Imaging seismic wave-fields with AlpArray and neighboring European networks

The AlpArray experiment and the deployment of Swath-D together with the dense permanent network in Italy allow for detailed imaging of the spatio-temporal imaging complexity of seismic wave-fields within the greater Alpine region. The distance of any point within the area to the nearest station is less than 30 km, resulting in an average inter-station distance of about 45 km. With a much denser deployment in a smaller region of the Alps (320 km in length and 140 km wide), the Swath-D network possesses an average inter-station distance of about 15 km. We show that seismogram sections with a spatial sampling of less than 5 km can be obtained using recordings of these regional arrays for just a single event. Multiply reflected body waves can be observed for up to 2 h after source time. In addition, we provide and describe animations of long-period seismic wave-fields using recordings of about 1300–1600 broadband stations for six representative earthquakes. These illustrate the considerable spatio-temporal variability of the wave-field’s properties at a high lateral resolution. Within denser station distributions like those provided by Swath-D, even shorter period body and surface wave features can be recovered. The decrease of the horizontal wavelength from to to surface waves, deviations from spherically symmetric wavefronts, and the capability to detect multi-orbit arrivals are demonstrated qualitatively by the presented wave-field animations, which are a valuable tool for educational, quality control, and research purposes. We note that the information content of the acquired datasets can only be adequately explored by application of appropriate quantitative methods accounting for the considerable complexity of the seismic wave-fields as revealed by the now available station configuration.

Direct-imaging DOEs for high-NA multi-spot confocal surface measurement

Diffractive lens arrays with overlapping apertures can produce spot arrays with high numerical apertures (NAs). Combined with low-NA objectives, they can measure a large area with high lateral resolution. However, for surface measurements, the axial resolution of such setups is still fundamentally limited by the objectives. In this work, we propose a new design of diffractive optical elements (DOEs) to overcome this problem. The proposed Direct-imaging DOEs can perform 3D high-NA multi-spot surface measurements. Laterally, a non-vanishing contrast up to 1448 lp/mm is measured with a USAF resolution target. Axially, an average height of 917.5 nm with a standard deviation of 49.9 nm is measured with a calibrated step height target of 925.5 nm.

Evolution of Adsorption Heights in the On-Surface Synthesis and Decoupling of Covalent Organic Networks on Ag(111) by Normal-Incidence X-ray Standing Wave

Structural characterization in on-surface synthesis is primarily carried out by Scanning Probe Microscopy (SPM) which provides high lateral resolution. Yet, important fresh perspectives on surface interactions and molecular conformations are...

Live monitoring of ROS-induced cytosolic redox changes with roGFP2-based sensors in plants

Plant cells produce reactive oxygen species (ROS) as by-products of oxygen metabolism and for signal transduction. Depending on their concentration and their site of production, ROS can cause oxidative damage within the cell, and must be effectively scavenged. Detoxification of the most stable ROS, hydrogen peroxide (H2O2), via the glutathione-ascorbate pathway may transiently alter the glutathione redox potential (EGSH). Changes in EGSH can thus be considered as a proxy of the oxidative load in the cell. Genetically encoded probes based on roGFP2 enable extended opportunities for in vivo monitoring of H2O2 and EGSH dynamics. Here, we report detailed protocols for live monitoring of both parameters in the cytosol with the probes Grx1-roGFP2 for EGSH and roGFP2-Orp1 for H2O2, respectively. The protocols have been adapted for live cell imaging with high lateral resolution on a confocal microscope and for multiparallel measurements in whole organs or intact seedlings in a fluorescence microplate reader. Elicitor-induced ROS generation is used as an example for illustration of the opportunities for dynamic ROS measurements that can easily be transferred to other scientific questions and model systems.

Multifunctional Reactive MALDI Matrix Enabling High-Lateral Resolution Dual Polarity MSI and Lipid C=C Position-Resolved MS2I

Local lipid variations in tissues are readily revealed with mass spectrometry imaging (MSI) methods and resulting lipid distributions serve as bioanalytical signatures to reveal cell- or tissue-specific lipids. Comprehensive MSI lipid mapping requires measurements in both ion polarities. Additionally, structural lipid characterization is necessary to link lipid structure to lipid function. Whereas some structural elements of lipids are readily derived from high-resolution mass spectrometry (MS) and tandem-MS (MSn), the localization of C=C double bonds (DBs) requires specialized fragmentation and/or functionalization methods. In this work, we identify a multifunctional matrix-assisted laser desorption/ionization (MALDI) matrix for spatially-resolved lipidomics investigations that reacts with lipids in Paternò-Büchi (PB) reactions during laser irradiation facilitating DB position assignment and allows dual polarity high-resolution MALDI-MSI and MALDI MS2I studies. By screening twelve compounds for improved ionization efficiency in positive/negative ion mode and PB functionalization yield compared to the previously introduced reactive MALDI matrix benzophenone, benzoylpyridine (BzPy) is identified as the best candidate. The multifunctional character of the new matrix enables DB localization of authentic standards belonging to twelve lipid classes and helps to assign 506/365 lipid features in positive/negative ion mode from mouse cerebellum tissue. The analytical capabilities of BzBy as a multifunctional MALDI-MSI matrix are demonstrated by imaging endogenous and PB-functionalized lipids in mouse kidney sections with 7 µm lateral resolution in both ion modes. Tracking diagnostic lipid DB position fragment ions in mouse pancreas tissue with down to 10 µm pixel size allows to identify islets of Langerhans associated lipid isomer upregulation or depletion. <br>

Multifunctional Reactive MALDI Matrix Enabling High-Lateral Resolution Dual Polarity MSI and Lipid C=C Position-Resolved MS2I

Local lipid variations in tissues are readily revealed with mass spectrometry imaging (MSI) methods and resulting lipid distributions serve as bioanalytical signatures to reveal cell- or tissue-specific lipids. Comprehensive MSI lipid mapping requires measurements in both ion polarities. Additionally, structural lipid characterization is necessary to link lipid structure to lipid function. Whereas some structural elements of lipids are readily derived from high-resolution mass spectrometry (MS) and tandem-MS (MSn), the localization of C=C double bonds (DBs) requires specialized fragmentation and/or functionalization methods. In this work, we identify a multifunctional matrix-assisted laser desorption/ionization (MALDI) matrix for spatially-resolved lipidomics investigations that reacts with lipids in Paternò-Büchi (PB) reactions during laser irradiation facilitating DB position assignment and allows dual polarity high-resolution MALDI-MSI and MALDI MS2I studies. By screening twelve compounds for improved ionization efficiency in positive/negative ion mode and PB functionalization yield compared to the previously introduced reactive MALDI matrix benzophenone, benzoylpyridine (BzPy) is identified as the best candidate. The multifunctional character of the new matrix enables DB localization of authentic standards belonging to twelve lipid classes and helps to assign 506/365 lipid features in positive/negative ion mode from mouse cerebellum tissue. The analytical capabilities of BzBy as a multifunctional MALDI-MSI matrix are demonstrated by imaging endogenous and PB-functionalized lipids in mouse kidney sections with 7 µm lateral resolution in both ion modes. Tracking diagnostic lipid DB position fragment ions in mouse pancreas tissue with down to 10 µm pixel size allows to identify islets of Langerhans associated lipid isomer upregulation or depletion. <br>