Wikipedia:Reference desk/Archives/Science/2009 September 25

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September 25

How to see and edit references to material properties?

1. When I look for a property of a specific material, e.g. melting point of CeBr3, there is a value in the table on the right, but no reference where this value was taken from. How can I see that? Is there a way to add a reference right next to the value?

2. Often there is a discrepancy in values of the same property from different sources. For example - one book says 722 C, another 733 C. It would be nice to list several values and references in the same table. How to do that?

Thank you!

1. In the Cerium(III) bromide article, at the very bottom of the info-box you'll see "Infobox references" - click on that and you'll be taken to Wikipedia:Chemical infobox - and the references at the bottom of that are the ones used for all of the info-boxes that use that system. You can add a reference for anything by adding <ref>reference information</ref>...including the data in that info-box...but I don't advise it in this case.
2. Normally - I'd say "be bold" - just go in and change it. But in this case, it looks like the chemistry department of Wikipedia have agreed on those sources as the "reputable" ones - and take their data from there automatically. Messing with that is likely to be a bad idea - possibly, one of your sources is wrong - or out of date - or the property is measured at different pressures or...who knows? If you think the value given in the article is incorrect then you should probably go to the "Talk" page for that article (click on the "discussion" tab) and discuss the issue there. In the case of Cerium(III) bromide, there is very little editor activity - so if you don't get a prompt answer from the talk page, you might try asking one of the more recent editors (look in the history tab) on their personal Talk page. Failing that, the Wikipedia:Chemical_infobox talk page or Wikipedia:WikiProject_Chemistry's talk page. Info-boxes aren't really the place to discuss differing opinions on something like your temperature example...if there are several reputable sources who cannot agree on some number, then probably this should be explained in the body of the article - with the most widely accepted number being placed into the info-box. Info-boxes are short, sweet, condensed information for someone who needs an answer without reading through pages of explanation. If we bloat them out with lots of complexity, they lose their value. This is definitely a case of "less is more".

SteveBaker (talk) 00:28, 25 September 2009 (UTC)

I've got to disagree - more is true - science does not selectively choose the 'best' boiling point... Figures from the 18th century may be ignored...

What you are describing is a like a whitewash - not to be encouraged.83.100.251.196 (talk) 00:48, 25 September 2009 (UTC)

I'd say add and change it, if references are not there add them, if multiple data values exist - mention them (unless one has been shown to be wrong) common with melting points for instance.

However if you are going to add a value make sure you've got the right source - this is almost always a publication in a chemical journal such as "journal of the american chemical society" - any text book will have taken their values from a journal, and should have a reference to the data.

To add two values do this value1<br>value2 - the "br" puts the values on a separate line

To be honest the current "link to infobox references" is not good, basically unnaceptable in quality for an encyclopedia , and useless for research. - it doesn't say which book, let alone the page number, and those books are not even the primary sources -typical amateur wikipedia bullshit - they probably think they've got that right as well . (Oh dear need to take a blue pill again, maybe even a green one...)83.100.251.196 (talk) 00:47, 25 September 2009 (UTC)

This is PRECISELY why I directed you to the various talk pages. I guarantee that this has been carefully considered and that you'll find the people there completely professional. I have no clue whether one source is more 'approved' than the other - but adding bogus or confusing data into the infobox is not doing our readers a good service and having a standard, agreed reference from which we get our data is the way to avoid a lot of confusing junk in those tables. The gold standard on Wikipedia is references - the more solid, more respected reference wins. However, the Ref Desk is not the place to debate that - please take your invective to Wikipedia:WikiProject_Chemistry. where this stuff has (presumably) been debated and agreed. SteveBaker (talk) 01:14, 25 September 2009 (UTC)

There are no references though are there? No. just a link to a list of books. This is the point.

As a hint for the very trusting - using the 'reference button' in the infobox for Cerium bromide - try to find the reference for the melting point - you might see what I mean.83.100.251.196 (talk) 01:48, 25 September 2009 (UTC)

Ehem: TAKE IT UP WITH WIKIPROJECT CHEMISTRY OR THE TALK PAGE FOR THE INFOBOX OR THE TALK PAGE FOR THE ARTICLE IN QUESTION. SteveBaker (talk) 13:44, 25 September 2009 (UTC)

Encyclopedia Britannica is the default "gold standard" encyclopedia, and their article on cerium doesn't even try to list a reference for melting point. They have no article at all on CeCl3. I'd be curious to know which professional encyclopedia you're comparing Wikipedia to. --Sean 21:22, 25 September 2009 (UTC)

Wikipedia:Manual_of_Style_(chemistry)/References_and_external_links#When_to_cite good enough?

Or even Wikipedia:Citing_sources#When_to_cite_sources " The purpose of citing sources is: To ensure that the content of articles can be checked by any reader or editor..." .. "..To help users find additional information on the topic..." - didn't think the purpose of supplying references would need to be explained at this stage.

Um, what does that have to do with my post? --Sean 11:06, 26 September 2009 (UTC)

You asked what encylcopedia I was comparing to (why I don't know) - the answer is, as best as I can give it to you: I was comparing to this encyclopedia, and the standards for this encyclopedia.83.100.251.196 (talk) 11:29, 26 September 2009 (UTC)

You could add references like this: (melting point of CeCl3) into the info box.

730-732C (99.99%) <ref>[http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Brochure/al_chemfile_v5_n13.Par.0001.File.tmp/al_chemfile_v5_n13.pdf Sigma Aldrich, Chemfiles Vol.5 No.13 p5] ''sigmaaldrich.com'' </ref> <br> 1005K (732C) <ref>The thermodynamic parameters of monomer and dimer molecules of cerium and praseodymium tribromides, Journal:High Temperature, Vol 48 No.3 June 2008, L. S. Kudin , M. F. Butman, V. B. Motalov, A. E. Grishin, A. S. Kryuchkov and G. A. Bergman [http://www.springerlink.com/content/9l0041t22574u0r4/ Springer Link abstract]{{dead link|date=February 2020|bot=medic}}{{cbignore|bot=medic}}</ref>

For more expert source citing see WP:Citing sources.83.100.251.196 (talk) 01:43, 25 September 2009 (UTC)

SB looks to have investigated this pretty well and given quite cromulent answers. I'll just add that in my experience a lot of template fields react quite negatively to inclusion of <ref> tags - in fact they sometimes 'asplode, so be very careful to use the Preview button. Also, we have a very handy WP:HELP desk where many editors are poised to give help on this kind of stuff. Franamax (talk) 06:06, 25 September 2009 (UTC)

A side comment - if you are working with these chemicals, Wikipedia's infobox should not be used as your reference - use an appropriate reference or MSDS. Wikipedia is only an encyclopedia, not a chemical guidebook; and it is impossible to guarantee the data in the most recent version at any instantaneous moment. Nimur (talk) 18:31, 25 September 2009 (UTC)

Don't forget melting point can be affected by crystal structure - i.e Polymorphism (materials science). I don't know how many inorganic chemicals exhibit this, but I was once told (on a crystallisation course) that at least 60% of organic compounds can be made to show polymorphism.  Ronhjones  ^(Talk) 21:46, 25 September 2009 (UTC)

I used sunscreen daily for a month, why am I still tan?

From the skin entry, I read that skin renews itself every 27 days. I've been wearing sunscreen (SPF 85) daily for the past month. So why do I still have a farmer's tan? --68.103.141.28 (talk) 00:33, 25 September 2009 (UTC)

Our article Sun tanning suggests that exposure to the UV components of sunlight has two relevant effects. The first and quicker (caused by UVA) is to darken (by oxidation) the melanin pigment already present in the epidermal (outer) layers of the skin and also to release more quickly the unoxidised melanin already formed in the deeper-lying melanocytes; this existing melanin may well be lost through the normal process of skin renewal (by continual shedding of the outermost layers) on such a time scale as you mention. However, the second effect (caused by UVB) is to stimulate (as a response to the damage caused by the greater-than-optimum UV exposure) the melanocytes into a higher level of melanin production (melanogenesis). This increased production level takes longer (about 72 hours) to start up after the initial damage occurs, but will also persist for longer after the damage's cessation before it begins to subside; in the meantime it will continue to create new melanin, and at a higher rate than before the damage started. It seems likely that the longer the damaging process has been going on, the longer the high level of melanogenesis will take to subside. 87.81.230.195 (talk) 01:44, 25 September 2009 (UTC)

which is the best synthesis for this product?

File:Enone-alkene.jpg

Enone electrophile, or alkene Grignard nucleophile?

I'm trying to synthesise (on pen and paper) the product shown. (My IUPAC nomenclature skills aren't that good yet, so I can't give you its name yet.)

The thing is, I don't know for sure which route is the "best". I'm not being graded for being environmentally friendly or having the most efficient reaction, but my friend thinks there may be problems with having an alkene Grignard (there were some iffy exam grading issues about it last year), and he suggests that I just have a methyl Grignard react directly with a precursor enone.

My objection: "but that's an enone ... not a ketone! Its properties are substantially different!" We're only supposed to use ketones, aldehydes and esters as starting materials though we can use hydrocarbons, halides and ethers as starting reagents. Does an enone qualify as being a ketone (to me it's like calling a ketone an aldehyde)?

And oh yeah, the important part -- the enone would seem to undergo a competing reaction at the beta-carbon, and you would destroy the conjugation stabilisation by reacting it at the carbonyl, whereas conjugate addition would still have a resonance-stabilised intermediate.

But said friend also gets higher grades than I do on orgo exams (usually), so would there be a good reason to choose an alternative to an alkenyl Grignard? John Riemann Soong (talk) 01:46, 25 September 2009 (UTC)

If I remember it correctly, Grignard does not do much conjugate addition. Vinyl Grignards should be fine. Tim Song (talk) 02:08, 25 September 2009 (UTC)

Is the carbonyl carbon actually the more reactive site in conjugate addition, just that as the net reaction proceeds, most of the reaction ends up happening at the beta-carbon because nucleophiles which make decent leaving groups (e.g. OCH3-) also get kicked out more? John Riemann Soong (talk) 06:02, 25 September 2009 (UTC)

Um, we are not kicking out OCH3- here. Tim Song (talk) 06:06, 25 September 2009 (UTC)

Sorry I was comparing Grignards with other classic nucleophiles. John Riemann Soong (talk) 07:55, 25 September 2009 (UTC)

I see. I don't know - initial attack at the beta-position forms the more stable carbanion, but organometallic reagents are a special case. In Grignard reaction, for instance, you'll note that when Cu(I) is present, G. does a 1,4-addition, but when Ce(III) is present, it becomes 1,2-. It's just messy. Tim Song (talk) 17:28, 25 September 2009 (UTC)

"Is the carbonyl carbon actually the more reactive site in conjugate addition?" :

Carbonyl vs conjugate addition - as I remember semi-empirical MO type calculations show a greater partial charge on 1C than 3C (sorry I can't explain the proceedure or link to it) - this makes 1C more likely for normal nucleophilic attack.

