Papers by Jose Alberto Rincon
Resumen del trabajo presentado ante el congreso sobre macroinvertebrados acuáticos celebrado en J... more Resumen del trabajo presentado ante el congreso sobre macroinvertebrados acuáticos celebrado en Julio 2018 en Quito, Ecuador
Effects of insect and decapod exclusion and leaf litter species identity on breakdown rates in a ... more Effects of insect and decapod exclusion and leaf litter species identity on breakdown rates in a tropical headwater stream
Se ha desarrollado un modelo de dinamica de flujo computacional del primer reactor en fase liquid... more Se ha desarrollado un modelo de dinamica de flujo computacional del primer reactor en fase liquida en una planta de produccion de polipropileno con la finalidad de estudiar el arrastre de particulas de polimero desde el reactor hacia los equipos aguas abajo del mismo que han presentando problemas de ensuciamiento. Los resultados indican que la energia cinetica disponible permite el arrastre de particulas por debajo de 60 µm, correspondientes a las particulas de prepolimero. La calibracion del instrumento de nivel del reactor de polimerizacion, para garantizar la entrada de prepolimero en la fase liquida del reactor, ha disminuido apreciablemente el ensuciamiento de dichos equipos. A computational fluid dynamics model has been developed to study the entrainment of polymer particles from the first polymerization reactor in a polypropylene plant, to downstream equipment which have presented fouling issues. The results indicate that kinetic energy available enable entrainment of particl...
Fundamental and Applied Limnology, 2000
ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases dur... more ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases during the dry and rainy seasons in a neotropical intermittent stream in Northwestern Venezuela. Invertebrates and physicochemical parameters were sampled during 9 months to assess temporal changes in biotic and abiotic variables. Macroinvertebrate densities decreased following either a high-flow or a stream drought. Three invertebrate assemblages were identified via PCA and cluster analysis. PCA ordination showed a temporal sequence between the sampling dates. A low flow association occurred in August, a period of rewetting after the stream drought in late July. A high-flow association was established by sampling dates (September and November) with the highest flows registered during the study, and an intermediate-flow association occurred during the longer dry period after the rainy season. The low-flow group was dominated by the Philopotamidae (65 %). The intermediate-flow group showed a more even distribution of macroinvertebrate abundances. The high-flow group was dominated by Philopotamidae, Leptophlebiidae, Chironomidae and Baetidae. The lowest richness and highest density values were observed for the low-flow group. Average physicochemical parameters also were different between the PCA groups. A gradient of physicochemical parameters was observed from the 'low-flow' group to the 'high-flow' group. Temporal flow changes probably structure macroinvertebrate communities during extreme episodes of drought or spates, but during intermediate flow periods some biotic processes may determine community structure.
Revista de Biología Tropical, 2016
The ecological condition of tropical Andean rivers are threatened by many human activities includ... more The ecological condition of tropical Andean rivers are threatened by many human activities including changes in land use and cover in watersheds. Current protocols diagnose the structural condition of streams but not their function. In this study we proposed an assessment tool using the leaf-litter breakdown as a measure of the functional condition and health of high Andean streams in Southern Ecuador, including methodology and threshold values adapted to local conditions. We selected 15 streams in three micro-basins (Mazán, Llaviuco and Matadero) within or in the vicinity of Cajas National Park where we deployed litterbags for 15, 28 and 64 days. We used two types of mesh (coarse and fine) for the litterbags in order to separate the contribution of macro-invertebrates and microorganisms in the decomposition process and also tested two different leaf substrates: Alder (Alnus acuminata) and Miconia (Miconia bracteolata). In each collection period we determined physical and chemical p...
