1,721,101 research outputs found
Modeling of gas-liquid reactors. Isothermal semibatch and continuous stirred tank reactors
No full textA computer code for the simulation of isothermal stirred gas-liquid reactors, both continuous and semibatch, has been developed. The models are constituted of two moduli. The first one describes the diffusion-reaction processes at the gas-liquid interphase, and is based on the film model. This modulus is the same for all reactors. The second one describes the time evolution (semibatch reactor) or the steady state behavior (continuous reactor) of the composition of the bulk liquid and gas phases, which depends on the specific reactor configuration and fluodynamics. The simulation code has been developed for the most general case, involving any type of kinetic scheme and reaction rate expressions, evaporation of volatile liquid components, recycle of condensed liquid from the condenser, etc. Specific numerical algorithms have been implemented for the solution of the mathematical models in all possible operating conditions. All fluodynamic and transport parameters are evaluated internally using selected semi-empirical relations derived from the literature. Thus the required input data to the computer code involve only the physicochemical properties of the involved chemical species and the kinetic parameters involved in the reaction rate expressions. The performance of the simulation models has been tested by comparison with experimental data for two processes of practical interest: catalytic oxidation of p-xylene and photochemical chlorination of p-xylene. (C) 1997 Elsevier Science Ltd
Stripping of ammonia from aqueous solutions of amino acids and inorganic ions
No full textThe stripping of ammonia from aqueous solutions of amino acids and strong electrolytes has been investigated both experimentally and theoretically. The experiments have been carried out in an isothermal stirred semibatch stripper. A good agreement between experimental data and model predictions has been obtained for all the examined operating conditions. The model accounts for all dissociation equilibria while it assumes ideal behavior for the liquid phase. It does not include any adjustable parameter, and so it can be readily extended to various systems of practical interest, such as those involved in the treatment of side-streams arising in the production of amino acids
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
Effect of l-arginine complementary food on stud dogs semen characteristics: preliminary results
No full textNormal semen characteristics are a prerequisite for male reproductive success. Several studies have shown that l-arginine enhances sperm motility in spermatozoa of goat, bull and mouse and, to a certain extent, also in asthenospermic humans. This study reports preliminary results on the effect of l-arginine complementary food supplementation on stud dogs semen characteristics. Fourteen healthy stud dogs, 3–12 years old, belonging to several breeds, with history of at least one unsuccessful breeding with females of proven fertility were enrolled. The dogs were submitted to a first unevaluated semen collection and subsequently to double collections and routine analysis, 7 and 21 days after, to define d0. L-arginine food supplementation (Riprofert , Marpet, Italy) started immediately after the second ‘basal’ collection and consisted of 600 mg L-aspartate arginine/dogs with body weight ranging between 6 and 30 kg/day for a total of 70 days. Semen was further analysed at day 35 (d35) and 70 (d70) after the beginning of supplementation. Results showed that sperm motility improved at d35 and d70 vs. d0 (p < 0.001) and again at d70 vs. d35 (p < 0.05); sperm morphology also improved at d35 and d70 vs. d0 (p ≤ 0.001) and again at d70 vs. d35 (p < 0.01). Sperm concentration did not change significantly. The preliminary results suggest that l-arginine food supplementation could be useful for sperm motility and morphology improvement in stud dogs with suspected infertilit
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
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