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July 13

equal pressure gas airlocks

What is the current state of the art on airlocks between gases of roughly equal pressure? Is there a reliable way to isolate each gas while allowing people and objects to pass between without using an intervening vacuum? How does it work?

I will explain the scenario in a little more detail.

A person needs to work in a hazardous gas environment, though the gasses are at roughly normal atmospheric pressure. He suits up in a sealed suit and brings his own air supply. When he's done, he needs to back to the normal air environment, but bring no gas with him. Is there an airlock like technology that does this? If you just try to pump one kind of gas out and another in, don't you either have a fatal vacuum in the middle, or just get mixed air? Is there a trick to avoid that, another system entirely, or does it just work and I'm not thinking about it properly?

Thanks for your help. (sorry, this was me. Editing in my signature) gnfnrf (talk) 01:41, 13 July 2013 (UTC)[reply]

Normally, when working in hazardous gas atmospheres, the hazardous gas would be kept at a slight negative pressure compared to the outside air -- this way, when people need to enter or exit the hazardous atmosphere (or in the case of an accidental breach), outside air will flow in but the hazardous gas won't flow out. 24.23.196.85 (talk) 05:30, 13 July 2013 (UTC)[reply]

I can imagine a horizontal interface might be fairly stable if the gasses are different weights, and especially if the lower one is also cooler - for example, an airlock between an upper inhabitable area and lower maintenance facilities in a floating base on Venus. Wnt (talk) 06:04, 13 July 2013 (UTC)[reply]

Do you have a specific gas or situation in mind? Most straightforward would be air purging in the airlock. There's a rule of thumb requiring six air exchanges to provide a 3-log reduction in airborne contamination. So it's simply blowing air through the chamber until it's diluted enough. The air goes to a scrubber or is dumped. An alternative would be a Suitport, but that seems a bit expensive. An air shower (room) is used for cleanrooms, together with an airlock.

Found a US Air force document CONTAMINATION CONTROL AREA – AIRLOCK –TOXIC FREE AREA PROCESS ANALYSIS (BRIEFING CHARTS), but that's more about "unplanned" decontamination it seems. Ssscienccce (talk) 00:19, 15 July 2013 (UTC)[reply]

No specific scenario. I started by thinking about humans on another planet with a dense but non oxygen-nitrogen atmosphere, but then I got to wondering about industrial processes, and was just generally curious. To clarify, though, you are saying that if you pump 6x the volume of the room out (to be filtered or rejected) and in as clean air, simultaneously, you will be left with 999 parts per 1000 of air, and 1 part per 1000 of the non-air gas left over?

That link looks very interesting and completely full of confusing acronyms and terminology. It'll take me a while to unpack it. Thanks. gnfnrf (talk) 20:26, 15 July 2013 (UTC)[reply]

Glycaemic Indices of Gluten-free flours.

A wide variety of gluten-free flours are now commonly advocated for consumption by persons with coeliac disease. These flours may also be advantageous for persons with diabetes or high post-prandial blood glucose levels, depending mainly on the the percentage of amylopectin in their starch, as reflected in a low glycaemic index (GI: rate of rise of blood glucose after a standard carbohydrate meal ). A low dietary amylopectin burden typically correlates with a beneficial low GI, leading to a reduced development of advanced glycation end-products (ACE), which are the cause of a variety of age-related diseases. Therefore a compilation of the GIs of a range of flours currently available and recommended for controlling coeliac disease would be helpful to persons wanting to manage their blood glucose levels in addition to any gluten sensitivity. Flour is used for baking breads around the world.

--19Grumpah42 (talk) 04:06, 13 July 2013 (UTC)[reply]

Do you have a question, or a desire for references? SemanticMantis (talk) 05:08, 13 July 2013 (UTC)[reply]

I think the OP is suggesting a new article, in which case they should ask at WP:Requested Articles. Rojomoke (talk) 07:26, 13 July 2013 (UTC)[reply]

I don't think that's at all a suitable topic for an encyclopedia article. The information may well belong somewhere on the web, but not here. Looie496 (talk) 15:00, 13 July 2013 (UTC)[reply]

But it could make a good list say: List of glycaemic indexes or perhaps spelled List of glycemic indexes or indeces. Graeme Bartlett (talk) 21:21, 14 July 2013 (UTC)[reply]

Looking for an Approachable In to Quantum Field Theory and Particle Physics (As in books)

I have a decent mathematics background (though analysis is not my strongest area) and know a decent bit of basic Quantum Theory (I've worked through a few texts), what I'd like to find is a specific type of book on the subjects mentioned. Most of the QFT and PP books I have are of three flavours: for physicists that are well acquainted with the experiments, motivations, and ideas being generalized; for mathematicians, meaning that the book becomes a book on applications of functional analysis and lie theory; or books full of toy models with vague shallow explanations tossed around. What I'd like is a book that is written as if it were physicists, but assumes the background of a mathematician (meaning that it explains the physics ideas and it isn't presented as theorems/proofs followed by a few lines about how particles are representations, then back to the general case.) It doesn't even need to cover the depths of these subjects, just enough that I could pick up a second more traditional book and follow it (with work, obviously). Sorry for the long question, I've spent a lot of time looking, but this is one of the few subjects I just can't find an in into. Thank you for any suggestions:-) Sorry for any poverty of clarity. Phoenixia1177 (talk) 10:13, 13 July 2013 (UTC)[reply]

CERN's education page provides several dozen free full textbooks; presentations, review papers, and websites. But let's be frank and honest. One does not "learn quantum field theory" by reading a textbook, any more than one learns to fly airplanes from the Airplane Flying Handbook. Like any advanced physics specialization, there are some prerequisites - time, money, and intellectual capacity. You will probably need one-on-one instruction, and interaction with others who are learning and using this type of physics, which means intensive study among experts in the field.

First, study and earn an undergraduate degree in physics, or mathematics with a strong concentration in physics, from an accredited university. This proves that you're capable of investing the time and money to tackle the field, and that you have the intellectual capacity for it. Next, enter into a program of graduate study in theoretical physics. After a year or two, apply for a special program, like one of the institutional exchanges or particle physics summer schools.

If you aren't able to follow that track, for any reason, then advanced particle physics probably isn't for you; if you still have interest in the topic, you might enjoy some of the material on the website I linked. Nimur (talk) 15:40, 13 July 2013 (UTC)[reply]

For an introduction to particle physics at a first-year undergraduate level I suggest The Ideas of Particle Physics by Coughlan, Dodd and Gripaios. Another good introduction that includes more cosmology is Quarks, Leptons and the Big Bang by Jonathan Allday. For an introduction to quantum field theory try Fundamental Forces of Nature - The Story of Gauge Fields by Kerson Huang. Gandalf61 (talk) 16:04, 13 July 2013 (UTC)[reply]

Thank you:-) I picked up the book by Huang this afternoon; I've read a decent bit of it, it's quite readable:-) I know I have a copy of From Operators to Path Integrals (same author) somewhere in my library (in quite a state of disarray at the moment...); looking at the excerpt on Amazon, it looks fairly readable, is this true of the rest? Do you know of anything along the lines of Quantum Field Theory: A Tourist Guide for Mathematicians, by Folland, that is slightly more elementary? That book is on the very edges of what I can follow, which makes it really hard to extract the physics out of it. I know I'm being weebly-woobly, and vague, here with my requests; for some reason this subject is a pain to navigate on my own (everything is too much physics or too little). I'm going to check out some of the links at the Cern site tonight, I haven't had a chance yet (it's easier to read on my Kindle at work).Phoenixia1177 (talk) 21:55, 13 July 2013 (UTC)[reply]

I'm not sure I understand what you are and aren't looking for, but I have a somewhat similar background and I remember enjoying Quantum Field Theory in a Nutshell by Anthony Zee (ISBN 978-0691140346, first chapter as a PDF), Diagrammatica by Martinus Veltman (ISBN 978-0521456920) and Introduction to Elementary Particles by David Griffiths (ISBN 978-0471603863). These are all undergraduate/graduate textbooks that emphasize concepts but also cover the mathematics in detail. -- BenRG (talk) 00:52, 16 July 2013 (UTC)[reply]

Thanks for the suggestions:-) I've read Griffiths, I've read several of his books, I like him as an author. Zee I, actually, have a copy of, but my books are in such disarray! I'll have to dig it up, though. I've never heard of Diagrammatica, but will definitely grab a copy this week. As for what I'm looking for, it's unusually hard to put in words. Essentially, the mathematics part isn't a problem (most of what I read is logic/set theory; but Lie theory and path integrals aren't at all terrifying). My difficulty is that most of the books for "mathematicians" are way to abstract, which is fine mathematically, but leaves me confused about where the physics comes in. On the other hand, the books for physicists are way too much "for physicists", if that makes sense. What I'd like to find is a book that isn't shy about the mathematics, but is very gentle in linking it up to actual physics. For example, most of the math I've seen relating to QCD makes sense to me, but everything I've read about it seems like it either spends its time doing math and never gets to the physical why; or it seems like a confusing rush of physics terms and conventions, which all seem impenetrably alien. Sorry if that's long, or unhelpful, but this is the only subject (Besides cutting edge Algebraic Geometry!) that just seems horribly impossible to learn. Thank you for the help:-)Phoenixia1177 (talk) 04:10, 16 July 2013 (UTC)[reply]

I recommend An Introduction To Quantum Field Theory by Michael E. Peskin and Dan V. Schroeder. Dauto (talk) 16:05, 16 July 2013 (UTC)[reply]

Bought a copy today; also grabbed Diagrammatica (I like what I've see in it thus far:-) ) and the book by Mandl and Shaw (which also looked kind of nice). Thank you all for your help:-) If anyone has anymore suggestions, I'd be willing to check them out; but I should have enough reading to occupy me for a while now:-)Phoenixia1177 (talk) 05:41, 17 July 2013 (UTC)[reply]

Lac-Mégantic derailment

In this article, Lac-Mégantic derailment, it states: "It is possible that some of the missing people were vapourized by the explosions." What would this mean exactly? Thanks. Joseph A. Spadaro (talk) 12:42, 13 July 2013 (UTC)[reply]

It would mean that it was so hot, they were basically incinerated, with no remains left. I doubt they were turned entirely into actual vapour, but certainly they could have mean cremated. Mingmingla (talk) 15:37, 13 July 2013 (UTC)[reply]

Probably a poor translation from French. It can be the French equivalent of "going up in smoke" / "leaving/being gone without trace", which is usually not literal either. - ¡Ouch! (^{hurt me} / _{more pain}) 16:49, 13 July 2013 (UTC)[reply]

Oops, wikt doesn't list that old meaning either. :( — Preceding unsigned comment added by One.Ouch.Zero (talk • contribs) 16:55, 13 July 2013 (UTC)[reply]

I suspect it might have simply been a word chosen for maximum emotional impact. "Vapourize" is more powerful than "burnt up". Incinerate might be too clinical or insensitive. Mingmingla (talk) 21:14, 13 July 2013 (UTC)[reply]

Do Canadians spell the word "vapourize"as in the article, presumably following British usage, or "vaporize" like folks in the US? The article should probably follow Canadian spelling conventions. Edison (talk) 02:16, 14 July 2013 (UTC)[reply]

Yes, Canadian spelling uses -our, e.g. colour, vapour, flavour, etc. as in British spelling. הסרפד (call me Hasirpad) 02:37, 14 July 2013 (UTC)[reply]

The usual British spelling is 'vaporise' or 'vaporize'. The dropping of the U also occurs in glamour -> glamorise. AndrewWTaylor (talk) 08:01, 14 July 2013 (UTC)[reply]

According to the Language Portal of Canada, vapourize is correct. So it's unlike either British or US English. Heron (talk) 10:46, 14 July 2013 (UTC)[reply]

I'm a Canadian, and have never even thought about spelling "vaporize" with a u. No more than "colourant" (which is apparently also our proper spelling, I see). Whatever the books say, it looks weird to me. "Vapour" and "colour" are cool, though.

Regardless of what the spelling conventions say, Wikipedia policy states that BOTH British (and, by extension, Canadian) English AND American English are equally appropriate in articles, and furthermore that edit warring over the use of British vs. American English is prohibited. So let's stick with whatever the article's creator decided, OK? 24.23.196.85 (talk) 01:05, 15 July 2013 (UTC)[reply]

Yeah, proper's fine. No edit war (or even edit) intended. I just, personally, wouldn't use the U. For what it's worth, a Google News search shows only the Toronto Star uses the U. Montreal, Ottawa, Vancouver and others just the O. InedibleHulk (talk) 02:33, 16 July 2013 (UTC)[reply]

No, it is not always up to the first contributor's choice of English version. If an article's topic is closely associated with one English-speaking country, then that country's version of English can be substituted for some other version the first contributor used. See Wikipedia:Manual of Style#Strong national ties to a topic. Canadian spelling and terminology are preferable in this article, regardless of what conventions were used by the initial contributor. Edison (talk) 20:04, 16 July 2013 (UTC)[reply]

As to the question, every solid that burns is vaporized, after being liquefied. Much of smoke is vapour (though the colour we see is from small solid soot). If it's hot enough, that vapour turns to plasma, which we call flames. And yes, it is also a more powerful word than burnt, implying no solids or liquids are left (which isn't true, there will virtually always be some ash). InedibleHulk (talk) 11:12, 14 July 2013 (UTC)[reply]

And I expect crispy critters is right out. The article Cremation indicates temperatures in the 1600-1800 Fahrenheit range. That "vaporizes" the flesh and leaves just the bone. So that could be compared with whatever the temperature estimates are for this railroad disaster. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:20, 14 July 2013 (UTC)[reply]

Probably somewhere around there. Some fires burned much longer here than they do in a crematorium, though. If there was a body in one of those fires, it could be more burnt than those you find in urns. Which is about as useful as pure vapour, so far as identifying it goes. InedibleHulk (talk) 14:30, 14 July 2013 (UTC)[reply]

Natives

Are Native Americans and Hawaiian and other indigenous people who have gone through mass epidemics due to weak immunities in historical times still seeing the effects of a weaker immune system or are modern high numbers in disease and death just the result of poverty in these groups? — Preceding unsigned comment added by KAVEBEAR (talk • contribs)

