Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods

Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on (111) Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al0.2Ga0.8N / AlN Bragg mirror followed by a lambda/2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2,mu m thick GaN layer is grown, and progressively thinned to a final thickness of lambda. Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3477450

Voltage controlled terahertz transmission through GaN quantum wells

We report measurements of radiation transmission in the 0.220--0.325 THz frequency domain through GaN quantum wells grown on sapphire substrates at room and low temperatures. A significant enhancement of the transmitted beam intensity with the applied voltage on the devices under test is found. For a deeper understanding of the physical phenomena involved, these results are compared with a phenomenological theory of light transmission under electric bias relating the transmission enhancement to changes in the differential mobility of the two-dimensional electron gas

Identifying factors likely to influence compliance with diagnostic imaging guideline recommendations for spine disorders among chiropractors in North America: a focus group study using the Theoretical Domains Framework

Background: The Theoretical Domains Framework (TDF) was developed to investigate determinants of specific clinical behaviors and inform the design of interventions to change professional behavior. This framework was used to explore the beliefs of chiropractors in an American Provider Network and two Canadian provinces about their adherence to evidence-based recommendations for spine radiography for uncomplicated back pain. The primary objective of the study was to identify chiropractors’ beliefs about managing uncomplicated back pain without xrays and to explore barriers and facilitators to implementing evidence-based recommendations on lumbar spine xrays. A secondary objective was to compare chiropractors in the United States and Canada on their beliefs regarding the use of spine x-rays. Methods: Six focus groups exploring beliefs about managing back pain without x-rays were conducted with a purposive sample. The interview guide was based upon the TDF. Focus groups were digitally recorded, transcribed verbatim, and analyzed by two independent assessors using thematic content analysis based on the TDF. Results: Five domains were identified as likely relevant. Key beliefs within these domains included the following: conflicting comments about the potential consequences of not ordering x-rays (risk of missing a pathology, avoiding adverse treatment effects, risks of litigation, determining the treatment plan, and using x-ray-driven techniques contrasted with perceived benefits of minimizing patient radiation exposure and reducing costs; beliefs about consequences); beliefs regarding professional autonomy, professional credibility, lack of standardization, and agreement with guidelines widely varied (social/professional role & identity); the influence of formal training, colleagues, and patients also appeared to be important factors (social influences); conflicting comments regarding levels of confidence and comfort in managing patients without x-rays (belief about capabilities); and guideline awareness and agreements (knowledge). Conclusions: Chiropractors’ use of diagnostic imaging appears to be influenced by a number of factors. Five key domains may be important considering the presence of conflicting beliefs, evidence of strong beliefs likely to impact the behavior of interest, and high frequency of beliefs. The results will inform the development of a theorybased survey to help identify potential targets for behavioral-change strategies

Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor

The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25–310 °C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor ( I ds > 1 A mm −1 ) to be defined (0.5 A mm −1 at 300 °C). The vertical breakdown voltage has been determined to be ∼850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current

Global Health Education: a cross-sectional study among German medical students to identify needs, deficits and potential benefits (Part 1 of 2: Mobility patterns & educational needs and demands)

<p>Abstract</p> <p>Background</p> <p>In recent years, education and training in global health has been the subject of recurring debate in many countries. However, in Germany, there has been no analysis of the educational needs or demands of medical students, or the educational deficits or potential benefits involved in global health education. Our purpose is to analyse international health elective patterns of medical students enrolled at German universities and assess whether or how they prepare for their electives abroad. We examine the exposure of medical students enrolled at German universities to training courses in tropical medicine or global health and assess students' perceived needs and demands for education in global health.</p> <p>Methods</p> <p>Cross-sectional study among medical students in Germany including all 36 medical schools during the second half of the year 2007. All registered medical students were eligible to participate in the study. Recruitment occurred via electronic mailing-lists of students' unions. We developed a web-based, semi-structured questionnaire to capture students' international mobility patterns, preparation before electives, destination countries, exposure to and demand for global health learning opportunities.</p> <p>Results</p> <p>1126 online-replies were received and analysed from all registered medical students in Germany (N = 78.067). 33.0% of all respondents (370/1126) declared at least one international health elective and of these, 36.0% (133/370) completed their electives in developing countries. 36.0% (131/363) did not prepare specifically at all, 59.0% (214/363) prepared either by self-study or declared a participation in specific preparation programmes. 87.8% of 5^thand 6^thyear students had never participated in a global health course and 72.6% (209/288) had not completed a course in tropical medicine. 94.0% (861/916) endorsed the idea of introducing global health into medical education.</p> <p>Conclusion</p> <p>Students in our sample are highly mobile during their studies. International health electives are common, also in developing countries. Formal preparation beyond self-study is virtually non-existent amongst our sample and the participation rate in courses of tropical medicine or global health is appallingly low. We have identified unmet perceived needs and the demand for more learning opportunities in global health in our sample, urging for reforms to adjust curricula to a globalising world.</p

Tools to overcome potential barriers to chlamydia screening in general practice: Qualitative evaluation of the implementation of a complex intervention

