3,020 research outputs found
Deep-Inelastic Onium Scattering
Using the colour dipole approach of the QCD perturbative (BFKL) Pomeron
exchange in onium-onium scattering, we compute the cross section for small but
hierarchically different onium sizes. A specific term dependent on the
size-ratio is generated. In deep inelastic onium scattering it appears as a
scaling violation contribution to the quark structure function near the BFKL
singularity. We find that the extension of the formalism for deep inelastic
onium scattering to the proton structure function provides a remarkably good
3-parameter fit to HERA data at small x with a simple physical interpretation
in terms of the dipole formulation.Comment: 10 pages, 2 Postscript figure
Relative amplitude index: A new tool for hemodynamic evaluation of periprosthetic regurgitation after transcatheter valve implantation
ObjectiveThe impact of paravalvular aortic regurgitation (PAR) on hemodynamic performance after transcatheter aortic valve implantation (TAVI) remains disputable. Common parameters such as the diastolic blood pressure or the blood pressure amplitude do not provide reproducible results. The aim of our study was to evaluate the impact of PAR on hemodynamics and outcome using the relative amplitude index (RAI).MethodsPAR was prospectively evaluated by echocardiography before discharge in 110 patients. The RAI was calculated according to the formula: RAI = [(Post-TAVI BP amplitude)/(Post-TAVI SBP) − (Pre-TAVI BP amplitude)/(Pre-TAVI SBP)] × 100%, where BP is blood pressure and SBP is systolic blood pressure. Correlations of increased RAI with perioperative outcome were investigated and factors influencing mortality were isolated.ResultsThe incidence of moderate and severe PAR after TAVI was 9% and 1%, respectively. Diastolic pressure or post-TAVI amplitude did not correlate to perioperative outcome. RAI increased from 2 when PAR was <2+ to 7 when PAR was ≥2+ (P = .006). A cut-off value of RAI ≥14 was associated with increased perioperative mortality (29 vs 5%; P = .013) and acute renal injury requiring dialysis (71 vs 18%; P = .001). RAI ≥14 was also associated with higher follow-up mortality at 1 year (57 vs 16%; P = .007). RAI ≥14 (odds ratio [OR], 3.390; 95% confidence interval [CI], 1.6-7.194; P = .00146), PAR ≥2+ (OR, 4.717; 95% CI, 1.828-12.195; P = .00135), and perioperative renal replacement therapy (OR, 12.820; 95% CI, 5.181-31.250; P = .00031) were found to be independent predictors of mortality at 1 year.ConclusionsThe RAI is a useful tool to predict perioperative and 1-year outcome in patients with PAR after TAVI
Strange form factors in the context of SAMPLE, HAPPEX, and A4 experiments
The strange properties of the nucleon are investigated within the framework
of the SU(3) chiral quark-soliton model assuming isospin symmetry and applying
the symmetry conserving SU(3) quantization. We present the form factors
, and the electric and magnetic strange form
factors incorporating pion and kaon asymptotics. The results
show a fairly good agreement with the recent experimental data from the SAMPLE
and HAPPEX collaborations. We also present predictions for future measurements
including the A4 experiment at MAMI (Mainz).Comment: 10 pages with four figures. RevTeX4 is used. Few lines are changed.
Accepted for publication in Phys.Rev.
Towards an unified description of total and diffractive structure functions at HERA in the QCD dipole picture
It is argued that the QCD dipole picture allows to build an unified
theoretical description -based on BFKL dynamics- of the total and diffractive
nucleon structure functions. This description is in qualitative agreement with
the present collection of data obtained by the H1 collaboration. More precise
theoretical estimates, in particular the determination of the normalizations
and proton transverse momentum behaviour of the diffractive components, are
shown to be required in order to reach definite conclusions.Comment: latex file with 5 encapsulated figures, 19 page
Costs and cost-effectiveness of delivering intermittent preventive treatment through schools in western Kenya
BACKGROUND: Awareness of the potential impact of malaria among school-age children has stimulated investigation into malaria interventions that can be delivered through schools. However, little evidence is available on the costs and cost-effectiveness of intervention options. This paper evaluates the costs and cost-effectiveness of intermittent preventive treatment (IPT) as delivered by teachers in schools in western Kenya. METHODS: Information on actual drug and non-drug associated costs were collected from expenditure and salary records, government budgets and interviews with key district and national officials. Effectiveness data were derived from a cluster-randomised-controlled trial of IPT where a single dose of sulphadoxine-pyrimethamine and three daily doses of amodiaquine were provided three times in year (once termly). Both financial and economic costs were estimated from a provider perspective, and effectiveness was estimated in terms of anaemia cases averted. A sensitivity analysis was conducted to assess the impact of key assumptions on estimated cost-effectiveness. RESULTS: The delivery of IPT by teachers was estimated to cost US 0.25 per child) whilst recurrent costs accounted for 86.8% (US 29.84 and the cost per case of Plasmodium falciparum parasitaemia averted was US 24.60 and 40.32 when the prices of antimalarial drugs and delivery costs were varied. Cost-effectiveness was most influenced by effectiveness of IPT and the background prevalence of anaemia. In settings where 30% and 50% of schoolchildren were anaemic, cost-effectiveness ratios were US$ 12.53 and 7.52, respectively. CONCLUSION: This study provides the first evidence that IPT administered by teachers is a cost-effective school-based malaria intervention and merits investigation in other settings
Rapidity gaps in perturbative QCD
We analyze diffractive deep inelastic scattering within perturbative QCD by
studying lepton scattering on a heavy quark target. Simple explicit expressions
are derived in impact parameter space for the photon wave function and the
scattering cross sections corresponding to single and double Coulomb gluon
exchange. At limited momentum transfers to the target, the results agree with
the general features of the ``aligned jet model''. The color--singlet exchange
cross section receives a leading twist contribution only from the aligned jet
region, where the transverse size of the photon wave function remains finite in
the Bjorken scaling limit. In contrast to inclusive DIS, in diffractive events
there is no leading twist contribution to from the lowest
order photon Fock state, and the cross section for heavy quarks is
power suppressed in the quark mass. There are also important contributions with
large momentum transfer to the target, which corresponds to events having high
transverse momentum production in both the projectile and target rapidity
regions, separated by a rapidity gap.Comment: 27 pages, LaTeX, 6 figures. Duplicate figure removed, paper unchange
Project management practices in engineering university
The article presents the analysis of usage of project management methodology in Tomsk Polytechnic University, in particular the experience with the course Project management which started 15 years ago. The article presents the discussion around advantages of project management methodology for engineering education and administration of the university in general and the problems impeding extensive implementation of this methodology in teaching, research and management in the university
Half Life of the Doubly-magic r-Process Nucleus 78Ni
Nuclei with magic numbers serve as important benchmarks in nuclear theory. In
addition, neutron-rich nuclei play an important role in the astrophysical rapid
neutron-capture process (r-process). 78Ni is the only doubly-magic nucleus that
is also an important waiting point in the r-process, and serves as a major
bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been
experimentally deduced for the first time at the Coupled Cyclotron Facility of
the National Superconducting Cyclotron Laboratory at Michigan State University,
and was found to be 110 (+100 -60) ms. In the same experiment, a first
half-life was deduced for 77Ni of 128 (+27 -33) ms, and more precise half-lives
were deduced for 75Ni and 76Ni of 344 (+20 -24) ms and 238 (+15 -18) ms
respectively.Comment: 4 pages, 3 figure
Resolving the complex structure of the dust torus in the active nucleus of the Circinus galaxy
To test the dust torus model for active galactic nuclei directly, we study
the extent and morphology of the nuclear dust distribution in the Circinus
galaxy using high resolution interferometric observations in the mid-infrared
with the MIDI instrument at the Very Large Telescope Interferometer. We find
that the dust distribution in the nucleus of Circinus can be explained by two
components, a dense and warm disk-like component of 0.4 pc size and a slightly
cooler, geometrically thick torus component with a size of 2.0 pc. The disk
component is oriented perpendicular to the ionisation cone and outflow and
seems to show the silicate feature at 10 micron in emission. It coincides with
a nuclear maser disk in orientation and size. From the energy needed to heat
the dust, we infer a luminosity of the accretion disk corresponding to 20% of
the Eddington luminosity of the nuclear black hole. We find that the
interferometric data are inconsistent with a simple, smooth and axisymmetric
dust emission. The irregular behaviour of the visibilities and the shallow
decrease of the dust temperature with radius provide strong evidence for a
clumpy or filamentary dust structure. We see no evidence for dust reprocessing,
as the silicate absorption profile is consistent with that of standard galactic
dust. We argue that the collimation of the ionising radiation must originate in
the geometrically thick torus component. Our findings confirm the presence of a
geometrically thick, torus-like dust distribution in the nucleus of Circinus,
as required in unified schemes of Seyfert galaxies. Several aspects of our data
require that this torus is irregular, or "clumpy".Comment: 20 pages, 16 figures, accepted for publication by A&
Final State Interaction Effects in pol 3He(pol e,e'p)
Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a
momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which
takes into account relativistic kinematics in the final state and a
relativistic one-body current operator. With an exact solution of the Faddeev
equation for the 3He-ground state and an approximate treatment of final state
interactions in the continuum good agreement is found with the experimental
data.Comment: 11 pages, 6 figures, submitted to Phys. Lett. B, revised version,
sensitivity study to relativity and NN-potential adde
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