It's not that they had weak immune systems as such, but that (1) they had never been exposed to endemic diseases of the Europeans, so what the latter consider "childhood diseases" struck the entire population at once, and (2) they did not have the inherited resistance to some diseases conferred by genes that made the latter resistant to the plague and hence also partially to HIV. μηδείς (talk) 16:57, 13 July 2013 (UTC)[reply]

You might want to read "The Arrow of Disease", a Discover magazine article. Basically, it states that Europe had a high enough population density that some diseases became endemic, causing people to gradually become more resistant to them. The diseases evolved, forcing human defenses to counter - a sort of arms race. America, Hawaii and other places mostly didn't have enough inhabitants sufficiently packed together to go through this process, so the more evolved European maladies struck them down in droves. That also explains why few New World illnesses troubled the Old. If a disease was deadly enough, it essentially killed itself off by wiping out the isolated tribe or group it first infected. At least, that's the way I understand it. I'm no expert. Clarityfiend (talk) 19:53, 13 July 2013 (UTC)[reply]

Yes, that's accurate. And Afro-Eurasia is the biggest island (and most highly populated) on the planet. μηδείς (talk) 20:07, 13 July 2013 (UTC)[reply]

But by that same token, the entirety of the Americas is not small and, if you believe the current thinking on the subject, they were chock-a-block with people. If Tenochtitlan had a pre-contact population of between 500,000 and a million people [1] then what exactly is your definition of "high enough population density"? That's a lot of people living in hot, wet, crowded, living conditions. A more likely difference is the lack of domesticated and farmed animals. Many old-world plagues are zoonotic (carried by animals) and this typically requires humans and animals to be living in close living conditions - something that happened all the time in Eurasia and not very frequently at all in the Americas. That differential behaviour caused the Eurasians to be exposed to many more diseases historically, altering their immune system's defenses. Matt Deres (talk) 23:22, 13 July 2013 (UTC)[reply]

To continue on from a similar angle, Eurasians and Americans practiced very different kinds of agriculture. In Eurasia, ploughing was widely used in a variety of different forms. Tilling the earth in that way also digs up soil dwelling bacteria and fungi, which may also bring contact with new diseases (example). Native Americans usually didn't go in much for ploughing and felling of trees since they lacked metal tools to do the work (try hacking down a hardwood tree or cut through thick soil with a stone implement and you'll see why they turned to slash-and-burn style agriculture). Burning stuff down rather than tilling it under greatly reduces the contact between people and soil bacteria. See hygiene hypothesis for some recent work that has shown the benefits of contact with, well, filth at an early age to build up the immune system. Matt Deres (talk) 00:14, 14 July 2013 (UTC)[reply]

The Americas weren't empty, but they were a very small portion of world population, with France outpeopling all of North America, see map. While it is widely speculated syphillis came from the New World, the majority of transmission of diseases wnt from the wider pool in which they were established to the smaller. μηδείς (talk) 01:07, 14 July 2013 (UTC)[reply]

I think it's fair to say that the Old World contained far more people than the Americas, even using the highest pre-Columbian population estimates for the latter. That said, I find your map highly dubious. I don't know how it calculated Native American populations, but these calculations are notoriously difficult given the scanty data available. Virtually every society was decimated by disease before seeing the first European. In the few regions that Europeans managed to visit early enough, nobody had the means or the interest to do a census until well after the region got depopulated. Working backwards from European records to pre-Columbian populations is difficult because you have to assume a fatality rate due to disease. If you change your assumption a tiny bit--from 93% to 96%, for example--your pre-Columbian estimate changes by a lot. Due to these difficulties different scholars arrive at wildly different estimates. See Population history of indigenous peoples of the Americas#Population overview for just a few. --Bowlhover (talk) 02:15, 14 July 2013 (UTC)[reply]

The highest population estimate I have ever heard for the entire Americas is 40 million, and that is far less than half of China or India, at most three or four times estimates for France. I am not quite sure what you find dubious, but I have no necessary problem with other maps if they are provided. The point is, the New World was a colonized area with very small founding populations moving through an arctic territory that would have been unlikely to bring many endemic diseases, and other than the dog, who had no domesticated animals with them to serve as disease reservoirs. The OP asked about weakened immune systems in Native Americans, and I have never heard of such a model. μηδείς (talk) 02:37, 14 July 2013 (UTC)[reply]

Population estimates run as high as 100 million for the Americas. Having read a bit about it (and heard the politicking behind the use of small numbers), I'm inclined to believe the 100 million estimate much more than the 10 million one. I've heard the immune system theory before; it's also discussed in the 1491 book here. The short version is that the crossing of Beringia created a population bottleneck and associated founder effect. One of those long term effects was a decrease in the number of HLAs. There's some advanced biochemistry involved there that's beyond me, but the numbers suggest that pre-Columbian New World populations even today are some ten times more likely to be susceptible to a given disease than an Old World population. Matt Deres (talk) 13:47, 14 July 2013 (UTC)[reply]

I am unfortunately quite familiar with people who believe the Americas were inhabited by sparse primitive tribes without civilization, but the political point is not relevant here. The total population numbers don't really matter for the immunity of the Americans, only the fact that the diseases the Europeans brought were not already endemic there because the Beringian founder populations didn't bring those diseases with them. Regardless of their size, had the Americas been founded but multiple waves out of the tropics/subtropics then Europeans moving there would have been at much higher risk of infection than the natives, compare what happened to British colonists who went to Africa or India. μηδείς (talk) 18:23, 14 July 2013 (UTC)[reply]

You're talking in circles. You say you're "unfortunately quite familiar" with that picture of the American populations, yet you happily cited that claptrap when you thought it suited. Fewer people than in all of France - preposterous! But then you throw both arguments away in exchange for... I'm not even sure what to call your last sentence, but it's no answer to anything the OP brought up, nor anyone else. The Americas had the people and the population densities to support all kinds of diseases (as evidenced post-1492), but they had few endemic ones for the reasons I've outlined above, centering mostly on different agricultural and animal domestication strategies. Matt Deres (talk) 21:00, 14 July 2013 (UTC)[reply]

You have a strange notion I think the difference between 40 and 100 million would matter. It has nothing to do with the small, relatively disease-free founding populations from Arctic Asia. How about I stipulate 250 million Native Americans at the time of Columbus? Would that cure the accusation of clap-trap? μηδείς (talk) 00:44, 15 July 2013 (UTC)[reply]

Actually, France had a population of 15 million around the time of Columbus. North America probably had fewer people, even according to most High Counters. The article I linked says "while it is difficult to determine exactly how many Natives lived in North America before Columbus,[5] estimates range from a low of 2.1 million (Ubelaker 1976) to 7 million people (Russell Thornton) to a high of 18 million (Dobyns 1983)." Thus, even the highest non-fringe population estimate of North America is comparable to the population of contemporary France. Most state societies in the Americas, and consequently most of the population, was in Mesoamerica, Peru, and possibly the Amazon shore. --Bowlhover (talk) 01:13, 15 July 2013 (UTC)[reply]

Aside from mere population density, proximity to livestock has as much to do with this kind of immunity. The big killers were essentially agriculture-related diseases: smallpox, the plague (rats associated with grain/close quarters), measles, all the gastrointestinal water-borne illnesses, etc. This is a central point in Guns Germs and Steel. Shadowjams (talk) 06:38, 15 July 2013 (UTC)[reply]

It's worth considering that, as syphilis alone still causes 500,000 stillbirths and miscarriages a year,^[2] among other things, and was once a very major cause of death for all ages, the death from New World diseases in the Old World may well have equalled the deaths caused by Old World diseases in the New after all. (It's a bit like gravity, where the tiny effect of a falling ball on the Earth is actually equal to its effect on the ball... it just doesn't seem so visible) Wnt (talk) 15:50, 15 July 2013 (UTC)[reply]

Does the human body only use glucose and ketone bodies as fuel?

I'm not entirely sure how to word my question, but the basic idea is this: does all the food we eat eventually just get converted into glucose one way or another so the body can use it as fuel? Like the proteins in a steak, are they eventually converted into glucose? ScienceApe (talk) 16:54, 13 July 2013 (UTC)[reply]

The simple answer is no (i.e. not all of the digestible nutrients in food, including protein, can be converted completely to glucose). That said, metabolism and specifically digestion is a really complex topic, with influences from degree of starvation and many other factors. Regarding protein digestion: after protein catabolism, amino acids are often re-used to make protein; however, under some conditions the process of amino acid catabolism can convert portions of many (not all) amino acids to things like acetyl-CoA that can be used on gluconeogenesis to generate glucose (under certain conditions). Similarly, fat digestion can convert fatty acids almost completely to acetyl-CoA. Your question about ketone bodies can be answered by reading about ketosis, but a short answer is that these compounds, which are part of starvation metabolism, are not usually used for energy by most healthy tissues. -- Scray (talk) 18:06, 13 July 2013 (UTC)[reply]

So is this the reason why if you just eat nothing but meat, you'll eventually lose weight? Because your body isn't producing much glucose and the amount of fat consumed and turned into adipose tissue doesn't outweigh the amount your body burns to produce more glucose? Also if your body only needs glucose for fuel, is it possible to have a diet consisting of only carbs and vitamin supplements? ScienceApe (talk) 18:24, 14 July 2013 (UTC)[reply]

This is a huge topic, so please understand we're simplifying things here greatly. Eating nothing but meat generally results in a high-protein, high-fat (low-carb) diet. I don't think there's a consensus on the principal mechanisms at work in ketogenic diet (i.e. extremely low-carb nutrition), but one component is probably the appetite-suppressant effects of ketosis (whether these diets are safe and effective, and for whom, is still unclear). Glucose is not adequate nutrition due to needs for essential fatty acids, minerals, vitamins, amino acids, etc - so carbs and vitamins won't do the job. -- Scray (talk) 23:01, 14 July 2013 (UTC)[reply]

(ec)No. Aside from a small amount of energy generated by glycolysis, most of the energy generated in mammalian cells comes from the citric acid cycle. Compounds can enter the cycle through a number of different pathways. While glucose goes through glycolysis and enters the cycle as pyruvate, and fats are broken apart to acetyl-CoA directly, amino acids (what proteins are made of) enter the cycle at different points depending on their identity. They don't have to go through glucose first. That said, the body can convert amino acids to glucose through the process of gluconeogenesis, though that consumes energy rather than produces it, so is only used if the body needs glucose for non-energy reasons. -- 67.40.215.195 (talk) 18:12, 13 July 2013 (UTC)[reply]

We actually have an article glucogenic amino acid that lists them. Note that glucose levels are kept up because it is absolutely required for energy, especially in the brain - even brief episodes of hypoglycemia can be lethal. (The brain also can use ketone bodies for a substantial fraction of its energy according to our article... have to admit, I didn't know that) Wnt (talk) 15:57, 15 July 2013 (UTC)[reply]

Peculiar cell nuclei

What cells of the human body contain unusual numbers of nuclei? I know that muscle cells merge and pool their nuclei. I think I knew once of neurone cells that have multiple nuclei - is that right? Why do granulocytes have peculiar-shaped nuclei? --217.16.212.250 (talk) 21:36, 13 July 2013 (UTC)[reply]

Take a look here for some information about neutrophil granulocytes, under the section "Normal cells with abnormal nuclei." Lord Arador (talk) 23:43, 13 July 2013 (UTC)[reply]

We have an article, Multinucleate, that would be helpful if it were in better shape. It may be helpful to consider that multinucleate cells can form through fusion (a syncytium) or failure of the cell to divide after nuclear division (a coenocyte). In answer to your question, in humans multinucleate giant cells can be found in at sites of inflammation, especially activated macrophages in granulomatous inflammation, giant-cell arteritis, and multinucleate hepatocytes in some forms of (especially neonatal) hepatitis. -- Scray (talk) 01:22, 14 July 2013 (UTC)[reply]

Is that the same as neonatal jaundice? μηδείς (talk) 03:28, 15 July 2013 (UTC)[reply]

No, the usual cause of neonatal jaundice is breakdown of fetal red blood cells at a rate that exceeds the newborn liver's capacity to conjugate bilirubin. That's generally temporary, as our article explains. Neonatal hepatitis (that article needs work!) is rarely the cause of neonatal jaundice. -- Scray (talk) 04:23, 15 July 2013 (UTC)[reply]

July 14

Need help identifying a catapillar

Spotted this little guy as I was working in my garden in Southern Norway, and am at a complete loss for what he is. He was munching away on a young aspen, and is roughly 4-5 cm long. Does anyone know what species he belongs to? WegianWarrior (talk) 13:58, 14 July 2013 (UTC)[reply]

Looks a lot like this one,[3] which I found by googling [yellow caterpillar], and which is called a Canadian Yellow Caterpillar. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:08, 14 July 2013 (UTC)[reply]

It's had a long swim from Canada to Norway! Agree it looks the same, but caterpillars are generally known by the name of the butterfly or moth that they pupate into. Alansplodge (talk) 14:38, 14 July 2013 (UTC)[reply]

Gotcha! It's an Elm sawfly, Cimbex americana. I found it through this forum which reports sightings in southern England, despite it being a native of North America (apologies to Bugs). It is "also know to feed on willow and some other plants" aspen being ~~a member of~~ related to the Willow family. Alansplodge (talk) 15:09, 14 July 2013 (UTC)[reply]

Here's a picture of an adult elm sawfly. Alansplodge (talk) 15:19, 14 July 2013 (UTC)[reply]

Any idea what the adult stage of the Canadian yellow is? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:17, 14 July 2013 (UTC)[reply]

Bugs, please follow my link to the topix.com forum in my post above and read the thread - this is also the source of your photo. Alansplodge (talk) 19:25, 14 July 2013 (UTC)[reply]

If I'm reading that correctly, it's not a "Canadian yellow caterpillar", but actually just another photo of the larva of an elm sawfly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:15, 14 July 2013 (UTC)[reply]

Correct. Alansplodge (talk) 07:27, 15 July 2013 (UTC)[reply]

Thank you all for helping out - and it certainly explains why I found no references in my Norwegian bug-books. WegianWarrior (talk) 17:31, 14 July 2013 (UTC)[reply]

Note that this is not a caterpillar - just looks like one. It's a member of the order Hymenoptera, and as the pictures linked above show, the adult is more like a wasp than a moth. -- Scray (talk) 17:51, 14 July 2013 (UTC)[reply]

Right, technically caterpillar is restricted to the lepidoptera, though informally, caterpillar sometimes means "crawly guy with legs" It is definitely a larva, but most people wouldn't call this sawfly larva a grub... so probably just larva is the best term. SemanticMantis (talk) 19:16, 14 July 2013 (UTC)[reply]

(Edit conflict) Yes, this blog says "True caterpillars have no more than five (5) pairs of prolegs, the “false legs” along the length of the abdomen that look like suction cups. Sawfly larvae have seven (7) pairs of prolegs." Alansplodge (talk) 19:20, 14 July 2013 (UTC)[reply]

As a side point of interest, sawfly larvae are often studied as a way of seeing into Evolution_of_eusociality, because the larvae exhibit some presocial behavior, while the adults are solitary. SemanticMantis (talk) 19:21, 14 July 2013 (UTC)[reply]

WegianWarrior, if you could update the details on your image, I can add it to our Sawfly article (there's a space waiting to be filled and it's a great photo). Alansplodge (talk) 09:10, 15 July 2013 (UTC)[reply]

Thank you - I just updated the description and requested a rename to a more suitable filename (ie "File:Elm sawfly larva (Cimbex americana).jpg"). WegianWarrior (talk) 11:22, 15 July 2013 (UTC)[reply]

It now adorns our article. Alansplodge (talk) 17:09, 15 July 2013 (UTC)[reply]

It looks so much like a new variation of Peep, I want to nibble on it. :-) StuRat (talk) 18:40, 15 July 2013 (UTC) [reply]

I do hope you are in the habit of frying your peeps first, then. μηδείς (talk) 02:23, 17 July 2013 (UTC)[reply]

Heavy legs

A friend said her legs felt heavy, so I was wondering how to measure their mass. I was modelling a leg as a rod with a variable mass distribution joined by a hinge to another rod representing the body also with an unknown mass distribution along it. Assume the axle between has zero mass,, you can have a second equal leg but it doesn't make any difference that I can see. It certainly can't be done by just measuring where the centre of gravity is with the leg in various positions and I don't see that measuring the moment of inertia is any help either.

Anyone like to suggest a way I could measure the mass of a leg in situ or do I have to tell her that unfortunately I really will need to cut off her leg to measure it? ;-) 21:08, 14 July 2013 (UTC)

A simple and approximate way would be to sit relaxed in a chair or lying down with the leg horizontal and rest the heel or calf on a bathroom scale. By relaxing, the leg muscles should neither push down on or lift the leg, and the hip joint should act as a simple hinge. An inaccuracy is that part of the weight is supported at the hip.and the hip and the scale would provide equal support only if the leg were of constant unit mass per unit length, which is not the case. .Edison (talk) 21:37, 14 July 2013 (UTC)[reply]

Unfortunately even if all the mass in each rod is concentrated at one point that doesn't work. If one keeps mr constant for each rod where r is the distance from the pivot and keeps the sum of the two weights constant one can vary the masses and not distinguish by those type measurements. One can move a mass over from one rod to the other without making any difference, for example split one in two and move half twice as far away and the other to the pivot. Then amalgamate that mass at the pivot into the massa in the other rod moving both to their common centre of gravity. There's no way to distinguish these two cases by these type measurements. Dmcq (talk) 23:11, 14 July 2013 (UTC)[reply]

Alternatively, you could measure the volume of the leg using a bath, and find the density using a CAT scanner, and multiply the two values.--Gilderien Chat|List of good deeds 21:51, 14 July 2013 (UTC)[reply]

That does sound like a possibility, not exactly a pure science method but probably very effective. I had a look at body fat percentage and I remember reading a while back about how they measured the volume of the lungs by the percentage of gas in exhaled air but I can't find there, anyway they seemed to do quite complicated things just to do that. I wonder if anyone just uses a scanner for that sort of thing nowadays. Dmcq (talk) 23:30, 14 July 2013 (UTC)[reply]

We have an article on Heavy legs, incidentally. Tevildo (talk) 23:01, 14 July 2013 (UTC)[reply]

Gosh Wikipedia does have an article on everything. Thanks very much. I'll tell her she's suffering from hypercondria ;-) 23:16, 14 July 2013 (UTC)

No, don't do that. It will serve no purpose and will be seen as a negative comment. Guide her towards the article and let her draw her own conclusion. and its hypochondria. Richard Avery (talk) 06:50, 15 July 2013 (UTC)[reply]

Place a large garbage can in a broader, shallower pan that will hold the overflow. Have her slowly get in the garbage can without sloshing. Measure the overflow, and assume she weighs the same as the displaced water. Also, a feeling of heaviness in the legs can be the sign of a severe medical condition. Have her call her doctor. μηδείς (talk) 00:40, 15 July 2013 (UTC)[reply]

Here's a reference> An article in a journal which discusses "heavy legs." Edison (talk) 01:49, 15 July 2013 (UTC)[reply]

There are even worse medical reasons than edema that can cause such symptoms, so, again, if it is a symptom and not just "do these pants make me look fat" she should contact a doctor immediately. μηδείς (talk) 03:25, 15 July 2013 (UTC)[reply]

She's quite healthy no worries - she was dancing and it had been a hot day. It's just me taking what's said literally and wondering about it. Anyway I rather like the one about the large garbage can, I think I'll suggest that one thanks ;-) Dmcq (talk) 07:20, 15 July 2013 (UTC)[reply]

A leg could be "heavier" because the volume was constant and the density increased, or because the volume increased at constant density, or some combination. One measurement would be to measure the circumference of ankle and calf when the legs are "heavy" and when they are not, to see if the volume varies. Edison (talk) 18:30, 15 July 2013 (UTC)[reply]

Severed legs aren't that hard to come by, either. Accidents, aggravated assault, etc. Those who ~~sever~~ serve in the military run a nonnegligible risk of losing a leg in a war, etc.

Maybe not exactly "not hard" but not extremely rare either. There should be some data on severed legs and their weight. Not sure how "available" , but anonymized data should exist quite abundantly. - ¡Ouch! (^{hurt me} / _{more pain}) 13:21, 16 July 2013 (UTC)[reply]

Quite hard to search for. I searched for "severed leg" + weigh, and excepting the three words "RuneScape" (which was the first return), "washed", and "ashore" (we need fresh legs). Still, the returns are usually about the victim's weight, or about items on sale (practical jokes (I hope, had to kill SafeSearch!)) - ¡Ouch! (^{hurt me} / _{more pain}) —Preceding undated comment added 13:30, 16 July 2013 (UTC)[reply]

July 15

"Hearing the wind"

When you crack a whip, you know how you "hear the wind"? If you threw a fastball and "heard the wind", how fast would an estimate be of that pitch? Albacore (talk) 02:45, 15 July 2013 (UTC)[reply]

...If you're gonna find the answer anywhere, it'll be at the Physics of Baseball webpage. In fact, you can even apply for a (competitive) fully-funded summer internship to elaborate on these studies! (Here's the summer 2004 final report).

