Age and experimental obstructive emphysema. A morphometrical study on the rat

Age, as a risk factor in the development of experimental obstructive emphysema, is proposed as the hypothesis of this study. Ninety-two Wistar rats were organized into two age groups: adult (16 weeks) and middle-aged (56 weeks). Each age group was subdivided into three groups: a control group, consisting of unmanipulated animals; a "cannula" group consisting of animals into whose trachea a cannula was implanted; and a "valve" group, consisting of animals into whose trachea a valve had been implanted. The survival was one month. A histomorphometric study was performed on the lungs and the results were compared statistically. Throughout the experiment the amount of food consumed by each animal and the variations in weight were monitored. After sacrifice, the lungs were processed for light microscopy. Thirteen histomorphometric variables were quantified and subsequently systematized into three groups: those which quantified the size of the distal airspace ("area of the alveolar section", "alveolar chord" and "mean linear intercept"): those which quantified the tissue ("wall thickness", "tissue density", "internal perimeter of each alveolar section", "internal alveolar perimeter per field" and "alveolar section/section perimeter"); and those which quantified the elastic fibre ("elastic fibre area", "elastic fibre perimeter", "elastic fibre area/elastic fibre perimeter", "elastic fibre density" and "elastic fibre density per tissue density"). The results were compared statistically and the sensitivity, specificity and misclassification indices were calculated, as well as the attributable and relative risk. From the results, it was observed that, in general, the animals of the valve and cannula groups in both age groups displayed a decrease in food intake and a body weight loss. The middle-aged animals were the only group which displayed significant differences in all the morphometric variables except wall thickness, when the cannula and valve groups were compared with the control group. In both the cannula and valve groups, the values of the variables which quantified the distal airspace increased, while the values of the variables which quantified the lung tissue and the elastic fibre decreased. In the manipulated middle-aged group, the attributable risk of developing emphysema was 56.66% and the relative risk 5.55; in the group of manipulated adult animals, the attributable risk was 23.55% and the relative risk 1.66. The results of this study lead us to propose that the middle-aged rats with experimental airflow obstruction displayed a greater risk of developing emphysema than the adult rats which were subjected to the same procedure.     

Development of a unified FDTD-FEM library for electromagnetic analysis with CPU and GPU computing

The present paper describes an optimized C++ library for the study of electromagnetics. The implementation is based on the Finite-Difference Time-Domain method for transient analysis, and the Finite Element Method for electrostatics. Both methods share the same core and are optimized for CPU and GPU computing. To illustrate its running, FEM method is applied for solving Laplace’s equation analyzing the relation between surface curvature and electrostatic potential of a long cylindrical conductor, whereas FDTD is applied for analyzing Thin Film Filters at optical wavelengths. Furthermore, a comparison of the performance of both CPU and GPU versions is analyzed as a function of the grid size simulation. This approach allows the study of a wide range of electromagnetic problems taking advantage of the benefits of each numerical method and the computing power of the modern CPUs and GPUs.     

Remote sensing and land cover area estimation

This article gives an overview of different ways to use satellite images for land cover area estimation. Approaches are grouped into three categories. (1) Estimates coming essentially from remote sensing. Ground data, are used as an auxiliary tool, mainly as training data for image classification, or sub-pixel analysis. Area estimates from pixel counting are sometimes used without a solid statistical justification. (2) Methods, such as regression, calibration and small area estimators, combining exhaustive but inaccurate information (from satellite images) with accurate information on a sample (most often ground surveys). (3) Satellite images can support area frame surveys in several ways: to define sampling units, for stratification; as graphic documents for the ground survey, or for quality control.

Cost-efficiency is discussed. Operational use of remote sensing is easier now with cheaper Landsat Thematic Mapper images and computing, but many administrations are reluctant to integrate remote sensing in the production of area statistics.     

Analysis of PVA/AA based photopolymers at the zero spatial frequency limit using interferometric methods

One of the problems associated with photopolymers as optical recording media is the thickness variation during the recording process. Different values of shrinkages or swelling are reported in the literature for photopolymers. Furthermore, these variations depend on the spatial frequencies of the gratings stored in the materials. Thickness variations can be measured using different methods: studying the deviation from the Bragg's angle for nonslanted gratings, using MicroXAM S/N 8038 interferometer, or by the thermomechanical analysis experiments. In a previous paper, we began the characterization of the properties of a polyvinyl alcohol/acrylamide based photopolymer at the lowest end of recorded spatial frequencies. In this work, we continue analyzing the thickness variations of these materials using a reflection interferometer. With this technique we are able to obtain the variations of the layers refractive index and, therefore, a direct estimation of the polymer refractive index.     

Combining topological sensitivity and genetic algorithms for identification inverse problems in anisotropic materials

The identification inverse problem is solved here for flaw detection in anisotropic materials by means of an innovative approach: the combination of Genetic Algorithm and the Topological Sensitivity in anisotropic elasticity. The Topological Sensitivity provides a measure of the susceptibility of a defect being at a given location. This is based on a linearized topological expansion, applying Boundary Integral Equations and using solely information of the non-damaged state. It is proved that the Topological Sensitivity provides an accurate tool for estimating the location and size of defects. First, it is shown that the minimum of the residual (cost function) topological sensitivity pinpoints the location and size of the actual flaws, and secondly, the minimization of the residual topological sensitivity is carried out using Genetic Algorithm. When the Genetic Algorithm is applied to the residual Topological Sensitivity instead of to the full residual, the applicability of this method is enhanced since the computational effort, which is the major drawback of this type of search methods, is drastically reduced. In this paper, the formulation for linearly anisotropic elastic media is composed for the case of circular flaws, although the procedure is extensible to other kinds of defects like elliptical cavities, elastic or rigid inclusions or cracks.     

Acrylic scaffolds with interconnected spherical pores and controlled hydrophilicity for tissue engineering

Polymer scaffolds are obtained in which the geometric characteristics (pore size, connectivity, porosity) and the physico-chemical properties of the resulting material can be controlled in an independent way. The interconnected porous structure was obtained using a template of sintered PMMA microspheres of controlled size. Copolymerization of hydrophobic ethyl acrylate and hydrophilic hydroxyethyl methacrylate comonomers took place in the free space of the template, different comonomer ratio gave rise to different hydrophilicity degrees of the material keeping the same pore architecture. The morphology of the resulting scaffolds was investigated by scanning electron microscopy (SEM), the porosity of the material calculated, and the mechanical properties compared with those of the bulk (non porous) material of the same composition.     

Characterization of polyvinyl alcohol/acrylamide holographic memories with a first-harmonic diffusion model

Several theoretical models have been proposed to predict the behavior of photopolymers as holographic recording materials. Basically these models have been applied to study thin layers (around 100 microm thick). The increasing importance of holographic memories recorded in photopolymers (thickness of > 500 microm) makes it necessary to extend the ideas proposed by these models to study thick photopolymer layers. We calculate the temporal evolution of the diffraction efficiencies for thick layers using a first-harmonic diffusion model, and the results obtained are compared with the corresponding values for thin layers. Furthermore, the values of the average diffusivity of the polymer chains after the grating is formed are also obtained. In general, we find that the monomer and polymer diffusivity increases when higher values of thickness are used.     

Clarifications to the paper "Holographic characteristics of a 1-mm-thick photopolymer to be used in holographic memories"

We have corrected typing errors related to the characterization of the dynamic range of the acrylamide photopolymer described in an earlier study [Appl. Opt. 42, 7008 (2003)]. The M number is expressed as M/# instead of M# as appears in the text. The value calculated from the experimental results that are included in the article is M/# = 3.8 instead of 38 as appears in the text.     

Effects of birth date and order in lactation performance of Iberian red deer (Cervus elaphus hispanicus)

This study discriminated between 2 effects (birth date and presence of older calves) assessed jointly in previous studies. Birth date delay produced similar effects to those reported previously: reduced milk and milk nutrient production in late-calving hinds, concentration of milk, substitution of protein by fat, greater body weight losses of dams (hinds), and reduced calf growth. Hinds in a group consisting of early- and late-born calves produced more milk, and calves grew more than their isolated counterparts. Evidence exists for consequences of foster suckling by early-born calves in mixed groups of early- and late-born calves at the end of the standard birth period, because these calves grew more than predicted by the milk production of their dams. In contrast, no detrimental effect was found in late-born calves of this group. Lack of differences might be due to the excess of hind milk production during the first 5 wk of lactation previously recorded in other experiments.