However see [1] p655 it explains using a variation of the 'hard' and 'soft' classification of nucleophiles to predict what type of addition occurs (see Lewis acids and bases#Hard and soft classification also HSAB)

Just to complicate things there are at least two more factors

1. A nucleophiles counter ion (eg Mg in grignard) may selectively complex to the O atom already mentioned above- this can force the nucleophile to attack a specific site. (There's an a example at Organocopper compound#Cu(III) intermediates , can't find one for enolate or grignard.)

2. Steric effects eg [2] page 385 C - as expected.

The 1,4 addition definately gives the most stable intermediate the enolate (as above) - this often doesn't affect the product as much as one might expect - though the O complexation of metal ions mentioned above is vaguely related...

comparison with OCH3-

Since C-C bond forming reactions are usually mostly irreversible under normal conditions - this makes a difference when comparing carbon nucleophiles with nucleophiles like OC(O)CH3 which actually have a change of undergoing realisitically reversible reactions at normal temperatures. So the answer is YES!83.100.251.196 (talk) 21:10, 25 September 2009 (UTC)

Can hydro electricity be used as a battery to store power produced by other means?

Recently, I heard that in Sydney, power excess to need was used to pump water uphill to a dam where it could be released later on to produce electicity via hydro turbines. It made me think about whether you could have systems where wind and solar power could be stored as raised levels of water as a matter of course, and released as and when needed. That would negate one of the main bugbears of solar and wind power, namely, that it is dependent on irregular and unpredictable power sources, which could be copious one day and absent the next. Is such a procedure adopted as a normal measure anywhere? Myles325a (talk) 04:51, 25 September 2009 (UTC)

It could be used in this manner, but it seems a horribly inefficient manner to do so. Storing potential electric power by pumping water into a reservoir would meet the technical definition of a "electrical storage device" like a battery, but I am not sure the massive losses involved in doing so would justify the act. It seems there would be much more efficient uses of power, from any source, than to "store" it in this manner. Plus, there's the problem that hydroelectric power itself creates serious environmental concerns; the creation of reservoirs destroys huge amounts of land, and that in itself is a fairly serious environmental concern. --Jayron32 04:56, 25 September 2009 (UTC)

Agreed, there is the original energy loss generating the power, energy loss in the pump motor, energy loss in the pump bypass flow, and energy loss regenerating electricity when the water comes down again through a turbine. However these schemes do exist, perhaps the Sydney example is the one I've read about. It will all depend on the economics of the particular situation.

Another method is to create large-scale "batteries" in a different medium. One example is here though it's not the commercial proposal I'm trying to find. The basic idea is to pump electrical energy into another medium, which is generally 100% efficient, then extract the energy in a single step using an electrical process. I can't find the exact proposed metals right now though! Franamax (talk) 05:20, 25 September 2009 (UTC)

Ahh, here's what I was thinking of. [3] Vanadium is the energy storage medium. Franamax (talk) 05:33, 25 September 2009 (UTC)

I'm not sure I understand. Isn't what you described in the opening sentence exactly what you're asking about? Pumped-storage hydroelectricity is the Wikipedia article on the subject, and it's used in quite a lot of places worldwide. AlmostReadytoFly (talk) 06:20, 25 September 2009 (UTC)

Op myles325a back here. Looking at Pumped-storage hydroelectricity, I was surprised to read that the cost of going down this path was nowhere near as onerous as I had thought. Quote: "Taking into account evaporation losses from the exposed water surface and conversion losses, approximately 70% to 85% of the electrical energy used to pump the water into the elevated reservoir can be regained.[1] The technique is currently the most cost-effective means of storing large amounts of electrical energy on an operating basis, but capital costs and the presence of appropriate geography are critical decision factors." 70 - 85% seems like a pretty decent slab, especially when you know that unless the power is stored, you lose it. Also, in the Sydney case, and I imagine in many others, the hydro dams were there to begin with. They were not built especially for this operation. But thanks to everyone who answered this question. You have made things a lot clearer for me. Myles325a (talk) 06:31, 25 September 2009 (UTC)

Here is an account of one US utility pumped storage project which can generate 1071 megawatts. A dispatcher for a U.S. utility told me that on one occasion of a summer heat wave, he had actually operated gas-fired peakers, the most expensive form of generation, at night when the load dropped to within the capability of the base-load units, to pump water into a similar pumped storage unit, so that the output from it would be available the following afternoon, as an alternative to rolling blackouts wen the load exceeded the capability of all generating units. Water can be pumped up into a reservoir, or it can be dropped into a reservoir deep underground, such as a cavern, or a manmade storage unit. Some cities have a "deep tunnel" to store rainwater during large rainfalls, which is later cleaned and sent out to the rivers or lakes. This avoids pollution with combined sanitary and storm sewer outputs. These reservoirs could also, in principle, be used for pumped storage. During heat waves, with no rain forecast for several days, river or lake water could be allowed to fall down to the reservoir, powering turbines. At night, the water could be pumped out, cleaned and returned to the lake. Early utilities had direct current generation, and had large batteries downtown, which could similarly load-shift or maintain the system during short generator outages. Energy can also be stored in Superconducting magnetic energy storage which are a more expensive hightech approach. Solar energy stored in some system would make sense only when the peak load was not during the heat of the day; why store the solar energy at the time you need it? Wind energy storage might make more sense. Edison (talk) 15:11, 25 September 2009 (UTC)

