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January 3

Air quality index and highest takes all

According to Air quality index, most of the AQI systems used by governments uses the "highest value takes all" approach, where out of each weighted pollutant concentration, the worst one is selected as the overall AQI and all other pollutants are ignored.

Is there any governmental/supranational institution that doesn't use this approach? I.e. they factor in the lesser pollutants in their AQI instead of dropping them.731Butai (talk) 12:23, 3 January 2016 (UTC)

There have been a wide variety of academic proposals for combined indices, most of which are unsatisfying in one way or another. As far as I know, the only national organization to adopt an approach that is not winner take all is the Canadian AQHI. On the subnational level, Hong Kong also has an approach that combines components [1]. Dragons flight (talk) 12:56, 3 January 2016 (UTC)

Thank you very much again! You've been an awesome help.

I read through the Hong Kong page([2]), but unfortunately they don't cite any references nor do they clarify exactly how their "Air Quality Health Index" is calculated. Is the Hong Kong AQHI formula the same as the Canadian AQHI formula , which came from this study[3]?731Butai (talk) 13:45, 3 January 2016 (UTC)

That seems to be just a general information page on the general HK government site. Nearly all the links there direct to the main HK government AQHI page, http://www.aqhi.gov.hk. On the main AQHI page, while the "About AQHI" section which is listed under "What's AQHI" tab on the page is somewhat unhelpful [4]; the method for calculation seems to be listed in the FAQ [5] which also listed under the "What's AQHI" tab on the page. There is also a link to the study they used to arrive at the health risk [6]. Nil Einne (talk) 14:31, 3 January 2016 (UTC)

Thank you! Seems like the Hong Kong formula is based on the Canadian one, and has various additions. This is great stuff. 731Butai (talk) 14:51, 3 January 2016 (UTC)

BTW, the HK study mentions some studies and proposals where amongst other things, combined indices were I think developed but appear to be (from what I can tell, and also what the HK report suggests) largely unused like that for the Cape Town "dynamic air pollution prediction system project" and the Provence Alpes Côte d'Azur Aggregate Risk Index. I presume these are some of the academic examples Dragons flight may have been thinking of. Nil Einne (talk) 15:00, 3 January 2016 (UTC)

Manhunt for suspect in recent TA shooting: Were tracking dogs used? If not why not?

I've seen some criticism of the way police handled the search for the suspect in the recent shooting in Tel Aviv. But one thing I did not see was any mention of tracking dogs. Yet the suspect left a bag in the store next door which I suppose would carry his scent. (You can see the relevant surveillance videos on numerous news sites). So I have two questions: 1. Was this a case where tracking dogs can do the job? (Assuming you know something about tracking dogs and/or have got some sources) 2. If this was such a case, have you seen anywhere any discussion of whether dogs were actually used, and if not, why not? The purpose of this question is more to use a real-life case in order to learn something about the capabilities of tracking dogs than anything else. Contact Basemetal here 17:04, 3 January 2016 (UTC)

I could not find any evidence of tracking dogs being used in this case. Maybe they did use them, but could not get new clues, so it was not worth reporting. Maybe they just assume from the beginning that it was useless. I know that it's easier for a dog to track a human in open nature. A crowded city implies many other human scents as background, which appears to be confusing. It is also useless if the human uses any vehicle to escape or a lift. --Scicurious (talk) 01:01, 4 January 2016 (UTC)

Which is more comprehensive regarding exercise problems? The Feynman Lectures on Physics or Course of Theoretical Physics by Landau & Lifshitz?

75.75.42.89 (talk) 21:15, 3 January 2016 (UTC)

Do you mean Feynman's text itself or including the complementary book of exercises (Exercises for The Feynman Lectures on Physics)? Feynman's Lectures have some exercises for beginners, but they are not enough. And there is also the Feynman's Tips on Physics.

Landau and Lifshitz is a series of rather short works and poor on exercises. There are legal free downloads of them available. So, take a look at them. --Scicurious (talk) 23:30, 3 January 2016 (UTC)

Biology

My biology teacher told the class that he could sit in a bowl of water and suck the water up through his anus via "reverse peristatis" to clean his intestines instead of using an enema. Is this remotely plausible? GrailKun (talk) 22:27, 3 January 2016 (UTC)

Ask him to demonstrate Such a technique is used in yoga and is called jala basti (see this). However it seems you have to use a tube (a bit like you use a straw). If your biology teacher says he doesn't have to use a tube he might be bragging although I can't imagine why anyone would want to brag about something like that. Contact Basemetal here 22:35, 3 January 2016 (UTC)

A case of bragging is one possibility. It's not the first time I hear someone bragging about this ability. Apparently this is something you can be proud of. The wiki article is Basti (Panchakarma)--Scicurious (talk) 23:22, 3 January 2016 (UTC)

I think he probably just wanted to reserve a place for his picture in the dictionary, right next to "over-share." - Nunh-huh 06:47, 4 January 2016 (UTC)

Flatulists draw in air through their anus (prior to expelling it for entertainment purposes), so presumably they can suck in water too.--Shantavira|^{feed me} 10:00, 4 January 2016 (UTC)

In yoga this is called sthala basti. In this case you don't use a tube. Even more impressive. Contact Basemetal here 10:58, 4 January 2016 (UTC)

For all I know next week he'll tell you he can suck the chrome off a trailer hitch. You sure he isn't looking for a date? :) Wnt (talk) 16:19, 4 January 2016 (UTC)

Also, it's a total misconception that intestines need to be "cleaned". Vespine (talk) 22:08, 4 January 2016 (UTC)

I will mention that User:Vespine has linked to "colon cleansing" while saying that the need for clearing one's intestines is a misconception. As an IBS sufferer who has had diverticulitis and a resection and hernia surgery as sequelae I can assure the OP that talking to a good gastroenterologist, who might prescribe something, is a better idea than assuming that medical attention is a mistake. See our WP:Disclaimer. μηδείς (talk) 21:50, 5 January 2016 (UTC)

I'm having trouble unpacking your comment, I certainly wasn't trying to suggest that medical attention is a mistake. I was refering to the failry common misconception that typical people without diagnosable medical conditions need to regularly "clean" their bowles or intestines, or that there is some "benefit" to doing it. Vespine (talk) 23:45, 5 January 2016 (UTC)

I am loathe to offer medical advice, my point was to specify that there are medically valid reasons why some people do need to use purgatives under medical supervision; it's not all hoakum. But basically I think that the phenomenon you are referring to, Vespine, is indeed a pseudo-scientific fad. μηδείς (talk) 03:50, 6 January 2016 (UTC)

Mercury bubble time-of-use meter

I can't find it in the archives, but within the past few months I remember a question about the identity of an electronic component consisting of a small mercury-filled tube with a visual gap in the mercury. While searching for somethign else, I came across our Mercury coulometer article, which does not appear to be linked from the ref-desks. If anyone is still interested in this topic, there's the article. DMacks (talk) 22:29, 3 January 2016 (UTC)

[7] -- Finlay McWalterᚠTalk 22:33, 3 January 2016 (UTC)

Thanks DMacks. I edited that archived section, adding a link to our article. -- ToE 03:13, 4 January 2016 (UTC)

Are you sure it's not a mercury tilt-switch? Those are quite common in all sorts of applications. SteveBaker (talk) 14:20, 4 January 2016 (UTC)

No I remember it too, by "small mercury filled tube", the OP means like that in an old mercury thermometer (the part with the scale). Vespine (talk) 21:59, 4 January 2016 (UTC)

Sharpness of cutting device a physical unit

Is there a physical unit for expressing the sharpness of a knife or it's ability to cut? The article Sharpness is just about a an English port in Gloucestershire and not of much use here. Is the ability to cut just a question of angle and hardness of the blade? --Scicurious (talk) 23:21, 3 January 2016 (UTC)

Lots of many different factors. Here's some:

1) A hard cutting edge.

2) A softer backing material to absorb the force and prevent the cutting edge from cracking (ceramic blades often lack this protection).

3) Thin blade, to reduce drag as it passes through.

4) Weight, to increase the force applied.

5) Length, to allow cutting longer items and get more leverage.

6) Proper care, such as keeping it sharpened and oiled, to prevent rust.

7) A good handle for proper grip.

