing more easily through materials is also not entirely true. Low-energy photons can also pass through materials, as ELF radio waves do when they penetrate the oceans.
The answer is that materials absorb different wavelengths by different amounts according to their atomic structures. At different wavelengths, different absorption mechanisms are at work. The Permittivity#Complex permittivity section has a nice graph that shows these different mechanisms. (Complex permittivity is a fancy name for the absorption coefficient.) You can see that the transmission of visible light is governed by electronic absorption: when the energy of a photon coincides with a difference in allowed electron orbits, the photon is absorbed, so the substance is opaque at that wavelength. Radio waves have longer wavelengths than visible light and are blocked only by electrically conductive materials, which concrete is not. Reinforced concrete, on the other hand, contains conductive steel bars which do block most radio wavelengths. Tunnels also tend to be built in soil or damp rocks, which are also electrically conductive and block radio waves for the same reason. Gamma rays and X-rays are different: they have extremely short wavelengths which are beyond the main electronic resonances of atoms, so they pass straight through most materials. --Heron19:39, 10 June 2006 (UTC)[reply]
There is a part of the complete answer that nobody wants to hear: Light doesn't pass through walls because if light did pass through them we wouldn't use that material to make walls out of. We'd use it for windows. If our eyes saw radio waves instead of visible light, well, first off we'd be calling radio waves "visible light". Then, we'd be using some other material for our walls. --Kainaw(talk)21:39, 10 June 2006 (UTC)[reply]
I was assuming that visible light describes the section of the electromagnetic spectrum that we, humans, can see.Yanwen02:50, 11 June 2006 (UTC)[reply]
Absorbtion isn't the only thing. Light also has trouble with white pigments (thin white paint) even though the ground-up pigment is transparent. The paint essentially acts as a mirror: any light going into the paint will hit a particle and be scattered, with almost all of the light ending up being reflected. But of the pigment particles were much smaller, the paint would be translucent like ice cubes in water. Or if the pigment particles were much smaller, the paint would also be transparent, like dissolved sugar molecules. If the transparent pigment particles are about the same size as light wavelength, then the paint becomes VERY white and VERY opaque. --Wjbeaty05:01, 11 June 2006 (UTC)[reply]
Neural network
Hello! I'm at loss to explain he difference between an artificial neural network and an ant colony, to find an analogy with this encyclopedia building (I am for the ants).
Basic needs and skills, and collaborative tasks, help ants build houses and domesticize other insects or mushrooms without any more learning. An ANN may seem to learn but through controlled input done by man. In both case, the results are surprizing and/or helpful to man. Also, which is closer to WP building process ? Any ideas ? Thanks. --DLL19:44, 10 June 2006 (UTC)[reply]
Probably an ant colony is a better metaphor for Wikipedia than a neural network. In a neural network, individual neurons don't have the slightest idea of what the big picture is; their output is simply a response to the input they receive from neighboring neurons, so their "knowledge" of the system is highly localized. Also, when a neural network is used to accomplish a task, it doesn't really split up the job into smaller pieces and assign the pieces to the individual neurons, because an individual neuron can't do anything. Instead it's the interaction of the neurons that causes the entire task to get done. So in some ways there are similarities between neural networks and Wikipedia, but I would go with the ant colony metaphor because the neurons in a neural network are a lot dumber than the network as a whole, whereas in an ant colony and in Wikipedia individual members can do a lot on their own. —Bkell (talk) 20:22, 10 June 2006 (UTC)[reply]
Thank you, We'll try to stick to that : individual members can do a lot. But do you think they knew what would be built when they started some years ago ? --DLL21:14, 10 June 2006 (UTC)[reply]
I imagine so. The results have stayed pretty true, at least, to the grand visions that people claim they started out with- huge encyclopedia that anyone can edit, on every topic under the sun. Black Carrot21:59, 10 June 2006 (UTC)[reply]
multiplexers
What are the advantages of Frequency Division Multiplexing over Time division Multiplexing?
For one thing, with frequency-division multiplexing, whenever a station has data to send it can begin transmission immediately. With time-division multiplexing, it must wait for its time slot. It might be cheaper to build equipment that can transmit with frequency-division multiplexing, because all you need is a simple transmitter that is set to transmit on a particular frequency; with time-division multiplexing, you have to have a transmitter that can sense when its time slot has arrived, and can transmit in bursts. But I only took a couple of electrical engineering courses, so I don't know what the circuits would be like. You might find more information in the multiplexing article. —Bkell (talk) 20:15, 10 June 2006 (UTC)[reply]
Chemeleon Frog
I saw a frog yesterday that seemed to be trying to blend into its environment. It was sitting on some metal (silverish), and most of its body had turned a whitish grey color, and its skin looked kind of wrinkled up. There was just a patch on its back that was still green and smooth. I thought only certain reptiles could do that. Black Carrot20:32, 10 June 2006 (UTC)[reply]
There are multiple species of frogs that can change color. Greem tree frogs normally change from green to yellow-brown. There's an african frog that can turn from green to white and another that can turn from white to brown. All in all, color change is not unique to reptiles. --Kainaw(talk)21:36, 10 June 2006 (UTC)[reply]
Walking the seashore with my grandson (7) he asked "what do crabs eat?" at the same time showing me two in his hands. I told him I thought they ate small fish and insects but I wasn't sure. He told me a friend had suggested that they ate seaweed. Maybe it's both, can you help please? I have looked at Crab and it didn't help. Abtract23:25, 10 June 2006 (UTC).[reply]
Don't be silly. They eat Purina Crab Chow! In the wild, hermit crabs eat fallen fruit, decaying wood, leaf litter, plants and grasses and almost anything that washes up on shore. Some carnivorous crabs (Telmessus acutidens and Charybdis japonica) eat mussels. Horseshoe crabs (which are apparently not "real" crabs) like worms, molluscs, and dead fish. In short, it seems crabs are not fussy eaters at all, and their preferred food depends on ths specific species you're considering... - Nunh-huh23:41, 10 June 2006 (UTC)[reply]
I want to connect my dvd player which has a scart, a composite and s-video,connectors to my 17 inch crt computer screen which has a vga in connector as usual on crt screens. How can I do that? Is there any adapter or connector, but not like the special external boxes which include tuners and so on. I only want this converter.. Thanx!!!!!!!!!!!!!!!!
The difficult thing with converting TV signals to VGA is that TV signals do have their own format, usually NTSC or PAL, and they do need to be converted. That's why most of the converters need a big external box to tune and convert, like this one. However, going the other way around, that is, connecting a VGA-out to a TV to display a computer screen on a TV is a lot simpler and can be done with a regular cable, like this. Searching Froogle will probably give you more products. -- Daverocks (talk) 01:43, 11 June 2006 (UTC)[reply]
If your computer has a video card that accepts S-video in, you should be able to get it to display on the monitor as long as both the DVD player and the monitor are hooked up to the computer.--inksT03:58, 11 June 2006 (UTC)[reply]
SCART connectors usually include RGB signals, which are closer to what a computer monitor expects than either composite or s-video. Searching google for 'scart vga' finds many products, for example this one or this one. The CRT manual (if you've thrown yours away, you can usually find something online) will tell if the monitor supports TV frequencies, which is not necessarily the case. Be warned that if you're sensitive to flicker, you may not be happy with a TV quality signal on a computer screen, since computer CRT displays are designed for higher refresh rates. 84.239.128.908:03, 11 June 2006 (UTC)[reply]
June 11
Spam
This may be going out on a limb, but I have a gmail account I am trying to fill. I get around 500emails a day atm and I want to increase this, any ideas?
Are you trying to see if you really have those 2.whatevef gigabytes of storage space or just trying to get viruses on a friends computer?
Lol - i figured someone would aks this...I have no way to proove it but im just trying to see how many i can fit in, and if i can outdo the gmail "always increasing" rate. Raven.x1609:28, 11 June 2006 (UTC)[reply]
Neopets (8years ago now) meant my first email address got/gets ~50+ spams a day.
My Neopets-linked account doesn't get much spam, but that might be because I was careful not to sign up for third-party sponsors during registration. Worth a try, though. I think you'd have more luck signing up for porn sites (if it's legal for you, of course). --AySz88\^-^16:22, 11 June 2006 (UTC)[reply]
What do you mean, "signing up"? Have you no faith in the egomaniacal greed of porn sites? Just wander through them for awhile, they'll find a way to find you. Black Carrot16:49, 11 June 2006 (UTC)[reply]
One sure way is to get the shortest, most predictable email address available. firstname_lastname@gmail.com style accounts are probably the worst for spam. freshofftheufoΓΛĿЌ 02:44, 12 June 2006 (UTC)[reply]
This is a cool experiment. I would like to know how it turns out. I recently read an article where a guy tried to delibarately expose a computer to as much malware as possible. ike989816:56, 12 June 2006 (UTC)[reply]
Specific weight of Helium under pressure and different temperature.
At what presure is the specific weight of Helium equal to air,
Temperature 20C, 0C, -50C and 100C. Thank you. Mike Engel.
The valance shells of the three atoms are altered, and it produces a different chemical. Kind of like how when Na and Cl come together... Na explodes on contact with water, and Cl is a poison gas. See this link for a great answer [9] from the US DOE.— TheMac Davis] ⌇☢ ญƛ.03:21, 11 June 2006 (UTC)[reply]
Water is made of hydrogen and oxygen because it is the result of hydrogen burning in an oxygen rich environment. You can think of it like burning wood. The result, along with as well as CO2 and water vapor, is ash, which does not burn. Or think of burning propane: the result is CO2 and water vapor, and often some CO and elemental carbon, all non-flammable. As Raven.x16 pointed out, hydrogen and oxygen have a lot of stored chemical energy, which is released by burning (the heat and light); the product resulting from any combustion has much lower stored chemical energy, so it is not flammable. --Ginkgo100talk · contribs03:36, 11 June 2006 (UTC)[reply]
Because so are the potentials of interactions. :) Speaking seriously, in a molecule of water atoms are binded together by electromagnetic forces -- and the "bond" is strong enough (by the way, could anyone answer what is the energy of it in say electronvolts? Thank you in advance!). So for atoms of H or O to take part in any reaction, first this "bond" must be destroyed, i.e. you must free the atoms first -- and to do it you need energy. So reactions with water molecule are much harder than with pure O or H atoms (or O2 and H2 molecules). ellol07:51, 11 June 2006 (UTC)[reply]
And now that I turn the page, my reference tables actually have an average bond energy table - 463 kJ/mol for an O-H bond, which is 4.80 electron volts per bond (and there are two per H2O), but that number isn't what I got.... >.< - I guess I'd trust those tables more. --AySz88\^-^01:49, 12 June 2006 (UTC)[reply]
Water is made of hydrogen and oxygen atoms. It's hydrogen and oxygen molecules that are flammable, because they consist of two of the same atoms. As soon as they are broken to form a water molecule their properties change. However, there's an explosive so hot that if you set it on top of a huge block of ice, it burns right through and makes the water (ice=water) so hot it turns back into hydrogen and oxygen and explodes (seen it on Brainiac). But you need a temperature of over 1000 degrees centigrade for such an explosion.
One of my science teacher's favourite tricks was the hydrogen/oxygen explosion. All that remained were a few drops of water. A more elaborate device, such as [this, separates the water out first.--Shantavira10:38, 11 June 2006 (UTC)[reply]
Check the title of the second column: Estimated infections per 10,000 exposures to an infected source. Each time you have intercourse with an HIV positive individual, those are your odds of becoming infected yourself. TenOfAllTrades(talk) 03:27, 11 June 2006 (UTC)[reply]
That value seems too low - I would think far more than 0.05% of those who have intercourse with an HIV-positive person would be infected. --AySz88\^-^04:31, 11 June 2006 (UTC)[reply]
You could always check the sources. Bear in mind this is per act. You could increase the chances tenfold in the course of a week. --Shantavira09:51, 11 June 2006 (UTC)[reply]
It does seem to counter the common perception of the virus as being deadly on contact. But, in looking at the pubmed source, it seems like a legitimate study. It is worth noting that there are several factors that can increase the odds, including age, advanced state of the disease, etc.
That would seem to be missing in the chart, isn't it? I would suspect that it's somewhere on the order of fellatio, but that's mere speculation. Also, it's not quite clear to me which party is the "receptive" party in fellatio, but I guess the "insertive" clears it up. And of course, there's the question of spitting versus swallowing -- I'd expect that to be a significant factor.
