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June 12

Atomic mass unit

Why are the values for 1 amu different if you use 1/12 the mass of a carbon-12 atom instead of 1/16 the mass of an oxygen-16 atom? The former has 12 nuclear particles of equal mass, and the latter has 16 nuclear particles of equal mass to each other and to the particles in a carbon-12 atom. --75.25.103.109 (talk) 00:41, 12 June 2010 (UTC)

See Binding energy#Mass deficit. The different nuclei have different binding energies, so different mass deficits. It's also worth nothing that protons and neutrons don't actually have the same mass (although it is very close). That doesn't affect your example, since they each have half protons and half neutrons, so the average mass is the same, but if you are talking about heavier nuclei (which need disproportionately more neutrons to be stable) it becomes an important factor. --Tango (talk) 00:48, 12 June 2010 (UTC)

Tornado recurrence rate

I remember reading this in a book at some point, but I have never been able to find it since. What is the recurrence rate of a tornado striking any given point in the tornado-active areas of the United States Great Plains, say in Kansas or Oklahoma? The statistic I remember reading was something on the order of once every *insert number above 500 here* years, but I have never been able to find the statistic again. The context I remember it being used in was to explain how very rare and against all odds such events as Codell, Kansas's (struck by tornadoes on May 20th of three consecutive years) or Mulhall, Oklahoma's (struck by two violent tornadoes within a 2 hour time frame) tornado events are. Ks0stm ^(T•C•G) 02:47, 12 June 2010 (UTC)

This site says "Even in tornado alley, a twister hits a given square mile only once every 700 years" but it's not well referenced. Regards, --—Cyclonenim | Chat  11:19, 12 June 2010 (UTC)

Being hit repeatedly in a short time period isn't too uncommon: a single storm may generate multiple tornadoes, which will tend to have similar tracks. --Carnildo (talk) 00:00, 17 June 2010 (UTC)

Female Survival

Ok, I know this will sound incredibly stupid, but I'm going to ask it anyway. If a woman was stranded somewhere without food or water, could she drink milk from her own breasts to survive? Or would the lack of nutrients cause the milk to lack any nutritional benefits? Could the energy and nutrients be recycled through the body< of would it be lost? If so, how quickly? Again, I know this sounds incredibly stupid, but I realize that I have been wondering about this for quite a while now. Thanks for the help, and please don't think I'm some kind of weirdo for asking this! Stripey the crab (talk) 03:10, 12 June 2010 (UTC)

Of course not! It takes energy to produce milk - and by the basic laws of thermodynamics, it must cost more energy to make than can possibly be gained by consuming it! SteveBaker (talk) 03:40, 12 June 2010 (UTC)

However, she might be advised to read up on urophagia before getting stranded.--Shantavira|^{feed me} 06:23, 12 June 2010 (UTC)

Conservation of energy 82.43.89.11 (talk) 11:24, 12 June 2010 (UTC)

Yes, she could, but the longer she lived on the less nutrional it would be until she died of starvation. You could survive a while on your own scabs, excrement, urine etc. Only a bit longer than going without food but it would prolong life nonetheless.--178.167.206.65 (talk) 13:41, 12 June 2010 (UTC)

But would there be any advantage to drinking your own milk? If you stop breast feeding, you'll soon stop lactating and I would imagine any milk left would be reabsorbed. --Tango (talk) 17:06, 12 June 2010 (UTC)

A transverse wave

Visit [1] and go to question 12. These are my answers for part a:
Frequency: 10 Hz, 10 Hz
Amplitude: 0.2m, 0.15m (or perhaps 0.14m)
Wavelength: 2m, 1m
Speed of wave: 20m/s, 10m/s

But now I'm stuck on question b. How do you do it?--220.253.96.217 (talk) 04:10, 12 June 2010 (UTC)

From your answers to part (a), you can determine that the transmitted pulse (travelling to the right on the heavy string) will have a smaller amplitude than the original pulse. I would think that the reflected pulse (travelling to the left on the light string) would have an even smaller amplitude (most of the energy will go into the transmitted pulse) but it will be travelling twice as fast as the transmitted pulse. If you take a snapshot at, say, 0.1 s after the original pulse arrives at the junction, then the transmitted pulse will have travelled 1m to the right, and the reflected pulse will have travelled 2m to the left. You are only expected to sketch the appearance of the two pulses, and part (b) is only worth 3 marks as opposed to 6 marks for the quantative answers in part (a), so you don't need to very precise. Gandalf61 (talk) 09:35, 12 June 2010 (UTC)

The answer can be found here [2] by the way, but what I want is not the answer itself, but how you work the answer out.--220.253.96.217 (talk) 11:12, 12 June 2010 (UTC)

Computer components from petrochemicals

Which computer components (if any) are made from which materials derived from petroleum? -- Wavelength (talk) 07:17, 12 June 2010 (UTC)

The Integrated circuit encapsulation, any Insulator (electrical), epoxy in the Printed circuit board, engineering plastics in the DVD drive, external parts eg keyboard keys.77.86.125.56 (talk) 08:10, 12 June 2010 (UTC)

And lest we forget all the electricity needed to build the components, and where that comes from. Regards, --—Cyclonenim | Chat  11:17, 12 June 2010 (UTC)

It is unlikely that the electricity to manufacture electronic components comes from petroleum (or even natural gas). See the charts in electricity generation. For the United States, half the energy for electricity comes from coal, natural gas is nearly a quarter, almost all of what is left is nuclear; and the remainder is a tiny sliver of renewables, bio-fuels, hydro-energy, and geothermal. A tiny (minuscule) fraction of electricity comes from petroleum. An even smaller fraction comes from solar production. Furthermore, most electronics components are manufactured overseas (specifically, China, where coal is overwhelmingly the largest source of the energy for electricity). Very little petroleum is used to provide energy during the manufacture of those electronic components. Nonetheless, petroleum is used in massive scales to transport the materials - and transportation is the single largest energy-consuming sector (if you can call it a single sector). Nimur (talk) 16:35, 12 June 2010 (UTC)

Thank you all for your answers. Although I was hoping for more detailed information, I appreciate the information provided.
-- Wavelength (talk) 15:06, 13 June 2010 (UTC)

How about the following: FR-4, Integrated circuit packaging, Integrated circuit encapsulation, Potting (electronics), Resin dispensing? In the old days, circuits were packed in ceramic; nowadays, plastics, epoxies, silicone derivatives, and resins are more common; silicone is made from Dimethyldichlorosilane, made from Chloromethane, made from methanol, which is made in industrial scales from natural gas (methane). Epoxies are often made from epichlorohydrin, which can be made from heavy asphaltenes, paraffins, and petroleum residues. Similarly, if you click through the "production" or "synthesis" sections of most of the other constituents, and trace back far enough, you'll find the eventual source chemicals. Most of the electronics are not at all derived from petroleum or petrochemicals - but the packaging (without which the electronics would be useless) are petrochemical-derivatives. Furthermore, photoresist (a critical step in modern VLSI electronics) is also a petrochemical derivative. Hopefully this is a little more specific for at least some sub-areas of the electronic components - your original question covers so broad a topic that it is difficult to be both complete and specific. Nimur (talk) 16:21, 13 June 2010 (UTC)

Thank you for the additional information. -- Wavelength (talk) 14:30, 14 June 2010 (UTC)

heat

my power went out today when it came back on my gas central heat only pumps out cold air not hot air. i dont have any AC. how do i fix this ? its like my thermostat isint communicating with my heater properly. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 08:12, 12 June 2010 (UTC)

It could be several problems. It could be a defective safety on your furnace to prevent keeping the flame on when no blower is on. It could be your thermostat, but that is more unlikely with battery powered thermostats. --Chemicalinterest (talk) 10:59, 12 June 2010 (UTC)

could the power going out ruined or damaged the thermostat? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 11:34, 12 June 2010 (UTC)

and whats weird it has a space for a battery but i havent used one in years. when the power came back on the thermostat wouldent even turn on and i had to put in batteries to even make the display show up. why is that? it ran for years fine on house power. in the past when the power went out it came back on no problem. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 11:42, 12 June 2010 (UTC)

If your system is anything like my gas-fired hot water central heating system, Alexsmith44, then if your heater is not heating the air the burners may not be lighting, which suggests that the pilot light that ignites them may be out; this pilot light usually maintains a high temperature in a thermocouple which, if not hot, prevents gas from flowing to the pilot light and the main burners in order to prevent a large escape of gas blowing up your house. (Lighting the pilot usually requires you to manually over-ride the pilot light cutoff until the thermocouple is up to temperature.) Lighting the pilot usually requires either piezolectric spark ignition (usually achieved mechanically by pushing a button) or a spark derived from a battery or the mains electrical supply.

Is your pilot light lit? If not, the power cut may have caused it to go off for safety reasons, and you need to relight it, which will require the relevant components to be in good shape and the exact procedure in your appliance manual to be followed. If you are in any doubt about any of this (for example, if you don't have the manual) then call a qualified gas appliance engineer - gas appliances are too dangerous to be tinkered with by someone who doesn't know what they're doing.

If none of this is relevant, and/or you do know what you're doing (though if so why are you asking here?) then you have my apologies, but please don't risk blowing up yourself and your building! 87.81.230.195 (talk) 18:09, 12 June 2010 (UTC)

can anyone explain why when the power came back on the thermostat wouldent even turn on and i had to put in batteries to even make the display show up.

There are almost certainly too many different configurations of this general sort of system for anyone to have a chance of diagnosing such problems unless you say exactly what make and model your system is (and even then there would be no guarantee that anyone answering here could do so).

One thing I should add to my previous post: if your system includes a pilot-light-heated thermocouple, it might have failed when or after the system went down, or when you tried to restart it. Such thermocouples are probably the most failure-prone component of gas-fired heating systems - my own boiler's thermocouple failed at least 3 times during a 20-year period.

Even if anyone answering here can correctly guess the cause of your problem, you're not going to be able to be sure they're right, you're probably not going to be able to fix it, and you're going to run the risk of causing more damage to the system or yourself if you try but get it wrong, so you're going to have to call in a qualified engineer who will be able to make a sure diagnosis and carry out a safe repair/replacement. He/she is the person to ask. 87.81.230.195 (talk) 04:24, 13 June 2010 (UTC)

Some thermostats run on electricity created from the heat of the pilot (and so don't need a mains or even a battery connection). But it won't work without a heat source. Rmhermen (talk) 00:27, 14 June 2010 (UTC)

I hope the OP didn't live here! 87.81.230.195 (talk) 03:28, 14 June 2010 (UTC)

BP gulf oil issue: Geology question

Forgive my ignorance on the matter, but I was just curious about something: the world is focusing on the oceans and shores and flora/fauna, etc etc (and rightly so). But emptying at an estimated rate of 40,000 gallons a day, what's happening to the pocket where the oil is originally coming from? At what point would the pressure/weight of the ocean collapse the oil pocket? What would be the extent of the damage this incurred, or would the "earth" not even notice (like earthquake or tsunami, etc)? – Kerαunoςcopia^◁_galaxies 10:08, 12 June 2010 (UTC)

In most cases extracting oil or gas from a reservoir has relatively minor effects, as the hydrocarbon in the rock pores is replaced by water. The thing to remember is that we're not talking about a hole in the ground filled with oil, but a rock with maybe 20% porosity. Mikenorton (talk) 10:22, 12 June 2010 (UTC)

Just to expand a little on my response above, as the oil comes out, the pressure in the reservoir will reduce, something known as depletion, and this will lead to some compaction of the reservoir unit from the pressure of the overlying rock. In some cases this has led to induced seismicity on a small-scale [3] and minor seafloor subsidence [4]. Mikenorton (talk) 13:30, 12 June 2010 (UTC)

The rock is like an oil-filled sponge, so there is no big underground cave that is emptied. That said, normal oil production could make the seafloor sink gradually as oil is emptied. From the top of my head I know of an offshore oil rig that sunk by 20 metres over a couple of decades, because the oil reservoar below it was compacting. If you'r looking for geological catastrophes caused by the oil industry, the Lusi mud volcano is a much more dramatic example. EverGreg (talk) 12:11, 14 June 2010 (UTC)

Great! Thank you for the responses! – Kerαunoςcopia^◁_galaxies 18:25, 16 June 2010 (UTC)

Cats and mirrors

A follow-up to the discussion above at Wikipedia:Reference_desk/Science#Sentience.2Fconsciousness, my cat will watch me reflected in dark glass (doors, windows, all at night, reflecting the lighted interior well), and if I walk up to him quietly and kneel down, he'll watch me, then turn around and come to me. He's also waited at the door to be let out, but instead of meowing at me me, he'll watch me in the reflection, and when I arrive, look up at me again. He's obviously aware that he's the "little guy" in the reflection and I'm the taller one lol. Um, I guess my silly question would be, what does this prove? – Kerαunoςcopia^◁_galaxies 10:15, 12 June 2010 (UTC)

it proves you have an enviable amount of free time! 92.230.234.180 (talk) 10:37, 12 June 2010 (UTC)

It means animals can understand mirrors. --Chemicalinterest (talk) 10:57, 12 June 2010 (UTC)

No, it means cats (not all animals) are aware of their own reflection and potentially other things in the reflection. Cats are creatures of habit, if they see a reflection every time before the door opens, they'll associate that reflection with an opening door. They're also acutely aware of their surroundings, just because he/she looks up at you as you arrive doesn't mean they necessarily saw you in the mirror. Regards, --—Cyclonenim | Chat  11:14, 12 June 2010 (UTC)

I don't see why any part of the OP's story means that cats are aware of their own reflection. The story was entirely about identifying a reflected human shape as a human (and the assumption about awareness of "the little guy" came out of the blue). The cat doesn't react to its own reflection as it might do to a real cat on the other side of the glass, but that doesn't indicate awareness, only some basic filtering out from the cat's attention of objects that move in sync with the cat's muscle movements. (There might be a name for this, I forget - proprioception?) 213.122.19.215 (talk) 11:26, 12 June 2010 (UTC)

How does anyone know that cats are not aware of their own reflection?--178.167.206.65 (talk) 13:44, 12 June 2010 (UTC)

See Mirror test. Deor (talk) 13:51, 12 June 2010 (UTC)

The problem with the mirror test is that it is incapable of distinguishing between self-awareness (in this sense, the ability to recognize that the object in the mirror is a reflection of the self) and self-consciousness (an ability to compare the reflection against an internal self-representation to note differences). Animals who fail the mirror test (such as cats and dogs) may in fact be aware that the mirror is reflecting them, but may not recognize that the test dye that the researcher placed on them is something unusual or abnormal. clearly some animals do fail the test completely (e.g. budgerigars and beta fish, who respond to reflections with affection/aggression, the way they would when confronted with a separate creature), and clearly some few non-human animals which are capable of self-consciousness, but there's a decent-sized grey area in between. --Ludwigs2 14:29, 12 June 2010 (UTC)

Wouldn't that be easy to check by first placing the paint somewhere that the cat doesn't need a mirror to inspect? I have a difficult time imagining a cat, looking down at its own paw and not being irritated by something that a researcher did to its fur. APL (talk) 15:28, 12 June 2010 (UTC)

you'd have to be careful not to be confused by cats' normal irritation at being messed with. for instance, if you were to put a cat under anesthesia first (so it wasn't aware of the process) and dye its paw blue, I am not at all sure how much the cat would be disturbed by its newly blue paw, assuming the dye was tasteless, odorless, not irritating, etc... Clearly primates would be disturbed by such things (as demonstrated by numerous pranks played on drunk dorm-mates), but cats and dogs? remember, cats and dogs are often taken if for grooming, which can involve extensive changes in bodily appearance as fur is shaved away, but they are not generally perturbed by it. --Ludwigs2 16:35, 12 June 2010 (UTC)

Clearly it implies that the cat does not fully understand mirrors, if it's treating the reflection and the person as separate entities. But I'm not sure that it even implies that very strongly. Even if it does understand mirrors it might be treating it as a separate entity for amusement. Cat's like toys. So I'm not sure that it proves or even strongly implies anything.

Anyway, The point of the mirror test is not to check if the animal understands mirrors in general, but to check if they can recognize their own image. APL (talk) 15:28, 12 June 2010 (UTC)

It surprises me how much importance people place on mirror recognition. For a cat to recognize its reflection in a mirror is not in principle different from recognizing its own paw when it looks at it -- the fact that the light bounces off a reflective surface before reaching the eye has no philosophical significance. All animals that are capable of damaging their own bodies need robust self-recognition mechanisms to prevent that from happening, and mirror recognition is just that same process in action, as far as I can see. It raises a number of interesting practical issues, certainly, but I don't understand why it would raise philosophical issues. Looie496 (talk) 17:21, 12 June 2010 (UTC)

This brings to mind the all the times I've seen cats fail to recognize their own paws, and accidentally start washing the furniture. 213.122.16.179 (talk) 19:23, 12 June 2010 (UTC)

Breathable boots

I was watching How It Works earlier and it showed a factory making breathable, waterproof boots using Gore-Tex. The commentator said that it keeps water out whilst allowing steam/sweat to leave because these molecules "are 20 times smaller than water molecules". I call bullshit on that, water molecules and steam molecules are going to be the same size because steam IS water, with more kinetic energy and less dense. This also raises the question of why steam would need to escape. As far as I'm aware, human feet don't get hot enough to generate steam! So how does this system really work? Regards, --—Cyclonenim | Chat  11:12, 12 June 2010 (UTC)

(commentator's explanation was wrong)

Goretex (which see) allows water vapour out via the tiny holes, but doesn't allow water droplets in. As you know water droplets tend to stick together, and thus do not tend to break up - so they don't/can't break into tiny water droplets to go through the tiny holes.77.86.125.56 (talk) 11:18, 12 June 2010 (UTC)

Also, water vapour forms below 100C - eg evaporation - when you sweat the water evaporates, but your skin is not at boiling point, the difference is that air below 100C can only have a certain smaller amount of water vapour in it.77.86.125.56 (talk) 11:21, 12 June 2010 (UTC)

Boiling point is the point where the pressure of the water vapour (see vapour pressure) is the same as the ambient pressure, which allows bubbles to form and rise to the surface, allowing very rapid evaporation. The amount of water vapour that can remain in the air is related (that amount is the vapour pressure), but it isn't the key difference, since it is a gradual change. --Tango (talk) 02:15, 13 June 2010 (UTC)

I would expect that condensation on the cool inner surface of the boots from the warm vapour from your warm body is going to ruin the breathability anyway. 92.15.30.42 (talk) 11:52, 12 June 2010 (UTC)

Grass in flower beds

I've always had a problem with lots of grass growing in my flower beds. I have two situations: a) ground dug up in the early spring, annual flower seeds sown. b) perennial or biannual plants sown last year, so the ground could not be dug over - the bed looks like uncut grass with leaves in it. Is there any solution to getting rid of the grass except pulling out every grass blade one by one, a Herculean task? Thanks 92.15.30.42 (talk) 11:44, 12 June 2010 (UTC)

Not really enough detail on what the plants are to answer this, and you might be better off in some of the excellent gardening forums around on the web. Depending on the perennial plants but in general grass is not very good at pushing through wood shreddings compared to many (but not all) perennials. Strimming down the grass as much as possible and then spreading a 2in layer of bark or wood chip over everything might work. --BozMo talk 12:46, 12 June 2010 (UTC)

That would probably kill all the plants as well though. 92.15.0.254 (talk) 18:08, 12 June 2010 (UTC)

This depends on whether the grass is perennial creeping or whether it is annually seeded. If it is annually seeded then you need to get on the job at regular intervals in the spring and summer and pull it out before it seeds. If the grass is a creeping perennial type then you have a much harder problem to solve. No amount of pulling out will kill the grass in the long term because you will almost certainly leave bits of root behind which will regrow, and they will come through wood chips without a problem! For perennial grass you will either have to dig up the whole plot at some point that will not disrupt the flower display or by very carefully using a small brush to apply herbicide to the grass - of course I understand this might be totally impractical. First determine by the careful removal of a dozen or so sample grass plants if they are annual (self-contained clumps with fine roots) or perennial (attached to underground spreading roots). It may be a mixture of both types. I hope for your sake it is the former. You are not alone [5] Caesar's Daddy (talk) 14:57, 12 June 2010 (UTC)

For particularly tough grass such as (couch grass), I find that the best solution is glyphosate weedkiller applied with a paint brush so as to avoid affecting the nearby plants. This requires lots of patience, but it is very effective. Dbfirs 15:47, 12 June 2010 (UTC)

Do you think it would work if I applied the weedkiller during the winter? Thanks 92.15.0.254 (talk) 18:12, 12 June 2010 (UTC)

The plant has to actually be growing, and not dormant to be killed in this way with glyphosate, but if your winter is warm enough for continual growth it should still kill it. Graeme Bartlett (talk) 21:56, 12 June 2010 (UTC)

gear box vs belt pulley

For an 18 KW motor (~25hp), I use a 'v' belt (c type) to convert the speed from 900 to 450 rpm. An alternative is to replace this with a gear box. I believe the advantage of the gear is higher efficiency although with maintenance issues. Now without having actual data about the difference in efficiencies of the 2 and the annual/monthly maintenance cost involved with the gear box, is there any reason to prefer one over the other? The load connected to the motor is prone to slight vibrations every now and then. Thanks —Preceding unsigned comment added by 122.169.217.4 (talk) 13:06, 12 June 2010 (UTC)

Wear on the belt system is primarily on the belt - maintenence is replace the belt, compare this with maintenence on the gears (which may not even be possible - once the teeth are worn that's often it.) - the device will be out of action for much longer.

87.102.84.163 (talk) 15:13, 12 June 2010 (UTC)

What about a chain drive?87.102.84.163 (talk) 15:19, 12 June 2010 (UTC)

Actually summarised here [6] one big factor is if slip is acceptable, and the size of those torque variations.87.102.84.163 (talk) 15:22, 12 June 2010 (UTC)

Vellus hair

In Vellus hair it is said that exceptions (for vellus hair) include the lips, the backs of the ears, etc. The back of the ears usually has a very soft down generally and a few thick strands of hair occasionally. Isn't this an error then/?--117.204.94.179 (talk) 13:28, 12 June 2010 (UTC)

Pure OR of course, but the backs of my ears lack any hair apart from a few thick strands on the edge of the helix. Mikenorton (talk) 14:54, 12 June 2010 (UTC)

The backs of my ears are hairless but those of my cat are furry. I changed the title for easier reference. Cuddlyable3 (talk) 16:45, 12 June 2010 (UTC)

Are you sure? Those hairs are usually not dark and very short and almost invisible. You can try to pick them closely between two fingertips. Maybe, they are visible when you stand against bright sunlight as coming through the door way of a bright morning.--117.204.82.21 (talk) 01:41, 13 June 2010 (UTC)

You could have some moles on the backs of the ears that produce dark hair, I suppose. --Tango (talk) 02:10, 13 June 2010 (UTC)

No, not growing on moles. I am talking of a soft, fair down. Unfortunately I don't have a girl friend now to check it with somebody else. --117.204.88.50 (talk) 05:14, 13 June 2010 (UTC)

How to get a sponsorship

Hello,

My research paper has got selected in an international conference by IEEE http://www.icmee.org/ . I was a student of my college a month ago when i submitted that paper.Currently i have passed out.So,i could not find that how could i arrange the huge sponsorship amount.scientists at that end,Kindly help.I have just graduated in b.tech mechanical Engineering. Pardon me for asking an off topic question. Sameerdubey.sbp (talk) —Preceding undated comment added 15:23, 12 June 2010 (UTC).

Welcome to the harsh world of science. You have to find funds to do research, it seems to me the most appropriate way in your case would be to apply for a Ph.D research position... 15:51, 12 June 2010 (UTC)

You could do well to write to people who work in your field of interest. Let them know that you know about their work (from publications?) and tell of your own. Suggest that you would like to meet at the conference. Listen to and value their advice. Cuddlyable3 (talk) 16:29, 12 June 2010 (UTC)

Your question is not entirely clear. Are you asking how you might obtain funding to cover the costs of attending the conference, or funding to cover the costs of continuing your research? If you need funds to attend the conference, I would be surprised if the college you were a member of cannot give you either a small grant for this purpose, or at least advice on where to apply elsewhere for one, since your achievement must reflect well on them. If you need funds to continue your career, again your former college ought to be able to give you advice, but attending the conference, talking to more senior scientists there about your paper, and asking them for advice or directly for employment would be one strategy. 87.81.230.195 (talk) 17:45, 12 June 2010 (UTC)

The OP is probably in India, where money does not grow on trees, and the conference is in Japan, which is expensive to visit. But the reality is that if the supervisor of the project can't fund the travel, it is unlikely that anybody else will. Some academic conferences pay for travel for a certain number of students, but IEEE is more business-oriented and probably doesn't. I should also point out that IEEE conferences generally accept everything that is submitted to them, so having a submission accepted isn't a mark of prestige. Looie496 (talk) 17:53, 12 June 2010 (UTC)

Sameer, I notice that quite a number of people on the Program Committee are from India. If one of them happens to be from your own college, or from nearby, you could contact him to ask for suggestions. Looie496 (talk) 18:06, 12 June 2010 (UTC)

One thing to bear in mind is the OP didn't actually say where their university/college was located. The OP is probably from India, but whether their university/college is there wasn't stated. I initially thought the OP has been studying at the US because they said 'college' but on second thought if they were doing a B.tech in ME they may have done it at something called a college in India. Nil Einne (talk) 22:40, 12 June 2010 (UTC)

Using sea water in toilets

What are the difficulties in using sea water (directly, without desalination etc) in Flush toilets ? Barring the additional cost of plumbing and also the problem of corrosion of the taps etc (which I suppose can be solved by using plastic or other corrosion resistant materials), what prevents us from implementing this ? It would save a lot of water (approx 20 liters per flush) - WikiCheng | Talk 17:01, 12 June 2010 (UTC)

A third problem is that waste water is treated with bacteria before the water is drained to seas/rivers/whatever, and currently known efficient bacteria won't live in salty water. If you manage to bioengineer salt resistant bacteria (if you are into biotech, there's a nice project for you, go for it!), I guess you are pretty much left with the financial equation: desalinate vs. invest in duplicate pipe systems. Or triplicate: where I live we have two drain systems, one for rainwater and one for sewage; salt water sewage might require a third one, unless you want to mix your kitchen sink sweet water sewage with the salty toilet sewage. 88.112.56.9 (talk) 17:20, 12 June 2010 (UTC)

The article Head (watercraft) notes the use of sea water to flush toilets on boats. In submarines the high external water pressure makes this difficult. Cuddlyable3 (talk) 17:49, 12 June 2010 (UTC)

One could also ask why we don't use grey water in toilets. I can't say for certain, but I imagine that it's primarily the difficulty of running/maintaining the extra set of piping and storage, rather than any properties of the water itself. Fresh water is still cheap enough in most places (especially with low flow toilets) not to be worth the hassle. Also, getting the sea water to Nebraska (or even 100 km inland) would be a hassle. -- 174.24.195.56 (talk) 18:02, 12 June 2010 (UTC)

Using industrial quality water is toilets is pretty common wherever it's cheap enough to have two sets of pipes (or simply not to pipe drinking water). Physchim62 (talk) 20:21, 12 June 2010 (UTC)

They have been doing exactly that in Hong Kong for quite a while now (see Water supply in Hong Kong). But unless it's a densely populated coastal city the cost of laying and maintaining 2 sets of pipes might more than offset the cost and fresh water savings. --antilived^{T | C | G} 01:39, 13 June 2010 (UTC)

Unless you also have separate sewers, using seawater would actually be harmful. If your home is connected to a sewer system, you can't really "waste" water. Any water you use is recycled by the next city downriver from you. (Each city picks up water from the river, uses it, treats, and puts in back in the river for the next city downstream to use.) So it should be obvious that putting salty water in a freshwater river is something you should avoid, both for the river itself, and also for the next city downstream. Home Kong probably has no one downstream - they probably dump their sewage into the ocean. Ariel. (talk) 09:56, 13 June 2010 (UTC)

They use sea water on oil platforms to flush the toilets. There is at least recorded accident because the same sea water system was used for heat exchangers for cooling live crude as well. The sea water had jammed up every directional valve and corroded through the heat exchanger resulting in a flammable gas mixture being evolved into the toilet through the cisterne. Someone was smoking on the toilet (am pretty sure the whole platform was a non smoking zone although the toilet was in the crew "safe haven") and got a nasty surprise. Which highlights I guess that handling seawater through conventional plumbing is not straightforward. --BozMo talk 13:55, 13 June 2010 (UTC)

Thanks for your answers ! I forgot to mention the phrase 'at least in the cities near the sea' in my question :-). But I am surprised that it seems to be an issue of cost and preventing accidents (as stated by BozMo) rather than any technical problem - WikiCheng | Talk 04:04, 14 June 2010 (UTC)

Watering plants

Is it beneficial to urinate over garden plants? Or would the salt in the urine be harmful to them? A Wikipedia article says that drinking urine in survival conditions should never be done due to its salt content, so would urine be harmful to plants too? 92.15.0.254 (talk) 18:20, 12 June 2010 (UTC)

They'd get burnt from the acid too. YOu should see what female dog urine does to lawns! --TammyMoet (talk) 19:38, 12 June 2010 (UTC)

Yes, mostly the acid. Try urinating over a test plant, if you wish. You will quite quickly (one or two weeks of regular urinating, I'd say) that the plant turns brown and dry, just as if it were dead from lack of water. However, I know from observation of urinated-over lawns that some plants, especially some species of moss, survive the urine and thrive, whereas grass is burned. Of course the moss then makes it harder for the grass to grow back. In short, unless you want a moss garden, don't. --Alþykkr (talk) 22:33, 12 June 2010 (UTC)

I would guess that the moss is still being harmed by the urine, just not as much as the grass, so benefits from the lack of grass. The benefit from there being less grass around could very easily be greater than the harm from the urine. --Tango (talk) 02:09, 13 June 2010 (UTC)

(Edit Conflict) Actually wetting plants with urine would, as already stated, probably 'burn' them, but (human) urine is a useful source of nitrogenous fertilizer for the soil; discussions of this I have heard/read in the past usually recommend storing it for a time in a (sealed) container rather than adding it 'fresh' (just keep a plastic screw-top bottle next to the toilet, and add to it as and when). Googling on "Urine gardening" returns many hits discussing the topic in detail. 87.81.230.195 (talk) 22:37, 12 June 2010 (UTC)

This is a common question on "Gardener's World" type programs. The consensus seems to be you should wee on your compost heap but not directly on to plants. All the panelists last time I heard this on the radio admitted they did this (even the ladies) although there were technique variations. --BozMo talk 14:05, 13 June 2010 (UTC)

On the other hand if they are weeds and your urine does kill them would seem an effective and fairly safe weed killer Nil Einne (talk) 06:03, 14 June 2010 (UTC)

And I should add that the salt in urine is very dependent on Diet, at least for NaCl. My Dad was some type of Diabetes specialist [7] who served as a ship's doctor on a Destroyer in the med in WW2 where sailors refused to take their salt tablets. He was fond of saying that when people were running salt deficit their urine had a lower salt content (meaning NaCl) than laboratory distilled water. He had measured it of course. --BozMo talk 10:37, 14 June 2010 (UTC)

brushed nickel

what is brushed nickel ? and can it cause dermatitis —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:05, 12 June 2010 (UTC)

See Nickel#Toxicity. hydnjo (talk) 20:25, 12 June 2010 (UTC)

yes but is brushed nickel the same as reg. nickel does it have a coating —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:29, 12 June 2010 (UTC)

According to the WP article "Brushed metal" it is perhaps hot rolled, annealed, pickled and passivated. Of course it can be coated (as anything else) but I don't think that's what you were asking. hydnjo (talk) 20:57, 12 June 2010 (UTC)

Rechargeable Battery: voltage rebound

When a device powered by rechargeable batteries depletes the battery, it stops working because the voltage is not high enough to power it. But I've noticed that if you leave the power off for a while, the voltage of the battery rises without charging. And if you wait long enough (10 min - 1 h) and then turn the device on, the it will work again, although probably with a low battery warning. I have seen this happen in cell phones, cameras, gameboys, and any device using rechargeable AA/AAA batteries.

What causes this voltage rebound? I'm taking about the NiMH and Li ion types mainly. --Yanwen (talk) 21:29, 12 June 2010 (UTC)

This is common across all cell types and is caused by Polarisation: "An effect produced upon the plates of a voltaic battery, or the electrodes in an electrolytic cell, by the deposition upon them of the gases liberated by the action of the current. It is chiefly due to the hydrogen, and results in an increase of the resistance, and the setting up of an opposing electro-motive force, both of which tend materially to weaken the current of the battery, or that passing through the cell." The effect vanishes when the battery is allowed to rest with no current. I'm looking for a Wikipedia article on this. Do we have one? Dbfirs 21:38, 12 June 2010 (UTC)

Depolarizer ? Battery chemistry is quite a big topic - I'm suprised there isn't more here.

Thanks, 87, I'd missed that. The effect still seems to be called polaris(z)ation, even though the chemistry varies. Dbfirs 07:57, 13 June 2010 (UTC)

... also from the history of cells at "Battery and Energy Technologies" [8] "Volta's simple voltaic cell cannot operate very long because bubbles of hydrogen gas collect at the copper electrode acting as an insulator, reducing or stopping further electron flow. This blockage is called polarisation. Daniell's cell overcomes this problem by using electrolytes which are compatible with the electrodes. Thus the zinc electrode is suspended in an electrolytic solution of zinc sulphate which is contained in the porous pot (Initial designs used sulphuric acid rather than zinc sulphate). The porous pot is in turn immersed in the copper sulphate solution which is contained in a glass jar into which the copper electrode is also suspended. The Daniell cell does not produce gaseous products as a result of galvanic action and copper rather than hydrogen is deposited on the cathode. Daniell's non-polarising battery was thus able to deliver sustained, constant currents, a major improvement on the Voltaic pile." The chemistry will be different in NiMH and Li ion types, but the principle is the same. The effect becomes more noticeable as the battery becomes weaker. Wikipedia does have a short paragraph at Primary_cell#Polarization. You might also be interested in this patent application. Dbfirs 21:52, 12 June 2010 (UTC)

The situation in Lithium batteries is different due to lack of production of Hydrogen - a similar effect may be produced in Li cells by locally (near the electrode) increased concentrations of Li+ ions reducing the cell EMF - these will take time to diffuse away. Note:this is one possibility - I haven't got a full analysis of the processes in Li cells.

I think this accumulation of reacted lithium is still a form of (ie is called) polarisation. 87.102.84.163 (talk) 01:03, 13 June 2010 (UTC)

Yes, the 2009 patent (above) uses the term "polarization" for the effect in Lithium cells. The original problem was with hydrogen, but the term just means accumulation of ions or molecules near to one (or both) of the poles. Dbfirs 08:06, 13 June 2010 (UTC)

Cauterization as an emergency measure

Why is it that cauterization is never mentioned as a possible (although obviously... not optimal) way to stop heavy bleeding in an emergency ? Is it only because of practical purposes (the emergency rescuer is unlikely to have a source of heat with him or near him), or because of inefficiency/dangers ? I know cauterization is extremely painful and causes tissue damage, but in the event bleeding can't be stopped even with a tourniquet (or if the tourniquet can no longer be maintained because of risk of limb loss), would cauterization be an interesting last-resort solution ? Thanks in advance, --Alþykkr (talk) 22:28, 12 June 2010 (UTC)

Probably because it is very rarely useful. Even tourniquets often aren't taught on first aid courses these days. Direct pressure, elevation and pressure points can do the job in pretty much all circumstances where tourniquets or cauterization would help. If cauterizing wounds was useful, it wouldn't be hard to include a suitable tool (either gas powered or electric) in the bags paramedics carry, or even in first aid kits. --Tango (talk) 22:58, 12 June 2010 (UTC)

According to the 'SAS survival manual' (probably not really - but that's what it was called, though I believe it was written by an ex-SAS guy) I had as a teen, cauterization is only to be used as a last resort in a situation where no rescue is imminent, say if your plane just crashed in the Andes (or something) and someone's legs are hanging off. There was a caveat that cauterization will actually cause some people to drop dead from shock. --Kurt Shaped Box (talk) 23:07, 12 June 2010 (UTC)

An observation by a nonmedical person: Cauterizing , say an artery after some traumatic amputation smacks of 18th century naval battles. But electrocautery does seem to be used today to stop small bleeders in operations. Edison (talk) 01:31, 13 June 2010 (UTC)

Indeed, it is used for small blood vessels that you can get to precisely. They only touch the cauterizing thing to the blood vessel itself. It is very different to cauterizing a wound from the outside with a big red-hot poker. That means there is no real tissue damage, other than to the blood vessel that has been damaged by severing it anyway. --Tango (talk) 02:06, 13 June 2010 (UTC)

June 13

Flaming blood

First, is there any way that a substance could be produced which would cause a person’s blood to burst into flames? Second, if such a substance could exist, could it be contained in a pill form?--99.251.239.89 (talk) 02:52, 13 June 2010 (UTC)

There are substances that burst into flame on contact with water (which blood mostly is), but nothing that could actually cause the blood itself to burn. If you used something that burst into flame on contact with water, it would have to be injected - if swallowed, it would burst into flame somewhere in the digestive system. --Tango (talk) 02:56, 13 June 2010 (UTC)

Potentially you could have a pyrophoric (air reactive) material which would cause the blood to erupt in flames when it hits the oxygen in air (but not while it's still in the body). Most pyrophoric substances are water reactive too, though, and even those that aren't may react with the dissolved oxygen in the blood, or will be toxic even without bursting into flames. -- 174.24.195.56 (talk) 04:23, 13 June 2010 (UTC)

I think if you got such a substance to a high enough concentration for it to work, it would be toxic. --Tango (talk) 15:32, 13 June 2010 (UTC)

One suggested (but implausible) explanation for Spontaneous human combustion is a high blood alcohol concentration. Mitch Ames (talk) 12:33, 14 June 2010 (UTC)

One more plausible interpretation of many of those cases, however, is that high blood alcohol causes the victims to fall asleep while smoking. Blood alcohol concentrations of less than 1% are lethal. There is just no way to get an aqueous 1% ethanol solution to ignite in air. TenOfAllTrades(talk) 12:47, 14 June 2010 (UTC)

No. "If such a substance could exist", we have no way of knowing whether it could be in pill form. Axl ¤ [Talk] 07:53, 15 June 2010 (UTC)

Well, blood is one way to make gelled gasoline, but it is used as a congealing agent. I lent out my main book on incendiaries so I'm not sure if I can help too much. Perhaps shotgun shells filled with something like pure sodium or magnesium? I'd think if it could survive being fired it would explode on contact with the water in the blood, which might be able to ignite something like thermite. I guess, now that I think about it, you'd want to have the outer bullet made out something like that, the thermite in the center, and the blood igniting the out coating which would start the thermite reaction. TheGoodLocust (talk) 00:56, 18 June 2010 (UTC)

Wouldn't humankind be capable of surviving an overacting solar flare after all?

At the end of this film, (apparently) everybody on Earth dies when a solar flare gets overactive enough to strike our planet. However, what if some people are in submarines? How deep underwater can this kind of solar flare cook anything? How thick would the submarine's walls need to be in order for everyone inside to withstand the onslaught, should a solar flare even be able to cook that far underwater in the first place?

Also, I think solar flares would only cook the daylight side of the planet. How long would this kind of solar flare stick around? Would it stick around long enough to cook the night side once it's morning for them?

Moreover, what of people who are currently underground - in subways, etc.? What of the people who got enough warning to get to a bomb/fallout shelter deep underground? How far underground would they have to be in order to stay safe?

If a handful of humankind could survive the Sumatra volcano 70,000 years ago, I'm sure we can survive rogue solar flares now. --Let Us Update Wikipedia: Dusty Articles 03:28, 13 June 2010 (UTC)

The human race has been around for about 2 million years in its current form, during that time there have been plenty of large solar flares, yet we are still here. The Earth's magnetic field and atmosphere protect us. The film is complete fiction with no basis in reality (were the telepathic aliens that can predict the future not a give-away?). --Tango (talk) 03:48, 13 June 2010 (UTC)

Thanks, T. So if a solar flare as large as in the movie happened real soon, can you confirm whether we'd be able to protect ourselves by either diving deep underwater or running deep underground as described above? Or how else would we manage to survive this kind of solar flare, if you know of other ideas? --Let Us Update Wikipedia: Dusty Articles 04:53, 13 June 2010 (UTC)

I suppose if the giant solar flare happened to coincide with the expected reversal of the Earth's magnetic field (sometime during the next few thousand years), then most of the mammals on Earth might be affected. There might be some extinctions, but it would be unlikely to include humans - there are just too many of us in too many different environments. Science has little experience on which to base predictions, so we can only guess. The flare at a time of very low magnetic field would have a drastic effect on civilization though. Dbfirs 07:37, 13 June 2010 (UTC)

You need a nearby GRB to do significant damage, see e.g. here. Count Iblis (talk) 18:05, 13 June 2010 (UTC)

The most likely scenario for significant disruption of our high-tech civilization is for a solar flare to overload and destroy large numbers of power transformers at northerly and southerly locations. Because the manufacturing capacity for power transformers is limited, it would take a long time to replace the transformers. Jc3s5h (talk) 18:17, 13 June 2010 (UTC)

Also see Inconstant Moon by Larry Niven and its TV version Inconstant Moon (The Outer Limits). --Stephan Schulz (talk) 11:27, 14 June 2010 (UTC)

virus more active during rainy season?

I read in a newspaper editorial that virus infecting human beings become more powerful during the rainy season. Is there in truth in it?--117.204.90.213 (talk) 05:16, 13 June 2010 (UTC)

Viruses tend to spread more rapidly when humans are in closer contact (e.g. in winter in some countries), but I don't know of any evidence that rain affects the virus itself. Can anyone find any research? Dbfirs 07:40, 13 June 2010 (UTC)

Not true, viruses are not lifeforms, they are just rather complex protein machinery. In winter, they are not changed structurally to appear any different to any other time of year, so there is no reason to believe a virus would become stronger in winter. However, weakened immune systems are at more risk of contracting diseases in cold, winter seasons. That's why a lot more people catch influenza over winter than at any other time of year, but it has nothing to do with the virus itself. Regards, --—Cyclonenim | Chat  10:24, 13 June 2010 (UTC)

When it comes to influenza, Influenza#Seasonal variations & Flu season deals with this somewhat. As with many things, the truth is we don't really understand that well why flus are seasonal. The greater close contact almost definitely plays a part (as Dbfirs has noted) but so could other things like the virus surviving on surfaces for longer (which may be partially due to changes in the viral structure from the different temperatures), dehydrated mucus and possibly a weakened immune system that Cyclonenim notes above. Lower vitamin D levels have also be proposed as a possible cause. One interesting thing is that while it's suggested a lower humidity may contribute, in tropical (& I think most subtropical ones) regions I suspect like wherever the OP is in India (Kerala?), the flu season tends to be the rainy months where some of the earlier mentioned factors would hold true or somewhat true but lower humidity generally wouldn't (although the humidity may always be fairly high so this could perhaps be why it's not a big factor). Our articles also discuss other potential factors like interaction with other diseases and school terms. As I've noted it's almost definitely a combination of factors but how much of contribution each one makes we obviously don't really know and potentially/probably? different ones in different regions. Nil Einne (talk) 13:07, 13 June 2010 (UTC)

Viruses and other infectious agents generally survive better in water than in dry air, and during the rainy season in hot climates there tend to be a lot of droplets of water floating around, as well as water on the ground that can be splashed. It makes a huge difference: during the colonial era in tropical Africa, it was considered nearly suicidal to travel during the rainy season -- almost all the exploration was done during the dry season. Looie496 (talk) 16:59, 13 June 2010 (UTC)

Are you sure the exploration wasn't more to do with mosquitos? Nil Einne (talk) 01:04, 14 June 2010 (UTC)

Maximum/Minimum Irradiance..?

Maximum/Minimum Irradiance (solar constant) range for a "Human habitable" planet/planet-moon
to have a habitable Global Annual Average Surface Temperature?
I am referring to a habitable planet for people, and not extremophiles.
I am referring to Global Annual Average Surface Temperature, as in 14°C for Earth,
and therefore don't mean Mercury's cold side, or Venus's upper atmosphere, or Pluto's core;
Pluto, Venus, Mercury, like planets could be habitable but are not in the Goldilocks Zone,
and I am only asking about heating by the parent star, which is the main factors,
any other factors spinning things better can't be counted on like influence of the parent star itself.
We may find "liquid water" near the core of Pluto, but the chances of people living there are nearly nil.
The solar contant for the Earth is 1366.08 Watts per Meter squared,
but that is for the semi-major axis (100%), but this value varies from 103.43% to 96.74%,
and Venus' varies from 193.93%-191.30%-188.73%, and Mercury's from 1058.11%-667.69%-459.36%.
I am confident in what I am asking and don't need question improvement suggestions,
or other angles, tangents and sidetracks; If you think there is something wrong with the question,
then you just don't understand it, and please don't bother.

Take for example a large moon of COROT-9b: (exoplanet.eu)
Star Radius = 0.94 sol
Star Te = 5625 K
Stefan–Boltzmann constant, σ = 5.67051E-8
Semi-major axis = d, in this case 0.407 (± 0.005) AU
Eccentricity = e, in this case 0.11 (± 0.04)
=(((0.94*6.955e8)^2*(5.67051e-8)*(5625^4)) / (0.4069*149597870690)^2) /1366.0875

PIO	Ecc. min. 0.07	Ecc. avg. 0.11	Ecc. max. 0.15
Periastron:	553.96%	604.88%	663.15%
Semi-major axis :	479.12%	479.12%	479.12%
Apastron:	418.48%	388.87%	362.29%

• Note that if the maximum is lowered then the minimum is raised.

I used this example because Europe's CoRoT space telescope team has obviously lied
to the journal Nature (3/10), reporting "CoRot-9b is circling its star in a "temperate" orbit.

Irrandiance Habitable Candidates?

This is not part of my question, just here for examples.

Planet	Radius (Sol)	Photosphere Temperature (K)	Semimajor axis (AU)	Orbital eccentricity	Perihelion Irradiance	Average Irradiance	Aphelion Irradiance	Period (Yrs.)
Mars	1.0	5778	1.523	0.0934	52.45%	43.11%	36.06%	1.8795
HD 141937 b	1.06	5821	1.52	0.41	151.57%	52.76%	26.54%	1.79
HD 187085 b		6011	2.05	0.47	191.84%	53.89%	24.94%	2.7
HD 23079 b	1.13	5848	1.65	0.1	68.65%	55.61%	45.96%	2.02
ups And d	1.631	6212	2.55	0.32	124.54%	57.59%	33.05%	3.56
HD 99109 b		5272	1.105	0.09	71.72%	59.39%	49.99%	1.20
HD 10697 b	1.72	5641	2.16	0.1	77.76%	61.60%	49.99%	2.947
HD 147513 b	1	5701	1.26	0.52	279.84%	64.47%	27.91%	1.48
HD 213240 b	1.5	5984	2.03	0.45	219.53%	66.41%	31.58%	2.6
HD 45364 c		5434	0.8972	0.0974	82.15%	66.93%	55.57%	0.939
HD 196885 b	1.79	6340	2.37	0.462	231.99%	67.15%	31.42%	3.65
HD 210277 b	1.1	5532	1.1	0.472	258.97%	72.20%	33.32%	1.21
HD 136418 b	3.4	5071	1.32	0.255	188.72%	74.90%	39.91%	1.27
HD 183263 b	1.21	5888	1.52	0.38	196.35%	75.48%	39.63%	1.73
HD 160691 b	1.245	5700	1.5	0.128	103.07%	78.37%	61.59%	1.76
HD 125612 b	1.05	5897	1.2	0.39	213.56%	79.47%	41.13%	1.37
HD 28185 b	1.03	5482	1.03	0.07	93.69%	81.03%	70.77%	1.05
HD 190228 b	3.02	5176	2.31	0.43	262.13%	85.17%	41.65%	3.09
Gliese 876 c	0.36	3350	0.132	0.266	162.61%	86.65%	53.73%	0.083
HD 188015 b	1.1	5520	1.19	0.15	120.50%	87.06%	65.83%	1.25
HD 16175 b	1.87	6000	2.1	0.59	548.49%	92.20%	36.47%	2.71
HD 100777 b		5582	1.03	0.36	237.79%	97.40%	52.66%	1.05
Earth	1.0	5778	1.0	0.01671022	103.43%	100.00%	96.74%	1.0
HD 108874 b	1.22	5407	1.051	0.07	119.47%	103.33%	90.25%	1.08
HD 155358 c		5760	1.224	0.176	155.02%	105.26%	76.11%	1.45
HD 142415 b	1.03	5834	1.05	0.5	425.29%	106.32%	47.25%	1.06
HD 20367 b	1.18	5929	1.25	0.23	185.73%	110.12%	72.79%	1.37
HD 82943 b	1.12	5874	1.19	0.219	182.79%	111.50%	75.03%	1.21
HD 221287 b		6304	1.25	0.08	136.29%	115.36%	98.90%	1.25
HD 45364 b		5434	0.6813	0.1684	167.83%	116.07%	85.02%	0.62
HD 92788 b	0.99	5559	0.97	0.334	221.33%	117.95%	73.13%	0.89
HD 153950 b	1.34	6076	1.28	0.34	329.92%	143.71%	80.04%	1.37
HD 69830 d	0.895	5385	0.63	0.07	166.74%	144.22%	125.96%	0.54
Venus	1.0	5778	0.723	0.0068	193.93%	191.30%	188.73%	0.6148

Given the best possible conditions, (that is I not asking for an atmosphere that is so large that it would be warm past the orbit of Mars, but the pressure would crush a person, and that kind of nonsense.) what would be a stable range for irradiance for a "habitable for people" Global Annual Average Surface Temperature on an Earth-like planet or planet-moon; The range must be larger than Earth's 103.43% to 96.74%, less than Mercury's 1058.11%, and more than Mar's 36.06%, but what are the maximum and minimums??
24.78.167.139 (talk) 05:26, 13 June 2010 (UTC)

You have obviously done a lot of research on this yourself, so you might be the best person to answer your own question. I must admit that I don't understand it because, as mentioned last time, so many other factors are relevant. Dbfirs 07:43, 13 June 2010 (UTC)

The papers cited in our Habitable_zone article might provide interesting reading, if you haven't already, to see what assumptions and models the authors used. As Dbfir says, you might be the most in-the-know person here about what you're after. Brammers (talk/c) 08:33, 13 June 2010 (UTC)

This is actually the first step to what I considered a more complex question, but it may be the other way around to answer this part, if I just plug in Albedo and Emissivity of the Earth, I could use a similar formula to calculate the Global Annual Average Surface temperatures of those same planets in the chart (or planet-moons there) but to make use of that angle of solving the problem I would then need to know what are realistic/stable Global Average Albedo's and realistic/stable Global Average Emissivity, Almost a catch 22. So, because of those suggestions I hunted down this MADSCI Question/Answer from long ago, because you may be right, I may have to go study cosmochemistry and geology to answer this question without anyone's help. 24.78.167.139 (talk) 09:53, 13 June 2010 (UTC)

I don't know why you are asking questions at the same time as saying "because Europe's CoRoT space telescope team has obviously lied to the journal Nature". Firstly accusations of lying in a scientific paper are very grave, perhaps you mean you believe they are mistaken in their results? Perhaps they mean something other than what you mean? Secondly you really need to show they are wrong before saying they are so why the questions about working it all out? Have you gone through their workings carefully? Dmcq (talk) 16:37, 13 June 2010 (UTC)

You have ignored the calculations above to make your comment; suggesting that such a planet is in the "habitable zone" is an ugly misrepresentation. 24.78.167.139 (talk) 06:27, 15 June 2010 (UTC)

The OP has asked variations on this question many times in the past. He or she seems unwilling to accept that there are huge uncertainties in the field of planetary science and extrasolar planet characterization. It is not possible to put a boundary on irradiance for the habitable zone unless you explicitly state your assumptions. Define habitable zone. Define a suitable temperature range. State your assumptions about the planetary parameters (albedo, atmospheric greenhouse effects, thermal re-emission, orbit parameters, and so on). Once you have defined those notions, it will be trivial to give you a "percentage" for the stellar irradiance to yield a particular temperature range. The biggest problem with your formulation is that you have jumped over these extremely critical problem definition stages and have started demanding numerical values. This is equivalent to demanding "how much fuel would an airplane take?" How can we answer such a question with a numerical value? You haven't asked for anything. We cannot give you a numerical value unless you specify your problem better. Nimur (talk) 17:44, 13 June 2010 (UTC)

Nonsense, the "Goldilocks zone" is that simplistic.
Also, your accusation is impotent to me as it was recommended to me that I keep asking
24.78.167.139 (talk) 06:27, 15 June 2010 (UTC)

Furthermore - regarding whether Deeg, Moutou, et al. "lied" in their paper: have you read the paper? Here it is: A transiting giant planet with a temperature between 250 K and 430 K. I wonder how you can be more specific than that: they tell you right in the title - the error bars are so uncertain that the planet temperature might be too cold for liquid water, the right temperature for liquid water, or too hot for liquid water. The error bars are so huge, that any possible scenario is plausible, based on available measurements and data analysis. Regarding whether they characterize this as "temperate":

“ Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a ‘temperate’ photospheric temperature estimated to be between

250 and 430 K.

