The influence of seasonalness on the structural characteristics of aquatic humic substances extracted from Negro River (Amazon state) waters: Interactions with Hg(II)

In this work, humic substances were extracted from water samples collected monthly from the Negro River basin in the Amazon state (Brazil) to study their properties in the Amazonian environment and interactions with the mercury ion considering the influence of seasonalness in this formation. The C/H, C/N and C/O atomic ratio parameters, functional groups, concentration of semiquinone-type free radicals, pH, pluviometric and fluviometric indices, and mercury concentrations were interpreted using hierarchical cluster analysis (HCA) and principal component analysis (PCA). The statistical analyses showed that when the pluviometric index was greater and the fluviometric index was smaller, the degree of humification of aquatic substances was greater. The following decreasing order of the degree of humification of the AHS collected monthly was established: Nov/02 to Feb/03 > Mar/02 to May/02 > Jun/02 to Oct/02. The greatest concentrations of mercury were detected in more humidified samples. These results suggest that due to inter and/or intra-molecular rearrangements, the degree of humification of aquatic humic substances is related to its affinity for Hg(II) ions. ©2007 Sociedade Brasileira de Química.

Multiple particle and cluster emissions from Zr following intermediate energies photo absorption

A new approach based on a N-a cluster photoabsorption model is proposed for the understanding of the puzzling steady increase behavior of the 90Zr (e, α) yield measured at the National Bureau of Standards (NBS) within the Giant Dipole Resonance and quasideuteron energy range. The calculation takes into account the pre-equilibrium emissions of protons, neutrons and alpha particles in the framework of an extended version of the multicollisional intranuclear cascade model (MCMC). Another Monte Carlo based algorithm describes the statistical decay of the compound nucleus in terms of the competition between particle evaporation (p, n, d, α, 3He and t) and nuclear fission. The results reproduce quite successfully the 90Zr (e,α) yield, suggesting that emissions of a particles are essential for the interpretation of the exotic increase of the cross sections.

Evaluation of neighborhood impacts caused by companies of the high-tech industrial cluster of São Carlos, SP, Brazil

The purpose of this study was to develop a methodology for evaluating neighborhood impacts using a Geographic Information System (GIS) and to apply the procedures to the companies of the High-Technology Industrial Cluster of São Carlos. To this end, an evaluation was made of the neighborhood impacts on the physical environment, urban components, quality of life, and urban infrastructure using impact matrices, and the impacts were assigned scores according to type, order, magnitude and duration. Fifty one companies were examined based on data provided by the companies themselves and on field surveys. The impacts are represented spatially in proportional symbols maps, based on the spatial distribution of the companies in the urban area of the city of São Carlos and the areas of influence of each company. The application of the proposed methodology served to validate it and indicated that the neighborhood impacts caused by the companies of this study are related to each company's type of activity, its size, and its occupation of the area. © 2008 Journal of Urban and Environmental Engineering (JUEE). All rights reserved.

Influence of cerium (IV) ions on the inorganic and organic phase for preparation of a siloxane-PMMA based film on tin plate substrate

Tinplate is one of the most widely used food canning materials, however, there are significant problems related to the use of tinplate cans, such as alterations in sensory features affecting food quality and corrosion phenomena of the canning material. To avoid corrosion problems different methods have been used for the passivation of tinplate such protective lacquers or different kinds of corrosion inhibitors (chromate and dichromate). However, chromates and dichromates are extremely harmful to the environment and can cause carcinogenic tumors to humans. An option, protective coatings obtained by the sol-gel process, act as a physical barrier, which isolates the surface of metal protecting from the corrosive agents. The aim of this work is to study the influence of addition of cerium (IV) ions in the inorganic and organic part of sol-gel processing in the formation of hybrid coatings based on siloxane-PMMA on tin plate. The coatings were obtained by dip-coating technique and evaluated by open circuit and impedance measurements, linear polarization and polarization curves obtained in 3.5% NaCl solution. The results have clearly shown the improvement on the protective properties of the Ce 4+ modified film when added into the organic phase, which can be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. © 2009 by NACE International.

El cluster del salmón: ¿un caso de desarrollo incluyente?

Incluye bibliografía

¿Es posible un cluster en torno al bauxita en el Estado de Pará?

Incluye Bibliografía

Aglomeraciones pesqueras en América Latina: ventajas asociadas al enfoque de cluster

Incluye Bibliografía

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Optical and transport properties of rare-earth trivalent ions located at different sites in sol-gel SnO2

Photoluminescence and photo-excited conductivity data as well as structural analysis are presented for sol-gel SnO2 thin films doped with rare earth ions Eu3+ and Er3+, deposited by sol-gel-dip-coating technique. Photoluminescence spectra are obtained under excitation with various types of monochromatic light sources, such as Kr+, Ar+ and Nd:YAG lasers, besides a Xe lamp plus a selective monochromator with UV grating. The luminescence fine structure is rather different depending on the location of the rare-earth doping, at lattice symmetric sites or segregated at the asymmetric grain boundary layer sites. The decay of photo-excited conductivity also shows different trapping rate depending on the rare-earth concentration. For Er-doped films, above the saturation limit, the evaluated capture energy is higher than for films with concentration below the limit, in good agreement with the different behaviour obtained from luminescence data. For Eu-doped films, the difference in the capture energy is not so evident in these materials with nanoscocopic crystallites, even though the luminescence spectra are rather distinct. It seems that grain boundary scattering plays a major role in Eu-doped SnO2 films. Structural evaluation helps to interpret the electro-optical data. © 2010 IOP Publishing Ltd.

Evolución y complejidad en el desarrollo de encadenamientos productivos en México: los desafíos de la construcción del cluster aeroespacial en Querétaro

Incluye bibliografía

La formación de un cluster en torno al turismo de naturaleza sustentable en Bonito, Brasil

Incluye Bibliografía

Formación y desarrollo de un cluster globalizado: el caso de la industria del salmón en Chile

Incluye Bibliografía

¿A Chilean wine cluster? governance and upgrading in the phase of internationalization

Includes bibliography

Una estrategia de desarrollo basada en recursos naturales: análisis 'cluster' del complejo de cobre de la Southern Perú

Incluye Bibliografía

Thermal behaviour of succinic acid, sodium succinate and its compounds with some bivalent transitions metal ions in dynamic N 2 and CO 2 atmospheres

Thermal stability and thermal decomposition of succinic acid, sodium succinate and its compounds with Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA) in nitrogen and carbon dioxide atmospheres and TG-FTIR in nitrogen atmosphere. On heating, in both atmospheres the succinic acid melt and evaporate, while for the sodium succinate the thermal decomposition occurs with the formation of sodium carbonate. For the transition metal succinates the final residue up to 1180 °C in N 2 atmosphere was a mixture of metal and metal oxide in no simple stoichiometric relation, except for Zn compound, where the residue was a small quantity of carbonaceous residue. For the CO 2 atmosphere the final residue up to 980 °C was: MnO, Fe 3O 4, CoO, ZnO and mixtures of Ni, NiO and Cu, Cu 2O.