12,414 research outputs found
X-ray iron-line emission from the SN 185 remnant
Radio and optical research was carried out in order to show that the supernova remnant RCW86 is a remnant of the earliest supernova event ever recorded in history (185 AD). The results are as follows: (1) an iron-line emission was found at 6.7 keV; (2) the temperature measured from HEAO-1 was approximately 6 keV; and (3) the equivalent width was consistent within the uncertainties with a cosmic iron abundance. These results support the identification of the supernova remnant RCW86 (it's X-ray source) with the historic supernova event
Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings
We measure an anomalous magnetoresistance peak within the lowest Landau level
(nu = 1) minimum of a two-dimensional hole system on (110) GaAs.
Self-consistent calculations of the valence band mixing show that the two
lowest spin-index Landau levels anticross in a perpendicular magnetic field B
consistent with where the experimental peak is measured, Bp. The temperature
dependence of the anomalous peak height is interpreted as an activated behavior
across this anticrossing gap. Calculations of the spin polarization in the
lowest Landau levels predict a rapid switch from about -3/2 to +3/2 spin at the
anticrossing. The peak position Bp is shown to be affected by the confinement
electrostatics, and the utility of a tunable anticrossing position for
spintronics applications is discussed.Comment: 4 pages, 4 figure
Oat variety characteristics for suppressing weeds
Oats are a valuable food source and useful in the crop rotation both in organic and conventional farming systems, partly because of their excellent weed suppression ability. Thomas Döring, Louisa Winkler and Nick Fradgley report new results that show how plant breeding can make oats even better
Attack of \u3ci\u3eUrophora Quadrifasciata\u3c/i\u3e (Meig.) (Diiptera: Tephritidae) A Biological Control Agent for Spotted Knapweed (\u3ci\u3eCentaurea Maculosa\u3c/i\u3e Lamarck) and Diffuse Knapweed (\u3ci\u3eC. Diffusa\u3c/i\u3e Lamarck) (Asteraceae) by a Parasitoid, \u3ci\u3ePteromalus\u3c/i\u3e Sp. (Hymenoptera: Pteromalidae) in Michigan
Urophora quadrifasciata (Meig.) a seedhead fly released in North America for biological control of Centaurea maculosa and C. diffusa is parasitized by a Pteromalus sp. Parasitism up to 60% of U. quadrifasciata was found in samples of seed heads of C. maculosa and C. diffusa collected from 54 of the 59 counties sampled in Michigan and in one sample of C. maculosa seed heads from Hennepin County, Minnesota. Parasitism of U. quadrifasciata has rarely been reported
Anomalous Rashba spin splitting in two-dimensional hole systems
It has long been assumed that the inversion asymmetry-induced Rashba spin
splitting in two-dimensional (2D) systems at zero magnetic field is
proportional to the electric field that characterizes the inversion asymmetry
of the confining potential. Here we demonstrate, both theoretically and
experimentally, that 2D heavy hole systems in accumulation layer-like single
heterostructures show the opposite behavior, i.e., a decreasing, but nonzero
electric field results in an increasing Rashba coefficient.Comment: 4 pages, 3 figure
High density limit of the two-dimensional electron liquid with Rashba spin-orbit coupling
We discuss by analytic means the theory of the high-density limit of the
unpolarized two-dimensional electron liquid in the presence of Rashba or
Dresselhaus spin-orbit coupling. A generalization of the ring-diagram expansion
is performed. We find that in this regime the spin-orbit coupling leads to
small changes of the exchange and correlation energy contributions, while
modifying also, via repopulation of the momentum states, the noninteracting
energy. As a result, the leading corrections to the chirality and total energy
of the system stem from the Hartree-Fock contributions. The final results are
found to be vanishing to lowest order in the spin-orbit coupling, in agreement
with a general property valid to every order in the electron-electron
interaction. We also show that recent quantum Monte Carlo data in the presence
of Rashba spin-orbit coupling are well understood by neglecting corrections to
the exchange-correlation energy, even at low density values.Comment: 11 pages, 5 figure
Rashba spin splitting in biased semiconductor quantum wells
Rashba spin splitting (RSS) in biased semiconductor quantum wells is
investigated theoretically based on the eight-band envelope function model. We
find that at large wave vectors, RSS is both nonmonotonic and anisotropic as a
function of in-plane wave vector, in contrast to the widely used linear and
isotropic model. We derive an analytical expression for RSS, which can
correctly reproduce such nonmonotonic behavior at large wave vectors. We also
investigate numerically the dependence of RSS on the various band parameters
and find that RSS increases with decreasing band gap and subband index,
increasing valence band offset, external electric field, and well width. Our
analytical expression for RSS provides a satisfactory explanation to all these
features.Comment: 5 pages, 4 figures, author names corrected, submitted to Phys. Rev.
First results of observations of transient pulsar SAXJ2103.5+4545 with the INTEGRAL observatory
We present preliminary results of observations of X-ray pulsar SAX
J2103.5+4545 with INTEGRAL observatory in Dec 2002. Maps of this sky region in
energy bands 3-10, 15-40, 40-100 and 100-200 keV are presented. The source is
significantly detected up to energies of keV. The hard X-ray flux in
the 15-100 energy band is variable, that could be connected with the orbital
phase of the binary system. We roughly reconstructed the source spectrum using
its comparison to that of Crab nebula. It is shown that the parameters of the
source spectrum in 18-150 keV energy range are compatible with that obtained
earlier by RXTE observatoryComment: 5 pages, 4 figures, accepted for publication in the Astronomy Letter
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