Fabian Ramirez | Universidad Rafael Landivar (original) (raw)

Papers by Fabian Ramirez

Revista Colombiana …, 2009

Resumen Propuesta: las vasculitis primarias se expresan de forma variable entre pacientes y entre... more Resumen Propuesta: las vasculitis primarias se expresan de forma variable entre pacientes y entre regiones, con frecuencias variables a través del mundo. Su incidencia promedio está calculada en 0, 3 a 20 casos por millón de habitantes. Nosotros describimos la ...

Journal of Alloys and Compounds, 2013

We study the nature of short-range magnetic interactions observed in the paramagnetic phase of co... more We study the nature of short-range magnetic interactions observed in the paramagnetic phase of colossal magnetoresistance compounds. Our results reveal that ferromagnetic-like interaction between Mn ions cannot be explained by the conventional double exchange mechanism. The results show evidence that the e g electrons are localized in Mn 3+ ions regardless the introduction of holes leading to ferromagnetic/antiferromagnetic superexchange-like interactions.

Brazilian Journal of Physics, 2014

Journal of Magnetism and Magnetic Materials, 2012

Magnetic, structural, and electric transport measurements at high temperatures were carried out o... more Magnetic, structural, and electric transport measurements at high temperatures were carried out on La 1Àx Ca x MnO 3 ; x ¼ 0. 20, 0.25, 0.30, 0.34, 0.40, and 0.45. All samples show a first-order structural phase transition from orthorhombic Pnma to rhombohedral R3c space group at T R2O . Magnetic susceptibility measurements show that the Curie-Weiss law is strictly obeyed in the rhombohedral phase as opposed to the orthorhombic phase where the effective magnetic moment has a temperature dependence. The electrical resistivity is well described by the small polaron hopping mechanism in the samples up to x ¼ 0.34. As the charge carriers are introduced into the system (x ¼ 0.40 and 0.45), this mechanism of hopping ceases to be valid. The value of Grüneisen parameter obtained through analysis of highresolution X-ray powder diffraction as a function of temperature increases abruptly for the sample with x ¼ 0.40. This is consistent with an increase in bending and stretchinglike frequency modes observed by Raman spectroscopy.

International Journal of Cardiology, 2011

International Journal of Cardiology, 2011

Acute Myocardial Infarction (AMI) is one of the main causes of mortality and disability in Colomb... more Acute Myocardial Infarction (AMI) is one of the main causes of mortality and disability in Colombia. The factors associated to a new event in surviving subjects to a first AMI in our population have not yet been fully identified.Two hundred and ninety five surviving subjects to a first AMI (58.8 ± 12.6 years) were included in a prospective cohort study between 2000 and 2006. Lipid profile, glycemia and plasma insulin levels were measured. Deaths of cardiovascular origin, a new AMI, unstable angina, heart failure, stroke, new myocardial revascularization or angioplasty were considered new cardiovascular events.The study included 61 (20.6%) women and 234 (79.4%) men. The mean follow up time was 50 ± 30 months with a 38.9% incidence of new events. Fifty five patients (18.6%) were diabetic. Bi-varied analysis identified as risk factors for a new cardiovascular event the presence of: hypertension, anterior descending coronary artery stenosis, intrahospital cardiac failure, age over 55, low income, lack of education, Killip III–IV, heart rate over 76 bpm, pulse pressure over 80 mm Hg, total cholesterol over 200 mg/dl and insulin over 10 IU/ml. After logistic regression analysis, the log values of insulin remained as the only significant predictor for new cardiovascular events.Hyperinsulinism was the most important factor associated to the occurrence of new cardiovascular events in Colombian patients with AMI, which emphasizes the pivotal role of insulin resistance in the physiopathologic mechanisms of atherosclerosis, especially in undeveloped countries.

Revista Colombiana …, 2009

Resumen Propuesta: las vasculitis primarias se expresan de forma variable entre pacientes y entre... more Resumen Propuesta: las vasculitis primarias se expresan de forma variable entre pacientes y entre regiones, con frecuencias variables a través del mundo. Su incidencia promedio está calculada en 0, 3 a 20 casos por millón de habitantes. Nosotros describimos la ...

Journal of Alloys and Compounds, 2013

We study the nature of short-range magnetic interactions observed in the paramagnetic phase of co... more We study the nature of short-range magnetic interactions observed in the paramagnetic phase of colossal magnetoresistance compounds. Our results reveal that ferromagnetic-like interaction between Mn ions cannot be explained by the conventional double exchange mechanism. The results show evidence that the e g electrons are localized in Mn 3+ ions regardless the introduction of holes leading to ferromagnetic/antiferromagnetic superexchange-like interactions.

Brazilian Journal of Physics, 2014

Journal of Magnetism and Magnetic Materials, 2012

Magnetic, structural, and electric transport measurements at high temperatures were carried out o... more Magnetic, structural, and electric transport measurements at high temperatures were carried out on La 1Àx Ca x MnO 3 ; x ¼ 0. 20, 0.25, 0.30, 0.34, 0.40, and 0.45. All samples show a first-order structural phase transition from orthorhombic Pnma to rhombohedral R3c space group at T R2O . Magnetic susceptibility measurements show that the Curie-Weiss law is strictly obeyed in the rhombohedral phase as opposed to the orthorhombic phase where the effective magnetic moment has a temperature dependence. The electrical resistivity is well described by the small polaron hopping mechanism in the samples up to x ¼ 0.34. As the charge carriers are introduced into the system (x ¼ 0.40 and 0.45), this mechanism of hopping ceases to be valid. The value of Grüneisen parameter obtained through analysis of highresolution X-ray powder diffraction as a function of temperature increases abruptly for the sample with x ¼ 0.40. This is consistent with an increase in bending and stretchinglike frequency modes observed by Raman spectroscopy.

International Journal of Cardiology, 2011

International Journal of Cardiology, 2011

Acute Myocardial Infarction (AMI) is one of the main causes of mortality and disability in Colomb... more Acute Myocardial Infarction (AMI) is one of the main causes of mortality and disability in Colombia. The factors associated to a new event in surviving subjects to a first AMI in our population have not yet been fully identified.Two hundred and ninety five surviving subjects to a first AMI (58.8 ± 12.6 years) were included in a prospective cohort study between 2000 and 2006. Lipid profile, glycemia and plasma insulin levels were measured. Deaths of cardiovascular origin, a new AMI, unstable angina, heart failure, stroke, new myocardial revascularization or angioplasty were considered new cardiovascular events.The study included 61 (20.6%) women and 234 (79.4%) men. The mean follow up time was 50 ± 30 months with a 38.9% incidence of new events. Fifty five patients (18.6%) were diabetic. Bi-varied analysis identified as risk factors for a new cardiovascular event the presence of: hypertension, anterior descending coronary artery stenosis, intrahospital cardiac failure, age over 55, low income, lack of education, Killip III–IV, heart rate over 76 bpm, pulse pressure over 80 mm Hg, total cholesterol over 200 mg/dl and insulin over 10 IU/ml. After logistic regression analysis, the log values of insulin remained as the only significant predictor for new cardiovascular events.Hyperinsulinism was the most important factor associated to the occurrence of new cardiovascular events in Colombian patients with AMI, which emphasizes the pivotal role of insulin resistance in the physiopathologic mechanisms of atherosclerosis, especially in undeveloped countries.