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R Grauer

Publications and source records attributed to R Grauer.

10 recordsLinked to original sources

Hyperbolic shock waves of the optical self-focusing with normal group-velocity dispersion.

The theory of focusing light pulses in Kerr media with normal group-velocity dispersion in (2+1) and (3+1) dimensions is revisited. It is shown that pulse splitting introduced by this dispersion follows from shock fronts that develop along hyperbolas separating the region of transverse self-focusing from the domain of temporal dispersion. Justified by a self-similar approach, this property is confirmed by numerical simulations using an adaptive-mesh refinement code.

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Anaesthesia for endoluminal repair of abdominal aortic aneurysms.

An audit of 100 patients undergoing elective abdominal aortic surgery either by open aortic repair (OAR group 50 patients) or endovascular aortic repair (EAR group 50 patients) was undertaken to document changes in anaesthetic technique and perioperative outcome. The data for the OAR group was collected retrospectively and thatfor the EAR group prospectively. Combined general anaesthesia and thoracic epidural anaesthesia was used in 44 of the OAR group whereas lumbar central neural blockade alone was used in 47 of the EAR group. The major differences between the two groups were that intraoperative blood loss was significantly less in the EAR group (OAR 1,674 +/- 1,008 ml, EAR 459 +/- 350 ml, P<0.001) and that no patient in the EAR group required admission to the Intensive Care Unit (ICU), whereas ICU time for the OAR patients was 29 +/- 22 hours. Hospital stay was also significantly different between the two groups (OAR 13 +/- 6 days, EAR 5 +/- 3 days, P<0.001). Major complications occurred in 20patients in the OAR group but only 4patients in the EAR group (P<0.001). EAR reduces blood loss, the requirement for ICU admission, and hospital stay. Central neural blockade is a satisfactory anaesthetic technique for EAR.

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Current-sheet formation in 3D ideal incompressible magnetohydrodynamics

The evolution of current density and vorticity in the ideal, inviscid incompressible magnetohydrodynamic equations in three dimensions is studied numerically. Highly effective resolutions are obtained by adaptive structured mesh refinement techniques. We report on results for three different initial conditions showing similar behavior: in the early stage of the evolution a fast increase in vorticity and current density is observed. Thereafter, the evolution towards nearly two-dimensional current sheets results in a depletion of nonlinearity.

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