1,789 research outputs found
The Framework of Anglo-Soviet Commercial Relations: The British View
Considering that a majority of elderlies are non-users of computers and Internet we developed a telemonitoring system for elderly heart failure (HF) home care patients based on digital pen technology - a technology never used before by this patient group. We implemented the system in clinical use in a 13 months long study. Fourteen patients (mean/median age 84 years) with severe HF participated. They accepted the technology and performed daily reports of their health state using the digital pen and a Health Diary form. Via the system the clinicians detected all HF-related deteriorations at an early stage and thereby prevented hospital re-admissions for all patients during the study, implying improved symptom control and large cost savings
Transport of Correlated Electrons through Disordered Chains: A Perspective on Entanglement, Conductance, and Disorder Averaging
We investigate electron transport in disordered Hubbard chains contacted to
macroscopic leads, via the non-equilibrium Green's functions technique. We
observe a cross-over of currents and conductances at finite bias which depends
on the relative strength of disorder and interactions. The finite-size scaling
of the conductance is highly dependent on the interaction strength, and
exponential attenuation is not always seen. We provide a proof that the
Coherent Potential Approximation, a widely used method for treating disorder
averages, fulfils particle conservation at finite bias with or without electron
correlations. Finally, our results hint that the observed trends in conductance
due to interactions and disorder also appear as signatures in the single-site
entanglement entropy.Comment: 5 pages, 4 figure
Effective bias and potentials in steady-state quantum transport: A NEGF reverse-engineering study
Using non-equilibrium Green's functions combined with many-body perturbation
theory, we have calculated steady-state densities and currents through short
interacting chains subject to a finite electric bias. By using a steady-state
reverse-engineering procedure, the effective potential and bias which reproduce
such densities and currents in a non-interacting system have been determined.
The role of the effective bias is characterised with the aid of the so-called
exchange-correlation bias, recently introduced in a steady-state
density-functional-theory formulation for partitioned systems. We find that the
effective bias (or, equivalently, the exchange-correlation bias) depends
strongly on the interaction strength and the length of the central (chain)
region. Moreover, it is rather sensitive to the level of many-body
approximation used. Our study shows the importance of the
effective/exchange-correlation bias out of equilibrium, thereby offering hints
on how to improve the description of density-functional-theory based approaches
to quantum transport
Partial self-consistency and analyticity in many-body perturbation theory: particle number conservation and a generalized sum rule
We consider a general class of approximations which guarantees the
conservation of particle number in many-body perturbation theory. To do this we
extend the concept of -derivability for the self-energy to a
larger class of diagrammatic terms in which only some of the Green's function
lines contain the fully dressed Green's function . We call the corresponding
approximations for partially -derivable. A special subclass of
such approximations, which are gauge-invariant, is obtained by dressing loops
in the diagrammatic expansion of consistently with . These
approximations are number conserving but do not have to fulfill other
conservation laws, such as the conservation of energy and momentum. From our
formalism we can easily deduce if commonly used approximations will fulfill the
continuity equation, which implies particle number conservation. We further
show how the concept of partial -derivability plays an important role in
the derivation of a generalized sum rule for the particle number, which reduces
to the Luttinger-Ward theorem in the case of a homogeneous electron gas, and
the Friedel sum rule in the case of the Anderson model. To do this we need to
ensure that the Green's function has certain complex analytic properties, which
can be guaranteed if the spectral function is positive semi-definite.The latter
property can be ensured for a subset of partially -derivable
approximations for the self-energy, namely those that can be constructed from
squares of so-called half-diagrams. In case the analytic requirements are not
fulfilled we highlight a number of subtle issues related to branch cuts, pole
structure and multi-valuedness. We also show that various schemes of computing
the particle number are consistent for particle number conserving
approximations.Comment: Minor changes, corrected typo
A Householder-based algorithm for Hessenberg-triangular reduction
The QZ algorithm for computing eigenvalues and eigenvectors of a matrix
pencil requires that the matrices first be reduced to
Hessenberg-triangular (HT) form. The current method of choice for HT reduction
relies entirely on Givens rotations regrouped and accumulated into small dense
matrices which are subsequently applied using matrix multiplication routines. A
non-vanishing fraction of the total flop count must nevertheless still be
performed as sequences of overlapping Givens rotations alternately applied from
the left and from the right. The many data dependencies associated with this
computational pattern leads to inefficient use of the processor and poor
scalability.
In this paper, we therefore introduce a fundamentally different approach that
relies entirely on (large) Householder reflectors partially accumulated into
block reflectors, by using (compact) WY representations. Even though the new
algorithm requires more floating point operations than the state of the art
algorithm, extensive experiments on both real and synthetic data indicate that
it is still competitive, even in a sequential setting. The new algorithm is
conjectured to have better parallel scalability, an idea which is partially
supported by early small-scale experiments using multi-threaded BLAS. The
design and evaluation of a parallel formulation is future work
Time Dependent Density Functional Theory meets Dynamical Mean Field Theory: Real-Time Dynamics for the 3D Hubbard model
We introduce a new class of exchange-correlation potentials for a static and
time-dependent Density Functional Theory of strongly correlated systems in 3D.
The potentials are obtained via Dynamical Mean Field Theory and, for strong
enough interactions, exhibit a discontinuity at half filling density, a
signature of the Mott transition. For time-dependent perturbations, the
dynamics is described in the adiabatic local density approximation. Results
from the new scheme compare very favorably to exact ones in clusters. As an
application, we study Bloch oscillations in the 3D Hubbard model.Comment: 4 pages, 3 figure
Contour calculus for many-particle functions
In non-equilibrium many-body perturbation theory, Langreth rules are an
efficient way to extract real-time equations from contour ones. However, the
standard rules are not applicable in cases that do not reduce to simple
convolutions and multiplications. We introduce a procedure for extracting
real-time equations from general multi-argument contour functions with an
arbitrary number of arguments. This is done for both the standard Keldysh
contour, as well as the extended contour with a vertical track that allows for
general initial states. This amounts to the generalization of the standard
Langreth rules to much more general situations. These rules involve
multi-argument retarded functions as key ingredients, for which we derive
intuitive graphical rules. We apply our diagrammatic recipe to derive Langreth
rules for the so-called double triangle structure and the general vertex
function, relevant for the study of vertex corrections beyond the
approximation
The Generalized Kadanoff-Baym Ansatz with Initial Correlations
Within the non-equilibrium Green's function (NEGF) formalism, the Generalized
Kadanoff-Baym Ansatz (GKBA) has stood out as a computationally cheap method to
investigate the dynamics of interacting quantum systems driven out of
equilibrium. Current implementations of the NEGF--GKBA, however, suffer from a
drawback: real-time simulations require {\em noncorrelated} states as initial
states. Consequently, initial correlations must be built up through an
adiabatic switching of the interaction before turning on any external field, a
procedure that can be numerically highly expensive. In this work, we extend the
NEGF--GKBA to allow for {\em correlated} states as initial states. Our scheme
makes it possible to efficiently separate the calculation of the initial state
from the real-time simulation, thus paving the way for enlarging the class of
systems and external drivings accessible by the already successful NEGF--GKBA.
We demonstrate the accuracy of the method and its improved performance in a
model donor-acceptor dyad driven out of equilibrium by an external laser pulse
Dynaflow ™ 48, a microfluidic chip solution for increasing throughput and data quality in patch-clamp-based drug screening
Ion channels are transm embrane proteins, found in virtually all cell types
throughout the human body. Ion channels underlie neural communication,
memory, behavior, every movement and heartbeat, and are as such prone to
cause disease if malfunctioning. Therefore ion channels are very important
targets in drug discovery. The gold standard technique for obtaining information
on ion channel function with high information content and temporal resolution is
patch-clamp. The technique measures the minute currents originating from the
movement of ions across the cellular membrane, and enables determination of
the potency and efficacy of a drug. However, patch-clamp suffers from serious
throughput restrictions due to its laborious nature. To address the throughput
problems we have developed a microfluidic chip containing 48 microchannels
for an extremely rapid, sequential delivery of a large number of completely
controlled solution environments to a lifted, patch-clamped cell. In this way,
throughput is increased drastically compared to classical patch-clamp perfusion
set-ups, with uncompromised data quality. The 48-microchannel chip has been
used for the characterization of drugs affecting ligand-gated ion channels
including agonists, antagonists and positive modulators with positive effects on
both throughput and data quality.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 dofinansowane zostało ze środków MNiSW w ramach działalności upowszechniającej naukę
CMA-Based CD and DGD Estimation in Presence of Experimental Higher Order PMD
We evaluate 3 methods for CD estimation using CMA filter tap coefficients. The performance of these methods are evaluated with respect to their accuracy and range. We also experimentally evaluate the CD estimation performance in presence of higher order PMD
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