709 research outputs found
Maurice Hall Haycock (1900-1988)
Maurice Haycock, mineralogist, geologist, photographer, musician, painter, historian, radio operator, died in Ottawa on December 23, 1988, at the age of 88 years. ... [Haycock is remembered for his many talents and achievements including receiving the Massey Medal from the Royal Canadian Geographical Society in 1980, receiving an Honourary Doctorate of Civil Laws degree from Acadia University in 1986 and the display, at Acadia, of a retrospective exhibition of more than 80 of his arctic paintings. A collection of his paintings resides at the University of Saskatchewan.
Changes in diet and trophic position of a top predator 10 years after a mass mortality of a key prey
After the disappearance of primary prey, seabirds exhibit gradually decreased breeding performance, and eventually the population size drops. Results are presented of an investigation into the diet of little penguins (Eudyptula minor) at Phillip Island, Australia, during a period when their key prey, pilchard (Sardinops sagax), declined dramatically. Data from stomach flushing (1982-2006) were used, supported by stable isotope (δ 15N, δ13C) analyses of blood samples (2003, 2004, and 2006). The effect of the pilchard mortality on penguin diet was immediate, the birds shifting to a diet almost devoid of pilchard, and this was followed by 2 years of low breeding success, with considerably fewer penguins coming ashore. During periods when pilchard was not part of the diet, penguins consumed prey of a higher trophic level, e.g. higher values of δ15N. Variability in penguin blood δ15N coincided with years of low prey diversity. The disappearance of pilchard resulted in a decrease in prey diversity and led penguins to >fish up> the foodweb, possibly because of the simplified trophic structure. After 1998, however, breeding success re-attained average levels and the numbers of penguins coming ashore increased, probably because of increased abundance of prey other than pilchard after a 3-year period of food scarcity. Although little penguins apparently compensated over time, a less-flexible diet could make them ultimately vulnerable to further changes in their foodweb. © 2010 International Council for the Exploration of the Sea.Peer Reviewe
Navigating beyond the Eurofetishist Frontier of Critical IR Theory: Exploring the complex landscapes of non-Western agency
This article argues that Critical IR theory’s (CIRT) claims to reflexivity, its engagement with “difference,” and its emancipatory stance are compromised by its enduringly Eurocentric gaze. While CIRT is certainly critical of the West, nevertheless its tendency toward “Eurofetishism”—by which Western agency is reified at the expense of non-Western agency—leads it into a “critical Eurocentrism.” While this Eurofetishism plays out differently across the spectrum of CIRT, nevertheless all too often the West is treated as distinct from the non-West such that a fully relational conception of the West—one in which the non-West shapes, tracks, and inflects the West as much as vice versa—is either downplayed or dismissed altogether. Our antidote to this problem is to advance such a relational approach that brings non-Western agency back in while simultaneously recognizing that such agency is usually subjected to structural constraints. This gives rise to two core objectives: first, that non-Western agency needs to be taken seriously as an ontologically significant process in world politics, and second, that it needs to be explored in its complex, manifold dimensions. Here we seek to move beyond the colonial binaries of non-Western “silence vs. defiance” and an “all-powerful West vs. powerless non-West.” For between these polarities lies a spectrum of instantiations of non-Western agency, running from the refusal to be known and categorized by colonial epistemes to mundane moments of everyday agency to the embrace of indigenous cosmologies through to modes of developmental and global agency. Sometimes these speak back to the West, and at other times they occur for reasons Other-wise. Ultimately we call for a relational sociology of global interconnectivities that problematizes CIRT’s Eurofetishization of the West as a separate, self-generating, self-directed, and hyper-autonomous entity
Predicted Planck Extragalactic Point Source Catalogue
An estimation of the number and amplitude (in flux) of the extragalactic
point sources that will be observed by the Planck Mission is presented in this
paper. The study is based on the Mexican Hat wavelet formalism introduced by
Cayon et al. 2000. Simulations at Planck observing frequencies are analysed,
taking into account all the possible cosmological, Galactic and Extragalactic
emissions together with noise. With the technique used in this work the Planck
Mission will produce a catalogue of extragalactic point sources above fluxes:
1.03 Jy (857 GHz), 0.53 Jy (545 GHz), 0.28 Jy (353 GHz), 0.24 Jy (217 GHz),
0.32 Jy (143 GHz), 0.41 Jy (100 GHz HFI), 0.34 Jy (100 GHz LFI), 0.57 Jy (70
GHz), 0.54 Jy (44 GHz) and 0.54 Jy (30 GHz), which are only slightly model
dependent (see text). Amplitudes of these sources are estimated with errors
below 15%. Moreover, we also provide a complete catalogue (for the point
sources simulation analysed) with errors in the estimation of the amplitude
below 10%. In addition we discuss the possibility of identifying different
point source populations in the Planck catalogue by estimating their spectral
indices.Comment: 13 pages, 2 figures, submitted to MNRA
The Emission of Electromagnetic Radiation from Charges Accelerated by Gravitational Waves and its Astrophysical Implications
We provide calculations and theoretical arguments supporting the emission of
electromagnetic radiation from charged particles accelerated by gravitational
waves (GWs). These waves have significant indirect evidence to support their
existence, yet they interact weakly with ordinary matter. We show that the
induced oscillations of charged particles interacting with a GW, which lead to
the emission of electromagnetic radiation, will also result in wave
attenuation. These ideas are supported by a small body of literature, as well
as additional arguments for particle acceleration based on GW memory effects.
