Generation and recombination of excited states in organic semiconductors

Tese (doutorado)—University of Brasília, Institute of Physics, 2015.Desde de a descoberta das propriedades de emissão de luz atribuídas aos semicondutores orgânicos baseados em grupos fenil na década de 90, esforços consideráveis têm sido empregados no estudo de propriedades fotofísicas desses materiais. Vantagens interessantes como facilidade de síntese, flexibilidade, baixo custo de produção e vasta área de aplicação tornam os semicondutores orgânicos atrativos para a indústria de eletrônicos, particularmente quando a fabricação de uma nova tecnologia de telas é considerada. Existem várias aplicações em potencial tais como células solares orgânicas, transistores de filme–fino e diodos emissores de luz orgânicos (OLDEs). A dinâmica de recombinação entre quase–partículas, de maneira a formar espécies excitadas, tem sido identificada como um processo importante nessas aplicações. Um dos desafios relevantes na ciência e tecnologia de semicondutores orgânicos é a caracterização dos efeitos de temperatura e impureza sobre a geração e recombinação entre quase–partículas. Com isso, o entendimento de como tais efeitos desempenham o papel de alterar a dinâmica de formação de novos produtos é de fundamental importância para o desenvolvimento de dispositivos optoeletrônicos mais eficientes. Nesta tese, a dinâmica de recombinação entre quase–partículas em semicondutores orgânicos é investigada numericamente sob influência de impurezas, interações coulombianas, temperatura e campo elétrico externo. O objetivo desse trabalho é fornecer um panorama físico dos produtos e seus respectivos rendimentos resultantes da recombinação entre diferentes tipos de quase–partículas em semicondutores orgânicos, principalmente quando os efeitos mencionados acima são levados em consideração, contribuindo para a compreensão deste processo, que pode fornecer orientações para aprimorar, por exemplo, a eficiência de processos que envolvam eletroluminescência em dispositivos optoeletrônicos tais como OLEDs.Since the discovery of light emitting properties on phenyl–based organic semiconductors in the 90’s, considerable efforts have been devoted to study the photophysical applications of conjugated polymers for development of new technologies in organic optoelectronic devices. The potential advantages in terms of ease of synthesis, flexibility, low cost, and large-area capability make the organic semiconductors attractive for the electronics industry, particularly when it comes to the promising development of a new display technology. There are many potential applications such as Organic Solar Cells, Thin–Film Transistors, and Organic Light Emitting Diodes (OLEDs). The recombination dynamics between quasi–particles, in order to generate excited species, has been identified as an important process in these applications. Furthermore, the products arising from the recombination mechanism as well as their final yields, have been shown to be directly related to the devices performance. One of the significant challenges in the science and technology of organic semiconductors is the characterization of the temperature and impurity effects on the generation and recombination of quasi–particles. Thus, understanding how such effects play the role of changing the formation dynamics of new products from the recombination process is of fundamental importance to the development of more efficient optoelectronic devices. In this thesis, the recombination dynamics between quasi–particles in organic semiconductors is numerically investigated under the influence of impurities, Coulomb interactions, temperature and an external electric field. The aim of this work is to give a physical picture of the products and their yields derived from the recombination of different kinds of quasi–particles in organic semiconductors, when the above–mentioned effects are considered and contribute to the understanding of these important processes, which may provide guidance to improve, for example, the electroluminescence yields in OLEDs

Doença de Chagas

Esta aula teve como objetivo divulgar dados sobre a Doença de Chagas. Essa contempla informações sobre o histórico da doença, epidemiologia, modos de transmissão, formas clínicas, tratamentos entre outros

Construction of a projection spectrograph and its use in optical spectroscopy classrooms demonstrations

This article describes a projection spectrograph for use in optical spectroscopy classrooms demonstrations. The apparatus is based on an overhead projector and permits the visualization of several phenomena such as, light dispersion by diffraction gratings, diffraction order, optical fluorescence, continuous and discrete optical emission spectra, and light absorption by liquids and solids. A historical survey about the optical spectroscopy development is also presented

On Merging Feature Engineering and Deep Learning for Diagnosis, Risk-Prediction and Age Estimation Based on the 12-Lead ECG

Objective: Machine learning techniques have been used extensively for 12-lead electrocardiogram (ECG) analysis. For physiological time series, deep learning (DL) superiority to feature engineering (FE) approaches based on domain knowledge is still an open question. Moreover, it remains unclear whether combining DL with FE may improve performance. Methods: We considered three tasks intending to address these research gaps: cardiac arrhythmia diagnosis (multiclass-multilabel classification), atrial fibrillation risk prediction (binary classification), and age estimation (regression). We used an overall dataset of 2.3M 12-lead ECG recordings to train the following models for each task: i) a random forest taking the FE as input was trained as a classical machine learning approach; ii) an end-to-end DL model; and iii) a merged model of FE+DL. Results: FE yielded comparable results to DL while necessitating significantly less data for the two classification tasks and it was outperformed by DL for the regression task. For all tasks, merging FE with DL did not improve performance over DL alone. Conclusion: We found that for traditional 12-lead ECG based diagnosis tasks DL did not yield a meaningful improvement over FE, while it improved significantly the nontraditional regression task. We also found that combining FE with DL did not improve over DL alone which suggests that the FE were redundant with the features learned by DL. Significance: Our findings provides important recommendations on what machine learning strategy and data regime to chose with respect to the task at hand for the development of new machine learning models based on the 12-lead ECG

