Sterolic and triterpenoidic constituents of stem bark of Drypetes gossweileri

Four compounds have been identified from the stem bark of Drypetes gossweileri by means of H-1- and C-13-NMR spectroscopy, stearic acid, methyl putranjate, and two new compounds: stigmasterol stearate and beta-sitosterol stearate.

Potentiometric determination of alendronate in pharmaceutical formulations

A simple, precise, fast and low-cost potentiometric method for alendronate determination in pharmaceutical formulations has been proposed. Alendronate present in tablets at the known concentration was potentiometrically titrated in an aqueous solution using a combined glass electrode coupled with an autotitrator. Determination limit of alendronate was 20.0 mug mL(-1). In the presence of common excipients, such as lactose, microcrystalline cellulose, glucose, croscarmellose sodium, starch, talc, magnesium stearate and titanium dioxide no interferences were observed. The method proposed was validated by determining alendronate in various dosage forms. The average RSD was 0.75%.

Influence of the network former on the properties of magnesium spinels

Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 and Mg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has.

Preparation of Fe-Cr-P-Co amorphous alloys by electrodeposition

The effects of bath composition and electroplating conditions on structure, morphology, and composition of amorphous Fe-Cr-P-Co deposits on AISI 1020 steel substrate, priorly plated with a thin Cu deposit, were investigated. The increase of charge density activates the inclusion of Cr in the deposit. However, above specific values of the charge density, which depend on the deposition current density, the Cr content in the deposit decreases. This Cr content decreasing is probably due to the significant hydrogen evolution with the increasing of deposition cur-rent and charge density. The effect of charge density on the content of Fe and Co is not clear. However, there is a tendency of increasing of Fe content and decreasing of Co content with the raising of current density. The Co is more easily deposited than the P, and its presence results in a more intense inhibition effect on the Cr deposition than the inhibition effect caused by P presence. Scanning electron microscope (SEM) analysis showed that Co increasing in the Fe-Cr-P-Co alloys analyzed does not promote the susceptibility to microcracks, which led to a good quality deposit. The passive film of the Fe-Cr-P-Co alloy shows a high ability formation and high protective capacity, and the results obtained by current density of corrosion, j(cor), show that the deposit with addition of Co, Fe31Cr11P28Co30, presents a higher corrosion resistance than the deposit with addition of Ni, Fe54Cr21P20Ni5. (C) 2004 Published by Elsevier B.V.

Arsenic as internal standard to correct for interferences in the determination of antimony by hydride generation in situ trapping graphite furnace atomic absorption spectrometry

The feasibility of using internal standardization (IS) to correct for interferences in hydride generation with in situ trapping in graphite furnace was evaluated. Arsenic was chosen as internal standard for Sb determination and Ir was used as permanent modifier. Fluctuations in the main parameters that affect the analytical results were minimized by IS and an effective contribution was verified in the studies of liquid phase interferences. Cobalt and Ni2+ were selected to illustrate the potential use of IS on the correction of interference by transition metals. The application of IS allows the Sb determination in samples containing up to 20-fold higher concentration of the Co2+ and Ni2+ when compared to the procedure without IS. The relative standard deviation of measurements varied from 0.3% to 0.7% and from 1.1% to 3.2% with and without IS, respectively. Recoveries within 92% and 107% of spiked aqueous solution containing Sb(III) and Sb(V) were found. (c) 2005 Elsevier B.V. All rights reserved.

Structural and thermal characterization of Zn2-xCoxTiO4

In this work, spinels with the general formula Zn2-xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 A degrees C. The powder precursors were characterized by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 A degrees C, which disappeared after cobalt addition, indicating that organic material elimination was favored.

Influence of doping on the preferential growth of alpha-MoO3

MoO3 is a lamellar material with applications in different areas, as solid lubricants, catalysis, solar cells, etc. In the present work, MoO3 powders, synthesized by the polymeric precursor method, were doped with nickel or cobalt. The powder precursors were characterized by TG/DTA. After calcination between 500 and 700 degrees C, the samples were characterized by X-ray diffraction, infrared and Raman spectroscopy and scanning electron microscopy. beta-MoO3 was obtained after calcination at low temperatures. With the temperature increase, alpha-MoO3 is observed, with a preferential growth of the (0 2k 0) planes, when the material is doped and calcined at 700 degrees C. Doping with nickel increases five times the preferential growth. As a consequence, plate-like particles are observed. (c) 2007 Elsevier B.V. All rights reserved.

Lanthanum-based perovskites obtained by the polymeric precursor method

Cobalt oxides, specially the ones with perovskite structure, are of a high technological interest, due to their interesting optical, electrical and magnetic properties. La(1 -x)Ca(x)CoO(3) powder samples were synthesized by the polymeric precursor method, with x varying from 0 to 0.4. The powder precursors were characterized by TG/DTA, XRD and IR. The TG curves showed several thermal decomposition steps; the first one is ascribed to the loss of water and the remaining steps are related to the combustion of the organic matter. The XRD patterns indicated only the presence of the perovskite phase. Moreover, the structure changes from rhombohedral to cubic, as calcium is added to the perovskite and the calcination temperature increases.

Evaluation of different rhodium modifiers and coatings on the simultaneous determination of As, Bi, Pb, Sb, Se and of Co, Cr, Cu, Fe, Mn in milk by electrothermal atomic absorption spectrometry

Different kinds of modifiers and coatings on the integrated platform of transversely heated graphite atomizer (THGA) have been tested for the simultaneous determination of two group of elements: the first, the more volatile, formed by arsenic, bismuth, lead, antimony and selenium; the second, the less volatile, formed by cobalt, chromium, cupper, iron and manganese in milk by electrothermal atomic absorption spectrometry. Different Rh-modifiers were studied, such as Rh-coated platforms (Rh), carbide plus rhodium coated platforms (W-Rh, Zr-Rh), carbide-coated platforms (W and Zr) with co-injection of RhCl3, solutions and uncoated platforms with injection of solutions of Pd(NO3)(2), Mg(NO3)(2), and RhCl3. Milk samples were diluted 1:10 in 1.0% HNO3 and injected into the tube. The mass of modifier deposited and co-injected in the tube and the use of end capped tubes were also evaluated in order to improve the electrothermal behavior of analytes. Integrated platform pretreated with W plus co-injection RhCl3 for first group and pretreated with W-Rh for second group were elected. For 20 mu L injected samples the analytical curves in the 5.0-20.0 mu g L-1 concentration range have good linear correlation coefficients (r > 0.998). Relative standard deviations (n = 12) are < 6% and the calculated characteristic masses are between 5 pg and 62 pg.

X-ray diffraction investigation of Co(II) ions in borosilicate glasses

The radial distribution functions of cobalt glasses with 6%, 8%, and 14% CoO are compared with those of suitable cobalt-free borosilicate matrices leading to difference distribution curves representative of the cobalt structural arrangement. Analysis of the curves indicates that cobalt ions are surrounded by approximately four oxygen neighbors at the distance expected for fourfold coordination. © 1986 American Institute of Physics.

Fadiga de grampos de retenção em prótese parcial removível. Efeito de ligas, espessuras e técnicas de fusão. Parte I.

The authors looked for the verification of the fatigue of retentive clasps utilized on the removable partial denture. According to this, it was idealized and built on assay machine, that through movements, simulate the insertion and removal of the clasp for a pattern tooth, manufactured on cobalt-chromium which has all the preparation normally utilized to the correct confection of this type of prosthesis. It was utilized three different commercial alloys based on cobalt-chromium: L1-Biosil; L2-Steldent; L3-Duracron. It was utilized the T clasp of Roach, with was tested upon three different proportions among width and thickness: E1-1.7;E2-2.0 and E3-2.3 and was casted through two casting techniques: F1-oxygen-gas and F2-oxygen-acetylene. The clasps were tested on the machine, which allowed the reading of the number of insertion and removal cycles made until fatigue appeared. The obtained results were submitted to the statistic analysis and the authors concluded that: a) L3 (Duracrom) obtained the best results followed by L1 (Biosil) and finally L3 (Steldent); b) among the analyzed thickness, the best results were obtained by E3, followed by E2 and after this E1; c) form the casting techniques, F2 gave us the best results.

Fadiga de grampos de retenção em prótese parcial removível. Efeito de ligas, espessuras e técnicas de fusão. Parte II.

The authors tested the T clasp of Roach in three differents proportions among width and thickness: E1-1.7; E2-2.0 and E3-2.3, with a constant length of 15 mm. These clasps were casted with three cobalt-chromium alloys (L1-Biosil; L2-Steldent and L3-Duracrom), through two casting techniques (F1-oxygen-gas and F2-oxygen-acetylene). The fatigue of the clasps were verified by using and assay machine, that through movements, simulate the insertion and removal of the clasps for a pattern which were obtained from a premolar, prepared in a surveyor. This machine detect the fatigue of the clasps and count the number of cycles of insertion and removal realized. The obtained results of the interaction between the analysed factors, were submitted to the statistic analysis and the authors concluded that: a) the interaction of factors, Alloy x Thickness, Alloy x Casting Technique and Thickness x Casting Technique did not change the order of effects that the factors showed separately but gave rise to effects of different magnitude for any observed sense; b) the simultaneous interaction of the factors Alloy x Thickness x Casting Technique confirmed the superiority of the L3 alloy, the thickness E3 and the F2 casting technique.

CELULOSE FIBROSA DO BAGACO DA CANA-DE-ACUCAR - AVALIACAO DA ACAO AGLUTINANTE/DESAGREGANTE EM COMPRIMIDOS CONTENDO FARMACO HIDROSSOLUVEL

In this work, a fibrous cellulose obtained from the sugar cane bagasse was analysed about its binder/disintegrating action and about its interference degree in the dissolution rate ('in vitro') of active principles, when incorporated in a compact system that has a water-soluble drug. It was used as reference drug the Lithium Carbonate, considering its solubility in water and it difficulties in the compressibility and flow rate. That cellulose was evaluated in a comparative study, involving another fibrous cellulose generally used in the tablet obtainment (Microcel 3E-200). After the experiment in methodologies of dry granulation and wet granulation, it was concluded that the analysed celluloses presents adequate binder/disintegrating efficience and they are equivalents in these aspect.

Caracterizacion metalografica de aleaciones metalicas utilizadas como biomateriales en implantes quirurgicos

In this work, the chemical structure, the microstructure and the surface morphology of two non-ferrous materials used in dental implants (Ti-6Al-4V and Co-Cr-Mo) were studied. This was done by chemical analysis, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and strength measurements (HV). Metallographic studies reveal that titanium alloy surface present a fine granular binary phase structure, while cobalt alloy present cast dendrite structures with an intense precipitation of carbides. To correlate the macro and microstructure with the mechanical behavior of the material, microhardness measurements were performed. Using the Vickers hardening method, the Ti-6Al-4V alloy yielded strength mean values smaller than the Co-Cr-Mo alloy. Their values are associated to the chemical composition and to the microstructural distribution of these materials. The Ti-6Al-4V alloy presents hardness similar to dental enamel, which suggests better performance as dental implant.