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Search Results: 1 - 10 of 482490 matches for " KARINA MARTíNEZ-TILLERíA "
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Conservación de la biodiversidad en Chile: Nuevos desafíos y oportunidades en ecosistemas terrestres y marinos costeros Biodiversity conservation in Chile: New challenges and opportunities in terrestrial and marine coastal ecosystems
CARMEN JORQUERA-JARAMILLO,J. M. ALONSO VEGA,JAIME ABURTO,KARINA MARTíNEZ-TILLERíA
Revista chilena de historia natural , 2012,
Abstract: La pérdida de la biodiversidad producida por el crecimiento demográfico, la demanda por recursos y la actividad productiva es contradictoria con el reconocimiento de su importancia. En ecosistemas terrestres, el Sistema Nacional de áreas Protegidas del Estado (SNASPE) contiene cerca del 19 % del territorio de Chile continental; aunque no representa todos los ecosistemas con especies amenazadas, puede ser complementado implementando nuevas áreas protegidas públicas (AP) y privadas (APP). El desarrollo de áreas marinas protegidas (AMP) es incipiente, y algunas iniciativas comparten la responsabilidad de conservación con los usuarios locales. En Chile, un conjunto de reglamentos, normas legales y tratados internacionales promueven distintas oportunidades de conservación en ecosistemas terrestres y marinos costeros, de las cuales emergen nuevos desafíos. Entre estos destacan, estandarizar la clasificación de especies según categorías de conservación en un protocolo internacional y optimizar las metodologías para seleccionar áreas prioritarias, ambos criterios indispensables para decidir qué y dónde conservar. Otro desafío es integrar el valor intrínseco de la biodiversidad con los servicios ecosistémicos que presta para instaurar una cultura participativa. Esto mejoraría la efectividad de las distintas estrategias de protección y uso sustentable de la biodiversidad al incorporar la educación y la participación ciudadana desde una perspectiva biocultural. La educación fomenta la conservación de la naturaleza al hacernos conscientes de nuestro entorno; mientras que la participación involucra a los ciudadanos como un actor más en la toma de decisiones, procurando la aplicación efectiva de las estrategias de conservación de la biodiversidad. Biodiversity loss caused by population growth, the demand of resources and productive activities is inconsistent with the recognition of its importance. In terrestrial ecosystems, the National State System of Protected Areas (SNASPE) contains about 19 % of continental Chile. Although it does not represent all the ecosystems with endangered species, it can be supplemented by implementing new public and private protected areas (PA and PPP, respectively). The development of Marine Protected Areas (AMP) is emerging, and some strategies share conservation responsibility with local stakeholders. In Chile, a set of regulations, laws and international treaties promote different conservation opportunities in land and marine coastal ecosystems. Some of the derived challenges involve standardizing the classification of species in cons
Production and performance of larvae and spat of pure and hybrid species of Mytilus chilensis and M. galloprovincialis from laboratory crosses
Toro,Jorge E; Oyarzún,Pablo A; Pe?aloza,Carolina; Alcapán,Angélica; Videla,Viviana; Tillería,Jorge; Astorga,Marcela; Martínez,Víctor;
Latin american journal of aquatic research , 2012,
Abstract: adult specimens of m. galloprovincialis from concepción bay and m. chilensis from yaldad bay, chile, were transferred to the laboratory to produce crosses of "pure" and "hybrid" species in order to evaluate early larval development and growth. these variables are important for understanding the dynamics of these two mussel species in this potential hybrid zone where they occur sympatrically. the study showed that fertilization occurred in all crosses and significant differences were not detected between pure lines and hybrids in terms of the percentage of eggs that developed into larvae. hybrid larvae and spat from both reciprocal crosses grew significantly more than those from pure lines, although valve length values were within the ranges reported in the literature.
