Thermal degradation and lifetime estimation of poly(ether imide)/carbon fiber composites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Zidovudine-poly (L-lactic acid) solid dispersions with improved intestinal permeability prepared by supercritical antisolvent process

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

Non ohmic gigahertz conductivity in pressed pellets of ClO4 doped poly(3-methylthiophene)

ESR measurements In pressed pellets of doped Poly(3-Methylthiophene)(P3MT) were performed at 10 K and 50 K after cooling the system slowly from room temperature to 110 K, quenching to 77 K and then to 10 K. ESR line asymmetry (A/B) as a function of microwave power was observed and 9.4 GHz conductivity was obtained from Dyson's theory. The data is discussed in terms of Charge-Density Wave (CDW) depinning. At 50 K the threshold electric field is estimated to be less than 1 V/cm. At 10 K a subtle pinning of the CDW was observed around 15 mW.

Photopatternable di-ureasil-zirconium oxocluster organic-inorganic hybrids as cost effective integrated optical substrates

Organic-inorganic hybrids containing methacrylic acid (McOH, CH(2)= C(CH(3))COOH)) modified zirconium tetrapropoxide, Zr(OPr(n))(4), classed as di-ureasil-zirconium oxo-cluster hybrids, have been prepared and structurally characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectroscopies, Si and C nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). XRD and SAXS results have pointed out the presence of Si- and Zr-based nanobuilding blocks (NBBs) dispersed into the organic phase. Inter-NBBs correlation distances have been estimated for the pure di-ureasil and a model compound obtained. by hydrolysis/condensation of Zr(OPr(n))(4):McOH (molar ratio 1: 1): d(Si) approximate to 26 +/- 1 angstrom and d(Zr) approximate to 16 +/- 1 angstrom, respectively. In the case of the di-ureasil-zirconium oxo-cluster hybrids, these distances depend on the Zr relative molar percentage (rel. mol. Zr %) (d(Si) ranges from 18 to 25 angstrom and d(Zr) from 14 to 23 angstrom, as the rel. mol. Zr % increases from 5 to 75), suggesting that the Si- and Zr-based clusters are interconstrained. Complementary data from FT-IR, FT-Raman, (29)Si and (13)C NMR, and AFM support to a structural model where McOH-modified Zr-based NBBs (Zr-OMc) are present over the whole range of composition. At low Zr-OMc contents (rel. mol. Zr % <30) the clusters are well-dispersed within the di-ureasil host, whereas segregation occurs at the 0.1 mu m scale at high Zr-OMc concentration (rel. mol. Zr % = 50). No Zr-O-Si heterocondensation has been discerned. Monomode waveguides, diffractions gratings, and Fabry-Perot cavities have been written through the exposure of the hybrid monoliths to UV light. FT-Raman has shown that the chemical process that takes place under illumination is the polymerization of the methacrylate groups of the Zr-OMc NBBs. The guidance region in patterned channels is a Gaussian section located below the exposed surface with typical dimensions of 320 mu m wide and 88 mu m deep. The effective refractive index is 1.5162 (maximum index contrast on the order of 1 x 10(-4)) and the reflection coeficient of the Fabry-Perot cavity (formed by a grating patterned into a 0.278 cm channel) is 0.042 with a free spectral range value of 35.6 GHz.

Production and characterization of poly-(3-hydroxybutyrate) from recombinant Escherichia coli grown on cheap renewable carbon substrates

