201 research outputs found

    The Impact Of Network Management On Outcomes In Governance Networks

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    __Abstract__ There is a large amount of literature and research on network management strategies. However, only a limited portion of this literature examines the relationship between network management strategies and outcomes (for an exception, see Meier and O'Toole 2001). Most of the research focuses on managerial activity or networking rather than on the question of which types of strategies matter the most for outcomes of complex processes in networks. This paper attempts to address the question of whether managerial strategies matter for outcomes and also explores which types of strategies have an effect on outcomes.The research is based on a survey sent to respondents involved in environmental projects in The Netherlands. The findings show that the number of employed network management strategies has a strong effect on perceived outcomes. The few variations in the effect of four constructed types of network management strategies found include exploring content, connecting, arranging, and process agreements

    Public Private Partnerships: added value by organisational form or management?

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    Summary The central idea of public private partnerships (PPPs) is that added value can be achieved from greater co-operation between public and private actors. In general, the literature speaks of PPPs in which public and private actors develop a more or less sustainable co-operation through which they realise products, services, or policies together, share risks and develop an organisation form to arrange this. The assumption is that a higher degree of PPP leads to more and better outcomes because public and private actors combine their knowledge and resources. One can find a wide array of organisational forms in which this co-operation is organized and the literature pays a great deal of attention to these forms. But is this organisational form really so important, or are the intensity and type of managerial strategies more important for the outcomes? Based on a large survey of individuals involved in Dutch environmental projects, we show that although the degree of PPP correlates positively with the outcomes of projects, this correlation disappears when we include in the analysis the number of managerial strategies employed. The organisational form does not have significant impact on outcomes and the conclusion we draw is that scholars and practitioners of public private partnerships should pay greater attention to the managerial efforts necessary to develop and implement PPPs

    Earth-like aqueous debris-flow activity on Mars at high orbital obliquity in the last million years

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    Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. This is testified by the widespread occurrence of mid-latitude gullies: small catchment-fan systems. However, there are no direct estimates of the amount and frequency of liquid water generation during these periods. Here we determine debris-flow size, frequency and associated water volumes in Istok crater, and show that debris flows occurred at Earth-like frequencies during high-obliquity periods in the last million years on Mars. Results further imply that local accumulations of snow/ice within gullies were much more voluminous than currently predicted; melting must have yielded centimetres of liquid water in catchments; and recent aqueous activity in some mid-latitude craters was much more frequent than previously anticipated

    Deformability and collision-induced reorientation enhance cell topotaxis in dense microenvironments

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    In vivo, cells navigate through complex environments filled with obstacles. Recently, the term 'topotaxis' has been introduced for navigation along topographic cues such as obstacle density gradients. Experimental and mathematical efforts have analyzed topotaxis of single cells in pillared grids with pillar density gradients. A previous model based on active Brownian particles has shown that ABPs perform topotaxis, i.e., drift towards lower pillar densities, due to decreased effective persistence lengths at high pillars densities. The ABP model predicted topotactic drifts of up to 1% of the instantaneous speed, whereas drifts of up to 5% have been observed experimentally. We hypothesized that the discrepancy between the ABP and the experimental observations could be in 1) cell deformability, and 2) more complex cell-pillar interactions. Here, we introduce a more detailed model of topotaxis, based on the Cellular Potts model. To model persistent cells we use the Act model, which mimicks actin-polymerization driven motility, and a hybrid CPM-ABP model. Model parameters were fitted to simulate the experimentally found motion of D. discoideum on a flat surface. For starved D. discoideum, both CPM variants predict topotactic drifts closer to the experimental results than the previous ABP model, due to a larger decrease in persistence length. Furthermore, the Act model outperformed the hybrid model in terms of topotactic efficiency, as it shows a larger reduction in effective persistence time in dense pillar grids. Also pillar adhesion can slow down cells and decrease topotaxis. For slow and less persistent vegetative D. discoideum cells, both CPMs predicted a similar small topotactic drift. We conclude that deformable cell volume results in higher topotactic drift compared to ABPs, and that feedback of cell-pillar collisions on cell persistence increases drift only in highly persistent cells

    Scour protection design in highly morphodynamic environments

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    Offshore wind parks are often developed in areas with a highly morphodynamic seabed. In order to keep the pile fixation level within acceptable limits for pile design, sophisticated scour mitigation strategies are required. This paper discusses the scour protection strategy for the NordergrĂĽnde Offshore Wind Farm, where 10m seabed level drops are predicted at some monopile locations. Physical model tests were performed to validate the scour protection design, focussing on correct falling apron behaviour and the stability of the loose rock scour protection. The outcome of the tests showed good correlation with a modified relative mobility parameter. Using this parameter, the scour protection was optimised for the individual pile locations

    Use of a porous membrane for gas bubble removal in microfluidic channels: physical mechanisms and design criteria

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    We demonstrate and explain a simple and efficient way to remove gas bubbles from liquid-filled microchannels, by integrating a hydrophobic porous membrane on top of the microchannel. A prototype chip is manufactured in hard, transparent polymer with the ability to completely filter gas plugs out of a segmented flow at rates up to 7.4 microliter/s per mm2 of membrane area. The device involves a bubble generation section and a gas removal section. In the bubble generation section, a T-junction is used to generate a train of gas plugs into a water stream. These gas plugs are then transported towards the gas removal section, where they slide along a hydrophobic membrane until complete removal. The system has been successfully modeled and four necessary operating criteria have been determined to achieve a complete separation of the gas from the liquid. The first criterion is that the bubble length needs to be larger than the channel diameter. The second criterion is that the gas plug should stay on the membrane for a time sufficient to transport all the gas through the membrane. The third criterion is that the gas plug travel speed should be lower than a critical value: otherwise a stable liquid film between the bubble and the membrane prevents mass transfer. The fourth criterion is that the pressure difference across the membrane should not be larger than the Laplace pressure to prevent water from leaking through the membrane

    The acceptance and use of the e-Health instrument 'The personal health check' in four Dutch municipalities:Lessons learned

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    This pilot study assessed the acceptance and use of the e-Health instrument “the Personal Health Check” (PHC) among clients and professionals in primary care settings. By filling in the online PHC instrument, participants were provided insights into their health and lifestyle. When results revealed an increased health risk, participants were advised to undertake additional lab tests measuring blood pressure and haemaglobin levels. Based on the online questionnaire and optional lab tests, participants then received a report that included individually-tailored feedback from the e-Health application about personal health risks and suggestions for health interventions. The PHC was implemented in 2016 in four Dutch municipalities that determined which neighbourhood(s) the PHC targeted and how participants were invited. The Unified Theory of Acceptance and Use of Technology was used as a theoretical framework to address our research questions. Methods used to assess acceptance were: PHC instrument data, data from additional questionnaires completed by PHC participants, focus groups with PHC participants and professionals in primary care, and telephone interviews with non-responders to the invitation to participate in the online PHC. Of the 21,735 invited, 12% participated. Our results showed that participants and professionals in this pilot were predominantly positive about the PHC. Participants reported that they made an effort to apply the PHC lifestyle advice they received. Almost all had the knowledge and resources needed to use the PHC online instrument. Invitations from general practitioners almost doubled participation relative to invitations from the sponsoring municipalities. The overall low response rate, however, suggests that the PHC is unsuitable as a foundation on which to develop local public health policy

    Regional and scale-specific effects of land use on amphibian diversity [poster]

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    Background/Question/Methods Habitat loss and degradation influence amphibian distributions and are important drivers of population declines. Our previous research demonstrated that road disturbance, development and wetland area consistently influence amphibian richness across regions of the U.S. Here, we examined the relative importance of these factors in different regions and at multiple spatial scales. Understanding the scales at which habitat disturbance may be affecting amphibian distributions is important for conservation planning. Specifically, we asked: 1) Over what spatial scales do distinct landscape features affect amphibian richness? and 2) Do road types (non-rural and rural) have similar effects on amphibian richness? This is the second year of a collaborative, nationwide project involving 11 U.S. colleges integrated within undergraduate biology curricula. We summarized North American Amphibian Monitoring Program data in 13 Eastern and Central U.S states and used geographic information systems to extract landscape data for 471 survey locations. We developed models to quantify the influence of landscape variables on amphibian species richness and site occupancy across five concentric buffers ranging from 300m to 10,000m. Results/Conclusions Across spatial scales, development, road density and agriculture were the best predictors of amphibian richness and site occupancy by individual species. Across regions, we found that scale did not exert a large influence on how landscape features influenced amphibian richness as effects were largely comparable across buffers. However, development and percent impervious surface had stronger influence on richness at smaller spatial scales. Richness was lower at survey locations with higher densities of non-rural and rural roads, and non-rural road density had a larger negative effect at smaller scales. Within regions, landscape features driving patterns of species richness varied. The scales at which these factors were associated with richness were highly variable within regions, suggesting the scale effects may be region specific. Our project demonstrates that networks of undergraduate students can collaborate to compile and analyze large ecological data sets, while engaging students in authentic and inquiry-based learning in landscape-scale ecology
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