1,720,959 research outputs found
Cytisine derivatives as ligands for neuronal nicotine receptors and with various pharmacological activities
No full textNeuronal nicotinic acetylcholine receptors (nAChRs) form a family of ACh-gated cation channels made up of different subtypes.
They are widely distributed in peripheral and central nervous systems and are involved in complex cerebral processes as learning,
memory, nociception, movement, etc. The possibility that subtype-selective ligands be used in the treatment of CNS disorders
promoted the synthesis of a large number of structural analogues of nicotine and epibatidine, two very potent nAChR agonists.
Pursuing our long standing research on the structural modification of quinolizidine alkaloids, we devoted our attention to cytisine,
another very potent ligand for many nAChR subtypes. Thus a systematic structural modification of cytisine was undertaken in
order to obtain compounds of potential therapeutic interest at peripheral as well as central level, with a particular concern for
achieving nAChR subtype selective ligands. Up to the present more than 80 cytisine derivatives, mainly of N-substitution and a few
by modifying the pyridone ring, have been prepared. The biological results, which concern so far about an half of the prepared
compounds, indicate that the introduction of a nitro group in position 3 of the pyridone nucleus further enhances the high affinity of
cytisine, while the introduction of substituents on the basic nitrogen, though reducing in different degrees the affinity, gives rise to
compounds with a higher selectivity for central (α4β2) versus gangliar (α3-containing) receptor subtype. On the other hand, the analgesic, antihypertensive and inotropic activities found in some N-substituted cytisines, represent an attractive starting point for the development of more active compounds
Nuove acquisizioni sulla ciclizzazione di Fischer di arilidrazoni del metil-lupinilchetone
No full textAndamento della ciclizzazione indolica di fenilidrazoni di alchil-(chinolizidin-1'-il)metilchetoni
No full text
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
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