467 research outputs found
Pharmacologie des anti-Xa et mécanismes d’action
RésuméLa famille des anticoagulants oraux s’agrandit et les anticoagulants oraux directs s’annoncent comme l’une des grandes révolutions thérapeutiques notamment après l’autorisation de leur utilisation chez les patients en fibrillation atriale par les autorités réglementaires. Cependant, ces médicaments ne sont pas dénués de particularités et nous aborderons dans cette revue de la littérature les principales caractéristiques pharmacologiques des nouveaux anti-Xa oraux directs.SummaryThe oral anticoagulant family is growing and the new oral anticoagulants have been heralded as an important therapeutic revolution, particularly after receiving regulatory authority approval for their use in stroke prevention in patients with atrial fibrillation. However, these drugs have some specific features. In this review, we shed light on the main pharmacological characteristics of the new direct anti-Xa inhibitors
An analysis of the fluctuations of the geomagnetic dipole
The time evolution of the strength of the Earth's virtual axial dipole moment
(VADM) is analyzed by relating it to the Fokker-Planck equation, which
describes a random walk with VADM-dependent drift and diffusion coefficients.
We demonstrate first that our method is able to retrieve the correct shape of
the drift and diffusion coefficients from a time series generated by a test
model. Analysis of the Sint-2000 data shows that the geomagnetic dipole mode
has a linear growth time of 13 to 33 kyr, and that the nonlinear quenching of
the growth rate follows a quadratic function of the type [1-(x/x0)^2]. On
theoretical grounds, the diffusive motion of the VADM is expected to be driven
by multiplicative noise, and the corresponding diffusion coefficient to scale
quadratically with dipole strength. However, analysis of the Sint-2000 VADM
data reveals a diffusion which depends only very weakly on the dipole strength.
This may indicate that the magnetic field quenches the amplitude of the
turbulent velocity in the Earth's outer core.Comment: 11 pages, 6 figure
EXAMENS MORPHOLOGIQUES, CARYOLOGIQUES, PHYSIOLOGIQUES ET PATHOLOGIQUES DE BOUCS STÉRILES SANS CORNES
Pénétrance de l'effet de stérilité totale lié au gène sans cornes p, chez les boucs
International audienc
Short-lived spots in solar-like stars as observed by CoRoT
Context. CoRoT light curves have an unprecedented photometric quality, having
simultaneously a high signal-to-noise ratio, a long time span and a nearly
continuous duty-cycle. Aims. We analyse the light-curves of four bright targets
observed in the seismology field and study short-lived small spots in
solar-like stars. Methods. We present a simple spot modeling by iterative
analysis. Its ability to extract relevant parameters is ensured by implementing
relaxation steps to avoid convergence to local minima of the sum of the
residuals between observations and modeling. The use of Monte-Carlo simulations
allows us to estimate the performance of the fits. Results. Our starspot
modeling gives a representation of the spots on these stars in agreement with
other well tested methods. Within this framework, parameters such as rigid-body
rotation and spot lifetimes seem to be precisely determined. Then, the
lifetime/rotation period ratios are in the range 0.5 - 2, and there is clear
evidence for differential rotation.Comment: 11 pages Accepted in A&
Assessing the importance and expression of the 6-year geomagnetic oscillation
The first time derivative of residual length-of-day observations is known to contain a distinctive 6 year periodic oscillation. Here we theorize that through the flow accelerations at the top of the core the same periodicity should arise in the geomagnetic secular acceleration. We use the secular acceleration of the CHAOS-3 and CM4 geomagnetic field models to recover frequency spectra through both a traditional Fourier analysis and an empirical mode decomposition. We identify the 6 year periodic signal in the geomagnetic secular acceleration and characterize its spatial behavior. This signal seems to be closely related to recent geomagnetic jerks. We also identify a 2.5 year periodic signal in CHAOS-3 with unknown origin. This signal is strictly axially dipolar and is absent from other magnetic or geodetic time series
Linking phytoplankton pigment composition and optical properties: A framework for developing remote-sensing metrics for monitoring cyanobacteria
International audienceThis study has been performed in the framework of a research program aiming to develop a low-cost aerial sensor for the monitoring of cyanobacteria in freshwater ecosystems that could be used for early detection. Several empirical and mechanistic remote-sensing tools have been already developed and tested at large scales and have proven useful in monitoring cyanobacterial blooms. However, the effectiveness of these tools for early detection is hard to assess because such work requires the detection of low concentrations of characteristic pigments amid complex ecosystems exhibiting several confounding factors (turbidity, blooms of other species, etc.). We developed a framework for performing high-throughput measurements of the absorbance and reflectance of small volumes (~= 20 mL) of controlled mixtures of phytoplankton species and studied the potential of this framework to validate remote-sensing proxies of cyanobacteria concentration. The absorption and reflectance spectra of single and multiple cultures carried a specific signal that allowed for the quantitative analysis of culture mixes. This specific signal was shown to be related to known pigment absorbance spectra. The concentrations of chlorophyll-a and -b, phycocyanin and phycoerythrin could be obtained from direct absorbance measurements and were correlated with the concentration obtained after pigment extraction (R2 ≥ 0.96 for all pigments). A systematic test of every possible two-band and three-band normalized difference between optical indices was then performed, and the coincidental correlation with chlorophyll-b (absent in cyanobacteria) was used as an indicator of non-specificity. Two-band indices were shown to suffer from non-specificity issues and could not yield strong and specific relationships with phycocyanin or phycoerythrin (maximum R2 0.8)
Erratum to: CDOM fluorescence as a proxy of DOC concentration in natural waters: a comparison of four contrasting tropical systems
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