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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    Layer breeding programmes in changing production environments : a historic perspective
    Leenstra, F. ; Napel, J. Ten; Visscher, J. ; Sambeek, F. Van - \ 2016
    Worlds Poultry Science Journal 72 (2016)1. - ISSN 0043-9339 - p. 21 - 36.
    breeding - cages - eggs - free range - genetics - husbandry - layers - welfare

    The housing and management of laying hens and their productivity has gone through enormous developments in the last century. Housing has changed from free-range systems, via battery cages to a variety of loose housing and different types of battery cages, and back to outdoor access systems. Although battery cages are still the main system used worldwide, the number of hens housed in aviaries and free-range systems has increased in Europe, Australasia and some parts of the USA, but aviaries and free-range systems are still considered a niche sector compared to caged housing. The following paper reviews how breeding and selection have responded to changes in housing and management and whether different types of housing require different breeding programmes and, more specifically, whether a dedicated breeding programme should be developed for aviary and free-range systems. From the available literature it was concluded that broadening the selection goal in existing lines is the best option for breeding programmes to provide genotypes that are suitable for a range of housing systems.

    Comparing foam and interfacial properties of similarly charged protein–surfactant mixtures
    Lech, F.J. ; Meinders, M.B.J. ; Wierenga, P.A. ; Gruppen, H. - \ 2015
    Colloids and Surfaces. A: Physicochemical and Engineering Aspects 473 (2015). - ISSN 0927-7757 - p. 18 - 23.
    sodium dodecyl-sulfate - bovine serum-albumin - air-water interfaces - beta-lactoglobulin - titration calorimetry - binding - sds - adsorption - rheology - layers
    The foam stability of protein–surfactant mixtures strongly depends on the charge of the protein and the surfactant, as well as on their mixing ratio. Depending on the conditions, the mixtures will contain free proteins, free surfactants and/or protein–surfactant complexes. To be able to compare different protein–surfactant mixtures, generic knowledge about the occurrence of each of these states and their relative contribution to foam stability is essential. In this work, the foam stability and interfacial properties of bovine serum albumin (BSA) mixed with sodium dodecyl sulphate (SDS) as well the binding of SDS to BSA as are studied at different molar ratios (MR). A comparison is made with ß-lactoglobulin (BLG) mixed with SDS. Both proteins and SDS are negatively charged at pH 7. The foam stability in the presence of small amounts (up to MR 1) of SDS is half the value of the pure protein solutions. The foam stability for both protein surfactant mixtures reaches a minimum at MR 20. A further increase of the MR leads to an increase of foam stability. The foam stability of BLG–SDS at MR >20 follows the foam stability of pure SDS solutions at equivalent concentrations, while BSA–SDS mixtures have an offset and begin to increase from MR >50. This behaviour was also reflected in the surface pressure and complex dilatational elastic moduli, and could be linked to the binding of the surfactant to the proteins. Both proteins bind SDS at high and low affinity binding sites. BSA's high affinity binding sites have a binding stoichiometry of 5.5 molSDS/molprotein, and BLG's high affinity binding site has a stoichiometry of 0.8 molSDS/molprotein (determined by isothermal titration calorimetry). Binding to the low affinity binding sites, occurs with a binding ratio, leading to an accumulation of free surfactants. While the basic mechanisms underlying the foam properties of mixed systems are not explained in detail by this approach, the foam stability plots of both protein surfactant mixtures could be superimposed using the concentration of free SDS.
    Langmuir monolayers of non-ionic polymers: Equilibrium of metastability? Case study of PEO and its PPO-PEO diblock copolymers
    Deschenes, L. ; Saint-Germain, F. ; Lyklema, J. - \ 2015
    Journal of Colloid and Interface Science 449 (2015). - ISSN 0021-9797 - p. 494 - 505.
    air-water-interface - poly(ethylene oxide) monolayers - interacting chain molecules - air/water interface - scaling description - statistical-theory - block-copolymers - liquid-films - surface - layers
    Stability and reorganization in Langmuir films of PEO in PEO homopolymers and PPO–PEO block copolymers were investigated using film balance measurements. The apparent fractional losses of EO segments transferred into the subphase resulting from successive compression–expansion cycles have been estimated. The apparent loss is mainly Gmax, Mn and time-dependent. At surface concentrations G ¿ 0.32 mg/m2, PEO films are in equilibrium. For 0.32 ¿ G ¿ 0.7 mg/m2, the losses remain modest. Further compression leads to densification of the monolayer, requiring the interplay of thermodynamics and kinetic factors In the plateau regime, the loss is higher and constant for 1 ¿ Gmax ¿ 2 mg/m2 upon maintaining the achieved surface area for 15 min. Similar losses were obtained for PEO homopolymers of high Mn and PPO353–PEO2295. It suggests that the PEO remains anchored in a metastable state at the air–water interface at surface concentration well above the onset of the plateau. Additional losses are incurred for PEO homopolymers for monolayers kept compressed in the plateau for 2 h. For the interpretation of these phenomena a combination of elements from self-consistent field theory and scaling is desirable with as a trend an increasing contribution of the latter with increasing surface concentration.
    Covalent Attachment of 1-Alkenes to Oxidized Platinum Surfaces
    Alonso Carnicero, J.M. ; Fabre, B. ; Trilling, A.K. ; Scheres, L.M.W. ; Franssen, M.C.R. ; Zuilhof, H. - \ 2015
    Langmuir 31 (2015)9. - ISSN 0743-7463 - p. 2714 - 2721.
    self-assembled monolayers - organic monolayers - gold - alkanethiols - functionalization - spectroscopy - activation - alkenes - layers - films
    We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The grafted alkyl layers display a hydrolytic stability that is comparable to that of alkyl thiols on Au. PtOx-alkene attachment is compatible with terminal ester moieties enabling further anchoring of functional groups, such as redox-active ferrocene, and thus has great potential to extend monolayer chemistry on noble metals.
    Competitive adsorption of the protein hydrophobin and an ionic surfactant: Parallel vs sequential adsorption and dilatational rheology
    Stanimirova, R. ; Marinova, K.G. ; Danov, K.D. ; Kralchevsky, P.A. ; Basheva, E.S. ; Stoyanov, S.D. ; Pelan, E.G. - \ 2014
    Colloids and Surfaces. A: Physicochemical and Engineering Aspects 457 (2014). - ISSN 0927-7757 - p. 307 - 317.
    air-water-interface - sodium dodecyl-sulfate - beta-casein - air/water interface - fluid interfaces - layers - hfbii - elasticity - stability - mixtures
    The competitive adsorption of the protein HFBII hydrophobin and the anionic surfactant sodium dodecyl sulfate (SDS) is investigated in experiments on parallel and sequential adsorption of the two components. The dynamic surface tension and the surface storage and loss dilatational moduli are determined by the oscillating bubble method. A new procedure for data processing is proposed, which allows one to collect data from many different runs on a single master curve and to determine more accurately the dependence of the dilatational elasticity on the surface pressure. Experiments on sequential adsorption are performed by exchanging the HFBII solution around the bubble with an SDS solution. Experiments with separate thin foam films bring additional information on the effect of added SDS. The results indicate that if HFBII has first adsorbed at the air/water interface, it cannot be displaced by SDS at any concentration, both below and above the critical micellization concentration (CMC). In the case of parallel adsorption, there is a considerable difference between the cases below and above the CMC. In the former case, SDS cannot prevent the adsorption of HFBII at the interface, whereas in the latter case adsorption of HFBII is absent, which can be explained with hydrophilization of the hydrophobin aggregates by the SDS in the bulk. The surface dilatational elasticity of the HFBII adsorption layers markedly decreases in the presence of SDS, but it recovers after washing out the SDS. With respect to their dilatational rheology, the investigated HFBII layers exhibit purely elastic behavior, the effect of dilatational viscosity being negligible. As a function of surface tension, the elasticity of the investigated interfacial layers exhibits a high maximum, which could be explained with the occurrence of a phase transition in the protein adsorption layer.
