The Piracicaba River basin: isotope hydrology of a tropical river basin under anthropogenic stress

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1/1000-2/1000. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

Quantum Computation in a Ising Spin Chain Taking into Account Second Neighbor Couplings

We consider the realization of a quantum computer in a chain of nuclear spins coupled by an Ising interaction. Quantum algorithms can be performed with the help of appropriate radio-frequency pulses. In addition to the standard nearest-neighbor Ising coupling, we also allow for a second neighbor coupling. It is shown, how to apply the 2π k method in this more general setting, where the additional coupling eventually allows to save a few pulses. We illustrate our results with two numerical simulations: the Shor prime factorization of the number 4 and the teleportation of a qubit along a chain of 3 qubits. In both cases, the optimal Rabi frequency (to suppress non-resonant effects) depends primarily on the strength of the second neighbor interaction.     

Sintering of a nano-crystalline metastable alumina

The influence of the heating rate on phase transformation and microstructural evolution during sintering of a de-agglomerated nanocrystalline, transition alumina was investigated. A low heating rate treatment allowed to decrease the α-Al₂O₃ crystallization temperature as well as to displace densification at lower temperatures, also implying a refinement of the fired microstructures. In addition, the set-up of sintering cycles in which the heating rate changed in the range 0.5–20°C min⁻¹ starting from intermediate, selected temperatures resulted in a further retention of a very fine and homogeneous grain size in final materials.     

Elementary constructive theory of Henselian local rings

We give an elementary theory of Henselian local rings and construct the Henselisation of a local ring. All our theorems have an algorithmic content. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characteristic Features of Magnetization Reversal of Exchange Coupled Tb–Co/FeNi Film Structures in a Temperature Range Including the Compensation Point of the Ferrimagnetic Layer

Physics of the Solid State - The results of the study of the magnetic properties of exchange coupled Tb–Co/FeNi film structures obtained by magnetron sputtering in a wide range of...     

Redox and electrocatalytic properties of mimochrome VI, a synthetic heme peptide adsorbed on gold

Mimochrome VI (MC-VI) is a synthetic heme peptide containing a helix-heme-helix sandwich motif designed to reproduce the catalytic activity of heme oxidases. The thermodynamics of Fe(III) to Fe(II) reduction and the kinetics of the electron-transfer process for MC-VI immobilized through hydrophobic interactions on a gold electrode coated with a nonpolar SAM of decane-1-thiol have been determined through cyclic voltammetry. Immobilization slightly affects the reduction potential of MC-VI, which under these conditions electrocatalytically turns over molecular oxygen. This work sets the premise for the exploitation of totally synthetic mimochrome-modified electrode surfaces for clinical and pharmaceutical biosensing.     

Palladium-catalyzed asymmetric benzylation of 3-aryl oxindoles

Herein we report palladium-catalyzed asymmetric benzylic alkylation with 3-aryl oxindoles as prochiral nucleophiles. Proceeding analogously to asymmetric allylic alkylation, asymmetric benzylation occurs in high yield and enantioselectivity for a variety of unprotected 3-aryl oxindoles and benzylic methyl carbonates using chiral bisphosphine ligands. This methodology represents a novel asymmetric carbon-carbon bond formation between a benzyl group and a prochiral nucleophile to generate a quaternary center.     

Screening and Production Study of Microbial Xylanase Producers from Brazilian Cerrado

Hemicelluloses are polysaccharides of low molecular weight containing 100 to 200 glycosidic residues. In plants, the xylans or the hemicelluloses are situated between the lignin and the collection of cellulose fibers underneath. The xylan is the most common hemicellulosic polysaccharide in cell walls of land plants, comprising a backbone of xylose residues linked by β-1,4-glycosidic bonds. So, xylanolytic enzymes from microorganism have attracted a great deal of attention in the last decade, particularly because of their biotechnological characteristics in various industrial processes, related to food, feed, ethanol, pulp, and paper industries. A microbial screening of xylanase producer was carried out in Brazilian Cerrado area in Selviria city, Mato Grosso do Sul State, Brazil. About 50 bacterial strains and 15 fungal strains were isolated from soil sample at 35 °C. Between these isolated microorganisms, a bacterium Lysinibacillus sp. and a fungus Neosartorya spinosa as good xylanase producers were identified. Based on identification processes, Lysinibacillus sp. is a new species and the xylanase production by this bacterial genus was not reported yet. Similarly, it has not reported about xylanase production from N. spinosa. The bacterial strain P5B1 identified as Lysinibacillus sp. was cultivated on submerged fermentation using as substrate xylan, wheat bran, corn straw, corncob, and sugar cane bagasse. Corn straw and wheat bran show a good xylanase activity after 72 h of fermentation. A fungus identified as N. spinosa (strain P2D16) was cultivated on solid-state fermentation using as substrate source wheat bran, wheat bran plus sawdust, corn straw, corncob, cassava bran, and sugar cane bagasse. Wheat bran and corncobs show the better xylanase production after 72 h of fermentation. Both crude xylanases were characterized and a bacterial xylanase shows optimum pH for enzyme activity at 6.0, whereas a fungal xylanase has optimum pH at 5.0–5.5. They were stable in the pH range 5.0–10.0 and 5.5–8.5 for bacterial and fungal xylanase, respectively. The optimum temperatures were 55C and 60 °C for bacterial and fungal xylanase, respectively, and they were thermally stable up to 50 °C.     

Passivation of the calcite surface with malonate ion

Samples of polycrystalline calcite were impregnated with solutions of malonic acid of three concentrations (5 x 10(-2), 5 x 10(-3) , and 5 x 10(-4) M) and different pH values (6.00, 7.00, and 8.00). The impregnation was carried out at room temperature to evaluate the adsorption of malonate ion in the calcite surface to optimize the conditions for possible application on limestone and marble in cultural heritage materials. The affinity of the malonate ion was determined through the potentiometric measurement of the surface charge and the corresponding adsorbed amounts by titration, Raman spectroscopy, and small-angle X-ray scattering (SAXS). The results indicate effective adsorption of the malonate ion on the surface at a pH value close to the point of zero charge (pHpzc approximately 8.20) and changes in some surface morphological properties such as the pore shape and the pore size distribution. The presence of a malonate adsorptive layer on calcite generates an interface interaction potential that may influence the reaction and transport mechanisms within the medium.