696 research outputs found
On the origin of M81 group extended dust emission
Galactic cirrus emission at far-infrared wavelengths affects many extragalactic observations. Separating this emission from that associated with extragalactic objects is both important and difficult. In this paper we discuss a particular case, the M81 group, and the identification of diffuse structures prominent in the infrared, but also detected at optical wavelengths. The origin of these structures has previously been controversial, ranging from them being the result of a past interaction between M81 and M82 or due to more local Galactic emission. We show that over an order of a few arcmin scales, the far-infrared (Herschel 250 mu m) emission correlates spatially very well with a particular narrow-velocity (2-3 km s(-1)) component of the Galactic HI. We find no evidence that any of the far-infrared emission associated with these features actually originates in the M81 group. Thus we infer that the associated diffuse optical emission must be due to galactic light-back scattered off dust in our galaxy. Ultraviolet observations pick out young stellar associations around M81, but no detectable far-infrared emission. We consider in detail one of the Galactic cirrus features, finding that the far-infrared HI relation breaks down below arcmin scales and that at smaller scales there can be quite large dust-temperature variation
Nosocomial COVID-19 infection : examining the risk of mortality. The COPE-Nosocomial Study (COVID in Older PEople)
In the United Kingdom, authority to conduct the study was granted by the Health Research Authority (20/HRA/1898), and in Italy by the Ethics Committee of Policlinico Hospital Modena (Reference 369/2020/OSS/AOUMO). Cardiff University was the study sponsor.Peer reviewedPostprin
Genetic, abiotic and social influences on sex differentiation in cichlid fishes and the evolution of sequential hermaphroditism
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73799/1/j.1467-2979.2005.00184.x.pd
Measurement of K^0_e3 form factors
The semileptonic decay of the neutral K meson, KL -> pi e nu (Ke3), was used
to study the strangeness-changing weak interaction of hadrons. A sample of 5.6
million reconstructed events recorded by the NA48 experiment was used to
measure the Dalitz plot density. Admitting all possible Lorentz-covariant
couplings, the form factors for vector (f_+(q^2)), scalar (f_S) and tensor
(f_T) interactions were measured. The linear slope of the vector form factor
lambda_+ = 0.0284+-0.0007+-0.0013 and values for the ratios |f_S/f_+(0)| =
0.015^{+0.007}_{-0.010}+-0.012 and |f_T/f_+(0)| = 0.05^{+0.03}_{-0.04}+-0.03
were obtained. The values for f_S and f_T are consistent with zero. Assuming
only Vector-Axial vector couplings, lambda_+ = 0.0288+-0.0004+-0.0011 and a
good fit consistent with pure V-A couplings were obtained. Alternatively, a fit
to a dipole form factor yields a pole mass of M = 859+-18 MeV, consistent with
the K^*(892) mass.Comment: 16 pages, 7 figures. submitted to Phys. Lett.
The use of sewage treatment works as foraging sites by insectivorous bats
Sewage treatment works with percolating filter beds are known to provide profitable foraging areas for insectivorous birds due to their association with high macroinvertebrate densities. Fly larvae developing on filter beds at sewage treatment works may similarly provide a valuable resource for foraging bats. Over the last two decades, however, there has been a decline in filter beds towards a system of “activated sludge”. Insects and bat activity were surveyed at 30 sites in Scotland employing these two different types of sewage treatment in order to assess the possible implications of these changes for foraging bats. Bat activity (number of passes) recorded from broad-band bat detectors was quantified at three points within each site. The biomass of aerial insects, sampled over the same period as the detector surveys, was measured using a suction trap. The biomass of insects and activity of Pipistrellus spp. was significantly higher at filter beds than at activated sludge sites. In addition, whilst foraging activity of Pipistrellus spp. at filter beds was comparable to that of adjacent “good” foraging habitat, foraging at activated sludge sites was considerably lower. This study indicates the high potential value of an anthropogenic process to foraging bats, particularly in a landscape where their insect prey has undergone a marked decline, and suggests that the current preference for activated sludge systems is likely to reduce the value of treatment works as foraging sites for bats
Search for R-Parity Violating Decays of Scalar Fermions at LEP
A search for pair-produced scalar fermions under the assumption that R-parity
is not conserved has been performed using data collected with the OPAL detector
at LEP. The data samples analysed correspond to an integrated luminosity of
about 610 pb-1 collected at centre-of-mass energies of sqrt(s) 189-209 GeV. An
important consequence of R-parity violation is that the lightest supersymmetric
particle is expected to be unstable. Searches of R-parity violating decays of
charged sleptons, sneutrinos and squarks have been performed under the
assumptions that the lightest supersymmetric particle decays promptly and that
only one of the R-parity violating couplings is dominant for each of the decay
modes considered. Such processes would yield final states consisting of
leptons, jets, or both with or without missing energy. No significant
single-like excess of events has been observed with respect to the Standard
Model expectations. Limits on the production cross- section of scalar fermions
in R-parity violating scenarios are obtained. Constraints on the supersymmetric
particle masses are also presented in an R-parity violating framework analogous
to the Constrained Minimal Supersymmetric Standard Model.Comment: 51 pages, 24 figures, Submitted to Eur. Phys. J.
Measurement of the Hadronic Photon Structure Function F_2^gamma at LEP2
The hadronic structure function of the photon F_2^gamma is measured as a
function of Bjorken x and of the factorisation scale Q^2 using data taken by
the OPAL detector at LEP. Previous OPAL measurements of the x dependence of
F_2^gamma are extended to an average Q^2 of 767 GeV^2. The Q^2 evolution of
F_2^gamma is studied for average Q^2 between 11.9 and 1051 GeV^2. As predicted
by QCD, the data show positive scaling violations in F_2^gamma. Several
parameterisations of F_2^gamma are in agreement with the measurements whereas
the quark-parton model prediction fails to describe the data.Comment: 4 pages, 2 figures, to appear in the proceedings of Photon 2001,
Ascona, Switzerlan
A measurement of the tau mass and the first CPT test with tau leptons
We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV
using tau pairs from Z0 decays. To test CPT invariance we compare the masses of
the positively and negatively charged tau leptons. The relative mass difference
is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.
Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays
The lifetime and oscillation frequency of the B0 meson has been measured
using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP.
The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the
production flavour of the B0 mesons was determined using a combination of tags
from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d
= 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first
error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.
First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons
We report the first observation of Z/gamma* production in Compton scattering
of quasi-real photons. This is a subprocess of the reaction e+e- to
e+e-Z/gamma*, where one of the final state electrons is undetected.
Approximately 55 pb-1 of data collected in the year 1997 at an e+e-
centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been
analysed. The Z/gamma* from Compton scattering has been detected in the
hadronic decay channel. Within well defined kinematic bounds, we measure the
product of cross-section and Z/gamma* branching ratio to hadrons to be
(0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV,
dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60
GeV, dominated by (e)egamma* production, this product is found to be
(4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo
event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters
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