205 research outputs found
Utilisation d'un «indice de réflexion» pour l'analyse rapide des sédiments lacustres
L'indice de réflexion ou réflectance donne une mesure de la teinte du sédiment entre le blanc (100 %) et le noir (0 %). Sa valeur est directement liée à la teneur en matiÚres organiques.Les relations entre l'indice de réflexion et les teneurs en carbone organique, en azote Kjeldahl et en carbonates sont données pour les sédiments de dix lacs différents.Une étude particuliÚre de prélÚvements superficiels et de prélÚvements profonds montre qu'une simple mesure de la réflectance donne une valeur approchée de la composition chimique.Thorough studies on many lakes in Franche-Comté, especially chemical and physical investigations concerning sediments, have been carried out for several years. Seventy-one sediment samples have been extracted at different points and depths of ten lakes in Franche-Comté. The upper stratum between 0 and - 2,5 cm were isolated and studied.A comparison of visual observations and results of chemical analysis have shown that the darkest sediments are those which contain the greatest amount of organic matter. This finds its origin in a particularity of Franche-Comté lake sediments, which are often composed of dark black organic matter in different evolutionary states, and clear mineral compounds such as calcium carbonate and detrital particles.Differences in colouration were particularly difficult to determine, so colours were defined by the reflexion factor of the sediment surfaces, after the sediments had been well dried and homogeneized.The reflectance index was measured with a reftectometer, which is generally used for determinations of dark smokes in air pollution. The reflectance index was defined between the values 0 and 100. The value 0 was obtained with a standard black glass and the value 100 with a white filter paper.Comparing reflectance indices and ignition loss has shown that there is an exponential relationship between these two parameters. These relationships were found to exist between the reflectance index and organic carbon, Kjeldahl nitrogen and carbonates.Ignition loss, organic carbon and Kjeldahl nitrogen proportions increase, but, on the contrary, carbonate proportions decrease when the reflexion index increases.The values calculated and observed were then compared and generally the difference does not appear to be too great. Once, relationships have been established, it becomes possible to use them, after measuring reflexion indices, to obtain quickly and easily a good approximation of the composition.Special relationships may also be calculated for an individual lake, as shown for St-Point Lake. If one mineral constituent prevails in the composition, it is possible to obtain a good estimation of this component.For this lake twenty-eight sediment samples were extracted and for each sample three strata were separated. The reflectance index was again defined between the values 0 and 100, but the value 100 was now obtained by using a flat calcium carbonate surface, as the principal mineral part of St-Point Lake consists of calcium carbonate.Recent results obtained from two lake sediments of the Massif Central indicate that such relationships also exist for these lakes and that this method of estimating the chemical composition can be generalised.The calculated composition may often be sufficient to estimate values required for others studies on the same lakes, especially biological studies, thus avoiding laborious and extensive chemical determinations
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
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
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
Do Deep Neural Networks Contribute to Multivariate Time Series Anomaly Detection?
Anomaly detection in time series is a complex task that has been widely
studied. In recent years, the ability of unsupervised anomaly detection
algorithms has received much attention. This trend has led researchers to
compare only learning-based methods in their articles, abandoning some more
conventional approaches. As a result, the community in this field has been
encouraged to propose increasingly complex learning-based models mainly based
on deep neural networks. To our knowledge, there are no comparative studies
between conventional, machine learning-based and, deep neural network methods
for the detection of anomalies in multivariate time series. In this work, we
study the anomaly detection performance of sixteen conventional, machine
learning-based and, deep neural network approaches on five real-world open
datasets. By analyzing and comparing the performance of each of the sixteen
methods, we show that no family of methods outperforms the others. Therefore,
we encourage the community to reincorporate the three categories of methods in
the anomaly detection in multivariate time series benchmarks
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
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
Comparison of the Hemostatic Efficacy of Pathogen-Reduced Platelets vs Untreated Platelets in Patients With Thrombocytopenia and Malignant Hematologic Diseases: A Randomized Clinical Trial
Importance: Pathogen reduction of platelet concentrates may reduce transfusion-transmitted infections but is associated with qualitative impairment, which could have clinical significance with regard to platelet hemostatic capacity.
Objective: To compare the effectiveness of platelets in additive solution treated with amotosalen-UV-A vs untreated platelets in plasma or in additive solution in patients with thrombocytopenia and hematologic malignancies.
Design, Setting, and Participants: The Evaluation of the Efficacy of Platelets Treated With Pathogen Reduction Process (EFFIPAP) study was a randomized, noninferiority, 3-arm clinical trial performed from May 16, 2013, through January 21, 2016, at 13 French tertiary university hospitals. Clinical signs of bleeding were assessed daily until the end of aplasia, transfer to another department, need for a specific platelet product, or 30 days after enrollment. Consecutive adult patients with bone marrow aplasia, expected hospital stay of more than 10 days, and expected need of platelet transfusions were included.
Interventions: At least 1 transfusion of platelets in additive solution with amotosalen-UV-A treatment, in plasma, or in additive solution.
Main Outcomes and Measures: The proportion of patients with grade 2 or higher bleeding as defined by World Health Organization criteria.
Results: Among 790 evaluable patients (mean [SD] age, 55 [13.4] years; 458 men [58.0%]), the primary end point was observed in 126 receiving pathogen-reduced platelets in additive solution (47.9%; 95% CI, 41.9%-54.0%), 114 receiving platelets in plasma (43.5%; 95% CI, 37.5%-49.5%), and 120 receiving platelets in additive solution (45.3%; 95% CI, 39.3%-51.3%). With a per-protocol population with a prespecified margin of 12.5%, noninferiority was not achieved when pathogen-reduced platelets in additive solution were compared with platelets in plasma (4.4%; 95% CI, -4.1% to 12.9%) but was achieved when the pathogen-reduced platelets were compared with platelets in additive solution (2.6%; 95% CI, -5.9% to 11.1%). The proportion of patients with grade 3 or 4 bleeding was not different among treatment arms.
Conclusions and Relevance: Although the hemostatic efficacy of pathogen-reduced platelets in thrombopenic patients with hematologic malignancies was noninferior to platelets in additive solution, such noninferiority was not achieved when comparing pathogen-reduced platelets with platelets in plasma.
Trial Registration: clinicaltrials.gov Identifier: NCT01789762
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