1,720,964 research outputs found
Flow in the anterior chamber of the eye with an implanted iris-fixated artificial lens
No full textFlow in the aqueous humour that fills the anterior chamber of the eye occurs in response to the production and drainage of the aqueous humour, and also due to buoyancy effects produced by thermal gradients. Phakic intraocular lenses are manufactured lenses that are surgically inserted in the eyes of patients to correct refractive errors. Their presence has a dramatic effect on the circulation of the aqueous humour, resulting a very different flow in the anterior chamber, the effects of which have not been extensively investigated. In this article we use a simplified mathematical model to analyse the flow, in order to assess the effect of the implanted lens on the pressure drop required to drive the flow and also on the wall shear stress experienced by the corneal endothelial cells and the cells of the iris. A high pressure drop could result in an increased risk of glaucoma, whilst raised shear stress on the cornea could result in a reduction in the density of endothelial cells there, and on the iris it could result in the detachment of pigment cells, which block the outflow of the eye, also leading to glaucoma. Our results confirm those of previous fully numerical studies, and show that, although the presence of the lens causes significant differences in the flow topology and direction, the typical magnitudes of the shear stress are not significantly changed from the natural case. Our semi-analytical solution allows us to perform a thorough study of the dependence of the results on the controlling parameters and also to understand the basic physical mechanisms underlying flow characteristics
A simple mathematical model of rhegmatogenous retinal detachment
No full textThe conditions under which rhegmatogenous retinal detachment occurs are poorly understood, which hampers the success rates of surgery. Fluid dynamical effects play a major role, and in this paper we analyse the tendency for the retina to detach further in both the case of a free flap giant retinal tear (GRT) and in the case of a retinal hole (RH). For this purpose we use a mathematical model to investigate the interaction between the fluid flow and the detached retina during saccadic eye movements. The governing equations are solved numerically using a code developed ad hoc. An idealised two-dimensional geometry is used and realistic values of almost all governing parameters are taken from the literature. For the cases of both GRT and a RH we investigate the tendency for the detachment to progress, analysing two different saccadic motions, different lengths of the detached retina, different attachment angles and, in the case of a RH, different hole diameters. In both cases we find that increasing the length of the detached retina increases the tendency for further detachment, while in the RH case, changing its diameter has little or no effect. We also find the existence of an attachment angle that maximises the tendency to detach, and the model indicates that RHs are more prone to detach further than GRTs. In spite of the fact that the model is highly idealised the results agree qualitatively well with the available clinical evidence
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Mathematical modelling of microcirculation in a poroelastic model of the liver, and its application to the study of ascites
Get PDFThe liver performs many vital functions in the body and has a natural ability to regenerate itself, except in the case of repeated or severe damage often caused by liver diseases. Damage due to liver disease occurs in the form of scarring of healthy liver tissue, a process known as fibrosis. Chronic fibrosis can lead to liver cirrhosis, a condition that is irreversible and often requires liver transplantation. Cirrhosis manifests itself in the form of increased tissue stiffness and decreased tissue permeability, which then leads to a marked decrease in blood perfusion and functioning of the liver tissue. As a homeostatic response, hepatic portal blood pressure also increases, which then leads to an increased outflow of excess interstitial fluid across the surface of the liver and into the surrounding peritoneal cavity. The abnormal accumulation of fluid in the peritoneal cavity is known as ascites and is characterised by large abdominal girth, abdominal pain and discomfort. The aim of this thesis was to model the microcirculation of blood and interstitial fluid in the liver, so as to investigate the changes in vasculature that lead to impaired blood perfusion and the formation of ascites. To that end, we have developed a dual-porosity, dual-permeability deformable model of the liver tissue using the Biot theory of poroelasticity. We then used the model as part of a compartmental model of the peritoneal cavity and investigated the effect of liver disease (fibrosis/cirrhosis) on the accumulation of fluid in the peritoneal cavity. By varying the degree of liver tissue stiffness, we simulated and compared different stages of liver fibrosis, as well as predicted the severity of the resulting ascites. This makes our model an improvement on the current literature, with the aim of future use in informing and improving disease treatment strategies.Open Acces
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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