73,180 research outputs found
Warm molecular hydrogen in outflows from Ultraluminous Infrared Galaxies
Ultraluminous infrared galaxies (ULIRGs) show on average three times more
emission in the rotational transitions of molecular hydrogen than expected
based on their star formation rates. Using Spitzer archival data we investigate
the origin of excess warm H_2 emission in 115 ULIRGs of the IRAS 1 Jy sample.
We find a strong correlation between H_2 and [FeII] line luminosities,
suggesting that excess H_2 is produced in shocks propagating within neutral or
partially ionized medium. This view is supported by the correlations between
H_2 and optical line ratios diagnostic of such shocks. The galaxies powered by
star formation and those powered by active nuclei follow the same relationship
between H_2 and [FeII], with emission line width being the major difference
between these classes (about 500 and 1000 km/sec, respectively). We conclude
that excess H_2 emission is produced as the supernovae and active nuclei drive
outflows into the neutral interstellar medium of the ULIRGs. A weak positive
correlation between H_2 and the length of the tidal tails indicates that these
outflows are more likely to be encountered in more advanced mergers, but there
is no evidence for excess H_2 produced as a result of the collision shocks
during the final coalescence.Comment: 16 pages, MNRAS accepted. Complete data tables and Spitzer spectra
are available at http://www.pha.jhu.edu/~zakamska/ULIRGS
Active control of primary mirror of an orbiting telescope with thermal excitation
The generalization is presented that was made to model a layered structure of a kind that represents a light-weighted mirror. This theory is presented along with the strategy for error suppression. The results of a variety of error-suppression studies are also presented. The computer programs for all parts of this study are included
Efficiency of autonomous soft nano-machines at maximum power
We consider nano-sized artificial or biological machines working in steady
state enforced by imposing non-equilibrium concentrations of solutes or by
applying external forces, torques or electric fields. For unicyclic and
strongly coupled multicyclic machines, efficiency at maximum power is not
bounded by the linear response value 1/2. For strong driving, it can even
approach the thermodynamic limit 1. Quite generally, such machines fall in
three different classes characterized, respectively, as "strong and efficient",
"strong and inefficient", and "balanced". For weakly coupled multicyclic
machines, efficiency at maximum power has lost any universality even in the
linear response regime
A monostrain test apparatus
Test apparatus is designed for determining tensile strength, modulus of elasticity, elongation, and thermal coefficient of contraction or expansion of uniformly shaped plastics, adhesives, and foam materials over temperature range of 700 to 90 K (800 to -300). Tests may be used in design quality control, and in evaluation of new adhesives and plastic materials
Opportunities for use of exact statistical equations
Exact structure function equations are an efficient means of obtaining
asymptotic laws such as inertial range laws, as well as all measurable effects
of inhomogeneity and anisotropy that cause deviations from such laws. "Exact"
means that the equations are obtained from the Navier-Stokes equation or other
hydrodynamic equations without any approximation. A pragmatic definition of
local homogeneity lies within the exact equations because terms that explicitly
depend on the rate of change of measurement location appear within the exact
equations; an analogous statement is true for local stationarity. An exact
definition of averaging operations is required for the exact equations. Careful
derivations of several inertial range laws have appeared in the literature
recently in the form of theorems. These theorems give the relationships of the
energy dissipation rate to the structure function of acceleration increment
multiplied by velocity increment and to both the trace of and the components of
the third-order velocity structure functions. These laws are efficiently
derived from the exact velocity structure function equations. In some respects,
the results obtained herein differ from the previous theorems. The
acceleration-velocity structure function is useful for obtaining the energy
dissipation rate in particle tracking experiments provided that the effects of
inhomogeneity are estimated by means of displacing the measurement location.Comment: accepted by Journal of Turbulenc
Investigation of refractory composites for liquid rocket engines Final report, 1 Oct. 1969 - 31 Oct. 1970
Oxidation resistance and high temperature tests of rhenium, tungsten, hafnium, and tantalum matrix composites with iridium in oxygen, fluorine, and boron atmospheres for liquid propellant engine
Adhesive for aluminum withstands cryogenic temperatures
Polyurethane adhesive mixed to various proportions with milled glass fibers match the thermal characteristics of 2014-T6 aluminum at cryogenic temperatures
Anomaly mediated neutrino-photon interactions at finite baryon density
We propose new physical processes based on the axial vector anomaly and
described by the Wess-Zumino-Witten term that couples the photon, Z-boson, and
the omega-meson. The interaction takes the form of a pseudo-Chern-Simons term,
. This term
induces neutrino-photon interactions at finite baryon density via the coupling
of the Z-boson to neutrinos. These interactions may be detectable in various
laboratory and astrophysical arenas. The new interactions may account for the
MiniBooNE excess. They also produce a competitive contribution to neutron star
cooling at temperatures >10^9 K. These processes and related axion--photon
interactions at finite baryon density appear to be relevant in many
astrophysical regimes.Comment: 4 pages, 2 figures; references adde
Current activities at IITRI on high- temperature protective coatings
Heat resistant protective coatings for use in liquid propellant rocket engine
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