6,986 research outputs found
From Topology to Generalised Dimensional Reduction
In the usual procedure for toroidal Kaluza-Klein reduction, all the
higher-dimensional fields are taken to be independent of the coordinates on the
internal space. It has recently been observed that a generalisation of this
procedure is possible, which gives rise to lower-dimensional ``massive''
supergravities. The generalised reduction involves allowing gauge potentials in
the higher dimension to have an additional linear dependence on the toroidal
coordinates. In this paper, we show that a much wider class of generalised
reductions is possible, in which higher-dimensional potentials have additional
terms involving differential forms on the internal manifold whose exterior
derivatives yield representatives of certain of its cohomology classes. We
consider various examples, including the generalised reduction of M-theory and
type II strings on K3, Calabi-Yau and 7-dimensional Joyce manifolds. The
resulting massive supergravities support domain-wall solutions that arise by
the vertical dimensional reduction of higher-dimensional solitonic p-branes and
intersecting p-branes.Comment: Latex, 24 pages, no figures, typo corrected, reference added and
discussion of duality extende
U-duality as General Coordinate Transformations, and Spacetime Geometry
We show that the full global symmetry groups of all the D-dimensional maximal
supergravities can be described in terms of the closure of the internal general
coordinate transformations of the toroidal compactifications of D=11
supergravity and of type IIB supergravity, with type IIA/IIB T-duality
providing an intertwining between the two pictures. At the quantum level, the
part of the U-duality group that corresponds to the surviving discretised
internal general coordinate transformations in a given picture leaves the
internal torus invariant, while the part that is not described by internal
general coordinate transformations can have the effect of altering the size or
shape of the internal torus. For example, M-theory compactified on a large
torus T^n can be related by duality to a compactification on a small torus, if
and only if n\ge 3. We also discuss related issues in the toroidal
compactification of the self-dual string to D=4. An appendix includes the
complete results for the toroidal reduction of the bosonic sector of type IIB
supergravity to arbitrary dimensions D\ge3.Comment: Latex, 28 page
Harmonic superpositions of non-extremal p-branes
The plot of allowed p and D values for p-brane solitons in D-dimensional
supergravity is the same whether the solitons are extremal or non-extremal. One
of the useful tools for relating different points on the plot is vertical
dimensional reduction, which is possible if periodic arrays of p-brane solitons
can be constructed. This is straightforward for extremal p-branes, since the
no-force condition allows arbitrary multi-centre solutions to be constructed in
terms of a general harmonic function on the transverse space. This has also
been shown to be possible in the special case of non-extremal black holes in
D=4 arrayed along an axis. In this paper, we extend previous results to include
multi-scalar black holes, and dyonic black holes. We also consider their
oxidation to higher dimensions, and we discuss general procedures for
constructing the solutions, and studying their symmetries.Comment: Latex, 23 page
Euclidean-signature Supergravities, Dualities and Instantons
We study the Euclidean-signature supergravities that arise by compactifying
D=11 supergravity or type IIB supergravity on a torus that includes the time
direction. We show that the usual T-duality relation between type IIA and type
IIB supergravities compactified on a spatial circle no longer holds if the
reduction is performed on the time direction. Thus there are two inequivalent
Euclidean-signature nine-dimensional maximal supergravities. They become
equivalent upon further spatial compactification to D=8. We also show that
duality symmetries of Euclidean-signature supergravities allow the harmonic
functions of any single-charge or multi-charge instanton to be rescaled and
shifted by constant factors. Combined with the usual diagonal dimensional
reduction and oxidation procedures, this allows us to use the duality
symmetries to map any single-charge or multi-charge p-brane soliton, or any
intersection, into its near-horizon regime. Similar transformations can also be
made on non-extremal p-branes. We also study the structures of duality
multiplets of instanton and (D-3)-brane solutions.Comment: Latex, 50 pages, typos corrected and references adde
Feasibility and evaluation of an emergency departmentâbased general practitioner streaming and treatment service
Rationale
Offering a primary care service that can provide good quality primary care at emergency departments may reduce pressure on usual emergency department (ED) services.
Aims and Objectives
To evaluate the acceptability, satisfaction, and potential impacts of a co-located primary care service at an emergency department.
Methods
This is a prospective feasibility study and service evaluation comprising a narrative summary of activity, satisfaction, well-being, and safety, and comparisons of wait times for ED services by patient category (âminorâ, âmajorsâ, âpaediatricâ or âresusâ) before and during the service operation. Patients and staff were asked using semistructured interview topic guides about service perception, well-being, representation within 48âh, safety concerns, and/or satisfaction. Wait times for patient categories in usual ED care service were in secondary care electronic records. Pathway changes were captured under primary care electronic records.
Results
Approximately 96% of general practitioner streaming and treatment (GPST) patients were seen within 1âh. There was a statistically significant reduction in ED patients with minor injuries or illnesses waiting >4âh for admission or discharge âbreachesâ during the 3 months that GPST was operating compared with the previous 3 months (pââ€â0.005). Wait times for other ED services did not significantly improve. A total of 769 walk-in patients received GPST consultation and 661 (86%) needed no further ED intervention. Fast discharge was a major determinant of patient satisfaction. No staff expressed dissatisfaction, but some suggested possible improvements in eligibility criteria and built environment design features.
