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Search Results: 1 - 10 of 211282 matches for " Eduardo G. Navarrete "
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Optimal Stochastic Pine Stands Harvest Rotation Policies  [PDF]
Eduardo Navarrete
Open Journal of Forestry (OJF) , 2015, DOI: 10.4236/ojf.2015.56053
Abstract: A new Faustmann optimal rotation harvesting stands’ problem under Brown geometric price and Logistic and Gompertz wood stock, diffusions is presented. The optimal cut policies for the stochastic Faustmann model and the single harvest rotation or Vicksell model are evaluated in the case of a Chilean Radiata pine forest company. The company cut policy validates the Vicksell model, its optimal cut policies overestimate the company policy cut in 1.2%, in the Gompertz case, and underestimate it in 2.3%, in the Logistic case. The Faustmann optimal cut policies present a larger underestimation of the company cut policy in 10.1%, in the Gompertz case, and in 21.5%, in the Logistic case. The preference for shorter evaluation period that the company shows is due to the organizational risk that the forest economic sectors has in Chile.
Enfermedad de Creutzfeldt-Jakob: Reporte de dos casos.
Carla Brevis C.,Catherine Navarrete G.,Eduardo López A.
Revista ANACEM , 2011,
Abstract: INTRODUCCIóN: La enfermedad de Creutzfeldt-Jakob (ECJ) es una enfermedad priónica neurodegenerativa que afecta el Sistema Nervioso Central (SNC), invariablemente mortal. Clasificada en esporádica, familiar e iatrogénica, se manifiesta por cuadro demencial subagudo, síntomas motores, visuales, y mioclonías. Presenta electroencefalograma (EEG) con actividad espicular pseudoperiódica; resonancia agnética (RM) con hiperintesidad de núcleos estriados y áreas de corteza cerebral; y líquido céfalo raquídeo (LCR) con aumento de proteína 14-3-3. Finalmente, un estudio histopatológico del cerebro establece la encefalopatía espongiforme. PRESENTACIóN DEL CASO: Se exponen dos casos de ECJ. Ambas mujeres, 44 y 67 a os, con alteración de la marcha, deterioro cognitivo y mioclonías, cuadro rápidamente progresivo hasta la dependencia absoluta. EEG en ambos casos compatible con ECJ, además de imágenes que revelan hiperintensidad en núcleos estriados y/o zonas de la corteza. Ambas cursaron con infecciones durante su hospitalización y se les realizó gastrostomía por presentar trastorno deglutorio severo. DISCUSIóN: El diagnóstico de ECJ se sospecha con la clínica, y se fundamenta con hallazgos característicos en RM, EEG y análisis de LCR. Ante la sospecha de la forma familiar se sugiere estudio genético, sin embargo, en el Hospital Clínico Herminda Martin (HCHM) no se realiza. Al ser una enfermedad invariablemente mortal y sin tratamiento, dificulta la decisión entre realización de estudios e intervenciones, contra el manejo expectante.
Extrahippocampal Desynchronization in Nonlesional Temporal Lobe Epilepsy
Jesús Pastor,Eduardo G. Navarrete,Rafael G. Sola,Guillermo J. Ortega
Epilepsy Research and Treatment , 2012, DOI: 10.1155/2012/823683
Abstract: Although temporal lobe epilepsy (TLE) is traditionally associated with both hypersynchronous activity in the form of interictal epileptic discharges and hippocampal sclerosis, recent findings suggest that desynchronization also plays a central role in the dynamics of this pathology. The objective of this work is to show the imbalance existing between mesial activities in patients suffering from mesial TLE, with normal mesial structures. Foramen ovale recordings from six patients with mesial TLE and one with lateral TLE were analyzed through a cluster analysis and synchronization matrices. None of the patients present findings in the MRI presurgical evaluation. Numerical analysis was carried out in three different situations: awake and sleep interictal and also during the preictal stage. High levels of desynchronization ipsilateral to the epileptic side were present in mesial TLE patients. Low levels of desynchronization were present in the lateral TLE patient during the interictal stage and almost zero in the preictal stage. Implications of these findings in relation with seizure spreading are discussed. 1. Introduction Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy, where the epileptogenic area is located at some part of the temporal lobe. Mesial TLE (MTLE) refers to those cases where the suspected source of epileptogenic activity is located in the mesial area of the temporal lobe [1], and lateral TLE (LTLE), instead, where the focus is located in the lateral side. MTLE is often associated with structural lesions and/or functional deficiency in one or several (dual pathology) mesial structures of the temporal lobe, with hippocampal sclerosis (HS) as the most common underlying abnormality [2]. However, pathological findings of damage in the amygdala and parahippocampal region, which in turn is subdivided into the entorhinal cortex (EC), perirhinal cortex (PC), and parahippocampal cortex (PPC), are also reported [3, 4]. A significant minority of MTLE patients have no pathological findings on magnetic resonance imaging (MRI), even though lateralization may be correctly performed by neurophysiological methods [5, 6]. Normal underlying mesial structures play a key role in our understanding of the pathogenesis of MTLE, as they oblige us to ask whether mesial sclerosis (MS) is either the cause or the effect in MTLE [7]. Pathophysiology in MTLE can be explained according to two models: (1) the “focal” model suggests that a single pathological region in the mesial temporal lobe is responsible for seizure origin, establishing a link
