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  • Molecular Diversity Preservation International  (2)
  • The Royal Society  (1)
  • 1
    Publikationsdatum: 2018-12-20
    Beschreibung: Anomalous diffusion has been most often argued in terms of a position fluctuation of a tracer. We here propose the other fluctuating observable, i.e., momentum transfer defined as the time integral of applied force to hold a tracer’s position. Being a conjugated variable, the momentum transfer is thought of as generating the anomalous diffusion paired with the position’s one. By putting together the paired anomalous diffusions, we aim to extract useful information in complex systems, which can be applied to experiments like tagged monomer observations in chromatin. The polymer being in the equilibrium, the mean square displacement (or variance) of position displacement or momentum transfer exhibits the sub- or superdiffusion, respectively, in which the sum of the anomalous diffusion indices is conserved quite generally, but the nonequilibrium media that generate the active noise may manifest the derivations from the equilibrium relation. We discuss the deviations that reflect the characteristics of the active noise.
    Digitale ISSN: 2073-4360
    Thema: Chemie und Pharmazie , Maschinenbau , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2021-03-19
    Beschreibung: Abiotic fixation of atmospheric dinitrogen to ammonia is important in prebiotic chemistry and biological evolution in the Hadean and Archean oceans. Though it is widely accepted that nitrate (NO3−) was generated in the early atmospheres, the stable pathways of ammonia production from nitrate deposited in the early oceans remain unknown. This paper reports results of the first experiments simulating high-temperature, high-pressure reactions between nitrate and komatiite to find probable chemical pathways to deliver ammonia to the vent–ocean interface of komatiite-hosted hydrothermal systems and the global ocean on geological timescales. The fluid chemistry and mineralogy of the komatiite–H2O–NO3− system show iron-mediated production of ammonia from nitrate with yields of 10% at 250 °C and 350 °C, 500 bars. The komatiite–H2O–NO3– system also generated H2-rich and alkaline fluids, well-known prerequisites for prebiotic and primordial metabolisms, at lower temperatures than the komatiite–H2O–CO2 system. We estimate the ammonia flux from the komatiite-hosted systems to be 105–1010 mol/y in the early oceans. If the nitrate concentration in the early oceans was greater than 10 μmol/kg, the long-term production of ammonia through thermochemical nitrate reduction for the first billion years might have allowed the subsequent development of an early biosphere in the global surface ocean. Our results imply that komatiite-hosted systems might have impacted not only H2-based chemosynthetic ecosystems at the vent-ocean interface but also photosynthetic ecosystems on the early Earth.
    Digitale ISSN: 2075-163X
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2018-09-01
    Beschreibung: Fluid inclusions in hydrothermal quartz in the 2.4 Ga Ongeluk Formation, South Africa, are expected to partially retain a component of the ancient seawater. To constrain the origin of the fluid and the quartz precipitation age, we conducted Ar–Ar dating for the quartz via a stepwise crushing method. The obtained argon isotopes show two or three endmembers with one or two binary mixing lines as the crushing proceeds, suggesting that the isotopic compositions of these endmembers correspond to fluid inclusions of each generation, earlier generated smaller 40 Ar- and K-rich inclusions, moderate 40 Ar- and 38 Ar Cl (neutron-induced 38 Ar from Cl)-rich inclusions and later generated larger atmospheric-rich inclusions. The K-rich inclusions show significantly different 40 Ar/ 38 Ar Cl values compared to the 38 Ar Cl -rich inclusions, indicating that it is difficult to constrain the quartz formation age using only fluid inclusions containing excess 40 Ar. The highest obtained 40 Ar/ 36 Ar value from the fluid inclusions is consistent with an expected value of the Ongeluk plume source, suggesting that the quartz precipitation was driven by Ongeluk volcanism. Considering the fluid inclusion generations and their compositions, the hydrothermal system was composed of crustal fluid and magmatic fluid without seawater before the beginning of a small amount of seawater input to the hydrothermal system.
    Digitale ISSN: 2054-5703
    Thema: Allgemeine Naturwissenschaft
    Publiziert von The Royal Society
    Standort Signatur Erwartet Verfügbarkeit
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