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  • 1
    Publication Date: 2012-04-15
    Description: Numerical modelling by finite element methods provides two significant insights into the formation of the giant amethyst geodes of the Paraná volcanic province: the conditions needed to open the cavities and the conditions that control their size and shape. Giant amethyst geodes were formed in the Cretaceous (135 Ma) in altered volcanic rocks by water vapour pressure (Δp) at about 0.5 MPa under an altered basalt cover of 5–20 m. Only rocks with Young’s modulus values (E) in the range 1–2 GPa can sustain ballooning, which is the growth of a cavity in a ductile medium by the pressure of water and its vapour. The size of the proto-geode is dependent on the water vapour pressure, which is directly related to thickness of the overlying basalt. Varying the yield points causes the formation of either prolate or oblate cavities. A low transition point (smaller than 0.18 MPa) generates a prolate-shaped cavity, whereas a high transition point (larger than 0.18 MPa) generates oblate proto-geodes. Proto-geodes are smaller when Young’s modulus is higher (rock is less altered) or when water vapour pressure is lower (because of thinner overburden of basalt). The calculations are an indication that the processes operative in the altered basalts led to the opening of giant cavities by ballooning.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
    Published by Wiley
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  • 2
    Publication Date: 2017-06-01
    Description: Terrestrial carbon export via inland aquatic systems is a key process in the global carbon cycle. It includes loss of carbon to the atmosphere via outgassing from rivers, lakes or reservoirs and carbon fixation in the water column as well as in sediments. This review focuses on headwater streams that are important because their stream biogeochemistry directly reflects carbon input from soils and groundwaters that becomes superimposed by additional inputs further downstream. Major drivers of carbon dioxide partial pressures ( p CO 2 ) in streams and mechanisms of terrestrial dissolved inorganic, organic and particulate organic carbon (DIC, DOC, and POC) influxes are summarized in this work. Our analysis indicates that the global river average p CO 2 of 3,100 ppmV is more often exceeded by contributions from small streams when compared to rivers with larger catchments (〉500 km 2 ). Because of their large proportion in global river networks (〉96 % of the total number of streams), headwaters contribute large – but still poorly quantified – amounts of CO 2 to the atmosphere. Conservative estimates imply that globally 36 % (i.e. 0.93 Pg C yr -1 ) of total CO 2 outgassing from rivers and streams originate from headwaters. We also discuss challenges in determination of CO 2 sources, concentrations and fluxes. To overcome uncertainties of CO 2 sources and its outgassing from headwater streams on the global scale, new investigations are needed that should include groundwater data. Such studies would also benefit from applications of integral CO 2 outgassing isotope approaches and multi-scale geophysical imaging techniques.
    Print ISSN: 8755-1209
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 1991-08-01
    Print ISSN: 0014-2956
    Electronic ISSN: 1432-1033
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 4
    Publication Date: 1991-08-01
    Print ISSN: 0014-2956
    Electronic ISSN: 1432-1033
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 5
    Publication Date: 2005-07-01
    Print ISSN: 0009-9236
    Electronic ISSN: 1532-6535
    Topics: Chemistry and Pharmacology , Medicine
    Published by Wiley
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  • 6
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A qualitative screening revealed the occurrence of lipase, esterase, protease, amylase, endo-1,4-β-D-glucanase, xylanase, pectinmethylesterase, polygalacturonase, catalase, β-D-glucosidase and β-D-galactosidase activities in the technical Aspergillus niger enzyme under study (Lipase 2212 D, Röhm). The isolation and purification of lipolytic activities were performed by combination of DEAE-Trisacryl M ion exchange chromatography, Sephadex G 50 gel filtration and hydrophobic chromatography using Phenylsepharose CL-4B. The individual purification steps were checked by specific enzyme visualization in ultrathin agar gels after ultrathin-layer isoelectric focusing (UIEF). Two UIEF homogeneous lipase isoenzymes (I and II) were isolated and characterized by the following parameters: isoelectric points (I: 4.0; II. 3.5); molecular weights (I: 31000 daltons; II: 19000 daltons); carbohydrate contents (I: 6%; II: 9%) and compositions; pH optima (I, II: 5-6); substrate specificities and various effectors.