1,720,965 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Efeito Ramsauer-Townsend: espalhamento de el?trons de Xe a baixas energias
No full textThe research sought to demonstrate from the experimental study of electron scattering by xenon atoms at low energies the Ramsauer-Townsend effect and thus compare the experimental results and theoretical literature approaches. This study was conducted in Modern Physics Laboratory at the Federal University da Fronteira Sul, submitting a gas thyratron (mod. 2D21) at different temperature conditions. Since such an effect would require the wave theory of quantum mechanics, this analysis was not possible from purely classical considerations, thus the formulation of scattering theory given by quantum mechanics is needed to explain this phenomenon. Thus, the research was to observe the Ramsauer-Townsend effect experimentally and compare with the theoretical results available in the literature. After the study was proposed an experimental script undergraduate level for the study of this effect, providing a discussion of the use of the Schrodinger equation in scattering phenomena at this level of education.A pesquisa buscou demonstrar a partir do estudo experimental de espalhamento de el?trons por ?tomos de Xen?nio em baixas energias o efeito Ramsauer-Townsend e com isso comparar os resultados experimentais e aproxima??es te?ricas da literatura. Este estudo foi realizado no laborat?rio de F?sica Moderna na Universidade Federal da Fronteira Sul, submetendo um tiratron a g?s (mod. 2D21) a diferentes condi??es de temperatura. Visto que o tal efeito requeria a teoria ondulat?ria da mec?nica qu?ntica, a an?lise deste n?o era poss?vel a partir de considera??es exclusivamente cl?ssicas, deste modo, a formula??o da teoria de espalhamento dada pela mec?nica qu?ntica foi necess?ria para explicar este fen?meno. Com isso, a pesquisa foi observar o efeito Ramsauer-Townsend experimentalmente e comparar com os resultados te?ricos dispon?veis na literatura. Ap?s, o estudo foi proposto um roteiro experimental em n?vel de gradua??o para o estudo deste efeito, proporcionando uma discuss?o do uso da equa??o de Schr?dinger nos fen?menos de espalhamento neste n?vel de ensino
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Espalhamento de pósitrons por moléculas utilizando um potencial de polarização ab initio
Get PDFTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Física, Florianópolis, 2013Um novo método de primeiros princípios foi desenvolvido neste trabalho, com o objetivo de considerar os efeitos de polarização de moléculas na presença de pósitrons lentos. Neste cenário, obtivemos seções de choque de baixas energias para pósitrons colidindo com moléculas de H2 e N2, na faixa de energias indo desde 0,1 até 10 eV. Algumas energias em específico foram estudadas para a molécula de H2 com o objetivo de comparar estes resultados com os da literatura. O modelo proposto aqui é baseado na ideia de que a polarização da nuvem eletrônica de uma molécula é causada exclusivamente pelas interações pósitron-elétron. Deste modo, o potencial de polarização é calculado como o valor esperado do hamiltoniano molecular na função de onda polarizada na qual a presença do pósitron é considerada em uma posição fixa, excluindo os termos elétron-elétron da interação. Este operador é avaliado para cada uma destas distâncias, resultando em um potencial de polarização dependente apenas desta coordenada. Os resultados obtidos são comparados com outras aproximações teóricas e experimentais, com uma concordância boa com alguns dados teóricos e outros cálculos mais elaborados. Particularmente, as seções de choque de pósitrons lentos colidindo com moléculas de N2 apresentadas aqui são os únicos resultados na literatura que concordam com os dados experimentais mais recentes. Este é um resultado muito satisfatório, pois o método proposto aqui pode ser aplicado para uma grande variedade de alvos moleculares, e os resultados esperados devem se comparar bem com as medidas mais recentes. Abstract: A new ab initio method is developed here in order to take into account the polarization effects of molecules in the presence of slow positrons. In this framework, we have obtained low-energy positron cross sections for H2 and N2 molecules, in the energy range of 0,1 to 10 eV. Some specific energies have been studied for the H2 molecule in order to compare its results with those in the literature. The model proposed here is based on the idea that the polarization of the electronic cloud of a molecule is caused exclusively by the positron-electron interactions. So, the polarization potential is calculated as the expected values of the molecular hamiltonian in a polarized wave function in which the positron presence is considered at a fixed distance, excluding the electron-electron interactions. This operator is evaluated for each of those fixed distances, resulting in the polarization energy dependent exclusively on that coordinate. The obtained results are compared to other theoretical and experimental approaches, giving an overall good agreement with some experimental data and more elaborated calculations. Particularly, the cross sections of slow positrons colliding with N2 molecules presented here are the only results in the literature which agrees with the more recent experimental data. This result is very satisfactory, as the proposed method can be applied to a wide variety of molecular targets, and the results are expected to be well comparable to the most recent measurements
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Cálculo das seções de choque para colisão de pósitrons em moléculas: Wagner Tenfen ; orientador, Sérgio Eduardo Michelin
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2009.Neste trabalho apresentamos estudos teoricos sobre a colisao de pósitrons com moleculas de qualquer geometria. Realizamos os cálculos para determinar as seçoes de choque elasticas para as moleculas N2O, H2O, NH3 e CH4, utilizando o metodo das fraçoes continuadas, no qual utilizamos um potencial de correlacao-polarizaçao local. Os resultados apresentados aqui estao em excelente concordancia com dados teoricos e experimentais contidos na literatura.In this work we present positron molecule scattering theoretical studies, using molecules with any geometry. We accomplished calculations in order to determine the elastic cross sections for the molecules N2O, H2O, NH3 and CH4, using the method of continued fractions, in wich we incorporate a local correlation-polarization potential. The results presented here are in excelent agreement with theorical and experimental data from literature
- …
