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Bioscience

Biomaterials

Search Publications

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Displaying 1276 - 1300 of 1729

Quantitation of Polymer End Groups Using MALDI TOF MS

July 1, 2002
Author(s)
A P. Weaver, Charles M. Guttman, Kathleen M. Flynn
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) has been employed to analyze polystryrene mixtures of molecular mass ca. 4000u. The component polymers of thes mixtures are identical except for their end groups

Some Issues in Particle Size and Size Distribution Characterization of Powders

July 1, 2002
Author(s)
Ajitkumar Jillavenkatesa, James F. Kelly, S J. Dapkunas
Size and size distribution measurement of powders are conducted using different techniques of size analysis.Underlying all these techniques are certain fundamental issues that influence the accuracy and reproducibility ofthe results. A thorough

Ceramic Based Layer Structures for Biomechanical Applications

June 1, 2002
Author(s)
Brian R. Lawn
A survey of recent advances in the analysis of ceramic-based layer structures for biomechanical applications is presented. Data on model layer systems, facilitating development of explicit fracture mechanics relations for predicting critical loads to

Compact Force Sensors for Low-Force Mechanical Probe Calibration

June 1, 2002
Author(s)
Douglas T. Smith, S Woody, Jon R. Pratt
The loading mechanisms of instrumented indentation machines are often calibrated using deadweights. In many cases, due to the geometry of the loading frame, the applied deadweight is tensile, while the indentation leads to be measured are compressive. In

Cracking in Brittle Laminates from Concentrated Loads

June 1, 2002
Author(s)
H Chai, Brian R. Lawn
A study is made of the crack resistance of multilaminates consisting of brittle layers interleaved with compliant interlayers and bonded to compliant substrates. Specific attention is paid to flexure generated radial cracks in the undersurfaces of

Crystal Structure of the Compound Bi 2 Zn 2/3 Nb 4/3 O 7

June 1, 2002
Author(s)
Igor Levin, T G. Amos, J Nino, Terrell A. Vanderah, I Reaney, C A. Randall, M T. Lanagan
The crystal structure of Bi2Zn2/3Nb4/3O7 was determined using a combination of electron, X-ray and neutron powder diffraction. The compound crystallizes with a monoclinic zirconolite-like structure (C2/c (No.15) space group, a=13.1037(9) , b=7.6735(3) , c

Effect of Loading Rate Upon Conventional Ceramic Microindentation Hardness

June 1, 2002
Author(s)
George D. Quinn, P J. Patel, Isabel K. Lloyd
Dynamic micro-indentation hardness was evaluated for a steel, sintered silicon carbide, and an aluminum oxynitride. There was negligible effect upon Vickers hardness when loading rate was varied by almost three orders of magnitude.

Elastic Moduli Data for Polycrystalline Oxide Ceramics

June 1, 2002
Author(s)
R G. Munro
A compilation of elastic moduli data, including Young's modulus, shear modulus, bulk modulus, and Poisson's ratio, is presented for polycrystalline oxide ceramics. The data have been collected from the technical literature, either as reported in textual or

Grain Growth and Twin Formation in 0.74 PMN-0.26 PT

June 1, 2002
Author(s)
Jay S. Wallace, J M. Huh, J Blendell, C A. Handwerker
The mechanisms controlling normal and exaggerated grain growth in lead magnesium niobate-lead titanate (PMN-PT) ceramics have been investigated by varying the PbO-based liquid phase volume fraction from 0.03 to 0.6 and sintering temperature form 900 C to

Structural Study of Li 1+x-y Nb 1-x-3y Ti x+4y O 3 Solid Solutions

June 1, 2002
Author(s)
L Farber, Igor Levin, A Borisevich, I E. Grey, Robert S. Roth, P K. Davies
The structures of Lil+x-yNbl-,-3yTix+4yO3 solid solutions within the so-called M-phase field in the Li2O-Nb2O5-TiO2system were investigated using HRTEM and single crystal X-ray diffraction. The results demonstrated the phasefield is comprised of a

Unraveling the Symmetry of the Hole States Near the Fermi Level in the MgB 2 Superconductor

June 1, 2002
Author(s)
Y Zhu, A R. Moodenbaugh, G Schneider, J W. Davenport, T Vogt, Q Li, G Gu, Daniel A. Fischer, J Tafto
We use x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) to study the near edge fine structure at the K-edge of boron in the superconductor M gB 2. We observe in XAS a peak of width 0.6 eV at the threshold of this K-edge

Accuracy and Reproducibility of X-Ray Texture Measurements on Thin Films

May 1, 2002
Author(s)
Mark D. Vaudin, G R. Fox, G -. Kowach
Rocking curve texture measurements were made on thin films of zinc oxide (ZnO) and platinum (Pt) using a powder x-ray diffractometer, and also, in the case of ZnO, an area detector. The intensity corrections for defocussing and other geometric factors were

Cracking in Ceramic/Metal/Polymer Trilayer Systems

May 1, 2002
Author(s)
H Zhao, P Miranda, Brian R. Lawn, X Z. Hu
Fracture and deformation in model brittle-outerlayer/metal-core/polymer substrate trilayer systems in concentrated loading are studied. Model systems for experimental study are fabricated from glass microscope slides glued with epoxy adhesive onto steel

Effect of Counterface Roughness on Abrasive Wear of Hydroxyapatite

May 1, 2002
Author(s)
Sergei Kalinin, S Jahanmir, L K. Ives
The present study was undertaken to evaluate the effect of surface roughness of glass-infiltrated alumina on the abrasive wear of hydroxyapatite using a pin-on-disk tribometer. Hydroxyapatite was used as a model material to simulate tooth enamel. The wear

In-Line Dielectric Monitoring During Extrusion of Filled Polymers

May 1, 2002
Author(s)
Anthony J. Bur, S C. Roth, M M. McBrearty
Dielectric measurements were made on clay filled polyethylene-ethyl vinyl acetate (EVA) copolymer nanocomposites during processing by extrusion. The results show that composites containing chemically treated clays display significant dielectric dispersions

Temperature Effects During Capillary Rheometry Testing

May 1, 2002
Author(s)
Anthony J. Bur, S C. Roth, H Lobo
A non-contact temperature monitoring technique based on fluorescence spectroscopy was used to measure the temperature of a polymer resin during capillary rheometry testing. Polyethylene and polycarbonate doped with a fluorescent dye, perylene, were used in

Tri-Alpha-Napthyl Benzene as a Crystalline or Glassy MALDI Matrix

April 19, 2002
Author(s)
Barry J. Bauer, Charles M. Guttman, Da-Wei Liu, William R. Blair
Tri-alpha-napthyl benzene (TANB) is used as a matrix in matrix-assisted laser desorption/ionization (MALDI) spectroscopy. Electrosprayed TANB is crystalline and has a melting point of 180 2 C. A glass of TANB is obtained with a glass transition temperature
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