Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• 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.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

November 23

Genetically engineering hair color and eye color

Is it true that hair and [[eye color are coded for by a single gene, and therefore would be the easiest to genetically modify (compared to other traits)? ScienceApe (talk) 02:55, 23 November 2013 (UTC)

No. I have linkified the relevant articles if you want to read them. μηδείς (talk) 03:05, 23 November 2013 (UTC)

Redshift experiments

The existence of dark energy AFAIK was deduced from differences between type-1 supernova derived distance and redshift-derived velocity of high-z galaxies. Surely all alternative hypotheses explaining these differences have been ruled out? So, for example, nonlinearity of redshift in the optical wave lengths at high-z velocities in general can be rejected how? Direct experiments? Which direct experiments measuring redshifts at the relevant velocities have been done? Any hint is welcome. --SCIdude (talk) 11:16, 23 November 2013 (UTC)

The origin of these hypotheses is Einstein's cosmological constant, which was explicitly introduced as a fudge factor rather than as part of a more "elegant" theoretical equation. The astronomical data you mention establish that the cosmological constant is, in fact, non-zero and has a definite measurable value. Dark energy is an hypothesis that attempts to explain why the cosmological constant is non-zero based on known existing physical phenomena - on metaphysical grounds, the answer "it just is, it's an inherent property of the vacuum that we can only measure rather than predict" isn't (apparently) acceptable. Tevildo (talk) 11:37, 23 November 2013 (UTC)

No, all alternate hypothesis cannot ever be ruled out. Your un-orthodox nonlinear redshift would require some huge revolution of physics though and is considered to have a negligible a priori probability. Dauto (talk) 14:12, 23 November 2013 (UTC)

So the Nobel prize is rather for the SN1A observation, like the one for CMB discovery by Penzias/Wilson. I misunderstood that, thanks. - SCIdude (talk) 18:31, 23 November 2013 (UTC)

To answer the other part of your question, about experiments that directly measure redshift at high velocities: Novotny et al. have done spectroscopy on ion beams at 0.33c, not too different from the recessional velocity of supernovae at z=1 or so [1]. This confirms the expected shifting of spectral lines. Moreover, synchrotron light sources and free electron lasers use ultrarelativistic electrons with Lorentz factor much higher than anything that comes into play for supernovae. If you try to somehow tweak the Lorentz transformations to give a different result for cosmological redshift, you will almost certainly break SSRL and FELs in a way that would be immediately noticeable. People do still perform experimental searches for Lorentz violation, but they're looking for tiny effects that would make no difference at all for the original data that provided evidence for accelerating expansion back in the 1990s. --Amble (talk) 22:35, 23 November 2013 (UTC)

Very good. Many thanks. Could you please augment the redshift article to include the relevant parts of your answer? - SCIdude (talk) 05:24, 24 November 2013 (UTC)

I'm afraid that might fall afoul of WP:SYNTH without some secondary sources to make the connection. --Amble (talk) 16:40, 24 November 2013 (UTC)

Structural elements

Are there any good diagrams which show which part of a cantilever structure are trusses, supports and cantilever members? And which ones are beams?Clover345 (talk) 12:20, 23 November 2013 (UTC)

This page goes through the terminology at a very basic level. Tevildo (talk) 12:53, 23 November 2013 (UTC)

I've looked for such sources a few times myself. Questions like what's the difference between beam and girder (http://www.eng-tips.com/viewthread.cfm?qid=164292).

Cantilever seems to be the easiest to identify: it's an overhanging part of a construction. A beam, a truss or any other construction can be supported at both ends; but you can also support it for example at the left end and somewhere in the middle, in which case the part of the construction to the right of that point is considered a cantilever.

A truss is a structural "unit" made up of straight elements connected as triangles. List of truss types should give you a good idea. You could consider it a metal plate where much of it is cut out to save weight but still keep the stiffness. The term is mostly used for a two dimensional structure, not sure if for example an antenna tower is considered a truss or a construction made of several trusses. The Allen truss bridge shown here has three trusses (or six, when you cross a bridge you have a truss to your left and a truss to you right) not one, because the parts are connected at only one point, so the bridge as a whole isn't stiff.

A support can mean different things. For example Truss#King_post_truss calls the top chords of the truss "supports". Cantilever uses the word for the points where the structure is "supported", the "external" connections you could say, which is the most common meaning I think. It can also mean the support column a truss rests on.

A beam is usually an element that has to bear a bending load: for example, a bridge can consist of two trusses, in between them is the deck that carries the traffic, this deck rests on top of beams that are connected to the two trusses. While the elements that make up the trusses only have to withstand either tensile or compressive forces (and a minor bending force due to their own weight), the beams are only or mainly subjected to bending forces.

Vocabulary of trusses explains some of the terminology and has diagrams. Keep in mind that the terms aren't always used consistently. Ssscienccce (talk) 17:28, 23 November 2013 (UTC)

How (non-rad) hard would it be to turn every cellphone into a radiation detector?

https://medium.com/war-is-boring/21dc0b023f1d Homeland Security Agency Wants to Turn People Into Nuclear Tripwires

Why not just mandate that this be used:

http://www.researchgate.net/publication/253023219_Detection_mechanisms_employing_single_event_upsets_in_dynamic_random_access_memories_used_as_radiation_sensors

To have every cellphone track the Single event upsets in its own chips and report to the cellphone network provider (and hence of course the NSA), whenever the rad counts hop over the background level? Hcobb (talk) 20:08, 23 November 2013 (UTC)

That would lead to too many false positives (from radon exposure, cosmic rays, even thunderstorms). Cell phones CANNOT reliably detect radiation that way -- this is a job for a dedicated instrument (such as that which DHS wants to use). 24.23.196.85 (talk) 21:06, 23 November 2013 (UTC)

I have to agree with 24.23.196.85 in part on this. At the current sophistication of cell phones they may be able to detect ionizing radiation but to be useful the Signal-to-noise ratio would need to be clear. However, having said that, if a thousand cell phones all reported an indication of a higher level of ionizing radiation above background, then yes, they could be used as trip wires.--Aspro (talk) 21:46, 23 November 2013 (UTC)

The memory chip area available for use as a detector in a cell phone would, for a start, be far too small, meaning no detection events for months at least, even with significant increases in radiation levels. Because the chip is enclosed in the cellphone case and hidden by internal structures, it would essentially only detect cosmic rays - not what Homeland Security would be most interested in. The electronics industry / electronics hobbyist magazine Elektor carried a series of articles last year or ealy this year on making a home made radiation detector using a standard commercially available semiconductor device as a detector, instead of a gieger tube. Read that article, and you'll see that a detector chip has to have sufficient area (of the order 1 x 1 mm - vastly bigger than even a large number of DRAM memory cells), and be enclosed in special pakaging that blocks light completely while letting low energy particles through. 60.228.240.47 (talk) 00:12, 24 November 2013 (UTC)

Memory uses error correction and detection. It used to be parity detection, but they grew the word line and sophistication so a 256 bit line can add 10-12 bits to correct either single bit or multiple bits. Usually this goes unseen to the user as the 270 or so bits still return a 256 bit corrected line. The ECC is flagged on access, not when the event happened. It cannot identify the cause of failure. An unreliable cell or noise could cause the error. As long as the device can correct it, it continues. Multi-bit failures that exceed the ECC capacity generate the parity type of halt/BSOD hardware error. The next question is how separate is neutron radiation from alpha particle radiation? Alpha particles dominate SEU from ionizing radiation in semiconductors not the least of which is the use of lead in packaging (although being phased out). I do not know if neutron radiation will cause enough ionization failures over background alpha radiation to be reliably detected. Feature size also makes cumulative damage difficult to measure in a single device. The mission for memory is to correct, not accumulate errors. To be honest, I think the best starting points are more like the CMOS digital camera arrays with methods to filter and isolate the radiation being sought. --DHeyward (talk) 04:44, 24 November 2013 (UTC)

Note that most phones do not have ECC. I'm not aware if there is even a LPDDR3 (or any LPDDR) standard for ECC, our article Mobile DDR doesn't mention one nor do I find anything from a quick search.

And it's perhaps worth remembering that most desktops and laptops don't have ECC memory either. (Remember you will generally need a Xeon on the Intel side. Although on the AMD side there is limited support with some/many?/most?/all? of the AM3+ CPUs but many of the motherboard manufacturers still don't bother to official support it.)

The CPU cache may or may not have ECC I'm not totally sure.

Either way, most desktops and laptops, let alone mobile devices don't even have the capability to clearly detect many errors. This isn't surprising, as many above have indicated, in normal circumsances these errors are so rare, they just aren't worth worrying about for non mission critical systems. (Some people even use servers an workstations without ECC.)

Sure you can do some sort of test with a known result like people do for stress testing to detect errors, but that won't do wonders for your battery life.

(Just to emphasise the earlier point, if you have done stress testing, you would know whether one of the memtest variants or whatever, with a stable system with nonECC RAM you can run for over a week or more with no errors on any test. Incidentally as far as I know from such tests, you can generally obtain reports of ECC failures from the CPU if you want to.)

Now I guess you could mandate ECC, some may even be happy for it for the obvious other benefits. But to force a feature which is not going to work very well for what you're want to achieve, when you could at least force something which is designed for the purpose, just seems dumb. Although I share concerns with our resident cranky Perth engineer who likes to pretend to be multiple people, that you still won't be able to achieve much given the size and design limitations and perhaps cost ones as well (edit: for clarification I mean even if you require chip purposely designed to monitor radiation levels).

Nil Einne (talk) 13:15, 24 November 2013 (UTC)

ECC is not just DRAM. SRAM on the microprocessor incorporates ECC. It's inherent and invisible to the system or user. ARM and Intel both have ECC on L2 Caches. --DHeyward (talk) 05:10, 25 November 2013 (UTC)

Not to mention that cellphone manufacturers really want to MINIMIZE the number of RAM errors - not MAXIMIZE them! What would be needed would be some kind of additional detector chip - and the cost of that makes this proposal impractical unless somehow a law were passed to require it - which seems overwhelmingly unlikely. SteveBaker (talk) 16:48, 24 November 2013 (UTC)

Oil for plastics

I think petroleum products are used in the manufacture of certain polymers. When viable oil runs out, will we see certain types of plastic that we still have now disappear? Are there already alternatives in place? — Preceding unsigned comment added by 78.148.107.181 (talk) 23:04, 23 November 2013 (UTC)

Bioplastic. -- Finlay McWalterჷTalk 23:44, 23 November 2013 (UTC)

Hey, thanks. I was aware that there were already polymers that could be manufactured using non-crude-oil-derived plastics but I was wondering whether there were certain applications not yet covered. — Preceding unsigned comment added by 78.148.107.181 (talk) 23:58, 23 November 2013 (UTC)

The earliest plastics were made from cellulose; see: Parkesine. -- Also: History of Plastic ...And from milk (casein); see: Casein / The Plastics Historical Society. ~E:71.20.250.51 (talk) 05:57, 24 November 2013 (UTC)

See also Fischer–Tropsch process. In addition to carbon monoxide, it is also possible to turn methane or carbon dioxide into synthetic hydrocarbon compounds, which could then be used to make traditional polymers. So running out of fossil fuels will not make traditional polymers disappear, but it would make them more expensive (digging something out of the ground is often far cheaper than making it from scratch). Due to this increased expense, you may still wind up seeing bioplastics instead. Someguy1221 (talk) 06:13, 24 November 2013 (UTC)

Indeed, we can make them, doesn't mean we will. Hard to find any Bakelite today. Unless you go to a chinese webshop. "Replacement Bakelite Saxophone Mouthpiece", two belgian inventions for the price of one! Ssscienccce (talk) 09:57, 24 November 2013 (UTC)

Firstly, I don't think we'll ever run out of oil. If we keep burning it at the rate we are, we'll cook the planet long before we run out of the stuff. However, if we somehow did, we can make perfectly good oil-substitutes from plants, bacterial mats, algea and so forth. The problem is that it takes a lot of energy to do that...often more than you get back from burning the resulting oil. However, for the purpose of making plastics, the energy consumption isn't likely to be the primary issue.

What might be a problem is that as we burn through the easy-to-dig-up oil we'll have to start being more agressive about mining oil shale and oil sands - which will certainly push up the cost of oil - possibly to the point where we don't want to use it for making plastics anymore.

Fortunately, there is no shortage of alternatives. We already make plastics like PLA (Polylactic acid) from corn starch or sugar cane...and PLA is a perfectly useful plastic for many applications. You can make sheets of the stuff, extrude it in a 3D printer, injection mold it and so forth. It's also biodegradable and recyclable - which is useful - and it's easy to adjust vrious chemical properties to vary the time before it degrades, the melting point and so forth.

There are many other useful plastics that can be made from plant material without going through the intermediate step of converting it to oil. Cellophane is made from wood pulp, cotton or hemp. Plastarch is like PLA but better for high temperature applications. Then there is PHB (Polyhydroxybutyrate) - which is made using micro-organisms. Then there are whole families of exotic materials like amorphous metal glasses which can be stronger than titanium and yet heat-formed just like a plastic.

Hence, I don't think we have anything to be concerned about here.

SteveBaker (talk) 16:43, 24 November 2013 (UTC)

I don't think he's concerned about running out of oil, he's asking if there are certain kinds of plastics that will disappear once the oil used to make them is no longer available. As you note, it's much more likely that we'll render oil too expensive to extract before we literally run out of it, but that doesn't alter the premise of the question. For example, polyvinyl chloride is the third most widely used plastic (according to our article) and it's made from the vinyl chloride monomer which is derived from petrochemicals. Once oil becomes too pricey, will we no longer have any PVC? I don't know, but that would seem to be the implication. Polyethylene is the most widely used plastic and our article notes that it's available in bioplastic form, so presumably, it's not one of the forms that would disappear (not that plastic really disappears, but you get the drift). Our article on polypropylene (the second most widely used plastic) is so full of jargon, I have no idea how it's actually made in real-world terms and so can't even register a guess. Matt Deres (talk) 18:35, 24 November 2013 (UTC)

PP, PE and PVC can also be made from natural gas or from coal -- so they won't "disappear" even if we run out of oil. 24.23.196.85 (talk) 03:09, 25 November 2013 (UTC)

Vinyl chloride is made from ethylene, which can be produced by steam cracking of fossil fuels, but the same process can also be applied to bio-ethanol. Basically, thermal cracking, steam cracking, hydrocracking apply high pressure and temperature to create a mixture of lots of chemicals, catalysts are added to increase the yield of useful products, the resulting mix is separated by distillation, unwanted chemicals are put through another cracking process. After all, heat and pressure is what produced the oil in the first place. It may be more costly when starting from biofuel, but that's no reason why it wouldn't be used. Look at gasoline production: light crude oil contains a lot of gasoline and diesel that can be extracted by simple fractional distillation, but we're also mining tar sands and using energy intensive processes to produce them. Ssscienccce (talk) 19:03, 25 November 2013 (UTC)

November 24

DNA to RNA to protein synthesis

When we say that a child resembles a parent, or that siblings resemble each other, other than things like hair color, I'd say we primarily focus on things like distance between the eyes, shape of the nose and chin and cheekbones, etc. Is it that biological design and construction of all of these physical features are directed by proteins? I mean, at first glance, I don't necessarily see how proteins are responsible for the structure of the human body -- I think of them more as directing function. But is that merely because science education focuses, perhaps, on physiology rather than anatomy, and the shape of bones and the relationship they share with other bones is also rigorously directed by proteins? DRosenbach ^{(Talk | Contribs)} 00:56, 24 November 2013 (UTC)

DNA is the basis for the creation/synthesis of proteins but for familial traits just look not further forward than DNA. When the fertilized ovum cell multiply, a chemical message it sent out. For instance. Some cell will be told “you are going to be a nose” (differentiation). Sandra Bullock and Barbra Streisand have very different honkers. That's not proteins; that is the arrangement of genetics. DNA/RNA doesn't come into it in this sense.--Aspro (talk) 02:00, 24 November 2013 (UTC)

Shape of organs is determined by development of the embryo which is both influenced by genetics and the environment. Genetics can do a lot of shaping via overlayed secretion of transcriptions factors, especially homeobox proteins; they are crucial for evolution of anatomy features. - SCIdude (talk) 05:38, 24 November 2013 (UTC)

It absolutely is the proteins, DRosen (honestly not sure what Aspro is talking about. Everything DNA does to the body is a result of its transcription). But understanding how proteins lead to body shapes is difficult to understand because you are talking about an interaction of massive scale - billions of cells each containing at least as many proteins of thousands of varieties. It is easier if you confine your self to looking at small effects in smaller animals. The entire DPY (dumpy) family of proteins in C. elegans, for instance, controls the length of the body, generally by controlling the properties of the extracellular matrix. And even in this case, researchers learned this by looking for extreme changes in body length/width. The philosophical equivalent would be trying to understand what controls height by looking at human dwarves, and indeed you can read about some of the genetic causes at Dwarfism#Causes (of course, a "genetic cause" exerts its effect through the presence or absence of a particular protein or RNA product). Understanding far more subtle differences in body shape is going to be far more difficult, since genetic causes may be hidden by natural variation. So I would not call this any sort of failure of education, but simply a result of the fact that emergent phenomena are very hard to predict, and can be equally difficult to explain. In case you are wondering why I am focused on explaining differences rather than explaining the phenomenon directly, this is just me thinking as a geneticist - the easiest way to learn about a machine is to break a piece and see what happens, or find a machine that's already broken and try to figure out how. There are researchers tackling this problem from the other direction, taking a minimal system and trying to use genes (and thus their protein products) to direct cells to assemble into particular shapes with particular dimensions. This research is slow-going and using it to explain the shape of an entire human body would be quite a leap. Someguy1221 (talk) 11:46, 24 November 2013 (UTC)

See morphogenesis. Gandalf61 (talk) 14:23, 24 November 2013 (UTC)

Kirchhoff's first law of spectroscopy

Kirchhoff's first law of spectroscopy says that "A hot solid object produces light with a continuous spectrum." I'm wondering why an hot object wouldn't emit a discrete spectrum. 74.15.137.253 (talk) 03:22, 24 November 2013 (UTC)

This is basically the behavior of a black body, which is a well-studied subject in physics. Kirchhoff is well known for studying black body radiation. --Jayron32 05:23, 24 November 2013 (UTC)

Because much more energy states are available. In a hot gas, it's individual atoms (or molecules) emitting, the electrons have a limited number of discrete energy levels they can occupy. In solids there are much more energy states possible. See density of states Ssscienccce (talk) 10:36, 24 November 2013 (UTC)

Thanks. I don't understand where these extra energy levels are coming from though... 74.15.137.253 (talk) 17:57, 24 November 2013 (UTC)

In two words: band theory. --Tardis (talk) 21:45, 24 November 2013 (UTC)

See also Spectral bands: molecules (like a diatomic gas) will have more energy states because the molecule can rotate and vibrate: the vibration or oscillation can be at once, twice, three times .. the harmonic frequency, and each transition between those can combine with an electron state transition, so instead of one line per possible electron transition you get a group of lines close together. The rotation can add more lines even closer together because the energies are smaller. The bigger the molecule the more combinations are possible, and in solids the spectrum will essentially be continuous (unless its a crystal where you may have band gaps) See also Energy_level#Energy_level_transitions and Rotational-vibrational spectroscopy Ssscienccce (talk) 21:26, 25 November 2013 (UTC)

Main Battle Tank

When you read the specifications of Challenger 2 and M1 Abrams you find that the speed of both vehicles off-road is 40 km/hr although they differ in their engines power , so why ? is it limit for any vehicle which drives off-road ? Tank Designer (talk) 12:32, 24 November 2013 (UTC)

There is a five ton weight difference between them. Rmhermen (talk) 13:52, 24 November 2013 (UTC)

But the M1 has higher power to weight ratio, and is faster on the road. Maybe it's the suspension, M1 uses torsion bar, Challenger has hydropneumatic suspension. You don't choose a more complex mechanism unless it offers some advantage, I guess... Ssscienccce (talk) 15:36, 24 November 2013 (UTC)

With something like a car, top speed is generally limited by air-resistance and small variations in the weight of the car or the size of the engine are less critical than how slippery the design of the body is. In a car, power-to-weight ratio has little to do with top speed - but everything to do with acceleration.

But tanks don't go fast enough for air-resistance to matter much and their complicated drive trains make frictional losses much more critical. Hence, any small variation in the way they are designed (and especially their weight) will have dramatic effects on their top speed for any given engine horsepower. Analyzing the reasons why one goes faster than another is likely to be a complicated business.

SteveBaker (talk) 16:16, 24 November 2013 (UTC)

Think you'll find this is a safety issue. A WW2 Sherman taking a bend too fast would over-steer and skid off sideways. The low loading per square foot of track gave it little grip. On soft ground the same manoeuvre would lose it one or both of its tracks (too much resistance to side forces). Not a good thing to happen in the middle of a battle. Then there is the issue of pitching up and down over rough terrain. In the heat of battle with the adrenalin coursing through the body, the bod driving, can go too fast and give himself whiplash. Again, this could occur at just the wrong moment in time. --Aspro (talk) 18:37, 24 November 2013 (UTC)

Also. At 40 km/h diving through rough scrub and into blind ground that one has not seen before and assuming the standard 1.5 second reaction time. Then the tank will have traveled (1.5 X 40 000) / 3600 = 16.6666667 metres be before the driver can even think “Oh Sh-one-T” and try to stop.--Aspro (talk) 18:56, 24 November 2013 (UTC)

I can't see that the "off road" speed is calculated in any scientific way. Is there a standard "off road" terrain? I can imagine that on some surfaces, either tank could almost reach their top road speed, while on others it would be a lot less than the 40 kph quoted. After all, the Land speed record is set "off road" isn't it? Alansplodge (talk) 20:55, 24 November 2013 (UTC)

One does not 'need' an "off road" speed calculated in any scientific way (other than injuries received). Jump into a 4x4 and head out off road at 25 mph (40 km/h). Notice, that even with seat belts on, if the ground is rough, you're being bounced up and down quite violently. That's on a modern vehicle with good suspension. Even though the modern tank cost a couple of million, the tank designers don't put a lot of effort into providing a smooth diver experience. So at 40 km/h the human body has a lot of kinetic energy that muscle power can not compensate for. The WP article also states that:The M1 Abrams' powertrain comprises a 1,500 shaft horsepower (1,100 kW) Honeywell AGT 1500 (originally made by Lycoming) multi-fuel gas turbine, and a six speed (four forward, two reverse) Allison X-1100-3B Hydro-Kinetic automatic transmission, giving it a governed top speed of 45 mph (72 km/h) on paved roads, and 30 mph (48 km/h) cross-country. With the engine governor removed, speeds of around 60 mph (97 km/h) are possible on an improved surface; however, damage to the drivetrain (especially to the tracks) and an increased risk of injuries to the crew can occur at speeds above 45 mph (72 km/h). Try driving across Dartmoor in a Landrover at just 25 mph and you will see what I mean. So tanks apparently are governed to keep the speeds to with in safe limits in all terrains. In the last Gulf War they may have well have had these limits raised, as the terrain was flat and the TV coverage showed them belting-a-long at fair rate on knots (well, the British built tanks did). But off the production line, they will only go so fast and no more.--Aspro (talk) 23:17, 24 November 2013 (UTC)

