Recent content by johnq2k7

  1. J

    Another energy fluence question work shown

    An x-ray field at a point P contains 7.5 x 10^8 photons/m^2-sec-keV, uniformly distributed from 10 to 100 keV. a.) What is the photon flux density at P? b.) What would be the photon fluence in one hour? c.) What is the corresponding energy fluence in SI units? work shown: a.) 7.5...
  2. J

    Hemodynamics Homework Help, Works shown

    How about part b.) Do you simply use, D_0= 2.6 cm D(34)= 10 um and substitute (D_0)^3 / (2^34)= 10 um How do you prove it? I'm sort of confused?
  3. J

    Hemodynamics Homework Help, Works shown

    How do you prove part a.) properly though, and for part c.) how do u derive the mean transit time equation from the information? please help
  4. J

    Hemodynamics Homework Help, Works shown

    Model the arterial tree as a simple branching network in which each junction is composed of a parent vessel and daughter vessels, each having a diameter related to the parent's via the cube law (D_n-1)^3= (D_n*a)^3 + (D_n*b)^3 which is approx. equal to 2*(D_n)^3 a.) Show that D_n/D_0=...
  5. J

    Another fourier transform nmr question work shown

    since t>0 and |t|=t and for t< 0 |t|= -t and since the inverse Fourier transform integral for t>=0 is given .. .u can add the the results for the inverse transform for t<=0 to the result to get Ge(f) however, how do u integrate the expression for neg. infinity to zero for integral of...
  6. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    in that case.. is the solution for X and part b correct? if that's the integral... it is an imaginary integral so how do u solve that part.. I'm confused?
  7. J

    How Does Gradient Direction Affect NMR Signal Characteristics?

    Suppose that you obtain a one dimension magnetic resonance image from two water-filled cubic shaped containers arranged as shown below. This diagram is a cross-section of the cubic containers in the x-y plane. figure description: -one of cube's is 2 cm wide, the other is 1 cm wide, and...
  8. J

    Another fourier transform nmr question work shown

    your right!.. i made a mistake it's actually Se(t)= Se(0) exp (-i(2pi(f0)(t))* exp (-|t|/T2*)? can you please help me with part a and b please
  9. J

    Another fourier transform nmr question work shown

    i forgot to include the echo signal info Se(t) info, which can be rep. by Se(t)= Se(0) exp (i(2pi(f0)(t))* exp (-|t|/T2*) from negative inf. to inf therefore, since the |t| is the magn. of t, therefore i assumed the img. part can be ignored which was helpful in my assumption. in my...
  10. J

    Another fourier transform nmr question work shown

    The "Free Induction Decay signal" (FID) is a particular type of NMR signal observed in both MRI and MRS. An idealized representation of the signal Sf(t) is given by Sf(t)= Sf(0) exp (-i2pi(f_0)(t))*exp(-t/T2*) t>=0 Sf(t)= 0 it was proven that Gf(f) corresponding to this signal is given...
  11. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    since e^(-a)<0.01 -a<(ln 0.01) therefore is the smallest value of a less than 0.01... ln 0.01?
  12. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    since, it asks for the magnitude of X, this is the 'real part of the solution so the imaginary part can be ignored right from my previous expression.. therefore i get X= e^{(-((T2-i(w-wo)T2^2)/(1+(w-wo)^2*T2^2))*T} =e^{(-((T2/(1+(w-wo)^2*T2^2))*T} therefore for part b, it's X=...
  13. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    so if it's gnew(w)= g_old(w)(1+X) isn't X=e^-aT or based on there expression X= e^{(-(T2-i(w-wo)T2^2)/(1+(w-wo)^2*T2^2)*T} for part b.) if T=a*T2 therefore how do u solve, do u simply sub in a*T2 for T into the expression X= |e^{(-(T2-i(w-wo)T2^2)/(1+(w-wo)^2*T2^2)*(a*T2)}|...
  14. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    then you would get the expression, S(0){-(e^(a*t))/a} from 0 to T so you would get: S(0)*-{((e^aT)/a)-(1/a)) how do you determine the expression for X then, if a= 1/T2 + i(w-w_0) therefore you get, S(0){-((e^(1/T2 + i(w-w_0)t)/a)) -1/(1/T2+ i(w-w_0)} what is X in this case? and...
  15. J

    How Does Finite Acquisition Time Affect the Spectrum of an NMR Signal?

    for the that integral... the expression consists of an imaginary number i with t.. and additionally your integrating the expression from 0 to T for t, therefore u can't integrat the T2 expression right?.. how do u you go about integrating the expression... i'm confused.. I'm sure it's easier...
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