1,720,961 research outputs found
The effect of n-alkanes in the degradation of dibenzothiophene and of organic sulfur compounds in heavy oil by a Pseudomonas sp.
No full textThe microbial degradation of organic sulfur compounds was examined in aerobic conditions employing a pure culture of aPseudomonas sp., isolated from the soil. The effect ofn-alkanes on the degradation of dibenzothiophene (DBT) showed that the assimilation of the sulfur compound by the microorganism is favoured byn-dodecane. Moreover, the saturated fraction was seen to enhance the degradation of the sulfur compounds to be found in a deasphaltenated heavy oil
Barrier and carrier effects of n-dodecane on the anaerobic degradation of benzothiophene by Desulfovibrio desulfuricans.
No full textn-Alkanes affect the degradation of aromatic sulfur compounds both in aerobic and in anaerobic conditions. Some authors have reported anaerobic desulfurization by sutfate-reducing bacteria. These catalytic reactions are biphydrodesulfurizations (BHDS). n-Dodecane has a barrier or carrier effect on benzothiophene degradation in the absence (growing cell condition) or presence (resting cell condition) of hydrogen in the head space of the batch. In addition, thermodynamic factors are very important in benzothiophene and dibenzothiophene degradation by the microorganism Desulfovibrio desulfuricans
On the use of chitosan immobilized b-glucosidase in wine-making: kinetics and enzyme inhibition
No full textThe kinetics of chitosan-immobilized beta-glucosidase and enzyme inhibition by several components of wine and must (glucose, fructose and terpenols) were studied. Optimum immobilization conditions were: temperature 25 degrees C, pH between 5.5 and 6.0, polymeric support dimension in the range 38-75 mu m, cross-linking time 30 min, glutaraldehyde concentration 0.5-1.0% w/v, 1 g of chitosan per 1000 units of beta-glucosidase. The immobilized enzyme retained 29% of the wet biocatalyst activity when freeze-dried and showed good stability (half-life roughly 2 years) when stored at 4 degrees C. Kinetics were tested at 25 degrees C following the hydrolysis of beta-nitrophenyl beta-D glucopyranoside and obey the Michaelis-Menten rate equation. K-m = 1.3 mM and the activation energy, 62.84 kJ mol(-1), are close to those of the free enzyme. The operational half-life was roughly 500 h. Glucose only depressed the enzyme activity according to a reversible non-competitive inhibition mechanism with K-i = 11.2 mM
On the use of chitosan immobilized beta-glucosidase in wine-making: kinetics and enzyme inhibition
No full textThe kinetics of chitosan-immobilized β-glucosidase and enzyme inhibition by several components of wine and must (glucose, fructose and terpenols) were studied. Optimum immobilization conditions were: temperature 25°C, pH between 5·5 and 6·0, polymeric support dimension in the range 38–75 μm, cross-linking time 30 min, glutaraldehyde concentration 0·5–1·0% w/v, 1 g of chitosan per 1000 units of β-glucosidase. The immobilized enzyme retained 29% of the wet biocatalyst activity when freeze-dried and showed good stability (half-life roughly 2 years) when stored at 4°C. Kinetics were tested at 25°C following the hydrolysis of p-nitrophenyl β-d glucopyranoside and obey the Michaelis-Menten rate equation. Km = 1·3 mM and the activation energy, 62·84 kJ mol−1, are close to those of the free enzyme. The operational half-life was roughly 500 h.Glucose only depressed the enzyme activity according to a reversible non-competitive inhibition mechanism with Ki = 11·2 mM
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
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