TEM observations on grain boundaries in sintered silicon, part 1

Grain boundaries in silicon with a predetermined orientation were prepared by the sintering of two single crystals. A combination of standard transmission electron microscopy and lattice imaging was used to investigate the structure of the boundaries produced. Low angle grain boundaries on (100) and (111) planes, and twin boundaries on (111) planes are discussed in detail

WFABC: a Wright-Fisher ABC-based approach for inferring effective population sizes and selection coefficients from time-sampled data

With novel developments in sequencing technologies, time-sampled data are becoming more available and accessible. Naturally, there have been efforts in parallel to infer population genetic parameters from these datasets. Here, we compare and analyze four recent approaches based on the Wright-Fisher model for inferring selection coefficients (s) given effective population size (Ne), with simulated temporal datasets. Furthermore, we demonstrate the advantage of a recently proposed ABC-based method that is able to correctly infer genome-wide average Ne from time-serial data, which is then set as a prior for inferring per-site selection coefficients accurately and precisely. We implement this ABC method in a new software and apply it to a classical time-serial dataset of the medionigra genotype in the moth Panaxia dominula. We show that a recessive lethal model is the best explanation for the observed variation in allele frequency by implementing an estimator of the dominance ratio (h)

Durability and generalization of attribution-based feedback following failure: Effects on expectations and behavioral persistence

Objective: This experiment investigated, following perceived failure, the immediate, long-term (i.e., durability), and cross-situational (i.e., generalization) effects of attribution-based feedback on expectations and behavioral persistence. Design: We used a 3×2 (Group×Time) experimental design over seven weeks with attributions, expectations of success, and persistence as dependent measures. Method: 49 novice participants were randomly assigned to one of three treatment (attributional feedback) groups: (a) functional (i.e., controllable and unstable); (b) dysfunctional (i.e., uncontrollable and stable); or (c) no feedback. Testing involved three sessions, in which participants completed a total of five trials across two performance tasks (golf-putting and dart-throwing). In order to track whether the attributional manipulation conducted within the context of the golf-putting task in Session 2 would generalize to a new situation, participants performed a dart-throwing task in Session 3, and their scores were compared with those recorded at baseline (in Session 1). Results: Analysis of pre- and post-intervention measures of attributions, expectations, and persistence revealed that the functional attributional feedback led to more personally controllable attributions following failure in a golf-putting task, together with increases in success expectations and persistence. In contrast, dysfunctional attributional feedback led to more personally uncontrollable and stable attributions following failure, together with lower success expectations and reduced persistence. These effects extended beyond the intervention period, were present up to four weeks post intervention, and were maintained even when participants performed a different (i.e., dart-throwing) task. Conclusions: The findings demonstrate that attributional feedback effects are durable over time and generalize across situations

Quantifying polymorphism and divergence from epigenetic data: a framework for inferring the action of selection

Epigenetic modifications are alterations that regulate gene expression without modifying the underlying DNA sequence. DNA methylation and histone modifications, for example, are capable of spatial and temporal regulation of expression-with several studies demonstrating that these epigenetic marks are heritable. Thus, like DNA sequence, epigenetic marks are capable of storing information and passing it from one generation to the next. Because the epigenome is dynamic and epigenetic modifications can respond to external environmental stimuli, such changes may play an important role in adaptive evolution. While recent studies provide strong evidence for species-specific signatures of epigenetic marks, little is known about the mechanisms by which such modifications evolve. In order to address this question, we analyze the genome wide distribution of an epigenetic histone mark (H3K4me3) in prefrontal cortex neurons of humans, chimps and rhesus macaques. We develop a novel statistical framework to quantify within- and between-species variation in histone methylation patterns, using an ANOVA-based method and defining an FST -like measure for epigenetics (termed epi- FST), in order to develop a deeper understanding of the evolutionary pressures acting on epigenetic variation. Results demonstrate that genes with high epigenetic FST values are indeed significantly overrepresented among genes that are differentially expressed between species, and we observe only a weak correlation with SNP density

An experimental evaluation of drug-induced mutational meltdown as an antiviral treatment strategy [preprint]

The rapid evolution of drug resistance remains a critical public health concern. The treatment of influenza A virus (IAV) has proven particularly challenging, due to the ability of the virus to develop resistance against current antivirals and vaccines. Here we evaluate a novel antiviral drug therapy, favipiravir, for which the mechanism of action in IAV involves an interaction with the viral RNA- dependent RNA polymerase resulting in an effective increase in the viral mutation rate. We utilize an experimental evolution framework, combined with novel population genetic method development for inference from time-sampled data, in order to evaluate the effectiveness of favipiravir against IAV. Evaluating whole genome polymorphism data across fifteen time points under multiple drug concentrations and in controls, we present the first evidence for the ability of viral populations to effectively adapt to low concentrations of favipiravir. In contrast, under high concentrations, we observe population extinction, indicative of mutational meltdown. We discuss the observed dynamics with respect to the evolutionary forces at play and emphasize the utility of evolutionary theory to inform drug development

Being one of us: Translating expertise into performance benefits following perceived failure

Is feedback delivered by an expert sufficient to improve performance? In two studies, we tested, following failure, the influence of group membership (ingroup/outgroup) and source expertise (high/low) on the effectiveness of attributional feedback on performance. Results revealed a significant interactive effect, showing an increase of performance only when the source was an expert ingroup member (Study 1). This interaction was replicated on performance and success expectations in Study 2, which were significantly higher for high compared to low expertise ingroup sources. These data suggest that sharing a common identity with those you lead may help convert expert performance advice into real performance benefits

Retail Price and Point of Sale Display of Tobacco in the UK: A Descriptive Study of Small Retailers

Background: Since the implementation of the 2002 Tobacco Advertising and Promotion Act, point-of-sale (PoS) tobacco displays are one of few remaining means of communication between the tobacco industry and customers in the UK. This study aimed to explore the characteristics of tobacco displays in a UK city, and particularly to assess the tobacco prices and promotional offers, types and pack sizes on display. Methods: Digital pictures of PoS displays were taken in 117 small retail shops in Nottingham in mid 2010. Data were analysed using Windows Photo Gallery software and SPSS version 16. Results: Just over half (52%) of cigarette packs on display were packs of 20, and 43 % packs of 10. Cigarette prices differed substantially between brands, ranging from £4.19 to £6.85 for 20-packs, and from £2.12 to £3.59 for 10-packs. Forty four percent of cigarette packs and 40 % of RYO (Roll-Your-Own) tobacco pouches, almost exclusively lower priced brands, were displayed with a pricemark, implying a promotional price offer. Eighty percent of 20-pack cigarette brand or brand variants on sale were priced below the EU-defined Most Popular Price Category (MPPC) for the UK in 2010; 45 % were priced below the Weighted Average Price (WAP), which replaced the MPPC in 2011. Conclusion: PoS displays communicate value by displaying a high proportion of lower cost brands, and smaller and hence lower-cost packs, and by displaying price discounts on packs. The MPPC substantially overestimated the prices at whic

A Biological Inventory of Meacham Cave (Independence County, Arkansas)

During September 2008 through June 2011, we compiled a biological inventory of Meacham Cave in Independence County, AR. Compared to other caves in the region, Meacham Cave houses few vertebrates, but non-aquatic invertebrates were relatively common. A transiently-increased bacterial load in the cave’s only pool of water indicated recent fecal contamination. The combination of vandalism, low vertebrate populations, and high coliform bacterial load reveals that human abuse of the cave has significantly disrupted its ecosystem. Gating the cave in such a way as to allow the movement of bats, salamanders and other animals, while excluding humans, may allow the cave ecosystem to recover. The close proximity of the cave to Lyon College makes it ideal for long-term investigation