The naming of gender-marked pronouns supports interactivity in models of lexical access
Eduardo Navarrete,Albert Costa
Psicológica , 2009,
Abstract: When a speaker names an object using a gender-marked pronominal form, the referent word corresponding to the target object has to be selected in order to access the grammatical gender. By contrast, the phonological content of the referent word is not needed. In two picture-naming interference experiments we explored whether the lexical selection of a referent word is affected by its phonological properties. In Experiment 1, Spanish participants named pictures using a sentence with a noun or a pronoun while ignoring words semantically or phonologically related. The results showed a semantic interference effect and a Phonological Facilitation Effect (PFE) in both type of utterances. In Experiment 2 the PFE was replicated with Italian participants in a different pronominal utterance. The PFE suggests that the lexical selection of the referent word is facilitated by the presentation of a distractor word phonologically related. These findings are consistent with the predictions of interactive models of lexical access.
Astrocytes Mediate In Vivo Cholinergic-Induced Synaptic Plasticity
Marta Navarrete,Gertrudis Perea,David Fernandez de Sevilla,Marta Gómez-Gonzalo,Angel Nú?ez,Eduardo D. Martín,Alfonso Araque
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001259
Abstract: Long-term potentiation (LTP) of synaptic transmission represents the cellular basis of learning and memory. Astrocytes have been shown to regulate synaptic transmission and plasticity. However, their involvement in specific physiological processes that induce LTP in vivo remains unknown. Here we show that in vivo cholinergic activity evoked by sensory stimulation or electrical stimulation of the septal nucleus increases Ca2+ in hippocampal astrocytes and induces LTP of CA3-CA1 synapses, which requires cholinergic muscarinic (mAChR) and metabotropic glutamate receptor (mGluR) activation. Stimulation of cholinergic pathways in hippocampal slices evokes astrocyte Ca2+ elevations, postsynaptic depolarizations of CA1 pyramidal neurons, and LTP of transmitter release at single CA3-CA1 synapses. Like in vivo, these effects are mediated by mAChRs, and this cholinergic-induced LTP (c-LTP) also involves mGluR activation. Astrocyte Ca2+ elevations and LTP are absent in IP3R2 knock-out mice. Downregulating astrocyte Ca2+ signal by loading astrocytes with BAPTA or GDPβS also prevents LTP, which is restored by simultaneous astrocyte Ca2+ uncaging and postsynaptic depolarization. Therefore, cholinergic-induced LTP requires astrocyte Ca2+ elevations, which stimulate astrocyte glutamate release that activates mGluRs. The cholinergic-induced LTP results from the temporal coincidence of the postsynaptic activity and the astrocyte Ca2+ signal simultaneously evoked by cholinergic activity. Therefore, the astrocyte Ca2+ signal is necessary for cholinergic-induced synaptic plasticity, indicating that astrocytes are directly involved in brain storage information.
Astrocytes Mediate In Vivo Cholinergic-Induced Synaptic Plasticity
Marta Navarrete equal contributor,Gertrudis Perea equal contributor,David Fernandez de Sevilla,Marta Gómez-Gonzalo,Angel Nú?ez,Eduardo D. Martín ,Alfonso Araque
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001259
Abstract: Long-term potentiation (LTP) of synaptic transmission represents the cellular basis of learning and memory. Astrocytes have been shown to regulate synaptic transmission and plasticity. However, their involvement in specific physiological processes that induce LTP in vivo remains unknown. Here we show that in vivo cholinergic activity evoked by sensory stimulation or electrical stimulation of the septal nucleus increases Ca2+ in hippocampal astrocytes and induces LTP of CA3-CA1 synapses, which requires cholinergic muscarinic (mAChR) and metabotropic glutamate receptor (mGluR) activation. Stimulation of cholinergic pathways in hippocampal slices evokes astrocyte Ca2+ elevations, postsynaptic depolarizations of CA1 pyramidal neurons, and LTP of transmitter release at single CA3-CA1 synapses. Like in vivo, these effects are mediated by mAChRs, and this cholinergic-induced LTP (c-LTP) also involves mGluR activation. Astrocyte Ca2+ elevations and LTP are absent in IP3R2 knock-out mice. Downregulating astrocyte Ca2+ signal by loading astrocytes with BAPTA or GDPβS also prevents LTP, which is restored by simultaneous astrocyte Ca2+ uncaging and postsynaptic depolarization. Therefore, cholinergic-induced LTP requires astrocyte Ca2+ elevations, which stimulate astrocyte glutamate release that activates mGluRs. The cholinergic-induced LTP results from the temporal coincidence of the postsynaptic activity and the astrocyte Ca2+ signal simultaneously evoked by cholinergic activity. Therefore, the astrocyte Ca2+ signal is necessary for cholinergic-induced synaptic plasticity, indicating that astrocytes are directly involved in brain storage information.
Prof. Manuel Fernández Tribute to Prof. Manuel Fernández
CLAUDIO NAVARRETE G
Revista Chilena de Cirugía , 2011,
Abstract:
Becas, inclusión social y equidad en el posgrado. Una aproximación desde el Programa Internacional de Becas para Indígenas
David Navarrete G.
Perfiles educativos , 2011,
Abstract: El presente artículo presenta una aproximación a los objetivos, estructura y resultados del Programa Internacional de Becas para Indígenas de la Fundación Ford (PIBI) en México a diez a os del inicio de sus operaciones. Plantea la necesidad de considerar el otorgamiento de becas como un mecanismo relevante para impulsar la inclusión social y la equidad en el sistema educativo universitario y de posgrado. Se expone el dise o y mecanismos de atención del PIBI orientados a asegurar el ingreso, permanencia y egreso de estudiantes indígenas que han cursado estudios de posgrado con apoyo del programa. En la parte final se analiza la composición del conjunto de candidatos a la beca, postulando que representan una muestra del más amplio universo de profesionistas indígenas que actualmente demanda este tipo de apoyos financieros y educativos.
Epístolas y cuentas de la negociación minera de Vetagrande, Zacatecas, 1791-1794, 1806-1809
David Navarrete G.
América Latina en la historia económica , 2011,
Abstract:
Stomatal frequency and gas exchange differs in two Blechnum species (Pteridophyta, Blechnaceae) with contrasting ecological breadth La frecuencia estomática e intercambio de gases difieren en dos especies de Blechnum (Pteridophyta, Blechnaceae) con distinto rango ecológico
Cristian Atala,Alfredo Salda?a,Eduardo Navarrete
Gayana. Botanica , 2012,
Abstract: In Chilean temperate forest, the fern Blechnum chilense has a wide ecological breath, but occur mainly in full sun habitats, while Blechnum mochaenum is restricted only to shady sites. We evaluated if the species with different ecological breath behave similarly in their anatomical and physiological traits. Maximal photosynthetic rate (Amax), Stomatal conductance (g s), evapotranspiration (E), and SLA (specific leaf area) were measured in situ in 20 individuals of each fern species. Additionally, we estimated the stomatal density (SD), stomatal index (SI), and stomatal size in leaves of each sampled individual. B. mochaenum, the shade-tolerant species, had lower SD, SI, A, and E, and higher stomatal size and SLA than B. chilense. Higher stomatal frequency could result in greater gas exchange in open sites for B. chilense. The leaf physiology of these fern species seems to depend partially on their stomatal traits. En el bosque templado de Chile, el helecho Blechnum chilense se encuentra principalmente en lugares abiertos y soleados, mientras que el helecho Blechnum mochaenum está restringido a lugares sombríos. En este estudio se evalúa si ambas especies de Blechnum, de lugares abiertos y sombreados, se comportan de manera similar respecto de sus rasgos anatómicos y fisiológicos, y si existe diferencia en la correlación entre estos rasgos. Se midió la tasa fotosintética máxima (Amax), conductancia estomática (g s), evapotranspiración (E) y SLA (área foliar específica) in situ en 20 individuos de cada especie de helecho. Adicionalmente, se estimó la densidad estomática (SD), el índice estomático (SI) y el tama o de los estomas en hojas de cada individuo muestreado. Blechnum mochaenum, la especies sombra-tolerante, presentó menor SD, SI, Amax y E, y mayor tama o de estomas y SLA que B. chilense. Una frecuencia estomática mayor podría resultar en una mayor tasa de intercambio de gases en los sitios abiertos para B. chilense. La fisiología de las hojas de estas especies de helechos parece depender, en parte, de las características estomáticas.
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