Wikipedia:Reference desk/Archives/Science/2014 January 6

= January 6 =

Soft tubing materials?
I figure I can shoe-horn this question into the science section as a question of materials. I would like to make an outfit like this but I don't know what kind of tubing would be the cheapest with longevity and flexibility. I tried PVC tubing but it is far too rigid. I need it to be soft and to be okay in the washing machine. --78.148.110.243 (talk) 04:48, 6 January 2014 (UTC)


 * PEX tubing is designed for plumbing applications, so is flexible, especially the smaller diameters. I'm not sure how it holds up to washing, but my guess is it would be OK if you avoid bleach, which tends to make plastics brittle or tacky.   StuRat (talk) 12:00, 6 January 2014 (UTC)


 * Not sure what you are up to. But PEX tends to be made from LDPE, which is a very crystalline material, and is going to be rather rigid.  Silicone hose is very flexible and easily available up to 1 inch ID, there is also rubber hose, flexible ducting hose made from butyl rubber - why not check out materials at your local builders store? They tend to be helpful in that kind of places, talk to the oldest and grumpiest guy, that fellow will know best.  93.102.216.165 (talk) 17:55, 6 January 2014 (UTC)

Trinucleotide repeat mutations
I am watching a Genetics class on YouTube, and it discusses Huntington's disease and mutations due to wrong number of copies being made of the repeated sequences. Here's the link. One thing I don't get, is that he seems to be saying that the copying errors only happen between generations (of individuals). So in the graph in the video you see each individual have 2 gene lengths, one from each copy he or she has. From what the professor says, I gather that DNA polymerase slips up. But aren't genes also copied during normal cell division, and wouldn't therefore multiple cells of the same person be likely to have different number of repeats as well? Am I misunderstanding something? --108.202.177.21 (talk) 07:15, 6 January 2014 (UTC)


 * You're correct, the slip ups could occur during mitosis just as easily as they occur during meiosis. However, mitotic mutations are rarely as hazardous to health, and the reason is that any particular mitotic mutation will inevitably effect only a small portion of your body's cells (the rare times they do affect your health are usually cancer). So although a future brain cell might spontaneously get a lengthened huntington's gene, it will only be that one cell and its relative handful of descendants amongst the entire rest of your brain. Unless the mutation occurred very early in development to affect a large enough number of brain cells, you probably wouldn't notice. Someguy1221 (talk) 07:27, 6 January 2014 (UTC)


 * See trinucleotide repeat disorders. It looks like there has been some interesting recent work in understanding the condition further, including the role of various DNA polymerases, miRNA hairpins that are diced up (a sort of cellular anti-spam mechanism) and the 26S proteasome.    I don't know, but the explanation for why it changes more between generations could turn out to be complex, based on multiple factors. Wnt (talk) 08:32, 6 January 2014 (UTC)


 * Thanks! --108.202.177.21 (talk) 18:01, 6 January 2014 (UTC)

To know how is the score or grade calculated for natural essential oils.
I trade in natural essential oils ..and there are customers who ask me this question which am unaware of. so i want your assistance in this.

In natural essential oils what is the highest score or grade may be, usually a scale from low to high depending on what is the rule in the book. for eg: is a 10 the highest or is a 1 the highest score ? — Preceding unsigned comment added by 116.202.170.56 (talk) 09:47, 6 January 2014 (UTC)


 * Nah, I haven't come across this. I suspect some of your customers are thinking the oils may be diluted in a carrier oil, a common practice, e.g. for massage oils, and they want to know the percentage dilution. Ads for essential oils generally say 100% pure, so I guess that is the figure they are looking for.--Shantavira|feed me 12:20, 6 January 2014 (UTC)


 * The only grading system I've come across (I'm an aromatherapist) is with ylang-ylang essential oil, which comes in different grades. Our article says they are extra, 1, 2 or 3. Otherwise I agree with Shantavira. --TammyMoet (talk) 19:17, 6 January 2014 (UTC)

The eyes have it.
I can't find any pictures. Does Peters' four-eyed frog really live up to its name? Clarityfiend (talk) 10:31, 6 January 2014 (UTC)


 * Google image search gives some results, but none of them look particularly four-eyed to me. AndrewWTaylor (talk) 10:45, 6 January 2014 (UTC)


 * Could Peters have found a mutant, which did indeed have 4 eyes ? StuRat (talk) 11:56, 6 January 2014 (UTC)


 * There are other four-eyed frogs, named presumably because of their markings. Nothing in any of the articles suggests they have more than the usual two eyes. Ribbit.--Shantavira|feed me 12:14, 6 January 2014 (UTC)


 * The extra "eyes" are poison glands, and they're at the other end of the frog: . --Amble (talk) 12:29, 6 January 2014 (UTC)


 * Great info. Would you like to add that to our articles ? StuRat (talk) 12:49, 6 January 2014 (UTC)


 * Sure, although that source is really just a blog. (That's not terrible but we can probably do better.)  Here's a Google book result with some more info: .  I may have time to add the info later today, if someone else hasn't already done it by then. --Amble (talk) 15:15, 6 January 2014 (UTC)


 * Excellent. Thanks. Clarityfiend (talk) 00:44, 7 January 2014 (UTC)


 * I added a few sentences to the articles that already mentioned common names with "four eyes". I don't know whether that common name also applies to other species in the genus, or whether the glands are as visually prominent in all species.  --Amble (talk) 14:42, 9 January 2014 (UTC)

Meaning of half-integer spin
Electron is a half-integer spin particle. But what is the meaning of half-integer spin? 106.209.249.198 (talk) 15:09, 6 January 2014 (UTC)


 * Does our Spin-½ article help?--Shantavira|feed me 16:31, 6 January 2014 (UTC)


 * Spin (physics) would be a good place to start. Red Act (talk) 18:18, 6 January 2014 (UTC)


 * At a really basic level, spin is quantized in units of the reduced Planck's constant. Every photon, red or blue, big or small, no matter how it's polarized, carries a spin of this amount.  So a spinning particle can change spin by interacting with photons by increasing or decreasing by 1 of these reduced Planck's constant units at a time.  Spin-1/2 particles are particles which have just two states, so they have to be 1 unit apart - but these are spins in opposite directions, which makes them +1/2 and -1/2. Wnt (talk) 18:29, 6 January 2014 (UTC)

Grrr...squirrels
One of these bushy-tailed rats is eating the outside trim of our bathroom. I looked him/her in the eye, through the window, but s/he didn't bat an eye and just kept on gnawing. What can I do to deter this beast? I've seen "deterrents" to use in the garden, and they basically tell you to boil water with chili peppers--what if I pour a bunch of hot sauce (Texas Pete, of course) on the window casing? Thanks, Drmies (talk) 15:12, 6 January 2014 (UTC)


 * Yea, I bet that would work. StuRat (talk) 15:43, 6 January 2014 (UTC)


 * Your last name does not inspire much confidence! :) Drmies (talk) 15:44, 6 January 2014 (UTC)


 * LOL. One downside of hot sauce might be that it could stain the wood red or brown.  But, unless you have some clear liquid to repel squirrels, I'd say stained wood is better than chewed wood.  You can always repaint it.


 * Also, I've noticed that squirrels don't see well through windows. I think they focus on the reflection rather than what's on the far side.  Try knocking on the window next time and see them run like hell. StuRat (talk) 15:47, 6 January 2014 (UTC)


 * Well, this squirrel couldn't care less about growling, rapping, or knocking. Furry little shit. I'm gonna go with that hot vinegar, the little bottles with peppers in it--shouldn't stain very much. Thanks, Drmies (talk) 18:48, 6 January 2014 (UTC)


 * Problem squirrel? No problem! http://i.imgur.com/TJ4oo.gif — Preceding unsigned comment added by 217.158.236.14 (talk) 16:05, 6 January 2014 (UTC)


 * LOL. That video also illustrates my point about squirrels apparently not being able to see through windows. StuRat (talk) 20:29, 6 January 2014 (UTC)
 * If that squirrel didn't have a name, it must now be called Rocky! I don't think the RSPCA/SPCA would approve! O:-) 220  of  Borg 09:40, 7 January 2014 (UTC)


