150 research outputs found
Cost-effectiveness of a quality improvement bundle for emergency laparotomy.
Background: The recent Emergency Laparotomy Pathway Quality Improvement Care (ELPQuiC) study showed that the use of a specific care bundle reduced mortality in patients undergoing emergency laparotomy. However, the costs of implementation of the ELPQuiC bundle remain unknown. The aim of this study was to assess the in-hospital and societal costs of implementing the ELPQuiC bundle. Methods: The ELPQuiC study employed a before-after approach using quality improvement methodology. To assess the costs and cost-effectiveness of the bundle, two models were constructed: a short-term model to assess in-hospital costs and a long-term model (societal decision tree) to evaluate the patient's lifetime costs (in euros). Results: Using health economic modelling and data collected from the ELPQuiC study, estimated costs for initial implementation of the ELPQuiC bundle were €30 026·11 (range 1794·64-40 784·06) per hospital. In-hospital costs per patient were estimated at €14 817·24 for standard (non-care bundle) treatment versus €15 971·24 for the ELPQuiC bundle treatment. Taking a societal perspective, lifetime costs of the patient in the standard group were €23 058·87, compared with €19 102·37 for patients receiving the ELPQuiC bundle. The increased life expectancy of 4 months for patients treated with the ELPQuiC bundle was associated with cost savings of €11 410·38 per quality-adjusted life-year saved. Conclusion: Implementation of the ELPQuiC bundle is associated with lower mortality and higher in-hospital costs but reduced societal costs
The second-order electron self-energy in hydrogen-like ions
A calculation of the simplest part of the second-order electron self-energy
(loop after loop irreducible contribution) for hydrogen-like ions with nuclear
charge numbers is presented. This serves as a test for the
more complicated second-order self-energy parts (loop inside loop and crossed
loop contributions) for heavy one-electron ions. Our results are in strong
disagreement with recent calculations of Mallampalli and Sapirstein for low
values but are compatible with the two known terms of the analytical
-expansion.Comment: 13 LaTex pages, 2 figure
Dual kinetic balance approach to basis set expansions for the Dirac equation
A new approach to finite basis sets for the Dirac equation is developed. It
solves the problem of spurious states and, as a result, improves the
convergence properties of basis set calculations. The efficiency of the method
is demonstrated for finite basis sets constructed from B splines by calculating
the one-loop self-energy correction for a hydrogenlike ion.Comment: 14 pages, 1 tabl
Evidence for the absence of regularization corrections to the partial-wave renormalization procedure in one-loop self energy calculations in external fields
The equivalence of the covariant renormalization and the partial-wave
renormaliz ation (PWR) approach is proven explicitly for the one-loop
self-energy correction (SE) of a bound electron state in the presence of
external perturbation potentials. No spurious correctio n terms to the
noncovariant PWR scheme are generated for Coulomb-type screening potentia ls
and for external magnetic fields. It is shown that in numerical calculations of
the SE with Coulombic perturbation potential spurious terms result from an
improper treatment of the unphysical high-energy contribution. A method for
performing the PWR utilizing the relativistic B-spline approach for the
construction of the Dirac spectrum in external magnetic fields is proposed.
This method is applied for calculating QED corrections to the bound-electron
-factor in H-like ions. Within the level of accuracy of about 0.1% no
spurious terms are generated in numerical calculations of the SE in magnetic
fields.Comment: 22 pages, LaTeX, 1 figur
New non-unitary representations in a Dirac hydrogen atom
New non-unitary representations of the SU(2) algebra are introduced for the
case of the Dirac equation with a Coulomb potential; an extra phase, needed to
close the algebra, is also introduced. The new representations does not require
integer or half integer labels. The set of operators defined are used to span
the complete space of bound state eigenstates of the problem thus solving it in
an essentially algebraic way
Loop-after-loop contribution to the second-order Lamb shift in hydrogenlike low-Z atoms
We present a numerical evaluation of the loop-after-loop contribution to the
second-order self-energy for the ground state of hydrogenlike atoms with low
nuclear charge numbers Z. The calculation is carried out in the Fried-Yennie
gauge and without an expansion in Z \alpha. Our calculation confirms the
results of Mallampalli and Sapirstein and disagrees with the calculation by
Goidenko and coworkers. A discrepancy between different calculations is
investigated. An accurate fitting of the numerical results provides a detailed
comparison with analytic calculations based on an expansion in the parameter Z
\alpha. We confirm the analytic results of order \alpha^2 (Z\alpha)^5 but
disagree with Karshenboim's calculation of the \alpha^2 (Z \alpha)^6 \ln^3(Z
\alpha)^{-2} contribution.Comment: RevTex, 19 pages, 4 figure
Electric dipole moment of the electron in YbF molecule
Ab initio calculation of the hyperfine, P-odd, and P,T-odd constants for the
YbF molecule was performed with the help of the recently developed technique,
which allows to take into account correlations and polarization in the
outercore region. The ground state electronic wave function of the YbF molecule
is found with the help of the Relativistic Effective Core Potential method
followed by the restoration of molecular four-component spinors in the core
region of ytterbium in the framework of a non-variational procedure. Core
polarization effects are included with the help of the atomic Many Body
Perturbation Theory for Yb atom. For the isotropic hyperfine constant A,
accuracy of our calculation is about 3% as compared to the experimental datum.
The dipole constant Ad (which is much smaller in magnitude), though better than
in all previous calculations, is still underestimated by almost 23%. Being
corrected within a semiempirical approach for a perturbation of 4f-shell in the
core of Yb due to the bond making, this error is reduced to 8%. Our value for
the effective electric field on the unpaired electron is 4.9 a.u.=2.5E+10 V/cm.Comment: 7 pages, REVTE
A useful form of the recurrence relation between relativistic atomic matrix elements of radial powers
Recently obtained recurrence formulae for relativistic hydrogenic radial
matrix elements are cast in a simpler and perhaps more useful form. This is
achieved with the help of a new relation between the and the
terms ( is a Dirac matrix and are constants) in the
atomic matrix elements.Comment: 7 pages, no figure
Experimental ionization of atomic hydrogen with few-cycle pulses
We present the first experimental data on strong-field ionization of atomic
hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10%
level between the data and an {\it ab initio} simulation over a wide range of
laser intensities and electron energies
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