Conclusion
Provision of GPST correlated with shorter waits for discharge from ED. Patient and staff experiences of GPST were positive
Chemically-specific dual/differential CARS micro-spectroscopy of saturated and unsaturated lipid droplets
We have investigated the ability of dual-frequency Coherent Antistokes Raman Scattering (D-CARS) micro-spectroscopy, based on femtosecond pulses (100 fs or 5 fs) spectrally focussed by glass dispersion, to distinguish the chemical composition of micron-sized lipid droplets consisting of different triglycerides types (poly-unsaturated glyceryl trilinolenate, mono-unsaturated glyceryl trioleate and saturated glyceryl tricaprylate and glyceryl tristearate) in a rapid and label-free way. A systematic comparison of Raman spectra with CARS and D-CARS spectra was used to identify D-CARS spectral signatures which distinguish the disordered poly-unsaturated lipids from the more ordered saturated ones both in the CH-stretch vibration region and in the fingerprint region, without the need for lengthy CARS multiplex acquisition and analysis. D-CARS images of the lipid droplets at few selected wavenumbers clearly resolved the lipid composition differences, and exemplify the potential of this technique for label-free chemically selective rapid imaging of cytosolic lipid droplets in living cell
Supergravity Instabilities of Non-Supersymmetric Quantum Critical Points
Motivated by the recent use of certain consistent truncations of M-theory to
study condensed matter physics using holographic techniques, we study the
SU(3)-invariant sector of four-dimensional, N=8 gauged supergravity and compute
the complete scalar spectrum at each of the five non-trivial critical points.
We demonstrate that the smaller SU(4)^- sector is equivalent to a consistent
truncation studied recently by various authors and find that the critical point
in this sector, which has been proposed as the ground state of a holographic
superconductor, is unstable due to a family of scalars that violate the
Breitenlohner-Freedman bound. We also derive the origin of this instability in
eleven dimensions and comment on the generalization to other embeddings of this
critical point which involve arbitrary Sasaki-Einstein seven manifolds. In the
spirit of a resurging interest in consistent truncations, we present a formal
treatment of the SU(3)-invariant sector as a U(1)xU(1) gauged N=2 supergravity
theory coupled to one hypermultiplet.Comment: 46 page
Assessing the implementability of telehealth interventions for self-management support: a realist review.
BACKGROUND: There is a substantial and continually growing literature on the effectiveness and implementation of discrete telehealth interventions for health condition management. However, it is difficult to predict which technologies are likely to work and be used in practice. In this context, identifying the core mechanisms associated with successful telehealth implementation is relevant to consolidating the likely elements for ensuring a priori optimal design and deployment of telehealth interventions for supporting patients with long-term conditions (LTCs). METHODS: We adopted a two-stage realist synthesis approach to identify the core mechanisms underpinning telehealth interventions. In the second stage of the review, we tested inductively and refined our understanding of the mechanisms. We reviewed qualitative papers focused on COPD, heart failure, diabetes, and behaviours and complications associated with these conditions. The review included 15 papers published 2009 to 2014. RESULTS: Three concepts were identified, which suggested how telehealth worked to engage and support health-related work. Whether or not and how a telehealth intervention enables or limits the possibility for relationships with professionals and/or peers. Telehealth has the potential to reshape and extend existing relationships, acting as a partial substitute for the role of health professionals. The second concept is fit: successful telehealth interventions are those that can be well integrated into everyday life and health care routines and the need to be easy to use, compatible with patients' existing environment, skills, and capacity, and that do not significantly disrupt patients' lives and routines. The third concept is visibility: visualisation of symptoms and feedback has the capacity to improve knowledge, motivation, and a sense of empowerment; engage network members; and reinforce positive behaviour change, prompts for action and surveillance. CONCLUSIONS: Upfront consideration should be given to the mechanisms that are most likely to ensure the successful development and implementation of telehealth interventions. These include considerations about whether and how the telehealth intervention enables or limits the possibility for relationships with professionals and peers, how it fits with existing environment and capacities to self-manage, and visibility-enabling-enhanced awareness to self and others
Should Native Pastures Be Fertilised?
Considerable research has been conducted in recent years demonstrating the ongoing benefits of phosphorus (P) fertiliser in achieving and maintaining higher levels of production from native pastures (Graham 2006; Garden et al. 2003; Lodge et al. 2003; Michalk et al. 2003). However Garden et al. (2003), Hill et al. (2004) and Dorrough et al. (2008) all question the sustainability of this practice by highlighting changes in species composition of these pastures with regard to increasing the introduced annual grass and broadleaf weed components at the expense of the native grasses and forbs but in most cases, these trends have been based on short term replicated data or based on qualitative survey data incapable of establishing causal relationships.
In the Monaro region of NSW, 70% of pastures are based on native species and are the cornerstone of livestock production. The Monaro Research, Development and Demonstration of Sustainable Grassland Management Project (MGP) was designed to determine if productivity could be increased without compromising the composition and bio-diversity values of these pastures
- âŠ