9,692 research outputs found
Chemiluminescence of asbestos-activated macrophages
Chemiluminescence, a measure of reactive oxygen release by phagocytes, was compared in peritoneal exudate macrophages elicited with chrysotile asbestos, Corynebacterium parvum and saline. Chrysotile asbestos- and C. parvum-activated macrophages produced significantly more chemiluminescence than saline-elicited macrophages. In a second series of experiments the ability of opsonized chrysotile asbestos to act as a trigger for the release of chemiluminescence was tested. Opsonized chrysotile asbestos produced a dose-related release of chemiluminescence from activated macrophages except at the highest dose where chemiluminescence was reduced due, possibly, to a toxic effect of chrysotile during the assay. Opsonized latex also triggered a dose-related chemiluminescent response from activated macrophages. The potential role of toxic reactive oxygen species, released from macrophages, in the development of asbestos-related pulmonary inflammation and fibrosis are discussed
How fast do Jupiters grow? Signatures of the snowline and growth rate in the distribution of gas giant planets
We present here observational evidence that the snowline plays a significant
role in the formation and evolution of gas giant planets. When considering the
population of observed exoplanets, we find a boundary in mass-semimajor axis
space that suggests planets are preferentially found beyond the snowline prior
to undergoing gap-opening inward migration and associated gas accretion. This
is consistent with theoretical models suggesting that sudden changes in opacity
-- as would occur at the snowline -- can influence core migration. Furthermore,
population synthesis modelling suggests that this boundary implies that gas
giant planets accrete ~ 70 % of the inward flowing gas, allowing ~ 30$ %
through to the inner disc. This is qualitatively consistent with observations
of transition discs suggesting the presence of inner holes, despite there being
ongoing gas accretion.Comment: 7 pages, 6 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Motion of the Tippe Top : Gyroscopic Balance Condition and Stability
We reexamine a very classical problem, the spinning behavior of the tippe top
on a horizontal table. The analysis is made for an eccentric sphere version of
the tippe top, assuming a modified Coulomb law for the sliding friction, which
is a continuous function of the slip velocity at the point of
contact and vanishes at . We study the relevance of the gyroscopic
balance condition (GBC), which was discovered to hold for a rapidly spinning
hard-boiled egg by Moffatt and Shimomura, to the inversion phenomenon of the
tippe top. We introduce a variable so that corresponds to the GBC
and analyze the behavior of . Contrary to the case of the spinning egg,
the GBC for the tippe top is not fulfilled initially. But we find from
simulation that for those tippe tops which will turn over, the GBC will soon be
satisfied approximately. It is shown that the GBC and the geometry lead to the
classification of tippe tops into three groups: The tippe tops of Group I never
flip over however large a spin they are given. Those of Group II show a
complete inversion and the tippe tops of Group III tend to turn over up to a
certain inclination angle such that , when they are
spun sufficiently rapidly. There exist three steady states for the spinning
motion of the tippe top. Giving a new criterion for stability, we examine the
stability of these states in terms of the initial spin velocity . And we
obtain a critical value of the initial spin which is required for the
tippe top of Group II to flip over up to the completely inverted position.Comment: 52 pages, 11 figures, to be published in SIAM Journal on Applied
Dynamical Syste
Summary models of crop production to address questions on resource-use interactions and efficiencies at farm-scale
Uniform Asymptotics for Polynomials Orthogonal With Respect to a General Class of Discrete Weights and Universality Results for Associated Ensembles: Announcement of Results
We compute the pointwise asymptotics of orthogonal polynomials with respect
to a general class of pure point measures supported on finite sets as both the
number of nodes of the measure and also the degree of the orthogonal
polynomials become large. The class of orthogonal polynomials we consider
includes as special cases the Krawtchouk and Hahn classical discrete orthogonal
polynomials, but is far more general. In particular, we consider nodes that are
not necessarily equally spaced. The asymptotic results are given with error
bound for all points in the complex plane except for a finite union of discs of
arbitrarily small but fixed radii. These exceptional discs are the
neighborhoods of the so-called band edges of the associated equilibrium
measure. As applications, we prove universality results for correlation
functions of a general class of discrete orthogonal polynomial ensembles, and
in particular we deduce asymptotic formulae with error bound for certain
statistics relevant in the random tiling of a hexagon with rhombus-shaped
tiles.
The discrete orthogonal polynomials are characterized in terms of a a
Riemann-Hilbert problem formulated for a meromorphic matrix with certain pole
conditions. By extending the methods of [17, 22], we suggest a general and
unifying approach to handle Riemann-Hilbert problems in the situation when
poles of the unknown matrix are accumulating on some set in the asymptotic
limit of interest.Comment: 28 pages, 7 figure
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