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May 2

How do scientist/astronomer figure out the star loss mass at giant/supergiant tip

I have heard when higher mass main sequence runs out of hydrogen and fuse helium by the time they get to giant or supergiant tip they lose roughly 7/8 of their mass. I don't know how do scientist figure out the variables, if the variable are guaranteed to be right, or they can as well guess out. I hear when sun gets to giant tip it will lose roughly 1/3 of the original mass, previous calculations shows 1/4. Do scientist even know how much mass sun will have lost when it gets to RGB and AGB tip, or they just group all the stars together and find a pattern. Or the variables they present is at least 70% cavity guess. Is there ways to say how much accuracies and errors academic research documents contains. Or the best answer is some academic paper contains more error, some academic paper may contain more accuracies. Is Academic research paper (=) dumping information they have available (+) fill in the gap (any missing and uncertain cavities they make wild guess). The thing is most people cannot see the guesses research documents have.--69.233.254.115 (talk) 01:30, 2 May 2013 (UTC)[reply]

Oops, everything is found over [1]. I forgot the query type so long ago.--69.233.254.115 (talk) 01:43, 3 May 2013 (UTC)[reply]

OK, glad you found it. I'll mark this Q resolved. StuRat (talk) 07:00, 3 May 2013 (UTC)[reply]

Resolved

Temple of the rats

See Karni_Mata#The_legend. Apparently rats are protected and fed there. So, what controls their population ? StuRat (talk) 03:53, 2 May 2013 (UTC)[reply]

From what I understand, they're only protected as long as they remain in the temple. When they venture outside, they are are at the mercy of their natural predators. Plasmic Physics (talk) 03:56, 2 May 2013 (UTC)[reply]

If I brought a few pet cats in, would that be trouble? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:05, 2 May 2013 (UTC)[reply]

I imagine 20,000 rats would make short work of "a few pet cats".--Shantavira|^{feed me} 15:26, 2 May 2013 (UTC)[reply]

That might depend on the sizes of the cats and the rats. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:38, 2 May 2013 (UTC)[reply]

A rat terrier would be a lot more trouble. Looie496 (talk) 16:58, 2 May 2013 (UTC)[reply]

Whatever it takes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:13, 2 May 2013 (UTC)[reply]

Hemorrhoid infections

Why don't hemorrhoids instantly become infected or cause serious infection that would surely result if an open wound on some other body part were so directly exposed to feces?68.36.148.100 (talk) 04:09, 2 May 2013 (UTC)[reply]

They are covered with "anoderm" (kinda like skin) - that presumably prevents fecal material from entering and infecting. SteveBaker (talk) 04:13, 2 May 2013 (UTC)[reply]

Butt, some break don't they? The blood in stool article says they are the #1 reason for it.68.36.148.100 (talk) 04:18, 2 May 2013 (UTC)[reply]

Only in New Jersey. Otherwise, see the section about fissures. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:39, 2 May 2013 (UTC)[reply]

Wow, I wanted to ask this exact same question a few days ago. Yes, it certainly seems that if blood gets into stool then stool might get into the blood. I wonder if there is some special amped up immune response in that area, and, if so, if we could learn to extend that the the rest of the body, when needed. StuRat (talk) 04:49, 2 May 2013 (UTC)[reply]

Best typo ever. Evanh2008 ^{(talk|contribs)} 01:54, 3 May 2013 (UTC)[reply]

Found [2], [3] but neither is quite what I'd call an answer. Wnt (talk) 01:37, 3 May 2013 (UTC)[reply]

Deballocker

Is it true that in World War 2, the Germans used a type of landmine that was specially designed to castrate its victims rather than kill them? 24.23.196.85 (talk) 05:36, 2 May 2013 (UTC)[reply]

Our article Anti-personnel mine explains that such mines are usually intended to injure, not kill, their victims. I guess that the German S-mine could earn a reputation as designed for castration since it was launched about a metre into the air before detonating. However, there is no way that the S-mine or other mines of the same type could be accurate enough to castrate someone, except by chance. Sjö (talk) 05:45, 2 May 2013 (UTC)[reply]

I agree - damage to the enemies' legs was the real goal of these things - take people out of action as effective combatants - but without killing them, so they clog up the medical facilities, consume resources behind the lines, slow any advance, cause uninjured fellow soldiers to take extra risks to save them...that kind of thing. Castrating someone won't necessarily stop them from fighting again in the future - but ripping their legs to shreds most certainly will. SteveBaker (talk) 13:15, 2 May 2013 (UTC)[reply]

On a pedantic note shouldn't it be "debollocker". Richard Avery (talk) 13:23, 2 May 2013 (UTC)[reply]

'Ballocks' is a known alternative spelling. Chaucer uses it in (I think) the Pardoner's Prologue, and there's a type of Renaissance fighting-knife known as a ballock-dagger (apparently due to the handle-shape, rather than any potential target). AlexTiefling (talk) 15:36, 2 May 2013 (UTC)[reply]

The late Kingsley Amis steadfastly used the spelling 'ballocks', and I think his son inherited the affectation. AndrewWTaylor (talk) 21:08, 2 May 2013 (UTC)[reply]

There is a famous letter to Abraham Lincoln which (among other things) urges him to "call my Bolics[sic] your Uncle Dick." Interesting that the word now seems to have died out altogether in the States... Tevildo (talk) 23:18, 3 May 2013 (UTC)[reply]

Richard, best to be frank about this. It's clear that pedantry is not your true calling (which may make you very happy). Your pseudopedanticism is betrayed by the absence of a comma after 'note' and a question mark at the end of your question. There are still openings at my Winter Pedantry School; special rates for Wikipedia editors. :) -- Jack of Oz ^[Talk] 20:53, 2 May 2013 (UTC) [reply]

We should also consider the effect such a weapon would have on enemy morale. While a dead soldier returned home and buried with honor can actual inspire patriotism, a live soldier returned home, but missing a few key bits and pieces, can rather have the opposite effect. Not many men will rush to the recruiting office after seeing that. StuRat (talk) 07:05, 3 May 2013 (UTC)[reply]

D&D vets know the S-Mine as "the ultimate balls check" - when it pops up, it'll determine with scientific rigor whether its or your balls are harder. With extreme prejudice.

Oz: Do I get discount if I take ten? - ¡Ouch! (^{hurt me} / _{more pain}) 08:21, 3 May 2013 (UTC)[reply]

By all means. You understand, of course, that you will be required to exhibit decilocation, and empower each of your decuplicate presences to have a separate one of your ten personalities. The auditors get a bit funny about me teaching an apparently almost empty classroom. -- Jack of Oz ^[Talk] 09:23, 3 May 2013 (UTC) [reply]

Of the S-Mine:- "...there were extraordinary escapes. The chaplain of the 5th Seaforth Highlanders trod on one which bounced up and knocked his glasses off; perhaps divine intervention prevented the main charge from exploding. Pfc Larry Treff of the US 26th Division was lucky enough to have one bounce up and hit him in the groin without exploding; he was thrown several feet but survived with minor injuries, though his groin area was 'so purple and swollen' that he was temporarily immobile."[4] Alansplodge (talk) 16:13, 3 May 2013 (UTC)[reply]

(un-indent) Thanks, folks! So I gather that German landmines in WW2 were designed to maim, but not specifically to castrate. 24.23.196.85 (talk) 19:39, 4 May 2013 (UTC)[reply]

Yes. Sadly, as usual, it takes us an entire page full of babble and small asides to come to that clear statement! SteveBaker (talk) 15:46, 5 May 2013 (UTC)[reply]

Deriving the momentum operator.

In quantum mechanics, given the canonical commutation relation $[{\hat {x}},{\hat {p}}_{x}]={\hat {x}}{\hat {p}}_{x}-{\hat {p}}_{x}{\hat {x}}=i\hbar$ and ${\hat {x}}=x$ , how can one derive the result ${\hat {p}}_{x}={\frac {\hbar }{i}}{\frac {\partial }{\partial x}}$ ? I was told that this can be done, though I am unsure how to go about doing this. -- — Trevor K. — 05:40, 2 May 2013 (UTC) — Preceding unsigned comment added by Yakeyglee (talk • contribs)

Well, you can show calculate the commutator

[{\hat {x}},{\hat {p}}_{x}]

as follows. If F is any function of x, then

[{\hat {x}},{\hat {p}}_{x}](F)=({\hat {x}}{\hat {p}}_{x}-{\hat {p}}_{x}{\hat {x}})(F)=x{\frac {\hbar }{i}}{\frac {\partial }{\partial x}}(F)-{\frac {\hbar }{i}}{\frac {\partial }{\partial x}}(xF)=x{\frac {\hbar }{i}}{\frac {\partial }{\partial x}}(F)-\left(x{\frac {\hbar }{i}}{\frac {\partial }{\partial x}}(F)+F{\frac {\hbar }{i}}{\frac {\partial }{\partial x}}(x)\right)=-{\frac {\hbar }{i}}F=i\hbar F

Strictly speaking, this is a confirmation rather than a derivation. It shows that

{\hat {p}}_{x}={\frac {\hbar }{i}}{\frac {\partial }{\partial x}}

satisfies the canonical commutation relation, but does not show that it is the only solution. Gandalf61 (talk) 08:02, 2 May 2013 (UTC)[reply]

It is a consequence of the De Broglie relations as can be seen in the article titled - of all things - Momentum operator. Dauto (talk) 19:20, 2 May 2013 (UTC)[reply]

this page has a derivation of the reverse relation where x = i hbar d/dp in the momentum representation (start at equation 198). The proof you're looking for is completely analogous. Dauto (talk) 19:36, 2 May 2013 (UTC)[reply]

There is a subtle issue involving the theory of distributions involved here. I tried to look this up, but I can't find it in my old university lecture notes. Basically, the argument should go as follows. We want express <x|p|psi> in terms of <x|psi> by invoking only the commutation relation and nothing else. Let's write:

<x|p|psi> = Integral dx' <x|p|x'><x'|psi>

Then we can evaluate the matrix element <x|p|x'> as follows:

x <x|p|x'> = <x|x p|x'> = <x|i hbar + p x|x'> = i hbar delta(x-x') + x' <x|p|x'>

Therefore, we have:

(x-x') <x|p|x'> = i hbar delta(x-x')

The problem is then that can't just divide both sides by x-x', as that doesn't yield a bona fide distribution. If have the equation x T = delta, where we use the official math notation T(f) for a a distribution T acting on a test function f, the solution is not T = 1/x delta, as that doesn't define a distribution, rather it is T = -delta' + A delta. We have

x T(f) = T (x f) = -delta'(x f) + A delta (x f) = delta[(xf)'] = f(0) = delta(f)

We thus have:

<x|p|x'> = -i hbar delta'(x-x') + A delta(x-x')

This then gives:

<x|p|psi> = Integral dx' <x|p|x'>psi(x') = -i hbar d psi(x)/dx + A psi(x)

The constant A must be put to zero by hand. You can always add a contant times the identity to an operator without that affecting the commutation relations. Count Iblis (talk) 15:45, 3 May 2013 (UTC)[reply]

Inert gas

I was reading Nitrogen asphyxiation and it says suicide using inert gas doesn't cause pain. Is that really true? Btw I'm NOT thinking about suicide just wondering cuz it's pretty crazy that you can die without feeling pain. Money is tight (talk) 08:04, 2 May 2013 (UTC)[reply]

Yes, it is logical that it is painless. Otherwise, how else could there be accidental death by this manner? Plasmic Physics (talk) 08:09, 2 May 2013 (UTC)[reply]

Since four fifths of the air we breathe all the time is nitrogen, our bodies are quite tolerant of it. What you're really talking about here is removing the oxygen from the air so that you're breathing 5/5ths nitrogen. If you tried to breath only carbon-dioxide (for example) you'd start hyperventilating and all sorts of nasty things would result because your body is aware that CO2 needs to be dealt with - but we breathe mostly nitrogen all the time - so our bodies don't notice anything except the lack of oxygen.

So we might as well forget about the nitrogen here. What we're talking about is lack of oxygen - Hypoxic hypoxia - and anoxia...some of the symptoms of this are:

Cyanosis -- you "turn blue" as your blood loses oxygen.
Headache -- not completely painless.
Visual impairment, decreased reaction time and impaired judgment time -- hardly painful.
Numbness, drowsiness and euphoria -- At least that's going to make the headache seem less bad.
Lightheaded or dizzy sensation, tingling in fingers and toes -- not exactly painful but unpleasant.
Nausea -- also not great.

But it depends on how fast it happens. The above symptoms are likely if the reduction in oxygen is relatively slow...but if it's fast then seizures (painful - and might cause you physical injury through falling or something) and if you're a man, priapism (which can be very painful) are also possible.

The amount of time it takes (and therefore how long you suffer these symptoms) is also tricky to get a grip on. If you still have oxygen rich air in your lungs, you can hold your breath for maybe 30 seconds - but if you fill them with pure nitrogen by hyperventilating, you could lose "useful" consciousness in under 10 seconds.

I think the devil is in the details here.

SteveBaker (talk) 13:07, 2 May 2013 (UTC)[reply]

In almost any situation where someone takes a sedative toxic substance like drugs or alcohol in sufficient amounts to kill them their death will be preceded by drowsiness leading to sleep and then coma, during which it is extremely unlikely that they will be conscious of pain. Indeed, enormous numbers of people die every day under the influence of pain relieving medication in hospitals and hospices all over the world. Richard Avery (talk) 13:19, 2 May 2013 (UTC)[reply]

Any exertion speeds up the effect. If firemen come running into a computer room where some inert gas has been released to suppress flames they may immediately fall down, if this happens just hold your breath, go in and drag them out straight away into the fresh air. Dmcq (talk) 13:45, 2 May 2013 (UTC)[reply]

I presume that there are two reasons for that though: Firstly (as I said above), when you're breathing hard (as you would be if you were running with all of that fireman's gear on) then whatever oxygen would otherwise remain in your lungs gets flushed out and replaced with the inert gas more rapidly than if you were breathing at a steady pace. Secondly, the exertion increases your oxygen needs so whatever oxygen is left in there gets used up more quickly. However, if holding your breath and then exerting yourself to get a victim out of there actually works - then the former is clearly of much more importance than the latter. SteveBaker (talk) 14:21, 2 May 2013 (UTC)[reply]

Certainly does as four firemen neatly laid out on the grass can testify ;-) I must admit the gas seemed a bit excessive as it caused damage to the ceiling with the extra pressure when it was released. Dmcq (talk) 14:49, 2 May 2013 (UTC)[reply]

Sorry guys, your answers here are a little messed up. Some bullshit has been posted above. Several things to note:-

Presumably SteveBaker meant increased reaction time.
Fireman are NOT in the least bit likely to immediately fall down, or even fall down after a while, if they enter a computer room where gas suppression was used, for several reasons, the most important of which are:-
The most common system used is Inergen and similar - in these systems the amount of inert gas is selected such that the oxygen content is brought down (by displacement) to about half normal, i.e, roughly 10% by vol. Almost all computer room fires go out at this level, and the ones that don't (such as burning paper) slow down dramatically. The gas mix also contains carbon dioxide, so that the room carbon dioxide is raised from the natural level of 0.03% to about 0.1%. This raises the blood CO2 level similarly, which stimulates humans to breath harder, so that the blood oxygen remains close to saturation. Less commonly, CO2 suppression has been used, as it has been in aircraft flightdecks. If you enter a room where it has been used, you will know it from the sensation (assuming you didn't notice the mandatory flashing lights and bell), and you will get out.
Take a typical fit male human: say 80 kg weight. By standard medical calculations, such a male will have 7% of body mass as blood, i.e., 5.6 kg of blood. Each kg of blood has very nearly 210 mL of oxygen bound to haemogobin per kg of blood, i.e., our 80 kg fireman has 1.2 litres of oxygen stored in his haemoglobin, not counting oxygen dissolved in plasma. Male lung total capacity is aprox 0.53 litres per 10 kg of body mass, so our 80 kg fireman will have about 0.2 x 0.53 x 8 = 0.85 litres of oxygen in his lungs on entry to the room. Total oxygen he has is then 0.85 + 1.2 = 2.05 litres. No problem will occur until blood oxygen drops below 90% saturation. A fit male exercising (assume fireman has run up the stairs) will consume oxygen (the VO2 rate) at approx 50 ml/kg/min. So he will consume 4 litres per min and it will take him about 30 seconds before any distress or problems occur at all. It will take a full minute in a zero oxygen atmosphere before he has much distress - plenty of time to either get out or put on oxygen mask, even if there is NO oxygen in the room. However, as there will be about half the normal level, he would have TWO full minutes to take action. Even if he has all oxygen flushed out of his lungs upon entry, he can still fully function on blood oxygen for one minute.
Firemen are trained - they won't be that silly.
Those of us who have flown in an airliner will recall the safety instructions - where they tell you that should a sudden decompression occur (which roughly halves the oxygen partial pressure), put on your oxygen mask, but it isn't urgent - you have plenty of time to ensure your childen have their masks on and working before you put yours on.

I have witnessed a test dump of Inergen gas in a large computer room - I was in the room at the time. I noticed no ill effects.

I once took a tour of a hospital on an open day. We were taken into an out of service operating theater. An aneasthetist explained all his equipment, one item of which was a blood oxygen saturation monitor, which works by shining light of two wavelengths thru your finger. While he was talking, I put it on - it said my O2 sat was 100%, as it should be for a conscious healthy human not doing anything but stand. I then pinched my nose closed and kept my mouth shut, to see what my blood O2 level would be when I could not hold my breath any longer. The aneasthetist seeing me do this said "There's one in every group!". I kept holding my breath while listening to his talk and glancing often at my watch. After 6 minutes, I could not hold my breath any longer, it was most uncomfortable. My blood O2 saturation was still showing 99%! And, no, the machine was not faulty. When I took a breath, the aneasthetist said "About average, mate."

Ratbone 60.230.212.134 (talk) 15:36, 2 May 2013 (UTC)[reply]

I assure you that what I said was true. There was a fifth fireman who called for help from a bunch of students to get his colleagues out and they revived quite quickly when brought out but whatever you say they did collapse going into the room. And yes they did look a bit sheepish about having ignored the warning light outside the room. We gave them some tea and a biscuit and they went away again. The point about some gases is you don't notice the effect until you conk out and if you have not been running you probably are okay for much longer. Dmcq (talk) 16:04, 2 May 2013 (UTC)[reply]

Well, my calculations are verifiable from relevant wikipedia articles and elsewhere. What you describe is simply not possible with Inergen systems and it's competitors. It could happen with a CO2 system, but only if a) the gas dump was excessive, meaning it had not been tested per code requirements, and b) they were really stupid firemen. While you can conck out without distress with inert gasses, entering a room with CO2 produces immediate distress, even with plenty of oxygen. Remember that: normal oxygen content of air is 20%; you need much less than that to function; air CO2 is less than 0.03% and any increase triggers heavier breathing. CO2 has been a standard system to put out aircraft cockpit fires. Not much point if it puts the pilots out as well. What country was this in?

The only other possiblity I can think of - if lead acid batteries had been used in a UPS system, people can be overcome by stybine gas - stybine is a product of antimony in the pressence of water and other substances. However, a) the fire woukd have to have reached the batteries, b) the batteries would have to be the type using lead antimony plates, not normal in UPS service, and c) you cannot recover spontaneously from stybine inhalation. Ratbone 60.230.212.134 (talk) 16:12, 2 May 2013 (UTC)[reply]

Believe what you wish but I have not said a single untruth in all the time I have been on Wikipedia. Dmcq (talk) 16:25, 2 May 2013 (UTC)[reply]

I'm going to call bullshit on Ratbone item #6 recollection of the Emergency oxygen system instructions. FAA advisory AC 121-24C (7/23/03) appendix 1, item #10 states "passengers should be advised to don their own oxygen masks before assisting children with their masks." and I can't recall ever hearing anything else. Time of useful consciousness suggests you really don't have much time to figure out what to do and then do it. DMacks (talk) 17:14, 2 May 2013 (UTC)[reply]

We have an article on Gaseous fire suppression which mentions several different kinds with different methods of action. Rmhermen (talk) 17:16, 2 May 2013 (UTC)[reply]

Yes, I got #6 round the wrong way. I note that the article cited by Rmermen gives times, designed so that an elderly passenger of unknown fitness or baby with mimimal oxygen capacity will be catered for, gives cruise altidue (and therfore roughly the same oxygen partial pressure) times of the same order I calculated for a fireman, who can be expected to be in excellent fitness and do much better. And, as I said, firemen should not need to spend much time figuring out what to do, because they are trained - which is why I find it hard to believe that 4 firemen would enter a CO2 supprosssed room ignoring the signs, lights, and sound, and if they did, they should recognise the meaning of their immdeiate distress (from their training) and leave. Ratbone 121.215.74.116 (talk) 01:06, 3 May 2013 (UTC)[reply]

I remember seeing a doco film about capital punishment where they illustrated the painlessness of nitrogen asphyxiation by placing a pig in a room with a feed trough in a fume cupboard that recirculated 100% nitrogen. The pig would stick its head in to eat, pass out from lack of oxygen and fall outside where it would resume normal breathing of air, then wake up and stick its head back in. As for Dmcq's suggestion that you hold your breath and try to save people that have been overwhelmed by some gas; both my confined space and certified atmosphere tester training are telling "don't do that". Most industrial fatalities involving gasses are from trying to save someone else. Only emergency response personnel should take part in rescues of this type. 202.155.85.18 (talk) 02:48, 3 May 2013 (UTC)t[reply]

Well the last one did come out for help rather than going in himself and I'd guess it was pretty safe as there were a number of people around, it wasn't as though they had to go far. Whatever about that one should wait for trained people I would have difficulty with sitting around letting people die, and I can swim 50 meters underwater quite easily so I really don't see there would be a problem. It was rather a few years ago so I'd guess their training is better now. Dmcq (talk) 08:02, 3 May 2013 (UTC)[reply]

The first thing they teach in first aid courses is "DRABC" - Danger, Response, Airway, Breathing, Circulation. Or the equivalent in other languages. "Danger" in this case means you first check that there is no danger to yourself, BEFORE attempting rescue. I agree with 202.155.85.18 - If I was aware that more than one person collapsed after entering a room, there's no way I would enter. You don't know just why they collapsed, and if you enter and collpse, that just might mean n+1 fatalities instead of just n falalities. You last bit about swimming is self contradictory - if you can function for x minutes without breathing, then so should firemen. The training of firemen won't have changed in this regard since the advent of computer rooms and the like back in the 1950's. What country did this supposed event occur in? Ratbone 121.215.32.211 (talk) 11:34, 3 May 2013 (UTC)[reply]

I have to agree with Dmcq on all points here as most of you appear to be confusing theory with real life situations. Now lets get back to the firemen. Yes they are trained and are not stupid. Yet training costs money. It is more than likely in Dmcq case that these firemen had never before rushed into a building full of Inergen. These call-outs are rare compared to putting out cars, set afire by vandals etc. All the adrenaline is pumping with a focus to get into the computer room as fast as possible and save human life. Yes, the theory that has no doubt been taught to them in the class room leads them to understand you can breath in this atmosphere. Yet. isn't this a little bit like going on holiday and on arrival playing ball with your kids only to find you have collapsed in a gaping heap - because of the altitude. The holiday brochure pointed out the altitude but still you played foot-ball! Yes, the higher CO2 invokes faster lung action but if the available oxygen is only half that as sea level when one's action causes a high biological oxygen demand then whoops. This can happen without warning because of oxygen debt. Put simply, once you have stop running do you immediately stop panting? Of course not. One has to keep a high rate of respiration to stop from passing out. So for a fireman in such a situation. Just suddenly realizing that respiration is distressed, one has left it too late -but hey, in the class room weren't we were told we can still breath in this atmosphere? I would be interested to know from a current fire-fighter if his/her training included the cost of going into an Intergen atmosphere. In the days of Halon, such exercises where prohibitively expensive because fire-services are paid for by local taxation and nobody like paying tax – so they didn't do it. It may be the same to day. Are there any fire-fighters here that have had gas suppression training for real?Aspro (talk) 18:32, 3 May 2013 (UTC)[reply]

I doubt that many firmen would have actually had experience of Inergen during training, because it is expensive. The test dump that I witnessed cost ~$80,000. However, firemen do get to experience oxygen starved and smoke filled chambers during their training - at least they do here in Australia. But they'll get to hear about Inergen in classroom talk.

At least here in Australia, when called out to commercial buildings large enough to have a computer room with fire suppression, their normal practice is to send at least one guy in with breathing apparatus anyway, as burning plastics and electronics in commercial buildings can emit a range hazardous fumes, and rooms can be filled with smoke.

In fire suppression systems, the oxygen content is only brought down to no less than half the normal value. This is well and truely enough to function normally on, providing breathing is stimulated, as the CO2 content of Inergen does. Yes, if you are exercising heavily it won't be enough - after all if we run at maximum speed, we get puffed out in a normal atmosphere. But if the firemen actually collapsed, their body oxygen demand would have drops to the rest value, so they should spontaneously recover - within less than a minute. That's not what Dcmq said. It is possible that if the computer room was in a third world country that Western standards of workmanship, commissioning tests, and firemen training were not up to the situation, which is why I asked twice "what country was it in?" However, as a) Dcmg's intial post reads a hypothethical, but later posts after a challenge changed that, b) it is quite unlikely for technical reasons as explained, and c) Dcmq has not come back and answered the question, I rather think his story is just a story. Maybe he heard about an incident he wasn't personally involved in, and the facts got muddled up in the gossip - chinese wisper effect.

Ratbone 121.215.32.202 (talk) 01:15, 4 May 2013 (UTC)[reply]

As I said above 'they revived quite quickly when brought out'. I am glad standards for construction and firemens' training are so good nowadays that none of the incidents in [5] can happen. Yes I do refuse to say where or when. Dmcq (talk) 09:09, 4 May 2013 (UTC)[reply]

Several things to note about the EPA report you linked to:-

You said the incident occured in a computer room. None of the incidents listed occurred in a computer room.
You said firemen were affected - but the reported incidents involved all sorts of other workers.
The most common gas system in computer rooms is Inergen, which will not aspixiate as expalined. All the reported incidents involved CO2 suppression.
Many of the incidents reported occurrerd in US Navy vessels. I don't know much about the USN, but I do know about the Australian Navy, which largely tries to emulate the USN and mostly buys the same ships and equipment. The Aust Navy is notorious for ignoring civilian safety standards, not training crews properly, and consequently have an accident rate to match.
Many of the incidents occurred in facilities totally unlike computer rooms and may well require a greater degree of oxygen dispalcement than do computer rooms.

Ratbone 124.178.43.47 (talk) 09:26, 4 May 2013 (UTC)[reply]

Inergen was only patented in 1989 and introduced in 1992. I don't know what gas was used. I think I have had enough of this so bye. Dmcq (talk) 09:50, 4 May 2013 (UTC)[reply]

Some are forgetting about partial pressure. In a normal atmosphere a fire fighter might recover in about a minute but CO2 is heavy and forms a low blanket. The lungs can't vent the blood CO2 so quickly in that environment. I was trained to get people out in 20 sec. If anyone collapsed – then were trained to endeavor to drag them out PDQ. One point I remember, is that on recover they may be disorientated – so get them out to a point of safety first. Don't leave them to find their own way out. This is sensible, when you consider how quickly fires can get out of control. For a fire-fighter in unfamiliar surroundings, this disorientation problem is even more critical. The company I worked for had its own fire brigade as first responders and to be in attendance when the professionals arrived, to advise them on where welding bottles and other hazards where situated. Fires can get out of control much faster than one can anticipate. This is why I support Dmcq , because I don't think any of Dmcq critics have actually under gone industrial firefighting instruction. Nor, have they seen the instruction films of actual conflagrations and the aftermath. To rub it in, they often contained graphic images of the remains of people that got it wrong. If fire fighting was a simple as some of Dmcq critics suggest, then we would not have all these deaths. Anyway, you have transgressed well off the OP question in pursuit of your faux augments.Aspro (talk) 18:32, 4 May 2013 (UTC)[reply]

Well, I have been personally involved in the construction of computer rooms as the project Engineer, and been involved in the specification and sign-off acceptance of Inergen fire suppression systems. So I do know something about it. Like 202.155.85.18 I hold Confined Space certification in accordance with Australian Govt legal requirments, as well as a Senior First Aid certificate. It certainly would violate the training for both to enter a room as Dcmq described. Regarding "all these deaths" as you wrote, well, the cited EPA report appears to cover a period of 30 years. There was not one single listing for an Inergen system - they are all CO2 or unstated. In 30 years in the USA (with a population of 270 million and thousands of computer rooms) there was just ONE death! Internationally there was a couple more. Almost all the incidents were not computer rooms. Incidentally, at least in my country, it is a legal requirment that any building that contains storage of hazardous chemicals or gasses must prominently display on the street frontage a standardised warning sign listing the classification of what's there - just so that firemen on arrival will know. When brigades get called out to commercial buildings, they consult their file on that building. Most building probably have no information, but if there is anything that materially alters risks to firemen or how any fire should be fought, the file will tell them. They do inspections now and then. Maybe things are not as good in other countries, though I would be suprised if we do it better than the USA or any European country - that's where we get out good ideas from. Ratbone 120.145.65.37 (talk) 03:28, 5 May 2013 (UTC)[reply]

When I said all these deaths it should have been clear form my context that I was talking about industrial fires in general. As you said: “Almost all the incidents were not computer rooms” Dmcq is obviously talking about an event with a legacy system. These days, buildings may have haz-chem signage but in a large complex there can still be doubt about exactly where the hazard is within, because welding bottles and other stuff are mobile. If first responders are not available to assist, then the whole site gets evacuated, ensuring that the fire can spread. The low death rate with CO2 suppression may be because people got dragged out in time. Your appearing to use modern practices that you have learnt to pass judgement on how thing were back then and their effectiveness, considering the technology available and systems in use back then. Next: “It certainly would violate the training for both to enter a room as Dcmq described.” Lets take a side swipe first. Before going down a coal mine, I was instructed that if I was told to use my respirator (of this type [6] I was to put it on and just calmly walk out – AND NOT TRY AND HELP ANYBODY THAT HAD COLLAPED. Asking 'why' we could not stop to help others, we told that we hadn’t been trained in such a way that we could help without putting ourselves in danger. If we delayed our exist we could collapsed ourselves and so would just present more problems for the rescuers (this respirators only had a 10 minute duration -just time to get into the next clear ventilated passage). Right, back to a conflagration in a commercial complex. Fires can spread so quick some-times that the company I worked for and many other companies, trained some of their staff, so that if an incident occurred we could either quickly deal with it ourselves (and not do something stupid like spaying water on burning aluminium swarf) so by the time it took the fire brigade to arrive, other employees did not end up as the blackened chard corpses that we saw in the training films. In short, your comments seem too insular to add value any to value to Dcmq's comments.--Aspro (talk) 21:55, 5 May 2013 (UTC)[reply]

ITC

I read Isothermal titration calorimetry and couldn't find answer to the following question: In context of protein complexs, in ITC expriment there is a "receptor" in the solution (in the cell), and a "lignad" that is titrated into the cell, is it possible to swap them? would we get the same affinity? (for example suppose we find affinty trypsin-BPTI: will we get the same results when (1) have trypsin in the cell and titrating BPTI, or (2) having BPTI in the cell and titrating trypsin). Thanks, 192.114.91.228 (talk) 10:01, 2 May 2013 (UTC)[reply]

In concept, I don't see why not, but in practice, I think you'd have an issue that you want to add a small aliquot to a larger amount of solution. Because it's hard to purify macromolecules to a very high concentration, you'd be better off using a concentrated chemical to add. Wnt (talk) 17:02, 3 May 2013 (UTC)[reply]

Origin of the belief that parrots eat crackers

Anyone know for sure? I heard that it was something to do with parrots on ships eating hardtack and saltine crackers. Yes, they will certainly eat crackers if available and apparently enjoy them, but it's not their main diet. --31.185.233.239 (talk) 20:52, 2 May 2013 (UTC)[reply]

Obviously. Cracker trees aren't native to the same range as parrots. Well, they do overlap a bit with the range of the Norwegian Blue parrot, but alas, I think that species is no more, ceased to be, expired and gone to meet his maker... --Jayron32 21:09, 2 May 2013 (UTC)[reply]

No, he's asleep!!! Richard Avery (talk) 07:18, 3 May 2013 (UTC)[reply]

And now for something completely different ... The phrase "Polly want a cracker" goes back at least as far as 1848.[7] As Cracker (food) notes, the cracker is said to have been invented in 1792. Clarityfiend (talk) 22:20, 2 May 2013 (UTC)[reply]

Or maybe parrots are all just mildly racist. --Jayron32 23:39, 2 May 2013 (UTC)[reply]

When people first started keeping parrots as pets, you couldn't just head to the nearest pet store and pick up a bag of Purina Parrot Chow. So, crackers were a food item which people had on hand, which parrots could also eat. If we think of the stereotypical parrot kept on a ship, then fresh food would have been only available during, and shortly after, stops at ports. In between, parrots would have to make do with things like crackers, as would the rest of the crew. If you had a parrot with an exceptional vocabulary, he might say "Polly wants some fresh food, but since that's not available, Polly will settle for a cracker". StuRat (talk) 05:44, 3 May 2013 (UTC)[reply]

Isn't this just a meme based on classic children's cartoons, the same as the notion that mice like cheese, which they really don't? μηδείς (talk) 08:18, 3 May 2013 (UTC)[reply]

Did they have classic children's cartoons back in 1848? Or only classic children? -- Jack of Oz ^[Talk] 09:12, 3 May 2013 (UTC)[reply]

Jack, if you first heard this from 19h century literature and not a cartoon or similar juvenile entertainment, I'll eat a roo raw. μηδείς (talk) 19:31, 3 May 2013 (UTC)[reply]

A cartoon or one's mother or whoever may well be where you or I first heard the expression. But the question is about the "origin" (see the header) of the belief behind the expression, hence the origin of the expression itself. It's an etymological matter as much as a scientific one. We've traced it to at least as far back as 1848 at this stage. -- Jack of Oz ^[Talk] 19:40, 3 May 2013 (UTC)[reply]

If you had read the post above then you will see this pre-dates children's cartoons: The Knickerbocker: Or, New-York Monthly Magazine, Volume 34 1849... page 544 [8]. Would you like salt and pepper on you're raw roo or would you rather eat it purely al fresco?--Aspro (talk) 20:01, 3 May 2013 (UTC)[reply]

Yes, and there's still not a single person reading this thread who didn't learn that little bit of obscure high culture from Looney Toons or the like. Next you'll say the first place anyone ever hears Wagner's in the opera house. μηδείς (talk) 02:02, 4 May 2013 (UTC)[reply]

Are you deliberately missing the point? The q is not about when, where and how you or I or Joe Bloggs first heard the expression "Polly want a cracker". It is about how that expression came into being in the first place, and more to the point, why anyone thought a parrot's favourite food would be man-made crackers. The belief and the expression weren't independently created millions of times over. They were created way back when, and ever since then people have been copying other people. -- Jack of Oz ^[Talk] 04:10, 4 May 2013 (UTC)[reply]

Maybe some of those kangaroo meringues that Noël Coward was talking about. -- Jack of Oz ^[Talk] 20:09, 3 May 2013 (UTC)[reply]

Stop it Oz. Your making me feel hungry and my doc has warned me that I'm already 'morbidly' obese. Mind you... a kangaroo meringues does sound like it's light and fluffy and Oh, what the hell, a little mouth-full or two (or three) will not not make any difference. Medeis... add a little garlic to my portion please.Aspro (talk) 20:26, 3 May 2013 (UTC)[reply]

As I recall the classic parrot, Captain Flint, it said "pieces of eight" and ate bark. I never heard "polly want a cracker" until much later, probably as spoken by Disney's parrot in a bit of role-reversal that was lost on me at the time. I suppose a person's predisposed notions about parrot behavior are highly conditioned by the order in which one is exposed to classic parrots in literature and film. Nimur (talk) 15:45, 3 May 2013 (UTC)[reply]

Here's something from 1948,[9] and you can safely assume that the "Polly want a cracker" thing is much old than that. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:04, 4 May 2013 (UTC)[reply]

There's no need for any such assumption. All you need to do is cast your eyes upwards and read where the expression is known to have been in existence exactly 100 years earlier, in 1848. And it almost certainly precedes that. -- Jack of Oz ^[Talk] 20:25, 4 May 2013 (UTC)[reply]

Not for me there isn't. But there might be if someone thinks it originated with a Robin Williams movie. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:51, 4 May 2013 (UTC)[reply]

Sorry, but why did you bother tracking down a 1948 source when we already had an 1848 source? -- Jack of Oz ^[Talk] 01:42, 5 May 2013 (UTC)[reply]

We're all overlooking something... when did parrots get to be named Polly? how do we even assume they're female? or that a male would want to be called Polly? Gzuckier (talk) 21:03, 3 May 2013 (UTC)[reply]

Read the posts above!:“Polly is a diminutive of Poll "as a female name, and name for a parrot," and Poll, altered from Moll, familiar form of Mary, is the traditional name for any parrot. The earliest quotation the OED gives for Polly as a name or designation for a parrot is from Ben Jonson's "Epigrams," 1616. ” If it is a he, then you can you can call him Joe. Or, if he is your-pal you can call him Al. He, she or it, wont care as long as Polly gets a cracker. They might have bird brains but they know how to train the humans around them to give them what they want. Aspro (talk) 21:41, 3 May 2013 (UTC)[reply]

Actually, Molly and Polly come from Mary. Moll or Poll would be single-syllable nicknames for Molly and Polly, as Mare is for Mary. How that figures into parrot names is anybody's guess. Maybe it's from "Paul"? As with the male bird in "Little Poll Parrot". ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:46, 4 May 2013 (UTC)[reply]

Paulie wants a cracker? --Jayron32 03:50, 4 May 2013 (UTC)[reply]

Various google items indicate that Poll is indeed a variant of Paul. So why Paul Parrot? Maybe just because it's nice and alliterative. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:59, 4 May 2013 (UTC)[reply]

I know a lovely lady named Polly. Her legal name is Paulette. -- Jack of Oz ^[Talk] 04:12, 4 May 2013 (UTC)[reply]

You can ask the World Parrot Trust.

World Parrot Trust - Ask an Expert

—Wavelength (talk) 04:28, 4 May 2013 (UTC)[reply]

Paulina cupit crustulum? Even the Romans were familiar with parrots, and could have asked polly if she wanted a cracker. Earliest known attestation is not proof of origin. We do, however, have documentary evidence. μηδείς (talk) 21:20, 4 May 2013 (UTC)[reply]

Maybe not proof of origin, but an earlier attestation still trumps a later one. -- Jack of Oz ^[Talk] 09:14, 6 May 2013 (UTC)[reply]

Electromagnetic induction thru an unclosed ring

in a changing magnetic field. It's easy to see how an EMF comes about in the case of a closed conducting ring fixed in place in a magnetic field, since the the change in flux is related to the change in the magnetic field, while the area enclosed by the ring is constant. But how can we explain what happens in an incomplete ring (suppose a piece of the ring is cut away, leaving it unclosed) on the basis of change in flux ? In other words, how can we define an area here, in the first place (an open ring develops an EMF, but no induced current of course) ? BentzyCo (talk) 21:02, 2 May 2013 (UTC)[reply]

Area enclosed has nothing to do with it. A straight wire moving across a magnetic field will have a voltage induced along it. The voltage is proportional to the length of the wire, the strength of the magnetic field, and the rate at which the field moves in respect to the wire. In the case of a uniform magnetic field moving through a conducting ring that is gapped at one point, there will be no voltage across the gap, as the voltage induced in each half-turn will be the same. In the case of a straight wire subject to a moving/changing magnetic field, which will have a voltage induced along it, current will flow if, and only if, the ends of the wire are connected to a circuit outside the magnetic field (or a part of the field that is of lower intensity). Ratbone 121.215.74.116 (talk) 00:51, 3 May 2013 (UTC)[reply]

Your 1st sentence is wrong. Completely wrong. Do you how AC voltage is produced ? And the rest of your reply is redundant, since you weren't tuned to what was asked and its context. It's an incomplete ring. Stationary. Nothing's moving. Only the intensity of the magnetic field is changing. BentzyCo (talk) 10:38, 3 May 2013 (UTC)[reply]

Well, if you know so much about it, why ask the question?

AC is commonly produced in an alternator, which, at its most basic, is a loop conductor rotating in a constant and evenly distributed magnetic field, the loop being interrupted at the slip rings and connected to a circuit external to the magnetic field. As rotation means, during each half rotation, half the loop is going one way thru the field and the other half is going in the reverse direction thru the field, the induced voltage in each half turn is such that they add around the loop, instead of opposing in the case of a loop moving bodily thru a field. At each half turn, the direction each half turn is moving wrt the field in the opposite direction, thus the voltage at the slip rings reverses. Practical alternators are of course more complex both in conductors and in magnetic arrangements, but all of us who studied electrical engineering have studied simple loop-in-field alternators in 1st year, and, usually, done tests on lab models.

Now back to your loop conductor in your question, any magnetic field not penetrating the conductor cannot be inducing any electric tension in it - so area can have nothing to with it. Or, looking at it another way, you could have a great number of parallelled conductors entirely within a magnetic field, so that a considerable amount of the field cuts a conductor. You still get the same voltage end to end and no current. A loop is just two parallel conductors. Ratbone 121.215.32.211 (talk) 11:02, 3 May 2013 (UTC)[reply]

a. Your reply should be relevant to the question asked, irrespective of backgroung of the person asking the question, either he knows something about physics or even more than that. It isn't. Your 1st row up there is patronizing, just because I'm on the side of the question. Isn't it legimate to ask and consult with colleagues ?

b. You repeat your previous mistake regarding the consistuent of the flux, the effective area traversed by the magnetic field lines. Again, the part of describing how AC current comes about is redundant too, and part of it even repeats what I said. In other words, AC current is a phenomenon originating from a periodically changing effective area. I hope you know what magnetic flux is, and what Faraday's law says.

c. I think it's evident from my both writings that I'm quite in the field. My question is thus of an irregular kind, very intriguing and interesting, and I wanted to share it with others. It was very cut and clear - what's the origin of EMF across a bent wire making an arc of, say, 270⁰ ?

d. A complete loop is exactly one round conductor. BentzyCo (talk) 12:37, 3 May 2013 (UTC)[reply]

The emf is equal to minus the integral of E dot ds from one end to the other, but this is path dependent. If you e.g. measure the voltage betwen the two ends using a volt meter, then what the voltmeter will indicate is given by minus the integral the closed path that includes the connecting wires to the voltmenter and the voltmeter itself. Then the Maxwell equation nabla times E = -1/c dB/dt, makes that equal to Faradays law where the area is the area enclosed by the integration path. Note that any fields generated by moving charges don't contribute, because their electric fields are conservative (integral of E dot ds along a closed contour vanishes), therefore you can compute the contour integral for the hypothetical cases where all conductors are relaced by insulators. Count Iblis (talk) 12:34, 3 May 2013 (UTC)[reply]

For an loop conductor, broken by an infintessimal gap in a uniform magnetic field, the EMF across the loop gap is always zero. It matters not whether the loop is moving through the field (or a moving field is moving across a stationary loop, or the magnetic field is increasing or decreasing in intensity. So long as the field is uniform, that is everywhere the same strength, the EMF across the small gap gap is zero. If the incomplete loop is in fact a straight wire at right angles to the field, and the field is changing, then there will be an EMF from end to end. A partial loop acts between these two extremes - you can consider it as a number of straight wire segments, and add up the EMF's to get the total, which must be between the two limiting cases of EMF. Note that any voltmeter and its connecting wires used to measure the emf must lie outside the field, or EMF's induced in the meter and wires will oppose the EMF in the loop conductor, resulting in reduced or zero reading. It is indeed odd to attack a person answering. Is BentzyCo a troll? Certainly he writes in an odd way - his 1st sentence in his question is a nonsense, for a start, and he seems to want an argument. Wickwack 121.215.147.92 (talk) 13:05, 3 May 2013 (UTC)[reply]

a. 1st: put your reply in its right place.

b. 2nd: Your last sentences are just offensive & insultive, and will be treated as such. "attacking an answering person" ?, "troll" ? "my 1st sentence is nonsence" ? "want an argument" ? Your claims are unsubstantiated, to say the least. Will you, please, remain on disciplinary ground ?

c. Concluding my claim in the 1st place: the previous replies weren't relevant to what was asked, deviating the discussion from its intended focus. I think you've to apologize, Thank you. BentzyCo (talk) 13:34, 3 May 2013 (UTC)[reply]

@BendtyCo: Please bear in mind that this is a volunteer service - and that even as a questioner here, you are bound by the Wikipedia guideline to Assume Good Faith. If you don't like the answers, don't use them. Ratbone is trying hard to be helpful and explain his thoughts on this matter - there is no need to insult him for doing so.

@Wickwack: Same deal...not cool: WP:AGF OK?

SteveBaker (talk) 14:17, 3 May 2013 (UTC)[reply]

It seems like the wire is a distraction. We're only interested in how the electrons move when exposed to a changing magnetic field - given that they can't usually leave the wire. Unless it's a superconductor the field lines enter it, so the electrons inside are exposed to a changing magnetic field and by Faraday's_law_of_induction#Maxwell.E2.80.93Faraday_equation experience electromotive force. I'm afraid I'm quite rusty with this topic but working through it you should be able to see how the EMF adds up even without a closed loop. I suppose it doesn't with a superconductor because the electrons at the outer edge can just madly move to compensate for any induced potential without any force ever ... needing to be applied??? Wnt (talk) 15:26, 3 May 2013 (UTC)[reply]

Let's take the magnetic field to be non-zero only withing the ring. We take it zero also at the location of all the conductors, e.g. put a long thin coil at the center of the loop, and let the current in that coil increase or decrease, the magnetic field is fully contained in the interior of the coil, which is well away from the boundary of the loop. The potential difference between the (infinitesimal) gap is simply the induced voltage as follows from Faraday's induction law. To see this, write the voltage difference as minus the integral of E dot ds from one end of the gap P to the other Q where E is the total electric field (both induced by the changing magnetic field and the build up of charges at the ends due to them responding to the induced electric field).

Then because the charges in the conductor will make the total electric field zero inside the conductor, we can add to the integral from P to Q across the gap, the integral from Q back to P taken over the conducting loop, as the latter integral is zero. We then have an integral along a closed path to which the Coulomb fields of the charges do not make a net contribution. So we can compute this integral by replacing the total electric field by the induced electric field that follows from nabla times E = -1/c dB/dt. Then Stokes theorem says that the integral along a closed path of E dot ds equals the integral of nabla times E over the area enclosed by the path, substituting -1/c dB/dt for nabla times E then yields the Faraday's law result. Count Iblis (talk) 14:13, 4 May 2013 (UTC)[reply]

Count Iblis, what's a nabla? What does all this double dutch mean in words of standard English? What is your conclusion wrt the OP's question?

In your second sentence, you've written "the magnetic field is fully contained in the interior of the coil" - a long thin coil. A magnetic field essentially stretches out to infinity, though it dies away in strength quite quickly cf electromagnetic radiation. The only case where a magnetic field is completely confined to within a coil, is where the coil is a perfectly even toriod made with thin sheet wire and zero distance between adjacent turns (that are never the less somehow insulated) - a rather theorectical situation.

. — Preceding unsigned comment added by 120.145.136.237 (talk) 15:56, 4 May 2013 (UTC)[reply]

See Nabla symbol - which should be familiar to anyone who knows anything about electromagnetic induction. 80.254.147.84 (talk) 11:47, 5 May 2013 (UTC)[reply]

Well, one learns something new every day. The lecturer I had in electromagnetics called it "del". My copy of Morrison says to pronounce it "del". Wickwack 120.145.80.171 (talk) 15:16, 5 May 2013 (UTC)[reply]

Yes, indeed, the _operators_ are called "del dot" and "del cross", but the _symbol_ is called "nabla". See Haddocks' Eyes. Tevildo (talk) 16:39, 5 May 2013 (UTC)[reply]

May 3

Dietary Reference Intake/Percent Daily Value

What's the relationship between Dietary Reference Intake and Percent Daily Values? Did the US government simply rename PDVs, perhaps when they made the food pyramid three-dimensional? PCV currently redirects to DRI, which doesn't mention PDV at all except in a single citation to a webpage that's now producing a 404 error, and a Google search didn't help. Nyttend (talk) 01:04, 3 May 2013 (UTC)[reply]

I think RDI is just the recommended amount of any particular "stuff" you should eat in a day, and so PDV is simply how much of that RDI any labelled food product contains. Just as a point of clarification, it's not technically the government which decides these things, these reccomendations are made by the Institute of Medicine which has a Congressional charter, but it's not in any way actually part of the government. Vespine (talk) 04:00, 3 May 2013 (UTC)[reply]

interesting that sometimes the RDI is the max amount of something you should eat, and sometimes it's the minimum amount. Tripped up a few students in health class. Gzuckier (talk) 21:10, 3 May 2013 (UTC)[reply]

recognizing a beetle

was photographed in East Talpiot, Jerusalem, Israel. anyone recognize? --SuperJew (talk) 05:11, 3 May 2013 (UTC)[reply]

Can't help with identity, although it looks like a weevil, but this site, What's that bug? is a very helpful resource. Richard Avery (talk) 07:15, 3 May 2013 (UTC)[reply]

It's not a weevil, they have snouts. μηδείς (talk) 08:16, 3 May 2013 (UTC)[reply]

This is a species of darkling beetle, possibly Adesmia abbreviata. --Dr Dima (talk) 08:27, 3 May 2013 (UTC)[reply]

here [10] [11] are two pages about it. --Dr Dima (talk) 08:36, 3 May 2013 (UTC)[reply]

I contacted this site: http://www.nature-of-oz.com/ I quote Oz Rittner: "This is Adesmia (genus), not possible to identify the species from this photo. It belongs to the Tenebrionidae family." 196.214.78.114 (talk) 08:52, 3 May 2013 (UTC)[reply]

The Lord sure do love Him some His beetles, don't He? Gzuckier (talk) 21:13, 3 May 2013 (UTC)[reply]

"inordinate fondness for stars and beetles", indeed [12]. --Dr Dima (talk) 22:20, 3 May 2013 (UTC)[reply]

Your use of some and his as specifiers at the same time is ungrammatical in the dialect you are attempting. It's like saying "This my book is interesting." μηδείς (talk) 01:57, 4 May 2013 (UTC)[reply]

Thanks a lot. Description updated. --SuperJew (talk) 17:57, 4 May 2013 (UTC)[reply]

Accelerator required for high intensity x-ray?

