Wikipedia:Reference desk/Archives/Science/2010 December 6

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December 6

Restriction endonuclease - etymology

What meaning is the word 'restriction' supposed to convey in the term 'restriction enzyme' or 'restriction endonuclease'? --90.219.114.59 (talk) 00:45, 6 December 2010 (UTC)

See Restriction enzyme.Smallman12q (talk) 00:55, 6 December 2010 (UTC)

Before the actual function of restriction enzymes was identified, it was known that many strains of bacteria contained factors that restricted which viruses could successfully infect them. This was late determined to occur as a result of enzymatic cleavage of viral DNA, in research that eventually yielded the first restriction enzymes. See restriction modification system for more information. Someguy1221 (talk) 00:56, 6 December 2010 (UTC)

Bladder - when you're empty, are you really empty?

I just read the article on urinary bladder. It was lacking the one thing I was interested in learning - just after you pee, when you feel empty, are you really empty? How much urine remains if you aren't? I'm guessing this could be estimated with some careful ultrasound work... If you know the answer, please also add it to the article! Thank you! The Masked Booby (talk) 02:23, 6 December 2010 (UTC)

I think the bladder really is empty, as gravity and the opening being at the bottom allows it all to drain out (with the exception of a few drops that adhere to the walls, due to surface tension). However, I've noticed that when I really have to urinate badly, I finish up and then a few minutes later there's more, maybe 1/3 the original amount. I attribute this to urine accumulating in the kidneys, which probably isn't good, as it could lead to kidney stones.[1] Once the bladder is emptied and the back pressure eliminated, the urine is free to quickly drain into the bladder. StuRat (talk) 02:39, 6 December 2010 (UTC)

Hence the phrase, "breaking the seal". Dismas|^(talk) 02:52, 6 December 2010 (UTC)

. . . but on the other hand don't believe everything your read on the internet. Richard Avery (talk) 08:15, 6 December 2010 (UTC)

Inability to urinate properly (start and stop) when wished are common symptoms of Benign prostatic hyperplasia, evident in over a third of men over age 80 years. Cuddlyable3 (talk) 08:16, 6 December 2010 (UTC)

I recall long beer drinking sessions of my youth (totally reformed now, of course!) when the lengths of time between needing to urinate shrank remarkably. Obviously new urine is being produced all the time, so within seconds after urinating a few new drops will appear. HiLo48 (talk) 21:45, 6 December 2010 (UTC)

Alcohol is also a diuretic, so it will tend to increase the frequency of urination. --Jayron32 21:50, 6 December 2010 (UTC)

The bladder is presumably compressed by muscles to empty it, rather than being the equivalent of a stretchy balloon which releases liquid smoothly when the outlet valve is opened. In addition I expect there is a controllable outlet valve equivalent. Is it possible that the described process of "1)pee freely until no more comes out, 2) wait 60 seconds or whatever, 3)pee freely an additional 1/3 or so of the original amount " could result from one mode of contraction (one set of muscles, or one mode of folding) following a different and initial mode? It seems to ask a lot of the kidneys for them to suddenly process such a large amount of urine. As for the "enlarged prostate" theory, if a balloon full of liquid has an outlet tube, and a clamp is tightened slightly on that tube, it do4es not result in an initial free flow of a lot of liquid, followed by a pause with no flow, followed by a second smaller phase of free flow. (This post should probably be signed "I.P. Freely") Edison (talk) 17:44, 7 December 2010 (UTC)

Is there even such a thing as a hybrid motorcycle?

The last time I looked at Harley-Davidson's product line, I didn't see such a motorbike.

I think I should help the environment even better than a Prius by having a hybrid motorcycle, but what marques have one? Thanks. --Let Us Update Wikipedia: Dusty Articles 06:01, 6 December 2010 (UTC)

According to this article from 2008, Honda is developing one which should be out in the next two years. So they have 25 days left to make good on their promises! Dismas|^(talk) 06:05, 6 December 2010 (UTC)

This slightly newer source suggests Yamaha is also supposed to have a hybrid motorcycle by 2010 (the above source also mentions Yamaha). They showed something at the 2009 [2] Tokyo AutoMoto Show but no sign since then that I saw. Nil Einne (talk) 07:27, 6 December 2010 (UTC)

A Motorized bicycle is a class of hybrid vehicle. For devoted friends of the environment, electric bicycles are making a comeback, see Hybrid vehicle#Two-wheeled and cycle-type vehicles. Cuddlyable3 (talk) 08:03, 6 December 2010 (UTC)

You would help the environment the most by cycling to work etc. Noodle snacks (talk) 10:38, 6 December 2010 (UTC)

I'm CLEARLY alive-and-well. Why am I STILL barred from donating blood/plasma?

It's only because I lived in Germany in my toddlerhood. They're afraid that I could develop CJD from possibly having eaten contaminated meat there. I thought CJD forms just MONTHS after eating such meat.

I haven't been in Germany in 20 years. I'm obviously still alive-and-well, with no signs of CJD. How long should I be alive & well to prove to a blood bank that I am fit to donate blood or plasma?

(I've been wondering about what could happen from lying about where I've been at some new blood/plasma bank somewhere because I know no harm could possibly come out of my donations. Sure, they'll conduct blood tests, but if I have stayed alive & well for 20 years since being in Germany, there's no way in hell that CJD viroxins will be found in my blood. Anyway, how could they find out about my lie, and what could happen if I did so?)

If there's no way to prove blood banks in the US that I truly am fit to donate, then what other countries would allow me to donate blood or plasma for money? Thanks. --70.179.178.5 (talk) 08:21, 6 December 2010 (UTC)

When was the last time you checked to see if you were eligible? Although the original 2002 restriction was on anyone who has spent more than six months in certain European countries such as Germany, the restriction has since been relaxed to only include people who have spent more than five years there.

Blood tests cannot ensure the safety of your blood, because there is no test to determine if a blood donor is infected while in the latent phase of vCJD.

I'm getting all this information from Creutzfeldt–Jakob disease#Blood donor restrictions. Red Act (talk) 08:48, 6 December 2010 (UTC)

Variant CJD is generally fatal after about a year from when symptoms arise, but some studies have suggested that this or similar prion diseases can have a very long latency period between the exposure and the onset of symptoms. For example, this points to a latency possibly as long as 50 years in some cases. Other researchers think the time is probably relatively short. Without knowing for sure though, it probably makes sense to err on the conservative side, and assume that people possibly exposed to CJD might remain asymptomatic for a long time. Dragons flight (talk) 09:05, 6 December 2010 (UTC)

The incubation period varies depending on how the infection occurs. According to page 85 of this paper, the estimated incubation period in individuals that acquired vCJD from a blood transfusion is 5 or 6 years, but the estimated incubation period in individuals that acquired vCJD by eating contaminated beef is between 13 and 40 years. Red Act (talk) 09:24, 6 December 2010 (UTC)

You might want to look up the source of the restriction in PubMed if you can find it, then email the corresponding author for advice. If anyone knows whether that cost/benefit analysis is still producing the same sign, they would. You can lie, but the penalties might be severe in some cases, including stiff liabilities if you're wrong. I would do a PubMed search for the corresponding author(s)' email address if I didn't have other work at the moment. Maybe someone else trying to answer can find it. Ginger Conspiracy (talk) 09:02, 6 December 2010 (UTC)

Please don't second-guess the established safety standards, and please don't lie to the screeners. This report from the US GAO found that paid donors of plasma products were 1.5 times more likely to donate an infectious unit than unpaid donors. Note also that the viral inactivation/removal strategies used to partly eliminate HIV, HBV, and HCV from pooled plasma products are of limited or unknown efficacy against prion particles. TenOfAllTrades(talk) 13:51, 6 December 2010 (UTC)

My boss lived in Scotland for some time and he is still not allowed to donate blood in Germany. This is really cool. In the US a German is not allowed to donate while in Germany anybody from Great Britain is not allowed. A solution might be donate for a British medical company. You might be a smaller risk than a native UK person--Stone (talk) 18:28, 6 December 2010 (UTC)

I had the same thing happen in Spain. Because I had been resident in the UK they deemed that the risk that I might have CJD was too high. There was not bovine spongiform encephalitis in Spain at that time. Ironically it arrived within 1 year of my refusal. I hate the term 'mad cow disease' because it is so inaccurate. It is a neurological disease not a psychiatric disorder. Richard Avery (talk) 19:58, 6 December 2010 (UTC)

Of course, if they donate in the UK they won't be paid, which they seem to want. 86.161.208.185 (talk) 23:35, 6 December 2010 (UTC)

This is not the language desk and English is my second or third language but are not a donation per definition unpaid, in other cases the blood is sold not donated or am I missing something? --Gr8xoz (talk) 04:22, 7 December 2010 (UTC)

Blood donations by paid donors are still referred to as donations. Blood_donation#Benefits_and_incentives has some information about the distribution of paid/unpaid donation. Sean.hoyland - talk 04:50, 7 December 2010 (UTC)

BSE is a serious risk, but given its risks, it's still a bit of a mystery. There are other possible vectors other than beef, including chronic wasting disease, which is a real concern for wild game. Shadowjams (talk) 11:00, 7 December 2010 (UTC)

I find it odd that I can't give blood in the UK now because I had a transfusion in 1981. Surely anything I caught would have become evident by now?Zzubnik (talk) 14:50, 7 December 2010 (UTC)

See the comments above about prion diseases. The latency period is poorly characterized and probably variable, but may run into decades — and there isn't any sort of reliable blood test, so we can't screen for it in donated blood. TenOfAllTrades(talk) 15:31, 7 December 2010 (UTC)

Normal decibel level in an office?

