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An investigation into wound infection and abscess formation in a mine
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Superconductivity induced by spark erosion in ZrZn2
We show that the superconductivity observed recently in the weak itinerant
ferromagnet ZrZn2 [C. Pfleiderer et al., Nature (London) 412, 58 (2001)] is due
to remnants of a superconducting layer induced by spark erosion. Results of
resistivity, susceptibility, specific heat and surface analysis measurements on
high-quality ZrZn2 crystals show that cutting by spark erosion leaves a
superconducting surface layer. The resistive superconducting transition is
destroyed by chemically etching a layer of 5 microns from the sample. No
signature of superconductivity is observed in rho(T) of etched samples at the
lowest current density measured, J=675 Am-2, and at T < 45 mK. EDX analysis
shows that spark-eroded surfaces are strongly Zn depleted. The simplest
explanation of our results is that the superconductivity results from an alloy
with higher Zr content than ZrZn2.Comment: Final published versio
Electron and ion stagnation at the collision front between two laser produced plasmas
We report results from a combined optical interferometric and spectrally resolved imaging study on colliding laser produced aluminium plasmas. A Nomarski interferometer was used to probe the spatio-temporal distribution of electron densities at the collision front. Analysis of the resulting interferograms reveals the formation and evolution of a localized electron density feature with a well-defined profile reminiscent of a stagnation layer. Electron stagnation begins at a time delay of 10 ns after the peak of the plasma generating laser pulse. The peak electron density was found to exceed 10^19 cm^−3 and the layer remained well defined up to a time delay of ca 100 ns. Temporally and spectrally resolved optical imaging was also undertaken, to compare the Al^+ ion distribution with that of the 2D electron density profile. This revealed nascent stagnation of singly charged ions at a delay time of 20 ns. We attribute these results to the effects of space charge separation in the seed plasma plumes
Some Directions beyond Traditional Quantum Secret Sharing
We investigate two directions beyond the traditional quantum secret sharing
(QSS). First, a restriction on QSS that comes from the no-cloning theorem is
that any pair of authorized sets in an access structure should overlap. From
the viewpoint of application, this places an unnatural constraint on secret
sharing. We present a generalization, called assisted QSS (AQSS), where access
structures without pairwise overlap of authorized sets is permissible, provided
some shares are withheld by the share dealer. We show that no more than
withheld shares are required, where is the minimum number
of {\em partially linked classes} among the authorized sets for the QSS. Our
result means that such applications of QSS need not be thwarted by the
no-cloning theorem. Secondly, we point out a way of combining the features of
QSS and quantum key distribution (QKD) for applications where a classical
information is shared by quantum means. We observe that in such case, it is
often possible to reduce the security proof of QSS to that of QKD.Comment: To appear in Physica Scripta, 7 pages, 1 figure, subsumes
arXiv:quant-ph/040720
What the resonance peak cannot do
In certain cuprates, a spin 1 resonance mode is prominent in the magnetic
structure measured by neutron scattering. It has been proposed that this mode
is responsible for significant features seen in other spectroscopies, such as
photoemission and optical absorption, which are sensitive to the charge
dynamics, and even that this mode is the boson responsibile for ``mediating''
the superconducting pairing. We show that its small (measured) intensity and
weak coupling to electron-hole pairs (as deduced from the measured lifetime)
disqualifies the resonant mode from either proposed role.Comment: 4 pages, no figur
Transport and Thermodynamic Evidence for a Marginal Fermi Liquid State in ZrZn
Measurements of low temperature transport and thermodynamic properties have
been used to characterize the non-Fermi liquid state of the itinerant
ferromagnet ZrZn. We observe a temperature dependence of the
electrical resistivity at zero field, which becomes like in an applied
field of 9 T. In zero field we also measured the thermal conductivity, and we
see a novel linear in dependence of the difference between the thermal and
electrical resistivities. Heat capacity measurements, also at zero field,
reveal an upturn in the electronic contribution at low temperatures when the
phonon term is subtracted. Taken together, we argue that these properties are
consistent with a marginal Fermi liquid state which is predicted by a
mean-field model of enhanced spin fluctuations on the border of ferromagnetism
in three dimensions. We compare our data to quantitative predictions and
establish this model as a compelling theoretical framework for understanding
ZrZn.Comment: 10 pages, 10 figure
Is a combination of varenicline and nicotine patch more effective in helping smokers quit than varenicline alone? A randomised controlled trial
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
In Memoriam: Henry Lane Bruner; Lowell Holbrook Chamberlain; Clyde W. Emmons; Annie Wilson Fleming; William Headrick Gemmill; Thomas J. Maney; Florence Willey Nichols; Henry Waldo Norris; Charles Dana Reed
Spin orthogonality catastrophe in two-dimensional antiferromagnets and superconductors
We compute the spectral function of a spin S hole injected into a
two-dimensional antiferromagnet or superconductor in the vicinity of a magnetic
quantum critical point. We show that, near van Hove singularities, the problem
maps onto that of a static vacancy carrying excess spin S. The hole creation
operator is characterized by a new boundary anomalous dimension and a vanishing
quasiparticle residue at the critical point. We discuss possible relevance to
photoemission spectra of cuprate superconductors near the anti-nodal points.Comment: (v1) 4 pages, 2 figures; field theory afficionados - see also
cond-mat/0011233; (v2) added figure of Monte Carlo data; (v3) corrected typo
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