11,178 research outputs found
Composition dependence of ion transport coefficients in gas mixtures
A simple momentum-transfer theory for the composition dependence of ion mobilities and diffusion coefficients in gas mixtures at arbitrary field strengths is corrected, extended, and compared with a similar theory based on momentum and energy transfer, and with results based on direct solution of the Boltzmann equation by Kihara's method. Final equations are recommended for predicting composition dependences, given only results on ion mobilities and diffusion coefficients in the pure component gases
Incoherent pion photoproduction on the deuteron with polarization observables I: Formal expressions
Formal expressions are developed for the general five-fold differential cross
section of incoherent -photoproduction on the deuteron including beam and
target polarization. The polarization observables of the cross section are
described by various beam, target and beam-target asymmetries for polarized
photons and/or polarized deuterons. They are given as bilinear hermitean forms
in the reaction matrix elements divided by the unpolarized cross section. In
addition, the corresponding observables for the semi-exclusive reaction are also given.Comment: 11 pages, 1 figur
Heavy Rainfall Warning Assessment Tool User Guide. Version 1.2
This report is a User Guide to a PC tool for assessing Heavy Rainfall Warnings. Development of the PC tool formed an important operational output of the Environment Agency and Met Office funded project: "Development of Rainfall Forecast Performance Monitoring Criteria. Phase 1: Development of Methodology and Algorithms" (Jones et al., 2003).
The Heavy Rainfall Warning (HRW) Assessment Tool is a toolkit for Microsoft Excel. The tool allows the user to configure an assessment framework for a particular format of Heavy Rainfall Warning, enter and save data for forecasts and ground-truths, and generate a range of performance measures and other statistics for new and previously saved data. Summary tables are presented using Excel's PivotTable feature, from which charts can also be generated.
Performance measures are provided to assess forecasts of heavy rainfall in continuous variable, categorical and probability form: these include bias, rmse, R-squared Efficiency, skill scores and the Continuous Brier Score
Psychic Distance and Country Image in Exporter–Importer Relationships
Conflicting evidence on the issue of psychic distance (PD) in international business relationships suggests the existence of misunderstood boundary conditions to its effect. This article argues that country image (CI) is a contingent factor to the effect of PD. Expectancy–value theory provides the theoretical foundations for this argument. Based on structural equation modeling, analyses for a sample of 358 exporter–importer relationships in the global wine industry provide empirical support. Product-related CI mitigates the negative impact of PD on the relational exchange orientation (REO) between firms. Specifically, a high level of PD dampens REO when product-related CI is poor, whereas a strong product-related CI helps firms facing such PD conditions to build REO irrespective. People-related CI has an indirect effect on REO through product-related CI. Our study contributes to explaining the paradox of distance and offers a fresh perspective on how to handle the issue of PD when relevant
Semi-empirical analysis of leptons in gases in crossed electric and magnetic fields, Part II: Transverse compression of muon beams
This article employs fluid equations to analyse muon beams in gases subject
to crossed electric and magnetic fields, focussing in particular on a scheme
proposed by D. Taqqu in 2006, whereby transverse compression of the beam is
achieved by creating a density gradient in the gas. A general criterion for
maximising beam compression, derived from first principles, is then applied to
determine optimal experimental conditions for {\mu ^ +} in helium gas. Although
the calculations require input of transport data for ({\mu ^ +}, He), which are
generally unavailable, this issue is circumvented by "aliasing" ({\mu ^ +}, He)
with (H{^ +}, He), for which transport coefficient data are available
Polarization observables in -photoproduction on the proton
For -photoproduction on the nucleon formal expressions are
developed for the five-fold differential cross section and the recoil
polarization including beam and target polarizations. The polarization
observables are described by various beam, target and beam-target asymmetries
for polarized photons and/or polarized nucleons. They are given as bilinear
hermitean forms in the reaction matrix elements divided by the unpolarized
cross section. Numerical results for the linear and circular beam asymmetries
for are obtained within an isobar model and are
compared with existing data. Predictions are also given for the target
asymmetry , and the beam-target asymmetries and
for circularly polarized photons.Comment: 19 pages, 8 figure
A historic jet-emission minimum reveals hidden spectral features in 3C 273
Aims. The aim of this work is to identify and study spectral features in the
quasar 3C 273 usually blended by its strong jet emission. Method. A historic
minimum in the sub-millimetre emission of 3C 273 triggered coordinated
multi-wavelength observations in June 2004. X-ray observations from the
INTEGRAL, XMM-Newton and RXTE satellites are complemented by ground-based
optical, infrared, millimetre and radio observations. The overall spectrum is
used to model the infrared and X-ray spectral components. Results. Three
thermal dust emission components are identified in the infrared. The dust
emission on scales from 1 pc to several kpc is comparable to that of other
quasars, as expected by AGN unification schemes. The observed weakness of the
X-ray emission supports the hypothesis of a synchrotron self-Compton origin for
the jet component. There is a clear soft-excess and we find evidence for a very
broad iron line which could be emitted in a disk around a Kerr black hole.
Other signatures of a Seyfert-like X-ray component are not detected.Comment: 4 pages. Accepted for publication in A&A Letter
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