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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    Haalbaarheidsstudie bio-afbreekbare plastic draagtasjes : technische en economische haalbaarheid en implicaties
    Oever, M.J.A. van den; Bolck, C.H. ; Bos, H.L. ; Molenveld, K. ; Zee, M. van der; Schennink, G.G.J. - \ 2014
    Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research nr. 1465) - 38
    bioplastics - kunststoffen - wegwerpmateriaal - haalbaarheidsstudies - polyethyleen - zakken - materialen uit biologische grondstoffen - biobased economy - economische haalbaarheid - economische aspecten - bioplastics - plastics - disposables - feasibility studies - polyethylene - bags - biobased materials - biobased economy - economic viability - economic aspects
    Dit rapport beschrijft de resultaten van een haalbaarheidsstudie naar de technische en economische haalbaarheid en implicaties van een verbod op dunne plastic draagtasjes in Nederland, met een eventuele uitzondering voor bioplastic draagtassen. In deze korte studie staan bioplastic draagtassen centraal. Het gaat hierbij om alle bioplastics, dus om zowel de biologisch afbreekbare plastics als om niet-biologisch afbreekbaar bioplastic zoals biobased polyetheen (bio-PE). Het is technisch haalbaar om conventioneel fossiele PE plastic draagtassen te vervangen door bioplastic draagtassen. Bio-PE heeft dezelfde eigenschappen als fossiel PE en kan derhalve 1 op 1 als vervanging dienen. Biologisch afbreekbare plastic draagtassen voldoen eveneens; ze zijn vooralsnog dikker en zwaarder dan PE draagtassen om aan de gebruikerseisen te voldoen. Een specifieke antwoord op de economische en technische effecten is niet te geven omdat de exacte beleidsmaatregel en met name daaraan ten grondslag liggende beoogde effecten nog niet duidelijk is. In dit rapport worden daarom verschillende elementen besproken die onderdeel kunnen worden van een eventuele beleidsmaatregel.
    Charge transport across metal/molecular (alkyl) monolayer-Si junctions is dominated by the LUMO level
    Yaffe, O. ; Qi, Y. ; Scheres, L.M.W. ; Puniredd, S.R. ; Segev, L. ; Ely, T. ; Haick, H. ; Zuilhof, H. ; Vilan, A. ; Kronik, L. ; Kahn, A. ; Cahen, D. - \ 2012
    Physical Review. B : Condensed Matter and Materials Physics 85 (2012)4. - ISSN 1098-0121
    self-assembled monolayers - electronic transport - molecular electronics - organic-molecules - chain monolayers - spectroscopy - polyethylene - conductance - films - photoemission
    We compare the charge transport characteristics of heavy-doped p(++)- and n(++)-Si-alkyl chain/Hg junctions. Based on negative differential resistance in an analogous semiconductor-inorganic insulator/metal junction we suggest that for both p(++)- and n(++)-type junctions, the energy difference between the Fermi level and lowest unoccupied molecular orbital (LUMO), i.e., electron tunneling, controls charge transport. This conclusion is supported by results from photoelectron spectroscopy (ultraviolet photoemission spectroscopy, inverse photoelectron spectroscopy, and x-ray photoemission spectroscopy) for the molecule-Si band alignment at equilibrium, which clearly indicate that the energy difference between the Fermi level and the LUMO is much smaller than that between the Fermi level and the highest occupied molecular orbital (HOMO). Furthermore, the experimentally determined Fermi level - LUMO energy difference, agrees with the non-resonant tunneling barrier height, deduced from the exponential length attenuation of the current.
    Sustainability aspects of biobased applications : comparison of different crops and products from the sugar platform BO-12.05-002-008
    Bos, H.L. ; Meesters, K.P.H. ; Conijn, J.G. ; Corre, W.J. ; Patel, M. - \ 2011
    Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1166)
    chemie op basis van biologische grondstoffen - biobased economy - duurzaamheid (sustainability) - suikergewassen - polymelkzuur - bioethanol - polyethyleen - landgebruik - broeikasgassen - emissie - energiegebruik - biobased chemistry - biobased economy - sustainability - sugar crops - polylactic acid - bioethanol - polyethylene - land use - greenhouse gases - emission - energy consumption
    In this study different uses of biomass are compared. In order to allow for a systematic comparison the study focuses on three different chemicals that can be produced from sugar. In this way it is also, in principle, possible to compare different crops for the production of the same product. The study focuses on the production of PLA (polylactic acid, a bioplastic), ethanol, and biopolyethylene (bio-PE, which is produced via ethanol). These three products can presently be produced from biomass and therefore form realistic cases. All three products are produced from sugars, and thus the systems can be decoupled at the sugar step. The sugar can be produced from different crops. In this study five different crops are compared: wheat, maize, sugar beet, sugar cane and Miscanthus. The sustainability aspects that we studied are non-renewable energy use (NREU), greenhouse gas (GHG) emission in the crop-product chain and direct land use for producing the bio-materials.
    Biobased polyethyleen : markt- en milieuaspecten
    Harmsen, P.F.H. ; Patel, M. - \ 2009
    kunststoffen - polyethyleen - duurzaamheid (sustainability) - industriële toepassingen - bioplastics - biobased economy - plastics - polyethylene - sustainability - industrial applications - bioplastics - biobased economy
    Polyethyleen of polyetheen (PE) is een veelgebruikt plastic dat wordt geproduceerd uit aardolie. Het is echter ook mogelijk PE te maken te maken uit hernieuwbare grondstoffen. Deze info sheet geeft info over biobased PE.
    Foliekas reëel alternatief bij koudere teelten: hoge lichtdoorlatendheid, lange levensduur en warmte-absorptie
    Kierkels, T. ; Raats, P. ; Hemming-Hoffmann, S. - \ 2007
    Onder Glas 4 (2007)4. - p. 45 - 47.
    kassen - folie - bouwconstructie - bouwmaterialen - bekleding, bouw - polyethyleen - polyethyleenfilm - polyvinylchloride - lage-energie teelt - lichtdoorlating - kostenanalyse - glastuinbouw - energiebesparing - greenhouses - foil - building construction - building materials - cladding - polyethylene - polyethylene film - poly(vinyl chloride) - low energy cultivation - light transmission - cost analysis - greenhouse horticulture - energy saving
    Foliekassen kampen met een imagoprobleem. Onderzoekers van Wageningen UR en KEMA denken dat tuinders met koudere teelten er verstandig aan zouden doen zo’n kas te overwegen. Elkellaags polyetheen geeft financiële voordelen ten opzichte van glas bij verschillende gewassen. Dubbellaags PE bespaart 30% energie maar springt er financieel slechter uit. F-Clean heeft veel voordelen, maar is wel duur. Toch is het eindplaatje bij F-Clean financieel positiever dan glas. Het wachten is op nieuwe folies. Die zijn in aantocht. Ze combineren hoge lichtdoorlatendheid, lange levensduur en warmteabsorptie met een gunstige prijs. Een groot voordeel van foliekassen is tevens de lagere investering
    A molecular model for cohesive slip at polymer melt/solid interfaces
    Tchesnokov, M.A. ; Molenaar, J. ; Slot, J.J.M. ; Stepanyan, R. - \ 2005
    Journal of Chemical Physics 122 (2005)21. - ISSN 0021-9606 - p. 214711 - 214722.
    wall slip - capillary-flow - melts - dynamics - surface - chains - polyethylene - dependence - transition - density
    A molecular model is proposed which predicts wall slip by disentanglement of polymer chains adsorbed on a wall from those in the polymer bulk. The dynamics of the near-wall boundary layer is found to be governed by a nonlinear equation of motion, which accounts for such mechanisms on surface chains as convection, retraction, constraint release, and thermal fluctuations. This equation is valid over a wide range of grafting regimes, including those in which interactions between neighboring adsorbed molecules become essential. It is not closed since the dynamics of adsorbed chains is shown to be coupled to that of polymer chains in the bulk via constraint release. The constitutive equations for the layer and bulk, together with continuity of stress and velocity, are found to form a closed system of equations which governs the dynamics of the whole "bulk+boundary layer" ensemble. Its solution provides a stick-slip law in terms of the molecular parameters and extruder geometry. The model is quantitative and contains only those parameters that can be measured directly, or extracted from independent rheological measurements. The model predictions show a good agreement with available experimental data
    Substrate sorption into the polymer matrix of Novozym 435 and its effect on the enantiomeric ratio determination
    Heinsman, N.W.J.T. ; Schroën, C.G.P.H. ; Padt, A. van der; Franssen, M.C.R. ; Boom, R.M. ; Riet, K. van 't - \ 2003
    Tetrahedron: Asymmetry 14 (2003). - ISSN 0957-4166 - p. 2699 - 2704.
    candida-rugosa lipase - enantioselective esterification - 2-methylalkanoic acids - 4-methyloctanoic acid - quantitative-analyses - water activity - resolution - polyethylene - absorption - hydrogels
    In the enantioselective esterification of 4-methyloctanoic acid with ethanol by immobilised Candida antarctica lipase B (Novozym 435®), the enantiomeric excesses determined during the course of the reaction deviated strongly from the theoretical values, leading to unacceptably large confidence intervals for the enantiomeric ratio (E value). This observation was in contrast to our previous findings for transesterification and hydrolysis reactions with this enzyme. Herein, the three reactions are compared; the anomalous results in the esterification reaction appear to be caused by adsorption of 4-methyloctanoic acid inside the enzyme beads. We found that on average 1.19 g of 4-methyloctanoic acid was incorporated per g of Novozym 435®. If the concentration of this substrate was adjusted accordingly in the calculations, the resulting E values showed acceptable confidence intervals. In previous research on transesterification reactions in excess apolar solvent (comparable affinity for the beads), sorption does not play an important role because only small amounts of substrate were lost. For hydrolysis reactions, sorption takes place but the acid is released from the beads upon titration and no effect on the E value is found. However, for esterification reactions, sorption should not be neglected since there is no driving force to release the acid from the beads.
    Predictive modeling of migration from packaging materials into food products for regulatory purposes
    Helmroth, I.E. ; Rijk, R. ; Dekker, M. ; Jongen, W.M.F. - \ 2002
    Trends in Food Science and Technology 13 (2002)3. - ISSN 0924-2244 - p. 102 - 109.
    polymer additive migration - worst-case migration - mathematical-models - free-volume - diffusion - polyethylene - polyolefins - temperature - partition - simulants
    Migration of low-molecular weight compounds is one of the most important problems of packaging plastics and other plastics intended to come into contact with food products. Since migration experiments are time consuming and expensive, predictive modelling has been introduced as a promising alternative. The main objective of this article is to review current knowledge on migration modelling and highlight the consequences of using modelling for regulatory purposes.
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