106 research outputs found
Thermodynamic behavior of IIA string theory on a pp-wave
We obtain the thermal one loop free energy and the Hagedorn temperature of
IIA superstring theory on the pp-wave geometry which comes from the circle
compactification of the maximally supersymmetric eleven dimensional one. We use
both operator and path integral methods and find the complete agreement between
them in the free energy expression. In particular, the free energy in the limit is shown to be identical with that of IIB string theory on
maximally supersymmetric pp-wave, which indicates the universal thermal
behavior of strings in the large class of pp-wave backgrounds. We show that the
zero point energy and the modular properties of the free energy are naturally
incorporated into the path integral formalism.Comment: 25 pages, Latex, JHEP style, v4: revised for clarity without change
in main contents, version to appear in JHE
Orbifolds and Flows from Gauged Supergravity
We examine orbifolds of the IIB string via gauged supergravity. For the
gravity duals of the A_{n-1} quiver gauge theories, we extract the massless
degrees of freedom and assemble them into multiplets of N=4 gauged supergravity
in five dimensions. We examine the embedding of the gauge group into the
isometry group of the scalar manifold, as well as the symmetries of the scalar
potential. From this we find that there is a large SU(1,n) symmetry group which
relates different RG flows in the dual quiver gauge theory. We find that this
symmetry implies an extension of the usual duality between ten-dimensional IIB
solutions which involves exchanging geometric moduli with background fluxes.Comment: 37 pages, harvma
R-symmetry and supersymmetry breaking in 3D WZ models
We analyze metastable supersymmetry breaking in 3D WZ models. We study the
regime of validity of the perturbative computation for superpotentials with
marginal and relevant couplings. Lifetime of the metastable states in presence
of a triangular potential barrier is estimated.Comment: 1+16 pages, 2 figures, JHEP3.cl
Performance of gastrointestinal pathologists within a national digital review panel for Barrett's oesophagus in the Netherlands: Results of 80 prospective biopsy reviews
Aims: The histopathological diagnosis of low-grade dysplasia (LGD) in Barrett's oesophagus (BO) is associated with poor interobserver agreement and guidelines dictate expert review. To facilitate nationwide expert review in the Netherlands, a web-based digital review panel has been set up, which currently consists of eight 'core' pathologists. The aim of this study was to evaluate if other pathologists from the Dutch BO expert centres qualify for the expert panel by assessing their performance in 80 consecutive LGD reviews submitted to the panel. Methods: Pathologists independently assessed digital slides in two phases. Both phases consisted of 40 cases, with a group discussion after phase I. For all cases, a previous consensus diagnosis made by five core pathologists was available, which was used as reference. The following criteria were used: (1) percentage of 'indefinite for dysplasia' diagnoses, (2) percentage agreement with consensus diagnosis and (3) proportion of cases with a consensus diagnosis of dysplasia underdiagnosed as non-dysplastic. Benchmarks were based on scores of the core pathologists. Results: After phase I, 1/7 pathologists met the benchmark scor
Calabi-Yau Volumes and Reflexive Polytopes
We study various geometrical quantities for CalabiâYau varieties realized as cones over Gorenstein Fano varieties, obtained as toric varieties from reflexive polytopes in various dimensions. Focus is made on reflexive polytopes up to dimension 4 and the minimized volumes of the SasakiâEinstein base of the corresponding CalabiâYau cone are calculated. By doing so, we conjecture new bounds for the SasakiâEinstein volume with respect to various topological quantities of the corresponding toric varieties. We give interpretations about these volume bounds in the context of associated field theories via the AdS/CFT correspondence
NEOnatal Central-venous Line Observational study on Thrombosis (NEOCLOT): Evaluation of a national guideline on management of neonatal catheter-related thrombosis
Background: In critically ill (preterm) neonates, central venous catheters (CVCs) are increasingly used for administration of medication or parenteral nutrition. A serious complication, however, is the development of catheter-related thrombosis (CVC-thrombosis), which may resolve by itself or cause severe complications. Due to lack of evidence, management of neonatal CVC-thrombosis varies among neonatal intensive care units (NICUs). In the Netherlands an expert-based national management guideline has been developed which is implemented in all 10 NICUs in 2014. Methods: The NEOCLOT study is a multicentre prospective observational cohort study, including 150 preterm and term infants (0-6 months) admitted to one of the 10 NICUs, developing CVC-thrombosis. Patient characteristics, thrombosis characteristics, risk factors, treatment strategies and outcome measures will be collected in a web-based database. Management of CVC-thrombosis will be performed as recommended in the protocol. Violations of the protocol will be noted. Primary outcome measures are a composite efficacy outcome consisting of death due to CVC-thrombosis and recurrent thrombosis, and a safety outcome consisting of the incidence of major bleedings during therapy. Secondary outcomes include individual components of primary efficacy outcome, clinically relevant non-major and minor bleedings and the frequency of risk factors, protocol variations, residual thrombosis and post thrombotic syndrome. Discussion: The NEOCLOT study will evaluate the efficacy and safety of the new, national, neonatal CVC-thrombosis guideline. Furthermore, risk factors as well as long-term consequences of CVC-thrombosis will be analysed
Adherence to pre-set benchmark quality criteria to qualify as expert assessor of dysplasia in Barrettâs esophagus biopsies â towards digital review of Barrettâs esophagus
Background: Dysplasia assessment of Barrettâs esophagus biopsies is associated with low observer agreement; guidelines advise expert review. We have developed a web-based review panel for dysplastic Barrettâs esophagus biopsies. Objective: The purpose of this study was to test if 10 gastrointestinal pathologists working at Dutch Barrettâs esophagus expert centres met pre-set benchmark scores for quality criteria. Methods: Ten gastrointestinal pathologists twice assessed 60 digitalized Barrettâs esophagus cases, enriched for dysplasia; then
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