6,167 research outputs found
Feasibility study of an optical radiometer for determining the composition of the Mars atmosphere from shock layer radiation during entry, volume II Final report
Optical radiometer feasibility study for determining composition of Mars atmosphere from shock layer radiation during entry - instrumentatio
Flux Compactifications of M-Theory on Twisted Tori
We find the bosonic sector of the gauged supergravities that are obtained
from 11-dimensional supergravity by Scherk-Schwarz dimensional reduction with
flux to any dimension D. We show that, if certain obstructions are absent, the
Scherk-Schwarz ansatz for a finite set of D-dimensional fields can be extended
to a full compactification of M-theory, including an infinite tower of
Kaluza-Klein fields. The internal space is obtained from a group manifold
(which may be non-compact) by a discrete identification. We discuss the
symmetry algebra and the symmetry breaking patterns and illustrate these with
particular examples. We discuss the action of U-duality on these theories in
terms of symmetries of the D-dimensional supergravity, and argue that in
general it will take geometric flux compactifications to M-theory on
non-geometric backgrounds, such as U-folds with U-duality transition functions.Comment: Latex, 47 page
Generalised Geometry for M-Theory
Generalised geometry studies structures on a d-dimensional manifold with a
metric and 2-form gauge field on which there is a natural action of the group
SO(d,d). This is generalised to d-dimensional manifolds with a metric and
3-form gauge field on which there is a natural action of the group .
This provides a framework for the discussion of M-theory solutions with flux. A
different generalisation is to d-dimensional manifolds with a metric, 2-form
gauge field and a set of p-forms for either odd or even on which there is a
natural action of the group . This is useful for type IIA or IIB
string solutions with flux. Further generalisations give extended tangent
bundles and extended spin bundles relevant for non-geometric backgrounds.
Special structures that arise for supersymmetric backgrounds are discussed.Comment: 31 page
Patient safety and estimation of renal function in patients prescribed new oral anticoagulants for stroke prevention in atrial fibrillation
OBJECTIVE: In clinical trials of dabigatran and rivaroxaban for stroke prevention in atrial fibrillation (AF), drug eligibility and dosing were determined using the Cockcroft-Gault equation to estimate creatine clearance as a measure of renal function. This cross-sectional study aimed to compare whether using estimated glomerular filtration rate (eGFR) by the widely available and widely used Modified Diet in Renal Disease (MDRD) equation would alter prescribing or dosing of the renally excreted new oral anticoagulants. PARTICIPANTS: Of 4712 patients with known AF within a general practitioner-registered population of 930 079 in east London, data were available enabling renal function to be calculated by both Cockcroft-Gault and MDRD methods in 4120 (87.4%). RESULTS: Of 4120 patients, 2706 were <80 years and 1414 were ≥80 years of age. Among those ≥80 years, 14.9% were ineligible for dabigatran according to Cockcroft-Gault equation but would have been judged eligible applying MDRD method. For those <80 years, 0.8% would have been incorrectly judged eligible for dabigatran and 5.3% would have received too high a dose. For rivaroxaban, 0.3% would have been incorrectly judged eligible for treatment and 13.5% would have received too high a dose. CONCLUSIONS: Were the MDRD-derived eGFR to be used instead of Cockcroft-Gault in prescribing these new agents, many elderly patients with AF would either incorrectly become eligible for them or would receive too high a dose. Safety has not been established using the MDRD equation, a concern since the risk of major bleeding would be increased in patients with unsuspected renal impairment. Given the potentially widespread use of these agents, particularly in primary care, regulatory authorities and drug companies should alert UK doctors of the need to use the Cockcroft-Gault formula to calculate eligibility for and dosing of the new oral anticoagulants in elderly patients with AF and not rely on the MDRD-derived eGFR
Anaplasmosis in a Hereford Cow
Anaplasmosis is a condition recognized more frequently in the bovine in recent years. However, even more important is the fact that it is becoming more prevalent in areas outside the epizootic areas. The organism was first observed by workers studying Texas cattle fever, therefore it is plausible these men were often seeing cattle with two conditions
A Chiral Perturbation Expansion for Gravity
A formulation of Einstein gravity, analogous to that for gauge theory arising
from the Chalmers-Siegel action, leads to a perturbation theory about an
asymmetric weak coupling limit that treats positive and negative helicities
differently. We find power counting rules for amplitudes that suggest the
theory could find a natural interpretation in terms of a twistor-string theory
for gravity with amplitudes supported on holomorphic curves in twistor space.Comment: 11 pages, LaTeX, no figures; v2: one reference adde
From p-branes to Cosmology
We study the relationship between static p-brane solitons and cosmological
solutions of string theory or M-theory. We discuss two different ways in which
extremal p-branes can be generalised to non-extremal ones, and show how wide
classes of recently discussed cosmological models can be mapped into
non-extremal p-brane solutions of one of these two kinds. We also extend
previous discussions of cosmological solutions to include some that make use of
cosmological-type terms in the effective action that can arise from the
generalised dimensional reduction of string theory or M-theory.Comment: Latex, 24 pages, no figur
"Test me and treat me" - attitudes to vitamin D deficiency and supplementation: a qualitative study
© 2015 BMJ Open, "Test me and treat me"-attitudes to vitamin D deficiency and supplementation: a qualitative study. This manuscript version is made available under the Creative Commons Attribution Licens
Canonical Formulation of A Bosonic Matter Field in 1+1 Dimensional Curved Space
We study a Bosonic scalar in 1+1 dimensional curved space that is coupled to
a dynamical metric field. This metric, along with the affine connection, also
appears in the Einstein-Hilbert action when written in first order form. After
illustrating the Dirac constraint analysis in Yang-Mills theory, we apply this
formulation to the Einstein-Hilbert action and the action of the Bosonic scalar
field, first separately and then together. Only in the latter case does a
dynamical degree of freedom emerge.Comment: 21 page
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