Materials Literature
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A quitosana é um polissacarídeo linear obtido da desacetilação da quitina. As propriedades físico-químicas da quitosana são função do grau médio de acetilacão <img border=0 id="_x0000_i1026" src="../../../../img/revistas/po/v13n4/19880x1.gif" align=absmiddle>e da massa molar média (<img border=0 id="_x0000_i1…
A method is reported for the fabrication of wires with extended pore structures. Nanospheres are initially infiltrated into the one-dimensional channels of alumina or polymer porous membranes. Metal is then electrochemically deposited within the channels. Removal of the membrane and nanospheres results in porous wires…
The one-pot corrole synthesis first reported by the Gross and Paolesse groups appears to have evolved into a remarkably general and predictable self-assembly based synthetic reaction. Gross's solvent-free procedure (refs 8 and 9) has proven particularly effective in our hands and, in fact, more general than originally…
Electron injection dynamics from Ru(dcbpyH 2 ) 2 (NCS) 2 (RuN3) and (Bu 4 N) 2 Ru(dcbpyH) 2 (NCS) 2 (N719) to nanocrystalline ZnO thin films were studied using transient IR spectroscopy. The injection dynamics using 400 nm excitation were found to be biphasic, consisting of a distinct <100 fs component (14−20%) and sl…
We present experimental transient absorption (TA) results on the dynamics of electron relaxation and electron transfer in cadmium sulfide quantum dots (QDs) grown by chemical bath deposition techniques on nanocrystalline oxide substrates. The quantum dots are prepared in situ in nanocrystalline titanium dioxide (TiO 2…
An effective method for synthesizing ZnS-core/carbon-sheath nanocables and nanocable-aligned ZnS tetrapod nanocrystals has been developed. Nanocable heterostructures and nanocable-linked ZnS tetrapods were synthesized in a controllable way. The tetrapods are single crystalline cubic ZnS with triangular-prism branches…
Recent experiments have shown that carbon nanotubes exhibit excellent electron field emisson properties with high current densities at low electric fields. Here we present theoretical investigations that incorporate geometrical effects and the electronic structure of nanotubes. The electric field is dramatically enhan…
Epitaxial cuprous oxide, Cu2O, nanocrystals are deposited electrochemically onto n-InP(001). The lattice of the Cu2O is rotated 45° around the common [001] axis normal to the substrate plane. The shape of the Cu2O nanocrystals depends on the pH of the solution. Nanopyramids form at pH 9, and nanocubes form at pH 12.
Al 2 O 3 reinforced by SiC whiskers (Al 2 O 3 /SiC‐W) was hot‐pressed to investigate the crack‐healing behavior. Semielliptical surface cracks of 100 μm in surface length were introduced using a Vickers indenter. The specimens containing precracks were crack‐healed at temperatures between 1000° and 1300°C for 1 h in a…
Metamaterials composed of metal-dielectric nanostructures are engineered to have an effective refractive index less than unity at optical wavelengths. The effect of total external reflection is demonstrated when light from vacuum is incident onto these materials at an angle exceeding the critical angle defined by Snel…
In this paper, we propose a new dynamic model to describe the hysteresis phenomenon in harmonic drives. The experimental observation of the dynamic torque-displacement relationship for a harmonic drive shows a hysteresis characteristic indicating the simultaneous presence of energy storage and energy dissipation mecha…
A review is presented of one-dimensional cutting lines that are utilized to obtain the physical properties of carbon nanotubes from the corresponding properties of graphite by the zone-folding scheme. Quantization effects in general low-dimensional systems are briefly discussed, followed by a more detailed considerati…
ClpX, a heat shock protein 100 chaperone, which acts as the regulatory subunit of the ATP-dependent ClpXP protease, is responsible for intracellular protein remodeling and degradation. To provide a structural basis for a better understanding of the function of the Clp ATPase family, the crystal structures of Helicobac…
The laser action in a dye-doped cholesteric liquid crystal has been investigated as a function of temperature. The discontinuous shift of the lasing wavelength has been observed. It has also been found that the shift of the stop band in the cholesteric liquid crystal is discontinuous when the size of the measured area…
A trans type of doubly N-confused isomer of NCP (trans-N2CP) was synthesized via N-confused fused porphyrin (NcFP). The aromatic feature of trans-N2CP due to 18pi electronic system is contrasted to the weak aromaticity of cis-derivative. The solid-state structure of trans-N2CP exhibits pi-stacking column, while the Cu…
Samples with the chemical formula Cu0.5Zn0.5Fe2−xRxO4 (R = La, Nd, Sm and Gd; x = 0 and 0.1) were prepared by the standard ceramic method. The real part of the dielectric constant ε′ and the ac electrical conductivity σac are measured and the dielectric loss tangent tan δ is calculated in the frequency range 50–105 Hz…
The introduction of a fifth group of amphiboles, the Na–Ca–Mg–Fe–Mn–Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 atoms per formula unit, with members whittakerite and ottoliniite, has been required by recent discoveries of B(Li,Na) amphiboles. These, and other new discoveries,…
We present results of a joint computational and experimental study for a series of annulated metalloporphyrins in order to establish structure−property relationships. Specifically, we have examined the effects of substitution by meso -tetraphenylation, tetrabenzo and tetranaphtho annulation, and effects of changing th…
The objective of this paper is to study the evolution of the failure probability of the concrete beams to estimate the service life of a sea bridge in the southeast region of Brazil. The mechanism of deterioration analyzed in the study was the corrosion of the reinforcing bars. The models utilized for that are related…
Flexible, free-standing piezo and pyroelectric composite with 0 to 3 connectivity was made up from Lead Zirconate Titanate (PZT) powder and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) copolymer. The pyroelectric and the piezoelectric longitudinal (d33) coefficients were measured. A 50/50 vol.% PZT/PVDF-HF…