<!--QuoteBegin-Carling+Jun 9 2004, 08:11 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (Carling @ Jun 9 2004, 08:11 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> I have max_fps set at 60 and it rare it drops below that. i never found any need for higher. <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd--> I'm pretty much sure you didn't play 1.0x....
<!--QuoteBegin-Soylent green+Jun 12 2004, 02:59 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (Soylent green @ Jun 12 2004, 02:59 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> <!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->If you look at a TV or monitor or other visual source that uses a CRT and outputs a frame rate significantly higher than that, it will appear to flash, or you'll see descending black lines move slowly down the screen. That's why, when you watch the news or some other TV program that shows active computer monitors, you can see that flashing and black lines - it's because the monitor is outputting faster than the TV station is broadcasting.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
This has nothing at all with the capabillites of the eye. This is because a CRT light up it's pixel during a very small intervall, it scans across the screen like when you read a paper and light one pixel up at a time. When you then have a camera filming this it will be out of sync with the monitor which may fill say 3.1 screens for every one the camera gets. part of the screen would have been overdrawn more times than another and look brighter than the other when viewed on TV, and the line where the difference in brightness occurs will appear to travel. This has nothing at all to do with the eye and isn't evidence of anything. <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd--> OT: (Well, the topic is now TV / CRT technology now, so not really)
Agreed, the TV issue is not a trick of the eye, but if you look again, I never said that. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo--> The "trick of the eye" was a referrence to the fact that you dont see the light/dark changes when you view the CRT normally. You should, as the pixels are not updated simultaneously, but line by line. This happens so fast that it is not noticeable.
The person who I quoted already mentioned the refresh rates, so I did not repeat it. Humph.
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Agreed, the TV issue is not a trick of the eye, but if you look again, I never said that.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
Agreed, but then again I never said that you did say that. <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo--> (|C9|Agent said it).
The reason it happens so fast that you don't notice with your eyes is after images. The transmission of information from rods and cones in your eye to the brain is not instantaneous but depends on the speed of various chemical reactions, these typically have a half-life, which isn't entirely unnoticable as a very short, bright, flicker will be extended in time and much fainter to a human viewer.
<!--QuoteBegin-Soylent green+Jun 14 2004, 12:32 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (Soylent green @ Jun 14 2004, 12:32 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> <!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Agreed, the TV issue is not a trick of the eye, but if you look again, I never said that.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
Agreed, but then again I never said that you did say that. <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo--> (|C9|Agent said it).
The reason it happens so fast that you don't notice with your eyes is after images. The transmission of information from rods and cones in your eye to the brain is not instantaneous but depends on the speed of various chemical reactions, these typically have a half-life, which isn't entirely unnoticable as a very short, bright, flicker will be extended in time and much fainter to a human viewer. <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd--> OK, call it quits.
But half-life for chemical reactions? WTH? :S
Wait a minute...
He's using science buzz words to fob me off! <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
Or is there some ligit use for half-life in terms of chemical equaitions? Like the time taken to reach a state of 50:50 reactant:product? :s
Eh, no. Half-life is (as if you didn't know this) the time required for a radioactive isotope to "shed" half of its mass. I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium. <!--emo&::nerdy::--><img src='http://www.unknownworlds.com/forums/html//emoticons/nerd.gif' border='0' style='vertical-align:middle' alt='nerd.gif' /><!--endemo-->
Take out "half-life" and the rest of his post is valid. I'm looking at his post time right now, and thinking that Soylent should get some sleep before posting <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo--> .
<!--QuoteBegin-5kyh16h91+Jun 14 2004, 04:24 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> (5kyh16h91 @ Jun 14 2004, 04:24 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> Eh, no. Half-life is (as if you didn't know this) the time required for a radioactive isotope to "shed" half of its mass. I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium. <!--emo&::nerdy::--><img src='http://www.unknownworlds.com/forums/html//emoticons/nerd.gif' border='0' style='vertical-align:middle' alt='nerd.gif' /><!--endemo-->
Take out "half-life" and the rest of his post is valid. I'm looking at his post time right now, and thinking that Soylent should get some sleep before posting <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo--> . <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd--> Hence my comment on buzzwords. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
Going wayyyyy off topic here,
n/m, there's physics boards on the net to post physics questions on .
