Critical exponents of the anisotropic Bak-Sneppen model

We analyze the behavior of spatially anisotropic Bak-Sneppen model. We demonstrate that a nontrivial relation between critical exponents tau and mu=d/D, recently derived for the isotropic Bak-Sneppen model, holds for its anisotropic version as well. For one-dimensional anisotropic Bak-Sneppen model we derive a novel exact equation for the distribution of avalanche spatial sizes, and extract the value gamma=2 for one of the critical exponents of the model. Other critical exponents are then determined from previously known exponent relations. Our results are in excellent agreement with Monte Carlo simulations of the model as well as with direct numerical integration of the new equation.Comment: 8 pages, three figures included with psfig, some rewriting, + extra figure and table of exponent

Compact and accurate models of large single-wall carbon-nanotube interconnects

Single-wall carbon nanotubes (SWCNTs) have been proposed for very large scale integration interconnect applications and their modeling is carried out using the multiconductor transmission line (MTL) formulation. Their time-domain analysis has some simulation issues related to the high number of SWCNTs within each bundle, which results in a highly complex model and loss of accuracy in the case of long interconnects. In recent years, several techniques have been proposed to reduce the complexity of the model whose accuracy decreases as the interconnection length increases. This paper presents a rigorous new technique to generate accurate reduced-order models of large SWCNT interconnects. The frequency response of the MTL is computed by using the spectral form of the dyadic Green's function of the 1-D propagation problem and the model complexity is reduced using rational-model identification techniques. The proposed approach is validated by numerical results involving hundreds of SWCNTs, which confirm its capability of reducing the complexity of the model, while preserving accuracy over a wide frequency range

Public policy and private incentives for livestock disease control

This article presents a dynamic bioeconomic model of livestock disease control that is unique in its integration of disease dynamics, inter‐species interaction, control‐induced migration, and individual optimising behaviour. Examination of the first‐order conditions highlights why profit‐maximising producers cannot be expected to eradicate disease. Results from an empirical application of the model confirm that the current mix of policies to control bovine tuberculosis in New Zealand is achieving lower levels of prevalence than would prevail in the absence of a national strategy. These policies do, however, appear to remove some of the individual incentive to control disease.International Relations/Trade, Livestock Production/Industries,

Natural resource management in the hillsides of Honduras: bioeconomic modeling at the micro-watershed level

The objective of this study is to simulate the effect of population pressure, market integration, technological improvement and policy decisions on natural resource management in the hillsides of Honduras. To do so, we developed a bioeconomic model that combines dynamic linear programming with a biophysical model, then applied this model to a typical microwatershed. Over recent years, farmers from the selected microwatershed have followed a "vegetables-intensive" pathway of development. We ran different scenarios with historical data over the period 1975 to 1995 and then projected 25 years into the future from 1995 to 2020. The results of the bioeconomic model presented in this paper help to test a number of induced innovation hypotheses. Many of our hypotheses are confirmed, but some of the model's results challenge conventional wisdom. The simulation results confirm that technology improvements such as irrigation and new varieties can help overcome diminishing returns to labor due to population pressure.Honduras., Natural resources., Water Management.,

Finiteness and Dual Variables for Lorentzian Spin Foam Models

We describe here some new results concerning the Lorentzian Barrett-Crane model, a well-known spin foam formulation of quantum gravity. Generalizing an existing finiteness result, we provide a concise proof of finiteness of the partition function associated to all non-degenerate triangulations of 4-manifolds and for a class of degenerate triangulations not previously shown. This is accomplished by a suitable re-factoring and re-ordering of integration, through which a large set of variables can be eliminated. The resulting formulation can be interpreted as a ``dual variables'' model that uses hyperboloid variables associated to spin foam edges in place of representation variables associated to faces. We outline how this method may also be useful for numerical computations, which have so far proven to be very challenging for Lorentzian spin foam models.Comment: 15 pages, 1 figur

Globalization and the health of Canadians: ‘Having a job is the most important thing’

Background Globalization describes processes of greater integration of the world economy through increased flows goods, services, capital and people. Globalization has undergone significant transformation since the 1970s, entrenching neoliberal economics as the dominant model of global market integration. Although this transformation has generated some health gains, since the 1990s it has also increased health disparities. Methods As part of a larger project examining how contemporary globalization was affecting the health of Canadians, we undertook semi-structured interviews with 147 families living in low-income neighbourhoods in Canada’s three largest cities (Montreal, Toronto and Vancouver). Many of the families were recent immigrants, which was another focus of the study. Drawing on research syntheses undertaken by the Globalization Knowledge Network of the World Health Organization’s Commission on Social Determinants of Health, we examined respondents’ experiences of three globalization-related pathways known to influence health: labour markets (and the rise of precarious employment), housing markets (speculative investments and affordability) and social protection measures (changes in scope and redistributive aspects of social spending and taxation). Interviews took place between April 2009 and November 2011. Results Families experienced an erosion of labour markets (employment) attributed to outsourcing, discrimination in employment experienced by new immigrants, increased precarious employment, and high levels of stress and poor mental health; costly and poor quality housing, especially for new immigrants; and, despite evidence of declining social protection spending, appreciation for state-provided benefits, notably for new immigrants arriving as refugees. Job insecurity was the greatest worry for respondents and their families. Questions concerning the impact of these experiences on health and living standards produced mixed results, with a majority expressing greater difficulty ‘making ends meet,’ some experiencing deterioration in health and yet many also reporting improved living standards. We speculate on reasons for these counter-intuitive results. Conclusions Current trends in the three globalization-related pathways in Canada are likely to worsen the health of families similar to those who participated in our study

Endogenous Structure of Polycentric Urban Area I: Isolated City

The purpose of this paper is to investigate how the interplay between production, commuting and commuting and costs shapes the economy at intra-urban level. Specifically, we study how economic integration affects the internal stricture of cities and how decentralizing of production and consumption of goods in secondary employment centers allows firms located in a large city to maintain their performance. The main distinctive feature of the model is two-dimensional city structure with variable number of secondary business districts. Several new results in urban economics are established, which all agree with empirical evidence and some of them cannot be obtained in framework of the linear city model.City structure; Secondary business centers; Commuting costs, Communication costs