Wikipedia:Reference desk/Archives/Science/2008 July 17

= July 17 =

Question regarding chemical hybridization
If one has a molecule which has coordinate covalent bonds - that is, both electrons for the bond are provided by one atom - how is hybridization calculated? For the atom providing the electrons, I believe the bond counts as an unshared pair of electrons, but does it affect the hybridization of the receiving atom? If so, how? As an example: I believe sulfuric acid, H2SO4, has two coordinate covalent bonds between the central sulfur and two of the oxygens. How would one calculate the hybridization for the oxygens? FlamingSilmaril (talk) 00:21, 17 July 2008 (UTC)


 * I believe once the bond has been formed, it is treated like any other covalent bond. It doesn't matter where the electrons came from; they are shared between the atoms the same as if it is a coordinate covalent bond, a "normal" bond, or from some sort of electrochemistry.  As the article says, it's an "artificial" distinction. --Bennybp (talk) 00:54, 17 July 2008 (UTC)


 * So for the example given, would the hybridization be 3 unshared pairs + 1 pair from the coordinate covalent bond = sp3? FlamingSilmaril (talk) 01:04, 17 July 2008 (UTC)


 * (Hopefully someone can correct me if I'm wrong; it's been years since I've done this). For the oxygens with a double bond to the sulfur, the hybridization would be sp2 - 2 hybrid orbitals containing the 2 loan lone pairs, and one containing the σ bond to the sulfur.  The leftover p orbital is used in the double (π) bond.  For the oxygens containing to the H group, the hybridization is sp3 - one containing the bond to the sulfur, one containing the bond to the hydrogen, and two containing lone pairs. --Bennybp (talk) 01:39, 17 July 2008 (UTC)


 * Okay, that makes sense. But are the bonds double (in which case sulfur would need an expanded octet) or coordinate covalent?  In my high school chem class they told us it would be coordinate covalent, but are they dumbing it down for simplified chem 1 purposes?  And if it's coordinate covalent, does that change things? Thanks for your help.  FlamingSilmaril (talk) 01:55, 17 July 2008 (UTC)
 * I think the above has missed a bit..
 * sulphur has d orbitals which which contribute to bonding From http://www.chemistry.mcmaster.ca/esam/Chapter_6/section_4.html : "Hybridization schemes involving d orbitals are also possible. They are important for elements in the third and succeeding rows of the periodic table. Although the elements of the third row do not possess occupied 3d orbitals in their ground electronic configurations, the 3d orbitals of phosphorus, sulphur and chlorine are low enough in energy that promoted configurations involving the 3d orbitals may be reasonably postulated to account for the binding in compounds of these elements. One consequence of the 'availability' of the 3d orbitals is that there are many exceptions to the octet rule in compounds of the third row elements"
 * That may still be debatable. (or no longer believed true). You probably don't have to worry about that anyway - d orbital contribution may only be partial.
 * The hybridisation on O is difficult - for the OH oxygens you can expect sp3 (as in water), for the =O oxygens you might expect that the double bond be provided by a p orbital - this means that the remainder of the orbitals can form sp2 or (sp and p).
 * It's worth noting that the S=O bond can be quite polar eg S+-O- ; negative charge on the oxygen tends to favour s or sp orbitals (I think)
 * (eg compare the stabilities of CH3-, CH2=CHundefined- and CH = CH- anions -also a first row element).
 * The SO bonds are double, the SOH bonds are single.
 * The S can be considered to have and expanded octet.
 * The S=O bonds can be considered to be dative from S to O or as a single bond sharing one electron each from S and O with O supplying a further dative bonding pair to S forming the double bond and expanding the S octet.

1.        OH             | -O-S2+-O- |            OH

2.        OH             | O=S=O |           OH

3.        O             ↑ HO-S-OH ↓           O

1,2 and 3 are all valid structures, 1 shows a polar covalent bond, 2 shows the double bonds, 3 shows the dative bonding form. NOTE only in 3. has sulphur not expanded its octet.

1 is unlikely because of the +2 charge, 2 is more likely because the S=O bonds are shown to be quite strong, for that reason the singly bonded form 3 is unlikely.

