55,138 research outputs found
The low energy expansion of the one-loop type II superstring amplitude
The one-loop four-graviton amplitude in either of the type II superstring
theories is expanded in powers of the external momenta up to and including
terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four
linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series
are obtained by integrating powers of the two-dimensional scalar field theory
propagator over the toroidal world-sheet as well as the moduli of the torus.
The values of these coefficients match expectations based on duality relations
between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected.
Conclusion unchange
Development and validation of an ELISA to detect antibodies to Corynebacterium pseudotuberculosis in ovine sera
Several enzyme-linked immunosorbent assays (ELISAs) have been developed for the detection of antibodies to Corynebacterium pseudotuberculosis, the causative agent of caseous lymphadenitis (CLA). However, none are commercially available in the UK. It was therefore necessary to develop a new, economic ELISA for use in a research project studying the epidemiology of CLA in UK sheep.
The ELISA with its diagnostic qualities is presented. The ELISA was developed using sonicated C. pseudotuberculosis and optimised to detect total antibody or IgG class antibody in serum. Receiver Operating Characteristic (ROC) curves were obtained and the area under the ROC curve was used to compare the sensitivity and specificity of the two ELISAs.
Both versions of the ELISA were evaluated on a panel of 150 positive reference sera and 103 negative reference sera. Using the test at 100% specificity, the sensitivity of detection of total antibody was 71% (95% confidence interval 63-78%), and the
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sensitivity of detection of IgG antibody to C. pseudotuberculosis was 83% (76-89%), which compares favourably with other reported ELISA tests for CLA in sheep. The sensitivity of the IgG antibody assay may be higher because of the greater affinity of IgG class antibodies compared with the IgM antibodies also detected by the total antibody ELISA.
The results of ROC analysis indicated that the IgG isotype ELISA was more accurate than the total antibody ELISA. The efficiency of the test was greatest when serum samples were run in a dilution series than when any single serum dilution was used. The ELISA is considered to be suitable for application in field studies of CLA in UK sheep
D-instanton partition functions
Duality arguments are used to determine D-instanton contributions to certain
effective interaction terms of type II supergravity theories in various
dimensions. This leads to exact expressions for the partition functions of the
finite N D-instanton matrix model in d=4 and 6 dimensions that generalize our
previous expression for the case d=10. These results are consistent with the
fact that the Witten index of the T-dual D-particle process should only be
non-vanishing for d=10.Comment: 20 pages, harvmac, typos corrected, reference adde
The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
The predicted orbital-period distribution of the subdwarf-B (sdB) population
is bi-modal with a peak at short ( 250 days) periods.
Observationally, many short-period sdB systems are known, but the predicted
long period peak is missing as orbits have only been determined for a few
long-period systems. As these predictions are based on poorly understood
binary-interaction processes, it is of prime importance to confront the
predictions with reliable observational data. We therefore initiated a
monitoring program to find and characterize long-period sdB stars. In this
paper we aim to determine the orbital parameters of the three long-period
sdB+MS binaries BD+29 3070, BD+34 1543 and Feige 87, to constrain their
absolute dimensions and the physical parameters of the components.
High-resolution spectroscopic time series were obtained with HERMES at the
Mercator telescope on La Palma, and analyzed to determine the radial velocities
of both the sdB and MS components. Photometry from the literature was used to
construct the spectral-energy distribution (SED) of the binaries. Atmosphere
models were used to fit these SEDs and to determine the surface gravities and
temperatures of both components of all systems. Spectral analysis was used to
check the results of the SEDs. An orbital period of 1283 +- 63 d, a mass ratio
of q = 0.39 +- 0.04 and a significant non-zero eccentricity of e = 0.15 +- 0.01
were found for BD+29 3070. For BD+34 1543 we determined P = 972 +- 2 d, q =
0.57 +- 0.01 and again a clear non-zero eccentricity of e = 0.16 +- 0.01. Last,
for Feige 87 we found P = 936 +- 2 d, q = 0.55 +- 0.01 and e = 0.11 +- 0.01.
BD+29 3070, BD+34 1543 and Feige 87 are long period sdB + MS binaries on
clearly eccentric orbits. These results are in conflict with the predictions of
stable Roche-lobe overflow models.Comment: 15 pages, 6 figures, Accepted by A&
Formulating Light Cone QCD on the Lattice
We present the near light cone Hamiltonian in lattice QCD depending on
the parameter , which gives the distance to the light cone. Since the
vacuum has zero momentum we can derive an effective Hamiltonian from
which is only quadratic in the momenta and therefore solvable by standard
methods. An approximate ground state wave functional is determined
variationally in the limit .Comment: 48 pages, 8 figure
General features of Bianchi-I cosmological models in Lovelock gravity
We derived equations of motion corresponding to Bianchi-I cosmological models
in the Lovelock gravity. Equations derived in the general case, without any
specific ansatz for any number of spatial dimensions and any order of the
Lovelock correction. We also analyzed the equations of motion solely taking
into account the highest-order correction and described the drastic difference
between the cases with odd and even numbers of spatial dimensions. For
power-law ansatz we derived conditions for Kasner and generalized Milne regimes
for the model considered. Finally, we discuss the possible influence of matter
in the form of perfect fluid on the solutions obtained.Comment: extended version of published Brief Repor
Information-theory-based solution of the inverse problem in classical statistical mechanics
We present a procedure for the determination of the interaction potential
from the knowledge of the radial pair distribution function. The method,
realized inside an inverse Monte Carlo simulation scheme, is based on the
application of the Maximum Entropy Principle of information theory and the
interaction potential emerges as the asymptotic expression of the transition
probability. Results obtained for high density monoatomic fluids are very
satisfactory and provide an accurate extraction of the potential, despite a
modest computational effort.Comment: 9 pages, 2 figure
Exact solutions of a particle in a box with a delta function potential: The factorization method
We use the factorization method to find the exact eigenvalues and
eigenfunctions for a particle in a box with the delta function potential
. We show that the presence of the potential
results in the discontinuity of the corresponding ladder operators. The
presence of the delta function potential allows us to obtain the full spectrum
in the first step of the factorization procedure even in the weak coupling
limit .Comment: 8 pages, 2 figures, to appear in American Journal of Physic
The development of low temperature curing adhesives
An approach for the development of a practical low temperature (293 K-311 K/68 F-100 F) curing adhesive system based on a family of amide/ester resins was studied and demonstrated. The work was conducted on resin optimization and adhesive compounding studies. An improved preparative method was demonstrated which involved the reaction of an amine-alcohol precursor, in a DMF solution with acid chloride. Experimental studies indicated that an adhesive formulation containing aluminum powder provided the best performance when used in conjunction with a commercial primer
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