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March 7

Reactions with super-heavy elements?

Hi there, just wondering if any reactions have been done with super-heavy elements that have long enough half-lives. (I'm guessing this would be done to see if they have similar properties to other elements in their respective groups.) If so, what reactions have been done and what been the outcomes? I'm also wondering if there is good reason for trying to create 'new' elements e.g. Element 119, i.e. are scientists looking for anything in particular, or is it just done in case these elements can be used in the future for something? If that is the case, what are the expected applications of these super-heavy elements? I've had a good search of Wikipedia but can't really find anything to help so any answers or thoughts would be much appreciated. Kind regards, Raywil (talk) 03:17, 7 March 2011 (UTC)

Island of stability. ~AH1^(TCU) 03:21, 7 March 2011 (UTC)

Many thanks for the reply: I know about the island of stability but didn't realise that the article described the potential applications of elements that make up the island. Now for the rest of my questions... Raywil (talk) 04:02, 7 March 2011 (UTC)

Thought I'd give this a sort of "bump" to see if anyone else has answers. Thanks. Raywil (talk) 22:49, 7 March 2011 (UTC)

I don't think practical (chemical) applications are likely, any time soon, since the cost of such lab-made chemical elements is likely to be prohibitively high. StuRat (talk) 17:48, 8 March 2011 (UTC)

Also it's too early to answer those questions. Till we make macroscopic amounts of those elements it's pretty hard to figure out applications for them. As for why they are making them, it's mainly curiosity, but also, maybe there will be some awesome application. No way to know till you (they) try. Ariel. (talk) 21:33, 8 March 2011 (UTC)

Many thanks for your thoughts; much appreciated. Raywil (talk) 19:15, 9 March 2011 (UTC)

The highest temperature

Is there any point such as kelvin zero for highest temperature?a. mohammadzade iran--78.38.28.3 (talk) 04:10, 7 March 2011 (UTC)

No.--Srleffler (talk) 05:26, 7 March 2011 (UTC)

You could consider -0 (negative zero, or zero approached from the left) to be the highest temperature, which like absolute zero, is unachievable. See negative temperature. Although depending on the system, positive infinity could be the actual maximum (and unachievable) temperature. Someguy1221 (talk) 07:18, 7 March 2011 (UTC)

A rather poor article but perhaps Absolute hot may be of interest. Nil Einne (talk) 10:24, 7 March 2011 (UTC)

By the current theories, temperature is the measure of the average speed of the particles. An approximate formula is $T={\frac {v_{avg}^{2}\pi M}{8}}$. (M is molecular mass). By this definition, you can have absolute zero with molecules of avg speed zero. Now, your maximum speed is the speed of light, and you can maximize temperature by plugging it in, but, this is the maximum temperature for a molecule with given molecular mass. Take a bigger molecule, and your temperature increases. So there's no maximum temperature. ManishEarth^{Talk • Stalk} 12:16, 7 March 2011 (UTC)

It's almost never a good idea to 'plug in' the speed of light if you're not very sure of the assumptions underlying a formula. Temperature is a measure of the average thermal energy per particle, which for a gas under reasonable conditions is roughly proportional to the average kinetic energy per particle. In classical mechanics, the kinetic energy of an object is proportional to its mass, and increases with the square of its velocity; that's were the v² term comes from in the equation you've used. This falls apart when you get to temperatures high enough that special relativity rears its ugly head. As you put more kinetic energy into a particle in order to increase its velocity, there will be an associated increase in its relativistic mass. The effect is negligible at any reasonable velocities and temperatures, but the particle's mass (and its kinetic energy) will asymptotically approach infinity as you bring its velocity closer and closer to the speed of light. Any hypothetical molecule travelling (impossibly) at the speed of light would have an infinite kinetic energy and therefore an infinite temperature. TenOfAllTrades(talk) 13:59, 7 March 2011 (UTC)

Indeed not only that but the aforementioned equation is missing a Boltzmann constant, and if true, would imply and absolute hot, as there exists only a finite mass; but alas, it is all irrelevant.— Preceding unsigned comment added by 129.67.37.227 (talk • contribs) 23:50, 7 March 2011 (UTC)

More importantly, the basic statement is wrong. Temperature is not a measurement of the average speed of the particles.

This is something that needs to be emphasized every time it comes up. The direct relationship between temperature and kinetic energy works only in one very simple, idealized case — an ideal gas made of individual particles (at normal temperatures, this means a monatomic element like helium or neon). In all other cases, the relationship breaks.

What temperature really is is a statistical concept. It's not about kinetic energy per se. --Trovatore (talk) 00:03, 8 March 2011 (UTC)

Temperature, despite the fact that we use it every day, really IS a very hard concept to get at. Personally, I find the explanation afforded by the Zeroth law of thermodynamics to be most satisfying; the general concept that temperature is defined in terms of thermal energy transfer; two bodies are empirically defined as the same temperature insofar as they are in thermal equilibrium; the temperature at any equilibrium can then be defined as dH/dS, (or dq/dS if you prefer) the relationship between heat and entropy at a particular thermal state. --Jayron32 06:24, 8 March 2011 (UTC)

See a previous discussion at: Wikipedia:Reference desk/Archives/Science/2009 July 14#The Limit of heat?. Staecker (talk) 13:22, 7 March 2011 (UTC)

You might say "absolute zero". Minus absolute zero, that is! See negative temperature. But that is a specialized usage of the idea. Wnt (talk) 05:50, 8 March 2011 (UTC)

exploding of supernova

how dos explode a supernova and how will be the fragment of its inner matter i couldn't find perfect explanation of this in encyclopedia. akbar mohammad zade iran march 2011--78.38.28.3 (talk) 04:18, 7 March2011 (UTC)

In existing nebula if the star matter be powder and dust or it remain molten?a. mohammadzade--78.38.28.3 (talk) 04:23, 7 March 2011 (UTC)

A supernova explodes when the core of a star collapses, causing extremely high pressures. These pressures cause the star to "bounce" back, blowing it to bits.

Stars are made mostly of hydrogen and helium, and the core of a star gone supernova has some carbon, oxygen, silicon, magnesium, and iron. Many of these are gases at most temperatures and pressures, and in the vacuum of outer space, most of them will be gases. Does this answer your question? --T H F S W (T · C · E) 04:53, 7 March 2011 (UTC)

thanks i think that might have gathered pieces ,then this gathered pieces will be molten, because of its condensed early condition and first density what have been observed in crab nebula .if that be gas then in which density?and how can it have 11000 degrees temperature?a. mohammadzade --78.38.28.3 (talk) 05:23, 7 March 2011 (UTC)

The density is very low - the only reason we're able to observe it, is because the nebula is so big. The temperature of the nebule is a measure of the average thermal energy per particle. (molecule, atome, etc.) Since the nebula is so sparse, an observer located inside the nebula would not notice a difference in temperature compared to outside the nebula. Plasmic Physics (talk) 10:06, 7 March 2011 (UTC)

To help to explain this, think of putting your hand into an oven at full temperature. If you touch something dense inside, like a pot, your hand would burn instantly. If you only touch the less dense air, then your hand heats up more slowly, and you might be able to take a few seconds without getting burnt. Now imagine that the air is a trillion times less dense, and your had wouldn't get hot at all (except for radiation from the sides of the oven, but we'll ignore that). StuRat (talk) 17:38, 8 March 2011 (UTC)

Petrochemical Distallation

Is it possible to sort a mixture of waste plastics using fractional distallation under an anoxic atmosphere? Plasmic Physics (talk) 09:56, 7 March 2011 (UTC)

In general, no, because plastics tend to decompose when heated, producing hydrocarbons and other products. You may get useful fuel out, but not gaseous plastic that you can then condense and reuse.[1][2][3][4] --Colapeninsula (talk) 11:51, 7 March 2011 (UTC)

Would increasing the pressure to several times atmospheric pressure have any effect on the rate of pyrolysis? Plasmic Physics (talk) 22:21, 7 March 2011 (UTC)

Where are the batteries on this bike?

Where does the energy come from for this? http://www.bbc.co.uk/news/uk-england-10858682 I cannot see any batteries. Can anyone explain what this is supposed to be doing? Thanks. 92.29.124.221 (talk) 12:42, 7 March 2011 (UTC)

They're in the pedal. You can see them on the video - they're the two objects on either side of the pedal, wrapped in a black shrinkwrap. The pedal has had a motor and batteries added. Assuming the user resists the attempt of the pedal to turn, the pedal and foot combined will drive the crank. --Tagishsimon (talk) 12:48, 7 March 2011 (UTC)

Thanks. I expect batteries that small will last about two minutes, so they are practically useless. 92.29.124.221 (talk) 12:52, 7 March 2011 (UTC)

They probably didn't developed the bike to be run all the time with these tiny batteries, but only to give you an added push. 80.58.205.34 (talk) 16:36, 7 March 2011 (UTC)

Excavations at ancient battle sites

What are the odds of finding the helmets, shields etc and human remains at the sites of ancient battles (such as Thermopylae)? Also I'm curious what would be the depth of digging to reach the weaponry and human remains in case of Thermopylae? —Preceding unsigned comment added by 89.76.224.253 (talk) 14:42, 7 March 2011 (UTC)

Just to note here that the helmets, shields and such would have been recycled by the victors and so you wouldn't have much chance of finding them. In Repton, UK, a number of male skeletons were found near the parish church in the last century, and it is speculated that these were victims of a Dark Age skirmish.Repton Church --TammyMoet (talk) 15:21, 7 March 2011 (UTC)

Just to be clear, what you're referring to is looting and/or grave robbery (depending on the circumstances) and is considered unethical and/or illegal depending on the jurisdiction. Unfortunately, the illegal antiquities trade has been going on since the "antiquities" were brand new, meaning that many, if not most, archaeological sites have been pretty seriously plundered of what non-archaeologists would consider valuable (cool stuff like weapons are in almost a high demand as the shiny stuff). I don't know the depth of the soil at Thermopylae, but our article at least indicates that the water levels have dropped since the battle took place, so at least they won't be underwater. Matt Deres (talk) 17:51, 7 March 2011 (UTC)

I think many other people have thought about this in the past and the likelihood of finding any remains now is, well, slight, and that's being optimistic. 86.4.187.76 (talk) 20:42, 7 March 2011 (UTC)

Technically, it's not unethical to dig up ancient artifacts and treasure; it's only unethical for poor people to profit from them, rather than license-holders and established institutions. Wnt (talk) 00:58, 8 March 2011 (UTC)

I'm sorry, but that's just incorrect; the problem has nothing to do with who profits, it's with what happens to both the artifacts and the state of the site. The people who raid such sites just dig holes all over, grab whatever they figure they can sell, and make off with whatever they can carry away, paying no attention to recording provenience of the pieces, horribly contaminating the site and artifacts to render most dating techniques unreliable, and literally destroying whatever gets in their way of making a buck. The pots and jewellery and neat looking human remains get sold off and lost from the archaeological record, to the detriment of everyone. Matt Deres (talk) 04:20, 8 March 2011 (UTC)

Just like to point out, the person asking didn't say they were going to dig up battlefields, they just asked a hypothetical question about what might be found at old battlefields. There's no need to get on your soapboxes, people. Pretend he/she is an archaeologist. --Colapeninsula (talk) 10:35, 8 March 2011 (UTC)

No soap-boxing intended. The OP's specifications on looking for the "cool" stuff are highly indicative of someone who isn't planning a proper dig. Not that I think they're actually planning on flying over with a pickaxe to start treasure hunting, but I wanted them to at least be aware that it's unethical (and usually illegal) to do so. Matt Deres (talk) 14:13, 9 March 2011 (UTC)

I wonder; if helmets, armor, shields, and weapons were there, if they would be totally corroded by now. I believe the Battle of Thermopylae occurred during the Iron Age, so it may have all rusted away, by now. Perhaps some high ranking soldiers might have had some gold accents on their items, but then those would have been even more likely to have been stolen. StuRat (talk) 17:26, 8 March 2011 (UTC)

Iron and bronze can indeed rust away, but that doesn't mean that nothing can be gained from it. In a proper excavation, even artifacts which have nominally been rusted away can still provide information by way of the rusty stains they leave in the soil. Estimates of counts, the metals used, the size and kinds of implements left behind, and more, can all be inferred from examining the soil closely. That could then be compared against other sites to provide evidence of changes in material culture, advance in metallurgy , and trade routes. Provided that someone hasn't dug the entire site up looking for a cool skull to stick on their mantle. Matt Deres (talk) 14:23, 9 March 2011 (UTC)

Budgerigar 'charming'?

How/why does this work? I think that this effect, or something like it has been discussed on here before in relation to other bird species. The guy in the video is a real veterinarian, who also has some 'mystic' beliefs which he draws on, alongside the traditional medicine (AFAIK) - but I'm personally sceptical that this is actually a 'mystic' phenomenon. Something is clearly happening here though, to render the budgie still and docile. Any ideas? --95.148.106.17 (talk) 15:10, 7 March 2011 (UTC)

He also does the same thing with a lovebird here while trimming its beak. --95.148.106.17 (talk) 15:16, 7 March 2011 (UTC)

Interesting.. Wonder if it is something similar to Chicken hypnotism.. That's what really annoys me about stuff like this, there's obviously something very cool and interesting going on and then he has to go and say that he's seen John of God do it to people who then have surgery standing up without anaesthetic, what a crock. Vespine (talk) 00:37, 8 March 2011 (UTC)

This one is even more extraordinary. It certainly seems woo-ish from the way he describes it - but he's obviously doing *something* that works. A parrot flipped on its back would normally bite (hard) and struggle to escape. --Kurt Shaped Box (talk) 02:23, 8 March 2011 (UTC)

Parrots peacefully scattered around in the landscape on their the backs (drunk) isn't an unusual sight in Queensland so they seem to have a "I'll just have a bit of a lie down for a while" mode. Sean.hoyland - talk 17:41, 8 March 2011 (UTC)

I can think of two triggers that might calm a bird:

1) The "time to sleep" trigger might occur when the light level goes down, such as covering the eyes (or entire cage) of a diurnal bird. This doesn't seem to have been used, in this case.

2) The "preening" trigger might occur in social birds, where they are preened by others. This might apply here, as stroking of the feathers may set this off. Thus, those birds which calmed down, when being preened by others, might have been more likely to survive and pass on their genes than those that became agitated. Do budgies preen each other ? StuRat (talk) 17:10, 8 March 2011 (UTC)

I'm actually not very impressed with this video. The bird tries to get away again and again and again, and he has to hold its wing awkwardly at one point to contain it. It's not obvious to me that a bird has to struggle to escape continuously, as opposed to once a minute as this one does, especially not when it's an old arthritic bird that has lived most of its life in a cage. It is apparent, of course, that the feel of a hand around its wings and/or being upside down has some effect, but this is scarcely magical. It reminds me of something from mouse work - supposedly, holding the mouse by the scruff of the neck keeps it from trying to get away when injected, but honestly, I suspect that any pain equivalent to such a pinch makes the mouse briefly play possum (or otherwise stop moving), and the specific technique is unimportant. Wnt (talk) 22:53, 8 March 2011 (UTC)

I believe the grabbing by the scruff of the neck is a method used by some mammal moms to carry their young with their mouth. I've seen it used on kittens. I believe this is another of those automatic signals that causes them to go limp, as kittens that struggled might have been left behind and died, while those that went limp survived to pass on their genes. However, I don't think this applies to any birds, since they don't carry their young in this manner. StuRat (talk) 10:46, 9 March 2011 (UTC)

I seem to recall reading somewhere (about 542 years ago?) that signficant pressure applied to the skin and soft tissues on the scruff of the neck of an animal induces the release of a bolus of endorphins and other, similar compounds into the bloodstream of the animal, generating a calming effect. If you would like me to find a recent reference, hit me up on my Talk page. CAVEAT: I've tried this with my wife when she becomes enraged with me, but it doesn't seem to work very well :-O

Best regards:

Cliff L. Knickerbocker, MS (talk) 13:35, 12 March 2011 (UTC)

Acrylamide in commercial breads

I buy 100% Whole Wheat breads from supermarkets, and try to purchase as few sugars as I can, but I'm not sure if anything can be done about acrylamide. Is making my own bread by boiling the only way to avoid the substance? (And no, I don't believe epidemiological studies.) Imagine Reason (talk) 19:08, 7 March 2011 (UTC)

How does one boil a bread? Dauto (talk) 19:55, 7 March 2011 (UTC

A bread what? I think we usually call it a loaf or a roll (or bap) 86.4.187.76 (talk) 20:40, 7 March 2011 (UTC)

Bagels are boiled. Ariel. (talk) 20:49, 7 March 2011 (UTC)

The idea with boiling is the temperature, not the actual boiling. All you need to do is cook the bread till it's cooked, but not browned. So avoid a heavy crust, and take it out when it's still pale. You should also make smaller bread, so the inside is fully cooked without having to heat the outside very much. If you are really worried, then cut off the crust. The inside of bread doesn't really go much above boiling (if it did it would dry out and become crust). Ariel. (talk) 20:49, 7 March 2011 (UTC)

So maybe picky children (who want their PB&J with the crusts cut off) were right all along. StuRat (talk) 18:30, 8 March 2011 (UTC)

I've noticed various brands of crustless bread in the supermarket - some new process, I think. 81.131.26.97 (talk) 04:44, 8 March 2011 (UTC)

I assumed they just cut the crusts off and used it for other things, like bread crumbs or animal feed. StuRat (talk) 18:30, 8 March 2011 (UTC)

I tried two brands: one seemed to have the crusts cut off as you say, the other had a thin layer of dense but pale bread instead of crust. 213.122.24.251 (talk) 23:44, 8 March 2011 (UTC)

I investigated this myself in the past. There is such a thing as steamed bread, and there are steamed bread rolls which are a Chinese thing.

I've never seen either of them for sale anywhere, but if steamed bread was done at high pressure it may be no better than ordinary bread. Steamed bread redirects to Chinese steamed rolls. Frying them as the article shows would introduce acrylamide into them.

Wholemeal bread has more acrylamide in it than white bread. Soda-bread has less acrylamide in it. Since acrylamide is associated with browning (by heat, not enzymic browning) then pale un-browned bread such as some pitta bread is likely to be safer. Any manufacturer who can supply acrylamide-free bread will make a fortune. By the way, crispbreads have very very large amounts of acrylamide in them. Cooking food in a microwave also results in acrylamide.

I'd be very interested to learn of any practical recipies for home-steamed bread or even rolls. 92.29.127.85 (talk) 20:53, 7 March 2011 (UTC)

Boston brown bread or hobo bread. Rmhermen (talk) 00:19, 8 March 2011 (UTC)

Thanks. The three and a half hour cooking time is something to think about, although on the other hand my bread machine takes longer than that. 92.15.0.66 (talk) 16:25, 8 March 2011 (UTC)

As an aside, the acrylamide scare is the unwarrented-panic-du-jour. If it is present in baked starchy goods, then it has been there for thousands of years, or roughly as long as humans have been baking bread. Whether or not, and at what levels, it is carcinogenic isn't nearly as important as the measurable health outcomes of consuming acrylamides on baked goods such as breads. In other words, does the eating of bread have a measurable impact on your likelyhood of dying of cancer, solely from the acrylamide content? How many cancer cases per year can be traced to acrylamide consumption from ordinary baked goods? I think you'll find these numbers to be vanishingling small, close to zero. On the list of risks to your own life, in terms of both length and quality, eating whole grain bread falls somewhere near the bottom. --Jayron32 04:58, 8 March 2011 (UTC)

Our physiology has evolved for many millions of years since the beginning of life. We only started cooking bread very recently. Evolution is not very sensitive to early deaths after you've had kids. 92.15.0.66 (talk) 16:23, 8 March 2011 (UTC)

We've been drinking alcohol for a long time, too. Ok, so it's much safer than beer, but we've been ignorant for most of our history. 66.108.223.179 (talk) 14:31, 8 March 2011 (UTC)

The Romans did not live very long because they were unwittingly poisoning themselves from the lead in their pipes and drinking vessels. I think they may also have added it to wine, not sure. They did not detect it was poisonous because everyone was consuming it. Before acrylamide was found in food, it was classified as a probable carcinogen. Now that its been discovered in food, then all of a sudden it becomes harmless? Can I remind you that a large proportion of people (do not recall exact proportion) die of cancer. So, probable carcinogen in food, and lots of people dying of cancer - surprised? 92.15.0.66 (talk) 16:12, 8 March 2011 (UTC)

Yes, it could be a problem, but we need more info to know if it really is a problem. That is, just how carcinogenic is it ? It would be impossible to avoid all carcinogens entirely, as you likely inhale several with every breath. So, then, since we can't avoid all carcinogens, the issue becomes avoiding the worst ones. StuRat (talk) 16:53, 8 March 2011 (UTC)

"Just how carcinogenic is it" you ask. "The European Chemical Agency added acrylamide to the list of substances of very high concern in March 2010.[5]". 92.15.20.212 (talk) 17:50, 8 March 2011 (UTC)

Your footnote didn't copy, do you have a link ? StuRat (talk) 18:26, 8 March 2011 (UTC)

Go to the Acrylamide article and find footnote number 5. 92.15.20.212 (talk) 20:56, 8 March 2011 (UTC)

OK, following the link I found a study that showed no evidence of it causing cancer in humans, but they did find it caused cancer in rats when given at the rate of 3 mg per kg of body mass per day. So, then, the question is whether the amount in bread comes close to that. I didn't find info for bread, but this site lists the level as 1.57 mg/kg for French fries ("chips" in British English): [5]. However, this is per kg of food, not per kg of body weight. So, you'd need to eat twice your weight in fries each day to have the same exposure level as rats had in the study. If bread has comparable levels, then the results should be similar. StuRat (talk) 22:41, 8 March 2011 (UTC)

There is "no evidence of it causing cancer in humans" because no one would do such an unethical experiment. The mice would have been fed acrylamide for a short time (they only live a year or two, maybe less) which is not the same as eating it over more than fifthy years for a human. The mice can show it is carcinogenic to mice and by inference mammals, but the dose in relation to bodyweight cannot be extrapolated due to the different time-scales inolved. 92.24.191.116 (talk) 23:46, 8 March 2011 (UTC)

They had results of 2 studies from chemical factory workers who had been exposed, but they showed no signs of any problems. Mice have much faster metabolic rates, which should cause them to show signs of cancer far quicker than in people. StuRat (talk) 04:07, 9 March 2011 (UTC)

I think you've misunderstood that. The study that resulted in acrylamide in food being discovered was a study of the workers in a factory that dealt with a lot of acrylamide. The big surprise was that the control group (people who did not work at the factory) had just as much acrylamide in them as the factory workers. You say "no signs of any problems" yet as said above, lots of people are dying of cancer all the time. The number of everyday things once assumed to be harmless but now believed to be carcinogenic is slowly increasing: for example cigarettes and asbestos. What's next?

Some third-world and other countries have much lower cancer rates than europe and north America. They could be countries were lower amounts of acrylamide are consumed, due to different customary diets. I'd be interested to read any cross-cultural study of acrylamide consumption.

You say "mice have much faster metabolic rates". The only thing that would speed metabolic chemical reactions would be a higher temperature. I don't think the body temperature of mice is much different from humans, particularly when considered on an absolute Kelvin scale. They are not red-hot. I do not think their slightly different temperaure would compensate for their lifespan of a year or two compared to the 50 to 100 years of humans. 92.28.254.54 (talk) 13:24, 10 March 2011 (UTC)

If the cancer develops by mutating a gene when a cell duplicates, then it will happen quicker if the cell duplicates more often, much as happens in animals with faster metabolic rates, like mice. As for there being less cancer in third world nations, that just because they die of war, malnutrition, and infectious diseases before they get old, when cancer is more prevalent. Also, while everyone may be exposed to some, the factory workers were exposed to much more, so should have shown increased mortality, if it really was dangerous at those levels. StuRat (talk) 02:13, 12 March 2011 (UTC)

There's no reason to think, apart from your imagination, that cells divide more frequently in small adult animals than large ones. You make assertions about cancer in the third world, but what evidence is this based on? Your imagination I presume. As far as I recall the factory workers and the control had similar amounts, so the factory was not contributing much. 92.15.6.232 (talk) 11:10, 12 March 2011 (UTC)

If you will tell me which part you doubt, then I will be glad to provide proof:

A) Cancer is more prevalent in the elderly.

B) Third world nations have fewer elderly people, as a percentage of their populations. StuRat (talk) 22:11, 12 March 2011 (UTC)

I wish you'd stop speculating all the time, the repetition is boring. OK, please quote the statistics that lead to your conclusions regarding 3rd. world cancer. Or could they be all in your imagination? 92.24.190.23 (talk) 22:32, 12 March 2011 (UTC)

You failed to tell me which part you doubt ? Is it A or B ? StuRat (talk) 22:39, 12 March 2011 (UTC)

You've avoided quoting any stats as requested. Where are they? Why cannot you provide them? I believe its customery and rather obviously required to compare cancer rates of populations at the same ages. I cannot see how listing a couple of platitudes has any significance. 92.15.8.206 (talk) 22:59, 12 March 2011 (UTC)

OK, then, let's see your proof that cancer rates are lower in 3rd world nations, when adjusted for age. You are the one who made the claim, not me, so you prove it. StuRat (talk) 23:16, 12 March 2011 (UTC)

As I wrote above: You've avoided quoting any stats as requested. Where are they? Why cannot you provide them? Stop trying to change the subject. Boredom, lazyness and the time of night here disincline me to search for that on Google. 92.15.8.206 (talk) 00:13, 13 March 2011 (UTC)

As for mice having a higher rate of cell division: "...metabolic rate and the rate of germ-cell division increase in smaller species...", from [6]. Now, if you are going to accuse me of "speculation", I will do the same to you. You can start by proving that cancer rates and acylimide consumption are lower in third world nations. StuRat (talk) 22:11, 12 March 2011 (UTC)

That paper is mainly about DNA maintenance and DNA evolution. Where does it say that the cells of small animals divide more frequently that those in large animals? Cannot see that anywhere. It says that smaller animals use more oxygen per unit weight, but you'd expect that as they have more surace area per unit volume so they have to burn more energy to maintain their body temperature. In any case, knowing oxygen usage per unit weight is a very very long way from allowing you to calculate the comparative dosage lethality of mice and men. 92.15.8.206 (talk) 22:59, 12 March 2011 (UTC)

Last sentence on page 4090. StuRat (talk) 09:20, 13 March 2011 (UTC)

Note that it could still be highly carcinogenic if you have a bottle of it, and yet be completely insignificant as a food safety risk, if the quantity in bread is small enough. For example, ozone is also a health risk, but the amount in the air we breath is typically low enough that it's not a concern. Only when we have elevated levels, as in cities with a pollution problem, do we need to do something about it. StuRat (talk) 18:35, 8 March 2011 (UTC)

OK, tell us, how little is harmless? How many scientists do you have working at the StuRat Laboratories? You must have a secret underground headquarters like Dr. No in James Bond. 92.15.20.212 (talk) 20:56, 8 March 2011 (UTC)

I don't have time to respond to that...I'm too busy petting a cat with one hand and adjusting the calibration on my missile launcher with the other. StuRat (talk) 23:11, 8 March 2011 (UTC)

It could be that there is no lower safe limit. 92.28.254.54 (talk) 13:24, 10 March 2011 (UTC)

Not really. The only way a single molecule could kill you is if it can reproduce and your immune system had no protection from it. And if one molecule could kill you, then all the people who ever ate burnt bread would drop dead immediately. Even the most dangerous substances almost always have some level of safe dosage. Many poisons are even given as meds (in a safe dosage, of course), like warfarin. StuRat (talk) 02:45, 12 March 2011 (UTC)

"And if one molecule could kill you, then all the people who ever ate burnt bread would drop dead immediately." I understand that cancers take 10 -20 years or more to kill you, so that dosnt make any sense. 92.24.190.23 (talk) 22:41, 12 March 2011 (UTC)

OK, they would drop dead in 10-20 years, then. That still doesn't happen, does it ? StuRat (talk) 23:17, 12 March 2011 (UTC)

How do you know? 92.15.8.206 (talk) 00:03, 13 March 2011 (UTC)

A single molecule of plutonium might be effective. With cancer-causing chemicals, the less chemical the less risk, but a single molecule would still have a small risk. 92.15.6.232 (talk) 11:06, 12 March 2011 (UTC)

A single atom of plutonium wouldn't cause much harm. We are constantly bombarded with radiation from external sources, which would far outweigh that one atom (get a Geiger counter and listen to all the clicks, some time). As for increased risk, when you get to the point where, if everyone on Earth had that level of exposure, not one of them would be likely to show any effect, that's no longer worthy of being considered an "increased risk". It would also cause many deaths to spend scarce resources to eliminate such a minuscule risk, when those resources could be better spent to reduce major risks, which kill millions each year, like smoking. StuRat (talk) 22:17, 12 March 2011 (UTC)

"A single atom of plutonium wouldn't cause much harm." Please give the research papers that provide the evidence for that conclusion - imagination dosnt count. 92.24.190.23 (talk) 22:37, 12 March 2011 (UTC)

The fact that we already have far more than on atom of plutonium is pretty good evidence that any one doesn't do much harm. I don't think you appreciate just how many atoms are in the human body. There are so many that pretty much some of any naturally occurring element is bound to be present. At this site they ran various calcs, and the lowest result was that the average human body would have about 197 atoms of plutonium: [7]. StuRat (talk) 23:42, 12 March 2011 (UTC)

It's not "pretty good evidence" at all. You can make an analogy with asbestos and asbestiosis (sp?) - the risk increases with exposure, but even people who have had a tiny exposure may sometimes get it. 92.15.8.206 (talk) 00:13, 13 March 2011 (UTC)

You know what? Instead of using the whole number scale, I think your reasoning is based on just three "numbers": more, same, less. Or perhaps: lots, average amount, small amount. Fascinating! 92.15.8.206 (talk) 23:06, 12 March 2011 (UTC)

I'm still waiting on proof that anything YOU say is anything beyond wild speculation. StuRat (talk) 23:46, 12 March 2011 (UTC)

Bad loser, lol! 92.15.8.206 (talk) 00:16, 13 March 2011 (UTC)

See also Post hoc ergo propter hoc. AndrewWTaylor (talk) 17:03, 8 March 2011 (UTC)

1. Everybody dies. 2. Death always has a cause. Given that "1" and "2" are self evidently true, IMHO, eating well is a higher priority than going to extreme weirdo paranoid lengths in a probably futile attempt to avoid just one of the practically infinite number of causes of death, particularly if that one happens to be responsible for a vanishingly small proportion of the total number of (human) deaths that have ever occurred. Don't sweat the small stuff, live well, die happy. Roger (talk) 20:17, 11 March 2011 (UTC)

Cleaning bones

Hello. I have some friends who found a coyote skull, broken into four pieces. I was thinking of gluing them together and making a stand for a nice display, but I need it cleaned first, and I need some small, invertebrate help to do it. If I were to put it in a terrarium with either mealworms or crickets for a while, would they get it all nice and clean for me, similar to Dermestidae beetles? --T H F S W (T · C · E) 19:25, 7 March 2011 (UTC)

Amazingly, we have already answered this question on the Reference Desk. See "Help Cleaning a Dog Skull" from May 2008, and "Part Two" of the same. Nimur (talk) 19:32, 7 March 2011 (UTC)

This subject actually comes up a lot - Rabbit, February 2008 (discussion regarding the use of beetles)... Nimur (talk) 19:39, 7 March 2011 (UTC)

Thank you, the above links were helpful, but you still did not answer my question: could I use either mealworms or crickets to clean a skull without damaging it? --T H F S W (T · C · E) 23:20, 7 March 2011 (UTC)

Crickets are omnivores and will apparently eat decaying organic matter. Our mealworm article indicates that they prefer vegetarian fare, so I'm unsure if they will be useful for cleaning your specimen. Previous responses have suggested ants. Nimur (talk) 00:06, 8 March 2011 (UTC)

(Edit Conflict) The articles to which you have already linked both suggest that these insects are primarily herbivores that may eat insect remains if that's all that's available, but do not mention any propensity for eating mammalian organic remains, which seems to me unlikely as it's far from their normal diet. You could simply try them both out - the bones are not going to suffer if either or both don't perform, and you can then try one of the other methods.

You might find some useful information in this post. 87.81.230.195 (talk) 00:07, 8 March 2011 (UTC)

(EC)Hmm, i'm not an expert but I don't think so. crickets and mealworms mostly eat vegetable matter, not decaying meat.. I just use flies and ants. if you have any "yard", buy a cheap bucket, put some holes in it, cover the skull and put a brick on it so a cat or something can't drag it off. Vespine (talk) 00:08, 8 March 2011 (UTC)

Also, if it gets to the stage where you are gluing it back together, I read that bone collectors use regular PVA glue: It's transparent, doesn't damage the bones, bonds well enough and can be washed off if required. Vespine (talk) 00:10, 8 March 2011 (UTC)

Hmmm. Is there anything wrong with your standard housefly/bluebottle maggots? Or how about simply boiling the skull? --Kurt Shaped Box (talk) 00:09, 8 March 2011 (UTC)

Normal house flies would take too long and the place would stink while they did their work (If THFSW is in the northern hemispeher, there also might not be many flying around at this time of year). Boiling the skull would be quick, easy, and thorough, so long as you don't mind a little grossness. FYI, the bones might not fit back together as neatly as you might hope; in living animals, the bones can bend slightly before breaking - if this critter was hit by a car or something, you might end up with a skull that looks warped or deformed. Matt Deres (talk) 01:08, 8 March 2011 (UTC)

I haven't actually seen the skull, some friends of mine found it. i don't know about the condition, it might not even be worth it to try to piece it together again. Just one question: will boiling the skull (sounds barbaric!) get rid of all the flesh and dirt? I think that this skull may have been underground for a long time, so cleaning it may be the only issue. --T H F S W (T · C · E) 05:30, 8 March 2011 (UTC)

In my experience, boiling in water alone will remove dirt but not all the flesh. The flesh does become softer and easier to remove, after many hours of boiling, and the skin and muscles fall off, but other parts remain attached, including cartilage and especially the marrow insides bones. Perhaps boiling it in bleach might be more effective. This would have to be done outside, say on a fire pit or grill, as you don't want your home filled with bleach fumes. Also, avoid using an iron pot, as the bleach would cause it to rust. StuRat (talk) 16:39, 8 March 2011 (UTC)

Sad story: I recently shot an 800 lb boar hog. I couldn't make head cheese from it for boring reasons, so I just put it in the woods for critters to eat the flesh off and I'd have an epic skull with enormous tusks. I screwed an eye hook into the skull and wired it to a tree. When I went back a week later it was gone. The wire had been broken off. :( --Sean 14:45, 8 March 2011 (UTC)

A rotting boar skull covered with maggots and flies sound very Lord of the Flies to me. StuRat (talk) 16:42, 8 March 2011 (UTC)

If only you had the foresight to embed a transmitter with a GPS device in the brains! Comet Tuttle (talk) 18:04, 8 March 2011 (UTC)

Instead of bleach use strong ammonia solution. It will dissolve the fat. Graeme Bartlett (talk) 04:44, 9 March 2011 (UTC)

Pistol shrimp & goby fish

The pistol shrimp often lives in symbiotic life with the goby fish. The pistol shrimp is almost blind, but is able to dig long galleries for their common home; the gobi does nothing, but watchs around with his big eyes, should a predator be approaching, in which case, he gives the alarm and quickly leads the shrimp back home. The shrimp also carries a kind of big and loud gun in one of his claw, that uses to shoot down his preys (the continuous gunshots of these guys even interfere with submarines' sonar system, they says). Apart the obvious side remark that God is apparently an addicted Marvel Comics reader, I wonder: how does the goby avoid being shot by his blind gunslinger friend? Thanks. --pma 22:04, 7 March 2011 (UTC)

I don't have an answer, but this has been sitting here a few hours now and I just have to say: this is the funniest, cutest and quirkiest subject / question I've seen here for a long time. I've probably read past it ten times and it still makes me smile, absolutely love it. :) Vespine (talk) 05:31, 8 March 2011 (UTC)

You mean DC Comics. According to the goby fish article, the symbiotic gobies are known as Watchmen. ;) (Sorry, no real answer yet - though I should say that the shrimp apparently knows how to target its prey) Wnt (talk) 05:47, 8 March 2011 (UTC)

I am shocked to learn that the pistol shrimp is blind, when that other famous slinger of shrimpoluminescence, the mantis shrimp, has the most complex eyes in nature. --Sean 15:18, 8 March 2011 (UTC)

Still no solid responses, so here's my (educated) guess:

• First, all sources I've seen describe the symbioses as being very species-specific, meaning that not just any goby will pair up with any tunnel-building shrimp. Thus, goby species specializing in pistol shrimp pairing probably do have behavioral or morphological ways of avoiding damage.
• One organ system that may be specialized to be resistant to shock is the lateral line. Although other systems are effected as well, this seems to be the most sensitive to shock, so that's the first place I'd look for shock resistance.
• The shockwave produced is directional according to this paper, [8]. So Wnt may be on to something: the shrimp may just keep the cone of damage away from its friend (which is often in actual physical contact with the shrimp, making this easier).

