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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    Stadium Coltan : artisanal mining, reforms and social change in eastern Democratic Republic of Congo
    Wakenge, Claude Iguma - \ 2017
    Wageningen University. Promotor(en): D.J.M. Hilhorst, co-promotor(en): K. Vlassenroot; J.G.R. Cuvelier. - Wageningen : Wageningen University - ISBN 9789463434560 - 210
    mining - conflict - economic sociology - cooperatives - reconstruction - poverty - rural sociology - workers - feedstocks - minerals - congo democratic republic - central africa - mijnbouw - conflict - economische sociologie - coöperaties - reconstructie - armoede - rurale sociologie - werkers - industriële grondstoffen - mineralen - democratische republiek kongo - centraal-afrika

    In the Democratic Republic of Congo (DRC), the mining sector has the potential to play a pivotal role in post-conflict reconstruction (World Bank, 2008), and artisanal mining sustains the livelihoods of millions people in the country (PACT, 2010). However, in the last 15 years, minerals from this artisanal mining have been ill-reputed. Eastern DRC has often been characterised by chronic instability and violent conflicts (Autesserre, 2010; Stearns, 2011) because it is widely believed that minerals in this region have attracted the greed of national and foreign armed groups, who benefit from the mining business.

    Although this ‘greed hypothesis’ has been criticised for its inconsistent performance in explaining resource-related conflicts (Le Billon, 2010; Ross, 2006), various national and international reform initiatives have gained momentum (Verbruggen et al., 2011). These initiatives aim to make the Congolese artisanal mining sector more transparent and to prevent ‘conflict minerals’ from entering the international market. In 2014, 13 reform initiatives—10 focusing on 3T (tantalum, tin and tungsten) and three on gold—were operational in eastern DRC (Cuvelier et al. 2014: 5). The implicit assumptions are that mining reforms will fully ‘clean’ artisanal mining of violence and corruption and that this will contribute to sustaining people’s livelihoods (Garrett and Mitchell, 2009: 12).

    This study investigated initiatives intended to ‘formalise’ artisanal mining in DRC—in other words, they aimed to bring mining under state control. The study especially focuses on the effects of one among these initiatives—the ITRI Tin Supply Chain Initiative (iTSCi)—on two groups of actors: miners (creuseurs) and middlemen (négociants). This thesis thus presents a fine-grained case study of the iTSCi. Designed by the International Tin Research Institute in 2009, iTSCi provides a means of determining the origin of 3T and documenting the trading chain for these minerals by ‘tagging and bagging’ the loads of 3T near miners’ shafts (at postes d’achat/selling points or buying stations), at counting offices (comptoirs) and in mineral depots, before the minerals are exported through the international market.

    This is a qualitative study undertaken at three coltan mining sites of northern Katanga: Kahendwa, Kisengo and Mai-Baridi. Coltan has been extracted at these sites since 2007. From March 2013 to September 2014, data were collected using participant observation of people’s practices (extraction/sale of coltan and various types of interactions between trading houses, cooperatives, mineworkers (creuseurs) and middlemen (négociants), as well as detailed in-depth interviews with creuseurs, négociants and their households. Data were also collected from the staff of mining cooperatives, trading houses, state authorities and civil servants—predominantly of the Service d’Assistance et d’Encadrement du Small-Scale Mining (SAESSCAM) and the Division des Mines. The last group of informants were a group of clandestine coltan négociants (known as hiboux—literally, ‘owls’), who were followed in the study.

    The purpose of this research is to study the micro-dynamics of changes after the reforms following the implementation of iTSCi. The study thus provides insights into how iTSCi is concretely implemented and how it has altered the organisation of mining and the trade of coltan. The study also aims to examine how this organisation affected creuseurs and négociants. The main research question of this study is as follows:

    How have initiatives to reform artisanal mining (iTSCi in particular) affected institutional change, how does this relate to changes in patterns of coltan production and trade, how were creuseurs and négociants affected by these changes, and how did these groups respond in the coltan mining areas of Kahendwa, Kisengo and Mai Baridi (northern Katanga) from 2009 to 2014?

    Analytically, the study adopted three main theoretical perspectives. First, an actor-oriented approach was taken, building on the premise that individual actors have the agency, knowledge and experience to reflect upon their situation and to respond to changes in their surrounding context (Giddens, 1984). Although the examined mining reforms consist predominantly of ‘ready-made’ techniques such as iTSCi’s ‘tagging and bagging’, analysing reforms with an actor orientation helps to highlight people’s reactions and responses. This includes how reform policies are applied in institutions (e.g. mining cooperatives), how they interact, how they are assigned meaning and how they are negotiated by social actors (Christoplos and Hilhorst, 2009).

    Second, the study builds on the sociology of economic life, which holds that economic action is a form of social action that is socially ‘embedded’, meaning that it is linked with or dependent on actions and institutions (such as social networks) that are noneconomic in content, goals and processes (Granovetter, 2005). This perspective facilitates the analysis of the livelihoods of négociants, including mechanisms of smuggling minerals into and beyond the mining areas where iTSCi is in force.

    Third, this thesis introduced the original concept of ‘enclaves of regulations’. These enclaves refer to the mining areas where iTSCi or other reforms are in force. This thesis has shown that, although these ‘enclaves’ appear to be ‘closed’ and insulated from the environment in terms of the locally applied rules for the mining and trading of minerals (e.g. ‘tagging and bagging’), in reality, such closure is not complete. This thesis has demonstrated that it would therefore be more appropriate to consider these ‘enclaves’ as semi-autonomous fields with porous boundaries.

    Apart from the introduction and the concluding chapters, this thesis is composed of five chapters. Chapter 2 explores the evolution of the mineral sector in the Katanga province. It analyses the history of mining, the initiation of artisanal mining and how the ongoing reforms have been informed by this history. In this chapter, it is shown that there is a long history of the organisation of mining in the Katangese province. The reforms therefore did not enter into a stage of anarchy, or an institutional void, but they added a layer to already existing forms of organisation.

    Chapter 3 focuses on mining cooperatives as newly introduced institutions aimed at governing the artisanal mining sites. Through a single case study, the chapter analyses how these cooperatives —especially the Coopérative des Artisanaux Miniers du Congo, CDMC—were introduced into the mining areas and how they interacted and blended with pre-existing miners’ organisations. This chapter demonstrates that cooperatives have been an emergent—rather than durable—solution in terms of representing the interests of artisanal miners.

    In Chapter 4, I provide a different perspective on ‘conflict minerals’. I thus introduce the notion of ‘reform conflicts’ to emphasise that, although ongoing reforms aim to sever the supposed linkages between the artisanal mining business and violent conflicts, these reforms have become a driving force behind the emergence of new conflicts over property rights and access to minerals.

    Chapter 5 is about livelihoods. It analyses how the reforms have influenced the livelihoods and socioeconomic position of négociants. This chapter also explores what kind of opportunities the reforms have offered to this group of mineral brokers often considered powerful in the mineral supply chain and explains what kind of constraints the négociants have confronted and why they have opted to diversify their livelihood portfolios. The chapter has shown that the reforms have affected this group of mineral brokers in different ways. Some négociants were well off, whereas others have been excluded from the mineral commodity chain. These findings contradict the widespread opinion that négociants are always abusive brokers in the mineral production and commodity chain.

    Chapter 6 analyses the responses of creuseurs and négociants to iTSCi. Although the mining sites where iTSCi is in force appear to be ‘enclaves of regulations’, I explore the strategies of creuseurs and négociants to bypass iTSCi and the reforms, especially around the coltan trade. This chapter demonstrates that coltan smuggling is a deeply rooted practice. Despite the reforms, smuggling continues in different forms.

    All of the elements highlighted above suggest that mining reforms have undergone a major shift, from addressing the initial problems associated with ‘conflict minerals’ to creating or reinforcing various types of problems, such as the influence of ‘big men’ in the mining business, coltan smuggling and the emergence of new conflicts over accessing minerals. This means that reform initiatives such as iTSCi should be based on knowledge about the actual situation. Thus, understanding and addressing these new types of problems calls for a comprehensive approach at both local and broader levels.

