1,720,958 research outputs found
Harvesting of microalgae biomass using ceramic microfiltration at high cross-flow velocity
No full textThis study aimed to investigate the harvesting of microalgae by microfiltration (MF) on a ceramic membrane at relatively high cross-flow velocity (CFV) of interest for commercial processes. Pilot-scale harvesting was conducted with algal suspensions (Chlorella vulgaris and Tisochrysis lutea (T-Iso)) and algal supernatants (Porphyridium cruentum) to assess the effect of feedstock characteristics and understand flux decline mechanisms. In total recycle mode (C. vulgaris, 1 g/L), high steady-state permeation flux around 200 L/m2/h was achieved. Total filtration resistance was mainly due to cake resistance (Rc, 57%) and pore adsorption and blocking (Ra, 40%). The process hydrodynamic conditions seemed to have relatively little effect on Chlorella cell integrity. In concentration mode, average permeate flux decreased from 441 to 73 L/m2/h with increasing feed concentration (C. vulgaris, 0.25–1 g/L); the contribution of Rc decreased (82 to 57%), while that of Ra rose (7 to 40%). With T-Iso suspensions and P. cruentum supernatants at 1 g/L, average permeate flux was 59 and 49 L/m2/h, respectively, with predominance of Rc and Ra, respectively. Distinct fouling mechanisms were inferred to explain the superior filterability of C. vulgaris. The results show that ceramic membrane MF at relatively high CFV could be a suitable option for harvesting certain microalgae including C. vulgaris
Couplage photobioréacteur-microfiltration tangentielle pour la production et la récolte à petite échelle de biomasse microalgale
Get PDFArthrospira platensis, plus couramment appelée spiruline, est une cyanobactérie dont les qualités nutritionnelles, reconnues de longue date, résultent de sa composition en protéines, en acides gras essentiels, en vitamines et en minéraux. Cette biomasse très digestible est utilisée dans les programmes de lutte contre la malnutrition et de réhabilitation nutritionnelle en Afrique. Dans les pays développés, la spiruline se positionne sur un marché de niche en nette expansion, porte par les productions a grande échelle mais aussi par le nombre croissant de petits producteurs qui se regroupent actuellement en associations pour nom1aliser et labelliser leurs productions. Cette microalgue est aussi cultivée de façon artisanale dans les pays en développement, notamment en Afrique. On utilise des bassins à ciel ouvert, quelquefois équipes de systèmes d'agitation en circuit ferme (raceways) pour améliorer la nutrition et l'oxygénation de la biomasse microlagale, ainsi que la photosynthèse. Ce type de production, généralement réalisés à grande échelle, contraint les producteurs du Sud à des investissements fonciers relativement onéreux. Ils ont souvent des problèmes sur la qualité de leur production, resultant de contaminations diverses de la biomasse produite, provenant de l'environnement du bassin qui est rarement protège par une serre. La maitrise, tant de la qualité que des couts de production, nous a conduits à rechercher une procédure de culture de microalgue répondant au mieux à cette problématique de production à petite échelle dans le contexte africain. Un procède innovant, peu couteux, pouvant produire à petite échelle de la biomasse de qualité selon un protocole reproductible de production microalgale, a été développé sur la base de la technique du photobioréacteur (PBR). Avec ce système semi-ferme de production, la qualité de la biomasse produite est constante et le rendement obtenu en matière sèche est reproductible. Pour chaque cycle de production de 30 j, le rendement est de 0,9 g.L-1 (85L). Ce PBR peut fonctiom1er dans un environnement de faible technicité et la technique de production s'affranchit des impacts non maitrises de l'environnement sur la culture: pollution, illumination, aération du milieu de culture. I1 peut être duplique localement, notamment pour augmenter la production totale de biomasse d'une même souche ou pour produire de la biomasse à partir diverses souches locales de microalgues. Le couplage de la production avec une technologie de récolte des microalgues, mettant en oeuvre des membranes minérales semi-industrielles sur le principe de la microfiltration tangentielle (MFT), permet la production de biomasses de microalgues de plus petites tailles que la spiruline, comme la chlorelle, l'isochrisis, ou d'autres petites souches locales qui présentent autant d'intérêt. De plus, la MFT permet la purification de l'eau utilisée pour le milieu de culture microalgale, le recyclage de l'eau après le cycle production pour son utilisation dans de nouveaux cycles ou son rejet dans le respect de l'environnement local
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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