Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Oil slick fate in 3D : predicting the influence of (natural and chemical) dispersion on oil slick fate
    Zeinstra-Helfrich, Marieke - \ 2016
    Wageningen University. Promotor(en): Tinka Murk, co-promotor(en): W. Koops. - Wageningen : Wageningen University - ISBN 9789462579279 - 174
    oil spills - pollution - adverse effects - oils - dispersion - models - thickness - olieverontreinigingen - verontreiniging - nadelige gevolgen - oliën - dispersie - modellen - dikte

    In certain conditions, (part of) an oil spill can disappear from the water surface through a process called natural dispersion. One available oil spill response option is to enhance this process by addition of dispersants (chemical dispersion). An informed decision for such response requires insight in the oil slick size WITH and WITHOUT treatment. This thesis aims to enable such assessment of net effectiveness, by providing a strategy for modelling the dispersion process.

    A plunging jet test was developed for investigating entrainment and droplet breakup. Using this set up the relevance of oil layer thickness was proven and an algorithm to model droplet sizes of dispersed oil was defined. The findings were applied in a model simulating dispersion and resurfacing as well as the wind-driven differential transport between the floating slick and suspended droplets. The simulation outputs help assess the added value (or not) of dispersant application in reducing the surface oil slick size for different oil types and conditions.

     

    DIMO, a plant dispersal model
    Wamelink, G.W.W. ; Jochem, R. ; Greft, J.G.M. van der; Franke, J. ; Malinowska, A.H. ; Geertsema, W. ; Prins, A.H. ; Ozinga, W.A. ; Hoek, D.C.J. van der; Grashof-Bokdam, C.J. - \ 2014
    Wageningen : Statutory Research Tasks Unit for Nature & the Environment (WOT Natuur & Milieu) (WOt-paper 37) - 12
    habitatverbindingszones - vegetatie - dispersie - landschapsecologie - modellen - habitat corridors - vegetation - dispersion - landscape ecology - models
    Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new areas due to climate change. Species survival in these cases may depend on increasing the connectivity of the landscape by engineering. To investigate and to predict the effects of isolation on the dispersal abilities of plant species, to increase spatial cohesion of a habitat network, to advise policy makers and spatial planners, we developed a simple GIS based dispersal model, DIMO. The model simulates dispersal and establishment of plant populations over a period of time in heterogeneous landscapes on a yearly basis. The model includes proxies for dispersal by wind, animals, water, and self-dispersal. Species establishment is based on habitat suitability maps and simulations include the effect of seed dormancy and generation time. A sensitivity analysis and validation were carried out. The model was validated with Juncus tenuis, an introduced species in the Netherlands. On average the difference between observed and simulated dispersal distance was 9.8 km for a distance of 155 km. The model was applied for a designed corridor in the South of the Netherlands. Model runs indicate that three of the five tested species were able to use the corridor. Two species could not, both due to lack of suitable habitat and one of them also due to lack of dispersal capacity. The results suggest that DIMO is able to evaluate the effectiveness of corridors, but also made clear that besides connectivity the present and future availability of suitable habitats in a corridor is of great importance. The model could be helpful for evaluating policy plans but also for policy making. It may be used for defining and implementation of adaptation measures to climate change on regional to continental scale. Key-words: dispersal, germination, spatial-explicit modeling, climate change, landscape fragmentation, ecological networks
    Synthesis of ecosystem vulnerability to climate change in the Netherlands shows the need to consider environmental fluctuations in adaptation measures
    Bodegom, P.M. van; Verboom-Vasiljev, J. ; Witte, J.P.M. ; Vos, C.C. ; Batholomeus, R.P. ; Geertsema, W. ; Cormont, A. ; Veen, M. van der; Aerts, R. - \ 2014
    Regional Environmental Change 14 (2014)3. - ISSN 1436-3798 - p. 933 - 942.
