Rock glacier inventory of the western Nyainqêntanglha Range, Tibetan Plateau, supported by InSAR time series and automated classification

The western Nyainqêntanglha Range on the Tibetan Plateau reaches an elevation of 7,162 m and is characterized by an extensive periglacial environment under semi-arid climatic conditions. Rock glaciers play an important part of the water budget in high mountain areas and recent studies suggest that they may even act as climate-resistant water storages. In this study we present the first rock glacier inventory of this region containing 1,433 rock glaciers over an area of 4,622 km. To create the most reliable inventory we combine manually created rock glacier outlines with an automated classification approach. The manual outlines were generated based on surface elevation data, optical satellite imagery and a surface velocity estimation. This estimation was generated via InSAR time series analysis with Sentinel-1 data from 2016 to 2019. Our pixel-based automated classification was able to correctly identify 87.8% of all rock glaciers in the study area at a true positive rate of 69.5%. In total, 65.9% of rock glaciers are classified as transitional with surface velocities of 1–10 cm/yr. In total, 18.5% are classified as active with higher velocities of up to 87 cm/yr. The southern windward side of the mountain range contains more numerous and more active rock glaciers. We attribute this to higher moisture availability supplied by the Indian Monsoon

Bestimmung flächenhafter vertikaler Landbewegungen entlang der deutschen Nord- und Ostseeküste

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Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors

Organometallic liquids provide good properties for ionization detectors. TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and Cherenkov photon readout for Positron Emission Tomography. In this work, we present studies for the handling of TMBi at different electric fields and under different environmental conditions to find applicable configurations for the suppression of electrical breakdowns in TMBi at room temperature. A simple glass cell with two electrodes filled with TMBi was constructed and tested under different operation conditions. Working at the vapour pressure of TMBi at room temperature of about 40 mbar and electric fields of up to 20 kV/cm in presence of a small oxygen contamination we found the formation of a discharge channel in the liquid and a steady increase in the current. Further reduction of pressure by pumping caused the TMBi to boil and a spontaneous combustion. Eliminating the oxygen contamination led the TMBi under the same condition to only decompose. When operating the setup under an argon atmosphere of 1 bar we did not observe breakdowns of the electrical potential up to field strengths of 20 kV/cm. Still, in presence of a small oxygen contamination fluctuating currents in the nA range were observed, but no decomposition or combustion. We conclude from our experiments that TMBi at room temperature in a pure argon atmosphere of 1 bar remains stable against electrical breakdown at least up to electric field strengths of 20 kV/cm, presumably because the formation of gaseous TMBi was prevented.Comment: 14 page, 8 figure

AJAM-A–tetraspanin–αvβ5 integrin complex regulates contact inhibition of locomotion

Contact inhibition of locomotion (CIL) is a process that regulates cell motility upon collision with other cells. Improper regulation of CIL has been implicated in cancer cell dissemination. Here, we identify the cell adhesion molecule JAM-A as a central regulator of CIL in tumor cells. JAM-A is part of a multimolecular signaling complex in which tetraspanins CD9 and CD81 link JAM-A to αvβ5 integrin. JAM-A binds Csk and inhibits the activity of αvβ5 integrin-associated Src. Loss of JAM-A results in increased activities of downstream effectors of Src, including Erk1/2, Abi1, and paxillin, as well as increased activity of Rac1 at cell–cell contact sites. As a consequence, JAM-A-depleted cells show increased motility, have a higher cell–matrix turnover, and fail to halt migration when colliding with other cells. We also find that proper regulation of CIL depends on αvβ5 integrin engagement. Our findings identify a molecular mechanism that regulates CIL in tumor cells and have implications on tumor cell dissemination.publishedVersio

Disruption of the Lipid-Transporting LdMT-LdRos3 Complex in Leishmania donovani Affects Membrane Lipid Asymmetry but Not Host Cell Invasion

Maintenance and regulation of the asymmetric lipid distribution across eukaryotic plasma membranes is governed by the concerted action of specific membrane proteins controlling lipid movement across the bilayer. Here, we show that the miltefosine transporter (LdMT), a member of the P4-ATPase subfamily in Leishmania donovani, and the Cdc50-like protein LdRos3 form a stable complex that plays an essential role in maintaining phospholipid asymmetry in the parasite plasma membrane. Loss of either LdMT or LdRos3 abolishes ATP-dependent transport of NBD-labelled phosphatidylethanolamine (PE) and phosphatidylcholine from the outer to the inner plasma membrane leaflet and results in an increased cell surface exposure of endogenous PE. We also find that promastigotes of L. donovani lack any detectable amount of phosphatidylserine (PS) but retain their infectivity in THP-1-derived macrophages. Likewise, infectivity was unchanged for parasites without LdMT-LdRos3 complexes. We conclude that exposure of PS and PE to the exoplasmic leaflet is not crucial for the infectivity of L. donovani promastigotes

