Rigorous Multicomponent Reactive Separations Modelling : Complete Consideration of Reaction-Diffusion Phenomena

This paper gives the first step of the development of a rigorous multicomponent reactive separation model. Such a model is highly essential to further the optimization of acid gases removal plants (CO2 capture, gas treating, etc.) in terms of size and energy consumption, since chemical solvents are conventionally used.Firstly, two main modelling approaches are presented: the equilibrium-based and the rate-based approaches. Secondly, an extended rate-based model with rigorous modelling methodology for diffusion-reaction phenomena is proposed. The film theory and the generalized Maxwell-Stefan equations are used in order to characterize multicomponent interactions. The complete chain of chemical reactions is taken into account. The reactions can be kinetically controlled or at chemical equilibrium, and they are considered for both liquid film and liquid bulk. Thirdly, the method of numerical resolution is described. Coupling the generalized Maxwell-Stefan equations with chemical equilibrium equations leads to a highly non-linear Differential-Algebraic Equations system known as DAE index 3. The set of equations is discretized with finite-differences as its integration by Gear method is complex. The resulting algebraic system is resolved by the Newton- Raphson method. Finally, the present model and the associated methods of numerical resolution are validated for the example of esterification of methanol. This archetype non-electrolytic system permits an interesting analysis of reaction impact on mass transfer, especially near the phase interface. The numerical resolution of the model by Newton-Raphson method gives good results in terms of calculation time and convergence. The simulations show that the impact of reactions at chemical equilibrium and that of kinetically controlled reactions with high kinetics on mass transfer is relatively similar. Moreover, the Fick’s law is less adapted for multicomponent mixtures where some abnormalities such as counter-diffusion take place

Potential Routes for Thermochemical Biorefineries

This critical review focuses on potential routes for the multi-production of chemicals and fuels in the framework of thermochemical biorefineries. The up-to-date research and development in this field has been limited to BTL/G (biomass-to-liquids/gases) studies, where biomass-derived synthesis gas (syngas) is converted into a single product with/without the co-production of electricity and heat. Simultaneously, the interest on biorefineries is growing but mostly refers to the biochemical processing of biomass. However, thermochemical biorefineries (multi-product plants using thermo-chemical processing of biomass) are still the subject of few studies. This scarcity of studies could be attributed to the limitations of current designs of BTL/G for multi-production and the limited number of considered routes for syngas conversion. The use of a platform chemical (an intermediate) brings new opportunities to the design of process concepts, since unlike BTL/G processes they are not restricted to the conversion of syngas in a single-reaction system. Most of the routes presented here are based on old-fashioned and new routes for the processing of coal- and natural-gas-derived syngas, but they have been re-thought for the use of biomass and the multi-production plants (thermochemical biorefinery). The considered platform chemicals are methanol, DME, and ethanol, which are the common products from syngas in BTL/G studies. Important keys are given for the integration of reviewed routes into the design of thermochemical biorefineries, in particular for the selection of the mix of co-products, as well as for the sustainability (co-feeding, CO2 capture, and negative emissions).Ministerio de Educación FPU Program (AP2010-0119)Ministerio de Economía y Competitividad ENE2012-3159

Diagnostic accuracy of a clinical diagnosis of idiopathic pulmonary fibrosis: An international case-cohort study

