Beach and cliff retreat induced by storm groups at Forte Novo,Algarve (Portugal)

Littoral cell dynamics may change through time as a reaction to modifications of the coastal system. Along the Vilamoura-Quarteira coastline, the construction of a groin field limited the sediment supply to the already narrow Forte Novo beach, located downdrift, enhanced wave action on the cliff base and lead to long-term persistent cliff retreat. This research uses a set of surveys from November 2009 to March 2010 to determine short-term soft cliff erosion associated to storm groups at this sediment starved area. Following the initial LiDAR survey, three subsequent surveys were performed using a reflectorless total station for monitoring the cliff face, and RTK-DGPS to monitor the position of the cliff top, the cliff foot and the topography of the adjacent beach. Results indicate an important reduction in beach levels during successive storms (without significant beach recovery in between), allowing waves to further attack the cliff base and contributing to further enhance the structural and permanent cliff retreat. This work demonstrates how a combination of magnitude and frequency of extreme events coupled with development of the coastline, has led to increased cliff-beach recession and to the permanent dislocation of the cliff face

Synthesis and properties of Co-doped titanate nanotubes and their optical sensitization with methylene blue

Here we report on a novel chemical route to synthesize homogenous cobalt doped titanate nanotubes (CoTNT), using an amorphous Co-doped precursor. The influence of the synthesis temperature, autoclave dwell time and metal doping on the structural and microstructural as well as on the optical properties of the synthesized titanate nanotubes is studied and discussed. The optical band gaps of the CoTNT samples are red shifted in comparison with the values determined for the undoped samples, such red shifts bringing the absorption edge of the CoTNT samples into the visible region. CoTNT materials also demonstrate particular high adsorption ability for methylene blue, the amount of the adsorbed dye being higher than the one predictable for a monolayer formation. This suggests the possibility of intercalation of the dye molecule between the TiO6 layers of the TNT structure. It is also shown that the methylene blue sensitized Co-doped nanostructures are highly stable under UV radiation and present a strong and broad absorption in the visible region.Comment: 31 pages, 3 tables, 7 figure

The Variable Polarity Plasma Arc Welding Process: Its Application to the Space Shuttle External Tank

This report describes progress in the implementation of the Variable Polarity Plasma Arc Welding (VPPAW) process at the External Tank (ET) assembly facility. Design allowable data has been developed for thicknesses up to 1.00 in. More than 24,000 in. of welding on liquid oxygen and liquid hydrogen cylinders has been made without an internal defect

Synthesis of sub-5 nm Co-doped SnO2_2 nanoparticles and their structural, microstructural, optical and photocatalytic properties

A swift chemical route to synthesize Co-doped SnO$_2$ nanopowders is described. Pure and highly stable Sn$_{1-x}$Co$_x$O$_{2-\delta}$ (0 $\le$ x $\le$ 0.15) crystalline nanoparticles were synthesized, with mean grain sizes < 5 nm and the dopant element homogeneously distributed in substitutional sites of the SnO$_2$ matrix. The UV-visible diffuse reflectance spectra of the Sn$_{1-x}$Co$_x$O$_{2-\delta}$ samples reveal red shifts, the optical bandgap energies decreasing with increasing Co concentration. The Urbach energies of the samples were calculated and correlated with their bandgap energies. The photocatalytic activity of the Sn$_{1-x}$Co$_x$O$_{2-\delta}$ samples was investigated for the 4-hydroxylbenzoic acid (4-HBA) degradation process. A complete photodegradation of a 10 ppm 4-HBA solution was achieved using 0.02% (w/w) of Sn$_{0.95}$Co$_{0.05}$O$_{2-\delta}$ nanoparticles in 60 min of irradiation.Comment: 29 pages, 2 tables, 10 figure

Dynamics of drinking water biofilm in flow/non-flow conditions

Drinking water biofilm formation on polyvinyl chloride (PVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE) and polypropylene (PP) was followed in three different reactors operating under stagnant or continuous flow regimes. After one week, a quasi-steady state was achieved where biofilm total cell numbers per unit surface area were not affected by fluctuations in the concentration of suspended cells. Metabolically active cells in biofilms were around 17-35% of the total cells and 6-18% were able to form colony units in R(2)A medium. Microbiological analysis showed that the adhesion material and reactor design did not affect significantly the biofilm growth. However, operating under continuous flow (0.8-1.9 Pa) or stagnant water had a significant effect on biofilm formation: in stagnant waters, biofilm grew to a less extent. By applying mass balances and an asymptotic biofilm formation model to data from biofilms grown on PVC and HDPE surfaces under turbulent flow, specific growth rates of bacteria in the biofilm were found to be similar for both materials (around 0.15 day(-1)) and much lower than the specific growth rates of suspended bacteria (around 1.8 day(-1))

The variable polarity plasma arc welding process: Its application to the Space Shuttle external tank

The technical history of the variable polarity plasma arc (VPPA) welding process being introduced as a partial replacement for the gas shielded tungsten arc process in assembly welding of the space shuttle external tank is described. Interim results of the weld strength qualification studies, and plans for further work on the implementation of the VPPA process are included

AVALIAÇÃO IN VITRO DA ATIVIDADE ANTI-Helicobacter pylori E POTENCIAL ANTIOXIDANTE DE EXTRATOS E FRAÇÕES DE Baccharis trimera (Less.) DC

Um dos principais fatores de risco para o desenvolvimento de úlceras e câncer gástrico é a infecção pela bactéria Helicobacter pylori, que é acompanhada por um considerável estresse oxidativo. No Brasil, a planta Baccharis trimera Less. (DC), conhecida como carqueja, é popularmente usada para tratar distúrbios gastrointestinais e do fígado. Nessa espécie já foram identificados taninos, flavonoides, saponinas, lactonas diterpênicas, sesquiterpenos, compostos fenólicos e óleos voláteis. Dessa forma, o objetivo do presente estudo foi avaliar a atividade anti-Helicobacter pylori do extrato aquoso, (EAq), etanólico (EE), hidroalcoólico (EH) de B. trimera e das frações, aquosa (FAq), hexânica (FHx), e acetonitrila/clorofórmio (FAC) obtidas a partir do EH, além de analisar a composição fitoquímica, e seus efeitos sobre radicais livres e oxidantes biológicos. Para todos os extratos e frações foi realizada a triagem fitoquímica e a determinação do teor de polifenóis, flavonoides e taninos totais. A atividade anti-Helicobacter pylori foi avaliada por meio do ensaio de microdiluição em caldo e pela capacidade de inibição da enzima urease. A morfologia bacteriana, após exposição às amostras, foi analisada por microscópio eletrônico de varredura (MEV) com o extrato e a fração que atingiram a concentração inibitória mínima (CIM90). A atividade antioxidante foi avaliada em ensaios de inibição de radicais sintéticos DPPH e ABTS como triagem inicial para todas as amostras. Os ensaios com os oxidantes biológicos, peróxido de hidrogênio (H2O2), ânion superóxido (O2 -), ácido hipocloroso (HOCl), radical hidroxil (HO ) e óxido nítrico (NO ), foram realizados com o EH, devido aos melhores resultados obtidos no ensaio anti-H.pylori e na triagem antioxidante inicial, além de suas frações, exceto a FHx, devido ao baixo desempenho na triagem antioxidante. A maior concentração de polifenóis foi encontrado no EH, flavonoides na FAC e taninos em FAq. No ensaio anti-H. pylori, a CIM90 foi de 512 &#956;g/mL para EH e 1024 &#956;g/mL para FAC a qual foi bactericida. A MEV mostrou alterações morfológicas como alongamento e lise celular nas amostras testadas, podendo sugerir alterações de parede, provavelmente através do comprometimento da síntese de peptideoglicano. No ensaio de inibição da enzima urease o resultado mais expressivo foi o exibido pela FAC, que inibiu 36,24% na maior concentração testada.O melhor resultado dentre os extratos na triagem antioxidante inicial foi do EH, que obteve os seguintes CE50: DPPH, 17,40 ± 0,52 e ABTS, 9,99 ± 1,21. Para as frações os melhores CE50 foram: DPPH, FAq, 27,41 ± 1,65 e ABTS, FAq, 10,80 ± 1,90.No ensaio de captura do O2 -, a FAq apresentou CE50 de 5,85 ± 0,86&#956;g/mL. No ensaio de inibição do HOCl, todas as amostras testadas conseguiram inibição maior que 50%, exceto a FAq. No ensaio de inibição do radical HO , NO e H2O2, os resultados foram melhores para FAC e seu CE50 foi de 2,90 ± 0,48, 132,13 ± 7,38 e 66,70 ± 2,30 &#956;g/mL, respectivamente. As análises indicam que B. trimera, especialmente o EH, e suas frações, FAq e FAC, podem apresentar compostos promissores para o prevenção e tratamento de doenças causadas por H. pylori. Estes resultados foram embasados pela relação entre a presença de compostos fenólicos e a inibição de oxidantes, além da observação de alterações na membrana bacteriana