1,720,987 research outputs found
Abnormal proximal-distal interactions in upper-limb of stroke survivors during object manipulation: A pilot study
No full textDespite its importance, abnormal interactions between the proximal and distal upper extremity muscles of stroke survivors and their impact on functional task performance has not been well described, due in part to the complexity of upper extremity tasks. In this pilot study, we elucidated proximal–distal interactions and their functional impact on stroke survivors by quantitatively delineating how hand and arm movements affect each other across different phases of functional task performance, and how these interactions are influenced by stroke. Fourteen subjects, including nine chronic stroke survivors and five neurologically-intact subjects participated in an experiment involving transport and release of cylindrical objects between locations requiring distinct proximal kinematics. Distal kinematics of stroke survivors, particularly hand opening, were significantly affected by the proximal kinematics, as the hand aperture decreased and the duration of hand opening increased at the locations that requires shoulder abduction and elbow extension. Cocontraction of the extrinsic hand muscles of stroke survivors significantly increased at these locations, where an increase in the intermuscular coherence between distal and proximal muscles was observed. Proximal kinematics of stroke survivors was also affected by the finger extension, but the cocontraction of their proximal muscles did not significantly increase, suggesting the changes in the proximal kinematics were made voluntarily. Our results showed significant proximal-to-distal interactions between finger extension and elbow extension/shoulder abduction of stroke survivors exist during their functional movements. Increased cocontraction of the hand muscles due to increased neural couplings between the distal and proximal muscles appears to be the underlying mechanism
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
THE IMPACT OF THE JOINT POSTURE ON FINGER NEUROMECHANICS
No full textThis dissertation presents a series of studies investigating the neuromechanical properties of the index finger with special emphasis on how these properties varied with finger posture. A cadaver study was performed to measure the mapping relationship between tendon force and the resulting fingertip force. A strong linear relationship between magnitude of the tendon force and magnitude of the produced fingertip force was confirmed, up to the force levels examined. The finger posture, however, strongly influenced both fingertip force direction and magnitude. Two fundamental hypotheses of finger biomechanical modeling were then tested in further cadaveric studies. The preliminary results supported the assumption of linear superposition of the contributions of individual tendon forces to the overall fingertip force, at least for two muscles up to the force levels tested. It is also confirmed that the index finger force was almost exclusively produced by the muscles of the index finger, with relatively minor contributions from the other compartments of flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), or extensor digitorum communis (EDC). An in-vivo human subject study was performed to examine muscle activation patterns during isometric fingertip force production across task directions and finger postures. It was shown that significant changes in muscle excitation patterns occurred, especially with variations in interphalangeal (IP) posture. These changes involved fundamental variation in the underlying pattern rather than just scaling of a given activation pattern. An anatomically correct force-based computer model of the index finger was built to study the roles of different structures and characteristics in finger task performance. The model was validated with the cadaver study result to display its reliability in predicting fingertip xiii force and dynamic movement for given tendon forces. The model was then employed to estimate some hard-to-measure variables including joint contact force and joint passive torque components. The simulation of tendon injuries with the model, including Boutonniere deformation and mallet finger, was able to predict the abnormal finger joint movements under these patho-mechanical conditions. The model simulation also suggested that fingertip force capacity was largely maintained after selected tendon pulley excision surgeries.PH.D in Biomedical Engineering, May 201
CABLE ACTUATED FINGER EXOSKELETON DEVELOPMENT AND EXAMINATION OF INDEX FINGER AND THUMB COUPLING
No full textFinger-thumb coordination is crucial to interacting with our environment. This coordination remains incompletely understood, even in neurologically intact individuals, and is difficult to study with current interface devices. Knowledge of finger-thumb relationships during dynamic movement facilitate identification of key impairment mechanisms following stroke and thus, help to guide rehabilitation strategies. Accordingly, a high-bandwidth, biocompatible finger exoskeleton is developed and implemented in a pilot study to investigate coupling between the finger and thumb during pinching movements. Performance of the Cable Actuated Finger Exoskeleton (CAFE) is analyzed in the lab and during interaction with human subjects, both neurologically intact and survivors of stroke. The exoskeleton is found to perform exceedingly well, exceeding nearly all design requirements lending to the continued use of the CAFE a research platform for human motor control of the hand. During experimental trials, participants move through index finger and thumb palmar pinching movements while the CAFE delivers perturbations during the closing and opening phases of movement. Two experiments are conducted, delivering reflexinducing or joint-locking perturbations to the index finger. Muscle EMG and thumb tip trajectory are recorded during movement and variations in these parameters immediately following perturbation demonstrate the effect of coupling of the index finger and thumb. Reflexive coupling is evidenced in both healthy and post-stroke individuals by heteronymous reflexes in the unstretched muscles of the thumb. Similarly, kinematic changes are apparent in thumb movement following impedance perturbations of the index finger in both populations. Coupling is observed to vary with phase of movement in x xiii intact participants, but not following stroke, suggesting a loss of modulation following stroke. Most notably: in survivors of stroke impedance perturbations to the index finger during the opening phase of movement results in dramatically increased thumb opening.PH.D in Biomedical Engineering, May 201
Variations on the Author
Get PDF“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
DESIGN OF A DYNAMIC MUSCULOSKELETAL MODEL OF THE HUMAN HAND FOCUSED ON FUNCTIONAL TASKS
No full textThis thesis explores the creation and validations of a simulated musculoskeletal model of the human hand with a focus on the aspects of pinching. Specifically, the thumb, index finger, and wrist were represented in OpenSim 3.3, using anatomical definitions for increased accuracy. Specifically, the inclusion of physiological axes of rotation at all joints, anatomically accurate passive joint torques, and appropriate moment arms for each muscle. The model was subsequently validated against experimental results found in literature. First, the digit tip force directions produced by each of the 15 muscles were compared to those obtained by loading the corresponding tendons in cadaveric specimens and measuring three-dimensional force generation at the tip of the thumb or index finger. Second, isometric force generation by activation of multiple muscles were compared. Finally, dynamic simulations were run using electromyographic (EMG) recordings as inputs. The capabilities of the model were then explored by using it to predict activation patterns from imposed movement and to simulate extension deficits in a hand affected by stroke. The model generated isometric force in the correct directions for most individual muscles, with the extensor pollicis brevis (EPB) showing the largest directional differences between cadaveric and simulated results. With combined muscle activation patterns the model simulated force profiles accurately, showing only a 5.3% mean squared error (MSE) from the actual force profile. In terms of force magnitudes between the model and simulated results, the model produced significantly lower force magnitudes, especially in the thumb. This validation was also found to be reasonably accurate to the expected motions. With the model anatomically validated, two different simulations were run using the model. First, known kinematics were applied to the model and the muscle activations were simulated; the resultant joint angles were found to match the expected within 10% MSE. Second, a stroke affected hand was simulated, with activation deficits added to each of the muscles individually. It was found through this that, in the model, the intrinsic muscles played a larger role in force production and dynamic motion than the extrinsic muscles. In all, these validations and simulations produce a promising groundwork for the use of this model for further simulation.M.S. in Biomedical Engineering, May 201
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
- …
