Improving market institutions and urban food supplies for the urban poor: a comparative study of Nigeria and Zambia.

This study examines the systems which govern the marketing opportunities for informal urban and peri-urban cultivators, and for rural producers, in our two study countries, Nigeria and Zambia and it explores the mechanisms of marketing food in urban areas. Our literature review illustrates how little is known about how these formal and informal regulatory systems currently operate. For example, the positive contribution of both urban-based and rural-based traders in providing an essential service to urban consumers has not been adequately analysed

Ecological degradation in cities: impact of urban agriculture In Harare, Zimbabwe

A journal article on the impact on the environment of urban agriculture in Zimbabwe.The effect of the increasingly widespread practice of urban agriculture in the City of Harare on the natural biodiversity was investigated. Vegetation surveys noting species presence-absence and abundance were undertaken in seven field areas, identifying the components of the natural vegetation of both the clay soil-type areas developed on basic rock, and the sandy soil-type areas developed on granite, that typify the city. Change brought about by the increasingly widespread practice of urban agriculture was determined, and knock-on effects for other aspects of the city's ecology were investigated. Most open space areas in Harare are vlei land. Detrended Correspondence Analysis (DCA) illustrated significant differences in the species composition of uncultivated vlei areas with distance from the vlei channel, reflecting change in the water-logging conditions of the soil. A higher diversity of faunal species, and larger species count, prior to cultivation was also noted. The effects of cultivation on the vegetation were a change in species composition (with the natural vegetation being replaced by mainly alien arable weeds), the loss of the spatial diversity in species presence and dominance, a significantly reduced ground cover, and a loss of habitat diversity. The implications of these changes for the amenity value of the city environment is discussed. The need for a more sensitive management of open-land areas within Harare, while the possibility of their conservation as areas of viable natural ecological diversity is still available, is highlighted

On the cosmological mass function theory

This paper provides, from one side, a review of the theory of the cosmological mass function from a theoretical point of view, starting from the seminal paper of Press & Shechter (1974) to the last developments (Del Popolo & Gambera (1998, 1999), Sheth & Tormen 1999 (ST), Sheth, Mo & Tormen 2001 (ST1), Jenkins et al. 2001 (J01), Shet & Tormen 2002 (ST2), Del Popolo 2002a, Yagi et al. 2004 (YNY)), and from another side some improvements on the multiplicity function models in literature. ...Comment: Astronomy Reports, in prin

Dark matter and structure formation a review

This paper provides a review of the variants of dark matter which are thought to be fundamental components of the universe and their role in origin and evolution of structures and some new original results concerning improvements to the spherical collapse model. In particular, I show how the spherical collapse model is modified when we take into account dynamical friction and tidal torques