Impurity segregation in graphene nanoribbons

The electronic properties of low-dimensional materials can be engineered by doping, but in the case of graphene nanoribbons (GNR) the proximity of two symmetry-breaking edges introduces an additional dependence on the location of an impurity across the width of the ribbon. This introduces energetically favorable locations for impurities, leading to a degree of spatial segregation in the impurity concentration. We develop a simple model to calculate the change in energy of a GNR system with an arbitrary impurity as that impurity is moved across the ribbon and validate its findings by comparison with ab initio calculations. Although our results agree with previous works predicting the dominance of edge disorder in GNR, we argue that the distribution of adsorbed impurities across a ribbon may be controllable by external factors, namely an applied electric field. We propose that this control over impurity segregation may allow manipulation and fine-tuning of the magnetic and transport properties of GNRs.Comment: 5 pages, 4 figures, submitte

Moral Disengagement Among Serious Juvenile Offenders: A Longitudinal Study of the Relations between Morally Disengaged Attitudes and Offending

The present study investigates the relation between moral disengagement – one’s willingness to conditionally endorse transgressive behavior – and ongoing offending in a sample of adolescent male felony offenders (N=1,169). In addition, the study attempts to rule out callous-unemotional traits as a third variable responsible for observed associations between moral disengagement and offending. A bivariate latent change score analysis suggests that reduction in moral disengagement helps to speed decline in self-reported antisocial behavior, even after adjusting for the potential confound of callous-unemotional traits. Declines in moral disengagement are also associated with declining likelihood of offending, based on official records. Given that both moral disengagement and offending tend to decrease over time, these findings suggest that changing attitudes toward antisocial behavior contribute to desistance from offending among delinquent youth

Deterring Serious and Chronic Offenders

This chapter examines ways of deterring serious and chronic offenders based on evidence from the Pathways to Desistance Study, which addresses the issue of perceptions of deterrence and looks into the mechanisms of deterrence for serious offenders. After a brief overview of the Pathways study, the chapter reviews empirical evidence that demonstrates the rationality of high-risk adolescents regarding involvement in crime. It argues that offenders take into account rational-choice perceptions in their offending decisions and goes on to discuss the elasticity and malleability of these perceptions, and whether adolescent offenders act differently when they change risk and cost perceptions. It also considers policy efforts aimed at maximizing deterrence among adolescent offenders and concludes by outlining future directions for theory and research

New Class of Precision Antimicrobials Redefines Role of Clostridium difficile S-layer in Virulence and Viability

There is a medical need for antibacterial agents that do not damage the resident gut microbiota or promote the spread of antibiotic resistance. We recently described a prototypic precision bactericidal agent, Av-CD291.2, which selectively kills specific Clostridium difficile strains and prevents them from colonizing mice. We have since selected two Av-CD291.2–resistant mutants that have a surface (S)-layer–null phenotype due to distinct point mutations in the slpA gene. Using newly identified bacteriophage receptor binding proteins for targeting, we constructed a panel of Avidocin-CDs that kills diverse C. difficile isolates in an S-layer sequence-dependent manner. In addition to bacteriophage receptor recognition, characterization of the mutants also uncovered important roles for S-layer protein A (SlpA) in sporulation, resistance to innate immunity effectors, and toxin production. Surprisingly, S-layer–null mutants were found to persist in the hamster gut despite a complete attenuation of virulence. These findings suggest antimicrobials targeting virulence factors dispensable for fitness in the host force pathogens to trade virulence for viability and would have clear clinical advantages should resistance emerge. Given their exquisite specificity for the pathogen, Avidocin-CDs have substantial therapeutic potential for the treatment and prevention of C. difficile infections

Spatial organization of Clostridium difficile S-layer biogenesis

Surface layers (S-layers) are protective protein coats which form around all archaea and most bacterial cells. Clostridium difficile is a gram-positive bacterium with an S-layer covering its peptidoglycan cell wall. The S-layer in C. difficile is constructed mainly of S-layer protein A (SlpA), which is a key virulence factor for these bacteria and an absolute requirement for disease. Studying the formation and maintenance of the C. difficile S-layer will allow the discovery of specific therapeutic interventions in the future. Here we use microscopy to examine the subcellular localization of S-layer growth and SlpA secretion. We observed formation of S-layer at specific sites that coincide with cell wall synthesis, while conversely the secretion of SlpA from the cell is delocalized. We conclude that this delocalized secretion of SlpA leads to a pool of precursor in the cell wall which is available to repair openings in the S-layer formed during cell growth or following damage

