Algebraic Rainich theory and antisymmetrisation in higher dimensions

The classical Rainich(-Misner-Wheeler) theory gives necessary and sufficient conditions on an energy-momentum tensor $T$ to be that of a Maxwell field (a 2-form) in four dimensions. Via Einstein's equations these conditions can be expressed in terms of the Ricci tensor, thus providing conditions on a spacetime geometry for it to be an Einstein-Maxwell spacetime. One of the conditions is that $T^2$ is proportional to the metric, and it has previously been shown in arbitrary dimension that any tensor satisfying this condition is a superenergy tensor of a simple $p$-form. Here we examine algebraic Rainich conditions for general $p$-forms in higher dimensions and their relations to identities by antisymmetrisation. Using antisymmetrisation techniques we find new identities for superenergy tensors of these general (non-simple) forms, and we also prove in some cases the converse; that the identities are sufficient to determine the form. As an example we obtain the complete generalisation of the classical Rainich theory to five dimensions.Comment: 16 pages, LaTe

Arterio-ureteral Fistula – a Systematic Review

AbstractObjective: to review published reports on arterio-ureteral fistula. Method: literature search. Results: eighty cases were identified. Primary fistulas were mainly seen in combination with aortoiliac aneurysmal disease. Secondary fistulas were seen after pelvic cancer surgery, often with radiation, fibrosis and ureteral stenting or after vascular surgery with synthetic grafting. The dominating symptom is massive haematuria, often with circulatory impairment. The clue to a rapid and correct diagnosis is a high degree of suspicion. Most frequently diagnosis has been obtained through angiography or pyelography. When there is a ureteral stent manipulation it will often provoke bleeding and lead to diagnosis. The fistula must be excluded and a vascular reconstruction made. Most frequently this has been obtained through occlusion of the fistula and an extra-anatomic reconstruction (femoro-femoral crossover). Recently stent-grafting has been successfully used but follow-up is short. Conclusion: arterio-ureteral fistula is rare and should be suspected in patients with complicated pelvic surgery and massive haematuria, especially where rigid ureteral stents have been placed

Reduction of requirement for leg vascular surgery during long-term treatment of claudicant patients with ticlopidine: Results from the swedish ticlopidine multicentre study (STIMS)

Objective:To study the effect of long-term treatment of the platelet inhibitor ticlopidine as secondary prevention against the need of vascular surgery in patients with intermittent claudication.Design:The Swedish Ticlopidine Multicentre Study (STIMS), was conducted in six medical and surgical clinics of university hospitals in Sweden.Methods:687 claudicants were randomised to ticlopidine 250mg bd or placebo and vascular surgery events were recorded prospectively over a 7-year period. Cox proportional hazards models of risk for leg vascular surgery were constructed using drug treatment and 11 putative risk factors for vascular disease as covariates. Surgical event-free survivals were compared by Kaplan-Meier analysis.Results:The overall rate of first operations was 2.4% per annum. More than half of these operations were in the aortoiliac region. One-quarter of patients operated during the period required further operations but amputation was rare. Ticlopidine treatment reduced the need for vascular reconstructive surgery by about half, both in intention-to-treat and on-treatment analyses (unadjusted relative risks 0.486, 95% CI 0.317–0.745: p < 0.001; 0.493, 95% CI 0.290–0.841: p < 0.01, respectively). In Cox model analysis only male sex was confirmed as a risk factor for surgery. Previous peripheral arterial surgery was the strongest predictor of the need for surgery. None of the risk factors examined interacted statistically with the effect of treatment with ticlopidine.Conclusion:In patients with intermittent claudication it seems possible to prevent the need for future vascular surgery by the use of platelet inhibition with ticlopidine

Cranial nerve injuries after carotid artery surgery. A prospective study of 663 operations

Objective:To establish the incidence of cranial nerve injuries caused by carotid artery surgery.Methods:During the years 1982 to 1992, 689 carotid artery operations were performed at Malmö General Hospital. Of these 656 were pre- and postoperatively examined at the Department of Phoniatrics concerning the function of the cranial nerves IX, X, and XII.Results:There was injury to one or more of the examined nerves after 75 operations (11.4%). In 70 (10.7%) operations the hypoglossal nerve was injured, in eight (1.2%) the recurrent laryngeal nerve, in two (0.3%) the glossopharyngeal nerve and in two (0.3%) the superior laryngeal nerve. Seven patients complained of postoperative hoarseness, but had no injuries. One hypoglossal and one recurrent nerve injury was permanent. Nerve injury was more frequent in operations performed with a shunt (p = 0.05), with patch closure (p = 0.01) and by a junior surgeon (p = 0.05).Conclusion:In a prospective series, the incidence of cranial nerve injuries after carotid surgery was significant but the vast majority were reversible