The voltage differential between cathode and anode in an x-ray tube translates into the "keV" rating of the resulting x-rays. Is it a requirement to use linear accelerators to get photons with higher energy. Or can one build a 50 MeV x-ray tube ..? An example being the Australian Synchrotron which generates 90 keV electrons using an electron gun and then accelerate these to 100 MeV. Electron9 (talk) 20:38, 3 May 2013 (UTC)[reply]

This might be an over simplification but once an x-ray or any other electromagnetic radiation setts off (emitted) – that's it. You can't give it extra electron volts in the real world. If you need harder x-rays then you need a greater differential. In the old days, one could tape a metal paper clip to a bromide paper and place it near to the TV tube – and hey presto – on developing you had an x-ray photo. A Synchrotron accelerates just the 'electrons' (read: increase of potential) so the electromagnetic radiation they 'stimulate ' (is that right in this context?) peak at higher energies. --Aspro (talk) 21:10, 3 May 2013 (UTC)[reply]

The reason linear accelerators (which accelerate electrons magnetically) are used for high energy X-rays in the medical filed and for industrial X-rays is because they are much more compact and cheaper that a conventional X-ray tube (which accelerates electrostatically) would be to get the same energy. Machinery to raise 20 MV at a useful current (several mA or more) needs large insulators and would need to be the size of a house, where as linear accelerator coil assembly is only the size of a couple of shoe boxes. That makes it a lot cheaper. A linear accelerator can be switched on and off virtually instantly, where as a many-megavolt power supply would take a second or maybe a few seconds to build up and die down - not very desirable.

The business of using a TV set to take X-Ray pictures is very nearly an urban myth. Except for the very early colour sets sold in the USA (1950's), the voltage used (about 17 to 20 kV depending on size) is not sufficient to get X-rays of sufficient energy to penetrate the picture tube front glass. The earliest coluor sets used up to 25 kV or so and a shunt triode regulator to regulate the voltage. These regulator tubes did emit very weak X-rays, but set manufactuers limited the X-Ray emission form the set by enclosing the regulator in a metal cage, and by arranging it so the the remaining X-Rays were directed downward thru the bottom case of the set, so that two thick layers of plywood, a metal sheet, and the floor of the dwelling would have to be penetrated.

Ratbone 58.167.231.148 (talk) 00:16, 4 May 2013 (UTC)[reply]

There's something wrong with the answer above.

Magnetic fields don't accelerate electrons, so it makes no sense to say something is accelerated magnetically
Magnetic fields bend the path of an electron bean, so it makes no sense to call an accelerator that uses magnetic fields a "linear accelerator"

Dauto (talk) 12:32, 4 May 2013 (UTC).[reply]

The magnetic keeps the beam on track and the electric field accelerate the particles/photons ..? Electron9 (talk) 13:36, 4 May 2013 (UTC)[reply]

A STATIC (constant) magnetic field will not accelerate electrons. However, a MOVING magnetic field produces electric tension, just as a moving electric field produces magnetic tension. By feeding the acelerating coils or cavities in a linac with an appropriate frequency, the electrons are accelerated without having to generate a high voltage. Linacs do generally use magnetic focusing, but that is done with addition structures, not the accelerating structures. Ratbone 120.145.203.168 (talk) 15:46, 4 May 2013 (UTC)[reply]

By electric tension you must mean electric field, which does indeed accelerate the electrons in a linear accelerator. I wouldn't call that "electrons magnetically accelerated". What you have is an electron riding a wave so that it is continuously accelerated by the varying electric field. Dauto (talk) 16:23, 4 May 2013 (UTC)[reply]

Put it this way: electrons get accelerated in linacs to a speed that would require millions of volts in a traditional Xray tube. But there are no large voltages anywhere in a linac. Just several structures in "line astern" carrying significant currents at appropriate frequencies. Ratbone 120.145.65.37 (talk) 03:00, 5 May 2013 (UTC)[reply]

What are the natural controls on Eh and pH?

What are the natural controls on Eh and pH (in areas of water) besides the amount of electronegative elements (eh) and the amount of acids (ph)?--149.152.23.34 (talk) 21:43, 3 May 2013 (UTC)[reply]

Think that's a very good question. Soil, is a mixture of many mineral and organic components. The answer of this question is not going to be straight forward. --Aspro (talk) 21:59, 3 May 2013 (UTC)[reply]

In general, see Soil pH and buffer (chemistry). More specifically, presence of limestone or sodium carbonate in the soil tends to prevent pH from going too low, or drives it up; whereas presence of humic acid / fulvic acid tends to prevent pH from going too high, or drives it down. Forest or swamp soils that are relatively poor in mineral content can be fairly acidic, while volcanic or some desert soils that are relatively poor in organic matter can be fairly alkaline. --Dr Dima (talk) 01:04, 4 May 2013 (UTC)[reply]

Was there ever a real species of dinosaur that resembled Barney?

In so much that it had the body shape and posture of a carnivorous dinosaur, but also had the blunt, wide herbivorous teeth? It's been a long time since I watched Barney The Dinosaur, but I think it's stated that he's a herbivore (or mostly so).

Discussion of the colour is optional. Though I don't suppose that a purple dinosaur would be out of the question, when you look at some of the colours we see in nature these days. Would it be any less wrong then showing them as being bright green?

Thanks. --146.90.56.134 (talk) 23:19, 3 May 2013 (UTC)[reply]

In my opinion Barney looks more like hadrosaurus than tyrannosaurus, but of course this is all just random. Looie496 (talk) 23:31, 3 May 2013 (UTC)[reply]

Barney was a guy. Don't you mean Dino?--Shantavira|^{feed me} 06:53, 4 May 2013 (UTC)[reply]

See Barney & Friends. HiLo48 (talk) 07:07, 4 May 2013 (UTC)[reply]

The members of Hevisaurus were of specific species.--Shirt58 (talk) 07:22, 4 May 2013 (UTC)[reply]

I'm not certain that the fossil record supports this particular behaviour, but it's not out of the question either. Alansplodge (talk) 20:17, 4 May 2013 (UTC)[reply]

Very few species of dinosaurs are known to have either spoken or sung in English. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:31, 5 May 2013 (UTC)[reply]

May 4

Trimmer vs shaver

What is the difference between electric trimmer and electric shaver? --Yoglti (talk) 01:43, 4 May 2013 (UTC)[reply]

About $15. μηδείς (talk) 01:52, 4 May 2013 (UTC)[reply]

The shavers are intened to get down to bare skin. The trimmer is intended to leave a short length of hair protruding above the skin ("stubble"). The trimmer likely has an adjustable setting to vary the amount of hair left, whereas the shavers have one setting ("as close to the skin as comfortably possible"). -- 71.35.109.118 (talk) 02:50, 4 May 2013 (UTC)[reply]

Just my original research; trimmers operate by a pair of toothed blades that slide past each other as one oscillates back and forth, like a small hedge clipper, while shavers are either a rotary blade that runs underneath a circular grill so that it nips the hairs off that stick through the grill, or a thin rectangular blade with lots of sharp slots which oscillates beneath a grill in similar fashion. the shaver appratus being thinner and thus more precise than the trimmer setup. Gzuckier (talk) 05:10, 5 May 2013 (UTC)[reply]

How energetic x-rays (kV) is required to reach above background?

How energetic x-ray photons (kV) is required for them to be stronger than background radiation ..? Electron9 (talk) 02:40, 4 May 2013 (UTC)[reply]

Your question does not make sense in the English language. I assume you meant to ask How energetic do X-ray photons (described in terms of the equivalent electron acceleration voltage) need to be to be stronger than the background radiation on Earth's surface? This is not a valid question. Do you mean the natural background radiation, or the averaged exposure due to nuclear fallout from accidents and explosions, medical X-rays taken during your life, use of nuclear isotopes in medical diagnosis and treatment etc? I will assume that you meant the natural background.

The higher the X-ray energy, the more penetrating it is. And if X-ray photons have fully penetrated a substance, then no energy was transfered to the substance and it cannot have been affected. This is why X-ray images taken to show bone structure are a lot less harmfull than X-rays taken to show soft tissue structure, where similar exposure times are used. It means that the natural X-ray exposure we experience includes X-rays from very high energy sources remote in the universe. In terms of exposure effects, very low energy man-made Xray sources very much over ride natural exposure.

Also note that in terms of effects on life, X-rays are just another sort of ionising radiation. The exposure to just natural X-rays is not important, but the total exposure to all sorts of ionising radiation can be.

Ratbone 124.178.43.47 (talk) 09:47, 4 May 2013 (UTC)[reply]

Maybe, he's talking about the cosmic microwave background? Plasmic Physics (talk) 10:43, 4 May 2013 (UTC)[reply]

I meant if you have a x-ray tube. How high acceleration voltage is needed to measure a higher dose than from ground rock (1 mSv/year?). I heard that CRT-TV-sets with acceleration voltage below circa 10 kV didn't make it out of the TV-set. So that only sets with higher voltage had any measurable radiation. Electron9 (talk) 13:30, 4 May 2013 (UTC)[reply]

Only the smallest CRT TV sets had an acceleration voltage as low as 10 kV. 17 to 20 kV is more typical for black and white sets, early colour sets were up to 25 kV. However, at typical voltages the X-rays are so soft normal materials used in sets (glass, wood, etc) stopped them.

You are still asking the wrong question - you are confusing photon energy with beam power. You can get a high effective dose from the lowest acceleration voltage that will produce X-rays of sufficient energy to penetrate the tube window - about 18 to 20 kV or so. You need to understand that Xray tubes are designed to produce Xrays - so the tube windows are constructed appropriately. TV sets are designed NOT to emit Xrays. For instance, the glass at the front of the picture tube is a three-layer sandwitch up to 18 mm thick and often lead loaded. Internally, older colour sets with internal parts such as the regulator triodes were designed so that Xrays from the triode had to pass through (typically) 2 layers of 12 mm plywood and a steel sheet barrier.

What affects dossage is the electron beam current and the exposure time. It is similar to exposing black and white photographic film with light. You can use a low power white light (say a 0.5 W krypton torch glode running at 4000 K filament temperature) or a high power light red light (say a 60 W globe run on low voltage so that the filament is running at only 1600 K and light output is reddish-orange). The first is analogous to making Xrays with a high voltage but a low beam current; the second is analogous to making Xrays with a low voltage but a high beam current. In both cases the higher power will have the greatest effect.

Not to be neglected is the fact that Xrays are emitted from Xray tubes in a fan-shaped beam, somwhat like light fans out from a light globe. This means that the further you are away from the Xray tube, the lower the dose, as you intercept a smaller fraction of the fan-shaped beam.

As I recall, you previously asked a question about making a homemade Xray apparatus. DON'T DO IT. You have so little undersanding of Xrays, you would be certain to cause harm to yourself and your friends.

As I said before, it is the low energy (ie from low acceleration voltage) that cause tissue damage. Very high energy Xrays pass through without lossing energy. If energy is not lost to the material passed through, there cannot be any effect on the material.

Ratbone 120.145.203.168 (talk) 15:21, 4 May 2013 (UTC)[reply]

There is information missing from your question. No matter how high the Voltage is, if no electron's are beamed down, no X-rays are produced. To answer your question you need to tell us the total number of electrons used by the machine per year. In other words, you have to tell us the current used by the machine. Other things to consider: How far from the X-ray source are you? Is there any radiation shielding? Dauto (talk) 15:28, 4 May 2013 (UTC)[reply]

Let's assume an x-ray tube and measurement 1 cm from the designed tube exit. If one study just one electron, how energetic (keV) does it have to be when striking the anode for the byproducts to just to make it out of the glass? before any shielding. If one electron makes it out, further electrons can make it. But if none makes it out, it won't matter how many there are. Ignoring the probabilistic nature of particles. Electron9 (talk) 16:09, 4 May 2013 (UTC)[reply]

Quite apart from the fact that what comes out depends on the thickness and type of glass, both of which will depend on the size and type of tube, which you haven't specified, it doesn't work that way, you can't calculate on the basis of a single electron, which may only result in one or 2 photons. Photons get absorbed on a statistical basis - some get thru, some don't. The fraction getting thru rises as the energy increases. Wickwack 120.145.8.232 (talk) 02:32, 5 May 2013 (UTC)[reply]

Spin

If the moon did not exist our earth would spin faster. How short would our days be on the equator? Pass a Method talk 06:26, 4 May 2013 (UTC)[reply]

Not necessarily. The most popular theory Giant impact hypothesis is that the moon was formed in an impact that span the earth up to have something like a five hour day. Otherwise it would probably have something in between the very long days of Mercury and Venus and the roughly equal day of Mars is my guess, maybe somebody has worked out a typical value to be expected. Dmcq (talk) 10:46, 4 May 2013 (UTC)[reply]

What makes you think the Earth would spin faster? Dauto (talk) 12:14, 4 May 2013 (UTC)[reply]

Using debatable assumptions: momentum must be conserved, ergo, lunar recesion decreases Earth's angular velocity. Plasmic Physics (talk) 12:31, 4 May 2013 (UTC)[reply]

Also tidal locking between the Earth and the Moon is transferring rotational energy from the Earth into orbital energy in the Moon, and friction in the tides converts some Earth rotational energy into heating the Earth. Both of these cause the length of Earthdays to gradually increase. BTW, the day/night cycle are the same length no matter where you are, (as long as you are not within the polar circles. Did you mean the length of daylight? CS Miller (talk) 14:11, 4 May 2013 (UTC)[reply]

I'm not the OP, I'm just infering their logic. I'm certain, they are refering to the period of the angular motion of the Earth, not the length of daylight. Plasmic Physics (talk) 04:43, 5 May 2013 (UTC)[reply]

Hassium

Emsley's Nature's Building Blocks (both editions) say that IUPAC did not feel Hesse merited having an element named after it as a reason for their changing the name to hahnium in 1994. Does anyone know why they felt this way? It's quite odd in light of all those elements named after places! The only reason I've found that they mentioned themselves is that they wanted elements named after Hahn and Meitner to stand side by side on the periodic table to honour their joint discovery of nuclear fission. (Yes, this is for an article.) Double sharp (talk) 08:51, 4 May 2013 (UTC)[reply]

How to get shine/glow in face like celebrities?

