23,099 research outputs found
Notes on SU(3) Structures in Type IIB Supergravity
We study solutions of type IIB supergravity with an SU(3) structure group and
four dimensional Poincare invariance and present relations among the bosonic
fields which follow from the supersymmetry variations. We make explicit some
results which also follow from the more general case of an SU(2) structure and
give some short comments applicable to general supersymmetric solutions. We
also provide simplified relations appropriate for duals of gauge theory
renormalization group flows, and use these to derive the supergravity solution
for a bound state of (p,q)5-branes and D3-branes.Comment: 14p, JHEP3.cls, v2 typos corrected, refs adde
Satellite-aided mobile communications limited operational test in the trucking industry
An experiment with NASA's ATS-6 satellite, that demonstrates the practicality of satellite-aided land mobile communications is described. Satellite communications equipment for the experiment was designed so that it would be no more expensive, when mass produced, than conventional two-way mobile radio equipment. It embodied the operational features and convenience of present day mobile radios. Vehicle antennas 75 cm tall and 2 cm in diameter provided good commercial quality signals to and from trucks and jeeps. Operational applicability and usage data were gathered by installing the radio equipment in five long-haul tractor-trailer trucks and two Air Force search and rescue jeeps. Channel occupancy rates are reported. Air Force personnel found the satellite radio system extremely valuable in their search and rescue mission during maneuvers and actual rescue operations. Propagation data is subjectively analyzed and over 4 hours of random data is categorized and graded as to signal quality on a second by second basis. Trends in different topographic regions are reported. An overall communications reliability of 93% was observed despite low satellite elevation angles ranging from 9 to 24 degrees
Tension dynamics and viscoelasticity of extensible wormlike chains
The dynamic response of prestressed semiflexible biopolymers is characterized
by the propagation and relaxation of tension, which arises due to the near
inextensibility of a stiff backbone. It is coupled to the dynamics of contour
length stored in thermal undulations, but also to the local relaxation of
elongational strain. We present a systematic theory of tension dynamics for
stiff yet extensible wormlike chains. Our results show that even moderate
prestress gives rise to distinct Rouse-like extensibility signatures in the
high-frequency viscoelastic response.Comment: 4 pages, 1 figure; corrected typo
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