Deuterium fractionation on interstellar grains studied with the direct master equation approach     

Tatiana Stantcheva  Eric Herbst 《Monthly notices of the Royal Astronomical Society》2003,340(3):983-988

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Small hypervelocity particles captured in aerogel collectors: Location,extraction, handling and storage     

Andrew J. Westphal  Christopher Snead  Janet Borg  Eric Quirico  Pierre‐Ivan Raynal  Michael E. Zolensky  Gianluca Ferrini  Luigi Colangeli  Pasquale Palumbo 《Meteoritics & planetary science》2002,37(6):855-865

Abstract— It has now been about a decade since the first demonstrations that hypervelocity particles could be captured, partially intact, in aerogel collectors. But the initial promise of a bonanza of partially‐intact extraterrestrial particles, collected in space, has yet to materialize. One of the difficulties that investigators have encountered is that the location, extraction, handling and analysis of very small (10 μm and less) grains, which constitute the vast majority of the captured particles, is challenging and burdensome. Furthermore, current extraction techniques tend to be destructive over large areas of the collectors. Here we describe our efforts to alleviate some of these difficulties. We have learned how to rapidly and efficiently locate captured particles in aerogel collectors, using an automated microscopic scanning system originally developed for experimental nuclear astrophysics. We have learned how to precisely excavate small access tunnels and trenches using an automated micromanipulator and glass microneedles as tools. These excavations are only destructive to the collector in a very small area—this feature may be particularly important for excavations in the precious Stardust collectors. Using actuatable silicon microtweezers, we have learned how to extract and store “naked” particles—essentially free of aerogel—as small as 3 μm in size. We have also developed a technique for extracting particles, along with their terminal tracks, still embedded in small cubical aerogel blocks. We have developed a novel method for storing very small particles in etched nuclear tracks. We have applied these techniques to the extraction and storage of grains captured in aerogel collectors (Particle Impact Experiment, Orbital Debris Collector Experiment, Comet‐99) in low Earth orbit.  相似文献   

Ground-based GPS imaging of ionospheric post-seismic signal     

Philippe Lognonné  Juliette Artru  François Crespon  Eric Jeansou  Jérôme Helbert  Pierre-Emmanuel Godet 《Planetary and Space Science》2006,54(5):528-540

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A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar   总被引：1，自引：0，他引：1  

Eric Emsellem  Paul Goudfrooij  Pierre Ferruit 《Monthly notices of the Royal Astronomical Society》2003,345(4):1297-1312

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Fracture sealing of quartzite under a temperature gradient: experimental results     

Christoph Hilgers  Eric Tenthorey 《地学学报》2004,16(4):173-178

Veined lithologies are formed by fracturing and sealing processes, with the veins representing former fluid conduits through the rock. Although detailed fieldwork and numerical simulations have provided a better understanding of vein growth, few studies have attempted to seal fractures and generate veins experimentally. In this pilot study, we subjected fractured quartzite to temperature gradients of 45–125 °C under hydrothermal conditions in a static fluid, with the aim of precipitating secondary quartz in the cooler portions of the fracture. Results show that secondary quartz precipitates due to the imposed temperature gradient, causing the initial fracture to seal locally. Although no systematic sealing pattern was observed along the fracture, samples subjected to higher temperatures exhibit a smaller fracture width and appear to have reacted more extensively. Electron microprobe mapping visualizes the spatial distribution of secondary quartz, which contains elevated concentrations of aluminium.  相似文献   

QUEST on DASI: a South Pole CMB polarization experiment     

Sarah Church  Peter Ade  James Bock  Melanie Bowden  John Carlstrom  Ken Ganga  Walter Gear  James Hinderks  Wayne Hu  Brian Keating  John Kovac  Andrew Lange  Eric Leitch  Olivier Mallie  Simon Melhuish  Anthony Murphy  Ben Rusholme  Creidhe O&#x;Sullivan  Lucio Piccirillo  Clem Pryke  Andy Taylor  Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083

QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓ_max2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005.  相似文献   

The importance of new rate coefficients for deuterium fractionation reactions in interstellar chemistry     

Helen Roberts  Eric Herbst  T. J. Millar 《Monthly notices of the Royal Astronomical Society》2002,336(1):283-290

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Stellar masses and star formation histories for 10⁵ galaxies from the Sloan Digital Sky Survey     

Guinevere Kauffmann  Timothy M. Heckman  Simon D. M. White  Stéphane Charlot  Christy Tremonti  Jarle Brinchmann  Gustavo Bruzual  Eric W. Peng  Mark Seibert  Mariangela Bernardi  Michael Blanton  Jon Brinkmann  Francisco Castander  Istvan Csábai  Masataka Fukugita  Zeljko Ivezic  Jeffrey A. Munn  Robert C. Nichol  Nikhil Padmanabhan  Aniruddha R. Thakar  David H. Weinberg  Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53

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Proton Irradiation of Centaur,Kuiper Belt,and Oort Cloud Objects at Plasma to Cosmic Ray Energy     

Cooper  John F.  Christian  Eric R.  Richardson  John D.  Wang  Chi 《Earth, Moon, and Planets》2003,92(1-4):261-277

Times for accumulation of chemically significant dosages on icy surfaces of Centaur, Kuiper Belt, and Oort Cloud objects from plasma and energetic ions depend on irradiation position within or outside the heliosphere. Principal irradiation components include solar wind plasma ions, pickup ions from solar UV ionization of interstellar neutral gas, energetic ions accelerated by solar and interplanetary shocks, including the putative solar wind termination shock, and galactic cosmic ray ions from the Local Interstellar Medium (LISM). We present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and in the LISM. Times in years to accumulate dosages ～100 eV per molecule are computed from the spectra as functions of sensible surface depth less than one centimeter at unit density.The collisional resurfacing model of Luu and Jewitt is reconsidered in thecontext of depth-dependent dosage rates from plasma, suprathermal,and higher energy protons, and global exposure, by micrometeoroiddust grain impacts, of moderately irradiated red material below athin crust of heavily irradiated neutral material. This material should be more visible on dynamically `cold’ objects in the ～40 AU region.  相似文献   

Assessment of sandstone deterioration at Ta Keo temple (Angkor): first results and future prospects     

Marie-Françoise André  Samuel Etienne  Denis Mercier  Franck Vautier  Olivier Voldoire 《Environmental Geology》2008,56(3-4):677-688

A first application of geomorphological methods to the assessment of sandstone deterioration at Angkor is presented. Damage diagnosis was carried out on the first eastern tier of the central pyramid of the 1,000 year-old Ta Keo temple. Methods combine field observations and measurements at 230 sampling points, high-resolution lasergrammetry and stereophotogrammetry on a 2-m² test zone, and SEM observations. The first results indicate that decay operates through a synergistic combination of weathering phenomena dominated by scaling and solution, and exhibits a high spatial variability. Percentages of deteriorated surfaces vary from 17.6 to 93.8%, and average stone recession values from 0.00 to 2.71 cm (minimum) and 0.34 to 5.49 cm (maximum). On the test-zone, stereophotogrammetry and 3D-mapping of the present and reconstructed initial states using lasergrammetry indicate that erosion scars up to 6 cm deep have formed since 1963. On the whole, the amount of deteriorated surfaces more than tripled between 1963 and 2008. The degree of implication of salts in stone decay remains unclear for most efflorescences are composed of calcite (CaCO3), with secondary importance of barite (BaSO4) and gypsum (CaSO₄·2H₂O). Future prospects aim to evaluate the impact on stone decay of the clearing out of the temple from the forest in the 1920s.  相似文献