So, hard to combine all those into a single rating. See Japanese swordsmithing for an example of how many of these factors are maximized. StuRat (talk) 02:07, 4 January 2016 (UTC)

I think most of that list kind of misses the point and specifically, I think the width of the cutting edge is perhaps one of the primary factors to actual "sharpness". Weight, length, care, handle etc are secondary factors to how WELL something can cut perhaps, but not 'sharpness', like a diamond grain is still the HARDEST natural substance, regardless of other factors like how big a scratch it can make, or something. For pure sharpness, you might find Obsidian interesting. In that article it describes the edge as just a few nanometers thick, i suspect if there was a unit for expressing sharpness, it would have been used in this article. Vespine (talk) 03:15, 4 January 2016 (UTC)

And it occurs to me also, just because something is very complex and multifaceted, would do nothing to hinder us making an arbitrary pragmatic scale, such as: "how much force you need to apply to a blade for it to slice through a 10cm cube of ballistic jelly." Not really much different to saying "how much energy it takes to heat up 1 cubic cm of water by 1 Degree". Vespine (talk) 03:21, 4 January 2016 (UTC)

The Japanese used tests just like this. A hair (or was it paper?) dropped on the sword from as close as possible and gets cut with only it's own weight in force is a good sword. They also used things that looked like a reed(?) fasces without the ax about 2 feet wide. Cutting it off in one chop was a sign of sharpness and skill. A rubber band getting cut by the weight of a metal arrowhead without the arrow is a test for deer hunters. Christopher Columbus' men tested sharpness with Indian kid legs and when they got bored they bet on who could cut through a Native American torso with one stroke. Sagittarian Milky Way (talk) 04:19, 4 January 2016 (UTC)

Quite a bit different, actually. For example, how ever much energy it takes to heat 1 cubic cm of water by 1 degree, you can bet it will take twice as much to heat 2 cubic cms, and that the source of the energy won't matter. Not so with a knife cutting through a cube. Also, the optimal angle of attack will vary. For some cutting devices, you push straight into the cube, in others you drag the blade almost parallel to the face, with others in between. The temperature of the blade and cube would also matter, as would how the blade had been sharpened, etc. Testing knives to decide "which is sharpest" would be more like testing cars to see "which is fastest" (where it would depend on track conditions, etc.). StuRat (talk) 04:23, 4 January 2016 (UTC)

You could make a scale as suggested, but I think only for a specific application. I have a friend who is a chef, and his favorite knife of choice is usually a tomato knife as it's better for general purpose cutting than a chef's knife (yes, i was surprised by that), even though it isn't sharp in the way a chef's knife is. So the particular part of the question regarding the ability for a knife to cut must depend on the material you want to cut, and the blade you're going to use, which I think would make it very difficult to specify a definitive unit for sharpness. A bread knife, for example, can easily cut a loaf of bread, and scissors are good for cutting paper, but you couldn't use either any of those tools effectively to perform the other jobs. The 'sharpness' depends entirely on the application. 95.146.213.181 (talk) 05:07, 4 January 2016 (UTC)

You're obviously right in saying that some tasks require a serrated blade, others smooth - and scissors provide a shear force rather than acting as a wedge like a knife. But I don't think that changes the OP's desire to measure sharpness. We're not being asked to measure "cutting power" - which would obviously be unreasonable given the differences in cutting styles. But it doesn't seem unreasonable to ask how narrow the cutting edge is or perhaps what the angle of the wedge close to the cutting edge is...and a handy scale to represent that might be the kind of thing that someone shopping for knives might want to use.

If I was a buyer of knives - it would be nice to know that blade X has a sharpness factor of 5 where blade Y has a sharpness factor of 6 but dulls easily and can only maintain a sharpness of 4 over the longer term.

However, there doesn't seem to be such a scale - so our OP is out of luck here.

SteveBaker (talk) 14:17, 4 January 2016 (UTC)

Microtome might be interesting, and it points out that of course the thinnest blades are only suitable for slicing soft objects so there is a definite difference between sharpness and being able to cut. 14:42, 4 January 2016 (UTC)

This question was asked a a few years ago. ISO 8442.5 is the international standard for kitchen implements. See also this device, a commercial sharpness tester. Tevildo (talk) 17:01, 4 January 2016 (UTC)

Ah yes thanks, should have thought of them - they have standards for everything so you can give a number to how slippery your floor is for instance. They're normally based on some human agreement of what's good for the purpose rather than anything universal you'd find in a physics book. Dmcq (talk) 11:39, 5 January 2016 (UTC)

Interesting enough, the comment mentioning the history behind the ISO standard, and also the testing device was only added about 8 months later [8] [9]. A good reminder that belated additions whether by IPs or whatever, should be welcomed if on topic and not in violation of any editing restriction or general policy. BTW I've now added the unsigned template [10] to help clarify. Nil Einne (talk) 18:24, 6 January 2016 (UTC)

January 4

Medication Dose and Weight

In general, do larger adults need higher doses of medication? For example, does someone who weighs 300 lbs need to take more aspirin than someone who weighs 150 lbs in order to get the same therapeutic benefit? I'm not wanting advice about any specific medication: I've always believed larger adults need more (since the adult dose is always higher than the children's dose), but I've never read anywhere that this is really true, and now I'm curious. OldTimeNESter (talk) 12:04, 4 January 2016 (UTC)

There is no uniform answer. Some drugs, such as fat soluble compounds, do need to be scaled accordingly. Other drugs, such as drugs that bind to blood proteins, often don't need be rescaled or would be adjusted by much less than expected based solely on excess weight. Here is a document giving some examples of dosing guidelines for obese patients for a variety of drugs. [11] Dragons flight (talk) 12:40, 4 January 2016 (UTC)

(EC) Body weight and size can definitely be a factors in determining the optimal dose of medication due to differing pharmacokinetics and possibly other reasons. However the relationship is not simple, for example it will depend on the precise drug. Likewise an obese patient may not require the same increase as someone who's larger but not obese, although pharmacokinetics in obese patients is not always as well studied (but for obvious reasons there's increasing interest). Certain drugs have a relatively high therapeutic index and limited side effects so it may be a certain dose works acceptably well for most adults, particularly if only taken for a short time. With others like anti-coagulants and anaesthesia it's generally more important that the dosage is within a fairly narrow optimal range. Also, size and weight aren't the only factors that may need to be considered. See e.g. [12] [13] [14] [15] [16] [17] [18] [19] for some discussion of these factors with various drugs. Nil Einne (talk) 12:55, 4 January 2016 (UTC)

(EC) Maybe in general, I'd say yes, but it's open to so many caveats. The dose of some medications is prescribed related to the size of a person, but even that is a guideline and the titration needs to be adjusted for the individual until the correct level of medication is reached. A 300lb person may need less of a medication than a 150lb person depending on the medication, the individual physiology, metabolism, general health, etc.

Regarding your point of adult vs child doses, there are many other factors other than body size that affect what is safe or effective, such as the ability for a child's relatively undeveloped internal organs to cope with medication (liver and kidneys spring to mind). Gastrointestinal differences between adults and children are significant when taking oral medication such as the aspirin you've suggested. Children take longer to break down oral medication in the stomach (as they have a lower level of gastric acid) and children younger than 6 months also have slow peristalsis, so the medication is absorbed at a relatively slow rate. I'm guessing that's why medication for children is more often in a liquid form, but I'm certainly not sure of that. Conversely children also have elevated metabolisms so for certain types of medication a child may actually need a higher dosage over time than an adult would. 95.146.213.181 (talk) 13:15, 4 January 2016 (UTC)

Thanks, all. It sounds like it's one of those generalities with so many exceptions that it's unwise to rely on it. OldTimeNESter (talk) 23:43, 4 January 2016 (UTC)

Italian scientific journal

A citation in a paper is given as "G.Vicentini & Omodei, Cim. 27, p204, 1899". Presumably "Cim" is an abbreviation of the title of some Italian scietific journal. What is its full title? 120.145.144.103 (talk) 15:50, 4 January 2016 (UTC)

Perhaps Il Nuovo Cimento. Dragons flight (talk) 16:03, 4 January 2016 (UTC)

Yes, and I think the citation is incorrect. The paper at http://www.sciencedirect.com/science/article/pii/S0031891439907032 gives the citation as G. Vicentini, D. Omodei; Nuovo Cim., 27 (1890), p. 204. Looie496 (talk) 16:19, 4 January 2016 (UTC)

Thanks to you both. Googling Vicentini Omodei Cim revealed nothing relavent, but googling Vicentini Omodei Nuovo Cimento revealed the paper at the top of the list. The poster formerly 120.145.144.103 120.145.26.149 (talk) 01:44, 5 January 2016 (UTC)

Are there dozens of models of computational linguistics?

