3,174 research outputs found
Duality for Jacobi group orbit spaces and elliptic solutions of the WDVV equations
From any given Frobenius manifold one may construct a so-called dual
structure which, while not satisfying the full axioms of a Frobenius manifold,
shares many of its essential features, such as the existence of a prepotential
satisfying the WDVV equations of associativity. Jacobi group orbit spaces
naturally carry the structures of a Frobenius manifold and hence there exists a
dual prepotential. In this paper this dual prepotential is constructed and
expressed in terms of the elliptic polylogarithm function of Beilinson and
Levin
The dispersive self-dual Einstein equations and the Toda lattice
The Boyer-Finley equation, or -Toda equation is both a reduction
of the self-dual Einstein equations and the dispersionlesslimit of the
-Toda lattice equation. This suggests that there should be a dispersive
version of the self-dual Einstein equation which both contains the Toda lattice
equation and whose dispersionless limit is the familiar self-dual Einstein
equation. Such a system is studied in this paper. The results are achieved by
using a deformation, based on an associative -product, of the algebra
used in the study of the undeformed, or dispersionless,
equations.Comment: 11 pages, LaTeX. To appear: J. Phys.
Multidimensional integrable systems and deformations of Lie algebra homomorphisms
We use deformations of Lie algebra homomorphisms to construct deformations of
dispersionless integrable systems arising as symmetry reductions of
anti--self--dual Yang--Mills equations with a gauge group Diff.Comment: 14 pages. An example of a reduction to the Beltrami equation added.
New title. Final version, published in JM
Limitation of energy deposition in classical N body dynamics
Energy transfers in collisions between classical clusters are studied with
Classical N Body Dynamics calculations for different entrance channels. It is
shown that the energy per particle transferred to thermalised classical
clusters does not exceed the energy of the least bound particle in the cluster
in its ``ground state''. This limitation is observed during the whole time of
the collision, except for the heaviest system.Comment: 13 pages, 15 figures, 1 tabl
Distinguishing the associations between daily mortality and hospital admissions and nitrogen dioxide from those of particulate matter: a systematic review and meta‐analysis
Objectives To quantitatively assess time-series studies of daily nitrogen dioxide (NO2) and mortality and hospital admissions which also controlled for particulate matter (PM) to determine whether or to what extent the NO2 associations are independent of PM.
Design A systematic review and meta-analysis.
Methods Time-series studies—published in peer-reviewed journals worldwide, up to May 2011—that reported both single-pollutant and two-pollutant model estimates for NO2 and PM were ascertained from bibliographic databases (PubMed, EMBASE and Web of Science) and reviews. Random-effects summary estimates were calculated globally and stratified by different geographical regions, and effect modification was investigated.
Outcome measures Mortality and hospital admissions for various cardiovascular or respiratory diseases in different age groups in the general population.
Results 60 eligible studies were identified, and meta-analysis was conducted on 23 outcomes. Two-pollutant model study estimates generally showed that the NO2 associations were independent of PM mass. For all-cause mortality, a 10 µg/m3 increase in 24-hour NO2 was associated with a 0.78% (95% CI 0.47% to 1.09%) increase in the risk of death, which reduced to 0.60% (0.33% to 0.87%) after control for PM. Heterogeneity between geographical region-specific estimates was removed by control for PM (I2 from 66.9% to 0%). Estimates of PM and daily mortality assembled from the same studies were greatly attenuated after control for NO2: from 0.51% (0.29% to 0.74%) to 0.18% (−0.11% to 0.47%) per 10 µg/m3 PM10 and 0.74% (0.34% to 1.14%) to 0.54% (−0.25% to 1.34%) for PM2.5.
Conclusions The association between short-term exposure to NO2 and adverse health outcomes is largely independent of PM mass. Further studies should attempt to investigate whether this is a generic PM effect or whether it is modified by the source and physicochemical characteristics of PM. This finding strengthens the argument for NO2 having a causal role in health effects
Position Paper on Practicable Performance Criteria for the Removal Efficiency of Volatile Radionuclides
As a result of fuel reprocessing, volatile radionuclides may be released from the facility stack if no processes are put in place to remove them. The radionuclides that are of concern in this document are 3H, 14C, 85Kr, and 129I. The question we attempted to answer is how efficient must this removal process be for each of these radionuclides? To answer this question, we examined the three regulations that may impact the degree to which these radionuclides must be reduced before process gases can be released from the facility. These regulations are 40 CFR 61 (EPA 2010a), 40 CFR 190(EPA 2010b), and 10 CFR 20 (NRC 2012). These regulations apply to the total radionuclide release and to a particular organ - the thyroid. Because these doses can be divided amongst all the radionuclides in different ways and even within the four radionuclides in question, we provided several cases. We first looked at the inventories for these radionuclides for three fuel types (PWR UOX, PWR MOX, and AHTGR), several burn-up values, and time out of reactor extending to 200 y. We calculated doses to the maximum exposed individual (MEI) with the EPA code CAP-88 (Rosnick 1992). Finally, we looked at two dose cases. Allocating all of the allowable dose to be used by the volatile radionuclides is one case, but, perhaps, unrealistic. In lieu of this, we arbitrarily selected a value of 10% of the allowable dose to be assigned to the volatile radionuclides. We calculated the required decontamination factors (DFs) for both of these cases, including the case for the thyroid dose for which 14C and 129I were the main contributors. With respect to 129I doses, we found that the highest dose was calculated with iodine as a fine particulate. The dose scaled as the fraction of the total 129I that was particulate. Therefore, we assumed for all of our calculations that 100% of the 129I was particulate and allow the user of the results given here to scale our calculated doses to their needs
Effects of Self-field and Low Magnetic Fields on the Normal-Superconducting Phase Transition
Researchers have studied the normal-superconducting phase transition in the
high- cuprates in a magnetic field (the vortex-glass or Bose-glass
transition) and in zero field. Often, transport measurements in "zero field"
are taken in the Earth's ambient field or in the remnant field of a magnet. We
show that fields as small as the Earth's field will alter the shape of the
current vs. voltage curves and will result in inaccurate values for the
critical temperature and the critical exponents and , and can
even destroy the phase transition. This indicates that without proper screening
of the magnetic field it is impossible to determine the true zero-field
critical parameters, making correct scaling and other data analysis impossible.
We also show, theoretically and experimentally, that the self-field generated
by the current flowing in the sample has no effect on the current vs. voltage
isotherms.Comment: 4 pages, 4 figure
Normal-Superconducting Phase Transition Mimicked by Current Noise
As a superconductor goes from the normal state into the superconducting
state, the voltage vs. current characteristics at low currents change from
linear to non-linear. We show theoretically and experimentally that the
addition of current noise to non-linear voltage vs. current curves will create
ohmic behavior. Ohmic response at low currents for temperatures below the
critical temperature mimics the phase transition and leads to incorrect
values for and the critical exponents and . The ohmic response
occurs at low currents, when the applied current is smaller than the
width of the probability distribution , and will occur in both the
zero-field transition and the vortex-glass transition. Our results indicate
that the transition temperature and critical exponents extracted from the
conventional scaling analysis are inaccurate if current noise is not filtered
out. This is a possible explanation for the wide range of critical exponents
found in the literature.Comment: 4 pages, 2 figure
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