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Search Results: 1 - 10 of 88666 matches for " JUAN CARLOS GARCIA BUITRAGO "
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Breve Compilación Metodológica para la Implementación de Controladores PID Análogos
Scientia Et Technica , 2009,
Abstract: Este articulo permite al lector apreciar una metodología sobre el como dise ar el control de posición de un servomecanismo de corriente directa (CD) y construirlo empleando amplificadores operacionales y elementos electrónicos de fácil manejo y bajo costo. El desarrollo de este articulo, esta pensado para lectores que tienen conocimientos mínimos en electrónica pero tienen conocimientos básicos de Control Automático. El controlador PID que se construirá al final del articulo es aplicable a cualquier proceso de una entrada / una salida, cuya se al de salida esté en el rango de 0 a 5 voltios de CD y la se al de entrada al proceso pueda ser una se al de 12 a +12 voltios de CD, 4 amperios
Dr. Héctor Peón Vidales
Juan Carlos Garcia Osornio
Coluna/Columna , 2010, DOI: 10.1590/s1808-18512010000100017
Emiss?o de gases de efeito estufa no ciclo de vida do etanol: estimativa nas fases de agricultura e industrializa??o em Minas Gerais
Claros Garcia, Juan Carlos;Von Sperling, Eduardo;
Engenharia Sanitaria e Ambiental , 2010, DOI: 10.1590/S1413-41522010000300003
Abstract: this research presents an estimate of greenhouse gas emissions (co2, ch4 e n2o) in the stages of agriculture and sugarcane industrialization for the production of ethanol in mills located in the state of minas gerais, brazil. life cycle assessment principles were considered in the quantification of emissions. the use of fuels, agricultural inputs, n2o emissions on soil, sugarcane burning emissions and use of chemical products of 11 mills were considered in this study. the results show a total emission of 1,539.60 kg co2eq/ha·year, considering as the main key sources: sugarcane burning and use of fuels, which account for more than 50% of the total emissions.
Gravitational Equilibrium in the Presence of a Positive Cosmological Constant
Marek Nowakowski,Juan Carlos Sanabria,Alejandro Garcia
Physics , 2001, DOI: 10.1103/PhysRevD.66.023003
Abstract: We reconsider the virial theorem in the presence of a positive cosmological constant Lambda. Assuming steady state, we derive an inequality of the form rho >= A (Lambda / 4 pi GN) for the mean density rho of the astrophysical object. With a minimum at Asphere = 2, its value can increase by several orders of magnitude as the shape of the object deviates from a spherically symmetric one. This, among others, indicates that flattened matter distributions like e.g. clusters or superclusters, with low density, cannot be in gravitational equilibrium.
Albumin-Associated Lipids Regulate Human Embryonic Stem Cell Self-Renewal
Francesc R. Garcia-Gonzalo, Juan Carlos Izpisúa Belmonte
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0001384
Abstract: Background Although human embryonic stem cells (hESCs) hold great promise as a source of differentiated cells to treat several human diseases, many obstacles still need to be surmounted before this can become a reality. First among these, a robust chemically-defined system to expand hESCs in culture is still unavailable despite recent advances in the understanding of factors controlling hESC self-renewal. Methodology/Principal Findings In this study, we attempted to find new molecules that stimulate long term hESC self-renewal. In order to do this, we started from the observation that a commercially available serum replacement product has a strong positive effect on the expansion of undifferentiated hESCs when added to a previously reported chemically-defined medium. Subsequent experiments demonstrated that the active ingredient within the serum replacement is lipid-rich albumin. Furthermore, we show that this activity is trypsin-resistant, strongly suggesting that lipids and not albumin are responsible for the effect. Consistent with this, lipid-poor albumin shows no detectable activity. Finally, we identified the major lipids bound to the lipid-rich albumin and tested several lipid candidates for the effect. Conclusions/Significance Our discovery of the role played by albumin-associated lipids in stimulating hESC self-renewal constitutes a significant advance in the knowledge of how hESC pluripotency is maintained by extracellular factors and has important applications in the development of increasingly chemically defined hESC culture systems.
Coloniza??o e les?o em fêmeas ingurgitadas do carrapato Rhipicephalus sanguineus causadas pelo fungo Metarhizium anisopliae
Garcia, Marcos Valerio;Monteiro, Antonio Carlos;Szabó, Matias Pablo Juan;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000500029
Abstract: the objective of this work was to verify the penetration of the fungus metarhizium anisopliae [metsch. (sorokin, 1883)], in to the rhipicephalus sanguineus ticks (latreille, 1806), as well as the lesions caused in the tissues of the acarus. the form of adherence and penetration of the fungus in the deep tissue was studied through scanning microscopy and the fungus action on the internal tissues was evaluated in conventional hystological sections. in order to evaluate these events, experimental infestations were conducted in 11 engorged females groups of the tick r. sanguineus, containing 12 engorged females in each. aiming this goal the engorged females were submited to a bath in a conidial suspension in a concentration of 108 conidia/ml during three minutes under manual agitation. in case of control groups the bath was done only in the suspension vehicle. ticks were processed for histological and scanning microscopy surveys at different intervals after the infection: 1 and 18h and one, two, three, four, five, six, seven, eight, nine and eleven days. it has been observed that the major part of the conidians have germinated within 18h after the inoculation and that the fungus the penetrated the acarus body, trough it′s tegument 48h after the infection. after the penetration the fungus colonized the tick?s body in a diffuse manner, without any preference for a specific tissue. among the lesions caused by the fungus, rupture of the tick?s intestinal wall and the dispersion of the fluid into the hemocel were the most outstanding features. death of the host occurred 96h pos-infection and the sporulation of the pathogen over the dead acarus began 120 to 144h pos-infection. this work aims to contribute to the establishement of techniques for biological control of the ticks by fungus as an ecological alternative for acaricides.