    Analyzing metabolomics-based challenge tests
    Vis, D.J. ; Westerhuis, J.A. ; Jacobs, D.M. ; Duynhoven, J.P.M. van; Wopereis, S. ; Ommen, B. van; Hendriks, M.M.W.B. ; Smilde, A.K. - \ 2015
    Metabolomics 11 (2015)1. - ISSN 1573-3882 - p. 50 - 63.
    glucose-tolerance test - insulin sensitivity - mathematical-models - component analysis - plasma metabolome - health - asca - reconstruction - phenotype - discovery
    Challenge tests are used to assess the resilience of human beings to perturbations by analyzing responses to detect functional abnormalities. Well known examples are allergy tests and glucose tolerance tests. Increasingly, metabolomics analysis of blood or serum samples is used to analyze the biological response of the individual to these challenges. The information content of such metabolomics challenge test data involves both the disturbance and restoration of homeostasis on a metabolic level and is thus inherently different from the analysis of steady state data. It opens doors to study the variation of resilience between individuals beyond the classical biomarkers; preferably in terms of underlying biological processes. We review challenge tests in which metabolomics was used to analyze the biological response. Specifically, we describe strategies to perform statistical analyses on the responses and we will show some examples of these strategies applied to a postprandial challenge that was used to study a diet with anti-inflammatory properties. Finally we discuss open issues and give recommendation for further research.
    Potential of tree-ring analysis in a wet tropical forest: A case study on 22 commercial tree species in Central Africa
    Groenendijk, P. ; Sass, U.G.W. ; Bongers, F. ; Zuidema, P.A. - \ 2014
    Forest Ecology and Management 323 (2014). - ISSN 0378-1127 - p. 65 - 78.
    climate-growth relationships - rain-forest - pterocarpus-angolensis - age - periodicity - management - dynamics - reconstruction - precipitation - west
    Implementing sustainable forest management requires basic information on growth, ages, reproduction and survival of exploited tree species. This information is generally derived from permanent sample plots where individual trees are monitored. Accurately estimating growth rates and especially tree ages from plots is however challenging, as plots often contain only few individuals of the exploited species and monitoring periods cover only a fraction of the life-span of most trees. Alternatively, tree-ring analysis is increasingly used to obtain accurate age estimates and growth rates for tropical tree species, especially in regions with seasonally harsh conditions. However, for species from wet tropical forests (>4000 mm year-1 rainfall) few tree-ring studies exist. Under persistent high levels of rainfall, formation of distinct tree rings is uncertain due to the lack of strong seasonal variation in climate factors. Here we evaluated the potential of applying tree-ring analysis on commercial tree species in a wet tropical forest in Central-Africa. For this purpose we screened the wood anatomy of 22 tree species for the presence of tree-ring structures and, on a subset of five species, we assessed crossdating potential and evaluated the annual character of tree-ring formation by radiocarbon dating. A total of 14 of the 22 tree species showed distinct tree-ring boundaries. Radiocarbon proved annual tree-ring formation in four of the five tested species. Crossdating between trees was problematic for all species and impeded exactly dating each detected ring and building tree-ring chronologies. We also show that diameter growth rates vary strongly between and among species, with important consequences for the calculation of future timber yields. Tree-ring analysis can thus be applied on tree species growing in wet tropical forests to obtain growth rates. We argue that tree-ring analysis should actually be applied on more tree species from different areas to obtain accurate, site specific growth data. This data is urgently required to design and improve sustainable forest management practices.
    Community-driven reconstruction in the Eastern Democratic Republic of Congo : capacity building, accountability, power, labour, and ownership
    Kyamusugulwa, P.M. - \ 2014
    Wageningen University. Promotor(en): Thea Hilhorst, co-promotor(en): Paul Richards; M. Mashanda. - Wageningen : Wageningen University - ISBN 9789461739032 - 251
    bewonersparticipatie - reconstructie - ontwikkelingsprogramma - capaciteitsopbouw - gemeenschappen - politieke macht - sociale processen - democratische republiek kongo - community participation - reconstruction - development programmes - capacity building - communities - political power - social processes - congo democratic republic
    This PhD research focuses on community-driven reconstruction (CDR): the social dynamics of target communities in post-conflict eastern Congo. The main research question: how do social dynamics and power relations influence decision making and implementation of CDR and how do perceptions of local people and International Rescue Committee (IRC) staff shape development in the communities of Burhinyi, Luhwindja and Kaziba?
    An exploratory study on the use of digital sculpting in conceptual product design
    Alcaide-Marzal, J. ; Diego-Más, J.A. ; Asensio-Cuesta, S. ; Piqueras Fiszman, B. - \ 2013
    Design Studies 34 (2013)2. - ISSN 0142-694X - p. 264 - 284.
    freehand sketches - cad tools - 3d - reconstruction - discovery - surfaces - features
    The product design process involves intensive manipulation of graphical data, from pencil sketches to CAD files. The use of graphic software is common among professionals in this field. Despite this, the conceptual design stage remains intensive in paper and pencil work, as CAD systems are still too rigid to allow a creative production of concepts. In this paper the use of digital sculpting software is proposed as a way of producing 3D sketches in the early stages of the process. An experiment is conducted to determine to which extent 3D sculpt sketches can be considered as a suitable tool for conceptual design. The results show a better performance of 2D drawings, but support the complementary use of digital sculpting.
    Paleo-pedological record of the Rocourt pedosequence at Veldwezelt-Hezerwater (Belgian Pleistocene loess belt): Part 2-Soil formation
    Vancampenhout, K. ; Langohr, R. ; Slaets, J. ; Buurman, P. ; Swennen, R. ; Deckers, J. - \ 2013
    Catena 110 (2013). - ISSN 0341-8162 - p. 8 - 23.
    climatic-change - pollen records - last - western - soils - reconstruction - europe - paleoclimates - pedogenesis - ferrolysis
    As the environment influences soil formation, Quaternary loess-paleosols provide an important, yet complex source on former climate and vegetation conditions. This study revises the paleopedological record of the Rocourt-complex, the pedostratigraphic marker for the Eemian and early Weichselian in the Belgian loess belt. Depth functions were established from an exceptionally well-preserved, in-situ sequence. Based on soil micromorphological features, total element contents, iron fractions and carbon content a reconstruction was made of the polygenetic formation of the Rocourt soil. Results indicate that only by combining multiple soil features, consistent information could be obtained. Furthermore, this study shows that cryogenic processes, transport of colloids, iron dynamics, redox-conditions, organic matter formation and biological activity were major soil forming processes. The hypothesis of six major stages of soil formation under varying climatic conditions was most supported by the data. During the warm to temperate oceanic climate of the Eemian, a strongly weathered argic horizon was formed. This horizon was later disrupted by reticulate ice segregation and stagnogley during the severe and prolonged cold conditions of the first cold stadial following the Eemian. Weak soil formation, during the relatively short continental St. Germain I interstadial, subsequently formed cambic soil properties and a humiferous horizon in a mixture of local and new sediments. These soils were disrupted by fragipan Formation, with its associated cryogenic structure, banded eluviation and redoxfront, during the succeeding stadial with periglacial conditions. During the St. Germain II, another A horizon formed in new, calcareous material during more stable climatic conditions, allowing organic matter build-up, eluviation of smectite and formation of pedogenetic iron. During the evolution from this warmer climate with forest or forested steppe to eventually periglacial open tundra, an accretionary humiferous soil concluded the last episode of soil formation before the onset of pleniglacial Weichselian conditions. (c) 2013 Elsevier B.V. All rights reserved.
    Fluvial terraces of the northwest Iberian lower Miño River.
    Viveen, W. ; Schoorl, J.M. ; Veldkamp, A. ; Balen, R.T. van; Vidal-Romani, J.R. - \ 2013
    Journal of Maps 9 (2013)4. - ISSN 1744-5647 - p. 513 - 522.
    sea-level change - tectonic activity - portugal - uplift - climate - reconstruction - pleistocene - evolution - incision - deposits
    A new fluvial terrace map with a tectonic framework for the northwest Iberian lower Miño River is presented. It is the first integrated map to cover the entire lower, 67-km reach of the Miño River, and to cover both the Spanish and Portuguese side of the river. The map is presented at a scale of 1:200,000, although its features were mapped at a scale of 1:5000. Various map layers can be viewed, such as a digital elevation model (DEM), fluvial sediment thickness layers, a palaeoflow direction layer, a lineament and fault layer, and two terrace and tectonic basin layers, showing up to 10 fluvial terraces and a floodplain level. Interpretation of the map shows that next to regional tectonic uplift and glacioeustacy, local basin subsidence and small-scale block movement are very important for the fluvial network, localised fluvial terrace formation, and preservation.
    Genome-scale metabolic model for Lactococcus lactis MG1363 and its application to the analysis of flavor formation
