369 research outputs found
Reconstruction for Renal Artery Aneurysm and its Effect on Hypertension
AbstractObjectives: many renal artery aneurysms (RAA) are diagnosed incidentally in the course of investigations for hypertension and their management is controversial. Aim: to review the results of renal artery reconstruction for RAA. Methods: between January 1978 and December 1998 111 RAR were performed in 81 kidneys in 71 patients. Results: fifty-nine patients were hypertensive, three had a creatinine >2.0 mg/dl and one was on dialysis. The principal underlying pathology was fibromuscular dysplasia (39) and atherosclerosis (17). The mean RAA diameter was 2.2 (range 1–15) cm overall and 3.5 (range 2–10) cm in four patients who presented with rupture. Fifty-one patients had renal artery stenosis. Autogenous material was used in 105 RAR. There was no 30-day mortality and the morbidity rate was 16%. The 5-year cumulative patency rate was 69%. Hypertension was cured in 25% and improved in 39%.Conclusions: RAR tested for RAA treats hypertension and reduces the risk of rupture and distal embolisation
Finite-size version of the excitonic instability in graphene quantum dots
By a combination of Hartree-Fock simulations, exact diagonalization, and
perturbative calculations, we investigate the ground-state properties of
disorder-free circular quantum dots formed in a graphene monolayer. Taking the
reference chemical potential at the Dirac point, we study N \leq 15 interacting
particles, where the fine structure constant {\alpha} parametrizes the Coulomb
interaction. We explore three different theoretical concepts: (i) Sucher's
positive projection ("no-pair") approach, (ii) a more general Hamiltonian
conserving both N and the number of additional electron-hole pairs, and (iii)
the full quantum electrodynamics (QED) problem, where only N is conserved. We
find that electron-hole pair production is important for {\alpha} 1. This
corresponds to a reconstruction of the filled Dirac sea and is a finite-size
version of the bulk excitonic instability. We also address the effects of an
orbital magnetic field.Comment: 9 pages, 10 figures, to appear in PR
Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory
Here, we review the historical development, current status, and prospects of
Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only
theory.Comment: 15 page
Reliable estimation of prediction uncertainty for physico-chemical property models
The predictions of parameteric property models and their uncertainties are
sensitive to systematic errors such as inconsistent reference data, parametric
model assumptions, or inadequate computational methods. Here, we discuss the
calibration of property models in the light of bootstrapping, a sampling method
akin to Bayesian inference that can be employed for identifying systematic
errors and for reliable estimation of the prediction uncertainty. We apply
bootstrapping to assess a linear property model linking the 57Fe Moessbauer
isomer shift to the contact electron density at the iron nucleus for a diverse
set of 44 molecular iron compounds. The contact electron density is calculated
with twelve density functionals across Jacob's ladder (PWLDA, BP86, BLYP, PW91,
PBE, M06-L, TPSS, B3LYP, B3PW91, PBE0, M06, TPSSh). We provide systematic-error
diagnostics and reliable, locally resolved uncertainties for isomer-shift
predictions. Pure and hybrid density functionals yield average prediction
uncertainties of 0.06-0.08 mm/s and 0.04-0.05 mm/s, respectively, the latter
being close to the average experimental uncertainty of 0.02 mm/s. Furthermore,
we show that both model parameters and prediction uncertainty depend
significantly on the composition and number of reference data points.
Accordingly, we suggest that rankings of density functionals based on
performance measures (e.g., the coefficient of correlation, r2, or the
root-mean-square error, RMSE) should not be inferred from a single data set.
This study presents the first statistically rigorous calibration analysis for
theoretical Moessbauer spectroscopy, which is of general applicability for
physico-chemical property models and not restricted to isomer-shift
predictions. We provide the statistically meaningful reference data set MIS39
and a new calibration of the isomer shift based on the PBE0 functional.Comment: 49 pages, 9 figures, 7 table
Photocounting measurements with dead time and afterpulses in the continuous-wave regime
The widely used experimental technique of continuous-wave detection assumes
counting pulses of photocurrent from a click-type detector inside a given
measurement time window. With such a procedure we miss out the photons detected
after each photocurrent pulse during the detector dead time. Additionally, each
pulse may initialize so-called afterpulse, which is not associated with the
real photons. We derive the corresponding quantum photocounting formula and
experimentally verify its validity. Statistics of photocurrent pulses appears
to be nonlinear with respect to quantum state, which is explained by the memory
effect of the previous measurement time windows. Expressions -- in general,
nonlinear -- connecting statistics of photons and pulses are derived for
different measurement scenarios. We also consider an application of the
obtained results to quantum state reconstruction with unbalanced homodyne
detection.Comment: 23 pages, 19 figure
Semi- and Non-relativistic Limit of the Dirac Dynamics with External Fields
We show how to approximate Dirac dynamics for electronic initial states by
semi- and non-relativistic dynamics. To leading order, these are generated by
the semi- and non-relativistic Pauli hamiltonian where the kinetic energy is
related to and , respectively. Higher-order
corrections can in principle be computed to any order in the small parameter
v/c which is the ratio of typical speeds to the speed of light. Our results
imply the dynamics for electronic and positronic states decouple to any order
in v/c << 1.
To decide whether to get semi- or non-relativistic effective dynamics, one
needs to choose a scaling for the kinetic momentum operator. Then the effective
dynamics are derived using space-adiabatic perturbation theory by Panati et. al
with the novel input of a magnetic pseudodifferential calculus adapted to
either the semi- or non-relativistic scaling.Comment: 42 page
Considerations for a European animal welfare standard to evaluate adverse phenotypes in teleost fish
No abstract available
Entanglement Measures for Single- and Multi-Reference Correlation Effects
Electron correlation effects are essential for an accurate ab initio
description of molecules. A quantitative a priori knowledge of the single- or
multi-reference nature of electronic structures as well as of the dominant
contributions to the correlation energy can facilitate the decision regarding
the optimum quantum chemical method of choice. We propose concepts from quantum
information theory as orbital entanglement measures that allow us to evaluate
the single- and multi-reference character of any molecular structure in a given
orbital basis set. By studying these measures we can detect possible artifacts
of small active spaces.Comment: 14 pages, 4 figure
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