Bioagro, Apr 1, 2005
Rendimiento de una plantación comercial de cacao ante diferentes dosis de fertilización con npk e... more Rendimiento de una plantación comercial de cacao ante diferentes dosis de fertilización con npk en el sureste del estado Táchira, Venezuela
Documentos De Economia Energetica, 2012
El objeto del siguiente estudio es apoyar a la CREG en la determinacion de las inversiones y gast... more El objeto del siguiente estudio es apoyar a la CREG en la determinacion de las inversiones y gastos de AOM eficientes para desarrollar la actividad de generacion en las ZNI con tecnologias que utilicen recursos de Energia Renovable (ER).Para cumplir con los objetivos propuestos, el estudio debe:A. Recopilar informacion tecnica de las diferentes tecnologias de generacion electrica que utilizan recursos renovables, como minimo para las tecnologias de pequenas centrales hidroelectricas (PCH), eolica, biomasa y solar, comercializadas por fabricantes o proveedores en Colombia. El consultor debera recopilar, por lo menos, informacion sobre la vida util de los equipos y horas diarias efectivas de operacion para sistemas individuales y centralizados de corriente continua y corriente alterna.B. Recopilar informacion de costos de suministro e instalacion de proyectos recientes de generacion electrica con recursos renovables en el ambito nacional e internacional para tener bases de comparacion.C. Determinar costos de suministro e instalacion de proyectos de generacion electrica con recursos renovables en las ZNI de Colombia, como minimo para las tecnologias de PCH, eolica, biomasa y solar, discriminando costo de los equipos, obras civiles, obras mecanicas, construccion de vias de acceso, equipos auxiliares como tableros, medidores, transformadores elevadores, protecciones, sincronismos de varias unidades de generacion, casetas para los equipos, obras o equipos de mitigacion ambiental, costos financieros durante la construccion, pruebas de puesta en operacion, etc.
Revista Colombiana De Quimica, 1988
Se mtoto to reactivtoad al CO de coques en una balanza termogravimétrica construtoa para tal fin.... more Se mtoto to reactivtoad al CO de coques en una balanza termogravimétrica construtoa para tal fin. Se utilizaron coques provenientes de to cartxxilzación de cartXMíes sotos y co-cartxNiizados con txeas de cartxin y de petróleo como aditivos. La reactividad del coque proveniente de caitton ooqulzabto no ae vto afectada apradablemento por ninguno de toe aditivos utilizados. Para toa cartxxfies de t>ajo rango to adtoión de breaa fUe tMnéfIca. El efecto de las breas fue dHerante para cada caitión. Se muestra que existo una buena conelación de to reaclivWad de tos coques con: Cartxxx) fyo. porcentaje de carbono e fndtoe de atoaNntoad de las cenizas.
The present work has the purpose of determining the zones of highest growth rate of Lemna sp (duc... more The present work has the purpose of determining the zones of highest growth rate of Lemna sp (duckweed) in Lake Maracaibo using a hydrodynamic circulation model (MIKE 3), and a mathematical model to estimate the rate of growth of this aquatic plant. The proposed mathematical model is developed starting from a study on modeling duckweed growth as a function of nitrogen carried out by Landesman, affected additionally by phosphorus, salinity and temperature parameters. After fitting the mathematical model to lake conditions, it is introduced to the computational hydrodynamic model to simulate growth of duckweed from january to november, which comprises a dry and a rainy season, characteristic of the area. The results of the simulations are compared with images of the lake from the MODIS the satellite, showing similarities in the areas of higher growth of duckweed. Also an analysis month by month of the re-sults is carried out, finding differences among the dry and rainy seasons; with a...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
En este trabajo, se presentan los resultados obtenidos luego del desarrollo de un simulador de pr... more En este trabajo, se presentan los resultados obtenidos luego del desarrollo de un simulador de problemas de flujo de fluidos en régimen laminar, estado estable, usando el método de volúmenes finitos basado en elementos, para dominios bidimensionales, llamado MEFVOC. De la revisión de referencias se observa con reiteración el uso de problemas típicos que permiten comprobar el buen funcionamiento del programa de cálculo, en dominios discretizados de forma estructurada. Por lo tanto, el aporte de este trabajo consiste en implementar computacionalmente el método, con la capacidad de reproducir la misma solución, pero al emplear una malla no estructurada, lo que facilita la extensión hacia geometrías complejas. Por el hecho de que los resultados obtenidos son congruentes con trabajos de otros autores en el área, al usar programas semejantes, está claro que el programa resuelve exitosamente los problemas planteados bajo las condiciones descritas.<br>The results obtained in the development of the computational program "MEFVOC", to simulate laminar incompressible and steady flows, using Element based Finite Volume Methods on unstructured and bidimensional grids, is presented in this paper. There are references to problems for testing and evaluating numerical techniques related with this method, but it is not common to find results on unstructured grids like the ones reached in this work. The implementacion makes easier the extention to complex geometries. The problems resolved demonstrate concordance with other authors, using structured grid. In fact, it can be concluded that the computational program developed, succesfully resolves the problems proposed under the described conditions.
