16,392 research outputs found
LANDSAT-4 multispectral scanner (MSS) subsystem radiometric characterization
The multispectral band scanner (mass) and its spectral characteristics are described and methods are given for relating video digital levels on computer compatible tapes to radiance into the sensor. Topics covered include prelaunch calibration procedures and postlaunch radiometric processng. Examples of current data resident on the MSS image processing system are included. The MSS on LANDSAT 4 is compared with the scanners on earlier LANDSAT satellites
Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. III. Radiation reaction for binary systems with spinning bodies
Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies. In particular we determine the effects of
radiation-reaction coupled to spin-orbit effects on the two-body equations of
motion, and on the evolution of the spins. For a suitable definition of spin,
we reproduce the standard equations of motion and spin-precession at the first
post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced
reaction effects on the orbital motion, but we find that radiation damping has
no effect on either the magnitude or the direction of the spins. Using the
equations of motion, we find that the loss of total energy and total angular
momentum induced by spin-orbit effects precisely balances the radiative flux of
those quantities calculated by Kidder et al. The equations of motion may be
useful for evolving inspiraling orbits of compact spinning binaries.Comment: 19 pages, small corrections, equivalent to published versio
The 13N(d,n)14O Reaction and the Astrophysical 13N(p,g)14O Reaction Rate
N()O is one of the key reactions in the hot CNO cycle
which occurs at stellar temperatures around 0.1. Up to now, some
uncertainties still exist for the direct capture component in this reaction,
thus an independent measurement is of importance. In present work, the angular
distribution of the N()O reaction at = 8.9
MeV has been measured in inverse kinematics, for the first time. Based on the
distorted wave Born approximation (DWBA) analysis, the nuclear asymptotic
normalization coefficient (ANC), , for the ground state of
O N + is derived to be fm. The
N()O reaction is analyzed with the R-matrix approach,
its astrophysical S-factors and reaction rates at energies of astrophysical
relevance are then determined with the ANC. The implications of the present
reaction rates on the evolution of novae are then discussed with the reaction
network calculations.Comment: 17 pages and 8 figure
Nature of the Darwin term and contribution to the Lamb shift for an arbitrary spin of the nucleus
The contact Darwin term is demonstrated to be of the same origin as the
spin-orbit interaction. The correction to the Lamb shift,
generated by the Darwin term, is found for an arbitrary nonvanishing spin of
the nucleus, both half-integer and integer. There is also a contribution of the
same nature to the nuclear quadrupole moment.Comment: 9 pages, latex, no figure
The Lennard-Jones-Devonshire cell model revisited
We reanalyse the cell theory of Lennard-Jones and Devonshire and find that in
addition to the critical point originally reported for the 12-6 potential (and
widely quoted in standard textbooks), the model exhibits a further critical
point. We show that the latter is actually a more appropriate candidate for
liquid-gas criticality than the original critical point.Comment: 5 pages, 3 figures, submitted to Mol. Phy
Highly relativistic spinning particle starting near in a Kerr field
Using the Mathisson-Papapetrou-Dixon (MPD) equations, we investigate the
trajectories of a spinning particle starting near in a Kerr
field and moving with the velocity close to the velocity of light
( is the Boyer-Lindquist radial coordinate of the
counter-rotation circular photon orbits). First, as a partial case of these
trajectories, we consider the equatorial circular orbit with .
This orbit is described by the solution that is common for the rigorous MPD
equations and their linear spin approximation. Then different cases of the
nonequatorial motions are computed and illustrated by the typical figures. All
these orbits exhibit the effects of the significant gravitational repulsion
that are caused by the spin-gravity interaction. Possible applications in
astrophysics are discussed.Comment: 10 pages, 12 figure
Fluid/solid transition in a hard-core system
We prove that a system of particles in the plane, interacting only with a
certain hard-core constraint, undergoes a fluid/solid phase transition
Patterns and processes underlying evolutionary significant units in the Platypleura stridula L. species complex (Hemiptera: Cicadidae) in the Cape Floristic Region, South Africa
Cicadas have been shown to be useful organisms for examining the effects of distribution, plant association and geographical barriers on gene flow between populations. The cicadas of the Platypleura stridula species complex are restricted to the biologically diverse Cape Floristic Region (CFR) of South Africa. They are thus an excellent study group for elucidating the mechanisms by which hemipteran diversity is generated and maintained in the CFR. Phylogeographical analysis of this species complex using mitochondrial DNA Cytochrome Oxidase I (COI) and ribosomal 16S sequence data, coupled with preliminary morphological and acoustic data, resolves six clades, each of which has specific host-plant associations and distinct geographical ranges. The phylogeographical structure implies simultaneous or near-simultaneous radiation events, coupled with shifts in host-plant associations. When calibrated using published COI and 16S substitution rates typical for related insects, these lineages date back to the late Pliocene - early Pleistocene, coincident with vegetation change, altered drainage patterns and accelerated erosion in response to neotectonic crustal uplift and cyclic Pleistocene climate change, and glaciation-associated changes in climate and sea level
Absence of correlation between built-in electric dipole moment and quantum Stark effect in InAs/GaAs self-assembled quantum dots
We report significant deviations from the usual quadratic dependence of the
ground state interband transition energy on applied electric fields in
InAs/GaAs self-assembled quantum dots. In particular, we show that conventional
second-order perturbation theory fails to correctly describe the Stark shift
for electric field below kV/cm in high dots. Eight-band calculations demonstrate this effect is predominantly due to
the three-dimensional strain field distribution which for various dot shapes
and stoichiometric compositions drastically affects the hole ground state. Our
conclusions are supported by two independent experiments.Comment: 4 pages, 4 figure
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