Are there any studies showing the average decibel level if you are sitting in the middle of an open-plan office filled with 50 people? My Iphone app shows an average of 55 decibels even when it is very quiet (by my own standard), that seems a very high number. I was expecting to read 25 or 35 at most. --Lgriot (talk) 12:52, 6 December 2010 (UTC)

According to this, 55 is just about right. Page 15 of this source lends credence to that figure as well. And finally, this agrees with the 50 db figure. Dismas|^(talk) 13:00, 6 December 2010 (UTC)

The table of examples in our article on sound pressure says that a "very calm" room is 20-30 dB and normal conversation at a distance of 1m is 40-60 dB. Gandalf61 (talk) 13:08, 6 December 2010 (UTC)

Thanks to both! So a conversation is a little lower than half the painful level! My iphone reading is accurate then. --Lgriot (talk) 14:08, 6 December 2010 (UTC)

In decibel scale, a 3dB increase is a doubling of the power, however the human ears exhibit a logarithmic response. CS Miller (talk) 14:53, 6 December 2010 (UTC)

Makes sense, so 60 db isn't half as intensive as 120 db, it is 20 times halved!!! Thanks --Lgriot (talk) 16:34, 6 December 2010 (UTC)

... or, slightly more accurately, one millionth of the power, because one "bel" represents a factor of ten in the power. Dbfirs 17:12, 6 December 2010 (UTC)

Brine instead of broth

Let's say I'm making a soup or bisque or something in which one of the main dry ingredients is olives. Rather than boil them in chicken/vegetable broth, would it be acceptable to substitute olive brine? Or would the chemical properties be different? I understand that broth generally has some fat in it, so maybe it would behave differently. LANTZY^TALK 13:39, 6 December 2010 (UTC)

Broth also usually contains stock as well, since most broths are made with bones as well as meat (technically, broth is made from meat, and stock is made from bones) and so broths often contain a sizable amount of gelatin. Many times, the "fatty" taste of broths are actually not fat at all, but gelatin, as gelatin adds that "slick" or "unctuous"(to use the chef's term) mouthfeel without adding fat. Also, since cured olives tend to be very salty, one of the purposes of reconstituting them in chicken broth would be to dilute the saltiness; reconstituting them in brine wouldn't accomplish this. The excess saltiness of the brine (which is likely much more salty than broth) may throw off the salt balance in the final dish, so be careful. --Jayron32 14:02, 6 December 2010 (UTC)

In that case, perhaps a half-and-half of broth and brine... LANTZY^TALK 17:48, 6 December 2010 (UTC)

Seriously, go for it. A big part of cooking is experimentation; if you have an idea for a dish, try it out. If it comes out awful, then you know your changes to the recipe may have been to blame. If it tastes good, then you just discovered something as well. I myself am an avid cook, and I will say for the record that some of my dishes have resulted in ordering pizza for the night. It happens. --Jayron32 17:51, 6 December 2010 (UTC)

Of course. Where's my spirit of adventure? I just hate the idea of wasting ingredients. In this case I'll go ahead and try it, because olives aren't an extravagance, and brine would just be dumped down the drain anyway. LANTZY^TALK 18:00, 6 December 2010 (UTC)

I think you'll find that if you use enough to taste the olives, the final result will be way too salty. But there is no harm in experimenting, if the ingredients are not too expensive. Looie496 (talk) 22:58, 6 December 2010 (UTC)

Eyeball judder

I'm fairly sure there's a name for this - when one's eyeballs briefly judder, like an underdamped robotic arm. What's it called? 81.131.24.249 (talk) 13:57, 6 December 2010 (UTC)

Saccade, or Physiologic nystagmus. 92.24.184.218 (talk) 14:15, 6 December 2010 (UTC)

Thanks! 81.131.24.249 (talk) 14:25, 6 December 2010 (UTC)

Bismuth oxychloride appearance

Is it shiny (pearlescent) and pale yellow-white? --Chemicalinterest (talk) 14:06, 6 December 2010 (UTC)

Just ordinary white powder. But it's usually tinted beige to darker skin tones in makeup. Ginger Conspiracy (talk) 10:40, 7 December 2010 (UTC)

Sources of gas and electric in the UK

I'm wondering where a) the gas I'm using is coming from - what proportion from Russia, what from the North Sea, etc? b) What proportion of the electricity I'm using is nuclear, wind-power, etc? Thanks 92.24.184.218 (talk) 14:36, 6 December 2010 (UTC)

For electricity, the National Grid show year-average figures on their site at http://www.fuelmix.co.uk/fuel_mix_info.htm/. CS Miller (talk) 15:57, 6 December 2010 (UTC)

Actually, that data seem to be out-of-date. CS Miller (talk) 16:16, 6 December 2010 (UTC)

The latest figures are here[3]. Alansplodge (talk) 10:37, 7 December 2010 (UTC)

A large chunk of the UK's gas supply comes from the Ormen Lange (gas field) in mid-Norway via the Langeled pipeline, potentially supplying 20% of the country's needs on its own. Mikenorton (talk) 23:51, 6 December 2010 (UTC)

This article[4] says that imported gas exceeded home production for the first time in 2010. Alansplodge (talk) 10:37, 7 December 2010 (UTC)

This graph[5] (on page 7 / 17) gives a projection of imports by type to 2024.

The very rough figures for 2009/2010 are:

50% - UKCS = UK Continental Shelf,

25% - Norway

15% - LNG = Liquefied natural gas imported by ship from the Americas and Middle East.

10% - BBL = Balgzand (Netherlands) to Bacton Line, which links to Nord Stream, the Russo–German gas pipeline. Alansplodge (talk) 11:56, 7 December 2010 (UTC)

simple:Halophile

Under the life style section, do I have the osmosis description correct? Thanks, Albacore (talk) 14:44, 6 December 2010 (UTC)

You may want to put a little clarifying statement at the front, something like "In osmosis, water tends to move from inside the cell to outside, in order to balance the salt concentrations on both sides of the cell membrane" or something like that. Your statement is correct, but may be unclear for someone who has never heard of osmosis. --Jayron32 15:03, 6 December 2010 (UTC)

I've looked for examples of slight halophiles, moderate halophiles, and extreme halophiles, but couldn't find any specific examples. What are some examples of each? Albacore (talk) 17:48, 11 December 2010 (UTC)

Color in anodization

How does color in anodization change the recyclability of aluminum components? /130.236.40.119 (talk) 14:53, 6 December 2010 (UTC)

Probably the way that your textbook tells you that it does. Or, perhaps, the way your teacher told you that it does in lecture. --Jayron32 15:04, 6 December 2010 (UTC)

Considering your quirky response I'm assuming you think this is some kind of homework, since this isn't the case I'd appreciate a serious response or non at all, thank you./90.239.94.250 (talk) 20:04, 6 December 2010 (UTC)

I don't believe it makes any difference. The color is various organic dyes that will just burn off when the aluminium is melted. The anodize article mentions that tin can be used as well, but I don't think that will be a problem - in general recyclers are geared up to handle mixed metals (no batch can possibly be perfect after all). Ariel. (talk) 21:40, 6 December 2010 (UTC)

Why Lorentz Transformation (LT) is correct?

