1,756 research outputs found
Volcanic impact on stratospheric aerosol chemistry
Samples collected by the National Center for Atmospheric Research (NCAR) using the multiple-filter sampler on the U-2 were analyzed. The sampler is capable of exposing a number of 110 mm filters in sequence to ram air flow. Two types of filters, IPC cellulose and polystrene, were used, both of which have high blank levels for the trace elements determined. The levels of most trace elements in the stratosphere are so low under normal circumstances that none can be seen. Results from the eruption of Mt. St. Helens, a mystery cloud (probably volcanic in origin) in 1982, and the El Chichonal eruption in 1983 are discussed. To improve the collection of particles for chemical analysis, a new sampling system was developed for use on the U-2. The sampler consisted of an electrostatic collection of particles between 1 and 0.001 micron diameter dierectly onto electron microscopic grids, followed by a thermal precipitation for the smaller particles. The system was built and tested in the laboratory, but never flown on the U-2
Simulation of quantum dynamics with quantum optical systems
We propose the use of quantum optical systems to perform universal simulation
of quantum dynamics. Two specific implementations that require present
technology are put forward for illustrative purposes. The first scheme consists
of neutral atoms stored in optical lattices, while the second scheme consists
of ions stored in an array of micro--traps. Each atom (ion) supports a
two--level system, on which local unitary operations can be performed through a
laser beam. A raw interaction between neighboring two--level systems is
achieved by conditionally displacing the corresponding atoms (ions). Then,
average Hamiltonian techniques are used to achieve evolutions in time according
to a large class of Hamiltonians.Comment: 14 pages, 6 figure
Dynamical preparation of laser-excited anisotropic Rydberg crystals in 2D optical lattices
We describe the dynamical preparation of anisotropic crystalline phases
obtained by laser-exciting ultracold Alkali atoms to Rydberg p-states where
they interact via anisotropic van der Waals interactions. We develop a time-
dependent variational mean field ansatz to model large, but finite
two-dimensional systems in experimentally accessible parameter regimes, and we
present numerical simulations to illustrate the dynamical formation of
anisotropic Rydberg crystals.Comment: 19 pages, 9 figure
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