Good question, but there seems to be a dearth of organismal biologists and ecologists here. Let us know if you find out any better answers. SemanticMantis (talk) 17:52, 9 March 2011 (UTC)

Also, I suspect the folks at the fishbase forum might be able to provide more information [9]. SemanticMantis (talk) 15:36, 10 March 2011 (UTC)

doxycycline

What was the antibiotic doxycycline first isolated from? 82.132.248.19 (talk) 23:22, 7 March 2011 (UTC)

Tetracycline_antibiotics#History has some background. While doxycycline is not directly covered, it seems that the tetracyclines in general seem to derive from various strains of Streptomyces bacteria. --Jayron32 23:38, 7 March 2011 (UTC)

Doxycycline is a semi-synthetic antibiotic: it can't be isolated from any organism because it doesn't naturally occur in any. I believe but can't find a reference, that's it's produced by chemically altering the naturally occurring tetracycline (obtained by fermentation with Streptomyces species). You may be interested in the history section of this article- Nunh-huh 03:09, 8 March 2011 (UTC)

FYI ... Having been awake for like 5 minutes, and with virtually zero brain function, I quickly type in the Google search phrase "Invention of Doxycycline" and got the WORST result I've ever SEEN from Google! It was so goofy, I just HAD to post it here. WOW! I think I will now make an attempt to re-boot my brain, and move on to something else. LOL!

Best regards

Cliff L. Knickerbocker, MS (talk) 13:43, 12 March 2011 (UTC)

March 8

Blood erythritol

The polyol erythritol is used as a sugar substitute. Although it is absorbed by the body and passed through the kidneys, it is not metabolized. It does not increase "blood sugar", i.e. blood glucose, it is a sugar alcohol. Even so, it actually has anti-oxidant effect.^[10] Even so, I have to ask: is erythritol also a kind of "blood sugar" -- i.e., does erythritol have any properties that duplicate those of an equal amount of glucose? For example, does it increase blood viscosity, cross-link proteins, or add to strain on the kidneys? Wnt (talk) 01:37, 8 March 2011 (UTC)

Gear trains

actually i have solved a gear train questions which is giving negetive value for number of tooth for one of the gears.what could i interpret from that. should i take absolute value of the number of tooth. 59.93.130.41 (talk) —Preceding undated comment added 06:42, 8 March 2011 (UTC).

We would need more information about what great train question you solved (i.e. what the math was). A negative number could mean you have an error, or perhaps it means the gear is rotating in reverse. It's impossible to say without knowing what formula you used. Ariel. (talk) 11:01, 8 March 2011 (UTC)

Q.

The annulus A in the gear shown in the figure rotates at 400 rpm about the axis of the fixed wheel S which has 80 theeth.The four armed spider is driven at 180 rpm.Determine the number of teeth required on wheel p. —Preceding unsigned comment added by 59.93.134.20 (talk) 12:46, 8 March 2011 (UTC)

I've tweaked the image to make it viewable. --Tagishsimon (talk) 12:49, 8 March 2011 (UTC)

Thanx for tweaking, Here when we solve we get number on tooth on annulus gear(red one ) to be -24.82.to solve remaining problem should we take modulus value of number of gears.Or it is having any significance. —Preceding unsigned comment added by 59.93.134.20 (talk) 13:07, 8 March 2011 (UTC)

Don't you worry about the fractional number of teeth as well? Dauto (talk) 15:26, 8 March 2011 (UTC)

Which gear is S and which one is p ? Gandalf61 (talk) 15:29, 8 March 2011 (UTC)

Typically "S" is the "Sun" (center) and "P" is the "Planet" gear (by analogy to orbits). See Sun and planet gear. In this case, we have one sun, four identical planets, and an outer-ring that the OP is calling the "Annulus" (A). Nimur (talk) 17:15, 8 March 2011 (UTC)

And can you show us your math ? StuRat (talk) 15:58, 8 March 2011 (UTC)

Ariel seems to be right. Epicyclic_gearing#Gear_ratio says that a negative result means rotation in the opposite direction. --Heron (talk) 19:17, 8 March 2011 (UTC)

I might be wrong, but I think the funny result is due to the given velocity ratio being impossibly high. By my reckoning it cannot exceed 2 and the question requires it to be 20/9. SpinningSpark 01:00, 11 March 2011 (UTC)

I'm not sure there's an upper bound on the velocity-ratio between the annulus and the drive-shaft. I think I solved this problem the day it was posted and obtained a reasonable, integer number of gear-teeth for the planet-gears (36). I can dig out my math on a scrap of paper out of my recycle-bin, if anyone's still interested in the worked solution. Nimur (talk) 14:58, 11 March 2011 (UTC)

Don't forget that the normal situation with planet gears is that the annular gear is fixed and the sun gear drives the planets. This question requires the sun to be fixed and the planets driving the annular ring. This is a completely different case. My reasoning is as follows: In one revolution of the spider, if the planets were not free to move independently, the annulus would be carried round one revolution also. However, since the planets are free to move, the annulus will be driven forward from this position (of exactly one revolution) by the turning of the planets. How far forward? - that would be the number of teeth on one planet times the number of times it rolls as it turns one revolution of the sun. If the sun (S) is n times the teeth of planet (P) then the forward position is nP or, with a little thought, equal to S. So the total roatation of the annulus for one rotation of the spider is 1+S/A. Since it is a physical requirement that S<A then 1<Rot_A/Rot_spider<2. A doubling of speed is the limiting case of infinitely large sun gear and annulus. I got a different numerical answer to the OP, but like the OP it was fractional and negative. SpinningSpark 15:33, 11 March 2011 (UTC)

Autotrophic respiration

We don't seem to have an article on root respiration (autotrophic respiration), although it seems to be a fairly mainstream topic. I am curious about the interaction between scion and rootstock on tolerance to waterlogging and couldn't even find the relevant mechanisms defined here. DId I miss it or could someone who has a clue (unlike me) start one? --BozMo talk 09:59, 8 March 2011 (UTC)

Perhaps the articles Autotroph or Photoheterotroph may help? - 220.101 talk^\Contribs 15:08, 8 March 2011 (UTC)

Basically there is zilch on Wikipedia on this rather major topic. I found a decent apparently RS elsewhere though which answered my questions [11] --BozMo talk 16:36, 11 March 2011 (UTC)

Flight angle

An accident occured in which the vehicle was twisted at flight angle. What does the term "flight angle" mean technically and also how is it used on day to day basis? aniketnik 16:26, 8 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

Probably, "flight angle" refers to either the angle of attack (the angle of elevation of the wing surface, relative to horizon, as a rotation along the pitch-axis); or to the pitch angle (the angle of the aircraft airframe, measured relative to the horizon, along the axis designated as the "pitch axis"). In the case of a catastrophic accident, those two angles might not be identical! See our diagram for the conventional layout; and on most fixed-wing aircraft, note that pitch and angle-of-attack of the wing surface are fixed relative to each other. Other important "angles" are described in our aircraft flight dynamics article, with animations. Your exact quote, "twisted at flight angle", sounds very ambiguous - it is possible that the intended meaning is that the aircraft was within its normal operating orientation limits and should not have stalled. If you provide a source for your exact quote, we may be able to interpret the intended meaning a little better. Nimur (talk) 17:00, 8 March 2011 (UTC)

spin

How can they force the spin axes into a horizontal alignment by imposing an electric field that alternates at radio frequencies like it says in this article http://findarticles.com/p/articles/mi_m1200/is_n11_v133/ai_6507705/ — Preceding unsigned comment added by Lufc88 (talk • contribs) 17:55, 8 March 2011 (UTC)

It would help us to better answer this question if you were to explain what exactly you are having difficulty with in that article. You might find what you are looking for in magnetic moment and Electron magnetic dipole moment. Simply put, a spinning electron is equivalent to a circulating loop of electric current and consequently has a magnetic field identical to a small dipole magnet. For this reason, the electron will be acted on by external magnetic fields and, in particular, will tend to align the axis of spin with the field. At least, this is the situation with classical field theory, to get the full picture quantum mechanics must be applied. When this is done it is found that the dipole moment can take on only certain quantised values. SpinningSpark 00:07, 11 March 2011 (UTC)

I have a question.

Elements which make life possible

Which element or elements makes life possible? I am also wondering if life can be inorganic instead of organic? Matthew Goldsmith 19:08, 8 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs)

This is covered in some detail in the article Hypothetical types of biochemistry. Short answer: there may be all sorts of different chemical configurations that can make life happen, but we haven't observed them yet. (Except maybe GFAJ-1, but that's a small modification of the general template, if it is real.) --Mr.98 (talk) 19:58, 8 March 2011 (UTC)

I added a better (sub)title; please try to make your title more useful in the future. Also, a question: Do you mean chemical elements, or "elements" like light, heat, water, and gravity ? StuRat (talk) 22:15, 8 March 2011 (UTC)

Carbon, hydrogen, oxygen, nitrogen, (phosphorus or arsenic), and sulfur are all necessary. --75.15.161.185 (talk) 01:10, 9 March 2011 (UTC)

Why wouldn't silicon based computer technology not qualify as life when it become self supporting? E.g., in the near future we may have robots that maintain themselves and the infrastructure that sustains them. Count Iblis (talk) 15:11, 9 March 2011 (UTC)

Some might argue that to be life it must be self-replicating rather than self-supporting, which goes to show that whether or not a machine is considered alive depends on ones definition of life. SpinningSpark 08:31, 11 March 2011 (UTC)

efficiency

how efficient are steam power plants like coal in converting heat to electricity in percentage? how efficient are antennas in converting em waves to electricity in percentage? — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:39, 8 March 2011 (UTC)

The answer is, of course, "it depends." Practically, a coal power station is about 40% efficient, per carnot efficiency and engineering practicality. Antennas can be very close to 100% "efficient," if your amplifier and signal path are impedance-matched to free space (377 Ω), if you count all power out in any direction. Read thermal power station efficiency, and antenna gain. Do you need help understanding those articles? Nimur (talk) 21:28, 8 March 2011 (UTC)

Thanks i think i understand — Preceding unsigned comment added by Lufc88 (talk • contribs) 17:49, 9 March 2011 (UTC)

Standardization in Redox Titrations

Hello. Is standardization of KIO₃ necessary before titrating against ascorbic acid if I am preparing KIO_3(aq) from its solid? Thanks in advance. --Mayfare (talk) 21:42, 8 March 2011 (UTC)

Hi Mayfare. I think you have to ask yourself what reasons might mean that weighing solid KIO₃ might not accurately tell you the molarity of the solution. Here are a few to consider...

• Purity of solute (KIO₃) as sold. Was the solute intended for use as a primary standard or is it just a ground-up radiation pill, etc?
• Storage. Has the solute been kept in an airtight container so that it can't react with atmospheric gases around the lab? Would that be an issue?
• Humidity. Is the solute totally dry? If not, how might you dry it before use?
• Purity of solvent (H₂O). You might get an extra mark for mentioning this!
• Accuracy of weighing. How much solute are you weighing out? What is the precision of the weighing device?
• Accuracy of dilution. What errors might you expect here?

Hope this helps. Try estimating the cumulative effect of the last two (Accuracy) points. - Pointillist (talk) 22:31, 8 March 2011 (UTC)

Inheritance traits and DNA

Is it possible to determine the skin tone, hair/eye color and blood group after studying the inheritance traits during DNA analysis? --89.76.224.253 (talk) 22:33, 8 March 2011 (UTC)

It certainly is in the DNA somewhere (barring the use of hair dye, colored contacts, and such), but I'm not sure if we know exactly where. It's sometimes vastly more complex than just one chunk of DNA which sets each trait. There might also be certain diseases or environmental factors which might have an effect (like sun-bleached hair). StuRat (talk) 23:06, 8 March 2011 (UTC)

(ec)There are some claiming to do this.[12][13] This is fairly embryonic, and I would keep an eye out for chicanery. Genetic testing to determine the blood type shouldn't be difficult, but I can't think of many situations in which it would actually be useful. After all, if you have blood, might as well go for a DNA match. Wnt (talk) 23:07, 8 March 2011 (UTC)

The Daily Mail article is (no surprise) extremely misleading. It says that theoretically in the future you could reconstruct certain details about a person's face from DNA. (Granted in theory you could do this to some degree — but we're a long way away in practice, and it's unclear if those details you could extrapolate would actually be useful in identification.) Then it says something like this was already done... because they used DNA to determine that a suspect was Black rather than white. That's not the same thing at all; it's relatively easy to guess what ethnicity/racial category someone would fall in based on their DNA (it's probabilistic, but you can say things like, "you carry genes are extremely prevalent in people from this part of the world as opposed to this part of the world" — which, in some situations, is probably enough to say, "this guy is probably pretty white looking or Asian looking or Black looking" — which is not terribly precise, but could be useful in identifying a suspect). It's totally different — one is modeling development (which is hard), the other is tracing origins (which is not as hard). --Mr.98 (talk) 23:21, 8 March 2011 (UTC)

It's not easy to say exactly where this line is crossed, because any statistical fact is meaningful. We shouldn't expect that one day the genetic information is worthless and the next you can draw the suspect's face - rather, there is a period when it can rule out some possible suspects and provide "most likely" values for some features. Wnt (talk) 23:38, 8 March 2011 (UTC)

Note that even ruling out suspects (or matching DNA) is (under currently used practices) still probabilistic. They do not currently sequence entire DNA sequences (though someday they may do this, once it gets really cheap), just a finite series of markers within them. The odds of two different sets of DNA being seen as identical under these procedures is small but not impossible. (And calculating those odds depends on what assumptions you make about the target populations.) It is to my understanding still quite rare to use DNA testing to say something about what your suspect should look like — usually DNA analysis is useful after you already have samples to compare against. --Mr.98 (talk) 00:36, 9 March 2011 (UTC)

Speed of back-and-forth motion

How to measure the speed of continous back-and-forth motion? One b&f move per second? -) —Preceding unsigned comment added by 89.76.224.253 (talk) 22:56, 8 March 2011 (UTC)

How about dividing the total distance traveled per cycle by the time for each cycle ? This will give you the average speed. However, if you want the instantaneous speed, which would be expected to be zero at the furthest extensions and (normally) at maximum in the center, that gets trickier. StuRat (talk) 23:03, 8 March 2011 (UTC)

If I continously make for example 0,5 m back and forth per 1 s, that would be 0,5 m/sec per cycle, I guess? But what about instances where speed is inequal? --89.76.224.253 (talk) 23:08, 8 March 2011 (UTC)

If it goes half a meter one way, then half a meter back, that's 1 meter total. If that happens in one second, then that's an average of 1 meter per second. However, the speed WILL be uneven. That is, it must stop and turn around at the end of it's motion at each end. This is what I was getting to with "instantaneous velocity", which is the speed at any given time. If we make some additional assumptions, like constant acceleration/deceleration and no rest time at each end, we might even be able to come up with a graph of the instantaneous velocity at each point in the cycle, from the data you supplied. StuRat (talk) 23:19, 8 March 2011 (UTC)

Do you mean Hertz? You could say that the motion has frequency v and then calculate the position = K sin (2 pi vt) and therefore velocity = 2 pi K v cos (2 pi vt) [the derivative]. (K is half the total distance moved; the 2 pi factor converts cycles per second to radians per second, which can be multiplied by seconds and input into the sin function) But only if it moves sinusoidally. It could just bounce back and forth at constant velocity, for example.

