Wikipedia:Reference desk/Archives/Science/2007 October 6

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October 6

Self sufficient communities

This is a follow up question to Planning for a bleak future on the Miscellaneous reference desk. I have two questions about closed communities:

1. What is the smallest possible genetically self sufficient community? (In other words, how big does an isolated community have to be so it will not die off through inbreeding?) 500? 1,000? 2,000?
2. How many acres of arable land/pasture is necessary to support an adult person year round? (x acres of land divided by x number of people in community). How would this differ between Subtropics, Humid continental and Temperate climates?

Thanks for your help! --S.dedalus 00:28, 6 October 2007 (UTC)

To answer the first question our article on a generation ship says about 500 people. However, there's no citation. And remember you won't necessarily need that many people, just that much genetic material. So a good cryofreezer and a lot of frozen eggs/sperm etc could do the trick with a very small population (assuming the stuff stays fresh for a very long time). Not sure about the second part though. --Cody Pope 01:15, 6 October 2007 (UTC)

For the first question, ask a hillbilly.

For the second question it would matter a lot on how much meat you want, because that takes up a lot more land, it is said. Also, you seem to assume a purely cultivation-based food supply. For the bleak future scenario, it makes more sense to rely on hunting/gathering because that way you won't have much stock that can be stolen. Of course, a combination of the two might be best - under uncertain circumstances, it's always best to put your eggs in as many baskets as possible. And a crossover might also be a good idea - plant the food, but not all in one spot, but spread out over different areas under different conditions, so a failed harvest will be limited and you won't run the risk of being completely out of food.

So there are many variables, but a good indication might be found in mediaeval subsistence farming. Open field system says each villager got 30 strips of 2000 m², so that's 60,000 m² per person, roughly 250 x 250 m (assuming that's really per person, not per family, which I rather expected to find). So a community of 500 would require about 100 km² or 10 km x 10 km. That's about the size of Amsterdam for a small village, which sounds like a lot. But farming was probably much less efficient in those days (as it is likely to be under the survival conditions we're talking about), and there were nowhere near as many people then, so it might still be fairly accurate. I guess most mediaeval villages were about that size and about 10 km apart. Of course, that may also be an explanation. Maybe they used that much space simply because that's what was available. DirkvdM 09:25, 6 October 2007 (UTC)

The Bible says two people are enough. I seem to remember Guns, Germs and Steel giving a figure for how much acreage is needed to support one person's foraging, but I can't recall the number. --Sean 14:00, 6 October 2007 (UTC)

Unless you've got a special situation (the Pacific Northwest salmon runs, for example), a hunter-gatherer society needs about one square mile of land per person. --Carnildo 22:15, 9 October 2007 (UTC)

Ian Robert Franklin coined the 50/500 rule (hmm, no articles on either.) It states that, as a rule of thumb, a species needs fifty members for probable short-term survival, and five hundred for long-term survival. A quick search for Franklin "50/500 rule" turns up a number of scholarly articles discussing the topic. GeeJo ^(t)⁄_(c) • 17:33, 6 October 2007 (UTC)

That number will vary wildly depending on whether subsequent breeding is carefully planned to maximise diversity or allowed to happen naturally. SteveBaker 17:40, 6 October 2007 (UTC)

Sean, the bible doesn't say two is enough. I used to think that, but then one day I read that part and it says Kain went out into the wide world, where he met another people ... which leaves the question where the hell they came from. DirkvdM 18:06, 6 October 2007 (UTC)

They came from the Flying Spaghetti Monster of course. Unless they came from the Invisible Pink Unicorn. ;-)

Atlant 23:49, 6 October 2007 (UTC)

That's sacrilage. You aren't supposed to say her name without adding 'bbhhh' or some similar honorific. You probably don't even have pinapple on your pizza. I may have to declare a jehad. SteveBaker 16:50, 7 October 2007 (UTC)

Spider ID

What species am I?

