Search

A historical analysis is given of the development by Larmor in 1900 of the Lorentz transformations of coordinates and time, and of electric and magnetic field components. The earlier work of Voigt is discussed.

A review is given in elementary terms of the diffraction of waves from helices, with special reference to the structure of DNA. The essential features of the experimental results are discussed.

A large class of problems in statistical physics is very simple when treated by means of the chemical potential. In this paper the chemical potential is applied to eight problems of physical interest, with particular emphasis on solid-state physics. The method could profitably be emphasized in junior or senior courses in statistical physics.

Two systems of biomolecules in solution are known to be represented by simple models which can be solved to give phase transitions in one dimension. The systems are double-stranded DNA and the helical polypeptides. We treat the very simple problem of the single-ended zipper. There is an interesting simialrity with the work of Nagle on the one-dimensional analog of the Slater model of KDP.

In Brownian motion the ensemble average of the product of the displacement and the random force is zero. This result was assumed by Langevin to be true, although it appears to contradict the intuitive feeling that the net displacement should be in the direction of the net impulse. The literature contains a statement that the Langevin assumption is incorrect, and this led us to an examination of the question. We show that the relevant correlation function in one dimension is 〈x (t) A (t−τ) 〉=2(kBT/M)[1−exp(−βτ)] which is zero at equal times and approaches 2(kBT/M) as τ→∞.

An elementary discussion for physicists is given of the thermodynamic instability of proteins and DNA. The biochemical explanation is given of how these molecules are grown in the face of a large unfavorable free energy difference, as much as 0.2 MeV for DNA of 106 bonds. The role of ATP is described as the major fuel of the biological world.

The transfer of momentum between a conduction electron and a crystal lattice is examined in detail. By physical considerations we are led to the expression (mm*)ij = δij+ ∑ GGiδδkj|aG(k)|2 for the reciprocal effective mass tensor, where G is 2π times a reciprocal lattice vector and aG(k) is a coefficient in the momentum representation of the Bloch eigenfunction: ψk = ∑ GaG(k) exp[i(G+k)·r]. This expression for the effective mass tensor is shown to be completely equivalent to the usual definition.