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Or is there some ligit use for half-life in terms of chemical equaitions? Like the time taken to reach a state of 50:50 reactant:product?<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
Yes it is a legitimate use of half-life as long as the assumption that the reaction is exponentially decreasing is correct, because then then half-life is well defined and as long as the listener please refrains from being too pedantic <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->. For an equilibrium reaction the "distance" from equilibrium and speed of reaction would have a well defined half-life(the concentration looks like k1e^-k2t plus some constant term that shifts the curve so that it goes towards equilibrium as time passes and not 0, take the time derivative to get the speed of reaction and you get rid of the constant term as a bonus), right?
Why does an exponential function have a well defined "half-life"?
Lets try some ascii art math <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo-->
n(t) = k1e^-k2t
lets call the half life T.
n(t0) = k1e^-k2t0
What we want for half life to be well defined is n(t0 + T) = n(t0)/2 for all t0.
We see that if T is choosen such that e^-k2T = 1/2 , T is the time it takes for half the substance or whatever to remain.
T = - ln (1/2)/k2 => T = ln(2)/k2.
Of course, here red, green and blue(these are all by cones) as well as brightness(rods) would have different half-lives.
If you expose someone to a brief monochrome flash of say, red, you would see something reminicent of a red flash that grows dimmer and dimmer over time but takes a long time to fully dissapear. Somewhat close to exponential function so I'm going to guess that it is(if there is some major limiting reaction that has a very large half-life, the intensity should look very close to exponentially decreasing if the brain doesn't do anything strange to the input.). The reformation of rhodopsin has a long half-life, ~1.5 minutes in cones and ~5 minutes in rods. This means that to get proper night vision you have to stop exposing yourself to light for a good 10 minutes at least.
edit: yeah, forgot to annoy you while I'm at it, your eyes could be said to be performing a sort of weighted time averaging of previous input and your nerves a delaying as well as relaying of the signal to the brain, and don't forget that fudge constant that absorbs how much vitamin a and carrots you've eaten and eye disorders.
If you want to, you can ascribe a bacterial culture a negative half-life but even I think that's pushing your luck.
(it's 5:40 in the morning and I'm not afraid to use my tiredness for questionable purposes <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->(I don't feel tired, just very easily amused, as you can see from me using the maximum number of emoticons allowed in a post)).
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Eh, no. Half-life is (as if you didn't know this) the time required for a radioactive isotope to "shed" half of its mass. I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
A chemical reaction in which reaction speed is exponentially decreasing never exactly reaches equilibrium mathematically, but for all intents and purposes there is some point after say, 20 half-lives when the reaction is pretty much all over and nothing much is going on. The usefullness of half-life is that it doesn't rely on how long it takes for the reaction to stop, but how quickly it is stopping and is easily messurable without ambiguities or judgement calls.
I think I follow. (Soylent, I have a new found respect for your science ability. Did you read Bio-something in Uni, or do you just have a passing interest in Opticology?)
One querry, Why would a reaction ever decrease in rate exponentially? Most reactions I can think of, or have studied in detail, have a linear decrease in rate simply due to fall in concentration of reactants.
Possibly a reaction with more than 2 reactants where the limiting factor is a reactant with a very low starting concentration?
Fudge contant/fudge factor: weird constant which really doesn't have a well defined origin(unlike more fundamental constant such as <s>h</s>, pi or e or well defined constants such as the concentration at the beginning of some experimint or something). You cannot ever tell someone what a particular fudge contant is or how it is derived, it either depends on too many things that you don't know or care about so you just absorb it all into a constant.
The cosmological constant is perfect example of a fudge factor. Einstein didn't think it made sense to have an expanding/contracting Universe so equations permitting he invented the cosmological constant to account for the(then) expected result that the Universe is not expanding or contracting and all was well until Hubble made some interesting discoveries about the expansion of the Universe.(Funny how we allways expect the Universe to be static and centered around us until proven wrong again and again).
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Why would a reaction ever decrease in rate exponentially?<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
Forcing me to think are we? <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo-->
Lets say you have a reaction where the rate of reaction is proportional to the amount of some substance you have.(lets call concentration C(t), the change in concentration then becomes dC/dt.) This is true if you have a substance where one molecule reacts with one molecule of another substance, and where one substance is in abundance.
This leads to a differential equation.
dC/dt = k1C
Which has the solution C = k2e^k1t (easy to check by just putting in this expression for C on the left hand side and seeing that it equals the right hand side). k2 is the beginning concentration and k1 depends on what substance you have.
Lets try a simple irreversible reaction.(*opens old chemistry books, proceeds to cough and open a window to air out the cloud of dust*)
This looks fun CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH, making "soap" of a short ester(sp?).
Lets call the concentration of booze C(t), the decrease in sodium hydroxide equals the decrease in ethyl acetate(sp?, mmmm pear). So we have some concentration, a, of sodium hydroxide and some concentration, b, of ethyl acetate.
dC/dt = k1(a - C)(b - C)
assume a < b.
Lets pick the boundary condition C(0) = 0. Nothing has reacted at t = 0.
Woot, it's separable. dC * 1/( (a - C)(b - C) ) = k1 dt
Allright so we are supposed to integrate the left with respect to dC and the right with respect to dt.
The left side is a bit tricky to integrate as it stands, at least to me so lets simplify.
First assume that 1/(a - C)(b - C) = A/(C - a) + B/(C - b) and then find what A and B must be to fullfill this, there is nothing preventing us from trying to do this and there is some mathematical proof that guarantees that it allways works out. To do this multiply both sides by (a - C)(b -C), expand and associate terms then solve the linear equation system:
With C close to zero we can remove the absolutes(sp?).
We know that C(0) = 0 since that was our desired boundary condition.
Put that in and see what we get out.
(ln a - ln b)/(a - b) = k2 => ln (a/b) /(a - b) = k2
ln ( (a - C)/(b - C) ) = k1(a - b)t + ln a/b <=> (a - C)/(b - C) = (a/b) e ^ k(a - b)t <=> a - C = (a/b)( b - C )e ^ k(a - b)t <=> C = a(1 - e^k(a - b)t)/(1 - e^k(a - b))
Ok so if the concentration of, say, sodium hydroxide is a few times higher than the concentration of ethyl acetate we will have approximately the case we had before(but now we are looking at a product of the reaction and not at the initial substance), and the rate of the reaction will have a decently well defined half-life. But it doesn't look like it would have a well defined half-life in general(oh bugger).
So it depends on what the situation is like in our eyes I guess. But empirically(go to the toilet, flash the ceiling light on and off quickly after your eyes have adapted to the darkness a bit) it does look somewhat close to exponentially decreasing, and an approximate half-life is not a completely haywire expectation.
The most cool thing about the eye(or rather the brains processing of information from the eyes) is how we are able to ignore all the defects without even seeing them. I mean, the fact that there's 0.4 degrees without the cones responsible for blue colour in foeva(central area of the eye responsible for high visual accuity when reading and stuff) and the blind spot. Is our brains actively guessing what's there and filling in the blanks without us noticing or what's going on?
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->. Did you read Bio-something in Uni, or do you just have a passing interest in Opticology?<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
No I just have a passing interest in everything. It's too bad you have to choose.
I feel sorry for people who haven't taken calculus....crappy keyboard symbols are still kinda confusing.
As for that blind spot thing....I have no idea why we don't normally notice it. Though I've done one of those funky paper tricks where a you move a piece of paper with a small speck on it a certain way, and suddenly the speck disappears. Really freaky.
Question: Are many biological reactions carried out until all products are exhausted or in this exponential decay method? Because I was under the impression that most reactions in the human body, that is most biological reactions, would only go to an equilibirum point, and exponentially decaying reactions have no equilibrium point.
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> Question: Are many biological reactions carried out until all products are exhausted or in this exponential decay method? Because I was under the impression that most reactions in the human body, that is most biological reactions, would only go to an equilibirum point, and exponentially decaying reactions have no equilibrium point.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
I'm far from the correct person to ask, I just have chemistry as an interest, but most things in the human body seem to be much more complex than just simple equilibrium reactions. A lot of it enzyme driven, and hormones and stuff come in to regulate things. The human body seem to be very good at keeping an equilibrium even if you try to offset it from equilibrium(e.g. body temperatur, blood pH).
Exponentially decaying reactions have the equilibrium point at 0, and simple reactions that tend to an equilibrium where one of the reactants is in large abundance will occur at an exponentially decaying rate(they look like an exponential curve offset so that it goes to the equilibrium and not to 0 when time goes to infinity). In the case of the eye, just wait in total darkness and there is nothing to break down rhodopsin in rods and it's equivalents in cones, it tends to an equilibrium where all rhodopsin has been reformed. This reaction occurs with an enzyme, enzymes aren't used up by the reaction so it seems quite likely that rhodopsin is reformed at an exponentially decaying rate, but wheter the signal from the eye from a single bright flash and then darkness looks like an exponential curve or not is another matter, but I suspect it might, it appears similar to an exponentially falling curve in general behaviour if you just blind yourself with a bright flash, falls initially very quickly but takes a long time to dissapear completely.