We conducted an international study of idiopathic pulmonary fibrosis (IPF) diagnosis among a large group of physicians and compared their diagnostic performance to a panel of IPF experts. A total of 1141 respiratory physicians and 34 IPF experts participated. Participants evaluated 60 cases of interstitial lung disease (ILD) without interdisciplinary consultation. Diagnostic agreement was measured using the weighted kappa coefficient (\u3baw). Prognostic discrimination between IPF and other ILDs was used to validate diagnostic accuracy for first-choice diagnoses of IPF and were compared using the Cindex. A total of 404 physicians completed the study. Agreement for IPF diagnosis was higher among expert physicians (\u3baw=0.65, IQR 0.53-0.72, p20 years of experience (C-index=0.72, IQR 0.0-0.73, p=0.229) and non-university hospital physicians with more than 20 years of experience, attending weekly MDT meetings (C-index=0.72, IQR 0.70-0.72, p=0.052), did not differ significantly (p=0.229 and p=0.052 respectively) from the expert panel (C-index=0.74 IQR 0.72-0.75). Experienced respiratory physicians at university-based institutions diagnose IPF with similar prognostic accuracy to IPF experts. Regular MDT meeting attendance improves the prognostic accuracy of experienced non-university practitioners to levels achieved by IPF experts

Procesos irreversibles en mecánica clásica

El problema de los procesos irreversibles es uno de los más fas­cinantes de la Física Teórica. Mientras en otros campos, tales como la teoría de valencia o pro­cesos de equilibrio la teoría básica se conoce perfectamente y las únicas dificultades que presentan son de carácter puramente mate­mático, el campo de los procesos irreversibles se halla en formación, no existiendo todavía unos conceptos y métodos básicos totalmente establecidos. La importancia que estos procesos tienen en el estudio de los fe­nómenos de transporte es fundamental, tanto para los sistemas me­cánico cuánticos como clásicos. El hecho de que casi todos los tra­bajos estudien este problema en Mecánica Cuántica, haciendo todo lo más alguna aproximación a la Mecánica Clásica, nos llevó a plan­tear este trabajo en el que se estudian los Procesos Irreversibles di­rectamente en Mecánica Clásica sin inclusión de Mecánica Cuántica, puesto que los fenómenos de transporte en el dominio clásico son de palpitante actualidad científica..

Procesos irreversibles en mecánica clásica

El problema de los procesos irreversibles es uno de los más fas­cinantes de la Física Teórica. Mientras en otros campos, tales como la teoría de valencia o pro­cesos de equilibrio la teoría básica se conoce perfectamente y las únicas dificultades que presentan son de carácter puramente mate­mático, el campo de los procesos irreversibles se halla en formación, no existiendo todavía unos conceptos y métodos básicos totalmente establecidos. La importancia que estos procesos tienen en el estudio de los fe­nómenos de transporte es fundamental, tanto para los sistemas me­cánico cuánticos como clásicos. El hecho de que casi todos los tra­bajos estudien este problema en Mecánica Cuántica, haciendo todo lo más alguna aproximación a la Mecánica Clásica, nos llevó a plan­tear este trabajo en el que se estudian los Procesos Irreversibles di­rectamente en Mecánica Clásica sin inclusión de Mecánica Cuántica, puesto que los fenómenos de transporte en el dominio clásico son de palpitante actualidad científica..

The pyrimido-pyrimidine derivative RA-642 protects from brain injury in a combined model of permanent focal ischemia and global ischemia reperfusion

The effects of pyrimido-p~ rimidine derivatives (dipyridamolc, RA-642 and mopydamole) on lipid peroxidation (inhibition of the production of malondialdehyde, MDA) in different regions of the rat brain were studied. Ferrous sulfate and ascorbic acid (FeAs) were used to induce lipid peroxidation via the formation of hydroxyl anions. The antiperoxidative effect of RA-642 (in the/~M range) was 10 times more potent than that of dipyridamole. Mopydamole did not exert any inhibitory effect on MDA production. In a model of ischemia reperfusion with bilateral occlusion of the common carotid arteries for 1 h and restoration of circulation for a period of 2 h, dipyridamole inhibited FeAs-induced MDA production but did not protect from postischemic brain tissue damage (measured by mitochondrial reduction of tetraphenyl tetrazolium). RA-642 inhibited FeAs-induced MDA production and showed 50-67% protection from tissue damage as compared with untreated animals, while mopydamole did not inhibit MDA production and showed 30-48% protection. No correlation was found between inhibition of lipid peroxidation and protection from brain tissue damage