Entity

Time filter

Source Type

Medellin, Colombia

The purpose of this study is to distinguish the forest of Belmira's Páramo from other land cover classes. Three LANDSAT images are available (1996, 2002 and 2003). Remote sensing analysis of the vegetation coverage includes image correction and classification and validation process. The COS(t) model and the quadratic interpolation function were used for image correction. The iterative self-organizing cluster analysis is considered for image non supervised classification and the maximum likelihood classifier is taken into account for image supervised classification. 70 GPS land observations and the error matrix analysis, were used for validation process. The Result is a map for each image, with two land cover categories: forest & non-forest. Classification error is 2% and map-land observations correspondence is 80%. However, the presence of clouds and shadows affect the remote sensing accuracy. Source


Catano J.C.,University of Antioquia | Echeverri L.M.,University of Medellin | Szela C.,Harvard University
Interdisciplinary Perspectives on Infectious Diseases | Year: 2012

Objective. This study evaluates the bacterial contamination rate of items in the hospital setting that are in frequent contact with patients and/or physicians. By determining the bacterial species and the associated antibiotic resistance that patients are exposed to. Methods. Hospital-based cross-sectional surveillance study of potential bacterial reservoirs. Cultures from 30 computer keyboards, 32 curtains, 40 cell phones, 35 white coats, and 22 ties were obtained. Setting. The study was conducted an urban academic 650-bed teaching hospital providing tertiary care to the city of Medellin, Colombia. Results. In total, 235 bacterial isolates were obtained from 159 surfaces sampled. 98.7% of the surfaces grew positive bacterial cultures with some interesting resistance profiles. Conclusion. There are significant opportunities to reduce patient exposure to frequently pathogenic bacteria in the hospital setting; patients are likely exposed to many bacteria through direct contact with white coats, curtains, and ties. They may be exposed to additional bacterial reservoirs indirectly through the hands of clinicians, using computer keyboards and cell phones. © 2012 J. C. Catao et al. Source


The firstand secondorder stiffness and load matrices of an orthotropic Timoshenko beamcolumn of symmetric cross section with semirigid connections including the effects of end axial loads (tension or compression) and shear deformations along the member are derived in a classical manner. Both matrices can be used in the stability, firstand the secondorder elastic analyses of framed structures made of Timoshenko beamcolumns with rigid, semirigid and simple connections of symmetric cross sections. The "modified" stability approach based on Haringx's model described by Timoshenko and Gere (1961) is utilized in all matrices. The proposed stiffness matrices can also be used in the inelastic analysis of frames whose members suffer from flexural degradation or, on the contrary, stiffening at their end connections. The closedform secondorder stiffness matrix and load vector derived and presented in this paper find great applications in the stability and secondorder analyses of framed structures made of beamcolumns with relatively low shear stiffness such as orthotropic composite polymers (FRP or composites) and multilayer elastomeric bearings commonly used in seismic isolation of buildings. The effects of torsional warping along the members are not included. Analytical studies indicate that the buckling load and the stiffness of framed structures are reduced by the shear deformations along the members. In addition, the phenomenon of buckling under axial tension forces in members with relatively low shear stiffness is captured by the proposed equations. Tension buckling must not be ignored in the stability analysis of beamcolumns with shear stiffness GAs of the same order of magnitude as EI/h2. The validity of both matrices is verified against available solutions of stability analysis and nonlinear geometric elastic behavior of beamcolumn structures. Five examples are included that demonstrate the effectiveness of the proposed method and corresponding matrices. Source


Mamtani M.,University of Texas Health Science Center at San Antonio | Anaya J.-M.,University of Medellin | He W.,University of Texas Health Science Center at San Antonio | Ahuja S.K.,University of Texas Health Science Center at San Antonio
Genes and Immunity | Year: 2010

Copy number variation (CNV) in the human genome is an important determinant of susceptibility to autoimmune diseases. Many autoimmune diseases share similar clinical and pathogenic features. Thus, CNVs of genes involved in immunity may serve as shared determinants of multiple autoimmune diseases. Here, we determined the association between CNV in the gene encoding FCGR3B with the risk of developing autoimmune diseases and whether the observed associations are modified by the CNV in CCL3L1 (CC chemokine ligand 3-like 1), a gene encoding a potent chemokine. In a cross-sectional study of 774 subjects, we estimated FCGR3B and CCL3L1 gene copy number in 146, 158 and 61 subjects with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and primary Sjögren's syndrome (SS), respectively, and 409 healthy controls. The median gene dose of FCGR3B in the study population was two. FCGR3B copy number or 2 was associated with an increased risk of SLE and primary SS but not RA. This association was mostly evident in subjects who also had two copies of CCL3L1. Thus, our data suggest that epistatic interactions between CNV of FCGR3B and CCL3L1, two immune response genes, may influence phenotypically related autoimmune diseases. © 2010 Macmillan Publishers Limited All rights reserved. Source


Cuervo F.I.,University of Medellin | Botero S.B.,National University of Colombia
Renewable and Sustainable Energy Reviews | Year: 2016

The design of market mechanisms that remunerates the reliability provided by a generator in a power market is a task that aims to ensure the normal operation of the system. For the case of a Hydro-Dominated system, when wind power is introduced and operated under the Merit-Order-Effect, it is possible to assess the effect of the displacement of hydro generation due to wind generation over the system's reliability in terms of firm energy; taking this into account a model that valuates the firm energy provided by wind power in a hydro-dominated system is proposed. This model considers the effect of wind power over the system's reservoirs and the market price of electricity; and valuates the firm energy as the net savings of the system related to the increase in the firm energy of the system when wind power is introduced. The results show that wind power under Merit-Order-Effect increases the firm energy of the system, and decreases the market price of electricity, being the net savings in comparison to the corresponding hydro-only system the reliability income that should be perceived by the wind power generator. © 2016 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations