16,502 research outputs found
Simulation of the trans-oceanic tsunami propagation due to the 1883 Krakatau volcanic eruption
International audienceThe 1883 Krakatau volcanic eruption has generated a destructive tsunami higher than 40 m on the Indonesian coast where more than 36 000 lives were lost. Sea level oscillations related with this event have been reported on significant distances from the source in the Indian, Atlantic and Pacific Oceans. Evidence of many manifestations of the Krakatau tsunami was a subject of the intense discussion, and it was suggested that some of them are not related with the direct propagation of the tsunami waves from the Krakatau volcanic eruption. Present paper analyzes the hydrodynamic part of the Krakatau event in details. The worldwide propagation of the tsunami waves generated by the Krakatau volcanic eruption is studied numerically using two conventional models: ray tracing method and two-dimensional linear shallow-water model. The results of the numerical simulations are compared with available data of the tsunami registration
Spitzer Mid-Infrared Spectroscopy of Infrared Luminous Galaxies at z~2 II: Diagnostics
We present mid-IR spectral decomposition of a sample of 48 Spitzer-selected
ULIRGs spanning z~1-3 and likely L_IR~10^12-10^13Lsun. Our study aims at
quantifying the star-formation and AGN processes in these sources which recent
results suggest have evolved strongly between the observed epoch and today. To
do this, we study the mid-IR contribution of PAH emission, continuum, and
extinction. About 3/4 of our sample are continuum- (i.e. AGN) dominated
sources, but ~60% of these show PAH emission, suggesting the presence of
star-formation activity. These sources have redder mid-IR colors than typical
optically-selected quasars. About 25% of our sample have strong PAH emission,
but none are likely to be pure starbursts as reflected in their relatively high
5um hot dust continua. However, their steep 30um-to-14um slopes suggest that
star-formation might dominate the total infrared luminosity. Six of our z~2
sources have EW6.2>~0.3um and L_14um>~10^12Lsun (implying L_IR>~10^13Lsun). At
these luminosities, such high EW6.2 ULIRGs do not exist in the local Universe.
We find a median optical depth at 9.7um of =1.4. This is consistent
with local IRAS-selected ULIRGs, but differs from early results on
SCUBA-selected z~2 ULIRGs. Similar to local ULIRGs about 25% of our sample show
extreme obscuration (tau_9.7>~3) suggesting buried nuclei. In general, we find
that our sources are similar to local ULIRGs, but are an order of magnitude
more luminous. It is not clear whether our z~2 ULIRGs are simply scaled-up
versions of local ULIRGs, or subject to fundamentally different physical
processes.Comment: 60 pages, 15 figures, accepted for publication in Ap
Conformal Anomaly and Critical Exponents of the XY-Ising Model
We use extensive Monte Carlo transfer matrix calculations on infinite strips
of widths up to 30 lattice spacing and a finite-size scaling analysis to
obtain critical exponents and conformal anomaly number for the
two-dimensional -Ising model. This model is expected to describe the
critical behavior of a class of systems with simultaneous and
symmetries of which the fully frustrated model is a special case. The
effective values obtained for show a significant decrease with at
different points along the line where the transition to the ordered phase takes
place in a single transition. Extrapolations based on power-law corrections
give values consistent with although larger values can not be ruled
out. Critical exponents are obtained more accurately and are consistent with
previous Monte Carlo simulations suggesting new critical behavior and with
recent calculations for the frustrated model.Comment: 33 pages, 13 latex figures, uses RevTeX 3.
The possible explanation of electric-field-doped C60 phenomenology in the framework of Eliashberg theory
In a recent paper (J.H. Schon, Ch. Kloc, R.C. Haddon and B. Batlogg, Nature
408 (2000) 549) a large increase in the superconducting critical temperature
was observed in C60 doped with holes by application of a high electric field.
We demonstrate that the measured Tc versus doping curves can be explained by
solving the (four) s-wave Eliashberg equations in the case of a finite,
non-half-filled energy band. In order to reproduce the experimental data, we
assume a Coulomb pseudopotential depending on the filling in a very simple and
plausible way. Reasonable values of the physical parameters involved are
obtained. The application of the same approach to new experimental data (J.H.
Schon, Ch. Kloc and B. Batlogg, Science 293 (2001) 2432) on electric
field-doped, lattice-expanded C60 single crystals (Tc=117 K in the hole-doped
case) gives equally good results and sets a theoretical limit to the linear
increase of Tc at the increase of the lattice spacing.Comment: latex2e, 6 pages, 7 figures, 1 table, revised versio
Simulation of the trans-oceanic tsunami propagation due to the 1883 Krakatau volcanic eruption
The 1883 Krakatau volcanic eruption has generated a destructive tsunami higher than 40 m on the Indonesian coast where more than 36 000 lives were lost. Sea level oscillations related with this event have been reported on significant distances from the source in the Indian, Atlantic and Pacific Oceans. Evidence of many manifestations of the Krakatau tsunami was a subject of the intense discussion, and it was suggested that some of them are not related with the direct propagation of the tsunami waves from the Krakatau volcanic eruption. Present paper analyzes the hydrodynamic part of the Krakatau event in details. The worldwide propagation of the tsunami waves generated by the Krakatau volcanic eruption is studied numerically using two conventional models: ray tracing method and two-dimensional linear shallow-water model. The results of the numerical simulations are compared with available data of the tsunami registration
Interplay between carrier and impurity concentrations in annealed GaMnAs intrinsic anomalous Hall Effect
Investigating the scaling behavior of annealed GaMnAs anomalous
Hall coefficients, we note a universal crossover regime where the scaling
behavior changes from quadratic to linear, attributed to the anomalous Hall
Effect intrinsic and extrinsic origins, respectively. Furthermore, measured
anomalous Hall conductivities when properly scaled by carrier concentration
remain constant, equal to theoretically predicated values, spanning nearly a
decade in conductivity as well as over 100 K in T. Both the qualitative
and quantitative agreement confirms the validity of new equations of motion
including the Berry phase contributions as well as tunablility of the intrinsic
anomalous Hall Effect.Comment: 4 pages, 5 figure
Controlled growth and characterization of epitaxially-laterally-overgrown InGaN/GaN quantum heterostructures
Crystal material quality is fundamentally important for optoelectronic devices including laser diodes and light emitting diodes. To this end epitaxial lateral overgrowth (ELO) has proven to be a powerful technique for reducing dislocation density in GaN and its alloys [1,2]. Implementation and design of ELO process is, however, critical for obtaining high-quality material with high-efficiency quantum structures for light emitters [3]. ©2010 IEEE
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