1,614 research outputs found
A Comparison of the High-Frequency Magnetic Fluctuations in Insulating and Superconducting La2-xSrxCuO4
Inelastic neutron scattering performed at a spallation source is used to make
absolute measurements of the dynamic susceptibility of insulating La2CuO4 and
superconducting La2-xSrxCuO4 over the energy range 15<EN<350 meV. The effect of
Sr doping on the magnetic excitations is to cause a large broadening in
wavevector and a substantial change in the spectrum of the local spin
fluctuations. Comparison of the two compositions reveals a new energy scale of
22 meV in La1.86Sr0.14CuO4.Comment: RevTex, 7 Pages, 4 postscript figure
Spacetime Embedding Diagrams for Black Holes
We show that the 1+1 dimensional reduction (i.e., the radial plane) of the
Kruskal black hole can be embedded in 2+1 Minkowski spacetime and discuss how
features of this spacetime can be seen from the embedding diagram. The purpose
of this work is educational: The associated embedding diagrams may be useful
for explaining aspects of black holes to students who are familiar with special
relativity, but not general relativity.Comment: 22 pages, 21 figures, RevTex. To be submitted to the American Journal
of Physics. Experts will wish only to skim appendix A and to look at the
pictures. Suggested Maple code is now compatible with MapleV4r
Detection of the Unusual Magnetic Orders in the Pseudogap Region of a High-Temperature Superconducting YBa2Cu3O6.6 Crystal by Muon-Spin Relaxation
We present muon spin relaxation (muSR) measurements on a large YBa2Cu3O6.6
single crystal in which two kinds of unusual magnetic order have been detected
in the pseudogap region by neutron scattering. A comparison is made to
measurements on smaller, higher quality YBa2Cu3Oy single crystals. One type of
magnetic order is observed in all samples, but does not evolve significantly
with hole doping. A second type of unusual magnetic order is observed only in
the YBa2Cu3O6.6 single crystal. This magnetism has an ordered magnetic moment
that is quantitatively consistent with the neutron experiments, but is confined
to just a small volume of the sample (~ 3%). Our findings do not support
theories that ascribe the pseudogap to a state characterized by loop-current
order, but instead indicate that dilute impurity phases are the source of the
unusual magnetic orders in YBa2Cu3Oy.Comment: 4 pages, 4 figure
Extreme cavity expansion in soft solids: damage without fracture
Cavitation is a common damage mechanism in soft solids. Here, we study this
using a phase-separation technique in stretched, elastic solids to controllably
nucleate and grow small cavities by several orders of magnitude. The ability to
make stable cavities of different sizes, as well as the huge range of
accessible strains, allows us to systematically study the early stages of
cavity expansion. Cavities grow in a scale-free manner, accompanied by
irreversible bond breakage that is distributed around the growing cavity,
rather than being localized to a crack tip. Furthermore, cavities appear to
grow at constant driving pressure. This has strong analogies with the
plasticity that occurs surrounding a growing void in ductile metals. In
particular we find that, although elastomers are normally considered as brittle
materials, small-scale cavity expansion is more like a ductile process. Our
results have broad implications for understanding and controlling failure in
soft solids
Global change, een wereld van verandering
College gegeven op 24 juni 1997 ter gelegenheid van het afscheid van Willem G. Mook als hoogleraar in de isotopenfysica aan de RijksUniversiteit Groninge
The Effect of Fossil Fuel and Biogenic CO, on the 13C and 14C Content of Atmospheric Carbon Dioxide
The normalization of a measured delta-14C value of atmospheric CO2 to a delta-13C value of -25 per mil does not take into account the presence of fossil fuel and biogenic CO2. In this paper, we try to assess these contaminations as well as the proper 14C content of "clean air".This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
Does the day of the week predict the presence of microbiologically confirmed ventilator-associated pneumonia?
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