    Flahaut, N.A.L. ; Wiersma, A. ; Bunt, B. van der; Martens, D.E. ; Schaap, P.J. ; Sijtsma, L. ; Martins Dos Santos, V.A.P. ; Vos, W.M. de - \ 2013
    Applied Microbiology and Biotechnology 97 (2013)19. - ISSN 0175-7598 - p. 8729 - 8739.
    amino-acid catabolism - streptococcus-lactis - cremoris mg1363 - steady-state - bacteria - growth - reconstruction - networks - systems - cheese
    Lactococcus lactis subsp. cremoris MG1363 is a paradigm strain for lactococci used in industrial dairy fermentations. However, despite of its importance for process development, no genome-scale metabolic model has been reported thus far. Moreover, current models for other lactococci only focus on growth and sugar degradation. A metabolic model that includes nitrogen metabolism and flavor-forming pathways is instrumental for the understanding and designing new industrial applications of these lactic acid bacteria. A genome-scale, constraint-based model of the metabolism and transport in L. lactis MG1363, accounting for 518 genes, 754 reactions, and 650 metabolites, was developed and experimentally validated. Fifty-nine reactions are directly or indirectly involved in flavor formation. Flux Balance Analysis and Flux Variability Analysis were used to investigate flux distributions within the whole metabolic network. Anaerobic carbon-limited continuous cultures were used for estimating the energetic parameters. A thorough model-driven analysis showing a highly flexible nitrogen metabolism, e.g., branched-chain amino acid catabolism which coupled with the redox balance, is pivotal for the prediction of the formation of different flavor compounds. Furthermore, the model predicted the formation of volatile sulfur compounds as a result of the fermentation. These products were subsequently identified in the experimental fermentations carried out. Thus, the genome-scale metabolic model couples the carbon and nitrogen metabolism in L. lactis MG1363 with complete known catabolic pathways leading to flavor formation. The model provided valuable insights into the metabolic networks underlying flavor formation and has the potential to contribute to new developments in dairy industries and cheese-flavor research.
    Nieuwe wegen naar ontwikkelingsgericht werken : handelingsperspectieven voor de overheid rond duurzame ontwikkeling en maatschappelijke acceptatie van veehouderij
    Os, J. van; Bokma-Bakker, M.H. ; Kuindersma, W. ; Selnes, T. ; Gies, E. - \ 2013
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2450)
    intensieve veehouderij - regionale planning - emissiereductie - landbouw en milieu - duurzaamheid (sustainability) - zandgronden - reconstructie - overijssel - gelderland - noord-brabant - limburg - intensive livestock farming - regional planning - emission reduction - agriculture and environment - sustainability - sandy soils - reconstruction - overijssel - gelderland - noord-brabant - limburg
    In samenwerking met de vier reconstructie-provincies Overijssel, Gelderland, Noord-Brabant en Limburg heeft Wageningen UR een onderzoek uitgevoerd naar mogelijkheden voor overheden om bij de vergunningverlening voor veehouderijbedrijven meer ontwikkelingsgericht te werken. Deze benadering is een aanvulling op de (huidige) praktijk waarin aanvragen vooral getoetst worden aan normen en maten, zoals bijvoorbeeld de grootte van het bouwblok. Belangrijkste conclusie is dat ontwikkelingsgericht werken inderdaad mogelijkheden biedt voor overheden om duurzaamheid en innovatie in de veehouderij te stimuleren. Tot nu toe werd vooral gestuurd op bouwblokken en milieunormen (o.a. stank en ammoniak), maar deze aanpak blijkt te star en te weinig stimulerend voor een duurzame en innovatieve veehouderij. In de nieuwe, ontwikkelingsgerichte werkwijze moet de economische ontwikkeling van veehouderijbedrijven hand in hand gaan met ontwikkelingen in duurzaamheid en met een dialoog met de directe omgeving. De vier provincies zijn eensgezind over deze gewenste richting, maar verschillen in hun aanpak.
    Characterization of Hubera (Annonaceae), a new genus segregated from Polyalthia and allied to Miliusa.
    Chaowasku, T. ; Johnson, D.M. ; Ham, R.W.J.M. van der; Chatrou, L.W. - \ 2012
    Phytotaxa 69 (2012). - ISSN 1179-3155 - p. 33 - 56.
    molecular phylogenetics - uvaria annonaceae - pollen morphology - chloroplast dna - evolution - genera - reconstruction - hypotheses - sequences - revision
    On the basis of molecular phylogenetics, pollen morphology and macromorphology, a new genus of the tribe Miliuseae, Hubera, segregrated from Polyalthia and allied to Miliusa, is established and described. It is characterized by the combination of reticulate tertiary venation of the leaves, axillary inflorescences, a single ovule per ovary and therefore single-seeded monocarps, seeds with a flat to slightly raised raphe, spiniform(-flattened peg) ruminations of the endosperm, and pollen with a finely and densely granular infratectum. Twenty-seven species are accordingly transferred to this new genus.
    Effect maatregelen reconstructie zandgebieden : pilotgemeente Gemert-Bakel
    Meulenkamp, W.J.H. ; Gies, T.J.A. - \ 2012
