Models of interference and their consequences for the spatial distribution of ideal and free predators (original) (raw)
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AAAI Spring Symposium Series, 2010
In this paper, we propose a model of the web of data as a graph of interlinked graphs which goes beyond the standard single-graph RDF semantics, describe two different ways in which a query on this structure can be answered, and characterize semantically each of these ways in terms of restrictions on the relation between the domain of interpretation of each single component graph.
Behavioral Ecology, 2010
Interference competition, the immediately reversible decrease in per capita foraging success with increasing forager density, has important implications for the distribution of foragers. Theoretical models predict the strength of interference at different prey densities for birds differing in dominance. Observational studies have been used to validate the theoretical predictions, but there is reason to believe that these nonexperimental studies suffer from confounding factors. We therefore manipulated forager density of oystercatchers Haematopus ostralegus foraging on live cockles Cerastoderma edule (low density: 1 bird per 50 m 2 and high density: 2 birds per 50 m 2 ) in a unique experimental facility closely mimicking natural feeding conditions. In the high-density situation, the intake rate was on average reduced by 36% compared with the interference-free intake rate. However, this effect depended on status with intake rate of subordinates being more strongly reduced than intake rate of dominants (245% vs. 225%). We could not investigate all possible mechanisms, but we observed that birds actively avoided each other, possibly to avoid kleptoparasitism. Our experiment shows that the decline in intake rate with increasing density of conspecifics is at least partly due to direct interactions between birds and possibly also to indirect interactions via prey depression but not to an unidentified confounding factor that covaries with intake rate and bird density, as may have been the case in nonexperimental field studies.
Friends and foes in foraging: intraspecific interactions act on foraging-cycle stages
Behaviour, 2006
Intraspecific interactions may increase or decrease foraging rates of individual consumers, and such facilitation or interference interactions should affect individual foraging economies as well as predator-prey processes at the population level. To mechanistically predict individual foraging performance, we need to investigate the effects of positive and negative interactions on separate foraging-cycle stages. We illustrate the importance and viability of examining the effects of facilitation and interference on different foraging-cycle stages using three piscivore species as a model system. We studied individual foraging behaviour when alone or in the presence of conspecifics, and show that northern pike foraging in the presence of conspecifics decrease attack frequencies and consumption rates, although no explicit agonistic behaviours were recorded. Pikeperch increase consumption rates in conspecific groups, possibly through a prey-mediated increase in capture success, as pikeperch showed no direct behavioural interactions. The actively cooperating Eurasian perch increase capture success and consumption rates in groups. The results demonstrate the need to combine behavioural studies of positive and negative effects of intraspecific interactions on foraging-cycle stages with quantifications of overall consumption rates. Pure behavioural observations may result in misinterpretations of the effects of interactions on foraging, while studies on consumption rates only would lack the mechanistic base of the obtained results. We also suggest that effects of intraspecific interactions during the foraging cycle should be incorporated in mechanistic models of facilitation and interference to elucidate the link between individual behaviours and higher-order processes.
Web of Data and Web of Entities: Identity and Reference in Interlinked Data in the Semantic Web
Philosophy & Technology, 2012
Using web standards, such as uniform resource identifiers (URIs), XML and HTTP, for naming and describing resources which are not information objects is the key difference between the Web as we know it today and the Semantic Web. Naming and interlinking this type of resources by HTTP URIs (instead of individual constants in a formal language) is the key feature which distinguishes traditional knowledge representation from web-scale knowledge representation. However, this use of URIs brought back attention to the old philosophical problem of identity and reference in a new form. In this paper, we analyze the new version of the problem, provide a formal model for dealing with it when interlinking knowledge on the Web, and argue for the need of a distinction between the use of URIs for describing and accessing resources, and the use of URIs for f ixing the reference. We show that in the current practice of linking data these roles are not clearly distinguished, and that this fact may cause unwanted effects and prevent some basic forms of data integration. We also discuss the role of an entity name system as a potential piece of infrastructure for fixing the reference in the Semantic Web.
Physics and Chemistry of Minerals, 2000
An in situ high-pressure (HP) X-ray diraction investigation of synthetic diopside and of the Ca 0.8 Mg 1.2 Si 2 O 6 clinopyroxene (Di 80 En 20 ) was performed up to respectively P=40.8 and 15.1 GPa, using high brilliance synchrotron radiation. The compression of the cell parameters is markedly anisotropic, with b b b c > b a > b asinb for any pressure range and for both diopside and Di 80 En 20 . The compressibility along the crystallographic axes decreases signi®cantly with pressure and is higher in Di 80 En 20 than in diopside. The b cell parameter decreases as well with pressure, at a higher rate in Di 80 En 20 . The cell volume decreases at almost the same rate for the two compositions, since in diopside a higher compression along a* occurs. A change in the mechanism of deformation at P higher than about 5±10 GPa is suggested for both compositions from the analysis of the strain induced by compression. In diopside at lower pressures, the deformation mainly occurs, at a similar rate, along the b axis and at a direction 145°f rom the c axis on the (0 1 0) plane. At higher pressures, instead, the deformation occurs mostly along the b axis. In Di 80 En 20 the orientation of the strain axes is the same as in diopside. The substitution of Ca with Mg in the M2 site induces at a given pressure a higher deformation on (0 1 0) with respect to diopside, but a similar change in the compressional behaviour is found. Changes in the M2 polyhedron with pressure can explain the above compressional behaviour. A third-order Birch-Murna-ghan equation of state was ®t to the retrieved volumes, with K=105.1(9) GPa, K¢=6.8(1) for diopside and K=107.3(1.4) GPa, K¢=5.7(3) for Di 80 En 20 ; the same equation can be applied for any pressure range. The elasticity of diopside is therefore not signi®cantly affected by Mg substitution into the M2 site, in contrast to the signi®cant stiening occurring for Ca substitution into Mg-rich orthopyroxenes.
Cell placement and neural guidance using a three-dimensional microfluidic array
Japanese Journal of Applied Physics, 2001
Several fabrication techniques for making three-dimensional arrays of micro-wells for biological cell patterning and single-neuron guidance are presented. Methods for making complex 3d high-aspect-ratio structures in poly-dimethylsiloxane (PDMS) membrane are explored. In this work, three-dimensional micro-molds are made directly on silicon wafers though inductively coupled plasma reactive ion etching (ICP-RIE), and also using SU-8 negative photoresist. Cell placement is achieved through an array of 50-µm square holes in a 150-100 µm thick PDMS membrane, which is placed on a glass substrate. Vertical holes in the membrane are linked by horizontal tunnels on the glass side of the membrane, for use in neural guidance or delivery of drugs or nutrients. The effectiveness of the membrane for cell placement, growth and guidance was tested using fluorescent yeast cells and PC12 neuronal cells.