The process of infection with bacteriophage phiX174, XXX. Replication of double-stranded phiX DNA

Intermediates involved in the replication of double-stranded phiX174 RF DNA have been identified and partially characterized. Analysis of pulse-labeled RF DNA suggests that the synthesis of progeny RF molecules involves, in part, the addition of nucleotides to linear complementary strands on a circular parental strand as template, so as to produce intermediate DNA strands of greater than viral length. Electron microscopy reveals DNA rings with "tails" and "double rings," which could be the intermediate structures. A model is postulated for the replication process

Evaluating Labour Adjustment Costs from Trade Shocks: Illustrations for the U.S. Economy Using an Applied General Equilibrium Model With Transactions

This paper presents a general equilibrium approach to calculating labour adjustment costs induced by trade policy changes or external sector shocks, which we illustrate by analyzing the adjustment consequences of eliminating quotas and tariffs on U.S. imports. In our approach, factor adjustments in the presence of transactions costs are endogenously determined within the equilibrium structure. The conventional way of calculating such labour adjustment costs is to use full equilibrium models which exclude adjustment costs, and apply exogenous estimates of duration of unemployment to implied intersectoral labour reallocations. By using an equilibrium model in which adjustment costs are absent, the conventional approach tends to overstate the amount of labour that moves to other sectors and hence introduces an upward bias to estimates of adjustment costs. As well, such an approach tends to ignore the impact on intersectoral wage rates. Our results suggest that concerns over adjustment problems should focus as much on the consequences of adjustment costs in impeding factor mobility, as on the magnitude of the adjustment costs themselves. Compared to the redistributive effects they induce by inhibiting labour movement in response to policy or other changes, these costs may be small.

The Welfare Cost of Distortions in the United States Tax System: A General Equilibrium Approach

Using a general equilibrium model of the United States economy,we examine the combined welfare cost of all taxes in the U.S. revenue system.We find that the welfare losses caused by distortionary taxation can be very large, both on average and at the margin.The marginal welfare loss to consumers from raising an additional dollar of revenue is in the range of 34 cents to 48 cents, depending on certain elasticities. This has very important implications for cost-benefit analysis.If a public project must be financed by distortionary taxes which cause dead-weight loss, this excess burden must be taken into account when we decide whether to undertake the project. Our calculations indicate that the marginal deadweight loss is between one-third and one-half of marginal revenues. This large wedge could cause us to approve many fewer projects than we would approve if we were to use the simple condition that the sum of the marginal rates of substitution should equal the marginal rate of transformation.The average deadweight loss per dollar of revenue is smaller than the marginal deadweight loss, but it is still substantial. We estimate that the present value of the gain from replacing the distortionary tax system with certain lump sum taxes would be in the range of $1.8 trillion to$3.1 trillion,or 13 cents to 22 cents per dollar of revenue. The gains would be about 60 percent as great if the existing system were replaced with a proportional income tax. Replacing the existing system with a consumption-type value-added tax would give even greater gains than those from switching to a proportional income tax.

An Investigation of the Use of Bandwidth Criteria for Rotorcraft Handling-Qualities Specifications

The objective of this study was to investigate bandwidth concepts for deriving rotorcraft handling-qualities criteria from data obtained in two simulator experiments conducted at the Aeromechanics Laboratory. The first experiment was an investigation of the effects of helicopter vertical-thrust-response characteristics on handling qualities; the second experiment investigated the effects of helicopter yaw-control-response characteristics. In both experiments, emphasis was on low-speed Nap-of-the-Earth (NOE) tasks