799 research outputs found
Pressurized carbonization of coal liquefaction by-product materials: Fluor Advanced Liquefaction and Parsons' POGO processes
Experiments were performed to determine the results of carbonization under pressure of three coal liquefaction product (or by-product) materials and thus supply data needed as a design base for two concepts for advanced coal liquefaction plants. Solid-liquid separation underflow (SLSU) and solvent from a hydroextraction process were carbonized at 900/sup 0/F in an inert atmosphere at pressures up to 400 psig. Vacuum still bottoms from the H-Coal process were pyrolyzed at 1100/sup 0/F in a methane atmosphere at 400 psig. Results from carbonization of hydroextraction solvent and SLSU show that (1) only 1 to 7 percent of the solvent is degraded during carbonization at 900/sup 0/F and 400 psig, (2) the heavier fraction of the residue contributed the most toward coke formation, and (3) increased pressure increases the degree of coking of the heavier fractions. Results from pyrolysis of the vacuum still bottoms material at 1100/sup 0/F and 400 psig indicated that (1) small amounts of liquid are produced, (2) a significant quality of gas is produced, and (3) higher temperature will probably be required to produce free-flowing char
Constraints on Type Ia Supernova Models from X-ray Spectra of Galaxy Clusters
We present constraints on theoretical models of Type Ia supernovae using
spatially resolved ASCA X-ray spectroscopy of three galaxy clusters: Abell 496,
Abell 2199 and Abell 3571. All three clusters have central iron abundance
enhancements; an ensemble of abundance ratios are used to show that most of the
iron in the central regions of the clusters comes from SN Ia. These
observations are consistent with the suppressed galactic wind scenario proposed
by Dupke and White (1999). At the center of each cluster, simultaneous analysis
of spectra from all ASCA instruments shows that the nickel to iron abundance
ratio (normalized by the solar ratio) is Ni/Fe ~ 4. We use the nickel to iron
ratio as a discriminator between SN Ia explosion models: the Ni/Fe ratio of
ejecta from the "Convective Deflagration" model W7 is consistent with the
observations, while those of "delayed detonation" models are not consistent at
the 90% confidence level.Comment: 20 pages, 2 figures, accepted by The Astrophysical Journa
Multiple Smaller Missions as a Direct Pathway to Mars Sample Return
Recent discoveries by the Mars Exploration Rovers, Mars Express, Mars Odyssey, and Mars Reconnaissance Orbiter spacecraft include multiple, tantalizing astrobiological targets representing both past and present environments on Mars. The most desirable path to Mars Sample Return (MSR) would be to collect and return samples from that site which provides the clearest examples of the variety of rock types considered a high priority for sample return (pristine igneous, sedimentary, and hydrothermal). Here we propose an MSR architecture in which the next steps (potentially launched in 2018) would entail a series of smaller missions, including caching, to multiple landing sites to verify the presence of high priority sample return targets through in situ analyses. This alternative architecture to one flagship-class sample caching mission to a single site would preserve a direct path to MSR as stipulated by the Planetary Decadal Survey, while permitting investigation of diverse deposit types and providing comparison of the site of returned samples to other aqueous environments on early Mar
A search for resonant production of pairs in $4.8\ \rm{fb}^{-1}p\bar{p}\sqrt{s}=1.96\ \rm{TeV}$
We search for resonant production of tt pairs in 4.8 fb^{-1} integrated
luminosity of ppbar collision data at sqrt{s}=1.96 TeV in the lepton+jets decay
channel, where one top quark decays leptonically and the other hadronically. A
matrix element reconstruction technique is used; for each event a probability
density function (pdf) of the ttbar candidate invariant mass is sampled. These
pdfs are used to construct a likelihood function, whereby the cross section for
resonant ttbar production is estimated, given a hypothetical resonance mass and
width. The data indicate no evidence of resonant production of ttbar pairs. A
benchmark model of leptophobic Z \rightarrow ttbar is excluded with m_{Z'} <
