Wikipedia:Reference desk/Archives/Science/2016 July 22

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July 22

Physiological signs

I stumbled across our article at dermatoglyphics and found it very interesting. Do we have similar kinds of pages for signs at other areas of the body, such as eyes, nails, and so on? There's a cat associated with that article that lists a few more isolated articles, but maybe there's something more comprehensive? Non-WP links would also be appreciated. Matt Deres (talk) 03:14, 22 July 2016 (UTC)

The broader version of this would seem to be anthropometry, our article on which lists a lot of specialties within, such as dermatoglyphics. Someguy1221 (talk) 09:50, 22 July 2016 (UTC)

Cool - thank you! Matt Deres (talk) 10:53, 22 July 2016 (UTC)

While you are discovering interesting articles related to this, double check to see if they are in the appropriate cat(s) and add them as appropriate. That way the next person won't have trouble finding them. --Guy Macon (talk) 15:38, 22 July 2016 (UTC)

Lapidary

Suppose you're trying to make a very thin (so thin as to be translucent), flat, mirror-smooth slice of an opaque gemstone with Mohs hardness between 5 and 6, and further suppose that you can't afford a professional-grade faceting machine. Given these conditions, which machine would give better results -- a power sander or a grinder? 2601:646:8E01:7E0B:7D92:4B92:BDBC:ACFB (talk) 08:20, 22 July 2016 (UTC)

I'm not sure any such machine will give reasonable results, as the tolerances involved are outside of what you need to perform the task. If I'm trying to figure out if the machine will work, I'd try to think a) what is the thicknes and b) what is the smoothness of the final product. Since sanders and grinders would both have a huge variance in their vibrational motion, you'd not be able to control how they grind your surface to such a precision as to get satisfactory results. In simple terms, you're using an axe to do a scalpel's job, and just as you can't reliable cut a 5 mm incision in a specific location by swinging an axe at full force, you likewise can't expect woodworking tools to do the fine cutting and polishing you're expecting. --Jayron32 11:00, 22 July 2016 (UTC)

Neither of these could give you a mirror finish as they are much too coarse. They could probably cut off the bulk, but then you would need to go very carefully, perhaps with hand held sharpening block. Then you will need finer and finer polish dusts to get to mirror smooth with imperfections under 1μm. Graeme Bartlett (talk) 11:26, 22 July 2016 (UTC)

That might work -- just tell me, how smooth a finish will I need to get a refraction index? 2601:646:8E01:7E0B:7D92:4B92:BDBC:ACFB (talk) 03:46, 23 July 2016 (UTC)

It seems like you could learn much by reading that faceting machine article and other articles on the device you want. Even though you can't afford it, it represents the technology you aspire to. Note, for example, the mention of pulmonary disease (from silicosis and the like, I assume) from breathing mineral dust, and the use of a drip to prevent this and to also keep heat from the grinding from cracking the stone. I'd say get an understanding of all such little technical points before you think about improvising, unless you want to run through multiple stones and/or lungs on your learning curve. Wnt (talk) 19:11, 22 July 2016 (UTC)

Are you kidding? I'm fully aware of the dust hazards -- I plan to wet down the rock before each pass and to wear a dust mask! 2601:646:8E01:7E0B:7D92:4B92:BDBC:ACFB (talk) 03:46, 23 July 2016 (UTC)

The OP does not state what type of grinder he has access to. If it is a surface grinder then the way I would tackle it would be to embed the lower part of the stone in epoxy putty upon a parallel plate. Then grind down to just above the putty. The putty itself will clog grinding wheel -so stop, before reaching that point. Also, clean the stone (with a suitable solvent, and even consider etching it with a quick dip in hydrofluoric acid in order for the epoxy to get a good bond). Then, with stone still embedded, hand-lap the the surface to a glass like finish on a lapping stone. Then release polished stone with an epoxy solvent and remount on parallel plate with epoxy glue with the polished face down. Grind down to within just a gnat's whisker on one's desired thickness. Then, hand-lap the wafer of stone on a lapping plate one again. Once a glass finish has been archived, release prepared and polished wafer by using an epoxy solvent once more. This gives a thin and transparent wafer. If it is a big and valuable stone, consider first using a thin abrasive paper disc to cut it into thin sections and repeat above process. With a power sander it is very difficult the achieve a flat surface (on a large specimens) . Try as one might, the edges get warn down the most. --Aspro (talk) 12:12, 23 July 2016 (UTC)

Well, I don't need the whole stone (and I can't use the whole stone, anyway, on account of it's opaque) -- it will be a synthetic and will probably come out of the reactor as a cylindrical slug, so I'll just need to cut a thin slice off the end and then grind it down to where it's translucent (which means grinding it down to a very thin slice indeed). Thanks for the advice, it sounds like a workable plan! 2601:646:8E01:7E0B:D5B2:91C:A132:E02D (talk) 00:36, 24 July 2016 (UTC)

Since you want to identify the mineral, there are also other ways. Consider hardness test, streak test, specific gravity, borax bead test. And the refractive index can be estimated from a small particle in those liquids with different refractive indexes. You can also measure the Brewster angle from a polarised light reflection. Graeme Bartlett (talk) 12:54, 23 July 2016 (UTC)

I'm actually not trying to identify an unknown stone -- I'm trying to check whether my synthetic stone (which I haven't actually synthesized yet -- I'm just putting the plumbing together at this point) is as close as possible to the real thing in terms of physical properties (which means I have to do all these tests, or at least as many of them as I can). (The best way, of course, would be by FTIR, but I can't afford that machine either and also have no room for it even if I could.) So you're saying that I might not need a perfectly smooth finish in order to measure the refractive index with a refractometer? Oh, and did I mention that the stone is opaque except in very thin sections? 2601:646:8E01:7E0B:D5B2:91C:A132:E02D (talk) 00:04, 24 July 2016 (UTC)

A very small crumb / piece of dust should also be thin enough to transmit light. You can use Optical relief or the Becke line test to get an estimate. Another idea is to find a lapidary club and ask someone for help. Perhaps you can borrow their equipment. You may be able to hire some machines too. TO measure reflection you will only need a smooth finish on a surface, and not cut it so thin that it becomes transparent. And that surface does not have to be too big, a square millimeter may be enough. Also an optical spectrogram may be useful. X ray crystallography can tell if you have the right mineral structure. Graeme Bartlett (talk) 01:43, 24 July 2016 (UTC)

Right, I plan to take an optical spectrum with a spectroscope -- for this I will need a piece which is translucent but not necessarily smooth, whereas for the refraction index I will need one which is smooth but not necessarily translucent. Of course, if the piece is both smooth AND thin, I can use it for both things (optical spectrum first, then refraction index). Did I understand you correctly? 2601:646:8E01:7E0B:D5B2:91C:A132:E02D (talk) 03:28, 24 July 2016 (UTC)

The high refractive liquids to look for are quinoline, cinnamon oil, and methylene iodide. You seem to have the idea about translucency, but you should also be able to get a spectrum from reflected light. Graeme Bartlett (talk) 09:01, 24 July 2016 (UTC)

Wouldn't that require a different technique altogether? 2601:646:8E01:7E0B:D013:7C29:7816:F57B (talk) 00:01, 25 July 2016 (UTC)

That is yet another technique. If no published spectrum is published you may have to measure from a comparison sample. Graeme Bartlett (talk) 12:57, 25 July 2016 (UTC)

You could try asking this on Arts & Crafts Stack Exchange, under the lapidary tag. If you do, be sure to link the instances of the question both ways. – b_jonas 13:23, 25 July 2016 (UTC)

Digging Earth

Peeps Earthlings,

I can’t recall if I asked this before, so I’m asking now, I would like to know if Earth diggers can reach the Earth’s core or not…

Regards.

Apostle (talk) 09:24, 22 July 2016 (UTC)

Not even close. The deepest hole ever drilled is the Kola Superdeep Borehole at a bit over 12 km. The deepest mine is the Mponeng Gold Mine at a little over 4 km. The outer core starts about 2,890 km below the surface. As you go deeper the temperature and pressure gets larger which limits the range of traditional digging / drilling technology. Dragons flight (talk) 09:36, 22 July 2016 (UTC)

Googling deepest hole on earth into Google would have answered that for you quickly regardless of how many times you've asked us. Matt Deres (talk) 10:52, 22 July 2016 (UTC)

Perhaps, but we have no rule that requires prior googling. And unlike google, we presumably can limit our responses to reliable sources. Google is not some magic sage, and often search results yield incorrect and misleading "answers". If you don't like to answer questions that are easy for you to answer, you are allowed to refrain from doing so ;) SemanticMantis (talk) 14:55, 22 July 2016 (UTC)

And now a word from our sponsor: Wikipedia, a friendly non-profit encyclopedia project, offers a Search field at the top of this screen that returns a fine selection of articles when one enters deepest hole on earth that compare favorably with anything a bloated profit-hungry advertising company might offer. AllBestFaith (talk) 16:15, 22 July 2016 (UTC)

One potential application of deep holes are Gravity trains, but these will likely remain theoretical thought experiments. SemanticMantis (talk) 14:57, 22 July 2016 (UTC)

Diggers encounter problems after only a few feet never mind thousands of miles deep Law of holes. Dmcq (talk) 16:57, 22 July 2016 (UTC)

Okay, thank you all for the information. I have to learn it some other time...

