1,874 research outputs found
A massive high density effective theory
We derive an effective theory for dense, cold and massive quark matter. To
this end, we employ a general effective action formalism where antiquarks and
quarks far from the Fermi surface, as well as hard gluons, are integrated out
explicitly. We show that the resulting effective action depends crucially on
the projectors used to separate quarks from antiquarks. If one neglects the
quark masses in these projectors, the Feynman rules of the effective theory
involve quark mass insertions which connect quark with antiquark propagators.
Including the quark masses into these projectors, mass insertions do not appear
and the Feynman rules are identical to those found in the zero-mass limit.Comment: 7 pages, 6 figure
Technology transfer: Transportation
Standard Research Institute (SRI) has operated a NASA-sponsored team for four years. The SRI Team is concentrating on solving problems in the public transportation area and on developing methods for decreasing the time gap between the development and the marketing of new technology and for aiding the movement of knowledge across industrial, disciplinary, and regional boundaries. The SRI TAT has developed a methodology that includes adaptive engineering of the aerospace technology and commercialization when a market is indicated. The SRI Team has handled highway problems on a regional rather than a state basis, because many states in similar climatic or geologic regions have similar problems. Program exposure has been increased to encompass almost all of the fifty states
Synthesis and Characterization of Thiol-Grafted Chitosan Beads for Mercury Removal
This study describes the synthesis and characterization of thiol-grafted chitosan beads for use as mercury (Hg) adsorbents. Chitosan flakes were manipulated into beads using a phase inversion technique, then crosslinked to improve porosity and chemical stability. Cysteine was grafted onto the beads in order to improve the adsorption affinity of Hg to the beads. The beads possessed an average diameter of 3.2 mm, porosity of 0.9, specific surface are of -100 m21g, average pore size of -120 Angstroms, and specific gravity of 2. The beads exhibited a high adsorption capacity for Hg: 2,2.5,3.5 and 8 mmoVg dry at pH values of 2.2,4, 5,and 7, respectively. By comparison ungrafted chtosan had a capacity of -1.2 mmoVg dry at pH 4. Adsorption of Hg onto the beads was modeled using the Freundlich isotherm. Hg adsorption kinetics was modeled as radial diffusion into an infinite sphere. The beads exhibited a high initial uptake rate comparable to other published chitosan bead data followed by a slower uptake rate suggesting pore diffusion as the rate-determining step
The cool wake around 4C 34.16 as seen by XMM-Newton
We present XMM-Newton observations of the wake-radiogalaxy system 4C34.16,
which shows a cool and dense wake trailing behind 4C34.16's host galaxy. A
comparison with numerical simulations is enlightening, as they demonstrate that
the wake is produced mainly by ram pressure stripping during the galactic
motion though the surrounding cluster. The mass of the wake is a substantial
fraction of the mass of an elliptical galaxy's X-ray halo. This observational
fact supports a wake formation scenario similar to the one demonstrated
numerically by Acreman et al (2003): the host galaxy of 4C34.16 has fallen into
its cluster, and is currently crossing its central regions. A substantial
fraction of its X-ray halo has been stripped by ram pressure, and remains
behind to form the galaxy wake.Comment: 9 pages, 6 figures, accepted for publication in MNRA
The Planetary Nebulae Spectrograph: the green light for Galaxy Kinematics
Planetary nebulae are now well established as probes of galaxy dynamics and
as standard candles in distance determinations. Motivated by the need to
improve the efficiency of planetary nebulae searches and the speed with which
their radial velocities are determined, a dedicated instrument - the Planetary
Nebulae Spectrograph or PN.S - has been designed and commissioned at the 4.2m
William Herschel Telescope. The high optical efficiency of the spectrograph
results in the detection of typically ~ 150 PN in galaxies at the distance of
the Virgo cluster in one night of observations. In the same observation the
radial velocities are obtained with an accuracy of ~ 20 km/sComment: Accepted by PASP, to appear November 2002; the figures have been
degraded for archival purpose
Channel-forming properties of cecropins and related model compounds incorporated into planar lipid membranes.
Integral Field Spectroscopy of 23 Spiral Bulges
We have obtained Integral Field Spectroscopy for 23 spiral bulges using
INTEGRAL on the William Herschel Telescope and SPIRAL on the Anglo-Australian
Telescope. This is the first 2D survey directed solely at the bulges of spiral
galaxies. Eleven galaxies of the sample do not have previous measurements of
the stellar velocity dispersion (sigma*). These data are designed to complement
our Space Telescope Imaging Spectrograph program for estimating black hole
masses in the range 10^6-10^8M_sun using gas kinematics from nucleated disks.
These observations will serve to derive the stellar dynamical bulge properties
using the traditional Mgb and CaII triplets. We use both Cross Correlation and
Maximum Penalized Likelihood to determine projected sigma* in these systems and
present radial velocity fields, major axis rotation curves, curves of growth
and sigma* fields. Using the Cross Correlation to extract the low order 2D
stellar dynamics we generally see coherent radial rotation and irregular
velocity dispersion fields suggesting that sigma* is a non-trivial parameter to
estimate.Comment: 11 pages, 30 figures, accepted for publication in ApJ
Why Buckling Stellar Bars Weaken in Disk Galaxies
Young stellar bars in disk galaxies experience a vertical buckling
instability which terminates their growth and thickens them, resulting in a
characteristic peanut/boxy shape when viewed edge on. Using N-body simulations
of galactic disks embedded in live halos, we have analyzed the bar structure
throughout this instability and found that the outer third of the bar dissolves
completely while the inner part (within the vertical inner Lindblad resonance)
becomes less oval. The bar acquires the frequently observed peanut/boxy-shaped
isophotes. We also find that the bar buckling is responsible for a mass
injection above the plane, which is subsequently trapped by specific 3-D
families of periodic orbits of particular shapes explaining the observed
isophotes, in line with previous work. Using a 3-D orbit analysis and surfaces
of sections, we infer that the outer part of the bar is dissolved by a rapidly
widening stochastic region around its corotation radius -- a process related to
the bar growth. This leads to a dramatic decrease in the bar size, decrease in
the overall bar strength and a mild increase in its pattern speed, but is not
expected to lead to a complete bar dissolution. The buckling instability
appears primarily responsible for shortening the secular diffusion timescale to
a dynamical one when building the boxy isophotes. The sufficiently long
timescale of described evolution, ~1 Gyr, can affect the observed bar fraction
in local universe and at higher redshifts, both through reduced bar strength
and the absence of dust offset lanes in the bar.Comment: 7 pages, 4 figures, ApJ Letters, in pres
Characterizing Bars at z~0 in the optical and NIR: Implications for the Evolution of Barred Disks with Redshift
Critical insights on galaxy evolution stem from the study of bars. With the
advent of HST surveys that trace bars in the rest-frame optical out to z~1, it
is critical to provide a reference baseline for bars at z~0 in the optical
band. We present results on bars at z~0 in the optical and NIR bands based on
180 spirals from OSUBSGS. (1) The deprojected bar fraction at z~0 is ~60% +/-6%
in the NIR H-band and ~44% +/-6% in the optical B-band. (2) The results before
and after deprojection are similar, which is encouraging for high-redshift
studies that forego deprojection. (3) Studies of bars at z~0.2-1.0 (lookback
time of 3-8 Gyr) have reported an optical bar fraction of ~30% +/-6%, after
applying cutoffs in absolute magnitude (M_V = 1.5
kpc), and bar ellipticity (e_bar >= 0.4). Applying these exact cutoffs to the
OSUBSGS data yields a comparable optical B-band bar fraction at z~0 of ~
34%+/-6%. This rules out scenarios where the optical bar fraction in bright
disks declines strongly with redshift. (4) Most (~70%) bars have moderate to
high strentgh or ellipticity (0.50 <= e_bar <= 0.75). There is no bimodality in
the distribution of e_bar. The H-band bar fraction and e_bar show no
substantial variation across RC3 Hubble types Sa to Scd. (5) RC3 bar types
should be used with caution. Many galaxies with RC3 types "AB" turn out to be
unbarred and RC3 bar classes "B" and "AB" have a significant overlap in e_bar.
(6) Most bars have sizes below 5 kpc. Bar and disk sizes correlate, and most
bars have a_bar/R_25~0.1-0.5. This suggests that the growths of bars and disks
are intimately tied.Comment: 11 pages, 17 figures, 3 tables, ApJ accepted, abridged abstract
below. Minor changes and shortened paper for ApJ limits. For high resolution
figures see http://www.as.utexas.edu/~marinova/paper1-highres.pd
Study of arc-jet propulsion devices Final report, 20 Nov. 1964 - 19 Dec. 1965
Energy transfer mechanisms in radiation, water, and regeneratively cooled, and MPD arc jet propulsion device
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