    klimaatverandering - ecosystemen - dispersie - ecohydrologie - climatic change - ecosystems - dispersion - ecohydrology - plant traits - species distribution - range shifts - water-flow - models - vegetation - biodiversity - conservation - conductance - terrestrial
    Climate change impacts on individual species are various and range from shifts in phenology and functional properties to changes in productivity and dispersal. The combination of impacts determines future biodiversity and species composition, but is difficult to evaluate with a single method. Instead, a comparison of mutually independent approaches provides information and confidence in patterns observed beyond what may be achieved in individual approaches. Here, we carried out such comparison to assess which ecosystem types in the Netherlands appear most vulnerable to climate change impacts, as arising from changes in hydrology, nutrient conditions and dispersal limitations. We thus combined meta-analyses of species range shifts with species distribution modelling and ecohydrological modelling with expert knowledge in two respective impact studies. Both impact studies showed that nutrient-poor ecosystems and ecosystem types with fluctuating water tables—like hay meadows, moist heathlands and moorlands—seem to be most at risk upon climate change. A subsequent meta-analysis of species–environmental stress relations indicated that particularly endangered species are adversely affected by the combination of drought and oxygen stress, caused by fluctuating moisture conditions. This implies that adaptation measures should not only aim to optimise mean environmental conditions but should also buffer environmental extremes. Major uncertainties in the assessment included the quantitative impacts of vegetation-hydrology feedbacks, vegetation adaptation and interactions between dispersal capacity and traits linked to environmental selection. Once such quantifications become feasible, adaptation measures may be tailor-made and optimised to conserve vulnerable ecosystem types
    Core-shell particles : experiments and self-consistent field modelling
    Iakovlev, P.A. - \ 2011
    Wageningen University. Promotor(en): Martien Cohen Stuart; Frans Leermakers, co-promotor(en): Mieke Kleijn. - [S.l.] : S.n. - ISBN 9789085858683 - 211
    afdeklagen - acrylaten - monomeren - nanotechnologie - dispersie - coatings - acrylics - monomers - nanotechnology - dispersion
    Effect of local weather on butterfly flight behaviour, movement, and colonization: significance for dispersal under climate change
    Cormont, A. ; Malinowska, A.H. ; Kostenko, O. ; Radchuk, V. ; Hemerik, L. ; Wallis de Vries, M.F. ; Verboom, J. - \ 2011
    Biodiversity and Conservation 20 (2011)3. - ISSN 0960-3115 - p. 483 - 503.
    klimaatverandering - weersgegevens - diergedrag - vliegen - lepidoptera - migratie - dispersie - climatic change - weather data - animal behaviour - flight - lepidoptera - migration - dispersion - british butterflies - range margins - habitat - landscapes - metapopulations - temperature - responses - search - models - wind
    Recent climate change is recognized as a main cause of shifts in geographical distributions of species. The impacts of climate change may be aggravated by habitat fragmentation, causing regional or large scale extinctions. However, we propose that climate change also may diminish the effects of fragmentation by enhancing flight behaviour and dispersal of ectothermic species like butterflies. We show that under weather conditions associated with anticipated climate change, behavioural components of dispersal of butterflies are enhanced, and colonization frequencies increase. In a field study, we recorded flight behaviour and mobility of four butterfly species: two habitat generalists (Coenonympha pamphilus; Maniola jurtina) and two specialists (Melitaea athalia; Plebejus argus), under different weather conditions. Flying bout duration generally increased with temperature and decreased with cloudiness. Proportion of time spent flying decreased with cloudiness. Net displacement generally increased with temperature. When butterflies fly longer, start flying more readily and fly over longer distances, we expect dispersal propensity to increase. Monitoring data showed that colonization frequencies moreover increased with temperature and radiation and decreased with cloudiness. Increased dispersal propensity at local scale might therefore lower the impact of habitat fragmentation on the distribution at a regional scale. Synergetic effects of climate change and habitat fragmentation on population dynamics and species distributions might therefore appear to be more complex than previously assumed
    Belang van dispersie bij herstel van waternatuur
    Didderen, K. ; Verdonschot, P.F.M. - \ 2010
    De Levende Natuur 111 (2010)3. - ISSN 0024-1520 - p. 24 - 29.
    hydrobiologie - migratie - duikers - waterdieren - dispersie - macrofauna - hydrobiology - migration - culverts - aquatic animals - dispersion - macrofauna
    Resultaten van herstelmaatregelen in wateren vallen vaak tegen, omdat de gewenste fauna niet (terug)komt. Een belangrijke reden hiervoor is dat (her)kolonisatie van waterfauna moet plaatsvinden vanuit bronpopulaties. Om meer te weten te komen over de dispersie van macrofauna en hun verplaatsing door het water is de barrièrewerking van duikers onderzocht. Dit leidt tot een aantal aanbevelingen.
    Dispersal failure contributes to plant losses in NW Europe
    Ozinga, W.A. ; Römermann, C. ; Bekker, R.M. ; Prinzing, A. ; Tamis, W.L.M. ; Schaminée, J.H.J. ; Hennekens, S.M. ; Thompson, K. ; Poschlod, P. ; Kleyer, M. ; Bakker, J.P. ; Groenendael, J.M. van - \ 2009
    Ecology Letters 12 (2009)1. - ISSN 1461-023X - p. 66 - 74.
    vegetatietypen - dispersie - plantengemeenschappen - noordwest-europa - vegetation types - dispersion - plant communities - northwestern europe - life-history traits - species richness - environmental-conditions - conservation - diversity - communities - extinction - landscape - ecology - fragmentation
    The ongoing decline of many plant species in Northwest Europe indicates that traditional conservation measures to improve the habitat quality, although useful, are not enough to halt diversity losses. Using recent databases, we show for the first time that differences between species in adaptations to various dispersal vectors, in combination with changes in the availability of these vectors, contribute significantly to explaining losses in plant diversity in Northwest Europe in the 20th century. Species with water- or fur-assisted dispersal are over-represented among declining species, while others (wind- or bird-assisted dispersal) are under-represented. Our analysis indicates that the 'colonization deficit' due to a degraded dispersal infrastructure is no less important in explaining plant diversity losses than the more commonly accepted effect of eutrophication and associated niche-based processes. Our findings call for measures that aim to restore the dispersal infrastructure across entire regions and that go beyond current conservation practices
    Adapting landscapes to climate change: examples of climate-proof ecosystem networks and priority adaptation zones
    Vos, C.C. ; Berry, P. ; Opdam, P. ; Baveco, H. ; Nijhof, B.S.J. ; O'Hanley, J. ; Bell, C. ; Kuipers, H. - \ 2008
    Journal of Applied Ecology 45 (2008)6. - ISSN 0021-8901 - p. 1722 - 1731.
    klimaatverandering - soortendiversiteit - habitatverbindingszones - natura 2000 - dispersie - modellen - climatic change - species diversity - habitat corridors - natura 2000 - dispersion - models - change impacts - habitat fragmentation - species distributions - land-use - biodiversity - conservation - dispersal - butterflies - decline - policy
    1. Climate change has been inducing range shifts for many species as they follow their suitable climate space and further shifts are projected. Whether species will be able to colonize regions where climate conditions become suitable, so-called 'new climate space', depends on species traits and habitat fragmentation. 2. By combining bioclimate envelope models with dispersal models, we identified areas where the spatial cohesion of the ecosystem pattern is expected to be insufficient to allow colonization of new climate space. 3. For each of three ecosystem types, three species were selected that showed a shift in suitable climate space and differed in habitat fragmentation sensitivity. 4. For the 2020 and 2050 time slices, the amount of climatically suitable habitat in northwest Europe diminished for all studied species. Additionally, significant portions of new suitable habitat could not be colonized because of isolation. Together, this will result in a decline in the amount of suitable habitat protected in Natura 2000 sites. 5. We develop several adaptation strategies to combat this problem: (i) link isolated habitat that is within a new suitable climate zone to the nearest climate-proof network; (ii) increase colonizing capacity in the overlap zone, the part of a network that remains suitable in successive time frames; (iii) optimize sustainable networks in climate refugia, the part of a species' range where the climate remains stable. 6. Synthesis and applications. Following the method described in this study, we can identify those sites across Europe where ecosystem patterns are not cohesive enough to accommodate species' responses to climate change. The best locations for climate corridors where improving connectivity is most urgent and potential gain is highest can then be pinpointed.
    A two-year study of Trichoptera caught on light in the Kaaistoep (The Netherlands).
    Higler, L.W.G. ; Spijkers, H. ; Wielink, P. van - \ 2008
    Entomologische Berichten 68 (2008)5. - ISSN 0013-8827 - p. 175 - 181.
    trichoptera - dispersie - natuur - noord-brabant - trichoptera - dispersion - nature - noord-brabant
    A screen and light source were operated at a fixed place in the Kaaistoep, a nature reserve near the city of Tilburg (province Noord-Brabant, TheNetherlands). Some 75 nights per year have been spent catching insects by hand, and among these many caddis flies (Trichoptera). We collected and identifïed caddis flies during 2005 and 2006. In both years together more than 16,000 specimens were caught, comprising 52 species, including quite some rare and unexpected species. Flight periods could be constructed, which sometimes showed great difference between the two years. Weather conditions are likely to be responsible for these differences.
