Scattering states of coupled valence-band holes in point defect potential derived from variable phase theory

In this article we present a method to compute the scattering states of holes in spherical bands in the strong spin-orbit coupling regime. More precisely, we calculate scattering phase shifts and amplitudes of holes induced by defects in a semiconductor crystal. We follow a previous work done on this topic by Ralph [H. I. Ralph, Philips Res. Rept. 32 160 (1977)] to account for the p-wave nature and the coupling of valence band states. We extend Ralph's analysis to incorporate finite-range potentials in the scattering problem. We find that the variable phase method provides a very convenient framework for our purposes and show in detail how scattering amplitudes and phase shifts are obtained. The Green's matrix of the Schroedinger equation, the Lippmann-Schwinger equation and the Born approximation are also discussed. Examples are provided to illustrate our calculations with Yukawa type potentials.Comment: 16 pages and 9 figure

Coulomb singularities in scattering wave functions of spin-orbit-coupled states

We report on our analysis of the Coulomb singularity problem in the frame of the coupled channel scattering theory including spin-orbit interaction. We assume that the coupling between the partial wave components involves orbital angular momenta such that $\Delta l = 0, \pm 2$. In these conditions, the two radial functions, components of a partial wave associated to two values of the angular momentum $l$, satisfy a system of two second-order ordinary differential equations. We examine the difficulties arising in the analysis of the behavior of the regular solutions near the origin because of this coupling. First, we demonstrate that for a singularity of the first kind in the potential, one of the solutions is not amenable to a power series expansion. The use of the Lippmann-Schwinger equations confirms this fact: a logarithmic divergence arises at the second iteration. To overcome this difficulty, we introduce two auxilliary functions which, together with the two radial functions, satisfy a system of four first-order differential equations. The reduction of the order of the differential system enables us to use a matrix-based approach, which generalizes the standard Frobenius method. We illustrate our analysis with numerical calculations of coupled scattering wave functions in a solid-state system

Competency mapping framework for regulating professionally oriented degree programmes in higher education

Recognition of the huge variation between professional graduate degree programmes and employer requirements, especially in the construction industry, necessitated a need for assessing and developing competencies that aligned with professionally oriented programmes. The purpose of this research is to develop a competency mapping framework (CMF) in this case for quantity surveying honours degree programmes. The graduate competency threshold benchmark (GCTB) is a key component of the CMF. Therefore, the CMF contains the mapping process, the template documents and the benchmark. The research adopted literature review, pilot study, case studies (including semi-structured interviews) and expert forum in developing the framework. The framework developed in this research provides new insight into how degree programmes map against competencies. Thus, the framework can be applied more widely, to other professional degree programmes, for monitoring and improving the quality and professional standards of construction degree programmes by accrediting bodies. This should connect construction graduates more effectively to the industry

Misuse of “Power” and other mechanical terms in sport and exercise science research

In spite of the Système International d’Unitès (SI) that was published in 1960, there continues to be widespread misuse of the terms and nomenclature of mechanics in descriptions of exercise performance. Misuse applies principally to failure to distinguish between mass and weight, velocity and speed, and especially the terms "work" and "power." These terms are incorrectly applied across the spectrum from high-intensity short-duration to long-duration endurance exercise. This review identifies these misapplications and proposes solutions. Solutions include adoption of the term "intensity" in descriptions and categorisations of challenge imposed on an individual as they perform exercise, followed by correct use of SI terms and units appropriate to the specific kind of exercise performed. Such adoption must occur by authors and reviewers of sport and exercise research reports to satisfy the principles and practices of science and for the field to advance

AD Leonis: Radial Velocity Signal of Stellar Rotation or Spin–Orbit Resonance?

AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days, as well as photometric signals: (1) a short-period signal, which is similar to the radial velocity signal, albeit with considerable variability; and (2) a long-term activity cycle of 4070 ± 120 days. We examine the short-term photometric signal in the available All-Sky Automated Survey and Microvariability and Oscillations of STars (MOST) photometry and find that the signal is not consistently present and varies considerably as a function of time. This signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set, which are separated in median time by 3.38 days. In contrast, the Doppler signal is stable in the combined High-Accuracy Radial velocity Planet Searcher and High Resolution Echelle Spectrometer radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period, or as a function of extracted wavelength. We consider a variety of starspot scenarios and find it challenging to simultaneously explain the rapidly varying photometric signal and the stable radial velocity signal as being caused by starspots corotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin–orbit resonance. For such a scenario and no spin–orbit misalignment, the measured v sin i indicates an inclination angle of 15°̣5 ± 2°̣5 and a planetary companion mass of 0.237 ± 0.047 M Jup

Tamoxifen for prevention of breast cancer: extended long-term follow-up of the IBIS-I breast cancer prevention trial

© Cuzick et al. Open Access article distributed under the terms of CC BY.http://dx.doi.org/10.1016/S1470-2045(14)71171-

Key conservation issues for migratory landand waterbird species on the world’s major flyways

Summary An estimated 19% of the world's 9,856 extant bird species are migratory, including some 1,600 species of land-and waterbirds. In 2008, 11% of migratory land-and waterbirds were classed by BirdLife International as threatened or near-threatened on the IUCN Red List. Red List indices show that these migrants have become more threatened since 1988, with 33 species deteriorating and just six improving in status. There is also increasing evidence of regional declines. Population trend data show that more Nearctic-Neotropical migrants have declined than increased in North America since the 1980s, and more Palearctic-Afrotropical migrants breeding in Europe declined than increased during 1970-2000. Reviews of the status of migratory raptors show unfavourable conservation status for 51% of species in the African-Eurasian region (in 2005), and 33% of species in Central, South and East Asia (in 2007). Land-use change owing to agriculture is the most frequently cited threat affecting nearly 80% of all threatened and nearthreatened species. However, while agricultural intensification on the breeding grounds is often proposed as the major driver of declines in Palearctic-Afrotropical migrants, some species appear to be limited by the quantity and quality of available habitat in non-breeding areas, notably the drylands of tropical Africa. Forest fragmentation in breeding areas has contributed to the declines of Nearctic-Neotropical migrants with deforestation in non-breeding areas another possible factor. Infrastructure development including wind turbines, cables, towers and masts can also be a threat. Over-harvesting and persecution remain serious threats, particularly at key migration locations. Climate change is affecting birds already, is expected to exacerbate all these pressures, and may also increase competition between migratory and non-migratory species. The conservation of migratory birds thus requires a multitude of approaches. Many migratory birds require effective management of their critical sites, and Important Bird Areas (IBAs) provide an important foundation for such action; however to function effectively in conserving migratory species, IBAs need to be protected and the coherence of the network requires regular review. Since many migratory species (c. 55%) are widely dispersed across their breeding or nonbreeding ranges, it is essential to address the human-induced changes at the wider landscape scale, a very considerable challenge. Efforts to conserve migratory birds in one part of the range are less effective if unaddressed threats are reducing these species' populations and habitats elsewhere. International collaboration and coordinated action along migration flyways as a whole are thus key elements in any strategy for the conservation of migratory birds

Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization.

The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD