245 research outputs found
Fixed Point Properties of the Ising Ferromagnet on the Hanoi Networks
The Ising model with ferromagnetic couplings on the Hanoi networks is
analyzed with an exact renormalization group. In particular, the fixed-points
are determined and the renormalization-group flow for certain initial
conditions is analyzed. Hanoi networks combine a one-dimensional lattice
structure with a hierarchy of small-world bonds to create a mix of geometric
and mean-field properties. Generically, the small-world bonds result in
non-universal behavior, i.e. fixed points and scaling exponents that depend on
temperature and the initial choice of coupling strengths. It is shown that a
diversity of different behaviors can be observed with seemingly small changes
in the structure of the networks. Defining interpolating families of such
networks, we find tunable transitions between regimes with power-law and
certain essential singularities in the critical scaling of the correlation
length, similar to the so-called inverted Berezinskii-Kosterlitz-Thouless
transition previously observed only in scale-free or dense networks.Comment: 13 pages, revtex, 12 fig. incl.; fixed confusing labels, published
version. For related publications, see
http://www.physics.emory.edu/faculty/boettcher
Renormalization Group for Critical Phenomena in Complex Networks
We discuss the behavior of statistical models on a novel class of complex âHanoiâ networks. Such modeling is often the cornerstone for the understanding of many dynamical processes in complex networks. Hanoi networks are special because they integrate small-world hierarchies common to many social and economical structures with the inevitable geometry of the real world these structures exist in. In addition, their design allows exact results to be obtained with the venerable renormalization group (RG). Our treatment will provide a detailed, pedagogical introduction to RG. In particular, we will study the Ising model with RG, for which the fixed points are determined and the RG flow is analyzed. We show that the small-world bonds result in non-universal behavior. It is shown that a diversity of different behaviors can be observed with seemingly small changes in the structure of hierarchical networks generally, and we provide a general theory to describe our findings
Restoration Handbook for Sagebrush Steppe Ecosystems with Emphasis on Greater Sage-Grouse HabitatâPart 3. Site Level Restoration Decisions
Sagebrush steppe ecosystems in the United States currently (2016) occur on only about one-half of their historical land area because of changes in land use, urban growth, and degradation of land, including invasions of non-native plants. The existence of many animal species depends on the existence of sagebrush steppe habitat. The greater sage-grouse (Centrocercus urophasianus) depends on large landscapes of intact habitat of sagebrush and perennial grasses for their existence. In addition, other sagebrush-obligate animals have similar requirements and restoration of landscapes for greater sage-grouse also will benefit these animals. Once sagebrush lands are degraded, they may require restoration actions to make those lands viable habitat for supporting sagebrush-obligate animals, livestock, and wild horses, and to provide ecosystem services for humans now and for future generations.
When a decision is made on where restoration treatments should be applied, there are a number of site-specific decisions managers face before selecting the appropriate type of restoration. This site-level decision tool for restoration of sagebrush steppe ecosystems is organized in nine steps.
âStep 1 describes the process of defining site-level restoration objectives.
âStep 2 describes the ecological site characteristics of the restoration site. This covers soil chemistry and texture, soil moisture and temperature regimes, and the vegetation communities the site is capable of supporting.
âStep 3 compares the current vegetation to the plant communities associated with the site State and Transition models.
âStep 4 takes the manager through the process of current land uses and past disturbances that may influence restoration success.
âStep 5 is a brief discussion of how weather before and after treatments may impact restoration success.
âStep 6 addresses restoration treatment types and their potential positive and negative impacts on the ecosystem and on habitats, especially for greater sage-grouse. We discuss when passive restoration options may be sufficient and when active restoration may be necessary to achieve restoration objectives.
âStep 7 addresses decisions regarding post-restoration livestock grazing management.
âStep 8 addresses monitoring of the restoration; we discuss important aspects associated with implementation monitoring as well as effectiveness monitoring.
