458 research outputs found

    Reconstructing the Inflaton Potential

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    A review is presented of recent work by the authors concerning the use of large scale structure and microwave background anisotropy data to determine the potential of the inflaton field. The importance of a detection of the stochastic gravitational wave background is emphasised, and some preliminary new results of tests of the method on simulated data sets with uncertainties are described. (Proceedings of ``Unified Symmetry in the Small and in the Large'', Coral Gables, 1994)Comment: 13 pages, uuencoded postscript file with figures included (LaTeX file available from ARL), FERMILAB-Conf 94/189

    Carbon-Enhanced Cement Clinker

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    A clinker for use in cement manufacturing includes a cement clinker mixture having crystals of an element that is less electronegative than carbon and carbon bonded to at least a portion of the crystals

    A Survey of Southern Illinois Aquatic Vascular Plants

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    Author Institution: Southern Illinois University, Carbondal

    From treebank resources to LFG F-structures

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    We present two methods for automatically annotating treebank resources with functional structures. Both methods define systematic patterns of correspondence between partial PS configurations and functional structures. These are applied to PS rules extracted from treebanks, or directly to constraint set encodings of treebank PS trees

    Neurogenin2 Expression in Ventral and Dorsal Spinal Neural Tube Progenitor Cells Is Regulated by Distinct Enhancers

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    AbstractThe basic helix-loop-helix transcription factor Neurogenin2 (NGN2) is expressed in distinct populations of neural progenitor cells within the developing central and peripheral nervous systems. Transgenic mice containing ngn2/lacZ reporter constructs were used to study the regulation of ngn2 in the developing spinal cord. ngn2/lacZ transgenic embryos containing sequence found 5′ or 3′ to the ngn2 coding region express lacZ in domains that reflect the spatial and temporal expression profile of endogenous ngn2. A 4.4-kb fragment 5′ of ngn2 was sufficient to drive lacZ expression in the ventral neural tube, whereas a 1.0-kb fragment located 3′ of ngn2 directed expression to both dorsal and ventral domains. Persistent β-gal activity revealed that the NGN2 progenitor cells in the dorsal domain give rise to a subset of interneurons that send their axons to the floor plate, and the NGN2 progenitors in the ventral domain give rise to a subset of motor neurons. We identified a discrete element that is required for the activity of the ngn2 enhancer specifically in the ventral neural tube. Thus, separable regulatory elements that direct ngn2 expression to distinct neural progenitor populations have been defined

    Hydrodynamic Detonation Instability in Electroweak and QCD Phase Transitions

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    The hydrodynamic stability of deflagration and detonation bubbles for a first order electroweak and QCD phase transition has been discussed recently with the suggestion that detonations are stable. We examine here the case of a detonation more carefully. We find that in front of the bubble wall perturbations do not grow with time, but behind the wall modes exist which grow exponentially. We briefly discuss the possible meaning of this instability.Comment: 12 pages, 3 figures available on request, Latex, FERMILAB--PUB--93/098--

    Series-Bosch Technology for Oxygen Recovery During Lunar or Martian Surface Missions

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    Longduration surface missions to the Moon or Mars will require life support systems that maximize resource recovery to minimize resupply from Earth. To address this need, NASA previously proposed a SeriesBosch (SBosch) oxygen recovery system, based on the Bosch process, which can theoretically recover 100% of the oxygen from metabolic carbon dioxide. Bosch processes have the added benefits of the potential to recover oxygen from atmospheric carbon dioxide and the use of regolith materials as catalysts, thereby eliminating the need for catalyst resupply from Earth. In 2012, NASA completed an initial design for an SBosch development test stand that incorporates two catalytic reactors in series including a Reverse WaterGas Shift (RWGS) Reactor and a Carbon Formation Reactor (CFR). In 2013, fabrication of system components, with the exception of a CFR, and assembly of the test stand was initiated. Standalone testing of the RWGS reactor was completed to compare performance with design models. Continued testing of Lunar and Martian regolith simulants provided sufficient data to design a CFR intended to utilize these materials as catalysts. Finally, a study was conducted to explore the possibility of producing bricks from spend regolith catalysts. The results of initial demonstration testing of the RWGS reactor, results of continued catalyst performance testing of regolith simulants, and results of brick material properties testing are reported. Additionally, design considerations for a regolithbased CFR are discussed
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