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211.
Tobias Owen 《Icarus》1976,28(2):171-177
Predictions for the total inventory of outgassed volatiles on Mars can be developed by studying volatiles in meteorites, terrestial rocks, and the atmospheres of Venus, the Moon, and the Earth. Two models are presented following the basic assumption that the devolatilization of Mars has been analogous to that of the Earth. The recent discovery of a high abundance of argon in the Martian atmosphere appears to indicate that Mars has outgassed as completely as the Earth, but present uncertainties and lacunae in the essential data set permit several other interpretations. 相似文献
212.
STATE ATLASES: FUNDING SOURCES AND THEMATIC CONTENT* 总被引:1,自引:0,他引:1
Is the thematic content of state atlases influenced by the primary sources of atlas funding, private or public? Maps portraying economic conditions, the physical environment, and population dominated state atlases produced between 1970 and 1986, accounting for over 80% of all thematic content. Funding sources effected modest differences in content. Publicly funded state atlases devoted more attention to introductory, physical, and cultural topics, and privately funded state atlases emphasized population, industrial, and agricultural themes. 相似文献
213.
Paul J. Umhoefer Tobias Schwennicke† Maya T. Del Margo Gabriela Ruiz-Geraldo† James C. Ingle Jr. ‡ William McIntosh§ 《Basin Research》2007,19(2):297-322
Transtensional basins are sparsely described in the literature compared with other basin types. The oblique‐divergent plate boundary in the southern Gulf of California has many transtensional basins: we have studied those on San Jose island and two other transtensional basins in the region. One major type of transtensional basin common in the southern Gulf of California region is a fault‐termination basin formed where normal faults splay off of strike‐slip faults. These basins suggest a model for transtensional fault‐termination basins that includes traits that show a hybrid nature between classic rift and strike‐slip (pull‐apart) basins. The traits include combinations of oblique, strike‐slip and normal faults with common steps and bends, buttress unconformities between the fault steps and beyond the ends of faults, a common facies pattern of terrestrial strata changing upward and away from the faults into marine strata, small fault blocks within the basin that result in complex lateral facies relations, common Gilbert deltas, dramatic termination of the margin of the basin by means of fault reorganization and boundary faults dying and an overall short basin history (few million years). Similar transtensional fault‐termination basins are present in Death Valley and other parts of the Eastern California shear zone of the western United States, northern Aegean Sea and along ancient strike‐slip faults. 相似文献
214.
Tobias Schaller H. Christoph Moor Bernhard Wehrli 《Aquatic Sciences - Research Across Boundaries》1997,59(4):345-361
Concentration profiles of Mg, K, La, Fe, Mn, V, Cr, As and Mo were determined in samples from a freeze core taken at the deepest
site of Baldeggersee in 1993. The special coring technique allowed an exact dating of the sediment samples and an annual resolution
of the profiles. Long term changes in benthic redox conditions produce diagnostic trends in several metal profiles. Fe, As
and Mn enrichments trace the onset of anoxia at the deepest site of the lake. High values of Mo concentrations and Cr/V ratios
indicate periods of stable anoxic conditions in a meromictic hypolimnion. A comparison of oxygen time series with metal profiles
between 1950 and 1990 indicates that Mn reacts sensitively to large seasonal variations of deep-water oxygen concentrations. 相似文献
215.
Crowdsourcing can efficiently complete tasks that are difficult to automate, but the quality of crowdsourced data is tricky to evaluate. Algorithms to grade volunteer work often assume that all tasks are similarly difficult, an assumption that is frequently false. We use a cropland identification game with over 2,600 participants and 165,000 unique tasks to investigate how best to evaluate the difficulty of crowdsourced tasks and to what extent this is possible based on volunteer responses alone. Inter‐volunteer agreement exceeded 90% for about 80% of the images and was negatively correlated with volunteer‐expressed uncertainty about image classification. A total of 343 relatively difficult images were independently classified as cropland, non‐cropland or impossible by two experts. The experts disagreed weakly (one said impossible while the other rated as cropland or non‐cropland) on 27% of the images, but disagreed strongly (cropland vs. non‐cropland) on only 7%. Inter‐volunteer disagreement increased significantly with inter‐expert disagreement. While volunteers agreed with expert classifications for most images, over 20% would have been mis‐categorized if only the volunteers’ majority vote was used. We end with a series of recommendations for managing the challenges posed by heterogeneous tasks in crowdsourcing campaigns. 相似文献
216.
Spectrophotometric scans of Mars and the Moon in the region 4000–5000 Å were obtained and ratioed. No evidence of any absorption greater than 3% is visible in the Martian spectrum. Using our own laboratory spectra of NO2 as well as the published work of Hall and Blacet (1952) we confirm Marshall's (1964) upper limit of 8 μm atmospheres (0.0008 cm amagat) for the abundance of NO2 in the atmosphere of Mars. 相似文献
217.
Ultra-high degree spherical harmonic analysis and synthesis using extended-range arithmetic 总被引:3,自引:2,他引:1
We present software for spherical harmonic analysis (SHA) and spherical harmonic synthesis (SHS), which can be used for essentially
arbitrary degrees and all co-latitudes in the interval (0°, 180°). The routines use extended-range floating-point arithmetic,
in particular for the computation of the associated Legendre functions. The price to be paid is an increased computation time;
for degree 3,000, the extended-range arithmetic SHS program takes 49 times longer than its standard arithmetic counterpart.
