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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Safeguarding water availability for food and ecosystems under global change : modelling and assessment of the role of environmental flows
Pastor, Amandine V. - \ 2017
University. Promotor(en): Pavel Kabat, co-promotor(en): Fulco Ludwig; Hester Biemans. - Wageningen : Wageningen University - ISBN 9789463431767 - 177
water availability - water management - flow - water deficit - food security - food production - global warming - aquatic ecosystems - waterbeschikbaarheid - waterbeheer - stroming - watertekort - voedselzekerheid - voedselproductie - opwarming van de aarde - aquatische ecosystemen

In a context of future population increase and intensification of water cycle by climate change, water demand for irrigation is projected to double. However, freshwater resources have been degraded the last decades especially in rivers via fragmentation, dam contraction and pollution. Flow alteration and degradation lead to 80% of freshwater ecosystem species loss. In this thesis, a robust and reliable Environmental Flow (EF) method was developed for global scale: the Variable Monthly Flow (VMF) method. This method allowed estimating EF deficit at global scale including its origin, timing, frequency and magnitude. By setting EFRs as priority user in a global vegetation and hydrological model (LPJmL), irrigation loss due to EFRs implementation were assessed at 30% leading to 5% global calorie loss. To maintain water allocation to humans and ecosystems under global change, food imports would require to increase by 15% especially from Latin America to South of Asia.

Light on phloem transport (an MRI approach)
Prusova, Alena - \ 2016
University. Promotor(en): Herbert van Amerongen, co-promotor(en): Henk van As. - Wageningen : Wageningen University - ISBN 9789462579156 - 130
solanum lycopersicum - phloem - light - flow - photoperiod - nuclear magnetic resonance - biophysics - magnetic resonance imaging - floëem - licht - stroming - fotoperiode - kernmagnetische resonantie - biofysica - kernspintomografie

This thesis (Light on phloem transport – an MRI approach) aims to answer the question whether phloem transport can be a limiting factor for photosynthesis efficiency (and ultimately causing a bottleneck towards achieving higher yields). To answer this key question, we manipulated the source: sink ratio within tomato (Solanum lycopersicum L.) while measuring phloem transport with magnetic resonance imaging (MRI) flowmetry. Additionally we compared phloem flow characteristics of two potato plants (Solanum tuberosum L.) which differed in source : sink ratio. In Chapter 2, the source strength was manipulated by varying the light intensity. An increase in phloem sap volume flow under higher light intensities was observed. However, under all light intensities applied, the phloem flow velocity was found to be constant (as has previously been suggested in other studies) although a clear diurnal pattern was observed. This finding does not fit in current models to describe the mechanism of phloem transport and a different mechanism must be at play. The results of this chapter demonstrate that increased levels of photo-assimilates are transported in sieve tubes, which are activated when needed by the plant. This is the first study which shows that plants activate individual sieve tubes when more photo-assimilates are available, yet maintain constant velocity. Those observations were in a tomato plant with pruned fruit trusses (i.e., in a simplified system). In Chapter 3, we investigated whether tomato plants still exhibit constant phloem flow velocity (with a diurnal pattern) under normal conditions, i.e., with strong sinks (tomato fruits) still attached. This was tested for both a long and short photoperiod by measuring flow characteristics with MRI flowmetry. We simultaneously monitored other plant processes like xylem flow rates with a heat balance sensor, net photosynthesis with gas exchange and stem diameter changes with a linear motion potentiometer. With this integrated approach, we revealed a correlation between night phloem volume flow, dark respiration and stem growth. We also conclusively showed that phloem volume flow performs a diurnal pattern under a variety of source-sink ratios which appears to be a normal behaviour for tomato plants growing under moderately-high light conditions. In chapters 2 and 3 we learned that under higher source strength a greater amount of phloem sap is transported, but the changes in flow were not accompanied by changes in velocity. To further our understanding of the mechanisms driving phloem transport, it is of interest to know how the sucrose concentration in phloem sap relates to phloem flow. In Chapter 4 we used an average T2 relaxation time in the phloem vascular tissue region to reveal the plant’s phloem carbon status under source manipulation. In this chapter we demonstrated that T2 relaxation time, when measured in parallel with phloem flow, can provide additional information about phloem region carbon status, i.e., changes in the T2 relaxation time are correlated with changes in sucrose concentration in the whole phloem region.