The aim of this study was to evaluate the glycogen content and determine the tissue condition ind... more The aim of this study was to evaluate the glycogen content and determine the tissue condition index (TCI) in samples of the estuarine clam Polymesoda solida collected from different areas in the Lake Maracaibo estuarine system, as an indicator of optimum habitat quality for establishing natural clam banks. Glycogen content was determined using the slightly modified procedure described by Naimo et al. (1998), and the tissue condition index was determined using the formula of Newton et al. (2001). A Pearson correlation analysis was performed to establish relationships between glycogen concentrations and tissue condition indexes (TCI), as was variance analysis to compare data between stations and samples. The results show no correlation between glycogen content and TCI. Average glycogen content was 117.77 mg/g of tissue, ranging between 23.81 and 428.02. The average TCI was 2.46, ranging between 1.54 and 3.69. The TCI indicates that on the average, clams have their maximum fattening pe...
We studied bacterial and fungal colonization during decomposition of leaf litter differing in che... more We studied bacterial and fungal colonization during decomposition of leaf litter differing in chemical composition in a small intermittent stream of northwestern Venezuela. Litter bags containing leaves of Tabebuia roseae, Ficus sp, Hura crepitans and Anacardium excelsum were incubated during 42 days in the stream. Six bags were retrieved after 2, 7, 14, 21, 28, 35 and 42 days and the mass loss was registered. Leaves were initially analyzed for N, P, Lignin and Polyphenols in order to assess the chemical composition of each species. Conidia of aquatic hyphomycetes were identified and quantified after in vitro incubation of leaves with filtered stream water. Bacteria were counted and identified using an epifluorescence microscope. The species H. crepitans and Ficus sp showed higher decomposition rates than T. roseae and A. excelsum. Higher conidia production was observed in Anacardium leaves, while bacterial density and biomass resulted higher in Hura leaves. Our results suggest that...
Freshwater Science, 2015
Many forested headwater streams are heterotrophic ecosystems in which allochthonous inputs of pla... more Many forested headwater streams are heterotrophic ecosystems in which allochthonous inputs of plant litter are a major source of energy. Leaves of riparian vegetation entering the stream are broken down by a combination of biotic and abiotic processes and, in most temperate and boreal streams, provide food and habitat for
Revista de Biología Tropical, 2014
High species richness of tropical riparian trees influences the diversity of organic detritus ent... more High species richness of tropical riparian trees influences the diversity of organic detritus entering streams, creating temporal variability in litter quantity and quality. We examined the influence of species of riparian plants and macroinvertebrate exclusion on leaf-litter breakdown in a headwater stream in the Luquillo Mountains of Puerto Rico. Leaf litter of Dacryodes excelsa (Burseraceae), Guarea guidonia (Meliaceae), Cecropia scheberiana (Moraceae), Manilkara bidentata (Sapotaceae), and Prestoea acuminata (Palmae) were incubated in litter bags in a pool of Quebrada Prieta. Fine mesh bags were used to exclude macroinvertebrates during leaf breakdown, and coarse mesh bags allowed access to decapod crustaceans (juvenile shrimps and crabs) and aquatic insects (mainly mayflies, chironomids, and caddisflies). D. excelsa and G. guidonia (in coarse-and fine-mesh bags) had significantly higher breakdown rates than C. scheberiana, M. bidentata, and P. acuminata. Breakdown rates were significantly faster in coarse-mesh bag treatments for all leaf types, thus indicating a positive contribution of macroinvertebrates in leaf litter breakdown in this headwater stream. After 42 days of incubation, densities of total invertebrates, mayflies and caddisflies, were higher in bags with D. excelsa and G. guidonia, and lower in P. acuminata, C. scheberiana y M. bidentata. Decay rates were positively correlated to insect densities. Our study highlights the importance of leaf identity and macroinvertebrate exclusion on the process of leaf litter breakdown in tropical headwater streams.
