414 research outputs found
Cinco años compartiendo la optometría con un público global y multidisciplinar
[Excerpt] The clinical and scientific activity in the field of optometry has experienced a rapid expansion in the last decades.1 In many places around the World, where this specialty was not developed in the middle of the 20th century, Optometry is now flourishing with new schools, training centers and other structures. This made possible to provide eye care to millions of people who otherwise would not be served. These strategies have been particularly important in Asia, Middle East, Africa and Latin America. Besides the publication of mainstream state of the art research results in the field of optometry and visual sciences,2, 3, 4 the Journal of Optometry has been committed to be a platform for sharing with a Global Audience the scientific and clinical information coming from or related with developing countries in those areas. The issue being published now is a good example, with a significant proportion of its information arising directly or indirectly from populations whose ocular characteristics and ocular morbidity are now better known. [...](undefined)info:eu-repo/semantics/publishedVersio
Acrylic resins in wet white
Content:
The purpose of this paper is to study the influence of acrylic resins on the properties of the hide when added in the pickling-tanning stage of a wet white process.
Among retanning products, acrylic resins are very frequently used because they lend very good properties to the hide on account of their high affinity for chromium. When applied during chrome tanning, these
resins provide the hides with high fullness, due to the strong interaction of the carboxylate groups with chromium.
Extensive bibliography is available on the application of acrylic resins in wet blue, where it is observed that the properties they provide to the hides depend basically on the type of monomers and molecular weight. However, less information is found when these products are applied in wet white tanning.
In this study, 9 resins with different molecular weights and different monomer compositions were selected.
Resins were applied to pelt leathers of Spanish origin split at 3.5 mm. Hides were cut along the backbone. A standard process was applied to the left halves and the same process adding the resin was applied to the right halves. The resin was added after adjusting the salt of the bath and before adding the pickling acids.
The COD was measured before and after adding formic and sulfuric acid, and the shrinkage temperature and the degree of whiteness of the tanned hide were assessed. Hides were retanned and fatliquored with a standard process, and degree of softness, thickness, color intensity and organoleptic properties (fluffiness, compactness and grain tightness) were assessed. Leather shrinkage under temperature was also assessed, and images of leather sections were obtained by scanning electron microscopy (SEM).
While acrylic resins did not increase shrinkage temperature, they did fix and/or deposit themselves in the interfibrillary spaces of the hide; indeed, highly reduced COD values after acidification in the pickling stage were observed. This study shows that homopolymeric acrylic resins provided fuller and fluffier hides, while the rest of resins practically did not improve the physical and organoleptic properties of the hides.
Take-Away:
Homopolymeric acrylic resins provided full er and fluffier hides, while the rest of resins practically did not improve the physical and organoleptic properties of the hides
Wet white tanning improvemen
Estimation of the mechanical properties of the eye through the study of its vibrational modes
Measuring the eye's mechanical properties in vivo and with minimally invasive
techniques can be the key for individualized solutions to a number of eye
pathologies. The development of such techniques largely relies on a
computational modelling of the eyeball and, it optimally requires the synergic
interplay between experimentation and numerical simulation. In Astrophysics and
Geophysics the remote measurement of structural properties of the systems of
their realm is performed on the basis of (helio-)seismic techniques. As a
biomechanical system, the eyeball possesses normal vibrational modes
encompassing rich information about its structure and mechanical properties.
However, the integral analysis of the eyeball vibrational modes has not been
performed yet. Here we develop a new finite difference method to compute both
the spheroidal and, specially, the toroidal eigenfrequencies of the human eye.
Using this numerical model, we show that the vibrational eigenfrequencies of
the human eye fall in the interval 100 Hz - 10 MHz. We find that compressible
vibrational modes may release a trace on high frequency changes of the
intraocular pressure, while incompressible normal modes could be registered
analyzing the scattering pattern that the motions of the vitreous humour leave
on the retina. Existing contact lenses with embebed devices operating at high
sampling frequency could be used to register the microfluctuations of the
eyeball shape we obtain. We advance that an inverse problem to obtain the
mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio)
measuring its normal frequencies is doable. These measurements can be done
using non-invasive techniques, opening very interesting perspectives to
estimate the mechanical properties of eyes in vivo. Future research might
relate various ocular pathologies with anomalies in measured vibrational
frequencies of the eye.Comment: Published in PLoS ONE as Open Access Research Article. 17 pages, 5
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The vitality of pattern recognition and image analysis
Editorial sobre la selección de mejores artículos presentados en la conferencia internacional IbPRIA 2015 celebrada en Madeira, Portugal
A System Dynamics model to predict the impact of COVID-19 in Spain
Sanz, MT.; Caselles, A.; Micó, JC.; Soler, C. (2020). A System Dynamics model to predict the impact of COVID-19 in Spain. 146-151. http://hdl.handle.net/10251/178213S14615
Gait Asymmetry Post-Stroke: Determining Valid and Reliable Methods Using a Single Accelerometer Located on the Trunk
Asymmetry is a cardinal symptom of gait post-stroke that is targeted during rehabilitation. Technological developments have allowed accelerometers to be a feasible tool to provide digital gait variables. Many acceleration-derived variables are proposed to measure gait asymmetry. Despite a need for accurate calculation, no consensus exists for what is the most valid and reliable variable. Using an instrumented walkway (GaitRite) as the reference standard, this study compared the validity and reliability of multiple acceleration-derived asymmetry variables. Twenty-five post-stroke participants performed repeated walks over GaitRite whilst wearing a tri-axial accelerometer (Axivity AX3) on their lower back, on two occasions, one week apart. Harmonic ratio, autocorrelation, gait symmetry index, phase plots, acceleration, and jerk root mean square were calculated from the acceleration signals. Test–retest reliability was calculated, and concurrent validity was estimated by comparison with GaitRite. The strongest concurrent validity was obtained from step regularity from the vertical signal, which also recorded excellent test–retest reliability (Spearman’s rank correlation coefficients (rho) = 0.87 and Intraclass correlation coefficient (ICC21) = 0.98, respectively). Future research should test the responsiveness of this and other step asymmetry variables to quantify change during recovery and the effect of rehabilitative interventions for consideration as digital biomarkers to quantify gait asymmetry
Jugar a extinguir ensambles: importancia de las oquedades de los árboles para la biodiversidad de insectos saproxílicos
The assessment of the relation between species diversity, species interactions and stability is a major goal for conservation strategies of saproxylic insects in Iberian Mediterranean woodlands. In these woodlands, tree hollows in standing living trees are key microhabitats for saproxylic biodiversity. We assess the variation in the tree hollow-saproxylic insect network among three woodland sites in the Cabañeros National Park (Spain), and evaluate their implications for saproxylic assemblages’ persistence, through simulations of three possible scenarios of loss of tree hollow microhabitats. The composition of tree hollows is closely related to biotic and ecological complexity of saproxylic networks, and together exhibit positive effects on network stability. By other side, different scenarios entail different reorganizations of saproxylic diversity of species and interactions, and the variation of the main interacting attributes. Woodlands providing higher proportion of large tree hollows are less sensitive to microhabitat loss. Conservation strategies for saproxylic insects in Iberian Mediterranean woodlands should consider woodland composition and configuration as key factors in the selection of priority conservation areas
Saproxylic beetles and syrphids (Coleoptera; Diptera: Syrphidae) of the “dehesa” from the western Iberian: the Biological Reserve of “Campanarios de Azaba” (Salamanca)
Se aporta la relación de especies de coleópteros y sírfidos saproxílicos que habitan en ecosistemas de dehesa del oeste ibérico. Se ha estudiado la Reserva Biológica de Campanarios de Azaba, provincia de Salamanca, designada en 2013 como primera Reserva Entomológica de España por la Asociación española de Entomología. Durante los 19 meses de muestreo se registraron 9.603 ejemplares de coleópteros saproxílicos pertenecientes a 157 especies (40 familias) y 477 ejemplares de sírfidos saproxílicos pertenecientes a 18 especies. Para la recolección del material se utilizaron trampas de emergencia y trampas de ventana. Entre los insectos capturados hay diez especies amenazadas, ya sea a nivel europeo o de España, que, a la vista de los resultados, mantienen poblaciones abundantes en este ecosistema de dehesa del oeste ibérico.We provide a checklist of the saproxylic beetles and syrphids species inhabiting the “dehesa” ecosystem from western Iberian. We have studied the Biological Reserve of “Campanarios de Azaba”, Salamanca province, designated in 2013 as the first Entomological Reserve by the “Asociación española de Entomología”. During the 19 months of sampling period a total of 9, 603 specimens of saproxylic beetles belong to 157 species (40 families) and 477 specimens of saproxylic syrphids belonging to 18 species. In order to collect the specimens we used both emergence and window traps. Among the captured insects are ten threatened species either at European and Spanish levels, which maintain abundant populations inhabiting this “dehesa” ecosystem.Esta investigación fue financiada por el Ministerio de Ciencia e Innovación (CGL2011-23658), Ministerio de Economía y Competitividad (CGL2012-31669) y Generalitat Valenciana (proyectos PROMETEO/2013/03412 y ACOMP/2014/140). A. R. H. agradece la beca predoctoral recibida por la Generalitat Valenciana a través del programa Santiago Grisolía (GRISOLIA/2010/080)
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