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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    Soil erosion along a transect in a forested catchment: Recent or ancient processes?
    Calitri, Francesca ; Sommer, Michael ; Meij, Marijn W. van der; Egli, Markus - \ 2020
    Catena 194 (2020). - ISSN 0341-8162
    239+240 Plutonium - Forest - Moraine landscape - Soil catena - Soil erosion

    Forested areas are assumed not to be influenced by erosion processes. However, forest soils of Northern Germany in a hummocky ground moraine landscape can sometimes exhibit a very shallow thickness on crest positions and buried soils on slope positions. The question consequently is: Are these on-going or ancient erosional and depositional processes? Plutonium isotopes act as soil erosion/deposition tracers for recent (last few decades) processes. Here, we quantified the 239+240Pu inventories in a small, forested catchment (ancient forest “Melzower Forst”, deciduous trees), which is characterised by a hummocky terrain including a kettle hole. Soil development depths (depth to C horizon) and 239+240Pu inventories along a catena of sixteen different profiles were determined and correlated to relief parameters. Moreover, we compared different modelling approaches to derive erosion rates from Pu data. We find a strong relationship between soil development depths, distance-to-sink and topography along the catena. Fully developed Retisols (thicknesses > 1 m) in the colluvium overlay old land surfaces as documented by fossil Ah horizons. However, we found no relationship of Pu-based erosion rates to any relief parameter. Instead, 239+240Pu inventories showed a very high local, spatial variability (36–70 Bq m−2). Low annual rainfall, spatially distributed interception and stem flow might explain the high variability of the 239+240Pu inventories, giving rise to a patchy input pattern. Different models resulted in quite similar erosion and deposition rates (max: −5 t ha−1 yr−1 to +7.3 t ha−1 yr−1). Although some rates are rather high, the magnitude of soil erosion and deposition - in terms of soil thickness change - is negligible during the last 55 years. The partially high values are an effect of the patchy Pu deposition on the forest floor. This forest has been protected for at least 240 years. Therefore rather natural events and anthropogenic activities during medieval times or even earlier must have caused the observed soil pattern, which documents strong erosion and deposition processes.

    Highly efficient mono-functionalization of knob-in-hole antibodies with strain-promoted click chemistry
    Bruins, Jorick J. ; Wouw, Criss van de; Koen, Wagner ; Lina, Bartels ; Albada, Bauke ; Delft, F.L. van - \ 2019
    Journal of the American Chemical Society 4 (2019). - ISSN 0002-7863 - p. 11801 - 11807.
    Knob-in-hole antibodies can be utilized to introduce a single tag for chemo-enzymatic functionalization. By either introducing a single C-terminal sortase tag (sortase-tag expressed protein ligation) or tyrosine tag (G4Y), mono-functionalization of the monoclonal antibody trastuzumab was achieved rapidly and in high yields. This method was applied to selectively and efficiently introduce a single fluorescent tag, cytokine or single-chain variable fragment, as well as produce clean homo dimers of trastuzumab.

    Invasive moth facilitates use of a native food plant by other native and invasive arthropods
    Harvey, Jeffrey A. ; Gols, Rieta ; Smith, Brittany ; Ode, Paul J. - \ 2019
    Ecological Research 34 (2019)5. - ISSN 0912-3814 - p. 659 - 666.
    cow parsnip - ecosystem engineer - facilitation - invasive moth - small hogweed

