1,721,006 research outputs found
Enhancing the potential of enantioselective organocatalysis with light
No full textOrganocatalysis - catalysis mediated by small chiral organic molecules - is a powerful technology for enantioselective synthesis, and has extensive applications in traditional ionic, two-electron-pair reactivity domains. Recently, organocatalysis has been successfully combined with photochemical reactivity to unlock previously inaccessible reaction pathways, thereby creating new synthetic opportunities. Here we describe the historical context, scientific reasoning and landmark discoveries that were essential in expanding the functions of organocatalysis to include one-electron-mediated chemistry and excited-state reactivity
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
Effect of sample preparation with or without shell liquor on contents and retentions of macro and micro elements in three species of bivalve mollusca
No full textFonti proteiche alternative nella produzione di orata (sparus aurata) a porzione ed effetti sulla qualità sensoriale
No full textQuesta indagine si proponeva di verificare la fattibilità qualitativa della sostituzione
della farina di pesce con fonti proteiche alternative nella produzione di orate (classe di
peso 300-400 g). Le fonti alternative in questione erano farina di Hermetia illucens
(Black soldier fly) allo stato larvale e un lievito autolisato derivante da Saccharomyces
cerevisiae.
L'enfasi della prova consisteva nel verificare la discriminabilità sensoriale dell'orata
allevata con diete contenenti le suddette materie prime rispetto ad una dieta di
controllo.
I test sensoriali sono stati eseguiti da un panel di dieci membri, seguendo l'approccio
QDA.
Sono stati identificati trentuno descrittori sensoriali: Odore per le vie dirette (Intensità
globale, Salso, Patate lesse, Pesce bollito, Polpo lessato, Latte bollito, Zucchino lesso,
Terra, Petto di pollo bollito), Aspetto (Colore, Proteine coagulate, Fioccosità visiva),
Tessitura (Durezza, Masticosità, Fibrosità, Percezione di umidità, Untuosità), Odore per
le vie retronasali (Intensità complessiva, Petto di pollo bollito, Patata lessa, Salmone al
vapore, Terra, Zucchino lesso, Polpo lessato), Gusti base (Salato, Dolce, Acido, Amaro,
Umami), Sensazioni di bocca (Metallico, Astringente).
Ogni descrittore sensoriale è stato collegato a due riferimenti che descrivono l'intensità
minima e massima trovata nel campione, al fine di ottimizzare sia la ripetibilità sia la
riproducibilità delle risposte sensoriali.
Una differenza marginalmente significativa è emersa solo per quanto riguarda l'odore di
zucchino lesso (P= 0,0572), con un valore leggermente superiore nella polpa delle orate
alimentate con la tesi contenente lievito autolisato (Saccharomyces cerevisiae)
In definitiva, nessun tratto sensoriale indesiderato è emerso nella carne di orata di
allevamento dopo la somministrazione di farina di larve di Hermetia illucens o di lievito
autolisato da Saccharomyces cerevisiae, il che dimostra l’applicabilità anche in diete
commerciali di queste due fonti proteiche alternative
Secondary amine-catalyzed asymmetric γ-alkylation of α-branched enals via dienamine activation
No full textThe direct and enantioselective γ-alkylation of α-substituted α,β-unsaturated aldehydes proceeding under dienamine catalysis is described. We have found that the Seebach modification of the diphenyl-prolinol silyl ether catalyst in combination with saccharin as an acidic additive promotes an SN1 alkylation pathway, while ensuring complete γ-site selectivity and a high stereocontrol. Theoretical and spectroscopic investigations have provided insights into the conformational behavior of the covalent dienamine intermediate derived from the condensation of 2-methylpent-2-enal and the chiral amine. Implications for the mechanism of stereoinduction are discussed. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich, Switzerland
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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