1,721,595 research outputs found
Humanization of porcine pulmonary valvulated conduits after decellularization and repopulation with human endothelial cells
No full textIntroduction. In heart valve surgical replacement, the most suitable hemodynamic properties and mechanical performances depend on the preservation of cusp anatomical shape and stromal structure. In addition, post-operatory valve calcification can be avoided only after removing all native cells from bioprostheses. Previously, complete cell extraction was achieved from porcine valve leaflets with concurrent preservation of their extracellular matrix (ECM) (1). These acellular scaffolds allowed "in vitro" repopulation with homologous valve interstitial cells, which also re-differentiated into all four cell phenotypes existing in heart valves (2). Methods. Porcine pulmonary valvulated segments (PVCs) were decellularized using combined non -denaturating neutral detergents Triton X-100 and Cholate, followed by Benzonase® digestion. Acellular PVCs were (i) orthotopically implanted in recipient pigs for 1-2 months, or (ii) "in vitro" seeded with endothelial cells derived from human umbilical cord (HUVEC), and incubated for 1-2 weeks. Histological and TEM-SEM ultrastructural analysis was performed, also after histochemical reactions for glycosaminoglycan (GAG) localization and laminin immuno-localization. Results. The treated PVCs exhibited complete cell remotion, good ECM preservation and surface reactivity for laminin. (i) After 2-month implantation, "in vivo" cell colonization spontaneously occurred by two distinct cell populations: endothelial-like cells, adhering to PVC luminal areas, and mesenchimal-like cells, migrating through PVC interstitium. (ii) After cell seeding and 1-week incubation, monolayers of human endothelial cells completely covered PVC luminal surfaces. Cell adhesion to the retained basal "lamina" and cell junction formation were also observed. In addition, valve interstitium was enriched by newly secreted GAGs at the subendothelial aspects. After cell seeding and 2-week incubation, micropinocytotic activity by endothelium and increased GAG-reactivity were observed. Conclusions. The decellularized PVCs are propensive for both (i) "in vivo" homologous cell repopulation, and (ii) "in vitro" heterologous endothelization with HUVEC. In addition, PVC stroma acquired more and more hybrid character because human-endothelium-generated GAGs were added to the native ECM macromolecules retained within the treated porcine PVCs. Thus these engineered PVCs appear as promising autologous-like, glutaraldehyde-free, and anti-thrombogenic bioprostheses. 1. Spina M., Ortolani F., El Messlemani A., Gandaglia A., Bujan J., Garcia-Honduvilla N., Vesely I., Gerosa G., Casarotto D., Petrelli L., Marchini M.: Isolation of intact aortic valve scaffolds for heart valve bioprostheses: extracellular matrix structure, prevention from calcification and cell repopulation features. J. Biomed. Mater. Res., 67, 1338-1350, 2003. 2. Bertipaglia B., Ortolani F., Petrelli L., Gerosa G., Spina M.,, Pauletto P., Casarotto D., Marchini M., Sartore S.: Cell characterization of porcine aortic valve and decellularized leaflets repopulated with aortic valve interstitial cells. Ann. Thorac. Surg., 75, 1274-1282, 2003
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
Il ruolo dei geni modulatori nella patogenesi della Fibrosi Cistica.
No full textSelezionato per la comunicazione orale. Premio per la migliore comunicazione al Convegno
Finite element analysis of side-load spring for McPherson front suspensions
No full textIn the present work, the operating conditions of “side-load” springs, which are typically employed in McPherson suspensions, were analysed by finite element analysis. The finite element model, including the spring and the upper and lower spring seats, is firstly described in the paper; the spring geometry was accurately obtained by a reverse engineering procedure based on two video cameras and a video projector. Surface to surface contact elements were defined between spring and seats; the initial assembling phase of the spring between the seats was also included in the finite element analysis.
The experimental rig, employed for spring characterisation, and the performed numerical analyses are then presented; results are discussed in comparison with experimental data, in terms of spring characteristic, side-load force and thrust axis spatial position, as a function of spring compression. A fully satisfactory agreement was generally observed between numerical results and experiments.
The effect of lower spring seat orientation on results was also investigated by numerical analysis. A higher inclination of the lower seat appeared to increase the side-load force; at the same time, for a given configuration, the thrust axis orientation, remained almost constant during suspension compression
Il ruolo dei geni modulatori nella patogenesi della Fibrosi Cistica.
No full textSelezionato per la comunicazione orale. Premio per la migliore comunicazione al Convegno
- …
