Wikipedia:Reference desk/Archives/Science/2010 April 26

= April 26 =

Stingray question
Do stingrays make a sound. I have looked extensively and have not found anything about stingrays making noises of any kind. thank you for considering this question. :)174.97.235.163 (talk) 00:45, 26 April 2010 (UTC)pat


 * Somehow I doubt it, as most fish don't (at least nothing we can hear). StuRat (talk) 00:51, 26 April 2010 (UTC)
 * Did you have something in mind, particular to a stingray? I used to have an electric catfish as a pet and it made lots of noise at night while electrocuting the minnows.  Perhaps a stingray makes a sound (in the most general sense of 'making a sound') when it thrashes it's stinger into predator/prey...I mean, more so than a goldfish, let's say.  DRosenbach  ( Talk 01:27, 26 April 2010 (UTC)
 * In this youtube video you can hear a clicking noise and you see a stingray: Octopus Attack - Fuertaventura 2009. Cacycle (talk) 06:53, 26 April 2010 (UTC)


 * Of course every type of fish makes sound as a result of water sliding over its body. When it comes to other types of sound, I wasn't able to find any reports in a quick Google Scholar search.  There are apparently certain types of fish that "vocalize" by vibrating their swim bladders, but elasmobranches (sharks and rays) don't seem to be among them as far as I can tell. Looie496 (talk) 17:10, 26 April 2010 (UTC)

is there an exit valve? what about on the scuba fireman where? and on oxygen tanks in a ambulance or hospital?


where does the exhaled air go —Preceding unsigned comment added by Tom12350 (talk • contribs) 01:36, 26 April 2010
 * This question was answered above. Look for the section about 2-3 days ago labeled "scuba".  -- Jayron  32  02:40, 26 April 2010 (UTC)

no they answered about scuba not scuba fireman where and on oxygen tanks in a ambulance —Preceding unsigned comment added by Tom12350 (talk • contribs) 05:21, 26 April 2010 (UTC)


 * In a hospital or ambulance oxygen is normally given in two ways. In an emergency where a patient has collapsed and respiration is administered with a mask and pump bag the pump bag apparatus has an exit valve. When oxygen is given over a longer period with a light mask or little tubes at the entrance to the nose then the excess oxygen just dissipates into the atmosphere as there is no closed circuit to contain it. I suspect that the equipment used by firemen is similar in design principle to an underwater scuba, a closed circuit with a one-way exhaust valve. Richard Avery (talk) 07:21, 26 April 2010 (UTC)


 * On the side of the mask. See if this article helps: Firemens SCBA apparatus and and Oxygen maskAnd see diagram on the right  --Aspro (talk) 07:23, 26 April 2010 (UTC)


 * And again, to be pedantic - the firemans' apparatus is an "SCBA" because the 'U' in "SCUBA" stands for "Underwater". SteveBaker (talk) 12:17, 26 April 2010 (UTC)

you say "light mask or little tubes at the entrance to the nose then the excess oxygen just dissipates into the atmosphere as there is no closed circuit to contain it."

but hows that because isint the mask tight? like is this pic ?

http://thumbs.dreamstime.com/thumb_54/1145221626xhnGC8.jpg

or this

http://fransonchiropractic.files.wordpress.com/2009/04/oxygen20mask.jpg

or this

http://www.watersafety.com/rescue-and-response-equipment/images/4225023.jpg —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:07, 26 April 2010 (UTC)

milk
can buffered solutions like milk be used to naturalize acids or will it not work cause its buffered. —Preceding unsigned comment added by Tom12350 (talk • contribs) 01:55, 26 April 2010 (UTC)
 * So long as you don't exceed the buffer capacity of the milk, yes, it can be used to neutralize acid. The property of a buffer is that it works to neutralize BOTH acid and base (more properly, a buffer is something that maintains a constant pH with the addition of either acids or bases).  See buffer for more info.  -- Jayron  32  02:39, 26 April 2010 (UTC)

what is the "the buffer capacity of the milk" —Preceding unsigned comment added by Tom12350 (talk • contribs) 05:20, 26 April 2010 (UTC)


 * Please start signing your posts by using four tildes like this: ~ . Please read the Buffer solution article for more info.  A buffer is basically an acid and its conjugate base.  That is, it consists of a pair of compounds that differ by a hydrogen ion, for example a solution that contained both acetic acid, HC2H3O2, and the acetate anion, C2H3O21- would be a buffer.  It works because, by adding either acid or base, the conjugate acid/base pair works by reacting with either an added acid OR an added base, and so neutralizes either.  Also, because the system is a dynamic equilibrium, the system obeys Le Chatelier's principle such that it resists all changes to return to its initial state.  The buffer capacity merely means that the buffer only exists so long as both parts of the conjugate acid/base pair exist in the solution.  If you add so much acid that you use up the base part of the buffer, then you no longer have a buffer, and you have exceeded the buffer capacity.  -- Jayron  32  05:27, 26 April 2010 (UTC)