To elaborate, suppose you have a piston that is driven by something that circles 0.25 m away from a central pivot once per second. Therefore the piston moves 0.5 m back and forth once per second. (Depending on the linkage I don't think this is precisely sinusoidal, but it could be) Time zero is the piston half extended, moving outward. The position of the piston is simply 0.25 m (2 pi t). When t = 0.25 it is 0.25, 0.5 it is 0, 0.75 it is -0.25, 1 it is 0.25 again. The velocity of the piston is (2 pi radians/cycle) (0.25 m) (1 cycle/second) cos (2 pi radians/cycle * 1 cycle/second * t). At t=0 this is 0.5 pi "radians" m/s = about 1.57 m/s. The decision to use radians in the velocity is momentarily confusing (both radians and cycles are in a sense "dimensionless") but radians signify the actual distance traveled, whereas cycles are merely a count of events. Wnt (talk) 23:24, 8 March 2011 (UTC)

Only a massless object could do that. Any real world object takes some time to accelerate and decelerate. However, the instantaneous velocity profile isn't necessarily sinusoidal, that's only true under constant acceleration. In the case of a ball being batted back and forth by a cat, for example, this wouldn't be the case. StuRat (talk) 23:23, 8 March 2011 (UTC)

I just edited the above a little, but to address your point, yes, there is at least some period of acceleration. But if the impact is elastic at either end, it would be a very small amount of time. Wnt (talk) 23:26, 8 March 2011 (UTC)

So, we should ask, what's driving this object to move back and forth ? This may help us to determine what type of motion and acceleration we're dealing with. StuRat (talk) 23:28, 8 March 2011 (UTC)

We have an article on the simple harmonic oscillator. This is the simplest type of "back and forth" motion modeled in physical systems. More complicated models deal more accurately with other types of motion. Nimur (talk) 23:37, 8 March 2011 (UTC)

You may need a stroboscope to measure it. 92.28.254.54 (talk) 13:38, 10 March 2011 (UTC)

March 9

dust mite covers and bed bugs

Will a special mattress cover designed to keep out dust mites (for those who are allergic) also keep out bed bugs, so that if bed bugs appear in the apartment, the person who lived there wouldn't have to throw out the mattress after eliminating the bed bugs? I guess I want to find out if a dust mite mattress cover could be part of preventative measures. I'm not asking medical advice. Thanks, 74.14.13.241 (talk) 00:02, 9 March 2011 (UTC)

Well it might act as a partial barrier, but bed bugs are particularly resourceful in gaining access to the sleeping body. There are accounts of them climbing up the bedroom wall and jumping off onto the bed, having calculated the appropriate parabolic trajectory! (No, I don't believe that, but I do believe that they will find their way round most obstacles to gain access to their food.) Treatment with insecticide is much more effective, but even that is not guaranteed. Dbfirs 00:11, 9 March 2011 (UTC)

Are you actually asking if the cover will keep them in? i.e. the bed bugs will be locked under the cover and can't reinfect the room? Assuming you kill all the ones in the room? It seems unnecessary to me - killing the bugs in the mattress is pretty easy compared to killing the ones hiding in the room. Also they can live for a year without food, even under that cover. As a general answer, the cover will do nothing, since the bed bugs can live in the room and then walk over to the person on the mattress. (Unlike mites they don't live inside the mattress, they hide on the mattress in seams.) And they can also hide in cracks in the floor or walls, etc. Ariel. (talk) 00:58, 9 March 2011 (UTC)

Antimatter explosion

Is it possible to determine/make an educated guess as to what a (hypothetical) antimatter explosion in air would actually look like? Would it appear similar to a nuclear bomb going off - but larger for the given mass of 'explosive' material? Would there be a mushroom cloud? Would the explosion be the same colour? --Kurt Shaped Box (talk) 00:25, 9 March 2011 (UTC)

It should look more or less like a nuclear explosion, which itself (from a superficial point of view) is just the creation of a gigantic expanding ball of heated air. The mushroom cloud is caused by it being close to the ground, and is not unique to a nuclear explosion (any explosion of a sufficient size will cause one if it is close enough to the ground to suck up dirt). I don't know about the color — nuclear explosions generally just look like the standard black body spectrum (a ball of fire), but you do get weird cloud colors because of the radiation involved, ionization of the air, etc. I don't know what kinds of things you'd get from an antimatter explosion but I'd imagine they would mostly look pretty similar, since the essential thing responsible for the appearance of a nuclear explosion (lots of heat energy all at once) is essentially the same. (I would not expect all of the effects to be the same, mind you. But you can't see neutrons, for example, so the fact that nukes let out gobs of neutrons doesn't really change how they look.) --Mr.98 (talk) 00:31, 9 March 2011 (UTC)

As a point of clarification, while a nuclear mushroom cloud can contain particulate material pulled up (and/or vaporized) from the ground, this is not required to form the cloud. When warm, moisture-laden low-altitude air is rapidly lifted up by the fireball and then cools, fine droplets of water condense out, forming the cap of the mushroom. (Even in the absence of soil and dust from the ground, the vaporized remains of the bomb and its casing rapidly condense to provide a rich supply of condensation nuclei for water droplet formation.) While very-high-altitude bursts won't form explosions, it is because they are unable to draw up enough warm, humid, air from lower altitudes—not because they can't suck up dirt. TenOfAllTrades(talk) 01:12, 9 March 2011 (UTC)

Well, you have to suck up something to get that mushroom stem. If you have an aerial burst (not even high altitude), you get a cloud, but not a "mushroom", like this.--Mr.98 (talk) 12:41, 9 March 2011 (UTC)

If you are reacting exactly equal amounts of the same element (rather than anti-matter in air) it will make almost 100% gamma rays (assuming you can mix the two fast enough, which is NOT easy). That type of explosion will not look like a normal explosion. It will ionize air to a tremendous distance, and will look more like an aurora than a fire. If you just drop anti matter through the air it will look either like a meteor, or a series of explosions (probably depending on how fast it moves through the air). It won't explode all at once, since the initial explosion will push away all the matter, leaving nothing to react with the antimatter. The explosion will then stop, letting matter back in, and it will cycle. If it's moving fast, then the fresh air arriving at the front will constantly provide matter to react with, and it will leave a trail of light. (But because most of the energy is being released in the front, it will rapidly slow down.) I am assuming it will take the form of fire because the two elements being reacted are not the same, so you have residual particles to carry energy as heat. If things match up however (perhaps you pick anti-silicon which has twice the atomic number of nitrogen in air), then you'll get mostly gamma rays and bursts of auroras (aurorae?). Ariel. (talk) 01:08, 9 March 2011 (UTC)

Are you sure it would look like an aurora? What I'm imagining would happen is that said gamma rays would collide with said air and heat them up (e.g. via Compton scattering), making it look like a pretty regular explosion to the naked eye. Similarly the bulk output of energy from a nuke is in the form of neutrons and rapidly moving fission products, which looks, to the naked eye, just like fire when it is done in an atmosphere. The only place you'd notice the difference is if you did it in a vacuum, with a nuke. But I'm not a physicist; this is just my understanding of the visible effects. --Mr.98 (talk) 12:41, 9 March 2011 (UTC)

No, I am not sure (I never got a chance to test the one we built in StuRats lab). But Compton scattering does not heat up air - rather it makes light that looks pretty much like an aurora. And unlike a nuke there aren't any neutrons or other particles left to cause heat effects. It's all neutrinos and photons. Ariel. (talk) 13:15, 9 March 2011 (UTC)

That's completely wrong. Gamma rays don't release their energy by Compton effect. They release it by pair creation that produces a particle shower which efficiently delivers the energy to the medium. I don't think your aurora-like explosion makes any sense whatsoever. The result would be very much like a nuclear explosion. Dauto (talk) 14:33, 9 March 2011 (UTC)

I'm not convinced. Because you have anti-matter (either from the original or the pair production) you can't have a proper particle shower - the shower is annihilated. Maybe some of it heats up the matter, but most will end up as gamma rays again. As further evidence, I heave never read anywhere (and I just checked again) that actual gamma rays from Gamma-ray bursts cause particle showers. If they did then the Compton Gamma Ray Observatory would not need to be in space, they could do it on the ground. Cosmic rays, i.e. protons do. But not gamma rays. Ariel. (talk) 21:51, 9 March 2011 (UTC)

You got it upside down. The observatory must be in space because the gamma rays are effectively blocked by the atmosphere. Read Gamma ray#Matter interaction for more details. notice that pair production becomes the dominant mode of interaction with matter for gamma rays with energy above 10 MeV. A proton-antiproton reaction releases roughly 2000 MeV. The point is moot because most of the energy is released in mesons, not gamma rays, and mesons interact with matter even more promptly than gamma rays do. Dauto (talk) 16:34, 11 March 2011 (UTC)

For further evidence, read Gamma-ray astronomy. Read the caption of the first picture which states "Gamma rays are absorbed by the atmosphere and must be studied from a space telescope.". Dauto (talk) 19:40, 11 March 2011 (UTC)

When I wrote my question, I was thinking something along the lines of an antimatter bomb of comparable physical size to that of a nuke, dropped on an enemy city from a B-52 (or whatever). I suppose that merely allowing the bomb to hit the ground and break open, exposing the antimatter (hitherto contained by a magnetic field in vacuum) to the air would be sufficient for the purposes of mass destruction? That said, what physical effect would a bomb that worked by colliding an equal quantity of elemental matter and anti-matter have on a city and its population - supposing that this massive 'gamma aurora' (and little else) was produced upon detonation? --Kurt Shaped Box (talk) 01:32, 9 March 2011 (UTC)

See Gamma-ray burst. It would sterilize all life. It probably would not do a lot of destruction, because while all those gamma rays eventually end up as heat, they travel quite far and the energy would be spread out. The ground right under the bomb would get hot, but again, the gamma rays would travel deep underground. Note: I'm speaking relatively - it would still be a massive bomb, just not as big as the energy calculations might lead you to expect. If I were designing an anti-matter bomb I would make two types. In both of them I would place the anti-matter in many small containment structures, and place matter right near each structure. The idea it to try to get the two to mix as thoroughly and rapidly as possible. In one type that would be all. I would let them mix, and let the gamma rays sterilize all life. In the second type I would surround the bomb with a tamper designed to absorb as much gamma ray energy as possible. This will turn it into heat and cause a massive physical explosion. This is good for attacking fortifications. StuRat can I join your lab? Ariel. (talk) 02:05, 9 March 2011 (UTC)

Sure, I'm always looking for new henchmen, since they occasional make mistakes and thus must be liquidated. StuRat (talk) 04:15, 9 March 2011 (UTC)

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

I'm not so sure about your speculation here, Ariel. The graph at right suggests gamma rays are absorbed by (transfer their energy to) the atmosphere pretty well. It's hard to say exactly what would happen, but I see no reason to doubt an antimatter weapon would be far more destructive by weight than a thermonuclear weapon no matter where or how you set it off. Please cite a source if you really believe otherwise.WikiDao ☯ 02:44, 9 March 2011 (UTC)

Well by weight no question at all. I was saying by energy. By total energy released, an anti-matter bomb would be less effective than a nuclear one, which in turn is less effective than a chemical bomb. But of course the available energy is far higher so that outweighs it. As far as the graph, that's for the entire depth of the atmosphere. Gamma rays are able to travel in air. Ariel. (talk) 02:58, 9 March 2011 (UTC)

This seems to imply a kilometer for gamma rays, which I guess isn't much. Ariel. (talk) 03:10, 9 March 2011 (UTC)

Your assumption that it's almost 100% gamma rays is incorrect; a significant amount of energy will be carried away by neutrinos. Nucleons and anti-nucleons create pions. While the neutral pions decay largely into gamma rays, the charged pions decay mostly into muons and muon antineutrinos; the muons in turn decay into muon neutrinos, electron antineutrinos and electrons. Icek (talk) 03:29, 9 March 2011 (UTC)

Addendum: And I forgot the positively charged pions, which decay into antimuons and muon neutrinos; the antimuons decay into muon antineutrinos, electron neutrinos and positrons, which can annihilate with the electrons. But the neutrinos will carry away some energy, as they hardly interact with matter. Icek (talk) 03:32, 9 March 2011 (UTC)

Our Antimatter weapon article says: "The effect of a large antimatter bomb would likely be similar to that of a nuclear explosion of similar size." WikiDao ☯ 01:41, 9 March 2011 (UTC)

That is correct. As Icek explained above, the matter-antimatter reaction produces mostly mesons, not gamma rays, and as I explained further above, gamma rays are absorbed by air just fine. Dauto (talk) 14:49, 9 March 2011 (UTC)

As others have said, the explosion should look similar to a nuclear explosion, but if you want a different looking explosion, an impact from a large object like an asteroid should produce a different looking explosion since the fireball would have a tendency to be sucked up into the ionized wake created by the asteroid as it traveled through the atmosphere. See, http://www.stardestroyer.net/Empire/Essays/Planet-Killers.html#Asteroid ScienceApe (talk) 18:29, 9 March 2011 (UTC)

Aftertaste

Why does chocolate have such an unpleasant aftertaste? Some other sweet foods have similar, but not quite as strong, aftertastes, as well. --75.15.161.185 (talk) 01:07, 9 March 2011 (UTC)

Try a different brand of chocolate. Also, personally, if I eat too much chocolate in a short period of time it starts tasting sour, so perhaps let your tongue rest first. Ariel. (talk) 01:13, 9 March 2011 (UTC)

But it's happened with other foods too, not just chocolate. Most foods with sugar or (to a lesser extent) starch also seem to have a bad aftertaste. Do the carbohydrates break down into acid? --75.15.161.185 (talk) 01:18, 9 March 2011 (UTC)

I find that an aftertaste is usually a sign that they added some nasty chemicals. Read the ingredients. If there are things in the list you can't pronounce, try a different brand without all the nasty added chemicals. StuRat (talk) 03:56, 9 March 2011 (UTC)

I can't rule out that some (thin) person gets an aftertaste from sugar. But U.S. chocolate lovers should beware: believe it or not, there are grinches making chocolate out of castor oil! (See PGPR) I'm talking about the main brands you see in the store aisle - check the ingredients.

Actually, what I really wonder is, what do they do with all the leftover ricin? Where do they farm all those plants? They must have accumulated enough to wipe out a large country by now, if they didn't throw it all out... Wnt (talk) 05:22, 9 March 2011 (UTC)

It really depends what kind of "unpleasant aftertaste" you're talking about. Cacao itself has a complex and bitter flavor, and so high quality chocolates with a high percentage of cocoa mass have a sharp bitterness that is considered part of the complexity of the flavor. Milk chocolate, especially of the Hershey's variety, has a somewhat sour taste which is considered characteristic of its process of production. Some of this is just how chocolate tastes — it is not a simple "sweet" flavor, but a mix of lots and lots of complicated (natural) chemicals that makes cacao such an interesting appeal flavor. --Mr.98 (talk) 17:31, 9 March 2011 (UTC)

I get unpleasant aftertastes and sometimes tongue pain from various foods (chocolate being one of them). But, I have geographic tongue, so it is just a side effect. If I continue to eat bad foods, I get tiny white bumps all over my tongue and it takes many hours for them to go away. -- kainaw™ 17:40, 9 March 2011 (UTC)

The story I heard was that American chocolate has a bad taste because the milk supplied by rail to an early factory would go rancid on its way there. This bitter taste became stuck as the flavour Americans expected in chocolate. European chocolate does not have a bitter taste, although european brands sold in North American have the bitter taste that Americans expect. I remember when out of curiosity I bought a Hershey bar being sold as a novelty here in the UK - I thought it had gone bad. I've never seen any other American chocolate being sold on this side of the Atlantic. 92.28.254.54 (talk) 13:36, 10 March 2011 (UTC)

That sounds plausible (an early processing method introduced a bitter flavour that is now expected by the consumer in modern equivalents). Unlike any other country I've been to, I find it more difficult in the US to find chocolate I like. Hershey's being particularly nasty I agree. M&M's are ok though and seem to taste the same as they do in the UK. Best place for chocolate? Belgium. Even the cheapest most generic chocolate based confectionary I could find (bought in their equivalent of Aldi or Lidl) was absolutely gorgeous! 213.120.209.248 (talk) 14:45, 10 March 2011 (UTC)

The rancid milk sounds like an urban legend, but Hershey is famous for having developed a cheap alternative process. There are many steps involved in making a good chocolate - the kind of cocoa bean, the kind of processing, and the ways in which greedy manufacturers try to replace the cocoa butter; whenever possible, American manufacturers choose the worst possible option. I suppose the real mystery is why Americans haven't learned to import chocolate like we do everything else. Wnt (talk) 21:04, 10 March 2011 (UTC)

I believe cocoa is bitter to start with, then some is "processed with alkali", which can only make it worse. It's only by adding massive quantities of fat and sugar to a tiny amount of cocoa that it becomes good tasting. StuRat (talk) 05:34, 12 March 2011 (UTC)

Activity series

Hey all. I am a first-year chemistry student and right now we are studying single-replacement reactions (example: AgNO₃+Na→Ag+NaNO₃, Na "replaces" Ag) and predicting products. In the reactivity series the teacher gave us, lithium is listed first before all the other metals; this version is also widespread around the internet ([14], [15], [16]). But, why is lithium above sodium and potassium? I thought metals lose electrons more easily as one moves down the table, and thus potassium should be more reactive than sodium should be more reactive than lithiu,m, and a professional chemist concurs with my reasoning. However my teacher insists her table is correct. Who is right? Thanks. 72.128.95.0 (talk) 02:28, 9 March 2011 (UTC)

Reactivity series has a quite different order. It also mentions that there are three different ways to define the order, so perhaps that explains the difference. (The article should really clarify which order the chart at the top uses, and ideally include 3 charts, one for each.) Ariel. (talk) 03:30, 9 March 2011 (UTC)

Equivalence at Inflection

Hello. Why is the equivalence at the point of inflection on a titration curve? Thanks in advance. --Mayfare (talk) 06:42, 9 March 2011 (UTC)

Tagishsimon (talk) 11:37, 9 March 2011 (UTC)

When you have a neutral solution and you start adding 3M base, the solution becomes basic, but no matter how much of the base you add, the solution will never exceed 3M - the more you add, the slower it approaches that concentration. Similarly, you can add a 3M acid and watch the solutions pH lower, but never quite reach that of the original acid. Titration is taking this process in reverse, so the equivalence point is also the point where adding just a bit of acid or base makes the largest change in pH - the change slows down from there - hence the point of inflection. SamuelRiv (talk) 19:45, 10 March 2011 (UTC)

aransremen

aransremen Penulisan lagu untuk menyingkat APA Yang disebut bertujuan Penulisan? —Preceding unsigned comment added by 118.97.15.21 (talk) 10:52, 9 March 2011 (UTC)

Google translate reckons this is Indonesian, and translates it as "aransremen Writing songs to abbreviate the APA The so-called -objective writing?" --Tagishsimon (talk) 11:37, 9 March 2011 (UTC)

There is a Indonesian reference desk. 118.97.15.21 might be better asking there. Or, if he can write in English, ask on the Humanities desk if the question is about music. CS Miller (talk) 12:35, 9 March 2011 (UTC)

Ah. The Indonesian desk appears not to be used often. CS Miller (talk) 12:38, 9 March 2011 (UTC)

It sounds like the question is something like what's the purpose of abbrevating/condensing song arrangements but I'm not really sure. Although I don't speak Indonesian it's not that dissimilar from Malay and while my Malay isn't that great, the grammar and sentence structure seems wrong. It doesn't even seem like the sort of informal language you may expect on the internet, it's almost like half the question is missing. BTW aransremen probably means wiktionary:aransemen and I'm pretty sure the apa is probably just wiktionary:apa i.e. what. I'm not sure why the 'yang' (that/the) and 'penulisan' (writing) are capitalised either. Nil Einne (talk) 14:11, 9 March 2011 (UTC)

Life expectancy according to age

Is the life expectancy is 80 years, what can an 80 years old expect? 80.58.205.34 (talk) 12:56, 9 March 2011 (UTC)

The article on Life expectancy might be reasonably useful for you to look at, but the article on Life table may be even more so (and the pictures and graphs used there-in). If I am reading the table correctly on the 'Life table' article, then it suggests that if you were a 66-67 year old living in the US, you would have a 0.01624% chance of dying before your next birthday, and would be expected to live for a further 17.7 years. I know that you asked specifically about somebody at age 80, but the table only goes to the 66-67 range.