With the solar storage might make sense in the winter if there is a large amount of people who have electric heaters. Granted in those places, solar might not make a great deal of sense to install as the solar power generated during the winter will be reduced. Googlemeister (talk) 15:24, 25 September 2009 (UTC)

Also, with wind energy, rather than convert the mechanical energy of the rotating windmill blades to electricity, then use that to power a water pump and turn it back into mechanical energy, you can just use the rotation of the blades, run through some gears and drive shafts, to pump water directly. This was historically used in the Netherlands as a way of pumping water. However, this method only works if the windmills are right by the water to be pumped. StuRat (talk) 15:24, 25 September 2009 (UTC)

This one in Wales has been going since 1963 - that's a long service. I went on a tour years ago inside it. IIRC they can be up to full generation speed (from stop) in 2-3 minutes, or if they know a peak is due (e.g. commercial break due in mainstream tv) then they can set the generators to idle (powered by the electrical grid), and can then deliver power on demand in under 30 seconds.  Ronhjones  ^(Talk) 19:00, 25 September 2009 (UTC)

This one isn't a dedicated pumped-storage facility, but it's been running since 1942. --Carnildo (talk) 22:23, 25 September 2009 (UTC)

On this note, it's my impression that Super grids, HVDC grids and smart grids are motivated to some degree by the desire to more effectively get electricity to pumped storage sites. In the European super grid the idea is that wind (and solar?) power from relatively far away could be used to pump water back across Norwegian dams, as is currently done on a much smaller scale with Danish wind power, I believe. TastyCakes (talk) 15:25, 25 September 2009 (UTC)

In a coastal setting, the "efficiency" can be much more than 100% if water is pumped up at high tide, and used to generate electricity at low tide. (Yes I know that energy is coming from the combined rotation of the earth-moon system so it only appears to be more than 100% efficient.). With suitable storage, this setup could use wind power to provide extra generation at (some) peak times. Dbfirs 12:01, 26 September 2009 (UTC)

enones with aldehydes

Are enones strictly reserved for alkenyl-ketone combinations? Why doesn't google turn up much for "vinyl aldehyde"? What happens if you don't have a second alkyl group attached to the carbonyl? Can acetaldehyde participate in enolate reactions? John Riemann Soong (talk) 05:14, 25 September 2009 (UTC)

Um, if it's an aldehyde, "enone" would not be my first guess as the structure's name. Acetaldehyde tends to polymerize under many enolate-forming conditions, but there are many tricks for forming its enolate or enol-ether. Acrolein is an important industrial chemical. And crotonaldehyde is important too (with an interesting synthesis related to your question!). DMacks (talk) 05:27, 25 September 2009 (UTC)

"alpha beta unsaturated aldehyde" or "α,β unsaturated aldehyde" is the generic term - though describing them as "enones" will be understood (by most) - though semantically incorrect.83.100.251.196 (talk) 11:35, 25 September 2009 (UTC)

As mentioned above - some search terms dont give good results due to a common name - most are for small molecules - though there are a few for flavour molecules too - cinnamaldehyde is another that springs to mind.83.100.251.196 (talk) 20:10, 25 September 2009 (UTC)

pkas of alcohols in THF, etc.

I think someone on here helped me discover that tertiary alcohols should actually have the lowest pKa of the alcohols if not for the fact that steric hindrance hinders the solvation stabilisation of the alkoxy ... would using sterically-interesting solvents like ether or THF help reveal this "true" order? (pKa's of all of them might go up tho) John Riemann Soong (talk) 05:57, 25 September 2009 (UTC)

The type of solvent you are thinking of is an "aprotic solvent" I think - but the difference is lack of the ability to hydrogen bond rather than steric.83.100.251.196 (talk) 11:41, 25 September 2009 (UTC)

It has to be steric somewhat -- othewise methanol wouldn't have a lower pKa than water. John Riemann Soong (talk) 13:15, 25 September 2009 (UTC)

Methanol is more acidic in water than water (not by much) - isn't this expected? It should be more acidic though - for instance when comparing OH bond strengths. (I might be getting figures mixed up)

If a aprotic solvent is used then the alkoxide won't be stabilised much - ie there won't be much solvation of the conjugate base - so the steric effects that prevent solvation should be minimised - isn't that what you meant?83.100.251.196 (talk) 20:15, 25 September 2009 (UTC)

reducing an alcohol without reducing a carbonyl/ketone

I have a synthesis problem ... using some variation of the aldol reaction (which is my issue), I have to synthesise a symmetric monoketone. I've decided to start out with two carbonyls and let one of them add to the other to create a molecule with a ketone group + a secondary hydroxy group (deprotonated, since this is all in LDA-THF conditions).

