Search results for " population dynamics"
showing 10 items of 35 documents
A Simple Noise Model with Memory for Biological Systems
2005
A noise source model, consisting of a pulse sequence at random times with memory, is presented. By varying the memory we can obtain variable randomness of the stochastic process. The delay time between pulses, i. e. the noise memory, produces different kinds of correlated noise ranging from white noise, without delay, to quasi-periodical process, with delay close to the average period of the pulses. The spectral density is calculated. This type of noise could be useful to describe physical and biological systems where some delay is present. In particular it could be useful in population dynamics. A simple dynamical model for epidemiological infection with this noise source is presented. We …
SIMULATING DEMOGRAPHY AND HUMAN DEVELOPMENT DYNAMICS
2014
[EN] A deterministic/stochastic model in which the demographic and the well-being subsystems of a country are involved and related is presented as a way to approach human development. The demographic subsystem is a side-by-side, single-gender, age-structured population dynamic model. The well-being subsystem states the dynamics of the United Nations Hybrid Human Development Index. The model has been validated in the case of Spain and Belgium. Some simulations have been performed with the model for the case of Spain in the 2009-2020 period to determine strategies and scenarios that could increase the life expectancy at birth per gender. Copyright © 2014 Taylor & Francis Group, LLC.
Hydrodynamism and its influence on the reproductive condition of the edible sea urchin Paracentrotus lividus
2013
Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodyna…
Time evolution of non-lethal infectious diseases: a semi-continuous approach.
2005
A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza.
Microbial Diversity in the Midguts of Field and Lab-Reared Populations of the European Corn Borer Ostrinia nubilalis
2011
Background: Insects are associated with microorganisms that contribute to the digestion and processing of nutrients. The European Corn Borer (ECB) is a moth present world-wide, causing severe economical damage as a pest on corn and other crops. In the present work, we give a detailed view of the complexity of the microorganisms forming the ECB midgut microbiota with the objective of comparing the biodiversity of the midgut-associated microbiota and explore their potential as a source of genes and enzymes with biotechnological applications. Methodological/Principal Findings: A high-throughput sequencing approach has been used to identify bacterial species, genes and metabolic pathways, parti…
La Valle dei Templi in epoca medioevale. Caratterizzazione antropologica e paleopatologica delle sepolture antistanti in Tempio della Concordia
2021
Riassunto ― Il lavoro presenta i risultati delle analisi bio-archeologiche effettuate su resti scheletrici umani rinvenuti in quattordici sepolture di epoca medioevale rinvenute nel Parco Archeologico della Valle dei Templi di Agrigento (Sicilia). L’obiettivo è stato l’acquisizione delle informazioni necessarie per la ricostruzione del profilo biologico di ciascun individuo, al fine di determinarne il sesso, la stima dell’età biologica alla morte, la stima della statura e la valutazione delle patologie e degli indicatori di stress occupazionale mediante le correnti metodologie e tecniche diagnostiche di tipo antropologico. Sebbene il cattivo stato di conservazione di alcuni individui non ne…
Graphical representation of some duality relations in stochastic population models
2007
We derive a unified stochastic picture for the duality of a resampling-selection model with a branching-coalescing particle process (cf. http://www.ams.org/mathscinet-getitem?mr=MR2123250) and for the self-duality of Feller's branching diffusion with logistic growth (cf. math/0509612). The two dual processes are approximated by particle processes which are forward and backward processes in a graphical representation. We identify duality relations between the basic building blocks of the particle processes which lead to the two dualities mentioned above.
Nonmonotonic Pattern Formation in Three Species Lotka-Volterra System with Colored Noise
2005
A coupled map lattice of generalized Lotka-Volterra equations in the presence of colored multiplicative noise is used to analyze the spatiotemporal evolution of three interacting species: one predator and two preys symmetrically competing each other. The correlation of the species concentration over the grid as a function of time and of the noise intensity is investigated. The presence of noise induces pattern formation, whose dimensions show a nonmonotonic behavior as a function of the noise intensity. The colored noise induces a greater dimension of the patterns with respect to the white noise case and a shift of the maximum of its area towards higher values of the noise intensity.
Role of sub- and super-Poisson noise sources in population dynamics
2020
In this paper we present a study on pulse noise sources characterized by sub- and super-Poisson statistics. We make a comparison with their uncorrelated counterpart. i.e. pulse noise with Poisson statistics, while showing that the correlation properties of sub- and super-Poisson noise sources can be efficiently applied to population dynamics. Specifically, we consider a termite population, described by a Langevin equation in the presence of a pulse noise source, and we study its dynamics and stability properties for two models. The first one describes a population of several colonies in a new territory with adverse environmental conditions. The second one considers the development of a sing…
The effectiveness of fish feeding behaviour in mirroring trawling-induced patterns
2017
The ability to observe and predict trawling-induced patterns at spatial and temporal scales that are relevant to inform realistic management strategies is a challenge which scientists have consistently faced in recent decades. Here, we use fish feeding behaviour, a biological trait easily impaired by trawling disturbance, to depict alterations in fish condition (i.e. individual fitness) and feeding opportunities. The benthivorous fish Mullus barbatus barbatus was selected as a model species. The observed trends of responses to trawling in prey species confirmed the effectiveness of a non-trawled zone in sustaining higher levels of diet diversity (e.g. quantity and quality of ingested prey) …