 * Additionally, you should probably also read up on Brønsted–Lowry acid-base theory which is the basis for understanding how buffers work. -- Jayron  32  05:30, 26 April 2010 (UTC)

i already read those. what is the "the buffer capacity of the milk" —Preceding unsigned comment added by Tom12350 (talk • contribs) 06:35, 26 April 2010 (UTC)
 * I just explained that. A buffer consists of an acid and its conjugate base mixed together in water.  If you add too much additional acid, you will consume all of the base, and thus destroy the buffer.  -- Jayron  32  12:02, 26 April 2010 (UTC)
 * I'm not sure but perhaps the OP wants to know what the buffer capacity of milk actually is, not what it means. Having said that I wonder whether the OP actually properly understands buffer capacity or thinks it's a simple value that tells you precisely how 'powerful' a buffer is. In any case, the buffer capacity would vary depending on the type of milk I presume. Edit: These should provide a basic overview on what the buffer capacity of milk actually is  . Also  if you can find it. Nil Einne (talk) 12:32, 26 April 2010 (UTC)


 * With a complex solution like milk, it would be quite impossible to calculate directly. You could certainly do an experiment to find the value for yourself. You would need to titrate the milk dropwise with a strong acid, and track the effect of the added acid on the milk's pH. Then you would need to do the same experiment, but with fresh milk and a strong base. The resulting graphs should tell you roughly how much acid or base you can add before exceeding the buffering capacity of the milk. (after edit conflict) It looks like Nil Einne found the results of some of those experiments above. -- Jayron  32  12:46, 26 April 2010 (UTC)


 * Yes is probably the most useful but needs a subscription. I have a tendency to reply and then search so often add my results after. I guess I should stop WP:AGF that the OP actually did a simple search before asking the question :-P Nil Einne (talk) 13:18, 26 April 2010 (UTC)

i dont need a exact value just a estimate. anyone know? —Preceding unsigned comment added by Tom12350 (talk • contribs) 21:56, 26 April 2010 (UTC)


 * From the article that requires a subscription: At pH7, the buffering capacity (dB/dpH) looks like it's around 0.02. It changes a lot depending on pH - eg. at pH 6 it's closer to 0.03. Aaadddaaammm (talk) 13:43, 27 April 2010 (UTC)

hats that mean? how strong a acid can it be used on —Preceding unsigned comment added by Tom12350 (talk • contribs) 21:15, 27 April 2010 (UTC)
 * "Used on" to do what? Maybe if you rephrase the original question, with more specifics about what you're actually trying to do we could help more. Aaadddaaammm (talk) 10:36, 28 April 2010 (UTC)

Source of pneumonia in bedridden elderly?
From what sources do the elderly often contract pneumonia? I'm thinking of bedridden individuals in nursing homes who are not likely to be able to spread it to other individuals in similar conditions, and who (because they're in the nursing home, not in hospital) by definition can't get hospital-acquired pneumonia. I don't see anything in our article that discusses the question, since it seems unlikely to me that the large number of elderly people who die from it are all infected with fungi, parasites, pneumonia-causing bacteria, or pneumonia-causing viruses when those around them don't have any of these problems. Nyttend (talk) 02:29, 26 April 2010 (UTC)
 * I think part of the problem is a lack of ability to clear the lungs while bedridden. Thus, any standard cold or flu can cause fluid accumulation in the lungs, which can suffocate the bedridden person.  I am pretty sure that is the impression I get from the issue.  I could be wrong though.  -- Jayron  32  03:50, 26 April 2010 (UTC)
 * Also see the short article Aspiration pneumonia, which describes any non-infectious pneumonia caused by the inhalation of material, including one's own saliva and mucus. My guess is that this could explain many of these elderly, bedridden pneumonia cases.  There's also Idiopathic interstitial pneumonia, "Idiopathic" being doctor speak for "We haven't the faintest clue what is causing this".  -- Jayron  32  05:37, 26 April 2010 (UTC)

Hubble's "visible spectrum" image of the Carina nebula
I'm wondering what the moon, or the earth would look like if an image were compiled in the same way that the Carina nebula was. (wavelengths detailed here). Is it relatively simple to attempt this? 219.102.220.42 (talk) 02:30, 26 April 2010 (UTC)


 * If you could obtain the raw images taken at those wavelengths which record  those spectral colours then yes. One could easily do the next stage of combining and balancing them in to one image. This image manipulation could be done with GIMP (which I have noticed the Jet Propulsion Laboratories in Pasadena have used)  or Photoshop, etc. This web page explains in plain language,  the technical bits about what needs to be  recorded .|DSLR Cameras and H-a Emission Nebulas. And what would Earth and the Moon look like? Well I sure: if people were able to mentally work that out, there would be no point using these imaging technique in the first place. However, the | United States Geological Survey Spectroscopy Lab has some images of Earth. And the Jet Pro Lab  has some images of the moon.  As always, Wikipedia has some articles:Imaging spectroscopy, Moon Mineralogy Mapper.--Aspro (talk) 08:00, 26 April 2010 (UTC)


