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Displaying 48226 - 48250 of 74141

Critical Gaps in Durability Data for FRP Composites in Civil Infrastructure

May 1, 2000
Author(s)
V M. Karbhari, Joannie W. Chin, D R. Reynaud
Although fiber reinforced polymer (FRP) composites are increasingly being used for the renewal of civil infrastructure, there are still some major questions related to the durability of these materials in a civil engineering environment. This concern is

DC Voltage Synthesis Using a Pulse-Quantized Josephson Voltage Source

May 1, 2000
Author(s)
Samuel Benz, Laurie Christian, Charles J. Burroughs, Clark A. Hamilton
We have synthesized and measured dc voltages using a bipolar pulse-quantized Josephson voltage waveform synthesizer. Bias current ranges were determined for 101 equally spaced dc voltage steps between -18.6 and +18.6 mV. The flatness of a step at -7.444 mV

Derivatization of Plastic Microfluidic Devices With Polyelectrolyte Multilayers

May 1, 2000
Author(s)
S L. Barker, Michael J. Tarlov, M L. Branham, J Xu, William A. MacCrehan, Michael Gaitan, Laurie E. Locascio
Microchannels fabricated in plastic materials by room temperature imprinting demonstrate large variability in surface charge as a result of the fabrication procedure. Surface charged groups are primarily localized on the channel walls and not on the

Domain Wall Traps for Low-Field Switching of Submicron Elements

May 1, 2000
Author(s)
Robert D. McMichael, J G. Eicke, Michael J. Donahue, Donald G. Porter
In magnetic random access memory, power consumption depends on the coercivity of the magnetic elements in the memory cells. In this article a new method is described that uses a domain wall trap element shape to reduce both the coercivity and the

Edge-Bevel Fracture Resistance of Three Direct-Filling Materials

May 1, 2000
Author(s)
R J. Hoard, F Eichmiller, Edward E. Parry, Anthony A. Giuseppetti
Edge strength is defined in this study as the resistance to fracture of the beveled extension normally located at the cavosurface margin of a dental restoration. The edge strength of direct-filling alloy restorations plays an important role in maintaining

Effective Fragment Potentials and the Enzyme Active Site

May 1, 2000
Author(s)
S E. Worthington, Morris Krauss
Optimization of the binding conformation of a substrate in an enzyme active site using ab initio quantum chemistry methods are intractable since the active site comprises several hundred atoms. However, the active site can be decomposed into an active and

Evaluation of Charge Penetration Between Distributed Multipolar Expansions

May 1, 2000
Author(s)
M A. Freitag, M S. Gordon, J H. Jensen, W J. Stevens
A formula to calculate the charge penetration energy that results when two charge densities overlap has been derived for molecules described by an effective fragment potential (EFP). The method has been compared with the ab initio charge penetration, taken

Exchange Bias Relaxation in CoO-Biased Films

May 1, 2000
Author(s)
Robert McMichael, Chang H. Lee, Mark D. Stiles, F Serpa, P J. Chen, William F. Egelhoff Jr.
Because the memory of the bias direction is carried by the antiferromagnetic order in exchange bias films, the stability of the antiferromagnetic order is critical to the existence of the exchange bias field. Ferromagnetic resonance was used to measure the

Experimental Determination of Electron Effective Attenuation Lengths in Silicon Dioxide Thin Films Using Synchrotron Radiation - I. Data Analysis and Comparisons

May 1, 2000
Author(s)
M Suzuki, H Ando, Yukihiru Higashi, H Takenaka, H Shimada, N Matsubayashi, M Imamura, S Kurosawa, S Tanuma, Cedric J. Powell
We have measured effective attenuation lengths (EALs) of 140 to 1100 eV electrons in ultrathin silicon dioxide layers using synchrotron radiation. These EALs were generally smaller than those reported previously although there was agreement with the values

Experimental Determination of Electron Effective Attenuation Lengths in Silicon Dioxide Thin Films Using Synchrotron Radiation - II. Effects of Elastic Scattering

May 1, 2000
Author(s)
Y Shimada, N Matsubayashi, M Imamura, M Suzuki, Yukihiru Higashi, H Ando, H Takenaka, S Kurosawa, S Tanuma, Cedric J. Powell
The effective attenuation lengths (EALs) of photoelectrons in thin silicon dioxide films on a Si(100) substrate were measured as a function of electron energy using synchrotron radiation as an energy-tunable excitation source. The ratios of EALs to

Experiments With Strontium in a Vapor Cell Magneto-Optic Trap

May 1, 2000
Author(s)
K R. Vogel, Tim P. Dinneen, Alan Gallagher, J L. Hall
In a ceramic vapor cell we have created a robust Sr magneto-optical trap that stores about 10 8 atoms with lifetimes > 200 ms. We eliminate the 5p 1P 1->4d 1 d2->5p 3P 2 leak and achieve a 10-fold improvement in trap lifetime by repumping the 5p 3Po.2 dark

Fibers, Percolation, and Spalling of High-Performance Concrete

May 1, 2000
Author(s)
Dale P. Bentz
While the strength and durability of high performance concretes (HPCs) are often greatly superior to conventional concretes under ambient conditions, their failure is sometimes rapid and dramatic during exposure to a fire, characterized by the explosive

Fire Performance of High Strength Concrete: Research Needs

May 1, 2000
Author(s)
Long T. Phan, Nicholas J. Carino
A compilation of fire test data which shows distinct behaviroal differences between HSC and NSC at elevated temperature is presented. The differences are most pronounced in the temperature range of 20 {degrees}C to 400 {degrees}C. What is more important is
Displaying 48226 - 48250 of 74141
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