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

On the incomputability of computable dimension

Using an iterative tree construction we show that for simple computable subsets of the Cantor space Hausdorff, constructive and computable dimensions might be incomputable

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.

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.

The simple economics of labor standards and the Gatt

labour standardsGATT