Evolution of an asymptomatic first stage of infection in a heterogeneous population

Pathogens evolve different life-history strategies, which depend in part on differences in their host populations. A central feature of hosts is their population structure (e.g. spatial). Additionally, hosts themselves can exhibit different degrees of symptoms when newly infected; this latency is a key life-history property of pathogens. With an evolutionary-epidemiological model, we examine the role of population structure on the evolutionary dynamics of latency. We focus on specific power-law-like formulations for transmission and progression from the first infectious stage as a function of latency, assuming that the across-group to within-group transmission ratio increases if hosts are less symptomatic. We find that simple population heterogeneity can lead to local evolutionarily stable strategies (ESSs) at zero and infinite latency in situations where a unique ESS exists in the corresponding homogeneous case. Furthermore, there can exist more than one interior evolutionarily singular strategy. We find that this diversity of outcomes is due to the (possibly slight) advantage of across-group transmission for pathogens that produce fewer symptoms in a first infectious stage. Thus, our work reveals that allowing individuals without symptoms to travel can have important unintended evolutionary effects and is thus fundamentally problematic in view of the evolutionary dynamics of latency.     

Developing leaders via experience: The role of developmental challenge, learning orientation, and feedback availability.

Prior research offers limited insight into the types of work experiences that promote leadership skill development and the ways that the person and context shape the developmental value of these experiences. In this article, the authors develop a series of hypotheses linking leadership skill development to features of the experience (developmental challenge), person (learning orientation), and context (feedback availability). Based on 225 on-the-job experiences across 60 managers, their results demonstrate that the relationship between developmental challenge and leadership skill development exhibits a pattern of diminishing returns. However, access to feedback can offset the diminishing returns associated with high levels of developmental challenge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion, plasticity, context, and regulation: Perspectives from affective neuroscience.

The authors present an overview of the neural bases of emotion. They underscore the role of the prefrontal cortex (PFC) and amygdala in 2 broad approach- and withdrawal-related emotion systems. Components and measures of affective style are identified. Emphasis is given to affective chronometry and a role for the PFC in this process is proposed. Plasticity in the central circuitry of emotion is considered, and implications of data showing experience-induced changes in the hippocampus for understanding psychopathology and stress-related symptoms are discussed. Two key forms of affective plasticity are described—context and regulation. A role for the hippocampus in context-dependent normal and dysfunctional emotional responding is proposed. Finally, implications of these data for understanding the impact on neural circuitry of interventions to promote positive affect and on mechanisms that govern health and disease are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The long-term effects of two group routines on accident prevention activities and accident statistics

We have previously reported that a combination of two group routines, an accident investigation group and a review group, led to improved accident prevention activities and accident statistics at one company over a three-year period. This article describes the use and effects of the two group routines during an additional 8 years. The investigation group assisted foremen in their accident investigations. The review group regularly discussed accidents that had occurred since the previous meeting and was responsible for checking on the implementation of accident prevention measures. As compared to the three years preceding the introduction of the routines, proposals for countermeasures increased by 19%. Accident frequency was reduced by 10% and accident severity by 35% during the period the routines were used. The largest improvements occurred during the first five years, after which variability in these measures increased. Both group routines were begun with minimal instruction and assistance and each was positively received by foremen and personnel involved. The results suggest that the routines could be of benefit to other companies.     

The location of motor vehicle crashes in Honolulu: a methodology for geocoding intersections

The use of a geographic information system to geocode motor vehicle accidents by intersection (or corner) matching is described. Starting with the basic street network of TIGER or another linear reference system, the process of geocoding is described as well as the types of errors that can be introduced from loosening matching conditions. With an administrative database, such as the 1990 and 1991 motor vehicle accident files from Honolulu, there are sources of error which require modifications to both the attribute and geographic databases in order to properly match records. We describe the nature of errors and provide a procedure for detection and correction of these records. The logic is applied to the 1991 motor vehicle accident file for Honolulu and a method for assessing the accuracy of the geocoding process under different matching conditions is developed. We argue against loosening street name conditions and show that significant error can be introduced. The method can be applied to other databases where intersection matching is required, though the specifics need to be tailored to the individual database. The use of Global Positioning System receivers may supplement or even replace this approach, though there are many problems associated with this technology as well. For the foreseeable future, algorithmic approaches, such as described here, are applicable to crash reporting and other spatially distributed phenomena. The results have implications for the development of the next generation of georeferencing software.     