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 299) - 34
    zandgronden - reconstructie - regionale planning - grote landbouwbedrijven - intensieve veehouderij - noord-brabant - sandy soils - reconstruction - regional planning - large farms - intensive livestock farming - noord-brabant
    De reconstructie van de zandgebieden is in de fase van uitvoering van de gemaakte plannen. Waar er bij de vaststelling van de reconstructieplannen niet of nauwelijks problemen waren, ontstaat er bij de uitvoering veel maatschappelijke onrust. Daarbij spitst de discussie zich vooral toe op de komst van zogenaamde megastallen. Door veel burgers wordt deze ontwikkeling als onwenselijk gezien. In de gemeente Gemert-Bakel in de provincie Noord-Brabant – één van de pilotgebieden van de reconstructie – komt op een voortvarende manier de uitvoering wel van de grond. De aanpak van deze gemeente staat vaak model voor de perspectieven van reconstructie in andere gebieden. Dit werkdocument geeft inzicht wat er bereikt is en welke factoren cruciaal waren voor de realisatie.
    Holocene vegetation and hydrologic changes inferred from molecular vegetation markers in peat, Penido Vello (Galicia, Spain)
    Schellekens, J. ; Buurman, P. ; Fraga, I. ; Martinez-Cortizas, A. - \ 2011
    Palaeogeography Palaeoclimatology Palaeoecology 299 (2011)1-2. - ISSN 0031-0182 - p. 56 - 69.
    climate-change - atmospheric pb - proxy climate - bog - reconstruction - precipitation - temperature - deposition - millennia - pollen
    Peat molecular chemistry reflects a combination of plant input and decomposition. Both vegetation community and the degree of decomposition of plant remains are highly dependent on depth and fluctuation of the water table and thus peat organic matter (OM) chemistry reflects past hydrological conditions. Changes in hydrology according to the OM composition (by pyrolysis-gas chromatography/mass spectrometry, pyrolysis-GC/MS) in a high-resolution sampled monolith of an 8000 years old peat deposit are presented. Analysis of 18 modern vegetation species resulted in molecular markers for Erica spp., Deschampsia flexuosa, Juncus bulbosus and Carex binervis, in addition to more general markers which enabled differentiation between woody, grass and moss vegetation. Factor analysis of 106 pyrolysis products quantified for all peat samples enabled identification of mineral (Factor 1) and hydrological (Factor 2) conditions of the bog. Depth profiles of vegetation markers showed good agreement with those of the scores of both factors and enabled the identification of 14 relatively wet periods, dating to 1430-1865 AD, 930-1045 AD, 640 AD, 270-385 AD, 190-215 AD, 135 AD, 45 BC-15 AD, 260-140 BC, 640-440 BC, 1055-960 BC, 1505-1260 BC, 2300 BC, 41902945 BC and 5700-5205 BC, which show excellent agreement with other palaeoclimatic studies in Europe. The results emphasize the importance of high-resolution sampling, in combination with the use of multiple vegetation markers and other peat OM characteristics for a proper interpretation of a peat record.
    Reply to the comment by MP Hijma & KM Cohen on the paper by Van de Plassche et al. (2010)
    Makaske, B. ; Hoek, W.Z. - \ 2011
    Netherlands journal of geosciences 90 (2011)1. - ISSN 0016-7746 - p. 55 - 57.
    sea - reconstruction
    Finsler Streamline Tracking with Single Tensor Orientation Distribution Function for High Angular Resolution Diffusion Imaging
    Astola, L.J. ; Jalba, A. ; Balmashnova, E. ; Florack, L. - \ 2011
    Journal of Mathematical Imaging and Vision 41 (2011)3. - ISSN 0924-9907 - p. 170 - 181.
    reconstruction - space - mri
    We introduce a new framework based on Riemann-Finsler geometry for the analysis of 3D images with spherical codomain, more precisely, for which each voxel contains a set of directional measurements represented as samples on the unit sphere (antipodal points identified). The application we consider here is in medical imaging, notably in High Angular Resolution Diffusion Imaging (HARDI), but the methods are general and can be applied also in other contexts, such as material science, et cetera, whenever direction dependent quantities are relevant. Finding neural axons in human brain white matter is of significant importance in understanding human neurophysiology, and the possibility to extract them from a HARDI image has a potentially major impact on clinical practice, such as in neuronavigation, deep brain stimulation, et cetera. In this paper we introduce a novel fiber tracking method which is a generalization of the streamline tracking used extensively in Diffusion Tensor Imaging (DTI). This method is capable of finding intersecting fibers in voxels with complex diffusion profiles, and does not involve solving extrema of these profiles. We also introduce a single tensor representation for the orientation distribution function (ODF) to model the probability that a vector corresponds to a tangent of a fiber. The single tensor representation is chosen because it allows a natural choice of Finsler norm as well as regularization via the Laplace-Beltrami operator. In addition we define a new connectivity measure for HARDI-curves to filter the most prominent fiber candidates. We show some very promising results on both synthetic and real data
