OMAR ESTRADA - Academia.edu (original) (raw)

Papers by OMAR ESTRADA

Revista Ciencias Tecnicas Agropecuarias, 2003

Caracterización de los bulbos húmedos creados con goteros de 4 y 8 L/h sobre sustratos orgánicos

Revista Ciencias Tecnicas Agropecuarias, 2009

RESUMEN. Uno de los elementos fundamentales a tener en cuenta a la hora de elegir la tecnología d... more RESUMEN. Uno de los elementos fundamentales a tener en cuenta a la hora de elegir la tecnología de riego a utilizar, es el relativo a su efectividad económica. El objetivo del presente trabajo es definir el efecto económico de dos aspectos relacionado con este método de riego en el cultivo del Papayo; el área de suelo a humedecer y el diseño de la red superficial. Con este fin se realizó una investigación en las que se evaluaron tres áreas humedecidas con diferentes diseños de red superficial (1. Un lateral con goteros por hilera de plantas, donde se logró mojar un 19.44% del espacio vital (AV), 2. Un lateral con microaspersores por hilera de plantas, donde se logró un 46,11% AV y 3. Dos laterales con goteros por hilera de plantas, donde se logró un 30,56% AV). También fue valorado a partir de los rendimientos obtenidos en la variante tres, la alternativa de utilizar un lateral por hilera de plantas con extensores a ambos lados, para sustituir el doble lateral y lograr la misma área humedecida (30,56%AV). Los resultados indican que la variante mas efectiva fue la dos, donde se alcanzó el mayor rendimiento (68,17 t/ha en ocho meses de cultivo), con un ingreso al capital de 635.48 /hayunarentabilidaddel6,15/ha y una rentabilidad del 6,15% con relación al capital invertido. Palabras clave: economía del riego, tipo de emisor, área a humedecer ABSTRACT. One of the fundamental elements to keep in mind when choosing the irrigation technology to be used is its economical effectiveness. The objective of the present paper is to define the economic effect of two aspects related to this irrigation method in Papaya tree cropping; the soil area to moisture and the design of the superficial net. In order to fulfill this purpose a research was carried out in which three wetted areas were evaluated with different designs of superficial net (1. A lateral pipe with droppers, where it was possible to wet 19,44% of the vital space (AV), 2. A lateral pipe with microsprinklers, where 46,11% was achieved AV and 3. Two lateral pipe with droppers for, where 30,56% AV was achieved). It was also valued starting from the yields obtained in the variant three, the alternative of using a lateral pipe per plant row with enlargements in both sides, for substituting the double pipe and to achieve the same wetted area (30,56%AV). The results indicate that the most effective variant was the two, getting the biggest yield (68,17 t/ha in eight months of cropping), with an income of 635.48 /hayunarentabilidaddel6,15, showing profitabilities of 6,15% with relation to the initial investment.

Revista Ciencias Tecnicas Agropecuarias, 2009

Manejo del riego por goteo en el cultivo del guayabo

Journal of Biological Chemistry, 2010

Crustacean cardioactive peptide (CCAP) and related peptides are multifunctional regulatory neuroh... more Crustacean cardioactive peptide (CCAP) and related peptides are multifunctional regulatory neurohormones found in invertebrates. We isolated a CCAP-related peptide (conoCAP-a, for cone snail CArdioactive Peptide) and cloned the cDNA of its precursor from venom of Conus villepinii. The precursor of conoCAP-a encodes for two additional CCAP-like peptides: conoCAP-b and conoCAP-c. This multi-peptide precursor organization is analogous to recently predicted molluscan CCAP-like preprohormones, and suggests a mechanism for the generation of biological diversification without gene amplification. While arthropod CCAP is a cardio-accelerator, we found that conoCAP-a decreases the heart frequency in Drosophila larvae, demonstrating that conoCAP-a and CCAP have opposite effects. Intravenous injection of conoCAP-a in rats caused decreased heart frequency and blood pressure in contrast to the injection of CCAP, which did not elicit any cardiac effect. Perfusion of rat ventricular cardiac myocytes with conoCAP-a decreased systolic calcium, indicating that conoCAP-a cardiac negative inotropic effects might be mediated via impairment of intracellular calcium trafficking. The contrasting cardiac effects of conoCAP-a and CCAP indicate that molluscan CCAP-like peptides have functions that differ from those of their arthropod counterparts. Molluscan CCAP-like peptides sequences, while homologous, differ between taxa and have

