Hocking M.D.,8888 University Drive |
Hocking M.D.,Simon Fraser University |
Hocking M.D.,University of Victoria |
Dulvy N.K.,8888 University Drive |
And 4 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2013
A general rule in ecology is that the abundance of species or individuals in communities sharing a common energy source decreases with increasing body size. However, external energy inputs in the form of resource subsidies can modify this size spectrum relationship. Here, we provide the first test of how a marine resource subsidy can affect size spectra of terrestrial communities, based on energy derived from Pacific salmon carcasses affecting a forest soil community beside streams in western Canada. Using both species-based and individual approaches, we found size structuring in this forest soil community, and transient community-wide doubling of standing biomass in response to energy pulses from Pacific salmon carcasses. One group of species were clear outliers in the middle of the size spectrum relationship: larval calliphorid and dryomyzid flies, which specialize on salmon carcasses, and which showed a tenfold increase in biomass in their size class when salmon were available. Thus, salmon subsidize their escape from the size spectrum. These results suggest that using a sizebased perspective of resource subsidies can provide new insights into the structure and functioning of food webs. © 2013 The Author(s) Published by the Royal Society. All rights reserved.
Dekker D.,3819 112 A Street N.W. |
Out M.,Augustin Hanicottestraat 15 |
Tabak M.,704 3061 Kent Avenue N.E. |
Ydenberg R.,8888 University Drive
Condor | Year: 2012
Kleptoparasitism in birds has been the subject of much research, and the Bald Eagle (Haliaeetus leucocephalus) is a known kleptoparasite. It has been reported to pirate ducks captured by Peregrine Falcons (Falco peregrinus), but ours is the first study to examine the effect of kleptoparasitic Bald Eagles on the kill rate of shorebird-hunting Peregrines and indirectly on a population of Dunlins (Calidris alpina) wintering in coastal British Columbia. Bald Eagles increased seasonally and yearly from October 2008 to January 2011. When eagles were scarce, Peregrines hunted ducks as well as Dunlins. Conversely, when eagles were numerous Peregrines hunted Dunlins only. In 56 instances, one or more eagles closely followed hunting Peregrines and retrieved 13 Dunlins dropped or downed by the falcons. The Peregrines were also kleptoparasitized by Gyrfalcons (Falco rusticolus), which pirated 11 Dunlins from Peregrines. Observed losses to kleptoparasites amounted to 24 (36%) of 67 Peregrines' captures. The kill rate per hour of observation was 0.05 hr-1 in October and November when eagles and Gyrfalcons were few but significantly higher at 0.18 hr-1 during January and February. In January 2011, when intraguild kleptoparasites were most abundant, the Peregrine's kill rate was 0.30 hr-1. These results support the hypothesis that kleptoparasites had an indirect effect on a population of wintering Dunlins because Peregrines compensated for prey lost to kleptoparasites by increasing their kill rate. © The Cooper Ornithological Society 2012.
Araujo H.A.,Canadian Department of Fisheries and Oceans |
Cooper A.B.,Simon Fraser University |
MacIsaac E.A.,8888 University Drive |
Knowler D.,Simon Fraser University |
Velez-Espino A.,Canadian Department of Fisheries and Oceans
Theoretical Population Biology | Year: 2015
This study develops a quantitative framework for estimating the effects of extreme suspended-sediment events (SSC>25mgL-1) on virtual populations of Chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon in a coastal watershed of British Columbia, Canada. We used a life history model coupled with a dose-response model to evaluate the populations' responses to a set of simulated suspended sediments scenarios. Our results indicate that a linear increase in SSC produces non-linear declining trajectories in both Chinook and coho populations, but this decline was more evident for Chinook salmon despite their shorter fresh-water residence. The model presented here can provide insights into SSC impacts on population responses of salmonids and potentially assist resource managers when planning conservation or remediation strategies. © 2015 Elsevier Inc.
Giabbanelli P.,8888 University Drive |
Crutzen R.,Maastricht University
JASSS | Year: 2013
Binge drinking is a complex social problem linked to an array of detrimental health effects. While binge drinking in youth has been analyzed extensively using traditional methods (e.g., regressions analyses), the adult population has received less attention, and recent work has exemplified the potential for simulations to help scholars and practitioners better understand the problem. In this paper, we used agent-based social network models to test a number of hypotheses on important aspects of binge drinking in a sample representative of the adult Dutch population. In particular, we found that a combination of simple social rules (choosing peers who are similar, being prompted to drink if at least a fraction of them drinks, and incorporating the context) was sufficient to correctly predict the behaviour of half of the binge drinkers and 4 out of 5 non binge drinkers. Furthermore, we used factorial analyses to examine the contribution and combination of hypotheses in predicting the behaviour of individuals, with results indicating that who we interact with may not matter so much as how we interact. Finally, we evaluated the potential for interventions that mediate interactions between people in order to reduce the prevalence of binge drinking and found that the impact of such interventions was non linear: moderate interventions would yield benefits, but stronger interventions may only be of limited further benefit. © JASSS.
Berenbrink P.,8888 University Drive |
Elsasser R.,University of Salzburg |
Sauerwald T.,University of Cambridge
Algorithmica | Year: 2015
We consider rumor spreading on random graphs and hypercubes in the quasirandom phone call model. In this model, every node has a list of neighbors whose order is specified by an adversary. In step i every node opens a channel to its ith neighbor (modulo degree) on that list, beginning from a randomly chosen starting position. Then, the channels can be used for bi-directional communication in that step. The goal is to spread a message efficiently to all nodes of the graph.For random graphs (with sufficiently many edges) we present an address-oblivious algorithm with runtime O(logn) that uses at most O(nloglogn) message transmissions. For hypercubes of dimension logn we present an address-oblivious algorithm with runtime O(logn) that uses at most O(n(loglogn)2) message transmissions.Together with a result of Elsässer (Proc. of SPAA’06, pp. 148–157, 2006), our results imply that for random graphs the communication complexity of the quasirandom phone call model is significantly smaller than that of the standard phone call model. © 2014, Springer Science+Business Media New York.