This spider jumps. Seen at Dennis railway station, Melbourne. Can anyone name the species? —Pengo 02:56, 6 October 2007 (UTC)

Well, it's clearly of the family Salticidae (jumping spider), but I'm not sure from that angle it will be easy to distinguish it from many of the very similar looking jumping spiders (many of which are generally brown, have large forward-facing eyes, and make that little sort of face). --24.147.86.187 04:09, 6 October 2007 (UTC)

Another angle.

How about this angle? —Pengo 04:29, 6 October 2007 (UTC)

There are over 5000 jumping spider species. I doubt it would be possible to find the exact species of the spider in your picture. The only way would be if a life specimen crawled through the series of tubes on the Internet for me to perform DNA testing, and then search for the sequence on PubMed. But if you'd be satisfied with just a genus or a family, I'd recommend using this site--Mostargue 12:39, 6 October 2007 (UTC)

There is a "find-a-spider" site for Australian spiders here. I went through all of the pictures for that particular family but didn't see any obvious 100% matches. --24.147.86.187 14:53, 6 October 2007 (UTC)

Better than the previous link, but unfortunately it focuses on Queensland spiders, and that's a far way from Victoria in distance and climate. —Pengo 23:26, 7 October 2007 (UTC)

Killing with sound

Is it possible to generate a sound that can kill a human? Either by the sheer power of it or by creating some kind of harmonic vibration that will shake the body apart? Exxolon 03:30, 6 October 2007 (UTC)

Massive ordnance air blast over-pressures the human with a pressure wave. It might be considered "killing with sound" but it's really more of a supersonic over-pressure. Nimur 04:27, 6 October 2007 (UTC)

See our article on sonic weaponry. General consensus seems to be that lethal sonic weapons are only possible underwater. Gandalf61 08:00, 6 October 2007 (UTC)

Monty Python had a suggestion for this - a joke that is so funny that the enemy will laugh themselves to death. Of course it can't be told by one single person, or they would themselves die. See the episode for solutions. DirkvdM 09:34, 6 October 2007 (UTC)

That would be The Funniest Joke in the World. DuncanHill 12:43, 6 October 2007 (UTC)

On a more serious note, one torturing method (which appears to be used in Guantanamo Bay, or that's where I think I got this from) is to expose people to white noise. Don't know if that could be lethal if used in excessive amounts. Can madness kill? DirkvdM 09:35, 6 October 2007 (UTC)

For a smaller scale version of a similar phenomenon, check out the pistol shrimp. Capuchin 10:28, 6 October 2007 (UTC)

That's more of a blast, a single wave, than a sound, which consists of several waves, or rather, is sustained longer. DirkvdM 18:10, 6 October 2007 (UTC)

In the past, on Sound pressure in the table was information on what dBa's effects on a human body would be. —Preceding unsigned comment added by Mac Davis (talk • contribs) 02:05, 7 October 2007 (UTC)

I checked reference number four on that article, and it states so: 195-190 (P) HUMAN EARDRUMS RUPTURE 50 % OF TIME -REF.2. and 202-198 (P) HUMAN DEATH FROM SOUND (SHOCK) WAVE ALONE. [Mac Δαvιs] ❖ 03:15, 7 October 2007 (UTC)

microbiological test

1. what are the Cleaning procedures in food production site? 2.what are the decision can be taken by quality assurance representative when the products are affected by microbiological problem? —Preceding unsigned comment added by 60.53.109.73 (talk) 04:49, 6 October 2007 (UTC)

These will differ according to site, the food being produced, and the regulations on the industry in the specific jurisdiction. You might want to take a look at this U.S. F.D.A. site which discusses Hazard Analysis and Critical Control Point procedures. - Nunh-huh 05:02, 6 October 2007 (UTC)

Spinal cord, ventral and dorsal tracts

In Kolb & Whishaw, Fundamentals of Human Neuropsychology (2003) is the following sentence: "In the spinal cord itself, the outer part consists of white matter or tracts, arranged so that with a few exceptions the dorsally located tracts are motor and the ventrally located tracts are sensory."
Is this correct? If I compare with pictures, for instance this one: http://faculty.etsu.edu/currie/images/neuro2.jpg, it seems to me that most dorsally located tracts are sensory and most ventrally located tracts are motor. Lova Falk 09:02, 6 October 2007 (UTC)

Spinal cord provides a description of the major tracts. I wonder if "Fundamentals of Human Neuropsychology" just makes that statement in passing or if they have a supporting figure or cited references. Here is another figure similar to those found in many textbooks. --JWSchmidt 15:25, 6 October 2007 (UTC)

That's just what I mean. Would you agree with me that it seems to be a mistake in the book? Lova Falk 09:06, 7 October 2007 (UTC)

I can't imagine a context in which that sentence would be true. From embryology to clinical practice to neurosurgery, it's well understood that the dorsal side is predominantly sensory, while the ventral side is motor. --David Iberri (talk) 15:39, 7 October 2007 (UTC)

Thank you for your very clear answer! I'm quite proud that I discovered this mistake :) Lova Falk 16:35, 7 October 2007 (UTC)

And you should feel proud! I find these sorts of stupid things all the time (I'm feeling a bit like a professional student these days, with all the textbook reading I've been doing lately). It makes me wish there was some universal page for submitting textbook errata. --David Iberri (talk) 00:41, 8 October 2007 (UTC)

Good idea! On the other hand, you could always create a Wikipedia article: List of textbook errata Lova Falk 17:19, 8 October 2007 (UTC)

See Errata at Wikibooks. --JWSchmidt 04:53, 9 October 2007 (UTC)

Whoa, that's cool. Thanks for the link, JWSchmidt. --David Iberri (talk) 04:44, 11 October 2007 (UTC)

Physics???

If we want to become a doctor when we grow up, is it necessary for us to take Physics, Chemistry and Biology in our secondary education?? Or will it be sufficient if we simply take Biology and Chemistry? —Preceding unsigned comment added by 219.74.132.62 (talk) 09:43, 6 October 2007 (UTC)

It varies significatly depending on which institution you choose to seek your degrees from. If you are beginning to plan what colleges you would like to attend, you should look on said colleges' websites for their admission and graduation requirements for their premed programs. My own university's premed program entails what some would consider a surprising amount of physics and mathematics, but I've seen others that require almost none, comparatively. Someguy1221 09:52, 6 October 2007 (UTC)

Basic physics will help you to understand the advanced chemistry and biology which you'll need to be a doctor. Additionally, the way things are approached in physics classes will give you a slightly different set of problem solving skills which may be of use in any profession. Finally, if you are going into certain specialties like orthopedics or radiology, you'll need to have a solid background in physics to understand the principles behind what you are doing. In short, it might not be necessary, but it'll be a good idea. -- 72.33.121.200 16:51, 6 October 2007 (UTC)

It also depends on the country in which you plan to train as a physician. In the US, for example, medical schools require that you take a significant amount of physics during your undergraduate training (usually a full year's worth) in order to be considered for admission. If you already had that physics during secondary school (the equivalent of high school in the US), you'd be in better shape to do well at university and then have a better chance at being accepted into and doing well in medical school. --David Iberri (talk) 18:01, 6 October 2007 (UTC)

RE: helium

as it is a natural resource how many years do we on earth have with the resource of helium, before it is gone? —Preceding unsigned comment added by 12.217.132.163 (talk) 15:02, 6 October 2007 (UTC)

You may find this article of interest. Cheers Geologyguy 15:11, 6 October 2007 (UTC)

Helium is a byproduct of nuclear fusion, so if that ever becomes a major power source, we probably won't run out of it. Assuming it doesn't, as the amount of helium left decreases, it will get more expensive and be used less. Mathematically, it should never run out completely. The same goes for deuterium if nuclear fusion does. — Daniel 15:34, 6 October 2007 (UTC)

Heheh! The amount of helium produced by fusion reactors would be truly microscopic! Think about the amount of energy created by a hydrogen bomb - a massive fusion reaction - but how much hydrogen do you think there is in the bomb? The helium created by reacting the hydrogen will weigh a tiny bit less than the hydrogen did. Worse still, some of the more interesting reactor designs actually consume helium (in the form of He³) - which we'd have to transport from the moon because the stuff is rare here on earth. SteveBaker 17:34, 6 October 2007 (UTC)

