1,720,989 research outputs found
Finite Element Simulations of Biphasic Articular Cartilages With Localized Metal Implants
No full textArticular cartilage is a specialized connective soft tissue that resides onthe ends of long-bones, transfers the load smoothly between the bones in diarthrodialjoints by providing almost frictionless, wear resistant sliding surfacesduring joint articulation. Focal chondral or osteochondral defects in articularcartilage are common and show limited capacity for biological repair. Furthermore,changes in the bio-mechanical forces at the defect site may makethe tissue more susceptible to continued degeneration. Alternatively, the contouredfocal resurfacing metal implant can be used to treat such full thicknesscartilage defects. Physiological and biomechanical studies on animal modelswith metal implant have shown good clinical outcomes. However, the mechanicalbehavior of cartilage surrounding the implant is not clearly known withrespect to the joint function after treating such defects with metal implantsand also to improve the implant design. We developed a simple 3-dimensionalfinite element model by approximating one of the condyles of the sheep kneejoint. Parametric study was conducted in the simulations to verify differentprofiles for the implant, positioning of the implant with respect to cartilagesurface, defect size and to show the mechanical sealing effect due to the wedgeshape of the implant. We found the maximal deformations, contact pressuresand stresses which constitute the mechanical behavior of cartilages. We alsoconfirmed that using a metal implant to fill the full thickness chondral defectsis more beneficial than to leave the defect untreated from mechanical point ofview. The implant should be positioned slightly sunk into the cartilage basedon the defect size, in order to avoid damage to the opposing surface. The largerthe defect size, the closer the implant should be to the flush. We also simulatedthe time dependent behavior of the cartilages. In all the simulations, a staticaxial loading was considered. The wedge shape of the implant provided themechanical sealing of the cartilage surrounding the implant. The determineddeformations in the cartilages immediately surrounding the implant are instrumentalin predicting the sticking-up of the implant into the joint cavity whichmay damage opposing soft tissues.QC 20101125</p
Modeling of constrained articular cartilage growth in an intact knee with focal knee resurfacing metal implant
No full textThe purpose of the present study was to develop a model to simulate the articular cartilage growth in an intact knee model with a metal implant replacing a degenerated portion of the femoral cartilage. The human knee joint was approximated with a simplified axisymmetric shape of the femoral condyle along with the cartilage, meniscus and bones. Two individually growing constituents (proteoglycans and collagen) bound to solid matrix were considered in the solid phase of the cartilage. The cartilage behavior was modeled with a nonlinear biphasic porohyperelastic material model, and meniscus with a transversely isotropic linear biphasic poroelastic material model. Two criteria (permeation and shear), both driven by mechanical loading, were considered to trigger the growth in the solid constituents. Mechanical loading with sixty heavy cycles was considered to represent daily walking activity. The growth algorithm was implemented for 90days after implantation. The results from simulations show that both cartilage layers were more stimulated near the implant which lead to more growth of the cartilage near the defect. The method developed in the present work could be a powerful technique if more accurate material data and growth laws were available.</p
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
- …
