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December 14
Why do faster moving fluids have lower pressure?
I understand the concept that as fluids (i.e. water/air) flow faster, their pressure drops. But what I don't understand is why. Please explain? --AstoVidatu03:16, 14 December 2006 (UTC)[reply]
A fluid rushing through a pipe is composed of molecules, and those molecules are all bouncing around, off of each other, and off of the walls of the pipe. How often they smack into the walls of the pipe results in pressure. For a given flow rate, they bounce into the walls at a certain rate which we then measure as the pressure. Now, if the flow of the fluid through the pipe is increased, think of what happens to the molecules... they are traveling faster down the pipe, and so fewer of them will smack into the pipe in any one particular place. Fewer molecules smacking into the wall of the pipe = lower pressure. At least that's how I remember it being explained to me in high school physics. 71.112.115.24605:27, 14 December 2006 (UTC):P[reply]
Wind and toilets
I live on the fifth floor of a ten-floor apartment building. When the wind speed gets up around 30 miles per hour, the water level in the toilet bowl is an inch lower than it is in calm weather. Why is this? --67.185.172.15804:18, 14 December 2006 (UTC)[reply]
Plumbing drains, including toilets, have in addition to the pipe which carries waste down to the sewer, an up vent which goes up to the roof. Its purpose is to prevent the draining water from siphoning the water out out of the U shaped trap, which is there to prevent sewer gasses from entering the living area. One way in which a high wind level could cause a drop in the toilet bowl level is if the air rushing past the vent on the roof lowers the pressure. If the air pressure in the vent stack were lower than the air pressure in the bathroom, the water level in the bowl would drop. One inch of water is not a huge pressure difference. Edison04:39, 14 December 2006 (UTC)[reply]
(Expanding on Edison's comments...) The water in the trap of your toilet bowl acts as a manometer between the air pressure inside your house and the air pressure in the plumbing vent stack. When the wind whips across the vent stack, the venturi effect lowers the pressure in the stack and the water in the toilet-bowl manometer shifts towards the vent stack. Unfortunately, unlike in a true manometer, it then sloshes over the upper edge of the trap and falls down the drain, permanently lowering the water level in your toilet bowl, at least until you flush the toilet and refill the trap again. If you catch this phenomenon in action, you may actually observe waves and motion in the water in the bowl.
Not quite.. The digital camera doesn't need a shutter - the ccd can recieve light all the time - and not be overexposed like a film. In fact a digital slr doesn't have a shutter proper as a normal slr - both will have the mirror, but only the non digital version has a focal plane shutter. So no digital camera needs a shutter - but a digital slr will have the moving mirror (which is a bit like a shutter).
'Shutter speed time' - the ccd is an array of light sensitive components - light falling on an element of the array will produce a voltage/current/resistance change - The longer this current is measured the more accurately it is known. So digital cameras do have a close analogy of shutter speed - the exposure time - short exposures will have more noise, longer exposures will have less noise but be prone to motion blur. Hope that answers all your questions.
"Your typical consumer digital camera uses what is called an Interline Transfer CCD, put simply the CCD can itself control the start / stop of when it measures light falling on it, otherwise known as an electronic shutter..." I'd suggest that this camera is aimed at people with more money than sense or who want to 'live in the past' why quote something saying " seems to directly contradict you" when actually reading the page confirms what I've been saying???87.102.19.9522:58, 14 December 2006 (UTC)[reply]
You said "no digital camera needs a shutter". It says that some digital cameras do need shutters — the exact logical negation. I asked a question, you answered incorrectly, get over it. —Keenan Pepper03:45, 15 December 2006 (UTC)[reply]
Actually they don't need shutters - the transfer of info. from the ccd is done electronically - using an electronic switch - there's no reason why at the start of an exposure the ccd could be blanked - and then at the end the resultant set of electrical signals be transfered over. Even in the case given above, so as I said "no digital camera needs a shutter" . And learn some manners as well.87.102.8.614:44, 15 December 2006 (UTC)[reply]
Suggest it's unneccessary but no doubt some advertising wanker has convinced people that "mechanical shutter = good quality" therefore a perferctly good digital camera is crippled because some idiot will buy it - and at 5 times the price of the equivalent product no doubt - does that sound like a realistic appraisal of 'the way things work'.. eg. Why buy a £5000 rolex when a £1 digital watch keeps better time? (<end of rant>)87.102.19.9523:11, 14 December 2006 (UTC)[reply]
Set your DSC to manual exposure (not every DSC supports this function)
Set to the widest aperture setting.
Set a reasonably long exposure time. Maybe more than 1 second.
Turn your DSC around so you can see the inside of its lens mechanism.
If you cannot see the shutter mechanism, you may adjust the mechanical zoom (usually wide angle).
If you still cannot see it, get a lamp or a flashlight.
If you have a wide-angle adapter, you may want to use it to magnify the mechanism.
When you think you see the mechanism, take a picture.
SEE! SEE! SEE! SEE! SEE! SEE! SEE! SEE!
If you cannot see it, adjust the zoom setting and take another picture.
SEE! SEE! SEE! SEE! SEE! SEE! SEE! SEE!
Under the MANUAL mode, you may find your fastest shutter setting be controlled by the aperture setting. Take my Canon PowerShot S3 IS for example, the fastest shutter speed is 1/3200 s under f/8.0 and 1/1600 under f/2.7 (aperture wide). This is a tell-tale sign of mechanical shutter.
If your camera supports long exposure, you may find it calibrates itself after a long exposure. Take my cam as an example, if I do a 15 s long exposure, it would:
Open the shutter and expose the CCD for 15 s. (Viewfinder ON)
Close the shutter. (Viewfinder OFF)
Save the picture to a buffer.
Expose the CCD for another 15 s while the shutter is closed.
Save the noise "picture" to the buffer as well.
Calculate an improved picture with the noise data.
Save the improved picture to the memory card.
Open the shutter. (Viewfinder ON)
The level of noise is subject to many real-time conditions such as the temperature and the age of your circuits. You cannot measure it in the factory and use the fixed value later. I only have one DSC so I cannot take a movie of it. Maybe you guys can take a shutter-open-shutter-closed movie. A camera with a larger and better CCD may not need to calibrate for the noise. My camera does not have a B or T exposure setting. It is simply not very practical to use a noisy chip to take a really long exposure. -- Toytoy15:42, 15 December 2006 (UTC)[reply]
chest muscles
can the dumbells be used to work the chest muscles?
Dumbell flat, incline or decline bench press (like barbell benchpresses but using dumbells) and dumbell flyes are the most common exercises. Some would recommend pullovers as well. As Anchoress says, you need to look up how to do them. --jjron12:52, 14 December 2006 (UTC)[reply]
The chest muscle which is visibly enlarged in body builders is Pectoralis Major. This is a powerful adductor, flexor, and internal rotator of the shoulder; hence any activity which produces this movement under strain will "work" the muscle:
Adduction - stand as if imitating the letter "T" with your arms out. Move hands forwards, bringing them in front of your chest, arms fully extended. This, bringing the upper limbs towards the midline, is called adduction
Flexion - stand up straight, as if at military drill. Bring your arm up, forwards, so you see your hand in front of your shoulder, arm fully extended and horizontal.
Int Rotation - stand up straight, upper arm against side, lower arm flexed at 90 degrees and hand out sideways. Move your hand round, using the elbw as a pivot, until your hand is across your lower chest
William Giaque
"He developed a magnetic refrigeration device of his own design in order to achieve this outcome, getting closer to absolute zero than many scientists had thought possible. This trailblazing work, apart from proving one of the fundamental laws of nature led to stronger steel, better gasoline and more efficient processes in a range of industries."
um....anyone know why this led to stronger steel and better gasoline??
given that the oxygen is as far as I know not made by a magnetic process, and oil refining does not need any o2 - unless you want explosions.. I'd say this is bullshit, an example of scientific discoveries being totally overplayed in terms of their industrial significance. However maybe I'm missing something - but I would suggest an ill informed journalist wrote this..(it's William Francis Giauque)83.100.174.7013:24, 14 December 2006 (UTC)[reply]
lol, you have quite the hubris to believe that hairless apes can significantly affect the biosphere. Read Lewis Thomas' " Lives of a Cell".
If you already believe that humans have ruined the enivoronment, I shan't try to convince you otherwise. Simply understand that nature changes, the world changes, not necessarily for the worse. It is impossible to accept that anything is static without suffering a mental breakdown or becoming a crusader for various causes that are outside of your control. —The preceding unsigned comment was added by 70.225.160.106 (talk • contribs).
That's one way of looking at it. Proponents of this are: The Bush administration, Michael Crichton, and anyone in the oil or car business. The other way of looking at it is that we're up to our knees in...trouble, and still digging. Proponents of this are: Anyone who's ever studied science. A bit of hyperbole, but that's the gist of the situation. yandman08:35, 14 December 2006 (UTC)[reply]
Unfortunately, the billions of people in the developing world need food, shelter, and water. And unfortunately for the eco-crusaders, this sometimes comes at the cost of the environment. Sorry, but people need to live, and the environment and species diversity comes second place.
How do you expect to convince a Brazilian lumberjack to quit his job and stop feeding his family because it bothers the conscience of some yuppie in the USA?
Sure, I'm being a little polemical, but these are things that need to be considered. —The preceding unsigned comment was added by 70.225.160.106 (talk • contribs).
Isn't it just wonderful that there are still poor people around whose indigence we rich people can use to justify our own excesses! --Rallette11:49, 14 December 2006 (UTC)[reply]
I am of the opinion that all harm done to the environment is manifested just as it is. That is to say, we need not worry that what we've done in the past has already doomed us in the future. The world is what it is. I don't buy 'doomsaying' at all, though pundits like Al Gore make a load of money doing it. Cheers. Vranak16:50, 14 December 2006 (UTC)[reply]
Just to butt in, we're not very good at guessing how it will be in 100 years. I wouldn't even guess at all. The margin of error is extremely large, and we haven't guessed how it will be hundred years in the future many times before to collect data on that. Climate systems are although cyclic, they are chaotic and nonlinear. We're still trying to figure out what happened in the past and present. X[Mac Davis] (DESK|How's my driving?) 22:10, 14 December 2006 (UTC)[reply]
Next century? Meteorologists can't tell me the weather next Tuesday!
Well my general sense is that a change in the environment is not necessarily a catastrophe, as long as it does not occur too rapidly. The Earth's environment changes all the time, and (thus far) life forms have managed adapt. But the problem seems to be that we're incurring a relatively rapid change that is comparable to a natural global catastrophe. Nature isn't able to adapt quickly enough, at least among the larger creatures. So we're putting the planet out of equilibrium and it will take a long time for a new balance to be reached. The ultimate cost we may end up paying is a mass die-off of humanity. But some humans will probably survive. We have some pretty clever members among our species, and we're highly adaptable. — RJH (talk) 17:48, 20 December 2006 (UTC)[reply]
canonical partition function
As V increases at constant T, why does En decrease?
units
what kind of value would be in units of K*cm (within P-chem)? These are not HW questions I'm attempting to reverse engineer my pchem midterm test questions from my graded test. Thanks.
how come whenever I eat a milk shake I get really dehydrated afterwards (1-3 hours after)?
Can you clarify what you mean by 'dehydrated'? Do you just mean you get thirsty or something else? From our dehydration article "Medically, dehydration is a serious and potentially life-threatening condition in which the body contains an insufficient volume of water for normal functioning." I find it hard to believe a milkshake is doing this to you! --jjron12:27, 14 December 2006 (UTC)[reply]
jees why does everyone here have to be such a Technical Tanya? dehydrated, really thirsty, yellow piss, etc. Great Living Luci, how do you live in society if you take everyone seriously? (maybe I'll post that one in Misc..)
Thirst (rather than dehydration) an hour or two afterwards does indeed suggest transient hyperglycemia and may be an early stage of diabetes. Dehydration cannot happen in two hours and is not a subjective sensation, but assuming he means thirst, anything that raises your plasma osmolality will make you feel immediately thirsty, and glucose is the prime candidate. A glucose tolerance test will confirm or refute it. alteripse01:40, 15 December 2006 (UTC)[reply]
There will also be a vast difference in how a Burger King milkshake makes you feel, and how a lovely homemade milkshake made in a modest agricultural town with good grass and good cows will make you feel! Vranak16:07, 15 December 2006 (UTC)[reply]
Conservation of Energy and Rolling a ball down a ramp
Hello. I was wondering if anyone would be able to help me with a query about my physics coursework?
What we have to do is talk about the conservation of energy, and how energy is never created or destroyed, and simply changes form, and then to prove this theory correct we had to roll a ball down a ramp at different heights, and time how long it took for the ball to reach the bottom.
Thats my planning and observing stages completed, but then for the analysis we have to link our experiment up to the theory of the conservation of energy, and I have absolutely no idea how it's relevent, am I missing an equation or anything?
I would greatly appreciate any help! Thanks.
--88.108.21.14207:38, 14 December 2006 (UTC)[reply]
OK. First, the experiment's wrong. But we'll get to that later, and don't worry, it's your teacher's fault. But telling him why he's wrong will surely give you extra points... You know how to calculate "gravitational potential" (or something like that) energy? Go and fetch the formula. You know how to calculate kinetic energy? Go and fetch that one, too. Hopefully you know the weight of the ball. Now, did you measure the speed of the ball at the end of the ramp, or did you measure the slope of the ramp? (If you did neither, you're in trouble...). yandman08:23, 14 December 2006 (UTC)[reply]
If you measured the speed of the ball, you just need to use all the formulas you've collected. If you've got the slope, you can find the projection of the gravitational force on the ramp (time to get out your sin and cos..), and then you're going to use Newton's laws to find out what you need.
And the experiment is wrong because it's not taking into account the fact that the ball is rolling. It takes energy to make something spin, and you're only measuring its speed, not its spin. Therefore, you're not taking into account all the energy the ball has at the end of the ramp, and if you do the experiment accurately enough, you'll see that the "final energy" is lower than the starting energy. Added to that, there's the friction losses, but they're negligible. yandman08:29, 14 December 2006 (UTC)[reply]
energy which goes to rolling is also likely negligable compared to the measurement techniques being used. If you want brownie, look up the formula that goes into rolling, and put an estimate on friction. Actually fuck that, derive the formula for the energy of rolling —Preceding unsigned comment added by 70.225.160.106 (talk • contribs) 08:32, 14 December 2006
I'm guessing that at the level you're at (A level?) the energy due to rotational inertia is ignored.(In any case it's sensible to solve the simplified case first and then include other variables..)
If I've understood correctly you need a link showing the relevance of conservation of energy to your experiment.. This is simple. The total energy should remain the same. In this case it means that the sum of kinetic energy (1/2mv2) and potential energy (mg x height) remains constant.. So if the ball drops y metres, it has lost mgy joules of potential energy (mass times gravity = force, force times distance = energy/work) so that energy lost should be compensated by in increase in kinetic energy ie 1/2mv2=mgh so v2=2gh. So you need the speed of the ball at a given height - you can get the speed from the slope of a graph of distance versus time. Did you measure the time to different points or just to the bottom?83.100.174.7012:51, 14 December 2006 (UTC)[reply]
I'll give you the rest of the clues.. Distance = vt +1/2at2 - you know the time, the initial velocity v should have been 0, a is the acceleration (=g sin f, where f = slope of the 'ramp' an angle), the final velocity is v=at, a as before, you measured t, so you can get the final velocity, and hence the final kinetic energy 1/2mv2, the change in potential energy is mg x height. If you're still stuck ask again..83.100.174.7013:16, 14 December 2006 (UTC)[reply]
e.coli
where can i get the perfect ultra structure of Escherichia coli bacterium?--hima 11:20, 14 December 2006 (UTC)
By "varying frequency of communication signal" do you mean amplitude modulation at other than the power frequency, or do you mean frequency modulation ? Various systems have been used for many decades as described in the article cited above. Electric utilities use amplitude modulated signals or unmodulated carrier transmitted over power lines for telemetry and for protective relaying. They have also used them for radiotelephone communications. One problem with using these systems for communicatind the state of the system back to the main dispatch center is that if the lines are knocked down, shorted to ground, or they overload and fail, is that the information transmission is lost with the power oine, leaving the dispatchers less able to communicate with generating stations and substations. Wavetraps have to be installed wherever transformers are connected to the powerline, which are band reject filters to isolate the radio signal from being shorted out by the transformer windings. They have to be tuned to the frequency of the carrier current signal. Frequencies below the AM broadcast band are typically used. Low power college AM radio services have been piped to dorms using carrier current at normal AM broadcast frequencies; the building wiring carries the signal to each room, without a broadcast license. Edison15:16, 15 December 2006 (UTC)[reply]
Science question on Miscellaneous Desk
Just a note to point out a science question on the Miscellaneous Desk:
Also in the derivation the modal distribution ie the distribution giving greatest value of W is found by ".. taking the derivative with respect to Ni, and setting the result to zero and solving for Ni yields the Maxwell-Boltzmann population numbers", but the mode is not the average - isn't the distribution supposed to represent the average distribution based on the assumptions. i.e. it should give a mean distribution and not the mode.83.100.174.7012:39, 14 December 2006 (UTC)[reply]
I don't know what the ad hoc correction is referring to, I've never heard of it. It sounds vague. As for your second question, the MB distribution can be interpreted as a probability distribution, so you can get all sorts of things like the mean, and the mode. It tells you much more than the average. The procedure you described does indeed give you the mode. The mode corresponds to the single peak of the curve, so if you differentiate this, the new function will be zero at precisely that point. --HappyCamper15:55, 14 December 2006 (UTC)[reply]
I was thinking that as the derived equation (on the wikipedia page) gives an energy distribution based on the mode - isn't this wrong for a statistical treatment - in terms of statistics the mode is definately not the average (in most/many cases). The mean(averaged) distribution is in fact a noticably different shape..(and a different equation). Interpreting the modal distribution as a probability distribution is wrong, eg if I toss two dice - take the modal value (ie 7) - I can not use this as a probability..83.100.174.7016:08, 14 December 2006 (UTC)[reply]
You know, I think the articles need to be fixed up a bit. I also I think I've misinterpreted your question. Have you taken a look at Maxwell–Boltzmann distribution? That was what I was thinking of, in particular, the equations at the bottom of the page. As far as I can tell, Ni itself is not the average, nor the mode in your original question. I'm sorry, the best I can do for now is to direct you to another source. If you have McQuarrie and Simon - (physical chemistry, a molecular approach) on hand, see chapter 17 pg. 693 - I think the idea you want to get out of this, is that (I will quote): "The probability that a system in an ensemble is in the state j with energy Ej(N,V) is proportional to ". That is the crux of a lot of results that follow in "classical" statistical mechanics. --HappyCamper16:50, 14 December 2006 (UTC)[reply]
Haven't got that specific book but have seen many similar.. My point is that the above (both) take an approximation to the actual average distribution - by taking the modal distribution (the one with the highest W - number of ways to obtain it). Unfortunately this discards all other distributions that contribute to the actual average distribution. This fact is often overlooked but I see no reason why it should not be mentioned as a 'flaw' in the derived equation in wikipedia even though some reputable books omit to mention it.83.100.174.7017:06, 14 December 2006 (UTC)[reply]
Ah, okay, I think you are using "modal" differently from how I am using it. The approximation is justified in part, by the extremely large numbers involved, but you are correct to say that there are a number of subtleties associated with this process. f(E_n) is not the same as f(v) - there is a change of variables that takes place in that derivation. --HappyCamper19:02, 14 December 2006 (UTC)[reply]
The derivation finds the distribution that has the greatest number of ways to obtain it ie W is maximum, this distribution is the modal one (see mode), the mean, or average distribution would take all the possible distributions (weighted by the number of ways to obtain them ie multiply by W as defined in the article).
Unfortunately the approximation is not justified (if you wish to use the distribution as a measure of probabilities) - since the average distribution is very different from the modal distribution.83.100.174.7019:17, 14 December 2006 (UTC)[reply]
The change of variables of course makes a difference - it the case of molecular speeds the x axis is scaled as the square root eg a plot with x~energy, becomes x~sqrt(energy) - this would cause a change in measured slope at a given point - but does not cause a change in form of the graph - eg from inverse exponential (e-kE) (note no hump) to the form given in Maxwell–Boltzmann distribution#Distribution of speeds (the graph now has a hump, why??); something is very wrong here.83.100.174.7019:22, 14 December 2006 (UTC)[reply]
Trick chemistry question.
Hey! I have a chemistry question here that I think maybe a trick question. It asks: Find the number of oxygen atoms in 25g of CO2. Is it 2? Or is it (after stoichemetry) 6.8 x 1023.
The way i thought of it is that there are two Oxygen atoms in the CO2 compound. But there are A LOT of Oxygen molecules in the 25g of it. Thanks for any feedback! --Agester14:35, 14 December 2006 (UTC)[reply]
There are no oxygen molecules in 25g of Co2, there are only Co2 molecules. It's not a trick question. Just divide 25g by (2*molar mass of oxygen + molar mass of carbon), multiply by a mole, multiply by two. Is that how you got 6.8E23? yandman14:43, 14 December 2006 (UTC)[reply]
Yeah, there's two oxygen atoms in each molecule of CO2, but there's lots of CO2 molecules in 25g of the stuff. As Yandman says, do the maths. --jjron14:55, 14 December 2006 (UTC)[reply]
Thanks for the help on that question! I thought it'd be the 6.8E23. However, I'm stuck on another tricky chem question. I don't feel the need to spam this desk with several topics of chem question but i'm really really stuck. The density of a 1.95 Molar solution of KBr in water is 1.16 g/mL. Find the molality of this solution. The formula weight of KBr is 119.0 AMU.
What I tried was assuming it's one liter as your volume. Therefore you'd have 1.95 moles. Convert that 1.95 moles into grams which came out to be 232.05g (or .23205 kg) and then tried to get the molality now by dividing moles over kg and got 8.4 Mol/kg. Which isn't a choice here.
Second attempt i tried to assume okay. I have one liter. Lets use that for the density. 1160g/1000mL. And tried to divide my moles into that and got 1.68 mol/kg which isn't a choice either.
What am I doing wrong? I know the second attempt was badly incorrect from the start but it was worth a stab. --Agester16:09, 14 December 2006 (UTC)[reply]
I would not expect the question to be constructed in this way...here would be my approach:
First find the molar mass of CO2 - that would be about 12 + 16 + 16 = 44 g / mol
Now, find the number of moles of CO2 you would have. That would be (25 g )/(44 g / mol) = 25/44 mol
Now, for each mole of CO2, there are 2 moles of O atoms. So that means, there are 25/44 * 2 = 25/22 mols of O atoms
Now, for each mole there are an Avogadro's number of particles. So that gives you (25/22 mols) * (6.022 *1023) = 6.843 *1023 which is precisely the answer that you got originally!
The core concept behind this question does not focus on densities, or whatnot. The question is really focusing on whether you understand what a "mole" is and whether you understand the relationships between the ratios of atoms that are in CO2 - you do not need to be concerned with the actual connectivity that exists between the atoms - that comes much later. --HappyCamper16:56, 14 December 2006 (UTC)[reply]
I read the question several times and was unable to think, like a robot in Star Trek given two comands at once. Bu what I get from the question is that the concept of molarity is hard to get for a non chemist.
200 people jump out of a plane. The density of air is zz pounds/cubicfoot all people fall in to water with a density of 1 ton/cubicmeter. How many people are there in the water. --Stone17:10, 14 December 2006 (UTC)[reply]
No the questioner wants to convert molarity to molality. The number you need is that water is 1 kg per liter. So a 1.95 molar solution divided by the mass of solution (1 kg) will get the answer (assuming you have a dilute solution at STP) Rmhermen18:44, 14 December 2006 (UTC)[reply]
So if I interpreted that right. Does that mean the Molality of the solution is 1.95 Mol/kg all along? After all if the assumed amount of water is 1 kg/L wouldn't that make the volume 1L mass 1kg therefore:
1 molar = 1.95 mole/ 1L
1.95 mole / 1 kg = 1.95 mol/kg
(and I assume it's STP too because the question doesn't list any other information on Temp or pressure.) However, what does the density have to do with this then? Just useless information? --Agester21:08, 14 December 2006 (UTC)[reply]
The confounding quantity here is of course the volume change associated with adding the KBr to water. We know that for a volume of solute (with mass ), we create a mixture of volume by adding a mass of the solvent (M=molarity; μ=molar mass), so that the mass of the solution is . We still know neither nor , but we additionally know . From that we can derive the ratio — obviously their individual values are irrelevant — and then calculate (m=molality). It all has to do with the volume change and (confusingly) with the different systems (before and after mixing) in reference to which molarity and molality are defined. Does that help? --Tardis22:33, 14 December 2006 (UTC)[reply]
I'm not quite to sure what you mean Tardis. What is p' (or p prime?). Most of your work there is a little confusing to me. Like i'm not sure what you mean by V' either. In addition, How do we conclude to this mass of our solute? Unless we assume we have 1L of water and say we have 1.95 moles and then use the Molar mass to find out how many grams. But even then, a similar question would be what is V' and how does the density play in effect?
also! I managed to find our volume of KBr by assuming our volume of water is 1L.
therefore we have 1.95 moles of KBr. With density in mind (1.16g/mL) i worked out 232.05g / V = 1.16 g/mL and volume eventually came out to 200 mL of KBr. I'm not sure if that helps us anymore or was just extra work but I tried throwing it around and stuff but no help for me. --Agester01:12, 15 December 2006 (UTC)[reply]
Um... ρ and are densities (as mentioned at the article, although for some reason it claims that uppercase rho is used there); the prime on one of them and on means that the variable applies to the solution and not to the solvent alone (that is, it applies to the latter state of the system; see the prime's meaning with regards to physics in its article). The mass of solute is derived from the definition of molarity (which is defined in terms of volume of solution); I left it in terms of precisely to avoid assuming any particular volume of water. Your calculation of the volume of KBr is flawed because you are dividing the mass of the solute by the density of the solution: the volume you get is the volume of solution which would have mass equal to the mass of KBr in a different amount of solution! If you can be more specific about what you don't understand (if anything, still) about the equations I wrote, that will help: it is extremely helpful to formalize the problem such that one does not make mistakes like operating on unrelated variables and being confused by numerical coincidences. --Tardis03:03, 15 December 2006 (UTC)[reply]
tonsilitis
is it possible to get tonsilitis even if you have had ur tonsils taken out.
sorry this question is up twice, i didnt think it went up b4 - skye
No problem - I've removed the repeat question. Strictly speaking, tonsilitis is an inflamation of the tonsils, so no, you can't have tonsilitis after your tonsils have been removed. But one of the symptoms of tonsilitis is a sore throat (pharyngitis), which has many other causes as well, so you might feel as though you have tonsilitis even though it is really something else. Usual disclaimers ... I have no medical training, we don't provide medical advice and you should see your doctor if in any doubt. Gandalf6115:16, 14 December 2006 (UTC)[reply]
ok so, if my friend has tonsilitis i could get the sore throat from the tonsilitis but not the actual tonsilitis cause i have no tonsils. does that make sense?
