1,721,084 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
Cyclopropyl building blocks for organic synthesis part 64 - Facile preparation of hexahydropyrrolo[3,2-e][1,4]diazepine-2,5-diones and tetrahydrofuro[1H][3,2-e][1,4]diazepine-2,5-diones by rearrangements of cyclopropylketimines and cyclopropylketones
No full text[GRAPHICS] Chlorolactames 2a-f reacted with sodium azide to give the cyclopropylketimines 3a-f (75-89%), and acid hydrolysis of 3c,d yielded the cyclopropylketones 6c,d (61-67%), Compounds 3a-f and 6c,d were transformed by heating (170-240 degreesC, sublimation) to the air-sensitive dihydropyrroles 4a-f (51-71%) and dihydrofurans 7c,d (85-91%), Oxidation of the dihydro derivatives 4a-f and 7c,d with DDQ led to novel types of pyrrolo[3,2-e][1,4]diazepinedione derivatives 5a-f (75-84%) and furo[H-1][3,2-e][1,4]diazepinediones 8c,d (91-93%)
Multislice CT angiography: Optimization of scan parameters in a vascular phantom.
No full textPurpose: The aim of this study is to determine the optimal scan parameters for the evaluation of experimental vascular stenoses with a multislice-helical CT. Material and Methods: A vascular phantom consisting of four tubes with an inner diameter of 8 mm and with experimental stenoses of 50%, 75% and 90% was scanned in different tube orientations using a multislice-CT scanner (LightSpeed QX/i, GE, Milwaukee, USA). Examinations were performed with increasing collimations (1.25-5mm), tube currents (100-300mA) and two different table speeds (0.75 HQ mode and 1.5 HS mode). Results: The most exact measurements were obtained in tubes angulated parallel to the scan direction with a collimation of 2.5 mm in the HQ mode (7.5 mm/rot.). An almost equivalent accuracy was obtained in the HS mode (15 mm/rot.) with a collimation of 2.5 mm when higher tube currents (300 mA) were employed. The degree of stenoses was overestimated when the tube was angulated perpendicular to the z-axis. Conclusion: Multislice-CT provides a good detection rate of vascular stenoses especially at 0 degrees and also at 45 degrees angulation in the HQ mode. The use of the HS mode with higher tube currents allows scanning of longer distances with almost identical accuracy
Diagnosis of pulmonary embolism and the underlying venous thrombosis by multi-slice CT.
No full textAim: To determine the value of multi-slice CT for the diagnosis of acute pulmonary embolism and an underlying venous thrombosis. Methods: 70 patients with clinically suspected acute pulmonary embolism were examined. Using multi-slice CT a combined examination of the pulmonary arteries and the veins of the lower limb, pe(vis and abdomen was performed. Only one single bo[us of 150 ml iopromid 300 was injected into a cubital vein with a flow of 4 ml/s. First, the pulmonary arteries were scanned with a slice thickness of 2.5 mm and a pitch of 1.5. On arrival of the contrast medium at the popliteal veins, indicated by bolus trakking, the veins of the lower limbs up to the end of the inferior vena cava were imaged using a slice thickness of 3.75 mm and a pitch of 1.5. The results could be compared with a ventilation-perfusion scan in 48 cases, with a Doppler ultrasound examination in 46 cases, and with a venography in 70 cases. Furthermore, the image quality of all arterial and Venous regions was subjectively assessed. Results: in all patients who underwent multi-slice CT the pulmonary arteries as well as the veins of the lower half of the body could be recorded completely. Regarding the pulmonary arteries the image quality showed excellent results for the central and segmental arteries. The region up to the 3rd division in subsegmental branches could be sufficiently judged. More peripherally, a diagnostic assessment was not possible. The image quality of the veins was excellent in all sections, except the calf, where a reliable diagnosis could not be made. The comparison with the other techniques confirmed the superiority of multi-slice CT concerning the central and segmental pulmonary arteries and the veins from the popliteal vein to the inferior vena cava. In contrast, peripheral pulmonary emboli can be detected more certainly in ventilation/perfusion scans. The veins of the calf can be evaluated more reliably with venography. Conclusion: Multi-slice CT proved to be an outstanding tool in the diagnosis of acute pulmonary embolism. The clinically suspected disease and a causing venous thrombosis can be detected in a fast and reliable way. At present, multi-slice CT is not suitable for the recognition of peripheral emboli. However, expected technical developments hold promise for future improvements
Recrystallization Experiments in Tensile Deformed <100>-Oriented Single Crystals of Copper-Phosphorus and Copper-Manganese Alloys
No full textThe recrysallization process in specimens of dilute CuP and CuMn alloys was investigated to determine those orientation relationships between recrystallized grains and deformation microstructure, which favour rapid grain growth. The specimens were prepared from tensile deformed -oriented single crystals. In the CuP alloy the largest recrystallized grains have near 20° or 53° orientation relationships to the deformation microstructure. In the CuMn alloy only the two orientation relationships 30° and 48° were found
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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