827 research outputs found
Topology Change of Coalescing Black Holes on Eguchi-Hanson Space
We construct multi-black hole solutions in the five-dimensional
Einstein-Maxwell theory with a positive cosmological constant on the
Eguchi-Hanson space, which is an asymptotically locally Euclidean space. The
solutions describe the physical process such that two black holes with the
topology of S^3 coalesce into a single black hole with the topology of the lens
space L(2;1)=S^3/Z_2. We discuss how the area of the single black hole after
the coalescence depends on the topology of the horizon.Comment: 10 pages, Some comments are added. to be published as a letter in
Classical and Quantum Gravit
A cautionary tale: the non-causal association between type 2 diabetes risk SNP, rs7756992, and levels of non-coding RNA, CDKAL1-v1
Journal ArticleCopyright © The Author(s) 2015. This article is published with open access at Springerlink.com.Aims/hypothesis: Intronic single nucleotide polymorphisms (SNPs) in the CDKAL1 gene are associated with risk of developing type 2 diabetes. A strong correlation between risk alleles and lower levels of the non-coding RNA, CDKAL1-v1, has recently been reported in whole blood extracted from Japanese individuals. We sought to replicate this association in two independent cohorts: one using whole blood from white UK-resident individuals, and one using a collection of human pancreatic islets, a more relevant tissue type to study with respect to the aetiology of diabetes. Methods: Levels of CDKAL1-v1 were measured by real-time PCR using RNA extracted from human whole blood (n = 70) and human pancreatic islets (n = 48). Expression with respect to genotype was then determined. Results: In a simple linear regression model, expression of CDKAL1-v1 was associated with the lead type 2 diabetes-associated SNP, rs7756992, in whole blood and islets. However, these associations were abolished or substantially reduced in multiple regression models taking into account rs9366357 genotype: a moderately linked SNP explaining a much larger amount of the variation in CDKAL1-v1 levels, but not strongly associated with risk of type 2 diabetes. Conclusions/interpretation: Contrary to previous findings, we provide evidence against a role for dysregulated expression of CDKAL1-v1 in mediating the association between intronic SNPs in CDKAL1 and susceptibility to type 2 diabetes. The results of this study illustrate how caution should be exercised when inferring causality from an association between disease-risk genotype and non-coding RNA expression.MRCNIH
A cautionary tale: the non-causal association between type 2 diabetes risk SNP, rs7756992, and levels of non-coding RNA, CDKAL1-v1
This is the final version of the article. Available from Springer Verlag via the DOI in this record.AIMS/HYPOTHESIS: Intronic single nucleotide polymorphisms (SNPs) in the CDKAL1 gene are associated with risk of developing type 2 diabetes. A strong correlation between risk alleles and lower levels of the non-coding RNA, CDKAL1-v1, has recently been reported in whole blood extracted from Japanese individuals. We sought to replicate this association in two independent cohorts: one using whole blood from white UK-resident individuals, and one using a collection of human pancreatic islets, a more relevant tissue type to study with respect to the aetiology of diabetes. METHODS: Levels of CDKAL1-v1 were measured by real-time PCR using RNA extracted from human whole blood (n = 70) and human pancreatic islets (n = 48). Expression with respect to genotype was then determined. RESULTS: In a simple linear regression model, expression of CDKAL1-v1 was associated with the lead type 2 diabetes-associated SNP, rs7756992, in whole blood and islets. However, these associations were abolished or substantially reduced in multiple regression models taking into account rs9366357 genotype: a moderately linked SNP explaining a much larger amount of the variation in CDKAL1-v1 levels, but not strongly associated with risk of type 2 diabetes. CONCLUSIONS/INTERPRETATION: Contrary to previous findings, we provide evidence against a role for dysregulated expression of CDKAL1-v1 in mediating the association between intronic SNPs in CDKAL1 and susceptibility to type 2 diabetes. The results of this study illustrate how caution should be exercised when inferring causality from an association between disease-risk genotype and non-coding RNA expression.This paper presents independent research funded by the Medical
Research Council (grant number MR/J006777/1) and supported
by the National Institute for Health Research (NIHR) Exeter Clinical
Research Facility. The views expressed are those of the authors and not
necessarily those of the Medical Research Council, UK National Health
Service, NIHR or the UK Department of Health
Uniqueness Theorem for Black Hole Space-Times with Multiple Disconnected Horizons
We show uniqueness of stationary and asymptotically flat black hole
space-times with multiple disconnected horizons and with two rotational Killing
vector fields in the context of five-dimensional minimal supergravity
(Einstein-Maxwell-Chern-Simons gravity). The novelty in this work is the
introduction in the uniqueness theorem of intrinsic local charges measured near
each horizon as well as the measurement of local fluxes besides the asymptotic
charges that characterize a particular solution. A systematic method of
defining the boundary conditions on the fields that specify a black hole
space-time is given based on the study of its rod structure (domain structure).
