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- ItemSoil hydraulic interpretation of nuclear magnetic resonance measurements based on circular and triangular capillary models(Hoboken, NJ : Wiley, 2021) Costabel, Stephan; Hiller, ThomasGeophysical nuclear magnetic resonance (NMR) applications are used to estimate pore size distributions (PSDs) of rocks and sediments. This is commonly realized by empirical calibration using information about the surface-to-volume ratio of the material. Recent research has developed joint inversion concepts for NMR relaxation data that provides the PSD with a minimum of information. The application requires the NMR signal of a sample at saturation and at least one at partial saturation and at known suction. The new inversion concept physically simulates the desaturation process as part of the forward operator. The cross-section of the model capillaries in the underlying bundle can be either circular or triangular. Our study investigates the performance of the NMR joint inversion to predict water retention function (WRF) and capillary-based hydraulic conductivity (Kcap) as functions of saturation for different sands. The angularity of the pores has no significant impact on the estimated WRF but affects the Kcap estimation significantly. Our study shows that the WRF is predicted reliably for sand samples under fast diffusion conditions. The Kcap estimations are also plausible but tend to systematic overestimation, for which we identified the tortuosity being the main reason. Because NMR relaxation data generally do not provide tortuosity information, a plausible tortuosity model remains an issue of classical calibration. Further development of the approach will thus consider tortuosity measurements (e.g., by electrical resistivity measurements and/or gradient NMR) and will consider the relaxation mechanisms outside fast diffusion conditions to enhance its applicability for coarse soils.
- ItemFeasibility study on prepolarized surface nuclear magnetic resonance for soil moisture measurements(Hoboken, NJ : Wiley, 2021) Hiller, Thomas; Costabel, Stephan; RadiÄ, Tino; Dlugosch, Raphael; MĆ¼llerāPetke, MikeIn the past few years, small-scale (2 m) prepolarized surface nuclear magnetic resonance (SNMR) has gained increasing interest in the research community. As recent studies demonstrated, the application of a strong prepolarization field enhances the SNMR signal of coils with a footprint <1 m2 up to a level that even enables investigations in urban areas. In particular, it is expected that this noninvasive method provides the soil moisture distribution in the upper 2 m of the subsurface in the near future. However, until now all field experiments have been carried out on water reservoirs only, in an approach to test and implement this rather new technique into the field of SNMR applications. We present the first prepolarized SNMR measurement on a real soil and demonstrate the general feasibility of this technique to qualitatively and quantitatively detect soil moisture in the upper first 0.5 m. Our soil moisture measurements are validated by independent time domain reflectometry data. To complement the field experiments with numerical simulations, we adapted the underlying SNMR spin dynamics simulations and account for prepolarization switch-off effects in the forward modeling of the SNMR excitation.
- ItemA novel universal algorithm for filament network tracing and cytoskeleton analysis(Hoboken, NJ : Wiley, 2021) Flormann, Daniel A.D.; Schu, Moritz; Terriac, Emmanuel; Thalla, Divyendu; Kainka, Lucina; Koch, Marcus; Gad, Annica K.B.; LautenschlƤger, FranziskaThe rapid development of advanced microscopy techniques over recent decades has significantly increased the quality of imaging and our understanding of subcellular structures, such as the organization of the filaments of the cytoskeleton using fluorescence and electron microscopy. However, these recent improvements in imaging techniques have not been matched by similar development of techniques for computational analysis of the images of filament networks that can now be obtained. Hence, for a wide range of applications, reliable computational analysis of such two-dimensional methods remains challenging. Here, we present a new algorithm for tracing of filament networks. This software can extract many important parameters from grayscale images of filament networks, including the mesh hole size, and filament length and connectivity (also known as Coordination Number). In addition, the method allows sub-networks to be distinguished in two-dimensional images using intensity thresholding. We show that the algorithm can be used to analyze images of cytoskeleton networks obtained using different advanced microscopy methods. We have thus developed a new improved method for computational analysis of two-dimensional images of filamentous networks that has wide applications for existing imaging techniques. The algorithm is available as open-source software.
