yolanda perez - Academia.edu (original) (raw)

Papers by yolanda perez

Research paper thumbnail of Reversible dehydration-hydration process in lead-free hybrid perovskites

Proceedings of the nanoGe Fall Meeting 2021, 2021

Research paper thumbnail of Two sensitive and rapid chromogenic assays of fondaparinux sodium (Arixtra) in human plasma and other biological matrices

Clinical laboratory, 2003

Fondaparinux is a synthetic selective inhibitor of factor Xa recently approved for thromboprophyl... more Fondaparinux is a synthetic selective inhibitor of factor Xa recently approved for thromboprophylaxis after major orthopedic surgery. Determination of its concentration gives valuable insight into specific pharmacokinetics or safety studies. The aim of the study was to develop direct, sensitive, precise and accurate assays of fondaparinux sodium in different biological matrices. Consistency with the recommended chromogenic assay for low molecular weight heparin required a similar method. However, recent data indicated some variability in the determination of anti-Xa level between commercial chromogenic assays. Consequently, we developed and validated two chromogenic methods (A and B) for assaying fondaparinux in plasma and other biological matrices. The assays are calibrated with fondaparinux, a pure chemical entity, and the result is expressed as amount (microg) of the fondaparinux calibrator. Results showed that precision was lower than 5.2% in plasma or plasma water and 13% in pl...

Research paper thumbnail of Lipid binding by the Unique and SH3 domains of c-Src suggests a new regulatory mechanism

Scientific Reports, 2013

c-Src is a non-receptor tyrosine kinase involved in numerous signal transduction pathways. The ki... more c-Src is a non-receptor tyrosine kinase involved in numerous signal transduction pathways. The kinase, SH3 and SH2 domains of c-Src are attached to the membrane-anchoring SH4 domain through the flexible Unique domain. Here we show intra-and intermolecular interactions involving the Unique and SH3 domains suggesting the presence of a previously unrecognized additional regulation layer in c-Src. We have characterized lipid binding by the Unique and SH3 domains, their intramolecular interaction and its allosteric modulation by a SH3-binding peptide or by Calcium-loaded calmodulin binding to the Unique domain. We also show reduced lipid binding following phosphorylation at conserved sites of the Unique domain. Finally, we show that injection of full-length c-Src with mutations that abolish lipid binding by the Unique domain causes a strong in vivo phenotype distinct from that of wild-type c-Src in a Xenopus oocyte model system, confirming the functional role of the Unique domain in c-Src regulation.

Research paper thumbnail of The promotional effect of Sn-beta zeolites on platinum for the selective hydrogenation of α,β-unsaturated aldehydes

Physical Chemistry Chemical Physics, 2013

Research paper thumbnail of Synthesis and reactivity of alkynyl niobocene complexes

Journal of Organometallic Chemistry, 2003

The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is descr... more The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is described. The niobium(III) derivatives of the general formula [Nb(h 5-C 5 H 4 SiMe 3) 2 (C Å/CR)(L)] where L is either carbonyl, phosphine, phosphite, or isocyanide, were prepared by the reaction of the bis(alkynyl)magnesium reagent with the corresponding cloro-niobocene precursor. In a similar manner the niobium(V) imido compounds, of the general formula, [Nb(Ä/NR?)(h 5-C 5 H 4 Rƒ) 2 (CÅ/CR)], were prepared. The characterization of these complexes is discussed. The reactivity of the alkynyl compounds towards oxidation and protonation has been studied.

Research paper thumbnail of Citrus limetta leaves extract antagonizes the hypertensive effect of angiotensin II

Journal of Ethnopharmacology, 2010

Ethnopharmacological relevance: Citrus limetta Risso (Rutaceae) is widely used in Mexico for heal... more Ethnopharmacological relevance: Citrus limetta Risso (Rutaceae) is widely used in Mexico for healing purposes, among them as antihypertensive treatment. Aim of the study: To assess the antihypertensive effect of C. limetta leaves as one of its ethnomedical uses. Materials and methods: The acute response of blood pressure to angiotensin II administration was measured in mice. Additionally, the acute oral toxicity profiles were determined. Results: The findings of the current investigation showed that different concentrations of the aqueous extract prevented the raise of systolic blood pressure (p ≤ 0.001 vs. vehicle), diastolic blood pressure (p ≤ 0.0002 vs. vehicle) and mean blood pressure (p ≤ 0.0000 vs. vehicle); with a dose dependent effect for diastolic pressures at 125-500 mg/kg dosages. The 500 and 1000 mg/kg doses inhibited the action of Ang II in similar extent to telmisartan. Toxic signs or deaths were not observed in mice treated at 2000 mg/kg of C. limetta extract. Conclusions: All doses of C. limetta aqueous extract, used in this assay, were safe and effective.

