Simplifying the interpretation of continuous time models for spatio-temporal networks

Autoregressive and moving average models for temporally dynamic networks treat time as a series of discrete steps which assumes even intervals between data measurements and can introduce bias if this assumption is not met. Using real and simulated data from the London Underground network, this paper illustrates the use of continuous time multilevel models to capture temporal trajectories of edge properties without the need for simultaneous measurements, along with two methods for producing interpretable summaries of model results. These including extracting ‘features’ of temporal patterns (e.g. maxima, time of maxima) which have utility in understanding the network properties of each connection and summarising whole-network properties as a continuous function of time which allows estimation of network properties at any time without temporal aggregation of non-simultaneous measurements. Results for temporal pattern features in the response variable were captured with reasonable accuracy. Variation in the temporal pattern features for the exposure variable was underestimated by the models. The models showed some lack of precision. Both model summaries provided clear ‘real-world’ interpretations and could be applied to data from a range of spatio-temporal network structures (e.g. rivers, social networks). These models should be tested more extensively in a range of scenarios, with potential improvements such as random effects in the exposure variable dimension.

     

Out there and in here: studying Eastern Europe in the West

This paper seeks to explore the challenge of studying geographies of Eastern Europe in Western Europe. It reflects on the growing relationships – imagined and material – between Eastern and Western Europe and engages in contemporary debates over 'relational geographies' to make a case for geographies which imagine our plural, European spatial connections, which connect different parts of the continent and which encourage the re-examination and renegotiation of ideas across East and West in the post-Cold War world. In these ways, the paper borrows from postcolonial frameworks and the ongoing reassessment of area studies to call for studies of Eastern and Western Europe which reinvigorate our "sense of Europe".     

Confronting Power and Environmental Injustice: Legacy Pollution and the Timber Industry in Southern Mississippi

Research has documented how grass-roots activists deploy the environmental justice frame to convey their grievances and demand their right to health and safety. While scholars have highlighted the widespread success of this frame, little attention has been paid to instances where the environmental justice frame fails to resonate. Drawing from social movements and environmental justice literatures, we examine how local discursive and cultural contexts can pose barriers to environmental justice claims. Our case is based on legacy pollution from a decommissioned creosote facility in Southern Mississippi. When black residents discovered the pollution in their neighborhood, they made repeated appeals to authorities for remediation and compensation. After being denied inclusion in a lawsuit filed by white residents, they formed an environmental justice organization to mobilize support for their campaign. Findings reveal the importance of both historical contextualization and the social situation of frame deployers in analyses of the environmental justice frame.     

A Hybrid Multi-Agent/Spatial Interaction Model System for Petrol Price Setting

This paper examines the use of multi‐agent simulations (MAS) to model the petrol market. The development of a purely agent based model for petrol prices is presented. Failings within this model are discussed and an alternative strategy for controlling the price of each petrol station based on population of customers is considered. Individual level modelling of customers is too computationally intensive; therefore a spatial interaction model was used to estimate the sales and linked to the agent system to create a hybrid model. To evaluate how effective this hybrid model was, a comparison was made with an existing data set of real petrol prices collected over a two month period. This was achieved both statistically and visually with the use of a Geographical Information System (GIS). Experimentation revealed that the hybrid model outperformed the agent model. Investigation into the behaviour and sensitivity of the system (for example, how prices diffuse spatially) was undertaken by means of idealised simulations.     

Making local futures tangible—Synthesizing, downscaling, and visualizing climate change scenarios for participatory capacity building

Local in its causes and global in its impacts, climate change still poses an unresolved challenge for scientists, politicians, entrepreneurs, and citizens. Climate change research is largely global in focus, aims at enhanced understanding, and is driven by experts, all of which seem to be insufficient to anchor climate change action in regional and local contexts. We present results from a participatory scenario study conducted in collaboration with the municipality of Delta in SW British Columbia, Canada. This study applies a participatory capacity building approach for climate change action at the local level where the sources of emissions and the mechanisms of adaptation reside and where climate change is meaningful to decision-makers and stakeholders alike. The multi-scale scenario approach consists of synthesizing global climate change scenarios, downscaling them to the regional and local level, and finally visualizing alternative climate scenarios out to 2100 in 3D views of familiar, local places. We critically discuss the scenarios produced and the strengths and weaknesses of the approach applied.     

Speciation of Arsenic Using Chelation Solvent Extraction and High Performance Liquid Chromatography

Research interest in speciation of arsenic stems from its species dependent behavior in the environment and in living organisms. The complexity of the matrix to be analyzed and low concentrations of target arsenic species that may be labile or difficult to chromatogram, indicate that a suitable pre‐treatment methodology is required. This study investigated the usefulness of chelation solvent extraction – high performance liquid chromatography (CSE‐HPLC) for the speciation of arsenic in water. It involved reacting arsenic with the chelant known for its affinity towards arsenic, followed by extraction, separation, and identification of the arsenic‐chelant‐arsenic complex. Arsenic species having different physicochemical properties were investigated. Species, such as, As₂O₃, As₃O₅, KH₂AsO₄, Na₂HAsO₄, and NaAsO₂ were detected as a group of closely eluted peaks with different retention times and spectral properties, whereas, the organic arsenic species CH₃Na₂AsO₃, o‐arsanilic acid, roxarson and triphenyl arsine separated quite well on the EnviroseP‐CM HPLC column. Key method parameters, such as, type of HPLC column, composition of mobile phase and organic solvents affecting peak resolution and sensitivity were optimized. Real environmental matrices contaminated with arsenic were analyzed under varying wavelengths (λ_max = 190, 210, 220, 234, 244, and 282 nm), with good precision. Different arsenic species were detected in these samples with excellent background and signal‐to‐noise ratios demonstrating the robustness of the method. The detection limit, reproducibility, selectivity, accuracy, and dynamic range of the calibration curves were evaluated.     

Pro-active management: the role of environmental flows in transboundary cooperative planning for the Okavango River system

Abstract

The Okavango River system flows through Angola, Namibia and Botswana. It is in near-natural condition and supports globally iconic wetlands and wildlife. The basin’s people are poor and development is inevitable: the next decade is critical. The river could become an example of responsible planning that resolutely addresses the three pillars of sustainable development. Recognizing this, the Member States completed a transboundary diagnostic analysis (TDA) in 2010 funded by the three governments and the Global Environment Facility. A central feature of the TDA was a basin-wide environmental flow assessment using the DRIFT (Downstream Response to Imposed Flow Transformation) holistic approach. This produced scenarios of increasing water resource use that spelled out the costs and benefits in terms of the health of the river ecosystem, associated social structures and local and national economies. The results were used to help create a transboundary strategic action programme, which the Member States are now beginning to act on. This article describes the DRIFT application, the findings and how these could be used to help achieve sustainable development.

Editor D. Koutsoyiannis; Guest editor M. Acreman

Citation King, J., Beuster, H., Brown, C., and Joubert, A., 2014. Pro-active management: the role of environmental flows in transboundary cooperative planning for the Okavango River system. Hydrological Sciences Journal, 59 (3–4), 786–800.     

Wheat as food, wheat as industrial substance; comparative geographies of transformation and mobility

Wheat is the world’s second largest crop, supplies 19% of human calories, and is the largest volume crop traded internationally. Its uniquely malleable physical properties make it a valued industrial substance, albeit often an invisible one, as well as a food. This combination of transformation, invisibility and mobility demands new ways of thinking about wheat geographies. In this paper we document and analyse several ‘moments’ in the life of Australian wheat; at the supermarket, in the lives of coeliac sufferers, in laboratories, industrial factories and on the farm. We illustrate diverse patterns of interaction with wheat. The major plane of differentiation is between wheat as food and wheat as industrial substance. The explicit connection of food to the human body tends to fix the identity of wheat, whether as healthy staple of the nation, or harmful poison to coeliacs who must negotiate its presence using the regulatory regime of food labelling. This is no small task given the ubiquity of wheat; our survey of 10,235 supermarket items found it in 29.5% of labelled food items. In contrast, when wheat is physically and chemically disassembled to become an industrial substance, its presence and identity become mutable, hidden and often invisible.     

热液矿床成矿作用研究新途径:数值模拟

热液矿床是最具有工业价值的矿床类型之一,传统矿床学研究在成岩成矿作用、成矿机制和成矿规律等方面已有丰硕成果,但仍存在一些尚无法有效回答的科学问题。近年来,数值模拟方法逐步应用于热液矿床的研究,已成为成矿过程定量研究的新手段。本文系统总结了近年来热液矿床成矿过程数值模拟研究的成果和进展,并对存在问题和发展趋势进行了分析和展望,以期进一步推动这一交叉学科领域的研究。