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Search Results: 1 - 10 of 157838 matches for " Maria I.;Rivadeneira "
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Numerical solution of the variational PDEs arising in optimal control theory
Costanza, Vicente;Troparevsky, Maria I.;Rivadeneira, Pablo S.;
Computational & Applied Mathematics , 2012, DOI: 10.1590/S1807-03022012000100003
Abstract: an iterative method based on picard's approach to odes' initial-value problems is proposed to solve first-order quasilinear pdes with matrix-valued unknowns, in particular, the recently discovered variational pdes for the missing boundary values in hamilton equations of optimal control. as illustrations the iterative numerical solutions are checked against the analytical solutions to some examples arising from optimal control problems for nonlinear systems and regular lagrangians in finite dimension, and against the numerical solution obtained through standard mathematical software. an application to the (n + 1)-dimensional variational pdes associated with the n-dimensional finite-horizon time-variant linear-quadratic problem is discussed, due to the key role the lqr plays in two-degrees-of freedom control strategies for nonlinear systems with generalized costs. mathematical subject classification: primary: 35f30; secondary: 93c10.
Eficacia de la acupuntura en el tratamiento de los síntomas postoperatorio en cirugía pediátrica ambulatoria
Salazar Diez,Mabel de la Caridad; Barranco Pedraza,Leonor; Díaz Rivadeneira,Maria Onelia; Baute Vilardell,Liliana;
Revista Archivo M??dico de Camag??ey , 2011,
Abstract: background: postoperative symptoms in ambulatory pediatric surgery constitute a health problem. its incidence and utilization of medications, in sensitive patients may be risky. objective: to evaluate the efficacy of acupuncture treatment in postoperative symptoms like: pain, nausea and vomiting, in ambulatory pediatric surgery. method: an early phase ii clinical trial was conducted, in order to determine the acupuncture′s efficacy of postoperative symptoms in children (10 to 14 years), at the teaching provincial pediatric hospital eduardo agramonte pi?a of camagüey from january to june 2009. the universe was constituted by 370 patients subject to ambulatory surgery and the sample was made up of 30 patients that fulfilled the inclusion criteria. variables analyzed were: anesthetic method, postoperative symptoms, pain evaluation scale and efficacy of therapeutics. results: the endotracheal general anesthesia prevailed in the 76, 67 %. the postoperative pain was presented in the 66, 67 %. vomiting in the 23, 33 % and nausea appeared in 10 % of patients, the last two disappeared completely. all patients with mild pain obtained satisfactory response. a good therapeutic efficacy in the 93, 33 % was demonstrated at the end of the treatment. conclusions: the pain was the most frequent postoperative symptom. nausea and vomiting were eliminated completely.
Abordaje extremo lateral transcondilar para resecar un meningioma anterior del foramen magno
Campero,Alvaro; Rivadeneira,Conrado;
Revista argentina de neurocirug?-a , 2006,
Abstract: objective: to describe the far-lateral transcondylar approach performed to remove a meningioma of the anterior portion of the foramen magnum. description: a woman, 24-years old, with tetraparesis, greater in the right side, and paresis of the ix, x, and xi right cranial nerves, with a 9 months history. the mri showed a tumor in the anterior aspect of the foramen magnum (isointense in t1 and t2, with homogeneous enhance after gadolinium administration). intervention. in december 2005 the surgery was performed (far-lateral transcondylar approach), with complete removal of the lesion. histology: cordoid meningioma. the patient had a good outcome, with complete recovery of her neurological deficits. in the last control she was asymptomatic. conclusion. in this case, the far-lateral transcondylar was the most appropriate approach to completely resect a meningioma of the anterior portion of the foramen magnum.
Grados días acumulados en naranjas y mandarinas sobre pie trifolio en la zona de Concordia (Entre Ríos)
Rivadeneira, M.F.
