25,617 research outputs found
Numerical Method for Shock Front Hugoniot States
We describe a Continuous Hugoniot Method for the efficient simulation of
shock wave fronts. This approach achieves significantly improved efficiency
when the generation of a tightly spaced collection of individual steady-state
shock front states is desired, and allows for the study of shocks as a function
of a continuous shock strength parameter, . This is, to our knowledge, the
first attempt to map the Hugoniot continuously. We apply the method to shock
waves in Lennard-Jonesium along the direction. We obtain very good
agreement with prior simulations, as well as our own benchmark comparison runs.Comment: 4 pages, 3 figures, from Shock Compression of Condensed Matter 200
Scotin, a novel p53-inducible proapoptotic protein located in the ER and the nuclear membrane
p53 is a transcription factor that induces growth arrest or apoptosis in response to cellular stress. To identify new p53-inducible proapoptotic genes, we compared, by differential display, the expression of genes in spleen or thymus of normal and p53 nullizygote mice after γ-irradiation of whole animals. We report the identification and characterization of human and mouse Scotin homologues, a novel gene directly transactivated by p53. The Scotin protein is localized to the ER and the nuclear membrane. Scotin can induce apoptosis in a caspase-dependent manner. Inhibition of endogenous Scotin expression increases resistance to p53-dependent apoptosis induced by DNA damage, suggesting that Scotin plays a role in p53-dependent apoptosis. The discovery of Scotin brings to light a role of the ER in p53-dependent apoptosis
The Impact of Contaminated RR Lyrae/Globular Cluster Photometry on the Distance Scale
RR Lyrae variables and the stellar constituents of globular clusters are
employed to establish the cosmic distance scale and age of the universe.
However, photometry for RR Lyrae variables in the globular clusters M3, M15,
M54, M92, NGC2419, and NGC6441 exhibit a dependence on the clustercentric
distance. For example, variables and stars positioned near the crowded
high-surface brightness cores of the clusters may suffer from photometric
contamination, which invariably affects a suite of inferred parameters (e.g.,
distance, color excess, absolute magnitude, etc.). The impetus for this study
is to mitigate the propagation of systematic uncertainties by increasing
awareness of the pernicious impact of contaminated and radial-dependent
photometry.Comment: To appear in ApJ
The bird: A pressure-confined explosion in the interstellar medium
The non-thermal radio continuum source G5.3-1.0, mapped at 20 cm with the Very Large Array (VLA) by Becker and Helfand, has an unusual bird-like shape. In order to determine possible interaction of this source with adjacent cold gas, we have mapped this region in the J=1-0 line of CO using the AT and T Bell Laboratories 7m antenna and the FCRAO 14m antenna. The map shown contains 1859 spectra sampled on a 1.5 arcminute grid; each spectrum has an rms noise of 0.2 K in 1 MHz channels. There are several molecular clouds at different velocities along the line of sight. The outer regions of a previously unknown Giant Molecular Cloud (GMC) at l=4.7 deg., b=-0.85 deg., v=200 km s(-1) appears to be interacting with G5.3-10: the molecular cloud has a bird-shaped hole at the position of the continuum source, except that the brightest continuum point (the bird's head) appears to be embedded in the cloud. The velocity of this GMC indicates it is within 2 kpc of the galactic center. The morphology suggests that a supernova or other explosive event occurred near the outside of the GMC, in a region where (n) is approximately 300 cm(-3), and expanded into a region of lower density and pressure. The pressures, densities, and velocity gradients of molecular clouds near the galactic center are on average higher than those of clouds near the Sun. We therefore expect that Type II supernovae near the galactic center would be distorted by their interactions with their parent molecular clouds
Field Testing of a Turnip Growing Protocol on New Zealand Dairy Farms
Summer droughts are a regular occurrence in central North Island districts of New Zealand, which causes pastures to wilt, lose their nutritive value and stop growing. The resulting summer feed gap depresses farm productivity (Clark et al., 1996). Turnips optimally sown mid-late October (more often sown in November or even December) are grown to fill this feed gap. Recorded average yields of 7.4 t dry matter (DM)/ha are below the economic breakeven point of 8-10 t DM/ha (Clark et al., 1996). A turnip growing protocol was developed from published data (Eerens & Lane 2004) and tested on commercial dairy farms
Monoids, Embedding Functors and Quantum Groups
We show that the left regular representation \pi_l of a discrete quantum
group (A,\Delta) has the absorbing property and forms a monoid
(\pi_l,\tilde{m},\tilde{\eta}) in the representation category Rep(A,\Delta).
Next we show that an absorbing monoid in an abstract tensor *-category C gives
rise to an embedding functor E:C->Vect_C, and we identify conditions on the
monoid, satisfied by (\pi_l,\tilde{m},\tilde{\eta}), implying that E is
*-preserving. As is well-known, from an embedding functor E: C->\mathrm{Hilb}
the generalized Tannaka theorem produces a discrete quantum group (A,\Delta)
such that C is equivalent to Rep_f(A,\Delta). Thus, for a C^*-tensor category C
with conjugates and irreducible unit the following are equivalent: (1) C is
equivalent to the representation category of a discrete quantum group
(A,\Delta), (2) C admits an absorbing monoid, (3) there exists a *-preserving
embedding functor E: C->\mathrm{Hilb}.Comment: Final version, to appear in Int. Journ. Math. (Added some references
and Subsection 1.2.) Latex2e, 21 page
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