1,720,969 research outputs found
Sintesi radicaliche di zuccheri ramificati e di disaccaridi 5 - 5' e 6 - 6' a partire da alogenozuccheri
No full textEffects of saxitoxin (STX) and veratridine on bacterial Na+ -K+ fluxes: a prokaryote-based STX bioassay
No full textSaxitoxin (STX) is a potent natural sodium channel blocker and represents a significant health concern worldwide. We describe here the antagonistic effects of STX and veratridine (VTD), an Na+ channel activator, on three gram-negative bacteria and their application to an STX bioassay. STX reduced the total cellular levels of both Na+ and K+, as measured by flame photometry, whereas VTD increased the cellular concentrations relative to control ion fluxes in the cyanobacterium Cylindrospermopsis raciborskii AWT205. Endogenous STX production in toxic cyanobacterial strains of C. raciborskii and Anabaena circinalis prevented cell lysis induced by VTD stress. Microscopic cell counts showed that non-STX producing cyanobacteria displayed complete cell lysis and trichome fragmentation 5 to 8 h after addition of VTD and vanadate (VAN), an inhibitor of sodium pumps. The addition of STX, or its analogue neoSTX, prior to treatment with VTD plus VAN prevented complete lysis in non-STX-producing cyanobacteria. VTD also affected cyanobacterial metabolism, and the presence of exogenous STX in the sample also ameliorated this decrease in metabolic activity, as measured by the cellular conversion of tetrazolium into formazan. Reduced primary metabolism was also recorded as a decrease in the light emissions of Vibrio fischeri exposed to VTD. Addition of STX prior to VTD resulted in a rapid and dose-dependent response to the presence of the channel blocker, with samples exhibiting resistance to the VTD effect. Our findings demonstrate that STX and VTD influence bacterial Na+ and K+ fluxes in opposite ways, and these principles can be applied to the development of a prokaryote-based STX bioassay
Rivestimenti di Ni-W amorfo per elettrodeposizione - AMORPHOUS NI-W COATINGS BY ELECTRODEPOSITION
No full textSi è studiato un processo di deposizione da bagno acido di rivestimenti di lega amorfa Ni-W, esaminando da
una parte gli effetti di alcuni parametri di composizione dell’elettrolita e dall’altra l’influenza della densità
di corrente e della sua modulazione a impulsi unipolari, pur in un campo limitato di parametri operativi. I
depositi ottenuti presentano un insieme di proprietà, allo stato di deposizione o dopo trattamento termico, di
sicuro interesse applicativo. La caratterizzazione dei depositi di lega amorfa Ni-W ha fatto emergere in particolare
quanto segue: (1) la struttura allo stato di deposizione è amorfa per tenore di tungsteno superiore a
circa 18% at., valore poco superiore al limite di solubilità del W nel Ni; (2) la durezza dei depositi aumenta col
tenore di W nell’intervallo di composizione 17-32%at. da circa 5 a 7,5 GPa, rispettivamente; (3) la struttura di
deposizione si mantiene inalterata dopo permanenza a 450°C per 6 h, secondo l’analisi di diffrazione di raggi
X; (4) le leghe al 30%at. di W manifestano all’aumentare della temperatura dapprima la trasformazione da
struttura amorfa a struttura cristallina quindi la separazione di una seconda fase entro la matrice Ni-W; (5) le
trasformazioni della struttura producono un aumento considerevole della durezza fino a valori di oltre 20 GPa,
secondo misure di indentazione a carco massimo di 50 mN
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
Rivestimenti di Ni-W amorfo per elettrodeposizione
Full text linkSi è sviluppato un processo di deposizione da bagno acido di lega amorfa Ni-W con un insieme di proprietà di sicuro interesse applicativo. Si è inoltre sperimentata la deposizione con modulazione di corrente in un campo di parametri operativi limitato, verificando così la possibilità di migliorare ulteriormente le prestazioni del processo. I risultati si possono sommariamente indicare nei termini seguenti: (1) la struttura dei depositi allo stato di deposizione è amorfa per tenore di tungsteno superiore a circa 18% at., valore poco superiore al limite di solubilità di W in Ni; (2) la durezza dei depositi aumenta col tenore di W nell’intervallo 17-32%at. da circa 5 GPa a 7,5 GPa, rispettivamente; (3) la struttura secondo XRD si mantiene inalterata dopo permanenza a 450°C per 6 h; (4) le leghe al 30%at. di W subiscono all’aumentare della temperatura la trasformazione da struttura amorfa a struttura cristallina seguita dalla separazione di una o due fasi intermetalliche entro la matrice Ni-W; (5) le trasformazioni della struttura producono un aumento considerevole della durezza fino a valori di circa 20 GPa (secondo misure di indentazione a carco massimo di 50mN)
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
- …
