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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8520-8529 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Multiple spin echoes arise after "nonlinear" evolution of coherences in the presence of modulated demagnetizing fields. Such modulations can be prepared, for example, with the aid of a sequence of two 90° radio-frequency pulses in the presence of pulsed or steady field gradients. The echo amplitudes are sensitively attenuated by translational diffusion so that diffusivities can be determined on this basis. Homo- and heteronuclear variants of multiple-echo pulse sequences are considered here. A formalism based on the Bloch/Torrey equations is presented that describes the features displayed by the experimental data. The resulting attenuation formula for the homonuclear case generally accounts for all radio-frequency and field gradient pulse intervals occurring in the frame of this "pulsed gradient nonlinear spin echo" technique. Furthermore, an analogous formalism is reported for the heteronuclear case where the two nuclear species may populate different molecules with different diffusivities. It is shown that, apart from the conventional attenuation mechanism due to incomplete refocusing of the coherences, there are three additional processes contributing to homo- and heteronuclear multiple-echo attenuation by diffusion: Leveling of the magnetization helix and hence of the z magnetization grid formed by the second radiofrequency pulse, further leveling of that z magnetization grid by displacements of the dipoles producing the grid, and molecular displacements relative to the spatially modulated demagnetizing field. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2015-05-11
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
    Format: application/zip
    Format: application/zip
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  • 3
    Publication Date: 2021-12-15
    Description: Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (~3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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