2,954 research outputs found
An Increasingly Negative Outlook: How Income Inequality Affects Personal Consumption Expenditures
This paper analyzes the effects of income inequality on real personal consumption expenditures (RPCE) within the United States. At first glance, income inequality and RPCE have both risen over time. This paper examines whether income inequality actually causes growth in RPCE. We created a time-series model explaining RPCE with six explanatory variables and data spanning 37 years. Using this model, we were able to determine that income inequality has a statistically significant effect on RPCE. This effect becomes increasingly negative when the distribution of income becomes less equal and there is growth in real income. Thus, our results refute the possibility that income inequality has a positive effect on RPCE
Discovery of Pulsed X-ray Emission from the SMC Transient RX J0117.6-7330
We report on the detection of pulsed, broad-band, X-ray emission from the
transient source RX J0117.6-7330. The pulse period of 22 seconds is detected by
the ROSAT/PSPC instrument in a 1992 Sep 30 - Oct 2 observation and by the
CGRO/BATSE instrument during the same epoch. Hard X-ray pulsations are
detectable by BATSE for approximately 100 days surrounding the ROSAT
observation (1992 Aug 28 - Dec 8). The total directly measured X-ray luminosity
during the ROSAT observation is 1.0E38 (d/60 kpc)^2 ergs s-1. The pulse
frequency increases rapidly during the outburst, with a peak spin-up rate of
1.2E-10 Hz s-1 and a total frequency change 1.8%. The pulsed percentage is
11.3% from 0.1-2.5 keV, increasing to at least 78% in the 20-70 keV band. These
results establish RX J0117.6-7330 as a transient Be binary system.Comment: 17 pages, Latex, aasms, accepted for publication in ApJ Letter
Identifying Fecal Pollution Sources through Antibiotic Resistance Analysis (ARA): Sand River, Aiken County, SC
2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen
The Burst and Transient Source Experiment Earth Occultation Technique
An Earth orbiting detector sensitive to gamma ray photons will see step-like
occultation features in its counting rate when a gamma ray point source crosses
the Earth's limb. This is due to the change in atmospheric attenuation of the
gamma rays along the line of sight. In an uncollimated detector, these
occultation features can be used to locate and monitor astrophysical sources
provided their signals can be individually separated from the detector
background. We show that the Earth occultation technique applied to the Burst
and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory
(CGRO) is a viable and flexible all-sky monitor in the low energy gamma ray and
hard X-ray energy range (20 keV - 1 MeV). The method is an alternative to more
sophisticated photon imaging devices for astronomy, and can serve well as a
cost-effective science capability for monitoring the high energy sky.
Here we describe the Earth occultation technique for locating new sources and
for measuring source intensity and spectra without the use of complex
background models. Examples of transform imaging, step searches, spectra, and
light curves are presented. Systematic uncertainties due to source confusion,
detector response, and contamination from rapid background fluctuations are
discussed and analyzed for their effect on intensity measurements. A sky
location-dependent average systematic error is derived as a function of
galactic coordinates. The sensitivity of the technique is derived as a function
of incident photon energy and also as a function of angle between the source
and the normal to the detector entrance window. Occultations of the Crab Nebula
by the Moon are used to calibrate Earth occultation flux measurements
independent of possible atmospheric scattering effects.Comment: 39 pages, 24 figures. Accepted for publication in the Astrophysical
Journal Supplement
Surface-driven electronic structure in LaFeAsO studied by angle resolved photoemission spectroscopy
We measured the electronic structure of an iron arsenic parent compound
LaFeAsO using angle resolved photoemission spectroscopy (ARPES). By comparing
with a full-potential Linear Augmented PlaneWave calculation we show that the
extra large Gamma hole pocket measured via ARPES comes from electronic
structure at the sample surface. Based on this we discuss the strong
polarization dependence of the band structure and a temperature-dependent
hole-like band around the M point. The two phenomena give additional evidences
for the existence of the surface-driven electronic structure.Comment: 6 pages, 6 figure
Instability Heating of Sympathetically-Cooled Ions in a Linear Paul Trap
Sympathetic laser cooling of ions stored within a linear-geometry, radio
frequency, electric-quadrupole trap has been investigated using computational
and theoretical techniques. The simulation, which allows 5 sample ions to
interact with 35 laser-cooled atomic ions, revealed an instability heating
mechanism, which can prevent ions below a certain critical mass from being
sympathetically cooled. This critical mass can however be varied by changing
the trapping field parameters thus allowing ions with a very large range of
masses to be sympathetically cooled using a single ion species. A theoretical
explanation of this instability heating mechanism is presented which predicts
that the cooling-heating boundary in trapping parameter space is a line of
constant (ion trap stability coefficient), a result supported by the
computational results. The threshold value of depends on the masses of
the interacting ions. A functional form of this dependence is given
Gamma ray monitoring of a AGN and galactic black hole candidates by the Compton Gamma Ray Observatory
The Compton Gamma-Ray Observatory's Burst and Transient Source Experiment (BATSE) has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both active galactic nuclei (AGN) and galactic black hole candidates (GBHC) such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Since the Crab is detected by the BATSE Large Area Detectors with roughly 25(sigma) significance in the 15-125 keV range in a single rise or set, a variation by a factor of two of a source having one-tenth the strength of Cygnus X-1 should be detectable within a day. Methods of modeling the background are discussed which will increase the accuracy, sensitivity, and reliability of the results beyond those obtainable from a linear background fit with a single rise or set discontinuity
Magnetism dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
The phonon dispersion was measured at room temperature along (0,0,L) in the
tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized
first-principles calculations imposing various types of antiferromagnetic order
are in better agreement with the experimental results than nonmagnetic
calculations, although the measurements were made well above the magnetic
ordering temperature, T_N. Splitting observed between two A_{1g} phonon modes
at 22 and 26 meV is only observed in spin-polarized calculations.
Magneto-structural effects similar to those observed in the AFe_2As_2 materials
are confirmed present in LaFeAsO. The presence of Fe-spin is necessary to find
reasonable agreement of the calculations with the measured spectrum well above
T_N. On-site Fe and As force constants show significant softening compared to
nonmagnetic calculations, however an investigation of the real-space force
constants associates the magnetoelastic coupling with a complex renormalization
instead of softening of a specific pairwise force.Comment: 7 pages, 4 figure
Diffuse Galactic Soft Gamma-Ray Emission
The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured
from the Galactic Center by the HIREGS balloon-borne germanium spectrometer to
determine the spectral characteristics and origin of the emission. The
resulting Galactic diffuse continuum is found to agree well with a single
power-law (plus positronium) over the entire energy range, consistent with RXTE
and COMPTEL/CGRO observations at lower and higher energies, respectively. We
find no evidence of spectral steepening below 200 keV, as has been reported in
previous observations. The spatial distribution along the Galactic ridge is
found to be nearly flat, with upper limits set on the longitudinal gradient,
and with no evidence of an edge in the observed region. The soft gamma-ray
diffuse spectrum is well modeled by inverse Compton scattering of interstellar
radiation off of cosmic-ray electrons, minimizing the need to invoke
inefficient nonthermal bremsstrahlung emission. The resulting power requirement
is well within that provided by Galactic supernovae. We speculate that the
measured spectrum provides the first direct constraints on the cosmic-ray
electron spectrum below 300 MeV.Comment: 26 pages, 7 figure, submitted to Ap
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