Ableitung vertikaler Landbewegungen an der deutschen Nord- und Ostseeküste aus GNSS- und PS-Auswertungen

Die Ableitung und Modellierung von vertikalen Landbewegungen an der deutschen Nord- und Ostseeküste hat u.a. das Ziel, den Einfluss der Landsenkung bzw. –hebung an der Küste von scheinbaren Pegelanstiegen trennen zu können. Für die Berechnung eines großräumigen landseitigen Bewegungsmodells ist es zunächst erforderlich die Höhenänderungen über längere Zeiträume aus GNSS- und Radarinterferometrie-Beobachtungen zu bestimmen. Im Rahmen dieses Beitrages werden die Berechnungsschritte und erste vorläufige Ergebnisse für die Höhenänderungen an den GNSS-Stationen für den Zeitraum von 2010 bis 2016, sowie Zeitreihen aus der PS-Interferometrie der Sentinel-1 Satelliten für die Jahre 2014 bis 2018 vorgestellt

Permafrost-Detektion mittels Fernerkundung und Geophysik auf dem tibetischen Plateau

In this study we combine geophysical techniques in the form of microwave remote sensing and Electrical Resistance Tomography (ERT) interferometry to study the extent of permafrost in the catchment of Lake Nam Co on the Tibetan plateau. Interferometric Synthetic Aperture Radar (InSAR) is a powerful technique to monitor permafrost related surface displacement processes on a large scale. However, the insensitivity of InSAR data regarding northward or southward directed motion and its inability to detect permafrost when no displacement occurs, impose significant limitations to its application in permafrost study. We highlight those limitations on a rock glacier within Qugaqie basin, a sub-catchment within the Nyainqêntanglha range, and show how ERT can be used to compensate for them. With this combined approach we will create an inventory of rock glaciers and constrain the extent of permafrost areas within the Nyainqêntanglha range

Surface displacement and velocity models at Lake NamCo (Tibetan Plateau) derived from Sentinel-1 data via InSAR time series analysis

These datasets display seasonal and multiannual surface displacement models based on microwave data of ESA's Sentinel-1 satellite system. The data was processed via Interferometric Aperture Radar (InSAR) time series techniques, using an adapted version of the Small BAseline Subset (SBAS) algorithm. The purpose of this study is to understand sediment flux mechanics, especially those related to permafrost and periglacial landforms, and how the changing climate may affect these processes in the NamCo area in the future. To that end we developped three surface displacement models. The freeze-thaw model describes seasonal surface displacement caused by freezing and thawing of the active layer in autumn and spring respectively. We observe vertical amplitudes of up to 20 mm in areas, where the water content of the soil is high. The multiannual velocity model shows the mean surface velocity over the entire time period of approximetly 3-4 years. Time series results of regions with a small slopes were decomposed from ascending and descending data to show the surface velocity component in vertical and east-west direction. Time series results of regions with a larger slope were projected in the downslope direction, with the assumption that creep and sliding processes are dominant, which transport sediment along the direction of the steepest slope. Most flat areas are relatively stable but we observe material accumulation near parts of the rivers and subsidence in some permafrost areas, which could be related to permafrost degradation. The fastest landforms are rockglaciers, which move with velocities of up to 24 cm/yr. The third model is the seasonal velocity model, where we compare the line-of-sight velocities of sloped areas in the summer months to the winter months. Most slopes slide signifcantly faster in summer, driven by the thawing ground due to higher air temperature and monsoonal rainfall, while most of the fastest moving landforms move with a constant velocity throughout the year

InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau

Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, increased precipitation and permafrost degradation. The latter in particular is associated with increased slope instability and an increase in mass-wasting processes, which pose a danger to infrastructure in the vicinity. Interferometric synthetic aperture radar (InSAR) analysis is well suited to study the displacement patterns driven by permafrost processes, as they are on the order of millimeters to decimeters. The Nyainqêntanglha range on the Tibetan Plateau lacks high vegetation and features relatively thin snow cover in winter, allowing for continuous monitoring of those displacements throughout the year. The short revisit time of the Sentinel-1 constellation further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study heave and subsidence in the valleys, seasonally accelerated sliding and linear creep on the slopes. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence. We observe a clear cycle of heave and subsidence in the valleys, where freezing of the active layer followed by subsequent thawing cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr−1. During the summer months surface displacement velocities more than double on most unstable slopes due to freeze–thaw processes driven by higher temperatures and increased precipitation. Specific landforms, most of which have been identified as rock glaciers, protalus ramparts or frozen moraines, reach velocities of up to 18 cm yr−1. Their movement shows little seasonal variation but a linear pattern indicating that their displacement is predominantly gravity-driven