Simulating Wde-area Replication

We describe our experiences with simulating replication algorithms for use in far flung distributed systems. The algorithms under scrutiny mimic epidemics. Epidemic algorithms seem to scale and adapt to change (such as varying replica sets) well. The loose consistency guarantees they make seem more useful in applications where availability strongly outweighs correctness; e.g., distributed name service

Wide-address spaces - exploring the design space

In a recent issue of Operating System Review, Hayter and McAuley [1991] argue that future high-performance systems trade a traditional, bus-based organization for one where all components are linked together by network switches (the Desk-Area Network). In this issue of Operating System Review, Leslie, McAuley and Mullender conclude that DAN-based architectures allow the exploitation of shared memory on a wider scale than just a single (multi)processor. In this paper, we will explore how emerging 64-bit processors can be used to implement shared address spaces spanning multiple machines

High-Tech Urban Agriculture in Amsterdam : An Actor Network Analysis

The agriculture and horticulture sector in the Netherlands is one of the most productive in the world. Although the sector is one of the most advanced and intense agricultural production systems worldwide, it faces challenges, such as climate change and environmental and social unsustainability of industrial production. To overcome these challenges, alternative food production initiatives have emerged, especially in large cities such as Amsterdam. Some initiatives involve producing food in the urban environment, supported by new technologies and practices, so-called high-tech urban agriculture (HTUA). These initiatives make cultivation of plants inside and on top of buildings possible and increase green spaces in urban areas. The emerging agricultural technologies are creating new business environments that are shape d by technology developers (e.g., suppliers of horticultural light emitting diodes (LED) and control environment systems) and developers of alternative food production practices (e.g., HTUA start-ups). However, research shows that the uptake of these technological innovations in urban planning processes is problematic. Therefore, this research analyzes the barriers that local government planners and HTUA developers are facing in the embedding of HTUA in urban planning processes, using the city of Amsterdam as a case study. This study draws on actor-network theory (ANT) to analyze the interactions between planners, technologies, technology developers and developers of alternative food production practices. Several concepts of ANT are integrated into a multi-level perspective on sustainability transitions (MLP) to create a new theoretical framework that can explain how interactions between technologies and planning actors transform the incumbent social\u2013technical regime. The configuration of interactions between social and material entities in technology development and adoption processes in Amsterdam is analyzed through the lens of this theoretical framework. The data in this study were gathered by tracing actors and their connections by using ethnographic research methods. In the course of the integration of new technologies into urban planning practices, gaps between technologies, technology developers, and planning actors have been identified. The results of this study show a lacking connection between planning actors and technology developers, although planning actors do interact with developers of alternative food production practices. These interactions are influenced by agency of artefacts such as visualizations of the future projects. The paper concludes that for the utilization of emerging technologies for sustainability transition of cities, the existing gap between technology developers and planning actors needs to be bridged through the integration of technology development visions in urban agendas and planning processe

Prairie pothole marshes as traps for nitrogen and phosphorous in agricultural runoff

Water quality of drainage influents and the lone effluent at Eagle Lake marsh, Iowa, was studied for 4 years (1976-1979). Because of drought conditions, there was no effluent from the marsh in 1976, 1977, or 1978. In 1979, the marsh was effective at removing inorganic N, especially N03-N, from runoff water passing through. It had little impact on levels of inorganic-P, total-P, and Kjeldahl-N; it was a net exporter of soluble organic carbon

The language of intervention: A review of concepts and terminology in wetland ecosystem repair

As programmes and projects aimed at addressing wetland degradation gain momentum in South Africa, it is critical that related ideas are communicated among and between researchers, practitioners, management agencies, land-owners and the general public in a common language. This paper explores the meaning of ‘restoration’ and ‘rehabilitation’; terms that we suggest are key to understanding and advancing South Africa’s efforts to address wetland degradation. In its essence, the paper is a critical review of wetland ecosystem repair concepts and terminology from local and international literature. The major products of the paper are proposed definitions of the terms ‘restoration’ and ‘rehabilitation’ in a South African wetland science and management context. Although the terms are often used interchangeably, we argue that their absolute distinction will allow scientists and practitioners to better understand what it is that ecosystem repair interventions aim to achieve. We suggest that the terms be distinguished on the basis of what could be considered their respective ecological starting points, where ‘restoration’ applies to part of a system or a system in its entirety that has been completely and permanently, but not irreparably altered, and essentially removed from the landscape, and ‘rehabilitation’ applies to part of a system or a system in its entirety that has not been removed from the landscape through complete and permanent alteration, but is in a degraded state. Thus, ‘wetland restoration’ is defined as the process of reinstating natural ecological driving forces within part or the whole of a completely and permanently altered wetland to recover former or desired ecosystem structure, function, biotic composition and ecosystem services, while ‘wetland rehabilitation’ is defined as the process of reinstating natural ecological driving forces within part or the whole of a degraded wetland to recover former or desired ecosystem structure, function, biotic composition and ecosystem services

Predictors for adherence to action plans for self-treatment of COPD exacerbations

Introduction/Aim: A minority of patients with chronic obstructive pulmonary disease (COPD) derives benefit fromself-management interventions that include action plans for self-treatment of COPD exacerbations. The aimof this studywas to identify predictors for adherence to action plans for self-treatment of exacerbations in COPD patients. Methods: Self-reported diary data from a subset of COPD patients who participated in a randomized controlled trial (COPE-II study) in the Netherlands was used to assess adherence to COPD action plans within a self-management intervention. Only patients with exacerbations were included. Successful self-treatment was defined as self-initiating a course of oral steroids/antibiotics within 2 days from the start of an exacerbation. A patient was defined as being adherent when in ≥75% of all exacerbations the self-treatment action plan was followed. Patient-level factors that showed a univariate association (P <0.10) with adherence were included in a multivariate logistic regression model to identify the predictors for adherence toCOPD self-treatment action plans (P <0.05). Results: Data from 66 patients (mean age 63.6 ± 8.0;men 56.1%) showed 387 exacerbations within 2 years of follow-up. Adherence to the action plans was observed in 37.9% of the patients and in 216 COPD exacerbations. Multivariate logistic regression analyses showed that being male (OR: 5.1; 95% CI: 1.5-17.3) and having no walking problems (EQ5D mobility, OR: 4.9; 95%CI: 1.5-16.4) were positively associatedwith being adherent to the action plan for self-treatment of COPD exacerbations. Conclusion: Our study results indicate that being male and having no walking problems are predictors for better adherence to COPD exacerbation action plans. This implies that exploring patients' mobility and offering more support to femaleCOPDpatients who are lessmobilemay positively influence the adherence to COPD exacerbation self-treatment action plans. More research is, however, required to confirm this