The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
a cheetah is the fastest land animal and can achieve a peak velocity of 100 km/h upto a distance less than 500 m.if it spots its prey at a distance of 100 m then what is the minimum time it will take to catch its prey if the average velocity attained by it is 90 km/h ? —Preceding unsigned comment added by 117.205.176.131 (talk) 00:33, 27 May 2010 (UTC)[reply]
Probably not as fast as you could solve this simple math problem on your own. Please do your own homework. --Jayron3200:37, 27 May 2010 (UTC)[reply]
Maybe the confusing part is the wording of the problem which is pretty bad! Assuming the subject is the cheetah every time they refer to "it" which makes more sense, this problem is very simple: How long does it take to travel 100m at a velocity of 90km/h. If you have a problem with this, you need to re read the chapter of your text book. Vespine (talk) 00:55, 27 May 2010 (UTC)[reply]
Do we need to account for the time it takes for the cheetah to accelerate to 90 km/h? I've also added a header ~AH1(TCU)01:37, 27 May 2010 (UTC)[reply]
Nope. It clearly states "average velocity" which takes all changes into account, including the acceleration from stop. Its as simple as finding out how long it takes to run 100m at 90 km/hr. --Jayron3201:44, 27 May 2010 (UTC)[reply]
You don't have enough information to give the minimum time. The prey could turn and run towards the cheetah, and you aren't told how fast the prey runs. --Trovatore (talk) 01:48, 27 May 2010 (UTC)[reply]
I remember getting questions this poorly worded all the time. Generally you are expected to make the fewest possible assumptions, if they didn't explicitly say the prey moves then you assume the prey doesn't move. It's a maths question not philosophy. The point about the prey and all that other stuff about top speed and 500m and all that are red herrings there to throw off the "logical" part of your brain. ;) Vespine (talk) 02:02, 27 May 2010 (UTC)[reply]
I assumed that the second "it" referred to the prey, and the prey attained a speed of 90 km/hr, with the cheetah chasing it at 100 km/hr, in which case the question is quite different (though still easily solvable). It is a poorly worded question, though. Buddy431 (talk) 03:06, 27 May 2010 (UTC)[reply]
That's the bad wording i was talking about. I think it makes more sense if you just assume the cheetah as the object of the question all the way through. Any time it says "it" or "its" assume cheetah. I think the question is essentially "How long does the prey initially have to react if the cheetah starts from 100m and can obtain an average speed of 90km/h over that distance." Vespine (talk) 04:14, 27 May 2010 (UTC)[reply]
You have identical objects at 300K, 300K, and 100K that are perfectly insulated from their surroundings. Using heat engines, what's the highest temperature to which any object can be raised?
If you assume that the 300K and 100K objects do work on the other 300K object at the Carnot efficiency, you get 354K. If you assume that the change in entropy is 0, you get 400K. Both approaches seem equally valid to me. Why do they give different answers? --99.237.234.104 (talk) 01:11, 27 May 2010 (UTC)[reply]
I don't fully understand your question, but heat pumps (is that what you mean by heat engine?) waste energy - so does that wasted energy count toward raising the temperature? Ariel. (talk) 03:08, 27 May 2010 (UTC)[reply]
Would you care to share your calculations with us to make our job of pinpointing any mistakes a little easier? Dauto (talk) 04:46, 27 May 2010 (UTC)[reply]
The calculations are quite simple, but long and tedious. Anyhow, here they are.
The entropy method: Suppose the final temperature of one 300K one 100K objects is T1. Suppose the other 300K object is raised to T2. 2T1+T2=300+300+100=700 due to conservation of energy. dS=dQ/T=c*dT/T=clnT, so for all three objects, the condition that total entropy change = 0 is equivalent to lnT1/100 + lnT1/300+lnT2/300=0. Solving the two equations gives T2=400K.
The brute force method: Suppose a 300K and a 100K object are used as the heat source and sink for a Carnot engine, and that the engine's work is used to raise the other 300K object's temperature. W=Qh(1-Tc/Th) and Qc=Qh*Tc/Th for a Carnot engine. Qc=Qh*Tc/Th is equivalent to -c*dTc=c*dTh*Tc/Th, or dTc/Tc=-dTh/Th. Solving this gives Tc*Th=T1T2, where T1 and T2 are the initial temperatures (100K and 300K). W=Qh(1-Tc/Th) is equivalent to dW=-c*dTh*(1-T1T1/Th^2). Solving this equation gives W=c(sqrt(T1)-sqrt(T2))^2. Setting this equal to the heat absorbed by the other 300K object, c*delta-T=c*(sqrt(T1)-sqrt(T2))^2 and delta-T=(sqrt(T1)-sqrt(T2))^2. This gives delta-T=54 degrees and final temperature=354K. --99.237.234.104 (talk) 05:07, 27 May 2010 (UTC)[reply]
The first method is not correct. The carnot cycle is reversible and does not increase the entropy but the subsequent conversion of the work produced by the cycle into heat delivered to the third system is not reversible and does increase entropy. dS=0 is incorrect. Dauto (talk) 05:55, 27 May 2010 (UTC)[reply]
On a second thought, if you are also allowed to use heat pumps (which are nothing more then heat engines running backwards), then it is possible to dump the work in the third body reversibly by pumping heat from one of the colder bodies into the hot one using the work extracted from the heat engine attached to the two fist bodies. If you are allowed to do that then the first method gives the correct answer. Dauto (talk) 14:33, 27 May 2010 (UTC)[reply]
Thank you, that makes sense. Yes, you're allowed to use heat engines, heat pumps, refrigerators, and absolutely anything else in the world except outside energy. --99.237.234.104 (talk) 03:27, 28 May 2010 (UTC)[reply]
Life span of May fly is 01 day while that of Banyan tree can be 200 yrs. What message do
you get from this data concerning BMR (Basic Metabolic Rate)? —Preceding unsigned comment added by 180.215.248.143 (talk) 08:35, 27 May 2010 (UTC)[reply]
You need to use a better translator and more words to describe your question. http://translate.google.ca/#
Falling under the category of having immortality describes those that do not decay towards death and/or those that can not be killed, ideally living forever, but these are always qualified by how immortality is bestowed, for example Adam & Eve were immortal until God left them, therefore it was a "conditional immortality." 24.78.167.139 (talk) 05:17, 29 May 2010 (UTC)[reply]
Synthetic life: human health-care implications?
Could the recent "digitally programmed" loops of DNA used to create synthetic bacteria be scaled up to create and repair the complex DNA in a human, for example to create new heart or hair cells? Or are macroscopic problems in tissue engineering a bigger block to replacing damaged body parts? [Trevor Loughlin]80.1.88.1 (talk) 10:43, 27 May 2010 (UTC)[reply]
I think we're far too early in this technology to really know what it's total health care potentials will be or whether there will be insurmountable difficulties. Don't expect to see direct health care implications for another 10-15 years, which is the general turn-around time for cutting edge technology before it becomes something "tamed" enough to start using in actual patient settings. --Mr.98 (talk) 13:17, 27 May 2010 (UTC)[reply]
As impressive as the "synthetic cell" accomplishment is, it took Venter's team about 15 years to develop the technology to where it is right now. They are many years away from being able to apply this to something on the scale of a human. First, as far as I can tell from reading the papers, the ability to synthesize a genome from scratch using current techniques will reach a certain size limit that depends on how much DNA the yeast cells can reliably recombine. I'm not sure what that limit is, but it will almost certainly be far below the size of the average human chromosome. Second, the researchers don't really understand the mechanism by which the genome transplantation works, and it isn't even clear if the technique will work in species other than Mycoplasma. I don't think it is realistic to expect that someone will try to synthesize an entire human genome and transplant it into a recipient cell for the purpose of tissue regeneration... we already have lots of experience with stem cells that will probably get there much faster. More likely they will start by synthesizing novel types of microbes that can do useful things. --- Medical geneticist (talk) 12:03, 28 May 2010 (UTC)[reply]
The article clearly states you have to remove the HCl byproduct to drive the reaction. The statements have footnote references. One of them, a free abstract of an article, states that there is also a temperature effect. DMacks (talk) 15:12, 27 May 2010 (UTC)[reply]
whats a good place to take my car up to 100 mph ? i tried my street late at night when no one was around but its not long enough i only get up to 70 mph. i dont want to do it on the highway cause i might get pulled over. whats a good secluded place to go to 100 mph ? —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:40, 27 May 2010 (UTC)[reply]
Find a sanctioned dragstrip in your area if you think 1/4 of a mile is enough distance to get up to the speed you want. Outside of that you have few legal options unless you want to drive to a dry lake. --Jmeden2000 (talk) 13:51, 27 May 2010 (UTC)[reply]
FWIW, you will need a car with very good acceleration to get up to 100 in a quarter mile. My, uh, friend, has had luck using short spurs between highways where they don't bother with speed traps. In a place where this was perfectly legal, of course. Also is your car in good shape? How are your tires and brakes? You don't want to travel at high speeds in a car that's not up to the job. Friday(talk)13:59, 27 May 2010 (UTC)[reply]
Along the lines of illegal options, though, trying this on the highway is much much safer than on surface roads. You'd be on a road more closely intended for 100 MPH and driving in one-way traffic moving more closely to 100 MPH. The former means you're less likely to have a one-car accident, and the latter means that in addition to reducing the chance of a two-car accident, you'll put the closing speed of the collision closer to 30 MPH than to 130 MPH. Finally, in the event that the police take notice of you, you'll all but certainly get more lenient treatment trying this on the highway. Now, all that said, follow Jmeden's advice above and find a dragstrip. And absolutely never try this again on a two-way street. — Lomn14:05, 27 May 2010 (UTC)[reply]
Go to Germany and drive on the Autobahn on a day where the traffic is incredibly light. They have no speed restriction there, assuming it is considered safe to do so. It's recommended you don't go above 85mph, but they aren't going to pull you over because you're doing more. 14:14, 27 May 2010 (UTC)Regards, --—Cyclonenim | Chat
I think it is an incredibely irresponsible thing to try to speed to 100mph in a city street late at night. I sincerely hope the police pulls you over. Dauto (talk) 14:23, 27 May 2010 (UTC)[reply]
Wow you aren't going to win friends with that argument... not to sidetrack this but people (like me) from time to time walk their dogs late at night (even at 3am) and would enjoy not having to dodge a car going ~100mph... At that speed you likely won't likely realize your observation of "no one was on it" was wrong until they are under your car. --Jmeden2000 (talk) 14:32, 27 May 2010 (UTC)[reply]
Additionally at speeds like that your margin of error is very low, and being surrounded by houses full of people is pretty dangerous. A residential area has a lot of people and a lot of property in it. Don't drive recklessly there even at 3am (when there are more people around than you probably realize). Go somewhere where there aren't any people at all so that if you lose control and total your car you don't kill anyone else in the process. In these situations it is not the "normal" that you prepare for and worry about, but the freak accident. Take some responsibility. --Mr.98 (talk) 14:47, 27 May 2010 (UTC)[reply]
i drove down the street first to make sure no one was walking and it also had a sidewalk. im not here for a moral lesson just give me advice how to do it. what do you mean by "short spurs between highways where they don't bother with speed traps. " where is that. —Preceding unsigned comment added by Tom12350 (talk • contribs) 14:42, 27 May 2010 (UTC)[reply]
On a residential street you're probably going three times the speed limit. If they catch you doing that, they won't bother writing a ticket. Your car will be towed and impounded, and you'll be handcuffed and put in prison. (Question : Are you certain that no one living in that neighborhood is a cop? Would you bet the next couple years of your left on it?) APL (talk) 15:58, 27 May 2010 (UTC)[reply]
Well I've had my car up to 100 mph on a UK motorway (quite by accident - I'd just bought it and didn't realise I didn't have to have my foot down as far as I was used to in my old car, your honour). I don't think you're in the UK though! Seriously, don't drive at that speed in a built-up area. While there may not be people walking around, if you lose control of your car (and at that speed it's ludicrously easy - maybe hitting a kerb will do it) then you may well land at first floor level in someone's house. I'm pretty sure they won't appreciate being woken by some twat parking a car in their bedroom - and I'm also pretty sure you wouldn't be alive to hear them scream at you for doing it. --TammyMoet (talk) 14:58, 27 May 2010 (UTC)[reply]
Find a local Track day event, and do it safely and legally. A residential area at 3am is the worst idea, people going out are likely to be making emergency trips (sick kid on the way to hospital), walking the dog, or cycling because its cool and safe. -- Q Chris (talk) 15:07, 27 May 2010 (UTC)[reply]
I recommend I-76 in eastern Colorado. A cop followed me for a couple miles (I was driving 95 mph) and finally just passed me. There is pretty much nobody out there. One thing to note, the road is not great, and I was not comfortable going above 110 on it. 65.121.141.34 (talk) 15:17, 27 May 2010 (UTC)[reply]
If you're determined to do it illegally, I don't see what the big deal is. Go out on the freeway and do it. You didn't need us to tell you that a good place to drive fast is the freeway? Surely you've noticed that a lot of people seem to do 80-90 on a regular basis? APL (talk) 15:58, 27 May 2010 (UTC)[reply]
You drove down a residential street, saw no one so you presumed there was no possibility someone would be out on the road at that time? You aren't aware then that people live in houses and yes, they do sometimes come out of their houses at 3 am and walk along their street after you 'checked for people', and no, they don't monitor to see if there's some person driving along the street to check if people are walking and presume that said person is later going to drive along the street at 100mph so they should wait until said person has finished driving along the street particularly given that said person doesn't sound like the sort of person likely to be able to safely drive at 100 mph so could easily lose control and kill them for the 'crime' of walking along the street after said person had driven along the street to look for people (or perhaps simply not being seen by said person).
Or for that matter you never considered that you could lose control and hit a house killing someone in it in process (not outside the realms of possibilities if you're driving at 100mph).
And yes, it is personal because although I don't live in the US so thankfully I'm unlikely to ever meet the OP, I do sometimes go out late at night (I don't drive so I'm either walking or cycling) and while I'm aware there are always going to be some risks, it's quite a different thing to meet someone who openly admits he's one of those security risks to people like me. Since I'm usually going to some shopping complex the latest tends to be slightly after midnight since that's the latest their open here, at Christmas time but it's always possible I would go out at that time, why shouldn't I? But apparently people like me don't matter because hey I wasn't supposed to be out so late and if I was I was somehow supposed to make sure people like the OP see me before they go driving along the street at 100mph. So don't bother telling me off for WP:NPA or WP:Civility, this message is well and truly deserved.
While it depends on the highway, your local police and other factors, if you regularly drive along a highway you are probably aware of the favourite spots for cops so the OP's best bet is to find one of them and try it. Perhaps a spur route perhaps just a part of the highway that doesn't tend to be monitored much (perhaps far from the main urban areas). Ultimately as APL said earlier, if you're determined to do it illegally, you can't expect a guarantee you won't be caught. Nil Einne (talk) 20:13, 27 May 2010 (UTC)[reply]
Please don't ever again do anything idiotic like drive at 100mph down a residential street, no matter whether or not you think there's nobody there. You may not know that in the US, in most states, exceeding 100mph is a felony, and I would hope the prosecutor would pile on charges of reckless endangerment and actually send you to prison for 3-5 years. Comet Tuttle (talk) 23:12, 27 May 2010 (UTC)[reply]
Actually I just read the article about reckless driving: in most states it's a misdemeanor punishable by 5 to 90 days in prison and up to $1000 in fines (and in some states a mandatory license suspension for 6 months), but can become a felony if you hurt someone. 67.170.215.166 (talk) 02:31, 29 May 2010 (UTC)[reply]
I think you'll find that if you find a local police station and drive past a few times at 100 mph, the police will consistently ignore you so you will not have any problems with getting arrested. --Phil Holmes (talk) 11:24, 28 May 2010 (UTC)[reply]
Do you have any idea what this sign means? In cleaning out my lab, I found it behind a solvent locker. It may have been there for decades. ike9898 (talk) 15:08, 27 May 2010 (UTC)[reply]
The first thing to decide, is whether its supposed to read
"not quite physics envelope but close" or
"not quite envelope physics but close".
I'd say the spacing is ambiguous, it could be read either way. Googling "envelope physics", yields almost exclusively hits containing "back of the envelope physics", which doesn't seem to make much sense without the introductory "back of the", at least not to my non-native ears. Googling "physics envelope", on the other hand, yields hits like "Adult tarantulas are pushing the physics envelope with exoskeleton size & so are very susceptible to damage from falls", there's a Nature article called "pushing the physics envelope" (which I can't read now, as I'm writing from my home PC). Another hit reads: "Does no one push the Physics Envelope anymore? Have we really reached the highest point in the helicopter design...". So it appears to me that "physics envelope" means "limits of what physics can achieve".
I think it is likely that it is supposed to read "not quite envelope physics but close, with "back of the envelope physics" being what it is referring to. See back-of-the-envelope calculation, it means "a rough calculation", as doing physics on the back of an envelope is less accurate than using a computer or something. So, applied logic is not quite as (in)accurate as doing physics calculations on the back of an envelope, but it is close. I guess somebody didn't like applied logic. --Cerebellum (talk) 16:40, 27 May 2010 (UTC)[reply]
I agree with the above (2 makes sense) ie
Hitting things with clubs < Handwaving < Applied logic < Back of envelope calculations < Full solution of multi-electron shrodinger equation ..etc...77.86.125.207 (talk) 17:01, 27 May 2010 (UTC)[reply]
Question - did the department you're at used to have an "Applied logic department"? - might have been a joke comment on the quality of research they did there , or something.77.86.125.207 (talk) 17:02, 27 May 2010 (UTC)[reply]
This building is highly interdisciplinary, and changing all the time, so figuring out if applied logic was being used at some undefined point in the past would be a significant task. ike9898 (talk) 18:52, 27 May 2010 (UTC)[reply]
"Envelope physics" means "physics that pushes the envelope" -- the envelope being the boundary between the possible and the impossible. So it's basically a bit of humor that means "we're not quite out at the bleeding edge but we're close to it". Looie496 (talk) 17:44, 27 May 2010 (UTC)[reply]
I'm not sure this discussion has converged on a single explanation, but I've certainly got a better idea than I did before. Thanks, everyone! (Further thoughts welcome) ike9898 (talk) 19:00, 27 May 2010 (UTC)[reply]
A bit off topic, but around the edges of the sticker one side is tinted blue and the other side orange. This effect appears visually as well for the edges of sources of light or bright reflections of light. ~AH1(TCU)18:43, 30 May 2010 (UTC)[reply]
How is temperature controlled onboard a commercial airplane ? I'm guessing that they lack heaters and A/C, but rather use the excess heat from the jet engines and the cold from the air at altitude to control temps. However, neither of these are available on the ground, and this might explain why the passenger compartment quickly overheats when a plane is stuck on the ground. (I suppose it could also get cold in very cold weather, at night, with an almost empty plane, where solar heating and heat given off by passengers would be minimal.) Also, has there been any thought to providing a truck that could drive out to a plane stuck on the tarmac, and hook it up to provide an external A/C or heat source ? Obviously the plane would need some place to connect to. I suppose the passenger door(s) could be opened and air could be pumped in one flexible duct and out another. I was on a plane that was only stuck like this for 15 minutes, and it got hot, so I wonder just how hot they get after many hours like this ? I've also noticed that they don't seem to overheat when parked at the gate, so do they have some external hook up they use to prevent this from happening there ? StuRat (talk) 16:47, 27 May 2010 (UTC)[reply]
Commercial airliners do have air conditioning units. Heating is achieved with an engine-bleed heat exchanger. When an aircraft is on the ground, with the main engines not running (but with passengers boarded), the auxiliary power unit is run, which has the same effect - even the APU has enough juice to run both heating and A/C. When at the stand, some airports have power hookups. I too have spent some uncomfortable time at EWR in the Summer on a plane with no APU at a stand with no hookup. After a (long) while they came up with some truck, which I think had a generator to do the job of the APU. Refs: http://www.b737.org.uk/airconditioning.htmhttp://www.boeing.com/commercial/cabinair/ecs.pdf -- Finlay McWalter • Talk17:23, 27 May 2010 (UTC)[reply]
“Any organic material kept in moist and dark conditions gets infected with fungus,
although there was no sign of fungus prior to it.” How fungus does make it possible,
although it is a microbe? —Preceding unsigned comment added by 180.215.248.62 (talk) 18:20, 27 May 2010 (UTC)[reply]
The original statement is clearly untrue - there must be either fungus or fungal spores in the air or in the original organic material in order for a fungus 'infection' to happen - in which case, the statement that "there was no sign of fungus prior to it" must be false. Perhaps there were no visible signs - but under close enough analysis, some kind of fungal material had to be present at the outset. SteveBaker (talk) 20:07, 27 May 2010 (UTC)[reply]
I think it means no visible sign, since there are always fungal spores around. We're all exposed, all the time, to to fungal spores, and if they do find somewhere moist area then they can settle. I don't see how dark conditions matter, fungi aren't damaged by light, at least not any of the fungi I've heard about. Regards, --—Cyclonenim | Chat 21:22, 27 May 2010 (UTC)[reply]
There was no mention that the organic material was kept in an air-tight container, only that it was kept dark and moist. An unlit basement would count, and there could be wet rot, bread mould, and other similar organisms in the air. CS Miller (talk) 14:24, 28 May 2010 (UTC)[reply]
First of all, fungus is not the same as a microbe (microorganism). More precisely, some fungi are microorganisms, and some are not; some microorganisms are fungi, and some are not. Second, as people have already said above, fungi do not "spontaneously generate", they grow from spores. The theory of Spontaneous generation has indeed been disproved for at least 200 years now. (On the other hand, the life on Earth may well have spontaneously generated in the first place; but that took a few billion years, see abiogenesis; and the first life forms were certainly nothing like the modern fungi). Third, not all organic material kept in moist and dark conditions gets infected with fungi. See putrefaction, decomposition, saponification, and fermentation. --Dr Dima (talk) 21:38, 27 May 2010 (UTC)[reply]
That's my point exactly. I was trying to explain that not all organic material kept in moist and dark condition gets infected (and decomposed) by fungi. Saponification is an example of such non-fungal process. Putrefaction is another example of a non-fungal process (putrefaction is mostly carried out by anaerobic bacteria.) --Dr Dima (talk) 06:55, 28 May 2010 (UTC)[reply]
smoke
wouldent the people in this vid get really stoned from the smoke in this vid
(This is a vid of opiumpoppies being destroyed by burning them.) I think that a: people are not standing in the smoke, and b: the flames might be hot enough to destroy the active ingredients. Regular smoking is not a flame, but rather embers which are cooler than a flame. Ariel. (talk) 21:45, 27 May 2010 (UTC)[reply]
Note that the burning includes all parts of the plant - not just the resin that contains the opium - thus it would be unpleasant to breath in. (like inhaling the smoke from burning straw). 77.86.125.207 (talk) 23:08, 27 May 2010 (UTC)[reply]
Alternatively a route to lead oxide (which should readily react with acids to form salts) - is by heating and stirring molten lead to effect the oxidation of lead - which can be removed from the surface.
I have some ancient lead solder that I dissolved in hydrochloric acid, leaving the lead and rosin behind. (I used the tin(II) chloride formed as a reducing agent). I was wondering if there was any way to form lead compounds from the lead powder left behind. --Chemicalinterest (talk) 20:08, 27 May 2010 (UTC)[reply]
Are you sure that it was lead solder and not tin solder? 'Cause lead chloride is only slightly soluble in HCl -- did you use a big excess of acid? 67.170.215.166 (talk) 07:02, 28 May 2010 (UTC)[reply]
What about using acetic acid from vinegar? Lead(II) acetate is well known and can apparently be synthesised by reaction of acetic acid with lead(II) oxide, PbO. You could first convert Pb to PbO by blasting it with a blowtorch or something.
No blow torch needed. As you have already lead powder you have a high surface area - the surface should be lead oxide already - dissolve the surface layer with acid, filter, wash, allow to dry - divide the powder again (allow time for another oxide layer to form) .. repeat. However this will produce finer and fine lead powder - which is not a good idea health wise.77.86.125.207 (talk) 21:06, 27 May 2010 (UTC)[reply]
The reducing power will always increase with concentration.. (avoiding the issue of what the thing in sodium amalgam actually is .. article claims Na2Hg - but I wouldn't count on it.) 77.86.125.207 (talk) 21:31, 27 May 2010 (UTC)[reply]
Possibly different compounds will be formed depending on the amount of Na [2] - suggests NaHg , Na2Hg ,Na3Hg -not sure if this is right - there are definately a lot of different species [3]
Na2Hg definately exists and is an Intermetallic - it's somewhere between a normal metal alloy and a salt - may look like a 'shiny ceramic'. The bonding can be considered primarily metallic (which is similar to a non directional covalent bond) but with polar character too - additionally the structures of isolated amalgams may not have all that much bearing on what may often be a solution of Na in Hg (or a mixture of different sodium/mercury intermetallics)- you coukd think of it as simply Na in solution in Hg, with some charge transfer from the Na to the surrounding Hg's - which will form a coordination shell similar to that found when Na+ is in solution in water solvated to Hg (it wouldn't affect the understanding of the redox chemistry much)- in general the actual situation in any Na/Hg mixture is complex.77.86.125.207 (talk) 21:38, 27 May 2010 (UTC)[reply]
The main thing to remember is that its action is by electron transfer, and that the electrode potential is not the same as that of pure sodium (amalgam is less reducing).
Crystal structures of NaHg, Na2Hg, Na3Hg etc have been determined, so these intermetallics are stable.
We posted here earlier, but were unfortunately dismissed. Allow us to rephrase our question so that your dilettantes are able to understand, and can hopefully help without deleting this post. Do crocodiles leave solid excrement or do they lose waste primarily through the skin and fluids. THANK YOU. —Preceding unsigned comment added by 129.67.38.99 (talk) 22:15, 27 May 2010 (UTC)[reply]
Given that people respond to you out of their goodwill, you could be a bit nicer, though when all google search returns are fosilized crap one may indeed wonder how that helps to find out something aout modern animals. The thing with crocodiles and such is that those are not animals of one species and charecteristics of diffrent spiecies may vary. The article says that they have no urine bladder, so it is more likely they don`t urinate. The fact that there is fosilized shit and unusal characteristics (such as getting rid of all the waste products by other means than shit) usualy are pointed out suggests that they shit. Also if you google crocodile anatomy you`ll notice that they have a cloaca, which is meant for sex, shit and urine, by looking up that, I found site on captive care of crocodiles, maybe you`ll find something there as people who keep them are quite likely to get up close and personal with crocodile shit, if it exists, their guide on determening the pet`s sex hints that they may shit if someone examines their butts [5] ~~Xil (talk) 23:56, 27 May 2010 (UTC)[reply]
Unless your results are majorly different from me, you don't even need to click the links. The fact that a book is talking about "Coronavirus Coronavirus-like particles were found by transmission electron microscopy in negatively stained faeces of four 2-3-year-old crocodiles from a ..." [6] and a research paper is talking about "found by electron microscopy in the faeces of farmed Nile crocodiles in South Africa" [7] and a FAQ on Crocodilian Captive Care says "The stool can often be very soft and difficult to collect - a croc's digestive system is very thorough. The faecal sample will enable the..." [8] and someone in a journal says "One of the highlights of this hour is to have pointed out to us crocodile faeces!" [9] is evidence enough that they shit. So I don't understand how the Google search 'helps very little' to anyone who bothered to actually take a glance thru it. And that's even if you ignore the fossilised faeces Xil discusses above that there are images of and is mentioned in "The 15 million year-old fossilised faecal matter, or coprolites, are each the size of a fist and bear clear impressions of prehistoric shark ..." [10] what's the second link for me. Of course, if you have any abouts that these are talking about crocodile faeces, you can click them to see it in context. Nil Einne (talk) 00:08, 28 May 2010 (UTC)[reply]
My previous response and another was removed as it also complained about linking to Google and treating the OP poorly, but I feel the response had substance and the previous poster did not answer what appears to be the OP question.
All the papers and coprolites say that solid excrement exists, but what is it? Does it excrete with urea like in birds? A very very difficult online hunt provides zero images of actual fresh croc dung, but does give a nice description of liquid excrement (Google books: Huchzermeyer. "Crocodiles: biology, husbandry, and diseases." Look up excrement or urine). What's interesting is that there is in fact very little urea in the urine, which is in direct contrast to birds (the white stuff in the poop is urea). I'm sad that for crocodiles and reptiles in general there is very little information online and surprisingly no pictures. Surprising because there's an entire human-excrement appreciation website called ratemypoo.com. SamuelRiv (talk) 16:36, 29 May 2010 (UTC)[reply]
In one of Roger Penrose's lectures (video here: http://www.youtube.com/watch?v=f477FnTe1M0 , part in question at 1:12), Penrose talks about some studies done on birdsongs. The studies supposedly had humans give an aesthetic rating the songs of male birds that were then followed in order to determine their reproductive success, and whether it had any statistical correlation with the humans' ratings.
If you know the height of a satellite above the Earth (h) and you also know the velocity with which the satellite rotates around the Earth (v) what calculation do you perform to determine the offset of the clock aboard the satellite due to the combined effects of special and general relativity?--Wikinv (talk) 02:26, 28 May 2010 (UTC)[reply]
I don't think there are any general relativity effects. The satellite is in free fall, so it's experiencing no acceleration (force). All you have is velocity, and of course that only has meaning in comparison to something, presumably the earth. The interesting part is that the earth is experiencing general relativity effects due to it's gravitational field, not the satellite. Ariel. (talk) 03:21, 28 May 2010 (UTC)[reply]
The offset I'm talking about is relative to a clock on the surface of the Earth, meaning that the effect of general relativity on board the satellite will be less than that on the surface of the Earth, so I think it will still have an effect. How do you do it for special relativity then?--Wikinv (talk) 03:36, 28 May 2010 (UTC)[reply]
Watch this video [11]. What I want to know is what calculation the presenter uses to arrive at his conclusion for the offset of the clock aboard the satellite.--Wikinv (talk) 04:32, 28 May 2010 (UTC)[reply]
How about this ? 04:40, 28 May 2010 (UTC)
That's special relativity only, which could still be useful. How would you use that formula to determine the offset of the clock aboard the satellite relative to the clock on the surface of the Earth given the velocity with which the satellite travels around the Earth?--Wikinv (talk) 04:43, 28 May 2010 (UTC)[reply]
Perhaps with a tick counter and identical clocks being synchronized (started) at some (identical) point in time and the counters then compared at some time in the future. 71.100.8.229 (talk) 05:14, 28 May 2010 (UTC)[reply]
(ec)So according to the video the clock will speed up by 45µs per day due to the difference in gravitational potential. Plugging values into the above formula you get:
=-0.00004565 s/day. At 3.87 km/s slow down by 7µs per day:
There's also a lot more going on, the relative velocities are constantly changing, the orbits are not spherical, etc. so there is also a periodic adjustment throughout the orbit, works out to between +70 and -70 nanoseconds.—eric05:28, 28 May 2010 (UTC)[reply]
You can get a decent approximation using the Schwarzschild metric, which is (using h instead of the usual r). If the orbit is circular (or approximately so) then , which leaves , or
.
That's the clock rate compared to a "stationary clock at infinity". To get the ratio between two clocks at finite heights, you compute clock1/clock2 = (clock1/clock∞) / (clock2/clock∞), or
where s is the satellite and r is the receiver. With factors of G and c put in, that's
.