900 GeV at 95% confidence level.Comment: accepted for publication in Physical Review D Sep 21, 201
Mineralogy, Petrology, Chronology, and Exposure History of the Chelyabinsk Meteorite and Parent Body
The Chelyabinsk meteorite fall on February 15, 2013 attracted much more attention worldwide than do most falls. A consortium led by JSC received 3 masses of Chelyabinsk (Chel-101, -102, -103) that were collected shortly after the fall and handled with care to minimize contamination. Initial studies were reported in 2013; we have studied these samples with a wide range of analytical techniques to better understand the mineralogy, petrology, chronology and exposure history of the Chelyabinsk parent body
A Self-Absorption Census of Cold HI Clouds in the Canadian Galactic Plane Survey
We present a 21cm line HI self-absorption (HISA) survey of cold atomic gas
within Galactic longitudes 75 to 146 degrees and latitudes -3 to +5 degrees. We
identify HISA as spatially and spectrally confined dark HI features and extract
it from the surrounding HI emission in the arcminute-resolution Canadian
Galactic Plane Survey (CGPS). We compile a catalog of the most significant
features in our survey and compare our detections against those in the
literature. Within the parameters of our search, we find nearly all previously
detected features and identify many new ones. The CGPS shows HISA in much
greater detail than any prior survey and allows both new and
previously-discovered features to be placed into the larger context of Galactic
structure. In space and radial velocity, faint HISA is detected virtually
everywhere that the HI emission background is sufficiently bright. This ambient
HISA population may arise from small turbulent fluctuations of temperature and
velocity in the neutral interstellar medium. By contrast, stronger HISA is
organized into discrete complexes, many of which follow a longitude-velocity
distribution that suggests they have been made visible by the velocity reversal
of the Perseus arm's spiral density wave. The cold HI revealed in this way may
have recently passed through the spiral shock and be on its way to forming
molecules and, eventually, new stars. This paper is the second in a series
examining HISA at high angular resolution. A companion paper (Paper III)
describes our HISA search and extraction algorithms in detail.Comment: 44 pages, including 13 figure pages; to appear in June 10 ApJ, volume
626; figure quality significantly reduced for astro-ph; for full resolution,
please see http://www.ras.ucalgary.ca/~gibson/hisa/cgps1_survey
Observation and Mass Measurement of the Baryon
We report the observation and measurement of the mass of the bottom, strange
baryon through the decay chain , where
, , and .
Evidence for observation is based on a signal whose probability of arising from
the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard
deviations. The mass is measured to be (stat.) (syst.) MeV/.Comment: Minor text changes for the second version. Accepted by Phys. Rev.
Let
Polarizations of J/psi and psi(2S) Mesons Produced in ppbar Collisions at 1.96 TeV
We have measured the polarizations of \jpsi and \psiprime mesons as
functions of their transverse momentum \pt when they are produced promptly in
the rapidity range with \pt \geq 5 \pgev. The analysis is performed
using a data sample with an integrated luminosity of about 800 \ipb collected
by the CDF II detector. For both vector mesons, we find that the polarizations
become increasingly longitudinal as \pt increases from 5 to 30 \pgev. These
results are compared to the predictions of nonrelativistic quantum
chromodynamics and other contemporary models. The effective polarizations of
\jpsi and \psiprime mesons from -hadron decays are also reported.Comment: 8 pages, 7 figures, published in Physical Review Letter
Measurement of and Production in Collisions at = 1.96 TeV
The Standard Model predictions for and production are
tested using an integrated luminosity of 200 pb of \ppbar collision data
collected at the Collider Detector at Fermilab. The cross sections are measured
selecting leptonic decays of the and bosons, and photons with
transverse energy GeV that are well separated from leptons. The
production cross sections and kinematic distributions for the and
are compared to SM predictions.Comment: 7 pages, 4 figures, submitted to PR
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