Harvesting graphics power for MD simulations

We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a congruential shift random number generator are presented. The performance of the GPU's is compared to their main processor counterpart. We achieve speedups of up to 80, 40 and 150 fold, respectively. With newest generation of GPU's one can run standard MD simulations at 10^7 flops/$.Comment: 12 pages, 5 figures. Submitted to Mol. Si

Systematics of proton emission

A very simple formula is presented that relates the logarithm of the half-life, corrected by the centrifugal barrier, with the Coulomb parameter in proton decay processes. The corresponding experimental data lie on two straight lines which appear as a result of a sudden change in the nuclear shape marking two regions of deformation independently of the angular momentum of the outgoing proton. This feature provides a powerful tool to assign experimentally quantum numbers in proton emitters.Comment: 4 pages, 3 figure

A relation between a between-item multidimensional IRT model and the mixture rasch model

Rasch model, multidimensional IRT models, mixture Rasch model, Saltus model,

?sR studies of superconductivity in eutectically grown mixed ruthenates

The low-temperature magnetic behavior of the double-layered ruthenate Sr 3Ru 2O 7, as grown from a eutectic Sr 2RuO 4-Sr 3Ru 2O 7 system, was investigated via zero- and transverse-field muon-spin rotation. The gradual increase of the muon relaxation rate observed below 2.5 K, even in the absence of applied magnetic fields, indicates the occurrence of a spontaneous breaking of time-reversal symmetry. The onset of the latter at a temperature above 1.5 K, the T c of the single phase Sr 2RuO 4, provides evidence about an unconventional superconducting state in the eutectic phase, which most likely takes place at the interface between the Sr 2RuO 4 and Sr 3Ru 2O 7 domains, or even inside the Sr 3Ru 2O 7 phase. We show that the superconducting state manifests a two-component behavior in the transverse-field response with change-over at about T=2.5 K and T=1.5 K. The comparison with zero-field μSR data in the Ru-Sr 2RuO 4 eutectic system rules out the possibility of spurious effects due to embedded Ru islands