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  • 1
    Series available for loan
    Series available for loan
    London : British Antractic Survey
    Associated volumes
    Call number: ZSP-164-54
    In: Scientific reports
    Type of Medium: Series available for loan
    Pages: 62 S., XI Taf. : graph. Darst., Kt. + 2 Kt.
    Series Statement: Scientific reports / British Antarctic Survey 54
    Branch Library: AWI Library
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  • 2
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    In:  Geochemistry Geophysics Geosystems (G3)
    Publication Date: 2020-02-12
    Description: Mantle plumes are hot upwellings of rock thought to originate at the core‐mantle boundary. As they rise through the mantle, their conduits may become tilted due to lateral large‐scale mantle flow. Recent tomographic images have revealed a strongly tilted plume conduit starting at the core‐mantle boundary beneath northern Baja California rising toward the Yellowstone hot spot from the southwest. Here we perform numerical computations of plumes deflected in large‐scale mantle flow with the aim of finding if realistic model parameter ranges exist that yield a good fit with the tomographically observed conduit. We restrict ourselves to models that yield reasonable results for plume conduit tilt and hot spot motion globally. These models require high viscosity ≈1023 Pa s at some lower mantle depths. For a plume head reaching the surface 17 Ma, corresponding to the start of the Columbia River Basalts, our models require rise times ≈80 Myr or longer to match the tilt of the conduit observed by tomography. We used several tomography models to determine mantle density with almost all models predicting southwestward flow in the lowermost mantle beneath the western United States. Exact details of the shape of the predicted conduit's southwesterly tilt vary, depending on the density and viscosity structures we used. In many cases we find comparatively strong tilts in two depth ranges, in the upper and lower portions of the mantle, which is also a characteristic of the tomographically observed conduit. We expect that future models may help to constrain large‐scale flow by matching these corresponding depth ranges.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
    Publication Date: 2020-10-02
    Description: Mantle plumes are likely initiated by large plume heads. Because mantle viscosity and its dependence on temperature and stress is poorly known, it is uncertain how long plumes take to rise through the mantle. Knowing this is important for constraining the total time until subducted material may resurface in mantle plume heads. Here we apply observational constraints to narrow down plume rise times. Firstly, the margins of Large Low Shear Velocity Provinces (LLSVPs) which probably represent piles of hot chemically dense material in the lowermost mantle are likely locations for plume generation. Here we model, as a function of rise time, the locations where plume heads start rising, such that plumes reach the surface at the observed hotspots. We find that these source locations agree well with LLSVP margins only for rise times of about 30 Myr or less. Different from other hotspots with likely deep source, Yellowstone is close to subduction zones and far from LLSVPs. Yet a recent tomography model shows a tilted plume conduit beneath, rising from the lowermost mantle. Here we compare modelled plume conduit shape, as a function of rise time, with tomography and find the best agreement for rise times of about 90 Myr or more. Comparatively slow rising could be due to a small plume head (corresponding to Columbia River Basalts being smaller than other Large Igneous Provinces). Faster rising of plumes near LLSVPs could also be due to hotter mantle, causing upward ambient mantle flow and reduced viscosity.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
    Publication Date: 2020-10-02
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 5
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    In:  Programme & abstract book
    Publication Date: 2020-10-02
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
    Publication Date: 2024-03-11
    Description: Applying molecular methods to fungi establishing lichenized associations with green algae or cyanobacteria has repeatedly revealed the existence of numerous phylogenetic taxa overlooked by classical taxonomic approaches. Here, we report taxonomical conclusions based on multiple species delimitation and validation analyses performed on an eight-locus dataset that includes world-wide representatives of the dolichorhizoid and scabrosoid clades in section Polydactylon of the genus Peltigera. Following the recommendations resulting from a consensus species delimitation approach and additional species validation analysis (BPP) performed in this study, we present a total of 25 species in the dolichorhizoid clade and nine in the scabrosoid clade, including respectively 18 and six species that are new to science and formally described. Additionally, one combination and three varieties (including two new to science) are proposed in the dolichorhizoid clade. The following 24 new species are described: P. appalachiensis, P. asiatica, P. borealis, P. borinquensis, P. chabanenkoae, P. clathrata, P. elixii, P. esslingeri, P. flabellae, P. gallowayi, P. hawaiiensis, P. holtanhartwigii, P. itatiaiae, P. hokkaidoensis, P. kukwae, P. massonii, P. mikado, P. nigriventris, P. orientalis, P. rangiferina, P. sipmanii, P. stanleyensis, P. vitikainenii and P. willdenowii; the following new varieties are introduced: P. kukwae var. phyllidiata and P. truculenta var. austroscabrosa ; and the following new combination is introduced: P. hymenina var. dissecta. Each species from the dolichorhizoid and scabrosoid clades is morphologically and chemically described, illustrated, and characterised with ITS sequences. Identification keys are provided for the main biogeographic regions where species from the two clades occur. Morphological and chemical characters that are commonly used for species identification in the genus Peltigera cannot be applied to unambiguously recognise most molecularly circumscribed species, due to high variation of thalli formed by individuals within a fungal species, including the presence of distinct morphs in some cases, or low interspecific variation in others. The four commonly recognised morphospecies: P. dolichorhiza, P. neopolydactyla, P. pulverulenta and P. scabrosa in the dolichorhizoid and scabrosoid clades represent species complexes spread across multiple and often phylogenetically distantly related lineages. Geographic origin of specimens is often helpful for species recognition; however, ITS sequences are frequently required for a reliable identification.
    Keywords: cryptic species ; identification key ; new taxa ; Peltigerales ; species delimitation
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 29 (1964), S. 2542-2545 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 664-670 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of medicinal chemistry 23 (1980), S. 180-184 
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3211-3219 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To extend the operating frequency band of earth-based interferometric gravitational wave (GW) detectors down to 1 Hz, an unconventional system is required that provides approximately a factor of one million vibration isolation for the horizontal and more for the vertical, starting at 1 Hz. To this end, a three-stage ultra-low-noise, high-performance active and passive isolation system is being designed and constructed in order to demonstrate that a high degree of reduction can be achieved for vibrations at the support points of a GW detector's final pendulum system. The first stage of this system has been fully characterized and is the main subject of this article. It is an equilateral triangular platform, 1.1 m on a side, with a total mass of 460 kg, including the vacuum system that will contain the other two stages. Active isolation is achieved by six servocontrol loops, using signals from low-frequency displacement sensors to feed back to noncontacting force transducers. The first stage has been actively isolated from vibrations in all six degrees of freedom by at least a factor of 100 at 1 Hz and above. The system noise limitations at 2 Hz and above are roughly 2×10−11 and 5×10−11 m/Hz for vertical and horizontal translations, respectively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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