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Search Results: 1 - 10 of 201697 matches for " Román Alvarez "
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Redefinition of the Terminus of the Middle America Trench  [PDF]
Román Alvarez
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.44070
Abstract:

The terminus of the Middle America Trench has been traditionally represented as an arc, concave towards the continent. Tres Marías Islands are located at the terminus of the Middle America Trench in western Mexico, and their location is not only intriguing but also a key to the re-construction of the position of Baja California peninsula before separation from the North America plate. Previous re-constructions suggested various places around the location of Tres Marías Islands for the position of the tip of the peninsula, and several converge to a position that invades the area occupied by the islands, offering no explanation for the overlap. Before peninsular separation from North America, the Guadalupe trench followed a smooth curve; recreating the position of this paleo-trench yields a baseline for fixing the position of the peninsula, as well as the original position of the Tres Marías Islands fragment. A new tectonic view of the structure of the Middle America Trench terminus is proposed, replacing the traditional arc representation with a series of en echelon blocks, the northernmost terminates at the Tres Marías Escarpment. The long sides of the blocks correspond to previously identified geological faults in the Bahía de Banderas region, while their offshore continuation is supported by topographic observations. As a test of this model I show the corresponding re-construction of the position of Baja California prior to separation from the North America plate and the positional evolution of the peninsula and the Tres Marías fragment from Chron 4n.2 (7.90 Ma) to Chron 3n.4 (5.12 Ma).

Southward Migration of Magmatic Activity in the Colima Volcanic Complex, Mexico: An Ongoing Process  [PDF]
Román Alvarez, Vsevolod Yutsis
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.69085
Abstract: The Colima Volcanic Complex trends in a nearly N-S direction in western Mexico, and one of itsstructures, Colima volcano, is the most historically active volcano in the country. Immediately to theN, there is another volcanic center called El Cántaro volcano, whose activity started around 1.7 Ma in its N portion and migrated to the S in various episodes. Volcanic activity migrated further south, from El Cántaro to the Colima Volcanic Complex where the southernmost manifestation, Hijos del Volcán domes, is located on the south slope of Fuego volcano. The above date appears to mark initiation of the rather continuous volcanic activity in the area. It has been noted that these volcanic manifestations lie on, or near the Rivera-Cocos inland plate boundary. Colima’s Fuego volcano is also the closest to the Middle America Trench, among the polygenetic volcanoes in Mexico. We submit that the anomalous location of volcanism in this area originates in an anomalous subduction process of the Rivera and Cocos plates and evoke a tectonic model, proposed elsewhere, to support the idea. Modeling gravimetric and aeromagnetic data we locate the magma chambers of the Fuego (active) and Nevado (extinct) volcanoes within a 65 mGals negative Bouguer anomaly elongated in a nearly N-S direction. The corresponding aeromagnetic map displays a magnetic high over the southern portion of the Fuego volcano edifice. We found two additional, associated structures whose anomalies have not been previously reported, which appear to follow the southward magmatic migration pattern. One of them is a collapse structure with a circular topographic expression, and the southernmost is a low-density intrusion ~1 km below sea level, associated with a moderate topographic bulge at the surface that we interpret as a magma body. Five lines cross the anomalies; gravimetric and magnetic fields are concurrently modeled along them to locate the magmatic bodies. In addition to the 2-D models we perform 3-D gravimetric and magnetic inversions. For each field a 3-D mesh is built under the area occupied by the Colima Volcanic Complex, the volume elements are then assigned density or magnetic susceptibility values and their surface contributions in various points are evaluated. The process is
Submarine topography and faulting in Bahía de Banderas, Mexico
Alvarez, Román;
Geofísica internacional , 2007,
Abstract: a digital elevation model of bahía de banderas and its offshore continuation to the middle america trench (mat) is built from a data set of 6872 bathymetric soundings. two new, offshore basins and several, previously unknown faults within the bay are also identified. the south flank of banderas canyon is considerably steeper than the north one. this asymmetry and the seismic activity present lead to propose that banderas canyon has a half-graben structure of the fault growth type, and reverse drag geometry, which originates in an extensional basin oriented n-s. the canyon is divided in two sections that trend in different directions. the older section of the canyon, trending e-w, is probably late miocene; the associated banderas fault is suggested to extend westward, down to the mat along a section that complements that of the half-graben. the section of banderas canyon trending ne and continuing into banderas valley is identified as a younger portion of the structure. the older and the younger portions of the canyon appear to be active presently. a group of faults also trending ne seem to be associated with the change in direction of the canyon. these results support the hypothesis that the structure of banderas canyon is a half-graben, and strengthen the idea that it is the limit between the region to the north that underwent extension in the miocene, and the region to the south that did not experienced it.
Prologo
Román Alvarez
Investigaciones geográficas , 1996,
Abstract:
Elaboración de un modelo de simulación del proceso de deforestación
Jean Fran?ois Mas,Valentino Sorani,Román Alvarez
Investigaciones geográficas , 1996,
Abstract: Con base en las camgra as f o d e s de 1982 y 1992 de una wna del sureste mexicano se detemmrou las áreas y trisas de deforesraoióu para cada b p de ntbierta forestal. Los resultados mdican que más de 400 000 ha fuem deformadas durante el pendo 1982-1992, lo que repcerca de 55% de la superficie f o d de 1982 La tasa de deforestauón en la zona estudiada es de 7.6% por aiio, pero se observan importantes diferencias entre los wios tipos de cubierta forestal; mientras las taras de defomm~ón son muy altas en las selvas, el bosque mesófüo y el k q u e de tás& (del orden del 9 al 10% por a o) son más bajas en los bosques templados de pino, p k encino, oyamel y otras miferas (2-3% por a o). En un siguiente paso, u ~ d o un sisrema de udümmción geográfica (SIC?), los mapas f o d e s de 1982 y de 1992 se cruzaron cada uno con el mapa de altura, pendiente y cercarúa a las vias de comunicación wn el u de obtener para cada una de sus clases la proporción de de áreaforestal desmiida. Luego se establecieron por regresión las ecuaciwes que rekcionan el porcentaje de área deforestada con la M e n t e y la distancia a vias de u>mun~cac~ón. Con base en estas eaiaciones, se elaboraron mapas de las zonas forestales & susceptibles de ser deforestadas.
Red tide evolution in the Mazatlán Bay area from remotely sensed sea surface temperatures
Raúl Aguirre Gómez,Román Alvarez,Olivia Salmerón García
Geofísica internacional , 1999,
Abstract: The evolution of a red tide episode in Mazatlán Bay, Mexico, during February 1996 is described from images of sea surface temperatures (SST), obtained from the advanced very high resolution radiometer (AVHRR). An initial nearshore high surface temperature of 24°C was followed by a sharp decrease of 2.5°C due to wind cooling. Finally, a warmer condition was re-established at the nearshore region. The sequence of satellite images showed potential for identifying short-term oceanic processes responsible for the development and behaviour of red tides. The 1.1-km spatial resolution of the AVHRR was adequate for latitudes around 23° N.
Formación de un solo hueso en el antebrazo con injerto vascularizado de peroné
Salles Betancourt,Guido Román; Marrero Riveron,Luis Oscar; Cabrera Viltres,Nelson; Alvarez Placeres,Leopoldo;
Revista Cubana de Ortopedia y Traumatolog?-a , 2005,
Abstract: a patient that presented cubitus and radius septic pseudoarthrosis, bone defect greater than 6 cm, proximal radio-cubital luxation, loss of the finger extensors and conserved nervous function, was treated. a reconstruction of the forearm was performed in 2 times to form one bone of the forearm with vascularized fibular graft of 12 cm. bone consolidation was attained 3 months after the operation.