When studying phloem transport in plants with magnetic resonance imaging (MRI) flowmetry, plants which are relatively easy to manipulate (e.g. fruit pruning) like tomato have so far been used. However, tomato plants (used in all three previous chapters) have relatively low sink strength beneath the MRI measurement site. A potentially preferable approach is to work with plants with strong sinks beneath the measurement site. In Chapter 5 we studied potato as a potentially better test subject for MRI flowmetry as it possesses strong sink below the MRI measurement site (i.e., developing tubers). For that purpose we used two potato plants (cv. Desiree) both with several developing tubers. One of the plants overexpressed the StSWEET gene (35S:StSWEET) which appears to have altered its source : sink ratio. As a result, the 35S:StSWEET plant transported 60% more phloem sap than Desiree WT. Strikingly, the average phloem flow velocity in both plants was the same and the greater amount of transported phloem sap in the 35S:StSWEET plant was accommodated by more sieve tubes than in Desiree WT. This finding agrees with the hypothesis about the conserved nature of phloem flow velocity, where volume flow is regulated by the number of active sieve tubes (Chapter 2 and 3). In this chapter we also demonstrate that a potato plant with developing tubers represents a good subject to study phloem transport with MRI flowmetry. We concluded that under optimal conditions (which are commonly met in greenhouses) phloem transport is likely to reach its maximum capacity and therefore photosynthesis could be limited by the export and transport of photo-assimilates because of the finite number of sieve tubes and constant flow velocity.

Organocatalysis in continuous flow
Berg, S.A. van den - \ 2016
University. Promotor(en): Han Zuilhof, co-promotor(en): Tom Wennekes. - Wageningen : Wageningen University - ISBN 9789462576636 - 217 p.
catalysis - organic chemistry - flow - microfluidics - alkenes - katalyse - organische scheikunde - stroming - alkenen

Continuous flow chemistry is an enabling technique in organic chemistry. Advantages include extremely fast mixing and heat transfer capabilities as well as rapid screening of reaction conditions. Combining continuous flow chemistry with solid-supported organocatalysis presents challenges that have been investigated in this thesis.

We have developed a technique to modify the surface of silicon carbide with alkenes using microwaves. Silicon carbide is an extremely tough bio-compatible material and is of interest as a solid support. By using monolayers of bifunctional alkenes we were able to perform follow-up reactions to attach other molecules of interest, thereby further modifying the surface chemistry of silicon carbide. The use of microwaves speeds up the attachment of monolayers by as much as sixteen times.

We have developed a new method for the surface functionalization of MCM-41, a type of mesoporous silica. Mesoporous silica is an interesting solid support for catalysts because of its large surface area. 1,7-octadiene can be covalently attached under mild conditions (24 h, 100 ºC). Follow-up thiol-ene click reactions can be performed using thiols. The use of 1,2-ethanedithiol leads to a material that can be reacted with the organocatalyst quinine, giving catalytically active mesoporous silica. This material was tested in flow and yielded full conversion of starting materials for the thio-Michael addition of 3-methoxythiophenol and 1-cyclohex-2-enone.

Sulfonic acid supported on mesoporous silica (SBA-15) made via co-condensation of a thiol-containing silica precursor was used in a packed-bed continuous flow setup. This solid-supported sulfonic acid efficiently catalyzes the protection and deprotection of various alcohols as the tetrahydropyranyl-, trimethylsilyl and dimethylphenylsilyl derivatives under continuous flow conditions. By passing the starting material (primary, secondary, benzylic and phenolic alcohols) together with the appropriate protecting group over the packed bed more than 100 mg of product was produced in flow.

Finally, the ring-opening polymerization of L-lactide using an organocatalyst was investigated. Using low catalyst loading and short residence times (0.25– 1.2% TBD catalyst, residence times as short as 2 s) well-defined poly(lactic acid) (PLA) is obtained with high (95–100%) monomer conversions and PDIs of typically 1.2. Use of the microreactor allows for a rapid screening of optimal reaction conditions, consistently yielding the optimal values for high conversion and low polydispersity. This quickly revealed that longer residence times will give rise to higher conversions and a concomitantly broader molecular weight distribution due to transesterification of the polymer backbone by TBD.

