4,143 research outputs found
Direct evidence for the magnetic ordering of Nd ions in NdFeAsO by high resolution inelastic neutron scattering
We investigated the low energy excitations in the parent compound NdFeAsO of
the Fe-pnictide superconductor in the eV range by a back scattering
neutron spectrometer. The energy scans on a powder NdFeAsO sample revealed
inelastic peaks at E = 1.600 eV at T = 0.055 K on both energy
gain and energy loss sides. The inelastic peaks move gradually towards lower
energy with increasing temperature and finally merge with the elastic peak at
about 6 K. We interpret the inelastic peaks to be due to the transition between
hyperfine-split nuclear level of the Nd and Nd isotopes with
spin . The hyperfine field is produced by the ordering of the
electronic magnetic moment of Nd at low temperature and thus the present
investigation gives direct evidence of the ordering of the Nd magnetic
sublattice of NdFeAsO at low temperature
Quantum key distribution using non-classical photon number correlations in macroscopic light pulses
We propose a new scheme for quantum key distribution using macroscopic
non-classical pulses of light having of the order 10^6 photons per pulse.
Sub-shot-noise quantum correlation between the two polarization modes in a
pulse gives the necessary sensitivity to eavesdropping that ensures the
security of the protocol. We consider pulses of two-mode squeezed light
generated by a type-II seeded parametric amplification process. We analyze the
security of the system in terms of the effect of an eavesdropper on the bit
error rates for the legitimate parties in the key distribution system. We also
consider the effects of imperfect detectors and lossy channels on the security
of the scheme.Comment: Modifications:added new eavesdropping attack, added more references
Submitted to Physical Review A [email protected]
Production of a Fermi gas of atoms in an optical lattice
We prepare a degenerate Fermi gas of potassium atoms by sympathetic cooling
with rubidium atoms in a one-dimensional optical lattice. In a tight lattice we
observe a change of the density of states of the system, which is a signature
of quasi two dimensional confinement. We also find that the dipolar
oscillations of the Fermi gas along the tight lattice are almost completely
suppressed.Comment: 4 pages, 4 figures, revised versio
George Biersack Selected to Serve on the Nominators Committee of the Emerson College
News release announces that Chairman of Communication Arts at the University of Dayton, George Biersack, has been selected to serve on the Nominators Committee of the Emerson College
Retinitis pigmentosa. A mimic of neurologic disease
Six patients with various forms of retinitis pigmentosa who were misdiagnosed as having neurologic disease are presented. In five of the patients, visual field defects were misinter-preted as being secondary to a neurologic rather than a retinal problem. In two patients, optic nerve drusen, which accompanied the retinal degeneration, were mistaken for papilledema. Since the diagnosis of retinitis pigmentosa is not always obvious on ophthalmoscopy, the clinician must be aware of the various manifestations of this disorder and be able to distinguish visual field defects on a retinal from a neurologic basis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26648/1/0000191.pd
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