Spin filtering in nanowire directional coupler

The spin transport characteristics of a nanowire directional electronic coupler have been evaluated theoretically via a transfer matrix approach. The application of a gate field in the region of mixing allows for control of spin current through the different leads of the coupler via the Rashba spin-orbit interaction. The combination of spin-orbit interaction and applied gate voltages on different legs of the coupler give rise to a controllable modulation of the spin polarization. Both structural factors and field strength tuning lead to a rich phenomenology that could be exploited in spintronic devices.Comment: 9 pages, 4 figure

Solving the time-dependent Schr\"odinger equation with absorbing boundary conditions and source terms in Mathematica 6.0

In recent decades a lot of research has been done on the numerical solution of the time-dependent Schr\"odinger equation. On the one hand, some of the proposed numerical methods do not need any kind of matrix inversion, but source terms cannot be easily implemented into this schemes; on the other, some methods involving matrix inversion can implement source terms in a natural way, but are not easy to implement into some computational software programs widely used by non-experts in programming (e.g. Mathematica). We present a simple method to solve the time-dependent Schr\"odinger equation by using a standard Crank-Nicholson method together with a Cayley's form for the finite-difference representation of evolution operator. Here, such standard numerical scheme has been simplified by inverting analytically the matrix of the evolution operator in position representation. The analytical inversion of the N x N matrix let us easily and fully implement the numerical method, with or without source terms, into Mathematica or even into any numerical computing language or computational software used for scientific computing.Comment: 15 pages, 7 figure

Systemic hemodynamic and regional circulatory effects of centrally administered endothelin-1 are mediated through ETA receptors

Central endothelin (ET) has been implicated in the regulation of the cardiovascular system. The effect of intracerebroventricular (i.c.v.) administration of ET-1 or IRL 1620 (5, 15 and 45 ng) on the systemic hemodynamics and regional circulation was studied in anesthetized rats using a radioactive microsphere technique. Systemic hemodynamics and regional blood circulation were determined before (baseline) and at 30 min after the injection of each dose of ET-1 or IRL 1620. Administration of saline (5 μl, i.c.v.) did not produce any significant cardiovascular effects. The lower doses of ET-1 (5 and 15 ng) did not produce any significant effect on blood pressure (BP), heart rate (HR), cardiac output (CO), stroke volume (SV), total peripheral resistance (TPR) and regional blood circulation. However, the higher dose (45 ng) produced a transient rise (26%) followed by a sustained fall (48%) in BP. The decrease in BP was accompanied by significant decreases in CO (44%) and SV (39%), while HR and TPR were not affected. ET-1 (45 ng, i.c.v.) also produced a significant reduction in blood flow to the brain (75%), heart (49%), kidneys (66%), GIT (40%), portal system (52%) and musculo-skeletal system (38%), while blood flow to the skin was not affected. To determine pharmacological specificity of the central effects of ET-1, studies were performed in rats pretreated with BQ-123, a specific ETA receptor antagonist. Pretreatment with BQ-123 (10 μg, i.c.v.), 15 min prior to the administration of ET-1, completely antagonized the systemic hemodynamic as well as the regional circulatory effects of ET-1 (45 ng, i.c.v.). In order to determine whether stimulation of central ETB receptors produces any cardiovascular effects, studies were performed using IRL 1620, a specific ETB receptor agonist. Administration of IRL 1620 (5, 15 and 45 ng, i.c.v.) did not produce any effect on systemic hemodynamics and regional blood circulation in rats. It is concluded that ETA but not ETB receptors are involved in the central cardiovascular actions of ET

What factors influence UK medical students' choice of foundation school?