The organocatalytic, metal-free continuous flow method described is rapid and mild enough to allow the use of a PEG-5,000 macroinitiator (yielding block copolymers), exo-BCN alcohol and even a base-labile tetrazine-derived alcohol, the latter of which cannot be used under traditional batch conditions. The resulting BCN-PLA and tetrazine-PLA materials were readily functionalized with small molecules and large polymers bearing azides and norbornenes via SPAAC and inverse electron demand Diels-Alder click chemistry.

Despite the challenges that arise, the combination of continuous flow chemistry and (solid-supported) organocatalysis is a powerful concept that warrants further investigation.

Multiple-contact discrete-element model for simulating dense granular media
Brodu, N. ; Dijksman, J.A. ; Behringer, R.P. - \ 2015
Physical Review. E, Statistical nonlinear, and soft matter physics 91 (2015)3. - ISSN 2470-0045 - 6 p.
emulsions - flow
This article presents a new force model for performing quantitative simulations of dense granular materials. Interactions between multiple contacts (MC) on the same grain are explicitly taken into account. Our readily applicable MC-DEM method retains all the advantages of discrete-element method simulations and does not require the use of costly finite-element methods. The new model closely reproduces our recent experimental measurements, including contact force distributions in full 3D, at all compression levels of the packing up to the experimental maximum limit of 13%. Comparisons with classic simulations using the nondeformable spheres approach, as well as with alternative models for interactions between multiple contacts, are provided. The success of our model, compared to these alternatives, demonstrates that interactions between multiple contacts on each grain must be included for dense granular packings.
Low-resolution modeling of dense drainage networks in confining layers
Pauw, P.S. ; Zee, S.E.A.T.M. van der; Leijnse, A. ; Delsman, J.R. ; Louw, P.G.B. de; Lange, W.J. de; Oude Essink, G.H.P. - \ 2015
Groundwater 53 (2015)5. - ISSN 0017-467X - p. 771 - 781.
grondwaterstroming - watervoerende lagen - modellen - klimaatverandering - groundwater flow - aquifers - models - climatic change - aquifer - simulation - intrusion - seepage - florida - system - field - flow
Groundwater-surface water (GW-SW) interaction in numerical groundwater flow models is generally simulated using a Cauchy boundary condition, which relates the flow between the surface water and the groundwater to the product of the head difference between the node and the surface water level, and a coefficient, often referred to as the “conductance.” Previous studies have shown that in models with a low grid resolution, the resistance to GW-SW interaction below the surface water bed should often be accounted for in the parameterization of the conductance, in addition to the resistance across the surface water bed. Three conductance expressions that take this resistance into account were investigated: two that were presented by Mehl and Hill (2010) and the one that was presented by De Lange (1999). Their accuracy in low-resolution models regarding salt and water fluxes to a dense drainage network in a confined aquifer system was determined. For a wide range of hydrogeological conditions, the influence of (1) variable groundwater density; (2) vertical grid discretization; and (3) simulation of both ditches and tile drains in a single model cell was investigated. The results indicate that the conductance expression of De Lange (1999) should be used in similar hydrogeological conditions as considered in this paper, as it is better taking into account the resistance to flow below the surface water bed. For the cases that were considered, the influence of variable groundwater density and vertical grid discretization on the accuracy of the conductance expression of De Lange (1999) is small.
Influence of Pluronic F127 on the distribution and functionality of inkjet-printed biomolecules in porous nitrocellulose substrates
Mujawar, L.H. ; Amerongen, A. van; Norde, W. - \ 2015
Talanta 131 (2015). - ISSN 0039-9140 - p. 541 - 547.
protein microarrays - spot morphology - block-copolymer - antibody - surfaces - additives - membrane - flow - hydrophobicities - orientation
The distribution of inkjet-printed biomolecules in porous nitrocellulose substrates often results in a non-homogeneous spot morphology commonly referred to as 'doughnut-shaped' spots. We have studied the influence of Pluronic F127 (an amphiphilic surfactant) on the functionality of inkjet-printed primary antibody molecules and on the final assay result by performing a one-step antibody binding assay in the nitrocellulose substrate. The primary antibody was printed with and without Pluronic, followed by the addition of double-labelled amplicons as antigen molecules and a fluorophore-labelled streptavidin as detection conjugate. The distribution of the fluorescence intensity down into the nitrocellulose substrate was investigated by confocal laser scanning microscopy in 'Z' stacking mode. Each horizontal slice was further analysed by applying a concentric ring format and the fluorescence intensity in each slice was represented in a colour-coded way. The mean and total fluorescence intensity of the antibody binding assay (fluorescent streptavidin) showed a peak at 0.2% (w/v) Pluronic F127. In addition, an improved spot morphology was observed also peaking at the same Pluronic concentration. Subsequently, we investigated the direct influence of Pluronic F127 on the location of the primary antibody molecules by labelling these molecules with the fluorophore Alexa-488. Our results show that upon increasing the concentration of Pluronic F127 in the printing buffer, the spot diameter increased and the number of primary antibody molecules bound in the spot area gradually decreased. This was confirmed by analysing the distribution of fluorescently labelled primary antibody molecules down into the membrane layers. We conclude that a particular ratio between primary antibody and Pluronic F127 molecules in combination with available substrate binding capacity results in an optimal orientation, that is Fab-UP, of the primary antibody molecules. Consequently, an increased number of antigen molecules (in our case the labelled amplicons) and of the fluorescent detection conjugate (streptavidin) will give an optimal signal. Moreover, distribution of the primary antibody molecules was more homogeneous at the optimal Pluronic F127 concentration, contributing to the better spot morphology observed.
Optimization of blue mussel (Mytilus edulis) seed culture using recirculation aquaculture systems
Blanco Garcia, A. ; Kamermans, P. - \ 2015
Aquaculture Research 46 (2015)4. - ISSN 1355-557X - p. 977 - 986.
toxicity - ammonia - nitrite - nitrate - growth - flow
By introducing recirculation aquaculture systems (RAS) in the nursery phase of the blue mussel (Mytilus edulis) (17–18 mm), we aimed at a similar growth and survival and a similar water quality compared to the commonly used flow-through systems (FTS). To calculate water flow and size of the biofilter, a series of experiments were done to determine clearance rate (9.26 mL min-1), pseudo faeces threshold (60 000 cells Pavlova lutheri mL-1), nitrogen production (0.00065 mg TAN h-1 ind-1 and 1.6 × 10-5 mg NO2–N h-1 ind-1) and oxygen consumption (0.03 ± 0.01 mg O2 h-1 ind-1). RAS showed no significant differences in water quality (0.06 mg TAN L-1; 7.7 mg O2 L-1) and growth performance of mussel seed specific growth rate (SGR = 5% day-1) after the experimental period of 4 weeks compared with FTS. The low water refreshment, 10% per day, as well as the constant chlorophyll concentrations (9.76 ± 1.06 µg L-1), suggests the potential of RAS as culture system for mussel seed.
Moisture transport in swelling media modelled with a Lattice Boltzmann scheme having a deforming lattice
Sman, R.G.M. van der - \ 2014
Journal of Food Engineering 124 (2014). - ISSN 0260-8774 - p. 54 - 63.
non-brownian suspensions - diffusion lattice - water transport - flow - simulations - profiles - kinetics - food - gels - validation
In this paper we present a novel numerical scheme for simulating the one-dimensional deformation of hydrogel material due to drying or rehydration. The scheme is based on the versatile Lattice Boltzmann method, which has been extended such that the computational grid (lattice) deforms due to shrinkage or swelling. This property of a deforming grid is new to the lattice Boltzmann method, and a detailed description of this new method is given. Via simulations we show that self-similar moisture concentration profiles occur in two periods in both drying and swelling processes: the penetration period and the regular regime. Given the property of self-similarity, we have been able to formulate a reduced-order model for the regular regime of swelling.
An operational, multi-scale, multi-model system for consensus-based, integrated water management and policy analysis: The Netherlands Hydrological Instrument
Lange, W.J. de; Prinsen, G.F. ; Hoogewoud, J.C. ; Veldhuizen, A.A. ; Verkaik, J. ; Essink, G.H.P.O. ; Walsum, P.E.V. van; Delsman, J.R. ; Hunink, J.C. ; Massop, H.T.L. ; Kroon, T. - \ 2014
Environmental Modelling & Software 59 (2014). - ISSN 1364-8152 - p. 98 - 108.
distributed modeling system - flow - simulation - interface - europeen - openmi - she
Water management in the Netherlands applies to a dense network of surface waters for discharge, storage and distribution, serving highly valuable land-use. National and regional water authorities develop long-term plans for sustainable water use and safety under changing climate conditions. The decisions about investments on adaptive measures are based on analysis supported by the Netherlands Hydrological Instrument NHI based on the best available data and state-of-the-art technology and developed through collaboration between national research institutes. The NHI consists of various physical models at appropriate temporal and spatial scales for all parts of the water system. Intelligent connectors provide transfer between different scales and fast computation, by coupling model codes at a deep level in software. A workflow and version management system guarantees consistency in the data, software, computations and results. The NHI is freely available to hydrologists via an open web interface that enables exchange of all data and tools. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (
Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly
Hooft, W.F. van; Greyling, B.J. ; Getz, W.M. ; Helden, P.D. van; Zwaan, B.J. ; Bastos, A.D.S. - \ 2014
PLoS One 9 (2014)11. - ISSN 1932-6203
heterozygosity-fitness correlations - bovine tuberculosis - syncerus-caffer - inbreeding depression - population-levels - complex traits - software - disease - wild - flow
Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important implications for our understanding not only of the evolutionary and ecological dynamics of sex-ratio distorters and suppressors, but also of the functioning of deleterious and sexually-antagonistic alleles, and their impact on population viability
The effect of spatial soil variation on the hydrology of a semi-arid Rocky Mountains catchment
Diek, S. ; Temme, A.J.A.M. ; Teuling, A.J. - \ 2014
Geoderma 235-236 (2014). - ISSN 0016-7061 - p. 113 - 126.
pedotransfer functions - front range - temporal stability - water-retention - colorado - sensitivity - parameters - dynamics - models - flow
Soil properties can exhibit strong spatial variability, even at the small catchment scale. However, the hydrological implications of actual variability remain widely unknown since the required data are not easily collected. This is especially true for observations of covariation between local soil properties and local hydrological ¿uxes (e.g. evapotranspiration and drainage) and/or vegetation. We studied the impact of soil variation on the discharge of an incised catchment in the Colorado Rocky Mountains. Soil variation was determined by ¿eld and laboratory work on 100 soil pro¿les in the catchment. Soils were found to have substantially variable properties but had on average sandy texture, weak structure and limited depth to bedrock. Observed soil properties were translated into hydraulic properties using pedotransfer functions and then used in a 1D hydrological model based on Richards' equation to quantify the effect on hydrological ¿uxes. Hydrological model results indicated that the ef-fect of soil variation on the variation of hydrological model outputs was larger than the effects of variation in to-pographic in¿uenced parameters. Dependent on the hydrological model output, variation in soil hydraulic parameters is more important than the variation in soil depth and vice versa. Spatial variation of hydrological characteristics is underestimated when spatial variation of the soil information is unknown. As a consequence, knowledge on the spatial variation of input data is important for policy and water-management in order to in-clude spatial variation in the prediction of dry season stream¿ow in semi-arid catchments.
Phase segregation through transient network formation in a binary particle suspension in simple shear: Application to dough
Opheusden, J.H.J. van; Molenaar, J. - \ 2014
Physical Review. E, Statistical nonlinear, and soft matter physics 89 (2014). - ISSN 1539-3755 - 8 p.
brownian dynamics simulations - wheat doughs - flow - microstructure - gluten - deformation - separation - migration
In this paper we describe a viscoelastic type of phase separation in a simulated binary fluid with a sticky and an inert component, without any external gradients. Phase segregation under simple shear occurs due to transient network formation of the sticky component, expelling the inert particles from the network. When model parameters are adjusted to reduce network formation and rearrangement, the segregation effect is significantly smaller or absent. The behavior is independent of shear rate; segregation increases mainly with shear strain. The model is applied to wheat dough. Recent experiments have shown that prolonged shear flow of wheat dough can even give macroscopic segregation.
Deterministic ratchets for larger-scale separation of suspensions
Lubbersen, Y.S. - \ 2014
University. Promotor(en): Remko Boom, co-promotor(en): Maarten Schutyser. - Wageningen : Wageningen University - ISBN 9789461739155 - 136
suspensies - scheiding - scheidingstechnologie - stroming - microfluidics - suspensions - separation - separation technology - flow

Solid-liquid separation is a very common process operation in the chemical and food industry. Current technologies, such as membrane separation, consume large amounts of energy and water and often suffer from fouling issues. A novel, promising separation principle was identified for possible large scale application. This principle has been studied in microfluidic systems and employs so-called deterministic ratchets. Ratchet separationrelies on particle interactions with a series of obstacle arrays positioned in a flow field. Particles above a critical size are forced from their streamlines and migrate into another direction than the main flow direction. The objective of this thesis was to understand the mechanisms relevant for suspension separation with deterministic ratchets and to develop guidelines for the design of this technology at a larger scale. An up-scaled device was developed to investigate separation of model suspensions with larger particles (~101 - ~102 µm). Experiments at increasing volume particle fractions yielded final particle concentrations up to 12 v/v% without particle accumulation. The separation efficiency was discovered strongly influenced by the hydrodynamic conditions. High speed camera images and fluid flow simulations provided insight that a vortex pair developed behind obstacles and that inertial forces improved displacement behavior of particles. Different designs suitable for larger-scale application were evaluated. A mirrored (axisymmetric) obstacle array was found more effective in displacement of particles. Different designs were identified for cleaning as well as concentration applications. Finally, a simple, but effective sparse ratchet design is proposed by replacing full obstacle arrays by selected single lines of obstacles. The degree of sparseness is found a design parameter for accommodating differences in concentrations. Although the application of the principle is still challenging for smaller particle diameters (~100 - ~101 µm), this study shows that the principle of deterministic ratchet separation holds potential for larger-scale separation of suspensions.

