1,720,967 research outputs found
Effects of extracellular fiber architecture on cell membrane shear stress in a 3D fibrous matrix
No full textInterstitial fluid flow has been shown to affect the organization and behavior of cells in 3D environments in vivo and in vitro, yet
the forces driving such responses are not clear. Due to the complex architecture of the extracellular matrix (ECM) and the difficulty
of measuring fluid flow near cells embedded in it, the levels of shear stress experienced by cells in this environment are typically
estimated using bulk-averaged matrix parameters such as hydraulic permeability. While this is useful for estimating average stresses,
it cannot yield insight into how local matrix fiber architecture—which is cell-controlled in the immediate pericellular environment—
affects the local stresses imposed on the cell surface. To address this, we used computational fluid dynamics to study flow through an
idealized mesh constructed of a cubic lattice of fibers simulating a typical in vitro collagen gel. We found that, in such high porosity
matrices, the fibers strongly affect the flow fields near the cell, with peak shear stresses up to five times higher than those predicted by
the Brinkman equation. We also found that minor remodeling of the fibers near the cell surface had major effects on the shear stress
profile on the cell. These findings demonstrate the importance of fiber architecture to the fluid forces on a cell embedded in a 3D
matrix, and also show how small modifications in the local ECM can lead to large changes in the mechanical environment of the cell
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
Synergy between 3D flow and VEGF directs capillary morphogenesis in vitro: experiments and theoretical mechanisms
No full textCell organization is largely orchestrated by extracellular gradients
of morphogenetic proteins. VEGF, an essential factor for capillary
formation, is stored in the extracellular matrix, but the mechanisms
by which it and other matrix-bound morphogens are mobilized to
form spatial gradients are poorly understood. Here, we suggest an
efficient mechanism for morphogen gradient generation by subtle
biophysical forces in an in vitro model of capillary morphogenesis.
Using a fibrin-bound VEGF variant that is released proteolytically
to mimic the in vivo situation, we report that low levels of
interstitial flow act synergistically with VEGF to drive endothelial
organization, whereas each stimulus alone has very little effect. To
help account for this synergy, we show how these slow flows can
bias the distribution of cell-secreted proteases, which leads, inter-
estingly, to the creation of an increasing VEGF gradient relative to
the cell and skewed in the direction of flow. In contrast, diffusion
alone can only account for symmetric, decreasing autocrine gra-
dients. Indeed, branching of capillary structures was biased in the
direction of flow only with the combination of VEGF and flow. This
work thus demonstrates a general mechanism of morphogen
gradient generation and amplification by small ubiquitous me-
chanical forces that are known to exist in vivo
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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