Modeling Urbanization and Economic Growth

The past quarter century has witnessed unprecedented economic progress in the Third World. Yet major problems have arisen, some of which are the consequences of the progress itself and may become serious constraints on future development. City growth is one such problem. Pessimists stress the developing countries' inability to cope with the resource and social systems requirements of rapid urban growth, thus prompting the term "over-urbanization". Optimists minimize the negative externalities and view urban growth as the key to raising average labor productivity and living standards. All of this experience has taken place under conditions of "population explosions". This paper presents a general equilibrium economic-demographic model which highlights various aspects of urbanization. Attention is focused on the determinants and consequences of rural-urban migration, on the resource demands of housing associated with rapid urbanization, on optimal land use between urban and rural activities, and on the allocation of investments to education and labor force training. The economic model is designed to be "representative" of a large group of developing countries, and it will eventually contain a fully elaborated demographic component. The model will be tested with Third World growth experience since the 1950s. It will then be used to analyze the sources of migration and urbanization, and to explore their interaction with distribution, accumulation and growth

Absolute Relativity in Classical Electromagnetism: the Quantisation of Light

A rigorous introduction of the underlying nature of space and time forces qualitatively new kinds of solutions in the classical theory of electromagnetism. A class of relativistic wave-functions are derived which are solutions to the first-order, free-space Maxwell equations. These describe all photons from radio to gamma waves and are governed by a single parameter: the exchange frequency. Though the theory remains that of classical, continuous electromagnetism, allowed travelling-wave solutions are quantised in that they come in \lumps" and their characteristic energy is proportional to frequency

Modeling Growing Economies in Equilibrium and Disequilibrium

The papers in this volume were presented and discussed at a meeting held at IIASA. The meeting's goals were to stimulate interaction and collaboration, and to encourage setting research priorities for the future. Indeed, it is in this latter area where the meeting appeared to yield some of its greatest benefits. It became clear from the deliberations that much needs to be done to better specify the microfoundations of general equilibrium models. More realistic specifications of "conflict resolution" in resource allocation, in both market and nonmarket economies, need to be developed. Equally importantly, much work is required to explore the role of economic disequilibrium in economic growth and development. "Equilibrium" and "disequilibrium" are positive, not normative concepts; neither view is right or wrong; neither will necessarily yield desired social outcomes at all stages of development, or across all regions. Rather, they yield quite different outcomes, which themselves should be subjects for scientific inquiry. The meeting pointed out the potential for expanding the conceptions of general equilibrium modeling to incorporate elements of disequilibrium analysis, so that this framework may not only be increasingly relevant to Eastern countries, but so that the possibilities of East-West interaction on critical aspects of resource allocation and economic growth can be enhanced

Urbanization and Development in the Third World

Roughly 1.8 billion people, 42 percent of the world's population, live in urban areas today, and this total is growing by almost 3 percent per year. Even more dramatic are the growth rates in large cities in developing countries. Rates of 5-8 percent are not uncommon, and the urban growth multipliers that they indicate are truly awesome - a doubling time of 8-15 years. Scholars and policy makers are divided on the issue of rapid urbanization and urban growth in the Third World. Some see these trends as effectively speeding up national processes of socioeconomic development; others believe their impacts to be largely undesirable and argue that they should be slowed down. Yet many of the determinants and consequences of urban and rural demoeconomic patterns of change are poorly understood, and there is an urgent need for improved methods of analyzing the fundamental issues and options that they bring about. The five papers in this collection, written by current or past scholars in the Area, are a representative sample of this research. Together with three papers by other authors (not included here) they form the proceedings of a symposium on urbanization in the Third World published by the journal "Economic Development and Cultural Change"

Treatment of hypertension following endotracheal intubation A study comparing the efficacy of labetalol, practolol and placebo

Labetalol, a new adrenergic receptor antagonist, has both a- and B-blocking properties. Intravenous labetalol (0,25 and 0,5 mg/kg), practolol (0,4 mg/kg) and saline (1 ml), injected prior to anaesthesia, were compared with respect to their effect on the haemodynamic consequences of direct laryngoscopy followed by the passage of an endotracheal tube. When compared with intravenous saline injection, both labetalol and practolol obtunded the tachycardia induced by endotracheal intubation. The higher dose of labetalol was more effective in reducing the hypertensive response than the lower dose of practolol. However, none of the regimens completely abolished the adverse haemodynamic consequences of laryngotracheal, manipulations

Injection of Ballistic Hot Electrons and Cool Holes in a Two-Dimensional Electron Gas

We have constructed a novel magnetic spectrometer to study the dynamics of hot electrons and cool missing electron states injected by quantum point contacts in the two-dimensional electron gas of a GaAs-AlxGa1-xAs heterostructure. The mean free path of these quasi-particles is found to be longer than recent theoretical estimates. The injection energy of the particles is found to be anomalously low as the point contact approaches pinch-off, and also for high bias voltages.

Aharonov-Bohm effect in a singly connected point contact

We report the discovery of an oscillation in the low-temperature magnetoresistance of a point contact in the two-dimensional electron gas of a GaAs-AlxGa1–xAs heterostructure. The oscillation is periodic in the magnetic field and is reminiscent of the Aharonov-Bohm effect in rings, although the geometry is singly connected. A possible mechanism for this quantum interference effect is tunneling between edge states across the point contact at the potential step at the entrance and the exit of the constriction

Tight-binding study of the influence of the strain on the electronic properties of InAs/GaAs quantum dots

We present an atomistic investigation of the influence of strain on the electronic properties of quantum dots (QD's) within the empirical $s p^{3} s^{*}$ tight-binding (ETB) model with interactions up to 2nd nearest neighbors and spin-orbit coupling. Results for the model system of capped pyramid-shaped InAs QD's in GaAs, with supercells containing $10^{5}$ atoms are presented and compared with previous empirical pseudopotential results. The good agreement shows that ETB is a reliable alternative for an atomistic treatment. The strain is incorporated through the atomistic valence force field model. The ETB treatment allows for the effects of bond length and bond angle deviations from the ideal InAs and GaAs zincblende structure to be selectively removed from the electronic-structure calculation, giving quantitative information on the importance of strain effects on the bound state energies and on the physical origin of the spatial elongation of the wave functions. Effects of dot-dot coupling have also been examined to determine the relative weight of both strain field and wave function overlap.Comment: 22 pages, 7 figures, submitted to Phys. Rev. B (in press) In the latest version, added Figs. 3 and 4, modified Fig. 5, Tables I and II,.and added new reference

Observation of excess conductance of a constricted electron gas in the fractional quantum Hall regime

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