There are other complicating factors that influence the likelihood of spreading HIV through sex. For instance, how infectious HIV-positive people are varies between cases and over time. Also, infection with other sexually transmitted diseases increases the risk of transmission. Finally, there are various sexual practices that may increase the risk of transmission, for instance dry sex. See our AIDS article for more information. --Robert Merkel03:22, 13 June 2006 (UTC)[reply]
Suffocating sensation when tired
After a long and tiring bicycle ride, I often get a sensation similar to smelling cigarette smoke from 6 m away. What is this smell? I don't think it's a hallucination, since it disappears if I breathe through my mouth.
I know that most of you think I'm a troll, because of the question I asked about suicide (and also because of several other reasons). I assure you that it was not a hoax, but please forget about the incident anyways. Now that you know so much about me, I often feel embarassed when making edits, and therefore do not make edits if I feel they'll embarass me. --Bowlhover03:59, 11 June 2006 (UTC)[reply]
It actually hadn't crossed my mind that you might be a troll. So, is this sensation one of "suffocating", or is it an odor "similar to smelling cigarette smoke"? And don't be too sure about the hallucination part. Not to say you're crazy or anything, but it's remarkably easy to fool your nose into smelling things. Many's the time during the summer months I've relaxed to the entirely nonexistent smell of eggnog. If it's a smell, have you considered it might be sweat? Black Carrot16:46, 11 June 2006 (UTC)[reply]
I'm very sensitive to cigarette smoke, so the smell of the smoke is suffocating. I haven't considered the possibility that the smell (if it exists) might be sweat, but no other sweating person smells like smoke. --Bowlhover01:06, 12 June 2006 (UTC)[reply]
Well, continuing with the detective work, I move to the next item in your description: the bike itself. Have you tried putting your face near the tires and seeing if the smell gets worse, or maybe the chain? If you carry a water bottle, could you trace it to that? And, of course, it's possible someone happens to smoke a lot, or burn wood/leaf/trash piles (if you live in that kind of area) around the time you go for rides. BTW, by "6 m", do you mean miles or meters? Black Carrot03:47, 12 June 2006 (UTC)[reply]
Are you asthmatic? Is it possible that you're short of breath after either a hard bicycle ride or cigarette smoke? Maybe that's why you smell the same? – b_jonas10:11, 12 June 2006 (UTC)[reply]
Psychology Experiment
What is the name of the psychology experiment that showed children a video of someone beating up an inflatable clown and then allowing them to do the same? 69.40.252.9505:18, 11 June 2006 (UTC)[reply]
I just found out about SquirrelMail. I looked at the screenshots and the interface looks beautifully simple, and I want to try this out. But there is no signup page on the site, and I can't find one. Are there any free webmail sites out there that use squirrelmail? --pile0nadestalk | contribs05:21, 11 June 2006 (UTC)[reply]
It appears the questioner doesn't fully understand what SquirrelMail is. It is a set of webpages that you put on your server so you can check the email on your server. That means that you must have a webserver and email server to put SquirrelMail on. It is not a free webmail service like Hotmail, YahooMail, or GoogleMail. --Kainaw(talk)19:45, 11 June 2006 (UTC)[reply]
I'm sure there are plenty of smaller webmail companies that use SquirrelMail. Some friends of mine run a site called Slashmail that uses it. (I won't post a link, since I'm not sure that it would not be considered blatant advertising.)
Question about plecostomus (a type of fish)
I posted a question on Talk:Plecostomus about two plecos I have — asking whether people think they're the same species or not. I've got several photos of both fish posted over there. Rather than repost everything over here, perhaps some fish experts could go have a look over on Talk:Plecostomus and let me know what you think? Richwales05:59, 11 June 2006 (UTC)[reply]
You don't need any special software - see this tutorial (it works for all kinds of flash files). I think it probably works best if you save the flash to your disk first, though I've been able to get it to use a URL too. --AySz88\^-^16:16, 11 June 2006 (UTC)[reply]
Maximum Heart Rate and Aerobic Threshold
I'm not asking this question because of my own fitness routine, so no need to tell me to ask my doctor. ;-) What I'm wondering is if there's normally a correlation between MHR and AT? I know most exercise advice puts the top percentage of MHR for aerobic exercise at 85%. I read on the triathalon page that athletes working at 92% MHR were working anaerobically; I had thought you had to be closer to 100% before hitting anerobic, but is there a predictable threshold? I don't mean it would be exactly the same for every person, but is there a ballpark?--Anchoress08:43, 11 June 2006 (UTC)[reply]
Salvia divinorum
What negative, if any, effects have been shown in the use of Salvia divinorum? In regards to health, both physically and mentally.
Baby seagulls have just hatched - what's the best food to give to the mother/father gull?
The herring gull nest on my roof now contains two tiny, fluffy little chicks. I've been feeding bread and kitchen scraps to the parent birds ever since they decided to nest here, but now the babies have hatched, I want to make sure that they get the best diet to ensure that both of them survivie and grow to be strong, healthy birds. What is the best food to give to the mother and father gull, so that they can regurgitate it for the chicks?
I'm pretty sure that bread will do. But remember that "caffeine, alcohol, chocolate, avocados, rhubarb, sprouted limas, fava beans and navy beans" are unsafe for most birds. They would probably appreciate fish if you can get some. But you also must remember that the gulls are most likely self-sufficient and will scour for their own food to feed their babies. You probably don't even have to worry about them, unless the parents are incapable of finding their own food or are hurt, etc. Just enjoy watching them in their nests. ;) --Proficient14:45, 11 June 2006 (UTC)[reply]
Chicks need a high protein diet, so bread is really not that good. Their natural diet is, of course, fish, so they will appreciate any scraps from the local fishmonger.--Shantavira15:48, 11 June 2006 (UTC)[reply]
Bread is not that good for gulls. It fills them up without providing much in the way of nutrition. Whilst it doesn't really harm them as such, there are better things you can be feeding them (e.g. meat or fish). Personally, my gulls always get cooked beef or pork. Just don't go mad with it - like I did... ;) --Kurt Shaped Box19:40, 11 June 2006 (UTC)[reply]
I've been going through my back issues of Popular Mechanics (I'm in year 2000 right now), and I find myself distressingly unable to determine whether the articles are astounding and innovative, or total bull. How do I track down sources on a magazine that has never given, and will never give, sources? For instance I have it open right now to an article on the "Lenticular Reentry Vehicle", cover story to the November issue. I've done what I can to track this thing down (which is very little): I've searched Wikipedia, and I've searched Google. I have yet to find a single site discussing it (including Wikipedia) that didn't use the article itself as the one and only source. And another: in October of that year, they have an article describing Ning Li's attempts to use a "Bose-Einstein condensate" to fight gravity. It's been six years since then, so there must be some kind of results from the project, even if they're negative. How do I track them down? Black Carrot17:35, 11 June 2006 (UTC)[reply]
Searching is certainly good, but you should also consider writing to the PM editors and the article author; you might get follow-up information that way. — LomnTalk19:11, 11 June 2006 (UTC)[reply]
I've also had similar qualms about PS-like magazines. As a popular magazine they are often printing rather big-sounding stories, often hinting at unrealized links to larger scientific questions, which always leave me wanting some kind of follow-up. I guess they just put their duty to entertain readers above educating them, and thus resolve to not print boring negative results whenever possible. After all, it is Popular Science and not Disciplined Science. freshofftheufoΓΛĿЌ 02:36, 12 June 2006 (UTC)[reply]
Yeah. I don't really want to e-mail them specifically, though, since I'm getting the feeling I'll want to check up on at least a dozen articles per issue. I think they'd get tired of it after awhile, if they helped at all. Anything else? Black Carrot03:32, 12 June 2006 (UTC)[reply]
Did the article by any chance mention the name of any of the researchers? Or perhaps the school, institution? It's usually pretty easy to contact researchers at universities through listings on their homepages. freshofftheufoΓΛĿЌ 05:51, 12 June 2006 (UTC)[reply]
That's a good idea. The first person I tried it on seems to have dropped off the map (except some fan sites, for some reason), though. I'll keep trying.
I have to say, I'm a bit disappointed. It seems like the people here would be good at finding stuff out. Doesn't anyone know of reliable science sites I could look some of this stuff up on? Black Carrot02:16, 13 June 2006 (UTC)[reply]
How's this for a basic rule. If the only place it's published is Popular Mechanics, treat it as slightly, but only slightly, more credible than Nexus. Like Popular Science, they have a history of transmogrifying wild speculations into supposedly rock-solid predictions; where do you think all the flying car articles come from?
In this specific case, the source of the article seems to be a combination of a formerly classified document retrieved under FOI, and a healthy dose of speculation based on historical research, much of which could well have been done on Wikipedia. Might I suggest that you write to the magazine and ask for a copy of the document they used, and suggest that in future they might place sources like that on their website? --Robert Merkel04:11, 13 June 2006 (UTC)[reply]
Different colours of cigarette smoke?
Just spent the afternoon sat on my sofa listening to music, smoking and chilling out whilst watching the clouds of smoke floating around the room in the sunlight. It was then that I noticed something that I'd never noticed before. With the sun behind it, the smoke rising from the tip of the cigarette has a blueish tinge to it, whilst smoke held in the mouth but not inhaled is white - and exhaled smoke is light grey in colour.
Something to do with moisture? I seem to recall an Isaac Asimov or Philip K Dick story in which the robot's disguise is foiled by the colour of his cigarette smoke. The rational given was the moisture droplets in the smoke. Skittle21:07, 11 June 2006 (UTC)[reply]
I'd cast my vote for an optical illusion. There isn't much in that article about color illusions, but there's some. Smoke held in your mouth is against a background of black or dark red, and is seen as lighter than it is. Smoke in the air is in its normal habitat, and is seen correctly, as light gray. Smoke against sunlight has to deal with 1)being against a strong light source (darker), and 2)being against yellow (bluish). Black Carrot22:11, 11 June 2006 (UTC)[reply]
Caused by the imprint left on your eye by the brighter yellow sunlight, gives everything a blue hint, I should suspect. PhilcTECI22:42, 11 June 2006 (UTC)[reply]
The article is only a stub, so I'm wondering if someone here might provide me a bit more information. The article explains that the brain's intake of oxygenated blood is restricted so that the stomach can metabolize large quantities of complex carbohydrates. Is the reason for sleepiness then simply because the brain can't get enough oxygenated blood and simply begins to shut down body systems so as to use less energy? When I eat way too much carbo-laden food (Chinese food, for example), I often drift off to sleep for several hours while still at the table, and I find this topic quite interesting. There's not much info online, though (perhaps there's a technical term for food coma that I don't know.). Thanks in advance, Johnny. 69.212.22.15719:55, 11 June 2006 (UTC)[reply]
There are a number of potential effects of food on arousal levels. There are some specific metabolites (e.g., tryptophan) with "dormitive properties" a la Moliere. Carbohydrates can affect level of autonomic arousal as well. alteripse02:33, 13 June 2006 (UTC)[reply]
(after edit conflict) I think the collision would be totally uninteresting. The two black holes will spiral into one another and merge into one mass, and that's about it. No EM-emitting accretion disc would be formed because neither black hole can emit/reflect radiation. --Bowlhover01:55, 12 June 2006 (UTC)[reply]
As ConMan says, some of the details of what happens when black holes collide are unknown. What happens to the singularities, for example? It's an open question. It's true that there will be large gravitational waves, though. This happens whenever very massive bodies collide. -lethetalk+05:09, 12 June 2006 (UTC)[reply]
'Irresistible force vs. imovable object' comes to mind WRT the singularities, as does the image of a snake trying to eat itself, for some reason. Gah! My head hurts even trying to think about trying to describe the concept of two 'infinite gravitational wells' of 'infinitely small (zero) volume and infinitely large density and temperature' being pulled into one another. :) --Kurt Shaped Box06:01, 12 June 2006 (UTC)[reply]
Yup, it's a thorny issue, and it's perfectly reasonable to imagine that there is no solution. It's been known since the 19th century that the classical theory of charged point particles contains inconsistent solutions. You can find solutions to Maxwell's equations where two point particles chase each other going faster and faster, a consequence of the fact that a point particle is really a singularity in the charge density. It's reasonable to expect that the same thing happens to singularities in the gravitational field. The issue with point charges was resolved with renormalization in the quantum theory, and one might expect that to figure out what happens to gravitational singularities will require a quantum description as well. We don't have one at present. -lethetalk+06:19, 12 June 2006 (UTC)[reply]
Well, I think that He doesn't believe in the theory of relativity, and isn't clever enough to understand string theory. I mean, let's work on getting Him to understand the theory of evolution, and then we'll think about introducing Him to black holes. -lethetalk+06:55, 12 June 2006 (UTC)[reply]
Didn't you hear? It was God that initiated the big bang. Unfortunately, He didn't have time to see whether it was good or not, as He was immediately anhiliated by the intense heat and radiation. :) --Kurt Shaped Box07:34, 12 June 2006 (UTC)[reply]
Nah, that's not what I heard. Word on the street where I'm from is that God created the world in 6 days about 5000 years ago, which makes Him about 13 billion years late for the big bang. -lethetalk+07:52, 12 June 2006 (UTC)[reply]
From the POV of an external observer, does it matter whether the singularities merge or not ? Could they even tell ? Sum the masses/charges/angular momenta of the merging black holes and you get the mass/charge/angular momentum of the merged object. According to the no hair theorem, those parameters completely characterise the final black hole. I don't think an external observer can tell anything about the distribution of mass inside the event horizon. Gandalf6108:45, 12 June 2006 (UTC)[reply]
But once the event hroizons have merged, how can an external observer tell whether there are one or two singularities ? If they could tell, wouldn't this be an exception to the no hair theorem ? I know the universal validity of the no hair theorem is controversial, but finding a simple exception would still be big news - especially if it did not involve quantum effects. Gandalf6111:00, 12 June 2006 (UTC)[reply]
If you find a way to merge the black holes without using quantum effects, then you've already made headlines, no matter what whether you've managed to conform to no hair or not. -lethetalk+14:21, 12 June 2006 (UTC)[reply]
Meaning of gull squawks/caws/cackles/etc. and body language?
Gulls seem to have a very complicated 'language', involving both vocalizations and body posture (i.e. the same call can mean different things in different situations depending on the position of the head and wings at the time). Is there an online resource that explains 'gull language' in detail? I'm quite close to some of my local gulls, having developed a rapport with them by feeding them on a daily basis. There is one bird in particular that I raised as a chick which is definitely trying to communicate with me. So far, I've figured out what a few of the calls directed towards me mean (e.g. lowering the head and flicking the beak whilst making a cheeping noise means 'I'm hungry/feed me', standing with an alert pose whilst making an 'ag ag ag' noise is some sort of greeting, and 'MWAAAK!' with wings slightly spread whilst hanging around outside means something like "Hey! We're here waiting for you!" etc.), but the majority of gull-to-gull communication eludes me (aside from the obvious alarm calls, 'let's gang up on that hawk' and 'back off'-type stuff). Sometimes the gulls will sit gesturing and gabbling at each other for minutes at a time...
Indeed. Some enthusiast would have probably studied this before. Maybe the language can be unique to gulls in certain areas and differ elsewhere. --Proficient00:48, 12 June 2006 (UTC)[reply]
I did once read somewhere that gulls from different parts of the world do not seem to regognize, or react to each others' calls. With regards to the gull I raised, I get the feeling (without trying to overly anthropomophize things) that she's trying to 'make me understand' something - she makes a series of soft clucking noises towards me that I've never heard from another gull before and gestures with her head constantly. She'll also peck at my shoes and legs when she's hungry. I had a very close bond with this bird ever since she was a couple of days old and I'm certain that she remembers and recognises me as an individual. Sometimes I wish I could think like a gull... --Kurt Shaped Box06:15, 12 June 2006 (UTC)[reply]
I'm interested in using an Altec 502i headset (designed for a computer, link here [10]) with my telephones. The product description on amazon says that I would need an "adapter", but it doesn't say what kind of adapter. What kind of adapter would I need? A link to an amazon.com item would be perfect. Thanks! -- Creidieki 01:32, 12 June 2006 (UTC)
Seizures and blood pressure
tyring to find info on seizures related to sudden blood pressure increse or decrease [unsigned]
Many insects like moths are attracted to light. This could present a major problem if moths develop to the point that they drive automobiles, as two moths driving in opposing directions would be drawn towards each other's headlights resulting in a head-on collision. What steps have been made to prevent this potential tragity? Mayor Westfall04:16, 12 June 2006 (UTC)[reply]
Members of arthropoda were actually a highly-evolved, starfaring civilization that was unfortunately wiped out by a doomsday device they created when a hapless mechanic got too enamored by the blinking lights on it and pressed the start button. Unfortunately, the stop button was not illuminated. -- Миборовский04:23, 12 June 2006 (UTC)[reply]
There is no problem. The moths will be attracted to the light, but the cars won't be, so the moths will leap out the window to their deaths, and the cars will float harmlessly into the ultra-rubber road barriers. freshofftheufoΓΛĿЌ 05:47, 12 June 2006 (UTC)[reply]
Wouldn't they crash into each other while trying to circle one another--that is if they are going in opposite directions, they're paths would curve into one another. Or would they...Now I have a math question that is bugging me because of this stupid question.
Say you have two moths flying toward each other carrying a light source. They are attracted to light 10 meters away, and their paralell paths are seperated by 5 m, would they crash into each other? I suspect this would depend on their initial velocities....Sounds like this would make a good text book calculus question. Anyone have an answer? XM12:21, 12 June 2006 (UTC)[reply]
Can there be non www websites (those that dont start with www.)--are there any? And can there be anything for the suffix part of the address--instead of/ .com .org .net .edu .uk etc.... Mayor Westfall04:43, 12 June 2006 (UTC)[reply]
To answer the first question: yes. You're on one. wikipedia doesn't require a www, and usually uses a language code. There is no restriction about this part of the URL. One website uses xxx instead of www, the physics arxiv. As for the second question, see top level domain for a list of what the final parts can be. -lethetalk+04:55, 12 June 2006 (UTC)[reply]
For the first part (the www and things that replace it), see subdomain (and you can have sub-subdomains and such). Within the domain name, things go from largest on the right to smallest on the left. --AySz88\^-^06:21, 12 June 2006 (UTC)[reply]
There was a crazy Math teacher in my college whose website was wwww. ... .br people always wondered what that could mean. Everyone knew he was a Nazi (really) so people usually associated that, like White World Wide Web and stuff like that. VdSV9•♫11:48, 13 June 2006 (UTC)[reply]
Birds' sexual organs
When two birds mate/have sex/whatever, what part of the bird's anatomy is stimulated in order for it to have an orgasm? As far as I know, most birds have no obvious external sexual organs (I know that a few species of birds do have a penis but for the sake of argument, I'm talking about the majority that don't). As anyone that's ever owned a male budgerigar can tell you, birds (or at least budgies) do have orgasms and will dry-hump just about anything in order to get themselves off - I'm not 100% sure about hen birds but I presume they get something out of it too, otherwise there'd be no incentive to mate. Basically, what part of the bird's anatomy is analogous to the penis or clitoris? —The preceding unsigned comment was added by 81.77.227.52 (talk • contribs) 22:09, June 11, 2006 (UTC)
Our article on birds probably mentions cloacas. There's enough animals that don't get any pleasure out of sex. In those cases they're simply acting on their instinct to survive and produce offspring. - Mgm|(talk)08:58, 12 June 2006 (UTC)[reply]
learning how to fix mobile phones
Hello All,Good Day.
I am hoping to learn the skill of fixing mobile phones. Which is both for hardware and software. I have access to buying all the necessary machines for doing this job, but I have no idea, how do I go about starting it, and how mobile phones work, and how to check, which part of the phone is not working, thus thereafter be able to fix it.
I did few searches on wiki, but nothing concrete showed up to guide me, so any help on how can I find such topics on wikipedia or any help on directing me to where I can find such specific help, will be highly appreciated.
Best regards,
Ken.
I'm sorry to say this, but if you have no ideas about the inner workings of a mobile phone, starting such a business on your own is probably a bad move. Try learning with a existing company first. (Also mobile phones differ in design between brands). HowStuffWorks.com should have a nice article on the subject of how phones work. - Mgm|(talk)08:55, 12 June 2006 (UTC)[reply]
This would not be a good medium-term business. Phones are gravitating towards the 'unfixable', like a memory chip or processor. Either phones become a single chip you put in your ear, or they keep the same format and become computers. --Zeizmic11:43, 12 June 2006 (UTC)[reply]
Your right there is little fixing possible at the PCB level with a board that fine but there are still many other things that can go wrong with a phone like gunk in the keypad and on contacts between various parts that can be fixed with simple dismantling cleaning and reassemblly, i have a feeling that this is a large part of what phone repair shops spend thier time doing. As for single chip in your ear unless voice recognition improves hugely i can't see people accepting it. Plugwash11:55, 12 June 2006 (UTC)[reply]
Civilization of birds
Suppose that humans became totally extinct, leaving the planet intact (i.e. no nuclear war, asteroid strike or anything like that) and that birds eventually evolved, over several million years, to fill the niche left behind. Which species of bird do you think would be the one to step up and assume the role of 'masters of the planet'? Parrots? Crows (these seem to be the most intelligent birds)? Anyone have any theories? --81.77.227.5206:33, 12 June 2006 (UTC)[reply]
Seagulls are tough and adaptable but the parrot species have a complex social structure and have already evolved the opposable 'thumb' (toe, in this case). Surely the ability to manipulate objects with more than a beak alone would be an advantage? --81.77.227.5207:15, 12 June 2006 (UTC)[reply]
Depends what you mean by "niche". The first bird to move into an empty house is always the pigeon, but they wouldn't be able to drive the buses. I would have thought mammals would be more likely to take over most of the opportunities. Some countries already have more sheep, cattle, or pigs than humans, so presumably the land would be left to them.--Shantavira07:50, 12 June 2006 (UTC)[reply]
Cattle and other domestic animals have, however, been overbred to produce as much milk or meat as possible, so that they are unable to move or react as fast as required "in the wild". Many of them would be unable to survive without humans. –Mysid(t)07:59, 12 June 2006 (UTC)[reply]
Who said that humans are the masters of the planet now? Us humans? Why aren't ants the masters? or beetles? or bacteria? ;-) —Bkell (talk) 08:48, 12 June 2006 (UTC)[reply]
Because bacteria have not formed cooperations that produce anti-humanic drugs, and ants & beatles don't spray chemicals on human cities to remove them from their habitat. XM13:11, 12 June 2006 (UTC)[reply]
If you want to be anal about it, ants do spray chemicals to remove just about anything edible from the environment. They are just more ecofriendly than humans. Humans kill the ants and let them rot. Ants make a chemical trail to a food source (could be a human) and rip it apart into little bite-size chunks. However, I do not like this question. Why should birds take over? Why should it be a land animal? Why not the dolphins? A proper question would be: If humans were gone, would there be an animal that would spread across the entire world, pushing out other animals and plants? --Kainaw(talk)13:30, 12 June 2006 (UTC)[reply]
I think it wouldn't be any kind of bird. It would be some kind of mollusc or insect, or crocodile. Dolphins would still be the most intelliegnt species (if they'd still be here) but of course they won't be the 'masters' but just continue to play joyfully as ever. – b_jonas09:06, 12 June 2006 (UTC)[reply]
To replace humans something would need the ability to use tools, and need hands and opposable digits, so monkeys seem the only likely successor, possibly through evolution, leading to another humanoid race. PhilcTECI19:37, 12 June 2006 (UTC)[reply]
But one that would look as different from chimps as we do (more or less, most likely). However, whoever "rules the world" after us might not be a "civilization," as the header implies. Dinosaurs, for example, were the top predators for a long time, but had limited mental capacity. I can imagine the descendents of eagles, say, coming "on top" without building a civilization. zafiroblue05 | Talk00:57, 13 June 2006 (UTC)[reply]
leaving aside the impossibility of assuming that any species of sub-species will achieve evolutionary success in the environment of the unknowable future I'd go with the 2 birds that can already be considered as tool users. That is the Raven which has been known to drop pebbles into water to raise the water level so it can drink; and the Indian Black kite which picks up burning branches & drops them somewhere a fire can start inorder to scare out prey. AllanHainey11:29, 13 June 2006 (UTC)[reply]
Whenever it comes to defining a creature that rules the world, why is aquatic life always completely ignored, despite water covering 70% of the surface of the earth. PhilcTECI15:25, 13 June 2006 (UTC)[reply]
I think the reason is based on moving under water. Even the smartest water creatures must have a fin to move around. If they don't have fins, they'll grow them, like whales (or, to be precise, they'll evolve to have them). The necessity for fins more or less precludes the development of anything like opposable thumbs, so they'll never really develop an extensive use of tools, and therefore will never have civilizations. zafiroblue05 | Talk21:39, 13 June 2006 (UTC)[reply]
what is the difference b/w velocity and acceleration?...please illustrate me with simple example. thanks — Preceding unsigned comment added by 80.247.152.121 (talk • contribs)
actually i m having problem understanding the term "rate of change of velocity"...can u kindly explain it please???
