oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 28 )

2018 ( 188 )

2017 ( 207 )

2016 ( 265 )

Custom range...

Search Results: 1 - 10 of 145832 matches for " F.; Varela "
All listed articles are free for downloading (OA Articles)
Page 1 /145832
Display every page Item
La alta monta a de los Andes del norte: el páramo, un ecosistema antropogénico
Varela, L. F.
Pirineos : Revista de Ecología de Monta?a , 2008,
Abstract: Current characteristics of Colombian páramos are closely related with the human presence; the history of this relation, based on evidence from climatological, palinological and cartographical studies, suggest interesting conclusions for ecosystem conservation and the surrounding Andean forests. The first páramo interventions were sporadic; later, the human imprint tended towards ritualistic livelihoods, and it is in the colonial times when dynamic transformation occurred, extending páramos both altitudinally and latitudinally. Today, in order to inform conservation policy it is important to keep in mind how the human presence influences the ecosystem transformation, to manifest Andean mountains’ management strategies and policies with a string of facts of the human livelihood and the natural history of the mountains in tropical America. Las características actuales de los páramos colombianos se relacionan estrechamente con la presencia humana; la historia de esta relación, sustentada en evidencias de estudios climatológicos, palinológicos y cartográficos, sugiere interesantes conclusiones para la conservación de este ecosistema y los bosques andinos que lo circundan. Las primeras intervenciones en el páramo eran esporádicas; posteriormente la huella humana se orientó hacia la vida ritual y es realmente en la época de la colonia donde se interviene en su dinámica de transformación, extendiendo el páramo tanto altitudinal como latitudinalmente. Hoy en día, para las directrices de conservación es importante tener en cuenta cómo influye la presencia humana en la transformación de los ecosistemas; manifestando en las políticas y estrategias del manejo de las monta as andinas un hilo acorde con la realidad vivida entre los humanos y la historia natural de las monta as del trópico americano.
Sistemas cambiarios: una visión desde la actualidad
Félix Varela Parache
Análisis Económico , 2004,
Abstract: En los últimos a os la evolución del sistema cambiario de los países más desarrollados se ha orientado hacia una flotación acompa ada de políticas monetarias regladas, ejercidas por bancos centrales independientes. En los países en desarrollo la solución es menos uniforme y la teoría de la bipolaridad constituye una simplificación excesiva no suficientemente respaldada por la realidad o por la teoría. Algunos países emergentes, con mayor desarrollo económico e institucional, se encuentran en el camino de aprender a flotar , a semejanza de los países desarrollados. Para el resto, la mejor alternativa es un régimen cambiario intermedio, que tenga en cuenta la experiencia de las crisis recientes.
Biochemistry of Bacterial Multidrug Efflux Pumps
Sanath Kumar,Manuel F. Varela
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms13044484
Abstract: Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in bacterial pathogens, these active multi-drug efflux mechanisms remain a major area of intense study, so that ultimately measures may be discovered to inhibit these active multi-drug efflux pumps.
Arbitrage in General Equilibrium  [PDF]
Oscar Varela
Modern Economy (ME) , 2012, DOI: 10.4236/me.2012.34051
Abstract: Normal trade in goods assumes two sectors that co-exist for reasons such as comparative advantage and interact via trade. Arbitrage trade in goods assumes two markets that artificially exist and converge via trade. Restoration of the law of one price via arbitrage creates one sector out of two, and in general equilibrium, equalizes opportunity cost of resources used in production. Arbitrage does not occur in a vacuum, such that when the high (low) price of a good decreases (increases) in its artificially segmented market during arbitrage, the supply of the good falls (rises), the resources used intensively in that good earn lower (higher) returns, affecting security prices, and the supply of those resources in that good’s production fall (rise).
Rheological effects in roll coating of paints
Varela López,F.; Rosen,M.;
Latin American applied research , 2002,
Abstract: the aim of this work is the study of the problems that arise during roll coating application of paints on steel sheets. we put in evidence the particular effects due to the non-newtonian properties of these fluids. at speeds above a certain critical value, the flow of paint through the applicator suffers a hydrodynamical instability called ribbing, which generates a patterned interface on the film applied. threshold of instability as well as waveform of the pattern is function of rheological properties of paints as well as surface tension. thixotropy of paints as well as shear-thinning behaviour has been determined for several industrial paints used in the steel industry, and correlated with levelling performance after application.
Rheological effects in roll coating of paints
F. Varela López,M. Rosen
Latin American applied research , 2002,
Abstract: the aim of this work is the study of the problems that arise during roll coating application of paints on steel sheets. We put in evidence the particular effects due to the non-Newtonian properties of these fluids. At speeds above a certain critical value, the flow of paint through the applicator suffers a hydrodynamical instability called ribbing, which generates a patterned interface on the film applied. Threshold of instability as well as waveform of the pattern is function of rheological properties of paints as well as surface tension. Thixotropy of paints as well as shear-thinning behaviour has been determined for several industrial paints used in the steel industry, and correlated with levelling performance after application.
Use of alternative fuels in cement manufacture. Effect on clinker and cement characteristics and properties
Puertas, F.,Blanco-Varela, M. T.
Materiales de Construccion , 2004,
