Physicothermal properties of aqueous sodium chloride solutions

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

Porosity and sealing ability of root fillings with gutta-percha and BioRoot RCS or AH Plus sealers. Evaluation by three ex vivo methods

To investigate the ability of BioRoot RCS, a tricalcium silicate-based root canal sealer and AH Plus to effectively fill the root canals of contralateral teeth using three evaluation methods, and to investigate also the correlation between the methods. The prepared root canals of ten pairs of contralateral mandibular premolar teeth were filled with gutta-percha and sealer using lateral compaction. The percentage of voids within the root canal was assessed by micro-computed tomography, whilst sealing ability was investigated by fluid transport and leakage of fluorescent microspheres. The interaction of sealer with dentine, and sealer penetration were assessed by confocal microscopy. The void volume, fluid flow, microsphere leakage and sealer interaction with dentine for both materials were compared. Nonparametric (Mann-Whitney) tests were used to compare the % void and fluid transport of the two sealers. Spearman correlation was used to assess the pairwise relationships between the techniques. The level of significance was set to 0.05. BioRoot RCS exhibited significantly more percentage of voids than AH Plus. There was no difference in fluid flow and microsphere penetration. BioRoot RCS exhibited a different pattern of sealer penetration and interaction with the dentine walls compared to AH Plus. For both materials, the pairwise correlations between the three techniques were close to zero, indicating weak relationships. MicroCT analysis revealed a higher void volume for BioRoot RCS. The other techniques did not show a difference between the sealing ability of the sealers. The correlation between the three ex vivo methods of assessment was weak demonstrating their complementarity rather than their concordance.

Estudos de técnicas de reinicialização em métodos level-set e suas aplicações em escoamentos bifásicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da lubrirrefrigeração na qualidade superficial de metais retificados

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

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Numerical simulation of drop impact and jet buckling problems using the eXtended Pom-Pom model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphological features of the epididymal epithelium of gerbil, Meriones unguiculatus

Principal cells of the ducts epididymis of the Mongolian gerbil showed ultrastructural characteristics of lining epithelium cells close related to processes of protein secretion, and transcytosis occurring between adjacent principal cells which were mainly verified in the initial segment. Principal cells also presented roles of fluid phase and adsorptive endocytoses, as well as autophagic and heterophagic lysosomal activities mainly observed in the caput epididymis. Columnar (principal) cells of the corpus epididymidis presented great number of variable vesicles and vacuoles distributed in all the cytoplasmic levels occurring a progressive coalescence pattern among them, which help to guarantee formation of cytoplasmic channels for fluid phase transport between the tubular lumen and epididymal interstitium. Clear cells were presented in the initial segment and predominately in the cauda epididymis epithelium of the gerbil and showed marked ultrastructural characteristics of endocytosis activities occurrence, perhaps directly related to the turnover of fluid phase of spermatozoa stored into the lumen of the distal tail. Other epididymal epithelium cells were verified and described such as basal, halo, apical and dark cells, but they did not presented special ultrastructural features. (c) 2007 Elsevier Ltd. All rights reserved.

Efficiency of extrinsic and intrinsic charge-carrier photogeneration processes obtained from the steady-state photocurrent action spectra of poly(p-phenylene vinylene) derivatives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Alguns estudos de fluxo de fluido utilizando software gráfico

Analisamos alguns modelos de fluxo de fluido utilizando o software gráfico F(C): Funções Complexas. Descrevemos as equações que expressam o potencial complexo, bem como a velocidade complexa para cada modelo. Os modelos estudados são fluxo uniforme, com fonte, com sumidouro, composto, circular e com obstáculo. Apresentamos o conceito de Domínio de Cores e o mecanismo de leitura dos gráficos. Cada modelo é apresentado de forma exemplificada, incluindo representações geométricas das curvas de fluxo e equipotenciais, bem como os gráficos do potencial complexo e velocidade complexa.

Exponential decay for Kirchhoff wave equation with nonlocal condition in a noncylindrical domain

In this paper, we prove the exponential decay as time goes to infinity of regular solutions of the problem for the Kirchhoff wave equation with nonlocal condition and weak dampingu(tt) - M (\\delU\\(2)(2)) Deltau + integral(0)(t) g(t - s)Deltau(.,s) ds + alphau(t) = 0, in (Q) over cap,where (Q) over cap is a noncylindrical domain of Rn+1 (n greater than or equal to 1) with the lateral boundary (&USigma;) over cap and alpha is a positive constant. (C) 2004 Elsevier Ltd. All rights reserved.

Electric characterization of a hybrid composite based on POMA/P(VDF- TrFE)/Zn2SiO4 : Mn using impedance spectroscopy

Understanding the microscopic origin of the dielectric properties of disordered materials has been a challenge for many years, especially in the case of samples with more than one phase. For polar dielectrics, for instance, the Lepienski approach has indicated that the random free energy barrier model of Dyre must be extended. Here we analyse the dielectric properties of a polymer blend made up with the semiconducting poly(o-methoxyaniline) and poly( vinylidene fluoride-trifluorethylene) POMA/P(VDF-TrFE), and of a hybrid composite of POMA/P(VDF-TrFE)/Zn2SiO4:Mn. For the blend, the Lepienski model, which takes into account the rotation or stretching of electric dipoles, provided excellent fitting to the ac impedance data. Because two phases had to be assumed for the hybrid composite, we had to extend the Lepienski model to fit the data, by incorporating a second transport mechanism. The two mechanisms were associated with the electronic transport in the polymeric matrix and with transport at the interfaces between Zn2SiO4: Mn microparticles and the polymeric matrix, with the relative importance of the interfacial component increasing with the percentage of Zn2SiO4: Mn in the composite. The analysis of impedance data at various temperatures led to a prediction of the theoretical model of a change in morphology at 190 +/- 40 K, and this was confirmed experimentally with a differential scanning calorimetry experiment.

Sintering of ultrafine undoped SnO2 powder

The sintering process of nanometric undoped SnO2 powder was studied. No macroscopic shrinkage was observed during the sintening process. Grain growth kinetics investigation showed that surface diffusion is the dominant mechanism in the temperature range 500-1300 degreesC. For temperatures higher than 1300 degreesC, high weight loss was measured, suggesting evaporation-condensation as the dominant mass-transport mechanism. Thermogravimetric analysis (TG) and mass spectroscopy studies showed that the surface contamination of the SnO2 particles by chemical species like H2O, OH- and CO2, has a strong influence on the role of mass transport controlled by surface diffusion. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Electrical characterization of SnO2 : Sb ultrathin films obtained by controlled thickness deposition

A representative study is reported on the electrical properties of SnO2: Sb. ultrathin films (thickness of 40-70 nm) produced by a deposition method based on aqueous colloidal suspensions of 3-5 nm crystalline oxides. The results revealed the films' electrical behavior in a range of 10-300 K, showing a strong dependence on dopant incorporation, with minimum resistivity values in 10 mol % of Sb content. All the samples displayed semiconductor behavior, but the transport mechanism showed a strong dependence on thickness, making it difficult to fit it to well-known models. In thicker films, the mechanism proved to be an intermediary system, with thermally activated and hopping features. Electron hopping was estimated in the range of 0.4-1.9 nm, i.e., in the same order as the particle size. (c) 2007 American Institute of Physics.

Electrical properties of YSZ/NiO composites prepared by a liquid mixture technique

We report the preparation and characterization of yttria-stabilized zirconia/nickel oxide composites (YSZ/NiO). This composite is the precursor material of the cermet YSZ/Ni, which is used as solid oxide fuel cell anode material. The performance of the anode is strongly dependent on the microstructural properties of the cermet. Therefore, the control of the microstructure of the YSZ/NiO composite is a key step for the fabrication of high-performance anodes. In this study, the composites were prepared by a modified liquid mixture technique. Scanning electron microscopy analysis evidenced the good dispersion of the phases and that NiO nanoparticles are spread over the YSZ surface. Sintered pellets were studied by X-ray diffraction and impedance spectroscopy. The main results show that the composite is comprised of a well-dispersed mixture of the two phases. The electrical conductivity data show that there is a strong dependence of the transport mechanism on the relative composition of phases. (c) 2005 Elsevier Ltd. All rights reserved.

The minimum quantity of lubricant (MQL) technique in the surface grinding of steel

This research aimed to analyze the viability of the minimum quantity of lubricant (MQL) technique towards different methods of lubri-refrigeration in surface grinding of steel, considering process quality, wheel life and the viability of using cutting fluids The proposal methods were the conventional (abundant fluid flow), the minimum quantity lubrication (MQL) and the optimized method with Webster nozzle (rounded) This analysis was carried out in equal machining conditions, through the assessment of variables such as grinding force, surface roughness, G ratio (volume of removed material/volume of wheel wear), and microhardness The results showed the possibility of improvement of the grinding process Besides, there is the opportunity for production of high quality workpieces with lower costs The MQL technique showed efficiency in machining with lower depths of cut The optimized method with Webster nozzle applies the fluid in a rational way, without considerable waste Hence, the results show that industry can rationalize and optimize the application of cutting fluids, avoiding inappropriate disposal, inadequate use and consequently environment pollution