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  • American Institute of Physics  (120.137)
  • American Chemical Society (ACS)  (66.957)
  • 2025-2025
  • 2015-2019  (137.867)
  • 1990-1994  (49.227)
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  • 1
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    Glucose as a Potential Chemical Marker for Ice Nucleating Activity in Arctic Seawater and Melt Pond Samples (2019)
    American Chemical Society (ACS)
    In:  EPIC3Environmental Science and Technology, American Chemical Society (ACS), 53(15), pp. 8747-8756, ISSN: 0013-936X
    Details
    Publikationsdatum: 2024-04-12
    Beschreibung: Recent studies pointed to a high ice nucleating activity (INA) in the Arctic sea surface microlayer (SML). However, related chemical information is still sparse. In the present study, INA and free glucose concentrations were quantified in Arctic SML and bulk water samples from the marginal ice zone, the ice-free ocean, melt ponds, and open waters within the ice pack. T50 (defining INA) ranged from −17.4 to −26.8 °C. Glucose concentrations varied from 0.6 to 51 μg/L with highest values in the SML from the marginal ice zone and melt ponds (median 16.3 and 13.5 μg/L) and lower values in the SML from the ice pack and the ice-free ocean (median 3.9 and 4.0 μg/L). Enrichment factors between the SML and the bulk ranged from 0.4 to 17. A positive correlation was observed between free glucose concentration and INA in Arctic water samples (T50(°C) = (−25.6 ± 0.6) + (0.15 ± 0.04)·Glucose(μg/L), RP = 0.66, n = 74). Clustering water samples based on phytoplankton pigment composition resulted in robust but different correlations within the four clusters (RP between 0.67 and 0.96), indicating a strong link to phytoplankton-related processes. Since glucose did not show significant INA itself, free glucose may serve as a potential tracer for INA in Arctic water samples.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
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  • 2
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    The Molecular Fingerprint of Fluorescent Natural Organic Matter Offers Insight into Biogeochemical Sources and Diagenetic State (2018)
    American Chemical Society (ACS)
    In:  EPIC3Analytical Chemistry, American Chemical Society (ACS), 90(24), pp. 14188-14197, ISSN: 0003-2700
    Details
    Publikationsdatum: 2024-04-09
    Beschreibung: Investigating the biogeochemistry of dissolved organic matter (DOM) requires the synthesis of data from several complementary analytical techniques. The traditional approach to data synthesis is to search for correlations between measurements made on the same sample using different instruments. In contrast, data fusion simultaneously decomposes data from multiple instruments into the underlying shared and unshared components. Here, Advanced Coupled Matrix and Tensor Factorization (ACMTF) was used to identify the molecular fingerprint of DOM fluorescence fractions in Arctic fjords. ACMTF explained 99.84% of the variability with six fully shared components. Individual molecular formulas were linked to multiple fluorescence components and vice versa. Molecular fingerprints differed in diversity and oceanographic patterns, suggesting a link to the biogeochemical sources and diagenetic state of DOM. The fingerprints obtained through ACMTF were more specific compared to traditional correlation analysis and yielded greater compositional insight. Multivariate data fusion aligns extremely complex, heterogeneous DOM data sets and thus facilitates a more holistic understanding of DOM biogeochemistry.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 3
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    Da Vinci’s observations of soaring birds (2017)
    American Institute of Physics
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Institute of Physics, 2017. This article is posted here by permission of American Institute of Physics for personal use, not for redistribution. The definitive version was published in Physics Today 70, no. 11 (2017): 78, doi:10.1063/PT.3.3773.
    Beschreibung: With only a minimal flapping, the wandering albatross can circumnavigate the globe. During its peregrinations over the Southern Ocean, the seabird exploits wind shear—the gradient of wind speed—to extract energy for its sustained flight. That same maneuver, called dynamic soaring, is used by pilots of radio-controlled gliders. In flights that take advantage of the shear associated with wind blowing over mountain ridges, the gliders reach air speeds of an astonishing 500 mph. Engineers are currently developing autonomous unmanned vehicles that can use the technique to supplement different sources of energy for sustained flight over the oceans. Possible applications include environmental monitoring, surveillance, and search and rescue.
