1,720,974 research outputs found
Establishment and Bioreactor Cultivation of Morinda Elliptica Cell Cultures for the Production of Anthraquinones
Get PDFMorinda elliptica (Rubiaceae) cell suspension cultures were established in
shake flask and bioreactor systems for the production of anthraquinones (AQ). To
improve AQ productivity at shake flask level, manipulations of media components
such as carbon, nitrogen, phosphate and myo-inositol; and cultural conditions such as
incubation temperature, light intensity, culture and inoculum age, were made. At
bioreactor level, the study was aimed at finding the best bioreactor operation with
minimmn foaming and wall-growth problem. Several strategies such as mode of
aeration, number of impellers, paddle orientation, antifoam addition and medium
fonnulations, were applied.
Murashige and Skoog's basal medium was found to be the best medium in
enhancing both cell growth and AQ production. By manipUlation of sucrose
concentration, hormone combination and concentration, culture age and inoculum age, the type of medium formulation used to grow inoculum, incubation temperature
and light intensity, three types of media were formulated - maintenance medium (M),
growth medium (G) and production medium (P). The toxic effects of nitrogen were
shown not a result of the individual effect of nitrogen toxicity per se but of both
individual and collective effects of NR₄⁺ and N0₃⁻ levels, in consonance with the
level of sucrose and the medium formulation used. Reduction in pH for cultures
grown in medium containing high concentration of NR₄⁺ was another contributing
factor for ammonium toxicity. Phosphate had little influence on cell growth and AQ
production though its absence could suppress growth completely. The phosphate
toxicity could also occur depending on sucrose level and medium formulation. Myoinositol
was not an absolute requirement in M elliptica cell suspension culture.
The growth of cell suspension cultures of M elliptica in G and P media were
sigmoidal. The AQ yields in P medium, of 2.9 and 4.5 gl⁻₁ with corresponding
overall productivity of 0.14 and 0.21 gl⁻₁ dl⁻₁ , under illumination and in the dark,
respectively, were among the highest amount of secondary metabolites and
productivities by plant cell suspension cultures. The formation of AQ displayed a
non-growth associated characteristic. High sucrose, glucose and fructose
concentration over the period of two weeks in P medium was suggested to cause
osmotic pressure on the cells which hindered rapid growth, leading to higher
accumulation of AQ. With increasing culture age to 36 month-old, the doubling time
was increased by 30% to 1.5 days; and 100% to l .6 days, in M and P medium,
respectively. The maximum cell concentration in LP(36) was however 35% lower
than LP(l8) while the AQ yield dropped sharply from 2.92 g l⁻₁ to a mere 0.55 g l⁻₁ .
The spent medium was observed more yellowish in LP(36) indicating that AQ was no
longer retained in the cell vacuole but released into the medium. The faster rate of
sucrose hydrolysis and uptake rate of glucose and fructose in LP(36) may have reduced the osmotic pressure in the medium which allows rapid cell growth and
diffusion of AQ
Enhanced anthraquinones production from adsorbent-treated Morinda elliptica cell suspension cultures in production medium strategy.
Get PDFContinuous removal of anthraquinones (AQ) by Amberlite polymeric adsorbents (XAD-4, XAD-7 and XAD-16) through in situ adsorption in Morinda elliptica cell suspension cultures is studied for product recovery and improvement of the overall titre. Ethanol was the best eluting solvent for effective recovery of AQ from all adsorbents. Pre-treatment of XAD-4 with sodium acetate not only enhanced intracellular AQ, but also AQ release and subsequent recovery from the adsorbent. The addition of sodium acetate pretreated XAD-4 on day 18 for 6-day contact period, achieved comparable cell growth to control (41 g/L), but with 1.3-fold higher intracellular AQ (124 mg/g DW) and two-fold increase in extracellular AQ (14.3 mg/L). High amount of adsorbent and longer contact period for the cultures entering stationary growth phase, stimulated AQ release and recovery but at the expense of cell growth. With 5–8.3 g XAD-4 adsorbent per litre M. elliptica culture in production (P) medium, between 60 and 90% AQ was recovered from extracellular AQ after 24–26 days of culture period
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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