Operator Ordering in Quantum Radiative Processes

In this work we reexamine quantum electrodynamics of atomic eletrons in the Coulomb gauge in the dipole approximation and calculate the shift of atomic energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji (DDC) formalism by considering the variation rates of physical observables. We then analyze the physical interpretation of the ordering of operators in the dipole approximation interaction Hamiltonian in terms of field fluctuations and self-reaction of atomic eletrons, discussing the arbitrariness in the statistical functions in second order bound-state perturbation theory.Comment: Latex file, 12 pages, no figures, includes PACS numbers and minor changes in the text with the addition of a new sectio

Distribution of 1.68 eV emission from diamond films

Free-standing polycrystalline chemical vapor deposition diamond films grown on a silicon wafer, with electrical behavior similar to values currently mentioned in the literature, present microheterogeneity. A detailed analysis by micro Raman shows how the diamond and nondiamond phases are distributed within the film and also the distribution of the silicon related luminescence. This luminescence is discussed in terms of two emitting centers close in energy. Absolute intensity of the diamond peak is not correlated with the good quality of the film as assessed by the Raman linewidth and ratio of this line to the nondiamond Raman line

Orientação desporto com pés e cabeça.

Este livro aborda, de forma transversal, todas as múltiplas áreas relacionadas com a modalidade desportiva Orientação. O capítulo “Orientação: Desporto Para Toda a Vida”, embora utilizando como base alguns textos já existentes, foi todo reescrito para dar uma introdução generalista ao mundo da Orientação. O segundo capítulo aborda a base da Orientação: o mapa. Assim, “Mapas de Orientação” fala sobre todo o universo dos mapas utilizados nas suas diversas disciplinas. De seguida surgem os capítulos “Orientação Pedestre - Traçado de Percursos” e “Orientação em BTT - Traçado de Percursos”, que se debruçam de forma aprofundada sobre o mais importante aspecto técnico para o sucesso de uma prova de Orientação, o trabalho do Traçador de Percursos. O capítulo “Corridas Aventura” trata de forma separada esta disciplina, devido às diferenças substanciais face às restantes disciplinas da Orientação. Também a “Orientação de Precisão”, designada, na língua inglesa, por Trail-O, tem o seu capítulo próprio. Nele se apresentam as virtudes desta disciplina e se faz uma descrição em pormenor do funcionamento de um percurso de Ori-Precisão. Alguns dos conteúdos deste capítulo são transversais à aprendizagem de diversas questões técnicas da Orientação. Os três capítulos seguintes surgem numa ideia de crescendo ao nível da preparação de actividades de aprendizagem e treino da Orientação. “Jogos Didácticos” descreve alguns jogos de abordagem às bases da Orientação, dirigidos essencialmente para crianças. “Aprendizagem da Orientação” aborda de forma detalhada as actividades a desenvolver nas diversas etapas de aprendizagem da Orientação. “Treino Técnico” explora, de forma simultaneamente teórica e prática, o desenvolvimento das diversas capacidades técnicas e tácticas essenciais para um bom orientista. “Desenvolvimento das Competências Psicológicas” analisa de forma superficial os diversos processos psicológicos que contribuem para a performance do praticante de Orientação. Com o capítulo “Organização de um Evento”, faz-se uma resenha das tarefas inerentes ao planeamento e organização de uma prova de Orientação, analisando os recursos técnicos, logísticos e humanos necessários. Sendo a Orientação uma modalidade intimamente ligada ao meio natural, este livro não podia deixar de ter o capítulo “A Orientação e o Ambiente” que aborda as questões ambientais ligadas a esta modalidade. A terminar este livro, três anexos que incluem um glossário de termos de Orientação

Application of biophysical factors and molecular markers to explain spatial genetic structure in strawberry tree using GIS tools