Latin American Journal of Aquatic Research, 2013
RESUMEN. Para aproximarse al rol que tiene el cangrejo de río Bottiella niceforei en el procesami... more RESUMEN. Para aproximarse al rol que tiene el cangrejo de río Bottiella niceforei en el procesamiento de materia orgánica, en una corriente intermitente al noroeste de Venezuela, se estudió su dieta natural, mediante el análisis del contenido del tracto digestivo entre junio 2009 y febrero 2010. Se determinó la abundancia de los cangrejos sobre la base de la proporción de individuos capturados por trampas, a lo largo del muestreo, y en cada pozo. Las mayores densidades ocurrieron en septiembre (2,7 ind trampa-1), seguido de junio (2,3 ind trampa-1) y julio (2,1 ind trampa-1), mientras que las menores se obtuvieron de noviembre a febrero, posiblemente debido al efecto erosivo de la corriente durante la época de lluvia. No se encontraron diferencias significativas en la abundancia y dieta entre pozos. De junio a noviembre, se encontró que el ítem más abundante en la dieta fue el detrito vegetal, con una frecuencia de ocurrencia promedio de 68%; en segundo lugar, materia animal (restos de peces) con 50% y detrito vegetal amorfo con 14%. Estos resultados demuestran la importancia de la participación del cangrejo B. niceforei en el procesamiento de la materia orgánica en forma de hojarasca en los pozos de caño Carichuano. Palabras clave: Bottiella niceforei, contenido estomacal, materia orgánica particulada gruesa, macroconsumidores, Venezuela. Diet of the freshwater crab Bottiella niceforei (Schmitt & Pretzmann, 1968) (Decapoda: Trichodactylidae) and its relationship with organic matter processing in an intermittent stream of northwestern Venezuela ABSTRACT. In order to study the role of the freshwater crab Bottiella niceforei in processing the organic matter in an intermittent stream of northwestern of Venezuela, we studied its natural diet by analyzing the gut contents during the period between June 2009 and February 2010. The abundance was determined based upon the proportion of individuals captured by traps throughout all the sampling period and on each pool. The highest crab densities occurred in September (2.7 ind trap-1), followed by June (2.3 ind trap-1) and July (2.1 ind trap-1); while the lowest were obtained in November and February, possibly due to the erosive effect of the current during the rainy season. No significant differences in the abundance and diet between pools were found. During the period from June to November it was found that the most abundant item in the crab diet was the plant detritus, with an average of 68%, followed by animal matter (fish remains), 50% on the average, and amorphous vegetal detritus with 14%. These results demonstrate the important participation of B. niceforei on the leaf litter processing in the pools of caño Carichuano.
