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Search Results: 1 - 10 of 212556 matches for " Fredyc; Pérez "
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In vitro antimalarial activity of fractions and constituents isolated from Tabebuia billbergii Actividad antimalárica in vitro de fracciones y constituyentes aislados de Tabebuia billbergii
Harold Gómez-Estrada,Ricardo Gaitán-Ibarra,Fredyc Díaz-Castillo,Hilda A Pérez
Revista Cubana de Plantas Medicinales , 2012,
Abstract: Introduction: in vitro antimalarial activity of naphthoquinones (1-5), isolated from Tabebuia billbergii (Bureau & K. Schum.) Standl., was investigated. Tabebuia billbergii, commonly known as guayacán, is a plant traditionally used in the Amazon in numerous conditions like bacterial and fungal infections, fever, syphilis, malaria, trypanosomiasis, as well as stomach and bladder disorders, and tumours. Objective: to study the dichloromethane extracts of both the trunk and the inner bark of Tabebuia billbergii and to demonstrate the antimalarial activity of some of its bioactive components. Methods: some bioactive components were evaluated for the antimalarial activity against Plasmodium berghei, by using the inhibition of the differentiation cycle of the parasite measure by the 3H-hypoxanthine incorporation and compared to that obtained for chloroquine. Results: conventional chromatographic techniques and bioassay-guided fractionation (Artemia salina) allowed isolating from the active fractions one naphthoquinone (lapachol) and four naphtho-furan-4,9-diones. These compounds proved to have an important antiplasmodial effect, with very encouraging IC50's, especially when compared to the results shown by Chloroquine in the same experiment. In addition, two triterpenes, β-sitosterol and stigmasterol, were obtained from the bark. Conclusions: the activity-guided fractionation (A. salina) of dichloromethane extracts of the trunk and the inner bark of Tabebuia billbergii led to the isolation and the identification of five quinonoid compounds with antiplasmodial effect. The significant inhibitory activity in vitro against Plasmodium berghei observed for compound 2-acetyl-naphtho-[2,3b]-furan-4,9-dione allow us to present them as a potential antimalarial compound. Introducción: se evaluó la actividad antimalárica in vitro de una serie de naftoquinonas (1-5), aisladas de Tabebuia billbergii (Bureau & K. Schum.) Standl., que es conocida comúnmente como guayacán, una planta utilizada tradicionalmente en la Amazonía en numerosos problemas de salud como infecciones bacterianas y fúngicas, fiebre, sífilis, paludismo, tripanosomiasis, así como en problemas estomacales, tumores y trastornos de la vejiga. Objetivo: estudiar los extractos en diclorometano tanto del tronco como la corteza interna de Tabebuia billbergii y evaluar la actividad antimalárica de algunos de sus componentes bioactivos. Métodos: la actividad antimalárica contra Plasmodium berghei se evaluó en algunos componentes bioactivos, por la inhibición del ciclo de la diferenciación de la medida de los parásit
In vitro antimalarial activity of fractions and constituents isolated from Tabebuia billbergii
Gómez-Estrada,Harold; Gaitán-Ibarra,Ricardo; Díaz-Castillo,Fredyc; Pérez,Hilda A; Medina,José D;
Revista Cubana de Plantas Medicinales , 2012,
Abstract: introduction: in vitro antimalarial activity of naphthoquinones (1-5), isolated from tabebuia billbergii (bureau & k. schum.) standl., was investigated. tabebuia billbergii, commonly known as guayacán, is a plant traditionally used in the amazon in numerous conditions like bacterial and fungal infections, fever, syphilis, malaria, trypanosomiasis, as well as stomach and bladder disorders, and tumours. objective: to study the dichloromethane extracts of both the trunk and the inner bark of tabebuia billbergii and to demonstrate the antimalarial activity of some of its bioactive components. methods: some bioactive components were evaluated for the antimalarial activity against plasmodium berghei, by using the inhibition of the differentiation cycle of the parasite measure by the 3h-hypoxanthine incorporation and compared to that obtained for chloroquine. results: conventional chromatographic techniques and bioassay-guided fractionation (artemia salina) allowed isolating from the active fractions one naphthoquinone (lapachol) and four naphtho-furan-4,9-diones. these compounds proved to have an important antiplasmodial effect, with very encouraging ic50's, especially when compared to the results shown by chloroquine in the same experiment. in addition, two triterpenes, β-sitosterol and stigmasterol, were obtained from the bark. conclusions: the activity-guided fractionation (a. salina) of dichloromethane extracts of the trunk and the inner bark of tabebuia billbergii led to the isolation and the identification of five quinonoid compounds with antiplasmodial effect. the significant inhibitory activity in vitro against plasmodium berghei observed for compound 2-acetyl-naphtho-[2,3b]-furan-4,9-dione allow us to present them as a potential antimalarial compound.
Actividad larvicida de extractos etanólicos de Tabernaemontana cymosa y Trichilia hirta sobre larvas de estadio III y IV de Aedes aegypti (Diptera: Culicidae) Larvicidal activity of ethanol extracts of Tabernaemontana cymosa and Trichilia hirta against III and IV stage larvae of Aedes aegypti (Diptera: Culicidae)
Fredyc Díaz Castillo,Sandra Marcela Morelos Cardona,Moisés Carrascal Medina,Yina Pájaro González