    Path planning for autonomous collection of eggs on floors
    Vroegindeweij, B.A. ; Willigenburg, L.G. van; Groot Koerkamp, P.W.G. ; Henten, E.J. van - \ 2014
    Biosystems Engineering 121 (2014). - ISSN 1537-5110 - p. 186 - 199.
    laying hens - prelaying behavior - layers
    A problem in loose housing systems for laying hens is the laying of eggs on the floor; these eggs need manual collection. This job is heavy and time-consuming and automated collection is desired. For collection using a robot, a collection path is required. A novel path planning algorithm is introduced for non-uniform repetitive area coverage (NURAC) paths and evaluated based on information about floor egg distribution probability. Firstly, a spatial map was developed that describes the potential for floor eggs at each location in a poultry house. Next, paths for floor egg collection are planned with a dynamic programming approach that covers the house floor area and frequently revisits locations with a high potential on floor eggs. These paths are compared with the paths used for floor egg collection by a farmer and evaluated with help of a simulated set of floor eggs. With respect to the average time eggs are present on the floor, paths planned for a robot are compared to two collection rounds of a farmer. With respect to the structure of the path and the number of visits to locations with a high potential, the robot paths outperform the farmer. Although optimality of the path is not guaranteed, the presented results are promising for the use of a robot to collect floor eggs, and will result in a reduction of the demand for manual labour. Extending the floor egg model with feedback information could further improve the results.
    On the collapse transition of a polymer brush: the case of lateral mobility
    Leermakers, F.A.M. ; Egorov, S.A. - \ 2013
    Soft Matter 9 (2013)12. - ISSN 1744-683X - p. 3341 - 3348.
    terminally attached chains - consistent field-theory - poor solvents - molecular-dynamics - tethered polymers - model - adsorption - interface - surfaces - layers
    We consider a polymer brush composed of end-grafted polymer chains. Classical theory advocates that a worsening of the solvent quality results in a smooth decrease of the brush height from a swollen to a dense brush. We report that a homogeneous brush under poor solvent conditions can have a negative surface pressure, indicating an instability in favour of lateral segregation. Also by using a two-gradient version of the self-consistent field (SCF) theory we show that, in contradiction to the classical result, but in line with the negative pressure, the collapse transition for laterally mobile chains has a first-order character, exemplified by the presence of a compact brush that coexists with a dilute gas of end-grafted chains. The dense brush assumes a pancake shape wherein the chains balance the stretching entropy against surface energies. The height of the pancake scales sub-linearly with the chain length because the local grafting density decreases with increasing chain length. In analogy with wetting studies we discuss how the spreading parameter has an influence on the pancake structure. Accordingly, the height increases with worsening of the solvent quality and decreases with increased affinity for the substrate. The two-phase state is expected in many practical situations
    Non-linear surface dilatational rheology as a tool for understanding microstructures of air/water interfaces stabilized by oligofructose fatty acid esters
    Kempen, S.E.H.J. van; Schols, H.A. ; Linden, E. van der; Sagis, L.M.C. - \ 2013
    Soft Matter 9 (2013)40. - ISSN 1744-683X - p. 9579 - 9592.
    air-water-interface - monolayers - layers - shear - viscoelasticity - adsorption - systems - foams
    In this paper, the rheological response of air/water interfaces, stabilized by various oligofructose fatty acid esters, to oscillatory dilatational deformations was studied and compared to the response of interfaces stabilized by sucrose esters. We have followed a traditional approach to surface rheology, where the development of the modulus as a function of time is studied as well as the frequency dependence of the modulus. We also adopted a different approach where we investigate in detail the amplitude dependence of the modulus. Finally, we studied the temperature dependence. We show that for an accurate characterization of the dilatational rheology of fluid-fluid interfaces with a complex microstructure, a protocol should be used that not only involves variations of surface pressure, frequency, and temperature, but also establishes amplitude dependence. We show that Lissajous plots of surface pressure versus deformation can be useful tools to help interpret surface dilatational behavior in terms of interfacial microstructure. The rheological response of interfaces stabilized by oligofructose esters differed significantly from the response of those stabilized by sucrose esters. Sucrose esters behaved like typical low molecular weight surfactants, and gave interfaces with relatively low moduli, a frequency scaling of the dilatational modulus with an exponent close to 0.5, and displayed no asymmetries in Lissajous plots. In contrast, the oligofructose esters gave, depending on the fatty acid tail, relatively high moduli, almost independent of frequency. Significant asymmetries were observed in the Lissajous plots, with strain hardening during compression and strain softening during extension. Our results suggest that the unusual rheological properties of interfaces stabilized by oligofructose esters may be the result of the formation of a two-dimensional soft glass phase by the oligofructose part of the ester.