The strawberry tree (Arbutus unedo L.) is a native species, water stress and low fertility soils tolerant, actively resistant to wildfires and widely distributed in Portugal. The fruit is used in the spirit production, the main source of income. Red fruits, with antioxidant potential, represent, also, a new market opportunity. The geographical isolation and extinction-recolonization dynamics are two factors causing strong genetic structure in metapopulations. We investigated how history, geography, and geoclimatic factors have affected population genetic structure, local adaptation, and, ultimately, its phylogeography. We examined patterns and levels of genetic diversity with nuclear microsatellites and cpDNA haplotypes in populations from across the species range. Under the project ARBUTUS (PTDC/AGR-FOR/3746/2012, Arbutus unedo plants and products quality improvement for the agro-forestry sector) 30 trees were selected, georeferenced, and leaves sampled, in 15 natural populations distributed throughout the country. With GIS tools, the stands were ecologically characterized, at a local scale, using lithology, topography, soil type, vegetation and wildfires records. This data was further used to distinguish Local Landscape Units (LLU) associated with each population. The populations were further clustered using large scale biogeographic and vegetation successions information and, this a priori hierarchy, together with the genetic structure information, was used to explain the species phytogeography. We aimed at finding the historical population demographic scenarios to explain the current patterns of genetic structure and diversity unfold for the species. The obtained information will be used in the species improvement, management and design of conservation programs

Structural, morphological and dielectric properties of ErNbO4 prepared by the sol-gel method

In this work, ErNbO4 samples were prepared using the sol-gel method, through the citrate route, and heat-treated at temperatures between 700 and 1600 °C. The structure was studied by X-ray diffraction and Raman spectroscopy. The crystallite size was estimated using the Rietveld refinement and the Sherrer's formula, presenting values from 31.27 to 86.65 nm and from 40.96 to 78.23 nm, respectively. The morphology was studied by scanning electron microscopy. The measurement of the complex permittivity was made using the small perturbation technique, with a cavity operating in TE105 mode, at resonant frequency of 2.7 GHz. The increase of the treatment temperature promoted the increase of the dielectric constant and the dielectric losses were still maintained with low values, allowing their potential application in electric storage devices. The dielectric constant of ErNbO4 in a zero porosity sample case was estimated and compared with the experimental values.publishe

Microwave dielectric permittivity and photoluminescence of Eu 2O3 doped laser heated pedestal growth Ta 2O5 fibers

Partilhar documento na coleção da comunidade Laboratório Associado I3NWe report the microwave dielectric properties and photoluminescence of undoped and europium oxide doped Ta2O5 fibers, grown by laser heated pedestal growth technique. The effects of Eu2O3 doping 1–3 mol % on the structural, optical, and dielectric properties were investigated. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for Eu2O3 doped Ta2O5 samples it increases, reaching up to 36 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. For this wide band gap oxide, Eu3+ optical activation was achieved and the emission is observed up to room temperature. Thus, the transparency and high permittivity make this material promising for electronic devices and microwave applications. © 2008 American Institute of Physics.FCT-PTDC/FIS/66262/06FCT-PTDC/CTM/66195/200

Three efficient numerical models to analyse the step problem in shallow water

In this paper, the problem of acoustic wave propagation in a waveguide of infinite extent is modelled, taking into account constant depth in each section of the sea. Efficient numerical strategies in the frequency domain are addressed to investigate two-dimensional acoustic wave propagation in a shallow water configuration, considering a step in the rigid bottom and a flat free surface. The time domain responses are obtained by means of an inverse Fast Fourier Transform (FFT) of results computed in the frequency domain. The numerical approaches used here are based on the Boundary Element Method (BEM) and the Method of Fundamental Solutions (MFS). In the numerical models only the inclined or vertical interface between the sub-regions of different depth are discretized, as Green׳s functions that take into account the presence of free and rigid surfaces are used. These Green׳s functions are obtained either by eigenfunction expansion or by Ewald׳s method. A detailed discussion on the performance of these formulations is carried out, with the aim of finding an efficient numerical formulation to solve the step problem in shallow water

Prognostic value of Dna and Mrna E6/e7 of human papillomavirus in the evolution of cervical intraepithelial neoplasia grade 2

