1,720,954 research outputs found
Role of Water Complexes in the Reaction of Propionaldehyde with OH Radicals
No full textThere has been considerable debate and speculation about the role of weakly bound complexes in radical molecule reactions in the gas phase, especially in atmospheric chemistry. Among the significant number of potentially important molecular aggregates in chemical reactions, water complexes are of particular interest. Beyond the well-known energy transfer role of water in complex-forming reactions, it has been shown that water may also have a catalytic effect on the kinetics of radical-molecule reactions because of reduced reaction barrier heights for the complexes. Here we report studies of the reaction of OH radicals and propionaldehyde in the presence and absence of water vapor between 300 and 60 K in Laval nozzle expansions. Water accelerates the overall reaction at low temperatures but much less pronounced than for the reaction of OH with acetaldehyde reported recently. Quantum chemical calculations help us to understand this behavior, which can be rationalized in terms of the stability of intermediate reaction complexes and the effect of water aggregation on the barrier separating prereactive complexes and products
Primary Steps in the Reaction of OH Radicals with Amino Acids at Low Temperatures in Laval Nozzle Expansions: Perspectives from Experiment and Theory
No full textRecent work has focused on the damaging effects of free radicals on biological molecules. This study investigates the kinetics of the attack of OH radicals Oil L-alanine ethyl ester in the gas phase in cold beams of Laval nozzle expansions. Experiments and high-level theory are used to understand the preferred site of attack by the OH radical. Optimizations of L-alanine and L-alanine ethyl ester show that the essential transition state features for hydrogen abstraction off the C(alpha), C(beta), and N are similar. The energetics show that for L-alanine, the C(alpha)-site, C(beta)-site, and N-site transition states are all below the reactants level. For L-alanine ethyl ester, however, the energetics for hydrogen abstraction off the C(alpha) and N are the preferred site of reaction. These findings are Supported by the observed negative temperature dependence of the rate constants of OH with alanine ethyl ester in Laval nozzle expansion experiments. More importantly, both the experiments and theory show that L-alanine ethyl ester provides a good model For gas phase studies of the amino acids such as L-alanine.Deutsche Forschungsgemeinschaft DFG [782
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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