Zur Frage nach der Resistenz verschiedener Tiere gegenüber Arsen

http://www.ester.ee/record=b3582455*es

Geodetic Stereo SAR With Small Multi-Directional Radar Reflectors

This paper evaluates the applicability and achievable SAR accuracy for octahedrons – a combination of eight corner reflectors with a common phase centre. In an experiment at the observatory in Wettzell from July to November 2015 these cost-efficient and mobile radar targets were measured with TerraSAR-X Staring Spotlight and High-Resolution Spotlight. Applying the geodetic stereo SAR concept, octahedrons are very robust for absolute 3D positioning through their backscattering in multiple directions. Using octahedrons with as size of 47 cm, we achieve 3σ standard deviations of about 3 cm for east, north and height components. For individual measurements in Staring Spotlight the standard deviation shows 1.4 cm in range and 3.2 cm in azimuth

Potential of global SAR positioning for geodetic applications - Lessons learned from TerraSAR-X and Sentinel-1

With our implementation of geodetic techniques for data processing and data corrections, spaceborne Synthetic Aperture Radar (SAR) has attained the possibility of fixing global positions of dedicated radar points at the low centimeter accuracy level. Such points can be created by passive radar corner reflectors, and the positioning method relies on the inherent ranging capabilities of SAR sensors. Thus, we may refer to the method as SAR imaging geodesy or geodetic SAR. Determining accurate long-term global positions of objects on the Earth’s surface is typically associated with Global Navigation Satellite Systems (GNSS) and one of the core elements of modern space geodesy. In order to do so, high-grade geodetic equipment with constant power supply, as well as the possibility for data transfer are required, limiting dense application on a large scale and poses difficulties for very remote areas with little or no infrastructure. Whereas certain regions like Japan or the San Andreas Fault are densely covered by GNSS such coverage may not be achievable everywhere on the globe. To improve the situation, we present a concept of jointly using SAR and GNSS for expanding geodetic positioning to applications requiring long-term coordinate monitoring. In future, the use of cost-effective passive reflectors in X-band SAR or low-cost battery-powered active transponders, which are currently in development for C-band SAR, could provide global coordinates anywhere where SAR imagery is acquired under multiple incidence angles. The main requirements are precise orbit determination, processing of the SAR imagery omitting geometric approximations, as well as the rigorous correction of perturbations caused by atmospheric path delay and signals of the dynamic Earth. If a reflector or transponder already has known reference coordinates, e.g. from co-location with GNSS, the perturbing signals can be mitigated for the surrounding radar points by applying differential SAR positioning techniques similar to differential GNSS, provided that all the points are included in the same radar image. In this contribution we discuss the geodetic SAR methods with respect to our experiences gained with the TerraSAR-X mission, and present first results of experiments carried out with Sentinel-1 data

Ultrasonic Guided Waves Simulation in SHM Design – Finite Element Modeling and Model Data Handling

Over the last years a lot of scientific work has been done regarding structural health monitoring (SHM) systems. Introducing SHM systems offer the possibility of saving weights going along with other advantages, e.g. an improved condition-based maintenance of the structure, decreasing fuel consumption. In case of thin-walled lightweight structures as they are used for aerospace applications SHM concepts based on ultrasonic guided waves are very promising. The large experimental effort of designing such SHM systems can be significantly reduced by accompanying simulations. Simulation techniques to analyze the guided wave propagation have been developed using different numerical methods, e.g. conventional and higher order finite element methods(FEM), elastodynamic finite integration technique (EFIT), finite cell methods. To investigate the static and dynamic behavior of thin-walled lightweight structures shell-type finite element models are widely used. For general purpose SHM simulations it is advantageous to employ these models also to analyze wave propagation phenomena without switching to a special tool. Only few modifications regarding mesh refinement are needed. Therefore, we present a strategy to simulate the guided wave propagation in layered composite structures by using finite shell elements of Reissner-Mindlin type. The results are benchmarked with experimental data coming from the Open Guided Waves project (http://openguidedwaves.de/). The usability of such simulations as well as the comparison with experimental data is simplified by easy access to the results in a standardized data format using open-source tools. Thus, we particularly focus on aspects of model and result data handling, post-processing and visualization. The implementations presented here are based on the recently introduced FE data standard VMAP (www.vmap.eu.com). The approach enables the combination of simulation data in a central data container coming from different analysis tools. It yields to an improved evaluation of the proposed SHM system and allows the direct comparison with experimental data

In-depth verification of Sentinel-1 and TerraSAR-X geolocation accuracy using the Australian Corner Reflector Array

