Digital Light Microscopy of Macroporous Ceramics Processed by Consolidation Casting with Mixtures of Native Starches

Porosity in starch consolidation casting technique is rightly related to original size and morphology of starch granules, leaving a pore structure after burning out. This work reports the results for the addition of different native potato and corn starch proportions in suspension,; with TiO(2) (rutile) powder. Gelling temperature have been defined after observation under light microscopy using a heating stage. Analysis of porous network and isolated pores have been clone from images of samples surfaces obtained by depth from focus reconstruction, revealing a qualitative correlation of pores characteristics and starches additions in suspensions, suggesting that the presence of isolated or interconnected pores can be handled by starches selection to control the amylopectin and amylose contents in slurries. Also, the analysis of porous fraction distribution shows no consistent pattern through specimens' volume according to starches in mixtures.

Esthetic Interim Acrylic Resin Prosthesis Reinforced with Metal Casting

Fabrication of an interim prosthesis is an important procedure in oral rehabilitation because it aids in determining the esthetics, phonetics, and occlusal relationship of the definitive restoration. The typical material (acrylic resin) used in interim prostheses commonly fails due to fractures. During extended oral rehabilitation with fixed partial prostheses, high strength interim prostheses are often required to protect hard and soft tissues, avoid dental mobility, and to allow the clinician and patient a chance to evaluate cosmetics and function before the placement of the definitive prosthesis. Furthermore, a satisfactory interim prosthesis can serve as a template for the construction of the definitive prosthesis. The maintenance of this prosthesis is important during treatment for protection of teeth and occlusal stability. Procedures to reinforce interim prostheses help to improve performance and esthetics in long-term treatment. Due to the low durability of acrylic resin in long-term use, the use of reinforcing materials, such as metal castings or spot-welded stainless steel matrix bands, is indicated in cases of extensive restoration and long-term treatment. This paper describes an easy technique for fabricating a fixed interim prosthesis using acrylic resin and a cast metallic reinforcement.

Mechanical, physical, and chemical characterization of Ti-35Nb-5Zr and Ti-35Nb-10Zr casting alloys

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

Determinação de parâmetros de validação de métodos cromatográficos para análise de 5-hidroximetilfurfural e açúcares em amostras de processo de produção de polímero biodegradável

A eficiência de métodos para análise de 5-hidroximetilfurfural por cromatografia líquida de alta eficiência com detecção na região do ultravioleta e determinação de sacarose, glicose e frutose por cromatografia líquida com detecção por índice de refração foi avaliada. Após otimização das condições analíticas, os principais parâmetros de validação (linearidade, limite de quantificação, limite de detecção, recuperação, sensibilidade e precisão) foram determinados e demonstraram que os procedimentos analíticos podem ser aplicados para o controle do processo de produção de poli(3-hidroxibutirato).

Influência da secagem, armazenamento e embalagem nos resultados da análise química de terra para fins de fertilidade

Amostras de terra provenientes de uma Terra Roxa Estruturada e um Latossol Vermelho Escuro textura média foram analisados quimicamente para se verificar a influência de embalagem (caixa de papelão saco de polietileno), tempo de armazenamento (1-32 dias) e processo de secagem (ao ar ou estufa a 60°C). A secagem foi o fator que mais influenciou a análise determinando variações nos resultados analíticos principalmente para pH e fósforo. O armazenamento apresentou influência apenas para fósforo trocável enquanto que a embalagem não influiu nos resultados. As variações dos resultados analíticos para pH, em função da secagem, e fósforo, em função da secagem e tempo de armazenamento, foram de ordem a alterar a interpretação da fertilidade quanto aos limites de classes.

EMBALAGEM INDIVIDUAL DE MANGAS CV. TOMMY ATKINS em FILME PLÁSTICO: EFEITO SOBRE A VIDA DE PRATELEIRA

Estudou-se o efeito da embalagem de policloreto de vinila (PVC) sobre a vida de prateleira de mangas cv. Tommy Atkins armazenadas sob refrigeração. Mangas no estádio de maturidade fisiológica, com casca verde ou levemente avermelhada, foram embaladas individualmente, com filme de 10mm de espessura, e armazenadas por 28 dias a 12ºC (80-90% UR). Frutos sem embalagem serviram de controle. Durante o período de armazenagem, foram feitas avaliações sensoriais utilizando o método de escala hedônica não estruturada para aceitação da aparência e do sabor, utilizando-se de 30 provadores não treinados por sessão. Determinou-se também a perda de massa, a acidez titulável e os teores de sólidos solúveis e vitamina C ao longo da armazenagem. As mangas embaladas apresentaram uma vida de prateleira de 21 dias contra 6 dias das não embaladas, e uma taxa de perda de massa 3,5 vezes menor que as não embaladas. em relação à taxa de degradação de vitamina C, não houve diferença entre os tratamentos. A combinação da embalagem com a armazenagem a 12ºC aumentou a vida de prateleira do produto pela redução da atividade metabólica e do desenvolvimento de podridão.

Otimização e validação de metodologia cromatográfica para determinação simultânea de composição monomérica em polímero biodegradável

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estimativa da composição gasosa em embalagem de atmosfera modificada contendo mangas (mangifera indica l.) Cv. Keitt

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Development and applications of three-dimensional gamma ray tomography system using ray casting volume rendering techniques

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

Evaluation of shear bond strength at the interface of two porcelains and pure titanium injected into the casting mold at three different temperatures

Statement of problem. Titanium has physical and mechanical properties, which have led to its increased use in dental prostheses despite casting difficulties due to high melting point and formation of oxide layers which affect the metal-ceramic bond strength.Purpose. This in vitro study evaluated the shear bond strength of the interface of 2 dental porcelains and pure titanium injected into a mold at 3 different temperatures.Material and methods. Using commercially pure (cp) titanium bars (Titanium, Grade I) melted at 1668degreesC and cast at mold temperatures of 430degreesC, 700degreesC or 900degreesC, 60 specimens were machined to 4 x 4 mm, with a base of 5 x 1 mm. The 4-mm surfaces were airborne-particle abraded with 100 mum aluminum oxide before applying and firing the bonding agent and evaluating the 2 porcelains (Triceram/Triline ti and Vita Titankeramik). Ten specimens were prepared for each temperature and porcelain combination Shear bond testing was performed in a universal testing machine, with a 500-kg load cell and crosshead speed of 0.5 mm/min. The specimens were loaded until failure. The interfaces of representative fractured specimens of each temperature were examined with a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Data for shear bond strength (MPa) were statistically analyzed by 2-way ANOVA and the Tukey test (alpha = .05).Results. The results showed significant differences for the metal/porcelain interaction effect (P = .0464). There were no significant differences for the 2 porcelains (P = .4250). The Tukey test showed a significant difference between the pair cp Ti 430degreesC Triceram and cp Ti 900degreesC Triceram, with respective mean values and SDs of 59.74 +/- 11.62 and 34.03 +/- 10.35 MPa.Conclusion. Triceram porcelain showed a bond strength decrease with an increase in the mold temperature for casting titanium. The highest bond strength for Vita porcelain and the best metal-ceramic interface observed with the SEM were found with the mold temperature of 700degreesC.

Sintering of zirconia composites obtained by slip casting

Composites containing a matrix of nanometric Ce-stabilized zirconia with an addition of micrometric monoclinic zirconia were processed by slip casting and sintered at a relatively low temperature. The ratio between nanometric and micrometric particles was determined according to the viscosity of the suspensions and the final density of the pellets. An optimum amount of micrometric particles was necessary to achieve improved suspension dispersion and higher pellet density. The amount of deflocculant in the suspensions containing the mixture of micrometric and nanometric particles was optimized by viscosity measurements. The pellets were characterized by dilatometry, Hg porosimetry, density measurement (the Archimedes method) and scanning electron microscopy. Despite the low green density obtained (35-38% of the theoretical density), densities as high as 97.5% were achieved after sintering. (C) 2001 Elsevier B.V. Ltd and Techna S.r.l. All rights reserved.

Validação de métodos para determinação do teor de 3-hidroxibutirato e 3-hidroxivalerato em polímero biodegradável

The efficiency of two methods for determining 3-hydroxybutyrate and 3-hydroxyvalerate content in the biopolymer (poly(3-hydroxybutyrate-co-3-hydroxyvalerate) has been evaluated. Both methods are based on (a) the hydrolysis of polymers, (b) the esterification with methyl (method A) and isoamilic alcohol (method B) and (c) analysis of the esters by gas chromatography using flame ionization detection (GC-FID). After optimization of the analytical conditions, the main validation parameters (linearity, quantification limit, detection limit, recovery, sensitivity and precision) were determined showing that both analytical procedures can be applied to control the process of poly(3-hydroxybutyrate) production. However, method B gives better analytical results than method A and has the advantage of not using chlorinated solvents.

Sintering of tin oxide processed by slip casting

Sintering of SnO 2 compacts, obtained through slip casting, was studied by means of dilatometry, Hg porosimetry, scanning electron microscopy, and density measurement (Archimedes method). Sintering is strongly influenced by the green microstructure. Moreover, the sintering mechanisms are not dependent on the slurries' solid content up to 50% of solids in volume. Above this value, agglomerates are formed, leading to differential sintering inside and among the agglomerates. Another important point is the reduction of the temperature of maximum shrinkage rate when compared to tin oxide processed by isostatic pressing. This reduction is more accentuated when ammonium hydroxide is added to the suspension. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.