238 research outputs found
Assessing baseflow index vulnerability to variation in dry spell length for a range of catchment and climate properties
Get PDFBaseflow index (BFI) prediction in ungauged basins has largely been based on the use of catchment physiographic attributes as dominant variables. In a context where changes in climate are increasingly evident, it is also important to study how the slow component of flow is potentially affected by climate. The aim of this study was to illustrate the impact of climate variability on the baseflow process based on analysis of daily rainfall characteristics and hydrological modelling simulation exercises validated with observed data. Ten catchments were analysed that span southern to northern Europe and range from arid Mediterranean to maritime temperate climate conditions. Additionally, more than 2,000 virtual catchments were modelled that cover an extended gradient of physiographic and climate properties. The relative amounts of baseflow were summarized by the BFI. The catchment slow response delay time (Ks) was assumed to be a measure of catchment effects, and the impact of climate properties was investigated with the dry spell length (d). Well-drained and poorly-drained groups were identified based on Ks and d, and their response to an increase or decrease in dry spell length was analysed. Overall, for either well- or poorly-drained groups, an extension in dry spell length appeared to have minor effects on the baseflow compared with a decrease in dry spell length. Under the same dry spell variation, the BFI vulnerability appeared higher for catchments characterized by large initial d values in combination with poorly-drained systems, but attributing an equal weight to the variations in d both in the case of dry and wet initial conditions, it is in the end concluded that the BFI vulnerability appears higher for systems laying in the transition zone between well- and poorly-drained systems. Copyright © 2018 John Wiley & Sons, Ltd
Management of gestational hypertension and mild pre-eclampsia at term
Get PDFZwangerschapshypertensie en preëclampsie compliceren 6-8% van alle zwangerschappen en vormen in Nederland de belangrijkste oorzaak van maternale morbiditeit en mortaliteit. Vaak is het ziektebeeld mild en treedt op in de aterme periode. Soms ontstaan ernstige complicaties, zoals eclampsie, abruptio placentae of het HELLP-syndroom. Wereldwijd was er tot nu toe geen overeenstemming over het beste beleid bij deze aandoeningen. Inleiding van de baring zou enerzijds maternale complicaties kunnen reduceren, maar anderzijds de kans op een sectio caesarea kunnen verhogen.
Het eerste deel van dit proefschrift beschrijft een multicentrisch gerandomiseerde klinische studie (HYPITAT trial (HYpertension and Pre-eclampsia Intervention Trial At Term)), uitgevoerd binnen het Verloskundige Consortium (www.studies-obsgyn.nl/hypitat). Wij onderzochten wat beter is voor vrouwen met een milde zwangerschapsgerelateerde aterme hypertensie: inleiden of afwachten, met het oog op klinische effectiviteit, maternale kwaliteit van leven en kosten. Deze studie werd uitgevoerd in 38 Nederlandse ziekenhuizen. In totaal werden 756 vrouwen gerandomiseerd voor inleiden (n=377) of afwachten (n=379). De resultaten wijzen uit dat inleiden de kans op maternale complicaties verkleint (31% versus 44%; RR 0.71; p<0.001), inleiden een tendens laat zien van minder sectio caesarea (14% versus 19%; RR0.75; p=0.085) en inleiden gemiddeld 831 euro per patiënt goedkoper is dan afwachten. De neonatale uitkomst en de maternale kwaliteit van leven is gelijk tussen beide strategieën. Daarom adviseren wij een inleiding van de baring bij vrouwen met een zwangerschapshypertensie of milde preëclampsie na 37 weken zwangerschap.
Het tweede gedeelte van dit proefschrift beschrijft welke factoren een slechte maternale uitkomst bij vrouwen met een aterme zwangerschapshypertensie of milde preëclampsie kunnen voorspellen. Voor deze studies hebben wij gebruik van de HYPITAT database.