Abstract: This paper compares industrial clinker and cement produced using conventional and alternative fuels (animal meal, tyres or a mixture of the two). The results show no relevant differences in terms of mineralogical composition between the clinker manufactured with alternative fuels and the product obtained using conventional fuel. Clinker produced with alternative fuels at any one factory have a very similar or even lower content in heavy metals than the product manufactured with conventional fuel in the same plant (with the sole exception of Zn when the alternative fuel used is shredded tyres). Mineralogical and morphological analyses reveal no significant differences between the two types of products that can be attributed to the type of fuel used in their manufacture. All six types of cement studied are compliant with the existing legislation as regards both physical and chemical properties. Cement compressive strength is found to be to legal standards regardless of the type of fuel used. Finally, the rheological properties of the cement paste are observed to be unaffected by the type of fuel. Se han estudiado clínkeres y cementos obtenidos en procesos industriales que han utilizado combustibles convencionales y combustibles alternativos (harinas cárnicas, neumáticos usados y mezclas de ambos). Los resultados obtenidos han demostrado que los clínkeres fabricados con los combustibles alternativos no presentan diferencias significativas en la composición mineralógica respecto a los obtenidos con combustibles convencionales. Los contenidos de metales pesados en los clínkeres procedentes de la misma fábrica (a excepción de los contenidos en Zn en aquéllos que utilizan neumáticos) son muy similares o incluso inferiores a los fabricados con combustibles convencionales. Los análisis mineralógico y morfológico de los clínkeres no evidencian diferencias asignables al tipo de combustible utilizado. Todos los cementos estudiados cumplen las normativas vigentes, tanto en relación a las características físicas como a las especificaciones químicas. El comportamiento mecánico de los cementos está ajustado a norma y es independiente del tipo de combustible utilizado. Finalmente, el comportamiento reológico de las pastas de cemento no se ve afectado por el tipo de combustible utilizado.
Problemas psicológicos y socio-laborales de las personas que sufren epilepsia, .
Félix Bermejo,M Varela,JA Forteza
Revista de la Asociación Espa?ola de Neuropsiquiatría , 1983,
Abstract: En primer lugar se exponen unas generalidades sobre el concepto actual de epilepsia, analizándose después, de forma panorámica, la problemática psicológica y socio-laboral de los epilépticos. La tercera parte de éstos presenta alteraciones psicológicas diversas, y sólo la mitad alcanza el mercado laboral competitivo. El estigma social que conlleva la epilepsia, limita, junto a los déficits individuales, la inserción social de estas personas. Se analiza el origen de la animadversión social hacia los epilépticos, que tiene una raíz psicosociológica, estudiándose los grupos sociales que contribuyen a su mantenimiento. Se concluye afirmando que es necesario un esfuerzo de los profesionales de la salud para propiciar la plena incorporación de estos sujetos en la sociedad.
Assessment of Student Skills for Critiquing Published Primary Scientific Literature Using a Primary Trait Analysis Scale
Manuel F. Varela,Marvin M. F. Lutnesky,Marcy P. Osgood
Journal of Microbiology & Biology Education , 2005, DOI: 10.1128/jmbe.v6i1.80
Abstract: Instructor evaluation of progressive student skills in the analysis of primary literature is critical for the development of these skills in young scientists. Students in a senior or graduate-level one-semester course in Immunology at a Masters-level comprehensive university were assessed for abilities (primary traits) to recognize and evaluate the following elements of a scientific paper: Hypothesis and Rationale, Significance, Methods, Results, Critical Thinking and Analysis, and Conclusions. We tested the hypotheses that average recognition scores vary among elements and that scores change with time differently by trait. Recognition scores (scaled 1 to 5), and differences in scores were analyzed using analysis of variance (ANOVA), regression, and analysis of covariance (ANCOVA) (n = 10 papers over 103 days). By multiple comparisons testing, we found that recognition scores statistically fell into two groups: high scores (for Hypothesis and Rationale, Significance, Methods, and Conclusions) and low scores (for Results and Critical Thinking and Analysis). Recognition scores only significantly changed with time (increased) for Hypothesis and Rationale and Results. ANCOVA showed that changes in recognition scores for these elements were not significantly different in slope (F1,16 = 0.254, P = 0.621) but the Results trait was significantly lower in elevation (F1,17 = 12.456, P = 0.003). Thus, students improved with similar trajectories, but starting and ending with lower Results scores. We conclude that students have greatest difficulty evaluating Results and critically evaluating scientific validity. Our findings show extant student skills, and the significant increase in some traits shows learning. This study demonstrates that students start with variable recognition skills and that student skills may be learned at differential rates. Faculty can use these findings or the primary trait analysis scoring scale to focus on specific paper elements for which they desire to improve recognition.
Synthesis and Evaluation of Highly Tolerant Pd Electrocatalysts as Cathodes in Direct Ethylene Glycol Fuel Cells (DEGFC)
F. Javier Rodríguez Varela,Sergio Fraire Luna,Oumarou Savadogo
Energies , 2009, DOI: 10.3390/en20400944
Abstract: Highly selective Pd electrocatalysts were synthesized by the formic acid (FA) method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence of ethylene glycol (EG, C 2H 6O 2), Pd/C exhibited a noteworthy electrochemical behavior and full tolerance to the organic molecule. No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the ORR ( E onset) toward more negative potentials was negligible on this cathode. As a comparison, commercial Pt/C was tested under the same conditions showing a poor selectivity for the ORR when EG was present. The detrimental effect of EG on the Pt electrocatalysts resulted in high intensity current density peaks due to the oxidation of EG and a significant shift in E onset. The evaluation of Pd/C in a DEGFC operating at 80 °C demonstrated its good performance as cathode material. Given these results, it is expected that highly efficient Pd-based cathodes can find application in DEGFCs.
Page 1 /145832
Display every page Item


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