3,831 research outputs found
On level crossings for a general class of piecewise-deterministic Markov processes
We consider a piecewise-deterministic Markov process governed by a jump
intensity function, a rate function that determines the behaviour between
jumps, and a stochastic kernel describing the conditional distribution of jump
sizes. We study the point process of upcrossings of a level by the Markov
process. Our main result shows that, under a suitable scaling , the
point process converges, as tends to infinity, weakly to a geometrically
compound Poisson process. We also prove a version of Rice's formula relating
the stationary density of the process to level crossing intensities. This
formula provides an interpretation of the scaling factor . While our
proof of the limit theorem requires additional assumptions, Rice's formula
holds whenever the (stationary) overall intensity of jumps is finite.Comment: 25 page
What is absolutely continuous spectrum?
This note is an expanded version of the author's contribution to the
Proceedings of the ICMP Santiago, 2015, and is based on a talk given by the
second author at the same Congress. It concerns a research program devoted to
the characterization of the absolutely continuous spectrum of a self-adjoint
operator H in terms of the transport properties of a suitable class of open
quantum systems canonically associated to H
Effects of inhaled acids on lung biochemistry.
Effects of respirable aerosols of sulfuric acid, ammonium sulfate, sodium sulfite, and ammonium persulfate on lungs of rats are reviewed. The literature regarding interactions between ozone or nitrogen dioxide and acidic aerosols (ammonium sulfate, sulfuric acid) is discussed. An unexpected interaction between nitrogen dioxide and sodium chloride aerosol is also discussed. An attempt is made to identify bases for prediction of how and when acid aerosols might potentiate effects of inhaled gases
Palm pairs and the general mass-transport principle
We consider a lcsc group G acting properly on a Borel space S and measurably
on an underlying sigma-finite measure space. Our first main result is a
transport formula connecting the Palm pairs of jointly stationary random
measures on S. A key (and new) technical result is a measurable disintegration
of the Haar measure on G along the orbits. The second main result is an
intrinsic characterization of the Palm pairs of a G-invariant random measure.
We then proceed with deriving a general version of the mass-transport principle
for possibly non-transitive and non-unimodular group operations first in a
deterministic and then in its full probabilistic form.Comment: 26 page
Optimization of nanostructured permalloy electrodes for a lateral hybrid spin-valve structure
Ferromagnetic electrodes of a lateral semiconductor-based spin-valve
structure are designed to provide a maximum of spin-polarized injection
current. A single-domain state in remanence is a prerequisite obtained by
nanostructuring Permalloy thin film electrodes. Three regimes of aspect ratios
are identified by room temperature magnetic force microscopy: (i)
high-aspect ratios of provide the favored remanent single-domain
magnetization states, (ii) medium-aspect ratios to yield
highly remanent states with closure domains and (iii) low-aspect ratios of lead to multi-domain structures. Lateral kinks, introduced to bridge the
gap between micro- and macroscale, disturb the uniform magnetization of
electrodes with high- and medium-aspect ratios. However, vertical flanks help
to maintain a uniformly magnetized state at the ferromagnet-semiconcuctor
contact by domain wall pinning.Comment: revised version, major structural changes, figures reorganized,6
pages, 8 figures, revte
Mucus glycoprotein secretion by tracheal explants: effects of pollutants.
Tracheal slices incubated with radioactive precursors in tissue culture medium secrete labeled mucus glycoproteins into the culture medium. We have used an in vivtro approach, a combined method utilizing exposure to pneumotoxins in vivo coupled with quantitation of mucus secretion rates in vitro, to study the effects of inhaled pollutants on mucus biosynthesis by rat airways. In addition, we have purified the mucus glycoproteins secreted by rat tracheal explants in order to determine putative structural changes that might by the basis for the observed augmented secretion rates after exposure of rats to H2SO4 aerosols in combination with high ambient levels of ozone. After digestion with papain, mucus glycoproteins secreted by tracheal explants may be separated into five fractions by ion-exchange chromatography, with recovery in high yield, on columns of DEAE-cellulose. Each of these five fractions, one neutral and four acidic, migrates as a single unique spot upon cellulose acetate electrophoresis at pH values of 8.6 and 1.2. The neutral fraction, which is labeled with [3H] glucosamine, does not contain radioactivity when Na2 35SO4 is used as the precursor. Acidic fractions I-IV are all labeled with either 3H-glucosamine or Na2 35SO4 as precursor. Acidic fraction II contains sialic acid as the terminal sugar on its oligosaccharide side chains, based upon its chromatographic behavior on columns of wheat-germ agglutinin-Agarose. Treatment of this fraction with neuraminidase shifts its elution position in the gradient to a lower salt concentration, coincident with acidic fraction I. After removal of terminal sialic acid residues with either neuraminidase or low pH treatment, the resultant terminal sugar on the oligosaccharide side chains is fucose. These results are identical with those observed with mucus glycoproteins secreted by cultured human tracheal explants and purified by these same techniques
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