Nernst-Planck Model applied to the kinetics of ionic exchange of the system PO4-3-Cl- in milk
Marín,Julissa; García,Cézar; Ala?a,Jorge; Martínez,Karina; Faría,José;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: the kinetics of ionic exchange was determined in milk for decrease of the content of salinity and increase of the stability of the milk, studying the effect of the operational variables: temperature, time of contact milk-resin, on the exchange process for the system ionic chloride-phosphate. the experimental methodology required the use of a reactor for batch with half agitation to exchange the ions chloride present in the solution with ions phosphate fixed to resin strongly basic anionic, during a period of 180 minutes. the content of chloride in the liquid phase was determined by the technique of valuation mercurometric and that of phosphate by spectophotometer. the kinetics data were adjusted in function of a kinetic model of ionic exchange developed starting from the theoretical model of nernst-planck that includes the diffusion mechanisms and ionic migration for any system ionic under control of the liquid phase.
Operational variable effects on heavy metals acid leaching present in fly ash
Pi?a,Lourdes; Eligleys,Dorante; García,Cézar; González,José A; Martínez,Karina;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2004,
Abstract: in this research work the operational variable effects are analyzed on vanadium and nickel acid leaching, both present in fly ash from fuel oil combustion. the samples used correspond to fly ash coming from a thermoelectric plant. the extraction procedure includes batch acid leaching varying: temperature, particle size, acid concentration and stirring time. metal content is determined by atomic absorption spectrophotometry. the following leaching conditions gave good vanadium recovery: a) 20% sulfuric acid, 40°c, original sample, 6 hours contact time and 4230 mgv/l maximum concentration. b) 20% nitric acid, 50°c, original sample, 6 hours contact time and 3869 mgv/l maximum concentration. c) 20% hydrochloric acid, 50°c, original sample, 4 hours contact time and 4290 mgv/l maximum concentration (with 100% extraction). the following leaching conditions gave good nickel recovery: a) 20% sulfuric acid, 40°c, original sample, 2 hours contact time and 294. 50 mgni/l maximum concentration. b) 20% nitric acid, 50°c, original sample, 6 hours contact time and de 325 mgni/l maximum concentration. c) 20% hydrochloric acid, 50°c, original sample, 6 hours contact time and 373.50 mgni/l maximum concentration. vanadium and nickel have been efficiently recovered from oil fly ash.
Modelo de Nernst-Planck aplicado a la cinética de Intercambio Iónico del sistema PO4-3-Cl- en leche Nernst-Planck Model applied to the kinetics of ionic exchange of the system PO4-3-Cl- in milk
Julissa Marín,Cézar García,Jorge Ala?a,Karina Martínez
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: Se determinó la cinética de intercambio iónico en leche para la disminución del contenido de sales y aumento de la estabilidad de la leche, estudiando el efecto de las variables operacionales: temperatura y tiempo de contacto leche-resina, sobre el proceso de intercambio para el sistema iónico cloruro-fosfato. Se utilizó un reactor por carga bajo agitación media para intercambiar los iones cloruro presentes en la solución con iones fosfato fijados a la resina aniónica fuertemente básica, durante un periodo de 180 minutos. El contenido de cloruro en la fase líquida se determinó por la técnica de valoración mercurométrica y el de fosfato por espectofotometría. Los datos cinéticos experimentales se ajustaron en función de un modelo cinético de intercambio iónico desarrollado a partir del modelo teórico de Nernst-Planck que incluye los mecanismos de difusión y migración iónica para sistemas iónicos bajo control de la fase líquida. Los resultados del ajuste cinético demuestran que el modelo propuesto se aproxima a la cinética experimental en la medida que se aumenta la temperatura del sistema y se favorece el control de la fase líquida. The kinetics of ionic exchange was determined in milk for decrease of the content of salinity and increase of the stability of the milk, studying the effect of the operational variables: temperature, time of contact milk-resin, on the exchange process for the system ionic chloride-phosphate. The experimental methodology required the use of a reactor for batch with half agitation to exchange the ions chloride present in the solution with ions phosphate fixed to resin strongly basic anionic, during a period of 180 minutes. The content of chloride in the liquid phase was determined by the technique of valuation mercurometric and that of phosphate by spectophotometer. The kinetics data were adjusted in function of a kinetic model of ionic exchange developed starting from the theoretical model of Nernst-Planck that includes the diffusion mechanisms and ionic migration for any system ionic under control of the liquid phase.