Also, I believe that in the context of your question, the life expectency of 80 years is the life expectency at birth, not at the point when somebody is 80 years old. Hope that helps to a certain extent. Darigan (talk) 13:07, 9 March 2011 (UTC)

Yes, I supposed that the life expectancy is at birth, not when you turn 80. 80.58.205.34 (talk) 13:26, 9 March 2011 (UTC)

Hi again, as a further reference - There is a complete table here http://www.ssa.gov/oact/STATS/table4c6.html (goes up to 119 years old) that gives the expected life expectency for US males and females from ages 0-119. So, a direct answer to your query - In the US, 80 year-old-males have a life expectency of 87.78 years (At birth it is 75.1), and females of 89.33 (at birth, 80.21). Those tables are quite interesting, thanks for asking that question (I wouldn't have come across them if you hadn't). Darigan (talk) 13:44, 9 March 2011 (UTC)

I doubt if many 80-year old males would expect to live for a further 87.78 years. Perhaps a further 7.78. Ghmyrtle (talk) 14:09, 9 March 2011 (UTC)

I believe the meaning was understood, I wasn't aware that by saying that an 80 year old US male had a life expectancy of 87.78 years meant that I was suggesting that he would live to counts fingers... not enough, shoes and socks come off.... be 167.78 years old - But happy to be corrected if that was the case. Darigan (talk) 14:20, 9 March 2011 (UTC)

According to life expectancy (as linked above) it does mean that, the source you used does also apparently use it with the same meaning. Nil Einne (talk) 18:21, 9 March 2011 (UTC)

Yes, I think the term is widely mis-used to mean "expected age at death". I was interested to see that the life expectancy of a US 80-year-old male was almost exactly the same (at just under six years) in 1950 as it was in 1850, and has subsequently risen by less than three years, so the answer to the OP's question is "less than nine years" for a male, and "about ten years" for a female American. Dbfirs 22:16, 9 March 2011 (UTC)

Ants that like sweat or human sweat?

This problem has bugged me for months: ants swarming my hands and feet for my sweat. Just today my laptop keyboard was intruded for that reason (I'm aware there's something like a keyboard sheet/protector but I like to touch the keyboard directly, and this isn't the main point), and I've tried doing Google search and searched archive here for an answer but no avail (unrelated: found sweat bee though, what an interesting world). A friend suggested it could be termite since the table-cupboard is made of wood, but I don't think they look like termites, and I've tried Googling termite sweat but no relevant results as well.

Situation: My campus hostel had a renovation and I moved in after, we got a new table-cupboard (err table + cupboard above, 2-in-1) and I'm using it. On the first few days I noticed ants were swarming the floor even after we cleaned the room. Sometimes they swarmed my feet when they're on the floor, and you know, you'd kill the ants without a second thought - that's when I realised they smell bad. The odour resembles one that's secreted by some other insects perhaps, I'm not sure. You'd definitely get the strong odour if you try killing like 5+ at once, and killing a swarm will definitely make you go "uuuuuuurghh".

These ants are black, with whitish yellow abdomen. They're quite aggressive towards me, but I'm sure it's because of my sweat that they bite me all the time.

How do I find out they're after my sweat is a long story... but an interesting point to note: while trying to find out, I purposely left my cup unwashed after drinking Milo (Nestle product, chocolate drink). After a week, only 2 ordinary black ants came, 1 of which I left it there for hours to see if it'd call its friends, but it looked like it just kept it to itself lol.

I've also tasted my sweat to make sure it doesn't taste sweet, and yes it's very salty as expected (fortunately!).

Now actually I'm just curious if they're an undiscovered species or if there's a new discovery for ants' behaviour.

Any thought is welcomed, thanks. — Yurei-eggtart 15:32, 9 March 2011 (UTC)

Assuming you are in Malaysia, this may be helpful. Malaysian ghost ants stink and are heavily attracted to water sources. -- kainaw™ 16:27, 9 March 2011 (UTC)

Yes I am from Malaysia. Thanks a lot for the link, I think this is the one, except the fact that I'm not used to seeing them up close. The ones I have here seem to be darker (oh my, does that mean they're more experienced?). I'm just a little bit disappointed they're already discovered and even known as pest. — Yurei-eggtart 16:55, 9 March 2011 (UTC)

Yes, they're very likely to be Tapinoma melanocephalum. A keyboard sheet/protector won't help. Your best bet is to do what other ant species do and use chemical interference. Since they rely on a hydrocarbon based trail system a giant wet soapy cloth washing away their lines of communication causes havoc. Sean.hoyland - talk 09:31, 10 March 2011 (UTC)

How many human species coexisted with eachother?

How many different human species lived during the same time period. I know the Homo Neanderthalis and the Homa sapien sapien were around at the same time. Except I am wondering if there are any others. Matthew Goldsmith 19:07, 9 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs) 19:06, 9 March 2011 (UTC)

Our homo article covers this thoroughly. The picture I've attaching shows the most important species but leaves out a lot of minor ones. Looie496 (talk) 19:28, 9 March 2011 (UTC)

The nice graph at Human evolution says it's just the Neanderthals. Comet Tuttle (talk) 19:30, 9 March 2011 (UTC)

The graph leaves out both homo floresiensis and the Denisova hominin, though. Looie496 (talk) 19:36, 9 March 2011 (UTC)

(Edit Conflict) I don't think that that nice graph is meant to be comprehensive, Comet Tuttle. From the figure attached by Looie496, plus generally available information, it seems likely that Homo neanderthalensis in Europe and early Homo sapiens in Africa and beyond coexisted in time with late Homo erectus in Asia, and perhaps Homo rhodesiensis in Africa. To these we can add the disputed Homo floresiensis and the recently discovered Homo denisovan, if they prove valid taxons. It seems quite possible that further new human species also coexisting in time with H sapiens will be discovered in the future. Bear in mind, Lightyearlight, that since various of these species emerged from various others and there are no agreed on sharp boundaries between some of them, there may be valid disagreement over which ones certain coexisting individuals belong to. {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 19:50, 9 March 2011 (UTC)

If we include Australopithecines in the definition of "human" then there were several species sharing the plains of Eastern and Southern Africa too. Roger (talk) 20:05, 9 March 2011 (UTC)

Couldn't various of these different "species" likely have interbred and had fertile offspring, such as modern humans and neanderthals, if not for geographical isolation from each other? Edison (talk) 19:32, 10 March 2011 (UTC)

I don't think that's known - and might never be. Matt Deres (talk) 14:38, 11 March 2011 (UTC)

Premature babies

Why isn't it yet possible to set up artificial transfer of oxygen and nutrients to a premature baby through its umbilical chord? Or even by setting up transfer through the placenta? Since they stick breathing tubes in and try to get the babies breathing with their under-developed lungs, I assume it's completely impossible at the moment. But, on the face of it, it would seem quite feasible given current technology, even if the complete artificial womb is a long way away.

So, what is specifically so difficult about this? 86.163.4.134 (talk) 21:20, 9 March 2011 (UTC)

I've wondered this too. The umbilical cord would not be possible (it closes), nor the placenta. But you can set things up just like in dialysis except with oxygenation instead of filtering. After some searching I found: Extracorporeal membrane oxygenation, which says: "Newborns cannot be placed on ECMO if they are under 4.5 pounds (2 kg), because they have extremely small vessels for cannulation, thus hindering adequate flow because of limitations from cannula size and subsequent higher resistance to blood flow". Seems to me this should be solvable, but I guess it isn't possible now. Ariel. (talk) 22:36, 9 March 2011 (UTC)

Why would they fool with tiny blood vessels when a premie is dying? Why not put in a PIC line like they do for an adult when the peripheral lines aren't adequate? Edison (talk) 19:29, 10 March 2011 (UTC)

N.B. We have an article PIC line. Wnt (talk) 20:59, 10 March 2011 (UTC)

I recently came acrros a documentary series called Baby ER on Zone Reality. Among other things medical personell was collecting blood for testing from a baby and explained that as the blood vessels are small their needles get cloged pretty fast, so they may need to take blood for testing from several sites. I guess drawing blood dosen`t take much time, so it might be yet another reason why they prefer ventilation and feeding tubes over trying to enrich blood with something ~~Xil (talk) 01:37, 11 March 2011 (UTC)

Seems there is another problem: "In infants aged less than 34 weeks of gestation several physiologic systems are not well-developed, specially the cerebral vasculature and germinal matrix, resulting in high sensitivity to slight changes in pH, PaO₂, and intracranial pressure. Preterm infants are at unacceptably high risk for intraventricular hemorrhage (IVH) if administered ECMO at a gestational age less than 32 weeks." Ariel. (talk) 08:09, 11 March 2011 (UTC)

Airbus 321, air speed

Resolved

 – thanks to Dolphin

When I was flying an A321 I observed a sharp shift in the refractive index of the air around the plane on two occasions.

1. In normal flight in a vertical line above the wing near the leading edge.
2. Outside the front of the engine when in glide flight before landing.

I assume that this is a shock waves indicating that the flow on one side is supersonic relative to the air plain. Is the flow supersonic before or after the shock wave?--Gr8xoz (talk) 23:18, 9 March 2011 (UTC)

Why do you assume it's supersonic? I don't know what caused it, but two other possibilities come to mind: The air is being compression heated, or the air is being compressed (or both). Either of those would cause a change in the refractive index. Ariel. (talk) 02:16, 10 March 2011 (UTC)

Gr8xoz is correct. This phenomenon is readily visible when travelling on any of the swept-wing jet airliners, providing you are sitting in a position that allows you to look along the wing, parallel to the leading edge. These aircraft are not supersonic but when flying at their cruising altitude they are transonic. This means the aircraft itself is not supersonic but as the air flows over the top surface of the wing at high speed, for a short distance it is supersonic relative to the wing. The air accelerates progressively as it passes the leading edge of the wing but it does not decelerate progressively. A shock forms, and as the air flows through the shock its speed (relative to the wing and the shock) suddenly decelerates to subsonic. Any gas, including air, approaches a shock at supersonic speed but the instant it emerges from the other side of the shock it is moving at a slower speed. The flow downstream of a normal shock is subsonic. (The flow downstream of an oblique shock is still supersonic but it has changed direction and is slower than the speed at which it approached the shock.) On either side of the shock there are different speeds, pressures, temperatures and densities. The difference in density on either side of the shock explains why the shock is sometimes visible, looking like a crack in a pane of glass. Dolphin (t) 02:35, 10 March 2011 (UTC)

OK so the speed is supersonic in front of the shock wave.(Relative to the wing) Thanks.--Gr8xoz (talk) 16:33, 10 March 2011 (UTC)

March 10

Cyclohexane smell

Why does cyclohexane smell like acetone? --70.244.234.128 (talk) 00:49, 10 March 2011 (UTC)

I don't think that they do. Cyclohexane has a sweet smell like benzene while acetone has a harsh smell. 75.41.110.200 (talk) 02:34, 10 March 2011 (UTC)

It has the same sort of "chemical" smell as acetone (and many other synthetic organic compounds, like paint, paint thinner, etc.). --70.244.234.128 (talk) 00:06, 11 March 2011 (UTC)

A "fuel savings device" question

I've read the articals here on fuel saving devices and understand that there is limited to no evidence of the value of the devices or the claims made by manufacturers. It appears that virtually all fuel saving devices are either additive based or impact the air flow and fuel mixture. However, I came across this (http://www.gfchips.com/fordf150.aspx) device that uses a computer chip to improve fuel economy, etc. Is there any validity to this company's approach (especially given the old adadage: if it sounds too good to be true, it probably is . . .")? 99.250.117.26 (talk) 01:14, 10 March 2011 (UTC)

I think if that chip really worked Ford would have done it already. Especially 60 more horsepower? They would love that. Even if this company thought of something Ford didn't, Ford has to be aware of it and would reverse engineer it. But one thing that really stood out is that they have a chip for every car in existence, and I'm sorry but there is no way in the world that is possible. Ariel. (talk) 02:14, 10 March 2011 (UTC)

It's a scam. See reviews here. --Stephan Schulz (talk) 10:21, 10 March 2011 (UTC)

I won't speak to this specific chip-model, which may be a scam. But electronic engine control is a real thing, and does improve fuel efficiency. Ford calls this EDIS and VCT; Honda calls it VTEC; and so on; these are special cases of an Engine Control Unit, a sophisticated computer/electronic box that "makes the engine go." The auto manufacturer usually "tunes" the car's ECU software, hardware, and the engine's mechanical systems for the best average performance. However, after-market "engine-chipping" is also a real thing - especially on the performance auto-enthusiast circuit (amateur racers and the like). You can tune for best performance for certain driving conditions. Here's a brief article Chip the engine which should give you an overview of the subject.

Will engine chipping give you 60 extra horsepower? Unlikely. Your engine has peak performance numbers; you can mechanically alter the engine to improve those specs, but not by a whole lot; and playing with your valve-timing isn't going to give you 50% more gas-mileage or horsepower. Custom engine-chipping will do things like moving your torque curve around so you get the car's peak performance at a different engine RPM; and it definitely can change your fuel efficiency (for better or for worse)! And as always, mucking with your car's ECU can be risky - if you screw up, you can permanently damage your car's mechanical systems, requiring costly repairs. Nimur (talk) 16:21, 10 March 2011 (UTC)

cdma2000

Hi there. Not really a _science_ question, but does anyone happen to know the theoretical ratio between the channel power (1.23 MHz bandwidth) and the RMS power for a cdma2000 SR1 signal? 80.254.147.84 (talk) 02:11, 10 March 2011 (UTC)

CDMA-2000 is pretty spectrum-filling, so I would "assume" for theoretical purposes that the spectrum is "flat" across the entire channel, and has a specified 3-dB frequency (or specified frequency rolloff rate). Since the signal is a digital QAM constellation with ~64 elements, it is actually pretty nasty when viewed as a pure frequency-spectrum; "theoretically" you should have 64 perfect frequency spikes; but as you of course know, the practical reality is that you have a fuzzy signal whose frequency-spread is determined by your QAM circuit's phase-noise specification. I doubt there's any use to construct a "thorough" theoretical model of the channel power - can you measure it? Otherwise, I'd report the channel power in watts per hertz (or mW/MHz, or other convenient unit), by "assuming" total RMS signal power divided by bandwidth; and spend some time spec`ing the out-of-band frequency rolloff to clean up my estimate. Two app-notes I found on the web search: Linear's AN99 LT5528 WCDMA ACPR, AltCPR and Noise Measurements discussing practical details for measurement; and Tektronix Digital Modulation technical series, Measuring ACPR of W-CDMA Signals with a Spectrum Analyzer. Don't underestimate the power of vendor app-notes - no matter how specific your need, you can probably search the major spectrum-analyzer manufacturers' public libraries, and if you've bought their equipment, you may be able to phone one of their engineers to discuss horrible engineering details with an experienced person. Nimur (talk) 16:46, 10 March 2011 (UTC)

Thanks for the info. The problem is not so much measuring the signal parameters - I have a waveform that purports to be cdma2000, but which has a 99% OBW of 1.275 MHz (as against the CHP bandwidth of 1.23 MHz). I was wondering if that was correct, and, if not, how incorrect it is. You're probably right that a more specialist arena is a better place for this sort of question, though. 80.254.147.84 (talk) 16:45, 11 March 2011 (UTC)

entanglement

would entanglement support the conclusion that given two entangled particles at some large distance apart, if one of the particles were to somehow cease to exist that the other would simultaneously cease to exist? —Preceding unsigned comment added by 98.221.254.154 (talk) 05:03, 10 March 2011 (UTC)

No. Ariel. (talk) 08:09, 10 March 2011 (UTC)

Presumably you want a longer answer, and to start with particles can't just cease to exist - they always turn into something else. And even if they did it does not mean the other one will too. If anything it would be the reverse - one particles ceases to exist, the other ones doubles. (That doesn't actually happen, but it's more realistic than the reverse.) Ariel. (talk) 08:09, 10 March 2011 (UTC)

It's fairly misleading to comment on what physics would do if you forced it to violate itself. —Preceding unsigned comment added by 129.67.37.227 (talk) 14:12, 10 March 2011 (UTC)

I agree - Ariel's first response, while ultra-brief, was probably the appropriate one! Trying to trace out the consequences of a physical contradiction only leads to more bizarre contradictions. Particles can not cease to exist. If you come up with a realistic physical scenario, we can apply some established rules of quantum-mechanics to model what would happen. For example, if a particle decays, then we can model the trajectories of the decay products, and see how the quantum wave-functions would propagate to (and affect) the entangled partner particle. But when you ask a "what if...", all we can meaningfully say is "then our rules don't apply, so we can't answer that." Nimur (talk) 16:55, 10 March 2011 (UTC)

I thought one of them could be annihilated with antiparticle?? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:32, 10 March 2011 (UTC)

You appear to misunderstand what annihilation means. Please see Annihilation - at least the introduction. -- kainaw™ 18:36, 10 March 2011 (UTC)

Perhaps the OP is thinking of one particle falling into a black hole? I have a meagre understanding of QM but wouldn't then the entanglement be destroyed but not the particle? Blakk and ekka 18:46, 10 March 2011 (UTC)

No effect of entanglement is detectable with measurements on only one particle. So if you "throw the other particle away" in the sense that you never measure anything about it again, entanglement ceases to matter, though it's theoretically still there. Throwing a particle into a black hole is one way of getting rid of it, but there are easier ways. -- BenRG (talk) 00:52, 11 March 2011 (UTC)