- ItemAcidāBase Interactions of Pyrazine, Ethyl Acetate, Diāalcohols, and Lysine with the cyclic Alumosiloxane (Ph2SiO)8[Al(O)OH]4 in View of Mimicking Al2O3(H2O) Surface Reactions(Hoboken, NJ : Wiley, 2020) Veith, Michael; Kolano, David; Huch, VolkerThe etherate of (Ph2SiO)8[Al(O)OH]4 can be transformed into the pyrazine adduct (Ph2SiO)8[Al(O)OH]4Ā·3N(C2H2)2N (1), the ethyl acetate adduct (Ph2SiO)8[Al(O)OH]4Ā·3H3CāC(O)OC2H5 (2), the 1,6āhexane diol adduct (Ph2SiO)8[Al(O)OH]4Ā·2HOāCH2(CH2)4CH2āOH (3) and the 1,4ācyclohexane diol adduct (Ph2SiO)8[Al(O)OH]4Ā·4HOāCH(CH2CH2)2CHāOH (4). In all compounds the OH groups of the starting material bind to the bases through OāHĀ·Ā·Ā·N (1) or OāHĀ·Ā·Ā·O hydrogen bonds (2, 3, 4) as found from singleācrystal Xāray diffraction analyses. Whereas in 1 only three of the central OH groups bind to the pyrazines, in 2 two of them bind to the same carbonyl oxygen atom of the ethyl acetate resulting in an unprecedented OāHĀ·Ā·Ā·OĀ·Ā·Ā·HāO double hydrogen bridge. The hexane diol adduct 3 in the crystal forms a oneādimensional coordination polymer with an intramolecularly to two OH groups grafted hexane diol loop, while the second hexane diol is connecting intermolecularly. In the cyclohexane diol adduct 4 all OH groups of the central Al4(OH)4 ring bind to different diols, leaving one alcohol group per diol uncoordinated. These āfreeā OH groups form an (OāHĀ·Ā·Ā·)4 assembly creating a threeādimensional overall structure. When reacting with (Ph2SiO)8[Al(O)OH]4 lysine loses water, turns into the cyclic 3āaminoā2āazepanone, and transforms through chelation of one of the aluminum atoms the starting material into a new polycycle. The isolated compound has the composition (Ph2SiO)12[Al(O)OH]4[Al2O3]2Ā·4 C6H12N2OĀ·6(CH2)4O (5).
- ItemCombining BatteryāType and Pseudocapacitive Charge Storage in Ag/Ti3C2Tx MXene Electrode for Capturing Chloride Ions with High Capacitance and Fast Ion Transport(Hoboken, NJ : Wiley, 2020) Liang, Mingxing; Wang, Lei; Presser, Volker; Dai, Xiaohu; Yu, Fei; Ma, JieThe recent advances in chlorideāion capturing electrodes for capacitive deionization (CDI) are limited by the capacity, rate, and stability of desalination. This work introduces Ti3C2Tx/Ag synthesized via a facile oxidationāreduction method and then uses it as an anode for chlorideāion capture in CDI. Silver nanoparticles are formed successfully and uniformly distributed with the layeredāstructure of Ti3C2Tx. All Ti3C2Tx/Ag samples are hydrophilic, which is beneficial for water desalination. Ti3C2Tx/Ag samples with a low charge transfer resistance exhibit both pseudocapacitive and battery behaviors. Herein, the Ti3C2Tx/Ag electrode with a reaction time of 3 h exhibits excellent desalination performance with a capacity of 135 mg Clā gā1 at 20 mA gā1 in a 10 Ć 10ā3 m NaCl solution. Furthermore, low energy consumption of 0.42 kWh kgā1 Clā and a desalination rate of 1.5 mg Clā gā1 minā1 at 50 mA gā1 is achieved. The Ti3C2Tx/Ag system exhibits fast rate capability, high desalination capacity, low energy consumption, and excellent cyclability, which can be ascribed to the synergistic effect between the battery and pseudocapacitive behaviors of the Ti3C2Tx/Ag hybrid material. This work provides fundamental insight into the coupling of battery and pseudocapacitive behaviors during Clā capture for electrochemical desalination.
- ItemSelective OutāofāPlane Optical Coupling between Vertical and Planar Microrings in a 3D Configuration(Hoboken, NJ : Wiley, 2020) Valligatla, Sreeramulu; Wang, Jiawei; Madani, Abbas; Naz, Ehsan Saei Ghareh; Hao, Qi; Saggau, Christian Niclaas; Yin, Yin; Ma, Libo; Schmidt, Oliver G.3D photonic integrated circuits are expected to play a key role in future optoelectronics with efficient signal transfer between photonic layers. Here, the optical coupling of tubular microcavities, supporting resonances in a vertical plane, with planar microrings, accommodating ināplane resonances, is explored. In such a 3D coupled composite system with largely mismatched cavity sizes, periodic mode splitting and resonant mode shifts are observed due to modeāselective interactions. The axial direction of the microtube cavity provides additional design freedom for selective mode coupling, which is achieved by carefully adjusting the axial displacement between the microtube and the microring. The spectral anticrossing behavior is caused by strong coupling in this composite optical system and is excellently reproduced by numerical modeling. Interfacing tubular microcavities with planar microrings is a promising approach toward interlayer light transfer with added optical functionality in 3D photonic systems.
