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May 16

London Blitz

How many apartment buildings can one V-2 rocket destroy? (Assume that these are your typical pre-World War 2 apartment buildings, five stories or so and unreinforced brick/masonry construction.) 67.170.215.166 (talk) 00:06, 16 May 2010 (UTC)

The best information I can find (after a very quick search) is in our article where it says: "A scientific reconstruction carried out in 2010 demonstrated that the V2 creates a crater 20m wide and 8m deep, throwing up around 3000 tons of material into the air." 20m isn't that much, so you are probably talking about 1-3 buildings destroyed with a few surrounding buildings damaged. V-2's weren't very accurate, though, and many of them didn't hit London at all. It is also worth nothing that there weren't many apartment buildings in London during WW2, they were mostly build after the war. During WW2, high density housing would have been almost all in the form of terraced houses. --Tango (talk) 00:23, 16 May 2010 (UTC)

Although the crater was 20m wide, the actual damage (you'll have had the explosion travelling through the air too) seems to be a little bigger from the third picture (of Finland Rd and Revelon Rd) on this site. There's a considerable chunk missing from the street about a dozen houses wide, although the site doesn't mention whether any extra were cleared for the new buildings. Our article on the V-2 says that although initially quite inaccurate, a radio guidance beam was eventually used that could plant the rocket within metres of its original target. One of the reasons that V-2s, on average, only killed a couple of people is the success of the Double Cross system, which used captured Nazi spies to feed back wonky information that gradually walked the V-2 hits away from central London and towards less densely-populated areas. Really quite ingenious. Brammers (talk) 08:20, 16 May 2010 (UTC)

Channel 4 in the UK recently had a program about this, Blitz Street. The last episode covered V2 bombs. It's available on 4od to UK and RoI residents here. CS Miller (talk) 15:27, 16 May 2010 (UTC)

Neutralization of Ingested Acids

I just ingested a salad with a generous amount of rice win vinegar (I like sour things) and some barbecue with a vinegar-based sauce. This occurs to me to be a large amount of acid ingested, so I was wondering how does the body rid itself of excess ingested acid?24.88.87.41 (talk) 02:19, 16 May 2010 (UTC)

See Acid-base homeostasis. One major source of buffering is the bicarbonate in the blood, which can react with protons to generate carbon dioxide (which you exhale) and water. Another way that the body excretes excess acid is in the form of renal tubular reabsorption of bicarbonate resulting in net acid excretion in the urine. That being said, I doubt that ingestion of normal amounts of vinegar in foods would cause any significant acidosis. --- Medical geneticist (talk) 02:41, 16 May 2010 (UTC)

Followup question about the premise: I had thought, with my very vague knowledge of the digestive tract, that the ingestion of any amount of, say, vinegar, would not add "net" acid to the body, because human stomach acid is so strong; whatever mechanism exists to neutralize the stomach acid that goes into the duodenum must be so powerful that weak acids like vinegar would be neutralized instantly, with the mechanism laughing at the puny vinegar. Comet Tuttle (talk) 06:51, 16 May 2010 (UTC)

The hydrochloric acid in the stomach is recycled. Acetic acid isn't. It's not really harmless to the body, just at low doses the body handles it, at higher doses it's actually dangerous. And see [1]. The hydrochloric acid in the body is recycled mainly in order to keep the acid/base balance correct. Adding extra acid does in fact disrupt that (as does vomiting, see: Metabolic alkalosis). Presumably the body can deal with an imbalance to a point, but beyond that it can cause serious damage. See also Metabolic acidosis and Acid-base imbalance. Ariel. (talk) 07:30, 16 May 2010 (UTC)

Thanks for the links! Comet Tuttle (talk) 16:30, 17 May 2010 (UTC)

Loons in Colorado? What bird is this?

I didn't think there were loons in Colorado. I'm currently tucked away in the Rockies, it's nightfall, and I'm hearing a bizarre "laughing" call, though the direction is impossible to tell (the sound echos around the valley I'm thinking). There is a large lake a bit off in the distance, however. The sound is similar to the laughing parts near the end (or second half) of the sound clip on the Loon#Etymology_and_taxonomy page. Before I check some reference books (Google wasn't being too helpful, though evidently there have been loons photographed around the state, I'm just not sure why they'd be here so soon), could there be some other animal that "laughs" like this? I have not heard any bugling (if there were, I'd think it was elk, anyway) or other sounds that were played in that clip. Any help would be great, thank you. – Kerαunoςcopia^◁_galaxies 03:10, 16 May 2010 (UTC)

Coyote? Rckrone (talk) 05:01, 16 May 2010 (UTC)

Interesting, didn't even occur to me. The coyotes can usually be heard howling right around dusk, but I'd never heard them "laughing" like this before. However, I thought I also heard "youngins", if that makes sense. So maybe they were just coyotes. I hope they do it again tomorrow. – Kerαunoςcopia^◁_galaxies 05:12, 16 May 2010 (UTC)

It isn't unusual to see loons in the Colorado area. I have been exploring the database of sight records at eBird.org and have found a map of reported sightings along with frequency counts. A link to that page is here: http://ebird.org/ebird/comonloonmap. eBird.org is a wonderful website for both tracking your personal birding escapades, and for examining birding data from around the Americas. A link to Common Loon sightings specifically in Colorado is provided here:http://ebird.org/ebird/commonloonmap/usa/colorado. A link to the average count of Common Loons throughout the year in Colorado is here: http://ebird.org/ebird/commonloon/usa/colorado/averagecount. I hope this helps clear up any questions, and keep on birding! Stripey the crab (talk) 14:55, 16 May 2010 (UTC)Stripey the crab

Awesome link. Okay, next question, because they're doing it again. It's definitely not coyotes. Why? Because the laughing (whoo whoo whoa whoa wah wah wah ah ah ah ah ah) is moving around, in circles... the sound is coming from a creek about 50 yards away from me, and I can hear it "traveling" at a high velocity in circles, and I haven't heard anything like this since I was about 20 feet from a bat and its nest (I think?)... the bat was making a weird vwum vwum vwuuuum sound with its wings and I managed to record it on Minidisc at the time. So ... could this be a very large bat, or just a really crazy bird? Again, it's dusk here, not yet nightfall, and the sound hasn't happened during the day. As for the coyotes, they did their usual barking and howling, but that's earlier in the evening, and yesterday I managed to track their source several hundred yards to the east, farther up the creek and into the mountains than this weird laughing sound. I can't imagine it's a loon now, but sure sounds eerie. Btw, Stripey the crab, interesting website, thanks again for posting. – Kerαunoςcopia^◁_galaxies 02:39, 18 May 2010 (UTC)

Okay, I recorded (very, very, very badly) the sound of the thing, and of course that's when a flock of geese — the only creatures on God's good earth I don't mind being hunted — and a plane decide to fly by. Anyway, expect something that sounds like it's from 1894 because I couldn't afford anything good at the time. I'll post it up here in a few minutes. – Kerαunoςcopia^◁_galaxies 02:59, 18 May 2010 (UTC)

So, does anyone know what bird or creature is this? File:Unknown bird call.ogg (Lots of white noise... I tried noise removal with Audacity and the result was really cool, but unusable. Apologies if I'm breaking some rule here, I'll {{db-author}} the sound file after a few days. – Kerαunoςcopia^◁_galaxies 03:29, 18 May 2010 (UTC)

Hurricanes crossing the equator

In recorded history, has there ever been a hurricane that has crossed the equator? --The High Fin Sperm Whale 04:56, 16 May 2010 (UTC)

According to the list of tropical cyclones, this has never happened. Cyclone Agni in the Indian Ocean in 2004 came close to the equator but did not cross it. However, in the article about the storm it appears to say that the center did cross, or may have crossed, the equator while the storm was still forming (the wording is a bit confusing). --Anonymous, 05:17 UTC, May 16, 2010.

I asked a question that was similar to this awhile back. The responses may be helpful: Link to August 22, 2009 Archive: Tropical_Cyclone_Crossing_The_Equator Falconus^{p t c} 19:57, 16 May 2010 (UTC)

The gist of it is, there has never been a TC known to cross the equator, but it isn't conclusively known whether or not it's possible. Juliancolton | ^Talk 13:07, 19 May 2010 (UTC)

medical malpractice

I've heard that the greatest abusers of drugs are not street addicts but doctors and nurses. Can anyone confirm or refute this? 71.100.0.29 (talk) 06:12, 16 May 2010 (UTC)

You're the one making the claim. Generally, it is the responsibility of the person making the positive assertion to provide evidence to back it up. Generally "I've heard" is a very unreliable source. We must assume that claims like this are false unless anyone can provide evidence to the contrary. --Jayron32 06:15, 16 May 2010 (UTC)

This article claims the rate of substance abuse among "pharmacists and some health care professionals" is higher than among the general populace, though this article mentions the anesthesiologist substance abuse rate is only around 2%. Googling "drug abuse by doctors", there seem to be numerous statements that it's hard to gauge the true rates because it's all hidden and confidential. Comet Tuttle (talk) 06:42, 16 May 2010 (UTC)

It seems unlikely but there are several problems in providing a statistical answer. First, how do you define a "street addict"? Someone who buys any illegal drug from a street seller? Someone who lives on the street because his illegal drug addiction has cost him his home? Someone who lives on the street because alcohol addiction cost him his home? Second, how do you define "substance abuse"? Do legal substances like tobacco and alcohol count? Any use at all, or just use to the point of impairment? Alcohol is certainly the most common substance abuse that leads to impairment among doctors and nurses. Third, it is possible to estimate substance abuse that leads to loss of medical or nursing license because that is published by the state boards of medicine or nursing. I can tell you that every quarter maybe a couple of doctors in a populous state lose their licences for drug related behavior, but most of those license losses are because the doctor broke the law (i.e., selling oxycontin to addicts) rather than because they were addicted. There are not public statistics on those doctors or nurses who quietly and voluntarily go to rehab. And obviously there are no public statistics on how many doctors and nurses are abusing substances but continue to function. So your question is simply not answerable as phrased. Finally, you do realize that substance abuse by professionals is not the same thing as "medical malpractice" and is only tangentially related? Substance abuse per se is not malpractice. alteripse (talk) 14:27, 16 May 2010 (UTC)

Another controversial, unsourced post about drugs. This trolling needs to stop. Regards, --—Cyclonenim | Chat  14:45, 16 May 2010 (UTC)

• When Health Professionals Abuse Drugs and Alcohol: Personal Problems and Public Health Consequences

• SPECIAL TREATMENT: Disciplining Doctors - Medical Boards Let Physicians Practice Despite Drug Abuse

• Drug Abuse among Doctors

• Physicians with Substance Abuse Issues

• Treating physician substance abuse

I agree. Please stop your personal attacks along with your trolling.

71.100.0.29 (talk) 05:07, 18 May 2010 (UTC)

For better or for worse, the methods and motives of doctors are generally 'given a pass' in mainstream discourse. If there is a serious discrepancy between what doctors do, and what is actually most useful to the patient, well, it's generally best to not go there. It's not a defensible approach, questioning whether drugs, surgeries, and the like are legitimate or not. Best to just assume they are. In my experience anyway. Vranak (talk) 01:28, 18 May 2010 (UTC)

After reading this article it would be hard not to agree, unless you were a member of the State Medical Board, which seems to object vehemently. 71.100.0.29 (talk) 04:50, 18 May 2010 (UTC)

'Banana' Snake

Good afternoon

I have been given some information regarding a snake that bites into the heads of bananas, the venom deposited, then a creature/person eats the fruit, succumbs to the venom and falls, thus creating the meal for this meat-eating snake.

Can anyone please verify this information?

Many thanks 88.108.223.239 (talk) 11:15, 16 May 2010 (UTC)

It sounds almost as unlikely as the liver-eating snake above, but I'm prepared to be amazed if anyone can come up with even a scrap of evidence. Dbfirs 11:25, 16 May 2010 (UTC)

(edit conflict)It seems unlikely, googling "banana snake poison" doesn't bring anything up. I found this which discusses using bananas poisoned by snakes and then being used as a poison. Why would a snake go to the bother of waiting for something to eat the particular banana it had bitten when it could just bite the animal instead? Where did you hear it from? 131.111.30.21 (talk) 11:28, 16 May 2010 (UTC)

As counter-evidence, this website: Department of Forensic Medicine, Maulana Azad Medical College, New Delhi, Indiasays: "The question is often asked, what would happen if one ingested the snake venom? Would he die? The answer is "no". Snake venom is a mixture of proteins which would be digested in the stomach. It is also suggested that snake venom is not absorbed from the gastric mucus membrane. However if a person is suffering from gastric ulcer, some snake venom may be absorbed through this ulcer and may pose danger to the person ingesting snake venom." Dbfirs 11:33, 16 May 2010 (UTC)

Sorry, I didn't realise that this is the same link as that provided by 131.111.30.21 Dbfirs 11:41, 16 May 2010 (UTC)

Also note that venom is not the same as poison.--Shantavira|^{feed me} 14:54, 16 May 2010 (UTC)

Banana Snake extra answer!!!

Hello again

Im sorry, being a newbie here, I am unaware how to make this part of the answer section of my original question.

Many thanks for the answers given so far.

I agree about why would the snake bite into the banana, and not go direct (cut out the middle man eh?)... it did cross my mind, but of course, there is no telling what instincts are driving the particular action, especially in a 'caught in a trap situation'.

In answer to the querie, I got it from my hubby who was told the info by a colleague who works for a banana processing plant in UK. (Fyfe's depot in Tilbury perhaps?) Anyway, he was telling hubby about the gas lined packing sacks, the 'antidote' spray to the gas and the fact that when the plants are removed from the sacks at some point during the process, scorpions can be seen scuttling around, as well as the snakes occassional appearances. These creatures are then 'dealt with' (official term???). Anyway, I was amazed by all this and wanted to verify the info re the snakes as of course if it's true, then everyone should be made aware.

Thank you re the info about the efficacy of the poison/venom and stomach...

I will keep hunting, and if I find any more, I will post back here to let any interested party know. Many thanks again, I much appreciate your help. 88.108.223.239 (talk) 16:04, 16 May 2010 (UTC) —Preceding unsigned comment added by 88.108.223.239 (talk) 16:02, 16 May 2010 (UTC)

It strikes me that there might be some confusion here. There are certainly poisonous/unpleasant animals that live in banana trees and potentially pose a threat to people who work with bananas (e.g. the Brazilian wandering spider). I don't think any of these pose a threat because they sting bananas and make them poisonous—this seems totally unlikely. But for someone who works with bananas, these kinds of things are probably not uncommon threats to watch out for, and there are probably means of controlling them built into the system. Rest assured, if consumers were at some kind of risk I'm sure people would have been aware of it by now (do you know anybody who has keeled over from eating a banana? Have you ever heard of such a thing? If not, then it's probably not a major risk). --Mr.98 (talk) 18:44, 16 May 2010 (UTC)

One banana? No. Many, many bananas? Yes. 206.252.74.48 (talk) 21:12, 17 May 2010 (UTC)

Onion Bully

Anyone have any credible suggestions about how Onion Bully works? It is a metal shoehorn that goes in the user's mouth while they cut onions that supposedly stops them from crying. Other than "tear science" and "the shoehorn tells your brain to turn off your tear ducts" can the wonderful persons of the science ref desk provide some clue as to how this (probably useless) invention might work? --Jabberwalkee (talk) 16:24, 16 May 2010 (UTC)

Most likely Placebo effect. ---- — Preceding unsigned comment added by 76.228.199.229 (talk)

I can't find any reference to it that isn't a recycling of the YouTube video or a reposting of a single Geekologie blog post. Based on the name and logo color scheme, I can't help but wonder if it's an elaborate hoax by The Onion. TenOfAllTrades(talk) 18:30, 16 May 2010 (UTC)

I think it is to do with the fact that it encourages you to breath through your mouth. I find it helps when cutting onions and there seems to be a fair amount of anecdotal advice on the web also suggesting this (e.g.. So basically there is no need to but the product, just breath through your mouth. 86.7.19.159 (talk) 18:46, 16 May 2010 (UTC)

I would just suck on a Jolly Rancher while cutting an onion, I wouldn't spend $10...wait, I get two for that price?! :D – Kerαunoςcopia^◁_galaxies 21:31, 16 May 2010 (UTC)

For what it's worth, I have terribly sensitive eyes and can usually tolerate cutting an onion if I am mindful to only breathe in through my mouth and not my nose. I suspect the metal itself has some sort of ionizing effect on your tastebuds and is a sort of sensory distraction against the impact on your other senses. --Jmeden2000 (talk) 18:25, 17 May 2010 (UTC)

One traditional way to avoid onion-related lacrimosity is to suck on a metal spoon. I suppose the Onion Bully works in the same way, and is intended for those without spoons in their kitchens. DuncanHill (talk) 21:34, 16 May 2010 (UTC)

The mechanism they describe, turning off the tear ducts, sounds like a bad idea! If my eyes are irritated by an onion, I personally would want the irritation washed away. Paul (Stansifer) 22:23, 16 May 2010 (UTC)

The slot in the device keeps an airway open between the lips so that inhaling is through the mouth instead of the nose. Cuddlyable3 (talk) 22:54, 16 May 2010 (UTC)

It works with any object placed in the mouth that protrudes and "blocks" the miniscule droplets of onion juice from hitting your eyeballs. My mom uses a big piece of bread like a sponge. but the makers of onion bully couldn't get rich of plain old bread!165.212.189.187 (talk) 16:41, 17 May 2010 (UTC)

In addition to the metal spoon technique DuncanHill mentions, a matchstick held in the teeth (red end out) is a supposed method of neutralizing the lacrimotic effects. I want to say it's even been suggested on cooking shows, possibly by the likes of Julia Child herself. The sulfur in the match counteracts the sulfur in the onion somehow, or so the theory goes. A quick google search brought up Yahoo answers, Askville, &c., but nothing very authoritative. Some sites suggest striking the match and blowing it out; some don't. Some jerk on the Internet (talk) 12:43, 18 May 2010 (UTC)

Exposure to Pornography

I'd like to preface this question by stating the obvious that children themselves should NEVER be sexualized. My question is regarding the dangers of exposure...There seems to be a perpetual debate regarding children witnessing sexual acts on tv and pornography on the internet. People spend lots of time filtering what their children see but besides a sense of shame about nudity is there really any evidence children will be psychological harmed from seeing sexual material? I wouldn't want my son or daughter to see internet porn but I'm wondering why I think that besides cultural norms. Surely back in prehistoric times people had sex out in public all the time so what changed and why do we now consider early exposure to be so harmful? TheFutureAwaits (talk) 20:21, 16 May 2010 (UTC)

Interesting question. You could take the prehistoric point even further and suggest that anyone who passed through puberty might have ended up reproducing, even in young teenage years. That would suggest to me that there's little chance of exposure to pornography at that age being harmful. Pre-teenage years is a different question altogether. Regards, --—Cyclonenim | Chat  21:04, 16 May 2010 (UTC)

Seriously beg to differ. We have no evidence either way of prehistoric attitudes; we do have evidence of social discomfort with parental nudity back 3000 years or more in our own culture (Genesis), and there is plenty of reason to think that the core stories and cultural values in it go back a lot farther. On the other hand, there is testimony from explorers and others that public sexuality in various non-Western cultures was not always hidden or an object of modesty or shame. However, both of those things are different from pornography, and speculation about prehistory is not very relevant to the question of how harmful exposure to modern pornography may be to modern children. I doubt one can separate out the social context: I would contend that certain items might be "porn" in one culture but not another, and that the effect of large exposure to children in the two cultures would be partly a function of whether it is considered "porn", with all the associated shame, guilt, taboo, etc that goes with it for children. There is evidence that exposure to substantial amounts of televised violence and sex changes attitudes of children, including both responses to them and lowered thresholds of engaging in it. Few people think that single exposures are especially harmful, and I doubt if anyone has tried to measure dose response. The other difficulty with answering this is that the kind of parents who allow children to view large amounts of porn are likely to be unusual in many ways, making it difficult to disentangle specific parenting actions. I am sure that if you google exposure of children to pornography you would get a fuller answer. alteripse (talk) 21:40, 16 May 2010 (UTC)

This might sound like a troll post but really, it's not, I'm at work so I can't exactly google for sources! Anyway, only a few months ago, some group in Canada tried to do a study into the effects of exposure to pr0n on the social life of college students, but they couldn't find enough students who didn't watch pr0n. It was reported in Nature magazine. Vespine (talk) 22:15, 16 May 2010 (UTC)

I must say it's not surprising. I assumed the original questioner was referring to pre-adolescent children, not young adults. It would be impossible to do even an ascertainment study in children. alteripse (talk) 23:16, 16 May 2010 (UTC)

I agree with alteripse that sexuality and pornography are different things, and mixing up cultural norms within a given culture always seems to be a recipe for social/individual problems. That said I do think that the bruhaha about protecting the children, especially in modern US politics, is often overblown. Original Research ahoy: When I was, I don't know, 9 or 10 or so, my friends (all male) and I were insatiably fascinated by the idea of nudity and sex (though we were definitely prepubescent—we, or at least I, were certainly not interested in having sex at this point), and sought out all sorts of pornography in our parents' closets, bathrooms, and other places they thought we were too innocent to root through. Reading Playboy was pretty exciting for us, in part because it was clearly taboo. I don't think it traumatized me, though perhaps this was because it was on my own terms, and I don't think it irreversibly screwed up my future love life, attitudes towards women, and so on (but really, who knows?). Now, I don't claim to know if it's the same thing for all children, or how much of that is due to my being white, American, and middle class, or how much it would be different if what we were exposed to wasn't the relatively mild Playboy spreads compared to, say, what passes for "hardcore pornography" on the internet these days. But I don't think it's a total given that even in this modern culture that all children are "innocents" until they magically become 18, or that anything sexualized before that will "scar" them in some horrible way. (I agree that you need to set an age of consent, for clear administrative purposes.) I think adults in the modern US (and probably elsewhere) have a peculiar way of forgetting what they were like as children in imagining how they would like their own children to act. --Mr.98 (talk) 02:21, 17 May 2010 (UTC)

The key factor here is that you "sexualized yourself" at a pace that worked for you. The trouble comes when predatory adults try to push children past what they're ready for. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:08, 17 May 2010 (UTC)

What does 'sexualized' really mean? Children have an erotic life just the same as adults. I guess you mean they shouldn't be exposed to or involved in anything shady. So, perhaps you mean they shouldn't be corrupted (clearly not, but idealism doesn't prevent it). Getting a kiss from daddy or the boy in school is not corrupting but it's naive to think there's no sexual element in it. Innocently sexual is still sexual. Vranak (talk) 08:40, 17 May 2010 (UTC)

The sexuality of adults vs. children is, to use a Larry Miller quote out of context, "like the difference between shooting a bullet and throwing it." ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:08, 17 May 2010 (UTC)

Concurred. But I'm always a bit suspicious when people start talking about 'sexualizing children'. Seems like a big red herring, so some other fishy business can carry on unnoticed. Vranak (talk) 16:24, 17 May 2010 (UTC)

Searching on PubMed (www.pubmed.gov) gave me (among others) the following article:

• Hennessy M, Bleakley A, Fishbein M, Jordan A (2009). "Estimating the longitudinal association between adolescent sexual behavior and exposure to sexual media content". J Sex Res. 46 (6): 586–96. doi:10.1080/00224490902898736. PMC 2783973. PMID 19382030.

Apart from the study itself, the article contains a lot of references which seem interesting. Gabbe (talk) 13:13, 17 May 2010 (UTC)

There's really no solid study of this, because of the ethics involved. To provide a proper, scientific study, you'd need a group of children who were intentionally exposed to porn or sexual situations, to judge their reactions against a control group. Not. Gonna. Happen.

That said, you can perform studies on people who self-reported as exposed to such situations, but that's invariably filtered through the lens of memory and social stigma. You could try studying victims of child abuse... but that inherently biases the study towards abusive exposure to sexuality. There's just no real, scientific way to get this kind of answer.

As an aside, Alfred Kinsey had done a study on the orgasmic capabilities of young children, which helped set aside the notion that children are asexual, but it wasn't without controversy; especially since a majority of it came from memory, along with interviews with men who had sexual interactions with children. — The Hand That Feeds You:^Bite 15:02, 19 May 2010 (UTC)

NG photo question

(Moved from misc desk)

OK, so this one[2] has puzzled me ever since I saw it in the magazine about 3 years ago. The bug on the right is a trap-jaw ant. The critter on the left is unidentified, and the caption is a bit vague. So my question is for all you insect experts out there: What's the bug on the left, and has the ant just bitten its head off, or what? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:47, 16 May 2010 (UTC)

This is a biology question. With no research I'd say the insect on the left is some sort of grasshopper, compare the picture that heads the WP article, not exact but . . .. The grasshopper's head has not been bitten off as you can clearly see its large multifaceted eyes and jaws. Richard Avery (talk) 07:34, 16 May 2010 (UTC)

Yes, looks very much like a grasshopper nymph, with its head pretty much intact. The only thing missing may be the tips of the antennae, not sure. --Dr Dima (talk) 01:42, 17 May 2010 (UTC)

What would be that part that seems to be lying on the leaf just to the grasshopper's left? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:22, 17 May 2010 (UTC)

Also, the caption in the article from which the picture came suggests the grasshopper is a "predator". First off, the ant seems to be bigger than the grasshopper. Secondly, I thought grasshoppers ate vegetation. So I'm just puzzled by what's really happening in this picture. Maybe NG was also, and just made something up? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:26, 17 May 2010 (UTC)

Are we looking at the same picture here? The one you linked to shows a grasshopper and an ant on the leaf. Grasshopper is on the left. Ant is on the right. There is nothing lying on the leaf, and there is nothing to the grasshopper's left. The picture is by Mark W. Moffett (he is well known). Or are you talking about something else entirely? --Dr Dima (talk) 04:41, 17 May 2010 (UTC)

BTW, "well known" implies "is very highly unlikely to make things up". --Dr Dima (talk) 04:49, 17 May 2010 (UTC)

Yes, a grasshopper on the left and a trap-jaw ant on the right. Just the other side of the grasshopper it looks like there's a severed grasshopper appendage. But maybe I'm misinterpreting things. Anyway, the original writeup in NG, as well as the description of this picture back on the parent page (not this specific page) talks about the ant defending itself against a predator. So is the grasshopper a predator to an ant? I wouldn't think so. But maybe they were just talking about the trap-jaw ant in general, and this was the best photo they had? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:49, 17 May 2010 (UTC)

The caption reads, "Do Not Blink: Set off by the touch of a prey insect against sensitive trigger hairs, the mandibles of the trap-jaw ant Odontomachus hastatus snap shut in the fastest reflex ever recorded in the animal kingdom. The ant's jaws accelerate from zero to 143 miles (230 kilometers) an hour in 0.13 milliseconds—2,300 times faster than the blink of an eye."

But that does not seem to describe the photo very well. I just thought someone here smarter than I am (which is probably most of you) might be able to see what I'm not seeing. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:56, 17 May 2010 (UTC)

Trap-jaw ants are predators. The jaws of a trap-jaw ant serve to kill and dismember prey, as well as to deter predators. These ants may even use their jaws to catapult themselves away from the danger if necessary, AFAIR. Grasshopper is prey. I don't think there's anything else in the picture, but I may be missing something, too. --Dr Dima (talk) 07:17, 17 May 2010 (UTC)

Well, duh, I said you all were smarter than me. The poor li'l ol' grasshopper would be the prey, not the predator. That still doesn't explain that seemingly severed piece sitting on the leaf behind the 'hopper's left side. I'm guessing the photographer was just glad he got such a nifty closeup, and the caption was just general information. The speed of the jaw is remarkable, but it's also quite small. The mandibles of an ant the size of an elephant probably wouldn't be able to snap shut quite so quickly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:47, 17 May 2010 (UTC)

May 17

Tomato and Corn

Why is a tomato a fruit? And is corn a vegetable or grain? wiooiw ^(talk) 01:55, 17 May 2010 (UTC)

See Tomato#Fruit or vegetable?. Dismas|^(talk) 02:04, 17 May 2010 (UTC)

(edit conflict) The term "vegetable" has no definition in horticulture; it is applied somewhat arbitrarily. Fruits, by definition, are the mature, seed-bearing ovaries of angiosperms (flowering plants). Grains (cereals) are those grasses of the family Poaceae. Here, I am assuming that by corn you are referring to maize; be careful with your use of the word, since "corn" can be used to refer to the principal cereal crop of a region. Intelligentsium 02:07, 17 May 2010 (UTC)

Most of the world's growers and consumers of corn mean corn, the tall stalk with big ears, when they say corn. Not "maize." Edison (talk) 03:48, 17 May 2010 (UTC)

The big, international seed companies use the term "maize" to avoid confusion among the English-speaking portion of their audience, which mean various things when they say "corn". Non-English speakers have other terms. In Spanish, choclo or cereal are used for the generic term "corn", whereas maíz is maize, trigo is wheat, cebado is barley, centeno is rye, etc. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:00, 17 May 2010 (UTC)

This is my favourite article on the tomato subject: Nix v. Hedden.Aaadddaaammm (talk) 15:01, 17 May 2010 (UTC)

Yes, referring to maize, thankyou. wiooiw ^(talk) 02:41, 17 May 2010 (UTC)

The more generic query

On the subject of fruits vs vegetables, back in high school (several decades ago) we were told the question was nonsense because biologically one is actually a subset of the other. You might as well ask, when seeing a four-wheeled vehicle on the street, "Is it a Ford, or is it a car?"

So, quite some years later, the question: is there any truth in that analogy, or is it just another "Go-away-kid-you-bother-me" response? DaHorsesMouth (talk) 02:47, 17 May 2010 (UTC)

Interesting perspective. wiooiw ^(talk) 02:52, 17 May 2010 (UTC)

"Vegetable" often refers to any kind of plant matter (consider the classic animal, vegetable, mineral trichotomy), so in that sense, it's totally correct. But culinarily, "vegetable" has a variable and vague, yet more specific, meaning. Paul (Stansifer) 03:06, 17 May 2010 (UTC)

If you read the intro and the "Fruits vs. Vegetables" section of our article "Vegetable", you'll see where the problem comes from. The conclusion is that if you are speaking scientifically, then all fruits are also vegetables - but not all vegetables are fruit. If you are speaking in a culinary sense - then fruits and vegetables are entirely separate categories - with no overlaps. However, some thing that are properly fruits are sometime mis-categorized by the general public, leading to considerable confusion (eg Tomatoes are fruit according to both scientific and formal culinary definitions - but the average person in the street considers them to be vegetables. They also consider Rhubarb to be 'fruit' when it is of course a stem - and therefore a vegetable. So now you have science, the culinary arts and common usage all coming up with wildly different definitions. Bottom line is: You decide! SteveBaker (talk) 03:27, 17 May 2010 (UTC)

According to Jewish law, a benediction praising the Almighty must be recited before eating any item of food or drink. The text of the benediction depends on the type of food eaten. For fruit it is בורא פרי העץ (who creates the produce of the tree); for vegetables it is בורא פרי האדמה (who creates the produce of the ground). Should one err and recite the benediction for vegetables over fruit, one has fulfilled one's obligation, the reason being that fruit is also produce of the ground. However should one err and recite the benediction for fruit over vegetables, one does not fulfil one's obligation since vegetables are not produce of the tree. Simonschaim (talk) 07:36, 17 May 2010 (UTC)

So why would anyone be stupid enough to risk the wrath of the almighty and eternal damnation? If I believed in all that nonsense, I'd be saying the vegetable benediction no matter what! No sense in risking a mistake! (Maybe you get extra points for using the more precise version?) SteveBaker (talk) 15:56, 17 May 2010 (UTC)

Can anyone provide one or more scriptural references about requiring those benedictions? -- Wavelength (talk) 16:11, 17 May 2010 (UTC)

Benedictions before eating food are Rabbinical injunctions. Scriptural support can be found at Psalms 24:1 and Psalms 115:16. Further details can be found in the Babylonian Talmud, tractate Berachot 35a-b. (An English translation of the Babylonian Talmud can be found on the internet.)Simonschaim (talk) 18:48, 17 May 2010 (UTC)

I found http://scripturetext.com/psalms/24-1.htm and http://scripturetext.com/psalms/115-16.htm, which can be harmonized by the earth having been entrusted to the human race, but I did not find any requirement of those benedictions. -- Wavelength (talk) 19:34, 17 May 2010 (UTC)

Wavelength: Please read the reference in the Babylonian Talmud, which I suggested. Yon can find it via Google - Soncino Talmud.Simonschaim (talk) 19:44, 17 May 2010 (UTC)

Caesar's last breath

I read in a Paul Zindel novel that every person in the world contains at least two atoms of Julius Caesar's last breath, or something along those lines. I find it hard to believe (and obviously impossible to prove), but do the nature of atoms allow for something like that to happen? Thanks!  ?EVAUNIT^{神になった人間} 02:44, 17 May 2010 (UTC)

If sufficient time for mixing has taken place, such that Caesar's breath were evenly mixed throughout the atmosphere - then I think this is believable. However, the issue of whether sufficient time has elapsed is a tricky one.

Let me crunch the numbers for you: According to Atmosphere of Earth, the atmosphere weighs in at about 5x10¹⁸ kg. According to [3], 65% of the mass of the human body is oxygen and only about 3% nitrogen, so let's ignore the nitrogen for the sake of simplicity. Therefore, an average 75kg human contains about 50kg of oxygen - which is therefore about one part in 10¹⁷ of the atmosphere. So if the mixing is even, we each have about 1/10¹⁷th of Caesar's last breath. A typical human lung capacity worth of air weighs about 5g - but only 20% of that is oxygen - so let's go with one gram. (oxygen says that a human consumes around 2g of oxygen per minute...so we're obviously in the right ballpark). That's 1/16th of a mole - or 1/16th of Avagadro's number worth of atoms (Avagadro's number is 6x10²³ and the atomic weight of oxygen is 16)...so his last breath comprised roughly 4x10²² atoms of oxygen . So 1/10¹⁷th of the that last breath would be around half a million oxygen atoms.

Conclusion: If atmospheric mixing is perfect and the majority of the oxygen in our bodies ultimately comes from the atmosphere (possibly via plants and animals that we eat - possibly by breathing) - then there are half a million oxygen atoms of Caesar's last breath in each of our bodies...plus some carbon, nitrogen and hydrogen atoms. I don't know where the number '2' comes from...but it all comes down to how good that mixing truly is...and I have no clue how to even guesstimate that! However, that's a pretty good sized ratio - there is a lot of room for uneven mixing. So I'd say that this claim is almost certainly true - perhaps even a fairly large underestimate.

SteveBaker (talk) 03:09, 17 May 2010 (UTC)

"Et least two, Brute!" ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:37, 17 May 2010 (UTC)

The Mixing time of the atmosphere is relatively short. The oceans complicate matters considerably though. It has a much longer mixing time and the exchange of oxygen atoms between the ocean and the atmosphere interferes in the simple calculation presented above by Steve. Dauto (talk) 03:31, 17 May 2010 (UTC)

"Et least two, Brute!" ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:37, 17 May 2010 (UTC)

I think the version I heard was about each breath you make, rather than your entire body. So we have 5x10¹⁸ kg of air in the atmosphere and 5g of air in each breath, so each breath makes up 10^-21 of the atmosphere. There are about 2x5/14x6x10²³ atoms in a breath, so each breath will have 400 atoms from Caesar's last breath. There is probably sufficient margin of error in this calculation for it to be consistent with the 2 atoms quoted by the OP. For the reasons given by BenRG, this calculation has no real world meaning, it is just a way of demonstrating how small atoms are. --Tango (talk) 16:19, 17 May 2010 (UTC)

The actual answer to this question is that it has no answer because atoms are quantum particles. If you shake a bottle of oxygen for 2000 years and then remove a few molecules, the molecules that you remove can't be identified with any molecules that went in. If anything, it would be better to say that each molecule that you pull out is an equal mixture of all the molecules that went in. (It does still make sense to talk about mixing efficiency, though—if the mixing is not perfect then you may be able to make more-or-less vague statements about the distribution of Caesar's last breath, though you can't say anything about individual molecules. But I think that 2000 years is enough to thoroughly scramble the atmosphere.) -- BenRG (talk) 08:15, 17 May 2010 (UTC)

Your response reminds me of this comic: [4]. While the individual atoms are indistinguishable from and identical to one another, the one that you put in the bottle is still unique. In a bottle of gas, the molecules will generally behave as largely classical entities – ping pong balls bouncing off one another – no need to treat them quantum mechanically. If I put one ping pong ball in a huge bottle of ping pong balls and then shake, I won't be able to identify the (apparently identical) ball I put in afterwards — but that doesn't mean that any sort of ping-pong-quantum entanglement has occurred; it just means that they all look the same. TenOfAllTrades(talk) 12:46, 17 May 2010 (UTC)

A similar question came up last year, here, regarding whether we have atoms in us that were once in our ancestors. It reached a similar conclusion to BenRG's answer. Oh wait it was BenRG who pointed it out last time too! 131.111.30.21 (talk) 09:20, 17 May 2010 (UTC)

By now we all get Baseball's joke. Cuddlyable3 (talk) 14:46, 17 May 2010 (UTC)

Can you supply a reference for this quantum mixing stuff? I've never heard this theory before, and I'm somewhat skeptical. Thanks! Aaadddaaammm (talk) 14:58, 17 May 2010 (UTC)

BenRG is right. The reference you are looking for is identical particles. Dauto (talk) 16:57, 17 May 2010 (UTC)

I don't agree with TenOfAllTrades criticism of BenRG's argument. The applicability of a classical model to compute physical observables is not relevant here. Of course, typical quantum effects like entanglement or interference cannot be observed, but quantum mechanics itself explains how that happens (via decoherence).

The point made by Ten is basically that if you put a molecule inside a container that already contains N identical molecules, you could follow in time where the molecule you put in moves to. So, if you take out a molecule from the container some time later, you can tell with certainty whether or not that was the same molecule that you put in earlier.

Let's first treat the molecules as non-interacting point particles and pretend that the container is perfectly isolated from the environment. To give Ten's argument as much room as possiblem, we assume that the intitial state after we put in the molecule is described by all the molecules being in some minimum uncertainty Gaussian state. Then, even though we have to explicitely symmetrize or anti-symmetrize the total wavefunction, you can still say that there is a Gaussian peak somewhere that wasn't there before the molecule was put in and that extra Gauusian peak will move due to the time evolution described by the Schrödinger equation. So, it looks like we can follow the extra molecule in time.

The problem here is that the width of the Gaussians will also become larger and larger over time. When there is substantial overlap between two Gaussians and you were to detect a molecule, you can no longer say which of the two Gaussians was responsible for that. Now, you can argue that the spreading of the wavefunction can be prevented by including interactions. However, including interactions between the molecules in the container alone won't work.

If you split the N+1 particle system as 1 plus environment consisting of the other N particles and argue that collisions lead to an effective collapse of the wavefunction, you end up with describing the state of the single particle as a statistical mixture of pure states. This is described by a density matrix. So, you then have an ensemble of narrow Gaussians, but they can then be more or less everywhere with equal probability after a short time. So, the information where your molecule is still gets lost. No surprise, of course, because the statistical description could never yield more information than the exact description.

But what if we include interactions with the environment outside the container? Even though that can work, this would amount to cheating as you then appeal to information that resides outside the system in this toy model, while in reality there is no "outside envirmonment". Count Iblis (talk) 15:32, 17 May 2010 (UTC)

TenOf AllTrades, unlike the pingpong balls which are only apparently identical, atoms are actually indistinguishable. BenRG is correct in his assesment. Dauto (talk) 16:57, 17 May 2010 (UTC)

The point is that you are all masking the reason for the little canard rather than explaining why it exists in the first place. While the "facts" about distinguishibility of individual molecules or atoms is somewhat debatable, that debate isn't really useful here. The purpose of the statement is to expose the sheer size of a number like Avogadro's number. Students have a hard time wrapping their heads around fantasticly large numbers. Additionally, since things like numbers of molecules and concentrations are often dealt with logarithmicly (using things like scientific notation and pH and other things like that) it can be very difficult to truly grasp how small molecules are, and how many of them there are in something. Considering that we all have over a billion oxygen atoms breathed by Caesar in his last breath in out lungs right now, and that such statement is mathematically verifiable via simple arithmetic is a useful demonstration of the scale of the numbers involved. The fact that quantum mechanics makes the statement incorrect doesn't matter, its supposed to be a heuristic exercise, not a scrupulously true statement. Yes, eventually, if a student goes far enough in their education, the more accurate models of molecular behavior should be taught. But a sixteen year old who is being exposed to chemistry for the first time is not likely intellectually prepared for such information when they are still trying to wrap their heads around the idea of the mole and stuff like that. The statement is mathematically accurate, and that is all that is needed here. --Jayron32 19:39, 17 May 2010 (UTC)

(ec) All of this quantum nit-picking is all very wonderful - but surely it doesn't matter whether the mixing is at the quantum level or at the classical ping-pong-ball-atom level. The average amount of atomic 'stuff' that was a part of Caesars' last breath is goind to be the same. I'll agree that one oxygen atom is pretty much as good as any other - and there is a philosophical question of whether two things that are quite utterly identical can be said to have separate identities - but the question isn't about whether we could measure the number of ex-Caesar atoms - merely if they are statistically likely to be present. One could (in principle) insert some fancy isotope of oxygen into the dying emperor's lungs and measure the amount in later generations...so it would be possible in principle to do some kind of physical measurement (if you knew in advance of course!). Mostly, this question is a wonderful thought experiment that really drives home just how ungodly huge Avagadro's number really is...and it does a great job of doing that, IMHO. SteveBaker (talk) 19:41, 17 May 2010 (UTC)

I generally agree with both of you (Jayron and Steve). But particle indistinguishability is interesting too. Saying that particles are "indistinguishable" in the QM sense is not the same as saying that they have identical properties. The theory allows for particles that have identical properties but aren't "indistinguishable". The three fermion generations would be an example if it weren't for the Higgs interaction giving them different masses. Indistinguishable particles have different statistics than merely identical particles, so this isn't a philosophical question. In undergraduate QM, indistinguishability has to be introduced by hand and seems arbitrary, but in quantum field theory it's automatic, therefore (getting philosophical here) I imagine that the "reason" for indistinguishability is the QFT reason. That reason is that particles are oscillations of a field, and two particles in the same state is an oscillation with twice the amplitude. How do you split that into two pieces? Well, you don't. The lesson from particle indistinguishability isn't that molecules are like ping-pong balls except for a quantum technicality; it's that gases have a wave nature as well as a particle nature. -- BenRG (talk) 05:50, 18 May 2010 (UTC)

But that still doesn't really affect the result. Asking whether the proportion of that wavey/particalish stuff that came from the wavey/particalish stuff that was in Caesars' lungs amounts to two-atoms' worth is still a perfectly reasonable question. All this quantum debate does is to change what it means for the air to be "adequately mixed". SteveBaker (talk) 14:30, 18 May 2010 (UTC)

It's worth using terms accurately. Steve Baker estimated above that a breath is about 5g, but that estimate is based on human lung capacity (about 5-6 L) when a "breath" (or "tidal volume") is about 1/10 of that. Thus, all of the estimates are about 10-fold too high. The numbers are still huge, but let's not confuse tidal volume with total lung capacity. One could argue that Caesar exhaled the contents of his lungs with his last breath, but one could also argue that his last inhalation was likely to have been at low volume - it seems better to stick with "breath" =~ "tidal volume" as a concept. -- Scray (talk) 01:59, 18 May 2010 (UTC)

That depends on how you define "last breath" - was it the air he breathed in just before he died? The air he breathed out just before he died? The total air in his lungs at the moment of death? Each of those things produce different results...I happened to pick the last of the three. The other two are tougher to estimate...did he <gasp> "Et Tu Brute" or did he merely whisper it? Did he yell "OW!" when the various knives went in? Did he die before breathing out or just after breathing out? However, all of this is irrelevant compared to the error bars in the "even mixing" assumption and the complications of oxygen exchange with the world's oceans, oxygen getting lost to corrosion of metals, etc, etc. Fortunately for this claim, the half million atoms calculation leaves plenty of room for "at least two" atoms to be present in each of us no matter which set of assumptions you choose. SteveBaker (talk) 14:24, 18 May 2010 (UTC)

Efficiency of digestion

I've heard that there is something in pineapple that helps break down certain proteins and thus makes it easier for your body to absorb? them. I'm wondering about something similar, but in a more general sense.

Is there anything that has a similar effect in a larger scale, e.g. a foodstuff that assists the bodies digestive system allowing for more efficient digestion, or a "habit", for example eating slower or more frequently. There are obviously a lot of people who would benefit from food having less impact on their bodies, but I'm asking about the opposite effect, for example if an athlete wanted to waste less by increasing the efficiency of their body when digesting foods/vitamins/minerals etc. Thanks! 219.102.220.188 (talk) 05:16, 17 May 2010 (UTC)

Why are you are assuming that exercising the digestive system by normal eating is a bad thing? If you ate baby food your whole life maybe your digestive system would atrophy and stop working properly all together… would you also assume wearing a pressurized gas mask that assists your lungs by helping you breathe would be a good thing? In general chewing your food properly isn't a bad idea, but I wouldn't systematically take "digestive aids" just to make the job easier. Just because it takes some effort doesn't mean it's not efficient. Vespine (talk) 06:18, 17 May 2010 (UTC)

I understand that there is a very fine line between "adding benefits to the body" and "doing something that the body isn't supposed to do", but I don't think I explained myself well. In the case of morbidly obese people, could it be said that the digestive system was incredibly "efficient"? Probably not, but in some way (in some cases, obviously this isn't the only cause of obesity, probably not even a major cause) the body transfers more of the food intake into fat/muscle/growth than an average person would. On the other hand, there are people that can eat ridiculous amounts of food with hardly any transfer into fat/muscle/growth. 210.165.30.169 (talk) 01:02, 18 May 2010 (UTC)

Pineapple contains Bromelain which helps break down protein (like meat). See Digestive enzyme for many others. But I'm not sure anyone actually eats those, they are usually made by the body. But I guess you could. Ariel. (talk) 08:00, 17 May 2010 (UTC)

They are sold as supplements, and people do use them. 210.165.30.169 (talk) 01:02, 18 May 2010 (UTC)

(slightly off-topic) The biggest aid to digestion ever invented by humans was cooking. A recent experiment where some volunteers ate only uncooked vegetarian food ended with them having to spend all day eating and still feeling hungry. Dbfirs 08:49, 17 May 2010 (UTC)

Papayas contain papain, another enzyme that breaks down protein. And you can buy a product called Bean-O that helps break down parts of beans that many people have difficulty digesting (so that they don't get processed by gut bacteria with notably gaseous results). Those are the only two I know of; there may be more. There are many more foods that have the opposite effect, by reducing the ability to absorb certain nutrients. Looie496 (talk) 16:21, 17 May 2010 (UTC)

Nutrition Stores sell digestive enzyme formulas that have almost every enzyme needed to breakdown all food. They are great for heartburn. But use them sparingly or your stomache will become dependent on them to digest your food. —Preceding unsigned comment added by 165.212.189.187 (talk) 16:30, 17 May 2010 (UTC)

I think the OP is still making a mistake in their assumptions: there are people that can eat ridiculous amounts of food with hardly any transfer into fat/muscle/growth. I doubt this has anything to do with efficiency of digestion. I thought Metabolism but that article isn't quite what I mean by that word either, maybe my idea of "metabolism" is a fallacy too. Vespine (talk) 05:40, 19 May 2010 (UTC)

Basal metabolic rate may be what you're abbreviating to metabolism, Vespine. --203.22.236.14 (talk) 12:56, 20 May 2010 (UTC)

is it possible to follow a diet that would lead to perfect digestion and no poop? 109.205.114.118 (talk) 11:26, 21 May 2010 (UTC)

Saltation velocity - appropriate factor of safety

I have used the rizk correlation to find the saltation velocity of reasonably fine particles (~100-200 micron) in dilute phase pneumatic conveying. what is an appropriate factor of safety to take? and is there some scientific backing to this factor or is it something just widely followed? —Preceding unsigned comment added by 125.17.148.2 (talk) 05:33, 17 May 2010 (UTC)

Our article, Saltation (geology), is not very detailed or numerical; but I found this textbook: Pneumatic conveying of solids: a theoretical and practical approach. You might be able to find it at a university library. With a title like that, I would bet it explains the practical and theoretical support for any of the equations it uses. Nimur (talk) 16:13, 17 May 2010 (UTC)

Thanks. I have that book - it certainly gives nice theoretical models for saltation velocity but doesnt mention the factor of safety sadly. —Preceding unsigned comment added by 122.172.37.82 (talk) 15:52, 18 May 2010 (UTC)

Is "dilute phase pneumatic conveying" solid or liquid? You should be able to follow methods used in aeolian sediment transport and/or in Leo van Rijn's (or other saltation-based) sediment transport formulas to know something about it. As for factor of safety: what are you concerned about? Particle impacts? Particle velocities? Awickert (talk) 02:15, 19 May 2010 (UTC)

I am not sure I follow. Pneumatic conveying is the transportation of fine particles through ducts by the use of flowing gases (gen air). Saltation velocity is the min air velocity req to keep the particles in suspension. Factor of safety is the factor by which SV is multiplied to ensure particles never settle down which may lead to choking of the ducts. I dont know about aeolian or LVR's formulae but they seem to b something else altogether right? —Preceding unsigned comment added by 125.17.148.2 (talk) 05:23, 19 May 2010 (UTC)

Ah, OK. I work in sediment transport often, in which "saltation velocity" is the particle velocity. I imagine that you could do a Rouse number-style balance on the grain between upwards-directed lift and downwards-directed settling and then make sure that this is well in favor of lift, but I can't give you any cut-and-dried answer. Awickert (talk) 06:04, 19 May 2010 (UTC)

Thanks. I will look into it. —Preceding unsigned comment added by 125.17.148.2 (talk) 12:25, 19 May 2010 (UTC)

Overclocking

Is overclocking my PC possible???What are the requirements??? And if it is possible....is it risky??And risky to what extent???Rohit.bastian (talk) 05:47, 17 May 2010 (UTC)

Apart from the fact that this would more suitably belong on the computer ref desk, you are probably much better off googling a beginner's guide to overclocking. It's not a subject that can be summarized in a paragraph and anything anyone writes here is probably written a hundred times before on websites all around the net. This might also be a good start Overclocking. Vespine (talk) 06:04, 17 May 2010 (UTC)

I should think that any chip manufacturer would be interested in seeing a nice high clock speed for their product, as high as they could possibly manage -- and still have a reliable product with minimal failure rates. So if you start overclocking you expose yourself to the possibility of problems. So ask yourself -- what good is a chip 20% faster than normal if it fails after 18 months, when you could have it for five years? Just food for thought -- these figures aren't based on any empirical research. I just would firmly expect Intel et el would set their chip speeds beneath the maximum for very good reasons. They've been doing this for a long time now. Vranak (talk) 08:26, 17 May 2010 (UTC)

Yes, most CPU's can be overclocked. But don't step them up too fast, or you will be left with a computer that won't start. Then you will have to move the CMOS reset jumper (at least that's how it is on my family's 9 going on 10 computers). --Chemicalinterest (talk) 10:42, 17 May 2010 (UTC)

Even if you overclock, unless you're doing something like overvolting or are allowing the CPU (or whatever) to get too hot & don't have sufficient cooling (which is always a problem) it's very rare the CPU will die in 18 months. In other words, 5 years+ is an entirely resonable expectation for a CPU lifespan even if overclocked. I'm not saying you won't reduce it, you may very well do so but in general if you know what you are doing the reduction in lifespan is not likely to be something the vast majority of people will notice.

You're wrong BTW about 'would be interested in seeing a nice high clock speed for their product, as high as they could possibly manage'. Why would they? That's not the way the market works in general be it CPUs or anything else. There's no point selling your CPUs at 3ghz if you can sell them at the same price but operating at 2.5ghz. You can sell some CPUs at a higher price for 3ghz, but it's unlikely you can expect to sell enough at 3ghz to make up for not selling any at 2.5ghz and if you just flood the market with 3ghz CPUs you create a glut. While these figures are completely made up, the general idea is sound. A manufacturer is going to want a decent range of CPUs for price differentiation depending on what the market demands and other things, if most of their CPUs can go close to the top speed, they just bin many of their CPUs lower then they have to be. They don't sell all their CPUs at the maximum possible clock speed and make a lower profit just to be kind.

Your point is well-taken, but a company whose processors are kept needlessly slow will not do well against a more honest and ambitious firm. Vranak (talk) 16:21, 17 May 2010 (UTC)

But Intel's only real competitor in the desktop and normal laptop space is AMD, and they do the same thing of course, as do competitors in most markets, and have problems for a variety of reasons achieving the high end that Intel does (at least when Intel isn't fooling around with stupid things like they were in the P4 era) nor have they ever been able to achieve the volume of Intel (one of the things that held them back in the P4/A64 era) so they aren't really a risk in that area anyway. Sure a competitor helps to keep prices down BUT they're not going to shot themselves in the foot by completing ignoring basic and sensible marketing practices. Note that if they did, it could easily be only several months before they're completely screwed themselves. Nil Einne (talk) 07:19, 20 May 2010 (UTC)

Also while process technology and other factors are always improving which enable you to achieve higher clock speeds or otherwise faster CPUs they won't always give you the advancement you desire at the rate you desire. Moore's law (from an engineering standpoint) generally holds over long timeframes, it may not always hold over shorter timeframes. If you flood the market with highspeed CPUs, then 6 months later you've only got 10% faster CPUs, then what? Far better to hold back your higher speeds so you can smooth out the speed increases.

