1,720,976 research outputs found
Produzione in fed-batch ripetuto di acido citrico da Yarrowia lipolytica con riciclo di biomassa per microfiltrazione tangenziale
No full textIn this work, citric acid production by Yarrowia lipolytica ATCC 20346 was studied in a laboratory-scale Membrane Recycle Bioreactor composed of a stirred fermenter coupled to a flat-membrane cross-flow microfiltration (CFMF) unit.
By increasing the number of production cycles, citrate productivity (R-p) tended to reduce in spite of the fact that the production medium had been integrated with vitamins, whereas the yield factor for citric acid production on glucose was found to be approximately constant. By operating with partial cell discharge (when using either the production media enriched with amounts of nitrogen and essential nutrients equivalent to the mass of cells disposed of, or the growth medium), it was possible to obtain the expected microbial biomass with no or very limited citrate excretion.
To minimise the contribution of the cell growth phase to the overall citrate productivity and yield on glucose, it would be convenient to subdivide the process into the following stages: growth phase, yeast recovery by CFMF; Ist prolunged fed-batch production using a pi-I-controller as an indirect feedback of simultaneous substrate and alkaline reagent feeding; yeast recovery by CFMF; 2nd prolunged fed-batch production
Effect of in-use cleaning methods on preventing permeate flux decline in cross-flow microfiltration
No full textWith reference io a model baker's yeast slurry, the average permeation flux of a cross-flow microfiltration (CFMF) module containing 20 polysulfone flat membranes with 200,000 molecular cutoff was preliminarily maximised with respect to two cleaning operation modes. Periodic membrane backflushing for as short as 30 s per unit filtration cycle of 5 min (rather than retentate recycling) appeared to be the best and simplest procedure capable of maintaining the overall time-averaged membrane permeability [N-p=11+/-3 g/(s . bar . m(2))] as high as (76+/-20)% of that observed with demineralised water, thus making CFMF of paramount value in cell recycling in secondary metabolite production
Repeated batch citrate production by Yarrowia lipolytica using yeast recycling by cross-flow microfiltration
No full textIn this work, the feasibility of cell recycle by cross-flow filtration in repeated batch citrate fermentation by Y. lipolytica was assessed by supplying a basic production medium devoid of nitrogen sources either as such (C1) or integrated (C2) with the main cofactors entering the Krebs cycle leading to citric acid. Despite a wide degree of dispersion, the experimental yield coefficients did not show a statistically significant dependence on the number of cell recycles performed, their average value (0.43+/-0.12 g citric acid/g glucose consumed) being practically in line with previous findings. Citrate productivity (R(P)) was correlated to yeast density (X(P)) for any generic i-th production cycle whatever the cell recycling mode used but the specific citrate productivity (m(P)) tended to decrease as the number of cell recycling was increased. Whereas the addition of vitamins to the basic production medium C1 appeared to be unable to maintain cell citrate excretion capability unaltered CFMF allowed cell recovery to be aseptically performed without severe membrane fouling problems provided that no more than 2 or 3 production cycles were performed
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
I calcestruzzi ed i materiali riciclati
No full textcoordinatore scientifico: prof. S. Lo Presti, Palermo, Ital
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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