Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

A porous silicon monolayer with porosity varying in depth was characterized using different optical methods. The results show that techniques based on reflectance in the visible region diverge in approximately 20% of those found by means of X-ray based methods. This divergence is associated to the wavelength dependence of the refractive index of both the porous structure and the infiltrated liquid inside the pores. The results suggest that the porous structure can be modeled as a set of spherical pores with radius ranging from 3.0 to 4.4 nm, in addition to cylindrical pores with radius and length varying between 22 and 42 nm, while its length does between 55 -102 nm. The porosity of the structure varies in depth between 65-81%.

The objective of this research is to determine the effect of microwaves on the concentration of casein in cow's milk for which it was used in a preliminary way a protein stability test, then a protein recognition by the method of Biuret and subsequently a quantification of proteins at 25 °C by the Sorensen method obtaining 1,17 g of casein (2.065 %). Five samples of milk of 10ml were taken each to be subjected to the microwave with exposure times of 10 s, 20 s, 30 s, 60 s and 120 s. Measuring the temperature at the end of them, which They were 29 °C, 35 °C, 44 °C, 52 °C and 77 °C. At the end of the exposure of the milk to the microwave, three aliquots of ten millilitres were taken of each of the samples to determine the percentage and amount of total casein using the Sorensen-Walker method followed by a casein isolation using an acid-base titration and addition of 1M acetic acid, concluding that the Total casein concentration in cow's milk is affected with the increase temperature inside the microwave, from a concentration of 2.065 % to 0.761 % of casein, affecting its nutritional value.  

SnO2 quantum dots were prepared via chemical precipitation assisted with ultrasonic waves. X-ray diffraction analysis (XRD) confirmed the tetragonal rutile structure of quantum dots SnO2 with crystallite size of 1.4 nm. The scanning electron microscopy (SEM) micrographs of the obtained powder sample show that the SnO2 quantum dots are agglomerated particles around 10 nm, while the transmission electron microscopy (TEM) images confirm that the crystallite size is similar to the measurement made by X-ray diffraction (XRD). The energy bandwidth of the quantum dots of SnO2 measured by UV Vis spectroscopy of diffuse reflection was 4.3 eV, showing a significant displacement attributed to the quantum confinement.  

Phytopathogenic fungi are one of the biggest problems affecting the agricultural sector, causing losses that exceed billions of dollars per year. In addition to this, antifungal resistance hinders the control of phytopathogenic fungi and it is necessary to find control alternatives of low cost that do not contaminate the environment. Therefore, the main objective of this project was to synthesize copper nanoparticles (NPs-Cu) and evaluate their antifungal activity against different phytopathogenic fungi. NPs-Cu were synthesized by the reduction method and characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The antifungal activity evaluation of the NPs-Cu was carried out against five species of phytopathogenic fungi (Fusarium solani, Fusarium verticillioides, Verticillium dahlie, Neofusicoccum sp, and Fusarium oxysporum). The results showed that the antifungal effect of NPs-Cu depends on the concentration used and species of fungus. Therefore, the NPs-Cu obtained have potential application to control phytopathogenic agents.

Se estudió la influencia de sílice de distinta procedencia y de cáscara de arroz incorporadas dentro de una matriz de polipropileno, evaluando el comportamiento físico-mecánico y morfológico de estos materiales compuestos, también evaluamos el efecto de compatibilizantes en la interfase. Establecemos que a mayor contenido de sílice, aumenta el módulo de Young, el porcentaje de absorción agua, la densidad aparente y disminuye la elongación a la ruptura, la resistencia al impacto y el índice de fluidez de los compuestos. El efecto del compativilizante VTES es mas eficiente enla interfase PP/sílice respecto al compativilizante MMI. Así mismo, establecemos que a mayor contenido de cáscara de arroz disminuye el módulo de Young, pero al utilizar compatibilizante MMI el módulo de Young y la resistencia a la tracción aumentan, consecuentemente la densidad aparente y el porcentaje de absorción de agua tienden a aumentar pero la resistencia al impacto y el índice de fluidez disminuyen, pero sus valores son mas representativos comparados a los compuestos PP/sílice. Todos los resultados están en función al incremento de sílice o cáscara de arroz en la matriz de polipropileno. Respecto al análisis térmico destacamos que con 50% de cáscara de arroz dentro de la matriz de polipropileno no existe variación de su temperatura de transición vítrea y temperatura de fusión.

The Present work aims at establishing the toxic effects on spermatogenesis of a single injection of the pesticide Malathion in young mice. For it, 50 young male Balb-C53 mice of 30 days of age was distributed aleatorily in two groups: Experimental (E) that received 1/3 de la LD50 of the commercial Malathion (Extrathion) diluted in corn oil injected intraperitoneally, and another Control (C) that only received corn oil for the same road. Treated mice and their controls were sacrificed in groups of 5 at: 4, 8, 18, 28 and 40 days after injection of the Malathion, for then to measure the count and morphology spermatic. After the injection of the Malathion was observed decrease of the spermatic count at 28 and 40 days postinjection (E: 458,00 and 519,80millons esp./ml vs C: 683,60 y 796,40millons esp./ml respectively, p£0,05) and increase of the teratozoospermia at 4 and 8 days postinjection (E: 13,60 y 8,40 % de esp. abnormal vs C: 4,60 y 2,40 % de esp. abnormal respectively, p£0,05). In conclusion the administration of a single dose of Malathion intraperitoneally it can affect the spermatogenesis of the young male mice.

This work presents a comparison between computational results, obtained through the use of the software EnergyPlus, and experimental results of the thermal behavior of an air-conditioned and non-air-conditioned environment. In order to do that, climatic data on radiation, wind speed and temperature were monitored in the period between the 11 and 20 of January 2002 and a climatic. Simultaneously, the temperatures of a test-room, situated on the 3rd floor of a building in the town of Porto Alegre, were collected. The suply and return temperatures of the air conditioners, situated in the testroom, were measured during the day, in 6 days of the monitoring period. The return air speed was measured and refrigeration sensitive capacity calculated. The results of the thermal load and the environmental temperature of the testroom obtained in the simulations were compared with the experimental data. There was a good agreement between thecomputational and experimental results.

Phospholipases D are enzymes present in all eucariotic organisms, it was first discovered in plants and in recent years, increasing attention has been paid to its roles in signal transduction in mammals. Human isoforms of this enzyme D1 and D2 were analyzed using bioinformatic tools, predicting their chemical properties responsible of their different levels of action. Besides, using local multiply alignment programs like MACAW with amino acid sequences from different organisms, three conserved blocks of sequences in all organisms were detected. Between Plant sequences and not with bacterial, high similarity was detected. When these conserved blocks of sequence was visualized in determined experimentally 3D structure of Phospolipase D from Streptomyces Sp , an structural zone having near these blocks of sequence, was observed. This zone is postulated like an important structural feature of these enzymes that possibly contain essential amino acid residues for their biological activity.

In the external gravitational field of the Gödel universe with cylindrical symmetry, exact solutions of the scalar field equation and energy spectrum of the corresponding scalar particles are obtained. First, we considered the scalar particles only in an external gravitational field of the Gödel universe. Then, we considered the particles interacting with an external electromagnetic field, which is at the same time in the external gravitational field of the Gödel universe. The solution of the scalar field equation is obtained in the form of Jacobi polynomials. The energy spectrum of scalar particles proves to be discrete, due to rotation of the universe.

The action of the brigades of health of the Traveling Local Equipment of Extramural Work in Health (ELITES) of the Ministry of Salud (MINSA) with support of the European Community, in benefit of the Peruvians from excluded zones, is little well-known. This service goes back to 1905. As of June of 1998 it was settled down like constant attention. The population of the communities when they became ill did not receive any type of attention, now are taken care of in medicine, odontology, nursing and obstetrics mainly. ELITES supports in the promotion and joint of the services organizing with the authorities of the communities in the formation of the Committees of Communal Development (CODECO). Also, it organizes and enables the health promoters. The members of the equipment arrive at the communities on foot carrying in their knapsacks the basic equipment, medicines and their personal effects. They share the food of the population and sleep in the atmospheres that they provide to them. The brigades are good image for the government in the aspect health.