It is how fast the speed changes. Let's say you're driving a sports car at 80 mph, and just for the fun of it accelerate to 90 mph. Let's also assume that it took, for example, 5 seconds to do that. Now your velocity has changed 10 mph in 5 seconds—this is the rate of change of your velocity. If the acceleration of same amount takes longer, the rate of change is smaller. The acceleration can be calculated by dividing the change of velocity by the time it takes; a = 10 mph / 5 s ≈ 2.93 ft/s². –Mysid(t)08:10, 12 June 2006 (UTC)[reply]
You're driving along the road at a steady 60 kph (or 16.66 meters/second). Then you speed up for 20 seconds until you reach 70 kph, then maintain that speed. In those 20 seconds, your velocity (= speed) increased from 60 to 70, an increase of 10 kph. 10 kph over a period of 20 seconds works out to be an acceleration of 13.9 centimeters per second per second. JackofOz08:15, 12 June 2006 (UTC)[reply]
As another example, if you're driving at a constant 100 km/h, then your velocity is 100 km/h, but your acceleration is zero, because your velocity isn't changing. If you decide to speed up, then as you speed up your acceleration will be positive and your velocity will increase; if you decide to slow down, then as you slow down your acceleration will be negative and your velocity will decrease. (As you slow down, your velocity will remain positive, as long as you're still moving forward, even though your acceleration is negative.) —Bkell (talk) 08:44, 12 June 2006 (UTC)[reply]
A change in direction is also a change in velocity, hence travelling at a constant speed in a cricle also has acceleration. PhilcTECI19:35, 12 June 2006 (UTC)[reply]
As a further example, you're driving along in your car at 200 km/h (55.5 meters per second), and you hit a brick wall, coming to a stop in ten milliseconds. Your acceleration is (55.5 m/s) / (0.01 s) = 5,550 meters per second per second, or about 555 times the force of gravity. Ouch. --Serie22:06, 12 June 2006 (UTC)[reply]
Which neatly illustrates the fundamental difference. Velocity is a measure of one effect of a force, whereas acceleration is a measure of force itself. JackofOz23:51, 12 June 2006 (UTC)[reply]
Body Volume
Can you please supply me with the average VOLUME of the human body? This can be answered in cubic inches or cubic centimeters, preferably the former. Many Thanks Dr. Robbie Brown.
Ask A Scientist discussed the same – it can be found out by dividing the average human mass by 0.001 kg/cm³. According to human weight, an average US male weighs about 80 kg, so the average volume of an US male would be 80,000 cm³. –Mysid(t)07:36, 12 June 2006 (UTC)[reply]
You could find out your own volume for yourself (although it's a bit messy). Fill a paddling pool to the rim with water and carefully step in and subnmerge yourself entirely. When you're done, step out and measure the amount of water still in the pool. The amount of water that spilled over when you went under is your volume. I don't recommend using your bath tub for this. After you get that amount of liters or gallons, cubic centimeters or inches are only a calculation away. - Mgm|(talk)08:51, 12 June 2006 (UTC)[reply]
Just weigh yourself. For a first approximation, your density is about the same as water: about one gram per cubic centimetre. (You can shift that by five percent or so depending on whether or not your lungs are full of air, and whether you count that as part of your volume.) Note, for your convenience, that Google can do unit conversions for you—follow the link for an example: 1 cm^3 in cubic inches. TenOfAllTrades(talk) 16:44, 12 June 2006 (UTC)[reply]
The calculs are plain. Man floats a little (nose, chin and toes), so his density is not very different from water's, this is what Ask a Scientist's constant says. 1 kg of water defines a volume of 1 liter or 1 dm3. So man's volume is its weight in dm3, 1000 x his weight in cm3. For in^3, try Gogle and search, eg, "80000 cubic cm in cubic inches" which gives 4882. --DLL16:44, 12 June 2006 (UTC)[reply]
A better approximation would be 1 kg body weight = 0.9L = 900ml. Non-average fat and muscle percentages change this. For a 70kg person, then 63L --Seejyb22:44, 12 June 2006 (UTC)[reply]
additives
which kind of organic nitrates are added to diesel?
Cyclic nitrates are usually used as a diesel fuel additive.They reduce the autogenous ignition temperature of diesel fuel more than aliphatic nitrates; bicyclic nitrates are more effective than monocyclic nitrates, ex- cyclohexyl nitrate .
Also, the organic nitrates proved to be the most suitable as components of starting fuels for diesel engines.
(Ref: Springerlink)
pop and pop3
i've encounterd within my mobile a computer term pop3 server wat is this??? and what is pop??....also there are two other terms WAP and secure WAP Network...please inform me about these!...thanks
i've a smartphone "i-mate sp3i"...and i want it to serve as modem for my PC. i tried to search for it on i-mate's official website but couldn't find any material...
actually i use gprs on my phone n browse websites but i want to browse these websites on my pc through mobile.i ensure you that my mobile has this option to act as modem for my PC..but i m unable to find that option..please help me????
IP address configuration
Hi, I need to configure my laptop as the DHCP client in the office but assign a static IP at home, for the broadband connection. As of now, I do this change manually every day. Is there a utility which will allow me to reconfigure these settings on the fly ? -- Wikicheng09:04, 12 June 2006 (UTC)
'[reply]
The manual way to change it would be to look into the properties of the network interface, then look at the properties of "TCP/IP settings" and changing it there. But there must be an API for easily changing these settings. I know it. -- Daverocks (talk) 13:50, 12 June 2006 (UTC)[reply]
I haven't tried it myself, but a bit of googling (the first hit for windows dhcp static bat if you must know) finds this. Create .bat files with those one-liner commands, make shortcuts for both to the desktop and Bob's your uncle (knock on wood). (notmyfaultifyoufryyourcomputer.)Weregerbil19:22, 12 June 2006 (UTC)[reply]
For a home science assignment I am doing an experiment on the effects of age on cognitive ability and memory. How I am doing this is getting some cards with 10 numbers, 10 letters and 10 mathematical questions on it. I get the subject to remember the numbers and letters for a set amount of time and after 5, 10 etc minutes I ask them to recall. I then record their success rate. I then ask them to complete the mathematical problems which I time. These two values I compare to other people from different ages etc.
In this type of experiment, what is the control? would it be the average of all scores?
Any improvements I could make to it?
Also, the assignment calls for a "background" section to be written as well as the Aim, Method, Results, Conclusion etc. In a formal experiment, what is the "background"?
Thanks
Wayne
You would not really have a "control", I don't think, although if you need one I suppose the average value of each age group would do (although this is certainly not a control in the strict sense). You could mention things like the standard deviation at each age group (which, I would imagine, would vary considerably as you get to the youngest and oldest members of the experiment). Your test sounds fine, but it does sound a little easy. I would imagine that most people can remember 10 letters in a row in 10 minutes. Maybe you could try lowering the time a little, to increase the spread of results? Batmanand | Talk11:26, 12 June 2006 (UTC)[reply]
They're not asking them to look at them for 10 minutes but to recall them after 10 minutes has passed. So increasing the time would make it harder, not lowering the time. Skittle12:50, 12 June 2006 (UTC)[reply]
They get the numbers and letters to remember and they only get to memorize it for 2/3 minutes. Then I test them after 5, 10 minutes and mabye 20 or 30 minutes. Wayne
Most studies on age and memory have to do with transfer of short-term memory to long-term memory. That takes at least 20 minutes until an event is completely removed from short-term memory and in long-term memory. So, you should work on testing both. After 5 or 10 minutes, you are certain that the events (the cards) are in short-term memory and not long-term memory. 20-30 minutes later, it is in long-term memory. Obviously, mistakes they make in short-term memory will continue into long-term memory (unless they make a lucky guess). Your hypothesis can be that older people have a greater loss in transfer from short to long-term than younger people. You can even expand to include children. Are children better or worse than young adults? --Kainaw(talk)13:23, 12 June 2006 (UTC)[reply]
I'm not sure that claim is completely accurate. The popular phrases "short-term memory" and "long-term memory" don't map directly onto the brain. When a subject is given a stimulus (e.g. a number on a card in this case) they will usually rehearse it by mentally repeating it. At this stage it is in working memory (or the phonological loop in Baddeley's terms). As long as the subject continues to rehearse it, for whatever amount of time, it will continue to be in working memory. It is for this reason that memory experiments often include a distractor task (e.g. simple arithmetic) between item presentation and test of memory retrieval. At the same time, the subject will be primed such that the stimulus will be more likely to be remembered given a cue or presentation of part of the stimulus (e.g. if the stimulus is a 9 digit number, given the first 5 digits). This is also a form of "short-term memory". Further, the details of the episode in which the stimulus was presented, as well as the stimulus itself, will be stored in the subject's hippocampus (part of "long-term memory") and will also leave a trace in other medial temporal lobe structures ("intermediate-term memory"). After a period of days, the content of the particular episode will slowly be consolidated into various association cortices (also considered "long-term memory"). The summary of the story is that a large number of different brain regions are all taking in the same stimulus and handling it in different ways, which do not all easily map onto a simple short/long-term distinction. Whew! That's a fair, quick summary... 128.197.81.18118:28, 12 June 2006 (UTC)[reply]
I defentantly like the idea of testing the performance of the short term versus the long term memory of different people. I have changed it so they will be tested after 5/10 minutes and 30/40 minutes, however I will not restest the maths problems as that is not a memory test. I was also thinking of noting if a subject says that he or she says that they "cannot remember" or he or she gives incorrect results as I may be able to draw some (dunno what though) conclusions from this. - Wayne
I belive that the best way to compare the results would be by using a t-test. You can read about the t-test here, and there's a pretty simple on-line calculator here. You don't need a control group, by the way, since you yourself are not manipulating any variable. Rather you are comparing two populations to see if there is a significant difference between them. — Asbestos | Talk (RFC)14:58, 12 June 2006 (UTC)[reply]
To answer the other part of your question: "Background" would be a description of what people generally write about memory, and how it changes with age. How long have people known it to happen? When do they say it should happen? Why does it happen? Quote a biology or physiology book. It would also include the difficulties that the changes you are measuring may be causing people, or the practical importance of the effect.. Background gives the reader a perspective on what you are testing, and why. --Seejyb22:12, 12 June 2006 (UTC)[reply]
phd or research in Bioinformatics
I complited my M.Sc Bioinformatics from Tamilnadu and would like to do Phd or research in Bioinformatics from Bangalore or from Tamilnadu. I want to know which all universities are providing the Phd or research cources and how to apply for the same. What all qualities and qualification is needed?
Concerned about the possibility of Duchenne's Muscular Dystrophy (MD) to future children by using the pedigree diagram and all other possibilities.
Scenario:
There is no evidence of MD on the husband's side of the family. The husband, the brother and the parents are normal.
The wife does not suffer from MD, and neither do her parents, but she has a brother who died from MD at the age of 7.
The couple have no children, but are anxious to start a family.
Please could anybody helps me with this.
Screen the mother for the mutation using haplotyping. If the mother is a carrier then there is a 50% chance of boys being affected and girls being carriers. Prenatal screening will allow potential fetuses to be tested for the mutation and aborted accordingly. --Username132 (talk) 14:35, 12 June 2006 (UTC)[reply]
Yep. Genetic counselor should be the one to help with all your information and decision-making needs. There are various associations in the UK, the USA (although this site looks more sentimental) and Australia, among others, that you may find helpful. There are associations in Canada and New Zealand and other countries too. They should be able to give you information and/or direct you to a specialist genetic counselor. Good luck with whatever decision you make. Skittle16:17, 12 June 2006 (UTC)[reply]
Balancing a chemical reaction =
Hello, I need to find the product of this reaction and balance it.
