Generators and Relations for O

Tate's algorithm for computing O for rings of integers in a number field has been adapted for the computer and gives explicit generators for the group and sharp bounds on their order – the latter, together with some structural results on the p-primary part of O due to Tate and Keune, gives a proof of its structure for many number fields of small discriminants, confirming earlier conjectural results. For the first time, tame kernels of non-Galois fields are obtained.     

Energy Transport in Weakly Anharmonic Chains

We investigate the energy transport in a one-dimensional lattice of oscillators with a harmonic nearest neighbor coupling and a harmonic plus quartic on-site potential. As numerically observed for particular coupling parameters before, and confirmed by our study, such chains satisfy Fourier’s law: a chain of length N coupled to thermal reservoirs at both ends has an average steady state energy current proportional to 1/N. On the theoretical level we employ the Peierls transport equation for phonons and note that beyond a mere exchange of labels it admits nondegenerate phonon collisions. These collisions are responsible for a finite heat conductivity. The predictions of kinetic theory are compared with molecular dynamics simulations. In the range of weak anharmonicity, respectively low temperatures, reasonable agreement is observed.     

Topochemical characterization of materials using 3D-SIMS

Summary The potential of 3D-SIMS for characterization of high molybdenum powder and sintered high purity molybdenum will be demonstrated. The concentration of the measured trace elements in the sintered molybdenum did not exceed 200 ppb. In the powder the concentration was found to be about 1 ppm. For material scientists it is very important to ascertain if the trace elements are homogeneously distributed or precipitated. Although the concentration of the elements of interest was rather low, qualitative images of the three dimensional distribution can be obtained.