湖北地区2001年度流感疫情分析

通过流感病毒分离、人群流感抗体水平测定和流行病学调查对 2 0 0 1年度 (2 0 0 1年 3月至 2 0 0 2年 3月 )湖北地区流感疫情进行了分析。结果表明 :本年度湖北武汉地区出现过两次流感季节性小流行 ,第一次在 2 0 0 1年 8～ 9月 ,主要由甲 1型流感病毒引起 ;第二次在 2 0 0 1年 12月至 2 0 0 2年 1月 ,以甲 3型流感病毒占优势。从病毒分离鉴定和抗体水平测定的情况分析 ,这次流行的甲 3型流感病毒与 1999年分离的毒株相比 ,可能发生了抗原性漂移     

石油生物催化脱硫的研究进展

石油生物催化脱硫技术是新兴的极具潜力的石油非加氢脱硫技术,在降低轻质油品生产成本、提高油品质量和环境保护等方面显示出潜在的优势,被誉为21世纪的石油脱硫技术。本文主要对石油生物催化脱硫技术特点、各种降解路线和研究现状进行了综述,指出了石油生物催化脱硫技术存在的问题,并提出了进一步研究发展的方向。     

生物发光法测定溶脲脲原体内微量ATP

目的　监测在液体培养基中生长的溶脲脲原体(Uu)细胞内微量ATP的变化趋势,方法　运用生物化学发光技术,建立ATP定量法。结果　Uu标准血清型1(U     

Nonparametric association analysis of bivariate left‐truncated competing risks data

We develop time‐varying association analyses for onset ages of two lung infections to address the statistical challenges in utilizing registry data where onset ages are left‐truncated by ages of entry and competing‐risk censored by deaths. Two types of association estimators are proposed based on conditional cause‐specific hazard function and cumulative incidence function that are adapted from unconditional quantities to handle left truncation. Asymptotic properties of the estimators are established by using the empirical process techniques. Our simulation study shows that the estimators perform well with moderate sample sizes. We apply our methods to the Cystic Fibrosis Foundation Registry data to study the relationship between onset ages of Pseudomonas aeruginosa and Staphylococcus aureus infections.     

Semiparametric transformation models for interval‐censored data in the presence of a cure fraction

Mixed case interval‐censored data arise when the event of interest is known only to occur within an interval induced by a sequence of random examination times. Such data are commonly encountered in disease research with longitudinal follow‐up. Furthermore, the medical treatment has progressed over the last decade with an increasing proportion of patients being cured for many types of diseases. Thus, interest has grown in cure models for survival data which hypothesize a certain proportion of subjects in the population are not expected to experience the events of interest. In this article, we consider a two‐component mixture cure model for regression analysis of mixed case interval‐censored data. The first component is a logistic regression model that describes the cure rate, and the second component is a semiparametric transformation model that describes the distribution of event time for the uncured subjects. We propose semiparametric maximum likelihood estimation for the considered model. We develop an EM type algorithm for obtaining the semiparametric maximum likelihood estimators (SPMLE) of regression parameters and establish their consistency, efficiency, and asymptotic normality. Extensive simulation studies indicate that the SPMLE performs satisfactorily in a wide variety of settings. The proposed method is illustrated by the analysis of the hypobaric decompression sickness data from National Aeronautics and Space Administration.