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Search Results: 1 - 10 of 4756 matches for " Henry Puerta "
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Dise?o de estrategias óptimas para la selección de portafolios, un análisis de la ponderación inversa al riesgo (PIR)
Puerta,Andrés; Laniado,Henry;
Lecturas de Economía , 2010,
Abstract: this article analyzes the behavior of the portfolio selection strategy that assigns to each asset a weight inversely proportional to individual risk (pir) in comparison with the classical mean-variance (mv), minimum variance (minvar) and 1/n strategies. in doing so and applied to the colombian stock market, this study performs out-of-sample estimates and provides conditions under which pir weights lead to less riskier strategies than the 1/n strategy. in conclusion, the evidence suggests that the pir strategy outperforms classical strategies in terms of profitability indicators, risk, sharpe ratio, turnover (cost) and turnover (stability).
Dise o de estrategias óptimas para la selección de portafolios, un análisis de la ponderación inversa al riesgo (PIR)
Andrés Felipe Puerta Molina,Henry Laniado Rodas
Lecturas de Economía , 2010,
Abstract: This article analyzes the behavior of the portfolio selection strategy that assigns to each asset a weight inversely proportional to individual risk (PIR) in comparison with the classical mean-variance (MV), minimum variance (MINVAR) and 1/N strategies. In doing so and applied to the Colombian stock market, this study performs out-of-sample estimates and provides conditions under which PIR weights lead to less riskier strategies than the 1/N strategy. In conclusion, the evidence suggests that the PIR strategy outperforms classical strategies in terms of profitability indicators, risk, Sharpe ratio, Turnover (cost) and Turnover (stability).
Hantavirus del nuevo mundo: Ecología y epidemiología de un virus emergente en latinoamérica The New-World Hantaviruses: Ecology and epidemiology of an emerging virus in Latin America
Henry Puerta,César Cantillo,James Mills,Brian Hjelle
Medicina (Buenos Aires) , 2006,
Abstract: Los hantavirus son un grupo de patógenos emergentes (familia Bunyaviridae; género Hantavirus) identificados como agentes etiológicos de la Fiebre Hemorrágica con Síndrome Renal (FHSR) en Europa y Asia y el Síndrome Cardiopulmonar por Hantavirus (SCPH) en las Américas. La FHSR está relacionada con roedores de las subfamilias Murinae y Arvicolinae y el SCPH con roedores de las subfamilias Sigmodontinae y Arvicolinae. Desde la identificación del SCPH en los EE.UU. en 1993, muchos casos de SCPH y un número cada vez mayor de hantavirus y sus roedores reservorios han sido identificados en Centro y Sud América. Estudios epidemiológicos han demostrado diferencias notables en las seroprevalencias de anticuerpos en humanos y roedores reservorios que oscilan entre el 1% y más del 40%. Hasta ahora han sido notificados en toda América más de 1500 casos de SCPH y aproximadamente más de 15 variantes de hantavirus genética y serológicamente distintos asociados a roedores sigmodontinos. Las formas clínicas leves-autolimitadas, moderadas y graves de la enfermedad, los antecedentes de transmisión persona a persona y una incidencia mayor de manifestaciones clínicas extrapulmonares que se diferencian de la enfermedad clásica descrita por primera vez en EE.UU., son aspectos importantes sobre la epidemiología de los hantavirus y el SCPH en Latinoamérica; sin embargo, la historia completa de los hantavirus está aún por escribirse, debido a la naturaleza dinámica de estos virus y sus patologías, y a la complejidad de los factores que intervienen en su aparición, establecimiento y diseminación en poblaciones humanas y animales. Latinoamérica continúa representando la porción del continente con una oportunidad única y desafiante para el estudio de la relación de los hantavirus con sus huéspedes reservorios naturales y las interacciones virus-roedor-humano. Probablemente más hantavirus podrían ser descritos en el futuro, y serían necesarios más datos para entender su diversidad y evolución. The hantaviruses are a group of emerging rodent-borne pathogens (family Bunyaviridae; Genus Hantavirus) that are etiologic agents for hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. HFRS is associated with rodents of the family Muridae, subfamilies Murinae and Arvicolinae; HPS is associated with rodents of the subfamily Sigmodontinae. Since the identification of HCPS in USA in 1993, a large number of cases of HPS and an increasing number of hantaviruses and rodent reservoir hosts have been identified in Central and S
Hantavirus del nuevo mundo: Ecología y epidemiología de un virus emergente en latinoamérica
Puerta,Henry; Cantillo,César; Mills,James; Hjelle,Brian; Salazar-Bravo,Jorge; Mattar,Salim;
Medicina (Buenos Aires) , 2006,
Abstract: the hantaviruses are a group of emerging rodent-borne pathogens (family bunyaviridae; genus hantavirus) that are etiologic agents for hemorrhagic fever with renal syndrome (hfrs) in europe and asia and hantavirus cardiopulmonary syndrome (hcps) in the americas. hfrs is associated with rodents of the family muridae, subfamilies murinae and arvicolinae; hps is associated with rodents of the subfamily sigmodontinae. since the identification of hcps in usa in 1993, a large number of cases of hps and an increasing number of hantaviruses and rodent reservoir hosts have been identified in central and south america. epidemiologic studies have demonstrated important differences in frequency of infection with hantaviruses in both human and rodent host populations. antibody prevalences in rodent and human populations may vary from less than 1% to more than 40%. currently, more than 1500 cases of hcps have been reported and more than 15 genetically distinct variants of hantaviruses, all associated with sigmodontine rodents, have been identified throughout the americas. several characteristics distinguish latin american hcps cases from the classical hcps described for the first time in the usa. these include a variation in severity of disease from moderate and self-limiting to severe, the demonstration of person-to-person transmission, and a somewhat higher incidence of extrapulmonary clinical manifestations in the south american form of hcps. nevertheless, our understanding of hantaviruses in the americas is still far from complete. the factors involved in the dynamics of these viruses in nature, their establishment and transmission within host populations and from hosts to humans, and the variable pathology of these viruses in humans are complex. it is likely that more hantaviruses will be described in the future, and much more data will be required in order to describe the diversity and evolution of this group of pathogens. latin america, as the center of diversity for sigmod
Primera evidencia serológica de infección por Hantavirus en roedores, en Colombia
Alemán,Ader; Iguarán,Haydeé; Puerta,Henry; Cantillo,César; Mills,James; Ariz,William; Mattar,Salim;
Revista de Salud Pública , 2006, DOI: 10.1590/S0124-00642006000400001
Abstract: objective: determining hantavirus infection prevalence in rodents in the córdoba department, colombia. methods: rodents were captured using sherman live-capture traps (8x9x23 cm; sherman traps, inc., tallahassee, fl) in peridomestic areas of córdoba. hantavirus igg antibodies were detected by elisa using sin nombre virus (snv) recombinant nucleocapsid antigen (cdc, atlanta, georgia, usa). results: 336 rodents were captured in 11 townships in the córdoba department (murinae: 249; sigmodontinae: 68; heteromyidae: 17; echimyidae: 2; 8,5 % overall trap success) during 79 nights of trapping between january 2003 and november 2004. hantavirus antibody seroprevalence was 2,1 % (7 out of 336 captures). prevalence by genus varied between 5,9 % (1 out of 17 heteromys) to 50 % (1 out of 2 proechimys). conclusions: snv-reactive antibody prevalence in rodents in córdoba, colombia, indicated that at least one hantavirus is endemic in rodents in northern colombia and is frequently transmitted to rural residents.
Ecología de la regeneración de Quercus ilex a escala de paisaje: importancia de los dispersores y depredadores de semillas para el reclutamiento
C. Puerta
Ecosistemas , 2008,
Abstract:
Características del hormigón para prefabricados de fachada
Puerta, Antonio
Informes de la Construccion , 1979,
Abstract: This article studies the advantages offered now by shock concrete and those to be offered in the future by polymerized concrete, over the traditional materials used in prefab facing models: various low porosity stones and marbles, artificial stone and vibrated concrete. Besides describing the properties of such materials, the work gives soma indications for their correct application in construction Jobs and certain recommendations to make the adopted solutions as aesthetical, rational, durable and economic as possible. Se estudian en este articulo las ventajas que ofrecen, el hormigón chocado en la actualidad y el hormigón polimerizado en el futuro, sobre los materiales tradicionalmente empleados en la prefabricación de fachadas: piedras y mármoles naturales de poca porosidad, piedra artificial y hormigón vibrado. Además de describirse las características de estos materiales, se dan unas indicaciones para la perfecta ejecución de las obras y ciertas recomendaciones al objeto de que la solución adoptada sea la más estética, racional, permanente y económica posible.
