1,721,110 research outputs found
Electron parallel compressibility in the nonlinear development of two-dimensional collisionless magnetohydrodynamic reconnection
No full textSome topological aspects of the magnetic reconnection phenomenon are summarized and recent numerical results, derived within a two-fluid model, of two-dimensional collisionless magnetic reconnection in presence of a strong guide field are reported. Both the Alfven and the whistler frequency range are investigated by including electron parallel compressibility effects that are related respectively to thermal effects and to density fluctuations. The Hamiltonian character of the system is emphasized as it drives the small scale dynamics through the presence of topological invariants. These determine the formation and the shape of small scale current and vorticity layers inside the magnetic island. Secondary fluid instabilities, mainly of the Kelvin-Helmholtz type, can destabilize these layers when a hydrodynamic type regime is achieved. The inclusion of parallel electron compressibility has stabilizing effects. In view of the limitations of the two-fluid modelling, possible developments axe briefly discussed such as the inclusion of Larmor-radius corrections, in lieu of a fully kinetic approach
Prevalence of nonspecific low back pain in schoolchildren aged between 13 and 15 years
No full textAIM:
To investigate the annual (2005) prevalence of nonspecific low back pain (LBP), defined as lumbago not attributed to recognizable, known specific pathology, in a population of adolescents.
METHODS:
We investigated 7542 school teenagers with a structured questionnaire consisting of demographic and anthropometric items, psychosocial factors and life style, presence and intensity of LBP, family history of LBP, and questions about whether the teenager had been referred to a physician for this problem. Univariate (t-test, Mann-Whitney U-test and chi-square test) and multivariate analyses (logistic regression) were performed.
RESULTS:
A total of 1180 (20.5%) teenagers reported one or more episodes of LBP, of whom 900 (76.3%) had consulted a health provider. A significantly greater percentage of LBP was found in the students who practised aerobics and swimming compared to the other sports. The search for risk factors in the whole population revealed no associations between LBP and the investigated anthropometrics or lifestyle items, whereas a significant association was found for gender (to be female), positive family history of LBP and absence of sports activity.
CONCLUSIONS:
Our study shows that nonspecific LBP is a frequent event in teenagers, particularly in females, sedentary children and those with a family history of LBP
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
Healthcare service use in adolescents with non-specific musculoskeletal pain
No full textAIM:
To estimate occurrence of non-specific musculoskeletal pain in a wide population sample of Italian adolescents, and to investigate their use of healthcare services (seeking of medical attention, referral for diagnostic tests and treatment use).
METHODS:
We investigated 7542 high-school adolescents (aged between 12 and 16 years) by a structured questionnaire and consisting of personal data, presence of pain, health provider consulted, referral for diagnostic tests and compliance with the prescribed treatments.
RESULTS:
In 3399 (45.1%) reported musculoskeletal pain (the most affected sites being the spine and knees), 2525 (74.2%) of whom had sought medical attention. Of the 2525 subjects who had sought healthcare, 1061 (42.0%) had consulted more than one health provider, 2410 (95.4%) had been referred for diagnostic tests, and some form of treatment had been recommended for 2445 (96.8%), but only 1694 (69.2%) had complied with prescribed therapies. The most important factors linked to health seeking behaviour were pain intensity, pain lasting longer than 3 months, injury, interruption to or absence of physical activity and localization in the spine and knee.
CONCLUSION:
Non-specific musculoskeletal pain is a frequent event in Italian adolescents and that a large number of these subjects consult a healthcare service
Analisi comparativa del comportamento posturale e muscolare in soggetti con corsetto ortopedico
No full textFattori predittivi di lombalgia in una popolazione di 7542 adolescenti
No full textCon il termine “rachialgie comuni o aspecifiche dell’età evolutiva”,
si intendono i dolori vertebrali in cui non sono identificabili patologie
di fondo che ne spieghino l'origine. Lo scopo di questo lavoro era quello di identificare la prevalenza
di rachialgie e gli eventuali fattori di rischio, in una popolazione di
adolescenti della Provincia di Padova. Il nostro studio è stato condotto nell’anno 2000 e sono stati inclusi
tutti gli studenti delle prime e seconde classi delle scuole superiori
della città di Padova e un più ristretto numero di studenti della terza
media. La nostra popolazione complessiva era composta da 7542
studenti (3777 maschi e 3765 femmine; l’età media era di 15 anni ±
1,21). Lo studio prevedeva l’autosomministrazione di un questionario strutturato
appositamente per questa ricerca, comprendente 50 items
basati sui principali fattori di rischio associati al mal di schiena, sulle
figure sanitarie interpellate, sui trattamenti eseguiti e sugli eventuali
benefici ottenuti.
In accordo con i dati della letteratura, dal nostro studio risulta che, nonostante
la lombalgia sia un evento frequente negli adolescenti, soprattutto tra
coloro che conducono una vita sedentaria o priva di attività fisica, la conoscenza
dei fattori di rischio è ancora scarsa e incompleta. Ulteriori studi sono
pertanto necessari per identificazione i soggetti a rischio e promuovere,
quindi, una prevenzione primaria nella lombalgia dell’adolescent
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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