Finally even if you can achieve higherspeeds, you also need to do it at whatever thermal design power you specify for your CPUs. If you can achieve a higher clockspeed but are above the TDP you specified, you either have to sell your CPU at a higher TDP or clock it lower. From an end user standpoint, if you know what you're doing, don't mind the additional noise and cooling requirements and have components to support such a TDP, then that's not a problem.

I'm not of course saying I recommend the OP overclocks. Actually if you have to ask at the RDS, I'm not sure if I would recommend it until you've done much more research. If things like Prime95 and stability testing (or if you think stability testing only means 'the computer doesn't crash') don't mean anything to you, if you don't know how to reset the CMOS etc, then personally I won't.

Nil Einne (talk) 12:35, 17 May 2010 (UTC)

Note that overclocking will probably not have any noticeable effects. CPU speed is one factor among many in the performance of modern desktop computers, and not the most important. Memory size and disk speed are more important for most things, and the graphics card is more important for games. A faster CPU probably won't have a noticeable effect, unless you're into protein folding or raytracing, which require little memory and lots and lots of computation. Paul (Stansifer) 13:56, 17 May 2010 (UTC)

The CPU chips that come off the production line probably have a spread of performance similar to a bell curve. The company quality controllers estimate values of the maximum and spread of the distribution. The sales department are concerned that equipment manufacturer customers should not reject chips so the clock rate they promise is far down the tail of the distribution. That means the majority of CPU's have much better potential clock rate than their specification. In other words a company with a reputation to protect supplying thousands of CPU's is more conservative about taking risk than an enthusiast interested in getting the most out of their PC needs to be. Cuddlyable3 (talk) 14:37, 17 May 2010 (UTC)

There are two reasons why (careful) overclocking works:

1. Manufacturers often run their manufactured chips through speed tests where they figure out which chips (by luck) happen to be able to run faster than others. They then sort the devices by speed range and sell them at different price points. However, if the speed selection is set at (say) 4GHz - they'll typically sell the ones that pass at 4GHz as 4GHz chips - and retest those that fail at (perhaps) 2GHz. Then they'll sell those that pass this second test as 2GHz chips and scrap the rest. Well, it might be that your 2GHz chip actually only just failed the 4GHz test and would actually run quite happily at (let's say) 3.5GHz. Of course, it might not and it could just as easily crap out at 2.1GHz.
2. Heat. What limits the speeds of many chips is heat. The faster you clock a chip, the hotter it gets. There comes a point where it'll overheat and die (possibly permenantly). If the chip was designed to work with a particular kind of heatsink and fan such as (let's say) DELL are prepared to use - then it will probably overheat if you just overclock it. However, if you can install substantially better cooling (eg using one of those fancy liquid cooling systems) then you can probably overclock the thing to the point where it would melt using the standard cooling system.

However, this is always a risky business - you may well end up with a computer that becomes flakey and crashes out or behaves weirdly - or doesn't work on warm days - do even dies an early death because of the extra heat it's experiencing. For that reason, I wouldn't recommend doing it unless this is an old computer that you don't much care about - and which you're only using for relatively unimportant jobs like playing games or surfing the web - where the occasional crash is worth the speedup. SteveBaker (talk) 15:48, 17 May 2010 (UTC)

Do people actually use computers for anything else? Matt Deres (talk) 16:21, 17 May 2010 (UTC)

I spent a few minutes trying to come up with a witty response to that, and couldn't think of one. Err...Instant messenging? Vimescarrot (talk) 19:08, 17 May 2010 (UTC)

Someone has to actually write the games...er...and I'd better stop writing RefDesk answers and get back to doing exactly that! SteveBaker (talk) 19:32, 17 May 2010 (UTC)

But playing games and surfing the web probably won't be improved by overclocking. Games tend to be GPU-bound and memory-bound, and surfing the Web is very IO-bound. I use a few CPU-bound programs (POV-Ray, Foldit) but making my test renders take 20 seconds instead of 25 is not so valuable that I'm willing to go to the trouble, let alone risk damaging my computer, or having it fail sporadically and not being able to track down the problem. Overclocking probably made sense back when CPU speeds weren't insanely much faster than memory and hard drives, and graphics acceleration didn't exist (Though apparently it is possible to overclock memory, also. That sounds more like it could be useful, if you're unusually risk-tolerant. But overclocking won't do anything about having too little RAM.), and you could play DOOM more smoothly with a 25% higher clock speed. Paul (Stansifer) 21:15, 17 May 2010 (UTC)

Yes, that's my impression as well. The people who most wanted to overclock were gamers and they've moved on to console games instead. I suppose there are still folks who find it fun or enlightening to see how much they cane tweak their hardware, but I'd guess that most people wouldn't want to risk it - even if the odds were actually pretty decent. If you're not in a position to upgrade or buy a new system, you're probably not in a great position to risk losing the old system, ya know? Matt Deres (talk) 23:53, 17 May 2010 (UTC)

It's also possible to overclock your GPU - so the argument that you shouldn't bother overclocking because you're typically GPU-bound (something I'm not sure I agree about) doesn't entirely hold water. SteveBaker (talk) 01:31, 18 May 2010 (UTC)

In fact, I don't really understand the memory comment either. In many cases, improving memory bandwidth by overclocking makes only a small difference in real world performance (timings sometimes help more although even then not necessarily that much). Of course if your CPU or app is significantly limited by memory bandwidth it will make a difference but this often isn't the case (well most of my knowledge is mostly 2-3 years out of date but I don't think things have changed that much, e.g. from a quick search [5]). Sure you can get great results with sythetic benchmarks, but who cares?

In addition, the risk of losing your computer is questionable for some overclockers. Yes there's a small risk, but how big if you know what you're doing? In particular unless you do something stupid, the chance anyone will know you overclocked your computer is slim if you don't tell them so while you may not be entitled to warranty support, it doesn't mean you won't get it and many people may not have ethical qualms about this for whatever reason (and obviously it's a complicated issue, some may argue it's difficult to know if their overclocking contributed to the failure), whatever the harm to non-overclockers and whatever others may think of them (and clearly the RD isn't the place to discuss such people, except to acknowledge they exist).

People seem to be forgetting that a slightly better processor can sometimes be double the price. In other words, you could get a cheapish processor and in some cases you could easily overclock it so it performs better then a processor which is close to double the cost (the more expensive processor would usually be more on average overclockable to a higher speed of course but it's irrelevant to the point). And even in the unlikely event it does die and either because your honest or the manufacturer can tell you did something dodgy it doesn't get replaced, you can buy a new one and you'd still spent the same as you would have if you got the more expensive one (and either decide to risk overclocking it again or you don't have the money to replace it don't). In such a case you're worse off then you would have been if you'd bought the more expensive processor but most people won't be such a case.

Even if you fiddle with the costs, considering the small risk of having to spend more, it may be worth it for many who choose to overclock. Do remember the price of the CPU is only going to be a part of the computer sometimes even a relatively small part. (I would note of course that the chance you'll kill all the components at the same time when overclocking one is slim to none, in fact in such a situation one may presume something, say the motherboard or PSU was inherently defective.) So even for an honest person the money equation may not work out in favour of buying the better processor and not overclocking. (If you throw in the cost of the time spent on overclocking perhaps.)

One final point. The question of stability and reliability is an interesting one. Anyone who's worked with computers enough knows that particularly when assembling your own with a variety of components, things can go wrong. (How many people really check out a mobo's memory compatibility chart?) If your lucky, these will be obvious. But what about errors that may not affect stability that greatly but may have some affect on reliability and are only likely to be easily detected by Intel Burn, Prime95, LinX or similar programs and of course memtest* for memory (note that if you think these sort of programs are simply supposed to make your computer crash, you may want to read up on them)?

While rare, you definitely can get these sort of errors with a new system and everything running at spec. How many people actually carry out such tests on their computer? Personally I'd probably trust an overclocked system, put together and well tested by someone who knows what they're doing then one running at spec but put together by someone who has little clue and only really browses the internet with the occasional solaitare on it. Yes the system run at spec, and put together and tested by someone who has a good idea of what they're doing would be even better but that's beside the point. (Of course there's also a question of component quality. E.g. without testing, I'd probably trust mildly overclocked good brand RAM then some junk noname brand someone bought off eBay running at spec. Or with testing if both come up fine perhaps even for a stronger overclock. Particularly if it was found the good brand can handle say 250 mhz but is run at 230mhz, the other brand craps out at even 205mhz from the stock 200mhz.)

I'm not saying that the stress test tools are perfect, the fact that particularly for CPUs you'll ideally want to use several different ones, and different ones are more likely to pick up errors in with different CPUs is good evidence for that, not that you really need any evidence. Clearly manufacturers have access to tools and far better knowledge of how to stress test what they manufacture but it's not a simple equation of overclocking=unreliable/untrustable, spec=reliable/trustable. In other words, I'm not suggesting I would recommend an overclocked system if the output really matters and you really can't afford the risk of stability problems, I wouldn't (although I would also probably recommend things like ECC memory and a bunch of other stuff in such circumstances).

(I should clarify in case there is any confusion that I use stability above to mean 'causes crashes and other such problems' and reliability to mean 'output is what it should be'. These aren't exactly standard distinctions and they are mostly one and the same, if the output isn't what it should be, this could easily cause a crash or related problem but I find it helpful to make the distinction because some reliability problems won't be noticed except in very rare or specific circumstances. E.g. if you happen to get a Prime95 error after 15 hours and then next time you run it for 30 hours no error and next time you get it in 8 hours, it's probably fair to say you won't often notice that problem.)

BTW, SB always point out the always GPU bound assertation for gaming is questionable but there are a number of other things e.g. video compression (with modern codecs e.g. x264) will often be CPU bound (GPU encoders are still fairly crap), finishing a job in 7 hours instead of 10 may very well be worth it for some people.

P.S. I'm obviously only talking about memory bandwidth with the CPU, not the GPU. I didn't really consider GPU overclocking at all.

P.P.S. I should add that while many lament the state of PC gaming, and there's hottest growth areas are probably the casual and MMO crowd which aren't generally that demanding it definitely isn't dead.

Nil Einne (talk) 01:07, 19 May 2010 (UTC)

Thank you mates..it was awesome info!!I never knew contacting wikipedia wud make things so awesome!!! —Preceding unsigned comment added by 117.204.3.236 (talk) 16:48, 18 May 2010 (UTC)

BTW, I suggest you clean your keyboard. It seems to have the annoying habit of repeating question marks and exclamation marks multiple times. StuRat (talk) 21:43, 19 May 2010 (UTC)

amtrak "service disruption"

does Amtrak "service disruption" mean a suicide

Not necessarily. When people suicide on the Caltrain, they often euphemize it for about an hour or so, but within a very short time, even the CalTrain officials are announcing what happened and where. In general, there are other reasons for service disruption, though suicides are real and frequent[6][7][8][9]. Counseling and a suicide prevention hotline is available now as a response to the issue. Trains around these parts are delayed for all kinds of other reasons - baseball games, unexpected ridership levels, weather, and so on; but suicides tend to be the longest disruptions to clear. Nimur (talk) 09:41, 17 May 2010 (UTC)

what do you mean by suicides tend to be the longest disruptions to clear.

It is likely that the suicide scene must be photographed before anything is moved, the train driver will need to be interviewed, counselled ("this wasn't in my job description!") and/or replaced, and diverse body parts may need to be collected and rejoined in a bag. All this takes time. Cuddlyable3 (talk) 14:16, 17 May 2010 (UTC)

Questioned? Replaced? Why? Can any train driver be responsible for any suicide when it is impossible to stop a train in such a short distance to avoid running over anyone who is stupid or bored with life enough to wander onto the tracks? --131.188.3.20 (talk) 14:43, 17 May 2010 (UTC)

The driver will need to be questioned just as any witness to any violent death would need to be questioned. As to replaced - the experience of someone doing a "one under" is very traumatic for the driver, and he will need time and support to deal with the feelings that result. I think I'm right in saying that in the UK drivers have to take time off and have counselling before returning to work after an incident like this - some never manage to return to driving trains. As to other reasons for the long time it takes to restore services - body parts can be scattered over considerable distance, or entangles with the underparts of the train. I used to work on the railways (not as a driver), and I can attest that "one unders" do take an age to clear up, as well as very seriously impacting on the emotional well-being of drivers and of those involved in clearing up the mess. As a result, my initial reaction to news of an event like this is one of anger towards the selfish so-and-so responsible, rather than one of sympathy for the emotional pain they must have been going through. DuncanHill (talk) 15:13, 17 May 2010 (UTC)

I can confirm that - I spent a little while making simulators for railroad locomotives. When the company I worked for first started to get into that business (we'd previously been making flight simulators), we put together a 'demo scenario' to show off to potential customers. Since we knew very little about the business, we did the thing where a school bus stalls out on a railway crossing - and just manages to get started and move out of the way as the locomotive gets there - the idea being to perhaps train drivers to be alert to the dangers and slam on the brakes. We showed it to our first customers and were told in no uncertain terms that we should NEVER show that kind of thing to their drivers! Firstly, under those circumstances, there is nothing they can do about it, the stopping distance of the train is such that if you can see a problem like this, it's already too late. Secondly drivers who had been though the stress of hitting something like a car or whatever would have those traumatic memories reawakened and that this is highly undesirable. There is no question that under such circumstances, the driver needs months of help and cannot return to work for an extended period after the event. (So that demo got flushed in pretty short order and replaced with something much less exciting!) SteveBaker (talk) 15:26, 17 May 2010 (UTC)

As a longtime Amtrak Capitol Corridor rider, I can tell you that service disruptions can be caused by mechanical breakdowns, floods, malfunctioning bridge damage sensors, track repairs, and police incidents -- not just suicides. Looie496 (talk) 16:15, 17 May 2010 (UTC)

And lots of causes for delay are euphemistically described obliquely. Delays on the MBTA are often described as due to "police department activity" or "fire department activity", which conjures up an image of some convention of uniformed people randomly deciding to have a party on the tracks. Probably, they don't want riders imagining that a giant inferno has consumed Park Street, when it's a minor fire. Another rail system might choose to call everything a "service disruption" because that's not a whole lot less informative. Paul (Stansifer) 00:58, 18 May 2010 (UTC)

Is the selfish gene shortsighted?

If a gene is successfully passed on to 2 children then it is traditionally considered successful. However what happens after that? The gene is only 50% likely to pass on to the next generation with there ultimately being diminishing returns. So why a gene fight to continue when it's inevitable it won't survive more than a few generations? The reasoning I can think of is in a small enough population a gene could gain dominance in every member of the population and then be immortal. But in large populations the odds of that seem exceedingly low. TheFutureAwaits (talk) 15:23, 17 May 2010 (UTC)

Genes don't fight. They get passed on randomly. What you are doing is anthropomorphising genetics by assigning things like "motive" and "purpose". Genes get passed on via a process known as "dumb luck". Sometimes, a gene provides an advantage over an alternative gene, and as such, it tends to cause its host to survive longer and have more kids. Sometimes, this occasionally results in the gene being spread to more and more organisms in successive generations. But its all a random process, and there is no "intent" on the part of a gene to "spread itself". It just happens randomly. Its like the snow on a busy street. The snow that gets thrown off the street onto the side of the street survives longer than the snow that gets thrown to the middle. This is just because it got thrown out of the path of the cars, not because it fought to get to the side of the road. Likewise, a gene that provides some benefit to its organism tends to get passed on not because it fought to survive, but because it happened to cause some benefit. But it had no agency in causing its own survival. --Jayron32 15:31, 17 May 2010 (UTC)

I'm not sure I agree with any of your assertions! I don't know that there is such a strict definition of what makes a gene "successful" - and you're wrong about the gene only having a 50% chance of being passed to the next generation. Remember that in each generation, the number of descendants of the animal/plant that has that gene increases - so even though the chances of it being passed on are only 50/50 in each offspring, the increase in the number of descendants (typically) more than doubles with each generation. For example, it has been shown that about one in two hundred men in the entire world have a gene on their Y chromosome that came from Genghis Khan. Certainly he had a lot of immediate offspring - but beyond that first generation, over 800 years, all of the subsequent spread has been fairly normal. So a truly successful gene can be present in 120 million offspring within about 40 generations. SteveBaker (talk) 15:36, 17 May 2010 (UTC)

(edit conflict):Why do you think that "the gene is only 50% likely to pass on to the next generation" ? If an individual carrying the gene mates with an individual not carrying the gene, then 50% of their offspring (on average) will carry the gene. And if carriers of the gene have a higher number of offspring (again, on average) than non-carriers then the proportion of gene carriers in the population will increase with each generation (up to a limit). Gandalf61 (talk) 15:41, 17 May 2010 (UTC)

I think Jayron's explanation is trying to point out that there is an element of randomness, even when a gene provides a clear advantage for an organism's survival or reproductive ability. The genes are not "motivated" to survive; but those genes which increase survival have a much better chance of proliferating. Nimur (talk) 16:03, 17 May 2010 (UTC)

Suffice to say, procreation has a long history of compelling people onwards and upwards. This whole business about genes competing is, as was said before, a little wrong-headed though. They are expressed, may become latent, may re-appear. Nothing is really gained or lost. It's all a flux, love it or hate it. Vranak (talk) 16:18, 17 May 2010 (UTC)

No, we haven't gained anything since diverging from our non-human ancestors. 67.243.7.245 (talk) 21:38, 17 May 2010 (UTC)

I disagree. I think the ability to eat extra mature farmhouse cheddar throughout our lives is a definite gain (you can keep your fashionable foreign rubbish - give me a decent cheddar any day!), and lactose tolerance in adulthood only evolved since we started domesticating animals a few thousand years ago. --Tango (talk) 23:31, 17 May 2010 (UTC)

It's also fairly unconvincing to dismiss the genius of Mozart, Handel, ABBA etc. I feel we may gained a thing or two since diverging from our simian ancestors, to be honest. The only question is whether you're in an appreciative mood or not. Vranak (talk) 01:11, 18 May 2010 (UTC)

Yeah - 67's claim is nuts. Of course we've evolved since then. We've evolved really noticable changes like a range of skin colors and hair types as we adapted to living in climates with differing amounts of sunlight. We've gotten taller and smarter. Lactose tolerance is a great example (and one I use a lot in discussions here) - because it seems to have evolved in just the last 4000 years in response to our ability to keep farm animals. Furthermore, that evolutionary change didn't overtake the entire population, which is why some people are still lactose intolerant in adulthood, just like all the other mammals. SteveBaker (talk) 01:27, 18 May 2010 (UTC)

As a general rule, people compete for their genetics to be passed on to their candidate of choice instead of someone else's genetics, the genes themselves do no competing. The genes present in people more adept at passing on their genetics are the genes most likely to proliferate. Other than that, I echo the answers above. Ks0stm ^(T•C•G) 19:13, 17 May 2010 (UTC)

Storage of vitamin D

A while ago, I bought some soft gel vitamin D supplements (5000 IU). The label says that it should be stored in a dry place. However, I recently read somewhere that vitamin D is very sensitive to UV radiation, so I put it in a dark place. But it still has been exposed to a small amount of UV radiation during the few weeks that it was on my table. I'm wondering by how much the vitamin D content of the pills has been degraded. The UV index is around 3 this time of year where I live during a few hours around afternoon. The windows of my room are often open. The vitamin D is inside a plastic bottle. The bottle is white colored, but it is still a bit transparent to light. I do think it does block UV radiation to some degree.

Another thing to consider here is that the soft gel pills themselves are tranparant, so the UV radiation can affect the whole pill and not just the surface. Count Iblis (talk) 17:21, 17 May 2010 (UTC)

I very much doubt that they would have stored pills that were susceptible to UV damage in a UV-transparent container. If the label had said "Keep in a DARK, dry place" then I'd be concerned - but since it doesn't, I'm pretty sure you're OK. Also, it's possible that the gel in the capsules themselves will be UV-opaque, even if they are transparent to visible light. (The glasses I wear are like that - perfectly transparent to the naked eye, but incredibly UV-opaque). If the capsules are blue-ish in color then they very likely are designed to be opaque to UV. SteveBaker (talk) 19:30, 17 May 2010 (UTC)

Plastic breaks up in sunlight, I think, so I'd keep any out of sunlight if I can. 67.243.7.245 (talk) 21:35, 17 May 2010 (UTC)

Well, it does - but it takes a long time. I guess if it's a really gigantic pot of pills and you took them at really infrequent intervals, the container might break down before you finished the supply - but I honestly don't think that's a real problem. SteveBaker (talk) 01:17, 18 May 2010 (UTC)

Some plastics break down (not up) in sunlight, but the vitamins shouldn't be affected too much. Vitamin D is formed in your body when sunlight strikes a particular molecule. It is formed by sunlight (under limited conditions, of course), not decomposed. Vitamin C may decompose in sunlight since it contains a reactive double C=C bond, making it a reducing agent that reacts with the oxygen in the air. --Chemicalinterest (talk) 11:55, 18 May 2010 (UTC)

I've read that vitamin D formed in the skin will actually break down due to the very UV radiation that formed it. This leads to a dynamical equilibrium when you spend a long time in the Sun. A fair skinned individual can get 10,000 to 20,000 IU of vitamin D from the Sun in an hour or so. But 100,000 IU per day for many weeks in a row is a potentially lethal overdose. But due to this dynamical equilibrium you'll never get such a dose from the Sun.

That's why I am a bit worried about the fact that I put the vitamin D bottle on my desk for a few weeks. So, I hope that SteveBaker is correct about the vitamin D pills plus container being made such that this is not an issue. Count Iblis (talk) 14:10, 18 May 2010 (UTC)

The various things Steve said about UV and pills may or may not be right, however the bit about the people that make the pills not being stupid enough to not say on the label that you need to keep them in the dark if that were the case is almost certainly right. --Tango (talk) 21:40, 18 May 2010 (UTC)

Doctors who do nearly everything when caring for patients

You know like you see on shows like House, where the same doctor, or small team of doctors are involved in every aspect of their patient's care - diagnosing, performing x-rays and scans, administering the medication, operating, taking blood/tissue/CSF samples, performing the lab tests themselves, etc.? I know that this doesn't really happen in American or UK hospitals any more but do any doctors still work like this in other parts of the world? Or is this just something from the 'olden days' that people still believe happens until they actually experience hospital treatment for themselves? As far as I know, veterinarians still work this way (don't know the proper name for it). --95.148.107.150 (talk) 20:47, 17 May 2010 (UTC)

It may well happen when there are very few medics around, for example in the field hospitals set up following natural disasters or wars. --Tango (talk) 23:57, 17 May 2010 (UTC)

The better physicians in Vienna, Austria do just that (apart from surgeries unless they also specialize in this specific kind of surgery). Surely there's supporting staff (like lab techs performing blood tests) but the patient rarely sees them (the professor takes blood sample himself). Starts at a thousand euro a visit. Most patients don't need their level of experise and are fed into the ordinary conveyor belt, which ultimately costs nearly the same. East of Borschov (talk) 05:54, 18 May 2010 (UTC)

Sex on high peaks

Is there any record of anyone ever having sex at the summit of any of the world's tallest mountains? Is there a definate record of the highest ever intercourse? 188.221.55.165 (talk) 21:59, 17 May 2010 (UTC)

See Sex in space, and Mile High Club. Comet Tuttle (talk) 22:48, 17 May 2010 (UTC)

Stella Wobble

How can a stella woble detect whether there is one or more than one planets around a star? Most of the show I watch assume there is only one planet. --Tyw7  (☎ Contact me! • Contributions)   Changing the world one edit at a time! 23:00, 17 May 2010 (UTC)

Have you read our article on methods of detecting extrasolar planets, and in particular the section on stellar wobble detection? Nimur (talk) 23:07, 17 May 2010 (UTC)

OK - so you understand that gravity works both ways - the star pulls on the planet - and the planet pulls on the star - so the position of the star is very slightly shiftedtowards the planet. So as the planet orbits, the star wobblesto stay a little bit closer to it.

That wobble is very small - but it's enough to slightly shift the frequency of the light coming from it - which you can measure with a suitably sensitive detector.

With just a single planet, you can figure out the frequency with which the star wobbles - which would be the period of the orbit of the planet (how long its' "year" is) - and therefore how far away it is from the star. From the amount of the wobble - and knowing the distance at which it orbits, you can deduce the mass of the planet. So with just one planet, the center of the star makes a little circle - once per orbit - and it's all very easy to understand.

Now, suppose there are two planets. The star is attracted to both of them. But they don't orbit the star at the same rate - one might take a year to go around the star (like the earth does) - the other might zip around every 3 months (like Mercury does). When both planets are on the same side of the star, it gets pulled in the same direction by both planets and it's much further off-center than it would be if there was just one. When the planets are on opposite sides of the star - their pulls tend to cancel each other out - and the star sits in the middle. At other times, they are pulling at right angles. If you plotted a map of the position of the star over a few years, it would look something like a spirograph picture. You can use a mathematical technique called Fourier analysis to figure out the separate frequencies and magnitudes of the shift due to each planet...and if your measurements are accurate enough - and done over a long enough period - you can figure out the contributions of many planets. Of course the smaller and more distant planets induce much smaller wobbles - which are tough to detect from such a long way off...so there is a practical limit to how much of this complex motion we can figure out - and to what degree planets are detectable at all. SteveBaker (talk) 01:13, 18 May 2010 (UTC)

Excellent summary. Just to clarify, however: Doppler spectroscopy is a separate technique from direct observation of the star's position. Both techniques have been used to identify or characterize extrasolar planets, but doppler (frequency-domain) methods are significantly more sensitive; direct observations can only even potentially work for our closest neighboring stars. Other methods include transit detection (careful and extremely precise measurement of the star's brightness to check for a planet crossing its path), and other advanced image and spectral processing techniques. Nimur (talk) 01:30, 18 May 2010 (UTC)

Right - so the 'transit detection' thing only works in the relatively unlikely case where the planet is orbiting in a plane such that it comes between the star and us here on earth - it's interesting because it offers the possibility that we could measure the diameter, albedo and atmospheric composition of the planet as well as it's mass and orbital radius. But because that orbital angle is just a lucky coincidence, you can't use it on every star that's out there. The doppler spectroscopy approach works better for getting mass and orbital radius - but still can't detect every extrasolar planet because when the planet's orbit is in a plane that's at right angles to our line of sight, the star's wobble is at right angles to our line of sight and doesn't produce a doppler shift. The direct measurement approach (where you literally just look at photos of the star and see if it moved from one month to the next) can solve that problem very well - but is only useful for "nearby" stars with gigantic planets because otherwise the wobble is too small to detect as a direct positional shift with our telescopes. However, you can use fourier analysis on the position, doppler and brightness variation of the star to discover multiple planets with all three techniques. SteveBaker (talk) 14:11, 18 May 2010 (UTC)

Just want to point out that the star wobbles away from the planet(s), not toward. The center of mass of the whole system doesn't wobble, and the star and planet(s) have to surround the center of mass on both/all sides. -- BenRG (talk) 06:19, 18 May 2010 (UTC)

Argh! Of course, you're right...my bad! SteveBaker (talk) 13:33, 18 May 2010 (UTC)

Also of interest is the detection of planets around radio pulsars. This is also a doppler-shift technique, but more precise than optical spectroscopy. The measurements of the PSR B1257+12 system are precise enough that the planet-to-planet gravitational interaction can be observed. -- Coneslayer (talk) 17:18, 18 May 2010 (UTC)

Purity of USP and food-grade glycerin

How do the two grades of glycerin compare, in terms of the allowable types and levels of impurities? --72.94.148.35 (talk) 23:36, 17 May 2010 (UTC)

USP glycerin just seems like it is approved for drug use, while food-grade is for food use. USP may be for food use, too. --Chemicalinterest (talk) 00:16, 18 May 2010 (UTC)

This document from the Soap and Detergent Association states that "The specifications for food grade glycerin given in the FCC are generally comparable to those given in the USP." If you need detailed information about contents, specifications, and required tests, you should probably directly compare the monographs in the FCC (Food Chemicals Codex) and the USP (United States Pharmacopeia). TenOfAllTrades(talk) 13:20, 18 May 2010 (UTC)

Thanks. I don't need very detailed information. The answer is good enough. --72.94.148.35 (talk) 04:39, 19 May 2010 (UTC)

May 18

CO2

Why does a can of pressurized carbon dioxide (in a liquid state) down so much when it is released (in a gaseous state)? Thanks. 173.179.59.66 (talk) 03:44, 18 May 2010 (UTC)

If by "down" you mean "get cold"; when a liquid evaporates into a gas it goes through a phase transition which involves Enthalpy of vaporization. In short, it takes energy to change a liquid into a gas, the energy is the heat in and around the canister which is absorbed by the carbon dioxide as it evaporates into a gas. The reason this might seem "strange" is because the boiling point of carbon dioxide is 57 degrees Celsius below freezing, we think 0 degrees C is some special "low" energy point, but it's actually 273 degrees Kelvin so still has a lot of energy for something like carbon dioxide. Vespine (talk) 04:19, 18 May 2010 (UTC)

The process by which a liquid or gas is allowed to expand freely is called throttling. During throttling the temperature changes and this is called the Joule–Thomson effect. Whether the temperature increases or decreases during throttling depends on the gas’s Joule-Thomson coefficient and its inversion temperature. Hydrogen and helium at room temperature warm as they are throttled to a lower pressure. Carbon dioxide, nitrogen and oxygen at room temperature cool as they are throttled to a lower pressure. Dolphin (t) 05:10, 18 May 2010 (UTC)

Are you saying that if you had a gas bottle with liquid helium in it and you released it, the gas bottle would not get cold? That doesn't sound right. I've never heard of Joule-Thomson effect (which isn't saying much) but looking at it, it seems to specifically refer to the temperature of the gas in situations where there is no heat exchange with the environment, which is certainly not the case when you just let gas out of a gas bottle, or a can. Vespine (talk) 06:34, 18 May 2010 (UTC)

A gas or liquid can be allowed to change from a higher pressure to a lower pressure in a variety of ways. The change can take place with no heat transfer to/from the surroundings (adiabatic), or it can take place with heat transfer. The change can be reversible, such as when it accompanies the raising of a weight and takes place slowly; or it can be irreversible, such as when it is allowed to "explode" out of its container. A reversible, adiabatic change takes place at constant entropy and the resulting temperature can be determined accurately by knowing that the entropy of the gas doesn't change. See isentropic process. An irreversible, adiabatic change is called throttling and takes place at constant enthalpy. See isenthalpic process. The resulting temperature can be determined accurately by knowing that the enthalpy of the gas doesn't change; also this resulting temperature will be significantly different to the isentropic process. The Joule-Thomson effect is the change in temperature during the isenthalpic process, not the isentropic process. The original question does not specify precisely what process is intended, but it talks about a can of liquid CO2 being discharged to the gaseous state. The idealized process which best represents this process is the throttling process, even though the isenthalpic process involves no heat transfer whereas discharging a can of CO2 will involve a small amount of heat transfer in the brief period of time that the discharge takes place. Dolphin (t) 12:48, 18 May 2010 (UTC)

To clarify, there is an important distinction between a case where helium gas is allowed to expand starting from room temperature, and where liquid helium is allowed to boil. The two cases are distinguished first by the fact that the latter involves a phase change (liquid to gas, soaking up enthalpy of vaporization) and second by the fact that they will occur at vastly different temperatures (the critical temperature of helium is about 5 kelvin, so you're never going to have liquid helium above that temperature — liquid helium will always be at a temperature below its inversion point if you're working under atmospheric pressure). TenOfAllTrades(talk) 13:12, 18 May 2010 (UTC)

By down I meant a decrease in temperature, I'm not too sure where the "down" came from lol. But thanks a lot for the explanation! 173.179.59.66 (talk) 05:52, 18 May 2010 (UTC)

When liquids boil, they absorb energy to change in the gaseous state. When air is pressurized it gets hotter. I can feel on an air pump sometimes that it gets hotter. Some gases may not behave in that way, but I think liquid helium becomes cold when it is released due to the rapid boiling, cooling it to very low temperatures. --Chemicalinterest (talk) 11:58, 18 May 2010 (UTC)

That's a good answer. Going into detail about isentropic processes and entropy and Joule–Thomson effect is way, way overboard for the question actually asked. Vespine (talk) 03:45, 19 May 2010 (UTC)

I think the anwers above are unclear, the throttling explanation seems to be about the temperature of the exiting gas after expansion, the question was about the temperature of the can and that has more to do with boiling and maybe isentropic expansion. Gr8xoz (talk) 00:21, 20 May 2010 (UTC)

percent of atmosphere

What percent of the entire Earth's atmosphere including that which is absorbed and released by water, etc. is released by human lungs of an average adult male upon exhaling? 71.100.0.29 (talk) 04:27, 18 May 2010 (UTC)

From Atmosphere of Earth we have total mass of 5×10¹⁸, from Lung volumes we have average male Tidal volume (Vt) of 500ml, from Density of air we have 1.2  kg/m³. A cubed meter is 1000l so 500ml of air is 1/2000th of 1.2kg = 6×10⁻⁴kg per breath. So it's just (6×10⁻⁴) / (5×10¹⁸) x 100 to get your percentage, i'm no good with so many zeros, my guess is 1.2×10⁻²⁰%, but I could be off by an order of magnitude or two. Someone better at maths can help me out. ;) Vespine (talk) 06:27, 18 May 2010 (UTC)

Your calculations look correct. --Chemicalinterest (talk) 12:00, 18 May 2010 (UTC)

Strange. I was no good with symbolic equations which contained space and used x's in place of *'s. I consulted with several of my friends as did you and they advised that I use the following symbology and syntax to get the following results. Many thanks human. May we also have exchange good like this in future time. (6 * (10^(-4))) / (5 * (10^18))) * 100 = 1.2 × 10-20 —Preceding unsigned comment added by 71.100.0.29 (talk) 18:54, 18 May 2010 (UTC)

Best extrasolar planet candidates for habitable moons based only on irradiance?

What discovered extrasolar planets are the best candidates for habitable moons
based on the heat/irradiance they, the planets, receive from their parent star?
1366 W/m² being the Earth's solar constant, therefore also the Moon's.
24.78.178.235 (talk) 06:44, 18 May 2010 (UTC)

Presumably, what you are getting at is the habitable zone, because this level of stellar radiation would yield a temperature near the triple point of water. We have a nice listing at Extraterrestrial liquid water#Beyond the Solar System. At this time, extrasolar planets are on the bare edge of detection; I know of no research claims about detection of a moon around an extrasolar planet. On the other hand, moons seem commonplace in our own solar system, so it seems plausible that any large extrasolar planet (and some dwarf planets, too) could be capable of having "habitable" moons in stable orbits. Of course, a necessary precursor to the question is, "define habitable". Nimur (talk) 09:08, 18 May 2010 (UTC)

With present detection methods, it's unlikely we're going to be able to detect moons around extrasolar planets unless they are truly gigantic and very close to the parent star - or perhaps are in an eclipsing orbit from our perspective and are large compared to the parent planet (like our moon or the Pluto/Charon pair). The odds of either of those things being true seem rather slim. If we're going to try and guess, we'd have to think in terms of large planets in the habitable zone of their parent stars - and just kinda hope that they'd have large enough moons with inhabitable atmospheres - but we don't have much evidence of the probability of that happening because we only know about the planets in our own solar system...of which there is just one (or arguably two or three) in the habitable zone. We have: List of extrasolar planets which contains all the data you need to estimate which are in the habitable zone - but it doesn't look like anyone did the actual calculations to enter that fact into the tables. SteveBaker (talk) 13:29, 18 May 2010 (UTC)

A note about the "habitable zone". This refers to a planet which is the proper distance from the star for liquid water. In the case of a moon around a huge planet (the only ones we can currently detect), the moon is not only heated by the star, but also from radiation and tidal warming from the planet, so the moon could be further away from the star and still have liquid water. StuRat (talk) 21:38, 19 May 2010 (UTC)

annealing aluminium from H-18 to H-O

We are blanking aluminium circles. We use alloy 1050 and 3003. During blanking we use H18 coils (hardness is H-18). After blanking we want to anneal these circles from H-18 to H-O temper. We have box type (batch type) Oven. We know we need to keep this in 343° to 413° C temperature to anneal these from H-18 to H-O but how much time is required to be kept in this temperature in a box type oven  ? Can anybody help us out in this ? —Preceding unsigned comment added by Ashvora (talk • contribs) 07:31, 18 May 2010 (UTC)

Not sure, but might I suggest trial and error ? That is, anneal it a bit, take it out, cool it, and test it, then anneal it some more, until you figure out the right length of time. StuRat (talk) 21:33, 19 May 2010 (UTC)

Type of intermodal container

These containers seem common in trains in japan [10] (not the tanks - the boxes). http://commons.wikimedia.org/wiki/File:JRF_19D-33700.JPG or http://commons.wikimedia.org/wiki/File:JNR_Container.jpg I don't think they are '10ft ISO's', but maybe they are? - does anyone know what standard they are? Can they be stacked..? Thanks. Sf5xeplus (talk) 12:00, 18 May 2010 (UTC) I think its something to do with this http://ja.wikipedia.org/wiki/JR%E8%B2%A8%E7%89%A9%E3%81%AE%E3%82%B3%E3%83%B3%E3%83%86%E3%83%8A%E5%BD%A2%E5%BC%8F - are these stackable? any compatability with ISO containers. Also does anyone know why 12ft length seems so popular when elsewhere 20ft+ is normal.? Can anyone give a link to background on this topic? thanks. (in particular: why was ISO standard not used) Sf5xeplus (talk) 13:47, 18 May 2010 (UTC)

length of menstruation

Why does menstruation take 2-7 days, rather than a short time (e.g. an hour or so)? After reading the articles on menstruation and the menstrual cycle, it states the normal length of the menstruation is 2-7 days, which I knew. But what I am curious is about is WHY it takes this long. I'm not sure if this is easy to answer, but it seems that it is a process that could happen quite quickly, rather than taking a few days, but it doesn't. Ballchef (talk) 12:33, 18 May 2010 (UTC)

Given the discomfort level many women feel during (and prior) to their menstruation, I'm not sure compressing that into a shorter timespan would be such a great thing - pain might multiply while the time divides, you know? In evolutionary terms, it might simply be better for women to be moderately uncomfortable for a longer period of time than extremely uncomfortable for a shorter, but still sizable, period of time. Matt Deres (talk) 14:09, 18 May 2010 (UTC)

Unscientific answers.
The following discussion has been closed. Please do not modify it.
It's serious business, and serious business generally isn't over in the blink of an eye. Vranak (talk) 14:34, 18 May 2010 (UTC) That's not a reason. Vimescarrot (talk) 17:06, 18 May 2010 (UTC) Well if sexuality was a light and breezy affair, then people wouldn't have any reason to menstruate, let's put it that way. Vranak (talk) 21:16, 18 May 2010 (UTC) That makes absolutely no sense. --Tango (talk) 21:35, 18 May 2010 (UTC) Exactly. Vranak (talk) 21:52, 18 May 2010 (UTC)

Per Menstruation#Evolution, the length of time has to do with the rate of cell growth for the uterine lining. This sort of low-level biological parameter is not easily changed - cells simply can not divide and multiply significantly faster. Our article links to some evolutionary biology research on the advantages and disadvantages of the process, e.g. The evolution of endometrial cycles and menstruation. Mostly, this evolutionary process was driven by the balance between the utility of internal fertilization versus the energy and nutrient cost to sustain this very complex process. Keep in mind that evolution is not a steady progression towards "optimal" - it is simply survival of the fittest random mutation during every intermediate step - so the development of modern menstruating mammals is the result of prior forms. See also, estrous, for a related process in other mammals. Nimur (talk) 00:58, 19 May 2010 (UTC)

Brilliant answer thanks! But still it wont stop my girlfriend from complaining. Ballchef (talk) 03:33, 19 May 2010 (UTC)

See Menstrual extraction for a quick painless method —Preceding unsigned comment added by 79.76.203.64 (talk) 18:56, 19 May 2010 (UTC)

And possibly illegal, depending on the Jurisdiction... Buddy431 (talk) 03:42, 20 May 2010 (UTC)

physics

when a hole is made from north pole of the earth to the south pole of the earth and a ball is put into it what is the time period of the oscillation of the ball —Preceding unsigned comment added by Mai ca lal jai kison (talk • contribs) 14:24, 18 May 2010 (UTC)

Question has come up before:

• http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2009_September_17#Gravity_at_the_center_of_a_body
• http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2009_September_11#Path_through_Earth

Answer in second link - some simplfiying assumptions are made to get an answer.77.86.10.27 (talk) 14:34, 18 May 2010 (UTC)

There's some more explane here http://answers.yahoo.com/question/index?qid=20080519084940AAMjRd0 77.86.10.27 (talk) 14:40, 18 May 2010 (UTC)

There's a step by step guide to one derivation in "A: The basic setup" http://amath.colorado.edu/courses/2460/2007fall/Labs/lab2/ 77.86.10.27 (talk) 14:40, 18 May 2010 (UTC)

Reliable looking answer here http://physics.ucsd.edu/students/courses/summer2008/managed/physics2a/documents/chap15.pdf Question 70 page 15 "The magnitude of the gravitational acceleration inside Earth is given..." 77.86.10.27 (talk) 14:43, 18 May 2010 (UTC)

But how would it be possible to keep such a hole from being completely flooded? :-) 67.170.215.166 (talk) 01:07, 19 May 2010 (UTC)

People here are not saying it is possible, just assuming no water or air, or lava in the hole. :-) Graeme Bartlett (talk) 12:43, 19 May 2010 (UTC)

Alkali acids

Is an alkali like NaOH an acid? --Chemicalinterest (talk) 15:37, 18 May 2010 (UTC)

OH- as an acid : see this quote :"The oxide ion, O²⁻, is the conjugate base of the hydroxide ion, OH⁻"

Na+ is also a weak lewis acid

In water it's always a base, the opposite of an acid.77.86.10.27 (talk) 15:42, 18 May 2010 (UTC)

So that means that OH^- is the conjugate acid of O^2-? --Chemicalinterest (talk) 15:58, 18 May 2010 (UTC)

Yes.77.86.10.27 (talk) 15:59, 18 May 2010 (UTC)

I plan to improve the articles dealing with chemicals that have a pH above 7. Do you think it would be good to add it, or it would just confuse people saying that a base is also an acid? --Chemicalinterest (talk) 16:03, 18 May 2010 (UTC)

Probably not a good idea to add - since any molecule with a hydrogen is potentially an acid - eg methane, hydrogen gas, etc. too many

It's sort of mentioned already in Superbase.

As far as I can tell the definition at Alkali is 100% correct already.

I think Alkali salts would be better moved to Basic salt : that's the only change I can see needs doing - not sure what other people will think.77.86.10.27 (talk) 16:19, 18 May 2010 (UTC)

Square wheels

Can anyone provide a proof/derivation for why the square wheel riding on catenaries thing works, as shown in the article? 173.179.59.66 (talk) 15:39, 18 May 2010 (UTC)

It looks like the wheel corner gets "stuck" in the down curve, but just rolls right out. Round wheels probably wouldn't work on there unless they are much bigger. --Chemicalinterest (talk) 16:05, 18 May 2010 (UTC)

And a round wheel would provide a bouncy ride (i.e., would never "work" in the same way): as it rises and falls over each bump, the axle does too. When the size of the square is perfectly matched to the dimensions of the catenary, the axle remains at a fixed height. Proof is just a bunch of calculus: probably start by assuming length of one side of the square is the same as the length of one arch of the catenary (they remain touching as the roll past each other). That means at any x position, you know the height of the catenary and also (by some trig) the offset of the center of the square from that x. And then (by some more trig) the distance from the center straight down to the height of contact. Our catenary article says square or any larger polygon can be used, and has a cite to more reading about this unusual geometric phenomenon. DMacks (talk) 18:43, 18 May 2010 (UTC)

One possibly non-obvious assumption that (I think) will need to be made is constant ratio of angular velocity to linear velocity. no idea what can happen if this isn't assumed (disclaimer: I've assumed what I've said is correct rather than actually knowing). not right on second thoughts.77.86.10.27 (talk) 19:50, 18 May 2010 (UTC)

I started trying to prove the catenary equation from the height of the axle, but then I found a much neater and more elegant proof here (along the lines suggested by DMacks above). The method can be extended to any regular polygon by truncating the catenary at a point corresponding to the exterior angle. Dbfirs 20:36, 19 May 2010 (UTC)

Planetary rings

Why some planets have rings and others do not have? —Preceding unsigned comment added by 113.199.143.2 (talk) 17:43, 18 May 2010 (UTC)

We don't know. Planetary rings are a big mystery. --Tango (talk) 18:28, 18 May 2010 (UTC)

But our Planetary ring article does have some information about the origins of them. DMacks (talk) 18:32, 18 May 2010 (UTC)

Note that planetary rings tend to be associated with gas giant planets such as Saturn; this suggests (but does not in itself prove) that there's a certain minimum size of planet below which it cannot acquire a ring. FWiW 67.170.215.166 (talk) 01:11, 19 May 2010 (UTC)

In fact, all of the gas giants in our solar system have rings: Rings of Jupiter, Rings of Saturn, Rings of Uranus, Rings of Neptune. Buddy431 (talk) 03:40, 20 May 2010 (UTC)

Dark Chocolate icing

I have a chocolate icing made of 49% dark chocolate and 51% melted margarine. After leaving it in the fridge for too long it turned to moose(?). Heating the sauce in a microwave caused the margarine and chocolate to separate so now there is melted chocolate sludge in a pool of melted margarine. How do i get the two to become one sauce again? Btw, 5 minutes of mixing did nothing. Simply south (talk) 18:30, 18 May 2010 (UTC)

A high speed electric whisk should emulsify it again hopefully. (maybe like this http://www.cookingtime.co.uk/index.php?act=viewProd&productId=1095 ? )77.86.10.27 (talk) 18:32, 18 May 2010 (UTC)

Adding some (or a lot) of cream might help as well.77.86.10.27 (talk) 18:35, 18 May 2010 (UTC)

I would like to still use it as icing but will try the whisk. Thanks. Simply south (talk) 18:38, 18 May 2010 (UTC)

According to http://chocomap.com/chocolate-making-tempering.php it's "chocolate seize" and cannot be reversed - I think cream may help solve this though..77.86.10.27 (talk) 18:40, 18 May 2010 (UTC)

If it has seized (and not just separated out) there are a thousand and one things you can try.. http://www.google.co.uk/search?q=chocolate+seize&hl=en&start=10&sa=N 77.86.10.27 (talk) 18:44, 18 May 2010 (UTC)

Thank you. Simply south (talk) 18:47, 18 May 2010 (UTC)

Turned to moose!!! Goddarn, take the dang thing outside and shoot it!!!! If it turned to mousse then follow the suggested advice. Caesar's Daddy (talk) 20:24, 18 May 2010 (UTC)

Swedish Chef tried it.DMacks (talk) 21:39, 18 May 2010 (UTC)

"First moose, then squirrel!" Edison (talk) 21:51, 18 May 2010 (UTC)

Aether vs. Quintessence

How did the powers that be determine that "aether" was not an acceptable term for "quintessence", when their definitions are from the same classic Greek idea? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:44, 18 May 2010 (UTC)

They're not the same -

• aether http://en.wiktionary.org/wiki/aether means air
• qunntessence http://en.wiktionary.org/wiki/quintessence means fifth essence

Classical elements only have 4 elements - thus air cannot be a fifth essence ??? 77.86.10.27 (talk) 18:55, 18 May 2010 (UTC)

The aether wikipedia article refers to it as a proposed "fifth element" why? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:00, 18 May 2010 (UTC) I'm not talking about semantics I'm talking about the ideas and theories behind the words. —Preceding unsigned comment added by 165.212.189.187 (talk) 19:04, 18 May 2010 (UTC)

Sorry my mistake (Ἀήρ was normal air) here Aether (mythology)

Quintessence is another term for aether ???77.86.10.27 (talk) 19:25, 18 May 2010 (UTC)

What exactly is it you are talking about? do you mean that Quintessence (physics) is different from definitions of aether ?77.86.10.27 (talk) 19:28, 18 May 2010 (UTC)

Giving them the same name would be confusing because they are used for completely different scientific theories. --Tango (talk) 19:32, 18 May 2010 (UTC)

In the Roman and medieval natural philosophy deriving from Aristotle, aether and quintessence were indeed synonymous—see Aether (classical element)#Fifth element. Who is it who "determine[d] that 'aether' was not an acceptable term for 'quintessence'"? Deor (talk) 21:53, 18 May 2010 (UTC)

As for why Aristotle posited such a fifth element, C. S. Lewis explains it well (The Discarded Image, pp. 3–4):

Aristotle, being interested both in biology and in astronomy, found himself faced with an obvious contrast. The characteristic of the world we men inhabit is incessant change by birth, growth, procreation, death, and decay. And within that world such experimental methods as had been achieved in his time could discover onlty an imperfect uniformity.... But the world studied by astronomy seemed quite different.... So far as he could find out, the celestial bodies were permanent; they neither came into existence nor passed away. And the more you studied them, the more perfectly regular their movements seemed to be.... It seemed reasonable to suppose that regions which differed in every observable respect were also made of different stuff. Nature was made of the four elements, earth, water, fire, and air. Air, then (and with air Nature, and with Nature inconstancy) must end before Sky began. Above the air, in true Sky, was a different substance, which he called aether.

—Deor (talk) 23:28, 18 May 2010 (UTC)

Tango, what are the two different theories, just the basics, thanks.98.221.254.154 (talk) 00:54, 19 May 2010 (UTC)

See luminiferous aether and quintessence (physics). Both of them are supposed to pervade all of space (and time), but aside from that they have nothing in common. -- BenRG (talk) 07:07, 19 May 2010 (UTC)

At an attempt at clarification - "aether" is a defunct theory for most scientists - so reusing a synonym won't be a problem for the majority of people.

If you want to know who repurposed the word I think the article Ostriker, Jeremiah P., and Paul Steinhardt, "The Quintessential Universe", Scientific American, vol. 284, no. 1 (January 2001) may be the place to start.

http://iopscience.iop.org/0264-9381/17/13/101/fulltext this article dates from 2000 - was that the original aim? to find out who coined the term 'quintessence' relating to dark matter?77.86.10.27 (talk) 11:42, 19 May 2010 (UTC)

This was in the aether theories article: The general attitude to this amongst physicists[who?] today is that although it is purely a matter of semantics, Einstein's comments stretch the word "aether" too far: it is argued that an "aether" with no mechanical properties doesn't correspond to the historical idea of aether, and so it is potentially misleading to apply this name to the spacetime field of general relativity.[citation needed]. Note the [who?] and [citation needed]. If it is so well known that the two theories are not the same why not update these? —Preceding unsigned comment added by 165.212.189.187 (talk) 13:26, 19 May 2010 (UTC)

Is this the sort of thing you wanted - [11] [12] , if the problem was different please be WP:BOLD or discuss on the relevant talk pages. I'm not sure what you want but I don't see anywhere in the articles problems. 77.86.10.27 (talk) 20:25, 19 May 2010 (UTC)

Whatever, even after reading both articles several times i still cant see a definitive difference between the two. Its like saying that originally a cucumber was considered a vegetable but now that it really is a fruit it should be renamed. —Preceding unsigned comment added by 98.221.254.154 (talk) 01:17, 20 May 2010 (UTC)

(Please link to the pages you are talking about)

The terms "Aether" and "Quintessence" are practically synonymous in their original meaning. But, they are not synonymous in later usages of the word.

If you want more info. please be more specific than 'i don't get it' because nobody can help you with that problem.!77.86.108.78 (talk) 11:00, 20 May 2010 (UTC)

So youre saying that meanings change over time. That is what I don't get. If their original meanings are practically identical then WHAT happened to change the meanings???165.212.189.187 (talk) 14:39, 20 May 2010 (UTC)

Yes, meanings of words change over time. This happens a lot.

In the meanings of the words in Aether (classical element) and Quintessence are synonymous only when "aether" refers to a fifth form of matter: because quintessence means "fifth essence", in later uses of the word "aether" such as Luminiferous aether where it does not refer to a fifth state of matter the two words are not neccesarily synonymous. Similarly Quintessence does not directly have the same meaning as Aether (mythology).

The earliest meanings are

• Aether - name one of the gods - see Aether (mythology) and a reference to "upper air" (at least as early as Hesiod 8th century BC)
  • Aether - as an element - comes later = probably by Aristotle - 5th century BC - approx 300 years later.
• Quintessence - means "fifth element/essence"

They're not the same meaning except when refering to Aether (classical element) when they happen to have the same overall meaning.

If you need more explanation please ask on the humanities or language desk as they would be better placed to explain the etymology, origins and meanings of these words.

To put it brutally to you - when you say "when their definitions are from the same classic Greek idea? " you were originally completely wrong : if you drop that assumption and read the articles everything should become clear. 77.86.115.45 (talk) 15:11, 20 May 2010 (UTC)

Native American Cradle Board and Infant Behavior Differences

Someone told me that when infants were placed in these cradle boards before they were able to walk that these infants were much less fussier and happier than of those infants who did not grow up these? Is this true? Please let me know if I did not make myself clear. Reticuli88 (talk) 18:51, 18 May 2010 (UTC)

It seems clear enough. But I don't know off hand of any scientific reason for this.--Chemicalinterest (talk) 21:04, 18 May 2010 (UTC)

See swaddling. StuRat (talk) 21:26, 19 May 2010 (UTC)

Right angles

Obviously not at a right angle to the ground if you're standing right next to it, but when viewed from far away, is this close enough?

Do right angles occur naturally? Jacob Lundberg (talk) 20:07, 18 May 2010 (UTC)

It depends on how perfect you want the right angle to be. Halite, for example, forms an isometric crystal, but as you'll see from the pictures, some of the angles are not quite exact. Matt Deres (talk) 20:18, 18 May 2010 (UTC)

Galena, too; and staurolite crystals can be twinned at right angles, as in the infobox image. Deor (talk) 21:44, 18 May 2010 (UTC)

Some fossils such as trilobites and strophomenid brachiopods (e.g. File:Leptaena sp + Rhynchonella sp.2 - Silurico medio.JPG) come pretty close to having right angles, such that they can be used to measure angular strain in deformed rocks by structural geologists. Mikenorton (talk) 20:47, 18 May 2010 (UTC)

A vine hanging to the ground, or a tree like the one to the right (if viewed from far enough away)? Comet Tuttle (talk) 22:08, 18 May 2010 (UTC)

If you break a silcon wafer (as used to make integrated circuits) that is 1-0-0 orientation, many of the pieces will form perfect right angles. --Phil Holmes (talk) 07:39, 19 May 2010 (UTC)

There are three right angles in space.77.86.10.27 (talk) 11:43, 19 May 2010 (UTC)

Fear of the dark

What does the latest research have to say about fear of the dark? Has evolutionary psychology tackled this topic? Barbara Ehrenreich popularized the fear of predators explanation in Blood Rites (1997), but surely Steven Pinker and others have opined on the matter? Any pointers would be helpful. Viriditas (talk) 21:05, 18 May 2010 (UTC)

In an earlier discussion on ghosts in the archive, it says that people generally use the sense of sight to detect most objects. In the dark, they don't have that sense fully, so they are restricted. The sense of hearing becomes much better, so a floorboard creacking could sound like someone sneaking up. It unsettles you. --Chemicalinterest (talk) 21:07, 18 May 2010 (UTC)

Yes, that's true. But many children are afraid of the dark, such that they imagine monsters and see fearful shapes in everyday objects, such as trees. Ehrenreich's explanation, that as primates, we were once prey for predators at night, explains a great deal. I'm wondering if anyone has followed up on this line of thought (early humans as prey) since 1997. Viriditas (talk) 21:11, 18 May 2010 (UTC)

I can't seem to find any more recent research than what you point out. Ehrenreich's hypothesis doesn't make a great deal of sense to me, what would be the point of being scared of the dark before we had a way of making light ourselves (i.e. fire)? What's more, being scared of the dark, and presumably making a fuss to your parents, would be disadvantageous as any predators out there would be directed right to you. CI's suggestion seems reasonable, being in the dark makes you more sensitive to other senses and can make you more paranoid. Perhaps children haven't learnt what all the possible sounds that they hear in the dark could represent, and being on the safe side, are therefore scared of them. 86.7.19.159 (talk) 21:45, 18 May 2010 (UTC)

Why would the predators be directed at you if you make a fuss or increase your alertness? I think they'd have an easier time if you stand still, fearless, while taking no precautions against the mysterious shape sneaking up on you. --99.237.234.104 (talk) 04:02, 19 May 2010 (UTC)

I don't think it requires any special explanation. We are primarily visual animals: that's how we find food, notice dangers, etc. Being in the dark takes away our primary means of sensing the world outside out bodies - heck, even within our bodies. When you stub your toe, you don't try using proprioception and inner pain sensors to determine how badly it's hurt, you twist your leg into an ungodly position and risk falling flat on your ass to see it. Like the posters above, I'm not too impressed with Ehrenreich's idea; like David Jones' An Instinct for Dragons it seeks to provide a theory when the bald facts might be explanation enough. Matt Deres (talk) 22:48, 18 May 2010 (UTC)

As I remember from my childhood, fear of the dark is mainly fear of what might be hidden in the dark. Ehrenreich's explanation seems so, well, obvious, that I'm surprised there is any controversy about it. It's not clear how it could be tested by an experiment though. Looie496 (talk) 00:50, 19 May 2010 (UTC)

Sorry for hitching a ride on someone else's question, but what possible explanations might there be for a person (such as myself) actually being more comfortable in the dark than in daylight? As a child I was scared of many things (dogs, bulldozers, power-line towers, etc., etc.), but I was never really scared of the dark -- I was actually more comfortable in the dark than in daylight. Thanks in advance 67.170.215.166 (talk) 01:18, 19 May 2010 (UTC)

I find darkness calm and relaxing too, maybe you associate it with peace and rest. Not every single little aspect of human nature necessarily has to have a categorized condition. I'm not an expert so I could be wrong about this one. But I mean, NOT being afraid of spiders isn't a "condition" right? So why would NOT being afraid of the dark be one? Maybe the condition you are looking for is "slightly uncomfortable during the day time", maybe you have daytime anxiety disorder.  ;) Vespine (talk) 05:36, 19 May 2010 (UTC)

Reduction of alkali metals

Why can some alkali metals be reduced by weaker reducing agents? An example would be cesium caesium reduced by magnesium. Does it have something to do with gaseous equilibrium? --Chemicalinterest (talk) 21:50, 18 May 2010 (UTC)

If entropy can be increased so that the Gibbs free energy is positive then things that seem to go against the energy barrier can happen. So yes if cesium can be produced as a low density gas in the reaction it will depart from the scene and not react back the other way. Graeme Bartlett (talk) 08:45, 19 May 2010 (UTC)

PS I hope you are not trying this at home. Graeme Bartlett (talk) 08:46, 19 May 2010 (UTC)

No I only have tiny amounts of lithium that burn brightly but I saw in cesium production that cesium dichromate is reacted with zirconium metal to yield cesium gas. I thought the dichromate would be a much stronger oxidizing agent than the Cs⁺ ion. But the cesium ion oxidizes the dichromate to form cesium gas. --Chemicalinterest (talk) 11:58, 19 May 2010 (UTC)

That sounds an unlikely mechanism, more likely the zirconium reduces the dichromate and the cesium ions. If you make that cesium compound hot enough it will make cesium vapour all by itself. When you get brown dwarfs or giant planets you will find alkali metal vapour lines in the spectrum. Graeme Bartlett (talk) 12:32, 19 May 2010 (UTC)

It doesn't mean the alkali metals are in the planet, it could mean that compounds of them exist. (Both Na and NaCl release a specific spectrum.) --Chemicalinterest (talk) 21:39, 19 May 2010 (UTC)

algae or other plants

Is there an algae or other plant that will grow in the arctic or elsewhere in sufficient quantities to absorb all of the excess carbon dioxide now produced by fossil fuels? 71.100.0.29 (talk) 22:43, 18 May 2010 (UTC)

Lichens grow in the Arctic some places. But they will not make any measurable difference to the carbon dioxide concentration. BTW, fossil fuels only put out a miniscule section of carbon dioxide compared to natural sources. If there is more carbon dioxide, plants will grow better, consuming more of it. (This may not be NPOV). --Chemicalinterest (talk) 22:46, 18 May 2010 (UTC)

That's not NPOV, it's false (unfortunately!) see soyface and have a read of Co2#Role_in_photosynthesis. Admittedly on a global scale it is very uncertain, along with changes in cloud cover, the response of forests to co2 is the biggest unknown in climate change models. 86.7.19.159 (talk) 08:05, 19 May 2010 (UTC)

Have you read Geoengineering and the various links? The most common proposal when it comes to using plants is ocean nourishment. Other proposals generally involve growing plants in a more normal fashion and then encapturing the carbon dioxide in some manner so it isn't released for a long time like Biochar and Bio-energy with carbon capture and storage. Nil Einne (talk) 23:08, 18 May 2010 (UTC)

But doesn't CO2 storage intail with it the long term danger of accidental or unintended release that would result in the deaths of trillions of animals, if not render animal life extinct? 71.100.0.29 (talk) 00:53, 19 May 2010 (UTC)

The straightforward method of "storage" is to grow plants such as trees, and then bury them underground. Calculations show that a depth of 10 feet would take them out of circulation for hundreds of years. I think its pretty clear that any unintended release from this reservoir would be extremely gradual. In any case, to get a fix on the numbers, compensating for the CO2 we add each year would require removing several billion tons of carbon from the system, and there is no way that can be done with lichen. Looie496 (talk) 00:57, 19 May 2010 (UTC)

Well I do know of a case in Florida in which a lot of tress were found underwater that had been there for a long time. When the trees were removed they were found not only to be free of decay but strong enough to use for building material. Not only that the trees had taken on aesthetic qualities which allowed them to be used to build furniture that was highly valued and returned to the excavators hundreds of fold of their initial investment. On those ground the idea might not only be good for sequestering carbon dioxide but making your descendants thousands of fold rich, owing also to inflation. 71.100.0.29 (talk) 01:18, 19 May 2010 (UTC)

Looie, I know this has been suggested (biochar) but what's the point in this until we stop digging up coal?! Why waste energy storing trees when they could just be burnt instead and the coal could be left in the ground? 86.7.19.159 (talk) 08:05, 19 May 2010 (UTC)

You can't make furniture out of coal. 71.100.0.29 (talk) 16:19, 19 May 2010 (UTC)

Exactly. It's really worse than that. Just look at the amount of coal it takes to feed a single power plant. It's something like one or two mile-long trains full of coal per day! Now, for carbon sequestration to work, you'd need AT LEAST one or two mile-long trains full of tree timber to be buried someplace PER DAY. It's actually an awful lot more than that because trees contain water and the carbon is reacted with oxygen and other stuff that means that to sequester the carbon from one ton of coal requires more like three tons of old-growth trees or five tons of pine or other fast-growth trees. So just imagine your little power station - covering a few hundred acres - then think about the size of forest and the scale of activity you'd need to fill up maybe 10 mile-long trains with cut lumber every single DAY, 365 days out of the year!! (And to do that sustainably!) In previous Ref Desk questions, I've done the math on this - and to cover the current coal consumption (ignoring gas and oil) of the USA alone, you'd need to plant an area more than twice the size of the USA with trees and harvest and bury them all every 15 years! Furthermore - you'd have to do all of that harvesting, hauling and sequestering without using any more energy in the process...or you'll need even more area and even more harvesting, hauling and sequestering!! Plus, you can't just dump trees in a handy lake someplace - it'll fill up amazingly fast - and besides, trees have this annoying tendancy to float! This is so far from being a practical proposition that it's completely laughable. SteveBaker (talk) 15:03, 19 May 2010 (UTC)

I believe it would be feasible to remove carbon biologically at a cost of $100 per ton or less. The problem is that currently coal itself only costs a bit more than $100 per ton (it was up to $150 before the economic crisis hit, but was as low as $30 back in 2000). That means that to finance the removal of all the carbon you'd have to impose a tax of close to 100% on coal, which is obviously a problem. For any other energy source it would be far less of a burden though. Even for crude oil you'd only have to charge about a 20% surtax, by my calculations. I doubt that the political will is there, but I feel this is something the world could handle if it decided to. Looie496 (talk) 20:41, 19 May 2010 (UTC)

That's just bullshit! It can't possibly work! It's not enough to "remove" this carbon "biologically" - it's still got to go someplace. You burn the two mile-long coal trains worth of coal - you somehow capture the many cubic kilometers of CO2 that this produces (every day!) and "biologically" you do what with it? The material has to go somewhere - conservation of mass and conservation of energy guarantees that! If your magic biology turns the CO2 back into carbon then it's going to need considerably more energy to do that than you got out of the coal in the first place (conservation of energy). If you're planning on using photosynthesis as the source of that energy than you have to use sunlight to do that - and you STILL have 10 mile-long trains full of whatever residue your biological process leaves behind...but hey - if that stuff is so rich in carbon - why not burn it? Well, if you can produce/capture more energy/carbon with your biological process - then why bother burning the coal in the first place? Simply build a closed-loop system where you burn a gazillion tons of bio-residue, turn it into CO2 - which your mysterious process then (photosynthetically) turns back into bio-residue that you can then burn. No coal, no coal-trains, no mining disasters, etc. What you've just invented is a solar power plant. The idea of taxing coal and all that nonsense would magically go away - and since your process can capture the CO2 from burning $100 worth of coal (or bio-residue) for just $100 - the process you describe should be just as cheap as burning coal. So either what you are talking about is complete bullshit - or you've just solved the world's energy crisis and we can shut down all of the coal-fired power plants. I suspect, it's not the latter! SteveBaker (talk) 15:04, 20 May 2010 (UTC)

Put simply, no, because if there was a plant or algae that could grow there it already would be. Take a look at antarctic flora - very few plants can grow there. Reasons for this are multiple: enzyme reactions become very slow, photoinhibition increases, photosynthesis decreases and water is less available at cold temperatures. To fix CO₂ plants need to open their stomata but if there is no water available (or if it's ice) then this won't happen. If (when) the arctic ice cap melts in the summer, more CO₂ will be fixed but the change in albedo from ice to water will far outweigh any benefit of increased photosynthesis. A more promising idea is to use cacti growing in deserts (which use the water efficient CAM photosynthesis) to fix carbon and sequester this elsewhere. But as I said above, doing this while still using fossil fuels is pretty pointless. 86.7.19.159 (talk) 08:05, 19 May 2010 (UTC)

• Strange that you should ask that question, as this has already happened in the past, see azolla event causing a global cooling catastrophe. Graeme Bartlett (talk) 08:43, 19 May 2010 (UTC)

It's worth pointing out that the original "sequestration" was the biogenic creation of fossil fuel in the first place: algae and peat absorbed atmospheric carbon by normal methods - photosynthesis and plant respiration (but over the course of hundreds, thousands, or millions of years). Then, those plants died and were buried (all the while, containing the carbon that they are made out of). Over geologic timescales, this kerogen turned into petroleum and other fossil fuel by geochemical, thermal, and even biological alteration. Now we are re-extracting this former plant-matter. The problem is that we have become so good at extracting it, that we can pull carbon out of the ground at a rate significantly faster than ordinary/natural plant life-cycles and geology can put it back into the ground. (At least, this is our concern, evidenced by the growing carbon concentration in our atmosphere). This is why there is research into carbon sequestration - we are looking for other ways to help improve the rate of carbon "re-absorption" - whether those methods are biological, mechanical, or otherwise. When we contemplate the scales, though, it just boils down to this: something must put the billions of tons of carbon that we extract back in the ground. Nimur (talk) 13:50, 19 May 2010 (UTC)

Interesting, DYK that only 70 years of photosynthesis were ever stored as fossil fuels? (Can't find the figures at the moment, but it does show that we could in theory remove CO₂ from the atmosphere relatively quickly once we stop producing it.) 131.111.30.21 (talk) 15:43, 19 May 2010 (UTC)

The key point here is that it's not enough for the plants to grow (thereby absorbing CO2). Something has to happen to the plants when they get old and die. If they simply sit there and decay - or are eaten by animals or are burned in a forest fire or something - then the carbon that they locked away will simply be released back into the atmosphere again and we're back to square one. If (somehow) the plant gets buried and instead of decaying and producing more CO2 and methane and other nasty greenhouse gasses - they get (ultimately) sequestered and after a gazillion years turn into coal and oil. This locks away the carbon and so long as no stupid humans come and dig it up again and burn it - it can be quite effective. But simply growing some moss and doing nothing else would only have a short-term benefit - roughly of the order of the lifespan of the first generation of plants...after that, the rate that these plants are absorbing CO2 would be balanced by the rate at which the extra plant decay adds to the CO2/Methane levels. SteveBaker (talk) 15:03, 19 May 2010 (UTC)

May 19

Nitroglycerin final ph

many people take Nitroglycerin for heart problems and its also added to gunpowder. since its made from nitric and sulfuric acid. wouldent it burn the mouth of the patient taking it and cause corrosive damage to the gun barrel? —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:31, 19 May 2010 (UTC)

Reviewing several nitroglycerine MSDS safety sheets from various sources, nearly all list "not applicable" for the pH. For example, Nitroglycerin MSDS from Duke University. There are other hazards, including flammability and shock sensitivity; for skin contact, the MSDS suggests immediately flushing with water (though this is contraindicated by the typical medical application, rubbing it on the skin - but medical nitroglycerin is often dissolved in propylene glycol and is not pure). I would speculate that pure nitroglycerine has an almost perfectly neutral pH, if anybody bothered to measure it, gauging from its chemical structure; keep in mind that just because a precursor chemical was a strong acid does not mean that the final product is also a strong acid. As far as reactivity with metals, no metals are counter-indicated on the MSDS. Nimur (talk) 00:49, 19 May 2010 (UTC)

Seenitroglycerin manufacture. Oxide atoms are basic, but they are "locked up" in the glycerol structure. When the strong H⁺ ions attack the glycerin (along with the nitrate), the oxide atoms react with the hydrogen ions to form water, which is neutral. --Chemicalinterest (talk) 11:55, 19 May 2010 (UTC)

It's true that there are components that act as acid and base and give water in the reaction process (leading to neutral product), but the question wasn't about why glycerin doesn't make things basic. Also, please read the production section you mentioned to see how it actually happens--the mechanism you explain is not correct. DMacks (talk) 14:14, 19 May 2010 (UTC)

There is no reaction on that page that shows how the acids are added to the glycerol to form an ester(an ester is the compound of an alcohol and an acid, it doesn't specify whether it's inorganic or organic). If it is esterification, then they react to form the ester(glyceryl trinitrate) and water. I'm just saying that the acids are neutralized, so there is not harm from protons like there is in the free acid. --Chemicalinterest (talk) 21:37, 19 May 2010 (UTC)

To quote the article, "The sulfuric acid produces protonated nitric acid species, which are attacked by glycerin's nucleophilic oxygen atoms. The nitro group is thus added as an ester C-O-NO2 and water is produced.". That's...pretty clearly not "Oxide atoms are basic, but they are "locked up" in the glycerol structure. When the strong H⁺ ions attack the glycerin (along with the nitrate), the oxide atoms react with the hydrogen ions to form water". The nitrate is what attacks the H⁺; the glycerin O remains within the structure. DMacks (talk) 23:13, 19 May 2010 (UTC)

This esterification reaction involves the replacements of the OH^- groups in the glycerol with NO₃- groups. The H₂SO₄ acts as a catalyst. The H⁺ from the nitric acid and the OH^- from the glycerin react to form water. So the simplest(not the mechanism of reaction, just the difference between reactants and products) formula would be glycerol + 3 nitric acid → glyceryl trinitrate + 3 water. You can see how the acid is neutralized. What makes nitro explosive is because the reducing carbon group is bonded to the oxidizing nitrate group. --Chemicalinterest (talk) 11:19, 20 May 2010 (UTC)

Aircraft repairs

Would a blowtorch burn in a monsoon? I'm planning to write a novel about a flight around the world, and in one of the proposed scenes the pilot, while getting ready to depart from Calcutta on the first day of monsoon season, discovers that the plane has been sabotaged at an earlier stop in Pakistan by clipping the generator wires, and decides to repair it by soldering the wires together. Unfortunately there's no power available to run the electric soldering iron (the plane's battery is dead, and the generator is obviously non-functional), so the soldering iron has to be heated using a soldering torch, which has to be used a safe distance away from the fully-fueled aircraft, in the torrential rain. What (if anything) is wrong with this picture? Thanks in advance! 67.170.215.166 (talk) 01:37, 19 May 2010 (UTC)

Twist the wires together along with a strand or two of soldering wire and then heat with the blow torch directly until the solder melts, that would work. I'd be more worried about taking off in a monsoon then soldering some wires together near a fueled plane, especially since presumably everything's going to be pretty wet. I've arced a battery under the hood of a "fully fueled" car by accident more then a few times without any explosions so far. I'm pretty sure you can even weld under the hood without too much risk, unless you directly contact the fuel lines or components. Vespine (talk) 03:35, 19 May 2010 (UTC)

Just a note that doesn't really answer your question. Cutting the generator wire may not be a logical way to sabotage an aircraft - piston aircraft do not need a functioning battery or alternator (which is the generator that charges the battery) to remain flying with the engine(s) running. They use magnetos. Without a functioning battery, you have to hand-prop the aircraft (which means turn the magnetos on and turn the propeller(s) by hand until the magnetos engage and the engine is running by itself, which I should mention is dangerous if you are not trained in doing that), because the starter won't work and the turn coordinator, radios, navigation equipment, lights, and some of the other gauges, such as the fuel guages, would not function. If the attitude indicator is electronic (which is typically not the case, at least not on single engine aircraft such as the one I fly), that would not work either. Vespine brings up a good point. You want your electronics working if you are going to be flying through clouds. A good pilot will make the choice not to fly for any reason if the weather is dangerous, but since it's a book, you have a lot of leeway ;-). Falconus^{p t c} 03:42, 19 May 2010 (UTC)

I think Falconus would agree that 90% of pilots in this situation would unhesitatingly hand-start the aircraft, because that's the macho thing to do. The least likely part of the whole scenario sounds like the pilot taking off in a monsoon at all. Comet Tuttle (talk) 06:01, 19 May 2010 (UTC)

Um, no, I would not agree with that at all... I was talking about what is technically possible, not what is the smartest thing to do. While there is not an inherent risk to flying without the electrical system (heck, some aircraft don't even have an electrical system), that is only under optimum conditions (excellent weather, no need to fly through airspace requiring a radio, etc). I personally would not be comfortable doing that even if I knew the area like the back of my hand. If the weather was going to be bad, the pilot would have to be a certifiable madman to make the decision to fly without the electronic navigational devices, various gauges, radios, and the electrical instruments. I seriously doubt that many pilots would choose to fly with no electronics for a long distance flight (I could see with a GPS, and a backup GPS) even in great weather. It just isn't worth it. There are a couple of pilots that are "macho" and they are the ones that end up in the news. Maybe a handful (I'm guessing) would seriously consider flying in a foreign land with an aircraft that does not have any of the equipment that they typically rely on, but of these, I can only hope that very few would be stupid enough to attempt it in poor weather. Most modern pilots operate under the "err on the side of caution" philosophy. People don't realize that, because those pilots don't end up in the news. Falconus^{p t c} 06:28, 19 May 2010 (UTC)

Also, I should mention that hand-propping works (in theory) on all piston aircraft, but is rather dangerous to attempt on tricycle gear aircraft, just because when you lean forward to push the prop down, your head gets way too close to the arc. That is another reason why I would never attempt it on the aircraft I fly (reason 1 being that nobody has ever shown me how). Falconus^{p t c} 06:33, 19 May 2010 (UTC)

If the airplane was sabotaged in Pakistan, how did it get to Calcutta in India? And if the sabotage was so minor that the pilot simply flew from Pakistan to Calcutta, why doesn't he just fly on to his next port and fix the damage there, or somewhere else where it will be more convenient and miles away from the monsoon? Dolphin (t) 12:14, 19 May 2010 (UTC)

To answer your questions in the order asked:

1)The presumable intent of the saboteur(s) was not to prevent the plane from taking off altogether, but to cause a dangerous failure once in the air (the Paki saboteur was presumably angry with the pilot for breaking sharia law and then resisting arrest);

2)To this effect, the wires on the generator (mounted on the starboard engine in this model of aircraft) have been cut and then loosely re-attached in such a way as to vibrate loose during flight (also, the machine screw holding one of the valves on the portside engine has been loosened, which will cause a failure further down the line), therefore the sabotage has gone unnoticed until after landing in Calcutta;

3)During the flight from Pakistan to India, the weather is for the most part CAVU, so one could get by without electrical power, whereas from Calcutta to the next stop (Bangkok) it's close to zero-zero -- therefore, for this flight it's absolutely imperative to have fully functioning flight instruments and a working power supply. 67.170.215.166 (talk) 23:43, 19 May 2010 (UTC)

Guys, the question has little to do with the above answers. All he wants to know is if a blowtorch will work in a torrential downpour. Googlemeister (talk) 12:53, 19 May 2010 (UTC)

Oxy-acetylene torches will even work under water (see underwater welding), because they provide both fuel and oxidizer. If the wind were very strong, it is conceivable that the flame would blow out, but I think it's reasonable to say the rain is not an issue. Nimur (talk) 13:52, 19 May 2010 (UTC)

The following "retro" methods of soldering are not suggested as being safe or practical for actual usage, and are only presented in the context of possible use in the fictional work described above. In practice, there would be danger of burns or of starting something on fire, and hazard from inhaling lead fumes. If the electric soldering iron is heated while the wind is blowing and it is getting rained on, it will cool off too much to melt the solder by the time the hero has run several paces from his "safe open flame" location to where the wires are. In the early 20th century, there were soldering irons which were designed to be heated by a torch, (see some at [13]), and they had several ounces of copper in the business end. They would stay hot a bit longer. Something with several ounces of metal and an insulated handle or a handle that could be gripped with Visegrip or similar pliers could be heated with a torch or fire and might stay hot enough to heat the copper wire as well as melting the solder (needed to avoid a cold soldered connection). Maybe a golf club could be pressed into service as such an improvised soldering iron (though with an unwieldy long handle) or a small hammer with a metal handle and a leather grip further insulated with rags could be used, but a larger torch than a little propane torch would be needed to heat it. Maybe some aviation fuel could be burned in a can to heat the found soldering iron. A soldering iron, to melt solder, does not need to be red hot, so if heated red hot, it would still be at working temperature after it cooled a bit. Another old soldering trick is the solderpot. The wire connection was twisted together and left dangling downward. The solder was melted in an iron pot over a flame, and lifted up so the wires dunked into the solder. If there is enough solder, and a metal can, like a metal measuring cup and any sort of fire, and pliers to hold the can with, this would be an easy solution to the problem. If you Google ehow solder pot there are detailed instructions for using a solder pot. Edison (talk) 15:31, 19 May 2010 (UTC)

Thanks everyone, I think I'll have my hero(ine) use a torch-heated soldering iron that he/she has in the toolkit as a backup for the electric iron. BTW, if it's safe to heat the wires directly with a blowtorch on a fully-fueled twin-engine plane that has more than a thousand gallons of 100-octane avgas on board (as Vespine claims), I don't see why using a torch to heat the soldering iron while in close proximity to said fully-fueled plane would pose a significantly bigger danger of "setting something (i.e. above-mentioned plane) on fire" -- if anything, the danger would be less in this case. And as for hazard from inhaling lead fumes, it's very much overblown -- lead is not so volatile as to give off more than a tiny bit of fumes at the temperatures involved, so the pilot's exposure won't be significant (even if said pilot is a pregnant woman) from doing this job just one time. IMHO a bigger danger would be either setting the plane on fire with the blowtorch, or getting your fingers chopped off afterward when hand-propping the engine. FWiW 67.170.215.166 (talk) 00:01, 20 May 2010 (UTC)

Notes like the one about lead fumes are just ass coverage in case someone in the future reads a good-faith ref desk posting and does something idiotic like sitting in a small closet with a boiling pot of lead solder for hours, then wants damages paid from the person who posted information. We live in a litigious society. The US government has regulations to prevent children eating bicycle gears which contain lead. Personally I like the narrative having the person take a pipe cap and make it into a solder pot, heated over some burning fuel. Edison (talk) 19:04, 20 May 2010 (UTC)

soap labels

i noticed that some liquid soap bottles have a paper label. (dr. bronners is one i think but there are others as well) that label dosent dissolve even in my shower.

A) what kind of paper do they use that dosent dissolve and B) what kind of ink do they use that dosent run and C) what kind of glue do they use that dosent dissolve but it also safe for skin contact ect. —Preceding unsigned comment added by Tom12350 (talk • contribs) 02:40, 19 May 2010 (UTC)

FYI...Dr. Bronner's paper labels do most certainly dissolve, which might explain why they don't use them as much anymore in their liquid soap products under the half-gallon size. Sounds like your bottle isn't getting wet. Long-term users of the good doctor will often buy the soap in bulk and transfer it to smaller bottles, which often lacks a label. It's true that the paper labels on the old bottles didn't come off easily, however, and could take up to six months or so if you reused the bottle as I describe above, so maybe there was some water-resistant protection, but I think the company phased out the paper labels on the smaller bottles to save trees. Viriditas (talk) 04:21, 19 May 2010 (UTC)

i dont use Dr. Bronner's that much but other soaps labels i have dont come off that easily . in general what are they made out of? —Preceding unsigned comment added by Tom12350 (talk • contribs) 05:31, 19 May 2010 (UTC)

The new bottles have silk-screened labels, so no paper. Keep in mind, this is one of the most famous liquid soap labels in the world, so you should be able to find out what the old label was made of very easily. You can contact the company here. There's a phone number listed on that page as well. Remember, DILUTE! OK! Viriditas (talk) 06:49, 19 May 2010 (UTC)

can we stop talking about dr. bronners. i said i have other soap labels i have dont come off that easily . in general what are they made out of? they are a type of paper im holding one right now. —Preceding unsigned comment added by Tom12350 (talk • contribs) 08:39, 19 May 2010 (UTC)

Lung cancer tumor eroding bone in rib

Hi There, My father was recently diagnosed with non-small cell lung cancer. The doctor said this has not spread to the bones but that it has eroded the rib at the tumor site. My question is what is the mechanism whereby the cancer causes the bone to erode? This is not a request for advice, I am wondering about the physiology of the bone deteriorating. Thanks! —Preceding unsigned comment added by 64.234.6.24 (talk) 04:41, 19 May 2010 (UTC)

I believe the erosion is simply due to pressure from the tumor, but I can't seem to find a citation to back this up. Regards, --—Cyclonenim | Chat  06:35, 19 May 2010 (UTC)

I would say metastasis (Lungs, bones, liver, and brain are the most common metastasis locations from solid tumors). AFAIK Lung cancer frequently sends metastasis to other organs through blood circulation. Metastasis are colonies of amorphous tumoral cells that substitute, in this case, bone tissue, making it more fragile. --151.51.20.38 (talk) 17:43, 19 May 2010 (UTC)

The docs were very specific, based on PET scan, that the cancer had not metastisized, rather the tumor had caused the bone to deteriorate. We will see the doc Monday and I will ask him about the mechanism of this as it seems the question is more difficult than I imagined. Thanks! —Preceding unsigned comment added by 64.234.6.24 (talk) 01:01, 20 May 2010 (UTC)

Perhaps the tumor is sucking too many nutrients from neighboring tissues? 67.243.7.245 (talk) 04:16, 20 May 2010 (UTC)

This section is a perfect example of why Wikipedia policy forbids giving medical advice. Looie496 (talk) 14:20, 20 May 2010 (UTC)

I don't believe this is an instance of a poster seeking medical advice, though you're welcome to take this up on the talk page, Looie496. (Granted, the reliability of the answers here is certainly dubious. Responders should remember that our goal is to provide detailed, factual, referenced responses to questions — not guesses.) TenOfAllTrades(talk) 15:09, 20 May 2010 (UTC)

In general, tumors (primary tumors and metastases) don't generally directly attack bone. Instead, they may secrete factors (proteins) which locally or systemically up-regulate the activity and growth of osteoclasts: cells that normally resorb bone at a carefully-maintained level. (While bones look static, they're actually continuously being taken apart and regenerated at a microscopic level. Osteoblasts build new bone, while osteoclasts trim it back; it's a dynamic equilibrium that responds to stress, strain, and fracture.)

There's a whole alphabet soup of different proteins which can be involved in shifting the balance from bone maintenance to bone destruction. Here's one paper – that I've linked to primarily because the fulltext is free – which specifically fingers MCP-1 in some non-small cell cancers; the discussion section towards the bottom of the article also lists a large number of factors identified in other studies.

To further complicate matters, the tumors don't have to secrete the osteoclast-stimulating factors themselves — the presence of an invasive tumor can trigger an inflammatory response in nearby cells which in turn drives osteoclast activation. This latter model is similar to a process of bone loss seen in inflammatory arthritis: [14] (that paper deals with cholesteatomas, but the idea is the same).

In other words, there are a number of mechanisms which can ultimately lead to overstimulation of osteoclasts and bone loss. I can't speculate on which might be active in any particular patient, and your father's oncologist is the one to talk to about treatment or prognosis options. TenOfAllTrades(talk) 15:54, 20 May 2010 (UTC)

Great, just what I was looking for. Thanks Ten! —Preceding unsigned comment added by 64.234.6.24 (talk) 16:57, 20 May 2010 (UTC)

safety of tinned food

Is it safe to eat tinned food that is past the use-by date? I have some tinned tomatoes that are about 4 years out of date, but it's a "best before" date rather than a use by date. I've checked the article, but it doesn't say there. Thanks in advance, It's been emotional (talk) 06:41, 19 May 2010 (UTC)

By definition, goods are not considered safe for consumption after the use by date.--Shantavira|^{feed me} 07:17, 19 May 2010 (UTC)

This article suggests that that may not be necessarily true: "Canned food retains its safety and nutritional value well beyond two years, but it may have some variation in quality, such as a change of color and texture. Canning is a high-heat process that renders the food commercially sterile. Food safety is not an issue in products kept on the shelf or in the pantry for long periods of time. In fact, canned food has an almost indefinite shelf life at moderate temperatures (75° F and below). Canned food as old as 100 years has been found in sunken ships and it is still microbiologically safe". Ghmyrtle (talk) 07:21, 19 May 2010 (UTC)

The integrity of the container is of paramount importance. Any rust? any dents? Discard the can. 218.25.32.210 (talk) 08:09, 19 May 2010 (UTC)

In part this will depend on how the canned food was sterilized. Some are irradiated thoroughly to kill off practically all microbes within the can, and this can leave the food with a use by date into tens of years. Whether it'll still taste good is a different matter. Regards, --—Cyclonenim | Chat  11:08, 19 May 2010 (UTC)

There is a reason they put a "best before" rather than a "use by". The former means that the texture or flavor may not be at it's absolute peak after that date - the latter means that you need to toss it out. So I would expect this stuff to be perfectly OK to eat. Most canned goods retain their edibility for decades. However, whether it still tastes OK is a different matter. Open one and find out! If it's been rotting for two years, you'll definitely know! SteveBaker (talk) 14:44, 19 May 2010 (UTC)

I would argue against the "just try it" method. Rotting is obvious, yes, but not all dangers come from rotten foods. Bacteria may set in that haven't really produced noticible decay. Bascially, the "use by"/"best before" date is the longest a company is willing to assert that the food is fresh and safe. Beyond that, you're taking a risk with the product. — The Hand That Feeds You:^Bite 15:15, 19 May 2010 (UTC)

With tomatoes one concern is corrosion of the can. The acid in tomatoes will quickly corrode an unprotected can. This is solved in the short term by lining the inside of the can with enamel or a layer of polycarbonate (yes, there's BPA in food cans). These will only last for a short time. After a while, they'll no longer be sufficient to protect the metal from acid errosion, and your tomatoes will get an off "metallic" flavor, or become unfit for consumption. -- 174.24.200.38 (talk) 16:13, 19 May 2010 (UTC)

I'd put inspection way over any date for determining if it's good. Is the can corroded, dented, bulging ? Toss it. If not, open it up. Are the tomatoes gray and bad smelling ? Toss them. If it looks and smells good, take a taste. If it tastes bad, toss it. If not, eat up. I've also had many items go bad before the USE BY date, it's more of a question of being 100% sterilized or not. If not, the food is unsafe almost right away. StuRat (talk) 17:57, 19 May 2010 (UTC)

If a can has been properly sterilized, there won't be even one single living microorganism in the whole thing. The "best before" dates are related to possible deterioration of the nutrients, not to bacterial growth. The speed of deterioration is tremendously dependent on temperature, though, so it's hard to set fixed time spans for usability. Looie496 (talk) 20:22, 19 May 2010 (UTC)

It's not just microorganisms that can be dangerous though. As Mr. 174 pointed out, there could be metal leaching into the food, perhaps to an extent to be harmful to the OP's health. It's not like canned tomatoes are that expensive; buy a new can. Buddy431 (talk) 04:25, 20 May 2010 (UTC)

Can coyotes co-exist with elk for any duration of time, without attacks?

Sorry for all the "wild animal kingdom" questions, but I'm on vacation and thought this board would have some biology experts about. Anyway, all I'm basing my question off of is what I could see through my binoculars and a Maglite pointed into the dark. A coyote was barking/howling about 20 feet away from me (I'm on a high porch facing a valley); he was loud enough to scare the daylights out of me when I was inside, and I quickly went out to listen to him. I could hear him sort of "quietly" grunting (when not howling). He stopped... so I ran inside to get the binoculars and flashlight, and when I returned, he was gone. However, a small herd of elk was grazing about 50 feet off to my right, and I saw two or three pair of "floating" eyes in the distance on the left. That meant the coyote was standing amidst this small herd, and I stood out there for probably 20 minutes waiting for a pack to take down one of the elk. But nothing happened. Is this ... normal? Any ideas what was going on? Was the coyote trying to spook the elk away? Cause it didn't work lol. Thanks so much in advance. And also if any birders are around, I'm still hoping for a bird call identification up in my "Loons in Colorado" question above. – Kerαunoςcopia^◁_galaxies 08:37, 19 May 2010 (UTC)

If the coyotes had just eaten, they might not want to eat the elk. But that doesn't explain why the elk weren't scared of them. --Chemicalinterest (talk) 11:42, 19 May 2010 (UTC)

I would be pretty surprised if a single coyote was any threat at all to an adult elk. That could explain their apathy, especially if the herd did not have any young. Googlemeister (talk) 12:48, 19 May 2010 (UTC)

Exactly. I don't like the chances of a coyote bringing down an elk, even if they have a partner, unless there is some exceptionally vulnerable herd member around. Those antlers aren't just for show. Vranak (talk) 12:57, 19 May 2010 (UTC)

Agreed, you'd need a wolf pack to hunt adult Elk. StuRat (talk) 17:50, 19 May 2010 (UTC)

Googlemeister, there was only one coyote from what I could tell, so maybe that's it. And I've seen entire roads closed off with signs saying "Closed until summer for elk calving", so maybe there weren't any young yet. I'm directly in the path of the elks' migration as they're always coming through here. So maybe one coyote decided to get a little possessive of his territory or something, it was kind of amusing. Thanks all for your replies, I greatly appreciate it. – Kerαunoςcopia^◁_galaxies 19:32, 19 May 2010 (UTC)

To be honest, I doubt the coyote calls had much to do with him trying to warn off the elk; it probably had more to do with letting other coyotes in the area know that he had claimed that bit of property. Matt Deres (talk) 20:32, 19 May 2010 (UTC)

Interesting. The Coyote article though mentions the territory thing doesn't happen until fall, and it's spring here now. But if that's the case, I kind of hope he returns. – Kerαunoςcopia^◁_galaxies 20:55, 19 May 2010 (UTC)

Turning off car

Over here in my city, we have timers on traffic signals that show how long till the signal turns green or red. I turn off the car when the timer is over 30 seconds( for it to turn green). I know that starting the car back on consumes fuel, but my question is how much time on the timer would make it feasible to turn off an average family sedan (mine is a 2000 Honda Civic). Thanks.--119.155.30.13 (talk) 10:34, 19 May 2010 (UTC)

Besides the cost in fuel, you should also calculate in the extra wear and tear on your starter. The starter for my Jeep is pretty cheap and it's a breeze to replace but yours might be different (more difficult/expensive). Dismas|^(talk) 10:55, 19 May 2010 (UTC)

An idling 4-cyl consumes around 1 liter per hour. Let's say you managed to save 10 minutes idle time each workday, it's around 40 liters annual savings. Is it worth it? If the car is out of warranty period, think of what Dismas said. IMO, if idle time becomes a financial (not just ethical) concern, you need to reconsider your daily route, place of work etc. East of Borschov (talk) 11:30, 19 May 2010 (UTC)

Recent BMWs turn of the engine automatically at any stop, and start it again when the accelerator is depressed. So the wear on the starter cannot be that bad. --Stephan Schulz (talk) 11:40, 19 May 2010 (UTC)

From what I had explained to me by a BMW salesman, the engine doesn't turn off-off. It's just a sort of really low "state". Rimush (talk) 13:11, 19 May 2010 (UTC)

I haven't seen an idle-shut-off feature listed on any of the marketingese at the BMW website; I suspect there's a misconception here. The Toyota Prius, however, does have the capacity to shut down when idle - but it has a completely different engine design, called the Hybrid Synergy Drive. In fact, it has no "starter motor" - the hybrid motor is the starter. This complete re-engineering changes the fuel-consumption/wear-and-tear tradeoff equation very significantly. But in an ordinary car, I would think that the extra wear on your starter is not worth the small fuel savings you may be getting by shutting down when idle. Nimur (talk) 13:39, 19 May 2010 (UTC)

They definitely had the feature on the BMW 1 Series in 2007-08. Maybe they discontinued it, or it's an Euro-only thing. Rimush (talk) 13:41, 19 May 2010 (UTC)

It is certainly a feature of some BMW cars.

On older cars without computer-controlled fuel injectors, I think the extra fuel used to restart the engine made it not worthwhile to stop the engine for the duration of a traffic signal. But modern cars can inject just exactly the right amount of gas to restart an already warm engine - so there is almost zero penalty for doing that - and killing the engine for even a brief stop turns out to be worthwhile.

However - there are some weird legal issues in some US states over cars that do this automatically - and the car manufacturers won't make different designs of cars for different states - so if just a couple of states have stupid laws, everyone is screwed (think about that the next time someone advocates increasing state's rights over federal government!). But certainly there are plenty of cars in Europe that do this. The MINI (which is a BMW brand) has different software in the USA and in the rest of the world specifically for this reason. The law here in Texas was designed to outlaw those remote starters that some people in cold climates use to start their cars 5 minutes before they go outside so that the engine and passenger compartment are nice and warm when they go to drive off. These things can be dangerous if someone leaves the car in gear by mistake or something. It seems that this law was written stupidly such as to disallow any device that causes the car to start without someone inside the car specifically commanding it to do so...or some such madness. Anyway - on my MINI (bought in the US), it doesn't do it - and on my sister's almost identical one (bought in the UK), it does. The Prius got away with it by saying that the engine doesn't directly drive the wheels - so technically it's just a generator. The answer to this question is that, yes, it does save gas to do that - and no, it doesn't noticably shorten the life of your starter motor. Even if it did, it, it also lengthens the life of the rest of your engine, clutch, water pump, belts, etc, so it would be a net win in any case. The latest MINI goes even one step further - when the engine has automatically stopped - and you push gently on the gas pedal, it rolls the car forwards using only the starter motor! Hence, when you are in heavy stop-start traffic, edging forwards a couple of feet at a time, you effectively have an electric car! It only restarts the engine when you get over one or two miles per hour, or if the battery is getting low, or if the cabin temperature gets high enough that the A/C has to turn on. I'm really pissed that some stupid outdated law prevents these kinds of intelligent fuel-saving ideas from being sold in the US market - even on cars that have all of the hardware to do it! SteveBaker (talk) 14:39, 19 May 2010 (UTC)

I see my error! Assuming that auto start-stop was a "luxury" feature, I checked the highest-end 7-series BMW, which does not have the option. Apparently auto start stop is only available on smaller BMWs - 1- through 3-series. Nimur (talk) 21:15, 19 May 2010 (UTC)

From occasionally driving and often being driven in a 2-3 year old 3-series BMW, I can, with very very very high certainty, state that at least the German model does indeed completely switch of the engine automatically when idling. It also switches off fuel injection completely if the car is engine-braking. --Stephan Schulz (talk) 18:45, 19 May 2010 (UTC)

The no-fuel-injection-during-engine-braking thing is a pretty common and well-established feature on cars with electronic fuel injection. My 1994 Civic did it, and I don't think it was particularly novel at that time. -- Coneslayer (talk) 19:58, 19 May 2010 (UTC)

Nuclear fuel

I read that Iran is swapping enriched uranium for nuclear fuel. What is the difference basically?--Mudupie (talk) 11:00, 19 May 2010 (UTC)

Enriched uranium discusses this at length, with diagrams to match. Regards, --—Cyclonenim | Chat  11:06, 19 May 2010 (UTC)

It's the level of enrichment—or, rather, the proportion of the isotope U-235 to the isotope U-238. Basically Iran is giving away a large storage of low enriched (3-5%) nuclear fuel, in return for a small amount of (ideally carefully controlled) fuel that is enriched to 20%, which is considered "highly enriched" even though it is not "bomb grade". The enrichment level determines in part what you can do with the fuel. 20% enriched fuel can run different types of reactors than 3-5% enriched fuel. In this case, I believe they want the 20% fuel to run a reactor that will make medical isotopes. (This is not a bad thing, in and of itself. Medical isotopes are good things.)

The reason for all of this is that ideally people don't want Iran to be able to enrich fuel to 20% on their own. The reason is not that 20% fuel can do anything interesting from a weapons point of view (it can't), but because the difference between 5% to 20% enrichment is actually a LOT larger than the difference between 20% and 90% enrichment. (This is, as first glance, counterintuitive—why should 5 to 20 be more than 20 to 90?—but it is because enrichment is exponential, to put it simply. This post goes into more detail as to why this is the case.) 90% enrichment is bomb-grade. So the goal here is to keep Iran from enriching their own material to 20%, because if they do that, they'll basically know how to make bomb-grade uranium. Giving them the 20% by itself is not necessarily dangerous, if it is monitored (so that it is not more enriched) and if they don't know how to enrich up to 20% on their own. Getting Iran to give away their existing stock ideally puts a limit on how much more enrichment they can do to it, and depletes the total number of bombs they could make if they enriched all of that fuel.

Note that there are some pretty obvious plans with the deal. Iran still intends to learn how to enrich its uranium to 20% anyway, and has kept enough low-enriched fuel that, if they did enrich it to 90%, they could have a bomb's worth of uranium. The U.S. analysts have largely viewed this as a "stalling" measure on Iran's part—to "give" a little bit so that sanctions don't kick in, while they work on their enrichment ability all the while. --Mr.98 (talk) 15:49, 19 May 2010 (UTC)

If you really believe that they want 20% enriched uranium to make "medical isotopes", then you must have your head under about two meters of sand. The thing is, 20% enriched uranium can actually do some interesting things from a weapons point of view without needing further enrichment -- if you stick it into a breeder reactor along with a lot of depleted uranium, then you can make "medical isotopes" indeed... 67.170.215.166 (talk) 00:15, 20 May 2010 (UTC)

Dirty bomb? --Chemicalinterest (talk) 11:12, 20 May 2010 (UTC)

That requires additional processing facilities and know-how that they likely don't have (nobody is alleging they have plutonium facilities), and the 20% they'd get from Turkey/Brazil would be heavily safeguarded anyway. I don't think there's any danger there other than them stalling. The risk of dirty bombs is exaggerated and certainly not what they are going after here. They do want the medical isotopes, in part because they want to be able to claim they've been doing civilian work on this all along. Their strategy from the beginning is to slowly get the infrastructure necessary to build multiple weapons if they wanted them. They wouldn't take the 20%, break safeguards, turn it into plutonium, and then try to turn that into a single weapon (if you could even get that out of 120kg of 20% fuel—the amount of plutonium produced even in a breeder reactor is small relative to the whole of the fuel mass, but I don't know the exact numbers). That would be the dumb approach. The smart approach would be to take the 20%, turn it into medical isotopes, show everybody how peaceful they are, drag out the UN process, continue developing U-235 enrichment capacity, divert other LEU into that, and get to the point where they could develop, say, a warhead a month if they wanted to. Then they have stealth nuke capability (like Israel), but have not yet violated the NPT in an explicit way, thus avoid sanctions, possibility of war, etc. Which is just a way of saying, one need not be blinkered about Iranian intentions to think that the 20% stuff is not going to be a military problem (it won't be). --Mr.98 (talk) 14:39, 20 May 2010 (UTC)

Thank you for the explanation. --Mudupie (talk) 11:13, 20 May 2010 (UTC)

Reverse of hydraulic diameter?

While modelling fluid flows often the hydraulic diameter concept is used to model a non-circular duct as a circular one. I need to model a circular pipe as an equivalent rectangular one. So 1)Can this be done? (2)If so will it be modelled only as a square or can it be modelled as a rectangular section with any width to height ratio I choose? (3)Is this done in simply a reverse manner to how the hydraulic dia is calculated or is there some other technique (or does it depend very much on my fluid flow process and cannot be generalized)? Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 12:34, 19 May 2010 (UTC)

What exactly are you modeling? In general, you can model anything as anything - you can model your pipe as a spherical cow if you like. The question really is, "what parameters and results will you derive from your model," and as a followup, "what errors are introduced by your modeling assumptions/simplifications?" For example, if you intend to solve your flow with a FDTD solver and derive a fluid-flow rate for the pipe, your effective pipe shape will dramatically affect the resulting flow-rate. But if your procedure approximates the rate by simply calculating a cross-sectional area, the actual shape is irrelevant. So - what parameters do you hope to derive from your model? Once we know those, we can help direct you towards estimating the errors that result from your modeling approximation. Nimur (talk) 13:32, 19 May 2010 (UTC)

I am modelling the pressure loss in a cyclone separator. I have a correlation which is based on the entry duct being rectangular whereas my actual duct is circular. the pressure drop is dependant (at least according to the relation) mainly on the width of the rectangular entry duct and only to a smaller extent on height. so how do i change my circular duct to an equivalent rectangular one? If i know that the ideal/ general width to height ratio is 1:3 can i form that equiv rectangle? or since the model is dependent on a particular dimension (width) rather than area i cannot model it at all? Thanks once again. —Preceding unsigned comment added by 122.172.10.93 (talk) 16:31, 19 May 2010 (UTC)

If it is the pressure loss in the cyclone separator it self and not the pipe I don't think there are any generic translation. This depends on the mixing of fluids with different velocities at different radius in the cyclone. You will need a empiric formula CFD-simulation or very complex calculations. As an approximation I would guess between the pressure loss for a square with the same side as the diameter and a square with the same diagonal as the pipe diameter. —Preceding unsigned comment added by Gr8xoz (talk • contribs) 22:08, 19 May 2010 (UTC)

engineering

What is the scope of jobs if i do electronics in engineering<BE>?? —Preceding unsigned comment added by Swet69kak (talk • contribs) 13:21, 19 May 2010 (UTC)

Electrical engineering is huge. I mean, really huge. If you obtain an undergraduate degree in electronics engineering, you may be qualified to work in semiconductor manufacturing, MEMS, analog circuit design, digital electronics, computer architecture, system integration, firmware programming, software engineering, image processing, information theory, telecommunications, radio science, energy, and more. Have you looked at our article, electrical engineering? Nimur (talk) 13:26, 19 May 2010 (UTC)

Electronic engineering is really huge. Sometimes confused with Electrical eng —Preceding unsigned comment added by 79.76.203.64 (talk) 18:49, 19 May 2010 (UTC)

Note that this vocabulary distinction differs by region. In the US, at least, electronics engineers often have a degree in "electrical engineering", though they have extensive training in electronics. Comet Tuttle (talk) 23:00, 19 May 2010 (UTC)

The great thing about doing a BE is that it teaches you to think like an engineer. In any real job, you rapidly find yourself applying the thinking skills to information that goes into greater depth than you learnt in your course. After a while, it becomes possible to apply that process effectively to fields that didn't feature in the course at all (I can point to Electronic Engineering graduates who, 20 years on, spend most of their day doing Aeronautical, Marine, Automotive and Hydraulic engineering mixed with project management).

