火焰原子吸收法测定植物叶片中的微量铅

通过炭化、灰化、混合酸消解和稀硝酸溶解的方法处理样品,利用火焰原子吸收法测定植物叶片中微量铅的含量。待测溶液在0.1～5.0μg.mL-1范围内有很好的线性关系,回归方程为A=0.1053C+0.0071,相关系数为0.9991,检出限为0.006μg.mL-1,特征浓度为0.031μg.mL-1/1%,平均回收率为100.28%。方法适用于测定各种植物叶片中的微量铅含量,可以据此评价环境质量。     

大学主体性的失落与建立现代大学制度

大学主体性的失落是当前大学危机的根源所在,其深层的本质在于学术自由精神的丧失。面对当前大学的危机与困境,学术自由应突破外部的社会限制和内部大学主体自身的限制,应以大学学术自由的理想为指针,结合大学的实际情况,积极构建具有我国特色的现代大学制度。     

Bayesian analysis of a marked point process: Application in seismic hazard assessment

Point processes are the stochastic models most suitable for describing physical phenomena that appear at irregularly spaced times, such as the earthquakes. These processes are uniquely characterized by their conditional intensity, that is, by the probability that an event will occur in the infinitesimal interval (t, t+Δt), given the history of the process up tot. The seismic phenomenon displays different behaviours on different time and size scales; in particular, the occurrence of destructive shocks over some centuries in a seismogenic region may be explained by the elastic rebound theory. This theory has inspired the so-called stress release models: their conditional intensity translates the idea that an earthquake produces a sudden decrease in the amount of strain accumulated gradually over time along a fault, and the subsequent event occurs when the stress exceeds the strength of the medium. This study has a double objective: the formulation of these models in the Bayesian framework, and the assignment to each event of a mark, that is its magnitude, modelled through a distribution that depends at timet on the stress level accumulated up to that instant. The resulting parameter space is constrained and dependent on the data, complicating Bayesian computation and analysis. We have resorted to Monte Carlo methods to solve these problems.     

Population constraints on pooled surveys in demographic hazard modeling

In non-experimental research, data on the same population process may be collected simultaneously by more than one instrument. For example, in the present application, two sample surveys and a population birth registration system all collect observations on first births by age and year, while the two surveys additionally collect information on women’s education. To make maximum use of the three data sources, the survey data are pooled and the population data introduced as constraints in a logistic regression equation. Reductions in standard errors about the age and birth-cohort parameters of the regression equation in the order of three-quarters are obtained by introducing the population data as constraints. A halving of the standard errors about the education parameters is achieved by pooling observations from the larger survey dataset with those from the smaller survey. The percentage reduction in the standard errors through imposing population constraints is independent of the total survey sample size.     

论新时期我国图书馆的服务功能与服务方式

新时期 ,新形势。随着我国社会主义市场经济体制的逐步建立 ,加入 WTO而融入世界经济发展大循环以及知识经济时代的到来 ,我国图书馆面临前所未有的机遇与挑战 ,要求图书馆要适应这种形势的变化 ,提供新的服务功能并采取新的服务方式。     

Unresolved Conflicts in the Regional Security System: The Case of the South Caucasus

The collapse of the USSR was accompanied by transformation of the South Caucasian latent ethnopolitical conflicts into local wars. Today the situation in the area of the conflicts is “neither war, nor peace”. Three unresolved conflicts of the South Caucasus can be considered as one of the most serious obstacles for establishing a regional security system.The article gives the general characteristics of these conflicts, the trends of their development, taking into account the time factor, and analyzes the behavioral models of the main players – de jure recognized and unrecognized de facto states of the South Caucasus. The basic objective of the main players should be to keep the situation on a level preventing the resumption of the armed conflicts. The attempts of forced resolution of the conflicts are fraught with destabilization of the situation not only in the area of any of these conflicts but in the whole region.     

多媒体英语教学的优势

本文旨在通过提出多媒体教学手段的多种优势以及诸多专家学者的观点,同时谈到笔者在使用多媒体进行外语教学过程中的一些切身体会,进行理论和实践上的论证,以发掘外语教学中利用多媒体教学手段进行创新性“教”与自主性“学”的可能性,并进一步加强学生的自主性学习以及自我调节性学习,使外语教师更加高效地利用多媒体的优势进行理想的外语教学,同时使外语教学手段更加具有开放性和实践性。     

企业的合约经济理论探索和统计检验

对企业本质的认识是微观经济学中的一个重要问题,其对中国的国企改革有着重要意义。本文中,我们对企业的合约本质进行了经济理论探索和统计检验,并突出关注企业的激励合约问题。