Manuel Garcia

ABSTRACT Bibliografía p. 261-290 1) Estudiar el desarrollo de la conciencia fonológico-silábica, detectando sus comienzos en niños prelectores hasta la consecución de un alto nivel. 2) Establecer sus posibles relaciones con el aprendizaje inicial de la lectura. 3) Plantean 5 hipótesis, 293 sujetos de Preescolar y ciclo inicial de EGB en el primer año y 220 en el segundo, pertenecientes a tres colegios públicos de Murcia. El objeto del trabajo es prevenir el fracaso en el aprendizaje inicial de la lectura

El análisis estadístico del diseño con grupo control no equivalente (GCNE) con variables dependientes numéricas ha sido un tema de gran interés durante la última dé- cada. Mucho menos interés ha demandado el análisis estadístico con variables depen- dientes categóricas, aunque las mismas ideas se aplican en ambos casos. No obstante, los problemas generados por el error de medida de

Los modelos mixtura son procedimientos apropiados para la valoración del acuerdo entre dos (o más) observadores que asumen que los objetos a clasificar se extraen de una población que constituye una mezcla de dos subpoblaciones finitas, la primera de las cuales representa acuerdo sistemático y la se- gunda acuerdo aleatorio y desacuerdo. Una generalización del modelo mixtura básico a cuatro

Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D2O or H2O at 80 degrees C. For NR and XR, ultrathin (approximately 100 A) films were prepared by spin-coating. Both D2O and H2O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H2O or D2O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H2O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D2O at 80 degrees C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D2O than with H2O.

PharrnaceuticaI houses that produce ⁹⁹Tc/⁹⁹Tc generators have on occasion received ⁹⁹Mo that contained a black precipitate. Addition of sodium hypochlorite to product bottles prior to shipment prevents precipitate formation, indicating the precipitate is a reduced form of Mo. The radiation effects of the dose from ⁹⁹Mo on the product and product bottle have been determined by irradiating simulated ⁹⁹Mo product

This study evaluated the robustness of two recent methods for analyzing multivariate repeated measures when the assumptions of covariance homogeneity and multivariate normality are violated. Specifically, the authors' work compares the performance of the modified Brown– ...