    Total loss and distribution of nitrogen and phosphorus in the outdoor run of organic laying hens
    Dekker, S.E.M. ; Aarnink, A. ; Boer, I.J.M. de; Groot Koerkamp, P.W.G. - \ 2012
    British Poultry Science 53 (2012)6. - ISSN 0007-1668 - p. 731 - 740.
    egg-production systems - range - productivity - welfare - layers - house - area
    1. The objective of this study was to determine the level and variation of the total mass, and load of nitrogen (N) and phosphorus (P) excreted into the outdoor run of organic egg production systems. 2. Three egg production farms with an aviary system and an outdoor run were selected for this study. Four measurements, one per season, were executed on each farm. 3. Mean content of N and P of a manure dropping was 14·0¿g N¿kg-1 and 3·12¿g P¿kg-1, mean mass of a dropping was 6·36¿g and mean dry matter content of a dropping was 238¿g¿kg-1. Mean rate of excretion in the outdoor run was 2·99 droppings per hen per h. Mean percentage of hens outside during the time the outdoor run could be accessed was lowest on Farm 1 (1·7%), highest on Farm 2 (16·0%), and intermediate on Farm 3 (7·1%). 4. On all farms an exponential decrease of the number of hens and of the load of N and P with increasing distance from the hen house was found. Load of N exceeded the fertilisation standard (of 170¿kg¿ha-1¿y-1) in the region at a 0 to 19¿m distance from the hen house on Farm 1, 0 to 146¿m on Farm 2 and 0 to 52¿m on Farm 3. 5. It is concluded that the husbandry system should be redesigned to solve the problem of overloading, unwanted loss of N and P to the environment and loss of N and P from the organic production cycle.
    The effect of particle size of wheat bran fractions on bread quality – Evidence for fibre–protein interactions
    Noort, M.W.J. ; Haaster, D.J. van; Hemery, Y. ; Schols, H.A. ; Hamer, R.J. - \ 2010
    Journal of Cereal Science 52 (2010)1. - ISSN 0733-5210 - p. 59 - 64.
    water unextractable solids - loaf volume - phenolic-acid - brown bread - breadmaking - pentosans - phytate - layers - grain
    The nature of the adverse effects of wheat bran fractions on bread-making quality was studied. Two fractions of bran, representing different tissue layers and having different compositions, were used. The particle size of the bran fractions was varied by various milling techniques. All fractions were added to white flour and water addition was adjusted to obtain dough with a constant consistency. Both dough-mixing properties and bread-making quality were affected by the addition of bran. The negative influence was enhanced when bran particle size was reduced. The effects on bread quality are strongly correlated to negative effects of bran on gluten network formation. The results show that fibre–gluten interactions are the main cause for the negative effects of fibres, rather than dilution of gluten, piercing of gas cells or particles disturbing the gluten network. Two possible explanations for the enhancement of the adverse effects when reducing the particle size of bran fractions are discussed: 1) increased interaction surface 2) liberation of reactive components due to cell breakage.
    Charge-driven and reversible assembly of ultra-dense polymer brushers: Formation and antifouling properties of a zipper brush
    Vos, W.M. de; Meijer, G. ; Keizer, A. de; Cohen Stuart, M.A. ; Kleijn, J.M. - \ 2010
    Soft Matter 6 (2010)11. - ISSN 1744-683X - p. 2499 - 2507.
    polyelectrolyte brushes - polystyrene surfaces - poly(ethylene oxide) - poly(acrylic acid) - core micelles - adsorption - silica - layers - scattering - film
    We investigated a new type of polymer brushes: the zipper brush. By adsorbing a diblock-copolymer with one charged block and one neutral block to an oppositely charged polyelectrolyte brush, a neutral polymer brush is formed on top of an almost neutral complex layer of polyelectrolytes. This neutral brush can be adsorbed in minutes and desorbed in seconds to restore the original polyelectrolyte brush. The zipper brush can be used, for example, as an antifouling layer to prevent protein adsorption. These characteristics are shown by fixed-angle optical reflectometry for the system of poly(N-methyl-2-vinyl pyridinium)-block-poly(ethylene oxide) (P2MVP-PEO) adsorbed to a poly(acrylic acid) (PAA) brush. After the diblock-copolymer has adsorbed (at pH 6), the charges of the PAA brush are almost completely compensated by the charges of the P2MVP block. The grafting density of the formed neutral brush can be controlled by the chain length and grafting density of the PAA brush, and by the chain length of P2MVP block. As the P2MVP blocks used in this study are much smaller than the PAA chains in the brush, the grafting density of the PEO brushes are found to be a multiplication of that of the PAA brush, and much higher grafting densities (up to 1.59 chains per nm2) can be obtained than previously reported for polymer brushes prepared by adsorption. At low pH, when the PAA is uncharged, only a few mg m-2 adsorb probably because of hydrogen bonding between uncharged PAA and PEO. As the pH increases the PAA becomes more charged and the adsorbed amount of diblock-copolymer increases strongly until pH 6 and then levels off between pH 6 and pH 10. At pH 6 and 10 high salt concentrations (above 250 mM) are needed to significantly reduce the adsorbed amount. The antifouling properties of the zipper brush were tested by exposing the brush to a number of different protein solutions. For the proteins lysozyme, fibrinogen, bovine serum albumin, and b-lactoglobuline the zipper brush completely prevented any adsorption, for cytochrome C a small amount of adsorption was observed
    Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics
    Sagis, L.M.C. - \ 2010
    Applied Rheology 20 (2010)2. - ISSN 1430-6395 - p. 24380 - 24380.
    extended irreversible thermodynamics - general formalism - surface rheology - dynamics - microbubbles - deformation - equilibrium - equation - systems - layers
    Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines in the areas of physics, chemistry, engineering, biology, and medicine. Currently used descriptions of surface rheology have a number of limitations, and in particular are hard to generalize to the large deformation regime. Data are often analyzed with constitutive equations based on straightforward generalizations of models developed for describing bulk phase rheology. Since the latter are in general designed to describe incompressible materials, they are not guaranteed to describe highly compressible interfaces correctly. Here we discuss a unified approach to surface rheology based on nonequilibrium thermodynamics (NET) that provides a consistent set of balance and constitutive equations for the unambiguous determination of surface rheological parameters, both near and far beyond equilibrium. A closer integration of experimental surface rheology and multiphase nonequilibrium thermodynamics would clearly be beneficial for both disciplines
    Bacteriological contamination, dirt, and cracks of eggshells in furnished cages and noncage systems for laying hens: An international on-farm comparison
    Reu, K. de; Rodenburg, T.B. ; Messens, W. ; Heyndrickx, M. ; Tuyttens, F. ; Sonck, B. ; Zoons, J. ; Herman, L. - \ 2009
    Poultry Science 88 (2009)11. - ISSN 0032-5791 - p. 2442 - 2448.
    housing systems - conventional cages - egg quality - health - performance - design - hybrid - layers - flora
    For laying hens, the effects of housing system on bacterial eggshell contamination and eggshell quality is almost exclusively studied in experimental hen houses. The aim of this study was to compare eggshell hygiene and quality under commercial conditions. Six flocks of laying hens in furnished cages and 7 flocks in noncage systems were visited when hens were about 60 wk of age. Farms from Belgium, the Netherlands, and Germany were included in the study. The following parameters were determined on eggs sampled at the egg belts: 1) bacterial eggshell contamination, as expressed by total count of aerobic bacteria and number of Enterobacteriaceae; 2) proportion of dirty eggs; and 3) proportion of cracked eggs and eggs with microcracks. Considerable within-flock differences were found in eggshell contamination with total count of aerobic bacteria, both for furnished cages (P 0.001, range 4.24 to 5.22 log cfu/eggshell) and noncage systems (P 0.001, range 4.35 to 5.51 log cfu/eggshell). On average, lower levels of contamination with total count of aerobic bacteria (4.75 vs. 4.98 log cfu/eggshell; P 0.001) were found on eggshells from furnished cages compared with noncage systems. Concerning Enterobacteriaceae, no significant difference in average eggshell contamination between both systems could be shown. The total percentage of cracked eggs was higher (P 0.01) in furnished cages (7.8%) compared with noncage systems (4.1%). This was, however, due to the high percentage of cracked eggs (24%) observed on one of the furnished cage farms. We conclude that bacteriological eggshell contamination and percentage of cracked eggs differed substantially between individual farms using the same housing system. This may also explain some discrepancies between the findings of the present study versus some findings of previous experimental studies or studies on a small number of farms. Although statistically significant, the average differences in bacteriological contamination of nest eggs between both housing systems have limited microbiological relevancy
    Interaction of particles with a polydisperse brush: A self-consistent-field analysis
    Vos, W.M. de; Leermakers, F.A.M. ; Keizer, A. de; Kleijn, J.M. ; Cohen Stuart, M.A. - \ 2009
    Macromolecules 42 (2009)15. - ISSN 0024-9297 - p. 5881 - 5891.
    protein adsorption - polymer brushes - chains - layers
    Two complementary theoretical approaches are used to study the effect of polydispersity oil (anti)fouling properties of a neutral polymer brush. Polydispersity is described using the Schulz-Zimm distribution. The Scheutjens-Fleer self-consistent-field (SF-SCF) formalism is used to consider the interaction between a single particle and a polydisperse brush with grafting density sigma, focusing on the influence of the polydispersity index. The larger the polydispersity, the easier it is for a small particle (with radius R similar to 1/(2 root sigma)) to penetrate the brush. Hence, the monodisperse brush is better suited to protect a surface against the adsorption of small particles compared to a corresponding polydisperse brush. The brush grafting density, however, remains the most important parameter for timing the brush antifouling properties against small particles. For large particles (modeled as a flat wall.) an opposite effect of polydispersity is found: it is harder to compress a polydisperse brush than it corresponding monodisperse brush, and thus a polydisperse brush is better suited to protect the Surface against adsorption of large particles. A less-detailed approach, based on the stacking of Alexander-de Gennes boxes, is used to study the adsorption of many particles into a polydisperse brush. Consistent with the single-particle data generated by the SF-SCF theory, for weak attraction between the particles and the brush the absolute adsorbed amount remains low but increases strongly as a function of polydispersity (from M-w/M-n = 1-2 by a factor of 2-4). Obviously, at higher attraction between the particles and the brush the adsorption increases, but a less strong dependence on the polydispersity index is observed.
    New ends to the tale of tails: adsorption of comb polymers and the effect on colloid stability
    Charlaganov, M. ; Kosovan, P. ; Leermakers, F.A.M. - \ 2009
    Soft Matter 5 (2009)7. - ISSN 1744-683X - p. 1448 - 1459.
    interacting chain molecules - statistical-theory - field theory - interfaces - surface - layers - macromolecules - weight
    In this paper we consider the classical problem of homopolymer adsorption at the solid–liquid interface and discuss its implications for colloidal stability. More specifically, our focus is on comb-like homopolymers in the strong adsorption limit. A self-consistent field analysis shows that for relatively long side chains but still much longer backbones, the adsorbed layer is dominated by the side chains near the surface, whereas at larger distances the layer has features that belong to the backbone. As a rule, homopolymer adsorption promotes flocculation of colloids. This is attributed to the long polymer chains that form bridges between the colloidal particles. However, the free ends of the chains do not participate in the bridging and thus contribute with a small repulsive term to the mainly attractive pair interaction. For comb polymers, the free ends of the side chains amplify the repulsion dramatically. As a result, in contrast to linear adsorbed homopolymers, comb polymers typically prevent flocculation
    Low Dietary Energy Concentration, High Nonstarch Polysaccharide Concentration, and Coarse Particle Sizes of Nonstarch Polysaccharides Affect the Behavior of Feather-Pecking-Prone Laying Hens
    Krimpen, M.M. van; Kwakkel, R.P. ; Peet-Schwering, C.M.C. van der; Hartog, L.A. den; Verstegen, M.W.A. - \ 2008
    Poultry Science 87 (2008). - ISSN 0032-5791 - p. 485 - 496.