It's not just a matter of what's safe or 'comfortable' for the crews; the tanks themselves are more fragile than they look. Tanks require a lot of maintenance and repair even under ideal circumstances. There are a lot of heavy moving parts, working under (mechanically) stressful conditions. Consider the M1—there's more than an hour of maintenance required for every hour of operation. A set of tracks are good for 1000 (really) to 2000 (ideally) miles. They suffer a failure that affects combat ability every couple of hundred miles. Remove the governors and start really shaking up that equipment and the enemy won't have to blow up your tanks—you'll do it for him. TenOfAllTrades(talk) 14:55, 25 November 2013 (UTC)

That would seem to be appallingly bad design. A track life of 2000 miles at an average speed of 20 km/hr is a life of 100 hours. I owned a Caterpillar D4 bulldozer at one time for work on my hobby farm. It was second hand, originally owned by a Shire council for towing road compaction equipment, firefighting, and landfill rubbish work. When I bought it, it had 16,000 hours on the clock, and it still had the original tracks, albiet seriously worn though perfectly usable. Such eqipment is considered obsolete now. Skid-steer machines "Bobcat" style ie machines with wheels and no tracks) have taken over most of the market, but bulldozers are still available, with rubber tracks. It has been found that rubber tracks last even longer and require no maintenance. 121.221.118.84 (talk) 23:43, 25 November 2013 (UTC)

But you did not have to guarantee combat readiness for your equipment! There is a difference between having a piece of equipment that works, and having a piece of equipment that can be trusted to work when lives depend on it! If you quantitatively study combat engineering, you will find that vast over-expenditure on preventative maintenance is a statistically better choice. Here's another book from the same library: Developing the Armored Force..., which is essentially an interview transcript with Major General Robert Sunell, who oversaw the U.S. Army's armored technologies and operations. He has much to say about maintenance, (and much more to say about tank track design choices). Nimur (talk) 01:12, 26 November 2013 (UTC)

Valid points in your first para Nimur, but the difference in track life is so extreme (100 hours versus >16,000 hours), and Cat bulldozer tracks so trouble free, that we just have to suspect something wrong with the tank tracks. Last purchase prices nothwithstanding, the military does get junk from time to time. Not all the time, but some of the time. 121.221.118.84 (talk) 02:22, 26 November 2013 (UTC)

Have you been driving your bulldozer for 16,000 hours through Golan Heights-style rocky terrain, off cliffs, and over land mines, while scout snipers fire fifty-caliber anti-materiel rifle rounds at your treads, all while enduring a barrage from 300,000 artillery rounds per hour per square kilometer? Because the M60 can only do that for about 250 500 hours (provided it's equipped with steel track). But it's sort of a high-maintenance vehicle. Nimur (talk) 02:38, 26 November 2013 (UTC)

Furthermore, the Cat D4 weighs about 5 tons - the M60 weighs 50 tons. Right there is a large part of the problem! The Cat's tracks are relatively lightweight and the stress on the links between them is small - but the M60 is an altogether more massive engineering problem. Worse still, the Cat's top speed is nowhere near 40km/hr - and even if it were that high, it doesn't spend much of it's operational life moving anywhere near top speed. The tank, on the other hand drives that fast anytime the terrain allows it. The force on the track links is going to depend critically on weight and speed. Worse still, the Caterpillar is designed to be reliable enough to last for thousands of hours with minimal maintenance - and doubtless there are aspects of it's engineering where compromises were made in other aspects of it's design to get that kind of reliability. But the M60 is designed to get in, do a job and get out again - then get hours of careful maintenance. If they have a trade-off to make between (let's suppose) minefield-survivability and track life - then you can guess which one wins. So it would be no surprise whatever if the lifespan of the tanks tracks were 160 times less than the Caterpillar. SteveBaker (talk) 14:22, 26 November 2013 (UTC)

Actually, the top speed of my D4 (in top gear) was about 30 km/hr. D4's were often used to tow road compaction devices at up to around 20 km/hr - the same order of magnitude as the tank's average speed. A D4 can weigh a lot more than 5 tons. The basic tractor weight of mine with the particular tracks (D4's were made with 2 optional track types) fitted was about 4.5 tonnes. The blade, blade arms, and hydraulics etc weighed another 3 tonnes, and I had a tree lever on it as well - about another tonne - total 8.5 tonnes. (A tree lever on a little D4 is perhaps not much use - the D4 has only enough traction to push over quite small trees, no more than about 150 mm trunk diameter - but I had the tree lever option anyway.) In any case, if you like, you can compere the tank with a D9 (50 tonne nominal weight typical) - which has at least the same track durability & reliability as the D4. You have a point perhaps about trading off performance against reliability, but hey, the difference is so extreme, you just have to question whether the tank has a deffective track design. 121.221.118.84 (talk) 15:15, 26 November 2013 (UTC)

SteveBaker is right. Applied engineering is all about choosing the best compromises to suit the intended use. My school mate's elder bother was a tank driver in the early seventies and he reckoned that in a tank in Germany at the start of WW3, his survival time in battle would be about thirty minutes before he was taken out. With aircraft. An engine in piston driven civilian light aircraft last about 1500 hours before an overhaul is required. A WW2 military aircraft need and engine change ever several hundred hours because they were operating on their extreme limits. It took about 160 hours to train a pilot who operational time was about 120 hours. A Private Pilots License can be gain in just about 27 hours. Exalance has a high price. WW2 German tanks were techno-logic engineering marvels compared with the Russian T45 tanks but the latter proved to be more reliable in battle. The engineering compromises of the Russian T45 were better chosen. Do you want your next D4 to have superior work performance and yet be happy that is spends much of its time in the workshop? Or do you want a long lasting bit of capital equipment that has its compromises chosen so that so that it is always earning you money? --Aspro (talk) 20:30, 27 November 2013 (UTC)

Good points, Aspro, but you have missed a point and made a bad comparison. An aircraft engine, particularly a WW2 piston aircraft engine, is a very complex piece of machinery where weight restrictions dictated severely compromising durability. Bulldozer tracks are extremely simple things - basically heavy plates of very hard steel joined by equally hardened steel pins, passing over specially shaped hard steel rollers running on plain bearings. The very opposite of rocket science and aircraft piston engines. I cannot see why tank tracks cannot also be similarly simple inherently durable engineering. Also, in WW2, production didn't really get underway until the War - and a lot of tanks and aircraft were models that did not exist before the war. WW2 was won and lost on industrial production capacity and went on for 4 years. So it was sensible to engineer them for a life of a few hundred hours (though in fact in non-war situations nearly all turned out to be very long lating). Wars today, and WW3 should it happen, won't happen that way. Equipment used will be what the military on each side has had on hand. Wars now will be won and lost within days on strategy and in-stock might. And when the war is won, the equipment will be returned home and continue as stock in hand and for training. Look at the the wars of USA vs Iraq, or Irag vs Kuwait - all over in days. Afganistan has been going on for years now, but that is a special case due to political mistakes and uses existing on-hand capital equipment anyway. All this means that equipment will not spend 90% of its time in combat like WW2, it now will spend 90% of its time in training and exercises. Since might is determined by $ budgets, the military must now optimise for long trouble free life. 1.122.117.242 (talk) 00:15, 28 November 2013 (UTC)

The the object of this Reference desk is to answer the OP's question, rather than tutor interjectors to the answers given.--Aspro (talk) 22:32, 28 November 2013 (UTC)

In the future tanks will be remote controlled drones and one won't have to worry about puny humans inside them. It'll cut down the required armor and ease a lot of problems but even so I'm not sure they'll be able to go much faster over rough ground. Dmcq (talk) 22:25, 25 November 2013 (UTC)

Once you have the concept of a drone - the entire concept of a tank may prove unimportant. Without human lives at risk, you can consider a vehicle that is little more than a gun on wheels - if dumping the armor makes it drastically cheaper (which I'm sure it does) then maybe you can have a lot more of them for the same $$$ cost. With more of them, and cheaper - you can more afford to lose them due to enemy action. These kinds of consideration will doubtless produce something that looks nothing like a tank in the end...just as a drone aircraft looks nothing like a conventional manned surveillance plane. Classic surveillance aircraft thinking pinnacled with the SR71 - one of the fastest aircraft in service...modern drone thinking resulted in the Predator - which is probably the slowest! Consequently, I think it's dangerous to speculate about how future drone "tanks" will be...my bet is that there won't be any tanks. SteveBaker (talk) 14:22, 26 November 2013 (UTC)

Just a question/observation - wouldn't the speed depend a lot on the track and groove depth? Thinkof of a tank like a train the lays down its own track, the potential throw the track off would depend mostly on speed and side stress and the depth of the guard to keep the wheels on the track. I think the speed of the tracked vehicle is determined by the track design and less by power and weight except as it relates to the stress on keeping the wheels on the track. --DHeyward (talk) 04:27, 26 November 2013 (UTC)

The tracks act as a flywheel - at a constant speed they do not absorb energy above that of ground friction. Cat D4's have two optional track widths - 6U and 7U. 7U's weigh significantly more, cost more, but there is no difference in performance or handling, except that 7U tracks offer greater drawbar pull in soft sand and mud. However I agree with previous respondents that the speed of a tank is most likely limited these days by the shocks and g-forces over rough ground that the humans inside can take. It wasn't always that way - the first tanks in WW1 were only meant to support infantry, so only needed enough power to go at walking speed. But armies soon realised that you could have tank vs tank battles, and high speed tank attacks cf shock and awe as a later American president put it. Then they were limitted by the size of engine that could be fitted within the hull. But engine technolgy has come a long way since, so engine size should not now be a limit to tank speed. I've not driven a tank, but I can tell you what it's like to drive a Cat D4 bulldozer at top speed (about 30 km/hr) on level ground - it's somewhat hairy and scary, as there is no springing in the suspension. As for driving a D4 at top speed or even at a human's running speed, over rough ground - forget it - it will buck like a mad horse, throw you through the air, and maybe kill you. Tanks have sprung suspension, but there is a limit to spring travel and what springs can achieve. Incidentally, a D4, which has a quite small engine, about 35 kW, is just about unstallable. If you hit a large tree, the tree will stop the D4 from moving, but the engine will keep threshing the tracks around, even if set to a low RPM, churning up clouds of dust & rocks and digging holes until the chassis hits the ground. 1.122.117.242 (talk) 03:03, 28 November 2013 (UTC)

Gluten and Salt

I'm reading On Food and Cooking, and it states that salt increases the elasticity of the gluten. How does this happen at a molecular level? Is it something specific to the chemistry of sodium or chloride ions? Mostly, I'm trying to make puff pastry without adding salt, and I'm trying to understand what I could use in lieu of NaCl to produce the functional effect. I'd like to avoid KCl if used in any significant amount because of taste concerns, but if it's a function of binding available water instead of something specific to the chemistry of the chloride salts, I'm guessing I could try sucrose instead? 2001:558:600A:2F:45D:4092:30A6:49E3 (talk) 21:31, 24 November 2013 (UTC)

I don't know the answer specifically, but I do know that the elasticity of gluten results from two factors: the tendency of gluten (protein) molecules to curl up, and their tendency to stick to other gluten molecules. Salt solutions can affect both of those things, but not as a function of binding water -- dissolved salt doesn't do that. Instead the ions work their way into the protein structure and alter the force geometries. Sugar would not have the same effect. Also putting any substantial amount of sugar into a dough will radically alter the result you get when you bake it.

