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Bioscience

Biomaterials

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Displaying 1576 - 1600 of 1729

Measuring Bimodal Crystallographic Texture in Ferroelectric PZT Thin Films

February 1, 2000
Author(s)
Mark D. Vaudin, G R. Fox
A powder x-ray diffraction method has been developed to measure the volume fraction of (111), (100), and randomly oriented PZT in 200 nm thick films used for FRAM applications. The integrated and peak intensities of 100, 110, 200 and 222 Bragg peaks from

New Calcium Tantalate Polytypes in the System Ca 2 Ta 2 O 7 - Sm 2 Ti 2 O 7

February 1, 2000
Author(s)
I E. Grey, Robert S. Roth
New calcium tantalate polytypes, with weberite related structures have been prepared by doping Ca 2Ta 2O 7 with Sm 2Ti 2O 7. Trigonal 6-layer (6T) and monoclinic 5-layer (5M) polytypes containing approximately equal to} 6 mol % and 10 mol % respectively of

Phase Relations of the SrO-Ho 2 O 3 -CuO x System

February 1, 2000
Author(s)
Winnie K. Wong-Ng, J Dillingham, Lawrence P. Cook
The phase diagram of the SrO-R 2O 3-CuOx system, where R=Ho, was investigated in air. The tie-line relationships of this system were determined. Two ternary phases were found, namely, the green phase SrHo 2CuO 5 and the A14-24 solid solution (Sr 14-xHo x

Subsolidus Phase Relations and Dielectric Properties in the SrO-Al 2 O 3 -Nb 2 O 5 System

February 1, 2000
Author(s)
Julia Y. Chan, Igor Levin, Terrell A. Vanderah, Richard G. Geyer, Robert S. Roth
Subsolidus phase equilibria in the SrO-Al 2O 3-Nb 2O 5 system were determined by synthesis of 75 compositions in air in the temperaturerange 1200-1600 C. Phase assemblages were determined by X-ray powder diffraction at room temperature. Two new ternary

Temperature Dependence of Molecular Orientation on the Surfaces of Semi-Fluorinated Polymer Thin Films

February 1, 2000
Author(s)
Jan Genzer, E Sivaniah, E K. Kramer, J G. Wang, H Koerner, K Char, Christopher K. Ober, B M. DeKoven, Robert A. Bubeck, Daniel A. Fischer, S Sambasivan
Near-edge X-ray absorption fine structure is used to investigate the temperature dependence of molecular orientation of semi-fluorinated liquid crystalline (SF-LC) mesogens, which are attached to the modified isoprene backbone of i) a polyisoprene

The Elastic Constants of Single Crystal Beta-Si 3 N 4

February 1, 2000
Author(s)
R Vogelgesang, M Grimsditch, Jay S. Wallace
Using Brillouin scattering, we have determined the five independent elastic constants of Β-Si 3N 4 single crystals. They are (in units of GPa) c 11 = 433(3), C 33=574(3), c 13 = 127(5), c 44 = 108(2), C 66 =119(4), and C 12 = C 11-2c 66 = 195(8), giving a

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
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