349 research outputs found
Surface scattering velocities in III-nitride quantum well laser structures via the emission of hybrid phonons
We have theoretically and numerically studied nitride-based quantum well (QW)
laser structures. More specifically, we have used a QW made with III-nitride
where the width of the barrier region is large relative to the electron mean
free path, and we have calculated the electron surface capture velocities by
considering an electron flux which is captured into the well region. The
process is assisted by the emission of the longitudinal optical phonons as
predicted by the hybrid (HB) model. The results of surface capture velocities
via the emission of HB phonons are compared to the emission of the dielectric
continuum phonons (Zakhleniuk et al 1999 Phys. Status Solidi a 176 79). Our
investigation shows that the two different phonon models predict almost the
same results for the non-retarded limit. Furthermore, the surface capture
velocities strongly depend on the size of the structure and the heterostructure
materials. Lastly, a comparison to the recent experimental values shows that
our model could accurately describe the experimentally measured parameters of
the quantum capture processes
Suppression of electron relaxation and dephasing rates in quantum dots caused by external magnetic fields
An external magnetic field has been applied in laterally coupled dots (QDs)
and we have studied the QD properties related to charge decoherence. The
significance of the applied magnetic field to the suppression of
electron-phonon relaxation and dephasing rates has been explored. The coupled
QDs have been studied by varing the magnetic field and the interdot distance as
other system parameters. Our numerical results show that the electron
scattering rates are strongly dependent on the applied external magnetic field
and the details of the double QD configuration.Comment: 13 pages, 6 figure
Refined Approaches for Estimating the Strength of Rock Blocks
Micro-discrete fracture networks (μDFNs) have been integrated into grain-based models (GBMs) within the numerical software UDEC to assess rock block strength through a series of unconfined compressive strength (UCS) tests of progressively larger in size numerical specimens. GBMs were generated by utilizing a Voronoi tessellation scheme to capture the crack evolution processes within the intact rock material, and μDFNs were separately created and embedded into the GBMs to simulate the effect of pre-existing defects. Various μDFNs realisations were generated stochastically within the software FracMan to assess the combined impact of defect intensity, persistence, strength and specimen size. The resulting synthetic rock block models were used to assess the “flawed” material strength at block scale through a rigorous sensitivity numerical analysis. The acquired results predict a progressive strength reduction with decreasing intact rock quality and certain trends are captured when rock block strength is expressed as a function of a newly proposed “Defect Intensity× Persistence” factor. This allow us to standardise the data along specific strength reduction envelopes and to propose generic relationships that cover a wide range of defect geometrical combinations, defect strengths and sample sizes. Accordingly, an attempt is undertaken to refine two existing empirical approaches that consider the effect of scale and micro-defects explicitly for predicting the UCS of rock blocks
AAV9-mediated SH3TC2 gene replacement therapy targeted to Schwann cells for the treatment of CMT4C
Type 4C Charcot-Marie-Tooth (CMT4C) demyelinating neuropathy is caused by autosomal recessive SH3TC2 gene mutations. SH3TC2 is highly expressed in myelinating Schwann cells. CMT4C is a childhood-onset progressive disease without effective treatment. Here, we generated a gene therapy for CMT4C mediated by an adeno-associated viral 9 vector (AAV9) to deliver the human SH3TC2 gene in the Sh3tc2−/− mouse model of CMT4C. We used a minimal fragment of the myelin protein zero (Mpz) promoter (miniMpz), which was cloned and validated to achieve Schwann cell-targeted expression of SH3TC2. Following the demonstration of AAV9-miniMpz.SH3TC2myc vector efficacy to re-establish SH3TC2 expression in the peripheral nervous system, we performed an early as well as a delayed treatment trial in Sh3tc2−/− mice. We demonstrate both after early as well as following late treatment improvements in multiple motor performance tests and nerve conduction velocities. Moreover, treatment led to normalization of the organization of the nodes of Ranvier, which is typically deficient in CMT4C patients and Sh3tc2−/− mice, along with reduced ratios of demyelinated fibers, increased myelin thickness and reduced g-ratios at both time points of intervention. Taken together, our results provide a proof of concept for an effective and potentially translatable gene replacement therapy for CMT4C treatment
Electronic structure of rectangular quantum dots
We study the ground state properties of rectangular quantum dots by using the
spin-density-functional theory and quantum Monte Carlo methods. The dot
geometry is determined by an infinite hard-wall potential to enable comparison
to manufactured, rectangular-shaped quantum dots. We show that the electronic
structure is very sensitive to the deformation, and at realistic sizes the
non-interacting picture determines the general behavior. However, close to the
degenerate points where Hund's rule applies, we find spin-density-wave-like
solutions bracketing the partially polarized states. In the
quasi-one-dimensional limit we find permanent charge-density waves, and at a
sufficiently large deformation or low density, there are strongly localized
stable states with a broken spin-symmetry.Comment: 8 pages, 9 figures, submitted to PR
European security in the 1990s and beyond : the implications of the accession of Cyprus and Malta to the European Union
For the last decade, the dramatic events in eastern and central Europe have (rightly)
dominated the security debate in Europe and, indeed, the wider world. One of the
consequences of this has been that the traditional neglect of the Mediterranean region has
been compounded. However, there are now signs-notably the recent Barcelona conference
at which the European Union's Mediterranean policy was relaunched and extended (to incorporate the grand design of a Mediterranean free trade area) - that the Mediterranean is, at last, receiving some of the attention it deserves and justifies.peer-reviewe
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A framework for comparative institutional research on HRM
This article argues that awareness of institutional context has been singularly lacking in the most influential areas of HRM. This lack of attention to external context has resulted in findings that fail to reflect reality. We offer a layered contextual framework embedded in economic institutional theory. We propose that it forms the basis of a comparative research agenda for HRM. We validate the framework using extant publications on institutionally based comparative HRM, drawing on findings from the Cranet research network published in the decade 2007–2017
Magnetic resonance imaging findings of cellular angiofibroma of the tunica vaginalis of the testis: a case report
Managing depression in primary care: A meta-synthesis of qualitative and quantitative research from the UK to identify barriers and facilitators
Reporting on the Seminar - Risk interpretation and action (RIA): Decision making under conditions of uncertainty
The paper reports on the World Social Science (WSS) Fellows seminar on Risk Interpretation and Action (RIA), undertaken in New Zealand in December, 2013. This seminar was coordinated by the WSS Fellows program of the International Social Science Council (ISSC), the RIA working group of the Integrated Research on Disaster Risk (IRDR) program, the IRDR International Center of Excellence Taipei, the International START Secretariat and the Royal Society of New Zealand. Twenty-five early career researchers from around the world were selected to review the RIA framework under the theme of \u27decision-making under conditions of uncertainty\u27, and develop novel theoretical approaches to respond to and improve this framework. Six working groups emerged during the seminar: 1. the assessment of water-related risks in megacities; 2. rethinking risk communication; 3. the embodiment of uncertainty; 4. communication in resettlement and reconstruction phases; 5. the integration of indigenous knowledge in disaster risk reduction; and 6. multi-scale policy implementation for natural hazard risk reduction. This article documents the seminar and initial outcomes from the six groups organized; and concludes with the collective views of the participants on the RIA framework
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