Horticultura Argentina , 2012,
Abstract: Entre Ríos province is well known for its citrus fruit production; however there is a lack of information in the phenological description and quantification for the area of Concordia. The aim of this study was to quantify the degree-day accumulation from flowering to harvest for different oranges and mandarins varieties. The study was conducted during four consecutive growing seasons (2005/06 to 2008/09), and the phenological stages were registered every 2 weeks in Newhall, Lane Late, Valencia Late, and Salustiana oranges; Satsuma Okitsu and Clemenules mandarins, and Ellendale and Nova hybrids, all grafted on trifoliate orange rootstock. Degree days (DD) were calculated over a base temperature of 12.5 °C. The beginning of flowering changed significantly with the year (P = 0.0002) being earlier during the 2006/07 growing cycle and later during the year 2007/08. There were also significant differences in the DD accumulation between cultivars (P = 0.0001) and year (P = 0.0029). The earliest maturing Satsuma Okitsu and Clemenules mandarins reached 2,029.37 and 2,112.35 ± 57 DD accumulation, respectively, whereas Valencia Late orange had the highest value (2,526.35 ± 57) DD accumulation.------------------------------------------------------------------------------------------------------------ La provincia de Entre Ríos se caracteriza por su producción de naranjas y mandarinas, sin embargo existen pocos datos que indiquen los momentos y duración de las etapas fenológicas para el cultivo de los cítricos. El objetivo de este trabajo fue cuantificar los grados días desde floración a cosecha de variedades comerciales de naranjas y mandarinas en la zona de Concordia, Entre Ríos. Se registraron quincenalmente los estadios de la floración en variedades de naranja Newhall, Lane Late, Valencia Late y Salustiana (Citrus sinensis (L.) Osbeck), mandarina Satsuma Okitsu (C. unshiu Marc.), Clemenules (C. clementina Hort. ex Tan) y los híbridos Ellendale (C. sinensis L. Osbeck × C. reticulata Blanco) y Nova [C. clementina Hort. ex Tan, x (C. paradisi Macf. x C. tangerina Hort. ex Tan)] sobre pie trifolio (Poncirus trifoliata L. Raf.) durante cuatro campa as (2005/06 a 2009/10). Se calculó los grados días (GD) con temperatura base de 12,5 °C desde plena floración a cosecha. La fecha de inicio de floración fue variable de acuerdo al a o (P = 0,0002) siendo más temprana durante 2006/07 y más tardía en 2007/08. Se encontraron diferencias en los GD acumulados por variedad (P = 0,0001) y a o (P = 0,0029). Las mandarinas de maduración temprana Satsuma Okitsu y Clemenules fueron l
El Contrato de Reporte y su Regulacion en la Legislacion Peruana
Manuel Porro Rivadeneira
Revista e-Mercatoria , 2010,
Abstract: Actualmente uno de los problemas críticos que afrontan las empresas es el del financiamiento, ante este panorama existen dos opciones principales para las empresas: generar recursos propios e incrementar su capital social con recursos obtenidos de diversas fuentes de financiación externa.Justamente en este segundo escenario, surge la opcion que nos ocupa en el presente artículo. Pretendemos entonces dar una perspectiva general del Contrato de Reporte, sus características, sujetos intervinientes, obligaciones principales, con especial enfasis en su regulación en la regulación jurídica Peruana y una breve mención de la legislacion extranjera.
Responsabilidad social empresarial en el Perú
Manuel Porro Rivadeneira
Revista e-Mercatoria , 2008,
Abstract: Como parte del crecimiento y el desarrollo de los agentes económicos se ha creído conveniente analizar una institución de reciente data que afecta de modo especial a los grupos de interés (stakeholders) unidos a la empresa, es por ello que la presente investigación pretende analizar de modo amplio y general los aspectos más relevantes de la Responsabilidad Social Empresarial así como aquellos de difícil tratamiento y de modo específico resolveremos la pregunta cómo ha avanzado en materia de instrumentalización y normatividad la Responsabilidad Social Empresarial en el Perú?
