Regression modeling of longitudinal binary outcomes with outcome-dependent observation times

Conventional longitudinal data analysis methods assume that outcomes are independent of the data-collection schedule. However, the independence assumption may be violated, for example, when adverse events trigger additional physician visits in between prescheduled follow-ups. Observation times may therefore be associated with outcome values, which may introduce bias when estimating the eect of covariates on outcomes using standard longitudinal regression methods. Existing semi-parametric methods that accommodate outcome-dependent observation times are limited to the analysis of continuous outcomes. We develop new methods for the analysis of binary outcomes, while retaining the exibility of semi-parametric models. Our methods are based on counting process approaches, rather than relying on possibly intractable likelihood-based or pseudo-likelihood-based approaches, and provide marginal, population-level inference. In simulations, we evaluate the statistical properties of our proposed methods. Comparisons are made to \u27naive\u27 GEE approaches that either do not account for outcome-dependent observation times or incorporate weights based on the observation-time process. We illustrate the utility of our proposed methods using data from a randomized controlled trial of interventions designed to improve adherence to warfarin therapy. We show that our method performs well in the presence of outcome-dependent observation times, and provide identical inference to \u27naive\u27 approaches when observation times are not associated with outcomes

Innovative Test Operations to Support Orion and Future Human Rated Missions

This paper describes how the Orion program is implementing new and innovative test approaches and strategies in an evolving development environment. The early flight test spacecraft are evolving in design maturity and complexity requiring significant changes in the ground test operations for each mission. The testing approach for EM-2 is planned to validate innovative Orion production acceptance testing methods to support human exploration missions in the future. Manufacturing and testing at Kennedy Space Center in the Neil Armstrong Operations and Checkout facility will provide a seamless transition directly to the launch site avoiding transportation and checkout of the spacecraft from other locations

Bubbles from Nothing

Within the framework of flux compactifications, we construct an instanton describing the quantum creation of an open universe from nothing. The solution has many features in common with the smooth 6d bubble of nothing solutions discussed recently, where the spacetime is described by a 4d compactification of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional description of this instanton reduces to that of Hawking and Turok. The choice of parameters uniquely determines all future evolution, which we additionally find to be stable against bubble of nothing instabilities.Comment: 19 pages, 6 figure

Economists on Deregulation of the American Legal Profession: Praise and Critique

Both law professors and economists are discussing deregulation of the American legal profession, often without consulting each other. This symposium essay reviews the book length deregulation argument entitled First Thing We Do, Let’s Deregulate All the Lawyers. The essay argues that Let’s Deregulate is a tremendous addition to the literature: it disregards laws various professional shibboleths and offers a crisp and persuasive argument that the current barriers to entry are very, very costly to law students, clients, and society at large. Let’s Deregulate estimates the 2004 lawyers’ earning premium at $64 billion. The estimation is high, but well supported. Even if the absolute figure is rejected, the finding that barriers to entry have raised lawyer salaries is patent and inescapable. There are two notable weaknesses to Let’s Deregulate, however. First, while the supply side argument (entry barriers result in fewer lawyers, reduced competition, and higher prices) is outstanding, the demand side argument is much less persuasive. Let’s Deregulate asserts that a raft of recent laws and regulations (including various environmental, class action, consumer protection and intellectual property laws) are inefficient and more costly than beneficial. This claim is difficult enough to prove empirically, but Let’s Deregulate piles on by claiming that the legal profession has been a prime mover in the creation of these laws. These two claims add an unnecessary degree of controversy and difficulty to an already unlikely mission. Critics of deregulation can thus characterize the entire effort as a politically motivated assault on disliked law, rather than an even-handed attempt to quantify the costs and benefits of lawyer regulation. Second, and more understandably, Let’s Deregulate misses some of the unique nuances of the market for lawyers. For instance, it suggests that state legislatures control lawyer regulation, and state supreme courts actually do. This is a critical distinction for any reform effort. The analysis also treats the market for lawyers as a monolith, and there is much evidence that there are two private markets for legal services: big law firms who compete internationally for large scale corporate work and everybody else – small firms and solo practitioners working for smaller businesses and individuals. Despite the critiques, the essay concludes that Let’s Deregulate is a tremendous addition to the literature and encourages more lawyer/economist cross-pollination on the topic

Writing in Britain and Ireland, c. 400 to c. 800

No abstract available

All-Sky LIGO Search for Periodic Gravitational Waves in the Early Fifth-Science-Run Data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100Hz and with the frequency\u27s time derivative in the range -5x10-9-0Hzs-1. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10-24 are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10-6, the search is sensitive to distances as great as 500pc