They have glow in face [13][14][15] How can I get this glow? Note it is not medical advice, just a health and beauty question. --Yoglti (talk) 09:03, 4 May 2013 (UTC)[reply]

That's just the choice of lighting on the part of the photographer, nothing more. Someguy1221 (talk) 09:08, 4 May 2013 (UTC)[reply]

These examples are paparazzi happy-snaps! What lighting choice have they got but their mono flash and ambient illumination?--Aspro (talk) 19:20, 4 May 2013 (UTC)[reply]

It's makeup too. Yes, even for Tom. Looie496 (talk) 14:50, 4 May 2013 (UTC)[reply]

See section: 'Add some glow:[16]--Aspro (talk) 19:15, 4 May 2013 (UTC)[reply]

And there's Photoshop and Airbrushing. HiLo48 (talk) 23:43, 4 May 2013 (UTC)[reply]

Oh yes Photoshop. That will only cost you about £400. Whereas GIMP is about £ 000,000,000 per free download Aspro (talk) 00:42, 5 May 2013 (UTC)[reply]

Yes, I'm well aware of that, but where I come from the word Photoshop has become a generic verb meaning to use any computer software to enhance/modify a digital image. Maybe I shouldn't have Wikilinked it. HiLo48 (talk) 00:47, 5 May 2013 (UTC)[reply]

A lower-case p would be indicated in that case (cf. thermos, hoover, xerox, google ...). -- Jack of Oz ^[Talk] 01:37, 5 May 2013 (UTC)[reply]

I haven't stopped putting a capital G on Google, even when using it as a verb. Has the lower case G become the recognised norm? Am I old and behind the times again? HiLo48 (talk) 01:42, 5 May 2013 (UTC)[reply]

Don't worry. I spend most of my life pretending to know what people are talking about. I even get it right sometimes. You have your good days and your bad days ...

But about Google: It has become far and away the most popular search engine; a lot of people would not even know there are others out there, or how to find their names. This means that those who do choose some other engine are consciously dissociating themselves from Google, and would not be using that word. So, maybe the verb has two existences and two meanings:

(a) google = to use any search engine in general (including Google); and

(b) Google = to use Google specifically (this would be used by people who use other search engines often enough that using Google, when and if they ever do, is a conscious choice).

Caveat: Most of the preceding is made up. -- Jack of Oz ^[Talk] 02:18, 5 May 2013 (UTC)[reply]

A high school student (obviously an excellent, reliable source) told me the other day that the most popular search term on Bing is "Google". (Actually, it's probably "google", but he didn't write it down, so I'll never know.) (Have we got far enough away from this topic yet? Sorry everyone.) HiLo48 (talk) 02:30, 5 May 2013 (UTC)[reply]

"Bing"? μηδείς (talk) 02:37, 5 May 2013 (UTC)[reply]

Yep, Bing. -- Jack of Oz ^[Talk] 02:53, 5 May 2013 (UTC)[reply]

Bing is used when you croon the internet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:28, 5 May 2013 (UTC)[reply]

efficiency

what is more efficient, a dolphin or shark moving its tale, OR, a machine as strong as the dolphin's or shark's muscles with a rotor? — Preceding unsigned comment added by 123lmon (talk • contribs) 13:16, 4 May 2013 (UTC)[reply]

Dolphins and sharks are much more efficient, they move their bodies in response to the actual flow of water so that it gets altered in the most optimal way. Count Iblis (talk) 13:34, 4 May 2013 (UTC)[reply]

Cooling of smartphones

Smartphones have nowadays as much as processing power as laptop did a while ago. However, when laptops had that much processing power, they had a cooling fan. Why don't smartphones don't need a cooling fan? Why do laptops need them? 123lmon (talk) 13:21, 4 May 2013 (UTC)[reply]

When a computer chip processes, that means electrons are whizzing around through it. That heats it up; if it heats up too much, it can actually melt the processor core. Newer chips can run much cooler than the ones of a few decades back — much cooler. The most common smartphone processor is known as ARM, and it was specifically engineered to have very low heat output and relatively low power requirements. So something on par with a smart phone, or even an iPad, doesn't really require a specialized cooling source, because they've been engineered to dissipate what little waste heat they have pretty effectively. (They don't alway succeed — the iPad will basically shut down if its internal temperature exceeds 95ºF.) Older processors, or modern processors of the speed that would be found in a laptop or desktop computer, still usually require fans to keep from overheating. --Mr.98 (talk) 13:43, 4 May 2013 (UTC)[reply]

Also the operating voltage of CPUs is gradually dropping - it used to be 5 Volts, and is now 0.8V (I think). The capacitance of each transistor is gradually decreasing, these both reduce the amount of power needed for each gate to change state, and thus for each operation the CPU performs. CS Miller (talk) 14:05, 4 May 2013 (UTC)[reply]

The low-power technology that permits all of that computation with such long battery life is the same thing that minimizes heat production. In the end, the energy from the battery turns (almost 100%) into heat inside the case...so things with long battery life and small batteries run cooler than things with short battery lives and large batteries. SteveBaker (talk) 14:06, 4 May 2013 (UTC)[reply]

I think smaller die geometries also plays into this. Electron9 (talk) 14:16, 4 May 2013 (UTC)[reply]

Also, the procesors used in cellphones where designed quite recently from scratch with an optimised instruction set. Intel compatible processors used in PC's and laptops have always been designed with backward compatibility stretching back to the original 8086 CPU designed in the early 1980's. Maintaining compatibility means they are a lot more complex internally. Also, the actual processor core is only part of what consumes power. A PC processor has to interface with external devices, external memory, and other bus devices. Cellphone procssors are one-chip devices that aviod the need for much power dissipating interface circuitry. Ratbone 120.145.203.168 (talk) 15:32, 4 May 2013 (UTC)[reply]

ARM goes back to 1983. I'd hardly call that "recently from scratch" ;-). It is a RISC architecture, although modern processors put a lot of additional functionality into silicon. --Stephan Schulz (talk) 22:26, 4 May 2013 (UTC)[reply]

To sum it up:

Efficient heat paths (little has really changed over the years however)
Less voltage
Less capacitance (due to less wire surface?)
Efficient use of existing gates (MIPS, ARM, etc)
Integrated peripherals

Electron9 (talk) 16:14, 4 May 2013 (UTC)[reply]

About the point of ARM and other RISC like architectures, note that Intel is desperately trying to compete in the tablet and smart phone market. (To a lesser extent, so is AMD in the tablet market.) The Atom (system on chip) isn't really used in any significant smart phones and even in tablets has only really found success in Windows 8 ones but most reviews have found that it isn't terrible, for example performance and battery life seem somewhat comparable to similar speced ARM devices. Edit: Although I believe one additional problem is the newer A15 and similar architectures e.g. Krait as well as their lower powered contemporaries e.g. A7 are now starting to become common and the current gen Atom SOCs are less able to compete. ~~Although this is likely helped a great deal by Intel's process advantage, in addition~~ even before the smart phone let alone tablet market really took off they were already heading quite heavily to power efficiency (including various ways of reducing power when idle). As for why they haven't had much success getting major manufacturers to use them in significant product lines, I suspect cost is a factor, even with Intel's efforts including discounting. Another reason is because there's little advantage even if it's not necessarily worse. In fact ARM has the advantange in the Android smart phone and tablet world. Although Dalvik is a VM, a fair few apps on the Android market place use the NDK and while there has been an x86 NDK for a while, you still have to convince developers to actually compile for it. Edit: Actually I removed the process advantage claim. Although Intel does generally have a process advantage and this may play a factor in the SOC, it's far from clear cut at the moment because their current SOCs are still using older processes. See also [17] which suggests an additional problem is Intel's baseband is still behind major competitors, obviously significant for smart phones and any tablets with mobile network support. Nil Einne (talk) 18:57, 4 May 2013 (UTC)[reply]

It looks like Intel is now trying to exploit its process advantage for the Atom processor rather than just thinking of it as the runt of the litter. They'll not be able to achieve a knock out and a monopoly so I don't see the strategy behind that as anything it does there will eat into the price differential it charges. I think they would have been better off just offering their process to others for the low end or even making ARM's themselves making sure it kept the differential and beggared the other manufacturers. Anyway I'm sure Intel's strategists are far more expert than me so the next few years should be quite interesting. Dmcq (talk) 07:46, 5 May 2013 (UTC)[reply]

Science of mating in humans

In humans, mating and relationships have evolved into being sophisticated but could it be argued that the process of "picking up" women in nightclubs actually takes this back to being more animalistic. — Preceding unsigned comment added by Clover345 (talk • contribs) 13:44, 4 May 2013 (UTC)[reply]

Well, it could certainly be argued - but I'm not sure that the argument would be a valid one. What exactly is your question here? If you're asking: "Is the process of picking up women in nightclubs 'animalistic' behavior?" then we first have to ask what is meant by "animalistic". We are, after all, animals. Animals have a huge range of mating behaviors - from female spiders that eat their mates immediately after copulation to love-birds that mate for life and die soon after their mate is killed. I'm sure you could find at least one other species that exhibits comparable behavior to the one you're referring.

However, I think you're somewhat missing the point here. You're probably seeing this behavior from only one side - the male. Sure, men go out to nightclubs with the specific goal of finding a woman to mate with...but women go to nightclubs in the knowledge that this is a common thing to happen. This in itself is a sophisticated, nuanced, layered behavioral pattern...it's not so different from composing sonnets and singing outside of a woman's bedroom window...or whatever else you'd consider "sophisticated". SteveBaker (talk) 14:03, 4 May 2013 (UTC)[reply]

A Martian would be better at answering this one. As homo-sapiens ourselves, we can't step back and objectively separate ourself from what we 'think we are' from our basic animal instincts. Humans (with the exception of a few of my neighbors) have also developed a complex form of 'culture' in conflict to our basic instinct. Picking up women in nightclubs is no different in modus operandi from searching for mates in 16th century church congregations. Anthropologists consider (or so they tell me) that both early and modern primitive groups consist of about 140 to 160 individuals. Once their juvenile children's hormones start running wild, they need to mix with other individuals of their same age but from different geographical locations (to avoid the instinctive aversion to incest and all that). In the modern world, one of these opportunities presents itself in nightclubs. 200 hundred years ago the equivalents could have been down at the bubbling brook were teenagers get together to go skinny-dipping and splash water at each other (– at least, that is what they probably told their parents when they got home that night – who in-turn had probably frequented the same spot on the bubbling brook when they were young). So the world goes round and round. Singing sonnets outside of a woman's bedroom window may have worked for Shakespeare in his time but in this modern age, it would likely end up with one being committed to a mental hospital for observation.Aspro (talk) 20:26, 4 May 2013 (UTC)[reply]

Or arrested for stalking. HiLo48 (talk) 22:53, 4 May 2013 (UTC)[reply]

Or as Jerry Seinfeld put it, "Yelling out the car window and honking the horn are about the best ideas we've come up with so far." ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:46, 4 May 2013 (UTC)[reply]

Are you saying Jerry_Seinfeld#Personal_life is a good role model?Aspro (talk) 21:29, 4 May 2013 (UTC)[reply]

You could do a lot worse. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:34, 4 May 2013 (UTC)[reply]

May 5

can one derive a language's grammar from sample code

Hello, this is out of idle curiosity, but can one derive a language's grammar from sample code? In other words, is it possible to write a program that, if fed code in some language wrote the EBNF that parsed the code , like this:
program xxx; var x: integer; begin x:=17; write(x); end. ===>
program::="program" ident; var-section main-block "."
var-section::="var" ident ":" type ";" etc, etc. (the names of the rules themselves need not be meaningful, obviously)
I suspect the program needs to have a way of knowing what the tokens are so it can tell between keywords and user-supplied identifiers. If the code sample was really big (it need not be a real program, either), such that it had every non-terminal in it and/or there were several snippets for when you can't put everything into one (one with no, one with a single and one with several variable declarations, for example), could one derive a complete grammar (or one of if there can be many) of the language? Thank you everyone in advance Asmrulz (talk) 01:42, 5 May 2013 (UTC)[reply]

Grammar induction is the article, though unsurprisingly the research focuses on natural languages. I don't know anything about this but I doubt you could find exactly the correct grammar of a programming language this way. Many programming languages don't have context-free (EBNF) grammars. For example the expression (A)(b) in C-like languages could be a type cast or a function call depending on how A was previously declared. -- BenRG 04:40, 5 May 2013 (UTC)

Hmmm...yes and no.

