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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    Influence of Pluronic F127 on the distribution and functionality of inkjet-printed biomolecules in porous nitrocellulose substrates
    Mujawar, L.H. ; Amerongen, A. van; Norde, W. - \ 2015
    Talanta 131 (2015). - ISSN 0039-9140 - p. 541 - 547.
    protein microarrays - spot morphology - block-copolymer - antibody - surfaces - additives - membrane - flow - hydrophobicities - orientation
    The distribution of inkjet-printed biomolecules in porous nitrocellulose substrates often results in a non-homogeneous spot morphology commonly referred to as 'doughnut-shaped' spots. We have studied the influence of Pluronic F127 (an amphiphilic surfactant) on the functionality of inkjet-printed primary antibody molecules and on the final assay result by performing a one-step antibody binding assay in the nitrocellulose substrate. The primary antibody was printed with and without Pluronic, followed by the addition of double-labelled amplicons as antigen molecules and a fluorophore-labelled streptavidin as detection conjugate. The distribution of the fluorescence intensity down into the nitrocellulose substrate was investigated by confocal laser scanning microscopy in 'Z' stacking mode. Each horizontal slice was further analysed by applying a concentric ring format and the fluorescence intensity in each slice was represented in a colour-coded way. The mean and total fluorescence intensity of the antibody binding assay (fluorescent streptavidin) showed a peak at 0.2% (w/v) Pluronic F127. In addition, an improved spot morphology was observed also peaking at the same Pluronic concentration. Subsequently, we investigated the direct influence of Pluronic F127 on the location of the primary antibody molecules by labelling these molecules with the fluorophore Alexa-488. Our results show that upon increasing the concentration of Pluronic F127 in the printing buffer, the spot diameter increased and the number of primary antibody molecules bound in the spot area gradually decreased. This was confirmed by analysing the distribution of fluorescently labelled primary antibody molecules down into the membrane layers. We conclude that a particular ratio between primary antibody and Pluronic F127 molecules in combination with available substrate binding capacity results in an optimal orientation, that is Fab-UP, of the primary antibody molecules. Consequently, an increased number of antigen molecules (in our case the labelled amplicons) and of the fluorescent detection conjugate (streptavidin) will give an optimal signal. Moreover, distribution of the primary antibody molecules was more homogeneous at the optimal Pluronic F127 concentration, contributing to the better spot morphology observed.
    Learning Apart Together: Towards an Integrated Competence Framework for Sustainable Entrepreneurship in Higher Education
    Lans, T. ; Blok, V. ; Wesselink, R. - \ 2014
    Journal of Cleaner Production 62 (2014). - ISSN 0959-6526 - p. 37 - 47.
    opportunity-identification - venture performance - firm performance - management - perspective - growth - exploitation - capabilities - recognition - orientation
    Sustainable entrepreneurs, i.e. those who proactively facilitate latent demands for sustainable development, are now in higher demand than ever before. Higher (business) education can play an important role in laying the foundation for these sustainable entrepreneurs. Traditionally, however, educational scholars focus either on the issue of education for sustainability or on entrepreneurship education. There is little work which explores and/or crosses the boundaries between these two disciplines, let alone work in which an effort is made to integrate these perspectives. In this article, a competence approach was taken as a first step to link the worlds of education for entrepreneurship and for sustainability because we postulate that both, apparently different, worlds can reinforce each other. Based on a literature review, focus group discussions with teachers in higher education (n = 8) and a structured questionnaire among students (n = 211), a set of clear, distinct competencies was developed, providing stepping stones for monitoring students' sustainable entrepreneurship development in school-based environments.
    From Subsistence Marketplaces Up, from General Macromarketing Theories Down: Bringing Marketing’s Contribution to Development into the Theoretical Midrange
    Ingenbleek, P.T.M. - \ 2014
    Journal of Macromarketing 34 (2014)2. - ISSN 0276-1467 - p. 199 - 212.
    service-dominant logic - public-policy - organizational culture - economic-development - product innovation - emerging markets - orientation - performance - systems - impact
    Marketing researchers have recently begun exploring the specific context of subsistence marketplaces in developing and emerging economies using a bottom-up approach. Such literature offers an increasing number of conceptual frameworks and theoretical approaches derived from or inspired by a sound understanding of the real-life contexts of subsistence marketplaces. This article draws attention to a complementary top-down approach that begins from basic thinking on marketing’s contribution to development and, through midrange theories, eventually connects with bottom-up insights into subsistence marketplaces. The top-down approach helps create a unique theoretical midrange for development-oriented research in marketing that is complementary to other disciplines in the development debate. A bottom-up and top-down shaped theoretical midrange promises transformative interventions that can attend to the specific context at hand, while connecting with basic marketing principles on development.
    Configuration of inter-organizational information exchange and the differences between buyers and sellers
    Peng, G. ; Trienekens, J.H. ; Omta, S.W.F. ; Wang, W. - \ 2014
    British Food Journal 116 (2014)2. - ISSN 0007-070X - p. 292 - 316.
    supply chain - media selection - communication - performance - satisfaction - orientation - indicators - constructs - quality - impact
    Purpose – The aim of this paper is to extend the understanding of the configuration of inter-organizational information exchange (IOIE) and the role of each aspect of IOIE in realizing potential communication benefits. Design/methodology/approach – A conceptual framework on the configuration of IOIE was developed by examining the relationships between companies in the poultry supply chain in China. A sample of 165 buying companies and a sample of 96 sellers were analyzed by partial least square modeling. Findings – Communication willingness plays a critical role in improving communication quality and realizing potential communication benefits. Modern media remain as a huge potential opportunity for improving performance. Meanwhile, the power of face-to-face communication should never be neglected, even in the coming Information Age. Higher communication frequency contributes to better understanding of companies' changing requirements and expectations. Taking use of senior managers and staff from different functions helps sellers grasp better changing markets. Communication quality is found as a multi-dimensional concept and plays a critical mediating role in realizing communication benefits. Originality/value – The proposition of the model of configuration of inter-organizational information exchange and the quantitative empirical examination of the model fills an important research gap.
    Understanding Positive Attitudes toward Helping Peers: The Role of Mastery Goals and Academic Self-Efficacy
    Poortvliet, P.M. ; Darnon, C. - \ 2014
    Self and Identity 13 (2014)3. - ISSN 1529-8868 - p. 345 - 363.
    achievement goals - performance goals - organizational citizenship - information exchange - seeking behaviors - early adolescents - job-satisfaction - motivation - task - orientation
    The present research was designed to document the relationship between mastery and performance goals and attitudes toward helping others, and to test the mediating role of self-efficacy. Two experiments (Studies 1 and 2) showed that students with mastery goals hold stronger positive attitudes toward helping peers, relative to students with performance goals. Furthermore, a field study (Study 3) indicated that students’ mastery goals were positively related to holding positive attitudes toward helping fellow students, whereas performance goals were not. Studies 2 and 3 indicated that this could be explained by the intra-individual process of academic self-efficacy. Finally, it was shown that a negative relationship existed between performance goals and helping peers only for individuals with relatively weak mastery goals
    The Norm Activation Model: An exploration of the functions of anticipated pride and guilt in environmental behaviour
    Onwezen, M.C. ; Antonides, G. ; Bartels, J. - \ 2013
    Journal of Economic Psychology 39 (2013). - ISSN 0167-4870 - p. 141 - 153.
    maximum-likelihood-estimation - self-conscious emotions - planned behavior - responsible behavior - decision-making - personal norms - intentions - choice - determinants - orientation
    The Norm Activation Model (NAM; Schwartz, 1977) is a vested model that explains altruistic and environmentally friendly behaviour. Although research states that anticipated pride and guilt are associated with the NAM, these associations are not yet fully understood. The current study provides an overview of the literature that refers to anticipated pride and guilt within the NAM. Moreover, we aim to increase our understanding of these associations through theoretical arguments and a study conducted in the Netherlands. We hypothesised that anticipated pride and guilt cause individuals to behave themselves in a manner that is in line with personal norms. This proposition regarding the self-regulatory function of anticipated pride and guilt was confirmed by our study; anticipated emotions mediate the effects of personal norms on behaviour. These associations remained after including the Theory of Planned Behaviour in the NAM, although in the integrated NAM–TPB model, anticipated emotions affected behaviour via behavioural intentions. Implications regarding these findings are discussed.
    Oriented antibodies as versatile detection element in biosensors
    Trilling, A.K. - \ 2013
    Wageningen University. Promotor(en): Han Zuilhof, co-promotor(en): Jules Beekwilder. - S.l. : s.n. - ISBN 9789461735683 - 168
    biosensoren - oppervlakten - oppervlaktechemie - oriëntatie - antilichamen - lama's - antistoftesten - mycobacterium tuberculosis - unimoleculaire films - immobilisatie - biosensors - surfaces - surface chemistry - orientation - antibodies - llamas - antibody testing - mycobacterium tuberculosis - unimolecular films - immobilization

    The aim of this thesis is to explore orientation of detection elements on biosensor

    surfaces. To this end, different strategies were combined such as surface chemistry and protein functionalization, with the aim to generate a platform for oriented immobilization of antibodies

    in biosensors. Chapter 2 investigates the formation of organic monolayers on

    oxide-free copper. Detailed studies were performed to characterize the monolayers

    and proof its quality. Apart from being the first oxide-free monolayers on copper

    reported thus far, further functionalization was successfully investigated.

    Chapter 3 gives an overview about approaches used to orient antibodies on surfaces.

    It also summarizes methods used to characterize the orientation of immobilized

    antibodies in a more direct manner.

    In chapter 4 a set of detection elements for tuberculosis bacteria is described. These

    are variable domains of llama heavy-chain antibodies, known as VHH proteins. A

    number of VHHs, selected by phage display, were expressed by Escherichia coli bacteria

    and characterized for binding towards Mycobacterium tuberculosis bacteria.

    Specificity of VHHs was investigated and the antigen was identified.

    In chapter 5 the impact of orientation on the analyte binding capacity was studied

    by SPR as model biosensor. Established techniques (NH2 coupling, biotyinylation)

    were used to immobilize VHHs, and a comparison between oriented and random

    immobilized VHHs was made. The effect of molecular weight, epitope number and

    affinity of the target analyte was investigated.

    In chapter 6, a novel coupling chemistry was used to immobilize VHHs, and in this case the same chemistry could be used for oriented and random immobilization. VHHs were engineered and functionalized with a non-natural amino acid to bear either one or five azide groups. Azide groups served as unique chemical handles on the VHHs and were used to click proteins onto a cyclooctyne-modified surface in an oriented and random approach. Spectacular effects on biosensor sensitivity were observed when VHHs were immobilized in an oriented manner.

    Finally, in chapter 7, the main results of this thesis are summarized and remaining

    problems as well as ideas for future research are discussed.