Is there any way to reduce an alcohol without reducing the ketone? I thought of reprotonating the alcohol, eliminating it to create an enone (!), and then attempt to hydrogenate the alkene bond. But I don't want to hydrogenate the ketone. Or perhaps I can hydrogenate the ketone into an alcohol (after the first alcohol group has left) and reoxidise it into a ketone? John Riemann Soong (talk) 09:06, 25 September 2009 (UTC)

Alkene and carbonyl are electronically different from each other (even if there is some interaction between them that allows them to react as a single unit). They are different enough that you can get a mechanism that works better at one place than the other, and pick a reaction that would affect one in particular, just like you could pick a different reaction that might work better due to the interacting nature of the two parts. Sometimes an enone acts like an ene, sometimes like an one, sometimes like an enone. DMacks (talk) 16:46, 25 September 2009 (UTC)

You can always use protecting groups if necessary. For ketones, the most common one is a ketal. Tim Song (talk) 17:16, 25 September 2009 (UTC)

For a link, see Protecting group and Acetal. --Jayron32 19:07, 25 September 2009 (UTC)

Limits of life expectancy

I was looking at the article on the 23th century, where the United Nations claims that life expectancy in developed countries will be around 150 to 200 years. Is this being over-optimistic ? There has to be limits to the lenght of life, notwithstanding the technological advances in medecine. Rachmaninov Khan (talk) 15:55, 25 September 2009 (UTC)

That article cites a source, World Population to 2300, which discusses assumptions about mortality rates. Page 7 specifically discusses life expectancy assumptions; Section II (pg. 10) goes in to several pages of discussion about long-range predictions. The best sound-bite summary is here: "By the time rising life expectancy becomes the dominant and indeed sole influence on (population) growth - in 2225 - it will be at 92.8 years and rising slowly." Predictions of other values of life expectancy, (150-200 year expectancies) are certainly optimistic, and I would not categorize them as the official prediction of the UN (even if they have been mentioned in this report, or its attached essay-section). Somebody want to tune up that article to match the cited source? Nimur (talk) 16:07, 25 September 2009 (UTC)

There is no getting around the fact that the body goes through a natural aging process, and this 150 to 200 years stuff is somebody's fantasy. Once you get to the 90 area, you're pretty well shot, and something vital is going to give out. →Baseball Bugs ^{What's up, Doc?} carrots 16:13, 25 September 2009 (UTC)

Maybe if you can have a clone standing by to donate organs to you you could have an average of 150-200, but otherwise I just do not see it happening. Now the oldest person alive hitting 150... Maybe. Googlemeister (talk) 16:41, 25 September 2009 (UTC)

One thing we know for sure, predicting human events, technology, etc, 20 years into the future is very hard, predicting such things 200 years into the future is just guessing. These things are very interesting to think about and debate, but in the end NO ONE can produce a prediction that is any way reliable. Some predictions might well turn out to be right, but you'll never know in advance which ones they are. ike9898 (talk) 17:38, 25 September 2009 (UTC)

Umm, we could probably get advances in DNA repair, have all sorts of cell cycle drugs as well as signal transduction drugs; someone could find a superbly good antioxidant gene product to replace Linus Pauling's suggestion of taking massive doses of Vitamin C. We may be able to use stem cell transplants; grow organs in a laboratory... John Riemann Soong (talk) 23:46, 26 September 2009 (UTC)

If you look at actual aging patterns over the past several hundred years, what you find is that rising life expetency isn't controlled as much by raising the top end (i.e. by the oldest people living longer), it is MUCH more controlled by raising the bottom end (i.e. by the less really young people dying). For most of human history, once you made it to physiological adulthood (say 16-21 years old or so), you could be expected to live to old age. There were ocassional punctuations of weird things like war and bubonic plague that would wipe out lots of people at all ages, but on average, people who lived to 21 lived into their 70's or older at about the same rate as today. Certainly, MORE people are living to their 70's today, but not as many more as the rising life expetency would lead one to believe. The two factors which have raised average life expetency are a) decreasing infant mortality and b) decreasing mother mortality. With less children dying of preventable childhood illness, and less mothers dying in childbirth, the number of people making it to their 20's has increased DRAMATICALLY in the past 200 years or so, and THAT is what has had the greatest effect on raising life expectency. So, if in the future the average life expectency were to go up to say, 90 years old, some of it would be because some people would be living into their 90's more often, but MOST of it would be due to more people living into their 20's more often. It would likely NOT be due to people living to 150 and dragging the average up... There's some very hard evidence that the human lifespan is programmed into our DNA (see telomere), and as such, we can expand the number of people who reach their "genetic maximum age", which for most people is likely very close to 100 years, but we probably have very little chance of changing that "genetic maximum age", without actually delving into human genetic engineering, which most people find a bit scary. --Jayron32 19:04, 25 September 2009 (UTC)

I would say your analysis is mostly right (although I would have thought that 70s was uncommon and most topped out at 60s), is there any evidence that a single person prior to 1800 reached the age of 100? Given the number of centenarians, we obviously increased the top end of the scale too. Of course in most things, the further you try to push something past it's natural tendencies, the harder it gets to push it further. Googlemeister (talk) 20:41, 25 September 2009 (UTC)

See List of centenarians. People from before about 1000 AD may be somewhat unreliable, but there are some notable centenarians from before about 1800. Consider: Edward Augustus Holyoke, Laurence Chaderton, Jorge da Costa, Tenkai. And these are just people who a) have articles and b) who someone thought to add to our List of Centenarians article. Extrapolate this excedingly small sample size across all of humanity, and it would be quite believable that there were MANY centenarians alive at any one time. --Jayron32 00:14, 26 September 2009 (UTC)

