4,186 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
Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
The proton temperature anisotropy in the solar wind is known to be
constrained by the theoretical thresholds for pressure anisotropy-driven
instabilities. Here we use approximately 1 million independent measurements of
gyroscale magnetic fluctuations in the solar wind to show for the first time
that these fluctuations are enhanced along the temperature anisotropy
thresholds of the mirror, proton oblique firehose, and ion cyclotron
instabilities. In addition, the measured magnetic compressibility is enhanced
at high plasma beta () along the mirror instability
threshold but small elsewhere, consistent with expectations of the mirror mode.
The power in this frequency (the 'dissipation') range is often considered to be
driven by the solar wind turbulent cascade, an interpretation which should be
qualified in light of the present results. In particular, we show that the
short wavelength magnetic fluctuation power is a strong function of
collisionality, which relaxes the temperature anisotropy away from the
instability conditions and reduces correspondingly the fluctuation power.Comment: 4 pages, 4 figure
Can Quantum Lattice Fluctuations Destroy the Peierls Broken Symmetry Ground State?
The study of bond alternation in one-dimensional electronic systems has had a
long history. Theoretical work in the 1930s predicted the absence of bond
alternation in the limit of infinitely long conjugated polymers; a result later
contradicted by experimental investigations. When this issue was re-examined in
the 1950s it was shown in the adiabatic limit that bond alternation occurs for
any value of electron-phonon coupling. The question of whether this conclusion
remains valid for quantized nuclear degrees of freedom was first addressed in
the 1980s. Since then a series of numerical calculations on models with gapped,
dispersionless phonons have suggested that bond alternation is destroyed by
quantum fluctuations below a critical value of electron-phonon coupling. In
this work we study a more realistic model with gapless, dispersive phonons. By
solving this model with the DMRG method we show that bond alternation remains
robust for any value of electron-phonon coupling
Dynamic coexistence of various configurations: clusters vs.nuclei
The presence of energy shells in metallic clusters and atomic nuclei leads to
a peculiar relation between the number of particles N and the structure, and
this leads to a strong correlation between the energy spectrum and N. An
analysis of experimental data leads to the conclusion that, in addition to the
static Jahn-Teller effect, the dynamic effect leading to the quantum
coexistence of different configurations (quantum oscillations) plays an
important role. Such suggested coexistence is an essential feature of clusters
as well as nuclei, both finite Fermi systems.Comment: 6 pages, 2 figure
Level Sets of the Takagi Function: Local Level Sets
The Takagi function \tau : [0, 1] \to [0, 1] is a continuous
non-differentiable function constructed by Takagi in 1903. The level sets L(y)
= {x : \tau(x) = y} of the Takagi function \tau(x) are studied by introducing a
notion of local level set into which level sets are partitioned. Local level
sets are simple to analyze, reducing questions to understanding the relation of
level sets to local level sets, which is more complicated. It is known that for
a "generic" full Lebesgue measure set of ordinates y, the level sets are finite
sets. Here it is shown for a "generic" full Lebesgue measure set of abscissas
x, the level set L(\tau(x)) is uncountable. An interesting singular monotone
function is constructed, associated to local level sets, and is used to show
the expected number of local level sets at a random level y is exactly 3/2.Comment: 32 pages, 2 figures, 1 table. Latest version has updated equation
numbering. The final publication will soon be available at springerlink.co
Application of Advanced Nondestructive Evaluation Techniques for Cylindrical Composite Test Samples
Two nondestructive methods were applied to composite cylinder samples pressurized to failure in order to determine manufacturing quality and monitor damage progression under load. A unique computed tomography (CT) image processing methodology developed at NASA Glenn Research was used to assess the condition of the as-received samples while acoustic emission (AE) monitoring was used to identify both the extent and location of damage within the samples up to failure. Results show the effectiveness of both of these methods in identifying potentially critical fabrication issues and their resulting impact on performance
On the Dynamics of solitons in the nonlinear Schroedinger equation
We study the behavior of the soliton solutions of the equation
i((\partial{\psi})/(\partialt))=-(1/(2m)){\Delta}{\psi}+(1/2)W_{{\epsilon}}'({\psi})+V(x){\psi}
where W_{{\epsilon}}' is a suitable nonlinear term which is singular for
{\epsilon}=0. We use the "strong" nonlinearity to obtain results on existence,
shape, stability and dynamics of the soliton. The main result of this paper
(Theorem 1) shows that for {\epsilon}\to0 the orbit of our soliton approaches
the orbit of a classical particle in a potential V(x).Comment: 29 page
Double Time Window Targeting Technique: Real time DMRG dynamics in the PPP model
We present a generalized adaptive time-dependent density matrix
renormalization group (DMRG) scheme, called the {\it double time window
targeting} (DTWT) technique, which gives accurate results with nominal
computational resources, within reasonable computational time. This procedure
originates from the amalgamation of the features of pace keeping DMRG
algorithm, first proposed by Luo {\it et. al}, [Phys.Rev. Lett. {\bf 91},
049701 (2003)], and the time-step targeting (TST) algorithm by Feiguin and
White [Phys. Rev. B {\bf 72}, 020404 (2005)]. Using the DTWT technique, we
study the phenomena of spin-charge separation in conjugated polymers (materials
for molecular electronics and spintronics), which have long-range
electron-electron interactions and belong to the class of strongly correlated
low-dimensional many-body systems. The issue of real time dynamics within the
Pariser-Parr-Pople (PPP) model which includes long-range electron correlations
has not been addressed in the literature so far. The present study on PPP
chains has revealed that, (i) long-range electron correlations enable both the
charge and spin degree of freedom of the electron, to propagate faster in the
PPP model compared to Hubbard model, (ii) for standard parameters of the PPP
model as applied to conjugated polymers, the charge velocity is almost twice
that of the spin velocity and, (iii) the simplistic interpretation of
long-range correlations by merely renormalizing the {\it U} value of the
Hubbard model fails to explain the dynamics of doped holes/electrons in the PPP
model.Comment: Final (published) version; 39 pages, 13 figures, 1 table; 2 new
references adde
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