Entity

Time filter

Source Type

Caracas, Venezuela

Sanchez M.,Venezuelan Institute for Scientific Research | Diaz R.D.,Jose Maria Vargas University | Cordova T.,University of Florida | Gonzalez G.,Venezuelan Institute for Scientific Research | Ruette F.,Venezuelan Institute for Scientific Research
Microporous and Mesoporous Materials | Year: 2015

The interactions between zeolites and templates in MFI and MEL (MEL1 and MEL2) structures combined with different conformations of tetrapropylammonium (TPA) and tetrabutylammonium (TBA) templates were investigated using DFT type methods. Molecular dynamics (MD) simulations were carried out with a tight binding code with London dispersion (DFTB-LD) approach to investigate the conformational space of templates before zeolite formation. Conformational preferences are in agreement with experimental results observed in zeolite using TPA and TBA templates when the temperature of synthesis changes. Zeolite-templates interactions were calculated by using both DFT-D and DFTB-LD methods. Analysis of intrinsic zeolite-template interactions and energy changes in zeolites and templates may explain experimental findings. Template distortion energies were evaluated at channel interception distances and anion-cation electrostatic effects were also included to account for template aggregation. A model of cation and anion distribution for MFI zeolite is presented. © 2014 Elsevier Inc. All rights reserved. Source


The Sociedad Económica de Amigos del País (SEAP) was an outstanding association founded with the objective of joining intellectual efforts to improve Venezuelan social conditions promoting progress through profitable economical activities in any discipline, and to develop public education. SEAP was a non-governmental cooperative group that held activities in Caracas during a decade since 1829. Dr. J.M. Vargas, physician, professor and politician, was founder member of SEAP and did some projects in botanical, educational, economical and health subjects. Source


Gracia Z.R.Q.,Jose Maria Vargas University
Informe Medico | Year: 2010

Senesence of cells is associated to special chromosome structures called telomere which have a very important role in replication and stabilization of chromosomes during ceil division. Telomere size has been linked to pathological changes observed in cardiovascular diseases, obesity and cancer. Recently, the pioneer research discoverers of telomer function deserved the Nobel Prize of Medicine in 2009. There is a close relationship between telomere length, nutrition and the emergence of transgenic foods. This article reviews this conection and prompts some questions about the consequences in future time this kind of food may have on humans. Source


Rodriguez C.,Jose Maria Vargas University | Guevara B.,Central University of Venezuela | Lobo G.,Central University of Venezuela
Informe Medico | Year: 2010

There are several anticonvulsivant drugs available with diverse mechanism of action and molecular targets, such as ion channels, receptors, enzymes, uptake systems and transporters, all of which allowing therapeutical versatility for effectively control of most epileptic patients. However, a remarkable number of patients remain with intractable seizures or undesirable side effects of medication. Basic and clinical studies of antiepileptic molecules have recognized at least three basic mechanisms of action: 1 ) Voltage gated ion channels modulation, 2) Increase of inhibitory GABA mediated neurotransmission and 3) Attenuation of glutamate excitatory neurotransmition. All these mechanisms decrease neuronal excitability. Some currently employed anticonvulsants act through more than one mechanism, so explaning its wide clinical spectrum. Neverthless, there is a possibility that some other cellular or molecular targets, not considered in the formerly three described mechanisms, are activated by antiepileptic drugs. Source


Rodriguez C.,Jose Maria Vargas University | Guevara B.,Central University of Venezuela
Informe Medico | Year: 2010

There are two major mechanisms proposed for anticonvulsant drug resistance: 1) reduced sensibility to drugs by alteration of pharmacological targets and 2) an active drug remotion from epileptogenic tissue due an over-expression of a particular class of non specifical ATP pumps known as multidrug resistance proteins (MDRs). This last mechanism proposed have more acceptation as it can match the fact that drug resistance is irrespective drug chemical nature and its mechanism of action. Source

Discover hidden collaborations