TV's in this country(UK) run on the PAL system, which is 60hz if I remember.. america uses the lesser quality NTSC which is only 50hz (why american programs have a fake plasticy look to them - the amount of lines is also smaller) so fps is about 50 to 60, and most cartoons use 30fps
I always had a frame limit of 60 fps.. but my aiming was bad (since going over to steam) and realised that my max fps was now set to 60 instead of 100.
the difference this makes is mainly on the movment.. using a marine i tried to move the aimer as slow as possible, and noticed that rather than moving smoothly it jumped large gaps at a time, so using a pistol you cant aim at skulks at extreme distances.. almost as if there was an invisible grid of squares on the screen.. and the point jumped between each corner of the grid squares
increasing my frame rate.. and reducing my mouse rate slightly has solved this.. now its very smooth, i can hold aim better.. and shoot the lips off a fly.
so im not overly convinced that 60fps is enough.. not for me anyway.. but the trouble is that the fps is never the same all the time.. it goes up and down, depending on whats on the screen..
I only use an FX5200 on a 21" monitor, and for the most part i get a consistent 99 fps
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->why american programs have a fake plasticy look to them - the amount of lines is also smaller)<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
No, it's because they use a different colour encoding sceme.
PAL and NTSC refer to the encoding scheme used.
There are many variants but:
PAL 720 x 576 pixels 50 Hz (620 lines, of which 44 are sync information and stuff)
NTSC 720 x 480 pixels 59.94 Hz
Less common: PAL-M(Laos and Brazil), the only PAL system with 59.94 Hz refresh rate.
PAL-I(UK, Hong kong, Ireland and Macao) 50 Hz, only minor things differ from regular PAL.(like sound offset)
So in general, PAL will have lower refresh rate and be excrusiatingly head ache inducing will NTSC will be less head ache inducing and uglier.
Comments
I'm pretty much sure you didn't play 1.0x....
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->If you look at a TV or monitor or other visual source that uses a CRT and outputs a frame rate significantly higher than that, it will appear to flash, or you'll see descending black lines move slowly down the screen. That's why, when you watch the news or some other TV program that shows active computer monitors, you can see that flashing and black lines - it's because the monitor is outputting faster than the TV station is broadcasting.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
This has nothing at all with the capabillites of the eye. This is because a CRT light up it's pixel during a very small intervall, it scans across the screen like when you read a paper and light one pixel up at a time. When you then have a camera filming this it will be out of sync with the monitor which may fill say 3.1 screens for every one the camera gets. part of the screen would have been overdrawn more times than another and look brighter than the other when viewed on TV, and the line where the difference in brightness occurs will appear to travel. This has nothing at all to do with the eye and isn't evidence of anything.
<!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd-->
OT: (Well, the topic is now TV / CRT technology now, so not really)
Agreed, the TV issue is not a trick of the eye, but if you look again, I never said that. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
The "trick of the eye" was a referrence to the fact that you dont see the light/dark changes when you view the CRT normally. You should, as the pixels are not updated simultaneously, but line by line. This happens so fast that it is not noticeable.
The person who I quoted already mentioned the refresh rates, so I did not repeat it. Humph.
<!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
Agreed, but then again I never said that you did say that. <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo--> (|C9|Agent said it).
The reason it happens so fast that you don't notice with your eyes is after images. The transmission of information from rods and cones in your eye to the brain is not instantaneous but depends on the speed of various chemical reactions, these typically have a half-life, which isn't entirely unnoticable as a very short, bright, flicker will be extended in time and much fainter to a human viewer.
Agreed, but then again I never said that you did say that. <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo--> (|C9|Agent said it).
The reason it happens so fast that you don't notice with your eyes is after images. The transmission of information from rods and cones in your eye to the brain is not instantaneous but depends on the speed of various chemical reactions, these typically have a half-life, which isn't entirely unnoticable as a very short, bright, flicker will be extended in time and much fainter to a human viewer. <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd-->
OK, call it quits.
But half-life for chemical reactions? WTH? :S
Wait a minute...
