Very Early Optical Afterglows of Gamma-Ray Bursts: Evidence for Relative Paucity of Detection

Very early observations with the Swift satellite of γ-ray burst (GRB) afterglows reveal that the optical component is not detected in a large number of cases. This is in contrast to the bright optical flashes previously discovered in some GRBs (e.g., GRB 990123 and GRB 021211). Comparisons of the X-ray afterglow flux to the optical afterglow flux and prompt γ-ray fluence is used to quantify the seemingly deficient optical, and in some cases X-ray, light at these early epochs. This comparison reveals that some of these bursts appear to have higher than normal γ-ray efficiencies. We discuss possible mechanisms and their feasibility for explaining the apparent lack of early optical emission. The mechanisms considered include, foreground extinction, circumburst absorption, Lyα blanketing and absorption due to high-redshift, low-density environments, rapid temporal decay, and intrinsic weakness of the reverse shock. Of these, foreground extinction, circumburst absorption, and high redshift provide the best explanations for most of the nondetections in our sample. There is tentative evidence of suppression of the strong reverse shock emission. This could be because of a Poynting flux-dominated flow or a pure nonrelativistic hydrodynamic reverse shock

Lessons from Fiascos in Russian Corporate Governance

"Bad corporate governance" is often invoked to explain poor enterprise performance, but the catch phrase is never precisely defined - neither its consequences for the real economy, nor its causes in particular countries has been adequately explained. This paper uses Russian enterprise examples to address these open questions in corporate governance theory. We define corporate governance by looking to the economic functions of the firm rather than to any particular set of national corporate laws. Firms exhibit good corporate governance when their managers maximize residuals and, in the case of investor-owned firms, make pro rata distributions to shareholders. First, using this definition, we develop a typology that shows the channels through which bad corporate governance can inflict damage on the real economy. The topology helps identify vulnerabilities to corporate governance problems that may appear in any country and it suggests a new way to tailor policy responses. Second, we explain the causes of poor corporate performance in Russia by looking to the particular conditions prevailing at privatization - untenable initial firm boundaries and insider allocation of firm shares - and the bargaining dynamics that followed. The focus on initial conditions helps expand a comparative corporate governance literature built on United States, Western European, and Japanese models. Lessons from Russian fiascos counsel caution as to "stakeholder" proposals - including labor or local communities in formal corporate governance - and generate testable hypotheses regarding potential losses from the multiple large block share ownerships typical of many U.S. firms, especially close corporations.

Maternal Characteristics and Child Problem Behaviors: A Comparison of Foster and Biological Mothers

The purpose of this exploratory study was to compare the parenting behavior, stress and support of foster mothers and biological mothers of young children. A sample of 60 mothers of young children (30 foster mothers, 30 biological mothers) completed measures of parenting behavior, parenting stress, child problem behaviors, and perceived social support. Findings indicated that biological mothers were single and younger than foster mothers. In addition, biological mothers utilized more verbal and corporal discipline than foster mothers, experienced greater parental distress and received less social support for their parenting. Implications of these findings are discussed

Is the Health Care System Working for Adolescents? Perspectives From Providers in Boston, Denver, Houston, and San Francisco

Assesses healthcare system services for adolescents in four urban areas. Includes provider perspectives on how health insurance, managed care, and other factors facilitate or impede access. Discusses innovative programs, and offers recommendations

Spatio-Temporal Low Count Processes with Application to Violent Crime Events

There is significant interest in being able to predict where crimes will happen, for example to aid in the efficient tasking of police and other protective measures. We aim to model both the temporal and spatial dependencies often exhibited by violent crimes in order to make such predictions. The temporal variation of crimes typically follows patterns familiar in time series analysis, but the spatial patterns are irregular and do not vary smoothly across the area. Instead we find that spatially disjoint regions exhibit correlated crime patterns. It is this indeterminate inter-region correlation structure along with the low-count, discrete nature of counts of serious crimes that motivates our proposed forecasting tool. In particular, we propose to model the crime counts in each region using an integer-valued first order autoregressive process. We take a Bayesian nonparametric approach to flexibly discover a clustering of these region-specific time series. We then describe how to account for covariates within this framework. Both approaches adjust for seasonality. We demonstrate our approach through an analysis of weekly reported violent crimes in Washington, D.C. between 2001-2008. Our forecasts outperform standard methods while additionally providing useful tools such as prediction intervals

Reformulation in planning

Reformulation of a problem is intended to make the problem more amenable to efficient solution. This is equally true in the special case of reformulating a planning problem. This paper considers various ways in which reformulation can be exploited in planning

EXPERIMENTAL METHODS IN CONSUMER PREFERENCE STUDIES

Controlled experimental auctions can be used to elicit preferences for food products. We describe results from two series of experiments in which subjects revealed their willingness-to-pay for safer food. In one series, the risk reduction technology was not specified; in the other, it was identified as food irradiation. The results provide some evidence on the acceptability of food irradiation as a risk reduction technology.Consumer/Household Economics,