3,551 research outputs found
Real time decoherence of Landau and Levitov quasi-particles in quantum Hall edge channels
Quantum Hall edge channels at integer filling factor provide a unique
test-bench to understand decoherence and relaxation of single electronic
excitations in a ballistic quantum conductor. In this Letter, we obtain a full
visualization of the decoherence scenario of energy (Landau) and time (Levitov)
resolved single electron excitations at filling factor . We show that
the Landau excitation exhibits a fast relaxation followed by spin-charge
separation whereas the Levitov excitation only experiences spin-charge
separation. We finally suggest to use Hong-Ou-Mandel type experiments to probe
specific signatures of these different scenarios.Comment: 14 pages, 8 figure
Structural build-up of cementitious paste under external magnetic fields
Engineering application processes of fresh concrete include transporting,
pumping, formwork casting, etc. Each process is a significant factor
influencing properties of fresh and hardened concrete. However, many contradicting
requirements of fresh concrete performances (such as structuration rate)
exist in these operation processes. Therefore, advanced techniques need to be
proposed to satisfy future challenges. Actively controlling the stiffness by
applying external magnetic fields would be a potential solution for the contradicting
requirements, and could make the pumping and casting processes smarter
and more reliable. In the present paper, the effects of magnetic field strength and
magnetizing time on structural build-up of cementitious paste are discussed. The
results show that higher magnetic field strengths result in higher percolation time
and lower phase angle at equilibrium state. However, the application of external
magnetic fields with low flux density has little effects on the viscoelastic behaviour
of cementitious paste. Under high magnetic field strengths, the viscousliquid
behaviour dominates the elastic-solid behaviour at early stage, while the
solid-like behaviour becomes more dominant with magnetizing time
NGC1377: An Extragalactic Proto-Starburst
NGC1377 is the archetype of a class of galaxies called nascent starbursts, selected by their very high infrared to radio continuum flux ratios and their high dust temperatures. This nearby galaxy is an ideal test case to refine the understanding of the mechanisms of the infrared-radio correlation of star-forming galaxies; to characterize the physical conditions of an embedded starburst at its very onset; and to gain a better knowledge of the activity of a class of ultraluminous galaxies sharing the main infrared-radio properties of NGC1377. We present new data on NGC1377 obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS) Legacy program and discuss briefly our interpretation of the combined optical, infrared and radio properties
Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes.
Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene-bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a. Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum-chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene-bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge-transfer-type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation
A Spitzer Unbiased Ultradeep Spectroscopic Survey
We carried out an unbiased, spectroscopic survey using the low-resolution
module of the infrared spectrograph (IRS) on board Spitzer targeting two 2.6
square arcminute regions in the GOODS-North field. IRS was used in spectral
mapping mode with 5 hours of effective integration time per pixel. One region
was covered between 14 and 21 microns and the other between 20 and 35 microns.
We extracted spectra for 45 sources. About 84% of the sources have reported
detections by GOODS at 24 microns, with a median F_nu(24um) ~ 100 uJy. All but
one source are detected in all four IRAC bands, 3.6 to 8 microns. We use a new
cross-correlation technique to measure redshifts and estimate IRS spectral
types; this was successful for ~60% of the spectra. Fourteen sources show
significant PAH emission, four mostly SiO absorption, eight present mixed
spectral signatures (low PAH and/or SiO) and two show a single line in
emission. For the remaining 17, no spectral features were detected. Redshifts
range from z ~ 0.2 to z ~ 2.2, with a median of 1. IR Luminosities are roughly
estimated from 24 microns flux densities, and have median values of 2.2 x
10^{11} L_{\odot} and 7.5 x 10^{11} L_{\odot} at z ~ 1 and z ~ 2 respectively.
This sample has fewer AGN than previous faint samples observed with IRS, which
we attribute to the fainter luminosities reached here.Comment: Published in Ap
Logarithmic behavior of degradation dynamics in metal--oxide semiconductor devices
In this paper the authors describe a theoretical simple statistical modelling
of relaxation process in metal-oxide semiconductor devices that governs its
degradation. Basically, starting from an initial state where a given number of
traps are occupied, the dynamics of the relaxation process is measured
calculating the density of occupied traps and its fluctuations (second moment)
as function of time. Our theoretical results show a universal logarithmic law
for the density of occupied traps , i.e., the degradation is logarithmic and its amplitude depends on the
temperature and Fermi Level of device. Our approach reduces the work to the
averages determined by simple binomial sums that are corroborated by our Monte
Carlo simulations and by experimental results from literature, which bear in
mind enlightening elucidations about the physics of degradation of
semiconductor devices of our modern life
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