Interview with William R. Klaus

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Quantifying the benefits of entry into local phone service

Local telecommunications competition was an important goal of the 1996 Telecommunications Act. We evaluate the consumer welfare effects of entry into residential local telephone service in New York State using household-level data from September 1999 to March 2003. We address the prevalence of nonlinear tariffs by developing a discrete/continuous demand model that allows for service bundling and unobservable provider quality. We find that the average subscriber to the entrants' services gains a monthly equivalent of $2.33, or 6.2% of her bill, in welfare from competition. These gains accrue primarily from firm differentiation and new plan introductions rather than from price effects

Quantifying the benefits of entry into local phone service

Local telecommunications competition was an important goal of the 1996 Telecommunications Act. We evaluate the consumer welfare effects of entry into residential local telephone service in New York State using household-level data from September 1999 to March 2003. We address the prevalence of nonlinear tariffs by developing a discrete/continuous demand model that allows for service bundling and unobservable provider quality. We find that the average subscriber to the entrants’ services gains a monthly equivalent of $2.33, or 6.2% of her bill, in welfare from competition. These gains accrue primarily from firm differentiation and new plan introductions rather than from price effects

Inversion of Airborne Contaminants in a Regional Model

We are interested in a DDDAS problem of localization of airborne contaminant releases in regional atmospheric transport models from sparse observations. Given measurements of the contaminant over an observation window at a small number of points in space, and a velocity field as predicted for example by a mesoscopic weather model, we seek an estimate of the state of the contaminant at the beginning of the observation interval that minimizes the least squares misfit between measured and predicted contaminant field, subject to the convection-diffusion equation for the contaminant. Once the ''initial'' conditions are estimated by solution of the inverse problem, we issue predictions of the evolution of the contaminant, the observation window is advanced in time, and the process repeated to issue a new prediction, in the style of 4D-Var. We design an appropriate numerical strategy that exploits the spectral structure of the inverse operator, and leads to efficient and accurate resolution of the inverse problem. Numerical experiments verify that high resolution inversion can be carried out rapidly for a well-resolved terrain model of the greater Los Angeles area

On the influence of the cosmological constant on gravitational lensing in small systems

The cosmological constant Lambda affects gravitational lensing phenomena. The contribution of Lambda to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study in the weak deflection limit of the equations of motion in the Schwarzschild-de Sitter metric. Due to Lambda the unresolved images are slightly demagnified, the radius of the Einstein ring decreases and the time delay increases. The effect is however negligible for near lenses. In the case of null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation, references added, results unchanged, in press on PR

Formulaic Language in Native and Second Language Speakers: Psycholinguistics, Corpus Linguistics, and TESOL

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89473/1/j.1545-7249.2008.tb00137.x.pd