The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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. [1][2][3] 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)[reply]
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)[reply]
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 me12:20, 6 January 2014 (UTC)[reply]
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)[reply]
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: [5]. 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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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 me16:36, 6 January 2014 (UTC)[reply]
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)[reply]
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").
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)[reply]
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. [6] More receipts here: [7] and here [8], Oh, and here as well [9]. 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)[reply]
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)[reply]
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 BugsWhat's up, Doc?carrots→ 03:15, 7 January 2014 (UTC)[reply]
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)[reply]
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 • talk22:28, 8 January 2014 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
Who would want to lug one of these out in to the wild to set up their tent? 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)[reply]
(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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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.
Does anyone know of any records (or interesting data) concerning wide variations in temperature readings? For example, (I am just making this up) ... On such-and-such a date, the temperature in such-and-such a city dropped (or rose) 75 degrees in a 24-hour period. Or that same type of data, perhaps in a one-hour period (or an even shorter interval). Another way to phrase this is that I am looking for the greatest temperature variation in the shortest amount of time. Thanks. Joseph A. Spadaro (talk) 03:44, 7 January 2014 (UTC)[reply]
Given the equation of state of a system (in the form of P=f(V,T)) can we find Cp, Cv and Joule-Thomson coefficient? I've been struggling to express these values in terms of derivatives of P, V and T with respect to each other and I've failed so far.--Irrational number (talk) 12:20, 7 January 2014 (UTC)[reply]
I think the equation of state alone doesn't give you enough information. For example the ideal gas equation can be a good aproximation for real gases and will give you Cv = Cp-nR, but you can't derive the heat capacity ratio from it, that will depend on the type of gas (on the degrees of freedom). Ssscienccce (talk) 05:27, 10 January 2014 (UTC)[reply]
NASA SDO sun photo
Hi all,
This photo shows a picture of the sun taken by NASA. Here gives an explanation of what it is showing. It says that it shows wavelengths of 5800 Angstroms to 94 Angstroms, which it sort of says is where the normal yellow and green sections come from (although I'm not sure about that). What are the ranges of wavelengths for the other sections, what types of EM radiation do they represent? Are these standard for an image like this? Bonus points: Why are the features in each of the sections like that (i.e. different from one another)? Thanks! 80.254.147.164 (talk) 12:20, 7 January 2014 (UTC)[reply]
Different temperatures produce different wavelengths of radiation. This is similar to how when you heat metal it goes from red hot to white hot. Thus, by looking at different wavelengths of radiation, we can focus on different temperature features. The surface is relatively cool compared with the interior and the corona. StuRat (talk) 14:24, 7 January 2014 (UTC)[reply]
What is the term for the temperature at which it is so cold that a malleable metal becomes brittle? (I want to find a chart for the temperature but don't know the name for what I'm looking for.) RJFJR (talk) 14:34, 7 January 2014 (UTC)[reply]
Toughness, the property of a metal to absorb shock without fracturing, is a function of temperature. You might be able to find data in a materials handbook or by scouring our articles and linked references for each metal of interest.
