Proeve van een kD - waardenkaart van Midden - West - Nederland

Een van de belangrijkste oorzaken van verzilting in Midden-West-Nederland is de kwel. Hierdoor wordt het oppervlaktewater van de polders belast met zout uit het diepere grondwater. In dit verband is het van belang de grootte en de variaties in het doorlatend vermogen van de ondergrond te kennen

Screening for salt tolerance in native and exotic shrub willow

Non-Peer ReviewedDryland salinity is a significant agronomic problem across the Canadian prairies, with an estimated four million hectares of salt-affected land. The potential exists to make better use of saline marginal lands by developing them into willow plantations as a bioenergy feedstock; however, relatively little is known about the salt tolerance of willow. Apart from limited anecdotal information, no empirical work has been done to examine willow growth on saline soil. The objective of this study was to compare the relative salt tolerance of 37 different native and exotic hybrid willow clones grown under controlled environment conditions on soils with varying salinity. The soils were collected along a hillslope catena influenced by saline seep salinity, containing high concentrations of sulfate salts, which commonly occurs within western Canada. Most willow clones tested in this study were able to tolerate slightly saline conditions (≤ 5.0 dS/m). In addition, several clones (Alpha, India, Owasco, Tully Champion, and 01X-268-015) showed no reduction in growth with moderate salinity (≤ 8.0 dS/m). This work should help to fill the current knowledge gap regarding the salt tolerance of willow and thus provide recommendations for which clones are best suited for establishment on salt-affected soils in Saskatchewan and abroad

Internal Migration and Regional Population Dynamics in Europe: Netherlands Case Study

This report summarises the presentations made and discussions held at the Second of the ESRC/JISC Workshops Planning for the 2001 Census. The report presents views of expert census users and summarises the recommendations to ESRC and JISC about what kinds of data from the 2001 Census should be requested from the UK Census Offices. The Workshops are supported by ESRC Award H507265031. The Census of Population is a very large exercise in data collection and processing. In 2001 some 25 million households in the United Kingdom will be contacted and asked to provide answers to a simple questionnaire of 25 to 30 questions. Such a task is likely to cost £125-150 millions to the Census Offices. Purchase of the data for academic research purposes is likely to cost ESRC and JISC some £1.5 to £2 millions directly and an equivalent amount indirectly on support over the following decade. It is therefore essential that the Population Census is very carefully planned beforehand and that the greatest possible value is extracted from the data collected. This edited collection of papers reports on presentations and discussions in the Fourth and Final Workshop in the series Workshops Planning for the 2001 Census - Determining Academic Community Needs and Strategy. The Fourth Workshop was entitled The 2001 Census: What do we really really want?. The aim was to gather together and summarise the principal recommendations of the First (Geography), Second (Interfaces) and Third (Special Data Sets) Workshops. The Workshop was twinned with another on The One Number Census: A Research Workshop, organised by Ludi Simpson. The One Number Census project is a major undertaking by the Census Offices to deal with anticipated underenumeration by estimating how many households and people are missed by the standard enumeration. Part 1 of the report on Look Up Tables and Area Statistics contains chapters by David Martin on the output geography proposals for 2001, by Seraphim Alvanides and Stan Openshaw on further developments to the methods being used to define output areas and by Bob Barr on what the Look Up Tables associated with the 2001 Census should be like. These chapters contain key recommendations on census output geography. Part 2 of the report puts forward recommendations for the preparation of Microdata - Samples of Anonymised Records and Longitudinal Data from the 2001 Census. Angela Dale summarises the conclusions of the SARs Sub-Group of the Census Offices' Output Working Group. Brian Dodgeon and Heather Joshi document the essential features of the 2001 Census Link to the Longitudinal Study and make a final plea for some new questions. Part 3 of the report reviews proposals for the improvement of Interaction Statistics from the 2001 UK Census. Paul Boyle and Phil Rees make radical proposals for revamping the provision of Migration Statistics. Martin Frost concentrates on ways of improving the accuracy of the Workplace Statistics. The fourth part of the report gathers together recommendations about information technology interfaces to census data, arguing that the tools and infrastructure are now in place to make networked and standalone access to the different types of data so much easier for the new user. Donald Morse and Alistair Towers review what interfaces to boundary data should look like. James Harris argues for the development of interfaces based on general data standards and the Web to access census statistics. Oliver Duke-Williams outlines how complex migration statistics can be presented for access in a simpler and easier to use interface. Ian Turton identifies how current software developments in Java programming will make possible delivering easy to use interfaces to microdata very simple. Finally, Paul Williamson describes a design of a data dictionary for all census data sets. In Part 5, recommendations are summarised. Phil Rees reports on the views of 140 respondents drawn from the different corners of the academic community. The final pages try to draw out some general points from the very large number of recommendations made in the Fourth Workshop

Forming Galaxies with MOND

Beginning with a simple model for the growth of structure, I consider the dissipationless evolution of a MOND-dominated region in an expanding Universe by means of a spherically symmetric N-body code. I demonstrate that the final virialized objects resemble elliptical galaxies with well-defined relationships between the mass, radius, and velocity dispersion. These calculations suggest that, in the context of MOND, massive elliptical galaxies may be formed early (z > 10) as a result of monolithic dissipationless collapse. Then I reconsider the classic argument that a galaxy of stars results from cooling and fragmentation of a gas cloud on a time scale shorter than that of dynamical collapse. Qualitatively, the results are similar to that of the traditional picture; moreover, the existence, in MOND, of a density-temperature relation for virialized, near isothermal objects as well as a mass-temperature relation implies that there is a definite limit to the mass of a gas cloud where this condition can be met-- an upper limit corresponding to that of presently observed massive galaxies.Comment: 9 pages, 9 figures, revised in response to comments of referee. Table added, extended discussion, accepted MNRA

Uniqueness in MHD in divergence form: right nullvectors and well-posedness

Magnetohydrodynamics in divergence form describes a hyperbolic system of covariant and constraint-free equations. It comprises a linear combination of an algebraic constraint and Faraday's equations. Here, we study the problem of well-posedness, and identify a preferred linear combination in this divergence formulation. The limit of weak magnetic fields shows the slow magnetosonic and Alfven waves to bifurcate from the contact discontinuity (entropy waves), while the fast magnetosonic wave is a regular perturbation of the hydrodynamical sound speed. These results are further reported as a starting point for characteristic based shock capturing schemes for simulations with ultra-relativistic shocks in magnetized relativistic fluids.Comment: To appear in J Math Phy

Greenhouse gas abatement on southern Australian grains farms: B iophysical potential and financial impacts

The agricultural sector generates a substantial proportion of global greenhouse gas (GHG) emissions through emissions of carbon dioxide (CO2) and nitrous oxide (N2O). Changes to agricultural practices can provide GHG abatement by maintaining or increasing soil organic carbon (SOC) stored in soils or vegetation, or by decreasing N2O emissions. However, it can be difficult to identify practices that achieve net abatement because practices that increase SOC stocks may also increase N2O emissions from the soil. This study simulated the net on-farm GHG abatement and gross margins for a range of management scenarios on two grain farms from the western and southern grain growing regions of Australia using the Agricultural Production Systems sIMulator (APSIM) model. The soils and practices selected for the study were typical of these regions. Increased cropping intensity consistently provided emissions reductions for all site-soil combinations. The practice of replacing uncropped or unmanaged pasture fallows with a winter legume crop was the only one of nine scenarios to decrease GHG emissions and increase gross margins relative to baseline practice at both locations over the 100-year simulation period. The greatest abatement was obtained by combining this practice with an additional summer legume crop grown for a short period as green manure. However, adding the summer legume decreased farm gross margins because the summer crop used soil moisture otherwise available to the following cash crop, thus reducing yield and revenue. Annual N2O emissions from the soil were an order of magnitude lower from sandy-well-drained soils at the Western Australian location (Dalwallinu) than at the other location (Wimmera) with clay soil, highlighting the importance of interactions between climate and soil properties in determining appropriate GHG abatement practices. Thus, greatest abatement at Dalwallinu was obtained from maintaining or increasing SOC, but managing both N2O emissions and SOC storage were important for providing abatement at Wimmera

Locally recurrent rectal cancer and distant metastases:is there still a chance ofcure?

Introduction: Patients with locally recurrent rectal cancer (LRRC) generally have poor prognosis, especially those who have (a history of) distant metastases. The aim of this study was to investigate the impact of distant metastases on oncological outcomes in LRRC patients undergoing curative treatment. Methods: Consecutive patients with surgically treated LRRC between 2005 and 2019 in two tertiary referral hospitals were retrospectively analysed. Oncological survival of patients without distant metastases were compared with outcomes of patients with synchronous distant metastases with the primary tumour, patients with distant metastases in the primary-recurrence interval, and patients with synchronous LRRC distant metastases. Results: A total of 535 LRRC patients were analysed, of whom 398 (74%) had no (history of) metastases, 22 (4%) had synchronous metastases with the primary tumour, 44 (8%) had metachronous metastases, and 71 (13%) had synchronous LRRC metastases. Patients with synchronous LRRC metastases had worse survival compared to patients without metastases (adjusted hazard ratio: 1.56 [1.15–2.12]), whilst survival of patients with synchronous primary metastases and metachronous metastases of the primary tumour was similar as those patients who had no metastases. In LRRC patients who had metastases in primary-recurrence interval, patients with early metachronous metastases had better disease-free survival as patients with late metachronous metastases (3-year disease-free survival: 48% vs 22%, p = 0.039). Conclusion: LRRC patients with synchronous distant metastases undergoing curative surgery have relatively poor prognosis. However, LRRC patients with a history of distant metastases diagnosed nearby the primary tumour have comparable (oncological) survival as LRRC patients without distant metastases.</p