513 research outputs found
Perturbation theory in a pure exchange non-equilibrium economy
We develop a formalism to study linearized perturbations around the
equilibria of a pure exchange economy. With the use of mean field theory
techniques, we derive equations for the flow of products in an economy driven
by heterogeneous preferences and probabilistic interaction between agents. We
are able to show that if the economic agents have static preferences, which are
also homogeneous in any of the steady states, the final wealth distribution is
independent of the dynamics of the non-equilibrium theory. In particular, it is
completely determined in terms of the initial conditions, and it is independent
of the probability, and the network of interaction between agents. We show that
the main effect of the network is to determine the relaxation time via the
usual eigenvalue gap as in random walks on graphs.Comment: 7 pages, 2 figure
The Effect of Variability on the Estimation of Quasar Black Hole Masses
We investigate the time-dependent variations of ultraviolet (UV) black hole
mass estimates of quasars in the Sloan Digital Sky Survey (SDSS). From SDSS
spectra of 615 high-redshift (1.69 < z < 4.75) quasars with spectra from two
epochs, we estimate black hole masses, using a single-epoch technique which
employs an additional, automated night-sky-line removal, and relies on UV
continuum luminosity and CIV (1549A) emission line dispersion. Mass estimates
show variations between epochs at about the 30% level for the sample as a
whole. We determine that, for our full sample, measurement error in the line
dispersion likely plays a larger role than the inherent variability, in terms
of contributing to variations in mass estimates between epochs. However, we use
the variations in quasars with r-band spectral signal-to-noise ratio greater
than 15 to estimate that the contribution to these variations from inherent
variability is roughly 20%. We conclude that these differences in black hole
mass estimates between epochs indicate variability is not a large contributer
to the current factor of two scatter between mass estimates derived from low-
and high-ionization emission lines.Comment: 76 pages, 15 figures, 2 (long) tables; Accepted for publication in
ApJ (November 10, 2007
Evaluating Empowerment Language During the First-Year Student Transition
Orientation programs can construct communication pieces that, using language balance, help students begin to define the institutional environment, their role within it, and the experiences they will have before and after enrollment. Additionally, orientation can host conversations about appropriate terms and phrases, as well as ways to define the institution and students themselves. Orientation can also begin a conversation about the institutional lexicon and whether the usage of words is delivering contradictory, confusing, or over-emphasized messages
A Synoptic, Multiwavelength Analysis of a Large Quasar Sample
We present variability and multi-wavelength photometric information for the
933 known quasars in the QUEST Variability Survey. These quasars are grouped
into variable and non-variable populations based on measured variability
confidence levels. In a time-limited synoptic survey, we detect an
anti-correlation between redshift and the likelihood of variability. Our
comparison of variability likelihood to radio, IR, and X-ray data is consistent
with earlier quasar studies. Using already-known quasars as a template, we
introduce a light curve morphology algorithm that provides an efficient method
for discriminating variable quasars from periodic variable objects in the
absence of spectroscopic information. The establishment of statistically robust
trends and efficient, non-spectroscopic selection algorithms will aid in quasar
identification and categorization in upcoming massive synoptic surveys.
Finally, we report on three interesting variable quasars, including variability
confirmation of the BL Lac candidate PKS 1222+037.Comment: AJ, accepted for publication 15 Dec 200
Spectral Variability of Quasars in the Sloan Digital Sky Survey. II: The C IV Line
We examine the variability of the high-ionizaton C IV line in a sample of 105
quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a
strong correlation between the change in the C IV line flux and the change in
the line width, but no correlations between the change in flux and changes in
line center and skewness. The relation between line flux change and line width
change is consistent with a model in which a broad line base varies with
greater amplitude than the line core. The objects studied here are more
luminous and at higher redshift than those normally studied for variability,
ranging in redshift from 1.65 to 4.00 and in absolute r-band magnitude from
roughly -24 to -28. Using moment analysis line-fitting techniques, we measure
line fluxes, centers, widths and skewnesses for the C IV line at two epochs for
each object. The well-known Baldwin Effect is seen for these objects, with a
slope beta = -0.22. The sample has a median intrinsic Baldwin Effect slope of
beta = -0.85; the C IV lines in these high-luminosity quasars appear to be less
responsive to continuum variations than those in lower luminosity AGN.
Additionally, we find no evidence for variability of the well known blueshift
of the C IV line with respect to the low-ionization Mg II line in the highest
flux objects, indicating that this blueshift might be useful as a measure of
orientation.Comment: 52 pages, 14 figures, accepted for publication in Ap
Cluster Winds Blow along Supercluster Axes
Within Abell galaxy clusters containing wide-angle tailed radio sources,
there is evidence of a ``prevailing wind'' which directs the WAT jets. We study
the alignment of WAT jets and nearby clusters to test the idea that this wind
may be a fossil of drainage along large-scale supercluster axes. We also test
this idea with a study of the alignment of WAT jets and supercluster axes.
Statistical test neighbours indicate no alignment of WAT jets towards nearest
clusters, but do indicate approximately 98% confidence in alignment with the
long axis of the supercluster in which the cluster lies. We find a preferred
scale for such superclusters of order 25 Mpc .Comment: Latex, 5 pages, with 5 postscript figures. To be published in MNRAS.
Slight revisions to coincide with journal text. Linked to color image at
http://kusmos.phsx.ukans.edu/~melott/images/A2634SUW.jp
Getting at the Moral Leadership of Education Deans
Vignettes were used to prompt four education deans to think aloud about ways in which they would resolve problems with embedded moral issues. Thematic coding was used to analyze the interview texts that had been tape recorded and transcribed. There was general support for the two moral themes of holding to broad social ideals and negotiating for mutually acceptable outcomes, but individual expressions of specific strategies and actions differed. The results of this study support a multi-dimensional approach to the study of the leadership of deans that simultaneously examines the moral, social, intellectual and emotional aspects of problem solving. The results also suggest a possible shift in the way to advertise and interview for education deans. The advertisement should ask prospective candidates to discuss their list of accomplishments in relation to personal leadership characteristics. The interview should include an administrative colloquium on the order of the pedagogical colloquium suggested by Shulman (1993)
MOABOSAURUS UTAHENSIS, N. Gen., N. SP., A New Sauropod From The Early Cretaceous (Aptian) of North America
https://deepblue.lib.umich.edu/bitstream/2027.42/136227/1/Contributions32No11-Low Resolution.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136227/2/Contributions32No11 - High Resolution.pd
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