玉米须提取液对尿液中草酸钙晶体形成的影响

本文采用X射线衍射(XRD)、红外光谱(FTIR)、扫描电子显微镜(SEM)等方法分析了玉米须提取液对正常人尿液中草酸钙晶体形成的影响,通过电导率法研究了草酸钙晶体生长的动力学过程,以及从生物矿化的角度对玉米须提取液影响尿液中草酸钙晶体的可能机理进行了探讨。由于玉米须提取液中有机酸或多糖的羟基、羰基等通过配位作用与Ca²⁺结合形成可溶性配位化合物,减少了Ca²⁺与Oxa^2-的结合能力,从而抑制了CaOxa的成核和生长。同时,可能由于玉米须提取液中有效成分与二水草酸钙(COD)的吸附点键合,增强了COD晶体在溶液中的热力学稳定性,进而抑制了COD晶体向热力学更稳定态的一水草酸钙(COM)晶体转变。结果显示,这种抑制作用随玉米须浓度增大而增大,且COD晶体尺寸随着玉米须浓度的增大而减小。玉米须抑制COD晶体向COM晶体转变的作用为开发预防和治疗尿结石的药物提供了启示。     

富含微量元素中药煎剂对2型糖尿病疗效观察

为了观察富含微量元素中药煎剂对2型糖尿病（T2DM）的疗效,将门诊64名血糖控制不满意的T2DM患者分为增加富含微量元素中药煎剂组（观察组）和不增加组（对照组）,服药3个月后比较。结果表明,观察组的空腹血糖（FPG）、空腹血清胰岛素（Fins）和糖化血红蛋白（HbA1c）3月后明显下降（P〈0．01）;3月后观察组的FPG、Fins和HbA1c较对照组明显下降（P〈0．01）。可见增加富含微量元素中药煎剂对血糖难以控制的T2DM的FPG、Fins和HbA1c能够起到有效控制作用。     

基于丙二酰胺的不对称双子表面活性剂的合成及其乳化性能

将二(3-二甲氨基丙基)丙二酰胺分别与溴代十六烷和溴代十四烷反应,生成的季铵盐化产物经丙酮-乙腈重结晶,得到含丙二酰胺基的不对称阳离子双子(Gemini)表面活性剂(命名为16-9-14),总收率为45.9%(以溴代十六烷计);利用红外光谱和核磁共振谱表征了合成产物的结构,采用电导法测定了其临界胶束浓度(CMC),采用滴体积法测定了其临界张力(γCMC),进而初步探讨了其发泡沫性能和乳化性能.结果表明,合成的Gemini表面活性剂的CMC为1.57×10-4 mol/L,γCMC为38.45mN/m;其发泡性能和乳化性能优于相应的单子表面活性剂.     

Dependency distance: A new perspective on syntactic patterns in natural languages

Dependency distance, measured by the linear distance between two syntactically related words in a sentence, is generally held as an important index of memory burden and an indicator of syntactic difficulty. Since this constraint of memory is common for all human beings, there may well be a universal preference for dependency distance minimization (DDM) for the sake of reducing memory burden. This human-driven language universal is supported by big data analyses of various corpora that consistently report shorter overall dependency distance in natural languages than in artificial random languages and long-tailed distributions featuring a majority of short dependencies and a minority of long ones. Human languages, as complex systems, seem to have evolved to come up with diverse syntactic patterns under the universal pressure for dependency distance minimization. However, there always exist a small number of long-distance dependencies in natural languages, which may reflect some other biological or functional constraints. Language system may adapt itself to these sporadic long-distance dependencies. It is these universal constraints that have shaped such a rich diversity of syntactic patterns in human languages.     

Synthesis of ZnO Photocatalysts Using Various Surfactants

Russian Journal of Physical Chemistry A - Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In...     

General admissibility for linear estimators in a general multivariate linear model under balanced loss function

A generalization of Zellner’s balanced loss function is proposed. General admissibility in a general multivariate linear model is investigated under the generalized balanced loss function. And the sufficient and necessary conditions for linear estimators to be generally admissible in classes of homogeneous and nonhomogeneous linear estimators are given, respectively.     

Viscoplastic flow in slightly varying channels with wall slip pertaining to a magnetorheological (MR) polishing process

In this paper, the first analytical endeavor into the fluid dynamic modeling of an MR polishing process is reported. The velocity and shear stress fields of an MR fluid running through a thin slippery channel with a slightly varying height are analytically solved using a bi-viscosity constitutive model and a Navier slip model. Estimations of the mechanical power density and the total power per unit depth applied onto the channel surfaces are also presented. Analytical solutions for the Couette–Poiseuille flow behavior of a bi-viscous fluid flowing through either parallel or non-uniform channels are obtained, and the associated necessary and sufficient conditions characterizing a total of 5 types of flow are derived.The behaviors of the fluid are examined through the use of a parametric diagram of Bingham number (Bn) and Couette number (Co), i.e., Bn–Co or 1/Bn–1/Co diagram, by changing the geometric and operating conditions. Using these diagrams, variations in the rheological characteristics of the flow are investigated in great detail, with a special focus on the movement of the pseudo-core region. Finally, the mechanical power density field obtained for the flow in a converging–diverging channel is used to explain the wear mechanism in the MR polishing process. The effects of the power density field and the total power on the material removal rate (MRR) and the within-workpiece nonuniformity (WIWNU) with respect to various geometric and operating conditions are evaluated.     

Uniform asymptotics for a multi-dimensional time-dependent risk model with multivariate regularly varying claims and stochastic return

This paper is devoted to asymptotic analysis for a multi-dimensional risk model with a general dependence structure and stochastic return driven by a geometric Lévy process. We take into account both the dependence among the claim sizes from different lines of businesses and that between the claim sizes and their common claim-number process. Under certain mild technical conditions, we obtain for two types of ruin probabilities precise asymptotic expansions which hold uniformly for the whole time horizon.     

Theoretical insights into the mechanism of photocatalytic reduction of CO2 over semiconductor catalysts

Photocatalytic reduction of CO₂ is one important approach to alleviate greenhouse gas emission and energy crisis, which has gained huge attention in the past decades. However, the lack of understanding complex reaction mechanism impedes new catalysts design. It is also very difficult to understand the mechanism by using only experimental approaches. For this concern, theoretical calculations can effectively supplement the experimental deficiency and thus play an important role. Recently theoretical calculations have been performed on adsorption, migration and reduction of CO₂ molecule on the photocatalyst surface, leading to useful information that have contributed greatly to this field. This review summarizes recent advances in first-principles calculations about CO₂ photoreduction over various semiconductor photocatalysts like metal oxides, sulfides and g-C₃N₄. The methods, models, adsorption and reaction pathways have been discussed in detail. The perspective about future investigation on the photocatalytic reduction of CO₂ using first principles calculations is also presented.