Exciton spectroscopy of hexagonal boron nitride using non-resonant x-ray Raman scattering

We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9 $\mathrm{\AA}^{-1}$ along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly $Y_{10}$-type Frenkel exciton with no other \textit{s}-, \textit{p}-, or \textit{d}- components. This conclusion is supported by a second, independent calculation of the \textbf{q}-dependent XRS cross-section based on the Bethe-Salpeter equation

Massive Open Online Courses and economic sustainability

Millions of users around the world have registered on Massive Open Online Courses (MOOCs) offered by hundreds of universities (and other organizations) worldwide. Creating and offering these courses costs thousands of pounds. However, at present, revenue generated by MOOCs is not sufficient to offset these costs. The sustainability of MOOCs is a pressing concern as they incur not only upfront creation costs but also maintenance costs to keep content relevant, as well as on-going facilitation support costs while a course is running and re-running. At present, charging a fee for certification seems to be a popular business model adopted by leading platform providers. In this position paper, the authors explore possible business models for courses, along with their advantages and disadvantages, by conducting a literature study and applying personal insights gained from attending various MOOC discussion fora. Some business models discussed here are: the Freemium model, sponsorships, initiatives and grants, donations, merchandise, the sale of supplementary material, selective advertising, data-sharing, follow-on events, and revenue from referrals. This paper looks at the sustainability of MOOCS as opposed to the sustainability of MOOC platforms, while observing the tight link between them

Who are with us: MOOC learners on a FutureLearn course

Massive Open Online Courses (MOOCs) attract learners with a variety of backgrounds. Engaging them using game development was trialled in a beginner’s programming course, “Begin programming: build your first mobile game”, on FutureLearn platform. The course has completed two iterations: first in autumn 2013 and second in spring 2014 with thousands of participants. This paper explores the characteristics of learner groups attracted by these two consecutive runs of the course and their perceptions of the course using pre- and post-course surveys. Recommendations for practitioners are offered, including when the audience is different to the one expected. A MOOC is unlikely to please everyone, especially with such large cohorts. Nevertheless, this course, using game development as a vehicle to teach programming, seems to have offered a balanced learning experience to a diverse group of learners. However, MOOC creators and facilitators should accept that a course cannot be made to please everyone and try to communicate clearly who the intended audience for the course are

Magnetic field symmetry of pump currents of adiabatically driven mesoscopic structures

We examine the scattering properties of a slowly and periodically driven mesoscopic sample using the Floquet function approach. One might expect that at sufficiently low driving frequencies it is only the frozen scattering matrix which is important. The frozen scattering matrix reflects the properties of the sample at a given instant of time. Indeed many aspects of adiabatic scattering can be described in terms of the frozen scattering matrix. However, we demonstrate that the Floquet scattering matrix, to first order in the driving frequency, is determined by an additional matrix which reflects the fact that the scatterer is time-dependent. This low frequency irreducible part of the Floquet matrix has symmetry properties with respect to time and/or a magnetic field direction reversal opposite to that of the frozen scattering matrix. We investigate the quantum rectification properties of a pump which additionally is subject to an external dc voltage. We split the dc current flowing through the pump into several parts with well defined properties with respect to a magnetic field and/or an applied voltage inversion.Comment: 13 pages, 4 figure

Judicialização de políticas públicas e ativismo judicial no contexto do estado constitucional: uma análise de precedentes do Supremo Tribunal Federal

A problemática da pesquisa está delimitada ao estudo dos fenômenos da judicialização e do ativismo judicial no contexto do Estado Constitucional, e nas implicações em relação ao princípio da separação dos poderes e a concretização de direitos fundamentais. Diante do tema proposto o problema limita-se a investigar se o Poder Judiciário tem atuado além dos limites de sua competência e dessa maneira ferindo o princípio da separação dos poderes. Justifica-se a pesquisa em razão da crescente incidência da manifestação dos fenômenos do ativismo judicial e da judicialização de políticas públicas no Brasil. Diante disso, observa-se que a busca ao Judiciário centra-se em questões de grande relevância social, em especial, demandas que visam a concretização de direitos fundamentais previstos na Constituição Federal de 1988, dentre as quais o direito fundamental a saúde e a educação. No modelo de Estado Constitucional, que prima pelo cumprimento da Constituição, as políticas públicas previstas na mesma, promovem na realidade a concretização dos direitos fundamentais. Neste sentido, o Poder Judiciário, notadamente o Supremo Tribunal Federal tem atuado em prol de assegurar tais demandas, no entanto, sabe-se que a competência para a elaboração e a implementação de políticas públicas primordialmente foram atribuídas ao Poder Executivo e ao Poder Legislativo. A metodologia empregada neste trabalho monográfico teve por base uma vertente de pesquisa jurídico-dogmática. Assim, na elaboração da monografia foi utilizado como fundamentação um referencial teórico, coletado mediante a realização de pesquisa bibliográfica e jurisprudencial. Apresentando como marco teórico autores como J. J. Gomes Canotilho, Antonio Enrique Perez Luño, Christine Oliveira Peter da Silva, Dimitri Dimoulis, Leonardo Martins e Ingo Wolfgang Sarlet. Contudo, verificou-se que a intervenção do Poder Judiciário em áreas predominantemente de outros Poderes no intuito de garantir direitos fundamentais, não fere a separação dos poderes, no contexto do Estado Constitucional. Ademais, a manifestação dos fenômenos do ativismo judicial e da judicialização de politicas públicas no contexto do Estado Constitucional, principalmente em razão da ideia de interdependência entre os poderes, favorece a concretização de direitos fundamentais

