4,348 research outputs found
Theory for ultrafast nonequilibrium dynamics in d-wave superconductors
We use density-matrix theory to calculate the ultrafast dynamics of
unconventional superconductors from a microscopic viewpoint. We calculate the
time evolution of the optical conductivity as well as pump-probe spectra for a
d-wave order parameter. Three regimes can be distinguished in the spectra. The
Drude response at low photon energies is the only one of those which has been
measured experimentally so far. At higher energies, we predict two more
regimes: the pair-breaking peak, which is reduced as Cooper-pairs are broken up
by the exciting pulse; and a suppression above the pair-breaking peak due to
nonequilibrium quasiparticles. Furthermore, we consider the influence of the
electron-phonon coupling, and derive rate equations which have been widely used
so far.Comment: 4 pages, 4 figure
Self-Consistent Theory of the Gain Linewidth for Quantum Cascade Lasers
The linewidth in intersubband transitions can be significantly reduced below
the sum of the lifetime broadening for the involved states, if the scattering
environment is similar for both states. This is studied within a nonequilibrium
Green function approach here. We find that the effect is of particular
relevance for a recent, relatively low doped, THz quantum cascade laser.Comment: 3 pages, figures include
Phase relaxation of Faraday surface waves
Surface waves on a liquid air interface excited by a vertical vibration of a
fluid layer (Faraday waves) are employed to investigate the phase relaxation of
ideally ordered patterns. By means of a combined frequency-amplitude modulation
of the excitation signal a periodic expansion and dilatation of a square wave
pattern is generated, the dynamics of which is well described by a Debye
relaxator. By comparison with the results of a linear theory it is shown that
this practice allows a precise measurement of the phase diffusion constant.Comment: 5 figure
Rapid changes in ice core gas records Part 2: Understanding the rapid rise in atmospheric CO2 at the onset of the Bølling/Allerød
During the last glacial/interglacial transition the Earth's climate underwent rapid changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A is accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP) 1A, whose exact timing is matter of current debate. In situ measured CO<sub>2</sub> in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10±1 ppmv in 230 yr at the same time. Allowing for the age distribution of CO<sub>2</sub> in firn we here show, that atmospheric CO<sub>2</sub> rose by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 larger than the CO<sub>2</sub> signal recorded in situ in EDC. Based on the estimated airborne fraction of 0.17 of CO<sub>2</sub> we infer that 125 Pg of carbon need to be released to the atmosphere to produce such a peak. Most of the carbon might have been activated as consequence of continental shelf flooding during MWP-1A. This impact of rapid sea level rise on atmospheric CO<sub>2</sub> distinguishes the B/A from other Dansgaard/Oeschger events of the last 60 kyr, potentially defining the point of no return during the last deglaciation
Contracts - Caveat Emptor - Implied Warranty of Habitability
The Pennsylvania Supreme Court has held that a builder-vendor impliedly warrants that a house is constructed in a reasonably workmanlike manner and fit for habitation.
Elderkin v. Gaster, 447 Pa. 118, 288 A.2d 771 (1972)
The Properties of Water in the Pressure-Temperature Landscape
Water represents the major component of most food systems. During thermal or high-pressure processing, physical and chemical properties of water are changed. The p-T diagram represents an obvious presentation of isoproperty lines and their pressure and temperature dependencies. In this work, 15 different properties of pure water are shown as isoproperty lines in the pressure-temperature landscape. By using functional relationships from the "International Association for the Properties of Water and Steam” and databases from the "National Institute of Standards and Technology,” highest accuracy is guaranteed. Applying the generated graphs, a compact overview is given and a wide range of thermal and high-pressure processes can easily be compared. The different pressure and temperature dependencies of all properties showed the complexity of medium conditions during thermal and high-pressure processing. An extended understanding of pressure-temperature dependencies will improve process concepts as well as industrial applications at high temperature and high isostatic pressur
Diurnal plasma-ACTH-levels in corticosteroid treated patients with congenital adrenal hyperplasia (CAH)
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