    The interaction of multiple champions in orchestrating innovation networks: Conflicts and complementarities
    Klerkx, L.W.A. ; Aarts, N. - \ 2013
    Technovation 33 (2013)6-7. - ISSN 0166-4972 - p. 193 - 210.
    structural holes - intermediaries - management - knowledge - industry - brokers - infrastructure - communities - orientation - leadership
    In networked or open innovation processes, so-called innovation communities have been identified in the innovation champion literature, in which innovation champions from different levels in the innovation system supposedly act as a team. It has however not been studied in detail to what extent and how different champions in innovation communities complement each other and act as a team. Applying the concept of innovation network orchestration to analyze the role and position of different kinds of champions as brokers in innovation networks, the purpose of this paper is to unravel the interaction between champions and what this entails in terms of role complementarities and conflicts as regards innovation network orchestration. This is done by using an explorative multiple case study approach in which three innovation journeys are analyzed. The results indicate that a distinction can be made between primary innovation communities, who act as aggregated orchestrators of the overall innovation network, and who in turn orchestrate secondary innovation communities in certain sub-networks. Here different kinds of champions complement each other and act as a team, but these complementarities are not a given: they are negotiated over time in interaction, and lack of reflection on each other’s roles may result in role conflicts. The main conclusion is that an oversimplified notion of innovation communities as a unified team of champions should be avoided: innovation communities themselves need a form of orchestration.
    Cortical microtubule arrays are initiated from a nonrandom prepattern driven by atypical microtubule initiation
    Lindeboom, J.J. ; Lioutas, A. ; Deinum, E.E. ; Tindemans, S. ; Ehrhardt, D.W. ; Emons, A.M.C. ; Mulder, B. - \ 2013
    Plant Physiology 161 (2013)3. - ISSN 0032-0889 - p. 1189 - 1201.
    plant-cells - nitella-tasmanica - self-organization - gamma-tubulin - arabidopsis - nucleation - mechanism - orientation - dynamics - reveals
    The ordered arrangement of cortical microtubules in growing plant cells is essential for anisotropic cell expansion and, hence, for plant morphogenesis. These arrays are dismantled when the microtubule cytoskeleton is rearranged during mitosis and reassembled following completion of cytokinesis. The reassembly of the cortical array has often been considered as initiating from a state of randomness, from which order arises at least partly through self-organizing mechanisms. However, some studies have shown evidence for ordering at early stages of array assembly. To investigate how cortical arrays are initiated in higher plant cells, we performed live-cell imaging studies of cortical array assembly in tobacco (Nicotiana tabacum) Bright Yellow-2 cells after cytokinesis and drug-induced disassembly. We found that cortical arrays in both cases did not initiate randomly but with a significant overrepresentation of microtubules at diagonal angles with respect to the cell axis, which coincides with the predominant orientation of the microtubules before their disappearance from the cell cortex in preprophase. In Arabidopsis (Arabidopsis thaliana) root cells, recovery from drug-induced disassembly was also nonrandom and correlated with the organization of the previous array, although no diagonal bias was observed in these cells. Surprisingly, during initiation, only about one-half of the new microtubules were nucleated from locations marked by green fluorescent protein-¿-tubulin complex protein2-tagged ¿-nucleation complexes (¿-tubulin ring complex), therefore indicating that a large proportion of early polymers was initiated by a noncanonical mechanism not involving ¿-tubulin ring complex. Simulation studies indicate that the high rate of noncanonical initiation of new microtubules has the potential to accelerate the rate of array repopulation.
    Best Practices for New Product Pricing: Impact on Market Performance and Price Level under Different Conditions
    Ingenbleek, P.T.M. ; Frambach, R.T. ; Verhallen, Th.M.M. - \ 2013
    Journal of Product Innovation Management 30 (2013)3. - ISSN 0737-6782 - p. 560 - 573.
    organizational research - contingency approach - buyers perceptions - strategies - orientation - industrial - quality - model - perspective - advantage
    To date, research on new product pricing has predominantly been approached as a choice between market skimming and penetration pricing. Despite calls for research that addresses other complexities in new product pricing, empirical research responding to these calls remains scarce. This paper examines three managerial price-setting practices for new products, i.e., value-informed, competition-informed, and cost-informed pricing. By engaging in these practices, managers can develop and compare quantifications in order to attain an introduction price for the product. The authors draw on consumer price perception literature, Monroe's pricing discretion model, and numerical cognition literature to develop hypotheses about the impact of price-setting practices on new product market performance and price level. By studying the effects on market performance and price level, the paper provides insights that may help explain the growth of new products and address the problems of underpricing. The hypotheses are tested in a management survey of 144 production and service