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Displaying 1576 - 1600 of 1721

Orientation of Surface Bound Proteins Studied by Near Edge X-Ray Absorption Fine Structure

January 25, 2000
Author(s)
L Gamble, J R. Long, P S. Stayton, Daniel A. Fischer, S Sambasivan, David G. Castner
The orientation of surface bound proteins may play an important role in the function and properties of materials to which they are adsorbed. Near edge absorption fine structure (NEXAFS) is a technique which allows the user to determine the presence of

Ab-Initio Energetics of Transition Metal Ordering in Decagonal Al-Co-Cu

January 21, 2000
Author(s)
M Widom, I Al-Lehyani, Yijun Wang, Eric J. Cockayne
We perform ab-initio total energy calculations for approximants to a model of decagonal A1CoCu. These calculations support previously proposed chemical ordering of Co and Cu atoms along tile edges. Preferred arrow orientations are identified and shown to

Generation of Quasicrystals Via a Single Cluster

January 21, 2000
Author(s)
Eric J. Cockayne
We present a columnar cluster with 46 atoms per repeat distance which forces a quasicrystal when space is filled by interpenetrating copies of itself. The atomic positions in the resultant quasicrystal are remarkably similar to those in models for real

Pressure Dependence of Instabilities in Perovskite PbZrO 3

January 21, 2000
Author(s)
Eric J. Cockayne, K M. Rabe
We have computed the frequencies of selected normal modes in perovskite PbZrO 3 (PZ) as a function of lattice parameter using local density functional theory variational linear response. The most significant instabilities that freeze in to give the

In Situ Characterization of Catalytic Propylene Oxidation on the Pt (111) Surface

January 17, 2000
Author(s)
A M. Gabelnick, A T. Capitano, D J. Burnett, Daniel A. Fischer, J L. Gland
The catalytic oxidation of propylene with both propylene and oxygen in the gas phase has been characterized on the Pt(111) surface. In situ soft x-ray kinetic and spectroscopic measurements using fluorescence detection have been used to characterize this

A Microshear Test to Measure the Bond Between Dental Composites and Dental Substrates

January 1, 2000
Author(s)
Walter G. McDonough, Joseph M. Antonucci, Gary E. Schumacher, Y Shimada
Mechanical property tests such as the diametral tensile, uniaxial tensile, biaxial flexural, shear, and transverse strength tests are commonly used for assessing the bond that forms between dental composites and dental substrates such as dentin and enamel

An Optical Sensor for Polymer Injection Molding

January 1, 2000
Author(s)
Anthony J. Bur, C L. Thomas
An optical sensor using fiber optics to access the mold cavity was used to monitor the mold filling and cooling phases of injection molding. The sensor consists of a sapphire window at the end of a sleeved ejector pin into which an optical fiber is

Direct Measurement of Valence-Charge Asymmetry by X-Ray Standing Waves

January 1, 2000
Author(s)
Joseph C. Woicik, E Nelson, P Pianetta
By detecting valence-photoelectron under condition of strong x-ray Bragg reflection, we have determined that a majority of GaAs valence charge resides on the anion sites of this heteropolar crystal, in quantitative agreement with the Ga-As bond polarity as

Factors That Affect Adhesion at the Fiber-Matrix Interface in Composites

January 1, 2000
Author(s)
Gale A. Holmes, E Feresenbet, E Pohl, Walter G. McDonough, D T. Raghavan, D Thompson
The development of methods to assess adhesion at the fiber-matrix interface in composite materials has been driven primarily by the recognition that the interface or interphase in many composite materials has a profound affect on the onset of failure in

Layer Perfection in Ultrathin InAS Quantum Wells in GaAs(001)

January 1, 2000
Author(s)
J A. Gupta, S P. Watkins, E D. Crozier, Joseph Woicik, D A. Harrison, D Jiang, I J. Pickering, B A. Karlin
X-ray diffraction (XRD), X-ray standing wave (XSW) and X-ray absorption fine structure (XAFS) measurements were used to assess the layer perfection and positions of 1 and 2 monolayer (ML) InAs quantum wells buried in GaAs(001). Photoluminescence (PL)

Model of Fatigue Damage in Strain Rate-Sensitive Composite Materials

January 1, 2000
Author(s)
S K. Lee, Tinh Nguyen, Tze J. Chuang
A Fatigue damage accumulation model based on the Paris law has been proposed for strain rate-sensitive polymer composite materials. A pre-exponent factor c 2/f and strain-rate sensitive exponent n is introduced. Numerical analysis of the model has been

Real-Time Dielectric Measurements During Extrusion of Filled Polymers

January 1, 2000
Author(s)
M M. McBrearty, Anthony J. Bur, S C. Roth
Mineral fillers are added to extend and modify physical properties of polymers. To achieve porcessing control of mixing, real-time measurements are needed. Previuos work has shown that dielectric sensors can measure concentrations of fillers in non-polar
Displaying 1576 - 1600 of 1721