Oh, and when I was doing research for the article Plymouth colony, I came across these figures from historian John Putnam Demos, who in his book A Little Commonwealth: Family Life in Plymouth Colony did an excellent demographic study of Plymouth (1620-1691). He noted that for males who reached their 21st birthday the average life expectency was 69, and 55% of those men reached their 70's, while less than 15% died before the age of 50. If you gave me these numbers for a modern western middle-class suburb in the 20th century, I would have thought them not unusual. The life expectancy at this time was being dragged down by women (an alarming number of whom died in childbirth) and by young children, who died mostly of childhood diseases we have mostly cured. Once you eliminate those factors, the "top end" of human life seems to have changed little in the intevening 350 years. --Jayron32 00:23, 26 September 2009 (UTC)

You've got it. The top end is pretty much where it was. 100 years old a hundred years ago "looks" like it does now. Families 100 years ago were often large, and often several would not survive infancy or teen years. What medical science has done is to make the possibility of living to 100 better. It has not made it possible to live forever. Sooner or later, something gives out. Heart failure at 100? Sure you get get a transplant - but by then your likely to be so frail you would not survive the surgery. Somehow people see death as a bad thing. But it's a good thing. It allows the young a chance to make their mark, to come up with innovations. If no one ever died, there would be no need to reproduce. Imagine a world where everyone is over 100 years old. Yikes. →Baseball Bugs ^{What's up, Doc?} carrots 01:43, 26 September 2009 (UTC)

Do naps make you taller?

Our article on human height says that the spine becomes compressed during the day, so you wake up at your full height and become shorter as the day progresses. It also says that you're at your minimum height five hours after leaving your bed.

Therefore, if I wanted to look tall at night, how long would I have to lie down in the evening? Would one hour suffice to fully decompress the spine? --Leptictidium (mt) 16:46, 25 September 2009 (UTC)

I doubt that the height is going to change very much. I recall that an astronaut was 3/8" taller after spending days in space, and that would be with microgravity, So I do not see how one is going to noticeably (without high precision measuring equipment) change their height by taking a nap. Googlemeister (talk) 20:36, 25 September 2009 (UTC)

I'm fairly sure that the difference between one's heights immediately after a night's (horizontal) sleep and after a day spent upright is sufficiently small as to be unnoticeable to onlookers (though it's enough for me to have to alter my car's rear-view mirror accordingly). Lying down for an hour would therefore be ineffectual in noticeably increasing one's height, although it might well make one more rested and refreshed and therefore perceptibly more vivacious and attractive. One could achieve a much more perceptible increase in height by wearing footwear with thicker soles and/or higher heels, and also by inserting lifts in them. 87.81.230.195 (talk) 02:08, 26 September 2009 (UTC)

Agreed, but perception of height (and to a slight extent actual height) is slightly infuenced by posture, and your muscles are less likely to hold you perfectly upright at the end of a tiring day ... but then some people are at their most alert in the evening. Dbfirs 11:45, 26 September 2009 (UTC)

Read a book that mentioned it, apparently you'll only lose a fraction of an inch during the day, though that can vary, for example running all day is likely to make you even shorter. You'd probably need to lie down for about 4-5 hours to gain that back.

Don't lie down at all in the evening and use the time you save to get a Bouffant hair styling. It will make you look taller.Cuddlyable3 (talk) 23:52, 26 September 2009 (UTC)

Wear platform shoes, a striped suit, and walk a chihuahua. Axl ¤ [Talk] 10:57, 27 September 2009 (UTC)

At Universal Studios I was shown a film set for cowboy films. Some of the doorways were unusually low and others were unusually high. The guide explained that the small doorways were used to make the hero look larger and the high dorways to make the heroinne look petite. Cuddlyable3 (talk) 23:45, 27 September 2009 (UTC)

is LDA miscible in methylene chloride? (do acyl chlorides react with THF?)

Need this fact in a jiffy for my problem set, cuz I think THF will react with acyl chloride? Or can I use THF safely with acyl chlorides? John Riemann Soong (talk) 17:34, 25 September 2009 (UTC)

Two quite different questions. LDA should not go anywhere near CH2Cl2. THF does not react with acyl chlorides. Tim Song (talk) 17:42, 25 September 2009 (UTC)

THF does react with acyl chlorides [4] - slowly but any acid, metal salts will accelerate it.83.100.251.196 (talk) 18:26, 25 September 2009 (UTC)

As mentioned above LDA can react with CH2Cl2 eg [5] - deprotonating it. (followed by further reactions)83.100.251.196 (talk) 18:38, 25 September 2009 (UTC)

Whoa hold on, what's the pKa of methylene chloride? John Riemann Soong (talk) 23:50, 26 September 2009 (UTC)

Anyone??? I'm really curious about this. John Riemann Soong (talk) 05:26, 28 September 2009 (UTC)

Dunno about CH2Cl2, but CHCl3 can be deprotonated by a strong base rather easily - t-BuOK is sufficient. Tim Song (talk) 06:05, 28 September 2009 (UTC)

Hmm, it can be deprotonated by sodium hydroxide too. Does this mean chloroform is more acidic than water? If so, why can't I find its pKa? John Riemann Soong (talk) 06:19, 28 September 2009 (UTC)

Try using a search engine - CHCl3 : [6] pKa 15 , or [7] pKa 24.1 (see J. Am. Chem. Soc. 105, 5380 (1983).) see [8] for the discrepancy. 83.100.251.196 (talk)

For CH2Cl2 see "dichloromethyllithium" - generated using LDA or stronger bases eg [9] p307 or [10] Not the same as the true dichloromethyl anion . You can probably guess at a value for the pKa. (Non conjugated hammett acidicity....)