Planta Medica, 2019

Common chronic conditions such as metabolic syndrome and diabetes are increasingly associated to ... more Common chronic conditions such as metabolic syndrome and diabetes are increasingly associated to metabolic and cardiovascular complications. Although Phyllanthus tenellus leaves have been used in decoctions as a popular remedy to control blood glucose levels and hypertension, its use needs a scientific basis. This study was therefore undertaken to report a phytochemical analysis of P. tenellus leaves and to test if the main active compound has potential to simultaneously tackle several pathophysiological features of metabolic syndrome and diabetes-related metabolic and vascular disorders such as hyperglycaemia, increased platelet activation, and endothelial dysfunction. We performed a partition of the methanolic extract of P. tenellus leaves among different organic solvents followed by chromatographic separation guided by the rat liver microsomal glucose-6-phosphatase assay. Two known tannins were identified by spectroscopic methods as pinocembrin-7-O-[3″-O-galloyl-4″,6″-(S)-hexahyd...

Avances En Quimica, 2012

La cinética de interconversión de astilbina a una mezcla de sus respectivos diasteroisómeros fue ... more La cinética de interconversión de astilbina a una mezcla de sus respectivos diasteroisómeros fue estudiada por espectroscopia de resonancia magnética nuclear empleando experimentos de irradiación selectiva (TOCSY) en dimetilsulfóxido. Se planteó un modelo que permitió establecer una tendencia al equilibrio para H-3 (interconversión de astilbina a neoisoastilbina)

Revista Latinoamericana De Metalurgia Y Materiales, Dec 1, 2013

El efecto de flujo fuente tiene importantes implicaciones en la calidad de partes inyectadas y mo... more El efecto de flujo fuente tiene importantes implicaciones en la calidad de partes inyectadas y moldeadas por compresión, debido a que afecta la orientación de las macromoléculas del polímero y por lo tanto, las propiedades mecánicas y ópticas de la parte final [1]. Cuando se utilizan materiales reforzados, los efectos del flujo fuente se hacen más críticos, ya que se afectan las orientaciones y distribuciones de las fibras. El efecto de flujo fuente es modelado usando un método sin malla, el método de funciones radiales (MFR). Se consideró una ranura plana en estado estacionario con un modelo de ley de potencias y el flujo de un fluido Newtoniano en un tubo vertical considerando efectos gravitacionales. Se encontró una buena correspondencia de los resultados con datos reportados en la literatura.

Investigación clínica, 2006

The crustacean nervous system is an important source of substances with diverse biological activi... more The crustacean nervous system is an important source of substances with diverse biological activities, particularly affecting invertebrate cardiocirculatory physiology. However, the effects of these substances on the cardiovascular system of higher vertebrates are not very well documented. The purpose of this study was to evaluate the effects of a cardioexcitatory substance (CES) isolated from the eyestalk of the shrimp Peneaus vanameii on rat cardiovascular function. The administration of a purified fraction of this substance raised mean arterial pressure by 37.33 +/- 5.00 mm Hg, pulse pressure 35.00 +/- 4.93 mm Hg and heart rate 80.00 +/- 12.83 beats/min over basal values (p < 0.01). Evaluation of the possible underlying mechanisms of this hypertensive and tachycardic effect reveled that dihydroergotamine pretreatment (20 microg/0.2 mL) reduced the effect of CES on mean blood pressure, but not on heart rate. Propranolol pretreatment (4 microg/0.2 mL) reduced the tachycardia, bu...

Metallocene Technology in Commercial Applications, 1999

This chapter compares the Metallocene Polyethylene (mPE) material with respect to low density pol... more This chapter compares the Metallocene Polyethylene (mPE) material with respect to low density polyethylene (LDPE) based on the characteristic curves and energy balance, while also discussing different blends of mPE/MB with respect to a reference blend, mPE/ linear low-density polyethylene (LLDPE) without the filler (TiO 2 ). Results are obtained under the same processing conditions and screw design. The comparison involves the analysis of the characteristic curves, pressure production, or consumption along the screw, temperature homogenization, and mechanical properties for each blend. The extrusion of metallocene resins is very different compared to the LDPE processing because these materials have an extended Newtonian plateau. Operation windows obtained in the chapter are more attractive for the industry due to the high productivity levels. The filler masterbatches act mainly as a processing aid due to the carrier selection (resins with a high melt index) and at the same time, a positive reinforcing effect can be achieved.

SPIE Proceedings, 2005

We report on the optical characterization and measurement of oxygen singlet quantum yield of Chlo... more We report on the optical characterization and measurement of oxygen singlet quantum yield of Chlorophyll and Chlorin e6 in water-ethanol mixtures by direct observation of thermal relaxation using time resolved thermal lens method. The analysis of the time-resolved curve allows the determination of the quantum yield of singlet oxygen formation. The quantum yield is deduced from the relative magnitudes of

SPIE Proceedings, 2004

We report on a new source of coherent red-light with perspective applications in laser photodynam... more We report on a new source of coherent red-light with perspective applications in laser photodynamic therapy. The red light is generated through stimulated Raman scattering (SRS) process by acetone of a frequency-doubled Nd:YAG nanosecond laser radiation (532 nm). The Stokes transition is found at 630 nm and with spectral line narrowing similar to the pump one. When pumping using the

Phytotherapy Research, 2005

From the methanol extract of Bauhinia megalandra fresh leaves, eight flavonoids were isolated and... more From the methanol extract of Bauhinia megalandra fresh leaves, eight flavonoids were isolated and evaluated by rat liver microsomal glucose-6-phosphatase (G-6-Pase) bioassay, which might be a useful methodology for screening antihyperglycaemic substances. All the flavonoids assayed showed an inhibitory effect on the intact microsomal G-6-Pase: quercetin and kaempferol exhibited the lowest effect; astilbin, quercetin 3-O-alpha-rhamnoside, kaempferol 3-O-alpha-rhamnoside and quercetin 3-O-alpha-arabinoside an intermediate effect. The highest inhibitory activity was shown by quercetin 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside and kaempferol 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;galloyl)rhamnoside. None of the flavonoids mentioned above showed an inhibitory effect on the disrupted microsomal G-6-Pase. Quercetin 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside and kaempferol 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside exhibited the lowest IC50 of all the flavonoids assayed. Also, the phlorizin IC50 is reported.

Phytotherapy Research, 1998

An aqueons extract of Bauhinia megalandra leaves causes a decrease of nearly 50% in the glucose p... more An aqueons extract of Bauhinia megalandra leaves causes a decrease of nearly 50% in the glucose production, from lactate or fructose, of rat liver slices incubated in Krebs-Ringer bicarbonate buffer supplemented with oleate-saturated albumin. In intact microsomes, the B. megalandra extract acts as a mixed non-competitive inhibitor of glucose-6-phosphatase. In the histone-disrupted microsomes the extract has no effect on glucose-6-phosphate hydrolysis. However in the presence of the extract, glucose-6-phosphatase activity was linear with time, as in the control, but at a lower level, reaching a plateau after 20 min. This suggests an inhibition of the catalytic subunit by accumulation of orthophosphate and/or glucose, as a consequence of the inhibition of its translocases (T2 and/or T3 respectively). Neither the intact nor the disrupted microsomal pyrophosphatase kinetics parameters were affected by the inclusion of the leaf extract. The above results strongly suggest that the main effect of the B. megalandra extract is the inhibition of the glucose-6-phosphate transporter (T1) of the microsomal glucose-6-phosphatase system; however, an inhibition of T3 was not ruled out. The glucose-6-phosphatase inhibition might explain the decrease in the liver slices neoglucogenic capacity and in turn could reduce glucose levels in diabetic patients.

Journal of Plastic Film & Sheeting, 2013

A computational model to design plastic food packaging is proposed. The model minimizes the cost ... more A computational model to design plastic food packaging is proposed. The model minimizes the cost of the multi-layer structure satisfying the specific product requirements, using a heuristic optimization algorithm. The product requirements are defined by the expected shelf life, the storage conditions, the water sorption isotherms of foods and the maximum allowable gain or loss of gases (O2, CO2, N2, etc.) and moisture for the packaged food. In order to assure the food shelf life, these product requirements should be fulfilled to estimate the maximum permeance values of the plastic package. The computational algorithm automatically generates different multi-layer film structures that satisfy the product requirements. This algorithm combines different polymeric materials taking into account the barrier properties and cost of each layer, the compatibility between layers, the maximum number of layers and the minimum and maximum film thickness for each layer. Temperature and relative hum...

