Materials Literature
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A direct-space strategy, in which global optimization is carried out on the Rwp hypersurface using a genetic algorithm combined with local minimization of Rwp, has been used to solve the crystal structure of the oligopeptide Phe-Gly-Gly-Phe directly from powder X-ray diffraction data.
We study energy spectra, eigenstates, and quantum diffusion for one- and two-dimensional quasiperiodic tight-binding models. As for our one-dimensional model system we choose the silver mean or ``octonacci'' chain. The two-dimensional labyrinth tiling, which is related to the octagonal tiling, is derived from a produc…
A new approach to the isolation of the water-soluble factors from nacre without any demineralization is described and examined their effect on fibroblast cells in culture. The soluble matrix in pure water from the nacre of Pinctada maxima was analysed by size-exclusion HPLC. Four fractions (SE1-SE4) of the water-solub…
Using a many-body approach based on single-particle pseudopotential wave functions, we calculate the dependence of the optical transitions in CdSe nanocrystals on the presence of ``spectator'' electrons or holes. We find that (i) as a result of the different localization of the electron and hole wave functions, the ab…
Fabrication of portland cements commonly depends on X-ray fluorescence (XRF), which measures the elemental compositions. XRF is used to adjust the raw material proportions and to control the process conditions. However, to predict the mechanical strength of the resulting concrete, it is essential to know the phase com…
We describe experiments which demonstrate that carbon atoms introduced into a fused-silica substrate by means of MeV ion implantation can, after suitable annealing, form nanocrystalline diamond. Unlike other methods of creating diamond, the coalescence of the carbon into diamond nanocrystals occurs when the samples ar…
Erbium-doped ZnO (ZnO:Er) thin films were fabricated by the KrF excimer laser ablation technique, which is a useful and simple technique to dope Er atoms on the order of 1020 cm−3 into a host material. As-prepared ZnO:Er films showing strong c-axis orientation with a hexagonal crystalline structure indicate a low elec…
We present a detailed investigation of the surface electronic structure of solid ${\mathrm{K}}_{3}{\mathrm{C}}_{60}$ in connection with its electronic transport properties. We find that the conductivity is extremely sensitive to the K concentration of the surface layer, and that the best-conducting samples with the hi…
Coordination of the pentatopic ligand 3 with AgI leads to the simultaneous self-assembly of two polynuclear architectures: a [4×5] grid-type species 10 and a quadruple-helicate 11, which contain twenty and ten silver ions, respectively. Their structures have been established by X-ray diffraction analysis of the crysta…
An empirical model based on cascade ``quenching'' and epitaxial recrystallization has been developed to describe the accumulation of the amorphous fraction during ion beam irradiation experiments. The model is based on the assumption that the amorphous fraction that remains after the formation of a cascade is related…
Structural models of alkali tellurite glasses, (M 2 O) x (TeO 2 ) l- x with M = Li, Na, K are presented. The glass structure was studied with neutron and X-ray diffraction, and, in the case of sodium, NMR. Real-space models of the glass structure were built using the reverse Monte Carlo algorithm. The distribution of…
The non-reversing heat flow, Δ H nr ( x ) near T g in ternary Ge x As x Se 1 − 2 x glasses is examined by temperature-modulated differential scanning calorimetry. The Δ H nr ( x ) term shows a deep minimum (which is almost zero) in the 0.09 < x < 0.14 range, identified with the intermediate phase , and an increase, bo…
Performance of plastics , Performance of plastics , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
Ferromagnetic transition in three-dimensional double-exchange models is studied by the Monte Carlo method. Critical temperature $T_{\rm c}$ is precisely determined by finite-size scaling analysis. Strong spin fluctuations in this itinerant system significantly reduce $T_{\rm c}$ from mean-field estimates. By choosing…
The depletion interaction between two spheres due to nonadsorbing ideal polymers is calculated from the polymer concentration profile using the excess (negative) adsorption. Computer simulations show that the polymer concentration profiles around two spheres are well described by the product function of the concentrat…
We report the first scanning tunneling microscopy (STM) study of single-crystalline anatase. Atomically resolved images of the (101) surface are consistent with a bulk-truncated $(1\ifmmode\times\else\texttimes\fi{}1)$ termination. Step edges run predominantly in the [010], $[1\ifmmode\bar\else\textasciimacron\fi{}11]…
Chiral amide- and urea-type organic gelators (1-6), based on cyclohexanediamine, have been prepared, and the superstructures of the organogels were evaluated by circular dichroism (CD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The CD spectrum of the amide-based organogel system 1…
The combination of the long-lived, spectrally pure emission of YbIII ions with the outstanding light-absorbing capabilities of organic dyes gives photoluminescent lanthanide complexes that are interesting candidates for use as a new class of luminescent labels for molecules of biomedical interest. The water-soluble co…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTRapid and Controlled Polymerization of Lactide by Structurally Characterized Ferric AlkoxidesBrendan J. O'Keefe, Susanne M. Monnier, Marc A. Hillmyer, and William B. TolmanView Author Information Department of Chemistry, University of Minnesota 207 Pleasant Street SE,…
Molecular-dynamics simulations were employed to study deformations on nickel nanowires subjected to uniaxial strain at 300 K using a recently reported embedded-atom (many body) model potential. This embedded-atom model can reproduce exactly the experimental second-order and third-order elastic moduli as well as the ph…