5,227 research outputs found
Note on Invariants of the Weyl Tensor
Algebraically special gravitational fields are described using algebraic and
differential invariants of the Weyl tensor. A type III invariant is also given
and calculated for Robinson-Trautman spaces.Comment: 3 pages, no figures, corrected expression (12
An Extended Radio Counterpart of TeV J2032+4130?
We carried out a 5-pointing mosaic observation of TeV J2032+4130 at 1.4 and
4.8 GHz with the VLA in April of 2003. The analysis of the 4.8GHz data indicate
weak wispy shell-like radio structure(s) which are at least partially
non-thermal. The radio data is compatible with one or more young supernova
remnants or perhaps the signature of large scale cluster shocks in this region
induced by the violent action of the many massive stars in Cyg OB2.Comment: Proc. 1st GLAST Symp. Feb 5-8, 2007, Stanford C
Efficient Spatial Redistribution of Quantum Dot Spontaneous Emission from 2D Photonic Crystals
We investigate the modification of the spontaneous emission dynamics and
external quantum efficiency for self-assembled InGaAs quantum dots coupled to
extended and localised photonic states in GaAs 2D-photonic crystals. The
2D-photonic bandgap is shown to give rise to a 5-10 times enhancement of the
external quantum efficiency whilst the spontaneous emission rate is
simultaneously reduced by a comparable factor. Our findings are quantitatively
explained by a modal redistribution of spontaneous emission due to the modified
local density of photonic states. The results suggest that quantum dots
embedded within 2D-photonic crystals are suitable for practical single photon
sources with high external efficiency
Development and application of operational techniques for the inventory and monitoring of resources and uses for the Texas coastal zone. Volume 1: Text
The author has identified the following significant results. Image interpretation and computer-assisted techniques were developed to analyze LANDSAT scenes in support of resource inventory and monitoring requirements for the Texas coastal region. Land cover and land use maps, at a scale of 1:125,000 for the image interpretation product and 1:24,000 for the computer-assisted product, were generated covering four Texas coastal test sites. Classification schemes which parallel national systems were developed for each procedure, including 23 classes for image interpretation technique and 13 classes for the computer-assisted technique. Results indicate that LANDSAT-derived land cover and land use maps can be successfully applied to a variety of planning and management activities on the Texas coast. Computer-derived land/water maps can be used with tide gage data to assess shoreline boundaries for management purposes
Development and application of operational techniques for the inventory and monitoring of resources and uses for the Texas coastal zone. Volume 2: Appendices
There are no author-identified significant results in this report
Cascaded exciton emission of an individual strain-induced quantum dot
Single strain-induced quantum dots are isolated for optical experiments by
selective removal of the inducing InP islands from the sample surface.
Unpolarized emission of single, bi- and triexciton transitions are identified
by power-dependent photoluminescence spectroscopy. Employing time-resolved
experiments performed at different excitation powers we find a pronounced shift
of the rise and decay times of these different transitions as expected from
cascaded emission. Good agreement is found for a rate equation model for a
three step cascade
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