Noise-induced current reversal in a stochastically driven dissipative tight-binding model

The cooperative effects induced by external random dichotomic and d.c. driving are studied for charge drift and diffusion in a one-dimensional dissipative tight-binding model. For a strongly correlated dichotomic field the effect of large diffusion acceleration is demonstrated. Additionally, it is shown that the averaged current direction can be inverted by applying a strongly correlated electric field (noise-induced negative conductivity).     

X-ray K-absorption studies of cobalt(II) semicarbazones

X-ray K-absorption edges along with their extended X-ray absorption fine structure (EXAFS) have been recorded using a laboratory XAFS spectrometer for the cobalt(II) semicarbazones viz., Co(emsc)₂Br₂, Co(emsc)₂SO₄, Co(mchsc)₂Br₂, Co(mchsc)₂SO₄ and Co(mchsc)₂(NCS)₂. The chemical shifts for these samples have been reported. The total phase shifts δ₁ and phase parameters β₁ for these samples have been estimated using the modified graphical method for the determination of bond distances. The variations in the values of chemical shift, phase parameter β₁ and average metal–ligand bond distances have been explained. The total phase shift values for the complexes indicate a linear variation with wave vector k.     

Topology-dependent entropic differences for chiral polypeptides in solvents

The entropy of topological conformations of helical biopolymers in a solvent is determined as a function of the chirality of winding. Probability distributions are obtained by taking all possible winding conformations of a polypeptide. The results show that between mirror image distributions, there is a difference in entropy arising from a net topological winding number and the interaction of a chiral solute with its environment. This interaction is reflected in a drift coefficient which varies from segment to segment along the length of a biopolymer.     

Sheffer多项式的渐近展开

本文利用组合分析中的循环指示表示方法,找到了Ｓｈｅｆｆｅｒ型多项式的渐近展开公式及余项估计,文末讨论了所得渐近公式的运用范围,