Proving you can cope with the academic rigour of a BE course also makes you attractive to all sorts of non-engineering employers (accountancy firms always used to like employing recent engineering graduates). Zeusfaber (talk) 19:27, 19 May 2010 (UTC)

moist towelettes

I watched the movie "The Book of Eli" back when it was playing and one thing that was a big trade item were moist towelettes, like the kind you use to clean your hands at a BBQ restaurant. I was wondering if those are a reasonable substitute for bathing in situations where a shower might not be available, like on a camping trip? I mean will one packet significantly reduce the BO, or would they need so many of the things that it would be inconvenient to haul dozens of them around? Googlemeister (talk) 13:38, 19 May 2010 (UTC)

The towelettes really vary in terms of the amount of liquid in them and they also gradually dry out over several months/years - even "sealed" as they are. I don't think they'd reasonably be useful for reducing BO, though; there's just too much "you" and not enough moisture in the packets to cover it all. Using one under each arm and one around the face/neck and one around the crotch might take some of the edge off, but after you've been sweating and in camp smoke for a few days, the stank (to use the technical term) is basically all over you - even your hair. Matt Deres (talk) 14:44, 19 May 2010 (UTC)

Exactly. And remember one of the opening scenes, where Eli says the good thing about no showers is that "You can smell hijackers a mile away", right before he's ambushed by the very same. Still, I think moist towelettes were a comfort item in that film, to, like Matt says, 'take the edge' off. Similar to the shampoo that Gary Oldman's character gave to his wife. Vranak (talk) 20:24, 19 May 2010 (UTC)

You'd be better off finding a stream or pond to wash off with (not necessarily in, mind you). In dryer climates, just rubbing sand on you can help clean off the sweat & grime, though it won't do quite so much for the smell. — The Hand That Feeds You:^Bite 15:28, 19 May 2010 (UTC)

You can always use a shower in a can to cover up the smell. 131.111.30.21 (talk) 17:23, 19 May 2010 (UTC)

Look in the baby aisle of your local supermarket - they'll have packets of moist wipes used for cleaning pooh off of babies rear-ends. That stuff is antibacterial so it should handle BO - and you get like 100 of them in a small container without a gazillion foil wrappers to lug around. SteveBaker (talk) 14:49, 20 May 2010 (UTC)

Beans growing on Crete

Does anyone know the name of the beans which grow on Crete and are used in locally produced "Coca-Cola" look a like called Fimi, these beans are also used by Nestlé. I forgot what they were called... I saw them growing in the wild in Crete... Sεrvιεи | T@lk page 16:54, 19 May 2010 (UTC)

Carob? Ghmyrtle (talk) 17:05, 19 May 2010 (UTC)

Still used, rusty aquaduct pipe lying in creek

At the tail end of a lake, the water rushes through a waterfall before continuing down a creek into the massive city-used reservoir eight miles away. Lying on top of some of this creek is a rusty pipe that is "picking up" some of the water and acting as an aquaduct to take it elsewhere (not sure where). The pipe is just resting on the surface of the creek; it's kind of gross. Are there any potential environmental or health concerns from this pipe touching future-drinking water? The pipe is slightly orange-ish in hue, with spots and discolorations on it. – Kerαunoςcopia^◁_galaxies 19:40, 19 May 2010 (UTC)

Almost certainly not - the orange patches are certainly rust - and iron is not a harmful element.77.86.10.27 (talk) 20:31, 19 May 2010 (UTC)

Even after it's oxidized? Is the amount of iron controlled at some point then? – Kerαunoςcopia^◁_galaxies 20:52, 19 May 2010 (UTC)

Rust is fairly insoluble in normal water, so it stays stuck to the pipe. If it goes into a water supply for humans it may be filtered to remove flakes and other gunk. Graeme Bartlett (talk) 21:16, 19 May 2010 (UTC)

Rust isn't harmful; it is a natural occurrent in the earth's crust. See hematite, the natural form of rust. --Chemicalinterest (talk) 21:33, 19 May 2010 (UTC)

Well, you can have too much of a good thing. I wouldn't expect the concentration of iron in the water coming off the pipe to be remotely high enough to be harmful, though. --Tango (talk) 21:46, 19 May 2010 (UTC)

If you are really concerned contact your local water authority or enviromental health agency (whatever they are called in your country) - better safe than sorry. The fact that a pipe links a water course to somewhere else raises the possibility of pollution by 'bad water' running in the opposite direction. In general though a rusty pipe in a water resovoir is not going to be a big problem.77.86.108.78 (talk) 11:03, 20 May 2010 (UTC)

Botfly

What actually happens if a human carries a botfly to full term in their flesh? Is there actually any lasting damage or health implications? No, not asking for medical advice here - I don't have botfly, nor does anyone I know. Just simple curiosity. --Kurt Shaped Box (talk) 20:21, 19 May 2010 (UTC)

Extracted human botfly larva. The arrow points to the larva's mouthparts

Dermatobia hominis captures a mosquito and lays an egg on it. Then when it feeds on a human the egg is transferred and a larva starts to develop (pictured) by feeding on flesh. Once it reaches full term it forces its way back out through the skin, falls to the ground and pupates. There was a great BBC Nature documentary showing it happen to a cow but I can't remember which it was. Searching the literature, the only problem caused seems to be myiasis (the larva feeding on your flesh). Adding "complication" to a search only comes up saying that it does not normally cause any complications. The danger comes if somebody attempts to remove the larvae and does a bad job, if the gut contents are spilled into your blood you could end up with a nasty infection (but having looked I can't find any recorded cases of what type of infection). So basically, like a good parasite should (to try and keep plenty of its hosts alive), it doesn't seem to cause any lasting damage. I spent the summer with some tropical biologists and heard a story of a professor who became so used to having the larvae that he no longer cared, once when at a football game, the larva decided it was time to leave, he took of his cap and out popped the grub, much to the disgust of those around him! That should probably be taken with a pinch of salt but I think it makes it clear that while being disgusting, they don't do any harm. 86.7.19.159 (talk) 21:45, 19 May 2010 (UTC)

Cracked disagrees. The bottom of this article says they can eat your brain. Of course, that problem wouldn't specifically be related to carrying it full-term... Vimescarrot (talk) 05:58, 20 May 2010 (UTC)

Hmm, that doesn't look like the most reliable source in the world. It also says that bullet ants "shriek" before they bite, but through personal experience I know that's not the case. It also has a picture of driver ants when its talking about the army ant, Eciton burchellii. Obviously if the mosquito happens to bite you in an important place then losing that bit of your body might be annoying - how exactly is the larva supposed to get through the skull though? —Preceding unsigned comment added by 86.7.19.159 (talk) 07:59, 20 May 2010 (UTC)

Certainly not a reliable source itself, but Cracked usually references some other source within its articles (I can't see it from here, it's blocked on this network). I think the idea was that to get to the brain it would simply float aruond the body (through blood vessels? I don't really remember) until it found somewhere it liked, then it'd settle down for a feast. 212.219.39.146 (talk) 08:02, 20 May 2010 (UTC)

That wouldn't work as they develop in the subcutaneous layers of the skin and don't enter the bloodstream. There are no sources in the article at all. _{To make things worse, they even stole the driver ant picture off this guy breaking the GFDL.} 131.111.30.21 (talk) 13:46, 20 May 2010 (UTC)

Through your ears? According to Myiasis#Clinical_presentation_in_humans, at least. Though this doesn't seem to be specifically referring to botflies. --Kurt Shaped Box (talk) 15:56, 20 May 2010 (UTC)

Evolution of movable eyeball

I know how the eyeball evolved, as per the WP article, but I can't think of an path for the eyeball to detach itself from the flesh around it, so that it can be moved. Is there there some speculative ideas on this? A google search [15] turns up a few hits, mainly from creationists questioning this. CS Miller (talk) 20:49, 19 May 2010 (UTC)

I have no idea how it actually happened, but it doesn't seem too difficult to me. Even a small amount of movement is beneficial, so it could start with an attached eyeball with a little flexibility and an appropriate muscle and gradually get less and less attached and more and more precise muscles until you reach the current state. --Tango (talk) 21:37, 19 May 2010 (UTC)

The most useful approach would probably be to compare the lamprey and hagfish, considered the two types of vertebrates with the most primitive body plans by most biologists. Lampreys have large movable eyes, but hagfish have lensless eyes with no exterior eye muscles. Looie496 (talk) 21:53, 19 May 2010 (UTC)

I've searched for some articles but it doesn't seem to have been discussed in any journals from what I can tell. This is because it is bound to be speculative and would be difficult to test so can't really be published in a journal. Tango's answer sounds very plausible, remember the amounts of time that evolution has to play with (unless you are an young earth creationist) and would be able to make infinite numbers of adjustments that would be either neutral or an improvement on previous eyes. Because eyes are so important, the selective pressure to improve would be strong. The creationist argument of irreducible complexity is pretty poor, this, the first hit in your link says that even the first eyes were complicated but ignores the fact that the simplest eyes would never have been fossilised! That also says "The fascinating thing about the evolution of the eye is its apparent sudden appearance" - this needs to be thought of on a geological time scale though - there have been huge changes to live today in the last few million years. There does not appear to be a convincing exact mechanism to show how the movement of the eye evolved, but remember that absence of evidence is not evidence of absence. The previous link ends with "For non-evolutionists there is no debate" - this is absolutely useless! You can't say that a theory is wrong without providing some alternative, more plausible explanation. Sorry for the rant - sounds like we're not really sure about it. 86.7.19.159 (talk) 22:10, 19 May 2010 (UTC)

It's of note that the eyeball is not totally detached by any definition. It is receded and has muscles that allow it to be pointed in different ways, but it still very much connected to the flesh. Receding into flesh would seem to make sense from a protection point of view; muscles to manipulate its location would also make sense. One can easily see how "half" of this capability would still be useful (humans only have "half" of the capability of, say, a chameleon), so that throws irreducible complexity out of the window (it is not an "all or nothing" type of thing). --Mr.98 (talk) 22:21, 19 May 2010 (UTC)

• I was under the impression that to get to the the the pin-hole state the retina evolved into the flesh, rather that the folds evolved outwards. It's the path from a lens-covered pit to a muscle-attached organ that I'm after.
• If the pit already had a lens before the sphere was moveable, then pointing the lens only at the object of interest is likely to reduce focusing accuracy.
• I can see that if the eyeball was on a stalk (a bit like snails'), then moving it into the body would be an advantage.
• 86.7--- / Mr98 - I'm not invoking argumentum ad ignorantiam, I'm trying to dispel my ignorance. CS Miller (talk) 22:58, 19 May 2010 (UTC)

The eyeball is still a lens-covered pit, isn't it? It's just a lens-covered pit that's also somewhat free to move from the surrounding flesh. I agree it's probably useless for the lens to be moved alone. The whole apparatus has to be moved together, which is why it might become somewhat less attached to the surrounding flesh. If you're thinking that the lens developed into the whole eyeball and the pit developed into the eye-socket that doesn't seem to make sense to me, although I'm just speculating. Rckrone (talk) 23:56, 19 May 2010 (UTC)

No, it is not necessary for the whole apparatus to move together. Salticidae have developed eyes where the lens is immobile but the retina moves. Of course Salticidae are arthropods, not chordates, and their eyes are not homologous to the eyes of the chordates. But no, the whole apparatus does not have to be moved together. Lampreys (already mentioned by Looie) indeed have an eyeball that is moved by extraocular muscles. (To be fair, lampreys have 5 extraocular muscles while most craniates -- from fish to mammals -- have 6; also, in contrast to most craniates, lamprey eyes are also focused by the extraocular muscles; AFAIK lampreys lack ciliary muscles in their eyes). This may suggest that lamprey eyes are indeed the most primitive "proper" craniate eyes extant. (Hagfish, on the other hand, is something of an enigma; either their eyes are the basal chordate eyes, or they have lost the advanced eyes their ancestors possessed, as the hagfish ecological niche does not require vision. There are reviews on that subject in literature. I recommend "Evolution of the vertebrate eye..." by Lamb, Collin, and Pugh, Nature Reviews Neuroscience (2007) v.8 pp. 960-975). This brings us back to the original question, how did the eyeball of the craniates evolve from the "cup" eyes of our basal deuterostome ancestors. Indeed, one mechanism by which hagfish may have lost the advanced eyes is neoteny. Larval stage of a lamprey has primitive eyes much like the hagfish; it is only during the lamprey metamorphosis that the proper eyeballs develop. Following the lamprey metamorphosis gives us a pretty good idea of what the eyeball evolution may have looked like. What happens is (1) light sensitive layer balloons laterally, forming a vesicle, (2) surface ectoderm is modified to form a lens, and (3) the extraocular muscles are formed from the mesoderm and the neural crest. Hope this helps. --Dr Dima (talk) 22:14, 20 May 2010 (UTC)

Trichlor illegal?

Is trichlor outlawed? It says so in the sodium hydroxide article. Thanks.--Chemicalinterest (talk) 21:32, 19 May 2010 (UTC)

it means trichloroethane (not Trichloroisocyanuric acid) , I've corrected the article [16]. Yes CCl3CH3 is outlawed.77.86.10.27 (talk) 21:59, 19 May 2010 (UTC)

Thanks. --Chemicalinterest (talk) 22:35, 19 May 2010 (UTC)

I still have some! Will I be arrested? Dbfirs 07:26, 20 May 2010 (UTC)

I think that it outlawed its production and sale, not its use (like halons). Naughty. You aren't concerned about the environment.--Chemicalinterest (talk) 11:06, 20 May 2010 (UTC)

Only a very small quantity - too little to be worth destroying (if that's possible). It has a very attractive odour, but I avoid inhaling it. Dbfirs 11:15, 20 May 2010 (UTC)

Which one is it? --Chemicalinterest (talk) 12:21, 20 May 2010 (UTC)

the 1,1,1 form was the most common - I used to have some Carbon tetrachloride - it too had a lovely smell - like many halocarbons (most of which are now banned or very heavily controlled) - you could hand it in to the local enviromental agency if you want rid of it (as an individual I doubt they would charge) - but company's probably have to pay to get rid of the stuff.77.86.115.45 (talk) 12:29, 20 May 2010 (UTC)

Yes, 1,1,1 (Liquid Paper thinner). Dbfirs 23:09, 20 May 2010 (UTC)

Wow, haven't seen any of that for over 2 decades - I think they banned it in the UK long before 1996 and replaced it with water or something - kids at school were sniffing it, - apparently the hallucinations they experienced interfered with paying attention in class or something...77.86.115.45 (talk) 23:47, 20 May 2010 (UTC)

Atomic mass unit

"A single atom of carbon-12 has a mass of 12 u exactly, by definition", according to Wikipedia's article on the atomic mass unit. Because electrons contribute slightly to the mass of an atom, the mass of the nucleus of a carbon-12 must be slightly less than 12u. But this would seemingly imply that protons and neutrons have a mass that's slightly less than 1u, but in fact they have a mass greater than 1u. So what's going on here? Is this a relativistic effect involving potential energy reducing mass, or what? 173.179.59.66 (talk) 22:46, 19 May 2010 (UTC)

Electrons generally wouldn't count in the mass number. The total mass of the electrons in an atom carbon-12 would be 0.003291 (approx.) u. --Chemicalinterest (talk) 22:58, 19 May 2010 (UTC)

A free carbon atom weighs slightly less than 6 loose protons + 6 loose neutrons. See nuclear binding energy. CS Miller (talk) 23:05, 19 May 2010 (UTC)

What you are observing here is that the mass of the assembled nucleus is less than the sum of the masses of the constituent particles. There is a loss of mass! See Mass defect where it says When the nucleons are grouped together to form a nucleus, they lose a small amount of mass, i.e., there is mass defect. The lost mass has been converted to energy according to Einstein’s formula $E=mc^{2}$ to hold the nucleus together against the electrostatic forces trying to disperse the positively-charged protons.

One amu is defined to be one-twelfth of the mass of a carbon-12 atom. As a consequence of the mass defect, the mass of a free neutron or proton is greater than one amu.

The mass defect is different for different elements, and different isotopes of any element. For example, the mass of the hydrogen-6 isotope is not 6 amu as you might expect from the definition of amu, but 6.045. Less mass is lost per nucleon in assembling a hydrogen-6 atom than in assembling a carbon-12 atom, possibly because hydrogen only has one proton so only one electrostatically-charged particle in its nucleus.

The mass of an electron is only 1/1836 that of a proton so the mass of all the electrons in an atom is not significant in the mass of the atom. Dolphin (t) 02:39, 20 May 2010 (UTC)

Whenever a net energy input is needed to pry something apart into its constituent pieces, conservation of energy together with E=mc² implies that the mass of the bound system must be less than the sum of the masses of the parts. This also applies to electromagnetically bound objects like atoms and to gravitationally bound objects like planets. "The lost mass has been converted to energy [...] to hold the nucleus together against the electrostatic forces trying to disperse the positively-charged protons" is incorrect. You have the sign backwards. If you have to spend energy to force like-charged objects together against their mutual repulsion, the binding energy/mass is positive, not negative. The negative binding energy of nuclei comes from the nuclear force. Electromagnetism contributes a positive binding energy, but not enough to make the binding energy positive overall. -- BenRG (talk) 03:38, 20 May 2010 (UTC)

May 20

Reservoirs for pumped storage hydroelectricity?

About what proportion of water reservoirs are presently configured for pumped storage hydroelectricity? How many are suitable? Enough to support 100% wind power in most countries? 71.198.176.22 (talk) 00:11, 20 May 2010 (UTC)

The article says there's 21.5 GW worth of capacity in my country -- not nearly enough to support 100% wind power. In any case, nuclear power would be much more reliable, practical and economical than wind power (though wind power could be used to supplement electricity production). 67.170.215.166 (talk) 01:03, 20 May 2010 (UTC)

I'm more interested in how many reservoirs could be converted to pumped storage during a transition to wind. I think you may be mistaken about the cost of nuclear. 71.198.176.22 (talk) 04:15, 20 May 2010 (UTC)

And pretty much bog-all in my country. Pretty much one, in fact. Again, not nearly enough to support "100% wind power". Tonywalton ^Talk 01:14, 20 May 2010 (UTC)

There's also Cruachan, Foyers and Ffestiniog in the UK. Loch Lomond/Loch Katrine (via Loch Arklett) could provide around 2.5hrs of average-load for the whole of the UK, for a 10m drop in water level (13km*1km at 300m elevation), however Loch Katrine is the major source of Glasgow's water supply. As for the OP's original question, as long as the tail race discharges into a large enough body of water, of the same salinity, then any conventional storage hydro station could be converted to pump storage. Another way to store electricity is to use giant sub-sea airbags, sodium sulfar batteries or to make hydrogen during windy periods. CS Miller (talk) 11:34, 20 May 2010 (UTC)

Deepest manmade pool

Listening to NPR this evening brought a question to mind. They were talking about the Deep Horizon oil spill and how much pressure the human body can take under water. So, my question is what is the deepest manmade pool ever made? By "deepest" I mean from the surface of the water to the deepest point in the pool. And by "pool", I mean any manmade hole or container which was built/dug specifically to contain water. Or a quarry or other such excavation that was later filled/allowed to fill with water. Dismas|^(talk) 04:54, 20 May 2010 (UTC)

Nemo 33 holds at least one record. Viriditas (talk) 09:44, 20 May 2010 (UTC)

Another type of record: Lock (water transport)#Very large locks says "the Oskemen Lock on the Irtysh River in Kazakhstan has a drop of 42 m".[17] The reference says it is the deepest lock. PrimeHunter (talk) 13:27, 20 May 2010 (UTC)

From Open-pit mining I came across the Big Hole which has been closed since 1914 if I understand the article correctly (and I presume was allowed to fill up with water since then) but has only filled up to a level of 40metres. I don't know if the level is stable or of hundreds of years from now it could be over 200m.

Then there's Adams Mine "the deepest being 183 m (600 ft), placing it below the water table; it is currently half filled with water" so I guess that's ~90m.

Finally I found Berkeley Pit which our article says "is filled to a depth of about 900 feet (270 m) with water" so I guess that's the winner so far. I wouldn't want to swim or dive in it though since our article also says it's "heavily acidic (2.5 pH level). The pit is laden with heavy metals and dangerous chemicals, including arsenic, cadmium, zinc, and sulfuric acid". It may have been higher except "In the 1990s plans were devised for solving the groundwater problem. Water flowing into the pit has been diverted to slow the rise of the water level. Plans have been made for more extensive treatment in the future. The Berkeley Pit has since become one of the largest Superfund sites."

Edit: I also came across Mir mine which I guess is filling with water although I don't know to what depth. [18] appears to show it with water (based on our article and the details mentioned I'm pretty sure it's the same thing even if they say it's in Eastern Serbia when it's actually in Eastern Siberian).

Nil Einne (talk) 15:39, 20 May 2010 (UTC)

Do you count artificial lakes formed by dams ? Some of the tallest dams are around 300m high, so the lakes behind them are probably of similar depth. Gandalf61 (talk) 15:46, 20 May 2010 (UTC)

Super-Kamiokande's detector-pool is just over 40m deep. I'm sure either NASA (weightlessness training) or the oil-rig safety companies (dropping a helicopter body into a pool) have deeper ones. CS Miller (talk) 21:49, 20 May 2010 (UTC)

What does "Da" mean?

Link: [19] What does "Da" mean?174.3.123.220 (talk) 05:07, 20 May 2010 (UTC)

Dalton (unit). DMacks (talk) 05:28, 20 May 2010 (UTC)

In what language? use the language ref. desk not science. —Preceding unsigned comment added by 165.212.189.187 (talk) 14:36, 20 May 2010 (UTC)

In every language:) It's a scientific unit of measurement, per the cited context, not an arbitrary word. DMacks (talk) 14:43, 20 May 2010 (UTC)

Also, it means yes in Russian. --Ouro (blah blah) 19:18, 20 May 2010 (UTC)

Spinning Tesla egg and stability

http://www.youtube.com/watch?v=brNBVDCeECg&feature=related Okay, so in this vid, the egg is initially spinning about one axis, but as it rotates faster it its axis of rotation (relative to the body) switches. I was wondering why this happened. I know that an object spinning about a principal axis with a minimum or maximum value for its corresponding moment of inertia will remain stable, but an egg has two moments of inertia that are equal, so I don't know what happens in this case. Thanks. 173.179.59.66 (talk) 05:40, 20 May 2010 (UTC)

Our article Tesla's Egg of Columbus cryptically refers to "gyroscopic action". The whole article is pretty poor; I don't even understand why a rotating magnetic field would cause a copper egg to rotate (does it set up induction currents in the egg that create their own field, and interact with the external one?). Buddy431 (talk) 12:44, 20 May 2010 (UTC)

You don't need to mess around with copper and magnets and all that stuff. Just take two regular hens' eggs. Hard-boil one and leave the other raw. Now spin them on their sides as fast as you can. The hard-boiled egg will gradually roll until the pointy-end is pointing straight up...the raw one will remain on it's side and stop spinning rather quickly. SteveBaker (talk) 14:44, 20 May 2010 (UTC)

That the raw egg will stop spinning is pretty clear to me. What I still don't understand is why the other egg will change orientation. I tried something with Euler's equations which I'm not sure is correct, but maybe it will be on the right track. Let the axis that runs through the end of the egg be axis 1, the axis that the egg is initially rotating in be axis 2, and axis 3 be perpendicular to the first two. These three axes will be principal axes, so Euler's equations can be applied:

${\begin{matrix}I_{1}{\dot {\omega }}_{1}+(I_{3}-I_{2})\omega _{2}\omega _{3}&=&0\\I_{2}{\dot {\omega }}_{2}+(I_{1}-I_{3})\omega _{3}\omega _{1}&=&0\\I_{3}{\dot {\omega }}_{3}+(I_{2}-I_{1})\omega _{1}\omega _{2}&=&0\end{matrix}}$

Initially, most of the spin will be in ω₂, but owing to perhaps to some pertubations or whatever, ω₁ and ω₃ are small but non-zero. Because they are small, the second term in the second Euler equation can be ignored, and we get that ω₂ is constant. Likewise, because I₃ = I₂, dω₁/dt=0 and ω₁ remains constant. However, if we differentiate the third equation and substitue the first equation into it, we arrive at the equation

$I_{3}{\ddot {\omega }}_{3}+{\frac {(I_{2}-I_{1})(I_{2}-I_{3})}{I_{1}}}{\omega _{2}}^{2}\omega _{3}=I_{3}{\ddot {\omega }}_{3}=0$

Meaning that ω₃ will increase at a constant rate. If so, then the pointy end of the egg will begin to rotate, either moving up or down depending on the sign of ω₃. However, there are still some pieces missing: first, for the egg's tip to move up, ω₃ will have to be positive, but Euler's equations seem to imply that it can just as easily be negative;, second, what causes ω₁ to increase; finally, are Euler's equations even applicable here, considering that the principal axes are themselves rotating with respect to the laboratory frame? Actually, I can see that ω₁ would increase to preserve the orientation of the egg's angular momentum, but Euler's equations seem to contradict that (and really, this is just an exercise in applying Euler's equations, so I would like to know why they don't work, or if there's a way to make them work). 173.179.59.66 (talk) 17:39, 20 May 2010 (UTC)

The difference compared to hard-boiled is a good clue--suggests that having the internal material be fluid might be key. Especially important might be that the yolk has a different density and is mobile within the object. DMacks (talk) 18:46, 20 May 2010 (UTC)

Oh, I get why the raw egg stops spinning. Centrifugal forces push the yolk to the edges of the egg, increasing the egg's moment of inertia, and so on. What remains a mystery (at least to me) is the behaviour of the hard-boiled (or copper) egg. 173.179.59.66 (talk) 18:56, 20 May 2010 (UTC)

ok stevebaker is right about the hardboiled egg (slightly excited person) another - clearly the overall axis of rotation stays the same - so angular conservation of momentum is preserved..

actually the explanation of why this happens is complex - handwaving more handwaving - it seems that instabilities in the rotation of the egg + friction lead to precession maybe not - and eventually the egg stands up (in a circularly symmetrical arragement that is stable with respect to the frictional effects that made it stand up in the first place...) - quite how the friction causes the precession effect is beyond me - perhaps someone else could give a proper explanation...? The two mathematicians were Moffat and Shimomura - perhaps someone on the maths desk has a better handle on this. (It's certainly not trivial to explain - and quite a acchievement to prove - I'm still not sure if this is finished with Critics attacked the paper because... one for the maths desk )

As for the electromagnetic - spinning - yes - it's an induction motor basically - this video http://www.youtube.com/watch?v=pgkxAQ3fPzg shows the same effect with a slightly less confusing allen key in the second half - works for most things that conduct basically.

Question - as I understand it the induction motor shouldn't work when the copper egg stands on its end since the egg is circularly symmetrical in the centre of rotation of the field - since the torque requires anisotropy in the field.. Can anyone help me with this - does the egg slow once it's upright - at most the induced electric current would rotate - but since the rotation is about the centre of symmetry of the egg when upright there will be little resistance to it changing - and little or no torque?? (ie would a copper ball spin in the same experiment??) Anyone know??77.86.115.45 (talk) 19:47, 20 May 2010 (UTC)

Pressure drop in branched pipe flow

I have a Y branch (both 45 degree) entering into a main duct. What is the associated pressure drop of the branch when (1)no fluid is flowing in the main duct (ie the branch is actually a sort of 'entry')? (2)fluid is flowing in the main duct? I would be grateful if anybody could give me either a correlation modelling the flow or the equivalent k factor or a relation in terms of bend loss etc Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 06:56, 20 May 2010 (UTC)

Ants

I woke up this morning to find Ants crawling all over my kitchen. I'm not sure how or why they got there as there is nothing for the blighters to eat except perhaps a few crumbs and I live two floors above ground so I'm surprised they made the effort.

Anyway, what's the best way of getting rid of them? My local hardware store has ant powder and also a spray of liquid for ants but which is better and how long will these take to work? They're only ordinary black ants, the type that are very common. GaryReggae (talk) 09:11, 20 May 2010 (UTC)

In the UK we have something called Nippon, which is a sort of gel. You put a blob of it where you saw the ants, and they are attracted to the stuff, which they consume and carry back to the nest, which then kills all the ants. It's quite funny watching all these ant drunkards queueing up to get to this stuff, and then staggering about trying to find their way home! It's about the most effective stuff I've found yet. --TammyMoet (talk) 09:25, 20 May 2010 (UTC)

Quite funny? Sounds like sadism :P Rimush (talk) 10:00, 20 May 2010 (UTC)

We occasionally get ants in our house, and use a prepackaged solid chemical composition in a plastic container. After a few hours, the ants get attracted to the trap. In a couple of days, you can see the ants are moving slower and diminishing. In a week, they should be completely gone. --Chemicalinterest (talk) 11:08, 20 May 2010 (UTC)

(edit conflict) Most sprays and powders kill ants pretty much in a few minutes - a good idea is to put in where they are getting in - like a minefield.

