Enzymic Hydrolysis Of Lignin—Carbohydrate Complexes Isolated From Kraft Pulp

Four carbohydrate samples extracted from kraft pulps are used as model substrates for studying the mechanism by which xylanase enhances subsequent bleaching of kraft pulp. Fourier transform infrared spectroscopy confirms that small amounts of aromatic molecules, probably lignin, remain associated with these carbohydrate samples. When the extracts are hydrolyzed with xylanase or acid, size exclusion chromatography shows a decrease in the molecular mass of their UV-absorbing constituents, as well as their carbohydrate constituents as determined by pulsed amperometric detection. The results are consistent with the hypothesis that xylanase prebleaching hydrolyzes the xylan portion of lignin-carbohydrate complexes to leave smaller lignin-containing macromolecules in pulp fiber, thus facilitating the removal of lignin components by bleaching chemicals.     

光电效应中阈能因素的探讨

简要叙述光电效应产生的微观机理，用反证法证明光子与自由电子之间不能发生光电效,廉洁奉公人而说明了影响光电效应截面的因素，指出电子的束缚能越大，光电效应截面就越大，并指出阈能只具有统计意义。     

Preparation and characterization of hyaluronan/chitosan scaffold cross‐ linked by 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide

A novel biocompatible scaffold was prepared by cross‐linking hyaluronan (HA) and chitosan (CS). The carboxyl groups of HA were activated by 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and then cross‐linked with amino groups of CS by forming amide bonds. The HA/CS scaffold thus prepared was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry. FTIR spectra showed that the absorbance of the amide (1550 cm^?1) and carbonyl (1633 cm^?1) bond in the cross‐linked scaffold was stronger than that in HA or CS. SEM micrographs showed that the cross‐linked scaffold produced at low EDC concentration had an intertwisted ribbon‐like microstructure, while the product prepared at higher EDC concentration had a porous structure. The concentration of EDC in the reaction system greatly affected the structure and properties of the HA/CS scaffold. The prepared scaffold could strongly resist degradation by hyaluronidase, free radicals in vitro and stress. Copyright © 2007 Society of Chemical Industry     

基于递阶偏最小二乘回归的数据分析

针对最小二乘法难以克服因子多重共线性对回归模型精度影响的不足和大坝观测数据分析中因变量较多的特征，引进递阶偏最小二乘法，对大坝安全监测变量及其影响因子进行递阶偏最小二乘回归分析，将建模预测分析方法通过递阶分层处理，可同时实现回归建模和数据结构简化，所建立的大坝安全监控模型精度可通过交叉有效性检验来控制．工程应用实例和模型对比分析研究表明，递阶偏最小二乘回归模型能有效克服由于各类因子变量间的多重共线性和因子变量数目较多而对模型拟合精度及其预测能力的影响，相对于传统回归模型有更好的解释能力，因而具有一定的实用价值．     

Effect of cross derivatives in discretization schemes in structured non-orthogonal meshes for compositional reservoir simulation

Corner-point meshes have been implemented in several commercial reservoir simulators due to their flexibility to deal with several important features of the hydrocarbon bearing-reservoirs, such as irregular boundaries, geologic fractures, and faults. Although this type of mesh presents an important step in discretization of the domains for reservoirs, some parts of the approximate equation in discretized formulations are neglected in most commercial simulators. The neglected terms are related to the cross derivatives and, in general, are neglected to produce the same Jacobian stencil as when Cartesian grids are employed. This work presents an investigation of the effect of cross derivatives in discretization schemes using structured non-orthogonal boundary-fitted meshes in conjunction with a compositional reservoir simulator. The main goal is to investigate the difference between the numerical results with and without the cross derivatives that arise when the Cartesian equations are written for a transformed plane. We used an in-house compositional reservoir simulator to carry out this study. The component mass balance equations for a compositional, multiphase, multi-component fluid flow are solved using a fully implicit reservoir simulator in conjunction with the finite volume method. The results of several reservoir simulation case studies that were performed to carry out this study are presented in this paper.     

Thermal performance of flat vapor chamber heat spreader

Experiments were performed to examine the spreading thermal resistance of centrally positioned heat sources and the thermal performance of a water charged, gravity assisted flat vapor chamber to be used for electronic cooling. Parametric studies including different heat fluxes and operating temperatures were conducted, and the effect of the relevant parameters on the cooling performance in terms of the spreading resistance was presented and discussed. The present vapor chamber heat spreader showed a heat removal capacity of 220 W/cm² with a thermal spreading resistance of 0.2 °C/W.     

对苯二甲酸二缩水甘油酯的合成

以对苯二甲酸和环氧氯丙烷为原料经开环和闭环反应合成了对苯二甲酸二缩水甘油酯,研究了开环时间、物料配比、碱浓度、碱用量、闭环时间及不同温度对反应的影响,最佳反应条件为:催化剂苄基三甲基氯化铵,升温回流时间20~30 min,50%氢氧化钠溶液0.25 mol,室温反应5.5 h,重结晶溶剂丙酮,反应总收率为68.9%。对产物的结构进行了表征,IR和NMR光谱数据显示与目标物结构一致。     

ENERGY LOSS AND ENERGY STRAGGLING OF LIGHT IONS IN FULLERITE

To determinate the stopping cross section in fullerite a feasible approach, taking into account the high radiation sensitivity and mechanical fragility of fullerite films, should be employed. In this work, the stopping cross sections of ¹H, ³H, ⁴He and ⁷Li ions for several selected energies were measured by Rutherford backscattering, neutron depth profiling and alpha spectroscopy using sandwich structures of samples composed of fullerite deposited on a firm substrate (Si, steel) with an intermediate marker (Au, N, Li, B, Pu). In addition, ion transmission through a thin C film supporting a fullerite layer was also utilized. The measured stopping cross sections follow the theoretical predictions calculated for carbon, but are systematically (10-35%) higher than the theoretical ones (with the exception of 5 — 5.5 MeV ⁴He). The observed deviation of the experimental data can partly be explained by the chemical state effects in fullerite, which accounts for about 20-50% of the difference. The measured energy straggling exceeds Bohr's value by a factor of about 2 for alpha spectroscopy and ion transmission, and 2.5 or 9.5 for Rutherford backscattering and neutron depth profiling, respectively. The discrepancy can be explained by a thickness variation, such as surface roughness of the fullerite films.     

环路反应器制备饱和脂肪酸甲酯的研究

用环路反应器进行椰油酸甲酯加氢制饱和甲酯的结构同搅拌釜对照，反应周期缩短６０％，对实验结果进行了动力学分析，表明环路反应器加氢为二级反应，搅拌釜加氢为一级反应。