companies. The results indicate which pricing practices are superior for the achievement of either higher market performance or higher prices in specific product and market conditions. Whereas value-informed pricing has an unambiguous positive impact on relative price level and market performance, the results also suggest that in many cases engaging in value-informed pricing is not enough. The effects of cost-informed and competition-informed pricing may differ depending upon the objective (market performance or higher prices), product conditions (product advantage and relative product costs), and market condition (competitive intensity). Engaging in inappropriate pricing practices leads to a decline in new product performance. Moreover, bad pricing practices make the positive effect of product advantage on the outcome variables disappear. The latter finding suggests that companies can jeopardize their efforts and investments in the new product development process if they engage in the wrong price-setting practices. The findings imply that managers should consider different factors in new product pricing. First, when launching a new product, they should determine their explicit pricing objective, either stressing market performance or a higher price level. To determine the most appropriate pricing practices, however, they should next assess their situation in terms of product advantage, relative product costs, and competitive intensity. Together with the pricing objective, these conditions determine the best pricing practice. On a higher level, the findings imply that companies should invest in knowledge development in order to engage in the appropriate pricing practices for each product launch
    Strategic Value Assessment and Explorative Learning Opportunities with Customers
    Nijssen, E.J. ; Hillebrand, B. ; Jong, J.P.J. de; Kemp, R.G.M. - \ 2012
    Journal of Product Innovation Management 29 (2012)Suppl. S1. - ISSN 0737-6782 - p. 91 - 102.
    product development - lead users - innovation - orientation - competence - alliances - firms - conceptualization - exploitation - antecedents
    This study recognizes that collaboration with customers for new product development may bring important financial benefits to firms, but at the same time may seriously hamper explorative learning. Many firms are approached by customers with requests to develop new products for them. While such requests may strengthen customer relationships and result in short-term financial gains, it may force a firm in technologically undesirable directions. As a result, many firms struggle with the dilemma of, on the one hand, responding to customer requests, and on the other hand, safeguarding the long-term competitive position of the firm. Firms with strong customer ties are particularly prone to this dilemma. Drawing on opportunity recognition literature, capability monitoring literature as well as goal setting theory, the authors have developed a framework arguing that Strategic Value Assessment (SVA) can help resolve this. SVA is defined as an a priori business evaluation of the value of a particular innovation collaboration, based on anticipated long-term strategic benefits. It helps innovative firms to focus on collaboration with customers with lead user status and to develop intense relationships, allowing for more effective knowledge transfer and learning. The framework is tested using data collected from a sample of 136 business-to-business firms in the Netherlands. The sampling frame was a panel of small and medium-sized high-tech enterprises. The study finds positive direct and indirect effects of SVA on explorative learning. In addition, the findings show that the intense collaboration/learning relationship is positively moderated by customer lead user status, and negatively moderated by customer dependence. The findings suggest that SVA is a useful heuristic for managers to utilize opportunities for innovation involving collaboration with customers.
    Potential for Grey wolf Canis lupus in the Netherlands : effects of habitat fragmentation and climate change on the carrying capacity and population dynamics
    Potiek, A. ; Wamelink, G.W.W. ; Jochem, R. ; Langevelde, F. van - \ 2012
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2349) - 66
    wolven - fauna - wildbescherming - wildbeheer - habitatfragmentatie - oriëntatie - nederland - populatiedynamica - wolves - fauna - wildlife conservation - wildlife management - habitat fragmentation - orientation - netherlands - population dynamics
    Recolonization of the Netherlands by wolves is likely to occur within 5 to 10 years, and for management reasons the habitat suitability should be understood. Therefore, I predicted the carrying capacity and population dynamics of the wolf in the Netherlands, and studied the effects of habitat fragmentation and climate change. The effects of climate change on soil processes, vegetation structure and prey abundance for wolves were simulated with the models SMART2 and SUMO2. I assessed the effects of habitat fragmentation by comparing a scenario with and without wildlife overpasses. Population dynamics were simulated applying the model METAPHOR. Due to climate change, primary productivity increased, resulting in higher prey availability. Wolf carrying capacity and population dynamics are hence positively affected by climate change, although the effect was smaller than for habitat fragmentation. The average number of adults after a 110 year model run more than doubled in the presence of overpasses compared to the scenario without. Population persistence is negatively affected by habitat fragmentation. This study indicates the importance of overpasses for carnivores, which therefore should be an integrated part of nature management.
