1,720,968 research outputs found
Simplified mitral valve modeling for prospective clinical application of left ventricular fluid dynamics
Full text linkThe fluid dynamics inside the left ventricle of the human heart is considered a potential indicator of long term cardiovascular outcome. In this respect, numerical simulations can play an important role for integrating existing technology to reproduce flow details and even conditions associated to virtual therapeutic solutions. Nevertheless, numerical models encounter serious practical difficulties in describing the interaction between flow and surrounding tissues due to the limited information inherently available in real clinical applications.
This study presents a computational method for the fluid dynamics inside the left ventricle designed to be efficiently integrated in clinical scenarios. It includes an original model of the mitral valve dynamics, which describes an asymptotic behavior for tissues with no elastic stiffness other than the constrain of the geometry obtained from medical imaging; in particular, the model provides an asymptotic description without requiring details of tissue properties that may not be measurable in vivo.
The advantages of this model with respect to a valveless orifice and its limitations with respect to a complete tissue modeling are verified. Its performances are then analyzed in details to ensure a correct interpretation of results. It represents a potential option when information about tissue mechanical properties is insufficient for the implementations of a full fluid-structure interaction approach
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
Numerical and experimental study
No full text2009/2010Fluid structure interaction (FSI) is one of fundamental phenomena encountered everywhere in nature or in industrial systems as well as one of the most studied and the most challenging topics in the fluid mechanics. Its research presents the core objective of this dissertation, along with experimental study of artificial heart devices. Better understanding of FSI could turn the still unexploited phenomenon into a powerful tool for resolving wealthy of multi-physics problems. Recently computational fluid dynamics community has been putting enormous efforts to uncover, make clear and answer yet numerous issues related to this developing topic. In addition, the FSI is often followed by the vortex formation, one more phenomena that could be both powerful driving force as well as distracting, disturbing occurrence. Consequently, this dissertation will begin with addressing some open issues related to the fluid-structure interaction associated with the simple system made of movable rigid leaflet and an unsteady viscous fluid flow. Such two-dimensional model, even if it appears extremely simple, is able to produce fairly rich flow features which deserve careful analytical and accurate numerical solution. Thus, we have performed a significant number of numerical experiments with the objective to uncover the role of the structure inertia in the overall behavior of the fluid-leaflet system, under the different flow recurrences. For that purpose, we have constructed a strong-coupling code and resolved the fluid and structure dynamics simultaneously, paying particular care of solution accuracy around the moving boundary. The complex problem of large fluid deformation in response to the rapid structure movements has been resolved by the time-dependent conformal mapping, exclusively developed for this specific physical arrangement. The numerical findings, even if theoretical in nature, allowed for the classification and characterization of body’s and fluid dynamics in functionality of different structure inertia and Strouhal numbers, which have been used as free parameters in all numerical experiments.
The study is completed by a brief analysis of the more realistic system of actual prosthetic heart valves. Besides many problems that follow the performance of mechanical heart valve prosthesis, the complications related to the complex blood-leaflet interaction are a key factor. The intraventricular flow is characterized by large vortical structures, without significant turbulence, in a smooth circulatory pattern that, in presence of pathological conditions or mechanical devices, could be disturbed. Thus, among the criteria for the assessment of mitral valve functionality and mechanical valve design are the proper vortical features inside the left ventricle. Until nowadays the standard mechanical valves, designed originally for the aortic replacement and without exceptions symmetrical, have never satisfied the regularity of natural vortical dynamics. Thus, we have been motivated to investigate the flow features downstream of asymmetrical prototypes, exclusively designed for the mitral replacement with attempt to better mimic the natural intraventricular flow. Experimental outcomes allowed for preliminary conclusions that the break of symmetry in the novel prosthesis creates the asymmetrical vortical flow in the left ventricle, which is more similar to the natural one, although the concept introduced by this prototype has to undergo deeper testing and careful improvements before querying in the real hearts.XXIII Ciclo198
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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