# Search results for query: *

1. ### Mean and SD of the inverse of a population

If one has the mean and standard deviation of a population, is it possible to calculate (or estimate) the mean and standard deviation of the inverse population (ie. 1/(every value in the original population)? Thank you!
2. ### Combining decibel levels

Ahh yes I see, thank you! However, does 20dB not correspond to a factor of 10, and 40dB to a factor of 100, given the fact it is dB SPL, and hence 20logx as opposed to 10logx? Also, the next part of the question asks - if the sound pressure of D is four times that of E, by how many decibels do...
3. ### Combining decibel levels

1. What is the total sound pressure levels of two identical tones, each 88db SPL, when added together? For this question, using the equation dB SPL = 20log(P/2*10^-5), I found the value of P where dB SPL = 88, then doubled this value, then fed it back into the equation, to obtain a value of...
4. ### Determining the voltage of a power source

Thanks for the reply. If 40mV was the total battery voltage, and there are 40mV across the capacitor, does that mean that there are 0v across the resistor? My physics is really rusty ever since I became a medic..!
5. ### Determining the voltage of a power source

See file below: http://img228.imageshack.us/img228/5797/screenshot20100527at215.png [Broken] This is for a biological membrane, but the principles are the same. I am asked what the value of the initial voltage, Vt is.The options are: What was the value of the initial voltage, Vt? A. +58 mV...
6. ### Medical Chest wall compliance

I was wondering what the changes would be if the a) the lung compliance decreased and b) the chest wall compliance decreased. Am i correct in thinking both would result in a fall in FRC, or would that only be for a fall in lung compliance? In addition, what would happen to other lung volumes...
7. ### Medical Radiograph of the abdomen

ah okay; i see it now. Thanks so much. Yes, there was an accompanying chest radiograph which showed the gas clearly, but i couldn't see it in the abdomen which is why i only asked about this image. Thanks you!
8. ### Medical Radiograph of the abdomen

Hmm I see your point. I made sure no identifiers etc were present but I guess i won't do it again! I see the inferior margin of the liver, but I am still unsure of where the falciform ligament is;is it the line which is crossing from the right over to the left in the midline at the top of the...
9. ### Medical Radiograph of the abdomen

Yes, I am a first year medical student. No, I would certainly not be hacking patients records or anything! The url is for "image shack", a popular image hosting website. Hmm yes I know the falciform ligament is the ligament attached the liver to the anterior abdominal wall and the diaphragm...
10. ### Medical Radiograph of the abdomen

It was amongst a number of radiographs accessible to us online for those at our college.
11. ### Medical Radiograph of the abdomen

I was struggling with the radiograph below;I am told that "the plain abdominal X-Ray shows the falciform ligament outlined by gas. This is the appearance of extraluminal gas." http://img687.imageshack.us/img687/1634/c03axrperf.jpg [Broken] However I am unable to see this; is it possible...
12. ### Biology Genetics Pedigree Diagram

thanks for the reply! I can't really think of anything... would it be possible for you to nudge me in the right direction? Thanks
13. ### Biology Genetics Pedigree Diagram

I was struggling with interpreting the following pedigree diagram: http://img245.imageshack.us/img245/715/photoon20100411at2211.jpg [Broken] I can see from the diagram that only females seem to be capable of transmitting the disease - not males - this lead me to believe it is X-linked. In...
14. ### State 4 Respiration

i was undertaking a question regarding a patient who had a mutation in their mitochondria, and hence experienced lethargy. A subsequent test of his mitochondria found his mitochondria to have an increased state 4 respiration, but a normal state 3 respiration. In order to explain this, I would...
15. ### Terminating PCR

I started to reply about how i still didnt understand, but then as I tried explaining why I saw the reason! Although the polymerase may go beyond the region of interest, on the next cycle, the primer will only bind to the start of the region of interest, and so after a few cycles, youll be left...
16. ### Terminating PCR

primers determine the 5' start of the new strand... not the 3' end?
17. ### Terminating PCR

I have a question regarding PCR which I was unable to find the answer to (maybe because its obvious and I am just not thinking of the reason!) How is PCR terminated? For instance, say you wish to amplify a 2kb length of dna, how does one ensure that just this 2kb region is amplified as opposed...
18. ### The cardiac cycle

I was struggling with the following question: In a frog heart preparation that is beating spontaneously, the longest part of the cardiac cycle involves: A. Contraction of the atria B. Contraction of the ventricle C. Relaxation of the ventricle D. Electrical conduction through the...
19. ### Kidney function question

i was struggling with the following question: Partial occlusion of one renal artery is likely to result in which ONE of the following: A. Increased renin secretion from both kidneys B. Increased sodium excretion C. Constriction of the efferent arteriole of the other kidney D. Dilatation of the...
20. ### Southern Blotting

Thanks so much for the reply; that's was what I thought logically made sense but I wanted to confirm it!
21. ### Southern Blotting

In southern blotting, how are the DNA bands visualised? i have read two conflicting methods; one using ethidium bromide stain, and one using DNA probes. Can either be used, or are the two distinct methods used in different circumstances? Thanks.
22. ### Loan with equal annual repayments

Sorry, I really don't know where to start; would it be possible for you to give me a nudge in the right direction so that i can work it through?
23. ### Loan with equal annual repayments