I think the question comes down to this -- can tonsils grow back?
I know other organs can -- so why not tonsils? I suppose it's possible. And thus, getting tonsilitus after having ones' tonsils removed is not unfathomable. Vranak16:54, 14 December 2006 (UTC)[reply]
thanks... skye
Sore throats and tonsillitis, whether viral or bacterial infections can be contagious. I have known strep throat to be passed from person to person. Many sore throats are dangerous and the bacteria causing them can be highly transmissable. Other sore throats are mononucleosis also highly contagious. A sore throat may be scarlet fever. Untreated strep can lead to rheumatic fever. Please call your doctor, since Ref Desk is not a good source for medical advice. Edison17:45, 14 December 2006 (UTC)[reply]
how would you investigate the relationship between the length of a metallic conductor and its resistance? a brief description wold be a huge help...thanks.83.71.61.20316:51, 14 December 2006 (UTC)[reply]
Take a wire - span it like clothesline that you have both ends at one side and a u-turn at the other - measure U and I of a battery at different place and draw a chart!--Stone17:01, 14 December 2006 (UTC)[reply]
See Electrical resistance and Ohm's Law. With a typical ohmmeter or digital multimeter, it may take a long length of very fine wire to get clear results. A spool of very small wire, like # 28 or #30 wire, obtainable at places like Radio Shack, or will have more easily measured resistance than a short length of say #12 wire or even #22 doorbell wire. Resistance varies with wire diameter and with what metal the wire is made of. You should touch the ohmmeter leads together and note the lead resistance, probably a few tenths of an ohm, and subtract that from resistance of the wire. Make sure the wire is bare and shiny where you connect the leads, either by just touching them to the wire or with alligator clips (measure and deduct the resistance of the alligator clip leads as well). Then measure the resistance of, say 1 foot, 50 feet, 100 feet, etc up to the total length. Note the room temperature and record it as part of your data, since resistance varies slightly with temperature. Graph your data and see the form of the relationship between length and resistance, with wire diameter and temperature held constant. You could also use separate ammeter and voltmeter to get a better hands on idea of what you are measuring. Edison18:00, 14 December 2006 (UTC)[reply]
If you don't have an ohm-meter, you can use a voltmeter, ammeter and Ohm's law. The basic principle is to vary length while keeping material wire is made from, cross-sectional area, and temperature constant. 80.169.64.2217:14, 15 December 2006 (UTC)[reply]
a maths proof
there are six people in a room. it is then certain that eiter:at least 3 people know each other
OR at least 3 people dont know each other. how is it certain?
Can there be a chemical bond between metals? What is that type of bond called?
Metal metal bonds are common in many to core complexes. There are single double ore triple bonded metals in some complexes.--Stone17:15, 14 December 2006 (UTC)[reply]
Tradition! The dentist is historically derived from a poorly trainned Barber, while a doctor is coming from a university. This diversion is still there and as a combination would mean reduced funding nobody is integrating both!--Stone17:56, 14 December 2006 (UTC)[reply]
Surgeons also started out as Barber surgeon in past centuries, and in some countries are called "Mister" rather than "Doctor." In the U.S. dentists are called "Doctor" as are surgeons. Dentists before the late 19th century were generally "tooth-drawers" with little training, but today get extensive medical training related to their specialty in their 8 years of college, then receive a Doctor of Dental Surgery or Doctor of Dental Medicine degree, then have to pass a state board exam (in the U.S.). They may then take several years of additional training in a speciality. Dentists in the U.K. have to take a shorter training course, per Dentistry, and get a Bachelor of Dental Surgery. Edison18:11, 14 December 2006 (UTC)[reply]
Aren't the teeth pretty well independant? If you studied neurology or hematology, you'd have to know all about the body. With teeth, you just have to know the mouth and jaw, and try not to cause infections.X[Mac Davis] (DESK|How's my driving?) 01:08, 15 December 2006 (UTC)[reply]
Barber surgeon was seen as not medicine. To cut of arms and legs is more like drawing teeth! Nowerdays the seperation is still there, but not that dentists are poorly trained! I hope nobody understood it this way! --Stone18:37, 14 December 2006 (UTC)[reply]
IANADentist, but the statement that the teeth are pretty well independent needs a wee response. Dentists (in the UK) spend 5 years at dental school, then a year as a vocational trainee before being allowed to practice independently. If they want to specialise in say Orthodontics they will spend an additional 2-3 years at a teaching hospital then do a 3 year Masters Degree in Orthodontics followed by an additional 2 years to become an Orthodontic consultant. Saying that the teeth are independent is like saying that the blood or nerves are independent. Dentists need to know about head, neck and throat cancers (since doctors very rarely look into people's mouths (as you'll know if you've ever been admitted to hospital.)) They will also need to know about congenitalcraniofacial abnormalities and the effects of various systemic diseases on the mouth, e.g. B12/folate deficiency, sarcoidosis etc. Mmoneypenny19:34, 15 December 2006 (UTC)[reply]
What is repsonsible for eye drying that comes with sleepiness?
Is this melatonin? Melatonin is secreted by the retina as the article states.
I believe that there's at least half a dozen different glands that secrete different oils across the surface of the eye, to keep it nice and lubricated as you blink. If there's a problem with these glands, or your body in general (which supplies nutrients to these glands) -- or if the room you're in has a lot of dust in it, then you'll get dry-eye. Sleepiness is associated with dry-eye, but it is not the cause per se. Vranak18:32, 14 December 2006 (UTC)[reply]
I think I read that this comes from blinking less unconciously, to try and get you to close your eyes for good so they are wet. When I don't wet my eyes by closing and er... squeezing my glands, they can get pretty dry and feel like fiberglass. eek! And this is in every climate (not just saying weather). X[Mac Davis] (DESK|How's my driving?) 20:10, 14 December 2006 (UTC)[reply]
With a choice between deboned and deskinned chicken breasts versus chicken breasts with skin and bones isn't it healthier to get the chicken breast with skin and bones since the body needs some fat too? 71.100.6.15220:31, 14 December 2006 (UTC)[reply]
Nope. I am overweight by 30 plus pounds though, have borderline high cholesterol and high blood pressure. Even using artificial sweeteners exclusively for well over a year (except for yogurt) I have an inability to come within or near 20 pounds of being overweight no matter what foods are in my diet or if I eat so little that I stay hungry. I can not swallow tuna or other meats unless lubricated with some oil or condiments or other foods like vegetables so if an "entirely" fat-free diet would be just as healthy I would do it. 71.100.6.15221:59, 14 December 2006 (UTC)[reply]
Health is a funny thing. In a 1567 monograph by Swiss physician Paracelsus, it was observed that "All things are poison and none are without poison," a phrase which is usually said "The dose makes the poison." Everybody and their diets are a little bit different and it can be harder to generalize than people say. We don't know you very personally, although I'm betting people will say to eat the deskinned one, since you have enough fat in your diet other places. X[Mac Davis] ::(DESK|How's my driving?) 22:18, 14 December 2006 (UTC)[reply]
The bones don't matter as you likely won't eat them anyway. The skin, however, and the fat right under the skin, are high in bad fat and bad cholesterol. You will get more than enough fat and cholesterol from lean, skinless chicken breasts. Ideally, you should get good fat and cholesterol from things like avocados, salmon, and vegetable oils (avoid partially hydrogenated oils, however). Avoid all trans-fats completely. StuRat01:21, 15 December 2006 (UTC)[reply]
You haven't asked for weight loss advice, but I'm going to give you some. Some people can't lose weight by controlling their diets, I'm one of them. Whether it's high protein, low calorie, low fat, I always plateau and no matter how much I reduce my food intake I don't lose weight. I have to exercise. Maybe that's true for you too. I suggest that you go and get a checkup and talk to your doctor about starting (or augmenting) an exercise plan. I should also say that - for me - aerobics are fine, but I don't lose weight with just aerobic exercise (walking, running, etc). However, when I do weight training, I drop weight like, well, weight. Get some sensible guidance from people in the know and get moving. Anchoress09:17, 15 December 2006 (UTC)[reply]
"The body needs some fat too" is correct, but do not deceive yourself, there is ample fat in lean chicken breast. The fat is in muscle cells, as well as in fat cells. In the case of chicken, there is much less fat "hidden" inside the muscle than is the case with "marbled" meat, like beef. This I have known for a long time, but I have not checked it myself, so I did some calculations based on data from the USDA website. I was surprised:
Chicken Breast With and Without Fat and Skin
(Yield from a 1 kg Chicken Prepared for Cooking.)
Fat(g) Energy(kJ)
Meat with skin and fat 10.15 1078
Meat (skin and fat removed) 3.89 810
Chicken Breast (fat and skin removed)Compared to Beef Filet of Tenderloin (all visible fat removed)
(Quantity of each is 100g)
Fat(g) Energy(kJ)
Chicken 3.03 632
Beef 11.12 912
So there is no risk of suffering from fat deficiency if you eat meat without visible fat - 3% fat for the leanest chicken, 11% for the leanest beef. Something you can look up for yourself: Lean pork has less fat than lean beef.
One final note: "Staying hungry" is not a criterion for deciding whether your diet is strict enough for you to be able to lose weight. If you look at the Hunger article (unfortunately at present not much more than a tag) you can click on the links there to get a better picture of the physiology of hunger. Inter alia, Leptin and Ghrelin are fashionable topics in this field. Well, now I need a peanut butter sandwich... --Seejyb21:45, 15 December 2006 (UTC)[reply]
Wanted to point out that even if your diet doesn't appear to help you lose weight, you're still likely to be far healthier if you adopt a healthier diet. Point being, just because you don't notice a difference in weight from eating chicken with the skin-on doesn't mean it's a good idea Nil Einne13:56, 21 December 2006 (UTC)[reply]
LOL I love peanut butter too but even though it is supposed to have more protein than calf's liver it has an awful lot of fat too. On peanut butter I gain weight almost as if I'm eating pure fat. If I could find a way not to be hungry then that would help a lot in reducing the number of calories I consume which is the problem as far as I've been told rather than either fat or protein. Its just that fat has a lot more calories than protein. Tried sipping constantly on sodas but the doc said not to do that anymore since I was putting myself at risk of contracting diabetes. 71.100.6.15213:57, 17 December 2006 (UTC)[reply]
Absolutely zero not really that cold?
Absolute zero has always facinated me in high school chemistry. The possibility of all molecular action stopping at a "mere" -273 below zero. Considering how hot things can get -- indeed is there even a maximum for heat? -- it seems we are living on the awfully cool side of the temperature universe. --24.249.108.13321:12, 14 December 2006 (UTC)[reply]
There is, in fact, a theoretical maximum temperature for the universe. Review Heat death of the universe, which is a very interesting concept. You might also want to read Big Freeze, which is about the cold death of the universe.