(ec) Note that it doesn't happen instantly at a certain temperature. Metals, and other materials, become steadily more brittle the colder they get. StuRat (talk) 14:55, 7 January 2014 (UTC)[reply]
The article embrittlement calls such a transition temperature the embrittlement temperature, though it specifically references plastics and rubbers, rather than metals. (Perhaps because of the gradual transition that StuRat mentions.) -- 160.129.138.186 (talk) 16:22, 7 January 2014 (UTC)[reply]
On the radio this morning they said that the railroads are keep extra crews on hand because they are worried about the train tracks breaking because of the cold snap. RJFJR (talk) 21:19, 7 January 2014 (UTC)[reply]
Why is the "HbA1c" designation given to Glycated hemoglobin, i.e. why isn't it called something else? I understand that "Hb" stands for hemoglobin, but I can't figure out what the significance of "A1c" is. Since I know that HbA1b, HbA1d, HbA2c, HbB1c, etc., are all redlinks, I assume that it's not something sequential, and I know it's not a typo for HbAlc. Nyttend (talk) 01:51, 8 January 2014 (UTC)[reply]
We did this a month or two ago, I think. Turns out it's not Hb A1c but rather HbA 1c — that is, subtype 1c of hemoglobin A. I think there are probably subtypes 1a and 1b as well, but maybe just no one's gotten around to writing about them. But anyway if you search the archives it should show up. --Trovatore (talk) 01:59, 8 January 2014 (UTC)[reply]
Why is it that timber is not used in bridges which require high loading capacities other than as decking? I am presuming it is because timber does not take axial load as well as rebar does but in the case of decking it is acceptable as it is likely to have more bending moments than axial loads, and timber takes bending moments better than concrete or rebar. Clover345 (talk) 15:57, 8 January 2014 (UTC)[reply]
Please define "high". Covered bridges went out of favor (from a structural perspective, not from an æsthetic or historic-preservation perspective) because they were more expensive than iron or steel in most places, and you also have the issue of timber being harder to produce in sizes that are good for long bridges. Imagine how hard it would be to get all the right timbers for something as large as the George Rogers Clark Memorial Bridge, for example. Nyttend (talk) 16:16, 8 January 2014 (UTC)[reply]
Also maintenance can be an issue. Steel just needs rust protection, and regular painting can prevent that. Wood, on the other hand, is vulnerable to dry rot, termites, burrowing beetles, woodpeckers, water damage, fire, etc. So, there's a lot more maintenance needed to keep wooden bridges in good working order. StuRat (talk) 18:09, 8 January 2014 (UTC)[reply]
As a terminological note, bridges aren't made of rebar, they are made of structural steel (Ok, maybe some people bridge their backyard creeks with rebar, but I suspect you're thinking about much larger bridges). The name "rebar" is generally reserved for unfinished, small diameter steel rods that are used in reinforced concrete. The structural steel article has a nice section comparing the pros and cons of steel compared to reinforced concrete.
As for your main question, there isn't much about timber bridges at bridge, but it does point out that most early bridges were not timber-only, but also used large amounts of masonry for structural load bearing. Timber bridge mentions that they are regaining in popularity in some areas, and has some good refs and external links, indicating they are currently used for high loads (i.e. automobile traffic), albeit for relatively short spans. The article and refs claim a ~50 yr life span, and comparable or reduced costs of construction and maintenance compared to other materials. Finally, timber is a renewable resource with (generally) lesser environmental impact than steel or reinforced concrete, and some governments might find that favorable. SemanticMantis (talk) 19:03, 8 January 2014 (UTC)[reply]
Steel and concrete don't seem like things we will run out of any time soon, being made from basic ingredients like iron, carbon, sand, lime, etc., which are abundant on the Earth. They also aren't particularly harmful to the environment, as the steel will rust away and the concrete break back up into rocks, in a few decades. StuRat (talk) 21:29, 8 January 2014 (UTC)[reply]