Local Haemodynamic Changes During Carotid Endarterectomy—The Influence on Cerebral Oxygenation

AbstractObjectives. To characterize carotid bifurcation haemodynamics and cerebral oxygenation during clamping and at reperfusion after carotid endarterectomy (CEA).Materials and methods. Sixty-two patients with a symptomatic high-grade stenosis of the internal carotid artery (ICA), who underwent CEA under general anaesthesia, were studied prospectively. Measurements of stump-pressure, volume flow (transit time flowmetry) and changes in cerebral oxygenation (near-infrared spectroscopy (NIRS)) were performed. Selective shunting was based on stump pressure only.Results. Stump pressure correlated with both ICA flow before clamping (r=0.45; p=0.03) and changes in cerebral oxygenation (rSO2) during clamping (r=0.61; p=0.002), the latter was reversed by shunt placement. ICA flow before clamping also correlated with changes in rSO2 during clamping (r=0.41; p=0.01).Conclusion. Measurements with transit time flowmetry and cerebral oximetry are technically easy and help to determine the need for selective shunting during CEA. High ICA flow before clamping in combination with a low stump pressure usually indicates the need for a shunt. Volume flow measurements may also be useful in the quality assessment of the CEA

Two dimensional Sen connections and quasi-local energy-momentum

The recently constructed two dimensional Sen connection is applied in the problem of quasi-local energy-momentum in general relativity. First it is shown that, because of one of the two 2 dimensional Sen--Witten identities, Penrose's quasi-local charge integral can be expressed as a Nester--Witten integral.Then, to find the appropriate spinor propagation laws to the Nester--Witten integral, all the possible first order linear differential operators that can be constructed only from the irreducible chiral parts of the Sen operator alone are determined and examined. It is only the holomorphy or anti-holomorphy operator that can define acceptable propagation laws. The 2 dimensional Sen connection thus naturally defines a quasi-local energy-momentum, which is precisely that of Dougan and Mason. Then provided the dominant energy condition holds and the 2-sphere S is convex we show that the next statements are equivalent: i. the quasi-local mass (energy-momentum) associated with S is zero; ii.the Cauchy development $D(\Sigma)$ is a pp-wave geometry with pure radiation ($D(\Sigma)$ is flat), where $\Sigma$ is a spacelike hypersurface whose boundary is S; iii. there exist a Sen--constant spinor field (two spinor fields) on S. Thus the pp-wave Cauchy developments can be characterized by the geometry of a two rather than a three dimensional submanifold.Comment: 20 pages, Plain Tex, I

Conserved Matter Superenergy Currents for Orthogonally Transitive Abelian G2 Isometry Groups

In a previous paper we showed that the electromagnetic superenergy tensor, the Chevreton tensor, gives rise to a conserved current when there is a hypersurface orthogonal Killing vector present. In addition, the current is proportional to the Killing vector. The aim of this paper is to extend this result to the case when we have a two-parameter Abelian isometry group that acts orthogonally transitive on non-null surfaces. It is shown that for four-dimensional Einstein-Maxwell theory with a source-free electromagnetic field, the corresponding superenergy currents lie in the orbits of the group and are conserved. A similar result is also shown to hold for the trace of the Chevreton tensor and for the Bach tensor, and also in Einstein-Klein-Gordon theory for the superenergy of the scalar field. This links up well with the fact that the Bel tensor has these properties and the possibility of constructing conserved mixed currents between the gravitational field and the matter fields.Comment: 15 page

Iatrogenic Vascular Injuries in Sweden. A Nationwide Study 1987–2005

ObjectivesTo study the epidemiology of vascular injuries, with special focus on Iatrogenic Vascular Injuries (IVIs) and time-trends.Design and methodsFrom the Swedish national vascular registry, Swedvasc, prospectively registered data on vascular injuries during 1987–2005 were analysed and cross-referenced for mortalityagainst the population registry.ResultsOf 1853 injuries, 48% were caused by iatrogenic, 29% penetrating and 23% blunt trauma. In the three groups median age was 68, 35 and 40 years, respectively. The annual incidence of procedures for vascular injuries increased from 1.2–1.6 per 100 000 inhabitants and the proportion of IVIs increased from 41 to 51%, during the period. Mortality was higher after IVI (4.9%) compared to non-IVI (2.5%). Patients with IVI also had more co-morbidities; 58% cardiac disease, 44% hypertension, and 18% renal dysfunction.Among 888 IVIs, right femoral arterial injury was the most frequent (37%). The most common vascular reconstruction was direct suture (39%) followed by by-pass or interposition graft (19%, of which prosthetics were used in over half the cases). Endovascular repair increased from 4.6% to 15% between 1987 and 2005.ConclusionsVascular injuries, in particular iatrogenic ones, appear to be increasing. Iatrogenic injuries affect vulnerable patients with co-morbidities and are associated with a high mortality