234 research outputs found
IRC préterminale : il n'est jamais trop tôt pour référer au spécialiste : Revue cochrane pour le praticien
Cette rubrique présente les résultats d'une revue systématique récente telle que publiée dans la Cochrane Library (www.thecochranelibrary.com). Volontairement limité à un champ de recherche circonscrit, cet article reflète l'état actuel des connaissances de ce domaine. Il ne s'agit donc pas de recommandations pour guider la prise en charge d'une problématique clinique considérée dans sa globalité (guidelines). Les auteurs de ce résumé se basent sur la revue systématique et ne remettent pas en question le choix des articles inclus dans la revue.
Scénario: Vous suivez un patient de 71 ans connu pour un diabète et une hypertension bien contrôlés, ainsi qu'une insuffisance rénale chronique de longue date, progressive, actuellement sévère (créatinine à 267 mmol/l, taux de filtration glomérulaire estimé (TFGe) à 21 ml/min/1,73 m2). Son état général est bon, son poids est stable et il ne présente pas de symptômes urémiques.
Question: Faut-il adresser ce patient à un néphrologue
Structural and magnetic dynamics of a laser induced phase transition in FeRh
We use time-resolved x-ray diffraction and magnetic optical Kerr effect to
study the laser induced antiferromagnetic to ferromagnetic phase transition in
FeRh. The structural response is given by the nucleation of independent
ferromagnetic domains (\tau_1 ~ 30ps). This is significantly faster than the
magnetic response (\tau_2 ~ 60ps) given by the subsequent domain realignment.
X-ray diffraction shows that the two phases co-exist on short time-scales and
that the phase transition is limited by the speed of sound. A nucleation model
describing both the structural and magnetic dynamics is presented.Comment: 5 pages, 3 figures - changed to reflect version accepted for PR
Optical Cherenkov radiation by cascaded nonlinear interaction: an efficient source of few-cycle energetic near- to mid-IR pulses
When ultrafast noncritical cascaded second-harmonic generation of energetic
femtosecond pulses occur in a bulk lithium niobate crystal optical Cherenkov
waves are formed in the near- to mid-IR. Numerical simulations show that the
few-cycle solitons radiate Cherenkov (dispersive) waves in the
\lambda=2.2-4.5\mic range when pumping at \lambda_1=1.2-1.8\mic. The exact
phase-matching point depends on the soliton wavelength, and we show that a
simple longpass filter can separate the Cherenkov waves from the solitons. The
Cherenkov waves are born few-cycle with an excellent Gaussian pulse shape, and
the conversion efficiency is up to 25%. Thus, optical Cherenkov waves formed
with cascaded nonlinearities could become an efficient source of energetic
near- to mid-IR few-cycle pulses.Comment: Extended version of Nonlinear Optics 2011 contribution
http://www.opticsinfobase.org/abstract.cfm?URI=NLO-2011-NTuA7. Submitted for
Optics Express special issue for NLO conferenc
Étude des marqueurs génétiques sanguins dans deux races de poneys de pologne
International audienc
Melting of magnetic order in NaOsO<sub>3</sub> by femtosecond laser pulses
NaOsO3 has recently attracted significant attention for the strong coupling between its electronic band structure and magnetic ordering. Here, we used time-resolved magnetic x-ray diffraction to determine the timescale of the photoinduced antiferromagnetic dynamics in NaOsO3. Our measurements are consistent with a sub-100 fs melting of the antiferromagnetic long-range order that occurs significantly faster than the lattice dynamics as monitored by the transient change in intensity of selected Bragg structural reflections, which instead show a decrease of intensity on a timescale of several ps
Temperature-dependent electron-phonon coupling in LaSrCuO probed by femtosecond X-ray diffraction
The strength of the electron-phonon coupling parameter and its evolution
throughout a solid's phase diagram often determines phenomena such as
superconductivity, charge- and spin-density waves. Its experimental
determination relies on the ability to distinguish thermally activated phonons
from those emitted by conduction band electrons, which can be achieved in an
elegant way by ultrafast techniques. Separating the electronic from the
out-of-equilibrium lattice subsystems, we probed their re-equilibration by
monitoring the transient lattice temperature through femtosecond X-ray
diffraction in LaSrCuO single crystals with =0.1 and 0.21.
The temperature dependence of the electron-phonon coupling is obtained
experimentally and shows similar trends to what is expected from the
\textit{ab-initio} calculated shape of the electronic density-of-states near
the Fermi energy. This study evidences the important role of band effects in
the electron-lattice interaction in solids, in particular in superconductors
The empirical basis for modelling glacial erosion rates
Glaciers are highly effective agents of erosion that have profoundly shaped Earth’s surface, but there is uncertainty about how glacial erosion should be parameterised in landscape evolution models. Glacial erosion rate is usually modelled as a function of glacier sliding velocity, but the empirical basis for this relationship is weak. In turn, climate is assumed to control sliding velocity and hence erosion, but this too lacks empirical scrutiny. Here, we present statistically robust relationships between erosion rates, sliding velocities, and climate from a global compilation of 38 glaciers. We show that sliding is positively and significantly correlated with erosion, and derive a relationship for use in erosion models. Our dataset further demonstrates that the most rapid erosion is achieved at temperate glaciers with high mean annual precipitation, which serve to promote rapid sliding. Precipitation has received little attention in glacial erosion studies, but our data illustrate its importance
Nanoscale depth-resolved coherent femtosecond motion in laser-excited bismuth
We employ grazing-incidence femtosecond x-ray diffraction to characterize the coherent, femtosecond laser-induced lattice motion of a bismuth crystal as a function of depth from the surface with a temporal resolution of 193 +/- 8 fs. The data show direct consequences on the lattice motion from carrier diffusion and electron-hole interaction, allowing us to estimate an effective diffusion rate of D=2.3 +/- 0.3 cm(2)/s for the highly excited carriers and an electron-hole interaction time of 260 +/- 20 fs
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