:::I never said we were running out of steel. But it is not considered a renewable resource. That is not really up for debate. Also, you could have done a little googling about concrete, or even looked at our own environmental impact of concrete, which says "The cement industry is one of the primary producers of carbon dioxide, a major greenhouse gas." Additionally, the article outlines other detrimental environmental effects due to altered runoff patterns which can increase flooding, as well as urban heat island effects. I also did not say that concrete was commonly considered a pollutant. The key idea is that it takes massive amounts of energy to make steel and concrete, which generally adds to our global CO_2 emissions. In contrast, growing trees for timber removes CO_2 from the atmosphere, and can in some cases timber production can be considered a carbon sink, which is a technique for climate change mitigation. See also life cycle analysis. My point is, your statement that concrete isn't particularly harmful to the environment is just wrong, from several perspectives. Now I've gotten far off topic, so I'll quit :) In the future, please read my words and links carefully before you try to contradict them, or at least bring something besides your own assertions to the table. SemanticMantis (talk) 22:09, 8 January 2014 (UTC)[reply]
And while timber can be grown in a sustainable manner, it often isn't, with clear-cutting, cutting of old growth forest, and deforestation being the result. Even growing it in a sustainable manner requires adding access roads, which also gives access to hunters (whether legal or poachers), endangering wild animal populations. And the fact that timber bridges aren't likely to last as long means that the extra replacement bridges need to be figured into the environmental cost. StuRat (talk) 14:00, 9 January 2014 (UTC)[reply]
[ec with StuRat] Also please note that concrete and steel can be used to build bridge types that aren't timber-suitable. Timber can work well for a truss bridge, but a cable-stayed bridge (see picture) and a suspension bridge really need other materials. Nyttend (talk) 21:34, 8 January 2014 (UTC)[reply]
I was reading the Highway hypnosis article thinking it would be describing a common phenomenon I am familiar with but it didn't. I googled the term and could not find any references to what I, and I'm sure many others have experienced. I'n not sure what to call it... "Stop and Go hypnosis"? I only ever experienced it when I was in high school (I'm quite a bit older now). It was always during rush hour and very little attention was really involved, just follow the car in front of me until I get to my destination (it was a pretty simple route). Most mornings I would at some point become aware that I had arrived at my destination without any memory of the drive there. It seems like I would "zone out" and "Viola!" I was at school. It was a very repetitive boring task and only happened in the morning when I was tired. This seems quite unlike what is described in the Highway hypnosis article as I would still have had to obey traffic lights and the flow of traffic without ever so much as a fender bender or even a close call. It seems the task had become so repetitive that my mind "decided" there was nothing novel about it and hence no new memories to form. I'd be interested to hear form others who have experienced this or if anyone has run across a name for the phenomenon I am describing for which perhaps there is no Wikipedia article for, or perhaps the information is in an article I cannot find. — TimL • talk21:16, 8 January 2014 (UTC)[reply]
Yes, I've experienced that. And a twist is where you must take most of a common route, but then take a turn near the end to arrive at a different destination. I find it quite difficult to make that turn, as my brain "goes on autopilot" and I arrive at the more usual destination. I suspect a different part of the brain is guiding my driving in that mode, where rather than reasoning out turns and such, it's simply going off memory. StuRat (talk) 21:23, 8 January 2014 (UTC)[reply]
Ah yes, that too I have experienced (a common route with with a different turn for a different destination), I have at times in the past found myself driving to one destination when I meant to drive to nother if they involve a same comon route. — TimL • talk21:34, 8 January 2014 (UTC)[reply]
My uncle used to have a job that required him to drive to two different locations depending on which day it was. He had a note card on his dashboard that had an arrow on each side pointing in opposite directions. To remind him of which direction he should turn out of his driveway each morning, he would flip the card over the previous night. Dismas|(talk)21:52, 8 January 2014 (UTC)[reply]
One of the main stretches I drive to go anywhere has four lanes, so I just have to remember to put myself in a different lane than the one I normally use for my commute if I'm going somewhere else. If I don't I'll end up at home or at work. Once, driving in from out of town I was on a road that used to be on my route to work and ended up automatically driving to my old apartment. The other thing about this "autopilot" mode that gets me is when something snaps me out of it on a rural route and I realize I don't actually know what road I'm on because I don't remember the last few turns. Katie R (talk) 13:35, 9 January 2014 (UTC)[reply]
