Assessing Effects on Long-term Survival after Early Termination of Randomized Trials

In this paper we present an approach to using historical control data to augment information from a randomized controlled clinical trial, when it is not possible to continue the control regimen to obtain the most reliable and valid assessment of long term treatment effects. Using an adjustment procedure to the historical control data, we investigate a method of estimating the long term survival function for the clinical trial control group and for evaluating the long term treatment effect. The suggested method is simple to interpret, and particularly motivated in clinical trial settings when ethical considerations preclude the long term follow-up of placebo controls. A simulation study reveals that the bias in parameter estimates that arises in the setting of group sequential monitoring will be attenuated when long term historical control information is used in the proposed manner. Data from the first and second National Wilms' Tumor studies are used to illustrate the method.     

二阶非线性时滞微分方程解的渐近性

本文建立了二阶非线性时滞微分方程解的渐近性结果及全局吸引定理,改进和推广了二阶线性方程和一阶非线性方程的已知定理。     

Growth and Heat Resistance Kinetic Variation Among Various Isolates of Salmonella and its Application to Risk Assessment

The abilities of cells of a particular type of bacteria to leave lag phase and begin the process of dividing or surviving heat treatment can depend on the serotypes or strains of the bacteria. This article reports an investigation of serotype-specific differences in growth and heat resistance kinetics of clinical and food isolates of Salmonella. Growth kinetics at 19 degrees C and 37 degrees C were examined in brain heart infusion broth and heat resistance kinetics for 60 degrees C were examined in beef gravy using a submerged coil heating apparatus. Estimates of the parameters of the growth curves suggests a small between-serotype variance of the growth kinetics. However, for inactivation, the results suggest a significant between-serotype effect on the asymptotic D-values, with an estimated between-serotype CV of about 20%. In microbial risk assessment, predictive microbiology is used to estimate growth and inactivation of pathogens. Often the data used for estimating the growth or inactivation kinetics are based on measurements on a cocktail--a mixture of approximately equal proportions of several serotypes or strains of the pathogen being studied. The expected growth or inactivation rates derived from data using cocktails are biased, reflecting the characteristics of the fastest growing or most heat resistant serotype of the cocktail. In this article, an adjustment to decrease this possible bias in a risk assessment is offered. The article also presents discussion of the effect on estimating growth when stochastic assumptions are incorporated in the model. In particular, equations describing the variation of relative growth are derived, accounting for the stochastic variations of the division of cells. For small numbers of cells, the expected value of the relative growth is not an appropriate "representative" value for actual relative growths that might occur.     

T型非线性电阻网络功率转移图的图解法

本文论述了利用非线性电阻的伏安特性，作出T型非线性电阻网络中任一元件的功率转移图的图解法．     

非单调二元非线性算子方程组的迭代求解

利用锥与半序理论和混合单调算子理论 ,讨论 Banach空间中非单调二元非线性算子方程组解的存在性与唯一性 ,并给出收敛于方程组解的迭代序列和误差估计 ,改进和推广了混合单调算子方程和一元算子方程的某些相应结果 .     

碎片化构筑的智力博弈——电影《太阳照常升起》叙事分析

《太阳照常升起》以崭新的视角和独特的叙述方式吸引着观众的视线。这种独特的叙事主要呈现为碎片化的特征,即从组合段叙事、非情节叙事、开放式结局三个方面对影片进行阐释,并展示导演和观众间的一种智力博弈。     

多变量过程自组织学习控制新方法及其实时实现

本文论述一种利用相联存储器系统的多变量自组织学习控制新方法及其实时实现。在线学习包含两个步骤:被控过程的动态输入—输出特性用仿视感控器的方式逐步存入一个相联存储器中,用来作为预测过程模型;依靠一种特殊的输出预测算法,利用预测过程模型并通过单步超前性能指标最优化来规划控制策略,经教练后的控制策略以同样的方式存入第二个相联存储器中。文中提出了一种特殊的采样和更新方法。通过仿真和实时应用证明了所述学习控制新方法的可行性。     

Constructing optimal designs for fitting pharmacokinetic models

We consider some computational issues that arise when searching for optimal designs for pharmacokinetic (PK) studies. Special factors that distinguish these are (i) repeated observations are taken from each subject and the observations are usually described by a nonlinear mixed model (NLMM), (ii) design criteria depend on the model fitting procedure, (iii) in addition to providing efficient parameter estimates, the design must also permit model checking, (iv) in practice there are several design constraints, (v) the design criteria are computationally expensive to evaluate and often numerical integration is needed and finally (vi) local optimisation procedures may fail to converge or get trapped at local optima.We review current optimal design algorithms and explore the possibility of using global optimisation procedures. We use these latter procedures to find some optimal designs.For multi-purpose designs we suggest two surrogate design criteria for model checking and illustrate their use.     

一种新的鲁棒自适应模糊控制器的设计及性能分析

针对一类连续时间非线性动态系统，根据李亚普诺夫分析方法设计了一种鲁棒自适应模糊控制器．这种自适应系统在受到有界的外部干扰或存在建模误差时具有鲁棒性．证明了控制算法是全局稳定的，跟踪误差可以收敛到零的一个邻域内