1,720,956 research outputs found
Silicone membrane contactors for volatile fatty acid (VFA) separation from cheese whey
No full textThe effect of pH and extraction temperature on flux, recovery, mass transfer coefficient and separationfactor of volatile fatty acids (VFAs) and alcohols from synthetic solutions and cheese whey fermentatewas investigated using a silicone membrane contactor with water as extractant. The silicone membraneallowed extraction of undissociated acids only, resulting in substantially higher recovery efficiencies at pH3 than at pH 5. Furthermore, the non-porous silicone membrane favoured extraction of longer chain overshorter chain acids. Caproic acid was extracted with the highest flux of 1.30 (± 0.02) g m−2h−1in shorttime (32 h), with a 41.5 % recovery efficiency at pH 3 and 20◦C, indicating the feasibility of its selectiveseparation from the VFA mixture. A similar trend was observed for alcohols, with butanol being extracted with a 39 % recovery efficiency at 40◦C, against 32 % and 19 % of propanol and ethanol, respectively, whilethe mass transfer coefficients were not affected by temperature. When applying the silicone membrane contactor to real cheese whey fermentate at pH 3, butyric and acetic acid were extracted with 21.5 % and7% recovery efficiency, respectively, suggesting the feasibility of the contactor for VFA recovery from real fermentate
Fermentative hydrogen production from cheese whey with in-line, concentration gradient-driven butyric acid extraction
No full textHydrogen (H2) generation from cheese whey with simultaneous production and extraction
of volatile fatty acids (VFAs) was studied in UASB reactors at two temperatures (20 and
35 C) and pH values (5.0 and 4.5). The extraction module, installed through a recirculation
loop, was a silicone tube coil submerged in water, which allows concentration-driven
extraction of undissociated VFAs. Operating conditions were selected as a compromise
for the recovery of both H2 and VFAs. Batch experiments showed a higher yield (0.9 mol H2
mol 1 glucoseeq.) at 35 C and pH 5.0, regardless of the presence of the extraction module,
whereas lower yields were obtained at pH 4.5 and 20 C (0.5 and 0.3 mol H2 mol 1 glucoseeq., respectively). VFAs crossed the silicone membrane, with a strong preference for butyric
over propionic and acetic acid due to its higher hydrophobicity. Sugars, lactic acid and
nutrients were retained, resulting in an extracted solution of up to 2.5 g L 1 butyric acid
with more than 90% purity. Continuous experiment confirmed those results, with production
rates up to 2.0 L H2 L 1 d 1 and butyric acid extraction both in-line (from the UASB
recirculation) and off-line (from the UASB effluent). In-line VFA extraction can reduce the
operating costs of fermentation, facilitating downstream processing for the recovery of
marketable VFAs without affecting the H2 production
Carboxylic acids production and electrosynthetic microbial community evolution under different CO2 feeding regimes
No full textMicrobial electrosynthesis (MES) is a potential technology for CO2 recycling, but insufficient information
is available on the microbial interactions underpinning electrochemically-assisted reactions. In this
study, a MES reactor was operated for 225 days alternately with bicarbonate or CO2 as carbon source,
under batch or continuous feeding regimens, to evaluate the response of the microbial communities,
and their productivity, to dynamic operating conditions. A stable acetic acid production rate of
9.68 g m-2 d-1, and coulombic efficiency up to 40%, was achieved with continuous CO2 sparging, higher
than the rates obtained with bicarbonate (0.94 g m-2 d-1) and CO2 under fed-batch conditions
(2.54 g m-2 d-1). However, the highest butyric acid production rate (0.39 g m-2 d-1) was achieved with
intermittent CO2 sparging. The microbial community analyses focused on differential amplicon sequence
variants (ASVs), allowing detection of ASVs significantly different across consecutive samples. This analysis,
combined with co-occurence network analysis, and cyclic voltammetry, indicated that hydrogenmediated
acetogenesis was carried out by Clostridium, Eubacterium and Acetobacterium, whereas
Oscillibacter and Caproiciproducens were involved in butyric acid production. The cathodic community
was spatially inhomogeneous, with potential electrotrophs, such as Sulfurospirillum and Desulfovibrio,
most prevalent near the current collector. The abundance of Sulfurospirillum positively correlated with
that of Acetobacterium, supporting the syntrophic metabolism of both organisms
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
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