 * Which elements do you want to use to make your images of the moon/earth? The picture basically shows areas where one element or another are more concentrated. If you use elements in the earths atmosphere, you'll have a white circle and nothing more, since those are basically perfectly mixed. If you choose elements on the ground, you'll see colors showing you where the elements you chose are more/less concentrated. Ariel. (talk) 08:05, 26 April 2010 (UTC)


 * Those nebula are emission nebulas wich emit light at particular wavelengths in a line spectrum. The earth and moon reflect are much more continuous spectrum, and so are not so easy to establish elemental composition by transition lines.  In visible light what you see will be a good clue, eg yellow iron oxide, green chlorophyll. Graeme Bartlett (talk) 09:10, 26 April 2010 (UTC)

Dibenzodiazepines follow-up
I notice all the compounds listed in Category:Dibenzodiazepines are antiaromatic. So it must not be a coincidence. I guess the antiaromaticity destabilisation must not be very large? I'm curious about the relationship between conformation and agonism / antagonism of the target receptors. AFAIK lysergic acid compounds are planar ... right? Or are they? I notice some resonance structures are antiaromatic in LSD too. John Riemann Soong (talk) 03:24, 26 April 2010 (UTC)
 * What counts most for receptor binding are shape and charge. Antiaromaticity per se does not have a direct effect on binding (whereas aromatic rings allow for specific interactions such as pi stacking). Cacycle (talk) 06:49, 26 April 2010 (UTC)
 * Regarding LSD, the indole part is definitely aromatic. If you're considering "all the resonance possibilities" (treating them as distinct structures that contribute to the overall "real" average structure), you can mostly disregard antiaromatic ones if there are others that are aromatic. If you have an alkene or lone-pair or something that "maybe could resonate into a ring, but that would make antiaromaticity", that piece of the structure probably does not do that, and thus acts like an independent functional group. DMacks (talk) 08:47, 26 April 2010 (UTC)


 * Thanks... I was wondering because it doesn't appear to be a factor in LSD, whereas I can envision resonance structures in clozapine that would make it aromatic, not antiaromatic, e.g. by simply drawing benzene a different way. You know what I mean? John Riemann Soong (talk) 20:11, 26 April 2010 (UTC)


 * If you're interested in stereoelectronics in medicinal chemistry, you might like to get a good book on the topic, like this one, or search the literature. I did a quick Google search for "stereoelectronic QSAR" and found several interesting-looking articles, including Dynamic QSAR: A New Search for Active Conformations and Significant Stereoelectronic Indices.


 * Further Wikipedia articles of interest:
 * Electronic effect
 * Pharmacophore
 * Quantitative structure-activity relationships


 * Books you could borrow from a library:
 * A. J. Kirby (1996) Stereoelectronic Effects (Oxford Chemistry Primers)


 * Ben (talk) 19:16, 26 April 2010 (UTC)

Life expectancy of nuclear power plants.
What is the average life expectancy of a nuclear generating station? How do plants built in the US differ from ones overseas in terms of longevity? ataricom (talk) 05:00, 26 April 2010 (UTC)
 * According to Nuclear power, a reactor can last as long as 40-60 years. Dismas |(talk) 07:27, 26 April 2010 (UTC)
 * Not if they are destroyed by sea level rise. ~ A H  1 (TCU) 23:14, 28 April 2010 (UTC)
 * So don't build them so close to water. BTW, isn't one of the reasons for building nuclear reactors the fact that they can generate electricity without polluting the atmosphere (barring an extremely unlikely Chernobyl-style catastrophic nuclear meltdown, of course)? 76.103.104.108 (talk) 02:08, 29 April 2010 (UTC)

Ant for ID
Hello! I must catch 10 of this type of ant everyday in my house. Is this a fire ant or a carpenter ant? What is the best way of getting rid of them, sort of calling an exterminator as a last resort? Could they be living outside my house in nests or in my house's foundation? I've found winged ants in my house, as well, which, as I understand, are the ones who help reproduce. Is that a bad sign? Any advice appreciated. Thanks.--el Aprel (facta-facienda) 08:17, 26 April 2010 (UTC)
 * If this was Australia I would say you had a sugar ant. Fill up all the holes they may come in through.  You can spray poison around, but may poison you and may not last either. Graeme Bartlett (talk) 09:04, 26 April 2010 (UTC)


