Synchrotron-radiated X-ray and neutron diffraction study of native cellulose

Precise determination of d-spacings and compositional ratio of cellulose I_α and I_β in various native cellulose samples was successfully carried out by synchrotron-radiated X-ray diffraction and time-of-flight (TOF) neutron diffraction from quasi-powder specimens. X-ray diffraction peaks were separated by the deconvolution method using six types of profile function: Gaussian, Lorentzian, intermediate Lorentzian, modified Lorentzian, pseudo-Voigt, and Pearson VII. In terms of R-factors, the pseudo-Voigt function gave the best fit with the observation, and was used for determination of d-spacings. The numerical results for Valonia cellulose were: dI_α (1 0 0) = 0.613 nm; dI_β (1 1 0) = 0.603 nm; dI_β (1 1 0) = 0.535 nm; dI_α (0 1 0) = 0.529 nm; I_α content = 0.65. The differences determined between dI_α (1 0 0) and dI_β (1 1 0) and between dI_β (1 1 0) and dI_α (0 1 0) were similar to those previously reported. Comparison between unresolved peaks for the two types of cellulose samples revealed a small but definite difference between dI_α (1 1 0) and dI_β (2 0 0). The TOF neutron diffractometry using deuterated samples confirmed this difference. This revised version was published online in August 2006 with corrections to the Cover Date.     

HCOO在Cu(110)、Ag(110)和Au(110)表面的吸附

采用密度泛函理论(DFT)以及广义梯度近似方法(GGA)计算了甲酸根(HCOO)在Cu(110)、Ag(110)和Au(110)表面的吸附. 计算结果表明, 短桥位是最稳定的吸附位置, 计算的几何参数与以前的实验和计算结果吻合. 吸附热顺序为Cu(110)(-116 kJ·mol-1)>Ag(110)(-57 kJ·mol-1)>Au(110)(-27 kJ·mol-1), 与实验上甲酸根的分解温度相一致. 电子态密度分析表明, 吸附热顺序可以用吸附分子与金属d-带之间的Pauli 排斥来关联, 即排斥作用越大, 吸附越弱. 另外还从计算的吸附热数据以及实验上HCOO的分解温度估算了反应CO2+1/2H2→HCOO的活化能, 其大小顺序为Au(110)>Ag(110)>Cu(110).     

Three Novel Bicyclic Taxoids from the Needles of the Chinensis yew, Taxus chinensis var mairei

PhytochemicalinvestigationontheneedlesofTaxuschinensisvar.mairei.resultedintheisolati=?nofthreenewbicyclictaxoids1--3alongwithtaxachitrieneA4'.Compoundl,lal, 14.5(c0.001,CHCI,),wasisolatedasacolorlessgummysubstance.TheiRspectrumshowedtheacetoxyanda,0-unsaturatedcarbonylsystembandsat1730and1650cm-l.HR-FAB-MSanalysisatm/z847.3152establishedthequasi-molecularforn'ulaasC.,H,=O.,Na([M Na] ,A(B-0.1mmu).ItsIH-NMRspectrum(Tablel)showedthecharacteristicsignalsoffourtertiarymethylgroupsoftaxo…     