"Since energy and momentum must be conserved, the particles are not actually made into nothing, but rather into new particles. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of the original pair are zero." OK, So one particle could be made into new particles while the other might not be? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:06, 10 March 2011 (UTC)

If the two particles are entangled, then any operator that acts on the wavefunction of Particle 1 can cause the wavefunction of Particle 2 to change. That is not synonymous with "the decay of Particle 1 forces the decay of Particle 2." It means that the operator must modify both wave-functions. Tragically, in efforts to "simplify" descriptions of quantum-mechanical treatments, pop-science books do not emphasize the precise nature of this statement: both wave-functions may be affected is not the same as information was transferred, nor the particles are linked together, nor the action on particle 1 caused an action on particle 2. Two entangled particles form a composite quantum-mechanical system. Certain operators must act on the composite system. The composite system's final result will depend on the operator and the composite system's prior quantum state. The state of either particle is a subset of the composite system. Nimur (talk) 20:46, 10 March 2011 (UTC)

"Any operator that acts on the wavefunction of Particle 1 can cause the wavefunction of Particle 2 to change" is incorrect. There's only one wavefunction, which describes the entire system. If the particles aren't entangled then you can factor the wavefunction into a product of separate wave functions for each particle, but if they are entangled then you can't. That's one way of defining entanglement. -- BenRG (talk) 00:52, 11 March 2011 (UTC)

Yes or no, can one decay and not the other? —Preceding unsigned comment added by 98.221.254.154 (talk) 00:41, 11 March 2011 (UTC)

Yes, one can decay and not the other. For example, one could be an electron (stable) and the other a neutron (unstable). They don't have to be particles of the same type. But "decay" doesn't mean "cease to exist". Decaying doesn't destroy entanglement. -- BenRG (talk) 00:54, 11 March 2011 (UTC)

Sorry, so there could be more than one "particle" in an entangled "pair"?98.221.254.154 (talk) 01:47, 11 March 2011 (UTC)

Yes, any number of particles can be entangled. -- BenRG (talk) 03:26, 11 March 2011 (UTC)

Is every particle in our galaxy entangled with every other one? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:41, 11 March 2011 (UTC)

Myasthenia Gravis

What is the right way of presentation "Myasthenic crisis" or "Myasthenia Crisis"? aniketnik 10:06, 10 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

To describe the occurrence of symptoms in a person with myasthenia gravis, you would call it a "myasthenic crisis." --- Medical geneticist (talk) 11:01, 10 March 2011 (UTC)

Feeling cold in the morning and body weight

Hello. When I wake up in the morning, I have a cold sensation that usually lasts an hour or more. When I mentioned about this to a friend, he said he has experienced the same, and it's related to having a metabolism that effieciently converts extra energy into heat, and that this is probably why we're both thin while we eat a lot and don't get much exercise. Could this be the case? 212.68.15.66 (talk) 10:09, 10 March 2011 (UTC)

If I were you I'd see a doctor. We're not allowed to give medical advice. --TammyMoet (talk) 20:02, 10 March 2011 (UTC)

I'm not ill, why would I? I've always felt chilly in the morning, but in fact I've been very healthy, I hardly ever catch any disease. What I'm asking is whether the "super metabolism" could explain the chilly feeling and my apparent "immunity" of gaining too much weight. 212.68.15.66 (talk) 07:50, 11 March 2011 (UTC)

OP it is quite possible for you to be quite ill without being aware of it! My original advice still stands. --TammyMoet (talk) 13:56, 11 March 2011 (UTC)

In my opinion you're overreacting, as there is nothing that suggest that the OP is ill in any way. I've always felt a bit cold when I wake up, and I too have been very healthy. Time for some LOGIC: The OP mentions his/her friend has experienced the same, and I also feel cold in the mornings usually for half an hour. Therefore, it's probably rather common, and if feeling cold in the mornings was related to a common medical condition, we would probably know about. On the other hand, it might be a symptom of a very slowly advancing terminal disease... but my money's on Looie496's suggestion on reluctance to leave the warm bed behind. Zakhalesh (talk) 20:46, 11 March 2011 (UTC)

I can think of two conditions which match the symptoms described by the OP, but our prohibition on diagnosing mean I can't even mention them. Both conditions are common in the Western world, and can remain undiagnosed for many years, silently causing many problems which, if diagnosis had been made earlier, would not have occured. --TammyMoet (talk) 21:23, 11 March 2011 (UTC)

Since interpreting everything as a sign of a disease is itself a disease, you'd better get yourself to a doctor right away, Tammy. :-) StuRat (talk) 00:45, 12 March 2011 (UTC)

I don't know what "a cold sensation" means. Nearly everybody experiences a circadian rhythm of body temperature in which the temperature drops during the night and rises around daybreak. Whether there is anything unusual about your sensations is unclear without a better description. Lots of people are averse to getting out from under warm covers on a chilly morning. (I don't consider this medical advice.) Looie496 (talk) 23:02, 10 March 2011 (UTC)

A few points:

1) If you turn the temperature down at night (or have an automatic thermostat that does so), it may actually be colder. Even if the temp is turned back up by the time you get out of bed, it still may take some time for the house to get up to the new temperature.

2) Activity warms you up, and a bit of exercise in the morning might do the trick.

3) It might be warmer in your bedroom, particularly under the covers, due to your body heat overnight, and walking into another room may cool you down. This seems to especially be a problem with bare feet on uncarpeted floors, as in the bathroom or kitchen. A cold toilet seat will also wake you right up. StuRat (talk) 00:50, 12 March 2011 (UTC)

Will Global Warming cause the Moon recede faster or slower from the Earth?

Global Warming will cause sea level rise. This will have some effect on the tidal friction the Moon experiences, causing the rate at which it recedes from the Earth to change a bit. Will this rate increase or decrease? Count Iblis (talk) 15:02, 10 March 2011 (UTC)

It will recede faster. With more liquid water instead of solid, the tidal friction will increase, so the moon's recession will occur faster. For partial support of that statement, see the second paragraph of Tidal acceleration#Angular momentum and energy. Red Act (talk) 15:24, 10 March 2011 (UTC)

On the other hand, by melting ice into water some of the mass that is now near the poles will move closer to the equator changing earth's Moment of inertia slowing down its rotation and therefore increasing the time between a high tide and the following low tide reducing the rate of the motion of the tides around the planet and decreasing the pace with which the moon is moving away from the earth :). Dauto (talk) 01:45, 11 March 2011 (UTC)

And note that any effect would be so slight it would be difficult or impossible to even measure. StuRat (talk) 00:39, 12 March 2011 (UTC)

Chemical catalog

In a chemical catalog item description, what is the meaning of something like (N/10)? For example, "Hydrocholric acid solution, 0.1N (N/10)". I am looking specifically at Cole Parmer and I've been unable to find any explanation in their information. ike9898 (talk) 16:56, 10 March 2011 (UTC)

N means 'normality'; it's a way to express concentration. See Concentration#Normality for details. TenOfAllTrades(talk) 17:53, 10 March 2011 (UTC)

Well, I understand that, but is "0.1N (N/10)" any but just completely redundant? ike9898 (talk) 19:30, 10 March 2011 (UTC)

Solution of NaOH at 40% m/m

I need to prepare a 100ml solution of NaOH at 40% m/m (in water). As NaOH absorbs the humidity in air, I have consulted an old Handbook, section sodium hydroxyde, concentration properties of, in varying concentrations but I am still unsure as to how much NaOH (in grams) I need. Please help.

Thank you very much. --192.197.51.41 (talk) 18:06, 10 March 2011 (UTC)

First, the preparation of weight/weight solutions is tackled by our RefDesk's foremost competitor here.

I should add that I'm a bit surprised to see "m/m" or "mass/mass" coming up. It seems from searches that this is in vogue for recent homework problems. On the one hand, yes, the number on the balance is in grams of mass; on the other, what the balance measures is weight.

Now the real question you have is what the purity of the NaOH is. You could run various tests on it, or try to purify it e.g. by baking it at high temperature to drive out the water, but the traditional chem lab way to handle the problem is to titrate the sodium hydroxide solution after you've made it, against a known standard. In this way you can adjust the molarity to be exactly right, and therefore the m/m value. (Though usually people titrate to get an exact molarity rather than an m/m value) Wnt (talk) 20:53, 10 March 2011 (UTC)

Thanks, I got it figured out. --192.197.51.41 (talk) 22:20, 10 March 2011 (UTC)

Does copier or printer ink contain metal?

I was wondering whether photocopier ink or laser-printer ink contains any metallic substances or metal compounds?

Thanks. 71.252.113.85 (talk) 20:37, 10 March 2011 (UTC)

It depends on the ink. Our article toner may help. Most toner is pure carbon (say, graphite powder), or something similar (like carbon black), but may also include a plasticizer, a binder, one or more liquid solvents, and so on. In general, these are synthetic polymers. Colored ink may contain pigment, which may include synthetic polymers, or metallic pigments. Nimur (talk) 20:51, 10 March 2011 (UTC)

Is it possible for the polymers in black copier or printer ink to be magnetic? 71.252.113.85 (talk) 03:03, 11 March 2011 (UTC)

Probability cloud of a free electron?

Would the probability cloud of a free electron look the same as an electron in the ground state bound to a hydrogen atom? ScienceApe (talk) 20:40, 10 March 2011 (UTC)

No, not as far as I can tell. Until you get a better answer, consider these related questions: why would you think that the electron_cloud would look the same in both cases? Compared to a 'free electron' (presumably with no other particles around), an electron bound in hydrogen has at least a few additional forces acting on it, especially the electric field generated by the proton. Shouldn't this difference in forces change the shape of the probability cloud (and perhaps radically so)? SemanticMantis (talk) 22:40, 10 March 2011 (UTC)

No --Gr8xoz (talk) 22:31, 10 March 2011 (UTC)

Without a nucleus to bind the cloud, the autorepulsion will cause the cloud formation to disolve. Plasmic Physics (talk) 22:41, 10 March 2011 (UTC)

Here's the problem. You can't formulate a wavefunction for an electron in free space. Let's trace out how we do it for a simplified quantum mechanical treatment of an electron in an Hydrogen atom: (see our article on Hydrogen atom, particularly the solution of the wave function.

• First, define a coordinate system by assuming the proton to be heavy and therefore immobile. (The hydrogen proton is located at the origin).
• Now, define the Coulomb potential - for practical purposes, this is $1/r$, where r is the radius from the origin. (How can you define the coordinate-system of the free electron, if there's no reference origin? You have to pick an origin at random, which isn't a problem, but then there's zero potential energy gradient, and so the electron has a probability of being anywhere relative to your undefined origin).
• Solve the Schrodinger equation using the Coulomb potential and normalize using physical constraints (probability that the electron exists somewhere must equal 1).

So, in free space - you don't have anything to define your wave-function, and the electron can be anywhere. The only thing you can do is measure an electron - determine its current state (its momentum and its position, subject to the uncertainty principle), and then you can predict where it will be next (which is, of course, anywhere, since it is unbound). When you measure it again, at some other position/momentum, the principle of indistinguishability means you can not know whether you've measured the same or a different electron! So, there's no way to predict the position of an electron in an unbound system (no defined coulomb potential). It has an equal probability of being anywhere; and anything you measure has a likelihood of being a different electron. Nimur (talk) 23:29, 10 March 2011 (UTC)

This is completely wrong. See Wave packet. Truthforitsownsake (talk) 02:17, 11 March 2011 (UTC)

Well, in actuality, I never apply quantum-mechanics when I'm describing free electrons. Most of the time, I can treat my plasmas as a superposition of an electron gas and an ion gas, and solve using classical or relativistic electrodynamics. By the very nature of the involved length, time, and energy scales, quantum-mechanical properties are less relevant to free electron clouds, in practice. I'm not surprised that my attempt to describe a quantum mechanical system for an electron gas sounds awkward. I respectfully disagree that my explanation is "completely wrong" - I think it's completely correct, although it's surely "stretching the limits of the conventional application of quantum mechanics." Nimur (talk) 14:54, 11 March 2011 (UTC)

The hydrogen atom orbitals are a complete basis for smooth electron wave functions that approach zero at infinity, so they don't tell you anything about the electron by themselves. An electron that's nowhere near the nucleus can still be described by a sum of these solutions. The only thing that's special about them is that they're energy eigenstates. If you remove the nucleus, leaving the background potential zero everywhere, then it's no longer possible to write down a basis of energy eigenstates, but I think that's just a pathological corner case. You can still work in some other basis like a wave-packet basis, or you can write down energy eigenstates if you add, say, a single nucleus a billion light years away. -- BenRG (talk) 02:35, 11 March 2011 (UTC)

magnetic earth

will we ever know for sure what is inside of the earth or if it is hollow will we ever know for sure what causes the earth's magnetic field — Preceding unsigned comment added by Lufc88 (talk • contribs) 21:41, 10 March 2011 (UTC)

I think we're pretty sure about the structure of the Earth. Is there any reason you don't believe the scientific explanations presented in that article? Geology and geophysics are evidence-based sciences, and there is a lot of evidence to back up the current theories. Have a read at those articles for details on the experimental toolkits available to help scientists gather evidence about Earth's interior. Nimur (talk) 21:46, 10 March 2011 (UTC)

We will never know anything about the world for sure, we could just be hallucinating or in a computer simulation. We have a rather good model for the structure of the earth, we may never know some finer details but as long as we can trust the measurements the overall structure are known, it is not hollow and could not be hollow since no known material would be strong enough to keep it from collapsing. --Gr8xoz (talk) 22:41, 10 March 2011 (UTC)

For why we know the Earth isn't hollow, see Hollow Earth#Contrary evidence. Also, the interior of the Earth has been mapped in detail using seismic tomography, without any evidence of any hollow space; see Seismology#Seismic waves.

As per Earth's magnetic field#Field characteristics, the currently accepted theory is that the Earth's magnetic field is primarily due to electric currents in the (liquid) outer core, similar to an electromagnet. This is called the dynamo theory, although a numeric model of the Earth's magnetic field consistent with the dynamo theory has not yet been achieved. Red Act (talk) 22:45, 10 March 2011 (UTC)

how can we prove that it is the dynamo effect any ideas — Preceding unsigned comment added by Lufc88 (talk • contribs) 22:49, 11 March 2011 (UTC)

The main way is by comparing Earth with other (terrestrial) planets and moons which lack a magnetic field. Venus doesn't appear to have one, and Mars appears to have a relatively weak one, as does our Moon. So, if these lack the molten iron outer core of the Earth, that's fairly good evidence that this is the reason. The Moon shows little evidence of recent volcanism, so that supports it being solid, not liquid. Mars shows signs of massive ancient volcanoes, but less activity more recently. More study is needed there. Venus is difficult to study, due to it's thick cloud cover and corrosive atmosphere. StuRat (talk) 00:31, 12 March 2011 (UTC)

March 11

18 year Lunar Perigee effects on tides?

I saw an article yesterday that said in mid-March the moon will be as close to the earth as it ever gets ("lunar perigee"), and that this is an 18 year cycle. Sadly, nothing of the sort is mentioned in Orbit of the Moon. I have two questions: 1) is this true and where on Wikipedia can I read more about it? 2) will this cause record high tides? if yes, what would the tidal variation be between the moon at its closest and furthest orbital positions? The Masked Booby (talk) 00:50, 11 March 2011 (UTC)

The mentioned 18 year cycle is probably a Saros cycle, which governs eclipses. The moon reaches perigee about once a lunar month, but the exact timing with respect to the phase of the moon changes. The Full moon cycle of about a year-and-a-bit would be the closest connection between lunar perigees and the size of tides -- we get the largest tides when the moon is close to us just at a spring tide. The Saros cycle arises from the interference between the full moon cycle and the moon's periodic movement north and south of the ecliptic (which also happens about once a month but again only roughly, due to the precession of the lunar orbit). –Henning Makholm (talk) 02:11, 11 March 2011 (UTC)

Henning has given an excellent response. On a general level do you remember (assuming you are old enough) any 'record' tides 18 years ago when the same circumstances pertained. I don't, and I've experienced more lunar phases than I care to mention ;-) Richard Avery (talk) 07:26, 11 March 2011 (UTC)

Diet theory

As far as I remember body stores excess energy in fat. If I have lost weight by eating less, does it follow that my body has used my fat instead of food, and since there is no fat available I should eat more now and I won`t get fat again? 89.235.211.162 (talk) 01:18, 11 March 2011 (UTC)

As our dieting article states, weight loss usually means that one has lost both fat mass and muscle mass. Could you rephrase your last sentence? It didn't make logical sense to me. I must mention that your questions about this may be deleted, or go unanswered, if you ask questions about your body, because that touches on our no-medical-advice policy — I would recommend asking questions about a hypothetical generic human instead. Comet Tuttle (talk) 01:43, 11 March 2011 (UTC)

Eating is not a medical issue and it is a biology question. I don`t see what is there not to understand. A person eats less. He or she loses weight. Assumption is that weight loss is result of body being forced to use fat to get necessary energy. Would it be healthier if person wouls start eating more, given that there is no more fat reserves to dig in? Will increasing food consumtion result in weight gain or will the body convert all food into energy stright away? 89.235.211.162 (talk) 02:46, 11 March 2011 (UTC)

If a person takes in more calories than they expend, the body will have a net positive amount of "energy" and will store it as fat. If a person takes in fewer calories than they expend, the body will have a net negative amount of "energy" and will respond by breaking down fat stores, then muscle if insufficient fat stores remain. If a person's caloric intake and expenditures are roughly equal, they will remain the same. One of Comet Tuttle's points was that what you (the OP) "should" do is dependent on a whole variety of factors and isn't really in the domain of the reference desk. It is doubtful that you have completely eliminated all of your fat stores, and we don't have any way of knowing whether you have altered your basal metabolic rate in the course of your weight loss (by increasing lean muscle mass, for example), or if your daily activity level has significantly increased (thus requiring higher caloric intake simply to break even). So, whether or not you can "eat more" without gaining the weight back is impossible to answer. The bottom line is that you can simply use a scale to weigh yourself (pick one time of the day and try to be consistent). This will answer your question. --- Medical geneticist (talk) 03:08, 11 March 2011 (UTC)

No, I moved to diffrent town for my studies, the only thing I altered was how much I eat, because I don`t like to cook and was hardly ever hungry. I like the result. However lately I am feeling hungry more often, although I eat as much as usually. Hence I wonder. 89.235.211.162 (talk) 04:21, 11 March 2011 (UTC)

Beware of yoyo dieting: losing weight, then gaining more back. It is the usual result of dramatic dieting and weightloss, because your body adapts to the lack of calories and starts to lay fat down more easily. If you find, in a few months time, you are heavy than you were before the weightloss, the only way to definitely break the cycle of steady weightgain is to not diet. 86.163.4.134 (talk) 09:42, 11 March 2011 (UTC)

I think I understand the logic behind your question. Let me state what I think you meant to ask, then answer that:

"Since we have fixed number of fat cells, if I eliminate all of them by dieting, will it then be impossible for me to gain weight since I no longer have any fat cells in which to store additional fat ?"

