6,163 research outputs found
On kinematical constraints in the hadrogenesis conjecture for the baryon resonance spectrum
We consider the reaction dynamics of bosons with negative parity and spin
or and fermions with positive parity and spin or
. Such systems are of central importance for the computation of
the baryon resonance spectrum in the hadrogenesis conjecture. Based on a chiral
Lagrangian the coupled-channel partial-wave scattering amplitudes have to be
computed. We study the generic properties of such amplitudes. A decomposition
of the various scattering amplitudes into suitable sets of invariant functions
expected to satisfy Mandelstam's dispersion-integral representation is
presented. Sets are identified that are free from kinematical constraints and
that can be computed efficiently in terms of a novel projection algebra. From
such a representation one can deduce the analytic structure of the partial-wave
amplitudes. The helicity and the conventional angular-momentum partial-wave
amplitudes are kinematically constrained at the Kibble conditions. Therefore an
application of a dispersion-integral representation is prohibitively
cumbersome. We derive covariant partial-wave amplitudes that are free from
kinematical constraints at the Kibble conditions. They correspond to specific
polynomials in the 4-momenta and Dirac matrices that solve the various
Bethe-Salpeter equations in the presence of short-range interactions
analytically.Comment: 18 page
Robust Multi-Image HDR Reconstruction for the Modulo Camera
Photographing scenes with high dynamic range (HDR) poses great challenges to
consumer cameras with their limited sensor bit depth. To address this, Zhao et
al. recently proposed a novel sensor concept - the modulo camera - which
captures the least significant bits of the recorded scene instead of going into
saturation. Similar to conventional pipelines, HDR images can be reconstructed
from multiple exposures, but significantly fewer images are needed than with a
typical saturating sensor. While the concept is appealing, we show that the
original reconstruction approach assumes noise-free measurements and quickly
breaks down otherwise. To address this, we propose a novel reconstruction
algorithm that is robust to image noise and produces significantly fewer
artifacts. We theoretically analyze correctness as well as limitations, and
show that our approach significantly outperforms the baseline on real data.Comment: to appear at the 39th German Conference on Pattern Recognition (GCPR)
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A cohort study of the associations between udder conformation, milk somatic cell count, and lamb weight in suckler ewes
A cohort study of 67 suckler ewes from 1 farm was carried out from January to May 2010 to investigate associations between udder conformation, udder half milk somatic cell count (SCC), and lamb weight. Ewes and lambs were observed at lambing. Ewe health and teat condition and lamb health and weight were recorded on 4 to 5 further occasions at 14-d intervals. At each observation, a milk sample was collected from each udder half for somatic cell counting. Two weeks after lambing, ewe udder conformation and teat placement were scored. Low lamb weight was associated with ewe SCC >400,000 cells/mL (−0.73kg), a new teat lesion 14 d previously (−0.91kg), suboptimal teat position (−1.38kg), rearing in a multiple litter (−1.45kg), presence of diarrhea at the examination (−1.19kg), and rearing by a 9-yr-old ewe compared with a 6-yr-old ewe (−2.36kg). High lamb weight was associated with increasing lamb age (0.21kg/d), increasing birth weight (1.65kg/kg at birth), and increasing number of days the ewe was given supplementary feed before lambing (0.06kg/d). High udder half SCC was associated with pendulous udders (9.6% increase in SCC/cm of drop) and greater total cross-sectional area of the teats (7.2% increase of SCC/cm2). Low SCC were associated with a heavier mean litter weight (6.7% decrease in SCC/kg). Linear, quadratic, and cubic terms for days in lactation were also significant. We conclude that poor udder and teat conformation are associated with high levels of intramammary infection, as indicated by increased SCC and that both physical attributes of the udder and SCC are linked to lamb growth, suggesting that selection of suckler ewes with better udder and teat conformation would reduce intramammary infection and increase lamb growth rate
Pauli paramagnetism of an ideal Fermi gas
We show how to use trapped ultracold atoms to measure the magnetic
susceptibility of a two-component Fermi gas. The method is illustrated for a
non-interacting gas of Li, using the tunability of interactions around a
wide Feshbach resonances. The susceptibility versus effective magnetic field is
directly obtained from the inhomogeneous density profile of the trapped atomic
cloud. The wings of the cloud realize the high field limit where the
polarization approaches 100%, which is not accessible for an electron gas.Comment: 5 pages, 4 figure
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Investigating an Adequate Level of Modelling for Energy Analysis of Domestic Buildings
This paper investigates what level of modelling is required to appropriately support energy analysis of domestic buildings. The paper analyses the effect of simplications made in thermal zoning and internal loads scheduling through a case study of a UK domestic building. The case study provides quantified effects of common simplications made in practice on the accuracy of energy predictions by making simplications in the model incrementally and estimating the effect of individual simplications on electricity and heating demand predictions
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