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Hybrid powder coatings (HPC) with low friction and high hardness enhance the sliding speed and allow interlocking or meshing products to slide effortlessly within each other, saving energy. In automobiles, they decrease fuel consumption and greenhouse gas emission. In the present work, a new insight of the key role played by the coverage density of triethoxyphenylsilane (TPS) grafted to SiO2 nanoparticles over the friction coefficient, hardness, elastic modulus, and roughness of HPC is presented for the first time. In all cases, a very low amount (0.1 wt %) of functionalized or unfunctionalized SiO2 nanoparticles were added to a powder-coating formulation based on polyester resin. HPC formulated with functionalized nanoparticles at a suitable coverage density (HPC–TPS3) exhibited significantly low friction coefficient (μ = 0.12), strong wear resistance (under dry sliding conditions at 1 and 5 N of load), low roughness (Rq = 3.5 nm), and high hardness and elastic modulus on the surface. We demonstrated tha...

Background and objectives: Emerging information indicates that glucose metabolism alterations are common after renal transplantation and are associated with carotid atheromatosis. The aims of this study were to investigate the prevalence of different glucose metabolism alterations in stable recipients as well as the factors related to the condition. Design, setting, participants, & measurements: A multicenter, cross-sectional study was conducted of 374 renal transplant recipients without pre- or posttransplantation diabetes. A standard 75-g oral glucose tolerance test was performed. Results: Glucose metabolism alterations were present in 119 (31.8%) recipients: 92 (24.6%) with an abnormal oral glucose tolerance test and 27 (7.2%) with isolated impaired fasting glucose. The most common disorder was impaired glucose tolerance (17.9%), and an abnormal oral glucose tolerance test was observed for 21.5% of recipients with a normal fasting glucose. By multivariate analysis, age, prednisone dosage, triglyceride/high-density lipoprotein cholesterol ratio, and β blocker use were shown to be factors related to glucose metabolism alterations. Remarkably, triglyceride levels, triglyceride/high-density lipoprotein cholesterol ratio, and the proportion of recipients with impaired fasting glucose were already higher throughout the first posttransplantation year in recipients with a current glucose metabolism alteration as compared with those without the condition. Conclusions: Glucose metabolism alterations are common in stable renal transplant recipients, and an oral glucose tolerance test is required for its detection. They are associated with a worse metabolic profile, which is already present during the first posttransplantation year. These findings may help planning strategies for early detection and intervention.

En los últimos años la nanotecnología ha permitido mejoras en múltiples áreas tecnológicas y el caso de los recubrimientos no es la excepción, sin embargo, son pocos los trabajos que se enfocan al campo de las pinturas en polvo. En este estudio se exploró la incorporación de nanopartículas dióxido de silicio (NPSiO2) funcionalizadas con cuatro tipos de organosilanos: 3-glicidil-epoxipropil-trimetoxi-silano, Polidimetil siloxano hidroxiterminado, Octil-trietoxi-silano y Fenil-trietoxi-silano, con la finalidad de mejorar la dispersión de las nanopartículas al ser incorporadas a una matriz de pintura en polvo. En base a las NPSiO2 funcionalizadas se eligieron 3 densidades de injerto (bajo, medio y alto) para ser incorporadas a la formulación original de pintura (0.1%wt), encontrando un incremento en la estabilidad térmica, así como cambios en las temperaturas de fusión y curado, las mediciones de brillo mostraron un incremento de 90.75 a 95.18 unidades, al incorporar NPSiO2 funcionalizadas. A su vez las pruebas de impacto dardo en las muestras donde se incoporaron nanopartículas mostraron un desempeño superior al tener una menor fragmentación de la pintura en cargas de 140 lb/in2 . Adicionalmente, se encontraron reducciones en el coeficiente de fricción de 0.54 hasta 0.12 lo que contribuyó de manera significativa a disminuir el desgaste. La mejora en las propiedades macroscópicas anteriormente mencionadas se atribuye a una buena dispersión de las nanopartículas funcionalizadas en la matriz. Para el caso del agente Fenil-trietoxi-silano se especula existe una incompatibilidad con la resina poliéster empleada como base para la fabricación de la pintura en polvo, la cual no presenta grupos aromáticos, X esta incompatibilidad ocasiona la migración de las nanopartículas hacia la superficie del recubrimiento, formando una capa de nanopartículas que aminora el coeficiente de fricción del recubrimiento, esto a su vez proporciona una mayor resistencia a la fricción y por ende menor desgaste. Este efecto se da principalmente al tener una densidad de injerto media. Por otra parte se exploró la incorporación de las nanopartículas funcionalizadas con tres densidades de injerto (bajo, medio y alto) y tres concentraciones (0.1, 0.5 y 1%) en una tela no tejida de nylon-6 mediante la técnica de electrohilado encontrando incremento en los valores de esfuerzo tensil y módulo de young de 26 y 49 veces respectivamente, a su vez la estabilidad térmica del material también se vio incrementada

Measurements show that in general salt is vertically well-mixed everywhere in the Great Bay Estuary, New Hampshire except near the river entrances at the head of the estuary. Dyer and Taylor’s (1973) modified version of Ketchum’s segmented tidal prism model has been applied to the Great Bay Estuarine System in order to predict high and low water salinity distribution for a specified river flow. The theory has been modified here to account for the mixing which occurs at the junction of two branches of an estuary. The mixing parameter, which in this model is related to the tidal excursion of water in the estuary, has been determined for different segments in the estuary on the basis of a comparison between predictions and a comprehensive data set obtained for a low river flow period. Using a mixing parameter distribution based on the low river flow calibration procedure the salinity distribution has been predicted for high river flow. The resulting salinity distribution compares favorably with observations for most of the estuary. The corresponding flushing times for water parcels entering at the head of the estuary during periods of low and high river flow is 54.5 and 45.9 tidal cycles respectively.