OK, the biggest flaw with that theory is that fat cells just shrink when you lose body fat, they don't disappear entirely. They can be removed, via surgery, but not all of them. This leads to the remaining fat cells getting even larger, and having many small fat cells provides for a smoother looking body than a few huge ones. But, if we could theoretically eliminate all of our fat cells, what would happen ? I suspect that you would die, or at least get diabetes, as burning fat is important to bridging long gaps between meals. And, on the other extreme, when you ate a big meal, if it couldn't be stored as fat, would your blood sugar skyrocket ? StuRat (talk) 00:07, 12 March 2011 (UTC)

Incidentally, one reason why you may be hungrier now is that you aren't getting all the nutrients you need. If you had an unhealthy diet, but ate 10x as much as you should have, then you might have managed to get all the vital nutrients just by volume, whereas now, if you continue to have an unhealthy diet, but just eat less, you may have deficiencies, leading you to crave more food. Make sure you have a healthy diet, and this problem should go away. StuRat (talk) 00:13, 12 March 2011 (UTC)

No, I wasn`t aware that number of cells is fixed, I thought body generates new cells and eliminates old cells (to extent, at least). I am acctualy concerned of the effect anonymous poster before you mentioned. So let me rephrase. I believe I am hungry because my body has depleted its fat reserves and wants to get more energy from food now. Up until now I ate as much as I craved, but I am worried that because of whole yo-yo dieting deal my body wants me to eat more than I acctualy need. So should I eat as much as I crave or only a little bit more? 84.52.32.137 (talk) 00:30, 12 March 2011 (UTC)

If eating as much as you craved made you overweight before, I suspect that it would do so, again. But, as I said, the answer to cravings isn't to eat more junk, it's to eat the proper amounts of the right things. StuRat (talk) 01:02, 12 March 2011 (UTC)

I ate what my parents served, not junk, though possibly too much bread, matter of fact I`ve been eating more junk food while losing weight than ever before. I currently eat stuff from all major food groups, mostly salad. So I see your point as valid, but I doubt it applies here (besides I guess lacking specific nutrients would cause cravings for a particular product, which contains them) 84.52.32.137 (talk) 01:26, 12 March 2011 (UTC)

Cravings aren't necessarily that specific. And if you've been eating more junk food while losing weight, that supports the idea that you may be malnourished. Salad is a good component of a healthy diet (although the common iceberg lettuce is almost devoid of nutrients), but you might not be getting enough protein. For that you need meat, dairy, beans, or nuts. StuRat (talk) 06:08, 12 March 2011 (UTC)

monopole

what would happen if you took a bunch of magnets shaped like a pyramid (with one pole at the top point and the other pole at the wide base) and then glued them together with all the top points facing in? —Preceding unsigned comment added by 98.221.254.154 (talk) 02:00, 11 March 2011 (UTC)

Your description of a magnetic "pole" as a point is unfortunately oversimplified. The simplest magnetic moment is inherently described as a dipole. A magnetic "pole" doesn't exist at one specific position in the magnet: it is an effective orientation - a preferred direction - that is built into the magnet. Complex ferromagnets have an effective average dipole moment, and so it's fun to draw this as a "north" pole region and a "south" pole region, but in truth, what you have is an net average orientation of all the individual microscopic orientations that make up the magnet. As such, the "north pole" doesn't exist "at the point" of the pyramid, nor the "south pole" at the "wide base." The entire magnet is polarized. Nimur (talk) 02:14, 11 March 2011 (UTC)

(ec) Their magnetic fields would cancel each other out, and only leave a slight inwards-pointing field in the middle of the faces of the resulting polyhedron, and a slight outwards-pointing field at the corners, or vice versa. Some distance from the compound object (say, two radii from the center) there would be practically no net field. –Henning Makholm (talk) 02:18, 11 March 2011 (UTC)

Ah yes, I didn't actually answer the original question! So, to directly answer what would happen: I can't quite follow the geometry the OP is envisioning, but it sounds like you've got a bunch of magnets oriented so that they want to repel each other. Well, if you squish them together, and maybe glue them in place, the result will be that from far away, you'll have an effectively larger, but weaker, magnet. And if you get really close near any of the individual pyramid-shaped magnets, you will find that your magnetic field is best described as a superposition of several individually-oriented dipole fields. (You might even find a way to mathematically re-represent that as one single higher-order moment, if you're pretty slick with math). Nimur (talk) 02:19, 11 March 2011 (UTC)

It could also be modelled as a superposition of two perpendicular linear quadrupoles, so I suppose it is an octopole. —Preceding unsigned comment added by 129.67.37.227 (talk) 02:41, 11 March 2011 (UTC)

Is it correct to compare a magnetic monopole to a one sided coin? Plasmic Physics (talk) 09:29, 11 March 2011 (UTC)

I don't mean a trick coin where both sides are either heads or tails, I mean a coin with literally only one side. Plasmic Physics (talk) 09:32, 11 March 2011 (UTC)

No. An electron is a "monopole" for charge after all. We have never found one for magnetism, but that doesn't mean it's illogical in the way a one sided coin (in a 3D world) is. Ariel. (talk) 10:00, 11 March 2011 (UTC)

I get the concept of a charge monopole, what would be a correct analogy then? Plasmic Physics (talk) 10:07, 11 March 2011 (UTC)

An electric charge monopole is totally described by its position and its charge magnitude. A magnetic dipole must include, at the minimum, its position, magnitude, and orientation. If you want to try and stretch this analogy, you could say a "magnetic monopole would be sort of like an arrow that doesn't point in any direction." In a sense, a magnetic dipole must be oriented - it's built in to the definition of a dipole to have a vector orientation; and our theory of magnetism requires the elementary magnetic unit to be a dipole. In the same way, if you had an arrow and it didn't point in any direction, ... well, you wouldn't have an arrow anymore. Nimur (talk) 14:47, 11 March 2011 (UTC)

I don't agree with all of the above. There sure is room in our current theory of magnetism for magnetic monopoles. Read 't Hooft–Polyakov monopole. That's why the search for a magnetic monopole is not considered a fool's errand. But they have never been observed and it is possible that they simply do not exist. A better analogy for the meaning of a monopole would be a rug that has been combed down away from a central position. Dauto (talk) 16:03, 11 March 2011 (UTC)

Insofar as you mean magnetic field lines would emanate from a monopole, yielding the hypothetical Gauss's law for magnetism, $\nabla \cdot \mathbf {B} =q_{m}$ - yes, that is how we would mathematically describe as a magnetic monopole, if it exists. And we would draw it on paper the way Dauto describes it. Is there room in our theory for it? Sure, with minor modification of Maxwell's equations, we could trivially add a magnetic monopole term; but to make those modified equations fit with experimental observation of physical reality will be a much more subtle and challenging problem. My tendency is to believe that the magnetic monopole does not exist, and is a contradiction against everything we physically observe about magnets, even if we could write equations to describe what it would hypothetically look like. Future experiment may disprove my belief - you're right that it's not futile (and indeed, is a worthwhile avenue for experimental physicists to pursue); so I'm open to the unlikely possibility of discovery of a magnetic charge. Nimur (talk) 16:35, 11 March 2011 (UTC)

The modified equation's fit just fine with experimental observations. I would like to clarify the point that 't Hooft–Polyakov monopoles are predicted to exist by the standard model of particles, so they are not as fringe as one might think. Dauto (talk) 16:48, 11 March 2011 (UTC)

Drugs

What affects do drugs have on the mitochondria in humans? How are other organelles affected? Albacore (talk) 02:20, 11 March 2011 (UTC)

Which drugs? We can't even begin to answer the question without specifics. --- Medical geneticist (talk) 02:55, 11 March 2011 (UTC)

Well, uncoupling agents are defined by their ability to (essentially) break down the electrical resistance of the mitochondrial membrane e.g. by acting as proton ionophores, discharging its energy unproductively. Oh, and rotenone works a different way, jamming the electron transfer apparatus. Wnt (talk) 04:42, 11 March 2011 (UTC)

Big rip or Big crunch?

Is it more likely for the universe to end in the concept "big rip" or "big crunch"? — Preceding unsigned comment added by Lightylight (talk • contribs) 04:29, 11 March 2011 (UTC)

Our article on the ultimate fate of the universe notes that current scientific data supports an open universe. That viewpoint is incompatible with a "big crunch", but does not necessarily support a "big rip" scenario. — Lomn 04:38, 11 March 2011 (UTC)

That article also says that the Big Freeze is "currently the most commonly accepted theory within the scientific community". There are a couple of variants of that scenario, depending on whether protons can or cannot ever decay. Gandalf61 (talk) 14:58, 11 March 2011 (UTC)

Zoologist specialising in Lepidoptera, "Busck", active beginning to mid C20?

Hi all,
The usual question: any clues about entomologist with either abbreviation "Busck." or full family name "Busck"? Binomial authority for Ypsolopha querciella amongst a whole lotta others. Google is not being friendly. Sounds Scandinavian, and first name initial may be "A".
Thank you! --Shirt58 (talk) 09:52, 11 March 2011 (UTC)

The "A" would appear to be "August" and his publications are listed at WorldCat. SpinningSpark 11:05, 11 March 2011 (UTC)

A F Braun, Lepidoptera, active mid C20

Hi all - same again. Binomial authority for Parectopa geraniella inter alia. Apologies for being such a bother. --Shirt58 (talk) 10:09, 11 March 2011 (UTC)

Annette F Braun [17], [18]. SpinningSpark 11:34, 11 March 2011 (UTC)

Japanese and Chinese earthquakes

Could there be any connection between the two earthquakes, or are they just coincidence? Thanks. 92.24.186.163 (talk) 14:06, 11 March 2011 (UTC)

As a first-order answer, "no, these are just coincidences." To explain in more detail, scientists have been studying earthquakes for a long time, and there are many theories about triggering earthquakes. There's a certain plausibility about massive geological events (like a powerful earthquake) affecting a geographically distant fault and triggering another earthquake; but unfortunately the data record is not clean enough to make a solid, scientific conclusion. Scientists have also investigated more indirect triggers for earthquakes, such as magnetic interactions between large sections of the Earth's interior; glacier, sediment, ocean/tidal, and other "variable" geological overburden loads, and so on. If you're interested, here are a few historically notable research papers: Earthquakes Cannot Be Predicted (1996); and my personal favorite work on earthquake prediction, Scientists debate new evidence for electromagnetic earthquake predictors (1991). (This paper triggered much heated debate). As you can see, most scientists do not believe there is any geological, seismic/teleseismic, electromagnetic, nor any pattern of animal behavior, nor any "telepsychic" method, that can predict earthquake incidence. But, reputable scientists continue to seek any sort of signals that might indicate earthquake precursors, or solidly indicate that one earthquake triggered a second one. Nimur (talk) 15:16, 11 March 2011 (UTC)

Thanks, interesting papers which I shall read, although the question is if there could be any connection between them, which is a different from asking about predicting them. 2.97.212.204 (talk) 16:22, 11 March 2011 (UTC)

Valid consideration: it's really two sides of the same coin. If Earthquake A causes Earthquake B, then there must be some physical mechanism (like a propagating seismic wave from A that disrupts the rock material strength along the fault-line for B). If there is such a connection, we should be able to observe it - or at least, identify what hypothetical "perfect, noiseless measurement instrument" would be required to observe it. And if we can observe A and measure its effects, we should be able to predict Event B. So the distinction between "A triggers B" and "A allows seismologists to predict B" is fairly moot. This is conceptually described with more rigorous scientific precision in the literature I linked. Nimur (talk) 16:45, 11 March 2011 (UTC)

Not really. Prediction is about things in the future, this is asking about things happening at the same time. In economics or finance, for example, there are series which are random and unpredictable yet which have a relationship with each other - in other words they may show Cointegration or Correlation. You've also forgotten that A and B may both be caused by some other factor. 92.15.24.90 (talk) 19:41, 11 March 2011 (UTC)

Earthquakes mostly are the result of movement of tectonic plates. Japan happens to lay on thee diffrent plates and there have been two previous earthquakes in the same region of China in recent years. If you take a look at maps in articles on both quakes and the ones on earthquake, you`ll see that they appear to be on different edges of Eurasian plate, close to diffrent fault lines and are moving in diffrent directions. It can be a coincidence. Though of course it could be that Eurasian plate has become particulary active. ~~Xil (talk) 21:37, 11 March 2011 (UTC)

To add to the list, there have been a number of large earthquakes in New Zealand lately, including the most recent one in Christchurch, and increased volcanic and seismic activity in Hawaii. One theory I've heard is that the Moon may cause this, by being closer than it has for the last 18 years (I'm not sure if this is true, the question posed a few above this should hopefully provide and answer). Since the Moon causes tides (along with the Sun), in water, and also causes hidden tides in the solid portion of the Earth (in the form of both stress and strain), it's not impossible that the Moon's gravitational effect could trigger quakes. Now, if so, the question would come up as to why it's all in the Western Pacific. Perhaps that region was "ready to blow" for other reasons, and the Moon just provided the spark. StuRat (talk) 23:54, 11 March 2011 (UTC)

The whole region is nutorious for seismic activity. See Pacific Ring of Fire for some statistics ~~Xil (talk) 00:54, 12 March 2011 (UTC)

Yes, but it appears to have increased recently. And I congratulate you on your "nutorious" spelling. :-) StuRat (talk) 00:59, 12 March 2011 (UTC)

I heard on tv two scientists say that earthquakes did tend to cluster together in time, even though they are in different places. 92.15.2.144 (talk) 00:57, 12 March 2011 (UTC)

Changing # of chromosomes in evolution

How do new species arrive that have a different number of chromosomes from their antecedents? I can see how the number could go down, actually, in theory, at least, but increasing-- where'd the DNA come from? Unless one of the already existent chromosomes split in the new species (seems like extremely high odds against that happening while not causing serious problems, let alone fitness) And yet many species of life have differing amounts of chromosomes, so it must happen. 20.137.18.50 (talk) 16:18, 11 March 2011 (UTC)

Polyploid plants can be formed from two monoploid parents, so the number of chromosomes can double in a single generation. Often, rather than suffering decreased fitness, many polyploid plants are quite hardy and robust, and specifically have characteristics desirable for agriculture. Many of our primary crop plants today are polyploid. See this section of our page for examples. There are other ways chromosome number can change, but this is a good place to start. SemanticMantis (talk) 16:32, 11 March 2011 (UTC)

You answered your own question. "It must happen". Which means that your intuition about the odds of that happening is simply incorrect. Dauto (talk) 16:42, 11 March 2011 (UTC)

That doesn't answer the how though, Dauto. 90.195.179.167 (talk) 16:44, 11 March 2011 (UTC)

Thanks, SemanticMantis, paleopolyploidy covers exactly what I was wondering about. Dauto, I didn't mean to doubt that it happens, I only meant to express my desire to understand how it happens, noting my perspective at the time given how easily bad things happen when genes get messed with. 20.137.18.50 (talk) 16:48, 11 March 2011 (UTC)

What makes you think that the splitting would have to mess up any genes? The splitting could happen between genes. There is a lot of non-coding DNA between genes in most Eukaryotes. Dauto (talk) 16:55, 11 March 2011 (UTC)

I don't have any specialized knowledge on the subject, and am glad to have any wrongheaded assumption I have made replaced by fact. 20.137.18.50 (talk) 17:10, 11 March 2011 (UTC)

One thing to bear in mind is that increasing the chromosome number by splitting one, or decreasing it by merging two, chromosomes (see Chromosome 2 (human) for an interesting example of the latter) does not involve creating or destroying any DNA, because differently-numbered chromosomes are not all the same size - indeed, they are conventionally numbered according to size order. When such merges and splits occur, individuals with them may initially still be able to reproduce with "unmodified" individuals because the two sets can still line up well enough: over time, the modification may multiply until modified individuals are regularly mating, and then the modification may, through some advantage, take over through Natural Selection.

Also, genes can migrate from one chromosome to another over generations, and smaller chromosomes may have shrunk by some of their genes having moved to larger ones: in time a chromosome could eventually dwindle away to nothing by this mechanism, again reducing the chromosome number. Some mitochondrial genes have over the aeons transferred from the mitocondria's single circular chromosome (I oversimplify) to nuclear DNA chromosomes, which is one reason why mitochondria can no longer operate as independent living organisms, and it has been suggested that the human Y chromosome (already our tiniest) will eventually disappear in this way (several human male-sex-determining genes are already on other chromosomes).

As others above have mentioned, sometimes the Chromosome complement can double "in one go" through polyploidy (I believe it's happened about 4 times in our own deep ancestry). When this happens the organism has a complete operating genome plus a "spare", and genes in the latter are then available to evolve new genes without losing the functions of the "originals". This could also happen if a single chromosome pair was doubled, or increased from 2 to 3, but sometimes such increases can cause deleterious effects, as in Trisomy 21.