Kocabas V.,8888 University Drive |
Dragicevic S.,Simon Fraser University |
McCann E.,Simon Fraser University
URISA Journal | Year: 2012
The link between theoretical complexity-based land-use models, more particularly agent-based models, and practical planning support systems (PSS) is not yet fully elaborated in the current literature. Land-use models that use agent-based approaches still need to be improved and robustly tested if they are to be used effectively as a component of PSS. The objective of this study is to propose a framework for the integration of agent-based models in PSS to simulate future land use and, thus, influence land-use policy and decision making. To achieve this end, a Bayesian Network-based Agent System (BNAS) model of urban land-use change has been integrated into a PSS. The model incorporates a geographic information system (GIS), Bayesian Networks (BNs), and agents that represent locational choice behavior of households and commercial firms. In testing the proposed agent-PSS framework for policy generation, this study uses three land-use change scenarios, each associated with different policies for urban development. The framework has been applied to simulations of land-use change in the city of Surrey, British Columbia. The results indicate that the BNAS model can be a useful practical tool to assist urban land-use planners in the examination of 'what-if' scenarios about land-use polices. It can shape the scope and character of decision making and future urban development.
Jaggernauth C.,8888 University Drive
Intelligent Systems Reference Library | Year: 2014
With the projected rise in the senior population, the use of biomedical devices play an indispensable role in the monitoring of the elderly, for staving off the onset of complications as well as providing peace of mind for family members and relief for care-givers. This chapter examines the modeling of the social aspect of biomedical device manufacturing in a lean manufacturing environment. The social aspect includes customer satisfaction with the product as it relates to increased sales. The type of modeling used is fuzzy cognitive. © Springer International Publishing Switzerland 2014.
Araujo H.A.,Simon Fraser University |
Page A.,Simon Fraser University |
Cooper A.B.,Simon Fraser University |
Venditti J.,Simon Fraser University |
And 3 more authors.
Hydrological Processes | Year: 2014
Erosion from logging road surfaces, cut slopes, banks, and ditches represents a chronic source of sediment input to streams that can degrade aquatic habitats. Road surface erosion is of particular concern because the magnitude of sediment generation when traffic levels are high can be large. Current models for predicting sediment production from roads require information on area-specific sediment delivery, which is not often available. Here, we developed a model to quantify suspended sediment concentrations (SSC) generated by forest roads surfaces under different conditions of use and density. This model is designed for a typical medium-size coastal watershed of British Columbia or the American Pacific Northwest, and was applied to the Chilliwack River watershed as a case study. The results illustrate that intensive use of forest roads combined with high road density can increase the number of extreme sedimentation events over a predetermined threshold. A comparison of the effects of road density and the level of road use suggests that the level of road use is more important than the road density for the generation of fine sediment from road surfaces. However, the model omits the impact of roads on mass movements in a watershed, which represent a major source of sediment in steep watersheds, so the effect of road density is likely more substantial than the model predicts. The model is an attempt to overcome field data limitations by using an empirical relation between SSC and traffic variables, and presents a starting point for more intensive field studies that could be used to validate it. © 2013 John Wiley & Sons, Ltd.
Poon L.,Simon Fraser University |
Zandberg W.,8888 University Drive |
Hsiao D.,8888 University Drive |
Erno Z.,8888 University Drive |
And 3 more authors.
ACS Nano | Year: 2010
Photothermal release of DNA from gold nanoparticles either by thermolysis of the Au-S bonds used to anchor the oligonucleotides to the nanoparticle or by thermal denaturation has great therapeutic potential, however, both processes have limitations (a decreased particle stability for the former process and a prohibitively slow rate of release for the latter). Here we show that these two mechanisms are not mutually exclusive and can be controlled by adjusting laser power and ionic strength. We show this using two different double-stranded (ds)DNA-nanoparticle conjugates, in which either the anchored sense strand or the complementary antisense strand was labeled with a fluorescent marker. The amounts of release due to the two mechanisms were evaluated using fluorescence spectroscopy and capillary electrophoresis, which showed that irradiation of the decorated particles in 200 mM NaOAc containing 10 mM Mg(OAc)2 with a pulsed 532 nm laser operating at 100 mW favors denaturation over Au-S cleavage to an extent of more than six-to-one. Due to the use of a pulsed laser, the process occurs on the order of minutes rather than hours, which is typical for continuous wave lasers. These findings encourage continued research toward developing photothermal gene therapeutics. © 2010 American Chemical Society.
Jackson M.,Culex Environmental |
Howay T.,Culex Environmental |
Belton P.,8888 University Drive
Canadian Entomologist | Year: 2013
Using a Center for Disease Control light trap Culiseta particeps (Adams) (Diptera: Culicidae) was collected on four occasions during the spring and summer of 2011. In addition, on 15 April 2011 a pupa was collected from a semi-permanent pool, reared to the adult stage and identified as C. particeps. The collection and identification of these mosquitoes marks the first time C. particeps has been reported in Canada. As there have been specimens identified in both the southwest coast of Alaska, United States of America and northwestern Washington State, United States of America, it is unsurprising that British Columbia, Canada is part of the natural habitat range of C. particeps. Copyright © 2013 Entomological Society of Canada.