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Although research has explained how plant roots mechanically stabilize soils, in this article we explore how root systems create networks of preferential flow and thus influence water pressures in soils to trigger landslides. Root systems may alter subsurface flow: Hydrological mechanisms that promote lower pore-water pressures in soils are beneficial to slope stability, whereas those increasing pore pressure are adverse. Preferential flow of water occurs in the following types of root channels: (a) channels formed by dead or decaying roots, (b) channels formed by decayed roots that are newly occupied by living roots, and (c) channels formed around live roots. The architectural analysis of root systems improves our understanding of how roots grow initially, develop, die, and interconnect. Conceptual examples and case studies are presented to illustrate how root architecture and diverse traits (e.g., diameter, length, orientation, topology, sinuosity, decay rate) affect the creation of root channels and thus affect preferential flow.

No generally accepted framework exists for constructing and evaluating measures of corruption. This article shows how the axiomatic approach of the poverty and inequality literature can be applied to the measurement of corruption. A conceptual framework for organizing corruption data is developed, and three aggregate corruption measures consistent with axiomatic requirements are proposed. The article also provides guidelines for empirical applications of corruption measures and discusses data requirements. A brief empirical example illustrates how each of the measures captures a distinct view of corruption that yields a different ranking. To the authors' knowledge, this article provides the first analysis of corruption measurement using an axiomatic framework.

Natural aquifers usually exhibit complex physical and chemical heterogeneities, which are key factors complicating kinetic processes, such as contaminant transport and transformation, posing a great challenge in the remediation of contaminated groundwater. Aquifer heterogeneity usually leads to a distinct feature, the so-called “anomalous transport” in groundwater, which deviates from the phenomenon described by the classical advection-dispersion equation (ADE) based on Fick’s Law. Anomalous transport, also known as non-Fickian dispersion or “anomalous dispersion” in a broad sense, can explain the hydrogeological mechanism that leads to the temporally continuous deterioration of water quality and rapid spatial expansion of pollutant plumes. Contaminants enter and then are retained in the low-permeability matrix from the high-permeability zone via molecular diffusion, chemical adsorption, and other mass exchange effects. This process can be reversed when the concentration of pollutants in high-permeability zones is relatively low. The contaminants slowly return to the high-permeability zones through reverse molecular diffusion, resulting in sub-dispersive anomalous transport leading to the chronic gradual deterioration of water quality. Meanwhile, some contaminants are rapidly transported along the interconnected preferential flow paths, resulting in super-dispersive anomalous transport, which leads to the rapid spread of contaminants. Aquifer heterogeneity is also an important factor that constrains the efficacy of groundwater remediation, while the development, application, and evaluation of groundwater remediation technologies are usually based on the Fickian dispersion process predicted by the ADE equation. Comprehensive studies of the impacts of non-Fickian dispersion on contaminant transport and remediation are still needed. This article reviews the non-Fickian dispersion phenomenon caused by the heterogeneity of geological media, summarizes the processes and current understanding of contaminant migration and transformation in highly heterogeneous aquifers, and evaluates mathematical methods describing the main non-Fickian dispersion features. This critical review also discusses the limitations of existing research and outlines potential future research areas to advance the understanding of mechanisms and modeling of non-Fickian dispersion in heterogeneous media.

Purpose There is strong experimental evidence that root systems substantially change the hydraulic properties of soil. However, the mechanisms by which they do this remain largely unknown. In this work, we made the hypothesis that a preferential flow of soil moisture occurs in directions which follow the orientation and distribution of roots within the soil, and that this phenomenon alters soil moisture flow patterns. Methods We modified Richards’ equation to incorporate root-oriented preferential flow of soil moisture. Using the finite element method and Bayesian optimisation, we developed a pipeline to calibrate our model with respect to a given root system. Results When applied to simulated root distributions, our model produced pore-water pressure profiles which agreed with those derived from experimental saturated hydraulic conductivity values of soils vegetated with willow and grass. Agreement improved for simulated root distributions where root segments were oriented in a more realistic way, suggesting that the hydraulic characteristics of vegetated soils are a consequence of root-oriented preferential flow. Conclusion By incorporating root-oriented preferential flow, our model improves the ability to describe and analyse water infiltration through vegetated soil. This could help optimise irrigation, forecast flood events and plan landslide prevention strategies.

Recent work investigating the development of the phonological lexicon, where edges between words represent phonological similarity, have suggested that phonological network growth may be partly driven by a process that favors the acquisition of new words that are phonologically similar to several existing words in the lexicon. To explore this growth mechanism, we conducted a simulation study to examine the properties of networks grown by inverse preferential attachment, where new nodes added to the network tend to connect to existing nodes with fewer edges. Specifically, we analyzed the network structure and degree distributions of artificial networks generated via either preferential attachment, an inverse variant of preferential attachment, or combinations of both network growth mechanisms. The simulations showed that network growth initially driven by preferential attachment followed by inverse preferential attachment led to densely-connected network structures (i.e., smaller diameters and average shortest path lengths), as well as degree distributions that could be characterized by non-power law distributions, analogous to the features of real-world phonological networks. These results provide converging evidence that inverse preferential attachment may play a role in the development of the phonological lexicon and reflect processing costs associated with a mature lexicon structure.

【Objective】Preferential flow through fissures at the front edge of coal mine dumps not only influences hydrological processes but also increases the risk of collapse and landslides. Understanding the factors that affect preferential flow can improve soil heap management and facilitate vegetation restoration. This paper experimentally investigates these factors.【Method】The experiment was conducted at the Shenglidong Open-Pit Coal Mine, Inner Mongolia. Field investigations, dye tracing, and digital imaging were employed to examine the distribution, migration, and dynamics of preferential flow.【Result】Preferential flow primarily occurred on both sides of the fissures, forming a ‘T’-shaped distribution near the fissures. At the soil surface, the dyed-stained area was uniform and continuous, indicating the dominance of matrix flow. As soil depth increased, both the dye-stained area and width decreased, which facilitated preferential flow. Among all fissures examined, second-category ground fissures exhibited the fastest preferential flow, characterized by the deepest dye staining and the most pronounced preferential flow under the same rainfall conditions. The dye-stained area ratios for the first, second, and third-category ground fissures were 27.23%, 31.97%, and 30.73%, respectively. This ratio decreased with soil depth, following an ‘S’ -shaped distribution. Additionally, the dye-stained area ratio varied between fissures, with ratios of 77.09%, 79.85%, and 126.17% for the first, second, and third-category fissures, respectively.【Conclusion】The dye-stained area ratio in ground fissures with smaller widths showed high variation and a dynamic pattern, enhancing preferential flow. The spatial variation of preferential flow in ground fissures was evident. These findings can help the development of strategies to improve the management and vegetation restoration of soil heaps in coal mining areas.

Preferential trade agreements have become common ways to protect or restrict access to national markets in products and services. The United States has signed trade agreements with almost two dozen countries as close as Mexico and Canada and as distant as Morocco and Australia. The European Union has done the same. In addition to addressing economic issues, these agreements also regulate the protection of human rights. InForced to Be Good, Emilie M. Hafner-Burton tells the story of the politics of such agreements and of the ways in which governments pursue market integration policies that advance their own political interests, including human rights. How and why do global norms for social justice become international regulations linked to seemingly unrelated issues, such as trade? Hafner-Burton finds that the process has been unconventional. Efforts by human rights advocates and labor unions to spread human rights ideals, for example, do not explain why American and European governments employ preferential trade agreements to protect human rights. Instead, most of the regulations protecting human rights are codified in global moral principles and laws only because they serve policymakers' interests in accumulating power or resources or solving other problems. Otherwise, demands by moral advocates are tossed aside. And, as Hafner-Burton shows, even the inclusion of human rights protections in trade agreements is no guarantee of real change, because many of the governments that sign on to fair trade regulations oppose such protections and do not intend to force their implementation. Ultimately, Hafner-Burton finds that, despite the difficulty of enforcing good regulations and the less-than-noble motives for including them, trade agreements that include human rights provisions have made a positive difference in the lives of some of the people they are intended-on paper, at least-to protect.