500 Kilovolt Cathode Rays

The high potential x-ray tube at the California Institute has been modified so as to permit either x-rays or cathode rays to be produced. Electron currents up to 35 microamperes have been obtained through an aluminum window. A typical magnetic velocity spectrum of the high speed electrons passing out of an aluminum window is presented. The high velocity limit corresponds to about 500 kilovolts when the transformer voltage is 600 kilovolts peak. The velocity spectrum appears to be continuous and no absorption anomalies due to aluminum and lead foil are evident. The time required to obtain a velocity spectrum was reduced to a few minutes by allowing the electrons after being magnetically deflected, to pass through a copper foil into the air. The outside of the foil is coated with calcium tungstate and the photographic plate is placed in contact with the tungstate. It is noted that part of the photographic action of the high speed electrons is due to fluorescence of the glass backing of the photographic plates

The Dual Economy in Long-run Development

This paper provides a dynamic model of the dual economy in which differences in productivity across sectors arise endogenously. Rather than relying on exogenous price distortions, duality arises because of differences between sectors in the separability of their fertility and labor decisions. The model demon- strates how a dual economy will originate, persist, and eventually disappear within a unified growth framework. It is also shown that agricultural productivity growth will exacerbate the ine±ciencies of a dual economy and slow down long-run growth.Dual economy, unfied growth, endogenous fertility

Agrarian Structure and Endogenous Financial System Development

The development of the financial system is shown, both historically and in contemporary data, to be adversely affected by inequality in the distribution of land. To accommodate these empirical findings, a theory is developed that highlights the incentives of landowners to oppose competition in the financial sector. The theory provides an explanation for the co-incident development of the financial sector and overall economy.Land Distribution, financial development, overlapping generations, financial institutions

Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

Quantum kinetic equations of motion for the description of the exciton spin dynamics in II-VI diluted magnetic semiconductor quantum wells with laser driving are derived. The model includes the magnetic as well as the nonmagnetic carrier-impurity interaction, the Coulomb interaction, Zeeman terms, and the light-matter coupling, allowing for an explicit treatment of arbitrary excitation pulses. Based on a dynamics-controlled truncation scheme, contributions to the equations of motion up to second order in the generating laser field are taken into account. The correlations between the carrier and the impurity subsystems are treated within the framework of a correlation expansion. For vanishing magnetic field, the Markov limit of the quantum kinetic equations formulated in the exciton basis agrees with existing theories based on Fermi's golden rule. For narrow quantum wells excited at the $1s$ exciton resonance, numerical quantum kinetic simulations reveal pronounced deviations from the Markovian behavior. In particular, the spin decays initially with approximately half the Markovian rate and a non-monotonic decay in the form of an overshoot of up to $10\,\%$ of the initial spin polarization is predicted.Comment: 17 pages, 3 figures, typographical errors corrected (Erratum published in Phys. Rev. B 96, 239904

Reciprocal Trade Agreements: Impacts on Bilateral Trade Expansion and Contraction in the World Agricultural Marketplace

The rapid increase in the number of bilateral and regional free-trade agreements since 1995 is a striking development. The proliferation of these agreements has raised questions about whether they have, in fact, opened markets, created trade, promoted economic growth, and/or distorted trade. This study uses panel data from 1975 to 2005 and a gravity framework model to identify the influence of reciprocal trade agreements (RTAs) on bilateral trade in the world agricultural marketplace. A benchmark, Heckman sample-selection and two generalized models, one of which accounts for RTA phase-in effects, are used to gauge the impact on partner trade of mutual as well as asymmetric RTA membership. Empirical results show that RTAs increase agricultural trade between member countries but decrease trade between member and nonmember countries. Interestingly, RTAs were found to be particularly effective at expanding agricultural trade and opening markets in developing countries when developing- country trading partners are part of the same agreement.trade policy, reciprocal trade agreements, bilateral, regional, missing trade, gravity models, Agricultural and Food Policy, International Development, International Relations/Trade,

Economic costs and payoffs of bilateral/regional trade agreements

The rapid increase in the number of bilateral and regional free-trade agreements since 1995 is a striking development. The proliferation of these agreements has raised questions among academicians and policymakers about whether they have, in fact, opened markets, created trade, promoted economic growth, and/or distorted trade. This study uses panel data from the 1975-2005 period and the gravity framework to identify the influence of bilateral/regional free-trade agreements on bilateral trade in merchandise, agriculture, and clothing sectors. A benchmark, Heckman sample-selection, and two generalized models, one of which accounts for reciprocal-free-trade-agreement phase-in effects, are used to gauge the impact on partner trade of mutual as well as asymmetric RTA membership.trade policy, bilateral, regional, missing trade, gravity models, reciprocal trade agreements, Agricultural and Food Policy,

NORTH AMERICAN AGRICULTURAL MARKET INTEGRATION AND ITS IMPACT ON THE FOOD AND FIBER SYSTEM

Economic change and market dynamics have fundamentally altered the structure and performance of agricultural markets in the United States, Canada, and Mexico within the last 25 years. Many factors have helped shape the current North American food and fiber system, including technological change, domestic farm policies, international trade agreements, and the economic forces of supply and demand. Ratification of NAFTA, for example, helped integrate the North American market, sparking a surge in trade and investment among the United States, Canada, and Mexico. In recent years, efforts to further integrate the continental market seem to have slowed. Broadening the scope of NAFTA to include institutional reforms that lead to a more unified system of commercial law, the establishment of common antitrust and regulatory procedures, harmonization of product standards, and increased coordination of domestic farm, market, and macroeconomic policies would deepen market integration and enhance market efficiency and growth within North America.agriculture, market integration, market segmentation, law of one price, price transmission, elasticities, exchange-rate pass-through, market efficiency, bilateral trade intensity, regional trade agreements, NAFTA, CUSTA, trade policy, WTO, GATT, Industrial Organization, International Relations/Trade, Marketing,