 * I'm not sure, but it does look like Camponotus sayi, red carpenter ant, to me. Red link for the red ant - isn't it ironic? Not really a harmful critter, there are much worse than it; but it can build nests (colonies) in wooden structures which is not something homeowners generally like. This article gives suggestions on how to deal with them, if that ant is really what I think it is. As I said, I am not sure. --Dr Dima (talk) 10:07, 26 April 2010 (UTC)


 * There are some more photos of Sayi on Wiki Commons --Aspro (talk) 12:50, 26 April 2010 (UTC)


 * Thanks! Forgot to mention I live in Florida. Are Camponotus sayi ants common here?--el Aprel (facta-facienda) 19:30, 26 April 2010 (UTC)


 * No. Unless of course, their there on vacation. 'Florida' has however, narrowed it down a bit. Here's our next suggestion. Go to | Florida Ants. On the right hand column, under the heading 'Tools” is a link entitled - Florida ants in Google Earth. This link then gives you a map of which ants occur in which localities. I don't know how accurate it is but it looks impressive.  In the mean time, see if they like water with some sugar added, because then use could try using  borax.--Aspro (talk) 20:43, 26 April 2010 (UTC)
 * Did you mean to type "THEY'RE there on vacation"? Cuddlyable3 (talk) 23:45, 26 April 2010 (UTC)


 * Mix a little jam with borax and smear it inside saucers, jar lids or the like, and leave them near where you find the ants. Replace daily. The ants come and eat the jam, and the borax poisons them. You get borax from places which sell old-fashioned cleaning materials (it's jolly useful stuff). DuncanHill (talk) 22:02, 26 April 2010 (UTC)

You could also get borax (sodium tetraborate decahydrate) at the grocery store. It is normally sold there for laundry freshening and a host of other uses. Are you sure you aren't talking about boric acid though? --Cheminterest (talk) 22:16, 26 April 2010 (UTC)


 * Not many grocers here sell borax anymore. I get mine at Boots the Chemists, and some old-fashioned hardware shops have it. Yes, I'm sure I mean borax. DuncanHill (talk) 22:32, 26 April 2010 (UTC)


 * I had a look at the "Florida ants" website, and think this is a Camponotus decipiens ant. I will try the borax solution. I remember treating another ant species, fire ants, with a powder poison that tricked worker ants to take back to their queen as food and exterminate the colony by killing the queen. Is there any poison like this for these carpenter ants? My guess is the borax solution only kills the ants that forage for it.--el Aprel (facta-facienda) 22:53, 26 April 2010 (UTC)


 * I think the powders of which you speak will contain borax or boracic acid. I've used the sweet borax mixture before, and after a few days what had been a steady stream of ants had reduced dramatically. DuncanHill (talk) 23:15, 26 April 2010 (UTC)


 * You will know if you have made the solution too strong because you will see dead ants. You want them to live long enough to get back and feed the others. The advantage of using borax has been already mention – its useful for so many other things and easier to buy.--Aspro (talk) 23:30, 26 April 2010 (UTC)


 * It you really want to see dead ants, you can leave out watermelon slices soaked in turpentine. They are highly attracted to the sugar, but the turpentine dissolves their exoskeleton.  In the morning, you end up with a lot of black smudges, which clearly identifies the path they were using to get back and forth between the watermelon and their nest. --  k a i n a w &trade; 00:41, 28 April 2010 (UTC)
 * Be careful with the turpentine and watermelon. Make sure no young child tries to eat it. --Chemicalinterest (talk) 11:50, 30 April 2010 (UTC)
 * I live in the United States, and I can buy borax at Pathmark or Shoprite easily in the laundry section. --Chemicalinterest (talk) 11:50, 30 April 2010 (UTC)
 * You can buy some ant traps (some say "kills the queen") at certain stores. --Chemicalinterest (talk) 11:50, 30 April 2010 (UTC)

Mold
Is mold killed by pouring boiling water on it? 87.108.22.140 (talk) 09:02, 26 April 2010 (UTC)
 * Yes if you can heat it to close to 100 degrees. Eucaryotes are not good at surviving high temperatures. You may be left with a stain however. Graeme Bartlett (talk) 09:06, 26 April 2010 (UTC)
 * Thank you! I knew I could rely on Wikipedia! 87.108.22.140 (talk) 09:10, 26 April 2010 (UTC)
 * Also remember that mold is not just the blue stuff on the surface, but has hyphae in the material ti is decaying, you have to heat that too. And also mold may make poison in food, so don't just rely on boiling to make it fit for eating (if it is food). Graeme Bartlett (talk) 10:31, 26 April 2010 (UTC)

100 degrees C, right? Also, for what it's worth Aflatoxin is the stuff you still have to worry about even after the mold is dead. --144.191.148.3 (talk) 18:35, 26 April 2010 (UTC)
 * Yeah 100° F will just make it wet. Graeme Bartlett (talk) 21:44, 26 April 2010 (UTC)

