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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    Het effect van bemesting op de ontwikkeling van perenbladvlo : Technische rapportage van de waarnemingen
    Helsen, H.H.M. ; Elk, P.J.H. van; Piquet, M. ; Maas, M.P. van der - \ 2015
    Praktijkonderzoek Plant en Omgeving, Bloembollen, Boomkwekerij en Fruit - 17
    fruitteelt - gewasbescherming - proeven op proefstations - peren - bemesting - kwaliteit na de oogst - hardheid - plantenplagen - ziektebestrijdende teeltmaatregelen - fruit growing - plant protection - station tests - pears - fertilizer application - postharvest quality - hardness - plant pests - cultural control
    Het hier beschreven onderzoek werd uitgevoerd in de proefboomgaard van PPO-Wageningen UR in Randwijk Daarvoor werd gebruik gemaakt van een volgroeid gewas Conference, waarop in 2012 een bemestingsproef was gestart waarbij de fosfaat- en stikstofgift werden gevarieerd. Op drie bemestingsregiems in die proef werd in 2013 en in 2014 het optreden van perenbladvlo gemeten. Op 13 juni 2013 had de behandeling N-hoog betrouwbaar meer perenbladvloeieren en -larven dan N-laag. N-middel was niet betrouwbaar verschillend van de beide andere behandelingen. De bemestingsbehandelingen hebben in de periode 2012 - 2014 geen verschil in productie tot gevolg gehad. Wel werd bij behandeling N-middel, die een grote fosfaat- (en stikstof-) bladbemesting kreeg, na lange bewaring een hogere hardheid vastgesteld. Dit kon worden verklaard door het effect van de fosfaatbladvoeding
    Proeftuin Randwijk: Fosfaatbladvoeding verhoogt hardheid Conference
    Maas, M.P. van der; Elk, P.J.H. van - \ 2015
    fruitteelt - peren - bemesting - fosfaat - hardheid - houdbaarheid (kwaliteit) - fruit growing - pears - fertilizer application - phosphate - hardness - keeping quality
    Op kalkhoudende gronden met minder fosfaat meer bereiken via bladvoeding in de perenteelt
    Sensorial analysis of polysaccharide-gelled protein particle dispersions in relation to lubrication and viscosity properties
    Chojnicka-Paszun, A. ; Doussinault, S. ; Jongh, H.H.J. de - \ 2014
    Food Research International 56 (2014). - ISSN 0963-9969 - p. 199 - 210.
    oral perception - perceived texture - size - gels - hardness - systems - fluid - foods
    In this work polysaccharide-protein gel particle dispersions were studied to identify relation between sensorial responses and their bulk rheological and tribological properties. Sensory analysis was performed by a trained panel using QDA to evaluate distinct mouth-feel perception. Attributes such as powdery, slipperiness, stickiness, and filmy were then correlated to tribological and rheological data of these dispersions. Since thickness perception masked scores of other attributes, all samples were tuned to obtain the same score in sensorial thickness to minimize its influence. The experimental survey presented in this work revealed an interesting set of correlations. The friction coefficient showed a negative correlation with slipperiness, while with other attributes the established relation was below a significant level. Attributes, such as stickiness, sliminess and filmy, correlated with viscosity data of the dispersions within a wide range of shear rates. In addition, a direct relation was found between the powdery attribute and the size of particles present in the dispersions. Moreover, the hardness of these particles seemed to have a strong influence on the steepness of this latter relation. (C) 2013 Elsevier Ltd. All rights reserved.
    Mining minimal motif pair sets maximally covering interactions in a protein-protein interaction network
    Boyen, P. ; Neven, F. ; Valentim, F.L. ; Dijk, A.D.J. van - \ 2013
    IEEE/ACM Transactions on Computational Biology and Bioinformatics 10 (2013)1. - ISSN 1545-5963 - p. 73 - 86.
    interaction sites - high-throughput - binding-sites - prediction - database - hardness
    Correlated motif covering (CMC) is the problem of finding a set of motif pairs, i.e., pairs of patterns, in the sequences of proteins from a protein-protein interaction network (PPI-network) that describe the interactions in the network as concisely as possible. In other words, a perfect solution for CMC would be a minimal set of motif pairs that describes the interaction behavior perfectly in the sense that two proteins from the network interact if and only if their sequences match a motif pair in the minimal set. In this paper, we introduce and formally define CMC and show that it is closely related to the red-blue set cover (RBSC) problem and its weighted version (WRBSC)--both well-known NP-hard problems for that there exist several algorithms with known approximation factor guarantees. We prove the hardness of approximation of CMC by providing an approximation factor preserving reduction from RBSC to CMC. We show the existence of a theoretical approximation algorithm for CMC by providing an approximation factor preserving reduction from CMC to WRBSC. We adapt the latter algorithm into a functional heuristic for CMC, called CMC-approx, and experimentally assess its performance and biological relevance. The implementation in Java can be found at >
    Interplay between product characteristics, oral physiology and texture perception of cellular brittle foods
    Vliet, T. van; Primo Martin, C. - \ 2011
    Journal of Texture Studies 42 (2011)2. - ISSN 0022-4901 - p. 82 - 94.
    sensory texture - investigate differences - mechanical-properties - fracture-behavior - chewing behavior - cooked potatoes - jaw movement - crispness - mastication - hardness
    Hard solid foods encompass a large variety of dry products as well as products with high water content. Most of these foods have a cellular structure, which is generally characterized by connected fairly rigid cell walls, enclosing a fluid material that may be liquid-like (fruit and vegetables) or a gas (mainly manufactured cellular foods). Typical for many hard solid products is their brittle fracture behavior, mostly accompanied by acoustic emission. The latter characteristic is essential for their crispy or crunchy character. Other main texture attributes are hardness and brittleness and for fruits and vegetables juiciness. The latter requires that the liquid content of the cells is released during mastication. Aspects of fracture behavior of cellular food products, oral processing of these products, and the interplay between product characteristics and perception of some main texture attributes (hardness and crispness) will be discussed. PRACTICAL APPLICATIONS It has become more and more clear that texture perception by consumers of hard solid (brittle) foods is based on the interplay between product structure, fracture behavior, oral processing and final grading by the brain. Better understanding of the relations between these aspects is essential for the production of healthy, tasteful food that is liked by consumers. This article focus on the interplay between physical properties of hard solid foods and oral processing in relation to the perception of selected texture attributes (hardness and crispness)
    Relationship between water activity, deformation speed, and crispness characterization
    Castro Prada, E.M. ; Primo Martin, C. ; Meinders, M.B.J. ; Hamer, R.J. ; Vliet, T. van - \ 2009
    Journal of Texture Studies 40 (2009)2. - ISSN 0022-4901 - p. 127 - 156.
    instrumental imitative tests - fast crack-propagation - cereal-based products - snack food-products - uniaxial compression - breakfast cereals - fracture properties - biting velocities - sensory crispness - hardness
    Very little is known on the rate dependency of the fracture behavior of crispy products as a function of water activity (Aw). Therefore, the effect of deformation speed on instrumental and sensory crispness was studied as a function of Aw. Deformation speed clearly affects the transition Aw range from crispy to non-crispy. At low deformation speed, the critical Aw was 0.40 ± 0.02 and at high deformation speed between 0.5 and 0.6. The transition was completed at an Aw = 0.56 ± 0.10 and 0.74 ± 0.00 for the low and high speed, respectively. The transition of sensory crispness at regular biting speed started at Aw = 0.48 and was completed at Aw = 0.75. The deformation speed effect is assumed to be caused by the viscoelastic nature of the material in the transition region causing it to behave locally relatively more viscous at low deformation speed and relatively more elastic at high deformation speed. This behavior depends on the plasticizer content, thus, Aw. For the product used in this study, the instrumental deformation speed that best correlate to sensory data is 10 to 40 mm/s. Sensory tests show that crispy attributes are perceived more intense when biting at higher speed
    Bioplastics: cellulose
    Bolck, C.H. ; Bos, H.L. - \ 2009
    cellulose - herkomst - toepassingen - taaiheid - hardheid - sterkte - bioplastics - biobased economy - cellulose - provenance - applications - toughness - hardness - strength - bioplastics - biobased economy
    Deze info sheet geeft een overzicht van de herkomst en toepassingsmogelijkheden van bioplastics uit cellulose. De tekst is gebaseerd op het boekje Bioplastics, één van de uitgaven uit de reeks Groene Grondstoffen
    Effect van DCS plus SmartFresh op kwaliteit Elstar
    Otma, E.C. - \ 2008
    De Fruitteelt 98 (2008)36. - ISSN 0016-2302 - p. 8 - 9.
