oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 7 )

2018 ( 15 )

2017 ( 13 )

2016 ( 13 )

Custom range...

Search Results: 1 - 10 of 9251 matches for " Gilberto;Rojas "
All listed articles are free for downloading (OA Articles)
Page 1 /9251
Display every page Item
Apertura económica- seguridad alimentaria y economía campesina Free market, tood security and peasant economy
Herrera Rojas Gilberto
Agronomía Colombiana , 1996,
Abstract: Las importaciones agrícolas sin restricciones que vinieron con la apertura económica, especialmente las de maíz y fríjol que se hicieron durante el segundo semestre de 1995, afectaron fuerte y negativamente a los productores colombianos, sobretodo a los campesinos. En estudios de caso realizados en la provincia Guanentina de Santander, se comprobó que los campesinos sufrieron fuertes pérdidas en la cosecha de fríjol del segundo semestre del a o anterior. Los precios al productor se derrumbaron a casi el 60% de los precios históricos, por culpa de las importaciones indiscriminadas de fríjoles provenientes de Canadá, Ctrína, USA, Ecuador y Perú (sin contar el contrabando que llegó por las fronteras de Ecuador y Venezuela). Los productores colombianos están muy lejos de poder competir con los precios internacionales que oscilaron entre US$ 0,40 y US$ 0,60 el kilogramo, mientras los costos de producción estaban por encima de los US$ 0,80 el kilo. Esa cosecha arruinó a miles de campesinos en Santander, algunos de los cuales emigraron hacia las ciudades de la costa atlántica. Las importaciones de maíz, el a o pasado, casi se duplicaron y los precios que recibieron los productores nacionales cayeron en casi un tercio. En 1996, los precios reaccionaron por factores coyunturales de corto y mediano plazo en USA y en la China. La tendencia en los mercados mundiales es que los grandes productores quebrarán la producción de países como el nuestro que dependerán, cada vez más, de las importaciones. Colombia está muy lejos de poder competir con los rendimientos, costos de producción y precios de Canadá, USA y Argentina. El dilema es que ambos cultivos son parte crucial de la seguridad alimentaria del campesinado y del país. Agricultural importation whithout restriction which come with international free market,especially com and kidney beans, durig the second semester of 1995, affecting strongly and negatively the colombian growres, especially the peasants. Some studies made in Guanentine Santander's province, show that the small farmers lot significant in kidney beans harvest during the second semester, last year. Grower's prices decreased around 60% of the historie prices, because of kidney beans importation from Canada, China, USA, Ecuador and Perú (without considering ilegal importation from Ecuador and Venezuela). Colombian growers are too far the compete with international prices which were around US$ 0,40 - 0,60 per Kg. While the production cost was US$ 0,80 per Kg, These harvet impovered thousands of santandereans peasantraies, some of them migrated to the Atl
Present importance of coffe production in some coffe grower communities and indian comunities in the Sierra Nevada de Santa Marta Importancia actual de la caficultora en algunas comunidades campesinas e indígenas de la Sierra Nevada de Santa Marta
Herrera Rojas Gilberto
Agronomía Colombiana , 1993,
Abstract: Coffe production followed by coffe growers and indian groups in the Sierra Nevada de Santa Marta, shows several differences regarding economical rationalityandtechnology. Coffe plays avery important role inthe economy and life quality ofthegrowers and indians. Traditional technology is generalized and has slowed down the deterioration of the Sierra, although life quality is very low. La caficultura que practican los campesinos y los grupos indlgenas de la Sierra Nevada de Santa Marta, tiene notables diferencias, tanto en la racionalidad económica, como en la lógica con la cual son atendidos los cultivos. El café juega un papel predominante en el sostenimiento de la economla y en la calidad de la vida de campecinos e indlgenas. La tecnologla tradicional, cuyo uso es generalizado, ha demorado el deterioro de ese inmenso maciso, aunuqe la calidad de la vida es bastante baja.
Optimization of sustaining swimming speed of matrinx? Brycon amazonicus: performance and adaptive aspects
Arbeláez-Rojas, Gustavo;Moraes, Gilberto;
Scientia Agricola , 2010, DOI: 10.1590/S0103-90162010000300001
Abstract: deleterious changes in metabolism, growth performance and body composition may be observed if fish are constrained to swimming continuously or intermittently at over-speeds. this study evaluates effects of four water speeds on growth, body composition and hematologic profile of juvenile matrinx?, brycon amazonicus. fish (33.3 ± 0.9 g and 13.44 ± 0.1 cm) were held for 90 days in five water speeds (0.0 - control, 1.0, 1.5, 2.0 and 2.5 body lengths per second - blat swimming speeds ranging on 1.0 and 1.5 bl s?1, in fish growth was 20% higher. hemoglobin and red blood cells at 1.5 bl s?1 increased 24% and 18% respectively; hematocrit was 17% higher in all exercised fish; protein content of white muscle at 1.0 bl s?1 was 2% higher; lipid deposition in red muscle at 1.0 bl s?1 was 22% higher and water retention 3% lower. crude energy levels enhanced 10% in all exercised fish; liver water retention was 6% lower at 1.0 bl s?1; liver lipid composition was 29% higher than control and 34% higher than 1.5 bl s?1; liver crude energy increased at 1.0 bl s?1 as compared with control and 2.5 bl s?1. lipid deposition in ventral muscle was 9% higher at 2.0 bl s?1. although high lipid deposition of matrinx? has been achieved in moderate swimming speeds, lipids may be the main fuel source to maintain the metabolic demands of exercised matrinx?. the best water flow speed for optimized growth of matrinx? ranged on 1.0 and 1.5 bl s?1.
Sorne considerations about university extension Algunas reflexiones sobre extensión universitaria
Herrera Rojas Gilberto,Polanco Rodríguez Henry
Agronomía Colombiana , 1994,
Abstract: La palabra tiene una connotación histórica que, de entrada, restringe las posibilidades de interacción entre la Universidad y los diferentes sectores, conglomerados, regiones, localidades y comunidades. Dicho término, acu ado en el siglo pasado, cobra vigencia en los a os cuarentas, para referirse a la necesidad de llevar el conocimiento tecnológico, desarrollado en los centros de investigación norteamericanos, para el sector rural y llevaba implícito el deseo de modernizar la agricultura de diferentes regiones del mundo, calcando la propia experiencia norteamericana, que se había dado en un contexto histórico y socioeconómico específico También estaba implícita una posición ideológica cómoda de asumir que la modernización era equivalente a desarrollo rural o, por lo menos, que la modernización generaba, paralelamente y en forma automática, el desarrollo rural.
Los plaguicidas utilizados en los últimos Cuarenta y cinco a os en Colombia
Herrera Rojas Gilberto,Polanco Rodríguez Henry
Agronomía Colombiana , 1995,
Abstract: Resulta oportuno y necesario hacer aportes al balance de casi medio siglo de Implementación de la tecnología de la revolución verde en la agricultura colombiana, cuando está promediando la última década de este siglo y cuando se vislumbra nuevas propuestas tecnológicas para la agricultura y todos padecemos un deterioro acelerado y dramático de los recursos naturales. La intención de este artículo es contribuir a la evaluación y al análisis de la dinámica de los principales cultivos y por ende de la utilización de plaguicidas en nuestra agricultura, desde los a os cincuenta. Para realizar el análisis de la evolución de los cultivos comerciales y la consiguiente utilización de insumos agrícolas, entre los cuales se destacan los plaguicidas, es conveniente elaborar una rese a acorde en los cambios más importantes que se han presentado desde 1950 en la economía en general y, en el sector agrícola en particular. Tal reencuentro se ajusta en función de la disponibilidad de la información.
Coliforms and Helminth Eggs Removals by Coagulation-Flocculation Treatment Based on Natural Polymers  [PDF]
Evelyn Zamudio-Pérez, Neftalí Rojas-Valencia, Isaac Chairez, Luis Gilberto Torres
Journal of Water Resource and Protection (JWARP) , 2013, DOI: 10.4236/jwarp.2013.511108
Abstract:

Wastewater from a municipal wastewater treatment plant (Mexico) was treated by a coagulation-flocculation using natural gums. The residual water was characterized in terms of organic load, and biological contaminants, i.e. total Coliforms (TC), fecal Coliforms (FC) and helminth eggs (HE). The sample has values of 2.8 × 107 MPN/100 ml, 8.48 × 106 MPN/100 ml and 470 HE/L is regarded to TC, FC and HH, respectively. The HE identified in the wastewaters were Diphyllobothrium latum, Ascaris lumbricoides, Hymenolepis nana and Toxocara canis. From several gums, Hydroxypropyl triammonium chloride guar gum (HPTAC-guar) was selected as the most adequate coagulant-flocculant for the class of municipal wastewater (MWW). A diminution of 82% for TC, 94% for FC and 99% for HE was obtained. Besides, the reduction of chemical oxygen demand (COD) and turbidity removals were 46% and 39% respectively. The natural gum mixed with Ca(OH)2, obtained removals of 52% for TC, 100% for HE, 47% for COD and 30% for turbidity.

Intera??o do exercício de nata??o sustentada e da densidade de estocagem no desempenho e na composi??o corporal de juvenis de matrinx? Brycon amazonicus
Arbeláez-Rojas, Gustavo Alberto;Moraes, Gilberto;
Ciência Rural , 2009, DOI: 10.1590/S0103-84782009000100031
Abstract: the aim of the present study was to gauge the effect of stocking density associated to the sustained swimming on the performance and body composition of matrinx? (brycon amazonicus) juveniles. the fish were initially sized at 12.3±0.5cm length and 18.4g±0.1g weight. they were distributed randomly in two groups: the first was arranged into three densities of 88, 176 and 353 fish m-3 and conditioned to swim at 1.0bl sec-1 in circular tanks of 250l for 70 days; the second was arranged in the same fish densities but in static waters performing six treatments with three repetitions. performance and body compositions were estimated in white and red muscles for both groups. the results express the growth and muscle composition change in response to the exercise and fish density. the fish maintained in moderate swimming at 176 fish m-3 depicted the best performance (p<0.05), reflected as best growth, weight uniformity, conditioning factor, feed conversion and survival. otherwise, the sustained swimming enhanced the white muscle protein concentration and the red muscle lipid deposition in the same group of fish. yet, the results were opposite in high fish densities. therefore, the rearing of matrinx? juveniles under moderate sustained swimming and near to 176 fish m-3 is suggested, since the best responses of growth and performance, and beneficial body changes were observed. these responses resulted in better body conditioning allowing higher tolerance to high fish densities.
Effect of the number of options on the quality of est reading comprehension multiple-choice exams
Berríos,Gilberto; Rojas,Carlina; Cartaya,Noela; Casart,Yris;
Paradígma , 2005,
Abstract: this study aims at identifying how the quality of english for science and technology (est) reading comprehension multiple-choice tests is affected by reducing the number of options in each item from 4 to 3. the literature proposes that 3-option multiple-choice tests have a similar quality to that of 4-option ones, demanding less effort and being more efficient. items from 2 exams administered in 2001 at universidad simón bolívar were modified. the new forms were administered in 2002. from a sample of about 25% of the population, descriptive statistics were obtained: mean difficulty, mean discrimination, and reliability coefficient. results confirm the practicality of the 3-option format without affecting the quality of the test. we recommend the adoption of this format for the reading program in question. a subsequent decision will need to address either increasing number of items or decreasing administration time.
Efecto de jugos vegetales sobre la producción de Daphnia pulex (Cladocera: Daphnidae) en condiciones de laboratorio
Rojas,Margarita L.; Navarrete,Norma A.; Elías,Guillermo; Contreras,Gilberto;
Revista de Biología Tropical , 1999,
