Search results for "FOS"

Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

2011

Abstract Background The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three dist…

A stoichiometric perspective on host-parasite interactions

2013

Quei bravi ragazzi di Ca' Bembo, ieri e oggi. Opinioni e racconti di notable Alumni per tracciare una storia dei laureati in Economia aziendale di Ve…

2015

Sono ormai trascorsi trent'anni dalla fondazione di ALEA e ben quaranta dacché uscirono da Ca' Foscari i primi laureati del corso di laurea in economia aziendale. Tale orizzonte temporale sembra sufficiente per dedicarsi allo studio delle origini di entrambi, nonché per valutare l'impatto che la formazione aziendalista ha avuto sui laureati di Ca' Bembo e – di converso – quello che i Cambembini hanno quindi profuso sul mondo delle organizzazioni. La ricorrenza del trentennale offre un'occasione privilegiata per riflettere sulla tradizione aziendalista veneziana anche guardando alle carriere di alcuni laureati eccellenti, interrogandoli sul loro passato a Ca' Foscari e sulla successiva traie…

Squeezing of Quantum Noise of Motion in a Micromechanical Resonator

2015

A pair of conjugate observables, such as the quadrature amplitudes of harmonic motion, have fundamental fluctuations which are bound by the Heisenberg uncertainty relation. However, in a squeezed quantum state, fluctuations of a quantity can be reduced below the standard quantum limit, at the cost of increased fluctuations of the conjugate variable. Here we prepare a nearly macroscopic moving body, realized as a micromechanical resonator, in a squeezed quantum state. We obtain squeezing of one quadrature amplitude $1.1 \pm 0.4$ dB below the standard quantum limit, thus achieving a long-standing goal of obtaining motional squeezing in a macroscopic object.

Nonlinear Relaxation in Population Dynamics

2001

We analyze the nonlinear relaxation of a complex ecosystem composed of many interacting species. The ecological system is described by generalized Lotka-Volterra equations with a multiplicative noise. The transient dynamics is studied in the framework of the mean field theory and with random interaction between the species. We focus on the statistical properties of the asymptotic behaviour of the time integral of the i-th population and on the distribution of the population and of the local field.

Noise in ecosystems: a short review

2004

Noise, through its interaction with the nonlinearity of the living systems, can give rise to counter-intuitive phenomena such as stochastic resonance, noise-delayed extinction, temporal oscillations, and spatial patterns. In this paper we briefly review the noise-induced effects in three different ecosystems: (i) two competing species; (ii) three interacting species, one predator and two preys, and (iii) N-interacting species. 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. The interaction parameter between the species is random …

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.

Comparison of non-Markovianity criteria in a qubit system under random external fields

2013

We give the map representing the evolution of a qubit under the action of non-dissipative random external fields. From this map we construct the corresponding master equation that in turn allows us to phenomenologically introduce population damping of the qubit system. We then compare, in this system, the time-regions when non-Markovianity is present on the basis of different criteria both for the non-dissipative and dissipative case. We show that the adopted criteria agree both in the non-dissipative case and in the presence of population damping.

Population dynamics of fossorial water vole (Arvicola terrestris scherman): a land use and landscape perspective

1997

Abstract This study investigates the effect of land use, and landscape composition and structure on the population dynamics of fossorial water vole (Arvicola terrestris scherman Shaw). Water vole populations were monitored from 1989 to 1994 in the Doubs department, France, by using index methods. Land use patterns were studied based on agriculture and forestry data from the French Ministry of Agriculture collected in 1956, 1970, 1979 and 1988. Grassland quality and landscape structure were studied based on field transects, combined with the assessment of landscape structure from maps at 1:25,000 scale. Outbreaks of water vole populations occurred as a wave, spreading from epicentres over mo…

Relaxion fluctuations (self-stopping relaxion) and overview of relaxion stopping mechanisms

2020

Journal of high energy physics 2005(5), 80 (2020). doi:10.1007/JHEP05(2020)080