贵州民族药秋海棠药材中多糖的含量测定

采用硫酸-苯酚法,以无水葡萄糖为对照品,于485nm处测定吸光度,测定秋海棠药材中多糖的含量。在3.01—10.54μg.mL-1范围内吸光度与葡萄糖溶液浓度的线性关系良好（r=0.9997）,平均回收率为98.06%,RSD为0.50%。该方法简便快速、准确可行,为秋海棠药材的质量控制提供了实验依据。     

动力学荧光法测定抗坏血酸

在稀硫酸介质中,抗坏血酸活化溴酸钾氧化孔雀绿的反应,使其荧光增强,建立了动力学荧光测定抗坏血酸的新方法。在最佳条件下,测定的线性范围为10—120μg/mL,方法的检出限为0.0158μg/mL。对浓度为20μg/mL的抗坏血酸进行11次平行测定相对标准偏差为2.6%。此方法已用于药剂中抗坏血酸的测定,结果满意。     

三氧化硫低温磺化法合成聚苯乙烯磺酸新工艺

利用三氧化硫在低温条件下与聚苯乙烯合成聚苯乙烯磺酸,反应速度快,副反应少,后处理简单,是一种绿色合成新工艺.实验结果发现,最佳的反应条件为:常压下-20℃时,以氯仿为溶剂,三氧化硫与聚苯乙烯按0.8∶1的质量比混匀,低速搅拌反应时间30min,老化30 min.溶剂与产物分离后,测定纯净产品的磺化度为92.45%.通过...     

Inverse problems for differential operators on trees with general matching conditions

Sturm–Liouville differential operators on compact trees with general matching conditions in internal vertices are studied. We establish properties of the spectral characteristics and investigate three inverse problems of recovering the operator either from the so-called Weyl functions, or from discrete spectral data or from a system of spectra. For these inverse problems, we prove the corresponding uniqueness theorems and obtain procedures for constructing their solutions by the method of spectral mappings.     

Student presentations in the classroom

For many years, the author has been involving his students in classroom teaching of their own classes. The day-to-day practice is described, and the advantages and disadvantages for both the instructor and the students are discussed. Comparisons with the Moore Method of teaching are made.     

Exact observability and controllability for a nonsimple elastic rod

In this paper, we prove exact observability, boundary and internal exact controllability results for a nonsimple elastic rod. By the spectral analysis method, it is shown that the considered problem has a sequence of eigenfunctions, which forms a Riesz basis for the state space. The exact observability is proved by application of a modified version of Ingham’s Theorem. Then, via the Hilbert Uniqueness method, we prove a boundary controllability result with only one controller and an internal controllability result.     

Infinite Systems of Quasilinear Differential Difference Inequalities and Applications

The article deals with the initial boundary value problem for an infinite system of first order quasilinear functional differential equations. A comparison result concerning infinite systems of differential difference inequalities is proved. A function satisfying such inequalities is estimated by a solution of a suitable Cauchy problem for an ordinary functional differential system. The comparison result is used in an existence theorem and in the investigation of the stability of the numerical method of lines for the original problem. A theorem on the error estimate of the method is given. The infinite system of first order functional differential equations contains, as particular cases, equations with a deviated argument and integral differential equations of the Volterra type.     

A COMPLETE ANALYSIS FOR SOME A POSTERIORI ERROR ESTIMATES WITH THE FINITE ELEMENT METHOD OF LINES FOR A NONLINEAR PARABOLIC EQUATION

ABSTRACT

A posteriori error estimates for semidiscrete finite element methods for a nonlinear parabolic initial-boundary value problem are considered. The error estimates are obtained by solving local parabolic or elliptic equations for corrections to the solution on each element. The convergence results improve previous results where unnecessary assumptions are imposed on the approximate solution and the elliptic projection of the exact solution.     

Analysis of a generalized Friedman’s urn with multiple drawings

We study a generalized Friedman’s urn model with multiple drawings of white and blue balls. After a drawing, the replacement follows a policy of opposite reinforcement. We give the exact expected value and variance of the number of white balls after a number of draws, and determine the structure of the moments. Moreover, we obtain a strong law of large numbers, and a central limit theorem for the number of white balls. Interestingly, the central limit theorem is obtained combinatorially via the method of moments and probabilistically via martingales. We briefly discuss the merits of each approach. The connection to a few other related urn models is briefly sketched.     

连续流动分析法测定土壤中的有效磷

为了提高土壤中有效磷的检测效率和方法的稳定性,研究了现代仪器分析方法-连续流动法测定土壤中有效磷的含量,对连续流动法与农业部标准方法NY/T 148-1990《石灰性土壤有效磷测定方法》、NY/T 1121.7-2006《酸性土壤有效磷的测定》的测定结果进行配对两处理t检验,结果表明：连续流动法与标准方法检测的结果不存在系统误差,样品测定的相对标准偏差均小于10％,连续流动法测定值的相对标准偏差较标准方法略小.同时,用连续流动法对土壤标准样品GBW 07413-GBW 07414（碱法）、GBW07416-GBW 07417（酸法）进行有效磷的测定,测定值与标准值相吻合.