Contributo para a melhoria do desempenho térmico das paredes de taipa

O uso da construção em terra remonta ao início da nossa civilização. Nas regiões do Alentejo e do Algarve existe ainda um grande número de edifícios com paredes em taipa, mas esta tecnologia tem vindo a cair em desuso desde meados do século passado. A construção em terra é altamente sustentável, já que a terra per si é um material 100% reutilizável e pode ser facilmente encontrado em quase todos os lugares do mundo. Os edifícios com paredes em taipa apresentam uma elevada inércia térmica o que, dadas as características climáticas de Portugal, beneficia o seu comportamento térmico. No entanto, seria desejável que a condutibilidade térmica da taipa fosse menor. As preocupações ambientais relativas ao consumo energético, associado ao conforto na habitação, e ao fabrico, transporte e aplicação dos materiais utilizados na construção, levou-nos a procurar novas soluções de tipologias construtivas em terra. Atendendo a estes aspetos e à melhoria da eficiência energética das habitações, neste trabalho são apresentados os resultados dos ensaios realizados em laboratório sobre novas soluções de construção em terra. O local selecionado para a recolha de amostras de terra foi Serpa. Foi feita a caracterização geotécnica do material terra e preparadas diversas composições com a incorporação de argila expandida e de regranulado de cortiça expandida. A argila expandida e o regranulado de cortiça expandida também foram escolhidos por serem isolantes térmicos produzidos a partir de matérias primas disponíveis nas regiões do Alentejo e do Algarve, regiões do nosso país com maior aptência para o uso da taipa. De maneira a caracterizar as diferentes composições sob o ponto de vista mecânico e do desempenho térmico, foram fabricados cubos com 10 cm de aresta e ensaiados de modo a se calcular a sua resistência à compressão e a sua condutibilidade térmica. Os resultados obtidos mostraram que a utilização deste tipo de tipologias construtivas em terra com a incorporação de argila expandida e de regranulado de cortiça expandida permite aumentar o seu desempenho, fazendo que seja possível adaptar esta tipologia às necessidades dos dias de hoje, nomeadamente às exigências estabelecidas pelo Regulamento das Características de Comportamento Térmico dos Edifícios (RCCTE). Os resultados desta investigação têm aplicabilidade, com as devidas adaptações, tanto em construções em taipa como em construções em adobe

Binary Collisions and the Slingshot Effect

We derive the equations for the gravity assist manoeuvre in the general 2D case without the constraints of circular planetary orbits or widely different masses as assumed by Broucke, and obtain the slingshot conditions and maximum energy gain for arbitrary mass ratios of two colliding rigid bodies. Using the geometric view developed in an earlier paper by the authors the possible trajectories are computed for both attractive or repulsive interactions yielding a further insight on the slingshot mechanics and its parametrization. The general slingshot manoeuvre for arbitrary masses is explained as a particular case of the possible outcomes of attractive or repulsive binary collisions, and the correlation between asymptotic information and orbital parameters is obtained in general.Comment: 12 pages, 7 figures, accepted for publication Dec'07, Celestial Mechanics and Dynamical Astronom

Two-dimensional multiscale entropy analysis: applications to image texture evaluation

Complexity measures, defined as measures of irregularity over time scales, are the subject of a growing number of studies as the information they reveal can find utility in a large field of applications. One of the most popular complexity measures is the multiscale entropy. Nevertheless, more and more algorithms dedicated to complexity analyses are proposed to improve the existing ones. However, such measures are available only for one-dimensional time series. For bidimensional data (images), no equivalent algorithm has been proposed to analyze irregularity over spatial scales. We herein introduce a new framework that extends the one-dimensional multiscale entropy (MSE1D) to the bidimensional case (MSE2D). Moreover, a variant of MSE2D is also ModMSE2D). The two new algorithms are tested as new texture analysis frameworks. They are applied to simulated and real data. Our results show that, compared with other existing texture analysis algorithms, MSE2D and ModMSE2D are suitable and powerful tools for image analysis and classification according to their texture patterns. While MSE2D is computationally faster than ModMSE2D, ModMSE2D is more robust to small image sizes. The two methods present interesting performances, and can be as useful as their unidimensional versions in two-dimensional applications

