975 research outputs found
The Hubble Space Telescope high speed photometer
The Hubble Space Telescope will provide the opportunity to perform precise astronomical photometry above the disturbing effects of the atmosphere. The High Speed Photometer is designed to provide the observatory with a stable, precise photometer with wide dynamic range, broad wavelenth coverage, time resolution in the microsecond region, and polarimetric capability. Here, the scientific requirements for the instrument are examined, the unique design features of the photometer are explored, and the improvements to be expected over the performance of ground-based instruments are projected
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Uranium accountability for ATR fuel fabrication, a computer simulation
A stochastic computer model has been designed to simulate the material control system used during the production of fuel plates for the Advanced Test Reactor. The model is designed so that manufacturing process and measurement parameters are fed in as input. Changes in the manufacturing process and measurement procedures are easily incorporated. Individual operations in the plant are described by program subroutines. By using this model values for Inventory Difference (ID) and Limit of Error on Inventory Difference (LEID) may be calculated for predetermined plant operating conditions. Furthermore the effect on ID and LEID produced by changing plant operating procedures and measurement technique may also be examined
Three-Point Functions in N=4 SYM Theory at One-Loop
We analyze the one-loop correction to the three-point function coefficient of
scalar primary operators in N=4 SYM theory. By applying constraints from the
superconformal symmetry, we demonstrate that the type of Feynman diagrams that
contribute depends on the choice of renormalization scheme. In the planar
limit, explicit expressions for the correction are interpreted in terms of the
hamiltonians of the associated integrable closed and open spin chains. This
suggests that at least at one-loop, the planar conformal field theory is
integrable with the anomalous dimensions and OPE coefficients both obtainable
from integrable spin chain calculations. We also connect the planar results
with similar structures found in closed string field theory.Comment: 34 pages, 9 figures, harvmac; references adde
Finite-Size Corrections to Anomalous Dimensions in N=4 SYM Theory
The scaling dimensions of large operators in N=4 supersymmetric Yang-Mills
theory are dual to energies of semiclassical strings in AdS(5)xS(5). At one
loop, the dimensions of large operators can be computed with the help of Bethe
ansatz and can be directly compared to the string energies. We study
finite-size corrections for Bethe states which should describe quantum
corrections to energies of extended semiclassical strings.Comment: 10 page
The dynamics of cosmological perturbations in thermal theory
Using a recent thermal-field-theory approach to cosmological perturbations,
the exact solutions that were found for collisionless ultrarelativistic matter
are generalized to include the effects from weak self-interactions in a
model through order . This includes the effects
of a resummation of thermal masses and associated nonlocal gravitational
vertices, thus going far beyond classical kinetic theory. Explicit solutions
for all the scalar, vector, and tensor modes are obtained for a
radiation-dominated Einstein-de Sitter model containing a weakly interacting
scalar plasma with or without the admixture of an independent component of
perfect radiation fluid.Comment: 32 pages, REVTEX, 13 postscript figures included by epsf.st
Open Spinning Strings and AdS/dCFT Duality
We consider open spinning string solutions on an AdS_4 x S^2-brane (D5-brane)
in the bulk AdS_5 x S^5 background. By taking account of the breaking of
SO(6)_R to SO(3)_H x SO(3)_V due to the presence of the AdS-brane, the open
rotating string ansatz is discussed. We construct the elliptic folded/circular
open string solutions in the SU(2) and the SL(2) sectors, so that they satisfy
the appropriate boundary conditions. On the other hand, in the SU(2) sector of
the gauge theory, we compute the matrix of anomalous dimension of the defect
operator, which turns out to be the Hamiltonian of an open integrable spin
chain. Then we consider the coordinate Bethe ansatz with arbitrary number of
impurities, and compare the boundary condition of the Bethe wavefunction with
that of the corresponding open string solution. We also discuss the Bethe
ansatz for the open SL(2) spin chain with several supports from the string
theory side. Then, in both SU(2) and SL(2) sectors, we analyze the Bethe
equations in the thermodynamic limit and formulate the `doubling trick' on the
Riemann surface associated with the gauge theory.Comment: 1+50 pages, 7 figures, JHEP style, references adde
May Measurement Month 2019: an analysis of blood pressure screening results from the United Kingdom and Republic of Ireland
In the UK, heart and circulatory diseases account for 29% of all deaths (14% through coronary heart disease and 8% through stroke). In 2015, the prevalence of hypertension was 20% in the UK and 23% in the Republic of Ireland. In 2019, 14% of people registered with a UK general practice had hypertension and yet it was the attributable risk factor for around half of all deaths from coronary heart disease or stroke. We participated in May Measurement Month 2019 to increase awareness of blood pressure (BP) measurement, and to identify the proportion of undiagnosed hypertension and degree of uncontrolled hypertension in the community. The 2019 campaign set up screening sites within the community at places of worship, supermarkets, GP surgeries, workplaces, charity events, community pharmacies, gyms, and various other public places. We screened 10194 participants (mean age 51 ± 18 years, 60% women) and found that 1013 (9.9%) were on antihypertensive treatment, while 3408 (33.4%) had hypertension. Of the 3408 participants with hypertension, only 33.5% were aware of their condition despite 98.8% having previous BP measurements. In those on antihypertensive medication, only 38.2% had controlled BP (<140 and <90 mmHg). Our UK and Republic of Ireland data demonstrate concerning levels of undiagnosed hypertension and sub-optimal BP control in many individuals with a diagnosis. This evidence supports a critical need for better systematic community and primary care screening initiatives
Using Rasch analysis to form plausible health states amenable to valuation: the development of CORE-6D from CORE-OM in order to elicit preferences for common mental health problems
Purpose: To describe a new approach for deriving a preference-based index from a condition specific measure that uses Rasch analysis to develop health states.
Methods: CORE-OM is a 34-item instrument monitoring clinical outcomes of people with common mental health problems. CORE-OM is characterised by high correlation across its domains. Rasch analysis was used to reduce the number of items and response levels in order to produce a set of unidimensionally-behaving items, and to generate a credible set of health states corresponding to different levels of symptom severity using the Rasch item threshold map.
Results: The proposed methodology resulted in the development of CORE-6D, a 2-dimensional health state description system consisting of a unidimensionally-behaving 5-item emotional component and a physical symptom item. Inspection of the Rasch item threshold map of the emotional component helped identify a set of 11 plausible health states, which, combined with the physical symptom item levels, will be used for the valuation of the instrument, resulting in the development of a preference-based index.
Conclusions: This is a useful new approach to develop preference-based measures where the domains of a measure are characterised by high correlation. The CORE-6D preference-based index will enable calculation of Quality Adjusted Life Years in people with common mental health problems
The classical R-matrix of AdS/CFT and its Lie dialgebra structure
The classical integrable structure of Z_4-graded supercoset sigma-models,
arising in the AdS/CFT correspondence, is formulated within the R-matrix
approach. The central object in this construction is the standard R-matrix of
the Z_4-twisted loop algebra. However, in order to correctly describe the Lax
matrix within this formalism, the standard inner product on this twisted loop
algebra requires a further twist induced by the Zhukovsky map, which also plays
a key role in the AdS/CFT correspondence. The non-ultralocality of the
sigma-model can be understood as stemming from this latter twist since it leads
to a non skew-symmetric R-matrix.Comment: 22 pages, 2 figure
Yang-Mills Duals for Semiclassical Strings
We consider a semiclassical multiwrapped circular string pulsating on S_5,
whose center of mass has angular momentum J on an S_3 subspace. Using the
AdS/CFT correspondence we argue that the one-loop anomalous dimension of the
dual operator is a simple rational function of J/L, where J is the R-charge and
L is the bare dimension of the operator. We then reproduce this result directly
from a super Yang-Mills computation, where we make use of the integrability of
the one-loop system to set up an integral equation that we solve. We then
verify the results of Frolov and Tseytlin for circular rotating strings with
R-charge assignment (J',J',J). In this case we solve for an integral equation
found in the O(-1) matrix model when J' J.
The latter region starts at J'=L/2 and continues down, but an apparent critical
point is reached at J'=4J. We argue that the critical point is just an artifact
of the Bethe ansatz and that the conserved charges of the underlying integrable
model are analytic for all J' and that the results from the O(-1) model
continue onto the results of the O(+1) model.Comment: 26 Pages, LaTeX; v2 Typos corrected, reference update
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