Strictly - no, it's not possible because you'd never know whether there might be some kind of construct that's not present in the example programs that you fed it. For example, you could pick an enormous corpus of C and C++ programs and never find a single one that uses the "goto" statement. I have written millions of lines of C/C++ code - and and read tens of millions more written by co-workers - and never once encountered a "goto". Even if you did find a few rare examples, it wouldn't be clear what the rules about jumping into and out of loops and subroutines are because you simply wouldn't have enough examples to deduce those things. I bet that it would be impossible to deduce the arcane rules for "goto" even if you took every C and C++ program ever written and analysed the whole lot.

But imperfectly - yes: Children can learn to understand and speak any language on the planet simply by listening to examples - and (in principle) anything that the human brain can do, you can do with a sufficiently powerful computer. However, children (and the adults they grow into) learn the language imperfectly...nearly everyone has some kind of failure of linguistics built into their brain.

SteveBaker (talk) 15:37, 5 May 2013 (UTC)[reply]

If the system only has source code, no it cannot extract the grammar. Children are able to learn laguage because they are exposed to two things: the language and its results. For instance Mother may say the word "custard" a few times while serving custard, so the child can associate the word custard with the actual stuff. Children also learn to speak because when they try it, their parents correct them. (Child: "wan custard"; Parent: "No, I want custard, please")

A computer program that deduces the grammar could in theory be constructed if it has access to both the source code, can run the source code, and can alter the source code. It motly cannot work out the complete grammar, for the reasons others have posted. Neither do humans ever completely master the vocabulary and grammar of spoken and written languages.

In practice, constructing a program that can deduce grammar of a computer language is probably not possible, because of the difficulty in understanding the meaning and scope of the output. I once wrote a program for an embedded processor in a hand held device. Each time you press the single "go" switch on it, after entering the 6-digit challenge number issued by the secure server you are trying to log into, it displays a 6-digit keycode that, with your own personal password, will enable you to log in. The keycode is generated by mashing the challenge (which was generated from a random number) and to the user appears to be another random number. No two challeges will ever be the same within a certain very low probability, and no two keycodes will ever be the same. Keying in the same challenge twice will give you two different keycodes. What is the proposed grammar extraction program to make of that?

Wickwack 120.145.68.194 (talk) 23:47, 5 May 2013 (UTC)[reply]

Sodium hydroxide for washing dishes?

If I add sodium hydroxide to the water when washing up, I can convert triglycerides to the dark side and have the cleanest dishes ever? — Preceding unsigned comment added by 78.144.202.9 (talk) 02:07, 5 May 2013 (UTC)[reply]

Sure, go ahead, wash your dishes with drain opener, what do we care? Just make sure you wear gloves and googles and rinse very thoroughly. Looie496 (talk) 03:13, 5 May 2013 (UTC)[reply]

Internet search engines have the most surprising uses. :) -- Jack of Oz ^[Talk] 03:18, 5 May 2013 (UTC) [reply]

Which triglycerides? Plasmic Physics (talk) 04:36, 5 May 2013 (UTC)[reply]

It doesn't matter, the lye will take care of any of them. --Jayron32 04:53, 5 May 2013 (UTC)[reply]

That depends on whether the lye is added in excess. Plasmic Physics (talk) 07:04, 5 May 2013 (UTC)[reply]

I'm just trying to figure out if the OP actually knows what they are talking about, because, by not defining 'triglycerides', there is no way to unambiguously interpret the question. Plasmic Physics (talk) 07:08, 5 May 2013 (UTC)[reply]

Triglycerides that make my dishes greasy? What are my options? 78.144.202.9 (talk) 07:15, 5 May 2013 (UTC)[reply]

Ordinary dishwashing liquid. NaOH is total overkill, and dangerous. -- Jack of Oz ^[Talk] 07:19, 5 May 2013 (UTC)[reply]

Doesn't that depend on how much I use? I could make it up to a less threatening concentration, or just add it to the water in its solid form... would it pop if I did that? — Preceding unsigned comment added by 78.144.202.9 (talk) 07:22, 5 May 2013 (UTC)[reply]

And when I said, what are my options, I meant re: the different types on triglycerides. — Preceding unsigned comment added by 78.144.202.9 (talk) 07:49, 5 May 2013 (UTC)[reply]

Sodium hydroxide is equally corrosive at all concentrations, except at 0 and 100 %. Varying the concentration only changes the reaction rate. Changing the amount, shifts the reaction equilibrium. Regardless, of concentration or amount of hydroxide used, it will still corrode glazes on cermics such as crockery, repeated use will strip the glaze off completely. While it does accomplish the task of degreasing, it also attacks the very thing you're trying to clean.

Note: it does not 'pop' when dissolved, that would be ~~sodium metal~~ igniting elemental hydrogen, given off by sodium metal. Plasmic Physics (talk) 08:26, 5 May 2013 (UTC)[reply]

Not to mention, how difficult it is to rinse off. If not rinsed completely, all food consumed from its surface will tase bitter and brackish, or similiar to baking soda, and it will damage your shelves. Plasmic Physics (talk) 03:38, 6 May 2013 (UTC)[reply]

It will also damage aluminium, zinc and tin. Rivets will tend to be eaten away. Graeme Bartlett (talk) 12:15, 5 May 2013 (UTC)[reply]

(Assuming those elemental forms and that type of object, are participant to this system.) Plasmic Physics (talk) 12:58, 5 May 2013 (UTC)[reply]

Adding to the list of others things you probably shouldn't wash your dishes in, you might enjoy this series from a professional chemist. Shadowjams (talk) 20:09, 5 May 2013 (UTC)[reply]

Pope alexander of the borgia family used vitriol or sulfur as a mood anhancer..

I cannot find anything anywhere on the internet about the ancient use of vitriol or sulfur as a mood enhancer nor how it was prepared and the side effects..can anyone please help me??

5/4/2013 10:28pm... — Preceding unsigned comment added by Jaime71355 (talk • contribs) 02:28, 5 May 2013 (UTC)[reply]

I'm afraid you might be mixed up -- I've never heard of anything like that and can't imagine how it would work. Is it possible that you're thinking of arsenic, which was sometimes used as a stimulant? Looie496 (talk) 03:18, 5 May 2013 (UTC)[reply]

Beef vs. chicken

Why is it alright to eat rare/medium beef but not chicken? Is salmonella not a problem with beef? DRosenbach ^{(Talk | Contribs)} 03:48, 5 May 2013 (UTC)[reply]

Because rare chicken tastes terrible. --Jayron32 04:04, 5 May 2013 (UTC)[reply]

Rare chicken is eaten in Japan, mostly in Kagoshima prefecture, in sashimi style like [18] and [19]. The taste is OK. But there's always a possiblity of Campylobacteriosis. I've eaten rare chicken twice, but nothing happened. Oda Mari (talk) 07:43, 5 May 2013 (UTC)[reply]

You can also get sick from undercooked beef. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:24, 5 May 2013 (UTC)[reply]

Neither is "alright" - you can get sick from any type of food. It's really about statistics; and you've no doubt been exposed to more educational campaigns advising you about poultry - because that's where the majority of the reported infections come from. You are more likely to find hazardous bacteria in commercially-raised chicken than in commercially-raised beef. You can get sick from any harmful bacteria; and those bacteria can live almost anywhere - fruits, vegetables, meats, poultry, and non-food sources... but according to a report I found by browsing the USDA.gov website's food safety pages, An Economic Assessment of Food Safety Regulations: The New Approach to Meat and Poultry Inspection, salmonella accounts for more than half of all food-borne illness death, and accounts for about the same percentage of total health-care expense. E. coli infections, typically found in beef but also including all other sources, accounts for less than one tenth that amount. There is much speculation about why this is true: it is plausible that in the "natural environment," more chickens have illness, per capita, than cows. It is plausible that chickens are raised in conditions that are less sanitary or less healthy than cows. It is plausible that different regulations concerning beef and poultry contribute to a different epidemiology. It is plausible that testing for salmonella is less effective - or that hazardous quantities of poultry-borne salmonella are harder to detect than hazardous quantities of other food-borne pathogens. (In fact, the report I linked details each of these possibilities, with additional data). Nimur (talk) 18:27, 5 May 2013 (UTC)[reply]

And it's not just about eating rare vs. well-cooked meat. There's also the issue of defrosting frozen cooked meat. You can do that once, but if there's any left unused, you should get rid of it. If you refreeze it and defrost it a second time, it would no longer be safe to eat. This is particularly a risk for chicken, but it's true for all meat to some degree. -- Jack of Oz ^[Talk] 20:02, 5 May 2013 (UTC)[reply]

Different species harbor different organisms and the risk/transmission profile for them differs. There's not a lot of design beyond that. The one thing Nimur didn't mention is processing practices. Chickens are processed in bulk differently than cattle (the cleaning and defeathering for instance), and that can facilitate cross contamination. That said, even a single chicken from the backyard, dressed individually should probably be fully cooked. Shadowjams (talk) 20:07, 5 May 2013 (UTC)[reply]

Does frequent reading/writing affect neurology of spoken language?

The phenomena described in this article seem like they could be explained more or less like so: "Fans speak by reading their mental writing aloud; mundanes write by transcribing their mental speech." Have any studies examined how frequent reading and writing, and infrequent speaking, affect the brain structures or activation patterns associated with language? Neon Merlin 05:43, 5 May 2013 (UTC)[reply]

Athletes and alcohol

This is a hypothetical question, not medical advice, because I'm not a professional athlete. Before athletes compete, they follow a strict diet but say for example if they had a heavy night of drinking, a few days before, not a night before, how would that affect their performance on the day because I'm sure a few athletes must have tried this before whether, intentional or not. — Preceding unsigned comment added by Clover345 (talk • contribs) 12:06, 5 May 2013 (UTC)[reply]

None directly; the body has plenty of time to metabolize alcohol in a few days' time. The most likely avenue of affecting performance, in my opinion, is for the drinking and associated behavior to result in an arrest. Being in jail, or being suspended for having been in jail, is a sure means of preventing an athlete from performing normally. — Lomn 13:09, 5 May 2013 (UTC)[reply]

What about junk food? Do you think that would affect then more a few days before since they follow such a strict diet normally? Clover345 (talk) 14:33, 5 May 2013 (UTC)[reply]

It doesn't have a significant effect, the diet is relevant only for the long term. On the short run what counts is only if you are getting enough calories. Count Iblis (talk) 15:34, 5 May 2013 (UTC)[reply]

As this is a reference desk, here's one; The effects of Alcohol on Endurance Performance. It highlights these effects on the day after drinking:

Dehydration
Potassium and sodium depletion
Impaired temperature regulation
Impaired balance and co-ordination
Reduced total work output

"... the ACSM recommends skipping anything beyond "low amount social drinking" for 48 hours prior to the event. It can take your body up to three days to purge itself of alcohol. One drink (sorry) over the course of an evening is your best bet." Alansplodge (talk) 16:46, 5 May 2013 (UTC)[reply]

You might find this article fascinating. Shadowjams (talk) 19:54, 5 May 2013 (UTC)[reply]

Optimizing learning habits

I've recently started playing games that are meant to improve the players' skill at solving simple arithmetic operations (such as 5×4 or 448÷32), which made me think about the way our brains study. For example, we will likely feel a bit uncomfortable whenever we make a mistake, which I suppose is the brain's way to make us more cautious. On the other hand, being too cautious would make us slower and therefore the learning process would take more time.

In order to accelerate my learning I wanted to know what consideration there are to the act of studying. What is the best time to study new information or to practice information that I've already learned? In the calculations games, should I prefer practicing each operation individually (first a list of additions, then subtraction and so forth) or all combined? Should I waste time to recalculate wrong results or should I move on? And how significant is it anyway?

In case the subject is too wide to detail, describing just the considerations of one habit (e.g. studying time) would also be great. I'm also interested in recommended books. Thanks! 79.181.175.168 (talk) 12:11, 5 May 2013 (UTC)[reply]

On whether to practice each operation individually or all combined, it really depends on what you want to achieve. If one particular operation is giving you problems, it would be a good idea to do that one individually. If you aren't having specific problems with any operation, it would be a good idea to do all combined, although I cannot quite remember the reason. Double sharp (talk) 15:11, 5 May 2013 (UTC)[reply]

Opinions differ widely on these sorts of things - from my own experience, there is no direct link from educational theory to educational practice to perfectly designed textbooks and educational systems. When you get to the act of "doing", there are just too many variables, and your own enjoyment of a system is one of them. But read up on Paul Pimsleur and spaced repetition. Basically, repeating immediately, then increasing the delay between each repetition, is the proven technique for memorising. This may or may not relate to solving mathematical puzzles, but I suggest it is a place to start. IBE (talk) 11:54, 6 May 2013 (UTC)[reply]

Is the blood test influenced by water?

