Stereoselective hydride transfer by aryl-alcohol oxidase, a member of the GMC superfamily

Primary alcohol oxidation by aryl‐alcohol oxidase (AAO), a flavoenzyme providing H₂O₂ to ligninolytic peroxidases, is produced by concerted proton and hydride transfers, as shown by substrate and solvent kinetic isotope effects (KIEs). Interestingly, when the reaction was investigated with synthesized (R)‐ and (S)‐α‐deuterated p‐methoxybenzyl alcohol, a primary KIE (≈6) was observed only for the R enantiomer, revealing that the hydride transfer is highly stereoselective. Docking of p‐methoxybenzyl alcohol at the buried crystal active site, together with QM/MM calculations, showed that this stereoselectivity is due to the position of the hydride‐ and proton‐receiving atoms (flavin N5 and His502 Nε, respectively) relative to the alcohol Cα‐substituents, and to the concerted nature of transfer (the pro‐S orientation corresponding to a 6 kcal mol^?1 penalty with respect to the pro‐R orientation). The role of His502 is supported by the lower activity (by three orders of magnitude) of the H502A variant. The above stereoselectivity was also observed, although activities were much lower, in AAO reactions with secondary aryl alcohols (over 98 % excess of the R enantiomer after treatment of racemic 1‐(p‐methoxyphenyl)ethanol, as shown by chiral HPLC) and especially with use of the F501A variant. This variant has an enlarged active site that allow better accommodation of the α‐substituents, resulting in higher stereoselectivity (S/R ratios) than is seen with AAO. High enantioselectivity in a member of the GMC oxidoreductase superfamily is reported for the first time, and shows the potential for engineering of AAO for deracemization purposes.     

Chlorate reduction capacity and characterisation of chlorate reducing bacteria communities in sediments of the rio Cruces wetland in southern Chile

This study investigated chlorate reduction kinetics in multiple samples of sediments from a longitudinal profile of a wetland located downstream of the effluent discharge of a cellulose plant, including characterisation of the bacterial communities involved. The sediments were exposed to different initial chlorate concentrations in microcosm tests, with and without the addition of acetate as an external electron donor, and in a matrix of natural water or a defined medium. At a high initial chlorate concentration of 100 mg/L, in the absence of an external electron source, the degradation curves presented first-order kinetics, influenced by electron donor availability. The first-order kinetic constant varied between 0.05 and 0.17 day⁻¹. Subsequently, when the initial chlorate concentration was reduced to 7 mg/L, a zero-order kinetic was obtained, with the kinetic constant presenting values between 1.1 and 1.3 mg/L-day. No correlation was observed between chlorate degradation kinetics and the location of the sampling points or the previous history of exposure to chlorate. Other factors evaluated, such as the availability of organic matter or the chlorate reducing bacteria count, also proved not to have any incidence on the results. The richness of chlorate reducing bacteria species in the different samples analysed were also similar, with the greatest similarity being found between cld genes in the samples from the upstream or downstream sampling points. Additionally, cld genes most similar to those present in PCRB like Dechlorospirillum sp., Alicycliphilus denitrificans, Dechloromonas agitata, Dechloromonas sp. LT1 and Ideonella dechloratans were detected. This study showed that the anaerobic sediments of the Cruces river wetland present a high potential for chlorate natural attenuation, regardless of the previous history of exposure to chlorate. This capacity is associated with the presence of a diverse community of chlorate reducing bacteria.     

A novel methodology to characterize tool-chip contact in metal cutting using partially restricted contact length tools

A novel methodology to map the friction and normal stress distribution on the rake face using Partially Restricted Contact Length Tools in orthogonal cutting tests is proposed. The influence of cutting speed, feed and coatings on tool-chip friction when machining AISI 1045 is analysed. The results demonstrate that the new methodology can replace the more difficult to use and less robust split-tool method. They confirm two clearly different contact zones: i) the sticking region, governed by the shear flow stress of the workpiece and ii) the sliding region, where the friction coefficient is higher than 1.     

Efficiency of urease and nitrification inhibitors in reducing ammonia volatilization from diverse nitrogen fertilizers applied to different soil types and wheat straw mulching

