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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Dermal absorption and toxicological risk assessment : pitfalls and promises
Buist, H. - \ 2016
University. Promotor(en): Ruud Woutersen; Ivonne Rietjens, co-promotor(en): J.J.M. van de Sandt. - Wageningen : Wageningen University - ISBN 9789462577275 - 200 p.
skin - absorption - permeability - in vitro - experiments - exposure assessment - risk assessment - toxicology - biocides - rodenticides - preservatives - disinfection - huid - absorptie - permeabiliteit - experimenten - blootstellingsbepaling - risicoschatting - toxicologie - biociden - rodenticiden - conserveermiddelen - desinfectie

Absorption of toxic substances via the skin is an important phenomenon in the assessment of the risk of exposure to these substances. People are exposed to a variety of substances and products via the skin, either directly or indirectly, while at work, at home or in public space. Pesticides, organic solvents and metalworking fluids are seen to be important contributors to adverse health effects due to occupational exposure via the skin. In daily life, cosmetics, clothing and household products are the most relevant commodities with respect to exposure via the skin.

Given the importance of skin exposure in the assessment of the risk of toxic substances, the objective of this thesis was to further develop, evaluate and improve methods for including skin absorption data this assessment.

In this thesis, four factors influencing dermal absorption, namely dermal loading (chapters 3 and 6), irritative/corrosive potential (chapters 3 and 4), frequency of exposure (chapters 3, 4 and 5) and the vehicle used (chapter 5), were investigated in more detail. Furthermore, a model to extrapolate infinite dose absorption data to finite dose conditions, baptized Dermal Absorption Model for Extrapolation (DAME), was developed and tested.

I

n chapter 2 of this thesis, the relationship between relative dermal absorption and dermal loading was investigated. Hundred-and-thirty-eight dermal publicly available absorption experiments with 98 substances were evaluated. The results obtained revealed that dermal loading ranged mostly between 0.001 and 10 mg/cm2. In 87 experiments (63%), an inverse relationship was observed between relative dermal absorption and dermal loading. On average, relative absorption at high dermal loading was 33 times lower than at low dermal loading. Known skin irritating and volatile substances less frequently showed an inverse relationship between dermal loading and relative absorption. It was concluded that when using relative dermal absorption in regulatory risk assessment, its value should be determined at or extrapolated to dermal loadings relevant for the exposure conditions being evaluated.

I

n chapter 3 of this thesis, a literature search was presented with the aim to investigate whether neglecting the effects of repeated exposure may lead to an incorrect estimate of dermal absorption. The results demonstrated that the effect of repeated versus single exposure does not demonstrate a unique trend. Nevertheless, an increase in daily absorption was frequently observed upon repeated daily exposure. The little information available mostly concerned pharmaceuticals. However, consumers and workers may be repeatedly exposed to other types of chemicals, like disinfectants and cleaning products, which often contain biocidal active substances that may decrease the barrier function of the skin, especially after repeated exposure. These biocidal products, therefore, may present a safety risk that is not covered by the current risk assessment practice since absorption data are usually obtained by single exposure experiments. Consequently, it was decided to investigate the importance of this issue for biocide safety evaluation. As the literature search revealed that hardly any data on absorption upon repeated dermal exposure to biocides are available, it was concluded that data need to be generated by testing.

To cover the entire range of biocidal products in such testing, a representative series of biocidal substances should be tested, making in vitro testing of dermal absorption the preferred choice over in vivo testing. Based on an inventory made, it appeared that the 16 product types represented among the biocidal products authorised in the Netherlands could be clustered into 6 more or less homogeneous categories based on similarity in active substances. This result could facilitate experimental testing by providing a basis for selection of a limited number of representative compounds to be evaluated.

I

n chapter 4 of this thesis, the importance of the effect of repeated dermal exposure on skin permeability for biocide safety evaluation was investigated, using a selection of nine representative biocides from the inventory made in chapter 3. The in vitro dermal penetration of tritiated water and [14C]propoxur was chosen as a measure of the permeability and integrity of human abdominal skin after single and repeated exposure. The results indicated that single and repeated exposure to specific biocidal products (e.g. the quaternary ammonium chlorides DDAC and ADBAC) may significantly increase skin permeability, especially when the compounds are applied at high concentrations, while a substance like formaldehyde may reduce skin permeability under specific conditions.

