65,217 research outputs found
Observing Conditions for Submillimeter Astronomy
Consistently superb observing conditions are crucial for achieving the
scientific objectives of a telescope. Submillimeter astronomy is possible only
at a few exceptionally dry sites, notably Mauna Kea, the Antarctic plateau, and
the Chajnantor region in the high Andes east of San Pedro de Atacama in
northern Chile. Long term measurements of 225 GHz and 350 \mu m atmospheric
transparency demonstrate all three locations enjoy significant periods of
excellent observing conditions. Conditions on the Chajnantor plateau and at the
South Pole are better more often than on Mauna Kea. Conditions are better
during winter and at night. Near the summit of Cerro Chajnantor, conditions are
better than on the Chajnantor plateau
Submillimeter Atmospheric Transparency at Maunakea, at the South Pole, and at Chajnantor
For a systematic assessment of submillimeter observing conditions at
different sites, we constructed tipping radiometers to measure the broad band
atmospheric transparency in the window around 350 m wavelength. The
tippers were deployed on Maunakea, Hawaii, at the South Pole, and in the
vicinity of Cerro Chajnantor in northern Chile. Identical instruments permit
direct comparison of these sites. Observing conditions at the South Pole and in
the Chajnantor area are better than on Maunakea. Simultaneous measurements with
two tippers demonstrate conditions at the summit of Cerro Chajnantor are
significantly better than on the Chajnantor plateau.Comment: Accepted by PAS
Supporting simulation in industry through the application of grid computing
An increased need for collaborative research, together with continuing advances in communication technology and computer hardware, has facilitated the development of distributed systems that can provide users access to geographically dispersed computing resources that are administered in multiple computer domains. The term grid computing, or grids, is popularly used to refer to such distributed systems. Simulation is characterized by the need to run multiple sets of computationally intensive experiments. Large scale scientific simulations have traditionally been the primary benefactor of grid computing. The application of this technology to simulation in industry has, however, been negligible. This research investigates how grid technology can be effectively exploited by users to model simulations in industry. It introduces our desktop grid, WinGrid, and presents a case study conducted at a leading European investment bank. Results indicate that grid computing does indeed hold promise for simulation in industry
A Convenient Synthetic Route to Partial-Cone p-Carboxylatocalix[4]arenes.
p-Carboxylatocalix[n]arenes have emerged as useful building blocks for the construction of a diverse range of supramolecular assemblies. A convenient route to a p-carboxylatocalix[4]arene that is locked in a partial-cone conformation is presented. The conformation gives the molecule markedly different topological directionality relative to those previously used in self- and metal-directed assembly studies
Spinful Composite Fermions in a Negative Effective Field
In this paper we study fractional quantum Hall composite fermion
wavefunctions at filling fractions \nu = 2/3, 3/5, and 4/7. At each of these
filling fractions, there are several possible wavefunctions with different spin
polarizations, depending on how many spin-up or spin-down composite fermion
Landau levels are occupied. We calculate the energy of the possible composite
fermion wavefunctions and we predict transitions between ground states of
different spin polarizations as the ratio of Zeeman energy to Coulomb energy is
varied. Previously, several experiments have observed such transitions between
states of differing spin polarization and we make direct comparison of our
predictions to these experiments. For more detailed comparison between theory
and experiment, we also include finite-thickness effects in our calculations.
We find reasonable qualitative agreement between the experiments and composite
fermion theory. Finally, we consider composite fermion states at filling
factors \nu = 2+2/3, 2+3/5, and 2+4/7. The latter two cases we predict to be
spin polarized even at zero Zeeman energy.Comment: 17 pages, 5 figures, 4 tables. (revision: incorporated referee
suggestions, note added, updated references
Condensation of achiral simple currents in topological lattice models: a Hamiltonian study of topological symmetry breaking
We describe a family of phase transitions connecting phases of differing
non-trivial topological order by explicitly constructing Hamiltonians of the
Levin-Wen[PRB 71, 045110] type which can be tuned between two solvable points,
each of which realizes a different topologically ordered phase. We show that
the low-energy degrees of freedom near the phase transition can be mapped onto
those of a Potts model, and we discuss the stability of the resulting phase
diagram to small perturbations about the model. We further explain how the
excitations in the condensed phase are formed from those in the original
topological theory, some of which are split into multiple components by
condensation, and we discuss the implications of our results for understanding
the nature of general achiral topological phases in 2+1 dimensions in terms of
doubled Chern-Simons theories
Ovarian and cervical cancer awareness: development of two validated measurement tools.
The aim of the study was to develop and validate measures of awareness of symptoms and risk factors for ovarian and cervical cancer (Ovarian and Cervical Cancer Awareness Measures)
On the equality of Hausdorff and box counting dimensions
By viewing the covers of a fractal as a statistical mechanical system, the
exact capacity of a multifractal is computed. The procedure can be extended to
any multifractal described by a scaling function to show why the capacity and
Hausdorff dimension are expected to be equal.Comment: CYCLER Paper 93mar001 Latex file with 3 PostScript figures (needs
psfig.sty
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