741 research outputs found
Center for the Advancement and Study of Tourism
The Center for the Advancement and Study of Tourism (CAST) was established in 1988 as part of the Governor\u27s economic development plan to stimulate tourism as a local and national industry. CAST was awarded a grant from the South Dakota Office of Economic Development to support the three primary Center activities: educational training, community outreach, and research. It is located at Black Hills State University and is funded by the state and by other grant monies
Proper Motions of PSRs B1757-24 and B1951+32: Implications for Ages and Associations
Over the last decade, considerable effort has been made to measure the proper
motions of the pulsars B1757-24 and B1951+32 in order to establish or refute
associations with nearby supernova remnants and to understand better the
complicated geometries of their surrounding nebulae. We present proper motion
measurements of both pulsars with the Very Large Array, increasing the time
baselines of the measurements from 3.9 yr to 6.5 yr and from 12.0 yr to 14.5
yr, respectively, compared to previous observations. We confirm the
non-detection of proper motion of PSR B1757-24, and our measurement of (mu_a,
mu_d) = (-11 +/- 9, -1 +/- 15) mas yr^{-1} confirms that the association of PSR
B1757-24 with SNR G5.4-1.2 is unlikely for the pulsar characteristic age of
15.5 kyr, although an association can not be excluded for a significantly
larger age. For PSR B1951+32, we measure a proper motion of (mu_a, mu_d) =
(-28.8 +/- 0.9, -14.7 +/- 0.9) mas yr^{-1}, reducing the uncertainty in the
proper motion by a factor of two compared to previous results. After correcting
to the local standard of rest, the proper motion indicates a kinetic age of ~51
kyr for the pulsar, assuming it was born near the geometric center of the
supernova remnant. The radio-bright arc of emission along the pulsar proper
motion vector shows time-variable structure, but moves with the pulsar at an
approximately constant separation ~2.5", lending weight to its interpretation
as a shock structure driven by the pulsar.Comment: LaTeX file uses emulateapj.cls; 7 pages, 4 figures, to be published
ApJ February 10, 2008, v674 p271-278. Revision reflects journal formatting;
there are no substantial revision
The pediatric asthma yardstick: Practical recommendations for a sustained step-up in asthma therapy for children with inadequately controlled asthma
A Proper Motion for the Pulsar Wind Nebula G359.23-0.82, "the Mouse," Associated with the Energetic Radio Pulsar J1747-2958
The "Mouse" (PWN G359.23-0.82) is a spectacular bow shock pulsar wind nebula,
powered by the radio pulsar J1747-2958. The pulsar and its nebula are presumed
to have a high space velocity, but their proper motions have not been directly
measured. Here we present 8.5 GHz interferometric observations of the Mouse
nebula with the Very Large Array, spanning a time baseline of 12 yr. We measure
eastward proper motion for PWN G359.23-0.82 (and hence indirectly for PSR
J1747-2958) of 12.9+/-1.8 mas/yr, which at an assumed distance of 5 kpc
corresponds to a transverse space velocity of 306+/-43 km/s. Considering
pressure balance at the apex of the bow shock, we calculate an in situ hydrogen
number density of approximately 1.0(-0.2)(+0.4) cm^(-3) for the interstellar
medium through which the system is traveling. A lower age limit for PSR
J1747-2958 of 163(-20)(+28) kyr is calculated by considering its potential
birth site. The large discrepancy with the pulsar's spin-down age of 25 kyr is
possibly explained by surface dipole magnetic field growth on a timescale ~15
kyr, suggesting possible future evolution of PSR J1747-2958 to a different
class of neutron star. We also argue that the adjacent supernova remnant
G359.1-0.5 is not physically associated with the Mouse system but is rather an
unrelated object along the line of sight.Comment: 8 pages, 4 figures, emulateapj format. Accepted for publication in
The Astrophysical Journa
Quantum state engineering on an optical transition and decoherence in a Paul trap
A single Ca+ ion in a Paul trap has been cooled to the ground state of
vibration with up to 99.9% probability. Starting from this Fock state |n=0> we
have demonstrated coherent quantum state manipulation on an optical transition.
Up to 30 Rabi oscillations within 1.4 ms have been observed. We find a similar
number of Rabi oscillations after preparation of the ion in the |n=1> Fock
state. The coherence of optical state manipulation is only limited by laser and
ambient magnetic field fluctuations. Motional heating has been measured to be
as low as one vibrational quantum in 190 ms.Comment: 4 pages, 5 figure
Association of asthma symptoms with peak particulate air pollution and effect modification by anti-inflammatory medication use.
