oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 5 )

2019 ( 229 )

2018 ( 281 )

2017 ( 284 )

Custom range...

Search Results: 1 - 10 of 224703 matches for " C. Vargas-Aburto "
All listed articles are free for downloading (OA Articles)
Page 1 /224703
Display every page Item
Optical effects by high energy electrons in additively colored KCl and KBr crystals
R. Aceves,R. Pérez-Salas,T.M. Piters,C. Vargas-Aburto
Revista mexicana de física , 2008,
Abstract: Radiation effects of high energy electrons on pure and additively colored (AC) KCl and KBr crystals have been studied by optical absorption in the 200-800 nm range at RT. Besides the main F-center related absorption band at 553 nm, the F+ 2 (670 nm) and F2 (740 nm) bands (R1 and R2 centers in old notation) ascribed to F centers aggregates in additively colored KCl are clearly observed. After electron irradiation with energy of 1.0 MeV and doses of 100 kGy or 3.5 MeV and 180 kGy, the F+ 2 and F2 bands are strongly diminished, the intensity of the F bands is increased and its peak lightly shifted to low energy at 558 nm. In KBr, the related absorption band maximum for the pure and AC samples after irradiation shows the same peak position as the F-center absorption. For AC KBr the intensity of this peak versus accumulative doses shows a maximum around 300 kGy but in pure KBr the peak continuously increases. In contrast, KCl does not show such dependence on accumulative doses. For both samples, the electron irradiation induce at least two bands in the 210-300 nm (UV bands) range that has been related with hole centers (V bands). The results have been analyzed in terms of surface close F centers and alkali and halogen ions desorption processes.
Optical effects by high energy electrons in additively colored KCl and KBr crystals
Aceves, R;Pérez-Salas, R;Piters, T.M.;Vargas-Aburto, C;Uribe, R.M.;
Revista mexicana de física , 2008,
Abstract: radiation effects of high energy electrons on pure and additively colored (ac) kcl and kbr crystals have been studied by optical absorption in the 200-800 nm range at rt. besides the main f-center related absorption band at 553 nm, the f+2 (670 nm) and f2 (740 nm) bands (r1 and r2 centers in old notation) ascribed to f centers aggregates in additively colored kcl are clearly observed. after electron irradiation with energy of 1.0 me v and doses of 100 kgy or 3.5 me v and 180 kgy, the f+2 and f2 bands are strongly diminished, the intensity of the f bands is increased and its peak lightly shifted to low energy at 558 nm. in kbr, the related absorption band maximum for the pure and ac samples after irradiation shows the same peak position as the f-center absorption. for ac kbr the intensity of this peak versus accumulative doses shows a maximum around 300 kgy but in pure kbr the peak continuously increases. in contrast, kcl does not show such dependence on accumulative doses. for both samples, the electron irradiation induce at least two bands in the 210-300 nm (uv bands) range that has been related with hole centers (v bands). the results have been analyzed in terms of surface close f centers and alkali and halogen ions desorption processes.
Petroleum biotechnology: Technology trends for the future
C Montiel, R Quintero, J Aburto
African Journal of Biotechnology , 2009,
Abstract: This paper comes out from the need to provide a general overview of the current biotechnology situation and its future impact on the petroleum industry. This important industrial sector already encounters challenges as the decreasing oil reserves, the fluctuating oil prices, the increasing demand of petroleum, fuels and petrochemicals and finally more strict environmental regulations. These challenges will persist and strengthen in the following years. Biotechnology has come a long way since the 1950's and today impacts different industrial sectors such as food, pharmaceutics, medicine, agriculture, textile, etc. Because of good experiences of the above industries, the petroleum industry interests is now in biotechnology as an alternative technology to resolve the challenges and needs of this worldwide important sector. We described throughout the paper the main factors that drive or restrain research and development (R&D) in biological processes applied to petroleum industry. Moreover, we identified several challenges and opportunities, where R&D in petroleum biotechnology plays an important role to surmount the industrial needs during the following years.
Perfil integral del candidato al Programa de Alta Exigencia Académica (PAEA) de la Facultad de Medicina de la Universidad Nacional Autónoma de México (UNAM)
Ingrid Vargas,Mónica Aburto,José Cortés,Asunción álvarez
Salud mental , 2010,
