Demand and Supply of Crop Infraspecific Diversity on Farms: Towards a Policy Framework for On-Farm Conservation

Interest is increasing worldwide in on-farm conservation as a component of a strategy to conserve crop genetic resources. On-farm conservation may require outside support to small-scale farmers in areas of crop domestication and diversity. This paper argues that crop infraspecific diversity maintained by farming households in these areas results from the interplay between demand and supply for this diversity (i.e., its loss may be demand- or supply-related). In the first instance, interventions should be aimed at increasing the value of crop diversity for farmers or decreasing the farm-level opportunity costs of maintaining diversity. In the second instance, interventions should decrease the transaction costs of accessing crop diversity. It may be difficult, however, to distinguish in empirical research, whether the constraints to diversity are demand- or supply-related. Therefore the process of supporting on-farm conservation should be kept as open as possible and both demand and supply interventions should be available.Crop Production/Industries,

Analysis of Participatory Research Projects in the International Maize and Wheat Improvement Center

Through a survey of scientists from the International Maize and Wheat Improvement Center (CIMMYT) in 2004, this study assessed the extent to which participatory methods had been used by the center, how they were perceived by the scientists, and how participatory research could be applied more effectively by CIMMYT and partners. Results for 19 CIMMYT projects suggest among other things that participatory approaches at the center were largely “functional”—that is, aimed at improving the efficiency and relevance of research—and had in fact added value to the research efforts. The authors suggest that CIMMYT should (1) create a more conducive environment for scientists to share experiences on such approaches and (2) better document their impacts on farmers’ livelihoods and well-being.Economic analysis, Research projects, Research methods, Quantitative analysis, Surveys, Statistics, Evaluation, Scientists, Research institutions, Mexico., Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies, E10, A50,

VARIETY CHARACTERISTICS AND THE LAND ALLOCATION DECISIONS OF FARMERS IN A CENTER OF MAIZE DIVERSITY

There is emerging interest in the prospects for enhancing farmers' management of genetic resources as a complementary strategy to ex situ conservation. Using a framework that combines a characteristics model with the notion of impure public goods, we investigate farmers' incentives to grow the varieties identified as important genetic resources.Land Economics/Use, Research and Development/Tech Change/Emerging Technologies,

Coupling between aging and convective motion in a colloidal glass of Laponite

We study thermal convection in a colloidal glass of Laponite in formation. Low concentration preparation are submitted to destabilizing vertical temperature gradient, and present a gradual transition from a turbulent convective state to a steady conductive state as their viscosity increases. The time spent under convection is found to depend strongly on sample concentration, decreasing exponentially with mass fraction of colloidal particles. Moreover, at fixed concentration, it also depends slightly on the pattern selected by the Rayleigh B\'{e}nard instability: more rolls maintain the convection state longer. This behavior can be interpreted with recent theoretical approaches of soft glassy material rheology.Comment: Eur. Phys. J. B 55, 101-107 (2007) The original publication is available at http://www.springerlink.co

PARTICIPATORY RESEARCH METHODS FOR TECHNOLOGY EVALUATION: A MANUAL FOR SCIENTISTS WORKING WITH FARMERS

This manual presents methods that enable agricultural scientist and farmers to evaluate technologies/practices jointly. The methods are specifically designed for participatory research on germplasm and soil fertility technologies, and they are illustrated with actual examples from three research projects. The manual begins by reviewing conceptual issues that are important in participatory research and presents information to assist researchers in selecting research sites and fieldwork participants. Next, the manual describes the rationale and associated methods for each major activity in farmer participatory research: diagnosing farmers' conditions, evaluating current and new technologies/practices, and assessing their impact. Goals, procedures, advantages, and limitations of each method are outlined. The manual also presents detailed information on analyzing data gathered through participatory methods, discusses differences between gathering data through participatory methods and more traditional structured farm surveys, and offers examples, based on field experience, of the choices and strategies involved in applying these methods.Research and Development/Tech Change/Emerging Technologies, Research Methods/ Statistical Methods,

On the Symmetries of Integrability

We show that the Yang-Baxter equations for two dimensional models admit as a group of symmetry the infinite discrete group $A_2^{(1)}$. The existence of this symmetry explains the presence of a spectral parameter in the solutions of the equations. We show that similarly, for three-dimensional vertex models and the associated tetrahedron equations, there also exists an infinite discrete group of symmetry. Although generalizing naturally the previous one, it is a much bigger hyperbolic Coxeter group. We indicate how this symmetry can help to resolve the Yang-Baxter equations and their higher-dimensional generalizations and initiate the study of three-dimensional vertex models. These symmetries are naturally represented as birational projective transformations. They may preserve non trivial algebraic varieties, and lead to proper parametrizations of the models, be they integrable or not. We mention the relation existing between spin models and the Bose-Messner algebras of algebraic combinatorics. Our results also yield the generalization of the condition $q^n=1$ so often mentioned in the theory of quantum groups, when no $q$ parameter is available.Comment: 23 page

Farmer Management of Maize Diversity in the Central Valleys of Oaxaca, Mexico: CIMMYT/INIFAP 1998 Baseline Socioeconomic Survey

Crop Production/Industries,

High titers of transmissible spongiform encephalopathy infectivity associated with extremely low levels of PrP in vivo

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Diagnosis of transmissible spongiform encephalopathy (TSE) disease in humans and ruminants relies on the detection in post-mortem brain tissue of the protease-resistant form of the host glycoprotein PrP. The presence of this abnormal isoform (PrPSc) in tissues is taken as indicative of the presence of TSE infectivity. Here we demonstrate conclusively that high titers of TSE infectivity can be present in brain tissue of animals that show clinical and vacuolar signs of TSE disease but contain low or undetectable levels of PrPSc. This work questions the correlation between PrPSc level and the titer of infectivity and shows that tissues containing little or no proteinase K-resistant PrP can be infectious and harbor high titers of TSE infectivity. Reliance on protease-resistant PrPSc as a sole measure of infectivity may therefore in some instances significantly underestimate biological properties of diagnostic samples, thereby undermining efforts to contain and eradicate TSEs.https://doi.org/10.1074/jbc.M704329200282pubpub4

Steady state fluctuation relations for systems driven by an external random force

We experimentally study the fluctuations of the work done by an external Gaussian random force on two different stochastic systems coupled to a thermal bath: a colloidal particle in an optical trap and an atomic force microscopy cantilever. We determine the corresponding probability density functions for different random forcing amplitudes ranging from a small fraction to several times the amplitude of the thermal noise. In both systems for sufficiently weak forcing amplitudes the work fluctuations satisfy the usual steady state fluctuation theorem. As the forcing amplitude drives the system far from equilibrium, deviations of the fluctuation theorem increase monotonically. The deviations can be recasted to a single master curve which only depends on the kind of stochastic external force.Comment: 6 pages, submitted to EP

Farmers' Taxonomies as a Participatory Diagnostic Tool: Soil Fertility Management in Chihota, Zimbabwe

Soil infertility is a major constraint to food production in the communal areas of Zimbabwe. Smallholders in the region recognize the problems of low soil fertility and have devised ways of coping with them. This study describes the use of farmers� taxonomies of themselves and their soils to identify and understand the options they have, and the constraints they face in managing poor soil fertility in Chihota, a sub-humid communal area of north central Zimbabwe. It is part of an effort by a group of agricultural researchers and extensionists working on improved soil fertility technologies, to better integrate their work with farmers in order to expose the latter to promising technologies, get feedback on the technologies merits and feasibility, and help farmers experiment with them. The results show that these farmers have relatively sophisticated taxonomies, which provide a good picture of the resources, constraints, and concerns they have about soil infertility and ways to manage it. The taxonomies are an important framework for integration of technical interventions with farmers� requirements, systems, and circumstances.participatory methods, soil fertility, local taxonomies, smallholders, Zimbabwe, Farm Management, Land Economics/Use,