1,363 research outputs found
Stress-induced nuclear accumulation is dispensable for Hog1-dependent gene expression and virulence in a fungal pathogen
The authors thank E. Veal for intellectual input. This work was funded by the UK Biotechnology and Biological Research Council [J.Q. BB/K016393/1; A.J.P.B. BB/K017365/1], the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) [D.M.M. NC/N002482/1] and the Wellcome Trust Strategic Award in Medical Mycology and Fungal Immunology [097377]). D.M.M. and A.J.P.B. are also supported by the MRC Centre for Medical Mycology at the University of Aberdeen (MR/N006364/1).Peer reviewedPublisher PD
Self-similar cosmologies in 5D: spatially flat anisotropic models
In the context of theories of Kaluza-Klein type, with a large extra
dimension, we study self-similar cosmological models in 5D that are
homogeneous, anisotropic and spatially flat. The "ladder" to go between the
physics in 5D and 4D is provided by Campbell-Maagard's embedding theorems. We
show that the 5-dimensional field equations determine the form of
the similarity variable. There are three different possibilities: homothetic,
conformal and "wave-like" solutions in 5D. We derive the most general
homothetic and conformal solutions to the 5D field equations. They require the
extra dimension to be spacelike, and are given in terms of one arbitrary
function of the similarity variable and three parameters. The Riemann tensor in
5D is not zero, except in the isotropic limit, which corresponds to the case
where the parameters are equal to each other. The solutions can be used as 5D
embeddings for a great variety of 4D homogeneous cosmological models, with and
without matter, including the Kasner universe. Since the extra dimension is
spacelike, the 5D solutions are invariant under the exchange of spatial
coordinates. Therefore they also embed a family of spatially {\it
inhomogeneous} models in 4D. We show that these models can be interpreted as
vacuum solutions in braneworld theory. Our work (I) generalizes the 5D
embeddings used for the FLRW models; (II) shows that anisotropic cosmologies
are, in general, curved in 5D, in contrast with FLRW models which can always be
embedded in a 5D Riemann-flat (Minkowski) manifold; (III) reveals that
anisotropic cosmologies can be curved and devoid of matter, both in 5D and 4D,
even when the metric in 5D explicitly depends on the extra coordinate, which is
quite different from the isotropic case.Comment: Typos corrected. Minor editorial changes and additions in the
Introduction and Summary section
Equivalence of three-dimensional spacetimes
A solution to the equivalence problem in three-dimensional gravity is given
and a practically useful method to obtain a coordinate invariant description of
local geometry is presented. The method is a nontrivial adaptation of Karlhede
invariant classification of spacetimes of general relativity. The local
geometry is completely determined by the curvature tensor and a finite number
of its covariant derivatives in a frame where the components of the metric are
constants. The results are presented in the framework of real two-component
spinors in three-dimensional spacetimes, where the algebraic classifications of
the Ricci and Cotton-York spinors are given and their isotropy groups and
canonical forms are determined. As an application we discuss Goedel-type
spacetimes in three-dimensional General Relativity. The conditions for local
space and time homogeneity are derived and the equivalence of three-dimensional
Goedel-type spacetimes is studied and the results are compared with previous
works on four-dimensional Goedel-type spacetimes.Comment: 13 pages - content changes and corrected typo
Collimation of a spherical collisionless particles stream in Kerr space-time
We examine the propagation of collisionless particles emitted from a
spherical shell to infinity. The number distribution at infinity, calculated as
a function of the polar angle, exhibits a small deviation from uniformity. The
number of particles moving from the polar region toward the equatorial plane is
slightly larger than that of particles in the opposite direction, for an
emission radius in extreme Kerr space-time. This means that the black
hole spin exerts an anti-collimation effect on the particles stream propagating
along the rotation axis. We also confirm this property in the weak field limit.
The quadrupole moment of the central object produces a force toward the
equatorial plane. For a smaller emission radius , the absorption of
particles into the black hole, the non-uniformity and/or the anisotropy of the
emission distribution become much more important.Comment: 11 pages, 8 figures; accepted for publication in CQ
Blocking two-component signalling enhances Candida albicans virulence and reveals adaptive mechanisms that counteract sustained SAPK activation
This work was funded by the UK Biotechnology and Biological Research Council [www.bbsrc.ac.uk] JQ (BB/K016393/1); AJPB (BB/K017365/1). The work was also supported by the Wellcome Trust [www.wellcome.ac.uk], JQ (086048, 097377); AJPB (097377)); LPE (097377). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
Consistent and inconsistent truncations. Some results and the issue of the correct uplifting of solutions
We clarify the existence of two different types of truncations of the field
content in a theory, the consistency of each type being achieved by different
means. A proof is given of the conditions to have a consistent truncation in
the case of dimensional reductions induced by independent Killing vectors. We
explain in what sense the tracelessness condition found by Scherk and Scharwz
is not only a necessary condition but also a {\it sufficient} one for a
consistent truncation. The reduction of the gauge group is fully performed
showing the existence of a sector of rigid symmetries. We show that truncations
originated by the introduction of constraints will in general be inconsistent,
but this fact does not prevent the possibility of correct upliftings of
solutions in some cases. The presence of constraints has dynamical consequences
that turn out to play a fundamental role in the correctness of the uplifting
procedure.Comment: Latex, 33 pages, 1 eps fig. v2: typos removed, refs. adde
Studying conformally flat spacetimes with an elastic stress energy tensor using 1+3 formalism
Conformally flat spacetimes with an elastic stress energy tensor given by a
diagonal trace-free anisotropic pressure tensor are investigated using 1+3
formalism. We show how the null tetrad Ricci components are related to the
pressure components and energy density. The 1+3 Bianchi and Jacobi identities
and Einstein field equations are written for this particular case. In general
the commutators must be considered since they supply potentially new
information on higher order derivatives of the 1+3 quantities. We solve the
system for the non rotating case which consist of ODEs of a spatial coordinate
Truncations driven by constraints: consistency and conditions for correct upliftings
We discuss the mechanism of truncations driven by the imposition of
constraints. We show how the consistency of such truncations is controlled, and
give general theorems that establish conditions for the correct uplifting of
solutions. We show in some particular examples how one can get correct
upliftings from 7d supergravities to 10d type IIB supergravity, even in cases
when the truncation is not initially consistent by its own.Comment: Latex, 23 page
Gravitomagnetic Accelerators
We study a simple class of time-dependent rotating Ricci-flat cylindrically
symmetric spacetime manifolds whose geodesics admit gravitomagnetic jets. The
helical paths of free test particles in these jets up and down parallel to the
rotation axis are analogous to those of charged particles in a magnetic field.
The jets are attractors. The jet speed asymptotically approaches the speed of
light. In effect, such source-free spacetime regions act as "gravitomagnetic
accelerators".Comment: 4 pages, 2 figures; v2: reference added; v3: slightly expanded
version accepted for publication in Phys. Lett.
Social innovation: worklessness, welfare and well-being
The UK Government has recently implemented large-scale public-sector funding cuts and substantial welfare reform. Groups within civil society are being encouraged to fill gaps in service provision, and âsocial innovationâ has been championed as a means of addressing social exclusion, such as that caused by worklessness, a major impediment to citizens being able to access money, power and resources, which are key social determinants of health. The aim of this article is to make the case for innovative âupstreamâ approaches to addressing health inequalities, and we discuss three prominent social innovations gaining traction: microcredit for enterprise; social enterprise in the form of Work Integration Social Enterprises (WISEs); and Self Reliant Groups (SRGs). We find that while certain social innovations may have the potential to address health inequalities, large-scale research programmes that will yield the quality and range of empirical evidence to demonstrate impact, and, in particular, an understanding of the causal pathways and mechanisms of action, simply do not yet exist
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