1,720,993 research outputs found
Subject-Specific Computational Musculoskeletal Modeling of Human Trunk in Lifting : Role of Age, Sex, Body Weight and Body Height
Full text linkRÉSUMÉ: Les troubles musculosquelettiques sont parmi les problèmes de santé les plus fréquents et les plus coûteux au monde. Les maux de dos figurent en deuxième position sur la liste des états chroniques les plus répandus au Canada et quatre adultes sur cinq souffriront de lombalgie un jour ou l'autre de leur vie. Les efforts excessifs sur la colonne vertébrale constituent l'un des facteurs de risque potentiels de lombalgie et peuvent initier ou générer de la douleur et de la dégénérescence des disques. À cet effet, plusieurs études s'accordent pour affirmer qu'une estimation juste des charges vertébrales est utile pour une prévention efficace des blessures et pour des programmes de réadaptation appropriés. Toutefois, il n'existe pas de méthodes directes pour mesurer les charges vertébrales et de plus, toutes les méthodes indirectes (comme la mesure de la pression intradiscale – PID – et l'estimation au moyen de prothèse discale instrumentée) sont invasives et limitées. Les modèles musculosquelettiques (MS) offrent toutefois une alternative intéressante en estimant de manière non invasive, économique et précise les forces musculaires, les charges vertébrales ainsi que la stabilité de la colonne vertébrale en tenant compte des différences individuelles. Dans cette thèse, un modèle MS du tronc par éléments finis (EF) guidé par la cinématique a été mis à niveau. L'architecture des origines et insertions musculaires a été améliorée, une unité vertébrale comprenant un disque déformable a été ajoutée (T11-T12) et un nouvel algorithme de mise à l'échelle a été introduit afin d'explorer les effets du sexe, de l'âge, du poids et de la taille sur la biomécanique et les charges appliquées sur la colonne vertébrale. Au moyen de données issues d'imageries médicales et à partir de principes biomécaniques, l'algorithme de mise à l'échelle a permis d'ajuster l'architecture musculaire (les bras de levier des muscles et les aires transverses), la géométrie et les propriétés passives ligamentaires de la colonne vertébrale ainsi que la charge gravitationnelle, le tout en fonction du sexe, de l'âge, du poids et de la taille. Une analyse de sensibilité a été effectuée au moyen d'une analyse factorielle multiple. Les données d'entrées du modèle (sexe, âge, poids et taille) ont été modifiées à l'intérieur de plages physiologiques (sexe : femme et homme ; âge : 35 à 60 ans ; poids : 50 à 120 kg ; taille : 150 à 190 cm) tandis que le modèle personnalisé par EF était guidé par une cinématique spécifique à l'âge et au sexe lors de différentes tâches de flexion avant avec ou sans charges manuelles. Des graphiques illustrant les effets principaux et des analyses de variance ont été utilisés pour évaluer les effets des données d'entrées sur le chargement au dos. Le poids du corps a été le facteur le plus influent, en expliquant 99 % du chargement lombaire en compression et 96 % de celui en cisaillement, alors que les effets de la taille, du sexe et de l'âge (30 kg/m2) is rising in both developed and developing countries, and has reached “global epidemic” proportions. Although obesity has been associated with various back problems (e.g., disc degeneration, vertebral fracture and back pain),the likely role of biomechanics in obesity-related back problems is still unknown. At identical BMI and BW, fat distribution varies substantially from one obese individual to another. Different obesity types have qualitatively been described as apple- and pear-shaped (or android and gynoid). Therefore, effects of obesity and obesity shapes on spinal loads and vertebral compression fracture were investigated by using the upgraded subject-specific model. At identical BW and BH, three distinct obesity shapes (corresponding to minimum, average and maximum waist circumferences) were reconstructed by using available anthropometric measurements of 5852 obese individuals and principal component analysis. Obesity markedly affected spinal loads; L4-L5 compression increased by 16% (2820 N vs 3350 N) in forward flexion without a hand-load when BMI increased from 31 kg/m2 to 39 kg/m2. Greater waist circumferences (apple-shaped obesity) in comparison with smaller waist circumferences (pear-shaped obesity) increased spinal loads to the extent of gaining 20 kg additional BW and the risk of vertebral fatigue fracture by up to ~7 times. Therefore, both obesity and obesity shapes substantially affected spine biomechanics and should be taken into account in subject-specific modeling of the spine. Apart from serving in the trunk strength quantification and electromyography (EMG) normalization, maximum voluntary exertions (MVEs) can be used to calibrate and validate MS models. The performance of the current upgraded subject-specific MS model was investigated by comparing estimated muscle activities with reported EMGs during various MVE tasks. Maximum muscle stresses of trunk muscles were also calculated for each subject individually. Estimated maximum muscle stresses varied substantially among subjects and different muscle groups; rectus abdominis and external oblique had the smallest (0.40±0.22 MPa) and largest (0.99±0.29 MPa) maximum muscle stresses, respectively. In sagittal symmetric MVEs (extension and flexion), estimated muscle activities were found in satisfactory agreement with measured reported EMGs while in lateral and axial MVEs, the agreement was rather weak. Females in general had smaller spinal loads. Peak spinal loads were obtained in extension MVE (~6000 N compression at L5-S1) while flexion MVE yielded the smallest spinal loads (~3000 N compression at L5-S1); subjects experienced rather large spinal loads (5500 N in compression and 1700 N in shear) under lateral and axial MVEs. Accurate prediction of maximum muscle stresses and comprehensive evaluation of the performance of a MS model require the consideration of MVE tasks in all directions with the application of both primary and coupled moments to the model. Accurate simulation of the passive ligamentous spine, as one of the integral components of a trunk MS model, is of great importance. Detailed FE models can accurately capture nonlinear and time-dependent responses of the spine; however, due to the significant computational costs of detailed FE models, simplified models (i.e., spherical joints/beams with linear/nonlinear passive properties) are commonly used in the trunk MS models. Therefore, the accuracy and validity of using simplified models and their anterior-posterior positioning in estimating kinematics of the ligamentous spine, muscle forces and spinal loads were investigated. Unlike beam elements, spherical joints overlooked translational degrees of freedom and failed to accurately predict kinematics of the lumbar spine particularly in the cranial-caudal direction. Nonlinear shear deformable beams and spherical joints were found to satisfactorily predict IDPs in comparison with in vivo measurements during various activities. In contrast, using beams or spherical joints with linear passive properties yielded valid results only in small to moderate flexion angles (<40o). Neglecting passive properties of joints (frictionless spherical joints) substantially increased compression and shear spinal loads by 32% and 63%. Shifting a simplified joint posteriorly (by 8 mm) increased spinal loads (compression and shear) by ~20% while an anterior shift (by 2 mm) decreased spinal loads by 10% and 18% in compression and shear directions. Moving simplified joint models posteriorly reduced also passive muscle forces of agonist muscles while increasing their active components. Simplified joint models with nonlinear passive properties should be located in -2 to +4 mm (+: posterior) range from the disc center for accurate predictions of spinal loads and active/passive muscle forces. Obtaining reasonably accurate results by MS models requires comprehensive data collection (e.g., kinematics, EMG), equipped laboratory, and sufficient training. Alternatively, easy to use regression equations have previously been developed to estimate spinal loads, but they do not take account of personalized anthropometric factors (e.g., BW and BH) based on a physiological approach and often overlook task asymmetry. Thus, in this work, subjects-specific regression equations were developed to predict spinal loads at lower spinal levels (L4-L5 and L5-S1) by using the upgraded KD-FE model, and the Accuracy of the model and regression equations were subsequently evaluated by com
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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