Effect of media-induced social distancing on disease transmission in a two patch setting

We formulate an SIS epidemic model on two patches. In each patch, media coverage about the cases present in the local population leads individuals to limit the number of contacts they have with others, inducing a reduction in the rate of transmission of the infection. A global qualitative analysis is carried out, showing that the typical threshold behavior holds, with solutions either tending to an equilibrium without disease, or the system being persistent and solutions converging to an endemic equilibrium. Numerical analysis is employed to gain insight in both the analytically tractable and intractable cases; these simulations indicate that media coverage can reduce the burden of the epidemic and shorten the duration of the disease outbreak.     

Regression modeling of semicompeting risks data

Semicompeting risks data are often encountered in clinical trials with intermediate endpoints subject to dependent censoring from informative dropout. Unlike with competing risks data, dropout may not be dependently censored by the intermediate event. There has recently been increased attention to these data, in particular inferences about the marginal distribution of the intermediate event without covariates. In this article, we incorporate covariates and formulate their effects on the survival function of the intermediate event via a functional regression model. To accommodate informative censoring, a time-dependent copula model is proposed in the observable region of the data which is more flexible than standard parametric copula models for the dependence between the events. The model permits estimation of the marginal distribution under weaker assumptions than in previous work on competing risks data. New nonparametric estimators for the marginal and dependence models are derived from nonlinear estimating equations and are shown to be uniformly consistent and to converge weakly to Gaussian processes. Graphical model checking techniques are presented for the assumed models. Nonparametric tests are developed accordingly, as are inferences for parametric submodels for the time-varying covariate effects and copula parameters. A novel time-varying sensitivity analysis is developed using the estimation procedures. Simulations and an AIDS data analysis demonstrate the practical utility of the methodology.     

链霉菌702产孢子固体培养基和培养条件的筛选

通过单因素实验、均匀设计和正交实验对链霉菌702产抱子培养基和培养条件进行筛选,筛选到的最佳培养基组成为：马铃薯2009／L,葡萄糖25g／L．最佳培养条件为培养温度37℃、培养时间5天和培养基初始pH值8．实验结果表明,采用优化后的培养基和培养条件,使链霉菌702产抱子数达到4．07亿,比原来培养基（高氏一号培养基）产抱予量提高了8．7倍,培养时间却从原来的7天缩短到现在的5天．     

具有时滞和反馈控制的非自治Schoner模型的持续生存与全局渐近稳定性

讨论了具有时滞和反馈控制的非自治Schoner模型,得到了系统一致持续生存和全局渐近稳定的充分条件．     

Optimization of an effective directed differentiation medium for differentiating mouse bone marrow mesenchymal stem cells into hepatocytes in vitro

We have used a uniform design to explore the most effective directed differentiation medium (MEDDM) for differentiating mouse bone marrow mesenchymal stem cells (mMSCs) into hepatocytes. Our methods involved arranging eight differentiation medium groups following uniform design. Flow cytometry was used to evaluate the percentage of ALB+ and CK18+ cells in each group. Factors and their concentrations in the MEDDMs were then identified. The MEDDMs were evaluated by their ability to differentiate mMSCs into hepatocytes by RNA and protein expressions and synthesis functions. FGF at 35 ng/ml and OSM at 30 ng/ml in the medium yielded the highest percentage of ALB+ and CK18+ cells. During directed differentiation using MEDDMs, ALB, CK18, TTR, AFP mRNAs were expressed. ALB and CK18 proteins were detected in the cells. The differentiated cells produced albumin and urea in a time dependent manner. Uniform design was adequate for choosing the MEDDM of mMSCs. MEDDM containing 35 ng/ml FGF and 30 ng/ml OSM was effective in differentiating mMSCs into hepatocytes.     

