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Papers by Rodrigo Grover Chavez Rivera
Latin American Journal of Physics Education, 2008
In this work we intend to measure the conceptual change produced in a group post-graduate program... more In this work we intend to measure the conceptual change produced in a group post-graduate program called "MECIBA" (Mejoramiento de las Ciencias en la Enseñanza Básica / Improving Science in Elementary Teaching), whose goal it is to enhance the quality of science teaching. To achieve this goal we designed and applied tests and interviews aimed to know more about the pre-conceptions that the participants had in two areas of Physics that were covered during the workshops: "Moving Objects" and "Nature of Light". With the results obtained on the pre and post tests, and the interviews made before each workshop to increase our knowledge of the preconceptions of the participants, we could observe an important improvement on the replacement of the preconceptions by formal conceptions, and also in the capacity to apply them to different situations, all of which are exposed through quantitative data.
Revista Mexicana De Fisica, Mar 1, 2007
In this work we analyze in detail the dynamical behavior of a quantum dot in presence of a unifor... more In this work we analyze in detail the dynamical behavior of a quantum dot in presence of a uniform time-dependent magnetic field, in the effective mass approximation. An exact solution for the time-evolved wave function is obtained when the initial state is a particular Fock- Darwin state. Moreover, we calculate the transition probability from an initial Fock-Darwin state to a
Revista Medica De Chile, Nov 26, 2014
Cienc Rural, 2006
ABSTRACT
Data Revues 01509861 Unassign S0150986111001143, Dec 19, 2011
Internal carotid artery; Fenestration; Aneurysm; Embolization Summary We report two cases of aneu... more Internal carotid artery; Fenestration; Aneurysm; Embolization Summary We report two cases of aneurysm located in a fenestration of the supraclinoid internal carotid artery, an extremely rare anatomical variant, and describe the feasibility of endovascular treatment using two different strategies applicable for each case. Each presented aneurysm had a particular location on the fenestration, which led to different endovascular approaches. In one case, the aneurysm arose from the proximal junction of fenestration, involving both of its limbs. For this aneurysm, the treatment strategy adopted aimed to achieve a selective exclusion. In the second case, two aneurysms arose from the minor limb of the fenestration, which could be entirely excluded, considering the absence of perforating arteries arising from that carotid segment. To our knowledge, these two cases are the first ICA fenestration aneurysms treated exclusively by endovascular approach, showing two treatment strategies using coils in association to two different endovascular devices (stent/TrisPan ® ). (C. Mounayer).
Revista Brasileira De Medicina Do Esporte, Dec 1, 2008
O objetivo deste trabalho foi comparar concentrações de estresse oxidativo em camundongos da linh... more O objetivo deste trabalho foi comparar concentrações de estresse oxidativo em camundongos da linhagem Balb-C submetidos a duas condições severas de alterações orgânicas: treinamento exaustivo de natação (overreaching - grupo OVER; n = 10) e inoculação por tumor ascítico de Ehrlich (grupo TAE; n = 10). A proposta foi analisar como as duas situações comprometiam o equilíbrio entre os sistemas oxidantes e antioxidantes. Foram investigados alguns marcadores de estresse oxidativo, tais como as substâncias reativas ao ácido tiobarbitúrico (TBARS) e concentrações da atividade da enzima antioxidante catalase (CAT) no hemolisado. Como marcadores de lesão celular, quantificaram-se concentrações plasmáticas das enzimas creatina quinase (CK) e aspartato transferase (AST); complementado; também se observaram padrões de alterações fisiológicas por meio da quantificação plasmática de creatinina e uréia. Como resultados mais importantes, pôde-se observar que, nas duas situações de limite orgânico, seja por exercício exaustivo (OVER) ou pela inoculação de TAE, houve queda abrupta na concentração da enzima CAT (decréscimos de 30%; p < 0,01 e 72%; p < 0,001, respectivamente, comparando-se com o grupo treinado - T). Quanto à concentração de peroxidação lipídica (TBARS), detectaram-se aumentos significativos para os grupos OVER e TAE em relação ao grupo T (52%, p < 0,01; 90%, p < 0,001, respectivamente). Níveis liberados de CK foram mais proeminentes no grupo OVER, enquanto que a quantidade de AST no plasma foi mais elevada no grupo TAE. Chegou-se à conclusão de que os organismos estudados possuem um mesmo perfil de estresse oxidativo em situações limites que envolvem exercício físico e doença. Tais resultados permitirão profissionais envolvidos com elaboração das cargas de treinamento físico a se preocuparem com os períodos recuperativos, o que impede a instalação do quadro de overreaching, o qual se mostrou tão severo, em termos de estresse oxidativo, quanto o de uma situação patológica.
Bol Hosp San Juan De Dios, Aug 1, 1986
PLOS ONE, 2016
A siphon is a device that is used to drain a container, with water rising inside a hose in the fo... more A siphon is a device that is used to drain a container, with water rising inside a hose in the form of an inverted U and then going down towards a discharge point placed below the initial water level. The siphon is the first of a number of inventions of the ancients documented about 2.000 years ago by Hero of Alexandria in his treatise Pneumatics, and although the explanation given by Hero was essentially correct, there is nowadays a controversy about the underlying mechanism that explains the working of this device. Discussions concerning the physics of a siphon usually refer to concepts like absolute negative pressures, the strength of liquid's cohesion and the possibility of a siphon working in vacuum or in the presence of bubbles. Torricelli understood the working principle of the barometer and the impossibility of pumping water out of wells deeper than 10.33 m. Following Torricelli's ideas it would also not be possible to build a siphon that drives pure water to ascend higher than 10.33 m. In this work, we report the first siphon that drives water (with surfactant) to ascend higher than the Torricellian limit. Motivated by the rising of sap in trees, we built a 15.4 m siphon that shows that absolute negative pressures are not prohibited, that cohesion plays an important role in transmitting forces through a fluid, and that surfactants can help to the transport of water in a metastable regime of negative pressures.
Bol Hosp San Juan De Dios, Dec 1, 1986
Ensenanza De Las Ciencias Revista De Investigacion Y Experiencias Didacticas, 2012
... Comisión Económica para América Latina y el Caribe (CEPAL) Evolución y distribución del ingre... more ... Comisión Económica para América Latina y el Caribe (CEPAL) Evolución y distribución del ingreso agrícola en América Latina: evidencia a partir de cuentas nacionales y encuestas de hogares Alberto Valdés William Foster Rodrigo Pérez Rodrigo Rivera Page 2. ...
Cerebral aneurysms are thin walled and stiffer compared with a normal artery. The current work de... more Cerebral aneurysms are thin walled and stiffer compared with a normal artery. The current work describes fluid structure interaction (FSI) simulations in a patient specific model of a cerebral aneurysm located in the ophthalmic region, using different wall thickness and elastic modulus for the artery and aneurysm. The geometry was reconstructed from a three dimensional angiography examination. The wall was assumed as elastic shell with variable thickness. The FSI model was calculated using the finite elements software ADINA. The fluid dynamics and solid mechanics predictions on the aneurysm wall were reported.
Physics Letters A, 2006
In this work we study the dynamics of electrons in presence of a uniform time-dependent magnetic ... more In this work we study the dynamics of electrons in presence of a uniform time-dependent magnetic field. An exact solution for the wave function time evolution is obtained when the initial state is a superposition of Landau levels. For a given time dependence of the magnetic field, the time-evolved wave function differs from the initial wave function by a dynamic phase factor.
![Research paper thumbnail of [Changes in cerebral blood flow velocity in supine and sitting position in patients with aneurysmal subarachnoid hemorrhage]](https://attachments.academia-assets.com/66550175/thumbnails/1.jpg)
](Revista médica de Chile, 2014
Early mobilization in intensive care units (ICU) provides respiratory, neurological and cardiovas... more Early mobilization in intensive care units (ICU) provides respiratory, neurological and cardiovascular benefits in hospitalized patients. However, the orthostatic effects of changing from a supine to a sitting position may interfere with cerebral hemodynamics of patients with aneurysmal subarachnoid hemorrhage (aSAH). To describe the changes in mean cerebral blood flow velocity (MCBFV) in supine and sitting position, in adult patients with aSAH, with asymptomatic vasospasm (AVS) or without vasospasm (VS) at a neurosurgical ICU. Descriptive case series study in 21 patients with aSAH, both with and without VS. They were positioned in a supine 30° position and then seated at the edge of bed for six minutes. MCBFV was measured by transcranial Doppler (TCD), and hemodynamic variables in both positions were registered. After this basal assessment and for 21 days after the episode of SAH, patients were seated once a day and signs of VS were recorded. No significant changes in MCBFV or hemo...
Latin American Journal of Physics Education, 2008
In this work we intend to measure the conceptual change produced in a group post-graduate program... more In this work we intend to measure the conceptual change produced in a group post-graduate program called "MECIBA" (Mejoramiento de las Ciencias en la Enseñanza Básica / Improving Science in Elementary Teaching), whose goal it is to enhance the quality of science teaching. To achieve this goal we designed and applied tests and interviews aimed to know more about the pre-conceptions that the participants had in two areas of Physics that were covered during the workshops: "Moving Objects" and "Nature of Light". With the results obtained on the pre and post tests, and the interviews made before each workshop to increase our knowledge of the preconceptions of the participants, we could observe an important improvement on the replacement of the preconceptions by formal conceptions, and also in the capacity to apply them to different situations, all of which are exposed through quantitative data.
Revista Mexicana De Fisica, Mar 1, 2007
In this work we analyze in detail the dynamical behavior of a quantum dot in presence of a unifor... more In this work we analyze in detail the dynamical behavior of a quantum dot in presence of a uniform time-dependent magnetic field, in the effective mass approximation. An exact solution for the time-evolved wave function is obtained when the initial state is a particular Fock- Darwin state. Moreover, we calculate the transition probability from an initial Fock-Darwin state to a
Revista Medica De Chile, Nov 26, 2014
Cienc Rural, 2006
ABSTRACT
Data Revues 01509861 Unassign S0150986111001143, Dec 19, 2011
Internal carotid artery; Fenestration; Aneurysm; Embolization Summary We report two cases of aneu... more Internal carotid artery; Fenestration; Aneurysm; Embolization Summary We report two cases of aneurysm located in a fenestration of the supraclinoid internal carotid artery, an extremely rare anatomical variant, and describe the feasibility of endovascular treatment using two different strategies applicable for each case. Each presented aneurysm had a particular location on the fenestration, which led to different endovascular approaches. In one case, the aneurysm arose from the proximal junction of fenestration, involving both of its limbs. For this aneurysm, the treatment strategy adopted aimed to achieve a selective exclusion. In the second case, two aneurysms arose from the minor limb of the fenestration, which could be entirely excluded, considering the absence of perforating arteries arising from that carotid segment. To our knowledge, these two cases are the first ICA fenestration aneurysms treated exclusively by endovascular approach, showing two treatment strategies using coils in association to two different endovascular devices (stent/TrisPan ® ). (C. Mounayer).
Revista Brasileira De Medicina Do Esporte, Dec 1, 2008
O objetivo deste trabalho foi comparar concentrações de estresse oxidativo em camundongos da linh... more O objetivo deste trabalho foi comparar concentrações de estresse oxidativo em camundongos da linhagem Balb-C submetidos a duas condições severas de alterações orgânicas: treinamento exaustivo de natação (overreaching - grupo OVER; n = 10) e inoculação por tumor ascítico de Ehrlich (grupo TAE; n = 10). A proposta foi analisar como as duas situações comprometiam o equilíbrio entre os sistemas oxidantes e antioxidantes. Foram investigados alguns marcadores de estresse oxidativo, tais como as substâncias reativas ao ácido tiobarbitúrico (TBARS) e concentrações da atividade da enzima antioxidante catalase (CAT) no hemolisado. Como marcadores de lesão celular, quantificaram-se concentrações plasmáticas das enzimas creatina quinase (CK) e aspartato transferase (AST); complementado; também se observaram padrões de alterações fisiológicas por meio da quantificação plasmática de creatinina e uréia. Como resultados mais importantes, pôde-se observar que, nas duas situações de limite orgânico, seja por exercício exaustivo (OVER) ou pela inoculação de TAE, houve queda abrupta na concentração da enzima CAT (decréscimos de 30%; p < 0,01 e 72%; p < 0,001, respectivamente, comparando-se com o grupo treinado - T). Quanto à concentração de peroxidação lipídica (TBARS), detectaram-se aumentos significativos para os grupos OVER e TAE em relação ao grupo T (52%, p < 0,01; 90%, p < 0,001, respectivamente). Níveis liberados de CK foram mais proeminentes no grupo OVER, enquanto que a quantidade de AST no plasma foi mais elevada no grupo TAE. Chegou-se à conclusão de que os organismos estudados possuem um mesmo perfil de estresse oxidativo em situações limites que envolvem exercício físico e doença. Tais resultados permitirão profissionais envolvidos com elaboração das cargas de treinamento físico a se preocuparem com os períodos recuperativos, o que impede a instalação do quadro de overreaching, o qual se mostrou tão severo, em termos de estresse oxidativo, quanto o de uma situação patológica.