    Organisms that invade new habitats exploit new resources or niches and influence native species. Here, we examine how an invasive moth, the parsnip webworm (Depressaria radiella, formerly D. pastinacella), facilitates interactions with other arthropods in spatially separated populations of native cow parsnip (Heracleum maximum) in the Rocky Mountains (New Mexico and Colorado). We compare this with results on small hogweed (Heracleum sphondylium) in the Netherlands, where both the plant and herbivore are native. Larvae of D. radiella feed in webs on ripening fruits of their food plants. Mature caterpillars descend the hollow stems into which they chew a hole, enter the stem and pupate. Other arthropods enter the stems through these holes. Plants in all populations of cow parsnip/hogweed contained either moth pupae and/or webworms mummified by their main parasitoid, Copidosoma sosares that also been introduced into parts of the United States. In both countries, earwigs (Forficula auricularia), which are also invasive in the United States, were the dominant arthropod to utilize webworm-perforated stems, although there was more within-site variability in abundance of earwigs in the United States than in the Netherlands. The woodlouse, Porcelio scaber, which is native to Eurasia but also established in the United States, was abundant in stems of Dutch hogweeds but absent in stems of American cow parsnips. Other native herbivores (e.g., mirid bugs), were collected in stems at sites in both continents. Moreover, the number of various arthropods found in perforated stems correlate positively with the number of holes found in these stems.

    Electrochemically Gated Long-Distance Charge Transport in Photosystem I
    López-Martínez, Montse ; López-Ortiz, Manuel ; Antinori, Maria Elena ; Wientjes, Emilie ; Nin-Hill, Alba ; Rovira, Carme ; Croce, Roberta ; Díez-Pérez, Ismael ; Gorostiza, Pau - \ 2019
    Angewandte Chemie-International Edition 58 (2019)38. - ISSN 1433-7851 - p. 13280 - 13284.
    current decay - electrochemical gating - electron transfer - photosynthesis - scanning tunneling microscopy

    The transport of electrons along photosynthetic and respiratory chains involves a series of enzymatic reactions that are coupled through redox mediators, including proteins and small molecules. The use of native and synthetic redox probes is key to understanding charge transport mechanisms and to the design of bioelectronic sensors and solar energy conversion devices. However, redox probes have limited tunability to exchange charge at the desired electrochemical potentials (energy levels) and at different protein sites. Herein, we take advantage of electrochemical scanning tunneling microscopy (ECSTM) to control the Fermi level and nanometric position of the ECSTM probe in order to study electron transport in individual photosystem I (PSI) complexes. Current–distance measurements at different potentiostatic conditions indicate that PSI supports long-distance transport that is electrochemically gated near the redox potential of P700, with current extending farther under hole injection conditions.

    Reconstructing rates and patterns of colluvial soil redistribution in agrarian (hummocky) landscapes
    Meij, Marijn van der; Reimann, Tony ; Vornehm, V.K. ; Temme, A.J.A.M. ; Wallinga, J. van; Beek, R. van; Sommer, M. - \ 2019
    Earth Surface Processes and Landforms 44 (2019)12. - ISSN 0197-9337 - p. 2408 - 2422.
    Humans have triggered or accelerated erosion processes since prehistoric times through agricultural practices. Optically stimulated luminescence (OSL) is widely used to quantify phases and rates of the corresponding landscape change, by measuring the last moment of daylight exposure of sediments. However, natural and anthropogenic mixing processes, such as bioturbation and tillage, complicate the use of OSL as grains of different depositional ages become mixed, and grains become exposed to light even long after the depositional event of interest. Instead, OSL determines the stabilization age, indicating when sediments were buried below the active mixing zone. These stabilization ages can cause systematic underestimation when calculating deposition rates. Our focus is on colluvial deposition in a kettle hole in the Uckermark region, northeastern Germany. We took 32 samples from five locations in the colluvium filling the kettle hole to study both spatial and temporal patterns in colluviation. We combined OSL dating with advanced age modelling to determine the stabilization age of colluvial sediments. These ages were combined with an archaeological reconstruction of historical ploughing depths to derive the levels of the soil surface at the moment of stabilization; the deposition depths, which were then used to calculate unbiased deposition rates. We identified two phases of colluvial deposition. The oldest deposits (~5 ka) were located at the fringe of the kettle hole and accumulated relatively slowly, whereas the youngest deposits (<0.3 ka) rapidly filled the central kettle hole with rates of two orders of magnitude higher. We suggest that the latter phase is related to artificial drainage, facilitating accessibility in the central depression for agricultural practices. Our results show the need for numerical dating techniques that take archaeological and soil‐geomorphological information into account to identify spatiotemporal patterns of landscape change, and to correctly interpret landscape dynamics in anthropogenically influenced hilly landscapes.
    Data from: An integrative phylogenomic approach illuminates the evolutionary history of cockroaches and termites (Blattodea)
    Evangelista, Dominic A. ; Wipfler, Benjamin ; Béthoux, Olivier ; Donath, Alexander ; Fujita, Mari ; Kohli, Manpreet K. ; Legendre, Frédéric ; Liu, Shanlin ; Machida, Ryuichiro ; Misof, Bernhard ; Peters, Ralph S. ; Podsiadlowski, Lars ; Rust, Jes ; Schuette, Kai ; Tollenaar, Ward ; Ware, Jessica L. ; Wappler, Torsten ; Zhou, Xin ; Meusemann, Karen ; Simon, S. - \ 2019
    Biosystematics
    dating - phyloecology - transcriptomes - palaeontology - systematics - maternal care - sociality - Blattodea - Carboniferous - Cenezoic - Isoptera - Jurrassic - Mesozoic
    Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus þ termites ¼ Tutricablattae; Lamproblattidae þ Tutricablattae ¼ Kittrickea; and Blattoidea þ Corydioidea ¼ Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blatto-dean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.
    An integrative phylogenomic approach illuminates the evolutionary history of cockroaches and termites (Blattodea)
    Evangelista, Dominic A. ; Wipfler, Benjamin ; Béthoux, Olivier ; Donath, Alexander ; Fujita, Mari ; Kohli, Manpreet K. ; Legendre, Frédéric ; Liu, Shanlin ; Machida, Ryuichiro ; Misof, Bernhard ; Peters, Ralph S. ; Podsiadlowski, Lars ; Rust, Jes ; Schuette, Kai ; Tollenaar, Ward ; Ware, Jessica L. ; Wappler, Torsten ; Zhou, Xin ; Meusemann, Karen ; Simon, Sabrina - \ 2019
    Proceedings of the Royal Society. B: Biological Sciences 286 (2019)1895. - ISSN 0962-8452
    Isoptera - Maternal care - Palaeontology - Sociality - Systematics - Transcriptomes

    Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus þ termites ¼ Tutricablattae; Lamproblattidae þ Tutricablattae ¼ Kittrickea; and Blattoidea þ Corydioidea ¼ Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blatto-dean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.

    Timing of Avian Breeding in an Urbanised World
    Jong, Maaike de; Eertwegh, Laura van den; Beskers, Ronald E. ; Vries, Peter P. de; Spoelstra, Kamiel ; Visser, Marcel E. - \ 2018
    Ardea 106 (2018)1. - ISSN 0373-2266 - p. 31 - 38.
    citizen science - hole breeding birds - light pollution - seasonal timing - urban gradient - urbanisation
    A large part of the world is urbanised, and the process of urbanisation is ongoing. This causes dramatic alterations of species' habitat such as increased night light, sound levels and temperature, along with direct disturbance by human activity. We used eight years of citizen science data from ten common bird species breeding in nest boxes throughout The Netherlands to study the relationship between urbanisation and a key life history trait, timing of breeding. We used nightly light levels in the form of sky brightness and light emission as a proxy for urbanisation as the dramatic change of the night-time environment is a prominent effect of urbanisation. We expected birds to lay earlier in areas with more light at night, i.e. in more urbanised areas. We found, however, no relationship between light levels and seasonal timing in the ten species studied. A limitation of our study is that there was only limited data for the areas that were urbanised most (e.g. inside cities). Most nest box study areas are located in areas with a limited level of urbanisation, and hence with relatively low light levels of light at night. The lack of data on breeding birds in more urbanised environments, which is a rapidly expanding habitat for an increasing number of species worldwide, should be the focus of attention and citizen science would be highly suitable to also provide data for such areas.
    Crumpling-based soft metamaterials : The effects of sheet pore size and porosity
    Mirzaali, M.J. ; Habibi, M. ; Janbaz, S. ; Vergani, L. ; Zadpoor, A.A. - \ 2017
    Scientific Reports 7 (2017). - ISSN 2045-2322 - 7 p.

    Crumpled-based materials are relatively easy to fabricate and show robust mechanical properties for practical applications, including meta-biomaterials design aimed for improved tissue regeneration. For such requests, however, the structure needs to be porous. We introduce a crumpled holey thin sheet as a robust bio-metamaterial and measure the mechanical response of a crumpled holey thin Mylar sheet as a function of the hole size and hole area fraction. We also study the formation of patterns of crease lines and ridges. The area fraction largely dominated the crumpling mechanism. We also show, the crumpling exponents slightly increases with increasing the hole area fraction and the total perimeter of the holes. Finally, hole edges were found to limit and guide the propagation of crease lines and ridges.

    Wetting dynamics of a collapsing fluid hole
    Bostwick, J.B. ; Dijksman, J.A. ; Shearer, M. - \ 2017
    Physical Review Fluids 2 (2017)1. - ISSN 2469-990X
    The collapse dynamics of an axisymmetric fluid cavity that wets the bottom of a rotating bucket bound by vertical sidewalls are studied. Lubrication theory is applied to the governing field equations for the thin film to yield an evolution equation that captures the effect of capillary, gravitational, and centrifugal forces on this converging flow. The focus is on the quasistatic spreading regime, whereby contact-line motion is governed by a constitutive law relating the contact-angle to the contact-line speed. Surface tension forces dominate the collapse dynamics for small holes with the collapse time appearing as a power law whose exponent compares favorably to experiments in the literature. Gravity accelerates the collapse process. Volume dependence is predicted and compared with experiment. Centrifugal forces slow the collapse process and lead to complex dynamics characterized by stalled spreading behavior that separates the large and small hole asymptotic regimes.
    Topography reconstruction of eroding landscapes – A case study from a hummocky ground moraine (CarboZALF-D)
    Meij, W.M. van der; Temme, A.J.A.M. ; Wallinga, J. ; Hierold, W. ; Sommer, M. - \ 2017
    Geomorphology 295 (2017). - ISSN 0169-555X - p. 758 - 772.
    Erosion processes, aggravated by human activity, have a large impact on the spatial variation of soil and topographic properties. Knowledge of the topography prior to human-induced erosion (paleotopography) in naturally stable landscapes is valuable for identifying vulnerable landscape positions and is required as starting point for erosion modelling exercises. However, developing accurate reconstructions of paleotopography provide a major challenge for geomorphologists. Here, we present a set of paleotopographies for a closed kettle hole catchment in north-east Germany (4 ha), obtained through different reconstruction approaches. Current soil and colluvium thickness, estimated from a dataset of 264 soil descriptions using Ordinary Kriging, were used as input for a mass balance, or were compared with a set of undisturbed soil thicknesses to estimate the amount of erosion. The performance of the different approaches was assessed with cross-validation and the count of mispredicted eroded, depositional or stable landscape positions.

    The paleotopographic reconstruction approach based on the average thickness of undisturbed soils in the study area showed the best performance. This thickness (1.00 m) is comparable to the average undisturbed soil thickness in the region and in line with global correlations of soil thickness as a function of rainfall and initial CaCO3 content. The performance of the different approaches depended more on mispredictions of landscape position due to the assumption of a spatially constant initial soil depth than on small variations in this depth. To conclude, we mention several methodological and practical points of attention for future topography reconstruction studies, concerning data quality and availability, spatial configuration of data and other processes affecting topography.
    Flow through a filter plate backed by a packed bed of spheres
    Sman, R.G.M. van der - \ 2017
    Chemical Engineering Science 158 (2017). - ISSN 0009-2509 - p. 154 - 163.
    Filtration - Fluid flow - Orifice - Simulation

    In this paper we perform direct numerical simulation (DNS) on the problem of fluid flow through a filter plate backed by a packed bed of spheres, resembling a cake layer on top of a membrane. For both the complete problem, and its single components (the filter plate and a bed of spheres of finite height) we have observed three flow regimes, depending on the Reynolds number. In each regime the flow resistance is showing a different scaling with the Reynolds number. In the Stokes flow regime the total flow resistance can be decomposed in linear independent components. The interior flows inside the filter holes and inside the packed bed follow the same correlations as hold for the single component. However, at the transition zone between filter plate and packed bed, there is a diverging flow in the first row of the packed bed, whose contribution in the flow resistance scales with the fractional hole to the power −1.5. Similar scaling exponent has been found earlier for the viscous-inertial regime with Reynolds numbers larger than 10, which has been modelled using the porous medium approach. Our findings suggest that also in the Stokes flow and the weakly flow regime the problem can also be solved with the same porous medium approach using the Navier-Stokes equation having Darcy–Brinkman terms incorporated. This investigation provides a good basis for developing more accurate analytical models for the flow resistance of membrane filters with a cake layer on top.

    Prenatal, but not early postnatal, exposure to a Western diet improves spatial memory of pigs later in life and is paired with changes in maternal prepartum blood lipid levels
    Clouard, Caroline ; Kemp, Bas ; Val-Laillet, David ; Gerrits, Walter J.J. ; Bartels, Andrea C. ; Bolhuis, J.E. - \ 2016
    FASEB Journal 30 (2016)7. - ISSN 0892-6638 - p. 2466 - 2475.
    Cholestero - Cognition - Fat - Prenatal programming programming - Refined sugar

    Maternal obesity and perinatal high-fat diets are known to affect cognitive development. We examined the effects of late prenatal and/or early postnatal exposure to a Western-type diet, high in both fat and refined sugar, on the cognition of pigs (Sus scrofa) in the absence of obesity. Thirty-six sows and their offspring were assigned to 1 of 4 treatments in a 2 3 2 factorial arrangement, with 8 wk prenatal and 8 wk postnatal exposure to a Western diet (enriched in fat, sucrose, and cholesterol) or control diets as factors. Compared to controls, piglets exposed to the prenatal Western diet showed enhanced working and reference memory during the acquisition and reversal phases of a spatial hole-board task. Mothers fed the prenatal Western diet had higher prepartum blood cholesterol and free fatty acid levels. Postnatal exposure to the Western diet did not affect piglet cognitive performance, but it did increase postpartum maternal and postweaning piglet cholesterol levels. The Western diet had no effect on maternal or offspring insulin sensitivity or leptin levels. In conclusion, a prenatal Western diet improved memory function in pigs, which was paired with changes in prepartum maternal blood cholesterol levels. These findings highlight the key role of late fetal nutrition for long-term programming of cognition.-Clouard, C., Kemp, B., Val-Laillet, D., Gerrits, W. J. J., Bartels, A. C., Bolhuis, J. E. Prenatal, but not early postnatal, exposure to a Western diet improves spatial memory of pigs later in life and is paired with changes in maternal prepartum blood lipid levels.

    Hole and vacuole formation during drying of sessile whey protein droplets
    Bouman, Jacob ; Venema, Paul ; Vries, Renko J. de; Linden, Erik van der; Schutyser, Maarten A.I. - \ 2016
    Food Research International 84 (2016). - ISSN 0963-9969 - p. 128 - 135.
    Droplet drying - Dynamics - Morphology - Process conditions - Protein solution

    Morphological development from droplet to particle during drying has strong influence on powder structure and functionality. We study the evolving morphological properties of whey protein droplets during single sessile droplet drying experiments as a well-defined model for spray drying. Sessile drying droplets were visualised with a camera and subjected to varying drying conditions such as temperature, initial protein concentration, presence of airflow and droplet rotation. The final particles were imaged by SEM and X-ray tomography. Under all conditions used, the droplets initially shrink steadily while at a specific point a hole nucleates. Subsequently, a vacuole develops until a rigid hollow particle is obtained. The location of the hole was found strongly dependent on the presence and the direction of the applied air flow. We hypothesise that in the early drying stage a skin forms, which becomes more rigid when the hole nucleates. The hole forms at the position where the local modulus of the skin layer is minimal and/or at the point below the skin where the local pressure is minimal, and that after the hole has nucleated, the vacuole develops mainly by evaporation of water through the hole.

    The (w)hole story : Facilitation of dead wood fauna by bark beetles?
    Zuo, Juan ; Cornelissen, J.H.C. ; Hefting, M.M. ; Sass-Klaassen, Ute ; Logtestijn, R.S.P. van; Hal, Jurgen van; Goudzwaard, Leo ; Liu, J.C. ; Berg, M.P. - \ 2016
    Soil Biology and Biochemistry 95 (2016). - ISSN 0038-0717 - p. 70 - 77.
    Bark holes - Community assembly - Inter-specific facilitation - Macro-fauna - Scolytinae - Wood decomposition

    Facilitation between species is thought to be a key mechanism in community assembly and diversity, as certain species create microhabitats for others. A profound characteristic of forest ecosystems is a large amount of dead wood which is colonised by a vast array of invertebrate species. Bark beetles (Scolytinae) feed and breed on dying or dead trees, puncturing holes into the bark and engraving inner bark and outer wood with their galleries. These holes and galleries might facilitate other invertebrates by providing access to the inner bark for shelter, feeding and reproduction. We tested this hypothesised facilitative interaction during the early decomposition phase of coarse woody debris of spruce (Picea abies L. Karst.) incubated in two environmentally contrasting forest sites in the 'common garden' experiment LOGLIFE. We sampled invertebrates in 25 cm diameter logs at different degrees of colonisation by bark beetles. Our results indicated that (1) bark beetles facilitated the entrance into spruce logs of other invertebrates with body width that matched the size of bark-beetle holes, and (2) the abundance of invertebrates was often positively related to the proportional surface area of inner bark consumed by bark beetles, but more so in the nutrient-rich site than in the nutrient poor site. This study provides the first quantitative test of facilitation between invertebrate clades in dead wood communities. Including facilitative interaction in community assembly studies may change some predictions about relationships between tree functional traits and invertebrate diversity and will lead to a more accurate and comprehensive understanding of dead wood communities.

    Can we explain the observed methane variability after the Mount Pinatubo eruption?
    Bândǎ, N. ; Krol, M. ; Weele, M. Van; Noije, T. Van; Sager, P. Le; Röckmann, T. - \ 2016
    Atmospheric Chemistry and Physics 16 (2016)1. - ISSN 1680-7316 - p. 195 - 214.

    The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported, and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as El Niño-Southern Oscillation (ENSO) and biomass burning events. Emissions of CO, NOX and non-methane volatile organic compounds (NMVOCs) also affected CH4 concentrations indirectly by influencing tropospheric OH levels. Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8-10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6-9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

    Prenatal, but not early postnatal, exposure to a Western diet enhances spatial memory of piglets in a hole-board task
    Clouard, Caroline - \ 2015
    Prenatal, but not early postnatal, exposure to a Western diet enhances spatial memory of piglets in a hole-board task
    Clouard, C.M. ; Kemp, B. ; Gerrits, W.J.J. ; Val-Laillet, D. ; Bolhuis, J.E. - \ 2015
    In: Proceedings of the Benelux ISAE conference 2015. - - p. 17 - 17.
    Reviews and syntheses: Soil N2O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis
    Lent, Jeffrey van; Hergoualc’h, K. ; Verchot, L.V. - \ 2015
    Biogeosciences 12 (2015)23. - ISSN 1726-4170 - p. 7299 - 7313.
    Deforestation and forest degradation in the tropics may substantially alter soil N-oxide emissions. It is particularly relevant to accurately quantify those changes to properly account for them in a REDD+ climate change mitigation scheme that provides financial incentives to reduce the emissions. With this study we provide updated land use (LU)-based emission rates (104 studies, 392 N2O and 111 NO case studies), we determine the trend and magnitude of flux changes with land-use change (LUC) using a meta-analysis approach (44 studies, 135 N2O and 37 NO cases) and evaluate biophysical drivers of N2O and NO emissions and emission changes for the tropics.

    The average N2O and NO emissions in intact upland tropical forest amounted to 2.0 ± 0.2 (n = 90) and 1.7 ± 0.5 (n = 36) kg N ha−1 yr−1, respectively. In agricultural soils annual N2O emissions were exponentially related to N fertilization rates and average water-filled pore space (WFPS) whereas in non-agricultural sites a Gaussian response to WFPS fit better with the observed NO and N2O emissions. The sum of soil N2O and NO fluxes and the ratio of N2O to NO increased exponentially and significantly with increasing nitrogen availability (expressed as NO3− / [NO3−+NH4+]) and WFPS, respectively; following the conceptual Hole-In-the-Pipe model. Nitrous and nitric oxide fluxes did not increase significantly overall as a result of LUC (Hedges's d of 0.11 ± 0.11 and 0.16 ± 0.19, respectively), however individual LUC trajectories or practices did. Nitrous oxide fluxes increased significantly after intact upland forest conversion to croplands (Hedges's d = 0.78 ± 0.24) and NO increased significantly following the conversion of low forest cover (secondary forest younger than 30 years, woodlands, shrublands) (Hedges's d of 0.44 ± 0.13). Forest conversion to fertilized systems significantly and highly raised both N2O and NO emission rates (Hedges's d of 1.03 ± 0.23 and 0.52 ± 0.09, respectively).

    Changes in nitrogen availability and WFPS were the main factors explaining changes in N2O emissions following LUC, therefore it is important that experimental designs monitor their spatio-temporal variation. Gaps in the literature on N oxide fluxes included geographical gaps (Africa, Oceania) and LU gaps (degraded forest, wetland (notably peat) forest, oil palm plantation and soy cultivation).

    Drying and hydration of proteins at high concentration
    Bouman, J. - \ 2015
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Renko de Vries. - Wageningen : Wageningen University - ISBN 9789462575509 - 161
    eiwit - wei-eiwit - zeïne - drogen - droogmethoden - geneesmiddeltoedieningssystemen - hydratatie - hydrofobiciteit - ph - vacuolen - protein - whey protein - zein - drying - drying methods - drug delivery systems - hydration - hydrophobicity - ph - vacuoles

    Proteins are the building blocks of life and serve a wide range of essential functions in organisms. Many metabolic reactions in organisms are catalysed by enzymes, DNA is replicated by proteins and in cells proteins often facilitate active transport of e.g. glucose or ions. Proteins also serve an essential functionality in foods, pharmaceutics, bioplastics and even clothing. Recently, the use of proteins towards higher concentrations is of interest for food, pharmaceutical and medical applications. Nevertheless, the preparation of products with desired product properties can be challenging, when approaching higher protein concentrations. Therefore, in this thesis we investigate proteins at higher concentrations, especially focussing on their drying and hydration behaviour.

    In part one of the thesis, the focus is on the dynamics of drying of proteins towards higher concentrations. Dense proteins systems have been scarcely studied compared to proteins at lower concentrations. We address drying behaviour where we focus on the use of whey protein isolate as a model system. In part two of the thesis we focus on the hydration properties of the corn protein zein, where we apply it as a drug excipient. In this part we also investigate the influence of hydration on the release behaviour of drugs into the hydration media.

    The drying part (part one) contains two studies. The first study is more fundamental in nature, focussing on the drying of a protein coating. In previous studies mainly the macroscopic properties of protein coatings after drying are investigated, leaving the drying dynamics virtually unexplored. Here we investigate the drying behaviour of the model protein β-lactoglobulin on multiple length scales with an unique combination of in-line techniques. On the microscopic length scale we use dynamic vapour sorption and magnetic resonance imaging while on a smaller length scales, we apply diffusing wave spectroscopy and IR-spectroscopy to monitor the drying process. For all used techniques, the changes in the measured physical properties of the coating as a function of water weight fraction Xw from Xw = 0.8 down to Xw = 0.2 are gradual. However, using dynamic vapour sorption and IR-spectroscopy we measure a sharp change below water weight fractions of Xw = 0.2. We hypothesise that changes in the molecular interactions caused by dehydration of the protein results in a change in the drying kinetics of the film.

    In the second study of part one, protein drying is approached on a more applied level, where we study the drying of a spherical droplet. We use single droplet drying as a methods that can model the spray drying process in a simplified and well-controlled way. Sessile droplets are subjected to varying drying conditions such as temperature, initial protein concentration, presence of airflow and droplet rotation. During these experiments the morphological development is monitored by a camera. After drying, scanning electron microscopy and X-ray tomography are used to examine the particles that are formed after complete drying. Irrespective of the conditions used, we observe an initial droplet shrinkage, followed by the nucleation of a hole in the droplet skin, which is followed by the formation of a vacuole. The drying conditions used, strongly influenced the location of the hole and the locking point prior to hole formation. We hypothesise that the location of the hole is caused by local inhomogeneities in protein concentration causing a the nucleation of the hole where the local skin modulus is lowest. Also the locking point of the droplet is found to be due to a inhomogeneity over the whole droplet caused by rapid evaporation. These results can be of importance to understand powder structure and functionality as obtained in spray drying.

    In the hydration part (part 2), we investigate the potential of zein as a sole excipient in macroscale caplets obtained by hot melt extrusion (HME) and injection moulding (IM). Zein is good candidate as a sustained release agent, because it is insoluble in two studies. In the first study zein matrices were loaded with the drug paracetamol. Physical mixtures of zein, water and crystalline paracetamol are extruded and injection moulded into caplets. Characterisation of these caplets is performed using differential scanning calorimetry, IR- spectroscopy, scanning electron microscopy and powder X-ray diffraction. The hydration and drug release kinetics from the caplet slices is measured. We find that the drug release kinetics is broadly independent of the dissolution medium and drug loading. The release kinetics is diffusion limited and could be well described by a 2D diffusion model. The results demonstrate that the drug release rate from zein caplet slices can be tuned by its dimensions.

    In the second study, a wider range of drugs differing in hydrophobicity is studied. Next to paracetamol, we have used two other model drugs: the hydrophobic indomethacin and the more hydrophilic ranitidine. The zein matrix is capable to stabilize the different dugs in a non-crystalline state, which is promising especially for increasing the bioavailability of poorly water-soluble drugs. Overall crystallinity of the drugs in the caplets increases with its degree of hydrophobicity. For the poorly soluble indomethacin, dissolution rates at low pH were higher from caplet slices, compared to the dissolution rates of indomethacin crystals by themselves. In addition, we found that the electrostatic interactions between zein and drugs can also be used to influence the release kinetics.

    Various aspects were found to be of importance both for drying and hydration of concentrated protein systems. The homogeneity during both processes deserves attention as its manipulation can strongly influence final properties if the system. Also the plasticising effect of water on dense proteins is often found essential, when understanding the dynamics of both drying and hydration processes. Finally protein hydrophobicity and its manipulation can provide a window of opportunities in many applications which are involve by drying or hydration.

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