The Statistics of the BATSE Spectral Features

The absence of a BATSE line detection in a gamma-ray burst spectrum during the mission's first six years has led to a statistical analysis of the occurrence of lines in the BATSE burst database; this statistical analysis will still be relevant if lines are detected. We review our methodology, and present new simulations of line detectability as a function of the line parameters. We also discuss the calculation of the number of ``trials'' in the BATSE database, which is necessary for our line detection criteria.Comment: 5 pages, 2 figures, AIPPROC LaTeX, to appear in "Gamma-Ray Bursts, 4th Huntsville Symposium," eds. C. Meegan, R. Preece and T. Koshu

Parallel Genetic Algorithm to Solve the Satisfiability Problem

This Paper Offers a Parallel Genetic Algorithm Solution to the Satisfiability Problem. It Combines Components of the Davis-Putnam Method and Genetic Algorithms for the Solution. This Solution is Useful in the Areas of Theorem Proving, Constraint Satisfaction Programming, and VLSI Design. the Algorithm is Implemented and Run on a Paragon. the Results Show Performance Improvement by Increasing the Number of Nodes. Two Parallel Methods Are Compared: One that Implements Interprocessor Communication and One that Does Not. the Results Show Performance Improvement with the Method that Uses Interprocessor Communication

The BATSE Gamma-Ray Burst Spectral Catalog. I. High Time Resolution Spectroscopy of Bright Bursts using High Energy Resolution Data

This is the first in a series of gamma-ray burst spectroscopy catalogs from the Burst And Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory, each covering a different aspect of burst phenomenology. In this paper, we present time-sequences of spectral fit parameters for 156 bursts selected for either their high peak flux or fluence. All bursts have at least eight spectra in excess of 45 sigma above background and span burst durations from 1.66 to 278 s. Individual spectral accumulations are typically 128 ms long at the peak of the brightest events, but can be as short as 16 ms, depending on the type of data selected. We have used mostly high energy resolution data from the Large Area Detectors, covering an energy range of typically 28 - 1800 keV. The spectral model chosen is from a small empirically-determined set of functions, such as the well-known `GRB' function, that best fits the time-averaged burst spectra. Thus, there are generally three spectral shape parameters available for each of the 5500 total spectra: a low-energy power-law index, a characteristic break energy and possibly a high-energy power-law index. We present the distributions of the observed sets of these parameters and comment on their implications. The complete set of data that accompanies this paper is necessarily large, and thus is archived electronically at: http://www.journals.uchicago.edu/ApJ/journal/.Comment: Accepted for publication: ApJS, 125. 38 pages, 9 figures; supplementary electronic archive to be published by ApJ; available from lead author upon reques

The Contribution of Pre-Existing Depression to the Acute Cognitive Sequelae of Mild Traumatic Brain Injury

Frontotemporal abnormalities and cognitive dysfunction, especially in verbal memory and information processing speed, occur in both mild traumatic brain injury (mTBI) and depression. Study 1 investigated the effect of depression on cognitive performance in a sample at risk of sustaining mTBI.Seventy-eight male undergraduates completed the Depression Anxiety Stress Scales (DASS), Digit Symbol Substitution Test (DSS), Hopkins Verbal Learning Test (HVLT), and Speed of Comprehension Test. A oneway analysis of covariance (using the top 25% and bottom 25% of DASS Depression subscale scorers) showed that HVLT recognition was significantly worse in the high scorers. Study 2 examined the effects of injury type and pre-existing depression on cognitive performance in a prospective emergency department sample (within 24 hours of injury). Fifty-eight participants with mTBI (29 with depression, 29 without depression) and 47 control participants (18 with depression, 29 without depression) completed the DSS, HVLT, and Speed of Comprehension Test. Participants with mTBI performed worse than controls (uninjured and orthopaedic-injured participants) on all tests. Participants with depression did not perform worse than participants without depression on the tests. However, there was a significant univariate interaction for HVLT recognition, participants in the mTBI group with depression exhibited worse recognition compared to participants without depression. Since word recognition was impaired in participants who were more depressed in both samples, this suggests that it is a consistent finding. More importantly, the results of Study 2 indicate that depression may interact with mTBI to impair word recognition during the acute phase after head injury

The effect of traumatic brain injury on drivers’ hazard perception

Individuals recovering from traumatic brain injury (TBI) often experience perceptual, cognitive, and motor deficits that adversely affect their driving. However, many individuals with TBI return to driving, despite evidence that they are at increased risk. This study examined the effects of TBI on drivers’ hazard perception, i.e. the ability to search the road ahead and quickly identify potentially dangerous traffic situations. Slower hazard perception has been associated with higher crash rates (e.g. Quimby et al., 1986), but hazard perception has never been assessed after TBI. A convenience sample of adults recovering from mild, moderate and severe TBI was recruited from the rehabilitation unit of a tertiary level hospital. Uninjured controls were recruited from the community. Participants completed a hazard perception test, in which they viewed videos of genuine traffic scenes filmed from the driver’s perspective and indicated as soon as they detected a potential traffic hazard (mean response latency was the main dependent measure). Participants also completed a simple spatial reaction time task, a digit symbol substitution task and several measures related to pre- and post-injury functioning. Preliminary results indicate that individuals with TBI were significantly slower to detect traffic hazards than controls. The findings may signify the need for hazard perception testing or training post-TBI before return to driving