35,429 research outputs found
AdS Strings with Torsion: Non-complex Heterotic Compactifications
Combining the effects of fluxes and gaugino condensation in heterotic
supergravity, we use a ten-dimensional approach to find a new class of
four-dimensional supersymmetric AdS compactifications on almost-Hermitian
manifolds of SU(3) structure. Computation of the torsion allows a
classification of the internal geometry, which for a particular combination of
fluxes and condensate, is nearly Kahler. We argue that all moduli are fixed,
and we show that the Kahler potential and superpotential proposed in the
literature yield the correct AdS radius. In the nearly Kahler case, we are able
to solve the H Bianchi using a nonstandard embedding. Finally, we point out
subtleties in deriving the effective superpotential and understanding the
heterotic supergravity in the presence of a gaugino condensate.Comment: 42 pages; v2. added refs, revised discussion of Bianchi for N
Use of record-linkage to handle non-response and improve alcohol consumption estimates in health survey data: a study protocol
<p>Introduction: Reliable estimates of health-related behaviours, such as levels of alcohol consumption in the population, are required to formulate and evaluate policies. National surveys provide such data; validity depends on generalisability, but this is threatened by declining response levels. Attempts to address bias arising from non-response are typically limited to survey weights based on sociodemographic characteristics, which do not capture differential health and related behaviours within categories. This project aims to explore and address non-response bias in health surveys with a focus on alcohol consumption.</p>
<p>Methods and analysis: The Scottish Health Surveys (SHeS) aim to provide estimates representative of the Scottish population living in private households. Survey data of consenting participants (92% of the achieved sample) have been record-linked to routine hospital admission (Scottish Morbidity Records (SMR)) and mortality (from National Records of Scotland (NRS)) data for surveys conducted in 1995, 1998, 2003, 2008, 2009 and 2010 (total adult sample size around 40 000), with maximum follow-up of 16 years. Also available are census information and SMR/NRS data for the general population. Comparisons of alcohol-related mortality and hospital admission rates in the linked SHeS-SMR/NRS with those in the general population will be made. Survey data will be augmented by quantification of differences to refine alcohol consumption estimates through the application of multiple imputation or inverse probability weighting. The resulting corrected estimates of population alcohol consumption will enable superior policy evaluation. An advanced weighting procedure will be developed for wider use.</p>
<p>Ethics and dissemination: Ethics approval for SHeS has been given by the National Health Service (NHS) Multi-Centre Research Ethics Committee and use of linked data has been approved by the Privacy Advisory Committee to the Board of NHS National Services Scotland and Registrar General. Funding has been granted by the MRC. The outputs will include four or five public health and statistical methodological international journal and conference papers.</p>
New string vacua from twistor spaces
We find a new family of AdS_4 vacua in IIA string theory. The internal space
is topologically either the complex projective space CP^3 or the "flag
manifold" SU(3)/(U(1)xU(1)), but the metric is in general neither Einstein nor
Kaehler. All known moduli are stabilized by fluxes, without using quantum
effects or orientifold planes. The analysis is completely ten--dimensional and
does not rely on assumptions about Kaluza--Klein reduction.Comment: 19 pages. v3: published version, further minor correction
Investigating physical and cognitive changes over two years in patients with moderate to late stage Parkinson’s Disease in Northumbria
Metachronal wave and hydrodynamic interaction for deterministic switching rowers
We employ a model system, called rowers, as a generic physical framework to
define the problem of the coordinated motion of cilia (the metachronal wave) as
a far from equilibrium process. Rowers are active (two-state) oscillators
interacting solely through forces of hydrodynamic origin. In this work, we
consider the case of fully deterministic dynamics, find analytical solutions of
the equation of motion in the long wavelength (continuum) limit, and
investigate numerically the short wavelength limit. We prove the existence of
metachronal waves below a characteristic wavelength. Such waves are unstable
and become stable only if the sign of the coupling is reversed. We also find
that with normal hydrodynamic interaction the metachronal pattern has the form
of stable trains of traveling wave packets sustained by the onset of
anti-coordinated beating of consecutive rowers.Comment: 11 pages, 7 figure
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