Spectroscopic and electrochemical characterization of polyaniline and a ruthenium complex, mer-[RuCl3(dppb)(py)], in the form of Langmuir-Blodgett films

Langmuir monolayers and Langmuir-Blodgett (LB) films have been produced from polyaniline and a biphosphinic ruthenium complex, referred to as Rupy. Strong, repulsive interaction between the two components led to a nonlinear change in area per molecule and surface potential with the concentration of Rupy in the mixed film. Molecular interaction was also denoted in the spectroscopic and electrochemical properties of the Y-type LB transferred films. The Raman spectra of mixed PANI-Rupy films indicated that the degree of oxidation of PANI increased linearly with the concentration of Ropy. With PANI being increasingly oxidized by presence of Rupy, the electroactivity of the mixed films decreased with the amount of Rupy, to become undetectable when the mixed LB film is 501 mol in Rupy. The presence of Rupy caused the electrical properties of the mixed LB films to be less sensitive to environmental changes. The electrical capacitance of a mixed film changed only by 15% when the sample was taken from vacuum to air, whereas the change was 215% for a pure PANI LB film.

Modification of surface properties of Ti-16Si-4B powder alloy by plasma immersion ion implantation

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

Structural and microstructural characterization of SrBi2(Ta0.5Nb0.48W0.02)(2)O-9 powders

SrBi2(Ta0.5Nb0.48W0.02)(2)O-9 powders (SBTN-W) were prepared by the polymeric precursor method. The influence of annealing temperature on the phase formation and specific surface area was evaluated. TG/DTA associated with X-ray diffraction (XRD) analyses showed the formation of perovskite phase at around 500-600 degrees C. An orthorhombic structure with A21am space group was identified by Rietveld refinement. BET analysis revealed that the specific surface area reduces with increasing thermal annealing. SEM micrographies showed grains in an almost-spherical morphology with the presence of agglomerates. (C) 2006 Elsevier B.V. All rights reserved.

Ceramic raw materials from the State of Maranhao, Brazil. Part 1: chemical and mineralogical characterization and technological properties of clays from Sao Luis, Rosario, Pinheiro and Mirinzal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ga-Modified Nanostructured ZnO: Characterization and Application in Dye-Sensitized Solar Cells

ZnO has received great attention in many applications due to its electronic and optical properties. We report on the preparation of ZnO and gallium-containing ZnO (ZnO:Ga) nanoparticles by the precipitation method. The nanoparticles have the wurtzite structure and a high crystallinity. Gallium ions are present as Ga(3+), as evidenced by the binding energies through XPS. Porosity and surface area of the powder increased under increasing gallium level, explained by the smaller particle size of ZnO:Ga samples compared with ZnO. The estimated optical band gap of ZnO was 3.2 eV, comparable to ZnO:Ga.

Development, characterization and clinical use of a biodegradable composite scaffold for bone engineering in oro-maxillo-facial surgery

We have developed a biodegradable composite scaffold for bone tissue engineering applications with a pore size and interconnecting macroporosity similar to those of human trabecular bone. The scaffold is fabricated by a process of particle leaching and phase inversion from poly(lactide-co-glycolide) (PLGA) and two calcium phosphate (CaP) phases both of which are resorbable by osteoclasts; the first a particulate within the polymer structure and the second a thin ubiquitous coating. The 3-5 mu m thick osteoconductive surface CaP abrogates the putative foreign body giant cell response to the underlying polymer, while the internal CaP phase provides dimensional stability in an otherwise highly compliant structure. The scaffold may be used as a biomaterial alone, as a carrier for cells or a three-phase drug delivery device. Due to the highly interconnected macroporosity ranging from 81% to 91%, with macropores of 0.8 similar to 1.8 mm, and an ability to wick up blood, the scaffold acts as both a clot-retention device and an osteoconductive support for host bone growth. As a cell delivery vehicle, the scaffold can be first seeded with human mesenchymal cells which can then contribute to bone formation in orthotopic implantation sites, as we show in immune-compromised animal hosts. We have also employed this scaffold in both lithomorph and particulate forms in human patients to maintain alveolar bone height following tooth extraction, and augment alveolar bone height through standard sinus lift approaches. We provide a clinical case report of both of these applications; and we show that the scaffold served to regenerate sufficient bone tissue in the wound site to provide a sound foundation for dental implant placement. At the time of writing, such implants have been in occlusal function for periods of up to 3 years in sites regenerated through the use of the scaffold.

Morphological and Histochemical Characterization of Gill Filaments of the Brazilian Endemic Bivalve Diplodon expansus (Kuster, 1856) (Mollusca, Bivalvia, Hyriidae)

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

In vitro characterization of intra-generic inhibition of growth in Salmonella typhimurium

The intra-generic inhibition of bacterial growth observed previously in vivo and in vitro with strains of Salmonella, Citrobacter and E. coli was studied in vitro using S. typhimurium strain F98. There was complete inhibition of multiplication of S. typhimurium when it was added to stationary-phase broth cultures of different Salmonella serotypes, but only partial inhibition when added to broth cultures of E. coli. The degree of inhibition between different mutants of F98 was affected by the numbers of bacteria of the inhibiting strain, but this was not the only factor, since exponential-phase bacterial cells were less inhibitory than stationary-phase cells. The inhibitory effect was produced at temperatures between 20°C and 40°C. The complete inhibition of growth observed between F98 mutants was abolished by ampicillin, rifampicin and streptomycin, but not by nalidixic acid. Inhibition was also prevented by separating the two cultures by a dialysis membrane. A Tnpho A Insertion mutant of F98 was produced which did not show inhibition in vitro but was still inhibitory in vivo. It is suggested that this complete inhibition of bacterial multiplication between organisms of the same genus, which is greater than that produced between organisms from different genera, is mediated by a cell surface protein.

Pore structure characterization of kaolin, metakaolin, and their acid-treated products using small-angle X-ray scattering

Pore structure of dealuminated kaolin and metakaolin was studied by small-angle X-ray scattering (SAXS). Both parent kaolin and metakaolin have about 10% of the total pore volume provided by globular pores with 105 Å mean pore size. Their surface area is about 14 m2/g. Acid dealumination of kaolin causes an increase of its globular pore volume without an appreciable change in the mean pore size, its surface area increasing up to about 90 m2/g. Acid dealumination of metakaolin enhances the globular pore volume, although there is generation of slit-shaped pores with a narrow thickness distribution whose mean value is 14 Å. This interlayer spacing causes an increase in surface area of about 190 m2/g by SAXS. © 1994.

Characterization of bornite (Cu5FeS4) electrodes in the presence of the bacterium Acidithiobacillus ferrooxidans

Bornite electrodes were characterized in the absence or in the presence of Acidithiobacillus ferrooxidans, which is an important microorganism involved in metal bioleaching processes. The presence of the bacterium modified the mineral/electrolyte interface, increasing the corrosion rate, as revealed by interferometric, AEM, ICP and EIS analyses. As a consequence of bacterial activity the electrode became porous, increasing its surface heterogeneity. This behavior was correlated with the evolution of impedance diagrams obtained during the time course of experiments. The main difference in these diagrams was the presence of an inductive feature (up to 44 h), which was related to bacterial action on the mineral dissolution, better than to its adhesion on the bornite. The total real impedance measured in presence of the bacterium was about 10 times lower than in its absence, due to the acceleration of the mineral dissolution, because an oxidant environment was maintained.

Comparative study using small-angle x-ray scattering and nitrogen adsorption in the characterization of silica xerogels and aerogels

A comparative study using small-angle x-ray scattering (SAXS) and nitrogen adsorption has been carried out in the structural characterization of silica xerogels and aerogels, obtained from tetraethoxysilane sonohydrolysis. The specific surface and the mean pore size as measured by both the techniques were found to be in notable agreement in all cases for aerogels and xerogels. According to the SAXS data, aerogels at 500 °C exhibit a mass fractal structure with fractal dimension D∼2.4 in the range between the correlation length ξ∼5.3 nm and a∼0.75 nm. An experimental method to probe the mass fractal structure of aerogels from exclusively nitrogen adsorption isotherms has been presented. For aerogels at 500 °C, we have found D∼2.4 in the range between the pore width 2rξ∼33 nm and 2ra∼4.5 nm, which is in notable agreement with the SAXS results (D ∼2.4, ξ∼5.3 nm, a∼0.75 nm) if we assign the pore width 2r probed by the Kelvin equation in the adsorption method to the Bragg distance 2π/q associated to the correlation length 1/q probed by SAXS.

Ethylcelullose microspheres containing sodium diclofenac: Development and characterization

The objective of the present study was the development and characterization of ethylcellulose microspheres containing diclofenac and the determination of the in vitro drug release profile. Microspheres were prepared by emulsification/solvent evaporation method using ethyl acetate as solvent for the polymer and water as non solvent. The microspheres were characterized by morphologic and granulometric analyses. The amount of encapsulated drug as well as its release profile in vitro were also determined. The product obtained was microparticles with smooth surface and narrow size distribution, about 50% of the particles being smaller than 5 μm. The methodology used allowed drug encapsulation with a good yield and the system provided a controlled release of diclofenac.

Microstructural characterization of layers produced by plasma nitriding on austenitic and superaustenitic stainless steel grades

High chromium content is responsible for the formation of a protective passive surface layer on austenitic stainless steels (ASS). Due to their larger amounts of chromium, superaustenitic stainless steels (SASS) can be chosen for applications with higher corrosion resistance requirements. However, both of them present low hardness and wear resistance that has limited their use for mechanical parts fabrication. Plasma nitriding is a very effective surface treatment for producing harder and wear resistant surface layers on these steel grades, without harming their corrosion resistance if low processing temperatures are employed. In this work UNS S31600 and UNS S31254 SASS samples were plasma nitrided in temperatures from 400 °C to 500 °C for 5 h with 80% H 2-20% N2 atmosphere at 600Pa. Nitrided layers were analyzed by optical (OM) and transmission electron microscopy (TEM), x-ray diffraction (XRD), and Vickers microhardness testing. Observations made by optical microscopy showed that N-rich layers were uniform but their thicknesses increased with higher nitriding temperatures. XRD analyses showed that lower temperature layers are mainly composed by expanded austenite, a metastable nitrogen supersaturated phase with excellent corrosion and tribological properties. Samples nitrided at 400 °C produced a 5 μm thick expanded austenite layer. The nitrided layer reached 25 lm in specimens treated at 500 °C. There are indications that other phases are formed during higher temperature nitriding but XRD analysis was not able to determine that phases are iron and/or chromium nitrides, which are responsible for increasing hardness from 850 up to 1100 HV. In fact, observations made by TEM have indicated that formation of fine nitrides, virtually not identified by XRD technique, can begin at lower temperatures and their growth is affected by both thermodynamical and kinetics reasons. Copyright © 2012 by ASTM International.

Biophysical characterization of the recombinant importin-α from neurospora crassa

Neurospora crassa has been widely used as a model organism and contributed to the development of biochemistry and molecular biology by allowing the identification of many metabolic pathways and mechanisms responsible for gene regulation. Nuclear proteins are synthesized in the cytoplasm and need to be translocated to the nucleus to exert their functions which the importin-α receptor has a key role for the classical nuclear import pathway. In an attempt to get structural information of the nuclear transport process in N. crassa, we present herein the cloning, expression, purification and structural studies with N-terminally truncated IMPα from N. crassa (IMPα-Nc). Circular dichroism analysis revealed that the IMPα-Nc obtained is correctly folded and presents a high structural conservation compared to other importins-α. Dynamic light scattering, analytical size-exclusion chromatography experiments and molecular dynamics simulations indicated that the IMPα-Nc unbound to any ligand may present low stability in solution. The IMPα-Nc theoretical model displayed high similarity of its inner concave surface, which binds the cargo proteins containing the nuclear localization sequences, among IMPα from different species. However, the presence of non-conserved amino acids relatively close to the NLS binding region may influence the binding specificity of IMPα-Nc to cargo proteins. Copyright © 2012 Bentham Science Publishers. All Rights Reserved.

Characterization of high density polyethylene (HDPE) reinforced with banana peel fibers

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