A Model for Setting Performance Objectives for Salmonella in the Broiler Supply Chain

A stochastic model for setting performance objectives for Salmonella in the broiler supply chain was developed. The goal of this study was to develop a model by which performance objectives for Salmonella prevalence at various points in the production chain can be determined, based on a preset final performance objective at the end of the processing line. The transmission of Salmonella through the broiler production chain was modeled. The prevalence at flock level was calculated from the measured prevalence at sample level. The transmission model is based on data on the occurrence of Salmonella collected in the Dutch broiler production chain during several years. The developed model can be used by policymakers and industry to determine economically and politically acceptable performance objectives for various points of the production chain and to draw conclusions about which interventions are most appropriate.     

Race, Class, and Gender Differences in High School Seniors' Values: Applying Intersection Theory in Empirical Analysis

Objective . This article demonstrates how intersection theory can be applied in empirical studies by testing whether an individual's race, class, and gender have interactive effects. Methods . Data on high school students' ratings of the importance of equality, money, career, and family from the Monitoring the Future study are used. A stepwise regression model is employed to determine first whether additive effects exist in the data, and then whether interactions exist among race, class, and gender characteristics. Results . Previous findings of additive effects were generally confirmed in the first stage of the regressions, with some exceptions. For the money and family values, significant interactions exist between some pairs of characteristics, but three-way interactions were not significant. For equality and career values, no significant interactions were found. Conclusions . Although there are times when additive models are sufficient to describe differences among groups, the omission of interaction terms can sometimes lead to misleading conclusions about the effects of race, class, and gender. Using intersection theory in empirical models will guard against this oversight and may lead to a broad theory of when significant race, class, and gender interactions should be expected.     

On the Limitations of Redundancies in the Improvement of System Reliability

Some program managers share a common belief that adding a redundant component to a system reduces the probability of failure by half. This is true only if the failures of the redundant components are independent events, which is rarely the case. For example, the redundant components may be subjected to the same external loads. There is, however, in general a decrease in the failure probability of the system. Nonetheless, the redundant element comes at a cost, even if it is less than that of developing the first one when both are based on the same design. Identical parts save the most in terms of design costs, but are subjected to common failure modes from possible design errors that limit the effectiveness of the redundancy. In the development of critical systems, managers thus need to decide if the costs of a parallel system are justified by the increase in the system's reliability. NASA, for example, has used redundant spacecraft to increase the chances of mission success, which worked well in the cases of the Viking and Voyager missions. These two successes, however, do not guarantee future ones. We present here a risk analysis framework accounting for dependencies to support the decision to launch at the same time a twin mission of identical spacecraft, given incremental costs and risk-reduction benefits of the second one. We illustrate this analytical approach with the case of the Mars Exploration Rovers launched by NASA in 2003, for which we had performed this assessment in 2001.     

Genetic Studies of Pathological Gambling: A Review of Methodology and Analyses of Data from the Vietnam Era Twin Registry

Twin studies represent an important and powerful approach to estimating the relative contributions of environmental and genetic factors to the expression of psychiatric illnesses. In this article, we first explain the rationale for using large populations of monozygotic and dizygotic twin pairs to estimate genetic and environmental contributions to a disorder and the statistical modeling associated with this approach. We then review results from studies of the Vietnam Era Twin Registry that use this methodology to examine the etiology of pathological gambling (PG) behaviors. The results provide strong evidence for genetic contributions to the development of PG in men and set the foundation for future studies aimed at identifying the manner in which specific genes and environmental factors individually and in conjunction contribute to PG.     

Impact of competitive conditions on supplier evaluation: a construction supply chain case study

This research proposes a multi-criteria decision-making (MCDM) framework and demonstrates the impact of competitive conditions on supplier evaluation process for construction supply chains. The paper focuses on the supply chain of a large-scale housing project in order to illustrate the role of competitive capability and suppliers’ profile and its influence on supplier evaluation based on prevailing supply/market conditions. Various scenarios are investigated to demonstrate the impact of competition on supplier evaluation. The contribution of the study lies in highlighting the impact of supply/market conditions on MCDM decisions causing supplier evaluation ‘imbalance’ and MCDM usage. It is expected that the study will be useful for project management, construction, supply chain management, sourcing professionals. The findings of the study are generalisable to projects-based situations such as petroleum refinery and ship building where bill of materials typically consists of thousands of items and a large number of suppliers are involved.     

Topological Performance Measures as Surrogates for Physical Flow Models for Risk and Vulnerability Analysis for Electric Power Systems

Critical infrastructure systems must be both robust and resilient in order to ensure the functioning of society. To improve the performance of such systems, we often use risk and vulnerability analysis to find and address system weaknesses. A critical component of such analyses is the ability to accurately determine the negative consequences of various types of failures in the system. Numerous mathematical and simulation models exist that can be used to this end. However, there are relatively few studies comparing the implications of using different modeling approaches in the context of comprehensive risk analysis of critical infrastructures. In this article, we suggest a classification of these models, which span from simple topologically‐oriented models to advanced physical‐flow‐based models. Here, we focus on electric power systems and present a study aimed at understanding the tradeoffs between simplicity and fidelity in models used in the context of risk analysis. Specifically, the purpose of this article is to compare performance estimates achieved with a spectrum of approaches typically used for risk and vulnerability analysis of electric power systems and evaluate if more simplified topological measures can be combined using statistical methods to be used as a surrogate for physical flow models. The results of our work provide guidance as to appropriate models or combinations of models to use when analyzing large‐scale critical infrastructure systems, where simulation times quickly become insurmountable when using more advanced models, severely limiting the extent of analyses that can be performed.     

Abuse and Parental Characteristics,Attributions of Blame,and Psychological Adjustment in Adult Survivors of Child Sexual Abuse

The purpose of this study was to examine the influence of abuse and parental characteristics on attributional content and determine the relative contribution of different attributions of blame in predicting psychological symptomatology among adult survivors of childhood sexual abuse. One hundred eighty-three female undergraduates with a history of childhood sexual abuse completed self-report questionnaires. Abuse characteristics were significantly related to attributions. Family- and perpetrator-blame accounted for significant variability in psychological symptomatology, beyond the contributions of abuse characteristics, family environment, and self-blame. Implications for research and treatment are discussed.     

Waivers of parental consent for sexual minority youth

ABSTRACT

The Society for Adolescent Health and Medicine emphasizes the need for research to focus on the health outcomes of sexual minority youth (i.e., lesbian, gay, bisexual, transgender, queer). However, sexual minority youth (SMY) are often less willing to participate in research studies where parental consent is required due to potential victimization and discrimination. This is a major concern given that more research is needed to understand the health needs of this population, especially in terms of suicide, substance use, and HIV prevention. The National Suicide Prevention Strategy classifies SMY as a high-risk group, emphasizing the need to explore suicide risks (along with other health outcomes) among this group. However, this high-risk classification also increases the safeguards necessary to conduct research with this population. Many researchers have argued for waivers of parental consent, but such waivers present with several ethical implications. This article discusses ethical principles, risks, benefits, safeguards, and potential alternative approaches to waivers of parental consent for SMY. We conclude by emphasizing the need for policy changes to allow parental consent waivers for research targeting SMY.