6,320 research outputs found
Nonadiabatic Josephson current pumping by microwave irradiation
Irradiating a Josephson junction with microwaves can operate not only on the
amplitude but also on the phase of the Josephson current. This requires
breaking time inversion symmetry, which is achieved by introducing a phase
lapse between the microwave components acting on the two{\dag} sides of the
junction. General symmetry arguments and the solution of a specific single
level quantum dot model show that this induces chirality in the Cooper pair
dynamics, due to the topology of the Andreev bound state wavefunction. Another
essential condition is to break electron-hole symmetry within the junction. A
shift of the current-phase relation is obtained, which is controllable in sign
and amplitude with the microwave phase and an electrostatic gate, thus
producing a "chiral" Josephson transistor. The dot model is solved in the
infinite gap limit by Floquet theory and in the general case with Keldysh
nonequilibrium Green's functions. The chiral current is nonadiabatic: it is
extremal and changes sign close to resonant chiral transitions between the
Andreev bound states.Comment: 13 pages, 7 figures, extended versio
Symbolic Solution of Linear Differential Equations
An algorithm for solving linear constant-coefficient ordinary differential equations is presented. The computational complexity of the algorithm is discussed and its implementation in the FORMAC system is described. A comparison is made between the algorithm and some classical algorithms for solving differential equations
Proposal for the observation of nonlocal multipair production: the biSQUID
We propose an all-superconducting three-terminal setup consisting in a carbon
nanotube (or semiconducting nanowire) contacted to three superconducting leads.
The resulting device, referred to as a "biSQUID", is made of four quantum dots
arranged in two loops of different surface area. We show how this biSQUID can
prove a useful tool to probe nonlocal quantum phenomena in an interferometry
setup. We study the measured critical current as a function of the applied
magnetic field, which shows peaks in its Fourier spectrum, providing clear
signatures of multipair Josephson processes. The device does not require any
specific fine-tuning as these features are observed for a wide range of
microscopic parameters -- albeit with a non-trivial dependence. Competing
effects which may play a significant role in actual experimental realizations
are also explored.Comment: 13 pages, 9 figure
Multipair DC-Josephson Resonances in a biased all-superconducting Bijunction
An all-superconducting bijunction consists of a central superconductor
contacted to two lateral superconductors, such that non-local crossed Andreev
reflection is operating. Then new correlated transport channels for the Cooper
pairs appear in addition to those of separated conventional Joseph- son
junctions. We study this system in a configuration where the superconductors
are connected through gate-controllable quantum dots. Multipair phase-coherent
resonances and phase-dependent multiple Andreev reflections are both obtained
when the voltages of the lateral superconductors are commensurate, and they add
to the usual local dissipative transport due to quasiparticles. The two-pair
resonance (quartets) as well as some other higher order multipair resonances
are {\pi}-shifted at low voltage. Dot control can be used to dramatically
enhance the multipair current when the voltages are resonant with the dot
levels.Comment: 6 page
Application of ERTS-1 data to the protection and management of New Jersey's coastal environment
The author has identified the following significant results. Photomaps, using MSS bands 5 and 7, have been prepared delineating the coastal zone as described in the Coastal Area Facility Review Act before the State Legislature. An upper wetlands boundary overlay has been prepared at 1:500,000 scale. The movement and dispersion of wastes in the New York Bight area are being plotted with each orbit. The possible impact of these wastes on the New Jersey shoreline is being quantified
Application of ERTS-A data to the protection and management of New Jersey's coastal environment
The author has identified the following significant results. Apparent sewage sludge disposal by barge has been detected approximately 12 miles offshore in an area with an approximate radius of 2.5 nautical miles. Verification is underway to determine whether this dumping is within one of the approved dump sites in the Bight. Analysis of all available historical and routine meteorological data in correlation with the observed phenomenon is necessary before final conclusions can be reached with respect to the effects of currents on the disposal of dumped wastes. Four effluent plumes emanating from the shoreline just south of Sandy Hook were observed and are moving in a southerly direction. Another plume is evident north of Barnegat Inlet and is moving almost directly offshore. This suggests that the more northerly plumes are under the influence of the tidal regime around New York Harbor much more than are the plumes further south along the New Jersey coast. Of further interest are what appear to be an internal wave phenomena approximately 75 miles east of the New Jersey coast. This same sort of phenomena has been observed repetitively off the coast of Oregon
Preclinical Assessment of HIV Vaccines and Microbicides by Repeated Low-Dose Virus Challenges
BACKGROUND: Trials in macaque models play an essential role in the evaluation of biomedical interventions that aim to prevent HIV infection, such as vaccines, microbicides, and systemic chemoprophylaxis. These trials are usually conducted with very high virus challenge doses that result in infection with certainty. However, these high challenge doses do not realistically reflect the low probability of HIV transmission in humans, and thus may rule out preventive interventions that could protect against “real life” exposures. The belief that experiments involving realistically low challenge doses require large numbers of animals has so far prevented the development of alternatives to using high challenge doses. METHODS AND FINDINGS: Using statistical power analysis, we investigate how many animals would be needed to conduct preclinical trials using low virus challenge doses. We show that experimental designs in which animals are repeatedly challenged with low doses do not require unfeasibly large numbers of animals to assess vaccine or microbicide success. CONCLUSION: Preclinical trials using repeated low-dose challenges represent a promising alternative approach to identify potential preventive interventions
Long Range Forces from Pseudoscalar Exchange
Using dispersion theoretic techniques, we consider coherent long range forces
arising from double pseudoscalar exchange among fermions. We find that Yukawa
type coupling leads to spin independent attractive potentials whereas
derivative coupling renders spin independent repulsive potentials.Comment: 27 pages, REVTeX, 3 figures included using epsfi
Entropy and Thermodynamic Temperature in Nonequilibrium Classical Thermodynamics as Immediate Consequences of the Hahn-Banach Theorem: I. Existence
The Kelvin-Planck statement of the Second Law of Thermodynamics is a
stricture on the nature of heat receipt by any body suffering a cyclic process.
It makes no mention of temperature or of entropy. Beginning with a
Kelvin-Planck statement of the Second Law, we show that entropy and temperature
-- in particular, existence of functions that relate the local specific entropy
and thermodynamic temperature to the local state in a material body -- emerge
immediately and simultaneously as consequences of the Hahn-Banach Theorem.
Existence of such functions of state requires no stipulation that their domains
be restricted to equilibrium states. Further properties, including uniqueness,
are addressed in a companion paper
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