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Displaying 49651 - 49675 of 73832

A Matrix Formalism of Hall Effects in Multicarrier Semiconductor Systems

September 14, 1999
Author(s)
Jin S. Kim
In this article, a matrix formalism of the Hall effects is presented for an arbitrary J-fold multicarrier semiconductor system. Explicit formulas are derived for important transport quantities such as the sheet resistance, the Hall coefficient, and the

Heteronuclear NMR and Crystallographic Studies of Wild-Type and H187Q Escherichia Coli Uracil DNA Glycosylase: Electrophilic Catalysis of Uracil Expulsion by a Neutral Histidine 187

September 14, 1999
Author(s)
A C. Drohat, G Xiao, M Tordova, J. Jagadeesh, K Pankiewicz, K A. Watanbe, G L. Gilliland, J T. Stivers
The nature of the putative general acid, His187, in the reaction catalyzed by Escherichia coli uracil DNA glycosylase (UDG) was investigated using X-ray crystallography and NMR spectroscopy. The crystal structures of H187Q UDG, and its complex with uracil

Modeling the Fillet Lifting Defect

September 11, 1999
Author(s)
Clare Bailey, William J. Boettinger
A multi-physics simulation tool is described which has the ability to simulate fluid flow, heat transfer including solidification, and stress evolution in a integrated manner. This modelling framework is used to predict the behavior of two solder materials

A Capacitance Standard Based on Counting Electrons

September 10, 1999
Author(s)
Mark W. Keller, Ali L. Eichenberger, John M. Martinis, Neil M. Zimmerman
A capacitance standard based directly on the definition of capacitance was built. Single-electron tunneling devices were used to place N electrons of charge e onto a cryogenic capacitor C, and the resulting voltage change ΔV was measured. Repeated

Advances in Concrete Mixture Optimisation. Keynote Paper

September 8, 1999
Author(s)
Kenneth A. Snyder, G J. Frohnsdorff, M Simons
The complexity of high performance concrete (HPC) mixture designs continues to increase, along with the number of criteria that a particuhu mixture must satisfy. Robust statistical methods exist that can be used to not only determine the mixture for a

Rapid Melting of Nb - 47 Mass % Ti: Effect of Heating Rate and Grain Size

September 8, 1999
Author(s)
William J. Boettinger, Daniel Josell, Sam R. Coriell, D Basak
The effect of heating rate and grain size on the melting behavior of Nb - 47 mass % Ti is measured. The experimental method uses rapid resistive self-heating of wire specimens at rates between 10(2 superscript) and 104 superscript) K/s and simultaneous

Smoothing of Mirror Substrates by Thin-Film Deposition

September 8, 1999
Author(s)
E Spiller, S Baker, E Parra, Charles S. Tarrio
Superpolished optical flats with high spatial frequency roughness below 0.1 nm have been commercially available for years. However, it is much more difficult to obtain figured optics of similar quality. We have obtained and tested the finish of figured

Total Variance, an Estimator of Long-Term Frequency Stability

September 5, 1999
Author(s)
Chuck Greenhall, David A. Howe, Donald B. Percival
Total variance is a statistical tool developed for improved estimates of frequency stability at averaging times up to one-half the test duration. As a descriptive statistic, total variance performs an exact decomposition of the sample variance of the

Diamond Wear in High Speed Grinding of Silicon Nitride

September 2, 1999
Author(s)
T W. Hwang, Christopher J. Evans
Diamond wear of single layer electroplated wheels was investigated in high speed grinding of silicon nitride. Grinding experiments were conducted at wheel speeds of 85 m/s and 149 m/s with the same material removal rate. Microscopic observations of the

A Heterodyne Interferometer With Subatomic Periodic Nonlinearity

September 1, 1999
Author(s)
C M. Wu, John R. Lawall, R Deslattes
A new to our knowledge heterodyne interferometer for differential displacement measurements is presented. It is, in principle, free of periodic nonlinearity. A pair of spatially separated light beams with different frequencies is produced by two acoustic

A Policy Perspective on Electronic Commerce

September 1, 1999
Author(s)
E Maxwell, S A. Wakid, J A. Moline
On July 1, 1997, President Clinton issued A Framework for Global Electronic Commerce identifying nine areas in which international agreements would be needed in order to preserve the Internet as a non-regulatory medium.The implementation of global

A Usability Case Study Using TREC and ZPRISE

September 1, 1999
Author(s)
L L. Downey, D M. Tice
This paper examines the challenges involved in conducting and informal usability case study based on the induction of a new information retrieval system to experienced users. We present a summary of activities performed during two iterations of usability

Analysis of Environmentally Induced DNA Damage by Capillary Electrophoresis

September 1, 1999
Author(s)
Z E. Nackerdien, B Siles, S Nivens, Donald H. Atha
Chemical pollutants, ionizing radiation, the products of aerobic metabolism and UV light are important metabolic and environmental factors contributing to DNA damage. Ionizing radiation, in paticular, induces damage in the form of single strand breaks

Atomic Weights and Isotopic Compositions

September 1, 1999
Author(s)
J S. Coursey, Robert A. Dragoset, D J. Schwab
The atomic weights are available for elements 1 through 111, and isotopic compositions or abundances are given when appropriate. The atomic weights data were published by T. B. Coplen in Atomic Weights of the Elements 1995, J. Phys. Chem. Ref. Data, 26 (5)
Displaying 49651 - 49675 of 73832
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