1,720,957 research outputs found
The influence of intraocular pressure and air jet pressure on corneal contactless tonometry tests
No full textThe air puff is a dynamic contactless tonometer test used in
ophthalmology clinical practice to assess the biomechanical properties
of the human cornea and the intraocular pressure due to the filling
fluids of the eye. The test is controversial, since the dynamic response
of the cornea is governed by the interaction of several factors which
cannot be discerned within a single measurement. In this study we
describe a numerical model of the air puff tests, and perform a
parametric analysis on the major action parameters (jet pressure and
intraocular pressure) to assess their relevance on the mechanical
response of a patient-specific cornea. The particular cornea considered
here has been treated with laser reprofiling to correct myopia, and the
parametric study has been conducted on both the preoperative and
postoperative geometries. The material properties of the cornea have
been obtained by means of an identification procedure that compares the
static biomechanical response of preoperative and postoperative corneas
under the physiological IOP. The parametric study on the intraocular
pressure suggests that the displacement of the cornea's apex can be a
reliable indicator for tonometry, and the one on the air jet pressure
predicts the outcomes of two or more distinct measurements on the same
cornea, which can be used in inverse procedures to estimate the material
properties of the tissue. (C) 2015 Elsevier Ltd. All rights reserved
Numerical estimation of stress and refractive power maps in healthy and keratoconus eyes
No full textKeratoconus is an eye condition caused by localized thinning of the corneal tissue, which leads to a characteristic cone-shaped protrusion of the cornea. We investigate the mechanical behavior of keratoconus and suspect keratoconus corneas versus healthy corneas by using patient-specific finite element models. Patient-specific geometries of the corneas are obtained from diagnostic images provided by corneal topographer, transformed into solid models, and discretized in hexahedral elements. For the diseased corneas, a suitable reduction of the stiffness is applied within a limited region of the cornea around the conus. After the identification of the stress-free configuration, the models are used to simulate pressurization tests up to 40 mmHg. The material parameters have been estimated within the stress-free configuration identification procedure. As expected, numerical results reveal a more compliant behavior for the diseased corneas in terms of apex displacement plots as a function of the intraocular pressure, with diseased corneas experiencing up to 44% increase in apex displacement compared to healthy corneas. The maps of the stress confirm, for the diseased corneas, a marked increase of the maximum tensile stress, on both anterior and posterior surfaces, to be ascribed mainly to the reduction of the corneal thickness. Stress maps also show, for keratoconus corneas, a marked increase of the ratio between posterior and anterior tensile stress in the conus. Numerical analyses are used to construct the refractive power maps, revealing clearly that the maximum dioptric power in keratoconus corneas is at the center of the cone-shape rather than at the apex
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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