2,862 research outputs found
Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins
We describe a new regime for low-field magnetoresistance in organic
semiconductors, in which the spin-relaxing effects of localized nuclear spins
and electronic spins interfere. The regime is studied by the controlled
addition of localized electronic spins to a material that exhibits substantial
room-temperature magnetoresistance (\%). Although initially the
magnetoresistance is suppressed by the doping, at intermediate doping there is
a regime where the magnetoresistance is insensitive to the doping level. For
much greater doping concentrations the magnetoresistance is fully suppressed.
The behavior is described within a theoretical model describing the effect of
carrier spin dynamics on the current
Tracking Fecal Pollution Sources in the Upper Reaches of the Horse Creek Watershed in Aiken County, SC
The Horse Creek watershed in Aiken County, SC, is known for its history of high coliform pollution. Previous studies have identified one particular tributary, Sand River, as being a major contributor to the upper portions of the watershed, but the source(s) remain unknown. Sand River drains Hitchcock Woods, an urban forest that is heavily used by equestrians; is transected by both old and new sewer lines; and is surrounded by older homes, some of which depend upon aging septic systems. In addition, Sand River in Hitchcock Woods receives an enormous volume of stormflow from the downtown area during rain events. This study focused on fecal pollution in two of Sand River’s smaller tributaries, Calico Creek and Cuthbert Branch
The Labour Government, the Treasury and the £6 pay policy of July 1975
The 1974-79 Labour Government was elected in a climate of opinion that was fiercely opposed to government intervention in the wage determination process, and was committed to the principles of free collective bargaining in its manifestoes. However, by December 1974 the Treasury was advocating a formal incomes policy, and by July 1975 the government had introduced a £6 flat rate pay norm. With reference to archival sources, the paper demonstrates that TUC and Labour Party opposition to incomes policy was reconciled with the Treasury's advocacy by limiting the Bank of England‟s intervention in the foreign exchange market when sterling came under pressure. This both helped to achieve the Treasury's objective of improving the competitiveness of British industry, and acted as a catalyst for the introduction of incomes policy because the slide could be attributed to a lack of market confidence in British counter-inflation policy
Correlation Between BATSE Hard X-ray Spectral and Timing Properties of Cygnus X-1
We have analyzed approximately 1100 days of Cygnus X-1 hard X-ray data
obtained with BATSE to study its rapid variability. We find for the first time
correlations between the slope of the spectrum and the hard X-ray intensity,
and between the spectral slope and the amplitude of the rapid variations of the
hard X-ray flux. We compare our results with expectations from current theories
of accretion onto black holes.Comment: 17 pages, 3 Postscript figures, uses aasms4.sty. Accepted for
publication in Astrophysical Journal Letter
Theory of Electron Spin Relaxation in ZnO
Doped ZnO is a promising material for spintronics applications. For such
applications, it is important to understand the spin dynamics and particularly
the spin coherence of this II-VI semiconductor. The spin lifetime
has been measured by optical orientation experiments, and it shows a surprising
non-monotonic behavior with temperature. We explain this behavior by invoking
spin exchange between localized and extended states. Interestingly, the effects
of spin-orbit coupling are by no means negligible, in spite of the relatively
small valence band splitting. This is due to the wurtzite crystal structure of
ZnO. Detailed analysis allows us to characterize the impurity binding energies
and densities, showing that optical orientation experiments can be used as a
characterization tool for semiconductor samples.Comment: 7 pages, 1 figure: minor changes Accepted by Phys. Rev.
The 1996 Soft State Transitions of Cygnus X-1
We report continuous monitoring of Cygnus X-1 in the 1.3 to 200 keV band
using ASM/RXTE and BATSE/CGRO for about 200 days from 1996 February 21 to 1996
early September. During this period Cygnus X-1 experienced a hard-to-soft and
then a soft-to-hard state transition. The low-energy X-ray (1.3-12 keV) and
high-energy X-ray (20-200 keV) fluxes are strongly anti-correlated during this
period. During the state transitions flux variations of about a factor of 5 and
15 were seen in the 1.3-3.0 keV and 100-200 keV bands, respectively, while the
average 4.8-12 keV flux remains almost unchanged. The net effect of this
pivoting is that the total 1.3-200 keV luminosity remained unchanged to within
about 15%. The bolometric luminosity in the soft state may be as high as 50-70%
above the hard state luminosity, after color corrections for the luminosity
below 1.3 keV. The blackbody component flux and temperature increase in the
soft state is probably caused by a combination of the optically thick disk mass
accretion rate increase and a decrease of the inner disk radius.Comment: 18 pages, 1 PostScript figure. Accepted for ApJ
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