15,789 research outputs found
Communication Management and Trust: Their Role in Building Resilience to “Surprises” Such as Natural Disasters, Pandemic Flu, and Terrorism
In times of public danger such as natural disasters and health emergencies, a country’s communication systems will be some of its most important assets because access to information will make individuals and groups more resilient. Communication by those charged with dealing with the situation is often critical. We analyzed reports from a wide variety of crisis incidents and found a direct correlation between trust and an organization’s preparedness and internal coordination of crisis communication and the effectiveness of its leadership. Thus, trust is one of the most important variables in effective communication management in times of “surprise.
Type II superconductivity in SrPd2Ge2
Previous investigations have shown that SrPd2Ge2, a compound isostructural
with "122" iron pnictides but iron- and pnictogen-free, is a conventional
superconductor with a single s-wave energy gap and a strongly three-dimensional
electronic structure. In this work we reveal the Abrikosov vortex lattice
formed in SrPd2Ge2 when exposed to magnetic field by means of scanning
tunneling microscopy and spectroscopy. Moreover, by examining the differential
conductance spectra across a vortex and estimating the upper and lower critical
magnetic fields by tunneling spectroscopy and local magnetization measurements,
we show that SrPd2Ge2 is a strong type II superconductor with \kappa >>
sqrt(2). Also, we compare the differential conductance spectra in various
magnetic fields to the pair breaking model of Maki - de Gennes for dirty limit
type II superconductor in the gapless region. This way we demonstrate that the
type II superconductivity is induced by the sample being in the dirty limit,
while in the clean limit it would be a type I superconductor with \kappa\ <<
sqrt(2), in concordance with our previous study (T. Kim et al., Phys. Rev. B
85, (2012)).Comment: 9 pages, 4 figure
Nearly Massless Electrons in the Silicon Interface with a Metal Film
We demonstrate the realization of nearly massless electrons in the most
widely used device material, silicon, at the interface with a metal film. Using
angle-resolved photoemission, we found that the surface band of a monolayer
lead film drives a hole band of the Si inversion layer formed at the interface
with the film to have nearly linear dispersion with an effective mass about 20
times lighter than bulk Si and comparable to graphene. The reduction of mass
can be accounted for by repulsive interaction between neighboring bands of the
metal film and Si substrate. Our result suggests a promising way to take
advantage of massless carriers in silicon-based thin-film devices, which can
also be applied for various other semiconductor devices.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
{BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters
We have initiated a long-term project, the BOAO photometric survey of open
clusters, to enlarge our understanding of galactic structure using UBVI CCD
photometry of open clusters which have been little studied before. This is the
second paper of the project in which we present the photometry of 12 open
clusters. We have determined the cluster parameters by fitting the Padova
isochrones to the color-magnitude diagrams of the clusters. All the clusters
except for Be 0 and NGC 1348 are found to be intermediate-age to old (0.2 - 4.0
Gyrs) open clusters with a mean metallicity of [Fe/H] = 0.0.Comment: 11 page
Common gauge origin of discrete symmetries in observable sector and hidden sector
An extra Abelian gauge symmetry is motivated in many new physics models in
both supersymmetric and nonsupersymmetric cases. Such a new gauge symmetry may
interact with both the observable sector and the hidden sector. We
systematically investigate the most general residual discrete symmetries in
both sectors from a common Abelian gauge symmetry. Those discrete symmetries
can ensure the stability of the proton and the dark matter candidate. A hidden
sector dark matter candidate (lightest U-parity particle or LUP) interacts with
the standard model fields through the gauge boson Z', which may selectively
couple to quarks or leptons only. We make a comment on the implications of the
discrete symmetry and the leptonically coupling dark matter candidate, which
has been highlighted recently due to the possibility of the simultaneous
explanation of the DAMA and the PAMELA results. We also show how to construct
the most general U(1) charges for a given discrete symmetry, and discuss the
relation between the U(1) gauge symmetry and R-parity.Comment: Version to appear in JHE
Effect of sintering temperature under high pressure in the uperconductivity for MgB2
We report the effect of the sintering temperature on the superconductivity of
MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting
properties of the non-heated MgB2 in this high pressure were poor. However, as
the sintering temperature increased, the superconducting properties were vastly
enhanced, which was shown by the narrow transition width for the resistivity
and the low-field magnetizations. This shows that heat treatment under high
pressure is essential to improve superconducting properties. These changes were
found to be closely related to changes in the surface morphology observed using
scanning electron microscopy.Comment: 3 Pages including 3 figure
Effects of Electron Correlations on Hofstadter Spectrum
By allowing interactions between electrons, a new Harper's equation is
derived to examine the effects of electron correlations on the Hofstadter
energy spectra. It is shown that the structure of the Hofstadter butterfly ofr
the system of correlated electrons is modified only in the band gaps and the
band widths, but not in the characteristics of self-similarity and the Cantor
set.Comment: 13 pages, 5 Postscript figure
The Effects of d_{x^2-y^2}-d_{xy} Mixing on Vortex Structures and Magnetization
The structure of an isolated single vortex and the vortex lattice, and the
magnetization in a -wave superconductor are investigated within a
phenomenological Ginzburg-Landau (GL) model including the mixture of the
-wave and -wave symmetry. The isolated single vortex
structure in a week magnetic field is studied both numerically and
asymptotically. Near the upper critical field , the vortex lattice
structure and the magnetization are calculated analytically.Comment: 14 pages, REVTeX, 2 EPS figures, Journal of Physics: Condensed Matter
(in press
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