3,543 research outputs found
Technique for producing wind-tunnel heat-transfer models
Inexpensive thin skinned wind tunnel models with thermocouples on certain surface areas were fabricated. Thermocouples were designed for measuring aerodynamic heat transfer in wind tunnels
The baroclinic instability in the context of layered accretion. Self-sustained vortices and their magnetic stability in local compressible unstratified models of protoplanetary disks
Turbulence and angular momentum transport in accretion disks remains a topic
of debate. With the realization that dead zones are robust features of
protoplanetary disks, the search for hydrodynamical sources of turbulence
continues. A possible source is the baroclinic instability (BI), which has been
shown to exist in unmagnetized non-barotropic disks. We present shearing box
simulations of baroclinicly unstable, magnetized, 3D disks, in order to assess
the interplay between the BI and other instabilities, namely the
magneto-rotational instability (MRI) and the magneto-elliptical instability. We
find that the vortices generated and sustained by the baroclinic instability in
the purely hydrodynamical regime do not survive when magnetic fields are
included. The MRI by far supersedes the BI in growth rate and strength at
saturation. The resulting turbulence is virtually identical to an MRI-only
scenario. We measured the intrinsic vorticity profile of the vortex, finding
little radial variation in the vortex core. Nevertheless, the core is disrupted
by an MHD instability, which we identify with the magneto-elliptic instability.
This instability has nearly the same range of unstable wavelengths as the MRI,
but has higher growth rates. In fact, we identify the MRI as a limiting case of
the magneto-elliptic instability, when the vortex aspect ratio tends to
infinity (pure shear flow). We conclude that vortex excitation and
self-sustenance by the baroclinic instability in protoplanetary disks is viable
only in low ionization, i.e., the dead zone. Our results are thus in accordance
with the layered accretion paradigm. A baroclinicly unstable dead zone should
be characterized by the presence of large-scale vortices whose cores are
elliptically unstable, yet sustained by the baroclinic feedback. As magnetic
fields destroy the vortices and the MRI outweighs the BI, the active layers are
unmodified.Comment: 19+3 pages, 20+1 figures. Accepted by A&A, final versio
Cardiac and skeletal muscle abnormality in taurine transporter-knockout mice
Taurine, a sulfur-containing β-amino acid, is highly contained in heart and skeletal muscle. Taurine has a variety of biological actions, such as ion movement, calcium handling and cytoprotection in the cardiac and skeletal muscles. Meanwhile, taurine deficiency leads various pathologies, including dilated cardiomyopathy, in cat and fox. However, the essential role of taurine depletion on pathogenesis has not been fully clarified. To address the physiological role of taurine in mammalian tissues, taurine transporter-(TauT-) knockout models were recently generated. TauTKO mice exhibited loss of body weight, abnormal cardiac function and the reduced exercise capacity with tissue taurine depletion. In this chapter, we summarize pathological profile and histological feature of heart and skeletal muscle in TauTKO mice
A Multi-Code Analysis Toolkit for Astrophysical Simulation Data
The analysis of complex multiphysics astrophysical simulations presents a
unique and rapidly growing set of challenges: reproducibility, parallelization,
and vast increases in data size and complexity chief among them. In order to
meet these challenges, and in order to open up new avenues for collaboration
between users of multiple simulation platforms, we present yt (available at
http://yt.enzotools.org/), an open source, community-developed astrophysical
analysis and visualization toolkit. Analysis and visualization with yt are
oriented around physically relevant quantities rather than quantities native to
astrophysical simulation codes. While originally designed for handling Enzo's
structure adaptive mesh refinement (AMR) data, yt has been extended to work
with several different simulation methods and simulation codes including Orion,
RAMSES, and FLASH. We report on its methods for reading, handling, and
visualizing data, including projections, multivariate volume rendering,
multi-dimensional histograms, halo finding, light cone generation and
topologically-connected isocontour identification. Furthermore, we discuss the
underlying algorithms yt uses for processing and visualizing data, and its
mechanisms for parallelization of analysis tasks.Comment: 18 pages, 6 figures, emulateapj format. Resubmitted to Astrophysical
Journal Supplement Series with revisions from referee. yt can be found at
http://yt.enzotools.org
- …