Investigation of Binding‐Site Homology between Mushroom and Bacterial Tyrosinases by Using Aurones as Effectors

Tyrosinase is a copper‐containing enzyme found in plants and bacteria, as well as in humans, where it is involved in the biosynthesis of melanin‐type pigments. Tyrosinase inhibitors have attracted remarkable research interest as whitening agents in cosmetology, antibrowning agents in food chemistry, and as therapeutics. In this context, commercially available tyrosinase from mushroom (TyM) is frequently used for the identification of inhibitors. This and bacterial tyrosinase (TyB) have been the subjects of intense biochemical and structural studies, including X‐ray diffraction analysis, and this has led to the identification of structural homology and divergence among enzymes from different sources. To better understand the behavior of potential inhibitors of TyM and TyB, we selected the aurone family—previously identified as potential inhibitors of melanin biosynthesis in human melanocytes. In this study, a series of 24 aurones with different hydroxylation patterns at the A‐ and B‐rings were evaluated on TyM and TyB. The results show that, depending on the hydroxylation pattern of A‐ and B‐rings, aurones can behave as inhibitors, substrates, and activators of both enzymes. Computational analysis was performed to identify residues surrounding the aurones in the active sites of both enzymes and to rationalize the interactions. Our results highlight similarities and divergence in the behavior of TyM and TyB toward the same set of molecules.     

Housing finance for lower income urban households in Zimbabwe

Housing finance systems in developing countries have been the subject of considerable international agency research and lending attention in recent years. The lack of availability of finance for public sector housing programmes and for the purchase of construction of housing by all income groups in urban areas is typically a major constraint on the ability of supply to meet demand. However, national efforts have often not dealt systematically with the housing finance system as a whole. The housing finance system in Zimbabwe is described and critically analysed in this paper, paying particular attention to the provision of funds for local authority housing programmes for low income residents, the place of housing finance institutions in the national finance system, the ability of the building societies to attract savings, and their lending programmes. The results of government measures to transfer responsibility for lending to low‐income households from local authorities to the building societies since the mid‐1980s are evaluated. It is concluded that Zimbabwe has an unusually well‐developed financial sector and housing finance system for a recently independent developing country. Although this evolved to meet the needs of the settler population, the extension of its activities into lending for low‐income aided self‐help housing was successful, within limits. However, events of the early 1990s demonstrate the vulnerability of such a system to the changes accompanying liberalisation. Suggestions are made for further possible reforms and the importance of monitoring the effects of economic liberalisation on the system and its beneficiaries stressed.     

An Optical System for Body Imaging from a Distance Using Near-TeraHertz Frequencies

We present the outline of the optical design of a TeraHertz (THz) imager for the detection of shrapnel-loaded improvised explosive devices (IED) devices at “stand-off” distances of 14–26 meters. The system will use 4 antenna-coupled TES detector arrays of 16 by 16 pixels cooled in a cryogen-free system with microwave readout to see beneath clothing at non-lethal detonation distances. A spatial resolution of ∼10 mm and close to video frame rates is anticipated.      

High voltage nickel manganese spinel oxides for Li-ion batteries

High voltage spinel oxides with composition LiMn_2 − xM_xO₄ (M, a transition metal element) have remarkable properties such as high potential, high energy density and high rate capability. We believe that these positive electrode materials could replace the widespread commercial layered nickel cobalt oxides in some applications. The present assessment highlights electrochemical performance of optimized LiNi_0.5Mn_1.5O₄ and substituted counterparts, all having a spinel structure (cubic close-packed oxygen array) similar to the relative LiMn₂O₄. To fully emphasize the benefit from high potential spinel oxides, tests have been performed versus lithium metal, Li₄Ti₅O₁₂ and graphite, using various electrode loadings (0.3-4.5 mAh cm⁻²) and cycling rates (from C/20 to 60C rate). Steady capacity retention (130-140 mAh g⁻¹ for nearly 500 cycles) and flat voltage (4.7 V vs. Li⁺/Li) have been obtained at C/5 rate at room temperature. Effect of cycling at high temperature has been shown to be less critical than for LiMn₂O₄. High voltage spinel oxides still sustain 100 mAh g⁻¹ and over after 400 cycles at 55 °C at 1C rate. Rate capability is also excellent, with only 4% loss of capacity when comparing C/8 and 8C rates (thin electrodes).     

Influence of farming conditions on colour and texture of European catfish (Silurus glanis) flesh

The colour of raw fillets and the texture of cooked fillets of European catfish (Silurus glanis) were studied. The catfish fillets resulted from two types of farming conditions used in France. Sensory and instrumental analyses were performed on the fillets. Two farming parameters were found to affect the colour and texture of European catfish fillets: water temperature and farming time. The shorter the farming time was, the lighter the fillets were, while a higher water temperature produced yellower and greener fillets. A higher water temperature and a longer farming time produced softer cooked fillets, while the higher the water temperature was, the less juicy the cooked fillets were. A good correlation and complementarity were observed between sensory and instrumental analyses of the colour and texture of European catfish fillets. Copyright © 2007 Society of Chemical Industry     

Characterization of bread breakdown during mastication by image texture analysis

The methods currently used to characterise food breakdown during mastication are not easily applicable to cohesive and heterogeneous products such as white bread (baguettes). During this study, we investigated the applicability of image texture analysis to characterising the kinetics of bread bolus formation during chewing. Food boluses were collected from five subjects chewing four different breads after 10, 20 and 30 chewing cycles or at swallowing. Images were acquired and analysed using the Grey level co-occurrence matrix (GLCM) method. Food boluses were successfully discriminated: 60–73% of the images were correctly classified into their respective chewing cycles. Incorrect classifications arose from overlapping between subsequent cycles. Among the texture features the contrast was identified as being the best marker of food degradation. Different kinetics of bolus formation were observed between breads. This method revealed specific patterns of food degradation between subjects, which could be explained by their mastication behaviour and chewing efficiency.     

Management of Alluvial Aquifers in Two Southern African Ephemeral Rivers: Implications for IWRM

This paper summarises innovative research into the assessment of long-term groundwater recharge from flood events in dryland environments of the Kuiseb (Namibia) and the Buffels (South Africa) rivers. The integrated water resource management (IWRM) policies and institutions affecting the exploitation of groundwater resources in each of these developing countries are compared. The relatively large alluvial aquifer of the Kuiseb River (～240 Mm³) is recharged from irregular floods originating in the upper catchment. Reported abstraction of 4.6 Mm³ per year is primarily consumed in the town of Walvis Bay, although the groundwater decay (pumping and natural losses along the period 1983–2005) was estimated in 14.8 Mm³ per year. Recharge is variable, occurring in 11 out of 13 years in the middle Kuiseb River, but only in 11 out of 28 years in the middle-lower reaches. In contrast, the Buffels River has relatively minor alluvial aquifers (～11 Mm³) and recharge sources derive from both lateral subsurface flow and floodwater infiltration, the latter limited to a recharge maximum of 1.3 Mm³ during floods occurring once every four years. Current abstractions to supply the adjacent rural population and a few small-scale, irrigated commercial farms are 0.15 Mm³ yr^???1, well within the long-term sustainable yield estimated to be 0.7 Mm³ yr^???1. Since independence in 1990, Namibia’s water resource management approach has focussed on ephemeral river basin management of which the Kuiseb Basin Management Committee (KBMC) is a model. Here, some water points are managed independently by rural communities through committees while the national bulk water supplier provides for Walvis Bay Municipality from the lower aquifers. This provides a sense of local ownership through local participation between government, NGOs and CBOs (community-based organisations) in the planning and implementation of IWRM. Despite the potential for water resource development in the lower Buffels River, the scope for implementing IWRM is limited not only by the small aquifer size, but also because basin management in South Africa is considered only in the context of perennial rivers. Since 2001, water service delivery in the Buffels River catchment has become the responsibility of two newly created local municipalities. As municipal government gains experience, skills and capacity, its ability to respond to local needs related to water service delivery will be accomplished through local participation in the design and implementation of annual ‘integrated development plans’. These two case studies demonstrate that a variety of IWRM strategies in the drylands of developing countries are appropriate depending on scales of governance, evolving policy frameworks, scales of need and limitations inherent in the hydrological processes of groundwater resources.     

High‐Energy Al/CuO Nanocomposites Obtained by DNA‐Directed Assembly

Over the next few years, it is expected that new, energetic, multifunctional materials will be engineered. There is a need for new methods to assemble such materials from manufactured nanopowders. In this article, we demonstrate a DNA‐directed assembly procedure to produce highly energetic nanocomposites by assembling Al and CuO nanoparticles into micrometer‐sized particles of an Al/CuO nanocomposite, which has exquisite energetic performance in comparison with its physically mixed Al/CuO counterparts. Using 80 nm Al nanoparticles, the heat of reaction and the onset temperature are 1.8 kJ g^?1 and 410 °C, respectively. This experimental achievement relies on the development of simple and reliable protocols to disperse and sort metallic and metal oxide nanopowders in aqueous solution and the establishment of specific DNA surface‐modification processes for Al and CuO nanoparticles. Overall, our work, which shows that DNA can be used as a structural material to assemble Al/Al, CuO/CuO and Al/CuO composite materials, opens a route for molecular engineering of the material on the nanoscale.     

On the construction of topology-preserving deformation fields

In this paper, we investigate a new method to enforce topology preservation on deformation fields. The method is composed of two steps. The first one consists in correcting the gradient vector fields of the deformation at the discrete level, in order to fulfill a set of conditions ensuring topology preservation in the continuous domain after bilinear interpolation. This part, although related to prior works by Kara?ali and Davatzikos, proposes a new approach based on interval analysis. The second one aims to reconstruct the deformation, given its full set of discrete gradient vectors. The problem is phrased as a functional minimization problem on the convex subset K of the Hilbert space V. The existence and uniqueness of the solution of the problem are established, and the use of Lagrange's multipliers allows to obtain the variational formulation of the problem on the Hilbert space V . Experimental results demonstrate the efficiency of the method.