âStep 9 takes the information learned from monitoring to determine how restoration actions in the future might be adapted to improve restoration success
Restoration Handbook for Sagebrush Steppe Ecosystems with Emphasis on Greater Sage-Grouse HabitatâPart 2. Landscape Level Restoration Decisions
Sagebrush steppe ecosystems in the United States currently (2015) occur on only about one-half of their historical land area because of changes in land use, urban growth, and degradation of land, including invasions of non-native plants. The existence of many animal species depends on the existence of sagebrush steppe habitat. The greater sage-grouse (Centrocercus urophasianus) is a landscape-dependent bird that requires intact habitat and combinations of sagebrush and perennial grasses to exist. In addition, other sagebrush-obligate animals also have similar requirements and restoration of landscapes for greater sage-grouse also will benefit these animals. Once sagebrush lands are degraded, they may require restoration actions to make those lands viable habitat for supporting sagebrush-obligate animals. Land managers do not have resources to restore all locations because of the extent of the restoration need and because some land uses are not likely to change, therefore, restoration decisions made at the landscape to regional scale may improve the effectiveness of restoration to achieve landscape and local restoration objectives. We present a landscape restoration decision tool intended to assist decision makers in determining landscape objectives, to identify and prioritize landscape areas where sites for priority restoration projects might be located, and to aid in ultimately selecting restoration sites guided by criteria used to define the landscape objectives. The landscape restoration decision tool is structured in five sections that should be addressed sequentially. Each section has a primary question or statement followed by related questions and statements to assist the user in addressing the primary question or statement. This handbook will guide decision makers through the important process steps of identifying appropriate questions, gathering appropriate data, developing landscape objectives, and prioritizing landscape patches where potential sites for restoration projects may be located. Once potential sites are selected, land managers can move to the site-specific decision tool to guide restoration decisions at the site level
Restoration Handbook for Sagebrush Steppe Ecosystems with Emphasis on Greater Sage-Grouse HabitatâPart 1. Concepts for Understanding and Applying Restoration
Sagebrush steppe ecosystems in the United States currently occur on only about one-half of their historical land area because of changes in land use, urban growth, and degradation of land, including invasions of non-native plants. The existence of many animal species depends on the existence of sagebrush steppe habitat. The greater sage-grouse (Centrocercus urophasianus) is a landscape-dependent bird that requires intact habitat and combinations of sagebrush and perennial grasses to exist. In addition, other sagebrush-obligate animals also have similar requirements and restoration of landscapes for greater sage-grouse also will benefit these animals. Once sagebrush lands are degraded, they may require restoration actions to make those lands viable habitat for supporting sagebrush-obligate animals. This restoration handbook is the first in a three-part series on restoration of sagebrush ecosystems. In Part 1, we discuss concepts surrounding landscape and restoration ecology of sagebrush ecosystems and greater sage-grouse that habitat managers and restoration practitioners need to know to make informed decisions regarding where and how to restore specific areas. We will describe the plant dynamics of sagebrush steppe ecosystems and their responses to major disturbances, fire, and defoliation. We will introduce the concepts of ecosystem resilience to disturbances and resistance to invasions of annual grasses within sagebrush steppe. An introduction to soils and ecological site information will provide insights into the specific plants that can be restored in a location. Soil temperature and moisture regimes are described as a tool for determining resilience and resistance and the potential for various restoration actions. Greater sage-grouse are considered landscape birds that require large areas of intact sagebrush steppe; therefore, we describe concepts of landscape ecology that aid our decisions regarding habitat restoration. We provide a brief overview of restoration techniques for sage-grouse habitat restoration. We conclude with a description of the critical nature of monitoring for adaptive management of sagebrush steppe restoration at landscape- and project-specific levels
Transferability of Car-Following Models Between Driving Simulator and Field Traffic