Numerical analysis of ice-induced stresses in the membrane electrode assembly of a PEM fuel cell under sub-freezing operating conditions

In this work, we report on numerical investigation on the behavior of a polymer electrolyte membrane fuel cell (PEMFC) during a non-optimized start-up procedure from (?20 °C) with a two-dimensional model that couple transport, electrochemical reaction, ice formation and accumulation and mechanical stress induced by ice. The results indicate that the regions with maximum values of ice saturation and von Mises stress are all located in the cathode catalyst layer (CL) and the micro pore layer (MPL) under the land; assuming a 5% ice expansion rate, predicts ice saturation of 0.95 in the cathode CL 240 s, and von Mises stress of 2.8 MPa in the membrane which is below the critical value for damage. However, in the CL the von Mises stress exceeds 15 MPa. Tensile stresses in particular are found to attain sufficiently high values to cause after only 150 s to potentially cause delamination and/or dislocation of particles resulting in higher bulk and interfacial resistance. The simulations indicate that ice-induced degradation may be prevented with measures that reduce the cold start time to under 75 s.     

Correspondence of Interactive Voice Response (IVR) reports of nicotine withdrawal, craving, and negative mood with questionnaire ratings.

This study focuses on comparing reports of nicotine withdrawal, craving, and depressive symptoms obtained using an Interactive Voice Response (IVR) system and several questionnaires. As part of a smoking cessation trial, daily reports of withdrawal, craving, and negative mood were collected using an IVR system for 7 days after participants attempted to quit smoking, and several pencil and paper questionnaires (i.e., the Minnesota Nicotine Withdrawal Scale, the Questionnaire on Smoking Urges, and the Center for Epidemiological Studies-Depression) were completed a week after the target quit date. The sample was composed of 378 daily smokers. Moderate to high correlations were found between the research questionnaires obtained at the end of the week and the corresponding daily IVR reports of nicotine withdrawal, craving, and depressive symptoms. However, the sample size decreased on each day of IVR reporting due to attrition. Thus, an appealing aspect of daily assessment using an IVR system is that it can provide additional data that are not obtained with paper and pencil assessments given once per week, but it will be important for future studies to concentrate on improving adherence with the IVR system in this population.     

Photoperiod-dependent modulation of anti-Müllerian hormone in female Siberian hamsters, Phodopus sungorus

Fertility and fecundity decline with advancing age in female mammals, but reproductive aging was decelerated in Siberian hamsters (Phodopus sungorus) raised in a short-day (SD) photoperiod. Litter success was significantly improved in older hamsters when reared in SD and the number of primordial follicles was twice that of females held in long days (LD). Because anti-Müllerian hormone (AMH) appears to inhibit the recruitment of primordial follicles in mice, we sought to determine whether the expression patterns of AMH differ in the ovaries and serum of hamsters raised in SD versus LD. Ovaries of SD female hamsters are characterized by a paucity of follicular development beyond the secondary stage and are endowed with an abundance of large eosinophilic cells, which may derive from granulosa cells of oocyte-depleted follicles. In ovaries from 10-week-old SD hamsters, we found that the so-called 'hypertrophied granulosa cells' were immunoreactive for AMH, as were granulosa cells within healthy-appearing primary and secondary follicles. Conversely, ovaries from age-matched LD animals lack the highly eosinophilic cells present in SD ovaries. Therefore, AMH staining in LD was limited to primary and secondary follicles that are comparable in number to those found in SD ovaries. The substantially greater AMH expression in SD ovaries probably reflects the abundance of hypertrophied granulosa cells in SD ovaries and their relative absence in LD ovaries. The modulation of ovarian AMH by day length is a strong mechanistic candidate for the preservation of primordial follicles in female hamsters raised in a SD photoperiod.     

Coping skills and treatment outcomes in cognitive-behavioral and interactional group therapy for alcoholism.

In the present study 128 alcohol dependent men and women received 26 weeks of group treatment in one of two modalities: Cognitive-behavioral treatment (CBT) intended specifically to develop coping skills or interactional therapy intended to examine interpersonal relationships. Coping skills and drinking were assessed prior to and after treatment and up to 18 months after intake. Results indicated that both treatments yielded very good drinking outcomes throughout the follow-up period. Increased coping skills was a significant predictor of outcome. However, neither treatment effected greater increases in coping than the other. Specific coping-skills training was not essential for increasing the use of coping skills. The results raise questions about the efficacy of specific treatment elements of CBT in treatment of alcohol dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)