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Search Results: 1 - 10 of 9556 matches for " Jose Avila "
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Conductive and convective heat transfer in fluid flows between differentially heated and rotating cylinders
Jose M. Lopez,Francisco Marques,Marc Avila
Physics , 2015, DOI: 10.1016/j.ijheatmasstransfer.2015.07.026
Abstract: The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the cylinders are assumed to be of infinite length or periodic in the axial direction, in which cases heat transfer occurs only through conduction as in a solid. We here investigate numerically heat transfer and the onset of turbulence in such flows by using both periodic and no-slip boundary conditions in the axial direction. We obtain a simple linear criterion that determines whether the infinite-cylinder assumption can be employed. The curvature of the cylinders enters this linear relationship through the slope and additive constant. For a given length-to-gap aspect ratio there is a critical Rayleigh number beyond which the laminar flow in the finite system is convective and so the behaviour is entirely different from the periodic case. The criterion does not depend on the Prandtl number and appears quite robust with respect to the Reynolds number. In particular, it continues to work reasonably in the turbulent regime.
A chemical imaging and Nano-ARPES study of well-ordered thermally reduced SrTiO3(100)
Emmanouil Frantzeskakis,Jose Avila,Maria C. Asensio
Physics , 2011, DOI: 10.1103/PhysRevB.85.125115
Abstract: The structural and electronic properties of thermally reduced SrTiO3(100) single crystals have been investigated using a probe with real- and reciprocal-space sensitivity: a synchrotron radiation microsopic setup which offers the possibility of Scanning Photoemission Microscopy and Angle Resolved Photoelectron Spectroscopy (ARPES) down to the nanometric scale. We have spectroscopically imaged the chemical composition of samples which present reproducible and suitable low-energy electron diffraction patterns after following well-established thermal reduction protocols. At the micrometric scale, Ca-rich areas have been directly imaged using high-energy resolution core level photoemission. Moreover, we have monitored the effect of Ca segregation on different features of the SrTiO3(100) electronic band structure, measuring ARPES inside, outside and at the interface of surface inhomogeneities with the identified Ca-rich areas. In particular, the interaction of Ca with the well-known intragap localized state, previously attributed to oxygen vacancies, has been investigated. Moreover, the combination of direct imaging and spectroscopic techniques with high spatial resolution has clarified the long-standing dilemma related to the bulk or surface character of Ca segregation in SrTiO3. Our results present solid evidence that the penetration depth of Ca segregation is very small. In contrast to what has been previously proposed, the origin of long-range surface reconstructions can unlikely be associated to Ca due to strong local variations of its surface concentration.
The Boussinesq approximation in rapidly rotating flows
Jose M. Lopez,Francisco Marques,Marc Avila
Physics , 2013, DOI: 10.1017/jfm.2013.558
Abstract: In commonly used formulations of the Boussinesq approximation centrifugal buoyancy effects related to differential rotation, as well as strong vortices in the flow, are neglected. However, these may play an important role in rapidly rotating flows, such as in astrophysical and geophysical applications, and also in turbulent convection. We here provide a straightforward approach resulting in a Boussinesq-type approximation that consistently accounts for centrifugal effects. Its application to the accretion-disk problem is discussed. We numerically compare the new approach to the typical one in fluid flows confined between two differentially heated and rotating cylinders. The results justify the need of using the proposed approximation in rapidly rotating flows.
Obtaining the Minimum Lethal Dose against Fasciola hepatica in Vitro Using Plant Extract Hexanes with Fasciolicide Activity and Toxicity Evaluation on CD1 Male Mice  [PDF]
Stephanie Ibarra-Moreno, Froylan Ibarra-Velarde, Jose Guillermo Avila-Acevedo
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.37106
Abstract: Fascioliasis is a parasitic disease of worldwide distribution affecting mainly cattle and sheep. Its importance lies in the economic losses it produces in the livestock industry. Its control is carried out by using a chemical fasciolicide showing resistance problems and environmental contamination. Looking for an alternative control for this disease the present study was aimed at determining the hexane anti-Fasciola hepatica in the in vitro effect of some plant extracts and the minimum lethal dose of the mentioned extracts. All selected plants were tested in vitro at concentrations of 500, 250, 125 and 50 mg/L):Achilleamillefolium (plumajillo), Artemisiaabsinthium (wormwood), Artemisia mexicana (estafiate), Castelatortuousa (chaparroamargo), Chenopodiumgraveolens (epazote de zorrillo), Gymnospermaglutinosum (popote) Justicia spicigera (muicle), Limpia critridora (cedron), Lippiagraveolens (oregano), Menthapiperita (Mint), Populus alba (alamo) and Thymusvulgaris (thyme). Subsequently proceeded to perform a toxicity study with these fractions in CD1 male mice 10-13 weeks of age, forming groups of 3-5 animals they were administered a single oral dose being (5 mg/kg, 50 mg/kg, 500 mg/kg, 2500 mg/kg and 5000 mg/kg) and were kept under observation 20 days, later were sacrificed and a kidney and liver histology was performed, finding the safety of the extracts. To perform the toxicity study with these fractions, groups of five CD1 male-mice were formed, they were treated with oral doses of 5, 50, 500, 2500 and 5000 mg/kg, administered with a cannule. All mice were kept under observation for 20 days. Finally they were sacrificed to perform histology of the kidney and liver in search of possible side effects. Results show that none of the extracts exhibited that fasciolocide activity for mice CD1 even at the highest dose thereforefinding the safety of the extracts.
The NT-ProBNP Test in Subjects with End-Stage Renal Disease on Hemodialysis Presenting with Acute Dyspnea: Is Knowing Worth the Cost?
Shaffer R. S. Mok,Jose Avila,Barry Milcarek,Richard Kasama
Emergency Medicine International , 2013, DOI: 10.1155/2013/836497
The NT-ProBNP Test in Subjects with End-Stage Renal Disease on Hemodialysis Presenting with Acute Dyspnea: Is Knowing Worth the Cost?
Shaffer R. S. Mok,Jose Avila,Barry Milcarek,Richard Kasama
Emergency Medicine International , 2013, DOI: 10.1155/2013/836497
Abstract: Background. The NT-ProBNP/BNP test has been validated as a marker for determining the etiology of acute dyspnea. In the setting of end-stage renal disease on hemodialysis (ESRD on HD), the utility of the NT-ProBNP/BNP test has not been validated. This study examines the clinical utility of the NT-ProBNP test in the setting of ESRD on HD patients presenting with acute dyspnea. Methods. A retrospective case series of 250 subjects were admitted to Cooper University Hospital, 07/2010-03/2011, with ESRD and HD presenting with dyspnea. The incidences of echocardiography, cardiology consultation, and NT-ProBNP elevated and normal were examined. Correlation coefficients were calculated for NT-ProBNP with age (years), estimated dry weight (kg), amount of fluid removed (L), and ejection fraction (EF in %) among other echocardiography parameters. Results. Of the total sample 235 patients had NT-ProBNP levels performed. Cardiology consults were placed in 68.8% and 58% who underwent echocardiography. Of those for whom an echocardiography was performed estimated mean EFs of 54.6%, 50.8%, and 61.7% were observed among the NT-ProBNP elevated group, normal group, and no NT-ProBNP group, respectively. No differences were detected in all other echocardiography measurements. No correlation was observed between NT-ProBNP and age ( ), baseline EDW ( ), amount of fluid removed ( ), or EF ( ). Conclusion. In the setting of ESRD on HD, the NT-ProBNP test has no clinical utility in determining the etiology of acute dyspnea. This can be demonstrated through echocardiographic and therapeutic parameters measured in this study. 1. Introduction Both N-Terminus Pro Brain Natriuretic Peptide (NT-ProBNP) and Brain Natriuretic Peptide (BNP) hormones have been used in patients presenting with a chief complaint of dyspnea to predict whether Left Ventricular Systolic Dysfunction (LVSD) is causative for this symptom. The breathing not properly data and studies by Morrison, et al. demonstrated a high positive predictive value (PPV) for predicting congestive heart failure as the etiology of patients presenting with dyspnea to the emergency department [1–5]. The sensitivity and specificity of the BNP assay has been reported to be high, if serum concentrations are greater than 100 picograms per milliliter (pg/mL) for BNP and 500?pg/mL for NT-ProBNP for predicting LVSD as the etiology of dyspnea [6, 7]. Thus with a high pretest probability, members of the emergency department utilize the NT-ProBNP and BNP in the decision tree to treat patients presenting with dyspnea. The presence of chronic
New Bounds for Ternary Covering Arrays Using a Parallel Simulated Annealing
Himer Avila-George,Jose Torres-Jimenez,Vicente Hernández
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/897027
Abstract: A covering array (CA) is a combinatorial structure specified as a matrix of N rows and k columns over an alphabet on v symbols such that for each set of t columns every t-tuple of symbols is covered at least once. Given the values of t, k, and v, the optimal covering array construction problem (CAC) consists in constructing a CA (N; t, k, v) with the minimum possible value of N. There are several reported methods to attend the CAC problem, among them are direct methods, recursive methods, greedy methods, and metaheuristics methods. In this paper, There are three parallel approaches for simulated annealing: the independent, semi-independent, and cooperative searches are applied to the CAC problem. The empirical evidence supported by statistical analysis indicates that cooperative approach offers the best execution times and the same bounds as the independent and semi-independent approaches. Extensive experimentation was carried out, using 182 well-known benchmark instances of ternary covering arrays, for assessing its performance with respect to the best-known bounds reported previously. The results show that cooperative approach attains 134 new bounds and equals the solutions for other 29 instances.
Registro de Pinus discolor Bailey et Hawksworth en la Sierra de Monte Grande, San Luis Potosí, México.
Jose Antonio Avila Naranjo,Edmundo Garcia Moya,Juan Antonio Reyes Aguero
Acta botánica mexicana , 1992,
Calcium and potassium silicates and the growth of Eucalyptus grandis seedlings Aplica o de silicatos de cálcio e de potássio e o crescimento de mudas de Eucalyptus grandis
Itamar Antonio Bognola,Lina Avila Clasen,Luziane Franciscon,Jose Luiz Gava
Pesquisa Florestal Brasileira , 2011, DOI: 10.4336/2012.pfb.66.83
Abstract: The use of silicate is a practice that has been frequently adopted in annual crops, although few studies have been conducted in order to verify its efficiency in forest tree species. The main objective of this research was to evaluate the effect of calcium and potassium silicates in the growth of seedlings of Eucalyptus grandis. The experiment was conducted in a greenhouse, in Alambari county, State of S o Paulo. A completely randomized experimental design was adopted, with eight treatments, three replications and 25 plants per plot, maintained at the field capacity moisture level. Seedlings were planted in plastic tubes using local substrate, basic fertilization and silicates. Diameter, height and fresh and dry biomass of the seedlings were determined 150 days after silicates treatments were applied. The use of silicates either in the substrate or through foliar application, in the production of eucalypt seedlings has proven to be inadequate when the substrate presents a balanced basic composition in terms of nutrients and pH. doi: 10.4336/2011.pfb.31.66.83 O uso de silicato é uma prática que vem sendo adotada com frequência em culturas anuais, muito embora poucos trabalhos tenham sido realizados com intuito de verificar sua eficiência em espécies florestais arbóreas. O objetivo principal desta pesquisa foi avaliar o efeito da aplica o de silicatos de cálcio e de potássio no crescimento de mudas de Eucalyptus grandis. O experimento foi conduzido em casa de vegeta o, no Município de Alambari, SP. O delineamento usado foi inteiramente ao acaso, com oito tratamentos, três repeti es e 25 plantas por parcela, sendo mantidas na umidade de capacidade de campo. As mudas foram plantadas em tubetes de plástico, utilizando substrato local, com aduba o básica e silicatos. Diametro de colo, altura e biomassa verde e seca das mudas foram determinados 150 dias após a aplica o dos silicatos. Verificou-se que a aplica o dos silicatos, via substrato ou foliar, em mudas de eucalipto, mostrou-se inadequada quando o substrato utilizado apresentou composi o básica equilibrada em termos de nutrientes e pH. doi: 10.4336/2011.pfb.31.66.83
Propuesta de un banco de colectores solares para climatizar una piscina y molino de bombeo para el espejo de agua de un hotel.
Leovel Ismael Aguiar Bola?os,Julio Esnard Long,Juan Israel Veliz Alonso,Jose Luis Sanchez Avila
Avanzada Científica , 2010,
Abstract: En este trabajo se realiza una propuesta de un banco de colectores solares para la obtención de agua caliente en la climatización de una piscina y otra de un molino de viento de extracción de agua salada a partir de energía eólica para el Hotel Sandals de Varadero. La revisión bibliográfica evidencia resultados acerca del comportamiento de la capacidad instalada para el calentamiento y extracción de agua a partir de energía renovable tanto en Cuba como en el Mundo. Se realiza el procesamiento de los datos climatológicos y se emplea Software TK Solver para dimensionar el sistema. El cálculo económico realizado como una variable factible la utilización de un banco de colectores solares en el calentamiento de la piscina y la extracción de agua salada de un pozo para los espejos de agua del hotel.
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