1,519 research outputs found
Determining the Gluon Distributions in the Proton and Photon from Two-Jet Production at HERA
Two-jet production from the direct photon contribution at HERA is a sensitive
measure of the small- gluon in the proton. We propose measurements of ratios
of the jet cross-sections which will clearly distinguish between gluons with or
without singular behaviour at small . Furthermore, we show that analogous
ratio measurements for the resolved photon contribution provide a sensitive way
of determining the gluon distribution in the photon.Comment: Rutherford Appleton Laboratory report RAL-93-071 7 pages 3 figs Fig2
and Fig3 included as psfile
Electronic damping of molecular motion at metal surfaces
A method for the calculation of the damping rate due to electron-hole pair
excitation for atomic and molecular motion at metal surfaces is presented. The
theoretical basis is provided by Time Dependent Density Functional Theory
(TDDFT) in the quasi-static limit and calculations are performed within a
standard plane-wave, pseudopotential framework. The artificial periodicity
introduced by using a super-cell geometry is removed to derive results for the
motion of an isolated atom or molecule, rather than for the coherent motion of
an ordered over-layer. The algorithm is implemented in parallel, distributed
across both and space, and in a form compatible with the
CASTEP code. Test results for the damping of the motion of hydrogen atoms above
the Cu(111) surface are presented.Comment: 10 pages, 3 figure
Double Diffraction Dissociation at High t
Diffractive scattering in the presence of a large momentum transfer is an
ideal place to study the short distance rapidity gap producing mechanism.
Previous studies (experimental and theoretical) in this area have focussed on
gaps between jets and on high- vector meson production. We propose the
measurement of double dissociation at high-. We examine the numerous
advantages to studying this more inclusive process and conclude that it is an
ideal place to study short distance diffraction.Comment: 12 pages, 8 figure
Multiparton Interactions in Photoproduction at HERA
The high energy photoproduction of jets is being observed at the ep collider,
HERA. It may be that the HERA centre-of-mass energy is sufficiently large that
the production of more than one pair of jets per ep collision becomes possible,
owing to the large number density of the probed gluons. We construct a Monte
Carlo model of such multiparton interactions and study their effects on a wide
range of physical observables. The conclusion is that multiple interactions
could have very significant effects upon the photoproduction final state and
that this would for example make extractions of the gluon density in the photon
rather difficult. Total rates for the production of many (i.e. > 2) jets could
provide direct evidence for the presence of multiple interactions, although
parton showering and hadronization significantly affect low transverse energy
jets.Comment: 21 pages, 8 figures include
The Use of IQ and Descriptions of People with Intellectual Disabilities in the Scientific Literature
Large-scale Roll Out of Electronic Longitudinal Mood-Monitoring for Research in Affective Disorders: Report From the UK Bipolar Disorder Research Network
Background Electronic longitudinal mood monitoring has been shown to be acceptable to patients with affective disorders within clinical settings, but its use in large-scale research has not yet been established. Methods Using both postal and email invitations, we invited 4080 past research participants with affective disorders who were recruited into the Bipolar Disorder Research Network (BDRN) over a 10 year period to participate in online weekly mood monitoring. In addition, since January 2015 we have invited all newly recruited BDRN research participants to participate in mood monitoring at the point they were recruited into BDRN. Results Online mood monitoring uptake among past participants was 20, and among new participants to date was 46 with participants recruited over the last year most likely to register (61). More than 90 mood monitoring participants engaged for at least one month, with mean engagement period greater than one year (58 weeks) and maximum engagement for longer than three years (165 weeks). There were no significant differences in the proportion of past and new BDRN participants providing data for at least 4 weeks (91, 92 respectively), 3 months (78, 82), 6 months (65, 54) or one year (51, 44). Limitations Our experiences with recruiting participants for electronic prospective mood monitoring may not necessarily generalise fully to research situations that are very different from those we describe. Conclusions Large-scale electronic longitudinal mood monitoring in affective disorders for research purposes is feasible with uptake highest among newly recruited participants
The interaction of a gap with a free boundary in a two dimensional dimer system
Let be a fixed vertical lattice line of the unit triangular lattice in
the plane, and let \Cal H be the half plane to the left of . We
consider lozenge tilings of \Cal H that have a triangular gap of side-length
two and in which is a free boundary - i.e., tiles are allowed to
protrude out half-way across . We prove that the correlation function of
this gap near the free boundary has asymptotics ,
, where is the distance from the gap to the free boundary. This
parallels the electrostatic phenomenon by which the field of an electric charge
near a conductor can be obtained by the method of images.Comment: 34 pages, AmS-Te
Companion animals are spillover hosts of the Multidrug-resistant human extraintestinal escherichia coli pandemic Clones ST131 and ST1193
Escherichia coli sequence types 131 (ST131) and 1193 are multidrug-resistant extraintestinal pathogens that have recently spread epidemically among humans and are occasionally isolated from companion animals. This study characterized a nationwide collection of fluoroquinolone-resistant (FQR) E. coli isolates from extraintestinal infections in Australian cats and dogs. For this, 59 cat and dog FQR clinical E. coli isolates (representing 6.9% of an 855-isolate collection) underwent PCR-based phylotyping and whole-genome sequencing (WGS). Isolates from commensal-associated phylogenetic groups A (14/59, 24%) and B1 (18/59, 31%) were dominant, with ST224 (10/59, 17%), and ST744 (8/59, 14%) predominating. Less prevalent were phylogenetic groups D (12/59, 20%), with ST38 (8/59, 14%) predominating, and virulence-associated phylogenetic group B2 (7/59, 12%), with ST131 predominating (6/7, 86%) and no ST1193 isolates identified. In a WGS-based comparison of 20 cat and dog-source ST131 isolates with 188 reference human and animal ST131 isolates, the cat and dog-source isolates were phylogenetically diverse. Although cat and dog-source ST131 isolates exhibited some minor sub-clustering, most were closely related to human-source ST131 strains. Furthermore, the prevalence of ST131 as a cause of FQR infections in Australian companion animals was relatively constant between this study and the 5-year-earlier study of Platell et al. (2010) (9/125 isolates, 7.2%). Thus, although the high degree of clonal commonality among FQR clinical isolates from humans vs. companion animals suggests the possibility of bi-directional between-species transmission, the much higher reported prevalence of ST131 and ST1193 among FQR clinical isolates from humans as compared to companion animals suggests that companion animals are spillover hosts rather than being a primary reservoir for these lineages
The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling
We investigate the effect that Rashba spin-orbit coupling has on the low
energy behaviour of a two dimensional magnetic impurity system. It is shown
that the Kondo effect, the screening of the magnetic impurity at temperatures T
< T_K, is robust against such spin-orbit coupling, despite the fact that the
spin of the conduction electrons is no longer a conserved quantity. A proposal
is made for how the spin-orbit coupling may change the value of the Kondo
temperature T_K in such systems and the prospects of measuring this change are
discussed. We conclude that many of the assumptions made in our analysis
invalidate our results as applied to recent experiments in semi-conductor
quantum dots but may apply to measurements made with magnetic atoms placed on
metallic surfaces.Comment: 22 pages, 1 figure; reference update
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