Background: Chlamydia trachomatis remains a significant public health problem. We used a complex intervention, with general practice staff, consisting of practice based workshops, posters, computer prompts and testing feedback and feedback to increase routine chlamydia screening tests in under 25 year olds in South West England. We aimed to evaluate how intervention components were received by staff and to understand what determined their implementation into ongoing practice. Methods: We used face-to-face and telephone individual interviews with 29 general practice staff analysed thematically within a Normalisation Process Theory Framework which explores: 1. Coherence (if participants understand the purpose of the intervention); 2. Cognitive participation (engagement with and implementation of the intervention); 3. Collective action (work actually undertaken that drives the intervention forwards); 4. Reflexive monitoring (assessment of the impact of the intervention). Results: Our results showed coherence as all staff including receptionists understood the purpose of the training was to make them aware of the value of chlamydia screening tests and how to increase this in their general practice. The training was described by nearly all staff as being of high quality and responsible for creating a shared understanding between staff of how to undertake routine chlamydia screening. Cognitive participation in many general practice staff teams was demonstrated through their engagement by meeting after the training to discuss implementation, which confirmed the role of each staff member and the use of materials. However several participants still felt unable to discuss chlamydia in many consultations or described sexual health as low priority among colleagues. National targets were considered so high for some general practice staff that they didn’t engage with the screening intervention. Collective action work undertaken to drive the intervention included use of computer prompts which helped staff remember to make the offer, testing rate feedback and having a designated lead. Ensuring patients collected samples when still in the general practice was not attained in most general practices. Reflexive monitoring showed positive feedback from patients and other staff about the value of screening, and feedback about the general practices testing rates helped sustain activity. Conclusions: A complex intervention including interactive workshops, materials to help implementation and feedback can help chlamydia screening testing increase in general practices

Global Health Education: a cross-sectional study among German medical students to identify needs, deficits and potential benefits (Part 2 of 2: Knowledge gaps and potential benefits)

<p>Abstract</p> <p>Background</p> <p>In Germany, educational deficits or potential benefits involved in global health education have not been analysed till now.</p> <p>Objective</p> <p>We assess the importance medical students place on learning about social determinants of health (SDH) and assess their knowledge of global health topics in relation to (i) mobility patterns, their education in (ii) tropical medicine or (iii) global health.</p> <p>Methods</p> <p>Cross-sectional study among medical students from all 36 medical schools in Germany using a web-based, semi-structured questionnaire. Participants were recruited via mailing-lists of students' unions, all medical students registered in 2007 were eligible to participate in the study. We captured international mobility patterns, exposure to global health learning opportunities and attitudes to learning about SDH. Both an objective and subjective knowledge assessment were performed.</p> <p>Results</p> <p>1126 online-replies were received and analysed. International health electives in developing countries correlated significantly with a higher importance placed on all provided SDH (p ≤ 0.006). Participation in tropical medicine (p < 0.03) and global health courses (p < 0.02) were significantly associated with a higher rating of 'culture, language and religion' and the 'economic system'. Global health trainings correlated with significantly higher ratings of the 'educational system' (p = 0.007) and the 'health system structure' (p = 0.007), while the item 'politics' was marginally significant (p = 0.053).</p> <p>In the knowledge assessment students achieved an average score of 3.6 (SD 1.5; Mdn 4.0), 75% achieved a score of 4.0 or less (Q₂₅= 3.0; Q₇₅= 4.0) from a maximum achievable score of 8.0. A better performance was associated with international health electives (p = 0.032), participation in tropical medicine (p = 0.038) and global health (p = 0.258) courses.</p> <p>Conclusion</p> <p>The importance medical students in our sample placed on learning about SDH strongly interacts with students' mobility, and participation in tropical medicine and global health courses. The knowledge assessment revealed deficits and outlined needs to further analyse education gaps in global health. Developing concerted educational interventions aimed at fostering students' engagement with SDH could make full use of synergy effects inherent in student mobility, tropical medicine and global health education.</p

The use of complementary and alternative medicine products in preceding two days among Finnish parents - a population survey

<p>Abstract</p> <p>Background</p> <p>The use of complementary and alternative medicines (CAM) has been extensively studied globally among adult and paediatric populations. Parents, as a group, had not been studied to assess their knowledge and attitude to CAM and general medicine use. This study is necessary since parents' attitude to medicine use is known to influence their child's attitude to medicine use later in life. We therefore aim to assess the extent and types of CAM use among Finnish parents, and to determine the factors that promote the CAM use. Also, we aim to determine parents' attitude to general medicine use.</p> <p>Methods</p> <p>Children less than 12 years old, as of spring 2007, were identified from the database of the Finnish Population Register Centre and were selected by random sampling. The parents of these children were identified and a questionnaire was sent to them. Only the parent who regularly takes care of the child's medicine was requested to fill the questionnaire. Cross-tabulations and Chi-square test were used to determine the associations between categorical variables. CAMs were defined as natural products that are not registered as medicines, such as homeopathic preparations, dietary food supplements, and traditional medicinal products.</p> <p>Results</p> <p>The response rate of the survey was 67% (n = 4032). The use of CAM was 31% in the preceding two days. The most commonly used CAM products were vitamins and minerals, followed by fish oils and fatty acids. Prescription and OTC medicines were used concomitantly with CAM by one-third of the parents. CAM was frequently used by parents over 30 years (33%), female parents (32%), highly educated parents (35%), and parents with high monthly net income (3000-3999 euros, 34%). The users of CAM had more negative attitudes towards medicines than non-users of CAM.</p> <p>Conclusions</p> <p>Our findings are in accordance with those of previous studies that women over 30 years of age with a high education and income typically use CAMs. Finnish parents seem to use CAMs as complementary rather than alternative to medicines. Health care professionals should take into consideration both the concomitant use as well as the negative attitudes among CAM users in encounters with the parents.</p

Appropriateness of treatment recommendations for PPI in hospital discharge letters

International audienc