Abordaje extremo lateral transcondilar para resecar un meningioma anterior del foramen magno
Alvaro Campero,Conrado Rivadeneira
Revista Argentina de Neurocirugía , 2006,
Abstract: Objetivo. Describir el abordaje extremo lateral transcondilar realizado para resecar un meningioma del sector anterior del foramen magno. Descripción. Mujer de 24 a os con una tetraparesia a predominio derecho y déficit de los nervios craneanos IX, X y XI del lado derecho, de 9 meses de evolución. La resonancia magnética mostró un proceso expansivo a nivel del sector anterior del foramen magno (isointenso en T1 y T2, captando en forma homogénea y bien marcada luego de la administración del gadolinio). Intervención. En diciembre de 2005 se realizó la cirugía (abordaje extremolateral transcondilar), con resección completa de la lesión. Anatomía patológica: meningioma cordoide. La paciente evolucionó mejorando completamente de su clínica neurológica, encontrándose actualmente sin ninguna secuela. Conclusión. En este caso el abordaje extremo lateral transcondilar fue la vía de elección para resecar completamente el meningioma del sector anterior del foramen magno. Objective: To describe the far-lateral transcondylar approach performed to remove a meningioma of the anterior portion of the foramen magnum. Description: A woman, 24-years old, with tetraparesis, greater in the right side, and paresis of the IX, X, and XI right cranial nerves, with a 9 months history. The MRI showed a tumor in the anterior aspect of the foramen magnum (isointense in T1 and T2, with homogeneous enhance after gadolinium administration). Intervention. In December 2005 the surgery was performed (far-lateral transcondylar approach), with complete removal of the lesion. Histology: cordoid meningioma. The patient had a good outcome, with complete recovery of her neurological deficits. In the last control she was asymptomatic. Conclusion. In this case, the far-lateral transcondylar was the most appropriate approach to completely resect a meningioma of the anterior portion of the foramen magnum.
BIG4 or Non-BIG4 Auditors: Their Impact on Audit Quality during the Global Financial Crisis  [PDF]
Maria I. Kyriakou, Augustinos I. Dimitras
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.85064
Abstract: The objective of this paper is to examine the relationship between auditor tenure and discretionary accruals as a proxy of audit quality. The main finding is that this relationship was found to be negative for BIG4 and non-BIG4 auditors in crisis and non-crisis periods, for both German and French companies. In addition, Italian and Spanish companies seem to interplay in crisis and non-crisis periods being either negative or not for BIG4 and non-BIG4 auditors. The findings imply that the larger the country, the better the audit quality and this seems to be confirmed by graphs and statistically by the one-sample T-test.
Initial values for Riccati ODEs from variational PDEs
Costanza, Vicente;Rivadeneira, Pablo S.;
Computational & Applied Mathematics , 2011, DOI: 10.1590/S1807-03022011000200005
Abstract: the recently discovered variational pdes (partial differential equations) for finding missing boundary conditions in hamilton equations of optimal control are applied to the extended-space transformation of time-variant linear-quadratic regulator (lqr) problems. these problems become autonomous but with nonlinear dynamics and costs. the numerical solutions to the pdes are checked against the analytical solutions to the original lqr problem. this is the first validation of the pdes in the literature for a nonlinear context. it is also found that the initial value of the riccati matrix can be obtained from the spatial derivative of the hamiltonian flow, which satisfies the variational equation. this last result has practical implications when implementing two-degrees-of freedom control strategies for nonlinear systems with generalized costs.
Patrones asociados a la conducta de desplazamiento local en Phymactis clematis Drayton (Anthozoa: Actiniidae)
RIVADENEIRA,MARCELO M.; OLIVA,EDUARDO;
Revista chilena de historia natural , 2001, DOI: 10.4067/S0716-078X2001000400012
Abstract: phymactis clematis drayton is the most abundant and one of the largest species of sea anemone along the south american coast. likewise other sea anemone species, the adults of the p. clematis would have an active ability to make local movements. however, these have not been properly described, and causal factors are unknown. in this work we try to describe some of the basic patterns associated to the local movement behavior in p. clematis, assessed indirectly from the presence of bare rock halos around individuals in two rocky intertidal sites in the coast of northern chile (cavancha and colorado chico). movements were more frequent and had a higher intensity at colorado chico, where over 50 % of individuals showed movements, although they were mainly lower than 60 mm in length. at colorado chico, movements would occur in individuals larger than 40 mm of pedal diameter, whereas their intensity would decrease with body size. we discussed that causes of higher movement activity at colorado chico could be associated to the higher abundance and lower inter-individual spacing, which would produce physical interference among individuals. in this way, we suggested that the patterns associated to the individual's body size would arise secondarily, being dependent on the levels of local abundance. despite local movements of p. clematis at colorado chico occurred at a scale of a few centimeters, they could be affecting significantly the inter-individual spacing, increasing the average nearest neighbor distance. we argue that local movements could be an effective mechanism reducing the intraspecific competition in p. clematis
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