Fiberoptically Multiplexed Medium Resolution Spectroscopy from the WIYN Telescope,Singlet D Neutral Oxygen,NH2, and H2O+     

Anderson  Christopher M. 《Earth, Moon, and Planets》1997,78(1-3):99-104

The WIYN 3.5-meter telescope and its Multi-Object Spectrograph (MOS) have been used to obtain simultaneous spectra at many points in the coma of Comet Hale-Bopp. Between 1996 October and 1997 April in excess of 7500 individual spectra were obtained, typically 96 at a time. On six nights the “Hydra” fiber positioner was used to sample a ring pattern of points about the nucleus with a minimum spacing of 40 arc seconds and a maximum radius of 22.5 arc minutes. On four nights a new “Densepak” fiber cable was used. In this configuration a 7 × 13 rectangular pattern of 91, 3 arc second fibers on 4 arc second centers was used. In most cases the bench spectrograph was used in the echelle mode with an interference filter to isolate a single order. The wavelength range from 6100 Å to 6400 Å was recorded with resolution of approximately 15,000. This spectral region contains the emission features of [OI], C₂, NH₂and H₂O⁺. From this mass of data we are beginning to extract the radial, azimuthal and temporal variations of many different spectral features. The radial profiles of [O I] λ6300 Å and NH₂ are reasonably well representable by the Haser model formalism, that of H₂O⁺ is not.  相似文献   

Natural Attenuation Reactions at a Uranium Mill Tailings Site, Western U.S.A.     

Chen Zhu  Greg M. Anderson  David S. Burden 《Ground water》2002,40(1):5-13

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Hydrate phase equilibria in porous media: effect of pore size and salinity     

Kasper K. Østergaard  Ross Anderson  Maria Llamedo  Bahman Tohidi 《地学学报》2002,14(5):307-312

ABSTRACT Considering the ever-increasing importance of marine gas hydrates, it is crucial to gain a better understanding of clathrate formation and decomposition in porous media. It is well established that, due to capillary effects, small-diameter pores – similar to those found in natural sediments – act to inhibit hydrate stability. However, accurate data constraining these effects are still lacking. Here, we present experimental methane clathrate dissociation data for 3.5 mass% methanol aqueous solutions in confined silica glass pores of narrow distribution (30.6, 15.8, and 9.2 nm mean diameters). These data have been used to validate a thermodynamic model for clathrate stability porous media. Experimental data show a marked improvement on literature data – which we attribute to the experimental and interpretative methods used – and are in good agreement with the model predictions. Results suggest that mass transfer of inhibitors (methanol) and dissolved gas during clathrate formation/dissociation within the porous network plays an important role in controlling gas hydrate equilibria.  相似文献   

Subglacial, phonolitic volcanism at Hoodoo Mountain volcano, northern Canadian Cordillera     

B. Edwards  J. Russell  R. Anderson 《Bulletin of Volcanology》2002,64(3-4):254-272

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Current awareness     

M. G. Anderson 《水文研究》2002,16(9):1879-1881

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Wide Field Imaging and the Velocity Structure in the Coma of Hale–Bopp     

Harris  Walter M.  Morgenthaler  Jeffrey P.  Scherb  Frank  Anderson  Christopher  Oliversen  Ronald J. 《Earth, Moon, and Planets》2002,90(1-4):45-56

The comae of very active comets have a substantiallymore complex coma than their weaker cousins.The primary cause of this is photolytic heating and collisionsthat occur over an ever-larger volume of the coma asQ_{H 2O} increases. Collisionswith the photochemical daughters ofwater in this regionmodify the radial distributions and outflowvelocity of each species, excite and quench metastableemissions, and introduce velocity gradients from photolyticheating. Comet Hale–Bopp was the first comet forwhich the collisional coma was both spatially resolvableand comparable in extent to the scale lengths ofmajor coma species. In the case of this object,the classical assumptions that make it possible toinvert radial emission line profiles, brightnesses, andlineshapes to production rate and velocity eitherdo not hold or require adjustment to work.Here we describe how a large collision zone modifies thecoma, how it affects the classical methods for obtainingproduction rate and velocity, and discuss how wide fieldimaging may be combined with modified versions ofsimple models to address the complications and extract somestructural information.  相似文献   

Water within,moving through,and shaping the Earth's surface: Introducing a special issue on water in the critical zone     

Ying Fan  Gordon Grant  Suzanne P. Anderson 《水文研究》2019,33(25):3146-3151

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Chronic and episodic acidification of streams along the Appalachian Trail corridor,eastern United States     

Douglas A. Burns  Todd C. McDonnell  Karen C. Rice  Gregory B. Lawrence  Timothy J. Sullivan 《水文研究》2020,34(7):1498-1513

Acidic atmospheric deposition has adversely affected aquatic ecosystems globally. As emissions and deposition of sulfur (S) and nitrogen (N) have declined in recent decades across North America and Europe, ecosystem recovery is evident in many surface waters. However, persistent chronic and episodic acidification remain important concerns in vulnerable regions. We evaluated acidification in 269 headwater streams during 2010–2012 along the Appalachian Trail (AT) that transits several ecoregions and is located downwind of high levels of S and N emission sources. Discharge was estimated by matching sampled streams to those of a nearby gaged stream and assuming equivalent daily mean flow percentiles. Charge balance acid-neutralizing capacity (ANC) values were adjusted to the 15th (Q15) and 85th flow percentiles (Q85) by applying the ANC/discharge slope among sample pairs collected at each stream. A site-based approach was applied to streams sampled twice or more and a second regression-based approach to streams sampled once to estimate episodic acidification magnitudes as the ANC difference from Q15 to Q85. Streams with ANC <0 μeq/L doubled from 16% to 32% as discharge increased from Q15 to Q85 according to the site-based approach. The proportion of streams with ANC <0 μeq/L at low flow and high flow decreased from north to south. Base cation dilution explained the greatest amount of episodic acidification among streams and variation in sulfate (SO₄²⁻) concentrations was a secondary explanatory variable. Episodic SO₄²⁻ patterns varied geographically with dilution dominant in northern streams underlain by soils developed in glacial sediment and increased concentrations dominant in southern streams with older, highly weathered soils. Episodic acidification increased as low-flow ANC increased, exceeding 90 μeq/L in 25% of streams. Episodic increases in ANC were the dominant pattern in streams with low-flow ANC values <30 μeq/L. Chronic and episodic acidification remain an ecological concern among AT streams. The approach developed here could be applied to estimate the magnitude and extent of chronic and episodic acidification in other regions recovering from decreasing levels of atmospheric S and N deposition.  相似文献   

EMERGING SOUTHEAST ASIA. A STUDY IN GROWTH AND STAGNATION. By Donald W. Fryer.     

A. G. Anderson 《New Zealand geographer》1971,27(2):216-218

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Direct-Drive Inertial Confinement Fusion Implosions on Omega     

S. P. Regan  T. C. Sangster  D. D. Meyerhofer  K. Anderson  R. Betti  T. R. Boehly  T. J. B. Collins  R. S. Craxton  J. A. Delettrez  R. Epstein  O. V. Gotchev  V. Yu. Glebov  V. N. Goncharov  D. R. Harding  P. A. Jaanimagi  J. P. Knauer  S. J. Loucks  L. D. Lund  J. A. Marozas  F. J. Marshall  R. L. Mccrory  P. W. Mckenty  S. F. B. Morse  P. B. Radha  W. Seka  S. Skupsky  H. Sawada  V. A. Smalyuk  J. M. Soures  C. Stoeckl  B. Yaakobi  J. A. Frenje  C. K. Li  R. D. Petrasso  F. H. SÉguin 《Astrophysics and Space Science》2005,298(1-2):227-233

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