50,643 research outputs found
Sympathetic cooling and collisional properties of a Rb-Cs mixture
We report on measurements of the collisional properties of a mixture of
Cs and Rb atoms in a magnetic trap at
temperatures. By selectively evaporating the Rb atoms using a radio-frequency
field, we achieved sympathetic cooling of Cs down to a few . The
inter-species collisional cross-section was determined through rethermalization
measurements, leading to an estimate of for the s-wave scattering
length for Rb in the and Cs in the magnetic
states. We briefly speculate on the prospects for reaching Bose-Einstein
condensation of Cs inside a magnetic trap through sympathetic cooling
Coarse Grained Liouville Dynamics of piecewise linear discontinuous maps
We compute the spectrum of the classical and quantum mechanical
coarse-grained propagators for a piecewise linear discontinuous map. We analyze
the quantum - classical correspondence and the evolution of the spectrum with
increasing resolution. Our results are compared to the ones obtained for a
mixed system.Comment: 11 pages, 8 figure
Relativistic Hadron-Hadron Collisions in the Ultra-Relativistic Quantum Molecular Dynamics Model (UrQMD)
Hadron-hadron collisions at high energies are investigated in the
Ultra-relativistic-Quantum-Molecular-Dynamics approach (UrQMD). This
microscopic transport model is designed to study pp, pA and A+A collisions. It
describes the phenomenology of hadronic interactions at low and intermediate
energies ( GeV) in terms of interactions between known hadrons and
their resonances. At high energies, GeV, the excitation of color
strings and their subsequent fragmentation into hadrons dominates the multiple
production of particles in the UrQMD model. The model shows a fair overall
agreement with a large body of experimental h-h data over a wide range of h-h
center-of-mass energies. Hadronic reaction data with higher precision would be
useful to support the use of the UrQMD model for relativistic heavy ion
collisions.Comment: 66 pages, Download the UrQMD model from
http://www.th.physik.uni-frankfurt.de/~urqmd/urqmd.htm
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Motherhood, Moral Authority and the Charismatic Matriarch in the Aftermath of Lethal Violence
Images of maternal suffering are an evocative and powerful means of communication in a world where the private grief of victims has increasingly become subject to commodification and public consumption. This article looks at the influence of bereaved mothers as symbols of respect, peace and dignity in the aftermath of violence, and as a result their persuasive presence in family activism. Drawing upon two case studies, this article explores the importance of victims’ stories in public life and, in particular, the presence of the charismatic matriarch in creating communities of solidarity, raising awareness of harms that have previously gone unheard and prompting policy change. It considers the ‘canonical’ story of the mother in public life and concludes by arguing that more attention should be paid to victims’ stories and their influence on policy-making, politics and eventually in becoming public grievances
Forty-Four Pass Fibre Optic Loop for Improving the Sensitivity of Surface Plasmon Resonance Sensors
A forty-four pass fibre optic surface plasmon resonance sensor that enhances
detection sensitivity according to the number of passes is demonstrated for the
first time. The technique employs a fibre optic recirculation loop that passes
the detection spot forty- four times, thus enhancing sensitivity by a factor of
forty-four. Presently, the total number of passes is limited by the onset of
lasing action of the recirculation loop. This technique offers a significant
sensitivity improvement for various types of plasmon resonance sensors that may
be used in chemical and biomolecule detections.Comment: Submitted for publication; patent disclosure submitte
Beyond deficiency:Potential benefits of increased intakesof vitamin K for bone and vascular health
Vitamin K is wellknown for its role in the synthesisof a number of blood coagulationfactors.During recent years vitaminK-dependent proteins werediscovered to be of vital importancefor bone and vascular health.Recommendations for dietary vitaminK intake have been made onthe basis of the hepatic requirementsfor the synthesis of bloodcoagulation factors.Accumulatingevidence suggests that the requirementsfor other functions thanblood coagulation may be higher.This paper is the result of a closedworkshop (Paris,November 2002)in which a number of Europeanvitamin K experts reviewed theavailable data and formulated theirstandpoint with respect to recommendeddietary vitamin K intakeand the use of vitamin K-containingsupplements
Coulomb corrections to the extrinsic spin-Hall effect of a two-dimensional electron gas
We develop the microscopic theory of the extrinsic spin Hall conductivity of
a two-dimensional electron gas, including skew-scattering, side-jump, and
Coulomb interaction effects. We find that while the spin-Hall conductivity
connected with the side-jump is independent of the strength of
electron-electron interactions, the skew-scattering term is reduced by the
spin-Coulomb drag, so the total spin current and the total spin-Hall
conductivity are reduced for typical experimental mobilities. Further, we
predict that in paramagnetic systems the spin-Coulomb drag reduces the spin
accumulations in two different ways: (i) directly through the reduction of the
skew-scattering contribution (ii) indirectly through the reduction of the spin
diffusion length. Explicit expressions for the various contributions to the
spin Hall conductivity are obtained using an exactly solvable model of the
skew-scattering.Comment: The Coulomb corrections to the spin-Hall conductivity and spin
accumulations to first order in strength of spin-orbit coupling and
electron-electron interactions are include
Non-sequential triple ionization in strong fields
We consider the final stage of triple ionization of atoms in a strong
linearly polarized laser field. We propose that for intensities below the
saturation value for triple ionization the process is dominated by the
simultaneous escape of three electrons from a highly excited intermediate
complex. We identify within a classical model two pathways to triple
ionization, one with a triangular configuration of electrons and one with a
more linear one. Both are saddles in phase space. A stability analysis
indicates that the triangular configuration has the larger cross sections and
should be the dominant one. Trajectory simulations within the dominant symmetry
subspace reproduce the experimentally observed distribution of ion momenta
parallel to the polarization axis.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.
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