Analysis of matched matrices

We consider the joint visualization of two matrices which have common rowsand columns, for example multivariate data observed at two time pointsor split accord-ing to a dichotomous variable. Methods of interest includeprincipal components analysis for interval-scaled data, or correspondenceanalysis for frequency data or ratio-scaled variables on commensuratescales. A simple result in matrix algebra shows that by setting up thematrices in a particular block format, matrix sum and difference componentscan be visualized. The case when we have more than two matrices is alsodiscussed and the methodology is applied to data from the InternationalSocial Survey Program.

Nutrientes y renovación del agua en aiguamolls de l’Empordà. (NE de la península Ibérica). Uso potencial de agua residual para la inundación de zonas húmedas

The monitoring of the ecological water quality of 'Aiguamolls de l’Empordà' Natural Park was carried out between September 1996 to August 1997. The aim was to evaluate the impact of effluent from a nearby wastewater treatment plant, on the flooding of marshes in the Natural Park. In this paper we present physical and chemical data together nutrient concentrations and its changes in the lentic system of the 'Aiguamolls de l’Empordà'. The ultimate aim was to evaluate the effect of reclaimed wastewater on the salt marsh system. Seasonal variation in nutrients concentrations and their relationship to turnover and source of water were analysed. Significant variation in the N/P ratio was related to water turnover. Confined systems presented lower values for this ratio. Taking into account the nutrient concentrations of the reclaimed water, which is rich in nitrogen, it is recommended flooding applied in zones with high water turnover and higher N/P ratios

Residual thermomechanical stresses in thinned-chip assemblies

A new technology for the three-dimensional (3-D) stacking of very thin chips on a substrate is currently under development within the ultrathin chip stacking (UTCS) Esprit Project 24910. In this work, we present the first-level UTCS structure and the analysis of the thermomechanical stresses produced by the manufacturing process. Chips are thinned up to 10 or 15 m. We discuss potentially critical points at the edges of the chips, the suppression of delamination problems of the peripheral dielectric matrix and produce a comparative study of several technological choices for the design of metallic interconnect structures. The purpose of these calculations is to give inputs for the definition of design rules for this technology. We have therefore undertaken a programme that analyzes the influence of sundry design parameters and alternative development options. Numerical analyses are based on the finite element method.

Residual Stress Measurement on a MEMS Structure With High-Spatial Resolution

A new approach to the local measurement of residual stress in microstructures is described in this paper. The presented technique takes advantage of the combined milling-imaging features of a focused ion beam (FIB) equipment to scale down the widely known hole drilling method. This method consists of drilling a small hole in a solid with inherent residual stresses and measuring the strains/displacements caused by the local stress release, that takes place around the hole. In the presented case, the displacements caused by the milling are determined by applying digital image correlation (DIC) techniques to high resolution micrographs taken before and after the milling process. The residual stress value is then obtained by fitting the measured displacements to the analytical solution of the displacement fields. The feasibility of this approach has been demonstrated on a micromachined silicon nitride membrane showing that this method has high potential for applications in the field of mechanical characterization of micro/nanoelectromechanical systems.

Density matrices and momentum distributions in 3He-4He mixtures

We report variational calculations, in the hypernetted-chain (HNC)-Fermi-HNC scheme, of one-body density matrices and one-particle momentum distributions for 3He-4He mixtures described by a Jastrow correlated wave function. The 4He condensate fractions and the 3He strength poles are examined and compared with the Monte Carlo available results. The agreement has been found to be very satisfactory. Their density dependence is also studied.

Unconventional magnetic behavior of iron-oxide nanoparticles in polymeric matrices

We report the results of magnetization and 57Fe Mössbauer spectroscopy measurements performed in the temperature range 5-300 K on composites containing iron¿oxide nanoparticles encased in polystyrene type resins. After carrying out a suitable field treatment in order to decouple the particles from the matrix, a fraction of the particles freely rotate in response to an applied magnetic field

Aplicaciones de la Teoría de Matrices en Matemática Discreta

Se describen algunas aplicaciones de la teoría de matrices a diversos temas pertenecientes alámbito de la matem\'atica discreta.

