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Biomaterials Science: An Introduction to Materials in Medicine, 3rd ed., Chapter I.1.4 Finite Element Analysis in Biomechanics
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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
Tailoring Electrospinning Fabrication for Scaffolds for Heart Valve Tissue Engineering
No full textPrevious work in controlling mechanical properties of electrospun scaffolds has largely been limited to altering the orientation of the fibrous network by either large rotational velocity or by altering the electric field during fabrication. Our lab has previously developed a technique to analyze the complete microstructural topology of electrospun scaffolds and extract key descriptors. In this project, we translated the target mandrel at varying speeds along its rotational axis in order to modify the microarchitecture without altering the fiber orientation angle. Using the algorithm mentioned above, we determined that increasing the translation speed resulted in a decrease in fiber intersections/μm2. Relating this measure to mechanical response, it appeared that higher fiber intersection densities were correlated with higher strain energies, and higher mechanical anisotropy (p<.001). Additionally, we demonstrate that concurrently electrospraying cell culture media during fabrication appears to amplify the effect of rastering on the scaffold mechanics. These results suggest that fiber orientation is not sufficient to describe the mechanical response of electrospun scaffolds. It is also demonstrated that soft tissue like anisotropy can be induced in electrospun scaffolds at low mandrel tangential velocity by the reduction of the translation velocity and the concurrent electrospraying of cell culture media, greatly facilitating ease of fabrication
A microstructure based mechanical model for planar fibrous scaffolds.
No full textCardiac valve and myocardium tissue regeneration has consistently raised interest for cell-seeded/microintegrated
planar fibrous scaffolds. Electrospun constructs, decellularized tissues and collagen/fibrin gels
often show a similar microstructure mainly characterized by the fibrous network topology. Microstructure
based mechanical modeling enable fabrication parameters and scaffolds morphology to be related to mesomacro
mechanical response. A novel approach to (1) characterize the material fibers network microarchitecture,
(2) reproduce stochastically equivalent fiber network models, and (3) predict the mechanical
response at meso-macro level is presented in this work. Electron micrographs (SEM) of electrospun poly
(ester urethane) urea (PEUU) scaffolds were analyzed using a custom made software [D’Amore et al
Biomat 2010; 31:(20) 5345-5354]. Two scaffolds families with isotropic and anisotropic structure
(orientation index: 0.5, 0.65 respectively) were studied. The following architectural descriptors have
identified for each scaffold family: fiber angle distribution, connectivity, fiber intersection density, fiber
diameter. Stochastically equivalent scaffolds models (250x250 μm) were generated minimizing the
differences in the above mentioned parameters between the real fiber networks and the simulated ones. The
nodes and rods models were imported into the ANSYS environment as beam elements with axial and
bending stiffnesses. A simple linear relation was adopted as constitutive model, thus structure mechanical
non-linearity was dictated entirely by network topology. FEA analysis was performed simulating equibiaxial
stretch conditions, the single fiber mechanical stiffness was the only parameter required to fit the
equi-biaxial experimental data. At the macro level the bulk mechanical response agreed well with the
experimental biaxial mechanical data, single fiber mechanical stiffness was ~380 kPa. At meso level under
applied deformation, the simulated fiber networks showed, as expected, that the fibers aligned in the
scaffold cross preferred direction carry higher forces. Fabrication parameters were connected to the
material structure throughout image analysis and the material architecture was connected in turn to the
mechanical behavior by FEA. The latter concept in conjunction with the multi-scale prediction capability of
the adopted approach provides evidence of its potential in guiding cardiac tissue engineering constructs
design and fabrication
Elastomeric Electrospun Polyurethane Scaffolds: The Interrelationship Between Fabrication Conditions, Fiber Topology, and Mechanical Properties
No full textElastomeric electrospun construct fabrication conditions are evaluated with regards to their effect on fiber topology and biaxial mechanical response. It is determined that fiber alignment alone is insufficient to predict mechanical response. Moreover, fiber intersection density is introduced as a quantifiable structural measure which can be manipulated to achieve mechanical anisotropy similar to that of native soft tissues
Effectiveness in psychiatric care: IV. Achieving effective medication management for major affective disorder.
No full textComprehensive Biomaterials, Chapter 94 “The Mechanics of Native and Engineered Cardiac Soft Tissue”.
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