Buchbesprechungen

Besprochen werden die folgenden vier Werke: Fey, J. Michael (1996): Biologie am Bach. Praktische Limnologie für Schule und Naturschutz; Fraedrich, Wolfgang (1996): Spuren der Eiszeit. Landschaftsformen in Europa; Schmidt, Eberhard (1996): Ökosystem See. Der Uferbereich des Sees; Schlosser, w., Cierny, J. (1996): Sterne und Steine - Eine praktische Astronomie der Vorzeit

Cold Tolerance of the Photosynthetic Apparatus: Pleiotropic Relationship between Photosynthetic Performance and Specific Leaf Area of Maize Seedlings

The objective of this study was to elucidate the genetic relationship between the specific leaf area (SLA) and the photosynthetic performance of maize (Zea mays L.) as dependent on growth temperature. Three sets of genotypes: (i) 19 S5 inbred lines, divergently selected for high or low operating efficiency of photosystem II (ΦPSII) at low temperature, (ii) a population of 226 F2:3 families from the cross of ETH-DL3 × ETH-DH7, and (iii) a population of 168 F2:4 families from the cross of Lo964 × Lo1016 were tested at low (15/13°C day/night) or at optimal (25/22°C day/night) temperature. The latter cross was originally developed to study QTLs for root traits. At 15/13°C the groups of S5 inbred lines selected for high or low ΦPSII differed significantly for all the measured traits, while at optimal temperature the groups differed only with regard to leaf greenness (SPAD). At low temperature, the SLA of these inbred lines was negatively correlated with ΦPSII (r= − 0.56, p < 0.05) and SPAD (r = − 0.80, p < 0.001). This negative relationship was confirmed by mapping quantitative trait loci (QTL) in the two mapping populations. A co-location of three QTLs for SLA with QTLs for photosynthesis-related traits was detected in both populations at 15/13°C, while co-location was not detected at 25/22°C. The co-selection of SLA and ΦPSII in the inbred lines and the co-location of QTL for SLA, SPAD, and ΦPSII at 15/13°C in the QTL populations strongly supports pleiotropy. There was no evidence that selecting for high ΦPSII at low temperature leads to a constitutively altered SL

AOCS for future multi-satellite geodesy missions

Missions like GRACE and GRACE-FO have successfully established a continuous time series of data for Earth gravity field estimation. The continuous observation of Earths gravitational field is essential for the understanding of Earths mass transportation and climate change. Since GRACE-FO is already in service and the demand of more accurate data series arises, new Mission concepts need to be investigated to guarantee the continuation of the data time series and to increase the accuracy of Earths gravity field estimation. The German Aerospace Center (DLR) Institute for Satellite Geodesy and Inertial Sensing and the ZARM, University of Bremen are developing a Multi-Purpose Space Mission Simulator in the scope of the DFG Collaborative Research Center 1464 TerraQ. The simulation platform is capable of modelling for the atmospheric, magnetic, radiative, and gravitational environment in orbit and their coupling into system and sensor-specific effects. This work focuses on extending the simulation environment with an attitude control system to investigate next-generation gravimetry mission (NGGM) concepts with multiple satellites. The attitude control system should be modeled in three parts: Sensors, State Estimator and Controller, and Actuators. The aim is to model a realistic attitude control system. Thus, the performance of different satellite constellation approaches, such as pendulum orbits, bender orbits, and swarm constellations can be examined with the help of the simulator. Requirements for the AOCS subsystem will be derived to evaluate the feasibility of such mission concepts and sensors. This paper presents the current status of the research

Investigation of future geodesy mission concepts for their feasibility and requirements to the AOCS subsystem

Missions like GRACE and GRACE-FO have successfully established a continuous time series of data for Earth gravity field estimation. The continuous observation of Earths gravitational field is essential for the understanding of Earths mass transportation and climate change. Since GRACE-FO is already in service and the demand of more accurate data series arises, new Mission concepts need to be investigated to guarantee the continuation of the data time series and to increase the accuracy of Earths gravity field estimation. The German Aerospace Center (DLR) Institute for Satellite Geodesy and Inertial Sensing, as well as ZARM University of Bremen, is developing a simulation environment called the Hybrid Simulation Platform for Space Systems (HPS) to examine future geodesy satellite mission concepts. The simulation platform is capable of modelling for the atmospheric, magnetic, radiative, and gravitational environment in orbit and their coupling into system and sensor-specific effects. This work focuses on next-generation gravimetry mission (NGGM) concepts with multiple satellites and different satellite constellation approaches, such as pendulum orbits, bender orbits and swarm constellations, being examined with the help of the HPS simulator. In addition, new quantum sensors are considered to measure Earths gravitational field which put increased requirements on the AOCS subsystem, especially when considering drag-free control concepts. Requirements for the AOCS subsystem will be derived to evaluate the feasibility of such mission concepts and sensors. In parallel, collaborations with experts in orbit propagation and quantum sensors are being established within the scope of the German Collaborative Research Center TerraQ focusing on the improvement of Gravity field determination both on ground and space level. This paper presents the current status of the research

