Physicochemical parameters and magnetic speciation of Iron in Nakivubo Channel and Lake Victoria waters

Magnetic speciation technique was used for the determination of iron species in Nakivubo Channel and Lake Victoria waters. The method consisted of a column of supported Dowex 1-X18, 20–50 US mesh (Cl) surrounded by movable permanent magnets. Dowex was supported by a porous material to permit adequate passage of the eluent through the column. In the presence of an external magnetic field, enhanced capacity for adsorption of iron III was observed. The enhanced capacity is primarily due to the magnetic field produced and ion exchange sorption mechanism. The results show that, most of the Iron in Nakivubo Channel waters is in reduced ferrous form while, in the Lake Victoria waters, it exists in the oxidized ferric form. Physicochemical parameters for the field samples are discussed in this study. Turbidity levels in catchments with substantial vegetation were significantly lower than those without. pH values up to 13 was observed for some of the point source. The physicochemical parameters along Nakivubo Channel waters were relatively higher than the Lake Victoria waters indicating slow increasing pollution load along the Nakivubo Channel.     

Visual Acuity in Day for Night

In film production, it is sometimes not convenient or directly impossible to shoot some night scenes at night. The film budget, schedule or location may not allow it. In these cases, the scenes are shot at daytime, and the ‘night look’ is achieved by placing a blue filter in front of the lens and under-exposing the film. This technique, that the American film industry has used for many decades, is called ‘Day for Night’ (or ‘American Night’ in Europe.) But the images thus obtained don’t usually look realistic: they tend to be too bluish, and the objects’ brightness seems unnatural for night-light. In this article we introduce a digital Day for Night algorithm that achieves very realistic results. We use a set of very simple equations, based on real physical data and visual perception experimental data. To simulate the loss of visual acuity we introduce a novel diffusion Partial Differential Equation (PDE) which takes luminance into account and respects contrast, produces no ringing, is stable, very easy to implement and fast. The user only provides the original day image and the desired level of darkness of the result. The whole process from original day image to final night image is implemented in a few seconds, computations being mostly local.     

Determination of the wear resistance of traditional ceramic materials by means of micro-abrasion technique

Micro-abrasion techniques enable the surface wear of materials to be studied with greater precision than provided by other methods. In addition to their reliability, micro-abrasion techniques allow the wear phenomenon of the top-most layers to be studied while assuring, in the case of thin coatings, that this is not influenced by the substrate.In the present study, micro-abrasion technique (cratering with a steel ball) was used to determine the wear resistance of traditional ceramic materials, as a complementary test to the methodologies on a macroscopic scale that are customarily used for this type of material. In order to adapt the test to these materials, the individual effect of each test condition on wear resistance was isolated, while keeping the other conditions constant. The following variables were studied: diameter and angular velocity of the ball, abrasive suspension feed rate and grain size, sample–ball contact angle and groove in the supporting drive shaft. The values established were validated by performance of the test on materials of a glassy nature.The micro-abrasion test is shown to be a useful method for studying wear performance of ceramic glazes.     

Start-up of an UASB reactor treating potato-starch wastewater using an alkalimetric follow-up procedure

Monitoring of volatile fatty acids (VFA) by gas chromatography or hydrogen with specific electrodes is used for the determination of instability in anaerobic reactors. However, such methods are not normally applied in full-scale reactors due to the need for expensive equipment. A two end-point alkalimetric method has been proposed in the literature for the follow-up and control of anaerobic digesters. This paper deals with results of the start-up and operation of a laboratory UASB (Upflow Anaerobic Sludge Blanket) reactor (5.61) treating potato-starch wastewater, where such an alkalimetric method was simultaneously used and compared with gas-chromatography VFA monitoring.     

Black liquor detoxification by laccase of Trametes versicolor pellets

Black liquors from a soda pulping mill were treated with the white‐rot fungus Trametes versicolor to detoxify and reduce colour, aromatic compounds and chemical oxygen demand (COD). The fungus was used in the form of pellets in aerated reactors (fluidized, stirred and air‐pulsed reactors). Reductions in colour and aromatic compounds of 70–80% and in COD of 60% were achieved. During the different experiments, laccase activity was detected but neither lignin peroxidase (LiP) nor manganese peroxidase activities were detected, although T versicolor is able to produce these enzymes. Experiments also showed a LiP activity inhibitory effect produced by lignin. From the results obtained, it can be concluded that there is a relationship between laccase production and toxicity reduction. This correlation responds to the equation Laccase production = 1.57 LN (toxicity reduction) ?16.40. Copyright © 2003 Society of Chemical Industry     

Analysis of digital images into energy-angular momentum modes

The measurement of continuous wave fields by a digital (pixellated) screen of sensors can be used to assess the quality of a beam by finding its formant modes. A generic continuous field F(x, y) sampled at an N × N Cartesian grid of point sensors on a plane yields a matrix of values F(q(x), q(y)), where (q(x), q(y)) are integer coordinates. When the approximate rotational symmetry of the input field is important, one may use the sampled Laguerre-Gauss functions, with radial and angular modes (n, m), to analyze them into their corresponding coefficients F(n, m) of energy and angular momentum (E-AM). The sampled E-AM modes span an N2-dimensional space, but are not orthogonal--except for parity. In this paper, we propose the properly orthonormal "Laguerre-Kravchuk" discrete functions Λ(n, m)(q(x), q(y)) as a convenient basis to analyze the sampled beams into their E-AM polar modes, and with them synthesize the input image exactly.     

Science, politics and image in Valencia: a review of urban discourse in the Spanish City

In the urban sphere, discourse is fundamental to the social and political construction of urban reality. The urban landscape is, in part, a result of those discourses. It is, as Richard Schein suggests, a discourse materialized. The production of these discourses throughout urban history both represented and constructed urban reality at any given time. For much of history, the written word was central to such discursive representations, literary formulations and even biological metaphors that sought to interpret the city both for local inhabitants and outsiders. Today, the photographic image has usurped the former dominance of the word. This article uses archival research to trace historical representations of Valencia, Spain, a European Mediterranean city with a strong medieval tradition. Beginning with a focus on the Fourteenth and Fifteenth Century, when Valencia was economic ‘head’ of the Kingdom of Aragon, this paper will follow how the city developed in concert with evolving intellectual and political representations of it. In doing so, I highlight the important and enduring role of the organic metaphor as a device which framed intellectual and political discourse, and ultimately planning and governing strategies, into urbanism of the Nineteenth and Twentieth Centuries (as reflected in the writings of Patrick Geddes). Throughout Valencia’s history, urban discourse has availed itself of biological and medical metaphors, even metaphors drawn from the field of physics, in order to construct a generally agreed-upon image of the urban society at particular historical moment. Analysing the role of such metaphors in urban discourse is fundamental to any full understanding of development in the Mediterranean city, historical or contemporary.     

Synthesis and structural characterisation of solid solutions Crx Ti1-2x-yVx+yO2at atmospheric pressure

Abstract

Solid solutions Cr_x Ti_1-2x-y V_x+yO₂ (0<x<0·15; 0·08<y<0·10) with rutile structure have been synthesised by firing mixtures of Cr₂O₃ , V₂O₅ , and TiO₂ (anatase) in air at 800–1200°C and characterised by X-ray diffraction and electron microscopy. An excess of vanadium content over the chromium content was investigated to include V ₄₊ in the solid solutions. A decrease in the c lattice parameter with increase in the degree of substitution x and a constancy with temperature in the rutile unit cell parameters were observed in the 900–1200°C range. The thermal stability of these rutile solid solutions and the colouration of glazes containing 5 wt-% samples indicate their potential for use as ceramic pigments.     

Infrastructures and tools for multiagent systems for the new generation of distributed systems

In order for multiagent systems to be included in real domains (media and Internet, logistics, e-commerce, and health care), infrastructures and tools for multiagent systems should provide efficiency, scalability, security, management, monitoring, and other features related to building real applications. Thus, infrastructures and tools that support multiagent systems are needed, especially those that promote the adoption of agent-based systems by designers and programmers in both academia and industry. This special issue is a selection of contributions whose preliminary versions were presented at the ITMAS 2010 workshop, which was held in conjunction with the International Conference on Autonomous Agents and Multi-agent Systems.     

Partial identities as a foundation for trust and reputation

This paper explores the relationships between the hard security concepts of identity and privacy on the one hand, and the soft security concepts of trust and reputation on the other hand. We specifically focus on two vulnerabilities that current trust and reputation systems have: the change of identity and multiple identities problems. As a result, we provide a privacy preserving solution to these vulnerabilities which integrates the explored relationships among identity, privacy, trust and reputation. We also provide a prototype of our solution to these vulnerabilities and an application scenario.