Modeling the mechanics of amorphous solids at different length and time scales

We review the recent literature on the simulation of the structure and deformation of amorphous glasses, including oxide and metallic glasses. We consider simulations at different length and time scales. At the nanometer scale, we review studies based on atomistic simulations, with a particular emphasis on the role of the potential energy landscape and of the temperature. At the micrometer scale, we present the different mesoscopic models of amorphous plasticity and show the relation between shear banding and the type of disorder and correlations (e.g. elastic) included in the models. At the macroscopic range, we review the different constitutive laws used in finite element simulations. We end the review by a critical discussion on the opportunities and challenges offered by multiscale modeling and transfer of information between scales to study amorphous plasticity.Comment: 58 pages, 14 figure

Modeling Acidification Recovery on Threatened Ecosystems: Application to the Evaluation of the Gothenburg Protocol in France

To evaluate the acid deposition reduction negotiated for 2010 within the UNECE LRTAP Gothenburg Protocol, sulphur and nitrogen deposition time-series (1880–2100) were compared to critical loads of acidity on five French ecosystems: Massif Central basalt (site 1) and granite (2); Paris Bassin tertiary sands (3); Vosges mountains sandstone (4) and Landes eolian sands (5). The SAFE model was used to estimate the response of soil solution pH and [A1] [BC] ratio to the deposition scenario. Among the five sites, critical loads were exceeded in the past at sites 3, 4 and 5. Sites 3 and 4 were still expected to exceed in 2010, the Protocol year. Further reduction of atmospheric deposition, mainly nitrogen, would be needed to achieve recovery on these ecosystems. At sites 3, 4 and 5, the delay between the critical load exceedance and the violation of the critical chemical criterion was estimated to be 10 to 30 years in the top soil and 50 to 90 years in the deeper soil. At site 5, a recovery was expected in the top soil in 2010 with a time lag of 10 years. Unexpectedly, soil pH continued to decrease after 1980 in the deeper soil at sites 2 and 5. This time lag indicated that acidification moved down the soil profile as a consequence of slow base cation depletion by ion exchange. This delayed response of the soil solution was the result of the combination of weathering rates and vegetation uptake but also of the relative ratio between base cation deposition and acid compounds

Reframing the Work of Rural Community Development: Case Studies in Innovative Rural Business Strategies

Much of community development work in this country is understood in urban terms - densely populated areas with attendant economies of scale, housing issues that can be addressed largely in isolation of economic development and infrastructure issues, micro-level service area focus without the need to address regional economies and housing markets, even simple communications and relationship-building opportunities.None of this is terribly surprising. After all, the community development field grew out of urban activism and experience.The translation of urban revitalization strategies and lessons learned into a rural community development model inevitably highlights the challenges unique to highly varied rural markets. The service area is typically numerous communities, sparsely populated, covering great distances. Absent are highly visible corporate headquarters and other traditional opportunities for local private partnership. Smaller municipalities are less likely to offer a full range of services to complement any nonprofit service delivery system.At first glance the challenges facing rural development seem daunting. Needs -- or everything that seems to be so glaringly absent -- outweigh assets. However, rural markets are well worth a second look. In the few years since NeighborWorks America launched its Rural Initiative, we've uncovered astonishing examples of innovation with enormous community impact in some of the most challenging markets in America.We think these innovations are well worth sharing. Rural markets are often the emerging markets for expanding regional economies. The closer we look at the work being done by community based organizations, and in particular, chartered members of the NeighborWorks network, the more we realize that these organizations function as front line economic engines for increased homeownership, infrastructure improvements, job creation and retention.This report documents the compelling attributes of six business strategies that are successfully transforming diverse rural markets across America. Our hope is that this exciting new information, the first of a series, will stimulate numerous and varied adaptations within the community development field and spur additional investment in rural development by the private and public sectors

The unanticipated challenges associated with implementing an observational study protocol in a large scale physical activity and GPS data collection

Background: Large-scale primary data collections are complex, costly, and time-consuming. Study protocols for trial-based research are now commonplace, with a growing number of similar pieces of work being published on observational research. However, useful additions to the literature base are publications that describe the issues and challenges faced while conducting observational studies. These can provide researchers with insightful knowledge that can inform funding proposals or project development work. Objectives: In this study, we identify and reflectively discuss the unforeseen or often unpublished issues associated with organizing and implementing a large-scale objectively measured physical activity and global positioning system (GPS) data collection. Methods: The SPACES (Studying Physical Activity in Children’s Environments across Scotland) study was designed to collect objectively measured physical activity and GPS data from 10- to 11-year-old children across Scotland, using a postal delivery method. The 3 main phases of the project (recruitment, delivery of project materials, and data collection and processing) are described within a 2-stage framework: (1) intended design and (2) implementation of the intended design. Results: Unanticipated challenges arose, which influenced the data collection process; these encompass four main impact categories: (1) cost, budget, and funding; (2) project timeline; (3) participation and engagement; and (4) data challenges. The main unforeseen issues that impacted our timeline included the informed consent process for children under the age of 18 years; the use of, and coordination with, the postal service to deliver study information and equipment; and the variability associated with when participants began data collection and the time taken to send devices and consent forms back (1-12 months). Unanticipated budgetary issues included the identification of some study materials (AC power adapter) not fitting through letterboxes, as well as the employment of fieldworkers to increase recruitment and the return of consent forms. Finally, we encountered data issues when processing physical activity and GPS data that had been initiated across daylight saving time. Conclusions: We present learning points and recommendations that may benefit future studies of similar methodology in their early stages of development

Effective boundary condition at a rough surface starting from a slip condition

We consider the homogenization of the Navier-Stokes equation, set in a channel with a rough boundary, of small amplitude and wavelength $\epsilon$. It was shown recently that, for any non-degenerate roughness pattern, and for any reasonable condition imposed at the rough boundary, the homogenized boundary condition in the limit $\epsilon = 0$ is always no-slip. We give in this paper error estimates for this homogenized no-slip condition, and provide a more accurate effective boundary condition, of Navier type. Our result extends those obtained in previous works, in which the special case of a Dirichlet condition at the rough boundary was examined