476 research outputs found
Low-latitude boundary layer clouds as seen by CALIPSO
The distribution of low-level cloud in the tropical belt is investigated using 6 months of Level 2 retrievals from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) at 333 m and 1 km horizontal resolutions. Regional patterns of tropical clouds emerge from the data, matching expectations from existing observations. The advantage of the lidar is highlighted by the distribution of cloud-top height, revealing the preponderance of low-level clouds over the tropical oceans. Over land, cloud top is more uniformly distributed under the influence of diurnal variation. The integrated cloud-top distribution suggests tropical, marine low-cloud amount around 25-30%; a merged CALIPSO-CloudSat product has a similar cloud-top distribution and includes a complementary estimate of cloud fraction based on the lidar detections. The low-cloud distribution is similar to that found in fields of shallow cumulus observed during the Rain in Cumulus Over the Ocean (RICO) field study. The similarity is enhanced by sampling near the RICO site or sampling large-scale conditions similar to those during RICO. This finding shows how satellite observations can help to generalize findings from detailed field observations
Stabilizing the intensity of a wave amplified by a beam of particles
The intensity of an electromagnetic wave interacting self-consistently with a
beam of charged particles as in a free electron laser, displays large
oscillations due to an aggregate of particles, called the macro-particle. In
this article, we propose a strategy to stabilize the intensity by re-shaping
the macro-particle. This strategy involves the study of the linear stability
(using the residue method) of selected periodic orbits of a mean-field model.
As parameters of an additional perturbation are varied, bifurcations occur in
the system which have drastic effect on the modification of the self-consistent
dynamics, and in particular, of the macro-particle. We show how to obtain an
appropriate tuning of the parameters which is able to strongly decrease the
oscillations of the intensity without reducing its mean-value
Análise estrutural de remanescentes da Floresta Ombrófila Mista sob diferentes intensidades de usos da terra.
Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
Analytical results on the magnetization of the Hamiltonian Mean Field model
The violent relaxation and the metastable states of the Hamiltonian
Mean-Field model, a paradigmatic system of long-range interactions, is studied
using a Hamiltonian formalism. Rigorous results are derived algebraically for
the time evolution of selected macroscopic observables, e.g., the global
magnetization. The high and low energy limits are investigated and the
analytical predictions are compared with direct -body simulations. The
method we use enables us to re-interpret the out-of-equilibrium phase
transition separating magnetized and (almost) unmagnetized regimes
Study of a zirconium getter for purification of xenon gas
Oxygen, nitrogen and methane purification efficiencies for a common zirconium
getter are measured in 1050 Torr of xenon gas. Starting with impurity
concentrations near 10^{-6} g/g, the outlet impurity level is found to be less
than 120*10^{-12} g/g for O2 and less than 950*10^{-12} g/g for N2. For methane
we find residual contamination of the purified gas at concentrations varying
over three orders of magnitude, depending on the purifier temperature and the
gas flow rate. A slight reduction in the purifier's methane efficiency is
observed after 13 mg of this impurity has been absorbed, which we attribute to
partial exhaustion of the purifier's capacity for this species. We also find
that the purifier's ability to absorb N2 and methane can be extinguished long
before any decrease in O2 performance is observed, and slower flow rates should
be employed for xenon purification due to the cooling effect that the heavy gas
has on the getter.Comment: 14 pages, 5 figure
Emissão de óxido nitroso de um nitossolo sob adubação orgânica e sistemas de preparo do solo.
Psi prime to J/psi Ratio Measurements in PHENIX at RHIC
The ratio of the over the production cross section in the
dielectron channel has been measured in 200 GeV collisions
with the PHENIX detector at RHIC. The analysis is based on fitting of the
dielectron invariant mass spectra in the area around the and
signals in order to extract a ratio over of 0.019statsys and a fractional feed-down contribution to
from of .Comment: 4 pages, 7 figures submitted to: Indian Journal of Physics (2010) -
Proceedings of the 20th International Conference on Ultra-Relativistic
Nucleus-Nucleus Collisions (QM2008
Tritium locked in silica using 248 nm KrF laser irradiation
In this Letter we report on selectively occluding tritium in a silica film on a silicon substrate using a combination of high-pressure tritium loading and 248 nm KrF laser irradiation. Sixty percent of tritium dissolved in the silica film was bonded by laser irradiation. The concentration of the bonded tritium was proportional to the total laser fluence. Tritium effusion experiments indicated that the laser-locked tritium existed stably in the glass matrix up to 400 °C. In this work we point a way to a safe and simple approach for the integration of on-chip radioisotope micropower sources for micromechanical and microelectronic applications. © 2006 American Institute of Physics
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