    Dispersie in gefragmenteerde landschappen
    Ozinga, W.A. - \ 2008
    Landschap : tijdschrift voor landschapsecologie en milieukunde 25 (2008)3. - ISSN 0169-6300 - p. 132 - 133.
    plantengemeenschappen - dispersie - migratie - fragmentatie - biodiversiteit - herstel - plant communities - dispersion - migration - fragmentation - biodiversity - rehabilitation
    Planten zijn voor het transport van hun zaden afhankelijk van wind, water en dieren. Deze externe transportmiddelen vormen in het landschap een complexe dispersie-infrastructuur voor zaden. Een sterke aantasting hiervan heeft geleid tot een vervlakking van de plantendiversiteit in Nederlandse landschappen
    Dispersie van macrofauna door duikers : resultaten van een labexperiment
    Didderen, K. ; Snoek, R.C. ; Verdonschot, P.F.M. - \ 2008
    Wageningen : Alterra (Alterra-rapport 1746) - 45
    fauna - dispersie - aquatisch milieu - herstel - oppervlaktewater - barrières - verspreiding - macrofauna - aquatische ecologie - fauna - dispersion - aquatic environment - rehabilitation - surface water - barriers - dispersal - macrofauna - aquatic ecology
    Na herstelmaatregelen blijft ecologisch herstel van oppervlaktewateren vaak uit. Een mogelijke oorzaak ligt in de capaciteit van de soorten om de afstand naar een hersteld oppervlaktewater te overbruggen. Om te onderzoeken welke factoren barrières opwerpen voor dispersie van macrofauna, is de verspreiding van organismen in dit onderzoek experimenteel onderzocht. Een veldsituatie van twee wateren verbonden door een duiker is nagebootst in het laboratorium. In totaal zijn zes verschillende type barrières onderzocht voor drie verschillende bewegings¬groepen. Uit het onderzoek komen enkele directe en indirecte barrières voor de verspreiding van verschillende bewegingsgroepen naar voren. Bij het uitvoeren van herstelmaatregelen kan rekening gehouden worden met deze bevindingen en de aangewezen barrières zouden verwijderd kunnen worden, opdat aquatische organismen zich sneller kunnen verspreiden.
    Beheer landschapselementen in Limburg : verslag veldwerkplaats Heuvelland in Cottessen-Camerig, 8 november 2007
    Cordewener, N. ; Ottburg, F.G.W.A. - \ 2007
    [S.l. : S.n. - 4
    fauna - flora - dispersie - hakhout - landschap - landschapsbeheer - natuurbeheer - limburg - fauna - flora - dispersion - coppice - landscape - landscape management - nature management - limburg
    Goede dispersiemogelijkheden zijn van belang voor het voortbestaan van veel plant- en diersoorten. Nederland is echter sterk versnipperd door talloze barrières zoals auto- en spoorwegen, kanalen en bebouwing. Landschapselementen als heggen, hagen, bermen, akkerranden en dijken kunnen helpen omdat ze corridors vormen tussen de natuurgebieden. Goede inrichting is echter lastig en soms conflicteren de doelstellingen voor bepaalde soorten met elkaar of met cultuurhistorie. Onderstaand enkele voorbeelden van landschapselementen in Limburg.
    Effecten van klimaatverandering op natuur overal zichtbaar
    Bron, W.A. ; Vliet, A.J.H. van - \ 2007
    Vakblad Natuur Bos Landschap 4 (2007)8. - ISSN 1572-7610 - p. 2 - 7.
