1,720,959 research outputs found
Síntese eletroquímica de azul da Prússia por varredura cíclica de potencial: Bruna Fernanda Baggio ; orientador, André Avelino Pasa, co-orientador, Vinícius C. Zoldan
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2014.O presente trabalho se concentra na preparação de filmes finos de Azul da Prússia (PB) sobre substratos de ouro através da síntese eletroquímica por varredura cíclica de potencial. A variação dos parâmetros de deposição bem como das superfícies utilizadas como substrato permitiu o estudo das propriedades do material. Com o objetivo de determinar as reações de formação dos filmes de PB, a massa eletrodepositada no substrato foi monitorada com o auxílio de uma microbalança de cristal de quartzo e foi observado um aumento linear da massa em função do tempo. As propriedades estruturais e morfológicas dos depósitos foram investigadas utilizando Difratometria de Raios-X (DRX) e Microscopia Eletrônica de Varredura (MEV), respectivamente; procedimentos que permitiram constatar que, quando modificado o substrato, os depósitos apresentam mudança na direção de crescimento. A caracterização ótica das amostras foi realizada por meio da técnica de Espectroscopia Ótica através de medidas de reflectância no intervalo de radiação do ultravioleta ao infravermelho próximo. A partir dessas medidas foi calculado o coeficiente de absorção do material ?? e utilizando o método de Tauc foram determinadas as energias correspondentes às transições óticas que ocorrem no PB. Essas transições se devem à transferência de carga entre orbitais FeIII e FeII e entre FeIII e FeIII(CN). Os valores de energia em que acontecem essas transições estão em concordância com resultados teóricos obtidos por cálculos de Teoria do Funcional de Densidade (DFT).Abstract : The present work focuses on the preparation of Prussian Blue (PB) thin films on gold surfaces by electrochemical synthesis by cyclic potential sweep. The different deposition parameters and surfaces used as substrates enabled study the properties of the material. In order to determine electrochemical reactions for PB films formation, the reduction and oxidation charges were took into account together with the electroplated mass on the substrate that was monitored with a quartz crystal microbalance and showed a linear increase as a function of time. The structural and morphological properties of deposits were investigated using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively; these procedures allowed to observe that deposits exhibited changes in direction of growth when the substrate is modified. The optical characterization of the samples were performed by Optical Spectroscopy through reflectance measurements of radiation in the range from ultraviolet (UV) to near infrared (NIR). From these measurements the material absorption coefficient (a) was calculated and using Tauc?s method were determined the energies corresponding to PB optical transitions due to molecular orbital charge transfer from FeIII to FeII and from FeIII to FeIII(CN). The transition energy values are in agreement with results obtained by Density Functional Theory (DFT)
Microscopia de tunelamento em moléculas de tetrafenilporfirina de Co em monocamadas isolantes de Cu2N sobre Cu(100)
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2019.Este trabalho tem por objetivo o estudo das propriedades de moléculas detetrafenilporfirina de cobalto (CoTPP) depositadas em superfíciescristalinas através da técnica de microscopia/espectroscopia detunelamento por varredura (STM/STS) de baixa temperatura. Omonocristal de Cu(110) e os filmes isolantes ultrafinos de Cu2N sobreCu(100) e Cu3N sobre Cu(110) foram utilizados como substratos. Asmonocamadas isolantes de nitreto de cobre são responsáveis pordesacoplar os níveis eletrônicos moleculares da banda contínua dosubstrato metálico, permitindo análises em condições que se aproximamdaquelas para moléculas livres. Esse desacoplamento eletrônicopossibilita, por exemplo, que modos vibracionais característicos dasmoléculas sejam observados. Durante a preparação da camada de Cu2Nsobre Cu(100) há a formação de duas regiões distintas no substrato, sendopossível estudar as porfirinas nas mesmas condições do sistema, mas emsítios de adsorção que diferem entre si. Tanto as imagens topográficasquanto a densidade eletrônica das moléculas de CoTPP se mostrambastante sensíveis ao local de adsorção e às diferentes superfíciesutilizadas. Dentre os resultados principais obtidos nesta tese estão:dependência da aparência das moléculas de CoTPP nas imagens de STMcom o substrato utilizado e com o potencial aplicado; bem como distintosvalores de energia dos orbitais moleculares (picos de STS); a deposiçãosobre a superfície Cu2N-Cu(100) permitiu acesso aos estados vibrônicosda molécula de CoTPP; e a observação do efeito Kondo no macrocicloporfirínico, limitado ao Co central das moléculas, quando posicionadasem sítios de interface entre Cu(100) e Cu2N, com TK = 127 K. A parteteórica foi desenvolvida através de cálculos de primeiros princípiosutilizando a teoria dos funcionais de densidade para a molécula de CoTPPsobre o substrato Cu2N-Cu(100).Abstract : The aim of this work is the study of cobalt tetraphenylporphyrin (CoTPP)molecules properties deposited on crystalline surfaces by low temperaturescanning tunneling microscopy/spectroscopy (STM/STS) technique. TheCu(110) monocrystal and monolayers of Cu2N on Cu(100) and Cu3N onCu(110) were used as substrates. Insulating monolayers of copper nitrideare responsible for reducing the coupling between the molecular energylevels and metal substrate surface, allowing the analysis in approximatedconditions for those of free molecules. This electronic decoupling allows,for example, the observation of characteristic molecules vibrationalmodes. The Cu2N layer preparation on Cu(100) leads to formation of twodistinct regions on the substrate, enabling the study of porphyrins undersame system conditions, however, at different adsorption sites. Bothtopographic images and the electron density of the CoTPP molecules arevery sensitive to the adsorption site and surfaces used as substrate. Amongthe main results obtained in this thesis are: the CoTPP moleculeappearance in the STM images depends on the substrate and the appliedpotential; as well as different molecular orbitals energy values (STSpeaks); CoTPP deposition on the Cu2N-Cu(100) surface enables theaccess to the vibrational states of CoTPP molecules; and the observationof the Kondo effect, with TK = 127 K, for molecules positioned atinterface sites, i.e., between Cu(100) and Cu2N. These effects are limitedto the the porphyrin macrocycle, to the central Co atom. Theoreticalstudies were developed for the CoTPP molecule on the Cu2N-Cu(100)substrate through ab initio calculations by density states theory
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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