INHIBITORY EFFECT OF 8-METHOXYPSORALEN PLUS ULTRAVIOLET-A ON INTERLEUKIN-1 PRODUCTION BY MURINE KERATINOCYTES

We report the effects of 8-methoxypsoralen (8-MOP) plus ultraviolet-A (UV-A) irradiation on interleukin-1 (IL-1) production by murine epidermal keratinocytes, correlating its effect on IL-1 with cell viability, DNA synthesis, and 8-MOP-DNA photoadduct formation. Freshly isolated murine keratinocytes were treated with various doses of 8-MOP (5-100 ng/mL; incubation time, 30 min) plus 1 J/cm2 UV-A and cultured for 1-3 days. The IL-1/epidermal cell-derived thymocyte-activating factor (ETAF) activity in both supernatant and cell extract was reduced proportionately with increasing doses of 8-MOP/UV-A. Interleukin-1 inhibitors induced by 8-MOP plus UV-A were not detected in either supernatant or cell extract. A clear reduction of the IL-1 production was induced by the treatment as low as 15 ng/mL 8-MOP plus 1 J/cm2 UV-A, which led to the formation of 0.52 8-MOP photoadducts per million DNa bases and affected neither cell viability nor DNA synthesis of the treated cells. Cells treated with 100 ng/mL 8-MOP and 1 J/cm2 UV-A exhibited 57% suppression of IL-1 production in both 2- and 3-day culture samples. This treatment resulted in the formation of 3.8 photoadducts per million bases as well as significant abrogation of DNA synthesis although cell viability was unchanged. These observations provide some insights into the phototoxicity mechanisms of 8-MOP and the effect of PUVA therapy on the cytokine regulation in keratinocytes.     

金属间化合物Ce(Ni1-xCux)2Al3的制备和热电特性

我们以Cu替代Ni,制备了金属间化合物Ce(Ni-xCux)2Al3(x=0.0,0.1,0.2,0.3,0.4),利用粉末X射线衍射法(XRD)对样品进行了表征.电阻率ρ(T)和热电势S(T)测量结果表明,由于Cu替代Ni使得单胞体积和3d传导电子数目增加,4f电子与传导电子之间的杂化减弱.近藤温度T-K随着x的增加而降低,体系趋于形成重电子系统.     

基于同步辐射光刻的三维微细加工方法

同步辐射光刻的三维聚甲基丙烯酸甲酯（Polymethyl Methacrylate,PMMA）微结构制造对X射线光刻掩膜板的吸收体形状和PMMA所吸收的X射线能量分布有直接影响,即三维PMMA微结构形状取决于X射线光刻掩膜板的吸收体形状。如果不对X射线光刻掩膜板进行补偿,在被曝光的结构中可观察到结构侧面的变形。研究了引起这种结构侧面变形的各种原因并提出X射线剂量对刻蚀深度非线性曲线是最直接的原因。基于X射线光刻掩膜板图形形状和实际制造的三维PMMA微结构的误差,X射线光刻掩膜板从双直角三角形变为双半圆图形使得微注射针阵列的强度得到增强。为了量化实际制造的三维PMMA微结构的误差,给出了X射线吸收能量分布与微结构的结构形状数据。     

High-resolution electron microscopy on cellulose II and α-chitin single crystals

Single-crystalline cellulose II and -chitin regenerated from low-molecular weight solutions using phosphoric acids as a solvent were investigated by electron diffraction together with high-resolution imaging. Cellulose II of two different degrees of polymerization (DP) were regenerated by precipitation either in water (DP = 15) or in ethanol (DP = 7), and the latter revealed better crystalline perfection. In both cases, the structures are in good accord with the previously published 2-chain monoclinic model. Although the lattice fringes of base planes of the crystal were identified by Fourier transform of negatives, the precise localization of cellulose molecules was not visualized due to local azimuthal fluctuation of the crystal. -Chitin was regenerated by precipitation only in ethanol. The crystals are flat ribbons with a smooth surface and, in structure, fit well a previous antiparallel-chain model because their ab electron diffraction patterns agree well with the proposed P212121 symmetry. Two-dimensional lattice images were obtained with a resolution up to 0.38 nm. Molecular packing in the unit cell was demonstrated clearly with the help of image processing, and corroborated by kinematical calculation of high-resolution images of -chitin. 0969--0239 © 1998 Blackie Academic & Professional     

硬软酸碱理论在材料研究中的应用 I: 二元β-W结构化合物超导性的研究

本文从键性的角度出发, 应用硬软酸碱原理, 研究了具有β-W结构二元化合物的超导性能, 用硬软酸碱理论的HS标度, 获得一个化合物预期的超导转变温度值的规则。ΔHS规则可以用作寻找新超导材料的指引。