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.

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    Mobilization of biomass for energy from boreal forests in Finland & Russia under present sustainable forest management certification and new sustainability requirements for solid biofuels
    Sikkema, R. ; Faaij, A.P.C. ; Ranta, T. ; Heinimö, J. ; Gerasimov, Y.Y. ; Karjalainen, T. ; Nabuurs, G.J. - \ 2014
    Biomass and Bioenergy 71 (2014). - ISSN 0961-9534 - p. 23 - 36.
    environmental impacts - wood - bioenergy - resources - fuel - alternatives - procurement - potentials - countries - products
    Forest biomass is one of the main contributors to the EU's renewable energy target of 20% gross final energy consumption in 2020 (Renewable Energy Directive). Following the RED, new sustainability principles are launched by the European energy sector, such as the Initiative Wood Pellet Buyers (IWPB or SBP). The aim of our study is the investigation of the quantitative impacts from IWPB's principles for forest biomass for energy only. We deploy a bottom up method that quantifies the supplies and the costs from log harvest until forest chip delivery at a domestic consumer. We have a reference situation with existing national (forest) legislation and voluntary certification schemes (scenario 1) and a future situation with additional criteria based on the IWPB principles (scenario 2). Two country studies were selected for our (2008) survey: one in Finland with nearly 100% certification and one in Leningrad province with a minor areal share of certification in scenario 1. The sustainable potential of forest resources for energy is about 54 Mm3 (385 PJ) in Finland and about 13.5 Mm3 (95 PJ) in Leningrad in scenario 1 without extra criteria. The potential volumes reduce considerably by maximum 43% respectively 39% after new criteria from the IWPB, like a minimum use of sawlogs, stumps and slash for energy, and by an increased area of protected forests (scenario 2A Maximum extra restrictions). In case sawlogs can be used, but instead ash recycling is applied after a maximum stump and slash recovery (scenario 2B Minimum extra restrictions), the potential supply is less reduced: 5% in Finland and 22% in Leningrad region. The estimated reference costs for forest chips are between €18 and €45 solid m-3 in Finland and between €7 and €33 solid m-3 in the Leningrad region. In scenario 2A, the costs will mainly increase by €7 m-3 for delimbing full trees (Finland), and maximum €0.3 m-3 for suggested improved forest management (Leningrad region). In scenario 2B, when ash recycling is applied, costs increase by about €0.3 to €1.6 m-3, depending on the rate of soil contamination. This is an increase of 2%, on top of the costs in scenario 2A.
    Robust Array-Based Coregulator Binding Assay Predicting ERa-Agonist Potency and Generating Binding Profiles Reflecting Ligand Structure
    Aarts, J.M.M.J.G. ; Wang, S. ; Houtman, R. ; Beuningen, R.M.G.J. van; Westerink, W.M.A. ; Waart, B.J. van de; Rietjens, I.M.C.M. ; Bovee, T.F.H. - \ 2013
    Chemical Research in Toxicology 26 (2013)3. - ISSN 0893-228X - p. 336 - 346.
    sediment-associated samples - estrogen-receptor-alpha - integral assessment - nuclear receptors - coactivators - discovery - screen - optimization - potentials - bioassay
    Testing chemicals for their endocrine-disrupting potential, including interference with estrogen receptor (ER) signaling, is an important aspect of chemical safety testing. Because of the practical drawbacks of animal testing, the development of in vitro alternatives for the uterotrophic assay and other in vivo (anti)estrogenicity tests has high priority. It was previously demonstrated that an in vitro assay that profiles ligand-induced binding of ERa to a microarray of coregulator-derived peptides might be a valuable candidate for a panel of in vitro assays aiming at an ultimate replacement of the uterotrophic assay. In the present study, the reproducibility and robustness of this coregulator binding assay was determined by measuring the binding profiles of 14 model compounds that are recommended by the Office of Prevention, Pesticides and Toxic Substances for testing laboratory proficiency in estrogen receptor transactivation assays. With a median coefficient of variation of 5.0% and excellent correlation (R(2) = 0.993) between duplicate measurements, the reproducibility of the ERa-coregulator binding assay was better than the reproducibility of other commonly used in vitro ER functional assays. In addition, the coregulator binding assay is correctly predicting the estrogenicity for 13 out of 14 compounds tested. When the potency of the ER-agonists to induce ERa-coregulator binding was compared to their ER binding affinity, their ranking was similar, and the correlation between the EC50 values was excellent (R(2) = 0.96), as was the correlation with their potency in a transactivation assay (R(2) = 0.94). Moreover, when the ERa-coregulator binding profiles were hierarchically clustered using Euclidian cluster distance, the structurally related compounds were found to cluster together, whereas the steroid test compounds having an aromatic A-ring were separated from those with a cyclohexene A-ring. We concluded that this assay is capable of distinguishing ERa agonists and antagonists and that it even reflects the structural similarity of ERa agonists, indicating a potential to achieve identification and classification of ERa endocrine disruptors with high fidelity
    Exploring the diversity of urban and peri-urban agricultural systems in Sudano-Sahelian West Africa: An attempt towards a regional typology
    Dossa, L.C. ; Abdulkadir, A. ; Amadou, H. ; Sangare, S. ; Schlecht, E. - \ 2011
    Landscape and Urban Planning 102 (2011)3. - ISSN 0169-2046 - p. 197 - 206.
    principal-components-analysis - farming systems - milk-production - burkina-faso - management - opportunities - classification - potentials - algorithm - countries
    Developing appropriate and innovative technologies and policies to respond to the challenges that urban and peri-urban agriculture (UPA) faces in West Africa requires a better understanding of the existing production systems. Although there is an increasing recognition of the importance of UPA in the region, its extent, forms and related practices may vary across countries and cities because of different socio-economic conditions and urbanization patterns. A systematic classification of the regional UPA systems is lacking but is necessary to allow for meaningful comparisons between cities and avoid misleading generalizations. The purpose of this study was to develop a typology of UPA households across three selected West African cities. Survey data from 318 UPA households (Kano: 99, Bobo Dioulasso: 111, Sikasso: 108) were submitted to principal components analysis for categorical variables (CATPCA). Next, the Two-Step cluster method was used to classify the households using object scores obtained from the CATPCA. Diversification of farm activities, farm resource endowment and production orientation were the major discriminating variables. In each city, four distinct UPA systems were identified, of which three were common to Kano, Bobo Dioulasso and Sikasso: commercial gardening plus field crops and livestock (59%, 18%, and 37%), commercial livestock plus subsistence field cropping (14%, 41%, and 7%), and commercial gardening plus semi-commercial field cropping (14%, 28%, and 30%). The fourth group was different at each location and was characterized as follows: commercial gardening plus semi-commercial livestock in Kano (13%), commercial field cropping in Bobo Dioulasso (13%) and commercial gardening in Sikasso (26%).
    Water-use strategies of six co-existing Mediterranean woody species during a summer drought
    Quero, J.L. ; Sterck, F.J. ; Martínez-Vilalta, J. ; Villar, R. - \ 2011
    Oecologia 166 (2011)1. - ISSN 0029-8549 - p. 45 - 57.
    nighttime transpiration - xylem cavitation - induced embolism - stomatal control - quercus-ilex - scots pine - plants - conductance - potentials - seedlings
    Drought stress is known to limit plant performance in Mediterranean-type ecosystems. We have investigated the dynamics of the hydraulics, gas exchange and morphology of six co-existing Mediterranean woody species growing under natural field conditions during a drought that continued during the entire summer. Based on the observed minimum leaf water potentials, our results suggest that the six co-existing species cover a range of plant hydraulic strategies, from isohydric to anisohydric. These differences are remarkable since the selected individuals grow within several meters of each other, sharing the same environment. Surprisingly, whatever the leaf water potentials were at the end of the dry period, stomatal conductance, photosynthesis and transpiration rates were relatively similar and low across species. This result contradicts the classic view that anisohydric species are able to maintain gas exchange for longer periods of time during drought stress. None of the plants showed the expected structural acclimation response to the increasing drought (reduction of leaf-to-sapwood area ratio), thereby rejecting the functional equilibrium hypothesis for our study system. Instead, three of the six species increased photosynthetic area at the branch level. The observed dissimilar patterns of gas exchange, hydraulics and morphology across species seem to be equally successful given that photosynthesis at the leaf level was maintained at similar rates over the whole dry period.
    Investigation of interactions between texture and ortho- and retronasal olfactory stimuli using psychophysical and electrophysiological approaches
    Roudnitzky, N. ; Bult, J.H.F. ; Wijk, R.A. de; Reden, J. ; Schuster, B. ; Hummel, T. - \ 2011
    Behavioural Brain Research 216 (2011)1. - ISSN 0166-4328 - p. 109 - 115.
    flavor perception - response alternatives - odor identification - swallowing process - release - mouth - taste - discrimination - integration - potentials
    Flavor is a result of the complex combination of olfactory, gustatory and trigeminal sensations perceived during oral processing of foods, including thermal, painful, tactile and/or kinesthetic effects. Aim of this study was to better understand interactions between synchronous tactile (texture) and olfactory (odor) sensations, using a psychophysical and an electrophysiological approach. Texture stimuli were aliquots of lean milk and thickened lean milk. A butter aroma was presented either orthonasally or retronasally after oral processing and before swallowing the oral stimulus or in the absence of an oral stimulus. Eighteen subjects (11 women, 7 men, mean age 24 years), naïve to the expected effects, rated both odor and texture intensity of each stimulus. Event-related potentials (ERP) were obtained from five recording positions. For the psychophysical data, the presence of an oral stimulus increased odor intensity, irrespective of odor presentation route. For the electrophysiological data, both early and late chemosensory ERPs were affected by odor conditions, texture conditions, and their respective interaction. In conclusion: (1) perceptual interactions occurred between food texture and odor, with cross-modal interactions being found for both orthonasal and retronasal odor administration, and (2) these interactions between texture and odor occur at both primary-sensory and cognitive evaluative levels of stimulus processing. The temporal dimension plays then a critical role in the investigation of odor–texture interactions.
    Evaluation of 1H NMR relaxometry for the assessment of pore size distribution in soil samples
    Jaeger, F. ; Bowe, S. ; As, H. van; Schaumann, G.E. - \ 2009
    European Journal of Soil Science 60 (2009)6. - ISSN 1351-0754 - p. 1052 - 1064.
    nuclear-magnetic-resonance - ray computed-tomography - field gradient nmr - organic-matter - porous-media - water - relaxation - diffusion - h-1-nmr - potentials
    1H NMR relaxometry is used in earth science as a non-destructive and time-saving method to determine pore size distributions (PSD) in porous media with pore sizes ranging from nm to mm. This is a broader range than generally reported for results from X-ray computed tomography (X-ray CT) scanning, which is a slower method. For successful application of 1H NMR relaxometry in soil science, it is necessary to compare PSD results with those determined from conventional methods. The PSD of six disturbed soil samples with various textures and soil organic matter (SOM) content were determined by conventional soil water retention at matric potentials between -3 and -390 kPa (pF 1.5–3.6). These PSD were compared with those estimated from transverse relaxation time (T2) distributions of water in soil samples at pF 1.5 using two different approaches. In the first, pore sizes were estimated using a mean surface relaxivity of each soil sample determined from the specific surface area. In the second and new approach, two surface relaxivities for each soil sample, determined from the T2 distributions of the soil samples at different matric potentials, were used. The T2 distributions of water in the samples changed with increasing soil matric potential and consisted of two peaks at pF 1.5 and one at pF 3.6. The shape of the T2 distributions at pF 1.5 was strongly affected by soil texture and SOM content (R2 = 0.51 - 0.95). The second approach (R2 = 0.98) resulted in good consistency between PSD, determined by soil water retention, and 1H NMR relaxometry, whereas the first approach resulted in poor consistency. Pore sizes calculated from the NMR data ranged from 100 µm to 10 nm. Therefore, the new approach allows 1H NMR relaxometry to be applied for the determination of PSD in soil samples and for studying swelling of SOM and clay and its effects on pore size in a fast and non-destructive way. This is not, or only partly, possible by conventional soil water retention or X-ray CT
    Molecular sabotage of plant defense by aphid saliva
    Will, T. ; Tjallingii, W.F. ; Thönnessen, A. ; Bel, A.J.E. van - \ 2007
    Proceedings of the National Academy of Sciences of the United States of America 104 (2007)25. - ISSN 0027-8424 - p. 10536 - 10541.
    calcium-binding proteins - sieve tubes - gel-electrophoresis - polyacrylamide gels - phloem - penetration - potentials - resistance - membrane - gossypii
    Aphids, which constitute one of the most important groups of agricultural pests, ingest nutrients from sieve tubes, the photoassimilate transport conduits in plants. Aphids are able to successfully puncture sieve tubes with their piercing mouthparts (stylets) and ingest phloem sap without eliciting the sieve tubes' normal occlusion response to injury. Occlusion mechanisms are calcium-triggered and may be prevented by chemical constituents in aphid saliva injected into sieve tubes before and during feeding. We recorded aphid feeding behavior with the electrical penetration graph (EPG) technique and then experimentally induced sieve tube plugging. Initiation of sieve tube occlusion caused a change in aphid behavior from phloem sap ingestion to secretion of watery saliva. Direct proof of "unplugging" properties of aphid saliva was provided by the effect of aphid saliva on forisomes. Forisomes are proteinaceous inclusions in sieve tubes of legumes that show calcium-regulated changes in conformation between a contracted state (below calcium threshold) that does not occlude the sieve tubes and a dispersed state (above calcium threshold) that occludes the sieve tubes. We demonstrated in vitro that aphid saliva induces dispersed forisomes to revert back to the nonplugging contracted state. Labeling Western-blotted saliva proteins with 45Ca2+ or ruthenium red inferred the presence of calcium-binding domains. These results demonstrate that aphid saliva has the ability to prevent sieve tube plugging by molecular interactions between salivary proteins and calcium. This provides aphids with access to a continuous flow of phloem sap and is a critical adaptation instrumental in the evolutionary success of aphids.
    The critical endpoint in phase diagrams of attractive hard spheres
    Fleer, G.J. ; Tuinier, R. - \ 2007
    Physica A 379 (2007)1. - ISSN 0378-4371 - p. 52 - 58.
    polymer-solutions - behavior - equation - state - model - c-60 - separations - potentials - simulation - particles
    We calculate the critical endpoint (cep) in phase diagrams of attractive hard spheres (HS), for both a Yukawa attraction and a polymer depletion potential, using approximate analytical theories. The cep corresponds to the minimum attraction range and the maximum contact potential for which liquid can exist. For both sytems we find essentially the same result: in the cep the attraction range is about one-third of the particle radius, and the attraction strength is around 2 kT. This same cep is found from simulations on particles interacting through a Lennard¿Jones-type potential. It thus seems that the cep is essentially independent of the details of the pair potential for any system with a smooth attractive pair potential.
    A simple relation for the concentration dependence of osmotic pressure and depletion thickness in polymer solutions
    Fleer, G.J. ; Skvortsov, A.M. ; Tuinier, R. - \ 2007
    Macromolecular Theory and Simulations 16 (2007)5. - ISSN 1022-1344 - p. 531 - 540.
    mean-field - chains - polystyrene - potentials - simulation - mixtures - equation - solvent - dilute - phase
    We propose simple expressions II/IIo = 1 + and (omega/omega(ex))(3 alpha-1) and (delta(0)/delta)(2) = 1 + (omega/omega(ex))(2 alpha) for the osmotic pressure II and the depletion thickness 6 as a function of the polymer concentration omega. Here, IIo and delta 0 correspond to the dilute limit, and omega(ex) is an extrapolation concentration which is of the order of the overlap concentration omega(ov). The De Gennes exponent a describes the concentration dependence of the semidilute correlation length xi similar to omega(-alpha) it is related to the Flory exponent nu through alpha = nu/(3 nu - 1.). The quantity omega(ex) is experimentally accessible by extrapolating the semidilute limit towards II = IIo or delta = delta(o). These expressions are exact in mean field, where the ratio omega(ex)/omega(ov) (0.49 for II, 0.41 for delta) follows from established models. For excluded-volume chains they describe simulation data excellently: in this case omega(ex)/omega(ov) is 0.69 for II and again 0.41 for delta. We find also very good agreement with experimental data.
    Nutrient and water addition effects on day- and night-time conductance and transpiration in a C3 desert annual
    Ludwig, F. ; Jewitt, R.A. ; Donovan, L.A. - \ 2006
    Oecologia 148 (2006)2. - ISSN 0029-8549 - p. 219 - 225.
    vapor-pressure deficit - stomatal conductance - plant nitrogen - predawn plant - great-basin - growth - photosynthesis - disequilibrium - potentials - mechanisms
    Recent research has shown that many C3 plant species have significant stomatal opening and transpire water at night even in desert habitats. Day-time stomatal regulation is expected to maximize carbon gain and prevent runaway cavitation, but little is known about the effect of soil resource availability on night-time stomatal conductance (g) and transpiration (E). Water (low and high) and nutrients (low and high) were applied factorially during the growing season to naturally occurring seedlings of the annual Helianthus anomalus. Plant height and biomass were greatest in the treatment where both water and nutrients were added, confirming resource limitations in this habitat. Plants from all treatments showed significant night-time g (~0.07 mol m-2 s-1) and E (~1.5 mol m-2 s-1). In July, water and nutrient additions had few effects on day- or night-time gas exchange. In August, however, plants in the nutrient addition treatments had lower day-time photosynthesis, g and E, paralleled by lower night-time g and E. Lower predawn water potentials and higher integrated photosynthetic water-use efficiency suggests that the nutrient addition indirectly induced a mild water stress. Thus, soil resources can affect night-time g and E in a manner parallel to day-time, although additional factors may also be involved
    Biomass and multi-product crops for agricultural and energy production - an AGE analysis
    Ignaciuk, A. ; Dellink, R.B. - \ 2006
    Energy Economics 28 (2006)3. - ISSN 0140-9883 - p. 308 - 325.
    general equilibrium-analysis - climate-change policy - bottom-up - top-down - bioenergy - potentials - market
    By-products from agriculture and forestry can contribute to production of clean and cheap (bio)electricity. To assess the role of such multi-product crops in the response to climate policies, we present an applied general equilibrium model with special attention to biomass and multi-product crops. The potential to boost production of bioelectricity in Poland through the use of multi-product crops turns out to be limited to only 2¿3% of total electricity production. Further expansion of the bioelectricity sector will have to be based on biomass crops explicitly grown for energy purposes. The competition between agriculture and biomass for scarce land remains limited. In the scenarios, production of agricultural goods decreases at most with 5%, and the largest price increase for agricultural goods amounts to 5%. These changes in production induce substantial changes in land allocation: around 250,000 ha is converted from agricultural production to forestry and willow plantations
    Electro-olfactograms are present when odorous stimuli have not been perceived
    Hummel, T. ; Mojet, J. ; Kobal, G. - \ 2006
    Neuroscience Letters 397 (2006)3. - ISSN 0304-3940 - p. 224 - 228.
    nasal-mucosa - olfaction - responses - potentials - epithelium - neurons
    After chemical stimulation of the human olfactory epithelium it is possible to record a negative response (electro-olfactogram, EOG) which is interpreted as the summated generator potential of olfactory neurons. The aim of the present investigation was to test whether the EOG is present when olfactory stimuli have not been perceived. Stimulation was performed with vanillin and eugenol at supraliminal and subliminal levels. Twelve healthy volunteers participated in the experiments. Stimuli were applied at an interstimulus interval of approximately 60 s. Although recordings were successful in 4 of the 12 subjects, for both stimulants EOG could be obtained even when the stimuli had not been perceived by the subjects. EOG recordings in response to supra- and subliminal stimuli exhibited no major differences, except for the onset of the EOG in response to subliminal eugenol-stimuli which were prolonged compared to supraliminal stimulation. All in all, the present data provide a physiological basis for the subliminal influence of odorous stimuli on human behavior.
    Concentration and Solvency Effects on the Pair Interaction between Colloidal Particles in a Solution of Nonadsorbing Polymer
    Tuinier, R. ; Fleer, G.J. - \ 2004
    Macromolecules 37 (2004)23. - ISSN 0024-9297 - p. 8764 - 8772.
    mesoscopic particles - depletion - dispersions - potentials - mixtures - spheres - chains - phase - adsorption - molecules
    Analytical expressions are derived for the polymer excess amount and the grand potential (surface free energy) of flat and spherical surfaces immersed in a solution of nonadsorbing polymer chains in the mean-field approximation. We start from a recent mean-field expression for the depletion thickness which takes into account not only the effect of the chain length N but also that of the polymer concentration b and the solvency . Simple expressions are obtained for the interfacial properties at a colloidal surface, using both the adsorption method and the osmotic route. For a sphere of radius a, the excess amount can be separated into a planar contribution = -b and a curvature correction c = -(2/12)bc2/a, where c is a "curvature thickness" which is close to (but smaller than) . The grand potential has a planar contribution = (2/9)b/ and a curvature part c = (/18)b/a. We test the results against numerical lattice computations, taking care that the boundary conditions in the continuum and lattice models are the same. We find good agreement up to a polymer segment volume fraction of 10%, and even for more concentrated solutions our simple model is reasonable. For spherical geometry we propose a new equation for the segment concentration profile which excellently agrees with numerical lattice computations. The results can be used as a starting point for the pair interaction between colloidal particles in a solution containing nonadsorbing chains, which is discussed in the following paper.
    A comparison of the adsorption of saliva proteins and some typical proteins onto the surface of hydroxyapatite
    Kawasaki, K. ; Kambara, M. ; Matsumura, H. ; Norde, W. - \ 2003
    Colloids and Surfaces. B: Biointerfaces 32 (2003)4. - ISSN 0927-7765 - p. 321 - 334.
    proline-rich proteins - bovine serum-albumin - human-enamel - in-vitro - synthetic hydroxyapatite - solid/liquid interfaces - dynamic method - pellicle - constituents - potentials
    Adsorption of protein from saliva on hydroxyapatite was compared with adsorption of several typical proteins with different electric charges, i.e. lysozyme, human serum albumin, @b-lactoglobulin and ovalbumin. Adsorbed amounts of these proteins were determined and electrophoretic mobilities of protein-covered hydroxyapatite particles were measured, at different values for the adsorbed mass and, therefore, at various degrees of surface coverage. Also, adsorption kinetics were investigated by streaming potential measurements of a hydroxyapatite surface in contact with a protein solution, allowing monitoring of changes in the zeta-potential of the protein-covered hydroxyapatite surface in real time. The adsorbed amounts show that, as compared to most of the other proteins, the saliva proteins have remarkably low adsorption affinity. The measured values for the electrophoretic mobilities indicate that the positively charged proteins in the saliva mixture preferentially adsorb onto the negatively charged hydroxyapatite surface; this is most pronounced at low protein concentration in solution (i.e. at low coverage of the surface by the protein). Preferential uptake of the positively charged saliva proteins during the initial stages of the adsorption process is also concluded from the results of the kinetics experiments. Preferential adsorption of positive proteins is somewhat suppressed by the presence of Ca^2^+ ions in the medium. The results suggest that an acquired pellicle on a tooth in an oral environment contains a significant fraction of positively charged proteins. The positively charged proteins in the pellicle reduce the zeta-potential at the tooth surface to low values; consequently, electrostatic forces are expected to play only a minor role in the interaction with other components (e.g. bacterial cells).
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