BACKGROUND: Some authors suggest that the absence of tillage in agricultural soils might have an influence on the efficiency of nitrogen applied in the soil surface. In this study we investigate the influence of no‐tillage and soil characteristics on the efficiency of a urease inhibitor (N‐(n‐butyl)thiophosphoric triamide, NBPT) and a nitrification inhibitor (diciandiamide, DCD) in decreasing ammonia volatilization from urea and ammonium nitrate (AN), respectively. RESULTS: The results indicate that ammonia volatilization in soils amended with urea was significantly higher than in those fertilized with AN. Likewise, the main soil factors affecting ammonia volatilization from urea are clay and sand soil contents. While clay impedes ammonia volatilization, sand favours it. The presence of organic residues on soil surface (no‐tillage) tends to increase ammonia volatilization from urea, although this fact depended on soil type. The presence of NBPT in urea fertilizer significantly reduced soil ammonia volatilization. This action of NBPT was negatively affected by acid soil pH and favoured by soil clay content. CONCLUSION: The presence of organic residues on soil surface amended with urea increased ammonia volatilization, and was particularly high in sandy compared with clay soils. Application of NBPT reduced ammonia volatilization although its efficiency is reduced in acid soils. Concerning AN fertilization, there were no differences in ammonia volatilization with or without DCD in no‐tillage soils. Copyright © 2011 Society of Chemical Industry     

An approach to hand biometrics in mobile devices

This paper focuses on hand biometrics applied to images acquired from a mobile device. The system offers the possibility of identifying individuals based on features extracted from hand pictures obtained with a low-quality camera embedded on a mobile device. Furthermore, the acquisitions have been carried out regardless illumination control, orientation, distance to camera, and similar aspects. In addition, the whole system has been tested with an owned database. Finally, the results obtained (6.0% ± 0.2) and the algorithm structure are both promising in relation to a posterior mobile implementation.     

Short communication: Identification of two polymorphisms in the goat lipoprotein lipase gene and their association with milk production traits

Lipoprotein lipase (LPL) is a glycoprotein that plays a central role in plasma triglyceride metabolism by hydrolyzing triglyceride-rich chylomicrons and very low density lipoproteins. The activity of milk LPL has been shown to differ among several goat breeds, suggesting the existence of a genetic polymorphism influencing the functional properties of this enzyme. We have characterized the complete coding sequence of the goat LPL gene in 18 individuals belonging to 3 breeds. The coding region of the goat LPL cDNA was 1,437 bp long and encoded a protein of 478 amino acids. Moreover, we have identified 2 single nucleotide polymorphisms (SNP) including a G50C missense mutation, which involved a Ser→Thr amino acid replacement at position 17 of the signal peptide, and a C2094T substitution in the 3′ untranslated region. A univariate mixed model was used to evaluate the association between LPL genotypes and milk production and composition in 130 Murciano-Granadina goats. The G50C SNP was suggestively associated with milk fat content and tended to affect the milk dry weight basis. The C2094T SNP was not associated with any of the measured traits.     

Robust speed estimation and control of an induction motor drive based on artificial neural networks

In this paper, a speed estimation and control scheme of an induction motor drive based on an indirect field‐oriented control is presented. On one hand, a rotor speed estimator based on an artificial neural network is proposed, and on the other hand, a control strategy based on the sliding‐mode controller type is proposed. The stability analysis of the presented control scheme under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. Finally, simulated results show that the presented controller with the proposed observer provides high‐performance dynamic characteristics and that this scheme is robust with respect to plant parameter variations and external load disturbances. Copyright © 2007 John Wiley & Sons, Ltd.     

Fungal Biofiltration of Toluene on Ceramic Rings

Fungal biofilters attain higher toluene elimination rates compared to bacterial systems. However, strong mycelia growth can cause clogging. In the present work, toluene biofiltration with the fungus Paecilomyces variotii CBS 115145 was tested with two rigid packing materials that allow high mycelia growth. The reactor had two 4.25?L sections, each packed with ceramic Raschig rings differing in water retention capacity and internal porosity. After optimizing nutrient solution delivery, an overall maximum elimination capacity of 245?g/m3/h was obtained. Higher elimination capacity (290?g/m3/h) was measured in the ceramic ring with lower water content, indicating the interest of such packing material for treating hydrophobic pollutants in fungal biofilters. Additional experiments with this support in a 2?L biofilter showed bacterial contamination, but the fungal activity was responsible for about 70% of the total removal. The support with less humidity showed greater aerial growth, which possibly improves removal efficiency by favoring the direct transfer of pollutants from the gas phase to the microorganism.     

An application of integer programming to playoff elimination in football championships

Football is the most followed and practiced sport in Brazil, with a major economic importance. Thousands of jobs depend directly on the activity of the football teams. The Brazilian national football championship is followed by millions of people, who attend the games in the stadiums, follow radio and TV transmissions, and check newspapers, radio, TV, and, more recently, the Internet in search of information about the performance and chances of their favorite teams. Teams which do not qualify for the playoffs lose a lot of money and are even forced to dismantle their structure. We comment and compare the complexity of playoff elimination in football and baseball championships. We present two integer‐programming models which are able to detect in advance when a team has already qualified for or been eliminated from the playoffs. Results from these models can be used not only to guide teams and fans, but are also very useful to identify and correct wrong statements made by the press and team administrators. The application and the use of both models in the context of the 2002 edition of the Brazilian national football championship are discussed.