If you guys don't mind, could you please give it to me in miles, kilomiles (I'm guessing, given for all kinds of digging, above), metre, feet/foot and any other known mathematics i.e. applicable, that diggers are using while digging, please? -- Apostle (talk) 05:23, 23 July 2016 (UTC)

If you have a problem like that just stick a line into Google search like "2,890 km in miles" (quotes not needed) and our AI overlord will condescend to enlighten you using an attofraction of its power. Dmcq (talk) 08:46, 23 July 2016 (UTC)

It comes on the first page! -- Apostle (talk) 03:58, 24 July 2016 (UTC)

Thanks all. Regards. -- Apostle (talk) 03:58, 24 July 2016 (UTC)

Civil engineering projects

In civil engineering projects, does the principal contractor and its site management staff (construction managers, project engineers) etc still have overall responsibility for the site when all the civils work is done and interior fitout/electrical wiring/IT etc starts? In other words, by the time the site is handed over to the client, is the finished product, in a usable state for whatever it's intended purpose is or does it still require some work? 2A02:C7D:B945:6400:2897:1BD0:7DBA:B99D (talk) 09:38, 22 July 2016 (UTC)

• It looks more like a law question to me. Are you sure you would not move your question to Wikipedia:Reference_desk/Humanities? Tigraan^{Click here to contact me} 10:45, 22 July 2016 (UTC)
• You also seem to be asking more generally about management and organizational structure. I'm not sure of the answer, but those will provide you some additional reading. I also agree with Tigraan that this isn't a Science question, and is more suited for the Humanities or Miscellaneous desk. --Jayron32 10:50, 22 July 2016 (UTC)

Wikipedia has an extensive article about contracts. A major Civil engineering contract usually defines various phases of construction, that may follow a Design–bid–build or Design–build delivery sequence. Good Project planning will ensure that actual progress is compared with the baseline schedule (possibly drawn on a Gantt chart) throughout the project such that responsibilities for any deviation or incompletion are identified. Payments should be tied to clearly defined acceptance criteria, and the contract may specify "penalty" deductions for delays. Legal disputes often arise after delivery if the concept "suitability for its (not it's) intended purpose" was not quantified at the outset in measurable, objective terms. AllBestFaith (talk) 12:23, 22 July 2016 (UTC)

QuestionEnergy efficiency of batteries

Is it more energy efficient to charge AA batteries and put them into device, or use 3 volt transformer plug to power device directly off mains socket? — Preceding unsigned comment added by 111.249.153.69 (talk) 12:28, 22 July 2016 (UTC)

The use of batteries involves energy losses in 1) manufacturing the batteries, 2) the battery charger circuit, and 3) the energy return loss (including self-discharge) of the batteries themselves. Using an AC adapter eliminates 1) and 3) above and the only remaining energy loss is likely similar to 2). Most of the energy losses mentioned can be felt as heat. The overall energy inefficiency of using batteries is the price you pay for portability. I corrected the header to identify the topic. AllBestFaith (talk) 12:43, 22 July 2016 (UTC)

Whilst agreeing fully with AllBestFaith's answer, I would just point out that there is an exception for devices that are seldom used and where a 3v transformer might be left switched on, consuming energy unnecessarily. This is quite common in some households. Dbfirs 14:08, 25 July 2016 (UTC)

Genetics and inheritance

when sexual partners have sex, unprotected is it true that they exchange some pf their genetical material? — Preceding unsigned comment added by Kaymcluke (talk • contribs) 13:10, 22 July 2016 (UTC)

When sexaul partners have sex, unprotected, do they exchange their gebetical material? — Preceding unsigned comment added by Kaymcluke (talk • contribs) 13:12, 22 July 2016 (UTC)

They don't exactly exchange, as there is no change in their genetics. However, their genetic material is combined to form a new organism (a zygote). Is this what you are asking? --T H F S W (T · C · E) 14:30, 22 July 2016 (UTC)

