Magnetic properties of mechanically alloyed Co–Ti powder

An amorphous phase containing traces of non-transformed Co and Ti powders was obtained by mechanical alloying nominal compositions of Co₆₇Ti₃₃ and Co₅₀Ti₅₀ in a high-energy ball-mill. These alloys were prepared from elemental powders of Co and Ti. The heat treatment of Co₆₇Ti₃₃ at 573, 873 and 1173 K crystallized nanoparticles of Co₂Ti and Co₃Ti compounds, while the same treatments conducted on Co₅₀Ti₅₀ resulted in the formation of Co₂Ti and CoTi nanoparticles. The saturation magnetizations reached a maximum value in the amorphous state and they decreased when the temperatures of the heat treatment rose. Demagnetizing interparticle interaction effects were estimated through hysteresis loops and initial magnetization curves using the Fourier technique.     

Magnetic resonance in beta-active nuclei 8Li at the doubled larmor frequency in LiF polycrystals containing dislocations

The nuclear magnetic resonance in beta-active nuclei ⁸Li at the doubled Larmor frequency in LiF polycrystals is studied before and after treating these polycrystals with an external pressure. A quantitative approach is proposed that makes it possible to calculate the parameters of the resonance line-shape function versus the dislocation structure of crystallites. Data suggesting that the samples under investigation that were subjected to a treatment with an external pressure develop dislocations whose Burgers vectors are parallel are obtained.     

一维无序体系电子跳跃导电研究

建立了电子隧穿电导模型,推导了一维无序体系新的直流电导公式.通过计算20000格点无序体系的直流电导率,分析了直流电导率和温度及外场电压的关系,讨论了无序度对直流电导的影响.计算结果表明,无序体系的直流电导率随无序度的增加而减小;外加电场较小时,电导率相对较大,且出现一系列峰值,电压较大时,电导率反而较小;无序体系在低温区出现了负微分电阻特性,电导率随温度的升高而增大,在高温区电导率随温度的升高而减小.计算结果和实验符合很好 关键词： 无序体系 电子隧穿 直流电导率     

Barrier-free intermolecular proton transfer in the uracil-glycine complex induced by excess electron attachment

The photoelectron spectra (PES) of anions of uracil-glycine and uracil-phenylalanine complexes reveal broad features with maxima at 1.8 and 2.0 eV. The results of ab initio density functional B3LYP and second order M?ller-Plesset theory calculations indicate that the excess electron occupies a π^* orbital localized on uracil. The excess electron attachment to the complex can induce a barrier-free proton transfer (BFPT) from the carboxylic group of glycine to the O8 atom of uracil. As a result, the four most stable structures of the anion of uracil-glycine complex can be characterized as the neutral radical of hydrogenated uracil solvated by the anion of deprotonated glycine. The similarity between the PES spectra for the uracil complexes with glycine and phenylalanine suggests that the BFPT is also operative in the case of the latter anionic species. The BFPT to the O8 atom of uracil may be related to the damage of nucleic acid bases by low energy electrons because the O8 atom is involved in a hydrogen bond with adenine in the standard Watson-Crick pairing scheme. Received 6 April 2002 Published online 13 September 2002     

液体可视图象序列中杂质小目标的检测方法

在分析红外图象和视图象差异的基础上，研究了一种适用于可视图像序列的运动小目标检测算法。受目标影响的象素点具有较弱的时间相关性，即相对普通象素点有较大的时间方差，根据此特征，用管道更新的方法产生新方差图象序列，再用管道更新的方法累积，增加信噪比，然后用基于统计均值的自适应门限方法分割出目标，最后将原图象的梯度倒数作为象素点强度的加权，有效地抑制灰度突变边界的传感器噪音，保存目标点。     

Renormalization of the two-photon vacuum polarization and the self energy vacuum polarization for a tightly bound electron

The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ) is used in order to derive the renormalized energy shift due to the gauge invariant K?llén-Sabry diagram of the two-photon vacuum polarization (VPVP) as well as the self energy vacuum polarization S(VP)E beyond the Uehling approximation. It is outlined, that no outer renormalization is required for the two-photon vacuum polarization and that only the inner renormalization has to be accomplished. It is shown that the so-called nongauge invariant spurious term is absent for a wide class of vacuum polarization (VP) diagrams if one applies the widely used spherical expansion of bound and free-electron propagator. This simplifies significantly calculations in bound state quantum electrodynamics. As one result of our paper the use of the BPHZ-approach in bound state QED is established. Received 28 September 2001     

Spontaneous formation of a system of highly ordered germanium nanoislands upon epitaxial deposition on profiled (111) silicon substrates under electromigration conditions

Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×10¹⁰ cm^?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures.     

Variant superfield representations

We discuss some variant superfield representations which can arise by the replacement of some of the usual fields in a multiplet with p-form gauge fields.     

Transfructosylation of rebaudioside A (a sweet glycoside of Stevia leaves) with Microbacterium beta-fructofuranosidase.

It was found that a beta-fructofuranosidase produced by Microbacterium sp. H-1 has potent trans-beta-fructofuranosylation activity from sucrose (donor). By means of this enzyme system, rebaudioside A (RA), the second major sweet steviol glycoside of the leaves of Stevia rebaudiana, was subjected to transfructosylation, affording a mono-beta-fructofuranosylated product (RA-F) in a high yield. The structure of RA-F was elucidated as beta-D-fructofuranosyl-(2----6)-beta-D-glucopyranosyl ester of steviol-13-O-[beta-D-glucopyranosyl-(1----2)]- [beta-D-glucopyranosyl-(1----3)]-beta-D-glucopyranoside. Some improvement in the quality of sweetness was observed for RA-F.