1,721,092 research outputs found
Gas-liquid mass transfer rates in unbaffled tanks stirred by PBT: scale-up effects and pumping direction
No full textUnbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a range of applications such as biochemical, food or pharmaceutical processes where the presence of baffles is undesirable for some reason. In this work, the mass transfer performance of unbaffled stirred tanks with pitched blade turbine, operating either in up-pumping or down-pumping mode, was investigated. The influence of impeller size and liquid viscosity were also investigated. The mass transfer intensity was measured by means of the Simplified Dynamic Pressure. Method: The measurements concerned both coalescent and non-coalescent (viscous) batches. Results: confirm that increasing apparatus size has a slightly positive effect on gas-liquid mass transfer coefficient. It was also found that when the PBT is operating in the up-pumping mode the formation of surface oscillations, which lead to undesired instabilities of the whole apparatus, is conveniently minimized. In the super-critical regime, the unbaffled tanks provide a performance comparable with that of the standard (baffled) bioreactors at the same power dissipation, which makes them a viable alternative for general fermentation operations and other gas–liquid reactions
Growing microalgae in a “quasi-isoactinic” photobioreactor
Full text linkThe aim of this work is setting up the conditions of an “iso-actinic” photobioreactor that is a photoreactor for the cultivation of microalgae in which the local volumetric rate of photon absorption (LVRPA), can be considered uniform to a good extent. We describe the composition of this cheap photoreactor and how we made it. The system is driven by an Arduino platform that makes it possible to control light intensity as well as light-dark cycles. Preliminary results obtained by growing Nannochloropsis gaditana, a microalga famous for its fat content, in this innovative reactor are presented. We finally observed how microalgae responds to flashing light irradiation
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
Inoculum of indigenous microalgae/activated sludge for optimal treatment of municipal wastewaters and biochemical composition of residual biomass for potential applications
Full text linkIn this work, municipal wastewater was treated with microalgal/activated sludge consortia. We aimed at
obtaining a positive interaction between the microalgae and the heterotrophic bacteria and identifying the best
combination for bioremediation purposes. A strain of Chlorella sp CW2 employed in this work was isolated from
AS and molecularly characterised in this work for the first time. This strain and another previously isolated strain
(Chlorella sp Pozzillo) were inoculated alone and in combination with AS in different ratios in wastewaters.
Microalgae/activated sludge growth curves were obtained by using a UV–vis spectrophotometer and a fluorimeter
to distinguish the contribution of the photosynthetic microorganisms to the total growth. The effectiveness
for the bioremediation of municipal wastewaters was evaluated by measuring the COD, the total
nitrogen and total phosphorous content at the end of batch cultivations. Overall, the best abatement was achieved
by the microalga Chlorella sp CW2 inoculated with activated sludge in the ratios 1:2 and 2:1, with a
decrease of 81.39 % ± 0.56, 86.12 % ± 0.43, 82.89 % ± 2.66 and 82.5 % ± 0.83, 72.66 % ± 0,46, 97.15 % ±
0.44 of COD, total nitrogen and total phosphorous, respectively. Finally, the residual biomass, constituted by a
sludge enriched in microalgae, was analysed for its content in carbohydrates, lipids and fatty acid in order to
suggest the best application for its valorisation. Considering the final composition of the obtained biomass and its
remediation potential, the most promising sample may be the microalga Chlorella sp CW2 inoculated with
activated sludge in the ratio 1:5
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
MODELLING OF THE GROWTH OF NANNOCHLOROPSIS GADITANA IN DIFFERENT REACTOR GEOMETRIES, EXPERIMENTAL KINETIC PARAMETERS FROM BATCH CULTURES AND BIOCHEMICAL ANALYSIS OF THE OBTAINED BIOMASS
No full textMicroalgae are unicellular and photosynthetic microorganisms that grow using inorganic salts, CO2 and light, and are applied in numerous industrial sectors due to their variety and properties. Due to the lack of information on how microalgae respond to external inputs and to the different environments in which they grow, today the industrial application is not exploited as it should.
It is therefore necessary to create models that allow to predict microalgal growth in different photobioreactors to improve our knowledge, still poorly investigated.
In this work the Monod equation for the specific growth rate was combined with the Lambert-Beer law for the non-homogeneous light distribution in a flat photobioreactor.
Model kinetic parameters related to the cultivation of the microalga Nannochloropsis gaditana were obtained from batch cultivations under different photon-flux densities inside a quasi isoactinic photobioreactor. These parameters were applied in a mathematical model, based on the geometric system considered, for obtaining microalgae growth curves.
Biochemical analyses on the obtained biomass were also executed at the end of each batch cultivation to assess how light distribution influences biomass composition.
The obtained model allowed to successfully predict the growth of the microalga Nannochloropsis gaditana in the different photobioreactor geometries
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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