According to xkcd (more exactly [20]), which is a half-way humorous cartoon but often with a realistic background, there are 12dozens of contradictory models of computational linguistics. Is that just an exaggeration? If not what are the models? Can't you deal with any problem statistically, provided you get enough data and crunching power? --Llaanngg (talk) 16:09, 4 January 2016 (UTC)

The cartoon doesn't say 12, it says "dozens". The reality, I think, is that there are roughly as many models of computational linguistics as there are computational linguists. Looie496 (talk) 16:22, 4 January 2016 (UTC)

OK, dozens not 12. But still, some could be non-contradictory and be grouped together. There is no need to count two slightly different statistical models as two. Otherwise, we get as many models as practitioners in any field. --Llaanngg (talk) 17:39, 4 January 2016 (UTC)

I thought there might be some more information on explainxkcd.com, but there is very little there. AndrewWTaylor (talk) 17:18, 4 January 2016 (UTC)

In the spirit of providing a reliable reference, perhaps some external literary criticism is in order.

That specific comic strip was harshly criticized in one of the early posts on xkcd sucks. The author of xkcd is criticized thusly: "...[H]e's looked to as a bit of an authority in the areas of science; when he says something in the context of science many people will take him at face value. And why not? He has a degree in physics, he's worked in the scientific field; he has experience on his side and many people will trust that experience. As such, he has an intellectual duty to be as straightforward as possible in that regard so as to not accidentally mislead his audience. I'm afraid that many people are going to walk away from this with a misshapen view..."

As much as it may pain readers of xkcd, Randall Munroe is not actually a science and technology expert: he is a professional cartoonist who incorporates themes of science and technology into his comic strip. Most of his readers don't know or notice the numerous technical errors and category errors that appear in the comic.

Strip 114 is a perfect example - which is why it was so called out - because in that work, its author makes a random, non-sequitor claim; munges some technobabble that sounds "nerdy"; and takes an unexpected pot-shot at a fellow cartoonist; and this somehow delights his reader audience, who overwhelmingly perceive the geek-jargon and its non-sequitor conclusion as some form of humor. Meanwhile, educated readers who understand the topic or the references see the strip as "misleading" and "misshapen." This theme occurs so frequently in xkcd that an entire website, xkcdsucks, was set up specifically to call out the strips that partake in this form of non-humor and non-science.

If you're looking for an alternative to Mr. Munroe's very heavily-promoted new book, "Thing Explainer", I would strongly recommend The Way Things Work, by David Macaulay. Macaulay's books are significantly more technically accurate - even when they take artistic license through their characteristic cartoonish flair. In addition to his great artwork, Macaulay's works include some incredible prose and narrative; it's a far shot better than Mr. Munroe's stilted minimalism.

Nimur (talk) 19:35, 4 January 2016 (UTC)

• "Not a science and technology expert" is overstated, I'd say; according to the page Nimur linked, Munroe has a physics degree and has worked in robotics for NASA. That implies at least a certain level of expertise. --76.69.45.64 (talk) 04:28, 5 January 2016 (UTC)

As I understand Nimur's comment above, he ackknowledges Munroe has a science background. But that makes things worse. Munroe managed to be seen as an expert when talking about many fields, however, he's not quite careful when talking about science or technology, and he is not focused on his field. He is seeking more the impact factor than accuracy. According to the sources linked above, xkcd could need a little bit of fact-checking. Denidi (talk) 14:57, 5 January 2016 (UTC)

I'm going to avoid the other aspects, but the mention of Ryan North was obviously a bit of good-natured ribbing. xkcd and Dinosaur Comics each link to the other, and Munroe has guest-written for the latter. --71.119.131.184 (talk) 21:39, 4 January 2016 (UTC)

Macaulay's books appear like a good source for a general view of how stuff works. However, it does not seem to enter into computational linguistics models, although I think it deals with some IT topics. Which literature deals with how language can be computed/modelled/processed? That is, where is the bit about dozens incompatible models refuted. Llaanngg (talk) 00:32, 5 January 2016 (UTC)

Computational linguistics from Plato, the Stanford Encyclopedia of Philosophy, reviews the foundations of the discipline and provides a good overview, including a literature survey. Nimur (talk) 01:14, 5 January 2016 (UTC)

Reservoirs are pernicious

In 1837, the Ohio House of Representatives debated expanding a natural lake to form a canal reservoir, and a related document (published on page 390 of the House's journal for that year) concluded by saying:

It may be further observed, that while reservoirs may, to some extent, be pernicious to the health of the adjacent country, yet, in this instance as there would be but little, if any, additional ground covered by converting this lake into a reservoir, there could be no consistent objection made to this arrangement.

Is this referring to the reservoir's potential to produce additional miasma, or are they talking about something else? The idea struck me as rather odd, and if it's not miasma-related, I don't know what to think. Nyttend (talk) 22:26, 4 January 2016 (UTC)

Were they perhaps concerned about Water stagnation? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:58, 4 January 2016 (UTC)

Map of the United States showing the distribution of deaths from malaria. Census of 1880.

Yes, almost certainly a reference to miasma/malaria, see History of malaria. I know it wasn't eradicated from NYC until last century. μηδείς (talk) 03:44, 6 January 2016 (UTC)

Agreed, but it was probably larger than just that. It was only relatively recently that wetland was understood to be important in any context. Nearly two hundred years ago, a marsh would have just been seen as wasted land that could have been used for farming or forestry or something. But, yeah, malaria was probably the response they would have given. Matt Deres (talk) 17:30, 6 January 2016 (UTC)

Here's a rather fortuitously relevant source: http://mentalfloss.com/article/73002/fascinatingly-filthy-how-bad-science-saved-lives-victorian-london μηδείς (talk) 21:24, 6 January 2016 (UTC)

Ground glass joints with 2.5 bar pressure relief valve?

I have some pretty thick glassware that I am pretty sure will withstand 2.5 atm of internal pressure (one is a sturdy Erlenmeyer flask used for vacuum filtration). I am trying to use this instead of more expensive pressure reactors because I don't really want to pay for a reactor that can withstand 60 bar of pressure (I am not hydrogenating anything -- my sole purpose is to run reactions in dichloromethane at a higher temperature, like 2.5 atm / 70C. 1 atm / 40C is too low) .

I have thought about purchasing made-in-China metal bombs with a pressure capacity of 60 bar, but I wouldn't be able to monitor the reaction, I wouldn't be able to use a magnetic stirbar (I am doing a DCM/water phase transfer catalysis reaction) and I really wouldn't want my reaction to run at 60 bar -- dichloromethane would boil at over 220-250 C (it's off the chart!) and it would basically destroy my sensitive intermediates and products. Or maybe I could use a metal bomb (which are still expensive) with a 2.5 bar pressure relief valve?

if I use a ground glass stopper with silicone grease -- how much pressure would build up inside my Erlenmeyer flask? I have tried looking for ground-glass-to-pressure-relief-valve attachments but I don't think I'm searching correctly. Any insights or possible hacks? Yanping Nora Soong (talk) 22:47, 4 January 2016 (UTC)

Would putting a metal pressure reactor in a water bath be a good moderating idea in place of a customized pressure relief valve? 100C is okay....220 C is way too much. Yanping Nora Soong (talk) 22:53, 4 January 2016 (UTC)

Once again,we do not do your hmework for you (see the guidelines at the top of the page), and Wikipedia is not a how-to WP:NOTHOWTO,so could you please explain why you are asking such questions? We can help with homework to a certain extent, but if you need professional advice you should be seeking elsewhere. μηδείς (talk) 04:04, 5 January 2016 (UTC)

Please seek expert advice, this can be very hazardous if you get it wrong. Don't trust strangers on the internet. I'm assuming there are people in your institute that can advise on this. (Also, obviously not homework, so just ignore Medeis). Fgf10 (talk) 09:46, 5 January 2016 (UTC)

Yeah, don't trust us - these desks are not rated for giving advice, only trying to share references to technical data. But if I were going to give advice I'd advise that if you're not trained in high pressure chemistry, don't mess with it. There's a reason we never learned this in our undergrad chemistry classes! It's inadvisable to try to build a pressure cooker bomb with the intent of setting it off at a distance, let alone with the hope and indeed urgent need that it not go off or else while you stand nearby monitoring the reaction! Surely you should be able to replace the solvent, or add something to it. This file I found on Google makes some suggestions like dibasic esters that have similar solvent properties and aren't so toxic, and might have higher BP also. I expect one of the local experts can provide more ideas. Wnt (talk) 15:59, 5 January 2016 (UTC)

One important detail you seem to be just starting to recognize: you don't have to run a reaction at the bp of the solvent at your chosen pressure-limit, that's just the maximum temperature you can use. A double boiler isn't exactly essoteric equipment, it's trivial to thermostat an oil bath or laboratory water bath to pretty much any temperature you like. DMacks (talk) 16:06, 5 January 2016 (UTC)