The dwindling of this precious natural resource is a direct corrolary of the disproportionate influence Big Balloon has over our government and policies. Enjoy your tiny voices and festive birthday parties while you still can!! 38.112.225.84 20:12, 6 October 2007 (UTC)

Helium comes from natural gas - 7% of natural gas is helium (that's a LOT!). However, just like natural gas, it's not a renewable resource. When we run out of natural gas, we run out of helium. It's reformed (very slowly) from radioactive decay - but (as our article explains) each cubic kilometer of the earth's crust forms just 3 liters of new helium gas per year...that's as close to nothing as you could imagine! So when we run out of natural gas...no more squeaky voices. SteveBaker 15:57, 7 October 2007 (UTC)

And to add a bit - that 7% is by no means across the board in all natural gas -- concentrations of that much are extraordinarily rare, and most of the world's helium comes from just a few natural gas fields (by far the largest in the Texas Panhandle, which produces something like 80% of world helium). Most natural gas fields do not contain helium in proportions to make recovery economic. Cheers Geologyguy 16:25, 7 October 2007 (UTC)

Yup, helium-shortage is all over the general-public news. DMacks 16:28, 7 October 2007 (UTC)

Yes - but right now, the shortage is one of our own making. It's not that the amount of helium underground is close to being exhausted (although that will happen eventually) - it's that the refineries have short term production and maintenance problems. Also, the level at which helium recovery from natural gas is 'economic' depends on the usual laws of supply and demand. As the easy-to-extract stuff becomes rarer, the price will increase and it will become economic to extract it from less right natural gas supplies. However, in the long term, it's a severe problem because whilst we can find alternatives to non-renewable fuel supplies (eg Replacing fossil fuels with nuclear, wind, solar, etc) - there is no alternative to helium in almost all of its applications - and no other economic supply will ever become available. The helium we release into the atmosphere eventually floats off into space and is lost forever. In an idea world, where we manage to stop burning fossil fuels (including natural gas) in order to fix the global warming problem, we'll end up pushing up the price of helium because it will no longer be a convenient by-product of natural gas production - but instead, we'd have to pump out natural gas, extract the valuable helium and somehow dispose of the 'waste product' natural gas without doing something harmful like burning it off. This will make even the 'easy to get at' helium vastly more expensive than it is now. SteveBaker 23:21, 7 October 2007 (UTC)

Feh. We'll just breed tritium and let it decay into helium-3. (And I can't decide whether I'm joking or not.)

Atlant 12:36, 8 October 2007 (UTC)

(Not...I hope). Using that approach is akin to practicing alchemy by turning lead into gold using a nuclear reactor. Yes, you could certainly do it - but economically?! SteveBaker 13:36, 8 October 2007 (UTC)

If helium can't react with anything chemically, then how would it run out? Wouldn't it remain in the atmosphere? Wouldn't the total amout of helium remain constant? --193.16.218.66 13:14, 8 October 2007 (UTC)

No - helium is very light (the second lightest gas after hydrogen) - therefore it floats up to the very top of the atmosphere and eventually drifts off into space. There is only 5 parts per million of helium in the air. SteveBaker 13:36, 8 October 2007 (UTC)

Some info about prodution and loss at Helium#Occurrence_and_production (would love to have more well-cited info in that section for Creation-"Science" reasons). DMacks 00:57, 9 October 2007 (UTC)

If you don't mind the risk of explosion, presumably Hydrogen is just as good for most purposes? That isn't going to run out anytime soon, and if it does we might have bigger problems than not being able to blow up balloons... 130.88.47.27 12:43, 11 October 2007 (UTC)

Just FYI re two uses of helium: Hydrogen isn't as useful at leak detection because the diatomic H₂ molecule is larger than an He atom. And because it burns, hydrogen is a lot less useful as a shielding gas in welding, although Argon may be a good substitute for Helium; I don't know enough about the specifics of gas-shielded welding.

