4,177 research outputs found
Flexible arms provide constant force for pressure switch calibration
In-place calibration of a pressure switch is provided by a system of radially oriented flexing arms which, when rotated at a known velocity, convert the centrifugal force of the arms to a linear force along the shaft. The linear force, when applied to a pressure switch diaphragm, can then be calculated
General approach for studying first-order phase transitions at low temperatures
By combining different ideas, a general and efficient protocol to deal with
discontinuous phase transitions at low temperatures is proposed. For small
's, it is possible to derive a generic analytic expression for appropriate
order parameters, whose coefficients are obtained from simple simulations. Once
in such regimes simulations by standard algorithms are not reliable, an
enhanced tempering method, the parallel tempering -- accurate for small and
intermediate system sizes with rather low computational cost -- is used.
Finally, from finite size analysis, one can obtain the thermodynamic limit. The
procedure is illustrated for four distinct models, demonstrating its power,
e.g., to locate coexistence lines and the phases density at the coexistence.Comment: 5 page
The GTC exoplanet transit spectroscopy survey. VI. A spectrally-resolved Rayleigh scattering slope in GJ 3470b
Aims. As a sub-Uranus-mass low-density planet, GJ 3470b has been found to
show a flat featureless transmission spectrum in the infrared and a tentative
Rayleigh scattering slope in the optical. We conducted an optical transmission
spectroscopy project to assess the impacts of stellar activity and to determine
whether or not GJ 3470b hosts a hydrogen-rich gas envelop. Methods. We observed
three transits with the low-resolution OSIRIS spectrograph at the 10.4 m Gran
Telescopio Canarias, and one transit with the high-resolution UVES spectrograph
at the 8.2 m Very Large Telescope. Results. From the high-resolution data, we
find that the difference of the Ca II H+K lines in- and out-of-transit is only
0.67 +/- 0.22%, and determine a magnetic filling factor of about 10-15%. From
the low-resolution data, we present the first optical transmission spectrum in
the 435-755 nm band, which shows a slope consistent with Rayleigh scattering.
Conclusions. After exploring the potential impacts of stellar activity in our
observations, we confirm that Rayleigh scattering in an extended
hydrogen/helium atmosphere is currently the best explanation. Further
high-precision observations that simultaneously cover optical and infrared
bands are required to answer whether or not clouds and hazes exist at
high-altitude.Comment: 12 pages, 11 figures, accepted for publication in A&
Exercise Prior to Pregnancy Enhances the Suppressive Function of Tregs in Offspring in a Mouse Model of Asthma
Regulatory T cells (Tregs) are a specialized subset of T cells responsible for peripheral tolerance and the mediation of inappropriate immune responses, such as those seen in asthma and allergy. Our lab is interested in the role that exercise plays in Treg responses. Using a mouse model of asthma, we have shown that exercise increases both the number and suppressive function of Tregs. It has been shown that exposing nursing dams to allergens confers protection against airway hyperresponsiveness and inflammation (trademarks of asthma) in pups exposed to the same allergen. In the present study, we wanted to determine if the exercise-induced increase in number and suppressive function of Tregs would be similarly passed from dams to their pups. Male pups from dams that were exercised prior to pregnancy (E) and pups from sedentary dams (S) were OVA-sensitized and challenged beginning at 4wks of age. Mice were sacrificed and tissues were taken for cell analysis. When co-cultured with CD4+CD25- responder cells, Tregs from E pups enhanced suppression of responder cells between 8.4-10% when compared to Tregs from S pups. While the number of Tregs from the mediastinal lymph node was not significantly different between E and S pups, there was a significant decrease in the number of CD4+ and CD8+ T cells in E pups from S pups (51.24% + 10.2 vs. 33.51% + 3.3 and 21.42% + 7.3 vs. 12.94% + 1.2, respectively), indicating a reduction in cellular infiltration and a muted immune response to allergen. Although not significant, there was a doubling of the number of Tregs in the thymus and bone marrow of E pups compared to S pups. This study indicates that exercise prior to pregnancy may confer some Treg-mediated protection against asthma
Measuring the effective complexity of cosmological models
