Hole concentration in a diluted ferromagnetic semiconductor

We consider a mean-field approach to the hole-mediated ferromagnetism in III-V Mn-based semiconductor compounds to discuss the dependence of the hole density on that of Mn sites in Ga_{1-x}Mn_xAs. The hole concentration, p, as a function of the fraction of Mn sites, x, is parametrized in terms of the product m*J_{pd}^2 (where m* is the hole effective mass and J_{pd} is the Kondo-like hole/local-moment coupling), and the critical temperature Tc. By using experimental data for these quantities, we have established the dependence of the hole concentration with x, which can be associated with the occurrence of a reentrant metal-insulator transition taking place in the hole gas. We also calculate the dependence of the Mn magnetization with x, for different temperatures (T), and found that as T increases, the width of the composition-dependent magnetization decreases drammatically, and that the magnetization maxima also decreases, indicating the need for quality-control of Mn-doping composition in diluted magnetic semiconductor devices.Comment: 4 pages, 3 figures, RevTeX 3; Fig. 1 changed, new references adde

Electronic and Structural Properties of Janus SMoSe/MoX2_2 (X=S,Se) In-plane Heterojunctions: A DFT Study

The electronic and structural properties of Janus MoSSe/MoX$_2$ (X=S,Se) in-plane heterojunctions, endowed with single-atom vacancies, were studied using density functional theory calculations. The stability of these structures was verified from cohesion energy calculations. Results showed that single-atom vacancies induce the appearance of flat midgap states, and a substantial amount of charge is localized in the vicinity of these defects. As a consequence, these heterojunctions presented an intrinsic dipole moment. No bond reconstructions were noted by removing an atom from the lattice, regardless of its chemical species. Our calculations predicted indirect electronic bandgap values between 1.6-1.7 eV.Comment: 10 pages, 5 Figure

(-)-tarchonanthuslactone Exerts A Blood Glucose-increasing Effect In Experimental Type 2 Diabetes Mellitus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A number of studies have proposed an anti-diabetic effect for tarchonanthuslactone based on its structural similarity with caffeic acid, a compound known for its blood glucose-reducing properties. However, the actual effect of tarchonanthuslactone on blood glucose level has never been tested. Here, we report that, in opposition to the common sense, tarchonanthuslactone has a glucose-increasing effect in a mouse model of obesity and type 2 diabetes mellitus. The effect is acute and non-cumulative and is present only in diabetic mice. In lean, glucose-tolerant mice, despite a slight increase in blood glucose levels, the effect was not significant.20350385049Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Institute of Chemistry/UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [proc. 13/07607-8]FAPESP [11/50514-5, 12/09254-2, 10/08673-6, 2009/53606-8

Perceptions of the impact of the COVID-19 pandemic on the work of science journalists: global perspectives

The article presents the results of a survey of science journalists from six world regions about their work during the COVID-19 pandemic. The responses show perception of increasing workload for most participants. Local scientists and peer-reviewed articles are the main sources. According to the respondents, scientists have become more available during the pandemic. The use of preprint articles was a frequent practice, but a considerable proportion declared they did not adopt different procedures when reporting them. Most also said they take fake news into account when writing their stories.info:eu-repo/semantics/publishedVersio

Pityriasis lichenoides: clinical and immunogenetic studies

Type of study: Prevalence study. Objectives: Despite pityriasis lichenoides is an uncommon dermatosis, we observed 12 cases in the last 3 years. By this means, we review clinical and histopathologic findings of all patients with pityriasis lichenoides seen at our Division. Furthermore, since pathogenic features of the disease are unknown, we performed HLA class I and II typings to search for possible immunogenetic markers for pityriasis lichenoides. Methods: Twenty-one patients with biopsy-proven diagnosis of pityriasis lichenoides were evaluated. HLA class I and II antigens were typed using conventional serological procedures. Results: Children and young adults were predominantly affected. Most of the cases were seen in fall and winter time. Typical disseminated lesions were observed more frequently. Both acute and chronic patterns were observed at histology. Compared to controls, the HLA-B17 antigen was overrepresented in patients (P< 0.005). Conclusions: Although pityriasis lichenoides remains a cutaneous disease of undetermined origin, our findings show that the disease is associated with the HLA-B17 antigen. .Modelo de estudo:Estudo de prevalência. Objetivos: Embora a pitiríase liquenóide seja uma dermatose incomum, 12 casos foram por nós observados nos últimos três anos. Assim, neste estudo, avaliamos os perfis clínicos e histopatológicos dos pacientes com pitiríase liquenóide, atendidos na Divisão de Dermatologia. Além disso, tipificamos os antígenos HLA de classes I e II nesses pacientes.Metodologia: Foram estudados 21 pacientes com diagnóstico clínico e histopatológico de pitiríase liquenóide. As tipificações dos antígenos de histocompatibilidade de classes I e II foram realizadas, utilizando-se métodos sorológicos. Resultados: A maioria dos casos ocorreu entre crianças e ou adultos jovens, no outono e inverno. As lesões típicas de forma disseminada foram as mais freqüentes. Os achados histopatológicos mostraram lesões dos tipos agudo e crônico. O antígeno HLA-B17 estava significantemente aumentado nos pacientes em relação aos controles (P<0,005).Conclusões: Embora a etiologia da pitiríase liquenóide não seja conhecida, os achados aqui relatados mostram que o marcador HLA-B17 é prevalente entre os doentes