Exploring Parents’ Experiences of Raising a Child with Sensorimotor Impairments and Expectations for Leisure Participation

Background: The objective of this descriptive study was to study parents’ experiences of raising a child with sensorimotor impairments and how leisure pursuits impact their expectations of their children. The development and participation in leisure activities is different for these children and could affect the parents’ hopes and dreams for their child’s future. Method: Six children between 5 and 8 years of age, with sensorimotor impairments, participated in a movement program that was held for eight sessions at an outpatient pediatric clinic to address praxis and sensory processing impairments. Six parent dyads were interviewed during the fifth, sixth, seventh, or eighth session of the program. Areas addressed in the semi-structured interviews included parenting challenges, school experiences, and sensorimotor impairments effect on the child’s leisure participation. Results: Five themes emerged following the interviews: (a) nobody prepares you for sensory problems, (b) positive and negative school support, (c) when they already feel left out or behind, (d) I know the team sports are 100% sensory, and (e) life challenges. Conclusion: The parents provided the practitioners with insight into their everyday lives, and this information is essential for making occupational therapy services more family-centered

Cowpea in evolving livestock systems

Demand for livestock products has been increasing through much of the semi-arid tropics and will likely continue to increase along with the use of purchased feedstuffs. As smallholder livestock systems evolve and become more market oriented, the type of diets fed to livestock may change and the importance of feed marketing may increase. Mixed crop–livestock systems are key to meeting this increasing livestock product demand and cowpea (Vigna unguiculata [L.] Walp.) fodder (haulms) is an important component of these systems in semi-arid regions of the tropics where its high nutritional quality allows it to be used as a supplement to livestock diets based on cereal stovers and other low-quality forages. Improving the nutritional quality of cowpea fodder for use by livestock is important to improving the productivity and profitability of these mixed farming systems. Legume fodders will remain an important part of changing livestock diets and the development of cowpea varieties that better feed both people and their farm animals will give farmers new and better choices for improving levels and efficiency of livestock production. Cowpea breeding programs have worked toward producing dual-purpose varieties that emphasize the production of grain and fodder since the late 1980s and have produced several that have become well accepted when tested on-farm. Systematic screening of cowpea genetic resources is important for advancing development of dual-purpose varieties. Involvement of cultivar release agencies and seed production programs are also important to advance the use of improved dual-purpose crop varieties

Electronic structure of the strongly hybridized ferromagnet CeFe2

We report on results from high-energy spectroscopic measurements on CeFe2, a system of particular interest due to its anomalous ferromagnetism with an unusually low Curie temperature and small magnetization compared to the other rare earth-iron Laves phase compounds. Our experimental results indicate very strong hybridization of the Ce 4f states with the delocalized band states, mainly the Fe 3d states. In the interpretation and analysis of our measured spectra, we have made use of two different theoretical approaches: The first one is based on the Anderson impurity model, with surface contributions explicitly taken into account. The second method consists of band-structure calculations for bulk CeFe2. The analysis based on the Anderson impurity model gives calculated spectra in good agreement with the whole range of measured spectra, and reveals that the Ce 4f -- Fe 3d hybridization is considerably reduced at the surface, resulting in even stronger hybridization in the bulk than previously thought. The band-structure calculations are ab initio full-potential linear muffin-tin orbital calculations within the local-spin-density approximation of the density functional. The Ce 4f electrons were treated as itinerant band electrons. Interestingly, the Ce 4f partial density of states obtained from the band-structure calculations also agree well with the experimental spectra concerning both the 4f peak position and the 4f bandwidth, if the surface effects are properly taken into account. In addition, results, notably the partial spin magnetic moments, from the band-structure calculations are discussed in some detail and compared to experimental findings and earlier calculations.Comment: 10 pages, 8 figures, to appear in Phys. Rev. B in December 200

The transition from the adiabatic to the sudden limit in core level photoemission: A model study of a localized system

We consider core electron photoemission in a localized system, where there is a charge transfer excitation. The system is modelled by three electron levels, one core level and two outer levels. The model has a Coulomb interaction between these levels and the continuum states into which the core electron is emitted. The model is simple enough to allow an exact numerical solution, and with a separable potential an analytic solution. We calculate the ratio r(omega) between the weights of the satellite and the main peak as a function of the photon energy omega. The transition from the adiabatic to the sudden limit takes place for quite small photoelectron kinetic energies. For such small energies, the variation of the dipole matrix element is substantial and described by the energy scale Ed. Without the coupling to the photoelectron, the corresponding ratio r0(omega) is determined by Ed and the satellite excitation energy dE. When the interaction potential with the continuum states is introduced, a new energy scale Es=1/(2Rs^2) enters, where Rs is a length scale of the interaction potential. At threshold there is typically a (weak) constructive interference between intrinsic and extrinsic contributions, and the ratio r(omega)/r0(omega) is larger than its limiting value for large omega. The interference becomes small or weakly destructive for photoelectron energies of the order Es. For larger energies r(omega)/r0(omega) therefore typically has a weak undershoot. If this undershoot is neglected, r(omega)/r0(omega) reaches its limiting value on the energy scale Es.Comment: 18 pages, latex2e, 13 eps figure