Free Secondary Education and the Changing Roles of the Heads of Public Schools in Tanzania: Are They Ready for New Responsibilities?  [PDF]
Henry Godda
Open Journal of Social Sciences (JSS) , 2018, DOI: 10.4236/jss.2018.65001
Abstract:
This study investigated the management capacity of heads of public secondary schools in the implementation of Free Secondary Education (FSE) policy in Singida municipality. The study was descriptive research survey which employed both qualitative and quantitative research designs. Questionnaires and interviews were used to collect data from 200 teachers, 10 school heads and 5 municipal secondary education officers. The findings indicated that heads of public secondary schools in Singida municipality possessed managerial skills to run their schools effectively despite of being faced by several challenges, like inadequate funds to cater for some of the school needs, misconception by parents that FSE policy catered for all the fees and rapid increase of student enrollment. The findings further revealed that school heads use informal and formal coping strategies like community participation and informal peer coaching to manage the challenges of FSE.
Methylenedioxymethamphetamine (MDMA, 'Ecstasy'): Neurodegeneration versus Neuromodulation
Elena Puerta,Norberto Aguirre
Pharmaceuticals , 2011, DOI: 10.3390/ph4070992
Abstract: The amphetamine analogue 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy’) is widely abused as a recreational drug due to its unique psychological effects. Of interest, MDMA causes long-lasting deficits in neurochemical and histological markers of the serotonergic neurons in the brain of different animal species. Such deficits include the decline in the activity of tryptophan hydroxylase in parallel with the loss of 5-HT and its main metabolite 5-hydoxyindoleacetic acid (5-HIAA) along with a lower binding of specific ligands to the 5-HT transporters (SERT). Of concern, reduced 5-HIAA levels in the CSF and SERT density have also been reported in human ecstasy users, what has been interpreted to reflect the loss of serotonergic fibers and terminals. The neurotoxic potential of MDMA has been questioned in recent years based on studies that failed to show the loss of the SERT protein by western blot or the lack of reactive astrogliosis after MDMA exposure. In addition, MDMA produces a long-lasting down-regulation of SERT gene expression; which, on the whole, has been used to invoke neuromodulatory mechanisms as an explanation to MDMA-induced 5-HT deficits. While decreased protein levels do not necessarily reflect neurodegeneration, the opposite is also true, that is, neuroregulatory mechanisms do not preclude the existence of 5-HT terminal degeneration.
El periodismo narrativo* o una manera de dejar huella de una sociedad en una época
Puerta,Andrés;
Anagramas -Rumbos y sentidos de la comunicación- , 2011,
Abstract: journalism and literature have nourished and fecundated themselves and have been involved in promiscuous and incestuous relationships. mutual borrowing and theft have been important for both disciplines. the only winner has been the reader who has been able to enjoy better literature and journalism. however, we should understand that there have been many failed attempts from both sides ending in a total failure for texts which are neither journalistic nor literary works. forms of a good journalism can also become a way of literature. journalism (narrative journalism, especially) is a way of writing which, due to its specific characteristics (including finding characters, recreating actions and contexts) has been a way of keeping a living memory of civilizations, a beating story, and is alive in those yellowish papers which become valid every time someone tries to study them. when talking about representing history, the main genre has been the report which is one of the genres with the highest contribution to narrative development in colombia and latin america. from the indias reporters to the new indias reporters, an exchange between literature and journalism has occurred generating successful results such as el camero written by juan rodríguez freile, gabriel garcía márquez's work, development of movements such as the modernism, times and forms of narration such as the novels known as violence novels. in our days, an impulse has been noticed with a group of writers trying to reflect reality of our continent in the search for a personal voice to give testimony of a specific period of time.
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