23,521 research outputs found

    Gateway Modeling and Simulation Plan

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    This plan institutes direction across the Gateway Program and the Element Projects to ensure that Cross Program M&S are produced in a manner that (1) generate the artifacts required for NASA-STD-7009 compliance, (2) ensures interoperability of M&S exchanged and integrated across the program and, (3) drives integrated development efforts to provide cross-domain integrated simulation of the Gateway elements, space environment, and operational scenarios. This direction is flowed down via contractual enforcement to prime contractors and includes both the GMS requirements specified in this plan and the NASASTD- 7009 derived requirements necessary for compliance. Grounding principles for management of Gateway Models and Simulations (M&S) are derived from the Columbia Accident Investigation Board (CAIB) report and the Diaz team report, A Renewed Commitment to Excellence. As an outcome of these reports, and in response to Action 4 of the Diaz team report, the NASA Standard for Models and Simulations, NASA-STD-7009 was developed. The standard establishes M&S requirements for development and use activities to ensure proper capture and communication of M&S pedigree and credibility information to Gateway program decision makers. Through the course of the Gateway program life cycle M&S will be heavily relied upon to conduct analysis, test products, support operations activities, enable informed decision making and ultimately to certify the Gateway with an acceptable level of risk to crew and mission. To reduce risk associated with M&S influenced decisions, this plan applies the NASA-STD-7009 requirements to produce the artifacts that support credibility assessments and ensure the information is communicated to program management

    Degradation of Chloroaromatics: Purification and Characterization of a Novel Type of Chlorocatechol 2,3-Dioxygenase of Pseudomonas putida GJ31

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    A purification procedure for a new kind of extradiol dioxygenase, termed chlorocatechol 2,3-dioxygenase, that converts 3-chlorocatechol productively was developed. Structural and kinetic properties of the enzyme, which is part of the degradative pathway used for growth of Pseudomonas putida GJ31 with chlorobenzene, were investigated. The enzyme has a subunit molecular mass of 33.4 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Estimation of the native Mr value under nondenaturating conditions by gel filtration gave a molecular mass of 135 ± 10 kDa, indicating a homotetrameric enzyme structure (4 × 33.4 kDa). The pI of the enzyme was estimated to be 7.1 ± 0.1. The N-terminal amino acid sequence (43 residues) of the enzyme was determined and exhibits 70 to 42% identity with other extradiol dioxygenases. Fe(II) seems to be a cofactor of the enzyme, as it is for other catechol 2,3-dioxygenases. In contrast to other extradiol dioxygenases, the enzyme exhibited great sensitivity to temperatures above 40°C. The reactivity of this enzyme toward various substituted catechols, especially 3-chlorocatechol, was different from that observed for other catechol 2,3-dioxygenases. Stoichiometric displacement of chloride occurred from 3-chlorocatechol, leading to the production of 2-hydroxymuconate.

    Low-Speed Yawed-Rolling Characteristics of a Pair of 56-Inch-Diameter, 32-Ply-Rating, Type 7 Aircraft Tires

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    The low-speed (up to 4 miles per hour) yawed-rolling characteristics of two 56 x 16 32-ply-rating, type 7 aircraft tires under straight-yawed rolling were determined over a range of inflation pressures and yaw angles for a vertical load approximately equal to 75 percent of the rated vertical load. The quantities measured or determined included cornering force, drag force self-alining torque, pneumatic caster vertical tire deflection, yaw angle, and relaxation length. During straight-yawed rolling the normal force generally increased with increasing yaw angle within the test range. The self-alining torque increased to a maximum value and then decreased with increasing angle of yaw. The pneumatic caster tended to decrease with increasing yaw angle

    Modulus Stabilization with Bulk Fields

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    We propose a mechanism for stabilizing the size of the extra dimension in the Randall-Sundrum scenario. The potential for the modulus field that sets the size of the fifth dimension is generated by a bulk scalar with quartic interactions localized on the two 3-branes. The minimum of this potential yields a compactification scale that solves the hierarchy problem without fine tuning of parameters.Comment: 8 pages, LaTeX; minor typo correcte

    Dark Matter and Dark Energy via Non-Perturbative (Flavour) Vacua

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    A non-perturbative field theoretical approach to flavour physics (Blasone-Vitiello formalism) has been shown to imply a highly non-trivial vacuum state. In a previous work, we implemented the approach on a simple supersymmetric model (free Wess-Zumino), with flavour mixing, which was regarded as a model for free neutrinos and sneutrinos. The resulting effective vacuum (called "flavour vacuum") was found to be characterized by a strong SUSY breaking. In this paper we explore the phenomenology of the model and we argue that the flavour vacuum is a consistent source for both Dark Energy (thanks to the bosonic sector of the model) and Dark Matter (via the fermionic one). Quite remarkably, besides the parameters connected with neutrino physics, in this model no other parameters have been introduced, possibly leading to a predictive theory of Dark Energy/Matter. Despite its oversimplification, such a toy model already seems capable to shed some light on the observed energy hierarchy between neutrino physics, Dark Energy and Dark Matter. Furthermore, we move a step forth in the construction of a more realistic theory, by presenting a novel approach for calculating relevant quantities and hence extending some results to interactive theories, in a completely non-perturbative way.Comment: 14 pages, 2 figure
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