ONIOM study of dissociated hydrogen and water on ZnO surface

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Water quality monitoring by nanostructured films in a sensing unit system

Presented here is a study about the capability of a sensing unit to detect changes in river water quality. In order to determine its accuracy, water quality was monitored at 11 points along the Veado River in Presidente Prudente, Brazil. To have a basis for comparison, a water quality index (WQI) was developed following methods previously applied in different watersheds. Results showed an accurate relationship between WQI and electric impedance readings detected by the sensing unit. Principal components analysis (PCA) was used to derive results in a form that can be correlated with WQI calculated for each sample point, which showed the potential application of this device.

Potential and costs for the production of electrolytic hydrogen in alcohol and sugar cane plants in the central and south regions of Brazil

This project verified the potential for the production of hydrogen via water electrolysis by using the exceeding electrical energy resultant from alcohol and sugar plants that use sugar cane bagasse as fuel. The studies were carried out in cogeneration plants authorized by the Electrical Energy National Agency (ANEEL). The processing history of sugar cane considered was based on the 2006/2007 harvests. The total bagasse produced, electrical energy generated and exceeding electrical energy in a year were calculated. It was obtained an average energy consumption value of 5.2 kWh Nm(-3) and the hydrogen production costs regarding the amount of sugar cane processed that ranged from US$ 0.50 to US$ 0.75 Nm(-3). The results pointed that the costs for the production of hydrogen via the bagasse exceeding energy are close to the production costs that use other sources of energy. As the energy generated from the bagasse is a renewable one, this alternative for the production of hydrogen is economical and environmentally viable. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Desinfecção da água utilizando aquecimento solar

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Determinação da eficiência de um coletor solar plano com aletas de vidro

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Análise numérica da convecção natural em dispositivos solar integrados coletor-tanque

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Utilização de procedimentos multivariados no consumo de água e energia elétrica em habitações sociais com sistema de aquecimento solar

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Análise numérica de uma geometria de coletor solar para sistemas de aquecimento de água

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dye-sensitized solar cell architecture based on indium-tin oxide nanowires coated with titanium dioxide

A new architecture for dye-sensitized solar cells is employed, based on a nanostructured transparent conducting oxide protruding from the substrate, covered with a separate active oxide layer. The objective is to decrease electron-hole recombination. The concept was tested by growing branched indium-tin oxide nanowires on glass using pulsed laser deposition followed by deposition of a sputtered titanium dioxide layer covering the wires. The separation of charge generation and charge transport functions opens many possibilities for dye-sensitized solar cell optimization. (c) 2007 Acta Materialia. Inc. Published by Elsevier Ltd. All rights reserved.

Study of water and dimethylformamide interaction by computer simulation

Monte Carlo simulations of water-dimethylformamide (DMF) mixtures were performed in the isothermal and isobaric ensemble at 298.15 K and 1 atm. The intermolecular interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term. The TIP4P model was used for simulating water molecules, and a six-site model previously optimised by us was used to represent DMF. The potential energy for the water-DMF interaction was obtained via standard geometric combining rules using the original potential parameters for the pure liquids. The radial distribution functions calculated for water-DMF mixtures show well characterised hydrogen bonds between the oxygen site of DMF and hydrogen of water. A structureless correlation curve was observed for the interaction between the hydrogen site of the carbonyl group and the oxygen site of water. Hydration effects on the stabilisation of the DMF molecule in aqueous solution have been investigated using statistical perturbation theory. The results show that energetic changes involved in the hydration process are not strong enough to stabilise another configuration of DMF than the planar one.

Water distribution in dentin matrices: Bound vs. unbound water

Objective. This work measured the amount of bound versus unbound water in completely-demineralized dentin.Methods. Dentin beams prepared from extracted human teeth were completely demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 g H2O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 g H2O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 g H2O/g dry mass (Drierite).Results. Exposure of the first layer of bound water to 0% RH for 5 min produced a -0.3% loss of bound water; in the second layer of bound water it caused a -3.3% loss of bound water; in the third layer it caused a -6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a -4 and -7% loss of bound water in the second layer, respectively; and a -17 and -23% loss of bound water in the third layer. Bound water represented 21-25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 and 35% of unbound water, respectively.Signcance. Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75 and 79% of total matrix water, the more such water can be removed, the more resin can be infiltrated. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Trichomes related to an unusual method of water retention and protection of the stem apex in an arid zone perennial species

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Penetração de peróxido de hidrogênio 38% no interior da câmara pulpar de dentes bovinos e humanos com ou sem restauração submetidos ao clareamento externo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Irrigação deficitária em videira de vinho cv. Syrah durante o período chuvoso no semiárido

Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA