Are small Sub-Sahara African farmers willing to pay for vegetative propagated orange fleshed sweetpotato planting material? Evidence from Central Mozambique

This paper evaluates farmers’ willingness to pay (WTP) for the vegetative propagated orange fleshed sweetpotato (OFSP) planting material that is many times considered as a public good. Famers’ WTP for OFSP vines was elicited by conducting a real choice experiment (RCE) among 121 small sweetpotato growers in central Mozambique with prior experience growing OFSP but with no participation in OFSP vine distributions in the previous 3 years of the experiment. Results reveals a higher farmers’ willingness to pay for OFSP varieties (US$0.07-0.12) compared to the non-orange planting material (US$ 0.03) and compared to the traditional subsidized price of clean sweetpotato vines (US$ 0.06) used in Mozambique. These results may encourage formation of a network of private vine multipliers that would supply permanently OFSP planting material in wider areas.Agricultural and Food Policy, Community/Rural/Urban Development, Consumer/Household Economics, Farm Management, Food Security and Poverty, Health Economics and Policy, International Development, Production Economics, Q16,

Monte Carlo Study of the Finite Size Effects on the Magnetization of Maghemite Small Particles

Monte Carlo simulations of a model for $\gamma$-Fe$_2$O$_3$ (maghemite) single particle of spherical shape are presented aiming at the elucidation the specific role played by the finite size and the surface on the anomalous magnetic behaviour observed in small particle systems at low temperature. The influence of the finite-size effects on the equilibrium properties of extensive magnitudes, field coolings and hysteresis loops is studied an compared to the results for periodic boundaries. It is shown that for the smallest sizes the thermal demagnetization of the surface completely dominates the magnetization while the behaviour of the core is similar to that of the periodic boundary case, independently of $D$. The change in shape of the hysteresis loops with $D$ demonstrates that the reversal mode is strongly influenced by the presence of broken links and disorder at the surface.Comment: Presented at the 8th Joint MMM-Intermag Conference, San Antonio, Texas, 7-11 January 2001. Session HF-09. To be published in J. Appl. Phys. 3 pages, 3 figure

Modelling exchange bias in core/shell nanoparticles

We present an atomistic model of a single nanoparticle with core/shell structure that takes into account its lattice strucutre and spherical geometry, and in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and interfacial regions. By means of Monte Carlo simulations of the hysteresis loops based on this model, we have determined the range of microscopic parameters for which loop shifts after field cooling can be observed. The study of the magnetic order of the interfacial spins for different particles sizes and values of the interfacial exchange coupling have allowed us to correlate the appearance of loop asymmetries and vertical displacements to the existence of a fraction of uncompensated spins at the shell interface that remain pinned during field cycling, offering new insight on the microscopic origin of the experimental phenomenology.Comment: 7 pages, 3 figures. Contribution presented at HMM 2007 held at Napoli 4-6 June 2007. To be published in J. Phys. Condens. Matte

Do Pesticide Hazards to Human Health and Beneficial Insects Cause or Result from IPM Adoption? Mixed Messages from Farmer Field Schools in Nicaragua

This paper analyzes the interaction between farmer training in pest management and effects on acute pesticide poisoning and populations of beneficial insects in Nicaragua. Using farm level data from Nicaraguan bean growers, including graduates of Farmer Field Schools (FFS), other integrated pest management (IPM) outreach methods, and farmers without exposure to IPM, we found that small farmers are influenced by pesticide-related acute illness experiences when adopting IPM practices and making decisions about pesticide use. However, exposure to IPM extension programs failed to reduce the use of highly toxic pesticides and increased the number of self-reported acute illness symptoms during the most recent bean crop season. IPM training did result in growth of beneficial insect populations.ecosystem service, integrated pest management, agricultural extension, Nicaragua, Farm Management, Q16,

Multi-Institutional Implementation of Farmer Field Schools among Nicaraguan Bean Growers. Do Different NGOs Perform Differently?

This paper analyzes how different characteristics of non-governmental organizations (NGOs) working as extension providers affect the delivery of agricultural technologies to farmers. Using farm level data from 436 Nicaraguan bean growers, we evaluate how the institutional characteristics of the NGOs that implement farmer field schools (FFS) affect their impacts on farmer choices of pest management inputs, their adoption of integrated pest management (IPM) and resulting net revenues and pesticide exposure from bean production. After controlling for endogeneity of participation in IPM training programs and for a clustered and stratified sample design, results reveal that institutional focus, expertise in IPM and the capacity of extension providers implementing FFS significantly influence FFS impacts on input choices and adoption of IPM. FFS participation by itself has no influence on farmer' pest management decisions or their net revenues.Crop Production/Industries,