Abstract: En la Facultad de Medicina, como en algunas otras de la Universidad Nacional Autónoma de México, existe un Programa de Alta Exigencia Académica (PAEA), el cual busca probar métodos de ense anza novedosos para formar recursos capaces de desarrollarse en condiciones especiales de trabajo. Esto se lleva a cabo por medio de un programa en que el alumno lleva, además de las actividades regulares establecidas en el currículum de la carrera, algunas otras planeadas específicamente para estos grupos y que demandan mayores exigencias para los estudiantes que forman parte de ellos. Dadas estas características del PAEA en la Facultad de Medicina, es prioritaria una evaluación integral de los candidatos que formarán parte del programa, la cual debe incluir aspectos cognoscitivos, emocionales, personales y sociales. Por ello, el objetivo de este estudio fue establecer el perfil de los alumnos del PAEA a partir del análisis y la comparación de las características de la población de candidatos que se postularon para ingresar a este programa durante la promoción 2009-2010. Material y métodos Estudio transversal comparativo en el cual se incluyó a todos aquellos estudiantes de primer ingreso (ciclo 2009-2010) que solicitaron de manera voluntaria ingresar al proceso de selección del PAEA, que tuvieron por lo menos 8.5 de promedio en el bachillerato y que completaron los instrumentos de evaluación. Se aplicaron: el Inventario Multifásico de la Personalidad Minnesota-2 (MMPI-2), la subescala de razonamiento abstracto del Test de Aptitudes Diferenciales (DAT), y una entrevista semiestructurada dise ada expresamente para esta evaluación. Los datos obtenidos se manejaron con estadísticos descriptivos, regresión lineal múltiple, regresión logística, análisis de clusters y análisis factorial...
Perfil integral del candidato al Programa de Alta Exigencia Académica (PAEA) de la Facultad de Medicina de la Universidad Nacional Autónoma de México (UNAM)
Vargas, Ingrid;Aburto, Mónica;Cortés, José;álvarez, Asunción;Ramírez, Claudia;Farfán, Aurora;Heinze, Gerhard;
Salud mental , 2010,
Abstract: the importance to assess in a comprehensive way the cognitive, emotional, personal and social features of the students entering medical school is recognized nowadays in order to select from the candidates, not just those with high cognitive abilities, but also the ones with a vocation and interest in the study of this science. these are characteristics that should be specially sought among the students of high performance academic groups. in the department of medicine, as it is in some other departments at the universidad nacional autónoma de méxico (unam), there is a special plan called high academic performance program (paea), which aims to test innovative teaching models to generate health resources able to operate in special working conditions. medicine students enrolled at the paea have a particular schedule which includes, in addition to the program established at the regular curriculum, some other specific activities, meaning greater demand for them. these special training includes activities such as: early introduction to research labs, based-problem learning, methodology workshops, introductory course in computing, and personalized assistance from academic tutors. it is because of these peculiar features, that, with this study, we aim to determine the profile of the students of the paea from the analysis and comparison of the candidates' characteristics. materials and methods this was a comparative cross-sectional study that included all the first entry students at the department of medicine who applied to enter the selection process of the paea at the 2009-2010 period. these candidates were required to ask voluntarily to be included in the selection process to be part of paea, and to demonstrate at least a high school grade of 8.5, and to complete the assessment instruments. for this study, the assessment instruments used were: minnesota multiphasic personality inventory (mmpi-2), differential aptitude test (dat) sub-scale of abstract reasoning, and a semi
Computed tomographic anatomy of the larynx in mesaticephalic dogs
Pérez,B; Gómez,M; Mieres,M; Galecio,JS; Yefi,C; Aburto,P;
Archivos de medicina veterinaria , 2010, DOI: 10.4067/S0301-732X2010000100013
Abstract: the aim of this work was to describe the normal anatomy of the larynx and its adjacent structures in mesaticephalic dogs by computed tomographic (ct) images and correlate those with anatomical sections. for that, 2 clinically normal young-adult mesaticephalic dogs with body weight of 12.8 kg and 18.5 kg, respectively were used. computed tomography of the larynx was performed in 2 dogs under general anesthesia and in dorsal recumbency. transverse images of the larynx with a slice thickness of 3 mm and a gap of 2 mm interval were obtained using a soft tissue window. ct images were correlated with anatomical cross-sections views. the central cavity of the larynx that includes the laryngeal vestibule, glottis and infraglottic cavities were observed as hypodense areas in all ct images. other spaces also identified included the piriform recess, the epiglottic vallecula and the laryngeal ventricles. the thyroid and the cricoid cartilages were clearly represented as linear hyperdense structures. the arytenoid cartilages were only minimally calcified due to the young age of the animals therefore poorly seen on ct. the epiglottis was identified as a transverse concave isodense structure. results indicated that ct provides an excellent method for imaging evaluation of the complex anatomy of the larynx in dogs.
Microencapsula??o de óleo essencial de laranja
ABURTO, Lucy C.;TAVARES, Débora de Queiroz;MARTUCCI, Enny Therezinha;
Ciência e Tecnologia de Alimentos , 1998, DOI: 10.1590/S0101-20611998000100010
Abstract: it was done microencapsulation of natural essencial orange oil through spray-drying. the purpose was to use the best proportion of wall materials among maltodextrin, acacia gum, and modified starch (capsul) in order to retain greater amount of orange oil. the orange oil (10%) and maltodextrin (36%) remained constant. three spray drying temperatures were employed: 180°c, 200°c and 220°c, therefore, nine final products were obtained. the superficial and inner oil concentrations were measured. the microcapsules were also examined through optical and scanning electron microscopy. the three temperatures employed did not affect the microencapsulation. the microstructure of the capsules were almost similar regardless the proportion employed among the carbohydrates to wall composition. at light microscopy it was observed a great heterogeneity of capsules diameters, and probably not smooth surfaces; at scanning electron microscopy it was clear that the walls displayed porosity over round surfaces. the best retention was given by the formula containing 10% of capsul, 10% of orange oil and 36% of maltodextrin, when total oil retention was 94%, regardless the drying temperature here employed.
Microencapsula o de óleo essencial de laranja
ABURTO Lucy C.,TAVARES Débora de Queiroz,MARTUCCI Enny Therezinha
Ciência e Tecnologia de Alimentos , 1998,
Abstract: Microcápsulas contendo óleo de laranja foram obtidas utilizando secagem por atomiza o. Para a análise da influência dos componentes na reten o total de óleo, prepararam-se três formula es com concentra es diferentes de goma arábica e amido modificado, mantendo constante a concentra o de maltodextrina (36%) e óleo (10%). As três fórmulas receberam três tratamentos térmicos (180°C, 200°C e 220°C), resultando na obten o de nove produtos. As reten es de óleo superficial e interno das microcápsulas foram quantificadas e um estudo microscópico da estrutura das microcápsulas foi realizado. Os resultados demonstraram que a microestrutura das cápsulas eram similares e que as três temperaturas empregadas n o alteraram a microencapsula o. A microscopia ótica revelou microcápsulas globosas, com diametros variáveis e superfícies irregulares. Ao microscópio eletr nico de varredura verificou-se que as faces das microcápsulas eram predominantemente rugosas, exibiam perfura es e quando quebradas demonstravam paredes porosas. A forma e os diametros das microcápsulas n o dependeram do amido modificado, mas sua presen a conferiu melhor reten o de óleo. A maior reten o de óleo, 94%, foi obtida com a fórmula contendo 10% de amido modificado, 36% de maltodextrina e 10% de óleo essencial de laranja, independente da temperatura de secagem.
Electrokinetic and hydrodynamic properties of charged-particles systems: From small electrolyte ions to large colloids
G. N?gele,M. Heinen,A. J. Banchio,C. Contreras-Aburto
Physics , 2013, DOI: 10.1140/epjst/e2013-02062-3
Abstract: Dynamic processes in dispersions of charged spherical particles are of importance both in fundamental science, and in technical and bio-medical applications. There exists a large variety of charged-particles systems, ranging from nanometer-sized electrolyte ions to micron-sized charge-stabilized colloids. We review recent advances in theoretical methods for the calculation of linear transport coefficients in concentrated particulate systems, with the focus on hydrodynamic interactions and electrokinetic effects. Considered transport properties are the dispersion viscosity, self- and collective diffusion coefficients, sedimentation coefficients, and electrophoretic mobilities and conductivities of ionic particle species in an external electric field. Advances by our group are also discussed, including a novel mode-coupling-theory method for conduction-diffusion and viscoelastic properties of strong electrolyte solutions. Furthermore, results are presented for dispersions of solvent-permeable particles, and particles with non-zero hydrodynamic surface slip. The concentration-dependent swelling of ionic microgels is discussed, as well as a far-reaching dynamic scaling behavior relating colloidal long- to short-time dynamics.
?QUé PERCEPCIóN TENEMOS DE LOS INSECTOSPALO (Insecta: Phasmatodea)?
VARGAS C,MAURICIO; ,;
Acta Biológica Colombiana , 2006,
Abstract: a compillatory study was carried out about the relationship that people have with stick and leaf insects (insecta: phasmatodea). stands out, the importance that these insects have in differents cultures, the form of appreciating them, perceiving and interacting with them. some etnotaxonomics aspects are described, as well as credo, uses and customs, graphic representations, and literary and film productions of these insects in different human groups. in this study it is proposed that etnophasmatology is the discipline dedicated to know the relationships that the different cultures have with the stick and leaf insects.
Page 1 /224703
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.