Geological evolution of the basement rocks in the east-central part of the Rondonia Tin Province, SW Amazonian craton, Brazil: U-Pb and Sm-Nd isotopic constraints

On the basis of geologic, petrologic, and U-Pb geochronologic data the basement rocks in the east-central part of the Rondonia Tin Province (RTP, southwestern Amazonian craton) are grouped into five lithologic associations: (1) tonalitic gneiss (1.75 Ga); (2) enderbitic granulite (1.73 Ga); (3) paragneiss; (4) granitic and charnockitic augen gneisses (1.57-1.53 Ga); and (5) fine-grained granitic gneiss and charnockitic granulite (1.43-1.42 Ga). The first three are related to development of the Paleoproterozoic Rio Negro-Juruena Province and represent the oldest crust in the region. The tonalitic gneisses and enderbitic granulites show calc-alkaline affinities and Nd isotopic compositions (initial epsilon(Nd) = +0-1 to -1.5; T-DM of 2.2-2.1 Ga) that suggest a continental arc margin setting for the original magmas. The paragneisses yield T-DM values of 2.2-2.1 Ga suggesting that source material was primarily derived from the Ventuari-Tapajos and Rio Negro-Juruena crusts, but detrital zircon ages and an intrusive granitoid bracket deposition between 1.67 and 1.57 Ga. The granitic and charnockitic augen gneisses show predominantly A-type and within-plate granite affinities, but also some volcanic arc granite characteristics. The initial epsilon(Nd) values (+0.6 to +2.0) indicate mixing of magmas derived from depleted mantle and older crustal sources. These rocks are correlated to the 1.60-1.53 Ga Serra da Providencia intrusive suite that reflects inboard magmatism coeval with the Cachoeirinha orogen located to the southeast. The fine-grained granitic gneiss and charnockitic granulites represent the first record of widespread magmatism at 1.43-1.42 Ga in northern Rondonia. Their geochemical signatures and the slightly positive initial epsilon(Nd) values (+0.7 to +1.2) are very similar to those of the most evolved granites of the calc-alkaline Santa Helena batholith farther southeast. U-Pb monazite and Sm-Nd whole-rock-garnet ages demonstrate that a high-grade tectonometa-morphic episode occurred in this region at 1.33-1.30 Ga. This episode attained upper-amphibolite conditions and is interpreted as the peak of the Rondonian-San Ignacio orogeny. The U-Pb and Sm-Nd data presented here and data published on rapakivi granites elsewhere indicate that the east-central part of the RTP is a poly-orogenic region characterized by successive episodes of magmatism, metamorphism, and deformation between 1.75 and 0.97 Ga. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Electrical transport properties of doped poly (p-phenylene)

An experimental study of the temperature dependent dc electrical conductivity of doped poly (p-phenylene) in the range of 50-300 K has been presented. The results have been analyzed in the framework of some hopping models. We have observed that hopping models are not consistent with the temperature dependence of the conductivity data over the entire temperature range of measurement. We find that the logarithmic conductivity is proportional to T-beta, wherethe exponent beta is independent of temperature. It is shown that the most probable transport process in this material for the entire range of temperature is due to multiphonon-assisted hopping of the charge carriers that interact weakly with phonons. The parameters obtained from the fits of the experimental data to this model appear reasonable.

Spectroscopic and thermal characterization in poly(p-phenylene vinylene)/sol-gel silica sample

The absorption and luminescence spectra for the poly(p-phenylene vinylene)/sol-gel silica with different thermal treatments were measured. A considerable increase in the luminescence was observed for the polymer introduced into SiO2 matrix with thermal treatment at 120 degreesC. The thermal diffusivity of these samples was measured using the thermal lens technique, and the obtained value 3.3 x 10(-5) cm(2)/s (sample treated at 37 degreesC) is practically independent of the thermal treatment (37-150 degreesC). (C) 2003 Elsevier B.V. All rights reserved.

In vitro biocompatibility of a novel membrane of the composite poly(vinylidene-trifluoroethylene)/barium titanate

This study was aimed at investigating the in vitro biocompatibility of a novel membrane of the composite poly(vinylidene-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT). Osteoblastic cells were obtained from human alveolar bone fragments and cultured under standard osteogenic condition until subconfluence. First passaged cells were cultured on P(VDF-TrFE)/BT and expanded polytetrafluoroethylene (e-PTFE - control) membranes in 24-well plates. Cell adhesion and spreading were evaluated at 30 min, and 4 and 24 h. For proliferation assay, cells were cultured for 1, 7, and 10 days. Cell viability was detected by trypan blue at 7 and 10 days. Total protein content and alkaline phosphatase (ALP) activity were measured at 7, 14, and 21 days. Cultures were stained with Alizarin red at 21 days, for detection of mineralized matrix. Data were compared by ANOVA and Student t test. Cell attachment (p = 0.001), cell number (p = 0.001), and ALP activity (p = 0.0001) were greater on P(VDF-TrFE)/BT. Additionally, doubling time was greater on P(VDF-TrFE)/BT (p = 0.03), indicating a decreased proliferation rate. Bone-like nodule formation took place only on P(VDF-TrFE)/BT. The present results showed that both membranes are biocompatible. However, P(VDF-TrFE)/BT presented a better in vitro biocompatibility and allowed bone-like nodule formation. Therefore, P(VDF-TrFE)/BT could be an alternative membrane to be used in guided tissue regeneration. (c) 2006 Wiley Periodicals, Inc.

Morphology of poly(vinylidene fluoride) and poly(o-metoxyaniline) blends

Blends of poly(o-methoxyaniline) - POMA - and poly(vinylidene fluoride) - PVDF - of various compositions were prepared from organic solvent solutions. Flexible, free-standing and stretchable films were obtained by casting, which were characterized by conductivity measurements, electron microscopy and differential scanning calorimetry. As expected, the blends conductivity increases with increasing contents of the conducting polymer. The onset of the conductivity at low contents of conducting polymer indicates a low percolation threshold for the blends. Despite the presence of the conductive host, the blends displayed the crystalline spherulitic morphology and the beta-phase characteristic of pure PVDF. This morphology appears to be destroyed, however, if the film is stretched by zone-drawing.

Two-phase separation observed in thermally treated pellets of ClO4- doped poly(3-methylthiophene) from electron spin resonance measurements

A pressed pellet of CIO (-)(4) poly (3-methylthiophene) (P3MT) was heated for two hours at 85 degrees C and suddenly dropped in liquid nitrogen. A change was observed around 220 K in the Electron Spin Resonance (ESR) spectra when the sample was slowly cooled from room temperature. ESR line asymmetry parameter (A/B) showed two spatially separated phases. One was identified as a small metallic-like phase. The other phase, the larger one, makes a transition to a semiconducting Charge-Density Wave (CDW) state.

NMR study of ion-conducting organic-inorganic nanocomposites poly(ethylene glycol) - Silica - LiClO4

Hybrid organic-inorganic ionic conductors, also called ormolytes, were obtained by dissolution of LiClO4 into silica/poly(ethylene glycol) matrices. Solid-state nuclear magnetic resonance (NMR) was used to probe the inorganic phase structure (Si-29) and the effects of the temperature and composition on the dynamic behavior of the ionic species (Li-7) and the polymer chains (H-1 and C-13). The NMR results between -100 and +90 degrees C show a strong correlation with ionic conductivity and differential scanning calorimetry experiments. The results also demonstrate that the cation mobility is assisted by segmental motion of the polymer, which is in agreement with the results previously reported for pure poly(ethylene oxide), PEG, electrolytes.