The sound we hear when air rushes past our ears actually has very little to do with the net velocity of the air (or of any object that's moving through the air). Sound is the vibration of air - its volume is determined by the amplitude of the oscillation; and the timbre of the sound is determined by the waveform shape of the oscillation. A "whoosh" is pretty much white noise. Air speed doesn't really enter into things, at least not as a direct first-order term. So, bulk velocity of the air is a secondary concern; and thus velocity of the acoustic transducer (the ball, or the whip) is even further removed from the intensity, volume, and sound we actually hear - it influences the sound in an indirect and subtle way. In practice, you might be able to empirically measure and then deduce a relation between the velocity of a ball and the amplitude of the "whoosh," but that relationship will be a little bit tenuous, because you're essentially trying to be quantitative about a very noisy signal.

In a little bit plainer English: you can make a loud "whoosh" using a slow moving object or a fast moving object. You can also make a quiet "whoosh" using a slow moving object or a fast moving object. The speed of the object is not the main factor in the "whoosh." Nimur (talk) 05:55, 15 July 2013 (UTC)[reply]

There are two situations I can think of (which doesn't mean there are only two...) - a reed (instrument) which vibrates due to its own characteristics, creating a sound that depends (among many things) on the speed of the wind, and whipcracking where the object moves at the speed of sound and all that sound emitted piles up into a little sonic boom. Wnt (talk) 15:33, 15 July 2013 (UTC)[reply]

I agree that some non-aerodynamic objects make a lot of noise in little wind by creating turbulence and perhaps snapping in the wind like a flag, while other objects create very little noise even in high winds, since they only create laminar flow. However, this Q was about a baseball, so, since we've eliminated the variable of the object type, the relative wind velocity should correspond quite well with the sound level. The only other remaining significant variables should be it's spin, and the air pressure, temperature, and humidity. StuRat (talk) 18:36, 15 July 2013 (UTC)[reply]

Why do you assert these speculations as if they are facts? We don't get to arbitrarily decide what should happen in aerodynamics. Just because you think velocity should affect audible noise doesn't mean it does. Turbulent airflow is probably one of the least intuitive, most difficult-to-speculate about, impossible-to-describe-using-simple-first-principles-of-physics subjects known to humans. As an example: one of the papers on the website I linked shows experimental data indicating that the asymmetric flow separation due to the rotation of the ball contributes to turbulent airflow. And sometimes in totally the opposite direction from that which is predicted by ordinary flow separation theory. A small scratch on the ball's surface may have more impact than the net bulk translational or rotational velocity of the ball. In another experiment, the presence of a very tiny "raised wire" on an experimental sphere changed laminar flow into turbulent flow with R=30,000. StuRat, when you assert that velocity is the chief factor - yet you have neither experimental data or theoretical explanation why you believe that should be true, you are conducting pseudoscience. This is worse than being wrong - if your fact was only wrong, we could correct it and move on with our lives. But instead, you are asserting a claim without any evidence. Your methodology is profoundly unscientific. Nimur (talk) 22:34, 15 July 2013 (UTC)[reply]

Descriptions of turbulence like this are always so fascinating. If small scratches and extensions have such an impact, why can't we use it? I mean, why can't we fly a few kites per acre on one side of a hurricane at sea to turn it, or have a computer-controlled mesh of thin wires up- or down-wind of a windmill to increase its output by a significant factor? Wnt (talk) 01:43, 16 July 2013 (UTC)[reply]

So what's happening with a Bullroarer that produces the sound? HiLo48 (talk) 09:13, 16 July 2013 (UTC)[reply]

Bullroarers produce a predominantly humming sound due to the rapid rotation about the long axis as you whirl it round on the end of the string/cord, somewhat like a fan or propellor makes a humming sound. This rapid rotation moves air in pulsations - first towards any point and then away. Bull roarers also produce a bit of shot noise (white noise or "hiss") as does any surface moviing through air, due to the random impact of air molecules on the moving surface. 1.122.182.232 (talk) 13:18, 16 July 2013 (UTC)[reply]

(ec) Lots of things are happening, and I can't pretend to list all of them: but here are some interactions that I would pay attention to. Air is rushing over the surface of the object; the object's motion is constrained by a semi-taut vibrating string whose tension varies with the speed of rotation; vibrations of the object and the air couple to the string. When tension changes, the resonant frequency and the acoustic damping change. If you modify the toy, replacing the shaped peg with something else of equal weight, the tension in the string should be identical; if you whirl it at the same speed, you may observe a change in the tone, timbre, and intensity of the sound. If you change the type of string to some other material - say, from an ordinary string to a guitar string, the sound will be totally different! If you spin an object that resonates at a particular frequency, including a tube-shaped peg, you can produce an almost clean, tonal sound - like a whistle or a flute. If you throw the whirling contraption - even if the peg reaches the same airspeed - does it produce the same "roaring" or whistling sound? Does that sound only happen when the string is taut and the object is rotating? How about if you start by whirling and then release the string, allowing the object to fly at the same speed, under its own inertia? How quickly does it stop "roaring"? How would it sound if you got a friend to drive you down the freeway, and you (safely) held the peg out the window at 65 mph?

This apparatus would be a good candidate for some fun experimental acoustics (to be conducted outdoors). The aspiring scientist could even set up a microphone to record the results. How does the sound frequency and volume change when you whirl at different speeds, or throw the object? Does the rotation rate modulate the tone? (It should, that's the basis of vibrato in the old-fashioned Leslie speaker). Just watch out if you're recording with a "smart"-device to analyze the sound - many smart devices now use digital post-processing to "denoise" and normalize the recording to a constant volume. Experimental physicists need to know everything about their measurement-apparatus, to prevent themselves from drawing erroneous conclusions about their data. Nimur (talk) 13:29, 16 July 2013 (UTC)[reply]

Noisy ladybirds (ladybugs)

I've just read a technical document which described a component making a noise like a ladybird... I just want to make sure that this is as rediculous as I think it is, since I've never heard them make any noise at all. MChesterMC (talk) 14:32, 15 July 2013 (UTC)[reply]

Pretty sure I've heard them [in the UK] make a fluttering sort of buzzing noise when they fly, especially to get off the ground. --Dweller (talk) 14:34, 15 July 2013 (UTC)[reply]

Yep, at liftoff, or if they happen to fly right by your ear, you'll hear a whirring buzzing sound. I'd imagine a loose fan or something could make a similar, if much louder, noise. SemanticMantis (talk) 14:52, 15 July 2013 (UTC)[reply]

This was a suggestion for an indicator noise, and the other examples given were the chirp of a grasshopper or a cricket, so I'm pretty sure the writer was just not thinking about what they were writing. MChesterMC (talk) 15:59, 15 July 2013 (UTC)[reply]

River swelling

What's the physics behind this video: http://www.youtube.com/watch?v=8sEdgHH9F10&feature=youtu.be ? What causes the river to empty and swell like that? 65.92.5.24 (talk) 15:41, 15 July 2013 (UTC)[reply]

It's hard to see quite what's going on without a better understanding of the geography, but when a ship moves in a narrow channel it can produce a soliton wave (a solitary wave of compression and then rarefaction which can retain its identity for a remarkable distance). Although solitons occur in all kinds of circumstances, they were first scientifically described when generated by canal boats. -- Finlay McWalterჷTalk 15:48, 15 July 2013 (UTC)[reply]

Perhaps Bernoulli effect is helpful? (not sure about that) Wnt (talk) 16:02, 15 July 2013 (UTC)[reply]

It's a small tsunami. That article explains the physics. Looie496 (talk) 16:14, 15 July 2013 (UTC)[reply]

Similar waves are sometimes created by tidal conditions called a tidal bore; the Severn Bore in England is a great favourite with surfers and kayakers. Alansplodge (talk) 17:14, 15 July 2013 (UTC)[reply]

A ship that size displaces an enormous amount of water. I calculate that a "Panamax" sized tanker displaces around four million cubic feet of water - and that one looked much bigger than that. As the tanker moves a distance equal to it's own length, four million cubic feet of water has to move out of it's way and somehow travel around the sides and beneath the vessel to fill in the "hole" it leaves behind the stern. Water is essentially incompressible - so it can't compress and decompress around the ship. So at typical tanker speeds of around 20mph (30 feet per second) - a 950 foot long Panamax ship covers it's own length in about 30 seconds, so the water has to flow around it at about 130,000 cubic feet per second! (Imagine filling and then draining, two olympic-sized swimming pools every second!)

When the vessel is close to land and in relatively shallow water, the water flow will be forced through narrow gaps beneath and on the shoreward side - so the speed of flow will greatly increase. It's not surprising then that water will be forced into (and then sucked out of) side-channels and inlets.

I'm not sure whether the Bernoulli effect is likely to kick in to a significant degree...but imagine if the small river in the video is connected to the larger channel with the ship in it somewhere off to the right of the camera. As the ship moved towards the point where it joins the ocean, the pressure ahead of the ship would build up, causing rapid water flow into the river - and as it passes, would cause a dramatic drop in pressure, causing rapid flow out of the river. At the point in time when the direction of flow reverses, you'd expect lots of turbulance and such - which would explain all of those big waves...but I'm not sure that's what's going on because the water level doesn't go up until after the flow direction reverses.

But if the small river connected to the ocean FAR to the left of the camera - then perhaps the initial flow towards the left is just the natural flow of the river and the temporary reversal is due to the pressure wave from the arrival of the ship - but delayed by a minute or two by the time it took for that wave to travel from the mouth of the river. We might expect an abrupt lowering of the water level sometime later as the pressure drops behind the stern of the ship - but maybe we don't see it because the video ends before that would have happened.

Similar arguments are possible if the camera person is standing on an island with the "river" connected to the ocean at both ends and the water was merely reacting to a build up of pressure before and after the ship.

I think that what we see in the video is consistent with any of the three possible connections between river and ocean...but without knowing exactly how the small river connects - it's hard to know for sure.

SteveBaker (talk) 13:58, 16 July 2013 (UTC)[reply]

It's a wake, although the effect in the canal is similar to a tsunami or a tidal bore. Causing a wake like that is illegal in most costal water in the US. It can be avoided by slowing down, although the pilot will not want to. The gentleman should contact his local coast guard or environmental protection agencies. μηδείς (talk) 21:51, 16 July 2013 (UTC)[reply]

This is a small canal (no current) off the St. Clair River in the Great Lakes system. The boat is a 1000-footer. Rmhermen (talk) 02:11, 17 July 2013 (UTC)[reply]

Then it's a matter of international treaty. In New Jersey the ship's action would be illegal, and the owners subject to fine. μηδείς (talk) 02:21, 17 July 2013 (UTC)[reply]

July 16

Carbon emission

I've had no luck at Talk:Greenhouse gas, so I'm reposting the question here: carbon emission redirects to greenhouse gas, but the article doesn't clearly explain what "carbon emissions" mean. It doesn't seem to refer to emission of elemental carbon, but does it encompass emissions of all compounds of carbon, only gaseous compounds of carbon or some other still? — Kpalion^(talk) 14:08, 16 July 2013 (UTC)[reply]

If editors agree on a definition, then the term and the definition can be added to "Glossary of environmental science".

—Wavelength (talk) 14:18, 16 July 2013 (UTC)[reply]

From my Google search of glossary environmental terms, I have checked most of the first 50 results and I have found the following.

http://www.epa.ie/irelandsenvironment/glossary/#C

"In the context of climate change, carbon dioxide released when substances, especially oil, gas, and coal, are burned by vehicles and planes, by factories and by homes."

http://www.bu.edu/sustainability/reference/glossary-of-terms/

"Polluting carbon substances released into atmosphere: carbon dioxide and carbon monoxide produced by motor vehicles and industrial processes and forming pollutants in the atmosphere"

—Wavelength (talk) 14:59, 16 July 2013 (UTC)[reply]

You might wish to consult Wikipedia:List of online reference desks/Science#Ecology (577).

—Wavelength (talk) 15:08, 16 July 2013 (UTC)[reply]

In the context of greenhouse gases, it mainly means CO2 but could also include methane, which is a very potent greenhouse gas but doesn't persist in the atmosphere for very long. Looie496 (talk) 15:11, 16 July 2013 (UTC)[reply]

Yes, "carbon emissions" is a little vague. You'll see it in press releases and such, but not usually in serious science writing (or if it is used, the scope is defined in the same article). I don't have time to check right now, but the authoritative/reliable bodies who might have a standard definition would be the IPCC and/or NOAA, who releases several freely-available white papers and technical documents that one could look into. When I'm at conferences that discuss this sort of thing, they usually present e.g. methane and CO2 (and others) in terms of Carbon_dioxide_equivalents. Basically, "tons of carbon" is not always meaningful, because different compounds have very different global warming potentials, even for the same amount of carbon per molecule. To my knowledge, solid carbon, (i.e. soot) is not ever considered an "emission" for the purposes of climate change studies. Soot particles will actually cool the atmosphere when in aerosol form, and when they settle, they become part of soil carbon (and hence are not emitted to the atmosphere). SemanticMantis (talk) 15:33, 16 July 2013 (UTC)[reply]

Totally off-topic, but I didn't find where to ask!

Some perpetual-motion believer(s) keep reverting Magnetic motor to represent it as aglorious future solution for humanity. What can be done, and how? Zarnivop (talk) 15:49, 16 July 2013 (UTC)[reply]

I have posted the article to the Fringe theories noticeboard, hopefully some editors will take a look at it to make it more neutral. You could also be bold and edit the article yourself! Mildly Mad^T_C 17:36, 16 July 2013 (UTC)[reply]

\i did that, but mt edits were reverted. I do not enjoy edit-wars, and it seems in this case the article should be fixed and locked. Thanks for your help! 109.67.255.233 (talk) 20:36, 16 July 2013 (UTC)[reply]

When on H. sapiens' evolutionary timeline did the equivalent of the hallux ("thumb" on lower limbs) stop being opposable?

