28,611 research outputs found
Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of air mass transport over East Asia
© Author(s) 2015. This is an Open Access article made available under the terms of the Creative Commons Attribution License 3.0 https://creativecommons.org/licenses/by/3.0/We use five years (2009-2013) of multiwavelength Raman lidar measurements at Gwangju, South Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust depending on its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modeling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground at which these plumes were transported: (case I) the dust layers passed over China at high altitude levels (> 3 km) until arrival over Gwangju, and (case II) the Asian dust layers were transported near the surface and within the lower troposphere (< 3 km) over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ depending on their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 for case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios (0.13 ± 0.04 at 532 nm), and higher lidar ratio (63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm) and Ångström exponents (0.98 ± 0.51). These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume depending on transport time if the pollution layer traveled over China at low heights, i.e., below approximately 3 km above ground. In contrast, we do not find such a trend if the dust plumes traveled at heights above 3 km over China. We need a longer time series of lidar measurements in order to determine in a quantitative way the change of optical properties of dust with transport time.Peer reviewedFinal Published versio
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Spin relaxation in mesoscopic superconducting Al wires
We studied the diffusion and the relaxation of the polarized quasiparticle
spins in superconductors. To that end, quasiparticles of polarized spins were
injected through an interface of a mesoscopic superconducting Al wire in
proximity contact with an overlaid ferromagnetic Co wire in the single-domain
state. The superconductivity was observed to be suppressed near the
spin-injecting interface, as evidenced by the occurrence of a finite voltage
for a bias current below the onset of the superconducting transition. The spin
diffusion length, estimated from finite voltages over a certain length of Al
wire near the interface, was almost temperature independent in the temperature
range sufficiently below the superconducting transition but grew as the
transition temperature was approached. This temperature dependence suggests
that the relaxation of the spin polarization in the superconducting state is
governed by the condensation of quasiparticles to the paired state. The spin
relaxation in the superconducting state turned out to be more effective than in
the normal state.Comment: 9 pages, 8 figure
Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene
We investigated the transient photoconductivity of graphene at various
gate-tuned carrier densities by optical-pump terahertz-probe spectroscopy. We
demonstrated that graphene exhibits semiconducting positive photoconductivity
near zero carrier density, which crosses over to metallic negative
photoconductivity at high carrier density. Our observations are accounted for
by considering the interplay between photo-induced changes of both the Drude
weight and the carrier scattering rate. Notably, we observed multiple sign
changes in the temporal photoconductivity dynamics at low carrier density. This
behavior reflects the non-monotonic temperature dependence of the Drude weight,
a unique property of massless Dirac fermions
N3LO NN interaction adjusted to light nuclei in ab exitu approach
We use phase-equivalent transformations to adjust off-shell properties of
similarity renormalization group evolved chiral effective field theory NN
interaction (Idaho N3LO) to fit selected binding energies and spectra of light
nuclei in an ab exitu approach. We then test the transformed interaction on a
set of additional observables in light nuclei to verify that it provides
reasonable descriptions of these observables with an apparent reduced need for
three- and many-nucleon interactions.Comment: Revised text due to journal referee comments. 6 pages, 2 figure
Faddeev calculation of pentaquark in the Nambu-Jona-Lasinio model-based diquark picture
A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark
in the diquark picture of Jaffe and Wilczek in which is a
diquark-diquark- three-body system. Nambu-Jona-Lasinio (NJL) model is
used to calculate the lowest order diagrams in the two-body scatterings of
and . With the use of coupling constants determined from the
meson sector, we find that interaction is attractive in s-wave
while interaction is repulsive in p-wave. With only the lowest three-body
channel considered, we do not find a bound pentaquark state.
Instead, a bound pentaquark with is obtained with a
unphysically strong vector mesonic coupling constants.Comment: 22 pages, 11 figures, accepted version in Phys. Rev. C. Summary of
main changes/corrections: 1. "which only holds at tree level" below the eq.
(23) is added. 2. In the last paragraph of p.23 we added a remark that the
coupling constant obtained from Lambda mass is different from the estimate as
obtained from the meson spectru
Critical phenomena in globally coupled excitable elements
Critical phenomena in globally coupled excitable elements are studied by
focusing on a saddle-node bifurcation at the collective level. Critical
exponents that characterize divergent fluctuations of interspike intervals near
the bifurcation are calculated theoretically. The calculated values appear to
be in good agreement with those determined by numerical experiments. The
relevance of our results to jamming transitions is also mentioned.Comment: 4 pages, 3 figure
- …