Materials Literature
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Mixed-metal mesocates [M2Pd3Br6L6]4− (M=TiIV, SnIV; L=4-diphenylphosphanyl-catecholate) have been synthesized, in which the two incommensurate symmetry elements generated by the different metal ions are linked by a rigid, bifunctional ligand to generate a C3h-symmetrical cluster (see picture).
We study both the longitudinal and transverse fluctuations of a semiflexible filament. Using scaling arguments and numerical simulations, we find several regimes for the longitudinal fluctuations which, for short times, scale as $〈\ensuremath{\delta}{r}_{\ensuremath{\Vert}}^{2}〉\ensuremath{\sim}{t}^{7/8}$ and are corr…
The fine-tuning of the critical temperature and the coercivity of compounds with two interpenetrating quasi-perpendicular honeycomblike networks (see diagram) are presented. Molecule-based magnets of formula [(Etrad)2M2{Cu(opba)}3]⋅S and mixed compounds of formula [Etrad2Mn2−2xCo2xCu3] were synthesized and their magne…
A molecular composite prepared by the solubilization of pyrene in poly(propyleneimine) dendrimers is investigated by fluorescence and absorption spectroscopy at a range of pH values. The release of pyrene is induced in acidic media, while pyrene incorporation is favored in basic environments, as shown here.
The morphology of surfaces of arbitrary orientation in the presence of step and kink Ehrlich-Schwoebel effects (SESE and KESE) during growth is studied within the framework of a model in which steps are continuous lines, and is illustrated by a simple solid-on-solid model. For vicinal surfaces KESE induces an instabil…
Annealing of amorphous Si/SiO2 superlattices produces Si nanocrystals. The crystallization has been studied by transmission electron microscopy and x-ray analysis. For a Si layer thinner than 7 nm, nearly perfect nanocrystals are found. For thicker layers, growth faults and dislocations exist. Decreasing the a-Si laye…
The normal state conductivity of a system of interacting large polarons is calculated within the Random Phase approximation and some numerical results are presented. The behaviour of the optical absorption as a function of the charge carrier density and of the temperature is analyzed for different values of the electr…
This paper contains the notes of lectures on the theory of interlayer exchange coupling presented at the 30-th Ferienschule of the Institut fuer Festkoerperforschung, Forschungszentrum Juelich, March 1999.
New framework materials composed of well-defined vanadium oxide clusters were prepared by low-temperature reactions and characterized by X-ray crystal structure analysis. The structures of these solids contain {V18O42} cages linked into two interpenetrating three-dimensional networks by bridging {M(H2O)4} groups (M=Fe…
In a recent Letter, Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] proposed a novel scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses. However, this approach cannot be applied to alkali germanate glasses whose alkali content varies by…
Noncompatibilized and compatibilized ABS–nylon1010 blends were prepared by melt mixing. Polystyrene and glycidyl methacrylate (SG) copolymer was used as a compatibilizer to enhance the interfacial adhesion and to control the morphology. This SG copolymer contains reactive glycidyl groups that are able to react with PA…
Meltrheological behavior, phase morphology, and impact properties of isotactic-polypropylene (iPP)-based blends containing ethylene–propylene copolymer (EPR) synthesized by means of a titanium-based catalyst with very high stereospecific activity (EPRTi) were compared to those of iPP/EPR blends containing EPR copolyme…
The results of a comparison between the effects of sodium hydroxide and calcium hydroxide on poly(ethylene terephthalate) fabrics are presented. Calcium hydroxide can produce weight-loss effects similar to an aqueous solution of sodium hydroxide. The effects of some treatment variables on weight loss, fiber diameter,…
The reactions between hexamethylenetetramine (HMTA) and compounds which model novolac resins have been studied by 13C- and 15N-NMR techniques. The dimer and tetramer compounds vary in molecular size and structure and react with HMTA to yield benzylamines and benzoxazine as the major initial-formed intermediates and co…
O crescente interesse em ampliar a previsibilidade dos fenômenos que ocorrem durante a fabricação de materiais cerâmicos por processos coloidais, como a variação da viscosidade de suspensões, tem estimulado a implantação de vários modelos teóricos com tal finalidade. Considerando a concentração de sólidos na suspensão…
Thin films of SrBi2Ta2O9 (SBT) were deposited on Si using Sol-Gel technique. The thicknesses of the films 200 nm (SBT2) and 400 nm (SBT4), respectively. SEM were studies showed most of the grains in the film are smaller than 0.1 μ. FTIR reflectivity measurements of the samples showed bands around 1260, 936(for SBT2),…
This paper presents experimental data on the bonding of CO and NO to vacuum-cleaved MgO(100) and NiO(100) and compares them with theoretical results. In the case of CO and NO on NiO(100) we find that the bonding energies obtained for the vacuum-cleaved single crystals agree well with results of recent studies on thin…
In EXAFS analysis of Rb-doped silicate glasses and of cetyltrimethylammonium bromide (CTAB) adsorbed on carbon black, the spline approximation of the atomic background is inadequate. Instead, a residuum obtained from absorption spectra of Rb and Br ions in aqueous solution after removal of the structural signal is use…
A bleomycin-binding protein, designated BLMT, encoded on the transposon Tn5 was crystallized using the vapour-diffusion method in a form suitable for X-ray diffraction analysis. Crystals were grown at pH 6.5 in 0.1 M sodium cacodylate and 0.2 M calcium acetate, using 25% PEG 6000 as a precipitant. They belong to the o…
Abstract The high-temperature γ -phase of lithium sodium carbonate ( γ -LiNaCO 3 , a = 8.311 Å, c = 3.386 Å, P [unk]) has been studied by X-ray diffraction and computer simulation methods. The results of computer simulation based on the ionic model and the temperature dependence of the superlattice reflection intensit…