(edit conflict)It's common enough that I was taught about it in Driver's Education back in the early 90s. And I've heard several people, both in my personal life and on television, talk about the idea of having gone through a stop sign knowing that they stopped but can't remember actually doing it. All because they've done it thousands of times before. I can't recall ever hearing a name for it though. Dismas|(talk)21:24, 8 January 2014 (UTC)[reply]
Thanks. Your references seem to suggest it is a pretty common but little studied phenomenon. It's almost as if I was a philosophical zombie on those morning drives! I suspect we all are for short periods of time. — TimL • talk21:48, 8 January 2014 (UTC)[reply]
For the general phenomenon, see automaticity, which is the term used in psychology. Our article lists highway hypnosis as an example. Even though your example is different, it is, to my understanding, still an example of automaticity. If I had to talk about it in a formal setting, I might call it "automaticity of city driving". If you search google scholar for various combinations of /automaticity driving memory/ you will find some relevant articles. SemanticMantis (talk) 23:59, 8 January 2014 (UTC)[reply]
Perhaps Automaticity applies here, but thing is, it's not just that I had "automated" driving to school and thus didn't need to think about what I was doing, it was more like I was driving to school without any awareness at all! — TimL • talk00:29, 9 January 2014 (UTC)[reply]
Automaticity does seem to describe this common phenomenon of driving a familiar route and not remembering it. If something unusual happens, such as an accident (hopefully not involving you), that will catch you attention because it's not part of the standard routine. I don't see this quote in the article, but I'm reminded of one of Yogi Berra's statements: "Ain't nobody can think and hit at the same time." An athlete trains himself in the mechanics so he can focus on the dynamics of a given situation rather than on the basics of "how to" do something. ←Baseball BugsWhat's up, Doc?carrots→ 04:53, 9 January 2014 (UTC)[reply]
Um, well, I don't actually know a whole lot about this. But that subsection looks like Original Synthesis to me, so I wouldn't say it forms a good basis for a move. Looie496 (talk) 04:54, 9 January 2014 (UTC)[reply]
The one difference is I had to be "half-asleep". I could always remember that I drove home, if not the drive itself. In the morning it was have if the drive had never happened, a somewhat disturbing phenomenon at first. It was a "How did I get here if I don't remember anything about the drive here?" sort of experience. It was more like an "automation coma" if I had to coin a term! — TimL • talk11:19, 9 January 2014 (UTC)[reply]
Yes, being sleepy does seem to figure in. Presumably the conscious part of the brain goes to sleep while the automatic part stays awake. I noticed when I took caffeine pills to stay awake for late night drives, this happened. That is, the caffeine kept my eyes opened, but the conscious part of the brain seemed to zone out. StuRat (talk) 13:44, 9 January 2014 (UTC)[reply]
It doesn't necessarily have anything to do with sleepiness. It can happen if you are intensely thinking about something unrelated while you are driving. It's just that either your episodic memory system doesn't form a record of events, or else that record is not easily accessible afterward. There isn't a whole lot of literature about this, but if you do a Google Scholar search for the phrase "driving without attention mode" (the name it was given by JS Kerr in a 1991 paper), you can find a few things. Looie496 (talk) 17:21, 9 January 2014 (UTC)[reply]
It is not just driving, it happens when you walk to work every morning as well. I cannot remember walking all the way to this building today, but I know I must have, since I am here. --Lgriot (talk) 09:26, 9 January 2014 (UTC)[reply]
I have always called this phenomenon of not consciously driving, driving on the reptilian brain. You can also witness its effects in other people. I normally try to drive at a constant speed slightly above the speed limit, and to avoid having a driver directly ahead of me. This means I am often either passing or being passed.
But you will notice on occasion someone will pull up behind you and just hover there, even in a relatively open road, where they could pass or at least switch lanes. You'll notice that if you gradually speed up or slow down they will stay with you. You can even gradually slow down to 10 or miles below the speed limit. As long as the road is mostly empty, and they don't notice others passing, they will stay in place behind you for quite a bit. It is like they have joined your herd, and placed you in the role of lead stallion, so that they can turn their minds off and parasitize on yours.
