1,479 research outputs found
Geometric factors influencing the diet of vertebrate predators in marine and terrestrial environments
No full textPredator–prey relationships are vital to ecosystem function and there is a need for greater predictive
understanding of these interactions. We develop a geometric foraging model predicting minimum
prey size scaling in marine and terrestrial vertebrate predators taking into account habitat
dimensionality and biological traits. Our model predicts positive predator–prey size relationships
on land but negative relationships in the sea. To test the model, we compiled data on diets of 794
predators (mammals, snakes, sharks and rays). Consistent with predictions, both terrestrial endotherm
and ectotherm predators have significantly positive predator–prey size relationships. Marine
predators, however, exhibit greater variation. Some of the largest predators specialise on small
invertebrates while others are large vertebrate specialists. Prey–predator mass ratios were generally
higher for ectothermic than endothermic predators, although dietary patterns were similar.
Model-based simulations of predator–prey relationships were consistent with observed relationships,
suggestin
Profile of author B.J. Morrison of Bar Harbor, plus a review of her most recent
No full textProfile of author B.J. Morrison of Bar Harbor, plus a review of her most recent novel, The Martini Effect
BIEN2 grafted phylogeny (rep. 1)
No full textPhylogeny of 81,274 terrestrial vascular plants found in the BIEN2 database (Enquist et al. 2016). To assemble this phylogeny a species-level multi-gene tree for ~65,000 species was made from the atpB-rbcL, ndhF, psbA, psbA-psbH, rbcL, and trnT-trnL-trnF regions via the software program PHLAWD (Smith et al. 2009), which automatically queries GenBank sequence records. The tree was estimated using RAxML 7.3.0 (Stamatakis 2006) with the unconstrained maximum likelihood search method and treePL[2] (Smith & O’meara 2012) was used to estimate divergence times. Remaining taxa from the 88,824 in the BIEN2 database without genetic data were randomly placed within their genus or removed if generic affinities were not known.
REFERENCES
Enquist, B.J., Condit, R., Peet, R.K., Schildhauer, M. & Thiers, B.M. (2016). Cyberinfrastructure for an integrated botanical information network to investigate the ecological impacts of global climate change on plant biodiversity. PeerJ Preprints, e2615v1.
Smith, S.A., Beaulieu, J.M. & Donoghue, M.J. (2009). Mega-phylogeny approach for comparative biology: an alternative to supertree and supermatrix approaches. BMC Evolutionary Biology, 9, 37.
Smith, S.A. & O’meara, B.C. (2012). treePL: divergence time estimation using penalized likelihood for large phylogenies. Bioinformatics, 28, 2689-2690.
Stamatakis, A. (2006). RAxML-VI-HPC: maximum likelihood-based phylogenetic analyses with thousands of taxa and mixed models. Bioinformatics, 22, 2688-2690
MV Ocean Endeavour cruise 13 Oct-06 Nov 2005. Seabed environmental survey of Angola Blocks 18 and 31
No full textThis cruise was carried out on behalf of BP Angola and comprised a seabed environmentalsurvey of Angola Blocks 18 and 31 (bathyal SE Atlantic). Seabed sampling was undertaken byMegacorer to provide samples for macrobenthos, hydrocarbon, heavy metal and particle sizeanalysis. Seabed photography (still and video) was undertaken with the NOC WASP vehicle.Baited, time-lapse camera deployments were undertaken using the BP ROBIO system(Oceanlab, Aberdeen). The survey spanned water depths of 1300-2050m over the AngolanMargin and included studies in and around seabed pockmarks and salt diapirs. Someindications of fluid flow and chemosynthetic communities were encountered.Should you wish to consult or cite this report please contact the author directly (Brian Bett,[email protected], +44 (0)23 80596355)
The Effect Of Error Correcting Coding On Indoor Wireless Communications Systems In The 20 - 60 GHz Region
No full textAs a follow-up of the literature study ’An Overview Of Indoor Wireless Communications Systems In Ilie 20 - 60 GHz Region’, published by B.J. Bout jand W.A. Schouten in December 1992, a further study has been performed to investigate the effect of Forward Error Correcting Coding on Indoor Wireless Communications Systems. This has been done by calculating the average fade- and non-fade duration as a function of the frequency and the Signal To Noise ratio. These results are conveyed to a Bit Error Probability. After that, the same calculations are done for the same channel, but with Forward Error Correcting Coding.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Transient energy growth modulation by temperature dependent transport properties in a stratified plane Poiseuille flow
No full textWe investigate the effect of temperature dependent thermal conductivity λ and isobaric specific heat c_P on the transient amplification of perturbations in a thermally stratified laminar plane Poiseuille flow. It is shown that for decreasing thermal conductivity the maximum transient energy growth is amplified with respect to the λ=1 case, while the opposite occurs for increasing λ. A reversed mechanism is induced by a variable c_p. Substantial maximum growth enhancement/suppression is found in the range of Prandtl numbers Pr which encompasses most fluids of practical interest. The relative growth modulation shows an optimum Pr under spanwise perturbations. For energy amplifying property distributions a speed-up of the transient to reach the maximum energy growth is observed at low Pr, while a slow-down is found at large Pr. The opposite is true when the property variations suppress the growth of perturbations
La escala metabólica en insectos apoya las predicciones del modelo WBE
