Signatures of series and parallel systems consisting of non disjoint modules

System signature is a useful tool to analyze coherent systems. In reliability theory, a large number of systems is actually the composition of disjoint subsystems (modules). However, in real life, there are situations in which the subsystems have common components. In this article, we consider the problem of obtaining signatures as well as minimal signatures of series and parallel systems that are composed of subsystems sharing a component. That is, these subsystems are no longer disjoint. Computational results are also presented to illustrate our findings.     

No association of serum PSA with vitamin D or total oxidant-antioxidant capacity in healthy men

Background and aim: Vitamin D deficiency and oxidative stress were suggested to be related to prostate cancer risk. We aimed to investigate the association of serum PSA concentration with vitamin D and total oxidant/antioxidant levels.

Materials and methods: A total of 95 healthy men were enrolled for the cross sectional study. Serum PSA, 25(OH)D, serum total oxidant status, and total antioxidant status were measured.

Results: Serum PSA was significantly negatively correlated with serum total oxidant status (r=??0.309, p?=?.003) but there was no significant correlation between PSA and 25(OH)D (p?=?.383) or total antioxidant levels (p?=?.233). After adjustment for age BMI and smoking status with multiple regression analysis, there was no significant association between serum PSA and total oxidant status.

Conclusion: We find no evidence for an association between PSA and vitamin D levels or serum total oxidant/antioxidant levels.     

Positives and negatives of online dating according to women 50+

ABSTRACT

To understand the positives and negatives of online dating according to the lived experience of older women, telephone interviews were conducted with 45 women ages 50+ who date online. Interviews were audio recorded, transcribed verbatim, and thematically team coded. The opportunity to expand one’s social network for both friendships and romantic partners, the ability to control dating risks and pace of relationship formation, and knowing more about one’s partner were significant reported benefits of online dating. Dating online also includes unique risks, such as pervasive lying, attempted financial exploitation in the form of scammers, and unwanted electronic sexual aggression.     

Estimators for the Population Mean in the Case of Missing Data

We propose a class of estimators for the population mean when there are missing data in the data set. Obtaining the mean square error equations of the proposed estimators, we show the conditions where the proposed estimators are more efficient than the sample mean, ratio-type estimators, and the estimators in Singh and Horn (2000 Singh , S. , Horn , S. ( 2000 ). Compromised imputation in survey sampling . Metrika 51 : 267 – 276 .[Crossref], [Web of Science ®] , [Google Scholar]) and Singh and Deo (2003 Singh , S. , Deo , B. (2003). Imputation by power transformation. Statist. Pap. 44:555–579.[Crossref], [Web of Science ®] , [Google Scholar]) in the case of missing data. These conditions are also supported by a numerical example.