(I used _ to denote a subscript.
H_2 = H(subscript)2 )
H_2CrO_4 + AgNO_3 → _____
This is a homework problem, but I would just like a little help, could someone point me in the right direction? I do not have a problem balancing these, but every problem like this in my textbook already has the product written and I cannot find how to actually find the product of these type of reactions if it is not given. Dont I need to know the charge of those compounds? I guess the problem is, I can find the product of reactions composed of individual atoms, or cations/anions that I know the charge of (like Nitrate, Phosphate etc.. which are in my book), but I do not know the charge of the compounds in this reacion. And would AgNO_3 be called Silver Nitrate?
Also, if anyone has any helpful tips about these types of problems, please share.
Where no charge is indicated, the charge is assumed to be zero (neutral). So H2CrO4 (chromic acid) has an overall charge of zero, as does silver nitrate.
The type of reaction here is called a double displacement reaction (also called a 'double replacement' reaction). When you dissolve those compounds in water, they break up into their component ions, and then figure out which anions can be paired off with which cations. You have to look for ions (anions/cations) that you recognize; you've probably got a list of common ones that you'll need to know. Hopefully that will get you started on your homework. TenOfAllTrades(talk) 14:51, 12 June 2006 (UTC)[reply]
I think the simplest thing to say is that you need to learn the charges of more ions. For this example, you have 2 H's in the first compound so you can figure out the charge on CrO_4 from that. For the second compound you should learn the NO_3 ion's charge (Ag also has a most common charge that is helpful to learn.) Rmhermen14:55, 12 June 2006 (UTC)[reply]
More to the point, once you remember that HNO3 is neutral, figuring out the charge of the NO3 ion is easy. Of course, it's harder with polyprotic acids, such as H2CO3 or H2SO4 since those may lose a variable number of hydrogens to give ions with different charges. —Ilmari Karonen (talk) 16:03, 12 June 2006 (UTC)[reply]
Large "digital frames" that you can hang on your wall to display your digital pictures are much more expensive than regular lcd computer monitors. Is there any way, using windows, that I could attach a second screen to my computer, hang it on the wall, and set it to show my photo-viewing screensaver? Any thoughts or advice? — Asbestos | Talk (RFC)16:58, 12 June 2006 (UTC)[reply]
That's feasible, but may be tricky to achieve. Another idea is to get a LCD TV, and use your digital camera. Most of them come with a form of video output, and support slideshows. This would involve the least amount of wiring and fuss with your PC. Also, LCD TVs are generally cheaper than LCD computer screens.
A second monitor is not difficult. You just need two video-outs. Dual-head cards make it very easy. As for the program, there are photo-viewing programs (doesn't Windows XP come with one built-in?). If you really like the screensaver version, you can run screensavers as programs. You don't have to lockup the computer. The problem you will have is that the mouse will tend to get lost when you accidentally drag to the second monitor. --Kainaw(talk)17:45, 12 June 2006 (UTC)[reply]
Not that I know of. It would, of course, depend on the video driver. All of the popular ones that I've used allow the mouse (and windows) to slide back and forth freely between the monitors. --Kainaw(talk)18:00, 12 June 2006 (UTC)[reply]
There exist mouse utilities that allow you to set boundries for the pointer. I could never reason why they would want to do that but it seems it would be useful in a situation like this. freshofftheufoΓΛĿЌ 02:23, 13 June 2006 (UTC)[reply]
I've never heard of anyone taking ATP as a supplement, if that's what you're asking. Your body makes more than enough ATP for its own purposes (the article in fact states "1 kilogram of ATP is created, processed and then recycled in the body."). As for knowing about ATP? I can't really see how knowing about ATP will affect your body building much — do you need to know how the CPU works to be able to use a computer? — but learning about ATP will probably play a part in your quest to understand high-school biology. — Asbestos | Talk (RFC)18:21, 12 June 2006 (UTC)[reply]
Yuck. I take back what I said above: it looks like there are a lot of people selling "ATP supplements" over the web, some even claiming that all but the puniest of "weekend warriors" really need their products to prevent strokes and what-not. In my view this is BS and they are selling snake-oil. The only piece of supporting evidence I could find skimming through Google Scholar was an article saying that it may help prevent brain damage after trumatic head injuries in rats. Unless you plan on getting hit in the head a lot, and are a rat, I personally don't see the point. — Asbestos | Talk (RFC)18:31, 12 June 2006 (UTC)[reply]
How? ATP is a cell's "energy currency," but all the ADP/ATP a cell needs is already present. The body is designed to derive its energy ultimately from carbohydrates, fats, and proteins, and it is stored in those forms as well. --Ginkgo100talk · contribs19:17, 12 June 2006 (UTC)[reply]
Genetics
Actually I'm brunet with a bit dark skin. If I marry a tall blue-eyed blonde, what is the probability of the nordic type person birth (any gender)? I read it's small because my type is in fact a dominant gene. And how many generations should pass (counting my offspring as first) to achieve the nordic type? Thanks :) --Brandспойт21:00, 12 June 2006 (UTC)[reply]
Hair_colour#Genetics, Eye_color#Genetics, and Skin_color#Genetic_determinants should help. Whether your kids display recessive characteristics, like blue eyes, depends on whether you're a carrier for that characteristic or not. Does anyone in your family have blue eyes? The "how many generations" question depends on who your children decide to breed with, and could only be answered with an estimate of probability. Black Carrot21:33, 12 June 2006 (UTC)[reply]
Assuming the trait is passed on through the simple dominant/recessive-type gene, a Punnett square will help you work out the probabilities from any breeding system you care to describe. I don't know how to work out anything more complicated than that. Black Carrot22:20, 12 June 2006 (UTC)[reply]
Neither eye color nor hair color are single-gene traits, nor is being a "nordic type person". And all of the various genes so far identified as being involved are assorted independently. There's no way to make any reasonable prediction here. If you want to play around with what's understood, search Online Mendelian Inheritance in Man (OMIM) for "hair color" or "eye color". It will give you some appreciation of how much more complicated the transmission of these supposedly simply traits is than most people seem to believe. - Nunh-huh22:45, 12 June 2006 (UTC)[reply]
If you have double dominant genes, which is likely if you have absoultely no family history of these traits, all of you children will inherit the dominant traits, and none have the recessive traits. PhilcTECI00:04, 13 June 2006 (UTC)[reply]
Wrong. These are not traits transmitted at a single gene locus. It makes no sense to discuss them in terms of dominant vs recessive when the actual specific genetics have not been characterized. - Nunh-huh00:34, 13 June 2006 (UTC)[reply]
Nunh-huh is correct, we simply do not know enough about the genetics of hair, skin and eye colour to accurately predict such things. The genes we do know of can give you some pointers, but unless you sequence your alleles, its very difficult to even speculate about these. Some recessive MC1R alleles predispose to fair skin, red/auburn/strawberry blonde hair and freckles. And SLC24A5 variation appears to corrolate with skin colour. There are also some recessive subclinical alleles of albinism genes (eg. Tyrosinase, Dopachrome Tautomerase and Tyrosinase related protein) that result in very pale skin and white/blonde hair. Oddly enough, the genetics behind Californian blondes (i.e. blonde hair, tanned skin) is currently unknown. It appears that it might have something to do with the structure of eumelanin biopolymers and is possibly dominant over red hair alleles.
So while it is not possible to accurately predict in any scientific way, what we do know would suggest the odds are against you producing "very Nordic" progeny. Since the paler phenotypes are often recessive (due to a loss of function in genes involved in melanogenesis) unless you are carrying recessive "Nordic genes" (which also appears unlikely), its probable your children will get an assortment of darker and lighter skin/hair genes. Exactly what that assortment means in terms of their manifest hair, skin and eye colour, well, thats anyone's guess. But its more likely to be something in between than at either extreme. Rockpocket01:49, 13 June 2006 (UTC)[reply]
Actually, I believe that mixed-race babies tend to have fair hair and colorful eyes. So you can get your little halfbreed Aryan. But just for a few years. -- Миборовский02:09, 13 June 2006 (UTC)[reply]
Charming. Genetic counseling from someone who finds "mixed-race babies", "half-breed", and "Aryan" to be useful categories. And is apparently unashamed! - Nunh-huh04:44, 13 June 2006 (UTC)[reply]
Hello. My name is Natasha and I am really in a bind. I really need help finding information on the genesis of life for crocodiles. It is a school project, and tommorow is the absolute last day to work on it. I did need websites bacause that is what everyone is giving me. If you find anything on Spermatogenesis, Oogenesis, Female Ovulation, Fertiliation, Embryonic Development, Birth, and Genetic Variation, please just copy and paste and send it to me. Thank-you so much.
Troubled grade 9
You need to do your own homework. Nobody here will do it for you. Also, cutting and pasting is not what your teacher is looking for. (And not the point of your education.) The point is for you to learn something about the subject and demonstrate that to the teacher. I'd recommend that you actually read the articles on the topics you listed, and then write the paper based on what you have learned from them. Fortunately, you have a whole 2 days. --Booch22:47, 12 June 2006 (UTC)[reply]
Hmm. Sorry about your bad planning! Our crocodile article doesn't help. Try searching google for "crocodile reproduction". There are some sites that you'll find that will be of use. [11], [12], etc. Similarly, "crocodile mating" and "crocodile fertilization" will all return useful results. - Nunh-huh22:53, 12 June 2006 (UTC)[reply]
Doesn't a human fetus aged less than 2 months look like a crocodile's ? The we evolve and/or regress but they become perfect crocos for Mr and Ms Vuitton. --DLL19:16, 13 June 2006 (UTC)[reply]
GMA 950
So the school I'm going to is reccomending that I get a Toshiba M400, they have some sort of special deal they're trying to negotiate.
Now here's my question: Will I be essentially screwed as far as all gaming goes? I'm really hoping not, cause I was hoping for a laptop for the next few years that I wouldn't want to throw off a cliff. Also, anyone have this computer? How's it work
Looks like I'm going to be stuck playing the games on my desktop whenever I get a chance to get home. Oh well, less Hard Drive space hogs I suppose. Also, I wanted to get Oblivion but it looks like it'd run on my ATI Radeon 9600 better.
Maybe I should just badger my parents into getting a MBP 2.16 Ghz for me (Looks to me that unless the school gets a spectacular deal, the Toshibas will only be ~$500 less than the MBP, which has specs at about twice the Toshiba, especially graphics card). — Ilyanep(Talk)22:53, 12 June 2006 (UTC)[reply]
It really depends what you mean by "gaming". Back when I played counter-strike, I considered a computer worthless if it couldn't run the game consistantly at 100fps+ without memory skips at 1024x768, or didn't have enough memory to smoothly concede minimizing the game client and loading third party programs.
Though CS is ancient, most current laptops still can't do that, but I'm guessing you won't be that hardcore for framerate. If you're into really pretty current FPSs or other depth-intense 3D games, then you'll probably be disappointed. I'm not sure how much better "sharing memory" methods are nowadays, but your vid card (and, of course, your screen) is really next to worthless as far as 3D gaming goes. On the other hand, RAM is sufficient and (if you get the 2ghz) there's probably loads of good games out there that you could run smoothly, as long as you manage your hard disk carefully to keep the cache file "cashing" smoothly.
Still, this computer is for school so you'd probably be better off using your laptop more productively... lets pretend the inadequacies are intended as a blessing to help you concentrate on your studies : ). freshofftheufoΓΛĿЌ 02:15, 13 June 2006 (UTC)[reply]
Oh pshaw, I've got to live at this place :D.
Thanks for the help. Hopefully if the tablet isn't required we can go with a laptop at the same cost that has an ATI Mobility Radeon X1600. — Ilyanep(Talk)02:51, 13 June 2006 (UTC)[reply]
They have begun issuing these to people I work with. What I don't get is, what's so special about the tablet feature? There is no way you can scribble half as fast or as accurately as you can type. I could see it making field work easier, since its a good way to navigate GUIs while being held in your hands. I don't see a single practical benefit to it for typical desk use, though. If you want to play Oblivion well, plan on spending a LOT for a laptop. And BTW, the reason no laptop can run CS at 100FPS is because no laptop has been made with a screen that refreshes that fast. Maybe because theres no perceivable benefit?
