Binary-Binary Interactions and the Formation of the PSR B1620-26 Triple System in M4

The hierarchical triple system containing the millisecond pulsar PSR B1620-26 in M4 is the first triple star system ever detected in a globular cluster. Such systems should form in globular clusters as a result of dynamical interactions between binaries. We propose that the triple system containing PSR B1620-26 formed through an exchange interaction between a wide primordial binary and a {\it pre-existing\/} binary millisecond pulsar. This scenario would have the advantage of reconciling the $\sim10^9\,$yr timing age of the pulsar with the much shorter lifetime of the triple system in the core of M4.Comment: 13 pages, uuencoded compressed postscript with figures, IASSNS-AST 94/4

CLIMATE AND SCALE IN ECONOMIC GROWTH

This paper introduces new data on climatic conditions to empirical tests of growth theories. We find that, since 1960, temperate countries have converged towards high levels of income while tropical nations have converged towards various income levels associated with economic scale and the extent of the market. These results hold for a wide range of tests. A plausible explanation is that temperate regions' growth was assisted by their climate, perhaps historically for their transition out of agriculture into sectors whose productivity converges across countries, while tropical countries' growth is relatively more dependent on gains from specialization and trade.International Development,

Africa's Growth Trap: A Political-Economy Model of Taxation, R&D and Investment

Why do so many African governments consistently impose high tax rates and make little investment in productive public goods, when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent. For pro-growth policies to become sustainable, commitment mechanisms or new production techniques would be needed.time consistency, agricultural policy, economic growth

Africa's growth trap: a political-economy model of taxation, R&D and investment.

Why do so many African governments consistently impose high tax rates and make little investment in productive public goods when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent. For progrowth policies to become sustainable, commitment mechanisms or new production techniques would be needed.time consistency, agricultural policy, tax regimes and growth.

AN AFRICAN GROWTH TRAP: PRODUCTION TECHNOLOGY AND THE TIME-CONSISTENCY OF AGRICULTURAL TAXATION, R&D AND INVESTMENT

Why do so many African governments consistently impose high tax rates and make little investment in productive public goods, when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent, primarily because production technology requires relatively large sunk costs. For pro-growth policies to become sustainable, commitment mechanisms or new production techniques would be needed.International Development, Research and Development/Tech Change/Emerging Technologies,

Climate and scale in economic growth.

This paper introduces new data on climatic conditions to empirical tests of growth theories. We find that, since 1960, temperate countries have converged towards high levels of income while tropical nations have converged towards various income levels associated with economic scale and the extent of the market. These results hold for a wide range of tests. A plausible explanation is that temperate regions' growth was assisted by their climate, perhaps historically for their transition out of agriculture into sectors whose productivity converges across countries, while tropical countries' growth is relatively more dependent on gains from specialization and trade.growth accounting, empirical growth models, endogenous growth

Racial stereotyping: survey of psychiatrists in the United Kingdom

No abstracts available

Rural Demography, Public Services and Land Rights in Africa: A Village-Level Analysis in Burkina Faso

This paper uses historical census data from Burkina Faso to characterize local demographic pressures associated with internal migration into river valleys after Onchocerciasis eradication, combined with a new survey of village elders to document change over time and differences across villages in local public goods provision, market institutions and land use rights. We hypothesize that higher local population densities are associated with more public goods and a transition from open-access to regulated land use. Controlling for province or village fixed effects, we find that villages’ variance in population associated with proximity to rivers is closely correlated with higher levels of infrastructure, markets and individual land rights, as opposed to familial or communal rights. Responding to population growth with both improved public services and private property rights is consistent with both scale effects in public good provision, and changes in the scarcity of land.

Experimental demonstration of a measurement-based realisation of a quantum channel

We introduce and experimentally demonstrate a method for realising a quantum channel using the measurement-based model. Using a photonic setup and modifying the bases of single-qubit measurements on a four-qubit entangled cluster state, representative channels are realised for the case of a single qubit in the form of amplitude and phase damping channels. The experimental results match the theoretical model well, demonstrating the successful performance of the channels. We also show how other types of quantum channels can be realised using our approach. This work highlights the potential of the measurement-based model for realising quantum channels which may serve as building blocks for simulations of realistic open quantum systems.Comment: 8 pages, 4 figure