1,720,957 research outputs found
Estabilidad térmica en endoperoxidos en solución: Ascaridol
Get PDFEstabilidad Térmica en Endoperoxidos en Solución. ASCARIDOLFil: Jeandupex, Rene. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; ArgentinaFil: Romanelli, Gustavo Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Cafferata, Lazaro. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Kinetics and Mechanism of Gas-Phase Thermolysis Using Headspace-Gas Chromatographic Analysis
Get PDFHeadspace gas chromatography is employed in order to study the thermal decomposition reaction of gaseous di-tert-butyl peroxide (DTBP) in the 130°C to 160°C temperature range and in the presence of n-hexane as the internal standard and nitrogen as the carrier gas. The reaction exclusively yields acetone and ethane as products. First-order kinetics are observed, including when the surface-to-volume ratio (S/V) of the Pyrex 20-mL vial employed as the reactor is increased by packing it with silanized glass wool. However, a small increase in the rate constant values is observed at each temperature, which supports a heterogeneous surface process in DTBP decomposition. The rate constant's dependence on the homogeneous unimolecular decomposition reaction corresponds to the O-O bond rupture of the DTBP molecule in a stepwise three-stage mechanism. Thus, the relevant question of the participation of a surface catalytic effect in the DTBP gas-phase thermolysis can easily be assessed through the procedure described in this work. In general, this is advantageous for the rapid investigation of the reaction kinetics of volatile compounds at different temperatures.Fil: Cafferata, Lazaro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Manzione, Carlos Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; Argentin
A kinetic and mechanistic study on the thermal decomposition reactions of cis- and trans- fused 1,2,4-trioxanes
Get PDFThe kinetics of the thermal decomposition reactions of artemisinine (1), a cis-fused 1,2,4-trioxane, and trans-3,3dimethyl-1,2,4-trioxane (6) in solutions of benzene, toluene, and methanol in sealed tubes were compared at temperatures between 100.1° and 171.4 °C. Pseudo first-order rate constant values were determined for conversions of both cyclic peroxides up to ca. 60%. The activation parameters and the composition of the reaction products were indicative of homolytic cleavage of their O-O bonds as the rate-determining steps followed by stepwise fragmentation. The free energies of activation (ΔG#) for 1 and 6 reactions in the aromatic solvents were calculated at the middle of each temperature range, giving values of 30.7 and 35.1 kcal/mol, respectively, which are evaluated considering their different molecular configurations. Furthermore, the rates of the thermal decomposition reactions of those trioxanes were sensitive to solvent effects.Fil: Cafferata, Lazaro. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Jeandupeax, Rene. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; ArgentinaFil: Romanelli, Gustavo Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Mateo, Carmen Margarita. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingenieria de Olavarria; ArgentinaFil: Jefford, Charles W.. Università degli Studi di Genova; Itali
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
- …
