1,720,961 research outputs found
Study of the reaction of bis- and tris-pyrylium and -thiopyrylium cations with methoxide ion. Electronic effects of the heterocyclic rings as substituents
No full textA Radical and An Electron Transfer Process are Compared in their Regioselectivities Towards a Molecule with Two Different C-I Bonds: Effect of Steric Congestion
No full textSteric compression in 1,4-diiodo-2,6-dimethylbenzene (2a) makes the C-I bond flanked by methyls substantially weaker (a buttressing effect) than the unhindered C-I bond. Calculations also confirm the weaker bonding interaction of the hindered C-I bond of 2a. This causes a remarkable regioselectivity toward the weaker bond in dehalogenation by stannyl radicals. Conversely, a much lower regioselectivity is found for a process -a photostimulated S(RN)1 reaction with the enolate ion of a ketone - which requires the conversion of 2a into a radical anion. A calculation of the BDE of the C-I bond for aa ArI.- system is offered. Finally, the hindered aryl radical intermediate resulting from cleavage of the weaker C-I bond of 2a(.-) shows a modest but detectable discrimination between reduction or substitution, this once again being due to the steric congestion
Relationship of personality traits and drug of choice by cocaine addicts and heroin addicts
No full textThe link between specific personality profiles and a single psychotropic drug of choice is still unclear and only partially explored. The present study compares three groups of male subjects: 85 patients manifesting heroin dependence (age: 30.07 +/- 2.78), 60 patients manifesting cocaine dependence (age: 31.96 +/- 3.1), and 50 healthy subjects from a random population sample (age: 33.25 +/- 1.45). The patients included in the study showed a long-lasting history of dependence on heroin or cocaine, respectively, 5.2 +/- 2.5 years, 4.6 +/- 2.9 years, and were stabilized in treatment, and abstinent, at least 4 weeks at the time of the diagnostic assessment. Heroin addicts (52.90%) were on methadone maintenance treatment. Cocaine addicts (11.60%) were treated with selective serotonin reuptake inhibitors. Personality traits were measured by the Minnesota Multiphasic Personality Inventory (MMPI-2) and Cloninger's Three-dimensional Personality Questionnaire (TPQ). Character and quantification of aggressiveness were measured by the Buss-Durkee Hostility Inventory (BDHI). Heroin-dependent patients (group A) scored significantly higher on hysteria, masculine-feminine and social introversion subscales of the MMPI, and significantly lower on the harm avoidance (HA) subscale of the TPQ than cocaine addicts. In contrast, scores on the MMPI for hypochondria, psychopathic deviance, and paranoia dimensions were more elevated in cocaine addicts than in heroin-dependent patients. Cocaine addicts scored higher than heroin addicts on the "direct" aggressiveness subscale and on the BDHI total score. Cocaine addicts did not differ from healthy controls on harm avoidance (behavioral control). Although cocaine addicts showed more consistent psychopathic deviance and overt aggressiveness than heroin addicts, higher harm avoidance (behavioral control), hypochondria (or worry about their health), and social extroversion may reduce their proneness to overt antisocial behavior and allow relatively higher levels of social integration. The study's limitations are noted
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
Association of the serotonin transporter promoter polymorphism with smoking behavior among adolescents
No full textSerotonin transporter promoter polymorphism (5-HTTLPR) genotype was previously found associated with smoking behavior, difficulty in quitting smoking, and nicotine addiction; with non-replicated findings and contrasting results. Aim of the present study was to evaluate the possible association between 5-HTTLPR genotype and smoking behavior among adolescents, in relationship with psychological characteristics. Two hundred and ten Caucasian high school students (aged 14-19 years); 103 non-smokers, who have never smoked nicotine; and 107 tobacco smokers have been genotyped. Aggressiveness levels and temperamental traits were measured in both smokers and non-smokers, respectively, utilizing Buss-Durkee Hostility Inventory (BDHI) and Cloninger Three-Dimensional Personality Questionnaire (TPQ). Data about school performance have been also collected. The short-short (SS) genotype frequency was significantly higher among smokers compared with non-smokers (P = 0.023). The odds ratio for the SS genotype versus the long-long (LL) genotype frequency was 1.17 [95% CL (0.30-2.05)], when smokers were compared with non-smokers. The SS genotype frequency was significantly higher among heavy smokers with early onset, compared with moderate smokers with late onset (P = 0.042). BDHI irritability scores, NS scores at TPQ, and school failure frequency were significantly higher in smokers than in non-smokers. Multivariate model-fitting analysis evidenced a significantly greater relationship of genotype with irritability levels (BDHI scores) (0.34, P < 0.001) and temperament traits (NS scores) (0.36, P < 0.001), than with school performance (rate of school under-achievements) (0.18, P < 0.05) and nicotine smoking (number of cigarettes) (0.24, P < 0.01). Accordingly, factor-analysis showed that gene polymorphism contributes more directly to BDHI scores and NS scores (0.73; 0.71) than to smoking behavior and school under-achievement (0.54; 0.51). Our data suggest that a decreased expression of the gene encoding the 5-HTT transporter, due to "S" promoter polymorphism, may be associated with smoking behavior among adolescents and increased risk to develop nicotine dependence, possibly in relationship to personality traits, temperamental characteristics, and school under-achievements
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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