201 research outputs found
Effects of landscape disturbance on the population dynamics and behaviour of moose (Alces alces) in the greater Pukaskwa ecosystem, Ontario
I studied the population dynamics, movements and home range of moose {Alces alces) in
the Greater Pukaskwa Ecosystem, Ontario, during 1995-1999. My study compared two
landscapes experiencing different management regimes: Pukaskwa National Park (PNP),
a wilderness park, and the adjacent Wildlife Management Unit #33 (WMU33), a multiuse
forest with commercial timber harvest (part of the White River Forest). I
hypothesized that because PNP was not disturbed (i.e., by fire or timber harvest) and
WMU33 was, the condition of moose and moose habitat carrying capacity would be
better in WMU33 than PNP. I used 5 triennial aerial moose surveys to assess population
dynamics and distribution, and 35 radio-collared adult female moose to assess
productivity, survival, marrow condition, blood condition, morphometries, movements
and home range. I found the mean moose density per plot in the most recent aerial
surveys to be slightly higher but not statistically different in WMU33 than PNP (0.332
and 0.273 moose/km2, respectively), and kriging demonstrated that most of the high
moose densities occurred in WMU33 and were increasing more than in PNP. Survival
rates were not significantly different between landscapes (93% in PNP and 89% in
WMU33), and were similar to findings of other studies. Marrow fat showed differences
among seasons, being highest in summer and lowest in late winter, but was not
significantly different between landscapes. Movements in PNP were greater than in
WMU33, and PNP moose showed distinct movements between summer and winter
ranges, which was not seen in WMU33. Seasonal movements were significant, with
summer being the greatest (22.0 m/hr in PNP and 20.1 m/hr in WMU33) and winter the
smallest (6.9 m/hr in PNP and 5.5 m/hr in WMU33). Annual MCP home range sizes were
significantly larger in PNP than WMU33 (70 and 43 km2, respectively). Home ranges
also showed significant season effects, being largest in summer and smallest in winter. In
my study, I found that moose occupying the WMU33 landscape have shown a slight
positive response to forest disturbance, caused by timber harvest, through increased
population density. I did not find statistically important differences in physical condition
of moose between the two landscapes, but moose in WMU33 made smaller movements
and had smaller home ranges than moose living in the undisturbed landscape of PNP
Demographic Patterns and Limitation of Grey Wolves, Canis lupus, in and Near Pukaskwa National Park, Ontario
In response to concern regarding the growth and long-term viability of the wolf population in and near Pukaskwa National Park, a study of demographic patterns and limitation of radio-collared wolves (Canis lupus) was completed between 1994 and 1998. The mean annual finite rate of increase (0.96) suggested that population growth of wolves was limited and declining slightly. Small pack sizes, high cumulative mortality, and low reproductive success also suggested a declining population. Two limiting factors, ungulate biomass and human-caused mortality, were examined to determine the importance of each in limiting the population growth of wolves. Ungulate biomass was involved because occurrence of natural-caused mortality was high (9 of 17 wolves) compared with other studies. In addition, consumption rates were low and similar to other studies where starvation and other signs of malnutrition were noted. Further, Moose densities in the study area were low to moderate and below thresholds indicating nutritional stress for wolves. Occurrence of human-caused mortality was high (8 of 17 wolves) suggesting that it was also an important limiting factor, particularly given the low availability of ungulate biomass and reproduction noted in this study. Based on present demographic patterns, ungulate biomass, and human-caused mortality, the wolf population likely will remain at present low densities or continue to decline
XMM-Newton and Swift observations of WZ Sge: spectral and timing analysis
WZ Sagittae is the prototype object of a subclass of dwarf novae, with rare
and long (super)outbursts, in which a white dwarf primary accretes matter from
a low mass companion. High-energy observations offer the possibility of a
better understanding of the disk-accretion mechanism in WZ Sge-like binaries.
We used archival XMM-Newton and Swift data to characterize the X-ray spectral
and temporal properties of WZ Sge in quiescence. We performed a detailed timing
analysis of the simultaneous X-ray and UV light curves obtained with the EPIC
and OM instruments on board XMM-Newton in 2003. We employed several techniques
in this study, including a correlation study between the two curves. We also
performed an X-ray spectral analysis using the EPIC data, as well as Swift/XRT
data obtained in 2011. We find that the X-ray intensity is clearly modulated at
a period of about 28.96 s, confirming previously published preliminary results.
We find that the X-ray spectral shape of WZ Sge remains practically unchanged
between the XMM-Newton and Swift observations. However, after correcting for
inter-stellar absorption, the intrinsic luminosity is estimated to be about
2.65X10^ 30 erg/s/cm^2 and 1.57X10^30 erg/s/cm^2 in 2003 and 2011,
respectively. During the Swift/XRT observation, the observed flux is a factor
of about 2 lower than that observed by XMM-Newton, but is similar to the
quiescent levels observed various times before the 2001 outburst.Comment: Accepted for publication on A&A.10 pages, 9 figure
Neutrino Oscillations and the Supernova 1987A Signal
We study the impact of neutrino oscillations on the interpretation of the
supernova (SN) 1987A neutrino signal by means of a maximum-likelihood analysis.
We focus on oscillations between with or
with those mixing parameters that would solve the solar
neutrino problem. For the small-angle MSW solution (, ), there are no
significant oscillation effects on the Kelvin-Helmholtz cooling signal; we
confirm previous best-fit values for the neutron-star binding energy and
average spectral temperature. There is only marginal overlap
between the upper end of the 95.4\% CL inferred range of and the lower end of the range of theoretical
predictions. Any admixture of the stiffer spectrum by
oscillations aggravates the conflict between experimentally inferred and
theoretically predicted spectral properties. For mixing parameters in the
neighborhood of the large-angle MSW solution (, ) the oscillations in the SN are adiabatic,
but one needs to include the regeneration effect in the Earth which causes the
Kamiokande and IMB detectors to observe different spectra. For
the solar vacuum solution (,
) the oscillations in the SN are nonadiabatic; vacuum
oscillations take place between the SN and the detector. If either of the
large-angle solutions were borne out by the upcoming round of solar neutrino
experiments, one would have to conclude that the SN~1987A
and/or spectra had been much softer than predicted by currentComment: Final version with very minor wording changes, to be published in
Phys. Rev.
Menus for Feeding Black Holes
Black holes are the ultimate prisons of the Universe, regions of spacetime
where the enormous gravity prohibits matter or even light to escape to
infinity. Yet, matter falling toward the black holes may shine spectacularly,
generating the strongest source of radiation. These sources provide us with
astrophysical laboratories of extreme physical conditions that cannot be
realized on Earth. This chapter offers a review of the basic menus for feeding
matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher
Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals
We briefly summarize the reported anomalous effects in deuterated metals at
ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on
important experiments as well as the theoretical basis for the opposition to
interpreting them as cold fusion. Then we critically examine more than 25
theoretical models for CF, including unusual nuclear and exotic chemical
hypotheses. We conclude that they do not explain the data.Comment: 51 pages, 4 Figure
The Interplay Between GUT and Flavour Symmetries in a Pati-Salam x S4 Model
Both Grand Unified symmetries and discrete flavour symmetries are appealing
ways to describe apparent structures in the gauge and flavour sectors of the
Standard Model. Both symmetries put constraints on the high energy behaviour of
the theory. This can give rise to unexpected interplay when building models
that possess both symmetries. We investigate on the possibility to combine a
Pati-Salam model with the discrete flavour symmetry that gives rise to
quark-lepton complementarity. Under appropriate assumptions at the GUT scale,
the model reproduces fermion masses and mixings both in the quark and in the
lepton sectors. We show that in particular the Higgs sector and the running
Yukawa couplings are strongly affected by the combined constraints of the Grand
Unified and family symmetries. This in turn reduces the phenomenologically
viable parameter space, with high energy mass scales confined to a small region
and some parameters in the neutrino sector slightly unnatural. In the allowed
regions, we can reproduce the quark masses and the CKM matrix. In the lepton
sector, we reproduce the charged lepton masses, including bottom-tau
unification and the Georgi-Jarlskog relation as well as the two known angles of
the PMNS matrix. The neutrino mass spectrum can present a normal or an inverse
hierarchy, and only allowing the neutrino parameters to spread into a range of
values between and , with .
Finally, our model suggests that the reactor mixing angle is close to its
current experimental bound.Comment: 62 pages, 4 figures; references added, version accepted for
publication in JHE
Mass Bounds on a Very Light Neutralino
Within the Minimal Supersymmetric Standard Model (MSSM) we systematically
investigate the bounds on the mass of the lightest neutralino. We allow for
non-universal gaugino masses and thus even consider massless neutralinos, while
assuming in general that R-parity is conserved. Our main focus are laboratory
constraints. We consider collider data, precision observables, and also rare
meson decays to very light neutralinos. We then discuss the astrophysical and
cosmological implications. We find that a massless neutralino is allowed by all
existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds.
EPJC versio
Computational Models of Stellar Collapse and Core-Collapse Supernovae
Core-collapse supernovae are among Nature's most energetic events. They mark
the end of massive star evolution and pollute the interstellar medium with the
life-enabling ashes of thermonuclear burning. Despite their importance for the
evolution of galaxies and life in the universe, the details of the
core-collapse supernova explosion mechanism remain in the dark and pose a
daunting computational challenge. We outline the multi-dimensional,
multi-scale, and multi-physics nature of the core-collapse supernova problem
and discuss computational strategies and requirements for its solution.
Specifically, we highlight the axisymmetric (2D) radiation-MHD code VULCAN/2D
and present results obtained from the first full-2D angle-dependent neutrino
radiation-hydrodynamics simulations of the post-core-bounce supernova
evolution. We then go on to discuss the new code Zelmani which is based on the
open-source HPC Cactus framework and provides a scalable AMR approach for 3D
fully general-relativistic modeling of stellar collapse, core-collapse
supernovae and black hole formation on current and future massively-parallel
HPC systems. We show Zelmani's scaling properties to more than 16,000 compute
cores and discuss first 3D general-relativistic core-collapse results.Comment: 16 pages, 5 figures, to appear in the proceedings of the DOE/SciDAC
2009 conference. A version with high-resolution figures is available from
http://stellarcollapse.org/papers/Ott_SciDAC2009.pd
Swift observations of the X-ray and UV evolution of V2491 Cyg (Nova Cyg 2008 No. 2)
We present extensive, high-density Swift observations of V2491 Cyg (Nova Cyg
2008 No. 2). Observing the X-ray emission from only one day after the nova
discovery, the source is followed through the initial brightening, the
Super-Soft Source phase and back to the pre-outburst flux level. The evolution
of the spectrum throughout the outburst is demonstrated. The UV and X-ray
light-curves follow very different paths, although changes occur in them around
the same times, indicating a link between the bands. Flickering in the
late-time X-ray data indicates the resumption of accretion.
We show that if the white dwarf is magnetic, it would be among the most
magnetic known; the lack of a periodic signal in our later data argues against
a magnetic white dwarf, however. We also discuss the possibility that V2491 Cyg
is a recurrent nova, providing recurrence timescale estimates.Comment: 12 pages, 8 figure (2 in colour), accepted for publication in MNRA
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