Economic causes and consequences of migrations within the context of under-development in West Africa

African Studies Center Working Paper No. 6INTRODUCTION: In recent discussions of development and inequality in Africa, at least three positions can be identified concerning relationships between rural-urban migration and inequality. The most simplistic and journalistic view is that migrants come to the cities only to find unemployment and miserable living conditions. The story, as usually depicted, identifies the problem as misguided persistence in migrating explanations based on the inappropriateness of educational curricula, lures of brights lights, and misinformation. Despite little evidence to support this view, many African politicians have identified persistent migration as the cause of urban poverty and have attempted to stop the flow of migrants through exhortation, administrative controls, and coercion. Actions seem to have been based on the notion that the problems of urban poverty will disappear if only the poor... [TRUNCATED

The Botswana National Migration Study: a conceptual framework

African Studies Center Working Paper No. 4

Holding fixture for a hot stamping press

A hand held guide for manually positioning a work piece between the anvil rib and tool of a hot die stamping press is described. A groove completed by interchangeable cover plates attached at one end of the guide conforms to a cross sectional dimension common to similar workpieces and, with a force fit, retentively holds each of the workpieces

Disordered asymmetric simple exclusion process: mean-field treatment

We provide two complementary approaches to the treatment of disorder in a fundamental nonequilibrium model, the asymmetric simple exclusion process. Firstly, a mean-field steady state mapping is generalized to the disordered case, where it provides a mapping of probability distributions and demonstrates how disorder results in a new flat regime in the steady state current--density plot for periodic boundary conditions. This effect was earlier observed by Tripathy and Barma but we provide treatment for more general distributions of disorder, including both numerical results and analytic expressions for the width $2\Delta_C$ of the flat section. We then apply an argument based on moving shock fronts to show how this leads to an increase in the high current region of the phase diagram for open boundary conditions. Secondly, we show how equivalent results can be obtained easily by taking the continuum limit of the problem and then using a disordered version of the well-known Cole--Hopf mapping to linearize the equation. Within this approach we show that adding disorder induces a localization transformation (verified by numerical scaling), and $\Delta_C$ maps to an inverse localization length, helping to give a new physical interpretation to the problem.Comment: 13 pages, 16 figures. Submitted to Phys. Rev.

High-temperature, high-pressure optical cell

The invention is an optical cell for containment of chemicals under conditions of high temperature and high pressure. The cell is formed of a vitreous silica tube, two optical windows comprising a vitreous silica rod inserted into the ends of a tube, and fused into position in the tube ends. Windows are spaced apart to form a cavity enclosed by the tube and the windows. A hole is drilled radially through the tube and into the cavity. Another vitreous silica tube is fused to the silica tube around the hole to form the stem, which is perpendicular to the long axis of the tube. The open end of the stem is used to load chemicals into the cavity. Then the stem may be sealed, and if desired, it may be shortened in order to reduce the volume of the cavity, which extends into the stem

Changing patterns of global-scale vegetation photosynthesis, 1982-1999

The primary objective of this research was to assess changes in global vegetation photosynthesis between 1982 and 1999. Global-scale Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data from the Pathfinder AVHRR Land (PAL) and Global Inventory Modeling and Mapping Studies (GIMMS) datasets were analysed for 96% of the non-Antarctic land area of the Earth. The results showed that between 1982 and 1999 over 30% of the Earth's land surface increased and less than 5% decreased in annual average photosynthesis greater than 4%. Although both the PAL and GIMMS datasets produced broadly similar patterns of change, there were distinct differences between the two datasets. Changes in vegetation photosynthesis were occurring in spatial clusters across the globe and were being driven by climate change, El Nino-Southern Oscillation (ENSO) events and human activity

The future of management: The NASA paradigm

Prototypes of 21st century management, especially for large scale enterprises, may well be found within the aerospace industry. The space era inaugurated a number of projects of such scope and magnitude that another type of management had to be created to ensure successful achievement. The challenges will be not just in terms of technology and its management, but also human and cultural in dimension. Futurists, students of management, and those concerned with technological administration would do well to review the literature of emerging space management for its wider implications. NASA offers a paradigm, or demonstrated model, of future trends in the field of management at large. More research is needed on issues of leadership for Earth based project in space and space based programs with managers there. It is needed to realize that large scale technical enterprises, such as are undertaken in space, require a new form of management. NASA and other responsible agencies are urged to study excellence in space macromanagement, including the necessary multidisciplinary skills. Two recommended targets are the application of general living systems theory and macromanagement concepts for space stations in the 1990s