Background: We aimed to identify the factors influencing UK medical student applicants’ choice of foundation school. We also explored the factors that doctors currently approaching the end of their 2-year program believe should be considered. Methods: A cross-sectional study was conducted during the 2013–2014 academic year. An online questionnaire was distributed to 2092 final-year medical students from nine UK medical schools and 84 foundation year-2 (FY2) doctors from eight foundation schools. Participants were asked to rank their top 3 from a list of 12 factors that could potentially influence choice of foundation school on a 5-point Likert scale. Collated categorical data from the two groups were compared using a chi-square test with Yates correction. Results: Geographic location was overwhelmingly the most important factor for medical students and FY2 doctors with 97.2% and 98.8% in agreement, respectively. Social relationships played a pivotal role for medical student applicants. Clinical specialties within the rotations were of less importance to medical students, in comparison to location and social relationships. In contrast, FY2 doctors placed a significantly greater importance on the specialties undertaken in their 2-year training program, when compared to medical students (chi-square; p=0.0001). Conclusion: UK medical schools should make their foundation program applicants aware of the importance of choosing rotations based on specialties that will be undertaken. Individual foundation schools could provide a more favorable linked application system and greater choice and flexibility of specialties within their 2-year program, potentially making their institution more attractive to future applicants

Tuning hole mobility in InP nanowires

Transport properties of holes in InP nanowires were calculated considering electron-phonon interaction via deformation potentials, the effect of temperature and strain fields. Using molecular dynamics, we simulate nanowire structures, LO-phonon energy renormalization and lifetime. The valence band ground state changes between light- and heavy-hole character, as the strain fields and the nanowire size are changed. Drastic changes in the mobility arise with the onset of resonance between the LO-phonons and the separation between valence subbands.Comment: 4 pages, 4 figure

Modernização da agricultura na mesorregião do Nordeste paraense (PA): determinantes e hierarquização.

O trabalho analisa o nível de modernização agrícola da mesorregião do Nordeste Paraense (PA). Para descrever o padrão tecnológico e a classificação relativa dos municípios, utilizou-se a técnica de análise fatorial. Os dados utilizados foram obtidos junto ao Instituto Brasileiro de Geografia e Estatística (IBGE). Os resultados mostram a existência de uma grande discrepância no nível tecnológico entre os municípios analisados, evidenciando um contraste nos indicadores relacionados à modernização da agricultura. Dos 45 municípios analisados, apenas quatro atingiram índices de modernização acima de 50%, quando comparados entre si. São eles: Tailândia, Igarapé-Açu, Curuçá e São Francisco do Pará. Do outro lado, os cinco municípios com níveis de modernização mais atrasados são: Mocajuba, Augusto Corrêa, Colares, Limoeiro do Ajuru e Cametá

Dinâmica populacional na Amazônia: o caso dos estados do Amazonas e Pará.

O estudo da dinâmica populacional demonstra a conformação de um dado território no que diz respeito a sua socioeconomia, condições ambientais e culturais, daí a importância de tais análises. Ao considerar a Amazônia, pôde-se notar que muitos surtos migratórios foram induzidos pelo governo brasileiro. Neste trabalho analisou-se a evolução populacional na região a partir de uma série histórica de dados do Instituto Brasileiro de Geografia e Estatística (IBGE), entre os anos de 1872 e 2007, particularmente os referentes aos estados do Amazonas e Pará, visto serem as áreas de colonização mais antiga na região. Constatou-se um crescimento populacional considerável no período analisado, acima da média nacional, tanto no Amazonas quanto no Pará, o que acena para a necessidade de uma melhor infraestrutura e organização de seu espaço territorial, assim como da modernização no setor agropecuário como forma estratégica de promover o desenvolvimento mais sustentável para a Amazônia

Composição centesimal e minerais de farinha extrudada de cascas e albedo de maracujá e arroz.

Edição dos Resumos do VI Congresso Latinoamericano e XII Congresso Brasileiro de Higienistas de Alimentos, II Encontro Nacional de Vigilância das Zoonoses, IV Encontro do Sistema Brasileiro de Inspeção de Produtos de Origem Animal, Gramado, abr. 2013