Wikipedia:Reference desk/Archives/Science/2007 August 15

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August 15

xenalights

information on xenalights as a air cooling technology —Preceding unsigned comment added by 72.222.165.50 (talk • contribs)

Xenalight makes a type of fiberoptic light. I do not know of any other product they produce. I do not know of any means of cooling with fiberoptic lights. -- Kainaw^(what?) 03:04, 15 August 2007 (UTC)

Hmm - I agree - it's a fibreoptic light. One claim for such lights is that they can deliver a lot of light without producing a lot of heat becaused the hot lamps can be placed a long way away and the light they generate carried to where you need it down the fibre bundle. So they don't cool the air, but they presumably do a great job of avoiding heating it up. SteveBaker 03:53, 15 August 2007 (UTC)

Cardio and Barfing

I have been doing a lot of intense cardio for the past 6 months, and recently I feel like barfing while running and I cant figure out why. I think its because I drink too much water before and during, but I have always drank a lot of water. Any ideas as to why I'm feeling like this? Thanks —Preceding unsigned comment added by 76.167.145.55 (talk • contribs)

... perhaps there is a difference between "intense" and "too intense" ...? something to consider ... (Joseph A. Spadaro 03:16, 15 August 2007 (UTC))

Motion sickness? Um, don't ask medical advice here, talk to your doctor. ←Ben^B4 03:44, 15 August 2007 (UTC)

I think we are getting a little too broad in our categorizing of questions under medical advice. This issue could certainly be discussed from a theoretical standpoint. Why would one feel nauseous while exercising? Mrdeath5493 04:09, 15 August 2007 (UTC)

I used to play soccer at a fairly competitive level and our coach would often make us run to the point where people would vomit. There's also anecdotal evidence linking intense cardio and vomiting with lactic acid build-up. Heat exhaustion, altitude, or simply overdoing it could also be relevant factors. Also, maybe read this [1]. The preceeding does not constitute medical advice, consult your physician, etc. -- 38.112.225.84 04:52, 15 August 2007 (UTC)

The cardio I used to do was way more intense, actually thinking about it, what I'm doing right now isn't really intense. I never really had this problem before, I think if it was motion sickness, it would have been present in the past.

I know when pushing too hard I use to get nauseous, but never when I was not pushing too hard or too long.

Same altitude in an air conditioned gym (I dont really even sweat a lot, well not excessively. Thanks for the article and everyones help.

I seriously disagree. When someone says "I'm exercising and I'm having these problems" they really need to see a doctor and we should tell them that. Discussing stuff from a 'theoretical' viewpoint in a case where someone needs to see a doctor it a very bad idea! Perhaps if the poster had said "I was speaking to a person I met in the gym and he said he was exercising a lot and..... This got me thinking, what could have caused this person's problems", then probably discussing things from a theoretical view point would be okay. (but please don't take this as an example to phrase your question so). Nil Einne 11:15, 15 August 2007 (UTC)

It could simply be a bad case of acid reflux from all that water, indeed.

This could be a brain tumor, too. Again, see a doctor. ←Ben^B4 17:49, 15 August 2007 (UTC)

You are telling us that something has changed which could have a serious cause. You really need to see a doctor so it can be checked out. Skittle 18:56, 15 August 2007 (UTC)

See this. Of course he needs to see a doctor, but that doesn't mean that the topic is off limits, does it? Are we to never mention nausea and exercise together again? Does it need a new thread? After 3 people declare that we can't give this person specific medical advice and to see a doctor, it seems perfectly acceptable to discuss this exact topic theoretically. I personally have nothing to add, because I'm not familiar with why this would happen. However, I fear that others who might be able to contribute something are being improperly discouraged.