    Beschreibung: 2018-11-01
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 4
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    Integration of triaxial testing and pore-scale visualization of methane hydrate bearing sediments (2019)
    American Institute of Physics
    In:  Review of Scientific Instruments, 90 (12). p. 124504.
    Details
    Publikationsdatum: 2021-01-08
    Beschreibung: Understanding mechanical interactions between hydrate and hosting sediments is critical for evaluating formation stability and associated environmental impacts of hydrate-bearing sediments during gas production. While core-scale studies of hydrate-bearing sediments are readily available and some explanations of observed results rely on pore-scale behavior of hydrate, actual pore-scale observations supporting the larger-scale phenomena are rarely available for hydrate-bearing sediments, especially with methane as guest molecules. The primary reasons for the scarcity include the challenge of developing tools for small-scale testing apparatus and pore-scale visualization capability. We present a testing assembly that combines pore-scale visualization and triaxial test capability of methane hydrate-bearing sediments. This testing assembly allows temperature regulation and independent control of four pressures: influent and effluent pore pressure, confining pressure, and axial pressure. Axial and lateral effective stresses can be applied independently to a 9.5 mm diameter and 19 mm long specimen while the pore pressure and temperature are controlled to maintain the stability of methane hydrate. The testing assembly also includes an X-ray transparent beryllium core holder so that 3D computed tomography scanning can be conducted during the triaxial loading. This testing assembly permits pore-scale exploration of hydrate-sediment interaction in addition to the traditional stress-strain relationship. Exemplary outcomes are presented to demonstrate applications of the testing assembly on geomechanical property estimations of methane-hydrate bearing sediments.
    Materialart: Article , PeerReviewed
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  • 5
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    Grand Canonical Monte Carlo Simulations on Phase Equilibria of Methane, Carbon Dioxide, and Their Mixture Hydrates (2018)
    American Chemical Society (ACS)
    In:  The Journal of Physical Chemistry B, 122 (42). pp. 9724-9737.
    Details
    Publikationsdatum: 2021-01-08
    Beschreibung: The cage occupancy plays a crucial role in the thermodynamic stability of clathrate hydrates and is an important quantity for understanding the CO2–CH4 replacement phenomenon. In this work, the occupancy isotherms of pure CH4, pure CO2, and their mixture in sI and sII hydrates are studied by GCMC + MD simulations. The adsorption of CH4 and CO2 + CH4 in the sI and sII hydrates can be categorized as the one-site Langmuir type. The calculated occupancy ratio θL/θS and the abundance ratio of CO2 to CH4 vary with the temperature and pressure, which provide the prerequisite information for the prediction of CH4 recovery yield at different conditions in the CO2–CH4 gas exchange process. The phase equilibria of clathrate hydrates of pure gases and mixtures are explored and the corresponding heat of dissociation and hydration numbers are determined. The current investigation provides new perspectives to understand the mechanism behind the gas adsorption behavior of clathrate hydrates.
    Materialart: Article , PeerReviewed
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  • 6
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    Classification of heterogeneous seafloor topography through surface slope distributions (1991)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 90 (4, Pt. 2). pp. 2255-2256.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: Seafloor topography is neither spatially homogeneous, nor does it obey Gaussian statistics; deviations from both of these assumptions are important from a geological and acoustic point of view. It has been found that the distribution of topographic slopes can be used as a primary tool for understanding the sources and extent of spatial heterogeneities and patterns on the seafloor. The covariance function has been widely used to characterize seafloor topography, but requires the assumption of Gaussian joint probability statistics to be valid. For heterogeneous topography characterized by large transient signals such as steep scarps and volcanoes, the covariance becomes dominated by the transients; in contrast the family slope distributions can still be used to derive stable descriptors for regions with large transient signals, as well as regions containing asymmetric features, and regions with only limited sampling. Knowledge of slopes is useful because a direct relation exists between the covariance and the slope distributions at different spatial scales. Studies of the slope distribution provide a means of identifying the presence of the non‐Gaussian elements in the topography, and flagging their spatial locations. The methods used here are demonstrated by applying them to three small patches of topography located within 20 km of each other in the Eastern Pacific. It is found that dominant azimuthal directions and dip angles differ widely between the patches. In addition, asymmetries in the cross‐sectional shapes of faulted abyssal hills are documented. [Work supported by ONR.]
