Modelling of AlAs/GaAs interfacial structures using high-angle annular dark field (HAADF) image simulations

High angle annular dark field (HAADF) image simulations were performed on a series of AlAs/GaAsinterfacial models using the frozen-phonon multislice method. Three general types of models were considered—perfect, vicinal/sawtooth and diffusion. These were chosen to demonstrate how HAADFimage measurements are influenced by different interfacialstructures in the technologically important III–V semiconductor system. For each model, interfacial sharpness was calculated as a function of depth and compared to aberration-corrected HAADF experiments of two types of AlAs/GaAs interfaces. The results show that the sharpness measured from HAADF imaging changes in a complicated manner with thickness for complex interfacialstructures. For vicinal structures, it was revealed that the type of material that the probe projects through first of all has a significant effect on the measured sharpness. An increase in the vicinal angle was also shown to generate a wider interface in the random step model. The Moison diffusion model produced an increase in the interface width with depth which closely matched the experimental results of the AlAs-on-GaAs interface. In contrast, the interface width decreased as a function of depth in the linear diffusion model. Only in the case of the perfect model was it possible to ascertain the underlying structure directly from HAADFimage analysis

University access for disadvantaged children: A comparison across countries

In this paper, we consider whether certain countries are particularly adept (or particularly poor) at getting children from disadvantaged homes to study for a bachelor’s degree. A series of university access models are estimated for four English-speaking countries (England, Canada, Australia and the USA), which include controls for comparable measures of academic achievement at age 15. Our results suggest that socioeconomic differences in university access are more pronounced in England and Canada than Australia and the USA and that cross-national variation in the socioeconomic gap remains even once we take account of differences in academic achievement. We discuss the implications of our findings for the creation of more socially mobile societies

Evaluation of a spring-powered captive bolt gun for killing kangaroo pouch young

Context: During commercial harvesting or non-commercial kangaroo culling programs, dependent young of shot females are required to be euthanased to prevent suffering and because they would be unlikely to survive. However, the current method for killing pouch young, namely a single, forceful blow to the base of the skull, is applied inconsistently by operators and perceived by the public to be inhumane. Aims: To determine whether an alternative method for killing pouch young, namely a spring-operated captive bolt gun, is effective at causing insensibility in kangaroo pouch young. Methods: Trials of spring-operated captive bolt guns were conducted first on the heads of 15 dead kangaroo young and then on 21 live pouch young during commercial harvesting. We assessed the effectiveness at causing insensibility in live animals and damage caused to specific brain areas. We also measured depth of bolt penetration and skull thickness. Performance characteristics (e.g. bolt velocity) of two types of spring-operated guns were also measured and compared with cartridge-powered devices. Key results: When tested on the heads of dead animals, the spring-operated captive bolt gun consistently produced a large entrance cavity and a well defined wound tract, which extended into the cerebrum, almost extending the full thickness of the brain, including the brainstem. When tested on live pouch young, the captive bolt gun caused immediate insensibility in only 13 of 21 animals. This 62% success rate is significantly below the 95% minimum acceptable threshold for captive bolt devices in domestic animal abattoirs. Failure to stun was related to bolt placement, but other factors such as bolt velocity, bolt diameter and skull properties such as thickness and hardness might have also contributed. Spring-operated captive bolt guns delivered 20 times less kinetic energy than did cartridge-powered devices. Conclusions: Spring-operated captive bolt guns cannot be recommended as an acceptable or humane method for stunning or killing kangaroo pouch young. Implications: Captive bolt guns have potential as a practical alternative to blunt head trauma for effective euthanasia and reducing animal (and observer) distress. However, operators must continue to use the existing prescribed killing methods until cartridge-powered captive bolt guns have been trialled as an alternative bolt propelling method. Additional keywords: animal welfare, blunt trauma, culling, euthanasia, humaneness, kangaroo harvesting

The Accessibility Quotient: A New Measure of Open Access

INTRODUCTION The Accessibility Quotient (AQ), a new measure for assisting authors and librarians in assessing and characterizing the degree of accessibility for a group of papers, is proposed and described. The AQ offers a concise measure that assesses the accessibility of peer-reviewed research produced by an individual or group, by incorporating data on open availability to readers worldwide, the degree of financial barrier to access, and journal quality. The paper reports on the context for developing this measure, how the AQ is calculated, how it can be used in faculty outreach, and why it is a useful lens to use in assessing progress towards more open access to research. METHODS Journal articles published in 2009 and 2010 by faculty members from one department in each of MIT’s five schools were examined. The AQ was calculated using economist Ted Bergstrom’s Relative Price Index to assess affordability and quality, and data from SHERPA/RoMEO to assess the right to share the peer-reviewed version of an article. RESULTS The results show that 2009 and 2010 publications by the Media Lab and Physics have the potential to be more open than those of Sloan (Management), Mechanical Engineering, and Linguistics & Philosophy. DISCUSSION Appropriate interpretation and applications of the AQ are discussed and some limitations of the measure are examined, with suggestions for future studies which may improve the accuracy and relevance of the AQ. CONCLUSION The AQ offers a concise assessment of accessibility for authors, departments, disciplines, or universities who wish to characterize or understand the degree of access to their research output, capturing additional dimensions of accessibility that matter to faculty

