285 research outputs found

    Morita Equivalence, Picard Groupoids and Noncommutative Field Theories

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    In this article we review recent developments on Morita equivalence of star products and their Picard groups. We point out the relations between noncommutative field theories and deformed vector bundles which give the Morita equivalence bimodules.Comment: Latex2e, 10 pages. Conference Proceeding for the Sendai Meeting 2002. Some typos fixe

    Deformation Quantization of a Certain Type of Open Systems

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    We give an approach to open quantum systems based on formal deformation quantization. It is shown that classical open systems of a certain type can be systematically quantized into quantum open systems preserving the complete positivity of the open time evolution. The usual example of linearly coupled harmonic oscillators is discussed.Comment: Major update. Improved main statements. 21 page

    Homogeneous spaces of Dirac groupoids

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    A Poisson structure on a homogeneous space of a Poisson groupoid is homogeneous if the action of the Lie groupoid on the homogeneous space is compatible with the Poisson structures. According to a result of Liu, Weinstein and Xu, Poisson homogeneous spaces of a Poisson groupoid are in correspondence with suitable Dirac structures in the Courant algebroid defined by the Lie bialgebroid of the Poisson groupoid. We show that this correspondence result fits into a more natural context: the one of Dirac groupoids, which are objects generalizing Poisson groupoids and multiplicative closed 2-forms on groupoids

    Integration of Dirac-Jacobi structures

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    We study precontact groupoids whose infinitesimal counterparts are Dirac-Jacobi structures. These geometric objects generalize contact groupoids. We also explain the relationship between precontact groupoids and homogeneous presymplectic groupoids. Finally, we present some examples of precontact groupoids.Comment: 10 pages. Brief changes in the introduction. References update

    Relative and Absolute Risk to Guide the Management of Pulse Pressure, an Age-Related Cardiovascular Risk Factor

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    BACKGROUND Pulse pressure (PP) reflects the age-related stiffening of the central arteries, but no study addressed the management of the PP-related risk over the human lifespan. METHODS In 4663 young (18-49 years) and 7185 older adults (≥50 years), brachial PP was recorded over 24-hour. Total mortality and all major cardiovascular events combined (MACE) were co-primary endpoints. Cardiovascular death, coronary events and stroke were secondary endpoints. RESULTS In young adults (median follow-up, 14.1 years; mean PP, 45.1 mmHg), greater PP was not associated with absolute risk; the endpoint rates were ≤2.01 per 1000 person-years. The adjusted hazard ratios expressed per 10-mmHg PP increments were less than unity (P≤0.027) for MACE (0.67; 95% CI, 0.47-0.96) and cardiovascular death (0.33; 95% CI, 0.11-0.75). In older adults (median follow-up, 13.1 years; mean PP, 52.7 mmHg), the endpoint rates, expressing absolute risk, ranged from 22.5 to 45.4 per 1000 person-years and the adjusted hazard ratios, reflecting relative risk, from 1.09 to 1.54 (P3-fold from age 55 to 75 years, whereas absolute risk rose by a factor 3. CONCLUSIONS From 50 years onwards, the PP-related relative risk decreases, whereas absolute risk increases. From a lifecourse perspective, young adulthood provides a window of opportunity to manage risk factors and prevent target organ damage as forerunner of premature death and MACE. In older adults, treatment should address absolute risk, thereby extending life in years and qualit

    Star products made (somewhat) easier

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    We develop an approach to the deformation quantization on the real plane with an arbitrary Poisson structure which based on Weyl symmetrically ordered operator products. By using a polydifferential representation for deformed coordinates x^j\hat x^j we are able to formulate a simple and effective iterative procedure which allowed us to calculate the fourth order star product (and may be extended to the fifth order at the expense of tedious but otherwise straightforward calculations). Modulo some cohomology issues which we do not consider here, the method gives an explicit and physics-friendly description of the star products.Comment: 20 pages, v2, v3: comments and references adde

    Generalized Kaehler Potentials from Supergravity

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    We consider supersymmetric N=2 solutions with non-vanishing NS three-form. Building on worldsheet results, we reduce the problem to a single generalized Monge-Ampere equation on the generalized Kaehler potential K recently interpreted geometrically by Lindstrom, Rocek, Von Unge and Zabzine. One input in the procedure is a holomorphic function w that can be thought of as the effective superpotential for a D3 brane probe. The procedure is hence likely to be useful for finding gravity duals to field theories with non-vanishing abelian superpotential, such as Leigh-Strassler theories. We indeed show that a purely NS precursor of the Lunin-Maldacena dual to the beta-deformed N=4 super-Yang-Mills falls in our class.Comment: "38 pages. v3: improved exposition and minor mistakes corrected in sec. 4

    Resistant Hypertension Trials and Tribulations

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    Introduction Our case concerns a 62-year-old white woman who was referred by her general practitioner in 2012 with a long-standing history of difficult to control blood pressure (BP). She had significant past medical history including an excised meningioma and an implantable cardiac defibrillator for a single episode of polymorphic ventricular tachycardia during general anesthesia. She also had a possible diagnosis of epilepsy and tablet-controlled type-2 diabetes mellitus. On referral to our clinic she was on 5 antihypertensive medications including enalapril 40 mg daily, bisoprolol 10 mg daily, lercanidipine 10 mg daily, losartan 50 mg daily, and indapamide 2.5 mg once daily. She was also on metformin and sodium valproate. In clinic, she appeared well. She complained of occasional headaches but had no other symptom of note. She had no significant family history of high BP. On examination, she had a body mass index in the normal range and after repeated measures, her clinic BP was found to be 195/110 mm Hg. There was very little else to find on examination, including no murmurs or renal bruits. On fundoscopy, she had grade 2 hypertensive retinopathy. Baseline investigations did not reveal anything untoward. She had a normal blood count, renal function, and electrolytes. On urinalysis, she had mild proteinuria, with a urine protein-creatinine ratio of 17 (laboratory reference value 0–13 mg/mmol). Her ECG showed sinus rhythm with a normal rate, axis, and voltage. Her echocardiogram did not show any evidence of left ventricular hypertrophy, left ventricular ejection fraction was 58%, and she had evidence of mild diastolic dysfunction. Ambulatory BP monitoring (ABPM) was performed and her mean 24-hour BP was 190/105 mm Hg. The range was 118/67 to 227/127 mm Hg, with >90% of readings >140/90 mm Hg. So, here, we have a patient with a diagnosis of resistant hypertension according to the definition in the European guidelines

    An Attribute-Based Approach to Classifying Community-Based Tourism Networks

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    This conceptual paper proposes the adoption of a collaborative network approach as a prospective means of improving success in implementing community-based tourism (CBT) initiatives. Drawing upon relevant literature, the researchers identify the key attributes that characterise a network-based approach. By proposing alternatives for each attribute, the research provides CBT practitioners with options for making informed decisions about how to build collaboration connecting individual CBT initiatives in multiple locations. The researchers discuss the implications of different approaches for power relations between stakeholders. The proposed framework provides a means of classifying existing CBT networks and analyses the types of network and the circumstances which lead to better outcomes for community development. Further empirical research is required to test the validity of the key network attributes and to develop a comprehensive classification system of CBT networks.School of Hotel and Tourism Managemen
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