Analysis of the relationship between quality and price of yam in Ghana - second round (NRI report no. 2428)

In 1997, NRI staff and officers from the Ghanaian Ministry of Food and Agriculture conducted two quantitative surveys of yam trading in Techiman market. The aim was to establish the importance of financial losses caused by poor yam quality and to measure the relationships between price and a series of quality defect variables. This report summarises the analysis of data gathered during the second survey. Data was analysed using multiple regression. Of the nine quality variables measured in the market, only "rotting" could be proved to have a significant influence on price. This result should not be interpreted to mean that other quality variables do not have an impact on price, merely that there was insufficient variation in quality for the statistical techniques to prove the existence of other price quality relationships. Moreover, at the time of the survey, these findings suggest that the financial losses caused by quality defects were slight. The report concludes with suggestions for improving the data gathering methodology for future surveys. In particular, it recommends extensive qualitative surveys to establish the incidence of quality defect related financial losses throughout the year. If these surveys indicate high financial losses, the research should attempt to establish the quantitative nature of price quality relationships using biased sampling techniques

Survey of yam trading practices and loss assessment in Techiman Market (NRI report no. R6505)

The aim of this report is to gain an understanding of the structure of yams marketing in and around Techiman Market in Ghana, and to understand the extent and impact of quality deterioration (called 'physical losses' in this report) on the farmers' and traders' revenues. It should be noted that the data collected on marketing margins and losses was collected using informal techniques which provide indicative results

Uncanny Objects and the Fear of the Familiar:Hiding from Akan Witches in New York City

This article examines the cosmology and secret practices of West African traditional priests in New York City in preventing the spread of witchcraft, an evil invisible spirit transmitted between female members of the Akan matrilineage. Explored is an uncanny dynamic as everyday habitus becomes increasingly strange in the world of a young Ghanaian woman in the Bronx, who has become petrified of insinuations of witchcraft from close family members. In trying to hide the young woman from infection by her fellow witches, Akan priests attempt to ‘capture’ her habits and everyday routines, calling upon the iconic magic of New York City in order to ‘misplace’ familiarity within the anonymity of Manhattan. In this process, the transmission of the witch’s spirit to the intended victim is disturbed as the victim’s life and things are moved. Nowhere to be found, the witch shifts her attention to other victims

Influence of slag composition on the stability of steel in alkali-activated cementitious materials

Among the minor elements found in metallurgical slags, sulfur and manganese can potentially influence the corrosion process of steel embedded in alkali-activated slag cements, as both are redox-sensitive. Particularly, it is possible that these could significantly influence the corrosion process of the steel. Two types of alkali-activated slag mortars were prepared in this study: 100% blast furnace slag and a modified slag blend (90% blast furnace slag? 10% silicomanganese slag), both activated with sodium silicate. These mortars were designed with the aim of determining the influence of varying the redox potential on the stability of steel passivation under exposure to alkaline and alkaline chloride-rich solutions. Both types of mortars presented highly negative corrosion potentials and high current density values in the presence of chloride. The steel bars extracted from mortar samples after exposure do not show evident pits or corrosion product layers, indicating that the presence of sulfides reduces the redox potential of the pore solution of slag mortars, but enables the steel to remain in an apparently passive state. The presence of a high amount of MnO in the slag does not significantly affect the corrosion process of steel under the conditions tested. Mass transport through the mortar to the metal is impeded with increasing exposure time; this is associated with refinement of the pore network as the slag continued to react while the samples were immersed

Transformation alimentaire du manioc = Cassava food processing

Une série d'essais expérimentaux a été menée dans des fermes au Ghana afin de déterminer si l'application, avant ou pendant le stockage, d'eau ou de fongicide (thiobadenzole) à des racines fraîchement récoltées contenues dans des sacs en polyéthylène ou dans des sacs de riz recyclés (polyéthylène tissé) pouvait prolonger leur durée de stockage. Les résultats indiquent que s'ils sont appliqués suffisamment tôt, tous ces traitements créent des environnements capables de prolonger la durée de stockage des racines de 3 à 5 jours jusqu'à 2 à 3 smemaines. Les traitements utilisant seulement de l'eau dans de sacs en polyéthylène ou recyclés peuvent prolonger les possibilités de stockage d'au moins 7 jours à condition que la contamination microbienne soit évitée. Il a été démontré que le thiobadenzole non seulement empêche le pourrissement microbien mais prolonge aussi l'aptitude au stockage des racines de la même manière que le traitement à l'eau. (Résumé d'auteur

Small footprint aluminosilicate matrix: refractory hybrid materials

This study investigates the effects of alumina, titania, boron nitride and silicon carbide additions on low energy (typical cure < 90oC) alkali reactive aluminosilicate matrix material properties as potential small environmental footprint refractory materials. The structure - property relationships of the aluminosilicate matrix - refractory hybrid materials were characterized for thermal performance. Electron microscopy complemented with X-ray diffraction and FTIR revealed the different reaction mechanisms occurring within the hybrid aluminosilicate matrix - refractory systems. Alumina and silicon carbide additions were found to react with the aluminosilicate matrix to a greater extent than boron nitride and titania. Thermogravimetric and differential thermal analysis indicate that thermal behaviour is predominantly dictated by water loss from the aluminosilicate matrix, with refractory additions playing a minor role. The reactivity of the refractory addition towards the aluminosilicate matrix influenced sample microstructure and thermal performance

Differences in elevated temperature performances of geopolymers made with metakaolinite and fly-ash

Abstract not available