454 research outputs found
Very Extended and at low levels, Gravity and Supergravity
We define a level for a large class of Lorentzian Kac-Moody algebras. Using
this we find the representation content of very extended and
(i.e. ) at low levels in terms of and
representations respectively. The results are consistent with the conjectured
very extended and symmetries of gravity and maximal supergravity
theories given respectively in hep-th/0104081 and hep-th/0107209. We explain
how these results provided further evidence for these conjectures.Comment: 16 pages, plain tex (equation 3.3 modified and one reference
expanded
Membrane Sigma-Models and Quantization of Non-Geometric Flux Backgrounds
We develop quantization techniques for describing the nonassociative geometry
probed by closed strings in flat non-geometric R-flux backgrounds M. Starting
from a suitable Courant sigma-model on an open membrane with target space M,
regarded as a topological sector of closed string dynamics in R-space, we
derive a twisted Poisson sigma-model on the boundary of the membrane whose
target space is the cotangent bundle T^*M and whose quasi-Poisson structure
coincides with those previously proposed. We argue that from the membrane
perspective the path integral over multivalued closed string fields in Q-space
is equivalent to integrating over open strings in R-space. The corresponding
boundary correlation functions reproduce Kontsevich's deformation quantization
formula for the twisted Poisson manifolds. For constant R-flux, we derive
closed formulas for the corresponding nonassociative star product and its
associator, and compare them with previous proposals for a 3-product of fields
on R-space. We develop various versions of the Seiberg-Witten map which relate
our nonassociative star products to associative ones and add fluctuations to
the R-flux background. We show that the Kontsevich formula coincides with the
star product obtained by quantizing the dual of a Lie 2-algebra via convolution
in an integrating Lie 2-group associated to the T-dual doubled geometry, and
hence clarify the relation to the twisted convolution products for topological
nonassociative torus bundles. We further demonstrate how our approach leads to
a consistent quantization of Nambu-Poisson 3-brackets.Comment: 52 pages; v2: references adde
Type 2 diabetes: a cohort study of treatment, ethnic and social group influences on glycated haemoglobin.
OBJECTIVES: To assess whether in people with poorly controlled type 2 diabetes (HbA1c>7.5%) improvement in HbA1c varies by ethnic and social group. DESIGN: Prospective 2-year cohort of type 2 diabetes treated in general practice. SETTING AND PARTICIPANTS: All patients with type 2 diabetes in 100 of the 101 general practices in two London boroughs. The sample consisted of an ethnically diverse group with uncontrolled type 2 diabetes aged 37-71 years in 2007 and with HbA1c recording in 2008-2009. OUTCOME MEASURE: Change from baseline HbA1c in 2007 and achievement of HbA1c control in 2008 and 2009 were estimated for each ethnic, social and treatment group using multilevel modelling. RESULTS: The sample consisted of 6104 people; 18% were white, 63% south Asian, 16% black African/Caribbean and 3% other ethnic groups. HbA1c was lower after 1 and 2 years in all ethnic groups but south Asian people received significantly less benefit from each diabetes treatment. After adjustment, south Asian people were found to have 0.14% less reduction in HbA1c compared to white people (95% CI 0.04% to 0.24%) and white people were 1.6 (95% CI 1.2 to 2.0) times more likely to achieve HbA1c controlled to 7.5% or less relative to south Asian people. HbA1c reduction and control in black African/Caribbean and white people did not differ significantly. There was no evidence that social deprivation influenced HbA1c reduction or control in this cohort. CONCLUSIONS: In all treatment groups, south Asian people with poorly controlled diabetes are less likely to achieve controlled HbA1c, with less reduction in mean HbA1c than white or black African/Caribbean people
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Dynamic hip screw fixation of subtrochanteric femoral fractures.
INTRODUCTION: A subtrochanteric proximal femur fracture occurs in the 5 cm of bone immediately distal to the lesser trochanter. UK national guidelines advise that adults with subtrochanteric fractures should be treated with an intramedullary nail (IMN). This study aims to compare peri-operative outcome measures of patients with subtrochanteric fractures treated with either an IMN or a dynamic hip screw (DHS) construct. MATERIALS AND METHODS: We retrospectively reviewed subtrochanteric fractures presenting at our institution over 4.5 years (October 2014-May 2019), classifying them into two treatment groups; IMN and DHS. These groups were compared on outcome measures including surgical time, blood loss, radiation dose area product (DAP), length of stay, re-operation rate and mortality. RESULTS: During the time period studied, 86 patients presented with a subtrochanteric fracture of the femur; with 74 patients (86%) receiving an IMN and 12 (14%) receiving a DHS. The comparative outcome measures reaching statistical significance were blood loss and radiation DAP. The DHS group showed a significantly lower mean blood loss of 776 ml compared to 1029 ml in the IMN group. Also, the DHS group showed a significantly lower mean DAP of 150.30 mGy cm2 compared to 288.86 mGy cm2 in the IMN group. CONCLUSION: Although UK national guidelines recommend treating all subtrochanteric fractures with an IMN; the outcome measures assessed in our study did not show use of an IMN to be superior to a DHS. The DHS group showed a lower estimated blood loss and a reduced DAP. This, along with the reduced financial cost associated with a DHS, may support the use of DHS over IMN for certain subtrochanteric fractures of the femur. There may not be a single favourable implant for the treatment of subtrochanteric fractures as a whole; instead different subtypes of fracture may be amenable to a number of fixation devices. Choice of implant should be determined locally and based on existing and future clinical and health economic research
A ten-dimensional action for non-geometric fluxes
The NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change
of field variables inspired by Generalized Complex Geometry. We obtain a new
metric and dilaton, together with an antisymmetric bivector field which leads
to a ten-dimensional version of the non-geometric Q-flux. Given the involved
global aspects of non-geometric situations, we prescribe to use this new
Lagrangian, whose associated action is well-defined in some examples
investigated here. This allows us to perform a standard dimensional reduction
and to recover the usual contribution of the Q-flux to the four-dimensional
scalar potential. An extension of this work to include the R-flux is discussed.
The paper also contains a brief review on non-geometry.Comment: 47 pages; v2: minor modifications, references added, version to be
published in JHE
T-Duality as a Duality of Loop Group Bundles
Representing the data of a string compactified on a circle in the background
of H-flux in terms of the geometric data of a principal loop group bundle, we
show that T-duality in type II string theory can be understood as the
interchange of the momentum and winding homomorphisms of the principal loop
group bundle, thus giving rise to a new interpretation of T-duality.Comment: 8 pages, latex 2e, new reference added, J.Phys.A: Fast Track
Publications (to appear
Duality Invariant Actions and Generalised Geometry
We construct the non-linear realisation of the semi-direct product of E(11)
and its first fundamental representation at lowest order and appropriate to
spacetime dimensions four to seven. This leads to a non-linear realisation of
the duality groups and introduces fields that depend on a generalised space
which possess a generalised vielbein. We focus on the part of the generalised
space on which the duality groups alone act and construct an invariant action.Comment: 59 pages (typos fixed and added comments
Sexual vulnerability and HIV seroprevalence among the deaf and hearing impaired in Cameroon
<p>Abstract</p> <p>Background</p> <p>This quantitative cross-sectional study examines sexual behaviour of a target group of hearing-impaired persons in Yaounde, the capital city of the Republic of Cameroon. It measures their HIV prevalence to enable assessment of their sexual vulnerability and to help reduce the gap in existing HIV serology data among people with disabilities in general and the deaf in particular.</p> <p>Methods</p> <p>The snowball sampling procedure was adopted as an adequate approach to meet this hard-to-reach group. A total of 118 deaf participants were interviewed for the behavioural component, using sign language as a means of data collection, while 101 participants underwent HIV serology testing. Descriptive analyses were done for behavioural data with Epi info software, while sera were tested by health personnel, using rapid and confirmation test reagents.</p> <p>Results</p> <p>From the results, it was clear that the hearing impaired were highly involved in risky sexual practices, as observed through major sexual indicators, such as: age at first sexual intercourse; condom use; and knowledge of sexually transmitted infections and AIDS. Furthermore, it was noted that the HIV prevalence rate of the hearing impaired in the capital of Cameroon was 4%, close to the prevalence in the city's general population (4.7%).</p> <p>Conclusions</p> <p>Such results suggest that there is a need for in-depth behavioural research and serological studies in this domain to better understand the determinants of risky sexual behaviour among the hearing impaired, and to propose operational prevention approaches for this group.</p
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