    Dendrochronology in the dry tropics: the Ethiopian case
    Wils, T. ; Sass-Klaassen, U. ; Eshetu, Z. ; Bräuning, A. ; Gebrenirstos, A. ; Couralet, C. ; Robertson, I. ; Touchan, R. ; Koprowski, M. ; Conway, D. ; Briffa, K.R. ; Beeckman, H. - \ 2011
    Trees-Structure and Function 25 (2011)3. - ISSN 0931-1890 - p. 345 - 354.
    climate-growth relationships - tree-ring analysis - pterocarpus-angolensis - rhizophora-mucronata - isotope ratios - stable carbon - africa - forests - dynamics - reconstruction
    Dendrochronology is developing outside temperate and boreal regions. Over the past decade substantial progress has been made in Mediterranean and wet tropical regions. However, research in dry tropical regions, notably those of sub-Saharan Africa, has remained fragmentary. Here, we try to identify the unique challenges and opportunities of dendrochronology in the dry tropics. First, we briefly review the status of dendrochronology outside temperate and boreal regions with an emphasis on sub- Saharan Africa. Subsequently, we focus upon one of those areas where dendrochronology in the dry tropics is at the forefront of scientific advance: Ethiopia. A detailed review of tree ring studies in the lowlands and highlands highlights the complexity of ring formation and made us identify four major types of growth ring expression: anatomically notdistinct rings, multiple rings per year, annual rings and multiple missing rings. This complex tree growth behaviour is associated with large-scale variations in precipitation regime (unimodal to multimodal) and relatively small-scale variations in tree sensitivity to water availability. Literature results are used to develop a scheme that can be used to predict differences in growth ring formation along gradients in these two factors. Because of the exceptional growth sensitivity of and the importance of local site conditions (topography, biological factors, etc.) for most trees sampled, those growing at the limits of their ecological amplitude are prone to possess multiple rings per year or multiple missing rings. In such circumstances, site selection should not always take place at the limits of the ecological amplitude of a species, but may sometimes have to be diverted to more mesic environments. Successful studies are now appearing, such as those reporting correlations between tree ring chronologies and Blue Nile river flows.
    Crossdating Juniperus procera from North Gondar, Ethiopia
    Wils, T. ; Robertson, I. ; Eshetu, Z. ; Touchan, R. ; Sass-Klaassen, U. ; Koprowski, M. - \ 2011
    Trees-Structure and Function 25 (2011)1. - ISSN 0931-1890 - p. 71 - 82.
    climate-growth relationships - tree-rings - pterocarpus-angolensis - precipitation - africa - dendrochronology - forest - c-14 - reconstruction - dynamics
    The application of dendrochronology in (sub)tropical regions has been limited by the difficulty in finding trees with distinct annual rings that can be crossdated. Here, we report successful crossdating of Juniperus procera trees from North Gondar, Ethiopia. The trees form annual rings in response to a unimodal rainfall regime. The selection of mesic locations ensured that the trees did not respond to intra-seasonal weather anomalies. Crossdating was achieved by comparison of the wood anatomy directly on the surface of the core samples and purpose-adapted skeleton plotting. Wood-anatomical anomalies, such as false and indistinct rings, were regarded as potentially replicated features and used in crossdating. COFECHA yielded site-specific mean series inter-correlations between 0.52 and 0.59. AMS radiocarbon dating during the bomb era indicated that dating uncertainty is ±1 year.
    Velper studenten werken aan reconstructie Gelderse Vallei
    Stobbelaar, D.J. ; Graaff, J. de - \ 2010
    Vakblad Natuur Bos Landschap 7 (2010)5. - ISSN 1572-7610 - p. 22 - 25.
    regionale planning - zandgronden - hoger onderwijs - reconstructie - ecologische hoofdstructuur - middelbaar beroepsonderwijs - gelderse vallei - regional planning - sandy soils - higher education - reconstruction - ecological network - intermediate vocational training - gelderse vallei
    Een reconstructie is een ingewikkeld proces omdat er vele partijen aan te pas komen, veel belangen op het spel staan, en de uitvoering van projecten vele fases moet doorlopen. Studenten van Van Hall Larenstein en Helicon (beide Velp) ondersteunden het proces door in de verschillende fasen onderzoek te doen. Dit artikel geeft voorbeelden van herinrichting voor: Voorthuizerpoort, Groote Flierd
    Branched glycerol dialkyl glycerol tetraethers in lake sediments: Can they be used as temperature and pH proxies?
    Blaga, C.I. ; Reichart, G.J. ; Schouten, S. ; Lotter, A.F. ; Werne, J.P. ; Kosten, S. ; Mazzeo, N. ; Lacerot, G. ; Damste, J.S.S. - \ 2010
    Organic Geochemistry 41 (2010)11. - ISSN 0146-6380 - p. 1225 - 1234.