Revista Cubana de Plantas Medicinales , 2012,
Abstract: Introducción: el mosquito Aedes aegypti es el principal vector de los virus del dengue y la fiebre amarilla. Una de las formas actuales para combatir estas enfermedades es el control del vector. Sin embargo, los problemas causados por los insecticidas sintéticos y la resistencia adquirida por los mosquitos, hacen cada vez más difícil esta lucha. Las plantas constituyen una fuente alternativa al uso de insecticidas sintéticos. Objetivos: evaluar la actividad larvicida para el mosquito Aedes aegypti, de los extractos etanólicos y fracciones activas, de diferentes órganos vegetales de las especies Trichilia hirta L. y Tabernaemontana cymosa Jacq. Métodos: en este estudio se utilizaron larvas de Aedes aegypti en estadios III y IV. Los extractos etanólicos totales se obtuvieron por maceración del material vegetal seco y molido, durante una semana y posterior secado a presión reducida con un rotoevaporador. La obtención de fracciones y subfracciones, se realizó por cromatografía de columna abierta, usando solventes de diferentes polaridades. La actividad larvicida se evaluó bajo protocolos recomendados por la Organización Mundial de la Salud. Resultados: los extractos etanólicos de corteza de Trichilia hirta y flores, corteza y hojas de Tabernaemontana cymosa, no mostraron actividad larvicida. El extracto de semillas de Trichilia hirta mostró una actividad moderada con una CL50 y CL90 de 219,2 y 331,4 mg/L respectivamente. El extracto etanólico de semillas de Tabernaemontana cymosa, la fracción F008 y la subfracción F011, mostraron una buena actividad larvicida con CL50 de 35,1; 20,9, y 14,98 mg/L, respectivamente. Conclusiones: según los resultados, se consideró como promisorio el extracto de semillas de Tabernaemontana cymosa para la obtención de metabolitos secundarios con actividad larvicida. Introduction: Aedes aegypti is the main vector of dengue and yellow fever. One way to combat these diseases today is the vector control. However, the problems caused by synthetic insecticides and the acquired resistance by mosquitoes, turn this control into a more difficult struggle every day. The plants offer an alternative source to the use of synthetic insecticides. Objectives: the objective of this study was to evaluate the larvicidal activity of the ethanol extracts and active fractions of different organs of Trichilia hirta L. and Tabernaemontana cymosa Jacq. Methods: in this study, Aedes aegypti larvae in III and IV stages were used. The total ethanol extracts were obtained by maceration of dried and ground plant material for a week and then dried at reduced p
Citizenship, Space and Democracy: Political Changes in the Context of Globalization  [PDF]
Gabriel Pérez Pérez
Open Journal of Political Science (OJPS) , 2017, DOI: 10.4236/ojps.2017.71003
Abstract: The article makes a theoretical reflection of space, which has been traditionally studied by geographers and citizenship, without making aside the empirical elements of this relationship. The first paragraph provides that studying the citizenship is necessarily linking it to the issue of democracy, and that, if there have been different approaches for spatial analysis at different scales, we have a diversity of forms and developments that have embraced democracy and citizenship. The second section is central to the theme of the city and it shows how they are given different manifestations and expressions of citizenship that responds to the transformation of public space and the fragmentation of the city. Finally, the third section deals with the theme on how their times currently can observe the emergence of new or different formations citizens. As a consequence of the global transformations, migratory transnational flows or social movements, citizens can be studied through different scales and spaces.
Transformation of the Political Theory: Cosmopolitan Citizenship and Democracy  [PDF]
Gabriel Pérez Pérez
Open Journal of Political Science (OJPS) , 2019, DOI: 10.4236/ojps.2019.92018
Abstract: This paper is concerned with the topic of cosmopolitan citizenship and its relation to democracy. We begin by highlighting the main postulates of Kantian cosmopolitanism, as many theorists Kant contributes an idea of cosmopolitan citizenship linked to the need to establish international political institutions that support citizenship beyond an exclusively moral dimension. We then discuss the issue of the transformation undergone by the nation state in the context of globalization, particularly the loss of sovereignty of the state and the growth of multinational companies, and how these changes have come to set a new scenario for the emergence of international actors and the basis for various citizenship practices in a cosmopolitan dimension. The nature and current reach of cosmopolitan citizenship is explored through two fundamental cases: the European Union, and ecologic citizenship. Finally, we discuss cosmopolitan democracy and which ought to be its characteristics, among which we identify the establishment of supranational political institutions, the consolidation of a global civil society, and the establishment of mechanisms for citizen participation beyond the traditional ones situated in the national sphere.
New Evidence on Rotational Dynamics  [PDF]
Luis Alberto Pérez
World Journal of Mechanics (WJM) , 2013, DOI: 10.4236/wjm.2013.33016
Abstract:


In this paper, the author confirmed a new theory to explain the mechanical behavior of macroscopic bodies. The confirmed hypothesis is the Theory of Dynamics Interaction by the Professor Gabriel Barceló. Barceló explained his theory in an article called “Analysis of Dynamics Fields in Noninertial Systems”, World Journal of Mechanics, Vol. 2, No. 3, 2012, pp. 175-180. This hypothesis holds that the mechanical behavior of macroscopic bodies in a non-inertial environment opens new assumptions on inertial fields and rotational dynamics. An associated experiment was presented to support the discussion in the paper. The author first became aware of the proposals of Professor Gabriel Barceló’s Theory of Dynamics Interaction through his 2006 article on Saturn planet rings, which suggested unsolved phenomena in rotational dynamics and the inception of a novel theory [1]. Intuitively, the author realized himself about the fact that the cosmos is mechanical from its smallest to its widest comprehensible appreciation. If material behavior is mechanical everywhere and every time, from a subatomic particle, wave or string, to a cluster of galaxies, then our understandable solutions must comply with the Laws of Motion, it could be believed.


Methodology and Equations of Mineral Production Forecast
—Part I. Crude Oil in the UK and Gold in Nevada, USA. Prediction of Late Stages of Production
 [PDF]

Sergio Pérez Rodríguez
Open Journal of Geology (OJG) , 2013, DOI: 10.4236/ojg.2013.35040
Abstract:

The equations of mineral production forecast link the change in time of mineral reserves with the production and the ratio of reserves to production. These equations allow us to model the development of the mineral resources evaluated at any scale. Probabilistic bidimensional charts made from montecarlo simulations provide intervals of confidence for the forecasts. The set of equations is devised and presented for a variety of applications to the oil and gas industry, as well to the production of any other mineral resource, either metals or non metals, whose ore deposit volumes and production might be quantified. The cases studied in the UK and USA are at late stages of production, periods for what the equations are most suitable to be applied without further adjustments. Experimental design allows the diagnosis of the likely values of the variables pertaining to the equations, in order to achieve the results provided by conventional production forecasts or to explore other scenarios of investigation. The method can be practical to evaluate commitments of production of mineral resources with time, to support strategic plans for companies, corporations, countries or regions based on those evaluations, for the screening and ranking of mineral assets based on their production potential and many other tasks where the prediction of future volumes of mineral production is required.

Methodology and Equations of Mineral Production Forecast. Part II. The Fundamental Equation. Crude Oil Production in USA  [PDF]
Sergio Pérez Rodríguez
Open Journal of Geology (OJG) , 2013, DOI: 10.4236/ojg.2013.36044
Abstract:

The fundamental equation of mineral production allows to model and design the dynamics of mineral production, however complex they are or could be. It considers not only the case of a constant production to reserves ratio for given intervals of time, but with a piecewise approach, it is also enabled to account the variation on time of this ratio. With a constant production to reserves ratio, the limit expression of the fundamental equation takes the form of an Erlang distribution with a fixed shape parameter. The rate parameter equals the scale factor. The discrete piecewise version, instead of considering the reserves and the production to reserves ratio being constant through certain intervals of time, updates both variables by units of time. This version, using either lineal or non lineal functions for the variables involved, let to model known production profiles or to forecast them by experimental design. The Hubbert’s linearization updated with recent data and the p-box method applied to determine ultimate recovery of U.S. crude oil reserves indicate official accounts underestimate them. The analysis of the ideal model of production based on Hubbert’s linearization and curve, can be made by decomposing it in the distribution with time of the reserves and of the production to reserves ratio. The distribution of reserves with time is synchronized for both the ideal Hubbert’s curve and real profiles, disregarding whether they match or not. The departure of real profiles from the ideal Hubbert’s curve lies on the differences or correspondences of the distribution with time of the production to reserves ratio. The MonteCarlo simulation applied to forecast US crude oil production for the next five years points to a slow decline, with average annual yields presenting a difference lower than 10% between the start and the end of the simulation.

Accounting Analysis of Economic Policy of Spain (2012)  [PDF]
Miguel Angel Pérez Benedito
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.43035
Abstract: The analysis of economic policy is made through a new methodology using the information provided by businesses to the Bank of Spain. The financial statements are the result of economic and financial transactions in a year and show a behavior that is likely to be measured by applying the Edgeworth’s box for analysis. This means that it is possible to measure the response of firms against market disruptions through an accounting interpretation of the information contained in the financial statements. The indicators obtained through this methodology measure a position taken in the Edgeworth’s box. Consequently, the observations obtained are random and therefore may explain the evolution of the economy of any country.
EDUCACION PARA LA CONVIVENCIA COMO CONTENIDO CURRICULAR: PROPUESTAS DE INTERVENCION EN EL AULA
Pérez Pérez,Cruz;
Estudios pedagógicos (Valdivia) , 1999, DOI: 10.4067/S0718-07051999000100007
Abstract: education for co-existence is becoming a priority in many educational centres, to the extent that they are being overwhelmed by high levels of conflictiveness in the classroom. making it necessary for teachers to equip themselves with new methods and techniques in order to face the problem in a global and precautionary way. in this article i analyze the matter from a curricular point of view, in considering that education for co-existence constitutes a content, or a group of contents concerning attitude, which must be the aim of teaching, learning and evaluation. the proposals for participation are based on four important areas: educative project, climate of democratic participation, class assemblies and learning of rules.
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