Agreed. But the MBP looks like it can run Oblivion at at least medium if not high settings. I think the Tablets are overpriced for a school setting. — Ilyanep(Talk)16:55, 13 June 2006 (UTC)[reply]
Don't forget to factor in the cost of the windows XP license (wink) in the total cost of that system, since O won't run on OS X as far as i know. Also, put priority on the 256mb vid ram, and 2GB of sys ram, I play O a lot and it ran like crap without those.
Oh well, I'll probably uninstall XP on the computer I'm working on right now and put linux on it [to make it a file server] and then use this copy of XP on that one. Then I can keep Win and OS X backups on here and it'll basically be a free file server. — Ilyanep(Talk)18:43, 13 June 2006 (UTC)[reply]
Odd Trait
What I was wondering was if talking during a T.V. show, or giving away the story is a recessive trait, because both my father's parents do so, thusly my dad and his sister also talk during shows. My mom doesn't and I don't, so would that make it recessive? schyler23:56, 12 June 2006 (UTC)[reply]
I think that reasoning and manner of thinking and choice, are all factors and none could be attributed to a single gene. It is mostly choice really, unless they have OCD. PhilcTECI00:00, 13 June 2006 (UTC)[reply]
Strong anecdotal evidence suggests that the need to control the remote control is inherited together with the Y-chromosome. - Nunh-huh03:38, 13 June 2006 (UTC)[reply]
A recessive genetic trait is passed on through a gene sequence on one half of a chromosome. If it is combined with a "dominant" sequence on the other, its instructions are effectively ignored in favor of those of its dominant partner. (I'd appreciate correction if I got the wording wrong.) Point is, that trait isn't recessive any more than a brunette is a tabby. However, were it being caused by an interaction of dominant and recessive genes, yes, that's what it could look like. Black Carrot17:45, 13 June 2006 (UTC)[reply]
Well, not one half of a chromosome, but one half of a chromosome pair, or one of a pair of chromosomes. And most geneticists would use "allele" rather than sequence. It's also not that recessive genes are ignored: they are usually transcribed and produce proteins, but the protein produced by the dominant allele has an effect that negates that of the recessive allele's protein. (For example, women who carry one allele for hemophilia (which is transcribed to produce a defective clotting factor VIII) and one allele for normal factor VIII produce both defective and normal proteins, and the normal protein is present in sufficient quantity that they do not usually experience clotting difficulties.) - Nunh-huh22:17, 13 June 2006 (UTC)[reply]
June 13
Guarani Indians from Asia
During a summer I spent in Paraguay, I saw a elementary school textbook that claimed that the Guaraní Indians (unlike other ethnic groups) originally came from South-east Asia (Malaysia, or around there), not over the Bering land bridge. The idea was something I'd never seen before, and what was most remarkable was that something that seemed at best rather pseudo-scientific to me was presented utterly as fact in government-sponsored textbooks. I'm wondering how an idea like that - which, after a little online and Wikipedia search, seems at best far-fringe, at worst entirely bogus - appeared in such a textbook. To be sure, a large part was some sort of national pride/chauvinism, as most Paraguayans have half-Guarani, half-European blood, still speak Guarani, and so on. (I should mention that many Paraguayans today look remarkably Asian, much more so than, say, North American Indians - perhaps partly because the "look," make-up wise, seems to be in style. But maybe only partly.) Still, there had to be some sort of (social?) scientific support for it, no matter how specious. But a little bit of research turns up little.
In short: is there any basis to a South-east Asian background of some South American ethnic groups? And how did such an idea make its way, untempered, into a government school textbook? zafiroblue05 | Talk01:18, 13 June 2006 (UTC)[reply]
I don't know anything about the veracity of the claims you refer to, or their likielihood but there is certainly nothing unusual about government sponsored (even local government) textbooks making false or unverified claims, pushing a particular point of view, leaving out embarassing facts & even plain lying. The most well known example of this is Japanese history textbook controversies and their treatment of Japansese actions in the Manchurian and second world wars. I believe that Chinese textbooks are also somewhat lacking in unbiased historical fact too & U.S.A. educational authorities have also been criticised for misrepresenting history in Lies My Teacher Told Me by James W. Loewen. AllanHainey11:53, 13 June 2006 (UTC)[reply]
Polynesian peoples, who originated in South East Asia (probably Taiwan and surrounding area), probably visited South America. The main evidence for this is the kumara, a sweet potato originating in Peru which is used through the eastern half of the Pacific, and which is not considered likely to have reached that area without being carried by people. However, there is no evidence of any genetic legacy being left in South America by Polynesians. My source is The Quest for Origins by K R Howe, ISBN 0-14-301857-4.-gadfium01:17, 14 June 2006 (UTC)[reply]
Okay, I'm officially stumped. I don't get it. People are capable of truly astounding backbends. I have proof. I've seen it: [13] So why, why, is nobody capable of making an equal frontbend? I've asked contortionists, I've left questions here, and I've searched Google, and I can't find a single person who's ever seen it. What actual physical reason is there for this to be so impossible? Black Carrot02:25, 13 June 2006 (UTC)[reply]
Maybe because the rib cage is in the way? In a backbend, the organs of the torso are stretched out, so they have to change shape, but not size. In a frontbend, there's nowhere for them to go. —Keenan Pepper02:52, 13 June 2006 (UTC)[reply]
The joints of the spine permit greater movement towards the back than the front. It's not like there's a hinge in the middle of the spine that bends equally both ways; the joints of the spine are quite complex and permit a greater freedom of motion in some directions, and less in others. When you bend forward, the spinal bodies get closer together and block further movement in that direction rather quickly. When you bend backward, the spinal bodies get further apart, and so don't prevent movement. - Nunh-huh03:37, 13 June 2006 (UTC)[reply]
I can see that shifting the organs would be a bit more difficult to the front, but would it really be that big a problem? Especially for skinny people like the one in that video.
I looked through our article on the spine, and I don't quite follow your argument. "Spinal bodies" seems to refer to the vertebrae themselves. You're saying a gap is produced between them when you lean back, but not when you lean forward? Black Carrot17:38, 13 June 2006 (UTC)[reply]
Yes. (An illustration would be best for demonstrating this, and I really can't draw, so this is primitive and schematic). .
Even with my crude drawing, I think you can see that there's greater range of motion at the joint when bending backwards. - Nunh-huh22:08, 13 June 2006 (UTC)[reply]
Wow, that's pretty awesome. Now, the backbends I've seen suggest that those gapes can become truly huge, without doing any damage. Why can't a similar gap form at the back? What's holding it together there that isn't holding it together in the front? Black Carrot22:32, 13 June 2006 (UTC)[reply]
Ligaments, muscles, bony configuration, etc. That's why the "fulcrum" of the joint is at the back of the spinal body, not the front. - Nunh-huh22:35, 13 June 2006 (UTC)[reply]
ELECTRONEGATIVITY
BY KNOWING THE ATOMIC NUMBER HOW CAN WE KNOW THE ELECTRONEGATIVITY ORDER OF THE ELEMENTS —The preceding unsigned comment was added by 202.88.227.171 (talk • contribs) .
What happens if a fully grown human eats a few million electrons? For example, if his food contains free electrons. What are the effects of electrons on a human stomach? 211.28.224.25010:58, 13 June 2006 (UTC)[reply]
All matter that you normally see living on Earth is composed of mainly three things, electrons, protons, and neutrons. The food you eat has billions and billions and billions and billions... of electrons in it!! — TheMac Davis] ⌇☢ ญƛ.11:25, 13 June 2006 (UTC)[reply]
I think he meant 'free electrons' (or may be negatively charged particles). Negatively charged bread, for example ? I don't think there will be any problem. The charges will get neutralised. If not, electron rich Faeces, may be ? -- Wikicheng11:55, 13 June 2006 (UTC)[reply]
Metal has a lot of valence electrons - those are "free". I've seen shows where they use gold foil as a cake decoration and nobody appeared to get sick when they ate it. I don't what it feels like to poop gold foil though. --Kainaw(talk)12:31, 13 June 2006 (UTC)[reply]
well, a couple hundred million extra electrons will do nothing, you probably "eat" this much all time in your mineral water. Electrons on a human stomach disperse to your skin.
The worst thing that could happen is that you would increse your electric potential and when you touched something electrically neutral there would be a small discharge with a shock. Much like when you walk dragging your feet on a large carpet. VdSV9•♫13:11, 13 June 2006 (UTC)[reply]
Look up Coulomb. A few million electrons is just nothing compared to it, and 1 coulomb is not very big.
yeah, what I meant on the "The worst that could happen" paragraph was in the case of a substantial amount of electrons, say... 10^16.
The human body can hold a considerable surplus of electrons with respect to the environment. I asked a related question here recently, and got an excellent answer: you might be interested to see the question, and the page that User:Heron pointed me to. --vibo56talk17:57, 13 June 2006 (UTC)[reply]
Redox reactions in steel manufacture.
Hi, I'm revising for my GCSE in Chemistry, and have seen mentioned in textbooks and on the specification that I have to know about the redox reactions involved in the Basic Oxygen Process of steel manufacture, when impurities are oxidised. Unfortunately I can't find much mention of them! Can anyone tell me simply what the redox reactions are for, say, silicon? I know it goes to SiO2, but I can't work out what the reduction and oxidation parts of the reaction are. Many thanks! --86.142.195.15811:02, 13 June 2006 (UTC)[reply]
Basic oxygen steelmaking and Slag might be of a little use. Otherwise, the main impurities present in pig iron are: Carbon, Sulpur, Phosphorus, and Silicon.
The carbon is oxidised to carbon monoxide and carbon dioxide, and the oxygen is reduced.
The elemental sulphur reacts with the magnesium/aluminium powder to form Magnesium/aluminium sulphide. The sulphur is reduced and the metal is oxidised (remember, Oxidation Is Loss of electrons).
The phosphorus is first oxidised to , Phosphorus pentoxide. This then reacts with the metal powder to form a Metal Phosphate via the reaction : (which you don't need to know for GCSE.)
The Silicon is, as you said, oxidised to and the oxygen reduced, but this can form acidic impurities in the steel, so it is reacted with CaO (from the decomposition of calcium carbonate) to form calcium silicates , which are scraped off as slag.
Thanks a lot! Much better than anything I could find. So would I be right in saying, for example, that the sulphur is removed like this (saying we use magnesium)?
So the redox would be
One other question though please, how would you do the redox for the carbon and oxygen reactions? I'm not sure whether to write carbon as +4 or -4, or even if I'm allowed to do that as it bonds covelently?
You're not technically "allowed" to use half equations for such covalent reactions as the oxidation of carbon, so you can approach it with a standard equation, or, if redox is absolutely required, by assigning the element with the highest electronegativity (i.e. oxygen), the negative oxidation state (i.e. ).
(edit conflict) What you've written above is roughly correct for the reduction of sulfur, except you meant to write rather than . As regards carbon, it's probably not helpful to express it as ions, but still in the carbon is in oxidation state +4. I guess the point is that even though it's a covalent bond, it's somewhat polarized (that is, the shared electrons are at any time more likely to be found near the oxygen than near the carbon), so in some sense the oxygen still partially receives electrons from the carbon, which is why the oxidation state is notionally +4 (and likewise +2 in CO). But bond polarization is probably A-level stuff. Arbitrary username19:34, 13 June 2006 (UTC)[reply]
Water Pressure
I have a 100 cubic metre water tank with a two inch pipe conected to the bottom of the tank. The pipe then drops 7.5m to a valve. My questions are:
Is it true that at the valve, 7.5m below the tank, I should have 0.75 bar of pressure?
If the pipe were to continue to drop to 10mts below the tank, and then return to 7.5mts (as in a siphon), would I still have 0.75 bar of pressure at the valve?
Does the length and/or diameter of the pipe influence the pressure?
Does the volume of water in the tank, or the shape of the tank i.e. (tall and narrow vrs. shallow and wide), have an influence on the pressure?
