丙酮中除虫脲溶液标准物质研制

采用重量-容量法制备丙酮中除虫脲溶液标准物质。准确称量国家二级标准物质除虫脲溶解到色谱纯丙酮中,通过A级容量瓶定容至500 mL,摇匀后分装到2 mL安瓿瓶内共460瓶,每瓶为1 mL,保持低温迅速封口,配制过程中室温保持在(20±2)℃。采用液相色谱法进行均匀性、稳定性检验和定值结果验证。从样品中随机抽取16瓶进行均匀性检验,经F检验表明,在95%的置信区间范围内该标准物质均匀性良好;采用t检验对标准物质稳定性进行检验,标准物质在12月内稳定性良好。对该标准物质的不确定度进行了评定,研制的丙酮中除虫脲溶液标准物质定值结果为100μg/mL,相对扩展不确定度为2%(k=2)。结果表明,该标准物质均匀性与稳定性良好,量值准确,可用于日常分析检测中的方法评价和仪器校准。     

Synthesis and Characterization of Poly（butylene adipate-co-terephthalate） Catalyzed by Rare Earth Stearates

Rare earth （Nd, Y, La, Dy） stearates have been synthesized and used as single component catalysts for the polycondensation of dimethyl terephthalate, adipic acid and 1,4-butanediol for the first time preparing biodegradable poly（butylene adipate-co-terephthalate） （PBAT） with high molecular weight, The microstructures of PBAT were characterized by ^1H NMR spectra. The PBAT exhibits good mechanical properties such as high tensile strength （ca. 20 MPa） and long break elongation （〉700%）.     

4D-QSAR analysis of a series of antifungal p450 inhibitors and 3D-pharmacophore comparisons as a function of alignment

A training set of 55 antifungal p450 analogue inhibitors was used to construct receptor-independent four-dimensional quantitative structure-activity relationship (RI 4D-QSAR) models. Ten different alignments were used to build the models, and one alignment yields a significantly better model than the other alignments. Two different methodologies were used to measure the similarity of the best 4D-QSAR models of each alignment. One method compares the residual of fit between pairs of models using the cross-correlation coefficient of their residuals of fit as a similarity measure. The other method compares the spatial distributions of the IPE types (3D-pharmacophores) of pairs of 4D-QSAR models from different alignments. Optimum models from several different alignments have nearly the same correlation coefficients, r(2), and cross-validation correlation coefficients, xv-r(2), yet the 3D-pharmacophores of these models are very different from one another. The highest 3D-pharmacophore similarity correlation coefficient between any pair of 4D-QSAR models from the 10 alignments considered is only 0.216. However, the best 4D-QSAR models of each alignment do contain some proximate common pharmacorphore sites. A test set of 10 compounds was used to validate the predictivity of the best 4D-QSAR models of each alignment. The "best" model from the 10 alignments has the highest predictivity. The inferred active sites mapped out by the 4D-QSAR models suggest that hydrogen bond interactions are not prevalent when this class of P450 analogue inhibitors binds to the receptor active site. This feature of the 4D-QSAR models is in agreement with the crystal structure results that indicate no ligand-receptor hydrogen bonds are formed.     

吸附理论的研究进展及其在吸附分离中的应用

综述了吸附理论的进展及其在吸附分离中的应用,并介绍了对气体分离过程至关重要的混合气的吸附模型或关联式。     

蛋白质组学技术在动物科学中的研究进展

蛋白质组学在后基因组时代以其独特的角度和重要的作用已成为生命科学领域研究的热点内容。动物科学作为生命科学的一个重要分支,其相关研究对人类的生活有着重要意义。为了系统地了解和展望蛋白质组学技术在动物科学中的研究进展,综述了蛋白质组学的概念及其相关技术,归纳和评析了近年来蛋白质组学在动物繁殖、营养、遗传育种和疾病防治方面的研究现状。     

日凌中断预测分析

本文阐述了太阳噪声干扰使通信广播卫星接收站信号中断的自然现象及规律,导出日凌中断与通信广播卫星定点及卫星接收站,位置关系的数学表示式。文中应用作者研究的“卫星电视接收网的系统分析”的计算机软件,预测卫星接收站信号发生日凌中断日期、时刻、持续天数和时间的部分计算实例。     

农业供应链金融能有效缓解企业的融资约束？——涉农企业参与精准扶贫的实证研究

农业供应链金融为涉农企业融资难问题提供了新思路。本文以上市涉农上市企业2016~2018年的财务数据为样本,探讨了农业供应链金融对缓解企业融资约束的影响,以及涉农企业参与精准扶贫对缓解融资约束的调节作用。研究发现:涉农企业普遍面临融资约束问题,而农业供应链金融显著缓解了涉农企业的融资约束,且对参与精准扶贫企业的融资约束缓解更为显著。本文揭示了:农业供应链金融能有效缓解涉农企业的融资约束问题,再次证明了农业供应链金融缓解涉农企业融资约束的重要性和必要性,拓展了供应链金融研究的领域,同时对企业参与精准扶贫,响应新时期涉农企业社会责任的具体要求,形成政府、企业等共同承担社会责任的多元化减贫治理机制,助力乡村振兴提供相应借鉴。     

关于随机变量期望方差的两个注记

文献[1]中给出了有关条件期望与三个随机变量独立的两个充要条件,本文通过几个反例说明其充分性是不成立的.分析了文献[4]中一个定理证明存在的错误,并给出了新的证明.     

A Tail Measure With Variable Risk Tolerance: Application in Dynamic Portfolio Insurance Strategy

Methodology and Computing in Applied Probability - Risk measures for tail risk have an important application in the dynamic portfolio insurance strategies. We propose a new risk measure called...     

三元Ⅲ─V半导体合金的基态有序结构

利用了自旋１／２二维Ｉｓｉｎｇ模型及其“不等式方法”,确定了三元Ⅲ─Ｖ半导体会金（００１）面外延生长中的二维平面基态有序结构和基态相图,并通过层状叠加得到了合金中可能出现的长程有序结构,较好地说明了实验发现的（００１）衬底外延生长中的长程有序现象．