1,721,004 research outputs found
Wurtz-type reductive coupling reaction of primary alkyl iodides and haloorganotins in cosolvent/H2O(NH4Cl)/Zn media as a route to mixed alkylstannanes and hexaalkyldistannanes
No full textMixed tetra-alkylstannanes R3SnR' (R = Et, n-Pr, n-Bu and RI = Me, Et, n-Pr, n-Bu, n-Pent) and R2SnR2' (R = n-Bu and R' = Me, Et, n-Pr, n-Bu) can be easily prepared in a one-pot synthesis via coupling reaction of alkyl iodides R'I with R3SnX (X = Cl, I) and R2SnCl2 compounds in cosolvent-H2O(NH4Cl) medium mediated by zinc dust. Coupling also occurs with (Bu3Sn)(2)O. It has been verified that reactions are possible only with primary alkyl iodides; with secondary alkyl iodides the coupling reaction fails. When alkyl chlorides and bromides are used ditin compounds are obtained instead of the unsymmetrical tetra-alkylstannanes. This represents a route to hexaalkyldistannane
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
Statins for the primary prevention of cardiovascular events in elderly patients: a picture from clinical practice without strong evidence from clinical trials
No full textStatins have been demonstrated to be beneficial for secondary prevention of cardiovascular (CV) events also in the elderly. However, a great debate is ongoing about the actual effectiveness in the primary prevention in this patient group. Notwithstanding the lack of strong evidence for primary prevention of CV events in the elderly, statins might be prescribed to elderly in general practice, thus contributing to increase the economic burden of this drug type on the Italian National Health System expenditure.
We have conducted an analysis using the general practice database of Caserta-1 Local Health Unit. We selected subjects that received at least one statin prescriptions during the years 2004-2005. We stratified statin users according to CV primary and secondary prevention.
The data show that 17.3% of statin users are aged 75 and older (median 78). Prevalence of statin use in elderly patients is 10.0%. Primary prevention of CV events represents the most frequent indication of use of statins in this age group (62.7%). In particular, 30.6% of elderly people receiving statins for primary prevention are new users. Almost 40% of statin users aged 75 and older received only one to five statin prescriptions within the study period.
Our data show a wide use of statins in patients aged 75 and
older, particularly for primary prevention of CV events. These results should be interpreted also in relation to economics.
Alternatively the risk of statin-related adverse events increases with age because of polytherapy and reduced hepatic and renal
function.
Economic impact and a benefit risk ratio assessment of statin therapy for primary prevention of CV events in elderly people should be taken into account
Burden of cardiovascular disease in elderly with Parkinson's disease who start a dopamine agonist agent
No full textIn recent years, some concerns have been raised about the association between the use of pergolide or cabergoline, ergotderived DA, and the development of fibrotic valvular heart disease.
AIM: To characterize the users of ergot-derived DAs and those that are not ergot derived in clinical practice, with particular regard to cardiovascular diseases, using a general practice database.
Of almost 120,000 subjects registered in the lists of 93 general practitioners enrolled, 1-year incident users of ergot- (cabergoline, lisuride, pergolide, and bromocriptine) and non-ergot-derived (pramipexole and ropinirole) DAs who had PD in 2004 or 2005 were selected.
Almost 70% of incident users of ergot-derived DAs were aged 65 and older (less than users
of non-ergot-derived DAs), in contrast with international guidelines.
A higher proportion (20%) of users of ergot-derived DAs have more than three concomitant CV diseases than do users of non-ergot-derived DAs (8%). Patients who start a therapy with ergotderived DAs are more likely (Po.05) to have heart failurethan those who use non-ergot-derived DAs. a significantly higher proportion (Po.05) of patients starting treatment with ergotderived DAs concomitantly received three or more cardiovascular medications than of users of non-ergotderived DAs. Overall, incident users of ergot-derived DAs ( 85% of these being cabergoline users) seem to have a worse cardiovascular profile than users of non-ergotderived DAs.
This finding should be considered in light of the warning of the heart valvular fibrosis risk associated with use of ergot-derived DAs in patients with P
Statins for the primary prevention of cardiovascular events in elderly patients: a picture from clinical practice without strong evidence from clinical trials.
No full textDispelling 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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