Estimating the sustainability of towed fishing-gear impacts on seabed habitats: a simple quantitative risk assessment method applicable to data-limited fisheries
Pitcher, C.R. ; Ellis, Nick ; Jennings, Simon ; Hiddink, Jan G. ; Mazor, Tessa ; Kaiser, Michel J. ; Kangas, Mervi I. ; Mcconnaughey, Robert A. ; Parma, Ana M. ; Rijnsdorp, Adriaan D. ; Suuronen, Petri ; Collie, Jeremy S. ; Amoroso, Ricardo ; Hughes, Kathryn M. ; Hilborn, Ray ; Freckleton, Robert - \ 2017
Methods in Ecology and Evolution 8 (2017). - ISSN 2041-210X - p. 472 - 480.
benthic fauna - depletion - ecological risk assessment - ecoystem-based fishery management - effects of trawling - recovery - resilience - sensivity - trawl footprints - vulnerability indicators
1. Impacts of bottom ﬁshing, particularly trawling and dredging, on seabed (benthic) habitats are commonly perceived to pose serious environmental risks. Quantitative ecological risk assessment can be used to evaluate actual risks and to help guide the choice of management measures needed to meet sustainability objectives. 2. We develop and apply a quantitative method for assessing the risks to benthic habitats by towed bottom-ﬁshing gears. The meth od is based on a simple eq uation for relative benthic status (RBS), derived by solving the logistic population growth equation for the equilibrium state. Estimating RBS requires only maps of ﬁshing intensity and habitat type – and parameters for impact and recovery rates, which may be taken from meta-analyses of multiple experimental studies of towed-gear impacts. The aggregate status of habitats in an assessed region is indicated by the distribution of RBS values for the region. The application of RBS is illustrated for a tropical shrimp-trawl ﬁshery. 3. The status of trawled habitats and their RBS value depend on impact rate (depletion per trawl), recovery rate and exposure to tra wling. In the shrimp-trawl ﬁshery region, gravel habitat was most sensitive, and though less exposed than sand or mudd y-sand, was most aﬀected overall (regional RBS = 91% relative to un-trawled RBS = 100%). Muddy-sand was less sensitive, and though relatively most exposed, was less aﬀected overall (RBS = 95%). Sand was most heavily trawled but least sensitive and least aﬀected overall (RBS = 98%). Region-wide , >94% of habitat area had >80% RBS because most tra wling and impacts were conﬁned to small areas. RBS was also applied to the region’s benthic invertebrate communities with similar results. 4. Conclu sions. Unlike qualitative or categorical trait-based risk assessments, the RBS method provides a quantitative estimate of status relative to an unimpacted baseline, with minimal requireme nts for input data. It could be applied to bottom-contact ﬁsh erie s world-wide, including situations where detailed data on characteristics of seabed habitats, or the abundance of seabed fauna are not available. The approach supports assessment against sustainability criteria and evaluation of alternative management strategies (e.g. closed areas, eﬀort management, gear modiﬁcations).
Intensive groundwater use and (in)equity: Processes and governance challenges
Hoogesteger van Dijk, J.D. ; Wester, P. - \ 2015
Environmental Science & Policy 51 (2015). - ISSN 1462-9011 - p. 117 - 124.
water - policies - india - sustainability - organizations - irrigation - strategies - management - highlands - depletion
Groundwater forms the basis for millions of rural and urban livelihoods around the world. Building on insights from the theory of access, in this article we present how groundwater development has brought much well-fare in many parts of the world; and how resulting intensive groundwater use is leading to ill-fare through aquifer overexploitation and processes of water accumulation and dispossession. We show the difficulty of state regulation and the modest achievements of other governance approaches that aim to solve existing groundwater problems. To study these processes we propose a framework of analysis that is based on the study of hydrosocial-networks, the political economy of groundwater and the domains and discourses that define groundwater access. Such analysis highlights the challenges of devising policies and modes of governance that contribute to social and environmental sustainability in intensively used aquifers. These we argue should build on an analysis of equity that scrutinizes the discourses, actors, powers and procedures that define groundwater access. By inciting debates on equity a first and fundamental step can be made toward advancing more inclusive groundwater governance that crucially engages the marginalized and addresses their groundwater problems, concerns and needs.
A metal ion charged mixed matrix membrane for selective adsorption of hemoglobin
Tetala, K.K.R. ; Skrzypek, K. ; Levisson, M. ; Stamatialis, D.F. - \ 2013
Separation and Purification Technology 115 (2013). - ISSN 1383-5866 - p. 20 - 26.
sickle-cell-disease - exchange chromatography - protein adsorption - bovine hemoglobin - human blood - separation - depletion - purification - adsorbers - removal
In this work, we developed a mixed matrix membrane by incorporating 20–40 µm size iminodiacetic acid modified immobeads within porous Ethylene vinyl alcohol (EVAL) polymer matrix. The MMM were charged with copper ions for selective adsorption of bovine hemoglobin in presence of bovine serum albumin. EVAL membrane without immobead and immobead alone showed low non-specific adsorption towards bovine hemoglobin and bovine serum albumin. Use of buffers with pH ¿6.8 i.e. pI of bovine hemoglobin resulted in high bovine hemoglobin adsorption. The developed mixed matrix membrane has a maximum static adsorption capacity of 219.5 mg bovine hemoglobin per g bead and the adsorption isotherm curve is of a Langmuir type. Under similar flow rates, the mixed matrix membrane showed significant low pressure drop compared to a packed bed column containing equal amount of beads. Maximum and faster (6 h) adsorption of bovine hemoglobin can be achieved through dynamic mode only using mixed matrix membrane and not by packed bed column and static mode of mixed matrix membrane. The mixed matrix membrane has three times selective adsorption of bovine hemoglobin than bovine serum albumin, from a binary mixture containing equivalent amounts of both proteins
The immunomodulatory nutritional intervention NR100157 reduced CD4+ T-Cell decline and immune activation: a 1-year multicenter randomized controlled double-blind trial in HIV-infected persons not receiving antiretroviral therapy (The BITE Study)
Cahn, P. ; Ruxrungtham, K. ; Gazzard, B. ; Norren, K. van; Diaz, R.S. ; Gori, A. ; Kotler, D.P. ; Vriesema, A. ; Georgiou, N.A. ; Garssen, J. ; Clerici, M. ; Lange, J.M.A. - \ 2013
Clinical infectious diseases 57 (2013)1. - ISSN 1058-4838 - p. 139 - 146.
virus type-1 infection - viral load - bovine colostrum - pathogenesis - restoration - enteropathy - prebiotics - depletion - survival - mucosa
Background The immunomodulatory nutritional product NR100157 was developed for human immunodeficiency virus (HIV)–infected individuals. We hypothesized that targeting the compromised gastrointestinal tract of HIV-infected individuals would result in systemic immunological benefits. Methods In a multicenter, randomized, controlled, double-blind trial, 340 HIV-1–positive adults not on antiretroviral therapy, with CD4+ T-cell counts
Near-bed gradients in particles and nutrients above a mussel bed in the Limfjorden: influence of physical mixing and mussel filtration
Petersen, J.K. ; Maar, M. ; Ysebaert, T. ; Herman, P.M.J. - \ 2013
Marine Ecology Progress Series 490 (2013). - ISSN 0171-8630 - p. 137 - 146.