After this has gone on for some while, you can break the spell by turning on your emergency blinkers. This has the brief effect of making it look like you have slammed on your breaks, although you haven't. They will also often then hit their brakes. Almost always they will then accelerate and pass you, often with a nasty, "you woke me up!", look. μηδείς (talk) 19:24, 9 January 2014 (UTC)[reply]
This is completely off-topic (sorry) but another phenomenon I have experienced is microsleep while driving. I often drove across the state of Florida (while in college on the other coast) while extremely fatigued and would find myself "coming into awareness" whenever my car started to drift out of the lane. I was certainly imperiling my life and the life of others, but I know I am not the only one! — TimL • talk01:59, 10 January 2014 (UTC)[reply]
This was discussed recently at [11]. (Incidentally, I started to feel drowsy on another trip and tried a related approach, namely, trying to recall details about the layout of a campus from undergraduate days, which seemed to work just as well as the job interview question approach or listening to political news. It strikes me that what the first two might have in common is that they call on long term memory, while the third seems prone to yield future arguments that become worth storing in memory. When I try to recall dreams it seems like there's a sort of incompatibility between memory and sleep, so I'm thinking there could be some idea there. But "automatic" memory, like singing a familiar song at the top of my lungs trying to stay awake, doesn't interfere with drowsiness much at all. Wnt (talk) 07:12, 10 January 2014 (UTC)[reply]
It is described at Mobile donating. I'll take a look at text messaging article to see if there is any reference to the mobile donating article. I googled "text messaging donations" to find the Wikipedia article. — TimL • talk21:53, 8 January 2014 (UTC)[reply]
All of these "Text XYZ to ###" messages are best ignored. They are unhelpful at best and complete scams at worst. If you really want to donate, either spend a lot (say >$100 via conventional means), or if you cannot afford that, don't donate and save for the next time. Paying for text messages to donate miniscule amounts is a waste. Somewhat off-topic, sorry, but in the long run it will get millions to the right places, rather than mobile network providers.217.255.149.135 (talk) 10:13, 9 January 2014 (UTC)[reply]
Not true. The only amount that goes to the carriers is whatever extra fee they charge for the text, if any. From www.mobilegiving.org, "100% of each donation is remitted directly from the wireless operators to the Mobile Giving Foundation, which in turns gives 100% to the recipient charity". mgive.org which the Red Cross uses has the same stipulation [12] — TimL • talk11:12, 9 January 2014 (UTC)[reply]
I'm pleased to see there are exceptions. I see that you have removed well referenced information from the mobile donating article. This is the referenced page, and although it was written a few years ago, the general situation is very unlikely to have changed; it would have been highly publicized if it had.--Shantavira|feed me08:28, 10 January 2014 (UTC)[reply]
January 9
Water
What is the weight of (i) fresh water and, (ii) sea water - per cubic meter at say, 20 degrees c? Then, how many more times denser are these when compared with air? 202.53.237.198 (talk) 09:38, 9 January 2014 (UTC)[reply]
Obviously those numbers are a little inexact because the density of air depends on temperature and pressure and also on humidity - so it varies quite a bit from place to place, from day to day and depending on the altitude that you measure it at. Sea water also varies in salinity (saltiness) depending on where you are and the depth at which you sample it - so the density can be quite variable...for example, there is a lot less salt in regions of the ocean when you're closer to the outlet of a large freshwater river or the outflow of a melting glacier. The density of water also changes quite a bit with temperature. SteveBaker (talk) 13:28, 9 January 2014 (UTC)[reply]
video of experiment in chemistry
Hi,
I'm looking for a tube or video of experiment in chemistry that can be preformed in high schools.
Does anyone have any idea?
Thank you. — Preceding unsigned comment added by 87.68.151.162 (talk) 17:20, 9 January 2014 (UTC)[reply]
I have to strongly warn you about "science" videos on YouTube - there is a massive culture there of people who fake these kinds of videos to produce "amazing effects you can do in your kitchen" types of thing - and a horrifyingly vast percentage of them are complete nonsense. We get people coming here asking us to explain them (or bust them) all the time - and quite often now we just take one look at the fact that it came from YouTube and not even bother to try to figure it out because we know that it's overwhelmingly likely to be bullshit.
My instinct with YouTube science videos is to assume that they are faked until it's proven that they aren't. Honestly, I'd be looking for old videos from "Bill Nye the Science Guy" or something.