Just as you say, such occurrances are rare, and non-deleterious ones rarer, but the deleterious ones are eliminated by Natural Selection, and there is so much time available over the millions of years over which evolution operates that the rare advantageous ones have time to accumulate. {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 21:30, 11 March 2011 (UTC)

Is there an example of a species with a variable number of chromosomes, where at least two of the variations could be described as "healthy" ? StuRat (talk) 23:44, 11 March 2011 (UTC)

Yes, Homo sapiens! This link refers to an individual from China with 44 chromosomes (22 pairs) as opposed to the usual 46, and I am sure I have recently read of a family in Scandinavia with the same count (though not necessarily due to the exact same variation), that I am momentarily unable to find references for. The latter family displays somewhat reduced but by no means destroyed interfertility with 46-chromosome individuals, because, as in my description of the Chromosome 2 merge above, the 2 unmerged chromosomes from a "normal" partner can still align well enough with their corresponding end-linked "double" chromosome to achieve homologous pairing. The individuals with 44 chromosomes are entirely healthy; they merely have the same genes packaged in a slightly different way. I suspect that this sort of variation is more common than hitherto realised (because who has been looking?), and I believe some other species more commonly show variable counts, but can't bring any to mind just now because it's past 5 in the morning! {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 05:24, 12 March 2011 (UTC)

Interesting, thanks. StuRat (talk) 05:59, 12 March 2011 (UTC)

That is a great link. Note that the man was actually the offspring of two people who both carried the translocation! So there's already some population out there (though probably very small) carrying this new chromosomal configuration.

What is interesting to consider is that if there are even just a few people like this man, it quickly reaches the point where outsiders are the ones with the "funny" chromosome pattern, in the sense that they'll be less capable of producing offspring with members of the group than they are with one another. Should it happen that group members are sitting on some good genes for some situation, this means that their group might spread out and start to dominate an area, and in this way start to look like a "new species" (though further barriers obviously would need to evolve) Wnt (talk) 07:16, 12 March 2011 (UTC)

There's also Przewalski's Horse which has 66 chromosomes and other horses have 64. It's debated whether it's a species or a subscpecies, partly because it can produce fertile offspring with other horse (sub)species. There's a discussion at the talk page that you might find interesting. I also recall reading about some small animal in the Middle East which had varying number of chromosomes in the same species. It might have been some kind of mongoose or rodent. I'll se what I can find.Sjö (talk) 08:09, 12 March 2011 (UTC)

Not exactly what I was looking for but http://www.talkorigins.org/indexcc/CB/CB141.html mentions the common house mouse and the plant genus Clarkia.Sjö (talk) 08:17, 12 March 2011 (UTC)

Strange breakers on Japanese Tsunami

There is a strange looking video of the tsunami coming onshore on CNN [19] (I can't figure out how to link to the video directly, you need to click on "Witness deals with quake terror" in the video gallery"). The wavefront is showing breakers only over a narrow and very well defined front. It does not seem to be due to the wave passing over an undersea obstruction as the breakers are long lasting and continue to show all the way in. What is the explanation for this? SpinningSpark 16:47, 11 March 2011 (UTC)

I also saw it. My impression is that the ground surface along that "strip" was different from the ground on either side of it - turbulent flow over a rougher surface flanked by less turbulence where the substrate is smoother. It also looked like the depth of the water in that area was only a metre or two so even relatively minor "texture" differences could cause a substantially different amount of visible turbulence on the water surface. Roger (talk) 19:41, 11 March 2011 (UTC)

It may be due to a sand bar. The shallower the water, the closer the waves and the more likely they are to break. In WW2, the spacing of the waves measured from aerial photographs was used to estimate the depth and slope of the D-day beaches using a mathematical formula. I have been unable to find an article about this formula: the nearest I could get is this Waves and shallow water but there may be a better article hiding somewhere. 92.15.24.90 (talk) 20:15, 11 March 2011 (UTC)

(edit conflict, replying to Roger) Yes, that's the obvious conclusion but I remain unconvinced for a couple of reasons. Firstly, the wake behind the breakers is ruler straight and constant width as if it was following a road, yet the effect continues up the beach where there is no sign of any lateral change in colour or texture of the substrate - I am sure that a change from sand to shingle, for instance, would be visible in the picture and such natural features are rarely so unnaturally straight. Secondly, I believe tubulence and/or friction caused by the substrate would cause a reduction in the wave velocity, but this is not borne out by the perfect straightness of the wavefront through the turbulent and non-turbulent sections. SpinningSpark 20:21, 11 March 2011 (UTC)

The type of wave may be a spilling breaker which explains why it keeps frothing for a long time. The second issue is why the white breaking part of the wave seems to keep a constant width for so long. This might be an illusion. The wave may be breaking as the instability in the crest and the resulting turbulence is spreading sideways at some fixed speed. Observed at a beach, such a domino-effect may seem rapid, but the same velocity observed from a helicopter seems small. Especially as we visually measure it not in metres per second but in percentages of the already wide breaking crest. It must also be taken into account that waves with a longer wavelength travels faster, so again our beach-aquired intuition about the forward speed of a wave versus the sideways spread of a collapse may not be correct. EverGreg (talk) 22:24, 11 March 2011 (UTC)

Looking at these videos, what seems striking is that the waves are actually able to move water upward in a given spot for a long period of time. In other words, there's a vast long hump of water with a strong horizontal momentum, so that it can wash right up over an obstacle. So I think we're seeing water that not merely is passing over a submerged obstacle, but which is actually striking an object that projects above the point where its surface was. Even so, it just vaults up over it and moves on. Wnt (talk) 07:10, 12 March 2011 (UTC)

The effect of the water piling up is due to the wave entering shallow water and is a "normal" effect of tsunamis. Unlike normal waves which are only on the surface, tsunami waves occupy the full depth of water. The foot of the wave is slowed by the substrate and the rest of the water piles up on top of it. SpinningSpark 09:07, 12 March 2011 (UTC)

Air circulation

What is the name for a large body of rotating air, something like an ocean gyre but in the air? --T H F S W (T · C · E) 19:38, 11 March 2011 (UTC)

A cyclone or anticyclone, depending on which way it is rotating. Looie496 (talk) 19:45, 11 March 2011 (UTC)

Note that the direction of rotation is different either side of the equator. Cyclones rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere and anticyclones do the opposite. The distinction that is not location dependent is that the pressure in a cyclone decreases towards the middle and in an anticyclone it increases towards the middle. Cyclones are also called low pressure cells and anticyclones are high pressure cells. Roger (talk) 19:55, 11 March 2011 (UTC)

Note that an ocean gyre is a more or less "permanent" pattern of circulation, though, lasting many thousands of years, at least, while a cyclone or anticyclone only lasts a small portion of a year. StuRat (talk) 23:25, 11 March 2011 (UTC)

The gyres are propelled by the winds. Specifically, they are propeled by the westerlies and the trade winds. The presence of the oceans forces the ocean motion into the gyre patterns. Dauto (talk) 00:56, 12 March 2011 (UTC)

This should be a synch...

There was recently a case where a baby was delivered at the side of the road, by the (non-medical) father, with paramedics on the phone. One thing the paramedics advised baffled me. After the baby was delivered, they said it was important to synch off the (uncut) umbilical cord, to prevent continuing blood flow between the mother and baby. Since no other string was available, the paramedics advised him to use the shoelaces from the shoes he was currently wearing. I can't imagine a less sterile item than those laces, and cringed when I heard that advise. So, my Q is, why is it so important to stop the blood flow immediately, rather than just wait for the ambulance to arrive ? StuRat (talk) 20:26, 11 March 2011 (UTC)

Just by the way, I think you mean cinch. --Trovatore (talk) 20:28, 11 March 2011 (UTC)

Thanks, I wasn't sure how to spell that, as it's not a word I normally use, at least in writing. StuRat (talk) 23:16, 11 March 2011 (UTC)

Why does the shoelace or whatever is used to tie the umbilical have to be sterile? The cord and placenta will be discarded soon anyway and the cord will be cut and properly clamped with a clean clamp when the ambulance arrives. The cord must be shut off asap because if it isn't nothing would prevent the baby's blood draining out through the placenta after it detatches from the uterus, which can happen very soon after the baby is born. Not shutting off the umbilical cord will result in a dead baby within minutes wheras a dirty shoelace might have a slight chance of making the baby ill hours or even days later - the choice is a no-brainer. Sterility is in any case massively overrated as a requirement for people who have normal functioning immune systems. We survived for millions of years without even having the concept of germs or sterility. Roger (talk) 20:43, 11 March 2011 (UTC)

We also survived for millions of years without the thumbs necisary to tie a knot or build a clamp, so shutting off the cord must not be manditory (although it might lower the death rate of baby and mother). —Preceding unsigned comment added by 205.193.96.10 (talk) 21:23, 11 March 2011 (UTC)

Animals bite off the umbilical cord, probably not a method that would be prefered by human fathers. Wouldn`t squeezing the cord shut and waiting for the ambulance work too, though, without creating risk for infection? ~~Xil (talk) 22:18, 11 March 2011 (UTC)

I'm not sure how biting the cord off would help prevent bleeding - it would increase it, surely? You'll probably need your hands for other things. Taking care of the mother and baby, delivering the placenta, etc.. Using a shoelace is the standard advice. --Tango (talk) 22:28, 11 March 2011 (UTC)

Yes, I would think biting off the cord would both cause bleeding and infection, due to all the germs in saliva, and the presumably undeveloped immune system in the offspring. What prevents these things from happening ? StuRat (talk) 23:19, 11 March 2011 (UTC)

I`m just saying that the argument about no thumbs might be invalid, I am not sure how the said animals don`t bleed to death. I believe in olden days they would cut the cord and tie a knot in it, not sure, if it is right, though, couldn`t find any quick information ~~Xil (talk) 00:38, 12 March 2011 (UTC)

As long as the unbilical cord is intact and not bleeding, then there is no route for infection to get it so you don't need to worry about sterility. Anyway, worst case scenario: you have to give the baby a shot of antibiotics. Not a big deal. We do (of course) have an article: Umbilical cord#Clamping and cutting. It doesn't discuss infection, but does discuss the pros and cons of clamping quickly, slowing and not at all (there doesn't seem to be a lot of difference). --Tango (talk) 22:28, 11 March 2011 (UTC)

March 12

Starvation and blindness

I have read that starvation can lead to temporary vision loss (and when the patient is returned to his or her regulat diet, the vision problems go away), is this true, and how?—Preceding unsigned comment added by 142.1.253.163 (talk) 21:08, 11 March 2011

If you have a vitamin A deficiency, you can go blind. Clarityfiend (talk) 01:29, 12 March 2011 (UTC)

how does a vacant space,hole( in electronis) have a mass?

in electronics mass of hole is considered . Hole is a vacant space created when electron is migrated to conduction band from the valance band. how can this free space have a mass? —Preceding unsigned comment added by 117.197.192.72 (talk) 01:24, 12 March 2011 (UTC)

It is not a real mass. It is an effective mass which basically mean that the hole moves around displaying a behavior which can be interpreted as if it was a particle with mass. Think about it. The hole moves about by having electrons jump from neighbor regions and filling the hole and living a vacancy behind. This motion is not instantaneous and respond to external forces (such as an external electric field) in such a way that we can interpret the whole thing as if a particle with positive charge and some non-zero mass was there. That's the hole. Dauto (talk) 02:19, 12 March 2011 (UTC)

Beyaz and Natazia

Where is the page for Beyaz so short at the moment? At the same time where is the page on Natazia as well? Basically, I would like to learn more about these birth control options. — Preceding unsigned comment added by Mybodymyself (talk • contribs) 03:57, 12 March 2011 (UTC)

WP does not have information on everything - yet. The article on Beyaz is short because no-one, including you, has added more information to it. The article on Natazia does not exist for very similar reasons. If you put 'Natazia' into google you will receive about 84,000 hits, some of these contain excellent information about Natazia. Richard Avery (talk) 08:23, 12 March 2011 (UTC)

Why is blood typing routine in Mexico, but not in the United States?

Question: Why is blood typing routine in Mexico, but not in the United States (outside of the contexts of blood-donation or surgery)?

Context: I'm in my mid 30s, was raised in the United States, now living in Mexico. I've never donated blood (shame on me!) or had surgery (knock on wood). Therefore I've never had any occasion to have ABO or Rh(D) blood-typing done. Neither I nor my parents know my blood type. (Father is A, mother is B, so I gather I could be anything, depending on their relative zygosity; no, I'm not asking you to determine paternity!).

It seems I'm not that unusual for someone from the USA; according to this website, 60% of Americans don't know (warning: this site also advocates the blood-type personality/diet quackery). More anecdotal confirmation: 1402 people on a US website professing blood-type ignorance.

Arriving in Mexico City, it appears that everybody here knows their blood type. It is requested on the driver license application, as well a myriad other government documents; it appears on taxi-driver medallions posted in every (legal) taxicab's rear passenger-side window. If the subject comes up, without fail every Chilango is incredulous that I don't know what to them is as basic a piece of personal information as one's birthdate or second (maternal) family name (whoops, I fail there, too!).

One Mexican friend has gone so far as to call my mother negligent and my doctor an idiot. "You need to know in case you're in an accident and need a blood transfusion!", she says. I reply, "My US doctor told me, 'You only get tested at the moment it becomes necessary, in the ER or blood donation van'." "But there's no time in an emergency! You could die while they're testing you!" Cue hysterical screaming.

More anecdotes: One of the poorest municipal governments in Mexico offers free blood-typing analysis

A Mexico State legislator proclaims obligatory blood type testing to be an unnecessary and irrelevant requisite for registering schoolchildren, implying that the practice is currently standard.

So what accounts for this difference? I accept my facts are all very anecdotal (perhaps there's a MEDLINE article somewhere beyond my search-fu), but what, if anything, could this say about respective medical practices/bureaucratic zeal of each society? Or other countries? Sorry for being long-winded!

--189.227.64.126 (talk) 04:03, 12 March 2011 (UTC) Gringo seudoanónimo

Knowing your blood type is useful for you and, really, only you. If you don't want to take the time to get a test (free from many places), then it is all on you. Once you decide to try and have children, then your blood type is important for the child also because there are possible complications based on the compatibility of the mother's and father's blood type. Chances are the mother's doctor will have both the mother and father checked. When my wife was first pregnant, her doctor had by blood type checked even though I already knew what it was - just to be sure. Beyond that, anything that may happen in which your blood type is important to others will include a blood type check. -- kainaw™ 04:20, 12 March 2011 (UTC)

I should have answered about the need for blood transfusion. It is safe to use O- blood while your blood type is checked (which takes minutes in an emergency, but 20-30 minutes under normal circumstances). By the time you finish some O- blood, your blood type will be known and you will likely be given your specific blood type. If, for some reason, there is no O- blood, O+ is usually safe to start with (with very rare complications). From what I've seen, O+ is usually in higher stock levels than O-, but I don't think that is because there is simply more O+ blood donated. I think it is because O- is used more. But, I never checked donation/usage statistics on that. I spend my time at the Red Cross doing experiments on how donating blood affects hypertension, diabetes, and hypercholesterolemia. I've only been surprised once: donating blood increases blood pressure for a few hours. Then, it is lowered for a couple days. I assumed it would be lowered for a few hours and then return to normal. But, it is late and I'm drifting quickly off topic. -- kainaw™ 04:27, 12 March 2011 (UTC)

(edit conflict)In an emergency, Rh-negative type O blood can be transfused about as safely as type-matched blood that has not been cross-matched. Thus, it's arguably more efficient to maintain a stock of type O blood than it is to depend on typing everyone and assuming that the blood type document they carry is accurate (many people carry identification that belongs to someone else, for a variety of reasons, and might not be in condition to explain during an emergency). As our Rh article I just linked points out, Rh negativity is much less common than Rh positivity, hence O^- donors are significantly less common than O⁺ donors. -- Scray (talk) 04:42, 12 March 2011 (UTC)

Tokyo's earthquake

2011 Sendai earthquake and tsunami: Most news sources claim that this earthquake is the biggest one ever recorded in Japan's modern history. However, Tokyo only experienced a seismic scale 5+ quake this time (thanks to the distance). This is big but not as big as the city-devastating quake the scientists warned about. So far most damages were caused by tsunami rather than the quake. Much of the city survived the quakes.

• http://www.jma.go.jp/jp/quake/20110311145349391-111446.html
• http://www.jma.go.jp/jp/quake/20110311150154391-111446.html

東京都　　震度５強　東京千代田区大手町　東京江東区東陽 ...

Tokyo Metropolitan area, seismic scale 5+: Chiyoda Ward, Koto Ward, ...

Does it mean that this earthquake is still not the big one feared by the scientists? -- Toytoy (talk) 04:20, 12 March 2011 (UTC)

The big earthquake that was to destroy Tokyo aka the next Kanto Quake was due in 1995. 139.130.57.34 (talk) 04:36, 12 March 2011 (UTC)

I think this was the big one feared by scientists. It may not have been directly on-target, but an 8.9 earthquake sure does release a lot of energy. I think it will be a while before the next big one. --T H F S W (T · C · E) 05:19, 12 March 2011 (UTC)

I noticed that very few buildings in Tokyo collapsed because of the earthquake. Much of the subway system remains undamaged. The tsunami caused much more damage than earthquake. Japan's buildings survived the seismic scale 5+ quake. Since there are many more faults even closer to Tokyo may cause earthquakes, I doubt that the next big one is still waiting to happen. However, this disaster reminds us the seriousness of tsunamis. They are probably even worse than earthquakes.

This earthquake is MUCH larger than the Great Hanshin earthquake of 1995. However, since the Hanshin earthquake's epicenter was almost under the cities, many highly-developed metropolitan areas experienced seismic scale 6 to 7 rocking and shaking. Buildings collapsed. People were killed or rendered homeless. This time Tokyo's citizens suffer much less. On the other hand, people living in some coastal areas were wiped out completely because of the killing tsunami. -- Toytoy (talk) 08:11, 12 March 2011 (UTC)

INDIA A SUPER POWER

I AM A STUDENT FROM GOA,INDIA. I AM A SCIENCE STUDENT OF 2011 BATCH. I THINK INDIA HAS A MULTIDIMENSIONAL MILITARY FORCE TO SECURE ITS TERRITORY AND ENOUGH MILITARY STRENGTH TO COMBAT ANY A THREAT.