Preparation of the Ca-diclofenac complex in solid state

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Localized modes of binary mixtures of Bose-Einstein condensates in nonlinear optical lattices

The properties of the localized states of a two-component Bose-Einstein condensate confined in a nonlinear periodic potential (nonlinear optical lattice) are investigated. We discuss the existence of different types of solitons and study their stability by means of analytical and numerical approaches. The symmetry properties of the localized states with respect to nonlinear optical lattices are also investigated. We show that nonlinear optical lattices allow the existence of bright soliton modes with equal symmetry in both components and bright localized modes of mixed symmetry type, as well as dark-bright bound states and bright modes on periodic backgrounds. In spite of the quasi-one-dimensional nature of the problem, the fundamental symmetric localized modes undergo a delocalizing transition when the strength of the nonlinear optical lattice is varied. This transition is associated with the existence of an unstable solution, which exhibits a shrinking (decaying) behavior for slightly overcritical (undercritical) variations in the number of atoms.

Preparation of hierarchically structured porous aluminas by a dual soft template method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparation of different basic Si-MCM-41 catalysts and application in the Knoevenagel and Claisen-Schmidt condensation reactions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The influence of thermal treatment on the preparation of PNM and PMN-PT thin films

Ferroelectric thin films belong to a class of materials with great technological importance in optic fibers, micro-electromechanical systems, and microprocessors and computers memories.The (1-x)PbMg1/3Nb2/3O3(x)PbTiO3 (PMN-PT) thin films, with x=0, 0.1, 0.35 and 0.5, were prepared by Pechini's process and deposited by spin-coating on Si(100), Pt/Ti/SiO2/Si(100) and quartz substrates. The goal of the present paper is to verify the thermal treatment influence on the perovskite phase formation, which is desirable for these applications. The phase formation was analyzed by X-ray diffraction. The film's surface was characterized by atomic force microscopy to analyze the roughness and the homogeneity. The results of this study indicate that the optimum conditions for obtaining the perovskite phase using a Pt/Ti/SiO2/Si(100) substrate, were drying each deposited layer at 140 degreesC (heating plate), and a final thermal treatment at 600 degreesC for 3 h in a closed system with a lead-rich atmosphere. (C) 2003 Elsevier B.V. All rights reserved.

The use of standard methodology for determination of antifungal activity of natural products against medical yeasts Candida sp and Cryptococcus sp

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

Preparation of silica with controlled pore sizes for enzyme immobilization

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

Preparation of SnO2 supported membranes with ultrafine pores

The colloidal route of the sol-gel process was used to prepare supported SnO2 membranes. The influence of the sol and monoelectrolyte concentrations on the formation of the gel layer by sol-casting on the top of macroporous alpha-Al2O3 support was described. The stability of the colloidal suspension as a function of the concentrations was analyzed from creep-recovery measurements. The calcined supported membranes were characterized by nitrogen adsorption-desorption isotherms and scanning electron microscopy. The set of results show that homogeneous membrane layers containing the smallest quantity of cracks are formed in a critical interval of sol (1.01 less than or equal to[SnO2]less than or equal to 1.4 M) and electrolyte (2.O less than or equal to[Cl-]less than or equal to 4.0 mM) concentrations. The samples prepared from concentrated suspensions present a lot of interconnected cracks which favors the peeling of the coated layer. The membranes have pores of average diameter of about 1 nm.

Preparation of composite retentive areas for removable partial denture retainers

A method is presented in which light-polymerized composite material is used to obtain retention for a removable partial denture when usable natural tooth undercuts are unavailable. The desired contour is waxed on a diagnostic cast with the use of a surveyor, captured in a light-polymerizing temporary restorative material, and reproduced in composite resin on the abutment teeth.

Preparation of zinc sodium polyphosphates glasses from coacervates precursors. Characterisation of the obtained glasses, and their applications

A soft chemistry route is described to obtain glasses in the P2O5-Na2O-ZnO-H2O. It is based on the addition of zinc salts to coacervates prepared from sodium polyphosphate. The processing of these coacervates leads to polyphosphate glasses with the same properties as those of glasses prepared in the classical way. So far, little work has been implemented in this system using 'coacervate route'. However, it makes an attractive method for coating and joining processes on the industrial scale. As the anion associated to zinc may take part in the adhesion mechanism, coacervate formation has been studied using zinc chloride, nitrate and sulphate as starting materials. The physical properties of the glasses obtained by this method are reported and potential applications of zinc and silver coacervate are described. (C) 2002 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

Application of standard and modified Judd-Ofelt theories to thulium doped fluoroindate glass

Fluoroindate glasses of the following compositions: (40-x)InF3-20ZnF(2)-16BaF(2)-20SrF(2)-2GdF(3)-2NaF-xTmF(3) with x = 1,3 mol% were prepared in a dry box under an argon atmosphere. The absorption spectra at room temperature in the spectral range 350-2200 nm were obtained. The spectra obtained for each sample had similar absorption and only the amplitude of the different bands changed as the concentration of Tm3+. The experimental oscillator strengths were determined from the areas under the absorption bands. Using the standard and modified Judd-Ofelt theory, intensity parameters Ohm(lambda) (lambda = 2,4,6) and (lambda = 2,3,4,5,6), respectively for f-f transitions of Tm3+ ions as well as transition probabilities, branching ratios and radiative lifetimes for each band were determined. The results are compared with those of other glasses described in the literature. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Preparation of Pb(Zr,Ti)O-3 thin films by soft chemical route

Lead zirconate titanate, Pb(Zr0.3Ti0.7)O-3 (PZT) thin films were prepared with success by the polymeric precursor method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Micro-Raman spectroscopy and X-ray diffraction (XRD) were used to investigate the formation of the PZT perovskite phase. X-ray diffraction revealed that the film showed good crystallinity and no presence of secondary phases was identified. This indicates that the PZT thin films were crystallized in a single phase. PZT thin films showed a well-developed dense grain structure with uniform distribution, without the presence of rosette structure. The Raman spectra undoubtedly revealed these thin films in the tetragonal phase. For the thin films annealed at the 500-700 degreesC range, the vibration modes of the oxygen sublattice of the PZT perovskite phase were confirmed by FT-IR. The room temperature dielectric constant and dielectric loss of the PZT films, measured at 1 kHz were 646 and 0.090, respectively, for thin film with 365 nm thickness annealed at 700 degreesC for 2 h. A typical P-E hysteresis loop was observed and the measured values of P-s, P-r and E-c were 68 muC/cm(2), 44 muC/cm(2) and 123 kV/cm, respectively. The leakage current density was about 4.8 x 10(-7) A/cm(2) at 1.5 V. (C) 2003 Elsevier Ltd. All rights reserved.

Preparation of ZnO nanoparticles: Structural study of the molecular precursor

The structure of zinc acetate derived precursor currently used in the sol-gel synthesis of ZnO nanoparticles is described. The reaction products obtained before and after reflux of ethanolic zinc acetate solution have been studied by UV-Vis, photoluminescence, FTIR and EXAFS at the Zn K edge. EXAFS results evidence for both precursor solutions a change from the octahedral coordination sphere of oxygen atoms characteristic of the solid zinc acetate dihydrate compound into a four-fold environment. The EXAFS spectra of precursor solutions can be satisfactorily reproduced using the molecular structure reported for Zn4O(Ac)(6) (Ac = COOCH3). UV-Vis and FTIR measurements are also in agreement with the formation of this oligomeric precursor. The structural modification is more pronounced after reflux at 80degreesC, because the increase of the Zn4O(Ac)(6) amount and the formation of nearly 3.0 nm sized ZnO nanoparticle.

Preparation of SrBi2Ta2O9 ferroelectric thick films by electrophoretic deposition using aqueous suspensions

SrBi2Ta2O9 ferroelectric thick films were prepared by electrophoretic deposition (EPD). For that, ceramic powders were prepared by chemical method in order to obtain compounds with chemical homogeneity. The polymeric precursor method was used for the synthesis of the SrBi2Ta2O9 powder. The crystallographic structure of the powder was examined by X-ray diffraction, and the surface area was determined by single point BET adsorption. The 0.03 vol% suspension was formed by dispersing the powder in water using two different polymers as dispersants: an ester polyphosphate (C213) and an ammonium polyacrilate (Darvan 821-A). The influence of the different dispersants on the powder surface properties were investigated by zeta potential measurements. The films were deposited on platinum-coated alumina and Pt/Ti/SiO2/Si substrates by electrophoretic deposition using a 4 mA constant current, for 10 min, with two parallel electrodes placed at a separation distance of 3 min in the suspension. Several cycles of deposition-drying of the deposit was carried out until the desired thickness was obtained. After thermal treatment at temperatures ranging from 700 to 1000degreesC, the films were characterized by X-ray diffraction and scanning electron microscopy.

Preparation of new glass systems by the polymeric precursor method for dental applications

Glass ionomer cements (GICs) are largely employed in Dentistry for several applications, such as luting cements for the attachment of crowns, bridges, and orthodontic brackets as well as restorative materials. The development of new glass systems is very important in Dentistry to improve of the mechanical properties and chemical stability. The aim of this study is the preparation of two glass systems containing niobium in their compositions for use as GICs. Glass systems based on the composition SiO2,Al2O3-Nb2O5-CaO were prepared by chemical route at 700degreesC. The XRD and DTA results confirmed that the prepared materials are glasses. The structures of the obtained glasses were compared to commercial material using FTIR, Al-27 and Si-29 MAS-NMR. The analysis of FTIR and MAS-NMR spectra indicated that the systems developed and commercial material are formed by SiO4 and AlO4 linked tetrahedra. These structures are essential to get the set time control and to have cements. These results encourage further applications of the experimental glasses in the formation of GICs. (C) 2004 Elsevier B.V. All rights reserved.