Aquatic and terrestrial invertebrate community responses to drying in chalk streams

Temporary streams are dynamic ecosystems that shift between wet and dry states and include the ‘winterbourne’ chalk streams of south England. Our understanding of temporary stream biodiversity is biased, with most research to date exploring aquatic invertebrate communities in benthic sediments during flowing phases. We surveyed the invertebrate communities of the Candover Brook chalk stream, comparing aquatic (benthic, hyporheic) and terrestrial communities in reaches with different flow permanence regimes. We used kick and Bou–Rouch sampling methods to collect aquatic invertebrates, and compared the terrestrial communities characterised by pitfall traps and ground searches and in different seasons. Although aquatic taxa richness was lower in temporary compared to perennial reaches, the total biodiversity of temporary stream channels was enhanced by contributions from both aquatic and terrestrial species, including several of conservation interest. We recommend that both aquatic and terrestrial communities should be considered in research and monitoring to characterise the biodiversity and ecological quality of temporary streams.     

Influence of crosslinking and plasticizing on the viscoelasticity of highly filled elastomers

Solid propellants, like all highly filled elastomers, exhibit a complex nonlinear viscoelastic behavior. The aim of this study was to establish the relationships between the structure and properties, which is needed to construct a robust constitutive law for these materials. An extensive design of experiments approach allowed us to quantify the influence of the curing agents and plasticizer molecules on the microstructure of the propellant and its viscoelastic properties. Swelling and gel permeation chromatography measurements described the microstructure of the propellant and prestrained dynamic mechanical analysis (PDMA) characterized the viscoelastic behavior. The curing agents reacted with polymer chain ends participating in the network, in the sol fraction, or in filler–binder links. Consequently, the polymer network was incomplete even in stoichiometric conditions, and a minimum of 10% of the polymer was free in the microstructure. In addition, preswelling the polymer with plasticizer molecules before curing modified the obtained network by decreasing the crosslink density in the binder and increasing it in the vicinity of the filler surface. This study provided new insight into the local deformation mechanisms controlling nonlinearity as measured by PDMA. The nonlinear behavior appeared between 0 and 1.7% prestrain in both the elastic and viscous parts of the behavior. The network reached its maximum extensibility in the elastic part and constrained the sol fraction in this extended mesh for the viscous part. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40392.     

Investigation of the Effect of Electrical Current Variance on Thermoelectric Energy Harvesting

The performance of thermoelectric modules for energy-harvesting applications is investigated, and a model is presented to predict module performance. Derived from energy conservation equations, the model predicts module performance by solving for the temperatures at both ends of the thermoelectric materials within a module. Unlike traditional methods, the model accounts for the effect of electrical current with respect to the load resistance by considering additional heat transfer by Joule heating and the Peltier effect. This establishes a nonlinear quadratic form of temperatures which can be solved by an iterative numerical solution. The model is extended to predict the performance of energy-harvesting systems, which may include connection of multiple thermoelectric modules in series to meet the necessary power requirements. However, a key issue with multiple module connection is the power reduction that arises when there are significant differences in module properties and/or the corresponding external conditions to which each individual module is exposed. Power reduction is thus investigated, as in some cases the overall power output for multiple modules can be less than the power output of a single module. For validation and comparison of the model, experimental support is provided for the case of two commercial thermoelectric modules connected in series. The model also provides optimum load resistances, and a system optimization of the number of modules for a designated heat sink to maximize power generation. The overarching goal of this work is to provide performance prediction and optimization considerations for actual thermoelectric energy-harvesting systems.     

Statistical implications of using moving violations to determine crash responsibility in young driver crashes

Traditional methods for determining crash responsibility – most commonly moving violation citations – may not accurately characterize at-fault status among crash-involved drivers given that: (1) issuance may vary by factors that are independent of fault (e.g., driver age, gender), and (2) these methods do not capture driver behaviors that are not illegal but still indicative of fault. We examined the statistical implications of using moving violations to determine crash responsibility in young driver crashes by comparing it with a method based on crash-contributing driver actions. We selected all drivers in police-reported passenger-vehicle crashes (2010–2011) that involved a New Jersey driver <21 years old (79,485 drivers < age 21, 61,355 drivers ≥ age 21). For each driver, crash responsibility was determined from the crash report using two alternative methods: (1) issuance of a moving violation citation; and (2) presence of a driver action (e.g., failure to yield, inattention). Overall, 18% of crash-involved drivers were issued a moving violation while 50% had a driver action. Only 32.2% of drivers with a driver action were cited for a moving violation. Further, the likelihood of being cited given the presence of a driver action was higher among certain driver subgroups—younger drivers, male drivers, and drivers in single-vehicle and more severe crashes. Specifically among young drivers, those driving at night, carrying peer passengers, and having a suspended or no license were more often cited. Conversely, fatally-injured drivers were almost never cited. We also demonstrated that using citation data may lead to statistical bias in the characterization of at-fault drivers and of quasi-induced exposure measures. Studies seeking to accurately determine crash responsibility should thoughtfully consider the potential sources of bias that may result from using legal culpability methods. For many studies, determining driver responsibility via the identification of driver actions may yield more accurate characterizations of at-fault drivers.     

The specificity of age-related decline in interpretation of emotion cues from prosody.

Older adults are not as good as younger adults at decoding prosodic emotions. We sought to determine the specificity of this finding. Performance of older and younger adults was compared on a prosodic emotion task, a “pure” prosodic emotion task, a linguistic prosody task, and a “pure” linguistic prosody task. Older adults were less accurate at interpreting prosodic emotion cues and nonemotional contours, concurrent semantic processing worsened interpretation, and performance was further degraded when identifying negative emotions and questions. Older adults display a pervasive problem interpreting prosodic cues, but further study is required to clarify the stage at which performance declines. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Learning from successful and failed experience: The moderating role of kind of after-event review.

The claim that appropriate "after-event review (AER)" may increase the relative value of drawing lessons from successes, as compared with failures, was examined in the present study. The study was a laboratory experiment in which the effect of type of AER (failure-focused, success-focused, failure- and success-focused, and no AER review) on performance improvement and causal attributions was tested under conditions of earlier success and earlier failure. In general, 2 results were demonstrated: (a) Drawing lessons from successful experience is feasible, and its effectiveness is contingent upon the type of AER. More specifically, after successful events, the most effective review is that of wrong actions, whereas after failed events, any kind of event review (correct or wrong actions) is effective. (b) AERs elicit more internal (as opposed to external) and specific (as opposed to general) attributions. These 2 classifications moderate the effect of AERs on task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polymers and carbon nanotubes—dimensionality, interactions and nanotechnology

The behavior of mixtures of polymers with carbon nanotubes are reviewed. The use of polymers as dispersing agents of individual CNT is described in detail. Two groups of polymer-CNT systems are presented. One corresponds to the case in which the polymer-CNT interactions modify the electronic properties of the tubes. The second case corresponds to the polymers end-tethered to the tubes. This case results in changing the inter-tube interactions from strongly attractive to repulsive, through the entropic (steric) polymer induced repulsions. It is shown that the shape and dimensionality of the tubes determines the strength, range and type of inter-tube van der Waals attractions and polymer induced repulsions. The experimental verification of these ideas, and their implications for tube dispersions and separation are discussed.     

Le style parental des beaux-péres dans les familles recomposées.

Several studies have shown the importance of the stepfather-stepchild relationship in the successful adaptation of young people to stepfamilies. Indeed, when there is a good affective relationship between a stepfather and stepchild, there is a lower risk of stepchild having problems. Though it is known that the quality of this relationship has an impact, there is still a great deal of uncertainty about the best way for stepfathers to fulfill their role. This article examines how the stepfather's parenting style influences the externalised and internalised behaviour problems of young people in stepfamilies. The data were obtained from interviews with 104 adolescents (63.5 % girls; 36.5 % boys) who answered the Youth Self-Report (Achenbach, 1991), the Parental Authority Questionnaire (Buri, 1991), and the Child Parental Acceptance-Rejection Questionnaire (Rohner, 1984). The results show that the majority of young people saw their stepfather as being involved in their upbringing. More than a third of the sample considered that their stepfather was authoritarian, and another third saw him as authoritative. The young people's level of adaptation was associated with the stepfather's parenting style. Young people who saw their stepfather as being authoritative or warm particularly benefited from the relationship. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aftereffects for face attributes with different natural variability: Adapter position effects and neural models.

Adaptation to distorted faces is commonly interpreted as a shift in the face-space norm for the adapted attribute. This article shows that the size of the aftereffect varies as a function of the distortion level of the adapter. The pattern differed for different facial attributes, increasing with distortion level for symmetric deviations of eye height and decreasing for asymmetric deviations. These results are interpreted in terms of different coding ranges for the 2 facial attributes, arising from differences in eye-height variability in natural face images (large for symmetric, small for asymmetric). Neural models developed in low-level vision also are applied to facial attributes, contrasting a 2-pool (norm-based) and a multichannel (exemplar-based) model. The adapter position effects generally support a norm-based model, as did a finding that perception of stimuli further from the norm than the adapter was shifted in the direction of the norm, rather than repulsed away from the adapter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)