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.     

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.     

Demographics of the gay and lesbian population in the United States: Evidence from available systematic data sources

This work provides an overview of standard social science data sources that now allow some systematic study of the gay and lesbian population in the United States. For each data source, we consider how sexual orientation can be defined, and we note the potential sample sizes. We give special attention to the important problem of measurement error, especially the extent to which individuals recorded as gay and lesbian are indeed recorded correctly. Our concern is that because gays and lesbians constitute a relatively small fraction of the population, modest measurement problems could lead to serious errors in inference. In examining gays and lesbians in multiple data sets we also achieve a second objective: We provide a set of statistics about this population that is relevant to several current policy debates.     

Attributions about Addiction among Latina Women

This cross-sectional, secondary analysis study utilizes data from a prior study of intergenerational substance use among Latina women (n = 316). We explored the influence of substance use frequency and type, as well as cultural and socioeconomic factors on attributions about addiction among a predominantly immigrant sample of Latina women. Women who were less proficient in English (an indicator of adoption of the receiving culture in the acculturation process) and more proficient in Spanish (an indicator of heritage-culture retention) endorsed more spiritual model attributions than women who were more proficient in English and less proficient in Spanish. Women were more proficient in Spanish more frequently endorsed the disease attribution model. Alcohol, marijuana use and non-medical sedative use were linked with spiritual, moral /character and disease attribution models respectively. Participants reporting higher education levels indicated less agreement with the moral/character model of addiction. Implications for culturally tailored social work interventions for Latina women are discussed.     

Motivational Enhancement Counseling Strategies in Delivering a Telephone-Based Brief HIV Prevention Intervention

Motivational enhancement therapy (MET) interventions are being increasingly added to the menu of behavioral interventions for HIV prevention. They present few logistical and psychological barriers for at-risk persons who are ambivalent about transmission risk reduction and appear to offer promise of being transferable to community based organizations and public health programs. We describe the principles of motivational interviewing, a counseling style often used in conjunction with MET, and demonstrate and discuss its application with case examples drawn from a recent pilot trial of a telephone-delivered brief motivational enhancement for HIV risk reduction with men who have sex with men (MSM).     

Reframing Resilience: Equitable Access to Essential Services

We urgently need to put the concept of resilience into practice if we are to prepare our communities for climate change and exacerbated natural hazards. Yet, despite the extensive discussion surrounding community resilience, operationalizing the concept remains challenging. The dominant approaches for assessing resilience focus on either evaluating community characteristics or infrastructure functionality. While both remain useful, they have several limitations to their ability to provide actionable insight. More importantly, the current conceptualizations do not consider essential services or how access is impaired by hazards. We argue that people need access to services such as food, education, health care, and cultural amenities, in addition to water, power, sanitation, and communications, to get back some semblance of normal life. Providing equitable access to these types of services and quickly restoring that access following a disruption are paramount to community resilience. We propose a new conceptualization of community resilience that is based on access to essential services. This reframing of resilience facilitates a new measure of resilience that is spatially explicit and operational. Using two illustrative examples from the impacts of Hurricanes Florence and Michael, we demonstrate how decisionmakers and planners can use this framework to visualize the effect of a hazard and quantify resilience-enhancing interventions. This “equitable access to essentials” approach to community resilience integrates with spatial planning, and will enable communities not only to “bounce back” from a disruption, but to “bound forward” and improve the resilience and quality of life for all residents.     

Combining forward and backward mortality estimation

Demographers often form estimates by combining information from two data sources—a challenging problem when one or both data sources are incomplete. A classic example entails the construction of death probabilities, which requires death counts for the subpopulations under study and corresponding base population estimates. Approaches typically entail ‘back projection', as in Wrigley and Schofield's seminal analysis of historical English data, or ‘inverse’ or ‘forward projection’ as used by Lee in his important reanalysis of that work, both published in the 1980s. Our paper shows how forward and backward approaches can be optimally combined, using a generalized method of moments (GMM) framework. We apply the method to the estimation of death probabilities for relatively small subpopulations within the United States (men born 1930–39 by state of birth by birth cohort by race), combining data from vital statistics records and census samples.     

Critical Assessment of the Foundations of Power Transmission and Distribution Reliability Metrics and Standards

The U.S. federal government regulates the reliability of bulk power systems, while the reliability of power distribution systems is regulated at a state level. In this article, we review the history of regulating electric service reliability and study the existing reliability metrics, indices, and standards for power transmission and distribution networks. We assess the foundations of the reliability standards and metrics, discuss how they are applied to outages caused by large exogenous disturbances such as natural disasters, and investigate whether the standards adequately internalize the impacts of these events. Our reflections shed light on how existing standards conceptualize reliability, question the basis for treating large‐scale hazard‐induced outages differently from normal daily outages, and discuss whether this conceptualization maps well onto customer expectations. We show that the risk indices for transmission systems used in regulating power system reliability do not adequately capture the risks that transmission systems are prone to, particularly when it comes to low‐probability high‐impact events. We also point out several shortcomings associated with the way in which regulators require utilities to calculate and report distribution system reliability indices. We offer several recommendations for improving the conceptualization of reliability metrics and standards. We conclude that while the approaches taken in reliability standards have made considerable advances in enhancing the reliability of power systems and may be logical from a utility perspective during normal operation, existing standards do not provide a sufficient incentive structure for the utilities to adequately ensure high levels of reliability for end‐users, particularly during large‐scale events.