In all cases the S is tetrahedral. Hope that explains something.87.102.86.73 (talk) 03:09, 17 July 2008 (UTC)


 * Ah, see the picture to the right. You are correct - sulfur contains an expanded octet - two double bonds, two single bonds, for a grand total of 12 valence electrons.  Perhaps your teacher misspoke or was incorrect in calling the bonds "coordinate covalent" (or dative, the term I had learned).  A double bond is of course a type of bond.  A coordinate covalent/dative bond is more of a description of how that bond got there. Once the bond is formed, it's more or less irrelevant how those electrons came to be shared.  [[Image:Sulfuric-acid-2D-dimensions.svg|thumb|150px|[[Sulfuric acid]] structure]]--Bennybp (talk) 02:56, 17 July 2008 (UTC)


 * Quick note about the hybridized d oribitals mentioned above - you are also correct. In some there can be hybridized sp3d, sp3d2, etc, in some compounds.  In this case, who knows.  Maybe I'll rummage through my inorganic book tonight. I'm just thankful he/she didn't ask what the hybridization was on sulfur.  Yet. :) --66.66.215.73 (talk) 03:28, 17 July 2008 (UTC)

(unindent) Thanks to everybody who has contributed to the discussion. I do have one question remaining: the article on thiosulfuric acid has the atoms arranged in a cross structure around a sulfur. An AP Chem book that my teacher used said that it is arranged in a straight line: H-O-S-O-S-O-H. It said this was more stable, because it was slightly more symmetrical. A quick glance however, does not show this structure anywhere on the internet. Can anybody shed some light on this? FlamingSilmaril (talk) 22:27, 17 July 2008 (UTC)


 * Your book may be wrong, or someone misinterpreted (what book is it?). The structure you gave (H-O-S-O-S-O-H) is 1.) Not linear. 2.) Not symmetric (well, maybe one rotational axis through the center oxygen). 3.) Not thiosulfuric acid. And 4.) Doesn't appear to exist.  (The structure was evaluated with ChemSketch,and named "dihydroxydithioxane", which gets zero hits on google and ChemFinder. --Bennybp (talk) 23:28, 17 July 2008 (UTC)


 * The structure is the same as sulpuric acid with a =S replacing a =O eg try http://images.google.co.uk/images?hl=en&q=thiosulfuric%20acid&um=1&ie=UTF-8&sa=N&tab=wi note the acid is unstable and only the salts exist. Sounds like that book is wrong? how can this be?87.102.86.73 (talk) 10:18, 18 July 2008 (UTC)

Can a kangaroo outbox a human boxer?
I'm sure most of us have heard the stories of human vs. kangaroo boxing matches (which are probably illegal in many parts of the world now) at carnival sideshows in the 19th century. What I'd like to know, is whether a trained boxing kangaroo could beat a skilled human boxer. There are some videos of man/kanagroo fights on YouTube - but they all seem to involve the human fighting half-heartedly or refusing to fight back at all for the purposes of comedy.

So, if a (good) boxer really went all out and genuinely tried to KO the 'roo - and the 'roo was likewise trying to inflict serious damage (both wearing gloves, of couse - this is a civilised sport!), which would be the more likely winner? --Kurt Shaped Box (talk) 01:30, 17 July 2008 (UTC)


 * You might wanna consult with PETA before calling punching a tethered animal a civilized sport. --Shaggorama (talk) 04:21, 17 July 2008 (UTC)
 * I have witnessed a boxing match between kangaroos. They don't follow rules, and also use their strong hind legs.  A kangaroo could out jump a boxer. Scratching with claws is part of their methods too. Graeme Bartlett (talk) 04:59, 17 July 2008 (UTC)


 * as graeme says, the hind leg claws can be used to deadly effect when they want to (eg on dogs).Polypipe Wrangler (talk) —Preceding comment was added at 05:06, 17 July 2008 (UTC)


 * Just to make it clear - I'm not *really* a full-contact human/kangaroo boxing advocate. :) --Kurt Shaped Box (talk) 08:57, 17 July 2008 (UTC)

As regards gloves and civilzed-ness: KSB, do you have the idea that when you put on gloves you do it to protect your opponent? No. You do it to protect your own hands, so you can hit your opponent harder. --Trovatore (talk) 05:09, 17 July 2008 (UTC)


 * No, it's to protect both. This is an example of what can happen when someone cheats and removes the padding from their gloves. --Kurt Shaped Box (talk) 08:50, 17 July 2008 (UTC)
 * That's talking about gloves+padding, versus gloves without padding. Gloves without padding still protect your hands. Put a bare-knuckle guy in the ring against a guy with gloves, I'll bet on the guy with gloves. The reason bare-knuckle fights could go 57 rounds or whatever is they just couldn't hit each other that hard. --Trovatore (talk) 17:06, 17 July 2008 (UTC)
 * My dad worked in a hospital emergency room for a while, and according to him, bare-knuckle bar fights end in either of two ways: (1) the guy throwing the first punch is strong, and breaks his own hand and his opponent's jaw, or (2) the guy isn't so strong, and only breaks his own hand. In either case, punching someone in the jaw with your bare hands is not a good idea. --Carnildo (talk) 20:48, 17 July 2008 (UTC)