Multinuclear nanoliter one-dimensional and two-dimensional NMR spectroscopy with a single non-resonant microcoil
Fratila, R.M. ; Gomez, M.V. ; Sykora, S. ; Velders, A.H. - \ 2014
Nature Communications 5 (2014). - ISSN 2041-1723
nuclear-magnetic-resonance - liquid-state nmr - to-noise ratio - multidimensional nmr - probe - f-19 - design - chip - flow - h-1-nmr
Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications. Here we show that a non-resonant planar transceiver microcoil integrated in a microfluidic chip (detection volume 25¿nl) can detect different nuclides in the full broad-band range of Larmor frequencies (at 9.4¿T from 61 to 400¿MHz). Routine one-dimensional (1D) and two-dimensional (2D), homo- and heteronuclear experiments can be carried out using the broad-band coil set-up. Noteworthy, heteronuclear 2D experiments can be performed in a straightforward manner on virtually any combination of nuclides (from classical 1H–13C to more exotic combinations like 19F–31P) both in coupled and decoupled mode. Importantly, the concept of a non-resonant system provides magnetic field-independent NMR probes; moreover, the small-volume alleviates problems related to field inhomogeneity, making the broad-band coil an attractive option for, for example, portable and table-top NMR systems
Improved management of winter operations to limit subsurface contamination with degradable deicing chemicals in cold regions
French, H.K. ; Zee, S.E.A.T.M. van der - \ 2014
Environmental Science and Pollution Research 21 (2014)15. - ISSN 0944-1344 - p. 8897 - 8913.
penetrating radar data - solute transport - spatial variability - soil heterogeneity - dc resistivity - porous-media - water - snow - flow - polarization
This paper gives an overview of management considerations required for better control of deicing chemicals in the unsaturated zone at sites with winter maintenance operations in cold regions. Degradable organic deicing chemicals are the main focus. The importance of the heterogeneity of both the infiltration process, due to frozen ground and snow melt including the contact between the melting snow cover and the soil, and unsaturated flow is emphasised. In this paper, the applicability of geophysical methods for characterising soil heterogeneity is considered, aimed at modelling and monitoring changes in contamination. To deal with heterogeneity, a stochastic modelling framework may be appropriate, emphasizing the more robust spatial and temporal moments. Examples of a combination of different field techniques for measuring subsoil properties and monitoring contaminants and integration through transport modelling are provided by the SoilCAM project and previous work. Commonly, the results of flow and contaminant fate modelling are quite detailed and complex and require post-processing before communication and advising stakeholders. The managers’ perspectives with respect to monitoring strategies and challenges still unresolved have been analysed with basis in experience with research collaboration with one of the case study sites, Oslo airport, Gardermoen, Norway. Both scientific challenges of monitoring subsoil contaminants in cold regions and the effective interaction between investigators and management are illustrated.
Segregation of Granular Particles by Mass, Radius, and Density in a Horizontal Rotating Drum
Arntz, M.M.H.D. ; Beeftink, H.H. ; Otter, W.K. den; Briels, W.J. ; Boom, R.M. - \ 2014
AIChE Journal 60 (2014)1. - ISSN 0001-1541 - p. 50 - 59.
size segregation - particulate systems - flow - simulation - cylinders - mixtures - dynamics - solids - behavior - motion
The impact of particle properties on segregation and mixing of bidisperse granular beds in a rotating horizontal drum have been studied by discrete element method (DEM) simulations. Bidispersities in radius, density, and mass have pronounced influences on the stationary mixing pattern, although they hardly affect the granules’ flow regime. At 50% fill level, all beds mix well for a Froude number of 0.56, corresponding to a flow regime intermediate to cascading and cataracting, while segregation occurs both at lower (rolling and cascading regime) and higher (cataracting/centrifuging regime) Froude numbers. These observations are explained qualitatively by noticing that the angular drum velocity dictates the flow regime, which in turn determines the effectiveness and direction of four competing (de)mixing mechanisms: random collisions, buoyancy, percolation, and inertia. A further dozen particle properties have been varied, including the friction coefficients and elastic modulus, but these proved inconsequential to the steady-state degree of mixing.
Traffic Responsive Control of Intersections with Predicted Arrival Times: A Markovian Approach
Haijema, R. ; Hendrix, E.M.T. - \ 2014
Computer Aided Civil and Infrastructure Engineering 29 (2014)2. - ISSN 1093-9687 - p. 123 - 139.
signalized intersections - optimization - system - video - model - flow
The dynamic adaptive control of traffic lights can be formulated as a Markov decision problem (MDP). This framework is hardly used, as solving an MDP can be very time-consuming and is only possible for simple infrastructures with a small number of traffic flows. Nevertheless, we show that the MDP framework can be used to construct control policies that approximately minimize the long-run average waiting time at intersections. The MDP-based approach is fast and thus allows real-time use of actual information on traffic conditions, like queue lengths and the arrival times of near-future arrivals. Simulation of an isolated intersection as well as a small network shows that the new policies with arrival information improve pretimed as well as exhaustive control. The new control policies and underlying algorithms scale up well to control networks.
The impact of aquifer heterogeneity on the performance of aquifer thermal energy storage
Sommer, W.T. ; Valstar, J.R. ; Gaans, P. van; Grotenhuis, J.T.C. ; Rijnaarts, H. - \ 2013
Water Resources Research 49 (2013)12. - ISSN 0043-1397 - p. 8128 - 8138.
heat-transport - solute transport - porous-media - hydraulic conductivity - geothermal systems - field - simulation - flow - macrodispersion - dispersion
Heterogeneity in hydraulic properties of the subsurface is not accounted for in current design calculations of aquifer thermal energy storage (ATES). However, the subsurface is heterogeneous and thus affects the heat distribution around ATES wells. In this paper, the influence of heterogeneity on the performance of a doublet well system is quantified using stochastic heat transport modeling. The results show that on average, thermal recovery decreases with increasing heterogeneity, expressed as the lognormal standard deviation of the hydraulic conductivity field around the doublet. Furthermore, heterogeneity at the scale of a doublet ATES system introduces an uncertainty in the amount of expected thermal interference between the warm and cold storage. This results in an uncertainty in thermal recovery that also increases with heterogeneity and decreases with increasing distance between ATES wells. The uncertainty in thermal balance due to heterogeneity can reach values near 50 percent points in case of regional groundwater flow in excess of 200 m/yr. To account for heterogeneity whilst using homogeneous models, an attempt was made to express the effect of heterogeneity by an apparent macrodispersivity. As expected, apparent macrodispersivity increases with increasing heterogeneity. However, it also depends on well-to-well distance and regional groundwater velocity. Again, the uncertainty in thermal recovery is reflected in a range in the apparent macrodispersivity values. Considering the increasing density of ATES systems, we conclude that thermal interference limits the number of ATES systems that can be implemented in a specific area, and the uncertainty in the hydraulic conductivity field related to heterogeneity should be accounted for when optimizing well-to-well distances.
Alternating electric fields combined with activated carbon for disinfection of Gram negative and Gram positive bacteria in fluidized bed electrode system
Racyte, J. ; Bernard, S. ; Paulitsch-Fuchs, A.H. ; Yntema, D.R. ; Bruning, H. ; Rijnaarts, H.H.M. - \ 2013
Water Research 47 (2013)16. - ISSN 0043-1354 - p. 6395 - 6405.
water treatment plants - urban waste-water - antibiotic-resistance - antimicrobial activity - escherichia-coli - inactivation - particles - cells - flow - viability
Strong electric fields for disinfection of wastewaters have been employed already for several decades. An innovative approach combining low strength (7 V/cm) alternating electric fields with a granular activated carbon fluidized bed electrode (FBE) for disinfection was presented recently. For disinfection performance of FBE several pure microbial cultures were tested: Bacillus subtilis, Bacillus subtilis subsp. subtilis, Enterococcus faecalis as representatives from Gram positive bacteria and Erwinia carotovora, Pseudomonas luteola, Pseudomonas fluorescens and Escherichia coli YMc10 as representatives from Gram negative bacteria. The alternating electric field amplitude and shape were kept constant. Only the effect of alternating electric field frequency on disinfection performance was investigated. From the bacteria tested, the Gram negative strains were more susceptible and the Gram positive microorganisms were more resistant to FBE disinfection. The collected data indicate that the efficiency of disinfection is frequency and strain dependent. During 6 h of disinfection, the decrease above 2 Log units was achieved with P. luteola and E. coli at 10 kHz and at dual frequency shift keying (FSK) modulated signal with frequencies of 10 kHz and 140 kHz. FBE technology appears to offer a new way for selective bacterial disinfection, however further optimizations are needed on treatment duration, and energy input, to improve effectiveness.
Distribution of biomolecules in porous nitrocellulose membrane pads using confocal laser scanning microscopy and high-speed cameras
Mujawar, L.H. ; Maan, A.A. ; Khan, M.K.I. ; Norde, W. ; Amerongen, A. van - \ 2013
Analytical Chemistry 85 (2013)7. - ISSN 0003-2700 - p. 3723 - 3729.
printed protein molecules - antibody microarrays - spot morphology - liquid-drops - additives - surfaces - flow
The main focus of our research was to study the distribution of inkjet printed biomolecules in porous nitrocellulose membrane pads of different brands. We produced microarrays of fluorophore-labeled IgG and bovine serum albumin (BSA) on FAST, Unisart, and Oncyte-Avid slides and compared the spot morphology of the inkjet printed biomolecules. The distribution of these biomolecules within the spot embedded in the nitrocellulose membrane was analyzed by confocal laser scanning microscopy in the “Z” stack mode. By applying a “concentric ring” format, the distribution profile of the fluorescence intensity in each horizontal slice was measured and represented in a graphical color-coded way. Furthermore, a one-step diagnostic antibody assay was performed with a primary antibody, double-labeled amplicons, and fluorophore-labeled streptavidin in order to study the functionality and distribution of the immune complex in the nitrocellulose membrane slides. Under the conditions applied, the spot morphology and distribution of the primary labeled biomolecules was nonhomogenous and doughnut-like on the FAST and Unisart nitrocellulose slides, whereas a better spot morphology with more homogeneously distributed biomolecules was observed on the Oncyte-Avid slide. Similar morphologies and distribution patterns were observed when the diagnostic one-step nucleic acid microarray immunoassay was performed on these nitrocellulose slides. We also investigated possible reasons for the differences in the observed spot morphology by monitoring the dynamic behavior of a liquid droplet on and in these nitrocellulose slides. Using high speed cameras, we analyzed the wettability and fluid flow dynamics of a droplet on the various nitrocellulose substrates. The spreading of the liquid droplet was comparable for the FAST and Unisart slides but different, i.e., slower, for the Oncyte-Avid slide. The results of the spreading of the droplet and the penetration behavior of the liquid in the nitrocellulose membrane may (partly) explain the distribution of the biomolecules in the different slides. To our knowledge, this is the first time that fluid dynamics in diagnostic membranes have been analyzed by the use of high-speed cameras.
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