I was undertaking the following problem: A man takes out a 5 year loan for \$10,000 with an annual interest of 8% with equal annual repayments. How much must be paid each year? I'm stuck as to where and how to start. Is there are particular equation which I should be using? Thanks
24. ### Heros and Fermats principle

Ah yes, i makes sense now. Thank you so much.
25. ### Heros and Fermats principle

http://img26.imageshack.us/img26/2615/43774076.th.jpg [Broken] Can someone please explain how to do this problem - I don't really know where to start. Thanks
26. ### Impulse homework problem

If body A exerts an impulse of say +2Ns on B, then does body A exert an impulse of -2Ns on B providing no external forces act? Thanks
27. ### Damped harmonic motion

Would I say y = 0.5ft^2 - (particular solution of the equation), and then find when dy/dt = 0, to find the time at which y is a max, and then subv this time back in, to find ymax, and then use the tension equation? Thanks

29. ### Equilibrium of a compound object

Thanks for the reply. Surely O - is not the point of contact - O is the centre of the upper disc. Thanks
30. ### Damped harmonic motion

For the tension, you forgot to divide by the natural length = a, and hence the a seems to fit! Thanks a lot for the help though, it makes sense now! How would I do the last part of finding the maximum tension in the spring? Thanks
31. ### Damped harmonic motion

http://img13.imageshack.us/img13/9091/53337497.th.jpg [Broken] Can someone please help me with the problem above? I am unable to start it. Clearly, using the constant acceleration "suvat" equations, 0.5ft^2 is the distance obtainined, however I am unable to proceed. Thanks in advance.
32. ### Coefficient of resistution problem

Thanks for the reply. Yes I know this, however I don't know how to proceed; how to I form the velocity in p and q from i and j? Thanks alot!
33. ### Coefficient of resistution problem

http://img190.imageshack.us/img190/3237/22080589.th.jpg [Broken] Can someone please guide me through part 5b - I am struggling to start this part of the question. Thanks in advance.
34. ### Equilibrium of a compound object

A closed container C consists of a thin uniform hollow hemispherical bowl of radius a, together with a lid. The lid is a thin uniform circular disc, also of radius a. The centre O of the disc coincides with the centre of the hemispherical bowl. The bowl and its lid are made of the same material...
35. ### Complex plane transformations

http://img34.imageshack.us/img34/5391/13262160.jpg [Broken] http://g.imageshack.us/img34/13262160.jpg/1/ [Broken] http://img46.imageshack.us/img46/7397/62501858.jpg [Broken] http://g.imageshack.us/img46/62501858.jpg/1/ [Broken] http://img7.imageshack.us/img7/2651/15142727.jpg [Broken]...
36. ### Capacitor and diode curcit for ac to dc voltage

http://img42.imageshack.us/img42/2461/49889005.th.jpg [Broken] My question is, why does the dc voltage vary with time in this way? Ply it is something to do with the diode allowing current to flow when it has 0.7V or more across it, allowing the capacitor to charge, and when the voltage...
37. ### Finding a transformation to transform a line in the z plane to a circle in the wplane

Thank you very much!
38. ### Transformations from the Argand plane

Ahh yes, thank you very much!
39. ### Finding a transformation to transform a line in the z plane to a circle in the wplane

http://img154.imageshack.us/img154/4286/70338217.th.jpg [Broken] I am able to do part a - however am unsure on how to do the second part. Please can someone help with this. Thanks

41. ### Reaction force between a Sphere and particle

http://img13.imageshack.us/img13/9112/70948888.th.jpg [Broken] I do not understand how circular motion can be occurring a point B - surely at B, the reaction force occurs in a direction away from O. Therefore, there is no resultant force that can be acting towards O, since the weight is...
42. ### Light in CD readers

Hi I am struggling with the problem below: http://img134.imageshack.us/img134/8977/03jan.th.jpg [Broken] I can do the first part, but don't know how to start the second part. Thanks
43. ### Engine efficiency

process A: isothermal compression at low temperature with an input of work of 83 J process B: constant volume increase in pressure with an energy input by heating of 200 J process C: isothermal expansion at high temperature with work output of 139 J process D: constant volume cooling to the...

Thank you!
45. ### Solving an equation involving sin and cos terms

Hi I was wondering if there is a non-numericla way to solve the following equation: 144 - 90sin x - 155.8cos x = 0 Thanks
46. ### Scalar product of position vectors

find values of t for f'(t) =0 I don't understand the significance of r.r, however. Thanks
47. ### Motion of a particle subject to a variable resisitive force

ah right, so why does it say in the ascent, as opposed to descent? Thanks
48. ### Motion of a particle subject to a variable resisitive force

http://img338.imageshack.us/img338/193/33379676.th.jpg [Broken] See the image above. I am able to get to (where x = distance): x = (1/2k)ln((g - k(V^2)(tan a )^2)/(g - kv^2)) If you let v = 0, and then multiply by mg, you find potential energy gained presumably - I don't understand why the...
49. ### Scalar product of position vectors

http://img520.imageshack.us/img520/9580/56788025.th.jpg [Broken] See the problem above. I can do all of the problem, barring the last part. I have found r and r.r: http://img520.imageshack.us/img520/1590/29349935.jpg [Broken] How does this allow me to find the minimum and maximum...
50. ### Circular motion in a vertical plane

Thanks for the reply, I have got it now.