GEOS - An optical memory and control unit

GEOS optical memory and control unit for controlling operation of optical beacon - digital delayed command system with high accuracy real time cloc

Using {\sc top-c} for Commodity Parallel Computing in Cosmic Ray Physics Simulations

{\sc top-c} (Task Oriented Parallel C) is a freely available package for parallel computing. It is designed to be easy to learn and to have good tolerance for the high latencies that are common in commodity networks of computers. It has been successfully used in a wide range of examples, providing linear speedup with the number of computers. A brief overview of {\sc top-c} is provided, along with recent experience with cosmic ray physics simulations.Comment: Talk to be presented at the XI International Symposium on Very High Energy Cosmic Ray Interaction

The kinetic mechanism of bacterial ribosome recycling.

Bacterial ribosome recycling requires breakdown of the post-termination complex (PoTC), comprising a messenger RNA (mRNA) and an uncharged transfer RNA (tRNA) cognate to the terminal mRNA codon bound to the 70S ribosome. The translation factors, elongation factor G and ribosome recycling factor, are known to be required for recycling, but there is controversy concerning whether these factors act primarily to effect the release of mRNA and tRNA from the ribosome, with the splitting of the ribosome into subunits being somewhat dispensable, or whether their main function is to catalyze the splitting reaction, which necessarily precedes mRNA and tRNA release. Here, we utilize three assays directly measuring the rates of mRNA and tRNA release and of ribosome splitting in several model PoTCs. Our results largely reconcile these previously held views. We demonstrate that, in the absence of an upstream Shine-Dalgarno (SD) sequence, PoTC breakdown proceeds in the order: mRNA release followed by tRNA release and then by 70S splitting. By contrast, in the presence of an SD sequence all three processes proceed with identical apparent rates, with the splitting step likely being rate-determining. Our results are consistent with ribosome profiling results demonstrating the influence of upstream SD-like sequences on ribosome occupancy at or just before the mRNA stop codon

Stringent Nucleotide Recognition by the Ribosome at the Middle Codon Position.

Accurate translation of the genetic code depends on mRNA:tRNA codon:anticodon base pairing. Here we exploit an emissive, isosteric adenosine surrogate that allows direct measurement of the kinetics of codon:anticodon University of California base formation during protein synthesis. Our results suggest that codon:anticodon base pairing is subject to tighter constraints at the middle position than at the 5'- and 3'-positions, and further suggest a sequential mechanism of formation of the three base pairs in the codon:anticodon helix

The Determinants of Takeovers: Recent Evidence from U.S. Thrifts

This paper uses a two-step methodology to examine the relationship between managerial cost inefficiency and the takeover of U.S. thrifts during a period of market liberalization and widespread takeover activity, 1994 to 2000. In the first stage using stochastic cost frontiers, we estimate controllable managerial cost inefficiency scores for all stock firms operating each year in 1994 to 2000. In a second stage, we use these scores to examine correlates of takeovers, focusing on cost inefficiency. For takeovers by banks, we find a significant negative relationship between cost inefficiency and takeover, suggesting an exit of more cost efficient firms from the thrift industry during this period. However, takeovers by thrifts are associated with other characteristics

Rational polynomial representation of ribonucleotide reductase activity

BACKGROUND: Recent data suggest that ribonucleotide reductase (RNR) exists not only as a heterodimer R1(2)R2(2 )of R1(2 )and R2(2 )homodimers, but also as tetramers R1(4)R2(4 )and hexamers R1(6)R2(6). Recent data also suggest that ATP binds the R1 subunit at a previously undescribed hexamerization site, in addition to its binding to previously described dimerization and tetramerization sites. Thus, the current view is that R1 has four NDP substrate binding possibilities, four dimerization site binding possibilities (dATP, ATP, dGTP, or dTTP), two tetramerization site binding possibilities (dATP or ATP), and one hexamerization site binding possibility (ATP), in addition to possibilities of unbound site states. This large number of internal R1 states implies an even larger number of quaternary states. A mathematical model of RNR activity which explicitly represents the states of R1 currently exists, but it is complicated in several ways: (1) it includes up to six-fold nested sums; (2) it uses different mathematical structures under different substrate-modulator conditions; and (3) it requires root solutions of high order polynomials to determine R1 proportions in mono-, di-, tetra- and hexamer states and thus RNR activity as a function of modulator and total R1 concentrations. RESULTS: We present four (one for each NDP) rational polynomial models of RNR activity as a function of substrate and reaction rate modifier concentrations. The new models avoid the complications of the earlier model without compromising curve fits to recent data. CONCLUSION: Compared to the earlier model of recent data, the new rational polynomial models are simpler, adequately fitting, and likely better suited for biochemical network simulations

Managerial Stock Ownership As A Corporate Control Device: When Is Enough, Enough?

It has long been accepted that managerial stock ownership, beyond some range of possible entrenchment, can be an effective means of aligning the interests of professional managers with those of a firm’s outside owners to the benefit of firm performance. In this paper, we offer evidence on the effectiveness of managerial stock ownership as a corporate control device by analyzing the behavior of 81 thrift institutions operating over the six-year period, 1989-1994. Based on the estimation of stochastic cost and profit frontiers, as well as other performance measures, our results suggest that managerial stock ownership provides an effective corporate control device. However, this device is only effective as managerial holdings surpass about 33% of outstanding shares for improvements in cost efficiency and about 40% for profit efficiency

Natural history and ecology of larval Lost River suckers and larval shortnose suckers in the Williamson River-Upper Klamath Lake System

We monitored larval Lost River and shortnose suckers from natal beds in the Williamson and Sprague rivers to nursery grounds in Upper Klamath Lake. Downstream movements occurred at night, in the middle of the channel, and on the falling limb of the hydrograph. Ages, sizes, and developmental stages of larvae from spawning beds and the river mouth were similar, while larvae collected contemporaneously from the lake tended to be larger and better fed. Our results indicate in-river rearing was rare, that a rapid outmigration to the lake was favorable for larval survival, and that modification of the lower Williamson River does not appear to have prohibited rapid entry or preclude access to Upper Klamath Lake. Within the Williamson River and Upper Klamath Lake, emergent macrophytes supported significantly higher abundance, larger mean sizes, and better fed larvae than submerged macrophytes, woody vegetation, or open water areas. Analysis of seven years of larval sucker production and survival corroborated the habitat analysis by identifying a positive relationship with emergent macrophyte availability as well as a positive relationship with air temperature and a negative relationship with high wind. These findings illustrate the importance of fast growth, appropriate habitat and calm hydrological conditions for larvae, and are highly consistent with other larval fish studies

Simulation of Water Cerenkov Detectors Using {\sc geant4}

We present a detailed simulation of the performance of water Cerenkov detectors suitable for use in the Pierre Auger Observatory. Using {\sc geant4}, a flexible object-oriented simulation program, including all known physics processes, has been developed. The program also allows interactive visualization, and can easily be modified for any experimental setup.Comment: Talk to be presented at the XI Symposium on Very High Energy Cosmic Ray Interaction