He's using science buzz words to fob me off! <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
Or is there some ligit use for half-life in terms of chemical equaitions? Like the time taken to reach a state of 50:50 reactant:product? :s
I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium. <!--emo&::nerdy::--><img src='http://www.unknownworlds.com/forums/html//emoticons/nerd.gif' border='0' style='vertical-align:middle' alt='nerd.gif' /><!--endemo-->
Take out "half-life" and the rest of his post is valid. I'm looking at his post time right now, and thinking that Soylent should get some sleep before posting <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo--> .
I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium. <!--emo&::nerdy::--><img src='http://www.unknownworlds.com/forums/html//emoticons/nerd.gif' border='0' style='vertical-align:middle' alt='nerd.gif' /><!--endemo-->
Take out "half-life" and the rest of his post is valid. I'm looking at his post time right now, and thinking that Soylent should get some sleep before posting <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo--> . <!--QuoteEnd--> </td></tr></table><div class='postcolor'> <!--QuoteEEnd-->
Hence my comment on buzzwords. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->
Going wayyyyy off topic here,
n/m, there's physics boards on the net to post physics questions on .
Yes it is a legitimate use of half-life as long as the assumption that the reaction is exponentially decreasing is correct, because then then half-life is well defined and as long as the listener please refrains from being too pedantic <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->. For an equilibrium reaction the "distance" from equilibrium and speed of reaction would have a well defined half-life(the concentration looks like k1e^-k2t plus some constant term that shifts the curve so that it goes towards equilibrium as time passes and not 0, take the time derivative to get the speed of reaction and you get rid of the constant term as a bonus), right?
Why does an exponential function have a well defined "half-life"?
Lets try some ascii art math <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo-->
n(t) = k1e^-k2t
lets call the half life T.
n(t0) = k1e^-k2t0
What we want for half life to be well defined is n(t0 + T) = n(t0)/2 for all t0.
n(t0 + T) = k1e^-k2(t0 + T) = k1(e^-k2t0)(e^-k2T)=e^-k2T*n(t0)
We see that if T is choosen such that e^-k2T = 1/2 , T is the time it takes for half the substance or whatever to remain.
T = - ln (1/2)/k2 => T = ln(2)/k2.
Of course, here red, green and blue(these are all by cones) as well as brightness(rods) would have different half-lives.
If you expose someone to a brief monochrome flash of say, red, you would see something reminicent of a red flash that grows dimmer and dimmer over time but takes a long time to fully dissapear. Somewhat close to exponential function so I'm going to guess that it is(if there is some major limiting reaction that has a very large half-life, the intensity should look very close to exponentially decreasing if the brain doesn't do anything strange to the input.). The reformation of rhodopsin has a long half-life, ~1.5 minutes in cones and ~5 minutes in rods. This means that to get proper night vision you have to stop exposing yourself to light for a good 10 minutes at least.
edit: yeah, forgot to annoy you while I'm at it, your eyes could be said to be performing a sort of weighted time averaging of previous input and your nerves a delaying as well as relaying of the signal to the brain, and don't forget that fudge constant that absorbs how much vitamin a and carrots you've eaten and eye disorders.
If you want to, you can ascribe a bacterial culture a negative half-life but even I think that's pushing your luck.
(it's 5:40 in the morning and I'm not afraid to use my tiredness for questionable purposes <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->(I don't feel tired, just very easily amused, as you can see from me using the maximum number of emoticons allowed in a post)).
I'm no chem major, but the time taken for a reaction to reach equilibrium is just...the time it takes for a reaction to reach equilibrium.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
A chemical reaction in which reaction speed is exponentially decreasing never exactly reaches equilibrium mathematically, but for all intents and purposes there is some point after say, 20 half-lives when the reaction is pretty much all over and nothing much is going on. The usefullness of half-life is that it doesn't rely on how long it takes for the reaction to stop, but how quickly it is stopping and is easily messurable without ambiguities or judgement calls.
I think I follow. (Soylent, I have a new found respect for your science ability. Did you read Bio-something in Uni, or do you just have a passing interest in Opticology?)
One querry,
Why would a reaction ever decrease in rate exponentially? Most reactions I can think of, or have studied in detail, have a linear decrease in rate simply due to fall in concentration of reactants.
Possibly a reaction with more than 2 reactants where the limiting factor is a reactant with a very low starting concentration?
