470 research outputs found

    Superconductivity in Group III-V Semiconductor AlN Under High Pressure

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    The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO) method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization). On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc) of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI: http://dx.doi.org/10.17807/orbital.v7i3.62

    Superconductivity in Group III-V Semiconductor AlN Under High Pressure

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    The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO) method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization). On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc) of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI: http://dx.doi.org/10.17807/orbital.v7i3.62

    The actions of the Brazilian agricultural sector in the context of climate change negotiations.

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    Brazil has always maintained a prominent position in negotiations within the United Nations Framework Convention on Climate Change, playing a major role in setting increasingly ambitious goals and encouraging consensus among Parties. With the purpose of reducing GHG emissions from the agricultural sector and disseminating and financing good agricultural practices, Brazil developed a platform of sustainable technologies and public policies, as the Low Carbon Agriculture Plan (the "ABC Plan"). This article reviews the main milestones of Brazil's role in the international negotiation on climate change, how these factors affected the Brazilian agricultural sector between 2009 and 2018 and the authors' personal view on this context. The objective is to provide an overview of Brazil's actions regarding the agricultural sector which contribute to the voluntary commitment assumed by the Brazilian government at COPs 15 and 21 and to provide a critical analysis of how these actions are being implemented. The main results show that low carbon agriculture has been consolidated as the main Brazilian strategy for sustainable rural development, but it is vital for our country to continue with these actions. O Brasil sempre manteve uma posição de destaque nas negociações da Convenção-Quadro das Nações Unidas sobre Mudança do Clima, desempenhando um papel importante no estabelecimento de metas cada vez mais ambiciosas e no incentivo ao consenso entre as Partes. Com o objetivo de reduzir as emissões de Gases de Efeito Estufa (GEE) do setor agrícola e disseminar e financiar boas práticas agrícolas, o Brasil desenvolveu uma plataforma de tecnologias e políticas públicas sustentáveis, como o Plano de Agricultura de Baixo Carbono (o "Plano ABC"). O presente artigo faz uma revisão dos principais marcos da atuação do Brasil no âmbito da negociação internacional sobre mudança do clima, como esses fatores afetaram o setor agrícola brasileiro, entre 2009 e 2018, e a visão pessoal dos autores sobre esse contexto. O objetivo é fornecer uma visão geral das ações do Brasil em relação ao setor agrícola, que contribuem para o compromisso voluntário assumido pelo governo brasileiro nas COPs 15 e 21 e para fornecer uma análise crítica de como essas ações estão sendo implementadas. Os principais resultados mostram que a agricultura de baixo carbono se consolidou como a principal estratégia brasileira para o desenvolvimento rural sustentável, porém é vital que o país continue com essas ações.Título em português: As ações do setor agropecuário brasileiro no contexto das negociações sobre mudança do clima

    Satisfaction and experience with colorectal cancer screening : a systematic review of validated patient reported outcome measures

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    Background: Patient satisfaction or experience with colorectal cancer screening can determine adherence to screening programs. An evaluation of validated patient reported outcome measures (PROMs) for measuring experience or satisfaction with colorectal cancer screening does not exist. Our objective was to identify and critically appraise validated questionnaires for measuring patient satisfaction or experience with colorectal cancer screening. Methods: We conducted a systematic review following the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology. We conducted searches on MEDLINE, EMBASE, PsychINFO, CINAHL and BiblioPRO and assessed the methodological quality of studies and measurement properties of questionnaires according to the COSMIN guidelines for systematic reviews of PROMs. PROSPERO registration number: CRD42019118527. Results: We included 80 studies that used 75 questionnaires, of which only 5 were validated. Four questionnaires measured satisfaction with endoscopy: two in the context of colorectal cancer screening (for colonoscopy and sigmoidoscopy) and two for non-screening endoscopy. One questionnaire measured satisfaction with bowel preparation. The methodological quality of studies was variable. The questionnaires with evidence for sufficient content validity and internal consistency were: the CSSQP questionnaire, which measures safety and satisfaction with screening colonoscopy, and the Post-Procedure questionnaire which measures satisfaction with non-screening endoscopic procedures. Conclusions: This systematic review shows that a minority of existing PROMs for measuring patient satisfaction with colorectal cancer screening are validated. We identified two questionnaires with high potential for further use (CSSQP and the Post-Procedure questionnaire)

    Computerized tomography texture analysis of pheochromocytoma: relationship with hormonal and histopathological data

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    Objectives Pheochromocytomas are rare tumors which can present with heterogeneous secretion profiles, clinical manifestations, and radiologic appearance. Under a histopathological point of view, they can be characterized as more or less aggressive with the Pheochromocytoma of the Adrenal gland Scaled Score (PASS) and the Grading system for Adrenal Pheochromocytoma and Paraganglioma (GAPP) score. The aim of this study is to analyze the texture analysis characteristics of pheochromocytoma and identify whether the texture analysis can yield information aiding in the diagnosis and the characterization of those tumors. Methods Radiological, biochemical, and histopathological data regarding 30 consecutive patients with histologically confirmed pheochromocytoma were analyzed. Images obtained in the unenhanced, late arterial, venous, and delayed phases were used for the texture analysis. Results Urinary epinephrine and metanephrine levels showed a significant correlation (R-2 = 0.946; R-2 = 699) in the multivariate linear model with texture features, as well as Ki-67 (R-2 = 0.397), PASS score (R-2 = 0.182), GAPP score (R-2 = 0.705), and cellularity showed a significant correlation (R-2 = 0.389). The cluster analysis based on radiomic features resulted in 2 clusters, with significative differences in terms of systolic and diastolic blood pressure values at the time of diagnosis (p = 0.025), GAPP score (4 vs 6, p = 0.05), histological pattern (1-2, p = 0.039), and comedonecrosis (0% vs 50%, p = 0.013). Conclusion In conclusion, our study provides the proof of concept for the use of texture analysis on contrast-enhanced CT images as a noninvasive, quantitative tool for helping in the characterization of the clinical, biochemical, and histopathological features of pheochromocytoma

    Strongly correlated quantum dots in weak confinement potentials and magnetic fields

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    We explore a strongly correlated quantum dot in the presence of a weak confinement potential and a weak magnetic field. Our exact diagonalization studies show that the groundstate property of such a quantum dot is rather sensitive to the magnetic field and the strength of the confinement potential. We have determined rich phase diagrams of these quantum dots. Some experimental consequences of the obtained phase diagrams are discussed.Comment: 5 pages, 7 figures, new and updated figure

    Defining anti-synthetase syndrome: a systematic literature review

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    OBJECTIVES: Anti-synthetase syndrome (ASSD) is a heterogeneous autoimmune disease characterised by multi-system involvement with a wide variety of manifestations. Validated classification criteria are necessary to improve recognition and prevent misclassification, especially given the lack of reliable and standardised autoantibody testing. We systematically reviewed the literature to analyse proposed ASSD criteria, characteristics, and diagnostic performance. METHODS: We searched PubMed and Embase databases (01/01/1984 to 06/11/2018) and the ACR and EULAR meeting abstracts (2017-2018). Sensitivities, specificities, positive, negative likelihood ratios and risk of bias were calculated for ASSD criteria and key variables reported in the literature. We performed meta-analysis when appropriate. RESULTS: We retrieved 4,358 studies. We found 85 proposed ASSD criteria from a total of 82 studies. All but one study included anti-synthetase autoantibody (ARS) positivity in the ASSD criteria. Most studies required only one ASSD feature plus anti-ARS to define ASSD (n=64, 78%), whereas 16 studies required more than one ASSD variable plus anti-ARS. The only criteria not including anti-ARS positivity required 5 ASSD clinical features. We found limited data and wide variability in the diagnostic performance of each variable and definition proposed in the literature. Given these limitations we only meta-analysed the performance of individual muscle biopsy and clinical variables in diagnosing ASSD, which performed poorly. CONCLUSIONS: The current ASSD criteria include a variety of serological, clinical, and histological features with wide variability amongst proposed definitions and the performance of these definitions has not been tested. This systematic literature review suggests the need for additional data and consensus-driven classification criteria for ASSD

    Heritability of Body Mass Index: A comparison between the Netherlands and Spain.

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    A high body mass index (BMI) is commonly used as an index of overweight and obesity. There is persistent evidence of high heritability for variation in BMI, but the effects of common environment appear inconsistent across different European countries. Our objective was to compare genetic and environmental effects on BMI in a sample of twins from two different European countries with distinct population and cultural backgrounds. We analysed data of adult female twins from the Netherlands Twin Register (222 monozygotic [MZ] and 103 dizygotic [DZ] pairs) and the Murcia Twin Register (Spain; 202 MZ and 235 DZ pairs). BMI was based on self-reported weight and height. Dutch women were taller and heavier, but Spanish women had a significantly higher mean BMI. The age related weight increase was significantly stronger in the Spanish sample. Genetic analyses showed that genetic factors are the main contributors to variation in height, weight, and BMI, within both countries. For height and weight, estimates of genetic variances did not differ, but for height, the estimate for the environmental variance was significantly larger in Spanish women. For BMI, both the genetic and the environmental variance components were larger in Spanish than in Dutch women
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