victorqedu

Hello I'm trying to calculate eGFR using the CKD-EPI formula but my results are wrong and don't know why. I use this site to check my results: https://qxmd.com/calculate/calculator_251/egfr-using-ckd-epi And I use this site for a very simple formula: https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/kidney-disease/laboratory-evaluation/glomerular-filtration-rate/estimating I'm testing on a white male 40 years of age and with serum Creatine 51 so the formula is: GFR = 141 × (Scr/0.9)-1.209 × (0.993)Age I calculated in many ways, this test is done directly at Postgsql database level: SELECT 141*POWER(51.0/0.9, -1.209)*POWER(0.993, 40) The result is 0.80 but the correct result should be 127.8. All values I checked give me a subunitary value and this is wrong. What do I apply wrong in the formula? Thank you.

This initiative is very good. This forum should have a section "Problem of the week" or something like this.

This hypothesis is very old and purely speculation. Is not actually a theory yet. The following is a quote from the last link I posted. http://www.space.com/22577-earth-life-from-mars-theory.html?cmpid=51463011319564 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890202/ http://science.slashdot.org/comments.pl?sid=4145815&cid=44712033

This is a great forum on all domain I posted. Does this forum represents an educational institution?

I understand this now. My last question remains: If the acceleration is not instant how do I compute the age of the twins ?

The answer to the original problem, when mouse changes directions at random is 2 years(in the mouse frame of reference). I got to 2 years ignoring earth and considering the mouse as an inertial frame with Lorentz factor = 2 with regard to the cat inertial frame. When the angle is changed acceleration is produced and the inertial frame is changed but because the speed remains constant the frames are equivalent. This is a proof of the fact that acceleration is not directly involved in space-time deformation. I have ignored the time between the start of the mouse and the start of the cat since in the original setup is unknown. Is this correct?

This is a very simple solution. And if the acceleration is not instant? How will I quantify now the age of the twins?

According to wikipedia example the Lorentz factor is calculated from the point of view of the stationary twin and is applied only to the space and time of the twin that accelerates.. http://en.wikipedia....pecific_example This solves the standard twin problem and is even intuitive. The question remains this: Let's say that there are 2 ships. Both are accelerating in opposite directions with a different acceleration for some time and then they return to the start point(still with asymmetric accelerations). Accelerations are still instant. Now I can't apply Lorentz factor. How do I compute the age of the each twin?

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Then what should I use to solve it? Or what should I read? I found the best example on wikipedia. http://en.wikipedia.org/wiki/Twin_paradox#Specific_example. This is a very good explanation. However I can't apply this sollution when both twins are accelerating. So let's say that there are 2 ships A and B Both are accelerating in opposite directions with a different acceleration for some time and then they return to the start point(still with asymmetric accelerations). How do I compute now the age of the each twin? I understand now that acceleration is not the main cause for the time dilation. Acceleration just "pushes" one twin in another inertial frame. From here one all time is different between the 2 twins. So time doesn't just dilates while accelerating, it is dilating when the acceleration has stopped and when the speed is constant because of the different frame of inertia.

This is what wikipedia says: Explanations put forth by Albert Einstein and Max Born invoked gravitational time dilation to explain the aging as a direct effect of acceleration. http://en.wikipedia.org/wiki/Twin_paradox I agree. The pressure can't be the cause. Otherwise a simply pressurized box with a clock inside will have a different time. However, the question is how do I apply the Lorentz equation to the the special relativity to explain twins paradox? I must apply for both twins, after they meet. And twin A should say that B is younger. And twin B should say that A is older. I don't see this happening using Lorentz factor. If I use Lorentz factor than: Twin A should say that B is younger. Twin B should say that A is younger.

I have not read all the post from here http://www.scienceforums.net/topic/74683-acceleration-is-not-important-in-the-twin-paradox/. But I think is counter productive to read it all. My original post is solved, I understand it. But bigger problems appeared now. My next question is about the twin paradox - just the standard version, using just special relativity. It seems to me that in that big post has been assumed something that has not been proved. Einstein special relativity theory has just 2 postulates: 1) All laws are the same in the same inertial frame. 2) c is constant. How do you conclude from these 2 postulates some asymmetry will make one twin older? And how do you conclude that the twin that left the earth will be younger and not the other way? I read how the Lorentz factor is derived and this is clear. I even saw a few explanations of the twin paradox that are very nice. Here they are: https://www.youtube.com/watch?feature=player_embedded&v=7ce970Pq82s But all of them have the same problem. If you watch from the other perspective you will see the same thing(the other twin will be younger) I understand that one twin makes a U turn and changes direction. But from the other twin perspective is the same symmetrical situation. The only difference is the pressure of the acceleration felt only by one twin. But I can't see how to fit this pressure in the 2 postulates stated. Pressure it's self should not interfere at all with relativity. So I can only conclude that the 2 twins will have the same age when they meet again? I don't think so. Can someone give some directions about this? Then why Hafele–Keating experiment show that running clocks run slow? Well, this is done in a gravity field. Maybe this is the answer. Maybe swansont was right. I can explain this only with general relativity. As I think to this problem it seems to me that acceleration is the key and the explanation can be done only with general relativity. After all gravity produces acceleration. And maybe acceleration alone produces space time deformation.

Where is this thread? I would like to make abstraction of general relativity for now.

This is what I understood: When A and B are travelling at high constant speed twoards eatch other then A will see B's clock running slow and viceversa. Next they start to decelerate. As a consequence of the deceleration A will se how B's clock is starting to move faster and faster until B's clock will catch up with A clock. As a consequence of the deceleration B will se how A's clock is starting to move faster and faster until A's clock will catch up with B clock. When they meet both clocks will move at the same rate because they are in the same frame o reference. Because the deceleration is the same for A and B the clocks will show the same time when they meet. Is this correct? But if : - A will feel no acceleration(constant speed) and - B would decelerate until it will be in the same frame of reference with A. The one that decelerates will bave the clock behind when they meet? Could I say that accelleration compresses space and slows time? And since only B will feel the pressure of the aceeleration only his frame will have slow time.

So there are 3 points of view. A, B and C. From C point of view both clocks are moving slow at the same rate. A ship and B ship will stop and both clocks will show the same time. But from A point of view B's running slower. And when A and B meet B's clock should be behind. A and C POV's are not in agreement. Where is the mistake?

Theoreticaly you can asume that they stop instantly. But let's assume that they stop in a simetric acceleration. You have exposed the problem as if both ships are in the same frame - c. My question would be how do I solve the paradox described? If from A's point of view B's clock is running slowly. And if from B's point of view A's clock is running slowly. They when they meet it should be a paradox because A will say that his clock is ahead and B will say that his clock is ahead. But these 2 statements can't be true at the same time.

Both ships are stopping instantly. So everything about them is simetrical. In this situation how do I solve the paradox?

If in the beginning the clock are sinchronized and if they fly in a straight line aproaching eatch other then witch clock will be ahead? I believe the answer is that they will be synchronized. But why? If from A's point of view B's clock is running slowly. And if from B's point of view A's clock is running slowly. They when they meet it should be a paradox because A will say that his clock is ahead and B will say that his clock is ahead. But these 2 statements can't be true at the same time. It looks like there is something fundamental about the theory of relativity that I don't see yet.

Hello. Relativity is not very clear to me and I will a question as simple as posible. Ship A and B are moving towards eatch other with very high speeds. First problem is how do I decide witch ship is in the inertial frame? The question appeared because of this deduction: From A's point of view B's clock is running slowly. As I think From A's point of view he is the inertial frame. From B's point of view A's clock is running slowly. As I think From B's point of view he is the inertial frame. The problem appears when they meet(they stop for a coffe break ) When they stop whos clock is behind? Thank you.

So quorum sensing can control only the population growth(how big each organ will be). And quorum sensing has nothing to do directly with the actual shape of the final product(the hearth by example). The shape is somehow made by these gradients. But the formation of the gradients is very unclear for me. If all cells are are made using the same template then how can they build these complex shapes? What I mean is: - let's say that in the beginning I have a single cell and I will try to obtain the hearth. - this cell multiplies by mitosis - all cells being identical they will signal the same thing to the surrounding cells so I can't see how the gradient will get a custom shape like the hearth - signals can be different only proportional with the population density - I can see only a spherical shape It looks like the gradients must be somehow coded in the genes.

Hello. DNA has been mapped and we know that DNA stores the information for all the proteins that are necessary for life. But how does DNA codes for the shape of a organ or for the amount of cells in the brain? How does DNA stores the information for when to stop growing? Can you give some detailed links? Thank you.