Determination of S17(0) from published data

The experimental landscape for the 7Be+p radiative capture reaction is rapidly changing as new high precision data become available. We present an evaluation of existing data, detailing the treatment of systematic errors and discrepancies, and show how they constrain the astrophysical S factor (S17), independent of any nuclear structure model. With theoretical models robustly determining the behavior of the sub-threshold pole, the extrapolation error can be reduced and a constraint placed on the slope of S17. Using only radiative capture data, we find S17(0) = 20.7 +/- 0.6 (stat) +/- 1.0 (syst) eV b if data sets are completely independent, while if data sets are completely correlated we find S17(0) = 21.4 +/- 0.5 (stat) +/- 1.4 (syst) eV b. The truth likely lies somewhere in between these two limits. Although we employ a formalism capable of treating discrepant data, we note that the central value of the S factor is dominated by the recent high precision data of Junghans et al., which imply a substantially higher value than other radiative capture and indirect measurements. Therefore we conclude that further progress will require new high precision data with a detailed error budget.Comment: 10 pages, 1 figure published versio

Efficient computation of the Shapley value for game-theoretic network centrality

The Shapley value—probably the most important normative payoff division scheme in coalitional games—has recently been advocated as a useful measure of centrality in networks. However, although this approach has a variety of real-world applications (including social and organisational networks, biological networks and communication networks), its computational properties have not been widely studied. To date, the only practicable approach to compute Shapley value-based centrality has been via Monte Carlo simulations which are computationally expensive and not guaranteed to give an exact answer. Against this background, this paper presents the first study of the computational aspects of the Shapley value for network centralities. Specifically, we develop exact analytical formulae for Shapley value-based centrality in both weighted and unweighted networks and develop efficient (polynomial time) and exact algorithms based on them. We empirically evaluate these algorithms on two real-life examples (an infrastructure network representing the topology of the Western States Power Grid and a collaboration network from the field of astrophysics) and demonstrate that they deliver significant speedups over the Monte Carlo approach. Fo

Implementing a Business Process Management System Using ADEPT: A Real-World Case Study

This article describes how the agent-based design of ADEPT (advanced decision environment for processed tasks) and implementation philosophy was used to prototype a business process management system for a real-world application. The application illustrated is based on the British Telecom (BT) business process of providing a quote to a customer for installing a network to deliver a specified type of telecommunication service. Particular emphasis is placed upon the techniques developed for specifying services, allowing heterogeneous information models to interoperate, allowing rich and flexible interagent negotiation to occur, and on the issues related to interfacing agent-based systems and humans. This article builds upon the companion article (Applied Artificial Intelligence Vol.14, no 2, pgs. 145-189) that provides details of the rationale and design of the ADEPT technology deployed in this application

Multiple-Scattering Series For Color Transparency

Color transparency CT depends on the formation of a wavepacket of small spatial extent. It is useful to interpret experimental searches for CT with a multiple scattering scattering series based on wavepacket-nucleon scattering instead of the standard one using nucleon-nucleon scattering. We develop several new techniques which are valid for differing ranges of energy. These techniques are applied to verify some early approximations; study new forms of the wave-packet-nucleon interaction; examine effects of treating wave packets of non-zero size; and predict the production of $N^*$'s in electron scattering experiments.Comment: 26 pages, U.Wa. preprint 40427-23-N9

Cooperating Agents for 3D Scientific Data Interpretation

Many organizations collect vast quantities of three-dimensional (3-D) scientific data in volumetric form for a range of purposes, including resource exploration, market forecasting, and process modelling. Traditionally, these data have been interpreted by human experts with only minimal software assistance. However, such manual interpretation is a painstakingly slow and tedious process. Moreover, since interpretation involves subjective judgements and each interpreter has different scientific knowledge and experience, formulation of an effective interpretation often requires the cooperation of numerous such experts. Hence, there is a pressing need for a software system in which individual interpretations can be generated automatically and then refined through the use of cooperative reasoning and information sharing. To this end, a prototype system, SurfaceMapper, has been developed in which a community of cooperating software agents automatically locate and display interpretations in a volume of 3-D scientific data. The challenges and experiences in designing and building such a system are discussed. Particular emphasis is given to the agents' interactions and an empirical evaluation of the effectiveness of different cooperation strategies is presented

Sum Rule Description of Color Transparency

The assumption that a small point-like configuration does not interact with nucleons leads to a new set of sum rules that are interpreted as models of the baryon-nucleon interaction. These models are rendered semi-realistic by requiring consistency with data for cross section fluctuations in proton-proton diffractive collisions.Comment: 22 pages + 3 postscript figures attache

PREDICTION OF AN OPTIMUM TECHNIQUE FOR THE WOMEN’S YURCHENKO LAYOUT VAULT

The purpose of this study was to identify an optimum technique for the women’s Yurchenko layout vault through an application of optimal control theory on a five-segment model consisting of the hand, whole arm, upper trunk, lower trunk and whole leg. An optimum technique for the vault was determined which, compared to the data, had greater post-flight amplitude and a better layout posture throughout post-flight. However, it involved a larger angular velocity of the segments and greater shoulder extension by about 9º, than the data. The impact phase of the optimum technique was shorter than the data by 0.003 s, and served to increase both the angular momentum of the model as well as the vertical horse takeoff velocity. There is thus, evidence of a ‘blocking technique’ during impact

Effect of repetitive brief episodes of ischemia on cell volume, electrolytes and ultrastructure

The effects of repeated brief episodes of ischemia on myocardial cell volume, electrolytes and ultrastructure were studied in dogs. Seventeen animals were divided into five groups. Group 1 underwent a single 10 minute occlusion of the circumflex coronary artery, with no subsequent reperfusion. Group 2 was similarly subjected to a 10 minute coronary occlusion, but was allowed a 20 minute reperfusion period. Group 3 underwent two 10 minute occlusions separated by 20 minutes of reperfusion and Group 4 underwent four 10 minute occlusions, each separated from the next by 20 minutes of reperfusion. Group 5 was subjected to a single, uninterrupted 40 minute occlusion.The anterior and posterior papillary muscles in each heart were sampled to compare nonischemic versus ischemic myocardium. No changes in myocardial water or electrolytes occurred during ischemia. However, reperfusion was associated with slight increases in tissue water and potassium, loss of magnesium and minimal changes in sodium or calcium ions. Electron microscopic analysis revealed signs of mild ischemic injury (absence of normal intramitochondrial granules, partial loss of glycogen and slight clumping of the nuclear chromatin) in posterior papillary muscle from Groups 1, 3 and 4. Group 2 showed complete recovery with 20 minutes of reperfusion, whereas Group 5 showed evidence of irreversible injury. There was no difference in the appearance of myocardium that had been subjected to one, two or four 10 minute occlusions. It is concluded that intermittent periods of reperfusion between brief episodes of coronary ischemia have a protective effect and prevent a cumulative deterioration of myocardial ultrastructure

Nucleon-nucleus optical potential in the particle-hole approach

Feshbach's projection formalism in the particle-hole model space leads to a microscopic description of scattering in terms of the many-body self-energy. To investigate the feasibility of this approach, an optical potential for O-16 is constructed starting from two previous calculations of the self-energy for this nucleus. The results reproduce the background phase shifts for positive parity waves and the resonances beyond the mean field. The latter can be computed microscopically for energies of astrophysical interest using Green's function theory.Comment: 8 pages, 6 figures. Submitted to Phys. Rev.