X-ray resonance scattering in a spherically symmetric coronal model     

Bernhard M. Haisch  E. Scott Claflin 《Solar physics》1985,99(1-2):101-109

In the solar corona the opacities of some of the prominent X-ray emission lines are on the order of 1 over typical coronal path lengths. We present and discuss a particular solution of the radiative transfer problem involving an extended, spherically symmetric coronal shell radiating isotropic, homogeneous emission in which single-scattering also takes place. Within the context of this simplified model we find that scattered radiation is an important contribution to the total emergent resonance line flux and that for the He-like family of resonance (r), intercombination (i), and forbidden (f) lines, the ratio G=(f + i)/r would decrease as a function of optical depth for disk-center emission in an extended spherically symmetric corona.  相似文献   

Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction   总被引：1，自引：0，他引：1  

Van Stempvoort D  Maathuis H  Jaworski E  Mayer B  Rich K 《Ground water》2005,43(2):187-199

When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature ( approximately 5 degrees C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34S and 18O. Sulfate concentrations had a strong positive correlation with delta13C values of bicarbonate, and sulfide was depleted in 34S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13C. Modeling indicates that the main source of this excess 13C-depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada.  相似文献   

A Late Pleistocene lacustrine transgression in the Fehmarn Belt,southwestern Baltic Sea     

Bernhard?NovakEmail author  Svante?Bj?rck 《International Journal of Earth Sciences》2004,93(4):634-644

In order to reconstruct the late Pleistocene seismic stratigraphy, 550 km of high-density 3.5 kHz sub-bottom seismic-reflection profiles were recorded within a 70 km² area in the narrow offshore border zone between Germany and Denmark. A depositional unit 3 was analysed for its seismic facies association, and in the central study area mound, oblique, channel, reflection-free, shingled, hummocky, broken and parallel associations occurred. The rims of the association shows mound, oblique, hummocky and minor parallel seismic facies. Stratigraphic control was available from 32 coring sites. In the central study area, unit 3 represents rhythmic layers of silt with fine sand and clay in an overall fining-upward 3 to 5-m-thick sequence. At the rim of the basin, the unit comprises fine sand, silt and rhythmic layers of silt with clay and fine sand. Unit 3 is proposed as having formed during the transgression of a lake, partly in contact with the Baltic Ice Lake, some time between 10.8–10.0 ¹⁴C ka BP. After 10.0 ¹⁴C ka BP the water body stagnated when contact with the Baltic Basin was cut off. Analysis of base level of the subunits implies tectonic activity resulting in subsidence of the central study area which could possibly have influenced the transgressive development.  相似文献   

Surficial Hydrocarbon Seep Infauna from the Blake Ridge (Atlantic Ocean, 2150 m) and the Gulf of Mexico (690–2240 m)     

Christie A. Robinson  Joan M. Bernhard  Lisa A. Levin  Guillermo F. Mendoza  & Jessica K. Blanks 《Marine Ecology》2004,25(4):313-336

Abstract.  Infauna, including foraminifera and metazoans, were enumerated and identified from five types of seep habitats and two adjacent non-seep habitats. Collections were made with the deep submergence research vessel 'Alvin' from three areas of active seepage in the Gulf of Mexico (Alaminos Canyon [2220 m], Atwater Canyon [1930 m], and Green Canyon lease block 272 [700 m]) and on the Blake Ridge Diapir [2250 m], which is located off the southeastern coast of the United States. The seep habitats sampled included four types of microbial mats ( Beggiatoa , Thioploca , thin and thick Arcobacter ) and the periphery of a large mussel bed. Sediments under large rhizopod protists, xenophyophores, were sampled adjacent to the mussel bed periphery. A non-seep site, which was >1 km away from active seeps, was also sampled for comparison. Densities of most taxa were higher in the Gulf of Mexico seeps than in Blake Ridge samples, largely because densities in the thick microbial mats of Blake Ridge were significantly lower. Diversity was higher in the Thioploca mats compared to other microbial-mat types. Within an ocean basin ( i.e. , Atlantic, Gulf of Mexico) we did not observe significant differences in meiofaunal or macrofaunal composition in Beggiatoa versus Thioploca mats or thin versus thick Arcobacter mats. Foraminifera represented up to 16% of the seep community, a proportion that is comparable to their contribution at adjacent non-seep communities. In general, the observed densities and taxonomic composition of seep sites at the genus level was consistent with previous observations from seeps ( e.g. , the foraminifers Bolivina and Fursenkoina , the dorvilleid polychaete Ophryotrocha ).  相似文献   

Nesseltalgraben,a new reference section of the last glacial period in southern Germany     

Christoph Mayr  Birgit Brandlmeier  Volker Diersche  Philipp Stojakowits  Uwe Kirscher  Renate Matzke-Karasz  Valerian Bachtadse  Michael Eigler  Ulrich Haas  Bernhard Lempe  Paula J. Reimer  Christoph Spötl 《Journal of Paleolimnology》2017,57(2):213-219

  相似文献   

U-Pb and Pb-Pb zircon dating of the older orthogneiss suite in the Silvretta nappe,eastern Alps: Cadomian magmatism in the upper Austro-Alpine realm     