Journal of Ethnopharmacology, 2001

A total of 21 extracts derived from 17 different plant species collected in Venezuelan Amazons ha... more A total of 21 extracts derived from 17 different plant species collected in Venezuelan Amazons have been tested for the following biological activities: cardiovascular activity, brine shrimp lethality, and inhibitory effects on the hydrolysis of glucose-6-phosphate in intact and disrupted microsomes. Eight extracts diminished rat blood pressure with or without changes in heart rate. The fruit extract of Swartzia leptopetala and the leaf and twig extract of Connarus lambertii resulted in death of experimental animals. The majority of extracts (17 extracts) showed significant toxicity against Artemia salina. Concerning the hydrolysis of glucose-6-phosphate, better inhibitory effects were observed in intact microsomes than in disrupted ones for all the extracts, suggesting that these extracts intervene with variable potency in glucose-6-phosphate transport through the microsomal membrane.

Rev. Inst. Nac. …, 2002

Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos del extracto metanóli... more Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos del extracto metanólico de las hojas de Hirtella castillanum se aislaron cuatro flavonoides: Quercetina (1), Quercetina-3-ramnósido (2), Miricetina (3) y mirecitina-3-ramnósido (4). De los ...

Rev. Inst. Nac. …, 2000

Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos (sephadex LH20 y síli... more Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos (sephadex LH20 y sílica gel RP-18) del extracto metanólico de las hojas de licania pittieri, se aislaron cinco flavonoides: quercetina (1), quercetina-3-galactósido (2), quercetina-3-rhamnósido ( ...

Revista Internacional De Ciencias Sociales Y Humanidades Sociotam, 2011

This study integrates the results of a psychophysiological profile and the effects of the present... more This study integrates the results of a psychophysiological profile and the effects of the presentation of positive words and images. Sixty athletes from Seville (average age, 21.6 years) participated in the study, divided by gender and type of sport (individual or team). Results indicate that there are significant differences in the comparison of the conditions, in particular in temperature of the left hand:

Revista Ciencias Tecnicas Agropecuarias, 2003

Caracterización de los bulbos húmedos creados con goteros de 4 y 8 L/h sobre sustratos orgánicos

Revista Ciencias Tecnicas Agropecuarias, 2009

RESUMEN. Uno de los elementos fundamentales a tener en cuenta a la hora de elegir la tecnología d... more RESUMEN. Uno de los elementos fundamentales a tener en cuenta a la hora de elegir la tecnología de riego a utilizar, es el relativo a su efectividad económica. El objetivo del presente trabajo es definir el efecto económico de dos aspectos relacionado con este método de riego en el cultivo del Papayo; el área de suelo a humedecer y el diseño de la red superficial. Con este fin se realizó una investigación en las que se evaluaron tres áreas humedecidas con diferentes diseños de red superficial (1. Un lateral con goteros por hilera de plantas, donde se logró mojar un 19.44% del espacio vital (AV), 2. Un lateral con microaspersores por hilera de plantas, donde se logró un 46,11% AV y 3. Dos laterales con goteros por hilera de plantas, donde se logró un 30,56% AV). También fue valorado a partir de los rendimientos obtenidos en la variante tres, la alternativa de utilizar un lateral por hilera de plantas con extensores a ambos lados, para sustituir el doble lateral y lograr la misma área humedecida (30,56%AV). Los resultados indican que la variante mas efectiva fue la dos, donde se alcanzó el mayor rendimiento (68,17 t/ha en ocho meses de cultivo), con un ingreso al capital de 635.48 /hayunarentabilidaddel6,15/ha y una rentabilidad del 6,15% con relación al capital invertido. Palabras clave: economía del riego, tipo de emisor, área a humedecer ABSTRACT. One of the fundamental elements to keep in mind when choosing the irrigation technology to be used is its economical effectiveness. The objective of the present paper is to define the economic effect of two aspects related to this irrigation method in Papaya tree cropping; the soil area to moisture and the design of the superficial net. In order to fulfill this purpose a research was carried out in which three wetted areas were evaluated with different designs of superficial net (1. A lateral pipe with droppers, where it was possible to wet 19,44% of the vital space (AV), 2. A lateral pipe with microsprinklers, where 46,11% was achieved AV and 3. Two lateral pipe with droppers for, where 30,56% AV was achieved). It was also valued starting from the yields obtained in the variant three, the alternative of using a lateral pipe per plant row with enlargements in both sides, for substituting the double pipe and to achieve the same wetted area (30,56%AV). The results indicate that the most effective variant was the two, getting the biggest yield (68,17 t/ha in eight months of cropping), with an income of 635.48 /hayunarentabilidaddel6,15, showing profitabilities of 6,15% with relation to the initial investment.