Using a solution of sodium hypochlorite will kill mold too, and turn whatever it is poured on white. --Cheminterest (talk) 22:13, 26 April 2010 (UTC)

CCs?
Are CCs listed on Wikipedia?

eg, 10cc ( or 10ccs )

- 193.61.111.53 (talk) 11:15, 26 April 2010 (UTC)


 * Try HERE. Dolphin  ( t ) 11:31, 26 April 2010 (UTC)


 * Unless you mean the music group, 10cc. AlmostReadytoFly (talk) 11:52, 26 April 2010 (UTC)


 * Also, see our orders of magnitude series entry for examples of things of a given volume: 1 E-5 m³. Paul (Stansifer) 12:17, 26 April 2010 (UTC)


 * Should I point out that this is probably a student of Loughborough College you're trying to get sense out of! --Aspro (talk) 12:21, 26 April 2010 (UTC)


 * And what's wrong with Loughborough? I'm from Loughborough, although I never went to college there. FiggyBee (talk) 00:50, 28 April 2010 (UTC)


 * I'm not referring to the good citizens of your fair town -nor you. Rather, I was err... well...   view their talk page and you might get my drift. Now don't you think they could have formulated the question better if they were serious? --Aspro (talk) 19:34, 28 April 2010 (UTC)


 * Just to be explicit about it, when doctors on television say things like "10 ccs of adrenaline, stat!", the "cc" are an abbreviation for cubic centimeter, which happens to be the same volume as a milliliter. Other senses of the abbreviation can be found, not surprisingly, on the page cc. -- 174.24.208.192 (talk) 15:32, 26 April 2010 (UTC)


 * "Worst case of ice-cream induced brain freeze I've ever seen, administer 10 cc's of hot fudge, stat !" - Simpsons Ice Cream Social. StuRat (talk) 16:26, 26 April 2010 (UTC)

Another abbreviation for cc is cm3.--Cheminterest (talk) 22:14, 26 April 2010 (UTC)

Kepler mission field of view
Is it true that field monitored by NASA Kepler telescope roughly 24 times bigger then Moon angular diameter (as visible from Earth surface)? 70.52.182.184 (talk) 14:01, 26 April 2010 (UTC)


 * According to our article section Kepler_Mission its field of view is about 12 degrees. As the moons diameter is about half of one degree that seem to be about right.--Aspro (talk) 14:08, 26 April 2010 (UTC)


 * (EC) Kepler's field of view is approximately 10 degrees square. The moon subtends an angle of approximately 0.54°. So about 20x or so, yes. --Tagishsimon (talk) 14:10, 26 April 2010 (UTC)

Chromoscope pictures of the galaxy
on the site.. http://www.chromoscope.net/ when we observe the X-ray picture of our galaxy, we can see sumthing like the picture has been struck by a tiger paw or sumthing like that, like torn up in between, where none of the other images show such a thing. what makes it so? Prady —Preceding unsigned comment added by 116.73.242.109 (talk) 15:04, 26 April 2010 (UTC)


 * It looks like missing data. Dauto (talk) 15:39, 26 April 2010 (UTC)


 * Yes, it's missing data. This is more of a problem with X-ray telescopes because of their much narrower field of view. Other space telescopes do record the same thing, but over time they record the missing bits with a second or third pass. Why this happens can be understood if one just considers the sinusoidal curved black streak. This was the part of the celestial sphere hidden from the telescope by the sun. If you look at this website you will see an animate representation of the the celestial sphere.  Refer to the section:  The tilt of the Earth's spin axis with respect to the ecliptic plane results in the Sun tracking out an seemingly sinusoidal path on the celestial sphere when viewed in the projection with the celestial equator horizontal.  So, in short,  the streaks and other black pixels are  due to the fact that it  is an incomplete scan of the of the celestial sphere.--Aspro (talk) 17:25, 26 April 2010 (UTC)

Who turns the machine off from a terminally ill patient?
If a decision was taken to turn the machines off, so that a terminally ill patient will die, who does physically push the button (or pulls the cable or whatever)?--Mr.K. (talk) 15:59, 26 April 2010 (UTC)


 * I'm guessing a nurse would do that. Dauto (talk) 16:00, 26 April 2010 (UTC)


 * That might make them legally liable, if it's later decided that proper authorization was lacking. For this reason, they may have the family member who requested that they "pull the plug" be the one who actually does it. StuRat (talk) 16:20, 26 April 2010 (UTC)


 * Do you have a reference for that? Matt Deres (talk) 16:56, 26 April 2010 (UTC)


 * (ec) Hmm. Do you have a source for that statement? It strikes me as very dubious. Looie496 (talk) 16:58, 26 April 2010 (UTC)


 * In general, a hospital's legal department would already have reviewed any request to "pull the plug" and certify that the requester has the proper authority and complies with any existing advance directives, etc. Once the lawyers sign off, I'd assume that the nurse is pretty well covered.  Dragons flight (talk) 17:07, 26 April 2010 (UTC)


 * I do also believe that you if it is legally allowed (and it is), there must be a way of doing it without being sued for it. However, I am still not sure that a nurse will do it. Isn't it a huge psychological burden on a nurse, if she has to constantly kill people?Mr.K. (talk) 17:15, 26 April 2010 (UTC)


 * There are many psychological burdens in nursing. Compared to telling parents that their child has just died, removing a feeding tube from an unconscious person who is shortly going to die anyway is not that high on the list. Looie496 (talk) 17:38, 26 April 2010 (UTC)


 * I wouldn't say telling parents their toddler went to heaven is a heavier burden than actually killing someone. In the former case you can just use a euphemism and comfort yourself with the thought that it was unavoidable. In the latter case, Jesus, how can you don't think about what you are doing? Mr.K. (talk) 17:51, 26 April 2010 (UTC)


 * a) It is not up to the nurse/physician to tell parents their child "went to heaven". b) Turning off life support is distinctly different than "killing" someone. c) Don't assume for an instant that the doctors and nurses involved in the care of a terminally ill person do not think deeply about what is happening on a daily basis. Let's keep this discussion about facts and not emotionally charged rhetoric.  --- Medical geneticist (talk) 22:59, 26 April 2010 (UTC)


 * I'm pretty sure you're all looking too much into this. The decision to pull the plug isn't made by the nurse, so they isn't responsible for the death even they did pull the plug physically. In the UK I think you need to have two consultant doctors who permit for life support to be switched off with the next of kin's consent, whereupon the nurse would switch it off. There is no real reason to feel guilt as I'm fairly confident the nurses will be of the same opinion as the doctors--that the person is dead anyway, merely being kept alive on machine. Regards, --— Cyclonenim | Chat 18:02, 26 April 2010 (UTC)
 * Besides which, there's always the possibility that the patient will stay alive even after the life support is removed... --TammyMoet (talk) 18:35, 26 April 2010 (UTC)
 * Not really. They go through thorough tests to make sure the person is really dead (which actually include disconnecting the machines for a while to see if the patient tries to breath on their own). While it is always possible that they have a mistake, the probability is negligible. --Tango (talk) 21:24, 26 April 2010 (UTC)


 * This is a reference desk. Please provide references when you give answers, instead of guessing. Here (page 4) is an article in which someone present at such an event wrote that a doctor and nurse were present, and the nurse switched off the breathing machine.  Comet Tuttle (talk) 20:04, 26 April 2010 (UTC)


 * I second that. The first two answers were "I'm guessing" and sheer speculation.  The original poster should look at the list of items under life support.  Cessation of medical therapies (inotropes, total parenteral nutrition, dialysis etc.) are ordered by the physician.  Feeding tubes and central IVs can be removed by nurses or doctors.  Withdrawal of mechanical ventilation is performed by a respiratory therapist.  Any of these steps would be discussed in detail with the next of kin or medical power of attorney.  Hospital legal or ethical consultation would only be needed if there were a conflict between the medical team and the patient's family. --- Medical geneticist (talk) 23:11, 26 April 2010 (UTC)


 * According to this source (very small area is visible), the physician may also be the one to flip the switch. The book cited, Sourcebook on death and dying by James A. Fruehling seems like it would also be a good source regarding the possibility of a physician being criminally prosecuted in such an instance, though you'd need to purchase the book to find out for sure. Matt Deres (talk) 22:39, 26 April 2010 (UTC)


 * According to my wife (who used to be an operating department Nurse many years ago), any of the medical team might actually "flip the switch". The decision is the doctors' - but whoever happens to be standing next to the machine at the time might physically throw the switch - which could be the doctor, a consultant, a nurse, an OR tech or the anesthesiologist.  It would be unlikely to be a relative or friend of the patient.  She says it's like a prescription - the doctor takes the decision and is responsible - everyone else is just doing what they are told...following instructions...nothing more...it's just like administering any other treatment.  Of course the actual making of the decision is an exceedingly complicated and legally 'careful' process involving lots of people.  SteveBaker (talk) 02:47, 27 April 2010 (UTC)

No medical person would ever ever ever ask a relative to unplug a respirator. Horrible and cruel idea. Doctors or nurses do it when they are convinced that doing so is not killing the person since they are already dead. Often if any of the care team seem squeamish about it but do not actually oppose doing to, a more senior person will take the responsibility for flipping a switch. It isnt a daily event even in a busy ICU and it is treated seriously by those involved. And all institutions have careful brain death protocols with multiple tests and independent consultations. Been there done that. alteripse (talk) 04:00, 27 April 2010 (UTC)


 * I can corroborate Alteripse's account. (I am a physician as well.) From the perspective of medical ethics/philosophy, there is a clear distinction between doing something which actively harms the patient versus removing care that was keeping the patient alive. The decision to withdraw elements of care is a complex one, one which is not undertaken lightly. It's made as a result of discussion between the physician, the patient and/or family, and other staff members. Note that the original question referred to a patient who is still alive but dependent on life support. In many cases, the patient himself may be able to direct that care be withdrawn, or have specified an advanced directive. In lieu of that, family members are consulted to determine the patient's wishes. After careful consideration, the physician will write the order, and typically the nurse will carry it out. The family member would not be the one to do so. While the death of a patient is always a difficult and sobering event, the actual act is not considered "killing the patient" (as opposed to, say, euthanasia [administering medication to hasten death]). The hospital's legal department is normally not involved in a case-by-case basis. It is true that there is in general, a psychological burden in working with people who are very ill and who die, and it is something that physicians, nurses, and other team members face on a daily basis. — Knowledge Seeker দ 22:08, 29 April 2010 (UTC)

Reactivity of Na or Ca
Is sodium or calcium more reactive? --Cheminterest (talk) 22:12, 26 April 2010 (UTC)
 * The elementary answer is at Reactivity series and boils down to "sodium". No doubt others will explain why my GCSE Double Science (which was the last time I heard of that) is inadequate and the question is really rather complicated. 128.232.241.211 (talk) 23:04, 26 April 2010 (UTC)
 * Yes, sodium is more reactive because it has only one electron in its outer shell, whereas calcium has two. Since sodium only has one, it is much easier to get rid of, making it more reactive. --The High Fin Sperm Whale 00:04, 27 April 2010 (UTC)
 * That's not actually a good explanation. Having more electrons in your shell increases electron shielding, causes things like spin pairing, etc. which actually makes electrons easier to get rid of -- assuming ENC is constant. The reason why sodium is more reactive than calcium is that calcium has an effective nuclear charge of about 2 while sodium only has an ENC value of around 1. John Riemann Soong (talk) 05:06, 27 April 2010 (UTC)
 * Both calcium and sodium metal are strong reducing agents: reactive enough to react with water. But compare the reactions: sodium vs. calcium. Buddy431 (talk) 00:41, 27 April 2010 (UTC)
 * Look at the Table of Standard Electrode Potentials; calcium is higher than sodium. --Chemicalinterest (talk) 20:10, 29 April 2010 (UTC)

Protein
1) What happens when someone does strength training and doesn't eat much protein afterward? How do the muscles repair themselves? Thanks. --Mudupie (talk) 23:33, 26 April 2010 (UTC)


 * Difficult to answer absolutely. What do you mean by 'much protein'? Lack of any nutrient will very likely lengthen post exercise recovery time. But more is not necessarily better. Note that in the early stages at least, strength can increase without increase in muscle mass, as the muscles are learning the new 'skill' of lifting weights.


 * In the 'west' we tend to eat far more protein than we need. If you have a good all round diet, you may not need any extra protein. Which I cannot judge. This website here has figures that seem consistent with current nutrition standards (Please don't pay too much attention to the ads for 'protein powders' etc!).


 * This one at (Massachusetts General Hospital) is aimed at adolescents,  Weight lifting and training, from which I quote: (my bolding)


 * "Since adolescents in the United States already eat a diet high in protein, there is no need for most adolescents to take protein supplements during weight training. And scientific studies have not supported any enhancement of muscle growth or strength from protein intake greater than the recommended amounts." para. 7, © 2010 Massachusetts General Hospital


 * Recommended 'normal protein' RDA (Recommended Dietary Allowance) is 0.8 grams per kilogram of lean bodyweight (1 kilogram=2.2 pounds).
 * If you exercise you need more.(Pregnant women need even more than weight lifters!)
 * For muscle building an intake of 1.6-2.2 grams per kilogram of bodyweight is recommended.
 * I think many of us exceed that intake, whether we exercise or not.(see quote above)
 * Too much protein can be bad for you (or give no advantage).
 * As is too little. see Protein-energy malnutrition


 * See also Body building, Protein (nutrient), Outline of nutrition, Nutrition, Human Nutrition, Diet (nutrition),and any related articles.  This ref Desk question from about 3 day ago may interest breakdown of muscles.
 * Feel free to ask more questions if I have not fully answered your query --220.101.28.25 (talk) 12:22, 27 April 2010 (UTC)


 * Addendum: Don't take what is here as 'gospel' truth. I suggest you read the references here, or in the articles I have referred you to yourself. Also, for personalised nutritional advice, consult a nutritionist or dietician. --220.101.28.25 (talk) 13:33, 27 April 2010 (UTC)


 * American scientists recently advised all but some professional athletes to stop taking protein supplements. They are not necessary. Imagine Reason (talk) 14:27, 27 April 2010 (UTC)