Kinetics of ion-exchange in raw and commercial pasteurized milk
Karina Martínez,Jorge Ala?a,José Ferrer,José Faría
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2006,
Abstract: En el presente trabajo se evaluó la cinética del intercambio iónico del sistema Na+-Ca++ en leche cruda y pasteurizada, para disminuir el contenido de sodio y aumentar el contenido de calcio en ambas leches. Los datos cinéticos del sistema iónico se ajustaron mediante la Ley de Fick, con un coeficiente de difusividad variable expresado por el modelo de Gilliland. La metodología experimental involucró el uso de un reactor por carga con agitación, donde las muestras de leche fueron puestas en contacto con resina catiónica IONAC C-249, a temperatura ambiente, durante un periodo de 6 horas. Las reacciones de intercambio se ajustaron a la toma de muestras en intervalos de 1 hora. La determinación del contenido de sodio y calcio en la fase láctea se realizó por espectrofotometría de absorción atómica. Los resultados demuestran que el intercambio del ion Na+ en la resina presenta una distribución tipo S y el proceso cinético se expresa a través del modelo de Gilliland dado por mientras el intercambio del ion Ca++ en la resina origina una distribución tipo C y el proceso cinético es dado por . In this work the ion-exchange kinetics of Ca++-Na+ system in raw and pasteurized milk was determined by decreasing the sodium, and increasing the calcium levels in milky media. The kinetics data of the ionic systems were fitted by the Fick’s law with a variable diffusion coefficient expressed by the Gilliland model. The experimental methodology involved the use of batch tests under agitation, constant temperature, between sample milk and cationic resin type Ionac C-249, during a contact period of 6 hours. The ion-exchange reactions were followed by sampling the liquid phase every one hour. In the milky phase the concentrations of sodium and calcium were determined by spectrophotometry of atomic absorption. The results show that the exchange of Na+ ions into resin presents a distribution pattern S and the kinetics can be expressed by Gilliland model as , on the other hand, the exchange of Ca++ ions presents a distribution pattern C and the kinetics given by .
Efecto del factor humectante en la determinación de viscosidades para mezclas crudo-solvente Moistening factor effect on the determination of viscosities for crude oil-solvent mixtures
Laurent Urdaneta,Karina Martínez,José González,Jorge Ala?a
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2008,
Abstract: En esta investigación se desarrolla un estudio exhaustivo del comportamiento reológico de mezclas crudo-solvente incorporando experimentalmente el factor humectante, el cual ha sido considerado como constante en investigaciones previas. Se desarrolla un modelo de flujo rotacional en coordenadas cilíndricas acoplado a las mediciones de viscosímetros y a la distribución del fluido en la región de medición, que permite predecir la viscosidad del crudo de una manera más precisa, analizando el comportamiento de la viscosidad de las mezclas a diferentes temperaturas y concentraciones. Se utilizaron tres diferentes viscosímetros: Brookfield, Ostwald y Cole-Parmer, empleando las mismas condiciones de mezcla, concentración y temperatura para todas las mediciones realizadas. Se concluyó que el factor humectante aumenta con el incremento de la velocidad angular y que disminuye con el aumento de la temperatura. Utilizando los parámetros resultantes de la calibración del viscosímetro Longitud efectiva Le y Factor humectante l y siguiendo el modelo teórico adaptado a la geometría Couette se obtienen valores de viscosidad aparente aproximados a los obtenidos experimentalmente. El error relativo promedio es de 14%. Todas las muestras, indican un comportamiento reológico no newtoniano-pseudoplástico. La viscosidad del crudo puede reducirse mediante aumento de temperatura y aumento de la cantidad de solvente. An exhaustive research study about the rheological behavior of the mixtures is developed through the experimental incorporation of the moistening factor, which had been considered as a constant in previous investigations. A model of rotational flow is developed in cylindrical coordinates joined to the viscometers measurements and to the fluid distribution in the measurement region, which lets predict the crude oil viscosity in a more accurate way, analyzing as well the viscosity behavior of different crude oil mixtures at various temperatures and concentrations. Three different viscometers were used at the same mixture, concentration and temperature conditions for each of the measurements made: Brookfield, Ostwald and Cole-Parmer. It was concluded that the moistening factor increases with the angular speed but it decreases with the temperature for crude oil mixtures. Apparent viscosity values, similar to the ones gotten experimentally, were obtained by using the calibration parameters of the instrument Effective Length and Moistening Factor and following the theoretical model adapted to the Couette geometry. The relative average error was 14%. All of the samples sho
Kinetics of ion-exchange in raw and commercial pasteurized milk
Martínez,Karina; Ala?a,Jorge; Ferrer,José; Faría,José; Ramones,Eduardo; García,Cézar;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2006,
Abstract: in this work the ion-exchange kinetics of ca++-na+ system in raw and pasteurized milk was determined by decreasing the sodium, and increasing the calcium levels in milky media. the kinetics data of the ionic systems were fitted by the fick?s law with a variable diffusion coefficient expressed by the gilliland model. the experimental methodology involved the use of batch tests under agitation, constant temperature, between sample milk and cationic resin type ionac c-249, during a contact period of 6 hours. the ion-exchange reactions were followed by sampling the liquid phase every one hour. in the milky phase the concentrations of sodium and calcium were determined by spectrophotometry of atomic absorption. the results show that the exchange of na+ ions into resin presents a distribution pattern s and the kinetics can be expressed by gilliland model as , on the other hand, the exchange of ca++ ions presents a distribution pattern c and the kinetics given by .
Concentración de vanadio y níquel en cenizas volantes por combustión controlada
González,José A.; García,Cézar; Machado,Analí; Rincón,Carlos; Villalobos,Elí; Martínez,Karina;
Interciencia , 2004,
Abstract: this study focuses, in view of their potential recovery, on the concentration of vanadium and nickel from ash by means of a process of controlled combustion of the fly ash from fuel oil at a thermoelectric plant located in the city of maracaibo, venezuela. four size fractions were prepared from the fly ash, including the original sample: 370-160, 160-96 and 96-74μm. the combustion temperatures were 400, 500 and 600oc and combustion times of 60, 90 and 120min. a 1200oc muffle type oven and hearths of stainless steel with 150ml capacity were used. the results showed that the sample with the finest grain size has the highest concentration of v and ni for a temperature of 500oc and a time of 60min.
Comparación Histológica e Inmunohistoquimica de Muestras de Tejido Procesadas por la Técnica Convencional o por el Método Simplificado de Acetonas
Martínez Rivera,Pablo; Pi?a Osuna,Ana Karina; Soto Domínguez,Adolfo; García Garza,Rubén;
International Journal of Morphology , 2011, DOI: 10.4067/S0717-95022011000200046
Abstract: the conventional technique (ct) using alcohol as a drying agent, is a useful method of histology and pathology in the laboratory. recently, a new simplified method with acetone (ta) was designed in an attempt to reduce the processing time of the tissues (12 to 4 hours), the cost of reagents, and as an important factor to have an accurate and prompt diagnosis . this study compared the histological and immunohistochemical parameters in breast cancer, colon and kidney specimens treated with both methods. the sections were stained with h & e or masson trichrome. immunohistochemistry study with antibodies specific for the identification of cytokeratin ae1/ae3, the estrogen receptor and progesterone receptor was also carried out. blind study was conducted by three specialists in morphology, who evaluated the nuclear staining, staining of the cytoplasm and friability or changes in tissue structure. the specificity and sensitivity of antibody binding were also evaluated. the values obtained for each parameter were statistically analyzed with student t test. our results show that the methods of ct and ta did not alter histological features as the pattern of staining, and tissue changes were detected. immunohistochemical positivity was similar for both methods. there was no statistical difference between tc and ta. our results suggest that implementation of the ta did not alter the histological and immunohistochemical properties and could be a useful method for morphological analysis.
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