Globalization, skilled migration and poverty alleviation: brain drains in context

The debate on the ‘brain drain’, or the emigration of skilled workers, is not new but it has taken on greater urgency in the context of a globalizing economy and ageing societies. Today, the developed world is perceived as poaching the best and the brightest from the developing world, thus prejudicing those countries of their chance of development. This paper starts with two guarded caveats: first, that any brain drain is as much internal within any country as it is among countries and, second, that the skilled migration system should not be seen in isolation from other types of migration. The paper reviews the data available for the analysis of skilled migration and identifies the main global trends. It goes on to examine the globalization of education and of health as reflected in the movement of students and health personnel. Large numbers of people from developing countries are being trained overseas and, of those trained at home, many cannot be absorbed productively into their economies of origin. The paper examines the case for a two-tiered health training system, one for global markets and the other for local markets. Retention and return of the skilled are examined through the potential for outsourcing in both education and health care. However, the association between the presence or absence of health personnel and the health status of a population is seen as simplistic. The paper concludes with an examination of policy contradictions within the global system towards skilled migration and offers pointers towards a more integrated approach

New stability results for long-wavelength convection patterns

We consider the transition from a spatially uniform state to a steady, spatially-periodic pattern in a partial differential equation describing long-wavelength convection. This both extends existing work on the study of rolls, squares and hexagons and demonstrates how recent generic results for the stability of spatially-periodic patterns may be applied in practice. We find that squares, even if stable to roll perturbations, are often unstable when a wider class of perturbations is considered. We also find scenarios where transitions from hexagons to rectangles can occur. In some cases we find that, near onset, more exotic spatially-periodic planforms are preferred over the usual rolls, squares and hexagons.Comment: 25 pages, 8 figure

Mathematical models for sleep-wake dynamics: comparison of the two-process model and a mutual inhibition neuronal model

Sleep is essential for the maintenance of the brain and the body, yet many features of sleep are poorly understood and mathematical models are an important tool for probing proposed biological mechanisms. The most well-known mathematical model of sleep regulation, the two-process model, models the sleep-wake cycle by two oscillators: a circadian oscillator and a homeostatic oscillator. An alternative, more recent, model considers the mutual inhibition of sleep promoting neurons and the ascending arousal system regulated by homeostatic and circadian processes. Here we show there are fundamental similarities between these two models. The implications are illustrated with two important sleep-wake phenomena. Firstly, we show that in the two-process model, transitions between different numbers of daily sleep episodes occur at grazing bifurcations.This provides the theoretical underpinning for numerical results showing that the sleep patterns of many mammals can be explained by the mutual inhibition model. Secondly, we show that when sleep deprivation disrupts the sleep-wake cycle, ostensibly different measures of sleepiness in the two models are closely related. The demonstration of the mathematical similarities of the two models is valuable because not only does it allow some features of the two-process model to be interpreted physiologically but it also means that knowledge gained from study of the two-process model can be used to inform understanding of the mutual inhibition model. This is important because the mutual inhibition model and its extensions are increasingly being used as a tool to understand a diverse range of sleep-wake phenomena such as the design of optimal shift-patterns, yet the values it uses for parameters associated with the circadian and homeostatic processes are very different from those that have been experimentally measured in the context of the two-process model

Motivations of UK students to study abroad: a survey of school-leavers

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Dynamic Systems Analysis of a Vehicle Suspension System

This research report deals with one system in a Computer Aided Instruction package in the Dynamic Systems and Control Theory fields for the college undergraduate students. It uses the computer to numerically solve the two degree of freedom equations of motion for a vehicle suspension system. Numerical solutions to the system differential equations are used to drive an animated display of the vehicle’s motion (vertical displacement and rotation about the center of gravity) on the video display terminal

Terrestrial gastropod responses to an ecosystem-level calcium manipulation in a northern hardwood forest

The effects of acid deposition on soil calcium (Ca), and in turn on land snail populations, have been of heightened concern for several decades. We compiled a 10 year record (1997–2006) of gastropod abundance on two small watersheds at the Hubbard Brook Experimental Forest, one of which was treated with a Ca addition in 1999. In years 3–7 post Ca addition, snail abundance in the treated watershed was 73% higher than in the reference area (p \u3c 0.001); there was no significant difference in the 3 years prior to treatment, and no significant difference in slug abundance in any year. We analyzed relationships between snail density and microsite spatial variation in leaf-litter Ca concentration, litter-layer thickness, tree species composition, slope, dead wood, and forest-floor light level. We found that snail abundance was significantly correlated with litter Ca concentration (p \u3c 0.001) and negatively correlated with the importance value of American beech (p = 0.05). Isotopic-tracer analysis indicated that, on average, 76% of Ca in snail shells 5 years post treatment was derived from the added Ca. However, interannual variation in snail numbers indicates that other factors beyond available Ca have a strong influence on snail abundance

Can weakly nonlinear theory explain Faraday wave patterns near onset?

The Faraday problem is an important pattern-forming system that provides some middle ground between systems where the initial instability involves just a single mode, and in which complexity then results from mode interactions or secondary bifurcations, and cases where a system is highly turbulent and many spatial and temporal modes are excited. It has been a rich source of novel patterns and of theoretical work aimed at understanding how and why such patterns occur. Yet it is particularly challenging to tie theory to experiment: the experiments are difficult to perform; the parameter regime of interest (large box, moderate viscosity) along with the technical difficulties of solving the free-boundary Navier–Stokes equations make numerical solution of the problem hard; and the fact that the instabilities result in an entire circle of unstable wavevectors presents considerable theoretical difficulties. In principle, weakly nonlinear theory should be able to predict which patterns are stable near pattern onset. In this paper we present the first quantitative comparison between weakly nonlinear theory of the full Navier–Stokes equations and (previously published) experimental results for the Faraday problem with multiple-frequency forcing. We confirm that three-wave interactions sit at the heart of why complex patterns are stabilised, but also highlight some discrepancies between theory and experiment. These suggest the need for further experimental and theoretical work to fully investigate the issues of pattern bistability and the role of bicritical/tricritical points in determining bifurcation structure