This paper summarizes recent empirical research on compliance costs and strategies and on permit market performance under the U.S. acid rain program, the first large-scale, long-term program to use tradeable emissions permits to control pollution. An efficient market for emissions permits developed in a few years, and this program more than achieved its early goals on time, and it cost less than had been projected. Because of expectation errors, however, investment was excessive, and permit prices substantially understate abatement costs. The tradeable permits approach has worked well, but it is not a miracle cure for environmental problems. Coauthors are Paul L. Joskow, A. Denny Ellerman, Juan Pablo Montero, and Elizabeth M. Bailey.

Clathrin-mediated endocytosis (CME) internalizes plasma membrane by reshaping small regions of the cell surface into spherical vesicles. The key mechanistic question of how coat assembly produces membrane curvature has been studied with molecular and cellular structural biology approaches, without direct visualization of the process in living cells; resulting in two competing models for membrane bending. Here we use polarized total internal reflection fluorescence microscopy (pol-TIRF) combined with electron, atomic force, and super-resolution optical microscopy to measure membrane curvature during CME. Surprisingly, coat assembly accommodates membrane bending concurrent with or after the assembly of the clathrin lattice. Once curvature began, CME proceeded to scission with robust timing. Four color pol-TIRF showed that CALM accumulated at high levels during membrane bending, implicating its auxiliary role in curvature generation. We conclude that clathrin-coat assembly is versatile and that multiple membrane-bending trajectories likely reflect the energetics of coat assembly relative to competing forces.

Title IV of the Clean Air Act Amendments of 1990 created a market for electric utility emissions of sulfur dioxide (SOZ), Recent papers have argued that flaws in the design of the auctions that are part of this market have adversely affected its performance. These papers incorrectly assume that trade can only occur at auctions, however. Our empirical analysis of the S02 emissions market shows that the auctions have become a small part of a relatively efficient market and that the auction design problems that have attracted the most attention have had no effect on actual market prices.

Measurements of O3, NO, NO2, peroxyacetyl nitrate (PAN), HNO3, and NOy were made during a 6‐week period in the summer of 1991 in Giles County, Tennessee. These data were analyzed to determine the factors controlling the relationship between O3 and NOy at this rural site. A strong association was observed between the O3 and NOx oxidation product (NOz = NOy ‐ NOx) levels. The higher O3 levels were associated with air masses impacted by higher NOx emissions that had been photochemically processed. An analysis of the data indicates that the ultimate O3 production is about 10 molecules of O3 produced for each molecule of NOx emitted. The analysis results also suggest that O3 net production continues until about 70% of the NOx has been converted into NOz. The PAN/HNO3 ratios observed suggest that the air masses in Giles County are composed of higher volatile organic carbon/NOx ratios than the air masses observed at other rural sites in eastern North America. A comparison of the data analysis results to model simulations and smog chamber experiments suggests that most of the time, Giles County is in an NOx‐limited regime for O3 production.