This article shows how the array of corner reflectors (CRs) in Queensland, Australia, together with highly accurate geodetic synthetic aperture radar (SAR) techniques—also called imaging geodesy—can be used to measure the absolute and relative geometric fidelity of SAR missions. We describe, in detail, the end-to-end methodology and apply it to TerraSAR-X Stripmap (SM) and ScanSAR (SC) data and to Sentinel-1interferometric wide swath (IW) data. Geometric distortions within images that are caused by commonly used SAR processor approximations are explained, and we show how to correct them during postprocessing. Our results, supported by the analysis of 140 images across the different SAR modes and using the 40 reflectors of the array, confirm our methodology and achieve the limits predicted by theory for both Sentinel-1 and TerraSAR-X. After our corrections, the Sentinel-1 residual errors are 6 cm in range and 26 cm in azimuth, including all error sources. The findings are confirmed by the mutual independent processing carried out at University of Zurich (UZH) and German Aerospace Center (DLR). This represents an improve�ment of the geolocation accuracy by approximately a factor of four in range and a factor of two in azimuth compared with the standard Sentinel-1 products. The TerraSAR-X results are even better. The achieved geolocation accuracy now approaches that of the global navigation satellite system (GNSS)-based survey of the CRs positions, which highlights the potential of the end-to-end SAR methodology for imaging geodesy

A user material interface for the Peridynamic Peridigm framework.

User materials (UMAT) in finite element codes allow the researchers or engineers to apply their own material routines. Simple software interfaces are specified to represent the material behavior in software. In order to use these already existing and often validated models to Peridynamics a UMAT interface is presented. It allows the simplified use of already existing material routines in the peridynamic framework Peridigm. The interface is based on the Abaqus UMAT definition and allows the integration of Fortran routines directly into Peridigm. The integration of already existing UMAT routines based in Peridigm eliminates the need for redevelopment and reprogramming material models from classical continuum mechanics theory. In addition, the same material model implementations are applicable in finite element as well as peridynamic simulations. This opens up new possibilities for analysis, verification and comparison. With this interface many material routines can be reused and applied to progressive failure analysis. The source code is stored in a GitHub repository

Exhaustion of Activated CD8 T Cells Predicts Disease Progression in Primary HIV-1 Infection

The rate at which HIV-1 infected individuals progress to AIDS is highly variable and impacted by T cell immunity. CD8 T cell inhibitory molecules are up-regulated in HIV-1 infection and associate with immune dysfunction. We evaluated participants (n = 122) recruited to the SPARTAC randomised clinical trial to determine whether CD8 T cell exhaustion markers PD-1, Lag-3 and Tim-3 were associated with immune activation and disease progression. Expression of PD-1, Tim-3, Lag-3 and CD38 on CD8 T cells from the closest pre-therapy time-point to seroconversion was measured by flow cytometry, and correlated with surrogate markers of HIV-1 disease (HIV-1 plasma viral load (pVL) and CD4 T cell count) and the trial endpoint (time to CD4 count <350 cells/μl or initiation of antiretroviral therapy). To explore the functional significance of these markers, co-expression of Eomes, T-bet and CD39 was assessed. Expression of PD-1 on CD8 and CD38 CD8 T cells correlated with pVL and CD4 count at baseline, and predicted time to the trial endpoint. Lag-3 expression was associated with pVL but not CD4 count. For all exhaustion markers, expression of CD38 on CD8 T cells increased the strength of associations. In Cox models, progression to the trial endpoint was most marked for PD-1/CD38 co-expressing cells, with evidence for a stronger effect within 12 weeks from confirmed diagnosis of PHI. The effect of PD-1 and Lag-3 expression on CD8 T cells retained statistical significance in Cox proportional hazards models including antiretroviral therapy and CD4 count, but not pVL as co-variants. Expression of 'exhaustion' or 'immune checkpoint' markers in early HIV-1 infection is associated with clinical progression and is impacted by immune activation and the duration of infection. New markers to identify exhausted T cells and novel interventions to reverse exhaustion may inform the development of novel immunotherapeutic approaches

CD32-Expressing CD4 T Cells Are Phenotypically Diverse and Can Contain Proviral HIV DNA.

