Evaluation of the effect of the stoichiometric ratio of Ca/Cu on the electrical and microstructural properties of the CaCu3Ti4O12 polycrystalline system

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

Influence of vanadium on electrical and microstructural properties of CaCu3Ti4O12/CaTiO3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Microstructural Characterization of Ti-6Al-7Nb Alloy After Severe Plastic Deformation

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

Microstructural Evolution of Ti-6Al-7Nb Alloy During High Pressure Torsion

Ti-6Al-7Nb alloys are being evaluated for biomedical applications, in substitution of the more conventional Ti-6Al-7V. Both types of alloys present a microstructure containing the alpha and the beta phases, which result in good compromise for mechanical applications. In the present work Ti-6Al-7Nb alloys were processed by High Pressure Torsion (HPT), varying the number of revolutions and thus the total imposed strain. X-Ray Diffraction (XRD) results revealed the formation of different crystallographic textures in samples subjected to HPT. Microhardness distribution, across the diameters of the disks, is rather homogeneous for all samples, with higher values for those subjected to 03 and 05 turns. Transmission electron microscopy (TEM) micrographs have showed that an ultra-fine grained microstructure was obtained in all the samples.

Cocaine mutagenicity and hepatocarcinogenicity evaluations in rodents

The mutagenicity (clastogenicity) and the carcinogenicity (promoting potential) of cocaine were evaluated, respectively, by the mouse bone marrow micronucleus test (study I) and by the initiated rat liver bioassay (study II). In study I, two administration routes (i.p. and i.v.) and two sampling times (24 and 48 hours) after cocaine treatment were studied. Swiss male mice were treated with cocaine at doses of 0, 18, 37, and 75 mg/kg and 0, 2, 4, and 8 mg/kg by i.p. and i.v. routes, respectively. No significant differences were observed between treated and negative control groups regarding the frequencies of micronuclei and the polichromatic/normochromatic erythrocyte (PCE/NCE) ratios. In study II, the development of putative preneoplastic foci of hepatocytes expressing the enzyme glutathione S-transferase placental form (GST-P+) was utilized as the end-point marker in a 8-week rat liver bioassay. The animals were initiated for carcinogenesis by a single i.p. sub-carcinogenic dose of diethylnitrosamine (DEN). After a 6-week exposure to 5 or 10 mg/kg of cocaine i.v. twice a week there was no enhancement of GST-P+ foci development above the values of the control DEN-only treated animals. Also, cocaine did not induce any toxicity as evidenced by the absence of alterations of rat body and liver weights and of liver biochemical function and morphology. The results suggest that cocaine does not have a mutagenic effect on the mouse bone marrow cells or promoting activity on the rat hepatocarcinogenesis process. Teratogenesis Carcinog. Mutagen. 18:199-208, 1998. (C) 1998 Wiley-Liss, Inc.

Comparison of pelvic floor muscle strength evaluations in nulliparous and primiparous women: a prospective study

OBJECTIVE: This study aimed to compare the pelvic floor muscle strength of nulliparous and primiparous women.METHODS: A total of 100 women were prospectively distributed into two groups: Group 1 (G1) (n = 50) included healthy nulliparous women, and Group 2 (G2) (n = 50) included healthy primiparous women. Pelvic floor muscle strength was subjectively evaluated using transvaginal digital palpation. Pelvic floor muscle strength was objectively assessed using a portable perineometer. All of the parameters were evaluated simultaneously in G1 and were evaluated in G2 during the 20(th) and 36(th) weeks of pregnancy and 45 days after delivery.RESULTS: In G2, 14 women were excluded because they left the study before the follow-up evaluation. The median age was 23 years in G1 and 22 years in G2; there was no significant difference between the groups. The average body mass index was 21.7 kg/m(2) in G1 and 25.0 kg/m(2) in G2; there was a significant difference between the groups (p = 0.0004). In G2, transvaginal digital palpation evaluation showed significant impairments of pelvic floor muscle strength at the 36(th) week of pregnancy (p = 0.0006) and 45 days after vaginal delivery (p = 0.0001) compared to G1. Objective evaluations of pelvic floor muscle strength in G2 revealed a significant decrease 45 days after vaginal delivery compared to nulliparous patients.CONCLUSION: Pregnancy and vaginal delivery may cause weakness of the pelvic floor muscles.

Clinical and Microbiologic Follow-Up Evaluations After Non-Surgical Periodontal Treatment With Erbium:YAG Laser and Scaling and Root Planing

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aging effects on the mongolian gerbil female prostate (Skene's paraurethral glands): Structural, ultrastructural, quantitative, and hormonal evaluations

Different from the classic view, the prostate is not a gland exclusive to the male, also being an organ of the female genital system presenting morphofunctional similarity between human and rodent. Thus structural, ultrastructural, morphometric-stereological features of the female prostate (Skene's paraurethral gland) and steroid serological levels were evaluated during young, adult, and senile ages in the Mongolian gerbil. The morphofunctional precocity of the female gland in comparison with the male gland occurring in young gland is probably associated with the female circulating steroid levels. The hormonal imbalance in senesce coincides with its susceptibility to histopathological lesions, such as epithelial hypertrophy, metaplasia, and intraepithelial neoplasia. Differently than that of males, the aging degeneration of the female gland involves the accumulation of lipofuscin granules. However, the alterations in senile prostate did not damage its functionality. These analyses reinforce the use of this experimental model for the comprehension of glandular morphofunctional aspects with special attention to senescence. Thus, the appreciation of this organ becomes relevant to avoid future discomfort to women's health.

A study of the microstructural characteristics of dental amalgams

Metallographic studies by scanning electron microscopy and energy dispersive spectroscopy carried out for two types of dental amalgam showing a porous multiphase material. Surface analysis shows that the structure of the Dispersalloy amalgam consists of gamma-Ag3Sn, gamma(1)-Ag2Hg3, eta'-Cu6Sn5, epsilon-Cu3Sn and eutectic Ag-Cu phases. while Velvalloy amalgam consists mainly of gamma, gamma(1) and gamma(2)-Sn7-8Hg phases. The latter phase presents an uniform distribution often associated with voids.

Influence of the substitution of Y2O3 for CeO2 on the mechanical and microstructural properties of silicon nitride

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

Electrical and microstructural properties of microwave sintered SnO2-based varistors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Microstructural and electric properties of bismuth-layered structured ceramics - SrBi2(Ta1-xNbx)O-9

Ceramic samples of SrBi2(Nb1-xTax)O-9 (0 less than or equal to x less than or equal to 1) were prepared by the solid state reaction method in order to investigate their structural and electrical features as well as obtain useful information to improve the properties of SrBi2(Nb1-xTax)O-9 as a thin film. The X-ray diffraction patterns and the scanning electronic microscopy photomicrographs show no secondary phases but the formation of a solid-state solution for all the composition. The ac conductivity of the samples, measured at 25 degreesC and 100 kHz frequency, decreases with the increase of Ta content. Such results were explained by intrinsic conductivity of pure components.

Microstructural, dielectric and ferroelectric properties of calcium-modified lead titanate thin films derived by chemical processes

Ferroelectric Pb1-xCaxTiO3 (x = 0.24) thin films were formed on a Pt/Ti/SiO2/Si substrate by the polymeric precursor method using the dip-coating technique for their deposition. Characterization of the films bq X-ray diffraction showed a perovskite single phase with a tetragonal structure after annealing at 700 degreesC. Atomic force microscopy (AFM) analyses showed that the film had a smooth and crack-free surface with low surface roughness. In addition, the PCT thin film had a granular structure with an 80 nm grain size. The thickness of the films observed by the scanning electron microscopy (SEM) is 550 nm and there is a good adhesion between the film and substrate. For the electrical measurements metal-ferroelectric-metal of the type capacitors were obtained, where the thin films showed good dielectric and ferroelectric properties. The dielectric constant and dissipation factor at 1 kHz and measured at room temperature were found to be 457 and 0.03. respectively. The remanent polarization and coercive field for the: deposited films were P-r = 17 muC/cm(2) and E-c = 75 kV/cm, respectively. Moreover. The 550-nm-thick film showed a current density in the order of 10(-8) A/cm(2) at the applied voltage of 2 V. The high values of the thin film's dielectric properties are attributed to its excellent microstructural quality and the chemical homogeneity obtained by the polymeric precursor method. (C) 2001 Elsevier science Ltd. All rights reserved.

The influence of yttrium on a typical SnO2 varistor system: Microstructural and electrical features

The influence of yttrium oxide, Y2O3, on the microstructure development of the SnO(2)center dot Co(3)O(4)center dot Nb2O5 typical varistor system was studied with scanning (SEM) and transmission (TEM) electron microscopies. The different phases present in the studied samples were characterized through XRD, EDS and selected area diffraction patterns (SAD). Particles of Co2SnO4 were observed with TEM in every sample, whereas clusters of the pyrochlore phase T2Sn2O7 were observed with SEM in samples with 0.05, 0.10 and 0.25 mol% of Y2O3. The higher non-linearity (a = 16) was achieved with the addition of 0.05 mol% of Y2O3. The influence of the secondary phases on the electrical properties is also addressed in this work. (c) 2005 Published by Elsevier B.V.