3,139 research outputs found
Investigating Mitophagy and Mitochondrial Morphology In Vivo Using mito-QC:A Comprehensive Guide
Renovation Can Double Pasture Production
Renovation is often recommended as the best method for improving pastures. Results of long-time studies are now available where renovated pastures have been compared with unimproved pastures in southern Iowa
On the properties of steady states in turbulent axisymmetric flows
We experimentally study the properties of mean and most probable velocity
fields in a turbulent von K\'arm\'an flow. These fields are found to be
described by two families of functions, as predicted by a recent statistical
mechanics study of 3D axisymmetric flows. We show that these functions depend
on the viscosity and on the forcing. Furthermore, when the Reynolds number is
increased, we exhibit a tendency for Beltramization of the flow, i.e. a
velocity-vorticity alignment. This result provides a first experimental
evidence of nonlinearity depletion in non-homogeneous non-isotropic turbulent
flow.Comment: latex prl-stationary-051215arxiv.tex, 9 files, 6 figures, 4 pages
(http://www-drecam.cea.fr/spec/articles/S06/008/
Satellite data relay and platform locating in oceanography. Report of the In Situ Ocean Science Working Group
The present and future use of satellites to locate offshore platforms and relay data from in situ sensors to shore was examined. A system of the ARGOS type will satisfy the increasing demand for oceanographic information through data relay and platform location. The improved ship navigation provided by the Global Positioning System (GPS) will allow direct observation of currents from underway ships. Ocean systems are described and demand estimates on satellite systems are determined. The capabilities of the ARGOS system is assessed, including anticipated demand in the next decade
Anatomy of the binary black hole recoil: A multipolar analysis
We present a multipolar analysis of the gravitational recoil computed in
recent numerical simulations of binary black hole (BH) coalescence, for both
unequal masses and non-zero, non-precessing spins. We show that multipole
moments up to and including l=4 are sufficient to accurately reproduce the
final recoil velocity (within ~2%) and that only a few dominant modes
contribute significantly to it (within ~5%). We describe how the relative
amplitudes, and more importantly, the relative phases, of these few modes
control the way in which the recoil builds up throughout the inspiral, merger,
and ringdown phases. We also find that the numerical results can be reproduced
by an ``effective Newtonian'' formula for the multipole moments obtained by
replacing the radial separation in the Newtonian formulae with an effective
radius computed from the numerical data. Beyond the merger, the numerical
results are reproduced by a superposition of three Kerr quasi-normal modes
(QNMs). Analytic formulae, obtained by expressing the multipole moments in
terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and
amount of ``anti-kick'' for each of the simulations. Lastly, we apply this
multipolar analysis to help explain the remarkable difference between the
amplitudes of planar and non-planar kicks for equal-mass spinning black holes.Comment: 28 pages, 20 figures, submitted to PRD; v2: minor revisions from
referee repor
High dimensional decision dilemmas in climate models
An important source of uncertainty in climate models is linked to the calibration of model parameters. Interest in systematic and automated parameter optimization procedures stems from the desire to improve the model climatology and to quantify the average sensitivity associated with potential changes in the climate system. Building upon on the smoothness of the response of an atmospheric circulation model (AGCM) to changes of four adjustable parameters, Neelin et al. (2010) used a quadratic metamodel to objectively calibrate the AGCM. The metamodel accurately estimates global spatial averages of common fields of climatic interest, from precipitation, to low and high level winds, from temperature at various levels to sea level pressure and geopotential height, while providing a computationally cheap strategy to explore the influence of parameter settings. Here, guided by the metamodel, the ambiguities or dilemmas related to the decision making process in relation to model sensitivity and optimization are examined. Simulations of current climate are subject to considerable regional-scale biases. Those biases may vary substantially depending on the climate variable considered, and/or on the performance metric adopted. Common dilemmas are associated with model revisions yielding improvement in one field or regional pattern or season, but degradation in another, or improvement in the model climatology but degradation in the interannual variability representation. Challenges are posed to the modeler by the high dimensionality of the model output fields and by the large number of adjustable parameters. The use of the metamodel in the optimization strategy helps visualize trade-offs at a regional level, e.g., how mismatches between sensitivity and error spatial fields yield regional errors under minimization of global objective functions
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