Browsing Artículos científicos by Issue Date
Now showing items 1-20 of 109
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Potencial del cultivo de hongos comestibles en Costa Rica
(Editorial de la Universidad Nacional, 1985-01-01)Sin lugar a duda la ubicación de Costa Rica es un privilegio desde el punto de vista ecológico. La gran diversidad de zonas de vida que existe permite cultivar una gran cantidad de vegetales, entre estos los hongos. Estas ... -
Carácteres generales, edad y crecimiento de anadara grandis (Pelecypoda Arcidae)
(Universidad Nacional (Costa Rica), 1986-01-01)Cálculos en el porcentaje de carne por peso análisis de la estructura poblacional de Anadara grandis se realizó entre abril de 1984 y marzo de 1985. El valor promedio del porcentaje de carne fue de 10,93 con un valor ... -
Producción de pescado seco-salado utilizando secadores solares
(Universidad Nacional (Costa Rica), 1986-01-01)La técnica de seco-salado de pescado es un método de preservación efectivo, rápido y barato que se ha utilizado durante cientos de años controlando la temperatura y la concentración de sal en proteínas como el pescado por ... -
Química y actividad fisiológica de metabolitos secundarios presentes en el género Amyris (Rutaceae)
(Universidad Nacional [Costa Rica], 1986-01-01)La familia Rutaceae comprende 1.600 especies agrupadas en 150 géneros, que viven en zonas templadas y tropicales del mundo, siendo numerosas en el sur de África y en Australia (Engler, 1964). La mayoría son plantas ... -
Obtención de acetato de celulosa a partir de desechos agroindustriales
(Universidad Nacional [Costa Rica], 1989-01-01)El propósito del presente trabajo fue encontrar usos alternativos para los residuos agrícolas. Se realizó la acetilación de celulosa de cáscara de piña, cáscara de arroz y aserrín. La reacción de acetilación se llevó a ... -
Evaluación farmacológica y química de Stachytarpheta jamaicensis (Verbenaceae)
(Universidad de Costa Rica, 1996)Afier intraperitoneal administration of gradual aqueous doses obtained from Stachytarpheta jamaicensis leaves, the following effects were observed in rats: a reduction of motor activity and the alarm reaction, ataxia, ... -
Evaluación química y biológica del efecto de extractos de plantas contra Plasmodium berghei
(Universidad de Costa Rica, 1996)Extracts from thirteen species of plants were evaluated by "in vivo" antimalarial test against Plasmodium berghei effects. Significant activities were observed in the ethyl acetate and aqueous extracts, elaborated of ... -
Arthropod biodiversity loss and the transformation of a tropical agro-ecosystem
(Chapman & Hall, 1997)The coffee (coffea arabica) agro-ecosystem in the Central Valley of Costa Rica was formerly characterized by a high vegetational diversity. This complex system has been undergoing a major transformation to capital-intensive ... -
An in vivo model to study the anti-malaric capacity of plant extracts
(Universidad de Costa Rica, 1998)An in vivo model to study the antimalaric effect of plant extracts is described. White mice (25-30g body weight) are treated subcutaneously with 0.6ml of the diluted extract starting seven days before P. berghei infection; ... -
Caracterización química de algunos desechos agroindustriales de Costa Rica
(Universidad Nacional [Costa Rica ], 1998-01-01)Se caracterizó químicamente las cáscaras de la piña y el aserrín de madera, la cascarilla de arroz, la brosa y el pergamino del café y se procedió a la separación de la lignina y la celulosa. Los análisis I R realizados ... -
Effect of the soft segment on the fatigue behavior of segmented polyurethanes
(Elsevier, 1999)Effect of the soft-segment structure and molecular weight on the microphase separation in segmented polyurethanes (SPU) was determined by means of differential scanning calorimetry, small-angle X-ray scattering, dielectric ... -
Anthrone and oxanthrone C,O-diglycosides from Picramnia teapensis
(Elsevier, 2000)Two C,O-diglycosylated compounds, the anthrone picramnioside F, and the oxanthrone mayoside C, were isolated from the stem bark of Picramnia teapensis, along with the previously reported anthraquinones, 1-O-b-d- and ... -
Orientation effect in poly (butylene succinate) fibers
(Polymers & Polymer Composites vol.11 no.1 51-56 2003, 2003)Fibers of poly (butylene succinate) (PBS) were prepared using a single screw extruder at various take-up speeds. Changes in fiber structure, morphology and physical properties were investigated using sonic velocity ... -
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 ... -
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 ... -
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 ... -
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. ... -
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 ...