This is equivalent to the formula from Seeber if you take (but even for a "stationary" ground receiver, is really nonzero because of the rotation of the Earth). This formula gives the average time discrepancy of the satellite and ground clocks over a long period of time. At any given moment, the ratio of the ground clock rate to the received signal from the satellite will be somewhat larger or smaller than this average, because of redshift/blueshift. -- BenRG (talk) 05:54, 28 May 2010 (UTC)[reply]
Look at the article Gravitational time dilation. That's the name of the effect you're asking about. From that page:
Circular orbits
In the Schwarzschild metric, free-falling objects can be in circular orbits if the orbital radius is larger than . The formula for a clock at rest is given above; for a clock in a circular orbit, the formula is instead
This is a consequence of the equivalence principle of general relativity (not special relativity). One related fact is that a monochromatic source of radiation will be observed with a lower frequency (longer wavelength, relative to the source) if the receiver is at a higher altitude (gravitational potential) and will be observed with a higher frequency if the receiver is at a lower altitude, due to the photons' losing (gaining) energy overcoming (having work done on by) the gravitational potential (gravitational redshift)Inasilentway (talk) 22:06, 1 June 2010 (UTC)[reply]
dam people
Paraphrasing Ronald Regan as having "...seen one tree, you've seen them all." where would be the best places to dam up the Grand Canyon and how much energy from fossil fuel would be replaced? 71.100.8.229 (talk) 02:31, 28 May 2010 (UTC)[reply]
Oooh! I know - they could call it the "Hoover Dam"...Oh...wait, did someone already use that name? Anyway, it produces 2080 MegaWatts. If I have my math right (and someone should check!) - that's equivalent to about 80,000 barrels of oil per hour. SteveBaker (talk) 04:03, 28 May 2010 (UTC)[reply]
Yeah but that is just one site where a large reservoir might be located. Take another look at the expanse of the Grand Canyon and you will see that if you are able to sacrifice the senic wonder in line with Regan's philosophy that you might be able to build another dam or 100. 71.100.8.229 (talk) 04:10, 28 May 2010 (UTC)[reply]
Lake Mead, which lies above Hoover Dam at the base of the Grand Canyon, has a water level of 1200 feet and a drop of about 500 feet. Lake Powell, at the other end of the Grand Canyon, has a base level of about 3100 feet. So that gives about 1900 feet of altitude to work with, meaning potentially around four times the output of Hoover Dam could be generated, assuming you dammed the entire Grand Canyon. Looie496 (talk) 04:28, 28 May 2010 (UTC)[reply]
Assuming there is enough water to work with. The Colorado River already doesn't reach the Gulf of California anymore; it hasn't for decades. Lake Mead's and Lake Powell's levels have dropped in recent years, there has been some serious speculation that their levels may drop below usable levels in the not-to-distant future. Additional dams are a veritable impossibility. There are similar problems on most western rivers; we've literally almost run out of usable dam sites in western North America; its why hydroelectric isn't seriously discussed anymore as a viable alternate energy source; there's no where else to put dams. --Jayron3204:38, 28 May 2010 (UTC)[reply]
Indeed - there is more talk these days of removing old dams than of building new ones. The issues of the region behind the dam silting up - and the river in front of it moving too slowly to sustain native wildlife have really put dams out of favor. You can buy a lot of windmills for the price of a major new dam! SteveBaker (talk) 02:56, 30 May 2010 (UTC)[reply]
How do Astronauts performing spacewalks deal with an itch?
Suppose the Astronaut has an itch at the tip of his/her nose and just began a 6 hr spacewalk, how would they handle that situation? I can't imagine them being able to slip their arm up through their spacesuit just to scratch an annoying itch. Thanks!Drummerdavid (talk) 03:58, 28 May 2010 (UTC)[reply]
I believe there is a little gizmo that sticks out into the helmet that the astronaut can turn his head around to in order to scratch against. It's put there for just such a reason - there is also a tube for sucking a little water or juice and some kind of an energy bar stick to chew on. SteveBaker (talk) 04:06, 28 May 2010 (UTC)[reply]
"The problem is the crossover?" What's that mean? --Anonymous, 16:55 UTC, May 28, 2010.
detergent
There are detergents specifically designed to remove oil and grease (hydrocarbons) from eating and cooking utensils by one end of the molecule attaching to the oil and the other to the water. Is there a detergent that will attach one end specifically to water and the other end to just soot or pure carbon? 71.100.8.229 (talk) 04:59, 28 May 2010 (UTC)[reply]
Not that I know of -- but detergents that remove oil and grease should in principle work pretty well to remove soot or coal dust. FWiW 67.170.215.166 (talk) 07:06, 28 May 2010 (UTC)[reply]
Incidentally, you don't need special detergents to do what's described by the OP. That's how regular old soap works (for non polar grease) Nil Einne (talk) 07:40, 28 May 2010 (UTC)[reply]
You mean you do not classify soaps and Surfactants as detergents? In any case I'm looking for a "detergent" where one end binds only with or specifically with carbon or carbon monoxide or carbon dioxide but with a hydrocarbon and it might not be known specifically as a "detergent". 71.100.8.229 (talk) 10:02, 28 May 2010 (UTC)[reply]
You said "There are detergents specifically designed to remove oil". Soap isn't 'specifically designed'. It's something that can occur naturally and people have been making before anyone had any understanding of the chemistry involved. (In addition, our article does say a distinction is sometimes made between soap and other surfactants as detergents, but that wasn't my point.) Nil Einne (talk) 12:50, 28 May 2010 (UTC)[reply]
Soap is made from fat and sodium hydroxide with sodium at one end of the molecule and hydroxide at the other same as many synthetic detergents. I recall a "detergent" with different ions at the end which had a greater affinity for various oils while the other end had a greater affinity for water. My memory is failing so maybe I'm just confused. 71.100.8.229 (talk) 03:53, 29 May 2010 (UTC)[reply]
Your description isn't quite right - I've put images of the chemical structures in - so you can see the difference between what you remember.77.86.47.199 (talk) 09:33, 29 May 2010 (UTC)[reply]
Okay I see. It was the sodium ion that was replaced with a hydroxide ion with the hydrocarbon chain remaining the same. Is ther a hydrocarbon chain then that will attach to soot or pure carbon specifically, assuming the sodium or hydroxide end is the one with affinity for water? 71.100.8.229 (talk) 03:17, 30 May 2010 (UTC)[reply]
(It's not hydroxide - in the diagrams it's carboxylate or sulphonate an organic sulphate)
Since like dissolves like a surfactant with a napthalene or anthracene at the end of the non-polar part might be a good choice for graphite based soot. Other soots are considerably oxidised, and contain many OH and C=O bonds - for a substance encouraging the suspension of soot particles you might consider a strong sugar solution - such as golden syrup.77.86.47.199 (talk) 14:42, 28 May 2010 (UTC)[reply]
Orbital stability
How would one go about showing that an inverse-sqaure force produces stable orbits (or how to check whether a given central force produces the like)? I tried googling, but most of the sites I was linked to dealt with mathematics that was beyond me (eigenvalues and so on). Are there simpler, calculus-based or, better yet, qualitative methods of answering such questions? 173.179.59.66 (talk) 05:37, 28 May 2010 (UTC)[reply]
Stability means decay of small perturbations. A small perturbation of a Kepler orbit will not decay, but will not grow either (to put this in the simplest terms, in the 1/r potential, gently nudging an orbiting body moves it from one closed orbit into a slightly different closed orbit). Therefore, it may be argued that a closed orbit of the two-body system with 1/r interaction potential exhibits a marginal stability. Actually, this is a far more general property of a broad class of so-called conservative systems (we don't have an article, but reading Conservative vector field may help anyway). Such systems don't normally have stable limit cycles; instead, depending on the initial conditions and the type of interaction, the behavior may be ergodic, or the system may be in a closed orbit, or the system may collapse into a singular state (see e.g. Coulomb collapse). --Dr Dima (talk) 07:22, 28 May 2010 (UTC)[reply]
Turns out we don't have an article on Coulomb collapse (for some reason I thought we did). I guess I'll have to explain briefly what it is. Imagine a classical 3-body (or N-body, N > 2) system with 1/r pairwise interaction where at least some of the interactions are attractive. (Classical -- neither quantum-mechanical nor relativistic -- gas of electrons and ions interacting pairwise via Coulomb potential is an example, hence the name; or imagine a cluster of gravitationally interacting stars and planets). When an electron gets close to an ion, it has higher-than-average kinetic energy; that's because the vicinity of an ion is a deep potential well for an electron. Electrons with higher-than-average kinetic energy tend to lose energy in collisions with other electrons. The more energy our classical electron loses, the deeper it falls into the potential well around an ion. The deeper it falls, the higher its kinetic energy becomes. (Remember that, on average, in a Kepler orbit the kinetic energy is minus one half of the potential energy; see Virial Theorem). In a classical system this will go ad infinitum, with r going to zero and the potential energy of the electron-ion pair going to minus infinity. This is known as the Coulomb collapse. Quantum-mechanical phenomena stabilize atomic orbitals against Coulomb collapse. Finite size and internal pressure of the star prevents gravitational systems from going into collapse. When this fails and the gravitational system does collapse, a black hole is formed (however, the energy released is still finite). --Dr Dima (talk) 07:53, 28 May 2010 (UTC)[reply]
Spoke and Hub
Are there any two commercial airports that would require a minimum of 5 flights to get from one to the other? Please note I mean standard commercial flights, nothing chartered or private. TheFutureAwaits (talk) 08:39, 28 May 2010 (UTC)[reply]
I wouldn't like to try it as Glasgow to Auckland is the best part of 32hrs, with 1.5hr stop-overs at each airport, I'd imagine Wellington and Christchurch are the same. CS Miller (talk) 11:47, 28 May 2010 (UTC)[reply]
As a general guide, I'd look for itineraries of the form
remote location → regional airline hub → major intercontinental hub → (new continent, change of airline) major intercontinental hub → regional hub → remote location
Bonus steps can be added if the intercontinental hubs are far enough apart that you need a fuel stop between them (as in London to Sydney). Good luck on your painfully long journey! TenOfAllTrades(talk) 13:58, 28 May 2010 (UTC)[reply]
I found one that would need ten, since it looks like Greenland does not like to use hubs. It is seasonal, but regularly scheduled while in season and would consist of
The inter-airport structure is analyzed in some detail in Guimera et al 2005. Basically, it fits a Small-world network model, which displays the popular Six Degrees of Kevin Bacon phenomenon. In most such networks, however, the usual "degree of separation" is significantly less than six. From Guimera, 56% of all pairs of cities are within 4 flights of each other, and the vast majority are within 5.
"The farthest cities in the network are RAF Mount Pleasant in the Falkland Islands and Wasu, Papua New Guinea: To get from one city to the other, one needs to take 15 different flights. From Mount Pleasant, one can fly to Punta Arenas, Chile, and from there fly to some hubs in Latin America. At the other end of the path, from Wasu one needs to fly to Port Moresby (Papua New Guinea), which requires a unique sequence of eight flights. In the center of the path, between Punta Arenas and Port Moresby, six different flights are needed. In contrast to what happens the ends of the path, in the central region of the path there are hundreds of different flight combinations, all of them connecting Punta Arenas and Port Moresby in six steps." - from Guimera et al 2005. SamuelRiv (talk) 04:44, 29 May 2010 (UTC)[reply]
As you see on the top of the reference desk page, it says that you can search for your applicable term in the search box on Wikipedia. If not try a Google search. Then, if you do not get your answers clearly you may ask. This is to prevent excess cluttering of the reference desk with basic questions that could be answered simply by a search.--Chemicalinterest (talk) 10:56, 28 May 2010 (UTC)[reply]
Can I have another simple meaning for the underlined phrase told by Einstein:
The precise formulation of the time-space laws was the work of Maxwell. Imagine his feelings when the differential equations he had formulated proved to him that electromagnetic fields spread in the form of polarised waves, and at the speed of light! To few men in the world has such an experience been vouchsafed . . so bold was the leap that his genius forced upon the conceptions of his fellow-workers
What he is saying is, "his idea was such a brilliant and unexpected one, that the fact that Maxwell was a genius was obvious to every other scientist once they heard of the idea." Does that clarify it? That is not a exact "translation" of what Einstein is saying, but should help you parse exactly what he's trying to indicate, I hope? --Mr.98 (talk) 14:47, 28 May 2010 (UTC)[reply]
Actually I don't think that's what it's saying at all - more like "His ideas were so advanced nobody understood them for years..."77.86.47.199 (talk) 14:57, 28 May 2010 (UTC)[reply]
You can read the full article here [13] p.489 left column (Einstein was quite a good writer)
There's some missing text where you have dots ".." - if you add that it makes more sense. I can't (work out how to) copy paste that article here - so you'll have to read the link.77.86.47.199 (talk) 14:48, 28 May 2010 (UTC)[reply]
I'll just type it in
"Meanwhile it took physicists some decades to grasp the full significance of Maxwell's discovery, so bold was the leap that his genius forced upon the conceptions of his fellow-workers" Science, May 24 1940, A. Einstein, article
That makes more sense with the rest of the sentence does it not?77.86.47.199 (talk) 14:51, 28 May 2010 (UTC)
Bold leap - is metaphorical, his ideas were completely different to what was understood (to be true) before
forced upon the conceptions - challenged what they thought was true (conception/conceive can mean what you think is true, as well as pregnancy. See the wiktionary entry, meaning 2)
Someone told me that Charles Darwin corresponded with Karl Marx, and that he had copies of Das Kapital and The Communist Manifesto. Is this true? --J4\/4 <talk> 15:56, 28 May 2010 (UTC)[reply]
As a learned man, he may have had those books. I see no mention of an association in the Charles Darwin article. Keep in mind that some people make an effort to discredit Darwin for their own reasons.. they apparently think that attacking the man himself somehow renders modern scientific findings invalid. See also Creation–evolution controversy. Friday(talk)16:10, 28 May 2010 (UTC)[reply]
There is no evidence that Darwin corresponded with Marx. Apparently Darwin sent a letter to someone else asking not to be mentioned in a book's dedication, and for some time it was thought this letter was to Marx when in fact it was not. See here and here and here for details. As for books, Darwin did indeed own Das Kapital, as Marx himself sent Darwin a copy. That copy now resides at Down House. Hope this helps. --Sean16:21, 28 May 2010 (UTC)[reply]
I'm not sure how your question relates to the section title you gave it - but back then, being well-read and having a rounded education stood for a lot - and reading ideas by people you don't agree with is one excellent way to get that kind of education. As the son of a wealthy doctor and financier, he would certainly have owned a large and diverse library - such was the mark of a well-to-do intellectual man of the mid-1800's. So we don't know that Darwin necessarily agreed with Marx - and even if they corresponded, that would not be considered unusual between intellectuals of the day when there was more of a spirit of open debate than we're (sadly) seeing these days. Darwin lived for 73 years - it would be exceedingly strange if the only thing he did in his entire life was to formulate the ideas behind evolution!
However, one thing is for 100% certain and that is that no effort to claim that Darwin was a pinko commie or a flaming gay or a religious fanatic (all of which I've seen claimed here by various religious nuts, young-earth creationist crazies and intelligent-design fanatics over the past year or so) will make the slightest difference to the scientific principle of evolution. The anti-evolution nutcases like to refer to believers in evolution as "Darwinists" in the hope that by pulling down the "Father of Evolution" they can end the belief in the scientific principle. Sadly, while that might have worked in the first few years after publication of "On the Origin of Species", we're way beyond that now. Science is an evidence-based practice - the people involved in finding that evidence don't matter beyond some small historical curiosity. The evidence for evolution is utterly overwhelming and only the most close-minded or ill-educated individuals could possibly be blind to that fact.
So maybe Darwin was a pinko, god-fearing, gay, child-molesting, lying, cheating, occultist (did I miss any?)...but that doesn't change the scientific fact that species change over time in reaction to their environment and on the basis of well-established genetic principles. We have tons of solid proof of that that are completely independent of Darwin. For what it's worth, I don't think Darwin was any of those things - he was a "gentleman naturalist" - a quiet contemplative man who didn't hold strong views about much beyond what he discovered. But that really doesn't matter a damn except to historians.
This screed and Chemicalinterest's response are off-topic and inappropriate. Opie asked a simple question about an interesting factoid in Darwin historiography (the case of the misfiled letter) and doesn't deserve this kind of knee jerk response. --Sean20:34, 28 May 2010 (UTC)[reply]
Solid proof? I do not stand for attacking people who believe in evolution (calling them names), but I do not hesitate to attack the philosophy. Anyone who attacks people (Darwin) while missing the subject (evolution) is like trying to kill a bear by shooting its leg: It weakens it, but it makes it much madder and more defensive. --Chemicalinterest (talk) 18:47, 28 May 2010 (UTC)[reply]
Marx did read Darwin, and wrote to Engels that "Darwin’s work is most important and suits my purpose in that it provides a basis in natural science for the historical class struggle."[14] Which is historically pretty interesting.