The lizard cerebral cortex as a model to study neuronal regeneration
Anais da Academia Brasileira de Ciências , 2002,
Abstract: The medial cerebral cortex of lizards, an area homologous to the hippocampal fascia dentata, shows delayed postnatal neurogenesis, i.e., cells in the medial cortex ependyma proliferate and give rise to immature neurons, which migrate to the cell layer. There, recruited neurons differentiate and give rise to zinc containing axons directed to the rest of cortical areas, thus resulting in a continuous growth of the medial cortex and its zinc-enriched axonal projection. This happens along the lizard life span, even in adult lizards, thus allowing one of their most important characteristics: neuronal regeneration. Experiments in our laboratory have shown that chemical lesion of the medial cortex (affecting up to 95% of its neurons) results in a cascade of events: first, massive neuronal death and axonal-dendritic retraction and, secondly, triggered ependymal-neuroblast proliferation and subsequent neo-histogenesis and regeneration of an almost new medial cortex, indistinguishable from a normal undamaged one. This is the only case to our knowledge of the regeneration of an amniote central nervous centre by new neuron production and neo-histogenesis. Thus the lizard cerebral cortex is a good model to study neuronal regeneration and the complex factors that regulate its neurogenetic, migratory and neo-synaptogenetic events.
Coloniza o e les o em fêmeas ingurgitadas do carrapato Rhipicephalus sanguineus causadas pelo fungo Metarhizium anisopliae
Garcia Marcos Valerio,Monteiro Antonio Carlos,Szabó Matias Pablo Juan
Ciência Rural , 2004,
Abstract: O presente trabalho teve como objetivo verificar a forma de penetra o do fungo Metarhizium anisopliae [METSCH. (SOROKIN, 1883)] em carrapatos da espécie Rhipicephalus sanguineus (LATREILLE, 1806), assim como as les es infringidas nos tecidos internos do ácaro. A forma de aderência e penetra o do fungo foi estudada através da microscopia eletr nica de varredura e a a o do fungo nos tecidos internos avaliada em sec es histológicas convencionais. Para observa o destes eventos, realizaram-se infec es experimentais em 11 grupos de fêmeas ingurgitadas do carrapato R. sanguineus contendo 12 fêmeas ingurgitadas cada. Para tal, as fêmeas ingurgitadas foram banhadas durante 3 minutos, sob agita o manual, em suspens o com concentra o 108 conídios/mL. No caso dos grupos controle o banho foi realizado apenas no veículo da suspens o. Os carrapatos foram processados para histopatologia e microscopia eletr nica em diversos tempos após a infec o, a saber: 1 e 18h, e um, dois, três, quatro, cinco, seis, sete, nove e onze dias. Observou-se que a maior parte dos conídios germinou em até 18h após a inocula o e que o fungo penetrou no ácaro através do tegumento 48h após a infec o. Após a penetra o, o fungo invadiu o corpo do hospedeiro promovendo uma coloniza o difusa, sem preferência aparente por tecidos específicos. Dentre as les es nos tecidos internos do ácaro, ressalta-se o rompimento da parede intestinal e vazamento do conteúdo para a hemocele. A morte do hospedeiro ocorreu entre 96 e 120h pós-infec o, e a esporula o do patógeno sobre o cadáver do ácaro iniciou-se em torno de 120 a 144h pós-infec o. Espera-se, com este trabalho, contribuir para o desenvolvimento e viabiliza o de técnicas de controle biológico dos carrapatos por fungos como alternativa ao uso de acaricidas.
Juan Carlos Juez N.,Gustavo Adolfo Garcia Lozada
CIMEL. Ciencia e Investigación Médica Estudiantil Latinoamericana , 2011,
Abstract: La disección coronaria (DC) es la division de las capas que conforman la arteria coronaria, tiene una incidencia de 0.07% a 1.1% en cateterismo cardíaco, siendo más frecuente en mujeres post parto. Las causas de DC se dividen en ateroescleróticas y no ateroescleróticas, existiendo relación del tabaco con la ateroesclerosis. Este caso presenta a un hombre de 43 a os, con tabaquismo pesado, en el contexto de un infarto agudo del miocardio secundario DC, por lo cual se hace una revisión del da o endotelial que produce el tabaquismo y la fisiopatología de la disección coronaria. La importancia de este reporte radica en la poca información que existe acerca de los factores de riesgo de este tipo de enfermedad y la presentación clínica inusual del caso.
Bosonic CNOT gates with Quantum Interrogation
Juan Carlos Garcia-Escartin,Pedro Chamorro-Posada
Physics , 2008, DOI: 10.1063/1.3131358
Abstract: We put forward a new CNOT gate scheme with atoms and ions based on quantum interrogation and a bosonic particle extension of the models of linear optics quantum computation. We show how the possibility of particle collision can provide the strong interaction that is needed for universal quantum gates. Two atom optics proposals are provided. Unlike previous schemes, these gates are at the same time nondestructive, valid for arbitrary inputs and can work with a probability as close to unity as desired in the lossless case. Data is encoded into position modes and the gates only require basic atom optics elements, which gives potentially simpler quantum computer implementations.
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