Materials Literature
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Abstract In polymer blends, the crystallization of the dispersed semicrystalline component depends on the type and distribution of the nucleating heterogeneities and on the level of the dispersion. Either fractionated or coincident crystallization may result. In this study, the effect of compatibilizers on the crystal…
A semiempirical molecular-dynamic density-functional approach is used to perform a systematic investigation of the stability, structure, and properties of quenched pure and hydrogenated amorphous carbon dependent on the mass density and the hydrogen concentration. By comparing the total structure energies for supercel…
We present a photoluminescence study of the free-exciton singlet and triplet ground states in GaTe as a function of temperature from 5 to 40 K. Over the range 5--25 K, the temperature variation of excitonic-emission line width and peak energy comes mainly from exciton--acoustic-phonon interactions via the deformation…
The photoluminescence and optical absorption properties of Zn-doped GaS crystals prepared by the iodine vapor transport method are reported. Undoped GaS crystals are also used for comparison. Zn substituted for a Ga site acts as an acceptor having a deep energy level and forms a complex with the iodine coactivator, wh…
A method of graphically representing complex dielectric data is described, which is particularly useful for situations where the Cole–Cole representation is unsuitable. The representation emphasizes the orientational dipolar contribution to the conductivity by plotting σχ″=ωεv(ε′−ε∞) vs σχ′=ωεvε″. We discuss the utili…
Measurements are reported on the electrical resistivity \ensuremath{\rho}(T) along the c axis of a single crystal of ${\mathrm{VO}}_{2}$, from the metal-insulator transition at T=333 K up to 840 K. The temperature dependence is very linear, and a fit to Bloch-Gr\"uneisen theory gives a residual resistivity ${\mathrm{\…
Stresses were measured in 〈111〉-textured Ag/Ni multilayered thin films from the substrate curvature and from lattice parameter measurements by x-ray diffraction. The difference between the total multilayer film stress and the layer deposition stresses can be attributed to a tensile interface stress of −2.27±0.67 J/m2.…
We present data concerning the dynamics of photoexcitation of defect centers in germanium-doped silica glass optical fibers and fiber preforms. It is shown that two-photon absorption of mode-locked and Q-switched light at 527 nm results in partial ionization of the germanium oxygen deficiency center (GODC) 400-nm lumi…
We report strong visible photoluminescence (PL) at room temperature from oxidized Si nanometer-sized spheres with a spherical crystalline Si (c-Si) core and an amorphous ${\mathrm{SiO}}_{2}$ (a-${\mathrm{SiO}}_{2}$) surface layer. The peak energy of the broad PL spectrum is about 1.65 eV, which is independent of the c…
Helically coiled forms of the carbon cage on the nanometer scale are theoretically proposed. The optimized surface construction for different types of helically coiled structures consisting of sevenfold, sixfold, and fivefold rings of carbon atoms is given. The thermal stability of various helical structures is studie…
Stealth liposomes have recently emerged as a promising antitumor drug delivery system, yet no studies have been reported to examine their dynamic behavior at the microcirculatory level. In this investigation, we have used in vivo fluorescence videomicroscopy to study the decay in plasma concentration and the interstit…
Abstract Various nylon 6‐clay hybrids, such as molecular composites of nylon 6 and silicate layers of montmorillonite and saponite, NCHs and NCHPs, respectively, have been synthesized. Sorption of water in those hybrids was measured to estimate the resistance to water permeation. The diffusion coefficient D and the pa…
A highly tetrahedrally bonded form on nonhydrogenated amorphous carbon (a-C) is produced by deposition from filtered medium-energy ion beams. A range of such films was grown and the ${\mathit{sp}}^{3}$-bonded fractions, plasmon energies, compressive stresses, and resistivities were measured as a function of ion energy…
The nonlinear optical behaviour of the organic crystal MBA-NP has been investigated at 1064 and 532 nm, with both nanosecond and picosecond pulses. The second-order effective susceptibility for second harmonic generation, and the damage thresholds compare favourably with those of most inorganic crystals. Two-photon ab…
A summary is given of theories founded on concepts such as roughening transitions, kinetic roughening, and connected nets which in principle allow the prediction of the conditions under which a crystal face (hkl) will grow as a flat face, by a layer mechanism, or as a rough face. Starting with Jackson's theory based o…
The growth kinetics of m-chloronitrobenzene crystals from acetone solutions were measured and analysed to see the effects of the presence of microcrystals in the solution. The microcrystals generated by the added fine crystals were found to cause significant enhancement of the growth rate by a factor of 2-5. Possible…
Vogel-Fulcher-Tammann temperature dependence of sigma ( sigma varies as exp(-E a /k(T-T 0 ))) was found in a KTiOPO 4 single crystal for the (001) direction. The values of T 0 and E a were 150 K and 0.16 eV respectively. Below 150 K fast ion transport can therefore be expected to be frozen.
The information required from optical assessment of nonlinear organic materials differs widely depending on the application envisaged for the material in question. Accordingly, a suitable assessment scheme must be devised which will give a reliable indication of the promise of these materials in a wide variety of appl…
The quest for more efficient nonlinear optical materials of increased optical quality is being spurred by the development of optical communication systems that require ultrafast broad band optical signal processing functions. Conversely, nonlinear optical phenomena enlarge traditional spectroscopic approaches to encom…
Atomic force microscopy was used to obtain images of lysozyme crystals growing in their native solution environment. The authors growth by both two-dimensional nucleation and screw dislocation mechanisms. Nucleation centres appeared to occur randomly over the surface, and were uncorrelated from layer to layer. Surface…