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Search Results: 1 - 10 of 209377 matches for " L. Saavedra "
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Chacaltaya: towards a solution of the knee ....?
O. Saavedra,L. Jones
Physics , 2001,
Abstract: Cosmic rays physics is currently being studied with rather sophisticated detectors running in a variety of experimental conditions and atmospheric depths around the world. In this paper we describe the reasons why cosmic ray physics experiments at high altitudes like Chacaltaya are so important for resolving some of the open problems in cosmic physics. A discussion on the future prospects of the high altitude mountain laboratories such as Chacaltaya for cosmic ray physics is presented.
Involvement of Estrogen Receptors in the Anxiolytic-Like Effect of Phytoestrogen Genistein in Rats with 12-Weeks Postovariectomy  [PDF]
Juan Francisco Rodríguez-Landa, Fabiola Hernández-López, Margarita Saavedra
Pharmacology & Pharmacy (PP) , 2012, DOI: 10.4236/pp.2012.34059
Abstract: Phytoestrogens are natural compounds found in some vegetables, and they replicate many of the physiochemical and physiological properties of estrogens, including the regulation of mood. The phytoestrogen genistein exerts anxiolytic-like effects in rats with a chronic absence of ovarian hormones, but the mechanism involved in this effect remains to be explored. The present study explored the participation of estrogen receptor-β in the anxiolytic-like effect of genistein (1.0 mg/kg, i.p., for 4 days) in Wistar rats with 12-weeks postovariectomy, considered as experimental model of post-surgical menopause. In the light/dark test, a useful tool for anxiety study and for the screening of anxiolytic drugs, genistein reduced the latency to enter and increased the time spent in the light compartment and significantly increased the frequency and time spent exploring the light compartment compared with the control group, which is considered as an anxiolytic-like effect at experimental level. All behavioral effects produced by genistein in the light/dark test were blocked by previous tamoxifen administration (5.0 mg/kg, s.c., for 6 days), a non selective antagonist for estrogen receptor-β. The effects produced by genistein or tamoxifen in this test were not related to significant changes in general motor activity evaluated in the open field test. In conclusion, the specific contribution of present investigation was identify that estrogen receptor-β is involved in the anxiolytic-like effect produced by phytoestrogen genistein in rats with a long-term absence of ovarian hormones; supporting the hypothesis that estrogen receptor-β participates in the regulation of anxiety associated with low concentration of ovarian hormones and in the anxiolytic-like effects produced by natural estrogenic compounds such as phytoestrogens.
Paleomadrigueras de roedores, un nuevo método para el estudio del Cuaternario en zonas áridas de Sudamérica
Betancourt,Julio L.; Saavedra,Bárbara;
Revista chilena de historia natural , 2002, DOI: 10.4067/S0716-078X2002000300005
Abstract: in arid and semi-arid regions of south america, historical evidence for climate and vegetation change is scarce despite its importance for determining reference conditions and rates of natural variability in areas susceptible to modern desertification. normal lines of evidence, such as pollen stratigraphies from lakes, are either rare or unobtainable in deserts; studies of late quaternary vegetation history are few and generally inconclusive. this gap in knowledge may be corrected with discovery and development of fossil rodent middens in rocky environments throughout arid south america. these middens, mostly the work of lagidium, phyllotis, abrocoma and octodontomys, are rich in readily identifiable plant macrofossils, cuticles and pollen, as well as vertebrate and insect remains. in the north american deserts, more than 2,500 woodrat (neotoma) middens analyzed since 1960 have yielded a detailed history of environmental change during the past 40,000 years. preliminary work in the pre-puna, monte and patagonian deserts of western argentina, the atacama desert of northern chile/southern peru, the mediterranean matorral of central chile, and the puna of the andean altiplano suggest a similar potential for rodent middens in south america. here we borrow from the north american experience to synthesize methodologies and approaches, summarize preliminary work, and explore the potential of rodent midden research in south america
Paleomadrigueras de roedores, un nuevo método para el estudio del Cuaternario en zonas áridas de Sudamérica Rodent middens, a new method for Quaternary research in arid zones of South America
Julio L. Betancourt,Bárbara Saavedra
Revista chilena de historia natural , 2002,
Abstract: Las zonas áridas y semiáridas de Sudamérica carecen de registros históricos exhaustivos de vegetación y clima, a pesar de la utilidad que ellos representan para el establecimiento de condiciones basales y tasas naturales de variabilidad en procesos abióticos y bióticos. Fuentes comúnmente utilizadas en el estudio de paleovegetación como el polen, son escasas en zonas áridas y semiáridas en Sudamérica, lo que se refleja en el limitado número de estudios vegetacionales durante el Cuaternario Tardío. El vacío existente en el conocimiento de la historia vegetacional de esta zona podría ser remediado gracias al descubrimiento y análisis de paleomadrigueras de roedores en ambientes rocosos. Estos depósitos, producidos por roedores de los géneros Lagidium, Phyllotis, Abrocoma y Octodontomys y posiblemente otros, son ricos en restos vegetales como ramas, hojas, polen o cutículas; y restos animales como fecas, huesos o insectos. Las paleomadrigueras de roedores han sido extensamente utilizadas en el estudio de zonas áridas en Norteamérica, donde más de 2.500 registros producidos por roedores del género Neotoma han sido analizadas desde 1960, permitiendo reconstruir una detallada historia de cambios vegetacionales y climáticos de los últimos 40.000 a os en el suroeste de Norteamérica. Investigaciones recientes han revelado la presencia de paleomadrigueras en la pre-puna, los desiertos del Monte y Patagonia del oeste argentino, el desierto de Atacama al norte de Chile y sur del Perú, el matorral Mediterráneo de Chile central, y la Puna del Altiplano Andino. Estos hallazgos fortalecen el gran potencial que dichos depósitos tienen para reconstruir la vegetación y el clima en Sudamérica. Con el fin de aportar elementos para la detección, uso y análisis de paleomadrigueras de roedores, entregamos una síntesis de los depósitos registrados hasta la fecha en Sudamérica, así como una descripción de sus probables agentes formadores. Basados en la experiencia Norteamericana entregamos además, un resumen de los métodos existentes para la detección y análisis de dichos depósitos, los sesgos asociados, así como el aporte potencial que su análisis podría representar en futuros estudios paleoecológicos en las zonas áridas y semiáridas de Sudamérica In arid and semi-arid regions of South America, historical evidence for climate and vegetation change is scarce despite its importance for determining reference conditions and rates of natural variability in areas susceptible to modern desertification. Normal lines of evidence, such as pollen stratigraphies from lakes, are either rare
Occupational Stress versus Cortisol Associated with Psychological Variables and Gender Differences among Women and Men in Nursing  [PDF]
Virginia Dresch, María del Pilar Sánchez-López, Ana Isabel Saavedra
Health (Health) , 2015, DOI: 10.4236/health.2015.77099
Abstract: The present research focused on a sample of Spanish male and female nurses to determine whether psychological variables are related to occupational stress and cortisol. Spanish male (n = 98) and female (n = 98) nurses, matched in diverse sociodemographic variables, completed measures of occupational stress, cortisol 8 am (8 h), and cortisol 8 pm (20 h), and psychological variables. Multivariable regression analyses revealed different patterns of association among the variables when analyzing subjective and (occupational stress) objective indicators (cortisol at 8 h and cortisol at 20 h). In male nurses, higher stress is related to worse self-perceived health, worse mental health, less cortisol measured at 8 h, and more morningness. For the female nurses, higher stress is related to being younger, worse self-perceived health, and less job satisfaction. The only similarities found in the target variables and the measures of stress studied in the groups of males and females are worse self-perceived health and worse mental health associated with more occupational stress.
Quantum state stability against decoherence
A. Krugel,L. Roa,C. Saavedra
Physics , 2006,
Abstract: We study the stability of the coherence of a state of a quantum system under the effect of an interaction with another quantum system at short time. We find an expression for evaluating the order of magnitude of the time scale for the onset of instability as a function of the initial state of both involved systems and of the sort of interaction between them. As an application we study the spin-boson interaction in the dispersive interaction regime, driven by a classical field. We find, for this model, that the behavior of the time scale for the onset of instability, with respect to the boson bath temperature, changes depending on the intensity of the classical field.
Estudio farmacocinético de amiodarona en perros
SAAVEDRA,I.; MANRíQUEZ,C.; GAETE,L.; MANTEROLA,L.; SAAVEDRA,M.; PINEDA,M.;
Archivos de medicina veterinaria , 1999, DOI: 10.4067/S0301-732X1999000200015
Abstract: pharmacokinetic variables of amiodarone were studied in six healthy dogs. plasma levels of amiodarone and its metabolite, desethylamiodarone, were determinated by hplc at different moments, after an i.v. administration as infusion of 5 mg/kg in two minutes. a compartment model independent pharmacokinetic analysis program was used to evaluate plasma levels of amiodarone vs time. the following results were obtained: auc: 9.95 ± 2.91 mg/ml/hr, b: 0.25 ± 0.27 l/hr, cl: 8.82 ± 1.95 ml/min./kg, tmr: 7.38 ± 1.52 hrs, t1/2b 5.056 ± 4.5 hrs and vd: 3.424 ± 2.3 l/kg. amiodarone pharmacokinetic disposition presented a rapid distribution and decrease from blood during the first 30 minutes after i.v. then it was slowly eliminated. it is concluded that amiodarone is an alternative to be considered in cardiac pathology in dogs, since the pharmacokinetic parameters, similar to those of human volunteers, can contribute to determine the apropiate dose to be administered
Evolución de la mortalidad y de los a?os de vida perdidos prematuramente relacionados con el consumo de alcohol en las Islas Canarias (1980-1998)
Bello,L.M.; Saavedra,P.; Serra,L.;
Gaceta Sanitaria , 2003, DOI: 10.1590/S0213-91112003000600007
Abstract: objective: the aim of this article was to describe death rates and years of life lost prematurely (yllp) in relation to alcohol consumption in the canary islands. the study covered the period between 1980 and 1998. methods: deaths from 1980 to 1998 were classified by age, sex, and cause using data obtained from the national institute of statistics (natural changes in the population). the number of alcohol-related deaths was calculated by year, sex, and age group using the attributable population fraction as proposed by the centers for disease control (usa). the yllp attributed to alcohol consumption were calculated for each cause of death by multiplying deaths by the attributable population fraction in 5-yearly age groups for both sexes (average span of five years), up to the age of 65 years. results: between 1980 and 1998, the number of alcohol-related deaths was 12,614, averaging 6.4% per year and with a male-to-female ratio of approximately 2:1. the main causes of death and yllp in both men and women were malignant neoplasms, diseases of the digestive system, and alcohol-related accidents, although accidents were by far the main cause producing 50.6% of alcohol-related yllp in men and 55.5% in women. over the study period, the incidence of cirrhosis of the liver and that of other chronic liver diseases (cie 571) decreased in men whilst remaining stable in women. conclusions: the finding that the percentage of alcohol-related deaths and cirrhosis of the liver remained high in the islas canarias between 1980 and 1998 highlights the need for educational strategies on the effects of alcohol, together with policies designed to reduce its consumption, particularly among the young.
Evolución de la mortalidad y de los a os de vida perdidos prematuramente relacionados con el consumo de alcohol en las Islas Canarias (1980-1998)
Bello L.M.,Saavedra P.,Serra L.
Gaceta Sanitaria , 2003,
Abstract: Objetivo: Describir la mortalidad y los a os de vida perdidos prematuramente (AVPP) relacionados con el alcohol en las Islas Canarias durante el período 1980-1998. Métodos: Las defunciones por edad, sexo y causa desde 1980 a 1998 se obtuvieron del Instituto Nacional de Estadística (Movimiento Natural de la Población). Se calculó la proporción de muertes relacionadas con el alcohol para cada a o, sexo y grupo de edad a partir de la fracción atribuible poblacional propuesta por los Centers for Disease Control (Estados Unidos). Para cada categoría diagnóstica, los a os de vida perdidos prematuramente relacionados con el alcohol fueron calculados multiplicando las defunciones por la fracción poblacional en grupos quinquenales de edad para ambos sexos hasta la edad de 65 a os. Resultados: Durante el período 1980-1998, el número de fallecimientos por causas relacionadas con el alcohol fue de 12.614, con un promedio del 6,4% anual y una razón varón/mujer de aproximadamente 2:1. Las neoplasias malignas, las enfermedades digestivas y los accidentes no intencionales relacionados con el alcohol presentan las mayores tasas de mortalidad y de AVPP tanto en varones como en mujeres; en particular, los accidentes no intencionales generan AVPP por encima de las otras causas, lo que supone el 50,6% del total de AVPP por causas relacionadas con el alcohol en varones y el 55,5% en mujeres. Durante el período de estudio, la cirrosis hepáticas y otras enfermedades crónicas del hígado (CIE 571) van decreciendo paulatinamente en los varones y se mantienen en las mujeres. Conclusiones: En el ámbito y período de estudio (Islas Canarias, 1980-1998), se ha observado que el porcentaje de fallecidos por causas relacionadas con el alcohol es elevado, incluyendo la mortalidad por cirrosis hepática. Por tanto, sería necesario potenciar el desarrollo de estrategias educativas y otras dirigidas para controlar su consumo, sobre todo en los jóvenes.
Estudio farmacocinético de amiodarona en perros Pharmacokinetic study of amiodarone in dogs
I. SAAVEDRA,C. MANRíQUEZ,L. GAETE,L. MANTEROLA
Archivos de medicina veterinaria , 1999,
Abstract: Se estudiaron las características farmacocinéticas de amiodarona en 6 perros mestizos sanos. Después de la aplicación de una infusión endovenosa de 5 mg/Kg. de peso en 2 minutos, se determinaron las concentraciones de la droga y de su metabolito principal, la desetilamiodarona, en tiempos predeterminados, usando el método analítico de HPLC que se describe. Las curvas de concentraciones plasmáticas en el tiempo fueron analizadas por un programa computacional, modelo farmacocinético independiente, obteniéndose los siguientes resultados: AUC: 9.95 ± 2.91 mg/mL/hr, b: 0.25 ± 0.27 L/hr, Cl: 8.82 ± 1.95 mL/min./Kg, TMR: 7.38 ± 1.52 hrs, t1/2b :5.056 ± 4,5 hrs y Vd: 3.424 ± 2.3 L/Kg. Los resultados obtenidos presentan una rápida distribución y disminución de amiodarona en la sangre en los primeros 30 minutos post-administración y, luego, una fase de eliminación lenta. Se concluye que amiodarona es una alternativa a ser considerada en las patologías cardíacas de los perros, ya que de los parámetros farmacocinéticos, parecidos a los obtenidos en humanos, se pueden deducir regímenes de dosis adecuados Pharmacokinetic variables of Amiodarone were studied in six healthy dogs. Plasma levels of amiodarone and its metabolite, desethylamiodarone, were determinated by HPLC at different moments, after an i.v. administration as infusion of 5 mg/Kg in two minutes. A compartment model independent pharmacokinetic analysis program was used to evaluate plasma levels of amiodarone vs time. The following results were obtained: AUC: 9.95 ± 2.91 mg/mL/hr, b: 0.25 ± 0.27 L/hr, Cl: 8.82 ± 1.95 mL/min./Kg, TMR: 7.38 ± 1.52 hrs, t1/2b 5.056 ± 4.5 hrs and Vd: 3.424 ± 2.3 L/Kg. Amiodarone pharmacokinetic disposition presented a rapid distribution and decrease from blood during the first 30 minutes after i.v. Then it was slowly eliminated. It is concluded that amiodarone is an alternative to be considered in cardiac pathology in dogs, since the pharmacokinetic parameters, similar to those of human volunteers, can contribute to determine the apropiate dose to be administered
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