Different strategies of reliability theory for the analysis of coherent systems have been studied by various researchers. Here, the Gini-type index is utilized as an applicable tool for the study and comparison of the ageing properties of complex systems. A new stochastic order in terms of Gini-type index is introduced to compare the speed of ageing of components and systems. The parallel-series and series-parallel systems with shared components are studied by their corresponding Gini-type indexes. Also, the generalization of Gini-type index for the multidimensional case is discussed, and is used to compare components lifetimes properties in the presence of other dependent components. It is shown that the ageing properties of a component lifetime can differ when the other components are working or have already failed. Numerous illustrative examples are given for better intuition of Gini-type and generalized Gini-type indexes throughout the paper

A mixture cure model relies on a model for the cure probability and a model for the survival function of the uncured subjects. For the latter, one often uses a Cox proportional hazards model. We show the identifiability of this model under weak assumptions. The model assumes that the cure threshold is the same for all values of the covariates, which might be unrealistic in certain situations. An alternative mixture cure model is the accelerated failure time (AFT) model. We also show the identifiability of this model under minimal assumptions. The cure threshold in this model depends on the covariates, which often leads to a better fit of the data. This is especially true when the follow-up period is insufficient for certain values of 2 M. Parsa and I. Van Keilegom the covariates. We study these two models via simulations both when the follow-up is sufficient and when it is insufficient. Moreover, the two models are applied to data coming from a breast cancer clinical trial. We show that the AFT and the Cox model both fit the data well in the region of sufficient follow-up, but differ drastically outside that region.

Introduction: Intravenous injection is one of the important principles in the treatment of most patients, which has complications such as catheter site infection that it is necessary to identify the factors that increase the prevalence of venous catheter infections. Therefore, the aim of this study was to evaluate the frequency of colonization and bacteremia caused by peripheral venous catheters in hospitalized children. Materials and Methods:This cross-sectional study was performed on 70 children with venous catheter. After recording demographic information, colonization and bacteremia caused by peripheral venous catheters in patients, Chi-square and Mann-Whitney tests were used to compare data. Results:The results of the present study showed that the frequency of bacterial colonization in peripheral catheters in children was 22.9% which was not related to the demographic characteristics of patients and their underlying disease history (P<0.05). The most common cultured bacterium was Staphylococcus epidermidis. Conclusion:Considering the prevalence of colonization in peripheral catheters in children, it is recommended that the necessary training be provided to the staff of this department and preventive measures be taken in high-risk individuals to reduce nosocomial infections and complications.

Abstract. Mean residual life and failure rate functions are ubiquitously employed in reliability analysis. The term of useful period of lifetime distributions of bathtub-shaped failure rate functions is referred to the flat rigion of this function and has attracted authors and researchers in reliability, actuary, and survival analysis. In recent years, considering the change points of mean residual life and failure rate functions has been extensively utelized in determining the optimum burn-in time. In this paper we investigate the difference between the change points of failure rate and mean residual life functions of some generalized gamma type distributions due to the capability of these distributions in modeling various bathtub-shaped failure rate functions.