As an experienced laboratory chemist, I can't emphasize enough that you should not perform an experiment that will raise the pressure in a sealed flask that is not specifically designed to handle that pressure. Consider other options such as using a higher boiling solvent such as 1,2-DCE in place of dichloromethane. I will also reiterate the concerns expressed above that you should not be asking for technical advice that has laboratory safety ramifications on a forum such as this. -- Ed (Edgar181) 17:02, 5 January 2016 (UTC)

Why do people think I keep asking homework questions? Also, replacing the dichloromethane is not an option -- dichloromethane is a reagent in the reaction. I'm using a two-phase reaction involving tetrabutylammonium bromide as a phase transfer catalyst. I cannot afford to use methylene bromide or methylene iodide. Yanping Nora Soong (talk) 19:01, 5 January 2016 (UTC)

ACE glass flasks and glass reactors designed to withstand high vacuum should be able to tolerate 2.5 atm of internal pressure yes? (That's around 36 psi). I'll probably buy an ACE glass pressure tube, but the pressures they're designed to handle are 150 psi (10 atm) and have been pressure-tested to withstand 15 atm. I guess if I ever intend to run reactions at a higher pressure I'll have a backup. They're sooo long though (20 cm) -- do they have to be completely immersed in solvent? Yanping Nora Soong (talk) 19:08, 5 January 2016 (UTC)

You should know better! It's one thing to withstand pressure, another to withstand vacuum. It's simply a different direction of force. Compare compressive strength and tensile strength. And vacuum never gets more than 1 atm away from 1 atm, while you're proposing a 1.5 atm pressure! There's no way anybody can tell you to try that, except as an experiment to see if it blows up (at a safe distance). Is what you're attempting something so proprietary and valuable that you can't just ask the chemists here or at university how to do it right? Wnt (talk) 19:23, 5 January 2016 (UTC)

At this point, I should point out some other obvious things I didn't think could be an issue, just so we're clear. To start with, I've been assuming that you were working in a fume hood with at least a sturdy raising sash, but now I don't know if you're taking even that precaution. I'm assuming you would not be boiling dichloromethane in a residential space, even if you don't explode a flask full of it all at once. I'm also assuming that this isn't some Alexei Shulgin recipe that would expose you to prosecution just for getting the reagents together for, as this is not exactly a discreet or private space for conversation and your purchasing records are very rarely confidential. Heck, in the U.S. they've prosecuted people on serious felony charges just for having a three necked round bottom flask and a meth recipe! I do not want to end up reading that an apartment building full of people was evacuated to hospital after toxic vapors poisoned them after someone asked how to make drugs on the Wikipedia reference desk. Are we clear? Wnt (talk) 19:53, 5 January 2016 (UTC)

Minor factual correction - I think you mean Alexander Shulgin, not Alexi. Tevildo (talk) 20:18, 5 January 2016 (UTC)

the reaction scheme is entirely of my own design, assembled from literature reactions, using amino acids as feedstock. I'm not making anything illegal or formally scheduled: I just have really bad treatment-resistant complex PTSD, rape trauma syndrome, and intense depression (which I didn't want to mention because I didn't want medical advice) and am making a promising NMDA receptor partial agonist that has been through a few phase I clinical trials. My psychiatrist can only prescribe me on-market meds tho. Also, most of my reactions are pretty mild, except for the reaction involving DCM. No poisonous gases, nothing really toxic etc. Tho I have to figure out where to dispose my phase transfer catalyst (it's a quat). Yanping Nora Soong (talk) 22:22, 5 January 2016 (UTC)

... this is now bordering on medical advice, and we don't give that. Even if you are asking only for scientific advice, our best recommendation, on safety grounds, has to be don't try this at home. Dbfirs 22:25, 5 January 2016 (UTC)

I worked in chemistry research for three years. I dropped out of my program due to depression and PTSD. I can't see how this is more dangerous than deep frying or working at a nail salon. As a first year researcher I would get mildly inebriated simply from cleaning up acetone and diethyl ether spills in the lab. I got pressure tube rated at 150 psi so now I don't have to worry, I guess. Yanping Nora Soong (talk) 22:39, 5 January 2016 (UTC)

We are glad to hear that you are not taking unnecessary risks. Exploding glass in your kitchen would be more dangerous than acetone. Dbfirs 23:36, 5 January 2016 (UTC)

Well, since you've told us that much you might as well give us the formula - at least we should scan the literature to see how the authors of that study made it, and see if we can sniff out any ongoing research you might have missed. I think it is instructive for you to work out how to do this synthesis, but not necessarily to do it, definitely not to use it. I cannot overemphasize how much we should not recommend you taking your experimental substance - even though you're not trying to make drugs, you're making something to take by a new experimental route, which is just as dangerous. Ever hear of MPTP? The inventors deserved some kind of medal for the advance of biological science, but I don't think they had a chance to collect! Do you have a way to characterize this substance, check all impurities? I doubt one acid-base extraction and a crystallization is going to cut it. Wnt (talk) 01:30, 6 January 2016 (UTC)

Also, while I don't know your situation ... it seems like a more straightforward solution is to stick with more reliable treatments while you see if you can get reinstatement or get transfer credit to continue your research training. If you want to try something unconventional, well, you surely know medical marijuana has some partial agonist activity on glutamate receptors and is pretty well known for its use for PTSD. You don't have to use yourself for a science experiment. Wnt (talk) 01:54, 6 January 2016 (UTC)

The more I think about this, the more I don't like it. A 150 psi pressure tube doesn't mean you "don't have to worry" - the higher the psi rating, the bigger the boom when your system explodes. Do you have a gauge to watch what the pressure is? With an experimental synthesis, you can't know for sure that it won't do something unexpected and produce a gas, so if you're just using a thermometer and expecting the pressure will be X based on a curve for methylene chloride, you could get a big surprise. Between pressure, fumes, fire, toxic impurities, and the very dubious safety of an experimental drug itself, there are a lot of ways to die here. This kind of drug development isn't generally done by people who can't afford methylene bromide - people ask for millions of dollars in taxpayer money, or spend exorbitant sums on venture capital, for a reason. Wnt (talk) 13:24, 6 January 2016 (UTC)

This is easy to say for someone without mental health issues or PTSD. Do you feel like dying at 1 am every night? Do you get panic attacks and flashbacks so bad you dissociate and lose sense of place and time? Yeah, it's risky, but much less risky than on-market treatments that don't work. Do you have a mental health issue so debilitating that your friends don't understand and keep asking you, "Why do you keep doing sex work when you're so smart?" Successfully treating my PTSD is my gateway out of prostitution and back into scientific research, so yeah. I would buy the experimental product on molport if I could, just that vendors are charging hundreds of dollars to make 500 mg. looool

Also according to the vapor pressure curve of DCM, you need a temperature of 120C to achieve an equilibrium vapor pressure of (150 psi / 8000 mm Hg). I'm pretty sure that it would be hard to exceed that even with a boiling water bath. Yanping Nora Soong (talk) 19:47, 6 January 2016 (UTC)

I feel terrible to hear that, but there are a lot of different kinds of psychological treatment. I cannot believe that a trained professional doesn't have as much a chance of coming up with some treatment that is more likely to be effective than a chemistry experiment. There are lots of things already known that affect glutamate receptors - why do you think this one is the one and only option? It isn't always healthy to mix scientific curiosity and other motivations - what are you going to do if you get a product, and it's 72% pure, and you don't know what the rest is? And you missed my point above: you can't go by the curve for DCM, because you have no way of knowing for sure that when you use the synthesis route you devised yourself, that you haven't even had us comment on, that it's not going to liberate ammonia or carbon dioxide or something in sufficient quantity to raise the pressure? Also, if you won't give the experts a chance, well, this is kind of a wacky idea, but I'm thinking as you're in New York you're close to the last remnants of the Yippies - the narks and the bankers may have moved in on Dana Beal and sacked Bleecker Street, but he still circulates around. [21] I bet that guy could recommend you twenty people in bad graces with the APA, who can recommend things none of us have ever heard of. Wnt (talk) 20:25, 6 January 2016 (UTC)

January 5

Fighting fire with fire

When fighting fire with fire, how do they know the right time to ignite the backburn? 2601:646:8E01:9089:5D45:D5AF:855B:E677 (talk) 01:16, 5 January 2016 (UTC)