EDIT:
Fudge constant?
Rhodopsin?
<!--emo&:(--><img src='http://www.unknownworlds.com/forums/html//emoticons/sad.gif' border='0' style='vertical-align:middle' alt='sad.gif' /><!--endemo-->
--
/me awards this topic "Most Deviation from orrginal post" award.
The cosmological constant is perfect example of a fudge factor. Einstein didn't think it made sense to have an expanding/contracting Universe so equations permitting he invented the cosmological constant to account for the(then) expected result that the Universe is not expanding or contracting and all was well until Hubble made some interesting discoveries about the expansion of the Universe.(Funny how we allways expect the Universe to be static and centered around us until proven wrong again and again).
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->Why would a reaction ever decrease in rate exponentially?<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
Forcing me to think are we? <!--emo&:D--><img src='http://www.unknownworlds.com/forums/html//emoticons/biggrin.gif' border='0' style='vertical-align:middle' alt='biggrin.gif' /><!--endemo-->
Lets say you have a reaction where the rate of reaction is proportional to the amount of some substance you have.(lets call concentration C(t), the change in concentration then becomes dC/dt.) This is true if you have a substance where one molecule reacts with one molecule of another substance, and where one substance is in abundance.
This leads to a differential equation.
dC/dt = k1C
Which has the solution C = k2e^k1t (easy to check by just putting in this expression for C on the left hand side and seeing that it equals the right hand side). k2 is the beginning concentration and k1 depends on what substance you have.
Lets try a simple irreversible reaction.(*opens old chemistry books, proceeds to cough and open a window to air out the cloud of dust*)
This looks fun CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH, making "soap" of a short ester(sp?).
Lets call the concentration of booze C(t), the decrease in sodium hydroxide equals the decrease in ethyl acetate(sp?, mmmm pear). So we have some concentration, a, of sodium hydroxide and some concentration, b, of ethyl acetate.
dC/dt = k1(a - C)(b - C)
assume a < b.
Lets pick the boundary condition C(0) = 0. Nothing has reacted at t = 0.
Woot, it's separable.
dC * 1/( (a - C)(b - C) ) = k1 dt
Allright so we are supposed to integrate the left with respect to dC and the right with respect to dt.
The left side is a bit tricky to integrate as it stands, at least to me so lets simplify.
First assume that 1/(a - C)(b - C) = A/(C - a) + B/(C - b) and then find what A and B must be to fullfill this, there is nothing preventing us from trying to do this and there is some mathematical proof that guarantees that it allways works out. To do this multiply both sides by (a - C)(b -C), expand and associate terms then solve the linear equation system:
1 =- Ab - Ba =>
0*C = AC + BC
-1 = Ab + Ba =>
A = -B
1 = Aa - Ab =>
A = -B
A = 1/(a - b)
B = -1/(a - b)
OK so lets integrate now.
Aln|C - a| + Bln|C - b| = k1t + k2 <=>
(ln|C - a| - ln|C -b|)/(a - b) = k1t + k2
With C close to zero we can remove the absolutes(sp?).
We know that C(0) = 0 since that was our desired boundary condition.
Put that in and see what we get out.
(ln a - ln b)/(a - b) = k2 => ln (a/b) /(a - b) = k2
ln ( (a - C)/(b - C) ) = k1(a - b)t + ln a/b <=>
(a - C)/(b - C) = (a/b) e ^ k(a - b)t <=>
a - C = (a/b)( b - C )e ^ k(a - b)t <=>
C = a(1 - e^k(a - b)t)/(1 - e^k(a - b))
Ok so if the concentration of, say, sodium hydroxide is a few times higher than the concentration of ethyl acetate we will have approximately the case we had before(but now we are looking at a product of the reaction and not at the initial substance), and the rate of the reaction will have a decently well defined half-life. But it doesn't look like it would have a well defined half-life in general(oh bugger).
So it depends on what the situation is like in our eyes I guess. But empirically(go to the toilet, flash the ceiling light on and off quickly after your eyes have adapted to the darkness a bit) it does look somewhat close to exponentially decreasing, and an approximate half-life is not a completely haywire expectation.
Rhodopsin ("rod"-opsin in rods <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html//emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif' /><!--endemo-->, lots of little jokes if you care to look at the names. There's also my favorite <a| bra-vector, |a> ket-vector, they often occur in this combination <a|b> (a scalar product). Put it togheter, what does it spell? bra©ket, cheesy huh?) is the photosensetive molecule in rods(brightness sensitive, high amplification, saturated quite quickly if you expose them to bright light). Cones have similar substances also named opsin something.