Atlant 16:40, 11 October 2007 (UTC)

Harvard Chart Method

This was a method presumably developed at Harvard University which was used to both replace Boolean Algebra and to automate the process of reducing logical equations to minimum form. Yet, I can find no reference to this method either at Harvard or at MIT. It was suggested that the method was developed by Howard Aiken preliminary to development of Aiken's Harvard Mark II. Does anyone have reference to the method or any other information regarding it? Clem 15:31, 6 October 2007 (UTC)

Karnaugh maps probably? Maybe Venn diagrams, Johnston diagrams, Truth tables, Quine–McCluskey algorithm, Logical graphs? I'm not aware of any that are specifically associated with Harvard/MIT - but the methods I linked to here are the common diagrammatic methods I can recall offhand. I'm betting you are thinking about Karnaugh maps - because that's the technique that's probably the most widely used. SteveBaker 17:14, 6 October 2007 (UTC)

Wikipedia once had an article about this and it cited: Hunter, William L. [10-1975]. Chapter 4, "The Laws of Logic, Boolean Equation Simplification - The Harvard Chart". Digital/Logic electronics Handbook(in English), pp.112-113, Blue Ridge summit, PA 17214: Tab Books / No. 774, 1975. ISBN 0-8306-5774-6, ISBN 0-8306-4774-0
--JWSchmidt 17:22, 6 October 2007 (UTC)

Check here.

But beyond references to that book - I can find no references to the technique. That Wikia article is a bit "out there" - claiming that one could prove the existance of God if only you had a big enough computer but that only God is smart enough to run the proof?!?! I don't think we should take it seriously as an article about logic! I don't have access to the book - and the little BASIC program in the article uses a horribly exhaustive approach that'll take vastly too long and vastly too much memory for anything with enough complexity to challenge manual techniques. Whatever this technique does, it's clearly not very useful or it would be in common use thirty some years after it's first description. Check out Karnaugh maps and Quine-McCluskey - those are the ways this stuff is done in practice. SteveBaker 15:31, 7 October 2007 (UTC)

Oddly enough the algorithm seems to work and for multiple states too, which I have never encountered. Have you tried any equations which do not work? Also, it sounds like the author is saying that computers are inferior to the concept of God by definition of God being given the attribute of handling an infinite number of variables whereas a computer can not. Seems like this might be in response to an argument by the North Vietnamese Hanoi Hannah during the Vietnam War that logic and therefore computers and therefore the State were superior to God as the basis for any political, social or economic system. Clem 18:17, 7 October 2007 (UTC)

I'm not saying it doesn't work - I'm just saying that it's an exceedingly brute-force approach and (as the author of the BASIC program admits), the amount or RAM and CPU time it consumes goes up very steeply with the number of variables - to the point where he thought his computer could only handle at most 32 variables (I think the algorithm would have taken an insanely large amount of time in that case though. SteveBaker 23:10, 7 October 2007 (UTC)

I wonder if there might be a more efficient method suitable for distributed processing. If so, a large number of variables might be possible, although of course far less than an infinite number, and what contribution such a program might make toward solving complex logical problems. Clem 23:58, 7 October 2007 (UTC)

Why bother when there are so many more efficient ways?! You seem to be under the impression that we don't have perfectly efficient ways to optimise logic expressions - when we're overrun by really efficient algorithms. Just peek under the hood of any modern compiler and you'll find logic and arithmetic optimisers right there in daily use! Read Quine–McCluskey algorithm...please! SteveBaker 13:40, 8 October 2007 (UTC)

The question is, has the algorithm been adapted or can it be adapted to minimization of multiple states? Clem 20:40, 8 October 2007 (UTC)

beams that reflect from bones

for long i'm looking for some rays or beams that can be transmitted and then sensed back as reflection of the same from bones. may be the rays are not reflecting merely from bones but it gets special deflection after reflecting from bones that can be sensed and hence can be concluded that the object from which the reflection has occured is bone. if some one could help... —Preceding unsigned comment added by Neel shah556 (talk • contribs) 16:09, 6 October 2007 (UTC)

X-rays? All waves will be absorbed/reflected/deflected to some degree by bones - and also by other materials in the body. So you can form images with X-rays, with ultrasound, with really bright light (shine a flashlight through your hand for example). The trick is to find waves that won't harm the person in the process of scanning them. SteveBaker 17:02, 6 October 2007 (UTC)

