169,245 research outputs found
Surveyor landing radar test program review Final report
Test program evaluation and modifications for Surveyor radar altimeter and Doppler velocity sensor syste
Charge and spin state readout of a double quantum dot coupled to a resonator
State readout is a key requirement for a quantum computer. For
semiconductor-based qubit devices it is usually accomplished using a separate
mesoscopic electrometer. Here we demonstrate a simple detection scheme in which
a radio-frequency resonant circuit coupled to a semiconductor double quantum
dot is used to probe its charge and spin states. These results demonstrate a
new non-invasive technique for measuring charge and spin states in quantum dot
systems without requiring a separate mesoscopic detector
NGC 4314. III. Inflowing Molecular Gas Feeding a Nuclear Ring of Star Formation
NGC 4314 is an early-type barred galaxy containing a nuclear ring of recent
star formation. We present CO(1-0) interferometer data of the bar and
circumnuclear region with 2.3 x 2.2 arcsec spatial resolution and 13 km/s
velocity resolution acquired at the Owens Valley Radio Observatory . These data
reveal a clumpy circumnuclear ring of molecular gas. We also find a peak of CO
inside the ring within 2 arcsec of the optical center that is not associated
with massive star formation. We construct a rotation curve from these CO
kinematic data and the mass model of Combes et al. (1992). Using this rotation
curve, we have identified the location of orbital resonances in the galaxy.
Assuming that the bar ends at corotation, the circumnuclear ring of star
formation lies between two Inner Lindblad Resonances, while the nuclear stellar
bar ends near the IILR. Deviations from circular motion are detected just
beyond the CO and H-alpha ring, where the dust lanes along the leading edge of
the bar intersect the nuclear ring. These non-circular motions along the minor
axis correspond to radially inward streaming motions at speeds of 20 - 90 km/s
and clearly show inflowing gas feeding an ILR ring. There are bright HII
regions near the ends of this inflow region, perhaps indicating triggering of
star formation by the inflow.Comment: 25 pages, uses aasms.sty. 7 Postscript figures, 12 JPEG figures.
Figures may be retrieved from
ftp://clyde.as.utexas.edu/pub/N4314COfigs.tar.g
SOUTHERN FARMERS EXPOSURE TO INCOME RISK UNDER THE 1996 FARM BILL
Arguably, since the 1930s, what farmers produced has been markedly influenced by farm programs. The 1996 farm bill affects farmers in terms of what they produce and their level of risk exposure. This paper investigates the farm level impacts of the 1996 farm bill on the South. Focus group perceptions of risk sources, observed acreage changes, and the farm level impact of increased price risk are evaluated.Agricultural and Food Policy, Agricultural Finance,
Mapping warm molecular hydrogen with Spitzer's Infrared Array Camera (IRAC)
Photometric maps, obtained with Spitzer's Infrared Array Camera (IRAC), can
provide a valuable probe of warm molecular hydrogen within the interstellar
medium. IRAC maps of the supernova remnant IC443, extracted from the Spitzer
archive, are strikingly similar to spectral line maps of the H2 pure rotational
transitions that we obtained with the Infrared Spectrograph (IRS) instrument on
Spitzer. IRS spectroscopy indicates that IRAC Bands 3 and 4 are indeed
dominated by the H2 v=0-0 S(5) and S(7) transitions, respectively. Modeling of
the H2 excitation suggests that Bands 1 and 2 are dominated by H2 v=1-0 O(5)
and v=0-0 S(9). Large maps of the H2 emission in IC433, obtained with IRAC,
show band ratios that are inconsistent with the presence of gas at a single
temperature. The relative strengths of IRAC Bands 2, 3, and 4 are consistent
with pure H2 emission from shocked material with a power-law distribution of
gas temperatures. CO vibrational emissions do not contribute significantly to
the observed Band 2 intensity. Assuming that the column density of H2 at
temperatures T to T+dT is proportional to T raised to the power -b for
temperatures up to 4000 K, we obtained a typical estimate of 4.5 for b. The
power-law index, b, shows variations over the range 3 to 6 within the set of
different sight-lines probed by the maps, with the majority of sight-lines
showing b in the range 4 to 5. The observed power-law index is consistent with
the predictions of simple models for paraboloidal bow shocks.Comment: 27 pages, including 11 figures. Accepted for publication in Ap
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