1,720,967 research outputs found
In-silico Vascular Growth and Remodeling Insights From Coupling Biology and Mechanics
No full textVascular growth and remodeling is a complex multi-step process, during which the vasculature attempts to maintain homeostasis in the blood vascular system by changing its micro
and macrostructure in response to alterations in its bio-chemo-mechanical environment. A
better understanding of this process is imperative to identifying better treatments for cardiovascular diseases, developing tissue-engineered constructs, and advancing our knowledge of
tumor angiogenesis. However, despite being the focus of research for the past three decades
and the wealth of information at our hands, a holistic theory, that can connect the microscale
alterations in the cellular behavior to the macroscale changes in the geometry and composition of the blood vessels, seems yet elusive. Computational models have been a valuable
tool in this regard. But, the utility of these models has remained limited, as the majority of
existing models either focus on the biology or the mechanics and, naturally, cannot capture
the emergent aspects of these complex processes. This work presents a novel Agent Based
- Finite Element Analysis modeling framework that allows us to study vascular adaptation
in response to changes in the mechanobiological stimuli. We studied the arterial wall under
normal conditions and during perturbations in biochemomechanical stimuli and proved the
stability of the model. In the last step, we utilized the model to study the effects of various
loading modes (uniaxial, biaxial, and equibiaxial) and serum concentration on the formation
and alignment of collagen fibers in Tissue Engineered Vascular Grafts. We showed that
biaxial loading is crucial for the physiological alignment of collagen fibers and serum concentration does not affect the alignment of the fibers but can affect the growth and remodeling
speed
A Multiscale Model of Leukocyte Transendothelial Migration During Atherogenesis
No full textA vast amount of work has been dedicated to understanding the role hemodynamics and cytokines play in leukocyte adhesion, trans-endothelial migration (TEM) and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. In this dissertation we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD) coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM) and hemodynamic effects of pulsatile blood flow via computational fluid dynamics (CFD). We found that using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing wall shear stress (WSS) at peak systole of the pulsatile flow waveform does. Moreover, using the model, we found leukocyte TEM increases monotonically with decreases in luminal volume. Specifically, neutrophils are primary cell type entering the wall at the genesis of plaque evolution and again the lumen caliber is altered for the first time. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM, suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall, this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution
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
Algorithms for Complex Explanation Queries
No full textRecently, there has been growing interest in developing machine learning systems that are
robust to minor perturbations in input and are explainable in that they are able explain
why they made a particular decision to a user. In this dissertation, we focus on a widely
used graph-based probabilistic representation called probabilistic graphical models (PGMs)
and propose a new unified constrained optimization task called constrained most probable
explanation (CMPE) problem over them. We show that in addition to the two aforementioned tasks, making models robust and explainable, many real-world tasks over PGMs can
be reduced to CMPE. We thoroughly analyze the computational complexity of CMPE and
develop specialized, practical algorithms for solving it. Specifically, we show that CMPE
is strongly NP-hard in general and thus unlikely to admit an efficient, polynomial time algorithm. However, it is only weakly NP-hard when the PGM exhibits certain structural
properties such as small k-separators.
To solve CMPE and upper bound its optimal value, we present novel efficient approaches
that combine graph-based partitioning techniques with approximation algorithms developed
in literature on the multiple choice knapsack problem (MCKP), number partitioning problem
and subset sum problem (SSP). We derive approximation and complexity guarantees for
our new algorithms and demonstrate via a large scale experimental evaluation on several
benchmark graphical models that compared to baselines such as random sampling and local search, our new algorithms are more accurate. We also encode CMPE as a mixed integer
linear program (MILP) and show that our approach is superior to open-source MILP solvers
such as SCIP
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
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