    fruitteelt - appels - hardheid - smaakversterkers - gewaskwaliteit - koelcellen - fruitbewaarplaatsen - zuurstof - proeven op proefstations - fruit growing - apples - hardness - flavour enhancers - crop quality - cold stores - fruit stores - oxygen - station tests
    AFSG onderzocht in het seizoen 2007/'08 of DCS (Dynamic Control System) bij SmartFresh behandelde appels dezelfde reductie van schilvlekjes geeft als bij onbehandelde appels, ook andere zuurstofcondities werden getest evenals de hardheid van Elstar
    Kwaliteitsverloopmodel voor appel en perzik krijgt meer vorm
    Derkx, M.P.M. ; Schaik, A. van - \ 2008
    De Fruitteelt 98 (2008)41. - ISSN 0016-2302 - p. 12 - 13.
    fruit - hardheid - gewaskwaliteit - rijpheid - testen - beslissingsmodellen - hardness - crop quality - maturity - testing - decision models
    Stikstofbemesting doet veel met de appel en zijn boom
    Maas, M.P. van der; Simonse, J.J. ; Kanne, H.J. ; Hof, M.C.J. op t - \ 2007
    De Fruitteelt 97 (2007)20. - ISSN 0016-2302 - p. 14 - 15.
    fruitteelt - appels - stikstofmeststoffen - stikstofgehalte - hardheid - groei - proeven op proefstations - bemesting - fruit growing - apples - nitrogen fertilizers - nitrogen content - hardness - growth - station tests - fertilizer application
    Uit onderzoek van PPO-fruit blijkt dat een laag stikstofbladgehalte in juni bij Elstar gepaard gaat met een hoge hardheid bij de pluk. Uit proeven is gebleken dat het stikstofgehalte niet altijd goed te sturen is via de stikstofbemesting. Ook de dracht en de groei hebben invloed op het stikstofgehalte en daarmee ook op de uiteindelijke hardheid
    Er is meer dan Ferrari-rood
    Hogendonk, L. ; Steenbergen, P. - \ 2005
    Groenten en Fruit. Algemeen 2005 (2005)37. - ISSN 0925-9694 - p. 29 - 29.
    rassenproeven - cultivars - rassen (planten) - capsicum - vruchtgroenten - vruchten - vastheid - hardheid - scheurende vruchten - kleur - gewasopbrengst - variety trials - cultivars - varieties - capsicum - fruit vegetables - fruits - firmness - hardness - fruit cracking - colour - crop yield
    Waarnemingen aan de rassenproeven rode paprika stookteelt 2004/2005. Er werden drie nieuwe rassen en het ras Ferrari beproefd
    Concurrentie voor het standaardras
    Steenbergen, P. ; Hogendonk, L. - \ 2005
    Groenten en Fruit. Algemeen 2005 (2005)37. - ISSN 0925-9694 - p. 31 - 31.
    rassenproeven - cultivars - rassen (planten) - capsicum - vruchtgroenten - vruchten - scheurende vruchten - hardheid - vastheid - kleur - gewasopbrengst - kwaliteit - variety trials - cultivars - varieties - capsicum - fruit vegetables - fruits - fruit cracking - hardness - firmness - colour - crop yield - quality
    vier nieuwe gele paprikarassen zijn in het teeltseizoen 2004/2005 op hub uiterlijk en productie beproefd, één nieuw ras is inmiddels door de inzender teruggetrokken. Derby werd als vergelijkingsras toegevoegd
    DCS-bewaring nu praktisch toepasbaar
    Geijn, F. van de - \ 2005
    De Fruitteelt 95 (2005)35. - ISSN 0016-2302 - p. 12 - 13.