Furthermore, if you actually read the Medical Disclaimer, you might notice that it does not prohibit such discussion. It just warns users to seek professional advice and not to rely on information submitted by users. It certainly seems to license theoretical discussion, rather than forbid it.
Mrdeath5493 19:31, 15 August 2007 (UTC)

The medical disclaimer applies to articles - the ref desk has different rules - one of which is: "The reference desk is not a place to seek professional advice on medical or legal matters, nor analyses, diagnoses or solutions to questioners' health or legal problems, and responses that could be construed as such must not be given." - so, nothing that could be construed as a diagnosis is allowed - which would obviously include "It could simply be a bad case of acid reflux". Writing a referenced article about some medical matter is OK - but issuing a diagnosis of a particular patient is to practice medicine without a license - which is illegal in many places in the world. SteveBaker 19:57, 15 August 2007 (UTC)

There must be some circumstance under which we could theoretically discuss cardio and barfing. What are the boundaries? Not under this thread? Not within so many days of the asked question? Is some sort of disclaimer at the beginning of an answer required? Or is it just off limits forever since someone asked about it in a way that seemed to be seeking medical advice (certainly not, I assume)? Don't think I'm being snarky, either. Discussing this can not be completely off limits. There just needs to be some explicit way of indicating that we are not giving medical advice. (I think the medical disclaimer is enough, but whatever.) I'm not sure anyone wants to diagnose or treat OP's that ask questions like this. These sorts of questions raise curiosity (at least they do in me) and I would like to see some sort of educated response. I think that people that are capable of answering such questions (from a standpoint that in no way diagnoses or treats the OP) are being unjustly discouraged

Mrdeath5493 00:19, 17 August 2007 (UTC)

I think the rules are pretty clear. Here on the reference desk, we are answering one specific person's question - and the advice we give could therefore be interpreted (by some blood-sucking lawyer) as diagnosing that persons medical condition. That's a no-no. Over in article space, we are not talking to a specific individual - we're obviously talking in general terms which means that we haven't heard a specific individuals list of symptoms and we can't possibly be said to be diagnosing that individual. A disclaimer that tells people who read that article that it's not specifically talking about them is legally defensible (we hope!) - but that disclaimer simply can't work here where we most definitely are giving medical advice to someone who came here to ask about their symptoms. So here on the ref desks - GIVE NO MEDICAL OR LEGAL ADVICE. It's a rule - it's a really simple rule. I think it's quite impossible to talk about cardio & barfing "in general terms" when we're responding to a particular person who claims to have those exact symptoms. Like it or not, what you say COULD be interpreted as offering him advice - which is flat out illegal in most places in the world. Perhaps there are some weasel-words that might get around that - but precisely because that is such a vague thing - and because Wikipedia itself could get dragged in as you get sued, we have to have a rather over-arching set of rules just to be on the safe side. So - discussing this most certainly can be off limits (and I believe it IS off limits in this case). You may think the rule is a bit over-the-top and that some improvement to it could be made - and I'm sure there is a forum where that can be discussed - but the rule is currently what the rule is, and you shouldn't break it. Look - it's only a matter of time until someone asks a medical question, someone here says "oh - this happens all the time - don't worry about it" (or something like that) - then, comforted that this is nothing, the person doesn't go to the doctor and subsequently dies. His grieving parents (or perhaps their insurance company) examine his PC's browser cache looking in desperation for anything that can explain their loss. They find the Wikipedia question - and find the answer given here - and in a fit of grief-stricken rage (or profit-driven search for a way to weasel out of a $5,000,000 payment) decide to sue Wikipedia. Wikipedias lawyers examine the situation and discovered that you violated the ref-desk's rules - as clearly laid out and often discussed here. Now the lawyers of (the insurers of) the parents of the dead kid turn on you - and in whatever state you and they live in, there is a law that says it's illegal to perform medicine without a license. Now YOU, PERSONALLY are being held liable to the kid's death - that's involantary manslaughter - you spend a large fraction of the rest of your life in jail and the accompanying fine bankrupts your wife and kids. Yeah - that's how serious this is! So - by all means campaign for a change in the rules (I'll be strenuously opposing you - so will others - which means you won't get a consensus for a change - so it won't happen). But right now, you have to obey the rules. I think we should take this more seriously - I think we need an admin to start handing out 24 hour bans to people who violate the rule so it's taken more seriously. SteveBaker 03:16, 17 August 2007 (UTC)

Well, at least I made my point clear. From the standpoint of practicality, you have swayed me. Although the situation you described is highly unlikely, it is totally possible. For it not to happen, I guess the structure of the rule in question should be overprotective. In a risk/reward analysis, there is comparatively little to gain and too much to lose.

On a side note, I got my undergraduate in Philosophy. Excellent argument. Too bad your not a lawyer...