Organizational decline research review: challenges and issues for a future research agenda

Organizational decline is related to the deterioration of the resource base and performance of an organization for a sustained period of time. Although some studies have been conducted, it remains an understudied phenomenon, despite its importance. The study of organizational decline is faced with challenges to improving and increasing research. In this study, we analyze the scientific field of organizational decline in business and management journals with a high impact factor. We conducted a mixed-method study: a bibliometric study of a sample of 214 articles, and a qualitative study with 41 authors. We used an analysis of citations, co-citations and factor analysis. This enabled the identification of the most influential works and their conceptual approaches. The interviews with the authors were analyzed using content analysis, which complemented our understanding of the challenges and problems facing the theme. The results show that organizational decline can be organized into three different aspects: organizational decline itself; studies on turnaround; and mortality. Specific challenges to overcome are related to a better definition, cognitive issues and other issues on decision-making and specific methodological problems. In addition, it is necessary to evaluate whether theories that explain growth are also able to explain decline.info:eu-repo/semantics/publishedVersio

FACTORS RELATED TO MOTOR DEVELOPMENTAL DELAY OF NEWBORNS

Introduction: Studies on the association between motor developmental delay and events observed during the neonatal period are performed after discharge. In such cases, the associations found may be interfered by factors occurring between discharge from the NICU and evaluation. Evaluate newborns before hospital discharge can prevent these effects.The purpose of this study is to identify factors related to motor developmental delay of newborns when being discharged from Neonatal Intensive Care Unit. The method chosen to carry out this investigation was a prospective cohort, populationbased and analytic-descriptive study, and 178 newborns were assessed through the Test of Infant Motor Performance. Binomial logistic regression has been developed for analyzing the associated factors. Among the results obtained, 58.4% of them were premature, 56.2% were low weight newborns and 59.0% were male. The participants were selected among those with the following characteristics: Birth Weight (BW) 2304.3 g, Gestational Age (GA) 35.33 weeks. Morbidity occurred in 23.6% of the participants and 34.8% showed changes in the motor performance (64.7% in the ones below 1501g and 27.8% in the ones above 1500g). Upon completion of the TIMP, it was possible to conclude that the factors associated with motor developmental delay in the binomial logistic regression were prematurity, seizures, being female

Ferramenta computacional para cálculo de coeficientes de pressão

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LEITURA E INTERATIVIDADE

Atualmente parece haver um consenso de que ler é uma  atividade  interativa  e  que,  para  o  processamento  do  significado  do  texto, associam-se três elementos fundamentais: o autor, o leitor e o  texto.  Esse  modo  de  leitura  é  comparado  a  um  jogo  interativo  que  precisa ser orientado por suas próprias estratégias e regras

Historical experiments simulations in physics education: a computational approach of the historical and empirical dimensions of science in classroom

Neste trabalho propomos a utilização de simulações computacionais de experimentos históricos no ensino de física como estratégia de resgate e articulação das dimensões histórica e empírica da física na sala de aula. Como exemplo, apresentamos uma classe de simulação computacional didática, caracterizada aqui como Simulação Didática Interativa (SDI), utilizando o software Modellus para apresentar a experiência do plano inclinado proposta por Galileu Galilei(1564-1642) em sua obra Discursos e Demonstrações Matemáticas em Torno de Duas Novas Ciências (1638), onde a lei da queda dos corpos é investigada.In this paper we propose the use of computer simulations of historical experiments in physics education as a strategy to recover and articulate the historical and empirical dimensions of scientific knowledge in the classroom. Particularly, we present a Didactic Interactive Simulation (DIS) using the software Modellus to rescue the experiment of the inclined plane described by Galileo Galilei in his work Discourse and Mathematical Demonstrations Concerning Two New Sciences (1638), in which he investigates the law of falling bodies

Epidemilogical aspects of a malaria focus in the districts of São Luis, MA

O estudo foi realizado na localidade de Residencial Paraíso, São Luis, Maranhão, de 1999 a 2001, com o objetivo de analisar os aspectos epidemiológicos da malária, tendo sido constatado que a localidade é receptiva e vulnerável. Houve 129 casos, com maior acometimento do sexo masculino e da faixa etária de 20 a 29 anos. O Plasmodium vivax foi o agente responsável pelas infecções, tendo como vetor o Anopheles aquasalis. Foram identificadas evidências de transmissão extradomiciliar.The study was developed in the neighborhood of Residencial Paraíso, São Luis, Maranhão, Brazil, from 1999 to 2001. The aim was to analyze the epidemiological aspects of malaria. The location is receptive and vulnerable to malaria. There were 129 cases. Men from 20 to 29 years of age were most involved. Plasmodium vivax was the agent of all cases and Anopheles aquasalis was the vector. There was no evidence of transmission occurring outside of the houses