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Age structure in neutral theory resolves inconsistencies related to reproductive-size threshold

Journal of Plant Ecology 2012年第1期5卷 64-71页

作者： James Rosindell Patrick A.Jansen rampal s.etienne Institute of Integrative and Comparative Biology Faculty of Biological SciencesUniversity of LeedsLeeds LS29JTWest YorkshireUK Institute of Bioinformatics and Evolutionary studies University of IdahoMoscowID 83844USA Center for Tropical Forest science Smithsonian Tropical Research InstitutePO Box 0843-03092BalboaAnconRepublic of Panama Centre of Ecosystem studies Wageningen UniversityPO Box 476700 AA Wageningenthe Netherlands Community and Conservation Ecology Centre for Ecological and Evolutionary StudiesUniversity of GroningenPO Box 111039700 CC Groningenthe Netherlands

Aims Neutral theory consists of a suite of models that assume ecological equivalence among individual *** have been most commonly applied to tropical forest tree communities either as null models or as *** models typically only include reproductive adults;therefore,fitting to empirical tree community data requires defining a reproductive-size threshold,which for trees is usually set arbitrarily to a diameter at breast height(DBH)of 100 *** inevitable exclusion of some reproductive adults and inclusion of some saplings cause a non-random sampling bias in neutral model ***,we investigate this problem and resolve it by introducing simple age structure into a neutral *** We compared the performance and sensitivity of DBH threshold of three variants of a spatially explicit neutral model:the traditional model,a model incorporating random sampling and a model with two distinct age classes—reproductive adults and *** the age-structured model,saplings are offspring from adults that disperse according to a Gaussian dispersal kernel around the *** only extra parameter is the ratio of adults to saplings,which is not a free parameter but directly *** used species–area relationships(sARs)to explore the predicted effect of saplings on the species richness at different scales in our *** then evaluated the three model variations to find the parameters required to maintain the observed level of species richness in the 50-ha plot on Barro Colorado Island(BCI).We repeated our analysis filtering the data at different minimum tree-size thresholds in order to find the effect this threshold has on our ***,we used empirical species–individual relationships(sIRs)to test the pre-existing hypothesis that environmental filtering is the primary cause of differences between the assemblage of saplings and that of adults on *** Findings Our age-structured neutral model was characterized by sARs that

关键词： neutral theory age structure sampling DBH

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Optical actuation of a micromechanical photodiode via the photovoltaic-piezoelectric effect

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Microsystems & Nanoengineering 2021年第2期7卷 167-175页

作者： A.rampal R.N.Kleiman Department of Engineering Physics McMaster UniversityHamiltonONL8S 4L7Canada Present address:CircuitMind Inc 185 Spadina AvenueTorontoONM5T 2C6Canada

Radiation pressure and photothermal forces have been previously used to optically actuate micro/nanomechanical structures fabricated from semiconductor piezoelectric materials such as gallium arsenide(GaAs).In these materials,coupling of the photovoltaic and piezoelectric properties has not been fully explored and leads to a new type of optical actuation that we call the photovoltaic-piezoelectric effect(PVPZ).We demonstrate this effect by electrically measuring,via the direct piezoelectric effect,the optically induced strain in a novel torsional *** micron-scale torsional resonator is fabricated from a lattice-matched single-crystal molecular beam epitaxy(MBE)-grown GaAs photodiode *** find that the strain depends on the product of the electro-optic responsivity and piezoelectric constant of *** photovoltaic-piezoelectric effect has important potential applications,such as in the development of configurable optical circuits,which can be used in neuromorphic photonic chips,processing of big data with deep learning and the development of quantum circuits.

关键词： resonator piezoelectric effect

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