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Search Results: 1 - 10 of 597440 matches for " M. J. Castillo "
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Modeling extreme values by the residual coefficient of variation
J. Castillo,M. Padilla
Statistics , 2015,
Abstract: The possibilities of the use of the coefficient of variation over a high threshold in tail modelling are discussed. The paper also considers multiple threshold tests for a generalized Pareto distribution, together with a threshold selection algorithm. One of the main contributions is to extend the methodology based on moments to all distributions, even without finite moments. These techniques are applied to Danish fire insurance losses.
ENFERMEDAD RESPIRATORIA EN POTROS: REPORTE DE 20 CASOS (2000-2004)
Castillo M. C.,Oliver O. J.
Revista de la Facultad de Medicina Veterinaria y de Zootecnia , 2006,
Abstract: Se presentan las principales características clínicas y paraclínicas de 20 casos de enfermedad respiratoria en potros menores de un a o de edad, admitidos en la Clínica de Grandes Animales de la Universidad Nacional de Colombia, entre los a os 2000 y 2004. Los datos obtenidos son similares a los que reporta la literatura. Los exámenes paraclínicos con mayor utilidad en el diagnóstico fueron el análisis del lavado traqueobronquial y los hallazgos en la radiografía de tórax; no obstante, en algunos casos, el examen clínico fue el único medio para llegar al diagnóstico y así instaurar una terapia temprana. Los problemas respiratorios son frecuentes en criaderos, no prestándoles la debida atención.
Assessing student understanding of physical hydrology
J. A. Marshall, A. J. Castillo,M. B. Cardenas
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2013,
Abstract: Our objective is to devise a mechanism to characterize and assess upper division and graduate student thinking in hydrology. We accomplish this through development and testing of an assessment tool for a physical hydrology class. The instrument was piloted in two sections of a physical hydrology course. Students were asked to respond to two questions that probed understanding and one question that assessed their ability to apply their knowledge, both prior to and after the course. Student and expert responses to the questions were classified into broad categories to develop a rubric to score responses. Using the rubric, three researchers independently blind-coded the full set of pre- and post-artifacts, resulting in 89% inter-rater agreement on the pre-tests and 83% agreement on the post-tests. The majority of responses made by students at the beginning of the class were characterized as showing only recognition of hydrology concepts from a non-physical perspective; post surveys indicated that the majority had moved to a basic understanding of physical processes, with some students achieving expert understanding. Our study has limitations, including the small number of participants who were all from one institution and the fact that the rubric was still under development. Nevertheless, the high inter-rater agreement from a group of experts indicates that the process we undertook is potentially useful for assessment of learning and understanding physical hydrology.
Assessing student understanding of physical hydrology
J. A. Marshall,A. J. Castillo,M. B. Cardenas
Hydrology and Earth System Sciences Discussions , 2012, DOI: 10.5194/hessd-9-10095-2012
Abstract: Our objective is to characterize and assess upper division and graduate student thinking in hydrology. We accomplish this through development and testing of an assessment tool for a physical hydrology class. Students were asked to respond to two questions that probed understanding and one question that assessed their ability to apply their knowledge. Student and expert responses to the questions were then used to develop a rubric to score responses. Using the rubric, three researchers independently blind-coded the full set of pre and post artifacts, resulting in 89% inter-rater agreement on the pre-tests and 83% agreement on the post-tests. This result has limitations, including the small number of participants who were all from one institution and the fact that the rubric was still under development. Nevertheless, the high inter-rater agreement from a group of experts is significant; the rubric we developed is a potentially useful tool for assessment of learning and understanding physical hydrology.