Integration of body temperature signals

When I'm cycling in the winter, my torso usually overheats while my face (and ears if exposed) and feet can get cold. I was wondering whether the body of humans or any other animal ever integrates temperature signals from different areas of the body to do something more sensible like delivering excess heat from the torso to the extremities? — Preceding unsigned comment added by 129.215.47.59 (talk) 22:13, 24 November 2013 (UTC)

The body does have pretty sophisticated mechanisms for thermoregulation. I would be cautious about "more sensible" - evolution would favor survival over comfort, and it seems likely that heat loss (the major lethal risk) would be greater with diversion of heat to the extremities, especially when the thermoregulation system cannot "know" how soon the body will find warmer shelter. So, I would start by defining "sensible" - or realizing that the body's system is quite good already. -- Scray (talk) 22:24, 24 November 2013 (UTC)

The body is already acting "sensible" by not moving more heat to an area that is loosing it quickly. Having your nose, fingers, ears or toes freeze is a lot better than having your core temperature drop. Also having those body parts freeze does not always mean you are going to loose them. Over the years I've frozen my nose and my fingers (those several times) and still have them all but my fingers do get cold very easily. See hypothermia and frostbite. CambridgeBayWeather (talk) 00:23, 25 November 2013 (UTC)

When the core temperature rises, the body will start sweating, hairs on the skin lie flat, preventing heat from being trapped by the layer of still air between the hairs. Arteriolar vasodilation occurs. This redirects blood into the superficial capillaries in the skin increasing heat loss by convection and conduction. But that alone is not enough to keep exposed skin warm, because you can't get enough heat to the skin to compensate the cooling by the cold air. Keep your hand in -20°C brine while you're in a sauna, and your hand will still suffer frost bite. Whether local cold affects the blood supply to that part of the body, I'm not sure, but blood viscosity increases at lower temperature, so that would decrease the flow in cold skin. Ssscienccce (talk) 14:39, 25 November 2013 (UTC)

• I've done quite a bit of winter cycling and experienced all these things. The mechanisms are a bit tricky. To begin with, when your core temperature begins to drop, the body reduces blood flow to the hands, feet, and face -- that's why they get cold. If you exercise enough to bring your core temperature above optimum, the peripheral blood flow will usually come back, especially to the hands. However, the switching is not immediate, and you might have to sweat pretty hard for a while to make it happen. I've done hard riding in 20 degree conditions with no gloves or face mask -- the usual effect is that for the first few minutes I feel a lot of pain, but then the "heat comes on" and my hands warm up and feel fine. For some reason, though, my feet usually get cold, even if I'm wearing good shoes and socks. Looie496 (talk) 17:01, 25 November 2013 (UTC)

Seems that blood flow in extremities is more sensitive to local temperature than ambient temperature according to this. It also mentions vasodilation when the temperature drops to 4°C (39°F), the Lewis hunting response, in which the alternating vasodilation and vasoconstriction occurs. At 10°C, constant vasoconstriction will occur, with blood flow dropping gradually for ten minutes and then staying constant at that low level (in Eskimos it takes 90 minutes). So your cold feet and warm hands may be because your feet aren't cold enough to initiate the Lewis hunting response. Ssscienccce (talk) 07:38, 26 November 2013 (UTC)

Snake bite article

The article on snake bites includes a section on first aid. Am I correct in thinking this equates to medical advice and that some of the details there should be removed? Bazza (talk) 22:39, 24 November 2013 (UTC)

Reference desk requests for urgent medical aid are different from discussion of medical matters in articles. Talk and articles are different things. I'm not going to specifics, just saying on a general level - which sort of reflects the underlying difference. 88.112.41.6 (talk) 22:53, 24 November 2013 (UTC)

It does make an interesting question. Where does one draw the line between medical information or knowledge and medical advise? Anyways, the applicable policy is WP:NOTHOWTO. While I do not think the problem is that it is medical advise, but that it is a "how to" section. The information on how snake bites are treated seems OK, but the step-by-step part should be removed. Help yourself if you like, Bazza, since you saw it. Richard-of-Earth (talk) 06:15, 25 November 2013 (UTC)

it's open to interpretation, it uses the imperative mood, but is it instructing the wikipedia reader or merely illustrating how most first aid guidelines instruct their readers? NOTHOWTO writes: "describing to the reader how other people or things use or do something is encyclopedic", so putting "they" in front of every sentence would fix the problem... WP:MEDICAL states: "Nothing on Wikipedia.org or included as part of any project of Wikimedia Foundation, Inc., should be construed as an attempt to offer or render a medical opinion or otherwise engage in the practice of medicine." Wile this disclaimer is compatible with providing general information on medical topics, it seems hard to reconcile with answering concrete requests for medical advice on the reference desk. Practicing medicine requires a patient (I think). There's no patient involved when writing an article, there may be when you answer questions from individuals. Ssscienccce (talk) 15:33, 25 November 2013 (UTC)

Permeability of rocks in the soda canyon

Are the rocks of the soda canyon in Colorado mostly permeable? — Preceding unsigned comment added by 99.146.126.108 (talk) 23:59, 24 November 2013 (UTC)

According to http://pubs.usgs.gov/sim/3224/SIM3224_pamphlet.pdf, the rocks of Soda Canyon are essentially all part of the Goodridge formation, which consists of sandy shale, sandstone, and cherty limestone. All of those should be pretty permeable. Looie496 (talk) 16:33, 25 November 2013 (UTC)

November 25

Identifying dinosaur species from tiny bone fragment

This query was prompted by seeing dinosaur-bone beads and jewelry at an art fair: given one of those items (which are tiny, spherical beads or cabochons and presumably retain no trace of their original shape), would it be possible to determine in a non-destructive manner what species (or even higher taxon) it came from? 69.111.191.53 (talk) 02:10, 25 November 2013 (UTC)

I am reminded of the Astragalus of Necrolemur, a paper I read several years ago. Its author made his entire career by identifying extinct primates almost exclusively from tiny ear-bone and wrist fragments. The scientific skeptic in me knows that there is at least a little hand-waving in the process; but the paper has many elements of rigorous palaeontological investigation. And its author has a certain literary flourish: announcing to a world who had been desperately holding its breath, "the previously unknown astragalus of the Eocene omomyid Necrolemur has been discovered." Finally! Nimur (talk) 15:35, 25 November 2013 (UTC)

Interesting... I don't blame him for sounding excited, though, because anything called the Astragalus of Necrolemur is clearly a magical McGuffin. (PS: I'm the OP, my IP just seems to have changed overnight.) 69.111.73.99 (talk) 16:58, 25 November 2013 (UTC)

It might be possible to say something on the basis of a bone-bead, because there are differences in bone density and perhaps one or two other aspects of structure that might survive in a fossil. But if the shape has been lost, it wouldn't be possible to identify the species or anything close to it. Looie496 (talk) 16:16, 25 November 2013 (UTC)

...all of which leads me to wonder whether the vendor of these items is really selling dinosaur bones in the first place. Since birds are now considered to be therapod dinosaurs, you might be getting an old chicken bone! SteveBaker (talk) 18:43, 25 November 2013 (UTC)

Except I don't think even the oldest of chicken bones would be fossilized. Unless there's a way to turn fresh bone into stone in a matter of days-- perhaps a Young Earth Creationist might know? 69.111.73.99 (talk) 21:27, 25 November 2013 (UTC)

Fossil says that fossils can be as recent as 10,000 years old - which (I presume) would mean that bird fossils might be much easier to obtain than a 66 million year old dinosaur. SteveBaker (talk) 23:42, 25 November 2013 (UTC)

Fair point, but according to Chicken#Origins domestic chickens probably don't go back quite that far (though presumably some related birds do). Also this page says that the avian fossil record is poor because birds have hollow bones. So I doubt that bird fossils would be more common than non-avian dinosaur ones (nor would their bone structure be as conducive to carving into beads, if they're hollow and more fragile). 69.111.73.99 (talk) 03:08, 26 November 2013 (UTC)

Electrochemistry question

Is the dropping mercury cathode still used for voltammetric analysis? I'm currently working on a design project for a multipurpose potentiostat which can make several different analyses using interchangeable electrodes and multimode software, but we can't agree on whether to include a polarography mode -- I'm in favor of at least making provision for it, while two of my teammates argue that it's not needed at all. Thanks in advance! 24.23.196.85 (talk) 03:20, 25 November 2013 (UTC)

Yes, there are several journal articles from the last decade discussing current DME applications, and potential applications (no pun intended). From what I can find, DMEs seems to be uncommon in polarography. Nonetheless, it seems appropriate to make provision for it as you suggest. Plasmic Physics (talk) 10:39, 25 November 2013 (UTC)

Electrolysis

Why is it so that electrowinned copper occasionally exhibits a latency when redissolving in concentrated hydrochloric acid? The electrolyte consists of mixed sulfates. Plasmic Physics (talk) 10:50, 25 November 2013 (UTC)

Lack of dissolved oxygen or oxides? Copper shouldn't dissolve in hydrochloric acid, should it? Maybe the answer by pisgahchemist here can shed some light... Ssscienccce (talk) 16:18, 25 November 2013 (UTC)

Copper will not dissolve in hydrochloric acid, but it will in nitric acid, due to the ability of nitric acid to oxidize the copper. It's the nitrate ion, not the acid part, that does the dissolving. See [2]. You get blue copper nitrate solution and brown nitrogen dioxide gas. But the chloride ion is a pretty crappy oxidizing agent, so HCl shouldn't do squat. --Jayron32 20:21, 25 November 2013 (UTC)

Does that mean I broke my copper, seeing as how it does dissolve? Plasmic Physics (talk) 21:26, 25 November 2013 (UTC)

Are you sure it was copper, and not already oxidized copper, like red Copper(I) oxide? Because dropping copper into concentrated HCl should do absolutely nothing interesting, per the Standard electrode potential (data page), which clearly shows that the E^o of Cu + 2H⁺ --> Cu²⁺ + H₂ to be -.340 V. Either you're providing some excess energy somewhere, or its simply not going to do anything. I can leave a penny in HCl overnight, and get a penny back the next day. It'll be a bit cleaner, but otherwise unchanged. --Jayron32 00:45, 26 November 2013 (UTC)

I'm positive it was copper. It does not seem likely that cuprous oxide would be deposited at the anode. Plasmic Physics (talk) 02:20, 26 November 2013 (UTC)

From this topic on Gold refining forum: "As I understand it, it seems that, once the HCl + oxygen dissolves a little copper, it becomes self-perpetuating, from the action of the copper chloride that is produced." Some tests another poster did seem to agree with that hypothesis.

There's a paper with the title "Dissolution of copper in hydrochloric acid solutions with dissolved molecular oxygen", available for $41.95. The abstract mentions this was in the presence of cupric chloride, and "the dissolution rate of copper exhibited first order kinetics with respect to CuCl2 concentrations above 0.01 mol dm⁻³" Ssscienccce (talk) 05:48, 26 November 2013 (UTC)

OK, so now that we've established that copper is attacked by oxygenated hydrochloric acid, let us get back to the original question - why does the reaction intermittently show a latency? Plasmic Physics (talk) 08:23, 26 November 2013 (UTC)

Oxygenated hydrochloric acid is likely forming chloroxy anions (hypochlorite, hypochlorite, chlorate, perchlorate, etc.) For example, ClO2(g) +  H+ +  e− <-> HClO2(aq) has a standard potential of +1.9 V, which is more than enough to oxidize copper. You would need enough dissolved oxygen to generate enough ClO2 in situe to actually do the reaction, but I suppose that it's possible. --Jayron32 18:40, 26 November 2013 (UTC)

Spectroscopic film ?