1,4-Dioxane-degrading consortia can be enriched from uncontaminated soils: prevalence of Mycobacterium and soluble di-iron monooxygenase genes

Two bacterial consortia were enriched from uncontaminated soil by virtue of their ability to grow on 1,4-dioxane (dioxane) as a sole carbon and energy source. Their specific dioxane degradation rates at 30°C, pH = 7 (i.e. 5.7 to 7.1 g-dioxane per g-protein per day) were comparable to those of two dioxane-metabolizing archetypes: Pseudonocardia dioxanivoransCB1190 and Mycobacterium dioxanotrophicusPH-06. Based on 16S rRNA sequencing, Mycobacterium was the dominant genus. Acetylene inhibition tests suggest that dioxane degradation was mediated by monooxygenases. However, qPCR analyses targeting the tetrahydrofuran/dioxane monooxygenase gene (thmA/dxmA) (which is, to date, the only sequenced dioxane monooxygenase gene) were negative, indicating that other (as yet unknown) catabolic gene(s) were responsible. DNA sequence analyses also showed threefold to sevenfold enrichment of group 5 and group 6 soluble di-iron monooxygenase (SDIMO) genes relative to the original soil samples. Whereas biodegradation of trace levels of dioxane is a common challenge at contaminated sites, both consortia degraded dioxane at low initial concentrations (300 μg l−1) below detectable levels (5 μg l−1) in bioaugmented microcosms prepared with impacted groundwater. Overall, this work shows that dioxane-degrading bacteria (and the associated natural attenuation potential) exist even in some uncontaminated soils, and may be enriched to broaden bioaugmentation options for sites experiencing insufficient dioxane catabolic capacity

Argon plasma treatment techniques on steel and effects on diamond-like carbon structure and delamination

Copyright © 2011 Elsevier B.V. All rights reserved.We demonstrate alteration in diamond-like carbon (DLC) film structure, chemistry and adhesion on steel, related to variation in the argon plasma pretreatment stage of plasma enhanced chemical vapour deposition. We relate these changes to the alteration in substrate structure, crystallinity and chemistry due to application of an argon plasma process with negative self bias up to 600 V. Adhesion of the DLC film to the substrate was assessed by examination of the spallated fraction of the film following controlled deformation. Films with no pretreatment step immediately delaminated. At 300 V pretreatment, the spallated fraction is 8.2%, reducing to 1.2% at 450 V and 0.02% at 600V. For bias voltages below 450V the adhesion enhancement is explained by a reduction in carbon contamination on the substrate surface, from 59at.% with no treatment to 26at.% at 450V, concurrently with a decrease in the surface roughness, Rq, from 31.5nm to 18.9nm. With a pretreatment bias voltage of 600V a nanocrystalline, nanostructured surface is formed, related to removal of chromium and relaxation of stress; X-ray diffraction indicates this phase is incipient at 450V. In addition to improving film adhesion, the nanotexturing of the substrate prior to film deposition results in a DLC film that shows an increase in sp3/sp2 ratio from 1.2 to 1.5, a reduction in surface roughness from 31nm to 21nm, and DLC nodular asperities with reduced diameter and increased uniformity of size and arrangement. These findings are consistent with the substrate alterations due to the plasma pretreatment resulting in limitation of surface diffusion in the growth process. This suggests that in addition to deposition phase processes, the parameters of the pretreatment process need to be considered when designing diamond-like carbon coatings.This work is partially supported by the Technology Strategy Board, reference BD266E

Emergence of Anti-Cancer Drug Resistance: Exploring the Importance of the Microenvironmental Niche via a Spatial Model