” — H.J. Deeg, Nature 464, 384-387 (18 March 2010)

They even put "temperate" in quotation marks - to indicate that this is a hand-wavey term! But they actually told you the temperature ranges that they have deduced. In science, we prefer quantitative analysis over vague terminology any day. Nimur (talk) 22:10, 13 June 2010 (UTC)

You may be correct but I didn't expect to have access to the Nature article which I expect is by subscription, I was going by this quote misused to sensationalize the idea that the Na'vi are there waiting. It looks to me like the same crap that happened with Gliese 581 c, the the discovery team got their errors sensationalize as correct, and then two other teams had to write correct/contradicting papers saying it is out of not in the "habitable zone." Both cases are shameless. I think -23°C is a joke (and you blindly quote that), let alone the self contradicting loop that "Hot Ice" would be needed to have the needed albedo at that irradiance, I'm not so easily fooled these very unlikely contradictory ideas, it would much more likely be steam and a runaway greenhouse gas effect. 24.78.167.139 (talk) 06:27, 15 June 2010 (UTC)

I would also point out that many journals will allow intelligent and reasoned feedback on articles within a few months after they are published. (For Nature [9] would probably be the correct way.) You can also contact the authors. However given the comments and questions you (24.78.167.139) left on the RD there's a good chance any feedback you have will be ignored. (Nature for example says "All contributions should be measured in tone, and should not contain inflammatory or otherwise intemperate language".) In particular, accusing the authors of lying is likely to get you automatically ignored which isn't surprising considering it's potentially defamatory (and this paper appears to include about 30 authors to boot). In other words beware the pitfalls befalling this infamous Conservapedia#Lenski dialogue [10]. But if you genuinely believe in your claims, consider writing a more reasoned and betterr worded response and submitting it rather then making claims to random people with no connection to the paper. In other words, put your money where your mouth is. If you have genuinely discovered a major error in the paper, I'm sure they'll be happy to know. Nil Einne (talk) 01:39, 14 June 2010 (UTC)

PIO	Ecc. min. 0.07	Ecc. avg. 0.11	Ecc. max. 0.15
Periastron:	553.96%	604.88%	663.15%
Semi-major axis:	479.12%	479.12%	479.12%
Apastron:	418.48%	388.87%	362.29%

$f=(R^{2}\sigma T^{4})/d^{2}\$
Ha, ha, ha; if I have "genuinely discovered a major error," a child could do the algebra. Venus receives only 191.30% of the heat the Earth does, Mercury 459.36% minimum. I apologize if anyone thinks I was referring to extremophiles even thought I did add a disclaimer to the question. As I said above, I will likely have to create the answer to this question on my own as no one seems to have constructive scientific input to offer. 24.78.167.139 (talk) 06:27, 15 June 2010 (UTC)

Considering if I understand your above messages correctly, you've accused the 30 or so authors of a scientific paper of lying without even having read the paper and instead going solely by a likely sensationalistic newspaper report yes it's hardly surprising you will have to do this on your own... I do await hearing the poor authors majorly embarassed and the major scandal involving Nature when it comes out this peer reviewed article contains a major error even a child could have noticed. Nil Einne (talk) 16:22, 15 June 2010 (UTC)

Not likely, the discovery team's paper for Gliese 581 c was left behind after the two other teams correct papers and hasn't been spoken of since except the qualifier in the article "it was first reported... (wrongly)." No one has retracted or apologized for that, and this will get swept under eventually in just the same way. The paper is obviously not worth reading if a child can prove it wrong. 24.78.167.139 (talk) 17:30, 15 June 2010 (UTC)

Children are taught not to use superfluous precision. Why do you have a chart with 3 or 4 decimal places on these values? Have you conducted sensitivity analysis? Can you provide error bounds, backed by data, to suggest that your work can sustain that level of precision? Yet you keep repeating these values as if 191.30% of the Earth's irradiance level is an important result, or indeed that there is such a degree of accuracy in the definition of the habitable zone. All the while, you seem to be missing the fact that the published results are not making such solid claims as you are - and then you accuse them of intentionally misrepresenting fact! 24.78, you are making serious accusations of scientific error, but you are providing us with little evidence of your own ability to understand and use standard scientific approaches. Throwing equations and data at an anonymous group of volunteers on Wikipedia is not the same as a properly reasoned scientific process that is required for a journal like Nature. The published numbers have been subject to scientific peer review. That is why those journals and the results they present are notable. There is room for error in science - peer review does not guarantee correctness - but it places a high degree of confidence that the claims can be backed up. Nimur (talk) 15:22, 16 June 2010 (UTC)

• -23°C is a lie,
  and true Venus at 191% of Earth's irradiance is not as important,
  but only to get an idea of how 663% of Earth's irradiance is! ("Temperate," my gluteus maximus.)
  My not bothering to chop of sig.difs. doesn't disprove anything, which makes your comments rather petty; it's always the last desperate criticism of someone who has nothing worse, "ooooh, too many sig.difs. it must wrong." If what you say was true at all you could have backed up what you say with some numbers of your own, but you have none I'm sure. If the quote above is even true, then -23°C is a lie.
  24.78.167.139 (talk) 02:23, 17 June 2010 (UTC)

• Another desperate false criticism is saying I placed 3 or 4 decimal paces in the charts arbitrarily, when I actually used figures from scientific work already done; the Earths eccentricity can be found here http://en.wikipedia.org/wiki/Earth
  and you will note that 0.01671123 is eight decimal places.24.78.167.139 (talk) 02:33, 17 June 2010 (UTC)

• - "If you think there is something wrong with the question, then you just don't understand it, and please don't bother." - 24.78.167.139 (talk) 02:33, 17 June 2010 (UTC)

is risk from smoking linear with amount smoked?

if person A smokes 1/5th as many cigarettes as person B, then is person A 1/5th as likely to get any health complications? (I read from the health effects of tobacco that it is "stochastic" (like a lottery) for many cancers, etc: either you get it or you don't.) 85.181.49.30 (talk) 09:27, 13 June 2010 (UTC)

I could be wrong, but I wouldn't imagine this is the case. For a cancer to occur, a complicated series of events needs to occur, a lot of things need to fail and you need to be quite unlucky. This is because you need genetic damage to be caused to cancer preventing genes and repair genes, AND THEN you need to have another situation where the gene which switches on and off cell division gets stuck on the 'on' switch. At this point, cell division becomes uncontrollable and you have yourself a tumor. But of course, there are any number of factors which can cause genetic damage and it's impossible to predict accurately for every day life. You can['t] predict which X-ray, gamma ray, carcinogen etc. which will directly cause the damage, so I'd believe it is indeed stochastic. Regards, --—Cyclonenim | Chat  10:29, 13 June 2010 (UTC)

Much like there is a concept of ED50 and LD50, when assertions are made about the association of tobacco consumption and cancer, it is merely a statistical significance that happens to be clinically significant as well. All posted data are averages. That being said, how do you get 1/5 of a lung cancer? It would also depend upon a potential carcinogenic plateau effect, and so percentages cannot be the only things stated (i.e. you'd have to provide absolute parameters as well). Currently, though, smoking can be classified by "pack years", and so person A who smokes 1PPD x 4 years and person B who smokes 2PPD for 2 years are both said to have smoked for 4 pack years. Do they necessarily match each other in terms of severity of risk? You certainly bring up a good point. DRosenbach ^{(Talk | Contribs)} 13:55, 13 June 2010 (UTC)

And again, it's worth emphasizing and reemphasizing the probabilistic nature of this. What these "risk" factors means is that out of a population of X number of people, Y number would be expected to have health complications. It doesn't really mean, "this individual has this particular chance of getting cancer"—cancer is not a rolling of dice. It also does not take into account the complexities of individual exposure—it cannot rule out all of the other variables involved. (For example, if you smoke and are exposed to high radon levels in your home, your chances of getting cancer are very high indeed, much higher than if you "just" smoke or if you "just" have high radon.) --Mr.98 (talk) 14:23, 13 June 2010 (UTC)

Let me guess - you're a smoker. 92.15.14.150 (talk) 20:04, 13 June 2010 (UTC)

Why would you assume that? I'm not a smoker, and I find it very irritating when people talk about smoking as leading inexorably to specific consequences for every person. Not only is it bad science and bad statistics, it's self-evidentally not true. If you misrepresent the risks of smoking as one set of consequences that happen to everyone, people only have to know one smoker who didn't experience those consequences to reject everything ever said about the dangers of smoking, since it was clearly not true. And most people know a smoker who didn't get lung cancer, for example. Far better to be honest about it. 86.164.69.239 (talk) 20:59, 13 June 2010 (UTC)

I'm not a smoker, and am quite against smoking. But that has nothing to do with whether I think people misunderstand the nature of probabilistic risk. I think that smoking is clearly a health problem without resorting to misunderstanding, and that such a misunderstanding leads to even more ridiculous pro-smoking positions like those outlined by 86.164. Truly "getting" what risk factor data actually means lets one actually make sensible choices and understand why anomalous results obviously exist (like the oft-cited grandparent who smoked every day and lived to age 95). --Mr.98 (talk) 21:57, 13 June 2010 (UTC)

Whilst I agree with 86 and Mr. 98, it's important not to overexagerate the risk of smoking, it's important to reinforce the idea that just because you might not get cancer, it doesn't mean you're going to live a good quality life. I'd venture to say that almost all life-long smokers are going to have inferior quality of life at some stage. They'll be less efficient at getting oxygen into their blood, so they're going to struggle more with exercise and even general living like climbing stairs (eventually). Not to mention the risk of COPD and other diseases. Cancer is a major effect of smoking, but not as common as respiratory distress. Regards, --—Cyclonenim | Chat  23:40, 13 June 2010 (UTC)

While they will almost certainly be less efficient at getting oxygen into their blood than they personally would otherwise have been, different people start from different positions, and have different reactions to the smoke, combining with other environmental effects. So, actually, there are going to be some people who smoke a pack a day for 60 years, and have no trouble climbing stairs. But there aren't going to be many of them, and there is currently no way for any individual to know whether they are going to be one of the tiny percentage who'll be okay, or whether they'll be like most people and experience respiratory distress. It really does matter (quite apart from being good science), because everyone has a "smoking athletic grandpa" story. 86.164.69.239 (talk) 19:45, 14 June 2010 (UTC)

I would expect that the curve of dose against cancer risk would be steep at first but then be less steep later. For example the increase in risk from shooting eleven rather than ten bullets at someone would be less than the increase in risk from firing 1 rather than zero bullets at someone. 92.15.14.150 (talk) 20:02, 13 June 2010 (UTC)

The British Doctors Study is the classic evidence for this. The study unequivocally proved the link between smoking and lung cancer, as well as several other diseases. This article shows that "carotid artery intima-media thickness [and therefore risk of stroke] increased with pack-years in both former and current smokers". However disease risk is not linearly associated with smoking; a "never-smoker" does not have zero risk of lung cancer. Axl ¤ [Talk] 17:02, 15 June 2010 (UTC)

Side note

Above I've mentioned the risk of COPD and other lung diseases as a result of smoking. I wonder if smoking can cause a linear decrease in respiratory health, and are there any studies that show this? Regards, --—Cyclonenim | Chat  23:44, 13 June 2010 (UTC)

What do you mean by "a linear decrease in respiratory health"? Axl ¤ [Talk] 07:57, 15 June 2010 (UTC)

Sorry, it was badly worded. Can smoking a certain number of cigarettes a day for a certain number of years be linked to a certain probability of having respiratory illnesses like COPD? Regards, --—Cyclonenim | Chat  17:06, 15 June 2010 (UTC)

Yes. Have a look at the British Doctors Study, in particular the "chart showing variation in mortality with amount smoked". Axl ¤ [Talk] 17:26, 15 June 2010 (UTC)

Primary afferent axons

So according to the textbook there's a different thermal threshold for different primary afferent axons fibres. How does it actually work? I don't really understand it. -Tactile.ab (talk) 11:12, 13 June 2010 (UTC)

In the same way that you have no problem understanding how there can be a temperature threshold for any type of nerve fiber, why can't you extrapolate in your mind that different nerve fibers can have different temperature thresholds. I think that's simple enough, unless you had something more specific. DRosenbach ^{(Talk | Contribs)} 13:47, 13 June 2010 (UTC)

It's a pretty complex question. The temperature dependence of action potentials is mainly a function of changes in the kinetics of voltage-gated sodium channels, but the point at which failure occurs is determined by the way these channels interact with other factors such as axon size and myelination. The failure point is especially different between myelinated and unmyelinated axons, because of their different mechanisms of conduction. The literature on this topic gets pretty technical, but if you are interested, here and an old paper that gives some of the basic phenomenology. Looie496 (talk) 16:40, 13 June 2010 (UTC)

Thanks! The link was quite helpful. -Tactile.ab (talk) 05:27, 14 June 2010 (UTC)

Ruth's Chris Steak House

They advertise that they cook their steaks at 1800°F -- firstly, what sort of oven are they using and secondly, I would think that such a high temperature would destroy the meat. Obviously it doesn't, but if anyone can explain, that would be great. DRosenbach ^{(Talk | Contribs)} 13:45, 13 June 2010 (UTC)

Responding to the second question first, I'll ask you one of my own — if you put a roast in a 400°F oven, when do you take it out? (Hint: it's not when the entire roast is 400°F throughout, now is it?) High external temperatures mean that you get some tasty, tasty chemistry going on at the surface of the meat (giving it that delightful 'sear', with all of its flavors and textures; depending on the meat, rubs, and glazes, there's going to be some combination of Maillard reaction, caramelization, and breakdown products of myoglobin). You only want to do that for a limited time — a long, dry heat will suck all the moisture out of your cut of meat and leave you with leather. Getting the sear (and the rest of the cooking) right is going to be a balancing act between time and cooking temperature. TenOfAllTrades(talk) 14:06, 13 June 2010 (UTC)

(ec)This is the temperature of the outside of the steak (which will char) but obviously the middle will see nothing like this temp. You can get this kind of temp with a pottery kiln; presumably they just put the meat in and out of one for enough time to the centre to get to 120C or so. Not vastly different to a barbeque I would say--BozMo talk 14:09, 13 June 2010 (UTC)

I hope you meant 120°F, not 120°C — or I'm not ever coming to one of your barbecues! TenOfAllTrades(talk) 14:15, 13 June 2010 (UTC)

... and I hope you really did mean 120°C or I wouldn't eat it! Dbfirs 14:52, 13 June 2010 (UTC)

120°C is way above water's boiling point — by the time the center reached that temperature, you would have driven off virtually all of the water from the meat. The inside would be leather, and the exterior would be burnt to a crisp. The interior of a solid cut of meat should be relatively free of pathogens; presuming that it has been handled properly, the nasty stuff is generally on the outside. (That's why it's important to cook ground beef all the way through, and one of the reasons why you shouldn't go impaling your raw steak with a meat fork — and why your prime rib roast only needs to be cooked to an internal temperature of 120-130°F for a nice medium-rare.) TenOfAllTrades(talk) 16:00, 13 June 2010 (UTC)

Wikipedia says you want the interior to reach about 160-165F (71-74C). I agree that 120C would destroy your dinner. --Tango (talk) 19:23, 13 June 2010 (UTC)

Our article has some bad cooking advice, then — and its numbers are different from those in the linked source ([11], purportedly based on USDA numbers). 160°F is a good target for ground beef, which as I noted should be cooked through to a higher temperature. For a roast, pull it out of the oven at around 130°F to hit medium rare (give or take a few degrees, exact temperature recommendations will vary from one cookbook to another: [12]). Let it rest, covered, for twenty minutes or so; the internal temperature will rise another 5-10°F as the outer layers come into thermal equilibrium with the core of the roast. TenOfAllTrades(talk) 20:04, 13 June 2010 (UTC)

The numbers are consistent with those in the source. The source is more detailed, so obviously the summary in the article won't be perfect, but it's about right. --Tango (talk) 20:52, 13 June 2010 (UTC)

Yes, 120°C would make a very tough meal, but the fat should prevent it turning to leather. I'd rather eat that than risk 120°F because I don't like "rare"! I'll compromise on somewhere mid-way between the extremes. Dbfirs 20:57, 13 June 2010 (UTC)

FWIW yes I meant F not C. --BozMo talk 10:10, 14 June 2010 (UTC)

I'll go out on a limb here and suggest that even the exterior surface of the steak never really reaches 1800°F (though it certainly gets quite a bit hotter than the interior, and quite a bit too warm for comfort). If you put your hand in a hot oven, does your skin instantly reach 500°F? TenOfAllTrades(talk) 14:15, 13 June 2010 (UTC)

Cooking at 1800° would be like putting meat in a hot fire. It would even be hot enough to melt salt (almost). --Chemicalinterest (talk) 18:39, 13 June 2010 (UTC)

I hope they limit cooking time at that temp to a very short time just for a final sear, and cook the steak at a somewhat lower temp for the majority of the cooking time. Otherwise, your steak will end up black and blue (burnt on the outside, raw in the center). Googlemeister (talk) 14:50, 14 June 2010 (UTC)

Allium Care

I grew a patch of allium this spring. They bloomed beautifully and are now green. Structurally they add to the architecture of the garden, but should I remove the heads and let the rest of the greens die back, as in tulips, or can I leave the heads as well as the greens to die back? So far they are sturdy and add to the garden in their green state as much as in their purple and white.

Barb —Preceding unsigned comment added by 75.72.20.144 (talk) 14:57, 13 June 2010 (UTC)

I can only say that I would leave the whole plant until it dies down naturally, because I find allium seed heads visually atractive. Why not experiment and leave some so you can see what they look like? If you don't like them you can cut them down. --TammyMoet (talk) 17:04, 13 June 2010 (UTC)

Hi Barb, I've got to say alliums are lovely. I had a rummage round to try to find a trusty source (since I'm not at home with Mum's big collection of thorough books by D. G. Hessayon) and the closest thing I could find is this guide from the UK's Telegraph newspaper. The gist is that if you don't want them spreading, just make sure to dead-head them before the seeds disperse, but until then you're fine. If you don't mind them spreading, you don't need to do anything. This seems to be the advice on other sites I could find too. Happy gardening, Brammers (talk/c) 19:52, 13 June 2010 (UTC)

According to Sarah Raven the fact the green is up for months before the flowers means you do not have to leave them to die back, you can cut the whole things down when the flowers die as they is already enough sugar stored in the bulbs by then. Certainly the green is starting to dry by full flower. We do cut back immediately but not for enough years to be absolutely sure of the advice. --BozMo talk 20:36, 15 June 2010 (UTC)

Dog whistles.

My new phone has a free App that simulates a dog whistle - the kind that is producing a short sound at a frequency higher than humans can hear - but within the range that dogs can hear. That much I understand.

But Scott (a black lab puppy - aged 6 months) has never been trained with a dog whistle...yet he reacts instantly and looks at me with head tilted to one side whenever I activate the thing. The software lets you set the frequency to all the way down to 80Hz - and if I whistle at 'normal' frequencies - one or two kilohertz - he totally ignores it.

Our article suggests that dog whistles can be used to inflict pain - but that seems hard to imagine at the pathetic volume that a cellphone speaker can produce (especially at what must be the upper limits it was designed to produce). Also, he doesn't seem to be distressed by this - his reaction seems more like puzzlement.

Why would Scott pay special attention to these very high pitched whistles and not the lower pitched stuff? Is there something out there in nature that his wolf ancestors evolved to react to?

SteveBaker (talk) 15:21, 13 June 2010 (UTC)

It may just be that it is unusual. He hears people whistling and phones ringing and other devices bleeping all the time and has learnt to ignore those because nothing interesting is associated with them. He probably hasn't heard a dog whistle before (since you say he hasn't been trained with one) so he is wondering what it is. --Tango (talk) 15:36, 13 June 2010 (UTC)

As to the pain I made an ultrasonic whistle once and was trying it out and couldn't hear a thing, but my mother came and complained about the noise and told me to stop it. Dmcq (talk) 16:06, 13 June 2010 (UTC)

That's unusual. Ability to hear high sounds usually diminishes with age - you should be able to hear it better than your mother. Of course, with only 2 people, the sample error is very high! (See The Mosquito for some more information.) --Tango (talk) 16:14, 13 June 2010 (UTC)

Yes I was quite surprised because I could hear bats okay so it must have been a quite high frequency. Dmcq (talk) 21:11, 14 June 2010 (UTC)

I don't think the answer to this is known, but it's interesting that rats and mice are known to emit ultrasonic vocalizations as distress calls -- that seems like something a dog might care about. Dogs also use high-pitched whines as distress calls, but they don't generally reach the ultrasonic range, so the relevance is unclear. Looie496 (talk) 16:51, 13 June 2010 (UTC)

Its thought that dogs evolved the ability of hear ultrasound for one of two reasons, according to Peters & Wozencraft, 1989; in Acoustic communication by fissiped carnivores. Pp. 14-56 in J. L. Gittleman, ed. Carnivore Behavior, Ecology, and Evolution, vol. 1. :

• To detect the ultrasonic cries of prey species (such as rodents, as Looie496 notes)
• Because newborn puppies communicate with their parents by ultrasonic vocalizations

In either case, you are probably hijacking instinctive neural circuits that your dog has tuned specifically to these wavelengths - which is why you are getting a behavioural response from him that regular whistles do not evoke. Whether your app might inflict distress is a matter of opinion, of course, but it might be worth noting that research facilities are very strict about the use of ultrasound within their animals houses. Largely because it could be distressful to rodent mothers who are caring for pups. Rockpocket 17:11, 13 June 2010 (UTC)

I am curious (and skeptical) that the cell phone has either the electronics or the acoustic capability to create true "ultrasonic". Even a desktop PC usually has a 44.1 kHz sampling rate, permitting a maximum synthesis of 22.050 kHz. But that's the software sampling rate. The hardware digital to analog converter, especially on a mobile phone, may have an even reduced range. The physical transducer inside the speaker might have a frequency response as poor as 5 or 10 kHz (these things are bargain-basement cheap devices). It's plausible that if you have a high-end phone designed to play music, it might have a full audio capability up to 20 kHz - but even that isn't "ultrasonic," so how exactly is the device outputting a dog whistle tone? (I suppose if the tone is at 19 kHz, you might hear a low volume or nothing; while the dog does hear everything; but that would be a "borderline" case - many humans can and do hear 19 or 22 kHz tones). Nimur (talk) 18:03, 13 June 2010 (UTC)

Don't forget about harmonics. Ariel. (talk) 19:17, 13 June 2010 (UTC)

According to our article, dog whistles generally use frequencies in the range 16-22 KHz. Looie496 (talk) 19:23, 13 June 2010 (UTC)

Well, it works! Either I'm lying about not being able to hear it - or my dog is telepathic! The software ("Dog Whistler" 1.2 for Android by Mobeezio) claims to produce sounds from 80Hz to 21.9kHz - with a default at 16kHz. Some people can hear 16kHz - others can't (I can't) - but even 21.9kHz works for my dog - and not may people can hear that. SteveBaker (talk) 00:46, 14 June 2010 (UTC)

I guess you might be irritating some humans, too - many can hear tones up to those frequencies! The Mosquito operates at 17 kHz, and claims that most adults don't hear it - but I've played around with audio and I know I'm able to pass a double-blind test at 19 kHz and higher. Nimur (talk) 01:08, 14 June 2010 (UTC)

(EC)Actually most modern desktop PCs would support at least 48kHz (since it's used by most DVDs and many other digital video sources). And HD chips are getting rather common probably helped by things like Intel's HD Audio iniative [13] meaning even cheap motherboards will often have a HD audio chip supporting at least 96 khz and probably 192 khz. Of course there is little benefit to humans from these high frequency ranges as ABX tests usually show. However the HD audio chips may be better in general. In terms of mobile phones, the teen buzz and similar rings tones (The Mosquito#Teen Buzz ringtone) have shown that many perhaps even most mobile phones are at a minimum capable of producing frequencies high enough that many adults can't hear them. (You can get different tones and test them and some fairly high frequencies seem to work but of course it's difficult to know what frequency the phone is actually producing without some sort of accurate recording/monitoring.) And these even seem to work with MP3 and I think AAC compressed versions tend to work although these aren't generally designed to keep such high frequencies well AFAIK. Bear in mind of course we aren't talking about accurate musical reproduction just some sort of noise sufficient for a listener to hear. (I tried it myself once on my cheap Panasonic VS2 and it did work, I did try a variety of frequencies up to about 21khz but I can't remember the cut off point where someone I tested it on was able to hear something, the lowest age was about ~21 so probably not the ideal test.) Nil Einne (talk) 01:22, 14 June 2010 (UTC)

As for cell phones not having sufficient volume, bear in mind that it takes far more energy to produce loud bass notes than treble, so cell phones are designed to produce lots of treble and very little bass. If this trend continues into the ultrasonic range, then a cell phone phone could produce a deafening ultrasonic sound without using up the battery quickly, if so designed. StuRat (talk) 17:13, 14 June 2010 (UTC)

Nuclear fusion physics and tokamak reactor design: from the ground up.

Assuming that a layman with 'high-school' level scientific knowledge wished to fully understand the complex physics underlying a tokamak fusion reactor, and had years in which to do so, what would be the essential building blocks of physics necessary to begin the long journey upward? An image that springs to mind is a pyramid of square blocks, each successive level allowing advance to the next. Another assumption (possibly mistaken) is that a full physics degree would involve units and modules not relevant to the specific subject of desired study. I emphasise that this is not a question regarding nuclear fusion itself, but rather an epistemological question about the long itinerary of subjects a student would have to follow to arrive at the final goal.

149.170.241.66 (talk) 19:08, 13 June 2010 (UTC)

To understand this stuff quantitatively, you will need a thorough base in electromagnetics, chemistry, plasma physics, atomic theory, and a healthy dose of nuclear physics. To support the quantitative understanding of these scientific concepts, you will also need several years' of mathematical theory beyond "high school" level - this typically means several courses in calculus and differential equations, a good level of linear algebra, and some fourier theory or complex analysis will help with the plasmas and the atomic theory. Amazingly, this is what you will study if you obtain an undergraduate degree in physics. (About the only other stuff required for a physics degree - material that would be "peripheral" to your fusion goal - would be one or two courses in "classical mechanics" - while not directly relevant to fusion, this knowledge and the associated techniques, like Hamiltonian mechanics, are essential to understanding the more sophisticated particle interaction theories that work at quantum scales). If you want to further study fusion, you will probably continue with several graduate courses in plasmas, electromagnetics, and (finally), material specifically on nuclear fusion. If you want to build Tokamaks, it will help to throw some engineering courses in the mix: a power electronics course, a few mechanical engineering courses (specifically, learning about vacuum systems); several engineering thermodynamics courses, and so on. Nimur (talk) 19:52, 13 June 2010 (UTC)

Nimur makes an good point in that an undergraduate degree in physics is very well suited to understand the fusion reactor. It's an interesting philosophical question if the physics degree is very well suited to all kinds of such projects, or if humanity is erecting only those constructions which can be conceived of and understood with a background in today's disciplines. Another epistemological question is what it means to know and understand the reactor. A typical answear to that would be "the ability to build it", in which case it becomes clear that no single person could "understand" the whole reactor. The material science involved in creating material that can withstand the heat and radiation is no less important than understanding the math of the chaotic plasma currents, the computer science needed to simulate and control it, the physics of fusion, or even a collection of so far unknown skills and knowledge, needed to tackle challenges in the construction which we are not yet aware of. With that in mind, your pyramid would be more like a branching tree. A trunk of undergraduate mathematics at the bottom, allowing access to branches to head off into areas of physics, mathematics, IT, engineering and other sciences.

EverGreg (talk) 12:04, 14 June 2010 (UTC) armchair philosopher

I would propose that physics is designed to be the systematic and quantitative analysis of any natural phenomenon. That is why, even though physics is conventionally taught to emphasize only a few subjects like "mechanics" and "electromagnetism", many prefixes exist to extend physics to the rest of the world: biophysics, chemical physics, space physics, material physics, semiconductor physics - physics is the set of systematic, mathematical approaches that are used to distill truth from controlled experimental observation. It just so happens (for historical reasons) that when we train new students to think about the world in this quantitative way, we start by teaching them about parabolic trajectories and simple harmonic oscillators. Those scenarios are simple example cases where the spherical cow approximation works for a much greater percentage of the time, and are thus suitable for beginners. From the philosophical point of view, I firmly believe that there is no problem that is solvable by other techniques, but intractable using physics-style methods. (I've gotten into some fierce debates with the soft science people, and especially those in the humanities, but I stand by my principles and have staked my career on them). So, to reiterate: physics is systematic and quantitative: mathematics is crucial for the "quantitative" part; the systematic approach comes from a lot of training and experience working with smaller problems, and a good bit of intuition. EverGreg's points are important: it's worrisome when our educational methods peg a person's skill-set, forcing them to merely extend prior knowledge and never to synthesize new knowledge. At the same time, modern systems are so complex that they would be totally impossible to build or operate without specialization of labor. I would consider "free thinking" to be a particular case of specialization of labor. We need some "cogs" who are highly skilled and highly trained, but will never synthesize knowledge outside the disciplinary constructs that were forced on them by our educational and socioeconomic system. And, we need some "not-cogs" - people who are not bound by the constraints of the system - who will learn from our prior knowledge, but expand human pursuits to other areas. (There's a good Asimov short story about this - the title eludes me - but they have accelerated the process of education with some sort of machine, bringing young children up to the point of advanced researchers within a few days. On a few rare individuals, the machine totally breaks, and they can not learn anything from it - but these individuals, while forced to slowly and manually learn everything that their fellow students learned instantaneously, are the only people capable of inventing or designing anything). Nimur (talk) 14:37, 14 June 2010 (UTC)

Profession by Isaac Asimov, 1957. 75.41.110.200 (talk) 20:01, 14 June 2010 (UTC)

formaldehyde

is formaldehyde a endocrine disruptor or reproductive toxin —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 21:02, 13 June 2010 (UTC)

Formaldehyde isn't usually classed as a reproductive toxin, that is, is doesn't have any specific effects on the reproductive system. However it is both toxic and carcinogenic, so it could cause reproductive problems through either of those mechanisms. It's hard to give a firm answer on the question of endocrine disruption, because there isn't any agreed "test" or "standard" for an endocrine disruptor. However, it isn't the sort of compound that one would expect to be an endocrine disruptor, and I've never seen anyone suggest that this is a significant hazard for formaldehyde. Physchim62 (talk) 22:15, 13 June 2010 (UTC)

Body hair

I saw an advertisement saying that removing body hair in young people at puberty can prevent its regrowth later in life. How is this done? Why does it work? It is without the use of chemicals or lasers to kill the follicles, of course. 76.229.192.126 (talk) 20:45, 13 June 2010 (UTC)

Is this some new technology? None of the conventional methods would prevent regrowth without destroying the follicles. Our article on Hair removal mentions lots of methods and includes some warnings. Dbfirs 21:02, 13 June 2010 (UTC)

You can't prevent hair growth without destroying the follicles. They constantly produce hair, so if they're live cells then they'll continue to do so. All methods of permanent hair removal work on this principle: they destroy follicles. Regards, --—Cyclonenim | Chat  23:46, 13 June 2010 (UTC)

Rule VI of Life "Never believe anything you see, read or hear in an advertisement". Richard Avery (talk) 07:12, 14 June 2010 (UTC)

Ploughing a field with dogs

Has any culture ever used working dogs to pull a plough in a farming context (not a snow plough)? Just saw a sled being pulled by huskys on TV and I thought about this for some reason. Thanks. --95.148.105.80 (talk) 23:29, 13 June 2010 (UTC)

consider the size of horse and dog hind leg

It's really not possible. Dogs aren't big or strong enough by a lot. See the image - and the difference is muscle volume.

77.86.111.26 (talk) 23:44, 13 June 2010 (UTC)

The nearest thing is Dogcart (dog-drawn) 77.86.111.26 (talk) 23:48, 13 June 2010 (UTC)

It takes a lot more force to pull a plough through earth than to pull a sled across snow: a single human can pull a loaded sled across snow, but it takes a team of humans to pull a plough! Physchim62 (talk) 02:14, 14 June 2010 (UTC)

Dogs are not as strong as horses (or mules, or oxen) but neither are humans, which have pulled plows when stronger animals were not available, as in 19th century and earlier wartimes or periods when draft animals were not readily available [14]. Multiple dogs would be required to exert the tractive effort of a draft animal. and small carnivores may be less efficient at pulling plows than large herbivores [15]. Edison (talk) 04:46, 14 June 2010 (UTC)

....and even a whole team of horses would get nowhere with a snow plough.--Shantavira|^{feed me} 09:10, 14 June 2010 (UTC)

Why not? Cuddlyable3 (talk) 12:29, 14 June 2010 (UTC)

Have you ever tried fitting snow shoes onto a horse??!! Physchim62 (talk) 18:25, 14 June 2010 (UTC)

Unfortunately I can't include a thumbnail of this picture, and can only link to it. Looie496 (talk) 19:24, 14 June 2010 (UTC)

June 14

Synthroid versus Armor thyroid

Synthroid synthetic thyroid replacement hormone is dosed in micrograms. Natural thyroid, such as Armour thyroid, produced by Forest Pharmaceuticals, made from porcine thyroid powder, is dosed in grains. Are there published equivalencies of efficacy of Synthroid micrograms versus Armour thyroid grains? How many grains of Armour would be equivalent to 100 micrograms Synthroid? Edison (talk) 04:07, 14 June 2010 (UTC)

Since they are fundamentally different (Thyrolar/Armour containing both T3 and T4) a comparison of efficacy per dose is particularly ineffective. (edit: I found the contents of Thyrolar here and it makes sense that efforts would be made to allow Thyrolar doses to line up with Armour but again it's synthetic vs porcine so IMHO there is still some room for error.) It all depends on how the patient reacts to the artificial sources, some people are better/worse at converting T4 (in levothyroxine) into T3, and the 'effective' amounts of either vary from person to person as well. If you want to take a very casual look at it, compare the available doses of Armour (1/4 grain to 5 grain) to Synthroid (25 mcg to 300 mcg) as those designing the drugs probably have a similar target audience. *This is advice is for research purposes only and not medical in nature, see your doctor for genuine advice on prescriptions* --144.191.148.3 (talk) 13:54, 14 June 2010 (UTC)

e/c The Desiccated thyroid extract article states that "One grain (about 60 mg) of desiccated thyroid contains about 38 mcg of T4 and 9 mcg of T3". But comparison may be difficult because of the T3 component which isn't a part of the Synthroid formulation. hydnjo (talk) 14:12, 14 June 2010 (UTC)

Rifling and slower bullets

If I understand the rifling article correctly, all sides of a rifle bullet continuously scrape against the inside of the barrel, along the entire barrel length; while in a smoothbore weapon, the bullet (or ball) is smaller than the internal diameter of the barrel, and the bullet basically ricochets a few times against the inside of the barrel before it exits. I assume the hugely larger amount of friction in the rifle would slow down the bullet a lot, compared to the smoothbore; though I might see how in a smoothbore weapon, the bullet wouldn't "capture" as much force from the gases expanding from the gunpowder explosion. So, in "equivalent" rifle and smoothbore weapons, how much slower is the rifle bullet immediately upon exiting the barrel? Comet Tuttle (talk) 04:23, 14 June 2010 (UTC)

I'm not sure a rifle would be slower. If the bullet continuously scrapes against the barrel, that means that the pressure wave from the explosion propelling the bullet stays entirely behind it, propelling it more efficiently. — DanielLC 05:59, 14 June 2010 (UTC)

Our article on internal ballistics has a section on energy transfer during the transit inside the barrel. Rifle rounds engage - they actually squish/expand/melt into the bore rifling, forming a metal-to-metal seal that is extremely precise. Virtually all of the pressure-volume work is transferred to the round. (Of course friction does cause some loss to heating the barrel, but this is much smaller in magnitude compared to the energy lost if there is a gas-escape from an improper round/barrel seal. It's hard to compare, because few rifles have an equivalent smoothbore version. Even those few firearm models that could be equipped with either barrel type are not "exactly" the same between rifled and smoothbore versions - the cartridges, calibers, propellant charges, and so on are different. Even the makeup of the bullet is different, because the materials and alloys that allow a rifle round to expand and engage the grooves are useless in a smoothbore. Typically, though, rifle rounds are faster than smoothbore rounds - this may be a design consequence, and not an effect of the rifling. Because rifle rounds can be more accurate and more stable in flight, it is possible to design them to fire faster, imparting more energy and resulting in more effective terminal ballistics (stopping power, penetration, or other desired ballistic property). Nimur (talk) 06:05, 14 June 2010 (UTC)

Interesting, thank you. Comet Tuttle (talk) 20:29, 14 June 2010 (UTC)

Why did SI standardize the mole?

The SI unit of amount of substance is the mole. But there existed already an SI unit, the joule per kelvin, J/K, as the Ideal gas law relates amount of substance n to pressure p, volume V and temperature T by pV = nRT where R is a constant conversion factor, the gas constant. If n is measured in mole then nR is measured in J/K. So I wonder why the mole is standardized as an SI unit? Using the J/K as unit for amount of substance would simplify all formulas involving R. Bo Jacoby (talk) 07:20, 14 June 2010 (UTC).

The Ideal Gas Law only relates to gases though, and as most substances manipulated or calculated aren't gases, that wouldn't be all that much use. --John (talk) 07:29, 14 June 2010 (UTC)

Well, the Ideal Gas Law in its derivation actually applies to the simplest distributed system in statistical mechanics, which in the real world turns out to be warm gases where collisions are rare. Thus using that as the basis for deriving a unit is completely justifiable a priori. Note Planck Units in particular set $k_{B}=1$, which is related to what OP suggests, though it still doesn't give a value for the unitless Avogadro's Number (in physics where we need Planck Units, we just count particles individually until the very end when we convert to real-world values using Avogadro). SamuelRiv (talk) 08:29, 14 June 2010 (UTC)

This is nineteenth century physics with no reference to atomic physics. The gas constant is quoted with 6 decimal digits (even if many substances are not gases). Perhaps this accuracy is insufficient? Bo Jacoby (talk) 13:07, 14 June 2010 (UTC).

The mole makes a convenient standard in that it also allows for one to relate atomic mass units (aka Daltons) to grams, in that 1 dalton-mole = 1 gram. (or 1 gram/mole = 1 dalton) The importance of Avogadro's number is that it is basically the number of particles that will allow that conversion to occur. In a very approximate sense, one mole of nucleons (protons or neutrons) weighs one gram, which is why the mole is so useful as a measure of amount. Specifically, to standardize the mole (since protons and neutrons don't have the same mass, and the mass of a nucleus is also not exactly the total mass of the individual nucleons due to mass-energy equivilances) we use the standard that exactly 12 grams of Carbon-12 contains exactly one mole of atoms. Yes, there are other hypothetical numbers which may be somewhat useful in counting particles in other applications, but the usefulness of Avogadro's number makes it a far more ideal number if you have to pick just one for the SI system. --Jayron32 06:07, 15 June 2010 (UTC)

Thank you for the explanation. I do not find it satisfactory however. The idea behind standardization of units is to clean up the mess, such that there is only one standard unit for each kind of quantity. But there are two SI units for amount of substance: the joule per kelvin and the mole, connected by a conversion factor R. One mole equals 8.31447 J/K. An ideal gas at p pascal and T kelvin contains p/T joule per kelvin per cubic meter. There are (1/k=) 7.24296×10²² molecules in a J/K. The dalton is not an SI unit for mass, and I still do not understand why the mole redundantly has been made an SI unit for amount of substance. Each extra unit gives rise to tiresome conversion factors and blocks the understanding of the subject matter. Bo Jacoby (talk) 09:19, 15 June 2010 (UTC).

You know that R=Lk (where k is the boltzmann constant) ..

• L has clear meaning, and is directly measurable, though somwhat abitrary (12g of Carbon?)
• R appears to be an experimental constant

... clearly there's a relationship between R and k

The origins of k are somewhat hairy to say the least, but if you have already got k , then you can derive R

I think the reason is that constants need to be abitrary rather than experimental (though k is experimental as far as I know it's obtained from a broader range of experiments and is not necessarily dependeant on L); if the value of k can be 'explained' then the situation changes.87.102.18.94 (talk) 10:27, 15 June 2010 (UTC)

The whole point of SI unit is to provide for the most accurate standards of measurements using currently available technology. It turns out that in practice we cannot use many of the fundamental physics relations/identities to do accurate measurements. So, we have ended up with quite a few "redundant" units. Defining the mole to be some precise number and thus effectively removing it from the SI sysem would amount to redefining the Kilogram, but this will only be done if this makes measurements of mass more accurate.

Compare this to the redefinition of the meter in terms of the second. Einstein could have suggested getting rid of the stupid factors of c and measure distances and time intervals in the same units in 1905, but it was only in the 1980s that this was also better from an experimental point of view. Count Iblis (talk) 23:32, 15 June 2010 (UTC)

Old medical terms

Partial question copied from WP:VPP by Gwinva (talk) 08:52, 14 June 2010 (UTC)

"I recently watched the old movie "Bell, Book and Candle" with Jimmy Stewart. In that movie there is a sign outside an herb shop listing various conditions that can be treated by the herbs. These names (as used in that time) were obviously common knowledge at the time (why else would they be used on public signage?) but some of them have fallen out of common usage or been replaced by more precise terminology. I wanted to know what diseases they meant so I went to Wikipedia and found very few answers. Here are the names I did not know, of which only two were actually helpful:

• Milk Leg <-- [redirects]
• Blood Disease <-- What medical conditions did this commonly refer to back then?
• Whites <-- I found no medical use of this term.
• Spleen Trouble <-- ?
• Catarrh <-- This is still called by the same name so this was just a word I didn't know.
• Hollow heels <-- ?
• Wobbles <-- I could only find an animal disease for this name. Was there a human one?
• Thrumps <-- ?

66.102.204.25 (talk) 08:02, 14 June 2010 (UTC)

• Whites = Leucorrhea. DuncanHill (talk) 08:53, 14 June 2010 (UTC)

You might do better on the language desk. I'm pretty sure that wobbles will be a folk term for movement disorders such as Parkinson's disease.--Shantavira|^{feed me} 09:17, 14 June 2010 (UTC)

Wobbles might be an abbreviation for collywobbles. Mitch Ames (talk) 12:23, 14 June 2010 (UTC)

It's possible that they are fictional diseases meant to parody outlandish patent medicine-style claims to cure anything. Nimur (talk) 14:44, 14 June 2010 (UTC)

It's also possible they were words used in that particular district and nowhere else. In the UK, many dialects have their own words for medical conditions and parts of the body. This page gives an example from close to my home patch: Staffordshire medical dialect --TammyMoet (talk) 15:20, 14 June 2010 (UTC)

These were in a mainstream film contemporary to circa 1958 New York City. At best the terms might have been "quaint" for that era but certainly would not have been obscure to the film's audience. 66.102.204.25 (talk) 18:49, 14 June 2010 (UTC)

• Hollow heels in humans - see Pes cavus. Could it also means something horse-related? Those old west drugstores would bunch human, horse and cattle ailments together, wouldn't they? East of Borschov (talk) 19:11, 14 June 2010 (UTC)

Very doubful it is a horse issue as this was set in 1958 Greenwich Village NYC, NY. :) 66.102.204.25 (talk) 19:18, 14 June 2010 (UTC)

Doubtful indeed :)) Good catch, I had to check the film article first. East of Borschov (talk) 19:28, 14 June 2010 (UTC)

• A complicating factor for figuring out modern names for historic diseases is a tendency for multiple diseases to be lumped together under their major symptom. For example, pancreatic cancer, appendicitis, kidney stones, and ovarian torsion might all be covered by the local name for "severe abdominal pain". --Carnildo (talk) 00:49, 16 June 2010 (UTC)

Understood. As an encyclopedia however we ought to be able to provide readers with some useful information even if it is to that effect. Perhaps a dab-type article that says "The term blood disease was used in the early half of 20th century America to ambiguously refer to one of the following conditions: ...". I would suspect on these there might be various medical writeups (perhaps from medical schools?) from the era that could support these facts. 66.102.198.18 (talk) 18:41, 16 June 2010 (UTC)

"Blood disease" and "Spleen trouble" are probably holdovers from humorism (which was still active in scientific medicine into the 19th century, and in folk medicine a good bit longer), and might refer to any of an assortment of conditions (from anemia to fevers to stress in the first case, and from dyspepsia to ulcers to insomnia or irritability in the second). --Ludwigs2 19:01, 16 June 2010 (UTC)

why water form fountain as it goes up?

Answer: water follows a parabolic trajectory

Try this(if u had never tried before): while watering tour garden hold pipe in such away that its mouth is towards sky(or just perpendicular to ground). Water coming out of the pipe will make fountain, it gets spread.

Now hold pipe's mouth towards the ground, u will notice that water gets stream lined as it falls. It makes a cone like structure whose base is mouth of pipe.

The Question Is

Why does this happen? Why not water forms fountain while falling and why not it becomes streamlined while going upwards? -IIT question [--Myownid420 (talk) 09:23, 14 June 2010 (UTC)]

When you point the hose up, the water coming down falls onto the water going up and they scatter each other. This doesn't happen when you point down since the water is all going in the same direction. Staecker (talk) 11:52, 14 June 2010 (UTC)

Water should stay in Laminar flow rather than turbulent flow regardless of whether the hose is pointing up or down (unless you tweak the nozzle when it is travelling upwards). The key variable is how long it stays in laminar flow whilst travelling upwards, primarily as a result of gravity overcoming the upwards force exerted when the water leaves the hose.FramingArmageddon (talk) 12:06, 14 June 2010 (UTC)

Yes, and having two streams of water intersect each other is a sure-fire way to create turbulence, meaning water goes every which way. One stream going up and another falling back down into it matches the bill, nicely. StuRat (talk) 16:58, 14 June 2010 (UTC)

If the droplets of water in the stream did not interact with each other, each one would follow a trajectory that traces part of a parabola, as shown in the picture. Just think about what happens to droplets that start upward along slightly different parabolas, as opposed to starting downward on slightly different parabolas. The upward-oriented ones give a lot more divergence. Looie496 (talk) 19:20, 14 June 2010 (UTC)

(Interesting question!!) The previous answers are excellent - I'd just add that for a given nozzle velocity, the water takes longer to reach the ground when it's aimed upwards than downwards - so any divergent effect will be greatly increased just because the droplets have more time to spread apart. But this is just a contributory factor - I think the previous answers are 90% of the reason. SteveBaker (talk) 00:00, 15 June 2010 (UTC)

Assuming a circular cross section of the water jet, the radius $\scriptstyle r$ will increase upwards as the velocity $\scriptstyle v$ decreases. $\scriptstyle \pi r^{2}v$ is the constant rate of flow of water $\scriptstyle =\pi r_{0}^{2}v_{0}$ where $\scriptstyle r_{0}$ is the radius of the pipe and and $\scriptstyle v_{0}$ is the initial velocity of the water. So $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{v}}}.$ The velocity relates to the height above the mouth of the pipe, $\scriptstyle h$ , by the energy conservation law $\scriptstyle gh+{\frac {v^{2}}{2}}={\frac {v_{0}^{2}}{2}}$ where $\scriptstyle g$ is the gravitational acceleration. So $\scriptstyle v={\sqrt {v_{0}^{2}-2gh}}$ , and $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{\sqrt {v_{0}^{2}-2gh}}}}=r_{0}{\sqrt[{4}]{\frac {v_{0}^{2}}{v_{0}^{2}-2gh}}}.$ The denominator becomes zero, and so the radius of the water jet becomes infinite, at $\scriptstyle h_{\max }={\frac {v_{0}^{2}}{2g}}.$ This marks a breakdown of the assumption that the cross section of the water jet is circular. The water splits into drops when accelerated outwards. It has nothing to do with turbulence. See surface tension. Bo Jacoby (talk) 10:10, 15 June 2010 (UTC).

B₂O₃

how do I get [[B₂O₃]] from Borax ?--אנונימי גבר (talk) 11:26, 14 June 2010 (UTC)

React the borax with hydrochloric acid until you have a slightly acidic pH. Boil the solution of boric acid and sodium chloride produced and cool. The boric acid should precipitate. Heat the boric acid crystals strongly with a blowtorch. They will dehydrate, leaving amorphous boron trioxide. --Chemicalinterest (talk) 12:56, 14 June 2010 (UTC)

Sliver nano

How can we produce a Siliver (Ag) nanoscale fibers (fiber diameter of less than 20 times that of a human hair)--אנונימי גבר (talk) 11:36, 14 June 2010 (UTC)

The article Silver nanoparticles refers to nanoscale particles rather than fibres, along with some production methods although I'm not sure if you were specfically after fibres, rather than particles. FramingArmageddon (talk) 12:08, 14 June 2010 (UTC)

http://www.google.co.uk/search?hl=en&q=nanowire+ag&cts=1276644607250&aq=f&aqi=&aql=&oq=&gs_rfai= this search turns up a few methods. 87.102.18.94 (talk) 23:31, 15 June 2010 (UTC)

(Cr - Pt)

• You can separate chromium from chromium alloy - Platinum (Cr - Pt) How?
  

I think you should give this alloy into a powerful disinfectant, then Platium (Pt) acts as a positive, Chromium (Cr) serves as the cathode (dissolves), then separated chromium salt!