What you need to know is the height of the water level in the tank. The pressure at the valve should be higher than the pressure at the top of the tank (which should be atmospheric ~ 1 bar), so it definately won't be 0.75 bar. The pressure at a given point, certainly as long as the water is fairly static (isn't moving) should depend only on its height and the pressure at the points where it is in contact with the air (ie, the surface at the top of the tank). You can calculate pressure differences by timesing height difference by density of substance by gravity. So the difference between the pressure at the top and the bottom of the pipe is 7.5m x 1 kg/L x 9.81 m/s2 giving an answer in pascals. Remember this is the increase in pressure as you go down the pipe. I assume you can convert pascals into bar. Skittle12:11, 13 June 2006 (UTC)[reply]
It depends on whether we're measuring absolute pressure or gauge pressure; recall that the latter is the difference between the pressure in the pipe and the ambient pressure outside. Also note that we don't usually answer homework questions here. TenOfAllTrades(talk) 13:01, 13 June 2006 (UTC)[reply]
We don't answer homework questions that ask us to do the homework for them, but I feel it is different if it looks like they've tried to answer, then ask if their answer is correct and if they've understood the concepts. Skittle14:37, 13 June 2006 (UTC)[reply]
And even if they're looking at gauge pressure, their answer is orders of magnitude wrong (assuming they don't have an extremely convenient height of water above the pipe), so I felt a little help would be ... helpful. I really hope they can converts pascals (unit) to bar (unit). Skittle14:43, 13 June 2006 (UTC)[reply]
Assuming the 7.5m to be measured from the top of the water, and that they're interested in the gauge pressure, 0.75 bar looks correct to within a few percent to me — certainly not off by orders of magnitude. If you don't believe me, ask Google (using Pascal's law). The discrepancy in the second decimal is due to the original poster approximating g as 10 ms-2. —Ilmari Karonen (talk) 22:30, 13 June 2006 (UTC)[reply]
To summarise: For a water column, open at the top, the pressure would increase by approximately 1 bar for every 10m difference between the surface of the water, and the "depth" of the point where you measure the pressure. This you learn when diving: 10m down you are under 2bar of pressure. The curves in the pipe between the surface and the measuring point do not affect the pressure at that point. The shape of the tank would change the distance between your pipe outlet and the top of the water, and therefore the total height of water, and therefore the pressure. If your measuring device is zeroed to atmospheric pressure, the reading at 7.5m would be 0.75, but if it were an absolute pressure that you are measuring, then the reading outside of the water would be 1bar, and at 7.5m it would be 1 + 0.75 = 1.75bar. --Seejyb23:20, 13 June 2006 (UTC)[reply]
What kind of "chemcial" or additives can be added in the process of manufacturing PE string so that the fish-net(for fish-farming) can be more durable, namely anti-aging and anti-corrosive.
Polyethylene is already fairly corrosion resistant and non-biodegradable, so what improvement is required exactly? I suppose you can use UHMWPE, and this is used in ropes (see Dyneema). IMO, nothing can be added to improve the rope durability unless the manufacturing method is altered, giving a different product. If mould resistance is required Triclosan can be added. Otherwise, not much. --Eh-Steve17:34, 13 June 2006 (UTC)[reply]
keyboard shortcuts
Hi, I didn't know where else to look, and this is not a computer-science, so it wouldn't be on the math RD.
Well, I've been using MS word and this is annoying me. sometimes I need to switch to read other documents that are open in word, and to do that, I have to minimize or restore the document I'm writing to, then click on the one behind it to bring it forward. I want to work with my document maximized within the word window, and not have multiple word windows.
So, Alt+Tab is not an option. For most programs, there is an alternative with Ctrl+Tab, and I often use it (I don't really like to rely much on the mouse to work, to maximize a window for instance, I always do: Alt, Spacebar, X), but it does not work in Word.
Finally, my question is: Does anybody know the friggin keyboard shortcut to alternate between multiple documents within an MSWord window? VdSV9•♫13:21, 13 June 2006 (UTC)[reply]
Ok, I figured out a way to do what I wanted. I closed both, then opened them again and they are number 1 and number 2 on the recently opened list, so I do Alt, A (in english it should be F to open the File menu), then 1 or 2 to go to the one I need.
But still it is not what I was looking for. So if anyone knows the answer to the question I would be grateful. VdSV9•♫13:37, 13 June 2006 (UTC)[reply]
What you are looking for is the keyboard combination CTRL-F6. This will sequentially bring to the front, one at a time, all the documents that are currently open.--Mark Bornfeld DDS15:30, 13 June 2006 (UTC)[reply]
Hello....I am interested in finding out about a rare disorder called Reflexive Neurovascular Disorder. I have searched the web and your website as well and have found nothing. Could you help me out? Thank you.
Try Google, your library, and the American Medical Association's website. If you find enough info and are a registered user, please make an article about it. Emmett517:00, 13 June 2006 (UTC)[reply]
Could it be that you are looking for "Reflex Neurovascular Dystrophy"? That would be a pain syndrome. If so, synonyms include Complex Regional Pain Syndrome (the "most modern" term) and Reflex Sympathetic Dystrophy (commonly used) --Seejyb19:26, 13 June 2006 (UTC)[reply]
Covalent bonds in HCl
Hi, I know that hydrogen chloride is bonded by a single covalent (sigma) bond, but does this involve an H 1s electron and a Cl 3p electron? This is what I was told at uni, but I was wondering why some sort of hybridisation (e.g. sp3) would not occur. (This would affect lone pairs and the exact nature of the sigma bond?) If this does not involve hybrid orbitals, what determines when this happens? Will this never happen for single-bonded diatomic molecules? Thanks. -postglock15:04, 13 June 2006 (UTC)[reply]
The H-Cl bond is simply a sigma bond between a 1s orbital and a 3pz orbital.
Hybridisation as you were refering to it will happen in the same atom. A hydrogen's 1s orbital won't hybridise with a chlorine's 3p, as they are separate atoms. See Orbital hybridisation. But, that might not be what you're asking.
If you're asking whether or not the chlorine orbitals hybridise before the bond with hydrogen is formed:
There is no reason for hybridisation to occur as Cl has a ground state configuration of [Ar] 3s² 3px² 3py² 3pz¹. This means that an sp3 cannot occur as the 3s can't be excited to give its electron to the 3pz, because that would form a single sp1 and 3 complete 3p orbitals. This means that the configuration:
Thanks for the reply. The second half is exactly what I was trying to ask. Why wouldn't the chlorine atom's electrons hybridise before it bonds. I thought perhaps that chlorine should theoretically be able to form 4 sp3 orbitals, with three of them already filled with lone electron pairs. I am afraid I don't quite understand your explanation though, and the information at Orbital hybridisation doesn't quite tell me enough. I thought this kinds of (sp3) hybridisation should be able to occur in chlorine, even with its ground state configuration? It seemed analogous to the sp3 hybridisation of O in water, with two sp3 orbitals "pre-filled" with lone pairs.
goes to:
why wouldn't
go to:
If this is possible for Cl, then this would be possible for HCl, which then suggests that the lone pairs would be seperated to minimise repulsion ala the VSEPR theory? -postglock18:15, 13 June 2006 (UTC)[reply]
In retrospect, when I look more carefully at the situation, there is no logical or quantum reason I can see why the above shouldn't happen, provided all sp3's are formed... In that case, the H-Cl bond is in fact a 1s to sp3 bond. Hmm... Your university teacher might have been oversimplifying. --Eh-Steve19:08, 13 June 2006 (UTC)[reply]
Hmmm... I've just checked further in my textbook, and it appears to agree with my lecturer. It gives an example of a heteronuclear diatomic molecule (HF) and says that the H 1s orbital and the F 2p orbital are involved. Unfortunately, this section is on molecular orbitals, and seems to ignore why this would not hybridise... -postglock03:16, 14 June 2006 (UTC)[reply]
One can rationalize why this could be true if one considers the shapes of the regions of electron density in s vs p atomic orbitals: s is spherical and closer to the nucleus, p is directional along an axis and further from the nucleus. Hybridizing some s into a p results in electron density closer and less directional than the p alone. If a covalent bond from atom A to atom B involves having electron density being directed towards B and displaced away from A, makes sense that this electron density would have a high p character on A. Remember that this is hand-waving, not proof: we use orbitals to explain observations; reality isn't a slave to our model:) DMacks05:23, 14 June 2006 (UTC)[reply]
Interesting, but I always thought that although p orbitals were more "directional" than sp3 in terms of "pointiness," sp3 orbitals were more directional in terms of having more density on one side. What I mean is that p orbitals are symmetrical across a plane normal to the radial axis, and sp3 orbitals would be denser on the side of the bond. I suppose you are right, these theories only model reality; if it has been observed that HCl (for example) has lone pairs that are at right angles to the bond rather than tetrahedrally, then the model would hold. I guess what I would want to know then is if this lack of hybridisation would occur generally for all diatomic molecules... Thanks for the reply! -postglock06:42, 14 June 2006 (UTC)[reply]
Carbon-14 detection threshhold
What are the minimum number of atoms that the most sensitive method of carbon-14 detection requires in order to make a reliable determination that carbon-14 is or is not present, i.e., the threshhold detection amount? ...IMHO (Talk) 17:41, 13 June 2006 (UTC)[reply]
Based on radiocarbon dating, it would seem to be more a question of relative concentration. The section in question notes lower bounds on total carbon per sample but there's no suggestion that a larger sample (i.e. more carbon atoms) yields a longer dateable timespan. — Lomn18:39, 13 June 2006 (UTC)[reply]
Modern carbon-14 detection uses accelerator based mass spectrometry, so if there is a single carbon-14 atom in the ionised sample, it will be detected. But, that probably wasn't your ideal answer. If you wanted to know about the minimum beta emission detection masked by background radiation, the article on radiocarbon dating says that the threshold age is 58000 to 62000 (which is silly, since it depends on the size of the sample). That is 10.5 half-lives, so the maths is pretty simple, provided the original sample size is known.--Eh-Steve18:46, 13 June 2006 (UTC)[reply]
What I am trying to find out is if we started with a mole of pure carbon-14 (or 14 grams or "sample size" or the maximum possible amount of carbon-14 in the organism when it stopped breathing, although in reality far less than 14 grams.) at what point would our Beta test equipment be unable to do its job due to the lack of sufficient emissions assuming the spectrographic analysis would always be able to do its job.
