Survival analysis in clinical trials: past developments and future directions

The field of survival analysis emerged in the 20th century and experienced tremendous growth during the latter half of the century. The developments in this field that have had the most profound impact on clinical trials are the Kaplan-Meier (1958, Journal of the American Statistical Association 53, 457-481) method for estimating the survival function, the log-rank statistic (Mantel, 1966, Cancer Chemotherapy Report 50, 163-170) for comparing two survival distributions, and the Cox (1972, Journal of the Royal Statistical Society, Series B 34, 187-220) proportional hazards model for quantifying the effects of covariates on the survival time. The counting-process martingale theory pioneered by Aalen (1975, Statistical inference for a family of counting processes, Ph.D. dissertation, University of California, Berkeley) provides a unified framework for studying the small- and large-sample properties of survival analysis statistics. Significant progress has been achieved and further developments are expected in many other areas, including the accelerated failure time model, multivariate failure time data, interval-censored data, dependent censoring, dynamic treatment regimes and causal inference, joint modeling of failure time and longitudinal data, and Baysian methods.     

Methods for estimating the number of the Cryptomeria red mite,especially with the removal by solutions

We compared the removal by solution, the represented count-area method and the beating, for the purpose of estimating the number of the Cryptomeria red mite. Among them the solution procedure provided the smallest standard error as per cent of the mean. 0.25 per cent unheated solution of sodium hydroxide is used for the summer generation, and also 0.25 per cent boiling one for the winter eggs. The mean proportion removed±standard error for the summer eggs and the winter eggs were 0.8770±0.0316 and 0.7920±0.0281 respectively, while 0.9894±0.0050 for the mites.     

Bayesian survival analysis using a MARS model

A Bayesian multivariate adaptive regression spline fitting approach is used to model univariate and multivariate survival data with censoring. The possible models contain the proportional hazards model as a subclass and automatically detect departures from this. A reversible jump Markov chain Monte Carlo algorithm is described to obtain the estimate of the hazard function as well as the survival curve.     

红螯螯虾体表附生切头涡虫类研究概述

随着红螯螯虾(Cherax quadricarinatus)养殖业的发展,附着于红螯螯虾体表的切头涡虫及其危害已引起养殖业者的广泛关注.本文介绍了切头涡虫的分类地位和分布,详细描述了切头涡虫外部形态和内部构造,并对切头涡虫的共生特性、食性、生活史、运动方式等生物学特点进行了概述,对切头涡虫的危害和防治进行了总结和讨论....     

Under-smoothed kernel confidence intervals for the hazard ratio based on censored data

In cancer clinical trials, it is often of interest in estimating the ratios of hazard rates at some specific time points during the study from two independent populations. In this paper, we consider nonparametric confidence interval procedures for the hazard ratio based on kernel estimates for the hazard rates with under-smoothing bandwidths. Two methods are used to derive the confidence intervals: one based on the asymptotic normality of the ratio of the kernel estimates for the hazard rates in two populations and another through Fieller's Theorem. The performances of the proposed confidence intervals are evaluated through Monte-Carlo simulations and applied to the analysis of data from a clinical trial on early breast cancer.     

乳粉中嗜热菌污染研究进展

嗜热菌是乳粉中的常见污染菌,是影响乳粉品质的一个重要因素。本文综述乳粉中嗜热菌的种类、污染源对乳品工业的危害及其控制手段的研究进展,为国内相关领域研究提供参考。     

Some Nutritional Factors Affecting Production of Biomass and Antifungal Metabolites of Coniothyrium minitans