What are you using this for? That probably makes a big difference in whether you use X-rays, T-rays, Ultrasound etc. — Daniel 15:51, 7 October 2007 (UTC)

Lethal acceleration/jerk

How much acceleration or jerk would kill a human being? --Anakata 16:25, 6 October 2007 (UTC)

Our article on g-force says that an unaided human (say, in a plane) will black out at 50m/s² (5 g) in the vertical direction, but can stand 12-17 g in the horizontal direction. "Any exposure to around 100 g or more, even if momentary, is likely to be lethal, although the record is 179 g." More facts and figures can be found in the article. -- 72.33.121.200 16:44, 6 October 2007 (UTC)

The article is interesting. BTW, if 72's comment is a bit unclear the record of 179 g is the record of an estimated g-force which someone is known to have survived. Nil Einne 01:21, 7 October 2007 (UTC)

I thought jerk was the rate of change of acceleration with time. —Preceding unsigned comment added by 88.109.198.32 (talk) 02:50, 7 October 2007 (UTC)

It might be worth discussing what actually causes the physical harm - is it the force, the acceleration, the change of momentum, the non-rigid-body motion which tears up internal organs? All of these are contributions to physical harm in a collision; to isolate the damage due only to acceleration is difficult in practice. It is commonly said that in any single automobile crash, three collisions cause death, in order of increasing harm: 1)the body of the car quickly decelerates; 2) The human flies forward until snapped back by a seatbelt or dashboard; 3) the human's internal viscera slam forward into the front of the ribcage. Nimur 03:55, 7 October 2007 (UTC)

So a seatbelt that 'gives a little' could be a lifesaver because it spreads out the deceleration and thus reduces the jerk? Or are they indeed somewhat elastic? They don't seem it, but it would have to be elasticity that only sets in under a much stronger stress than a human can exert by simply pulling it. DirkvdM 07:50, 7 October 2007 (UTC)

Seatbelts are a little elastic - but that's not the point. The idea is that there shouldn't be a jerk. If you have a 40mph crash and are not wearing a seatbelt, then as the car crumples and slows down gradually from 40mph to 0mph, your body carries on at 40mph. Only when the car has more or less come to a stop do you smack into the dashboard/steering wheel at more or less 40mph. If you are firmly attached to the car - then as the car slows down gradually - so does your body. The seatbelt allows you to slow down gradually and take advantage of the crumple-zones built into the car body. Some cars have seatbelt pre-tensioners built into the seatbelt receptacle down by the parking brake - these fire off like an airbag and pull the seatbelt tight to try to keep you firmly tied to the seat. Seatbelts are a bit elastic though - and after an accident, they are permenantly stretched. For this reason, it's very important to replace the seatbelts after a significant accident. SteveBaker 15:06, 7 October 2007 (UTC)

Ah yes, of course, I get the first bit now. The second bit, does, however seem to confirm what I was suggesting. There is of course still an added advantage to some elasticity in the seat belt. But how much so they stretch? Might there still be some more room for improvement? For the driver, however, there might be the risk of his head slamming into the steering wheel, I suppose. And some people might wear it too loosely, so one has to compensate for that. Ok, never mind then. :) DirkvdM 18:54, 7 October 2007 (UTC)

Yep - a small amount of elasticity obviously helps to decrease the acceleration still further - but (as you can tell from trying to stretch one) - they are designed to stretch only a tiny amount - and even then only under large forces. If you go to a junk yard and look at wrecked cars, you can see how the seatbelts suffer - it's pretty noticable that they've stretched close to the attachment points. One of the things to look for when you buy a suspiciously cheap used car is the state of the seatbelts. SteveBaker 23:05, 7 October 2007 (UTC)

Hmmm, wouldn't the crumpled front be a dead give away? :)

Btw, I can't remember having ever seen a car junk yard in the Netherlands. Or anywhere else for that matter, except in the US. That's worth a new question. Miscellaneous, I suppose. DirkvdM 06:01, 8 October 2007 (UTC)