As for Darwin's correspondence, it has been meticulously categorized as part of the Darwin Correspondence Project, which is still a work-in-progress. Darwin did correspond with Marx in 1873, thanking him for sending him a copy of Das Kapital, and expressing that he wished he understood more of "the deep & important subject of political Economy."[15] The full digitized version of the letter appears in the link above. It does not appear they had an extensive correspondence and it appears that they would have corresponded long after Darwin came up with the ideas and even execution of The Origin of Species. Which is understandable—Darwin certainly had an interest in political philosophy (Malthus was a major inspiration), but he wasn't much of a heavy reader of such things. After 1869 he was a major British intellectual figure, so it's no surprise that Marx read him and perhaps vice versa (though I doubt it). As for any implications on his own politics, Darwin was many things, but a Communist he was not. He was rather conservative by most political standards of his day—he read the British equivalent of Fox News as his regular newspaper (for details on this, see R. Colp, Jr., "Charles Darwin: Slavery and the American Civil War," Harvard Library Bulletin 26 (1978), 471-489), which occasionally led him to rather retrograde opinions (he was extremely anti-North for most of the Civil War, even though he was a passionate abolitionist). --Mr.98 (talk) 00:08, 29 May 2010 (UTC)[reply]
Training your body to not be lactose intolerant
Someone I know said they were diagnosed as a child to be lactose intolerant, but then as an adult they are no longer lactose intolerant. Then a friend of hers said that she trained her body into not being lactose intolerant anymore by gradually introducing milk products into her body over a long period of time. Is this possible? Is what her friend saying true? ScienceApe (talk) 15:58, 28 May 2010 (UTC)[reply]
There are a few papers that point toward such a thing, but a more important point is that numerous studies show that the majority of people who think they are lactose-intolerant aren't really, except in a psychological sense. (In many people who think they are lactose intolerant, milk with the lactose removed produces the same symptoms as whole milk.) Looie496 (talk) 16:28, 28 May 2010 (UTC)[reply]
Syrup
1 Hi. More of a cooking question than science but here goes .. Does corn syrup taste different from golden syrup (I know what golden syrup tastes like, but haven't seen corn syrup in the UK. I would be comparing the light corn syrups with golden syrup. Also what does 'karo' taste like.
2 Does anyone have enough expertise to say what flavour chemicals are present in these syrups, if any. I guess it's lower concentrations of whatevers in molasses/treacle that makes golden syrup golden.. ? ? 77.86.47.199 (talk) 17:10, 28 May 2010 (UTC)[reply]
there doesn't seem to be an answer to any of my questions there (apart from the possibility of a salt trace in there - depending on method) - obviously I don't know what if any taste differences there are between glucose, fructose and sucrose - I thought there was something else in there beyond sugar, in low concentrations that gives it a different taste to say - pure glucose?77.86.47.199 (talk) 17:21, 28 May 2010 (UTC)[reply]
I'd be somewhat surprised if anyone here can give you a definitive answer on the relative taste of golden syrup and corn syrup, but you never know. As a practical matter, though, no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor. It's a cheap sweetening agent — you put it in rather than on things, and the things you put it in should have enough of their own flavor to overwhelm any from the syrup. --Trovatore (talk) 18:44, 28 May 2010 (UTC)[reply]
"no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor" - so you have never poured Karo over your pancakes then. Especially dark Karo on cornmeal cakes, mmm. 75.41.110.200 (talk) 19:22, 28 May 2010 (UTC)[reply]
I would have said that golden syrup has a pretty distinctive taste, while corn syrup, especially light, non-vanilla flavored corn syrup, is relatively tasteless. Just my non-scientific opinion, though. Buddy431 (talk) 21:19, 28 May 2010 (UTC)[reply]
Its ironic that Marx, of all people, should marry into the aristocracy. None of his descendants appear to have survived into the present time. How did Marx support himself and his family while writing Capital? 92.15.30.36 (talk) 20:24, 28 May 2010 (UTC)[reply]
a. Use the humanties desk, and b. Read Karl Marx as the answer to your question is in that article: "Marx's major source of income was from the support of Friedrich Engels, who was drawing a steadily increasing income from the family business in Manchester." 77.86.47.199 (talk) 20:55, 28 May 2010 (UTC)[reply]
(ec) Blue cheese. "Probiotic" is a marketing term rather than a scientific one, so it isn't particularly well defined (or defined at all, really). You can decide for yourself whether the bacteria in blue cheese count as probiotic or not. --Tango (talk) 19:17, 28 May 2010 (UTC)[reply]
A tiny bit, maybe. The yeast is supposed to be removed before bottling, for bottled beer, or it being put in a barrel, for lager. Real ale is put in the barrel with yeast still in it, but you are supposed to leave barrels to settle after tapping them before serving, so there shouldn't be any yeast in the actual served beer. --Tango (talk) 22:34, 28 May 2010 (UTC)[reply]
Not true... even after allowing the beer to clear, there is still a small amount of yeast in suspension, even in very bright beer. Exactly how much depends on the yeast's flocculance character (I'm a 10th level beer nerd). – ClockworkSoul22:37, 28 May 2010 (UTC)[reply]
Like I said, you may (ok, will) get a tiny bit. It's an insignificant amount, though (both in terms of digestive health and continued fermentation). --Tango (talk) 00:38, 29 May 2010 (UTC)[reply]
I concur. Some British and many Belgian bottled beers (for example) contain a very noticeable quantity of yeast in order to cause a secondary fermentation in the bottle; one may either pour carefully to leave this at the bottom of the bottle, or deliberately mix it into the beer, according to taste: although much of this yeast may have died (especially if the bottle is well matured) enough usually remains alive to enable re-cultivation.
Cask beer (as opposed to filtered keg beer) typically contains an even higher proportion of live yeast than bottled beer, and although finings are added to make this flocculate and settle out, much remains invisibly in suspension (and knowlegeable drinkers don't object to a degree of cloudiness due purely to yeast). Having worked at scores of beer festivals, I have often observed glasses of visually clear beer, left undrunk overnight, having by morning a couple of millimetres' thickness of settled out yeast at the bottom. 87.81.230.195 (talk) 02:36, 29 May 2010 (UTC)[reply]
I am looking for an author ( possibly an anthropologist, maybe a professor from the Seattle area ( Pacific Northwest )) who wrote a book called " Second Genesis " theorizing about brain growth in early hominid during the drying of the Mediterranean Sea following the closing of the Gibraltar Strait.
Men were separated in " Terrariums " ( his word ) created by the rivers flowing into the Mediterranean as the sea receded lower into its basin, depositing more salt at the bottom.This book is probably 30 or 40 years old and dated the time of the discovery of a Nile Canyon now submerged, which proved the drying and high salt content of the Mediterranean.
Daniel —Preceding unsigned comment added by 96.50.111.4 (talk) 19:00, 28 May 2010 (UTC)[reply]
Sounds like Genesis Revisited: A Revolutionary New Solution to the Mystery of Man's Origins (1979), by Glenn G. Strickland (apparently an engineer rather than an anthropologist). Description here—scroll down to the post by "Morphane". Deor (talk) 19:51, 28 May 2010 (UTC)[reply]
Unpleasant materials
I have an aversion to some textiles (don't know exactly which ones), that give me the creeps. When I touch them long enough (especially directly with bare hands), I experience very creepy feelings and the hands nearly sweat. Particularly, I had a jacket that nearly tormented me. Maybe someone has the same. Why is that? 213.154.25.253 (talk) 19:18, 28 May 2010 (UTC)[reply]
Could it be what it's made of - do you have the labels - a lot of people don't like polyester, also fleeces/corduroy/others feel unpleasent to some since the ends of the fibre point up (like tiny brushes). Or maybe the jacket was rubbery , some people done like that - even a small percentage of lycra to make the material more stretchy can impart a rubbery feel. 77.86.47.199 (talk) 19:30, 28 May 2010 (UTC)[reply]
How odd. Do these same people dislike the feel of other furry things, such as kittens? Are you implying that the ends of the fibers stab into delicate skin and cause pain, or what? 81.131.68.87 (talk) 19:50, 28 May 2010 (UTC)[reply]
I've experienced a similar reaction - so, no, you're not alone. It's hard to describe. Artificial fabrics that cling to my fingers kind of creep me out. Cheaply made fake fur, for example, always seems to have too much friction and the oils from your hand sometimes make weird squeaking noises when you wipe them on it. Yuck. Matt Deres (talk) 00:12, 29 May 2010 (UTC)[reply]
I'm stroking a teddy bear right now (presumably polyester fur) in an effort to work out what you mean, and I really don't get it. Sure, it doesn't feel quite like real fur, and it has slightly more friction, and I guess it makes a bit more rustling noise (it doesn't squeak!) ... so all in all it feels slightly different from real fur. So why is that disturbing? Is it an uncanny valley effect? That relies on our inbuilt instincts for identifying humans, though, and it's not like we have an instinctive affinity for the feel of real fur - or maybe you guys do? 81.131.23.148 (talk) 04:17, 29 May 2010 (UTC)[reply]
I'm designing an experiment to measure the effect of a treatment on the composition of substance. Of course I want do replications, but the right or most sensible way to go about this is less obvious that it might seem.
I could:
Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample once
Apply the treatment to one sample of the substance, and then measure the composition of the treated sample five times
Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample five times
Repeating the treatment is much more 'expensive' that repeating the composition measurement. Although I want to be thorough, I need to make efficient use of my resources. Can you help me understand how I should be thinking about these different alternatives? If you can point me to somewhere that I could read about this issue, that would help. I've searched, but I must be using the wrong terminology because I haven't found much.
ike9898 (talk) 19:48, 28 May 2010 (UTC)[reply]
If you don't do the 5x5 experiment you won't know anything about one of the two possible errors.
Experiment 2 gives you some indication of the error of measuring the composition. You can't really say much about the experimental error in treatment of the substance until you measure this.
If you are certain within yourself that one of the two errors is likely to be small (eg you think the treatment process is reliable and consistent, or you think the measurement of the composition is so reliable that you only need to do one measurement) then you could do experiment 1 or 2. but you have no statistical knowledge about the error at all.
Straight answer: What I'd suggest is do experiment 2 once (maybe with more than 5 measurements) - so you have an idea of the statistical error in the measurement - this should then give you enough information to know how many times you need to do the measurent for future samples to get a reliable answer:77.86.47.199 (talk) 20:47, 28 May 2010 (UTC)[reply]
Process 1 is valid, and process 3 probably won't be much better. Process 2 is not valid unless you are sure that all samples are the same. The crucial point is that when you calculate a mean and standard error, the samples that go into the calculation have to be completely independent of each other, and they have to be chosen randomly from the distribution. That means if you apply process 3, you would have to calculate the mean separately for each of your 5 samples, and then use the calculated means as input to a 5-sample check. But in any case you're putting the cart before the horse: you need to have a well-defined hypothesis to test in order to properly design an experiment, and you didn't state what your hypothesis is. Looie496 (talk) 20:49, 28 May 2010 (UTC)[reply]
OP here. Well, I'm not sure what my hypothesis is, but let me explain what I am trying to do, which is slightly more complex than what I described. There's not just one treatment; the treatment is a continuous independent variable, and I intend to perform experiments with treatment variable set at 5 different values. I want to produce is a figure that shows the composition at the various settings for the treatment. I think I'd also like to be able to fit a curve to the results. ike9898 (talk) 21:29, 28 May 2010 (UTC)[reply]
Suggest following my straight answer above - do 5 (or 10) measurements with one sample - this gets you an error bar for that measurement. For the others if you don't have time(/don't want) to do repeat experiments you can use the same error bar (probably best to scale as a percentage error) for the other measurements (assuming you do only one measurement per sample) - if plotting this as a graph you should clearly state and distinguish the proper and extrapolated error bars (eg solid for measured error, dotted for extrapolated) - though there is no substitute for actual measurements, and some people may take issue with extrapolated error bars...
As for curve fitting - It helps if you have a hypothetical equation first (ie a hypothesis) - do you have one, otherwise you could guess the curve - (see also Curve fitting) - though the problem here is that logarthymic/quadratic/exponential curves can look much like a straight line if the range of points is small. Not sure how much info you need on curve fitting. A quick look at this [19] suggests it's a good introduction though searching for "curve fitting" turns up many results of use - often the URLS that end with .ac. are useful since they are from universities.77.86.47.199 (talk) 22:11, 28 May 2010 (UTC)[reply]
"Dichroic liquids" / dyes
Has anyone ever seen a phenomenon like this before? It is quite remarkable imo. Does anyone have any ideas as to what might be causing it? Perhaps it is a colloid with suspended particles being of different color than the solvent they are suspended in; whereby transmitted light is absorbed by the solvent at selective wavelengths but absorbed at all wavelengths by the dispersed solid particles, which also simultaneously scatter light at selective wavelengths (green).
Thank you very much that is fascinating - this article [20] suggests that methanol / chloroform mixtures, though miscible can show localised regions where hydrophobic and hydrophilic ends of molecules agglomerate - ie like micelles (I would assume that dyes contain both hydrophilic and hydrophobic parts) - could a micelle like structure explain the optical properties?
I also think it may be some sort of colloid or emulsion - the green colour looks 'diffuse' as if it is particulate, whereas the purple color is clear. I'm not sure if it is coincidence that the green colour is the complement of the purple colour or not (ie green+purple=white)
Also towards the end of the video he says that the transmitted light (ie the light going through the liquid and out the bottom) is still purple - so that suggests no chemical change and that the green light is backscattered. Also when pouring the liquid it looks like thin films and the edges of the liquid look purple - suggesting that the green colour is cause by a bulk volume of liquid - again suggesting a colloid or emulsion or similar.77.86.47.199 (talk) 21:11, 28 May 2010 (UTC)[reply]
I think is a combination of reflectance and absorption. If you have a material that absorbs and reflects green light it would explain this. When the liquid is shallow, you see the green reflection. Little light is absorbed because there isn't much liquid (so it's mainly white with a tinge of magenta). However the human eye is much more sensitive to green, so the small amount of green light that is reflected is noticeable. When the liquid is deep a lot of green light is absorbed, leaving behind the magenta light. This mixes with a small amount of green that is reflected, but there is enough magenta, that that is what you see. On top of that the reflection is directional - so the green is reflected away from you. If you have a youtube account, link to this page in the video comments. Ariel. (talk) 23:36, 28 May 2010 (UTC)[reply]
I posted a comment on his blog, except I'm not sure comments are working. My suggestion is reabsorption by the competing molecules - the blue light reflected off the methanol is absorbed by the red chloroform and re-emitted as green (because the red dye is a reflection of white light - depending on the black body model, it'll look somewhat greener when a bluer-color light is shone). The converse occurence also happens, such that the net result is green. This occurs with magnitude not seen in other solutions I think because both chloroform and methanol are linear-polar, where ethanol is bent. Thus I think the chloroform and methanol align in the mixture and thus re-absorb each other's light much more effectively. But I do physics, not chemistry. SamuelRiv (talk) 04:25, 29 May 2010 (UTC)[reply]
2 gallons
i drink 1 gallon water a day. sometimes i drink 2 gallon water a day. when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this common occurrence. —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:56, 28 May 2010 (UTC)[reply]
Drinking too much water can be very dangerous - people have died from doing that. Check out our article on Water intoxication. Daily intake recommendations for water depend on how much you exercise and how much body weight you have. Most web sites say that a typical person should drink eight 8oz drinks per day - that's just a half of a US gallon - others say 1.2 liters - or a third of a gallon per day. But this depends on body weight and exertion levels...you might well need more if you do heavy work. Drinking about one liter per hour is considered to be most a healthy person should consume because that's the fastest a pair of healthy kidneys can process the stuff into the bladder. 2 gallons is 7.5 liters - so if someone were to drink that much over (let's say) an 8 hour period - then they would be pushing the limits and entering into life-threatening territory. Those are the facts.
However, we're not allowed to offer medical advice here - so if you are concerned, you should consult a doctor.
