Información Investigador: Marante Garrido, María Eugenia

Maestría4429I - 2003; Candidato - 2000;Modelado y simulación del comportamiento de sólidos y estructuras. Métodos numéricos en ingeniería. Teoría del daño y sus aplicaciones en problemas de Ingeniería sísmica.Octubre de 2004+58 274 2402862;+58 274 2402873Facultad de Ingenierí[email protected]

Análisis de vigas tubulares de acero estructural sometidas a flexión biaxial mediante la teoría del daño concentrado

En este trabajo se desarrolla un modelo matemático basado en la teoría del daño concentrado, que permite predecir el grado de deterioro de vigas de acero estructural de pared delgada sometidas a flexión biaxial. El fenómeno más significativo en este caso es la aparición y desarrollo del pandeo local. Para modelar este proceso, se admite que los fenómenos ineslásticos pueden ser concentrados en las rótulas plásticas. Se introduce entonces una variable de daño, que puede tomar valores entre cero y uno, que caracteriza el nivel de panadero local en el miembro estructural. La evolución del daño es descrita mediante la introducción de un domino de pandeo local que puede ser comparado al dominio elástico empleado en la teoría de la plasticidad convencional. El modelo es validado mediante la simulación numérica de ensayos experimentales realizados en el Laboratorio de Mécanica Estructural de la Universidad Centroccidental Lisandro Alvarado.Peer Reviewe

Análisis de vigas tubulares de acero estructural sometidas a flexión biaxial mediante la teoría del daño concentrado

En este trabajo se desarrolla un modelo matemático basado en la teoría del daño concentrado, que permite predecir el grado de deterioro de vigas de acero estructural de pared delgada sometidas a flexión biaxial. El fenómeno más significativo en este caso es la aparición y desarrollo del pandeo local. Para modelar este proceso, se admite que los fenómenos ineslásticos pueden ser concentrados en las rótulas plásticas. Se introduce entonces una variable de daño, que puede tomar valores entre cero y uno, que caracteriza el nivel de panadero local en el miembro estructural. La evolución del daño es descrita mediante la introducción de un domino de pandeo local que puede ser comparado al dominio elástico empleado en la teoría de la plasticidad convencional. El modelo es validado mediante la simulación numérica de ensayos experimentales realizados en el Laboratorio de Mécanica Estructural de la Universidad Centroccidental Lisandro Alvarado.Peer Reviewe

Portal of damage: A web-based finite element program for the analysis of framed structures subjected to overloads

Portal of damage: A web-based finite element program for the analysis of framed structures subjected to overloads (Marante, María E.; Suárez, Lorena; Quero, Adriana; Redondo, Jorge; Vera, Betsy; Uzcategui, Maylett; Delgado, Sebastián; León, Luis Núñez, Leandro R.; Flórez-López, Julio) Abstract This paper describes a web-based finite element program called portal of damage. The purpose of the program is the numerical simulation of reinforced concrete framed structures, typically buildings, under earthquakes or others exceptional overloads. The program has so far only one finite element based on lumped damage mechanics. This is a theory that combines fracture mechanics, damage mechanics and the concept of plastic hinge. In the case of reinforced concrete frames, the main mechanism of deterioration is cracking of concrete. Cracking in a frame element is lumped at the plastic hinges. Cracking evolution in the plastic hinge is assumed to follow a generalized form of the Griffith criterion. The behavior of a plastic hinge with damage is described via the effective stress hypothesis, as used in continuum damage mechanics. The portal that can be accessed using any commercial browser (explorer, netscape, etc.) allows to: (a) Create an account in a server. (b) Make use of a semi-graphic pre-processor to create an input file with a digitalized version of the structure. (c) Run a dynamic finite element program and monitor the state of the process. (d) Download or upload input and output files in text format. (e) Make use of a graphic [email protected]@ula.ve, [email protected]@[email protected], [email protected]@ula.veNivel monográfic

Differential clinical characteristics and prognosis of intraventricular conduction defects in patients with chronic heart failure

Intraventricular conduction defects (IVCDs) can impair prognosis of heart failure (HF), but their specific impact is not well established. This study aimed to analyse the clinical profile and outcomes of HF patients with LBBB, right bundle branch block (RBBB), left anterior fascicular block (LAFB), and no IVCDs. Clinical variables and outcomes after a median follow-up of 21 months were analysed in 1762 patients with chronic HF and LBBB (n = 532), RBBB (n = 134), LAFB (n = 154), and no IVCDs (n = 942). LBBB was associated with more marked LV dilation, depressed LVEF, and mitral valve regurgitation. Patients with RBBB presented overt signs of congestive HF and depressed right ventricular motion. The LAFB group presented intermediate clinical characteristics, and patients with no IVCDs were more often women with less enlarged left ventricles and less depressed LVEF. Death occurred in 332 patients (interannual mortality = 10.8%): cardiovascular in 257, extravascular in 61, and of unknown origin in 14 patients. Cardiac death occurred in 230 (pump failure in 171 and sudden death in 59). An adjusted Cox model showed higher risk of cardiac death and pump failure death in the LBBB and RBBB than in the LAFB and the no IVCD groups. LBBB and RBBB are associated with different clinical profiles and both are independent predictors of increased risk of cardiac death in patients with HF. A more favourable prognosis was observed in patients with LAFB and in those free of IVCDs. Further research in HF patients with RBBB is warranted

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved