Competition between surface relaxation and ballistic deposition models in scale free networks

In this paper we study the scaling behavior of the fluctuations in the steady state $W_S$ with the system size $N$ for a surface growth process given by the competition between the surface relaxation (SRM) and the Ballistic Deposition (BD) models on degree uncorrelated Scale Free networks (SF), characterized by a degree distribution $P(k)\sim k^{-\lambda}$, where $k$ is the degree of a node. It is known that the fluctuations of the SRM model above the critical dimension ($d_c=2$) scales logarithmically with $N$ on euclidean lattices. However, Pastore y Piontti {\it et. al.} [A. L. Pastore y Piontti {\it et. al.}, Phys. Rev. E {\bf 76}, 046117 (2007)] found that the fluctuations of the SRM model in SF networks scale logarithmically with $N$ for $\lambda <3$ and as a constant for $\lambda \geq 3$. In this letter we found that for a pure ballistic deposition model on SF networks $W_S$ scales as a power law with an exponent that depends on $\lambda$. On the other hand when both processes are in competition, we find that there is a continuous crossover between a SRM behavior and a power law behavior due to the BD model that depends on the occurrence probability of each process and the system size. Interestingly, we find that a relaxation process contaminated by any small contribution of ballistic deposition will behave, for increasing system sizes, as a pure ballistic one. Our findings could be relevant when surface relaxation mechanisms are used to synchronize processes that evolve on top of complex networks.Comment: 8 pages, 6 figure

Social distancing strategies against disease spreading

The recurrent infectious diseases and their increasing impact on the society has promoted the study of strategies to slow down the epidemic spreading. In this review we outline the applications of percolation theory to describe strategies against epidemic spreading on complex networks. We give a general outlook of the relation between link percolation and the susceptible-infected-recovered model, and introduce the node void percolation process to describe the dilution of the network composed by healthy individual, $i.e$, the network that sustain the functionality of a society. Then, we survey two strategies: the quenched disorder strategy where an heterogeneous distribution of contact intensities is induced in society, and the intermittent social distancing strategy where health individuals are persuaded to avoid contact with their neighbors for intermittent periods of time. Using percolation tools, we show that both strategies may halt the epidemic spreading. Finally, we discuss the role of the transmissibility, $i.e$, the effective probability to transmit a disease, on the performance of the strategies to slow down the epidemic spreading.Comment: to be published in "Perspectives and Challenges in Statistical Physics and Complex Systems for the Next Decade", Word Scientific Pres

COBRA Subsidies for Laid-Off Workers: An Initial Report Card

Reviews the implementation of the government subsidy of COBRA health insurance premiums for laid-off workers in the 2009 stimulus package and its effects on COBRA enrollment and medical spending. Considers policy implications for access and affordability

Federal Subsidy for Laid-Off Workers' Health Insurance: A First Year's Report Card for the New COBRA Premium Assistance

Analyzes how the subsidy for laid-off workers' costs to continue their health coverage, included in the 2009 stimulus bill, affected enrollment. Considers determining factors, implications of health reform for extending the subsidy, and lessons learned

Multifunctional Agriculture, Quality of Life and Policy Decisions: an Empirical Case

The TOP-MARD research project (Toward a Policy Model of Multifunctional Agriculture and Rural Development), that will be here described in its Italian version, links farmers’ behaviour with their economic, social and environmental effects, showing the difference between a behaviour guided by market profitability only and one guided by the interest of a broader social group. It was financed by EU in 11 European countries, and it took place in 2006-2008. The TOP-MARD research defined a 10-modules model (POMMARD), that links use of land and production techniques to several dimensions of a context (quantitative and qualitative, from economic to social and environmental) and to the quality of life of its population. STELLA, a Systems Thinking software, has been used in order to develop the POMMARD model. The POMMARD model is partially supply-driven with demand constraints: land use and its dynamics produce a mix of marketable and non-marketable goods, that impact other sectors and the territory through an I-O or a SAM, and through the consequences of their production on the quality of life. Labour requirements and demography can produce – therefore – immigration, and contribute to job creation and dynamics. Public intervention influences local resources and human behaviour. Farmers can choose their style of production and land use, that are the “key drivers” of change: when land is converted from a land use to another or from a conventional to a non-conventional style of production, there occurs a change in the vector of inputs (means of production and workers) and in the vector of outputs, that also comprehends public goods. Provision of public goods increases the quality of life. Rural areas become therefore more attractive to younger generations, encouraging them to stay rather than migrate, and attracting new-comers. Tourism can also be influenced by the attractiveness of the area, which can contribute further income, within the limits of tourism capacity and seasonality. Starting from the actual systematic links, the model considers the main variables (population, income, …) under different policy scenarios: providing suggestions to policy makers about the possible effects of exogenous shocks, such as policy measures, on rural development and quality of life.Multifunctional Agriculture, Quality of Life, Policy Decision., Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Food Consumption/Nutrition/Food Safety, Labor and Human Capital,