A numerical model to simulate the tidal dispersion of radionuclides in the English Channel

A numerical model to simulate the tide-induced dispersion of conservative radionuclides in the English Channel has been developed. The model solves the shallow-water hydrodynamic equations and, simultaneously, the advection diffusion dispersion equation. The hydrodynamic model has been tested by comparing measured and computed currents for medium, neap and spring tides over the Channel and the dispersion part of the model has been tested by comparing measured and computed concentrations of 125Sb, 99Tc and 137Cs in the Channel. These radionuclides are released from a nuclear fuel reprocessing plant. Model results are in good agreement with observations. The effect of wind on the dispersion patterns has also been studied.European Union FI4PCT960046Comisión Interministerial de Ciencia y Tecnología (CICYT) AMB97-1720-C

Looking at the informal economy: a case study concerning Luanda's minibus taxi industry

The role, characteristics and increasing factors of the minibus taxi industry in urban economies (Kenya, Senegal, and Nigeria, among others) have been studied in various African countries. Many studies have been carried out on these matters with the support of the World Bank, through SSTAP or in the context of SITRASS research programs. There has been almost no research on this subject in Lusophone Africa.subject in Lusophone Africa. Machimbombo is the Angolan expression for bus. The machimbombos was the only means of transport providing urban mobility in Luanda, the Angolan capital city, at the time of independence and in the first years which followed. Over the last 25 years there have been significant changes in the urban landscape due to the prolonged civil war and the political and economic transformations.Fundação para a Ciência e a Tecnologia, Ministério da Ciência, Tecnologia e Ensino Superio

The sea surface salinity in the Tropical Atlantic between 10°S and 30°N seasonal and interannual variations (1977-1989)

The sesonal and interannual variations of the Sea Surface Salinity (SSS) are analysed in the Tropical Atlantic (15°S-30°N, 80°W-15°E) from observations collected by merchant ships between 1977 and 1989 and earlier by ORSTOM research vessels. The harmonic analysis of SSS shows a well defined seasonal cycle both within a 5°N-15°N zonal belt and west of 50°W at higher latitudes. In the Eastern Atlantic between 10 and 20°N (along the shipping lanes West Africa-South Africa and West Africa-Brazil), SSS increased from 1977 to 1985, particularly near 10°N. SSS variability is mostly related to the river outflow (Amazon, Orinoco and Congo) west of 40°W and in Southern Gulf of Guinea. In the Eastern Atlantic, precipitation associated with the ITCZ largely control the SSS seasonal variations. (Résumé d'auteur

Farm-nonfarm linkages in rural sub-Saharan Africa

This paper is an accumulation, over the past 25 years, of a body of detailed work examining the structure of Africa's rural, nonfarm economy. First, it systematically reviews empirical evidence on the nature and magnitude of the African rural, nonfarm economy. It then explores differences across locality and size, across countries and over time, in an effort to assess likely patterns of growth. A subsequent review of key production and consumption parameters allows an estimate of the magnitude of the agricultural growth multipliers in Africa. The paper concludes with a brief discussion of policies and programs that will be necessary if farm-nonfarm growth linkages are to achieve their full potential.Banks&Banking Reform,Agricultural Knowledge&Information Systems,Municipal Financial Management,Environmental Economics&Policies,Economic Theory&Research