Publications by authors named "Polhill J"

The COVID-19 pandemic is a major shock to society in terms of health and economy that is affecting both UK and global food and nutrition security. It is adding to the 'perfect storm' of threats to society from climate change, biodiversity loss and ecosystem degradation, at a time of considerable change, rising nationalism and breakdown in international collaboration. In the UK, the situation is further complicated due to Brexit.

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This paper addresses the highly relevant and timely issues of global trade and food security by developing an empirically grounded, relation-driven agent-based global trade model. Contrary to most price-driven trade models in the literature, the relation-driven agent-based global trade model focuses on the role of relational factors such as trust, familiarity, trade history and conflicts in countries' trade behaviour. Moreover, the global trade model is linked to a comprehensive nutrition formula to investigate the impact of trade on food and nutrition security, including macro and micronutrients.

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Resource distribution networks are the infrastructure facilitating the flow of resources in both biotic and abiotic systems. Both theoretical and empirical arguments have proposed that physical systems self-organise to maximise power production, but how this trajectory is related to network development, especially regarding the heterogeneity of resource distribution in explicitly spatial networks, is less understood. Quantifying the heterogeneity of resource distribution is necessary for understanding how phenomena such as economic inequality or energetic niches emerge across socio-ecological and environmental systems.

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Article Synopsis
  • The text discusses how a debt-based economy perpetuates the need for more debt to sustain economic growth, while the impacts of this cycle on environmental sustainability are not well understood.
  • The study specifically focuses on Indonesia, the largest producer of palm oil reliant on debt, and uses an Agent-Based Model to analyze the effects of economic and conservation forces on food production, climate regulation, and biodiversity from 2018 to 2050.
  • Findings suggest that while debt-driven economic forces can aid environmental conservation, achieving true sustainability in the long term requires reducing dependency on debt and increasing government intervention to protect the environment.
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  • Tropical countries face challenges in agricultural production, climate change, and biodiversity conservation, revealing a conflict between forces that promote forest protection and those that drive deforestation for development.
  • This research uses an integrated Agent-Based Model to analyze land-use change in Queensland's Wet Tropics region, assessing how different landscape configurations impact biodiversity and ecosystem services like sugarcane production and carbon sequestration.
  • Unlike many tropical areas, the model indicates that a "Business As Usual" approach in this region positively balances economic and conservation goals, highlighting effective governance and socio-economic factors that support sustainability.
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This paper develops an empirical agent-based model to assess the impacts of Brexit on Scottish cattle farms. We first identify several trends and processes among Scottish cattle farms that were ongoing before Brexit: the lack of succession, the rise of leisure farming, the trend to diversify and industrialise, and, finally, the phenomenon of the "disappearing middle", characterised by the decline of medium-sized farms and the polarization of farm sizes. We then study the potential impact of Brexit amid the local context and those ongoing social processes.

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Article Synopsis
  • * The current economic model fails to adequately consider how debt affects the environment, raising questions about the sustainability of natural resources in relation to economic growth.
  • * The study introduces an Agent-Based Model that shows that while debt can cause issues, the real problem lies in how private actors misuse debt, which leads to unsustainable extraction of resources and misalignment with conservation efforts.
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Background: Obesity may be the most predominant risk factor for recurrence following ventral hernia repair. This is secondary to significantly increased intra-abdominal pressures, higher rates of wound complications, and the technical difficulties encountered due to obesity. Medically managed weight loss prior to surgery is difficult.

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Abdominal wall reconstruction (AWR) is often required for hernias created after temporary abdominal closure (TAC). Demographic and clinical data from patients undergoing TAC and AWR between January 1, 1992, and December 31, 2002, were collected and univariate analysis performed. Temporary abdominal closure and AWR were performed in 21 patients.

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A novel approach to generalisation is presented that is able, under certain circumstances, to guarantee the generalisation to binary-output data for which no targets have been given. The basis of the guarantee is the recognition of a persistent global minimum error solution. An empirical test for whether the guarantee holds is provided which uses a technique called target reversal.

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