- ItemTesting bias adjustment methods for regional climate change applications under observational uncertainty and resolution mismatch(Hoboken, NJ : Wiley, 2020) Casanueva, Ana; Herrera, Sixto; Iturbide, Maialen; Lange, Stefan; Jury, Martin; Dosio, Alessandro; Maraun, Douglas; GutiĆ©rrez, JosĆ© M.Systematic biases in climate models hamper their direct use in impact studies and, as a consequence, many statistical bias adjustment methods have been developed to calibrate model outputs against observations. The application of these methods in a climate change context is problematic since there is no clear understanding on how these methods may affect key magnitudes, for example, the climate change signal or trend, under different sources of uncertainty. Two relevant sources of uncertainty, often overlooked, are the sensitivity to the observational reference used to calibrate the method and the effect of the resolution mismatch between model and observations (downscaling effect). In the present work, we assess the impact of these factors on the climate change signal of temperature and precipitation considering marginal, temporal and extreme aspects. We use eight standard and state-of-the-art bias adjustment methods (spanning a variety of methods regarding their natureāempirical or parametricā, fitted parameters and trend-preservation) for a case study in the Iberian Peninsula. The quantile trend-preserving methods (namely quantile delta mapping (QDM), scaled distribution mapping (SDM) and the method from the third phase of ISIMIP-ISIMIP3) preserve better the raw signals for the different indices and variables considered (not all preserved by construction). However, they rely largely on the reference dataset used for calibration, thus presenting a larger sensitivity to the observations, especially for precipitation intensity, spells and extreme indices. Thus, high-quality observational datasets are essential for comprehensive analyses in larger (continental) domains. Similar conclusions hold for experiments carried out at high (approximately 20 km) and low (approximately 120 km) spatial resolutions. Ā© 2020 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society.
- ItemContact Aging Enhances Adhesion of Micropatterned Silicone Adhesives to Glass Substrates(Hoboken, NJ : Wiley, 2020) Thiemecke, Jonathan; Hensel, RenĆ©The transfer of biological concepts into synthetic micropatterned adhesives has recently enabled a new generation of switchable, reversible handling devices. Over the last two decades, many design principles have been explored that helped to understand the underlying mechanics and to optimize such adhesives for certain applications. An aspect that has been overlooked so far is the influence of longer hold times on the adhesive contacts. Exemplarily, the pullāoff stress and work of separation of a micropatterned adhesive specimen are enhanced by factors 3 and 6, respectively, after 1000 min in contact with a glass substrate. In addition to such global measures, the increase of adhesion of all individual micropillars is analyzed. It is found that contact aging varied across the microarray, as it drastically depends on local conditions. Despite great differences on the micropillar scale, the adhesion of entire specimens increased with very similar power laws, as this is determined by the mean contact ageing of the individual structures. Overall, contact aging must be critically evaluated before using micropatterned adhesives, especially for longāterm fixations and material combinations that are chemically attractive to each other.
- ItemVoltageāControlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites(Hoboken, NJ : Wiley, 2020) Zehner, Jonas; Soldatov, Ivan; Schneider, Sebastian; Heller, RenĆ©; Khojasteh, Nasrin B.; Schiemenez, Sandra; FƤhler, Sebastian; Nielsch, Kornelius; SchƤfer, Rudolf; Leistner, KarinHigh energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redoxābased (magnetoāionic) voltage control of magnetism is a promising roomātemperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magnetoāionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltageāinduced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial ināplane anisotropy. In the initial iron oxide/iron films, NĆ©el wall interactions stabilize a blocked state with high coercivity. During the voltageātriggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magnetoāionic deblocking mechanism, which relies on changes of the NĆ©el wall interactions, and of the microstructural domaināwallāpinning sites. With this approach, voltageācontrolled 180Ā° magnetization switching with high energyāefficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defectācontrolled materials in general.
- ItemLabelāFree Imaging of Cholesterol Assemblies Reveals Hidden Nanomechanics of Breast Cancer Cells(Hoboken, NJ : Wiley, 2020) Dumitru, Andra C.; Mohammed, Danahe; Maja, Mauriane; Yang, Jinsung; Verstraeten, Sandrine; del Campo, Aranzazu; Mingeot-Leclercq, Marie-Paule; Tyteca, Donatienne; Alsteens, DavidTumor cells present profound alterations in their composition, structural organization, and functional properties. A landmark of cancer cells is an overall altered mechanical phenotype, which so far are linked to changes in their cytoskeletal regulation and organization. Evidence exists that the plasma membrane (PM) of cancer cells also shows drastic changes in its composition and organization. However, biomechanical characterization of PM remains limited mainly due to the difficulties encountered to investigate it in a quantitative and labelāfree manner. Here, the biomechanical properties of PM of a series of MCF10 cell lines, used as a model of breast cancer progression, are investigated. Notably, a strong correlation between the cell PM elasticity and oncogenesis is observed. The altered membrane composition under cancer progression, as emphasized by the PMāassociated cholesterol levels, leads to a stiffening of the PM that is uncoupled from the elastic cytoskeletal properties. Conversely, cholesterol depletion of metastatic cells leads to a softening of their PM, restoring biomechanical properties similar to benign cells. As novel therapies based on targeting membrane lipids in cancer cells represent a promising approach in the field of anticancer drug development, this method contributes to deciphering the functional link between PM lipid content and disease.