426 research outputs found
Two-photon interference with two independent pseudo-thermal sources
The nature of two-photon interference is a subject that has aroused renewed
interest in recent years and is still under debate. In this paper we report the
first observation of two-photon interference with independent pseudo-thermal
sources in which sub-wavelength interference is observed. The phenomenon may be
described in terms of the classical statistical distribution of the two sources
and their optical transfer functions.Comment: Phys. Rev. A 74, 053807 (2006
Two-photon interference with true thermal light
Two-photon interference and "ghost" imaging with entangled light have
attracted much attention since the last century because of the novel features
such as non-locality and sub-wavelength effect. Recently, it has been found
that pseudo-thermal light can mimic certain effects of entangled light. We
report here the first observation of two-photon interference with true thermal
light.Comment: 4 pages, 5 figures, PRA72, 043805 (2005
Scaling Behavior of the Quantum Phase Transition from a Quantum Anomalous Hall Insulator to an Axion Insulator
The phase transitions from one plateau to the next plateau or to an insulator
in quantum Hall and quantum anomalous Hall (QAH) systems have revealed
universal scaling behaviors. A magnetic-field-driven quantum phase transition
from a QAH insulator to an axion insulator was recently demonstrated in
magnetic topological insulator sandwich samples. Here, we show that the
temperature dependence of the derivative of the longitudinal resistance on
magnetic field at the transition point follows a characteristic power-law that
indicates a universal scaling behavior for the QAH to axion insulator phase
transition. Similar to the quantum Hall plateau to plateau transition, the QAH
to axion insulator transition can also be understood by the Chalker-Coddington
network model. We extract a critical exponent k~ 0.38 in agreement with recent
high-precision numerical results on the correlation length exponent of the
Chalker-Coddington model at v ~ 2.6, rather than the generally-accepted value
of 2.33.Comment: 24 pages, 4 figures, comments are welcom
The Second-Order Talbot Effect with Entangled Photon Pairs
The second-order Talbot effect is analyzed for a periodic object illuminated
by entangled photon pairs in both the quantum imaging and quantum lithography
configurations. The Klyshko picture is applied to describe the quantum imaging
scheme, in which self-images of the object that may or may not be magnified can
be observed nonlocally in the photon coincidences but not in the singles count
rate. In the quantum lithography setup, we find that the second-order Talbot
length is half that of the classical first-order case, thus the resolution may
be improved by a factor of two.Comment: To appear in Phys. Rev.
An Updated Search of Steady TeV Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array
Using the data taken from Tibet II High Density (HD) Array (1997
February-1999 September) and Tibet-III array (1999 November-2005 November), our
previous northern sky survey for TeV ray point sources has now been
updated by a factor of 2.8 improved statistics. From to
in declination (Dec) range, no new TeV ray point
sources with sufficiently high significance were identified while the
well-known Crab Nebula and Mrk421 remain to be the brightest TeV ray
sources within the field of view of the Tibet air shower array. Based on the
currently available data and at the 90% confidence level (C.L.), the flux upper
limits for different power law index assumption are re-derived, which are
approximately improved by 1.7 times as compared with our previous reported
limits.Comment: This paper has been accepted by hepn
Tertiary-Treated Municipal Wastewater is a Significant Point Source of Antibiotic Resistance Genes Into Duluth-Superior Harbor
In this study, the impact of tertiary-treated municipal wastewater on the quantity of several antibiotic resistance determinants in Duluth-Superior Harbor was investigated by collecting surface water and sediment samples from 13 locations in Duluth-Superior Harbor, the St. Louis River, and Lake Superior. Quantitative PCR (qPCR) was used to target three different genes encoding resistance to tetracycline (tet(A), tet(X), and tet(W)), the gene encoding the integrase of class 1 integrons (intI1), and total bacterial abundance (16S rRNA genes) as well as total and human fecal contamination levels (16S rRNA genes specific to the genus Bacteroides). The quantities of tet(A), tet(X), tet(W), intI1, total Bacteroides, and human-specific Bacteroides were typically 20-fold higher in the tertiary-treated wastewater than in nearby surface water samples. In contrast, the quantities of these genes in the St. Louis River and Lake Superior were typically below detection. Analysis of sequences of tet(W) gene fragments from four different samples collected throughout the study site supported the conclusion that tertiary-treated municipal wastewater is a point source of resistance genes into Duluth-Superior Harbor. This study demonstrates that the discharge of exceptionally treated municipal wastewater can have a statistically significant effect on the quantities of antibiotic resistance genes in otherwise pristine surface waters
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