Other anti-ant products contain a poison that the ants carry back to the nest - thus killing the queen or whatever. These work in the longer term - and usually come in a box with a hole for the ants to get in. This is the type chemicalinterest mentions above

Googling the name of the products will probably get you the answer - the MSDS of each product should be available online - it's fairly likely that many products use the same poison - it will be mentioned in the MSDS.77.86.108.78 (talk) 11:11, 20 May 2010 (UTC)

Of course, in the long term, they'll probably keep coming back until you eliminate whatever brought them there in the first place. You know the drill: keep the kitchen clean, keep food in sealed containers (flour, sugar especially), wipe up spills immediately, etc. Buddy431 (talk) 12:39, 20 May 2010 (UTC)

I have found that putting a line of Raid around wherever they are coming in seems to work pretty well. It kills a bunch of them but presumably not the whole colony. But I don't recall getting repeat business from the same colony. --Mr.98 (talk) 14:30, 20 May 2010 (UTC)

Thanks for all your help folks! I would have bought some 'Nippon' as it is apparently very good and kills the whole colony, however my local hardware shop didn't have any so I got a spray instead which contains 'Cypermethrine'. Spray it on an ant and it kills it almost instantly. I can't figure out where they are coming in but I have sprayed the surfaces around where there seemed to be a lot of ants. I also realised what they were coming in for - I had left an empty bottle on the side with some dregs of fruit juice in - this actually proved a very effective trap - there were literally DOZENS of dead ants in there! Anyway, a couple of hours after spraying and I haven't seen any more ants. Fingers crossed! GaryReggae (talk) 18:23, 20 May 2010 (UTC)

If the ants do not carry it back to the queen, the nest doesn't die though. --Chemicalinterest (talk) 20:34, 20 May 2010 (UTC)

NaI (Tl) temperature effect

hello, it is observed that the light output from thre NaI (Tl) crystal falls with either rise or fall of temperature. can any body help why tis happen. and what is the mechanism that causing the phenmena. 59.90.213.38 (talk) 11:23, 20 May 2010 (UTC)

Thallium iodide article says that conditions to avoid are heat, so it may decompose into the elements when heated. The thallium iodide article says the NaI crystals are doped with TlI, but the NaI article says that the NaI crystals are doped with Tl (elemental?). --Chemicalinterest (talk) 11:38, 20 May 2010 (UTC)

Thallium is probably in the form of Thallium iodide - a description of the background is here [20]

Quote: Bob immediately sent off for some pure sodium iodide, and obtained a quantity of thallium iodide as well from Fort Belvoir, Virginia, where research on crystal counters was being conducted. He placed some NaI together with, as he put it, a "pinch" of thallium iodide in a crucible, and simply torched the powder. When it cooled down, he placed a small amount of the resulting glaze on a photographic plate, together with naphthalene, and repeated the irradiation experiment with the radium source. The response of the NaI(Tl), Bob told me, was tremendous. He knew then that he had found a wonderful scintillation material.

The search temp should be "Sodium iodide thallium effeciency temperature" or similar - this turns up http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B73DP-4V3M8DT-X&_user=10&_coverDate=04/15/1982&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5c38b40ce51202ea554194ce49ce42ae which states a positive efficiency gain with temperature, which is explained in terms of emmision of light being related to adjacent thallium ("thallium dimers") in the crystal. (The article is not free on the web unfortuntately). I don't know if this theory is considered broadly correct but assume it is.

For the role of Thallium dimers in the scintillation process the key article appears to be by "Van Sciver" (Name: W. J. Van Sciver) : searching "van sciver thallium dimers" helps here.

This article is typical http://ieeexplore.ieee.org/Xplore/login.jsp?reload=true&url=http://ieeexplore.ieee.org/iel5/23/4324068/04324090.pdf%3Farnumber%3D4324090&authDecision=-203

I can't find any free resources on this on the internet. This isn't my subject - hopefully someone more expert will be able to explain more.77.86.115.45 (talk) 12:08, 20 May 2010 (UTC)

Karma

Is there any way to disprove the existence of karma? TheFutureAwaits (talk) 11:59, 20 May 2010 (UTC)

I don't think so - at the simplest level : "cause and effect" most scientists would eaily accept it to be broadly true, at more human or abstract levels; such as karma obtained through thoughts or words it is probably too subjective to be scientifically analysed to the level of proof or disproof.77.86.115.45 (talk) 12:14, 20 May 2010 (UTC)

Good things happen and bad things happen. In the immediate present our actions can result in positive and negative consequences, so if I punch a bouncer at a nightclub, the chances are I'll get beaten up in return. But if the consequence is entirely unrelated to the initial good or bad deed, there is clearly no link to a magical force. It's just two random events colliding with human irrationality (just as some people believe in good luck charms). Regards, --—Cyclonenim | Chat  12:57, 20 May 2010 (UTC)

No, definitely not. Most (if not all) versions of karma allow for the effect to come in a different life than the cause (see reincarnation). To disprove karma we would have to either disprove reincarnation or show that even if reincarnation exists, it doesn't include a concept of karma. Neither of those is falsifiable. --Tango (talk) 13:56, 20 May 2010 (UTC)

I don't honestly think so. I reckon, point of fact, that it would be easier to make a convincing case for its existence, than to break the same. Immoral people do tend to attract bad outcomes for themselves, from what I have witnessed. Having a reckless disregard for other people's feelings often means you are inattentive to matters that could set you back. Vranak (talk) 14:38, 20 May 2010 (UTC)

Karma simply means that actions have consequences. You don't need to have much life experience to realize that's true. Belief in rebirth, caste, etc is not a prerequisite to appreciating the truth of karma.--Shantavira|^{feed me} 15:13, 20 May 2010 (UTC)

It's probably far too broadly defined. To disprove something you need a specific claim. You could disprove specific claims about karma. For example you could take a thousand murderers and a thousand confirmed nice people and have them play games of chance against each other and see if the nice people are more likely to win, but if that shows no proof of Karma, someone who believed karma existed would simply say that it doesn't work like that.

Beyond that, some definitions of Karma are less about mystical forces, and more about the reactions and interactions of the people around you. For those definitions of karma it's actually a real effect caused by human's social instincts.

This sort of thing is why scientists try at all times to be very specific about their definitions. Laymen often interpret it as nit-picking, or trying to wiggle out of making a firm statement, but it's really just an important first step. APL (talk) 15:19, 20 May 2010 (UTC)

I think it would be fair to make a very reserved, but testable, claim that captures the overall principle: for example, "people who do nice things for others tend to get rewarded." Now, even this claim has some issues. What counts as a "nice thing"? What counts as a reward? To what extent do we intend to show a correlation? To what extent do outliers discredit the hypothesis? (There are plenty of nice people who have come to tragic ends). But at least this makes a stride towards a falsifiable, testable hypothesis. A scientist can then proceed to test the validity of the hypothesis. Game theory has contributed a significant body of research modeling and estimating peoples' behaviors and rewards. Surely there are also sociological papers that research this effect: The modeling of sharing: Effects associated with vicarious reinforcement, symbolization, age, and generalization. Now, to what extent does this capture the concept of karma? Karma is a vaguely defined semi-philosophical/semi-religious concept with thousands of interpretations. But if you want to restrict the claim to the concept that good behavior statistically yields better outcomes (with numerous caveats and exceptions), then that is a scientific claim with a good deal of evidence to support it. Nimur (talk) 16:23, 20 May 2010 (UTC)

Certainly one could imagine a statistical test for this. However, I suspect that the results would "prove" that Karma exists - in as much as people who do nice things tend to do better in life. But separating out the psychological feeling of well-being you get from doing someone a good turn from some mystical/religious interpretation would be much harder. How would you eliminate this "placebo effect"? There is also the issue of correlation versus causation. Could it be, for example, that people who are doing well in life tend to be nicer towards others? That seems like a reasonable hypothesis. We'd also have to be much more careful about the meaning of the term than is generally accepted. For example, we might try to devise a kind of double-blind study where people perform some act which they think is a good act - but which for reasons they aren't told is actually either "good" or "utterly evil"! If you found that those people that unknowingly were behaving in an evil manner did worse in life than the ones doing actual good in the world - then you'd have a very different conclusion than if they each performed equally. But do the "rules" of Karma say that merely having good intentions is enough to win you the rewards even if your actions are doing horrible things? If so then we can't use that test. SteveBaker (talk) 21:02, 20 May 2010 (UTC)

I'd argue the opposite of what most people seem to be saying. Bad things happen to good people. Wars and natural disasters don't spare "good people". Of course then you could argue that good people get a better afterlife or reincarnation, including that makes it completely unfalsifiable. Forgetting the subjectivity of what it means to be "good" to begin with..Vespine (talk) 22:35, 20 May 2010 (UTC)

Defocus calculation

I have a lens which is focused to 5 feet. There are two points of light, one 3 feet away and another 6 feet away. How would I calculate the defocus blur (like the spread) of those points of light at the film plane given a focal length and aperture? How would I generalise this to work at all focus distances, including infinity? Lewis Collard! (lol, internet) 12:15, 20 May 2010 (UTC)

Probably the easiest way to see how to do the calculation is to draw a diagram. Light spreads from the point and hits every part of the lens. All the light that hits the lens gets redirected toward the focal point, so the size of the beam just past the lens starts out at the full size of the aperture and then decreases linearly down to zero between there and the focal point. Past that it grows again at the same rate. Use the formula on the focal length article to find the proper distance of the screen from the lens to get a focused image for the light at 3 feet, and compare that to the actual distance. Rckrone (talk) 17:13, 20 May 2010 (UTC)

There might be a suitable formula in Circle of confusion depending on exactly what info. you needed.77.86.115.45 (talk) 18:45, 20 May 2010 (UTC)

An easier way to see what's going on is to trace rays backwards from the film. All rays from a point on the film are refracted in the lens and reconverge to a point in the focal plane, then diverge beyond that. This traces out a double cone with one base at infinity and the other base at the aperture (and with the aperture's size and shape). Any light source inside that cone (and only those light sources) will make a spot on that point of the film. This is easy to remember and visualize and it tells me what I usually want to know: how much blurring will happen at a given distance, in units of physical length at that distance. It also tells you the behavior at infinity: the angular confusion at infinity is the apex angle of the cone. If you want the size perspective-scaled to a different plane for some reason, then you need to multiply by d/D, where d and D are the distances from the lens to the plane of interest and the plane of the light source, respectively. If d is the film plane, and you want to calculate it from the focal plane distance L and the focal length f, then d = 1 / (1/f − 1/L). Only these more complicated formulas appear in the circle of confusion article, together with more complicated diagrams, making things look much harder than they really are. -- BenRG (talk) 21:55, 20 May 2010 (UTC)

(more complex/accurate method) If you want to know the 'shape' of the defocus blur (ie the distribution of light in the focal plane) - you can do this mathematically - you need a good understanding of vectors/trigonometry/equivalent - (I assume the light points are on the focal axis) - you need to calculate the path of light as it travels from light source, is refracted in the lens, and then the intersection of the ray with the focal plane - this equation needs to be found as a function of angle the light ray makes with the lens axis - then obtaining the distribution (blur spread equation) by integrating over angle from 0 to the angle at which the ray makes with the aperture (at a given f stop)...

For parallel lines (ie point at infinity) you may need to use a slightly different integration (though assuming the light intensity of the parallel rays is constant with distance off axis is a good approximation for all normal lens) - (unless you are good enough at maths to have made your equations so that they don't "go silly" when point source distance = infinity.

You can also use a computer to help you do this (numerical integration) - there are also commercial products that do this - ray tracing or optics design - I don't know of any free ones - but no doubt they exist if you look hard enough (ask...)

Technically you need the forms of the len(s) you are using (ie the equation of the surface of the lens) - but you can simplify by just assuming a simple single lens even if your actual set is complicated and compound.. Ask if you need more..77.86.115.45 (talk) 18:17, 20 May 2010 (UTC)

Are you after a Depth Of Field Calculator? .. Vespine (talk) 22:29, 20 May 2010 (UTC) I corrected the displayed name of your link and hope you don't mind. Cuddlyable3 (talk) 23:16, 20 May 2010 (UTC)

particle board desk.

i have a particle board desk. i noticed there is "lip" where the top meets the edge there is a small gap where the veneer is glued. there are small white granules in there that appears to be a glue. is this Urea Formaldehyde? or some other type of glue. some came out and it is sticky. —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:11, 20 May 2010 (UTC)

Probably the glue (aka resin) - Particle_board#Manufacturing suggests a number of possible glues, of which urea-formaldehyde is one likely possibility, I don't know of an easy way to distinguish the different glues.77.86.115.45 (talk) 14:41, 20 May 2010 (UTC)

Oh - if it's the glue holding on the veneer it may not be the same as the glue used to make the board - for wood veneers standard "wood glue" is applicable, for non-wood veneers (ie waterproof type plastic veneers) I don't know what sort of glue they use commercially.77.86.115.45 (talk) 17:59, 20 May 2010 (UTC)

For plastic veneers, it's usually some kind of contact-adhesive, I believe. Certainly when you do the job yourself, that's what the DIY stores recommend. SteveBaker (talk) 20:30, 20 May 2010 (UTC)

Yes - I've used araldite to mend these - I think (certain in some cases) the plastic veneers are produced with one side already coated with adhesive (and a peel off protective film) (ie like sellotape but much stronger) - this wouldn't be likely to produce any "white granules" - I think they will be from the particle board itself.77.86.115.45 (talk) 21:06, 20 May 2010 (UTC)

What's the deal with ants and icing sugar?

Inspired by the ant question above. Is it true that ants will refuse/be unable to cross a line of icing sugar poured on the ground/floor upon which they are marching? Never had enough ants in my house to bother trying it, never felt the urge to dick around with the ants outside - but it's a factoid (folk wisdom?) that I've heard various people repeating over and over again down the years. --Kurt Shaped Box (talk) 16:04, 20 May 2010 (UTC)

Mmmh according to [21] it's a line of chalk not sugar - though I would guess they wouldn't cross a sugar line since oncee they found it their journey would be complete ("mission complete.found sugar.return to base.bring friends")...

Another possibility is ants dislike for fine powders .. eg Diatomaceous earth (also Boric acid Borax) - all of which look like sugar - could this be a source of the story??77.86.115.45 (talk) 16:17, 20 May 2010 (UTC)

I don't think that ants will refuse to eat icing sugar. Boric acid and borax are toxic to ants. --Chemicalinterest (talk) 17:33, 20 May 2010 (UTC)

Not quite the same subject but something I am curious about relating to ants - would double-sided tape be an effective way of catching them? Would they walk across it? If they refused to cross it then I imagine putting a line of it across where they enter would stop them from coming in.GaryReggae (talk) 18:25, 20 May 2010 (UTC)

Possibly.. depending on the glue used you might even find that they like the taste of it and are eating it..77.86.115.45 (talk) 18:32, 20 May 2010 (UTC)

Thanks very much for the answers so far, folks. Seems to make sense... --Kurt Shaped Box (talk) 23:47, 20 May 2010 (UTC)

Blood work accuracy

How can you tell if a lab provides accurate blood test results or just randomly spits out numbers ? Are they rated for accuracy in any way ? I'm in Michigan. StuRat (talk) 17:47, 20 May 2010 (UTC)

There some letters after the name, and stuff listed here Medical_Laboratory_Scientist#Certification_and_licensing - one way to tell if the lab is legit.. 77.86.115.45 (talk) 17:50, 20 May 2010 (UTC)

That's about whether individual technicians are qualified to do the tests, I'm more asking if the labs actually bother. If nobody outside the lab double-checks them or if there's no consequences for just faking the tests, I'd be worried about the results. My brother does delivers for such a lab, and they don't bother keeping frozen samples frozen, so that makes me wonder about the labs in general. StuRat (talk) 18:25, 20 May 2010 (UTC)

Um we're referring to the US here, the land of the massive lawsuit. Do you really think there's no consequence for just faking the test? Also if your lab uses certified or licensed medical laboratory scientists then they would surely have some obligation to ensure they don't just 'fake the test' and if they do, are likely to suffer similar penalties that other professionals failing in their professional obligations would. If you want to know if you lab has any such people on staff, you'd best ask them. Forgot to mention that I'm guessing many may also have a pathologist or two or more on staff or perhaps even in charge who is a doctor so of course has the same professional obligations as other doctors.

Edit: I'm presuming of course you've already read the obvious article Medical laboratory which mentions such things as "Accreditation is done by the Joint Commission, AABB, and other state and federal agencies. CLIA 88 or the Clinical Laboratory Improvement Amendments also dictate testing and personnel" and "Now many labs have a compliance officer with mandatory annual meetings about compliance for all employees" (although that appears to be more about defrauding the US governments and insurers and stuff), but still want more info?

Nil Einne (talk) 18:49, 20 May 2010 (UTC)

Well I don't know about the US but here in the UK as a lab scientist I'm not going to just be churning out random numbers, we churn out the results we get from our experiments. If there are discrepancies in the results, they would be done again. Most labs have individual benchmarks for each test for what is normal, i.e. how much of everything should be in the blood of someone in the condition that's presented to them. I suppose it could be different in the UK because the NHS will have shared generic lab values, but I don't see why it'd be that different in the US. Regards, --—Cyclonenim | Chat  19:13, 20 May 2010 (UTC)

The doctors sending samples to that lab would very quickly realise if the results they were getting didn't match the symptoms their patients were presenting with. --Tango (talk) 20:31, 20 May 2010 (UTC)

Yes, but I don't trust doctors or accreditation boards, a few bucks under the table will probably shut up any investigations. And this is the US, so I have to assume full regulatory capture of any agency tasked with regulating the labs, meaning they now work to cover up any problems found at the labs, rather than to protect the public. As for lawsuits, it seems to me that it would be impossible to question a lab's results, especially if they destroy the sample, once testing is completed. And they could always claim the doctor gave them the wrong sample. So, how can I personally verify whether a given lab gives accurate results ? Are there websites like, say, "RateMyLab.com", where people can report problems ? StuRat (talk) 21:13, 20 May 2010 (UTC)

If you don't trust doctors, why are you worried about lab tests? Surely you don't use the healthcare system, so don't have any tests run. --Tango (talk) 22:06, 20 May 2010 (UTC)

I'd like to have some simple tests done (cholesterol and such), and would rather bypass a doctor entirely, if possible, if I could find a lab that I can actually trust. StuRat (talk) 22:29, 20 May 2010 (UTC)

If you had two tests done and the results were the same then you could fairly assume that both labs were ok. If they differed then one (or both) were wrong.. Can't you get home tests for chloresterol etc nowadays anyway?? (I assume you have some faith left in the chemists that produce these? or are they under suspicion too ? :) ! )77.86.115.45 (talk) 23:13, 20 May 2010 (UTC)

I would have slightly more faith in a test which can be done completely at home (versus one you must mail back). The reason is that they could be easily double-checked for accuracy by the consumer. StuRat (talk) 23:26, 20 May 2010 (UTC)

Also, is there any evidence of the accreditation boards actually suspending or revoking lab accreditation for any cause other than lack of payment of dues ? That would help to restore my faith (somewhat). Otherwise, I have about as much faith in them as in financial rating services which provided top notch ratings to failing banks. StuRat (talk) 21:17, 20 May 2010 (UTC)

It seems to me you have a rather large distrust of the entire US health care system. If you don't trust the people who are actively out there each day to save lives and help people, who do you trust? Surely not a bureaucracy or regulatory agency... Regards, --—Cyclonenim | Chat  22:09, 20 May 2010 (UTC)

You must have missed it when I said it before, so I will repeat it.

1) I would tend to trust consumer ratings over "official" ratings, any day. So, is there a web site where labs are rated by consumers ?

2) I also said that, while I inherently mistrust them, I could be convinced that the "official" agencies are actually doing their jobs if there was some evidence that they do, such as suspensions and revocations of accreditation (for causes other than nonpayment of dues). So, is there any such evidence ? StuRat (talk) 22:26, 20 May 2010 (UTC)

In Australia, the vast majority of pathology is done by a small handful of large chain labs, or it might now even be just one: Healthscope, since they purchased Gribbles Pathology a few years ago, which was "the other" big lab. These places would have strict operating procedures and audits and stuff. I really just can't believe a lab would get away with faking tests "wholesale" for very long. What would be their motivation? To save money by just printing off tests instead of really doing them? And doctors and the regulatory organizations would "cover up" their fraud? What would be their motivation for that? The lab is paying them all off? That's just ridiculous. Sure there would be cases of negligence, or even fraud, but to suggest it's "institutionalized", with the participation and support of the WHOLE health community is what I'd call paranoia. Where I WOULD distrust blood tests is if they are provided by a naturopath or some other "alternative health" practice not in a well known accredited lab, in that case I think you have good reason to be sceptical about any blood work you get done. Vespine (talk) 22:55, 20 May 2010 (UTC)

I think you're taking me a bit too literally. I doubt that any labs fake all their results, but perhaps some fake a few, and others just do sloppy work (like the one where my brother works that never bothers to keep samples frozen, even thought they must be for accurate results). But I'm just interested to know if any action is ever taken against bad labs. That is, do they have any incentive to do a good job, or is keeping their costs down their only goal ? StuRat (talk) 23:16, 20 May 2010 (UTC)

Breathing in Helium

Why does breathing in helium cause the human voice to become squeakier? I've gone through some websites on the matter, and they all say that it's because the speed of sound in helium is greater than in air, but I'm a little unsatisfied with this. It's not really an explanation; I still can't "see" why helium produces this effect. I figure that there are specific resonance frequencies in our voice box, and that changing the speed of sound in the voice box will change the resonance frequencies, but I'm at a loss as to why the frequencies will be shifted upwards with an increase in the speed of sound. Can anyone give a better description of what's happening? 173.179.59.66 (talk) 19:03, 20 May 2010 (UTC)

The shape of the larynx determines the wavelength of the sound. The vibrations aren't produced by the tissue in the larynx itself vibrating (as in a guitar string), but rather by allowing the air to vibrate within the space it creates (as in an organ pipe). That's why you won't get any vibration without air flow. Higher speed of sound with the same wavelength means higher frequency. Rckrone (talk) 19:28, 20 May 2010 (UTC)

What I said seems to be contradicted by the vocal folds article, so to be honest I'm a bit confused about this myself. The resonant frequency of the vocal folds should not depend on the type of gas that's next to them. Rckrone (talk) 19:42, 20 May 2010 (UTC)

First of all, here's a nice thing on speed-of-sound calculations and the Straight Dope relevant article. Taking in helium puts some of the gas in your vocal tract which does mean the speed of sound is faster. However, the difference in pitch should come about more when the sound leaves your mouth (which may be why, and I'M NOT AN EXPERT ON ACOUSTICS, you don't hear yourself with a high voice as much as others do). Your vocal cords vibrate with the same frequency and the energy of the wave should stay the same which gives it a longer wavelength, so when it transitions to the slower speed of normal air, that's when the frequency of the sound wave increases, resulting in an overall higher pitch. This is what I think occurs.

The relevant equation, by the way, is c=f*L, or the speed of sound equals frequency times wavelength, and E~c*f, or energy is proportional to speed of sound times frequency. When energy stays equal but the speed of sound drops between helium and air, the frequency must increase (energy is conserved). SamuelRiv (talk) 19:36, 20 May 2010 (UTC)

... so if you listened in helium, everyone would have a deep voice? Dbfirs 22:53, 20 May 2010 (UTC)

Natural undersea oil spills

The oil leak in the Gulf is apparently a major ecological disaster, resulting from a relatively tiny opening to the seafloor from an oil deposit below the sea. Are these oil deposits immune to natural processes which could create an opening, such as an earthquake creating a fracture which allows flow up into the ocean, or a volcano which fractures the thick rock dome above the oil? Do geologists find evidence that there has ever been a significant natural undersea oil leak? Even in ancient times, people found natural seeps on dry land. Wouldn't there be similar underwater oil seeps of varying flow rates? Edison (talk) 19:10, 20 May 2010 (UTC)

Yes. Oil does ooze naturally from shallow deposits as this article discusses - and it doesn't take a volcano or even an earthquake to make that happen. There are plenty of places up on dry land where this happens too (See La Brea Tar Pits, for example) - humans have been scooping the stuff up and using it for thousands of years (See Oil_industry#Early_history). Although the magnitude of this seepage is tiny because the pressures are so small. In the gulf right now, you have to understand that the drilling rig had bored down through 18,000 feet of rock below the 5,000 feet of water. So the likelyhood of oil coming through all that rock in that area naturally is pretty slim! But the weight of 18,000 feet of rock pushing down on the oil - means that it is squirting upwards with tremendous pressure. Our article on the oil spill points out that the total oil reserves at that site are 50 million barrels...but if it's really coming out at 100,000 barrels a day - as some are estimating - that reserve is shrinking noticably! SteveBaker (talk) 20:27, 20 May 2010 (UTC)

See Tarball (oil) - some of the refs mak it clear that these are found naturally as well as man made

eg http://pubs.usgs.gov/of/2009/1225/ (unfortunately searching for "tarball" in the oil sense is difficult - due to computer usage of the term.) I've heard of them before and believe them to be well known to beachcombers.77.86.115.45 (talk) 21:14, 20 May 2010 (UTC)

(ec)See also Asphalt volcano for an example of a past natural underwater oil seep. People involved with exploring for hydrocarbons make use of satellite photos to identify natural oil slicks from such underwater seeps to show that there is a working source rock down there. They have to do repeat surveys, of course, to try and remove the unnatural ones (ships cleaning tanks etc.). Mikenorton (talk) 21:16, 20 May 2010 (UTC)

newtonian fluids

Is Mercury a newtonian fluid —Preceding unsigned comment added by 82.201.241.168 (talk) 21:35, 20 May 2010 (UTC)

on the whole yes [22] 77.86.115.45 (talk) 21:43, 20 May 2010 (UTC)

Biomedical control systems

hello i am searching for an application of the control systems in the biomedical field but i'm stuck and i cannot get all what i want, it must have block diagram and meaningful description,,,,,any one could help me?? —Preceding unsigned comment added by 41.196.197.43 (talk) 22:04, 20 May 2010 (UTC)

You need to be a little more specific. Manufactoring control systems, or control systems pertaining to regulations? Regards, --—Cyclonenim | Chat  22:15, 20 May 2010 (UTC)

Publishing scientific literature.

I just have a few questions about publishing research.

1. ) How is it decided what journal any piece of scientific research will get published in? Does the research team just pick one they think is the most suitable? I've heard reference to top tier, and 2nd and 3rd tier journals.
2. ) Is there a process to decide which tier they will try to be published in? Surely no one says "my research is pretty dodgy, I'll try to publish in 3rd tier"?
3. ) What happens if a paper is not accepted for publishing? Are there costs involved in submitting a paper to a journal if it is rejected?
4. ) Can you just keep trying less and less reputable journals until you hit one that will publish your research?
5. ) Is there some place where these kind of introductory questions to this subject are addressed? I've read the Academic publishing and Scientific literature but they don't really cover these "idiots guide to publishing scientific literature" kinds of questions. Vespine (talk) 23:15, 20 May 2010 (UTC)

The researchers (or institution) submits a paper to the journal of their choice - in general they will pick one that is applicable, some are more prestigious than others, some are more "technical" than "theoretical" etc. The submitted paper is reviewed before publishing by the publisher, and other researchers. Peer review is key here. I'm not aware of charges for submission of papers - most journals publish the rules of submission online eg [23]. Yes you can keep trying until someone accepts it...(better if you know your limits at the start) Last question - probably a good way would be to pick a journal, and look up their submittence method online - should give a good idea of the method if not the practice.. Another good way would be to ask here :) I anticipate many other people will be able to give much more insight into the process here. (oh.. you often need a referee to support your submittal of a paper to a journal - usually someone old and well respected in the field etc ... or at least the department you work in will exert some control over what you put forward for publishing - they don't want you submitting any old tat and giving them a bad name .. etc .. this probably varies a lot from place to place) 77.86.115.45 (talk) 23:26, 20 May 2010 (UTC)

eg here are some of the info pages for Angewandte Chemie specifically to do with how referees judge the article and decide if it's recommended for acceptance [24] . 77.86.115.45 (talk) 23:37, 20 May 2010 (UTC)