نتایج جستجو برای: population fluctuation

تعداد نتایج: 719135  

Journal: :Social Choice and Welfare 2001
Nicolas Gravel

The work of John Broome hardly needs an introduction to the readership of Social Choice and Welfare. It is a rare example of an intellectual e¤ort of a high quality which has managed to remain in the di¢ cult boundary zone between economics and philosophy. Ethics out of Economics is a collection of papers which, with one exception,1 have all been published by the author in the last ten years. T...

2000
J. W. Moffat

A brief review is given of the present observational data in cosmology. A review of a new bimetric gravity theory with multiple light cones is presented. The physical consequences of this gravity theory for the early universe are analyzed. 1 Status of Observational Cosmology The ten most significant parameters to be determined in observational cosmology are: 1. Age of the universe: t0 2. The Hu...

2007
Zoltan Eisler Janos Kertesz

∝ 〈n|A〉2α with 1/2 ≥ α ≥ 1 when a parameter A (usually the system size) is varied. A can be the strength of the node, the capitalization of the firm or the area of the habitat. On the other hand, quantities often obey gap scaling meaning that their density function depends on, say, the system size A as P (n|A) = nF (n/A). This note describes that these two notions cannot coexist except when α =...

2009
Matthew Parker Alex Kamenev

Competitive birth-death processes often exhibit an oscillatory behavior. We investigate a particular case where the oscillation cycles are marginally stable on the mean-field level. An iconic example of such a system is the Lotka-Volterra model of predator-prey competition. Fluctuation effects due to discreteness of the populations destroy the mean-field stability and eventually drive the syste...

2009
Richard Anton Braun Huiyu Li John Stachurski

We propose a generalized look-ahead estimator for computing densities and expectations in economic models. We provide conditions under which the estimator converges globally with probability one, and exhibit the asymptotic distribution of the error. Our estimator is more efficient than other Monte Carlo based approaches. Numerical experiments indicate that the estimator can provide large increa...

2017
Xin-Feng Zhao Yi-Qi Hao Quan-Guo Zhang

Habitat productivity may affect the stability of consumer-resource systems, through both ecological and evolutionary mechanisms. We hypothesize that coevolving consumer-resource systems show more stable dynamics at intermediate resource availability, while very low-level resource supply cannot support sufficiently large populations of resource and consumer species to avoid stochastic extinction...

Journal: :کشاورزی (منتشر نمی شود) 0
حسن قهاری استادیار حشره شناسی، گروه کشاورزی دانشگاه آزاد اسلامی واحد شهرری، تهران مهرداد طبری مربی پژوهش، مؤسسه تحقیقات برنج کشور، آمل، مازندران

striped rice stem borer, chilo suppressalis (lepidoptera: pyralidae) is one of the major pests in north part of iran which causes serious damage. the last larval instar overwinters in the stem of weeds around the fields. regarding the importance of weeds as overwintering habitat, population density of larvae was studied in three areas; low-, mid-, and up-lands of mazandaran province and also on...

Journal: :Brazilian journal of biology = Revista brasleira de biologia 2012
L P M Brandão T Fajardo E Eskinazi-Sant'anna S Brito P Maia-Barbosa

The fluctuation of the population of Daphnia laevis in Lake Jacaré (Middle River Doce, Minas Gerais) was monitored monthly (at one point in the limnetic region) for six years (2002-2007) as part of the Program of Long-Term Ecological Research (LTER/UFMG). The following parameters were also monitored: water temperature, pH, electrical conductivity, dissolved oxygen, chlorophyll a, total phosphor...

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