 * In the UK you can get something called Squirrel Stop at garden centres, which is basically the same stuff as pepper spray. No doubt you can buy some equivalent elsewhere. Just spray it onto the trim.--Shantavira|feed me 16:36, 6 January 2014 (UTC)


 * Having rescued and raised orphan squirrels in the past, I can sympathize with your frustration with their obstinacy in this regard. The solution you proposed yourself is one of the more ideal ones, especially if you don't want to do actual harm to the critter (which it seems from your comments you don't).  If you buy a commercial product, be sure you know its ingredients in detail, as oversight on these products isn't always the best (who all is really going to make a fuss if it harms the pest or kills it outright?), which can further be a problem if you have a pet capable of eating a squirrel corpse.  All of that being said, there is also the more traditional method of fixing a replica bird-of-prey on the roof immediately above, but squirrels are quite clever and unlikely to be fooled indefinitely by this ploy.  It's also worth noting that the squirrel is likely not eating the trim in the sense of consuming it; squirrels gnaw for a variety of practical reasons that have nothing to do with dietary needs. Primarily this behaviour is a result of the fact that, like virtually all rodents, their teeth grow for the duration of their lives and must be constantly worn down; generally the upper and lower incisors grow to meet eachother for this purpose, but in cases of malocclusion, it's possible the squirrel is chewing like crazy to forestall the eventual grisly fate of having the lower teeth puncture the roof of his/her mouth and grow into the upper skull -- it's not always so easy being a squirrel!  Even squirrels lacking this condition tend to gnaw a great deal.  Other reasons for this behaviour include to the production of nesting material and simply because the squirrel is trying to get at something or into somewhere.  If you figure out the cause of the behaviour you may have still other avenues to explore.  For example, if it's looking for nest material, you can always provide an alternative, if you don't have problems with being extorted by a rodent. ;)  Good luck, and I hope you find a simple solution so the situation need not come to more drastic means; I know they can be irritating at times, but they really are cool little creatures and usually can be made to coexist without being too destructive to property with a little effort and luck. Snow (talk) 21:00, 6 January 2014 (UTC)


 * Yes, I wouldn't mind all the squirrels around my home if they hadn't broken into our attic (one also did a Santa impression and came down the chimney to leave us a few "gifts").


 * Leaving the squirrel a board to gnaw on might be a good idea, too. StuRat (talk) 21:20, 6 January 2014 (UTC)


 * Same here: they've lived in our attic before, and I can't help but think that this one was simply trying to bite its way in. The yard is full of trees and other woody material so there's plenty of other things to gnaw on. As far as my intent is concerned: I could want to kill them, but there's so many of them that there's no point to it. I do not believe this varmint scares easily easily and it clearly wipes its little rodent ass with my demands as a homeowner, so let's see how it handles Texas Pete Pepper Sauce, and what it thinks of the list of ingredients. Drmies (talk) 21:36, 6 January 2014 (UTC)


 * I picture it running really fast after it eats it, while yelling "Areba ! Areba !". StuRat (talk) 21:46, 6 January 2014 (UTC)


 * Arriba! Arriba! Richard Avery (talk) 07:45, 7 January 2014 (UTC)


 * God did not put squirrels on this earth to coarse this type of mayhem. He put them here so we could all enjoy squirrel pie. More receipts here:  and here, Oh, and here as well  . In fact there, are so many edible  solutions  to this problem, that I wonder why squirrels have not been put on the Endangered species list.  Mind you, I'm a fine one to talk – all I have in my fridge is several remnants of roast turkey, some two (?)  week old minces pies and a lot of stuff  that would require a DNA test to establish their origin. Ugh... Something in the back of the fridge just moved – is it coming out of hibernation?--Aspro (talk) 00:18, 7 January 2014 (UTC)


