The electronic band structure and optical properties of boron arsenide

We compute the electronic band structure and optical properties of boron arsenide using the relativistic quasiparticle self-consistent $GW$ approach, including electron-hole interactions through solution of the Bethe-Salpeter equation. We also calculate its electronic and optical properties using standard and hybrid density functional theory. We demonstrate that the inclusion of self-consistency and vertex corrections provides substantial improvement in the calculated band features, in particular when comparing our results to previous calculations using the single-shot $GW$ approach and various DFT methods, from which a considerable scatter in the calculated indirect and direct band gaps has been observed. We find that BAs has an indirect gap of 1.674 eV and a direct gap of 3.990 eV, consistent with experiment and other comparable computational studies. Hybrid DFT reproduces the indirect gap well, but provides less accurate values for other band features, including spin-orbit splittings. Our computed Born effective charges and dielectric constants confirm the unusually covalent bonding characteristics of this III-V system.Comment: 7 pages, 3 figure

Cranial morphology of the Plio-Pleistocene giant madtsoiid snake Wonambi naracoortensis

New material and additional morphological details of a rare and phylogenetically significant large fossil snake, Wonambi naracoortensis Smith, 1976, are described from Pleistocene and Pliocene cave deposits in southern South Australia. The new data refute some previous interpretations of the morphology of this species, and have implications for the phylogenetic position of Wonambi relative to extant snakes and other fossils, including other Madtsoiidae. The nature of contacts among palatal, braincase, snout, and mandibular elements imply similar functional attributes to those of extant anilioid snakes: maxillae from multiple individuals show corrugated contact surfaces for the prefrontal, implying a tight suture; structures on the anterior and medial surfaces of the palatine choanal process are interpreted as forming extensive contacts with the vomer and parasphenoid; and the distinctly bounded facets on the basipterygoid processes and pterygoid imply little or no capacity for anteroposterior sliding of the palatopterygoid arch, hence absence of the macrostomatan 'pterygoid walk'. On the frontal, interolfactory pillars were either absent or very slender, and a deep, sculptured contact surface for the nasal implies a prokinetic joint was also absent. Margins of the frontal and parietal indicate broad entry of the sphenoid into the ophthalmic fenestra, as in Dinilysia. Similarity of elements and features of the braincase (trigeminal foramen, ear region, and basipterygoid processes) with both lizards and extant snakes show that differences between snakes and other squamates have sometimes been overstated. The case for macrostomatan affinities of Wonambi is not supported by new evidence.John D. Scanlo

Labor problems of the junior high school teachers

Thesis (M.A.)--Boston University, 194

Costs as an aid to management

A cost system, in order to secure the best results, should, among other things, enable the manufacturing executive to know the departments or operations which require attention and thus enable him to reduce costs. A system that points out to the management wherein the actual performances differ from set standards, enables the management to concentrate on these differences and institute measures that are necessary to correct them. This article explains how standards are prepared and how comparisons of actual costs against standards are made. It also brings out how cost records are converted into efficiency data and gives a method of gauging production. It explains also the use made of reports covering departmental expense, efficiency and inventories

Brief 5: Enhancing Environmental Governance for Sustainable Development: Function-Oriented Options

The 2012 United Nations Conference on Sustainable Development, Rio+20, is likely to determine the future direction of the institutional framework for sustainable development and for international environmental governance. As States move towards the ‘sharp end’ of their negotiations, it is important to analyse some of the risks and benefits of the identified options for the reform of international environmental governance and offer pragmatic ideas on how to make best use of existing resources and structures

Understanding Student Computational Thinking with Computational Modeling

Recently, the National Research Council's framework for next generation science standards highlighted "computational thinking" as one of its "fundamental practices". 9th Grade students taking a physics course that employed the Modeling Instruction curriculum were taught to construct computational models of physical systems. Student computational thinking was assessed using a proctored programming assignment, written essay, and a series of think-aloud interviews, where the students produced and discussed a computational model of a baseball in motion via a high-level programming environment (VPython). Roughly a third of the students in the study were successful in completing the programming assignment. Student success on this assessment was tied to how students synthesized their knowledge of physics and computation. On the essay and interview assessments, students displayed unique views of the relationship between force and motion; those who spoke of this relationship in causal (rather than observational) terms tended to have more success in the programming exercise.Comment: preprint to submit to PERC proceedings 201

TraceGen: user activity emulation for digital forensic test image generation

Digital forensic test images are commonly used across a variety of digital forensic use cases including education and training, tool testing and validation, proficiency testing, malware analysis, and research and development. Using real digital evidence for these purposes is often not viable or permissible, especially when factoring in the ethical and in some cases legal considerations of working with individuals' personal data. Furthermore, when using real data it is not usually known what actions were performed when, i.e., what was the ‘ground truth’. The creation of synthetic digital forensic test images typically involves an arduous, time-consuming process of manually performing a list of actions, or following a ‘story’ to generate artefacts in a subsequently imaged disk. Besides the manual effort and time needed in executing the relevant actions in the scenario, there is often little room to build a realistic volume of non-pertinent wear-and-tear or ‘background noise’ on the suspect device, meaning the resulting disk images are inherently limited and to a certain extent simplistic. This work presents the TraceGen framework, an automated system focused on the emulation of user actions to create realistic and comprehensive artefacts in an auditable and reproducible manner. The framework consists of a series of actions contained within scripts that are executed both externally and internally to a target virtual machine. These actions use existing automation APIs to emulate a real user's behaviour on a Windows system to generate realistic and comprehensive artefacts. These actions can be quickly scripted together to form complex stories or to emulate wear-and-tear on the test image. In addition to the development of the framework, evaluation is also performed in terms of the ability to produce background artefacts at scale, and also the realism of the artefacts compared with their human-generated counterparts

Investigation of Pollution in a Karst Aquifer Utilizing Optical Brightener

Optical brightener is an additive to laundry detergents and is found contaminating groundwater. Its concentration may rapidly and inexpensively be determined by fluorescence techniques, and because its source is human wastewater, its presence in groundwater serves as a direct indication of pollution from septic tanks, sewer leaks, and landfills. A total of 105 wells and springs in an area within the Inner Bluegrass Karst Region near Lexington, Kentucky, were described and sampled. Analyses were made for optical brightener (430 samples), total coliform (91), fecal coliform (93), and fecal streptococci (90). As many as 20 optical brightener and 4 bacterial samples were analyzed from a single site during the period from May 20, 1984 to June 17, 1985. Data were also collected on spring discharges, well water.levels, and other site characteristics. Statistical analysis of the relationship between optical brightener and the bacterial indices showed low correlations for both springs and wells, in ·contrast to an earlier study. Although time constraints have precluded a thorough analysis of the data, the difference between the results of the two studies appear to be related to differing site populations and analytic and statistical procedures. The data further suggest that the low correlations between optical brightener and the bacterial indices may be a result of bacterial contamination being largely derived from animal waste and other non-human sources, and that optical brightener may be a more reliable indicator of human contamination