Practically, all chemotherapeutic agents lead to drug resistance. Clinically, it is a challenge to determine whether resistance arises prior to, or as a result of, cancer therapy. Further, a number of different intracellular and microenvironmental factors have been correlated with the emergence of drug resistance. With the goal of better understanding drug resistance and its connection with the tumor microenvironment, we have developed a hybrid discrete-continuous mathematical model. In this model, cancer cells described through a particle-spring approach respond to dynamically changing oxygen and DNA damaging drug concentrations described through partial differential equations. We thoroughly explored the behavior of our self-calibrated model under the following common conditions: a fixed layout of the vasculature, an identical initial configuration of cancer cells, the same mechanism of drug action, and one mechanism of cellular response to the drug. We considered one set of simulations in which drug resistance existed prior to the start of treatment, and another set in which drug resistance is acquired in response to treatment. This allows us to compare how both kinds of resistance influence the spatial and temporal dynamics of the developing tumor, and its clonal diversity. We show that both pre-existing and acquired resistance can give rise to three biologically distinct parameter regimes: successful tumor eradication, reduced effectiveness of drug during the course of treatment (resistance), and complete treatment failure

Band-gap Shift In Cds Semiconductor By Photoacoustic Spectroscopy: Evidence Of A Cubic To Hexagonal Lattice Transition

The band-gap energies of the CdS semiconductor are obtained by a photoacoustic spectroscopy (PAS) technique over a range of temperature of thermal annealing (TTA), in which the evolution of the sample structure is characterized by x-ray diffraction patterns. The PAS experiment gives a set of data for the band-gap shift in the region of the fundamental absorption edge. With increasing TTA the band-gap shift increases up to a critical TTA when its slope decreases in a roughly symmetrical way. It is suggested that at this temperature a cubic to hexagonal-lattice transition occurs.64329129

Anthocyanin pigments in strawberry

The anthocyanin composition was analysed in strawberry fruits from five different cultivars (cv. Eris, Oso Grande, Carisma, Tudnew and Camarosa). Twenty-five defined anthocyanin pigments were detected, most of them containing Pelargonidin (Pg) as aglycone; some cyanidin (Cy) derivatives were also found. Glucose and rutinose were the usual substituting sugars, although arabinose and rhamnose were also tentatively identified; some minor anthocyanins showed acylation with aliphatic acids. A relevant aspect was the detection of anthocyanin-derived pigments, namely 5-carboxypyranopelargonidin-3-glucoside and four condensed pigments containing C–C linked anthocyanin (Pg) and flavanol (catechin and afzelechin) residues. Total anthocyanin content ranged between 200 and 600mg/kg, with Pg 3-gluc constituting 77–90% of the anthocyanins in the strawberry extracts followed by Pg 3-rut (6–11%) and Cy 3-gluc (3–10%). A notable variability was found among the anthocyanin concentrations in samples of a same variety and harvest, indicating a strongly influence of the degree of maturity, edaphic-climatic factors and post-harvest storage

Analysis of asymmetric T-stub components: experimental and numerical approach

Este artículo presenta el análisis mediante técnicas numéricas y experimentales de componentes T-equivalente asimétricas, refiriéndose ésta al posicionamiento de los pernos respecto al alma del perfil. El objetivo principal de realizar este análisis es el de evaluar la influencia de dicha asimetría en la rigidez y sobre todo en la resistencia final, y compararlas a las de componentes simétricas. Se definen dos modelos numéricos para analizar el comportamiento: uno matricial de barras rígidas y otro con elementos finitos sólidos. Los resultados obtenidos con ambos modelos se comparan con ensayos experimentales, tanto para para una componente simétrica como una asimétrica, obteniéndose un error menor del 10 % para el cálculo de la rigidez e inferior al 20% para la resistencia final. Se comprueba que, como cabía esperar, la asimetría repercute en una redistribución de la carga en los pernos, produciéndose un fallo prematuro del conjunto con respecto a la configuración simétrica. Por tanto, puede deducirse que los análisis numéricos realizados son capaces de cuantificar dicha redistribución.The analysis of asymmetric T-stub components by the position of bolts respect to the web, has been carried out using numerical and experimental approaches. The main objective of this analysis is to evaluate the influence of such asymmetry on the stiffness and strength. A matrix frame model with beam-column elements and rigid connections has been developed as well as with solid elements. Results obtained with these numerical models have been compared with those obtained from experimental tests carried out, for both symmetrical and asymmetrical components, obtaining errors below 10% for stiffness and lower than 20% for the final strength. It was found, as expected, that the asymmetry leads to a redistribution of the load on the bolts, causing premature failure of the assembly. Therefore the numerical analysis performed is capable of quantifying such redistribution.Peer Reviewe