Alumina developed by pre-gelling starch consolidation (PSC)

In this paper, pre-gelling starch was used to consolidate alumina-dense ceramic suspensions. The colloidal processing of the ceramic was prepared with alumina and commercial potato starch, and slips were prepared with 55 vol% of solids and 0.5 wt.% of starch. This small amount of starch was possible because of a previous pre-gelling starch treatment, resulting in more homogeneous suspensions and particles smaller than starch granules. Additionally, Sucrose was also used as a dispersion aid. After sintering, the samples were analysed according to their mechanical properties. These processes produced ceramics with a 93% relative density, 325 MPa flexural strength, and a Weibull module whose value wits m = 10, maintaining the capacity of this process to produce complex geometric shaped ceramics. (C) 2008 Elsevier Ltd. All rights reserved.

Influence of cassava starch content and sintering temperature on the alumina consolidation technique

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation of strip rolling directly from the semi-solid state

defect metal alloy strip when thixorolling directly from the semi-solid state. To facilitate the study lead/tin alloys were chosen for their relatively low operating temperature. The objective is to extrapolate these findings to the higher temperature aluminium, alloys. Three alloys (70%Pb30%Sn, 60%Pb-40%Sn, 50%Pb-50%wtSn) were used particularly to study the influence of the solidification interval. The equipment consists of a two roll mill arranged as an upper and lower roller, where both rollers are driven at a controlled speed. The lower roller is fed with semi solid alloy through a ceramic nozzle attached to the lower end of a cooling slope. Several types of nozzle and their position at the roller were tested. This produced different solidifications and consequently different finished strip. The alloys were first cast and then poured onto the cooling slope through a tundish in order to create a continuous laminar flow of slurry and uniformity of metal strip quality. The pouring was tested at different positions along the slope. The cooling slope was coated with colloidal graphite to promote a smooth slurry flow and avoid the problem of adherence and premature solidification. The metallic slurry not only cools along the slope but is also initially super-cooled to a mush by the lower roller whilst at room temperatures, thus enabling thixorolling. It was also found that the nozzle position could be adjusted to enable the upper roller to also contribute to the solidification of the metallic slurry. However the rollers and the cooling slope naturally heat up. Temperature distribution in these zones was analysed by means of three thermocouples positioned along the cooling slope and a fourth in the base of the semi solid pool within the nozzle. The objective being to design an optimum pouring and cooling system. The formed strip was cooled down to room temperature with a shower of water. Microstructures of the thixorolling process were analysed. The differences in solidification conditions resulted in differing qualities of finished strip and corresponding defect types, all of which are a serious quality issue for the rolled product.

Screening of Formulation Variables for the Preparation of Poly(epsilon-caprolactone) Nanocapsules Containing the Local Anesthetic Benzocaine

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

Processo de difusão com agregação e reorganização espontânea em uma rede 2D

Difusive processes are extremely common in Nature. Many complex systems, such as microbial colonies, colloidal aggregates, difusion of fluids, and migration of populations, involve a large number of similar units that form fractal structures. A new model of difusive agregation was proposed recently by Filoche and Sapoval [68]. Based on their work, we develop a model called Difusion with Aggregation and Spontaneous Reorganization . This model consists of a set of particles with excluded volume interactions, which perform random walks on a square lattice. Initially, the lattice is occupied with a density p = N/L2 of particles occupying distinct, randomly chosen positions. One of the particles is selected at random as the active particle. This particle executes a random walk until it visits a site occupied by another particle, j. When this happens, the active particle is rejected back to its previous position (neighboring particle j), and a new active particle is selected at random from the set of N particles. Following an initial transient, the system attains a stationary regime. In this work we study the stationary regime, focusing on scaling properties of the particle distribution, as characterized by the pair correlation function ø(r). The latter is calculated by averaging over a long sequence of configurations generated in the stationary regime, using systems of size 50, 75, 100, 150, . . . , 700. The pair correlation function exhibits distinct behaviors in three diferent density ranges, which we term subcritical, critical, and supercritical. We show that in the subcritical regime, the particle distribution is characterized by a fractal dimension. We also analyze the decay of temporal correlations

Silver nanoparticles: influence of stabilizing agent and diameter on antifungal activity against Candida albicans and Candida glabrata biofilms

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Proteomic Analysis of Urine in Rats Chronically Exposed to Fluoride

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

Mononuclear phagocytes in the blood of turtles characterized by ultrastructural and cytochemical analyses and by phagocytic activity

Ultrastructural and cytochemical characteristics of mononuclear phagocyte cells in turtles are not well described in the literature, especially in Phrynops hilarii. Thus, the aim of this study was to evaluate these characteristics in the mononuclear phagocyte cells and their phagocytic activity in vitro using the turtle P. hilarii as an experimental animal model. The six turtles used in the study were observed in two seasons, spring and summer. Results showed that mononuclear phagocytes incubated only in diluted solution or with colloidal charcoal have cytoplasm phagolysosomes. The cells incubated with colloidal charcoal and further exposed to the cytochemical reaction for acid P-glycerophosphatase, showed cytoplasm phagolysosomes filled by charcoal particles being digested and some positively stained lysosomes. Acid P-glycerophosphatase positive reaction was present in lysosomes and inside the phagolysosomes, while acid cytidine 5-monophosphatase staining occurred in lysosome surroundings. A positive reaction for trimetaphosphatase was also found inside phagolysosomes. In conclusion, the presence of lysosomal enzymes like trimetaphosphatase and cytidine-5'-sodium monophosphate, in the circulating blood of P. hilarii indicate that mononuclear phagocytes participate in the phagocytic process by gathering many phagocytic cells and forming multinucleated giant cells, which probably have a role in the blood clearance process. (C) 2008 Elsevier Ltd. All rights reserved.

Proteomic analysis of kidney in rats chronically exposed to fluoride

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

Physicochemical characterization of nanoparticles formed between DNA and phosphorylcholine substituted chitosans

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

Tracing source and evolution of suspended particles in the Rio Negro Basin (Brazil) using chemical species of iron

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanopore size growth and ultrafiltration performance of SnO2 ceramic membranes prepared by sol-gel route

Supported ceramic membranes have been produced by the sol-casting procedure from aqueous colloidal suspensions prepared by the sol-gel route. Coatings on a tubular alumina support have been successfully performed leading to crack free layers. Samples have been sintered at 400, 500 and 600 degreesC, and the effect of heating treatment on the nanostructure and on the ultrafiltration properties are analyzed. The characterization has been done by high resolution scanning electron microscopy, nitrogen adsorption-desorption isotherms, water permeation and cut-off determination using polyethylene glycol standard solutions. The micrographs have revealed that grains and pore size increase with the temperature, whereas their shape remains invariant. This results is in agreements with N-2 adsorption-desorption analyses, which have revealed that the mean pore size diameter increases from 4 to 10 nm as the sintering temperature increases from 400 to 600 degreesC, while the total porosity remains constant. Furthermore, the tortuosity, calculated from water permeability, is essentially invariant with the sintering temperatures. The membranes cut-off, determined with a retention rate equal to 95%, are 3500, 6500 and 9000 g . mol(-1) for 400, 500 and 600 degreesC, respectively, showing that the permeation properties of SnO2 ultrafiltration membranes can easily be controlled by sintering condition.

SAXS and UV-Vis combined to Quick-XAFS monitoring of ZnO nanoparticles formation and growth

Time-resolved X-ray absorption-fine structure (Quick-XAFS) and UV-Vis absorption spectroscopies were combined for monitoring simultaneously the time evolution of Zn-based species and ZnO quantum dot (Qdot) formation and growth during the sol-gel synthesis from zinc oxy-acetate precursor solution. The time evolution of the nanostructural features of colloidal suspension was independently monitored in situ by small angle X-ray scattering (SAXS). In both cases, the monitoring was initialized just after the addition of NaOH solution (B = [OH]/[Zn] = 0.5) to the precursor solution at 40 degrees C. Combined time-resolved Quick-XAFS and UV-Vis data showed that the formation of ZnO colloids from the zinc oxy-acetate consumption achieves a quasi-steady-state chemical equilibrium in less than 200s. Afterwards, the comparison of the ZnO Qdots size and Guinier gyration radius evidences a limited aggregation process coupled to the Qdots growth. The analysis of the experimental results demonstrates that the nanocrystal coalescence and Ostwald ripening control the kinetics of the Qdot growth.

Well-Alloyed PtFe/C Nanocatalysts of Controlled Composition and Same Particle Size: Oxygen Reduction and Methanol Tolerance

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

Synthesis and characterization of mesoporous TiO2 nanostructured films prepared by a modified sol-gel method for application in dye solar cells

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