We derive order of magnitude power calculations for various initial charge
distributions accelerated by GWs. The resulting power emission is extremely
small for all but very strong GWs interacting with large quantities of charge.
If the results here are confirmed and supplemented, significant consequences
such as attenuation of early universe GWs could result. Additionally, this
effect could extend GW detection techniques into the electromagnetic regime.
These explorations are worthy of study to determine the presence of such
radiation, as it is extremely important to refine our theoretical framework in
an era of active GW astrophysics.Comment: Appears in Gravitational Wave Astrophysics, Editor C.F. Sopuerta,
Astrophysics and Space Science Proceedings, Volume 40. ISBN
978-3-319-10487-4. Springer International Publishing Switzerland, 2015, p.
30
Feeding ecology of five commercial shark species of the Celtic Sea through stable isotope and trace metal analysis
In order to trace their feeding habits, stable carbon and nitrogen isotope ratios (delta(15)N and delta(13)C), as well as trace metal concentrations (Zn, Cd, Fe, Cu, Se and Hg) were analysed in the tissues of five commercial shark species from the Celtic Sea: the tope shark Galeorhinus galeus, the black-mouthed catshark Galeus melastomus, the starry smooth hound Mustelus asterias, the spiny dogfish Squalus acanthias and the lesser-spotted dogfish Scyliorhinus canicula. Our results were compared to previously described stomach contents and isotopic composition of potential preys. Isotopic ratio delta(15)N suggested that tope sharks fed at a higher trophic level (16.7 parts per thousand in the muscle) than the other species, reflecting its piscivorous diet. The lower values of spiny dogfish (11.6 parts per thousand in the muscle) might be explained, amongst other things, by either its migratory behaviour or its preference for preys from lower trophic levels. Cd and Hg were correlated with isotopic ratios delta(13)C and delta(15)N, and were shown to be diet-related whereas Zn, Fe and Cu seemed much more linked to species-specific metabolism. Although this multidisciplinary approach is revealed as a useful tool for the study of shark ecology, the lack of known trophic fractionation suggests that isotopic data be compared to traditional diet analyses. (c) 2005 Elsevier Ltd. All rights reserved.Peer reviewe
Combining stable isotope analysis and conventional techniques to improve knowledge of the diet of the European Roller Coracias garrulus
Diet studies are crucial for understanding the ecology and evolution of species, as well as for establishing appropriate conservation and management strategies. However, they remain methodologically challenging due to variation between seasons, sites, sexes or age groups and even variation between individuals. Due to method-specific characteristics and biases, a combination of existing techniques can overcome the inherent limitations of each technique and provide a more accurate and broad picture of species’ food preferences. Here, we examine diet information obtained using three different assessment methods to better understand the trophic ecology of the European Roller Coracias garrulus, a species targeted by conservation measures in Europe. First, we analysed regurgitated pellets and video recordings to report the diet composition of adult and nestling Rollers, respectively. Secondly, we used stable isotope analysis (SIA) to investigate adult sexual diet segregation as well as to confirm the main findings regarding adult and nestling diets obtained through conventional methods. Based on the analysis of pellets, the diet of adult Rollers was dominated by Coleoptera, while camera images revealed that the diet of nestlings was dominated by Orthoptera, mainly grasshoppers and bush crickets. Blood isotopic signatures of adult and nestling Rollers confirmed the results obtained through pellet and video recording techniques. Of the 45 three methods, pellet analysis contained the most comprehensive trophic information regarding the detectable prey spectrum and prey species contribution, and also provided basic diet information to inform the SIA. Our results also highlight the potential of SIA for assessing intra-specific variation in diet by sampling individuals of known age and sex, which is often unfeasible through conventional approaches. SIA analysis showed no differences in δ13C and δ15N ratios of blood between males and females and a high degree of overlap amongst isotopic niches, suggesting no sex-specific partitioning in resource use. Overall, we showed that the combination of different methods could be used to gain new and clearer insights into avian trophic ecology that are essential for informing habitat management aiming to improve availability of foraging resources
Large-scale power in the CMB and new physics: An analysis using Bayesian model comparison
Published versio
An Excursion-Theoretic Approach to Stability of Discrete-Time Stochastic Hybrid Systems
We address stability of a class of Markovian discrete-time stochastic hybrid
systems. This class of systems is characterized by the state-space of the
system being partitioned into a safe or target set and its exterior, and the
dynamics of the system being different in each domain. We give conditions for
-boundedness of Lyapunov functions based on certain negative drift
conditions outside the target set, together with some more minor assumptions.
We then apply our results to a wide class of randomly switched systems (or
iterated function systems), for which we give conditions for global asymptotic
stability almost surely and in . The systems need not be time-homogeneous,
and our results apply to certain systems for which functional-analytic or
martingale-based estimates are difficult or impossible to get.Comment: Revised. 17 pages. To appear in Applied Mathematics & Optimizatio
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