I added a note on Talk:Supraorbital ridge asking for help. Each article has a talkpage to help discuss/coordinate edits, so maybe someone who watches that article will be able to provide the missing information. Or if someone here has it, please add it there. DMacks (talk) 21:43, 9 January 2014 (UTC)[reply]
The article is in part based on an old (public domain) edition of Gray's Anatomy, so that is probably where those references are cited. The most recent PD version (from 1918) is online hereRojomoke (talk) 21:44, 9 January 2014 (UTC)[reply]
In the Further reading section, there are DOI links to online copies of the journal articles. Usually, you can view the summary but need to pay to read the entire article. ~E:71.20.250.51 (talk) 22:02, 9 January 2014 (UTC)[reply]
When you see weird shrapnel on Wikipedia articles, always click the History tab. Click "500" so you have some room to work in, and hunt around until where the shrapnel turns up, and by trial and error you can hit the revision (There's also a tool WP:Wikiblame but I forget where the link is) Anyway I quickly came up with [13] which says it is text taken from another article (for Endo and a few others - let me know if that isn't all of them) and also has a citation list. Wnt (talk) 22:11, 9 January 2014 (UTC)[reply]
I got to work on the last section and found many of the references; my feeling is that the ones missing are probably better replaced with some later references that come up on search. It looks like Google Scholar is a good search for this topic - just go to scholar.google.com and put in "supraorbital", one of the author names mentioned, and optionally a year, and you'll come up with plenty, including less dated references. I'm afraid I'd have to get more interested in the science to finish the job, though... maybe someone else could lend a hand with this fascinating task? :) Wnt (talk) 23:03, 9 January 2014 (UTC)[reply]
Science of romantic relationships between ethnic groups
Is there any scientific evidence to suggest whether there is either a genetic based or environmental based preference for romantic relationships? Traditionally, people fell in love with their race but as different ethnic groups became integrated into multicultural societies, it seems that there are more inter-racial relationships than ever before. However, is there still a tendency to find the same race more attractive due to generics? Clover345 (talk) 22:13, 9 January 2014 (UTC)[reply]
See also Claus Wedekind. There is significant evidence women prefer men whose sweat indicates they are as genetically unrelated in regard to their immune-system genes as possible. μηδείς (talk) 23:09, 9 January 2014 (UTC)[reply]
The first part of your question your comment about "traditionally" is simple: more racial integration will increase the chances of interracial relationship. After all, you couldn't very well have married a Chinese person as a white person if there weren't any Chinese people around to marry (such as is the case for me). Mingmingla (talk) 03:31, 10 January 2014 (UTC)[reply]
Also, cultural taboos against interracial relationships prevented people from mingling with those from other races until quite recently. Enforced racial segregation was still commonplace in the USA until the 1970's - and even after it was abolished, the taboo lingered on and only slowly diminished - it still hasn't completely vanished even today. The taboo doesn't come from the people falling in love with people from other races - it comes from those around them who didn't happen to feel that attraction. So even though we may be wired to seek genetic diversity - that instinct is easily suppressed by the greater instinct to not have the crap beaten out of you by KKK members! SteveBaker (talk) 14:27, 10 January 2014 (UTC)[reply]
January 10
Ships
Apparently, and I have no reason not to believe this, if two large ships travel parallel alongside each other they experience a force which will tend to draw them together. I have heard that this is due to the increased flow speed of the water causing a pressure drop in this region (analogous to an aerofoil). However I have also heard that the effect is due to the ships edges acting as the plates in the Casimir effect and restricting the wavelength of waves which can be sustained by constructive interference too a small range of values, and that this imbalance towards the spectrum of waves on either side of the ships results in a net force pushing the ships together. Is it known if either or both of these explanations is correct? — Preceding unsigned comment added by 86.134.72.50 (talk) 00:43, 10 January 2014 (UTC)[reply]
The reason the ships are drawn together is best explained through the rather mundane classical physics explanations like Bernoulli's principle and the Venturi effect. Invoking a quantum mechanical effect like the Casimir effect (again, unless it is being done as an analogy, between the two superficially similar, though unrelated, phenomena) is unnecessary. The reason the ships are drawn together is is a Venturi effect situation (which is a special condition of the Bernoulli principle). As water passes through the constricted space between the two ships, the fluid pressure between the ships drops and the ships are "sucked" together. --Jayron3202:57, 10 January 2014 (UTC)[reply]
