Browsing Artículos científicos by Issue Date
Now showing items 21-40 of 189
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Addition of nanosilicas with different silanol content to thermoplastic polyurethane adhesives
(Elsevier, 2005-08-15)Three nanosilicas with different silanol contents were prepared by treatment of hydrophilic fumed silica with dimethyldichlorosilane. This treatment reduced the silanol content and produced the particle agglomeration of ... -
Influence of the electrical interface properties on the rheological behavior of sonicated soy lecithin dispersions
(Universidad Nacional (Costa Rica), 2007)A significant effect, on the rheological behavior, due to the electrical properties of vesicles formed from concentrated soy lecithin dispersions have been studied in this work. The rheopectic behavior of concentrated soy ... -
An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer
(Elsevier, 2008)The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer ... -
Control in vitro de garrapatas (Boophilus microplus; Acari: Ixodidae) mediante extractos vegetales
(Universidad de Costa Rica, 2008)Hydro-alcohol extracts of ten tropical plants were tested by the immersion method on mature ticks (Boophilus microplus Canestrini 1887). The biological evaluation was made with raw hydro alcoholic extracts (R-OH) to determine ... -
Composite soy lecithin–decylpolyglucoside vesicles: A theoretical and experimental study
(Elsevier, 2008)In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a ... -
Kinetics of Isothermal Degradation Studies in Adhesives by Thermogra vimetric Data: Effect of Hydrophilic Nanosilica Fillers on the Thermal Properties of Thermoplastic Polyurethane-Silica Nanocomposites
(Recent Patents on Nanotechnology, 2008)The kinetics of thermal degradation process on thermoplastic polyurethanes (TPUs) adhesives with hydrophilic nanosilicas was studied using isothermal thermogravimetric analysis within the temperature range from 360 °C ... -
Initial validation of ozone measurements from the High Resolution Dynamics Limb Sounder
(Advancing earth an space science, 2008)Comparisons of the latest High Resolution Dynamics Limb Sounder (HIRDLS) ozone retrievals (v2.04.09) are made with ozonesondes, ground-based lidars, airborne lidar measurements made during the Intercontinental Chemical ... -
Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixing
(Wiley Inter Science, 2009)Composites of carbon nanofibers (CNFs), oxidized car bon nanofibers (ox-CNFs), and shape-memory thermo plastic polyurethane (TPU) were prepared in a chaotic mixer and their shape-memory properties evaluated. The polymer ... -
Kinetics of anaerobic degradation of screened dairy manure by upflow fixed bed digesters: Effect of natural zeolite addition
(Taylor & Francis, 2009)The effect of the hydraulic retention time (HRT) on the performance of two up-flow anaerobic fixed bed digesters (UFAFBDs) packed with waste tire rubber (D1) and waste tire rubber and zeolite (D2) as micro-organism ... -
Influence of iron oxide nanoparticles on the rheological properties of hybrid chitosan ferrogels
(Elsevier, 2009)Magnetite nanoparticles have been successfully synthesized in the presence of chitosan using an in situ coprecipitation method in alkali media. This method allows obtaining chitosan ferrogels due to the simul taneous ... -
Manejo de Mercancías Químicas peligrosas en puerto Caldera, Puntarenas, Costa Rica
(Universidad Nacional (Costa Rica), 2009)Puerto Caldera, ubicado en Puntarenas, Costa Rica, en uno de los puertos más importantes de Centroamérica, ya que a través de él se trasiegan por año aproximadamente 1.5 millones de toneladas métricas de carga de diferentes ... -
Determinación de la concentración de sólidos suspendidos totales (SST) y metales pesados en la cuenca del Río Morote, Nicoya, Guanacaste
(Universidad Nacional (Costa Rica), 2009)Se determinó la concentración de solidos suspendidos totales y metales pesados en la cuenca del río Morote. El estudio abarco seis campañas de muestreo entre abril del 2003 y mayo del 2005. Los puntos de muestreos seleccionados ... -
Analysis of non-covalent interactions between the nanoparticulate fillers and the matrix polymer as applied to shape memory performance
(The Royal Society of Chemistry, 2010)Non-covalent interactions between filler particles and polyurethanes were investigated using fluorescence emission spectroscopy. The results were used in the analysis of shape memory (SM) performance of polyurethanes. ... -
Calidad del agua de los ríos de la microcuenca IV del Río Virilla
(Universidad Nacional (Costa Rica), 2010)En la evaluación de la calidad del agua de los cauces de los Ríos Tibás, Lajas, Tranqueras y Tures de la Microcuenca IV del Río Virilla se aplicaron dos índices basados en parámetros físicos, químicos y bacteriológicos con ... -
Análisis de los accidentes químico-tecnológicos presentados en la gran área metropolitana durante el período de 1998-2005
(Universidad Nacional (Costa Rica), 2010)Durante el periodo 1998-2005, la unidad de Materiales Peligrosos del Instituto Nacional de Seguros (MATPEL) atendió 329 emergencias químico-tecnológicas en Costa Rica, de las cuales 255 ocurrieron en la Gran Área Metropolitana ... -
Biodegradable polyurethanes from sugar cane biowastes
(Cellulose chemistry and technology, 2011)In a previous work, it was demonstrated that 70% of the molasses isolated from the biowaste generated by the agro-industrialization of sugar cane allow obtaining composite materials with adequate mechanical properties ... -
First Measurements of Biogenic Hydrocarbons in Air in a Tropical Cloudy Forest, Monteverde, Costa Rica
(David Publishing Compan, 2011)Measurements of biogenic hydrocarbons in ambient air were carried out during 2008 in a cloud y tropical forest in Monteverde, Costa Rica. Isoprene, α-pinene, β-pinene, 3-carene, d-limonene and γ-terpinene were sampled by ... -
Chemical constituents from Zanthoxylum setulosum (Rutaceae)
(Universidad Nacional, Costa Rica, 2011-02-10)Following our phytochemical studies of Costa Rican plants, in this work we report the isolation and identification of eight compounds from aerial parts of Zanthoxylum setulosum (Rutaceae). They were identified as the ... -
Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites
(Elsevier, 2011-10-27)Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox- CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using ... -
Chemical and functional characterization of antimicrobial metabolites isolated from ascidian Rhopalaea Birkelandi
(Universidad Nacional (Costa Rica), 2011-12)Marine ecosystems have a very large diversity of resources, most of them still partially unknown, and a few others exploited for development of new industrial and toxicological products. The objective of this investigation ...