Revista Ciencias Tecnicas Agropecuarias, 2009

Manejo del riego por goteo en el cultivo del guayabo

Journal of Biological Chemistry, 2010

Crustacean cardioactive peptide (CCAP) and related peptides are multifunctional regulatory neuroh... more Crustacean cardioactive peptide (CCAP) and related peptides are multifunctional regulatory neurohormones found in invertebrates. We isolated a CCAP-related peptide (conoCAP-a, for cone snail CArdioactive Peptide) and cloned the cDNA of its precursor from venom of Conus villepinii. The precursor of conoCAP-a encodes for two additional CCAP-like peptides: conoCAP-b and conoCAP-c. This multi-peptide precursor organization is analogous to recently predicted molluscan CCAP-like preprohormones, and suggests a mechanism for the generation of biological diversification without gene amplification. While arthropod CCAP is a cardio-accelerator, we found that conoCAP-a decreases the heart frequency in Drosophila larvae, demonstrating that conoCAP-a and CCAP have opposite effects. Intravenous injection of conoCAP-a in rats caused decreased heart frequency and blood pressure in contrast to the injection of CCAP, which did not elicit any cardiac effect. Perfusion of rat ventricular cardiac myocytes with conoCAP-a decreased systolic calcium, indicating that conoCAP-a cardiac negative inotropic effects might be mediated via impairment of intracellular calcium trafficking. The contrasting cardiac effects of conoCAP-a and CCAP indicate that molluscan CCAP-like peptides have functions that differ from those of their arthropod counterparts. Molluscan CCAP-like peptides sequences, while homologous, differ between taxa and have

Planta Medica, 2019

Common chronic conditions such as metabolic syndrome and diabetes are increasingly associated to ... more Common chronic conditions such as metabolic syndrome and diabetes are increasingly associated to metabolic and cardiovascular complications. Although Phyllanthus tenellus leaves have been used in decoctions as a popular remedy to control blood glucose levels and hypertension, its use needs a scientific basis. This study was therefore undertaken to report a phytochemical analysis of P. tenellus leaves and to test if the main active compound has potential to simultaneously tackle several pathophysiological features of metabolic syndrome and diabetes-related metabolic and vascular disorders such as hyperglycaemia, increased platelet activation, and endothelial dysfunction. We performed a partition of the methanolic extract of P. tenellus leaves among different organic solvents followed by chromatographic separation guided by the rat liver microsomal glucose-6-phosphatase assay. Two known tannins were identified by spectroscopic methods as pinocembrin-7-O-[3″-O-galloyl-4″,6″-(S)-hexahyd...

Avances En Quimica, 2012

La cinética de interconversión de astilbina a una mezcla de sus respectivos diasteroisómeros fue ... more La cinética de interconversión de astilbina a una mezcla de sus respectivos diasteroisómeros fue estudiada por espectroscopia de resonancia magnética nuclear empleando experimentos de irradiación selectiva (TOCSY) en dimetilsulfóxido. Se planteó un modelo que permitió establecer una tendencia al equilibrio para H-3 (interconversión de astilbina a neoisoastilbina)

Revista Latinoamericana De Metalurgia Y Materiales, Dec 1, 2013

El efecto de flujo fuente tiene importantes implicaciones en la calidad de partes inyectadas y mo... more El efecto de flujo fuente tiene importantes implicaciones en la calidad de partes inyectadas y moldeadas por compresión, debido a que afecta la orientación de las macromoléculas del polímero y por lo tanto, las propiedades mecánicas y ópticas de la parte final [1]. Cuando se utilizan materiales reforzados, los efectos del flujo fuente se hacen más críticos, ya que se afectan las orientaciones y distribuciones de las fibras. El efecto de flujo fuente es modelado usando un método sin malla, el método de funciones radiales (MFR). Se consideró una ranura plana en estado estacionario con un modelo de ley de potencias y el flujo de un fluido Newtoniano en un tubo vertical considerando efectos gravitacionales. Se encontró una buena correspondencia de los resultados con datos reportados en la literatura.