BTW, the 8 cups a day thing has no scientific basis at all. Someone just made it up. The only recommendation is to drink when you are thirsty. Drinking more than that just makes you more likely to get dehydrated (since your kidneys are accustomed to a lot of water, and if you don't constantly drink you will get dehydrated, since the kidneys are still excreting water at the usual pace). It takes a little while for the kidneys to get used to a new water level. See Drinking water#Requirements. Ariel. (talk) 23:31, 28 May 2010 (UTC)[reply]
Let's cut out the alarmist health crap. A healthy human can easily handle two gallons (~8 Liters) of water a day (source: [21]) (Note, though, that there are a number of diseases/disorders/etc. that can hinder the body's ability to process water. Echoing Steve, if you're concerned, see a doctor). Buddy431 (talk) 00:40, 29 May 2010 (UTC)[reply]
Well, using Steve's own number we find that that 2 gallons is fine. I don't know why Steve is using 8 hours as the length of a day... As long as you drink the 2 gallons spread out over the whole day and there are no exceptional circumstances (that's the bit we can't cover here and you need to see a doctor for), you should be fine (in the short term, at least - I have heard from reliable sources that there is a possibility that people drinking too much water "wear out" their kidneys over years. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
Thirst is a very bad way to determine when to drink. If you are thirsty, you should definitely drink, but that isn't enough. A lot of people aren't good at noticing thirst, so they would only be drinking when they are already approaching dehydration. The colour of your urine is a better measure - it should be pretty much clear. If it is green/yellow, you need to drink more. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
It's not "alarmist health crap". If you drink two gallons of water as fast as you possibly can - it could easily kill you. If you drink two gallons over 7 hours then you'll be consuming it at a higher rate than a healthy pair of adult kidneys can handle it - and it's likely that the resulting dilution of your blood will make you feel very strange - kinda like being intoxicated. If you drink that much over 24 hours, you should be perfectly OK. However, how do any of us respondents know whether the OP has healthy kidneys or unusually low body mass - or is a child? Are these "US Gallons" - because if not, then the risks are even higher than I estimated. Over how much time is the OP consuming this amount? We don't know any of those things - and because this is a potentially fatal situation, we MUST err on the side of caution. Two US gallons per day is an awful lot...and it's most certainly in the range where side-effects are possible. Since our OP explicitly expresses noticable symptoms from drinking that much - we have to consider the strong possibility of water intoxication. That's a potentially fatal condition, so we must not dismiss the possibility out of hand - and Buddy431 is taking an exceedingly irresponsible action by doing so. This is a situation where bad advice given on the ref desk could literally kill our questioner! Caution is therefore strongly advised here. Since we're most certainly not allowed to diagnose a medical condition, we should explain the facts in general terms and advise our OP to discuss this with a doctor - which is precisely what I did. SteveBaker (talk) 18:22, 29 May 2010 (UTC)[reply]
Let me echo the anon. If one is drinking whenever one gets thristy, and hence staying comfortable, then what physiological benefit is there to drinking more than that? Obviously, the color of urine can indicate how much water was excreted with the urine, but is the person who drinks more and has light urine actually measurably healthier than the person with darker urine by any other objective measure? Dragons flight (talk) 09:00, 29 May 2010 (UTC)[reply]
"If [mild to moderate] dehydration is chronic (ongoing) it can affect kidney function and may lead to the development of kidney stones. It can also cause:
From your link, "Mild to moderate dehydration: The first sign of dehydration is thirst." So again, if one consistently satisfies ones thirst, what evidence is there that drinking more beyond that matters? Dragons flight (talk) 19:38, 29 May 2010 (UTC)[reply]
The problem is that a lot of people don't notice thirst (or mistake it for hunger). That's why the standard advice for checking you are drinking enough is to check the colour of your urine. If you follow the "Diagnosis" link at the top of that page you'll see it talks a lot about urine and doesn't mention thirst once. --Tango (talk) 20:45, 29 May 2010 (UTC)[reply]
I certainly don't welcome kidney stones. I notice though the diagnosis page says if "it is unusually dark in colour, you are probably dehydrated." Which is vague, of course, but it doesn't say "it should be almost clear" or "it shouldn't be yellow". I appeal to the fact that everybody knows urine is greenish yellow. 81.131.66.87 (talk) 00:54, 30 May 2010 (UTC)[reply]
Mine isn't. Mine is almost clear. The reason a lot of people "know" urine is greenish yellow is because a lot of people don't drink enough. --Tango (talk) 22:10, 30 May 2010 (UTC)[reply]
i live in a very hot place thats why i drink 1 gallon a day. my question is when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this possible.
I believe people who take a lot of multivitamins tend to end up with strange colour pee from all the vitamins being excreted. Perhaps when your pee is more dilute since the strange colours aren't so noticeable this is making you think there's something wrong. In addition see placebo. Nil Einne (talk) 00:35, 29 May 2010 (UTC)[reply]
It isn't vitamins you feel, it is salt. As a former desert resident myself, I know that it's quite difficult to keep your electrolytes in balance when you consume that much fluid. Drinking even a part of it as Gatorade or another sports drink reduces the problem quite a bit. Even something like ice tea causes less of that feeling than drinking straight water. When I did midsummer bike rides in Tucson, I would regularly down a gallon or more of unsweetened unchilled ice tea afterward, and it worked pretty well for me. Looie496 (talk) 00:38, 29 May 2010 (UTC)[reply]
Multivitamins don't really do anything (unless you have a vitamin deficiency, which you won't have as long as you aren't pregnant and have a good diet), so you won't really be able to tell the difference. It is all in your head. (Yes, there have been studies that show a benefit to multivitamins beyond placebo. There have also been studies showing a benefit to homoeopathy beyond placebo. You need to look at more than one study to draw a conclusion.) --Tango (talk) 00:43, 29 May 2010 (UTC)[reply]
Let's be honest though. There are plenty of people, even in the West, who don't eat a terribly balanced diet and could benefit from a multivitamin. We shouldn't be making any assumptions about Tom's eating habits, health, or nutrient situation. That's exactly what our medical advice guidelines are for; we haven't examined Tom, and we don't know his his history. It's irresponsible to recommend either taking or not taking a multivitamin. Buddy431 (talk) 00:50, 29 May 2010 (UTC)[reply]
it is not placebo. i dont eat vegetables or fruit. so if i dont take a vitamin i feel it. i also think "placebo" is a scam by lying psychiatrists —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:51, 29 May 2010 (UTC)[reply]
In that case, it is almost certainly more important that you start eating fruit and vegetables than that you change your water consumption. A multivitamin is not a good substitute (it is better than nothing, but far far worse than a good diet - it doesn't contain any fibre for one thing). Placebos are definitely real - they are used in an enormous amount of medical research (and some treatment) that has nothing to do with psychiatry and a lot of people would have noticed if the effect didn't exist. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
Actually, it is you who have derailed the question, because here on the Reference Desk, other editors generally never just let a comment like that pass, whether you like Anti-psychiatry or not. You weren't actually being told that your feeling had anything to do with the placebo effect. So, on your placebo comment, our placebo article makes it clear that there is definitely a placebo effect. The article also mentions at least one study that concluded that placebos had no clinically important effect, though these studies have been controversial. Comet Tuttle (talk) 02:36, 29 May 2010 (UTC)[reply]
If you could find multivitamins with relatively little taste and placebo pills that look (and taste) the same [23] you could test this yourself. (The great difficulty here would be getting multivitamin pills and placebo pills that taste and look the same.) Get a friend to toss a coin, and decide whether to put the real pills or placebo into a container. Then either leave them for you or hand them over without saying anything or exchanging looks. Try these for a few days. If you can genuinely 'feel' the difference, you should have no problem working out if these are the genuine pills or the placebos. Don't talk to your friend about this. When you've done, ask your friend for another batch (using the same or a similar container), tossing a coin or whatever to choose whether to give you the real pills or the placebos, and again without talking in any way about the brief or current batch. Again decide whethere they are the genuine multivitamin pills or placebos. Repeat 6 more times.
After these 8 repetitions, ask your friend for list of when the container had placebos and when they had genuine multivitamin pills. (8 repetitions isn't really enough but hey I'll be generous.) If in all 8 repetitions you correctly identified when you had real pills or placebos (which should be no problem if you can feel the difference) then people would be more willing to accept perhaps you really can feel it when you don't take your multivitamins (although I'd be more inclined to believe the pills didn't actually taste and look exactly the same) and you can be more confident in your believe that you really can feel the difference.
Note that the placebo effect has been observed in many cases outside of the medical field. E.g. people who are convinced they can hear the difference between various types of speaker wires.
Er, placebos are an important and well-established part of scientific medicine. (Mostly in regards to double-blind drug research.) They're not really connected with psychiatry. Even if every psychiatrist in the world suddenly admitted they were making their entire field up and were nothing more than a pack of liars the fact of placebos would be unchanged because our knowledge of placebos doesn't come from psychiatrists, it comes from medical researchers. APL (talk) 06:44, 29 May 2010 (UTC)[reply]
Getting back to the original question, vitamins A, D, E and K are fat soluble. It is difficult to see how they could be 'flushed out' through the kidneys. This implies that the feeling you are getting is not related exactly to the 'lack' or otherwise of vitamins. Caesar's Daddy (talk) 07:08, 29 May 2010 (UTC)[reply]
And also back to the original question, I have kidney problems and have to drink a certain amount each day and no more. If that happens, my electrolyte balance is thrown out, and I feel quite sickly. I guess that's what's happening to you: you've drunk more than your body needs, and the balance of your constitution has been shaken. So in a sense you're right, but it's not the vitamins you're feeling the loss of. (Apologies if this constitutes medical advice, if it is can someone more experienced that I am delete it.) --TammyMoet (talk) 07:54, 29 May 2010 (UTC)[reply]
That would only be the case if the OP also has kidney problems (healthy kidneys should be able to deal with the extra water, as long as it isn't drunk over too short a period of time). So, if you are right, it is very important that the OP go and talk to a doctor. --Tango (talk) 16:20, 29 May 2010 (UTC)[reply]
All water soluble vitamins will be excreted, the level generally dependent on how much you consume. However interesting enough the level of vitmain B12 excretion may be dependent on urine output [24]Nil Einne (talk) 19:01, 29 May 2010 (UTC)[reply]
This is getting dangerously close to our no medical advice guideline so feel free to remove it if you feel it necessary but if you are able to feel it when you don't take your multi vitamins, it's more likely to be a general 'poor'/'unwell' feeling then anything specific therefore in line with some of the above answers, I wonder if you're getting to the level where you're taking too much water with 2 gallons which in itself may lead to such a feeling and may also negativelly affect the ability of your body to excrete other stuff like vitamins (i.e. you may have too high a level), which could also lead to such a feeling. So anyway, yeah I agree with people above you may want to see a doctor. Nil Einne (talk) 18:12, 30 May 2010 (UTC)[reply]
May 29
Sun Distance
How much closer would the sun have to be before we'd all die? I will also accept the scenario where we have to stay inside specially built igloo houses, for fear of death in the outside world.74.104.107.137 (talk) 02:24, 29 May 2010 (UTC)[reply]
If we're considering "specially built igloo houses" (ie technologically sophisticated living quarters) then we could survive much closer to the sun. We could imagine solar-powered refrigeration units keeping us cool - perhaps in some underground situation. With such technology, we could live much closer to the sun than halfway. Also, consider some place like Mercury: The sunny side gets up to about 500C and would be utterly unlivable - even with high tech habitation. But the 'dark side' is at -170C - which is way too cold. Someplace between those two extremes, there ought to be a place on the boundary between the sunlit and dark sides of the planet where there would be perpetual twilight and we could live - albeit with some fancy technology. Since Mercury is the closest body to the sun, that is the limit. Of course if we're talking about stars in general - then I'm sure there are other stars with planets even closer in than Mercury that could sustain sufficiently high-tech humans. Another problem with living close to a star would be radiation - but again, if you have an entire planet between you and the star, you'll be reasonably well protected. SteveBaker (talk) 17:59, 29 May 2010 (UTC)[reply]
Mercury doesn't have twilight. You need an atmosphere for that. Twilight is defined as the time between sunset and it getting dark (for a given definition of dark, which depends on what you are doing). If there is no atmosphere, then it will get completely dark as soon as the sun sets (well, a mountain just on the other side of the terminator might reflect some light, I suppose, but it's unlikely to be enough to be considered twilight). A habitable ring near the terminator of a tidally locked planet (you seem to be assuming a tidally locked planet) is a feature of sci-fi and could happen, but it requires an atmosphere to moderate the temperature gradients. --Tango (talk) 20:54, 29 May 2010 (UTC)[reply]
That's true. But without an atmosphere, you're obviously not going to be wandering around on the surface without a lot of technology. Assuming you're living in a well-engineered habitat, the important thing is that you're able to control the temperature cheaply and easily. If you live close to the terminator - you could run pipes with water or some other liquid flowing through them out onto the sunny side and the dark side of a small hill - and by controlling the flow rates get water at any desired temperature. The other nice thing about a tidally locked planet is that you can erect solar panels that are at the perfect angle to collect sunlight without having to make them turn to face the sun - and you don't need backup batteries because there is never any cloud cover and it's never nighttime. With a perpetual/limitless 600 degC temperature differential, you could also use steam engines to generate power. With ample electricity and no problems with heating or refrigeration, it's actually not such a terrible place to set up home. But if you are close to the terminator, any object with even a modest albedo that's sticking up into the sunlight would provide ample illumination into the areas in shadow. But given the level of radiation coming from the sun and a planet with no magnetic field to deflect it - you're not going to be going out onto the surface anywhere near the terminator! SteveBaker (talk) 23:45, 29 May 2010 (UTC)[reply]
One problem with a tidally locked planet that has an atmosphere, though, is that the temperature gradient would create hurricane-force winds that would blow you away before you could say "convection". Looks like Tango completely forgot about that :-) 67.170.215.166 (talk) 02:53, 30 May 2010 (UTC)[reply]
On second thoughts, you don't need an atmosphere to moderate the temperatures - the ground will do that. You just have a build your settlement underground. The surface will have a sudden 600 degree temperature jump, but the temperature a few metres underground will be gradual. I'm starting to like your idea! A venue for Wikimania 2100, perhaps? --Tango (talk) 23:56, 29 May 2010 (UTC)[reply]
Maximum/Minimum Irradiance for "Human habitable" planet temperatures?
(Third time's a charm)
I keep trying to create a simple model for anyone who wants to speculate on a planet having habitable temperatures for people (not extremophiles) based on Irradiance.
Take for example HD 38801 b: Star Radius = 2.53 sol Star Te = 5222 K Stefan–Boltzmann constant, σ = 5.67051E-8 Semi-major axis = d, in this case 1.7 Eccentricity = e, in this case 0 Emissivity = ε, (Earth=0.62009) Albedo = A, (Earth=0.3)
=((((R^2)*σ*(Te^4)*(1-A))/(4*ε*(d±(d*e))^2))^0.25)-273.15
So I can get a global annual average temperature for a planet,
If I assume a global average albedo and a global average emissivity
Albedo
εmissivity
0.20
0.25
0.30
0.35
0.40
0.45
0.80
5°C
1°C
-4°C
-9°C
-14°C
-20°C
0.75
10°C
5°C
0.7°C
-4°C
-10°C
-15°C
0.70
15°C
10°C
5°C
0.3°C
-5°C
-10°C
0.65
20°C
16°C
11°C
5°C
-0.1°C
-6°C
0.60
26°C
21°C
16°C
11°C
5°C
0.5°C
0.55
33°C
28°C
23°C
17°C
11°C
5.4°C
Ignoring the perspective that single value Albedo and Emissivity are very
simplistic, since "Global Annual Average Temperature" is also but it exists:
A) at what levels of irradiance (max/min) does this become moot?
B) what combinations of Albedo & Emissivity are unrealistic or possible??