Further reading suggests the point I am looking for is a the point where Background Radiation is too great for the emissions from c-14 to be distinquished. Does anyone know where that point is in terms of number of c-14 atoms or is it just an arbitary point that varies with other variables like equaipment sensitivity, etc.? Also does anyone know the maximum possible amount of c-14 or what the 100% value of c-14 is? ...IMHO (Talk) 23:37, 13 June 2006 (UTC)[reply]
Carbon-14 vs.Nitrogen-14(number of atoms)
Years
Carbon-14
Nitrogen-14
0
602,214,150,000,000,000,000,000
0
5,730
301,107,075,000,000,000,000,000
301,107,075,000,000,000,000,000
11,460
150,553,537,500,000,000,000,000
451,660,612,500,000,000,000,000
17,190
75,276,768,750,000,000,000,000
526,937,381,250,000,000,000,000
22,920
37,638,384,375,000,000,000,000
564,575,765,625,000,000,000,000
28,650
18,819,192,187,500,000,000,000
583,394,957,812,500,000,000,000
34,380
9,409,596,093,750,000,000,000
592,804,553,906,250,000,000,000
40,110
4,704,798,046,875,000,000,000
597,509,351,953,125,000,000,000
45,840
2,352,399,023,437,500,000,000
599,861,750,976,563,000,000,000
51,570
1,176,199,511,718,750,000,000
601,037,950,488,281,000,000,000
57,300
588,099,755,859,375,000,000
601,626,050,244,141,000,000,000
63,030
294,049,877,929,688,000,000
601,920,100,122,070,000,000,000
68,760
147,024,938,964,844,000,000
602,067,125,061,035,000,000,000
74,490
73,512,469,482,421,900,000
602,140,637,530,518,000,000,000
80,220
36,756,234,741,210,900,000
602,177,393,765,259,000,000,000
85,950
18,378,117,370,605,500,000
602,195,771,882,629,000,000,000
91,680
9,189,058,685,302,730,000
602,204,960,941,315,000,000,000
97,410
4,594,529,342,651,370,000
602,209,555,470,657,000,000,000
103,140
2,297,264,671,325,680,000
602,211,852,735,329,000,000,000
108,870
1,148,632,335,662,840,000
602,213,001,367,664,000,000,000
114,600
574,316,167,831,421,000
602,213,575,683,832,000,000,000
120,330
287,158,083,915,710,000
602,213,862,841,916,000,000,000
126,060
143,579,041,957,855,000
602,214,006,420,958,000,000,000
131,790
71,789,520,978,927,600
602,214,078,210,479,000,000,000
137,520
35,894,760,489,463,800
602,214,114,105,240,000,000,000
143,250
17,947,380,244,731,900
602,214,132,052,620,000,000,000
148,980
8,973,690,122,365,950
602,214,141,026,310,000,000,000
154,710
4,486,845,061,182,980
602,214,145,513,155,000,000,000
160,440
2,243,422,530,591,490
602,214,147,756,577,000,000,000
166,170
1,121,711,265,295,740
602,214,148,878,289,000,000,000
171,900
560,855,632,647,872
602,214,149,439,144,000,000,000
177,630
280,427,816,323,936
602,214,149,719,572,000,000,000
183,360
140,213,908,161,968
602,214,149,859,786,000,000,000
189,090
70,106,954,080,984
602,214,149,929,893,000,000,000
194,820
35,053,477,040,492
602,214,149,964,947,000,000,000
200,550
17,526,738,520,246
602,214,149,982,473,000,000,000
206,280
8,763,369,260,123
602,214,149,991,237,000,000,000
212,010
4,381,684,630,061
602,214,149,995,618,000,000,000
217,740
2,190,842,315,030
602,214,149,997,809,000,000,000
223,470
1,095,421,157,515
602,214,149,998,905,000,000,000
229,200
547,710,578,757
602,214,149,999,452,000,000,000
234,930
273,855,289,378
602,214,149,999,726,000,000,000
240,660
136,927,644,689
602,214,149,999,863,000,000,000
246,390
68,463,822,344
602,214,149,999,932,000,000,000
252,120
34,231,911,172
602,214,149,999,966,000,000,000
257,850
17,115,955,586
602,214,149,999,983,000,000,000
263,580
8,557,977,793
602,214,149,999,991,000,000,000
269,310
4,278,988,896
602,214,149,999,996,000,000,000
275,040
2,139,494,448
602,214,149,999,998,000,000,000
280,770
1,069,747,224
602,214,149,999,999,000,000,000
286,500
534,873,612
602,214,149,999,999,000,000,000
292,230
267,436,806
602,214,150,000,000,000,000,000
297,960
133,718,403
602,214,150,000,000,000,000,000
303,690
66,859,201
602,214,150,000,000,000,000,000
309,420
33,429,600
602,214,150,000,000,000,000,000
315,150
16,714,800
602,214,150,000,000,000,000,000
320,880
8,357,400
602,214,150,000,000,000,000,000
326,610
4,178,700
602,214,150,000,000,000,000,000
332,340
2,089,350
602,214,150,000,000,000,000,000
338,070
1,044,675
602,214,150,000,000,000,000,000
343,800
522,337
602,214,150,000,000,000,000,000
349,530
261,168
602,214,150,000,000,000,000,000
355,260
130,584
602,214,150,000,000,000,000,000
360,990
65,292
602,214,150,000,000,000,000,000
366,720
32,646
602,214,150,000,000,000,000,000
372,450
16,323
602,214,150,000,000,000,000,000
378,180
8,161
602,214,150,000,000,000,000,000
383,910
4,080
602,214,150,000,000,000,000,000
389,640
2,040
602,214,150,000,000,000,000,000
395,370
1,020
602,214,150,000,000,000,000,000
401,100
510
602,214,150,000,000,000,000,000
406,830
255
602,214,150,000,000,000,000,000
412,560
127
602,214,150,000,000,000,000,000
418,290
63
602,214,150,000,000,000,000,000
424,020
31
602,214,150,000,000,000,000,000
429,750
15
602,214,150,000,000,000,000,000
435,480
7
602,214,150,000,000,000,000,000
441,210
3
602,214,150,000,000,000,000,000
446,940
1
602,214,150,000,000,000,000,000
452,670
0
602,214,150,000,000,000,000,000
bios viruses
hi my old laptop has not worked for a month for so now
its a bit expencive to get fiexd, so i lent it to a friend who sead they would look at it. they say it has a bios virus, i was wondering what a bios virus is?
That would be a Computer virus which has somehow affected your computer's Basic Input Output System. The BIOS is a small program that tells your computer how to startup. Although BIOS viruses are said to be rare, once your BIOS has been corrupted, there is not much that can be done. The term itself is a little misleading, as the virus does not "live" in the BIOS and can not replicate itself from there. But if your computer has been affected, the terminology is the least of your worries. --LarryMac20:33, 13 June 2006 (UTC)[reply]
I am taking my final A-level physics paper in a couple of days and one section of the exam focuses on how well we can use our knowledge of physics drawn together for situations that aren't explicitly taught in our course. To get to the point, one of the questions from a previous paper asks us to explain how it is possible for a shoe to be shiny and black, which conflict from my understanding since black absorbs light, but for something to be shiny light must be reflected. I guessed that some white light must be reflected at the parts that appear shiny, but I had trouble putting it into words and explaining it properly. I also couldn't find any articles that were relavant to this.
For my second question, and I apologize if it is answered in the Proportionality_(mathematics) article, would a be proportional to b if and c was non-zero? Or are two quantities only proportional if one equals 0 when the other is also 0? Thanks very much, Krackpipe20:17, 13 June 2006 (UTC)[reply]
Just to answer the second question, it's only actually proportional if c=0. But for c non-zero you can still talk about it being "linearly related". Arbitrary username20:24, 13 June 2006 (UTC)[reply]
The short answer to the first question is, there is still a lot of light reflected from a black object. It is just a lot less than from the objects around it. Walt20:28, 13 June 2006 (UTC)[reply]
(edit conflict) Re the first question, there is a little specular reflection, but what doesn't get reflected specularly is almost all absorbed. If instead there was a little diffuse reflection and the rest was absorbed, then you'd probably describe the color as dark gray (at least if the reflectivity was reasonably wavelength-independent within the visible spectrum). Arbitrary username20:30, 13 June 2006 (UTC)[reply]
Indeed. A shiny black surface consists of a shiny surface, which specularly reflects some of the light, over a black material that absorbs (most of) the rest. These don't have to be different materials, but often they are. To be shiny, a material has to have a smooth surface and a high index of refraction (for details, see Fresnel reflection). In case of a black shoe, the shiny layer presumably consists mostly of shoe polish, whereas in the case of, say, obsidian, the glass both reflects light that hits its surface and rapidly absorbs any light that doesn't get reflected. —Ilmari Karonen (talk) 22:52, 13 June 2006 (UTC)[reply]
Formula for heptyl rocket fuel
A few weeks ago heptyl rocket fuel was in the news. What is the chemical structure of heptyl?
Adjusting Depth Of Feild On Regular Digital Camera
Is it possible to achieve depth of field effects (where parts are out of focus) without an SLR? They're just too big and inconvenient, not to mention expensive. Are there any digital cameras with a single lens that will allow me to control depth of field by varing the position of the lens? -Username132 (talk) 14:18, 12 June 2006 (UTC)[reply]
It's nasty with the smaller digital cameras, but at least you can try lots of times, and delete the losers. Almost all of these cameras lock their focus and aperature on a 'half click', you then move the camera to the subject and do a full press. For reduced depth of field you need dimmer light so the camera opens up more. You could lock the camera in a shadow, and then take a picture in brighter light, but then you would have to do some post-processing on the computer. --Zeizmic15:06, 12 June 2006 (UTC)[reply]
In other words, it's a function of aperture size; the larger the aperture the greater the depth of field effect, which means that this effect is better with a larger lens such as those found on SLRs.--Shantavira15:21, 12 June 2006 (UTC)[reply]
Any camera which allows you to set the aperture size will be able to vary the Depth of field. However, the smaller size of the imaging device may limit what is possible. Assuming one has a camera with the capability, then taking a series of pictures of the same subject, varying the F stop in each one, should reveal the capabilities of that particular camera. --LarryMac15:44, 12 June 2006 (UTC)[reply]
The perceived effect also depends a lot on the focus distance: the easiest way to get nice blurry backgrouds with a compact is simply to switch to macro mode and get real close to the target. That way you maximize the ratio of background and foreground distance.
Also, digicams can do absurdly short exposures. In the fully automatic mode ("P" or "auto") the camera may try to balance the aperture and the exposure time, but if you want you can switch to aperture priority mode ("A") and shoot at the maximum aperture (i.e. smallest f number) in pretty much any lighting just fine. —Ilmari Karonen (talk) 15:53, 12 June 2006 (UTC)[reply]
Simply, to reduce field of focus: use maximum aperture - if that is what you can set; or: use fastest speed - if that is what you can set. The latter forces the camera to open the lens as much as possible. The technique you describe of "moving the lens" I presume to mean "zooming" i.e. altering the focal lenght of the lens system. If that is your only option, then using the maximum "zoom in" for an object a fixed distance from you will reduce the depth of field. --Seejyb22:01, 12 June 2006 (UTC)[reply]
Zooming in might be counterproductive, though. My digital camera, for example, has an aperture range of f/2.6 to f/8.0 when zoomed all the way out, but only f/5.6 to f/8.0 when zoomed all the way in. --Serie00:11, 13 June 2006 (UTC)[reply]
Also, many digital cameras won't focus very close, even in macro mode, unless zoomed all the way out. That, combined with the aperture range issue, means it's often better to zoom out and get close to the subject than to zoom in and shoot from further away. Of course, that only works if the subject is a) inanimate, b) slow, or c) tame. —Ilmari Karonen (talk) 11:50, 13 June 2006 (UTC)[reply]
It's very, very hard to get significant depth of field effects in compact digital cameras, even if they have manual aperture controls (and some of the better models do). As our depth of field article explains, the depth of field is larger with a smaller film (or sensor). Compact digitals have tiny sensors compared to digital SLRs, let alone 35mm film. Maybe you could buy a second-hand film SLR for the purpose if you are specifically setting out to take advantage of this effect? --Robert Merkel
Adding onto what has already been said, if you can't directly change your aperture or shutter speed settings, your camera may have a "Portrait" mode or similar mode where the camera attempts to limit the depth of field. Your camera manual should explain more on this.--Tachikoma04:22, 13 June 2006 (UTC)[reply]
See here, basically get as close to your subject as possible, use as long focal length as possible and use the largest aperature. Can be done, but much easier with a SLR. Stefan09:19, 13 June 2006 (UTC)[reply]
Question
There is a compact camera on ebay with Focal Length 7.7-23.1mm f/2.8-4.9 (35mm film equivalent: 37-111mm) - looking at the depth of field article, I will have a depth of field limited to only close up subjects. Look at the example photos my f/ numbers are restricted between 2.8-4.9 which means I can take the second daffodil picture and the cat picture only. I clearly have misunderstood. Explain how, please?
Going for a compact camera will not allow you to achieve much when it comes to Depth of field. If you really want to be able to go artistic but don't want an slr, there are many cameras out there with an APS Size sensor many manual controls (thats what you want) and good lens quality without interchangeable lenses. I leave you with a quote from the wiki to explain
...this means that smaller cameras have deeper depth of field than larger cameras. This can be an advantage or disadvantage, depending on the desired effect. A large format camera is better for photographs where the foreground and background are blurred (cf. bokeh), while a small camera maximizes depth of field, so that objects behind or in front of the focus plane are still in good focus. This difference between formats goes away if the cameras are compared with equal aperture diameters rather than equal f-numbers; but the smaller camera can not usually use a large aperture diameter, so can not achieve a very limited depth of field.
I remember hearing somewhere that people were researching a type of craft that spun rapidly lifting it into the air. My question is has anyone ever heard of this or am I just crazy? If you have heard of it is there any kind of link you could give me to further my quest?
Thermoplasma and Mycoplasma both lack cell walls. "L-forms" (which have no cell walls) of other bacteria which usually have cell walls, can be induced by various culture media and antibiotics.
Dunno, but you should look at the literature to see what media have been used. As Miborovsky points out, temperture will be key.
Dunno, but Pseudomonas is noted for its motility characteristics, including swimming, swarming, and twitching, which result in its tendency to form films. It might also have something to do with oxygen tension at the surface vs. the rest of the medium. - Nunh-huh06:18, 14 June 2006 (UTC)[reply]
Television,Broadband&Media
What is a longform of "RiTV" which is an interactive television,broadband & media solution ?
Is there any special video codec of RiTV ?
Thanks!
The Mac Davis] ⌇☢ ญƛ. 02:52, 7 June 2006 (UTC)
The Mac Davis] ⌇☢ ญƛ. 22:36, 7 June 2006 (UTC)
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