1,720,953 research outputs found
Glasses doped with rare earth ions for high energy radiation detectors
No full textVidros fluorofosfatos (FP) com diferentes razões de fosfato/fluoreto (P/F), foram estudados com a finalidade de combinar e compreender a sinergia entre a excelente capacidade de formação vítrea dos vidros fosfatos com as propriedades ópticas favoráveis dos fluoretos (e.g. alta eficiência de emissão de íons terras raras (TR) devido a baixas energias de fônon). A incorporação de íons TR nos vidros associada às características acima citadas têm sido amplamente estudadas para aplicações em dispositivos fotônicos de alta eficiência. Neste trabalho, propomos um novo sistema vítreo baseado em polifosfato de gálio, fluoreto de gálio e de metais de alcalinos terrosos com diferentes razões P/F na seguinte composição: xGa(PO3)3 – (39,5-x)GaF3 – 20SrF2 – 20ZnF2 – 20BaF2 – 0,5Eu2O3 (x = 5; 10; 15; 20 e 25). O íon Eu3+ foi utilizado como sonda estrutural, com o intuito de compreender e correlacionar as propriedades fotoluminescentes com a razão P/F, e caracterizar a evolução estrutural no ambiente químico dos TR. Portanto, a caracterização das propriedades físico-químicas dos vidros foi realizada através de análises estruturais, térmicas e espectroscópicas (Raman, UV-vis, fotoluminescência de emissão e excitação, calorimetria diferencial exploratória e medidas de densidade volumétrica). Os resultados permitiram correlacionar os parâmetros obtidos por espectroscopia de fotoluminescência do íon Eu3+ com a evolução estrutural para as amostras com diferentes relações P/F. Os resultados evidenciam que o ambiente local do íon TR é dominado por ligantes fluoretos, enquanto sua estrutura vítrea é dominada por unidades de ortofosfato e ligações P–O–Ga. Adicionalmente, a amostra base que apresentou boa estabilidade térmica com menor relação P/F foi escolhida e dopada com Ce3+ para estudos de potencial aplicação como detector de radiação ionizante. A dopagem foi feita a partir da composição nominal: (10-x)Ga(PO3)3 – (90-x)(30GaF3 – 20SrF2 – 20ZnF2 – 20BaF2) – xCeCl3 (x = 0,25; 0,5; 1; 2; 4; 5 e 6) e suas propriedades fotofísicas foram estudadas. Os vidros dopados com Ce3+ apresentaram uma banda larga de emissão entre 300 e 400nm, característica de transições 5d1 → 4f1 (2F5/2) com tempo de vida na faixa de dezenas de nanossegundos. Após excitação por raios X, uma emissão larga também foi observada entre 300 e 700nm. Para as amostras dopadas com Eu3+, a principal emissão observada está em torno de 610nm, permitindo a detecção por fotomultiplicadoras (PMT) disponíveis comercialmente e bastante sensíveis nesta região. Em geral, as características dos vidros obtidos neste trabalho indicam a potencialidade dos mesmos como cintiladores.Fluorophosphate (FP) glasses with different concentrations of phosphate/ fluoride (P/F) were studied in order to combine and understand the synergy between the excellent glass forming ability of phosphate glasses with the favorable optical properties of fluorides (e.g. high efficiency emission of dopant rare earth(RE) ions due to low phonon energies). The incorporation of RE ions in glasses associated with the characteristics mentioned above have been widely studied for applications in high efficiency photonic devices. In this work, we propose a new vitreous system based on gallium polyphosphate, gallium fluoride and alkaline earth metals with different P/F ratios in the following composition: xGa(PO3)3 – (39,5-x)GaF3 – 20SrF2 – 20ZnF2 – 20BaF2 – 0.5Eu2O3 (x = 5; 10; 15; 20 and 25). The Eu3+ ion was use as a structural probe, with the aim of understanding and correlating the photoluminescent properties with the P/F ratio, and characterizing the structural evolution in the chemical environment of RE. Therefore, the characterization of the physical-chemical properties of the glasses was carried out using structural, thermal and spectroscopic analysis techniques (Raman, UV-vis, emission and excitation photoluminescence, differential exploratory calorimetry and volumetric density measurements). The results allowed correlating the parameters obtained by Eu3+ ion photoluminescence spectroscopy, with the structural evolution for samples with different P/F ratios. The results show that the local environment of the RE ion is dominate by fluoride ligands, while orthophosphate units and P–O–Ga bonds dominate its glassy structure. Additionally, the sample that showed good thermal stability with the lowest P/F ratio was chose and doped with Ce3+ for potential application as an ionizing radiation detector. Doping was performed based on the nominal composition: (10-x)Ga(PO3)3 – (90-x)(30GaF3 – 20SrF2 – 20ZnF2 – 20BaF2) – xCeCl3 (x = 0.25; 0.5; 1; 2; 4; 5 and 6) and their photophysical properties were studied. Glasses doped with Ce3+ showed a broad emission band between 300 and 400 nm, characteristic of 5d1 → 4f1 (2F5/2) transitions with lifetimes in the range of tens of nanoseconds. After X-ray excitation, a broad emission was also observed between 300 and 700 nm. For samples doped with Eu3+, the main emission observed is around 610 nm, allowing detection by photomultiplier tubes (PMT) commercially available and very sensitive in this region. In general, the characteristics of glasses indicate their potential as scintillators
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
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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