Determination of oxygen permeability in soft contact lenses using a polarographic method : estimation of relevant physiological parameters

This work reports the apparent oxygen transmissibility Dk/t)app of four silicone hydrogel (Si-Hy) contact lenses (CLs). A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations combining the instrument oxygen transmissibility (IOT) and corneal parameters such as corneal thickness, corneal permeability, and oxygen flux across the cornea. From these results, the biological oxygen apparent transmissibility (BOAT), equivalent oxygen percentage (EOP), partial pressure, (ptc), of oxygen at the cornea-CL interface and oxygen flux, (jc), were also obtained. This method allows the evaluation of the physiological environment under the lens using the formulations described in previous studies. The oxygen performance of four Si-Hy materials was evaluated using a polarographic cell coupled to a permeometer. Measurements of the apparent transmissibility, (Dk/t)app, and permeability, Dk, were performed in stacks containing from 1 to n repeated lenses and, from the values obtained, the error involved in the measurements in single samples was estimated. It was found that the values of (Dk/t)app and Dk obtained following the two different procedures (stack method and measurement of single sample) were significantly different from the nominal values given by the manufacturer, particularly for some samples. However, the impact of these differences on the values of the other physiologically relevant parameters (BOAT, EOP, ptc, and jc) was not significant. Furthermore, these parameters were similarfor the four lenses in spite of the different (Dk/t)app measured. The relationships of (Dk/t)app with theremaining physiological parameters were calculated and graphically represented for open and closed-eyelid conditions.Dirección General de Investigación Científica y Técnica (DGICYT) - bolsa MAT-2005-05648-C02-01Instituto de la Pequeña y Mediana Industria Valenciana (IMPIVA) - bolsa IMCOVA-2006/20.European Social Funding (ESF) - Contrato #8281/2002 para o bolseiro J.M.G.-M.Fundação para a Ciência e Tecnologia (FCT

¿De qué hablamos cuando hablamos de Humanidades Digitales?

Parece que las Humanidades Digitales actuales fueron Humanist Computing o Computación/Informática Humanística hasta 2004, cuando John Unsworth, uno de los editores del fundamental A Companion to Digital Humanities, decidió este nombre algo más amplio y por qué no “marketinero” para titular el volumen. En esta nueva etapa en las Humanidades Digitales conviven las más diversas disciplinas humanistas con el trabajo del mundo de la programación, generando desde bibliotecas digitales,repositorios, a recursos digitales para visualización de actividades y de objetos hasta el momento invisibles a nuestros ojos como la música, y abogan por una reflexión acerca de los modos de acceder al conocimiento a través de su materialidad.Facultad de Humanidades y Ciencias de la Educació

En un futuro muy cercano las Humanidades serán Humanidades Digitales o no serán nada. Entrevista a José Manuel Lucía Megías

Entrevista a José Manuel Lucí­a Megí­a

Humanidades Digitales: Construcciones locales en contextos globales

Proceedings of the II International Conference of the Argentine Association of Digital Humanities/ Asocición Argentina de Humanidades Digitales (AAHD). "Humanidades Digitales: Construcciones locales en contextos globales". 47 articles in Spanish and Portuguese

Molecular Dynamics Simulations of Proton Conduction in Sulfonated Poly(phenyl sulfone)s

Full molecular dynamics was used to simulate separately the diffusion of naked protons and H₃O⁺ hydrated protons across sulfonated poly(phenyl sulfone)s. Simulations were carried out for wet membranes with the following characteristics:  ion-exchange capacity, 1.8 mequiv/g of dry membrane; water uptake, 10−30%; temperature range, 300−360 K. The diffusion coefficient of naked protons is nearly 1 order of magnitude higher than that of the hydrated protons for the membranes with the lower water uptake (10%). For the membranes with higher water uptake the ratio between the diffusion coefficients of the two particles reduces to about half an order of magnitude. The conductivity of the naked protons increases from 21.4 × 10⁻³ to 52.5 × 10⁻³ S/cm when the water uptake increases from 10% to 30%. For hydrated protons the conductivity increases from 1.54 × 10⁻³ to 7.57 × 10⁻³ S/cm. The conductivities obtained through simulations carried out at 300 K for the hydrated proton across membranes with water uptake 18% and 30% are roughly similar to those experimentally measured for a membrane with ion exchange capacity = 1.8 mequiv/g and water uptake = 24.3%. Simulated conductivities of both naked protons and hydrated protons follow Arrhenius behavior.This work was supported by the Comunidad de Madrid through the grant interfaces S-505/MAT-0227, Fondos Europeos de Desarrollo (FEDER), and Fondo Social Europeo (FSE). Financial support was also supplied by the Dirección General de Investigación Científica y Técnica (DGICYT) (grant MAT 2005-05648-C02-02)

Relaxation behavior of semiflexible polymers at very low frequencies

[EN] The dielectric activity of poly(monocyclohexylmethylene itaconate) (PMCI) and poly(dicyclohexylmethylene itaconate) (PDCI) in the glassy region and in the glass-rubber transition is studied by thermostimulated discharge current (TSDC) techniques. The spectra obtained by global TSDC experiments show a prominent alpha-glass-rubber relaxation peak with maxima located at 97 and 55 degrees C for PMCI and PDCI, respectively, following in decreasing order of temperature for a well developed beta absorption and a comparatively low intensity relaxation. Better resolution of the relaxation behavior of these polymers in the glassy region is obtained by calculating the components of the complex dielectric permittivity epsilon* at extremely low frequencies from partial TSDC experiments. The ac spectra thus obtained suggest that the beta absorption is composed by two relaxations, each of them presumably associated with the motions of a side group. The differences observed in these spectra with those reported for the beta mechanical relaxation reported for these polymers in the literature are interpreted in terms of the restrictions that the side groups produce in the conformational space of phase of the backbone. These restrictions also explain the small changes in enthalpy in the glass-rubber transition which preclude the possibility of obtaining the glass-rubber transition temperature of these polymers by differential scanning calorimetric techniques. (C) 1997 American Institute of Physics.Díaz Calleja, R.; Sanchis Sánchez, MJ.; Alvarez, C.; Riande, E. (1997). Relaxation behavior of semiflexible polymers at very low frequencies. Journal of Applied Physics. 81(8):3685-3691. doi:10.1063/1.364743S3685369181

La cultura de los datos: Actas del II Congreso Internacional de la Asociación Argentina de Humanidades Digitales

Proceedings of the 3rd conference of the Asociación Argentina de Humanidades Digitales (AAHD), Rosario, Argentina, 2018

¿De qué hablamos cuando hablamos de Humanidades Digitales?

Parece que las Humanidades Digitales actuales fueron Humanist Computing o Computación/Informática Humanística hasta 2004, cuando John Unsworth, uno de los editores del fundamental A Companion to Digital Humanities, decidió este nombre algo más amplio y por qué no “marketinero” para titular el volumen. En esta nueva etapa en las Humanidades Digitales conviven las más diversas disciplinas humanistas con el trabajo del mundo de la programación, generando desde bibliotecas digitales,repositorios, a recursos digitales para visualización de actividades y de objetos hasta el momento invisibles a nuestros ojos como la música, y abogan por una reflexión acerca de los modos de acceder al conocimiento a través de su materialidad.Facultad de Humanidades y Ciencias de la Educació