1,721,022 research outputs found
solubilization of the membrane-bound sialidase from pig brain by treatment with bacterial phosphatidylinositol phospholipase C
No full textThe total pellet from pig forebrain (from which the cytosolic sialidase was completely washed out) was treated with phosphatidylinositol phospholipase C (PIPLC) and centrifuged at high speed. The supernatant contained sialidase and 5'-nucleotidase activities. The greatest liberation of sialidase was obtained after incubation for 20 min with PIPLC at 37°C using pH 6.0 and a ratio between PIPLC (as units) and protein of 1.6. Under these conditions, the release of sialidase, 5'-nucleotidase, and protein was 22, 50, and 18.5%, respectively. On treatment with PIPLC, a purified preparation of pig brain neuronal (synaptosomal) membranes released 28% of its sialidase, whereas a purified preparation of pig brain lysosomes did not liberate any sialidase activity. The pH optimum of sialidase present in the supernatant obtained after PIPLC treatment of the total pellet was 4.2, the same as that of the enzyme embedded in the membrane. When this supernatant was subjected to ammonium sulfate fractionation, 88% of its sialidase, having a pH optimum of 4.2, was recovered in the fraction precipitated between 20 and 45% of salt saturation and subsequently dialyzed. Ammonium sulfate treatment caused the appearance of a second sialidase activity, having a pH optimum of 6.6 and behaving on fractionation similarly to the pH 4.2 sialidase. The K(m) and V(max) values of pH 4.2 and pH 6.6 sialidase were similar (1.48 x 10-4 and 0.98 x 10-4 M for K(m) and 1.6 and 1.4 mU/mg of protein for V(max), respectively), whereas the stability on standing at 4°C or exposure to freezing and thawing cycles was greater for pH 4.2 sialidase. Both enzyme activities could be separated by Sepharose 6B column filtration in a unique fraction that was eluted between catalase and bovine serum albumin. These results suggest that (a) the plasma membrane fraction from pig forebrain contains two sialidases (pH 4.2 and 6.6) that are presumably linked via a glycosylphosphatidylinositol anchor, sensitive to PIPLC action, and (b) pH 6.6 sialidase may be in the membrane under the inhibition of a factor that is liberated by PIPLC treatment and removed during ammonium sulfate fractionation and subsequent dialysis
La scienza della vegetazione per l'analisi e la gestione ambientale (44° Congresso della Società Italiana di Scienza della Vegetazione)
No full textLa scienza della vegetazione è un settore avanzato delle scienze ecologiche. Dalla vegetazione, dai diversi stati di questo sistema che deriva dai processi di aggregazione delle popolazioni di specie vegetali, dipende infatti la diversità ambientale e la diversità del paesaggio. Il Convegno ha presentato i risultati più recenti e significativi ottenuti nelle ricerche sull'ecologia della vegetazione, offrendo un panorama delle loro potenzialità applicative.
Le applicazioni nella gestione ambientale su cui il Convegno ha focalizzato i suoi lavori riguardavano la conservazione e la gestione degli habitat, che sono lo spazio della biodiversità, e il monitoraggio a diversi livelli di scala degli effetti ecologici del “global change”, che caratterizza i nostri tempi.
Il Convegno si è tenuto a Ravenna dal 27 al 29 febbraio 2008. I lavori si sono svolti attraverso tre sessioni, con relazioni ad invito, di studiosi italiani ed europei, ed una sessione poster
Evolution of vegetation under intensive grazing : Two examples in North-western Italian mountains
No full textRe-utilization of abandoned grasslands by intensive grazing was investigated in two areas of the Appennino Ligure-Piemontese, at 596 and 820 m. Vegetation analysis was carried out for a period of 4 and 7 years, respectively, in the two environments. In the location with greater environmental limitations, intensive grazing made it possible to overcome certain constraints, increasing floristic richness and homogeneity. In the better location, able to sustain higher grazing pressure, grazing-tolerant species increased their presence, with the creation of communities characterized by a few species
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
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
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
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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