浅谈电解质分析仪的质量控制

介绍了XD683电解质分析仪的质量控制,它涉及仪器本身、所用的试剂、分析过程的各个环节及仪器维护和检查校准等。     

巨尾桉在岩溶石山生境中的适应性研究（Ⅰ）：春季光合生理生态学特性

以岩溶石山生境的3年生巨尾桉人工林为研究对象,采用LI-6400型便携式光合仪测定巨尾桉在春季的叶片净光合速率(Pn)及其他生理生态因子日变化,同时测定巨尾桉光合-光响应曲线,并通过相关分析和通径分析探讨净光合速率与其他生理生态因子的关系。结果表明:巨尾桉光合-光响应曲线符合Walker的非直线双曲线模型。巨尾桉的光饱和点为1 340μmol.m-2.s-1,光补偿点为14.68μmol.m-2.s-1,表观量子效率(AQY)为0.06mol.mol-1,具有阳生植物的特点。净光合速率日变化呈现"单峰型"的特点。蒸腾速率(Tr)、气孔导度(Gs)和大气CO2浓度(Ca)是影响巨尾桉叶片净光合速率日变化的重要因子。巨尾桉有较高的水分利用效率,说明巨尾桉具有适应岩溶石山干旱的特征或避旱策略。     

Pressurized solvent extraction of pure food grade starch

A commercial pressurized solvent extractor was used to remove lipid and non-lipid material from cornstarch using n-propanol/water and ethanol/water mixtures. Yields and chemical composition of the extract fractions were determined. Cornstarch samples were characterized using pasting properties and shear storage modulus measurements. The n-propanol/water extracted slightly higher amounts of both lipids and non-lipids. The lipid fractions contained mostly linoleic, palmitic and oleic free fatty acids. The non-lipid fraction contained mostly protein in the form of zein. The extracted starch had lower peak and setback viscosities than did the unextracted starch. The starch extracted with n-propanol/water had the lowest shear storage modulus values. Conversely, the samples extracted with ethanol/water had the highest shear storage modulus values. It is hypothesized that low amounts of zein present in conjunction with the starch is responsible for this observed effect.     

Evolutionary dynamics of taxonomic structure

The distribution of species among genera and higher taxa has largely untapped potential to reveal among-clade variation in rates of origination and extinction. The probability distribution of the number of species within a genus is modelled with a stochastic, time-homogeneous birth-death model having two parameters: the rate of species extinction, μ, and the rate of genus origination, γ, each scaled as a multiple of the rate of within-genus speciation, λ. The distribution is more sensitive to γ than to μ, although μ affects the size of the largest genera. The species : genus ratio depends strongly on both γ and μ, and so is not a good diagnostic of evolutionary dynamics. The proportion of monotypic genera, however, depends mainly on γ, and so may provide an index of the genus origination rate. Application to living marine molluscs of New Zealand shows that bivalves have a higher relative rate of genus origination than gastropods. This is supported by the analysis of palaeontological data. This concordance suggests that analysis of living taxonomic distributions may allow inference of macroevolutionary dynamics even without a fossil record.     

Characterization of in vitro cultured bone marrow and adipose tissue‐derived mesenchymal stem cells and their ability to express neurotrophic factors

MSCs (mesenchymal stem cells) have attracted attention as a promising tool for regenerative medicine and transplantation therapy. MSCs exert neuroprotective effects by secreting a number of factors in vitro and in vivo. Similar characteristics are found in ADSCs (adipose‐derived stem cells) and BMSCs (bone marrow stromal cells). Multipotent capability, easy accessibility and rapid proliferation of ADSCs have been established. Our main objective was to compare cell viability, growth rate, expression of neurotrophic factors and nestin genes in ADSCs and BMSCs. Cell doubling time and proliferation rate indicate that ADSCs has a higher proliferation rate than BMSCs. ADSCs and BMSCs express a similar pattern of CD71 and CD90 markers. Nestin immunostaining showed that ADSCs and BMSCs are immunopositive. The expression of neurotrophic factors genes in ADSCs proved similar to that of BMSCs genes. Thus adipose tissue stem cells with a high proliferation rate can express nestin and neurotrophic factor genes. Therefore ADSCs may be useful in future cell replacement therapies and help improve neurodegenerative diseases.     

药物动力学中矩量计算的方法

本文给出了计算药物动力学的矩的一种方法,并给出了截断误差公式。最后,通过例题,将梯形法、对数梯形法及文[5]的方法以及本文的方法,作了比较,并可看出本文方法算出的结果最为精确。     

A Formula for the Gini Coefficient and its Decomposition

This paper is concerned with the Gini coefficient as a concentration measure of the distribution. The proposed formula for the computation of the Gini coefficient allows its decomposition according to different sub-groups of the initial population, either exactly or approximately.