Efforts to both characterize and eradicate the HIV reservoir have been limited by the rarity of latently infected cells and the absence of a specific denoting biomarker. CD32a (FcγRIIa) has been proposed to be a marker for an enriched CD4 T cell HIV reservoir, but this finding remains controversial. Here, we explore the expression of CD32 on CD3+CD4+ cells in participants from two primary HIV infection studies and identify at least three distinct phenotypes (CD32low, CD32+CD14+, and CD32high). Of note, CD4 negative enrichment kits remove the majority of CD4+CD32+ T cells, potentially skewing subsequent analyses if used. CD32high CD4 T cells had higher levels of HLA-DR and HIV co-receptor expression than other subsets, compatible with their being more susceptible to infection. Surprisingly, they also expressed high levels of CD20, TCRαβ, IgD, and IgM (but not IgG), markers for both T cells and naïve B cells. Compared with other populations, CD32low cells had a more differentiated memory phenotype and high levels of immune checkpoint receptors, programmed death receptor-1 (PD-1), Tim-3, and TIGIT. Within all three CD3+CD4+CD32+ phenotypes, cells could be identified in infected participants, which contained HIV DNA. CD32 expression on CD4 T cells did not correlate with HIV DNA or cell-associated HIV RNA (both surrogate measures of overall reservoir size) or predict time to rebound viremia following treatment interruption, suggesting that it is not a dominant biomarker for HIV persistence. Our data suggest that while CD32+ T cells can be infected with HIV, CD32 is not a specific marker of the reservoir although it might identify a population of HIV enriched cells in certain situations

CD32-Expressing CD4 T Cells Are Phenotypically Diverse and Can Contain Proviral HIV DNA.

Efforts to both characterize and eradicate the HIV reservoir have been limited by the rarity of latently infected cells and the absence of a specific denoting biomarker. CD32a (FcγRIIa) has been proposed to be a marker for an enriched CD4 T cell HIV reservoir, but this finding remains controversial. Here, we explore the expression of CD32 on CD3+CD4+ cells in participants from two primary HIV infection studies and identify at least three distinct phenotypes (CD32low, CD32+CD14+, and CD32high). Of note, CD4 negative enrichment kits remove the majority of CD4+CD32+ T cells, potentially skewing subsequent analyses if used. CD32high CD4 T cells had higher levels of HLA-DR and HIV co-receptor expression than other subsets, compatible with their being more susceptible to infection. Surprisingly, they also expressed high levels of CD20, TCRαβ, IgD, and IgM (but not IgG), markers for both T cells and naïve B cells. Compared with other populations, CD32low cells had a more differentiated memory phenotype and high levels of immune checkpoint receptors, programmed death receptor-1 (PD-1), Tim-3, and TIGIT. Within all three CD3+CD4+CD32+ phenotypes, cells could be identified in infected participants, which contained HIV DNA. CD32 expression on CD4 T cells did not correlate with HIV DNA or cell-associated HIV RNA (both surrogate measures of overall reservoir size) or predict time to rebound viremia following treatment interruption, suggesting that it is not a dominant biomarker for HIV persistence. Our data suggest that while CD32+ T cells can be infected with HIV, CD32 is not a specific marker of the reservoir although it might identify a population of HIV enriched cells in certain situations

Geodätisches SAR zur Höhenmessung von Gezeitenpegelstationen

This thesis analyses how small and cheap radar targets can be used for height measurements of tide gauge stations around the Baltic Sea. For the first time reflecting octahedrons, a combination of eight corner reflectors with a common phase centre, are utilized as SAR targets. Four of these octahedrons and one tophat are installed at the geodetic observatory in Wettzell and measured from July to September 2015 with TerraSAR-X staring spotlight and high resolution spotlight modes. The backscattering of the reflectors in different directions enables to combine ascending and descending satellite orbits to get better results for 3D-positions. This is a crucial advantage compared to ordinary corner reflectors. The octahedron shows theoretically and practically higher backscattering values and therefore better localization accuracy than the tophat. The 3D target positions are estimated on the basis of four staring spotlight acquisitions. They have residuals less than 1.7 cm in horizontal position and about 5 cm in height compared to the independent reference coordinates. The mean error of the octahedrons accounts for ±1.6 cm in range und ±3.1 cm in azimuth direction to the estimated 2D position. The residuals of the single measurements for the octahedrons show a high correlation to the large corner reflector already installed in Wettzell. Thus usual SAR errors like atmosphere and satellite orbit are higher than the localization errors of the octahedrons. The tested reflectors are suitable for installation at tide gauge stations, because they are able to measure the vertical land movement, which has to be separated from the sea level. The available models for vertical land movement have one considerable disadvantage: they can only take account of linear movements – unlike measurements. Among these octahedrons are by far the cheapest options. A simulation for the tide gauge station in Oulu (Finland) shows that octahedrons can achieve a height accuracy of 1.5 cm consid