For any individual mass, however, there is no upper bound for "heat," as energy in a particle with mass can grow without bound as the particle approaches the speed of light. Hipocrite - «Talk»21:21, 14 December 2006 (UTC)[reply]
Yes, it does seem we are living on the cold side. It is easy for me to heat something by way more than 273 Celsius, and impossible to cool it more than 273 Celsius starting from zero Celsius. Edison15:21, 15 December 2006 (UTC)[reply]
Seeing how they would carry ~8 .30cal machine guns, which yield a lot of rounds, there's probably a damn good chance they did. I'm not sure how easy it would be to find actual reports, however. Saying the RAF is strafing its own people wouldn't be good for morale, so the civilian deaths were probably chalked up to enemy fire.--138.29.51.25101:42, 15 December 2006 (UTC)[reply]
latent heat
What is going on inside a molecule during a phase change that causes or allows energy to be absorbed yet without producing an increase in temperature? Adaptron22:50, 14 December 2006 (UTC)[reply]
I haven't done heat science in a while, though i'm starting to learn thermochemistry now...but if I remember correctly the molecules are gaining potential energy during the change, and not actual kinetic energy that you would see as the temperature incereases? I'm not sure, but check out the wikipedia articles of state changes and different types of energy. 74.102.89.24100:30, 15 December 2006 (UTC)[reply]
The energy goes to either making or destroying the bonds between the molecules. For example with water, when either boiling or melting the energy goes towards breaking the hydrogen bonds between the water molecules. -anonymous649402:16, 15 December 2006 (UTC)[reply]
Basically, in a substance, the atoms that make it up are pulled toward eachtother by intermolecular forces (Hydrogen, Ionic, and Covalent bonds, London dispersion forces, etc.). As the atom gains energy it moves faster and faster, "bouncing around" until it finally gains enough energy to overcome the intermolecular forces, and breaks free. However, one must remember that when boiling a liquid, or during any phase change, not all of the atoms/molecules have enough energy to break free and undergo phase change(See Maxwell-Boltzmann Distribution on Wikipedia, or here). For any temperature, molecules are moving at different speeds. As a result, only a given amount of the substance has enough energy for phase change (only those moving over a speed of "x" change - the number of the molecules with that speed increases with temperature). That's why when you boil water the whole pot of it doesn't go "poof" into water vapor, and the phase change takes place over the time (i.e. the bubbles of H2O gas released from the pot). --AstoVidatu02:30, 15 December 2006 (UTC)[reply]
Why then do certain substances such as carbon dioxide skip the liquid phase entirely and go "poof" i.e., go from being a solid directly to a gas? Adaptron05:41, 15 December 2006 (UTC)[reply]
See also Gibbs free energy. In short, despite the fact that less energy would be required to turn the CO2 into a liquid instead of a gas, leaving more energy to become heat and therefore entropy, the increased entropy (disorder) of the gas phase makes it preferable. At a high enough pressure, it requires so much energy to give the gas a volume appropriate to its temperature and mass that it becomes more profitable (in terms of entropy) to move to the liquid phase and use the energy to provide disordering thermal motion. Does that help? --Tardis21:06, 15 December 2006 (UTC)[reply]
So then if "disordering thermal motion" is a variable like volume, pressure and temperature what is the equation that includes it as a variable? Adaptron10:07, 17 December 2006 (UTC)[reply]
Make sure to judge how much you know about electrical engineering and physics already. If you don't know where to get a capacitor for this, you might not be a good candidate for trying to build it, which is presumably what you are doing. Ebay always works, :) X[Mac Davis] (DESK|How's my driving?) 19:25, 16 December 2006 (UTC)[reply]
While not looking for medical advice, I am curious to biochemical reason why I get extremely sleepy after eating lots of salty foods (olives, snack chips, processed cheese). It's like a dense sleepitime fog falls over me and I routinely fall asleep if I'm sitting down. I jokingly refer to as as a "sodium coma". It's a different feeling the typical post-Thanksgiving carb overload. --72.202.150.9201:47, 15 December 2006 (UTC)[reply]
Sleepiness from NaCl is not an expected response. Could it be that the foods contain Tryptophan, and that you are sensitive to this? The article has a list of foods rich in this amino acid; you may wish to compare that with your sleepy snacks experience. --Seejyb15:09, 15 December 2006 (UTC)[reply]
There is no equivalent "reversal" agent for cocaine or amphetamines. People who overdose on cocaine or amphetamines are treated symptomatically; they may be sedated; they will be treated for complications such as fever, convulsions, or heart attack if they occur. - Nunh-huh04:36, 15 December 2006 (UTC)[reply]
No medical advice was asked for, and none was given. Please take note of what "medical advice" actually is, and please stop leaving messages suggesting it was given when it wasn't. - Nunh-huh04:29, 16 December 2006 (UTC)[reply]
Would it be correct to say steroids cause the expansion of muscle fibers and Growth Hormone causes an increase in the number of muscle fibers?
Anabolic steroids can increase muscle mass, but can cause "elevated cholesterol (increase in LDL, decreased HDL levels), acne, elevated blood pressure, hepatotoxicity, and alterations in left ventricle morphology." Growth hormone increases the number of muscle cells in Danio fish but not in Zebra fish (I am in a rush, so cannot find the ref now, but will look later). Humans are like Zebra fish, so taking growth hormone to develop muscles is a waste of time. --Seejyb16:38, 15 December 2006 (UTC)[reply]
Sleep paralysis? During sleep, the body is paralyzed to prevent the dreamer from acting out his dream. Sometimes, the body is paralyzed too soon, when it is still awake. Hallucinogens can occur for the same reason dreams occur, and of course, nobody can be certain why dreams occur. --Bowlhover05:07, 15 December 2006 (UTC)[reply]
Sea star mentions that a starfish may regenerate from as few as a single ray, but as Nunh-huh mentioned above, the starfish you describe is pining for the fjords. - CHAIRBOY (☎) 05:42, 15 December 2006 (UTC)[reply]
'E's not pinin'! 'E's passed on! This starfish is no more! He has ceased to be! 'E's expired and gone to meet 'is maker! 'E's a stiff! Bereft of life, 'e rests in peace! If you hadn't shellacked 'im to the diorama 'e'd be pushing up the daisies! 'Is metabolic processes are now 'istory! 'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisibile!! - Nunh-huh05:46, 15 December 2006 (UTC)[reply]
While some animals can survive dehydration, a starfish is not one of them. I tried once, and got a soggy, dead, starfish. (It didn't smell nearly as pleasant as you might imagine.) StuRat22:25, 15 December 2006 (UTC)[reply]
If you take the starfish, place it in 700 ml of water at hand temperature, cover with a lid, and microwave for about 4 minutes on maximum power, it may be woken up by the sudden blast of warmth combined with microwave energy, and this can trigger its rejuvenation.
Of course, there is the other 99.3% of a chance that you'll end up with a really impressive explosive superheated mush coating your microwave's interior, but thats just the risk you have to take if you want to revive such creatures from their descent into the abyss. FT2(Talk | email)01:00, 17 December 2006 (UTC)[reply]
Hallucinogens in palliative care?
Have hallucinogens ever been used or proposed for palliative care? It seems to me that they could, at least in theory, do three things to help a terminally ill patient who is no longer capable of communicating with others (whether due to blindness and deafness, loss of speech, diminished mental functioning or just institutionalization without access to loved ones): relieve boredom, decrease awareness of physical distress, and provide spiritual experiences that might help reconcile them to their upcoming death. NeonMerlin06:13, 15 December 2006 (UTC)[reply]
Hmmm... I don't know. I suppose somebody who has information on the legal constraints surrounding drug administration might know. Anchoress12:55, 15 December 2006 (UTC)[reply]
Yes, they have been proposed and used for palliative care. This BBC reportgives an overview of possible uses. Note that this use does not refer to persons who cannot communicate, but that any therapy is guided by the patients' reports of an improvement of quality of life. Another way of thinking about this: 1. When a person cannot communicate, then only medical signs can be treated (not symptoms, since these rely on reporting). 2. Signs can usually be managed by "conventional" medications. 3. Is there such a sign as "lack of hallucinations"? --Seejyb16:17, 15 December 2006 (UTC)[reply]
I don't have much in the way of sources... try erowid's vault which has huge archives on psychoactive drugs and their research. But yes, in the period between discovery of psychoactive drugs such as LSD, and their banning by the US Government, they were extensively tested for use in therapy, palliative care, and many other situations. FT2(Talk | email)00:56, 17 December 2006 (UTC)[reply]
Repetition speed for strength exercises- fast or slow
Hi there,
Could someone tell me what are the pros and cons to different repetition speeds when doing weight exercises?
Best regards,
Amsbam
I have only anecdotal information (that which I've gleaned from various fitness instructors), such as that fast reps are to be undertaken with caution because it increases the likelihood of injury; slow reps are better because they work the muscle better, etc. But I have no references for those assertions. You might want to look at some of these links, which seem to have more info. Good luck, and maybe someone with more information/education will chime in. Anchoress08:55, 15 December 2006 (UTC)[reply]
Appreciate the insight Anchoress, thanks.
Withdrawal of Supplies of amitripyline tablets
Here in the Seville area it is impossible to obtain amitriptyline tablets at present, since the begining of December. The story is that the pharmacists don't know why the supplies have stopped. They say possibly a change of tablet or change of package. In my experience, decades as a nurse, this is unprecedented. Has it happened elsewhere? Does anybody know what the real reason is? Thanks in anticipation
(Assuming you are not from Spain, but from Ohio) The information on shortages, kept by the FDA, can be found here, but amitriptyline is not mentioned. I assume you would then have to look for a local problem. Another ref desk editor may have local knowledge. --Seejyb16:03, 15 December 2006 (UTC)[reply]
That type of supply disruption is not unique to medications (but may be a far more serious issue there) and is often caused by having a single supplier system. Another risk is usage of the just in time delivery system, where stocks are intentionally kept low to reduce storage costs. With the combination of the two, virtually any production or distribution problem can cause severe shortages. StuRat22:16, 15 December 2006 (UTC)[reply]
OK, thanks for that.
You're welcome. I also looked at the FDA site on drug shortages: [1], but they don't list any shortage of amitripyline. I couldn't find any mention of a general shortage in Spain, either. StuRat05:12, 16 December 2006 (UTC)[reply]
Audio - Centre Channel Extractor on Adobe Audition
I suppose this should be a computer/software question but it mainly involves science so:
How is it possible that one can isolate the "centre" channel of a stereo audio track?
I understand how it's possible to remove the "centre" channel using one inverted channel combined with the non-inverted other channel.
To use an equation:
LC (left, centre) + -RC (minus right, minus centre) = L-R - thus removing the centre channel.
It's impossible to remove the centre channel using this method, so how does a piece of software do it?
Not sure how this jibes with your equations, but a speaker connected from left channel phase to right channel phase, neglecting the ground connection of each channel, might extract the center channel (or maybe it completely suppressed the center channel!). Dolby prologic does fancier combinations; that's just a 1970's trick. Not sure how your Adobe Audition would correspond, since that trick was physical wiring. Edison15:28, 15 December 2006 (UTC)[reply]
This would completely cancel the centre channel - which is very easy and simple maths. I'm talking about actually isolating the centre channel, disregarding the left and right (side) channels. Adobe Audition can do this. I don't know how though. I'm sure it's probably a closely guarded secret by Adobe, but would be interested to know if anyone has any theories.
Out of phase separation (oops) is a very simple equation and process based on analogue waveform manipulation, Adobe's "centre channel extractor" must be very complicated and purely digital. Any thoughts?
I'm no sound engineer, but it seems that once you've cancelled the centre channel (left plus inverted right), you could just "subtract" what's left from the original signal in the same way (original plus inverted (left plus inverted right)) to get only the thing you cancelled, i.e. the centre. Maelin (Talk | Contribs) 02:19, 19 December 2006 (UTC)[reply]
No because:
(LeftCentre) + Minus(RightCentre) = (LeftMinusRight) (cancelling the centre channel)
Your proposal is to take that result and subtract it from the original to get pure centre channel, but what happens is:
(LC) + (-RC) = (L-R)
(L-R) + -(LRCC) = (-L+R-CC)
End result: Same as original source but with one inverted side channel.
I don't know about all your plus and minus stuff, but I do know that if you can eliminate the center channel, you can also isolate it. There may be an easier method, but what I do is 1:eliminate the center channel 2:mix both the new and the original signals into mono (that is, into two mono signals, one with the center and one without it), panning one completely left and one completely right. In that new mix, sound that had previously been in either the left or right channel(but not both) in the stereo mix is now equally in both left and right channels. The sounds from the original mix that were in the "center" channel are now off to one side. 3: Now eliminate the new "center" channel, the original center will be all that remains. Here is a little diagram to help explain my ramblings. I have used the letters A B and C to represent different sounds.
Left Right Left Center Right Step 1 Left Right
original: AC BC = A C B Remove Center Channel: A B
Step 2 Left Right Left Center Right Step 3 Left Right
pan signals: ABC(or.) AB(new) = C AB Remove Center Channel: C
Don't guess carpenter ants do as much damage as termites but I'm looking for an ant type that is small enough to chase down termites inside the tunnels they make in wood. 71.100.6.15219:46, 15 December 2006 (UTC)[reply]
An insect inspector told me the Carpenter Ants dig out a hole in the wood to make their nest. Termites actually EAT the wood. So yeah, termites are more destructive. 12.10.127.5821:10, 15 December 2006 (UTC)[reply]
To expand, carpenter ants do not destroy 'good' wood, termites do (that is the EAT bit). If you have a problem with carpenter ants then you have rotten wood, which is a problem without the aggrevation of the ants. David D.(Talk)21:42, 15 December 2006 (UTC)[reply]
Read the articles and see what you think. These types of reports are always open to interpretation. Primarily it depends on how many people were involved in the study. David D.(Talk)17:46, 15 December 2006 (UTC)[reply]
Well, to be honest, does it matter? The risk will be there anyway, it's not like "ohhh, I'm circumcided, now I go do unprotected sex with strangers because I'm invulnerable to aids." Good sex habits cuts the risk by 99% 212.10.217.12221:28, 15 December 2006 (UTC)[reply]
for the record, out of every 10,000 (ten thousand) people that have sex, only 5 people get an HIV transmission. There are far more dangerous things than sex, unless of course you're so horny that you have sex every day.—Preceding unsigned comment added by 70.225.160.106 (talk • contribs)
For clarity, the following factual answer uses correct medical terminology in an appropriate and responsible sense. Please do not delete this answer just because you are offended by this terminology or the acts that it describes. To be clear about the statistics in the previous answer, the average rate of HIV infection for unprotected penile-vaginal intercourse where one partner has HIV is indeed 5 in 10,000 acts for the male ("insertive") partner. However, the infection rate is 10 in 10,000 acts for the female ("receptive") partner in penile-vaginal intercourse, and it is 50 in 10,000 acts for for the receptive partner in anal intercourse - see HIV#Transmission and AIDS#Transmission and prevention. Also, note that these are average figures. Infectivity varies over a wide range according to the progress of the illness in the infected partner, and the presence of other sexually transmitted infections greatly increase the rate of HIV transmission. So the risk of infection from a single unprotected sexual act with an infected partner may be much higher than these average figures. There is indeed some evidence that circumcision reduces the infection rate for the insertive partner. However, a far more effective way to protect both partners from the sexual transmission of HIV and other STIs is to correctly use a condom. Gandalf6109:54, 16 December 2006 (UTC)[reply]
Understand that condoms have a finite effectiveness. Condoms can break at rates as low as 90-95%. So what that means is that receptive anal sex with a condom is about as risky as insertive fellatio. Regular sex with a condom 10 times (many people do that in a week easy) is as risky as insertive fellatio. —The preceding unsigned comment was added by 70.225.160.106 (talk) 16:21, 16 December 2006 (UTC).[reply]
Any statistics can only be a guide, and often not a very acurate one. For example, here are some confounds (unplanned-for factors which influence or confuse results):
What type of "condom" are we going to use. there's no "average" condom, a specific person usually has one consistent choice - thin, ribbed, normal, strong, length, tightness, age, manufacturer, storage conditions, lubricant used
What kind of sex and how do you do it - vaginal, oral, anal, long duration, brief, shallow thrusts, deep thrusts, fast, slow. Again, these are often quite consistent person to person.
How aware and careful are you about your condom use - before sex, how it is on the penis during sex, and its removal after sex. Likewise consistent.
So the problem is, that Jim has regular vaginal sex, he habitually uses a strong condom, his girlfriend likes it gentle, and he orgasms after 2 minutes in which time the condom stays where it was put. Andrew has anal sex and likes it rough, he's buys the ordinary condoms his local store sells.... their risks for each act will be very different, and that's consistent. Lessons:
Be very wary of applying generalized statistics to one situation where the situation may consistently not match the basis of the statistics
Think about safe sex in the context of your love life, not some other persons.
I recently left some copper on one side and some iron on the other side of a dish full of 30% phophoric acid and bubbles started coming from both metals and the iron began to take on a copper color. Does this mean that any acid will cause self-plating without an external current being supplied or does this only happen in phosphoric acid or is this really self-plating at all? 71.100.6.15218:34, 15 December 2006 (UTC)[reply]
There could have been some copper oxide on the copper that would react with the acid forming a copper compound - this would then plate the iron in the same way a copper sulphate solution does. Question - after a while was the copper clean (ie pink) - if you add more iron does it continue to plate with copper - I'm guessing that your mixture will only have a limited copper plating capacity.87.102.8.620:24, 15 December 2006 (UTC)[reply]
Also copper phosphate is usually insolouble in water - which makes me slightly suprised you got any copper plating at all.. The same goes for Iron phosphate as far as I know - I would have expected to get a layer of metal phosphate on the surface of each metal and not much more - just goes to show how experiments are more valuble than theories.87.102.8.620:38, 15 December 2006 (UTC)[reply]
Checking again after an hour revealed that the release of bubbles had slowed way down. Only the bottom portion of the iron up to the level of the top of the copper seems to be plated. The color is somewhat pink and flat. Above this the iron is turning black whereas when it was in the acid before the copper was added it was flat gray. I'm wondering if the acid is separated into copper phosphate and iron phosphate such that the layer surrounding the pink area is the copper phosphate while the area above is the layer of iron phosphate. The copper is somewhat dark but not black or real dark. 71.100.6.15221:46, 15 December 2006 (UTC)[reply]
What color is Iron Phosphate? If it is reddish, then it may imitate the color of copper as the Iron begins to react with the phosporic acid, leaving a residue 'plated' to the Iron surface. 12.10.127.58 21:10, 15 December 2006
'pink and flat' as you describe it is how copper usually looks when it's initially plated - take it out of the liquid and it will slowly change to more common red copper colour as it oxidises in air.87.102.3.15922:29, 15 December 2006 (UTC)
Can you expand on " Only the bottom portion of the iron up to the level of the top of the copper seems to be plated" - these seems to me to mean that some of the iron has gone black and some pink.. All the iron is submerged in the acid? and the copper is not touching it?[reply]
Check now after about 3 hours hear is what I see...
has the acid got any colour now (copper phosphate probably blue or green) - it is possible that any dissolved salt eg Copper phosphate would settle towards the bottom in a still liquid. By the way the bubbles may not neccessarily by hydrogen - but may be simply dissolved air coming out of the liquid on the metal - this is not unlikely.87.102.8.14122:09, 15 December 2006 (UTC)[reply]
The green colour is almost certainly a dissolved copper compound (though to complicate things some iron compounds are also green).
Looks like any dissolved copper has stayed at the bottom - this isn't unrealistic as long as you don't stir the liquid. Is the black layer transparent ie clear or is it a precipitate ie made of suspended solid? (Also did you mix the acid with water - sometimes you could get a layer of water sitting on top of a layer of acid.)
From your diagram it looks like some copper has dissolved and diffused along the bottom plating the iron as expected. I'm a bit confused about the black layer as I wouldn't expect it to float to the top. Clearly coating the iron with copper prevents the competing reaction which is formation of iron phosphate. I'd guess no more bubbles have been formed? It sounds like what is happening is slow corrosion of both metals in acid with some competing chemical plating (this is electroless plating). As a suggestion I'd suggest adding another bit of iron just to see if it reacts in the same way. Also you could (if you have a pipette or similar) remove some of the liquid from the top, middle and bottom layers and see what effect that has on a new iron piece in three separate bottles..
As to your original question - this is electroless plating - usually to electrolessly plate with copper you would need a copper salt eg copper sulphate, is this case though it looks like the copper salt is beeing made 'in situ' by reaction of the copper with the acid. This situation is restricted to phosphoric acid - it would happen with other acids as well; though copper is not very reactive and how much dissolves would depend on the acid used - nitric acid dissolves copper easily but sulphuric acid dissolves copper very slowly.87.102.3.15923:57, 15 December 2006 (UTC)[reply]
If I stir up the acid a lot then the bubbles increase again. The dark layer at the top disperses somewhat in the acid and makes it a bit darker and cloudy. The copper now seems to be somewhat coated with a light layer of iron oxide, i.e., rust. Before taking a sample of each layer to test reactions with iron I have placed the iron in contact with the copper. This has slightly increased the bubbles from the iron but not by a whole lot. I’m curious if electroless plating done in this or a better way can be made sufficient enough to serve as a corrosion barrier for iron in air.71.100.6.15201:22, 16 December 2006 (UTC)[reply]
I think in general electroless plating would be done with a already prepared solution of the metal to plate with, eg in a simple example you would place the iron in a copper sulphate solution - it's not really as good a method as electroplating - since once the iron is covered with a thin layer off copper no more is deposited - so only very thin coatings can be obtained - for a corrosion barrier electroplating, galvanising, or parkerizing would probably be preferable. The layer produced by electroless plating just isn't thick enough to give really good long term resistance to corrosion - though it is better than no coating at all.87.102.4.18011:51, 16 December 2006 (UTC)[reply]
So then the difference between electroplating and electroless plating is not that in electroless plating all of the metal in the solution is used up which in an electroplating is replaced by the atoms in the anode but because the cathode (in this case) reaches electrical equilibrium as soon as it is covered with copper? 71.100.6.15215:14, 16 December 2006 (UTC)[reply]
You've got the difference right, sort of, I not sure if my answers were clear enough..
Obviously you know what electroplating is and how it works.
In electroless plating the reaction stops not because of an equilibrium being reached (being pedantic), because there will still be iron under the copper to react and probably copper still in solution. The plating stops because all the iron surface will be covered with copper - the copper forms a barrier preventing any more iron reacting. Once the iron is all coated with copper it is effectively electrochemically 'insulated' from the solution.
Also with electroless plating some of the iron must dissolve to get copper coating - it's the reaction Fesolid + Cu2+solution >>> Fe2+solution + Cusolid, this means that the 'iron' must be more reactive than the copper, (so silver and gold plating also work). However in electroplating the iron does not need to react - since the reduction of the metal in solution is done 'electrically' - so Iron can be electroplated with metals that would not normally react eg Ni or Cr.
Yes, that is what I was asking (although it appears that there is such a thing as Electroless nickel plating). This would explain how flaw in the iron might be "corroded" beyond and acceptable amount if electricity were not used to do the plating. In other situations it seems that electroless plating might actually be beneficial for this reason by helping to expose certain flaws at least using phosphoric acid. Would all acids cause iron to disolve or just phosphoric acid? 71.100.6.15213:24, 17 December 2006 (UTC)[reply]
yes, that's right. answer - most acids will dissolve iron, including weak acids like vinegar (acetic acid), a few don't (concentrated nitric) becauase they 'pacify' the iron surface see http://www.cci.ethz.ch/experiments/Passivierung_Fe/en/stat.html. (Note I think electroless plating is sometimes used to coat iron/steel with copper prior to electroplating with chrome - a bit like a primer as used in paints).87.102.13.23516:06, 17 December 2006 (UTC)[reply]
The iron wire now removed from the phosphoric acid shows copper plating where the bubbles rose to the surface as well. some parts of the wire remain black but other parts have already acquired a surface coating of rust. I'm now going to put some nickel in a clean batch of phosphric acid and then put in some iron after the nickel that is left is removed in hopes of doing the electroless nickel plating. 71.100.6.15221:00, 17 December 2006 (UTC)[reply]
Why is the temporal resolution of the compound eye higher than that of the human eye? Please don't tell me "The compound eye has a higher flicker fusion rate." because that is only a restatement. Which are the processes in which the compound eye / visual system is faster and why is it? Falk Lieder18:52, 15 December 2006 (UTC)[reply]
My understanding is that the answer would be found in the second link - if it existed:) In the compound eye the rhodopsin is a bistable molecule - on absorbing a photon it changes from metarhodopsin, the retinal changing to the all-trans form. On absorbing a second photon, the metarhodopsin changes back to rhodopsin. It is the first change that initiates depolarisation, via a G-protein coupled mechanism. The second reaction simply restores sensitivity, i.e. it does not cause any further depolarisation. This flip-flop of rhodopsin-metarhodopsin-rhodopsin occurs repeatedly, it is quick, it does not deplete the supply of rhodopsin, and explains the rapid response of the compound eye. In vertebrates, by contrast, rhodopsin undergoes "bleaching" - the retinal splits off from the opsin protein, and the rhodopsin now has to be regenerated by relatively slow enzymatic means. So the difference seems to lie in how quickly the rhodopsin at a specific site can be regenerated. If the regeneration / recovery time is short, then a higher frequency flicker can be detected, but if it is slow, then the sequential flickers fuse at slower rates. The difference between the two rhodopsins (compound eye and vertebrate eye) lies in the opsin, not in the retinal part of the molecule - all animals have essentially the same photosensitive retinal component. The opsins differs, and determine wavelength sensitivity, whether the metarhodopsin can be directly reactivated, or whether it bleaches and has to be resynthesised. I hope this helps, and please ask if my explanation is dense - unfortunately I do not have a reference with me. --Seejyb01:34, 16 December 2006 (UTC)[reply]
Have any high temperature nuclear waste repositories been designed to concentrate the high temperature waste and use the heat to perform work such as boiling and thereby distilling water (through heat exchangers of course)? Adaptron19:03, 15 December 2006 (UTC)[reply]
No. The risk of contaminating ground water is very high already. When cheap fossil fuels abound, why bother messing with dangerous toxic wastes to produce energy? 70.225.160.106 04:13, 16 December 2006 (UTC)
By putting nuclear waste to beneficial use the deliberate effort to eliminate it as a source of contamination would be greatly enhanced. Besides naturally occuring deposits Natural nuclear fission reactor of radioactive material have been found which at one time had critical mass and were shielded only by overlayment and groundwater. Adaptron16:01, 16 December 2006 (UTC)[reply]
Digitising photos
More of an "advice" than a "knowledge" question, but I'm hoping you wizards of the reference desk will be able to help me nonetheless :). I have a large number (several hundreds) of photos printed from 35mm film, with their original negatives. I would like to digitise them if possible, with the aim of being able to print off the digitised versions (instead of having to take the negative into the photo shop to have the reprint made). I have experimented with the scanner at work, but the quality from scanning the photos in is not all that great (even after fiddling with the settings for awhile) - plus, for several hundred photos, it's not necessarily the best solution. Does anyone have ideas for digitising photos to "reprintable" quality? A film scanner, maybe? Thanks in advance for any tips! — QuantumEleven20:13, 15 December 2006 (UTC)[reply]
Yeah, I would try a film (negative) scanner. Personally I have found them to be somewhat spotty, so you should really try to make sure you read reviews for them and possibly try out one yourself if you have the ability to. As for scanning the prints themselves, is the "scanner at work" an old mopier beast, or is it a relatively new flat-bed scanner? If it is not the former, that might be the source of your poor quality — you might want to try out a more up-to-date dedicated scanner. In my experience many old scanners and mopiers and things like that have far inferior quality to even a cheap flat-bed made in the last year or two. --140.247.240.12720:55, 15 December 2006 (UTC)[reply]
I believe many places where you can develop film will now also give you a digital version on disk, for a price, of course. The advantage is, you only have to pay once, and can make all the copies you want after that. StuRat22:08, 15 December 2006 (UTC)[reply]
most of them give you 1.5 MP images at a crappy JPEG quality. doing it yourself is better.
That would be suitable for e-mail, but your right, is grossly insufficient for "reprintable" quality. On the other hand, only the most expensive scanners would have any hope of reproducing a photograph without a noticeable loss of quality. StuRat05:02, 16 December 2006 (UTC)[reply]
Get a scanner (Minolta, Nikon..) that's made for scanning film. many of them come with a tray that will feed uncut film rolls or 4-strips automatically, and software that will crop it properly and spit out a series of high-quality JPEGs or TIFFs.
Just a thought... would projecting the negatives on to a screen and taking the photographs using a digital camera help ? Of course, you'll need to convert the photos into their 'negatives' using some software on your PC to get the original colours. Besides, you'll also need a projector... --WikiCheng | Talk10:25, 16 December 2006 (UTC)[reply]
It would be very hard to get the colors right in something like that (even more so if doing it from negatives). And most digital cameras are going to have far less resolution in the final file than you could get from a scanner. Better to scan directly. --24.147.86.18715:47, 16 December 2006 (UTC)[reply]
There are a number of commercial services that will scan negatives for you, which can be cheaper and less time-consuming than scanning them on your own. Do a Google search for "negative scanner" and look at the sponsored links (ScanCafe looks pretty promising). howcheng {chat}18:37, 18 December 2006 (UTC)[reply]
Tobacco Addictiveness
Could somebody tell me the exact addictiveness of tobacco and it's addictiveness compared to other drugs? A link to where the info was aquired and/or a trustworthy source for this information would also be nice (somewhere other than Wikipedia). BeefJeaunt20:28, 15 December 2006 (UTC)[reply]
How would you quantify "addictiveness" ? One way I could think of is as a percentage of people who are unable to quit. StuRat22:04, 15 December 2006 (UTC)[reply]
Okay, forget "exact addictiveness". How addictive is tobacco compared to other common/well-known drugs, eg. cocaine, marijuana, alcohol, etc. I read here that nicotine "with a 90% addiction rate, is the most addictive of all drugs". I'm somewhat skeptical and would like to have this information verified (if at all possible). I also read that 70% of current smokers have tried to quit at NIDA's site, so I already have that statistic. I'm writing a thesis for grade 10, "Marijuana Vs. Tobacco", just in case anybody's suspicious.
I think this site will answer your question: [2] added by —AySz88\^-^ to replace [3]. Check out the chart at the end, especially. They tested nicotine, heroin, cocaine, alcohol, caffeine, and marijuana, and found marijuana to be the least addictive, with an approximate tie with caffeine. StuRat04:50, 16 December 2006 (UTC)[reply]
To avoid pre-disposing people to the findings of the article, I replaced the link above with a plain text version of the news article. (The original had a bunch of interpretations and highlighting to point people to one specific finding which isn't really relevent.) —AySz88\^-^04:21, 18 December 2006 (UTC)[reply]
Conjunctivitus
I am NOT seeking medical advice here or anything, but I would like to know: what are the symptoms of conjunctivitus; and what are the cures and/or preventions? thanks Herbynator22:28, 15 December 2006 (UTC)[reply]
Conjunctivitis explicitly states symptoms and treatments. Preventative measures you can take: avoid touching/rubbing/itching your eyes/face/nose as much as you can, scratch your face with your (upper) arm if you can't resist an itch. This will help prevent bacterial conjunctivitis (which requires innoculation of the eye directly) and viral conjunctivitis (which usually spreads from the nasal cavities). Talk to your physician about medications that reduce the symptoms of seasonal allergies if your conjunctivitis is allergenic, or find some way to avoid whatever allergens you can't deal with.Tuckerekcut22:46, 15 December 2006 (UTC)[reply]
December 16
pyramid power
does anyone know the official site for this gym equipment hosted by brooke burke on TV? could it have made my abs not aligned?
are you suggesting thats a bad thing? abs that are built but not aligned are pretty sexy. they look more rugged and natural ;)
Explosives
Why is TNT usually used as a unit of energy or explosive power? For example, the recent nuke test in North Koria was classified as a "sub-kiloton" explosion, meaning the explosion was smaller than that of a kiloton of TNT. Is it because TNT is the most explosive (exluding nukes) or because it's widely available or what?
Also does any one have some stats on how other explosive compare with TNT (in eplosive energy-per-mass), particularly: C4, nitroglycerin, gun powder, fine black powder.
As to the first question, I think it's just that in 1945 TNT was one of the widely known and widely used explosives. --Anonymous, December 16, 03:50 (UTC).
TNT equivalent was used for discussing nuclear weapons yields since 1945. The ability to detect the explosive yield of the first nuclear test (the Trinity test) was first calibrated against 100 tons of TNT, which is probably the source of the unit. It has since been standardized as a fixed number (see Ton#ton_of_TNT) for use in such discussions. They are used for nuclear weapons out of convention, and are continued as such for comparative purposes. --24.147.86.18722:56, 16 December 2006 (UTC)[reply]
What sort of apple was this?
My father was recently given what looked like an apply by a patient of his. I believe it may be a fruit of Korean extraction. It was like an apple, but larger--about grapefruit-sized--and the skin was brown and rough. The inside was textured more like a pear than an apple, and it tasted very faintly of starfruit. We kept it for nearly a week before eating it, but it was still very crisp. It came in a webbed-styrofoam sheath. What sort of apple was it, if it was indeed an apple? (None of the other pomes look likely. grendel|khan01:42, 16 December 2006 (UTC)[reply]
I ve heard the main function of the large intestine is to remove liquid from the er, mixture! How does this water get extracted and then get passed to the kidneys for excretion?--Light current01:50, 16 December 2006 (UTC)[reply]
"Water, as always, is absorbed in response to an osmotic gradient. The mechanism responsible for generating this osmotic pressure is essentially identical to what was seen in the small intestine - sodium ions are transported from the lumen across the epithelium by virtue of the epithelial cells having very active sodium pumps on their basolateral membranes and a means of absorbing sodium through their lumenal membranes. The colonic epithelium is actually more efficient at absorbing water than the small intestine and sodium absorption in the colon is enhanced by the hormone aldosterone." [4]. The water enters the bloodstream, which passes through the kidenys. - Nunh-huh01:55, 16 December 2006 (UTC)[reply]
When does education start, age, and type of training goes on there?
Were may I find these tpyes of answers?02:31, 16 December 2006 (UTC)
Thank you, Lisa 02:31, 16 December 2006 (UTC)~
Hi, Lisa. Try reading the article on Japan, following the links, and then getting back to us if any of your questions remain unanswered? Good luck. Anchoress02:34, 16 December 2006 (UTC)[reply]
I've been wondering this lately. How do the many opioids relate to a standard - such as morphine? What is the statistical data that can tell me this, how is it measured - in-vivo? I stumbled across some non-cited powerpoint presentation over at [5] but other than that, I don't know where that information comes from, and haven't been able to find anything with a simpler chart of the relation, so I figured someone might know more than I at the health reference desk. Thanks. Edit: Mostly oral ingestion, but intravenous would also be interesting. - x1987x(talk)05:07, 16 December 2006 (UTC)[reply]
That's a fairly standard chart of the sort which can be found in pharmacology texts. Generally they are made from research on rats (in which the rat is given a certain dose of one of the opiates and subjected to painful stimuli). Note that the information is specifically about potency in its technical definition: it relates to the amount of analgesia produced by a certain weight of the drug. This is important when trying to replace one drug with another, but not terribly important otherwise. The common use of the term potency relates to "effectiveness", or the amount of analgesia provided by a safe dose of the medication, and the table doesn't speak to that at all. You don't care how many milligrams you have to take, only that the dose you need to take is safe. - Nunh-huh23:10, 16 December 2006 (UTC)[reply]
There are numerous charts, with different opioids, depending on the availability of the substance in the country of origin. The term to search for is "opioid conversion table". Apart from that, pharmacological reviews of individual opioids usually give a strength relative to morphine. I'll get back in the morning (now 02:00 here). But thanks, this does sound like a suitable subject for an article. --Seejyb23:08, 17 December 2006 (UTC)[reply]
I couldn't figure out the search term, thanks. Yeah, strengths of the many opioids aren't talked about much. And I had no idea where to look for such tables, let alone build a page from them. Thanks..--x1987x(talk)02:42, 18 December 2006 (UTC)[reply]
thank you but it is not specific. I am in an urgent need for the size of particles removed buring different processes of wastewater treatment.
Chirag11109:43, 16 December 2006 (UTC)[reply]
what is the calorific value of biogas? how much of water can it heat?
what are the main constituent of biogas?
A note here, the refdesk is not Google. We can't give you "general information" about things, and if you're looking for information on biogas, we have an article on it. If you're going to ask more than one question, put them in one header. (I fixed this) --WootyWoot?contribs09:22, 16 December 2006 (UTC)[reply]
I agree that similar questions from the same person should all be put in the same section, but dissimilar question should be posted separately StuRat22:07, 17 December 2006 (UTC)[reply]
Applying general rules for articles to questions, comments and responses on the reference desk is inappropriate. Where the content of articles represent a consensus questions, comments and responses on the reference desk for many reasons do not. In fact, fooling around with other people's comments, questions and responses so that they suit your own 13 year old spoiled self is highly inappropriate and you need to stop. 71.100.6.15220:16, 17 December 2006 (UTC)[reply]
Also Wooty needs to learn that the purpose of the reference desk is to help others and to allow them to help each other rather than to indulge in the policies of one's 13 year old spoiled self. 71.100.6.15218:16, 16 December 2006 (UTC)[reply]
To return to the question: Wikipedia's article is not helpful. Cleaned biogas has the same calorific value as natural gas. I do not have figures on boiling water, but I do have: 1 cubic meter of biogas can:
Yield enough electricity to light 60 -100 watt bulb for 6 hours
Presumably you are talking about the old analogue TV system that is still used in some parts of the world like the US. I also assume you are talking NTSC? Look at Television, PAL and NTSC. I would have to look it up, but I believe it may be due to the reduced strength of the color sub carrier that is used for synchronisation of the color decoders. Also, there is only half the power transmitted for the chrominance signay compared to the luminance, so there is a 3 dB difference already present.
When there is no color sync signal, a circuit called a 'color killer' is switched on to avoid blotches of random color being displayed on the screen. This killer also operates in the case of simple monochrome transmissions. 8-) --Light current14:46, 16 December 2006 (UTC)[reply]
Thanks, but I guess my question comes down to why the color signal is weaker than the monochrome in the first place. Was a decision made at some point that people would be willing to view a program without color, so the color signal should be given a lower priority and hence strength ? StuRat15:21, 16 December 2006 (UTC)[reply]
Hey StuRat, it took a bit of reading, but here is the answer from the YUV Article:
Another advantage of YUV is that some of the information can be discarded in order to reduce bandwidth. The human eye has fairly little color sensitivity: the accuracy of the brightness information of the luminance channel has far more impact on the image discerned than that of the other two. Understanding this human shortcoming, standards such as NTSC reduce the amount of data consumed by the chrominance channels considerably, leaving the eye to extrapolate much of the color. NTSC saves only 11% of the original blue and 30% of the red. The green information is usually preserved in the Y channel. Therefore, the resulting U and V signals can be substantially compressed.
Yeah its all about bandwidth really and cramming a quart (color + lum) into a pint(lum only) pot. THe eye is much less sensitive to color accuracy than brightness. Also to conseve bw, almost half of the am signal generated is supressed leaving only a 'vestigial' lower sideband. This keeps the channel width to about 6.6 MHz. Over here we used to call the US system Never twice the same color (NTSC) cos of its poor performance compared to PAL! --Light current17:51, 16 December 2006 (UTC)[reply]
Does this PAL stuff apply to computer monitors as well? I recently purchased a computer monitor named "Reflex" from a thrift store which I could not find any info for until I found a link in Europe and read somewhere that these monitors are not available in the USA. Could the PAL thing be the casue? Adaptron20:50, 17 December 2006 (UTC)[reply]
Quote from our page on PAL:
Some engineers jokingly expand NTSC to "Never Twice the Same Color" or "Not the Same Color" while referring to PAL as "Perfect At Last", "Peace At Last", or "Pay for Additional Luxury"!
