12,628 research outputs found
Origin of the different conductive behavior in pentavalent-ion-doped anatase and rutile TiO
The electronic properties of pentavalent-ion (Nb, Ta, and
I) doped anatase and rutile TiO are studied using spin-polarized
GGA+\emph{U} calculations. Our calculated results indicate that these two
phases of TiO exhibit different conductive behavior upon doping. For doped
anatase TiO, some up-spin-polarized Ti 3\emph{d} states lie near the
conduction band bottom and cross the Fermi level, showing an \emph{n}-type
half-metallic character. For doped rutile TiO, the Fermi level is pinned
between two up-spin-polarized Ti 3\emph{d} gap states, showing an insulating
character. These results can account well for the experimental different
electronic transport properties in Nb (Ta)-doped anatase and rutile TiO.Comment: 4 pages, 5 figure
Electromagnetically induced transparency and four-wave mixing in a cold atomic ensemble with large optical depth
We report on the delay of optical pulses using electromagnetically induced
transparency in an ensemble of cold atoms with an optical depth exceeding 500.
To identify the regimes in which four-wave mixing impacts on EIT behaviour, we
conduct the experiment in both rubidium 85 and rubidium 87. Comparison with
theory shows excellent agreement in both isotopes. In rubidium 87, negligible
four-wave mixing was observed and we obtained one pulse-width of delay with 50%
efficiency. In rubidium 85, four-wave-mixing contributes to the output. In this
regime we achieve a delay-bandwidth product of 3.7 at 50% efficiency, allowing
temporally multimode delay, which we demonstrate by compressing two pulses into
the memory medium.Comment: 8 pages, 6 figure
Spatial state Stokes-operator squeezing and entanglement for optical beams
The transverse spatial attributes of an optical beam can be decomposed into
the position, momentum and orbital angular momentum observables. The position
and momentum of a beam is directly related to the quadrature amplitudes, whilst
the orbital angular momentum is related to the polarization and spin variables.
In this paper, we study the quantum properties of these spatial variables,
using a representation in the Stokes-operator basis. We propose a spatial
detection scheme to measure all three spatial variables and consequently,
propose a scheme for the generation of spatial Stokes operator squeezing and
entanglement.Comment: submitte
Manifestations of Extra Dimensions in a Neutrino Telescope
Theories with large extra dimensions provide the possibility that a flavor
neutrino, localized in a 3+1 brane, can mix with a singlet neutrino living in
the bulk. This mixing leads to unconventional patterns of neutrino matter
oscillations and we examine in details how these oscillations depend upon two
parameters: the brane-bulk coupling and the effective mass of the
flavor neutrino inside matter. We find that high energy GeV)
neutrinos, to be detected by neutrino telescopes, can give signals of
extra dimensions. With a 1 k neutrino telescope extra dimensions with
radius down to can be tested directly, while for smaller radius an
indirect evidence can be established.Comment: 14 pages, 5 figures, added conclusion
Discrete Painlevé equations from Y-systems
We consider T-systems and Y-systems arising from cluster mutations applied to quivers that have the property of being periodic under a sequence of mutations. The corresponding nonlinear recurrences for cluster variables (coefficient-free T-systems) were described in the work of Fordy and Marsh, who completely classified all such quivers in the case of period 1, and characterized them in terms of the skew-symmetric exchange matrix B that defines the quiver. A broader notion of periodicity in general cluster algebras was introduced by Nakanishi, who also described the corresponding Y-systems, and T-systems with coefficients.
A result of Fomin and Zelevinsky says that the coefficient-free T-system provides a solution of the Y-system. In this paper, we show that in general there is a discrepancy between these two systems, in the sense that the solution of the former does not correspond to the general solution of the latter. This discrepancy is removed by introducing additional non-autonomous coefficients into the T-system. In particular, we focus on the period 1 case and show that, when the exchange matrix B is degenerate, discrete Painlev\'e equations can arise from this construction
False-negative results using Neisseria gonorrhoeae porA pseudogene PCR - a clinical gonococcal isolate with an N. meningitidis porA sequence, Australia, March 2011
The gonococcal porA pseudogene is a popular target for in-house Neisseria gonorrhoeae PCR methods. With this study we present two novel findings: the first case of an N. gonorrhoeae porA pseudogene PCR false-negative result caused by sequence variation, and in the same organism, the first description of a clinical N. gonorrhoeae strain harbouring an N. meningitidis porA sequence
Efficiency of the Incomplete Enumeration algorithm for Monte-Carlo simulation of linear and branched polymers
We study the efficiency of the incomplete enumeration algorithm for linear
and branched polymers. There is a qualitative difference in the efficiency in
these two cases. The average time to generate an independent sample of
sites for large varies as for linear polymers, but as for branched (undirected and directed) polymers, where
. On the binary tree, our numerical studies for of order
gives . We argue that exactly in this
case.Comment: replaced with published versio
- …