1,720,963 research outputs found
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
A slightly suppressive dose of L-thyroxine does not effect bone turnover and bone mineral density in pre- and postmenopausal women with nontoxix goitre.
No full textThere are controversial reports on the potential role of L-thyroxine administration as a risk factor for osteoporosis. We studied bone mass and metabolism in a homogeneous series of 50 Caucasian women, 25 premenopausal and 25 postmenopausal, having nontoxic goitre treated with slightly suppressive L-thyroxine doses (50-200 micrograms/day) with subnormal serum TSH and normal thyroid hormone levels. These patients were matched with 50 controls for age, sex, body mass index, menopausal and thyroid disease. Patients and controls were also investigated for minor determinants of bone loss, such as hereditary and life-style factors. Patients and controls filled in a questionnaire and underwent physical examination, routine laboratory tests and calciotropic and thyroid hormone assay. Bone mineral turnover was evaluated by determining serum osteocalcin, alkaline phosphatase, tartrate-resistant acid phosphatase, calcium, phosphate, urine hydroxyproline/creatinine and calcium/ creatinine ratio. Bone mineral density was measured by dual-energy X-ray absorptiometry at the lumbar spine, femoral neck, trochanter and Ward's triangle. No difference in bone mineral density or biochemical markers was found between patients and controls; bone density and turnover were significantly affected by menopausal status. No relationship between bone density or turnover values and L-thyroxine administration was found. A significant positive correlation was found between osteocalcin and the hydroxyproline/creatinine ratio in premenopausal and postmenopausal patients, but not in controls. Our study suggests that slightly suppressive L-thyroxine administration in nontoxic goitre can activate bone turnover but constitutes neither an actual risk factor for bone loss nor, consequently, for osteoporotic fractures
Influences of Different Air-Inhibition Coatings on Monomer Release, Microhardness, and Color Stability of Two Composite Materials
No full textThe aim of this study was to evaluate the effect of light-curing protocols on two modern resin composites using different air-inhibition coating strategies. This was accomplished by assessing the amount of monomer elution, surface microhardness, and composite discoloration in different storage conditions. A total of 120 specimens were prepared using Filtek Supreme XTE (3M ESPE, Seefeld, Germany) and CeramX Universal (Dentsply DeTrey, Konstanz, Germany). Specimens were light-cured in air as per manufacturer's instructions or in the absence of oxygen. This latter condition was achieved using three different approaches: (i) transparent polyester strip; (ii) glycerin; (iii) argon gas. Specimens were assessed for release of monomers, Vickers hardness, and discoloration after storage in different solutions. The results were analyzed with ANOVA one-way test followed by Student-Newman-Keuls test. Moreover, multiple comparisons of means were performed using the Student t-test (p<0.05). The amount of monomers released from the tested specimens was very low in all conditions. The presence of oxygen induced some decrease in microhardness. The highest discoloration values, for both materials, were obtained after ageing in red wine. In case finish and polish procedures are awkward to achieve in posteriors composite restoration, light-curing in the absence of oxygen should be considered, especially when performing composite restoration in esthetic areas
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
Effects of Dental Methacrylates on Oxygen Consumption and Redox Status of Human Pulp Cells
No full textSeveral studies have already demonstrated that the incomplete polymerization of resin-based dental materials causes the release of monomers which might affect cell metabolism. The aim of this study was to investigate the effects of triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, urethane dimethacrylate, and 2-hydroxyethyl methacrylate on (1) cellular energy metabolism, evaluating oxygen consumption rate, glucose consumption, glucose 6-phosphate dehydrogenase activity, and lactate production, and (2) cellular redox status, through the evaluation of glutathione concentration and of the activities of enzymes regulating glutathione metabolism. Methods. Human pulp cells were used and oxygen consumption was measured by means of a Clark electrode. Moreover, reactive oxygen species production was quantified. Enzymatic activity and glucose and lactate concentrations were determined through a specific kit. Results. Triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, and 2-hydroxyethyl methacrylate induced a decrease in oxygen consumption rate, an enhancement of glucose consumption, and lactate production, whilst glucose 6-phosphate dehydrogenase and glutathione reductase activity were not significantly modified. Moreover, the monomers induced an increase of reactive oxygen species production with a consequent increase of superoxide dismutase and catalase enzymatic activities. A depletion of both reduced and total glutathione was also observed. Conclusion. The obtained results indicate that dental monomers might alter energy metabolism and glutathione redox balance in human pulp cells
Erythrocyte glutathione transferase: a new biomarker in chronic kidney diseases which correlates with plasma homocysteine
No full textAbstract Homocystein (Hcy) is an important cardiovascular risk factor and it is present at high concentrations in more than 90% uremic patients. Glutathione transferases (GSTs) are a superfamily of enzymes involved in cell detoxification. Previous studies reported an increased expression of erythrocyte glutathione transferase (e-GST) in end-stage renal disease patients on maintenance hemodialysis (MHD). We re-evaluated the e-GST levels in 62 MHD patients, 50 controls and studied the correlation between this enzyme and the plasma homocysteine (Hcy). A new automated procedure for GST activity, validated by intra-assay and inter-assay measurements and by recovery experiments, showed a significant increase of e-GST activity. No correlation has been found between e-GST activity and hemoglobin, transferrin, sideremia and markers of systemic inflammation. For the first time a significant correlation was observed between increased plasma Hcy levels and e-GST activity (P < 0.0001) in MHD patients (Tab 1). The correlation between the increased level of e-GST and plasmatic Hcy concentration in MHD patients is of particular interest: plasma hyperhomocysteinemia in fact, is considered a cardiovascular risk factor and it is often associated to renal failure (van Guldener 2006). The autoxidation of this sulfur-containing amino acid produces hydrogen peroxide and high levels of Hcy reduces the bioavailability of nitric oxide forming S-nitrosohomocysteine and inhibiting NOS. Increased levels of e-GST are certainly the effect (and not the cause) of an increased cell toxicity. Thus, the correlation found in the present study between hyperhomocysteinemia and e-GST indicates that high levels of Hcy may be merely a consequence of high levels of circulating toxins. Whatever the primary cause(s) of increased levels of e-GST and Hcy in MHD patients, the present findings suggest that e-GST could be a good marker for toxin exposition and its determination may fulfill a useful probe to assess the efficiency of dialytic procedures in MHD patients. The e-GST activity could be a new biomarker useful to substitute or to be complementary to the time consuming and expensive Hcy determination in MHD patients
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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