I saw on a science show where they held up a "special film" to a neon light, and the film then showed a series of lines, the spectrum of neon. Presumably this works because each line on the film is opaque to all but one narrow frequency of light. What is the name of this special film, where can I get some, and how much does it cost ? StuRat (talk) 14:08, 25 November 2013 (UTC)

Maybe it was a diffraction grating? DMacks (talk) 14:15, 25 November 2013 (UTC)

While I obviously can't definitively say that what StuRat saw was a diffraction grating, that demonstration certainly works with a diffraction grating. Assuming you are based in the US there are several formats of diffraction grating available from Edmund Scientific, such as these, which cost $7.95 for 15, or in fashionable cardboard glasses format for a dollar fifty. Equisetum (talk | contributions) 14:53, 25 November 2013 (UTC)

Some of those say they are "single-axis" and others say "double axis". I'm guessing that single axis is the one I saw ? With double axis, would I see two spectrographs overlapping, at right angles ? If so, what's the use in that ?StuRat (talk) 21:42, 25 November 2013 (UTC)

With christmas time coming up you can probably find those glasses locally for a couple of bucks, if you don't mind the spectrum ending up displayed as images of snowflakes or "happy holidays" instead of nice clear bars. :-) They also show up around the 4th of July for watching fireworks. Katie R (talk) 17:36, 25 November 2013 (UTC)

Sounds annoying, but I will look for them. I wonder how to determine which local stores would have them. StuRat (talk) 21:44, 25 November 2013 (UTC)

My mother-in-law in the Detroit area works at English Gardens, a garden center chain, and usually brings home a few pairs every year. If you happen to be near one it would be worth checking out. They work best with point sources - I think the idea is to use them to look at Christmas lights . Now that I think about it, they're probably a lot more interesting with LED lights than incadescent. I've pointed a laser through them, and it ends up projecting the image very clearly onto the wall. Katie R (talk) 12:52, 26 November 2013 (UTC)

Social inhibition of urination

Why do some people find themselves unable to urinate when standing next to someone else at a urinal? Does this phenomenon have a name? How prevalent is it? 129.215.47.59 (talk) 17:26, 25 November 2013 (UTC)

In laymen's terms, it is called piss shy; that link is a redirect to the real article Paruresis --Jayron32 17:44, 25 November 2013 (UTC)

It has also slightly more tastefully been called Shy bladder. Mingmingla (talk) 17:46, 25 November 2013 (UTC)

You've tasted what? --Jayron32 17:50, 25 November 2013 (UTC)

Drinking urine is blue. Well, the link is, whether or not methylene blue is used. DMacks (talk) 18:09, 25 November 2013 (UTC)

I notice that the article states "The codes and procedures for drug testing in sports are set by the World Anti-Doping Agency (WADA). Enquiries to WADA reveal that their doping codes do not cater for the condition at all, and they say they have never had any reports of problems with it." Yet a report on a WADA website mentions "Elite athletes have to undergo doping-controls. In over 50% of cases delays occur because the athlete experiences a sudden inability to urinate. 46% of these delays exceed one hour." Ssscienccce (talk) 21:50, 25 November 2013 (UTC)

Sounds like they need some cross-transfer of ideas. Those of us who are male, and old enough to have potential prostate problems, sometimes have doctors order a urine external flow test. For this you are requested by a (usually) pretty nurse to urinate while she uses a simple gadget to measure the flow rate in ml per second. When she is ready, she tells you to "let it go!" and then maybe says "is that the best you can do?". Nurses usually tell you to imagine having a shower while peeing - it works nearly every time apparently. 121.221.118.84 (talk) 02:40, 26 November 2013 (UTC)

It has also been called Bashful bladder syndrome. Richerman (talk) 18:13, 25 November 2013 (UTC)

I suspect that bashing someone with a full bladder in said area could be a way of overcoming the problem... DMacks (talk) 18:25, 25 November 2013 (UTC)

Nope. The feeling to go completely leaves. A similar condition is an overwhelming need to go when arriving home regardless of feeling before. Brain is a weird mind farking thing. --DHeyward (talk) 08:38, 26 November 2013 (UTC)

Funnily enough, the thing that's telling you that info about your brain is ... your brain. It seems to have a low opinion of itself. Maybe time for a brain transplant, and this time try to get one with a little bit more self-esteem.  :) -- Jack of Oz ^{[pleasantries]} 09:14, 26 November 2013 (UTC)

I suffer from it, I call it stage fright. I grew up in a European country where urinals were not common, never got used to urinating with other people beside me. Vespine (talk) 03:45, 27 November 2013 (UTC)

Platinum Daniell cell

If I were to make a Daniell cell with a platinum cathode instead of copper and platinum chloride instead of copper sulphate, would I need platinum(II) chloride or platinum(IV) chloride? I am asking this question on behalf of user:DPL bot who keeps bugging me for an answer, but I don't know. SpinningSpark 18:55, 25 November 2013 (UTC)

Liquids at zero pressure

Are there any substances that exist as a liquid at zero pressure? — Preceding unsigned comment added by 74.15.137.253 (talk) 19:56, 25 November 2013 (UTC)

Zero pressure (like absolute zero) is an idealized state that does not really exist, except as an asymptote you can approach, but never realize. A perfect vacuum cannot be realized. As soon as you put a liquid into a vacuum, it will start to evaporate instantly, and then you don't have a vacuum anymore. --Jayron32 20:18, 25 November 2013 (UTC)

True. Is there a substance that doesn't sublimate at zero pressure? 74.15.137.253 (talk) 21:09, 25 November 2013 (UTC)

That would imply a vapor pressure of zero at a temperature above 0° K, not sure if that is possible, wouldn't quantum effects, uncertainty principle statistical randomness prevent that? Ssscienccce (talk) 22:06, 25 November 2013 (UTC)

There is no such thing as zero pressure, and by extension, there is no such thing as a substances that exist as a liquid at zero pressure. Plasmic Physics (talk) 07:02, 26 November 2013 (UTC)

The fact that asteroids exist implies that those solids do not sublimate much at temperatures and pressures near 0, as found in deep space. StuRat (talk) 07:03, 26 November 2013 (UTC)

Sublimation of solids at near absolute vacuum become a significant factor when discussion the heat death scenario of the end of the universe. Plasmic Physics (talk) 07:54, 26 November 2013 (UTC)

What would happen if you started heating the asteroid, but kept it in a zero pressure environment? Would it ever melt? Is there any substance in deep space that wouldn't melt if you heated it? 74.15.137.253 (talk) 02:20, 27 November 2013 (UTC)

Depending on the asteroid's constitution, it may melt or sublimate when heated in the low pressure environment of space. Diamonds are found in space, they sublime instead of melting. Plasmic Physics (talk) 05:11, 27 November 2013 (UTC)

Woops, I meant to ask if there was any substance that *would* melt in deep space. 74.15.137.253 (talk) 20:38, 27 November 2013 (UTC)

One substance that may not melt is Buckminsterfullerene, it can sublime, but has no known liquid state, even under pressure a triple point or critical point has not been observed. (Hope this is right!) Graeme Bartlett (talk) 09:47, 27 November 2013 (UTC)

Could you please clarify this comment? Why doesn't zero pressure exist(at least as an idealization)? 74.15.137.253 (talk) 02:18, 27 November 2013 (UTC)

Quantum fluctuations cause there to always be a non-zero pressure. Essentially the same reason, why zero Kelvin is unattainable. Plasmic Physics (talk) 05:11, 27 November 2013 (UTC)

The pressure of a gas is dependent on the speed of the molecules (the temperature), their atomic mass, and the number per unit volume. Even if there is 1 hydrogen molecule per km³ at 2.7 Kelvin (the cosmic background temperature), there will be some pressure. According to the ideal gas law, this would be a pressure of 2.7 * 10^-32 Pa. Very close to a vacuum, but not quite. CS Miller (talk) 19:54, 27 November 2013 (UTC)

Entirely sterile rooms

Which facilities commonly have absolutely sterile (including air) rooms and do such compartments have some specific name? I assume that operation rooms and many scientific facilities don't have sterile air as well. Perhaps in such highly bioclean rooms food wouldn't mold and corpses wouldn't corrupt? 93.174.25.12 (talk) 22:56, 25 November 2013 (UTC)

I've heard of the 'clean room'. Plasmic Physics (talk) 23:05, 25 November 2013 (UTC)

That's a cleanroom. Note that they are not sterile, but have a "controlled level of contamination." SemanticMantis (talk) 23:24, 25 November 2013 (UTC)

Note: Rare New Microbe Found in Two Distant Clean Rooms; November 06, 2013, Jet Propulsion Laboratory ~E:71.20.250.51 (talk) 23:35, 25 November 2013 (UTC)

Manufacture of sterile active pharmaceutical ingredients is generally conducted within clean rooms; these can't be sterilised later, unlike sterile medical supplies like syringes, bandages, pads, swabsticks which are usually sterilised after production and packaging by applying ethylene oxide in a vacuum chamber. (thats's why the packaging is made of porous paper); others are the preparation of vaccines and parenteral products (food that is administered by infusion), an example of hands-on training of aseptic processing can be seen here. Air in operating rooms is filtered 20-25 times per hour to achieve low numbers of airborne pathogens (source), absolute sterility isn't really necessary for patients with a working immune system. Complete aseptic environment is most important when working with products that are a good growth medium for bacteria or molds, that have to be stored for a period of time and that would be damaged or destroyed when sterilized after production. Regarding specific names: "aseptic (filling, finishing, processing) core" is widely used, in job ads for example. Ssscienccce (talk) 01:38, 26 November 2013 (UTC)

Bear in mind that any food or corpse introduced into such an environment would bring their sources of corruption with them. I doubt rate of decay would be much different, unless they were irradiated or otherwise sterilized first. Rojomoke (talk) 05:32, 26 November 2013 (UTC)

Engineering definition

I recently heard a definition of engineering I've never heard before, coming from a former engineering director. He said that engineering is not the application of science to design, build and maintain new products, structures and services but the application of science to make money. Is this definition correct? Can't this definition be used for any discipline under a for profit company, which is most disciplines? — Preceding unsigned comment added by Clover345 (talk • contribs) 23:54, 25 November 2013 (UTC)

That sounds more like cynicism or sarcasm than a "definition". ~E:71.20.250.51 (talk) 00:02, 26 November 2013 (UTC)

A common engineering maxim is "engineers make for a penny what any fool can make for a pound". Cynisism it may be, but there is some truth in it. To me, engineering is about making things in a professional environment and very little about applying scientific principles. As a practising engineer 99% of what we did (I am retired now) was based on experience rather than hard science worked out from first principles. SpinningSpark 00:13, 26 November 2013 (UTC)

Do you think it's only a handful of detailed design teams which are concerned with hard science? Clover345 (talk) 00:13, 27 November 2013 (UTC)

There's lots of them but usually with a directed outcome. A lot of research grants are really hard science engineering. Room temperature super-conductors for example is an engineering problem. Super-string theory is not. --DHeyward (talk) 00:23, 27 November 2013 (UTC)

There is more than one way to say what is realy the same thing. Previous posters have nailed it. Another way is what I was taught in company induction training in my first job after campleting engineering at university: Engineering is about the Three M's - Where is the (specialised) Machinery comming from? Where is the (skilled) Manpower comming from? Where is the Money coming from (loans? other financing?) ? These three questions are what senior engineers, engineering managers, and the heads engineering companies are fundamentally concerned about. 121.221.118.84 (talk) 00:42, 26 November 2013 (UTC)

I think it defines the person who said it more than it defines engineering. He never heard of nonprofit organizations, open-source, volunteers, hobbies? Working on an irrigation project in the third world, building a three stage amateur rocket, designing nuclear weapons, it's all engineering... Ssscienccce (talk) 02:05, 26 November 2013 (UTC)

Here's one of a series of strips of Dilbert talking about engineering.[3] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:40, 26 November 2013 (UTC)

Engineering is about producing products quickly, cheaply and with high quality. But you can only pick two of those. It runs the gambit of the three combinations of two choices. --DHeyward (talk) 00:18, 27 November 2013 (UTC)

That is a specilised branch of engineering called production engineering. A much greater range of employment for engineers has nothing to do with producing products. Consider the consulting engineer who is called in to check the structural analysis of a proposed bridge, or work out the safety of an existing bridge that has been hit by a ship. Or an engineer ensuring safety and relaibility on an electric power transmission line. And it is absolutely not true that an engineer has to pick 2 out of quick, cheap, and quality. Many cases are a balance of all three, and the sign of a good engineer is to achieve all three in good measure. Quality is fitness for purpose. Consider resistors used in electronics. These are turned out by the millions at a fraction of a cent each. Each one conforms to a specification, which has allowable variation in dimensions and electrical properties. There is absolutely no point in making them to a tighter spec, or gold plating the leads. The appliance, radio, microwave oven or whatever will not work ANY better. Resistors fail in service very very rarely. Hence they are totally fit for purpose and the quality is very very high. 121.221.4.89 (talk) 04:54, 27 November 2013 (UTC)

You're missing the point. Maybe it's easier to understand it as one constraint is fixed and the other two are variable. You can always find an engineer/firm willing to do it quicker, cheaper or higher quality (consulting, production, design, etc) and an engineers "product" is not the finished good like a resistor, it's the design. Those are three fundamental tradeoffs. It's a truism and maxim, not something that is applied to any one particular product that may be in various stages of maturity. For example, take the engineering firms that put out oil well fires. There are lots. The most famous are usually quick with excellent results but they ain't cheap. If you find a firm that's just as quick and cheaper, guess why they are cheaper? They aren't "worse" and still fill their niche and do their job. Same with your bridge consultant. Same with transmission line design. Your "sign of a good engineer" is nonsense. None of those constraints are a measure of goodness of the engineer. Iterative designs are subject to those constraints as well which is your resistor example and production engineering. The manufacturer can make the resistor from a higher quality design at the cost of time and expense. --DHeyward (talk) 11:06, 27 November 2013 (UTC)

Well, DHeywood, you've not only missed the point yourself, you have no idea what you are talking about. An engineer's role does not end in a design, it begins with a design.

