Bio-film formation on stainless steels Part 2. The role of seasonal changes, seawater composition and surface roughness

Bio-film formation on type 254 SMO stainless steel in Arabian Gulfwater was followed by measuring the variation of the open circuit potentials of test coupons under a variety of conditions. The time-potential curves exhibited two plateaus corresponding to oxide thickening and later to bio film development. The rate of film formation was found to depend on the ambient seawater temperature, which varied with the season. The reduction of the biological activity of the water through additions of pre-boiled and cooled seawater resulted in the retardation of bio-film formation and in the shift of the final steady-state potential towards less positive values. Similar behaviour was obtained when concentrating seawater by the addition of solid salt. The simultaneous reduction of biological activity and of salt content resulted. The characteristics ofthe formed bio-film depend on the nature ofthe metal surfaces. Smooth surfaces allowed the development of thin clear films while thicker dark films formed on coarse rough surfaces. These were usually associated with the growth of worm-like structures, initiating crevice and pitting corrosion.     

Silicone-containing polymer matrices as protective coatings: Properties and applications

The paper addresses the technologically important problem of porous building materials protection, e.g. sandstone, limestone, marble against soiling. Protective coatings applied to the surface of porous building material should be characterized by very efficient water vapour permeability and self-cleaning properties.     

The effect of heating rate on yields and compositions of oil products from esparto pyrolysis

Recently, much research has been focused on liquid oil from biomass pyrolysis, which is considered as an alternative to conventional fossil fuels. This paper studies the effect of heating rate on both the yields and the chemical composition of the oil product obtained from pyrolysis of esparto which is the most important biomass in Morocco. The pyrolysis experiments of esparto was performed in a fixed bed reactor under argon atmosphere with different heating rate: 50, 150 and 250°C min^?1. The maximum conversion of esparto in oil of pyrolysis was obtained with fast pyrolysis 68.5% at 550°C. The FT‐IR and ¹H NMR analysis showed that the oil of pyrolysis formed principally by aliphatic compound. The analysis elemental showed that the H/C ratio increase and O/C decrease as the heating rate increase. The PCV improved slightly from 33.5 to 34.8 MJ kg^?1. The oil obtained with higher heating rate has chemical properties similar to diesel that can be used with an economic and environmental advantage. Copyright © 2006 John Wiley & Sons, Ltd.     

阿拉伯东部地区宗教文化对传统建筑的影响

伊斯兰教和阿拉伯语是西亚地区统一的主要特征.它们构成了这些国家的共性,然而又有一些因素可将西亚世界区分开来,宗教就是其中2一。阿拉伯国家都是穆斯林国家, 它们的建筑是世界伊斯兰建筑的一部分,“伊斯兰建筑”概念本身就体现了宗教在地域建筑特征形成过程中所起的作用。地域性文化是地域性建筑的重要构成,宗教文化则是地域性文化诸因素之一。     

Induced electrodeposition of tungsten with nickel from acidic citrate electrolyte

Induced electrodeposition of Ni–W alloys was carried out onto steel substrates from acidic citrate baths (pH 4.5) under different conditions of concentration of electrolyte, current density and temperature. Bright and highly adherent Ni–W deposits were successfully obtained with a relatively high cathodic current efficiency CCE (80–85%). The CCE increases greatly with increasing pH and Ni²⁺ ion content in the bath. The W% in the alloy deposits is in the range of 4–20 wt% depending on the operating condition. The W content in the deposit was found to increase with an increase in Ni²⁺ ion content, pH and temperature. The surface morphology was examined by scanning electron microscopy while the structure of the alloy was examined by X-ray diffraction analysis.     

Using reconfiguration for efficient management of replicated data

Replicated data management protocols have been proposed that exploit a logically structured set of copies. These protocols have the advantage that they provide limited fault-tolerance at low communication cost. The proposed protocols can be viewed as analogues of the read-one write-all protocol in the context of logical structures. In this paper, we start by generalizing these protocols in two ways for logical structures. First, the quorum-based approach is applied to develop protocols that use structured read and write quorums, thus attaining a high degree of data availability for both read and write operations. Next, the reconfiguration or views approach is developed for these structures, resulting in protocols that attain high degrees of availability at significantly low communication cost for read operations. In this sense, the proposed protocols have the advantages of the read-one write-all protocol for low-cost read operations as well as the majority quorum protocol for high data availability. Finally, we generalize the reconfiguration approach to allow for the dynamic reconfiguration of the database system from one replica management protocol to another. This allows database systems to adapt to an evolving and dynamic application environment     

I-SceI-induced gene replacement at a natural locus in embryonic stem cells

Gene targeting is a very powerful tool for studying mammalian development and physiology and for creating models of human diseases. In many instances, however, it is desirable to study different modifications of a target gene, but this is limited by the generally low frequency of homologous recombination in mammalian cells. We have developed a novel gene-targeting strategy in mouse embryonic stem cells that is based on the induction of endogenous gap repair processes at a defined location within the genome by induction of a double-strand break (DSB) in the gene to be mutated. This strategy was used to knock in an NH2-ezrin mutant in the villin gene, which encodes an actin-binding protein expressed in the brush border of the intestine and the kidney. To induce the DSB, an I-SceI yeast meganuclease restriction site was first introduced by gene targeting to the villin gene, followed by transient expression of I-SceI. The repair of the ensuing DSB was achieved with high efficiency (6 x 10[-6]) by a repair shuttle vector sharing only a 2.8-kb region of homology with the villin gene and no negative selection marker. Compared to conventional gene-targeting experiments at the villin locus, this represents a 100-fold stimulation of gene-targeting frequency, notwithstanding a much lower length of homology. This strategy will be very helpful in facilitating the targeted introduction of several types of mutations within a gene of interest.     

Oxygen reduction on oxide/polypyrrole composite electrodes: effect of doping anions

Multilayered composite electrodes on glassy carbon, GC, having the structure GC/PPy/PPy(Ox)/PPy, with PPy the polypyrrole and Ox a mixed valence oxide of transition metals, exhibit high reactivity and stability towards the oxygen reduction reaction (orr), when the orr proceeds electrocatalytically on the oxide particles dispersed throughout the inner layer, PPy(Ox). However the nature and concentration of the doping anions, A, of PPy have a profound effect on the resulting orr currents, due to their effects on the conductivity and morphology of the PPy layers. The paper shows and discusses these effects in the case of the composite electrode with Ox = Cu_1.4Mn_1.6O₄ and A = Cl⁻, ClO₄⁻, NO₃⁻, PF₆⁻ and SO₄²⁻, in acid solution (pH 2.2). Optimal conditions were encountered with Cl⁻.     

The exergy fields in transport processes: Their calculation and use

This paper is a brief review of the method for analyzing the space and time dependent exergy and irreversibility fields in processes. It presents the basic equations, the method for their use, major literature sources, and three examples from the authors' work: flow desiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Law analysis are used to attempt process improvement suggestions.     

Performance of radial-basis function networks for direction ofarrival estimation with antenna arrays

The problem of direction of arrival (DOA) estimation of mobile users using linear antenna arrays is addressed. To reduce the computational complexity of superresolution algorithms, e.g. multiple signal classification (MUSIC), the DOA problem is approached as a mapping which can be modeled using a suitable artificial neural network trained with input output pairs. This paper discusses the application of a three-layer radial-basis function neural network (RBFNN), which can learn multiple source-direction findings of a six-element array. The network weights are modified using the normalized cumulative delta rule. The performance of this network is compared to that of the MUSIC algorithm for both uncorrelated and correlated signals. It is also shown that the RBFNN substantially reduced the CPU time for the DOA estimation computations