15,491 research outputs found
Topological Insulators from Spontaneous Symmetry Breaking Induced by Electron Correlation on Pyrochlore Lattices
We study an extended Hubbard model with the nearest-neighbor Coulomb
interaction on the pyrochlore lattice at half filling. An interaction-driven
insulating phase with nontrivial Z_2 invariants emerges at the Hartree-Fock
mean-field level in the phase diagram. This topological insulator phase
competes with other ordered states and survives in a parameter region
surrounded by a semimetal, antiferromagnetic and charge ordered insulators. The
symmetries of these phases are group-theoretically analyzed. We also show that
the ferromagnetic interaction enhances the stability of the topological phase.Comment: 8 pages, 5 figures, accepted for publication in J. Phys. Soc. Jp
Differential Host Immune Responses after Infection with Wild-Type or Lab-Attenuated Rabies Viruses in Dogs.
METHODOLOGY/PRINCIPAL FINDINGS: The experimental infection of dogs with TriGAS induced high levels of VNA in the serum, whereas wt RABV infection did not. Dogs infected with TriGAS developed antibodies against the virus including its glycoprotein, whereas dogs infected with DRV-NG11 only developed rabies antibodies that are presumably specific for the nucleoprotein, (N) and not the glycoprotein (G). We show that infection with TriGAS induces early activation of B cells in the draining lymph nodes and persistent activation of DCs and B cells in the blood. On the other hand, infection with DRV-NG11 fails to induce the activation of DCs and B cells and further reduces CD4 T cell production. Further, we show that intrathecal (IT) immunization of TriGAS not only induced high levels of VNA in the serum but also in the CSF while intramuscular (IM) immunization of TriGAS induced VNA only in the serum. In addition, high levels of total protein and WBC were detected in the CSF of IT immunized dogs, indicating the transient enhancement of blood-brain barrier (BBB) permeability, which is relevant to the passage of immune effectors from periphery into the CNS.
CONCLUSIONS/SIGNIFICANCE: IM infection of dogs with TriGAS induced the production of serum VNA whereas, IT immunization of TriGAS in dogs induces high levels of VNA in the periphery as well as in the CSF and transiently enhances BBB permeability. In contrast, infection with wt DRV-NG11 resulted in the production of RABV-reactive antibodies but VNA and antibodies specific for G were absent. As a consequence, all of the dogs infected with wt DRV-NG11 succumbed to rabies. Thus the failure to activate protective immunity is one of the important features of RABV pathogenesis in dogs
Multispacecraft current estimates at swarm
During the first several months of the three-spacecraft Swarm mission all three spacecraft camerepeatedly into close alignment, providing an ideal opportunity for validating the proposed dual-spacecraftmethod for estimating current density from the Swarm magnetic field data. Two of the Swarm spacecraftregularly fly side-by-side in closely similar orbits, while the third at times approaches the other two. Thisprovides a data set which under certain assumptions of stationarity of the magnetic field can produce 2, 3, 4,5 (or more) point measurements, which can be cross compared. We find that at low Earth orbit the use oftime-shifted positions allow stable estimates of current density to be made and can verify temporal effects aswell as validating the interpretation of the current components as arising predominantly from field-alignedcurrents. In the case of four-spacecraft configurations we can resolve the full vector current and therefore cancheck the perpendicular as well as parallel current density components directly, together with the qualityfactor for the estimates directly (for the first time in situ at low Earth orbit)
Characteristics of atmospheric mercury deposition and size-fractionated particulate mercury in urban Nanjing, China
A comprehensive measurement study of mercury wet deposition and
size-fractionated particulate mercury (Hg<sup>P</sup>) concurrent with
meteorological variables was conducted from June 2011 to February 2012 to
evaluate the characteristics of mercury deposition and particulate mercury
in urban Nanjing, China. The volume-weighted mean (VWM) concentration of
mercury in rainwater was 52.9 ng L<sup>ā1</sup> with a range of 46.3ā63.6 ng L<sup>ā1</sup>.
The wet deposition per unit area was averaged 56.5 Ī¼g m<sup>ā2</sup> over
9 months, which was lower than that in most Chinese cities, but much
higher than annual deposition in urban North America and Japan. The wet deposition
flux exhibited obvious seasonal variation strongly linked with the amount of
precipitation. Wet deposition in summer contributed more than 80% to the
total amount. A part of contribution to wet deposition of mercury from
anthropogenic sources was evidenced by the association between wet
deposition and sulfates, as well as nitrates in rainwater. The ions correlated most
significantly with mercury were formate, calcium, and potassium, which
suggested that natural sources including vegetation and resuspended soil
should be considered as an important factor to affect the wet deposition of
mercury in Nanjing. The average Hg<sup>P</sup> concentration was 1.10 Ā± 0.57 ng m<sup>ā3</sup>.
A distinct seasonal distribution of Hg<sup>P</sup> concentrations was
found to be higher in winter as a result of an increase in the PM<sub>10</sub>
concentration. Overall, more than half of the Hg<sup>P</sup> existed in the particle
size range less than 2.1 Ī¼m. The highest concentration of Hg<sup>P</sup> in
coarse particles was observed in summer, while Hg<sup>P</sup> in fine particles
dominated in fall and winter. The size distribution of averaged mercury
content in particulates was bimodal, with two peaks in the bins of < 0.7 Ī¼m
and 4.7ā5.8 Ī¼m. Dry deposition per unit area of Hg<sup>P</sup> was
estimated to be 47.2 Ī¼g m<sup>ā2</sup> using meteorological conditions and
a size-resolved particle dry deposition model. This was 16.5% less than
mercury wet deposition. Compared to Hg<sup>P</sup> in fine particles, Hg<sup>P</sup> in
coarse particles contributed more to the total dry deposition due to higher
deposition velocities. Negative correlation between precipitation and the
Hg<sup>P</sup> concentration reflected the effect of scavenging of Hg<sup>P</sup> by
precipitation
Photometric Variability in the CSTAR Field: Results From the 2008 Data Set
The Chinese Small Telescope ARray (CSTAR) is the first telescope facility
built at Dome A, Antarctica. During the 2008 observing season, the installation
provided long-baseline and high-cadence photometric observations in the i-band
for 18,145 targets within 20 deg2 CSTAR field around the South Celestial Pole
for the purpose of monitoring the astronomical observing quality of Dome A and
detecting various types of photometric variability. Using sensitive and robust
detection methods, we discover 274 potential variables from this data set, 83
of which are new discoveries. We characterize most of them, providing the
periods, amplitudes and classes of variability. The catalog of all these
variables is presented along with the discussion of their statistical
properties.Comment: 38 pages, 11 figures, 4 tables; Accepted for publication in ApJ
A topological insulator surface under strong Coulomb, magnetic and disorder perturbations
Three dimensional topological insulators embody a newly discovered state of
matter characterized by conducting spin-momentum locked surface states that
span the bulk band gap as demonstrated via spin-resolved ARPES measurements .
This highly unusual surface environment provides a rich ground for the
discovery of novel physical phenomena. Here we present the first controlled
study of the topological insulator surfaces under strong Coulomb, magnetic and
disorder perturbations. We have used interaction of iron, with a large Coulomb
state and significant magnetic moment as a probe to \textit{systematically test
the robustness} of the topological surface states of the model topological
insulator BiSe. We observe that strong perturbation leads to the
creation of odd multiples of Dirac fermions and that magnetic interactions
break time reversal symmetry in the presence of band hybridization. We also
present a theoretical model to account for the altered surface of BiSe.
Taken collectively, these results are a critical guide in manipulating
topological surfaces for probing fundamental physics or developing device
applications.Comment: 14 pages, 4 Figures. arXiv admin note: substantial text overlap with
arXiv:1009.621
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