A design is what designers (so called creative people) do, not what an engineer does. Consider buildings and bridges: an architect (what designers are called in the construction industry) does the design, put simply, what it will look like. Design is related to art, and is taught in completely different university courses to engineering. An engineer takes the design and performs engineering analysis to determine a sound structure, dimensioning of power, water, and aircon to conform to the architect's vision. Consider a TV set. TV manufacturers employ designers who work out what a new model will look like, shape, colours, finish, location of controls, to comply with fashion or trends. Designers would not know a wire from their waist. Similarly, engineers usually know little or nothing about how to do design. The engineer by rational analysis and calculation works out the electronic circuit and selects parts and dimensional detail to conform to the designer's design. Interestingly, good consumer electronics designers get paid more than engineers - TV sets and toasters are bought by poeple emotionally tied to appearance, and matching what they might want is not easy and needs talent.

I have over 45 years experience as an engineer. I can thus certainly do engineering, but I can't do design -in part because I am not fashion conscious. Part of my career was responsibility for electric power stations. My role/responsibility did not end with a design (The owners/clients generally got their own in-house team or contractor to do the design - in this case essentially the tender specification against which my company and others submitted tender responses). My responsibility was to work out the engineering details, project manage (ie arrange and coordinate manpower, machines, and cash flow) them to completion and handover of completed power stations to the owners. Finished goods as it were. But it did not/does not end there. There is an ongoing responsibility to look after waranty claims if any, and monitor operations so that over time the owner achieves reliable and profitable operation, and engineer and arrange corrective action if appropriate.

You've missed the point entirely on resistors. They are built to a specification. As long as they conform to the spec, that's all that is required. Building to a higher "quality" is pointless. That applies to all manner of engineering parts and products.

121.221.4.89 (talk) 15:38, 27 November 2013 (UTC)

November 26

Must an element's pth ionization energy be greater than its qth ionization energy if p>q?

I think the issue of 12th ionization energy of Aluminium in Molar ionization energies of the elements has been left there for some years. There is a note saying 12th ionization energy, which is 223366KJmol^-1 "Should be less than the 13th; perhaps 201266." 201266 is the value in Ionization energies of the elements (data page), while 223366 seems unreferenced. By the way, is it possible that 12th ionizaton energy is greater than 13th one?--chao xian de lun zi (talk) 01:45, 26 November 2013 (UTC)

Feel free to change it, I saw a graph of the ionization energies in a book, no exact values given but the 12th was in the region of 200000, and definitely lower than the 13th, so 201266 seems reasonable, certainly better than 223366. Ssscienccce (talk) 15:33, 26 November 2013 (UTC)

Real life transformer

In real life, do they match the primary coil turns with designed input voltage (so 220v means 220 primary coil turns)? Because in science questions I frequently encounter 120v for 240 turn coil 140.0.229.39 (talk) 13:28, 26 November 2013 (UTC)

It's strictly the ratio of the turns of the two coils that matters. The resulting voltage can vary very quickly if the input voltage changes. Hcobb (talk) 13:47, 26 November 2013 (UTC)

The number of turns per volt depends on the core area, the frequency and the maximum flux density of the core (limited by saturation losses) ; the rated power VA determines the core area needed, say for example 10 cm² for 100VA (at 50Hz). The Transformer universal emf equation gives you the E_rms that the maximum flux density will produce: E_rms=4.44.f.a.N.B_peak With a maximum flux density of 1.5 Tesla and a frequency of 50 Hz, you get E_rms/N=333a, a= 0.001m² so E_rms/N=0.333. So a core of 10 cm² will require 3 turns per volt. Ssscienccce (talk) 15:27, 26 November 2013 (UTC)

Numbers in exam/revision questions rarely have anything to do with real life examples. They are chosen more to make it easy for the writer to set, the student to calculate, and the teacher to check. It is frequntly the case that if your answer isn't a whole number or a simple fraction then you have done something wrong in a test question. Conversely, in real life answers are rarely simple or whole numbers. A mains transformer will usually have many more turns on the primary than the number of input volts. SpinningSpark 15:36, 26 November 2013 (UTC)

I have spent a fair amount of time working with transformers and offer an observation (which could be readily backed up by references). I really liked Ssscienccce's response with very specific design information. When the other windings of a transformer are open(unloaded), and you excite the primary winding with its rated voltage at rated frequency, the transformer and the winding should act as an inductor with sufficient inductive reactance to limit the exciting current to a reasonable low value. Thus there will be a minimum number of primary turns for satisfactory operation. If you had too few turns in the winding, excessive exciting current would flow, causing overheating of the winding or blowing a fuse, even if there were no load on other windings. This exciting current has both real (overcoming resistance of the wire) and reactive components. To the extent other windings are then "loaded" by drawing current to a load, the primary current will increase above the exciting current. A caveat: in a large utility transformer the initial inrush of exciting current will vary somewhat depending on the point in the cycle it is energized and the previous recent magnetization history of the transformer. Edison (talk) 17:39, 26 November 2013 (UTC)

Possibility of chromatophore bacteria using complex pigmentation for crypsis

Is there a chemical reason why there could not be chromatophore bacteria that use the right pigments to achieve the same level of crypsis as chameleons, if not better? I'm aware no such species of microorganism is known to exist, however would a living incredibly stealthy pigment goo be as scientifically impossible as something like faster than light speed time travel? I cannot think of a reason such a bacteria would have access to all those pigments in nature without being mobile like higher organisms such as chameleons; so I'm assuming this would have to be made by scientists or be from space. Even an example from science fiction of such a bacteria would be welcomed. CensoredScribe (talk) 22:11, 26 November 2013 (UTC)

Would visual camouflage help a bacterium hide? The only bacteriovores i can think of do not hunt by sight. Someguy1221 (talk) 01:03, 27 November 2013 (UTC)

I agree with you that visual camouflage is largely ineffective against most animals as they rely more on smell; however if the pigments it used were highly poisonous as well, like a lot of commercial paints, that could give the bacteria an additional level of protection against predators. Smell would also not be a factor in anaerobic conditions, like an asteroid; I don't know why it develop camouflage in a cave where there is little if any visible light. Nor would being able to survive on it's own be important where it artificially created in a laboratory environment; where that the case it's only means of survival could well be in forming a symbiotic relationship with humans.

Coincidentally, some of the photorhabdus toxins are bright red, but I don't think that has anything to do with warding off predators, and certainly nothing to do with camouflage. Someguy1221 (talk) 03:04, 27 November 2013 (UTC)

Bacterivores basically hunt by touch, not by sight or smell. As our bacterivore article obscurely points out, the only way for bacteria to camouflage themselves is by altering their cell wall chemistry. Looie496 (talk) 02:21, 27 November 2013 (UTC)

Acid rusted tools

I accidentally exposed some of my sockets in my cheap socket set to very concentrated hydrochloric acid and now they've rusted up. Can they be saved? It's not a fancy set but I'd like to keep them if I can. I'm not sure how they were manufactured/what their composition is. --78.148.107.181 (talk) 22:12, 26 November 2013 (UTC)

A l-o-n-g time since I had a chemistry class, so chemistry experts please be kind. This is not advice, but Hydrochloric acid says the acid is used to remove rust from steel, in a "pickling" process which has as inputs the acid, surface rust, and the iron itself and , with results ferrous chloride and water. There would be some loss of the metal, and perhaps pitting. Perhaps the acid removed a protective chrome layer. An article about mild steel in hydrochloric acid notes pitting and evolution of hydrogen [4]. Have you tried washing it to remove acid residue, drying, wirebrushing to remove rust (while wearing suitable personal protection against eye injury or inhalation of particles and spraying with WD40 to discourage additional rust? If there is significant pitting and loss of metal I'd pitch the damaged sockets, since "cheap" socket sets can be had for a few dollars, and they will be even less useful than they started out, especially the works inside a ratcheting socket wrench. [5] says that while concentrated hydrochloric acid removes rust from steel, a dilution of the acid causes rapid rusting. Edison (talk) 23:57, 26 November 2013 (UTC)

The acid just removed the very thin coat of oil that is applied in the factory, allowing oxidization to precede rapidly. Get some more hydrochloric acid (an excellent rust remover) and diluted down to 5%. Adding acid-to-water. The original strength will be written on the container (use some eye protective goggles). Dunk all sockets in this, until the rust has been removed ( just a few minutes will do). Wash in boiled water and 'immediately' coat in oil. Anything will do, like engine oil but something really tenacious like Wynn’s engine oil additive or STP engine oil additive is even better. Wipe off surplus oil. --Aspro (talk) 00:17, 27 November 2013 (UTC)

If you want to avoid messing around with hydrochloric acid, there are plenty of rust treatments out there that chemically remove the rust - most car parts stores stock many kinds. But (as Aspro points out) - the important thing is that you should wipe your tools with an oily rag afterwards to prevent the rust from coming back. (You should do this periodically with most metal tools anyway.) SteveBaker (talk) 14:56, 27 November 2013 (UTC)

If you choose a propriety rust Rust Treatment, steer clear of a Rust converter. That will just stabilizes the crud and so the sockets may no longer fit over the nut. Hydrochloric Acid based treatments are better. Phosphoric acid is not bad but it tends to leave a coat on the metal and so not so good for high tolerance parts. The advantage of these branded products are that they sold at the most effective dilution strength (but you pay dearly for the added water and product marketing). So they are very expensive. As you appear to already have access to hydrochloric, a little dilution should be a cheaper and a more edifying option. As soon as the sockets are clean, drain and wash in a little acetone to remove the water and drain again. Then heat until they are 100 plus Celsius over an electric cooker ring (acetone is flammable so drain well). That will drive off the last of the moister and make it easier for the oil to thoroughly coat them. Wynns is so tenacious you wont probably need to re-oil in you life time. I think I can say this with a little confidence as I used to de-rust things in an R&D lab. Yet as Steve indicates it is a good habit to get into. Every year, we religiously re-oil our gardening tools before winter and often during use, so that some, have now lasted several generations. This is especially important for tools like scythes (they are far quicker than a modern string trimmer as they give you a wider sweep (they keep you fit too). The razor thin edge is constantly being wiped clean of the protective oils by friction. So they need daily wiping with an oilrag to stop the morning dew coating it with rust. But once rust permeates the blade, that really sharp edge can never be recovered. Linseed oil is recommended for the wooden handles. --Aspro (talk) 18:55, 27 November 2013 (UTC)

November 27

Correct approach to deriving the shell theorem?