Glutatión peroxidasa (GSH-Px) en las patologías asociadas a deficiencias de selenio en rumiantes Glutathione peroxidase (GSH-Px) in ruminants associated to selenium deficiency pathologies
M LOPEZ ALONSO,M MIRANDA,J HERNANDEZ,C CASTILLO
Archivos de medicina veterinaria , 1997,
Abstract: El selenio constituye uno de los micronutrientes esenciales para los animales, siendo necesario un adecuado aporte de este elemento en la dieta para el mantenimiento de la salud y de la reproducción. La mayor parte del selenio se encuentra contenido en el interior de las células rojas como componente de la glutatión peroxidasa (GSH-Px, E.C. 1.11.1.9), enzima que juega un papel central en los procesos celulares de óxido-reducción, al suponer un importante mecanismo de defensa celular contra las formas de oxígeno altamente reactivas (radicales libres) que se producen en el organismo durante el metabolismo aerobio habitual. En este trabajo se examinaron detalladamente los mecanismos patogénicos de las alteraciones orgánicas que obedecen a deficiencias de selenio en rumiantes. La incapacidad del animal de responder al ataque peroxidativo de los radicales libres en todos estos procesos hace que se piense en la GSH-Px dependiente de selenio como el mecanismo principal de actuación de este elemento, y por ello esta enzima se convierte en una medida indirecta de gran importancia en el diagnóstico clínico de procesos carenciales de selenio Selenium is an essential microelement for animals; an adequate level of this element is necessary in the diet, to maintain health and reproduction. Most of the selenium is in the erythrocytes as a component of the enzyme glutathione peroxidase (GSH-Px. E.C. 1.11.1.9). This enzyme plays a major role in the cellular antioxidant defense system against oxygen radicals (free radicals), potentially harmful pro-oxidants that are produced during aerobic metabolism. In this work the pathogenic mechanisms of selenium deficiencies in ruminants were examined. The inability of the animal to react against peroxidative damage of free radicals in all of these nutritional deficiencies indicates that GSH-Px represents the main functions of selenium in the organism, and it makes this enzyme a very important tool for clinical diagnosis
Parámetros bioquímico-endocrinos de utilidad en la etapa del crecimiento y desarrollo del Ovejero Alemán, Doberman y Gran Danés
CASTILLO,V.; MARQUEZ,A.; RODRIGUEZ,M.; LALIA,J.;
Archivos de medicina veterinaria , 1997, DOI: 10.4067/S0301-732X1997000100012
Abstract: to control the process of growth, the factors that intervene in it and the parameters useful to evaluate these factors must be taken into account. information about the normal biochemical-endocrine values according to age, breed and sex, is scarce in veterinary medicine . 800 normal puppies (350 german sheepdogs, 270 dobermans and 180 great danes) from buenos aires city and surroundings, divided according to age, sex and breed were evaluated. the age of the puppies ranged between 30 days and 8 months (after this age, growth was not considered significant). ca, inorganic phosphorus (pi), total protein (tot. prot.), albumine, creatinine phosphokinase (cpk), serum alkaline phosphatase (sap) and mg were determined. triiodotironine (t3) , tiroxine (t4) and free tiroxine (ft4) were evaluated by the radio immune assay method. statistical methods used were: percentiles 3, 50 and 97, one way anova, tukey and bonferroni tests. there were no significant differences (p 0.05) due to breed and sex. significant differences (p < 0.05) according to age were found only for: sap, pi, tot. prot., cpk and t4. the ca, mg, albumine, t3 and ft4 did not present significant differences according to age (p 0.05). it was concluded that normal biochemical and endocrine values will help in the prophylaxis, precocious and accurate diagnosis of the etiology that affects growth
Hallazgo de Ehrlichia canis en Chile, informe preliminar
LóPEZ,J.; CASTILLO,A.; MU?OZ,M.; HILDEBRANDT,S.;
Archivos de medicina veterinaria , 1999, DOI: 10.4067/S0301-732X1999000200008
Abstract: the first case of canine ehrlichiosis detected in chile is described. it is caused by the rickettsia ehrlichia canis and carried by the vektor rhipicephalus sanguineus. the clinical diagnosis was confirmed in germany using the immunofluorescent antibody test (ifa)
Mimetic finite difference methods in image processing
Bazan, C.;Abouali, M.;Castillo, J.;Blomgren, P.;
Computational & Applied Mathematics , 2011, DOI: 10.1590/S1807-03022011000300012
Abstract: we introduce the use of mimetic methods to the imaging community, for the solution of the initial-value problems ubiquitous in the machine vision and image processing and analysis fields. pde-based image processing and analysis techniques comprise a host of applications such as noise removal and restoration, deblurring and enhancement, segmentation, edge detection, inpainting, registration, motion analysis, etc. because of their favorable stability and efficiency properties, semi-implicit finite difference and finite element schemes have been the methods of choice (in that order of preference). we propose a new approach for the numerical solution of these problems based on mimetic methods. the mimetic discretization scheme preserves the continuum properties of the mathematical operators often encountered in the image processing and analysis equations. this is the main contributing factor to the improved performance of the mimetic method approach, as compared to both of the aforementioned popular numerical solution techniques. to assess the performance of the proposed approach, we employ the catté-lions-morel-coll model to restore noisy images, by solving the pde with the three numerical solution schemes. for all of the benchmark images employed in our experiments, and for every level of noise applied, we observe that the best image restored by using the mimetic method is closer to the noise-free image than the best images restored by the other two methods tested. these results motivate further studies of the application of the mimetic methods to other imaging problems. mathematical subject classification: primary: 68u10; secondary: 65l12.
