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  • Books  (5)
  • Other Sources  (42)
  • ddc:550  (22)
  • ddc:551.9  (20)
  • LC QA9  (5)
  • English  (47)
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  • 2020-2023  (42)
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  • Books  (5)
  • Other Sources  (42)
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  • 2020-2023  (42)
  • 2010-2014
  • 2005-2009
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  • 1
    Unknown
    Ancient Formal Logic (1951)
    Amsterdam : North-Holland Pub. Co
    Details
    Keywords: DDC 510/.01 ; LC QA9
    Pages: Online-Ressource (vii, 122 pages)
    ISBN: 9780444703583
    URL: http://www.sciencedirect.com/science/bookseries/0049237X/2
    Language: English
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  • 2
    Unknown
    The Propositional Logic of Boethius (1951)
    Amsterdam : North-Holland Pub. Co
    Details
    Keywords: DDC 510/.01 ; LC QA9
    Pages: Online-Ressource (x, 79 pages)
    ISBN: 9780444533661
    URL: http://www.sciencedirect.com/science/bookseries/0049237X/1
    Language: English
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  • 3
    Unknown
    On the Metamathematics of Algebra (1951)
    Amsterdam : North-Holland Pub. Co
    Details
    Keywords: DDC 510/.01 ; LC QA9
    Pages: Online-Ressource (vi, 195 pages)
    ISBN: 9780444533692
    URL: http://www.sciencedirect.com/science/bookseries/0049237X/4
    Language: English
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  • 4
    Unknown
    An Essay In Modal Logic (1951)
    Amsterdam : North-Holland Pub. Co
    Details
    Keywords: DDC 510/.01 ; LC QA9
    Pages: Online-Ressource (vi, 90 pages)
    ISBN: 9780444533708
    URL: http://www.sciencedirect.com/science/bookseries/0049237X/5
    Language: English
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  • 5
    Unknown
    Outlines of a Formalist Philosophy of Mathematics (1951)
    Amsterdam : North-Holland Pub. Co
    Details
    Keywords: DDC 510/.01 ; LC QA9
    Pages: Online-Ressource (vii, 75 pages)
    ISBN: 9780444533685
    URL: http://www.sciencedirect.com/science/bookseries/0049237X/3
    Language: English
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  • 6
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    Iron Exports From Catchments Are Constrained by Redox Status and Topography (2022)
    Details
    Publication Date: 2022-04-04
    Description: Fe(III) hydroxides stabilize organic carbon (OC) and P in soils. Observations of rising stream Fe concentrations are controversially posited to result from a flushing of iron‐rich deeper soil layers or a decrease of competing electron acceptors inhibiting Fe reduction (NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ and SO42− $\mathrm{S}{{\mathrm{O}}_{4}}^{2-}$). Here, we argue that catchment topography constrains the release of Fe, OC, and P to streams. We therefore incubated organic topsoil and mineral subsoil and modified the availability of NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$. We found that Fe leaching was highest in topsoil. Fe, OC, and P released at quantities proportional to their ratios in the source soil. Supply of NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ reduced Fe leaching to 18% and increased pore water OC:Fe and P:Fe ratios. Subsoil, however, was an insignificant Fe source (〈0.5%). Here, the leached quantities of Fe, OC and P were highly disproportionate to the soil source with an excess of released OC and P. We tested if experimental findings scale up using data from 88 German catchments representing gradients in NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ concentration and topography. Average stream Fe concentrations increased with decreasing NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ and were high in catchments with shallow topography where high groundwater levels support reductive processes and topsoils are hydrologically connected to streams; but Fe concentrations were low in catchments with steep topography where flow occurs primarily through subsoils. OC:Fe and P:Fe ratios in the streams similarly varied by NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ and topography. This corroborates the findings from the laboratory experiment and suggests that catchment topography and competing electron acceptors constrain the formation of Fe‐reducing conditions and control the release of Fe, OC, and P to streams.