mytilus-edulis-l - pelagic food-web - boundary-layer - grazing impact - phytoplankton - flow - depletion - plankton - culture - biomass
The aim of this field study was to investigate the role of mussels on near-bed layer characteristics at different hydrodynamic regimes in a micro-tidal system. At Løgstør Broad, the Limfjorden, Denmark, we deployed ‘siphon mimics’ to sample chlorophyll a (chl a), particulate organic carbon (POC) and inorganic nutrients at different distances above the bottom. This was done without disturbing water column gradients and in a manner similar to mussel incurrent flow. Mimics were deployed at 2 sites: a site with a relatively dense mussel bed and a nearby sandy site without mussels. During the 2 wk field campaign, physical conditions in the fjord varied from extremely calm weather with low waves to quite windy with high waves. Results showed that under all conditions, the vertical concentration profiles of chl a were significantly depleted towards the mussel bed due to mussel filtration, whereas the degree of chl a depletion was correlated to wave height. Nutrient profiles consistently showed increasing concentration profiles towards the bed, identifying the mussel bed and the sediment as a source of nutrients with the highest gradients during the period with high waves. In conclusion, the near-bed concentrations of seston and nutrients in this study were temporally variable and closely linked to the physical structure of the water column.
Effect of diet on plasma tryptophan and serotonin in trained mares and geldings
Alberghina, D. ; Giannetto, C. ; Visser, E.K. ; Ellis, A.D. - \ 2010
Veterinary Record 166 (2010)5. - ISSN 0042-4900 - p. 133 - 136.
serum tryptophan - sex-differences - horses - exercise - behavior - brain - blood - availability - depletion - glucose
Concentrations of tryptophan (TRP) and serotonin (5-HT) in plasma were measured in 36 moderately trained Dutch warmblood horses after eight weeks on a high fibre (n=18) or high starch (n=18) diet. Samples were taken three hours after feeding, when the horse was at rest, either at 11.00 or 14.00 hours. Plasma 5-HT and pH were significantly higher in horses fed a high fibre diet than those fed a high starch diet (P
Sustainable use of phosphorus : EU tender ENV.B1/ETU/2009/0025
Schroder, J.J. ; Cordell, D. ; Smit, A.L. ; Rosemarin, A. - \ 2010
Wageningen : Plant Research International (Report / Plant Research International 357) - 122
fosfor - kringlopen - duurzaamheid (sustainability) - verarming - verliezen - natuurfosfaat - gebruiksefficiëntie - landbouwbeleid - europese unie - phosphorus - cycling - sustainability - depletion - losses - rock phosphate - use efficiency - agricultural policy - european union
As sustainable phosphorus use will sooner or later become essential for global food security, action is needed. As far as the required actions are concerned, the report has identified short-term and long-term policy options which could improve the current level of phosphorus use efficiency in agriculture. The report emphasizes, however, that policies should not be developed in isolation, let alone for agriculture only, but that all parts of the chain, that is primary production, processing and consumption, should be addressed in an integrative way. The current reliance on imported rock-based phosphorus (‘3 kg P per European citizen per year’) can not be continued in the long run. To become truly sustainable, phosphorus use efficiency must approach a level close to 100% in each chain. Therefore, a full recycling of phosphorus will become a condition sine qua non for global and European food security. The urgency of policies and measures needed for that will be determined by the phosphate rock reserves considered exploitable (including geopolitically and legally accessible), the prevention of accumulation and losses, the size of the global population and its preferences in terms of food, feed, fibers and fuels, and its appreciation of biodiversity. This will require drastic adjustments to the way we manage agriculture, and it may also require adjustments to our society as a whole, including the processing of our ‘wastes’.
Phosphorus in agriculture: global resoources, trends and developments : report to the Steering Committee Technology Assessment of the Ministery of Agriculture, Nature and Food Quality, The Netherlands, and in collaboration with the Nutrient Flow Task Group (NFTG), supported by DPRN (Development Policy review Network)
Smit, A.L. ; Bindraban, P.S. ; Schröder, J.J. ; Conijn, J.G. ; Meer, H.G. van der - \ 2009
Wageningen : Plant Research International (Report / Plant Research International 282) - 36
gewasproductie - bodemvruchtbaarheid - fosfor - kringlopen - hulpbronnenbehoud - verarming - wereld - agro-ecosystemen - schaarste - crop production - soil fertility - phosphorus - cycling - resource conservation - depletion - world - agroecosystems - scarcity
In agroproduction systems recycling of phosphorus should be the general principle. This holds for manure, crop residues and other organic rest products. Especially the cattle feedlot industry can be a market for DGGS, being a co-product of the distillery industries. Recovery from seawater is a possible alternative for the re-use of phosphorus. These and other aspects are reviewed in this inventory on a world scale
Time dependence in jamming and unjamming
Parker, A. - \ 2009
Wageningen University. Promotor(en): Erik van der Linden. - [S.l. : S.n. - ISBN 9789085853879 - 99
gels - stabiliteit - dynamica - reologie - verouderen - sedimentatie - thixotropie - verarming - uitvlokking - xanthan - gelatine - evenwicht - gels - stability - dynamics - rheology - aging - sedimentation - thixotropy - depletion - flocculation - xanthan - gelatin - equilibrium
Three different food systems have been studied: emulsion/polymer mixtures, gelatin gels and carrageenan gels. Typically, samples are trapped, or jammed, far from equilibrium. The simple jamming paradigm suggests that, once in the jammed state, these systems are static. This useful approximation is often too simple, since these systems frequently evolve in time. Their evolution has been measured systematically. Where possible, these results have been placed in the context of the physics of out-of-equilibrium systems.
The emulsion/polymer mixtures are a model for salad dressing. The emulsions alone are colloidally stable, but become inhomogeneous, due to the effects of gravity. With sufficient polymer, they can be apparently stable (jammed) for months, but then quite suddenly start to sediment – the system unjams. The kinetics of this delayed sedimentation is measured as a function of the key parameters. A new model is proposed for the mechanism by which polymers stabilize emulsions.
Solutions of gelatin form gels when cooled, due to the formation of portions of helix. A new model relating the amount of helix to the elasticity is described. The gels always evolve slowly. At steady state, the rate of evolution of the elasticity is constant in log(time), so this system conforms to Struick’s physical aging scenario. The effect of temperature changes on the evolution of gels is extremely complex. The results show that there is a deep analogy between this behavior and that of spin glasses, which are exotic magnetic phases.
Gels of iota carrageenan, a seaweed polysaccharide, have unique rheological properties: they regel almost instantly after strong mixing. This property is used in the dairy industry, but has not been studied previously. The kinetics of recovery after shear has been measured for water gels and milk gels.
Contaminants and microorganisms in Dutch organic food products: a comparison with conventional products
Hoogenboom, L.A.P. ; Bokhorst, J.G. ; Northolt, M.D. ; Vijver, L.P.L. van de; Broex, N.J.G. ; Mevius, D.J. - \ 2008
Food Additives and Contaminants 25 (2008)10. - ISSN 0265-203X - p. 1195 - 1207.
solid-phase extraction - bound metabolites - eggs - residues - wheat - campylobacter - mycotoxins - depletion - quality - tissues
Organic products were analysed for the presence of contaminants, microorganisms and antibiotic resistance and compared with those from conventional products. No differences were observed in the Fusarium toxins deoxynivalenol and zearalenone in organic and conventional wheat, during both a dry period and a very wet period which promoted the production of these toxins. Nitrate levels in head lettuce produced organically in the open field were much lower than those in conventional products. In iceberg lettuce and head lettuce from the greenhouse, no differences were detected. Organically produced carrots contained higher nitrate levels than conventional products. Both organic and conventional products contained no residues of non-polar pesticides above the legal limits, although some were detected in conventional lettuce. Organic products contained no elevated levels of heavy metals. Salmonella was detected in 30% of pig faeces samples obtained from 30 organic farms, similar to the incidence at conventional farms. At farms that switched to organic production more then 6 years ago no Salmonella was detected, with the exception of one stable with young pigs recently purchased from another farm. No Salmonella was detected in faeces at the nine farms with organic broilers, and at one out of ten farms with laying hens. This is comparable with conventional farms where the incidence for Salmonella lies around 10%. Campylobacter was detected in faeces at all organic broiler farms, being much higher than at conventional farms. One of the most remarkable results was the fact that faeces from organic pigs and broilers showed a much lower incidence of antibiotic resistant bacteria, except for Campylobacter in broilers. It is concluded that the organic products investigated scored as equally well as conventional products with regard to food safety and at the same time show some promising features with respect to antibiotic resistance.
Protein-polysaccharide interactions: The determination of the osmotic second virial coefficients in aqueous solutions of ß-lactoglobulin and dextran
Schaink, H.M. ; Smit, J.A.M. - \ 2007
Food Hydrocolloids 21 (2007)8. - ISSN 0268-005X - p. 1389 - 1396.
bovine serum-albumin - phase-separation - depletion - mixtures - pressure - lysozyme - systems - model - size - dimerization
Solutions containing dextran and solutions containing mixtures of dextran +ß-lactoglobulin are studied by membrane osmometry. The low concentration range of these solutions is considered. From the measured osmotic pressures the virial coefficients are obtained. These are analyzed using the osmotic virial coefficient of ß-lactoglobulin solutions published earlier by us [Schaink, H.M., & Smit, J. A.M. (2000). Determination of the osmotic second virial coefficient and the dimerization of beta-lactoglobulin in aqueous solutions with added salt at the isoelectric point. PCCP, 2, 1537¿1541]. The second cross-virial coefficient A12 is found to be positive indicating a repulsive and probably mainly steric interaction between neutral in nature dextran and and practically uncharged ß-lactoglobulin (pH=5.18). The measurements show that the ß-lactoglobulin has only a small tendency to form multimers in the presence of dextran. The phase diagram of solutions of dextran+Whey Protein Isolate (appr. 60% ß-lactoglobulin) is also presented. The McMillan¿Mayer equation of state that considers only the second virial coefficients is found to be unreliable for the extrapolation up to the concentrations at which phase separation is expected Keywords: Proteins; Polysaccharides; Osmotic pressure; Virial coefficients; Phase separation
The determination of biurea: a novel method to discriminate between nitrofurazone and azodicarbonamide use in food products
Mulder, P.P.J. ; Beumer, B. ; Rhijn, J.A. van - \ 2007
Analytica Chimica Acta 586 (2007)1-2. - ISSN 0003-2670 - p. 366 - 373.
performance liquid-chromatography - mass-spectrometry - bound metabolites - semicarbazide - furazolidone - antibiotics - depletion - tissues - liver
Recently doubts have arisen on the usefulness of semicarbazide as marker residue for the illegal use of the antibiotic nitrofurazone (NFZ) in aquaculture and poultry production. Most notably azodicarbonamide (ADC) has been implicated as an alternative source of semicarbazide. ADC is used in some countries as a dough conditioner at concentrations up to 45 mg kg¿1. The use of ADC-treated flour or dough in coated or breaded food products may generate false non-compliant results in the analytical method for nitrofurazone metabolites, which is currently in use. During the dough preparation process ADC is largely reduced to biurea, which can be considered as an appropriate marker residue of ADC. Thus far no methods have been published for the determination of biurea in food commodities. Due to its polar nature it is very difficult to generate sufficient retention on conventional C18 HPLC columns. With a TSK amide HILIC type column good retention was obtained. A straightforward extraction-dilution protocol was developed. Using a mixture of dimethyl formamide and water biurea was nearly quantitatively extracted from a variety of fresh, coated and processed products. Mass spectrometric detection was performed with positive electrospray ionisation. The sensitivity and selectivity of the mass spectrometer for biurea was very good, allowing detection at concentrations as low as 10 ¿g kg¿1. However, in some extracts severe ion suppression effects was observed. To overcome the implications of ion suppression on the quantitative performance of the method an isotopically-labelled biurea internal standard was synthesized and incorporated in the method. The method developed can be used effectively in nitrofurazone analysis to eliminate the risk of false non-compliant results due to the presence of azodicarbonamide-treated components in the food product.
The influence of social interactions on the foraging path of Bewick's Swans Cygnus columbianus bewickii
Klaassen, R.H.G. ; Nolet, B.A. ; Bankert, D. - \ 2006
Ardea 94 (2006)3. - ISSN 0373-2266 - p. 477 - 484.
tundra swans - behavior - information - habitat - efficiency - migration - depletion - foragers - patterns - tubers
The efficiency in which high-density food patches are found is determined by the way foragers move between patches. In this study we explore the effect of social interactions on the foraging path, in particular the distance moved between patches. We studied Bewick¿s Swans Cygnus columbianus bewickii that foraged on belowground tubers of Fennel Pondweed Potamogeton pectinatus. We accurately mapped the foraging path of individual swans and determined the distances between visited patches. 24% of inter-patch movements are associated with social interactions. When a swan retreats from a patch because it is chased away by another swan, it moves a significantly larger distance to a patch than if the movement is not associated with a social interaction. Such longer movements are thought to reduce the rate at which high-density patches are encountered, and thus the energy gain rate a swan can achieve. We observed a strong social hierarchy in which families are dominant over pairs and singletons, and pairs are dominant over singletons, which represents a producer¿scrounger model. Singletons were most frequently observed to retreat from patches and are consequently thought to achieve the lowest gain rates, and also as a result exhibit the slowest speed of movement between patches. However singletons might partly compensate for more frequent retreats from patches by moving larger distances to arrive at the front edge of a flock where they encounter unexploited resources.
Adsorption and desorption of reversible supramolecular polymers
Zweistra, H.J.A. ; Besseling, N.A.M. - \ 2006
Physical Review. E, Statistical nonlinear, and soft matter physics 74 (2006)2. - ISSN 1539-3755 - p. 021806/1 - 021806/10.
interacting chain molecules - equilibrium polymers - living polymers - monte-carlo - statistical-theory - surface forces - lattice - depletion - stiffness - micelles
We report numerical mean-field results on the quasichemical level of approximation that describe adsorption of reversible supramolecular polymers at a flat interface. Emphasis is laid on the regime of strong adsorption from a dilute solution. There are two differences with respect to macromolecular polymer adsorption: (i) adsorption sets in at relatively high monomer concentrations of the surrounding solution, and (ii) the surface is filled within a much narrower concentration range. Contrary to macromolecular polymers, supramolecular polymers can therefore be desorbed by dilution of the equilibrium solution by solvent within an experimentally accessible concentration window. Based on simple thermodynamic arguments, we provide a quantitative explanation why supramolecular polymers adsorb at relatively high concentrations. Moreover, we discuss the (by comparison) narrow concentration window wherein filling of the surface occurs. This is attributed to the cooperative nature of supramolecular polymer adsorption. The degree of cooperativity is quantified by means of the Hill parameter n
Comparison of bruises ad mortality, stress parameters, and meat quality in manually and mechanically caught broilers.
Nijdam, E. ; Delezie, E. ; Lambooij, E. ; Nabuurs, M.J.A. ; Decuypere, M.P. ; Stegeman, J.A. - \ 2005
Poultry Science 84 (2005)3. - ISSN 0032-5791 - p. 467 - 474.