    Materialart: Article , PeerReviewed
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  • 7
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    High‐frequency bottom backscattering: Roughness versus sediment volume scattering (1992)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 92 (2). pp. 962-977.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: High‐frequency bottom acoustic and geoacoustic data from three well‐characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.
    Materialart: Article , PeerReviewed
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  • 8
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    Ray-trace modeling of acoustic Green's function based on the semiclassical (eikonal) approximation (2016)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 140 (4). pp. 2695-2702.
    Details
    Publikationsdatum: 2020-07-16
    Beschreibung: The Green's function (GF) for the scalar wave equation is numerically constructed by an advanced geometric ray-tracing method based on the eikonal approximation related to the semiclassical propagator. The underlying theory is first briefly introduced, and then it is applied to acoustics and implemented in a ray-tracing-type numerical simulation. The so constructed numerical method is systematically used to calculate the sound field in a rectangular (cuboid) room, yielding also the acoustic modes of the room. The simulated GF is rigorously compared to its analytic approximation. Good agreement is found, which proves the devised numerical approach potentially useful also for low frequency acoustic modeling, which is in practice not covered by geometrical methods.
    Materialart: Article , PeerReviewed
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  • 9
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    Sources of variability in consonant perception of normal-hearing listeners (2015)
    American Institute of Physics
    In:  The Journal of the Acoustical Society of America, 138 (3). pp. 1253-1267.
    Details
    Publikationsdatum: 2020-05-11
    Beschreibung: Responses obtained in consonant perception experiments typically show a large variability across stimuli of the same phonetic identity. The present study investigated the influence of different potential sources of this response variability. It was distinguished between source-induced variability, referring to perceptual differences caused by acoustical differences in the speech tokens and/or the masking noise tokens, and receiver-related variability, referring to perceptual differences caused by within- and across-listener uncertainty. Consonant-vowel combinations consisting of 15 consonants followed by the vowel /i/ were spoken by two talkers and presented to eight normal-hearing listeners both in quiet and in white noise at six different signal-to-noise ratios. The obtained responses were analyzed with respect to the different sources of variability using a measure of the perceptual distance between responses. The speech-induced variability across and within talkers and the across-listener variability were substantial and of similar magnitude. The noise-induced variability, obtained with time-shifted realizations of the same random process, was smaller but significantly larger than the amount of within-listener variability, which represented the smallest effect. The results have implications for the design of consonant perception experiments and provide constraints for future models of consonant perception.
    Materialart: Article , PeerReviewed
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  • 10
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    Use of Waste-Derived Biochar to Remove Copper from Aqueous Solution in a Continuous-Flow System (2017)
    American Chemical Society (ACS)
    In:  Industrial & Engineering Chemistry Research, 56 (44). pp. 12755-12762.
    Details
    Publikationsdatum: 2020-02-06
    Beschreibung: The discharges from industrial processes constitute the main source of copper contamination in aqueous ecosystems. In this study we investigated the capacity of different types of biochar (derived from chicken manure, eucalyptus, corncob, olive mill and pine sawdust) to remove copper from aqueous solution in a continuous-flow system. The flow rate of the system strongly influenced the amount of copper retained. The adsorption to the corncob biochar varied from 5.51 to 3.48 mg Cu g-1 as the flux decreased from 13 to 2.5 mL min-1. The physicochemical characteristics of biochar determine the copper retention capacity and the underlying immobilization mechanisms. Biochars with high inorganic contents retain the largest amounts of copper and may be suitable for using in water treatment systems to remove heavy metals. The copper retention capacity of the biochars ranged between ~1.3 and 26 mg g-1 and varied in the following order: chicken manure 〉 olive mill 〉〉 corncob 〉 eucalyptus 〉 sawdust pine.
    Materialart: Article , PeerReviewed
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