30,216 research outputs found
DAIRY DISPUTES IN NORTH AMERICA: A CASE STUDY
Agribusiness, International Relations/Trade,
Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy
A renewed attempt to detect radio recombination lines from external galaxies
has resulted in the measurement of lines from several bright starburst
galaxies. The lines are produced by hydrogen ionized by young, high-mass stars
and are diagnostic of the conditions and gas dynamics in the starburst regions
without problems of dust obscuration. We present here detections of the lines
H91alpha and H92alpha near 8.6 GHz from the starburst nuclei in NGC 3256, NGC
4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line
emitting region as a collection of H II regions, we derive the required number
of H II regions, their temperature, density, and distribution.Comment: 6 pages, to appear in "Proc 331. Heraeus Seminar: The Evolution of
Starbursts", Bad Honnef, Germany, Aug 16 - 20, 2004, Eds: S. Huettemeister,
S. Aalto, D.J. Bomans, and E. Manthe
The off-axis channel macroplate
High-gain microchannel plates (MCPs) which utilize curvature of the channel to inhibit ion feedback (C-plate MCRs) have demonstrated excellent performance characteristics. However, C-plate MCPs are at present costly to fabricate, and the shearing process used to curve the channels produces a low device yield. Described here is a totally new type of high-gain MCP structure in which each channel has an axially symmetric curvature. Initial tests of proof-of-concept units of these MCPs with 75-micron-diameter channels (macroplates) suggest that their performance characteristics have the potential to be equal to those of a C-plate MCP while the fabrication process is no more complex than that of a conventional straight-channel MCP
The ground state of a spin-1/2 neutral particle with anomalous magnetic moment in a Aharonov-Casher configuration
We determine the (bound) ground state of a spin 1/2 chargless particle with
anomalous magnetic moment in certain Aharonov-Casher configurations. We recast
the description of the system in a supersymmetric form. Then the basic physical
requirements for unbroken supersymmetry are established. We comment on the
possibility of neutron trapping in these systems
Relating supercooling and glass-like arrest of kinetics for phase separated systems: studies on doped CeFe and (La,Pr,Ca)MnO
Coexisting ferromagnetic and antiferromagnetic phases over a range of
temperature as well as magnetic field have been reported in many materials of
current interest, showing disorder-broadened 1st order transitions. Anomalous
history effects observed in magnetization and resistivity are being explained
invoking the concepts of kinetic arrest akin to glass transitions. From
magnetization measurements traversing novel paths in field-temperature space,
we obtain the intriguing result that the regions of the sample which can be
supercooled to lower temperatures undergo kinetic-arrest at higher
temperatures, and vice versa. Our results are for two diverse systems viz. the
inter-metallic doped CeFe which has an antiferromagnetic ground state, and
the oxide La-Pr-Ca-Mn-O which has a ferromagnetic ground state, indicating the
possible universality of this effect of disorder on the widely encountered
phenomenon of glass-like arrest of kinetics
Frequency shift keying in vortex-based spin torque oscillators
Vortex-based spin-torque oscillators can be made from extended spin valves
connected to an electrical nanocontact. We study the implementation of
frequency shift keying modulation in these oscillators. Upon a square
modulation of the current in the 10 MHz range, the vortex frequency follows the
current command, with easy identification of the two swapping frequencies in
the spectral measurements. The frequency distribution of the output power can
be accounted for by convolution transformations of the dc current vortex
waveform, and the current modulation. Modeling indicates that the frequency
transitions are phase coherent and last less than 25 ns. Complementing the
multi-octave tunability and first-class agility, the capability of frequency
shift keying modulation is an additional milestone for the implementation of
vortex-based oscillators in RF circuit.Comment: 6 pages, 5 figure
Resonant Leptogenesis with nonholomorphic R-Parity violation and LHC Phenomenology
In R-parity violating supersymmetric models both leptogenesis and the correct
neutrino masses are hard to achieve together. The presence of certain soft
nonholomorphic R-parity violating terms helps to resolve this problem. We
consider a scenario where the lightest and the second-lightest neutralino are
nearly degenerate in mass and enough CP-asymmetry can be produced through
resonant leptogenesis. In this model, the lighter chargino and the lightest
neutralino are highly degenerate. We have relatively lighter gauginos which can
be produced at the LHC leading to heavily ionizing charged tracks. At the same
time this model can also generate the correct neutrino mass scale. Thus our
scenario is phenomenologically rich and testable at colliders.Comment: 17 pages, 7 figures, Numerical results are improved and new plots are
added, Journal version. arXiv admin note: text overlap with
arXiv:hep-ph/0006173 by other author
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