Mrdeath5493 05:35, 17 August 2007 (UTC)

Journal Cell Publication Period

Is the journal "Cell" published biweekly or bimonthly? The disambiguation page for the word "cell" says it is bimonthly, but I understand it to be biweekly, which is what the main article says. Is there a difference I am missing, or can I change this? 131.215.240.27 03:28, 15 August 2007 (UTC)

It's published biweekly (every two weeks). I'll change the disambiguation page. Flyguy649 ^talk _contribs 03:32, 15 August 2007 (UTC)

There is general confusion over bi-, some people using it as "twice-" and some using it as "every two". There is a similar confusion over semi-. It might be worth avoiding using these prefixes where possible. Capuchin 08:16, 15 August 2007 (UTC)

For biweekly you could use fortnightly I guess but what about bimonthly? Every two months? Bimestrial is probably more confusing. The confusion may partial arise from biennially I guess Nil Einne 11:06, 15 August 2007 (UTC)

Glazing

what is segar formula,please elaborate —Preceding unsigned comment added by Naray2007 (talk • contribs)

Do you mean agar? Lanfear's Bane

Or sugar? Capuchin 11:49, 15 August 2007 (UTC)

A quick google turns up that it's something to do with the chemical composition of pottery glazes. Nothing stands out as being particularly enlightening, though. 147.197.230.174 11:58, 15 August 2007 (UTC)

According to [2]:

Segar Blue Glaze - cone 9-10

(KPG)

3360 G-200 feldspar

1440 whiting

1040 ball clay

2160 flint

240 rutile

320 red iron oxide

----------------------------------------------

8560

(I hope this means more to our OP than it does to me!)

SteveBaker 12:42, 15 August 2007 (UTC)

I was thinking more of glazed doughnuts (mmmmmm). Capuchin 13:09, 15 August 2007 (UTC)

If you like your doughnuts glazed in ground up flint and red iron oxide...go ahead. If you're hungry, I think there is still some of that cookie left - about five posts up from here. SteveBaker 13:13, 15 August 2007 (UTC)

READING BURRETTES IN TITRATION

Assuming you are given a 50litres burrate which are not callibrated stepwiselly i.e each location isnt labeeled, can u take the burrete reading in the opposite direction knowing well that you will arrive at thesame answer. i.e

INITIAL READING 50.00 35.00

FINAL READING 35.00 15.00

Knowing well that the reading of a callibrated burette is

00.00 15.00

15.00 30.00

BUT IT IS STILL THEASME VALUE OF ANSWER.

OKEWOLE OLUWASEYI

—Preceding unsigned comment added by 80.88.140.24 (talk • contribs) 10:51, 15 August 2007

If you mean what I think you do, yes, it's the difference between the values that's the titre. (Also, a 50 litre burette?) 147.197.230.174 10:57, 15 August 2007 (UTC)

I somehow think a mili was missing from somewhere. Nil Einne 11:00, 15 August 2007 (UTC)

Wow! A coral atoll (click on the link) was missing? Maybe you mean a milli...? :-) Carcharoth 16:22, 15 August 2007 (UTC)

One half of a lip-synching vocal duo? Edison 17:59, 15 August 2007 (UTC)

Internet in Africa

I'm looking for a map that shows the distribution of internet access (or something along those lines) in Africa. My dream would be to find something about cross-border internet connections in Africa (who's communicating with whom, etc.), but I doubt there's anything about this topic in particular. So any type of map in that direction would be interesting: Internet access, internet usage, possibly the most important internet cables (i.e. hardware), you name it.