The Reference Desk is not a forum for presenting novel physics theories. Please stop reposting your original work. TenOfAllTrades(talk) 15:44, 6 December 2010 (UTC)
The following discussion has been closed. Please do not modify it.
I think it is because Lorentz is very lucky. Why? I have at least three reasons: 1. Because there is a Galilean Transformation (GT) ready for him so that he did not have to establish his famous theory from scratch. 2. When he applied “ruler contraction” to GT and established x'=γ(x-vt), he was correct by pure luck. You see, before the origin point O’ of the moving system S’ meets the origin point O of the rest system S, we have x’-OO’ = x and after that we have x’+OO’ = x; so that based on OO’ = v|t’| as measured in S’ we should have x’= γx-vt’, not x'=γ(x-vt). But then why LT is correct? 3. Lorentz is so lucky that I can show you t’= γt is always true if we apply “ruler contraction” to GT, so that x'= γx-vγt=γ(x-vt) and then x'=γ(x-vt) must be correct! Here is my way to establish t’= γt. 3-1. Let B (b,0,0) be a point in S. When b<0, let observers in S record the time that the origin point O' of S' moves from B to O by Δt = (0-t) and the distance between B and O by BO, we have BO = |v|Δt; let observers in S' measure the time O' moves from B to O by Δt' = (0-t') then we can calculate the distance between B and O as measured in S' by (BO)' = |-v|Δt'. 3-2. Based on hypothesis of ruler contraction, we have (BO)' = γBO so that |-v|Δt' = γ|v|Δt, then we have △t’=γ△t. Since it is the same as (0-t')=γ(0-t) so that t’=γt. That means when O' is at B, the time relationship between S' and S is t’=γt. 3-3. Let us go through quite the same procedure for the rest scenario. When O' is at B while b>0, t’=γt is also true. When b=0, t'=t=0, so that t’=γt. That means we have now derived that for any location of O', t’=γt is always true.Jh17710 (talk) 15:40, 6 December 2010 (UTC) Why Lorentz Transformation (LT) is useful? I think the main reason that we like to keep LT is because most of contemporary physicists believe that LT is correct. If you check all textbooks introduced LT and currently recommended by teachers, you will find out most of them confirmed that LT is correct. However, in the real world, I think LT is useless, why? 1. If we apply the time equation in LT to the spatial equation in LT, we will get the spatial equation of inverse LT, x=γ(x'+vt'). That means, both of LT and inverse LT are coexist at the same time. 2. It is not easy to understand what will happen if constant velocity v and constant velocity –v coexist at the same time. We may think, it will be v=0, but not sue about it. There is a better way to see it clearly. If we put the missing time equation in LT, t’=γt, and the missing time equation in inverse LT, t=γt’, together; let them to coexist, then we can derive γ=1. That means, mathematically we can derive v=0 from γ=1. 3. Since the relative velocity must be zero in LT and in the inverse LT, LT is almost useless in the real world.Jh17710 (talk) 15:18, 6 December 2010 (UTC) Is there a question here? Wikipedia's reference desks are not for making general statements or starting general discussions. If you wish to ask a factual question we can answer for you, then ask. If you wish to invent your own system of physics, please do so elsewhere. --Jayron32 15:33, 6 December 2010 (UTC) I will ask real question next time. Thanks. This is not an obvious question. My question is behind the characters which is "Do you know any textbook states LT is wrong?", I should ask question like that. Sorry for my mistake.Jh17710 (talk) 15:47, 6 December 2010 (UTC) Why Special Relativity (SR) is wrong? I think there are at least two reasons: 1.The main reason is because of LT is correct. Since the missing time equation in LT, t’=γt, must be correct if LT is correct so that the time equation that SR claimed, t’=t/γ, must be wrong. 2. The second reason is interesting. If we assume two clocks A and B have same model number and exactly same clock speed. Then we put them to run at same speed v on two circles of the same radius on one plane with the closest point Pa and Pb apart from each other 0.1 meter away. We also assume that whenever A is at Pa, B is at Pb. Now, we have created a “paradox of clock” in SR. When A is at Pa, we can compare the time of clock A and B; the problem is, since the relative speed between A and B is about 2v, according to SR, their clock speeds should be different so that we have a conflict scenario at Pa and Pb that the clock A runs slower than B and the clock B runs slower than A at the same time.Jh17710 (talk) 15:18, 6 December 2010 (UTC) Look, as I stated above, this is not the place to start a debate or a discussion. In the previous three or four times you have started this exact same discussion, many different editors have explained to you where your initial assumptions were incorrect. Everytime this has been done, you have ignored them and started a new discussion with the exact same incorrect statements. Please stop this, it is becoming disruptive. If you have a factual question that we can answer for you, please ask it. This reference desk is not the appropriate forum to propose wild ideas or to start debates over the validity of established physics. --Jayron32 15:36, 6 December 2010 (UTC)

Thanks for your kindly response. I will stop doing this. I will just ask question.Jh17710 (talk) 15:54, 6 December 2010 (UTC)

I encourage you to read the article Twin paradox that is relevant to your "paradox of clock". Cuddlyable3 (talk) 00:01, 7 December 2010 (UTC)

Physics Textbook

Do you know any textbook states Lorentz Transformation (LT) is wrong? If yes, what is it and what is the main reason? Thanks.Jh17710 (talk) 16:02, 6 December 2010 (UTC)

What you don't understand is that the Lorentz transform is mathematically correct but physically wrong. might help. I do not know LT but google helps.--Stone (talk) 16:25, 6 December 2010 (UTC)

Thanks. Is this a textbook? Do you know any teacher used it as a textbook since year 2005?Jh17710 (talk) 17:44, 6 December 2010 (UTC)

An advanced Google search for the exact phrase "Storm in Physics" (the name of the book) in the .edu domain doesn't turn up one single hit.[6] A search for the exact phrase "Ricardo Carezani" (the author) in the .edu domain[7] only turns up four pages: a page of links in which Carezani is listed in the "Fringe Science" section,[8] a page of links that includes him under a section entitled "UFOs, Fringe Science and Others",[9] a rant by Carezani about how the 126 authors of a paper in Physical Review Letters describing an experiment that showed that neutrinos exist (contrary to Carezani's beliefs) are a kind of "Secret Society" that's publishing wrong and misleading information,[10] and the abstract of a 1982 paper Carezani coauthored describing an experiment which wound up showing that special relativity was correct and Carezani was wrong.[11][12] The search does not turn up anyone in the current educational community who treats his ideas seriously, much less anyone who uses his book for teaching a class. Red Act (talk) 23:34, 6 December 2010 (UTC)

(e/c)You state above, in the thread that has now been closed, "I will ask real question next time. Thanks. This is not an obvious question. My question is behind the characters which is 'Do you know any textbook states LT is wrong?'" How is this question now a "real question"? You do know the answer to that already, right? So what point are you trying to make? WikiDao ☯ (talk) 16:28, 6 December 2010 (UTC)

No, I really don't know. Do you know the answer? My point is, if some textbook states LT is wrong, I like to know what is the main reason that textbook provides. If no one can provide a good answer, then, I know that it is really hard to find one of such a textbook. I really appreciate the help from this open website. Thanks.Jh17710 (talk) 17:44, 6 December 2010 (UTC)

I am not aware of any physics textbook which is both generally regarded as reliable which also states that the Lorentz transformations are invalid or wrong. The world being what it is, I would not be shocked to find if someone had published something somewhere which did state this, but as an educator myself, I have not seen any such textbooks used in any classroom or educational setting. --Jayron32 17:49, 6 December 2010 (UTC)

Thanks a lot, Jayron.Jh17710 (talk) 18:34, 6 December 2010 (UTC)

A transform is not a theory or statement and therefore cannot be right or wrong. This whole section doesn't make the slightest bit of sense. Looie496 (talk) 01:30, 7 December 2010 (UTC)

It could be wrong if there was a mathematical error in it. It could also be considered wrong if it were useless; that is if applying the Lorentz Transformation resulted in incorrect physical solutions; that is if the solution it predicts disagrees with experimental results. As far as I know, neither of this is the case. That is, the Lorentz Transformation is mathematically correct, and consistent with experimental results regarding Special Relativity. --Jayron32 04:55, 7 December 2010 (UTC)

Chicken meat and pork

Does chicken meat contain more harmful microorganisms then pork? Which animal carries fewer pathogenic diseases? Thanks-Shahab (talk) 17:34, 6 December 2010 (UTC)

It would probably be hard to quantify it. If raised properly, with proper waste management and feeding, butchering, and cooking procedures, poultry and pork should be generally safe and free from harmful microorganisms. Contaminants can be introduced at any part of the life cycle of the animal or post-death, whether in the animal's diet or as a result of improper butchering or storage, but I am not aware that any particular animal is more or less susceptible to contaminants as a general matter, as long as best practices regarding raising of the animals and preparation of the meat is followed. --Jayron32 17:47, 6 December 2010 (UTC)

It used to be the case that trichinosis from improperly handled pork was a problem, but due to improved husbandry practices that is no longer the case (at least in the US). There are about 12 cases of trichinellosis reported each year. Compare that to around 140 thousand cases of salmonellosis each year, which can taint any kind of meat, eggs or plants. In short, there is nothing pork-specific that is a big threat, but there are things that can affect any food stuffs. This is different in countries where they feed their pigs meat and garbage. --Sean 19:16, 6 December 2010 (UTC)

If I recall, not all of the trichinellosis cases were caused by pork either. You can get it from improperly cooked wild game. Googlemeister (talk) 19:54, 6 December 2010 (UTC)

However, note that there are significantly more cases of illness from contaminated chicken eggs each year than from either beef eggs or pork eggs. :-) StuRat (talk) 21:31, 6 December 2010 (UTC)

Under ordinary circumstances meat of any sort continues virtually no microorganisms. They get into it only from contamination during processing, and obviously the level of contamination is determined by how the meat is processed. In chicken, however, if the skin is included, it would naturally continue some level of microbial content -- but from a healthy animal, there ought not to be any microbes in muscle-meat. Looie496 (talk) 22:52, 6 December 2010 (UTC)

Looie and StuRat can you give me sources for the above statements. Thanks to everyone-Shahab (talk) 06:20, 7 December 2010 (UTC)

I think you should re-read what StuRat wrote before asking for sources :) Ariel. (talk) 08:33, 7 December 2010 (UTC)

Oops..lol-Shahab (talk) 10:10, 7 December 2010 (UTC)

In the case of trichinosis, it's not a handling issue. The parasite larvae are actually in the flesh itself. But again, it's rare in places with good animal husbandry practices. --Sean 19:59, 7 December 2010 (UTC)

Those aren't microorganisms, though, they are little worms. Looie496 (talk) 20:46, 7 December 2010 (UTC)

In that case, the article needs to make clear (and in an explicit manor) that these are classed as parasitic micro-organisms as it took the use of a microscope to first explain causative agent of these conditions. Who can do that?--Aspro (talk) 21:26, 7 December 2010 (UTC)

I'm not sure that the line between microorganisms and macroorganisms is a sharp one. If the standard is whether or not it can be seen with the naked eye, you are still likely to have differences between the eyesight of the observer and the size of each individual within the species. If a person with extremely sharp eyesight can spot a giant of the species, does this disqualify it ? If a person with only average eyesight can't spot a dwarf or juvenile, does this make it qualify ? Whether the organism is moving, the same color as the background, and in darkness or lit at an angle (so it casts a long shadow) would also come into play. It's a more difficult line to draw than if Pluto is a planet or not. StuRat (talk) 19:00, 8 December 2010 (UTC)

Perfect machines?