Second-order parameter estimation

This work provides a general framework for the design of second-order blind estimators without adopting anyapproximation about the observation statistics or the a prioridistribution of the parameters. The proposed solution is obtainedminimizing the estimator variance subject to some constraints onthe estimator bias. The resulting optimal estimator is found todepend on the observation fourth-order moments that can be calculatedanalytically from the known signal model. Unfortunately,in most cases, the performance of this estimator is severely limitedby the residual bias inherent to nonlinear estimation problems.To overcome this limitation, the second-order minimum varianceunbiased estimator is deduced from the general solution by assumingaccurate prior information on the vector of parameters.This small-error approximation is adopted to design iterativeestimators or trackers. It is shown that the associated varianceconstitutes the lower bound for the variance of any unbiasedestimator based on the sample covariance matrix.The paper formulation is then applied to track the angle-of-arrival(AoA) of multiple digitally-modulated sources by means ofa uniform linear array. The optimal second-order tracker is comparedwith the classical maximum likelihood (ML) blind methodsthat are shown to be quadratic in the observed data as well. Simulationshave confirmed that the discrete nature of the transmittedsymbols can be exploited to improve considerably the discriminationof near sources in medium-to-high SNR scenarios.

Technical Note: Dissolved organic matter fluorescence a finite mixture approach to deconvolve excitation-emission matrices

The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves individual EEMs is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimisation algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. The EEMs of a simple artificial mixture of fluorophores and DOM samples collected in a Mediterranean river are used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

Determinación del volumen gástrico residual: en busca de la mejor evidencia

Introducción: La determinación del volumen gástrico residual es una práctica frecuente en pacientes críticos, pero hay falta de consenso acerca de la conveniencia de reintroducir o desechar el contenido gástrico aspirado (CGA). Objetivo: Determinar el grado de evidencia científica acerca de la eficacia de 2 intervenciones-reintroducción/rechazo- del CGA en pacientes críticos. Material y métodos: Revisión sistemática de la evidencia disponible acerca de la conveniencia de reintroducir o desechar el CGA. Proceso: a) establecimiento de los criterios de inclusión/exclusión; b) determinación de la estrategia de búsqueda (palabras clave e itinerarios); c) vaciado de las bases de datos: MEDLINE, CINAHL, CUIDEN, IME, SCIELO y COCHRANE. Búsqueda por método indirecto y vaciado manual de índices; d) lectura crítica independiente y contrastada, utilizando la plantilla CASPe, y e) contraste de resultados del análisis crítico. Resultados: Los itinerarios de búsqueda generan más de 800 referencias que, una vez depuradas, permiten seleccionar 54. Después de su lectura, sólo 4 se centran realmente en cuestiones relacionadas con la reintroducción/rechazo del CGA: 2 revisiones, un estudio observacional y un ECA de muestra pequeña. La heterogeneidad de estos estudios no permite emplear técnicas de metaanálisis. Por ello se analizan por separado los resultados de cada estudio. Mediante este proceso se obtiene un resultado final que demuestra un bajo grado de evidencia científica. Conclusiones: Hay escasa evidencia científica acerca de la conveniencia, la seguridad y los beneficios de ambas intervenciones. Es difícil establecer un protocolo de cuidados, por lo que se planteó realizar un estudio experimental para establecer las indicaciones y contraindicaciones de ambas intervenciones.

To return or to discard? Randomised trial on gastric residual volume management

Background: The control of gastric residual volume (GRV) is a common nursing intervention in intensive care; however the literature shows a wide variation in clinical practice regarding the management of GRV, potentially affecting patients" clinical outcomes. The aim of this study is to determine the effect of returning or discarding GRV, on gastric emptying delays and feeding, electrolyte and comfort outcomes in critically ill patients. Method: A randomised, prospective, clinical trial design was used to study 125 critically ill patients, assigned to the return or the discard group. Main outcome measure was delayed gastric emptying. Feeding outcomes were determined measuring intolerance indicators, feeding delays and feeding potential complications. Fluid and electrolyte measures included serum potassium, glycaemia control and fluid balance. Discomfort was identified by significant changes in vital signs. Results: Patients in both groups presented similar mean GRV with no significant differences found (p=0.111), but participants in the intervention arm showed a lower incidence and severity of delayed gastric emptying episodes (p=0.001). No significant differences were found for the rest of outcome measurements, except for hyperglycaemia. Conclusions: The results of this study support the recommendation to reintroduce gastric content aspirated to improve GRV management without increasing the risk for potential complications.

El efecto residual inmunosupresor de la ciclofosfamida no es necesario para evocar la respuesta inmunosupresora condicionada

El objetivo es comprobar si el efecto residual inmunodepresor de la ciclofosfamida contribuye a la evocación de la respuesta de anticuerpos condicionada. Se condicionaron ratones no consanguíneos, machos, con el estímulo condicionado sacarina al 0,15% y con el estímulo incondicionado ciclofosfamida, a 50 y 250 mg/kg. A los 4 días del condicionamiento con 50 mg/kg de ciclofosfamida, o a los 14 días del condicionamiento con 250 mg/kg de ciclofosfamida, los ratones se inmunizaron con glóbulos rojos de rata y, a continuación, bebieron la disolución de sacarina. Se comprobó que i) la dosis más baja de ciclofosfamida no generó efecto residual, mientras que la dosis más alta si, y ii) en ningún caso, la presentación de sacarina disminuyó la respuesta de anticuerpos anti-glóbulos rojos de rata. Se concluye que no se produjo condicionamiento de la respuesta de anticuerpos, tanto si el efecto residual de la ciclofosfamida está presente, como si está ausente.

On the Rule of Mixtures for Predicting Stress-Softening and Residual Strain Effects in Biological Tissues and Biocompatible Materials

In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects. For the isotropic energy part, we select the amended non-Gaussian strain energy density model, while the energy fiber effects are added by considering the equivalent anisotropic volumetric fraction contribution, as well as the isotropized representation form of the eight-chain energy model that accounts for the material anisotropic effects. Furthermore, our proposed material model uses a phenomenological non-monotonous softening function that predicts stress softening effects and has an energy term, derived from the pseudo-elasticity theory, that accounts for residual strain deformations. The model’s theoretical predictions are compared with experimental data collected from human vaginal tissues, mice skin, poly(glycolide-co-caprolactone) (PGC25 3-0) and polypropylene suture materials and tracheal and brain human tissues. In all cases examined here, our equivalent material model closely follows stress-softening and residual strain effects exhibited by experimental data

Language recovery and evidence of residual deficits after nonthalamic subcortical stroke: A 1 year follow-up study

A variety of language disturbances including aphasia have been described after subcortical stroke but less is known about the factors that influence the long-term recovery of stroke-induced language dysfunction. We prospectively examined the role of the affected hemisphere and the lesion site in the occurrence and recovery of language deficits in nonthalamic subcortical stroke. Forty patients with unilateral basal gangliastroke underwent language assessment within 1 week, 3 months and 1 year after stroke. Disturbances in at least one language domain were observed in 35 patients during the first week post stroke including aphasia diagnosed in 11 patients. Importantly, the appearance of deficits after stroke onset and the improvement of language function were not determined by the site of subcortical lesion, but instead were critically influenced by the affected hemisphere. In fact, the language impairments following left and right basal ganglia stroke mirrored the language dysfunction observed after cortical lesions in the same hemisphere. A significant overall language improvement was observed at 3 months after stroke, although residual deficits in languageexecutive function were the most commonly observed impairment at 1 year follow-up. Although a substantial improvement of language function can be expected after nonthalamic subcortical stroke, our findings suggest that language recovery may not be fully achieved at 1 year post