Study of the Partial Substitution of Pb by Sn in Cs–Pb–Sn–Br Nanocrystals Owing to Obtaining Stable Nanoparticles with Excellent Optical Properties

Halide perovskites are revolutionizing the photovoltaic and optoelectronic fields with outstanding performances obtained in a remarkably short time. However, two major challenges remain: the long-term stability and the Pb content, due to its toxicity. Despite the great effort carried out to substitute the Pb by a less hazardous element, lead-free perovskite still remains more unstable than lead-containing perovskites and presents lower performance as well. In this work, we demonstrate the colloidal preparation of Cs–Pb–Sn–Br nanoparticles (NPs) where Sn is incorporated up to 18.8%. Significantly, we have demonstrated that the partial substitution of Pb by Sn does not produce a deleterious effect in their optical performance in terms of photoluminescence quantum yield (PLQY). We observed for the first time a positive effect in terms of enhancement of PLQY when Sn partially substitutes Pb in a considerable amount (i.e., higher than 5%). PLQYs as high as 73.4% have been obtained with a partial Pb replacement of 7% by Sn. We present a systematic study of the synthesis process in terms of different growth parameters (i.e., precursor concentration, time, and temperature of reaction) and how they influence the Sn incorporation and the PLQY. This high performance and long-term stability is based on a significant stabilization of Sn2+ in the NPs for several months, as determined by XPS analysis, and opens an interesting way to obtain less Pb-containing perovskite NPs with excellent optoelectronic properties

O perfil da delegação brasileira na World Gymnaestrada de Lausanne/Suiça - 2011

O Brasil tem participado da Gymnaestrada Mundial desde a sua segunda edição em 1957, porém, até o momento, há poucos indicadores acerca do perfil dos grupos que representaram o país nas diferentes edições deste evento. A presente pesquisa teve como objetivo apresentar o perfil da delegação brasileira participante na XIV Gymnaestrada Mundial realizada em Lausanne/Suíça em 2011, destacando aspectos como: número de participantes e de grupos, faixa etária, gênero, principais influências gímnicas dos grupos, apoio financeiro recebido, interesses turísticos e tipologia das instituições representadas. Trata-se de um estudo descritivo, cujos dados foram coletados por meio de um questionário respondido pelos representantes dos grupos brasileiros. Entre as principais considerações identificamos: maior concentração de grupos da região sudeste, predominância feminina tanto com respeito aos ginastas como aos responsáveis pelos grupos, percentual significativo de acompanhantes, heterogeneidade nas faixas etárias dos participantes com predominância de crianças e adolescentes, percentual relevante de grupos que se consideram como de Ginástica Geral/Ginástica para Todos, quantidade significativa de grupos que receberam algum apoio financeiro para a participação, metade dos grupos com vinculação a escolas ou universidades, indicação de que todos os responsáveis pelos grupos possuem formação superior em Educação Física, e aproximadamente metade deles com nível de pós-graduação

Femtosecond Two-Photon Absorption Spectroscopy Of Copper Indium Sulfide Quantum Dots: A Structure-Optical Properties Relationship

We have interpreted the two-photon absorption spectrum of water-soluble copper indium sulfide (CIS) QDs with stoichiometry 0.18 (Cu), 0.42 (In), and 2 (S) and an average diameter of approximately 2.6 nm. For that, we employed the wavelength-tunable femtosecond Z-scan technique and the parabolic effective-mass approximation model, in which the excitonic transition energies were phenomenologically corrected due to the stoichiometry of the nanocrystal. This model considers a conduction band and three valence sub-bands allowing excitonic transitions via centrosymmetric (Δl = ±1, where l is the angular momentum of the absorbing state) and non-centrosymmetric (Δl = 0) channels. In such case, this became relevant because the CIS QDs with chalcopyrite crystalline structure is a non-centrosymmetric semiconductor. Thus, our experimental results pointed out two 2 PA allowed bands located at 715 nm (2hv = 3.47 eV) and 625 nm (2hv = 3.97 eV) with cross sections of (6.3 ± 1.0) x 102 GM and (4.5 ± 0.7) x 102 GM, respectively. According to the theoretical model, these 2 PA bands can be ascribed to the 1P1/2(h3) → 1S3/2(e) (lower energy band) and 1P1/2(hheavy) → 1S3/2(e) (90%)/(10%)1P1/2(hsplit-off) → 1P3/2(e) (higher energy band) excitonic transitions. A good agreement (magnitude and spectral position) between the experimental and theoretical data were obtained. However, our experimental data suggest that the higher-energy 2 PA band may have other contributions due to the mixing between the heavy- and the light-hole bands, which the effective mass model does not take into consideration

