Multipliers on Dirichlet type spaces

In this article we examine Dirichlet type spaces in the unit polydisc, and multipliers between these spaces. These results extend the corresponding work of G. D. Taylor in the unit disc. In addition, we consider functions on the polydisc whose restrictions to lower dimensional polydiscs lie in the corresponding Dirichet type spaces. We see that such functions need not be in the Dirichlet type space of the whole polydisc. Similar observations are made regarding multipliers.Comment: 21 page

Uptake of Improved Technologies in the Semi-arid Tropics of West Africa: Why is Agricultural Transformation Lagging Behind?

During the last 3 decades, donors and governments have invested in the development and dissemination of new technologies in the semi-arid tropics of West Africa. Though a wide range of improved technologies has been developed, adoption remains low without a significant impact on crop productivity, rural income and poverty. Agricultural transformation as occurred in East Asia has not yet occurred in the semi-arid tropics of West Africa. This paper uses data from a regional survey of rural households in 3 countries in West Africa (Burkina Faso, Mali, and Niger) to identify the determinants of uptake of improved technologies. Limited productivity gain is found to be a major constraint to the uptake of technologies. In addition, poorly functioning institutions, lack of information or poor exposure of farmers to agricultural innovations, and poor functioning or missing markets have also hindered the uptake of many new technologies.institutions, technology, markets, road infrastructure, information, agricultural productivity, International Development,

Experimental electron shielding studies Technical summary report

Electron shielding - comparison of thick target energy straggling and angular distributions with Monte Carlo calculation

Nonlinear Interchange Modes Near Marginal Stability

The nonlinear stability of the ideal magnetohydrodynamic interchange mode, at marginal conditions, is studied. The interchange mode is made to be at marginal conditions by providing a constant magnetic field that is just sufficiently strong enough to balance the mode growth. How nonlinearity affects the stability of the interchange mode is analyzed for three different systems. We first consider introducing small amplitude perturbations on a two-dimensional system. We show that if the fractional deviation from marginality is given by a small parameter b, then perturbation amplitudes of order b1/2 can cause the system to become nonlinearly unstable. The analysis is corroborated by a nonlinear, compressible, magnetohydrodynamic simulation that shows excellent agreement with the result, including the amplitude scaling. We then extend the analysis to a three-dimensional system where, we show that, the perturbations separate into two different modes. The first mode is shown to be isomorphic to the two-dimensional case and, thus, has the same dynamics, i.e. nonlinearly unstable; however, we show that the second mode is nonlinearly stable. The latter modes are shown to satisfy line-tied boundary conditions. The third system we consider is a two-dimensional system with perturbations introduced as deformations of the boundaries. We show that these small distortions can penetrate deep in the magnetized plasma and become globally amplified. The amplification is shown to be inversely proportional to b. Additionally, we show that nonlinearities can cause the system to become unstable for distortions of order b3/2