No full textLa asociación funcional entre el tamaño corporal y la tasa metabólica (BS-MR) es una de las cuestiones más intrigantes de la fisiología ecológica. En general, se observa un exponente de escala promedio de 3/4 en los taxones de animales y plantas. El valor numérico de 3/4 se predice teóricamente bajo la versión optimizada del modelo de red de suministro de recursos vasculares de West, Brown y Enquist. Sin embargo, recientemente se ha propuesto que los insectos expresen un exponente de escala numéricamente diferente y, por lo tanto, se ha rechazado la aplicación del modelo de red WBE a los insectos. Aquí, volvemos a analizar si tal variación está respaldada por una desviación global en todos lostaxones de insectos a nivel de orden y familia para evaluar si taxones específicos influyen en la escala metabólica de los insectos.The functional association between body size and metabolic rate (BS–MR) is one of the most intriguing issues in ecological physiology. An average scaling exponent of 3/4 is broadly observed across animal and plant taxa. The numerical value of 3/4 is theoretically predicted under the optimized version of West, Brown, and Enquist's vascular resource supply network model. Insects, however, have recently been proposed to express a numerically different scaling exponent and thus application of the WBE network model to insects has been rejected. Here, we re-analyze whether such variation is indeed supported by a global deviation across all insect taxa at the order and family levels to assess if specific taxa influence insect metabolic scaling. We show that a previous reported deviation is largely due to the effect of a single insect family (Termitidae)
Interim report on the seabed environmental survey of Angola Blocks 18 and 31 (MV Ocean Endeavour cruise 2005)
No full textThis report is based on initial (at sea) observations of the seabed environment and fauna of Angola Blocks 18 and 31 as assessed during the MV Ocean Endeavour environmental survey (13 Oct-06 Nov, 2005). The report draws on the appearance and other physical characteristics of core samples and on photographic observations of the seafloor from deployments of the NOCS WASP system and the BP ROBIO lander. The megabenthos and fish populations appear to be consistent with a quiescent, fine-sedimented, bathyal region. No living cold seep (or comparable) communities were encountered during the survey. However, site ME1 (Block 31, large pockmark) has cemented sediments, both within the sediment column and at the sediment surface, and the fragmented shell remains of what appear to be large cold seep mussels; an extant community may be present in this vicinity. Other bivalve molluscs (both living and dead) of possible chemosynthetic nature were recovered from other sites (Block 31, on the periphery of diapiric features).Should you wish to consult or cite this report please contact the author directly (Brian Bett, [email protected], +44 (0)23 80596355).<br/
Collected reports of commercial deep-water surveys carried out north and west of Shetland during RRS Charles Darwin cruise 123C3-4
No full textRRS Charles Darwin cruise 123C3-4 formed part of the Atlantic Margin Environmental Survey(AMES) and also carried out commercially funded deep-water seabed surveys. This contribution detailsthose activities and comprises four sections:Part A. Report of seagoing operations and seabed observations undertaken in Tranche 4 (West ofShetland) on behalf of Enterprise. This report addresses a survey of the deep (1030-1275m) Faroe-Shetland Channel (61°36´N 001°55´W) encompassing a range of habitats (open slope; lineated slope,contourite band; basin floor). These habitats are readily distinguished in terms of their megabenthiccommunities; example photographs of the seafloor and its associated fauna are provided.Part B. Report of seagoing operations and seabed observations undertaken in Tranches 65-67 (Northof Shetland) on behalf of Statoil and BP. This report addresses a survey of the deep (900-1000m) slopeNorth of Shetland (62°20´N 000°10´E) in a region of silty sand contourite deposit. The megabenthiccommunities are dominated by cerianthid anemones and stalked sponges and also notable for theoccurrence of ‘giant’ seapens (Umbellula sp.). An intriguing observation is made of two occurrences (atseparate sites some 7km apart) of fabric bags on the seafloor that appear to have attracted (scavenging)gastropods and prompted the deposition of numerous egg masses. Example photographs of the seafloorand its associated fauna are provided.Part C. Report of seabed observations made in the vicinity of Texaco site TX1: observation of a“tubeworm” patch. This report addresses a survey of the deep (1550m) Faroe-Shetland Channel floor(61°55´N 003°00´W). The survey is notable for recording what appeared to be small (c. 20m across)discrete patch of what appeared to be tubeworms (Siboglinidae). Example photographs of the seafloorand its associated fauna are provided.Part D. Assessment of Texaco site TX1 environmental data. This report addresses a survey of the deep(1550m) Faroe-Shetland Channel floor (61°55´N 003°00´W) and provides an analysis of physicochemical(hydrocarbons, heavy metals, sediments) and biological parameters (macrobenthos) at thesurvey site compared with 35 other sites in the deep Faroe-Shetland Channel obtained during theAtlantic Frontier Environmental Network surveys of 1996 and 1998.Should you wish to consult or cite this report or any of its constituent parts please contact the author directly(Brian Bett, [email protected], +44 (0)23 80596355)
Effect of viscosity and density gradients on turbulent channel flows
No full textWe perform Direct Numerical Simulations (DNS) of a turbulent channel flow with temperature dependent density and viscosity. The Navier-Stokes equations are solved using their low Mach number formulation. In the simulations performed, the fluid is internally heated and the temperature at the walls is fixed. The friction Reynolds number based on half channel height and wall friction velocity is Reτ = 395. The modulation of turbulence, which is caused by the density and viscosity gradients, is characterized using the semi-local scaling of Huang et al. [1995, JFM]
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