The Complexity of Infinite Computations In Models of Set Theory

We prove the following surprising result: there exist a 1-counter B\"uchi automaton and a 2-tape B\"uchi automaton such that the \omega-language of the first and the infinitary rational relation of the second in one model of ZFC are \pi_2^0-sets, while in a different model of ZFC both are analytic but non Borel sets. This shows that the topological complexity of an \omega-language accepted by a 1-counter B\"uchi automaton or of an infinitary rational relation accepted by a 2-tape B\"uchi automaton is not determined by the axiomatic system ZFC. We show that a similar result holds for the class of languages of infinite pictures which are recognized by B\"uchi tiling systems. We infer from the proof of the above results an improvement of the lower bound of some decision problems recently studied by the author

Performance calculations for 200-1000 MWe MHD/steam power plants

The effects of MHD generator length, level of oxygen enrichment, and oxygen production power on the performance of MHD/steam power plants ranging from 200 to 1000 MW in electrical output are investigated. The plants considered use oxygen enriched combustion air preheated to 1100 F. Both plants in which the MHD generator is cooled with low temperature and pressure boiler feedwater and plants in which the generator is cooled with high temperature and pressure boiler feedwater are considered. For plants using low temperature boiler feedwater for generator cooling the maximum thermodynamic efficiency is obtained with shorter generators and a lower level of oxygen enrichment compared to plants using high temperature boiler feedwater for generator cooling. The generator length at which the maximum plant efficiency occurs increases with power plant size for plants with a generator cooled by low temperature feedwater. Also shown is the relationship of the magnet stored energy requirement of the generator length and the power plant performance. Possible cost/performance tradeoffs between magnet cost and plant performance are indicated

Heckscher-Olin Theory and Non-Competitive Markets

This paper derives statements of the Heckscher-Ohlin Theorem which remain valid in the presence of market power. Following Helpman (1 984a), the paper explores restrictions on permissible trade patterns that are implied by the post-trade equilibrium conditions of Heckscher- Ohlin theory. Restrictions on the patterns of commodity trade are derived to complement Helpman's factor content version of the competitive Heckscher-Ohlin theory, and the introduction of factor market power is shown to leave the validity of these restrictions unaffected, Restrictions on the pattern of Heckscher-Ohlin trade in the presence of product market power are also derived, and conditions are stated under which Helpman's competitive factor content restrictions continue to hold.

A Theory of Gradual Trade Liberalization

This paper proposes a theory of gradual trade liberalization. I consider countries that are limited to self-enforcing arrangements in their trade relations. I argue that enforcement problems associated with the maintenance of low cooperative tariffs are exacerbated by the presence of resources in the import-competing sector that are (or potentially could be) earning rents from their sector-specific skills. Intuitively, by being able to transform into rents a portion of what otherwise would be dead weight loss under a tariff hike, the presence of such resources makes deviation from a low cooperative tariff to a high tariff more desirable for the deviating country, and makes punishments under reciprocally high tariffs less painful. Hence, the presence of rent-collecting resources in an import-competing sector acts as a deterrent to trade liberalization. But if an initial 'round' of liberalization can induce at least a portion of these resources in the import-competing sector to relocate to the rest of the economy, and if by not using their sector-specific skills these resources stand to lose them, then the enforcement issues associated with their presence will also diminish over time, and further rounds of liberalization are made possible by the effects of the initial round. I formalize this gradual process of trade liberalization, and explore the consequences of a failed round of liberalization for the ability to maintain current levels of cooperation.

Testing a Roy Model with Productivity Spillovers: Evidence from the Treatment of Heart Attacks

Productivity spillovers are often cited as a reason for geographic specialization in production. A large literature in medicine documents specialization across areas in the use of surgical treatments, which is unrelated to patient outcomes. We show that a simple Roy model of patient treatment choice with productivity spillovers can generate these facts. Our model predicts that high-use areas will have higher returns to surgery, better outcomes among patients most appropriate for surgery, and worse outcomes among patients least appropriate for surgery. We find strong empirical support for these and other predictions of the model, and decisively reject alternative explanations commonly proposed to explain geographic variation in medical care.

An economic theory of GATT

GATT;economic theory

Fiscal Shenanigans, Targeted Federal Health Care Funds, and Patient Mortality

The federal government spends billions of dollars each year on programs designed to increase the resources available to hospitals that serve the poor. This paper explores the intended and unintended effects of such targeted funds. First, how do these funds distort the behavior of state and local governments who wish to appropriate the funds for other uses? Second, to the extent that these funds do increase resources in the targeted hospitals, do patients benefit? We use the rapid and uneven growth in Medicaid Disproportionate Share Hospital (DSH) payments across states and hospitals to answer these questions. We identify states that were most able to appropriate DSH funds and show that, while DSH payments to public hospitals in these states were systematically diverted, DSH payments to other hospitals and in other states were not diverted. Additional resources that were made available to hospitals (rather than appropriated by the state) were associated with significant declines in infant and post-heart attack mortality. A range of evidence suggests that these improvements were due to better hospital care. Overall, our analysis implies that public subsidies can be an effective mechanism for improving medical care and outcomes for the poor, but that the impact is limited by the ability of state and local government to divert the targeted funds.