13,065 research outputs found
Axial and pseudoscalar current correlators and their couplings to eta and etaprime mesons
Correlators of singlet and octet axial currents, as well as anomaly and
pseudoscalar densities have been studied using QCD sum rules. Several of these
sum rules are used to determine the couplings f^8_eta, f^0_eta, f^8_etaprime
and f^0_etaprime. We find mutually consistent values which are also in
agreement with phenomenological values obtained from data on various decay and
production rates. While most of the sum rules studied by us are independent of
the contributions of direct instantons and screening correction, the
singlet-singlet current correlator and the anomaly-anomaly correlator improve
by their inclusion.Comment: 31 pages, 11 figure
A novel platform for isotype-specific testing of autoantibodies.
The objective of this study was to test if a novel platform could be used for isotype-specific autoantibody testing in humans. Further, we evaluated if testing with this novel platform enables earlier detection of insulin autoantibodies in individuals that have first-degree relatives with type-1 diabetes than currently used approaches. Longitudinal serum samples from participants were collected before and after they converted to become positive for insulin autoantibodies by the current standardly used assays. Using a novel plasmonic gold chip platform, we tested these samples for IgM isotype-specific autoantibodies. Serial serum samples from individuals without diabetes were also tested as a comparison control cohort. Our results demonstrate proof-of-concept that a plasmonic gold chip can specifically detect the IgM insulin autoantibody. Five out of the six individuals that converted to being positive for insulin autoantibodies by standard testing had significant IgM autoantibodies on the plasmonic chip platform. The plasmonic chip platform detected IgM autoantibodies earlier than standard testing by up to 4 years. Our results indicate that the plasmonic gold platform can specifically detect the IgM isotype autoantibodies and suggest that combining isotype-specific testing with currently used approaches enables earlier detection of insulin autoantibodies in individuals that have first-degree relatives with type 1 diabetes
Rectification in one--dimensional electronic systems
Asymmetric current--voltage () curves, known as the diode or
rectification effect, in one--dimensional electronic conductors can have their
origin from scattering off a single asymmetric impurity in the system. We
investigate this effect in the framework of the Tomonaga--Luttinger model for
electrons with spin. We show that electron interactions strongly enhance the
diode effect and lead to a pronounced current rectification even if the
impurity potential is weak. For strongly interacting electrons and not too
small voltages, the rectification current, , measuring
the asymmetry in the current--voltage curve, has a power--law dependence on the
voltage with a negative exponent, , leading to a bump in the
current--voltage curve.Comment: 9 pages; 3 figure
Bayesian inference for orbital eccentricities
Highest posterior density intervals (HPDI's) are derived for the true
eccentricities of spectroscopic binaries with measured values e ~ 0. These
yield upper limits when e is below the detection threshold e_th and seamlessly
transform to upper and lower bounds when e > e_th. In the main text, HPDI's are
computed with an informative eccentricity prior representing orbital decay due
to tidal dissipation. In an appendix, the corresponding HPDI's are computed
with a uniform prior and are the basis for a revised version of the
Lucy-Sweeney test, with the previous outcome e = 0 now replaced by an upper
limit. Sampling experiments with known prior confirm the validity of the
HPDI's.Comment: 7 pages, 6 figures. Error in terminology corrected. Results
unchanged. Accepted by Astronomy & Astrophysic
Lattice dynamics and reduced thermal conductivity of filled skutterudites
The great reduction in thermal conductivity of skutterudites upon filling the
``void'' sites with Rare Earth (RE) ions is key to their favorable
thermoelectric properties but remains to be understood. Using lattice dynamic
models based on first principles calculations, we address the most popular
microscopic mechanism, reduction via rattling ions. The model withstands
inelastic neutron scattering and specific heat measurements, and refutes
hypotheses of an anharmonic RE potential and of two distinct localized RE
vibrations of disparate frequencies. It does indicate a strong hybridization
between bare La vibrations and certain Sb-like phonon branches, suggesting
anharmonic scattering by harmonic RE motions as an important mechanism for
suppression of heat conductivity.Comment: modified version resubmitted to PRB. Results unchanged, text changed
substantiall
Polyneuropathy associated with IgA monoclonal gammopathy of undetermined significance
Although polyneuropathies associated with IgM and IgG monoclonal gammopathies have been well described, polyneuropathy with IgA monoclonal gammopathy of undetermined significance (MGUS) is less commonly seen and has not been well studies. We reviewed the clinical and electrodiagnostic features of 5 such patients, and the sural nerve biopsy findings in 4 of them. One patient was diabetic, while 4 were free of other diagnoses commonly associated with neuropathy. Clinical presentations were varied. Electrodiagnostic and histological studies ranged from primary demyelination to primary axon loss to a mixed axonal/demyelinating picture. Three patients who were treated appeared to respond to prednisone or intravenous gamma globulin, despite clear clinical, electrodiagnostic, and histological differences. We conclude that the polyneuropathy associated with IgA MGUS is heterogeneous, similar to that in IgM and IgG MGUS. A trial of immunomodulating therapy appears to be warranted in such patients if the neuropathy is sufficiently servere. © 1993 John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50156/1/880160113_ftp.pd
Strategy bifurcation and spatial inhomogeneity in a simple model of competing sellers
We present a simple one-parameter model for spatially localised evolving
agents competing for spatially localised resources. The model considers selling
agents able to evolve their pricing strategy in competition for a fixed market.
Despite its simplicity, the model displays extraordinarily rich behavior. In
addition to ``cheap'' sellers pricing to cover their costs, ``expensive''
sellers spontaneously appear to exploit short-term favorable situations. These
expensive sellers ``speciate'' into discrete price bands. As well as variety in
pricing strategy, the ``cheap'' sellers evolve a strongly correlated spatial
structure, which in turn creates niches for their expensive competitors. Thus
an entire ecosystem of coexisting, discrete, symmetry-breaking strategies
arises.Comment: 6 pages, 6 figures, epl2; 1 new figure, include nash equilibrium
analysis, typo fixe
High Scale Physics Connection to LHC Data
The existing data appears to provide hints of an underlying high scale
theory. These arise from the gauge coupling unification, from the smallness of
the neutrino masses, and via a non-vanishing muon anomaly. An overview of high
scale models is given with a view to possible tests at the Large Hadron
Collider. Specifically we discuss here some generic approaches to deciphering
their signatures. We also consider an out of the box possibility of a four
generation model where the fourth generation is a mirror generation rather than
a sequential generation. Such a scenario can lead to some remarkably distinct
signatures at the LHC.Comment: 23 pages, no figures. Based on invited lectures at the 46th Course at
the International School of Subnuclear Physics- Erice -Sicily: 29 August -7
September, 200
Semiclassical Effects and the Onset of Inflation
We present a class of exact solutions to the constraint equations of General
Relativity coupled to a Klein - Gordon field, these solutions being isotropic
but not homogeneous. We analyze the subsequent evolution of the consistent
Cauchy data represented by those solutions, showing that only certain special
initial conditions eventually lead to successfull Inflationary cosmologies. We
argue, however, that these initial conditions are precisely the likely outcomes
of quantum events occurred before the inflationary era.Comment: 22 pages, file written in RevTe
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