4,106 research outputs found
Rescue, rehabilitation, and release of marine mammals: An analysis of current views and practices.
Stranded marine mammals have long attracted public attention. Those that wash up dead are, for all their value to science, seldom seen by the public as more than curiosities. Animals that are sick, injured, orphaned or
abandoned ignite a different response. Generally, public sentiment supports any effort to rescue, treat and return them to sea.
Institutions displaying marine mammals showed an early interest in live-stranded animals as a source of specimens -- in 1948, Marine Studios in St. Augustine, Florida, rescued a young short-finned pilot whale (Globicephala
macrorhynchus), the first ever in captivity (Kritzler 1952). Eventually, the public as well as government agencies looked to these institutions for their recognized expertise in marine mammal care and medicine. More recently,
facilities have been established for the sole purpose of rehabilitating marine mammals and preparing them for return to the wild. Four such institutions are the Marine Mammal Center (Sausalito, CA), the Research Institute for
Nature Management (Pieterburen, The Netherlands), the RSPCA, Norfolk Wildlife Hospital (Norfolk, United Kingdom) and the Institute for Wildlife Biology of Christian-Albrects University (Kiel, Germany).(PDF contains 68 pages.
Local lipschitzness of reachability maps for hybrid systems with applications to safety
Motivated by the safety problem, several definitions of reachability maps, for hybrid dynamical systems, are introduced. It is well established that, under certain conditions, the solutions to continuous-time systems depend continuously with respect to initial conditions. In such setting, the reachability maps considered in this paper are locally Lipschitz (in the Lipschitz sense for set-valued maps) when the right-hand side of the continuous-time system is locally Lipschitz. However, guaranteeing similar properties for reachability maps for hybrid systems is much more challenging. Examples of hybrid systems for which the reachability maps do not depend nicely with respect to their arguments, in the Lipschitz sense, are introduced. With such pathological cases properly identified, sufficient conditions involving the data defining a hybrid system assuring Lipschitzness of the reachability maps are formulated. As an application, the proposed conditions are shown to be useful to significantly improve an existing converse theorem for safety given in terms of barrier functions. Namely, for a class of safe hybrid systems, we show that safety is equivalent to the existence of a locally Lipschitz barrier function. Examples throughout the paper illustrate the results
A homomorphism between link and XXZ modules over the periodic Temperley-Lieb algebra
We study finite loop models on a lattice wrapped around a cylinder. A section
of the cylinder has N sites. We use a family of link modules over the periodic
Temperley-Lieb algebra EPTL_N(\beta, \alpha) introduced by Martin and Saleur,
and Graham and Lehrer. These are labeled by the numbers of sites N and of
defects d, and extend the standard modules of the original Temperley-Lieb
algebra. Beside the defining parameters \beta=u^2+u^{-2} with u=e^{i\lambda/2}
(weight of contractible loops) and \alpha (weight of non-contractible loops),
this family also depends on a twist parameter v that keeps track of how the
defects wind around the cylinder. The transfer matrix T_N(\lambda, \nu) depends
on the anisotropy \nu and the spectral parameter \lambda that fixes the model.
(The thermodynamic limit of T_N is believed to describe a conformal field
theory of central charge c=1-6\lambda^2/(\pi(\lambda-\pi)).)
The family of periodic XXZ Hamiltonians is extended to depend on this new
parameter v and the relationship between this family and the loop models is
established. The Gram determinant for the natural bilinear form on these link
modules is shown to factorize in terms of an intertwiner i_N^d between these
link representations and the eigenspaces of S^z of the XXZ models. This map is
shown to be an isomorphism for generic values of u and v and the critical
curves in the plane of these parameters for which i_N^d fails to be an
isomorphism are given.Comment: Replacement of "The Gram matrix as a connection between periodic loop
models and XXZ Hamiltonians", 31 page
Gas-liquid mass transfer : a comparison of down-and up-pumping axial flow impellers with radial impellers
The performance of a down- and up-pumping pitched blade turbine and A315 for gas-liquid dispersion and mass
transfer was evaluated and then compared with that of Rushton and Scaba turbines in a small laboratory scale
vessel. The results show that when the axial flow impellers are operated in the up-pumping mode, the overall
performance is largely improved compared with the down-pumping configuration. Compared with the radial
turbines, the up-pumping A315 has a high gas handling capacity, equivalent to the Scaba turbine and is
economically much more efficient in terms of mass transfer than both turbines. On the other hand, the uppumping
pitched blade turbine is not as well adapted to such applications. Finally, the axial flow impellers in the
down-pumping mode have the lowest performance of all the impellers studied, although the A315 is preferred of
the pitched blade turbine
Field Induced Nodal Order Parameter in the Tunneling Spectrum of YBaCuO Superconductor
We report planar tunneling measurements on thin films of
YBaCuO at various doping levels under magnetic fields. By
choosing a special setup configuration, we have probed a field induced energy
scale that dominates in the vicinity of a node of the d-wave superconducting
order parameter. We found a high doping sensitivity for this energy scale. At
Optimum doping this energy scale is in agreement with an induced
order parameter. We found that it can be followed down to low fields at optimum
doping, but not away from it.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.
The constraint equations for the Einstein-scalar field system on compact manifolds
We study the constraint equations for the Einstein-scalar field system on
compact manifolds. Using the conformal method we reformulate these equations as
a determined system of nonlinear partial differential equations. By introducing
a new conformal invariant, which is sensitive to the presence of the initial
data for the scalar field, we are able to divide the set of free conformal data
into subclasses depending on the possible signs for the coefficients of terms
in the resulting Einstein-scalar field Lichnerowicz equation. For many of these
subclasses we determine whether or not a solution exists. In contrast to other
well studied field theories, there are certain cases, depending on the mean
curvature and the potential of the scalar field, for which we are unable to
resolve the question of existence of a solution. We consider this system in
such generality so as to include the vacuum constraint equations with an
arbitrary cosmological constant, the Yamabe equation and even (all cases of)
the prescribed scalar curvature problem as special cases.Comment: Minor changes, final version. To appear: Classical and Quantum
Gravit
Leptonic decay constants f_Ds and f_D in three flavor lattice QCD
We determine the leptonic decay constants in three flavor unquenched lattice
QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm
quarks in the Fermilab heavy quark formalism. Our preliminary results, based
upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV
and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is
statistical while the is the combined systematic uncertainty.Comment: Talk presented at Lattice2004(heavy), Fermilab, June 21-26, 2004. 3
pages, 2 figure
Belugas and Narwhals: Application of New Technology to Whale Science in the Arctic
... In the course of the research reported in this issue, there have been few observations of tagged whales after release, and this may be unavoidable, given the remoteness, harshness, and darkness of Arctic field conditions. However, on those occasions when there has been follow-up, the results have been informative and useful. For example, observations of scarred tissue on the backs of previously tagged white whales appeared to confirm the supposition that tagging has no lingering effect on animal health or behaviour .... Changes in blood constituents of animals recaptured within a few weeks after tagging ... are about what one would expect, given that some tissue damage and stress are inevitably associated with capture and tagging procedures. ... The ten studies published in this special issue are pieces of a much larger puzzle. Stock- and even site-specific studies have been typical for beluga research, largely because of management concerns. Findings, therefore, are often reported in what seems like a fragmentary manner, and this is reflected in the somewhat miscellaneous nature of the present compilation as well. Eventually, we expect a unified picture to emerge for both the beluga and the narwhal. Until it does, this collection of papers should be seen as one more in a series of benchmarks, each of which helps to elucidate what is known about the whales, the tools available for studying them, and questions that remain to be addressed. ..
Covariant Poisson equation with compact Lie algebras
The covariant Poisson equation for Lie algebra-valued mappings defined in
3-dimensional Euclidean space is studied using functional analytic methods.
Weighted covariant Sobolev spaces are defined and used to derive sufficient
conditions for the existence and smoothness of solutions to the covariant
Poisson equation. These conditions require, apart from suitable continuity,
appropriate local integrability of the gauge potentials and global weighted
integrability of the curvature form and the source. The possibility of
nontrivial asymptotic behaviour of a solution is also considered. As a
by-product, weighted covariant generalisations of Sobolev embeddings are
established.Comment: 31 pages, LaTeX2
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