Effect of Relative Humidity in High Temperature Oxidation of Ceria Nanoparticles Coating on 316L Austenitic Stainless Steel

A solution of 20 wt. % colloidal dispersion of Cerium Oxide (CeO2) in 2.5% of acetic acid, was used for depositing a coating film on an austenitic stainless steel 316L. Cerium compounds have been distinguished as potential corrosion inhibitors in coatings over several alloys. The oxidation behavior of the cerium oxide coating on 316L austenitic stainless steel alloy was evaluated in dry and humid environments, the weight changes (W/A) was monitored as a function of time using a custom built Thermogravimetrical Analysis (TGA) instrument at temperatures of 750C, 800C and 850C, and different relative humidity levels (0%, 10% and 20%) respectively. The parabolic oxidation rate and activation energy is calculated experimentally for each relative humidity level. A measurement of the effective diameter size of the ceria nanoparticles was performed using a Light Scattering technique. A characterization of the film morphology and thickness before the oxidation was executed using Atomic Force Microscopy (AFM) Microstructure and chemical composition of the oxidized coated substrates were analyzed using Scanning Electronic Microscopy (SEM) with energy dispersive spectroscopy (EDS). X-Ray Diffractometer (XRD) was used to characterize oxides formed in the surface upon isothermal treatment. A comparison of activation energy values obtained to identify the influence of relative humidity in the oxidation process at high temperature was conducted. Cerium oxides coating may prevent crevice corrosion and increase pitting resistance of 316L relative to the uncoated substrate at high temperatures and different levels of relative humidity acting as a protective oxidation barrier. The calculated parabolic rate constants, kp, at the experimental temperatures tend to increase as a function of humidity levels. The activation energy tends to increase proportionally to higher level of humidity exposures. At 0% relative humidity a value of 319.29 KJ/mol of activation energy is being obtained and at 20% is 366.10 KJ/mol. For the 10% an approximate value of 343.00 KJ/mol has been estimated based on the projection of the kp values at 750C and 800C. The presence of the CeO2 coating film, reduced the oxidation kinetics and provided good cyclic oxidation resistance at increments of relative humidity

Simulations of phytoplankton dynamics in El Gergal Reservoir, Southern Spain (PROTECH)

The Mediterranean region is characterised by a variable climate with most of the rain falling during the winter and frequent summer droughts. Such warm, dry periods are ideal for the growth of large algal blooms that often consist of potentially toxic Cyanobacteria. This makes the management of water for human use particularly challenging in such a climate and it is important to understand how such blooms can be avoided or at least be reduced in size. PROTECH (Phytoplankton RespOnses To Environmental CHange) is a model that simulates the dynamics of different species of phytoplankton populations in lakes and reservoirs. Its distinct advantage over similar models is its ability to simulate the relative composition of the algal flora, allowing both quantitative and qualitative conclusions to be drawn e.g. whether Cyanobacteria could be a potential problem. PROTECH has been applied primarily to lakes and reservoirs in northern Europe. Recently, however, the model has been applied to water bodies in lower latitudes, including Australia to a water supply reservoir in the south of Spain, El Gergal. El Gergal is the last in a chain of reservoirs that supply water to the city of Seville. It was brought into service in April 1979 and has a maximum storage volume of 35 000 000 m3. This article summarises the application of PROTECH in order to simulate the following problems: • the effect of a large influx of Ceratium biomass into El Gergal from another reservoir • the effect of using alternative water sources instead of the Guadalquivir River (used occasionally to raise water levels in El Gergal) • the effect of installing tertiary sewage treatment on the Cala River • the effect of simulated drought conditions on phytoplankton in the reservoir

Temporal and spatial variations in the quality of water in El Gergal Reservior, Seville, Spain

It is often difficult to define ‘water quality’ with any degree of precision. One approach is that suggested by Battarbee (1997) and is based on the extent to which individual lakes have changed compared with their natural ‘baseline’ status. Defining the base-line status of artificial lakes and reservoirs however, is, very difficult. In ecological terms, the definition of quality must include some consideration of their functional characteristics and the extent to which these characteristics are self-sustaining. The challenge of managing lakes in a sustainable way is particularly acute in semi-arid, Mediterranean countries. Here the quality of the water is strongly influenced by the unpredictability of the rainfall as well as year-to-year variations in the seasonal averages. Wise management requires profound knowledge of how these systems function. Thus a holistic approach must be adopted and the factors influencing the seasonal dynamics of the lakes quantified over a range of spatial and temporal scales. In this article, the authors describe some of the ways in which both long-term and short-term changes in the weather have influenced the seasonal and spatial dynamics of phytoplankton in El Gergal, a water supply reservoir situated in the south of Spain. The quality of the water stored in this reservoir is typically very good but surface blooms of algae commonly appear during warm, calm periods when the water level is low. El Gergal reservoir is managed by the Empresa Municipal de Abastecimiento y Saneamiento (EMASESA) and supplies water for domestic, commercial and industrial use to an area which includes the city of Seville and twelve of its surrounding towns (ca. 1.3 million inhabitants). El Gergal is the last of two reservoirs in a chain of four situated in the Rivera de Huelva basin, a tributary of the Guadalquivir river. It was commissioned by EMASESA in 1979 and since then the company has monitored its main limnological parameters on, at least, a monthly basis and used this information to improve the management of the reservoir. As a consequence of these intensive studies the physical, chemical and biological information acquired during this period makes the El Gergal database one of the most complete in Spain. In this article the authors focus on three ‘weather-related’ effects that have had a significant impact on the composition and distribution of phytoplankton in El Gergal: (i) the changes associated with severe droughts; (ii) the spatial variations produced by short-term changes in the weather; (iii) the impact of water transfers on the seasonal dynamics of the dinoflagellate Ceratium

Diagnóstico y propuestas para la revitalización de las Sierras de Teruel (Gúdar-Javalambre y Maestrazgo).

Aún son numerosos los espacios rurales en Aragón que siguen padeciendo dinámicas poblacionales negativas. Este artículo realiza en un conjunto de municipios de montaña que comparten estas dinámicas, un análisis clínico a este territorio en tres fases: examen territorial, diagnóstico y prescripción. El examen y diagnóstico se centra en las causas del despoblamiento, y en analizar algunas de las principales infraestructuras de comunicación, servicios básicos y políticas territoriales elementales del desarrollo rural, para pasar a una posible prescripción en forma de esbozo de estrategia de revitalización territorial

Nonlocal smoothing and adaptive morphology for scalar- and matrix-valued images

In this work we deal with two classic degradation processes in image analysis, namely noise contamination and incomplete data. Standard greyscale and colour photographs as well as matrix-valued images, e.g. diffusion-tensor magnetic resonance imaging, may be corrupted by Gaussian or impulse noise, and may suffer from missing data. In this thesis we develop novel reconstruction approaches to image smoothing and image completion that are applicable to both scalar- and matrix-valued images. For the image smoothing problem, we propose discrete variational methods consisting of nonlocal data and smoothness constraints that penalise general dissimilarity measures. We obtain edge-preserving filters by the joint use of such measures rich in texture content together with robust non-convex penalisers. For the image completion problem, we introduce adaptive, anisotropic morphological partial differential equations modelling the dilation and erosion processes. They adjust themselves to the local geometry to adaptively fill in missing data, complete broken directional structures and even enhance flow-like patterns in an anisotropic manner. The excellent reconstruction capabilities of the proposed techniques are tested on various synthetic and real-world data sets.In dieser Arbeit beschäftigen wir uns mit zwei klassischen Störungsquellen in der Bildanalyse, nämlich mit Rauschen und unvollständigen Daten. Klassische Grauwert- und Farb-Fotografien wie auch matrixwertige Bilder, zum Beispiel Diffusionstensor-Magnetresonanz-Aufnahmen, können durch Gauß- oder Impulsrauschen gestört werden, oder können durch fehlende Daten gestört sein. In dieser Arbeit entwickeln wir neue Rekonstruktionsverfahren zum zur Bildglättung und zur Bildvervollständigung, die sowohl auf skalar- als auch auf matrixwertige Bilddaten anwendbar sind. Zur Lösung des Bildglättungsproblems schlagen wir diskrete Variationsverfahren vor, die aus nichtlokalen Daten- und Glattheitstermen bestehen und allgemeine auf Bildausschnitten definierte Unähnlichkeitsmaße bestrafen. Kantenerhaltende Filter werden durch die gemeinsame Verwendung solcher Maße in stark texturierten Regionen zusammen mit robusten nichtkonvexen Straffunktionen möglich. Für das Problem der Datenvervollständigung führen wir adaptive anisotrope morphologische partielle Differentialgleichungen ein, die Dilatations- und Erosionsprozesse modellieren. Diese passen sich der lokalen Geometrie an, um adaptiv fehlende Daten aufzufüllen, unterbrochene gerichtet Strukturen zu schließen und sogar flussartige Strukturen anisotrop zu verstärken. Die ausgezeichneten Rekonstruktionseigenschaften der vorgestellten Techniken werden anhand verschiedener synthetischer und realer Datensätze demonstriert

Photodegradation of nimodipine and felodipine in microheterogeneous systems

Indexación: Web of Science; ScieloThe photochemical behavior of nimodipine (NIMO) and felodipine (FELO), photolabile drugs widely used as antihypertensive calcium channel blockers, is studied in constrained media. Specifically, we are interested in the kinetic analysis of 4-aryl-1,4-dihydropyridine photodegradation processes when they are incorporated in biological-mimicking systems like micelles or liposomes. In order to establish if the nature of the head of surfactant (ionic or nonionic) could be important modulating the photo-reactivity of these drugs, we studied the photodegradation of NIMO and FELO incorporated in micelles formed with sodium dodecyl sulfate (SDS, anionic), dodecyl-pyridinium chloride (DPC, cationic) and mono lauryl sucrose ester (MLS, nonionic) as surfactants. Additionally, the results of the photodegradation of these compounds in liposomes were also included. The results clearly indicate that both dihydropyridines studied, NIMO and FELO, are located near to the interface, but the surface charge of micelles does not affect neither, the photodegradation rate constant nor the photodegradation products profile. The absence of singlet oxygen generation in micellar media is consistent with the proposition of these 4-aryl-1,4-dihidropyridines located near to the interface of the micelle, where a polar environment is sensed. In addition, the ethanol preferential location on membranes and dihydropyridine enhanced photodegradation by alcohol presence are interesting results to consider in future research.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072012000300025&nrm=is

Instability of shallow lakes : a matter of the complexity of factors involved in sediment and water interaction?