FORMAÇÃO E ATUAÇÃO DOCENTE EM GINÁSTICA NAS UNIVERSIDADES PÚBLICAS DA REGIÃO NORTE DO BRASIL

Este estudo objetivou mapear a formação e atuação acadêmica de docentes que atuam na área da Ginástica nas Instituições de Ensino Superior (IES) públicas da região Norte. Para isso, foram analisados websites e documentos oficiais de nove IES, além do Currículo Lattes de 24 docentes destas instituições. Os dados indicam, em geral, a atuação de docentes não-especialistas em Ginástica, isto é, com formação acadêmica em áreas distintas. Ademais, o número de publicações científicas sobre Ginástica se mostra tímido quando comparado a outras regiões brasileiras. Sobre orientações e ações extensionistas, há um número expressivo de atividades, porém concentradas em poucas IES, com destaque para UFAM, UEPA e UFPA. Por fim, identificamos maior envolvimento em ações – Ensino, Pesquisa e Extensão – das modalidades Ginástica Artística e Ginástica Rítmica, o que corrobora a produção de literatura

Survival After Lung Transplantation for Chronic Hypersensitivity Pneumonitis: Results From a Large International Cohort Study

Repeated exposure to antigens via inhalation is the primary cause of hypersensitivity pneumonitis, a form of interstitial pneumonia. The chronic form of hypersensitivity pneumonitis leads to progressive loss of respiratory function; lung transplantation is the only therapeutic option for chronically ill patients. The ESTS Lung Transplantation Working Group conducted a retrospective multicentred cohort study to increase the body of knowledge available on this rare indication for lung transplantation. Data were collected for every patient who underwent lung transplant for hypersensitivity pneumonitis in participating centres between December 1996 and October 2019. Primary outcome was overall survival; secondary outcome was freedom from chronic lung allograft dysfunction. A total of 114 patients were enrolled from 9 centres. Almost 90% of patients were diagnosed with hypersensitivity pneumonitis before transplantation, yet the antigen responsible for the infection was identified in only 25% of cases. Eighty per cent of the recipients received induction therapy. Survival at 1, 3, and 5 years was 85%, 75%, and 70%, respectively. 85% of the patients who survived 90 days after transplantation were free from chronic lung allograft dysfunction after 3 years. The given study presents a large cohort of HP patients who underwent lung transplants. Overall survival rate is higher in transplanted hypersensitivity pneumonitis patients than in those suffering from any other interstitial lung diseases. Hypersensitivity pneumonitis patients are good candidates for lung transplantation

A silicon imaging calorimeter prototype for antimatter search in space: experimental results

Abstract This report presents the results obtained with a prototype silicon-tungsten (Si-W) electromagnetic calorimeter, conceived as a fine-grained imaging device to carry out studies of the antimatter component in primary cosmic radiation. The calorimeter prototype contains 20 x , y sampling layers interleaved with 19 showering material planes. One sensitive layer is obtained with two silicon strip detectors (Si-D) (60 × 60) mm 2 , each divided into 16 strips, 3.6 mm wide; the two detectors are assembled back to back with perpendicular strips. This allows the transverse distributions of the shower in both coordinates at each sampling (0.5 X 0 ) to be pictured. The basic characteristics of the design and the experimental results obtained on a test beam at the CERN proton synchrotron (PS) for electrons and pions are reported. The main results presented are the response of the calorimeter to the electron at various energies (1–7 GeV), and the transverse shower profiles at different calorimeter depths as well as the patterns of the electromagnetic shower and those of the interacting and non-interacting pions. The capability of the calorimeter in measuring the direction of the incoming electromagnetic particle from the pattern of the shower has been evaluated at different energies. These results are encouraging in view of the possible use of this detector to search for high-energy γ sources in space

Silicon calorimeter for cosmic antimatter search

Abstract The silicon sampling calorimeter presented is conceived as a fine grained imaging device to carry out studies of the anti-matter component in the primary cosmic radiation; it will be used in balloon payload program starting in 1993. The first sampling layer (48×48 cm2) of this silicon calorimeter has been completed and successfully tested. We report the first results form studies performed at the CERN PS t7 beam. The complete calorimeter contains 20 xy sampling layers (strip pitch 3.6 mm) interleaved with 19 showering material planes (tungsten 0.5 X0). This allows to picture the transverse distributions of the shower in both coordinates at each sampling. The outstanding imaging capabilities reflects in high particle identification power. Preliminary results from beam tests performed with antiprotons at 3.5 GeV on a tower prototype of the calorimeter are reported