• [Currently, I do not know what the appropriate reagents for reaction!]
  

--אנונימי גבר (talk) 11:57, 14 June 2010 (UTC)

I am not wealthy so I do not have platinum. If I wanted to separate that, I would use a nonoxidizing acid such as hydrochloric acid. The chromium would dissolve, leaving the platinum behind.

I'm sorry, but a disinfectant is used to kill bacteria and viruses, not to separate metal alloys. --Chemicalinterest (talk) 13:00, 14 June 2010 (UTC)

I think he was talking about oxidants, which he somehow confused with disinfectants. John Riemann Soong (talk) 22:04, 15 June 2010 (UTC)

A good way to separate is by electrorefining. Make the alloy the positive terminal, use a dilute acid solution, chromium should be deposited at the negative terminal, with Pt separating out as a solid.

Chemical alternatives include dissolving both, and selectively precipitating one or the other from the solution. Both elemental articles give selective methods for precipitating the elemental ions from solutions.87.102.18.94 (talk) 12:49, 15 June 2010 (UTC)

Relativity

Sir, I am a Higher secondary student.i am very interested in highly advanced theories of physics sush as relativity,Black holes,Galaxies,Time,General relativity etc.I have already referred many articles on Wikipedia but the problem is that every article contains many complex terms which are very difficult for me to understand.Please suggest an article or a website that would help me understand the basic concepts. —Preceding unsigned comment added by Vishnuthelegend (talk • contribs) 11:58, 14 June 2010 (UTC) Changed layout of question. Cuddlyable3 (talk) 12:21, 14 June 2010 (UTC)

Articles on advanced physics assume that the reader know about elementary physics. You cannot really understand Einstein before you understand Newton and Maxwell. Bo Jacoby (talk) 12:56, 14 June 2010 (UTC).

Try plain old physics. --Chemicalinterest (talk) 13:02, 14 June 2010 (UTC)

Try here: http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html Ariel. (talk) 00:29, 15 June 2010 (UTC)

C L I

Is there any way one can fool Caller Line Identification on the landline or mobile phone ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

From the article you linked to: Most service providers however, allow the caller to block caller ID presentation through the vertical service code *67. --Dismas|^(talk) 13:48, 14 June 2010 (UTC)

Yeah, that's what I am asking - if the service provider does not allow such facility. Is there some software or hardware hacking type trick one can do ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

We have an article all about this: Caller ID spoofing. SteveBaker (talk) 23:54, 14 June 2010 (UTC)

I know about the article, but what I want is some practical straight forward and fool-proof easy way that one can actually do !— Preceding unsigned comment added by Jon Ascton (talk • contribs)

Is it just me or are you being deliberately confusing? In your first post you asked for a method of "fool" caller ID, so I gave you a way to block it. Then you added an additional requirement, which wasn't in your original question, about what happens if the carrier doesn't allow for *67. And you asked for some software or hardware suggestions. Those are spelled out at the article that SteveBaker pointed out to you. Now you tell us that you already read that article and, for whatever reason, those solutions still don't work for you. So, what about the options in the caller ID spoofing is it that you don't care for? Dismas|^(talk) 04:37, 15 June 2010 (UTC)

The web page below needs to be updated with the correct new information regarding the list of SVHC's.

Substance of very high concern

Please update the web page with the most current list of SVHC's. Thanks Rick Morrison —Preceding unsigned comment added by 63.97.59.73 (talk) 13:42, 14 June 2010 (UTC)

I have copied this non-question to the discussion page of said article. Caesar's Daddy (talk) 13:51, 14 June 2010 (UTC)

Noted on behalf on WP:CHEM, it's on my list of things to do in the morning. Physchim62 (talk) 23:24, 14 June 2010 (UTC)

 Done Physchim62 (talk) 09:44, 15 June 2010 (UTC)

How does pre-birth gender selection work?

I read someplace that nowadays, parents are able to choose the gender of their unborn child. How does that work? More importantly, how much does it cost? Since it's most likely too expensive in the US, in what countries could it be done for the lowest prices? --Let Us Update Wikipedia: Dusty Articles 14:19, 14 June 2010 (UTC)

Another important question is "is it legal?". In many countries, it isn't. Sex selection answers that, and how it works. You can probably find costs by googling. --Tango (talk) 14:50, 14 June 2010 (UTC)

Looks like it is legal, here is a clinic offering such a procedure in the US. Price is stated as around $18K. Link. Regards, --—Cyclonenim | Chat  17:05, 14 June 2010 (UTC)

It is legal in the US. It isn't elsewhere, eg. most of Europe, China, India, etc.. --Tango (talk) 23:19, 14 June 2010 (UTC)

There are two different things to discuss here: There are many (fairly cheap) techniques that can bias the probability of you getting a male or a female child - simple things like subtle pH variations at the moment of conception can change the statistics. But to absolutely guarantee a male or a female child is more likely to require serious medical intervention - which is much more ethically difficult (eg you might test the sex of the fetus and abort when the gender is not what you want - that is practiced (often illegally) in several places in the world) - or perhaps much more costly (eg in-vitro fertilization). SteveBaker (talk) 23:48, 14 June 2010 (UTC)

So what other countries is it legal in, where anyone would perform it for a far lower price than in the US? --Let Us Update Wikipedia: Dusty Articles 11:32, 15 June 2010 (UTC)

Birdsong Study

In one of Roger Penrose's lectures (video here: http://www.youtube.com/watch?v=f477FnTe1M0 , part in question at 1:12), Penrose talks about some studies done on birdsongs. The studies supposedly had humans give an aesthetic rating the songs of male birds that were then followed in order to determine their reproductive success, and whether it had any statistical correlation with the humans' ratings.

Does anyone know this study (or these studies)? I'd appreciate a citation or journal link! Inasilentway (talk) 14:34, 14 June 2010 (UTC)

Some good links (including studies) on this Google search. Not sure if it's helpful, but it's a start. Regards, --—Cyclonenim | Chat  17:02, 14 June 2010 (UTC)

How hot am I ?

I've noticed that I can't accurately judge if I'm hot or not. I certainly can tell if objects are hot, and if the air is hot, and if my forehead is hotter than my hand, but the only method I have to tell if I am overheating is if I'm covered in sweat. (The sweating means that my body is able to tell that it's hot, even if I can't.) This system doesn't work when in a hot tub, and the first sign I have that I'm getting hot is that I become listless and find it hard to breath enough air. So, am I unusual or does everybody lack an ability to judge their own temperature accurately ? StuRat (talk) 17:27, 14 June 2010 (UTC)

You're normal (well, as normal as a Wikipedian can be! ;)). Thermoception is relative. All it can do is tell you if something in contact with your skin is hotter than your skin or colder than it (and how much so). You can compare your symptoms in a hot tub with Hyperthermia#Signs and symptoms. An added complication is that the symptoms of hyperthermia are quite different to the symptoms of fever, despite both involving your body temperature being above normal (the cause is very different). --Tango (talk) 17:46, 14 June 2010 (UTC)

Funnily when I was working in West Africa and contracted Plasmodium falciparum Malaria the first inkling (and immediate self diagnosis) was turning off the aircon and switching on the heating in a car parked in full sun with an outside temp of 37C. I found myself wondering why I had never switched the heating knob in the car before and then it sunk in. With a core temperature steaming upwards the car seemed cold and I was shivering. --BozMo talk 18:09, 14 June 2010 (UTC)

A simple answer is that your sweat is cooling you down so you don't feel hot. If you feel hot that means your cooling mechanism (sweating) is malfunctioning or overpowered. --Chemicalinterest (talk) 18:28, 14 June 2010 (UTC)

Sweat doesn't work in a hot tub. Obviously sweat on those parts of your body that are underwater can't evaporate, and sweat on the rest of your body won't evaporate much because the air around you will be very humid. --Tango (talk) 19:07, 14 June 2010 (UTC)

There are medical issues that inhibit the brain's ability to sense if the body is hot or cold. As this is a medical issue, I will not make any attempt to diagnose this problem. However, I feel that it is important to point out that this (and pretty much any "Am I normal" question) is asking for a diagnosis of normality. -- kainaw™ 19:14, 14 June 2010 (UTC)

Medical issues aside - mostly the reason we can't tell whether we're hot or cold is because body temperature is well regulated. You can feel whether you are gaining or losing heat to the environment (which is how you know whether the air is hot or cold) - but it's likely that your core temperature is close to whatever is normal for you in all but fairly extreme circumstances. When the environment overpowers your thermoregulation system, you're already in some distress - and you feel the symptoms of that. Your hot tub experience is obviously a case like that. SteveBaker (talk) 23:42, 14 June 2010 (UTC)

Reminds me of a Dilbert in which the boss wakes up and, to his surprise, finds that his underwear, coffee mug and desk are all clammy -- finally, Dilbert suggests that maybe his hands are clammy. I forgot the rest. DRosenbach ^{(Talk | Contribs)} 12:00, 15 June 2010 (UTC)

Sweathog

Thanks. To follow up, if I can't tell when I'm getting hot, how does my body know when to sweat ? StuRat (talk) 15:24, 16 June 2010 (UTC)

Explosion

In a powerful explosion, how long is there between when the explosive detonates and you die? --76.77.139.243 (talk) 19:20, 14 June 2010 (UTC)

At the risk of stating the bleedin' obvious, it depends on the relative positions of the explosive and your body. Even a low power explosive could kill you instantly depeif it goes off on your head or chest. --TammyMoet (talk) 19:29, 14 June 2010 (UTC)

It depends on the time the ₎)) shock wave takes to hit you. Once it hits, then you die. --Chemicalinterest (talk) 19:45, 14 June 2010 (UTC)

People have been blown to a red mist and tiny bits by an explosion. Death is in milliseconds. At the other extreme, someone might be fatally injured by an explosion but linger for any long period before succumbing to the effects, which might include, for instance,sever and ultimately fatal burns, being in a persistant vegitative state, or paralysis leading to fatal complications a long time after. Edison (talk) 20:13, 14 June 2010 (UTC)

As Chemicalinterest says, it depends how far away you are. My grandparents all survived the nuclear bombings of Hiroshima and Nagasaki quite easily, because they were in the eastern USA when it happened. Nyttend (talk) 05:51, 15 June 2010 (UTC)

Shock wave in air travels at several hundred meters per second (more than a speed of sound but less than a thermodynamic limit, which for an ideal gas is 4 times the speed of sound). Fragments from the explosion may travel faster than the shock wave and further than the shock wave. Divide the distance (in meters) from you to the explosion by roughly 1000 m/s, and you will get the order-of-magnitude time (in seconds) before you get hit. (Order of magnitude means that the estimate may well be wrong by a factor of 2 or 3 either way). How long you stay alive after getting hit depends on the nature of your injuries, as Edison explained above. Massive brain injury may be considered instant; anything else may take a few seconds or a few years to take effect. --Dr Dima (talk) 20:33, 14 June 2010 (UTC)

My father survived a direct impact of a bomb in World War 2 - it hit his house. Dad himself had taken shelter under the stairs. He died 64 years later. So this is a bit of an unanswerable question.--TammyMoet (talk) 09:42, 15 June 2010 (UTC)

That must have been a spectacularly slow bomb! – ClockworkSoul 02:51, 16 June 2010 (UTC)

soy

are the estrogen's in soy; fat or water soluble ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 23:02, 14 June 2010 (UTC)

Well, [16] says: "Phytoestrogens are estrogens contained in plants. They have a chemical structure similar to the human hormone estrogen. They have a weak estrogen effect when eaten. The most commonly studied are the isoflavones...". Our articles on Phytoestrogens and isoflavones have much additional information...but I couldn't see any direct statement about solubility. I guess we'll have to wait for one of our expert chemists to swing by with an answer. SteveBaker (talk) 23:34, 14 June 2010 (UTC)

Natural estrogens are fat-soluble, as are pretty much all natural steroids. Physchim62 (talk) 00:18, 15 June 2010 (UTC)

so does soybean oil contain estrogen's ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:42, 15 June 2010 (UTC)

Definition of Horology???

I was looking at the Horology article and found it to be inconsistent, horology is defined as "the art or science of measuring time.", but then only talk about mechanical clocks and watches. To me this seams rather much like an article on transportation only discussing different kinds of bags, no ships, trains,trucks and so on.

Is horology only the study of historical/mechanical watches and clocks or does it include modern electronic clocks, GPS-clock synchronization, atomic clocks, astronomical observations of for example radio pulsars and so on??? Gr8xoz (talk) 23:10, 14 June 2010 (UTC)

Wiktionary (and several other dictionaries that I looked at) says: Horology: The art, science and technology of timekeeping and timekeepers, such as clocks, watches and sundials. - which certainly includes modern stuff like digital clocks. However, I would bet good money that almost all actual, practicing horologists are really only interested in mechanical clocks and sundials. The people who care about modern electronic/atomic timekeeping are in the fields of electronics and physics. That being the case, I think our article does a reasonable job of covering the practical nature of horology. Remember - the article isn't about clocks themselves. It's about the nature of the study of clocks. I agree though that we could at least mention more modern timepieces - IF we can find some reference to that kind of thing in a horology journal or whatever. At any rate, this discussion should really be held on the Talk:Horology page, not here on the reference desk - but I see you've already added a comment there with no response. I think you should go to Wikipedia_talk:WikiProject_Time. Of course if you feel strongly about this - you can always fix the article yourself...but I strongly encourage you to provide references for any statements you include. SteveBaker (talk) 23:24, 14 June 2010 (UTC)

The modern and precise measurement of time (eg, "atomic clocks") is usually seen as a subbranch of metrology, because it affects and depends on many other areas of physics. The one exception might be the network of observatories which keeps UTC in time with the Earth's (slightly irregular) rotation, but I would bet that they consider themselves astronomers and not horologists: horologists are people who can actually make a working clock or watch, and deserve every respect for that skill! Physchim62 (talk) 00:27, 15 June 2010 (UTC)

Again, I agree that's what practicing horologists actually do - but that's not what the word means. Also, your interpretation would include people who fabricate atomic clocks, digital watches or crystal oscillators for computers - which is not what people who'd describe themselves as horologists actually do - nor is "horology" what people who make such things describe what they are doing. What we have here is a disconnect between what dictionaries say the word means - and it's actual modern day usage. This is not an uncommon problem because dictionaries tend to lag decades behind changes in usage. SteveBaker (talk) 11:43, 15 June 2010 (UTC)

June 15

Help resolve date discrepancy of an event by finding contemporaneous citation(s)

Regarding the article Rüppell's Vulture -

This bird is considered to be the world's highest flying based on examination of feathers found in a jet engine that collided with a bird over Abidjan, Cote d'Ivoire at an altitude of 11,000m on November 29, 1973 -OR- the same date in 1975.

The source cited in article (Flight Migration by Alerstam) states 1973, however a web search finds other reliable sources quote that the event happened in 1975, an example being [[17]]. A google search doesn't particularly favor one year over the other - both dates show up frequently in a search.

To resolve the discrepancy I have tried to find an article published in 1973, 1974, 1975 or 1976 that references this event so I can establish the correct year.

I have searched the online archives at flightglobal.com and newyorktimes.com looking for any articles published from 1973 to 1976 that include the word "vulture" or "cote d'ivoire" and did not find any articles that reference the event.

I have not been able to turn up any references to the particulars of the aircraft involved (military? civilian? private? commercial? airline? flight number?...) but have assumed that the following is probably accurate:

• The aircraft was jet powered
• Event happened on November 29th
• Event happened in 1973 -or- 1975
• Event happened over Abidjan, Cote d'Ivoire
• Event happened at or around 11,000m (36,100 ft) or 37,000 ft altitude

I do not have easy access to printed archives of potentially relevant scientific journals, nor do I even know which journals would be relevant. I am not associated with a university/company that might give me "free" access to online versions of scientific journals via an organizational subscription.

If you can turn up a relevant, authoritative citation that is contemporaneous to the event, please either cite it here so I can update the article or edit the article adding the exact date and citation. Obviously if we find something published in 73 or 74 the 1975 date can't be correct, plus I'm hoping that any article contemporaneous to the event will simply state the date it happened, resolving the discrepancy without question.

I'm also willing to do more work myself, but I need the ornithology and/or aviation and/or reference experts to give me some ideas on where to look next.

Thanks. Ch Th Jo (talk) 00:48, 15 June 2010 (UTC)

(I edited this to provide more information.)

Usually Google Scholar gives better results for things like this than Google Web. I was able pretty quickly to find that the original source everybody cites is Collision between a vulture and an aircraft at an altitude of 37,000 feet, R. C. Laybourne, The Wilson Bulletin, Wilson Ornithological Society, 1974. Looie496 (talk) 03:20, 15 June 2010 (UTC)

Thanks, that's perfect. Before now I wasn't aware of Google Scholar, so thanks for that as well. Ch Th Jo (talk) 18:25, 15 June 2010 (UTC)

laxatives

Hi All. First, let me be clear that this is in no way a medical question! I was reading a trivia book and there was a story about an inmate wo used large amounts of laxatives to get skinny enough to squeeze (barey) through the bars and escape (he was caught later). My question is: what are the health risks of using large dosages of laxatives in order to "slim down?" 99.250.117.26 (talk) 01:42, 15 June 2010 (UTC)

This certianly sounds like a medical question... See the article Laxatives#Problems_with_use. The more pressing question is that how the inmate obtained large amouts of laxatives needed, and how he got through the bars which go both up and down and left to right ;) 01:47, 15 June 2010 (UTC) —Preceding unsigned comment added by 76.229.161.119 (talk)

side effects would be extreme dehydration, electrolyte imbalance, cramping... Fragrantforever —Preceding unsigned comment added by Fragrantforever (talk • contribs) 05:42, 15 June 2010 (UTC)

At the risk of stating the bleedin' obvious, we have a diarrhea article. Vimescarrot (talk) 06:02, 15 June 2010 (UTC)

Anorexia and Bulimia might have some info you'd find relevant. 63.17.59.215 (talk) 11:29, 15 June 2010 (UTC)

I'd be surprised that they'd put the bars far enough apart to allow your head to get through - and no amount of laxatives are going to shrink the size of your skull. The problem with trivia books is that they have a lot of incentive to include amazing "facts" and almost zero incentive to check that they are actually true - they are the biggest purveyors of untruth outside of the Internet! If it actually happened that way - there ought to be more sources backing it up. SteveBaker (talk) 11:53, 15 June 2010 (UTC)

Oddly enough this is reported by what might be classed as reliable sources; Google for /robert cole laxative/ for example and you'll see mentions in The Guardian and New Statesman. Of course, maybe these are just passing on trivia, but this appears to be a reliable secondary source. Tonywalton ^Talk 12:09, 15 June 2010 (UTC)

Digital Camera

If one wants to buy a digital camera, how much mega-pixel is ideal ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

If you just want to view images on your computer, 2 or 3 megapixels is fine. If you want to generate large images for printing or reproduction in magazines, then you need as high as possible. ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

The chances are that any camera currently on the market will have more pixels than you need. See The Megapixel Myth (compare megahertz myth). There are a lot of other features that differentiate point-and-shoot cameras. For example, some do better in low-light conditions than others; some have better flash illumination; some have optical viewfinders while others don't; some let you control the exposure time and aperture, while others don't; some can take wider angle photos than others; some have tiltable LCD screens; some have better lenses, and some just plain take better looking pictures. Sites like dpreview.com can help you compare picture quality and features of different models. -- BenRG (talk) 05:17, 15 June 2010 (UTC)

Agree with the others, megapixels are largely irrelevant over 8-10MP unless you're wanting to make large scale prints of your photographs (I'm talking exhibition-size prints). Most cameras on the market offer this amount of megapixels because it sounds impressive even if you just want to do some photos at a friend's wedding. There are many other factors that are more important, especially with single lens reflex (SLR) cameras, most importantly of which are the speed of the lenses/apertures, ISO, noise reduction etc. Regards, --—Cyclonenim | Chat  10:01, 15 June 2010 (UTC)

I'll second the above, except I'll suggest that the "largely irrelevant" threshold is even lower. 5-6 MP, on a camera with a good lens, is more than sufficient for general use. I've blown up pictures from my 6 MP camera to 30"x20" with excellent results. If you're not going to print stuff larger than 8"x10", you can go even lower -- 3-4 MP would be fine. And as Cyclonenim noted, at this point, every new camera with a decent lens will be at this point or higher. You might want to check various consumer magazines; I'd expect that Consumer Reports (among others) has done several digital camera evaluations. — Lomn 13:10, 15 June 2010 (UTC)

You want to leave some room for people to crop and use the so called "Digital zoom". APL (talk) 14:21, 15 June 2010 (UTC)

However, CCD chips come in limited sizes. Within a given class of cameras, more pixels usually means smaller pixels, which means more thermal noise. So you may get a higher nominal resolution, but more details will be lost in the noise, and the image will look washed-out. 5 megapixels used to be the sweet spot when I looked a while back. --Stephan Schulz (talk) 14:58, 15 June 2010 (UTC)

Nobody has mentioned battery life! This is one of the the most differentiating parameters left between otherwise "equivalent" performance cameras. If this factor is important, consider the negative impact of a larger sensor, LCD screen, and more powerful processor that often go along with "high-end" cameras. This is a parameter which can vary widely between different vendors. Nimur (talk) 14:58, 15 June 2010 (UTC)

Nanostructure induced flavorings

Reading the taste and taste bud articles didn't really help answer something I've been wondering about for a long time:

Is it possible for a surface to have a microstructure (nanostructure?) at the molecular level that interacts with and stimulates taste receptors? Chemically, I guess it would be like a catalyst, that doesn't actually react with anything but instead aids in a reaction.

Such a surface would have a permanent flavor, wouldn't it? Is it feasible? ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

Not really. As our article on taste buds points out, taste is generated by flavour components which are dissolved in saliva, so your nanostructured surface wouldn't get to the receptors it needs to, even if it were capable of stimulating those receptors (which isn't certain itself). In addition, much of our experience of flavour comes not from the taste buds but from smell receptors in the back of the nose – flavour is a combination of taste and smell, which is why food tastes bland when you have a cold. Obviously your surface would be volatile, and so could stimulate the smell receptors. Physchim62 (talk) 10:01, 15 June 2010 (UTC)

Moreover, taste receptors are not really on the tongue surface as much as they are on the surfaces of the taste buds, and that would even more specifically be on the lateral walls of the very small projections you may be able to see on your tongue. It would be pretty difficult to get a surface to match up with these receptors to produce the taste you'd be looking for. And Physchim62's mention of olfactory involvement is right on -- so little of "taste" is actually taste. But assuming you'd be going for a purely sweet taste (incorporating no odor, let's say), You'd have to get your nanostructure to act as ligands to the taste receptors. That's like asking for an inert nanosurface to be able to excite a muscle by reacting with the acetylcholine receptors of the neuromuscular junction -- highly unlikely. You's be able to do it with a liquid medium, and I actually do this every morning. I call it Snapple :) DRosenbach ^{(Talk | Contribs)} 12:27, 15 June 2010 (UTC)

OK, thanks. I'm not convinced of two things: (1) that the components need to be dissolved in saliva, as I can taste things that don't seem to be soluble (certain oils, nonpolar solvents, etc.) - I guess it's sufficient to be liquid; (2) that a sense of smell is needed, unless I have olfactory receptors in my mouth (my nose really doesn't work for smelling). As DRosenbach pointed out, some sweet substances have no odor.

I think what I'm really curious about is whether there are any solid substances that would have a permanent flavor without actually dissolving. Nanostructure was one possibility I thought of, but there may be a way to stimulate taste receptors chemically without actually modifying the phase of the stimulant. ~Amatulić (talk) 21:29, 15 June 2010 (UTC)

Blackberry Vs I Phone

We are big fans of the I Phone and we have been using the I Phone since its launch with very satisfying results. Initially we had the 2G 16 gb version which still works like a dream and we also have a 3G and the latest 3GS model. The I Phone 4 hasnt launched here and Im sure it would be part of our family soon.

My husband and I were talking to a friend yesterday over coffee and he was raving about his Blackberry and he said the blackberry can do several things the I Phone cant even imagine:)))

I didnt retort but I thought let me ask this question to my friends here on Wikiepedia who have a scientific bend of mind.

This question is not about personal likes and dislikes. I want to scientifically compare these two phones. When I googled it, the search results only speak about the virtues of one or the other. I would like a feature by feature comparison or a point by point comparison.

My Question is : I Phone Vs the Blackberry - what are your thoughts, ease of operation, aesthetic looks, functions, pricing - what are the plus points and negetives of these phones.

Pls feel free to give your feedback. Fragrantforever 05:39, 15 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

For a 'scientific' comparison of the phones, the best thing to do would be to try to find the manual or description of features on the appropriate manufacturers' websites. As for opinions on aesthetic looks, pricing etc, these things are probably better sought on an internet forum (either a couple of neutral ones, or one that seems pro-iPhone and one that seems pro-Blackberry to play them off against each other) rather than a reference desk. Bear in mind that the iPhone 4 was announced only a few days ago so a lot of old comparison articles are out of date. Brammers (talk/c) 08:18, 15 June 2010 (UTC)

In Japan it's apparently very common for people to pick a phone based on features - they compare a checklist and whichever one has more wins - even if they never use those features. It results in phones packed with everything, and yet totally unusable. See this article about it. So it's impossible to compare a phone that way. Compare a phone based on what YOU will use it for. Now obviously there could be features that you would like but are not aware are possible. But just straight comparing features will give you information - but not useful information. Ariel. (talk) 09:04, 15 June 2010 (UTC)

Broadly it depends what you're wanting to do with it, I've not seen any scientific comparisons, but a number in sites like Lifehacker and Really Mobile do user comparisons. As the iPhone is increasingly being seen as an enterprise business phone it's being competed against the Blackberry but the majority of comparisons that I've seen don't include Blackberry as it's a very different device.

It's worth looking at the heritage, the Blackberry grew from a need to have a handheld email device and it's developed from that basis. The iPhone is designed first and foremost as a handheld computer.

I would suggest that you need to do your own comparison from the available information, run Blackberry, iPhone, Android and WebOS against one another.

Of course Ease of Use and aesthetics are both qualitative not quantitative so not particularly scientific measures.

By way of providing a baseline my company has recently made a decision about a new phone deployment for all of our consultants. We compared Blackberry, WebOS, Android and iPhone, opting for the iPhone as the most appropriate for our needs given the cost options that were on the table from our supplier. Blackberry is quite an old fashioned device in comparison to the other three.

ALR (talk) 10:38, 16 June 2010 (UTC)

My wife has an iPhone. She loves it, but doesn't like the fact that she can't use YouTube or most other video sites because they use Flash video, which Steve Jobs is allergic to. According to our article, the Blackberry has had Flash capability since Nov, 2009, so that would seem to be a huge plus for anyone who likes watching streaming videos. Matt Deres (talk) 16:18, 16 June 2010 (UTC)

meringue food technology

Unsatisfied with meringue bases bought from a local store (and the squirty cream can) and wishing to emulate the excellent meringue from a village store further down the road (even the big stores don't seem to make them) I stirred two egg whites, a bit of sodium bicarbonate,cornflour and masses of castor and granulated sugar until it became semi-solid, and then put it in my fan oven for two and a half hours at 100 C. The result was like a bland lump of concrete, and I don't know where the sweet flavour of all that sugar went. Do the good meringues use microwave cooking, or is there some other secret? —Preceding unsigned comment added by 80.1.88.16 (talk) 08:52, 15 June 2010 (UTC)

Castor as in Castor oil? Why would you put that in? Also, I wouldn't put in any sodium bicarbonate, add a little cream of tartar and give it some extra whipping time for fluffiness. But in general I would start with a known working recipe, then experiment from there. Ariel. (talk) 08:59, 15 June 2010 (UTC)

The OP undoubtably means castor sugar (also spelled caster), a very fine-grained suger used in cooking, and mentioned somewhere in the Sucrose article. 87.81.230.195 (talk) 09:13, 15 June 2010 (UTC)

There are three different types of meringue, according to this site: BBC Food: Meringues. You need to ascertain from the village store which type of meringue they make and follow the correct recipe. Cooking desserts is much more chemistry than cooking savoury food is, and if you don't follow meringue recipes then you will inevitably fail. I think the problem you had originally had was to do with failing to whisk the egg whites before adding anything else, but really you need to follow the recipe. --TammyMoet (talk) 09:35, 15 June 2010 (UTC)

Shirley Corriher list four types in Cookwise: soft, hard, Swiss, and Italian. Soft meringue, as used in lemon meringue pie, use about 2 tablespoons sugar per egg white, with sugar added gradually. Hard meringues, as used in hard meringue candies, use about ¼ cup sugar per egg white. Swiss meringue is very stiff and used for decorations/icing, and is made by beating sugar and eggs over boiling water. Italian meringue is used in puddings, and is made by drizzling a "hard-ball stage" (248F/120C) sugar syrup into well beaten egg whites. Corriher adds cornstarch to soft meringues, but omits it for hard meringues (indicating that the cornstarch keeps them from being "light"). I've never heard anyone advocate adding basic ingredients (like sodium bicarbonate), it's always slightly acidic, like cream of tartar or using a copper bowl. The acid stabilizes the foam. By adding base you may have overbeaten the whites before they set, causing them to be tough. For soft meringue, you want to beat just until the "soft peak" stage (where peaks form when you pull the beaters out of the foam, but where the the tops curl over under their own weight). For hard meringues, you beat a little further, until the "hard peak" stage (glossy peaks form, but don't curl over). Note that you don't need bicarb for leavening - the bubbles in meringue come from the whipping process, not from carbon dioxide generation. -- 174.24.195.56 (talk) 14:56, 15 June 2010 (UTC)

Make that five types - four from Shirley Corriher and the industrial meringue from the OP. Richard Avery (talk) 17:55, 15 June 2010 (UTC)

Instability of Manganese(III) fluoride

Why is manganese(III) fluoride so unstable? Manganese(III) oxide is much more stable, even though oxide is more easily oxidized than fluoride. --Chemicalinterest (talk) 11:40, 15 June 2010 (UTC)

It's not unstable (the article was misleading when it said that it will release F₂ on heating). It may well hydrolyse in moist air, but then so will most metal fluorides – that's why you must store them in polythene bottles instead of glass bottles – and hydrolysis is not what we usually mean by "unstable".

2MnF₃ + 3H₂O → Mn₂O₃ + 6HF

So, to anticipate your next question: "why do they hydrolyse?" Because the oxides are even more stable, and hydrogen fluoride is a pretty low energy molecule as well. And why are the oxides even more stable? Well the quick answer is because their lattice energy is higher. If you take the approximation of a pure ionic bond (not a very good approximation for the transition metals, but for the sake of illustration), then Coulomb's Law says that the strength of the bond is proportional to the product of the two opposing charges: so an Mn³⁺–O²⁻ ionic bond is (roughly) twice as strong as an Mn³⁺–F⁻ ionic bond. There are several other factors that come into it as well, but I'll leave you with this for starters! Physchim62 (talk) 12:03, 15 June 2010 (UTC)

Fluorides normally react with glass to form hexafluorosilicates. I thought that it spontaneously released F₂ gas, which is what I had a hard time believing. --Chemicalinterest (talk) 12:23, 15 June 2010 (UTC)

The release of F₂ is incorrect, at least at normal temperatures (all halides will decompose if you heat them strongly enough, but we're talking about thousands of degrees for most of them). As for fluorides reacting with glass to form hexafluorosilicates, the reaction is very slow in the absence of moisture: but, as you usually have a bit of moisture around when you're using these things, it is much better to store them in polythene bottles than to have a glass bottle shatter as you pick it up off the shelf! Physchim62 (talk) 12:30, 15 June 2010 (UTC)

Can you check the temp? [18] says decomposes at 600C - there's a difference between decomposes liberating F2, and melts (or boils) whilst retaining the same stoichiometry - I think the original statement may be roughly correct.87.102.18.94 (talk) 13:04, 15 June 2010 (UTC)

Also many flourides do not decompose at temperatures below that which will produce atomic fluroine - eg MnF2 - I think the difference is between 'eventually decomposes to elements' and 'decomposes with formation of a more stable flouride'87.102.18.94 (talk) 13:06, 15 June 2010 (UTC)

(it is unstable - but we need the Temp.) See also [19] and http://www.1911encyclopedia.org/Manganese - "manganic flouride".87.102.18.94 (talk) 13:11, 15 June 2010 (UTC)

Fair enough. I was going on Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1224. ISBN 978-0-08-022057-4., which says it is "thermally stable". Physchim62 (talk) 13:39, 15 June 2010 (UTC)

It's good to at least 300C :) —Preceding unsigned comment added by 87.102.18.94 (talk) 19:30, 15 June 2010 (UTC)

They might be talking about the hydrate, (one link was) though I still think decomposition to CoF2 is likely.87.102.18.94 (talk) 17:31, 15 June 2010 (UTC)

Decomposition to MnF₂ is more plausible! ;-) Physchim62 (talk) 19:33, 15 June 2010 (UTC)

Bats, birds and convergent evolution

I remember reading once about theory of convergent evolution, and as an example, the text offered that it was much more parsimonious to speculate that insects, birds and bats (which are very different organisms) each evolved flight independently than to suggest that they had a much more recent common ancestor that evolved flight once and then split into these three lineages afterward. So I was wondering just how different bats and birds are and I came up with the following list. If anyone can add constructively to my pondering, that'd be great.

1. Bats are mammals in every sense of the word and birds are not. Perhaps this is the most glaring imparsimoneousness of the suggestion that a recent common ancestor of bats and birds produced bats that then converged perfectly with a previously existing mammal line.
2. Another likely glaring imparsimoneousness of the aforementioned speculation relates to the evolutionary timeline, with which I am altogether unfamiliar. I sort of got stuck at the Reptiliomorpha article because it seems that there's lots of bird/reptile talk but not a lot of bird mammal talk about convergence/divergence.
3. For me, it seems very difficult to discuss any physiologic/anatomic differences because I don't know how to give the proper weight to the evolutionary significance of any particular convergence/divergence, as I'm merely a freelance zoologist and not an evolutionary biologist. Mammals converged with birds with Protheria in terms of cloaca and egg-laying, so who's to say that any of the various traits we all know that separate birds from bats (beaks, etc.) count for that many parsimony points in the tally I'm trying to make?

DRosenbach ^{(Talk | Contribs)} 12:19, 15 June 2010 (UTC)

The "traditional" argument (from the days before routine DNA sequencing) comes from the structure of the skull, in particular the temporal fenestrae (openings in the side of the skull). All birds (and most modern reptiles) are diapsid, that is they have two temporal fenestrae on either side of the skull; all mammals (including bats and Protheria) are synapsid, that is they have a single temporal fenestra on each side of the skull. The appearance of temporal fenestrae dates to a bit more than 300 million years ago, long before there were any creatures that could be described as mammals or birds, and has been preserved through later fossils, so it's thought that the temporal fenestrae are a marker for evolutionary divergence. Physchim62 (talk) 12:56, 15 June 2010 (UTC)

Very helpful -- thanx! DRosenbach ^{(Talk | Contribs)} 15:41, 15 June 2010 (UTC)

If I personally were writing a textbook, I would not frame this issue in terms of parsimony -- parsimony is a useful criterion mainly when the evidence is relatively sparse. In this case we know enough to actually tell the story of how things happened -- we know for example that protostomes and deuterostomes (the superphyla containing insects and vertebrates respectively) diverged over 500 million years ago, when complex life existed only in the sea, and that synapsids and diapsids diverged over 300 million years ago, when no vertebrate could fly and even walking was pretty crude. Looie496 (talk) 16:10, 15 June 2010 (UTC)

Looie -- I think you're making my point without even realizing it. The reason why we can state "we know what happened" even though no one was there is because it makes sooooooo much sense to state proposition A and so little sense to state proposition B. Proposition A would be that synapsids and diapsids split and then much much much later, each developed their own flying organisms, while proposition B would be that the split occurred between flying and nonflying and that convergent evolution brought some initial divergents back to what appears to have been a continuous line of protostome heritage. Granted it sounds a bit odd to anyone who has even a somewhat realistic perspective of evolutionary biology, but I'd say that I meet less than 1 new person a day who would have such a grasp. On the contrary, I find that once explained, the parsimony argument will essentially state the same thing but be more palatable to the untrained mind. Thanks for your additions to the response -- it served to concretize my understanding of this matter. DRosenbach ^{(Talk | Contribs)} 20:45, 15 June 2010 (UTC)

The problem with any theory of extreme convergent evolution in which so very many attributes of mammals, birds and insects would have had to be converged - is that the flight mechanisms of birds, bats and mammals are dramatically different. If they came from common ancestors, why don't insects and bats have feathers? Why do birds use modified fore-arms to form the structure of their wings - where bats are using modified fingers and insects are using yet some other modified structure (the 'notum'). Their flight mechanisms are so spectacularly different, it's really inconceivable that these flight mechanisms evolved from some common ancestor. It's not reasonably to say that flight is a "convergent feature" of birds, bats and insects because the underlying mechanisms are not remotely similar. So there are NO features that birds, bats and insects share that are closer to each other than they are to other animals in their class. A bat's wing is much more similar to (say) a mouse's fore-feet than it is to a bird's wing. The flight muscles of an insect are not remotely related to the flight muscles that a bird use. This hypothesis is so far from being possible - it's utterly untenable. SteveBaker (talk) 22:39, 15 June 2010 (UTC)

This just keeps getting better -- Thanks Steve. DRosenbach ^{(Talk | Contribs)} 02:07, 16 June 2010 (UTC)

It doesn't address your question directly, but it's important to note that relationship markers are specifically chosen that would not generally be influenced by natural selection. Besides fenestrae, one of the favourite markers used are the foramina of the skull. While they're obviously required for blood vessels and/or nerves, their exact number and placement won't usually be exposed to evolutionary pressure. For example, if the supraorbital artery was to come of from the middle of the frontal bone instead of the supraorbital notch, it's not likely that it would exert much pressure in terms of differing levels of offspring survival. Our article doesn't mention it, but I believe the relationship between Nanotyrannus and T. rex, for example, was determined using one or more of the facial nerve foramina. The point being, of course, is that the last thing you want to use is something that will directly affect genetic survival; if you wanted to determine whether your boots and coat were made by the same manufacturer, you wouldn't try to examine the materials (those would be made to "suit the environment"), you'd check the label, which wouldn't be under that pressure. Matt Deres (talk) 16:40, 16 June 2010 (UTC)

question about the supernova

do stars makes a small explodes/core collapses before they explode as a supernovae or novae? do the information in this link means that? and if this is right, how much of time between every explode and the other? do this happen with a certain types of the supernovae? and do information in this section of the supernova article talking about the same thing? (quote: "This process repeats several times; each time the core collapses, and the collapse is halted by the ignition of a further process involving more massive nuclei and higher temperatures and pressures.") --Abbad Dira (talk) 12:34, 15 June 2010 (UTC).

For the first, it's important to note that novae and supernovae are two completely different processes that just happen to have unfortunately similar names (because, from Earth, they appear superficially similar). The APOD link refers to novae, and our article notes that "astronomers theorize... that most, if not all, novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years" (a citation is provided). So yes, they have an ongoing pattern of explosions, which probably vary in size to some extent or another.

For supernovae, what you've quoted refers to internal fusion processes, which are unrelated to externally falling matter as discussed at the nova reference. Those collapses are the result of the star exhausting its supply of fusible material at current core temperatures and pressures. When fusion ceases, the forces counterbalancing gravity cease and the core begins to collapse. That collapse leads to ever higher temperatures and pressures, until conditions are such that a heavier element becomes fusible and a new temporary balance is restored, up until a nickel-iron core forms, which leads to the supernova. The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions (see Eta Carinae for one current example), but there are no small-scale supernovae before the actual supernova. — Lomn 13:04, 15 June 2010 (UTC)

thank you very much. quote:

"The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions"

can this flares makes a notable changes in the star magnitude? and thank you again --Abbad Dira (talk) 07:35, 16 June 2010 (UTC).

Beer nutritious

Is it appropriate to call beer "nutritious" as we do in our Ale article? In what sense is "Small beer" "highly nutritious"? The Hero of This Nation (talk) 13:51, 15 June 2010 (UTC)

Lots of calories, if you consider that nutrition. --Chemicalinterest (talk) 14:36, 15 June 2010 (UTC)

If you consider Real ale, then the yeast will provide plenty of B vitamins. In years gone by, when water was in short supply if not downright poisonous, then beer would be a very useful source of nutrition, not to mention hydration. Small beer, being the drink of the poor, would have provided a large chunk of their daily nutritional requirements. Some countries classify beer as "liquid bread" (I believe that's the case in Belgium, where their licensing laws allow beer to be sold as a food), which makes sense because the ingredients are essentially the same. And of course, if you drink beers such as wheat beers, which are neither filtered nor allowed to drop clear, you're getting plenty of nutrients from the suspended sediment. --TammyMoet (talk) 14:42, 15 June 2010 (UTC)

Beer only provides some B vitamins. Chronic alcoholics go mental because their liquid diet lacks one of the B vitamins in particular, I forget which. Other consumables provide far better nutrition - for example an apple or apple juice. So beer cannot be said to be "nutritious" enough to warrant calling it so. 92.15.28.6 (talk) 23:13, 15 June 2010 (UTC)

You're thinking of pellagra, generally caused by a niacin (vitamin B₃) deficiency. Alcoholics with pellagra have typically gone so far as to have abandoned food all together. It makes sense that they would probably also prefer distilled liquors to the far more nutritious beer. – ClockworkSoul 02:44, 16 June 2010 (UTC)

It is also lacking B12 for example, and probably others. If you ranked all commonly available drinkable items according to how "nutritious" or healthy they are, then I expect beer would come towards the bottom of the list. Calling it "nutritious" is a weasel word that is meant to label it as healthy, when it is not. 92.28.251.43 (talk) 11:30, 16 June 2010 (UTC)

The context the word "nutritious" is used is small beer in medieval Europe. Small beer is thick and unfiltered. It would probably wind up near the top of your nutrition list of commonly available medieval beverages. APL (talk) 14:32, 16 June 2010 (UTC)

Especially if the rest of the list is whole milk, wine, and "the water everyone's been shitting in". :-) Matt Deres (talk) 16:44, 16 June 2010 (UTC)

Quite! And also bear in mind that describing something as "nutritious" or even "highly nutritious" is very far from saying that it supplies all nutritional needs and that one could live on it with no other dietary input. Incidentally, "small beer" was so called because it had the lowest alcoholic content of the various 'grades' (usually three) available. 87.81.230.195 (talk) 17:36, 16 June 2010 (UTC)

Transplanted lungs

This link from Yahoo! news describes a 28 year old British cystic fibrosis patient who received a lung transplant from a deceased smoker. The British government official overseeing transplant stated that a transplant isn't a guarantee of a "brand new" organ but that smokers' lungs can function normally. If anyone out there is a doctor or nurse, researcher, student, etc. experienced with the respiratory system, how plausible are that official's comments? A "brand new" organ is not admittedly neither necessary or possible in the case of human transplants, but as a general remark, would medical science approve of transplanting a smoker's lungs? Or only if they were a really light smoker? Is a matter of degree (spectrum) or of kind?--达伟 (talk) 14:00, 15 June 2010 (UTC)

The problem as I understand is that so few lungs area available for transplant that such 'sub-optimal' organs are being used. The main issue appears to be that the recipient was not informed. Mikenorton (talk) 14:10, 15 June 2010 (UTC)

[20] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail. :[21] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail.

These [22] [23] [24] discuss some of the problems relating to sub-optimal organs. They also mention that the criteria are changing anyway. However I would note it's not clear whether the lungs in question were considered sub-optimal under the criteria. Presuming the donor was a light smoker say half a pack a day for 30 years then the donor may not have meet the 20 pack-years if I understood it correctly and the lung functions may have been considered sufficient. Of course those are from Australia anyway and over 10 years old.

From the refs, I gather one of the problems is that transplant authorities don't like recepients cherry-picking organs (and I can understand this). While they may support informed consent, the consent needs to be given before hand so you can't list the donor's lifestyle and potential risk factors afterhand and ask them only to find they reject the organ and then it potentially goes to waste if you can't find another recepient in time. And I would guess filling out a 50 question yes or no on all the potential risks for a profile beforehand on what they're willing to accept is way too complicated particularly given the fact you really want to patient to actually understand the risks and not just think 'well that sounds bad' so you'll need to explain to them (and even I think we've established before most people are bad at evaluating risks).

Ultimately as with many things medical, it's a delicate balancing act between too much information which will just confuse the patient and lead to what many would consider poor decision making and ensuring informed consent.

When it comes to a smokers lungs the cancer risk (similar to the e.g. HIV and Hepatitis C risks one of the refs mentioned) from a smokers lungs particularly given the immuno-suppresants that would have to be used is an obvious concern.

Nil Einne (talk) 15:24, 15 June 2010 (UTC) Nil Einne (talk) 15:24, 15 June 2010 (UTC)

On the other hand, you have to weigh up the benefits to the patient. If I had the choice of five miserable years of life with a terminal illness against ten better years of life then being killed by my transplanted organ, I know which option I'd choose! [the time-scales are only for illustration, BTW: we don't know the prognoses of this patient] Physchim62 (talk) 15:43, 15 June 2010 (UTC)

Well yes. Although I think that's obvious, otherwise the issue of sub-optimal organs wouldn't even come in to it. In this particular case, the patient doesn't seem to be happy with what happened so I presume that at least meant they weren't likely to die in a few weeks. And I presume it also meants they weren't expected to die within a few years even with a highly successful transplant with excellent lungs. But perhaps I'm presuming too much. In terms of choice it doesn't seem to have come in to it here which is the primary reason why it hit the news. But as illustrated in the refs and also in my summary paragraph (which I albeit added after your message although I didn't get an EC) this isn't that surprising and doesn't mean there was any wrongdoing. On a personal note from the very limited information available I do feel if I were in the women's circumstances I would be glad I got something but as I said there's very little information. In any case, the patient must believe they would have survived long enough to get a 'better' (by which I mean in their opinion) set of lungs. Nil Einne (talk) 15:52, 15 June 2010 (UTC)

This article gives a nice overview. In particular, "The major concern for using donors with a history of cigarette smoking is the potential for poor lung function due to the obstructive pulmonary disease and the risk of transplanting an undetected primary or metastatic cancer or for developing a malignancy in the donor lung in the years after the transplant.... There are, however, no studies that directly address how much cigarette smoke exposure a donor may have before the lungs are not safe to use for transplantation. A donor history of smoking should therefore not prevent the use of donor lungs for transplantation." Axl ¤ [Talk] 17:44, 15 June 2010 (UTC)

The official's comment: "lungs from a smoker can be working perfectly normally" certainly is plausible. The key word is "can". Axl ¤ [Talk] 17:46, 15 June 2010 (UTC)

The main thing from smoking actually is cardiovascular disease, because of what nicotine does to the endocrine system. A lot of heart attacks coincide with being a smoker... which is probably half the reason for being out of breath. John Riemann Soong (talk) 15:46, 16 June 2010 (UTC)

clump of matter

Why isn't the universe one big clump of matter surrounded by space? 71.100.13.202 (talk) 14:51, 15 June 2010 (UTC)

Because all the way back at the Big Bang, the inflationary epoch laid down the seeds of structure formation via fluctuations. We observe later evidence of this in the cosmic microwave background radiation, the anisotropies of which are explained by the Big Bang model. Or, in short, because explosions are messy, uneven things. That's a very rough approximation, but it's a fair one. Later on, dark energy and the acceleration of the expansion of the universe play a role, too. — Lomn 15:17, 15 June 2010 (UTC)

For the first real proof of this, see COBE mission. Regards, --—Cyclonenim | Chat  17:15, 15 June 2010 (UTC)

It is a very profound question, OP (you should be a scientist), and while the generally-accepted theory for the singular universe (which indeed was a big clump of matter/energy) is inflation, at this point it still like saying "it is because it is". It's a great answer for "how", but not "why". While I have no problem accepting some "philosophically tidy" explanations for the cause of the Big Bang (such as chaotic inflation), there are many layers of complexity lying beneath, and if the history of science teaches us anything, a revolution in thinking occurs when that complexity is realized to indicate something even more simple. So indeed, why isn't the universe one big clump of matter? SamuelRiv (talk) 18:50, 15 June 2010 (UTC)

I assume that by "...be a scientist..." you mean obtain a degree in science and pursue science as a career. While that is great for people who want to live in a groove it is not so good for people who want unfettered comprehension; i.e., people who can not see the forest for the trees. 71.100.13.202 (talk) 23:29, 15 June 2010 (UTC)

Anthropic principle. Why isn't always the right question.-RunningOnBrains^(talk) 20:36, 15 June 2010 (UTC)

Sorry OP71.100, I should have said "become a scientist". I assumed (perhaps unjustly) you were a wide-eyed high-school student. And as I am in physics, I am possibly the "grooviest" if I take your meaning correctly - but those are the types of questions and philosophical concerns we do have to ask ourselves, even when dealing with everyday matter.

For example, right now we are working on a stable state that appears for a large number of moving things, ie a crowd of people walking across a bridge. This new stable state was discovered mathematically two years ago, but we don't have any record of it existing because nobody thought to look for it. The question of the "forest" now is whether or not it appears everywhere simply because it should, according to our results - were we so satisfied with our understanding of stable systems ten years ago that we ignored this state, even if it appeared, as some external complexity? These questions are important. SamuelRiv (talk) 01:24, 16 June 2010 (UTC)

Definition of "Earth's surface" for purposes of defining meteorites

If a meteor falls in a big city, lands on the top of a skyscraper, and somehow survives in one piece, is it considered a meteorite? The intro to Meteorite says: "A meteorite is a natural object originating in outer space that survives impact with the Earth's surface". Do definitions generally require it to land on dirt or in water, or does anything attached to dirt or water qualify? Nyttend (talk) 15:18, 15 June 2010 (UTC)

Yes. If it landed on a skyscraper, and the skyscraper is on the surface of the Earth, then it landed on (planet) Earth. (The word Earth here does not mean soil.)--Shantavira|^{feed me} 15:58, 15 June 2010 (UTC)

I think it means it's no longer whizzing through the air. So if you caught it in mid air it counts too, as long as you slowed it down. Ariel. (talk) 19:08, 15 June 2010 (UTC)

The distinction is between objects that burn up in the atmosphere and objects that don't. Even if you float yourself in a big old blimp and manage to catch one with a kevlar oven mitt, it's still a meteorite because it didn't burn up.

You might want to coat your kevlar with asbestos, because that will be one hot rock! Googlemeister (talk) 20:00, 15 June 2010 (UTC)

Not necessarily. The linked article says in part:

"Meteorites are sometimes reported to be warm to the touch when they land, but they are never hot. Reports, however, vary greatly, with some meteorites being reported as "burning hot to the touch" upon landing,[11][12] and others forming a frost upon their surface."

Most of the light visible from a falling meteor actually come from shocked and heated air. Only the outermost layer of the meteoroid itself gets heated up much, and this is then cooled both by heat exchange with the bulk of its interior (which is at outer-space temperature) and with the airflow as it drops after having slowed to terminal velocity. 87.81.230.195 (talk) 21:19, 15 June 2010 (UTC)

Am I misunderstanding something or is the quote sentence completely illogical and should be fixed? It seems like it's saying that "Meteorites are never hot, but sometimes they are burning hot". APL (talk) 14:41, 16 June 2010 (UTC)

I understood it to imply that some reports of meteorites being burning hot immediately after landing have been made, but were erroneous and based on a false assumption. However, of the three references cited in connection with this passage one is ambiguous, since it reports a meteorite being found in a hole made by a simultaneous lighting strike, one reports a small meteorite being hot to the touch within a minute of landing, and one reports a large meteorite being frost-coated. It makes some sense that the temperature might be size related. I agree that the passage needs some correction. 87.81.230.195 (talk) 17:31, 16 June 2010 (UTC)

Memory

Resolved

I asked this question before but didn't really get the type of answer I was hoping for, probably because I wasn't specific in my wording, so here goes again. What are some scientifically proven ways (techniques, foods, chemicals, etc) that improve memory? 82.43.90.93 (talk) 15:21, 15 June 2010 (UTC)

At the risk of sounding extremely stupid, have you considered revision? This is the most widely used technique to improve your recollection of a certain topic by simply repeating your study of it. If you're referring to a direct, automatic increase in memory, then I recommend reading the article on nootropics, but it's not well sourced. Regards, --—Cyclonenim | Chat  17:12, 15 June 2010 (UTC)

Have you not actually read the replies to your question on the Miscellaneous desk? --TammyMoet (talk) 17:19, 15 June 2010 (UTC)

I have read them, and as I said in my question here they aren't what I wanted. I realize my question on the Miscellaneousdesk was vague, so I've reworded my question and asked again on the science desk, hoping for a response that deals with scientifically proven methods, perhaps even with references.... 82.43.90.93 (talk) 17:52, 15 June 2010 (UTC)

He forgot. Axl ¤ [Talk] 17:48, 15 June 2010 (UTC)

Cross your fingers and say a prayer, while rubbing your lucky rabbit's foot. PMID 20511389 Rockpocket 17:59, 15 June 2010 (UTC)

There are no known methods that make memory substantially better in a general way across all situations. Stimulants such as amphetamine and caffeine improve memory while they are active, but the effects don't outlast the drug. Gaining knowledge about a domain improves memory for things in that domain, for example expert chess players have good memory for chess positions. And there are tricks such as the Method of Loci that can help in memorizing lists of arbitrary items. But there is no known treatment that makes memory "stronger" in a general way. Looie496 (talk) 18:04, 15 June 2010 (UTC)

Thank you for the informative answer :) 82.43.90.93 (talk) 18:08, 15 June 2010 (UTC)

Maybe these things will help: environmental enrichment, social stimulation, lack of social isolation [25], [26], [27]. Physical exercise, curcumin, and loads of other stuff in the nootropics article. --Mark PEA (talk) 18:16, 15 June 2010 (UTC)

So you haven't actually taken any notice of what I said, which was a practical method to improve your memory - that of writing things down and saying them out loud? It's a teaching method I have both experienced as a learner and used as a teacher. It works, otherwise I wouldn't have given it you. --TammyMoet (talk) 20:19, 15 June 2010 (UTC)

That is rote learning. What if the OP is trying to improve their memory skills so that if they were to witness a crime, they would give a reliable account of the events (as it's well documented how poor eye witness testimony is). You can't witness a crime and then ask the criminal to wait there whilst you write down what they are wearing, and say it out loud etc. --Mark PEA (talk) 21:10, 15 June 2010 (UTC)

To be honest, I don't think anyone in that situation will remember accurately everything they saw. The BBC did some research, which they aired recently, on just how unreliable witness testimony is. When I've been in those situations, I've stopped as soon as I can and wrote down what I can remember of the key points. This is an explanation of why eyewitness testimony is unreliable. http://www.open2.net/eyewitness/johanna_motzkau_witness_memory.html And another one: http://www.bbcfocusmagazine.com/feature/psychology/far-i-can-remember --TammyMoet (talk) 17:32, 16 June 2010 (UTC)

matter versus spirit

Why is matter even necessary? why isn't everything just spirit? 71.100.13.202 (talk) 15:24, 15 June 2010 (UTC)

Who says it's "necessary"? But this is way off into philosophy, and not a referenceable science question. — Lomn 15:33, 15 June 2010 (UTC)

Because every physical building block in our frame of reference is made of matter. If you figure out how to exist without being tied to matter, then it could become a debatable point. Until then, as Lomn said, it's just a matter of philosophy and maybe spirituality.

Without matter, where does 'spirit' come from? Your personality is entirely based upon matter, whether or not we understand it. Without this matter (the brain), you don't have thought or spirit. Regards, --—Cyclonenim | Chat  17:13, 15 June 2010 (UTC)

"Spirit" can be known as matter that is not understood by man. --Chemicalinterest (talk) 17:23, 15 June 2010 (UTC)

I've never heard it used in that sense, just as something that refers to our thoughts and personalities in a non-physical sense. It seems fairly evident, to scientists at least, that any/all of our thoughts are mere atomic interactions that are not understood. Regards, --—Cyclonenim | Chat  17:47, 15 June 2010 (UTC)

Even if you start with an assumption that the world is pure spirit, you find that it is governed by a number of regularities. Traced to the most fundamental level, these regularities show up as the laws of physics, such as conservation of energy, conservation of momentum, the Heisenberg Uncertainty Principle, and the principle of relativity, among others. The concept of matter can be viewed as a surrogate for these consistent regularities in our experience. Looie496 (talk) 17:33, 15 June 2010 (UTC)

Or... we can take the converse of that above and assert instead that because at the fundamental level it seems everything is described beautifully by largely a priori mathematical constructs, then no matter how we slice it the world is Rational, comprehensible, and perhaps even simply spiritual (entirely of the mind)? And wouldn't you know it, we even have an article! Definitely worth reading about and thinking about (even though I personally agree with what Looie summarized above). SamuelRiv (talk) 18:57, 15 June 2010 (UTC)

Basically: I think, therefore I am. Regards, --—Cyclonenim | Chat  20:38, 15 June 2010 (UTC)

Regards what? 71.100.13.202 (talk) 23:15, 15 June 2010 (UTC)

"Regards" is a formal way of ending a statement or later. It's like "yours sincerely" but slightly less formal. Regards, --—Cyclonenim | Chat  11:07, 16 June 2010 (UTC)

"Microrefineries" in the Gulf states

What would make impossible the idea of setting up small-sized refineries in which boats take in loads of crude instead of fish and get it into some kind of commercially usable format (if making gasoline is, as I already suspect, out of the question) they could make money off of? 20.137.18.50 (talk) 16:00, 15 June 2010 (UTC)

It's certainly not impossible, but rather a question of whether it's economical (or legal). Without doing research, I'd guess mostly the former: economy of scale is important to the oil industry. — Lomn 16:10, 15 June 2010 (UTC)

Keep in mind that the quantity (and concentration) of oil that is ecologically harmful is much smaller than the quantity (and concentration) of oil that is economical/profitable to collect. Otherwise, BP would be out there scooping up "every last drop" of spilled oil and selling it. Nimur (talk) 04:49, 16 June 2010 (UTC)

Carbon-based life more plentiful if system richer in Carbon?

"HD 108874 b is a gas giant announced in 2003. The orbit lies in the star's habitable zone. It is expected that any moons orbiting this planet are enriched in carbon, and are thus quite different than the silicate-rich bodies in our Solar System."

• Is a planet or planet-moon in system richer in Carbon likely to have more plentiful Carbon-based life than the average rock?? 24.78.167.139 (talk) 17:39, 15 June 2010 (UTC)

Leaving aside the fact we have no evidence of life anywhere except Earth? It's fairly obvious that if you have more carbon, you have a greater chance of carbon-based life than places where there are less carbon. At least it is to me. Regards, --—Cyclonenim | Chat  17:50, 15 June 2010 (UTC)

Well, it's obvious that you need a certain amount of carbon to support carbon-based life, but once you have that amount of carbon it isn't obvious whether more carbon would make life more likely. There is a theory that, if the conditions are suitable, life is essentially certain to arise (the main evidence for that is that life arose on Earth almost as soon as conditions were vaguely suitable, although it remained single-celled for several billion years, if memory serves). If it is certain, then the probability can't increase. --Tango (talk) 18:03, 15 June 2010 (UTC)

Sounds like a ton of observer bias in that theory, and with a sample size of about 1. Googlemeister (talk) 18:15, 15 June 2010 (UTC)

Yep. It's the best we can do, though. --Tango (talk) 20:22, 15 June 2010 (UTC)

Yes to all of the above, but we can make some assertions based on absolute chemistry. One thing that seems essential to current life is the rich variety of stable polymer compounds formed by carbon-chain-type molecules, something which does not occur to such a degree with atoms that bond preferentially on less than 4 points (so no nitrogen- or oxygen-based life on Earth). The second thing worth noting is that carbon, nitrogen, and oxygen are the first heavy elements formed in bulk in stellar fusion, at least for small-medium stars - so we don't have lithium or boron in high quantities at all, even though boron at least might form an excellent basis for polymer chemistry (??? I'm not a chemist - help me out here ???).

The alternative often given in sci-fi is silicon-based life, mostly because silicon forms in high quantities (most abundant heavy element in the Earth's crust) and bonds almost identically to carbon (right below it on the periodic table, so kinda like a heavy carbon: C++ ). However, that heaviness might be precisely what makes it a less-suitable candidate for forming life, as with weight comes decreasing electronegativity, so decreasing bond strength. I think those (again, not a chemist) are the fundamental assertions that we can make absolutely without having an example of life outside Earth. SamuelRiv (talk) 19:07, 15 June 2010 (UTC)

The issue is that silicon doesn't form pi bonds very well... it's less electronegative than hydrogen, the most abundant element in the universe. Thus Si-H bonds are considerably more activated (electron density on the outside) than C-H bonds (electron density near the middle part of the molecule). An important part of biochemistry is the ability for carbon to be both electron-donating or electron-withdrawing at the right moments, leading to rich aldol chemistry .... we don't see this with silicon. John Riemann Soong (talk) 19:23, 15 June 2010 (UTC)

Boron has a valency of 3 so, for the reasons you give, it isn't a good basis for polymers. It tends to form crystals with itself, rather than chains. --Tango (talk) 20:31, 15 June 2010 (UTC)

I wuv you guys! SamuelRiv (talk) 01:27, 16 June 2010 (UTC)

I look at the origin of life as a chemical reaction (or series of chemical reactions). In this case, more carbon would only increase the likelihood of the given reaction if carbon is the limiting reagent. If not, then more won't help, and could even hurt, if it displaces other reagents which are needed. StuRat (talk) 05:05, 16 June 2010 (UTC)

The last comment reads (If I may paraphrase) that excess Carbon can stifle the evolution of life because a certain amount of other elements need to be free. Have I got that correct? Awesome point by the way. So I coin the phrase "Diamond Desert Planet." 24.78.167.139 (talk) 05:59, 16 June 2010 (UTC)

well, keep in mind that carbon only makes up maybe 15%-20% of an organism (for humans it's 18%). The primary component, of course, is water, and the nature of a cell is to enclose a balanced environment which maintains a liquid solution of chemicals properly balanced for organic chemical reactions. Excess carbon (like other excess chemicals) is simply expelled from the cell to maintain that balance, so an environment with a great surplus of carbon materials might in fact be poisonous unless that carbon is bound up in non-water-soluble materials. --Ludwigs2 06:24, 16 June 2010 (UTC)

And to take this a bit further, I would expect that having all of the necessary ingredients for life in the same ratio as they are found in life is most likely to produce life. Thus, around 15-20% carbon would be ideal. Additional carbon might help if it displaces other elements not needed for life, but would be detrimental if it displaces other elements which are needed and in short supply on that planet. StuRat (talk) 15:15, 16 June 2010 (UTC)

Hummingbird feeders

I found a couple of interesting discussions in the archives, but nothing with regards to what I'd like to ask: Do hummingbird feeders need those plastic yellow flower parts? I ask because I have a feeder and it's hanging outside, but the plastic yellow flowers went missing (who knows what drove someone into removing them in the first place) and I'm hoping the birds can still figure out where the energy source is. – Kerαunoςcopia^◁_galaxies 18:10, 15 June 2010 (UTC)

No, at least not after the humming birds know where the feeders are. You may not attract the birds as quickly without the fake flowers or red die, but once they know where to find the nectar they don't need the visual cues. --Ludwigs2 19:25, 15 June 2010 (UTC)

You're right, they found the feeder and they couldn't care less about the flowers. The red dye is marketing BS though. The feeder is bright red, and that's obviously all they needed; I refuse to poison wildlife with the same additives we put in our own food to make our cheese look like cheese and bread look like wheat bread. It's sick. But anyway, feeder working fine, I was just curious. – Kerαunoςcopia^◁_galaxies 22:01, 15 June 2010 (UTC)

Probably a safe idea not to use it - there are plenty of allergies and side-effects that have occurred in humans due to food dyes (consider yellow #13). Since it's even harder to monitor the eggs and, umm, hyperactivity of hummingbird chicks, I'd think the sugar-plus-distilled-(tap)-water combo is safest. Good for you, OP. SamuelRiv (talk) 01:33, 16 June 2010 (UTC)

A hyperactive hummingbird sounds like it might flap so fast it's wings would fly off. :-) StuRat (talk) 04:57, 16 June 2010 (UTC)

Thanks SamuelRiv. I'll also caution against using distilled water, which could cause electrolyte imbalances. source: [28]. – Kerαunoςcopia^◁_galaxies 06:22, 16 June 2010 (UTC)

I wonder, is that something specific to hummingbirds, or is that just a retelling of the oft-repeated legend that distilled water will cause electrolyte imbalances in humans.

Of course, humans don't drink five times their body weight in bottled water... APL (talk) 14:14, 16 June 2010 (UTC)

why doesn't centrifugation do some major damage to live cells?

The protocol I'm using to culture live HeLa cells calls for separation of the cells to be cultured from the old culture media via centrifuge ... I think at around 5000 rpm for 8 minutes. I can understand using this technique when trying to extract DNA -- we don't care about cells down the line, but live cells that are still metabolising, probably even still replicating DNA or even dividing? And HeLa cells (being cancer cells) are even all the more susceptible to metabolic or DNA damage.

Also why the emphasis on separating the cells from almost all traces of the previous buffer? Is it to prevent bacterial contamination? I mean, the cells seemed to be doing fine in the previous buffer -- or is it to induce the 'fresh serum effect'? John Riemann Soong (talk) 20:41, 15 June 2010 (UTC)

I don't know the answer to the first part of your question but I suspect it has to do with the fact that water behaves as a more viscous fluid at small scales, so that the flow of solution around cells and organelles as they move will be laminar and probably slow, thereby minimising potentially damaging shear forces. However that is just a guess. Also the fact that the cells will be almost neutrally buoyant will mean that the compressive forces on the cells will be much lower than would be expected intuitively, potentially preventing "crushing injuries" (again just an educated guess). For the second part: are you trypsinizing your cells before transfer (to detach them from the old flask), if so the trypsin needs to be removed or you will probably select for trypsin resistant cells, making future passage difficult. If you are culturing your HeLa in suspension rather than as attached cells this protocol from sigma-aldrich [29] says that centrifugation is only necessary if the previous medium has become acidic (i.e. yellow for phenol red indicator medium). I guess that this is because you need to reduce the amount of old medium added to the the new culture in this case to ensure the new culture starts at the correct pH. Some old medium is still added back in this protocol to ensure the correct growth factors are present etc. (unlikely to be an issue for HeLa cells). So my thoughts would be: for attached culture centrifugation is necessary to remove trypsin, for suspension culture centrifugation is probably not necessary but does no harm. I would say that the chance of removing bacterial contatamination by centrifugation is tiny (you could never remove all of the contaminated supernatent) and the extra handling steps probably slightly increase the risk of contamination if anything. Equisetum (talk | email | contributions) 21:38, 15 June 2010 (UTC)

OK, so you're sticking them on 5000 rpm, and it takes them eight minutes to make their way down to the end of the centrifuge tube; you're worried about the shear force... what's the shear force you put them under during the half-a-second that you squirt them out the end of a pipette then? ;-) Physchim62 (talk) 23:14, 15 June 2010 (UTC)

I may not have been very clear (actually, on reading it back I wasn't very clear ;)) but that is exactly my point - they take eight minutes because (I think) of the viscosity of the water surrounding them as well as their buoyancy, therefore shear force is not a problem. As you quite rightly point out the forces on cells will likely be much greater when pipetting than when centrifuging. Equisetum (talk | email | contributions) 23:27, 15 June 2010 (UTC)

A bit of back-of-the-envelope tells me that for any reasonably-sized benchtop centrifuge, 5000rpm will be equivalent to an rcf of about 1000-4000g, depending on rotor diameter. (And we're probably closer to the low end of that.) That sounds like a lot, until you realize that buoyancy is going to nullify a lot of that difference. The specific gravity of nucleated mammalian cells is generally on the order of 1.03 to 1.04, while the specific gravity of cell culture medium is somewhere north of 1.01 (mostly water, but topped up with salts and glucose, plus some other goodies.) That means that your cell spinning at 1000g is actually only experiencing a net force equivalent to 20-30g in air. While 20g is a lot for a human being, on the scale of a cell it's pretty negligible.

That said, unless there's a special reason why you're trying to get squeeze out all the old medium and get a really tightly packed pellet, 1000+g for a full eight minutes seems a bit excessive. I mean, 30 seconds at 300-500g is sufficient to pull down HeLa cells in a 15mL tube (unless you're using an oddly-high-density medium); I did it yesterday. TenOfAllTrades(talk) 15:06, 16 June 2010 (UTC)

Just a follow up question from the first respondent: Why exactly is 20-30g negligible on the scale of a cell? I know that it is, and it makes intuitive sense but I can't remember the precise physical reason why and that bugs me. I know that the force would be smaller according to F=ma, so force scales with mass/volume, so I guess the answer lies with what strength/resistance to deformation scales with?? Equisetum (talk | email | contributions) 20:46, 16 June 2010 (UTC)

Isolating elemental silicon

How can I isolate elemental silicon from quartz (SiO₂) without any expensive equipment? --75.25.103.109 (talk) 21:55, 15 June 2010 (UTC)

Try an aluminothermic process; react finely powdered aluminum with finely powdered silicon dioxide and ignite with a magnesium strip. PS: I think there might be something about the high melting point of silicon dioxide that would stop the reaction. --Chemicalinterest (talk) 22:10, 15 June 2010 (UTC)

You mean a 'silicon thermite' reaction - see here http://amazingrust.com/experiments/how_to/thermite.html#SiO2 or thermite

With access to an open fire (either coal, or coke, or a blacksmiths forge) mix powdered carbon (coke will do) with sand in a ceramic pot, and heat to about 2000C .. see Silicon#Production 87.102.18.94 (talk) 22:19, 15 June 2010 (UTC)

Open fires are generally not hot enough. That is why an electric arc furnace is normally used. --Chemicalinterest (talk) 10:59, 16 June 2010 (UTC)

If you use the reaction for its heat, then it is a thermite; but if you use the reaction in the extraction of metals, it is an aluminothermic reaction. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

Yes, it's a bit like a thermite reaction, so only do it on a small scale! Magnesium powder works better than aluminium powder in my experience. No need to ignite, just heat strongly in a covered crucible. Physchim62 (talk) 23:01, 15 June 2010 (UTC)

But how do you plan to separate the silicon from the oxides formed? Graeme Bartlett (talk) 01:58, 16 June 2010 (UTC)

Which reaction? - the silicon would be expected to be produced molten and sink to the bottom... but Alumina can be dissolved in NaOH.Sf5xeplus (talk) 02:36, 16 June 2010 (UTC)

That's one reason why magnesium is better than aluminium. With an excess of magnesium powder, you can simply dissolve the magnesium oxide (and excess magnesium) in dilute hydrochloric acid to leave elemental silicon. Not very pure silicon, mind, but enough to say that you've done it. Physchim62 (talk) 02:03, 16 June 2010 (UTC)

You can dissolve Al₂O₃ and Al powder in HCl too, just as well as Mg. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

reducing agents milder than NaBH4

AFAIK NaBH4 is still a little overkill... and a little pricey for some reactions with strong redox potentials. Redox-wise, are there any milder reagents that will reduce:

• chloramines into amines
• Ag(III) to Ag(0)
• peroxyethers (ROOR') into alcohols (ROH + R'OH or maybe an ether + alcohol)

Is it possible to couple the oxidation of formaldehyde to formic acid to actually reduce another aldehyde to an alcohol? (actually I'll cover this below). John Riemann Soong (talk) 22:15, 15 June 2010 (UTC)

ok I'll bite a bit:

• NaBH₄ is nearly dirt cheap at £30 for 100g, and down to 1/3 of that at kg quanties, plus the low 'molecular' weight of ~37g/mol they're practically giving it away..

Anyway - something cheaper:

• Hydrogen reduction - H₂ is cheap, but the catalysts can be expensive. Not everyone wants to work with hydrogen gas.
• Electrochemical reduction = particularily electrode generated H_{surface atom} is a nice way if you can get it to work. very cheap and safe.
  • For Ag(III) direct electrochemical reduction.
• Other cheap methods - all I can think of is acid + Zn or Fe or Sn ... (also Fe(II) and Sn(II) reductions) - you might have to do original research to see if it works. There's too many possibilities here for me to search all of them.
• For the chloramine possibly Mg reduction.87.102.18.94 (talk) 22:39, 15 June 2010 (UTC)

A rusty iron nail will do all of those reductions at negligeable cost: I can't guarantee the isolated yield after work-up, mind... Physchim62 (talk) 22:55, 15 June 2010 (UTC)

Why do you need it rusty? --Chemicalinterest (talk) 11:02, 16 June 2010 (UTC)

Because you want to keep your clean nails for hammering into things! Seriously, the role of the rust is just to make sure the reaction mixture can find it's way to some iron underneath – a "clean" metal surface usually has a good tough layer of oxide on it (this is why aluminium foil doesn't spontaneously burst nto flames) and that can slow down the reaction to the point of uselessness. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

A nail dipped in HCl should contain some reactive iron on the surface rather than a passivating layer. --Chemicalinterest (talk) 13:29, 16 June 2010 (UTC)

Would ascorbic acid be good for any of them? --Chemicalinterest (talk) 11:12, 16 June 2010 (UTC)

Ascorbic acid would certainly do the silver reduction, as would glucose for that matter. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

How do I activate these carbohydrate reducing agents? Do they need a catalyst? John Riemann Soong (talk) 16:34, 16 June 2010 (UTC)

Ooops, I was actually thinking Au(III)... I only started with gold recently so it's really weird for me to be using Au so often... John Riemann Soong (talk) 16:33, 16 June 2010 (UTC)

Au+++ should be easily reduced by any reducing agent, such as glucose or iron(II). --Chemicalinterest (talk) 20:59, 16 June 2010 (UTC)

using one aldehyde to reduce another aldehyde (product: alcohol and carboxylic acid)

It seems to me that aldehydes could disproportionate.

Consider the following reaction:

2 H2(CO) + HOH ----> HCOOH + CH3OH

Using standard heats of formation I think the overall reaction is -160 kJ/mol

Using acetaldehyde to produce acetic acid and ethanol, the reaction is less exothermic: -90 kJ/mol but it still seems sufficient to get a nice controlled reaction with the right catalyst. What catalyst would allow this disproportionation to occur? I assume that the reaction might be even more reactive if the formaldehyde wasn't stabilised by water but maybe dissolved in the right solvent.

Finally, is there any way to aim not for disproportionation but to actually have aldehydes reduce other carbonyl compounds? I imagine this would be quite useful. Maybe the reaction already exists? John Riemann Soong (talk) 22:32, 15 June 2010 (UTC)

You mean like the Cannizzaro reaction - as the article says for aldehydes with beta-carbon H atoms the aldol reaction predominates.87.102.18.94 (talk) 22:42, 15 June 2010 (UTC)

See also Cannizzaro_reaction#Variations for the 'finally' part .. yes.87.102.18.94 (talk) 22:43, 15 June 2010 (UTC)

The crossed Cannizzaro reaction with formaldehyde as the reducing agent is relatively common. Formaldehyde is cheap, so you can afford to throw away the formic acid by-product in a small scale synthesis. The practical problem is getting the formic acid out of the product mix. However, disproportionation is not the only self reaction that aldehydes can undergo: see paraldehyde, for example! Physchim62 (talk) 22:51, 15 June 2010 (UTC)

Something I find interesting is why aldehydes are less stable on average than alcohols or carboxylic acid derivatives, i.e. both oxidising and reducing an aldehyde is thermodynamically favourable. Are esters and carboxylic acids less electrophilic than aldehydes/ketones? I remember from electron density diagrams, esters/acids are somewhat turquoise? If so, why do some aldehydes not form stable acetals? John Riemann Soong (talk) 16:29, 16 June 2010 (UTC)

You're right...the carbonyl of an ester (or acid) is stabilized by resonance, whereas an aldehyde/ketone is not. And an aldehyde is also fairly unhindered, and the H electronics may play a role as well. So a carbonyl is still a very stable thing, but some carbonyls are much "less stabilized" by whatever makes a carbonyl stable. So some carbonyls are highly reactive and tend to form acetals given the opportunity. Formaldehyde is a pretty common case...exists as the hydrate when mixed with water, easily forms polyacetal chains and rings by itself. DMacks (talk) 18:16, 16 June 2010 (UTC)

Unknown concentration of NaOH

50.0 mL of 1.5 mol/L HCl was mixed with 40 mL of NaOH of unknown concentration. The temperature increased by 8.4 K. a) Calculate the heat of neutralisation of the reaction. b) Calculate the concentration of the NaOH used.
H = mcΔT/n
So 50*4.184*8.4/n
n?
n??
--203.22.23.9 (talk) 23:44, 15 June 2010 (UTC)

The HCl and NaOH should react in a 1:1 mole ratio. So moles of HCl = moles of NaOH. You can find the moles of HCl from the info you wrote above. That also equals the moles of NaOH. You can use that number of moles, and the volume to calculate the concentration. --Jayron32 01:40, 16 June 2010 (UTC)

Question makes no sense as asked - the assumption that moles HCl=moles NaOH is the only way to get a definate answer - but makes no sense - how could they know how much HCl to add if NaOH conc. was unknown.. We will never know.87.102.18.94 (talk) 03:32, 16 June 2010 (UTC)

No, they are given a concentration and a volume of HCl initially, to which the NaOH is added. Calculating the moles (n) of HCl is trivially easy to do. The question is easily answerable, and is of a type which most students should be able to solve in any introductory chemistry class. --Jayron32 03:35, 16 June 2010 (UTC)

If it had said neutralised or titrated then it would make sense.87.102.92.166 (talk) 14:46, 16 June 2010 (UTC)

I think "m" should be 90, i.e. 40+50. The whole thing's heating up, not just the HCl. - Jarry1250 ^{[Humorous? Discuss.]} 14:06, 16 June 2010 (UTC)

June 16

What value is associated with "low impedance"?

What value is associated with "low impedance"? I know that in wire, the material, gauge, and length all contribute to the impedance. I continually see references to "low impedance", but is there a quantifiable answer to the value? —Preceding unsigned comment added by Blinstedt (talk • contribs) 00:33, 16 June 2010 (UTC)

It probably depends on the application. What sort of use are thinking of? --Jayron32 01:39, 16 June 2010 (UTC)

BTW, impedance is basically resistance as applied to A/C (like sound in a speaker wire). Ariel. (talk) 01:50, 16 June 2010 (UTC)

Blinstedt's question contains a hidden error. In wire, the length and diameter, and the resistivity of the material, all influence the resistance of the wire. Resistance is the ratio of potential difference (voltage) to direct current. Impedance is the ratio of potential difference to alternating current. Inductors have significant impedance because they prevent an alternating emf from causing as high a current as would occur if the emf was steady. Capacitors have low impedance because they allow an alternating emf to drive a continuous current (albeit a sinusoidal current.) So a low-impedance circuit has high values of capacitance and/or low values of inductance, and conversely a high-impedance circuit has low capacitance and/or high values of inductance. A thick piece of copper wire might have low resistance, but when used in series with a large inductor it becomes part of a high-impedance circuit. Conversely, a thin piece of copper wire might have high resistance, but when used in series with a large capacitor it becomes part of a low-impedance circuit. Dolphin (t) 03:10, 16 June 2010 (UTC)

You are mistaken. Please read the articles: Electrical impedance, Electrical reactance.—eric 03:22, 16 June 2010 (UTC)

People often use impedance as a synonym for Electrical reactance as dolphin has, I often make this error too. and see below.87.102.18.94 (talk) 03:28, 16 June 2010 (UTC)

I'll try = for power transmission low impedence means less than 1ohm. much less. For other applications such as audio inputs and outputs the answer is a bit different.

But we need to differentiate between reactive and resistive impedance too see Electrical_impedance#Device_examples for an explanation.87.102.18.94 (talk) 03:26, 16 June 2010 (UTC)

"High" and "low" are completely relative to your application so we cannot answer the question without more information. For example, when specifying a power transformer for a substation, typically a "standard impedance" transformer has an impedance of 10% or less, whereas a high impedance transformer would be 15% or more. There is no absolute impedance value that defines "high" or "low". Zunaid 09:03, 16 June 2010 (UTC)

To give another example: in the audio world, the most common low-impedance load is a loudspeaker, which usually has a value between 4 and 150 ohms, while an input to an amplifier, typically 10 kilohms or more, is considered high impedance. There is no exact dividing line between the two. --Heron (talk) 13:27, 16 June 2010 (UTC)

Atom with some muons

If there is an atom with a muon or two replacing the electrons, do those muons sit in the same orbital as the electron they replace, or do they have their own, non-overlapping, series? And if it's their own series, does that mean the atom would then behave chemically as something else (because the outermost electrons are in a different shell)? Ariel. (talk) 01:41, 16 June 2010 (UTC)

Did you read the article in question? The section titled "Muonic atoms" discusses the exact issue you have, as does the linked article Exotic atom#Muonic atoms and the article Muonium discusses the exact opposite (where an antimuon replaces a proton). --Jayron32 01:54, 16 June 2010 (UTC)

These articles do not however answer the question about orbitals. Graeme Bartlett (talk) 01:55, 16 June 2010 (UTC)

Ah, of course. I would suspect that the orbital organization of a muonic atom would have to be different; since a muon has 200x the mass of an electron, its angular momentum would by necessity then be different, and a key component of orbital organization is angular momentum. See quantum numbers for a brief discussion of the role of angular momentum in orbital organization, or Azimuthal quantum number for a more detailed discussion. --Jayron32 03:05, 16 June 2010 (UTC)

To first approximation, an atom with X protons and N muons replacing electrons will have the same chemistry as an atom with X-N protons and no muons (provided X >> N). The muons have an independent series of quantum numbers and occupy much tighter orbits than electron, so effectively each muon results in one proton's worth of charge being hidden from the electron cloud so that the rest of the system behaves as if the nucleus was of lower charge. Dragons flight (talk) 03:17, 16 June 2010 (UTC)

Haha Dragons, are you willing to pull out Griffiths/Shankar and go through the derivations, as my copies are in storage? SamuelRiv (talk) 09:20, 16 June 2010 (UTC)

overcharging a handycam or mobile phone battery

why do some manufacturers advice us against leaving the batteries of handycam or mobile phones connected to the chargers for too long/ What happens when you over charge a battery? Fragrantforever 06:50, 16 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

There is a message on your talk page about signing posts that you might find helpful. ;-) Caesar's Daddy (talk) 07:30, 16 June 2010 (UTC)

If you leave a battery on a charger constantly it overheats, then dries out. The charger charges it till it's full, then the extra energy just goes to waste heating up the battery. The heat eventually dries it out, and then it doesn't work anymore. Depending on the chemistry of the battery it might damage it in other ways (rechargeable batteries are pretty delicate and are easy to damage). Lithium ion batteries especially get damaged if they overcharge even a little, so all of them include limiting circuity to prevent this. Another thing that can happen is the water in the battery gets electrolyzed into hydrogen and oxygen, which then either leaks out of the battery, causes it to swell, or (hopefully) gets recombined back to water, releasing some heat in the process.

If you want to store a battery most of them are best stored in a half charged state, except for lead acid which needs to be fully charged at all times. Ariel. (talk) 09:10, 16 June 2010 (UTC)

Note that smart chargers detect when the battery is fully charged and then stop charging it. Cell phone chargers seem to do this, for example. Unfortunately, many other chargers don't and there doesn't seem to be any standard way of labeling devices so you can tell if your charger is smart or stupid. However, if the instructions include that warning, it's probably the bad type of charger, so do as they suggest. StuRat (talk) 15:08, 16 June 2010 (UTC)

Thanks for the responses, Ceaser's daddy, I do add 4 tildes ( or whatever its called) at the end of all my posts and I thout that means signing my posts, it still says unsigned entry- which prompts you to drop a comment like that with a wink. 213.130.123.12 (talk) 10:22, 16 June 2010 (UTC)

You appear to have modified your default signature in such a way that SineBot does not recognize it. (See User:SineBot#What it looks for.) If you want to keep your linkless signature, you may wish to opt out of SineBot's scrutiny. 58.147.52.243 (talk) 10:56, 16 June 2010 (UTC)

Bad idea. See Wikipedia:Signatures#Links Nil Einne (talk) 18:33, 16 June 2010 (UTC)

yawning + stretching euphoria

why do you get euphoria when yawning + stretching in the morning (or any time of day, especially if you are a feline)? 92.224.204.156 (talk) 08:35, 16 June 2010 (UTC)

I'm not sure about the stretching, but yawning is a way of getting more oxygen into your blood which would make you more alert. Regards, --—Cyclonenim | Chat  11:21, 16 June 2010 (UTC)

That's what I thought too until I read up on this recently (trying to understand contagious yawning) and found that there is actually no data to support it. As far as I can tell, stretching feels good because it reduces muscle stiffness, and yawning may be a sort of stretching of the lungs. Looie496 (talk) 14:55, 16 June 2010 (UTC)

Evolutionarily speaking, things "feel good" which are (or were) helpful for passing on our genes. Stretching helps prevent injury and thus could keep our ancestors alive long enough to reproduce. As for yawning, the benefits there are less clear. StuRat (talk) 15:03, 16 June 2010 (UTC)

Will poppy seeds in processed horse feed test false positive for Synephrine in the urine or could slippery elm bark powder contain Synephrine.

Our race horse had a pre race urine sample taken which tested positive for Synephrine. My husband has been a trainer for thirty odd years and has never had a positive swab until now. Prior to the swab, we had started using processed feed in a pellet form, that was a bonus prize from a win we had with one of our horses. I read somewhere that poppy seeds, which were profuse here in Australia at the time and visible in unprocessed feed, can give a false positive for Synephrine and suspected that this may be the cause of the positive swab. I cannot find the article now to present to the stewards inquiry. Is this true? Will poppy seeds cause this result? Also we used slippery elm bark powder, which was guaranteed to be a legal substance that was safe to use when racing. We used this to prevent/relieve stomach ulcers that can be prevalent in race horses. —Preceding unsigned comment added by Traveloz (talk • contribs) 10:23, 16 June 2010 (UTC)

I've heard of poppy seeds giving false positives for opiate tests, but not for this. Synephrine is similar structurally to neo-synephrine which can give false positives for amphetamine/methamphetamine tests, but my previous point stands: poppy seeds shouldn't be giving false positives for synephrine, but instead for opiates. I'm not sure about slippery elm bark powder. I suspect you'd need to talk to a veterinary pharmacist for a conclusive answer. Regards, --—Cyclonenim | Chat  11:20, 16 June 2010 (UTC)

Volume of a drop

I have a tap that drips about once a second. I'm wondering how much water it is wasting a year. Drop (liquid) does not say what the volume is. Do not know if tap drops are always a particular size or if they vary. 92.28.251.43 (talk) 13:41, 16 June 2010 (UTC)

You could do an experiment... just put a liquid measuring cup under the tap, and record how long it takes to reach a certain volume. Google can make the calculation easy: example. -- Coneslayer (talk) 13:47, 16 June 2010 (UTC)

Drops will vary in size, but drops from a single source like this one should be consistent with themselves. Some of the math behind this is discussed at drop (liquid). However, you don't need that to estimate how much water you're wasting. Instead, grab a measuring cup (the one with the smallest graduations you have) and place it under the leak for a set period of time (longer is better, as long as you don't overflow the cup). You can then extrapolate annual leakage based on that short term. Suppose, for instance, that you got 1/4 cup of water in one hour's time. That would become 1/4 (cup/hour) * 24 (hours/day) * 365 (days/year) / 16 (cups/gallon) for about 140 gallons of water wasted per year. You could similarly estimate the volume of an individual drop. — Lomn 13:52, 16 June 2010 (UTC)

I agree with the previous responses. The reason is that there's a fair amount of error both in estimating the volume of a drop and in estimating the time increment between them. Collecting a larger volume over a larger time period will reduce both those errors and thus give a far more accurate total. However, use a tall, narrow container to collect the water, such as a vase. This will reduce water loss from splashing and evaporation. You can then pour it into a measuring cup. StuRat (talk) 14:54, 16 June 2010 (UTC)

Is there an approximate answer for the volume of a tap drop please? 92.28.251.43 (talk) 16:14, 16 June 2010 (UTC)

http://www.google.co.uk/search?q=volume+of+water+drop&hl=en&start=10&sa=N shows that the generally used figure is 1/20ml or 0.05ml ie 20,000 drops in a litre.87.102.92.166 (talk) 16:26, 16 June 2010 (UTC)

But, as we've noted, that doesn't mean your water drops will be 1/20 ml or anything like it. However, it would be trivial to determine this experimentally. StuRat suggests an excellent method above. — Lomn 18:39, 16 June 2010 (UTC)

~ (Tobacco vs. other illegal, recreational drugs)

So if I wanted to trade my legal cigarette smoke for illegal recreational drugs instead, in order to maintain whatever utility I think I get from the tobacco smoking, while expressly making the trade (with concommitant justice risk) in order to reap certain comparative health benefits for the same level of utility, would I be able to do so? As for the utility part, I shall have to judge, but for the health part, I think you can help me. Viz.

• How do the health effects of tobacco use compare with the health effects of other, illegal, recreational drugs?

Specifically, what is most comparable in its effects both during consumption and in terms of deletirious health consequences? Note: because in my estimation there are something like a few million dollars of salaries going into Wikipedia shills, I would like to mention that I have absolutely no relationship with tobacco or any other drug other than being a simple consumer. 84.153.246.145 (talk) 13:57, 16 June 2010 (UTC)

I changed your useless title to one which actually identifies the question. StuRat (talk) 14:51, 16 June 2010 (UTC)

At what point did the OP mention cannabis? There are other illegal drugs which can be vaporised or smoked, so I've renamed again accordingly. Regards, --—Cyclonenim | Chat  15:02, 16 June 2010 (UTC)

OK, but please always leave the original title, both so they can use it as a search term and so everyone knows what I was talking about when I said the original title was useless. I've therefore added the original title (a single tilde), back in. StuRat (talk) 15:28, 16 June 2010 (UTC)

To answer your question, I recommend reading these links: Health effects of tobacco, effects of cannabis, heroin#Risks of use and cocaine#Effects and health issues. Of course, there are other drugs, and if you search for their articles you'll usually find either a separate article on their health effects, or a subsection discussing it. Regards, --—Cyclonenim | Chat  15:04, 16 June 2010 (UTC)

Thanks, I'm pretty sure heroin and cocaine are off the scale in terms of risk versus tobacco, though. Isn't there something comparable? (op here) 84.153.246.145 (talk) 15:35, 16 June 2010 (UTC)

This chart should help. Note, that while I personally am not so convinced it's accurate (for example I think solvents are more dangerous than alcohol), it's probably a good start. (My main objection is how the raw data was combined into a mean.) Anyway, based on it Khat seems like the best choice. Ariel. (talk) 15:52, 16 June 2010 (UTC)

And that proves your point. Khat causes severe psychosis. The Somali community in Leicester (where I used to teach) are campaigning to get it put on the banned list in the UK because it causes more social harm in that commmunity than any other drug, legal or otherwise. But you wouldn't know that from that chart! When I get chance (later on tonight) I'll try and find the research they've used in their campaign. --TammyMoet (talk) 16:31, 16 June 2010 (UTC) Here's one: http://informahealthcare.com/doi/abs/10.3109/00048679409075648 --TammyMoet (talk) 17:24, 16 June 2010 (UTC)

I wonder where chewing of Coca leaves falls on the chart? (It is not the same thing as doing concentrated cocaine.) Off the top of my head that seems like it is probably a similar trade-off as tobacco, perhaps even a bit better for one (similar physical effects, but without the obvious lung problems). It's not illegal everywhere, but it is in the United States, so that satisfies the "illegality" component. This is not medical advice in the slightest—there are probably long-term health risks associated with chewing Coca leaves, and how they stack up against long-term risk from cigarettes, I honestly don't know. --Mr.98 (talk) 17:23, 16 June 2010 (UTC)

Interesting - I wonder where this chart came from, and what it was designed to do? for instance, yes, chewing cocoa leaves should be far less dangerous that snorting concentrated cocaine. further, while cannabis ounce for ounce might be comparable to cigarettes in terms of toxins, no one smokes 20 cigarrette-sized joints a day. consumption is probably less that 1/20th that of tobacco even in the heaviest pot smokers. Hashish might be different, of course. I'm really curious about the positioning of LSD, though - LSD is entirely non-addictive and has negligible physiological effects on the body (I don't even think researchers have discovered a toxic dose level for it). It really should be down close to 0,0, though that's not a recommendation for use (LSD is not a drug that should be taken casually, because it has intense psychological ramifications). --Ludwigs2 19:15, 16 June 2010 (UTC)--Ludwigs2 19:15, 16 June 2010 (UTC)

Is it useful to read the chart as whatever has the lowest total score is the most desirable? Presumably if you were to try to replace one with another you would have to give one addiction in favor of another addiction, right? Assuming that the "dependence" is the reliance on the effect of the drug that you develop. If that is the case then isn't it more appropriate to think of it as dependence divided by harm? Since trying to replace a high-dependence, high-harm drug with a low-dependence, low-harm drug is likely to result in failure due to your body still craving the old drug? Remember, the OP did say that he was interested in the "utility" of the drug vs smoking which means he would have to supplant his cigarette addiction with whatever addiction this new drug offered. This is an interesting (if morbid) thought experiment. How about not being addicted to any drug? Why isn't that on the chart? --144.191.148.3 (talk) 19:27, 16 June 2010 (UTC)

Regrowing of human skin and its color

The other day I saw an African-American firefighter. He had suffered a serious burn on his face at some point in his life, but the skin was all grown back. However, the skin was nowhere close to the tone that the rest of his skin was so it looked like a mask. Just a white patch around his mouth and dark brown skin everywhere else on his face. I know that skin color has a lot to do with melanin, but I am wondering why it didn't grow back the same color that it was previously. Is there only so much melanin in the body? Thanks, The Reader who Writes (talk) 15:20, 16 June 2010 (UTC)

The same applies to skins of naturally paler colours - the new growth is even paler. I don't know the reason though, except to note that skin naturally grows darker as it ages and is exposed to UV. Dbfirs 15:43, 16 June 2010 (UTC)

It's likely that the burn was of a significant enough degree to damage the melanocytes which lie at the bottom of the epidermis. Bad first degree burns and all second and third degree burns cause this damage. I suspect that the burn was bad enough to prevent the repopulation of melanocytes to the area. Regards, --—Cyclonenim | Chat  16:19, 16 June 2010 (UTC)

A display that doesn't suffer from glare

I was checking out some of the next gen display technologies like Laser TV, and Field Emission Displays. But one thing all these displays have in common is that bright sunlight creates large amounts of glare. Is there any display technology, present or future, that will not suffer from glare while delivering high definition/quality visuals? And I'm talking about broad sunlight, like if you had your laptop or whatever out in the park in the middle of the day.

What about holograms? Don't know how advanced this technology is, but in some sci fi games, and movies they use holograms as displays in their futuristic worlds. How well will they work in broad sunlight? 148.168.127.10 (talk) 15:46, 16 June 2010 (UTC)

This isn't an answer, more of a point to ponder, but how can you create a device which emits light, but doesn't reflect it back when it shines on it's surface? I would have thought any coating that prevents glare would also darken the image. Regards, --—Cyclonenim | Chat  16:21, 16 June 2010 (UTC)

My wife has read her Kindle on the beach in extremely glaring sunlight. So, that is one very anti-glare display. However, it is only black-and-white. -- kainaw™ 16:23, 16 June 2010 (UTC)

That's the answer. ePaper. Currently only available in monochrome, but color ePaper displays are in development. APL (talk) 16:33, 16 June 2010 (UTC)

I would think any reflective capable display would also work similarly. These are usually monochrome and of course also require ambient lighting to see which may be undesirable in some circumstances. One option is for a combined display which can operate in either reflective or transmissive modes like the OLPCs or Pixel Qi although these still operate in monochrome in reflective mode. Or perhaps a transflective liquid crystal display. Nil Einne (talk) 18:24, 16 June 2010 (UTC)

Conservation of energy

What's the difference/resemblance between the conservation of energy and the first law of thermodynamics? /Natox (talk) 17:05, 16 June 2010 (UTC)

Quoting from the article: "The first law of thermodynamics [is] an expression of the principle of conservation of energy." If you want to get picky, the FLoT addresses non-isolated systems by expanding the system in question until it's isolated. — Lomn 18:33, 16 June 2010 (UTC)

No difference. The 1st law of thermodynamics is The conservation of energy applyed to thermodynamic systems. Dauto (talk) 20:56, 16 June 2010 (UTC)

Spider indentification

what kind of granddaddy long legs spider is white with black spots, and has two front yellow fangs? —Preceding unsigned comment added by 71.50.164.12 (talk) 17:05, 16 June 2010 (UTC)

It's hopeless without a picture. If by granddaddy-long-legs you mean a harvestman, then many if not most of them (and there are over 200 species in US) have spotted or wavy patterns of dark gray or brown with white or beige, and some indeed have pale chelicerae and pedipalps. Leiobunum vittatum is fairly common and may fit the bill, but there are many others, too. However, granddaddy-long-legs may also refer to Pholcidae. Which is it? --Dr Dima (talk) 18:20, 16 June 2010 (UTC)

You also have to tell us where you saw it. --Sean 19:43, 16 June 2010 (UTC)

Protein percentage in muscle by mass

Hello. Can someone please tell me what is the percentage of protein in muscle by mass, or in other words, roughly how many grams of protein can I expect to find in 100 grammes of an average muscle. Thank you.--Leptictidium (mt) 18:12, 16 June 2010 (UTC)

You might find list of foods by protein content informative, but that lists muscles in an edible state, which presumably means cooked, so some protein loss might occur in that process. --Sean 19:45, 16 June 2010 (UTC)

Stronger reducing agent than azide

What is the strongest stable reducing agent? --Chemicalinterest (talk) 19:10, 16 June 2010 (UTC)

Strongest base

There's a redirect at strongest acid but not at strongest base, so what's the strongest base? --76.77.139.243 (talk) 19:16, 16 June 2010 (UTC)

Tert-Butyllithium - It has a pKa of greater than 50 if my memory serves. Regards, --—Cyclonenim | Chat  20:00, 16 June 2010 (UTC)

We have an article about superbases. For example, swapping tBuLi to tBuK makes it stronger. DMacks (talk) 20:07, 16 June 2010 (UTC)

How can I make it not possible to throw things

I don't want people throwing things in my apartment, how do I make it so you have to place things, you can't throw them (anything)? Note: I don't think I ever throw anything at all, but I would like the change to be reversible in case there is some bad consequence I didn't think of,l. Would I have to change inertia (inertial dampers?) air viscosity, or what, and how would you do it, 85.181.146.84 (talk) 19:50, 16 June 2010 (UTC)

You can't. Next question! — Lomn 20:07, 16 June 2010 (UTC)

Concur, you can't have inertial dampers because they don't exist in that sense, we're not in the Star Trek universe unfortunately. You can't change the air viscosity because you'd have to have a solid to prevent things from moving, thus you couldn't move either. You'd be encased! Regards, --—Cyclonenim | Chat  20:12, 16 June 2010 (UTC)

Get everyone out of the apartment. Close and lock the door from the outside. Throw away the key. Problem solved. --Sean 20:23, 16 June 2010 (UTC)

Move to an Earth-like planet with a gravitational field strong enough to make everyday objects impossible to lift. Don't expect to be walking anywhere. (Is such a planet possible, or would the increased gravity cause fundamental differences precluding Earthlikeness? 20:32, 16 June 2010 (UTC)Vimescarrot (talk)

Invest in friends who don['t throw things. it will be worth the money in the long run. --Ludwigs2 20:31, 16 June 2010 (UTC)

This is an exercise in apartment design. Furnish your apartment with only objects that cannot practically be thrown. Areas that need small objects (Kitchens?) could be constructed so cramped that throwing items is impractical.

That's really the only answer, there's no way to adjust the laws of physics in your room in such a way that things can't be thrown, but they can still move when carried. (Otherwise you could fill the apartment with concrete, or Lucite.)APL (talk) 20:38, 16 June 2010 (UTC)

The telomeres of Turritopsis nutricula

I'm a layman with respect to biology, but from what I have read, the telomeres of chromosomes for most species get a little shorter with each cell division until a cell can't divide anymore. But at List of long-living organisms, it says "Turritopsis nutricula is capable of cycling from a mature adult stage to an immature polyp stage and back again. This means that there may be no natural limit to its life span." I know it's not certain whether there's a causal relationship between telomere length and aging, but limitless life span seems to necessarily imply limitless ability to divide. So does Turritopsis nutricula not lose any telomere length at all on each cell division, or does it keep adding as much as it loses, or something else? I saw the abstract at the link entitled "Telomerase activity is not related to life history stage in the jellyfish Cassiopea sp." at the bottom of Turritopsis nutricula but didn't really understand it. Thanks. 20.137.18.50 (talk) 19:59, 16 June 2010 (UTC)

Number of deep sea oil rigs worldwide

How many deep sea oil rigs are there worldwide and how many are owned by which major oil companies.

I can not find this information in any Wikipedia articles.

Gary Tennison gtennison@PTSstaffing.com

don't forget not to get your hopes up as these eggs are delicious for many predators. 92.229.12.200 (talk) 20:58, 16 June 2010 (UTC)

Cumberland Slider Turtles

We recently had a turtle lay her eggs in our garden. We live on the North Fork of the Holston River in Tennessee. How long will it be before we see these hatch? —Preceding unsigned comment added by 173.105.80.255 (talk) 20:37, 16 June 2010 (UTC)

Is it fair to say that Nuclear Power plants are environmentally friendly?

Because we all know about nuclear waste. But can it be said that as long as the nuclear waste is either properly disposed of or recycled, that a nuclear power plant is enivronmentally friendly, and produces no negative impact to the environment? 148.168.127.10 (talk) 20:43, 16 June 2010 (UTC)

Yes, it is actually a lot easier to dispose of nuclear energy than it sounds. It is certainly much more environmentally friendly than fossil fuels, since a rice-grain size piece of ²³⁵U produce as much energy as three tons of coal or fourteen barrels of oil, so certainly a rice-sized piece of nuclear waste does much less damage to the environment than all the CO₂ produced by fossil fuels. --The High Fin Sperm Whale 20:51, 16 June 2010 (UTC)