The most cool thing about the eye(or rather the brains processing of information from the eyes) is how we are able to ignore all the defects without even seeing them. I mean, the fact that there's 0.4 degrees without the cones responsible for blue colour in foeva(central area of the eye responsible for high visual accuity when reading and stuff) and the blind spot. Is our brains actively guessing what's there and filling in the blanks without us noticing or what's going on?
<!--QuoteBegin--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->. Did you read Bio-something in Uni, or do you just have a passing interest in Opticology?<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
No I just have a passing interest in everything. It's too bad you have to choose.
As for that blind spot thing....I have no idea why we don't normally notice it. Though I've done one of those funky paper tricks where a you move a piece of paper with a small speck on it a certain way, and suddenly the speck disappears. Really freaky.
Question: Are many biological reactions carried out until all products are exhausted or in this exponential decay method? Because I was under the impression that most reactions in the human body, that is most biological reactions, would only go to an equilibirum point, and exponentially decaying reactions have no equilibrium point.
Question: Are many biological reactions carried out until all products are exhausted or in this exponential decay method? Because I was under the impression that most reactions in the human body, that is most biological reactions, would only go to an equilibirum point, and exponentially decaying reactions have no equilibrium point.<!--QuoteEnd--></td></tr></table><div class='postcolor'><!--QuoteEEnd-->
I'm far from the correct person to ask, I just have chemistry as an interest, but most things in the human body seem to be much more complex than just simple equilibrium reactions. A lot of it enzyme driven, and hormones and stuff come in to regulate things. The human body seem to be very good at keeping an equilibrium even if you try to offset it from equilibrium(e.g. body temperatur, blood pH).
Exponentially decaying reactions have the equilibrium point at 0, and simple reactions that tend to an equilibrium where one of the reactants is in large abundance will occur at an exponentially decaying rate(they look like an exponential curve offset so that it goes to the equilibrium and not to 0 when time goes to infinity). In the case of the eye, just wait in total darkness and there is nothing to break down rhodopsin in rods and it's equivalents in cones, it tends to an equilibrium where all rhodopsin has been reformed. This reaction occurs with an enzyme, enzymes aren't used up by the reaction so it seems quite likely that rhodopsin is reformed at an exponentially decaying rate, but wheter the signal from the eye from a single bright flash and then darkness looks like an exponential curve or not is another matter, but I suspect it might, it appears similar to an exponentially falling curve in general behaviour if you just blind yourself with a bright flash, falls initially very quickly but takes a long time to dissapear completely.
america uses the lesser quality NTSC which is only 50hz (why american programs have a fake plasticy look to them - the amount of lines is also smaller) so fps is about 50 to 60, and most cartoons use 30fps
I always had a frame limit of 60 fps.. but my aiming was bad (since going over to steam) and realised that my max fps was now set to 60 instead of 100.
the difference this makes is mainly on the movment.. using a marine i tried to move the aimer as slow as possible, and noticed that rather than moving smoothly it jumped large gaps at a time, so using a pistol you cant aim at skulks at extreme distances.. almost as if there was an invisible grid of squares on the screen.. and the point jumped between each corner of the grid squares
increasing my frame rate.. and reducing my mouse rate slightly has solved this.. now its very smooth, i can hold aim better.. and shoot the lips off a fly.
so im not overly convinced that 60fps is enough.. not for me anyway.. but the trouble is that the fps is never the same all the time.. it goes up and down, depending on whats on the screen..
I only use an FX5200 on a 21" monitor, and for the most part i get a consistent 99 fps
SADE-yX
No, it's because they use a different colour encoding sceme.
PAL and NTSC refer to the encoding scheme used.
There are many variants but:
PAL 720 x 576 pixels 50 Hz (620 lines, of which 44 are sync information and
stuff)
NTSC 720 x 480 pixels 59.94 Hz
Less common: PAL-M(Laos and Brazil), the only PAL system with 59.94 Hz refresh rate.
PAL-I(UK, Hong kong, Ireland and Macao) 50 Hz, only minor things differ
from regular PAL.(like sound offset)
So in general, PAL will have lower refresh rate and be excrusiatingly head ache inducing
will NTSC will be less head ache inducing and uglier.