Non-parametric Back-projection of HIV Positive Tests using Multinomial and Poisson Settings

Back-projection is a commonly used method in reconstructing HIV incidence. Instead of using AIDS incidence data in back-projection, this paper uses HIV positive tests data. Both multinomial and Poisson settings are used. The two settings give similar results when a parametric form or step function is assumed for the infection curve. However, this may not be true when the HIV infection in each year is characterized by a different parameter. This paper attempts to use simulation studies to compare these two settings by constructing various scenarios for the infection curve. Results show that both methods give approximately the same estimates of the number of HIV infections in the past, whilst the estimates for HIV infections in the recent past differ a lot. The multinomial setting always gives a levelling-off pattern for the recent past, while the Poisson setting is more sensitive to the change in the shape of the HIV infection curve. Nonetheless, the multinomial setting gives a relatively narrower point-wise probability interval. When the size of the epidemic is large, the narrow probability interval may be under-estimating the true underlying variation.     

BALANCED ARRAYS AND WEIGHING DESIGNS

Dey (19711, Saha (1975), Kageyama & Saha (1983) and others have shown how optimum chemical balance weighing designs can be constructed from the incidence matrices of balanced incomplete block (BIB) designs. In this paper, it is shown that weighing designs can be constructed from some suitably chosen two-symbol balanced arrays of strength two, which need not always be incidence matrices of BIB designs. The findings lead us to construct new optimum chemical balance weighing designs from incidence matrices of BIB designs.     

Efficient designs for animal carcinogenicity experiments

In a typical carcinogenicity study, animals, usually rats or mice. are divided into a control and two to three dose groups of 50 or more by randomization. A chemical is administered at a constant daily dose rate for a major portion of the lifetime of the test animals, for example, two years. In general, such an experiment is expensive and time consuming In this paper, we propose an efficient design with reduced sample size and/or shortened study duration. An equal number of animals per dose group is considered in this study. A power study of the age-adjusted trend test, for the turnor incidence rate for single-sacrifice experiments proposed by Kodell et al. (Drug Information Journal, 1997) is conducted. A Monte Carlo simulation study is performed to compare the performance of the trend test for the standard design and various reduced designs. Based on the Kodell et al. test, the 21-month study duration with sample size 50 per group is recommended as the best, reduced design over the traditional 2-year study design with the same sample size.     

The prevalence and incidence of HIV among injection drug users: A five year panel study

Six hundred and one injection drug users (IDUs) who attended drug treatment programs in Miami, Florida, were enrolled in a panel study to determine the prevalence and incidence of human immunodeficiency virus (HIV) and associated risk factors. A structured questionnaire which elicited injection and sexual behaviors was administered and blood was obtained by venipduncture. All participants were reassessed at six month intervals for 5 years. The baseline prevalence of HIV was 16.3%. African–Americans had a prevalence of HIV (37.1%) that was significantly higher than that of non-Hispanic whites (7.6%); the prevalence of HIV among Hispanics was 27.2%. Persons who were more than thirty years of age were more likely to test HIV positive (17.8%) than were younger participants (9.7%). The annual incidence per 1000 person-years of exposure for the 503 initially seronegative participants was consistently low for each year of the study. The 5 year incidence was 4.1 per 1000 person years; 7.5 for men and 1.7 for women, 7.5 for African–Americans and 3.8 for non-Hispanic whites. No Hispanic participants seroconverted. Multivariate logistic techniques were used to identify the independent risk factors for HIV prevalence. Earlier injection, ethnicity, and income were independently associated with HIV serostatus. A history of a sexually transmitted disease was marginally associated with HIV prevalence. Low incidence probably is a function of the reduction of risk behavior that occurred over the course of the study and the stage of the epidemic.     

Row similarity in binary-valued matrices

An algorithm is developed for calculating the probability distribution of the number of matches between two specified rows of a matrix of zeroes and ones. Cases covered include row totals fixed, column totals fixed, and column totals and the two specified rows' totals fixed. The results are applied to presence-absence data on six species of ground finches on 23 Galàpagos islands and two constructed examples.     

《一个馒头引发的血案》的后现代意义

2005至2006的年末岁初,由电影大片《无极》所引发的轰动,被网络娱乐片《一个馒头引发的血案》的火爆所冲击,同时也引发了影视界、网络界、法律界、评论界等各方面的不同反响。笔者认为将其简单地称为“网路恶搞”是不恰当的。从社会心理、艺术审美以及思维模式、创作方式的发展变化来看,它具有明显的后现代主义文化特征,甚至可以说是其在中国发生发展的一个信号,一个标志性的事件。     

九一八事变后国民党内宪政态度的分歧

九一八事变爆发后,国内掀起了一场宪政运动的潮流。一些国民党上层人物也表态要求结束训政,实施宪政,推行民主政治,反对一党专政。但是,他们的出发点有所不同,一部分人为国家民族而呼吁;另一部分人则纯出于个人私利而将宪政作为政治斗争的工具。与此同时,以蒋介石为首的实权派公然表示反对。     

The pattern of child sexual abuse in northern ireland

A team from the Departments of Child Psychiatry, Royal Belfast Hospital for Sick Children, and of Epidemiology and Public Health, Queens University Belfast, conducted a study in 1987 of the reported incidence of child sexual abuse in Northern Ireland. The incidence rate of established cases of child sexual abuse was 0.9 per 1000 children under the age of 17 years. Further analysis of all the cases of sexual abuse (suspected, alleged and established) and an estimation of the potential under-ascertainment indicated that the actual rate was between 0.9 per 1000 and 1.85 per 1000 children. Data obtained from a detailed structured questionnaire on each sexually abused child was analysed. The results are presented in relation to the child, age and sex; the abuse, type and duration; the abuser, sex, age and relationship to the child; and outcome factors, initial psychological sequelae, physical signs and symptoms, and social sequelae.