Nature of "hydrogen bond" in the diborane-benzene complex: covalent, electrostatic, or dispersive?

Motivated by the recent discovery of unusual "hydrogen bonding"-like interaction between a borane system and benzene molecules in a molecular crystal, we carried out quantum mechanical calculations on a model complex, diborane-benzene cluster. The aim is to understand the nature of this unique interaction, which is expected to play an essential role in this novel class of molecular crystals. As analyzed in the present study, the interaction between diborane and benzene is special in the following aspects: (1) this interaction is mostly dispersive; (2) the observed pseudodirectionality with one of the diborane bridge hydrogen directed toward the benzene centroid minimizes the van der Waals contact; and (3) in the "hydrogen bond" map, this interaction is located in a unique region, which is presently populated by a few known molecular complexes with very different chemical characteristics. It is anticipated that the results from the present analysis will provide meaningful guidance for molecular engineering with diborane-benzene as a building block and for stabilization of this and possible other hydrogen bonds by dispersive contributions.     

电沉积SiC颗粒增强抗磨复合材料

采用电刷镀技术制取Ｎｉ－Ｗ－Ｃｏ／ＳｉＣ颗粒增强抗磨复合材料,分析了ＳｉＣ颗粒沉积量的影响因素,并研究了复合材料的磨损特性,实验结果表明,复合材料具有较高的硬度和耐磨性。     

"Ljung"型随机算法的收敛性

本文研究了“Ｌｊｕｎｇ”算法的收敛条件,给出了两类条件下的收敛定理,并将收敛定理推广到观察值更复杂的情形     

黑芥（Brassica nigra）核型和Giemsa C带带型的研究

研究了黑芥的核型和染色体的Ｇｉｅｍｓａ Ｃ带带型，黑芥有８对染色体，４对是中部着丝粒染色体，其中４对是亚中部着丝粒染色体，在４对亚中部着丝粒染色体中有２对具随体，黑芥的核型公式为２ｎ＝２ｘ＝１６＝８ｍ＋４ｓｍ＋４ｓｍ（ＳＡＴ）用ＨＳＧ法得到ＧｉｅｍｓａＣ带带型，黑芥的Ｃ带带型为ＣＩＴ型，黑芥的染色体具有着丝粒带、中间带，端带和全带，黑芥的ＧｉｅｍｓａＣ带带型公式为２ｎ＝２ｘ＝１６＝ＣＩＴ型＝２Ｃ＋     

A new approach for noninvasive skin blood imaging in microcirculation

A new noninvasive method is proposed for optically imaging blood under skin. A mini-mirror is used to guide the light incident onto the skin surface, while blocking specularly reflected light from the tissue. Moreover, by using two linear polarizers at right angles, the specular reflection can be reduced further, while also blocking the rough surface scattered light. A circular polarizer may be used to obtain the same effect. As a result, the blood flow beneath the surface of skin can be visualized clearly. The effect of the mini-mirror is also analyzed theoretically and experimentally.     

Imaging of small nanoparticle-containing objects by finite-element-based photoacoustic tomography

We present semiquantitative photoacoustic images of small nanoparticle-containing objects having a wide range of contrast levels relative to the background. The images are obtained by a finite-element reconstruction algorithm that is based on the Helmholtz-like photoacoustic wave equation in the frequency domain. Our reconstruction approach is an iterative Newton method coupled with combined Marquardt and Tikhonov regularizations that can extract the spatial distribution of relative optical absorption property in heterogeneous media. We demonstrate experimental images in single- and multiple-object configurations with a circular scanning photoacoustic tomographic system. The results obtained show that millimeter-size nanoparticle-containing objects can be clearly detected in terms of position, size, and relative optical properties.