Interesting - I learn something new everyday :). Struck. Tim Song (talk) 18:52, 25 September 2009 (UTC)

I seem to remember making an amide using generic amine + tertiary amine proton trap in THF - adding acid chloride dropwise to a cooled mixture - I got away with it since the other stuff reacted faster. - but it's worth watching out for. It should have polymerised (brown glue is the usual sign of this).83.100.251.196 (talk) 18:59, 25 September 2009 (UTC)

JRS, this is five questions in one day. You're pushing it. Regards, Looie496 (talk) 17:55, 25 September 2009 (UTC)

Maybe we can point the OP to a good chemistry textbook suitable for his level, and remind him that Wikipedia is an encyclopedia - not a substitute for actually learning the material?? Around these parts, it appears that Introduction to Organic Laboratory Techniques is the standard for labs and Vollhardt's Organic Chemistry is the standard for classroom theory. Nimur (talk) 18:33, 25 September 2009 (UTC)

I'm not sure but I think JRS is already a student, and so should have access to a library, book, and a recommended reading list.. However given his interest in organic synthesis there is another resource I can recommend which is the Alfa Aesar "Research Chemicals and materials" catalogue (it used to be a different company - "Lancaster chemicals" I think) - along side the lists of chemicals they supply are included standard and interesting reactions for many organic compounds, including references and links to review articles - It's a treasure trove of information if you've got the time to browse. (Possibly other catalogues do this - I don't know). It's given away so getting hold of one shouldn't be difficult/83.100.251.196 (talk) 18:52, 25 September 2009 (UTC)

I don't want to drive JRS away -- the fact that people are willing to answer his questions means that they are basically okay. I would just like to see him limit himself a bit. Looie496 (talk) 22:43, 25 September 2009 (UTC)

There's a daily limit to questions? I mean I do have resources but it's hard to find appropriate information from a large stack of books and it's hard to ask a book specific questions, and it's equally difficult when google is being obnoxious and won't return you relevant results. Why in the world isn't it easier to have a central database giving you pKa's of every common chemical? John Riemann Soong (talk) 23:50, 26 September 2009 (UTC)

Because the people who know the pKa's do not want to type the information in for the tens of thousands of chemicals? Googlemeister (talk) 18:38, 29 September 2009 (UTC)

No H1N1 deaths in Germany or China? Or just none reported?

China reports over 14000 cases of H1n1, and Germany reports over 19000. In other countries, the death rate among those infected has been about 5% in Brazil, 1.4% in the US, 5.8% in Argentina, and 3% in India. For the four countries with the most deaths, the combined case total of 89612 and death total of 2589 yield a combined death rate of 2.8% I acknowledge that the number of cases is understated in places with widespread outbreaks, since in the US they aren't doing tests much now that most cases of flu are H1N1. Wouldn't this apply to China as well, since they are no more blessed with unlimited testing resources than the US? No country other than Germany and China has nearly so many reported cases and zero reported deaths. Is it likely that the death angel is magically passing over Germany and China, or that their medical systems are far superior to those of the four countries with the most deaths, or that people are dying of H1N1 in Germany and China, but the deaths are being attributed to other causes such as pneumonia(a common sequel of flu), or other chronic health problems? Edison (talk) 18:56, 25 September 2009 (UTC)

It could also be that H1N1 is being undreported in the countries with deaths (say they only caught a fraction of H1N1 cases where the patient did not die). In that case, the lethality rate could be much much lower then 2.8%. Even if that knocked it down to something like 0.2% though, it is still very unlikely that with 14,000 and 19,000 cases respectively, no one died. Googlemeister (talk) 20:29, 25 September 2009 (UTC)

I suspect it is something like you speculate at the end, that the cause of death is being recorded as something else. It certainly jives with what I have heard about how China dealt with epidemics in recent history (e.g., SARS), where it sees accurate reporting as a potential threat to its civic government. I don't know why Germany would be doing something similar though. --Mr.98 (talk) 21:50, 25 September 2009 (UTC)

There was an Alfred Hitchcock tv show in the early 1950's. called "The Vanishing Lady." An old woman and her daughter check into a hotel room. The old lady vanishes; there is no record she was ever there, because the officials of the town don't want the ill effects of a plague case to hamper tourism. I suspect something of that sort might be going on in the two countries. Cover up, much? How could Hong Kong have 20 deaths and the rest of China zero deaths? Edison (talk) 01:37, 26 September 2009 (UTC)

As to my experience doctors can not (or don't take the effort to) tell if someone's "cold" is caused by bacteria or by viruses. I always wondered how they suddenly got the ingenuity to tell one flu strain from the other. 95.112.142.248 (talk) 13:45, 26 September 2009 (UTC)

In the U.S., they collect a throat or nasal swab and can do a quick check of less accuracy, or send it away for accurate analysis. They no longer test every suspected case, but in a fatality which might be from H1N1 they ought to be doing the accurate test, even in China and Germany. Edison (talk) 19:40, 26 September 2009 (UTC)

I don't know of such practice in Germany but then I didn't die of H1N1 and so I can't tell for sure, but when I last was to a doctor about one year ago he didn't use such a method. Does anyone know if it's overly expensive or why this is not common practice? 95.112.187.254 (talk) 07:53, 27 September 2009 (UTC)

When you visited your doctor a year ago, presumably you did not come in complaining of flu symptoms, so there would have been no reason for him to do a flu test. Nor, obviously, did you proceed to die from the illness, so there was no reason for a pathologist to do the test, as he should do when a patient dies from what might be H1N1. Edison (talk) 14:30, 27 September 2009 (UTC)

Well, the symptoms were indeed flu-like but, see, if there was not a policy against original research I would have died of H1N1 only to see if the test would have been performed .... 95.112.187.254 (talk) 16:18, 27 September 2009 (UTC)

18285 cases of swine flu in mainland China, but not a single death. A miracle? The first death reported in Germany, a woman weighing 397 ponds (180 kilograms)], out of 19,703 cases. Edison (talk) 04:01, 29 September 2009 (UTC)

Internal and External Obturator Muscles

Are the internal and external obturator muscles in humans connected in the middle and therefore constitute one continuous muscle or are they completely separate muscles?

The 1958 edition of Gray's Anatomy describes the "relations" of the Obturator internus on page 669 as follows:

Within the pelvis, the anterolateral surface of the muscle is in relation with the obturator membrane and inner surface of the lateral wall of the pelvis; its pelvic surface, with the obturator fascia, and the origin of the Levator ani, and with the sheath which surrounds the internal pudendal vessels and pudendal nerve (p. 603). The pelvic surface forms the lateral boundary of the ischiorectal fossa. Outside the pelvis, the muscle is covered by the Gluteus maximus, is crossed by the sciatic nerve, and rests on the back of the hip joint. As the tendon of the Obturator internus emerges from the lesser sciatic foramen it is overlapped both above and below by the two Gemelli, which form a muscular canal for it; near its insertion the Gemelli pass in front of the tendon and form a groove in which it lies.

No mention of the Obturator externus at all; and that muscle is covered on the following page, without mention of the Obturator internus. So I think it's safe to say that the two muscles are completely separate.

--Anonymous, 19:49 UTC, September 25, 2009.

Unknown units or abbreviation in an engineering document

In the technical sheets for an item (a 'lubricator' for pneumatic systems) I came across this:

Minimum dripping flow rate (l/min (ANR))

I need to know what the ANR means. Thx, ike9898 (talk) 20:37, 25 September 2009 (UTC)

Well, I found the answer myself (see here). This is widely used abbreviation that you will, never, never guess the origin of unless you read the linked page. ike9898 (talk) 20:48, 25 September 2009 (UTC)

Atmosphere normale de reference. Tevildo (talk) 20:53, 25 September 2009 (UTC)

In English, we often use STP, Standard conditions for temperature and pressure. However, some use 25°C ("chemical standard temperature") while I have seen others use 0°C ("thermodynamics standard temperature"); the same goes for pressure (which has many "standard" values varying by a few percent), so be wary if the actual, exact value is very important. Nimur (talk) 20:59, 25 September 2009 (UTC)

Drunk but not drunk?

What are some medical conditions with symptoms similar to being drunk? --Carnildo (talk) 22:11, 25 September 2009 (UTC)

Mild concussion, "drunk disease" - something to do with candida , parkinsons disease, Dementia pugilistica, some forms of Ataxia, Alcoholism (obviously -poor taste joke).83.100.251.196 (talk) 22:30, 25 September 2009 (UTC)

Hypoglycaemia. --Mark PEA (talk) 23:26, 25 September 2009 (UTC)

Hypoxia can make you feel euphoric. Dismas|^(talk) 00:25, 26 September 2009 (UTC)

Being in love :-) Mitch Ames (talk) 01:35, 26 September 2009 (UTC)

Try an adrenaline rush, or the aftereffects of massive (aerobic) exercise as dopamine floods your system. =) Once after a good night of dancing -- without alcohol mind you -- I was amazed at how quite intoxicated and spontaneously sociable I was being, and my inhibition went down considerably. John Riemann Soong (talk) 04:35, 26 September 2009 (UTC)

Assuming you mean in a nightclub, many things can contribute to this. The (loud) music, the crowding, the social proof of others socialising, the lack of lighting. Drunk people also have much to say, so it is easy to maintain conversation with them. --Mark PEA (talk) 10:40, 26 September 2009 (UTC)

Stroke victims have died because negligent law officers assumed they were extremely drunk. Vimescarrot (talk) 12:50, 26 September 2009 (UTC)

Citation?

[11], [12], [13]. I first heard of this sort of thing happening from Private Eye some months ago, which was highly critical of the officers in question, though none of my citations are the particular incident which the Eye talks about. Vimescarrot (talk) 21:47, 26 September 2009 (UTC)

You get your news from Private Eye?!?! Wow! That's incredible! (For Americans: That's kinda like saying you get your news from Mad magazine). SteveBaker (talk) 15:34, 27 September 2009 (UTC)

Hyperventilation. Cuddlyable3 (talk) 23:44, 26 September 2009 (UTC)