10,399 research outputs found
Permanent-magnet atom chips for the study of long, thin atom clouds
Atom-chip technology can be used to confine atoms tightly using permanently magnetised videotape along with external magnetic fields. The one-dimensional (1D) gas regime can be realised and studied by trapping the atoms in high-aspect-ratio traps in which the radial motion of the system is confined to zero-point oscillation
The polar temperature of Venus
Interferometric and polarization measurements of polar regions of Venu
Laser communication system for controlling several functions at a location remote to the laser
A multichannel laser remote control system is described. The system is used in areas where radio frequency, acoustic, and hardware control systems are unsatisfactory or prohibited and where line of sight is unobstructed. A modulated continuous wave helium-neon laser is used as the transmitter and a 360 degree light collector serves as the antenna at the receiver
Bose-Einstein Condensation on a Permanent-Magnet Atom Chip
We have produced a Bose-Einstein condensate on a permanent-magnet atom chip
based on periodically magnetized videotape. We observe the expansion and
dynamics of the condensate in one of the microscopic waveguides close to the
surface. The lifetime for atoms to remain trapped near this dielectric material
is significantly longer than above a metal surface of the same thickness. These
results illustrate the suitability of microscopic permanent-magnet structures
for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com
Bose-Einstein Condensation on a Permanent-Magnet Atom Chip
We have produced a Bose-Einstein condensate on a permanent-magnet atom chip
based on periodically magnetized videotape. We observe the expansion and
dynamics of the condensate in one of the microscopic waveguides close to the
surface. The lifetime for atoms to remain trapped near this dielectric material
is significantly longer than above a metal surface of the same thickness. These
results illustrate the suitability of microscopic permanent-magnet structures
for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com
The Partition Function of Multicomponent Log-Gases
We give an expression for the partition function of a one-dimensional log-gas
comprised of particles of (possibly) different integer charge at inverse
temperature {\beta} = 1 (restricted to the line in the presence of a
neutralizing field) in terms of the Berezin integral of an associated non-
homogeneous alternating tensor. This is the analog of the de Bruijn integral
identities [3] (for {\beta} = 1 and {\beta} = 4) ensembles extended to
multicomponent ensembles.Comment: 14 page
First principles study of intrinsic point defects in hexagonal barium titanate
Density functional theory (DFT) calculations have been used to study the nature of intrinsic defects in the hexagonal polymorph of barium titanate. Defect formation energies are derived for multiple charge states and due consideration is given to finite-size effects (elastic and electrostatic) and the band gap error in defective cells. Correct treatment of the chemical potential of atomic oxygen means that it is possible to circumvent the usual errors associated with the inaccuracy of DFT calculations on the oxygen dimer. Results confirm that both mono- and di-vacancies exist in their nominal charge states over the majority of the band gap. Oxygen vacancies are found to dominate the system in metal-rich conditions with face sharing oxygen vacancies being preferred over corner sharing oxygen vacancies. In oxygen-rich conditions, the dominant vacancy found depends on the Fermi level. Binding energies also show the preference for metal-oxygen di-vacancy formation. Calculated equilibrium concentrations of vacancies in the system are presented for numerous temperatures. Comparisons are drawn with the cubic polymorph as well as with previous potential-based simulations and experimental results
Spectroscopy, Equation Of State And Monopole Percolation In Lattice QED With Two Flavors
Non-compact lattice QED with two flavors of light dynamical quarks is
simulated on lattices, and the chiral condensate, monopole density and
susceptibility and the meson masses are measured. Data from relatively high
statistics runs at relatively small bare fermion masses of 0.005, 0.01, 0.02
and 0.03 (lattice units) are presented. Three independent methods of data
analysis indicate that the critical point occurs at and that
the monopole condensation and chiral symmetry breaking transitions are
coincident. The monopole condensation data satisfies finite size scaling
hypotheses with critical indices compatible with four dimensional percolation.
The best chiral equation of state fit produces critical exponents
(, ) which deviate significantly from mean
field expectations. Data for the ratio of the sigma to pion masses produces an
estimate of the critical index in good agreement with chiral
condensate measurements. In the strong coupling phase the ratio of the meson
masses are ,
and , while on the weak coupling side of the
transition , ,
indicating the restoration of chiral symmetry.\footnote{\,^{}}{August 1992}Comment: 21 pages, 24 figures (not included
Towards an Integrated Model of Enterprise Systems
An enterprise system consists of a number of components or building blocks. It is common to use views or models of the enterprise that contain a selection of these components (dependent on the intended usage of the model). The premise is that if these views are considered systems in their own right then the total enterprise system is actually a system‐of‐systems. Difficulty arises however when the boundaries between the systems overlap ‐ it is therefore necessary to have an integrated model of the total enterprise that can cope with these overlaps and hence interactions between the systems. Within this paper there will be two main areas of work described; firstly the development of models/tools of soft enterprise characteristics; and secondly how these characteristics may be included in an integrated model of an enterprise system. Case studies of UK organisations (primarily within the defence industry) were undertaken to provide context to the results
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