    De komst van de wolf (Canis lupus) in Nederland : een 'factfinding study'
    Groot Bruinderink, G.W.T.A. ; Jansman, H.A.H. ; Jacobs, M.H. ; Harmsen, M. - \ 2012
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2339) - 69
    wolven - fauna - wildbescherming - wildbeheer - habitatrichtlijn - oriëntatie - nederland - wolves - fauna - wildlife conservation - wildlife management - habitats directive - orientation - netherlands
    In 2000 waren er voor het eerst weer wolven met jongen in Duitsland in de regio Lausitz (Saksen), grenzend aan Zuidwest-Polen. De populatie breidt zich sindsdien geleidelijk uit. Op voorhand uitsluiten dat ze in Nederland opduiken is niet reëel, maar het is onvoorspelbaar waar en wanneer de wolf zal opduiken in Nederland. Aanbevolen wordt dat Nederland cf. het bepaalde in de Conventie van Bern een wolvenbeschermingsplan op gaat stellen, om de wolf cf. het bepaalde in de Habitatrichtlijn op te nemen in de lijst van beschermde soorten en om leefgebied(en) voor de wolf aan te wijzen. In het rapport worden een groot aantal andere aanbevelingen gedaan voor beleidsvoorbereiding op grond van feitenonderzoek. In veel gevallen wordt samenwerking met het buitenland aanbevolen.
    Self-improvement and cooperation: How exchange relationships promote mastery-approach driven individuals’ job outcomes
    Poortvliet, P.M. ; Giebels, E. - \ 2012
    European Journal of Work and Organizational Psychology 21 (2012)3. - ISSN 1359-432X - p. 392 - 425.
    leader-member exchange - achievement goals - performance goals - task motivation - social motives - orientation - commitment - behavior - work - ability
    In the present research we argue that mastery-approach goals may be beneficial in social achievement contexts because these goals lead to constructive exchange relationship building. An examination of three methodologically complementary studies revealed that mastery-approach goals lead to more cooperative and higher-quality exchange relationships than performance-approach goals and are, ultimately, associated with better job outcomes, as well. The results of a questionnaire study demonstrated that mastery-approach goals are more strongly related to cooperative motives and more weakly related to competitive motives than performance-approach goals. Furthermore, an experimental study indicated that mastery-approach driven individuals show a higher concern for others and are more strongly inclined to cooperate with an exchange partner when engaged in a complex reasoning task than performance-approach driven individuals. Finally, an organizational field study showed that team–member exchange mediates the effect of mastery-approach goals on job performance, job satisfaction, and organizational commitment
    Perverse effects of other-referenced performance goals in an information exchange context
    Poortvliet, P.M. ; Anseel, F. ; Janssen, O. ; Yperen, N.W. van - \ 2012
    Journal of Business Ethics 106 (2012)4. - ISSN 0167-4544 - p. 401 - 414.
    achievement goals - multiple-goal - orientation - mastery - task - motivation - behavior - model - work - satisfaction
    A values-centered leadership model comprised of leader stakeholder and economic values, follower values congruence, and responsible leadership outcomes was tested using data from 122 organizational leaders and 458 of their direct reports. Alleviating same-source bias concerns in leadership survey research, follower ratings of leadership style and follower ratings of values congruence and responsible leadership outcomes were collected from separate sources via the split-sample methodology. Results of structural equation modeling analyses demonstrated that leader stakeholder values predicted transformational leadership, whereas leader economic values were associated with transactional leadership. Follower values congruence was strongly associated with transformational leadership, unrelated to transactional leadership, and partially mediated the relationships between transformational leadership and both follower organizational citizenship behaviors and follower beliefs in the stakeholder view of corporate social responsibility. Implications for responsible leadership and transformational leadership theory, practice, and future research are discussed.
    Analysing, pursuing and networking: Towards a validated three-factor framework for entrepreneurial competence from a small firm perspective
    Lans, T. ; Verstegen, J.A.A.M. ; Mulder, M. - \ 2011
    International Small Business Journal 29 (2011)6. - ISSN 0266-2426 - p. 695 - 713.
    opportunity identification - test statistics - farm business - performance - conceptualization - orientation - knowledge - patterns - growth - work
    XMoving beyond general personal traits as predictors for success, a growing volume of research acknowledges that entrepreneurial core processes are enabled by specific competencies which can be learned, further refined and developed. The research objective of this article is to develop a framework for entrepreneurial competence in a well-defined small firm sector by elaborating and empirically validating an existing categorization of entrepreneurial competence. The dataset includes 348 small firm owner-managers who participated in an educational programme, established to pursue new business opportunities in the Dutch agri-food sector. Exploratory factor analysis and confirmatory factor analysis revealed that three domains constitute the heart of entrepreneurial competence in this small firm context: 'analysing', 'pursuing' and 'networking'. These three competence domains provide professionals active in sector development, small business support and (vocational) education with an empirically valid framework of clearly discernible elements of entrepreneurial competence. This framework also encompasses insights on education and learning.
