This article develops a framework to examine households' joint decision to acquire information on new technologies and the adoption of the technology in the presence of uncertainty. The empirical application involved a sample of 406 dairy farmers in Tanzania. Education, scale of production, household size, age, and liquidity constraints are hypothesized to be the determinants of information acquisition and adoption decisions. The empirical evidence indicates that information acquisition and adoption decisions are made jointly. The findings also show that human capital and scale of operation positively and significantly affect the decision to acquire information and to adopt the technology, while liquidity constraints negatively impact on the decision to adopt, as well as the extent of adoption. Copyright © 2008 John Wiley & Sons, Ltd.

Continental spring carbonates are perfect examples of the interaction of biotic and abiotic processes, and they preserve evidence of the velocity of the flow and the chemical composition of the spring water. This study focuses on non-marine carbonates from fossil and active springs from the Bongongo and Ngol areas along the Cameroon Volcanic Line in South-West Cameroon. Here, hydrothermal fluids reach the surface giving rise to small thermal springs, with temperatures between 31 and 49°C, and streams creating waterfalls, terracettes and barrage carbonate deposits. Petrographic analyses of these carbonates revealed that they are made up of stacked laminae of fibrous coarse crystals of low-Mg calcite and laminae of alternate microsparite and micrite. The fibrous coarsely crystalline calcite, often with feather-like fabric, grows from thin layers of micrite and peloids. Filaments of putative microbial origin are preserved within this peloidal micrite. The laminated microsparite and micrite microfacies is characterised by an intricate mesh of hollow filaments of microbial origin. The long feather-like crystals of calcite formed in fast-flowing water where the enhanced CO 2 degassing has favoured the precipitation of CaCO 3 . The laminated micrite and microsparite, on the other hand, are probably formed in ponds where degassing and CO 2 removal was lower and the calcite precipitation was fostered by microbial activity. The fast-forming carbonates show higher Ce contents and very low total rare earth elements, revealing a preferential uptake of Ce with respect to other rare earth elements. This process would explain the positive or null Ce anomaly in continental spring carbonates elsewhere. The geochemical composition of these carbonates can be used as proxy for the characterisation of fluid/rock interactions between the groundwater and the substratum and for the characterisation of the sources of calcium and other elements that constitute tufa and travertines. The samples from Ngol are characterised by light rare earth element enrichment while those from Bongongo are overall enriched in heavy rare earth elements. Carbonates from both localities have a strong positive Eu anomaly (>4), suggesting a contribution | 103 BISSE Et al.