Bernhard Müller  Urs Stefan Klötzli  Markus Flisch 《International Journal of Earth Sciences》1995,84(3):457-465

Two orthogneiss suites dominate the Silvretta nappe. Primary crystallization of the larger suite (younger orthogneisses) is assumed to be Ordovician in age. The second, adjacent magmatic suite consists of older, alkaline to calc-alkaline, ultrabasic, basic to intermediate and granitic rocks known as older orthogneisses. U-Pb data of multigrain zircon fractions, as well as single zircon stepwise evaporation ²⁰⁷Pb/²⁰⁶Pb results suggest a latest Proterozoic to early Cambrian intrusion age for the protoliths of the older orthogneisses as both dating methods yield early Cambrian crystallization ages of 526±7 and 519±7 Ma for an alkaline granite gneiss; similar results were obtained for two neighbouring calc-alkaline orthogneisses (²⁰⁷Pb/²⁰⁶Pb ages of 533 ± 4 and 568 ± 6 Ma, respectively). The crystal habitus corresponds to P5, S19 and S9 zircons of magmatic origin. Whole-rock initial Sr isotope ratios indicate a primitive source. The igneous protoliths of these older orthogneisses represent a fragment of a Cadomian (Pan-African) crust found in places within the basement of the European Hercynides.  相似文献   

How Episodic Coral Breakage Can Determine Community Structure: A South African Coral Reef Example     

Bernhard  Riegl Andrea  Riegl 《Marine Ecology》1996,17(1-3):399-410

Abstract. Africa's southernmost coral reefs are situated in Natal Province, South Africa. The Natal coast is exposed to open Ocean swells and episodic storm swell conditions. Benthic communities on these reefs differentiated into three community types: shallow reefs (8–18 m) were dominated by alcyonacean corals and low-growing, massive Scleractinia; intermediate reefs (18–25 m) were dominated chiefly by branching and tabular Scleractinia of the genus Acropora (A. austera, A. clathrata); deep reefs were not dominated by corals but by sponges. Breakage and recovery experiments indicated that the difference in Acropora dominance between shallow and intermediate sites was caused by breakage in high swell conditions. Survival of experimentally produced A. austera fragments was significantly higher in intermediate than in shallow sites, where higher surge made re-attachment and regeneration unlikely. Also, colony morphology was adapted to differential surge conditions: colonies on the shallow reefs were smaller with shorter branches, while on intermediate reefs they were much bigger with long, widely spreading branches. Episodic breakage and low fragment survival due to high water-motion thus excluded branching corals from shallow reef sites.  相似文献   

Über die Berechnung sämtlicher Feldgrössen aus der Vertikalintensität und deren Anwendung auf die Auswertung von Schwerebildern     

Bernhard Kosbahn 《Pure and Applied Geophysics》1949,15(1-2):27-36

Zusammenfassung In nachstehender Untersuchung wird in umfassender Weise gezeigt, wie sich aus der Karte der Vertikalintensität einer lokalen, für sich allein betrachteten Schwerestörung sämtliche anderen Feldgrössen und Ableitungen berechnen lassen. Es ergibt sich dadurch die Möglichkeit, den Verlauf des störenden Kraftfeldes auch unter der Erdoberfläche zu berechnen und aus einem Kraftlinienbild unmittelbar den Aufbau der Inhomogenitäten im Untergrund zu erkennen.

---

Summary It is shown that the picture of a local anomaly in gravity (U _z ) may give the basement of structural calculations to an extend that was not known till now. FromU _z all other terms and derivations of the field of gravity are obtainable such asU, U _x ,U _y ,U _zz ,U _zzz , etc. The knowledge of these terms enables us to pursue the lines of gravity under the surface and thus to recognise immediately the characterising features of the structure itself.

  相似文献   

Klima und Artbildung     

Rensch  Bernhard 《International Journal of Earth Sciences》1952,40(1):137-152

International Journal of Earth Sciences - Der kurze Vortrag bezweckt lediglich, durch einige generelle Betrachtungen dem Paläontologen Anregungen bei Diskussionen über das Thema...  相似文献   

Illuminated and shadowed contour lines: improving algorithms and evaluating effectiveness     

James D. Eynard  Bernhard Jenny 《International journal of geographical information science》2016,30(10):1923-1943

Shadowed contour lines vary line width. Illuminated contour lines additionally vary color based on an angle of illumination. Illuminated and shadowed contour lines date back to the mid-nineteenth century, but their effectiveness compared to conventional contour lines has not been fully examined. Currently, illuminated and shadowed contour lines are not widely used in computer-based cartography because they are not included in most GIS apmaking software. This article introduces improvements to existing algorithms for creating illuminated and shadowed contour lines from digital elevation data. A software package is made available to allow mapmakers to more easily make customized illuminated and shadowed contour maps. A user study comparing illuminated and shadowed contour lines to conventional contour lines and shaded relief with approximately 400 participants was conducted. Results indicate that map-readers can interpret relative height differences between points better and quicker with illuminated contour lines than regular contour lines or shaded relief. Study participants were able to select absolute maxima on an unlabeled illuminated contour map and a labeled regular contour map with equal accuracy and speed. These findings suggest that illuminated contour lines could be used more frequently for improved visualization of terrain and other surface data on maps.  相似文献