Comparación de dos métodos de coagulación del látex (Hevea brasiliensis) en el Magdalena Medio Colombiano

El caucho (Hevea Brasiliensis) es un cultivo ampliamente producido en la zona del Magdalena Medio colombiano. Para obtener, a partir del látex, caucho natural, se utilizan coagulantes que permitan su solidificación, siendo el ácido fórmico del uso más extendido. Sin embargo, sustancias como estas tienen consecuencias en quienes las manipulan y en el medio ambiente. En el presente trabajo se compararon métodos convencionales y no convencionales (ácido cítrico natural) para determinar características, propiedades, ventajas y desventajas del caucho coagulado usando diferentes sustancias. Inicialmente se presentan los sistemas de producción de caucho en Colombia y el beneficio de esta planta, así como un marco geográfico sobre el Magdalena Medio (región analizada). Posteriormente, se describe el diseño experimental usado utilizado para la comparación y los resultados de las pruebas realizadas. El ácido fórmico se destaca por su rapidez, aunque resulta más caro que el ácido cítrico. Al final de proceso, ambos tratamientos generan láminas de excelente calidad. El ácido cítrico, por su parte, produce mejores resultados en elasticidad e impacto ambiental.Abstract. Rubber (Hevea Brasiliensis) is a widely used crop in Colombian Magdalena Medio zone. In order to obtain natural rubber from latex, coagulants are used for solidification, and formic acid is the most used for these purposes. However, these substances have consequences on the people who handle them and the environment. In this research, conventional and non-conventional solidification methods (natural citric acid) are compared for determining differences, similarities, properties, advantages and disadvantages between both ways of coagulating rubber. In the first part of this paper, particular topics of Colombian rubber production systems, the way to get latex from the plant and Magdalena Mediozone are analyzed. Then, experimental design used for comparing the two methods is explained. In the last part, results of the experiments are discussed. Formic acid is faster for coagulation, but it is more expensive than citric acid and, at the end of the process, both treatments produce excellent quality rubber sheets. Citric acid, on its behalf, gives better results in elasticity and environmental impact.Otr

Application of model based systems engineering methods to development of combat system architectures

Navy acquisition activities frequently produce combat system architectures based on existing systems rather than stakeholder requirements. This approach limits software component reuse which, in turn, limits potential application to other platforms. The objective of this Capstone project was to develop a methodology for creating complex combat system architectures that emphasize the use of Software Product Lines (SPLs), requirements traceability, integrated supportability and Modeling and Simulation (M&S) early and throughout the approach. To address this objective, an integrated methodology that utilizes Model Based Systems Engineering (MBSE) to create open, supportable combat system architectures was developed. The methodology was evaluated by applying it to a naval surface combatant Anti-Air Warfare (AAW) mission area. Application of the methodology led to the following major findings: (1) Proven systems engineering practices, languages and tools can be integrated with the MBSE approach for developing complex architectures, (2) Creation of domain centered SPLs facilitates planned reuse and allows for assessment to candidate architectures, (3) Requirements traceability can be achieved by using a combination of modeling languages and tools, (4) M&S application can extend beyond operational scenarios to address life cycle cost, and (5) Engineers and logisticians can effectively use MBSE to integrate supportability into design. Overall, this project demonstrated the benefits of an MBSE approach tailored to developing affordable and supportable combat system architectures that meet mission requirements.http://archive.org/details/applicationofmod10945693

Sistema de información georeferenciado

IP 7105-07-005-93LIBRO(S): Analisis de los sistemas agropecuarios del departamento de Nortede Santander / Hernando Mendez;Aldana..(et al.) -- Analisis de los sistemas agropecuariosdeldepartamento de Santander / Hernando Mendez;Aldana -- Analisis agroecologico y caracterizacion de losagroecosistemasde los departamentos de Atlantico;Bolivar, Cordoba y Sucre / Fernando Villamizar Rosas ..(etal.)'-- Analisis agroecologico y caracterizacion de;los agroecosistemas de los departamentos de Amazonas, Caqueta,Guainia, Putumayo y Vaupes / Fernando;Villamizar Rosas..(et al.) -- Analisis agroecologico y caracterizacion delos agroecosistemas de los;departamentos de Huila y Tolima / Fernando Villamizar..(etal.)'-- Analisis agroecologico y caracterizacion de;los agroecosistemas de los departamentos de Cesar, Guajiray Magdalena --Estructura de la produccion;agropecuaria de la region Tolima, Huila y Suroccidente deCundinamarca / Diego Miranda..(et. al.

Switching TNF antagonists in patients with chronic arthritis: An observational study of 488 patients over a four-year period

The objective of this work is to analyze the survival of infliximab, etanercept and adalimumab in patients who have switched among tumor necrosis factor (TNF) antagonists for the treatment of chronic arthritis. BIOBADASER is a national registry of patients with different forms of chronic arthritis who are treated with biologics. Using this registry, we have analyzed patient switching of TNF antagonists. The cumulative discontinuation rate was calculated using the actuarial method. The log-rank test was used to compare survival curves, and Cox regression models were used to assess independent factors associated with discontinuing medication. Between February 2000 and September 2004, 4,706 patients were registered in BIOBADASER, of whom 68% had rheumatoid arthritis, 11% ankylosing spondylitis, 10% psoriatic arthritis, and 11% other forms of chronic arthritis. One- and two-year drug survival rates of the TNF antagonist were 0.83 and 0.75, respectively. There were 488 patients treated with more than one TNF antagonist. In this situation, survival of the second TNF antagonist decreased to 0.68 and 0.60 at 1 and 2 years, respectively. Survival was better in patients replacing the first TNF antagonist because of adverse events (hazard ratio (HR) for discontinuation 0.55 (95% confidence interval (CI), 0.34-0.84)), and worse in patients older than 60 years (HR 1.10 (95% CI 0.97-2.49)) or who were treated with infliximab (HR 3.22 (95% CI 2.13-4.87)). In summary, in patients who require continuous therapy and have failed to respond to a TNF antagonist, replacement with a different TNF antagonist may be of use under certain situations. This issue will deserve continuous reassessment with the arrival of new medications. © 2006 Gomez-Reino and Loreto Carmona; licensee BioMed Central Ltd