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| Registros recuperados: 501 | |
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| Lewis, P.. |
| This chapter reviews the way in which 3D plant and canopy models have been used in the field of remote sensing. The focus of the chapter is on remote sensing of crops at microwave and optical wavelengths, although other applications are discussed. A brief review of remote sensing of crops is presented, followed by an evaluation of the motivation for using various types of 3D models with remotesensing data. A discussion of current issues and areas requiring future work is provided. |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1385 |
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| Mensah-Bonsu, A.; Burger, K.. |
| This chapter models migration decisions as joint individual and family decisions and develops a model in which family members can migrate on the condition that they remit more than they would have contributed as resident household member. The upper bound on remittances is set by their own net benefits after migration. The paper uses cross-sectional data collected in 2000 from northeast Ghana to investigate the effect of farm household population, family landholding and the perceived soil quality on migration and remittance decisions of members of the farm household in Northeast Ghana. Nested logit and Tobit models estimation techniques are employed. The empirical results confirm the negative effect that per-capita farmland size has on the probability of... |
| Tipo: Conference proceedings |
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| Ano: 2008 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1581 |
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| Schippmann, U.; Leaman, D.; Cunningham, A.B.. |
| With the increased realization that many wild medicinal and aromatic plant (MAP) species are being over-exploited, a number of agencies are recommending that wild species be brought into cultivation systems. Others argue sustainable harvest to be the most important conservation strategy for most wild-harvested species, given their contributions to local economies and their greater value to harvesters over the long term. Besides poverty and the breakdown of traditional controls, the major challenges for sustainable wildcollection include: lack of knowledge about sustainable harvest rates and practices, undefined land use rights and lack of legislative and policy guidance. Identifying the conservation benefits and costs of the different production systems... |
| Tipo: Conference proceedings |
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| Ano: 2006 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1225 |
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| Struik, P.C.; Cassman, K.G.; Koornneef, M.. |
| In the future, more food needs to be produced with increasingly scarce natural resources. Genomics can play a key role in accelerating yield gains because it helps to improve our understanding of genetic traits and assists in breeding for better crop performance. The scientific muscle of genomics attracted tremendous research investments, but the efficiency with which these investments are paying off is still low. How can we accelerate the application of molecular genetics to our understanding of crop physiology and subsequently to crop improvement? The missing link is a more detailed understanding of the effects of gene function on crop performance at field level under agronomically relevant conditions captured in robust, physiology-based mechanistic... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1314 |
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| Buck-Sorlin, G.; Kniemeyer, O.; Kurth, W.. |
| The incorporation of some genetic and physiological processes in a developmental model of Hordeum vulgare L. (barley) is presented. The model exhibits different hierarchical scales and has been conceived as a Relational Growth Grammar (RGG). RGG is a new formalism that has been developed as an extension of L-Systems and implemented using a new modelling language, eXtended Lsystems (XL). Models written in XL can be executed using the interactive, Java-based modelling platform GroIMP, which has been developed for this purpose. The barley model proper is a set of morphogenetic rules. These are combined with a set of rules representing a metabolic network simulating some key steps of the biosynthesis of gibberellic acid (GA1). The transport of GA1 and GA19 (a... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1387 |
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| Moss, M.R.; Okey, B.W.. |
| The term ‘cultural landscape’ is examined from the perspective of its generally accepted use in various parts of the world. Contrasts exist due to the different cultural histories, academic affiliations and to the practitioners of the concept. Presently the term appears to have greater currency and relevance to landscape planning in Europe. To provide a broad perspective, cultural landscapes are examined, from within the Eastern Deciduous Forest Biome of North America, with particular reference to the province of Ontario, Canada. Here the consequences of a landscape structure onto which human attributes of landscape have been imposed is used as a basis for comparison with the longer, organic evolution of landscape as manifest in Northwestern Europe. More... |
| Tipo: Conference proceedings |
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| Ano: 2004 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1014 |
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| Kang, M.Z.; De Reffye, P.. |
| Plant growth and development depend on both organogenesis and photosynthesis. Organogenesis sets in place various organs (leaves, internodes, fruits, roots) that have their own sinks. The sum of these sinks corresponds to the plant demand. Photosynthesis of the leaves provides the biomass supply (source) that is to be shared among the organs according to their sink strength. Here we present a mathematical model – GreenLab – that describes dynamically plant architecture in a resource-dependent way. The source and sink functions of the various organs control the biomass acquisition and partitioning during plant development and growth, giving the sizes and weights of organs according to their position in the plant architecture. Non-linear least-square method... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1372 |
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| Hoshen, M.B.; Morse, A.P.. |
| Malaria is one of the leading causes of death in the developing world today. While prevention and treatment methods are available, their large-scale usage is a major drain on governmental budgets, and not applied whenever necessary. For this reason, understanding the endemicity of a region will allow the efficient implementation of suitable prevention methods. More importantly, the prediction of extraordinary malaria outbreaks will allow the recruitment of emergency facilities before transmission becomes widespread. In addition, climate change may influence the endemicity pattern of a region, causing malaria incidence to rise in areas in which it was non-existent or controlled. For all these purposes, a seasonal to decadal malaria forecast is needed. A... |
| Tipo: Conference proceedings |
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| Ano: 2005 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/959 |
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| Sadok, W.; Boussuge, B.; Welcker, C.; Tardieu, F.. |
| Expansive growth of organs has a very large genotype × environment (G×E) interaction. Maximum leaf expansion rate observed in the absence of stress and of evaporative demand has a genetic variability which is usually smaller than environmental effects. The mechanisms driving the reduction in leaf growth rate under stress, namely changes in cell division rate, in cell-wall mechanical properties and in turgor, and their signalling pathways, interact in such a way that a bottom-up approach from genes to the G×E interaction cannot be envisaged. We propose an approach combining modelling and genetic dissection of model parameters. Three genotype-dependent parameters are considered for analysing the G×E interaction for leaf elongation rate of maize. The maximum... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1297 |
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| Chapman, S.C.; Wang, J.; Rebetzke, G.J.; Bonnett, D.G.. |
| There are many sources of variability in gene–phenotype associations. During the measurement of genotype and phenotype and during selection, researchers must deal with experimental error in trials; gene-gene interaction (epistasis) for sub-traits and observed traits; trait-trait interaction (pleiotropy) and gene- or genotype-by-environment interaction. These effects can be structured in a framework that allows simulation of the entire gene-environment ‘landscape’. Studies of these landscapes have been published by others. Here we aim to explain with simple examples some of the types of insights that can be made. A current challenge for breeders working with simple marker–phenotype associations is to design selection strategies that can rapidly create new... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1294 |
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| Bremmers, H.. |
| In this paper principles for accounting in supply chains will be developed. The three principles we introduce are: the reciprocity in information access, asset investment and retrieval, and matching risks and returns. The principles provide guidance in managerial and stakeholder decision making, monitoring and control. The information that management and other stakeholders need is based on these standards. The use of the supply-chain accounting principles increases transparency. Transparency is one of the main elements of what Fowler et al (2004) call ‘virtually embedded ties’. We argue that transparency should replace, or at least supplement, relational trust in supply channels. We argue also that technological innovation, such as electronic chain-wide... |
| Tipo: Conference proceedings |
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| Ano: 2006 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1139 |
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| Dillon, P.. |
| Due to economic, environmental and animal-welfare constraints, it is envisaged that in the future a larger proportion of the milk produced in temperate regions will be produced from grazed pasture. However, with the selection of modern higher-production dairy cows, increased emphasis on product quality and issues associated with nitrogen leaching, soil compaction, greenhouse-gas emissions and animal welfare, pasture-based systems will also require higher per-animal productivity in the future. This will necessitate the development of grazing systems designed to maximize daily herbage intake per cow, while at the same time maintain a high-quality pasture over the entire grazing season. Daily grass DM intake will be maximized by adhering to important sward... |
| Tipo: Conference proceedings |
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| Ano: 2007 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/1243 |
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| Scott, T.W.; Morrison, A.. |
| Using genetically modified mosquitoes to control vector-borne diseases will require specific, quantitative targets for the extent to which populations of competent mosquito vectors need to be reduced in order to produce predictable public-health outcomes. Unfortunately, dengue researchers do not have an entomological measure for predicting the risk of human dengue infection and disease that is as effective as they would like. The situation is further complicated by the fact that contemporary dengue control is based on the assumption, which has not been thoroughly tested, that a reduction in adult Aedes aegypti population densities will decrease risk of virus transmission. Ae. aegypti eradication is not considered feasible and there are no commercially... |
| Tipo: Conference proceedings |
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| Ano: 2004 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/849 |
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| Rodriguez, R.. |
| Agriculture represents in Brazil roughly one third of GDP; a quarter of employment and 42% of exports. During the last 15 years, the cultivated area increased with 24%, but production more than doubled. Much attention is given to innovation in new technologies, fertilizers and agrochemicals for enhancing productivity. Supply in the agribusiness sector is continuously increasing, and Brazil has become a major exporter of coffee, sugar, soybeans and meat to the EU, US and Asian markets. Even while there is still some room for expansion, it is recognized that most of future agricultural growth must come from productivity improvement. Open markets are in the benefit of their consumers, but countries are entitled to maintain some subsidies for environmental and... |
| Tipo: Conference proceedings |
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| Ano: 2006 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/969 |
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| Graff, G.; Roland-Holst, D.; Zilberman, D.. |
| This paper examines the challenges and opportunities facing the agricultural biotechnology sector as it works to sustain innovations and further propagate its benefits into the new century. Drawing on US experience, we survey the milestones of technological, legal and economic precedence and discuss institutional mechanisms for public and private partnership that can help agricultural biotechnology fulfil its immense promise. In particular, we emphasize the importance of the public sector in facilitating private agency, via promotion of basic research, dissemination of innovations, and as a guarantor of property rights |
| Tipo: Conference proceedings |
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| Ano: 2005 |
URL: http://library.wur.nl/ojs/index.php/frontis/article/view/928 |
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| Registros recuperados: 501 | |
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