2,523 research outputs found
A Semiparametric Approach to Estimate Engel curves using the US Micro Data
The study estimates Engel curves using cross-section data from the 2003 US consumer expenditure survey (CES). We focus on finding adequate specification for modeling the demographic characteristics using parametric, nonparametric, and semiparametric techniques. The empirical results indicate parametric Working-Leser or Piglog specification was sufficient for most budget shares except for transportation where semiparametric specification had support.Consumer/Household Economics,
Development of a superconductor magnetic suspension and balance prototype facility for studying the feasibility of applying this technique to large scale aerodynamic testing
The basic research and development work towards proving the feasibility of operating an all-superconductor magnetic suspension and balance device for aerodynamic testing is presented. The feasibility of applying a quasi-six-degree-of freedom free support technique to dynamic stability research was studied along with the design concepts and parameters for applying magnetic suspension techniques to large-scale aerodynamic facilities. A prototype aerodynamic test facility was implemented. Relevant aspects of the development of the prototype facility are described in three sections: (1) design characteristics; (2) operational characteristics; and (3) scaling to larger facilities
The APEX-CHAMP+ view of the Orion Molecular Cloud 1 core - Constraining the excitation with submillimeter CO multi-line observations
A high density portion of the Orion Molecular Cloud 1 (OMC-1) contains the
prominent, warm Kleinmann-Low (KL) nebula that is internally powered by an
energetic event plus a farther region in which intermediate to high mass stars
are forming. Its outside is affected by ultraviolet radiation from the
neighboring Orion Nebula Cluster and forms the archetypical photon-dominated
region (PDR) with the prominent bar feature. Its nearness makes the OMC-1 core
region a touchstone for research on the dense molecular interstellar medium and
PDRs. Using the Atacama Pathfinder Experiment telescope (APEX), we have imaged
the line emission from the multiple transitions of several carbon monoxide (CO)
isotopologues over the OMC-1 core region. Our observations employed the 2x7
pixel submillimeter CHAMP+ array to produce maps (~ 300 arcsec x 350 arcsec) of
12CO, 13CO, and C18O from mid-J transitions (J=6-5 to 8-7). We also obtained
the 13CO and C18O J=3-2 images toward this region. The 12CO line emission shows
a well-defined structure which is shaped and excited by a variety of phenomena,
including the energetic photons from hot, massive stars in the nearby Orion
Nebula's central Trapezium cluster, active high- and intermediate-mass star
formation, and a past energetic event that excites the KL nebula. Radiative
transfer modeling of the various isotopologic CO lines implies typical H2
densities in the OMC-1 core region of ~10^4-10^6 cm^-3 and generally elevated
temperatures (~ 50-250 K). We estimate a warm gas mass in the OMC-1 core region
of 86-285 solar masses.Comment: 11 pages, 9 figures, accepted by A&
Decaying neutralino dark matter in anomalous models
In supersymmetric models extended with an anomalous different
R-parity violating couplings can yield an unstable neutralino. We show that in
this context astrophysical and cosmological constraints on neutralino decaying
dark matter forbid bilinear R-parity breaking neutralino decays and lead to a
class of purely trilinear R-parity violating scenarios in which the neutralino
is stable on cosmological scales. We have found that among the resulting models
some of them become suitable to explain the observed anomalies in cosmic-ray
electron/positron fluxes.Comment: 19 pages, 3 figures. References added, typos corrected, accepted
version in Phys Rev
Camp Elizabeth, Sterling County, Texas: An Archaeological and Archival Investigation of a U.S. Army Subpost, and Evidence Supporting Its Use by the Military and Buffalo Soldiers
The Center for Archaeological Research (CAR) of The University of Texas at San Antonio (UTSA) engaged in a two-phase contract with the Texas Department of Transportation (TxDOT) to complete archaeological and archival investigations of the Camp at the Head of the North Concho (41 STIll). The camp, known locally as Camp Elizabeth, was a military outpost of Fort Concho in San Angelo, Texas, and is now located approximately nine miles northwest of Sterling City along V.S. Highway 87. The camp lies within the right-of-way along V.S. 87 that will be impacted by a highway improvement project.
CAR\u27s archaeological and archival investigations confirmed the presence of the former military occupation of the camp during the late-nineteenth century. No evidence supporting a legendary presence of the Texas Rangers at Camp Elizabeth was found. Archival evidence that the Buffalo Soldiers, African-American troops, were stationed at Camp Elizabeth is presented. Archaeological excavations identified numerous features, including a farrier\u27s shop
Classical and Non-Relativistic Limits of a Lorentz-Invariant Bohmian Model for a System of Spinless Particles
A completely Lorentz-invariant Bohmian model has been proposed recently for
the case of a system of non-interacting spinless particles, obeying
Klein-Gordon equations. It is based on a multi-temporal formalism and on the
idea of treating the squared norm of the wave function as a space-time
probability density. The particle's configurations evolve in space-time in
terms of a parameter {\sigma}, with dimensions of time. In this work this model
is further analyzed and extended to the case of an interaction with an external
electromagnetic field. The physical meaning of {\sigma} is explored. Two
special situations are studied in depth: (1) the classical limit, where the
Einsteinian Mechanics of Special Relativity is recovered and the parameter
{\sigma} is shown to tend to the particle's proper time; and (2) the
non-relativistic limit, where it is obtained a model very similar to the usual
non-relativistic Bohmian Mechanics but with the time of the frame of reference
replaced by {\sigma} as the dynamical temporal parameter
A rotating molecular jet in Orion
We present CO(2-1), CO(2-1), CO(6-5), CO(7-6), and SO(6) line
observations made with the {\it IRAM 30 m} and {\it APEX} radiotelescopes and
the {\it Submillimeter Array} toward the highly collimated and extended
southwest lobe of the bipolar outflow {\it Ori-S6} located in the Orion South
region. We report, for all these lines, the detection of velocity asymmetries
about the flow axis, with velocity differences roughly on the order of 1 km
s over distances of about 5000 AU, 4 km s over distances of about
2000 AU, and close to the source of between 7 and 11 km s over smaller
scales of about 1000 AU. We interpret these velocity differences as a signature
of rotation but also discuss some alternatives which we recognize as unlikely
in view of the asymmetries' large downstream continuation. This rotation across
the {\it Ori-S6} outflow is observed out to (projected) distances beyond 2.5
10 AU from the flow's presumed origin. Comparison of our
large-scale and small-scale observations suggests the rotational velocity to
decline not faster than 1/R with distance R from the axis; in the innermost few
arcsecs an increase of rotational velocity with R is even indicated. The
magnetic field lines threading the inner rotating CO shell may well be anchored
in a disk of radius 50 AU; the field lines further out need a more
extended rotating base.Comment: Accepted by Astronomy and Astrophysic
Orion KL: The hot core that is not a "Hot Core"
We present sensitive high angular resolution submillimeter and millimeter
observations of torsionally/vibrationally highly excited lines of the CHOH,
HCN, SO, and CHCN molecules and of the continuum emission at 870
and 1300 m from the Orion KL region, made with the Submillimeter Array
(SMA). These observations plus recent SMA CO J=3-2 and J=2-1 imaging of the
explosive flow originating in this region, which is related to the
non-hierarchical disintegration of a massive young stellar system, suggest that
the molecular Orion "Hot Core" is a pre-existing density enhancement heated
from the outside by the explosive event -- unlike in other hot cores we do not
find any self-luminous submillimeter, radio or infrared source embedded in the
hot molecular gas. Indeed, we do not observe filamentary CO flow structures or
"fingers" in the shadow of the hot core pointing away from the explosion
center. The low-excitation CHCN emission shows the typical molecular
heart-shaped structure, traditionally named the Hot Core, and is centered close
to the dynamical origin of the explosion. The highest excitation CHCN lines
are all arising from the northeast lobe of the heart-shaped structure, {\it i.
e.} from the densest and most highly obscured parts of the Extended Ridge. The
torsionally excited CHOH and vibrationally excited HCN lines appear to
form a shell around the strongest submillimeter continuum source. Surprisingly
the kinematics of the Hot Core and Compact Ridge regions as traced by CHCN
and HCN also reveal filament-like structures that emerge from the dynamical
origin. All of these observations suggest the southeast and southwest sectors
of the explosive flow to have impinged on a pre-existing very dense part of the
Extended Ridge, thus creating the bright Orion KL Hot Core.Comment: Submitted to A&
Determination of nanogram microparticles from explosives after real open-air explosions by confocal Raman microscopy
Explosives are increasingly being used for terrorist attacks to cause devastating explosions. The detection of their post-blast residues after an explosion is a high challenge, which has been barely investigated, particularly using spectroscopic techniques. In this research, a novel methodology using confocal Raman microscopy has been developed for the analysis of post-blast residues from ten open-air explosions caused by ten different explosives (TNT, RDX, PETN, TATP, HMTD, dynamite, black powder, ANFO, chloratite, and ammonal) commonly used in improvised explosive devices. The methodology for the determination of post-blast particles from explosives consisted of examining the samples surfaces with both the naked eye, first, and microscopically (10x and 50x), immediately afterward; and finally, analysing the selected residues by confocal Raman spectroscopy in order to identify the post-blast particles from explosives. Interestingly, confocal Raman microscopy has demonstrated to be highly suitable to rapidly, selectively and non-invasively analyse post-blast microscopic particles from explosives up to the nanogram range
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