Photophysics of pentacene-doped picene thin films

Here were report a study of picene nano-cristalline thin films doped with pentacene molecules. The thin films were grown by supersonic molecular beam deposition with a doping concentration that ranges between less than one molecules of pentacene every 104 picene molecules up to about one molecule of pentacene every 102 of picene. Morphology and opto-electronic properties of the films were studied as a function of the concentration of dopants. The optical response of the picene films, characterized by absorption, steady-state and time-resolved photoluminescence measurements, changes dramatically after the doping with pentacene. An efficient energy transfer from the picene host matrix to the pentacene guest molecules was observed giving rise to an intense photoluminescence coming out from pentacene. This efficient mechanism opens the possibility to exploit applications where the excitonic states of the guest component, pentacene, are of major interest such as MASER. The observed mechanism could also serve as prototypical system for the study of the photophysics of host guest systems based on different phenacenes and acenes.Comment: 15 pages, 6 figure

A prática pedagógica do professor de Engenharia Agronômica

This research aimed to identify the pedagogical practice used by the teacher of Agricultural Engineering, the conceptions of the learning process as well as the degree to which the theoretical concepts of the teacher are coherent with his/her pratice. The pedagogical practice was defined as the regular/customary teaching procedures. The objects of the study were the teachers and the students of Agricultural Engineering at ESALQ - Piracicaba Campus, University of São Paulo. Oral presentation with blackboard, notes and overhead projection was the method most frequently used by the teachers, who, therefore, become the central agent in the teaching process. Because participation in scientific events is very frequent, teaching contempts are constantly updated.Esta pesquisa procurou identificar a prática pedagógica do professor de Engenharia Agronômica, quais as concepções do processo de aprendizagem e em que medida o conceito teórico do professor é coerente com a sua prática. A prática pedagógica foi aqui delimitada como sendo o cotidiano do professor na execução de seu ensino. O público alvo foram os docentes e discentes do Curso de Engenharia Agronômica da Escola Superior de Agricultura "Luiz de Queiroz"- Campus de Piracicaba da USP. O método expositivo foi predominante, apoiado no uso do quadro negro e retroprojetor. O professor nesse método é a figura central do processo ensino-aprendizagem. A freqüência bastante acentuada em Congressos tem trazido uma atualização constante em termos de conteúdo

Cross-Flow turbine design for variable operating conditions

The potential energy hidden in water resources is becoming more and more a significant economic value. The value of the hydroelectric energy is often magnified by the proximity of the turbine to pumps or other energy sinks owned by the same water manager. Cross-flow or Banki-Michel turbines are a very efficient and economic choice that allows a very good cost/benefit ratio for energy production located at the end of conduits carrying water from a water source to a tank. In the paper the optimum design of a cross-flow turbine is sought after, assuming a flow rate variable in time. Regulation of the discharge entering in the turbine is a key issue, which is faced adopting a shaped semicircular segment, moved inside the main case around the rotating impeller. The maximum efficiency of the turbine is attained by setting the velocity of the particles entering the impeller at about twice the velocity of the rotating system at the impeller inlet. If energy losses along the pipe are negligible, closing and opening the inlet surface with the semicircular segment allows always a constant hydraulic head and a constant velocity at the impeller inlet, even with different flow rate entering values. Observed reduction of the turbine efficiency along with the inlet surface reduction is first investigated; a design methodology, using also CFD simulations, is then proposed; finally, the same methodology is applied to a real site in Sicily, selected in the context of the HYDROENERGY P.O. - F.E.S.R. European project

Novas metodologias para avaliar a qualidade da carne - avaliação da qualidade da carne e derivados pela ressonância magnética nuclear.

Neste trabalho, serão apresentadas as principais aplicações da ressonância magnética nuclear (RMN) na avaliação da qualidade de carne e de seus derivados. O fenômeno da RMN é observado em todos os materiais que contenham núcleos atômicos com número impar de prótons e/ou de nêutrons. Trata-se de isótopos que apresentam momento magnético e spin nuclear e que, quando colocados em um campo magnético (ímã), passam a pressionar com uma freqüência característica (freqüência de ressonância), que normalmente ocorre na faixa da onda de rádio ou de rádiofreqüência. Assim, com a irradiação (excitação) da amostra com esta onda de rádio específica, a amostra passa a emitir o seu sinal de rádio, que é o sinal de RMN. A intensidade, a freqüência e a duração do sinal são proporcionais à concentração, à composição química e à mobilidade do material, respectivamente

Herdabilidade do tamanho do umbigo em fêmeas da raça Canchim.

O presente trabalho teve por objetivo estimar a herdabilidade do tamanho do umbigo e sua correlação com o peso aos 12 meses de idade, na raça Canchim.Resumo

Preimplantation biopsy predicts delayed graft function, glomerular filtration rate and long-term graft survival of transplanted kidneys

Background The predictive value of preimplantation biopsies for long-term graft function is often limited by conflicting results. The aim of this study was to evaluate the influence of time-zero graft biopsy histological scores on early and late graft function, graft survival and patient survival, at different time points. Methods We retrospectively analyzed 284 preimplantation biopsies at a single center, in a cohort of recipients with grafts from live and deceased donors (standard and nonstandard), and their impact in posttransplant renal function after a mean follow-up of 7 years (range 1–16). Implantation biopsy score (IBS), a combination score derived from 4 histopathological aspects, was determined from each sample. The correlation with incidence of delayed graft function (DGF), creatinine clearance (1st, 3rd and 5th posttransplant year) and graft and patient survival at 1 and 5 years were evaluated. Results Preimplantation biopsies provided somewhat of a prognostic index of early function and outcome of the transplanted kidney in the short and long term. In the immediate posttransplantation period, the degree of arteriolosclerosis and interstitial fibrosis correlated better with the presence of DGF. IBS values between 4 and 6 were predictive of worst renal function at 1st and 3rd years posttransplant and 5-year graft survival. The most important histological finding, in effectively transplanted grafts, was the grade of interstitial fibrosis. Patient survival was not influenced by IBS. Conclusions Higher preimplantation biopsy scores predicted an increased risk of early graft losses, especially primary nonfunction. Graft survival (at 1st and 5th years after transplant) but not patient survival was predicted by IBS