Yes, it's definitely Bernoulli's principle in action. The extent to which the Casimir effect operates only happens when objects are the width of a few atoms apart. It has nothing to do with waves because the effect happens in dead calm seas. There is nothing complicated or exotic going on here. You can see Bernoulli's principle in action just by holding two sheets of paper about an inch apart and gently blowing your breath between them - you'll see that they are drawn together (which is probably the exact opposite of what you would naively expect). In that case, the air is moving and the paper is still - where in the case of the ships, the ships are moving and the water is still - but it's the exact same deal. SteveBaker (talk) 06:07, 10 January 2014 (UTC)[reply]
Thanks for your answers, but I think you have been too quick to dismiss the alternative possibility. Maybe I didn't explain well. So to be clear, the effect I described is analogous to the Casimir effect, I was not supposing it was 'the' Casimir effect. Two straight edges do enforce quantisation conditions on the oscillatory modes permissible in the water between the ships. The Casimir effect usually applies to the quantisation condition enforced on the EM field, whereas here it is on the water surface. I was never under the impression that it was an electromagnetic force pushing the ships together, but that doesn't preclude a hydrodynamic effect of analogous origin. — Preceding unsigned comment added by 128.40.61.82 (talk) 11:33, 10 January 2014 (UTC)[reply]
It seems reasonable to suspect that they're analogous, but I think that they aren't, because the Casimir force is purely quantum (loop-level). If whatever is drawing the ships together has an analogue in quantum electrodynamics, it ought to show up at the tree level. For the same reason I think that the "water wave analogue of the Casimir effect" linked earlier is not really an analogue, the AJP article notwithstanding. The random water waves are analogous to an EM radiation bath, not to vacuum fluctuations, and the effect that pushes the plates together in the tub is more like LeSage gravity. I may be missing something, though. -- BenRG (talk) 12:46, 10 January 2014 (UTC)[reply]
I think you're doing the experts here a disservice by suggesting that we dismissed your hypothesis without thought. We didn't. The idea that water waves are exerting some kind of force on the boats is clearly busted with the simple observation that this effect happens in completely calm water. Also, any effect that depends on the energy of very small waves to accelerate two gigantic thousand ton ships together is a non-starter from a conservation of energy perspective - and you'd find that in calmer water, the effect would be greatly diminished compared to in high wave conditions...which it's not. Furthermore - we know that the bernoulli effect must operate here - so even if you were right, the contribution from your analogous-to-casimir effect would be utterly negligible compared to the forces due to the venturii effect. This is definitely the bernoulli principle - people have known that this is the cause of the effect that you describe for at least a couple of hundred years. The "Where is the energy coming from?" question means that your hypothesis is busted without us having to understand the details of what you're trying to explain. SteveBaker (talk) 14:19, 10 January 2014 (UTC)[reply]
I would try it out with small boats in a bath tub (not too small, surface tension might pull them together). The venturi principle sounds nice, but the water doesn't necessarily have to go faster: if you push a funnel through water, the water outside the funnel will move faster relative to the funnel than the water inside. Depending on the shape of the ships and the depth of the water, they could be pushing most of the water between them forward, in which case the water level would be higher than on the outsides and the pressure would push them apart. Ssscienccce (talk) 07:25, 10 January 2014 (UTC)[reply]
Watch out with the Bernoulli principle btw, google gives 464000 hits for Bernoulli misconceptions (our article on Bernoulli lists some of them). The static port of an airplane is connected to the altimeter, which would give strange results if air pressure was determined by air speed. Coandă effect in particular is often mistaken for Bernoulli. Ssscienccce (talk) 12:24, 10 January 2014 (UTC)[reply]
I've always thought it was simply due to waves and/or wind. They hit one ship with full force, while the other is somewhat protected from them by the first ship, so doesn't move as much. If I am correct, the only time they wouldn't be drawn together by waves or wind is if both happen to move along the direction of the parallel hulls. StuRat (talk) 17:52, 10 January 2014 (UTC)[reply]
Now we can see plainly enough that this has been applied twice, on x and t and x' and t'. The time-dependent Schroedinger equation is also recognizable:
Time-dependent Schrödinger equation(general)
With both terms to one side. Now where we separate the passing geek from the true physics acolyte is when we try to work out the Hermitian adjoint of the Schroedinger equation... though I can search for it online and find [15] which describes the 'famous Von Neumann "master" equation for the density matrix. But I'd still be lying if I claimed I could check whether the equation you've asked about is right or wrong! Wnt (talk) 15:14, 10 January 2014 (UTC)[reply]
since they are the force carriers of forces that keep the nucleons together I'd expect their weight should affect the weight of the nucleus but not.. why? thanx --192.35.17.11 (talk) 17:11, 10 January 2014 (UTC)[reply]
