1,974 research outputs found
Atrial high-rate episodes: prevalence, stroke risk, implications for management, and clinical gaps in evidence
Self-terminating atrial arrhythmias are commonly detected on continuous rhythm monitoring, e.g. by pacemakers or defibrillators. It is unclear whether the presence of these arrhythmias has therapeutic consequences. We sought to summarize evidence on the prevalence of atrial high-rate episodes (AHREs) and their impact on risk of stroke. We performed a comprehensive, tabulated review of published literature on the prevalence of AHRE. In patients with AHRE, but without atrial fibrillation (AF), we reviewed the stroke risk and the potential risk/benefit of oral anticoagulation. Atrial high-rate episodes are found in 10-30% of AF-free patients. Presence of AHRE slightly increases stroke risk (0.8% to 1%/year) compared with patients without AHRE. Atrial high-rate episode of longer duration (e.g. those >24 h) could be associated with a higher stroke risk. Oral anticoagulation has the potential to reduce stroke risk in patients with AHRE but is associated with a rate of major bleeding of 2%/year. Oral anticoagulation is not effective in patients with heart failure or survivors of a stroke without AF. It remains unclear whether anticoagulation is effective and safe in patients with AHRE. Atrial high-rate episodes are common and confer a slight increase in stroke risk. There is true equipoise on the best way to reduce stroke risk in patients with AHRE. Two ongoing trials (NOAH-AFNET 6 and ARTESiA) will provide much-needed information on the effectiveness and safety of oral anticoagulation using non-vitamin K antagonist oral anticoagulants in patients with AHRE.info:eu-repo/semantics/publishedVersio
Shot noise spectrum of superradiant entangled excitons
The shot noise produced by tunneling of electrons and holes into a double dot
system incorporated inside a p-i-n junction is investigated theoretically. The
enhancement of the shot noise is shown to originate from the entangled
electron-hole pair created by superradiance. The analogy to the superconducting
cooper pair box is pointed out. A series of Zeno-like measurements is shown to
destroy the entanglement, except for the case of maximum entanglement.Comment: 5 pages, 3 figures, to appear in Phys. Rev. B (2004
Current noise of a quantum dot p-i-n junction in a photonic crystal
The shot-noise spectrum of a quantum dot p-i-n junction embedded inside a
three-dimensional photonic crystal is investigated. Radiative decay properties
of quantum dot excitons can be obtained from the observation of the current
noise. The characteristic of the photonic band gap is revealed in the current
noise with discontinuous behavior. Applications of such a device in
entanglement generation and emission of single photons are pointed out, and may
be achieved with current technologies.Comment: 4 pages, 3 figures, to appear in Phys. Rev. B (2005
Non-equilibrium Entanglement and Noise in Coupled Qubits
We study charge entanglement in two Coulomb-coupled double quantum dots in
thermal equilibrium and under stationary non-equilibrium transport conditions.
In the transport regime, the entanglement exhibits a clear switching threshold
and various limits due to suppression of tunneling by Quantum Zeno localisation
or by an interaction induced energy gap. We also calculate quantum noise
spectra and discuss the inter-dot current correlation as an indicator of the
entanglement in transport experiments.Comment: 4 pages, 4 figure
Character of eigenstates of the 3D disordered Anderson Hamiltonian
We study numerically the character of electron eigenstates of the three
dimensional disordered Anderson model. Analysis of the statistics of inverse
participation ratio as well as numerical evaluation of the electron-hole
correlation function confirm that there are no localized states below the
mobility edge, as well as no metallic state in the tail of the conductive band.
We discuss also finite size effects observed in the analysis of all the
discussed quantities.Comment: 7 pages, 9 figures, resubmitted to Physical Review
Phase transitions and dark-state physics in two-color superradiance
We theoretically study an extension of the Dicke model, where the
single-particle Hamiltonian has three energy levels in Lambda-configuration,
i.e. the excited state is coupled to two non-degenerate ground states via two
independent quantized light fields. The corresponding many-body Hamiltonian can
be diagonalized in the thermodynamic limit with the help of a generalized
Holstein--Primakoff transformation. Analyzing the ground-state energy and the
excitation energies, we identify one normal and two superradiant phases,
separated by phase transitions of both first and second order. A phase with
both superradiant states coexisting is not stable. In addition, in the limit of
two degenerate ground states a dark state emerges, which seems to be analogous
to the dark state appearing in the well known stimulated Raman adiabatic
passage scheme.Comment: 9 pages, 6 figure
Frequency-dependent counting statistics in interacting nanoscale conductors
We present a formalism to calculate finite-frequency current correlations in
interacting nanoscale conductors. We work within the n-resolved density matrix
approach and obtain a multi-time cumulant generating function that provides the
fluctuation statistics, solely from the spectral decomposition of the
Liouvillian. We apply the method to the frequency-dependent third cumulant of
the current through a single resonant level and through a double quantum dot.
Our results, which show that deviations from Poissonian behaviour strongly
depend on frequency, demonstrate the importance of finite-frequency
higher-order cumulants in fully characterizing interactions.Comment: 4 pages, 2 figures, improved figures & discussion. J-ref adde
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