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In 1988, an extensive geophysical experiment was performed on the Lofoten passive continental margin, which was formed by the continental break-up between Greenland and northern Norway at 58 Ma. The geological units of the outer Lofoten margin are characterized by seaward-dipping reflectors (SDRs) and landward flood basalt, which extends up to 100 km landwards of SDRs. In this study, we obtain the P-wave velocity structure beneath the Lofoten Basin, the SDRs, and the landward flood basalt by use of ocean-bottom seismograph refraction profiling, and we also discuss the formation of the northern Norwegian passive continental margin.In the Lofoten Basin the crust is of oceanic type, consisting of sedimentary layers, oceanic laver 2 (4.9−5.5 km s−1), layer 3A (6.3−6.8 km s−1) and layer 3B (7.0−7.1 km s−1). Beneath the SDRs the crustal layers are identical to those of the Lofoten Basin, but the thickness of the lower crust, which represents the same velocity as layer 3B, increases to 5 km towards the continent side, and a high-velocity lower crustal layer (7.3 km s−1) is formed at the base of the crust. The ocean-continent transition zone is situated between the landward side of the SDRs and the northward continuation of the Vøring Plateau Escarpment. In this region the velocity of the lower crust gradually decreases and approaches the lower crustal velocity beneath the Lofoten Islands (6.8 km s−1). The model also indicates that the high-velocity layer disappears in this region. Comparing our model with the crustal structure on the Vøring margin, it is clear that the lower crustal body (≥7 km s−1) thickens southwards along the northern Norwegian continental margin. Recent results from petrological and geophysical studies of the generation of the oceanic crust have shown that increasing the temperature of the upwelling asthenospheric material increases the thickness of the oceanic crust. We interpret this as that the oceanic crust in the southern area in the Vøring-Lofoten margin was generated by hotter material than that of the northern area.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 43 (1993), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: About 20 ovaries of the whitefish ‘Blaufelchen’ (Coregonus lavaretus L.) of Lake Constance (Bodensee) were collected annually from 1964-1991. Absolute and relative fecundity peaked in the early 1980s, lagging about 2 years behind the maximum of total-P in the water (during the circulation period). Out of the biological time-series of Lake Constance, whitefish fecundity is the only one known to follow the phosphorus curve, and this may be the first time-series documented case of parallel trend reversal in the trophic state of a lake and fish biology. It is concluded that fish fecundity serves, at best, as an unspecific monitor of the overall well-being of the fish.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The highly stable Ca2+ binding protein, parvalbumin, is prevalent in fish white muscle tissue. The properties of this protein make it a promising antigen for use as a specific biomarker for fish identification. Parvalbumin was purified from white muscle of an adult common snook Centropomus undecimalis using ammonium sulfate precipitation, size-exclusion chromatography (SEC) and anion-exchange HPLC. Parvalbumins were characterized by the presence of an 11-kDa band following gradient-SDS gel electrophoresis and by their immunoreactivity against mouse anti-parvalbumin antibodies. Anion-exchange chromatography of the parvalbumin fraction separated from the SEC column yielded nine fractions. Subsequent analysis of these fractions by isoelectric focusing gel electrophoresis led to a total of seven parvalbumin isotypes, which may lend themselves as biomarkers in fish identification. The presence of these seven parvalbumin isotypes was confirmed independently by reversed-phase HPLC. A dilution endpoint immunoassay was developed for C. undecimalis parvalbumin using a monoclonal antibody directed against its highly conserved calcium binding site. The utility of parvalbumin isotype distribution and specific monoclonal antibodies against fish parvalbumin in species identification is discussed.
    Type of Medium: Electronic Resource
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  • 10
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    AGU (American Geological Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 19 (4). pp. 997-1024.
    Publication Date: 2020-01-22
    Description: Mapped unconsolidated sediments cover half of the global land surface. They are of considerable importance for many Earth surface processes like weathering, hydrological fluxes or biogeochemical cycles. Ignoring their characteristics or spatial extent may lead to misinterpretations in Earth System studies. Therefore, a new Global Unconsolidated Sediments Map database (GUM) was compiled, using regional maps specifically representing unconsolidated and quaternary sediments. The new GUM database provides insights into the regional distribution of unconsolidated sediments and their properties. The GUM comprises 911,551 polygons and describes not only sediment types and subtypes, but also parameters like grain size, mineralogy, age and thickness where available. Previous global lithological maps or databases lacked detail for reported unconsolidated sediment areas or missed large areas, and reported a global coverage of 25 to 30%, considering the ice‐free land area. Here, alluvial sediments cover about 23% of the mapped total ice‐free area, followed by aeolian sediments (∼21%), glacial sediments (∼20%), and colluvial sediments (∼16%). A specific focus during the creation of the database was on the distribution of loess deposits, since loess is highly reactive and relevant to understand geochemical cycles related to dust deposition and weathering processes. An additional layer compiling pyroclastic sediment is added, which merges consolidated and unconsolidated pyroclastic sediments. The compilation shows latitudinal abundances of sediment types related to climate of the past. The GUM database is available at the PANGAEA database (https://doi.org/10.1594/PANGAEA.884822).
    Type: Article , PeerReviewed
    Format: text
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