A Search for Gamma-Ray Burst Optical Emission with the Automated Patrol Telescope

The Automated Patrol Telescope (APT) is a wide-field (5 X 5 deg.s), modified Schmidt capable of covering large gamma-ray burst (GRB) localization regions to produce a high rate of GRB optical emission measurements. Accounting for factors such as bad weather and incomplete overlap of our field and large GRB localization regions, we estimate our search will image the actual location of 20-41 BATSE GRB sources each year. Long exposures will be made for these images, repeated for several nights, to detect delayed optical transients (OTs) with light curves similar to those already discovered. The APT can also respond within about 20 sec. to GRB alerts from BATSE to search for prompt emission from GRBs. We expect to image more than 2.4 GRBs/yr. during gamma-ray emission. More than 5.1 will be imaged/yr. within about 20 sec. of emission. The APT's 50 cm aperture is much larger than other currently operating experiments used to search for prompt emission, and the APT is the only GRB dedicated telescope in the Southern Hemisphere. Given the current rate of about 25% OTs per X/gamma localization, we expect to produce a sample of about 10 OTs for detailed follow-up observations in 1-2 years of operation.Comment: 4 pages latex + 3 ps figures. Download a single tar file of ps at http://panisse.lbl.gov/public/bruce/optgrbsearch.tar.g

The Calculus of M-estimation in R with geex

M-estimation, or estimating equation, methods are widely applicable for point estimation and asymptotic inference. In this paper, we present an R package that can find roots and compute the empirical sandwich variance estimator for any set of user-specified, unbiased estimating equations. Examples from the M-estimation primer by Stefanski and Boos (2002) demonstrate use of the software. The package also includes a framework for finite sample variance corrections and a website with an extensive collection of tutorials

A mathematical model of the tetrapyrrole biosynthesis pathway

The tetrapyrrole biosynthesis pathway is a key part in chlorophyll production and is essential for plant survival. It involves numerous interacting compounds and, crucially, light. The understanding of the complex regulation processes involved has been the focus of extensive experimental research providing a large source of data. A particular set of data, concerned with the modelling described in this report, involves 24 hour timecourse data from seedlings exposed to constant light, following a three day period of growth from seed in darkness. This data includes the levels of key components such as chlorophyll, ATP, chlorophyllide and proto-chlorophyllide. Amongst the questions posed in the study-group were: i) Can the timecourse data be predicted by a model? ii) Can it predict the dierences in levels of various components in found mutant strains. To address these questions, we present in this report a model consisting of a coupled system of nonlinear ODEs that describes a simplied version of the tetrapyrrole pathway based on mass action laws. Model simulations produced results that agree qualitatively well with most, but not all, of the available timecourse data obtained from wild-type and mutant strains. Nearly all of the model's parameters are not known, so the values used in these simulations are based on estimates of the relative timescales of the reactions. An attempt at improving these estimates using data tting techniques is also discussed

Food habits and growth of young-of-year striped bass in Cherokee Reservoir, Tennessee

Of 109,675 striped bass young-of-year stocked at Quarryville in June 1979, only 70 were recaptured; none of the 80,480 stocked in June 1980 were recovered. Of a similar number of hybrids (80,000) stocked in June 1980, 206 were collected for food habits and growth analyses. Chironomidae and Crustacea were the primary food items of striped and hybrid bass introduced into the reservoir. Striped bass switched from invertebrates to fish (primarily Clupeidae) at 20 cm or approximately one year after stocking. Hybrids over 5.1 cm consumed small fish shortly after they were stocked and continued as they grew larger. Food habits of white bass were also examined and compared to striped and hybrid bass. All three species were often observed feeding at the interface between the substrate and the water column. Preferred sub-strates ranged from a sand-clay mixture to a muddy-soft mixture. Striped bass stocked at an average length of 3.5 cm grew approximately 21.7 cm in one year. Hybrids attained a similar length, 21.5 cm, after only 7 months\u27 growth. Condition factors (K) were similar for both striped and hybrid bass (0.8 to 1.3) during their first year of growth

Mirage Torsion

Z_NxZ_M orbifold models admit the introduction of a discrete torsion phase. We find that models with discrete torsion have an alternative description in terms of torsionless models. More specifically, discrete torsion can be 'gauged away' by changing the shifts by lattice vectors. Similarly, a large class of the so-called generalized discrete torsion phases can be traded for changing the background fields (Wilson lines) by lattice vectors. We further observe that certain models with generalized discrete torsion are equivalent to torsionless models with the same gauge embedding but based on different compactification lattices. We also present a method of classifying heterotic Z_NxZ_M orbifolds.Comment: 26 pages, 3 figures, v2: matches version published in JHE

A note on discrete R symmetries in Z6-II orbifolds with Wilson lines

We re-derive the R symmetries for the Z6-II orbifold with non-trivial Wilson lines and find expressions for the R charges which differ from those in the literature.Comment: 13 pages, 3 figure