I

n chapter 5 of this thesis, the in vitro dermal absorption kinetics of the quaternary ammonium compound didecyldimethylammonium chloride (DDAC) during single and repeated exposure was studied in more detail. In addition, the influence of biocidal formulations on the absorption of DDAC was investigated, because it was expected that formulation characteristics may be another factor influencing its dermal absorption. The analysis of biocidal products on the Dutch market, reported in chapter 3, indicated that DDAC is often used in combination with other active ingredients. DDAC was most frequently combined with formaldehyde, glutaraldehyde and/or alkyldimethylbenzyl­ammo­nium chloride (ADBAC). Consequently, commercial formulations containing one or more of these additional active ingredients were selected, in addition to one formulation containing only DDAC as an active ingredient. The selected commercial formulations tended to reduce skin penetration of DDAC. This was most pronounced with the formulation containing the highest concentration of formaldehyde (196 mg/mL) and glutaraldehyde (106 mg/mL), which reduced the flux of DDAC across the skin by 95%. The reduction caused by the only tested formulation containing no other active ingredients than DDAC, and thus incorporating no aldehydes, was smallest, and did not reach statistical significance.

I

n chapter 6 of this thesis, a simple in silico model to predict finite dose dermal absorption from infinite dose data (kp and lag time) and the stratum corneum/water partition coefficient (KSC,W) was developed. This model was tentatively called Dermal Absorption Model for Extrapolation (DAME). As dermal exposure may occur under a large variety of conditions leading to quite different rates of absorption, such a predictive model using simple experimental or physicochemical inputs provides a cost-effective means to estimate dermal absorption under different conditions.

To evaluate the DAME, a series of in vitro dermal absorption experiments was performed under both infinite and finite dose conditions using a variety of different substances. The kp’s and lag times determined in the infinite dose experiments were entered into DAME to predict relative dermal absorption value under finite dose conditions. For six substances, the predicted relative dermal absorption under finite dose conditions was not statistically different from the measured value. For all other substances, measured absorption was overpredicted by DAME, but most of the overpredicted values were still lower than 100%, the European default absorption value for the tested compounds.

In conclusion, our finite dose prediction model (DAME) provides a useful and cost-effective estimate of in vitro dermal absorption, to be used in risk assessment for non-volatile substances dissolved in water at non-irritating concentrations.

I

n chapter 7 of this thesis, the results of the research reported in chapters 2 to 6 were put into perspective, the pitfalls and promises emanating from them discussed and general conclusions drawn. The possible influence of vehicles on absorption and the possible impact of irritative or corrosive vehicles or chemicals on the skin barrier have been demonstrated in this thesis. An in silico predictive model tentatively called DAME was developed, which enables the user to evaluate a variety of dermal exposure scenarios with limited experimental data (kp and lag time) and easy to obtain physicochemical properties (MW and log KOW). The predictions of our experiments reported in chapter 6 were compared to those of the Finite Dose Skin Permeation (FDSP) model published on the internet by the US Centers for Disease Control and Prevention (CDC). DAME outperformed FDSP (R2 of the correlation predicted/measured potential absorption 0.64 and 0.12, respectively). At present, the applicability domain of DAME is limited to non-volatile substances dissolved in aqueous solvents. However, in future the model will be adapted to include volatile substances as well.

Altogether, it is concluded that dermal exposure can be an important factor in risks posed by chemicals and should be taken into account in risk assessment. The methods to actually do this are still open for further improvement to better account for the various factors influencing skin penetration and to develop adequate combinations of in vitro and in silico models that can accurately predict human dermal absorption.

Electrostatic separation for functional food ingredient production
Wang, J. - \ 2016
University. Promotor(en): Maarten Schutyser, co-promotor(en): Remko Boom. - Wageningen : Wageningen University - ISBN 9789462576513 - 176 p.
particles - fractionation - separation - electrostatic separation - sieving - nitrogen - polystyrenes - wheat gluten - arabinoxylans - starch - milling - lupinus - rice bran - food - experiments - deeltjes - fractionering - scheiding - elektrostatische scheiding - zeven (activiteit) - stikstof - polystyrenen - tarwegluten - arabinoxylanen - zetmeel - maling - rijstzemelen - voedsel - experimenten

Summary

Dry fractionation is a promising alternative to wet extraction processes for production of food ingredients, since it uses hardly any water, consumes less energy and retains the native functionality of the ingredients. It combines milling and dry separation to enrich agro-materials in specific components such as protein. Electrostatic separation recently emerged as a novel dry separation process and it relies on electrostatic forces for separation. Though the potential of electrostatic separation to fractionate agro-materials has been demonstrated, the effectiveness in terms of purity and yield and the influence of process parameters on charging and separation of food ingredients have not yet been systematically studied. Therefore, the objective of this thesis was to gain better understanding of the charging and separation behaviour of model and agro-materials, provide insight in the critical factors for successful electrostatic separation and explore the potential of this separation method to different agro-materials.

The charging step is critical to the effectiveness of electrostatic separation and is influenced by many factors. Chapter 2 presents characterization of the charging behaviour of single-component model particles in nitrogen gas flowing through aluminium tubes, using a lab-scale electrostatic separator. Polystyrene particles and wheat gluten were used as model particles. Higher gas velocities led to a higher specific charge by increasing the normal component of impact velocity. Smaller particles gained more specific charge than larger ones because of their higher surface to volume ratio and their sensitivity towards gas flow pattern changes. Longer charging tube lengths allowed more contact between the particles and the wall and therefore resulted in higher specific charge. The relative humidity of the nitrogen gas flow within the range 0 – 60% had no influence on the charging behaviour of both model particles.

Chapter 3 demonstrates the potential of applying electrostatic separation to enrich arabinoxylans from wheat bran with the same lab-scale electrostatic separator. A combination of larger particle size, higher gas velocity and shorter charging tube was preferred for separation, because it sufficiently charged the particles while agglomeration was minimized. Electrostatic separation with the optimum setting achieved a similar enrichment in arabinoxylans (from 23% to 30% dry matter basis) as sieving does. However, the combination of electrostatic separation and sieving further improved the enrichment and resulted in a fraction with an arabinoxylans content of 43% dry matter basis, which is around the maximum achievable purity that can be reached by dry fractionation.

To allow better defined charging and separation experiments, a bench-scale electrostatic separator was designed and constructed. With this custom-built separator, the charging and separation of model mixtures prepared from wheat gluten and starch were studied in chapter 4. The net charge of gluten-starch mixtures was not simply the sum of the charge of the two individual components, indicating that particle-particle interactions play an important role. We hypothesized that the formation of agglomerates between oppositely charged particles negatively influenced separation, which was supported by the fact that the dispersibility for mixtures of the two components was lower compared to that of individual components. We found that during electrostatic separation of mixtures, it is important to find the optimal condition that provides sufficient charge to charges, but avoids agglomeration between oppositely charged particles. This could be achieved by the combination of lower dosing rate and higher gas flow rate.

Chapter 5 reports on dry fractionation by combining milling and electrostatic separation with the custom-built bench-scale separator, providing an alternative to wet extraction of protein from lupine seeds. Relatively coarse milling was preferred because it disclosed sufficient protein bodies from the matrix, while avoiding poor dispersibility of the powder due to its very fine particle size. With the optimal settings of single-step electrostatic separation, a fraction with 57.3 g/100 g dry solids could be obtained. The protein content was further improved to 65.0% dry matter basis after two more separation steps, which is 15% higher than obtained by air classification. The yield of the protein enriched fraction was further increased by recycling the fractions from the filter bags, but this was accompanied by a decrease in protein content and vice versa. A significant shift towards better yield and purities was achieved by re-milling the flour that was not collected on the electrodes. A final fraction with a protein content of 65.1% dry matter basis and a yield of 6% was obtained, which recovered 10% of the protein in the original flour.

Chapter 6 explores the possibility of enriching dietary fibre from defatted rice bran by dry fractionation, where the custom-built bench-scale electrostatic separator was used. All three tested separation routes produced fibre-enriched fractions with similar yield (20 – 21 % of the milled flour) and fibre content (67 – 68 % dry matter basis), which recovered 42 – 48 % of the fibre from the original flour. The enriched fractions obtained by a two-step electrostatic separation process contained more small particles compared to the other two, which resulted in different functional properties. Compared to the total dietary fibre extracted by the enzymatic-gravimetric method, the enriched fractions by dry fractionation had a similar water retention capacity and oil binding capacity. This suggests that the fibre-enriched fractions by dry fractionation can be applied in foods and provide similar technological properties and physiological effects as the wet-extracted dietary fibre does.

Chapter 7 concludes the thesis with a general discussion on the main findings, based on which two schemes for protein enrichment and fibre enrichment were proposed. Subsequently the challenges to achieve a successful electrostatic separation for agro-material and up-scaling are discussed. Finally, the chapter ends with an outlook on future research.

This thesis provided insight in the key factors for successful electrostatic separation. It demonstrated the potential of applying this separation method for functional ingredient production from different agro-materials and also gave directions for further improvement and scaling-up.

Afgraven, bodemtransplantaties en uitstrooien van maaisel op voormalige landbouwgronden
Noppen, F. van; Bosch, M. ; Wubs, E.R.J. ; Haanstra, L. ; Verbaan, D. ; Houwelingen, G.D.B. van; Philippona, J. ; Ekeris, R. van; Putten, W.H. van der; Bezemer, T.M. - \ 2015
De Levende Natuur 116 (2015)5. - ISSN 0024-1520 - p. 222 - 226.
heidegronden - heidegebieden - herstelbeheer - ecologisch herstel - natuurontwikkeling - bodem - bodembeheer - experimenten - natuurbeheer - gelderland - veluwe - heathland soils - heathlands - restoration management - ecological restoration - nature development - soil - soil management - experiments - nature management
Op de Reijerscamp bij Wolfheze zijn de effectiviteit van bodemtransplantaties en het uitstrooien van maaisel voor het ontwikkelen van heide en heischraal grasland op een voormalig landbouwgebied vergeleken. Deze natuurherstelmaatregelen zijn toegepast en getest in gebieden waar de toplaag van de bodem (de voormalige bouwvoor) is afgegraven en in niet-afgegraven gebieden. Wat zijn de resultaten van dit experiment en welke meerwaarde levert bodemtransplantatie voor natuurontwikkeling op?
Obese kweekvissen krijgen zwemtraining
Voorde, M. ter; Palstra, A.P. - \ 2015
De Volkskrant Magazine (2015). - p. 50 - 52.
kweekvis - aquacultuurtechnieken - obesitas - lichaamsbeweging - experimenten - fitheid - aquacultuur - diergezondheid - palingen - dierenwelzijn - farmed fish - aquaculture techniques - obesity - exercise - experiments - fitness - aquaculture - animal health - eels - animal welfare
Vis moet zwemmen, is het adagiumvan visfysioloog Arjan Palstra, maar kweekvissen doen dat te weinig. Dus dwingt hij ze in zijn lab in Yerseke. Ze knappen ervan op en –belangrijk voor de kwekers – ze groeien harder.
Shocks, preferences, and institutions: experimental evidence from Sub-Saharan Africa
Cecchi, F. - \ 2015
University. Promotor(en): Erwin Bulte. - Wageningen : Wageningen University - ISBN 9789462572621 - 198
ontwikkelingseconomie - afrika ten zuiden van de sahara - institutionele economie - experimenten - veldwerk - keuzegedrag - verandering - shock - conflict - economische analyse - development economics - africa south of sahara - institutional economics - experiments - field work - choice behaviour - change - economic analysis

Both preferences and institutions are central to economic theory. Insofar as they cannot be taken as given, it is important to understand how they are formed, and how they “respond” to shocks. This thesis investigates the endogenous formation of preferences and institutions. It presents field-experimental evidence from Sub-Saharan Africa – specifically Uganda, Sierra Leone, and Ethiopia – gradually zooming out through different levels of responses to shocks. It starts by looking at the formation of individual preferences in utero and during childhood. Next, it explores the endogeneity of rational choice among adults. Finally, it looks at the cumulative outcome of these responses in terms of changes in local norms and informal institutions. Shocks are thought of in their broadest possible definition. Conflict is a shock, but so is the introduction of exogenously planned and implemented institutions, or the penetration of statutory law into predominantly customary settings.

Chapter 2 investigates the fetal origins of preferences for cooperation. I study the effect of prenatal trauma on the cooperation of those born during the Lord’s Resistance Army insurgency in northern Uganda. I find that a rise in the relative length of the index finger with respect to the ring finger – a marker for prenatal hormonal shock – reduces the child’s probability of contribution to the public good. I interpret this as evidence that prenatal trauma may affect later-life individual preferences, and that the nine months in utero may be more important than previously thought.

Chapter 3 looks at the preferences for competition towards in- and out-groups, in relation to conflict exposure. I study aggressiveness and willingness to compete among youth in Sierra Leone, using the group dynamics generated by a local football tournament to separate in- and out-group behavior. I find that football players that experienced more intense exposure to violence are more likely to get a foul card during a game. Also, I isolate competitiveness from aggressiveness in the lab, and find that conflict exposure increases the willingness to compete towards the out-group—not the in-group. I conjecture that violent conflict is not only a destructive process, but that it may also trigger autonomous transformations in believes and preferences.

Chapter 4 explores the endogeneity of rational choice among adults. I study the relationship between market exposure and rationality in rural Ethiopia, through a laboratory experiment involving sesame brokers and farmers. Following a randomly assigned trading session in a competitive auction, I find that farmers and brokers selected for the treatment behave more rationally than their peers in the control group. Markets are thus not only neutral institutions; they change the way people make decisions. I speculate that, in the presence of endogenous rationality, a rapid market expansion may offer dynamic efficiency gains, but that it may also affect the distribution of rents and wealth at the local and regional levels.

Chapter 5 investigates the relationship between formal and informal institutions. I study the dynamics of social capital – proxied by contributions to a public goods game – in response to the introduction of a formal insurance scheme in southwestern Uganda. I find that formal insurance crowds-out social capital, but that it is not those adopting the formal insurance who reduce their contributions (as predicted by theory). Instead, social capital erodes because of the uninsured. I argue that this is consistent with “weapons of the weak” theories, emphasizing social embeddedness. Those who fear to lose from this inequality-increasing innovation respond with the only “weapons” at hand—by reducing cooperation in other domains.

Chapter 6 looks at how the penetration of formal law affects customary legal institutions. I study the effects of introducing a formal legal alternative on the arbitration decisions of real customary judges in Ethiopia. I find that introducing a legal fallback reduces arbitration biases and draws the decisions of customary judges significantly closer to the formal law. At the same time, agents disfavored by the custom do not take advantage of their increased bargaining power. I argue that most effects of increased competition between formal law and customary legal institutions may rise from changes in the latter, rather than from plaintiffs seeking justice under the rule of law.

While each chapter is envisioned as a self-standing contribution to economic literature, the crosscutting thread is equally crucial. Not always do endogenous responses to shocks fit existing economic theory. Rather, the evidence presented sometimes highlights unforeseen dynamics. It moreover strongly rejects the notion of passive acceptance of shocks; individuals and institutions “respond” to shifting circumstances through “rational” – although not necessarily conscious – behavioral changes. These findings contribute to the understanding of the micro-foundations of preferences and institutions, and emphasize the need to continuously underpin theoretical predictions with empirical evidence.

WHYDRY; Verkorten van de droogstand van melkvee: effecten op de melkproductie, energiebalans en koe- en kalfgezondheid
Knegsel, A.T.M. van - \ 2014
Wageningen : Wageningen University, leerstoelgroep Adaptatiefysiologie - 156
melkproductie - energiebalans - diergezondheid - koeien - kalveren - experimenten - melkopbrengst - lactatie - melkinterval - melkveehouderij - gustperiode - milk production - energy balance - animal health - cows - calves - experiments - milk yield - lactation - milking interval - dairy farming - dry period
Van Knegsel, A.T.M. (Editor), 2014. WHYDRY: Verkorten van de droogstand van melkvee: effecten op de melkproductie, energiebalans en koe- en kalf-gezondheid. Wageningen University, Wageningen, Nederland. 156 blz. Sinds het begin van de 20ste eeuw worden melkkoeien enkele weken voor de verwachte kalfdatum drooggezet, d.w.z. niet meer gemolken. Het doel van deze droogstand is om de melkproductie in de daaropvolgende lactatie te maximaliseren. Daarnaast kunnen koeien met subklinische mastitis tijderns de droogstand behandeld worden met antibiotica. Recent is er discussie ontstaan of een droogstand van 6 tot 8 weken nog wel optimaal is vanwege een aantal redenen. Ten eerste is de vraag of een maximale melkproductie nog steeds wenselijk is, omdat een hoge melkproductie in begin lactatie wordt geassocieerd met een hoge ziekte-incidentie. Ten tweede is het droogzetten van hoogproductief melkvee met nog een hoge dagproductie bij droogzetten een risico voor uiergezondheid. Ten derde is sinds 2013 in Nederland het gebruik van antibiotica in de veehouderij sterk gelimiteerd. Dit geldt ook voor de antibiotica gebruikt in de droogstand, zgn. droogzetters. Deze antibiotica bepalen mede de lengte van de toegepaste droogstand, vanwege de wachttijd na gebruik van droogzetters voor de levering van melk. Het doel van WHYDRY was om via een integrale aanpak te onderzoeken wat de consequenties zijn van het verkorten van de droogstand voor melkproductie, melksamenstelling, energiebalans en koe- en kalfgezondheid. Het onderzoeksproject WHYDRY bestond hoofdzakelijk uit een groot dierexperiment waarin koeien 2 lactaties zijn gevolgd onder gecontroleerde omstandigheden. Binnen dit experiment zijn 168 Holstein-Friesian koeien random toegewezen aan een van de drie droogstandslengtes (0, 30 of 60 dagen) en een van twee lactatierantsoenen (glucogeen of lipogeen). Daarnaast is er een separaat experiment uitgevoerd naar pensontwikkeling van koeien met verschillende droogstandslengtes en zijn de melkcontrolegegevens geanalyseerd van 11 praktijkbedrijven die al een verkorte droogstand toepasten. De resultaten van WHYDRY laten zien dat het verkorten of weglaten van de droogstand resulteert in een verschuiving van de melkproductie van de kritische periode na afkalven naar de periode vóór afkalven wanneer de koe makkelijk in haar energiebehoefte kan voorzien. De verschillen in melkproductie en energiebalans tussen koeien met verschillende droogstandslengtes waren aanzienlijk. Verkorten van de droogstand resulteerde in beperkte reductie in melkproductie en melkopbrengst, maar met een duidelijke verbetering van de energiebalans in de daaropvolgende lactatie. Verkort droog zetten had geen gevolgen voor het celgetal in de melk, biestkwaliteit, antistofconcentratie in het bloed van de kalveren of groei van de kalveren. Een tweede lactatie opnieuw verkort droogzetten was goed mogelijk. Daarmee kan het verkorten van de droogstand naar 30 dagen een interessante strategie zijn om de energiebalans in vroege lactatie te verbeteren zonder dat het gevolgen heeft voor de totale lactatieproductie. Dit geldt zeker wanneer geen rekening gehouden hoeft te worden met de wachttijd van eventuele droogzetters en het gewenst is de melkproductie van koeien met een hoge dagproductie op 60 dagen voor afkalven de lactatieperiode te verlengen. Weglaten van de droogstand resulteerde in een sterke reductie in melkproductie en melkopbrengst, maar de energiebalans (qua duur en diepte) en metabole gezondheid werden sterk positief beïnvloed. Biestkwaliteit was significant minder, wat ook resulteerde in een lagere concentratie antistoffen in het bloed van de kalveren tot 6 weken leeftijd, maar daarna niet meer. Verder bestond het risico dat koeien vervetten en niet persistent genoeg waren om een tweede lactatie tot 4 aan afkalven gemolken te worden. Voor bepaalde koeien leek deze strategie echter wel succesvol. Koeien met een hoge dagproductie enkele maanden voor afkalven kenden geen negatieve gevolgen voor de melkproductie in de totale volgende lactatie wanneer zij gemolken werden tot aan afkalven. Onafhankelijk van droogstandslengte was ook het voeren van een glucogeen rantsoen in vroege lactatie gunstig voor de energiebalans en metabole gezondheid, in vergelijking met een meer lipogeen rantsoen.
Lokschapen vangen teken in het bos
Sikkema, A. ; Wieren, S.E. van - \ 2014
Wageningen UR/Stichting voor Duurzame Ontwikkeling
schapen - gastheer parasiet relaties - vangmethoden - lokken - natuurgebieden - borrelia burgdorferi - humane ziekten - lyme-ziekte - infectieziekten - insecticiden - experimenten - wetenschappelijk onderzoek - bosecologie - sheep - host parasite relationships - trapping - baiting - natural areas - human diseases - lyme disease - infectious diseases - insecticides - experiments - scientific research - forest ecology
De Wageningse onderzoeker Sip van Wieren wil lokschapen inzetten om teken weg te vangen in natuurgebieden. Op die manier kunnen schaapskuddes er voor zorgen dat mensen prettig kunnen recreëren in het bos.
Lokschapen tegen teken
Wieren, S.E. van - \ 2014
Wageningen UR
schapen - gastheer parasiet relaties - lokken - humane ziekten - lyme-ziekte - vangmethoden - experimenten - natuurgebieden - bosecologie - sheep - host parasite relationships - baiting - human diseases - lyme disease - trapping - experiments - natural areas - forest ecology
Teken vormen een lastig probleem voor bezoekers van natuurterreinen en bossen. Onderzoekers gaan nu met ‘lokschapen’ teken vangen.
Moestuin op mars lijkt haalbaar
Kleis, R. ; Wamelink, G.W.W. - \ 2014
Resource: weekblad voor Wageningen UR 8 (2014)10. - ISSN 1874-3625 - p. 9 - 9.
landbouwplantenteelt - buitenaardse bodemtypen - bodem-plant relaties - teelt - experimenten - crop husbandry - soil types (extraterrestrial) - soil plant relationships - cultivation - experiments
Ruimtepioniers die hun eigen groenten willen kweken, kunnen waarschijnlijk beter op Mars terecht dan op de maan. Tuinkers kiemt, bloeit en vormt zaad op Marsgrond. Maanbodem is niet zuur genoeg voor plantengroei.
De eerste fase van het Input-Outputproject : compost
Sonnenberg, A.S.M. ; Blok, C. - \ 2011
Paddestoelen : onafhankelijk vakblad voor Nederland en België 2011 (2011)4. - ISSN 1380-359X - p. 14 - 17.
eetbare paddestoelen - substraten - compost - innovaties - productieprocessen - landbouwkundig onderzoek - experimenten - edible fungi - substrates - composts - innovations - production processes - agricultural research - experiments
In het kader van het 'Input-Output' project van WUR tracht men in een experimentele champignonteelt in Wageningen sluitende balansen te generen voor de belangrijkste parameters bij de benutting van compost. Dat levert interessante data op..
Muggenplaagje voor de wetenschap
Verdonschot, P.F.M. ; Kleis, R. - \ 2011
Resource: weekblad voor Wageningen UR 6 (2011)1. - ISSN 1874-3625 - p. 10 - 10.
culicidae - culex - experimenten - diergedrag - experiments - animal behaviour
Experiment brengt vlieggedrag van mug in kaart.
Ziek en Zeer : Hoe voorkom je Pseudo-kurkstip in tulpen?
Vink, P. - \ 2011
BloembollenVisie 2011 (2011)222. - ISSN 1571-5558 - p. 23 - 23.
kurkstip - tulpen - bloembollen - gewasbescherming - experimenten - afwijkingen, planten - plantenziekten - cork spot - tulips - ornamental bulbs - plant protection - experiments - plant disorders - plant diseases
In dit artikel over het voortgezet diagnostisch onderzoek bij PPO een verslag van het onderzoek naar mogelijkheden om Pseudo-kurkstip bij tulpen te voorkomen. Uit het onderzoek is gebleken dat de oplossing nog altijd moet worden gezocht in de bewaartemperatuur direct na de oogst van de tulpenbollen.
Mogelijk hogere productie bij betere beheersing gewasstructuur : 3D-model maakt uitproberen mogelijk
Vos, J. ; Heuvelink, E. ; Kierkels, T. - \ 2011
Onder Glas 8 (2011)4. - p. 38 - 39.
glastuinbouw - sierteelt - rozen - experimenten - lichtvallen - lichtverdeling - simulatiemodellen - 3d visualisatie - snijbloemen - greenhouse horticulture - ornamental horticulture - roses - experiments - light traps - light distribution - simulation models - 3d visualization - cut flowers
Als een rozenteler de structuur van zijn gewas beter kan sturen, haalt hij wellicht meer productie van hogere kwaliteit. Een samenwerkingsverband van onderzoekers werkt aan een 3D-model, zodat je op de computer kunt uitproberen welk effect een bepaalde ingreep heeft. Cruciaal daarbij is een beter inzicht in de knopuitloop. Daar zijn veel van de deelonderzoeken op gericht.
Substraatbedden Chrysant - 2 september 2010: Voortgang en resultaten vierde teeltronde
Vermeulen, T. ; Blok, C. ; Wurff, A.W.G. van der; Khodabaks, M.R. - \ 2010
cultuur zonder grond - chrysanten - bloementeelt - zand - grondbakken - veengronden - bekistingen - experimenten - soilless culture - chrysanthemums - floriculture - sand - soil bins - peat soils - formwork - experiments
Informatieposter over gebruik van verschillende substraatbedden bij de vierde teeltronde van chrysanten.
Bladvlekken in laurierkers: Xanthomonas of Pseudomonas?
Doorn, J. van; Dalfsen, P. van; Kuik, A.J. van; Hollinger, T.C. ; Pham, K.T.K. ; Martin, W.S. - \ 2010
bladvlekkenziekte - afwijkingen, planten - bacteriën - gewasbescherming - detectie - kennis - vervolg - pesticiden - experimenten - leaf spotting - plant disorders - bacteria - plant protection - detection - knowledge - follow up - pesticides - experiments
Samenvattende beschrijving van een onderzoek naar bladvlekken in laurierkers. Gaat het hier om Xanthomonas of Pseudomonas?
Bestrijding stengelaaltjes door inundatie
Vreeburg, P.J.M. ; Korsuize, C.A. - \ 2010
inundatie - bloembollen - gewasbescherming - fysische gewasbeschermingsmethoden - ditylenchus dipsaci - aaltjesdodende eigenschappen - nematodenbestrijding - experimenten - onderzoek - flooding - ornamental bulbs - plant protection - physical control - nematicidal properties - nematode control - experiments - research
Poster over de bestrijding van stengelaaltjes door inundatie. Bescherijving van een proef met inudatie door buizen te vullen met grond, te besmetten met aaltjes en vervolgens verschillende inundatie-regimes toe te passen. Inundatie had na 12 weken effect, dus het advies is om inundatie gedurende 12 weken uit te voeren in de zomermaanden.
Betrekken van boereninitiatieven in een leer- en experimenteer strategie voor duurzame ontwikkeling van de veehouderij
Spoelstra, S.F. ; Elzen, B. - \ 2010
Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 355) - 17
duurzaamheid (sustainability) - boeren - leervermogen - experimenten - strategisch management - sustainability - farmers - learning ability - experiments - strategic management
Based on the theory of Strategic Niche Management farmers initiatives, individually as well as in a certain coherence, are considered and treated as a set of experiments for learning on opportunities and barriers for sustainable development
Bestrijding van Echinothrips americanus
Pijnakker, J. ; Leman, A. ; Ramakers, P.M.J. - \ 2010
thripidae - bestrijdingsmethoden - chemische bestrijding - experimenten - onderzoek - control methods - chemical control - experiments - research
Poster over de bestrijding van Echinothrips americanus.
Telen zonder zon krijgt brede introductie (interview met o.a. Leo Marcelis)
Honkoop, E. ; Marcelis, L.F.M. - \ 2010
Groenten en Fruit Magazine 2010 (2010)4. - ISSN 1879-7318 - p. 46 - 47.
tuinbouw - teelt onder bescherming - kunstlicht - landbouwkundig onderzoek - economische haalbaarheid - teelt in meer lagen - experimenten - glastuinbouw - geconditioneerde teelt - klimaatkamerproeven - energiebesparing - horticulture - protected cultivation - artificial light - agricultural research - economic viability - multistorey cropping - experiments - greenhouse horticulture - conditioned cultivation - growth chamber experiments - energy saving
Net zoals water geven van de planten niet meer afhangt van de regen, zo zou het licht op de planten niet langer moeten afhangen van de aanwezigheid van zonlicht. Want de zon is gratis, maar komt met alle nadelen en grillen van de natuur.
Substraatbedden chrysant - 14 januari 2001: Voortgang en resultaten tweede teeltronde
Vermeulen, T. ; Blok, C. - \ 2010
cultuur zonder grond - innovaties - chrysanten - teeltsystemen - experimenten - onderzoek - soilless culture - innovations - chrysanthemums - cropping systems - experiments - research
Poster met een beschrijving van een onderzoek naar het vinden van geschikte substraatbedden voor Chrysant.
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