Materials Literature
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A tenacificação da matriz vítrea de poliestireno (PS) pela adição de borracha polibutadiênica, que tem como conseqüência um aumento de sua resistência ao impacto, origina um polímero com características singulares, o Poliestireno de Alto Impacto (HIPS). Durante a polimerização in situ de estireno em uma solução de bor…
The visualization of mesopores and defects in porous molecular sieves, as well as of the incorporation dynamics and spatial distribution of guest molecules, is achieved by optical confocal microscopy of single crystals immersed in solutions of fluorescent dyes. The Figure shows a fluorescence image of a silicalite cry…
The bending and tapering of microtwin needles at the interface between two martensite laminates in ${\mathrm{Ni}}_{65}{\mathrm{Al}}_{35}$ are addressed. A theory is presented, based on the assumption that the microstructure is essentially stress-free; it predicts a linear relationship between the bending and tapering…
Single crystals of γ-Li 3 PO 4 have been grown from flux. The 4 × 8 × 9-mm crystals have the cleavage along the [010] and [120] directions. The anisotropy in ionic conductivity in the grown crystals, ((σ ‖ a )/(σ ‖ b ) = 2.5 and (σ ‖ a )/(σ ‖ c ) = 1.3), is explained by specific features of the γ-Li 3 PO 4 structure.
Direct formation of a large vacancy loop by displacement cascade in α-Fe has been observed for the first time in a molecular dynamics (MD) computer simulation study. This phenomenon occurred in one anomalous run out of 100 simulations of 50 keV primary knock-on atom energy cascades, in which one large displacement cas…
Ab initio coupled perturbated Hartree−Fock calculations, using 6-31G** basis sets, on a heterocyclic zwitterionic molecule with a σ-spacer between the donor and the acceptor ring shows a static first hyperpolarizability (β 0 ) of around 240 × 10 -30 esu. Substitution of electron withdrawing functional groups, such as…
Optical absorption of nanocrystalline thin films can be influenced by the presence of both porosity and grain size effects. If both are present simultaneously, their effects are difficult to separate. In this study it is shown that the combination of uv-vis transmittance and reflectance measurements on porous CeO2 fil…
Monte Carlo simulations have been performed for the linear tangent hard sphere model. The models considered in this work consisted of m=3, 4, 5, 6, and 7 monomer units. For the models m=3 and m=4 we find an isotropic fluid and an ordered solid. For the m=5 model we find the sequence of phases isotropic–nematic–smectic…
We discuss mathematical models of capillary flow in complex geometries representative of the void spaces formed between fibers in a textile yarn. Moisture transport in textile yarns and fabrics is an important factor affecting physiological comfort. We have extended an existing analytical model for capillary flow in c…
This paper discusses environmental management and technical considerations for the decommissioning, closure and reclamation of a mine site. The management and technical aspects discussed include planning; decommissioning, closure and reclamation design basis and performance measures; implementation; monitoring; and fi…
We discuss the behaviour of a thin soap film facing a frame element: the pressure in the Plateau border around the frame is lower than the film pressure, and the film thins out over a certain distance λ( t ), due to the formation of a well-localized pinched region of thickness h ( t ) and extension w ( t ). We constru…
Microstructural changes associated with the martensitic transformation from cubic (parent phase) to trigonal (R phase) which occurs with decreasing temperature in Ti50Ni48Fe2 have been intensively studied by in-situ electron microscopy. Although the parent phase shows a characteristic microstructure with small domains…
Abstract Weathering profiles developed on the top surface of a bentonite (containing Al-Mg montmorillonite) and a K-bentonite (containing mixed-layer illite-smectite (I-S)) under Central European temperate conditions were studied by XRD, HRTEM, FTIR, K-Ar and chemical analyses. Weathering of montmorillonite results in…
The morphological metastability of spontaneous crystallization from the melt of short-chain semiflexible homopolymers was studied through dynamic Monte Carlo simulations of a lattice multiple-chain system. Frictional hindrance for the sliding diffusion of the chains in the crystallites was employed to enhance the meta…
Red single crystals of AuSO4 have been obtained by evaporating a solution of Au(OH)3 in concentrated sulfuric acid. The crystal structure (orthorhombic, Pbca, Z = 8, a = 854.9(2), b = 824.9(3), c = 1001.1(4) pm) exhibits the dumbbell shaped Au24+ cation (bond length Au–Au: 249 pm) which is coordinated by two chelating…
BaTi 1- x Mn x O 3 solid solutions with 0≤ x ≤0.04 were synthesized in reducing atmosphere ( P O2 <10 -9 Pa) and in air at 1350°C for 2 h. The effect of Mn ions with different valences on the crystal structure of BaTiO 3 was studied by the room-temperature Raman scattering, electron spin resonance (ESR) and X-ray p…
Esters or carbonates of N-hydroxypyridine-2-thione (Barton esters) were appended to either carboxymethyl or hydroxypropyl cellulose. Irradiation of the cellulose bound Barton esters in monomer initiated free radical graft copolymerization with minimal concomitant homopolymerization. Grafting of styrene to carboxymethy…
A method for estimating the signal-to-noise ratio from a single image is presented in this paper. The autocorrelation-based technique requires that image details be correlated over distances of a few pixels, while the noise is assumed to be uncorrelated from pixel to pixel. The latter is shown to be a good approximati…
The infrared to visible upconversion processes have been investigated for ${\mathrm{Nd}}^{3+}$-doped chalcohalide glasses with different halide modifiers by using steady-state and time-resolved laser spectroscopy. Two different upconversion mechanisms have been identified depending on the infrared excitation wavelengt…
Allosteric regulation of key metabolic enzymes is a fascinating field to study the structure-function relationship of induced conformational changes of proteins. In this review we compare the principles of allosteric transitions of the complex classical model aspartate transcarbamoylase (ATCase) from Escherichia coli,…