 * AFAIK, if you break your hand when punching someone, it's usually down to bad technique. For some reason, when untrained people punch, they tend to connect with the fourth and fifth knuckles. Not that I'm a scrapper - but I think the trick is to strike with the second and third, with a straight wrist behind. --Kurt Shaped Box (talk) 22:57, 17 July 2008 (UTC)


 * Odd. The claim is that half the padding had been removed from the gloves and that that allowed Resto (who is referred to as "soft-hitting") to beat the good guy half to death (or, if we ignore the DUI as the article does, all the way). But boxing gloves are much more padded than those used in MMA - even half the padding would leave them bulkier than a UFC fighter's gloves. Lewis and Resto are rightly demonized, but the key element here was the incompetent referee who apparently didn't feel the need to check the fighter's equipment or stop a bout that had obviously become a slaughter. Matt Deres (talk) 10:53, 17 July 2008 (UTC)


 * I don't really know much about the UFC - but does a typical bout of theirs involve 10x3min rounds of mostly punching someone in and around the face? I thought that it was more of a grappling-based sport? The Collins-Resto fight is on YouTube in its entirity, btw - it doesn't actually look massively uneven until the last three rounds or so. Even then, it was only in the final round that Collins was struggling to stay on his feet. The damage inflicted was cumulative. --Kurt Shaped Box (talk) 15:04, 17 July 2008 (UTC)


 * A typical bout is 3x5 minutes, but a title match is 5x5 minutes. While they don't experience the sheer number of punches to the face that a boxer would get, they also get to enjoy kicks, knees, and forearms to the head. I stopped watching boxing as I got into watching MMA style events; while that was mostly driven by the (IMO) more exciting style of contest, I also preferred the sportsmanship and style of refereeing. Maybe it's gotten better over the last decade, but when I was watching boxing it seemed that the refs were doing everything in their power to allow the superior fighter the chance to KO his opponent, rather than simply stopping the fight (as a TKO) when it became obvious that the match had really already been decided. Not having been pummelled myself (!), I tend to agree with Bas Rutten that a quick finish to a fight is much better for the health of the fighters than a prolonged battle with standing counts and more frequent breaks between rounds. In MMA, the referee (or designated other) also inspects the equipment immediately prior to the bout to make sure everything is up to spec. Matt Deres (talk) 16:37, 17 July 2008 (UTC)

Concentration of biotin in egg yolk.
On a number of websites I've read that despite egg whites containing a substance that removes biotin from the body, egg yolks contain so much biotin to make these effects unimportant. I have however been unable to come up with a source for this -- Wikipedia's own article on biotin mentions that egg yolk contains biotin, but does not reference a source that I can see.

Another Wikipedia article (http://en.wikipedia.org/wiki/Tamago_kake_gohan) states that "Eggs contain many nutrients and protein which are denatured when cooked; therefore it is thought that eating them raw maximises the beneficial effects of these nutrients. The egg yolk contains more than enough levels of biotin to compensate for the high levels of avidin in raw egg white, which binds to the B-vitamin biotin, preventing their absorption and potentially causing a deficiency if the yolk is not consumed with the white." The source it sites for this is a pdf of a letter about, amongst other things, whether wolves should be classed as dogs, and it doesn't exactly inspire confidence in the claim. I'm just looking for a source that gives some exact figures...

Additionally, there is often a claim made that salmonella contamination in eggs only comes about if the chicken is ill, and thus if you buy organic or free range eggs then it is less likely to be infected with salmonella. I have been unable to find a source for this claim either.

Many thanks for any information you can provide. —Preceding unsigned comment added by 217.42.183.162 (talk) 01:43, 17 July 2008 (UTC)

A farmer friend of mine fed raw eggs to his dog too often, the dog's hair fell out and the vet correctly diagnosed this as a problem. Polypipe Wrangler (talk) 05:09, 17 July 2008 (UTC)


 * After searching on Google, I found, , and , all of which claim there is insufficient avidin in an egg to bind all of the egg's biotin. However, according to this paper, "The yolk of an egg is rich in biotin, but the white usually contains more than enough avidin to inactivate the yolk biotin."
 * On the matter of salmonella, the U.K. Food Standards Agency found no statistically significant correlation between production type and incidence (see ).
 * Hope this helps. --Bowlhover (talk) 09:19, 17 July 2008 (UTC)
 * Just a historical note: the discovery of avidin/biotin binding and its effects upon the body was by observing a strange ailment affecting a number of athletes who had only one thing in common: they all had been consuming a number of raw eggs (not just the whites, but whole eggs) for a period of at least several weeks. The ailment turned out to be biotin deficiency caused by the sequestration of the vitamin by the avidin in the raw egg. – ClockworkSoul 18:07, 17 July 2008 (UTC)

litmus
What reaction takes place during the litmus test? please give the equation. —Preceding unsigned comment added by Connect gangadhar (talk • contribs) 03:37, 17 July 2008 (UTC)


 * Litmus paper contains a variety of indicator dyes. The reaction that takes place is a simple acid-base proton (or hydroxide)exchange of the form HIn -> H+ + In-. Indicators are special in that when they lose or gain protons, the absorptive properties of the molecule as a whole are changed. The Phenolphthalein article has some good structures that might help you understand how the conjugated system in the molecule is effected by pH change. --Shaggorama (talk) 04:31, 17 July 2008 (UTC)


 * Fixed your confusing typo. --Anon, 05:34 UTC, July 17.

Dream length
What is the average length of a dream? Doing a quick google search gives me results ranging from dreams lasting a split second to experiencing dreams in real time. --Metalcore424 (talk) 09:17, 17 July 2008 (UTC)
 * I don't think today it can reliably be measured. In this case measurement of the system drastically affects what we are trying to measure, which would lead to unscientific data and results. Mac Davis (talk) 00:04, 18 July 2008 (UTC)
 * Not only that, but you have the problem of what defines a dream; I have had one right after the other, and I would think there was no space in between them, though I'll admit there could have been and I'd never know it. If they can come one after the other, why does your brain change...well..plots? Hmmm, maybe reading the article will help me some witht hat one.209.244.30.221 (talk) 17:35, 20 July 2008 (UTC)

Chicxulub & the Deccan Traps: Antipodal Connection?
Given the continental drift over the past 65 million years, it seems as if the impact crater and the caldera were on almost precisely opposite sides of the globe at the time of the event. Are there any theories that somehow make a connection between these two? Frunobulax (talk) 14:45, 17 July 2008 (UTC)


 * As dating accuracy gets better, the results repeatedly show that the Deccan Traps predate the Chicxulub crater. It is possible that they happened at the same time - but at this time not widely accepted.  If it is proven that they happened at the same time, that will not prove causation. -- k a i n a w &trade; 14:59, 17 July 2008 (UTC)


 * Thanks! Frunobulax (talk) 15:02, 17 July 2008 (UTC)


 * They say that the Deccan Traps is the result of a deep mantle plume. These types of plumes happen from time to time all over the world without any special provocation, although the Deccan Traps is a particularly splendid example. Some people have suggested that the impact which caused the nearby Shiva crater may have disturbed the mantle and triggered the plume which formed the Deccan Traps. But really, who knows? Plasticup  T / C 19:02, 17 July 2008 (UTC)


 * I've added links to the title. StuRat (talk) 22:43, 20 July 2008 (UTC)

Funny feeling in your forehead
You know that funny feeling in your forehead when you place something close to your forehead or inbetween your eyes (especially if it's pointed like a pencil)? How does that work? It seems to activate even if I close my eyes. I never really understood how it works or why. ScienceApe (talk) 15:17, 17 July 2008 (UTC)


 * I don't get a funny feeling. Can you describe it in any more detail? I wouldn't recommend putting pointy things too near your eyes though.--Shantavira|feed me 15:54, 17 July 2008 (UTC)


 * It seems to work more when someone else does it. Have someone point their finger inbetween your eyes or near your forehead. Don't let them touch your head though, but you'll get a funny feeling in your forehead. ScienceApe (talk) 16:00, 17 July 2008 (UTC)


 * I definitely know the feeling you mean, but I can't think of what it could be called to search for it here or on google. Fribbler (talk) 16:07, 17 July 2008 (UTC)
 * To me it has always felt like a sedative/tranquillizing feeling, though why I don't know. I also noticed it once whilst playing a particular PC war game, when the gun turret of a tank was facing directly at me on the screen, so I guess it doesn't have to be a physical object in front of you. --Mark PEA (talk) 17:10, 17 July 2008 (UTC)


 * I know this feeling is claimed to exist in Beyond This Horizon by Robert Heinlein, but I can't say I've ever experienced it or encountered any other serious reference to it. 79.66.90.252 (talk) 17:08, 17 July 2008 (UTC)


 * It feels like blood rushing to the area, so maybe it is my body anticipating an impact from the object directly in front of me. Plasticup  T / C 18:51, 17 July 2008 (UTC)


 * I think it is probably due to your eyes trying to see it in your peripheral vision. I don't feel anything nearly at all when I do it with my eyes closed. --98.217.8.46 (talk) 03:52, 18 July 2008 (UTC)
 * Amazing. I've never noticed (and probably never actually felt) it before. Mac Davis (talk) 00:03, 18 July 2008 (UTC)
 * Could the finger be touching the little hairs on your skin? Graeme Bartlett (talk) 02:44, 18 July 2008 (UTC)


 * Since the eyes and brain are very sensitive areas, I suspect the sensation is to warn of a potentially-dangerous object. It still exists when the eyes are closed because when you deliberately induce the feeling with an object, you're well aware of the object's position.  When an item unexpectedly gets close to the forehead, I think wind and changes in the amount of light received by the eyes can reveal its location.  --Bowlhover (talk) 08:47, 18 July 2008 (UTC)


 * Is there a name for this sensation? ScienceApe (talk) 19:59, 18 July 2008 (UTC)
 * 'Aversion to things being close to your face.' --Shaggorama (talk) 20:11, 18 July 2008 (UTC)
 * That would be a description, not a name. ScienceApe (talk) 18:32, 19 July 2008 (UTC)


 * I don't know it is the same but my forehead seems much more sensitive to heat or cold than the rest of my face. I can easily tell if there is a hand a couple of inches in front of my forehead with my eyes closed because of the heat. You might feel it as blood rushing to the area. Dmcq (talk) 20:08, 18 July 2008 (UTC)


 * ESP Aura personal bubble its basically latent esp in non-phsycis, and goes to prove that most people are phsycic to a certain degree. It used to happen to me in a hardware store I used to visit, one isle had many habgers for bags of screws and such like and was basically 6 inch rods of metal in an isle 10meters long, 4 feet high and one of there every 10 square cm or so really wierd feeling walking down that isle, i had to avoid it in the end.

Why would a dark brown haired man find about 4 red beard hairs?
I am 27 years old and am a typical Peruvian in terms of aperance. I have dark brown eyes and hair, both my parent as well and all of my grandparents (all Peruvian). Recently I have decided to let my beard grow a little and I ran into a total of 4 red hairs. I have had white hairs on my head, but not on my beard. Is it normal to have a few hairs of a different color? I am a healthy man maybe a little rounder than what I would like. I stand at 5'9 and weigh 176lb, so I don't think malnutrition would be a cause. Why would I have 4 hairs that are of a different color that are not white? —Preceding unsigned comment added by 167.211.65.80 (talk) 15:23, 17 July 2008 (UTC)


 * This is a reference desk. It is not a place to list symptoms and ask for a diagnosis.  Anyone who answers this question with a proposed diagnosis will be doing you a disservice.  Please see a medical expert for a proper diagnosis. -- k a i n <font color='#3300cc'>a <font color='#0000ff'>w &trade; 17:19, 17 July 2008 (UTC)


 * The OP doesn't seem to be looking for a diagnosis for a medical condition, just a simple explanation about why he might have variation in his hair color. – ClockworkSoul 18:00, 17 July 2008 (UTC)


 * I agree, calling a question about why hairs come in different colors a request for a medical diagnosis is absolutely absurd. Let's be reasonable here. StuRat (talk) 22:33, 20 July 2008 (UTC)


 * Variation in body hair colour in males is not untypical. The genetic basis of red hair is pretty well understood and there is a reported heterozygote effect (having one copy of a specific gene variant) resulting in red beard hair colour in males who do not have red hair on their head. Why one has just occasional red hairs isn't really known, but is probably due to localized perturbation of the melanocytes in those hair follicle, resulting in the production of phaeomelanin rather than eumelanin. Rockpock  e  t  19:11, 17 July 2008 (UTC)


 * I have dark blonde hair, but a few red hairs in my beard. It was less alarming in my case because my father and brother have red hair, but I don't think it is uncommon, especially when you are young. <font color="#0080FF">Plasticup  <font color="#2A8E82">T /<font color="#2A8E82"> C 19:05, 17 July 2008 (UTC)


 * I know a girl who is complete red-headed/blonde hair colour type except for one black hair on her arm. It doesn't seem that unusual, really. —<font face="Trebuchet MS" size="2px">CycloneNimrod <font face="Trebuchet MS" size="1">Talk? 19:17, 17 July 2008 (UTC)


 * I've noticed that some of my eyebrow hairs are a different color and texture. Interestingly, those are the hairs that don't know when to stop growing and must be clipped back.  It's like there are two completely different types of hair there.  It sounds like you might have this happening with your beard. StuRat (talk) 22:33, 20 July 2008 (UTC)

Zebra foals
Is the number of foals that a zebra can give birth to in one single go always 1, or have there been cases of multiple births in zebras? Thanks. Leptictidium (mt) 16:21, 17 July 2008 (UTC)
 * Several sources by searching google (here) suggest that usually one foal is born at a time, but twins are possible (yet extremely rare). —<font face="Trebuchet MS" size="2px">CycloneNimrod <font face="Trebuchet MS" size="1">Talk? 17:14, 17 July 2008 (UTC)

Free articles
Upon what criteria do the publishing companies of journals decided to make a particular article free-access? How does it benefit them. Just a curiosity. Thanks in advance. <font color="#800080">—Ketan <font color="#000000">Panchal <font color="#2F4F4F"> t aL K  16:39, 17 July 2008 (UTC)
 * They might do this as a loss-leader, i.e. a way of getting notice taken of their journal. Many have a policy of making all articles free-access after six months, a year or two years. By that time the number of paid-for hits has probably decreased to nearly nothing anyway. They'll discuss the policy with the journal editor or editorial board. Different journals are aimed at different markets. Itsmejudith (talk) 18:26, 17 July 2008 (UTC)


 * Sometimes, when you publish in an academic journal, you can choose whether to make an article freely available or only available to pay for that journal's subscribers. To make it freely available, the author/institution typically has to pay thousands of dollars. Thus, it is not particularly common. Gjmulhol (talk) 19:58, 17 July 2008 (UTC)


 * A major consideration currently is that the U.S. National Institutes of Health requires public access by 12 months after publication for any work they fund. See: . Scray (talk) 00:07, 18 July 2008 (UTC)


 * Thanks a lot everyone! That was very informative. <font color="#800080">—Ketan <font color="#000000">Panchal <font color="#2F4F4F"> t aL K  07:07, 18 July 2008 (UTC)

Beer head
What is the fucntional role of the foam head on a glass of beer? I've heard different explanations and found the beer and beer head articles lacking: the latter explained the physics behind why beer has a head, but not the gastronomy. Why is it important for some beers to have a certain kind of head/pour and not others? Variations I've heard usually mention some or all of the following: head... I imagine some or all of these are probably true, but I can't find a decent source to back it up. In any event, the article could use a little expansion from a knowledgeable party. --Shaggorama (talk) 17:11, 17 July 2008 (UTC)
 * ...prevents the aroma from escaping prematurely
 * ...retains carbonation
 * ...guards against "oxidation" (though no one has ever told me of what component of the beer)
 * ...keeps the alcohol from evaporating (unlikely)
 * ...helps keep the beer cold (really unlikely)
 * Most of these explanations range from unlikely to slightly silly. Beer head doesn't really affect carbonation or aroma, but is diagnostic of it (I'll explain below), and has little to do with decreasing beer oxidation (which is not a factor over the amount of time it takes to drink a beer). The simplest reason for the head on a beer is because people like it: it's aesthetically pleasing and adds a lovely texture to the entire beer-drinking experience. The size and color of a beer head is influenced by a number of factors, including the amount of protein in the beer (more protein equals more foam, and too much deviation from the standard for the style can indicate problems in the brewing process), the degree of carbonation (again, deviation from the standard can suggest bad things), and the temperature of the beer at the time of the pour (temperature greatly influences taste and aroma; also colder beers develop less of a head, while warmer ones may easily overtop). The perfect head on a beer is therefore a good indicator that all of these vital attributes are in a good balance. Hope this helps. – ClockworkSoul 17:57, 17 July 2008 (UTC)
 * people like it or not. True, on mainland Europe, for example, most beers will be served with a nice head as it indicates that the beer is sparkling and fresh (hence the reason why some longlasting industrial beers have to add chemicals to produce the head) as opposed to flat or stale. But beware of your average UK pub dweller who is susceptible to throwing his pint at the barman if there is any head at all. I think the general feeling, somehow, is that it robs you of beer. From my experience though even in the UK some head is appreciated on a lager as long as its not more than a 1/4 inch thick or so. Also, each beer has its own optimal head (wether it's aesthetical or else I don't know) and you'll find some beers like the Belgian Duvel for which the head is higher than the liquid beer (although the glass it should be served in is thinner at the top so the foam might be less by volume). I think traditionally beers didn't really keeps for much more than a week and were at their best a few days after brewing, so the head is a good indication of how fresh the beer is. 190.190.224.115 (talk) 21:26, 17 July 2008 (UTC)


 * "I think the general feeling, somehow, is that it robs you of beer." Yes. If you've got a pint glass and two inches of head on the beer, you do not have a pint of beer. It's a way for the unscrupulous to short-change people. But some adverts are trying to convince the British to think in a European fashion about it and go for a beer with a tall head. Oh the lobsters! 79.66.90.252 (talk) 22:27, 17 July 2008 (UTC)


 * The foam on beer has been compared with the volt-amps-reactive (VARS) which come with electrical power (WATTS). Wouldn't be the same without'em. Edison (talk) 04:45, 18 July 2008 (UTC)

What is the coal-fired power plant with the highest capacity?
I was interested in finding out which coal-fired power plant has the highest capacity, and it seems to come down to two: Bełchatów Power Station and Kendal Power Station. According to the Kendal Power Station page, it is the "largest", which I assume to mean it has the highest capacity. But it has a capacity which is listed as being lower than the Bełchatów station is listed at. I can't find a good source for the capacity of either one of these, and Kendal uses the company's Web site as its source, which is hardly an unbiased source.

I guess I would like to know if there is a good source for this information, and what is a good metric for comparing the size of coal-fired power stations. -- timc  talk   17:20, 17 July 2008 (UTC)


 * As coal-fired power plants are generally designed to produce electricity, maximum electricity production is probably a good metric. And you can probably trust the company's website for that sort of data. <font color="#0080FF">Plasticup  <font color="#2A8E82">T /<font color="#2A8E82"> C 18:45, 17 July 2008 (UTC)


 * I suggest that the answer lies in the definition of "plant" versus "unit" as to where the largest coal burner is to be found. Edison (talk) 04:41, 18 July 2008 (UTC)


 * I can't find a site for Bełchatów, so determining its capacity is difficult. Wikipedia says it is 4400 MW, and Google suggests that this is correct.  If so, that is higher than the capacity that is listed for Kendal (4116 MW), even though Eskom says that Kendal is the largest.  Perhaps the issue is that Eskom is using the superlative "largest", which doesn't necessarily mean that it has the highest generating capacity.  But if that is the case, what metric are they using? --  timc  talk   15:06, 18 July 2008 (UTC)
 * I too found a few spots using Google that confirm Belchatow is rated at 4400 MW. Another metric could possibly be total output in MWh, so if Belchatow has more downtime or more units out of service, it could rank lower. Another possibility is that someone at Eskom just decided to put it on their website. I can't find any reliable source that actually shows a comparison, just news articles that could be repeating the company's own claim. I would say perhaps the articles should be changed to show that Kendal claims to be the largest, although Belchatow has a higher rated output. Franamax (talk) 21:54, 18 July 2008 (UTC)

Interesting question! I'll follow up with a few people here at work to find out. Perhaps it WAS the largest in the past? The metric used is definitely power production in MW rather than energy. I've only ever heard this claim being spoken of in terms of the MW output. Will follow up and let you know Watt the feedback is :P  Zun aid  ©  ®  10:55, 21 July 2008 (UTC)
 * How ubiquitous is Wikipedia? I'm getting replies from people here quoting the Wikipedia articles! This is just going round in circles at the moment, I think the best bet would be to contact whoever operates the Belchatow Power Station for this information. There was also mention that Kendal maybe the largest "dry cooled" coal fired power station.  Zun aid  ©  ®  08:56, 22 July 2008 (UTC)

Electromagnetic hover thingy
Hi all. I'm looking for information about a device that has been circulated around the web as a "levitation" or "antigtrav" device. The General layout is a (usually triangular) light wood frame with some (copper?) wires and a bit of electronics. As far as I could tell, theses things actually do hover, by "somehow" using electromagnetic fields to accelerate air downward. What are those things called, and how exactly do they work (or was it a hoax after all?) I wasn't able to find any information on Wikipedia, it would be grat if this stuff could be mentioned at Antigrav and perhaps corss-linked at EHD_thruster (even if this is a hoax i'd hope to find information about it on wikipedia).