We introduce a statistical measure of the effective model complexity, called
the Bayesian complexity. We demonstrate that the Bayesian complexity can be
used to assess how many effective parameters a set of data can support and that
it is a useful complement to the model likelihood (the evidence) in model
selection questions. We apply this approach to recent measurements of cosmic
microwave background anisotropies combined with the Hubble Space Telescope
measurement of the Hubble parameter. Using mildly non-informative priors, we
show how the 3-year WMAP data improves on the first-year data by being able to
measure both the spectral index and the reionization epoch at the same time. We
also find that a non-zero curvature is strongly disfavored. We conclude that
although current data could constrain at least seven effective parameters, only
six of them are required in a scheme based on the Lambda-CDM concordance
cosmology.Comment: 9 pages, 4 figures, revised version accepted for publication in PRD,
updated with WMAP3 result
Ar-40 to Ar-39 dating of pseudotachylites from the Witwatersrand basin, South Africa, with implications for the formation of the Vredefort Dome
The formation of the Vredefort Dome, a structure in excess of 100 km in diameter and located in the approximate center of the Witwatersrand basin, is still the subject of lively geological controversy. It is widely accepted that its formation seems to have taken place in a single sudden event, herein referred to as the Vredefort event, accompanied by the release of gigantic amounts of energy. It is debated, however, whether this central event was an internal one, i.e., a cryptoexplosion triggered by volcanic or tectonic processes, or the impact of an extraterrestrial body. The results of this debate are presented
Rotating Boson Stars and Q-Balls
We consider axially symmetric, rotating boson stars. Their flat space limits
represent spinning Q-balls. We discuss their properties and determine their
domain of existence. Q-balls and boson stars are stationary solutions and exist
only in a limited frequency range. The coupling to gravity gives rise to a
spiral-like frequency dependence of the boson stars. We address the flat space
limit and the limit of strong gravitational coupling. For comparison we also
determine the properties of spherically symmetric Q-balls and boson stars.Comment: 22 pages, 18 figure
Static black hole solutions with axial symmetry
We construct a new class of asymptotically flat black hole solutions in
Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theory. These black hole
solutions are static, and they have a regular event horizon. However, they
possess only axial symmetry. Like their regular counterparts, the black hole
solutions are characterized by two integers, the winding number and the
node number of the gauge field functions.Comment: 14 pages, including 4 postscript figures, LaTe
Self-sustaining sound in collisionless, high-beta plasma
Using analytical theory and hybrid-kinetic numerical simulations, we
demonstrate that, in a collisionless plasma, long-wavelength ion-acoustic waves
(IAWs) with amplitudes (where is
the ratio of thermal to magnetic pressure) generate sufficient pressure
anisotropy to destabilize the plasma to firehose and mirror instabilities.
These kinetic instabilities grow rapidly to reduce the pressure anisotropy by
pitch-angle scattering and trapping particles, respectively, thereby impeding
the maintenance of Landau resonances that enable such waves' otherwise potent
collisionless damping. The result is wave dynamics that evince a weakly
collisional plasma: the ion distribution function is near-Maxwellian, the
field-parallel flow of heat resembles its Braginskii form (except in regions
where large-amplitude magnetic mirrors strongly suppress particle transport),
and the relations between various thermodynamic quantities are more
`fluid-like' than kinetic. A nonlinear fluctuation-dissipation relation for
self-sustaining IAWs is obtained by solving a plasma-kinetic Langevin problem,
which demonstrates suppressed damping, enhanced fluctuation levels, and weakly
collisional thermodynamics when IAWs with are
stochastically driven. We investigate how our results depend upon the scale
separation between the wavelength of the IAW and the Larmor radius of the ions,
and discuss briefly their implications for our understanding of turbulence and
transport in the solar wind and the intracluster medium of galaxy clusters.Comment: 25 pages, 10 figures, Journal of Plasma Physics, in pres
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