1,720,958 research outputs found
Competition between epithelial tissue elasticity and surface tension in cancer morphogenesis
No full textWe derive a continuum mechanical model to capture the morphological changes occurring at the pretumoral stage of epithelial tissues. The proposed model aims to investigate the competition between the bulk elasticity of the epithelium and the surface tensions of the apical and basal sides. According to this model, when the apico-basal tension imbalance reaches a critical value, a subcritical bifurcation is triggered and the epithelium attains its physiological folded shape. Based on data available in the literature, our model predicts that pretumoral cells are softer than healthy cells
Surface accretion of a pre-stretched half-space: Biot's problem revisited
No full textMotivated by experiments on dendritic actin networks exhibiting surface growth, we address the problem of the stability of this growth process. We choose as a simple, reference geometry a biaxially stressed half-space growing at its boundary. The actin network is modeled as a neo-Hookean material. A kinetic relation between growth velocity and a stress-dependent driving force for growth is utilized. The stability problem is formulated and results are discussed for different loading and boundary conditions, with and without surface tension. Connections are drawn with Biot's 1963 surface instability threshold
Young modulus of healthy and cancerous epithelial tissues from indirect measurements
Full text linkWe propose a new method to estimate the ratio between the Young modulus of a healthy epithelial tissue and a cancerous tissue. Our method is based on a mechanistic approach. We regard the epithelium as a thin layer made of an isotropic hyperelastic material between two material surfaces endowed with surface tension. We derive a mechanical model which takes into account thickness change through a kinematical descriptor whose value, in the absence of mechanical loads, is determined by the competition between surface tension and bulk elasticity. Based on this model, we derive a relation between equilibrium thickness, surface tension, and bulk energy, along with a formula for the ratio between the Young modulus of the healthy and the cancerous tissue in terms of apico-basal pMLC2 intensity and tissue thickness, which are accessible to direct observation at the tissue-wide level through recently-developed experimental techniques. When assessed on the basis of our result, available experimental data confirm that cancerous epithelial tissues are softer than healthy tissues
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
From species diffusion to poroelasticity and the modeling of lamina cribrosa
No full textThe Lamina Cribrosa is a part of the optic nerve head acting as a scaffold for collecting the retinal ganglion cell axons. It can be modeled as a poroelastic material where the saturated porosity stands for the capillary network running inside the collagen beams. Our aim is to study the interaction between tissue porosity, deformation and hemodynamics. To this end we first focus on the derivation of a poroelastic model in a rather general case, using as a prototype a model of species diffusion in an elastic material. Then we outline the clinical significance of the mechanical behavior of the Lamina Cribrosa and show, through numerical simulations, how an increased intraocular pressure results in a deformation affecting porosity and blood perfusion. We emphasize how the model behavior relies on the free energy expression
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
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