Not a subject expert, but I believe the primary issue in when to ignite controlled burns is the weather. The wind needs to be blowing the right way, towards the main fire, and to be reliable: no sudden changes in wind speed or direction. Aside from that I don't think there's a specific time when it's "right" to start the fire (besides "before the main fire is on top of you" I suppose). The basic idea is to burn fuel with a fire that goes towards the fire you're fighting. Then there's nothing left to burn, and the "bad" fire ideally just dies. --71.119.131.184 (talk) 01:52, 5 January 2016 (UTC)

There's the aspect of burning the fuel before the main fire arrives, but there's also an effect of changing the direction the air is flowing. Firestorm discusses cases where fires change air flow patterns. So, in this case the timing would be more critical, since the wind direction can only be changed while the fire is actually burning. StuRat (talk) 02:32, 5 January 2016 (UTC)

My only knowledge of this is from seeing it done on television and I can't see anything online that describes it too well so I'll describe what I've seen from memory. As a fire burns it consumes oxygen and, in the case of large fires, they consume massive amounts. As the fire advances it sucks in the air all around it creating a vortex and the base of the vortex extends well in front of it. The firefighters stand in front of the advancing firewall and wait until they feel the air around them being pulled in towards the fire - which becomes pretty obvious as it creates an increasing rush of wind. At that point they light the fuel (forest litter, saplings, branches etc.), retire quickly and hope that the consumption of all available fuel leaves the fire with nothing to burn and nowhere to go. Needless to say, it's very dangerous, it's only used as a last resort, and it can make things worse.[22],[23] Richerman (talk) 11:18, 5 January 2016 (UTC)

Perhaps the best place to start reading is: the United States Forest Service webpage, Managing Wildfires. Also note that some states - like California - have massive state-level organizations (e.g., CalFIRE), and though there is much cooperation, these different organizations sometimes follow different rules and strategic policies for fire management.

Federally organized wildfire fighters use backburning, including drip torch crews. For prescribed fires - those that are set intentionally for land management - a specialist who is an expert in forestry management writes up an environmental assessment, and a bunch of paperwork process is required to make sure that the burn will be safe and legal. At a high level, this process is explained in the Guidance for Implementation of Federal Wildland Fire Management Policy document.

Here are a few great resources published by our Forest Service:

• What the blazes is a prescribed fire?
• Fire Management Today - a free periodical publication: each issue contains case-studies, technology and science reviews, and the latest and greatest news on federal wildfire management
  • The current issue has a whole exposé on using smart-phone apps and other technology for data fusion to combine weather, aerial firefighter reports and photos, and ground crew information, to make better on-the-spot decisions
• Training Resources - linking to several short courses, training facilities, and other resources to help promote good fire-fighting policies
• Interagency Prescribed Fire Planning and Procedures Guide, a detailed technical guide from the National Wildfire Coordinating Group that explains how to plan and implement a wildland fire by intentional ignition

Forestry is a big deal, and it's very scientific: you can get an advanced scientific degree in forest management, economics, ecology, and industrial applications. Proper management of natural resources is very important, for ecological and economic reasons; this discipline has therefore developed very rigorous techniques and theory. For example, here is information from the Forest Management program at my alma mater.

Nimur (talk) 15:46, 5 January 2016 (UTC)

Thanks, everyone! So from what you told me, when the wind shifts toward the main fire is the right time to break out the driptorch? (BTW, I'm NOT planning to do any controlled burning on my property or elsewhere -- only highly-trained firefighters are allowed to do it because it's so dangerous, that much I know.) 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 05:36, 7 January 2016 (UTC)

Where can I find a map of average daily temperature range in the US?

I can't seem to find one. Average seasonal range is easy to find but not average range between a day's high and low. Sagittarian Milky Way (talk) 01:30, 5 January 2016 (UTC)

At yr.no, you can get graphs of average high and low temperatures per month for a specific place, such as Washington D.C.. The data the graphs are based on is fairly old, though, and probably available elsewere as well. --NorwegianBlue ^talk 07:07, 5 January 2016 (UTC)

That would be a lot of work to make even a rudimentary map yourself. I wonder if there's one already made where it shows average daily range. For instance, the average daily range where I live is around 15°F, it should be more where there's more continentality and/or aridity (when I saw one of those charts for Montana I was like holy crap, it's 90°F in the day and 50°F at night). Sagittarian Milky Way (talk) 07:26, 5 January 2016 (UTC)

Average Daily Temperature Range

Seasonal Temperature Range for mean temperature

Annual Average Temperature Map

Occasionally, just occasionally, someone will ask a question like this and get really awesome results. I created the three images at right about two years ago in my professional capacity as Lead Scientist for Berkeley Earth. I've now arranged to release these images under CC-BY. The first image shows the average diurnal temperature range and should answer your question. Note that diurnal range also has a strongly seasonal component, and these are the annual averages. The second image is a similar map for seasonal temperature range since you also mentioned that. (Siberia is a hard place to live, though actually not so bad in the summer.) The last map shows the annual average temperature. For the record, I haven't added these images to any articles, so if someone can find some suitable page(s) to add these materials it would be appreciated. Dragons flight (talk) 10:56, 5 January 2016 (UTC)

That's very neat, thanks. I put them in a new article continentality cause I didn't want to mess with the important and image-filled climate, climatology and temperature articles. Others are welcome to think of other articles or see if they want to mess with those three. Sagittarian Milky Way (talk) 18:08, 5 January 2016 (UTC)

And the article was redirected back to humid continental climate. It wasn't very good but maybe continentality should redirect to continental climate instead? Humid continental is not very accurate as most of Alaska and Siberia is very continental (Verkhoyansk! 99°F to -90°F) but classified as subarctic climate. Sagittarian Milky Way (talk) 22:33, 5 January 2016 (UTC)

Great images. What are those two odd spots of large temperature differences in Poland on the first map? Mountainous regions? Fgf10 (talk) 12:08, 5 January 2016 (UTC)

No, not mountains. Basically I don't know. It is an odd enough blip that when I originally made this map I did go back and double check that this quirk was really in the input data, but nothing there looked crazy. I don't think it is an error or bad data (though I wouldn't totally rule that out either). If it isn't an error, my guess would be more variable local weather, but I don't have any really convincing explanation for a weather pattern like that either. Dragons flight (talk) 12:31, 5 January 2016 (UTC)

How interesting! Fair enough, cheers for the reply. Fgf10 (talk) 14:54, 5 January 2016 (UTC)

Maybe somebody forgot Poland. --71.119.131.184 (talk) 16:50, 5 January 2016 (UTC)

Those dots on Poland are interesting. I think the southern one might be the Błędów Desert, a man-made region of barren sand around a medieval silver mine, which our article on Poland describes as the country's "only desert". My guess is there's another man-made feature that hasn't been properly credited. Though I should also note that the area of high temperature extremes is bigger than the feature as marked on the map. Apparently it had been spreading, though recent efforts partially reversed this. Come back in a thousand years and I suppose much of Europe may be a double for the Australian outback... Wnt (talk) 18:59, 5 January 2016 (UTC)

The file pages say that it's extrapolated from weather stations so if the closest stations to the Błędów Desert one(s) are far away that could make it look very big. Sagittarian Milky Way (talk) 22:33, 5 January 2016 (UTC)

What's with the average daily temperature range in Antarctica ?

(Top chart.) There seems to be very little change for the most part, but one spot has quite a lot. Why is that ? StuRat (talk)

How many viable human DNA combinations are there?

Calculations that I found regarding DNA permutations seem to consider all combinations. However, many of these are obviously not viable humans. What is the total number of DNA combination minus the total number of combinations that would produce deeply disable, brain-dead or dead humans?--Scicurious (talk) 16:55, 5 January 2016 (UTC)

I doubt this is a question that can be answered (currently), given that we do not know gene expression or even protein folding into usable shapes well enough or fast enough to make such a determination. We're still figuring out even basics of expression such as epigenetics. --OuroborosCobra (talk) 17:00, 5 January 2016 (UTC)

Seconded. However, I will say that the vast majority (probably 99.9999%+) won't be viable. There are many proteins that are absolutely required for life, and it may only take a single base pair change for those to be dysfunctional. A random scramble will almost always result in something lethal. Fgf10 (talk) 17:49, 5 January 2016 (UTC)

I agree that the number in incalculable, but would argue that the nonviable mutation rate would not approach 100%. There are vast stretches of DNA in which most mutations would be neutral. Even for critical genes, there are databases full of variant genes (e.g. Online Mendelian Inheritance in Man), not all associated with a disease state. There is a bias towards the presence of a disease state in the databases, since health issues are the likely reason a search was initiated. The number of possible viable mutations and the total number are possible mutations are so vast that ratios are difficult to calculate, especially given that the probabilities have to be weighted since not all mutations are equally probable. additional reading BiologicalMe (talk) 18:31, 5 January 2016 (UTC)

Ignore User:Fgf10. The answer is potentially infinite, given non-coding junk DNA. μηδείς (talk) 21:09, 6 January 2016 (UTC)

Well, in a way it's all academic, since we can't calculate it. However, in your example, OMID mutations are those found in living humans. Therefore you can automatically say none of the mutations that would cause embryonic lethality are in there. In other words, the most lethal mutations will not be in that database. Furthermore, all those mutations are changes to an established, viable genome. If you were to generate a de novo genome randomly, what would be the changes you get even one working promoter for instance? For a viable human, you don't need one correct sequence, you need thousands. Fgf10 (talk) 18:43, 5 January 2016 (UTC)

Although as the previous responses have pointed out it is impossible to calculate precisely, I think we can safely say that there is a practically unlimited number of possibilites for a viable human genome. Even if just 0.0001 % of the 3 billion+ base pairs can be changed arbitrarily without effecting viability, you get over 10^1800 possible combinations, vastly more than can be realized in the lifetime of a billion universes. - Lindert (talk) 11:33, 6 January 2016 (UTC)

I agree - the answer is definitely "enough". Enough to make it astronomically unlikely that no two humans will ever (by chance alone) have identical DNA for as long as humanity can survive. But putting a number to it is an exceedingly complicated question who's answer lies far beyond what we currently know. SteveBaker (talk) 17:50, 6 January 2016 (UTC)

Lol, independent variables. You know there's an exception. :) Wnt (talk) 20:38, 6 January 2016 (UTC)

radio-activity

Is it possible for big storages of fissionable material with high ratios of released-binding-energy-expected per unit volume, to release subatomic reaction energy spontaneously causing unintended destruction ? :-) Thank you — Preceding unsigned comment added by Vijay Chary (talk • contribs) 18:33, 5 January 2016‎ (UTC)

I think the answer to your question is "no". Now, many fissile elements are radioactive, so they give off energy through radioactive decay, which can include spontaneous fission. This is why particularly radioactive materials need to be handled carefully. But, you're not going to get a nuclear chain reaction unless you do stupid things with large quantities of material (in which case you may get a criticality accident). Generating a self-sustained nuclear reaction, which you need for nuclear power or nuclear weapons, is actually difficult; a lot of people have this misconception that a nuclear reactor can explode like a nuclear bomb, but this is wrong. The problems with nuclear waste storage revolve around safely storing it while it decays. It would cause "unintended destruction" if not stored properly, but through radiation poisoning, not a big kaboom. --71.119.131.184 (talk) 20:14, 5 January 2016 (UTC)

A nuclear reactor can explode like a regular bomb, though. Sagittarian Milky Way (talk) 22:37, 5 January 2016 (UTC)

I don't know if the bit " a lot of people have this misconception that a nuclear reactor can explode like a nuclear bomb" is accurate. Of course, this depends on your definition of "a lot", but I would be shocked if this is true when "a lot " means "most people." On the other hand, people believe all sort of crazy stuff and one conspiracy theorists or the other would be delighted to scare people. Denidi (talk) 01:17, 6 January 2016 (UTC)

The movie Aliens might have contibuted to this misconception, since the nuclear reactor in that movie did indeed undergo a nuclear explosion once it lost coolant. I wonder if there is any way one could, if foolish enough to do so, design a nuclear reactor where this was actually possible. StuRat (talk) 05:42, 6 January 2016 (UTC)

Don't they have military-only designs that use weapons-grade fuel? I'm not up on nuclear physics but 1. It'd be really stupid to design it to go supercritical if the rods were pulled out fully. 2. It's not easy to make a nuclear bomb not fizzle if you've never made one before so unless the containment dome does something wonderful in extending the percent that fissions before it blows itself apart it might not be able to reach a traditional atomic bomb size (14-20 kilotons or so). Maybe you could keep tons of bomb-grade fuel subcritical with enough control rods so if you did a really stupid design like control rods that fall completely out of the fuel at the speed of gravity if the positioning electromagnets fail then maybe you could get another Hiroshima. Sagittarian Milky Way (talk) 16:22, 6 January 2016 (UTC)

I seem to recall an almost-as-stupid design where, while the control rods themselves would retard the reaction, the steel tips on the end had the reverse effect, by reflecting particles back into the core when first inserted. Thus, if you inserted lots of rods all at once, you could create a runaway reaction. I think it just caused a conventional explosion, though.

I suppose you could also get a rogue nation, like Iran, building a nuclear reactor designed to generate a nuclear explosion, if attacked, to discourage anyone from attacking (whether due to fallout concerns or the political consequences of causing it). StuRat (talk) 21:19, 6 January 2016 (UTC)

That was the RBMK reactor used at Chernobyl among other places, except it was graphite, not steel. And yes, it was stupid; the RBMK reactor is a fairly unsafe design built with the first priority being cheap and quick production of plutonium for nuclear weapons, with power generation as a side effect. After the Chernobyl accident they retrofitted the reactors to remove some of the more dangerous parts of the design, including that. --71.119.131.184 (talk) 21:45, 6 January 2016 (UTC)

"A lot" doesn't inherently mean "most", i.e. "a majority". It can just as easily mean a significant minority. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:49, 6 January 2016 (UTC)

Look at Fissile material for the difference between fissile and fissionable. Also, check out Natural nuclear fission reactor about a prehistoric natural reactor in Gabon about 2 billion years ago, which was similar to your question. Tobyc75 (talk) 20:24, 6 January 2016 (UTC)

This is an exercise in semantics, really. A fizzle yield is not exactly a bomb, but it can separate enough hydrogen to blow up a containment building, and once the fallout is on the way you don't want to be there. Any storage pond of high level radioactive waste is just waiting for the power to go out, the diesel generators to fail, and they start catching on fire and producing a terrible mess. So call it a really poorly made, really dirty nuclear bomb, and you're at least technically right. Wnt (talk) 20:33, 6 January 2016 (UTC)

anthropology

If some members of anthropoid 'herds' evolved into proto-humanoid 'tribes', why does the community of anthropologists claim that this actually occurred in south afrika ?  :-) — Preceding unsigned comment added by Vijay Chary (talk • contribs) 18:33, 5 January 2016‎ (UTC)

I took the liberty of splitting your questions into different sections. Anyway, the generally-accepted view that modern humans arose in Africa is known as the Out-of-Africa theory; that article may be informative. There's a lot of evidence for this. I'm not quite sure what you're asking exactly. Our recent (on evolutionary time scales) ancestors were not herd animals; "herd" has a specific meaning in biology and zoology. Primates, including humans, are generally tribal, living in tribes of between a handful to a few hundred individuals. Humans are believed to have lived similarly before the advent of agriculture. (Dunbar's number might be of some interest.) Also, modern humans are believed to have arisen more in East Africa than farther south, though you might be using "South Africa" to refer to all of Sub-Saharan Africa. --71.119.131.184 (talk) 20:14, 5 January 2016 (UTC)

Addressing a couple of possible misunderstandings suggested by the OP's wording . . . .

A member (i.e. an individual) never evolves into anything. Evolution happens to populations of many individuals over numbers of generations, whereby the carriers of some alleles ('versions') of genes die before reproducing more often, while carriers of other alleles of those genes die before reproducing less often, resulting in a descendant population with different proportions of the differing alleles (in some cases, the proportion might be zero). Accumulations of such allele differences may eventually give rise to noticeable physiological differences.

Very occasionally, more major changes (such as a doubling of a whole gene, a whole chromosome, or even a whole genome) may occur which give rise to noticeable differences immediately, and also result in "surplus" genes that can mutate to take up new functions, which might be beneficial, because the original copies of the gene(s) is/are still carrying out its/their original functions.

The reason most (though not all) anthropologists think human (or better, hominin) evolution probably took place in East and/or South Africa is because that's where we've found most of the oldest fossils of likely ancestors or near-ancestors of our particular human/hominin species, Homo sapiens sapiens. This however depends in part on where conditions favourable to preserving and finding fossils exist (fossilisation is a very rare event), and where we've looked so far: more discoveries elsewhere could, and might, modify those presumptions, because that's how Science 'works'. {The Poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 21:29, 5 January 2016 (UTC)

I disagree with your final statement, that might have been true 100 years ago, but since genetic studies over the last 30 years I don't believe fossils are the reason, or even the main reason why most anthropologists accept the Recent_African_origin_of_modern_humans model. Our article has some good info about the evidence. Vespine (talk) 00:19, 6 January 2016 (UTC)

I concur, but the OP's "anthropoid to humanoid" wording was ambiguous as to whether he was asking about (or even understood distinctions between) Homo sapiens, earlier Homo spp, and other/earlier hominins, and therefore what time frame he was taking about. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 12:47, 6 January 2016 (UTC)

Elements past period 7

With the seventh period of the Periodic Table filled in, is it going to take a massive additional effort to get period 8 elements? Bubba73 ^{You talkin' to me?} 20:28, 5 January 2016 (UTC)

I don't know who the best person to ask is. For anyone answering this question, please try to focus primarily on ununennium (element 119) and unbinilium (element 120) and not too much about elements 121 and up. Georgia guy (talk) 20:39, 5 January 2016 (UTC)

Attempts at those two is noted in our ununennium and unbinilium articles. Extended periodic table is our larger-perspective article on "beyond period 7" possible stability details, etc. DMacks (talk) 20:45, 5 January 2016 (UTC)

To get 119 and 120? No. To get anything above that? Yes. Double sharp (talk) 15:30, 6 January 2016 (UTC)

January 6

Homocysteine elevated

Recommendations for reducing levels of homocysteine

Presuming that you mean in humans, is what you're looking for covered in the Hyperhomocysteinemia article? Cannolis (talk) 02:17, 6 January 2016 (UTC)

Isn't that medical advice? It is impossible to know if a person is taking enough nutrients without a homocysteine blood test. So, go ask a doctor if you need on. --Denidi (talk) 16:41, 6 January 2016 (UTC)

It's not medical advice when you're giving a general indication, rather than prescribing to a specific patient. But in any case, the article above already says so much we'll be hard pressed to think of more (and if we do, we really ought to add it there and just ping here after we do) Wnt (talk) 20:35, 6 January 2016 (UTC)

Destroyer

Hello!

1. What is the difference between an 'atomic' bomb and a 'hydrogen' bomb? What does each do? - simplistically.
2. What is more powerful from the two enquoted above, or is it a 'molecular' destroyer?

Mr. Zoot Cig Bunner (talk) 20:15, 6 January 2016 (UTC)

See atomic bomb, then fission bomb and thermonuclear bomb (a hydrogen fusion bomb being the most common type). The latter is far more powerful, but uses the former to trigger it. A fission bomb is where atoms split apart, releasing energy, and a fusion bomb is where atoms fuse together, releasing energy. It might seem confusing that atoms can release energy either when splitting or joining, but, in general, larger radioactive atoms (like some isotopes of uranium and plutonium) release energy by splitting, while smaller atoms (like isotopes of hydrogen) release energy when fusing.

Not quite sure what you mean by a "molecular destroyer", but any molecule near a nuclear explosion will be destroyed, although no significant additional energy is typically released in that process (with a possible exception for fires that spread). You also might be interested in the theoretical antimatter bomb, which would be on the order of 10 thousands times more powerful yet. StuRat (talk) 20:19, 6 January 2016 (UTC)

Oh, great Stu, you and your gee dee antimatter bomb advocacy. Next you'll have the Romulans destroying Vulcan. μηδείς (talk) 21:06, 6 January 2016 (UTC)

In the Star Trek universe, I would have expected wider use of antimatter bombs, since they used matter/antimatter reactors to power their star ships. Specifically, a warp-capable torpedo could drop out of warp on the target and detonate immediately, with enough power to destroy a planet. But star ships within sight of each other, firing volleys back and forth, seems more exciting, so that's what we got. StuRat (talk) 21:14, 6 January 2016 (UTC)

Standard 24th century photon torpedoes carry 1.5 kg each of matter and antimatter (hydrogen specifically), giving on the order of 64 megaton yield. Do some maths and see what's needed to actually destroy a planet..... 82.8.32.177 (talk) 22:42, 6 January 2016 (UTC)

Well, it shouldn't be a problem to carry 1000x as much, maybe a million times as much. By comparison, a B-52 carried 31,500 kg in bombs, some 20 thousand times as much. StuRat (talk) 22:54, 6 January 2016 (UTC)

A B-52 load of mixed matter/antimatter would have a yield of 2.84x10²¹ J. The Chixalub impact is estimated at 1x10²⁴ J. Still would barely make a dent. 82.8.32.177 (talk) 23:02, 6 January 2016 (UTC)

Then try a million times as much. What was the weight of the Enterprise supposed to be ? Try that much. StuRat (talk) 23:11, 6 January 2016 (UTC)

How tall could an artificial mountains be?

Using just known materials, how high could we pile them (formed like a mountain)? Would that be a less expensive, less risky possibility to go to space? That is, a pile built century after century reaching more than 50 miles high.--Scicurious (talk) 21:23, 6 January 2016 (UTC)

No. The current highest mountains give you an idea for what the limit is. All sorts of things happen to cause that limit. The ground underneath compresses, there is erosion from the top down, there are landslides, etc. And realize that it doesn't just take twice the effort to build a mountain twice as high. It would also be twice the diameter, which means 8 times the volume and mass (not counting compression), and the materials have to be lifted higher, so require more time and energy per block. So, you could well be looking at 16 times the effort to make a mountain twice as high. And the current tallest mountains at 5.5 miles high are nowhere near into space, so you would need to double the height (and increase the effort by 16), many times to get there.

A better approach might be to create a launch tube in an existing mountain, so the ship will leave the top at high speed, not having used any of the onboard fuel yet. StuRat (talk) 21:31, 6 January 2016 (UTC)

Consider Olympus Mons, a mountain the size of France and about three times the height of Mt Everest. Consider how much effort it would take to "build" a mountain of that size and then consider it's still just a "wart" on the surface of mars, you would need a mountain 4 times the height to get to space. Vespine (talk) 21:38, 6 January 2016 (UTC)

And it's only as large as it is due to Mars' reduced surface gravity (0.376 g, or about 3/8ths as much as Earth). StuRat (talk) 21:41, 6 January 2016 (UTC)

The cone building limit is approximately:

${\sigma _{c} \over \rho g}$

where $\sigma _{c}$ is the limit of compressional stress, $\rho$ is the density of the material, and g is the surface gravity. For granite (limit ~200 MPa, density ~3 g/cm³), this works out to about 7 km, which is also about the prominence of the highest mountains. Most materials with better stress limits are also denser so it isn't easy to find materials that can be piled higher. I'm not really sure if any easily available material would allow one to reach 100 km or other extreme height. Dragons flight (talk) 22:05, 6 January 2016 (UTC)

People have seriously thought along the lines of "building a stairway to heaven", though you wouldn't do it by building a mountain. A space elevator is a commonly-discussed idea; see non-rocket spacelaunch for others. --71.119.131.184 (talk) 22:40, 6 January 2016 (UTC)

Something that will work against any attempt to build such a mountain is isostasy - the lithosphere will be warped downwards under the load - that's why mountains have roots. On a very short timescale this may not matter too much, but over millennia it will become important. Mikenorton (talk) 22:53, 6 January 2016 (UTC)

What does that mean, “mountains have roots”? —Tamfang (talk) 04:39, 7 January 2016 (UTC)

Also, another thing worth discussing: even if we could magically create a mountain that reaches into space, if you want to stick things into orbit from the mountain's peak you still have to impart a bunch of energy to them. Objects wouldn't "float" into orbit if you released them from the peak; Earth's gravity is still pulling down on them. "There's no gravity in space" is a very common misconception, but it's obviously wrong (what keeps the Moon in orbit around the Earth?). To stay in orbit around Earth, you need to be moving really fast. You're weightless in orbit because you're in freefall; your orbital motion cancels out the gravitational pull of whatever you're orbiting. (Suggested resources for understanding this more: Newton's cannonball, [24], [25]) For a rocket used for an orbital launch, most of its fuel is used to impart sideways motion, not to make it go up. Proposals for non-rocket spacelaunch often revolve around a way to impart energy to the payload from an external source, instead of using fuel carried as part of the payload. This avoids "the tyranny of the rocket equation". --71.119.131.184 (talk) 00:08, 7 January 2016 (UTC)

What about a "mountain" consisting of a pyramid or cone shaped framework, made of light but strong materials, rather than it being solid? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:37, 7 January 2016 (UTC)

Rules restricting use of centi, deci, deca, hecto SI prefixes.

I heared that SI has special rules restricting the use of centi, deci, deca, hecto SI prefixes, namely that unlike the other prefixes, these prefixes are recommended only for certain particular units of measure, and possibly for certain uses of those units. Where can I find a description of these rules? I'd prefer a description easily accessible on the internet. – b_jonas 21:47, 6 January 2016 (UTC)

Not sure where to list them, but they are mostly going to be "only use them where it is currently customary", like cm. StuRat (talk)

Maybe, but if I am wrong and such rules aren't available, I'd like at least a description of the customary use of those prefixes. The difficulty here is that the use of prefixes in everyday topics differs by location, and the use in professional contexts may differ by area of expertise. In particular, decagrams are commonly used in informal speech in Hungary to measure food items, such as meat products or cheese when bought in amounts smaller than 0.5 kg, but in some other countries it isn't used for such a purpose. Similarly, deciliters and centiliters are used in everyday speech about liquids. – b_jonas 10:25, 7 January 2016 (UTC)

I can't find any rule suggesting their usage should be restricted on the BIPM site. See e.g. [26] [27]. I did find [28] (and other sites replicating the same thing) which say

The prefix hecto- to centi- are not 'preferred prefix' but referred to as 'other prefix' by SI .... Le Système International d'Unités (SI) name the prefix giga and nano, milliard and milliardth respectivly. The wording shown here was approved by the General Conference on Weights and Measures and has been adopted in practice.

But I can't find this or any reference to preferred prefix or other prefix anywhere on the BIPM site. So either it isn't on the site in English, my search is screwing up, or the wording above is confusing and the "preferred prefix part isn't coming from the BIPM or the GCWM. (The wording is also confusing because it doesn't discuss deca etc.)

National standards and other bodies and style guidlines may however have their own rules rejecting or discouraging the use of these prefixes. E.g. [29] [30] [31] [32] [33] [34]

13:02, 7 January 2016 (UTC)

What's the smallest or shortest building that'd be measurably weaker if it didn't follow Earth's curve?

Inspired by the mountain question, I wonder the above. The Boeing factory is about 100 meters tall and a half mile square, did they build the walls "not parallel" because of the curvature of the Earth? Did they have to mathematically alter the shape of the roof of the Aalsmeer Flower Building for its vast square kilometer size? How long would a catenary arch on a spherical planet have to be for it to be measurably weaker than the best shape for a globe? Does this shape have a name, too? Sagittarian Milky Way (talk) 22:54, 6 January 2016 (UTC)

Not sure if you really have to alter your plans in building construction to account for the curvature of the Earth. That is, there is a certain amount of tolerance in every joint, and that may well add up to more than enough to counter the effect. For example, the I-beams at the top would be slightly farther apart than at the bottom, but that spread would just be in the location of the rivets. Each vertical beam is likely made to be "normal to the Earth" using a plumb-bob, rather than "parallel to the rest". StuRat (talk) 23:17, 6 January 2016 (UTC)

And one more: How heavy could a structure on strong, geologically stable bedrock in a tectonically dead place be before you start affecting the crust? What would happen if you exceeded the pounds per square inch level of whatever the strong, stable bedrock is made out of without screwing with the crust? Sagittarian Milky Way (talk) 23:10, 6 January 2016 (UTC)

Read geotechnical engcineering to get an idea of what is involved. Graeme Bartlett (talk) 07:23, 7 January 2016 (UTC)

I don't know about buildings, but suspension bridges are built with towers that are vertical but are further apart at the top than at the bottom due to the curvature of the earth. For example, the Humber bridge has 155m (510ft) towers that differ by 34mm (1.3 inches) and the Verrazano-Narrows Bridge has 693ft (211 m) towers that differ by 1 and 5/8ths inches (41 mm). Widneymanor (talk) 11:14, 7 January 2016 (UTC)

Aversion to IQ tests

I noticed that I have a certain aversion to IQ tests so that I can't complete them and know my IQ. Out of 40-60 questions that an IQ test seems to contain I can't go beyond approximately 5th question (and certainly not beyond 10th). After first initial tests, as they get more complicated, I'm like "f*ck it" and quit, as I can't force myself to think further. Do some other people have the same issue or was it mentioned somehow before? Thanks.--93.174.25.12 (talk) 23:44, 6 January 2016 (UTC)

Certainly people with test anxiety have difficulty taking tests, but because of reference desk policy (see the top of the page) we cannot diagnosis any particular reason or reasons why you have had difficulty taking an IQ test. Hellmari (talk) 00:12, 7 January 2016 (UTC)

I agree with the above. What could possibly be relevant here is if there WAS any specific codified considerations for people who have trouble completing the "standard" test, but that almost certainly would not be part of any "online" IQ test which the vast majority of are not "official" in any way. You'd probably need input from someone who actually works with "official" tests whether they have special rules for people with attention disorders and such things, maybe they allow more time, or allow short breaks between every 5 questions (that's just speculation). It would seem to me that while this might not be "common" surely it would have to be common enough. Vespine (talk) 00:22, 7 January 2016 (UTC)

You need to figure out a way to make answering questions "fun" for you. I'd venture a guess that a large percentage of ref desk regulars enjoy taking such tests. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:37, 7 January 2016 (UTC)

January 7

Why does $\ 80\cdot 10^{-6}=8\cdot 10^{-5}$?

I'm trying to understand why $\ 80\cdot 10^{-6}=8\cdot 10^{-5}$? What is the explanation? 92.249.70.153 (talk) 01:13, 7 January 2016 (UTC)

Not sure if this will enlighten you, but (1) Number a x number b = (ten times smaller number a) x (ten times larger number b), or (2) $\ 80\cdot 10^{-6}=8\cdot 10^{1}\cdot 10^{-6}=8\cdot 10^{-5}$ Clarityfiend (talk) 01:43, 7 January 2016 (UTC)

Compare a simplified case: $\ 80\cdot 10^{-2}=8\cdot 10^{-1}$. Do they look equal to you?--Denidi (talk) 01:45, 7 January 2016 (UTC)

Which is another way of saying 80/100 = 8/10, or 80 x 0.01 = 8 x 0.1. Clarityfiend (talk) 01:54, 7 January 2016 (UTC)

(ec)You should review Exponentiation#Negative_exponents. Here's one way to look at it. Pardon the Fortran-style notation:

80 * 10**-6

= (80 * 1/10) * 1/10 * 1/10 * 1/10 * 1/10 * 1/10

= (8) * 1/10 * 1/10 * 1/10 * 1/10 * 1/10

= 8 * 10**-5

←Baseball Bugs ^{What's up, Doc?} carrots→ 01:55, 7 January 2016 (UTC)

N.B. The $\cdot$ is the dot product.
Sleigh (talk) 01:58, 7 January 2016 (UTC)

While the dot sign can be used for the dot product, it can also be used to denoted regular multiplication, as explained in the first bullet point under Multiplication#Notation and terminology. Usage is determined by context, and in this case, where neither multiplicand nor multiplier are vectors, it is clear that regular multiplication and not the dot product is intended. -- ToE 07:27, 7 January 2016 (UTC)

Also see scientific notation. Bubba73 ^{You talkin' to me?} 02:52, 7 January 2016 (UTC)

Perhaps the negative exponents are getting you confused. So, let's look at an example that uses only positive exponents: $\ 7\cdot 10^{3}=70\cdot 10^{2}$. In this example, both expressions mean 7,000. The first expression means 7 times 1,000 and the second expression means 70 times 100. Which both mean 7,000 as a final product. Your example with negative exponents is in the same vein. Joseph A. Spadaro (talk) 08:14, 7 January 2016 (UTC)

Also, a suggestion. You might be better served at the Math Help Desk. Joseph A. Spadaro (talk) 08:17, 7 January 2016 (UTC)

Carbon monoxide

Is there any Wikipedia article about mass carbon monoxide poisonings? In particular, there was one steam train that got stuck in a tunnel and the smoke killed everyone -- anyone happen to know when that happened? 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 05:39, 7 January 2016 (UTC)

Hmm, and the wiki page on Balvano comes up second in a google search on some obvious terms. Ask your mum to put google on your computer, and show you how to use it. Sheesh, as we used to say. Greglocock (talk) 08:04, 7 January 2016 (UTC)

Hel-LO! How would I know to look for Balvano if I'm not Italian?! Take your snarky rudeness and shove it, cocksucker! 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 13:03, 7 January 2016 (UTC)

• The link is Balvano train disaster. The disaster happened in Italy in March 1944 (just after the fall of the fascist government - the chaos of that era explains why the train was overloaded and running on low-grade coal). Category:Deaths from carbon monoxide poisoning will help you find others, although the only other mass death in that category is the Myojo 56 building fire. Smurrayinchester 09:06, 7 January 2016 (UTC)

Thanks! That's what I'm looking for. (Actually, I've already found it, but thanks for the effort anyway!) 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 13:03, 7 January 2016 (UTC)

Just to be helpful, do you want me to add the Myojo 56 building fire to Category:Deaths from carbon monoxide poisoning?