Institution
National Institute of Standards and Technology
Government•Gaithersburg, Maryland, United States•
About: National Institute of Standards and Technology is a government organization based out in Gaithersburg, Maryland, United States. It is known for research contribution in the topics: Laser & Scattering. The organization has 26667 authors who have published 60661 publications receiving 2215547 citations. The organization is also known as: National Bureau of Standards & NIST.
Topics: Laser, Scattering, Neutron scattering, NIST, Spectroscopy
Papers published on a yearly basis
Papers
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TL;DR: In this article, an optical atomic clock based on quantum-logic spectroscopy of the S 0↔ −3 P 0 transition in Al −+ was proposed, with a systematic uncertainty of 9.4×10 −19 and a frequency stability of 1.2×10−15 −15/sqrt[τ].
Abstract: We describe an optical atomic clock based on quantum-logic spectroscopy of the ^{1}S_{0}↔^{3}P_{0} transition in ^{27}Al^{+} with a systematic uncertainty of 9.4×10^{-19} and a frequency stability of 1.2×10^{-15}/sqrt[τ]. A ^{25}Mg^{+} ion is simultaneously trapped with the ^{27}Al^{+} ion and used for sympathetic cooling and state readout. Improvements in a new trap have led to reduced secular motion heating, compared to previous ^{27}Al^{+} clocks, enabling clock operation with ion secular motion near the three-dimensional ground state. Operating the clock with a lower trap drive frequency has reduced excess micromotion compared to previous ^{27}Al^{+} clocks. Both of these improvements have led to a reduced time-dilation shift uncertainty. Other systematic uncertainties including those due to blackbody radiation and the second-order Zeeman effect have also been reduced.
464 citations
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01 Jul 2000TL;DR: The TREC-8 Question Answering (QA) Track was the first large-scale evaluation of domain-independent question answering systems and was used to investigate whether the evaluation methodology used for document retrieval is appropriate for a different natural language processing task.
Abstract: The TREC-8 Question Answering (QA) Track was the first large-scale evaluation of domain-independent question answering systems. In addition to fostering research on the QA task, the track was used to investigate whether the evaluation methodology used for document retrieval is appropriate for a different natural language processing task. As with document relevance judging, assessors had legitimate differences of opinions as to whether a response actually answers a question, but comparative evaluation of QA systems was stable despite these differences. Creating a reusable QA test collection is fundamentally more difficult than creating a document retrieval test collection since the QA task has no equivalent to document identifiers.
463 citations
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TL;DR: In this article, a semi-circular bend specimen is used to determine the mode I fracture toughness of sedimentary rocks using three different core-based specimens and tests were performed on a typical laboratory compression or tension load frame.
Abstract: The International Society for Rock Mechanics has so far developed two standard methods for the determination of static fracture toughness of rock. They used three different core-based specimens and tests were to be performed on a typical laboratory compression or tension load frame. Another method to determine the mode I fracture toughness of rock using semi-circular bend specimen is herein presented. The specimen is semi-circular in shape and made from typical cores taken from the rock with any relative material directions noted. The specimens are tested in three-point bending using a laboratory compression test instrument. The failure load along with its dimensions is used to determine the fracture toughness. Most sedimentary rocks which are layered in structure may exhibit fracture properties that depend on the orientation and therefore measurements in more than one material direction may be necessary. The fracture toughness measurements are expected to yield a size-independent material property if certain minimum specimen size requirements are satisfied.
461 citations
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TL;DR: Octacalcium Phosphate and Hydroxyapatite: Crystallographic and Chemical Relations between Octacalium Phosphates and Hydroxypatite as mentioned in this paper.
Abstract: Octacalcium Phosphate and Hydroxyapatite: Crystallographic and Chemical Relations between Octacalcium Phosphate and Hydroxyapatite
460 citations
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TL;DR: In this paper, the structural and magnetic phase transitions in Fe1+ySexTe1-x.068Te exhibits a first-order phase transition near 67 K with a tetragonal-to-monoclinic structural transition and simultaneously develops a collinear antiferromagnetic (AF) order responsible for the entropy change across the transition.
Abstract: We use bulk magnetic susceptibility, electronic specific heat, and neutron scattering to study structural and magnetic phase transitions in Fe1+ySexTe1-x. Fe1.068Te exhibits a first-order phase transition near 67 K with a tetragonal-to-monoclinic structural transition and simultaneously develops a collinear antiferromagnetic (AF) order responsible for the entropy change across the transition. Systematic studies of the FeSe1-xTex system reveal that the AF structure and lattice distortion in these materials are different from those of FeAs-based pnictides. These results call into question the conclusions of present density-functional calculations, where FeSe1-xTex and FeAs-based pnictides are expected to have similar Fermi surfaces and therefore the same spin-density wave AF order.
460 citations
Authors
Showing all 26760 results
Name | H-index | Papers | Citations |
---|---|---|---|
Zhong Lin Wang | 245 | 2529 | 259003 |
John A. Rogers | 177 | 1341 | 127390 |
J. N. Butler | 172 | 2525 | 175561 |
Yury Gogotsi | 171 | 956 | 144520 |
Zhenan Bao | 169 | 865 | 106571 |
Gang Chen | 167 | 3372 | 149819 |
Michel C. Nussenzweig | 165 | 516 | 87665 |
Donald G. Truhlar | 165 | 1518 | 157965 |
Tobin J. Marks | 159 | 1621 | 111604 |
Jongmin Lee | 150 | 2257 | 134772 |
Galen D. Stucky | 144 | 958 | 101796 |
Thomas P. Russell | 141 | 1012 | 80055 |
William D. Travis | 137 | 605 | 93286 |
Peter Zoller | 134 | 734 | 76093 |
Anthony G. Evans | 130 | 576 | 65803 |