Do you have any idea where to find that kind of materials? Thanks, Ibn Battuta 16:55, 15 August 2007 (UTC)

PS: I'd rather use materials that do not just display information for each country; if possible, I'd like to prevent using political borders as sorting criteria. Thanks, Ibn Battuta 17:02, 15 August 2007 (UTC)

Many areas in Africa are not well served by terrestrial Internet, but there are at least ten separate providers of satellite IP service taht covers all of Africa. When you use satellite service, each terminal is topologically "closer" to the hub and the the Internet core than they are to each other: the ping time from such a terminal to Wikipedia is approximately half the ping time to a terminal in a village 20 km away, and the IP addresses reflect the IP address space of the hub, not the African country. Each ISP's hub can be anywhere that is visible to the satellite, e.g. in Europe. Of course, much of the population will be in larger towns and cities with terrestrial internet connections ranging from poor to excellent. -Arch dude 17:21, 15 August 2007 (UTC)

The Internet isn't like the telephone network. You can't tell who is talking to whom by looking at a wiring map of the Internet - there is no way to know whether the bulk of the traffic from (say) South Africa is going to Wikipedia's servers or in local communications or in communications with users in (say) Kenya. Even if people in Kenya and South Africa were talking to each other in great numbers, the odds are good that they'd be using Gmail or MySpace to do it - so the actual communication pathways would probably still go to big servers outside of the African continent even if two people in the same town were talking to each other. For example - my sister and I use the same mail server (my Webhosting company gives me 700 free email accounts - so why not?) - but she lives in UK and I live in USA. When she emails her neighbour, the email travels from UK to USA, where it sits on the server and is then sent off to the neighbour in UK - how could you possibly tell the difference between a communication between two people in the UK and a communication to a location in the USA? You are asking a question that cannot be answered - even in principle. SteveBaker 17:37, 15 August 2007 (UTC)

Maybe I didn't express myself clearly enough: I'm looking for maps, not just general information. :o) And yes, I'm very aware that the internet doesn't work like the phone, that's why I said the information is probably not available. (It would require extensive surveys, which are probably not even available for industrialized nations.) So the other option are maps of 1.) hardware (e.g., those hubs -- are there maps about their distribution? Else I've found so far only this map) or 2.) statistics (how many households use the internet, how many hours/week or /month do people spend online on average etc.). Thanks, Ibn Battuta 18:18, 15 August 2007 (UTC)

Hole in a spacesuit

An astronaut doing a spacewalk had to return to the shuttle early today because of a tiny hole in the outer layer of his glove. That got me thinking -- just what would happen if that tiny hole had penetrated through all the layers of the glove? Would the astronaut had suffocated (as would happen with no spacesuit at all)? -- Mwalcoff 22:46, 15 August 2007 (UTC)

A micrometeorite, a sharp edge from a broken piece of metal or a tool, or even the end of a piece of wire could cause a puncture. The NASA Extravehicular Mobility Unit, the space suit used on extravehicular activities is apparently one large pressurized system, and a leak anywhere would soon bleed away the oxygen needed to sustain life.[3] The life support system would release stored oxygen, so the size of the hole which cause a leak would be an important factor. A pinhole would lead to a sudden end to an EVA and a race for the airlock. A large cut might be catastrophic. In sci fi stories, there were devices such as pressure cuffs in space suits which could be suddenly inflated to seal off the hand, foot, arm or leg which had the leak, preserving life at the cost of injury to or loss of the isolated part. Again, time would be of the essence. The suit reportedly has only 4.7 pounds per square inch, less than 1/3 of normal Earth air pressure, so direct pressure on a puncture would slow the leak. A sticky patch (think NASA quality duct tape) held on with pressure could seal many leaks, but I have not seen that they have that readily available. They do have a rule to inspect the gloves every half hour because of tears found in the past which penetrated the outer layer. Self sealing suit and glove materials have been developed which have in the lab sealed 2 mm holes, with research ongoing to extend the capability to 4 mm holes [4]. This self-sealing capability would add 15 pounds or 5% to the EMU mass, an would increase the mass much less if only applied to the gloves, but making the gloves thicker without losing dexterity might be a challenge. I would at least go with Space Duct Tape. Edison 23:11, 15 August 2007 (UTC)

Michael L. Gernhardt was aked this question. [5] His response:

"If we got a small hole [in our spacesuit], our oxygen would start coming out of the spacesuit, and the pressure would start to drop. If the pressure drops too far, then you'll get the bends, and if it drops below about 2.5 psi, then you don't have enough oxygen to maintain useful consciousness. Now, we have a device called the Secondary Oxygen Pack on the back of our backpack, and it's got a whole lot of oxygen in it, and it would be able to support a small leak for—depends on how small it is—but for at least 30 minutes. So for a small leak, we'd have our secondary-oxygen system kick in, and we'd be heading back to the airlock and repressurizing, and we'd be fine. A big leak—like a big hole in the suit, say a half-inch hole or something like that, or if your glove blew off—would pretty much be a real bad day for you." Rockpocket 23:15, 15 August 2007 (UTC)

