Evaluation of mechanical and thermal properties after chemical degradation of PVC and HDPE geomembranes

Chemical compatibility between geomembranes and site-specific waste liquids should be assessed since the waste liquids are highly complex mixtures. This paper presents some considerations about the chemical compatibility of geomembranes and some results of mechanical tests in HDPE and PVC geomembranes that were exposed to leachate and chemical residue (niobium). PVC and HDPE geomembranes of two thicknesses were tested: 1.0, 2.0 mm (PVC) and 0.8, 2.5 mm (HDPE). The results obtained show that after exposure the PVC geomembranes (1.0, 2.0 mm) were more rigid and stiffer than fresh samples. The HDPE geomembranes, on the other hand, when exposed to leachate and niobium residue presented increases in deformation. Melt flow index (MFI) tests were also carried out to verify the oxidation. © 2013 ejge.

The correlation between electronic structure and antimalarial activity of alkoxylated and hydroxylated chalcones

Chalcones have shown potential to several pharmacological applications including antimalarial properties. We employed multivariate data analysis to correlate the antimalarial activity with electronic structure descriptors obtained through quantum mechanical calculations. The results show high statistical significance and bring valuable insights in order to design new compounds. © 2013 Springer Science+Business Media New York.

Quantum mechanical modeling of excited electronic states and their relationship to cathodoluminescence of BaZrO3

First-principles calculations set the comprehension over performance of novel cathodoluminescence (CL) properties of BaZrO3 prepared through microwave-assisted hydrothermal. Ground (singlet, s*) and excited (singlet s** and triplet t**) electronic states were built from zirconium displacement of 0.2 Å in {001} direction. Each ground and excited states were characterized by the correlation of their corresponding geometry with electronic structures and Raman vibrational frequencies which were also identified experimentally. A kind of optical polarization switching was identified by the redistribution of 4dz2 and 4dxz (Zr) orbitals and 2pz O orbital. As a consequence, asymmetric bending and stretching modes theoretically obtained reveal a direct dependence with their polyhedral intracluster and/or extracluster ZrO6 distortions with electronic structure. Then, CL of the as-synthesized BaZrO3 can be interpreted as a result of stable triplet excited states, which are able to trap electrons, delaying the emission process due to spin multiplicity changes. © 2013 AIP Publishing LLC.

Eumelanin thin films: Solution-processing, growth, and charge transport properties

Eumelanin pigments show hydration-dependent conductivity, broad-band UV-vis absorption, and chelation of metal ions. Solution-processing of synthetic eumelanins opens new possibilities for the characterization of eumelanin in thin film form and its integration into bioelectronic devices. We investigate the effect of different synthesis routes and processing solvents on the growth, the morphology, and the chemical composition of eumelanin thin films using atomic force microscopy and X-ray photoelectron spectroscopy. We further characterize the films by transient electrical current measurements obtained at 50% to 90% relative humidity, relevant for bioelectronic applications. We show that the use of dimethyl sulfoxide is preferable over ammonia solution as processing solvent, yielding homogeneous films with surface roughnesses below 0.5 nm and a chemical composition in agreement with the eumelanin molecular structure. These eumelanin films grow in a quasi layer-by-layer mode, each layer being composed of nanoaggregates, 1-2 nm high, 10-30 nm large. The transient electrical measurements using a planar two-electrode device suggest that there are two contributions to the current, electronic and ionic, the latter being increasingly dominant at higher hydration, and point to the importance of time-dependent electrical characterization of eumelanin films. This journal is © 2013 The Royal Society of Chemistry.

Analysis of electronic structure of boron nitride nanotubes with different positions of intrinsic impurities

The pristine boron nitride nanotubes have a large direct band gap around 5 eV. This band gap can be engineered by doping. We investigate electronic structure of the doped hexagonal boron nitride (5,5) nanotubes using the linearized augmented cylindrical wave method. In particular, this work focuses on systematical study of the band gap and the density of states around the Fermi-level when the nanotubes are doped by intrinsic impurities of two substitutional boron atoms in a super cell and a comparative analysis of the relative stability of three structures studied here. This corresponds to 3.3% of impurity concentration. We calculate 29 configurations of the nanotubes with different positions of the intrinsic impurities in the nanotube. The band gap and density of states around the Fermi level show strong dependence on the relative positions of the impurity atoms. The two defect sub bands called D^∏(B) appear in the band gap of the pristine nanotube. The doped nanotubes possess p-type semiconductor properties with the band gap of 1.3-1.9 eV.

Effect of calcium on the structural properties of Ba(1-x)Ca (x) TiO3 particles synthesized by complex polymerization method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of Sm3+ doping on the dielectric properties of CaCu3Ti4O12 ceramics synthesized via autocombustion

Ca-1 -xSmxCu3Ti4O12 (x = 0.0, 0.2, 03) electronic ceramics were fabricated via the chemical route using metal nitrate solutions in order to improve the dielectric properties of this ceramic. X-ray diffraction (XRD) analysis indicated the formation of a single CaCu3Ti4O12 (CCTO). Grain size of the samples doped with Sm3+ was in the range of 1-2 mu m, as opposed to 50-100 mu m in the pure samples of CCTO. The cutoff frequency with the doping was remarkably shifted, from 1 MHz (pure CCTO) to 10 MHz (doped CCTO). Meanwhile, the real dielectric (epsilon(r)) and imaginary dielectric (epsilon '') constants showed a decrease as the doping was increased. (C) 2013 Elsevier B.V. All rights reserved.

Structural and thermal properties of spray-dried methotrexate-loaded biodegradable microparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Phenomenological Interpretation of Impedance/Capacitance Measurements on Organic Electronic Devices Under Illumination

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

Electronic transport in patterned graphene nanoroads

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

Effect of the length of alkyl side chains in the electronic structure of conjugated polymers

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

Effect of Zn2+ ions on the structure, morphology and optical properties of CaWO4 microcrystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Transport properties of polycrystalline boron doped diamond

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hybridization effects on the out-of-plane electron tunneling properties of monolayers: is h-BN more conductive than graphene?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of the concentration of Sb2O3 on the electrical properties of SnO2 varistors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)