159 research outputs found

    Quasicircles and width of Jordan curves in CP1

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    We study a notion of ‘width’ for Jordan curves in (Formula presented.), paying special attention to the class of quasicircles. The width of a Jordan curve is defined in terms of the geometry of its convex hull in hyperbolic three-space. A similar invariant in the setting of anti-de Sitter geometry was used by Bonsante–Schlenker to characterize quasicircles among a larger class of Jordan curves in the boundary of anti de Sitter space. In contrast to the AdS setting, we show that there are Jordan curves of bounded width which fail to be quasicircles. However, we show that Jordan curves with small width are quasicircles

    The induced metric on the boundary of the convex hull of a quasicircle in hyperbolic and anti-de Sitter geometry

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    Celebrated work of Alexandrov and Pogorelov determines exactly which metrics on the sphere are induced on the boundary of a compact convex subset of hyperbolic three-space. As a step toward a generalization for unbounded convex subsets, we consider convex regions of hyperbolic three-space bounded by two properly embedded disks which meet at infinity along a Jordan curve in the ideal boundary. In this setting, it is natural to augment the notion of induced metric on the boundary of the convex set to include a gluing map at infinity which records how the asymptotic geometry of the two surfaces compares near points of the limiting Jordan curve. Restricting further to the case in which the induced metrics on the two bounding surfaces have constant curvature K 2 Å’ 1; 0/ and the Jordan curve at infinity is a quasicircle, the gluing map is naturally a quasisymmetric homeomorphism of the circle. The main result is that for each value of K, every quasisymmetric map is achieved as the gluing map at infinity along some quasicircle. We also prove analogous results in the setting of three-dimensional anti-de Sitter geometry. Our results may be viewed as universal versions of the conjectures of Thurston and Mess about prescribing the induced metric on the boundary of the convex core of quasifuchsian hyperbolic manifolds and globally hyperbolic anti-de Sitter spacetimes

    Strategic and operational considerations for the Extended Enterprise: insights from the aerospace industry

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    The Extended Enterprise (EE) paradigm has been adopted in the civil aerospace industry to enhance collaboration and product innovation among supply chain partners. Nevertheless, key aspects of this collaborative form remain poorly understood. In particular, the interrelation of strategic and operational considerations has received little attention in the literature. Our study aimed to investigate this area, using two dyads as case studies, where three companies were involved in an EE form of collaboration. The primary case company was a leading manufacturer in the civil aerospace industry that employs EE principles on both upstream and downstream sides of its supply chain. The other two case companies were key suppliers embedded in the EE. This paper aimed to develop a more complete understanding of how sharing risks and rewards results in effective collaboration among EE partners with key strategic and operational results

    Hospitalisation for bed rest for women with a triplet pregnancy: an abandoned randomised controlled trial and meta-analysis

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    BACKGROUND: This abandoned randomised controlled trial assessed the effects of hospitalisation from 24 to 30 weeks gestation for women with a triplet pregnancy on the risk of preterm birth. METHODS: Women with a triplet pregnancy and no other condition necessitating hospital admission were approached for participation in the study, and randomised to either antenatal hospitalisation (hospitalised group), or to routine antenatal care (control group). The randomisation schedule used variable blocks with stratification by parity, and a researcher not involved with clinical care contacted by telephone to determine treatment allocation by opening the next in a series of consecutively numbered, opaque, sealed envelopes. Primary study outcomes were preterm birth (defined as birth less than 37 weeks gestation) and very preterm birth (defined as birth less than 34 weeks gestation), and the development of maternal pregnancy induced hypertension. The trial was ceased prior to achieving the calculated sample size due to difficulties in recruitment. The results of this randomised controlled trial were then combined with the results of another comparing bed rest in women with a triplet pregnancy. RESULTS: Seven women with a triplet pregnancy were recruited to the trial, with three randomised to the hospitalisation group, and four to the control group. There were no statistically significant differences between the two groups for the primary outcomes birth before 37 weeks (3/3 hospitalisation group versus 4/4 control group; relative risk (RR) not estimable), birth before 34 weeks (3/3 hospitalisation group versus 2/4 control group; RR 2.00 95% Confidence Intervals (CI) 0.75–5.33) and pregnancy induced hypertension (1/3 hospitalisation group versus 1/4 control group; RR 1.33 95%CI 0.13–13.74). When the results of this trial were incorporated into a meta-analysis with the previous randomised controlled trial assessing hospitalisation and bed rest for women with a triplet pregnancy, (total sample size 26 women and 78 infants), there were no statistically significant differences identified between the two groups. CONCLUSION: The results of this trial and meta-analysis suggest no benefit of routine hospitalisation and bed rest for women with a triplet pregnancy to reduce the risk of preterm birth. The adoption or continuation of a policy of routine hospitalisation and bed rest for women with an uncomplicated triplet pregnancy cannot be recommended

    Usability, acceptability, and feasibility of two technology-based devices for mental health screening in perinatal care: A comparison of web versus app

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    The use of Information and Communication Technologies (web pages and apps) in mental health has boosted. However, it is unknown which of these two devices can be better in terms of feasibility and acceptability. Our aim is to compare the feasibility, usability, and user satisfaction of two devices (web vs mobile application) of an online program for perinatal depression screening called HappyMom. In total, 348 and 175 perinatal women registered into HappyMom web and app version, respectively. The assessment protocol included different biopsychosocial evaluations (twice during pregnancy and thrice in the postpartum) and a satisfaction questionnaire. Results showed that a higher percentage of women in the web sample (27.3–51.1%) responded to each assessment compared to the app sample (9.1–53.1%). A smaller proportion of women in web sample never responded to any assessments. By contrast, the percentage of women who responded to all assessments was higher in app sample (longitudinal retention sample was 4.6% of web users and 9.1% of app users). In general, high satisfaction was found in both web and app users. Our result showed that online assessment methods are feasible and acceptable by perinatal women. However, dropout rates are a real problem that urge a solution that will be discussed further in the paper. Web and App devices present different advantages and limitations. The choice of one of them must be made taking into account the study’s objective, the sample characteristics, and the dissemination possibilities

    Sustainability centres and fit: how centres work to integrate sustainability within business schools

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    For nearly as long as the topic of sustainable business has been taught and researched in business schools, proponents have warned about barriers to genuine integration in business school practices. This article examines how academic sustainability centres try to overcome barriers to integration by achieving technical, cultural and political fit with their environment (Ansari, Fiss, & Zajac, 2010). Based on survey and interview data, we theorise that technical, cultural and political fit are intricately related, and that these interrelations involve legitimacy, resources and collaboration effects. Our findings about sustainability centres offer novel insights on integrating sustainable business education given the interrelated nature of different types of fit and misfit. We further contribute to the literature on fit by highlighting that incompatibility between strategies to achieve different types of fit may act as a source of dynamism
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