Also, an analysis of known solutions with disconnected horizons is carried out
as an example of an application of this theorem.Comment: 28 pages, 5 figures. v3: Further improvements on uniqueness theorem,
Lemma introduced for clarity of derivation, new quantities introduced to
treat special case with zero flux, refs. added, typos fixe
Charged Black Holes in a Rotating Gross-Perry-Sorkin Monopole Background
We present a new class of stationary charged black hole solutions to
five-dimensional Einstein-Maxwell-Chern-Simons theories. We construct the
solutions by utilizing so called the squashing transformation. At infinity, our
solutions behave as a four-dimensional flat spacetime plus a `circle' and hence
describe a Kaluza-Klein black hole. More precisely, our solutions can be viewed
as a charged rotating black hole in a rotating Gross-Perry-Sorkin monopole
background with the black hole rotation induced from the background rotation.Comment: 25 pages, 6 figure
Spin diffusion/transport in -type GaAs quantum wells
The spin diffusion/transport in -type (001) GaAs quantum well at high
temperatures ( K) is studied by setting up and numerically solving the
kinetic spin Bloch equations together with the Poisson equation
self-consistently. All the scattering, especially the electron-electron Coulomb
scattering, is explicitly included and solved in the theory. This enables us to
study the system far away from the equilibrium, such as the hot-electron effect
induced by the external electric field parallel to the quantum well. We find
that the spin polarization/coherence oscillates along the transport direction
even when there is no external magnetic field. We show that when the scattering
is strong enough, electron spins with different momentums oscillate in the same
phase which leads to equal transversal spin injection length and ensemble
transversal injection length. It is also shown that the intrinsic scattering is
already strong enough for such a phenomena. The oscillation period is almost
independent on the external electric field which is in agreement with the
latest experiment in bulk system at very low temperature [Europhys. Lett. {\bf
75}, 597 (2006)]. The spin relaxation/dephasing along the diffusion/transport
can be well understood by the inhomogeneous broadening, which is caused by the
momentum-dependent diffusion and the spin-orbit coupling, and the scattering.
The scattering, temperature, quantum well width and external magnetic/electric
field dependence of the spin diffusion is studied in detail.Comment: 12 pages, 6 figures, to be published in J Appl. Phy
Charged black rings in supergravity with a single non-zero gauge field
General charged black ring solution with two angular momenta, a charge and a
dipole charge is found by the inverse scattering method. The solution is
presented in a relatively concise form in which its symmetries are manifest.
The regularity conditions are found and the physical characteristics of the
regular solution are expressed via its parameters.Comment: Misprints corrected, references added, JHEP forma
Opposite field septum magnet system for the separation of charged particle beams
Abstract-The Japan Hadron Facility (JHF) accelerator complex comprises a 50-GeV main synchrotron, a 3-GeV rapid-cycling synchrotron, and a 400-MeV linac. The accelerators provide high-intensity, high-energy proton beams for various scientific fields. These high-intensity, high-energy accelerators, especially the 50-GeV main synchrotron, impose tight demands on the injection/extraction septum magnets for a thin structure, large aperture and high operating field. But to manufacture high field septum magnets on the condition of a large aperture is very difficult because of its extraordinarily strong electromagnetic force due to the self-field. To cope with these tight demands, new design concepts of septa are required. An opposite-field septum magnet system is one of the solutions to realize a thin septa or very high-field septum magnets
G2 Dualities in D=5 Supergravity and Black Strings
Five dimensional minimal supergravity dimensionally reduced on two commuting
Killing directions gives rise to a G2 coset model. The symmetry group of the
coset model can be used to generate new solutions by applying group
transformations on a seed solution. We show that on a general solution the
generators belonging to the Cartan and nilpotent subalgebras of G2 act as
scaling and gauge transformations, respectively. The remaining generators of G2
form a sl(2,R)+sl(2,R) subalgebra that can be used to generate non-trivial
charges. We use these generators to generalize the five dimensional Kerr string
in a number of ways. In particular, we construct the spinning electric and
spinning magnetic black strings of five dimensional minimal supergravity. We
analyze physical properties of these black strings and study their
thermodynamics. We also explore their relation to black rings.Comment: typos corrected (26 pages + appendices, 2 figures
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