219 research outputs found
The nodal gap component as a good candidate for the superconducting order parameter in cuprates
Although more than twenty years have passed since the discovery of high
temperature cuprate superconductivity, the identification of the
superconducting order parameter is still under debate. Here, we show that the
nodal gap component is the best candidate for the superconducting order
parameter. It scales with the critical temperature over a wide doping
range and displays a significant temperature dependence below in both the
underdoped and the overdoped regimes of the phase diagram. In contrast, the
antinodal gap component does not scale with in the underdoped side and
appears to be controlled by the pseudogap amplitude. Our experiments establish
the existence of two distinct gaps in the underdoped cuprates
Evolution of the gaps through the cuprate phase-diagram
The actual physical origin of the gap at the antinodes, and a clear
identification of the superconducting gap are fundamental open issues in the
physics of high- superconductors. Here, we present a systematic electronic
Raman scattering study of a mercury-based single layer cuprate, as a function
of both doping level and temperature. On the deeply overdoped side, we show
that the antinodal gap is a true superconducting gap. In contrast, on the
underdoped side, our results reveal the existence of a break point close to
optimal doping below which the antinodal gap is gradually disconnected from
superconductivity. The nature of both the superconducting and normal state is
distinctly different on each side of this breakpoint
Forced Symmetry Breaking from SO(3) to SO(2) for Rotating Waves on the Sphere
We consider a small SO(2)-equivariant perturbation of a reaction-diffusion
system on the sphere, which is equivariant with respect to the group SO(3) of
all rigid rotations. We consider a normally hyperbolic SO(3)-group orbit of a
rotating wave on the sphere that persists to a normally hyperbolic
SO(2)-invariant manifold . We investigate the effects of this
forced symmetry breaking by studying the perturbed dynamics induced on
by the above reaction-diffusion system. We prove that depending
on the frequency vectors of the rotating waves that form the relative
equilibrium SO(3)u_{0}, these rotating waves will give SO(2)-orbits of rotating
waves or SO(2)-orbits of modulated rotating waves (if some transversality
conditions hold). The orbital stability of these solutions is established as
well. Our main tools are the orbit space reduction, Poincare map and implicit
function theorem
Three-dimensional magnetic resonance imaging for groundwater
International audienceThe surface nuclear magnetic resonance method (SNMR) is an established geophysical tool routinely used for investigating one-dimensional (1D) and sometimes 2D subsurface water-saturated formations. We have expanded the tool by developing a 3D application. 3D-SNMR is a large-scale method that allows magnetic resonance imaging of groundwater down to about 80 m. Similar to most surface geophysical methods, 3D-SNMR has limited resolution, but it is effective for investigating water-saturated geological formations larger than several tens of meters. Because the performance of the method depends on variable survey conditions, we cannot estimate it in general. For demonstration purposes, we present an example of numerical modeling under fixed conditions. Results show that under certain conditions it is possible to detect a water volume as small as 500 m(3) and the detection threshold depends on the ambient electromagnetic noise magnitude and on the location of the target volume relative to the SNMR loops. The 3D-SNMR method was used to investigate accumulated water within the Tete Rousse glacier (French Alps). Inversion of the field measurements made it possible to locate the principal reservoir in the central part of the glacier and estimate the volume of accumulated water. These results were verified by 20 boreholes installed after the 3D-SNMR results were obtained and by pumping water out of the glacier. Very good correspondence between the 3D-SNMR and borehole results was observed
The clinical Pseudomonas fluorescens MFN1032 strain exerts a cytotoxic effect on epithelial intestinal cells and induces Interleukin-8 via the AP-1 signaling pathway
International audienc
Electronic structure in underdoped cuprates due to the emergence of a pseudogap
The phenomenological Green's function developed in the works of Yang, Rice
and Zhang has been very successful in understanding many of the anomalous
superconducting properties of the deeply underdoped cuprates. It is based on
considerations of the resonating valence bond spin liquid approximation and is
designed to describe the underdoped regime of the cuprates. Here we emphasize
the region of doping, , just below the quantum critical point at which the
pseudogap develops. In addition to Luttinger hole pockets centered around the
nodal direction, there are electron pockets near the antinodes which are
connected to the hole pockets by gapped bridging contours. We determine the
contours of nearest approach as would be measured in angular resolved
photoemission experiments and emphasize signatures of the Fermi surface
reconstruction from the large Fermi contour of Fermi liquid theory (which
contains hole states) to the Luttinger pocket (which contains hole
states). We find that the quasiparticle effective mass renormalization
increases strongly towards the edge of the Luttinger pockets beyond which it
diverges.Comment: 11 pages, 9 figure
Interactive comment on âMonitoring water accumulation in a glacier using magnetic resonance imagingâ by A. Legchenko et al.
