31,370 research outputs found
The Potential of Spaced-based High-Energy Neutrino Measurements via the Airshower Cherenkov Signal
Future space-based experiments, such as OWL and JEM-EUSO, view large
atmospheric and terrestrial neutrino targets. With energy thresholds slightly
above 10^19 eV for observing airshowers via air fluorescence, the potential for
observing the cosmogenic neutrino flux associated with the GZK effect is
limited. However, the forward Cherenkov signal associated with the airshower
can be observed at much lower energies. A simulation was developed to determine
the Cherenkov signal strength and spatial extent at low-Earth orbit for
upward-moving airshowers. A model of tau neutrino interactions in the Earth was
employed to determine the event rate of interactions that yielded a tau lepton
which would induce an upward-moving airshower observable by a space-based
instrument. The effect of neutrino attenuation by the Earth forces the viewing
of the Earth's limb to observe the nu_tau-induced Cherenkov airshower signal at
above the OWL Cherenkov energy threshold of ~10^16.5 eV for limb-viewed events.
Furthermore, the neutrino attenuation limits the effective terrestrial neutrino
target area to ~3x10^5 km^2 at 10^17 eV, for an orbit of 1000 km and an
instrumental full Field-of-View of 45 degrees. This translates into an
observable cosmogenic neutrino event rate of ~1/year based upon two different
models of the cosmogenic neutrino flux, assuming neutrino oscillations and a
10% duty cycle for observation.Comment: Contribution to the 32nd ICRC, Beijing, China, August 2011;
Paper#1331, 4 pages, 4 figure
Mission-oriented requirements for updating MIL-H-8501. Volume 2: STI background and rationale
A supplement to the structure of a new flying and ground handling qualities specification for military rotorcraft structure is presented in order to explain the background and rationale for the specification structure, the proposed forms of criteria, and the status of the existing data base. Critical gaps in the data base for the new structure are defined, and recommendations are provided for the research required to address the most important of these gaps
OH(1720 MHz) Masers As Signposts of Molecular Shocks
We present observations of molecular gas made with the 15-m James Clark
Maxwell Telescope toward the sites of OH(1720 MHz) masers in three supernova
remnants: W28, W44 and 3C391. Maps made in the 12CO J=3-2 line reveal that the
OH masers are preferentially located along the edges of thin filaments or
clumps of molecular gas. There is a strong correlation between the morphology
of the molecular gas and the relativistic gas traced by synchrotron emission at
centimeter wavelengths. Broad CO line widths (dV=30-50 km/s) are seen along
these gaseous ridges, while narrow lines are seen off the ridges. The ratio of
H2CO line strengths is used to determine temperatures in the broad-line gas of
80 K, and the 13CO J=3-2 column density suggests densities of 10^4-10^5 cm{-3}.
These observations support the hypothesis that the OH(1720 MHz) masers
originate in post-shock gas, heated by the passage of a supernova remnant shock
through dense molecular gas. From the observational constraints on the density,
velocity and magnetic field we examine the physical properties of the shock and
discuss the shock-production of OH. These OH(1720 MHz) masers are useful
``signposts'', which point to the most promising locations to study supernova
remnant/molecular cloud interactions.Comment: ApJ (in press
Evaluation of surface water resources from machine-processing of ERTS multispectral data
The surface water resources of a large metropolitan area, Marion County (Indianapolis), Indiana, are studied in order to assess the potential value of ERTS spectral analysis to water resources problems. The results of the research indicate that all surface water bodies over 0.5 ha were identified accurately from ERTS multispectral analysis. Five distinct classes of water were identified and correlated with parameters which included: degree of water siltiness; depth of water; presence of macro and micro biotic forms in the water; and presence of various chemical concentrations in the water. The machine processing of ERTS spectral data used alone or in conjunction with conventional sources of hydrological information can lead to the monitoring of area of surface water bodies; estimated volume of selected surface water bodies; differences in degree of silt and clay suspended in water and degree of water eutrophication related to chemical concentrations
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