No. To my knowledge, unless you have a UHF input to your monitor, then Pal is not relevant. PAL refers to phase reversal every line of the color subcarrier when transmitted. Your monitor will be RGB or composite video or some such thing and of course gives you much better picture than the TV- doesnt it?--Light current20:55, 17 December 2006 (UTC)[reply]
Homologous vs Analogous
If I want to talk about two proteins, one in humans and the equivalent (related by evolution) protein in say, a mouse, are these proteins said to be homologous or analagous? --Username132 (talk) 14:15, 16 December 2006 (UTC)[reply]
Analagous proteins do the same thing in different organisms, homologous proteins are the same thing in different organisms. Droud15:01, 16 December 2006 (UTC)[reply]
You'll want to check out homology (biology). It's got a description of the different types of homology there. Gene sequences are (almost) never precisely identical from one species to the next; often you'll see discussions that describe the degree of sequence homology as a percentage. TenOfAllTrades(talk) 15:45, 16 December 2006 (UTC)[reply]
Your description would suggest they are actually orthologous proteins, to be more specific (assuming by equivalent you mean "the most closely related protein in the mouse"). Rockpocket03:51, 17 December 2006 (UTC)[reply]
If you're trying to identify a pill that you've been given, this site lets you search on drug name, pill imprints, colour, and shape. It outputs a table of photographs of all the hits it comes up with. This site], meanwhile, lets you upload a picture of a pill and then you wait (and hope) for someone to identify it for you. (It's sort of like the Reference Desk here.) TenOfAllTrades(talk) 19:47, 16 December 2006 (UTC)[reply]
Because of the different lifespan of red and white cells, it probably depends of their kind. According to Arizona Science Center, ca. 2 million die per second, so 172,800,000,000 die in 24 h. --Brandспойт01:11, 17 December 2006 (UTC)[reply]
That seems like a rather large number, unless my math is off. Speaking only of red blood cells (and most of the blood cells are RBCs), their normal life-span is 120 days (this can be lower in intensively training athletes). Each day about 1% of RBCs are replaced. The blood volume in one human is approximately 4.7 liters or 4700 milliliters. There are about 5 million RBCs per milliliter. So that's 23,500,000,000 RBCs/human, and 1% of that is 235,000,000 replaced per day. Calculating another way, if there are 23,500,000,000 and they are replaced in 120 days, each day about 430,833,333 are replaced. So maybe a good estimate would be 300,000,000 RBCs/day. - Nunh-huh02:19, 17 December 2006 (UTC)[reply]
"Full" valence shell is a misnomer, of course. All atoms "want" is an s2p6 arrangement. A "full" valence shell would be 2n2 electrons, where n is the number of the shell. This s2p6 arrangement seems to have the highest ionisation energy, and lowest electron affinity, of any, and that is why it is a "stable" arrangement. --G N Frykman08:51, 17 December 2006 (UTC)[reply]
It's also possible that full valence shells have a spherically symmetrical distribution of 'charge' whereas unfilled shells don't - it's possible to make the link with the stability of full shells through 'hand waving' explanations.87.102.13.23516:10, 17 December 2006 (UTC)[reply]
Note that Tin forms +2 and '+4' oxidation states - in the +2 case the valence shell is not full - but the complounds are stable - however the s shell is full.
In general this phenomona happens because there is a big gap in energy between the full valence shell and the state with "full valence shell plus one electron" - the difference is so large that it's very rare to find the valence shell 'overfilled' (I can't think of a single example), however having partially filled valence shells does sometimes happen (though the resultant products are reactive).
As others have said, and perhaps I can just re-phrase, the metaphor of atoms as "wanting" agents is a bad approach to this. If you take for granted that full valence shells is the most stable condition, then by definition it is what atoms are going to fall into when they get the opportunity. Why stable states are, by definition, more stable, is a much more difficult and problematic question, because you are really trying to take apart what the definition of "stability" really is in physical terms. If I understand this correctly, which I don't pretend to necessarily do. --24.147.86.18720:34, 17 December 2006 (UTC)[reply]
That seems like a good explanation - the first part. As I see it the problematic part is explaning why 'octets' and the like are stable - which is reasking the question again - even the latest theories of the atom don't actually explain why certain states are stable, or why the stabilty occurs at certain values 2,8,18 etc. There are formulas giving the number of electrons in each successive valence shell - but unfortunately no explanation of why those formulas (and not others) apply..83.100.132.12122:16, 17 December 2006 (UTC)[reply]
Ha, I remember in grade 9 and 10 science where to explain bonding, when you had ionic forms of atoms, they'd be the happiest with full valence shells, so in order that they don't become unhappy, they bond. 74.102.89.24100:26, 18 December 2006 (UTC)[reply]
A tank with decaying larvae? You probably should drain the tank. I've heard that a thin layer of oil on the water surface will suffocate the larvae by plugging their breathing tubes. But then you'd have both the dead larvae and some rancid oil. --Wjbeaty04:29, 17 December 2006 (UTC)[reply]
I seem to remember that somewhere the WHO used styrofoam beads to cover the surface of ponds and prevent mosquitos from breeding without interfering with the fish living there. Dr Zak05:01, 17 December 2006 (UTC)[reply]
Why not just skim them? And may I say that (for whatever reason, I'm not squeamish about bugs or much else), this is the grossest topic I've ever seen on the RD? ;-\ Anchoress05:07, 17 December 2006 (UTC)[reply]
Get a local river fish (like, say, a trout) into the tank it will efficiently get rid of all the larvae. Depending on a lot of factors it can either stay there for a rather long time or you will have to release it back into the river. Keria17:14, 17 December 2006 (UTC)[reply]
yes that's a real solution - but suggest a smaller fish - remember the fish will polute the water. Hillstream loach and Chaetostoma (bulldog) plecs have actually been (reported) to have been used for this purpose. I wouldn't suggest trying this though - if the larvae are all eaten the fish will probably starve, die, rot and then pollute the water even worse!83.100.132.12117:45, 17 December 2006 (UTC)[reply]
Barrier netting, mounted on a suitable frame, to stop mosquitoes getting to the water, if the reservoir tank does not have a lid.
One of the Juvenile hormones (methoprene, pyriproxyfen) for killing an established infestation. The mosquito dunk idea seems pretty good, but I have never used the stuff (on reading the name I first thought it was a joke about a food or drink of some kind:)), and I wonder what it does to a lab bacteriological test.
Filter through basin of clean river sand if water is not clear, though a simple fine sieve regularly is mostly good enough. Clean filter regularly.
Depending on your circumstances, you could chlorinate and filter the water with high tech apparatus, but unless you have serious contamination (lab test for bacteria - people tend to under utilise these facilities) it should not be necessary. --Seejyb20:51, 17 December 2006 (UTC)[reply]
Maybe you'll get more help at a bodybuilding or similar forum. From the quick search I did though, everyone was saying that's just the way it is for some people. They also says it better to have non-symmetrical [but defined] abs than a loads of fat.. --Username132 (talk) 10:07, 17 December 2006 (UTC)[reply]
Which kinds of cells undergo cellular respiration?
I can't seem to find exactly what kind of organisms undergo cellular respiration. Which ones do besides plants and animals? Is it just eukaryotes? Thanks. --Proficient06:40, 17 December 2006 (UTC)[reply]
Don't they all? I mean, the cellular respiration article defines it as "the metabolic reactions and processes that take place in a cell to obtain chemical energy from fuel molecules". That seems pretty universal to me; I dunno. --Spoon!07:55, 17 December 2006 (UTC)[reply]
It is this "breathing" connotation of respiration which seems to cause confusion, and one has to blame earlier generations of biologists for this. Retrospectively it was not a good choice. Remember that: viruses are not "cells", so they have no cellular respiration mechanisms. Here is a question to consider: Erythrocytes do not contain mitochondria; do the have cellular respiration? --Seejyb21:07, 17 December 2006 (UTC)[reply]
Sustained release tablets are standard pills which dissolve slowly and are generally taken twice a day to maintain therapeutic drug levels. The Extended Release versions consist of an insoluble shell filled with an aqueous solution of the drug. A small hole in the insoluble shell (covered over by a permeable membrane) allows the slow diffusion of the medication out of the pill over an extended period, allowing once a day dosing. (This is a drug delivery mechanism originally designed for Procardia XL). - Nunh-huh11:01, 17 December 2006 (UTC)[reply]
Quick release tabs dissolve all at once, being compounded with something like starch. The SR is formulated so that the active ingredient is embedded in a matrix of insoluble substance (various: some acrylics, even chitin, these are often patented) so that the dissolving drug has to find its way out through the holes in the matrix. In some SR formulations the matrix physically swells up to form a gel, so that drug has first to dissolve in matrix, then exit through the outer surface. I believe that the holes in XL tabs are laser drilled. You may find that some SR and XL preparations use different salts of the active drug (I do not know whether this is true of bupropion). This is apparently something to do with the binding and solubility is in the matrix. Since novel delivery systems are patented, and quite profitable, specific manufacturing information is rather difficult to find. Maybe we should try the patent office:) --Seejyb23:00, 17 December 2006 (UTC)[reply]
Does the build up of sediment in the bottom of the water tank as well as the corrosion of the tank come from the reaction of the copper electrode and the iron lining of the tank and pipes or does it come from the temperature change of the water? Adaptron14:05, 17 December 2006 (UTC)[reply]
I think most of it comes from the water itself. You will get sediment in a plastic tank too. Filtration can only remove so much gunk.--Shantavira14:51, 17 December 2006 (UTC)[reply]
A bit of both. Sedimentation just happens when you hold water still in any tank, and there's not much you can do about it other than clean it out from time to time. Galvanic action, on the other hand, requires very specific conditions. A magnesium sacrificial rod is often used to stop this effect. Some corrosion will still occur with the rod, but at a greatly reduced rate. StuRat14:52, 17 December 2006 (UTC)[reply]
Thanks. Galvanic action answers most of my question and that the corrosion comes from the reaction of oxygen in the water with the iron in the tank which the magnesium electrode prevents by reacting with the oxygen first. What I am wondering now is whether an electric current through an inert electrode would substitute for the magnesium or whether possibly some form of hydrogen interface or injection could be used? Adaptron15:17, 17 December 2006 (UTC)[reply]
But what is the overall goal ? I would think a continuous electrical current would cost more than the magnesium rod, and could also pose a safety hazard. Another option is to line the water heater with something inexpensive and corrosion resistant, like glass. That does make them very heavy, unfortunately. StuRat21:59, 17 December 2006 (UTC)[reply]
Tin Reactions
As part of a lab, pieces of tin metal were emmersed in copper(II) nitrate and hydrochloric acid. Contrary to the activity series of metals, however, reactions did not take place. Are there any explanations for this? I have looked all over the internet. Thanks. -- Sturgeonman15:31, 17 December 2006 (UTC)[reply]
It's possible than the tin is coated with layer of tin oxide on the surface preventing reaction with the copper sulphate. I can't explain why it would not react with hydrochloric acid.83.100.132.12117:55, 17 December 2006 (UTC)[reply]
I have a very difficult question, one which many career anatomist, two physiatrists, and a hand surgeon have not been able to answer, but I thought maybe I'd get lucky here. Put your hand palm side down on a flat surface. Now flex your fourth digit so that it is bent under your palm, and the proximal phalange is flat on the surface. All other fingers should be straight. Now try to extend your third digit. Notice that there is a small range of movement. Now reposition your hand so that the third digit is flexed underneath and attempt to extend the fourth digit. In this case, there is no range of movement whatsoever. Why is it that extension is possible in one situation but not in the other? Consider that it is possible to move the "immobile" digit through extension with another mechanism (like the other hand) without pain, and that this phenomenon occurs with the second and third digit in the positions above too. Tuckerekcut16:27, 17 December 2006 (UTC)[reply]
Actually, experiment proves that a small range of movement is possible, but only through quite a considerable amount of pain in the bent finger, as the controlling tendon is placed under extreme strain. (Thanks for putting me through that!) The answer is that while there are indeed four tendons in the back of the hand, one for extending each finger, there are only three muscles (located in the wrist) controlling those tendons, one for the little finger and two shared between the three middle fingers. Find someone with low body fat and watch them flexing the fingers to see the tendons move through the skin on the back of the hand; or get a hand from your anatomy friends, remove the skin, and play with the muscles of the wrist yourself. (On the base of the hand it's much simpler; each segment has its own muscle, although not everyone has the neurological ability to address those muscles separately.) Thus when one finger is at full flexion, the body is unable to restore the adjacent finger to full extension, because when the muscle pulls on the adjacent finger's tendon it is also pulling on the flexed finger's tendon - which cannot be extended. EdC18:47, 17 December 2006 (UTC)[reply]
None of my colleagues were able to extend the fourth digit in the situation described, if you were able to, kudos to you. However I am most interested in knowing why there is such a difference in the difficulty between the third and fourth digits as described. I realize that the extensor digitorum provides extension for digits two through five, with ex. dig. minimi and indicus adding in for 2 and 5, but this does not explain the difference in difficulty, which really is the part that stumps me. Tuckerekcut20:35, 17 December 2006 (UTC)[reply]
Incidentally, I meant no sarcasm with my last remark, if it seemed that way. I also wanted to point out that the pain seems (to me) to be in the muscular region of the extensor muscle, rather than the tendinous region, thus weakening your argument slightly. Tuckerekcut20:38, 17 December 2006 (UTC)[reply]
Nah, to me it's definitely in the tendon, where it passes through the knuckle. I have a feeling the reason I'm able to do that might be that I broke my middle finger a while back, so it probably doesn't count.