Thanks, 24.78.167.139 (talk) 06:35, 29 May 2010 (UTC)[reply]
Have you had a look at Atmosphere of Venus. Venus reflects two thirds of the light and yet its surface temperature is higher than that of Mercury. Even so there is a zone high up in its atmosphere which just might be okay for microbes. Dmcq (talk) 09:03, 29 May 2010 (UTC)[reply]
I came upon this chart in a search and realized this illustrates well the idea that there are a lot of possibilities but some are unrealistic. - 24.78.167.139 (talk) 17:36, 30 May 2010 (UTC)[reply]
So the button cell I have must be a silver oxide or manganese dioxide cell with a tiny bit of mercury added to it. I was wondering if I could open it up and dissolve the mercury(II) oxide. But there isn't enough. --Chemicalinterest (talk) 16:26, 29 May 2010 (UTC)[reply]
If I might intercept the question - aren't those flashing LED shoes that kids used to wear back in the early 1990s using a liquid Hg amalgam to complete the circuit? Are those banned too? SamuelRiv (talk) 17:10, 29 May 2010 (UTC)[reply]
For my understanding the chemistry of mercury is interesting, but to use mercury cells as a source for experiments is not very good. Working with mercury is unpleasant and I would only do it in a lab with a fume hood. The chemistry of manganese and vanadium is similar interesting and both metals are by far less toxic!--Stone (talk) 22:04, 29 May 2010 (UTC)[reply]
How about zinc - excluding the absense of a +1 oxidation state much of the chemistry is 'similar' to mercury, it's not particularly toxic, and readily available. Yes I know zinc is boring - but it's not what you've got it's what you do with it...83.100.138.38 (talk) 14:15, 30 May 2010 (UTC)[reply]
I have an old mercury dial thermostat, if you really need some mercury..... Not sure it's safe to mail it though. Maybe offer to replace thermostats for people for free? But please do be careful. Ariel. (talk) 02:34, 30 May 2010 (UTC)[reply]
It's illegal to send mercury (or anything that contains mercury) by mail -- the reason is because mercury dissolves aluminum (including Boeings and Airbuses, and DC-3's too) -- so if the stuff leaks out, it could cause a nasty crash. Clear skies to you 67.170.215.166 (talk) 02:58, 30 May 2010 (UTC)[reply]
No I didn't ask for Hg metal, asked for HgO or mercury(II) compounds. Forget about Hg; NH2Cl and Cl2 are enough toxicity, not to mention Cr6+. --Chemicalinterest (talk) 19:43, 30 May 2010 (UTC)[reply]
I should explain some more! The famous fictional vampire is said to have been very loosely based on (and named after) the exceedingly nasty Vlad III the Impaler - who was arguably a much nastier person than the fictional Dracula. The name "Count Dracula" is attributed to this guy - because: "His Romanian surname Dracula (also spelled "Draculea", "Drakulya"), by which Vlad was referred to in several documents, means "Son of the dragon" and points to his father, Vlad Dracul, who received that moniker from his subjects because he had joined the Order of the Dragon. Dracul, from the Latin word Draco, meaning "dragon", is derived from the Greek word Δράκων (Dracon), though in modern Romanian it means "devil".". He was a Prince of Wallachia - not a "Count".
Of course, we must never forget that bloodsuckers still lurk among us. Like legends of yore, they will rise again. But seriously, the Vampire article is terrific, and the Vampire lifestyle briefly discusses and links to this unique teen subculture, though without a "Dracula"-like leadership. SamuelRiv (talk) 18:16, 29 May 2010 (UTC)[reply]
By the way, he has not much to do with Transylvania, which was then part of the Kingdom of Hungary. He was the ruler of Wallachia (a country roughly corresponding to today's Southern Romania), maybe the name "Transylvania" sounded more spooky to Bram Stoker and chose that instead. --131.188.3.20 (talk) 21:36, 29 May 2010 (UTC)[reply]
Notice that Transylvania is a real place, though, even if Vlad is from just South of there. (The word means "across the woods", and Vlad was just across the woods from there.) Also note that vampire bats are real, and really do suck blood from the living, although humans are only rarely their target, and they are in the Americas, not anywhere near Romania. StuRat (talk) 01:38, 30 May 2010 (UTC)[reply]
I don't think the WHO or UNICEF manufacture them directly. Rather, they publish standards, and encourage individual nations to produce and distribute the solutions ([27]). I don't know where you are, so I can't really help hook you up with free packets (if free packets are even available in your area). Here's the WHO's recipe, if you wanted, you could make your own: [28]. Otherwise, there appear to be a number of commercial sellers online if you're not able to get free packets. For more information on oral rehydration in general, see our article Oral rehydration therapy. If you gave us more information on where you are, and what you need it for, we can probably help you better. Buddy431 (talk) 20:32, 29 May 2010 (UTC)[reply]
If you are in a disaster area, then aid agencies or the national authorities drop free ORS from planes and helicopters and set up distribution centres where you can queue for the stuff. If you aren't in a disaster area, then you might be able to get it free from health clinics, etc., but you probably have to buy it or make it yourself. --Tango (talk) 21:00, 29 May 2010 (UTC)[reply]
im in the usa can i get it?
Echoing Tango, I'd check any local health clinics. It seems doubtful to me that you'd be able to get it free in the US, but I don't really know. You can also probably buy some at a local drug store (though it may be marketed specifically for infants, i.e. Pedialyte). Sports drinks, such as Gatorade, are pretty good for this sort of thing as well (you won't get it free, but the prices aren't outrageous). You can also make a pretty good substitute with just sugar and salt (13 g sugar, 3 g salt per liter of water, as per the WHO composition) (though having the potassium and citrate are of course preferable). The question is, what's it for? If you or your kid has diarrhea, you may want to talk to a doctor or other medical professional anyway. They may be able to suggest the best solution. Buddy431 (talk) 22:40, 29 May 2010 (UTC)[reply]
I would be very surprised if you can't buy it in US drug stores. You certainly can in the UK (I think there are different versions for adults and children). --Tango (talk) 23:32, 29 May 2010 (UTC)[reply]
Yes and it tastes revolting! I'd much prefer to get a glass of diluted Ribena, add a pinch of salt, and drink it in one! --TammyMoet (talk) 07:30, 30 May 2010 (UTC)[reply]
If it tastes revolting, you don't need it. When you are dehydrated you lose the ability to taste salt and suddenly ORS starts to taste nice! I don't think there is enough sugar in Ribena for that recipe to match the WHO recipe - you need to add some extra sugar too. Otherwise, I can't see a problem with adding flavouring like Ribena to ORS. --Tango (talk) 15:01, 30 May 2010 (UTC)[reply]
Does that mean you've gone into local health clinics and local drug stores as suggested above, and asked? Did they not offer suggestions of where you might be able to get it? It also occured to me from the above posts that you may want to try some sort of travel/adventure/outdoor oriented store (a bit like Kathmandu (company) here in NZ). I presume if you've looked all over the USA you've already looked in places like Walmart. Nil Einne (talk) 09:11, 31 May 2010 (UTC)[reply]
I hope you can help me as I have had no luck in finding the answer to this question. If someone is addicted to & using crystal meth almost daily, can the meth get stored in fat cells, then later be released into the system when increased physical activity burns off fat? My son has been through rehab & swears he isn't useing and his moods & attitudes would seem to back up his words, however, he recently started work with a landscaping company & it is very hard work. Suddenly his weekly UA tests are reading positive & he is steadfastly denying that he is useing again. Thanks for any possible help71.34.135.9 (talk) 20:41, 29 May 2010 (UTC)[reply]
This happens with THC from cannabis and various other hallucinogens, so it wouldn't surprise me. Can't find a specific citation though. Regards, --—Cyclonenim | Chat 21:13, 29 May 2010 (UTC)[reply]
Gosh, best of luck to you and your son. I hope you can find a doctor to defend this concept, because coming off of something like that is so utterly important and it would be terrible if he lost his job and perhaps sink into a vulnerable state (especially since construction is great work). SamuelRiv (talk) 18:43, 30 May 2010 (UTC)[reply]
Salty Q
It's good to eat salt tablets when in the desert yet bad to drink saltwater when in a lifeboat. Why the diff ? StuRat (talk) 21:49, 29 May 2010 (UTC)[reply]
Precisely. Seawater is just too salty. You can drink it as a source of salt, but only if you drink enough fresh water with it (or, preferably, dilute it with fresh water). Likewise, you shouldn't eat salt tablets in the desert unless you have plenty of water with them. --Tango (talk) 23:14, 29 May 2010 (UTC)[reply]
Dude, you mixed ammonia and bleach? That's like the one thing that everyone's told not to do with cleaning chemicals. Our Ammonia article says that Chloramines can be formed. Our Bleach article also has some of the reactions possible, including the possibility of making Hydrazine. I hope you're being careful. Buddy431 (talk) 02:02, 30 May 2010 (UTC)[reply]
I absolutely agree with Buddy (and others). Did you really have to mix these together yourself to see what happens? There is plenty of stuff on the internet telling you what will happen. After reading a bunch of your questions and answering them (under an IP address, I have since signed up with an actual user ID) I should warn you that all of these exotic reactions and metals (chromium, lead, mercury) can be very dangerous. If you are doing this at home, what sort of apparatus do you have for these experiments? What do you do for waste disposal? My apologies if you are already doing this in a safe environment.
Don't get me wrong, I think that it is great that you want to learn about chemistry, and experiments can be a great way to understand something, but be careful! I'd recommend asking your science teachers, but I seem to remember from a previous post that your chemistry teacher is a dolt - don't ask him/her. Maybe someone else in the department can help you get some background material on your proposed experiments, or even let you use some equipment at school. I am a chemist myself, so I think that it is absolutely awesome whenever students are interested in chemistry, but there is a lot more to it than pretty colours, funny reactions and party tricks. To answer your original question, Buddy is right, chloramine will be produced and this may or may not be the gas observed. It could be chloramine, or it could be ammonia evaporating if the reaction is exothermic.Pmdove (talk) 03:04, 30 May 2010 (UTC)[reply]
I totally agree, but the bleach/hypochlorite reaction is almost universally presented totally wrongly in all internet discussions - the reaction is actually used to treat water, and is nothing like the hazard presented someplaces online. Nevertheless Chloramine is produced in considerable quantities.. Be Safe. 83.100.138.38 (talk) 14:12, 30 May 2010 (UTC)[reply]
Actually chloramine is likely to remain in solution, and the gas is likely to be nitrogen. Both NHCl2 and NCl3 are not stable in alkaline solutions and will not be present in the very basic NH3 / NaOCl mixture to any significant extent (except as intermediates) (They are formed in acid solutions) (also MSDS reports present a worse case scenario - not what will typically happen). This thesis gives some of the background [29] intro upto p.10 (the internet is full of worst case 'mis-information' that does not apply in strogly alkaline solutions.) All the reactions are exothermic, so de-gasing of NH3 is also a possibility as stated above.
Nevertheless the reaction is still not advisable due to Chloroamine produced, and the heat produced (which could be considerable with concentrated NH3 and bleach).83.100.138.38 (talk) 14:02, 30 May 2010 (UTC)[reply]
see also [30] The reaction is used in water treatment - and called "Breakpoint chlorination" Breakpoint chlorination involves the use of chlorine (in the form of gas or sodium hypochlorite solution) to chemically oxidize ammonia and convert it to nitrogen gas.p.2 (14th page adobe reader count)83.100.138.38 (talk) 14:07, 30 May 2010 (UTC)[reply]
See this article for a technical explanation of complications. Check down about 5 or 6 blue headings until you come to "Complications". Bielle (talk) 03:05, 30 May 2010 (UTC)[reply]
Birth Defects
An Anonymous editor (149.135.96.120) asked at the New contributors' help page; "What are possible birth defects to a baby that can be caused by the mother being morbidly obese while pregnant? Thank you" ;"Could you please inform me of what birth defects can arise?" -- wiooiw (talk) 02:57, 30 May 2010 (UTC)[reply]
From the abstract of “Maternal obesity and morbid obesity: the risk for birth defects in the offspring” found here comes:
Maternal prepregnancy morbid obesity was associated with neural tube defects OR 4.08 (95% CI 1.87-7.75), cardiac defects OR 1.49 (95% CI 1.24-1.80), and orofacial clefts OR 1.90 (95% CI 1.27-2.86). Maternal obesity (BMI > or = 30) significantly increased the risk of hydrocephaly, anal atresia, hypospadias, cystic kidney, pes equinovarus, omphalocele, and diaphragmatic hernia. CONCLUSION: The risk for a morbidly obese pregnant woman to have an infant with a congenital birth defect is small, but for society the association is important in the light of the ongoing obesity epidemic.
An "OR" is an odds ratio. A "CI" is the confidence interval. Simply put, there is about a 4-fold (range from 1.87 to 7.75) increased chance for an obese woman to have a baby with a neural tube defect. The "odds ratio" can be multiplied with the baseline odds of having a baby with a neural tube defect to calculate an actual risk, which is usually still quite small for the individual (as noted above), but when considering millions of births the increased risks amount to an important public health problem. --- Medical geneticist (talk) 11:46, 30 May 2010 (UTC)[reply]
One additional risk is that obese women often don't seem to notice they are pregnant as soon and those around them may not notice all all. They might just normally have an irregular period and figure that's what's happening, since the "baby bump" isn't as apparent. This could lead to consuming alcohol, smoking, or taking drugs which should be avoided during pregnancy. In extreme cases (probably with some denial tossed in), obese women may not even know they are pregnant until they give birth. StuRat (talk) 03:36, 30 May 2010 (UTC)[reply]
I'm not sure that's true. Having a bump is a relatively late symptom; the woman is more likely to be concerned with no period and morning sickness, which come before the bump. By your logic we'd have loads of women not knowing they were pregnant until the bump came, and that comes later than the missed period or morning sickness. Regards, --—Cyclonenim | Chat 19:17, 30 May 2010 (UTC)[reply]
It's not common - but just Google for "gave birth didn't know pregnant" and you'll find that it's not exactly unknown either! SteveBaker (talk) 02:13, 31 May 2010 (UTC)[reply]
Obesity can be associated with all sorts of endocrine dysfunction, such as polycystic ovarian syndrome, so the woman may be having such irregular menstrual periods that she really doesn't notice missing her period. The morning sickness, who knows... it's so variable between women that it isn't really a reliable clue about pregnancy. Anyway, SteveBaker is right, this is not unheard of. There's even a Discovery channel television series about it. --- Medical geneticist (talk) 03:15, 31 May 2010 (UTC)[reply]
Females of Saturniidae moths will start laying unfertilized eggs a few days after eclosion if they cannot find a mate by then (note that the imago stage of Saturniidae has a typical lifespan of only about a week). Nothing will hatch from unfertilized eggs, though, since (as StuRat said already) Saturniidae are incapable of parthenogenesis. --Dr Dima (talk) 06:12, 30 May 2010 (UTC)[reply]
Drew Brees Sports Science
I had some questions about what I thought was some spurious science in a video I saw today, http://www.youtube.com/watch?v=tVoqA-LKGb4. To begin with, the whole football player/archer comparison is quite silly in my opinion, but the questions I had concern the physics at the end. First off, while my physics may be a little rusty, the term "gyroscopic torque" seems like a load of bull to me. Then they talk about gravity inducing a torque, but isn't the only torque on the ball caused by aerodynamic influences and the like? They also mention that the ball wobbles at an "ideal" rate of three wobbles per five spins. But isn't the rate of precession for a small angle of wobble always fixed? And can anyone give a reason why a small wobble would be better (as opposed to no wobble)? And while I'm at it, what causes the ball to dip with its nose always pointing to where it's headed? I might have asked this question a while back, and the answer involved the Magnus effect, but how does this make the dip so perfect? Thanks. 173.179.59.66 (talk) 03:58, 30 May 2010 (UTC)[reply]
First of all, Olympic archers shoot from 70 meters - this guy was throwing from 20 yards - so let's keep that all in perspective for that video (though still impressive). They did confuse the torque a little bit: The ball is a gyroscope, as you probably know, and therefore exerts resistance to anything trying to change its axis of rotation. The force of gravity is trying to do just that, so a "gyroscopic torque" is exerted to preserve the ball's direction (I wouldn't use that term - they were just using it to sound all-sciencey). As for the wind going around the ball, there is a airfoil effect for sure and that probably acts in concert to counter gravity. At the end of the day, the "equations" are best worked out by the feedback in distance and grace that the athlete feels.