20.137.2.50 (talk) 16:43, 16 July 2013 (UTC)[reply]

I think it has not been fully opposable at least since Australopithecus afarensis appeared. Ruslik_Zero 19:15, 16 July 2013 (UTC)[reply]

This article [4] in Science says, regarding Ardipithecus ramidus, that "The foot has a widely abducent hallux, which was not propulsive during terrestrial bipedality. However, it lacks the highly derived tarsometatarsal laxity and inversion in extant African apes." I'll let you decide if that counts as "opposable". SemanticMantis (talk) 19:21, 16 July 2013 (UTC)[reply]

Yes, the transition seems gradual. See the images at the bottom of Australopithecus sediba. μηδείς (talk) 19:33, 16 July 2013 (UTC)[reply]

First embryonic stem cell transplantation in lab rats

I've been looking at the history of embryonic stem cells under the embryonic stem cell page; however it does not specify many of the details of the first transplant in mice which, I assume would have been recorded. Specifically I was wondering whether they transplanted the embryo into one of the two mice who actually parented it; or whether the receiving mouse was completely unrelated to the embryo. Also I am curious how long the scientists waited between the menstrual extraction and the transplantation; and whether prolonged culturing or cryonic freezing was involved in this process. Thank you for your assistance in clarifying this matter. — Preceding unsigned comment added by CensoredScribe (talk • contribs) 20:41, 16 July 2013 (UTC)[reply]

Energy into matter...

Inspired by the 'Why can't I run an electric heater in reverse to cool a room?' question above...

What's standing in the way of us creating a device that could (just for example) gather the energy from sunlight and convert it into gold? Per Einstein, this should theoretically be possible, correct? Matter can be converted into energy and energy can be converted into matter? --Kurt Shaped Box (talk) 21:14, 16 July 2013 (UTC)[reply]

"What's standing in the way"? Entropy !--Aspro (talk) 21:28, 16 July 2013 (UTC)[reply]

Well you can collect sunlight and turn it into useful energy in the form of electricity see solar electricity. The next stage of making matter or antimatter can be done in particle accelerators. But note these are very expensive and inefficient. Actually producing gold will need you to assemble protons and neutrons into a nucleus. There is a high level of electric charge in the nucleus that repels other protons, and the nucleus is very small, so it makes it hard to fuse your proton into a smaller nucleus. See synthesis of precious metals and nuclear transmutation. Chrysopoeia is the production of gold, but there is not much content in this article. Graeme Bartlett (talk) 21:30, 16 July 2013 (UTC)[reply]

What's standing in the way is the prohibitive cost and extreme inefficiency of such a device. Anyone who can afford to build the device can build a gold mine and get gold much more quickly, at much lower cost. Anyone who can harness huge amounts of solar power can sell it to the grid, instead of using it to produce a few atoms of gold at a time. If gold ever runs out on Earth, mining the asteroids would still be a more economic option. If even the asteroids run out, and humans still haven't colonized other planets, gold would hold the same status as the rare earth elements do today. In other words, the extreme difficulty of obtaining gold would make it useless as a store of value, and nobody would try to obtain gold for economic purposes. --Bowlhover (talk) 23:41, 16 July 2013 (UTC)[reply]

Let's run some numbers on this... E=mc^2, so to get 1kg of gold, you need about (3x10^8)^2 =~ 10^17 J of energy, =3x10^10 kWh. A quick googling shows that electricity in the US is about $0.12 per kWh, so this will cost a bit shy of $4x10^9. The price of 1kg of gold on the open market is about $40,000 a kilogram, so around a hundred thousand times less. And that's befor considering the inefficiencies everyone else has highlighted. MChesterMC (talk) 08:11, 17 July 2013 (UTC)[reply]

Not a thing stands in the way. Why would you want to create such a device? Plasmic Physics (talk) 08:24, 17 July 2013 (UTC)[reply]

Taking the original calculation back to the original 'solar powered' version, it's also worth noting that the mean insolation at the sunniest places on Earth (like the Sahara) is only about 2500 kWh per square meter year—and much less at those places further from the Equator and/or subject to those inconvenient 'cloud' thingies. If you were able to wring every single joule out of every solar photon striking the Earth and apply it to this process with perfect efficiency (it is to laugh), you would still need completely cover 12 square kilometers to get that kilogram of gold in a year. In reality, of course, even the best commercial solar panels are only about 20% efficient at converting sunlight to electricity, so multiply the area required by five. And then note that the nuclear transmutation processes described above will be vastly less energy-efficient than that, since real life isn't always like Star Trek.

Worse still, in 2011, about 2700 tons of gold were mined. At 60 square kilometers per kilogram of gold, that would require 160 million square km of solar panels (all located in the Sahara desert....) The total land surface area of the Earth is only about 149 million square km, much of which is located in less-than-ideal-for-solar-energy locations. TenOfAllTrades(talk) 13:19, 17 July 2013 (UTC)[reply]

July 17

How do people sleep during daylight conditions?

Ny-Ålesund at 79°N claims the world's northernmost hotel, which should be able to locate a sleep mask for their guest. If not, try the airport. DreadRed (talk) 11:13, 17 July 2013 (UTC)[reply]

I brought dark curtains with me, otherwise I would have gone mad! 83.109.151.51 (talk) 09:54, 17 July 2013 (UTC) (Count Iblis posting from his vacation address)[reply]

Maybe this requires more explanation. Are you being forced to sleep during the day and be up at night, or are you maybe posting from very high northern latitudes with a marked lack of darkness? HiLo48 (talk) 10:00, 17 July 2013 (UTC)[reply]

The latter, I'm now at the Northernmost hotel on Earth and they don't have decent curtains. 83.109.151.51 (talk) 10:08, 17 July 2013 (UTC)[reply]

Everybody's different. Whether it's noon or midnight when I'm sleepy, I just close my eyes and fall asleep. But then, I may have already gone around the bend. Clarityfiend (talk) 10:13, 17 July 2013 (UTC)[reply]

After working all night, I find it rather easy. Dismas|^(talk) 10:17, 17 July 2013 (UTC)[reply]

Yes, genuine physical tiredness does it for me. HiLo48 (talk) 10:35, 17 July 2013 (UTC)[reply]

You can get eye masks or maybe improvise a blindfold. --TammyMoet (talk) 11:04, 17 July 2013 (UTC)[reply]

I wonder if the OP was expecting a scientific answer? I sometimes plonk another pillow over my head and if angled correctly can block out most of the light. This also helps to block out barking dogs, screaming children and nagging wives. Sandman1142 (talk) 11:30, 17 July 2013 (UTC)[reply]

Yeah, a pillow works fine for me, too. I used to angle it to avoid near suffocation, but now I'm used to breathing straight through it. Actually handy for drowsiness. And yes, works great for muffling sound, too, especially feather pillows (I plug wet toilet paper in my ears, just to be sure). A bit hot some days, but beats laying awake all night (or day). InedibleHulk (talk) 11:36, July 17, 2013 (UTC)

A sleep mask combined with high-quality earplugs will shut out most of the potential interferences. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:10, 17 July 2013 (UTC)[reply]

The earplug article warns of health risks which is why I prefer a pillow. As it is, I use headphones far too often, which has a related set of prolonged use dangers such as tinnitus and higher risk of infection. At the risk of asking a medical question, does anyone here have similar concerns? Sandman1142 (talk) 12:53, 17 July 2013 (UTC)[reply]

It helps to block out blue light from your field of vision for one hour prior to attempting to sleep to increase your serotonin levels. Plasmic Physics (talk) 13:10, 17 July 2013 (UTC)[reply]

Measuring rate of rotation by the Doppler effect

Follow-up from this question about the cricket revometer, how can the rate of rotation of an object be detected by the Doppler effect? Apparently this has been done for Venus, does it work for smaller objects - for instance the ball in a sports game? ManyQuestionsFewAnswers (talk) 13:31, 17 July 2013 (UTC)[reply]