Titin--springing back to youth?

Mutations in the muscle protein titin have been linked to dilated cardiomyopathy, a condition in which the heart chambers are enlarged and blood is ineffectively pumped, in humans and in animal models. This protein, which is a component of sarcomeres, provides essential scaffolding for other muscle proteins and acts as a spring to confer passive elasticity on the cardiomyocyte. Several titin isoforms exist, and they display varying size and degrees of elasticity. We review two interesting reports that show how variations in titin isoforms might be implicated in cardiac failure.     

Using the integrative model of behavioral prediction to understand college students’ STI testing beliefs,intentions, and behaviors

ABSTRACT

Objectives: To identify salient behavioral determinants related to STI testing among college students by testing a model based on the integrative model of behavioral (IMBP) prediction. Participants: 265 undergraduate students from a large university in the Southeastern US. Methods:Formative and survey research to test an IMBP-based model that explores the relationships between determinants and STI testing intention and behavior. Results: of path analyses supported a model in which attitudinal beliefs predicted intention and intention predicted behavior. Normative beliefs and behavioral control beliefs were not significant in the model; however, select individual normative and control beliefs were significantly correlated with intention and behavior. Conclusions: Attitudinal beliefs are the strongest predictor of STI testing intention and behavior. Future efforts to increase STI testing rates should identify and target salient attitudinal beliefs.     

Implementation issues for consumer-directed programs: comparing views of policy experts, consumers, and representatives

An increasing number of aging community providers and consumers support consumer-direction (CD) in long-term care services. In regard to devolution, consumer-direction goes beyond the usual approach of shifting responsibilities from the federal government to state governments to bring programs "closer to the people." Consumer-direction goes even further by placing resources directly in the hands of consumers. Yet, many questions remain unanswered regarding how to implement CD personal assistance services in general, and especially for older persons. This article describes the importance of examining views from multiple key stakeholders involved in implementing CD programs. We report on three background studies that have informed the Cash and Counseling Demonstration and Evaluation (CCDE) design and implementation-policy expert interviews as well as surveys and focus groups with consumers and representatives. As a fourth data source, we drew upon experiences in designing the CCDE and initial results from the first year of implementation. Each of the three studies on its own provided essential information for planning the CCDE. However, when we examined the studies together, and added CCDE design and implementation experiences, views expressed by the different stakeholders formed a type of multi-perspective "dialogue" that expanded our knowledge about implementing CD services. We hope this increased knowledge will help expand the availability of such services for consumers of any age who want to direct their own care.     

Unweaving leaving: the use of models in the management of employee turnover

This paper offers a review of the literature on labour turnover in organizations. Initially, the importance of the subject area is established, as analyses of turnover are outlined and critiqued. This leads to a discussion of the various ways in which turnover and its consequences are measured. The potentially critical impact of turnover behaviour on organizational effectiveness is presented as justification for the need to model turnover, as a precursor to prediction and prevention. Key models from the literature of labour turnover are presented and critiqued.     

Benefits of Hybrid Lateral Transshipments in Multi‐Item Inventory Systems under Periodic Replenishment

Lateral transshipments are a method of responding to shortages of stock in a network of inventory‐holding locations. Conventional reactive approaches only seek to meet immediate shortages. The study proposes hybrid transshipments which exploit economies of scale by moving additional stock between locations to prevent future shortages in addition to meeting immediate ones. The setting considered is motivated by retailers who operate networks of outlets supplying car parts via a system of periodic replenishment. It is novel in allowing non‐stationary stochastic demand and general patterns of dependence between multiple item types. The generality of our work makes it widely applicable. We develop an easy‐to‐compute quasi‐myopic heuristic for determining how hybrid transshipments should be made. We obtain simple characterizations of the heuristic and demonstrate its strong cost performance in both small and large networks in an extensive numerical study.     

Repurposing Materials and Waste through Online Exchanges: Overcoming the Last Hurdle

Online material and waste exchanges (OMWEs) provide online channels to repurpose by‐products, unused materials and waste from industrial and commercial facilities. Unfortunately, OMWE's also have challenges. First, sellers may have access to other disposal options and, as a result, may not fully commit to the exchange. Second, buyers can face high uncertainty about the product exchanged and the transaction being undertaken. Overcoming these challenges is the “last hurdle” to making OMWEs successful. This study investigates the factors that reduce the buyers' uncertainty and increase the sellers' commitment to the OMWE. We analyze novel transaction‐level data from an online exchange (MNExchange.org) combined with other archival public records on county‐level repurposing and disposal statistics. First, we find that regional repurposing policies and alternatives have a complementary effect on sellers' commitment toward OMWEs, resulting in increased OMWE exchanges. However, regional disposal policies and alternatives have a substitution effect on sellers' commitment, resulting in reduced exchange success. Further, greater product and transaction information reduce the buyer's uncertainty and increase exchange success. Finally, the analysis shows that users' (buyers and sellers) heavily rely on their prior experience with OMWEs. Specifically, higher familiarity between the buyer–seller pair and familiarity with the OMWE system leads to higher likelihood of exchange success. This study lays the foundation for understanding OMWEs and has important implications for developing policies and operations to increase online transactions of by‐products, materials and wastes.     

Identification Properties of Recent Production Function Estimators

This paper examines some of the recent literature on the estimation of production functions. We focus on techniques suggested in two recent papers, Olley and Pakes (1996) and Levinsohn and Petrin (2003). While there are some solid and intuitive identification ideas in these papers, we argue that the techniques can suffer from functional dependence problems. We suggest an alternative approach that is based on the ideas in these papers, but does not suffer from the functional dependence problems and produces consistent estimates under alternative data generating processes for which the original procedures do not.     

An Empirical Approach to Sufficient Similarity: Combining Exposure Data and Mixtures Toxicology Data

When assessing risks posed by environmental chemical mixtures, whole mixture approaches are preferred to component approaches. When toxicological data on whole mixtures as they occur in the environment are not available, Environmental Protection Agency guidance states that toxicity data from a mixture considered “sufficiently similar” to the environmental mixture can serve as a surrogate. We propose a novel method to examine whether mixtures are sufficiently similar, when exposure data and mixture toxicity study data from at least one representative mixture are available. We define sufficient similarity using equivalence testing methodology comparing the distance between benchmark dose estimates for mixtures in both data‐rich and data‐poor cases. We construct a “similar mixtures risk indicator”(SMRI) (analogous to the hazard index) on sufficiently similar mixtures linking exposure data with mixtures toxicology data. The methods are illustrated using pyrethroid mixtures occurrence data collected in child care centers (CCC) and dose‐response data examining acute neurobehavioral effects of pyrethroid mixtures in rats. Our method shows that the mixtures from 90% of the CCCs were sufficiently similar to the dose‐response study mixture. Using exposure estimates for a hypothetical child, the 95th percentile of the (weighted) SMRI for these sufficiently similar mixtures was 0.20 (i.e., where SMRI <1, less concern; >1, more concern).