    biodiversiteit - habitats - soorten - temperatuur - klimaatverandering - dispersie - agrobiodiversiteit - biodiversity - habitats - species - temperature - climatic change - dispersion - agro-biodiversity
    De sterke stijging van de temperatuur sinds 1988 leidt tot grote zichtbare veranderingen in de Nederlandse natuur. Het groeiseizoen is enkele weken langer geworden. Een groot aantal warmteminnende soorten breidt zich uit of vestigt zich. Het is nog grotendeels onduidelijk hoe natuur en landschap gaan veranderen als gevolg van verwachte temperatuurstijgingen tot 2,8 graden Celcius in de komende veertig jaar. In dit artikel nadere aandacht voor vogels, planten, vlinders, mossen, achteruitgang van soorten in relatie tot temperatuurveranderingen
    Report of the workshop on the application of dispersants in the North Sea
    Tamis, J.E. ; Karman, C.C. - \ 2007
    Den Helder : IMARES (Report / Wageningen IMARES nr. C105/07) - 27
    olieverontreinigingen - verontreinigende stoffen - waterverontreiniging - milieubescherming - dispersie - noordzee - oil spills - pollutants - water pollution - environmental protection - dispersion - north sea
    In the Netherlands, the use of detergents in oil spill response had been banned since the 1970s. The main reasons for this change in policy are that in recent years new dispersant products have become available which are less environmentally harmful (high biodegradability, low toxicity) and more effective (less product necessary and applicable to a broader range of oil types and circumstances). In addition, there is a desire to harmonize international policy for oil spill response in the North Sea region, where most countries apply dispersants as a secondary option. In the Netherlands the plan is to use detergents only in those cases where mechanical response is not enough for preventing the oil slick from moving into an ecologically or economically sensitive area. In order to effectively permit the application of dispersants, defining conditions and a decision tree are required. This workshop was organized to discus what is needed in a decision tree that can be used in a practical application framework.
    Dispersie : herstelde petgaten en de rol van dispersie
    Didderen, K. - \ 2007
    Wageningen : Alterra (Alterra-rapport 1564) - 67
    aquatische gemeenschappen - moerassen - plassen - herstel - dispersie - invasies - ecologie - vissen - waterkwaliteit - macrofauna - noordwest-overijssel - biologisch waterbeheer - aquatic communities - marshes - ponds - rehabilitation - dispersion - invasions - ecology - fishes - water quality - macrofauna - noordwest-overijssel - biological water management
    Als herstelmaatregelen in oppervlaktewateren succesvol worden uitgevoerd, blijkt vaak dat de gewenste soorten niet of slechts gedeeltelijk terugkeren, ondanks gunstige abiotische omstandigheden. De oorzaak ligt waarschijnlijk in de mogelijkheden van de soorten, om de afstand af te leggen tussen het herstelgebied en dichtstbijzijnde populatie. In dit onderzoek is specifiek nagegaan hoe het dispersievermogen is van indicatorsoorten in petgaten
    Ontwikkeling geurverspreidingsmodule voor beleidsinstrument stankregulering veehouderij : toepassingmogelijkheden van het NNM
    Hofschreuder, P. ; Ogink, N.W.M. - \ 2005
    Wageningen : Agrotechnology & Food Innovations (Rapport / Wageningen UR, Agrotechnology & Food Innovations 551) - ISBN 9789067549509 - 61
    stankemissie - geurstoffen - stankbestrijding - huisvesting, dieren - dispersie - modellen - beleid - veehouderij - odour emission - odours - odour abatement - animal housing - dispersion - models - policy - livestock farming
    Natuur over en onder wegen
    Bekker, H. ; Grift, E.A. van der - \ 2005
    Groen : vakblad voor groen in stad en landschap 61 (2005)10. - ISSN 0166-3534 - p. 6 - 9.
    fauna - dispersie - wegen - wildbescherming - wildpassages - fauna - dispersion - roads - wildlife conservation - wildlife passages
    In Nederland worden elk jaar miljoenen gewervelde dieren doodgereden. Maatregelen op het gebied van ontsnippering en resultaten daarvan komen in dit themanummer aan de orde. Dit eerste artikel geeft een inleiding
    De onverwachte terugkeer van de bever in Vlaanderen; kansen, knelpunten en ondersteunende matregelen
    Niewold, F.J.J. - \ 2004
    Wageningen : Alterra (Alterra-rapport 996) - 41
    dieren - Castor fiber - geïntroduceerde soorten - introductie - dispersie - bedreigde soorten - wildbescherming - België - Castoridae - monitoring - populatiedynamica - vlaanderen - animals - Castor fiber - introduced species - introduction - dispersion - endangered species - wildlife conservation - Belgium - Castoridae - monitoring - population dynamics - flanders
    Dit rapport beschrijft de recente ontwikkelingen van de verschillende bevergroepen in Vlaanderen, zoals die zijn ontstaan na herintroducties langs de landsgrenzen en een niet geautoriseerde herintroductie van een twintigtal bevers in het dal van de Dijle in april 2003. In het dal van de Dijle stroomopwaarts van Leuven was gedurende de winter van 2003-2004 een aaneengesloten beverpopulatie aanwezig bestaande uit 16-22 dieren, verdeeld over ca. elf vestigingen met mogelijk vijf reproductieve eenheden (RE¿s). Stroomafwaarts van Leuven waren twee afzonderlijke vestigingen van eenlingen aanwezig. Het opzetten van een monitoring en het geven van voorlichting zijn de belangrijkste flankerende maatregelen. Herintroducties stroomafwaarts van Leuven en langs de Schelde en Durme worden noodzakelijk geacht voor de gewenste uitbreiding van de beverpopulatie in het Scheldebekken. Bij voorkeur zal hierbij gebruik worden gemaakt van Elbebevers.
    Realisatie van robuuste verbindingen, van kennis naar praktijk
    Reijnen, M.J.S.M. ; Opdam, P.F.M. ; Vos, C.C. - \ 2003
    De Levende Natuur 104 (2003)6. - ISSN 0024-1520 - p. 254 - 260.
    natuurbescherming - dispersie - migratie - fauna - regionale planning - nederland - ecologische hoofdstructuur - natuurtechniek - nature conservation - dispersion - migration - fauna - regional planning - netherlands - ecological engineering - ecological network
    Achtergrondsartikel, met gegevens over ecosysteemtypen, doelsoorten, ecoprofielen, basismodellen voor verbindingen, doelstellingen, landschappelijke inpassing en de feitelijke uitvoering
    Segregative phase separation in aqueous mixtures of polydisperse biopolymers
    Edelman, M.W. - \ 2003
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): R.H. Tromp. - [S.l.] : S.n. - ISBN 9789058088772 - 94
    gelatine - dextraan - dispersie - scheiding - segregatie - mengsels - polymeren - tweefasesystemen - fasen (chemie) - gelatin - dextran - dispersion - separation - segregation - mixtures - polymers - two-phase systems - phases
    Keywords: biopolymer, gelatine, dextran, PEO, phase separation, polydispersity, molar mass distribution, SEC-MALLS, CSLM The temperature-composition phase diagram of aqueous solutions of gelatine and dextran, which show liquid/liquid phase segregation, were explored at temperatures above the gelation temperature of gelatine. It turned out that the compositions of coexisting phases show practically no dependence on temperature between 40oC and 80oC. Also, the total polymer concentration at which phase separation occurred was found to be nearly independent on temperature. These observations suggest an entropy driven phase separation. Phase separation is found to be accompanied by strong fractionation of the molar mass distribution in the two phases. Molar mass distributions in coexisting phases were investigated using Size Exclusion Chromatography with MultiAngle Laser Light Scattering. The molar mass of the native material and concentration appeared to be the only factors that affected the final molar mass distributions, temperature having no effect. The results show that in the molar mass range where fractionation is the strongest, i.e. roughly below the maximum in the distribution, fractionation is governed by a Boltzmann factor , where DG denotes the free energy involved in transferring a polymer with a certain length from the enriched to the depleted phase, and in this case turns out to be proportional to the molar mass. The phase behaviour of aqueous mixtures of poly(ethylene oxide) (PEO) and dextran is also studied. From the temperature dependence we conclude that the phase separation between PEO and dextran is partly caused by sterical interactions. From the equilibrium phase volumes of the phase separated mixture and the shape of the temperature-composition phase diagram of PEO and dextran we conclude that also the decrease of solvent quality of water for PEO at increasing temperatures is involved. It is suggested that the characteristics of the PEO-water interaction can affect the degree of fractionation. This suggestion is based on the observation that the degree of fractionation is not a simple exponential function of the molar mass. Adsorption of high molar mass dextran at the interface between gelatine and dextran during the phase separation of aqueous mixtures of these two polymers is also studied. This adsorption is observed after macroscopic phase separation as well as during the phase separation. In the last case, the system is studied with Confocal Scanning Light Microscopy. For this purpose, the dextran is covalently labelled with fluorescein 5-isothiocyanate (FITC). It turns out that the adsorption of high molar mass dextran is highly affected by the labelling. The adsorption of labelled dextran leads to a stable film between the two coexisting phases, thus preventing dextran droplets to coalesce. If the degree of labelling increases above a certain level, the labelled dextran does not lead to a stable film, but is preferentially present in the gelatine-rich phase.
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