Experimental and numerical analysis of mass transfer in liquid films under counter-current gas

Two-phase flow dynamics affects several industrial processes and technologies. In the chemical industry, the capture of carbon dioxide through absorption units relies upon the interaction between a thin liquid film and the flue gas. These two phases flow in a counter-current fashion, resulting that the interface might be disturbed with occurrence of waves. The waviness of the interface increases the interacting area and enhances the mass transfer between the two phases, e.g. more CO2 is absorbed into the liquid. In addition, if the phases are reactive, and this is often the case of absorption and distillation technologies, the chemical reactions at the gas-liquid interface also influence the mass transfer rate. In this work, we investigate the absorption of carbon dioxide into an aqueous solution of monoethanolamine. The experimental set-up consists of an inclined channel where a thin film falling under the action of gravity is sheared by a counter-current gas flow driven by an applied pressure gradient. Through titration of samples, we measure the absorption occurring at different flow conditions, by varying the liquid flow rate, the gas speed and its composition, as well as the pressure inside the channel. It is observed that an increase of the liquid load leads to a decrease of the absorption rate, whereas when the gas speed is increased, so does the absorption rate. Interestingly, the amount of CO2 absorbed into the liquid is not affected by the CO2 starting concentration of the solvent, at least until saturation is reached. Aiming to support the experimental results with numerical simulations, we implement a novel module for mass transfer in our level-set flow solver taking into account a variant of the ghost-fluid formalism. Our in-house flow solver applies the level-set method along with a continuous surface-tension model; it is also developed to run on super-computer through distributed or shared-memory architecture. The hydrodynamics module of this flow solver has been already validated against linear and non-linear theory, as well as experiments. With the implementation of the mass-transfer module, we validate the scenarios with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we implement the chemical reaction numerical module to perform analysis of the absorption rate in reactive flows, and try to reproduce the above-mentioned experimental results in order to explore the active role of the waves at the interface

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Sur l'aérage naturel des anciennes galeries de mines en zone montagneuse : expérimentation et modélisation

L'aérage des anciennes mine était crucial pour le travail du mineur d'autrefois. Dans la plupart des régions montagneuses, les galeries étaient équipées de puits d'aérage. Cependant, le percement d'un puits n'était pas entrepris d'emblée et de nombreuses galeries courtes sont dépourvues de tels systèmes. C'est alors la ventilation naturelle, convective, qui assure le renouvellement de l'air. Il semble qu'au delà d'une distance seuil, l'aérage naturel n'est pas pour renouveler l'air vicié. Nous abordons ici le fonctionnement physique d'une galerie horizontale de mine par trois méthodes quantitatives. D'abord, l'approche expérimentale, fondée sur l'ajustement empirique, donne une première expression de la vitesse de l'air dans la galerie en fonction du contraste de température intérieur-extérieur. Cela permet de quantifier le taux de renouvellement d'air respirable et précise la distance (de l'ordre de 50 m) à partir de laquelle l'aérage devient un réel problème. Ensuite, un calcul théorique précise cette loi sous la forme : (voir article) où T(ext) et T(fond) sont les températures à l'extérieur et en fond de mine, g est l'accélération de la pesanteur, H la hauteur de la galène et x la distance depuis son entrée. Enfin, on aborde ce problème aérodynamique grâce à un code d'éléments finis industriel, approche qui valide le fonctionnement qualitatif du système, sans aboutir toutefois à la convergence en raison, sans doute, du fort découplage entre l'extérieur de la mine et le fond de la galerie., ASEPAM-Association Spéléologique pour l 'Etude et la Protection des Anciennes Mines. Sur l'aérage naturel des anciennes galeries de mines en zone montagneuse

Investigating the Role of the Stringent Response in Lipid Modifications during the Stationary Phase in E. coli by Direct Analysis with Time-of-Flight-Secondary Ion Mass Spectrometry

Escherichia coli is able to rapidly adjust the biophysical properties of its membrane phospholipids to adapt to environmental challenges including starvation stress. These membrane lipid modifications were investigated in glucose starved E. coli cultures and compared to a ΔrelAΔspoT (ppGpp0) mutant strain of E. coli, deficient in the stringent response, by means of time-of-flight-secondary ion mass spectrometry (TOF-SIMS). Recent advances in TOF-SIMS, through the implementation of gas cluster ion beams (GCIBs), now permit the analysis of higher mass species from native, underivatized, biological specimen, i.e., intact bacterial cells. Cultures in stationary phase were found to exhibit a radically different lipid composition as compared to cultures in the exponential growth phase. Wild-type E. coli reacted upon carbon starvation by lipid modifications including elongation, cyclopropanation, and increased cardiolipin formation. Observations are consistent with variants of cardiolipins (CL), phosphatidylglycerols (PG), phosphatidylethanolamines (PE), phosphatidic acids (PA), and fatty acids. Notably, despite having a proteomic profile and a gene expression profile somewhat similar to the wild-type during growth, the ppGpp0 mutant E. coli strain was found to exhibit modified phospholipids corresponding to unsaturated analogues of those found in the wild-type. We concluded that the ppGpp0 mutant reacts upon starvation stress by elongation and desaturation of fatty acyl chains, implying that only the last step of the lipid modification, the cyclopropanation, is under stringent control. These observations suggest alternative stress response mechanisms and illustrate the role of the RelA and SpoT enzymes in the biosynthetic pathway underlying these lipid modifications

GM1 locates to mature amyloid structures implicating a prominent role for glycolipid-protein interactions in Alzheimer pathology

While the molecular mechanisms underlying Alzheimer\u27s disease (AD) remain largely unknown, abnormal accumulation and deposition of beta amyloid (AD) peptides into plaques has been proposed as a critical pathological process driving disease progression. Over the last years, neuronal lipid species have been implicated in biological mechanisms underlying amyloid plaque pathology. While these processes comprise genetic features along with lipid signaling as well as direct chemical interaction of lipid species with A beta mono- and oligomers, more efforts are needed to spatially delineate the exact lipid-A beta plaque interactions in the brain. Chemical imaging using mass spectrometry (MS) allows to probe the spatial distribution of lipids and peptides in complex biological tissues comprehensively and at high molecular specificity. As different imaging mass spectrometry (IMS) modalities provide comprehensive molecular and spatial information, we here describe a multimodal ToF-SIMS- and MALDI-based IMS strategy for probing lipid and A beta peptide changes in a transgenic mouse model of AD (tgAPP(ArcSwe)). Both techniques identified a general AD-associated depletion of cortical sulfatides, while multimodal MALDI IMS revealed plaque specific lipid as well as A beta peptide isoforms. In addition, MALDI IMS analysis revealed chemical features associated with morphological heterogeneity of individual A beta deposits. Here, an altered GM1 to GM2/GM3 ganglioside metabolism was observed in the diffuse periphery of plaques but not in the core region. This was accompanied by an enrichment of A beta 1-40arc peptide at the core of these deposits. Finally, a localization of arachidonic acid (AA) conjugated phosphatidylinositols (PI) and their corresponding degradation product, lysophosphatidylinositols (LPI) to the periphery of A beta plaques was observed, indicating site specific macrophage activation and ganglioside processing

Effects of home-based exergaming on cardio-metabolic and cognitive health in physically inactive individuals.

AIMS To examine the effects of a home-based exergame training over 6 weeks on cardio-metabolic and cognitive health, as well as training adherence, in physically inactive individuals. MATERIALS AND METHODS Twenty participants were equipped with an exergame system specifically designed for use at home. Each participant performed at least three weekly exercise sessions at ≥80% of their individual maximum heart rate, over 6 weeks. Exercise duration increased biweekly until 75 min of vigorous exercise were performed in Weeks 5 and 6. Maximum oxygen uptake (VO2max ), cardio-metabolic profiling, and neuro-cognitive tests were performed at baseline and study end. Additionally, training adherence was assessed via training diaries. RESULTS After 6 weeks of home-based exergaming, VO2max increased significantly, while there was a significant decrease in heart rate (resting and maximum), blood pressure (systolic, diastolic and mean), and low-density lipoprotein cholesterol. Dynamic balance and reaction time improved after 6 weeks of exergaming. Training adherence was 88.4%. CONCLUSIONS Home-based exergaming induced a clinically relevant increase in VO2max , a determinant of cardiovascular health, accompanied by further improvements in cardiovascular, metabolic and neuro-cognitive parameters. Exergaming may, therefore, offer an innovative approach to increasing regular physical activity, improving metabolic risk profile, and preventing chronic diseases

Correlative Chemical Imaging and Spatial Chemometrics Delineate Alzheimer Plaque Heterogeneity at High Resolution

We present a novel, correlative chemical imaging strategy based on multimodal matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI), hyperspectral microscopy, and spatial chemometrics. Our workflow overcomes challenges associated with correlative MSI data acquisition and alignment by implementing 1+1-evolutionary image registration for precise geometric alignment of multimodal imaging data. This enabled multivariate statistical modeling of multimodal imaging data using a novel multiblock orthogonal component analysis approach to identify covariations of biochemical signatures between and within imaging modalities at MSI pixel resolution. We demonstrate the method’s potential through its application towards delineating chemical traits of Alzheimer’s disease (AD) pathology. Here, trimodal MALDI MSI of transgenic AD mouse brain delineates beta-amyloid (Aβ) plaque-associated co-localization of lipids and Aβ peptides. Finally, we establish an improved image fusion approach for correlative MSI and functional amyloid microscopy. This allowed high resolution prediction of correlative, multimodal MSI signatures towards distinct amyloid structures within single plaque features critically implicated in Aβ pathogenicity