130,367 research outputs found
Production of L(+) and D(-) lactic acid isomers by Lactobacillus casei subsp. casei DSM 20011 and Lactobacillus coryniformis subsp. torquens DSM 20004 in continuous fermentation
No full textWith the aim of producing L(+) and D(-) lactic acid to be employed in poly-lactic acid polymer production, for biomedical applications, the strains Lactobacillus casei subsp. casei DSM 20011 and Lactobacillus coryniformis subsp. torquens DSM 20004 were studied in a conventional chemostat mode using various dilution rates. The results obtained showed that the dilution rate influences the fermentation pattern, modifying various fermentation parameters. Nevertheless, the product and biomass yields remained constant and the ratio of the L(+) and D(-) isomers of lactic acid was not affected by the dilution rate. The optimal glucose concentration on inlet feed medium was also determined for the L. coryniformis fermentation
Production of L- and D-lactic acid isomers by Lactobacillus casei subsp. casei DSM 20011 and Lactobacillus coryniformis subsp. torquens DSM 20004 in continuous fermentation
No full textWith the aim of producing L(+) and D(−) lactic acid to be employed in poly-lactic acid polymer production, for biomedical applications, the strains Lactobacillus casei subsp. casei DSM 20011 and Lactobacillus coryniformis subsp. torquens DSM 20004 were studied in a conventional chemostat mode using various dilution rates. The results obtained showed that the dilution rate influences the fermentation pattern, modifying various fermentation parameters. Nevertheless, the product and biomass yields remained constant and the ratio of the L(+) and D(−) isomers of lactic acid was not affected by the dilution rate. The optimal glucose concentration on inlet feed medium was also determined for the L. coryniformis fermentation
Solids distribution and rising velocity of buoyant solid particles in a vessel stirred with multiple impellers
No full textThe distribution of buoyant solid particles in agitated suspensions has been studied. The investigation was carried out in a baffled vessel characterised by an aspect ratio equal to four and stirred with four radial impellers. Dilute suspensions of single-sized spherical particles of expanded polystyrene (density equal to 90.7 kg/m3) in water were used. Solid concentration was measured with a non-intrusive optical technique. Measurements were performed along the axis of the reactor to obtain steady-state vertical profiles (that increase from the vessel base to the top) as well as at fixed elevations to determine their transient after a pulse of solids injected at the bottom.
Both the steady-state profiles and the transient concentration curves were interpreted in terms of the axial dispersion model with sedimentation. By data treatment the rising velocity in the agitated system could be determined, which proved to be significantly smaller than the rising velocity in a still liquid. The ratio of these two velocities is in reasonable agreement with a correlation of the ratio of the settling velocities for heavy particles with the ratio of the Kolmogorov microscale to particle diameter established in the past
Role of CFD techniques in discriminating experimental solids concentration data in stirred suspensions and modelling of the solids concentration profiles in a pilot reactor
No full textIn this work, the suitability of an optical probe for studying local solid particle distribution in agitated systems and of Computational Fluid Dynamics (CFD) as a means to discriminate among the experimental data is investigated. Solids concentrations are determined in a high-aspect-ratio baffled tank stirred with three Rushton turbines by means of a fibre-optical probe and by CFD simulations. The local analysis of the simulated liquid flow field allows to better understand the source of differences in the measured solid concentrations that are obtained by changing the angular orientation of the probe in a few specific positions and, therefore, to identify the best operating mode for the measurements. The predicted radial and axial solid concentration profiles are then compared with the experimental data obtained with the most reliable probe orientation and very good agreement is found. This study allows to point out that, once proper computational strategies are selected, the usefulness of CFD simulations is twofold: they can be adopted for obtaining reliable predictions of various parameters in solid-liquid systems and used for gaining a better understanding of the complex fluid flow features of turbulent multiphase flows
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Solids distribution and rising velocity of buoyant solid particles in a tank stirred with multiple turbines: a simplified approach for the study of sparged gas-liquid reactors (Paper 7.4)
No full textThe distribution of buoyant solids in agitated suspensions has been studied. The investigation was carried out in a baffled vessel characterised by an aspect ratio equal to four and stirred with four radial impellers. Dilute suspensions of single-sized spherical particles of expanded polystyrene (density equal to 90.7 kg/m3) in water were used. Solid concentration was measured with a non-intrusive optical technique. Measurements were performed along the axis of the reactor to obtain steady-state vertical profiles as well as at fixed elevations to determine the concentration transient after a pulse of solids injected at the bottom. Both the transient concentration curves and the steady-state profiles were interpreted by means of the axial dispersion model with sedimentation. The particle rising velocity in the agitated system was determined by data treatment; it proved to be significantly smaller than the free-rising velocity, i.e. the rising velocity in a still liquid. The ratio of these two velocities is in reasonable agreement with a correlation of the ratio of the settling velocities of heavy particles with the ratio of the Kolmogorov microscale to particle diameter established previously
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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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