323 research outputs found
Endoluminal Repair of a Contained Thoracic Aortic Rupture Due to Primary Staphylococcal Aortitis
AbstractWe report a case of primary infectious thoracic aortitis with contained rupture of the descending thoracic aorta caused by Staphylococcus aureus and successfully treated with a rifampicin-rinsed aortic stent graft
The impact of superficial femoral artery (SFA) occlusion on the outcome of proximal sartorius muscle transposition flaps in vascular surgery patients
ObjectivesTo demonstrate the feasibility and safety of proximal sartorius muscle rotational flaps in patients with peripheral occlusive artery disease.MethodsRetrospective analysis of 53 patients with 56 proximal sartorius muscle flaps. Indication for a flap procedure was postoperative calcitrant lymphorrhea in nine, graft at risk in 13, and graft infection in 34 procedures. Pre- and postoperative patencies of the superficial femoral artery (SFA) and profundal femoral artery (PFA) were documented. Flap viability, wound healing, and limb salvage were examined at follow-up.ResultsIn 59% of the procedures in this series, the SFA was occluded. The PFA was patent in all patients. Flap viability (100% vs 94%), rate of new (4% vs 6%), and recurrent infections (9% vs 6%), loss of vascular reconstruction rate (9% vs 9%), and limb salvage rate (100% vs 88%) did not differ significantly between the SFA patent and the SFA occluded group. There were four new infections (7%) and three recurrent infections (5.5%) during follow-up, five of which led to a loss of reconstruction. In four of those five patients, the sartorius flap was viable. Two patients died during the immediate postoperative period from septic multi-organ failure (3%). At a median follow-up of 6.4 months, 54 flaps were viable and wound closure was achieved in all surviving 51 patients. Limb salvage rate was 93%.ConclusionsBiologic protection procedures as local muscle flaps are vital adjuncts to vascular surgery techniques in the treatment of complicated wounds in the groin. Occlusion of the SFA in the presence of a patent PFA is not associated with an increased risk of flap loss in proximal sartorius muscle rotational flaps
The wave equation on singular space-times
We prove local unique solvability of the wave equation for a large class of
weakly singular, locally bounded space-time metrics in a suitable space of
generalised functions.Comment: Latex, 19 pages, 1 figure. Discussion of class of metrics covered by
our results and some examples added. Conclusion more detailed. Version to
appear in Communications in Mathematical Physic
Cognitive appraisal as a mechanism linking negative organizational shocks and intentions to leave
The past two decades have seen a significant rise in both frequency and size of mergers and acquisitions in the US, many of which have been associated with considerable interruption of organizational activities and a host of negative outcomes for employees. In this study of 763 US-based airline employees, we identify threat appraisal as a key mechanism explaining the relationship between four change-related variables (quality of change communication, procedural fairness in restructuring, change management history, and anxiety about change) and employee turnover intentions. Results indicate that turnover intentions are influenced by quality of change communication, procedural fairness in restructuring, and anxiety about change as mediated by threat appraisal. We also found that job embeddedness moderated the relationships of quality of change communication and procedural fairness in restructuring with threat appraisal. Our focus on malleable levers of withdrawal offers theoretical and practical insights into how turnover intentions can be influenced
Deflection of Highly Relativistic Particles in a Gravitational Field
A novel approach to the calculation of the deflection of highly relativistic
test particles in gravitational fields is described. We make use of the
light-like boosts of the gravitational fields of the sources. Examples are
given of the deflection of highly relativistic particles in the Schwarzschild
and Kerr gravitational fields, in the field of a static, axially symmetric,
multipole source and in the field of a cosmic string. The deflection of
spinning particles is also discussed.Comment: 18 pages, 2 figures, accepted for publication in Classical and
Quantum Gravit
Generalized Fourier Integral Operators on spaces of Colombeau type
Generalized Fourier integral operators (FIOs) acting on Colombeau algebras
are defined. This is based on a theory of generalized oscillatory integrals
(OIs) whose phase functions as well as amplitudes may be generalized functions
of Colombeau type. The mapping properties of these FIOs are studied as the
composition with a generalized pseudodifferential operator. Finally, the
microlocal Colombeau regularity for OIs and the influence of the FIO action on
generalized wave front sets are investigated. This theory of generalized FIOs
is motivated by the need of a general framework for partial differential
operators with non-smooth coefficients and distributional data
Coupling a Point-Like Mass to Quantum Gravity with Causal Dynamical Triangulations
We present a possibility of coupling a point-like, non-singular, mass
distribution to four-dimensional quantum gravity in the nonperturbative setting
of causal dynamical triangulations (CDT). In order to provide a point of
comparison for the classical limit of the matter-coupled CDT model, we derive
the spatial volume profile of the Euclidean Schwarzschild-de Sitter space glued
to an interior matter solution. The volume profile is calculated with respect
to a specific proper-time foliation matching the global time slicing present in
CDT. It deviates in a characteristic manner from that of the pure-gravity
model. The appearance of coordinate caustics and the compactness of the mass
distribution in lattice units put an upper bound on the total mass for which
these calculations are expected to be valid. We also discuss some of the
implementation details for numerically measuring the expectation value of the
volume profiles in the framework of CDT when coupled appropriately to the
matter source.Comment: 26 pages, 9 figures, updated published versio
Isomorphisms of algebras of Colombeau generalized functions
We show that for smooth manifolds X and Y, any isomorphism between the
special algebra of Colombeau generalized functions on X, resp. Y is given by
composition with a unique Colombeau generalized function from Y to X. We also
identify the multiplicative linear functionals from the special algebra of
Colombeau generalized functions on X to the ring of Colombeau generalized
numbers. Up to multiplication with an idempotent generalized number, they are
given by an evaluation map at a compactly supported generalized point on X.Comment: 10 page
Distributional sources for black hole initial data
Black hole initial data is usually produced using Bowen-York type puncture
initial data or by applying an excision boundary condition. The benefits of the
Bowen-York initial data are the ability to specify the spin and momentum of the
system as parameters of the initial data. In an attempt to extend these
benefits to other formulations of the Einstein constraints, the puncture method
is reformulated using distributions as source terms. It is shown how the
Bowen-York puncture black hole initial data and the trumpet variation is
generated by distributional sources. A heuristic argument is presented to argue
that these sources are the general sources of spin and momentum. In order to
clarify the meaning of other distributional sources, an exact family of initial
data with generalized sources to the Hamiltonian constraint are studied;
spinning trumpet black hole initial data and black hole initial data with
higher order momentum sources are also studied.Comment: Code available at https://github.com/SwampWalker/LeapingMonke
Symmetries and geodesics in (anti-)de Sitter spacetimes with nonexpanding impulsive waves
We consider a class of exact solutions which represent nonexpanding impulsive
waves in backgrounds with nonzero cosmological constant. Using a convenient
5-dimensional formalism it is shown that these spacetimes admit at least three
global Killing vector fields. The same geometrical approach enables us to find
all geodesics in a simple explicit form and describe the effect of impulsive
waves on test particles. Timelike geodesics in the axially-symmetric
Hotta-Tanaka spacetime are studied in detail. It is also demonstrated that for
vanishing cosmological constant, the symmetries and geodesics reduce to those
for well-known impulsive pp-waves.Comment: 16 pages, 3 figures, LaTeX 2e. To appear in Class. Quantum Gra
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