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Se desarrolló una metodología de secado para Pinus caribaea var. hondurensis, empleando horno de microondas doméstico (HMO), consistente de pulsos de radiación y períodos de enfriamiento, que consume 92% menos energía y 58% menos tiempo. Las propiedades físicas y mecánicas se midieron en condición seca al HMO, equilibrio higroscópico (EH) y secado...
There is a growing concern about the presence of pesticide residues in agricultural land because they constitute an environmental risk and a source of human exposure. In this work, the presence of these residues and the risk of exposure was determined in the micro-watershed of Los Zarzales, Rivas Dávila municipality, Mérida, Venezuela. Soil samples...
Se desarrolló una metodología para el aprovechamiento sostenible de los residuos de aserrín de Pinus caribaea var. honduresis proponiendo aplicaciones diferentes a bioenergía. Se elaboraron dos formulaciones de briquetas aglutinadas con almidón de maíz: 25/75 almidón/aserrín (lote A) y 36/64 almidón/aserrín (lote B). Los mejores resultados se obtuv...
El presente trabajo es un estudio experimental que forma parte del proceso de caracterización de la cámara de combustión del motor del cohete sonda ULA-1A, desarrollado por el Programa de Ciencias Espaciales de la Universidad de Los Andes, Mérida, Venezuela. El motor del ULA-1A utiliza granos de combustible sólido compuesto por nitrato de potasio (...
Resumen: El presente trabajo es un estudio experimental de la eficiencia de la combustión en un motor cohete de combustible sólido, perteneciente al programa de ciencias espaciales de la Universidad de Los Andes. El objetivo principal fue la evaluación de la combustión en este motor, el cual utiliza granos de combustible sólido compuesto, del tipo...
Given the toxic nature of pesticides and their usual application in agricultural crops grown for human consumption, the aim of this study was to determine the presence of pesticide residues in peel and pulp of potato (Solanum tuberosum L.), harvested at the Rivas Dávila Municipality of Mérida, Venezuela. For analysis, the SPE-HPLC-DAD method was us...
Due to the intensive use of pesticides in agriculture, the presence of residues of these substances in food products, as well as the human health risk that they involve, seem to be inevitable. The objective of the present study was to determine the presence of pesticide residues in strawberry (Fragraria x ananassa), cultured in the Municipality of...
In the late 40s, the "green revolution" was introduced in Latin America, which was an industrial farming model based on the application of synthetic chemicals; thereafter, it created a situation of dependence on these products, with the pesticides being the most relevant among them. The inappropriate and excessive use of pesticides in agriculture h...
The strong demand for agricultural production has led to an indiscriminate use of agrochemicals causing the decline in the quality of surface waters. In the agricultural community of Bailadores, Municipality of Rivas Davila, Mérida State, Venezuela, the rivers of Las Tapias, Las Playitas and Mocoties were monitored for the presence of pesticide res...
La fuerte demanda de producción agrícola conlleva al uso indiscriminado de agroquímicos causando el desmejoramiento de la calidad de las aguas superficiales. En la comunidad agrícola de Bailadores, municipio Rivas Dávila, Estado Mérida, Venezuela, fueron monitoreados los ríos Las Tapias, Las Playitas y Mocoties por la presencia de residuos de plagu...
The aim of this study was to determine the presence of pesticides in drinking water from six aqueducts in a region of intense agricultural activity in the state of Merida, Venezuela. The study was conducted for four continuous weeks, between May and June 2008. Pesticide residues were analyzed by solid phase extraction (SPE) and liquid chromatograph...
Photochemical analysis of secondary compounds in lichens from the Venezuelan Andean snow and glacier zones (4800-5000 m) was carried out in order to determine the absorbance capacity of UV radiation in the UVA, UVB and UVC ranges and to characterize the probable UV-protective function. Spectrotometric (UV-VIS, NIR, FTIR, MS, NMR) and chromatographi...
Abstract: The first scientific initiative from the Venezuelan universities to fully develop probe rockets comes from the Universidad de Los Andes by the support of the Chancellor's Commission Space Science Program. A team of multi-and interdisciplinary researchers was conformed in January 2006 in order to develop a solid propellant rocket having sc...
The effects of prenatal expossure to paraquat (PQ) were studied on postnatal development of mouse parietal cerebral cortex, in particular, the ontogenesis of amino acid synaptic transmission. Pregnant NMRI mice were separated into two groups: the experimental group received 5 doses of 10 mg PQ/kg body weight, between days of gestation (G)12 and G20...
Primary cultures of mouse parietal cortex, prepared between postnatal day 3 (P3) and P9, were studied using transmission electron microscopy and HPLC of excitatory (aspartate and glutamate) and inhibitory neurotransmitters (glycine, GABA and taurine) to determine their morphological and functional development. Relations between excitation and inhib...
In this paper, a detailed analysis of the UV-screening strategies of the fungus Fusarium alkanophyllum is offered using spectroscopic (UV-VIS, FTIR), chromatographic (TLC, HPLC) and physiological analysis methods. Fusarium alkanophyllum showed an optimum growth when exposed to UV radiation at 253.7 (inducing DNA and protein damages) or 354.5 nm (in...
The goal of this study was to analyze the effects of prenatal exposure to the pesticides paraquat (PQ) and mancozeb (MZ) on the development of synaptic transmission in mouse cerebellar cortex. Pregnant NMRI mice were treated with either saline, 10 mg/kg PQ, 30 mg/kg MZ or the combination of PQ + MZ, between gestational days 12 (E12) and E20. Variat...
There is evidence that space energy sources could give place to the appearance of phosphorylated nucleosides outside of Earth.
These compounds may have been delivered mainly by interplanetary dust particles due to the lower temperatures experienced during
atmospheric deceleration and impacts to the terrestrial surface. In this report, we communicat...
This study documents the variation in the amino acid neurotransmitter contents during mouse parietal cortex development, from embryonic day 13 (E13) until young adulthood, between postnatal day 21 (P21) and P30. Taurine, an inhibitory neurotransmitter and neuromodulator, is the most abundant neurotransmitter in the developing neocortex, whereas, at...
The possible occurrence on the surface of the early Earth, Mars and Venus of hydrocarbon environments mainly composed by acyclic alkane molecules ⩾n-C18 has been revised. These hydrocarbons could be accumulated from the contribution of endogenous Fischer–Tropsh-type reactions and post-impact recombination reactions, as well as from exogenous source...
The fungus termed Fusarium alkanophyllum Palacios-Prü & V. Marcano is able to grow in and degrade several saturated hydrocarbons in the presence of UV radiation at or , H2O2, and CO2, with little or no oxygen and with minimum water requirements showing several phenotypes and optimal growth. Further, this species is also able to produce important am...
The development of spinal cord interneurons and the formation of interneuronal synaptic connections has received little attention; the most comprehensively studied developing circuit has been the connection between motoneurons and the muscle they innervate. All motoneurons are cholinergic whereas spinal interneurons are mostly glutamatergic, glycin...
A mixture of six DL-amino acids in prebiotic proportions were immersed in heavy mineral oil, warmed up to 240°C and exposed to the action of spark discharges on a mixture of H2O and CO2 gases. Water soluble products were analyzed by Fourier transformed infrared spectroscopy (FTIR) showing yields of peptide-like compounds characterized by amidine li...
The growth of microorganisms under extreme environmental conditions such as exposure to UVC and UVB radiations, low or high temperatures, absence of oxygen, minimum water supply, and very low pH has been known for many years. This fact motivated the development of studies under in vitro conditions similar to those of the early Earth and extraterres...
It is generally agreed that the life have originated between 3500–3800 Myr ago (Orgel 1998). Before 3600 Myr, the oceans would probably have been repeatedly vaporized by large impacts, which could sterilize the planet eliminating small and large molecules and life itself (Maher & Stevenson 1988, Sleep et al. 1989, Zahnle & Sleep 1997, Lyons & Vasav...
The developmental changes in the levels of amino acid neurotransmitters were analyzed by high pressure liquid chromatography during mouse olfactory bulb neurogenesis, from embryonic day (E)13 until the young adult age, between postnatal days (P)30 and P40. During the embryonic period, high levels of glutamate, aspartate and GABA were observed, with...
There is evidence that, in the early Earth, a considerable diversity of hydrocarbons produced endogenously or delivered by meteorites, comets and IDPs, could be presents on its surface, in the atmosphere and hydrosphere (Kvenvolden et al. 1970, Deamer et al. 1989, Chyba & Sagan 1992, McCollom et al. 1999). The formation of such hydrocarbons may be...
The origin of life is hardly understandable in the adverse conditions of the early Earth (Maher & Stevenson 1988, Zahnle & Sleep 1997) unless the formation of different lengths of carbon compounds, as well as amino acids and primitive nucleobases aggregates, are conceived under the effect of a protective mechanism (Miller & Bada 1988, Bada et al. 1...
The variation in the levels of excitatory (glutamate and aspartate) and inhibitory (GABA, glycine and taurine) neurotransmitters during neurogenesis in mouse cerebellum, from embryonic day (E) 15 until the young adult stage, was analyzed by high-pressure liquid chromatography. Between E15 and E21, high contents of GABA, glutamate and aspartate were...
The fungus termed Fusarium alkanophilum Palacios-Prü & V. Marcano sp. nov. is able to grow in and degrade several saturated hydrocarbons in presence of UV-radiations, NH3, H2O2 and CO2, with little or no oxygen and minimum water requirements showing several phenotypes and optimal growth. Therefore, different simulation experiments were done to eval...
Mecanografiado Tesis (Magister Scientiae) -- Universidad de Los Andes, Facultad de Medicina, Postgrado en Ciencias Médicas Fundamentales , Mérida, 2004 Incluye bibliografía
