3,731 research outputs found

    Thermal Conduction and Multiphase Gas in Cluster Cores

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    We examine the role of thermal conduction and magnetic fields in cores of galaxy clusters through global simulations of the intracluster medium (ICM). In particular, we study the influence of thermal conduction, both isotropic and anisotropic, on the condensation of multiphase gas in cluster cores. Previous hydrodynamic simulations have shown that cold gas condenses out of the hot ICM in thermal balance only when the ratio of the cooling time (tcoolt_{\rm cool}) and the free-fall time (tfft_{\rm ff}) is less than 10\approx 10. Since thermal conduction is significant in the ICM and it suppresses local cooling at small scales, it is imperative to include thermal conduction in such studies. We find that anisotropic (along local magnetic field lines) thermal conduction does not influence the condensation criterion for a general magnetic geometry, even if thermal conductivity is large. However, with isotropic thermal conduction cold gas condenses only if conduction is suppressed (by a factor 0.3\lesssim 0.3) with respect to the Spitzer value.Comment: 7 pages, 4 figures; replaced by the MNRAS-accepted versio

    Mothering at a distance and disclosure of maternal HIV to children in Kingston, Jamaica

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    Accepted for publication in a forthcoming issue of Population Horizons, an open access peer-reviewed journal by The Oxford Institute of Population Ageing.Existing guidelines (WHO, 2011) advise caretakers and professionals to disclose children’s and their caretakers’ HIV status to children, despite a lack of evidence concerning the potential implications in resource-constrained settings. Our research uses feminist Interpretative Phenomenological Analysis (IPA) to explore the experiences of HIV positive mothers in Kingston, Jamaica, focusing on their lived experiences of talking to their children about maternal HIV. This paper will focus on the concept of mothering at a distance and how this presents additional challenges for HIV positive mothers who are trying to establish emotional closeness in relation to talking to their children about their HIV. Using Hochschild’s concept of emotion work and examples from the interviews, we highlight the difficult contexts informing women’s decisions when negotiating discussions about their HIV. Women may choose full, partial or differential disclosure or children may be told their mother’s HIV status by others. Disclosure policy, we argue, reflects Anglo-Northern constructions of the family and parenting which may not adequately reflect the experiences of poor urban mothers in low and middle income countries. We argue that policy needs to recognise culturally-specific family formations, which, in Jamaica includes absent fathers, mothering at a distance and mothering non-biological children. This article reflects on the experiences of an under-researched group, poor urban Jamaican women practising mothering at a distance, using a novel methodological approach (IPA) to bring into relief unique insights into their lived experiences and will contribute to the global policy and research literature on HIV disclosure. Keywords: Feminist IPA, HIV disclosure, mothering, emotion workPeer reviewedFinal Accepted Versio

    Necessary Conditions for the Generic Global Rigidity of Frameworks on Surfaces

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    A result due in its various parts to Hendrickson, Connelly, and Jackson and Jord\'an, provides a purely combinatorial characterisation of global rigidity for generic bar-joint frameworks in R2\mathbb{R}^2. The analogous conditions are known to be insufficient to characterise generic global rigidity in higher dimensions. Recently Laman-type characterisations of rigidity have been obtained for generic frameworks in R3\mathbb{R}^3 when the vertices are constrained to lie on various surfaces, such as the cylinder and the cone. In this paper we obtain analogues of Hendrickson's necessary conditions for the global rigidity of generic frameworks on the cylinder, cone and ellipsoid.Comment: 13 page
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