Abstract: we tested the enriching effect of radish leaf (raphanus sativus) and spinach leaf (spinacea oleracea) extracts when added separately to the fermented wheat bran (triticum aestivum) for producing daphnia pulex. the experiments were conducted in 20 l glass bottles containing 14 l of dechorinated tap water. the initial inoculation density was 200 organisms/bottle. the cultures were allowed to grow for 21 days; during this time the controls received only the fermented wheat bran (triticum aestivum), while the test containers received either extract of radish leaf (raphanus sativus) or that of spinach leaf (spinacea oleracea), in addition to ferment wheat bran (triticum aestivum). we also measured some physico-chemical variables of the medium during the experimental period. these are: water temperature, dissolved oxygen, ph, conductivity, alkalinity and total hardness. these variables remained more or less the same in all test bottles reflecting non-significant variations. after the test period, the net production of d. pulex in terms of numbers was: 1 722 organisms/bottle in the controls while that receiving radish leaf (raphanus sativus) extract with 7 997 organisms/bottle and that with spinach leaf (spinacea oleracea) extract with 8 921 organisms/bottle. test of analysis of variance showed significant differences among the cultures (fisher p< 0.005). this study showed that the enrichment of fermented wheat bran (triticum aestivum) with spinach (spinacea oleracea) extract was a better nourishing source of food for culturing daphnia pulex under laboratory conditions.
Efecto de jugos vegetales sobre la producción de Daphnia pulex (Cladocera: Daphnidae) en condiciones de laboratorio
Margarita L. Rojas,Norma A. Navarrete,Guillermo Elías,Gilberto Contreras
Revista de Biología Tropical , 1999,
Abstract: El objetivo fue probar el efecto enriquecedor del jugo de hojas de rábano (Raphanus sativus) y de espinaca (Spinacia oleracea), sobre un patrón de fermento de salvado de trigo (Triticum aestivum) en la producción de Daphnia pulex. Los experimentos se llevaron a cabo en botellas de vidrio de 20 l de capacidad, llenadas con agua del grifo desclorada a un volumen de 14 l. Los cultivos tuvieron una duración de 21 días, durante los cuales las botellas testigo tan solo recibieron fermento de salvado de trigo (Triticum aestivum) y las botellas experimentales (I, II y III), en el primer caso recibieron la combinación de fermento y el jugo de hojas de rábano (Raphanus sativus), y en el segundo caso el fermento y el jugo de espinaca (Spinacia oleracea). La tasa de siembra en ambos experimentos fue de 200 organismos/botella. Durante el desarrollo de los cultivos se evaluaron: temperatura del agua, oxígeno disuelto, pH, conductividad, alcalinidad y dureza total. Los parámetros ambientales se comportaron de manera similar en ambos experimentos, sin mostrar variaciones drásticas, ni grandes diferencias en sus registros. Las producciones netas obtenidas para la D. pulex fueron de: 1 722 organismos/botella en las testigo, 7 997 org/botella en las de rábano (Raphanus sativus), y de 8 921 org/botella en las de espinaca (Spinacia oleracea). De acuerdo con los datos de producción el análisis de varianza encontró diferencias significativas entre los cultivos (Fisher p< 0.005) y estableció que la combinación del fermento enriquecido con el jugo de espinaca (Spinacia oleracea) es la mejor alternativa alimenticia para la Daphnia pulex en condiciones de laboratorio. We tested the enriching effect of radish leaf (Raphanus sativus) and spinach leaf (Spinacea oleracea) extracts when added separately to the fermented wheat bran (Triticum aestivum) for producing Daphnia pulex. The experiments were conducted in 20 l glass bottles containing 14 l of dechorinated tap water. The initial inoculation density was 200 organisms/bottle. The cultures were allowed to grow for 21 days; during this time the controls received only the fermented wheat bran (Triticum aestivum), while the test containers received either extract of radish leaf (Raphanus sativus) or that of spinach leaf (Spinacea oleracea), in addition to ferment wheat bran (Triticum aestivum). We also measured some physico-chemical variables of the medium during the experimental period. These are: water temperature, dissolved oxygen, pH, conductivity, alkalinity and total hardness. These variables remained more or less the same in al
Page 1 /9251
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.