Investigación clínica, 2006

The crustacean nervous system is an important source of substances with diverse biological activi... more The crustacean nervous system is an important source of substances with diverse biological activities, particularly affecting invertebrate cardiocirculatory physiology. However, the effects of these substances on the cardiovascular system of higher vertebrates are not very well documented. The purpose of this study was to evaluate the effects of a cardioexcitatory substance (CES) isolated from the eyestalk of the shrimp Peneaus vanameii on rat cardiovascular function. The administration of a purified fraction of this substance raised mean arterial pressure by 37.33 +/- 5.00 mm Hg, pulse pressure 35.00 +/- 4.93 mm Hg and heart rate 80.00 +/- 12.83 beats/min over basal values (p < 0.01). Evaluation of the possible underlying mechanisms of this hypertensive and tachycardic effect reveled that dihydroergotamine pretreatment (20 microg/0.2 mL) reduced the effect of CES on mean blood pressure, but not on heart rate. Propranolol pretreatment (4 microg/0.2 mL) reduced the tachycardia, bu...

Metallocene Technology in Commercial Applications, 1999

This chapter compares the Metallocene Polyethylene (mPE) material with respect to low density pol... more This chapter compares the Metallocene Polyethylene (mPE) material with respect to low density polyethylene (LDPE) based on the characteristic curves and energy balance, while also discussing different blends of mPE/MB with respect to a reference blend, mPE/ linear low-density polyethylene (LLDPE) without the filler (TiO 2 ). Results are obtained under the same processing conditions and screw design. The comparison involves the analysis of the characteristic curves, pressure production, or consumption along the screw, temperature homogenization, and mechanical properties for each blend. The extrusion of metallocene resins is very different compared to the LDPE processing because these materials have an extended Newtonian plateau. Operation windows obtained in the chapter are more attractive for the industry due to the high productivity levels. The filler masterbatches act mainly as a processing aid due to the carrier selection (resins with a high melt index) and at the same time, a positive reinforcing effect can be achieved.

SPIE Proceedings, 2005

We report on the optical characterization and measurement of oxygen singlet quantum yield of Chlo... more We report on the optical characterization and measurement of oxygen singlet quantum yield of Chlorophyll and Chlorin e6 in water-ethanol mixtures by direct observation of thermal relaxation using time resolved thermal lens method. The analysis of the time-resolved curve allows the determination of the quantum yield of singlet oxygen formation. The quantum yield is deduced from the relative magnitudes of

SPIE Proceedings, 2004

We report on a new source of coherent red-light with perspective applications in laser photodynam... more We report on a new source of coherent red-light with perspective applications in laser photodynamic therapy. The red light is generated through stimulated Raman scattering (SRS) process by acetone of a frequency-doubled Nd:YAG nanosecond laser radiation (532 nm). The Stokes transition is found at 630 nm and with spectral line narrowing similar to the pump one. When pumping using the

Phytotherapy Research, 2005

From the methanol extract of Bauhinia megalandra fresh leaves, eight flavonoids were isolated and... more From the methanol extract of Bauhinia megalandra fresh leaves, eight flavonoids were isolated and evaluated by rat liver microsomal glucose-6-phosphatase (G-6-Pase) bioassay, which might be a useful methodology for screening antihyperglycaemic substances. All the flavonoids assayed showed an inhibitory effect on the intact microsomal G-6-Pase: quercetin and kaempferol exhibited the lowest effect; astilbin, quercetin 3-O-alpha-rhamnoside, kaempferol 3-O-alpha-rhamnoside and quercetin 3-O-alpha-arabinoside an intermediate effect. The highest inhibitory activity was shown by quercetin 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside and kaempferol 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;galloyl)rhamnoside. None of the flavonoids mentioned above showed an inhibitory effect on the disrupted microsomal G-6-Pase. Quercetin 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside and kaempferol 3-O-alpha-(2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-galloyl)rhamnoside exhibited the lowest IC50 of all the flavonoids assayed. Also, the phlorizin IC50 is reported.

Phytotherapy Research, 1998

An aqueons extract of Bauhinia megalandra leaves causes a decrease of nearly 50% in the glucose p... more An aqueons extract of Bauhinia megalandra leaves causes a decrease of nearly 50% in the glucose production, from lactate or fructose, of rat liver slices incubated in Krebs-Ringer bicarbonate buffer supplemented with oleate-saturated albumin. In intact microsomes, the B. megalandra extract acts as a mixed non-competitive inhibitor of glucose-6-phosphatase. In the histone-disrupted microsomes the extract has no effect on glucose-6-phosphate hydrolysis. However in the presence of the extract, glucose-6-phosphatase activity was linear with time, as in the control, but at a lower level, reaching a plateau after 20 min. This suggests an inhibition of the catalytic subunit by accumulation of orthophosphate and/or glucose, as a consequence of the inhibition of its translocases (T2 and/or T3 respectively). Neither the intact nor the disrupted microsomal pyrophosphatase kinetics parameters were affected by the inclusion of the leaf extract. The above results strongly suggest that the main effect of the B. megalandra extract is the inhibition of the glucose-6-phosphate transporter (T1) of the microsomal glucose-6-phosphatase system; however, an inhibition of T3 was not ruled out. The glucose-6-phosphatase inhibition might explain the decrease in the liver slices neoglucogenic capacity and in turn could reduce glucose levels in diabetic patients.

Journal of Plastic Film & Sheeting, 2013

A computational model to design plastic food packaging is proposed. The model minimizes the cost ... more A computational model to design plastic food packaging is proposed. The model minimizes the cost of the multi-layer structure satisfying the specific product requirements, using a heuristic optimization algorithm. The product requirements are defined by the expected shelf life, the storage conditions, the water sorption isotherms of foods and the maximum allowable gain or loss of gases (O2, CO2, N2, etc.) and moisture for the packaged food. In order to assure the food shelf life, these product requirements should be fulfilled to estimate the maximum permeance values of the plastic package. The computational algorithm automatically generates different multi-layer film structures that satisfy the product requirements. This algorithm combines different polymeric materials taking into account the barrier properties and cost of each layer, the compatibility between layers, the maximum number of layers and the minimum and maximum film thickness for each layer. Temperature and relative hum...

Journal of Ethnopharmacology, 2001

A total of 21 extracts derived from 17 different plant species collected in Venezuelan Amazons ha... more A total of 21 extracts derived from 17 different plant species collected in Venezuelan Amazons have been tested for the following biological activities: cardiovascular activity, brine shrimp lethality, and inhibitory effects on the hydrolysis of glucose-6-phosphate in intact and disrupted microsomes. Eight extracts diminished rat blood pressure with or without changes in heart rate. The fruit extract of Swartzia leptopetala and the leaf and twig extract of Connarus lambertii resulted in death of experimental animals. The majority of extracts (17 extracts) showed significant toxicity against Artemia salina. Concerning the hydrolysis of glucose-6-phosphate, better inhibitory effects were observed in intact microsomes than in disrupted ones for all the extracts, suggesting that these extracts intervene with variable potency in glucose-6-phosphate transport through the microsomal membrane.

Rev. Inst. Nac. …, 2002

Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos del extracto metanóli... more Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos del extracto metanólico de las hojas de Hirtella castillanum se aislaron cuatro flavonoides: Quercetina (1), Quercetina-3-ramnósido (2), Miricetina (3) y mirecitina-3-ramnósido (4). De los ...

Rev. Inst. Nac. …, 2000

Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos (sephadex LH20 y síli... more Resumo: Mediante fraccionamientos por solubilidad y métodos cromatográficos (sephadex LH20 y sílica gel RP-18) del extracto metanólico de las hojas de licania pittieri, se aislaron cinco flavonoides: quercetina (1), quercetina-3-galactósido (2), quercetina-3-rhamnósido ( ...

Revista Internacional De Ciencias Sociales Y Humanidades Sociotam, 2011

This study integrates the results of a psychophysiological profile and the effects of the present... more This study integrates the results of a psychophysiological profile and the effects of the presentation of positive words and images. Sixty athletes from Seville (average age, 21.6 years) participated in the study, divided by gender and type of sport (individual or team). Results indicate that there are significant differences in the comparison of the conditions, in particular in temperature of the left hand: