424 research outputs found
Beluga, Delphinapterus leucas, Distribution and Survey Effort in the Gulf of Alaska
Beluga, Delphinapterus leucas, distribution in the Gulf of Alaska and adjacent inside waters was examined through a review of surveys conducted as far back as 1936. Although beluga sightings have occurred on almost every marine mammal survey in northern Cook Inlet (over 20 surveys reported here), beluga sightings have been rare outside the inlet in the Gulf of Alaska. More than 150,000 km of dedicated survey effort in the Gulf of Alaska resulted in sightings of over 23,000 individual cetaceans, of which only 4 beluga sightings (5 individuals) occurred. In addition, nearly 100,000 individual cetaceans were reported in the Platforms of Opportunity database; yet, of these, only 5 sightings (39 individuals) were belugas. Furthermore, approximately 19 beluga sightings (>260 individuals), possibly including resightings, have been reported without information on effort or other cetacean sightings. Of the 28 sightings of belugas outside of Cook Inlet, 9 were near Kodiak Island, 10 were in or near Prince William Sound, 8 were in Yakutat Bay, and 1 anomalous sighting was well south of the Gulf. These sightings support archaeological and commercial harvest evidence indicating the only persistent group of belugas in the Gulf of Alaska occurs in Cook Inlet
Non-integrability of the mixmaster universe
We comment on an analysis by Contopoulos et al. which demonstrates that the
governing six-dimensional Einstein equations for the mixmaster space-time
metric pass the ARS or reduced Painlev\'{e} test. We note that this is the case
irrespective of the value, , of the generating Hamiltonian which is a
constant of motion. For we find numerous closed orbits with two
unstable eigenvalues strongly indicating that there cannot exist two additional
first integrals apart from the Hamiltonian and thus that the system, at least
for this case, is very likely not integrable. In addition, we present numerical
evidence that the average Lyapunov exponent nevertheless vanishes. The model is
thus a very interesting example of a Hamiltonian dynamical system, which is
likely non-integrable yet passes the reduced Painlev\'{e} test.Comment: 11 pages LaTeX in J.Phys.A style (ioplppt.sty) + 6 PostScript figures
compressed and uuencoded with uufiles. Revised version to appear in J Phys.
Beluga, Delphinapterus leucas, Habitat Associations in Cook Inlet, Alaska
A review of available information describing habitat associations for belugas, Delphinapterus leucas, in Cook Inlet was undertaken to complement population assessment surveys from 1993-2000. Available data for physical, biological, and anthropogenic factors in Cook Inlet are summarized followed by a provisional description of seasonal habitat associations. To summarize habitat preferences, the beluga summer distribution pattern was used to partition Cook Inlet into three regions. In general, belugas congregate in shallow, relatively warm, low-salinity water near major river outflows in upper Cook Inlet during summer (defined as their primary habitat), where prey availability is comparatively high and predator occurrence relatively low. In winter, belugas are seen in the central inlet, but sightings are fewer in number, and whales more dispersed compared to summer. Belugas are associated with a range of ice conditions in winter, from ice-free to 60% ice-covered water. Natural catastrophic events, such as fires, earthquakes, and volcanic eruptions, have had no reported effect on beluga habitat, although such events likely affect water quality and, potentially, prey availability. Similarly, although sewage effluent and discharges from industrial and military activities along Cook Inlet negatively affect water quality, analyses of organochlorines and heavy metal burdens indicate that Cook Inlet belugas are not assimilating contaminant loads greater than any other Alaska beluga stocks. Offshore oil and gas activities and vessel traffic are high in the central inlet compared with other Alaska waters, although belugas in Cook Inlet seem habituated to these anthropogenic factors. Anthropogenic factors that have the highest potential negative impacts on belugas include subsistence hunts (not discussed in this report), noise from transportation and offshore oil and gas extraction (ship transits and aircraft overflights), and water quality degradation (from urban runoff and sewage treatment facilities). Although significant impacts from anthropogenic factors other than hunting are not yet apparent, assessment of potential impacts from human activities, especially those that may effect prey availability, are needed
Microscopic expressions for the thermodynamic temperature
We show that arbitrary phase space vector fields can be used to generate
phase functions whose ensemble averages give the thermodynamic temperature. We
describe conditions for the validity of these functions in periodic boundary
systems and the Molecular Dynamics (MD) ensemble, and test them with a
short-ranged potential MD simulation.Comment: 21 pages, 2 figures, Revtex. Submitted to Phys. Rev.
The resonance spectrum of the cusp map in the space of analytic functions
We prove that the Frobenius--Perron operator of the cusp map
, (which is an approximation of the
Poincar\'e section of the Lorenz attractor) has no analytic eigenfunctions
corresponding to eigenvalues different from 0 and 1. We also prove that for any
the spectrum of in the Hardy space in the disk
\{z\in\C:|z-q|<1+q\} is the union of the segment and some finite or
countably infinite set of isolated eigenvalues of finite multiplicity.Comment: Submitted to JMP; The description of the spectrum in some Hardy
spaces is adde
Microcanonical temperature for a classical field: application to Bose-Einstein condensation
We show that the projected Gross-Pitaevskii equation (PGPE) can be mapped
exactly onto Hamilton's equations of motion for classical position and momentum
variables. Making use of this mapping, we adapt techniques developed in
statistical mechanics to calculate the temperature and chemical potential of a
classical Bose field in the microcanonical ensemble. We apply the method to
simulations of the PGPE, which can be used to represent the highly occupied
modes of Bose condensed gases at finite temperature. The method is rigorous,
valid beyond the realms of perturbation theory, and agrees with an earlier
method of temperature measurement for the same system. Using this method we
show that the critical temperature for condensation in a homogeneous Bose gas
on a lattice with a UV cutoff increases with the interaction strength. We
discuss how to determine the temperature shift for the Bose gas in the
continuum limit using this type of calculation, and obtain a result in
agreement with more sophisticated Monte Carlo simulations. We also consider the
behaviour of the specific heat.Comment: v1: 9 pages, 5 figures, revtex 4. v2: additional text in response to
referee's comments, now 11 pages, to appear in Phys. Rev.
Controlling complex networks: How much energy is needed?
The outstanding problem of controlling complex networks is relevant to many
areas of science and engineering, and has the potential to generate
technological breakthroughs as well. We address the physically important issue
of the energy required for achieving control by deriving and validating scaling
laws for the lower and upper energy bounds. These bounds represent a reasonable
estimate of the energy cost associated with control, and provide a step forward
from the current research on controllability toward ultimate control of complex
networked dynamical systems.Comment: 4 pages paper + 5 pages supplement. accepted for publication in
Physical Review Letters;
http://link.aps.org/doi/10.1103/PhysRevLett.108.21870
New Algorithm for Mixmaster Dynamics
We present a new numerical algorithm for evolving the Mixmaster spacetimes.
By using symplectic integration techniques to take advantage of the exact Taub
solution for the scattering between asymptotic Kasner regimes, we evolve these
spacetimes with higher accuracy using much larger time steps than previously
possible. The longer Mixmaster evolution thus allowed enables detailed
comparison with the Belinskii, Khalatnikov, Lifshitz (BKL) approximate
Mixmaster dynamics. In particular, we show that errors between the BKL
prediction and the measured parameters early in the simulation can be
eliminated by relaxing the BKL assumptions to yield an improved map. The
improved map has different predictions for vacuum Bianchi Type IX and magnetic
Bianchi Type VI Mixmaster models which are clearly matched in the
simulation.Comment: 12 pages, Revtex, 4 eps figure
Efficient estimation of energy transfer efficiency in light-harvesting complexes
The fundamental physical mechanisms of energy transfer in photosynthetic
complexes is not yet fully understood. In particular, the degree of efficiency
or sensitivity of these systems for energy transfer is not known given their
non-perturbative and non-Markovian interactions with proteins backbone and
surrounding photonic and phononic environments. One major problem in studying
light-harvesting complexes has been the lack of an efficient method for
simulation of their dynamics in biological environments. To this end, here we
revisit the second-order time-convolution (TC2) master equation and examine its
reliability beyond extreme Markovian and perturbative limits. In particular, we
present a derivation of TC2 without making the usual weak system-bath coupling
assumption. Using this equation, we explore the long time behaviour of exciton
dynamics of Fenna-Matthews-Olson (FMO) protein complex. Moreover, we introduce
a constructive error analysis to estimate the accuracy of TC2 equation in
calculating energy transfer efficiency, exhibiting reliable performance for
environments with weak and intermediate memory and strength. Furthermore, we
numerically show that energy transfer efficiency is optimal and robust for the
FMO protein complex of green sulphur bacteria with respect to variations in
reorganization energy and bath correlation time-scales.Comment: 16 pages, 9 figures, modified version, updated appendices and
reference lis
Mixmaster universe in Horava-Lifshitz gravity
We consider spatially homogeneous (but generally non-isotropic) cosmologies
in the recently proposed Horava-Lifshitz gravity and compare them to those of
general relativity using Hamiltonian methods. In all cases, the problem is
described by an effective point particle moving in a potential well with
exponentially steep walls. Focusing on the closed-space cosmological model
(Bianchi type IX), the mixmaster dynamics is now completely dominated by the
quadratic Cotton tensor potential term for very small volume of the universe.
Unlike general relativity, where the evolution towards the initial singularity
always exhibits chaotic behavior with alternating Kasner epochs, the
anisotropic universe in Horava-Lifshitz gravity (with parameter lambda > 1/3)
is described by a particle moving in a frozen potential well with fixed (but
arbitrary) energy E. Alternating Kasner epochs still provide a good description
of the early universe for very large E, but the evolution appears to be
non-ergodic. For very small E there are harmonic oscillations around the fully
isotropic model. The question of chaos remains open for intermediate energy
levels.Comment: 1+35 pages, 4 figure
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