Electrode biomaterials based on immobilized laccase. Application for enzymatic reduction of dioxygen

Three different methods of immobilization of the laccase enzyme have been studied by measuring the enzyme activity of the bioelectrode and its catalytic efficiency for dioxygen reduction in the presence of the 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) as a redox mediator. One approach has consisted in laccase entrapment in polypyrrole matrix electrogenerated on the electrode surface. The two other approaches have concerned the grafting of laccase on an original aminopolypyrrole film and the complexation of laccase with avidin and biotin reagents. The laccase activity and the catalytic current of dioxygen reduction have demonstrated the efficiency of covalent grafting to aminopolypyrrole film. The polymer thickness was a key parameter of the catalytic efficiency and stability of this type of biocathode.     

Changes in stable isotopes, lignin-derived phenols, and fossil pigments in sediments of Lake Biwa, Japan: implications for anthropogenic effects over the last 100 years

We measured stable nitrogen (N) and carbon (C) isotope ratios, lignin-derived phenols, and fossil pigments in sediments of known ages to elucidate the historical changes in the ecosystem status of Lake Biwa, Japan, over the last 100 years. Stable N isotope ratios and algal pigments in the sediments increased rapidly from the early 1960s to the 1980s, and then remained relatively constant, indicating that eutrophication occurred in the early 1960s but ceased in the 1980s. Stable C isotope ratios of the sediment increased from the 1960s, but decreased after the 1980s to the present. This decrease in stable C isotope ratios after the 1980s could not be explained by annual changes in either terrestrial input or algal production. However, when the C isotope ratios were corrected for the Suess effect, the shift to more negative isotopic value in atmospheric CO(2) by fossil fuel burning, the isotopic value showed a trend, which is consistent with the other biomarkers and the monitoring data. The trend was also mirrored by the relative abundance of lignin-derived phenols, a unique organic tracer of material that originated from terrestrial plants, which decreased in the early 1960s and recovered to some degree in the 1980s. We detected no notable difference in the composition of lignin phenols, suggesting that the terrestrial plant composition did not change markedly. However, we found that lignin accumulation rate increased around the 1980s. These results suggest that although eutrophication has stabilized since the 1980s, allochthonous organic matter input has changed in Lake Biwa over the past 25 years.     

Novel biocatalysts based on S-layer self-assembly of Geobacillus stearothermophilus NRS 2004/3a: a nanobiotechnological approach

The crystalline cell-surface (S) layer sgsE of Geobacillus stearothermophilus NRS 2004/3a represents a natural protein self-assembly system with nanometer-scale periodicity that is evaluated as a combined carrier/patterning element for the conception of novel types of biocatalyst aiming at the controllable display of biocatalytic epitopes, storage stability, and reuse. The glucose-1-phosphate thymidylyltransferase RmlA is used as a model enzyme and chimeric proteins are constructed by translational fusion of rmlA to the C-terminus of truncated forms of sgsE (rSgsE (131-903), rSgsE(331-903)) and used for the construction of three principal types of biocatalysts: soluble (monomeric), self-assembled in aqueous solution, and recrystallized on negatively charged liposomes. Enzyme activity of the biocatalysts reaches up to 100 % compared to sole RmlA cloned from the same bacterium. The S-layer portion of the biocatalysts confers significantly improved shelf life to the fused enzyme without loss of activity over more than three months, and also enables biocatalyst recycling. These nanopatterned composites may open up new functional concepts for biocatalytic applications in nanobiotechnology.     

Heat capacity and electrical conductivity of non-stoichiometric U4O9-y from 300 to 1200 K

The heat capacity and the electrical conductivity of non-stoichiometric U₄O_9-y with various compositions were measured simultaneously by direct heating pulse calorimetry from 300 to 1200 K. As well as the heat capacity anomaly due to the α-β transition around 350 K, two small heat capacity anomalies due to the β-γ transition were observed around 1000 and 1100 K, which are superimposed on a monotonie increase in the heat capacity above 800 K, presumably due to the onset of the γ-U₄O_9-y-UO_2+x transition. The change in the slope of the electrical conductivity curve as also observed at the phase transitions. The excess entropy due to the overall transition from α-U₄O₉to UO_2+x was evaluated to be 5.95 J K^-1mol^-1, which is in agreement with the value calculated on the assumption that the excess entropy consists of the contribution of the electronic disordering of U⁴⁺ and U⁵⁺ ions and that of the atomic disordering of oxygen atoms.     

Perceptions of unity and distinctiveness as determinants of attraction.

