930 research outputs found
Oral Immunization of Wildlife Against Rabies: Concept and First Field Experiments
The possibility of immunizing carnivores against rabies with live attenuated vaccine administered by the oral route was raised by North American scientists in the 1960s. Subsequently, several American and European teams tested different vaccine strains in the laboratory for efficacy and safety and studied vaccine stabilization, vaccine delivery systems, baIt acceptance by wl1d ammals, and bait distribution schemes. The first field trial of a cloned SAD (Street Alabama Dufferin) strain in baits designed to immunize foxes orally ~as conducted in an Alpine valley in Switzerland in 1978. A population containing ∼60% immune foxes at the valley entrance stopped the spread of the disease into untreated upper parts of the valley. T~e strategic use of oral vaccination of foxes in additional regions of SWItzerland resulted m freedom from the zoonosis in four-fifths of the country
128Xe and 130Xe: Testing He-shell burning in AGB stars
The s-process branching at 128I has been investigated on the basis of new,
precise experimental (n,g) cross sections for the s-only isotopes 128Xe and
130Xe. This branching is unique, since it is essentially determined by the
temperature- and density-sensitive stellar decay rates of 128I and only
marginally affected by the specific stellar neutron flux. For this reason it
represents an important test for He-shell burning in AGB stars. The description
of the branching by means of the complex stellar scenario reveals a significant
sensitivity to the time scales for convection during He shell flashes, thus
providing constraints for this phenomenon. The s-process ratio 128Xe/130Xe
deduced from stellar models allows for a (9+-3)% p-process contribution to
solar 128Xe, in agreement with the Xe-S component found in meteoritic presolar
SiC grains.Comment: 24 pages, 9 figures, accepted for publication in Astophysical Journa
Nekhoroshev theorem for the periodic Toda lattice
The periodic Toda lattice with sites is globally symplectomorphic to a
two parameter family of coupled harmonic oscillators. The action
variables fill out the whole positive quadrant of . We prove that in
the interior of the positive quadrant as well as in a neighborhood of the
origin, the Toda Hamiltonian is strictly convex and therefore Nekhoroshev's
theorem applies on (almost) all parts of phase space.Comment: 28 page
The impact of metallic contacts on propagation losses of an underlying photonic crystal waveguide
In view of an electrically pumped photonic crystal-based semiconductor optical amplifier (SOA), we investigate optical mode propagation in 2D PhC waveguides in the presence of metal contacts for carrier injection. Our photonic crystal (PhC) devices are manufactured in the InP/InGaAsP material system. For the loss measurements, we have fabricated contact strips as narrow as 300nm with a sub-50nm placing accuracy on top of W3 waveguides. We study the influence of their position and width on optical power transmission through passive waveguides with respect to viability for future active devices. Our experimental results are complemented by numerical studies (FDTD, plane-wave expansion method)
Asymptotic Giant Branch models at very low metallicity
In this paper we present the evolution of a low mass model (initial mass
M=1.5 Msun) with a very low metal content (Z=5x10^{-5}, equivalent to
[Fe/H]=-2.44). We find that, at the beginning of the AGB phase, protons are
ingested from the envelope in the underlying convective shell generated by the
first fully developed thermal pulse. This peculiar phase is followed by a deep
third dredge up episode, which carries to the surface the freshly synthesized
13C, 14N and 7Li. A standard TP-AGB evolution, then, follows. During the proton
ingestion phase, a very high neutron density is attained and the s-process is
efficiently activated. We therefore adopt a nuclear network of about 700
isotopes, linked by more than 1200 reactions, and we couple it with the
physical evolution of the model. We discuss in detail the evolution of the
surface chemical composition, starting from the proton ingestion up to the end
of the TP-AGB phase.Comment: Accepted for Publication on PAS
The s-process branching at 185W
The neutron capture cross section of the unstable nucleus 185W has been
derived from experimental photoactivation data of the inverse reaction
186W(gamma,n)185W. The new result of sigma = (687 +- 110) mbarn confirms the
theoretically predicted neutron capture cross section of 185W of sigma = 700
mbarn at kT = 30 keV. A neutron density in the classical s-process of n_n =
(3.8 +0.9 -0.8} * 1e8 cm-3 is derived from the new data for the 185W branching.
In a stellar s-process model one finds a significant overproduction of the
residual s-only nucleus 186Os.Comment: ApJ, in pres
The effect of 12C + 12C rate uncertainties on s-process yields
The slow neutron capture process in massive stars (the weak s-process)
produces most of the s-only isotopes in the mass region 60 < A < 90. The
nuclear reaction rates used in simulations of this process have a profound
effect on the final s-process yields. We generated 1D stellar models of a 25
solar mass star varying the 12C + 12C rate by a factor of 10 and calculated
full nucleosynthesis using the post-processing code PPN. Increasing or
decreasing the rate by a factor of 10 affects the convective history and
nucleosynthesis, and consequently the final yields.Comment: Conference proceedings for the Nuclear Physics in Astrophysics IV
conference, 8-12 June 2009. 4 pages, 3 figures. Accepted for publication to
the Journal of Physics: Conference Serie
Mortality attributable to ambient fine particulate matter and nitrogen dioxide in Switzerland in 2019: use of two-pollutant effect estimates
INTRODUCTION: Air pollution health risk assessments have traditionally used single-pollutant effect estimates for one proxy ambient air pollutant such as PM(2.5). Two-pollutant effect estimates, i.e. adjusted for another correlated pollutant, theoretically enable the aggregation of pollutant-specific health effects minimizing double-counting. Our study aimed at estimating the adult mortality in Switzerland in 2019 attributable to PM(2.5) from a single-pollutant effect estimate and to the sum of PM(2.5) and NO(2) from two-pollutant estimates; comparing the results with those from alternative global, European and Swiss effect estimates. METHODS: For the single-pollutant approach, we used a PM(2.5) summary estimate of European cohorts from the project ELAPSE, recommended by the European Respiratory Society and International Society for Environmental Epidemiology (ERS-ISEE). To derive the two-pollutant effect estimates, we applied ELAPSE-based conversion factors to ERS-ISEE PM(2.5) and NO(2) single-pollutant effect estimates. Additionally, we used World Health Organization 2021 Air Quality Guidelines as counterfactual scenario, exposure model data from 2019 and Swiss lifetables. RESULTS: The single-pollutant effect estimate for PM(2.5) (1.118 [1.060; 1.179] per 10 mug/m(3)) resulted in 2240 deaths (21,593 years of life lost). Using our derived two-pollutant effect estimates (1.023 [1.012; 1.035] per 10 mug/m(3) PM(2.5) adjusted for NO(2) and 1.040 [1.023; 1.058] per 10 mug/m(3) NO(2) adjusted for PM(2.5)), we found 1977 deaths (19,071 years of life lost) attributable to PM(2.5) and NO(2) together (23% from PM(2.5)). Deaths using alternative effect estimates ranged from 1042 to 5059. DISCUSSION: Estimated premature mortality attributable to PM(2.5) alone was higher than to both PM(2.5) and NO(2) combined. Furthermore, the proportion of deaths from PM(2.5) was lower than from NO(2) in the two-pollutant approach. These seemingly paradoxical results, also found in some alternative estimates, are due to statistical imprecisions of underlying correction methods. Therefore, using two-pollutant effect estimates can lead to interpretation challenges in terms of causality
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