TĂȘte Rousse is a small polythermal glacier located in the Mont Blanc area
(French Alps) at an altitude of 3100 to 3300 m. In 1892, an outburst flood
from this glacier released about 200 000 m3 of water mixed with ice,
causing much damage. A new accumulation of melt water in the glacier was not
excluded. The uncertainty related to such glacier conditions initiated an
extensive geophysical study for evaluating the hazard. Using
three-dimensional surface nuclear magnetic resonance imaging (3-D-SNMR), we
showed that the temperate part of the TĂȘte Rousse glacier contains two
separate water-filled caverns (central and upper caverns). In 2009, the
central cavern contained about 55 000 m3 of water. Since 2010, the
cavern is drained every year. We monitored the changes caused by this pumping
in the water distribution within the glacier body. Twice a year, we carried
out magnetic resonance imaging of the entire glacier and estimated the volume
of water accumulated in the central cavern. Our results show changes in
cavern geometry and recharge rate: in two years, the central cavern lost
about 73% of its initial volume, but 65% was lost in one year after
the first pumping. We also observed that, after being drained, the cavern was
recharged at an average rate of 20 to 25 m3 dâ1 during the winter
months and 120 to 180 m3 dâ1 in summer. These observations
illustrate how ice, water and air may refill englacial volume being emptied
by artificial draining. Comparison of the 3-D-SNMR results with those
obtained by drilling and pumping showed a very good correspondence,
confirming the high reliability of 3-D-SNMR imaging
Laboratory-based evaluation of legionellosis epidemiology in Ontario, Canada, 1978 to 2006
BACKGROUND: Legionellosis is a common cause of severe community acquired pneumonia and
respiratory disease outbreaks. The Ontario Public Health Laboratory (OPHL) has conducted most
testing for Legionella species in the Canadian province of Ontario since 1978, and represents a
multi-decade repository of population-based data on legionellosis epidemiology. We sought to
provide a laboratory-based review of the epidemiology of legionellosis in Ontario over the past 3
decades, with a focus on changing rates of disease and species associated with legionellosis during
that time period.
METHODS: We analyzed cases that were submitted and tested positive for legionellosis from 1978
to 2006 using Poisson regression models incorporating temporal, spatial, and demographic
covariates. Predictors of infection with culture-confirmed L. pneumophila serogroup 1 (LP1) were
evaluated with logistic regression models.
Results: 1,401 cases of legionellosis tested positive from 1978 to 2006. As in other studies, we
found a late summer to early autumn seasonality in disease occurrence with disease risk increasing
with age and in males. In contrast to other studies, we found a decreasing trend in cases in the
recent decade (IRR 0.93, 95% CI 0.91 to 0.95, P-value = 0.001); only 66% of culture-confirmed
isolates were found to be LP1.
CONCLUSION: Despite similarities with disease epidemiology in other regions, legionellosis appears
to have declined in the past decade in Ontario, in contrast to trends observed in the United States
and parts of Europe. Furthermore, a different range of Legionella species is responsible for illness,
suggesting a distinctive legionellosis epidemiology in this North American region
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