232 research outputs found
Simple decision rule for risk stratification of elderly with acute type B aortic dissection
No full textModeling of a trickling filter reactor for the hydrolysis of corncob leaf
No full textgraficas, ilustraciones, tablasEl desarrollo de nuevos procesos es un tema de gran interés para la ingeniería de reactores, ya que se hace necesario mejorar e implementar nuevas prácticas en la industria que garanticen un futuro sostenible mediante la transformación de diferentes materiales. En general, la aplicabilidad de estos procesos a escala comercial está limitada por la complejidad de las reacciones en serie que se dan y las tecnologías de baja eficiencia, lo que conduce a que sean económicamente inviables. Por lo tanto, es necesario un profundo conocimiento del proceso y su operatividad para proponer tecnologías innovadoras que contribuyan a superar las restricciones mencionadas, mejorando así la incorporación de nuevos procesos para la transformación de materiales lignocelulósicos. En esta disertación, se desarrolló un nuevo concepto de reactor percolador para la producción y extracción de azúcares como: xilosa, glucosa, manosa, arabinosa y galactosa o subproductos como el furfural. Este proceso se desarrolló utilizando desechos biodegradables como la hoja de mazorca debido a que un material económico y de alta disponibilidad en Colombia.
El análisis del reactor se realizó en tres etapas: el modelamiento del reactor percolador mediante el software de Matlab® y la integración de este modelamiento con sección experimental para obtener los parámetros cinéticos que modelan la hidrólisis de la hemicelulosa y finalmente optimización de las concentraciones de los azúcares.
En la etapa del modelamiento del reactor percolador, se obtuvieron las ecuaciones del balance de masa que predecían las concentraciones de los productos y subproductos de la descomposición de la hemicelulosa de la hoja de mazorca. Para la obtención del modelamiento se realizó una caracterización del material lignocelulósico, obteniendo así los porcentajes de hemicelulosa, celulosa y lignina presentes en la materia para ser adaptados al modelo. El modelamiento del reactor percolador se desarrolló mediante el software Matlab®, utilizando una subrutina de optimización global y el comando fmincon para minimizar la función objetivo que consistía en minimizar la sumatoria de los residuales al cuadrado.
Una vez obtenido el modelamiento, éste se ajustó con los resultados de los datos experimentales de la hidrólisis de la hoja de mazorca. El ajuste del modelo del reactor percolador se realizó mediante un diseño secuencial obteniéndose la estimación de parámetros cinéticos, para esto primero se seleccionó las condiciones iniciales experimentales, luego se ajustaron los parámetros, seguidamente se utilizó el modelo secuencial para la predicción de nuevas condiciones de operación. Se hizo necesario la verificación de la calidad de la predicción del modelo (varianza de los parámetros del modelo), donde la varianza se ajustó a un valor máximo del 6%, para termina el proceso de ajuste.
Finalmente, con los parámetros cinéticos ajustados, se optimizaron las ecuaciones de los balances que mostraban el comportamiento de la producción de azúcares para obtener concentraciones máximas de xilosa y furfural, por medio de nuevas rutinas de software Matlab®, con el comando fmincon. La productividad del sistema fue más alta que la obtenida en otros reactores para hidrólisis de este tipo de materiales. El desempeño obtenido con estos reactores muestra el potencial de la tecnología desarrollada y es la fuerza impulsora para continuar investigando la optimización de los procesos. (Texto tomado de la fuente)The development of new processes is a topic of great interest for reactor engineering, since it is necessary to improve and implement new practices in the industry that guarantee a sustainable future through the transformation of different materials. The applicability of these processes on a commercial scale is limited by the complexity of the series reactions involved and the low efficiency technologies, which leads to their economic unfeasibility. Therefore, a deep knowledge of the process and its operability is necessary to propose innovative technologies that contribute to overcome the mentioned restrictions, thus improving the incorporation of new processes for the transformation of lignocellulosic materials. In this dissertation, a new concept of percolator reactor was developed for the production and extraction of sugars such as xylose, glucose, mannose, arabinose and galactose or by-products such as furfural. This process was developed using biodegradable wastes such as corncob leaves because it is an inexpensive and highly available material in Colombia.
The reactor analysis was carried out in three stages: modeling of the percolator reactor using Matlab® software and integration of this modeling with experiments to get the kinetic parameters that model the hydrolysis of hemicellulose and finally optimization of the product concentrations.
In the modeling stage of the percolator reactor, mass balance equations were derived to predict the concentrations of the products and by-products from the decomposition of the hemicellulose of the corncob leaf. For the simulation model, a characterization of the lignocellulosic material was performed to measure the percentages of hemicellulose, cellulose, and lignin present in the material to be included in the model. The modeling of the percolator reactor was developed using Matlab® software, using a global optimization subroutine and the fmincon command to minimize the objective function that consisted of minimizing the sum of the squared residuals.
The simulation model was adjusted with the results of the experimental data of the hydrolysis of the cob leaf. The parameters were fitted by a sequential design of experiments, first the initial experimental conditions were selected, then the parameters were adjusted, then the sequential model was used for the prediction of new operating conditions for the next experimental. It was necessary to verify the quality of the model prediction (variance in the model parameters). The variance was adjusted to a value of 5%.
Finally, with the model of the percolator reactor, the operating conditions were optimized to attain maximum concentrations of xylose and furfural. The productivity of the percolator reactor is higher than the one reached by other reactors for hydrolysis of this type of materials. The performance of a percolator reactor is superior to the conventional batch and plug flow reactors.MaestríaMagíster en Ingeniería - Ingeniería QuímicaQuímica Y Procesos.Sede Manizale
Acute Aortic Dissection in the elderly: Clinical characteristics, management, and outcomes in the current era
No full textMortality in type B acute aortic dissections in the current era: Results from the International Registry of Aortic Dissection (IRAD)
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Clinical characteristics and in-hospital outcomes of patients with cardiac tamponade complicating acute type A aortic dissection
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The Calbindin-D28k binding site on inositol monophosphatase may allow inhibition independent of the lithium site of action
No full textAmong numerous reported biochemical effects the lithium-inhibitable enzyme inositol-monophosphatase (IMPase) remains a viable target for lithium's therapeutic mechanism of action. Calbindin-D28k (calbindin) interacts with IMPase enhancing its activity. In the present study in silico modeling of IMPase-calbindin binding using the program MolFit indicated that the 55-66 amino acid segment of IMPase anchors calbindin via Lys59 and Lys61 with a glutamate in between (Lys-Glu-Lys motif). The model further suggested that the Lys-Glu-Lys motif interacts with residues Asp24 and Asp26 of calbindin. Indeed, we found that differently from wildtype calbindin, IMPase was not activated by mutated calbindin in which Asp24 and Asp26 were replaced by alanine. Calbindin's effect was significantly reduced by a peptide with the sequence of amino acids 58-63 of IMPase (peptide 1) and by six amino-acid peptides including at least part of the Lys-Glu-Lys motif. The three amino-acid peptide Lys-Glu-Lys or five amino-acid peptides containing this motif were ineffective. Intracerebroventricular administration of peptide 1 resulted in a significant antidepressant-like reduced immobility in the Porsolt forced swim test (FST) compared with mice treated with a scrambled peptide or artificial cerebrospinal fluid. Based on the sequence of peptide 1, and to potentially increase the peptide's stability, cyclic and linear pre-cyclic analog peptides were synthesized. One cyclic and one linear pre-cyclic analog peptides exhibited an inhibitory effect on calbindin-activated brain IMPase activity in vitro. These findings may lead to the development of molecules capable of inhibiting IMPase activity at an alternative site than that of lithium
Predicting in-hospital mortality in acute type A aortic dissection: Lessons from the International Registry of Aortic Dissection (IRAD)
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