Well, more precisely, a sex act could result in the combination of genetic material to form a zygote, but it isn't guaranteed to do so. Sperm is released during sex (assuming a healthy, fully-functional male), but whether or not a viable ovum is present is more a matter of chance and/or planning as the egg is not released due to the sex act itself. Dragons flight (talk) 15:29, 22 July 2016 (UTC)

If I wanted to learn more about this topic, I'd start reading at Human embryogenesis and Fertilisation and follow further links to articles that discuss various aspects thereof in more detail. --Jayron32 15:19, 22 July 2016 (UTC)

If you are asking whether genetic material from the male partner is permanently incorporated into the genome of the female partner, and vice versa, then the answer is no. The emotional and physical consequences of sex may change people's lives in many ways, including the possibility of pregnancy and sexually transmitted infections; however, the only transfer of genes is from parents to child. There is no incorporation of genetic material from one partner into the other partner. Dragons flight (talk) 15:29, 22 July 2016 (UTC)

Presumably the OP is not speaking of microbes such as STD's. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:26, 22 July 2016 (UTC)

(edit conflict) All of that also applies for a same-sex couple, of course - though no zygote can be formed, except maybe in extraordinary circumstances such as those listed at Disorders_of_sex_development. Tigraan^{Click here to contact me} 16:27, 22 July 2016 (UTC)

• The "inheritance" in the thread title suggests that the questioner wants to know about incorporation of the sex partner's DNA in the genome of the individual, and the answer would seem to be "No" from the above answers. But in another sense of "exchange" I wish to point out Locard's Principle. Wikipedia's article is Locard's exchange principle.which says that after any encounter each person will leave some trace evidence and take away some trace evidence. In this instance each participant might well retain some DNA from the other participant, until time and bathing remove it. This could include DNA from semen or vaginal fluids, skin cells, blood or the roots of hairs. Tests are now so sensitive that ridiculously small traces are found. In one recent case, DNA was turning up at many and varied crime scenes, and it turned out to be from a technician at the factory where the swabs used in testing were made. In another case, trace DNA was found under the fingernail of a millionaire murdered in a mansion and matched to a homeless man. It turned out to behave been transferred inadvertently a paramedic who had been at the death scenes and who had earlier treated the homeless man and picked up his dna on a medical device.. (I read this in some reliable online news article in the last 2 weeks but do not have a handy link. The point is that DNA detection is very sensitive and perhaps so sensitive as to provide false leads). Edison (talk) 16:56, 22 July 2016 (UTC)
  • Found the article about the false positives from DNA trace analysis:"The false promise of DNA testing," The Atlantic, June 2016. Techs in the past have made huge errors and botched basic DNA tests, sending innocent people to prison. Now they are delivering analyses of trace DNA from a fingerprint or a microscopic drop of sweat or saliva, even when in a mixture of DNA contributions.Edison (talk) 17:09, 22 July 2016 (UTC)
    • Here is a good article from 2015 that discusses secondary DNA transfer. Which probably takes us far afield of the OP's question, but given the direction of the tangent, I thought it an interesting article. --Jayron32 17:37, 22 July 2016 (UTC)
• Possibly - at least male to female when a fetus is involved. See fetomaternal microchimerism where children's cells can be detected in many mothers even years later and so will contain some of the father's DNA. Rmhermen (talk) 19:20, 22 July 2016 (UTC)

Radioactive heat from radium

Resolved

If I had a gram of radium metal, how much would it heat the environment around it? Would anything much happen if I put it on a wooden table? (Assuming for the purpose of this question that I am well-protected from the radiation.) Double sharp (talk) 15:26, 22 July 2016 (UTC)

$1\,{\text{gram}}{1\,{\text{mole}} \over 226\,{\text{gram}}}{6.02\times 10^{26}{\text{atoms}} \over 1\,{\text{mole}}}{ln(2) \over 1600\,{\text{years}}}{4.87\,{\text{MeV}} \over 1\,{\text{atom}}}=28.5\,{\text{W}}$

Warm, but less hot than a typical incandescent light bulb. Dragons flight (talk) 15:41, 22 July 2016 (UTC)

Thank you! Double sharp (talk) 15:57, 22 July 2016 (UTC)

• Minor nitpicks to Dragons flight's math: this is assuming one gram of pure radium (it tends to be diluted in other stuff), of the 226 isotope (the usual one), and I suspect the 4.87MeV figure refers to the whole radiation, which may or may not dissipate as heat as it meets the table (but going by the WP article, most of the radiation is alpha decay, which does get stopped shortly). Tigraan^{Click here to contact me} 16:18, 22 July 2016 (UTC)

Radium is a reactive so-called alkali earth metal, and will oxidize rapidly in ordinary air. You will have to keep the radium either in a vacuum jar or a jar containing a non-reactive gas (nitrogen, argon, etc.) or in a hydrocarbon liquid. Robert McClenon (talk) 17:46, 22 July 2016 (UTC)

• Bear in mind 1 gram is a very small amount of metal (it would be a cube about 5 mm on each side, roughly the size of a small piece of gravel) pressed right up against the table. Let's assume that 1/6th of the energy is absorbed by the wood (since we're dealing with a cube), in a thin layer immediately under the cube (I read that alpha particles are stopped by a sheet of paper, so presumably they don't go much further in wood. Let's be generous and say the bulk of the flux is absorbed by a volume 5mm * 5mm * 1mm). If you ignore heat flow, that bit of wood is going to heat up by about 700 C per second. In reality, you'll get a fair bit of conduction and air cooling, but I built a simple model in a thermal simulator, and it calculated that the wood would reach its burning point - and the radium would reach melting point - very quickly (within a few seconds). Presumably this is why there are no pictures of pure radium on the internet - it's not a thing that can actually exist in a stable state. Think about it this way: what would happen if you were to take the coil out of a lightbulb and press it right against a wooden table? Smurrayinchester 18:36, 22 July 2016 (UTC)

You're right. I wasn't very careful in thinking about the volume being heated. If it is really a pure gram that would get very hot. If it is 1 gram mixed in a base of 99% some other metals (rather more likely), then the resulting temperature would be less. One would need to know more about how the radium is distributed. Dragons flight (talk) 21:53, 22 July 2016 (UTC)

You mean they never found that mine? --Trovatore (talk) 21:07, 22 July 2016 (UTC)

“ Some say that the Northern Lights are the glare of the Arctic ice and snow;

And some that it's electricity, and nobody seems to know.
But I'll tell you now—and if I lie, may my lips be stricken dumb—
It's a mine, a mine of the precious stuff that men call radium.
It's a million dollars a pound, they say, and there's tons and tons in sight.
You can see it gleam in a golden stream in the solitudes of night.
And it's mine, all mine—and say! if you have a hundred plunks to spare,
I'll let you have the chance of your life, I'll sell you a quarter share.

”

Plenty (ok, a few) pictures of radium are on the internet. On wiki(p|m)edia, we even have File:Radium-226.jpg of the isotope in question. DMacks (talk) 19:44, 22 July 2016 (UTC)

The Wikimedia photo is poorly labelled. The image is (purportedly) of a "check source" for a CD V-700 Geiger counter. It's a little bit of radioactive material attached to the instrument that you can use to verify that the probe is working when you're in the field. Its actual radium content is quite low; the measured activity of the source is on the order of 8 nanocuries, meaning that the vast majority of the metal present is non-radioactive filler. I suspect that something similar is true of most other photos you will find of "radium-226" on the internet. TenOfAllTrades(talk) 20:05, 22 July 2016 (UTC)

File:Radium226.jpg is a more clearly described image. Not a chunk, but a possibly pure-ish surface layer (though unknown how thick the layer is or how completely covered the substrate is). DMacks (talk) 21:41, 22 July 2016 (UTC)

It looks like an extremely thin and spotty film (although admittedly, radium does go yellow-brown when exposed to air). Certainly nowhere near 1 gram. Smurrayinchester 21:50, 22 July 2016 (UTC)

Hot humid weather and joints

I asked a similar question some time ago and got the answer "nobody knows". Here's hoping for an answer to this one! And this is definitely not a request for medical advice. I know what to do thank you.

I have noticed that when the temperature reaches above about 24 degC and the relative humidity over 70, my arthritic joints are in a worse condition than when the temperature is lower and the humidity is lower. Why would this be? --TammyMoet (talk) 18:11, 22 July 2016 (UTC)

Take a look at the results of this Google Scholar search and take your pick. Rheumatoid arthritis patients show weather sensitivity in daily life, but the relationship is not clinically significant from 1999 seems to sum up most of the results. Alansplodge (talk) 18:24, 22 July 2016 (UTC)

See Weather pains. Loraof (talk) 22:07, 22 July 2016 (UTC)

Blimey we do have an article on everything! Thank you!--TammyMoet (talk) 09:40, 23 July 2016 (UTC)