Instability and extreme fluctuations in water quality characterizing shallow lakes are to a large extent due to rapid changes in the internal supply rates of nutrients. In fact, is in these systems that sediment and water interaction plays a major role in nutrients' dynamics. For this study, a double-approach perspective with both field measurements and laboratory experiments has been used in order to determine the contribution of physical, biological, and chemical mechanisms to nutrients' dynamics in two shallow adjacent lakes in Andalusia (Spain). Despite their geographic proximity, strong differences between the study systems have been recognised. In the Lake Honda, the high nutrient concentrations, which ultimately support a large algal biomass, are the result of: i. Resuspension of the surface sediment favoured by its morphometry, hydrologic regime and sediment granulometry. ii. Intense organic matter mineralization due to the labile nature of the organic settled matter (planktonic). In Lake Nueva, by contrast, physical constrains (i.e. wind-induced resuspension) have a limited effect due to the coarse surface sediment and to the development of macrophytes (Najas marina, Potamogeton pectinatus). In addition, the structurally more complex organic matter of its sediment regulates the low nutrients turnover. In this lake, nutrient exchange rates across the sediment-water interface are also controlled by chemical processes, such as P adsorption onto CaCO3, a mechanism that is favoured by the high Ca+2 concentration in the interstitial water. In this way, the joint effect of physical, chemical, and biological mechanisms determine the fast nutrients' benthic regeneration in Lake Honda, while in contrast, a large fraction of the nutrients present in the sediment of the Lake Nueva is in particle form.La inestabilidad y las extremas fluctuaciones en la calidad del agua que caracterizan a los lagos someros, se deben en gran medida, a cambios rápidos en la carga interna de nutrientes. De hecho, es en éstos sistemas, donde la interacción agua-sedimento juega un papel esencial en la dinámica de los nutrientes. Para este estudio, se ha empleado una doble aproximación, basada tanto en datos de campo como en experimentos en laboratorio, para determinar la contribución de mecanismos físicos, químicos y biológicos a la dinámica de los nutrientes en dos lagunas costeras en Andalucía (España). A pesar de su proximidad geográfica, se han reconocido fuertes diferencias entre ambos sistemas. En la laguna Honda, las elevadas concentraciones de nutrientes, que en última instancia soportan una elevada biomasa algal, son el resultado de: i. Resuspensión del sedimento superficial, favorecida por la morfometría, el régimen hídrico y la granulometría de su sedimento. ii. Intensa mineralización de la materia orgánica debida al carácter lábil de la materia orgánica sedimentada (origen planctónico). En la laguna Nueva, por el contrario, el impacto de los factores físicos (p.e. resuspensión inducida por el viento) se encuentra limitado por la gruesa granulometría del sedimento superficial así como por el desarrollo de macrófitos (Najas marina, Potamogeton pectinatus). Más aún, la naturaleza estructuralmente más compleja de la materia orgánica presente en su sedimento determina unas menores tasas de regeneración de nutrientes. En esta laguna, las tasas de intercambio de nutrientes a través de la interfase agua-sedimento se encuentran, además, controladas por procesos químicos, tales como la precipitación de P sobre CaCO3, mecanismo que se encuentra favorecido por las elevadas concentraciones de Ca+2 presentes en el agua intersticial. Por tanto, es la conjunción de mecanismos físicos, químicos y biológicos los que determinan la rápida regeneración béntica de nutrientes en la laguna Honda; mientras que, por el contrario, una importante fracción de los nutrientes presentes en el sedimento de la laguna Nueva se encuentra en forma particulada

Estudio de los sistemas sostenibles implementados en la construcción de vivienda unifamiliar en la ciudad de Bogotá

Trabajo de investigaciónLo que se busca con este estudio, entre otras cosas, es orientar a los usuarios promotores de vivienda y consumidores finales sobre la existencia y métodos de sistemas sostenibles que pueden ser implementados en las construcciones de viviendas unifamiliares, llevando a cabo una pronta implementación de los mismos y así contribuir a la preservación del medio ambiente y a una mejor calidad de vida de la población nacional.EspecializaciónEspecialista en Gerencia de Obras Civile

Adaptive continuous-scale morphology for matrix fields

In this article we consider adaptive, PDE-driven morphological operations for 3D matrix fields arising e.g. in diffusion tensor magnetic resonance imaging (DT-MRI). The anisotropic evolution is steered by a matrix constructed from a structure tensor for matrix valued data. An important novelty is an intrinsically one-dimensional directional variant of the matrix-valued upwind schemes such as the Rouy-Tourin scheme. It enables our method to complete or enhance anisotropic structures effectively. A special advantage of our approach is that upwind schemes are utilised only in their basic one-dimensional version. No higher dimensional variants of the schemes themselves are required. Experiments with synthetic and real-world data substantiate the gap-closing and line-completing properties of the proposed method