Predictor species: Improving assessments of rare species occurrence by modeling environmental co-responses

Designing an effective conservation strategy requires understanding where rare species are located. Because rare species can be difficult to find, ecologists often identify other species called conservation surrogates that can help inform the distribution of rare species. Species distribution models typically rely on environmental data when predicting the occurrence of species, neglecting the effect of species\u27 co-occurrences and biotic interactions. Here, we present a new approach that uses Bayesian networks to improve predictions by modeling environmental co-responses among species. For species from a European peat bog community, our approach consistently performs better than single-species models and better than conventional multi-species approaches that include the presence of nontarget species as additional independent variables in regression models. Our approach performs particularly well with rare species and when calibration data are limited. Furthermore, we identify a group of “predictor species” that are relatively common, insensitive to the presence of other species, and can be used to improve occurrence predictions of rare species. Predictor species are distinct from other categories of conservation surrogates such as umbrella or indicator species, which motivates focused data collection of predictor species to enhance conservation practices

Electrochemically controlled growth and positioning of suspended collagen membranes

Two independently recognized in vitro polymer aggregation variables, electric field and pH, can be used in concert to produce suspended membranes from solutions of type I collagen monomers, without need of a supporting substrate. A collagen network film can form at the alkalineacidic pH interface created during the normal course of water electrolysis with parallel plate electrodes, and the anchoring location can be controlled by adjusting the bulk electrolyte pH. Electrosynthesized films remain intact upon drying and rehydration and function as ion separation membranes even in submillimeter channels. This approach could benefit lab-on-a-chip technologies for rational placement of membranes in microfluidic devices

The design, construction and performance of the MICE scintillating fibre trackers

This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 ElsevierCharged-particle tracking in the international Muon Ionisation Cooling Experiment (MICE) will be performed using two solenoidal spectrometers, each instrumented with a tracking detector based on diameter scintillating fibres. The design and construction of the trackers is described along with the quality-assurance procedures, photon-detection system, readout electronics, reconstruction and simulation software and the data-acquisition system. Finally, the performance of the MICE tracker, determined using cosmic rays, is presented.This work was supported by the Science and Technology Facilities Council under grant numbers PP/E003214/1, PP/E000479/1, PP/E000509/1, PP/E000444/1, and through SLAs with STFC-supported laboratories. This work was also supportedby the Fermi National Accelerator Laboratory, which is operated by the Fermi Research Alliance, under contract No. DE-AC02-76CH03000 with the U.S. Department of Energy, and by the U.S. National Science Foundation under grants PHY-0301737,PHY-0521313, PHY-0758173 and PHY-0630052. The authors also acknowledge the support of the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan

New Young Star Candidates in BRC 27 and BRC 34

We used archival Spitzer Space Telescope mid-infrared data to search for young stellar objects (YSOs) in the immediate vicinity of two bright-rimmed clouds, BRC 27 (part of CMa R1) and BRC 34 (part of the IC 1396 complex). These regions both appear to be actively forming young stars, perhaps triggered by the proximate OB stars. In BRC 27, we find clear infrared excesses around 22 of the 26 YSOs or YSO candidates identified in the literature, and identify 16 new YSO candidates that appear to have IR excesses. In BRC 34, the one literature-identified YSO has an IR excess, and we suggest 13 new YSO candidates in this region, including a new Class I object. Considering the entire ensemble, both BRCs are likely of comparable ages, within the uncertainties of small number statistics and without spectroscopy to confirm or refute the YSO candidates. Similarly, no clear conclusions can yet be drawn about any possible age gradients that may be present across the BRCs.Comment: 54 pages, 19 figures, accepted by A

Design, development and validity testing of the Gang Affiliation Risk Measure (GARM)

This study aimed to create a measure of risk for gang affiliation, for use in the UK. A pilot stage invited gang affiliated and non-gang affiliated participants between the ages of 16–25 years to retrospectively self-report on 58 items of risk exposure at the age of 11 years. Based on performance of these items, a 26-item measure was developed and administered to a main study sample (n=185) of gang affiliated and non-gang affiliated participants. Categorical Principal Component Analysis was applied to data, yielding a single-factor solution (historic lack of safety and current perception of threat). A 15-item gang affiliation risk measure (GARM) was subsequently created. The GARM demonstrated good internal consistency, construct validity and discriminative ability. Items from the GARM were then transformed to read prospectively, resulting in a test measure for predictive purposes (T-GARM). The T-GARM requires further validation regarding its predictive utility and generalisability. However, this study has resulted in the first measure of gang affiliation, with promising results