63 research outputs found
Geometry of intensive scalar dissipation events in turbulence
Maxima of the scalar dissipation rate in turbulence appear in form of sheets
and correspond to the potentially most intensive scalar mixing events. Their
cross-section extension determines a locally varying diffusion scale of the
mixing process and extends the classical Batchelor picture of one mean
diffusion scale. The distribution of the local diffusion scales is analysed for
different Reynolds and Schmidt numbers with a fast multiscale technique applied
to very high-resolution simulation data. The scales take always values across
the whole Batchelor range and beyond. Furthermore, their distribution is traced
back to the distribution of the contractive short-time Lyapunov exponent of the
flow.Comment: 4 pages, 5 Postscript figures (2 with reduced quality
Anisotropic diffusion on sub-manifolds with application to Earth structure classification
AbstractWe introduce a method to re-parameterize massive high dimensional data, generated by nonlinear mixing, into its independent physical parameters. Our method enables the identification of the original parameters and their extension to new observations without any knowledge of the true physical model. The suggested approach in this paper is related to spectral independent components analysis (ICA) via the construction of an anisotropic diffusion kernel whose eigenfunctions comprise the independent components. However, we use a novel anisotropic diffusion process, utilizing only a small observed subset Y¯, that approximates the isotropic diffusion on the parametric manifold MX of the full set Y. We employ a Nyström-type extension of the independent components of Y¯ to the independent components of Y, and provide a validation scheme for our algorithm parameters choice. We demonstrate our method on synthetic examples and on real application examples
DISTINGUISHING THE ROLES OF NATURAL AND ANTHROPOGENICALLY FORCED DECADAL CLIMATE VARIABILITY Implications for Prediction
Given that over the course of the next 10–30 years the magnitude of natural decadal variations may rival that of anthropogenically forced climate change on regional scales, it is envisioned that initialized decadal predictions will provide important information for climate-related management and adaptation decisions. Such predictions are presently one of the grand challenges for the climate community. This requires identifying those physical phenomena—and their model equivalents—that may provide additional predictability on decadal time scales, including an assessment of the physical processes through which anthropogenic forcing may interact with or project upon natural variability. Such a physical framework is necessary to provide a consistent assessment (and insight into potential improvement) of the decadal prediction experiments planned to be assessed as part of the IPCC's Fifth Assessment Report
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Preimplantation genetic testing guidelines of International Society of Reproductive Genetics
The International Society of Reproductive Genetics (ISRG) assembled a workgroup made up of clinicians, clinical laboratory directors, and scientists for the purpose of creating the guidelines for preimplantation genetic testing (PGT). The most up-to-date information and clinical insights for the optimal PGT practice were incorporated in these guidelines. Recommendations are provided for embryologists, medical geneticists, clinical laboratorians, and other healthcare providers to improve the wellbeing of patients seeking assisted reproductive treatment and their offspring
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