2,303 research outputs found

    Cohomology of bundles on homological Hopf manifold

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    We discuss the properties of complex manifolds having rational homology of S1×S2n1S^1 \times S^{2n-1} including those constructed by Hopf, Kodaira and Brieskorn-van de Ven. We extend certain previously known vanishing properties of cohomology of bundles on such manifolds.As an application we consider degeneration of Hodge-deRham spectral sequence in this non Kahler setting.Comment: To appear in Proceedings of 2007 conference on Several complex variables and Complex Geometry. Xiamen. Chin

    Positivity of relative canonical bundles and applications

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    Given a family f:XSf:\mathcal X \to S of canonically polarized manifolds, the unique K\"ahler-Einstein metrics on the fibers induce a hermitian metric on the relative canonical bundle KX/S\mathcal K_{\mathcal X/S}. We use a global elliptic equation to show that this metric is strictly positive on X\mathcal X, unless the family is infinitesimally trivial. For degenerating families we show that the curvature form on the total space can be extended as a (semi-)positive closed current. By fiber integration it follows that the generalized Weil-Petersson form on the base possesses an extension as a positive current. We prove an extension theorem for hermitian line bundles, whose curvature forms have this property. This theorem can be applied to a determinant line bundle associated to the relative canonical bundle on the total space. As an application the quasi-projectivity of the moduli space Mcan\mathcal M_{\text{can}} of canonically polarized varieties follows. The direct images RnpfΩX/Sp(KX/Sm)R^{n-p}f_*\Omega^p_{\mathcal X/S}(\mathcal K_{\mathcal X/S}^{\otimes m}), m>0m > 0, carry natural hermitian metrics. We prove an explicit formula for the curvature tensor of these direct images. We apply it to the morphisms SpTSRpfΛpTX/SS^p \mathcal T_S \to R^pf_*\Lambda^p\mathcal T_{\mathcal X/S} that are induced by the Kodaira-Spencer map and obtain a differential geometric proof for hyperbolicity properties of Mcan\mathcal M_{\text{can}}.Comment: Supercedes arXiv:0808.3259v4 and arXiv:1002.4858v2. To appear in Invent. mat

    Attosecond electron spectroscopy using a novel interferometric pump-probe technique

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    We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original attosecond pulse. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multi-path interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the attosecond pulse duration.Comment: 5 pages, 4 figure

    Semliki Forest virus strongly reduces mosquito host defence signaling

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    The Alphavirus genus within the Togaviridae family contains several important mosquito-borne arboviruses. Other than the antiviral activity of RNAi, relatively little is known about alphavirus interactions with insect cell defences. Here we show that Semliki Forest virus (SFV) infection of Aedes albopictus-derived U4.4 mosquito cells reduces cellular gene expression. Activation prior to SFV infection of pathways involving STAT/IMD, but not Toll signaling reduced subsequent virus gene expression and RNA levels. These pathways are therefore not only able to mediate protective responses against bacteria but also arboviruses. However, SFV infection of mosquito cells did not result in activation of any of these pathways and suppressed their subsequent activation by other stimuli

    Three-dimensional numerical simulation of blood flow in mouse aortic arch around atherosclerotic plaques

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    Atherosclerosis is a progressive disease, involving the build-up of lipid streaks in artery walls, leading to plaques. Understanding the development of atherosclerosis and plaque vulnerability is critically important since plaque rupture can result in heart attack or stroke. Plaques can be divided into two distinct types: those likely to rupture (vulnerable) or less likely to rupture (stable). In the last decade, researchers have been interested in studying the influence of the mechanical effects (blood shear stress, pressure forces and structural stress) on the plaque formation, progression and rupture processes but no general agreement has been found. The purpose of the present work is to include more realistic conditions for the numerical calculations of the blood flow by implementing real geometries with plaques in the numerical model. Hemodynamical parameters are studied in both diseased and healthy configurations. The healthy configuration is obtained by removing numerically the plaques from three dimensional geometries obtained by micro-computed tomography. A new hemodynamical parameter is also introduced to relate the location of plaques to the characteristics of the flow in the healthy configuration

    SYZ mirror symmetry for hypertoric varieties

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    We construct a Lagrangian torus fibration on a smooth hypertoric variety and a corresponding SYZ mirror variety using TT-duality and generating functions of open Gromov-Witten invariants. The variety is singular in general. We construct a resolution using the wall and chamber structure of the SYZ base.Comment: v_2: 31 pages, 5 figures, minor revision. To appear in Communications in Mathematical Physic

    Burden of allergic rhinitis and impact of MP-AzeFlu from the patient perspective : pan European patient survey

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    Funding for this research was provided by Mylan Inc. Acknowledgements We thank Dr Ruth B Murray (Medscript NZ Ltd) for assistance in drafting and editing this manuscript.Peer reviewedPublisher PD

    Ventricular arrhythmias and sudden death in adults after a Mustard operation for transposition of the great arteries

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    Aims To examine the prevalence of sustained ventricular tachycardia (VT) and sudden death (SD) in adults with atrial repair of transposition of the great arteries (TGA) and to determine associated risk factors. Methods and results In a single-centre review, we studied the outcome of 149 adults (mean age 28 ± 7 years) who had undergone a Mustard operation for TGA. During a mean follow-up of 9 ± 6 years, sustained VT and/or SD occurred in 9% (13/149) of the cohort. Sustained VT/SD was more likely to occur in patients with associated anatomic lesions [hazard ratio (HR) 4.9, 95% CI 1.5-16.0], with NYHA class ≥III (HR 9.8, 95% CI 3.0-31.6) and with an impaired subaortic right ventricular (RV) ejection fraction (EF) (HR 2.2, 95% CI 1.2-4.0 per 10% decrease in EF). There was an inverse correlation between the RV-EF and both age and QRS duration. Patients with a QRS duration ≥140 ms were at highest risk of sustained VT/SD (HR 13.6, 95% CI 2.9-63.4). Atrial tachyarrhythmia was detected in 66 (44%) patients, but was not a statistically significant predictor of sustained VT/SD in our adult population (HR 2.7, 95% CI 0.6-13.0). Conclusion Sustained VT/SD in adults after a Mustard operation for TGA are more common than previously described. Age, systemic ventricular function, and QRS duration are interrelated and are associated with VT/SD. A QRS duration ≥140 ms helps to identify the high risk patien

    Geometric Aspects of the Moduli Space of Riemann Surfaces

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    This is a survey of our recent results on the geometry of moduli spaces and Teichmuller spaces of Riemann surfaces appeared in math.DG/0403068 and math.DG/0409220. We introduce new metrics on the moduli and the Teichmuller spaces of Riemann surfaces with very good properties, study their curvatures and boundary behaviors in great detail. Based on the careful analysis of these new metrics, we have a good understanding of the Kahler-Einstein metric from which we prove that the logarithmic cotangent bundle of the moduli space is stable. Another corolary is a proof of the equivalences of all of the known classical complete metrics to the new metrics, in particular Yau's conjectures in the early 80s on the equivalences of the Kahler-Einstein metric to the Teichmuller and the Bergman metric.Comment: Survey article of our recent results on the subject. Typoes corrrecte
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