Design of the Annular Suspension and Pointing System (ASPS) (including design addendum)

The Annular Suspension and Pointing System is an experiment pointing mount designed for extremely precise 3 axis orientation of shuttle experiments. It utilizes actively controlled magnetic bearing to provide noncontacting vernier pointing and translational isolation of the experiment. The design of the system is presented and analyzed

Unravelling a fulvene based Replicator: Experiment and Theory in Interplay

A self-replicating system based on a cycloaddition of a fulvene derivative and a maleinimide is investigated using a two-pronged approach combining NMR spectroscopy with computer simulations. In the course of the reaction, two diastereomers are formed with identical rates in the absence of replication. When replication is enabled, a network emerges in which one diastereomer takes over the resources as a "selfish" autocatalyst while exploiting the competitor as a weak "altruist". The structure and dynamics of the reaction network is studied using 1 D and 2 D NMR techniques supported by dynamically averaged ab initio chemical shifts and ab initio molecular dynamics simulations. It is shown that this combination is a powerful means to understand the observed experimental behaviour in great detail

Direct, on-the-fly calculation of unresolved resonance region cross sections in Monte Carlo simulations

The theory, implementation, and testing of a method for on-the-fly unresolved resonance region cross section calculations in continuous-energy Monte Carlo neutron transport codes are presented. With this method, each time that a cross section value is needed within the simulation, a realization of unresolved resonance parameters is generated about the desired energy and temperature-dependent single-level Breit-Wigner resonance cross sections are computed directly via use of the analytical ψ − χ Doppler integrals. Results indicate that, in room-temperature simulations of a system that is known to be highly sensitive to the effects of resonance structure in unresolved region cross sections, the on-the-fly treatment produces results that are in excellent agreement with those produced with the well-established probability table method. Additionally, similar agreement is observed between results obtained from the on-the-fly and probability table methods for another intermediate spectrum system at temperatures of 293.6 K and 2500 K. With relatively tight statistical uncertainties at the ∼ 10 pcm level, all on-the-fly and probability table keff eigenvalues agree to within 2σ. Also, we use the on-the-fly approach to show that accounting for the resonance structure of competitive reaction cross sections can have non-negligible effects for intermediate/fast spectrum systems. Biases of up to 90 pcm are observed. Finally, the consequences of the on-the-fly method with respect to simulation runtime and memory requirements are briefly discussed.United States. Department of Energy (Consortium for Advanced Simulation of Light Water Reactors. Contract DE-AC05-00OR22725

Surface acoustic waves in finite slabs of three-dimensional phononic crystals

We study theoretically, by means of layer-multiple-scattering techniques, the propagation of elastic waves through finite slabs of phononic crystals consisting of metallic spheres in a polyester matrix, embedded in air. In particular, we focus on the study of modes localized on the surfaces of the structure. Their origin and behavior, as well as the physical parameters that influence and determine their appearance, are investigated in detail. Our results reveal the existence of absolute phononic frequency gaps in these finite structures, and point out the possibility, under an appropriate choice of the parameters, of tunable regions of frequency free of propagating and/or surface-localized modes. © 2008 The American Physical Society.Peer Reviewe

Road and street smart lighting control systems as a new application area of the hot-potato protocol

This paper presents the new application area of the hot-potato routing protocol, which is a “last-mile” communication network for controlling systems of road and street lighting. Four variants of the hot-potato protocol are analyzed with use of the graph theory. For the assessment of the traffic parameters the ETX parameter is used in relation to the length of the shortest path. Proposed methods are independent of the media type and can be implemented either in wireless or PLC

Selfishness versus functional cooperation in a stochastic protocell model

How to design an "evolvable" artificial system capable to increase in complexity? Although Darwin's theory of evolution by natural selection obviously offers a firm foundation, little hope of success seems to be expected from the explanatory adequacy of modern evolutionary theory, which does a good job at explaining what has already happened but remains practically helpless at predicting what will occur. However, the study of the major transitions in evolution clearly suggests that increases in complexity have occurred on those occasions when the conflicting interests between competing individuals were partly subjugated. This immediately raises the issue about "levels of selection" in evolutionary biology, and the idea that multi-level selection scenarios are required for complexity to emerge. After analyzing the dynamical behaviour of competing replicators within compartments, we show here that a proliferation of differentiated catalysts and/or improvement of catalytic efficiency of ribozymes can potentially evolve in properly designed artificial cells. Experimental evolution in these systems will likely stand as beautiful examples of artificial adaptive systems, and will provide new insights to understand possible evolutionary paths to the evolution of metabolic complexity