I'm talking about when less-than-scrupulous chop shops repair the bodywork (or weld together the front end of one car and the back end of another)...the car never drives well again because nothing is straight and all sorts of internal structures have crumpled so the car isn't safe. Those guys almost never replace the seat belts - so you have a cosmetically nice-looking car - with horrific internal damage. Inspecting the seat belts can often tell you a lot. Incidentally, the amount of wear on the seatbelts can often tell you that a car has been 'clocked' (it's odometer wound backwards to make it look less worn out than it really is). SteveBaker 18:14, 8 October 2007 (UTC)

Schizophrenia vs. multiple personality disorder

I just wanted to know how schizophrenia has become confused with multiple-personality disorder. I can't think of many similarities between the two. Was this due to a movie or something?--Avant Guard 17:46, 6 October 2007 (UTC)

Schizophrenia vs. Multiple personality disorder.--Mostargue 18:02, 6 October 2007 (UTC)

The incorrect conflation of the two is pretty logical, actually. The distinction between a "split mind" and a "multiple personality" is not intuitively obvious. I was pleased to learn that The first known misuse of the term to mean "split personality" was in an article by the poet T. S. Eliot in 1933.. --jpgordon^∇∆∇∆ 18:16, 6 October 2007 (UTC)

It might help, Avant Guard, to understand that the original concept of the "split" was between three processes of the mind. The understanding of the situation, the emotion felt about the situation and the response to that emotion. I am grossly simplifying the concept. What is really irritating and frankly misleading is the common use by media idiots who use the term 'schizophrenic' as a synonym for having uncertain or opposing views about something, as in "the US government is showing a schizophrenic attitude to the recent reports from Whateverland". Pah! Richard Avery 21:54, 7 October 2007 (UTC)

Finding acid disassociation constants

Is there a website anywhere that lists Acid Disassociation Constants (ka or pKa) values? I'm trying to find the value for the indicator (also a weak acid) Eriochrome Black T but I haven't had any luck searching on the web. I'm finding a whole bunch of MSDS information but that isn't helping. If anyone has a site they can link to me that would be great.--GTPoompt(talk) 18:30, 6 October 2007 (UTC)

this site has a small list, but doesn't seem to contain the particular acid you're looking for. This page seems to be a journal that undertook extensive research, but unless you're already a member, it looks like you've got to pony up $30 to see the results. I'm no expert, so I can't tell you for sure, but the chart on the upper right hand corner of page 6 (page 26729?) of this PDF may give you a general starting point. --Ybbor^Talk 18:41, 6 October 2007 (UTC)

pKa=6.65 @ 25 C from http://ecb.jrc.it/IUCLID-DataSheets/1787617.pdf page 5 - check for yourself for correctness87.102.115.31 13:22, 7 October 2007 (UTC)

positron

what are the possible positions of a positron in an atom along with their justifications?193.251.135.126 19:13, 6 October 2007 (UTC)

The possible positions of a positron are:

1. Not in the atom

That's all (unless you're talking about antimatter). Positrons have positive charge, and so could not be bound in an atom. I have no idea what you mean by 'justifications'. --ColinFine 20:49, 6 October 2007 (UTC)

It could also be in positronium, which you could consider an atom. Someguy1221 20:57, 6 October 2007 (UTC)

And of course there are radioactive atoms that emit positrons, but that doesn't mean they have positrons in them. The positrons are created in the decay event. -- BenRG 11:46, 7 October 2007 (UTC)

Antihydrogen counts as an atom, surely? Algebraist 14:38, 7 October 2007 (UTC)

I said 'unless you're talking about antimatter'! --ColinFine 20:22, 7 October 2007 (UTC)

psychology

What are the relationships between the parasympathetic division and deep breathing?

What are the relationship between the sympathetic division and jogging? —Preceding unsigned comment added by 4.238.183.72 (talk) 21:08, 6 October 2007 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. See our articles on sympathetic division, deep breathing and jogging. -- 68.156.149.62 02:04, 7 October 2007 (UTC)

Here you can find a discussion on breathing and the autonomic nervous system. Lova Falk 10:36, 7 October 2007 (UTC)