During the past few decades, there have been two parallel streams of driving behavior research: models using trajectory data collected from the field (using video recordings, GPS, etc.) and models using data from driving simulators (in which the behavior of the drivers is recorded in controlled laboratory conditions). Although the former source of data is more realistic, it lacks information about the driver and is typically not suitable for testing effects of future vehicle technologies and traffic scenarios. In contrast, driving behavior models developed with driving simulator data may lack behavioral realism. However, no previous study has compared these two streams of mathematical models and investigated the transferability of the models developed with driving simulator data to real field conditions in a rigorous manner. The current study aimed to fill this research gap by investigating the transferability of two car-following models between a driving simulator and two comparable real-life traffic motorway scenarios, one from the United Kingdom and the other one from the United States. In this regard, stimulusâresponseâbased car-following models were developed with three microscopic data sources: (a) experimental data collected from the University of Leeds driving simulator, (b) detailed trajectory data collected from UK Motorway 1, and (c) detailed trajectory data collected from Interstate 80 in California. The parameters of these car-following models were estimated by using the maximum likelihood estimation technique, and the transferability of the models was investigated by using statistical tests of parameter equivalence and transferability test statistics. Estimation results indicate transferability at the model level but not fully at the parameter level for both pairs of scenarios
Analysis reveals potential rangeland impacts if Williamson Act eliminated
California budget cuts have resulted in dramatic reductions in state funding for the Williamson Act, a land protection program that reduces property taxes for the owners of 15 million acres of California farms and rangeland. With state reimbursements to counties eliminated, the decision to continue Williamson Act contracts lies with individual counties. We investigated the consequences of eliminating the Williamson Act, using a geospatial analysis and a mail questionnaire asking ranchers for plans under a hypothetical elimination scenario. The geospatial analysis revealed that 72% of rangeland parcels enrolled in Williamson Act contracts contained habitat important for statewide conservation goals. Presented with the elimination scenario, survey respondents reported an intention to sell 20% of their total 496,889 acres. The tendency of survey participants to respond that they would sell land was highest among full-time ranchers with low household incomes and without off-ranch employment. A majority (76%) of the ranchers who reported that they would sell land predicted that the buyers would develop it for nonagricultural uses, suggesting substantial changes to California's landscape in a future without the Williamson Act
The role of inflammation in epilepsy.
Epilepsy is the third most common chronic brain disorder, and is characterized by an enduring predisposition to generate seizures. Despite progress in pharmacological and surgical treatments of epilepsy, relatively little is known about the processes leading to the generation of individual seizures, and about the mechanisms whereby a healthy brain is rendered epileptic. These gaps in our knowledge hamper the development of better preventive treatments and cures for the approximately 30% of epilepsy cases that prove resistant to current therapies. Here, we focus on the rapidly growing body of evidence that supports the involvement of inflammatory mediators-released by brain cells and peripheral immune cells-in both the origin of individual seizures and the epileptogenic process. We first describe aspects of brain inflammation and immunity, before exploring the evidence from clinical and experimental studies for a relationship between inflammation and epilepsy. Subsequently, we discuss how seizures cause inflammation, and whether such inflammation, in turn, influences the occurrence and severity of seizures, and seizure-related neuronal death. Further insight into the complex role of inflammation in the generation and exacerbation of epilepsy should yield new molecular targets for the design of antiepileptic drugs, which might not only inhibit the symptoms of this disorder, but also prevent or abrogate disease pathogenesis
Not a limitless resource: ethics and guidelines for destructive sampling of archaeofaunal remains
Publisher's version (Ăștgefin grein)With the advent of ancient DNA, as well as other methods such as isotope analysis, destructive sampling of archaeofaunal remains has increased much faster than the effort to collect and curate them. While there has been considerable discussion regarding the ethics of destructive sampling and analysis of human remains, this dialogue has not extended to archaeofaunal material. Here we address this gap and discuss the ethical challenges surrounding destructive sampling of materials from archaeofaunal collections. We suggest ways of mitigating the negative aspects of destructive sampling and present step-by-step guidelines aimed at relevant stakeholders, including scientists, holding institutions and scientific journals.
Our suggestions are in most cases easily implemented without significant increases in project costs, but with clear long-term benefits inthe preservation and use of zooarchaeologicalmaterial.his work was supported by the Icelandic Research Fund grant no. 162783-051, Finnish Academy grant no. SA286499, the European Unionâs Horizon 2020 research and innovation programme under the Marie SkĆodowskaCurie grant agreement no. 749226 and Estonian Research Council grant nos. PRG29 and IUT 20-7.Peer Reviewe
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