 * You could try hiring a falconer to go after the rats, too -- hawks just LOVE eating squirrel for lunch! Also, if you have a cat, maybe you could let it loose on the squirrels and see if that scares them away? 2601:9:3200:467:6109:95AD:B0F7:600D (talk) 02:52, 7 January 2014 (UTC)
 * I was likewise thinking that if the OP could acquire the services of an owl or a falcon or a hawk, there's a good chance the squirrel population in that vicinity would decrease quickly, one way or another. Kind of a precedent for this approach occurred at the San Francisco Giants ballpark, which was plagued by various flocks of birds for some time, until hawks started hanging out there, and the other birds went away. ←Baseball Bugs What's up, Doc? carrots→ 03:15, 7 January 2014 (UTC)
 * The OP actually has a hawk in the neighborhood--but also pecan trees, in huge numbers. Also, I'm not about to start eating squirrel, thanks very much. Drmies (talk) 03:35, 8 January 2014 (UTC)
 * I was thinking more of San Jose State University, which had a huge population of squirrels until a pair of peregrine falcons built their nest on the roof of the new library, after which they thinned out the squirrels in short order. 2601:9:3200:467:6109:95AD:B0F7:600D (talk) 02:28, 8 January 2014 (UTC)
 * You might want to talk to your local electric utility, while I don't have a reference at hand, at least here in west central Florida, squirrels chewing into electrical equipment for whatever reason are a significant cause of power outages. — TimL &bull; talk 22:28, 8 January 2014 (UTC)

White pepper powder. Deters most things that sniff around for their food.

Competition between aldol and Claisen
Hi, I don't know if this is the correct place to ask this question, but on the talkpage of user:Jü I have posted a question about competition between an aldol and a Claisen reaction, because I would like to write something about it on Wikipedia. Unfortunately, Jü was not able to tell me more about the various effects that can take place on those specific substrates, and I am not sure if I have the correct information to complement the article on aldol reactions. Please read this section first to obtain some background information. Thanks in advance! Best regards, Capaccio (talk) 19:24, 6 January 2014 (UTC)
 * Hoping to keep the existing discussion together, I responded there. But for anyone interested, executive summary is "it's well-known that esters are generally noticeably less reactive as electrophiles than aldehydes are". DMacks (talk) 22:11, 6 January 2014 (UTC)

Release static charge from reverse side of glass
I have a full size business office copier that copies through scanning – the paper run through and is scanned as it passes over the glass. Unfortunately, what happens sometimes is that little particles get stuck to the reverse side of the glass. When that happens your copies get lines in them because the copier is scanning each page across that glass with the object behind it. The way I fix this is to take off the glass and clean the backside of it but it's quite a pain. Is there a way to make the particles that are stuck on the back through static electricity fall away by neutralizing the charge from the other side of the glass so that the gass can remain in place? By the way, I am well aware that the methods proposed might be such that they would work, but also fry the copier's electronics. I am curious from an academic standpoint, even if actually doing the solutions proposed would be highly inadvisable.--71.167.166.18 (talk) 19:39, 6 January 2014 (UTC)
 * The preliminary question seems to be whether the static charge on the glass is positive or negative. In the former case, it should be possible to use an electron gun to remove the charge. If it's the latter, then a radioactive isotope which decays primarily via alpha particle emission might neutralize the glass. DavidLeighEllis (talk) 19:55, 6 January 2014 (UTC)
 * The idea of using alpha-radiation to discharge static sounds pretty scary - but those little brushes that photographers use do just that. They have a tiny amount of polonium 210 in them. SteveBaker (talk) 20:50, 7 January 2014 (UTC)
 * On a perhaps more practical note, one might be able to apply an antistatic agent to the reverse side of the glass, which could then be grounded. DavidLeighEllis (talk) 20:09, 6 January 2014 (UTC)
 * Wouldn't that prevent the xerox machine from working in the first place, because it DEPENDS on static electricity to make the toner stick to the copy? 2601:9:3200:467:6109:95AD:B0F7:600D (talk) 02:46, 7 January 2014 (UTC)
 * The copier depends on the toner sticking to the drum, not the underside of the glass. DavidLeighEllis (talk) 17:37, 7 January 2014 (UTC)
 * Yes, exactly. I'd want to ask why the stuff is getting there in the first place.  I suspect that there is some other component inside the copier that needs cleaning - and the lack of that is what's causing toner to get stuck under the glass.  I'd suspect a grungy corona wire or something. SteveBaker (talk) 20:50, 7 January 2014 (UTC)

collapsible pneumatic (i.e. inflatable) rods/poles (as in a tent)
can you talk about the theoretics and practicalities of collapsible pneumatic (i.e. inflatable) rods/poles. I googled it but found this huge design: http://www.firstprincipals.com/Airzone.htm

Why are the 'rods' so thick (like a tire)? Couldn't they just be thin but at high pressure? What if they were made of stronger material, like Kevlar?

I presume the physics are kind of that tires need a little "give" so that's why they're larger. what about a collapsible pole? if the material is strong enough (kevlar/carbon nanotubing) can it be thin but very rigid? I'm just throwing out ideas. I don't know the actual physics, theoretical and practical, that govern this and would like to learn more. Thank you. 212.96.61.236 (talk) 20:25, 6 January 2014 (UTC)


 * AirCompressorHusky.JPG When we're talking about supports like this, it's easiest to talk about them in terms of a Beam (structure), specifically Thin walled beams. The stiffness (and therefore strength) of these types of structures is essentially dependent on 2 things: the thickness of the beam, and the stiffness of the material.  So, to make a hollow tent pole adequately strong, we can either make thin poles out of a really strong material (like traditional metal tent poles), or make thicker poles out of weaker materials (like the inflatable fabric ones you linked to).  It's also possible to make a fabric structure stronger by filling with higher-pressure air (which effectively makes the walls stiffer by making it more difficult for them to move--think of something like a car's airbags, which look nice and fluffy but actually absorb quite a bit of force), but as you mentioned, there are practical considerations with both maintaining that pressure, and creating it in an environment where you would use a tent.  130.76.96.156 (talk) 21:24, 6 January 2014 (UTC)


 * (ec) How could you fill them with high pressure ? The idea of low pressure is so you can pump them up easily, say with a bicycle pump.


 * I would be concerned about the long term durability of the tent poles. I'd expect small holes to develop in them, making them useless until patched. StuRat (talk) 21:29, 6 January 2014 (UTC)

The tent example is just because that's what came up when I googled "inflatable pole." I was thinking like a piece of home furniture that would be pumped up once very slowly until it's incredibly rigid. What prevents this - the fact that rods aren't strong enough to support the high pressure? Would a theoretical more tensile material then support this usage case? Is it the 'risk' (i.e. explosion due to a pinprick.) I would just like to know where to start. In my mind's eye, it seems reasonable that a backpack could inflate, when plugged in, into a portable dresser for example. you just plug it in and it inflates. but the existing designs don't seem to make this practical... so...why not? 212.96.61.236 (talk) 21:57, 6 January 2014 (UTC)


 * It would never be like a solid object. The higher the pressure, the less it would compress when touched, but it would always compress somewhat.  I don't think people want dressers that move when they put something on them (and I can't imagine the drawers sliding in and out on it).  Of course, there are furniture items that people do like to be soft, like mattresses, couches, etc., so those could be made inflatable.  One problem I've found with such items, though, is that they don't "breathe".  Thus, your sweat doesn't evaporate through them, but rather pools up and becomes quite uncomfortable.  This can be remedied by thick layers of cloth between you and the inflatable portion.


 * One other possible use for inflatable rods on furniture is as "bumpers". If you've ever stubbed a toe or hit your leg on a coffee table, you appreciate the need for these.


 * To add to the popping risk (better not have a cat with claws), the plastics might also outgas toxic chemicals into the air. Also, I don't think an inflatable membrane will last for decades, as most people expect their furniture to do.  StuRat (talk) 22:16, 6 January 2014 (UTC)


 * So, I actually meant for portable furniture, like going to a hotel. If you are "okay" with the membranes  buckling somewhat - could they be stiff enough under high pressure to be as good as weak unreinforced plastic/cardboard, for example?  212.96.61.236 (talk) 22:28, 6 January 2014 (UTC)


 * Sure, but what hotels don't provide furniture ? You'd probably still want some rigid pieces, like a wooden top for you inflatable table.  Also keep in mind that pumps tend to make noise.  Electrical pumps can be quite loud, while hand pumps are more quiet but take longer.  And the guests on either side will probably suspect you are pumping up a rubber woman. :-) StuRat (talk) 22:36, 6 January 2014 (UTC)

I was just curious about it. For example lots of hotels don't really provide a truly large clothes rack. If it were a triangular type of structure with tessalated (triangular) sections that go down to the ground (i.e. feet that break it into sections) and an inflated center pole to hang things on (spaced by the feet), I wonder if it could support a decent amount of clothing hanging upright down from it. Also, after the initial pumping, why can't it stay inflated like a tire? Don't some airtight things hold pressure well? 212.96.61.236 (talk) 01:08, 7 January 2014 (UTC)


 * I think you're a little ahead of your time. I would expect that the same sort of people who came up with 3D printing will soon invent an addressible fabric - one which can be made to fold up in a wide range of origami patterns, complete with self-adhesions - and with a small hydrogen fuel cell and repetitive motion it should even be able to pump up its enclosed spaces to reasonable pressures.  I dunno, I'll guess... 2019 for the press release. Wnt (talk) 05:46, 7 January 2014 (UTC)


 * Doing a google image search for inflatable beams gives some interesting examples! 122.108.189.192 (talk) —Preceding undated comment added 07:33, 7 January 2014 (UTC)


 * A collapsible clothes rack is probably easier to do without anything inflatable, especially if it doesn't need to be freestanding, but can hang off something like a curtain rod or the bathroom door. For example, you could hang a wire, with loops for each hanger, between two attachment points on opposite corners of the room.  Think about how much more portable this would be than an inflatable unit and pump.  StuRat (talk) 17:50, 7 January 2014 (UTC)


 * Something like this comes to mind... :-) 130.76.96.155 (talk) 21:12, 7 January 2014 (UTC)


 * It's worth thinking for a moment about the math involved.


 * The problem with bend-resistance for long inflatable tubes is that the cloth offers great strength in tension - but almost zero in compression.  So when the tube bends, only the pressure of the air inside resists that movement - and then only because of a reduction in the volume of the tube as it bends.


 * Imagine (for the sake of argument) a 5cm wide, square-cross-section tube.  If you bend it through 90 degrees, then the volume inside the tube decreases by about 5x5x5 = 125cm3.  If the cloth doesn't stretch at all - then the pressure inside the tube increases - but by how much depends on its length.  So if the tube is one meter long - then the volume inside the tube is 5x5x100=2500cm3 and the pressure inside increases by about 5% - and that's what provides the force needed to unbend the tube.  However, if you double the length of the tube - then the pressure increase is only 2.5% and the unbending force is half as much.   If you reduce the diameter of the tube to just 1cm - then only 1cm3 of air is displaced and the pressure increase in a 1m tube only goes up by 1% - that's why fatter tubes work better.


 * In a real-world tube, the cloth is bound to stretch a little bit as the pressure increases - until it reaches some limit beyond which it won't stretch much more.  That means that small pressure increases exert much less force on straightening the tube than you'd otherwise expect.  Worse still, the volume of air that's displaced is going to be proportional to the sine of the bend angle - and sin(small-angle) is a very small number.  So if the bend in the tube is only very slight - then the volume reduction will be very small indeed and the proportionate pressure increase will be correspondingly tiny.  As the bend angle increases, the amount of volume removed goes up rapidly.   That means that while you might make inflatable tubes that won't bend by a large amount - it's almost impossible to make tubes that are really stiff because small-angle bends produce very little pressure increase - and that's likely to be somewhat absorbed by the stretch in your cloth.  So your tubes are basically going to be very floppy.


 * The trick here is to use inflatable tubes in structural ways that they are good at - which is not in copying the properties of a wooden or metal structure. Ideally, you want to be using them in compression along their length and in tension rather than in bend-resistance situations.   That suggests that using groups of three tubes made into triangular 'trusses' would be a better way to build a structure using them.
 * SteveBaker (talk) 13:01, 8 January 2014 (UTC)