Rashba spin-orbit coupling and spin relaxation in silicon quantum wells

Silicon is a leading candidate material for spin-based devices, and two-dimensional electron gases (2DEGs) formed in silicon heterostructures have been proposed for both spin transport and quantum dot quantum computing applications. The key parameter for these applications is the spin relaxation time. Here we apply the theory of D'yakonov and Perel' (DP) to calculate the electron spin resonance linewidth of a silicon 2DEG due to structural inversion asymmetry for arbitrary static magnetic field direction at low temperatures. We estimate the Rashba spin-orbit coupling coefficient in silicon quantum wells and find the $T_{1}$ and $T_{2}$ times of the spins from this mechanism as a function of momentum scattering time, magnetic field, and device-specific parameters. We obtain agreement with existing data for the angular dependence of the relaxation times and show that the magnitudes are consistent with the DP mechanism. We suggest how to increase the relaxation times by appropriate device design.Comment: Extended derivations and info, fixed typos and refs, updated figs and data. Worth a re-downloa

Healthcare professionals' self-reported experiences and preferences related to direct healthcare professional communications:a survey conducted in the Netherlands

Background: In Europe, Direct Healthcare Professional Communications (DHPCs) are important tools to inform healthcare professionals of serious, new drug safety issues. However, this tool has not always been successful in effectively communicating the desired actions to healthcare professionals. Objective: The aim of this study was to explore healthcare providers' experiences and their preferences for improvement of risk communication, comparing views of general practitioners (GPs), internists, community pharmacists and hospital pharmacists. Methods: A questionnaire was developed and pilot tested to assess experiences and preferences of Dutch healthcare professionals with DHPCs. The questionnaire and two reminders were sent to a random sample of 3488 GPs, internists and community and hospital pharmacists in the Netherlands. Descriptive statistics were used to describe demographic characteristics of the respondents. Chi squares, ANOVAs and the Wilcoxon signed rank test were used, when appropriate, to compare healthcare professional groups. Results: The overall response rate was 34% (N=1141, ranging from 24% for internists to 46% for community pharmacists). Healthcare providers trusted safety information more when provided by the Dutch Medicines Evaluation Board (MEB) than by the pharmaceutical industry. This was more the case for GPs than for the other healthcare professionals. Respondents preferred safety information to be issued by the MEB, the Dutch Pharmacovigilance Center or their own professional associations. The preferred alternative channels of drug safety information were e-mail, medical journals and electronic prescribing systems. Conclusions: Safety information of drugs does not always reach healthcare professionals through DHPCs. To improve current risk communication of drug safety issues, alternative and/or additional methods of risk communication should be developed using electronic methods and medical journals. Moreover, (additional) risk communication coming from an independent source such as the MEB should be considered. Special effort is needed to reach GPs

Modest effect of p53, EGFR and HER-2/neu on prognosis in epithelial ovarian cancer: a meta-analysis

Background: P53, egfr and her-2/neu are the most frequently studied molecular biological parameters in epithelial ovarian cancer, but their prognostic impact is still unequivocal. We performed a meta-analysis to more precisely estimate their prognostic significance. Methods: Published studies that investigated the association between p53, egfr and her-2/neu status and survival were identified. Meta-analysis was performed using a dersimonian-laird model. Publication bias was investigated using funnel plots and sources of heterogeneity were identified using meta-regression analysis. Results: A total of 62 studies were included for p53, 15 for egfr and 20 for her-2/neu. P53, egfr and her-2/neu status had a modest effect on overall survival (Pooled hr 1.47, 95% Ci 1.33-1.61 For p53; Hr 1.65, 95% Ci 1.25-2.19 For egfr and hr 1.67, 95% Ci 1.34-2.08 For her-2/neu). Meta-regression analysis for p53 showed that figo stage distribution influenced study outcome. For egfr and her-2/neu, considerable publication bias was present. Conclusions: Although p53, egfr and her-2/neu status modestly influences survival, these markers are, by themselves, unlikely to be useful as prognostic markers in clinical practice. Our study highlights the need for well-defined, prospective clinical trials and more complete reporting of results of prognostic factor studies. British journal of cancer ( 2009) 101, 149-159. Doi: 10.1038/Sj.Bjc.6605112 Www.Bjcancer.Com published online 9 june 2009 (C) 2009 Cancer research uk

UMA INVESTIGAÇÃO SOBRE O PAPEL MOTIVADOR DO TUTOR DE ACORDO COM A VISÃO DOS ALUNOS DOS CURSOS DE CAPACITAÇÃO DO MINISTÉRIO DA SAÚDE.

A motivação é um dos elementos essenciais para uma aprendizagem eficiente e de qualidade. Um aluno motivado aprende melhor, uma vez que todo aluno é motivado pelo êxito ou inibido pelo fracasso. No ensino a distância a motivação dos alunos é o centro das atenções no processo educacional, uma vez que se tem o reconhecimento de que a aprendizagem é um processo pessoal, sistemático e reflexivo e que depende do despertar do aluno para suas potencialidades, que pode ser sozinho ou com ajuda do tutor. O presente estudo relata uma pesquisa realizada com os três cursos de capacitação a distância, do quarto módulo, oferecidos aos funcionários do Ministério da Saúde em parceria com a Universidade Federal de Santa Catarina – UFSC, sendo que esta parceria existe desde 2007 para os cursos de capacitação. Os cursos são oferecidos em módulos de quarenta e cinco e de sessenta horas. Este estudo tem com o objetivo investigar a postura motivadora do tutor na visão dos alunos que estão finalizando os cursos do quarto módulo de capacitação. Trata-se de um estudo de caso, com uma pesquisa bibliográfica e descritiva, tendo uma abordagem quantitativa. Este estuda destaca que os alunos sentem-se motivados a continuar perseverantes nos cursos de capacitação em estudo-aprendizagem através de uma comunicação clara e contínua, uma vez que a dificuldade com o uso das tecnologias de informação e comunicação (internet, AVEA) são os maiores fatores de dificuldade do aluno do Mistério da Saúde