Maxima of hourly data from outdoor monitors may capture adverse effects of outdoor particulate matter (PM) exposures in asthmatic children better than do 24-hr PM averages, which form the basis of current regulations in the United States. Also, asthmatic children on anti-inflammatory medications may be protected against the proinflammatory effects of air pollutants and aeroallergens. We examined strengths of pollutant associations with asthma symptoms between subgroups of asthmatic children who were on versus not on regularly scheduled anti-inflammatory medications, and tested associations for different particle averaging times. This is a daily panel study of 22 asthmatic children (9-19 years of age) followed March through April 1996 (1,248 person-days). They lived in nonsmoking households in a semirural area of Southern California within the air inversion mixing zone (range, 1,200-2,100 feet) with transported air pollution from urban areas of Southern California. The dependent variable derived from diary ordinal scores is episodes of asthma symptoms that interfered with daily activities. Minimum to 90th-percentile levels of exposures at the outdoor monitoring site were 12-63 microg/m(3) for 1-hr PM < 10 microm in aerodynamic diameter (PM(10)); 8-46 microg/m(3) for 8-hr PM(10); 7-32 microg/m(3) for 24-hr PM(10); 45-88 ppb for 1-hr O(3); 6-26 ppb for 8-hr NO(2); 70-4,714 particles/m(3) for 12-hr daytime fungi; and 12-744 particles/m(3) for 24-hr pollen. Data were analyzed with generalized estimating equations controlling for autocorrelation. There was no confounding by weather, day of week, or linear time trend. Associations were notably stronger in 12 asthmatic children who were not taking anti-inflammatory medications versus 10 subjects who were. Odds ratios (95% confidence intervals) for asthma episodes in relation to lag 0 minimum to 90th-percentile pollutant changes were, respectively, 1-hr maximum PM(10), 1.92 (1.22-3.02) versus 0.96 (0.25-3.69); 8-hr maximum PM(10), 1.68 (0.91-3.09) versus 0.75 (0.18-3.04); 24-hr average PM(10), 1.35 (0.82-2.22) versus 0.80 (0.24-2.69); 1-hr maximum O(3), 1.28 (0.75-2.17) versus 0.76 (0.24-2.44); 8-hr maximum NO(2), 1.91 (1.07-3.39) versus 1.08 (0.30-3.93); 12-hr fungi, 1.89 (1.24-2.89) versus 0.90 (0.35-2.30); 24-hr pollen, 1.90 (0.99-3.67) versus 0.85 (0.18-3.91). Pollutant associations were stronger during respiratory infections in subjects not on anti-inflammatory medications. Although lag 0 1-hr maximum PM(10) showed the strongest association, the most robust associations were for lag 0 and 3-day moving averages (lags 0-2) of 8-hr maximum and 24-hr mean PM(10) in sensitivity analyses testing for thresholds. Most pollutant effects were largely driven by concentrations in the upper quintile. The divergence of exposure-response relationships by anti-inflammatory medication use is consistent with experimental data on inflammatory mechanisms of airborne pollutants and allergens
Calculations of the A_1 phonon frequency in photoexcited Tellurium
Calculations of the A_1 phonon frequency in photoexcited tellurium are
presented. The phonon frequency as a function of photoexcited carrier density
and phonon amplitude is determined. Recent pump probe experiments are
interpreted in the light of these calculatons. It is proposed that, in
conjunction with measurements of the phonon period in ultra-fast pump-probe
reflectivity experiments, the calculated frequency shifts can be used to infer
the evolution of the density of photoexcited carriers on a sub-picosecond
time-scale.Comment: 15 pages Latex, 3 postscript figure
Physical properties of misfit-layered (Bi,Pb)-Sr-Co-O system: Effect of hole doping into triangular lattice formed by low-spin Co ions
Pb-doping effect on physical properties of misfit-layered (Bi,Pb)-Sr-Co-O
system, in which Co ions form a two-dimensional triangular lattice, was
investigated in detail by electronic transport, magnetization and specific-heat
measurements. Pb doping enhances the metallic behavior, suggesting that
carriers are doped. Pb doping also enhances the magnetic correlation in this
system and increases the magnetic transition temperature. We found the
existence of the short-range magnetic correlation far above the transition
temperature, which seems to induce the spin-glass state coexisting with the
ferromagnetic long-range order at low temperatures. Specific-heat measurement
suggests that the effective mass of the carrier in (Bi,Pb)-Sr-Co-O is not
enhanced so much as reported in NaCoO. Based on these experimental
results, we propose a two-bands model which consists of narrow and
rather broad bands. The observed magnetic property and
magnetotransport phenomena are explained well by this model
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