Is it possible for an electric space heater to be anything but 100% efficient? If less, where does the wasted energy go? Let's assume the thing is quiet and there are no windows that would let energy escape as visible light. --Sean 19:20, 6 December 2010 (UTC)

An electric device may have a complex impedance, (equivalently, a power factor other than 1.0). Roughly stated, this represents the power that is reflected back to the electric-plant; in other words, it's related to the effect your device has on the efficiency of the transmission line. A space heater rarely has any significant inductive or capacitive component; therefore its reactance is close to zero; but let's assume otherwise for the example. If the space-heater has a non-zero reactance, it means that in addition to the heat it "burns off" inside your house, it's also forcing extra heat to be dissipated in the transmission wires from the electric power station (by reflecting some un-used power that was not burned in your house, back into the transmission wires). It does this by forcing the voltage and current out of phase: "pulling" current from the power station; not using it or burning it; and then sending it back across the transmission wires. As a consequence, it's forcing the power-station to work a little harder for no benefit to you. So, when you measure "efficiency", you need to define how big of a system you care about: if you only worry about home-efficiency, you start measuring at the circuit-box in your garage; but if you care about city-wide efficiency, you need to think about power factor correction on a massive scale. (Electric companies already do this at the power substation level). Nimur (talk) 19:43, 6 December 2010 (UTC)

However domestic electric power is not distributed on constant impedance transmission lines. Cuddlyable3 (talk) 23:47, 6 December 2010 (UTC)

OK, so for the purposes of my power bill they're perfect, but not when considered as part of the power grid. But let's imagine I have a Mr. Fusion in my home that puts off heat. If the purpose of the machine is to heat the home, then it would in fact be 100% efficient, right? I guess it's a philosophical point in that I've always understood 100% efficient machines to be impossible, but if you adjust your desires to have heat -- waste or otherwise -- as the desired result then it is possible. Thanks for the detailed response. --Sean 22:07, 6 December 2010 (UTC)

If you look "wide" enough, everything is perfectly efficient of course, but practically speaking it's not. For example to heat your house with natural gas you need to exhaust the waste products, which will steal some heat. With your Mr. Fusion you also loose some energy in the form of the waste products of the reactor. The bigger issue is how to "concentrate" the energy source. Once you have a concentrated energy source, you can probably get good efficiency, maybe even 100% - but making that energy source in the first place is not 100% efficient. Ariel. (talk) 22:39, 6 December 2010 (UTC)

I suppose that's all true, but the main thing is that the thermodynamic efficiency limit is a technical property of heat engines. It's not a broad statement about the unattainability of perfection in this corrupted world. A perfect heater is a 0% efficient heat engine, which is allowed since 0% is less than the theoretical maximum efficiency. -- BenRG (talk) 07:33, 7 December 2010 (UTC)

And of course that's 100% efficient in the sense that 100% of the energy becomes heat. Not necessarily in the sense that it uses the least possible energy for the given situation. (If it heats your home unevenly you may have to crank it way up so that no parts of your home are uncomfortably cold.) Sorry, I don't mean to keep harping on this point, but it feels important to make sure we don't equate "100% efficient" with "perfect". APL (talk) 02:24, 8 December 2010 (UTC)

(P.S. As a purely philosophical point, I'll bet most heaters make some noise, some small percentage of which would escape your home before it degraded to heat! Probably some EM interference as well? That'll take you down a fraction of a percentage point!) APL (talk) 02:24, 8 December 2010 (UTC)

Relativity and Time Dilation

Resolved

I know that relative time slows the faster one travels, e.g. the twins paradox. I'd read that a difference of nanoseconds can be realised between a transatlantic jet and a stationary atomic clock. What about the international space station? That makes around 15 and 16 orbits of the Earth per day, and clocks up speeds of around 17,500 mph. The ISS has been in orbit for 10 years and 72 days. If I'd put an atmoic clock on the ISS prior to launch, and had kept one near the lanch site. What would the differences in times be? (I'm a mathematician, so I'd like some formulas, and would rather not someone say "a lot".) — Fly by Night (talk) 22:37, 6 December 2010 (UTC)

17,500 MPH is about 0.000026c, where c is the speed of light. Plugging that into the equation for Time dilation#Time dilation due to relative velocity gives the ratio of times (the Lorentz factor) to be about γ = 1 + 3.40x10^-10, which over the course of 10 years 72 days gives a difference of about 3.92 seconds. Red Act (talk) 00:06, 7 December 2010 (UTC)

That's a perfect reference desk answer. You answered my question, and you gave me links for further reading. Thanks for that; it's appreciated! — Fly by Night (talk) 00:10, 7 December 2010 (UTC)

Follow-up

How would one calculate the time difference due to the difference in gravity, and what would that be? WikiDao ☯ (talk) 00:30, 7 December 2010 (UTC)

If I remember correctly, calculate the centrifugal force (acceleration) that is equivalent to the force of gravity you wish to calculate. The linear speed of the rotating body is the equivalent speed. Ariel. (talk) 00:43, 7 December 2010 (UTC)

Per RedAct above the ISS has a time difference of about 3.9 seconds due to special relativity. What I'm wondering is what time difference is due to the difference in gravitational field strength between ground and low-earth-orbit. WikiDao ☯ (talk) 01:11, 7 December 2010 (UTC)

The ISS has an altitude between 278 km and 460 km, so I'll take the average and use a figure of 369 km. Using the equation for Δτ_g at Hafele–Keating experiment#Equations, I calculate the time difference due to gravitational time dilation over 10 years, 72 days to be 0.013 s. Red Act (talk) 01:32, 7 December 2010 (UTC)

Interesting, thanks. :) And I found this cool graphic at Error analysis for the Global Positioning System#Relativity:

WikiDao ☯ (talk) 02:31, 7 December 2010 (UTC)

The Ariel Sharon Diet

People go to extremes to lose weight, and are often willing to seriously jeopardize their health in order to do so. Imagine this: A fat guy flies to Medellín or Bangkok and checks into a clinic, the only one of its kind in the world. He is put in a coma, for several weeks or even months, depending on his wealth and ambition. During this time he receives only a minimum of intravenous nutrition, or perhaps no nutrition at all - merely water with some vitamins. The fat steadily wastes away. That is to say, he starves. Being unconscious, he is spared the unpleasant sensations associated with starvation. No patience or "will power" is required. (Indeed, this is a major selling point of the procedure.) When the subject has reached his target weight, or when his account has been depleted (whichever comes first), his body is gradually reintroduced to solid food (so as to prevent refeeding syndrome), and only then is he revived and discharged. I imagine most western governments would frown on this kind of "therapy", hence its implementation in east Asia or South America or wherever. Never mind the legal and ethical red tape. Never mind the long-term health effects. My question is this: As a quick fix, would it be medically feasible? LANTZY^TALK 22:29, 6 December 2010 (UTC)

Being in a coma increases risks of all sort of health problems and death, from things as basic as bed sores to having health symptoms (like heart pains) they don't communicate to anyone. Wouldn't a less severe version of this therapy be to just lock the person up, and only provide them with a healthy diet, until they reach their goal weight ? Self-control wouldn't be an issue. I suppose they would feel deprived, but They would certainly feel worse upon waking from a coma to find their muscles had atrophied, their skin had deteriorated, etc. StuRat (talk) 22:54, 6 December 2010 (UTC)

"I think they'd get used to a good, healthy diet in a few days and then be OK with it." Pfft, have you never been on a diet? If you're losing weight at any significant rate, you're burning more calories than you're eating, and you feel deprived. Why do you think people yo-yo diet? 86.161.208.185 (talk) 23:21, 6 December 2010 (UTC)

I think I should expand my answer. I'm talking about a HEALTHY diet, by which I mean one that only gradually causes weight loss, say at a pound a week. Crash diets which cause rapid weight loss are neither healthy nor sustainable. Now a diet that causes the loss of a pound a week and is otherwise complete and healthy shouldn't be all that much of a burden to bear. I'm sure the patient would prefer to eat more, and less healthy, food, but being a bit hungry isn't exactly equivalent to torture. StuRat (talk) 04:52, 7 December 2010 (UTC)

The Minnesota Starvation Experiment (see article) studied a controlled weight loss of 25% by under-feeding. The article Starvation is also relevant. The Ref. Desk cannot speculate "would it be medically feasible?", noting that medical ethics demand more than just not quite killing a person.Cuddlyable3 (talk) 23:41, 6 December 2010 (UTC)

When I framed the question, did I not give specific instructions to disregard ethical considerations? I suppose my view of the word "medical" does not necessarily exclude unethical behavior. Blame my background in lexicography. Very well, I withdraw the adjective. Would the procedure I describe be biologically feasible? I do not ask if it would be healthy or conscionable or peachy-keen. And "The Ref Desk cannot speculate..."?? Honestly, Cuddles, do you suppose that I'm planning to open a Coma-Slim weight loss clinic in my basement, and all I need is technical approval from Dumbledore42 on the Wikipedia Reference Desk? LANTZY^TALK 04:33, 7 December 2010 (UTC)

If you are in a coma, and fed minimal calories, you will lose weight. Period. The rest of the procedure is an ethical question; whether the risks associated with a coma are so harmful as to outweigh the advantage from a lower weight. That is 100% an ethical question, because it asks someone to weigh values against one another and choose the least harmful path. Biologically, you lose weight if you take in less calories than you expend. --Jayron32 04:51, 7 December 2010 (UTC)

I would think they could hire people to put you through some kind of electrical workout regimen while you are in your coma to speed weight loss and prevent muscle atrophy. Googlemeister (talk) 17:31, 7 December 2010 (UTC)

the fix here is to not put you in a coma, just keep you pumped full of drugs so that you remain conscious and can eat, exercise, etc. but will have no recollection later. not sure what drugs do that. Gzuckier (talk) 13:41, 8 December 2010 (UTC)