 * That is one of the the points I was trying to get across, though I was assuming 'normal' amateur training. If you have a link to the data you mention I'd like to read it. :-) --220.101.28.25 (talk) 14:35, 27 April 2010 (UTC)

Thanks! I have a lot of reading to do :) --Mudupie (talk) 17:44, 27 April 2010 (UTC)


 * Thank you for your thanks, Mudupie. You will find the subject can be rather contentius, as the bodybuilding.com website says at one point. It tends to be weight-lifter/bodybuilders on one vs scientific studies/researchers on the other. (Or perhaps purveyors of supplements vs nutritionists.) Views can be very divided. Educating yourself in this area is very wise, and can be very interesting! But again professional advice should be heeded, not someone with a possible conflict of interest trying to sell you a 'supplement'.! --220.101.28.25 (talk) 21:06, 27 April 2010 (UTC)

Soda Bottle Rocket
In science we are doing a project that involves us making rockets out of ordinary 2 liter soda bottle. We are allowed to modify the bottle in any way that we want. I could not find any information on how to find an ideal nozzle size for a given rocket. The wikipedia article on water rockets says that many people create a nozzle 9mm in diameter. I did not know if there was a means of calculating from chamber diameter, or more likely pressure (around one hundred psi in my case) what an ideal nozzle size would be. Additionally that 9mm nozzle is for a water rocket, and the means of propulsion for our rockets is compressed air. I was also wondering if anybody knew a way to connect two soda bottles, for added chamber volume, that could withstand 100 psi. If so, how should chamber diameter be proportioned to chamber length? —Preceding unsigned comment added by 71.112.13.57 (talk) 23:46, 26 April 2010 (UTC)
 * I think you need some water in there - it is the water being pushed out by the compressed air that propels the rocket. --Tango (talk) 23:53, 26 April 2010 (UTC)


 * We've got an article - water rocket, and if you google soda bottle rocket you should find lots of "how to" guides to help you. DuncanHill (talk) 23:56, 26 April 2010 (UTC)


 * 100 psi is pushing it - these bottles are rated at 100psi and tested to 150psi when new...but this site says they may start to deform at 80psi when you have used bottle. So be really careful - stand well back - and FOR SURE don't be tempted to push it over 100psi!  I strongly agree with DuncanHill - you need water as propellant if you want to make this thing really fly well.  I don't see how using two bottles can help.  You double the energy stored in the rocket - but you also double the weight (more than double it, probably because you've got to attach them together somehow.  Real world rockets benefit from having multiple thrusters because they have payload other than the motors themselves...and even then, they used a staged approach where they drop the first stage motor before firing the second stage - so the second stage doesn't have to lift the weight of the first stage.  Because you can't increase the volume - and you can't (evidently) change the propellant - so the trick is going to be to keep the weight down and to get the nozzle diameter right.
 * The scientific answer here lies in the "Tsiolkovsky rocket equation". It says that the 'delta-v' of the rocket depends on the log of (the mass of the fully fuelled rocket divided by the empty mass of the rocket) - multiplied by the exhaust velocity.  Notice that the heavier the fully-fuelled rocket - and the lighter the empty rocket, the faster it will go.  That's why you need some water in there...air at 100psi weighs very little indeed compared to a 2 liter soda bottle...so ln(m1/m2) is only a little bit bigger than zero.  So you need a hell of a lot of exhaust velocity...so we're back to that nozzle again.  Picking a decent nozzle is probably going to require some experimentation...there are equations, but they are touchy.  The shape of the outlet matters in ways that are hard to figure out without supercomputers and such...so experimentation is the answer. SteveBaker (talk) 01:14, 27 April 2010 (UTC)
 * I second Steve Baker's "experimentation" suggestion. The trick is that you want to fill with enough water, and design the nozzle and air pressure charge, so that the air pressure equalizes at the exact instant that you run out of water.  That way, you aren't carrying heavy, useless water around with you as inert mass.  At the same time, if you put too little water in, and you have air pressure left over when all the water has already sprayed out, your rocket isn't making the most efficient conversion of potential energy (air pressure) into momentum.  Swapping out nozzles is hard - so start with one rocket with a reasonable size nozzle; and vary your experimental parameters: quantity of water, and pressure of air added.  Keep in mind that stored energy in this case is equal to pressure times volume - and the water isn't compressing.  So, your total stored energy will decrease if you add more water (because you have less volume of air, so the P V product is smaller; but if you add water, your total momentum may increase because you have added mass.  So, the question all boils down to: what is the optimum ratio of water to air to maximize the mass of water and its exit velocity, integrated over time?  Try changing your parameters and experimenting and recording/graphing the data.  When you have a lot of experiments, change the nozzle and see what changes.  It's not likely that a mathematical treatment will actually be very useful here, because the messy parameterization details are so uncertain that even a computational solution would be prone to error.  Nimur (talk) 14:24, 27 April 2010 (UTC)