20,321 research outputs found
Does environment affect the star formation histories of early-type galaxies?
Differences in the stellar populations of galaxies can be used to quantify
the effect of environment on the star formation history. We target a sample of
early-type galaxies from the Sloan Digital Sky Survey in two different
environmental regimes: close pairs and a general sample where environment is
measured by the mass of their host dark matter halo. We apply a blind source
separation technique based on principal component analysis, from which we
define two parameters that correlate, respectively, with the average stellar
age (eta) and with the presence of recent star formation (zeta) from the
spectral energy distribution of the galaxy. We find that environment leaves a
second order imprint on the spectra, whereas local properties - such as
internal velocity dispersion - obey a much stronger correlation with the
stellar age distribution.Comment: 5 pages, 2 figures. Proceedings of JENAM 2010, Symposium 2:
"Environment and the formation of galaxies: 30 years later
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Research Factsheet: Woodfuel experiment - North Thurlbar, Newton Rigg
An experiment has been set up to assess the economic viability and environmental impacts of woodfuel harvesting in North Thurlbar, a small wood land on the University of Cumbria Newton Rigg campus estate. This factsheet describes the aim of the study and the experiment design
A Feynman-Kac Formula for Anticommuting Brownian Motion
Motivated by application to quantum physics, anticommuting analogues of
Wiener measure and Brownian motion are constructed. The corresponding Ito
integrals are defined and the existence and uniqueness of solutions to a class
of stochastic differential equations is established. This machinery is used to
provide a Feynman-Kac formula for a class of Hamiltonians. Several specific
examples are considered.Comment: 21 page
Study of porous wall low density wind tunnel diffusers
Porous wall wind tunnel diffusers used with low density hypersonic nozzl
Old and New Fields on Super Riemann Surfaces
The ``new fields" or ``superconformal functions" on super Riemann
surfaces introduced recently by Rogers and Langer are shown to coincide with
the Abelian differentials (plus constants), viewed as a subset of the functions
on the associated super Riemann surface. We confirm that, as originally
defined, they do not form a super vector space.Comment: 9 pages, LaTex. Published version: minor changes for clarity, two new
reference
Numerical Modelling and Calibration of CFS Framed Shear Walls under Dynamic Loading
This paper describes the numerical modeling using OpenSees of steel sheathed cold-formed steel framed shear wall test specimens under dynamic loading. Two modeling phases were carried out; the first phase comprised non-linear models calibrated using existing reversed cyclic shear wall test data, and the second phase involved more advanced models calibrated using data from dynamic shake table tests of single- and double-storey shear walls as well as other ancillary test programs. The second phase models incorporated the behaviour of the hold-downs, floor framing and blocked bare frame, in addition to the sheathing. The final calibrated models were able to accurately predict the displacement and force response time histories of the single- and double-storey shear wall specimens. These calibrated models will later be relied on for Incremental Dynamic Analyses (IDA) of representative building structures to evaluate seismic design provisions for cold-formed steel framed shear walls to be used in conjunction with the National Building Code of Canada (NBCC)
A generalization of Hausdorff dimension applied to Hilbert cubes and Wasserstein spaces
A Wasserstein spaces is a metric space of sufficiently concentrated
probability measures over a general metric space. The main goal of this paper
is to estimate the largeness of Wasserstein spaces, in a sense to be precised.
In a first part, we generalize the Hausdorff dimension by defining a family of
bi-Lipschitz invariants, called critical parameters, that measure largeness for
infinite-dimensional metric spaces. Basic properties of these invariants are
given, and they are estimated for a naturel set of spaces generalizing the
usual Hilbert cube. In a second part, we estimate the value of these new
invariants in the case of some Wasserstein spaces, as well as the dynamical
complexity of push-forward maps. The lower bounds rely on several embedding
results; for example we provide bi-Lipschitz embeddings of all powers of any
space inside its Wasserstein space, with uniform bound and we prove that the
Wasserstein space of a d-manifold has "power-exponential" critical parameter
equal to d.Comment: v2 Largely expanded version, as reflected by the change of title; all
part I on generalized Hausdorff dimension is new, as well as the embedding of
Hilbert cubes into Wasserstein spaces. v3 modified according to the referee
final remarks ; to appear in Journal of Topology and Analysi
Radar studies of the planets
The radar measurements phase of the lunar studies involving reflectivity and topographic mapping of the visible lunar surface was ended in December 1972, but studies of the data and production of maps have continued. This work was supported by Manned Spacecraft Center, Houston. Topographic mapping of the equatorial regions of Mars has been carried out during the period of each opposition since that of 1967. The method comprised extended precise traveling time measurements to a small area centered on the subradar point. As measurements continued, planetary motions caused this point to sweep out extensive areas in both latitude and longitude permitting the development of a fairly extensive topographical map in the equatorial region. Radar observations of Mercury and Venus have also been made over the past few years. Refinements of planetary motions, reflectivity maps and determinations of rotation rates have resulted
Evolution, Explosion and Nucleosynthesis of Core Collapse Supernovae
We present a new set of presupernova evolutions and explosive yields of
massive stars of initial solar composition (Y=0.285, Z=0.02) in the mass range
13-35 Msun. All the models have been computed with the latest version (4.97) of
the FRANEC code that now includes a nuclear network extending from neutrons to
Mo98. The explosive nucleosynthesis has been computed twice: a first one with
an hydro code and a second one following the simpler radiation dominated shock
approximation (RDA).Comment: 20 pages, 10 figures, 12 tables. Accepted for publication on Ap
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