    terrestrial organic-matter - crenarchaeotal membrane-lipids - bit index - water temperatures - reconstruction - transport - palaeothermometer - distributions - assemblages - holocene
    A series of surface sediments from 82 lakes of variable water depth and size was analyzed for glycerol dialkyl glycerol tetraethers (GDGTs) in order to investigate the potential of the MBT/CBT (methylation ratio/cyclization ratio of branched tetraethers) as a continental palaeothermometer in lacustrine environments. Branched GDGTs dominated in most sediments, as indicated by the high branched vs. isoprenoid tetraether (BIT) values. We observed that CBT and MBT varied substantially. Mean annual air temperature (MAAT reconstructed) and pH values were calculated using the CBT and MBT values and the calibration from the global soil data set. The MBT/CBT inferred temperatures were considerably lower than measured values. Nevertheless, there was a significant correlation between MAAT reconstructed and MAAT observed on site, although there was still considerable scatter (r(2) 0.47). Lacustrine sediments integrate organic remains of organisms in a lake and its drainage basin, thereby offering a unique opportunity for calibrating MBT and CBT, as small scale variability is averaged out. Since the source of the branched GDGTs in the lake sediments is ambiguous, it is not clear whether only temperature and pH in the catchment area are the driving factors. Therefore, even in lake sediments with high concentrations of branched GDGTs the straightforward application of MBT/CBT as palaeoproxies may be difficult given the uncertainties regarding their source and origin.
    Botsende beelden; innoveren bij maatschappelijke tegenwind, een vertooganalyse van het Gemend Bedrijf
    Horlings, L.G. ; Hinssen, J. ; Hermans, F. - \ 2010
    Tilburg : Telos en TransForum - 93
    intensieve dierhouderij - agro-industriële complexen - clustering - innovaties - regionale voedselketens - recycling - reconstructie - midden-limburg - besluitvorming - intensive husbandry - agroindustrial complexes - clustering - innovations - regional food chains - recycling - reconstruction - midden-limburg - decision making
    Het Nieuw Gemengd Bedrijf is een initiatief van vier ondernemers die samen met kennisinstellingen werken aan een samenwerkingsverband van plantaardige en dierlijke productiebedrijven die hun afval- en grondstofstromen koppelen. Het Nieuw Gemengd Bedrijf is gepland in het landbouwontwikkelingsgebied aan de Witveldweg in Horst aan de Maas - buitengebied kern Grubbenvorst - en omvat een concreet voorstel voor een agropark met intensieve veehouderij. Het landbouwont-wikkelingsgebied (LOG) Witveldweg is 211 hectare groot. In de nabije omgeving liggen de kernen Melderslo, Horst, Lottum, Lomm en Grubbenvorst. Het initiatief Nieuw Gemengd Bedrijf in Horst aan de Maas vindt plaats in de context van een Nederlandse landbouw in een metropolitane omgeving. De beleidsinzet vanuit het ministerie van LNV is om tot duurzamere agrarische productie te komen (LNV, Strategische Verkenning 2009-2019).
    Regulatory Network Identification by Genetical Genomics: Signaling Downstream of the Arabidopsis Receptor-Like Kinase ERECTA
    Terpstra, I.R. ; Snoek, L.B. ; Keurentjes, J.J.B. ; Peeters, A.J.M. ; Ackerveken, G. van den - \ 2010
    Plant Physiology 154 (2010)3. - ISSN 0032-0889 - p. 1067 - 1078.
    wrky transcription factor - defense responses - plant development - mpk4 activation - expression - map - differentiation - resistance - protein - reconstruction
    Gene expression differences between individuals within a species can be largely explained by differences in genetic background. The effect of genetic variants (alleles) of genes on expression can be studied in a multifactorial way by application of genetical genomics or expression quantitative trait locus (eQTL) mapping. In this paper we present a strategy to construct regulatory networks by application of genetical genomics in combination with transcript profiling of mutants that are disrupted in single genes. We describe the network identification downstream of the receptor-like kinase ERECTA in Arabidopsis (Arabidopsis thaliana). Extending genetical genomics on the Landsberg erecta/Cape Verde islands (Ler/Cvi) recombinant inbred population with expression profiling of monogenic mutants enabled the identification of regulatory networks in the, so far elusive, ERECTA signal transduction cascade. We provide evidence that ERECTA is the causal gene for the major hotspot for transcript regulation in the Arabidopsis Ler/Cvi recombinant inbred population. We further propose additional genetic variation between Ler and Cvi in loci of the signalling pathway downstream of ERECTA, and suggest candidate genes underlying these loci. Integration of publicly available microarray expression data of other monogenic mutants allowed us to link ERECTA to a downstream MAPK signalling cascade. Our study shows that microarray data of monogenic mutants can be effectively used in combination with genetical genomics data to enhance the identification of genetic regulatory networks.
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