Interaction between poly(ethylene glycol) and C12E8 investigated by dynamic light scattering, time-resolved fluorescence quenching, and calorimetry

Dynamic light scattering (DLS), time-resolved fluorescence quenching (TRFQ), and isothermal titration microcalorimetry have been used to show that, in dilute solution, low molecular weight poly(ethylene glycol) (PEG, M-w = 12 kDa) interacts with the nonionic surfactant octaethylene glycol n-dodecyl monoether, C12E8, to form a complex. Whereas the relaxation time distributions for the binary C12E8/water and PEG/water systems are unimodal, in the ternary mixtures they may be either uni- or bimodal depending on the relative concentrations of the components. At low concentrations of PEG or surfactant, the components of the relaxation time distribution are unresolvable, but the distribution becomes bimodal at higher concentrations of either polymer or surfactant. For the ternary system in excess surfactant, we ascribe, on the basis of the changes in apparent hydrodynamic radii and the scattered intensities, the fast mode to a single micelle, the surface of which is associated with the polymer and the slow mode to a similar complex but containing two or three micelles per PEG chain. Titration microcalorimetry results show that the interaction between C12E8, and PEG is exothermic and about 1 kJ mol(-1) at concentrations higher than the CMC of C12E8. The aggregation number, obtained by TRFQ, is roughly constant when either the PEG or the C12E8 concentration is increased at a given concentration of the second component, owing to the increasing amount of surfactant micelles inside the complex.

Gelation of siloxane-poly(oxypropylene) composites

The viscoelastic properties of siloxane-poly(oxypropylene) (PPO) nanocomposites prepared by the sol-gel process has been analyzed during gelation by dynamic rheological measurements. The changes of storage and loss moduli, complex viscosity and phase angle has been measured as a function of time showing the newtonian viscosity of the sol in the initial step of gelation, and its progressive transformation to a viscoelastic gel. The rheologic properties have been correlated to mass fractal, nearly linear growth models and percolation theory. This study, completed by quasi-elastic light scattering and Si-29 solid state nuclear magnetic resonance measurements, shows that the mechanisms of gelation of siloxane-PPO hybrids depend on the molecular weight of the polymer and on the pH of the hybrid sol. For hybrids prepared in acid medium, a polymerization involving silicon reactive species located at the extremity of the polymer chains and presenting a functionality f = 2 occurs, forming a fractal structure during the first stage of sol-gel transition. For samples prepared under neutral pH, the fractal growth is only observed for hybrids containing short polymer chains (M-w similar to 130 gmol(-1)). The fractal dimensionality determined from the change in the rheological properties, indicates that the fractal growth mechanism changes from reaction-limited to diffusion-limited aggregation when the molecular weight of the PPO increases from 130 to 4000 gmol(-1) and as catalyst conditions change from acidic to neutral. Near the gel point, these hybrid gels have the typical scaling behavior expected from percolation theory. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Unusual interactions binding iron tetrasulfonated phthalocyanine and poly(allylamine hydrochloride) in layer-by-layer films

Molecular-level interactions are found to bind iron tetrasulfonated phthalocyanine (FeTsPc) and the polyelectrolyte poly(allylamine hydrochloride) (PAH) in electroactive layer-by-layer (LBL) films. These interactions have been identified by comparing Fourier transform infrared (FTIR) and Raman spectroscopy data from bulk samples of FeTsPc and PAH with those from FeTsPc/PAH LBL films. of particular importance were the SO3- -NH3 interactions that we believe to bind PAH and FeTsPc and the interactions between unprotonated amine groups of PAH and the coordinating metal of the phthalocyanine. The multilayer formation was monitored via UV-vis spectroscopy by measuring the increase in the Q band of FeTsPc at 676 nm. Film thickness estimated with profilometry was ca. I I Angstrom per bilayer for films adsorbed on glass. Reflection absorption infrared spectroscopy (RAIRS) revealed an anisotropy in the LBL film adsorbed on gold with FeTsPc molecules oriented perpendicularly to the substrate plane. Cyclic voltammograms showed reproducible pairs of oxidation-reduction peaks at 1.07 and 0.81 V, respectively, for a 50-bilayer PAH/FeTsPc film at 50 mV/s (vs Ag/Ag+). The peak shape and current dependence on the scan rate suggest that the process is a diffusion controlled charge transport. In the presence of dopamine, the electroactivity of FeTsPc/PAH LBL films vanishes due to a passivation effect. Dopamine activity is not detected either because the interaction between Fe atoms and NH2 groups prevents dopamine molecules from coordinating with the Fe atoms.