Objective: This study aimed at evaluating whether human papillomavirus (HPV) groups and E6/E7 mRNA of HPV 16, 18, 31, 33, and 45 are prognostic of cervical intraepithelial neoplasia (CIN) 2 outcome in women with a cervical smear showing a low-grade squamous intraepithelial lesion (LSIL).Methods: This cohort study included women with biopsy-confirmed CIN 2 who were followed up for 12 months, with cervical smear and colposcopy performed every three months.Results: Women with a negative or low-risk HPV status showed 100% CIN 2 regression. The CIN 2 regression rates at the 12-month follow-up were 69.4% for women with alpha-9 HPV versus 91.7% for other HPV species or HPV-negative status (P < 0.05). For women with HPV 16, the CIN 2 regression rate at the 12-month follow-up was 61.4% versus 89.5% for other HPV types or HPV-negative status (P < 0.05). The CIN 2 regression rate was 68.3% for women who tested positive for HPV E6/E7 mRNA versus 82.0% for the negative results, but this difference was not statistically significant.Conclusions: The expectant management for women with biopsy-confirmed CIN 2 and previous cytological tests showing LSIL exhibited a very high rate of spontaneous regression. HPV 16 is associated with a higher CIN 2 progression rate than other HPV infections. HPV E6/E7 mRNA is not a prognostic marker of the CIN 2 clinical outcome, although this analysis cannot be considered conclusive. Given the small sample size, this study could be considered a pilot for future larger studies on the role of predictive markers of CIN 2 evolution. © the authors.This study aimed at evaluating whether human papillomavirus (HPV) groups and E6/E7 mRNA of HPV 16, 18, 31, 33, and 45 are prognostic of cervical intraepithelial neoplasia (CIN) 2 outcome in women with a cervical smear showing a low-grade squamous intraepithelial lesion (LSIL).Methods: This cohort study included women with biopsy-confirmed CIN 2 who were followed up for 12 months, with cervical smear and colposcopy performed every three months.Results: Women with a negative or low-risk HPV status showed 100% CIN 2 regression. The CIN 2 regression rates at the 12-month follow-up were 69.4% for women with alpha-9 HPV versus 91.7% for other HPV species or HPV-negative status (P < 0.05). For women with HPV 16, the CIN 2 regression rate at the 12-month follow-up was 61.4% versus 89.5% for other HPV types or HPV-negative status (P < 0.05). The CIN 2 regression rate was 68.3% for women who tested positive for HPV E6/E7 mRNA versus 82.0% for the negative results, but this difference was not statistically significant.Conclusions: The expectant management for women with biopsy-confirmed CIN 2 and previous cytological tests showing LSIL exhibited a very high rate of spontaneous regression. HPV 16 is associated with a higher CIN 2 progression rate than other HPV infections. HPV E6/E7 mRNA is not a prognostic marker of the CIN 2 clinical outcome, although this analysis cannot be considered conclusive. Given the small sample size, this study could be considered a pilot for future larger studies on the role of predictive markers of CIN 2 evolution9152

Censored Bayesian models for genetic evaluation of age at first calving in Brazilian Brahman cattle

We compared different Bayesian models to handle censored data for genetic parameters estimation of age at first calving (AFC) in Brazilian Brahman cattle. Data from females with AFC above 1825 days of age were assumed to have failed to calve and were considered as censored records. Data including information of 53, 703 cows were analyzed through the following methods: conventional linear model method (LM), which consider only uncensored records; simulation method (SM), in which the data were augmented by drawing random samples from positive truncated normal distributions; penalty method (PM), in which a constant of 21 days was added to censored records; and the bivariate threshold-linear method (TLcens). The LM was the most suited for genetic evaluation of AFC in Brazilian Brahman cattle based on the predictive ability evaluation through cross-validation analysis. The similar results for LM and PM regarding Spearman correlations, and the higher percentages of selected animals in common, indicated that there was not relevant reranking of animals when censored records were used. In summary, the heritability estimates for AFC ranged from 0.09 (TLcens) to 0.20 (LM). Given its poor predictive performance, the SM is not recommended for handling censored records for genetic evaluation of AFC

Electrical, morphology and structural properties of biodegradable nanocomposite polyvinyl-acetate/ cellulose nanocrystals

In this work, the dielectric properties and the electrical conductivity of polyvinyl acetate (PVAc) polymer doped with cellulose nanocrystals (CNC), extracted from the date palm rachis, are reported. We investigate the filler effect on the molecular mobility of the PVAc polymer chains and the charge transport properties of this material. PVAc/CNC films structure was characterized by powder X-Ray diffraction (XRD), showing the crystalline behavior of the cellulose filler. The dielectric properties were investigated using impedance spectroscopy, in the frequency range of 102–106 Hz and temperatures from 200 to 350 K. A β relaxation, assigned to the motions of the -OCOCH3 side groups, and α relaxation, associated with the glass transition of the PVAc matrix, can be detected.publishe