I know the easy approach to proving the shell theorem is to take a point particle, integrate all the force elements over an infinitesimally thin shell, integrate over all shells, and then integrate all the point particles. I now asked myself, why not do it all at once? The problem is that it arises in a nested volume integral.

Here, let V₁ and V₂ represent the regions occupied by my two spherical objects (assuming they do not overlap). Let the center of the first object be at the origin, and let d be a displacement vector between a mass element in the first object and another mass element in the other object, taken to point towards the second object. Let dM be a mass element of the first object and dm a mass element of the second. Let u, v, and w represent the position of dm and x, y, and z the position of dM (u=v=w=x=y=z=0 at the center of V₁, the u-axis coincides with the x-axis, the v-axis with the y-axis, and the w-axis with the z-axis). Let f(R) and g(r) be the densities of the two objects respectively (they are functions of the radius only, as required by the shell theorem), and finally, let the center of the second sphere be located at a displacement vector of X=<A,B,C>. G is the universal gravitation constant.

Then: $\mathbf {F} =-G\iiint \limits _{V_{1}}(\iiint \limits _{V_{2}}{\frac {dm*\mathbf {d} }{d^{3}}})dM=-G\iiint \limits _{V_{1}}f({\sqrt {x^{2}+y^{2}+z^{2}}})(\iiint \limits _{V_{2}}{\frac {\mathbf {d} *g(\Vert \mathbf {d} -\mathbf {X} \Vert )}{d^{3}}}dV_{2})dV_{1}$ $=-G\iiint \limits _{V_{1}}(\iiint \limits _{V_{2}}{\frac {f({\sqrt {x^{2}+y^{2}+z^{2}}})((u-x)\mathbf {\hat {i}} +(v-y)\mathbf {\hat {j}} +(w-z)\mathbf {\hat {k}} )g({\sqrt {(u-x-A)^{2}+(v-y-B)^{2}+(w-z-C)^{2}}})dV_{2}}{((u-x)^{2}+(v-y)^{2}+(w-z)^{2})^{\frac {3}{2}}}})dV_{1}$

In the integration, X is fixed but arbitrary, so the six variables of integration are u, v, w, x, y, and z. As you can see, I don't have many ideas on how this reduces to (using my notation) $\mathbf {F} ={\frac {-GMm\mathbf {X} }{X^{3}}}$, because f and g are arbitrary continuous functions of one variable that determine the densities of the two objects as functions of their radii, and entire integrand is very convoluted. If I were to evaluate the whole thing using one set of substitutions, then the Jacobian determinant would have to be of order 6 (!). Therefore, I have to do something to simplify the mathematics. I know this is a convoluted approach, but really, this is what is really done when we apply the shell theorem - summing up the forces contributed by all the possible pairs of mass elements. If the above notation is not correct, how would this "all-at-once" approach be executed?--Jasper Deng (talk) 01:39, 27 November 2013 (UTC)

(edit conflict)At another glance, $-G\iiint \limits _{V_{1}}f({\sqrt {x^{2}+y^{2}+z^{2}}})dV_{1}$ reduces to -GM, but the remaining integrand is still overly convoluted.--Jasper Deng (talk) 01:46, 27 November 2013 (UTC)

Oh, wait, you can't do that because the second integral is a function of x,y, and z.--Jasper Deng (talk) 01:49, 27 November 2013 (UTC)

Historical humans and race

Trolling
The following discussion has been closed. Please do not modify it.
Did the historical early humans were of different races like today or were one race? If they were one race then what did they look like, and if they had different race, how many and how did each look like? Also, which races of today have Neanderthal genes?74.14.28.186 (talk) 04:00, 27 November 2013 (UTC) I don't know. I suppose it depends if you believe in God !.--122.111.241.205 (talk) 04:12, 27 November 2013 (UTC) See Homo sapien and Neanderthal. --DHeyward (talk) 04:15, 27 November 2013 (UTC) I don't know what it has to do with god, and to DHeyward, which races today will have a Neanderthal admixture? In history of Homo Sapien, did it start with one race or many race?74.14.28.186 (talk) 04:24, 27 November 2013 (UTC) The OP's IP address geolocates to Toronto, so one possibility is that he is thinking of the traditional US/Canadian view of race, with blacks, whites, hispanics, etc. The current most popular, out of Africa, view is that humans didn't start out that way. They would have been a fairly homogeneous group, with the current differences evolving as people settled in different parts of the world. HiLo48 (talk) 04:31, 27 November 2013 (UTC) I agree !.--Die Antwoorde (talk) 04:27, 27 November 2013 (UTC) I kinda meant race in genetic sense and skeletal sense, you can tell from bones and genes and the appearance the race of individual, and if they were homogenous, what did they look like? And how did the different races adapt, how they developed different appearance and genome, and were there mental adaptations like brain function, behaviour, intellgence and that kind of thing? How did it help the different races?74.14.28.186 (talk) 04:47, 27 November 2013 (UTC) The above is yet another twist on the same racist theme by the Toron-troll. I've turned him in and he should be blocked soon. ←Baseball Bugs What's up, Doc? carrots→ 05:12, 27 November 2013 (UTC) Should have added the IP that refactored my original response and his kind edit summary here. --DHeyward (talk) 10:11, 27 November 2013 (UTC) To explain how is this racist, please?74.14.28.186 (talk) 05:23, 27 November 2013 (UTC) I think that the original question is valid and not racist.--Dr. Madhattan (talk) 06:22, 27 November 2013 (UTC) ...even if based on ignorance of what race really is. HiLo48 (talk) 07:39, 27 November 2013 (UTC) Touche. Die Antwoorde (talk) 07:45, 27 November 2013 (UTC)

Our Neanderthal article says "An estimated 1 to 4 percent of the DNA in Europeans and Asians (French, Chinese and Papua probands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (Yoruba and San probands)". On the other hand, Neanderthal genome project says "99.7% of the base pairs of the modern human and Neanderthal genomes are identical". So colour me confused. Can someone explain how to reconcile these two statements ? Gandalf61 (talk) 12:11, 27 November 2013 (UTC)

Not an expert, but I find the "99.7% base pairs" to be somewhat misleading. As I understand it, we share somewhere around 70% with fruit flies and over 99% with chimpanzee's. I suspect the difference is when comparing uniquely human DNA between various groups do we find 1-4% of it being shared with ancient neanderthal DNA. As I understand it, the human genome went through a "narrowing" experience where most variations died off and then recovered with all modern DNA traceable to the narrowed surviving strain. How and when ancient neanderthal DNA would have re-entered or whether the narrowing was not universal is what I believe is the focus of research. --DHeyward (talk) 14:24, 27 November 2013 (UTC)

(ec)The problem is that 99.7% of base pairs being identical between two species doesn't tell you much. We share 98.8% of our DNA with Chimpanzees, and 50% of our DNA is shared with bananas - men and women have only 97% of our DNA in common...so a male human shares much more DNA with male chimpanzees than with female humans (which, my wife tells me, explains a lot!). But base-pair comparisons are not the same thing as numbers of genes shared. Take (for example) the gene that allows adults to digest lactose: "LCT". It only differs by a single base-pair from the defective version of that gene that causes lactose intolerance. But look at the numbers here:

• The LCT gene contains about 50,000 base-pairs - only one of which has to be wrong for it to be counted as "the gene for lactose intolerance" rather than "the gene that allows us to digest lactose".
• We have about 20,000 genes.
• Human DNA contains about 3,000,000,000 base-pairs.

So if we imagine two people who are identical twins - except that one of them is lactose intolerant - their DNA is identical to within one part in three billion, but their genes are only identical to within one part in twenty thousand. As percentages, those two numbers are radically different - yet both descriptions are talking about a single base-pair difference. Now, the question is whether the Neanderthal article is talking about percentages of base-pairs or percentages of genes. The article also qualifies that percentage as being of "non-modern" DNA - so it's (presumably) excluding genetic changes since the time of extinction of Neanderthals - where the Neanderthal genome project is talking about the amount of difference between modern humans and Neanderthal...but doesn't really make sense because it's saying that we're more like neanderthals now than we were back in "non-modern" times?!?

There are plenty of other sources of confusion possible here. You'll also find articles saying that (for example) first cousins share 12.5% of their DNA...which as a strict count of base-pairs is clearly nonsense because that would our cousins more different from us (by far) than we are from bananas! What is probably meant is that 12.5% of the natural genetic variation that makes us unique from other humans is the same between first cousins...which would mean that (of course) we're much more similar to each other than we are to chimpanzees, neanderthals or bananas.

I agree that both articles should qualify those percentages much more carefully...it's a mess.

SteveBaker (talk) 14:51, 27 November 2013 (UTC)

How to produce magnesium carbonate?

I want to produce 100g of magnesium carbonate by using magnesium sulfate and sodium bicarbonate. How much magnesium sulfate and sodium bicarbonate do I need? And how much water do I need to mix it up? Thank u :-) — Preceding unsigned comment added by 110.159.119.154 (talk) 06:54, 27 November 2013 (UTC)

This appears to be a stoichiometry question. Are you doing this for homework?--Jasper Deng (talk) 07:10, 27 November 2013 (UTC)

How you do it is to work out how many moles of magnesium carbonate you want to make. Work out your chemical formula. Work out how many moles of each ingredient you want, then multiply by the formula weight of each raw material to work out the mass required. You will have to know the amount of water in the magnesium sulfate hydrate that you have.

Adding nitrogen gas to chemical bottle to protect from moisture in the air

I have DEPC in a bottle which is still unopened. The manufacturer's instructions state that moisture from the air will cause it to decompose and so a layer of nitrogen (or argon) gas should be layered over the DEPC before closing the bottle. I have access to liquid nitrogen. Can this be used to protect the chemical from the atmosphere? The mist surrounding nitrogen is presumably water vapour from the air, right? I don't want that getting to the DEPC! --78.148.107.181 (talk) 09:23, 27 November 2013 (UTC)

What is DEPC? See Guiness in the composition section. N₂ is used in bottling. Also, nitrogen , especially in the large commercial liquid nitrogen tanks, are very dangerous as an asphyxiation hazard. Don't do it indoors if you don't have oxygen sensors. Unlike CO₂, your body does not react to higher levels of nitrogen (or Argon or Helium) and people pass out and then die before they even know the oxygen level is low. There is no feeling of shortness of breath or anxiety like with CO₂. Many have died working with nitrogen in confined spaces.. --DHeyward (talk) 10:07, 27 November 2013 (UTC)

Diethyl pyrocarbonate? Depending on what you are using it for, the minimal amount of decomposition resulting from moisture in the air trapped in the bottle as you close it might be acceptable. Liquid nitrogen would not be an ideal source of dry nitrogen because of the impracticality of handling a small amount of it without exposing it to air causing condensation of moisture, as you suggest. Laboratories commonly have inert gas lines, such as dry nitrogen. If you access to something like that, that would be ideal - blow a light stream of nitrogen into the top of the bottle as you are closing it. Otherwise, just minimize the amount of time you have the bottle opened to air. -- Ed (Edgar181) 10:21, 27 November 2013 (UTC)

I agree, a lab will either have an inert gas line for such purpose, or high-purity, dry nitrogen from a cylinder with a pressure regulator. If it's not the first time DEPC is being used, so if you're asking us because you don't want to bother the people who will know the correct procedure at your lab, reconsider. If it is the first time DEPC will be used, then consider buying a flushing system before proceeding, or take Edgar181's advice and minimize the amount of time the bottle is open. Don't improvise, in my experience, when improvised procedures go wrong, the results are often much worse than the problem one was trying to fix. Ssscienccce (talk) 11:52, 27 November 2013 (UTC)

I know we have carbon dioxide lines but I think they might be solely for connecting to cell culture incubators. I already consulted people in our lab and they were unaware that the manufacturer advises this protection from atmospheric moisture. 129.215.47.59 (talk) 12:53, 27 November 2013 (UTC)

There will be very few biology labs with a nitrogen line, as the OP says, CO₂ lines are common, but N₂ certainly not (I've never seen them anyway). Anyway, might be better to make up a stock solution in a suitable solvent (EtOH?), rather than opening the stock bottle repeatedly. Must admit having never made up stocks myself, don't use it much. People are far too paranoid in RNA work! Fgf10 (talk) 16:57, 27 November 2013 (UTC)

If you're looking for dry nitrogen in a biological department/institute try a serious biochemistry lab, a structural biology lab or a protein production core facility - these are the people that seem to have cylinders of it in our institute. You can take some back to your lab in a balloon attached to some sort of valve with a rubber band - attach it to a needle to fill the bottle with nitrogen before closing. As far as being too paranoid around RNA, that does rather depend on what you are doing - if you are just doing some basic qPCR on large samples (and make sure you reverse transcribe with random hexamers like you're supposed to) then yes, excess paranoia is not justified, but if you are trying to, for example, do long-read cDNA sequencing from tiny amounts of non-optimal starting material a healthy paranoia is just what you need. I have to say that most biology labs have probably been using DEPC for years without the precaution of storage under inert gas, but then most biology labs probably wouldn't notice if their DEPC was totally ineffective. Equisetum (talk | contributions) 21:26, 27 November 2013 (UTC)

DEPC is hydrolysed to EtOH and CO2, so if an EtOH solution is acceptable then the OP has nothing to worry about. A quick calculation shows that if a 1 liter bottle is used for small doses of 2 ml, and each time 20 ml air at 20°C and 50% humidity enters the bottle, then by the time there's 100 ml DEPC left it will have absorbed 20mg water, and therefore contain about 100 mg ethanol. Assuming DEPC + H2O -> 2EtOH + 2CO2 is the only reaction that occurs, but that's something I'm not sure about. If it's stable at room temperature then why does it have to be stored at 2 to 8 degrees C, and why do I find references to a publication titled "Spontaneous hazardous chemical explosion of unopened bottles of diethyl pyrocarbonate"... Ssscienccce (talk) 22:34, 27 November 2013 (UTC)

It is not hard to rig a nitrogen bottle to a line with a needle on the end. You put a rubber septum on the stock bottle insert your positive pressure nitrogen line and insert your needle or canula to draw off your sample. No difficult contruction required. Standard practice when your chemicals burst into flame in open air. 75.41.109.190 (talk) 20:16, 27 November 2013 (UTC)

Penguins near the South Pole

How close, at best, can penguins (no matter the species) come to the South pole? --80.122.110.238 (talk) 12:33, 27 November 2013 (UTC)

According to Penguin, they spend about half their time in the water, so it's unlikely they would venture very far from the ocean. Given that, whatever the closest penguin habitat is to the geographic south pole, would be about as close as they would get to it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:55, 27 November 2013 (UTC)

I suggest you watch the documentary March of the Penguins. The Emperor penguins walk far inland on Antarctica to breed, apparently to get away from any predators. A secondary benefit might be the elimination of the unfit from the breeding pool, as they can't make the journey. And they also seem to fast the whole time, living off their fat stores. It's an amazing feat. StuRat (talk) 21:20, 27 November 2013 (UTC)

If you look at the breeding areas of the Emperor penguin they probably come to as near as something like 1000km of the pole. They'd probably be quite happy wandering around the pole in the middle of Winter, it's just there isn't any food around there and they're safe enough where they do breed. Dmcq (talk) 13:03, 27 November 2013 (UTC)

Looking at that range again i looks like they go within 500km of the pole. Dmcq (talk) 13:09, 27 November 2013 (UTC)

Are you looking at the map? The text says 77°. If the Emperor penguin gets closest (and I suspect it does) then this says they reach 78° south which is about 720 nautical miles (1,330 km; 830 mi) from the South Pole. Thincat (talk) 13:24, 27 November 2013 (UTC)

This set me thinking about the famous Worst Journey in the World to get an Emperor penguin egg at Cape Crozier for which our article now says "Cape Crozier is within a restricted area and permission is required to visit it". The Heroic Age of Antarctic Exploration has drawn to a close! Thincat (talk) 13:33, 27 November 2013 (UTC)

Presumably the penguins are exempt from that restriction? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:40, 27 November 2013 (UTC)

The map at Emperor penguin shows it living further than 85° south (I think). But is this really true? Antarctic Plateau specifically says penguins don't live there "... because there is nothing there for them to eat". Thincat (talk) 13:52, 27 November 2013 (UTC)

The southernmost point of the Amundsen Coast is just over 300 mi (500km) from the pole; that's not the plateau (which rises dramatically just south of there). But it is the depths of the Ross Ice Shelf, so I too don't see what penguins (who live off fish) would eat there either. -- Finlay McWalterჷTalk 14:02, 27 November 2013 (UTC)

Yes, I was wrong to mention the plateau. This suggests they (and Adelie penguins) live on the northern edge of the Ross Ice Shelf but no further south. 78° near enough. Thincat (talk) 14:35, 27 November 2013 (UTC)

If I get the map straight, there is a little bit of breeding (green) area within 80°, close to 81°, which would mean a distance of roughly 1000-1100 km. --KnightMove (talk) 19:11, 27 November 2013 (UTC)

Old style mechanical railway signal boxes

Why did the signalmen always use a cloth when operating the levers? SpinningSpark 14:14, 27 November 2013 (UTC)

"The steel lever handles were cleaned every week with emery cloth and it was more than my life’s worth to pull a lever by grasping it with my hands as this would corrode the metal. It was necessary to hold the lever with a duster provided so as not to tarnish the brightwork." [6] AndyTheGrump (talk) 14:19, 27 November 2013 (UTC)

Suicide

Do any other animals (or living things) commit suicide? Or is this phenomenon only seen in humans? Thanks. Joseph A. Spadaro (talk) 20:11, 27 November 2013 (UTC)

Bees invariably die after stinging - which they do in protection of their hives. So yes, there is at least one kind of animal that does that kind of thing. SteveBaker (talk) 20:28, 27 November 2013 (UTC)

Thanks, Steve. Well, your answer made me re-think my original question. The bee situation is not really a suicide, correct? That is, they don't choose to end their life; they choose to sting (which then has the "side-effect" of ending their life). For example, say that I saw that a child was about to get hit by a car; I jump in front of the car to save the child's life; the child is saved, but I die. I would not really call that a "suicide", even though I made a choice that had the effect of losing my life. That is (sort of) how I see the bee stinging situation; it is a death, but not really a suicide. So ... I guess what I meant in my original question was more along the lines of this: do any other animals/living beings commit suicide in the same way that humans do (i.e., they are typically sad and/or depressed; they feel that life is not worth living, for whatever reason; and, as such, they make an affirmative decision to end their life)? Thanks. Joseph A. Spadaro (talk) 20:49, 27 November 2013 (UTC)

If you insist on that interpretation of your question, then we cannot possibly answer it. We don't really know for 100% sure what other people are really thinking - let alone animals. Can we be sure that people who commit suicide really understand what death truly means? If we can't be sure with people - then we stand no chance. Every conceivable instance we might come up with can always be countered with "Did they really know they'd die - did they truly understand what death actually is?"...so we have no answer for you. SteveBaker (talk) 21:02, 27 November 2013 (UTC)

Thanks, again. Two points. (Point 1) Certainly, we do know how/what human beings are really thinking. No? I think there is a lot of data about human suicide. Perhaps, we can't know "100%" of what the dead person was thinking (of course). But, there are suicide survivors, etc., that provide quite a bit of data about the human phenomenon of suicide. It's not as if we are "stabbing in the dark", as far as human suicide is concerned. (Point 2) I thought I remember reading/seeing somewhere about how elephants (or was it apes?) expressed grief, sadness, etc., at the death of one of their own; and they even had some sort of funeral ritual. Which led me to the thought that animals, on some level, can experience sadness and grief (and perhaps depression?). Who knows (of course)? But, I wondered if science ever studied this phenomenon among animals. Thanks. Joseph A. Spadaro (talk) 21:08, 27 November 2013 (UTC)

I think we can at least infer what animals understand. For example, elephants will go out of their way to visit the bones of their dead relatives. This implies that they associate those bones with their memories of those relatives, and have some concept of death. StuRat (talk) 21:07, 27 November 2013 (UTC)

I think an essential component of suicide is understanding what death is and that your actions will result in your death. I doubt if a bee qualifies here. There are also animals that, when stressed, will stop eating until they die, but I doubt if that's intentional suicide. Whales sometimes beach themselves repeatedly, and this might be suicide, or maybe their navigation system is just messed up somehow. It's not clear. See whale beaching. StuRat (talk) 20:56, 27 November 2013 (UTC)

In general, humans can talk and animals can't. That makes it all the more difficult to know what's in an animal's head. That doesn't mean human suicides are readily explainable all the time. But at least there's a chance. Some years ago I recall seeing some show about suicides on the Golden Gate Bridge. They had a couple of survivors, who both said that the moment they let go, they wished they hadn't. I expect a lot of suicides don't necessarily want to die, they just want the pain to go away. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:40, 27 November 2013 (UTC)

Is it a fact that ghosts are/aren't real?

In a discussion, a user argued that it is fact that there is no such thing as ghosts. Regarding the validity of this statement, is it a proven fact that ghosts do not exist? I understand that here are skeptics, but is there any hard evidence that they do not exist? Admiral Caius (talk) 20:27, 27 November 2013 (UTC)

It's hard to prove a negative.

We can say that there is absolutely zero scientific evidence for their existence - and that if they did exist, it would violate all manner of scientific principles that we believe to be well-established.

People keep attributing all sorts of qualities to ghosts that would make them undetectable (they are invisible, maybe they only show up to people who believe in them, maybe they are insubstantial, maybe...maybe, maybe)- this is probably an unfalsifiable hypothesis. The question you have to ask is that if there is no solid evidence of the existence of something - why would you believe in it instead of all of the other infinite number of things for which there is also no evidence. Why would you believe in ghosts, but not (for example) believe my claim that there are families of purple piano-playing Aardvarks living in caves on the dark side of the moon? If you (more reasonably) say that all unprovable things are equally likely - then there are a literal infinity of things that you'd have to believe in. At that point, you realize that this is impossible - and the only logical way to proceed is to believe in none of them...until/unless some evidence appears to confirm them. This is the essence of ideas such as Russel's teapot and Occams razor which, while not hard-and-fast rules, are never the less rational ways to proceed with you life.

SteveBaker (talk) 20:39, 27 November 2013 (UTC)

Another interesting thought is that, if ghosts hang out where they died, you would expect a far greater density of ghosts in places like Rome, which have been heavily populated for centuries. So, I'd expect constant ghost sightings there. StuRat (talk) 20:51, 27 November 2013 (UTC)

Who says there aren't frequent sightings in Rome? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:24, 27 November 2013 (UTC)

Eating indigestible foods: what's the point?

As the title suggests, I want to find out what benefit the human body receives from eating foods generally seen as indigestible.

My reason for asking is that I'm quite curious as to why we consume foods such as Sweetcorn and Broad (Lima) beans, where we essentially see most of what goes in, "come out" pretty much intact.

Do we actually derive any nutritional benefit from foods we basically don't break down during the digestive process?

Thanks in advance for any help.

CharlieTheCabbie (talk) 22:02, 27 November 2013 (UTC)

See Dietary fiber. When I were a lad, this was the universal panacea for all known medical conditions, although medical opinion seems to have changed. Tevildo (talk) 22:21, 27 November 2013 (UTC)

Killing animals with carbon dioxide

If I'm not mistaken, the UK Home Office approves the use of carbon dioxide for killing (some?) animals in certain circumstances. Is this considered humane? My understanding is that carbon dioxide build up is what causes the unpleasant aspects of suffocation, whereas nitrogen gas would be much more peaceful. Is it to ensure safety of the operators? --78.148.107.250 (talk) 23:46, 27 November 2013 (UTC)