1,721,131 research outputs found
Inefficient epidemic spreading in scale-free networks
No full textHighly heterogeneous degree distributions yield efficient spreading of simple epidemics through networks, but can be inefficient with more complex epidemiological processes. We study diseases with nonlinear force of infection whose prevalences can abruptly collapse to zero while decreasing the transmission parameters. We find that scale-free networks can be unable to support diseases that, on the contrary, are able to persist at high endemic levels in homogeneous networks with the same average degree
A Cartogram is Worth a Thousand Maps: The Multi-faced Image of Our Earth
No full textProcess-dependent representations of our Planet have the power of clarifying us immediately what is going on and where it is happening. The use of cartograms instead of traditional colored maps makes evident that unevenness is the law, rather than the exception, in many important issues for humans and other species
Ecosystem Conservation and Management: Models and Application
No full textThis textbook provides basic quantitative models allowing researchers and decision makers to a) assess viability of threatened populations and evaluate the success of species reintroductions, b) estimate invasion abilities of alien species, c) evaluate the persistence of metapopulations subjected to habitat destruction and fragmentation, d) analyze policies and strategies for the sustainable harvesting of biological resources, and e) assess the course of human and nonhuman diseases and the possible containment measures. Air and water pollution, overexploitation of renewable resources (e.g. marine fish stocks and forests), massive land-use change together with climate change impact the Earth biodiversity and impair the functioning of ecosystems. Globalization increases the risk of diffusion of alien species and new pathogens. A panoply of numerical problems mainly based on real data from the ecological literature enables the reader to practice the presented modelling tools. presented modelling tools
A minimal model for forest fire regimes
No full textWe show in this paper how the characteristics of fire recurrence in forests can be theoretically derived from simple information concerning forest morphology. The task is accomplished by means of a minimal model encapsulating a few assumptions on the interactions between overstorey and understorey species and on the mechanisms of fire development and transmission. The main difference with other models for fire prediction and simulation is that, here, fire is an endogenous variable with purely deterministic dynamics. Nevertheless, the analysis shows that fire recurrence can be chaotic for parameter values corresponding to Mediterranean forests. By contrast, the model shows that boreal forests and savannahs must experience periodic fires. These general results are in agreement with the studies carried out on many different forests in this century
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