19,608 research outputs found
Low solar absorptance and emittance surfaces utilizing vacuum deposited techniques Final report, 1 Jun. 1967 - 25 Mar. 1968
Optical properties and stability of vacuum deposited silver and dielectric film coating
Quantum signal transmission through a single-qubit chain
A system of a two-level atom of an impurity (qubit) inserted into a periodic
chain coupled to the continuum is studied with the use of the effective
non-Hermitian Hamiltonian. Exact solutions are derived for the quasistationary
eigenstates, their complex energies, and transport properties. Due to the
presence of the qubit, two long-lived states corresponding to the ground and
excited states of the qubit emerge outside the Bloch energy band. These states
remain essentially localized at the qubit even in the limit of sufficiently
strong coupling between the chain and the environment when the super-radiant
states are formed. The transmission through the chain is studied as a function
of the continuum coupling strength and the chain-qubit coupling; the perfect
resonance transmission takes place through isolated resonances at weak and
strong continuum coupling, while the transmission is lowered in the
intermediate regime.Comment: In this version we added the case of large N and the case when the
excitation energy of bare qubit is below the band boundary of the bare chain.
The captions to some figures are modified. Some new references are adde
A cost-benefit analysis of pathways to work for new and repeat incapacity benefits claimants
This latest research forms part of a comprehensive independent evaluation of Pathways to Work. The report is based on a cost-benefit analysis conducted by a consortium of researchers from the Institute for Fiscal Studies, the University of Maryland, Baltimore County and the Policy Studies Institute. It examines whether the financial benefits from Pathways are larger or smaller than its costs and the generalisability of some of the quantitative findings. The estimates of costs and benefits relate to new and repeat incapacity benefits claimants in the seven original Jobcentre Plus districts. The overall findings provide a favourable impression of the financial benefits of the Pathways to Work for new and repeat incapacity benefits claimants, for the Exchequer and hence, for society as a whole
Solar-radiation-induced damage to optical properties of ZnO-type pigments Technical summary report, Jul. 1966 - Feb. 1968
Mechanisms of solar radiation damage to optical properties in zinc oxide pigments in visible and infrared region
Formation of laser plasma channels in a stationary gas
The formation of plasma channels with nonuniformity of about +- 3.5% has been
demonstrated. The channels had a density of 1.2x10^19 cm-3 with a radius of 15
um and with length >= 2.5 mm. The channels were formed by 0.3 J, 100 ps laser
pulses in a nonflowing gas, contained in a cylindrical chamber. The laser beam
passed through the chamber along its axis via pinholes in the chamber walls. A
plasma channel with an electron density on the order of 10^18 - 10^19 cm-3 was
formed in pure He, N2, Ar, and Xe. A uniform channel forms at proper time
delays and in optimal pressure ranges, which depend on the sort of gas. The
influence of the interaction of the laser beam with the gas leaking out of the
chamber through the pinholes was found insignificant. However, the formation of
an ablative plasma on the walls of the pinholes by the wings of the radial
profile of the laser beam plays an important role in the plasma channel
formation and its uniformity. A low current glow discharge initiated in the
chamber slightly improves the uniformity of the plasma channel, while a high
current arc discharge leads to the formation of overdense plasma near the front
pinhole and further refraction of the laser beam. The obtained results show the
feasibility of creating uniform plasma channels in non-flowing gas targets.Comment: 15 pages, 7 figures, submitted to Physics of Plasma
Superfield Realizations of Lorentz and CPT Violation
Superfield realizations of Lorentz-violating extensions of the Wess-Zumino
model are presented. These models retain supersymmetry but include terms that
explicitly break the Lorentz symmetry. The models can be understood as arising
from superspace transformations that are modifications of the familiar one in
the Lorentz-symmetric case.Comment: 10 page
Tidal Heating of Extra-Solar Planets
Extra-solar planets close to their host stars have likely undergone
significant tidal evolution since the time of their formation. Tides probably
dominated their orbital evolution once the dust and gas had cleared away, and
as the orbits evolved there was substantial tidal heating within the planets.
The tidal heating history of each planet may have contributed significantly to
the thermal budget that governed the planet's physical properties, including
its radius, which in many cases may be measured by observing transit events.
Typically, tidal heating increases as a planet moves inward toward its star and
then decreases as its orbit circularizes. Here we compute the plausible heating
histories for several planets with measured radii, using the same tidal
parameters for the star and planet that had been shown to reconcile the
eccentricity distribution of close-in planets with other extra-solar planets.
Several planets are discussed, including for example HD 209458 b, which may
have undergone substantial tidal heating during the past billion years, perhaps
enough to explain its large measured radius. Our models also show that GJ 876 d
may have experienced tremendous heating and is probably not a solid, rocky
planet. Theoretical models should include the role of tidal heating, which is
large, but time-varying.Comment: Accepted for publication to Ap
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