A patient with C protein deficiency and multiple thromboses. case report Paciente con deficiencia de proteína C y múltiples trombosis: reporte de caso
Alejandro Román González,Wálter Darío Cardona Maya,María Leonor Alvarez Peláez,Luis Ignacio Tobón Acosta
Iatreia , 2007,
Abstract: Inherited thrombophilias are an important group of diseases that should be taken into account in the study of patients with thromboembolic disease, particularly in those whose clinical presentation includes frequent and recurrent thrombotic episodes at young age, in unusual sites, and a familial history of thrombosis. We report the case of a patient with C protein deficiency which developed deep venous thromboses of both legs when he was 36 and 37 years old. At 51 years of age he suffered from mesenteric thrombosis requiring surgical treatment and small intestine transplantation. His father had deep venous thrombosis. This is the first report of C protein deficiency in the Colombian literature. Other inherited thrombophilias such as the G20210A mutation in the prothrombin gene and actor V Leiden were absent. Se debe considerar un estado de hipercoagulabilidad primaria o trombofilia heredada en los pacientes con enfermedad tromboembólica venosa. La sospecha clínica se debe dirigir a los pacientes con presentación temprana, recurrente, familiar o en sitios anatómicos poco usuales. En este reporte se describe el caso de un paciente con déficit de proteína C de la coagulación, quien desarrolló trombosis venosa profunda del miembro inferior derecho a los 36 a os y un a o después, trombosis venosa profunda del miembro inferior izquierdo. A la edad de 51 a os presentó trombosis de vasos mesentéricos que condujo a una resección intestinal extensa lo que obligó a un trasplante de intestino delgado. Su padre había presentado trombosis venosa de los miembros inferiores. Se descartó la presencia asociada de la mutación G20210A de la protrombina y del Factor V Leiden. Hasta donde sabemos, es el primer caso de deficiencia de proteína C de la coagulación informado en la literatura colombiana.
On the Prediction of the Occurence of dates of GLEs
Jorge Pérez-Peraza,Alan Juárez-Zú?iga,Julián Zapotitla-Román,Manuel Alvarez-Madrigal
Physics , 2013,
Abstract: Ground level enhancements (GLEs) are relativistic sol particles measured at ground level by a worldwide network of cosmic ray detectors. These sporadic events are associated with solar flares and are assumed to be of a quasi-random nature. Their study gives us information about their source and propagation processes, about the maximum capacity of the sun as a particle accelerator engine, about the magnetic structure of the medium traversed, etc. Space vehicles may be damaged by this kind of radiation, as well as electric transformers and gas pipes at high latitudes. As a result, their prediction has turned out to be very important, but because of their random occurrence, up to now few efforts to this end have been made. The results of these efforts have been limited to possible warnings in real time, just before GLE occurrence, but no specific dates have been predicted well enough in advance to prevent possible hazards. In this study we show that, in spite of the quasi-stochastic nature of GLEs, it is possible to predict them with relative precision, even for future solar cycles. We reproduce previous GLE events and present results for future events.
Treatment of Severe Hypertriglyceridemia with Continuous Insulin Infusion
Yesica Rodríguez Santana,Andrea Nimo Román,Iker García Sáez,José Manuel López Alvarez,Eduardo Consuegra Llapur,Rafael González Jorge
Case Reports in Critical Care , 2011, DOI: 10.1155/2011/293917
Abstract: Severe hypertriglyceridemia (SH) represents a therapeutic emergency because of the possibility of developing cardiovascular events and hyperlipemic acute pancreatitis (PA). Most patients with SH suffer primary or genetic abnormality in lipid metabolism in combination with a precipitating factor such as uncontrolled diabetes mellitus, alcoholism, and drug intake. The standard treatment of hypertriglyceridemia (HTG) with omega 3 fatty acids and fibrates, along with dietary changes, has no effect on an emergency situation. There are no clinical guidelines to SH, but therapy with insulin, heparin, a combination of both, plasmapheresis, or octreotide have been tested succesfully. We report the case of a 10-year-old girl with clinical acute pancreatitis and diabetic ketoacidosis debut, along with incidental finding of an SH, who had a good outcome after treatment with insulin intravenous infusion.
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