11,348 research outputs found
Characterisation of periodically poled materials using nonlinear microscopy
Periodically poled crystalline materials are extremely attractive for processes such as second harmonic generation and optical parametric generation due to their very high conversion efficiency. For optimal performance, fabrication of poled regions with sub-micron tolerance is required. In this paper we introduce multi-photon laser scanning luminescence microscopy as a powerful minimally-invasive measurement technique which provides information about internal device structure with high spatial resolution that cannot be easily obtained with existing methods. A comparative study of confocal and multi-photon imaging of periodically poled crystalline materials is also performed
Quantum Operation Time Reversal
The dynamics of an open quantum system can be described by a quantum
operation, a linear, complete positive map of operators. Here, I exhibit a
compact expression for the time reversal of a quantum operation, which is
closely analogous to the time reversal of a classical Markov transition matrix.
Since open quantum dynamics are stochastic, and not, in general, deterministic,
the time reversal is not, in general, an inversion of the dynamics. Rather, the
system relaxes towards equilibrium in both the forward and reverse time
directions. The probability of a quantum trajectory and the conjugate, time
reversed trajectory are related by the heat exchanged with the environment.Comment: 4 page
Gravitationally Lensed Gamma-Ray Bursts as Probes of Dark Compact Objects
If dark matter in the form of compact objects comprises a large fraction of
the mass of the universe, then gravitational lensing effects on gamma-ray
bursts are expected. We utilize BATSE and Ulysses data to search for lenses of
different mass ranges, which cause lensing in the milli, pico, and femto
regimes. Null results are used to set weak limits on the cosmological abundance
of compact objects in mass ranges from 10 to 10 . A
stronger limit is found for a much discussed universe dominated
by black holes of masses , which is ruled out at the
90% confidence level.Comment: 14 pages, 4 figures, fixed minor corrections. Accepted for
publication in ApJ(L
Atom detection in a two-mode optical cavity with intermediate coupling: Autocorrelation studies
We use an optical cavity in the regime of intermediate coupling between atom
and cavity mode to detect single moving atoms. Degenerate polarization modes
allow excitation of the atoms in one mode and collection of spontaneous
emission in the other, while keeping separate the two sources of light; we
obtain a higher confidence and efficiency of detection by adding
cavity-enhanced Faraday rotation. Both methods greatly benefit from coincidence
detection of photons, attaining fidelities in excess of 99% in less than 1
microsecond. Detailed studies of the second-order intensity autocorrelation
function of light from the signal mode reveal evidence of antibunched photon
emissions and the dynamics of single-atom transits.Comment: 10 pages, 10 figures, to be published in Phys. Rev.
Neutron Activation Analysis of Aluminum in Postmortem Human Lung Tissue
Author Institution: Department of Biology, Denison UniversityNeutron activation analysis was used to assay trace quantities of aluminum in postmortem human lung tissue samples. Dried accurately weighed lung tissue samples were activated in a 3.3 x 1()13 neutrons/cm2/sec thermal neutron flux and analyzed using a lithiumdrifted germanium detector and 4096 channel gamma spectrophotometer. The 1778 kcv gamma photon emitted by Al28 was quantified using the comparator technique with highly purified aluminum cyclohexane butyrate as the Al standard. The aluminum content of human lung tissue was shown not to be related to occupational exposure to industrial fiberglass. Residents of Akron, Ohio, were shown to have significantly higher concentrations of aluminum in their lungs than do residents of Newark, Ohio. A set of normal concentrations for aluminum in postmortem human lung tissue was developed, based on neutron activation analysis. The relative simplicity, accuracy, and precision of this technique suggest its use in further studies of this type
Live sheep trade from Australia summary information for 1996
This report provide summary information about mortalities in sheep and cattle during sea transport
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