Pharmacy workers in Kenya need training and support on medical abortion information and referrals to prevent unsafe service provision

Despite the centrality of pharmacists in the provision of abortion services in Kenya, little is known about their medical abortion (MA) knowledge, attitudes, or practices. This policy brief reports on a study that set out to bridge this gap in the evidence. The report concludes that comprehensive training for pharmacy workers could improve the quality of MA provision and referrals, and help pharmacy workers identify opportunities to simultaneously provide clients with information on contraception and STI prevention. Such efforts would be in line with current Kenyan government policies to reduce the public health burden caused by the prevalence of unsafe abortion and HIV, and within the boundaries of the current legal framework

Structure of Hordeum vulgare NADPH-dependent thioredoxin reductase 2. Unwinding the reaction mechanism

Thioredoxins (Trxs) are protein disulfide reductases that regulate the intracellular redox environment and are important for seed germination in plants. Trxs are in turn regulated by NADPH-dependent thioredoxin reductases (NTRs), which provide reducing equivalents to Trx using NADPH to recycle Trxs to the active form. Here, the first crystal structure of a cereal NTR, HvNTR2 from Hordeum vulgare (barley), is presented, which is also the first structure of a monocot plant NTR. The structure was determined at 2.6 Å resolution and refined to an R (cryst) of 19.0% and an R (free) of 23.8%. The dimeric protein is structurally similar to the structures of AtNTR-B from Arabidopsis thaliana and other known low-molecular-weight NTRs. However, the relative position of the two NTR cofactor-binding domains, the FAD and the NADPH domains, is not the same. The NADPH domain is rotated by 25° and bent by a 38% closure relative to the FAD domain in comparison with AtNTR-B. The structure may represent an intermediate between the two conformations described pre­viously: the flavin-oxidizing (FO) and the flavin-reducing (FR) conformations. Here, analysis of interdomain contacts as well as phylogenetic studies lead to the proposal of a new reaction scheme in which NTR–Trx interactions mediate the FO to FR transformation

Smoke-water enhances in vitro pollen germination and tube elongation of three species of Amaryllidaceae

AbstractSmoke-water prepared from burning plant material and smoke-derived compounds significantly promote seed germination and enhance growth of many plant species. Since large amounts of smoke are generated and released into the air during wildfires, it is possible that angiosperm pollen germination and pollen tube elongation may be affected by plant-derived smoke even when the plants are some distance from the fire. We assessed the effect of smoke on pollen germination and pollen tube elongation for three species of Amaryllidaceae that occur naturally in areas prone to winter fire in South Africa. In vitro pollen germination and pollen tube growth of Clivia gardenii, Cyrtanthus mackenii and Scadoxus multiflorus were assessed by preparing hanging drop slides with different concentrations of smoke-water, karrikinolide and 3,4,5-trimethylfuran-2(5H)-one combined with Brewbaker and Kwack's medium and a sucrose and boric acid medium. These slides were incubated for 2h at 25°C. Pollen germination and pollen tube lengths were recorded by capturing images with a compound microscope aided by a digital camera. Low concentrations of smoke-water (1:1000 and 1:2000 v:v) significantly increased pollen germination and pollen tube length in the three species, when applied alone or in combination with either Brewbaker and Kwack's medium or sucrose and boric acid medium. Low concentrations of smoke-water significantly increased in vitro pollen germination and pollen tube growth even when no additional calcium was added. Consequently, smoke from grassland fires may have favourable implications for the reproductive process of flowering plants

Heavy metal contamination in South African medicinal plants: A cause for concern

AbstractThe quality and safety of herbal medicines is becoming a major concern worldwide particularly due to contamination by heavy metals. The present study quantified the levels of heavy metals in frequently used South African medicinal plants and determined the variations in certain biological activities and phytochemical compositions. Eleven plant species were obtained from both muthi shops (MS) (commercial outlets) and from open street markets (OSM) for comparison. Samples were dried, powdered and digested using microwave acid-assisted digestion. The digested solutions were analysed for heavy metals using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Plants were classified based on their elemental composition using chemometric techniques. Powdered plant samples were extracted using 70% acetone and screened for antibacterial activity against E. coli and S. aureus. Phytochemical analyses were carried out to determine total phenolic and flavonoid content. Of the 22 samples analysed, Bulbine natalensis obtained from OSM and Alepidea amatymbica obtained from MS exhibited high levels of Al [5559 and 4392mg/kg dry weight (DW)] and Fe (4164 and 4465mg/kg DW) respectively. Levels of As and Hg were above the World Health Organization permissible limits in most of the samples analysed. Hierarchical cluster analysis classified the samples into four groups based on their metallic analyte concentrations. Group one having low metal content and group four having a high metal content. In general, plant samples with high levels of metals yielded greater antibacterial activity. However, antibacterial activity recorded in this study is not an indicator of high levels of heavy metal contamination as some samples despite the high levels of metal exhibited low antibacterial activity. The variations in the amounts of phenolics and flavonoids in the evaluated samples could have probably been that some of the plant samples may have been harvested from different localities or at different times of the year, perhaps plant age or degree of storage. The results highlighted the need for in-depth risk and quality assessments