    A statistical analysis of fibre size and shape distribution after compounding in composites reinforced by natural fibres
    Moigne, N. Le; Oever, M.J.A. van den; Budtova, T. - \ 2011
    Composites Part A: Applied Science and Manufacturing 42 (2011)10. - ISSN 1359-835X - p. 1542 - 1550.
    flax straw fibers - mechanical-properties - polypropylene composites - polymers - length - orientation - wheat - microstructure - morphology - strength
    Using high resolution optical microscopy coupled with image analysis software and statistical methods, fibre length and aspect ratio distributions in polypropylene composites were characterized. Three types of fibres, flax, sisal and wheat straw, were studied. Number and surface weighted distributions were used to demonstrate the presence and amount of elementary fibres, fibre bundles and particles. A large number of small particles that are usually not taken into account were found. The obtained fibre length and aspect ratio distributions were successfully fitted by a two-parameter Weibull model. No significant effect of fibre concentration on the length and aspect ratio distributions was detected for 20% and 40% flax-based composite. Fibre type was found to be a very important parameter influencing size and shape distributions: flax is broken into long elementary fibres, sisal-based composite contains non-dispatched bundles and elementary fibres and wheat straw-based composite has bundles and large and small particles.
    A framework for modelling business processes in demand-driven supply chains
    Verdouw, C.N. ; Beulens, A.J.M. ; Trienekens, J.H. ; Vorst, J.G.A.J. van der - \ 2011
    Production Planning & Control 22 (2011)4. - ISSN 0953-7287 - p. 365 - 388.
    operations management - information-systems - science research - design science - technology - organizations - opportunities - orientation - challenges - redesign
    Demand-driven supply chains are highly dynamic networks of different participants with different allocations of business processes and different modes of control and coordination. Companies must be able to take part in multiple supply chain configurations concurrently and to switch rapidly to new or adjusted configurations. This imposes stringent demands on information systems and requires a modelling approach that (1) combines high-level models for supply chain design with detailed models for engineering the accompanying information systems and (2) enables rapid instantiation of specific supply chain configurations from a repository of standard building blocks. This article designs a process modelling framework that enhances such an approach. Building on the terminology and process definitions provided by the Supply Chain Operations Reference model, it models supply chain configurations as specific sets of transformations, control systems and coordination mechanisms. The designed modelling framework is applied in a case study in the Dutch flower industry.
    Toward a more social understanding of achievement goals: The interpersonal effects of mastery and performance goals
    Poortvliet, P.M. ; Darnon, C. - \ 2010
    Current Directions in Psychological Science 19 (2010)5. - ISSN 0963-7214 - p. 324 - 328.
    orientation - exchange - behavior
    The current article presents an overview of recent research into social outcomes that accompany the pursuit of achievement goals. On the basis of investigations in various subdisciplines of psychology, we conclude that mastery goals—striving to improve one’s own performance—lead to investments in exchange relationships, endorsement of reciprocity norms, and active efforts to integrate different opinions. In contrast, performance goals—striving to outperform others—may result in rather maladaptive social behaviors. We point to three promising avenues for future research: Social consequences of achievement goals could be studied from a multiple-goal perspective, different levels of analysis should be taken into account, and the role of status differences should be examined
    Effects of polyelectrolyte complex micelles and their components on the enzymatic activity of lipase
    Lindhoud, S. ; Norde, W. ; Cohen Stuart, M.A. - \ 2010
    Langmuir 26 (2010)12. - ISSN 0743-7463 - p. 9802 - 9808.
    humicola-lanuginosa lipase - charged block-copolymers - interfacial activation - orientation - surface - core
    The enzymatic activity of Hl-lipase embedded in complexes of poly-2-methylvinylpyridinium-co-poly(ethylene oxide) (P2MVP41-PEO205) and poly(acrylic acid)(PAA139) is studied as a function of the PAA139 + P2MVP41-PEO205 complex composition. The measurements revealed that there are several factors that influence the enzymatic activity. When incorporated in micelles, the activity of lipase is increased, which suggests that the micelles favor the active state. The activity may further increase because the substrate tends to accumulate to the micelles. It is found that the presence of PAA139 alone also increases the enzymatic activity somewhat. Increasing of the ionic strength decreases the enzymatic activity in all systems. However, at ionic strengths where the micelles are disintegrated (>0.5 M), the activity of lipase in the presence of both polyelectrolytes is still higher than the activity of free lipase. At 0.7 M NaCl it was found that lipase in the presence of (just) P2MVP41-PEO205 is more active than lipase without this additive.
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