1,320 research outputs found
Wellposedness of an elliptic-dispersive coupled system for MEMS
In this work, we study the local wellposedness of the solution to a nonlinear
elliptic-dispersive coupled system which serves as a model for a
Micro-Electro-Mechanical System (MEMS). A simple electrostatically actuated
MEMS capacitor device consists of two parallel plates separated by a gas-filled
thin gap. The nonlinear elliptic-dispersive coupled system modelling the device
combines a linear elliptic equation for the gas pressure with a semilinear
dispersive equation for the gap width. We show the local-in-time existence of
strict solutions for the system, by combining elliptic regularity results for
the elliptic equation, Lipschitz continuous dependence of its solution on that
of the dispersive equation, and then local-in-time existence for a resulting
abstract dispersive problem. Semigroup approaches are key to solve the abstract
dispersive problem.Comment: 27 page
Scaling of anisotropy flows in intermediate energy heavy ion collisions
Anisotropic flows (, and ) of light nuclear clusters are
studied by a nucleonic transport model in intermediate energy heavy ion
collisions. The number-of-nucleon scalings of the directed flow () and
elliptic flow () are demonstrated for light nuclear clusters. Moreover,
the ratios of of nuclear clusters show a constant value of 1/2
regardless of the transverse momentum. The above phenomena can be understood by
the coalescence mechanism in nucleonic level and are worthy to be explored in
experiments.Comment: Invited talk at "IX International Conference on Nucleus-Nucleus
Collisions", Rio de Janeiro, Aug 28- Sept 1, 2006; to appear on the
proceeding issue in Nuclear Physics
The contribution of the IGM and minihalos to the 21 cm signal of reionization
We study the statistical properties of the cosmological 21 cm signal from
both the intergalactic medium (IGM) and minihalos, using a reionization
simulation that includes a self--consistent treatment of minihalo
photoevaporation. We consider two models for minihalo formation and three
typical thermal states of the IGM -- heating purely by ionization, heating from
both ionizing and photons, and a maximal "strong heating" model.
We find that the signal from the IGM is almost always dominant over that from
minihalos. In our calculation, the differential brightness temperature,
of minihalos is never larger than 2 mK. Although there are
indeed some differences in the signals from the minihalos and from the IGM,
even with the planned generation of radio telescopes it will be unfeasible to
detect them. However, minihalos significantly affect the ionization state of
the IGM and the corresponding 21 cm flux.Comment: 13 pages, 12 figures, accepted by MNRA
Theory of free space coupling to high-Q whispering gallery modes
A theoretical study of free space coupling to high-Q whispering gallery modes
both in circular and deformed microcavities are presented. In the case of a
circular cavity, both analytical solutions and asymptotic formulas are derived.
The coupling efficiencies at different coupling regimes for cylinder incoming
wave are discussed, and the maximum efficiency is estimated for the practical
Gaussian beam excitation. In the case of a deformed cavity, the coupling
efficiency can be higher if the excitation beam can match the intrinsic
emission well and the radiation loss can be tuned by adjusting the degree of
deformation. Employing an abstract model of slightly deformed cavity, we found
that the asymmetric and peak like line shapes instead of the Lorentz-shape dip
are universal in transmission spectra due to multi-mode interference, and the
coupling efficiency can not be estimated from the absolute depth of the dip.
Our results provide guidelines for free space coupling in experiments,
suggesting that the high-Q ARCs can be efficiently excited through free space
which will stimulate further experiments and applications of WGMs based on free
space coupling.Comment: 8 pages, 4 figure
Scaling of Anisotropic Flow and Momentum-Space Densities for Light Particles in Intermediate Energy Heavy Ion Collisions
Anisotropic flows ( and ) of light nuclear clusters are studied by
Isospin-Dependent Quantum Molecular Dynamics model for the system of Kr
+ Sn at intermediate energy and large impact parameters.
Number-of-nucleon scaling of the elliptic flow () are demonstrated for the
light fragments up to = 4, and the ratio of shows a constant
value of 1/2. In addition, the momentum-space densities of different clusters
are also surveyed as functions of transverse momentum, in-plane transverse
momentum and azimuth angle relative to the reaction plane. The results can be
essentially described by momentum-space power law. All the above phenomena
indicate that there exists a number-of-nucleon scaling for both anisotropic
flow and momentum-space densities for light clusters, which can be understood
by the coalescence mechanism in nucleonic degree of freedom for the cluster
formation.Comment: 8 pages, 3 figures; to be published in Physics Letters
Expression and Regulation of Osteoprotegerin in Adipose Tissue
PURPOSE:
Osteoprotegerin (OPG), a potent inhibitor of osteoclastic bone resorption, has a variety of biological functions that include anti-inflammatory effects. Adipocytes and osteoblasts share a common origin, and the formation of new blood vessels often precedes adipogenesis in developing adipose tissue microvasculature. We examined whether OPG is secreted from adipocytes, therefore contributing to the prevention of neovascularization and protecting the vessels from intimal inflammation and medial calcification.
MATERIALS AND METHODS:
The mRNA expression of OPG and receptor activator of NF-kappaB ligand (RANKL) was measured in differentiated 3T3L1 adipocytes and adipose tissues.
RESULTS:
OPG mRNA expression increased with the differentiation of 3T3L1 adipocytes, while RANKL expression was not significantly altered. OPG mRNA was expressed at higher levels in white adipose tissue than in brown adipose tissue and was most abundant in the epididymal portion. In differentiated 3T3L1 adipocytes, Rosiglitazone and insulin reduced the OPG/RANKL expression ratio in a dose- and time- dependent manner. In contrast, tumor necrosis factor-alpha (TNF-alpha) increased the expression of both OPG and RANKL in a time-dependent manner. The OPG/RANKL ratio was at a maximum two hours after TNF-alpha treatment and then returned to control levels. Furthermore, OPG was abundantly secreted into the media after transfection of OPG cDNA with Phi C31 integrase into 3T3L1 cells.
CONCLUSION:
Our results indicate that OPG mRNA is expressed and regulated in the adipose tissue. Considering the role of OPG in obesity-associated inflammatory changes in adipose tissue and vessels, we speculate that OPG may have both a protective function against inflammation and anti-angiogenic effects on adipose tissue.ope
An Elevated Reservoir of Air Pollutants over the Mid-Atlantic States During the 2011 DISCOVER-AQ Campaign: Airborne Measurements and Numerical Simulations
During a classic heat wave with record high temperatures and poor air quality from July 18 to 23, 2011, an elevated reservoir of air pollutants was observed over and downwind of Baltimore, MD, with relatively clean conditions near the surface. Aircraft and ozonesonde measurements detected approximately 120 parts per billion by volume ozone at 800 meters altitude, but approximately 80 parts per billion by volume ozone near the surface. High concentrations of other pollutants were also observed around the ozone peak: approximately 300 parts per billion by volume CO at 1200 meters, approximately 2 parts per billion by volume NO2 at 800 meters, approximately 5 parts per billion by volume SO2 at 600 meters, and strong aerosol optical scattering (2 x 10 (sup 4) per meter) at 600 meters. These results suggest that the elevated reservoir is a mixture of automobile exhaust (high concentrations of O3, CO, and NO2) and power plant emissions (high SO2 and aerosols). Back trajectory calculations show a local stagnation event before the formation of this elevated reservoir. Forward trajectories suggest an influence on downwind air quality, supported by surface ozone observations on the next day over the downwind PA, NJ and NY area. Meteorological observations from aircraft and ozonesondes show a dramatic veering of wind direction from south to north within the lowest 5000 meters, implying that the development of the elevated reservoir was caused in part by the Chesapeake Bay breeze. Based on in situ observations, Community Air Quality Multi-scale Model (CMAQ) forecast simulations with 12 kilometers resolution overestimated surface ozone concentrations and failed to predict this elevated reservoir; however, CMAQ research simulations with 4 kilometers and 1.33 kilometers resolution more successfully reproduced this event. These results show that high resolution is essential for resolving coastal effects and predicting air quality for cities near major bodies of water such as Baltimore on the Chesapeake Bay and downwind areas in the Northeast
Flow Measurements via Two-particle Azimuthal Correlations in Au + Au Collisions at sqrt(s_NN) = 130 GeV
Two particle azimuthal correlation functions are presented for charged
hadrons produced in Au + Au collisions at RHIC sqrt(s_NN) = 130 GeV. The
measurements permit determination of elliptic flow without event-by-event
estimation of the reaction plane. The extracted elliptic flow values v_2 show
significant sensitivity to both the collision centrality and the transverse
momenta of emitted hadrons, suggesting rapid thermalization and relatively
strong velocity fields. When scaled by the eccentricity of the collision zone,
epsilon, the scaled elliptic flow shows little or no dependence on centrality
for charged hadrons with relatively low p_T. A breakdown of this epsilon
scaling is observed for charged hadrons with p_T > 1.0 GeV/c for the most
central collisions.Comment: 6 pages, RevTeX 3, 4 figures, 307 authors, submitted to Phys. Rev.
Lett. on 11 April 2002. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (will be made) publicly
available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
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