Actividad inhibitoria de cepas del género Bacillus spp. contra dermatofitos.
Sosa Brice?o,M; Castillo Colombo,C; Scorza,J;
Revista de la Sociedad Venezolana de Microbiología , 2004,
Abstract: samples of domestic animals excrement, coming from trujillo state, were processed for sporulate bacteria isolation belonging to bacillus gender, in order to assay them against dermatophytes and to determine their antifungal activity. a total of 52 strains of sporulate bacteria were isolated, which the biggest number was isolated in hens (19 strains), followed by goatishes (12 strains). in bovines, equines and porcines, 7 strains were isolated of each one of the samples. of 60 patients, attended in the dermatology consulting "josé witremundo torrealba" investigations centre, university nucleus "rafael rangel", andes university in trujillo, to present different affections of the skin, 3 different species from dermatophytes were isolated: trichophyton rubrum, trichophyton mentagrophytes and microsporum canis. of 52 strains of bacillus gender isolated in our laboratory, 23% (12 strains) were active to inhibit t. mentagrophytes and t. rubrum growth. against m. canis, 21% (11 isolated strains) showed inhibitory activity. we highlight that this antifungal activity takes place in relatively simple and economic culture media, which suggests the discovery of a new field of applied investigation.
A New Route Towards The Preparation Of A Biodegradable Nanocomposite Based On Chitin Whiskers From Exoskeleton Of Shrimp And Polycaprolacton
Castillo,Verónica; Matos,Mireya; Müller,Alejandro J.;
Revista Latinoamericana de Metalurgia y Materiales , 2003,
Abstract: the main objective of this work was to explore the possibility of future preparation of nanocomposites using a-chitin whiskers as a reinforcing agent and poly( e -caprolactone), pcl, as the matrix polymer. whiskers were successfully obtained as a result of the acid hydrolysis of purified chitin extracted previously from the exoskeleton of shrimp. these whiskers had a form factor of 15, with an average length of 300 nm. once an aqueous suspension of chitin whiskers was produced, we developed a method in this paper to change the solvent (first to methanol and then to toluene), in order to incorporate the nano-fibers in non-water soluble polymers like pcl. a non flocculating suspension of the whiskers in toluene was prepared by means of the incorporation of a suitable surfactant. the dispersion of the whiskers was better in the aqueous medium than in toluene, indicating that the dispersion in the latter medium could be improved if a more efficient surfactant is found. finally, preliminary experiments showed that pcl/chitin whiskers films can be prepared by first dissolving the pcl in the toluene suspension and later evaporating the solvent. differential scanning calorimetry experiments demonstrated that a nucleating effect of the whiskers on the pcl was induced as well as a small increase in crystallinity. the efficiency of the chitin whiskers as nucleating agents for pcl was estimated by comparing the increased in crystallization temperature obtained with that of ideally self-nucleated material. when 5% chitin was employed a nucleating efficiency closed to 40% was achieved as well as 20% increase in crystallinity.
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