Research paper thumbnail of A spatial multicriteria decision making tool to define the best agricultural areas for sewage sludge amendment

Environment International, 2012

Sewage sludge amendment on agricultural soils has recently become a practice of heightened intere... more Sewage sludge amendment on agricultural soils has recently become a practice of heightened interest, as a consequence of sewage sludge production increase. This practice has benefits to soil and crops, however it may also lead to environmental contamination, depending on the characteristics of the fields. In order to define the suitability of the different agricultural fields to receive sewage sludge, a spatial tool is proposed. This tool, elaborated in GIS platform, aggregates different criteria regarding human exposure and environmental contamination. The spatial tool was applied to a case study in the region of Catalonia (NE of Spain). Within the case study, each step of the tool development is detailed. The results show that the studied region has different suitability degrees, being the appropriate areas sufficient for receiving the total amount of sewage sludge produced. The sensitivity analysis showed that "groundwater contamination", "distance to urban areas", "metals concentration in soil" and "crop type" are the most important criteria of the evaluation. The developed tool successfully tackled the problem, providing a comprehensive procedure to evaluate agricultural land suitability to receive sewage sludge as an organic fertilizer. Also, the tool implementation gives insights to decision makers, guiding them to more confident decisions, based on an extensive group of criteria.

Research paper thumbnail of Interviews

Dimensions of Critical Care Nursing, 1989

Research paper thumbnail of Peptide Assembly on the Membrane Determines the HIV-1 Inhibitory Activity of Dual-Targeting Fusion Inhibitor Peptides

Scientific Reports, 2019

Novel strategies in the design of HIV-1 fusion/entry inhibitors are based on the construction of ... more Novel strategies in the design of HIV-1 fusion/entry inhibitors are based on the construction of dual-targeting fusion proteins and peptides with synergistic antiviral effects. In this work we describe the design of dual-targeting peptides composed of peptide domains of E2 and E1 envelope proteins from Human Pegivirus with the aim of targeting both the loop region and the fusion peptide domains of HIV-1 gp41. In a previous work, we described the inhibitory role of a highly conserved fragment of the E1 protein (domain 139–156) which interacts with the HIV-1 fusion peptide at the membrane level. Here, two different dual-targeting peptides, where this E1 peptide is located on the N- or the C-terminus respectively, have been chemically synthesized and their antiviral activities have been evaluated with HIV pseudotyped viruses from different clades. The study of the functional behaviour of peptides in a membranous environment attending to the peptide recognition of the target sites on gp...

Research paper thumbnail of 547 PB 093 EFFECT OF THE APPLICATION OF SPROUTING PROMOTERS ON TWO POTATO CULTIVARS (Solanum tuberosum L.)

HortScience, 1994

In tubers `Kennebec' and `Russet' were applied acetylene, carbide and ethylene to promote... more In tubers `Kennebec' and `Russet' were applied acetylene, carbide and ethylene to promote sprouting, subsequently the tubers were stored at temperatures of 10 and 15 C. The experiment was a completely randomized, factorial design. The evaluations were done weekly. `Kennebec' sprouted from the second week of applied the treatments to 10 and 15 C while `Russet' sprouted only to 15 C. In the fourth evaluations the effect of promoters was not significantly different to the control. `Kennebec' at 10 C showed greater percentage of sprouting and number of sprout/tuber with respect to `Russet', but at 15 C were not detecte significant differences between the cultivars for these parameters. Number of sprout/tuber in `Kennebec' was not affected by the promoters but `Russet' treated with acetylene and carbide at 10 C showed the largest number of sprout/tuber. The greater sprout length was presented by `Kennebec' in both temperatures.

Research paper thumbnail of Quality Parameters in Four Melon Hybrids Stored at Different Temperatures

HortScience, 1996

Melon fruit (Cucumis melo L.) from Chando, Concorde, Explorer, and Durango hybrids, collected fro... more Melon fruit (Cucumis melo L.) from Chando, Concorde, Explorer, and Durango hybrids, collected from a Sante Ines farmer from Rio Tocuyo, were stored at 5, 10, and 18°C and room temperature for 7, 14, and 21 days with the objective of getting the response of melon hybrids in relation to quality characteristics. The soluble solids content and dry matter were not significant in the studied hybrids, titratable acidity was higher at 5°C, Chando had the highest values. Explorer had the highest pH values and soluble solids: titratable acid ratio at room temperature. Reducing and total sugars had the lowest values at 18°C and room temperature, Chando had the highest values. Concorde had the highest values for fresh weight loss at room temperature during 21 days of storage.

Research paper thumbnail of Marcadores manuales en el discurso narrativo en la lengua de señas venezolana

Research paper thumbnail of Schéma méthodologique pour le dessin et l'implantation d'un SIG

Tarraco Cuadernos De Geografia, 1995

Research paper thumbnail of La norma en la lenguade señas venezolana

Sapiens Revista Universitaria De Investigacion, 2007

presenta de gran valor en virtud de las implicaciones de este asunto en tres ámbitos fundamentale... more presenta de gran valor en virtud de las implicaciones de este asunto en tres ámbitos fundamentales. El primero es el lingüístico debido a su importancia en el proceso de construcción de una gramática de la LSV. El segundo es el social, pues contribuiría al reconocimiento de la cultura sorda del país. Y el tercero es el educativo ya que supone una pieza clave para una planificación pedagógica verdaderamente bilingüe-bicultural para los Sordos venezolanos. En este sentido, el presente estudio se propone realizar un análisis de aspectos que permiten hacer una aproximación al tema referido a la norma en la LSV. En esta tarea analítica, se suscribió la concepción coseriana de norma enmarcada en la visión tricotómica del lenguaje propuesta por este lingüista y constituida por tres conceptos fundamentales: habla / norma / sistema. Asimismo, se consideraron como elementos directrices ciertos aspectos que en el

Research paper thumbnail of Galacto configured N-aminoaziridines: a new type of irreversible inhibitors of β-galactosidases

Org. Biomol. Chem., 2015

N-Aminoaziridines are potent irreversible inhibitors of galactosidases.

Research paper thumbnail of Assay method for the carboxylic acid metabolite of clopidogrel in human plasma by gas chromatography–mass spectrometry

Journal of Chromatography B: Biomedical Sciences and Applications, 1998

This paper describes a GC-MS method for the analysis of the carboxylic acid metabolite (SR26334, ... more This paper describes a GC-MS method for the analysis of the carboxylic acid metabolite (SR26334, II) of methyl (+)-(S)-alpha-(o-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5( 4H)-acetate hydrogensulfate (clopidogrel, SR 25990, I) in plasma and serum. The analytical procedure involves a robotic liquid-liquid extraction with diethyl ether followed by a solid-liquid extraction on C18 cartridges. The derivatization process was performed using n-ethyl diisopropylethylamine and alpha-bromo-2,3,4,5,6-pentafluoro toluene. A structural analogue (III) of II, was used as internal standard. The 1/X2; weighted calibration curve obtained in the range 5-250 ng/ml was well described by a quadratic equation. The extraction efficiency was better than 48% over the range studied; for the internal standard it averaged 51% at 50 ng/ml. Precision ranged from 3.6 to 15.8%, and accuracy was between 92 and 114%. Dilution has no influence on the performance of the method which could then be used to quantitate plasma samples containing up to 25000 ng/ml. The limit of quantification was 5 ng/ml. The method validation results indicate that the performance characteristics of the method fulfilled the requirements for assay methods for use in pharmacokinetic studies.

Research paper thumbnail of Propuesta de un modelo de evaluación multicriterio para la incorporación de lodos de depuradora en suelos agrícolas

Research paper thumbnail of A case study for imaging complex structures in the Andean Thrust Belt of Bolivia

SEG Technical Program Expanded Abstracts 2006, 2006

We designed an unconventionally unique seismic workflow entirely in shot-receiver domain to obtai... more We designed an unconventionally unique seismic workflow entirely in shot-receiver domain to obtain an accurate earth model and earth image in areas with irregular topography, complex near-surface, and complex subsurface. We applied the workflow to 2-D seismic data from the Sub-Andean Thrust Belt of Bolivia and delineated a series of significant imbricate structures. The data were acquired using a common-spread recording geometry whereby the receiver spread was fixed for most of the shots. A total of 1.260 receiver groups with 20,000m maximum offset was placed along a nearly 33,000-m line traverse in the dominant structural dip direction at a 25-m interval. We included in the analysis a total of 518 shots at a 100-m interval along the line traverse, beginning at one end of the line. The topography is extremely rugged and elevations vary between 829-1,512 m along the line traverse. The unique aspects of the analysis woırkflow are: (1) The near-surface model is estimated by nonlinear tomography applied to first-arrival times that accounts for topography, and resolves lateral and vertical velocity variations. The corrections for the near-surface are performed by a combination of shotreceiver statics, refraction-based residual statics, and wavefield datuming-an essential requirement for imaging from irregular topography. (2) The subsurface modeling and prestack imaging are both performed from topography, not from a flat datum, based on rms and interval velocities estimated at reflector positions, not at reflection positions.

Research paper thumbnail of Effect of a Polyphenol-Rich Extract from Aloe vera Gel on Experimentally Induced Insulin Resistance in Mice

The American Journal of Chinese Medicine, 2007

Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology ass... more Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology associated with the metabolic syndrome, myocardial ischemia, and hypertension. Finding an adequate treatment for this pathology is an important goal in medicine. The purpose of the present research was to investigate the effect of an extract from Aloe vera gel containing a high concentration of polyphenols on experimentally induced insulin resistance in mice. A polyphenol-rich Aloe vera extract (350 mg/kg) with known concentrations of aloin (181.7 mg/g) and aloe-emodin (3.6 mg/g) was administered orally for a period of 4 weeks to insulin resistant ICR mice. Pioglitazone (50 mg/kg) and bi-distilled water were used as positive and negative controls respectively. Body weight, food intake, and plasma concentrations of insulin and glucose were measured and insulin tolerance tests were performed. The insulin resistance value was calculated using the homeostasis model assessment for insulin resist...

Research paper thumbnail of Towards nucleopeptides containing any trifunctional amino acid

Tetrahedron, 1999

Nucleopeptides incorporating, besides the linking residue, other trifunctional amino acids such a... more Nucleopeptides incorporating, besides the linking residue, other trifunctional amino acids such as lysine, arginine, tryptophan, serine, threonine and tyrosine have been obtained following stepwise solid-phase assembly. The best alternatives for the protection of the ...

Research paper thumbnail of Reversible dehydration-hydration process in lead-free hybrid perovskites

Proceedings of the nanoGe Fall Meeting 2021, 2021

Research paper thumbnail of Two sensitive and rapid chromogenic assays of fondaparinux sodium (Arixtra) in human plasma and other biological matrices

Clinical laboratory, 2003

Fondaparinux is a synthetic selective inhibitor of factor Xa recently approved for thromboprophyl... more Fondaparinux is a synthetic selective inhibitor of factor Xa recently approved for thromboprophylaxis after major orthopedic surgery. Determination of its concentration gives valuable insight into specific pharmacokinetics or safety studies. The aim of the study was to develop direct, sensitive, precise and accurate assays of fondaparinux sodium in different biological matrices. Consistency with the recommended chromogenic assay for low molecular weight heparin required a similar method. However, recent data indicated some variability in the determination of anti-Xa level between commercial chromogenic assays. Consequently, we developed and validated two chromogenic methods (A and B) for assaying fondaparinux in plasma and other biological matrices. The assays are calibrated with fondaparinux, a pure chemical entity, and the result is expressed as amount (microg) of the fondaparinux calibrator. Results showed that precision was lower than 5.2% in plasma or plasma water and 13% in pl...

Research paper thumbnail of Lipid binding by the Unique and SH3 domains of c-Src suggests a new regulatory mechanism

Scientific Reports, 2013

c-Src is a non-receptor tyrosine kinase involved in numerous signal transduction pathways. The ki... more c-Src is a non-receptor tyrosine kinase involved in numerous signal transduction pathways. The kinase, SH3 and SH2 domains of c-Src are attached to the membrane-anchoring SH4 domain through the flexible Unique domain. Here we show intra-and intermolecular interactions involving the Unique and SH3 domains suggesting the presence of a previously unrecognized additional regulation layer in c-Src. We have characterized lipid binding by the Unique and SH3 domains, their intramolecular interaction and its allosteric modulation by a SH3-binding peptide or by Calcium-loaded calmodulin binding to the Unique domain. We also show reduced lipid binding following phosphorylation at conserved sites of the Unique domain. Finally, we show that injection of full-length c-Src with mutations that abolish lipid binding by the Unique domain causes a strong in vivo phenotype distinct from that of wild-type c-Src in a Xenopus oocyte model system, confirming the functional role of the Unique domain in c-Src regulation.

Research paper thumbnail of The promotional effect of Sn-beta zeolites on platinum for the selective hydrogenation of α,β-unsaturated aldehydes

Physical Chemistry Chemical Physics, 2013

Research paper thumbnail of Synthesis and reactivity of alkynyl niobocene complexes

Journal of Organometallic Chemistry, 2003

The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is descr... more The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is described. The niobium(III) derivatives of the general formula [Nb(h 5-C 5 H 4 SiMe 3) 2 (C Å/CR)(L)] where L is either carbonyl, phosphine, phosphite, or isocyanide, were prepared by the reaction of the bis(alkynyl)magnesium reagent with the corresponding cloro-niobocene precursor. In a similar manner the niobium(V) imido compounds, of the general formula, [Nb(Ä/NR?)(h 5-C 5 H 4 Rƒ) 2 (CÅ/CR)], were prepared. The characterization of these complexes is discussed. The reactivity of the alkynyl compounds towards oxidation and protonation has been studied.

Research paper thumbnail of Citrus limetta leaves extract antagonizes the hypertensive effect of angiotensin II

Journal of Ethnopharmacology, 2010

Ethnopharmacological relevance: Citrus limetta Risso (Rutaceae) is widely used in Mexico for heal... more Ethnopharmacological relevance: Citrus limetta Risso (Rutaceae) is widely used in Mexico for healing purposes, among them as antihypertensive treatment. Aim of the study: To assess the antihypertensive effect of C. limetta leaves as one of its ethnomedical uses. Materials and methods: The acute response of blood pressure to angiotensin II administration was measured in mice. Additionally, the acute oral toxicity profiles were determined. Results: The findings of the current investigation showed that different concentrations of the aqueous extract prevented the raise of systolic blood pressure (p ≤ 0.001 vs. vehicle), diastolic blood pressure (p ≤ 0.0002 vs. vehicle) and mean blood pressure (p ≤ 0.0000 vs. vehicle); with a dose dependent effect for diastolic pressures at 125-500 mg/kg dosages. The 500 and 1000 mg/kg doses inhibited the action of Ang II in similar extent to telmisartan. Toxic signs or deaths were not observed in mice treated at 2000 mg/kg of C. limetta extract. Conclusions: All doses of C. limetta aqueous extract, used in this assay, were safe and effective.

Research paper thumbnail of A spatial multicriteria decision making tool to define the best agricultural areas for sewage sludge amendment

Environment International, 2012

Sewage sludge amendment on agricultural soils has recently become a practice of heightened intere... more Sewage sludge amendment on agricultural soils has recently become a practice of heightened interest, as a consequence of sewage sludge production increase. This practice has benefits to soil and crops, however it may also lead to environmental contamination, depending on the characteristics of the fields. In order to define the suitability of the different agricultural fields to receive sewage sludge, a spatial tool is proposed. This tool, elaborated in GIS platform, aggregates different criteria regarding human exposure and environmental contamination. The spatial tool was applied to a case study in the region of Catalonia (NE of Spain). Within the case study, each step of the tool development is detailed. The results show that the studied region has different suitability degrees, being the appropriate areas sufficient for receiving the total amount of sewage sludge produced. The sensitivity analysis showed that "groundwater contamination", "distance to urban areas", "metals concentration in soil" and "crop type" are the most important criteria of the evaluation. The developed tool successfully tackled the problem, providing a comprehensive procedure to evaluate agricultural land suitability to receive sewage sludge as an organic fertilizer. Also, the tool implementation gives insights to decision makers, guiding them to more confident decisions, based on an extensive group of criteria.

Research paper thumbnail of Interviews

Dimensions of Critical Care Nursing, 1989

Research paper thumbnail of Peptide Assembly on the Membrane Determines the HIV-1 Inhibitory Activity of Dual-Targeting Fusion Inhibitor Peptides

Scientific Reports, 2019

Novel strategies in the design of HIV-1 fusion/entry inhibitors are based on the construction of ... more Novel strategies in the design of HIV-1 fusion/entry inhibitors are based on the construction of dual-targeting fusion proteins and peptides with synergistic antiviral effects. In this work we describe the design of dual-targeting peptides composed of peptide domains of E2 and E1 envelope proteins from Human Pegivirus with the aim of targeting both the loop region and the fusion peptide domains of HIV-1 gp41. In a previous work, we described the inhibitory role of a highly conserved fragment of the E1 protein (domain 139–156) which interacts with the HIV-1 fusion peptide at the membrane level. Here, two different dual-targeting peptides, where this E1 peptide is located on the N- or the C-terminus respectively, have been chemically synthesized and their antiviral activities have been evaluated with HIV pseudotyped viruses from different clades. The study of the functional behaviour of peptides in a membranous environment attending to the peptide recognition of the target sites on gp...

Research paper thumbnail of 547 PB 093 EFFECT OF THE APPLICATION OF SPROUTING PROMOTERS ON TWO POTATO CULTIVARS (Solanum tuberosum L.)

HortScience, 1994

In tubers `Kennebec' and `Russet' were applied acetylene, carbide and ethylene to promote... more In tubers `Kennebec' and `Russet' were applied acetylene, carbide and ethylene to promote sprouting, subsequently the tubers were stored at temperatures of 10 and 15 C. The experiment was a completely randomized, factorial design. The evaluations were done weekly. `Kennebec' sprouted from the second week of applied the treatments to 10 and 15 C while `Russet' sprouted only to 15 C. In the fourth evaluations the effect of promoters was not significantly different to the control. `Kennebec' at 10 C showed greater percentage of sprouting and number of sprout/tuber with respect to `Russet', but at 15 C were not detecte significant differences between the cultivars for these parameters. Number of sprout/tuber in `Kennebec' was not affected by the promoters but `Russet' treated with acetylene and carbide at 10 C showed the largest number of sprout/tuber. The greater sprout length was presented by `Kennebec' in both temperatures.

Research paper thumbnail of Quality Parameters in Four Melon Hybrids Stored at Different Temperatures

HortScience, 1996

Melon fruit (Cucumis melo L.) from Chando, Concorde, Explorer, and Durango hybrids, collected fro... more Melon fruit (Cucumis melo L.) from Chando, Concorde, Explorer, and Durango hybrids, collected from a Sante Ines farmer from Rio Tocuyo, were stored at 5, 10, and 18°C and room temperature for 7, 14, and 21 days with the objective of getting the response of melon hybrids in relation to quality characteristics. The soluble solids content and dry matter were not significant in the studied hybrids, titratable acidity was higher at 5°C, Chando had the highest values. Explorer had the highest pH values and soluble solids: titratable acid ratio at room temperature. Reducing and total sugars had the lowest values at 18°C and room temperature, Chando had the highest values. Concorde had the highest values for fresh weight loss at room temperature during 21 days of storage.

Research paper thumbnail of Marcadores manuales en el discurso narrativo en la lengua de señas venezolana

Research paper thumbnail of Schéma méthodologique pour le dessin et l'implantation d'un SIG

Tarraco Cuadernos De Geografia, 1995

Research paper thumbnail of La norma en la lenguade señas venezolana

Sapiens Revista Universitaria De Investigacion, 2007

presenta de gran valor en virtud de las implicaciones de este asunto en tres ámbitos fundamentale... more presenta de gran valor en virtud de las implicaciones de este asunto en tres ámbitos fundamentales. El primero es el lingüístico debido a su importancia en el proceso de construcción de una gramática de la LSV. El segundo es el social, pues contribuiría al reconocimiento de la cultura sorda del país. Y el tercero es el educativo ya que supone una pieza clave para una planificación pedagógica verdaderamente bilingüe-bicultural para los Sordos venezolanos. En este sentido, el presente estudio se propone realizar un análisis de aspectos que permiten hacer una aproximación al tema referido a la norma en la LSV. En esta tarea analítica, se suscribió la concepción coseriana de norma enmarcada en la visión tricotómica del lenguaje propuesta por este lingüista y constituida por tres conceptos fundamentales: habla / norma / sistema. Asimismo, se consideraron como elementos directrices ciertos aspectos que en el

Research paper thumbnail of Galacto configured N-aminoaziridines: a new type of irreversible inhibitors of β-galactosidases

Org. Biomol. Chem., 2015

N-Aminoaziridines are potent irreversible inhibitors of galactosidases.

