Mid-infrared imaging of WL 16: the spatial distribution of the hydrocarbon emission features     

Moore  Emerson  Skinner  Meixner  Arens  & Jernigan 《Monthly notices of the Royal Astronomical Society》1998,299(4):1209-1214

We present arcsec-resolution images at 8.2, 10.0 and 11.3 μm of the unusual young object WL 16 in Ophiuchus, which has an extended envelope of fluorescing hydrocarbon molecules. To the limit of achieved sensitivity, the faint 10.0-μm continuum has a surface-brightness distribution that is not distinguishable from those at 8.2 and 11.3 μm, where the luminosity is known to be dominated by the polycyclic aromatic hydrocarbon (PAH) emission features. We conclude that the 10-μm continuum either arises from non-equilibrium heating of small dust grains that are well mixed with the hydrocarbons or is quasi-continuous emission from the PAH particles themselves, rather than thermal equilibrium emission from macroscopic dust grains, and that there is no significant silicate absorption variation across the source. The extended hydrocarbon emission may trace a flattened, equatorial distribution of circumstellar material or arise in bipolar lobes. The former case is slightly favoured, based on currently available data, and would imply that WL 16 is a relatively evolved Herbig Ae star, the equatorial plane of which has been almost cleared of normal dust, leaving only fluorescing hydrocarbons and larger coagulated particles as a possibly transient fossil of the original circumstellar disc.  相似文献   

Impact of wildfire on source water contributions in Devil Creek,CA: evidence from end‐member mixing analysis     

Helen Y. Jung  Terri S. Hogue  Laura K. Rademacher  Tom Meixner 《水文研究》2009,23(2):183-200

A geochemical and end‐member mixing analysis (EMMA) is undertaken in Devil Canyon catchment, located in southern California, to further understanding of watershed behaviour and source water contributions after an acute and extensive wildfire. Physical and chemical transformations in post‐fire watersheds are known to increase overland flow and decrease infiltration, mainly due to formation of a hydrophobic layer at, or near, the soil surface. However, less is known about subsurface flow response in burned watersheds. The current study incorporates EMMA to evaluate and quantify source water contributions before, and after, a catchment affected by wildfires in southern California during the fall of 2003. Pre‐ and post‐fire stream water data were available at several sampling sites within the catchment, allowing the identification of contributing water sources at varying spatial scales. Proposed end‐member observations (groundwater, overland flow, shallow subsurface flow) were also collected to constrain and develop the catchment mixing model. Post‐fire source water changes are more evident in the smaller and faster responding sub‐basin (interior sampling point). Early post‐fire storm events are dominated by overland flow with no significant soil water or groundwater flow contribution. Inter‐storm streamwater in this smaller basin shows an increase in groundwater and a decrease in soil water. In the larger, baseflow‐dominated system, source water components appear less affected by fire. A slight increase in lateral flow is observed with only a slight decrease in baseflow. Changes in the post‐fire flow regimes affect nutrient loading and chemical response of the basin. Relatively rapid recovery of the chaparral ecosystem is evidenced, with active re‐growth and evapotranspiration evidenced by the fourth post‐fire rainy season. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Temporal and spatial variability of cation and silica export in an alpine watershed,Emerald Lake,California     

T. Meixner  J. R. Shaw  R. C. Bales 《水文研究》2004,18(10):1759-1776

A reaction set of possible mineral weathering reactions is proposed to explain observed cation and silica export for the Emerald Lake watershed, a small Sierra Nevada, California catchment. The reaction set was calculated through a stoichiometric mole‐balance method, using a multiyear record of stream flow and snowpack chemical analyses and site‐specific mineral compositions. Reaction‐set calculations were intended to explore how the processes controlling stream cation and silica export depend on differing bedrock mineralogy across the catchment as snowmelt and runoff patterns change over the year. Different regions within the watershed can be differentiated by lake inflow subdrainages, each exhibiting different stream‐flow chemistry and calculated weathering stoichiometry, indicating that different silica and cation generation processes are dominant in wet steep portions of the catchment. Short‐term differences in stream concentrations were assumed to reflect ion exchange equilibria and rapid biological processes, whereas long‐term persistent stream concentration differences in different areas of the catchment were assumed to reflect spatial variability in mineral weathering stoichiometry. Mineralogical analyses of rock samples from the watershed provided site‐specific chemical compositions of major mineral species for reaction calculations. Reaction sets were evaluated by linear regression of calculated versus observed differences between snowmelt and stream‐flow chemistry and by a combined measure. Initially, single weathering reactions were balanced and evaluated to determine the reactions that best explained observed stream chemical export. Next, reactions were combined, using mineral compositions from different rock types to estimate the dependence of ion fluxes on lithology. The seasonal variability of major solute calculated fluxes is low, approximately one order of magnitude, relative to the observed three orders of magnitude variability in basin discharge. Reaction sets using basin‐averaged lithology and Aplite lithologies gave superior explanations of stream chemical composition. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Ein neues Euklasvorkommen in den Ostalpen     

Heinz Meixner 《Mineralogy and Petrology》1957,6(3):246-251

Ohne ZusammenfassungMit 2 Textabbildungen  相似文献   

Pumpellyit (Lotrit) von der Lieserschlucht bei Spittal a. d. Drau,Kärnten     

E. Flügel-Kahler  H. Meixner 《Mineralogy and Petrology》1963,8(3):449-453

Zusammenfassung Ein lange unbestimmtes, nadeliges Mineral aus der bekannteu, mineralreichen Kalksilikatparagenese von der Lieserschlucht (Lit. 4) wurde optisch und röntgenographisch alsPumpellyit (Lotrit) identifiziert.  相似文献   