Thanks! -- Duesentrieb-formerly-Gearloose (?!) 19:24, 17 July 2008 (UTC)

Found it: Ionocraft aka Lifter. Will do the linking. Cheers -- Duesentrieb-formerly-Gearloose (?!) 20:01, 17 July 2008 (UTC)
 * Not a big deal, and certainly not "antigravity." Edison (talk) 04:38, 18 July 2008 (UTC)
 * Sure... but one of the things often claimed to use antigravity. And since that was more or less the only thing i could remember about it, having it under "Conventional effects that mimic anti-gravity effects" seems helpfull and correct. -- Duesentrieb-formerly-Gearloose (?!) 13:39, 19 July 2008 (UTC)

Webless spider
What kind of 1 inch spider would build a short tube type burrow without a trap door under a countertop appliance and then wait at the entrance and chase passing ants no bigger than the tips of its legs? Is there a known spider that would chase such ants and if so how would it eat them if it caught them? --<font face="rage italic" size="4.5" color="LightSteelBlue"> adaptron (talk) 20:54, 17 July 2008 (UTC)

...never mind. It is the Brown recluse spider. --<font face="rage italic" size="4.5" color="LightSteelBlue"> adaptron (talk) 02:20, 18 July 2008 (UTC)

I hit "edit" all ready to post a smart-ass answer like "With its jaws, fool" and then realized - I don't actually know how spiders consume their prey, and damned if I can find it anywhere on the wiki. Anyone know? --Random832 (contribs) 15:36, 18 July 2008 (UTC)
 * Most spiders inject their prey with digestive juices, so the bug/whatever liquifies from the inside. Then they just suck out the pre-digested... stuff. &mdash;  The Hand That Feeds You :Bite 13:52, 19 July 2008 (UTC)


 * I was going to point out that it could be any funnel spider and most likely the brown recluse. As for chasing prey - that is not normal for any spider I've seen - and I've seen a lot of documentaries on weird spiders.  The most common spider will catch prey in a web.  Then, there are the ones that wait in a hole (or similar) and surprise prey as it passes by the opening.  Finally, there are spiders that drop down on prey from above.  Chasing isn't really anything I've seen.  As for eating them - spiders inject digestive fluids into the prey and then drink the digested insides back out. -- <font color='#ff0000'>k <font color='#cc0033'>a <font color='#990066'>i <font color='#660099'>n <font color='#3300cc'>a <font color='#0000ff'>w &trade; 15:52, 18 July 2008 (UTC)


 * Brown recluses catch prey by chasing and pouncing on them, rather than by catching them in a web. They are very speedy litle sprinters, and as a result are hard to kill. Edison (talk) 19:19, 18 July 2008 (UTC)
 * They also do horrible stuff to human flesh. It actually necrotizes the flesh. If you do a Google Image Search on "brown recluse bite"... well, I hope you haven't eaten recently. o.o &mdash;  The Hand That Feeds You :Bite 13:52, 19 July 2008 (UTC)

Research in statistics
I am trying to do a comparative study of two treatments in age ans sex matched individuals. How do I randomise them for a treatment? —Preceding unsigned comment added by Mudigere (talk • contribs) 21:56, 17 July 2008 (UTC)
 * Firstly you must think of the research ethics. Are you sure it is ethical to treat one of each pair and not the other? Technically, you can randomise by generating random numbers in a computer package such as SPSS or even Microsoft Excel. But should you be doing this kind of research on your own without access to the advice of more experienced researchers? Itsmejudith (talk) 22:00, 17 July 2008 (UTC)
 * He said it's a study comparing two treatments, not a study comparing treatment to non-treatment. That's the standard way of doing such studies. I agree, however, that such studies should have the support of a qualified statistician from the start if they are meant to taken seriously - as Ronald Fisher apparently said, "To call the statistician after the experiment is done may be no more than asking him to perform a postmortem examination: He may be able to tell you what the experiment died of." --Tango (talk) 00:21, 18 July 2008 (UTC)
 * Yes, I should have read the post more carefully. Even so, ethics is also something that needs to be fully considered at the design stage. Itsmejudith (talk) 07:20, 18 July 2008 (UTC)