Still, this a purely mechanical problem; the neurological wiring doesn't enter into it. Think of the hand as a series of hinges with springs to force them shut (the flexor muscles).
When the ring finger is fully flexed, the extensor tendon is close to full stretch. When the middle finger is fully flexed, even more so; when the index finger is fully flexed the extensor tendon is almost completely at full stretch. Thus when the ring finger is flexed the tendon can still be retracted a short distance, extending the other fingers. When the middle finger is extended the tendon can be retracted a little, giving less movement in the index finger than when the ring finger is extended, but even when the tendon is fully retracted this is insufficient to overcome the residual tension in the ring finger, so it does not extend.
Oh, and I'm not sure why it is possible to extend the ring finger when it's the index finger that's flexed. I suspect some amount of rotation or lateral movement is going on with the tendon, or it might be due to lateral banding. I'd have to get a hand to play with to be sure. --EdC02:41, 18 December 2006 (UTC)[reply]
Fish mate
Someone told me of a deep sea fish specie of which the male is a 10th the size of the female. When finding a partner the male grabs the female and taps into her blood system (?) and insures she has a constant suply of sperm. The female then feeds for him and the male lives off their joint bloodstreams. What is the name of the fish? Are there other examples of such extreme couplings? Thank you. Keria17:06, 17 December 2006 (UTC)[reply]
"When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were females"..."When a male of one of these species hatches .... extremely well developed olfactory organs .... They have no digestive system, and thus are unable to feed independently. They must find a female anglerfish, and quickly, or else they will die."..."When he finds a female, he bites into her flank, and releases an enzyme which digests the skin of his mouth and her body, fusing the pair down to the blood vessel level"..."then atrophies into nothing more than a pair of gonads"..."when the female is ready to spawn, she has a mate immediately available"...83.100.132.12119:02, 17 December 2006 (UTC)[reply]
I saw this video [7] on ebaumsworld and it says that a parasitic worm controls a crickets mind and forces it to commit suicide. While I know thats probably not true, can anyone tell me what exactly happened in this video? Imaninjapiratetalk to me17:54, 17 December 2006 (UTC)[reply]
This sort of parasite mind control has been a popular recent topic - even as it relates to humans. Can't find any links right now though. Rmhermen18:08, 17 December 2006 (UTC)[reply]
It's a Nematomorpha, otherwise known as a Gordian Worm. It apparently does make the grasshoppers seek out water and drown themselves, returning the worm to the water. Super creepy. I added a super-legit reference to the article (Nature, 2006) which is where that video is from. --24.147.86.18720:01, 17 December 2006 (UTC)[reply]
Another similar example of brain control might be the rabies virus, which attacks the brain, increasing the aggressive tendencies of an animal, making it bite other animals and thus spread rabies to new hosts. StuRat21:52, 17 December 2006 (UTC)[reply]
A similar phenomenon is the "brainwashing" of carpenter ants by the Cordyceps unilateralis fungi. The fungal spores get into the ant via its spiracles and starts to grow mycelia filaments inside the ant, being careful to avoid any vital organs. When its ready to sporulate, it projects mycelia to the ants brain. It then forces the ant to climb to the top of a plant and attach itself firmly to a leaf by biting with its mandibles. Now that its in a suitable position, the fungus will eat the ant's brain, sprout outwards through its head and explode, showering the area with spores that will try to invade other ants. As told in the BBC's Planet Earth, When other ants detect that one of their own has been infected, the carry the unfortunate ant as far away from their nest to die, in the hope that when the fungus sporulates, it will limit the chances of infecting the entire colony. There are lots of different types of fungus that do this, with different species being specific for diffferent types of arthropod. You can see more info, including footage here. Rockpocket23:20, 17 December 2006 (UTC)[reply]
I don't think the parasitic barnacle sacculina driectly attacks the crab's brain, but it does attack its gonads to sterilise it, and then uses the crab's mating behaviour for its own procreation. --ColinFine23:41, 17 December 2006 (UTC)[reply]
Of course, it's the "mind control" idea that intrigues the press, but it's a little bit silly and anthropomorphic. These are parasites that cause a change in behavior in their hosts, but there's no "mind control" in play. - Nunh-huh01:25, 18 December 2006 (UTC)[reply]
No, I wasn't. I suppose there is one, but that wasn't what I was trying to point out, which is that "control" implies the existence of a will on the part of the controlling agent, which is certainly lacking in these instances. - Nunh-huh02:00, 18 December 2006 (UTC)[reply]
I'd call effecting a very calculated and deliberate change in behavior "mind control" under most people's common definitions. I'm not sure what other definition of "mind control" one would want to use. --24.147.86.18701:48, 18 December 2006 (UTC)[reply]
If it were "calculated" or "deliberate", you'd have a point. But it's not, as there is no intelligent agency doing any calculating or deliberating. That's precisely the point. - Nunh-huh01:58, 18 December 2006 (UTC)[reply]
There doesn't have to be an intelligent agency, that's the beauty of natural selection—you can render "nature" itself as a theoretical selecting agency. In any case, I don't think you've yet given a good reason for not considering it "mind control". Anything which can directly alter an organisms mental behavior in such a dramatic way sounds like "mind control" to me. --24.147.86.18703:25, 18 December 2006 (UTC)[reply]
Sensitiveish Microphone Advice
I want a microphone that will pick up my voice from a few meters away so I can have Skype conversations when I leave my headphones somewhere or just don't feel like wearing them. My old headphone needs to be right near my face in order to pick up my voice clearly and is therefore not sensitive enough. Can someone advise me on how to choose a suitable (cheapest microphone effective at three meters for Skype) microphone on ebay? Micrphone type? Sensitivity level likely needed? --Username132 (talk) 19:29, 17 December 2006 (UTC)[reply]
Have you looked up microphone? You need to decide if you want unidirectional or omnidirectional response. I suspect you want omni to pickup your voice wherever you are in the room. It looks like you need an omni with a large diaphragm [8]. Have you considered using a LS in reverse? 8-)--Light current19:39, 17 December 2006 (UTC)[reply]
I don't think that will work, even with a great microphone. To hear the other party you'll have to run Skype's output through the PC's speakers - and the microphone will hear that too. It's very hard to position things so you don't just get runaway feedback, and even then it'll sound garbage. If you must do this, you need to get a proper speakerphone attachment. Speakerphones implement advanced DSP algorithms to suppress feedback and echo. Googling for "skype speakerphone" shows a number of manufacturers make compatible units. I've not used their Skype unit, but Polycom's other conference phones are very good (not not at all cheap). -- Finlay McWalter | Talk19:51, 17 December 2006 (UTC)[reply]
Yes Finlay is correct in that on a 2 wire line (full duplex) system you do need some sort of hybrid transformer system to prevent positive feedback. These are naturally buit in to (speaker) phones. I'm not sure if the Skype has such a hybrid system built in. One way to test would be to bring the headset mic close to the ear phones and listen for howling. If no howling then youre ok and the separate mic idea should work/.8-)--Light current20:13, 17 December 2006 (UTC)[reply]
I really meant sonic echo, not electrical feedback (although if both parties had such homebrewed speaker & mic systems, you'd get insane sonic feedback too). That's sound (the remote party talking) coming out of the speakers, it bounces off walls and stuff, and flies back into that nice sensitive omnidirectional microphone. And because your room probably has four or more hard walls (plus the ceiling, plus large pieces of furniture) then the mic receives not one echo but one for each such surface, each at a different delay from the original sound. That's why fancy speakerphones play a little tune when you turn them on - they're measuring the echoes of those different surfaces, and their frequency-absorption characteristics. -- Finlay McWalter | Talk20:26, 17 December 2006 (UTC)[reply]
[According to Beth], I should bake my cake mixture for one hour at 180 C. After baking for just 20 minutes, the thing began to burn and make smoke. Is Beth really evil, or is there another, less sinister explanation? --Username132 (talk) 21:12, 17 December 2006 (UTC)[reply]
I wonder if the oven (I set to 350) is in Faranheit or Celcius... it's an oven in the Netherlands, but wouldn't an oven that goes to 350 Celcius be quite special and expensive? Maybe I should set the temperature lower and or have heat come from only the bottom of the oven (instead of also the top). --Username132 (talk) 21:37, 17 December 2006 (UTC)[reply]
Heat come from the top? Sounds like you've turned on the grill! My friend has an oven where it is possible to do this too. If you are baking you only want the heat from the bottom. Also, 180 degrees C is medium low, so depends what the scale of your oven is, what's the minimum and max you can set it to? My oven is in C and it goes from about 100 to 300 I think, so 350 might not be outrageous if it's near the top of the scale. Vespine22:10, 17 December 2006 (UTC)[reply]
I suspect there's a problem with the temp sensor in your oven and it's not kicking off when it reaches the proper temp. Do you have a meat thermometer ? If so, stick it in the oven and see what it says the temp is. StuRat22:16, 17 December 2006 (UTC)[reply]
There could also be a problem with the temp selection dial. Does it seem to turn properly or does it turn with difficulty or show some other problem ? StuRat22:33, 17 December 2006 (UTC)[reply]
I agree with StuRat, get an oven thermometer so that you know in future exactly what that oven is doing - if you are baking cakes it sounds as if you are settling in for a longish stay. A baking neighbor may have one to lend. To what maximum is the oven marked? If it is in the region of 500 or more, then it is almost certainly in °F, but then I would expect an oven in the Netherlands to use the Celsius scale. Generally: If the pan is placed directly over the heating element one can burn the bottom of the cake, it may need to be shielded by a separate baking tray. The upper element/grill would not normally be used during baking (sometimes for preheating) --Seejyb22:39, 17 December 2006 (UTC)[reply]
That iffy, it's either a Fahrenheit-scale oven that doesn't go very high or a Celsius scale oven that gets very hot, indeed, perhaps a self-cleaning oven ? StuRat23:57, 17 December 2006 (UTC)[reply]
Or is it attached to the ocean floor ? Does this vary from summer to winter ? If it is attached, is there a risk of it breaking free soon due to global warming ? StuRat22:30, 17 December 2006 (UTC)[reply]
Yes, it floats (there is no land under most of it - the nearest bits of solid land to the North Pole are Ellesmere Island and Greenland). There is nothing "stopping" the ice from floating away (bit of ice, also known as icebergs, break off the polar ice cap all the time! The Titanic hit one, for instance...), but this doesn't affect the cap as a whole, because it only "exists" where the temperature is cold enough. As a thought experiment to understand this: Take the ice cap as it is at present, and move it a bit in one direction. Some of it will now be in a warmer region of the world (nearer the Equator), that bit will melt, while a bit of ocean in a colder part of the world will now become exposed, that bit will freeze. End result: The ice cap stays where it is.
Of course, the ice cap shrinks and expands considerably between summer and winter!
Something to remember about the northern polar cap: melting bits of it (because of global warming) will not change sea levels, because when you melt ice that's floating in water, the overall level of water doesn't change. Melting ice sheets which sit on top of land (eg Antarctica), that's where the problem is, for any melting there equates to a sea level rise.
That pic seems to show that the ice touches land (Greenland and Ellesmere Island), even in summer, but just barely. Perhaps in just a few years that land bridge will be gone and it will be free to drift ? StuRat00:06, 18 December 2006 (UTC)[reply]
This image suggests that pretty soon, around Greenland and Ellesmere island will be about the only place the ice remains. Makes sense; in the open ocean the water gets heated up by sun and currents, but around the land the ice gets protected and replenished by calving glaciers. --EdC03:08, 18 December 2006 (UTC)[reply]
Neurologist/Neurosurgeon
I read both articles, but what are the actual practioners doing? Are neurologist and neurosurgeon synonymous ? does a neurologist only give medication ? Thanks in advance.-- ExpImptalkcon22:37, 17 December 2006 (UTC)[reply]
Well, drugs is one option. Diet modification is another. In the case of stroke victims, they may need to relearn certain things and in the case of epilepsy victims, they may need to learn to avoid certain things which trigger seizures (blinking red lights, for example). StuRat00:09, 18 December 2006 (UTC)[reply]
trismus &faciculations of upperlimb during menstrual cycle
married women aged 29yrs with h/o subserosal fibroid (4.5*2.3cms ) (primary infertility )h/o trismus& fasiculation during menstrual cycleon &off episodes -2yrs .Are these symptoms related to menstrual cycle 0r there might be systemic cuase —The preceding unsigned comment was added by 202.54.91.201 (talk) 03:56, 18 December 2006 (UTC).[reply]
19:24, 15 December 2006 (UTC)