Bol Hosp San Juan De Dios, Aug 1, 1986
PLOS ONE, 2016
A siphon is a device that is used to drain a container, with water rising inside a hose in the fo... more A siphon is a device that is used to drain a container, with water rising inside a hose in the form of an inverted U and then going down towards a discharge point placed below the initial water level. The siphon is the first of a number of inventions of the ancients documented about 2.000 years ago by Hero of Alexandria in his treatise Pneumatics, and although the explanation given by Hero was essentially correct, there is nowadays a controversy about the underlying mechanism that explains the working of this device. Discussions concerning the physics of a siphon usually refer to concepts like absolute negative pressures, the strength of liquid's cohesion and the possibility of a siphon working in vacuum or in the presence of bubbles. Torricelli understood the working principle of the barometer and the impossibility of pumping water out of wells deeper than 10.33 m. Following Torricelli's ideas it would also not be possible to build a siphon that drives pure water to ascend higher than 10.33 m. In this work, we report the first siphon that drives water (with surfactant) to ascend higher than the Torricellian limit. Motivated by the rising of sap in trees, we built a 15.4 m siphon that shows that absolute negative pressures are not prohibited, that cohesion plays an important role in transmitting forces through a fluid, and that surfactants can help to the transport of water in a metastable regime of negative pressures.
Bol Hosp San Juan De Dios, Dec 1, 1986
Ensenanza De Las Ciencias Revista De Investigacion Y Experiencias Didacticas, 2012
... Comisión Económica para América Latina y el Caribe (CEPAL) Evolución y distribución del ingre... more ... Comisión Económica para América Latina y el Caribe (CEPAL) Evolución y distribución del ingreso agrícola en América Latina: evidencia a partir de cuentas nacionales y encuestas de hogares Alberto Valdés William Foster Rodrigo Pérez Rodrigo Rivera Page 2. ...
Cerebral aneurysms are thin walled and stiffer compared with a normal artery. The current work de... more Cerebral aneurysms are thin walled and stiffer compared with a normal artery. The current work describes fluid structure interaction (FSI) simulations in a patient specific model of a cerebral aneurysm located in the ophthalmic region, using different wall thickness and elastic modulus for the artery and aneurysm. The geometry was reconstructed from a three dimensional angiography examination. The wall was assumed as elastic shell with variable thickness. The FSI model was calculated using the finite elements software ADINA. The fluid dynamics and solid mechanics predictions on the aneurysm wall were reported.
Physics Letters A, 2006
In this work we study the dynamics of electrons in presence of a uniform time-dependent magnetic ... more In this work we study the dynamics of electrons in presence of a uniform time-dependent magnetic field. An exact solution for the wave function time evolution is obtained when the initial state is a superposition of Landau levels. For a given time dependence of the magnetic field, the time-evolved wave function differs from the initial wave function by a dynamic phase factor.
Revista médica de Chile, 2014
Early mobilization in intensive care units (ICU) provides respiratory, neurological and cardiovas... more Early mobilization in intensive care units (ICU) provides respiratory, neurological and cardiovascular benefits in hospitalized patients. However, the orthostatic effects of changing from a supine to a sitting position may interfere with cerebral hemodynamics of patients with aneurysmal subarachnoid hemorrhage (aSAH). To describe the changes in mean cerebral blood flow velocity (MCBFV) in supine and sitting position, in adult patients with aSAH, with asymptomatic vasospasm (AVS) or without vasospasm (VS) at a neurosurgical ICU. Descriptive case series study in 21 patients with aSAH, both with and without VS. They were positioned in a supine 30° position and then seated at the edge of bed for six minutes. MCBFV was measured by transcranial Doppler (TCD), and hemodynamic variables in both positions were registered. After this basal assessment and for 21 days after the episode of SAH, patients were seated once a day and signs of VS were recorded. No significant changes in MCBFV or hemo...