Reinforcement theories of attraction have difficulty in accommodating the findings that individuals met in a negative context are sometimes liked more than individuals met in a positive context and that the sequence of positive and negative affect can often influence attraction more than the proportion of positive to negative affect. To understand these effects, one may have to consider how an individual's organization of information within a context affects evaluations. Two experiments were conducted with 178 undergraduates in which the relationship between 2 strangers was manipulated. Results suggest that (1) generalization of affect occurred when the 2 strangers were perceived as a unit and (2) when the 2 strangers were perceived as distinct from one another, the valence of one was compared to that of the other, and a contrast effect emerged. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of agriculture on water quality of Lake Biwa tributaries, Japan

We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO(3), SO(4), NO(3), Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta(34)S values of SO(4) in the river water converged to 0+/-2 per thousand as the SO(4) concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO(3) concentration increased. In particular, both the delta(34)S values (0+/-2 per thousand) and the (87)Sr/(86)Sr ratios (0.7117+/-0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta(34)S values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable (87)Sr/(86)Sr in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO(3), owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO(3) and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries.     

A Nash equilibrium solution in an oligopoly market: The search for Nash equilibrium solutions with replicator equations derived from the gradient dynamics of a simplex algorithm

The present analysis applies continuous time replicator dynamics to the analysis of oligopoly markets. In the present paper, we discuss continuous game problems in which decision-making variables for each player are bounded on a simplex by equalities and non-negative constraints. Several types of problems are considered under conditions of normalized constraints and non-negative constraints. These problems can be classified into two types based on their constraints. For one type, the simplex constraint applies to the variables for each player independently, such as in a product allocation problem. For the other type, the simplex constraint applies to interference among all players, creating a market share problem. In the present paper, we consider a game problem under the constraints of allocation of product and market share simultaneously. We assume that a Nash equilibrium solution can be applied and derive the gradient system dynamics that attain the Nash equilibrium solution without violating the simplex constraints. Models assume that three or more firms exist in a market. Firms behave to maximize their profits, as defined by the difference between their sales and cost functions with conjectural variations. The effectiveness of the derived dynamics is demonstrated using simple data. The present approach facilitates understanding the process of attaining equilibrium in an oligopoly market.     

Chemical modification at and within nanopowders: Synthesis of core‐shell Al2O3@TiON nanopowders via nitriding nano‐(TiO2)0.43(Al2O3)0.57 powders in NH3

Here, we demonstrate the potential utility of using chemical modification to reorganize metastable nanoparticles into nanostructured nanoparticles without coincidentally inducing extensive necking/sintering. The motivation for this effort derives from the concept that chemical reduction in a single component in a mixed‐metal nanoparticle will create segregated islands of a second immiscible phase. Given the very high chemical energies inherent in nanoparticles, the formation of even smaller islands of a second phase can be anticipated to lead to extremely high interfacial energies that may drive these islands to diffuse to cores or surfaces to form core‐shell structures that minimize such interfacial energies. Thus, ammonolysis of (TiO₂)_0.43(Al₂O₃)_0.57 composition nanopowders where both elements are approximately uniformly mixed at atomic length scales, under selected conditions (1000°C) for various periods of time at constant NH₃ flow rates leads primarily to the reduction in the Ti species to form TiN or TiON which then appears to diffuse to the surface of the particles. The final products consist of Al₂O₃@TiON core‐shell nanopowders that remain mostly unaggregated pointing to a new mechanism for modifying nanopowder chemistries and physical properties.     

Stabilization of meat suspensions by organogelation: A rheological approach

The stabilization of suspensions is a relevant issue in several industrial applications and particularly in the food area. Water‐based systems are widely studied and they are commonly stabilized by the addition of hydrocolloids (such as polysaccharides or proteins) whereas for oil‐based products less information is available. In this paper, oil‐based meat suspensions are investigated, and the addition of organogelators is proposed as a potential solution to the stability problems currently observed in some practical applications. Investigated suspensions are obtained by grinding a meat phase with vegetable oil blends, thus yielding products typically used in the traditional southern Italian diet as spreadable spicy sauces or as oil‐based dressings for pizzas. The effects of proposed additives were investigated by destabilizing the modified suspensions (by centrifugation) and comparing their rheological characteristics and oil loss to those of the unmodified systems (i.e., without addition of stabilizers). It was observed that both additives exert a stabilizing action, even if one of them (monoglycerides of fatty acids) is more effective than the other, even at a very low concentration. The adopted rheological approach has proved very useful to determine the type and amount of the proper organogelator to be used as an oil suspension stabilizer.