Heider Balance in Human Networks

Recently, a continuous dynamics was proposed to simulate dynamics of interpersonal relations in a society represented by a fully connected graph. Final state of such a society was found to be identical with the so-called Heider balance (HB), where the society is divided into two mutually hostile groups. In the continuous model, a polarization of opinions was found in HB. Here we demonstrate that the polarization occurs also in Barabasi-Albert networks, where the Heider balance is not necessarily present. In the second part of this work we demonstrate the results of our formalism, when applied to reference examples: the Southern women and the Zachary club.Comment: 9 pages, 5 figures. Presented on 8th Granada Seminar on Computational and Statistical Physics, Modeling Cooperative Behavior in the Social Sciences, Granada, Spain, 7-11 February 200

Impacts of climate change on plant diseases – opinions and trends

There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods

Effects of Mountain Pine Beetle on Fuels and Expected Fire Behavior in Lodgepole Pine Forests, Colorado, USA

In Colorado and southern Wyoming, mountain pine beetle (MPB) has affected over 1.6 million ha of predominantly lodgepole pine forests, raising concerns about effects of MPB-caused mortality on subsequent wildfire risk and behavior. Using empirical data we modeled potential fire behavior across a gradient of wind speeds and moisture scenarios in Green stands compared three stages since MPB attack (Red [1–3 yrs], Grey [4–10 yrs], and Old-MPB [∼30 yrs]). MPB killed 50% of the trees and 70% of the basal area in Red and Grey stages. Across moisture scenarios, canopy fuel moisture was one-third lower in Red and Grey stages compared to the Green stage, making active crown fire possible at lower wind speeds and less extreme moisture conditions. More-open canopies and high loads of large surface fuels due to treefall in Grey and Old-MPB stages significantly increased surface fireline intensities, facilitating active crown fire at lower wind speeds (>30–55 km/hr) across all moisture scenarios. Not accounting for low foliar moistures in Red and Grey stages, and large surface fuels in Grey and Old-MPB stages, underestimates the occurrence of active crown fire. Under extreme burning conditions, minimum wind speeds for active crown fire were 25–35 km/hr lower for Red, Grey and Old-MPB stands compared to Green. However, if transition to crown fire occurs (outside the stand, or within the stand via ladder fuels or wind gusts >65 km/hr), active crown fire would be sustained at similar wind speeds, suggesting observed fire behavior may not be qualitatively different among MPB stages under extreme burning conditions. Overall, the risk (probability) of active crown fire appears elevated in MPB-affected stands, but the predominant fire hazard (crown fire) is similar across MPB stages and is characteristic of lodgepole pine forests where extremely dry, gusty weather conditions are key factors in determining fire behavior

Influência da segregação granulométrica e do emprego de aditivos de moagem na adequação de cinzas de casca de arroz como coproduto

RESUMO A cinza de casca de arroz (CCA) é um resíduo proveniente da combustão da casca de arroz utilizada como biomassa na produção de energia. Esta cinza é gerada em grandes quantidades e possui baixa massa específica, o que dificulta o seu gerenciamento, pois demanda muito espaço para o devido armazenamento e descarte. A CCA possui um elevado teor de sílica em sua composição, fator este que pode torná-la um material atrativo para vários segmentos industriais. Neste contexto, este trabalho tem como objetivo avaliar a influência do beneficiamento físico da cinza de casca de arroz, por meio de processos de segregação granulométrica e moagem, com e sem o uso de aditivos, nas características deste material e na sua adequação como coproduto. A metodologia experimental utilizada para o desenvolvimento deste trabalho envolveu a segregação e moagem da CCA (com e sem aditivos de moagem), caracterização química, física e estrutural das amostras de CCA bruta, segregadas e moídas. Os resultados obtidos indicam que a segregação granulométrica se apresenta como fator determinante para a utilização da CCA como coproduto. Com relação à moagem, pode-se verificar que o diâmetro médio das partículas diminui e a massa específica das amostras aumenta, com o aumento do tempo de moagem. Entretanto, verifica-se que os aditivos usados neste trabalho, nas concentrações testadas, não influenciam significativamente na redução do diâmetro das partículas