I'm sure I remember reading that very small holes to appear in suits and they are not noticed until returning to the space craft, because they are too small (i mean bordering microscopit) to notice or to have much effect. SGGH ^speak! 00:17, 16 August 2007 (UTC)

I'm not answering the initial question here but you may want to google self healing polymers which can potentially heal damage to their structure many times... try [6] for a bit of interesting info. --Cosmic joker 00:47, 16 August 2007 (UTC)

In the movie Event Horizon, one of the crew members goes into an airlock and floats out into space without a suit. Blood comes out of his eyes and stuff. They get him back and he survives. Is that survival realistic? --Seans Potato Business 00:36, 16 August 2007 (UTC)

See Vacuum#Effects_on_humans_and_animals, Human_adaptation_to_space#Effects_on_humans and Explosive decompression. Exxolon 00:50, 16 August 2007 (UTC)

Something similar happens in various moments throughout the Gundam franchise, Generally someone closes their eyes and covers their ears, opens something suddenly enough that the oxygen rushes out and 'manages to survive' by staying within the oxygen stream until they get to whatever they were jumping to (which generally is only a few seconds) --Lucid 02:35, 16 August 2007 (UTC)

So the aptly named scientist Robert Boyle put small animals in a vacuum and observed the effects. Perhaps they felt "ebullient." The scene from "2001 Space Oddesy" is plausible, in which a man survives brief vacuum exposure. Edison 04:04, 16 August 2007 (UTC)

You would think that NASA could just have astronauts wear a standard high altitude type masks insider their helmets. Then even if there suite was punctured they’d still get oxygen. Yes, the person might suffer decompression sickness and might eventually freeze to death after a long while, but they would have a much greater chance of making it back to the lock or being rescued. --S.dedalus 06:19, 16 August 2007 (UTC)

S.dedalus, that's exactly what I'm wondering: Can you survive in vacuum as long as you can breath and don't freeze to death? If so, I really don't understand why they don't have a two-part suit, with a mask for oxygen, and mere heating for the rest (plus a bit of pressure as long as necessary). I'm sure that NASA debated that at some point and apparently rejected the idea. So is a vacuum just below the pressure that a human body can survive? Or what is the problem? --Ibn Battuta 07:53, 16 August 2007 (UTC)

The standard NASA and Russian suits have been filled throughout with one zone of breathable gas, pure oxygen at relatively low pressure. The low pressure may make it easier to move around, since the curse of space suit design has been that if bending reduces the total volume, the gas pressure resists the movement. A lot of cleverness has gone into making joints such that bending the arm or leg does not cause a volume change. A new proposal, "skin tight suits" is discussed in Space suit. These would have a skin tight pressure garment (with heating or cooling, naturally) surrounding the body with a gas supply only to the face. That way, movement would not be opposed by the gas pressure. If such a suit were punctured, there could be tissue damage from fluid exposed to the vacuum boiling, or from simple blood loss accelerated by the lack of external air pressure, but see the "space duct tape" notion above for possible repairs. There are sharp edges from rocks on the moon and mars as well as when working with equipment in extravehicular activities. If there is ever conflict in space, it would be useful to not have an impact from a small projectile not be inevitably quickly fatal. A Mars explorer with a hole in the arm of the skintight suit (which did not threaten the continuity of the breathing air supply) could rescue himself much more easily than if the oxygen were rushing out at a rate which dropped the breathing supply to too low a pressure to sustain life, or which quickly used up the supply in the tank. Such a suit would have to have a moisture absorbing layer, to allow the skin itself to "breath" by expelling moisture. The present suits have a life supprt system which absorbs this moisture. Edison 16:10, 16 August 2007 (UTC)

The only known suit puncture was partly sealed by the astronaut's own blood (on STS-37 [7]). And wasn't noticed until examination back on Earth so a puncture need not be catastrophic. Rmhermen 01:18, 17 August 2007 (UTC)[8] Rmhermen 01:18, 17 August 2007 (UTC)