Glutamate decarboxylase-derived IDDM autoantigens displayed on self-assembled protein nanoparticles

The recombinant ferritin heavy chain (FTN-H) formed self-assembled spherical nanoparticles with the size comparable to native one. We tried to express the GAD65 COOH-terminal fragments, i.e., 448-585 (GAD65(448-585)), 487-585 (GAD65(487-585)), and 512-585 (GAD65(512-585)) amino acid fragments, using FTN-H as N-terminus fusion expression partner in Escherichia coli. All of recombinant fusion proteins (FTN-H::GAD65(448-585), FTN-H::GAD65(487-585), and FTN-H::GAD65(512-585)) also formed spherical nanoparticles due probably to the self-assembly function of the fused ferritin heavy chain. The antigenic epitopes within GAD65(448-585), GAD65(487-585), and GAD65(512-585) against insulin-dependent diabetes mellitus (IDDM) marker (autoantibodies against GAD65) were localized at the surface of the spherical protein nanoparticles so that anti-GAD65 Ab could recognize them. Protein nanoparticles like FTN-H seem to provide distinct advantages over other inorganic nanoparticles (e.g., Au, Ag, CdSe, etc.) in that through the bacterial synthesis, the active capture probes can be located at the nanoparticle surface with constant orientation/conformation via covalent cross-linking without complex chemistry. Also it is possible for the protein nanoparticles to have uniform particle size, which is rarely achieved in the chemical synthesis of inorganic nanoparticles. Thus, the recombinant ferritin particles can be used as a three-dimensional (spherical) and nanometer-scale probe structure that is a key component in ultra-sensitive protein chip for detecting protein-small molecule interactions and protein-protein interactions.     

Persistence,stability and level crossings in an integrodifferential system

Dynamical characteristics of an integrodifferential system modelling two species competition with hereditary effects are investigated; in particular we derive sufficient conditions for the persistence of the species, existence of an attracting periodic solution and level-crossings of solutions about the periodic solution.Supported by an OPRS fellowship from Flinders UniversityPartially supported by the Australian Research Council, Grant M67G15340110     

一个造血模型的全局吸引性和周期解相交

本文将Mackey和Glass提出的一个造血模型推广到具有周期系数和无穷时滞的情形．研究该模型的全局吸引性和周期解相交,并相应地得到两个充分条件.     

一个具有干预策略的肺结核模型的阈值动力学行为（英文）

文献[4]研究了肺结核传播的动力学行为.该文献仅从数值模拟上分析了疾病的传播和不同策略对疾病传播的影响.本文从理论上对疾病传播和不同策略对疾病传播的影响进行了分析.主要结论如下：得到了模型的基本再生数R_0.R_0决定了疾病传播的动力学行为：如果R_0〈1,则模型仅有一个无病平衡点且是局部渐近稳定的,若R_0〉1则模型存在一个地方病平衡点并且疾病是一致持续的.本文还得到了无病平衡点全局渐近稳定的充分条件.     

Ratio estimation with measurement error in the auxiliary variate

Summary .  With auxiliary information that is well correlated with the primary variable of interest, ratio estimation of the finite population total may be much more efficient than alternative estimators that do not make use of the auxiliary variate. The well-known properties of ratio estimators are perturbed when the auxiliary variate is measured with error. In this contribution we examine the effect of measurement error in the auxiliary variate on the design-based statistical properties of three common ratio estimators. We examine the case of systematic measurement error as well as measurement error that varies according to a fixed distribution. Aside from presenting expressions for the bias and variance of these estimators when they are contaminated with measurement error we provide numerical results based on a specific population. Under systematic measurement error, the biasing effect is asymmetric around zero, and precision may be improved or degraded depending on the magnitude of the error. Under variable measurement error, bias of the conventional ratio-of-means estimator increased slightly with increasing error dispersion, but far less than the increased bias of the conventional mean-of-ratios estimator. In similar fashion, the variance of the mean-of-ratios estimator incurs a greater loss of precision with increasing error dispersion compared with the other estimators we examine. Overall, the ratio-of-means estimator appears to be remarkably resistant to the effects of measurement error in the auxiliary variate.