    Description: Plain Language Summary: Iron is the second most abundant metal in the crust; its cycle is tightly connected to those of carbon, oxygen, and sulfur. The oxidized form (FeIII) is almost insoluble, but Fe can be mobilized by complexation or microbial Fe reduction. Both processes depend on availability of organic C. We found that Fe concentrations in streams were constrained by the topography of catchments and NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ abundance. Shallower catchments are characterized by higher groundwater tables connecting the organic topsoils efficiently to streams. NO3− $\mathrm{N}{{\mathrm{O}}_{3}}^{-}$ suppresses Fe reduction as a competing electron acceptor to Fe. We conclude that trends in soil wetness or atmospheric N deposition can change the stability of Fe and thus the release of PO43− $\mathrm{P}{{\mathrm{O}}_{4}}^{3-}$ and harmful metals to surface waters.
    Description: Key Points: Organic topsoils leach substantial amounts of Fe when incubated in the absence of NO3, a competing electron acceptor that inhibits Fe reduction. Shallow catchments with fluvially coupled topsoils and low NO3 availability release 200 fold more Fe than steep ones with high NO3 abundance. Catchment topography and NO3 availability explain 62%–64% of the variability of Fe concentration and OC:Fe and P:Fe ratios across 88 streams.
    Description: EFRE‐Europe
    Description: https://doi.org/10.4211/hs.43601618877945c5a46b715aa98db729
    Keywords: ddc:551.9
    Language: English
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  • 7
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    Probability Distributions of Radiocarbon in Open Linear Compartmental Systems at Steady‐State (2022)
    Details
    Publication Date: 2022-06-26
    Description: Radiocarbon (14C) is commonly used as a tracer of the carbon cycle to determine how fast carbon moves between different reservoirs such as plants, soils, rivers, or oceans. However such studies mostly emphasize the mean value (as Δ14C) of an unknown probability distribution. We introduce a novel algorithm to compute Δ14C distributions from knowledge of the age distribution of carbon in linear compartmental systems at steady‐state. Our results demonstrate that the shape of the distributions might differ according to the speed of cycling of ecosystem compartments and their connectivity within the system, and might contain multiple peaks and long tails. The distributions are also sensitive to the variations of Δ14C in the atmosphere over time, as influenced by the counteracting anthropogenic effects of fossil‐fuel emissions (14C‐free) and nuclear weapons testing (excess 14C). Lastly, we discuss insights that such distributions can offer for sampling and design of experiments aiming to capture the precise variance of Δ14C values present in the multi‐compartmental ecosystems.
    Description: Plain Language Summary: Radiocarbon (14C) is a radioactive isotope of carbon prominent in environmental sciences for tracing the dynamics of ecosystems, especially as recent changes in atmospheric radiocarbon allow tracking excess 14C created by nuclear weapons testing in the atmosphere on timescales shorter than what can be determined using radioactive decay. For climate change mitigation, a crucial uncertainty is the time carbon captured through photosynthesis spends in ecosystems before being released. For this purpose, radiocarbon can be valuable as a biological tracer; however, it is necessary to accurately link the real age of carbon and its radiocarbon age, as they usually differ. Forests and soils are open systems, connecting components with intrinsically different cycling timescales, so that the mean age comes from an age distribution that is usually unknown. Here, we developed an algorithm to compute the 14C contents for models consisting of multiple interconnected carbon pools. Our approach offers more accurate estimations of the mean 14C content of the system and computations of the distribution of 14C within the system at different points in time. Results obtained from this method can provide additional insights on the dynamics of the carbon cycle in multiple compartments, and can help to better interpret observations.
    Description: Key Points: Probability distributions of radiocarbon in ecosystem compartments can be derived from carbon age distributions. The shape of these distributions vary according to the speed of carbon cycling and the year of observation. Probability distributions of radiocarbon provide insights to study carbon dynamics and to interpret radiocarbon data.
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: Max‐Planck‐Gesellschaft (MPG) http://dx.doi.org/10.13039/501100004189
    Description: https://doi.org/10.5281/zenodo.6373329
    Keywords: ddc:551.9
    Language: English
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  • 8
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    An Adaptive Hybrid Vertical Equilibrium/Full‐Dimensional Model for Compositional Multiphase Flow (2022)
    Details
    Publication Date: 2022-06-26
    Description: Efficient compositional models are required to simulate underground gas storage in porous formations where, for example, gas quality (such as purity) and loss of gas due to dissolution are of interest. We first extend the concept of vertical equilibrium (VE) to compositional flow, and derive a compositional VE model by vertical integration. Second, we present a hybrid model that couples the efficient compositional VE model to a compositional full‐dimensional model. Subdomains, where the compositional VE model is valid, are identified during simulation based on a VE criterion that compares the vertical profiles of relative permeability at equilibrium to the ones simulated by the full‐dimensional model. We demonstrate the applicability of the hybrid model by simulating hydrogen storage in a radially symmetric, heterogeneous porous aquifer. The hybrid model shows excellent adaptivity over space and time for different permeability values in the heterogeneous region, and compares well to the full‐dimensional model while being computationally efficient, resulting in a runtime of roughly one‐third of the full‐dimensional model. Based on the results, we assume that for larger simulation scales, the efficiency of this new model will increase even more.
    Description: Key Points: A compositional vertical equilibrium model is coupled to its full‐dimensional counterpart. A criterion is developed to adaptively identify and assign regions where the vertical equilibrium model is applicable during simulation. A test case of hydrogen storage in a heterogeneous porous aquifer demonstrates efficiency and accuracy of the hybrid model.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: https://git.iws.uni-stuttgart.de/dumux-pub/Becker2021b.git
    Keywords: ddc:551.49 ; ddc:550
    Language: English
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  • 9
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    Multi‐Band Raman Analysis of Radiation Damage in Zircon for Thermochronology: Partial Annealing and Mixed Signals (2022)
    Details
    Publication Date: 2022-06-24
    Description: Four zircon Raman bands were previously calibrated to give consistent estimates of the accumulated self‐irradiation α‐dose in unannealed volcanic samples. Partial annealing of radiation damage produces inconsistent values because of differences in the relative annealing sensitivities. The damage estimates based on the external rotation band (DER) at ∼356 cm−1 and that based on the ν2(SiO4) band (D2) at ∼438 cm−1 are the most and least sensitive to damage annealing. The D2/DER‐ratio thus provides a numerical estimate of the extent of geologic annealing that a zircon sample has experienced. This ratio characterizes the thermal history of a zircon sample but also its state of radiation damage during the course of its geologic history, and thus the manner in which this state influences other thermochronologic methods. Meaningful interpretation of the zircon Raman age requires that the spectra are free of measurement artifacts. The major artifacts result from micrometer‐scale gradients of the damage densities within a zircon grain due to uranium and thorium zoning. The micrometer‐sized sampled volume may span different densities, producing overlapping spectra, causing apparent peak broadening, overestimated damage densities, and zircon Raman ages. The D3/D2‐ratio of the damage densities calculated from the ν3(SiO4) and ν2(SiO4) bands, most and least affected by overlap, is an efficient indicator of a meaningless signal. It reveals overlap in annealed and unannealed samples, because the used bands have similar responses to annealing. Multi‐band Raman maps can be converted to damage‐ratio maps for screening zircon mounts, and selecting spots for thermochronologic investigations.
    Description: Plain Language Summary: Radioactive processes cause damage to the lattice of zircon crystals. This damage can be measured with a Raman instrument. Such measurements are important for methods determining the ages and thermal histories of zircon grains in rocks. Thus, the Raman measurements must be reliable and meaningful. This work proposes tools for detecting effects that hinder the interpretation of zircon Raman data. These effects are mixed signals and loss of damage due to exposure to elevated temperatures in the geologic environment. Zircon Raman spectra have different bands that respond differently to mixed signals and temperature. The ratio of the damage estimates from the least and most temperature‐sensitive bands thus indicates partial annealing. Raman spectra of zoned zircons often straddle areas with different lattice damage. Their overlapping signals cause artificial band broadening, and a damage overestimation. The ratio of the damage estimated from the least and the most affected bands identifies mixed signals and allows to reject unsuitable samples. The damage ratios can also be plotted in maps for damage screening and for selecting optimal spots for measurements.
    Description: Key Points: Annealing and inhomogeneous damage are two main factors hindering radiation‐damage estimation for zircon Raman dating. Comparison of internal and external Raman bandwidths allows to detect partial annealing of radiation damage in zircon. Comparison of internal Raman bandwidths allows to detect artifactual broadening in zoned zircon.
    Description: Studienstiftung des Deutschen Volkes (Studienstiftung) http://dx.doi.org/10.13039/501100004350
    Description: http://dx.doi.org/10.25532/OPARA-155
    Keywords: ddc:549 ; ddc:551.9
    Language: English
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  • 10
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    The Vertical Structure and Entrainment of Subglacial Melt Water Plumes (2022)
    Details
    Publication Date: 2022-06-22
    Description: Basal melting of marine‐terminating glaciers, through its impact on the forces that control the flow of the glaciers, is one of the major factors determining sea level rise in a world of global warming. Detailed quantitative understanding of dynamic and thermodynamic processes in melt‐water plumes underneath the ice‐ocean interface is essential for calculating the subglacial melt rate. The aim of this study is therefore to develop a numerical model of high spatial and process resolution to consistently reproduce the transports of heat and salt from the ambient water across the plume into the glacial ice. Based on boundary layer relations for momentum and tracers, stationary analytical solutions for the vertical structure of subglacial non‐rotational plumes are derived, including entrainment at the plume base. These solutions are used to develop and test convergent numerical formulations for the momentum and tracer fluxes across the ice‐ocean interface. After implementation of these formulations into a water‐column model coupled to a second‐moment turbulence closure model, simulations of a transient rotational subglacial plume are performed. The simulated entrainment rate of ambient water entering the plume at its base is compared to existing entrainment parameterizations based on bulk properties of the plume. A sensitivity study with variations of interfacial slope, interfacial roughness and ambient water temperature reveals substantial performance differences between these bulk formulations. An existing entrainment parameterization based on the Froude number and the Ekman number proves to have the highest predictive skill. Recalibration to subglacial plumes using a variable drag coefficient further improves its performance.
    Description: Plain Language Summary: In a world of global warming, the melting of glaciers terminating as floating ice tongues into the oceans of Arctic and Antarctic regions allows those glaciers to flow faster and hence to make a considerable contribution to global mean sea‐level rise. Underneath the ice‐ocean interface, turbulent currents of the order of 10 m thickness (so‐called plumes) develop that transport the melt water from the grounding line where the glacier enters the ocean toward the calving front that marks the seaward end of the glacier. At its base, ambient relatively warm and salty ocean water is mixed into the plumes and is vertically transported toward the ice‐ocean interface, where the melting is increased due to the additional heat supply. Understanding these processes is essential for their incorporation into computer models for the prediction of such melt processes. In this study, an accurate simulation model for the water column is constructed that is able to consistently reproduce these processes. The algorithms developed here are proven to provide reliable results also for models with only a few grid points across the plume and can therefore be implemented into climate models with surface‐following coordinates to more accurately simulate future scenarios of sea level rise.
    Description: Key Points: A vertically resolving model with second‐moment turbulence closure has been constructed for subglacial plumes. Convergent numerical formulations for the ocean‐to‐ice fluxes of momentum, freshwater and heat have been derived from an analytical model. Model results are consistent with bulk parameterizations for the entrainment of ambient water.
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.5281/zenodo.6203838
    Keywords: ddc:550
    Language: English
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