Recent content by johndoe3344

  1. J

    Proving Congruences of Primes: Show 2^((p-1)/2) = +1 (mod p)

    I came across this: Show that if p denotes an odd prime, then 2^((p-1)/2) = +1 (mod p). So basically, this is asking me to show that p|2^((p-1)/2)-1 AND p|2^((p-1)/2)+1 But I'm stuck from there. What am I missing? Could someone help me with the proof?
  2. J

    Fick's Second Law: Laplace Transform to solve PDE in Spherical Coords

    Fick's second law in general form: \frac{\partial C}{\partial t} = D\nabla^2 C In spherical form: \frac{\partial C}{\partial t} = D\frac{1}{r^2}\frac{\partial}{\partial r}\left( r^2\frac{\partial C}{\partial r} \right) (Assume all changes in phi and theta to be zero, so we are only concerned...
  3. J

    Why Is the Set of Real Numbers Larger Than the Set of Natural Numbers?

    I was reading about this topic of my own leisure, and I came across something that I couldn't quite understand. The solution of Galileo's Paradox is that the set of natural numbers and the set of perfect squares are both infinite sets of the same cardinality (namely aleph 0). This I can...
  4. J

    What is the relationship between ker(A) and ker(A^TA)?

    Hi, thanks for your response. What do you mean my shorthand? I only said that B = A transpose because I didn't know how to write the superscript T on the forums (is that what you meant?) Does showing that ker(A^T*A) is a subset of ker(A) show that they are equal?
  5. J

    What is the relationship between ker(A) and ker(A^TA)?

    B= A transpose What is the relation between ker(BA) and ker(A)? I was told that they are equal to each other, but I can't figure out why. ker(A) => Ax = 0 ker(BA) => BAx = 0 so that BA is a subset of A. This shows that ker(BA) =0 whenever ker(A) = 0, but how does this also show that...
  6. J

    DNA/Codon probability question

    Homework Statement A library of randomly synthesized duplex DNA strands (length = 6 bp) is generated. What percentage of these sequences would you expect that the restriction enzyme BamH1 (restriction site = GGATCC) would recognize? a. 0% b. 0.02% c. 0.48% d. 0.07% Homework...
  7. J

    Regarding Equilibrium Constant

    Thanks a lot. That cleared it up for me.
  8. J

    Regarding Equilibrium Constant

    Homework Statement Not really a textbook question, but I've read from numerous sources that changing the concentration of the reactants/products won't change the equilibrium constant. Why isn't this contradictory? Assume the reaction: xX + yY <---> zZ where x,y,z are the coefficients of...
  9. J

    Interpretation of double mutants in signaling pathways

    I found this in my notes, and I memorized it, but I have no idea why this is. Could anyone shed some light: Given: A mutation in A gives repressed reporter expression, while a mutation in B gives constitutive reporter expression. If: A double mutation in A and B gives repressed reporter...
  10. J

    Question regarding hydrophobic forces

    I've been reading a bit, and I thought I understood it, but now I'm really confused: I know that hydrophobic forces at room temperature are almost entirely entropy driven: because a system aims for maximal entropy, it pushes non-polar molecules into an aggregate in order to reduce the...
  11. J

    Determinant Relationship: det(A) and det(-A) for n x n Matrices

    So since multiplying each row of a scalar by the constant gives us det(B) = k*det(A)... If we multiply each row of a n x n matrix by the same constant, i.e. n times, then the formula would be for the case of k = -1: det(B) = [(-1)^n]*det(A) Which would explain the difference for odd n...
  12. J

    Determinant Relationship: det(A) and det(-A) for n x n Matrices

    Why are we multiplying each individual row/column by a scalar? When we multiply the matrix by a scalar, doesn't this automatically distribute the scalar to every single entry of the matrix? I guess what I'm confused at is this: Suppose we let the square matrix B be obtained from matrix...
  13. J

    Determinant Relationship: det(A) and det(-A) for n x n Matrices

    For an n x n matrix A, what is the relationship between det(A) and det(-A)? I tried it with a 1x1 matrix, and det (-A) = - det (A) I tried it with a 2x2 matrix, and det(A) = det(-A) I tried it with a 3x3 matrix, and the results were the same as that with a 1x1. This leads me to believe...
  14. J

    Regarding Orthogonal Transformations

    Thanks for all the help. But wait, so is the solution unique or not unique?
  15. J

    Regarding Orthogonal Transformations

    I follow up to this part: "where [v]_(u) is the coordinate vector of v in the base (u) which is a column vector." What do you mean specifically? What would be the basis of u? Is it [1,0,0] [0,1,0] [0,0,1]? If so, how would I go about constructing [v]_(u)?
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