Search results for "POPULATIONS"
showing 10 items of 493 documents
Spatio-temporal behaviour of the deep chlorophyll maximum in Mediterranean Sea: Development of a stochastic model for picophytoplankton dynamics
2013
In this paper, by using a stochastic reaction-diffusion-taxis model, we analyze the picophytoplankton dynamics in the basin of the Mediterranean Sea, characterized by poorly mixed waters. The model includes intraspecific competition of picophytoplankton for light and nutrients. The multiplicative noise sources present in the model account for random fluctuations of environmental variables. Phytoplankton distributions obtained from the model show a good agreement with experimental data sampled in two different sites of the Sicily Channel. The results could be extended to analyze data collected in different sites of the Mediterranean Sea and to devise predictive models for phytoplankton dynam…
Modeling of Sensory Characteristics Based on the Growth of Food Spoilage Bacteria
2016
During last years theoretical works shed new light and proposed new hypothesis on the mechanisms which regulate the time behaviour of biological populations in different natural systems. Despite of this, the role of environmental variables in ecological systems is still an open question. Filling this gap of knowledge is a crucial task for a deeper comprehension of the dynamics of biological populations in real ecosystems. In this work we study how the dynamics of food spoilage bacteria influences the sensory characteristics of fresh fish specimens. This topic is crucial for a better understanding of the role played by the bacterial growth on the organoleptic properties, and for the quality …
Noise Induced Phenomena in the Dynamics of Two Competing Species
2015
Noise through its interaction with the nonlinearity of the living systems can give rise to counter-intuitive phenomena. In this paper we shortly review noise induced effects in different ecosystems, in which two populations compete for the same resources. We also present new results on spatial patterns of two populations, while modeling real distributions of anchovies and sardines. The transient dynamics of these ecosystems are analyzed through generalized Lotka-Volterra equations in the presence of multiplicative noise, which models the interaction between the species and the environment. We find noise induced phenomena such as quasi-deterministic oscillations, stochastic resonance, noise …
Rural Municipalities and Change in Local School Structure: Comparing Room of manoeuvre among Rural Municipalities in Latvia and Norway
2018
Rural depopulation, decreasing numbers of children and general centralization combined with high expectations to education, are factors that challenge rural communities and school structures in Latvia and Norway. The ambition of this article is to explore and compare the role of the municipality and other levels of governance in making decisions on school structure in rural municipalities. The research method is a multiple case study approach, supported by survey data. Through the lenses of multi-level governance theory, we have investigated how national frames like regulations and educational expectations are affecting local decision-making. Local politicians navigate between national fram…
The Principle of Stasis: Why drift is not a Zero-Cause Law
2016
This paper analyses the structure of evolutionary theory as a quasi-Newtonian theory and the need to establish a Zero-Cause Law. Several authors have postulated that the special character of drift is because it is the default behaviour or Zero-Cause Law of evolutionary systems, where change and not stasis is the normal state of them. For these authors, drift would be a Zero-Cause Law, the default behaviour and therefore a constituent assumption impossible to change without changing the system. I defend that drift's causal and explanatory power prevents it from being considered as a Zero-Cause Law. Instead, I propose that the default behaviour of evolutionary systems is what I call the Princ…
Adaptation to fluctuations in temperature by nine species of bacteria
2018
Rapid environmental fluctuations are ubiquitous in the wild, yet majority of experimental studies mostly consider effects of slow fluctuations on organism. To test the evolutionary consequences of fast fluctuations, we conducted nine independent experimental evolution experiments with bacteria. Experimental conditions were same for all species, and we allowed them to evolve either in fluctuating temperature alternating rapidly between 20°C and 40°C or at constant 30°C temperature. After experimental evolution, we tested the performance of the clones in both rapid fluctuation and in constant environments (20°C, 30°C and 40°C). Results from experiments on these nine species were combined meta…
Narrativa dei Caraibi nel nuovo millennio
2020
L’etichetta “Letterature franco-caraibica” utilizzata, per convenzione, dalla critica per indicare unitariamente la produzione letteraria in lingua francese della regione centrale del Continente americano è assai impropria. La regione dei Caraibi abbraccia, infatti, sia alcune delle isole dell’arcipelago delle Piccole Antille (Martinica, Guadalupa), sia l’isola di Haïti, che fa parte delle Grandi Antille, che la Guiana incastonata sulla costa orientale dell’America meridionale. Pur nella diversità dei movimenti ideologici e degli avvenimenti storici che si sono succeduti nella regione, le opere letterarie degli scrittori caraibici francofoni, nel loro insieme, hanno oscillato, e continuano …
Caraibi: un "archipel inachevé"
2018
L’etichetta “Letterature franco-caraibica” utilizzata, per convenzione, dalla critica per indicare unitariamente la produzione letteraria in lingua francese della regione centrale del Continente americano è assai impropria. La regione dei Caraibi abbraccia, infatti, sia alcune delle isole dell’arcipelago delle Piccole Antille (Martinica, Guadalupa), sia l’isola di Haïti, che fa parte delle Grandi Antille, che la Guiana incastonata sulla costa orientale dell’America meridionale. Pur nella diversità dei movimenti ideologici e degli avvenimenti storici che si sono succeduti nella regione, le opere letterarie degli scrittori caraibici francofoni, nel loro insieme, hanno oscillato, e continuano …
Tracking trace elements from soil to Lebanese bread and Populations Exposure
2021
In Lebanon, the agri-food industry represents 18% of the industrial sector and yet food safety remains a major problem. In this interdisciplinary thesis, we followed the Trace Elements (TEs) in the Lebanese white bread sector "from farm to fork" based on the reality on the ground, and on two links in the sector: (i) the geogenic or anthropogenic origin of TEs present in the soil and their transfer to the wheat grain, for which 10 plots cultivated in wheat, covering the diversity of soils, irrigation practices and anthropogenic environments of the central Bekaa were chosen ; (ii) the exposure of populations to TEs present in bread, for which a survey of consumption habits across Lebanon was …
Evolutionary transition to the ectomycorrhizal habit in the genomes of a hyperdiverse lineage of mushroom‐forming fungi
2022
International audience; Summary The ectomycorrhizal (ECM) symbiosis has independently evolved from diverse types of saprotrophic ancestors. In this study, we seek to identify genomic signatures of the transition to the ECM habit within the hyper-diverse Russulaceae. We present comparative analyses of the genomic architecture and the total and secreted gene repertoires of 18 species across the order Russulales of which 13 are newly sequenced, including a representative of a saprotrophic member of Russulaceae, Gloeopeniophorella convolvens. The genomes of ECM Russulaceae are characterized by a loss of genes for plant cell-wall degrading enzymes (PCWDEs), an expansion of genome size through in…