Hydrological drought explained
Get PDFDrought is a complex natural hazard that impacts ecosystems and society in many ways. Many of these impacts are associated with hydrological drought (drought in rivers, lakes, and groundwater). It is, therefore, crucial to understand the development and recovery of hydrological drought. In this review an overview is given of the current state of scientific knowledge of definitions, processes, and quantification of hydrological drought. Special attention is given to the influence of climate and terrestrial properties (geology, land use) on hydrological drought characteristics and the role of storage. Furthermore, the current debate about the use and usefulness of different drought indicators is highlighted and recent advances in drought monitoring and prediction are mentioned. Research on projections of hydrological drought for the future is summarized. This review also briefly touches upon the link of hydrological drought characteristics with impacts and the issues related to drought management. Finally, four challenges for future research on hydrological drought are defined that relate international initiatives such as the Intergovernmental Panel on Climate Change (IPCC) and the ‘Panta Rhei’ decade of the International Association of Hydrological Sciences (IAHS)
Density of the f-statistic in the linear model with arbitrarily normal distributed errors
Get PDFEstimation;mathematische statistiek
Coordination of External Policies: Feudal Fiefdoms to Coordinate
No full textAs a formal requirement across policies, coordination is a concern in the commission regular decision-making. Although it might be met with reluctance on the part of services, it is enshrined in the organization of the commission. The renewed commitment of the lisbon treaty to the coherence of eu’s external action has added an inter-institutional dimension to the challenge, in turn leading the commission to adapt. How and to what extent are external policies coordinated within the commission? this paper builds on a two-level approach—using the service and political levels—to analyse the responsibilities, resources and actual contributions of the different actors towards coordination. It argues that, despite the respective principles, the instruments available and the actors specifically engaged in coordination-related activities, coordinating external policies remains a challenge.keywordssecretariat generalpolicy coordinationcommission servicelisbon treatyexternal policythese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves
Process-based modelling
No full textThe chapter describes two categories of process-based models, namely, hydrological and socio-hydrological models. It starts with an explanation of the modelling chain from climate drivers via process-based models to identification of hydrological and socio-hydrological drought characteristics. Then, the first category of process-based models is introduced, that is, hydrological models, which are divided in three types: spatially lumped, semi-distributed and spatially distributed models. Spatially distributed models are further subdivided based on whether they simulate lateral groundwater flow (GWfl) or not (nGWfl). An example model of each of these three types, including an application is given, that is, HBV (spatially lumped, semi-distributed), PCR-GLOBWB (spatially distributed model, nGWfl) and SIMGRO (spatially distributed model, GWfl). The second category of process-based models, that is, the socio-hydrological models, is also divided into three types: coupled-component, system-dynamics and agent-based models. The chapter addresses calibration and validation of process-based models and concludes with some guidance on how to select an adequate model, considering also the associated uncertainty.</p
Optimizing flow rates in a queueing network with side constraints
Get PDFNetwork Analysis;operations research
Learning by doing:enhancing hydrology lectures with individual fieldwork projects
No full textHydrology teaching deals with processes happening outside the classroom, which calls for active-learning methods to complement lectures. In a geography undergraduate course, new teaching methods and assessment were designed, in which students investigated a river of their choice by completing homework tasks and presenting their results on a poster. During a 3-year implementation process, the changes were evaluated using a combination of formal and informal student and lecturer feedback. Students mentioned that they enjoyed doing the project and that it helped their understanding of theory, their research skills, and their ability to select, organize and present information. Questionnaire results showed that, over the implementation period, students’ perceived value of homework increased strongly, while their perceived value of lectures remained high. In informal feedback, students noted that they enjoyed learning about where they live, preferred doing the projects individually and seeing each other’s projects, and spent more time on the coursework when assessed. When looking back in interviews, students commented that the projects had prepared them well for their dissertation and summer job. The advantage of using homework-based projects complementing lectures is the strong link between theory and practice, which could be further enhanced by discussing the homework in the lectures.</p
The effect of systematic misperception of income on the subjective poverty line
Get PDFIncome Distribution;macroeconomics
Drought in the Anthropocene
Get PDFDrought management is inefficient because feedbacks between drought and people are not fully
understood. In this human-influenced era, we need to rethink the concept of drought to include the
human role in mitigating and enhancing drought
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