Development of a virtual environment for quantum technologies on satellite based next-generation gravimetry missions

The success of GRACE-FO and its predecessors has demonstrated to the scientific community the benefits of satellite gravimetry for monitoring mass variations on the Earth’s surface and its interior. However, the demand for increasingly higher spatial and temporal resolution of gravity field solutions has brought into focus the need for next-generation gravimetry missions (NGGMs). To this end, the German Aerospace Center (DLR) has established the Institute for Satellite Geodesy and Inertial Sensing, which investigates the potential of quantum technologies for NGGMs. Currently, quantum sensors for gravity field satellite missions are being developed, which include cold atom interferometry (CAI) gradiometers and optical clocks. In addition, quantum accelerometers and quantum inertial sensors are being studied for the application on satellites. NGGM concepts are analyzed using the Hybrid Simulation Platform for Space Systems (HPS) developed by ZARM (University of Bremen) and DLR. With the adaptation of HPS for the French MICROSCOPE mission, HPS was already capable of simulating the dynamics of the satellite and its test masses on a helio-synchronous orbit in an altitude of 700 km. The simulation included environmental models for the atmosphere, magnetic field, radiation, and gravity field, as well as a detailed model of the on-board capacitive sensors. Efforts have been made to extend the simulation platform to include quantum sensors. This introduces new challenges for pointing accuracy and noise determination, which place more stringent requirements on the computation of environmental disturbances in lower orbits suitable for NGGMs. Therefore, satellite vibration and thermal models are being investigated for use in HPS, with the goal of providing a complete testbed for quantum technologies in gravimetry missions. This paper presents the current status of the research

Reference mirror misalignment of cold atom interferometers on satellite-based gravimetry missions

The success of GRACE-FO and its predecessors has demonstrated the benefits of satellite gravimetry for monitoring mass variations on the Earth’s surface and its interior. However, the demand for increasingly higher spatial and temporal resolution of gravity field solutions has brought into focus the need for next-generation gravimetry missions (NGGMs). Therefore, we investigate the hybridization of electrostatic accelerometers (E-ACC) with cold atom interferometers (CAI), which can reduce the instrumental error contribution of the E-ACC, e.g. by enabling in-flight estimation of E-ACC bias parameters, and reduce systematic effects in gravity field solutions by proving drift free measurements. However, these sensors introduce more stringent requirements on the computation of environmental disturbances in lower Earth orbits, as the alignment of the CAI’s reference mirror has to be controlled precisely. Therefore, the movement of the CAI’s reference mirror inside the satellite is analyzed using the Hybrid Simulation Platform for Space Systems (HPS) developed by DLR and ZARM (University of Bremen). Misalignments and vibrations of the reference mirror cause an additional CAI phase shift, which introduces measurement inaccuracies. Our work examines the translational displacement, rotational misalignment and angular velocity of the reference mirror, due to forces transferred by the coupling link between mirror and satellite. This helps to compare different hybridization concepts and to improve noise and signal models for CAI accelerometers

Genetic structure and history of Swiss maize (Zea mays L. ssp mays) landraces

ISSN:0925-9864ISSN:1573-510

Cold Tolerance of the Photosynthetic Apparatus: Pleiotropic Relationship between Photosynthetic Performance and Specific Leaf Area of Maize Seedlings

ISSN:1380-3743ISSN:1572-978

Gasdermin-A3 pore formation propagates along variable pathways

Gasdermins are main effectors of pyroptosis, an inflammatory form of cell death. Released by proteolysis, the N-terminal gasdermin domain assembles large oligomers to punch lytic pores into the cell membrane. While the endpoint of this reaction, the fully formed pore, has been well characterized, the assembly and pore-forming mechanisms remain largely unknown. To resolve these mechanisms, we characterize mouse gasdermin-A3 by high-resolution time-lapse atomic force microscopy. We find that gasdermin-A3 oligomers assemble on the membrane surface where they remain attached and mobile. Once inserted into the membrane gasdermin-A3 grows variable oligomeric stoichiometries and shapes, each able to open transmembrane pores. Molecular dynamics simulations resolve how the membrane-inserted amphiphilic β-hairpins and the structurally adapting hydrophilic head domains stabilize variable oligomeric conformations and open the pore. The results show that without a vertical collapse gasdermin pore formation propagates along a set of multiple parallel but connected reaction pathways to ensure a robust cellular response.ISSN:2041-172