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A study of the dynamical characteristics of inertia–gravity waves in the Antarctic mesosphere combining the PANSY radar and a non-hydrostatic general circulation model
This study aims to examine the dynamical characteristics of gravity waves
with relatively low frequency in the Antarctic mesosphere via the first
long-term simulation using a high-top high-resolution non-hydrostatic general
circulation model (NICAM). Successive runs lasting 7 days are performed using
initial conditions from the MERRA reanalysis data with an overlap of 2 days
between consecutive runs in the period from April to August in 2016. The data
for the analyses were compiled from the last 5 days of each run. The
simulated wind fields were closely compared to the MERRA reanalysis data and
to the observational data collected by a complete PANSY (Program of the
Antarctic Syowa MST/IS radar) radar system installed at Syowa Station
(39.6∘ E, 69.0∘ S). It is shown that the NICAM mesospheric
wind fields are realistic, even though the amplitudes of the wind
disturbances appear to be larger than those from the radar observations.
The power spectrum of the meridional wind fluctuations at a height of 70 km
has an isolated and broad peak at frequencies slightly lower than the
inertial frequency, f, for latitudes from 30 to 75∘ S, while another isolated peak is observed at frequencies of approximately
2π∕8 h at latitudes from 78 to 90∘ S. The
spectrum of the vertical fluxes of the zonal momentum also has an isolated
peak at frequencies slightly lower than f at latitudes from 30 to 75∘ S at a height of 70 km. It is shown that these isolated
peaks are primarily composed of gravity waves with horizontal wavelengths of
more than 1000 km. The latitude–height structure of the momentum fluxes
indicates that the isolated peaks at frequencies slightly lower than f
originate from two branches of gravity wave propagation paths. It is thought
that one branch originates from 75∘ S due to topographic gravity
waves generated over the Antarctic Peninsula and its coast, while more than
80 % of the other branch originates from 45∘ S and includes
contributions by non-orographic gravity waves. The existence of isolated
peaks in the high-latitude region in the mesosphere is likely explained by
the poleward propagation of quasi-inertia–gravity waves and by the
accumulation of wave energies near the inertial frequency at each latitude.</p
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Photoluminescence, recombination induced luminescence and electroluminescence in epoxy resin
Dielectric breakdown of epoxies is preceded by light emission, or so-called electroluminescence, from the solid-state material. Very little is known about the luminescence properties of epoxies. The aim of this paper is to derive information that can be used as a basis to understand the nature of the excited states and their involvement in electrical degradation processes. Three different kinds of stimulation were used to excite the material luminescence. Photoluminescence was performed on the base resin, the hardener and the cured resin. Luminescence excited by a silent discharge has been analysed to identify which of the luminescent centres are optically active upon the recombination of electrical charges and could therefore act as charge traps. Finally, the electroluminescence spectrum has been acquired and compared with the previous ones. Although the identification of the origin of these emissions is far from being complete, it has been found that the photoluminescence from the cured resin is due to in-chain chromophores, which acts as trapping centres. The excited states involved in photoluminescence also seems to be involved in electroluminescence, but other components are detected as well, which could be due to the degradation of the resin molecule under the effect of the electric stress
Comparison of Bond Character in Hydrocarbons and Fullerenes
We present a comparison of the bond polarizabilities for carbon-carbon bonds
in hydrocarbons and fullerenes, using two different models for the fullerene
Raman spectrum and the results of Raman measurements on ethane and ethylene. We
find that the polarizabilities for single bonds in fullerenes and hydrocarbons
compare well, while the double bonds in fullerenes have greater polarizability
than in ethylene.Comment: 7 pages, no figures, uses RevTeX. (To appear in Phys. Rev. B.
Tuning of metal-insulator transition of two-dimensional electrons at parylene/SrTiO interface by electric field
Electrostatic carrier doping using a field-effect-transistor structure is an
intriguing approach to explore electronic phases by critical control of carrier
concentration. We demonstrate the reversible control of the insulator-metal
transition (IMT) in a two dimensional (2D) electron gas at the interface of
insulating SrTiO single crystals. Superconductivity was observed in a
limited number of devices doped far beyond the IMT, which may imply the
presence of 2D metal-superconductor transition. This realization of a
two-dimensional metallic state on the most widely-used perovskite oxide is the
best manifestation of the potential of oxide electronics
Quantum-mechanical model for particles carrying electric charge and magnetic flux in two dimensions
We propose a simple quantum mechanical equation for particles in two
dimensions, each particle carrying electric charge and magnetic flux. Such
particles appear in (2+1)-dimensional Chern-Simons field theories as charged
vortex soliton solutions, where the ratio of charge to flux is a constant
independent of the specific solution. As an approximation, the charge-flux
interaction is described here by the Aharonov-Bohm potential, and the
charge-charge interaction by the Coulomb one. The equation for two particles,
one with charge and flux () and the other with () where
is a pure number is studied in detail. The bound state problem is solved
exactly for arbitrary and when . The scattering problem is
exactly solved in parabolic coordinates in special cases when takes integers or half integers. In both cases the cross sections obtained
are rather different from that for pure Coulomb scattering.Comment: 12 pages, REVTeX, no figur
Role of multiple subband renormalization in the electronic transport of correlated oxide superlattices
Metallic behavior of band-insulator/ Mott-insulator interfaces was observed
in artificial perovskite superlattices such as in nanoscale SrTiO3/LaTiO3
multilayers. Applying a semiclassical perspective to the parallel electronic
transport we identify two major ingredients relevant for such systems: i) the
quantum confinement of the conduction electrons (superlattice modulation) leads
to a complex, quasi-two dimensional subband structure with both hole- and
electron-like Fermi surfaces. ii) strong electron-electron interaction requires
a substantial renormalization of the quasi-particle dispersion. We characterize
this renormalization by two sets of parameters, namely, the quasi-particle
weight and the induced particle-hole asymmetry of each partially filled
subband. In our study, the quasi-particle dispersion is calculated
self-consistently as function of microscopic parameters using the slave-boson
mean-field approximation introduced by Kotliar and Ruckenstein. We discuss the
consequences of strong local correlations on the normal-state free-carrier
response in the optical conductivity and on the thermoelectric effects.Comment: 11 pages, 4 figure
The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641
We present new observations of the highest-redshift quasar known, ULAS
J1120+0641, redshift , obtained in the optical, at near-, mid-, and
far-infrared wavelengths, and in the sub-mm. We combine these results with
published X-ray and radio observations to create the multiwavelength spectral
energy distribution (SED), with the goals of measuring the bolometric
luminosity , and quantifying the respective contributions from the
AGN and star formation. We find three components are needed to fit the data
over the wavelength range m: the unobscured quasar accretion
disk and broad-line region, a dusty clumpy AGN torus, and a cool 47K modified
black body to characterise star formation. Despite the low signal-to-noise
ratio of the new long-wavelength data, the normalisation of any dusty torus
model is constrained within . We measure a bolometric luminosity
ergs, to which the three components contribute
, respectively, with the remainder provided by the extreme UV
m. We tabulate the best-fit model SED. We use local scaling
relations to estimate a star formation rate (SFR) in the range /yr from the [C] line luminosity and the
m continuum luminosity. An analysis of the equivalent widths of the
[C] line in a sample of quasars suggests that
these indicators are promising tools for estimating the SFR in high-redshift
quasars in general. At the time observed the black hole was growing in mass
more than 100 times faster than the stellar bulge, relative to the mass ratio
measured in the local universe, i.e. compared to , for ULAS J1120+0641 we measure .Comment: Accepted for publication in A&A. 10 pages, 5 figures, 5 table
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