Materials Literature
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Spin-polarization is known to lead to important {\it magnetic} and {\it optical} effects in open-shell atoms and elemental solids, but has rarely been implicated in controlling {\it structural} selectivity in compounds and alloys. Here we show that spin-polarized electronic structure calculations are crucial for predi…
Ab initio molecular dynamics simulation is used to investigate the structure and dynamics of liquid Se at temperatures of 870 and 1370~K. The calculated static structure factor is in excellent agreement with experimental data. The calculated radial distribution function gives a mean coordination number close to 2, but…
Abstract The role of molecular weight distribution on the spinnability, structure, and properties of melt‐spun isotactic polypropylene filaments was studied with the aim of clearly distinguishing the effect of the breadth of the distribution from the effect of the average molecular weight and resin melt flow rate (MFR…
The composition, growth mechanism, and phases of carbon nitride thin films obtained from the reaction of laser ablated carbon and atomic nitrogen have been investigated. The nitrogen composition was found to increase to a limiting value of 50% as the fluence was decreased for laser ablation at both 532 nm and 248 nm.…
The defects and the morphology of stain etched porous Si of 60% to 70% porosity have been studied by electron paramagnetic resonance (EPR), scanning tunneling microscopy (STM), and Raman spectroscopy. The samples contain two pore phases with dimensions in the 1 and 10 nm range and present both visible and infrared pho…
Uridine phosphorylase from E. coli (Upase) has been crystallized using vapor diffusion technique in a new monoclinic crystal form. The structure was determined by the molecular replacement method at 2.5 A resolution. The coordinates of the trigonal crystal form were used as a starting model and the refinement by the p…
We report the first three dimensional x-ray study of the recently discovered twist grain boundary smectic- $C$ phase $({\mathrm{TGB}}_{C})$. Unlike the predictions of the original Renn-Lubensky model for TGB phases (and the experimental observations in the untilted ${\mathrm{TGB}}_{A}$ phase), the smectic layers in th…
We solve the approximate renormalization group found by Niu and Nori for a quasiperiodic tight-binding Hamiltonian on the Fibonacci chain. This enables us to characterize analytically the spectral properties of this model.
The effects of liquid methanol on the photoluminescence intensity and FTIR spectra of red and blue emitting porous silicon were investigated. Hydrogen passivated red emitting samples exhibit quenching and recovery of photoluminescence intensity and broadening of the Si-Hx stretch bands upon exposure to liquid methanol…
Films of composition 0.27 PbO, 0.24 ZrO2, 0.27 TiO2, 0.22 NiO, and containing micrometer sized lead zirconate titanate (PZT) crystallites and nanometer sized nickel particles have been synthesized by a sol-gel technique. Metal particles have diameters in the range 2.0–7.6 nm. The films exhibit values of dielectric con…
The crystal structure of MgTe has been studied in a diamond anvil cell using energy dispersive x-ray diffraction to 60 GPa at room temperature. The first pressure-induced structural phase transformation among magnesium chalcogenides was observed for MgTe at $P\ensuremath{\approx}1\ensuremath{-}3.5$ GPa. The new phase…
Proteins in a biological membrane can be idealized as disks suspended in a thin viscous sheet surrounded by a fluid of lower viscosity (Saffman 1976). To determine the effect of hydrodynamic interactions on protein diffusivities in non-dilute suspensions, we numerically solve the Stokes equations of motion for a syste…
Recent observations of growing and collapsing bubbles in flows over axisymmetric headforms have revealed the complexity of the ‘micro-fluid-mechanics’ associated with these bubbles (van der Meulen & van Renesse 1989; Briancon-Marjollet et al. 1990; Ceccio & Brennen 1991). Among the complex features observed we…
Results of experiments using a number of techniques to study the nature of convection in a mushy layer generated by directional solidification of aqueous ammonium chloride solutions are reported. The techniques include flow visualization using a dye tracing method to study convection within the mushy layer before and…
The enzyme, carbonic anhydrase, has been incorporated within poly(lactic-co-glycolic acid) microspheres using a double emulsion and solvent evaporation technique. The protein stability problems during the microsphere formulation procedure and during the release period were examined in relation to the protein release k…
A method that combines thin film deposition and physical masking techniques has been used for the parallel synthesis of spatially addressable libraries of solid-state materials. Arrays containing different combinations, stoichiometries, and deposition sequences of BaCO(3), Bi(2)O(3), CaO, CuO, PbO, SrCO(3), and Y(2)O(…
Exceptionally large pore sizes have recently been reported for polyacrylamide gels grown in the presence of polyethylene glycol. We present small angle static light scattering measurements performed during the evolution of this peculiar gelation process. We give evidence that the large pores are generated by a microse…
Hysteresis effects are distinct in that they remain after the initial causes are removed. The term itself is derived from the Greek ύστερέω meaning to come later, and was first coined for the explanation of scientific phenomena by the physicist James Alfred Ewing (1881a). The initial application was to the thermo-elec…
We have developed a set of techniques for performing large scale ab initio calculations using multigrid accelerations and a real-space grid as a basis. The multigrid methods permit efficient calculations on ill-conditioned systems with long length scales or high energy cutoffs. The technique has been applied to system…
Abstract Polypropylene/polyamide‐6 (70:30) blends, containing dispersed discrete polyamide‐6 microphases as matrix reinforcement, represent attractive materials for engineering applications. In order to enhance impact resistance, ethene/propene (EPM) was incorporated as a second separately dispersed microphase using r…