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Search Results: 1 - 10 of 462 matches for " Sanhueza "
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Potential emissions of Kyoto and Non-Kyoto climate active compounds in the production of sugarcane ethanol
Sanhueza,Eugenio;
Interciencia , 2009,
Abstract: sugarcane ethanol is the most commercially developed liquid biofuel. the potential emissions of kyoto and non-kyoto protocol climate active compounds in the production of sugarcane ethanol in agricultural lands are evaluated herein. various scenarios are considered, such as low or high n2o emission from n-fertilizers, inclusion or not of pre-harvest burning, uncontrolled or controlled emissions in bagasse based boilers, and 20 or 100 years time horizons in gwps. the co2 emitted in ethanol fuel combustion is recycled during sugarcane "re-growing" and does not count as greenhouse gas. however, even though many uncertainties remain, the available information allows estimating that co2-eq emissions are very large when ethanol production is based on pre-harvest burning and there is non-controlled particle emission in boilers. in these scenarios, compared with the combustion of equivalent amounts of gasoline, higher co2-eq emission would take place. halting sugarcane field burning would not be sufficient to revert the situation, especially in a 20-years time horizon. only when more environmental friendly procedures are applied, a significant saving of co2-eq emissions occurs at 20 and 100-years horizon scenarios. in all scenarios, non-kyoto protocol compounds make an important net contribution. therefore, if a real evaluation of climate active compounds emissions is to be reached, it would be crucial to include these compounds in life cycles studies. to reduce uncertainties, especially of non-kyoto compounds, additional research is needed.
Agroetanol ?un combustible ambientalmente amigable?
Sanhueza,Eugenio;
Interciencia , 2009,
Abstract: concerns about energetic security and climate change have driven the present boom of agrofuels. unfortunately, their development occurs before appropriate environmental impact studies have been made and a strong debate has been generated. the main arguments against agroethanol are reviewed herein. agrofuels have a positive net energy balance; for sugarcane ethanol it is ~8 while for corn ethanol it is <1.5; in theory, cellulosic ethanol may reach up to 36. co2 emitted by bioethanol combustion does not count as a greenhouse gas; however, during its production such gases are emitted. in the production of corn ethanol there is only a small saving of emissions. the reduction with sugarcane ethanol is very favorable when only gases included in the kyoto protocol are considered; however, when other climate active compounds are considered, co2-eq emission would surpass that produced by equivalent amounts of gasoline. agroethanol production promotes the transformation of natural soils, with loss of biodiversity and enormous co2 emissions. intensive mono-crops promote erosion, pollute waters and decrease productivity and stability of ecosystems. agrofuels compete for arable soils and are, in part, responsible for food price increases. the polemics about genetically engineering organisms will be exacerbated with the increased use of agrofuels. ethanol combustion in vehicles presents some disadvantages to gasoline, does not decrease cancer risk, increases photochemical smog in cities and increases methane emission. the eventual arrival of cellulosic ethanol could improve the situation. however, the present production potential could only replace a small percentage of liquid fossil fuels, maintaining oil dependence.
Methane soil-vegetation-atmosphere fluxes in tropical ecosystems
Sanhueza,Eugenio;
Interciencia , 2007,
Abstract: recently, a surprising discovery indicated that, by an unknown process, vegetation emits methane to the atmosphere. this finding could have serious implications in atmospheric chemistry, climate, and mitigation of global change. in order to evaluate the magnitude of the tropical vegetation source, a re-evaluation of results obtained at various venezuelan ecosystems is made. ch4 fluxes from the soil-grass system in savanna ecosystems indicate that grasses produce ch4 at ~10ng·m-2·s-1. furthermore, ch4 accumulation within the nocturnal mixing layer at the guri site, which is affected by savanna and forest emissions, was used to make a rough upper limit estimation of <70ng·m-2·s-1 for ch4 emission from forest vegetation. these estimates are likely to be somewhat low as they do not take into account the light-induced production of ch4 by the vegetation. global extrapolation of these fluxes indicates that, ignoring the possible stimulating effects of solar radiation, savanna and forest vegetation result in ch4 emissions of ~5tg·yr-1 and <22tg·yr-1, respectively. these estimates are in agreement with the lower estimates based on laboratory ch4 flux measurements, reported in the literature. on the other hand, the global extrapolation of the atmosphere-soil uptake fluxes results ch4 sinks of ~1.3tg·yr-1 in savannas and of 3.3tg·yr-1 in forests. in conclusion, venezuelan field measurements support the discovery that vegetation emits ch4. however, global extrapolation indicates that tropical vegetation would contribute modestly to global methane emission, which, additionally, is offset in part by savanna and forest ch4 soil uptake. most likely, carbon sequestration benefits from forestation should not be significantly affected by ch4 emissions by trees.
EL OBJETIVO DEL INSTITUTO PEDAGóGICO NO ES EL DE FORMAR GEóGRAFOS: HANS STEFFEN Y LA TRANSFERENCIA DEL SABER GEOGRáFICO ALEMáN A CHILE. 1893-1907
SANHUEZA,CARLOS;
Historia (Santiago) , 2012, DOI: 10.4067/S0717-71942012000100006
Abstract: this article discusses the educational praxis in hans steffen as a professor at the pedagogical institute of santiago between the late nineteenth and early twentieth centuries. in a sense this work defines the framework in which steffen conceived the discipline of geography, particularly in germany. this article looks to determine the main topics and discussions that allowed this subject matter to be transformed into an institutionalized scientific discipline. second, it analyzes the materials that steffen read on different topics and discussions in order to identify his influences. finally, we study how such topics and discussions were applied to their classes at the pedagogical institute, as to the plans and programs for the study of geography that steffen helped to write for the chilean educational system between 1893 and 1907.
Un saber geográfico en acción: Hans Steffen y el litigio patagónico 1892-1902
SANHUEZA,CARLOS;
Magallania (Punta Arenas) , 2012, DOI: 10.4067/S0718-22442012000100002
Abstract: this article examines the work of hans steffen as geographer of the government of chile between 1892 and 1902 in the litigation against argentina for the delimitation of patagonia. this conflict confronted two scientific criteria to address the political boundaries: the division of water, or "divortium aquarum" defended by chile and the notion of the highest peaks of the range, or "main chain", supported by argentina. here we analyze how steffen prepared the chilean position, from his explorations and studies, and for the court of arbitration in london, where both views were defended.
TAMA?O DE FAMILIA Y ORDEN DE NACIMIENTO EN CHILE: USANDO GEMELOS COMO EXPERIMENTO NATURAL
SANHUEZA,CLAUDIA;
Revista de análisis económico , 2009, DOI: 10.4067/S0718-88702009000200005
Abstract: this study estimates the causal effect of family size and birth order on educational attainment of individuals in the long run. following recent literature we use the presence of twins as an instrumental variable for family size and fixed effects model for birth order. the results suggest that in chile there is a negative relationship between family size and individuals' educational achievements. moreover, it shows a strong significant and positive effect of being a big brother. however, in larger families there is a nonlinear effect in which middle siblings are less favored.
Actinomicosis Toraco-pleuro-pulmonares
FERNANDO SANHUEZA
Revista chilena de pediatría , 1946,
Abstract:
Casos clínicos de tuberculomas encefálicos de evolución favorable
FERNANDO SANHUEZA
Revista chilena de pediatría , 1946,
Abstract:
Bases de la conducta y problemas siquiátricos en el ni o menor de 3 a os
FERNANDO SANHUEZA
Revista chilena de pediatría , 1960,
Abstract:
RAFAEL SAGREDO BAEZA y MIGUEL áNGEL PUIG-SAMPER MULERO, editores, Imágenes de la Comisión Científica del Pacífico en Chile
Carlos Sanhueza
Historia (Santiago) , 2008,
Abstract:
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