chickens - rates - transport - depletion - poultry - machine - plants - dead - hand
A field trial was conducted to compare manual catching of broilers with a mechanical catching method. Both methods were compared with respect to the incidence of bruises and dead on arrival, stress parameters, and meat quality. Also the dynamics of corticosterone, glucose, and lactate were investigated on the day broilers were killed. The broilers originated from 8 commercial broiler farms; visits were made on the day of catching during spring and autumn of 2001. Broilers of one house were caught manually, and those of the second house were caught mechanically. Plasma samples were taken before catching started, 30 min after the start of catching, 30 min before the end of catching, and at exsanguination of broilers from the first- and last-loaded transport vehicles. Postmortem measurements of pH, temperature, and water-holding capacity were made. Mechanical catching was associated with higher DOA percentages than manual catching in spring, although the difference was not significant in autumn. Catching method did not influence the percentage of bruises or meat quality. Moreover, corticosterone levels indicated that both methods induced the same amount of stress. The dynamics of corticosterone, glucose, and lactate levels showed a similar pattern. Plasma levels increased at the start of catching, and they further increased during transport, shackling, and stunning. However during catching itself, no large changes were observed. Our findings indicated that attempts to reduce stress in broilers during the last day of life could better be focused on factors other than catching
Nutritional deficiency in Dutch primary care: data from general practice research and registration networks
Wayenburg, C.A.M. van; Laar, F.A. van de; Waal, M.W.M. de; Okkes, I.M. ; Akker, M. van den; Veen, W.J. van der; Schellevis, F.G. ; Staveren, W.A. van; Binsbergen, J.J. van; Weel, C. van - \ 2005
European Journal of Clinical Nutrition 59 (2005)Suppl.1. - ISSN 0954-3007 - p. S187 - S194.
obstructive pulmonary-disease - quality-of-life - chronic heart-failure - hospitalized-patients - weight-loss - malnutrition - mortality - depletion - cachexia
Objective: To explore incidence and prevalence rates of nutritional deficiency in adults in general practice. Methods: Six Dutch general practice research and registration networks supplied incidence and prevalence rates of nutritional deficiency by the International Classification of Primary Care (ICPC) or 'E-list' labels ('loss of appetite, feeding problem adult, iron, pernicious/folate deficiency anaemia, vitamin deficiencies and other nutritional disorders, weight loss'). In case of disease-related nutritional deficiency, we asked whether this was labelled separately ('co-registered') or included in the registration of the underlying disease. Results: 'Iron deficiency anaemia' had highest incidence (0.3-8.5/1000 person years), and prevalence rates (2.8-8.9/1000 person years). Nutritional deficiency was mostly documented in the elderly. In two networks 'co-registration, was additional, two only documented the underlying disease and two did not specify 'co-registration'. No clear difference was found between networks considering the difference in 'co-registration'. Conclusion: Nutritional deficiency is little documented in general practice, and generally is not registered separately from the underlying disease
Concentration and Solvency Effects on the Pair Interaction between Colloidal Particles in a Solution of Nonadsorbing Polymer
Tuinier, R. ; Fleer, G.J. - \ 2004
Macromolecules 37 (2004)23. - ISSN 0024-9297 - p. 8764 - 8772.
mesoscopic particles - depletion - dispersions - potentials - mixtures - spheres - chains - phase - adsorption - molecules
Analytical expressions are derived for the polymer excess amount and the grand potential (surface free energy) of flat and spherical surfaces immersed in a solution of nonadsorbing polymer chains in the mean-field approximation. We start from a recent mean-field expression for the depletion thickness which takes into account not only the effect of the chain length N but also that of the polymer concentration b and the solvency . Simple expressions are obtained for the interfacial properties at a colloidal surface, using both the adsorption method and the osmotic route. For a sphere of radius a, the excess amount can be separated into a planar contribution = -b and a curvature correction c = -(2/12)bc2/a, where c is a "curvature thickness" which is close to (but smaller than) . The grand potential has a planar contribution = (2/9)b/ and a curvature part c = (/18)b/a. We test the results against numerical lattice computations, taking care that the boundary conditions in the continuum and lattice models are the same. We find good agreement up to a polymer segment volume fraction of 10%, and even for more concentrated solutions our simple model is reasonable. For spherical geometry we propose a new equation for the segment concentration profile which excellently agrees with numerical lattice computations. The results can be used as a starting point for the pair interaction between colloidal particles in a solution containing nonadsorbing chains, which is discussed in the following paper.
Interactions between surfaces in the presence of nonadsorbing equilibrium polymers
Gucht, J. van der; Besseling, N.A.M. - \ 2003
Journal of Physics-Condensed Matter 15 (2003). - ISSN 0953-8984 - p. 6627 - 6645.
living polymers - reversible polymers - adsorption - depletion - lattice - segregation - particles - monomers
The behaviour of a solution of equilibrium polymers (or living polymers) between two surfaces is studied using a Bethe–Guggenheim lattice model for molecules with orientation-dependent interactions. The average monomer concentration, the average length of the chains and the interaction between the surfaces are calculated as a function of the separation distance between the surfaces. When the gap is in full equilibrium with a homogeneous bulk solution, the equilibrium polymers cause a depletion attraction, which becomes stronger with increasing bulk monomer concentration. The range of the interaction passes through a maximum as a function of the concentration. In dilute solutions the range of the interaction increases and the strength decreases with increasing bonding energy, while above the overlap concentration the bonding energy is irrelevant. For restricted equilibrium between the gap and the bulk, when the amount of polymer in the gap is determined by the flow of fluid out of the gap upon compression, the interaction becomes repulsive. This repulsion becomes stronger with increasing concentration and depends only very weakly on the bonding energy. Two limiting cases for the fluid flow were considered: (i) perfect-slip conditions at the surfaces, resulting in a constant monomer concentration in the gap and (ii) no-slip conditions at the surfaces, resulting in a parabolic flow profile of solution out of the gap
Fosfaat: sleutelfactor bij natuurontwikkeling op voormalige landbouwgronden?
Sival, F.P. ; Chardon, W.J. - \ 2003
Vakblad Natuurbeheer (2003)1. - ISSN 1388-4875 - p. 10 - 11.
natuurbescherming - landgebruik - landbouwgrond - fosfaat - fosfaten - bodem - bodemchemie - bodemeigenschappen - voedingsstoffenovermaat - mineraalovermaat - voedingsstoffenbeschikbaarheid - verarming - vegetatie - vegetatiebeheer - bodembeheer - natuur - natuurtechniek - nature conservation - land use - agricultural land - phosphate - phosphates - soil - soil chemistry - soil properties - nutrient excesses - mineral excess - nutrient availability - depletion - vegetation - vegetation management - soil management - nature - ecological engineering
Bij de realisering van de ecologische hoofdstructuur en bij de reconstructie van gebieden met intensieve veehouderij komt veel landbouwgrond vrij voor natuurontwikkeling. De bodems hiervan zijn vaak rijk aan voedingstoffen door langdurige bemesting en zijn verdroogd door ontwatering. Verschralende maatregelen vinden vaak plaats om condities te creëren voor voedselarme vegetatie. Maar helaas zijn de pogingen vaak zonder succes
Negative effects of UVB-irradiated phytoplankton on life history traits and fitness of Daphnia magna
Lange, H.J. de; Reeuwijk, P.L. van - \ 2003
Freshwater Biology 48 (2003). - ISSN 0046-5070 - p. 678 - 686.
ultraviolet-b radiation - fatty-acid composition - food quality - offspring fitness - pulex - zooplankton - algae - consequences - depletion - survival
1. We tested the effect of ultraviolet-B (UVB)-irradiated phytoplankton on life history characteristics of Daphnia magna . Two phytoplankton species were used, Chlamydomonas reinhardtii and Cryptomonas pyrenoidifera . The phytoplankton species were cultured under photosynthetically active radiation (PAR) conditions, and under PAR supplemented with ultraviolet-A and ultraviolet-B radiation, and fed to Daphnia . 2. Life history traits of Daphnia were negatively affected when fed on UVB-irradiated Cryptomonas . Size at maturity was depressed and fewer juveniles with lower fitness were produced in the UVB treatments. In the Chlamydomonas experiment, no significant effects were found. 3. The cause of the observed UVB effects is likely to be constraints in food quality. Ultraviolet-B radiation thus has the potential of inhibiting energy transfer from the first to the second trophic level.