Volume 1: Symposia, Parts A and B, 2006
A Liquid-Liquid Cylindrical Cyclone separator (LLCC) is a device used in the petroleum industry t... more A Liquid-Liquid Cylindrical Cyclone separator (LLCC) is a device used in the petroleum industry to separate the oil-water mixture obtained from the well. The use of this device has not been widespread due to the lack of tools for predicting its separation capability. This paper presents a numerical and experimental study of the fluid dynamic performance of this type of cylindrical cyclone separators. The use of numerical simulations would reduce the time and cost necessary to obtain information for predicting the behavior of the equipment. The objective of this study is to determine if CFD (Computational Fluid Dynamics) techniques are able to reproduce the behavior of a LLCC separator. The CFD software examined was ANSYS-CFX 5.6 TM and numerical simulations were carried out using the dispersed model with oil as the dispersed phase. The oil and water mixture entering the separator is divided due to centrifugal and buoyancy forces in an upper (oil rich) exit and a bottom (water rich) exit. The separation capability is determined as the maximum amount of water removed from the mixture with the minimum amount of oil content in the water rich exit. The experiments were conducted in a transparent LLCC separator that allows the visualization of the mixture and the measurement of the oil content. Experiments were conducted for three variables: mixture velocity and water content at the entrance, and the split ratio. The split ratio is defined as the bottom exit flow rate divided by the water flow rate at the entrance. The results showed that CFD tools are able to reproduce the oil content obtained from the experiments for all analyzed conditions. Additionally, the mixture distribution images from numerical and experimental data showed good agreement. This study confirms the capacity of CFD tools for the multiphase flow analysis of LLCC separators.
Solar Energy, 2001
The thermal performance of a solar passive cooling system (SPCS) under a hot and humid climate is... more The thermal performance of a solar passive cooling system (SPCS) under a hot and humid climate is experimentally and numerically evaluated. The experimental data were obtained from two full scale cells, with identical walls, but different roof configurations. One cell has a highly-insulated roof and the other has an SPCS incorporated consisting of a thermal mass (water), which is cooled by evaporation and long wave nocturnal radiation. The study was conducted taking into account the local climatic conditions of Maracaibo, a topical city located in Venezuela. The numerical evaluation was accomplished using the computational code 'EVITA' which is based on the finite volume approach with high order bounded treatment of the convective terms. A PISO-like solution algorithm is used to solve the transient form of the continuity, momentum and energy equations. It has been demonstrated experimentally and numerically that under a hot and humid climate, it is possible to keep the indoor temperature below the outdoor temperature, using a passive cooling technique of a roof pond. The numerical results obtained using the model have demonstrated that the computational code used is a suitable cost-efficient alternative for the thermal performance evaluation of SPCS.
Apunts. Medicina de l'Esport, 2006
CASO CLÍNICO Deportista de natación sincronizada de 15 años de edad, mujer, que entrena a un nive... more CASO CLÍNICO Deportista de natación sincronizada de 15 años de edad, mujer, que entrena a un nivel de alta especialización, con un volumen semanal de 25 h (preparación física y entrenamiento técnico específico), que consultó por la aparición de petequias en las extremidades inferiores. En la anamnesis no destacaban antecedentes patológicos de interés, solamente la toma de ibuprofeno 15 días antes (600 mg cada 8 h), por un cuadro digestivo etiquetado como de origen viral. En la exploración, presentaba buen estado general, estaba bien hidratada y afebril. Se observaron múltiples petequias localizadas en ambas extremidades inferiores (piernas, muslos y, con menor intensidad, glúteos), de color rojo, de un diámetro de entre 1 y 5 mm, no palpables e indoloras (fig. 1). El resto de la exploración física fue anodina. Entre los exámenes complementarios se llevó a cabo un analítica sanguínea, que evidenció: hematocrito, 38,1%, fosfatasa alcalina, 344 U/l-1 , creatinacinasa, 278 U/l-1 , inmunogloteulina (Ig) A, 378 mg/dl-1 , anticuerpos IgG antinucleares negativos, complemento C3, 98 mg/dl-1 , complemento C4, 11,8 mg/dl, pruebas de función renal, estudio de coagulación y resto de parámetros sanguíneos dentro de la normalidad. Sedimento de orina, 1 leucocito cada 2-3 campos. El cultivo de orina fue negativo. Sangre en heces, negativo. Ecografía abdominal, normal. El diagnóstico se orientó como una púrpura de Schönlein-Henoch, sin afección sistémica, y se indicó reposo deportivo y dieta blanda, con controles de su evolución. La evolución fue en brotes sucesivos, a los 10, 30 y 50 días tras el brote
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Papers by Jose Alberto Rincon