    appels - opslag - luchtdichte opslag - koudeopslag - gasbewaring - voorzieningen voor de opslag - opslagplaatsen - kooldioxide - zuurstof - hardheid testen - hardheid - toegepast onderzoek - apples - storage - airtight storage - cold storage - controlled atmosphere storage - storage equipment - warehouses - carbon dioxide - oxygen - hardness testing - hardness - applied research
    Met het Dynamic Control System (DCS) kan het zuurstofgehalte in ULO-cellen veilig verlaagd worden op basis van de ethanolcontrole van het bewaarde fruit. Na jarenlang onderzoek kan deze vorm van bewaring nu in de praktijk worden toegepast voor Elstar en Jonagold. Wellicht volgt al snel de toepassing voor andere rassen en producten
    SmartFreshTM : onderzoek en praktijkervaringen seizoen 2004/'05
    Verschoor, J. - \ 2005
    De Fruitteelt 95 (2005)32. - ISSN 0016-2302 - p. 18 - 19.
    appels - houdbaarheid (kwaliteit) - bewaartijd - opslagkwaliteit - smaak - smaakpanels - hardheid - textuur - vastheid - vochtgehalte - dehydratie (fysiologisch) - aroma - apples - keeping quality - storage life - storage quality - taste - taste panels - hardness - texture - firmness - moisture content - dehydration (physiological)
    Dit is het eerste seizoen dat SmartFreshTM grootschalig werd toegepast op met name Elstar en Jonagold in Nederland. De praktijkintroductie werd begeleid met onderzoek door Agrotechnology & Food Innovations (A&F). Resultaten van dit onderzoek dat deels in de praktijk werd uitgevoerd, worden hier gepresenteerd
    Kwaliteit spuitwater heeft in specifieke gevallen invloed op werking middelen
    Zeeland, M.G. van; Schans, D.A. van der; Lotz, L.A.P. - \ 2005
    Gewasbescherming 36 (2005)2. - ISSN 0166-6495 - p. 95 - 97.
    gewasbescherming - herbiciden - dicamba - glyfosaat - bentazon - waterkwaliteit - spuiten - dosering - toedieningshoeveelheden - hulpstoffen - toevoegingen - zuurgraad - waterhardheid - hardheid - plant protection - herbicides - dicamba - glyphosate - bentazone - water quality - spraying - dosage - application rates - adjuvants - additives - acidity - water hardness - hardness
    Gewasbeschermingsmiddelen worden vaak in lagere doseringen dan de etiketdosering toegepast, om zo het milieu te ontzien en kosten te besparen. Andere factoren, zoals de waterkwaliteit, worden daardoor belangrijker voor het slagen van de bespuiting. De zuurgraad (pH) van het water en allerlei ionen of deeltjes in het water kunnen moleculen van de werkzame stof binden en zodoende de effectiviteit van de bespuiting benadelen. Om de werking van gewasbeschermingsmiddelen te verbeteren zijn waterconditioners en hulpstoffen ontwikkeld en op de markt gebracht. Onderzocht wordt onder welke omstandigheden en voor welke middelen deze hulpmiddelen nodig zijn
    Copper toxicity in relation to surface water-dissolved organic matter: biological effects to Daphnia magna
    Kramer, K.J.M. ; Jak, R.G. ; Hattum, B. van; Hooftman, R.N. ; Zwolsman, J.J.G. - \ 2004
    Environmental Toxicology and Chemistry 23 (2004)12. - ISSN 0730-7268 - p. 2971 - 2980.
    koper - toxiciteit - organische stof - waterverontreiniging - daphnia magna - biologische beschikbaarheid - nederland - waterbodems - copper - toxicity - organic matter - water pollution - daphnia magna - bioavailability - netherlands - water bottoms - biotic ligand model - humic-acid - ceriodaphnia-dubia - ion activity - metals - hardness - bioaccumulation - complexation - cadmium - speciation
    Water quality standards for copper are usually stated in total element concentrations. It is known, however, that a major part of the copper can be bound in complexes that are biologically not available. Natural organic matter, such as humic and fulvic acids, are strong complexing agents that may affect the bioavailable copper (Cu2+) concentration. The aim of this study was to quantify the relation between the concentration of dissolved natural organic matter and free Cu2+ in surface waters, and the biological effect, as measured in a standardized ecotoxicological test (48 h¿median effective concentration [EC50] Daphnia magna, mobility). Six typical Dutch surface waters and an artificial water, ranging from 0.1 to 22 mg/L dissolved organic carbon (DOC), were collected and analyzed quarterly. Chemical speciation modeling was used as supporting evidence to assess bioavailability. The results show clear evidence of a linear relation between the concentration of dissolved organic carbon (in milligrams DOC/L) and the ecotoxicological effect (as effect concentration, EC50, expressed as micrograms Cu/L): 48-h EC50 (Daphnia, mobility) = 17.2 × DOC + 30.2 (r2 = 0.80, n = 22). Except for a brook with atypical water quality characteristics, no differences were observed among water type or season. When ultraviolet (UV)-absorption (380 nm) was used to characterize the dissolved organic carbon, a linear correlation was found as well. The importance of the free copper concentration was demonstrated by speciation calculations: In humic-rich waters the free Cu2+ concentration was estimated at ¿10¿11 M, whereas in medium to low dissolved organic carbon waters the [Cu2+] was ¿10¿10 M. Speciation calculations performed for copper concentrations at the effective concentration level (where the biological effect is considered the same) resulted in very similar free copper concentrations (¿10¿8 M Cu) in these surface waters with different characteristics. These observations consistently show that the presence of organic matter decreases the bioavailability, uptake, and ecotoxicity of copper in the aquatic environment. It demonstrates that the DOC content must be included in site-specific environmental risk assessment for trace metals (at least for copper). It is the quantification of the effects described that allows policy makers to review the criteria for copper in surface waters.
    SmartFresh TM bewijst zich in de praktijk
    Wild, J.P.J. de; Schaik, A.C.R. van - \ 2004
    De Fruitteelt 94 (2004)24. - ISSN 0016-2302 - p. 8 - 9.
    appels - opslag - koudeopslag - proeven - houdbaarheid (kwaliteit) - bewaartijd - voedselkwaliteit - hardheid - plantengroeiregulatoren - rijpingsperiode - apples - storage - cold storage - trials - keeping quality - storage life - food quality - hardness - plant growth regulators - maturation period
    Praktijkproeven van A&F wijzen erop dat SmartFreshTM het kwaliteitsverlies in de bewaring van appelen tegengaat, maar vooral de hardheid tijdens uitstraling verbeter
    The vertical ground reaction force and the pressure distribution on the claws of dairy cows while walking on a flat substrate
    Tol, P.P.J. van der; Metz, J.H.M. ; Noordhuizen-Stassen, E.N. ; Back, W. ; Braam, C.R. ; Weijs, W.A. - \ 2003
    Journal of Dairy Science 86 (2003)9. - ISSN 0022-0302 - p. 2875 - 2883.
    bovine claw - cattle - lameness - locomotion - prevalence - hardness - biotin - hoof
    The pressure distribution under the bovine claw while walking was measured to test the hypotheses that the vertical ground reaction force is unevenly distributed and makes some (regions of the) claws more prone to injuries due to overloading than others. Each limb of nine recently trimmed Holstein Friesian cows was measured five times while walking over a Footscan pressure plate firmly embedded on a Kistler force plate. The pressure plate had a spatial resolution of 2.6 sensors/cm2 and was sampled simultaneously with the force plate with a temporal resolution of 250 measurements/s. Five moments during the stance phase were selected on basis of the force plate recording for the analysis of the pressure distribution: heel strike, maximum braking, midstance, maximum propulsion, and push off. At the forelimbs, the vertical ground reaction force was equally distributed between medial and lateral claw. At the hind limbs at heel strike, the force was exerted almost completely to the lateral claw. During the rest of the stance phase the load shifted towards the medial claw, until, at push off, it was more or less equally divided between both claws. The average pressures determined were 50 to 80 N/cm2. Maximum pressures increased from 90 to 110 N/cm2 at heel strike to 180 to 200 N/cm2 at push off. It was concluded that at the hind limb these pressures constitute a major threat to overloading particularly for the softer parts of the lateral claw, e.g., the sole and bulb area
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