Substrate-induced bandgap in graphene on hexagonal boron nitride

We determine the electronic structure of a graphene sheet on top of a lattice-matched hexagonal boron nitride (h-BN) substrate using ab initio density functional calculations. The most stable configuration has one carbon atom on top of a boron atom, the other centered above a BN ring. The resulting inequivalence of the two carbon sites leads to the opening of a gap of 53 meV at the Dirac points of graphene and to finite masses for the Dirac fermions. Alternative orientations of the graphene sheet on the BN substrate generate similar band gaps and masses. The band gap induced by the BN surface can greatly improve room temperature pinch-off characteristics of graphene-based field effect transistors.Comment: 5 pages, 4 figures, Phys. Rev. B, in pres

Molecular genetics of cardiomyopathy: changing times, shifting paradigms

The original publication is available at http://www.cvja.co.za/Includes bibliographyCongestive heart failure is a major problem in developed and developing countries alike. Primary dysfunction of the heart muscle accounts for a significant proportion of patients with a non-ischaemic cause of heart failure. Application of genetic techniques has facilitated identification of some molecular causes of the inherited form of these diseases, dramatically increasing our understanding of the pathogenesis of these primary, previously termed ‘idiopathic’, cardiomyopathies over the last few decades. Knowledge of the different causes is beginning to coalesce into aetiological principles underlying the clinically distinguished cardiomyopathies. Hypertrophic cardiomyopathy (HCM) now appears to be a disease caused by a dysfunctional sarcomere, dilated cardiomyopathy (DCM), a disease of myocytic structural instability, and arrhythmogenic right ventricular cardiomyopathy, a disease of accelerated myocyte death. The aetiology of both HCM and DCM probably also involves cardiac energy imbalances, while additional factors modify the clinical expression in all cardiomyopathies. Even though our knowledge of the genetic aetiology of the cardiomyopathies is still incomplete, it already has relevant clinical significance. Elucidation of the full genetic contribution to the development and progression of the cardiomyopathies represents a new challenge in the study of these diseases, and will undoubtedly lead to new therapeutic approaches in the not-too-distant future.Publishers' versio

Current land bird distribution and trends in population abundance between 1982 and 2012 on Rota, Mariana Islands

The western Pacific island of Rota is the fourth largest human-inhabited island in the Mariana archipelago and designated an Endemic Bird Area. Between 1982 and 2012, 12 point-transect distance-sampling surveys were conducted to assess bird population status. Surveys did not consistently sample the entire island; thus, we used a ratio estimator to estimate bird abundances in strata not sampled during every survey. Trends in population size were reliably estimated for 11 of 13 bird species, and 7 species declined over the 30-y time series, including the island collared-dove Streptopelia bitorquata, white-throated ground-dove Gallicolumba xanthonura, Mariana fruit-dove Ptilinopus roseicapilla, collared kingfisher Todiramphus chloris orii, Micronesian myzomela Myzomela rubratra, black drongo Dicrurus macrocercus, and Mariana crow Corvus kubaryi. The endangered Mariana crow (x̄  =  81 birds, 95% CI 30–202) declined sharply to fewer than 200 individuals in 2012, down from 1,491 birds in 1982 (95% CI  =  815–3,115). Trends increased for white tern Gygis alba, rufous fantail Rhipidura rufifrons mariae, and Micronesian starling Aplonis opaca. Numbers of the endangered Rota white-eye Zosterops rotensis declined from 1982 to the late 1990s but returned to 1980s levels by 2012, resulting in an overall stable trend. Trends for the yellow bittern Ixobrychus sinensis were inconclusive. Eurasian tree sparrow Passer montanus trends were not assessed; however, their numbers in 1982 and 2012 were similar. Occupancy models of the 2012 survey data revealed general patterns of land cover use and detectability among 12 species that could be reliably modeled. Occupancy was not assessed for the Eurasian tree sparrow because of insufficient detections. Based on the 2012 survey, bird distribution and abundance across Rota revealed three general patterns: 1) range restriction, including Mariana crow, Rota white-eye, and Eurasian tree sparrow; 2) widespread distribution, low abundance, including collared kingfisher, island collared-dove, white-throated ground-dove, Mariana fruit-dove, white tern, yellow bittern, black drongo, and Micronesian myzomela; and 3) widespread distribution, high abundance, including rufous fantail and Micronesian starling. The Mariana crow was dispersed around the periphery of the island in steep forested land-cover types. In contrast, the Rota white-eye was restricted to the high-elevation mesa. Only for the white-throated ground-dove was there a significant difference among cover types, with lower occupancy in open field than in forested areas. Vegetation was included in the best-fit occupancy models for yellow bittern, black drongo, Micronesian myzomela, and Micronesian starling, but vegetation type was not a significant variable nor included in the top models for the remaining five species: white tern, island collared-dove, Mariana fruit-dove, collared kingfisher, and rufous fantail. Given declining population trends, the Rota bird-monitoring program could benefit from establishing threshold and alert limits and identifying alternative research and management actions. Continued monitoring and demographic sampling, in conjunction with ecological studies, are needed to understand why most bird species on Rota are declining, identify the causative agents, and assess effectiveness of conservation actions, especially for the Mariana crow

Long-term follow-up of R403W MYH7 and R92W TNNT2 HCM families : mutations determine left ventricular dimensions but not wall thickness during disease progression

The original publication is available at http://www.cvja.co.za/CVJA holds the copyrightThe clinical profile and prognosis of patients with hypertrophic cardiomyopathy, a primary cardiac muscle disease caused mostly by mutations in sarcomeric protein-encoding genes, have been linked to particular disease-causing mutations in the past. However, such associations are often based on cross-sectional observations, as longitudinal studies of the progression of the disease in genotypically defined patients are sparse. Most importantly, the relative contribution of age, gender and genetic cause to disease profile and progression has not yet been reported, and the question remains whether one or more of these factors could mask the effect of the other(s). Methods: We previously described cross-sectional family studies of two hypertrophic cardiomyopathy (HCM)-causing mutations, R92WTNNT2 and R403WMYH7, both associated with minimal hypertrophy, but with widely different life expectancies. We re-investigated 22 and 26 R92WTNNT2 and R403WMYH7 mutation carriers in these and additional South African R92WTNNT2 families after a mean 11.08 ± 2.79 years, and compared the influence of the two mutations, in the context of age and gender, on disease progression. Results: We demonstrated a positive correlation between age and interventricular septal thickness for both mutations, with more than a third of all mutation carriers developing clinically recognised hypertrophy only after the age of 35 years. This period of hypertrophically silent HCM also coincided with the years in which most sudden cardiac deaths occurred, particularly in male R92WTNNT2 carriers. Statistical analyses indicated that the particular mutation was the strongest determinant of left ventricular remodelling; particularly, LVESD increased and EF reduction was noted in the majority of R403WMYH7 carriers, which may require clinical follow-up over the longer term. Conclusions: Statistical modelling of follow-up data suggests that an interplay between unidentified, possibly genderassociated factors, and the causal mutation are the determinants of eventual cardiac function and survival, but not of the extent of hypertrophy, and emphasises the need for long-term follow-up even in individuals with apparently mild disease.Publishers' Versio

Bacterial communities in the rumen of Holstein heifers differ when fed orchardgrass as pasture vs. hay

The rich and diverse microbiota of the rumen provides ruminant animals the capacity to utilize highly fibrous feedstuffs as their energy source, but there is surprisingly little information on the composition of the microbiome of ruminants fed all-forage diets, despite the importance of such agricultural production systems worldwide. In three 28-d periods, three ruminally-cannulated Holstein heifers sequentially grazed orchardgrass pasture (OP), then were fed orchardgrass hay (OH), then returned to OP. These heifers displayed greater shifts in ruminal bacterial community composition (determined by automated ribosomal intergenic spacer analysis and by pyrotag sequencing of 16S rRNA genes) than did two other heifers maintained 84 d on the same OP. Phyla Firmicutes and Bacteroidetes dominated all ruminal samples, and quantitative PCR indicated that members of the genus Prevotella averaged 23 % of the 16S rRNA gene copies, well below levels previously reported with cows fed total mixed rations. Differences in bacterial community composition and ruminal volatile fatty acid (VFA) profiles were observed between the OP and OH despite similarities in gross chemical composition. Compared to OP, feeding OH increased the molar proportion of ruminal acetate (P = 0.02) and decreased the proportion of ruminal butyrate (P < 0.01), branched-chain VFA (P < 0.01) and the relative population size of the abundant genus Butyrivibrio (P < 0.001), as determined by pyrotag sequencing. Despite the low numbers of animals examined, the observed changes in VFA profile in the rumens of heifers on OP vs. OH are consistent with the shifts in Butyrivibrio abundance and its known physiology as a butyrate producer that ferments both carbohydrates and proteins

Confocal sputtering of conformal α-β phase W films on etched Al features

The authors report on thin-film processing improvements in the fabrication of superconducting quasiparticle-trap-assisted electrothermal-feedback transition-edge sensors used in the design of cryogenic dark matter search detectors. The work was performed as part of a detector upgrade project that included optimization of a new confocal sputtering system and development of etch recipes compatible with patterning 40 nm-thick, α-β mixed-phase W films deposited on 300–600 nm-thick, patterned Al. The authors found that their standard exothermic Al wet etch recipes provided inadequate W/Al interfaces and led to poor device performance. The authors developed a modified Al wet-etch recipe that effectively mitigates geometrical step-coverage limitations while maintaining their existing device design. Data presented here include scanning electron microscope and focused ion beam images of films and device interfaces obtained with the new Al etch method. The authors also introduce a method for quantitatively measuring the energy collection efficiency through these interfaces

Black carbon as an additional indicator of the adverse health effects of airborne particles compared with PM10 and PM2.5.

Current air quality standards for particulate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM(10)) or ≤ 2.5 μm (PM(2.5))] as a metric. It has been suggested that particles from combustion sources are more relevant to human health than are particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration