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Search Results: 1 - 10 of 854744 matches for " J. A. Márquez "
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A Comparative Study on the Structural and Vibrational Properties of Two Potential Antimicrobial and Anticancer Cyanopyridine Derivatives  [PDF]
María J. Márquez, María B. Márquez, Pablo G. Cataldo, Silvia A. Brandán
Open Journal of Synthesis Theory and Applications (OJSTA) , 2015, DOI: 10.4236/ojsta.2015.41001
Abstract: 2-Hydroxy-4,6-dimethylpyridine-3-carbonitrile and 2-chloro-4,6-dimethylpyridine-3-carbonitrile compounds have been studied from a theoretical point of view in order to know their structural and vibrational properties in gas and aqueous solution phases by means of Density Functional Theory (DFT) calculations. The stable structures in both media were optimized by using the hybrid B3LYP/6-31G* method and the solvent effects in aqueous solution were studied by using the integral equation formalism of the polarizable continuum model (IEFPCM) employing the selfconsistent reaction field (SCRF) method. Detailed vibrational analyses for both compounds in the two phases were performed combining the DFT calculations with Pulay’s Scaled Quantum Mechanics Force Field (SQMFF) methodology. The different interactions for both compounds were analyzed by means of the bond orders, atomic charges, solvation energies, dipole moments, molecular electrostatic potentials and force constants parameters. The nature of the interactions was studied by using different descriptors.
Spectrum and Generation of Solutions of the Toda Lattice
D. Barrios Rolanía,J. R. Gascón Márquez
Discrete Dynamics in Nature and Society , 2009, DOI: 10.1155/2009/237487
Abstract: Sufficient conditions for constructing a set of solutions of the Toda lattice are analyzed. First, under certain conditions the invariance of the spectrum of () is established in the complex case. Second, given the tri-diagonal matrix () defining a Toda lattice solution, the dynamic behavior of zeros of polynomials associated to () is analyzed. Finally, it is shown by means of an example how to apply our results to generate complex solutions of the Toda lattice starting with a given solution.
Mid- and Far-Infrared Photometry of Galactic Planetary Nebulae with the AKARI All-Sky Survey
Phillips, J. P.;Márquez-Lugo, R. A;
Revista mexicana de astronomía y astrofísica , 2011,
Abstract: we provide mid- and far-infrared photometry of 857 galactic planetary nebulae (pne) using data derived from the akari all-sky survey. these include fluxes at 9 and 18 μm obtained with the infrared camera (irc), and at 65, 90, 140 and 160 μm using the far-infrared surveyor (fis). it is noted that the ir luminosities of the youngest pne are comparable to the total luminosities of the central stars, and subsequently decline to where d > 0.08 pc. this is consistent with an evolution of pne dust opacities, and appreciable absorption in young and proto-pne. we also note that there is little evidence for the evolution in ir/radio flux ratios suggested by previous authors. the fall-off of dust temperatures with increasing nebular diameter is similar to that determined in previous studies, whilst levels of lyα heating are <0.5 of the total energy budget of the grains. there appears to be an evolution in the infrared excess (ire) as nebulae expand, with the largest values occurring in the most compact pne.
Potencial cosechable de la Ostra Crassostrea rhizophorae (Guilding), en la ciénaga grande de Santa Marta, Colombia
Hernández J. Carlos A.,Márquez Germán
Acta Biológica Colombiana , 1987,
Abstract: The potencial standing crop of oyster Crassostrea rhizophorae has been calculated as 938,6 tons oyster meat per year (wet-weight) for market sized oyster, in the northern zone of the Cienaga Grande de Santa Marta. It has been estimated that the oyster-bank area within this zones covers 3.000.000 sq.m. The calculated actual oyster standing crop for that area during this research (April-November 1982) was 3,9 tons of oyster-meat (wet-weight) and the actual catch 2,0 tons (in the same period). This reduction in the actual standing crop of oyster is mainly the result of: 1. The low prolonged salinity and the sediment causes mass mortality on oyster population; 2. Deterioration of the quality and available amounts of supporting shell substratum, required by oyster seedling attach and growth until they reach comercial size. Se cuantificó la oferta potencial de la ostra Crassostrea rhizophorae (Guíldíng, 1828) en 938,6 toneladas de carne/a o (peso húmedo) para ostras con talla comercial en la zona norte de la Ciénaga Grande de Santa Marta. Se estimó que el área de los bancos en esta zona es de 3.000.000 metros cuadrados. La oferta real de ostra en el periodo de estudio (abril-noviembre de 1982) fue de 3,9 toneladas carne (peso húmedo) y se estimó que se cosecharon aproximadamente 2,0 toneladas carne (peso húmedo). Esta variación en la oferta natural de ostra se debe principalmente a: 1. Baja prolongada de la salinidad que junto con la sedimentación ocasiona la mortalidad masiva de las poblaciones de ostras; 2. Deterioro de la calidad y cantidad del sustrato de concha que requieren las "semillas" de ostras para fijarse y crecer hasta alcanzar tallas comerciales.
Paleontología y ambientes sedimentarios del Triásico medio, Muschelkalk, de la Cordillera Ibérica 1: Cuencas y Valencia. Espa a
Márquez-Aliaga, A.,López Gómez, J.
Estudios Geologicos , 1989, DOI: 10.3989/egeol.89455-6510
Abstract: The Muscbelkalk Facies of tbe SE. Iberian Ranges is formed by tbe Landete Dolomites (d.L.), Mas Sandstones, Marls and Gypsum (a.m.y.M) and Ca ete Dolomites and Limestone (d.c.C.) Formations. This paper deals on tbe paleontology and sedimentary environments of the two carbonatic Formations (d.L. and d.c.C.). Ten sections all over the area have been studied in detail and nine facies associations, each one formed by sequences less than 2m. thick, have been differenciated. Possibly, due to the dolomitization, fossil register is in general considered to be scaree and badly preserved. The analysis of the sequences reveals three different subenvironments (shoal, lagoon and sabkha). Two episodes can be differenciated for each carbonatic formation during the development of the depositional system: first, a short-lived transgression fol1owed by a longer regresive period. By far, the most abundant fossils are Molluscs of Bivalvia Class, forming a benthonic association dominated by suspensivores. The bivalves are found in both carbonated units, although in the upper one the faunistic richness and specific diversity are higher. The taphonomic analysis reveals some autochtonous associations in both formations. The bivalve association found at the last beds of the upper Muschelkalk Facies of the lberian Ranges is known as tbe Teruel Fauna , well represented in the Villora and Henarejos sections. The association consists on endo and epibisate Bivalves and some cemented ones, and represents different shallow carbonatic marine subenvironments. A Section Type has been cboosen and divided into 4 and 5 main levels or parts (for d.L. and d.c.C. respectively). Each of these parts is dominated by the abundance of one of the facies associations. Las unidades dolomías de Landete (d. L.), areniscas, margas y yesos del Mas (a.m.y.M.) y dolomías y calizas de Ca ete (d.c.C.) (Anisiense-parte inferior del Camiense, Triásico mediosuperior) de base a techo respectivamente, constituyen la Facies Muscbelkalk al SE. de la Rama Castel1ana de la Cordil1era Ibérica. Este trabajo enfoca el estudio paleontológico y de los medios sedimentarios de las dos unidades carbonatadas (d.L. y d.c.C.). Para ello, se han utilizado 10 columnas estratigráficas a lo largo de todo el área de estudio en las cuales se han diferenciado 9 asociaciones de facies constituidas cada una por una secuencia característica de menos de 2 m. de espesor. Se ha escogido una serie tipo en la que se han diferenciado 9 tramos constituidos cada uno de el10s por la repetición de una misma secuencia de las anteriormente citadas.
A statistical analysis of electric self-potential time series associated to two 1993 earthquakes in Mexico
L. Flores-Márquez,J. Márquez-Cruz,A. Ramírez-Rojas,G. Gálvez-Coyt
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2007,
Abstract: Recent studies related with earthquake prediction involve statistical studies of the ground electric self-potential behavior. Published results about the complexity of this kind of processes encourage us to study the statistical behavior of the ground electric self-potential recorded in Guerrero state, Mexico. This region is characterized by high seismicity. The electric self-potential variations were recorded in the Acapulco station directly from the ground. The sampling period was four seconds and the data were stored from March to December of 1993. Two significant earthquakes (EQs) occurred near this station, 15 May and 24 October whose magnitudes were Mw=6.0 and Mw=6.6 respectively. A preliminary processing was carried out consisting of a moving average of the original time series in order to filter the very high frequencies and to complete short lacks of data and outliers. Then, a visual inspection of the complete filtered signal was performed to search some seismic electric signals (SES), which were ambiguously depicted. Subsequently, a detrending of μ=0 was applied with the windows of 3.3, 6.6 and 10 h. Later, the analysis of the spectral exponent β was made, showing changes during the total period examined, and the most evident changes occurred during the preparation mechanism of the Mw=6.6 EQ. Fifteen days before the 24 October EQ, a Brownian-noise like behavior was displayed (β≈2), having a duration of about two days. In addition a Higuchi fractal method and wavelet analysis were made confirming the presence of the β-anomaly.
Degradación y recuperación de varistores de ZnO
Ramírez, M. A.,Bueno, P. R.,Valera, J. A.,Márquez, M. A.
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2006,
Abstract: In the present work it was studied the main aspect that influences on degradation and physical-chemical properties at grainboundary region of metal oxide varistors and its consequences on microstructure and nonohmic electric properties. Based on the comprehension of the degradation aspects it was proposed some methodologies to recover the varistors nonohmic properties after being failed with long (2000 μs) and short current pulses (8/20 μs). Our analysis shown that one of the cause of degradation process is related to the lowering of oxygen species amount at grain-boundary region. Therefore, it is possible to re-promote oxygen enrichment of such regions by specific thermal treatments in rich oxygen atmospheres (the best condition found in the present work was temperatures around 900°C for 2 h at an oxygen flux of 15 l/h). The proposed nonohmic properties recovering procedure appear to be valid for all kind metal oxide varistors studied and is very important from technological point of view. En este trabajo se estudia el fenómeno de la degradación eléctrica en varistores basados en ZnO y los factores físico-químicos que influyen en ella, así como su efecto sobre la microestructura y propiedades eléctricas. Con la comprensión de los fenómenos de degradación se proponen metolodogías para recuperar varistores después de fallados con pulsos de corriente de larga (2000 μs) y corta duración (8/20 μs). Los análisis mostraron que una de las causas de degradación es la pérdida de especies de oxígeno en el borde de grano, permitiendo implementar un tratamiento térmico posterior en atmósfera enriquecida de oxígeno para recuperar las propiedades del varistor (temperatura de 900°C por dos horas y 15 l/h de flujo de oxígeno, fue la mejor condición). El procedimiento de recuperación propuesto es válido para todos los sistemas varistores con base en óxido metálico, sean comerciales o no y es de gran interés tecnológico, pues torna viable el reciclaje de una gran cantidad de piezas cerámicas que actualmente son descartadas sin ningún uso.
Granulocytic Sarcoma Presenting as Atypical Mastoiditis with Facial Paralysis: Description of a Case
M. Crovetto,J. A. Márquez,C. Ere o,J. Elexpuru,R. Crovetto,A. Martinez
Case Reports in Otolaryngology , 2011, DOI: 10.1155/2011/191852
Abstract: We describe a case of temporal granulocytic sarcoma in a 26-year-old patient after apparent molecular remission of an acute myeloid leukaemia. He complained of otodynia with hearing loss and facial paralysis on the right side. He was treated with chemotherapy and self-transplant haematopoietic stem cells. He was cured clinically, molecular remission of the haematological processes was achieved, and he remained asymptomatic for three years. Facial paralysis and hearing loss associated with temporal GS should be treated with chemotherapy. Aggressive surgery may complicate the clinical course of the disease and it should be avoided.