    egg-production - performance - protein - strains - plumage - hybrids - layers - fiber - whole
    An experiment was conducted with 504 non-cage-housed ISA Brown laying hens from 18 to 40 wk of age to investigate the separate effects of dietary energy concentration, nonstarch polysaccharide (NSP) concentration, and particle sizes of added NSP source on the eating behavior, feather-pecking behavior, and hen performance of laying hens. Hens were allotted to 1 of 6 dietary treatments according to a 2 x 3 factorial arrangement, with 7 replicates per treatment. The factors were control and low energy concentration (2,825 vs. 2,540 kcal/kg), control and high NSP concentration (133 vs. 195 g/kg), and fine vs. coarse particle size of the added NSP source in the high-NSP diets. We hypothesized that eating time would be increased by feeding low-energy diets or coarsely ground, high-NSP diets, or both, resulting in reduced feather-pecking behavior, without negatively affecting hen performance. Energy reduction, NSP addition, and coarse grinding of NSP increased eating time by 14.2% (P = 0.001), 17.2% (P <0.001), and 7.9% (P = 0.075), respectively, compared with the control level of these factors. Addition of NSP decreased eating rate (g/min) by 21.0% (P = 0.010). Layers already performed gentle feather-pecking behavior during the fifth week of the rearing period. Dietary treatments did not affect the maximal level of feather condition scores, but arise of feather damage was delayed by 10 wk in hens fed low-energy, coarsely ground, NSP-rich diets compared with hens fed control diets. Hens fed the control NSP diets showed reduced culling rates, because of less cannibalistic pecking, when energy concentration was decreased (44.1 vs. 13.1%), whereas in the high-NSP diets, culling rate decreased slightly when hens were fed the low-energy diets (31.6 vs. 28.6%; P = 0.071). Hens that were fed the low-energy diets compensated for the 10% reduction in energy concentration by a 9.3% higher maximal feed intake (143.0 vs. 130.8 g/d). Hen performance and BW gain of the hens were not affected by dietary treatments. We concluded that hens that were fed low-energy or high (coarsely ground)-NSP diets spend more time on feed intake, compared with hens that were fed the control diets. As a result, hens in some treatments showed less feather-pecking behavior.
    Direct observation of adhesion and spreading of emulsion droplets at solid surfaces
    Dresselhuis, D.M. ; Aken, G.A. van; Hoog, E.H.A. de; Cohen Stuart, M.A. - \ 2008
    Soft Matter 4 (2008). - ISSN 1744-683X - p. 1079 - 1085.
    in-water emulsions - o/w emulsions - lubrication - tribology - friction - coalescence - chocolate - membrane - tissue - layers
    Sensory perception of fat is related to orally perceived in-mouth friction. From this perspective, we investigate adhesion and spreading of emulsion droplets on solid surfaces and connect it to the ability of food emulsions to lower friction. Furthermore, we study what the contribution is of the separate colloidal forces on droplet adhesion. The effect of saliva on adhesion and spreading is also briefly investigated.Using a flow cell in combination with light microscopy and video imaging allowed us to clearly distinguish between adhered and spread emulsion droplets. The capability to make this distinction between adhesion and spreading experimentally is new and provided us with the insight that the occurrence of spreading is essential for lowering friction. Mainly electrostatic, steric and hydrophobic interactions of the droplets with solid surfaces are found to determine adhesion and subsequent spreading of emulsion droplets. This was investigated by varying the adsorbed amount of protein, the ionic strength of the emulsion as well as the hydrophobicity of the solid surface. Especially the hydrophobic interaction between droplet and surface is shown to be crucial for droplet adhesion and spreading. Saliva is of minor importance for adhesion and spreading. This work gives insight in the way emulsion droplets interact with solid surfaces and the type of colloidal interactions that play a role. The information it provides can be used to develop emulsions that are reasonably stable during the shelf life of the product, but do spread on oral surfaces, thus lowering friction and enhancing fat perception
    Experimental evidence of lateral flow in unsaturated homogeneous isotropic sloping soil due to rainfall
    Sinai, G. ; Dirksen, C. - \ 2006
    Water Resources Research 42 (2006). - ISSN 0043-1397 - 12 p.
    downward water-flow - surface hydrology - hillslope infiltration - moisture flow - vadose zone - anisotropy - transient - dynamics - runoff - layers
    This paper describes laboratory experimental evidence for lateral flow in the top layer of unsaturated sloping soil due to rainfall. Water was applied uniformly on horizontal and V-shaped surfaces of fine sand, at rates about 100 times smaller than the saturated hydraulic conductivity. Flow regimes near the surface and in the soil bulk were studied by using dyes. Streamlines and streak lines and wetting fronts were visually studied and photographed through a vertical glass wall. Near wetting fronts the flow direction was always perpendicular to the fronts owing to dominant matrix potential gradients. Thus, during early wetting of dry sloping sand, the flow direction is directed upslope. Far above a wetting front the flow was vertical due to the dominance of gravity. Downslope flow was observed during decreasing rainfall and dry periods. The lateral movement was largest near the soil surface and decayed with soil depth. Unstable downslope lateral flow close to the soil surface was attributed to non-Darcian flow due to variable temporal and spatial raindrop distributions. The experiments verify the theory that predicts unsaturated downslope lateral flow in sloping soil due to rainfall dynamics only, without apparent soil texture difference or anisotropy. This phenomenon could have significant implications for hillside hydrology, desert agriculture, irrigation management, etc., as well as for the basic mechanisms of surface runoff and erosion.
    Assessing the Extent of Protein Intermolecular Interactions at Air-Water Interfaces Using Spectroscopic Techniques
    Jongh, H.H.J. de; Wierenga, P.A. - \ 2006
    Biopolymers 82 (2006)4. - ISSN 0006-3525 - p. 384 - 389.
    surface shear rheology - air/water interface - ovalbumin - adsorption - layers - dynamics
    There is an ongoing debate about whether a protein surface film at an air-water interface can be regarded as a gelled layer. There is literature reporting that such films show macroscopic fracture behavior and a rheology comparable to three-dimensional protein bulk-networks. Ifthis is the case, a complete description of the formation of adsorbed layers should include a transition from single, freely moving proteins to a gelled layer. This report presents studies using spectroscopic techniques, such as infrared, fluorescence and neutron spectroscopy, or ellipsometry, to derive molecular insight in situ to substantiate the intermolecular networking in surface films of chicken egg ovalbumin. It is concluded that protein films, generated by equilibrium adsorption from the bulk, behave as a densely packed colloidal repulsive particle system, where the proteins still have a significant rotational mobility, have a predominantly retained globular fold, and show distinct (lateral) diffusion. Applied stresses on the surface film (by compressions of the interface) may result in protein denaturation and aggregation. This process renders a surface film from a colloidal particle into that of a gelled system.
    Compression/expansion rheology of oil/water interfaces with adsorbed proteins. Comparison with the air/water surface
    Benjamins, J. ; Lyklema, J. ; Lucassen-Reynders, E.H. - \ 2006
    Langmuir 22 (2006)14. - ISSN 0743-7463 - p. 6181 - 6188.
    liquid-liquid interface - beta-casein adsorption - air-water-interface - fluid interfaces - hexadecane/water interface - flexible proteins - drop tensiometer - layers - monolayers - macromolecules
    Dynamic interfacial tensions and surface dilational moduli were measured for four proteins at three fluid interfaces, as a function of time and concentration. The proteins-ß-casein, ß-lactoglobulin, bovine serum albumin, and ovalbumin - were adsorbed from aqueous solution against air, n-tetradecane, and a triacylglycerol oil. The sinusoidal interfacial compression/expansion, at frequencies ranging from 0.005 to 0.5 Hz, was effected in a dynamic drop tensiometer suited to viscous oil phases. Generally, at interfacial pressures up to 15 mN/m, dilational moduli were purely elastic at frequencies from 0.1 Hz. In this elastic range, in-surface relaxation either was essentially completed or had not yet started within a time on the order of 10 s. Within this time span, protein exchange with the bulk solution was negligible. In cases where in-surface relaxation was completed in the imposed time, the moduli depended only on the equilibrium ¿(¿) relationship. We interpret these results in terms of a simple two-dimensional solution model, based on a Gibbs dividing surface, accounting for nonideal mixing to the first order with respect to both entropy and enthalpy. Interfacial mixing enthalpy is shown to have a major effect on the elasticity, with both quantities increasing in the sequence triacylglycerol ¿ tetradecane ¿ air. We also suggest a strong correlation between enthalpy and clean-interface tension that increases in the same order. At each interface, the enthalpy increases with increasing molecular rigidity: ß-casein ¿ ß-lactoglobulin ¿ bovine serum albumin ¿ ovalbumin. Best agreement with the experimental data was obtained with a recently extended version of the model accounting for proteins adopting smaller molecular areas with increasing surface pressure. For interfacial pressures above 15 mN/m, the moduli were generally no longer purely elastic, with viscous loss angles ranging up to 36 degrees. In this range of high pressures, the moduli depended on relaxation mechanisms for which specific kinetic models must be developed
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