The ability of the mycoparasite Coniothyrium minitans to utilize a range of C and N sources and vitamins for growth, pycnidial formation and antifungal metabolite production was examined using a defined liquid medium. Coniothyrium minitans was able to use all the C sources tested, with the exception of D -xylose, and all the N sources tested, although growth was generally better on organic N sources rather than NO 3 -N. Increasing C:N ratios from 9:1-202:1 with N constant (2.0 g L -l L -alanine) resulted in steadily increasing yields, whereas increasing C:N ratios with C constant (40.0 g L -l D -glucose) gradually decreased yield. Addition of thiamine to the glucose-alanine basal medium resulted in the greatest increase in growth but biomass was still less than that achieved using an undefined molasses-yeast medium. Pycnidial production was generally low or failed to occur in the basal medium + C + N sources in the absence of vitamins, but addition of thiamine consistently led to abundant pycnidial formation. Molasses-yeast static culture provided greater biomass and conidial yields than molasses-yeast shaken culture. Incorporation of C. minitans culture medium into potato dextrose broth (10% v/v) resulted in consistent reduction in growth of Sclerotinia sclerotiorum irrespective of C, N or vitamin content of the basal medium or whether molasses-yeast medium was used. This is the first report of consistent production of antifungal metabolites by C. minitans .     

Alteration of energy-linked functions in rat hepatic mitochondria following aflatoxin B1 administration

Respiratory activity in hepatic mitochondria have been examined following administration of the carcinogen aflatoxin, (AFB₁) to rats. Measurement in isolated mitochondria of respiration rates in presence of ADP (state 3) and after its depletion (state 4) revealed that these rates were not significantly altered in livers of rats obtained 4–8 hours after single injection of AFB₁ (7 mg/kg of body weight). After 12–24 hours, however, a generalized inhibition in state 3 respiration rate and ADP phosphorylation rate had been evident with several FAD- and NAD-linked oxidizing substrates. But the ADP:0 ratio did not show any alteration. State 4 respiration rates, on the other hand, were increased remarkably (38–94% depending on substrate used), thereby recording in each case a decrease in respiratory control ratio (state 3:state 4 ratio), indicating probable damage to mitochondrial membrane as a result of AFB₁ ingestion. This was also evident from greater basal ATPase and Mg²⁺-ATPase activities and low total ATPase activity. After 48–72 hours of AFB₁ treatment, the respiratory rates as well as the ATPase activities returned to normal levels, suggesting probable recovery of mitochondrial functions from the toxic effects of AFB₁. © 1997 John Wiley & Sons, Inc.     

Water quality index,Labeo rohita,and Eichhornia crassipes: Suitable bio-indicators of river water pollution

The present study investigated the water quality index (WQI) of the Kshipra river at Dewas, Madhya Pradesh, India, using native fish Labeo rohita, and plant Eichhornia crassipes. The temperature, pH, dissolved oxygen, alkalinity, turbidity, and dissolved solids were found to be within the prescribed limits. However, heavy metals concentration exceeded the limit except for Cu and Zn. Their occurrence in river water was as follows: Ni > Fe > Cd > Cr > Mn > Zn > Cu. Among these heavy metals, Cd was found to be highly bioavailable, whereas Zn was the least bioavailable metal. Based on WQI, the water was found to be unfit for drinking, and the high WQI value was due to the presence of Cr and Cd. In fish tissues (muscle, liver, gut, gills, and kidney), the highest and lowest metal pollution index was found in gills (45.03) and kidneys (12.21), respectively. Bioaccumulation of these metals resulted in significant depletion of energy reserves (protein, glucose, and glycogen) and also altered hematological parameters. Moreover, liver function tests showed hepatic damage in the exposed fish. In-plant, both the bioaccumulation and mobility factor exceeded 1 for all these metals. On the other hand, the translocation factor was found to be beyond 1 for Fe, Ni, and Zn. These high values make this plant fit for phytoextraction of Mn, Fe, Cu, Zn, and Cd and phytostabilization of Cr in water. Moreover, consumption of L. rohita from the Kshipra River does not pose a non-cancer risk as the target hazard quotient was below 1, but it may pose cancer risk because of the presence of Cr in the range of 1.402 × 10^?3 to 1.599 × 10^?3.