Pumpellyit in Miarolen des Granits vom Königskopf bei Braunlage im Harz,Deutschland     

Prof. Dr. Heinz Meixner 《Mineralogy and Petrology》1965,10(1-4):341-348

Zusammenfassung Abweichend zu den bisher bekannten Pumpellyitparagenesen in vorwiegend basischen Gesteinen, wird hier das etwas überraschende Auftreten von Pumpellyit in Granitmiarolen des harzes beschrieben. Pumpellyit schiebt sich in der Sukzession und danach wohl auch im Bildungsverlauf zwischen Epidot und Zeolithen ein. Das Mineral, oft übersehen oder nicht richtig erkannt, ist ebenso in granitischen Miarolen anderer Gebiete zu erwarten, wie auch seine Erkennung als Schwermineral erst in den Anfängen steckt.

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Summary In contrast to hitherto known parageneses of pumpellyite in predominantly basic rocks, the somewhat surprising occurrence of pumpellyite in miaroles of granite of the Harz mountains is here reported. Pumpellyite enters in the succession between epidote and zeolite. This mineral, often overlooked or not correctly recognized, can also be expected to occur in miaroles of granites in other areas. It is only beginning to be recognized as a heavy mineral.

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Herrn Professor Dr.F. Machatschki zum 70. Geburtsag gewidmet.  相似文献   

The global gas and dust budget of the Large Magellanic Cloud: AGB stars and supernovae, and the impact on the ISM evolution     

M. Matsuura  M. J. Barlow  A. A. Zijlstra  P. A. Whitelock  M.-R. L. Cioni  M. A. T. Groenewegen  K. Volk  F. Kemper  T. Kodama  E. Lagadec  M. Meixner  G. C. Sloan  S. Srinivasan 《Monthly notices of the Royal Astronomical Society》2009,396(2):918-934

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Isotopic evidence (Sr/Sr, δLi) for alteration of the oceanic crust at deep-rooted mud volcanoes in the Gulf of Cadiz, NE Atlantic Ocean     

Florian Scholz  Christian Hensen  Anja Reitz  Rolf L. Romer  Volker Liebetrau  Anette Meixner  Stephan M. Weise  Matthias Haeckel 《Geochimica et cosmochimica acta》2009,73(18):5444-5459

The chemical and isotopic composition of pore fluids is presented for five deep-rooted mud volcanoes aligned on a transect across the Gulf of Cadiz continental margin at water depths between 350 and 3860 m. Generally decreasing interstitial Li concentrations and ⁸⁷Sr/⁸⁶Sr ratios with increasing distance from shore are attributed to systematically changing fluid sources across the continental margin. Although highest Li concentrations at the near-shore mud volcanoes coincide with high salinities derived from dissolution of halite and late-stage evaporites, clayey, terrigenous sediments are identified as the ultimate Li source to all pore fluids investigated. Light δ⁷Li values, partly close to those of hydrothermal vent fluids (δ⁷Li: +11.9‰), indicate that Li has been mobilized during high-temperature fluid/sediment or fluid/rock interactions in the deep sub-surface. Intense leaching of terrigenous clay has led to radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.7106) in pore fluids of the near-shore mud volcanoes. In contrast, non-radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.7075) at the distal locations are attributed to admixing of a basement-derived fluid component, carrying an isotopic signature from interaction with the basaltic crust. This inference is substantiated by temperature constraints from Li isotope equilibrium calculations suggesting exchange processes at particularly high temperatures (>200 °C) for the least radiogenic pore fluids of the most distal location.Advective pore fluids in the off-shore reaches of the Gulf of Cadiz are influenced by successive exchange processes with both oceanic crust and terrigenous, fine-grained sediments, resulting in a chemical and isotopic signature similar to that of fluids in near-shore ridge flank hydrothermal systems. This suggests that deep-rooted mud volcanoes in the Gulf of Cadiz represent a fluid pathway intermediate between mid-ocean ridge hydrothermal vent and shallow, marginal cold seep. Due to the thicker sediment coverage and slower fluid advection rates, the overall geochemical signature is shifted towards the sediment-diagenetic signal compared to ridge flank hydrothermal environments.  相似文献   

Influences of topographic index distribution on hydrologically sensitive areas in agricultural watershed     

Lianqing Xue  Ruiling Bao  Thomas Meixner  Guang Yang  Jingnan Zhang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(8):2235-2242

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An Analytical Footprint Model For Non-Neutral Stratification   总被引：9，自引：6，他引：9  

Robert Kormann  Franz X. Meixner 《Boundary-Layer Meteorology》2001,99(2):207-224

We propose an analytical model for the so-called footprint of scalar fluxes in the atmospheric boundary layer. It is the generalization of formulations already given in the literature, which allows to account for thermal stability. Our model is only marginally more complicated than these, and it is therefore simple enough to be applicable for a routine footprint analysis within long-term measurements. The mathematical framework of our model is a stationary gradient diffusion formulation with height-independent crosswind dispersion. It uses the solution of the resulting two-dimensional advection – diffusion equation for power law profiles of the mean wind velocity and the eddy diffusivity. To find the adjoint Monin–Obukhov similarity profile, we propose two different approaches, a purely analytical one and a simplenumerical error minimalization.  相似文献