I saw a nurse that say that if someone don't drink water before he come to a blood test, then his blood wouldn't come out as properly. My questions are: 1. Is it true? 2. Assuming this is true, How long it takes to the water to come into the blood circulation from the moment of the drinking. מוטיבציה (talk) 21:10, 5 May 2013 (UTC)[reply]

What 'blood test' would that be referring to. Richard Avery (talk) 21:40, 5 May 2013 (UTC)[reply]

Drinking a lot of water can dilute the blood - which I suppose would affect measurements of the amount of some substance per milliliter of blood...so yes, I assume it's true. Healthy kidneys are able to excrete 1 litre of water per hour...so the time it takes to return to normal will be at least one hour for every liter you drank. SteveBaker (talk) 22:23, 5 May 2013 (UTC)[reply]

It seems to me the question refers more to cases where people are (mildly) dehydrated and have low blood pressure as a result, causing problems with drawing blood... Count Iblis (talk) 23:08, 5 May 2013 (UTC)[reply]

As the OP supposes, it is not a question of affecting lab measurements, it is a question of how easy or difficult it is for the nurse to get blood out of the patient. Mild dehydration in basically healthy patients does not affect difficulty in drawing blood. In elderly patients, and in patients who have been given intravenous chemotherapy, the peripheral veins that are normally chosen to draw blood, which are the same ones they tend to choose for intravenous drips, tend to harden and partially close down. In such patients, drawing blood can be quite difficult, but if they drink plenty of water 20 to 60 minutes before, it can be easier. In my experience, (as an elderly patient who has had chemo) it seems to depend on the experience and skill of the nurse. Older nurses, and nurses that have specialised in taking blood (phlebotomists) don't seem to have a problem regardless, as they will choose a better vein, and they are better at getting the canula in. Time of day also matters. If a doctor orders a blood test that requires fasting (for which the normal way is to get the blood taken before breakfast), on a cold morning nurses cannot get blood out of my arm veins at all - blood has to be taken from a foot vein, which requires a doctor's direct supervision for some reason. Wickwack 120.145.68.194 (talk) 23:27, 5 May 2013 (UTC)[reply]

Just a slight correction, the term is phlebotomist, it has nothing to do with plebs or botany :) Vespine (talk) 02:28, 6 May 2013 (UTC)[reply]

Last summer my GP practice had a notice up to the effect that patients who have booked morning blood tests should drink a pint of water after they get up and before they come for their blood test, so the phlebotomist there obviously think it affects the process. --TammyMoet (talk) 10:33, 6 May 2013 (UTC)[reply]

Interesting. I have about 6 blood tests a year these days, and the issue has never been raised. When it's a fasting test, they always ask when was the last time I ate; but otherwise, no questions. -- Jack of Oz ^[Talk] 10:41, 6 May 2013 (UTC)[reply]

You have to book an appointment to get blood taken, Tammy?? Another reason why I'm glad I don't live in the UK and have to put up with the NHS. We in Australia (not noted for a good caring medical system either) just rock up when we get round to it. I've never had to wait more than 5 minutes. Wickwack 121.221.85.77 (talk) 14:19, 6 May 2013 (UTC) [reply]

May 6

A few chemistry questions

A few chemistry questions… Please explain how to solve (no calculator allowed).

Assume that gaseous substance A undergoes a first order reaction to form gaseous substance B. At a certain temperature, the partial pressure of gas A drops to 1/8 of its original value in 242 seconds. What’s the half life for this reaction at this temperature?

I just plugged in numbers for the original value, calculated the new value, then looked at the answer choices and figured out the half-life. But how would this be done mathematically (without answer choices)? The answer is 80.7 seconds.

Equal masses of He and Ar are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 11 atm?

The answer is 10 atm. How?

A 160 mg sample of NaOH (MM=40) is dissolved to prepare an aqueous solution with a volume of 200 mL. What is the molarity of sodium hydroxide in 40 mL of this solution?

The answer is .0200 M. The only explanation I can come up for this is that the molarity in 200 mL is .02 M, but then why wouldn’t it change when looking at it for 40 ml? Does it not change? Molarity changes with volume though?

If .15 mol of K2CO3 and .10 mol of KBr are dissolved in sufficient water to make .20 L of solution, what is the molar concentration of K+ in the solution?

The answer is .40 M. How?

Vessel A containts 32 grams of O2 gas while Vessel B contains 32 grams of CH4 gas. Find the ratio of the pressures of the gas in Vessel A to Vessel B and the ratio of the average kinetic eneriges in vessel A to Vessel B.

For the pressures, I just found the mole ratio was 1:2 and said moles is proportional to atm, so it’s 1:2. That’s correct answer. Is that correct logic?

How do you find the ratio of the average kinetic energies? I thought it was r1/r2 = r_1/r_2 = √(M_2/M_1 ) but that answer would be 1:1.4 yet the answer key says the ratio is 1:1.

Thank you!!! --Jethro B 00:42, 6 May 2013 (UTC)[reply]

Generally, a functional knowledge of simple arithmetic and introductory algebra are considered prerequisites before students begin stoichiometry. Each of these questions are essentially solved by trivial application of simple algebra. (With a little rounding and liberal application of critical thinking, you can solve much more difficult problems than these with no calculator - even pencil/paper are unnecessary for these problems). Other questions are spot-checks to verify that you understand terminology (like the difference between concentration and volume). Can you help us understand your background so we can lead you in the right direction? Nimur (talk) 01:35, 6 May 2013 (UTC)[reply]

If you believe that the stoichiometry and algebra is simple, then please provide some answers for me... I don't have an issue with algebra or stoichiometry. However, you can't just do stoichiometry in each of these problems - they test information across various units and different things need to be applied for each one to understand how to do the stoichiometry. The picture here isn't stoichiometry, but rather the specific units each question deals with, whether it's solubility, gas laws, kinetics, etc...

So if someone could provide an explanation of how to solve them (or some of them), and I note that they are not all the same stoichiometry, I'd appreciate it.

P.S. If you're really interested in my background, you can send me an email - it's not something I will publicly reveal. I will say that I consider myself skilled in the subject area and have proven this in the necessary courses by scoring highest, but there are always specific little things that you either don't know or forget (to put this in context, these are selected from a document of 75 questions, and are the ones I have trouble with. It's just a few, but I'd like to know how to solve them). --Jethro B 02:06, 6 May 2013 (UTC)[reply]

I have no idea how much chemistry you, as an otherwise-anonymous poster, already know. If you're a new student of chemistry, you deserve some directed conceptual explanations. If you're an advanced grade-schooler, you need some detailed help with mathematics you wouldn't know yet. And if you're a physics undergraduate, you need a stern talk about life-choices, and we need to yell "apply the equipartition theorem" at you (for the last problem). Without knowing what type of help you need, it's difficult to help you.

For example, "Equal masses of He and Ar are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 11 atm?" Look up the atomic mass of Helium and Argon if you don't already know them. Helium's atomic mass is four, and argon's is forty (for the purposes of our discussion, without a calculator, and ignoring some irrelevant decimal places). The ratio 4:40 is simplified to 1:10; and the question gives you a total partial pressure of 11... one plus ten is eleven. The math is alarmingly simple - but only if you already know that partial pressure is proportional to the molar mass ratios. That is a simple fact, but it's one you need to learn somewhere (presumably in a chemistry class). Do you need help with these concepts or do you just need a reminder to apply them?

Every other problem had a similarly simple arithmetic answer, as long as you recognized the concept that was being asked. Nimur (talk) 02:52, 6 May 2013 (UTC)[reply]

These questions look like they're on the level of College level chem/AP Chem, which I know. Yes, if you can do what you did with the pressure question - state what concept is applied here and how - that's great. I don't need a detailed explanation, I should be able to understand it. The helium, with the lower mass, would exert more pressure than the Argon? --Jethro B 03:18, 6 May 2013 (UTC)[reply]

Here's my attempt to point you in the correct direction for these questions. An additional overall hint is don't be afraid to start slinging algebraic equations around. You might have an idea of how to solve things "if only I knew T (or V, or ...)". Don't get discouraged - just try representing it by a variable and calculate through algebraically. It's quite possible that the T's or V's will cancel and you'll find you don't actually need to know them to solve.

Equal masses of He and Ar ... as Nimur discusses above - the key point is that partial pressures are distributed like the molar ratio of the gasses (each individual molecule contirbutes equally to the pressure for ideal gasses).
Assume that gaseous substance A undergoes a first order reaction ... You'll need to undestand what a first order reaction is. Drawing from examples of first order reactions, it should be clear what the reaction and stochiometry is. From that, you should be able to calculate final amounts of A & B from the given partial pressures, and from the starting and ending amounts and the rate equation determine the half life.
A 160 mg sample of NaOH ... Questions can have superflous information to catch out those people who are blindly combining numbers. If you're confident in your understanding of what molarity is, the 40 mL shouldn't throw you.
If .15 mol of K2CO3 ... Start by calculating what the molarity of the K2CO3 and KBr would be seperately in the final solution. Then figure out what each would contribute with respect to K+ ions. The final K+ concentration is simply the total contribution for the K+ ions.
Vessel A containts 32 grams... This is a straightforward application of the ideal gas law. You can do PV=nRT for both vessels to find the ratios of pressures. Likewise, you can also write the equation for the average kinetic energy, then take the ratio and cancel like terms. One catch is that they're likely talking about the per molecule or per mole average, rather than a per mass average or something like that, so keep that in mind as you write the expression for the average kinetic energy.

Hopefully that should be sufficient to get you on your way. -- 71.35.116.214 (talk) 04:22, 6 May 2013 (UTC)[reply]

I want to change a reference on the Elephant Cognition page.

I posted the following comment on the Elephant Cognition talk page but nothing has been done to change it.

The source [Dubroff, M Dee (August 25, 2010). "Are Elephants Smarter than Humans When It Comes to Mental Arithmetic?". Digital Journal. Retrieved 2010-08-29.] Is just an flake article talking about the journal article [Irie-Sugimoto, Naoko ; Kobayashi, Tessei ; Sato, Takao ; Hasegawa, Toshikazu."Relative quantity judgment by Asian elephants ( Elephas maximus )"Animal Cognition, 2009, Vol.12(1), pp.193-199]. Shouldn't the actual journal article be cited with the link being something like <http://journals.ohiolink.edu/ejc/article.cgi?issn=14359448&issue=v12i0001&article=193_rqjbaem> ? — Preceding unsigned comment added by reku68 (talk) 19:57, 22 April 2013 (UTC) — Preceding unsigned comment added by 129.110.5.89 (talk)

What kind of bug is this?

Hi there. For the last few weeks, I've been finding little bugs, about one every day or so. I get rid of it, but there's usually one there the next day anyway. It's very rare for me to see more than one at once, but it has happened. They almost always appear in the same area of the room, and whenever I see them they're always on a wall, and rather low to the ground. I don't recall ever seeing them outside of this room, either. I was wondering if anyone could help me identify what it might be? I took a Photo of the bug (apologies for image quality, it's the best I could get out of my old iPhone 3GS camera). I live in England, in case this helps narrow it down. Thanks for any help I might receive. 86.134.231.216 (talk) 12:29, 6 May 2013 (UTC)[reply]

It looks like a shield/stink bug. I don't know which species though. Plasmic Physics (talk) 12:46, 6 May 2013 (UTC)[reply]

To test it, does it stink when you try and catch it, or otherwise disurb it? Plasmic Physics (talk) 12:50, 6 May 2013 (UTC)[reply]

I don't think so. They move so slowly (hell, if I look straight at one it's hard to tell whether it's moving at all - it's only when I look away for a bit and then look back that I can tell it's moved, usually), and they're incredibly tiny (three millimetres top estimate). I can't rule it out for certain though, as I didn't try actively sniffing it or anything like that. If I see another one, I'll update. The last time I had a visitor I asked her, and she guessed at woodworm, though she stressed it was just a guess. I looked at all the insects linked in the woodworm article, though, and they all looked too elongated, whereas these are all rounder. I haven't noticed any wood damage on anything wooden nearby, either. 86.134.231.216 (talk) 13:07, 6 May 2013 (UTC)[reply]

I don't know much about bugs (I'm sure there's a word for the logical study of bug, probably not bugology), but I do know that species can vary considerably in size within the same superfamily. Take Tessaratomidae, they are a famly under stink bug, and they are giants compared to the other families. I would not be surprised if there was a family of dwarf stink bugs, of which this one is a member. I ny case, that's just my opinion. Plasmic Physics (talk) 13:20, 6 May 2013 (UTC)[reply]