Although the biopolymer poly-(3-hydroxybutyrate), P[3HB], presents physicochemical properties that make it an alternative material to conventional plastics, its biotechnological production is quite expensive. As carbon substrates contribute greatly to P[3HB] production cost, the utilization of a cheaper carbon substrate and less demanding micro-organisms should decrease its cost. In the present study a 23 factorial experimental design was applied, aiming to evaluate the effects of using hydrolysed corn starch (HCS) and soybean oil (SBO) as carbon substrates, and cheese whey (CW) supplementation in the mineral medium (MM) on the responses, cell dried weigh (DCW), percentage P[3HB] and mass P[3HB] by recombinant Escherichia coli strains JM101 and DH10B, containing the P[3HB] synthase genes from Cupriavidus necator (ex-Ralstonia eutropha). The analysis of effects indicated that the substrates and the supplement and their interactions had positive effect on CDW. Statistically generated equations showed that, at the highest concentrations of HCS, SO and CW, theoretically it should be possible to produce about 2 g L(1) DCW, accumulating 50% P[3HB], in both strains. To complement this study, the strain that presented the best results was cultivated in MM added to HCS, SBO and CW ( in best composition observed) and complex medium (CM) to compare the obtained P[3HB] in terms of physicochemical parameters. The obtained results showed that the P[3HB] production in MM (1.29 g L(-1)) was approximately 20% lower than in CM (1.63 g L(-1)); however, this difference can be compensated by the lower cost of the MM achieved by the use of cheap renewable carbon sources. Moreover, using differential scanning calorimetry and thermogravimetry analyses, it was observed that the polymer produced in MM was the one which presented physicochemical properties (Tg and Tf) that were more similar to those found in the literature for P[3HB].

Hemocompatibility of poly(epsilon-caprolactone) lipid-core nanocapsules stabilized with polysorbate 80-lecithin and uncoated or coated with chitosan

The hemocompatibility of nanoparticles is of critical importance for their systemic administration as drug delivery systems. Formulations of lipid-core nanocapsules, stabilized with polysorbate 80-lecithin and uncoated or coated with chitosan (LNC and LNC-CS), were prepared and characterized by laser diffraction (D[4,3]: 129 and 134 nm), dynamic light scattering (119 nm and 133 nm), nanoparticle tracking (D50: 124 and 139 nm) and particle mobility (zeta potential: -15.1 mV and + 9.3 mV) analysis. In vitro hemocompatibility studies were carried out with mixtures of nanocapsule suspensions in human blood at 2% and 10% (v/v). The prothrombin time showed no significant change independently of the nanocapsule surface potential or its concentration in plasma. Regarding the activated partial thromboplastin time, both suspensions at 2% (v/v) in plasma did not influence the clotting time. Even though suspensions at 10% (v/v) in plasma decreased the clotting times (p < 0.05), the values were within the normal range. The ability of plasma to activate the coagulation system was maintained after the addition of the formulations. Suspensions at 2% (v/v) in blood showed no significant hemolysis or platelet aggregation. In conclusion, the lipid-core nanocapsules uncoated or coated with chitosan are hemocompatible representing a potential innovative nanotechnological formulation for intravenous administration. (C) 2012 Elsevier B. V. All rights reserved.

Complexation of 2-acetylpyridine- and 2-benzoylpyridine-derived hydrazones to copper(II) as an effective strategy for antimicrobial activity improvement

Complexes [Cu(2AcPh)Cl]center dot 2H(2)O (1), [Cu(2AcpClPh)Cl]center dot 2H(2)O (2), [Cu(2AcpNO(2)Ph)Cl] (3), [Cu(2BzPh)Cl] (4). [Cu(2BzpClPh)Cl] (5) and [Cu(2BzpNO(2)Ph)Cl] (6) were obtained with 2-acetylpyridine-phenylhydrazone (H2AcPh), 2-acetylpyridine-para-chloro-phenylhydrazone (H2AcpClPh), 2-acetylpyridine-para-nitro-phenylhydrazone (H2AcpNO(2)Ph), 2-benzoylpyridine-phenylhydrazone (H2BzPh), 2-benzoylpyridine-para-chloro-phenylhydrazone (H2BzpClPh) and 2-benzoylpyridine-para-nitro-phenylhydrazone (H2BzpNO(2)Ph). The hydrazones showed poor antibacterial effect against Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa but demonstrated significant antifungal activity against Candida albicans. Upon coordination to copper(II) the antibacterial and antifungal activities appreciably increased. H2AcpClPh, H2BzpClPh and their copper(II) complexes (2) and (5), respectively, were as active as fluconazole against C. albicans. (C) 2012 Elsevier Ltd. All rights reserved.

Preparation and characterization of poly(vinyl butyral)-polyaniline-montmorillonite nanocomposites

Poly(vinyl butyral)-polyaniline-sodium montmorillonite nanocomposites were prepared via polymerization of aniline between clay mineral platelets at two different pH levels (2.0 and 5.0), followed by dispersion of the polyaniline-sodium montmorillonite nanocomposite in a poly(vinyl butyral) solution. A comparison was made of the effect of the pH levels and the polyaniline-sodium montmorillonite nanocomposite precursor on the final structures of the poly(vinyl butyral) nanocomposites and their electrical conductivities. X-ray diffraction patterns revealed the formation of nanocomposites at both pH levels. UV-Vis spectra indicated that the polyaniline formed at both pH levels was conductive, with the UV-Vis spectra presenting a band at 420 nm corresponding to the polaronic form and the beginning of a new band at 600 nm indicating the presence of polaronic segments. FTIR spectra revealed the peaks of the groups present in polyaniline and poly(vinyl butyral) nanocomposites. The electrical conductivities of the polyaniline and poly(vinyl butyral) nanocomposites prepared at pH 2.0 were lower than those of the same nanocomposites prepared at pH 5.0, probably due to the lower formation of polyaniline chains in a more acidic dispersion and to the final configuration of polyaniline in the nanocomposites.

In vitro and in vivo evaluation of the biocompatibility of a calcium phosphate/poly(lactic-co-glycolic acid) composite

This study assess the effects of bioceramic and poly(lactic-co-glycolic acid) composite (BCP/PLGA) on the viability of cultured macrophages and human dental pulp fibroblasts, and we sought to elucidate the temporal profile of the reaction of pulp capping with a composite of bioceramic of calcium phosphate and biodegradable polymer in the progression of delayed dentine bridge after (30 and 60 days) in vivo. Histological evaluation of inflammatory infiltrate and dentin bridge formation were performed after 30 and 60 days. There was similar progressive fibroblast growth in all groups and the macrophages showed viability. The in vivo study showed that of the three experimental groups: BCP/PLGA composite, BCP and calcium hydroxide (Ca(OH)(2)) dentin bridging was the most prevalent (90 %) in the BCP/PLGA composite after 30 days, mild to moderate inflammatory response was present throughout the pulp after 30 days. After 60 days was observed dentine bridging in 60 % and necrosis in 40 %, in both groups. The results indicate that understanding BCP/PLGA composite is biocompatible and by the best tissue response as compared to calcium hydroxide in direct pulp capping may be important in the mechanism of delayed dentine bridge after 30 and 60 days.

Is the poly (methylene blue)-modified glassy carbon electrode an adequate electrode for the simple detection of thiols and amino acid-based molecules?

This paper describes the preparation, characterization, and use of poly (methylene blue) (PMB)-modified glassy carbon electrodes (GCE) (GCE-PMB) in the detection of the thiols L-cysteine (L-CySH) and N-acetyl cysteine (Acy), and the herbicide glyphosate (GLYP) in pH 5.3 aqueous solution. The polymer film prepared by electropolymerization showed different characteristics such as robustness, stability, and redox properties satisfactorily. The surface coverage concentration (Gamma) of PMB was found to be 7.90 x 10(-9) - mol cm(-2). Moreover, we observed strong adhesion of the polymer film to the electrode surface. The results using GCE-PMB as a sensor indicated that this modified electrode exhibited electrocatalytic activity toward the detection of thiols and glyphosate in 0.1 mol L-1 KO (pH 5.3). Meanwhile, strong adsorption of the analytes on the GCE-PMB electrodes was also observed. Otherwise, using a low concentration (1 x 10(-4) mol L-1) of L-cysteine and N-acetyl cysteine and 8.9 x 10(-6) mol L-1 of glyphosate, separately, it was possible to observe a well-defined electrochemical response, thus providing an opportunity to further understand the applicability of PMB as a sensor for amino acid-based molecules. (C) 2012 Elsevier B.V. All rights reserved.

Evaluation of the flexural strength and elastic modulus of resins used for temporary restorations reinforced with particulate glass fibre

Objective: The flexural strength and the elastic modulus of acrylic resins, Dencor, Duralay and Trim Plus II, were evaluated with and without the addition of silanised glass fibre. Materials and methods: To evaluate the flexural strength and elastic modulus, 60 test specimens were fabricated with the addition of 10% ground silanised glass fibres for the experimental group, and 60 without the incorporation of fibres, for the control group, with 20 test specimens being made of each commercial brand of resin (Dencor, Duralay and Trim Plus II) for the control group and experimental group. After the test specimens had been completed, the flexural strength and elastic modulus tests were performed in a universal testing device, using the three-point bending test. For the specimens without fibres the One-Way Analysis of Variance and the complementary Tukey test were used, and for those with fibres it was not normal, so that the non-parametric Mann-Whitney test was applied. Results: For the flexural strength test, there was no statistical difference (p > 0.05) between each commercial brand of resin without fibres [Duralay 84.32(+/- 8.54), Trim plus 85.39(+/- 6.74), Dencor 96.70(+/- 6.52)] and with fibres (Duralay 87.18, Trim plus 88.33, Dencor 98.10). However, for the elastic modulus, there was statistical difference (p > 0.01) between each commercial brand of resin without fibres [Duralay 2380.64 (+/- 168.60), Trim plus 2740.37(+/- 311.74), Dencor 2595.42(+/- 261.22)] and with fibres (Duralay 3750.42, Trim plus 3188.80, Dencor 3400.75). Conclusion: The result showed that the incorporation of fibre did not interfere in the flexural strength values, but it increased the values for the elastic modulus.

Coordination of water to organolead(IV) nitrates: The examples of [PbPh2(NO3)(2)(H2O)(2)] and [PbMe3(NO3)(H2O)]

The compound [PbPh2(NO3)(2)(H2O)(2)] was synthesized and characterized by spectroscopic methods (IR; H-1, C-13 and Pb-207 NMR) and mass spectrometry. An X-ray diffraction study showed that the crystal is a supramolecular tridimensional network of hydrogen-bonded PbPh2(NO3)(2)(H2O)(2) units in which the Pb atom is octacoordinated and adopts a distorted hexagonal bipyramidal geometry, with four O (bidentate nitrate) and two O (water) atoms in equatorial positions and two C-phenyl atoms in axial positions. The crystal of [PbMe3(NO3)(H2O)], obtained as a byproduct in the synthesis of PbMe2(NO3)(2), contains chains of hydrogen-bonded PbMe3(NO3)(H2O) units in which the Pb atom is pentacoordinated with a slightly distorted trigonal bipyramidal environment. In this arrangement the three C-methyl atoms are equatorial and the O atoms from the monodentate nitrate and the water molecule are axial. (C) 2011 Elsevier Ltd. All rights reserved.

On the Reaction of Lupulones, Hops beta-Acids, with 1-Hydroxyethyl Radical

Lupulones, hops beta-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 x 10(8) and 2.6 x 10(8) L mol(-1) s(-1) at 25.0 +/- 0.2 degrees C in ethanol water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is Delta G degrees = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops beta-acids as the reaction centers rather than the beta,beta'-triketone moiety.

Terbium(III) and dysprosium(III) 8-connected 3D networks containing 2,5-thiophenedicarboxylate anion: Crystal structures and photoluminescence studies

Two novel coordination polymers with the formula {[Ln(2)(2,5-tdc)(3)(dmso)(2)].H2O}(n) (Ln = Tb(III) for (1) and Dy(III) for (2)), (2,5-tdc(2-) = 2,5-thiophenedicarboxylate and dmso = dimethylsulfoxide) have been synthesized by the diffusion method and characterized by thermal analysis, vibrational spectroscopy and single crystal X-ray diffraction analysis. Structure analysis reveals that 2,5-tdc(2-) play a versatile role toward different lanthanide ions to form three-dimensional metal-organic frameworks (MOFs) in which the lanthanides ions are heptacoordinated. Photophysical properties were studied using excitation and emission spectra, where the photoluminescence data show the high emission intensity of the characteristic transitions D-5(4 ->) F-7(J) (J= 6, 5, 4 and 3) for (1) and (F9/2 -> HJ)-F-4-H-6 (J = 15/2, 13/2 and 11/2) for (2), indicating that 2,5-tdc(2-) is a good sensitizer. (C) 2012 Elsevier Ltd. All rights reserved.