Cambios en la etiología, resultados y características de los pacientes con hemorragia digestiva aguda grave a lo largo del periodo 1999-2005
Garrido,A.; Márquez,J. L.; Guerrero,F. J.; Leo,E.; Pizarro,M. A.; Trigo,C.;
Revista Espa?ola de Enfermedades Digestivas , 2007, DOI: 10.4321/S1130-01082007000500006
Abstract: objectives: to analyze the evolution of the following variables in patients admitted to a blood unit for gastrointestinal bleeding throughout 1999-2005: etiology, comorbid diseases, use of nsaids/anticoagulants, and mortality. material and methods: we analyzed the evolution of the following causes of gib that required admission to the blood unit from 1999 to 2005: duodenal ulcer (du), gastric ulcer (gu), portal hypertension (pht), and others. we also analyzed changes in the percentage of patients admitted with comorbid disease, use of nsaids/anticoagulants, and mortality. results: 1,611 patients with a mean age of 60.45 years (59.7-61.2) were included in this study; 76.41% were males (74.3-78.5). du was the cause of bleeding in 22.20% of cases (20.2-24.3), gu in 18.40% of cases (16.6-20.4), and pht in 33.60% of cases (31.3-36.0). in all, 34.5% (32.6-37.3) of patients were taking nsaids, 7.1% (6.0-8.6) were receiving anticoagulant therapy, 72.6% (70.4-74.8) presented with comorbid disease, and overall mortality was 6.27% (5.16-7.59). throughout the 1999-2005 period there was an increase in the number of patients with comorbid diseases (p < 0.02), and a decrease in cases of du (p < 0.04), without significant differences in the remaining variables. conclusions: du, gu and pht account for three quarters of admissions to our blood unit. over the last seven years, there has been a decrease in cases due to du, and an increase in patients with comorbid disease; overall mortality rates have remained stable.
Transfusion requirements in patients with gastrointestinal bleeding: a study in a Blood Unit at a referral hospital Requerimientos transfusionales en pacientes con hemorragia digestiva: estudio en una Unidad de Sangrantes de un hospital de referencia
A. Garrido,J. L. Márquez,F. J. Guerrero,M. A. Pizarro
Revista Espa?ola de Enfermedades Digestivas , 2006,
Abstract: Objectives: 1. To study transfusion requirements in the Department of Gastroenterology of a Tertiary Referral Hospital, and their evolution over the last seven years. 2. To analyze risk factors associated with greater erythrocyte transfusion requirements. Patients and methods: erythrocyte transfusion requirements were compared for patients admitted to the Department of Gastroenterology at Hospital Virgen del Rocío, Seville, from 1999 to 2005. Clinical data of interest have been analyzed in order to determine factors associated with greater transfusion requirements. Results: 1,611 patients with a mean age of 60.45 years (59.7-61.2) were included in this study; 76.41% were males. Gastric ulcers were the cause of bleeding in 18.4% of cases (with 69% requiring transfusions); duodenal ulcers caused 22.2% of cases (with 52.9% requiring transfusions), and portal hypertension caused 33.6% of cases (with 90.2% requiring transfusions). Upper and lower gastrointestinal bleeding of unknown origin requires transfusions in 88.9 and 96.2% of cases, respectively. A multivariate logistic regression analysis showed that clinical presentations such as hematemesis (odds ratio = 3.12), hematochezia (odds ratio = 33.17), gastrointestinal hemorrhage of unknown origin (odds ratio = 6.57), and hemorrhage as a result of portal hypertension (odds ratio = 3.43) were associated with greater transfusion requirements for erythrocyte concentrates. No significant differences were observed between the percentages of patients who received transfusions from 1999 to 2005. Conclusions: 1. No differences have been observed between the percentages of patients who received transfusions over the last seven years at our Department of Gastroenterology. 2. Patients presenting with hematemesis or hematochezia, in addition to those with bleeding of unknown origin or from portal hypertension, are prone to have greater transfusion requirements.
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