Regeneration of poly-L-lysine modified carbon electrodes in the accumulation and cathodic stripping voltammetric determination of the cromoglycate anion

Cromoglycate is accumulated on a poly-L-lysine (PLL) modified carbon electrode best from pH 4 solution, where it is anionic and the PLL is cationic, and at which pH the cromoglycate gives a good reduction peak at -0.82 V. The PLL film can be regenerated readily by washing the electrode with 3 M sodium hydroxide solution, in which the PLL is deprotonated. Regeneration of the film is not required as frequently when larger amounts of PLL are incorporated into it. This allows standard addition procedures to be carried out without regenerating the electrode. Linear calibration graphs have been obtained typically in the range 0.1 - 1.5 mug ml(-1). Detection limits have been calculated to be 10 ng ml(-1). The standard addition method has been applied satisfactorily to diluted urine solutions. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Influence of solution treatment on the adsorption and morphology of poly(o-methoxyaniline) layer-by-layer films

It is shown that the adsorption and morphological properties of layer-by-layer films of poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS) are affected dramatically by different treatments of the POMA solutions employed to prepare the films. Whereas the dimension of the globular structures seen by atomic force microscopy increases non monotonically during film growth in parent POMA solution, owing to a competition of adsorption/desorption processes, it changes monotonically for the fractionated POMA. The roughness of the latter films depends on the concentration of the solution and saturates at a given size of the scan window. This allowed us to apply scaling laws that indicated a self-affine mechanism for adsorption of the treated POMA.

Modification of glassy carbon electrodes with a poly-L-lysine/glutaraldehyde film

A film of poly-L-lysine (PLL) adheres better to the surface of a glassy carbon electrode when the PLL is partially cross-linked by means of glutaraldehyde. A film composition of 97.5% PLL/2.5% glutaraldehyde gives good adhesion and retains the anionic exchange capability of the PLL. The performance of the film was tested with hexacyanoferrate(III) using electrochemical and nonelectrochemical accumulation.

Fibrin adhesive implant in wound healing repair of dental sockets with topical application of epsilon aminocaproic acid: Histological analysis

The aim of the study was to evaluate wound healing repair of dental sockets after topical application of 5% epsilon-aminocaproic acid (EACA) and the use of fibrin adhesive implant in rats under anticoagulant therapy with warfarin. Sixty Albinus wistar rats were used, divided into three groups of 20. In Group I, the animals were given 0.1 mL/100 mg of 0.9% saline solution per day, beginning 6 days before dental extraction and continuing throughout the experimental period. In Group II, the animals received 0.03 mL of sodium warfarin daily, beginning 6 days before the surgery and continuing until the day of sacrifice; after tooth extractions, the sockets were filled with fibrin adhesive material. In Group III the animals were treated as in Group II, and after extractions, the sockets were irrigated with 5 mL of 5% EACA and filled with the same fibrin adhesive material. All groups presented biological phases of wound healing repair, the differences being evident only in the chronology. The results obtained in Group III were very similar to those of Group I in the last period of wound repair, whereas Group II presented a late chronology compared to the other groups. © 2005 Wiley Periodicals, Inc.

Determination of iodide and idoxuridine at a glutaraldehyde-cross-linked poly-L-lysine modified glassy carbon electrode

The detection limit (about 0.017 mu g mL(-1)) for voltammetric determination of iodide (peak at +0.87 V vs. Ag/AgCl at pH 2) at a glutaraldehyde-cross-linked poly-L-lysine modified glassy carbon electrode involving oxidation to iodine was found to be several orders of magnitude lower than that for the voltammetric determination on a bare glassy carbon electrode. This method was applied successfully to the determination of iodide in two medicinal formulations. Idoxuridine was determined indirectly at the same electrode by accumulating it first at -0.8 V vs. Ag/AgCl. At this potential the C-I bond in the adsorbed idoxuridine is reduced giving iodide, which is then determined at the modified electrode. The method was successfully applied to the determination of idoxuridine in a urine sample.