The extended-range SHS and SHA routines allow us to test existing routines for SHA and SHS. A comparison with the publicly
available SHS routine GEOGFG18 by Wenzel and HARMONIC SYNTH by Holmes and Pavlis confirms what is known about the stability of these programs. GEOGFG18 gives errors <1 mm for latitudes [-89°57.5′, 89°57.5′] and maximum degree 1,800. Higher degrees significantly limit the range
of acceptable latitudes for a given accuracy. HARMONIC SYNTH gives good results up to degree 2,700 for almost the whole latitude range. The errors increase towards the North pole and
exceed 1 mm at latitude 82° for degree 2,700. For a maximum degree 3,000, HARMONIC SYNTH produces errors exceeding 1 mm at latitudes of about 60°, whereas GEOGFG18 is limited to latitudes below 45°. Further extending the latitudinal band towards the poles may produce errors of several
metres for both programs. A SHA of a uniform random signal on the sphere shows significant errors beyond degree 1,700 for
the SHA program SHA by Heck and Seitz. 相似文献
218.
Tobias Schneider Denise Rimer Christoph Butz Martin Grosjean 《Journal of Paleolimnology》2018,60(3):381-398
Eutrophication, prompted by anthropogenic activities and climate change has led to multiple adverse effects in freshwater systems across the world. As instrumental measurements are typically short, lake sediment proxies of aquatic primary productivity (PP) are often used to extend the observational record of eutrophication back in time. Sedimentary pigments provide specific information on PP and major algal communities, but the records are often limited in the temporal resolution. Hyperspectral imaging (HSI) data, in contrast, provide very high seasonal (sub-varve-scale) resolution, but the pigment speciation is limited. Here, we explore a combined approach on varved sediments from the Ponte Tresa basin, southern Switzerland, taking the advantages of both methods (HSI and high performance liquid chromatography, HPLC) with the goal to reconstruct the recent eutrophication history at seasonal to interannual resolution. We propose a modified scheme for the calibration of HSI data (here: Relative Absorption Band Depth between 590 and 730 nm RABD590–730) and HPLC-inferred pigment concentrations (here: ‘green pigments’ {chlorophyll a and pheophytin a}) and present a calibration model (R2?=?0.82; RMSEP?~?12%). The calibration range covers >?98% of the spectral index values of all individual pixels (68 µm?×?68 µm) in the sediment core. This allows us to identify and quantify extreme pigment concentrations related to individual major algal blooms, to identify multiple algal blooms within one season, and to assess interannual variability of PP. Prior to the 1930s, ‘green pigment’ concentrations and fluxes (~?50 µg g?1;?~?2 µg cm?2a?1, chlorophyll a and pheophytin a) and interannual variability was very low. From the 1930s to 1964, chlorophyll a and pheophytin a increased by a factor of ~?4, and ββ-carotene appeared in substantial amounts (~?0.4 µg cm?2a?1). Interannual variability increased markedly and a first strong algal bloom with ‘green pigment’ concentrations as high as 700 µg g?1 is observed in 1958. Peak eutrophication (~?12 µg cm?2a?1 chlorophyll a and pheophytin a) and very high interannual variability with extreme algal blooms (‘green pigment’ concentrations up to 1400 µg g?1) is observed until ca. 1990, when eutrophication decreases slightly. Maximum PP values after 2009 are likely the result of internal nutrient cycling related to repeated deep mixing of the lake. 相似文献
219.
Nickschick Tobias Flechsig Christina Meinel Cornelia Mrlina Jan Kämpf Horst 《International Journal of Earth Sciences》2017,106(8):2915-2926
International Journal of Earth Sciences - The Hartoušov mofette field in NW Bohemia, Czech Republic, is characterized by strong CO2 degassing from the Lithospheric Mantle. In a test survey... 相似文献
220.
Tobias Lienen Klas Lüders Hannah Halm Anke Westphal Ralf Köber Hilke Würdemann 《Environmental Earth Sciences》2017,76(6):261
Aquifer thermal energy storage may result in increases in the groundwater temperature up to 70 °C and more. This may lead to geochemical and microbiological alterations in the aquifer. To study the temperature effects on the indigenous microbial community composition, sediment column experiments at four different temperatures were carried out and the effluents were characterized geochemically and microbiologically. After an equilibrium phase at groundwater temperature of 10 °C for 136 days, one column was kept at 10 °C as a reference and the others were heated to 25, 40 and 70 °C. Genetic fingerprinting and quantitative PCR revealed a change in the bacterial community composition and abundance due to the temperature increase. While at 25 °C only slight changes in geochemical composition and gene copy numbers for bacteria were observed, increasing concentrations of total organic carbon in the 40 °C column were followed by a strong increase in bacterial abundance. Thermophilic bacteria became dominant at 70 °C. Temporary sulfate reduction took place at 40 and 70 °C and this correlated with an increased abundance of sulfate-reducing bacteria (SRB). Furthermore, a coexistence of SRB and sulfur-oxidizing bacteria (SOB) at all temperatures indicated an interaction of these physiological groups in the sediments. The results show that increased temperatures led to significant shifts in the microbial community composition due to the altered availability of electron donors and acceptors. The interplay of SRB and SOB in sedimentary biofilms facilitated closed sulfur cycling and diminished harmful sulfur species. 相似文献