I'm not familiar with the Magnus effect until reading the article, after which I remember us playing around with that in grad school when we were discussing table tennis with the Chinese students (and we derived most of it ourselves). So when a football spins on the axis on which it's thrown, it should curve a bit like a sliced golf ball, which is definitely not desirable. My guess is what the previous people told you is that the precession (wobble) is a way to counteract that slice effect. It would make sense to me, sorta, without doing the math. Sports physics is very interesting, but I really hate trajectories. SamuelRiv (talk) 19:13, 30 May 2010 (UTC)[reply]
One purpose of having attic vents is to vent the smoke out of the attic in case of a house fire -- or else the flammable pyrolysis gases would build up in the attic and form an explosive mixture with the air, which could cause a dangerous smoke explosion or flashover as soon as the firefighters open a door or window in the attic (not to mention that it could choke someone up if not properly vented). 67.170.215.166 (talk) 05:29, 30 May 2010 (UTC)[reply]
Warm, moist air which permeates up from the house in winter can cause condensation within the cold, uninsulated, attic space. This condensation then encourages the growth of fungi and moulds which may be harmful to the wooden structure of the roof. In extreme cases moisture may drip back onto the ceiling and cause watermarks. Ventilating the attic/roof space keeps the space dry. Caesar's Daddy (talk) 07:42, 30 May 2010 (UTC)[reply]
Here in Texas, the heat that builds up in the attic space is enough to dramatically increase your air conditioning costs in the summer even when the attic floor is well insulated. Venting the attic (and even using a fan to get airflow through there) is a huge help. SteveBaker (talk) 15:29, 30 May 2010 (UTC)[reply]
The chief purpose of attic ventilation is to remove moisture that escapes from the interior of the house through poorly-sealed penetrations in the ceiling membrane that can be found in even a well-constructed house. Once it reaches the attic, it will condense on cool surfaces like the roof sheathing. There is no practical reason to keep an unoccupied attic warm in winter - the insulation above the ceiling is supposed to be of sufficient thickness and provided with a vapor barrier. If moisture builds up, it will compromise the insulation's effectiveness, grow mildew and rot the structure. I've never seen any reference to smoke ventilation - the small scale of typical vents would have no practical effect on even a small fire. In warm climates or in summer, roof ventilation will help keep the attic a few degrees cooler, although the effect in most cases is marginal unless you've installed a fan or are using light-colored roofing. Insulation deals with a warm-cold transition better than a cool-hot gradient (it gets heat-saturated), so any cooling of the attic, however slight, will help the air conditioning system.
Even if the attic is occupied, in most cases it is wise to have a ventilated airspace between the insulation and the roof sheathing. Exceptions would be found in a well-installed sprayed insulation installation, or in construction using structural insulated panels, which won't transmit water vapor. Acroterion(talk)15:48, 30 May 2010 (UTC)[reply]
container ship
If the crew of a container super ship spotted a person floating on a raft in the middle of the Pacific would they be obligated to stop and pick the person up? 71.100.8.229 (talk) 05:19, 30 May 2010 (UTC)[reply]
Primer on sailing the high seas. Super container ships, run at speeds of -teens up to approx. 20 knots. While this is not technically fast on land (1 kt is ~1,852 km/h), it causes their braking distance to amount to around a kilometer (give or take) on sea. So in the simplest case it would take them a while to stop/turn/whatever. An immediate stop is not possible.
Such a ship, however, in a situation just like the one described by the OP, is obliged by maritime law to help directly (i. e. by lifebuoy or whatever, time permitting) or indirectly (i. e. by sending out a distress call or informing vessels nearby that a person is in distress) anybody who may be out on sea in distress. Apart from strictly legal requirements, seamen are often plain helpful to each other in what goes just a little bit beyond simple human readiness to help. Father's a sailor, that's how I know. HTH. --Ouro (blah blah) 05:52, 30 May 2010 (UTC)[reply]
Ouro is correct about the distance required to stop or turn a large vessel such as a container ship. To reverse direction and return to a point previously passed, such as when rescuing a man overboard, requires careful maneuvering and navigating. See Man overboard rescue turn. Dolphin(t)11:00, 30 May 2010 (UTC)[reply]
Surely they'd have a lifeboat or some kind of zodiac inflatable that they could use to pick up the survivor without the need to stop the container ship? SteveBaker (talk) 15:26, 30 May 2010 (UTC)[reply]
Imagining the situation you described, I am seeing a lost sailor trying to reach the released lifeboat and the mother ship disappearing behind the horizon ;) I suppose they could release a lifeboat on the spot, but should at least stop and wait for the guy to reach the ship in order for the rescue to be complete, provided the floating person had enough stamina left to reach the vessel in the first place, seeing as they could have been lost at sea for days without proper food... I guess it depends on the exact situation, i. e. if the person is spotted ahead (like, if the vessel had not passed by them yet, and on seagoing ships lookout is usually maintained via radar and binoculars during watch so as to notice everything, because a radar will probably not pick out a person floating in the water), then the ship could react more quickly by stopping and could probably be able to come to a full stop somewhere around where the person is. A person spotted far off would require much more manoeuvering. If you're worried about delaying the ship that's delivering important cargo, do not - afaicr, delayed ship arrivals aren't all that extraordinary, especially on longer routes. --Ouro (blah blah) 15:53, 30 May 2010 (UTC)[reply]
Freefall lifeboat
Usually there aren't traditional lifeboats, or a semi-rigid inflatable in a state of instant readiness. Lifeboats on bulk carriers and tankers, which are prone to sudden, catastrophic failure, and some container ships, are usually freefall-style, and aren't suitable for going out and picking somebody up. Acroterion(talk)15:58, 30 May 2010 (UTC)[reply]
Good photo. However, there are usually others as well, though, which pop out on contact with water and can be recovered, and as such ships usually have at least a small crane or something to hoist things like i. e. crates on board, it is not impossible. I have work and I'm sitting here. --Ouro (blah blah) 16:07, 30 May 2010 (UTC)[reply]
They sit inside all the time, Robin, always ready, because nobody ever knows when they will be needed to take action. --Ouro (blah blah) 11:11, 31 May 2010 (UTC)[reply]
I believe any ship that can't stop quickly enough to deal with a MOB (either someone from their own ship falling over the side, or someone else they just happen to pass close to) is required by international law to carry a powered boat suitable for such rescues. It wouldn't take too long for that smaller boat to catch back up with the larger ship, assuming the larger ship started slowing down straight away. (In fact, WP:WHAAOE: MOB boat - it's very short and doesn't mention legal requirements, though.) --Tango (talk) 16:27, 30 May 2010 (UTC)[reply]
Meditation and sleep
Can you sleep less if you meditate? The guy who told me this, also told me you can levitate through meditation, so I am not quite sure I should believe him on this point. On the other hand, it sounds plausible that you might need less sleep if you have less stress along the day. -Mr.K.(talk)12:47, 30 May 2010 (UTC)[reply]
Regarding levitation, I read that the monks in Tibet and elsewhere sit cross-legged in their cells, and with a lot of practise they can jump into the air while maintaining that posture, leading to stories and photos of levitation. 92.15.12.12 (talk) 13:42, 30 May 2010 (UTC)[reply]
That's a really funny image; somehow I doubt that it would look like levitation, as opposed to a bizarre form of hopping. Anyway, concerning the question, it would make sense, and there are claims by proponents that that happens, but I couldn't spot much in the scientific literature to support it. A more common report is that meditation increases sleep in some people by reducing stress-related insomnia. Looie496 (talk) 14:37, 30 May 2010 (UTC)[reply]
Meditation might temporarily make you less tired even given the lack of sleep, but I wouldn't count on it over longer periods as sleep deprivation sets in. Stress can contribute to either insomnia or hypersomnia. Techniques like yoga and taichi may lower your stress, but again any reduced need for sleep is probably only temporary. ~AH1(TCU)18:11, 30 May 2010 (UTC)[reply]
Ecological implications of eradicating malaria-carrying mosquitoes
What would be the ecological implications of eradicating Anopheles mosquitoes, particularly Anopheles gambiae, which are responsible for transmitting malaria? I don't mean from the huge decrease in human mortality, with the population pressures that would be likely to result, but in terms of the effect on whatever else (apart from malaria itself) which relies on these mosquitoes for its life. DuncanHill (talk) 16:40, 30 May 2010 (UTC)[reply]
I had many a fishtank when I was a kid and now as an adult, I just bought a 20 gallon for my family to enjoy. As a kid, I completely ignored pH, ammonia/nitrogen and everything else that relates to "water management" and everything always went great -- I did, however, worry about chlorine and made it a rule to use 1-day-old tap water when adding/exchanging. So my question is now that I'm starting again, was it dumb luck that things worked out or is it really not such an issue assuming one has a good filter and does exchange water about once every 2 months (and to give you an idea of the hardiness/sensitivity of the fish that I will include in my tank, it will most likely consist of danios, gouramis and catfish).
And then as a follow up, the fishtank article has a bunch of photos -- about halfway down is one of a sad looking tank while the upper most photo in the article displays a beautifully decorated tank. Would I only be able to get all those plants in there and keep them alive if I take care of the pH, salinity, ammonia, etc. or what? DRosenbach(Talk | Contribs)17:46, 30 May 2010 (UTC)[reply]
You'd need to watch the nitrate and ammonia levels in the tank, as those are the biggest killers of aquarium fish. Cleaning the feces from the tank by vacuuming the substrate regularly should do the trick. ~AH1(TCU)18:02, 30 May 2010 (UTC)[reply]
With the caveat that I know absolutely nothing about tropical fish, my experience in the areas that I do know something about is that most of the advice you read on any given topic is aimed at getting you to spend money on stuff. Looie496 (talk) 23:40, 30 May 2010 (UTC)[reply]
That question is a whole book in itself ..
firstly what sort of filter did you use/are you planning to use
secondly you might be lucky with plants (I wasn't)
thirdly for having a successful planted aquarium the conditions and set up can change considerably compared to conditions for a successful non-planted equation
fourthly - no it doesn't need to be an exercise in water testing and chemistry , (but it can be if you want)
fiftly - one big factor that must be considered is the requirement for CO2 for plant growth - luckily fish breath out CO2 - unluckily strong filtration can de-gas the water of CO2
sixthly - your fish might eat the plants... especially if the plants are soft leaved and the fish are omnivores - one of the more successful experiences I had was with carnivorous and heavy eating catfish and soft leaved plants - the fish made the fertiliser, and the plants grew in it...
seventhly - some plants are easy, others are hard to grow - just like fish.
I'd like to recommend a book - in fact most I've seen contain about the same info - in general the tricky bit is growing both fish and plants in the same aquarium.94.72.235.30 (talk) 23:42, 30 May 2010 (UTC)[reply]
I used to run 2 tanks and am now running one - a Rio 300 (about 3x larger than yours). When we initially set up our first tank (about the size you're talking about) I knew nothing about the chemistry of tanks and my initial fish (mostly guppies) pretty much all died fairly quickly. I then learnt about the chemistry, and it became clear that the probably died of ammonia poisoning. The best way to avoid this is to start with few fish and add them slowly, so the bacteria in the tank can grow to accommodate the larger ammonia load. You need 2 types of bacteria - ones that convert the ammonia to nitrite, and others that convert nitrite to nitrate. You don't need to add them - they grow of their own accord. I would recommend testing for ammonia in a new tank if you do nothing else. If it gets too high, change some of the water. You can use tap water but you must use a additive to remove the chlorine. You should also count on making regular water changes in order to keep the nitrates down - I change about 4 to 5 gallons of water each week and would recommend you do the same. --Phil Holmes (talk) 11:31, 31 May 2010 (UTC)[reply]
Controlled burns on oil and hurricanes
Hi. Let's say that a medium-sized hurricane was threatening the Gulf Coast, and was heading directly for the Deepwater Horizon oil spill. If controlled burns were set over a large portion of the oil, what if any effect would that have on the hurricane? Would the extra heat fuel the hurricane, or would it cause the storm to expand and unravel, or expand to have a dangerous storm surge, or disrupt its eyewall, or cause it to change direction, or would the surge of the storm cause the oil to pool underneath the eye, or would it cause upwelling that cooled the oil, or would it create more shear and tornadoes, or would the storm plow the fires into the coast? Thanks. ~AH1(TCU)18:00, 30 May 2010 (UTC)[reply]
There is no way to really predict what would happen. Weather is chaotic by nature, so the hurricane would react differently for different sizes, shapes, orientations, temperatures, durations and positions of fires. We know large fires can create storms; there was a large vortex—called a tornado by some—caused by an oil tank fire in California in 1926 that killed two people after traveling almost a mile away from the fire. Pyrocumulus are a well-documented phenomenon whereby clouds and even thunderstorms can be created by large fires. However, I feel it would be impossible to predict the effects, and they would probably not be good. Hurricanes are basically a giant heat engine; adding more heat just isn't a good idea. Not to mention that, with the amount of rain and waves generated by the average hurricane, it seems likely that the fire would just go out.-RunningOnBrains(talk)20:22, 30 May 2010 (UTC)[reply]
On top of which modelling the burning oil is hellish tricky. Rough waves mean the oil forms a moussy emulsion with sea water: when we tried (twenty years ago) replicating the mousse to try to burn it we found the characteristics were incredibly sensitive to how well mixed the emulsion was, as well as the exact crude characteristics including how long it had been on the surface losing volatiles. We even looked at floating wicks in it etc but it is not going to be burning well in a storm, not so much because of the rain but from the breaking waves. The only good news is that oil is basically biodegradable; in a decade all traces will have gone eaten by bugs and the sensitive nature sites will be mainly back and happy. Of course some Corals and some oil companies might not survive the "obvious" solution of time. --BozMotalk21:14, 30 May 2010 (UTC)[reply]
Hurricanes are FAR bigger than that (than tornadoes or pyrocumulus). The heat from fire would have no measurable affect at all. The change in the water/air interface might have an affect, but I don't think it'll be big. The energy released in a hurricane is on the scale of hundreds of nuclear bombs. Ariel. (talk) 21:44, 30 May 2010 (UTC)[reply]
Would the huge fire generating a pyrocumulus storm be likely to cause rotation and gradually become a tropical depression (and then tropical storm, followed by hurricane)? Falconusptc23:41, 30 May 2010 (UTC)[reply]
Unlikely. Ariel is correct in that it would be very unlikely to have any effect at all; pyrocumulus storms are on the order of a few kilometers. Hurricane formation depends more on large-scale features than storm-scale features. I was just playing devil's advocate in saying that if you managed to make a fire big enough to effect a hurricane, it might only serve to strengthen the storm. Careful using that "nuclear bomb" analogy though...nuclear bombs are near-instantaneous events, while hurricanes can last weeks.-RunningOnBrains(talk)00:59, 31 May 2010 (UTC)[reply]
new LED lightbulbs
I've heard that a new generation of LED light bulbs are coming out soon. Will they come on quickly (the main problem with compact flourescent bulbs is the time it takes them to get bright.) Bubba73(You talkin' to me?), 21:07, 30 May 2010 (UTC)[reply]
It depends what you mean by 'new generation of LED light bulbs'. LED are continually improving, and light bulbs for existing fixtures already exist. In other words, there are what could be called new generations of LED light bulbs probably every year. One of the biggests problems is probably cost particularly for bright lights. There should be some decent replacements for 60W incandescent lightbulbs coming out at the end of this year or early next year (some decent ones may already exist), these were demonstrated at the recent Light Fair in the US. [32][33] Expect them still to cost quite a bit though. Sorry misread the question, see the next answer. Nil Einne (talk) 21:33, 30 May 2010 (UTC)[reply]
LED lightbulbs are already here - I have three of them in my home and I'm typing by the light from one of them right now! They don't need any time to 'warm up' like CFL's do. They use less electricity than any other type of light - are longer-lived than any other kind - and they are actually made of clusters of LED's so when they do fail, they tend to do so one LED at a time - so they rarely just go black like a failed incandescent or CFL. However, they are still hideously expensive - and unless you want one as a gimmick or you are a fanatical tree-hugger, you should probably wait for the prices to drop. They aren't close to being cost-effective yet. Mine are cool because you can adjust the color to any RGB value, remotely from your PC...I like a slightly yellowish light - but...hold on...there...now the light is blue-ish...and now pink! LED Xmas tree lights were in most stores last Christmas - and specialized lighting for swimming pools and hot-tubs have been using LED's for at least 10 years (my 10 year old hot-tub has LED lighting). SteveBaker (talk) 02:09, 31 May 2010 (UTC)[reply]
(EC with both above) I originally thought you asked 'are the next gen LEDs coming out soon' but then realised I was mistaken. Glad that it was still of interest. I've been following this area recently, more from a torch/flashlight angle but I've of course read or thought of things related to LEDs that may be of interest even from a lightbulb perspective.
Another interesting this is that Cree (who were mentioned in some of the above links in other areas) are also going to release the XM-L LED in (Northern hemisphere) Autumn of this year [34][35]. This is supposed to be rated to output 750 lumens from a single die emitter (in other words a single continuous LED) which they say is equivalent to a 60W incandescent (although based on our Incandescent light bulb, they probably mean a 60W 220V bulb rather then a 110V one). I suspect the 750 lumens is the maximum of the LED bin at the time of their release, in other words the LED they release might only be rated for something like 675-750 lumens (there is always variance, LEDs are sold as bins and guaranteed to output something in that range at whatever the maximum rated current for the LED) however I still find it an interesting development.
I don't however know whether it will actually be used much in replacement bulbs for incandescent lightbulb types (like the E27), there are already multi-die LEDs (basically they stick 4 or more LEDs on a package and connect them, somewhat similar to some earlier dual core and quad core CPUs) like the Cree MC-E & SSC P7 which are rated for slightly higher output [36] and have been available since early 2008 but don't seem to be used much for this purpose that I could find (of course most manufacturers don't say what LEDs they're using).
It may be because they tend to have poor Colour Rendering Index compared to what people are releasing for other LED light replacements. (Also the maximum output is usually those with the colour temperature of the cool white/bright daylight variety which don't tend to be so popular in the West.) Also these LEDs aren't necessarily the most cost effective from a $/lumens area. Or other factors, I don't really know much about (as said, I don't really know that much about light bulb replacement designs).
BTW, there's also the Luminus SST-50 and SST-90 which are also already available but again don't seem to be used light bulb replacement that I've seen. These use what's called a photonic lattice so can also be called a single die but are somewhat different from more traditional emitters. If you looked at the earlier DealExtreme link you may notice the currently available best bin of the SST-90 outputs when driven with (the maximum rate) 9 A, 2350-2820 lumens! According to our incandescent light bulb article, the minimum is equivalent to a 135W 110V bulb.
But even so, don't expect those sort of outputs to be done in a typical light bulb replacement anytime soon (meaning perhaps within the next year or so). One of the things I didn't mention above is for such high outputs, temperature really starts to become a problem which will not only kill the LED if it gets too hot but reduces effiency too (i.e. light output). (In addition to the heat output from the LED, the driver/regulator of the LED also can output a fair amount of heat since it's unlikely to be close to 100% efficient.) Incandescents and even CFLs can get quite hot, but they can survive such temperatures, LEDs can't. You need good heatsinking and I don't think from what I've read you're likely to be able to provide sufficient heatsinking for something like a E27 to do that (perhaps particularly given the variety of fixtures, including some enclosed, that may be used). Well unless you have some active cooling which is obviously unlikely to be considered suitable for household usage. Of course the fact the heat is a problem means effiency (lumens/watt) is important. See also some discussion [37].
Of course all these are obviously used for general/fixed lighting purposes, flashlights are clearly only a tiny proportion of what they're used for, this mentions a few. Other custom light fixtures (perhaps also fluorescent tube replacements) can obviously better accomodate the heatsinking/cooling requirements then having to design for existing bulb types. [38]
P.S. To avoid confusion, the current draws are at the forward voltage of the LED which is likely to be something in the 3-4 V range.
P.P.S. As a brief mention of cost. For the P7, you can get an LED with some sort of driver suitable for a torch for about US$15 with shipping from China/HK (i.e. this is a retal price). However the optics, heatsinking, driver suitable for main voltage are obviously going to add a fair bit. A cheap P7 based torch which uses rechargable lithium ion batteries is about $30 from China/HK (again with shipping). However these often don't draw and therefore use the maximum rated 2.8A for the P7. I would guess $40+ is likely for a light bulb replacement.
This is not a medical question, more just looking for confirmation of what seems common sense to me. The other day, my friend informed me that I should stop using my gas powered lawn mower and buy an electric one; he told me that I could get carbon monoxide poisining from using it to cut the grass. Being that I would be using it outside, this sounds rather unlikely to me. So, in short, is there any possible validity to what he is saying? 67.163.183.146 (talk) 21:58, 30 May 2010 (UTC)[reply]
If you cut the grass with a gasoline-powered mower in a small enclosed room with no ventilation, carbon monoxide poisoning is a real hazard. Edison (talk) 22:07, 30 May 2010 (UTC)[reply]
I don't know exactly, but of all of the people that use gasoline lawnmowers responsibly (i.e. not in the living room of their house), I haven't heard of any cases of CO poisoning. Millions of people presumably use them, so if it was a serious risk, I suspect that it would be a very well-known thing. Falconusptc23:43, 30 May 2010 (UTC)[reply]
I have a hard time imagining getting much exposure to CO outdoors, even with a typically fume spitting lawnmower engine; people just don't spend that much time mowing lawns, and outdoors, the risk is greatly diminished. Most of the Google hits relate to not running the mower in a shed or garage, for example. All that being said, lawnmowers (and other gasoline powered yard tools) are notorious for not having very clean or well filtered engines. See, for example, [39], as well as a source from the epa: [40]. So even if it's not a health risk, your mower may be hurting the environment. Buddy431 (talk) 00:43, 31 May 2010 (UTC)[reply]
(edit conflict) Carbon monoxide poisoning is only a hazard in encloses spaces, or in some extreme circumstance that I can't think of right now. It is metabolized quickly, and exposure to oxygen is the antidote, so it has no cumulative effect such as those seen with methyl mercury and other environmental contaminants of concern. Thus there really is no reason I could think of that gas mowers would be dangerous.-RunningOnBrains(talk)00:51, 31 May 2010 (UTC)[reply]
There are lots of reasons to consider getting an electric lawnmower (gas mowers are horribly polluting, noisy, heavy and a pain in the neck to maintain as they get older) - but I agree that if used in a reasonable way, carbon monoxide poisoning isn't one of them. SteveBaker (talk) 02:00, 31 May 2010 (UTC)[reply]
The hows are explained at Time reversibility - for gravity (ie 'newtonian' gravity) the following section applies: "If a deterministic process is time reversible, then the time-reversed process satisfies the same dynamical equations as the original process, AKA reversible dynamics; the equations are invariant or symmetric under a change in the sign of time"
The last sentence above gives the simple way to tell. eg consider motion under gravity as a function of time.
OP here: I would think this means that any time derivative changes sign, and hence a second time derivative preserves sign. So for something like gravity, where d2r/dt2 = (GM/r3)r, nothing changes when time changes sign, so the motion is identical, except the velocity changes sign so the particle will travel in the opposite direction. Is this right? 173.179.59.66 (talk) 02:56, 31 May 2010 (UTC)[reply]
I learned in dental school that nothing reduces the internal production of cholesterol -- 1 mg of the 1.7-1.8mg daily cholesterol necessary for an adult human male is produced by the body as a given. DRosenbach(Talk | Contribs)01:51, 31 May 2010 (UTC)[reply]
Exogenous substances can certainly reduce the internal production of cholesterol. See statin. However, the body will compensate for the decreased cholesterol production and shunt the available cholesterol to the most important functions. According to our bile acid article, "the body produces about 800 mg of cholesterol per day and about half of that is used for bile acid synthesis" so you can bet that bile acid production will still get a significant proportion of the available cholesterol. In addition, about 90% of bile acids are recycled. This is the mechanism of the cholesterol-lowering effect of bile sequestrant drugs. According to bile acid, "since bile acids are made from endogenous cholesterol, the enterohepatic circulation of bile acids may be disrupted to lower cholesterol. Bile acid sequestrants bind bile acids in the gut, preventing reabsorption. In so doing, more endogenous cholesterol is shunted into the production of bile acids, thereby lowering cholesterol levels. The sequestered bile acids are then excreted in the feces." This indicates that bile acid production is pretty important and will likely be maintained in the face of reduced cholesterol synthesis. That being said, it would probably be possible in extreme cases to get such dramatic reduction of cholesterol that bile acid production might eventually be impaired. --- Medical geneticist (talk) 03:05, 31 May 2010 (UTC)[reply]
Deepwater Horizon oil slick - why not burn it off?
Is there any particular reason that bombarding the slick with napalm, or white phosphorus bombs near the point of orign, in order to burn the oil off before it reaches the coast hasn't been considered? Would this actually work? Or would it make an even bigger mess in the long term? --95.148.107.248 (talk) 01:18, 31 May 2010 (UTC)[reply]
They have been burning surface oil almost since day one [41] but the oil is only concentrated enough to burn in certain places...I believe the reason is that it's being released so far below the ocean surface that it diffuses too much to be effectively burned by the time it reaches the surface. Don't take my word for it though, just speculation. -RunningOnBrains(talk)01:27, 31 May 2010 (UTC)[reply]
Why not just stick something like an industrial-strength version of an umbrella or deflated balloon down the pipe to block it, is what I wonder. 92.28.254.179 (talk) 10:33, 31 May 2010 (UTC)[reply]
Living in an Attic
I live in an attic with dormers and it gets REAAAAAAAALLLY hot in the summer months -- so hot that the largest AC that fits in my living room window is a 12000BTU and it doesn't do nearly a good job of lowering the temp. I think it's because the dormers are the inside surface of the actual roof and the sun bakes my apartment. What can I do to achieve normal room temp in this case? DRosenbach(Talk | Contribs)01:54, 31 May 2010 (UTC)[reply]
I know that the formula for gravitational acceleration is . Is this valid to all distances, or is there somehow a distance at which it's rendered invalid? In other words, do 433 Eros and Rigel have any absurdly-tiny effects on me? I've read Newton's law of universal gravitation, but I can't find anything to answer my question. Nyttend (talk) 02:54, 31 May 2010 (UTC)[reply]
I'm well aware, by the way, that we can't measure the effects of Eros' and Rigel's gravities if they do exist as far away as Earth. Nyttend (talk) 02:55, 31 May 2010 (UTC)[reply]
The answer depends somewhat on whom you are asking :) . Professor Mordehai Milgrom of Weizmann Institute has a theory that says it is not valid at all distances, but the "majority opinion" (if there is such a thing in physics) is that it is valid at all distances. --Dr Dima (talk) 03:06, 31 May 2010 (UTC)[reply]
Yes, as far as we can tell the gravity formula is valid for all distance and indeed rigel has a effect on you. But, as you pointed out, those distant forces are too small to be measured directly and we cannot be sure if the inverse square formula is really valid for all distances. Nevertheless we know that an effect exists (even if the formula chages at some distance) because we know that the sun (and other stars) orbit the center of the milkyway under its gravitational atraction. We also know that gravity acts at distances as far as galaxy superclusters or more, otherwise theose superclusters would not exist. Dauto (talk) 03:33, 31 May 2010 (UTC)[reply]
There is a quote that goes something like: "If you had an error in measurement of one atom radius in the position of an object many light years distant, it would make it impossible for you to correctly calculate the position of an atom of gas after some number of collisions." (I tried but I just can't find the original quote.) So yes, gravity from distant objects influences events on earth. (The person who said it actually calculated the various numbers, and I really wish I could find the quote again.) 11:22, 31 May 2010 (UTC)
Chemical reaction within a thin film of a chemical solution
Hey guys,
My lab project involves research on the next generation of clean energy. I need to deposit a special organic film on a surface and the reaction should happen in a thin chemical solution.
I noticed that with the same chemical concentration, the reaction rate of a thin solution (like 5mm thick) is much slower, ~25%, than that of the bulk reaction. What may be the reason? How can I increase the reaction rate of a thin solution?
Hi, so you've got a reactive film applied to a surface and immerse the surface and film to a depth of 5mm in your solution? And that when you cover it much deeper in solution, it goes a bit faster? I can't think of any obvious causes for that, but some of the other users of the reference desks have much more chemistry-fu than I have. All I can suggest is that you help the products (assuming they're still in solution) move away from the film surface by circulating the solution with a pump or a stirrer. This should reduce the dependence of the reaction upon diffusion rate. Brammers (talk/c) 11:46, 31 May 2010 (UTC)[reply]
It is not entirely clear what you mean by that. A standing electromagnetic wave (say, in a cavity of a resonator) is trapped in space, but "propagates through time" as you put it. A traveling electromagnetic wave in vacuum, on the other hand, will always travel no matter what frame of reference you are in. In other words, if you try to chase a photon in vacuum, you will never succeed. --Dr Dima (talk) 06:30, 31 May 2010 (UTC)[reply]
I mean to be trapped in its point (say on a surface), not occupying any space as in the cavity where I believe it is still propagating but reflecting back and forth. The reason I ask this is to understand how energy is conserved as its power is varying with time and there are times electric and magnetic fields both tend to zero.--Email4mobile (talk) 07:01, 31 May 2010 (UTC)[reply]
I'm generally thinking about energy regardless if it were in a particle or wave form. I formulated a similar question several months ago (see here) and understood that energy is almost quantized in such case provided that transformation period is above Plank time. Here we are studying a wave and I don't know if energy has to be conserved within space-time or can also be conserved at a particular time (i.e.:Is power conservative?). These are some of the problems I still can't imagine beside relativity (I'll post some question about it later). Grateful for your assistance.--Email4mobile (talk) 08:09, 31 May 2010 (UTC)[reply]
There are no times that the E and B fields go to zero. An electromagnetic plane wave in vacuum just moves in some direction at the speed c; it doesn't grow or shrink or otherwise change as it propagates. You will detect changes in the E and B fields as the wave passes you, but that's because you're measuring different parts of it at different times. -- BenRG (talk) 09:50, 31 May 2010 (UTC)[reply]
Not sure if this answers your question, but a photon can not exist if it doesn't move. But, you can store the energy and properties of the photon (in an atom), and while stored it doesn't move. (And photons always travel at exactly the speed of light, in matter the photon is constantly being absorbed and re-emitted, this causes it to appear to slow down.) Ariel. (talk) 10:59, 31 May 2010 (UTC)[reply]
computer and manual hospital procedures
MedScape only checks for drug interactions and not for effect interactions. For instance mydriatic medications do not interact with Simvastatin purse but the effects of Phenylephrine, which dilates pupils, and the effects of Simvastatin which reduces Cholesterol are counter-indicated since Simvastatin indicates high cholesterol and restricted blood vessels and Phenylephrine which will further dilate or restrict blood vessels should not be given for this consequential or secondary interaction. My question is do American and British hospital procedures require computer or manual checking for such drug effect secondary interactions I will call implication conflicts here? 71.100.8.229 (talk) 07:07, 31 May 2010 (UTC)[reply]
Things to eat in a prehistoric environment.
Let's say you're zapped millions of years back into the past to a time when the biosphere was much different from the way it is today. The biggest obstacle to survival (right after avoiding being eaten) would be to get something to eat. Obviously, meat would be a safe bet, since you can't really go too wrong with it (except in the rare cases where it's poisonous), but not only is meat difficult to acquire, it's also not something that you could easily live entirely off of.
So what kinds of plants would you be able to eat in prehistoric times? What do we know about the edibility of various extinct plant taxa? Is there a way you can test a plant for edibility?
Obviously, the answer would be different depending on what era of history you were dropped into. So I'll give five options here:
Lately, I conducted an experiment in my house to verify a different, simple but similar evidence to that of Michelson–Morley experiment. A laser pointer was fixed to a wall, 3 meters high and vertically pointing to the ground such that incident light spotted on a graph paper (1x1 mm grids). Reducing temperature effects to minimum, I have been monitoring the light spot for few months (day and night) from time to time and the maximum offset achieved was less than 1 mm (perhaps due to temperature slight variation and different thermal coefficients). This makes me feel convinced about Michelson–Morley experiment.
If light were assumed moving with respect to ether (or absolute speed in space) it should of course have a maximum offset occurring within 12 hours, ; where x is the maximum shift (expected to occur within only 12 hours), h is the height or vertical distance light has propagated, v is Earth maximum known speed (let's say the same as galaxies'), and c is the light speed in air/vacuum. Given h=3m, v ≥ 220 km/s; thus x should be ≥ 4.4mm which is not verified in my experiment.
