1,720,961 research outputs found
A preliminary diffusion tensor and magnetization transfer magnetic resonance imaging study of early-onset multiple sclerosis
No full textBackground: Early-onset multiple sclerosis (MS) typically has a more favorable course than adult-onset disease. Objective: To assess the extent of microscopic tissue damage in the brain and cervical cord of patients with early-onset MS. Design: During a single magnetic resonance imaging session, images of the brain and spinal cord were obtained using diffusion tensor and magnetization transfer magnetic resonance imaging. Patients: We studied 13 patients with early-onset MS and 10 healthy volunteers. Results: Compared with control subjects, patients with early-onset MS showed only a slight increase of the average mean diffusivity of the normal-appearing brain tissue. Conclusion: The relatively modest central nervous system damage detected in these patients might explain why early-onset MS typically has a more favorable clinical course than adult-onset MS
Characteristics of chronic MS lesions in the cerebrum, brainstem, spinal cord, and optic nerve on T1-weighted MRI
No full textCognitive impairment in multiple sclerosis is associated to different patterns of gray matter atrophy according to clinical phenotype.
No full text"Objective: To investigate whether cognitive impairment in multiple sclerosis (MS) patients is associated to different patterns of gray matter (GM) atrophy and T2-visible lesion distribution according to the clinical phenotype. Experimental Design: Twenty-two relapsing remitting (RR), 29 secondary progressive (SP), and 22 primary progressive (PP) MS patients, and 39 healthy controls underwent high-field structural magnetic resonance imaging and an extensive neuropsychological battery. Voxel-wise distribution of GM damage and T2-lesions was compared between cognitively impaired (CI) and cognitively preserved (CP) patients according to their clinical phenotype. Principal Observations: Thirty-nine MS patients were CI. In all MS groups, regional GM loss was correlated with cognitive impairment. Different patterns of regional distribution of GM atrophy and T2-visible lesions were found between CI vs. CP MS patients, according to their clinical phenotype. No areas were significantly more atrophied in CI SPMS vs. CI RRMS patients. Conversely, compared with CI PPMS, CI SPMS patients had a significant GM loss in several regions of the fronto-temporal lobes, the left hypothalamus and thalami. While in RRMS and SPMS patients there was a correspondence between presence of T2 visible lesions and GM atrophy in several areas, this was not the case in PPMS patients. Conclusion: Distinct patterns of regional distribution of GM damage and T2-visible lesions are associated with cognitive impairment in MS patients with different clinical phenotypes. The correspondence between lesion formation and GM atrophy distribution varies in the different forms of MS.
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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