1,720,986 research outputs found
Adsorption dynamics with interfacial reaction
No full textAbstract: A quantitative theoretical model is developed for the surfactant adsorption from oil solution to the oil/water interface in a time scale from seconds to hours. The kinetic model takes into consideration the diffusion of surfactant molecules in the oil phase to the oil/water interface and the surface transformation between two adsorption conformations namely from conformation 1 to conformation 2 of surfactant molecules. Conformation 1 is supposed soluble in the oil phase. but conformation 2 is assumed to be insoluble in oil. Further, this model is based on the diffusion penetration theory associated with a reversible surface reaction of the first order that describes the surface transformation from conformation 1 to conformation 2. Both conformations are assumed to be insoluble in the aqueous phase. A general analytical expression is derived for the relaxation of interfacial tensions that is convenient for both. numerical calculations and for asymptotic analysis. At short and long diffusion relaxation times the extrapolated equations are deduced. To illustrate the applicability of-this model, the obtained equations are applied to the dynamic interfacial tensions generated by two carotenoids (i.e., ethyl ester of beta-apo-8'-carotenoic acid and beta-carotene, all trans isomers), that independently adsorb from the hexane phase to the hexane/water interface. The model calculations show the characteristic times for the carotenoid adsorption in terms of diffusion relaxation and kinetic relaxation times at the hexane/water interface. The surface reaction rate constants yield to mean values of 8.2 10(-4) s(-1) for ethyl ester of beta-apo8'-carotenoic acid and of 1.3 10(-3) s(-1) for beta-carotene. This model describes very well the experimental interfacial tension isotherms for the two biosurfactants studied. The calculated results are in good agreement with the molecular structure of the two carotenoids adsorbed at the hexane/water interface
IN MEMORIAM PROFESSOR EMIL CHIFU (1925-1997)
No full textThis year, we commemorate the 20th death anniversary of Professor Emil Chifu. 2017 also marks 40 years from the first scientific research project proposed by Professor Chifu and accepted for exploring in cosmos by NASA (National Aeronautics and Space Administration) of the United States of America. As a prominent Romanian scientist, Professor Emil Chifu was an outstanding physical chemist, recognized by the international scientific community. He was one of the founders of the modern science of colloids, surfaces and membrane phenomena, thermodynamics and hydrodynamics of thin layers formed by surface active substances self-assembled into supramolecular structures at liquid interfaces. Professor Emil Chifu has created a modern research school in thermodynamics and physical chemistry of colloids and surfaces, at the Faculty of Chemistry and Chemical Engineering within Babes-Bolyai University in Cluj-Napoca (UBB). Currently, this school is known as the Center of Research in Physical Chemistry and is accredited within UBB
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
Relationship between dentifrices based on hydroxyapatites and human enamel remineralization
No full textEnamel demineralization is an intricate process that holds significant clinical consequences, being a central part of the emergence and progression of various dental problems, most notably dental caries. This demineralization of tooth enamel is linked to a variety of factors, including the composition of oral microbiota and that of saliva, the prevalence of sugar consumption or acidic soft drinks, and, of course, oral hygiene practices. The oral microbiome plays a role in generating organic acids that foster an environment conducive to enamel breakdown. Additionally, a decrease in saliva production can lower the oral environment’s ability to neutralize acids and support the remineralization process, thereby intensifying demineralization. Dentifrices enriched with biomimetic hydroxyapatites are important in preventing demineralization as they not only help with oral hygiene but also provide key ions that help strengthen enamel. Considering their similarity to the natural component in enamel, synthetichydroxyapatites have recently emerged as potent remineralizing agents. Hence, this work aims to illustrate in a simple and concise manner, some of the aspects involved in enamel demineralization and its subsequent remineralization, namely in the relationship between enriched toothpastes containing biomimetic hydroxyapatites and their remineralization eficacy
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
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