Swapping trajectories: a new wall-induced cross-streamline particle migration mechanism in a dilute suspension of spheres

Binary encounters between spherical particles in shear flow are studied for a system bounded by a single planar wall or two parallel planar walls under creeping flow conditions. We show that wall proximity gives rise to a new class of binary trajectories resulting in cross-streamline migration of the particles. The spheres on these new trajectories do not pass each other (as they would in free space) but instead they swap their cross-streamline positions. To determine the significance of the wall-induced particle migration, we have evaluated the hydrodynamic self-diffusion coefficient associated with a sequence of uncorrelated particle displacements due to binary particle encounters. The results of our calculations quantitatively agree with the experimental value obtained by \cite{Zarraga-Leighton:2002} for the self-diffusivity in a dilute suspension of spheres undergoing shear flow in a Couette device. We thus show that the wall-induced cross-streamline particle migration is the source of the anomalously large self-diffusivity revealed by their experiments.Comment: submited to JF

The Perceived Impact of the In-Trust Agreements on CGIAR Germplasm Availability: An Assessment of Bioversity International's Institutional Activities

This study assesses the generation and consequences of the In-Trust Agreements (ITAs) that established the legal status of the CGIAR germplasm as freely available for the benefit of humanity under the auspices of FAO. The analysis looks at the history of the ITAs and focuses on the role of Bioversity International in research and other activities in influencing, facilitating and enabling the ITA negotiations. Results confirm the central role of Bioversity and policy research in the negotiations process. Concepts developed during the ITA negotiations contributed toward subsequent multilateral negotiations that eventually culminated in the International Treaty on Plant Genetic Resources

Is cryopreservation a viable method for long-term conservation of coffee biodiversity?

This brief summarizes the findings of the 2008 study carried out by Bioversity International and its partners that investigated two major issues relating to conservation of coffee germplasm: 1. What are the real threats to and losses of coffee germplasm held globally in field genebanks? 2. How do the costs of cryopreservation compare with those of maintaining coffee field collections for long-term conservation? The study shows that the costs of cryopreservation should not be considered prohibitive to establishing duplicate, back-up collections of coffee. If cryopreservation is adopted as a complement to field genebanks, the costs of cryopreservation must be added to existing costs of field conservation. However, field collections could be reduced and at least partly between cryopreservation and field collection to ensure the longterm, cost-efficient conservation of coffee genetic resources. This study investigated coffee as a test case, but the results are relevant to other species that are difficult to conserve using the traditional method of seed drying and low-temperature storage. The underlying objective of the study was to assess the potential impact of the widespread adoption of cryopreservation for more species and in more genebanks

The impact of Bioversity International’s African leafy vegetables programme in Kenya

An effort by Bioversity and several partners in Kenya increased production, consumption and marketing of a wide range of African leafy vegetables (ALVs) and improved household welfare. Between 1996 and 2004, Bioversity International worked with partners in Kenya to revive the interest of researchers and ordinary people in these valuable foods. An impact assessment study showed that nearly two-thirds of households growing ALVs increased their income from ALVs, while nearly half had increased their consumption of ALVs. Bioversity was ranked as the most influential partner in promoting production and use of ALVs and in raising awareness of the value of ALVs

Medicinal and aromatic plants improve livelihoods in Yemen

The aim of this brief is to analyze the impact of a set of interventions related to conservation and use of neglected and underutilized species (NUS) on people’s livelihoods. Specifically a simultaneous three-equation model of households’ participation on undertulized crops conservation and income generation activities is applied to evaluate the outcome of a pilot research project implemented by Bioversity International in Yemen between 2002 and 2005. Results generated show a relation between project participation and the perceived yield increase demonstrating the importance for farmers to actively participate in the project’s activities and subsequently apply agronomic practices learnt to improve their livelihood. The generated benefits incentivized farmers to continue to apply the interventions beyond the lifetime of the project ensuring thus a sustainable process in which exogenous interventions, once adopted by farmers become integrant part of farmer’s agronomic practices

Evaluating the impact of the Vavilov-Frankel Fellowship Programme

The Vavilov-Frankel Fellowship Programme awards two fellowships annually to young scientists from developing countries, to enable them to carry out innovative research on the conservation and use of plant genetic resources (PGR). Since 1994, 39 scientists from 24 countries have taken part in the programme. An evaluation of the impact of the Vavilov-Frankel Fellowships (VFF) reveals that overall the VFF Programme has met its stated goals of contributing to the scientific capacity of the Fellows and their home institutes, and of fostering the conservation and use of PGR. The evaluation also indicated ways in which the Fellowship Programme could be improved, and these are now being implemented

Home gardens in Nepal

Home gardens have traditionally played an important role in the production of food, fodder, fuel, medicines, spices, flowers and building materials throughout Nepal. These small areas of land close to the homestead—often incorporated within a larger farming system—harbour high biodiversity, provide a large share of families food consumption and contribute income. Due to their small size, however, home gardens have been overlooked as a way of improving the nutritional diversity and livelihoods of poor rural communities. The ‘Home Garden Project’ in Nepal, set to turn this around. This publication is part of the Bioversity International’s series of Impact Assessment Briefs that aim to inform readers about the major results of evaluations carried out by the centre. The Briefs summarize conclusions and methods of more formal papers published in peer-reviewed journals

Integrated agricultural research in Malawi

Around 50% of Malawi’s rural communities are living in poverty, with 25% still living in ‘ultra poverty’ with high rates of malnutrition. The cultivation of vegetable crops can provide an income, while indigenous vegetables in particular can contribute significantly to vitamin and mineral intake. While the climate is favourable for vegetable production, the lack of quality seed varieties, combined with poor pest and disease deterrents, hinder vegetable cultivation and both production and consumption has remained low. Agricultural research on improving productivity in sub-Saharan countries previously suffered from limited funding and poor intergration of key stakeholders. A more integrated approach has been proposed. With the help of Bioversity International, farmers were trained to conduct research towards improved vegetable production, marketing and ultimately, improved nutrition and incomes. This publication is part of the Bioversity International’s series of Impact Assessment Briefs that aim to inform readers about the major results of evaluations carried out by the centre. The Briefs summarize conclusions and methods of more formal papers published in peer-reviewed journals