Research paper thumbnail of Assay method for the carboxylic acid metabolite of clopidogrel in human plasma by gas chromatography–mass spectrometry

Journal of Chromatography B: Biomedical Sciences and Applications, 1998

This paper describes a GC-MS method for the analysis of the carboxylic acid metabolite (SR26334, ... more This paper describes a GC-MS method for the analysis of the carboxylic acid metabolite (SR26334, II) of methyl (+)-(S)-alpha-(o-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5( 4H)-acetate hydrogensulfate (clopidogrel, SR 25990, I) in plasma and serum. The analytical procedure involves a robotic liquid-liquid extraction with diethyl ether followed by a solid-liquid extraction on C18 cartridges. The derivatization process was performed using n-ethyl diisopropylethylamine and alpha-bromo-2,3,4,5,6-pentafluoro toluene. A structural analogue (III) of II, was used as internal standard. The 1/X2; weighted calibration curve obtained in the range 5-250 ng/ml was well described by a quadratic equation. The extraction efficiency was better than 48% over the range studied; for the internal standard it averaged 51% at 50 ng/ml. Precision ranged from 3.6 to 15.8%, and accuracy was between 92 and 114%. Dilution has no influence on the performance of the method which could then be used to quantitate plasma samples containing up to 25000 ng/ml. The limit of quantification was 5 ng/ml. The method validation results indicate that the performance characteristics of the method fulfilled the requirements for assay methods for use in pharmacokinetic studies.

Research paper thumbnail of Propuesta de un modelo de evaluación multicriterio para la incorporación de lodos de depuradora en suelos agrícolas

Research paper thumbnail of A case study for imaging complex structures in the Andean Thrust Belt of Bolivia

SEG Technical Program Expanded Abstracts 2006, 2006

We designed an unconventionally unique seismic workflow entirely in shot-receiver domain to obtai... more We designed an unconventionally unique seismic workflow entirely in shot-receiver domain to obtain an accurate earth model and earth image in areas with irregular topography, complex near-surface, and complex subsurface. We applied the workflow to 2-D seismic data from the Sub-Andean Thrust Belt of Bolivia and delineated a series of significant imbricate structures. The data were acquired using a common-spread recording geometry whereby the receiver spread was fixed for most of the shots. A total of 1.260 receiver groups with 20,000m maximum offset was placed along a nearly 33,000-m line traverse in the dominant structural dip direction at a 25-m interval. We included in the analysis a total of 518 shots at a 100-m interval along the line traverse, beginning at one end of the line. The topography is extremely rugged and elevations vary between 829-1,512 m along the line traverse. The unique aspects of the analysis woırkflow are: (1) The near-surface model is estimated by nonlinear tomography applied to first-arrival times that accounts for topography, and resolves lateral and vertical velocity variations. The corrections for the near-surface are performed by a combination of shotreceiver statics, refraction-based residual statics, and wavefield datuming-an essential requirement for imaging from irregular topography. (2) The subsurface modeling and prestack imaging are both performed from topography, not from a flat datum, based on rms and interval velocities estimated at reflector positions, not at reflection positions.

Research paper thumbnail of Effect of a Polyphenol-Rich Extract from Aloe vera Gel on Experimentally Induced Insulin Resistance in Mice

The American Journal of Chinese Medicine, 2007

Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology ass... more Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology associated with the metabolic syndrome, myocardial ischemia, and hypertension. Finding an adequate treatment for this pathology is an important goal in medicine. The purpose of the present research was to investigate the effect of an extract from Aloe vera gel containing a high concentration of polyphenols on experimentally induced insulin resistance in mice. A polyphenol-rich Aloe vera extract (350 mg/kg) with known concentrations of aloin (181.7 mg/g) and aloe-emodin (3.6 mg/g) was administered orally for a period of 4 weeks to insulin resistant ICR mice. Pioglitazone (50 mg/kg) and bi-distilled water were used as positive and negative controls respectively. Body weight, food intake, and plasma concentrations of insulin and glucose were measured and insulin tolerance tests were performed. The insulin resistance value was calculated using the homeostasis model assessment for insulin resist...

Research paper thumbnail of Towards nucleopeptides containing any trifunctional amino acid

Tetrahedron, 1999

Nucleopeptides incorporating, besides the linking residue, other trifunctional amino acids such a... more Nucleopeptides incorporating, besides the linking residue, other trifunctional amino acids such as lysine, arginine, tryptophan, serine, threonine and tyrosine have been obtained following stepwise solid-phase assembly. The best alternatives for the protection of the ...