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result(s) for
"Ziethe, R."
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On-Ground Performance and Calibration of the ExoMars Trace Gas Orbiter CaSSIS Imager
by
Casciello, A.
,
Thomas, N.
,
Johnson, M.
in
Aerospace Technology and Astronautics
,
Astronomical instruments
,
Astrophysics and Astroparticles
2017
The European Space Agency’s ExoMars Trace Gas Orbiter (TGO) seeks to investigate the biological or geological origin of trace gases found on Mars. The TGO carries a payload of four instruments in order to reach its scientific goals, including the Colour and Stereo Surface Imaging System (CaSSIS). CaSSIS is a colour and stereo telescopic camera that will be capable of taking high-resolution images of the martian surface. Before shipment of the instrument for integration onto the TGO, a detailed calibration campaign was performed, and a number of calibration products were gathered and utilised as part of the in-flight calibration campaign. This paper presents the results of on-ground calibration measurements carried out in order to assess the pre-flight performance of CaSSIS. All indications are that CaSSIS will perform very well on arrival at Mars and will be successful in reaching its scientific objectives.
Journal Article
Rheological controls on the terrestrial core formation mechanism
2009
Iron core differentiation of terrestrial planetary bodies is thought to have occurred simultaneously with planetary accretion. The exact mechanisms of core formation, however, remain incompletely understood. One model proposes that cores are formed from numerous smaller iron cores from predifferentiated planetesimals. To further understand this mechanism for forming Mars‐ and Earth‐sized bodies, we present here systematic numerical simulations. Our models include a non‐Newtonian temperature‐, pressure‐ and strain rate–dependent viscoplastic rheology. Four different core formation regimes are being observed in the study, as a function of activation volume, friction angle, Peierls stress, and the initial temperature state of the body. We derive scaling laws, which show the importance of shear heating localization and plastic yielding as mechanisms to drive planetary differentiation in planetary interiors, that are in good agreement with numerical simulations. Results indicate that the effective rheology of the planetary body has a major effect on the core formation mechanism: while bodies with a weak rheology generally show a diapiric mode of core formation, the interior of planetary bodies with a stiff rheology can be fractured or displaced toward the surface. On Earth‐sized protoplanets, the water content seems also to have a significant influence on the mode of core formation. Results indicate a time scale of differentiation of a few million years, significantly shorter than expected from the Stokes sinking time in a Newtonian medium.
Journal Article
Development of a time-dependent numerical model for the assessment of non-stationary pharyngoesophageal tissue vibrations after total laryngectomy
by
Ziethe, Anke
,
Luegmair, Georg
,
Patel, Rita R.
in
Biological and Medical Physics
,
Biomechanics
,
Biomedical Engineering and Bioengineering
2015
Laryngeal cancer due to, e.g., extensive smoking and/or alcohol consumption can necessitate the excision of the entire larynx. After such a total laryngectomy, the voice generating structures are lost and with that the quality of life of the concerning patients is drastically reduced. However, the vibrations of the remaining tissue in the so called pharyngoesophageal (PE) segment can be applied as alternative sound generator. Tissue, scar, and geometric aspects of the PE-segment determine the postoperative substitute voice characteristic, being highly important for the future live of the patient. So far, PE-dynamics are simulated by a biomechanical model which is restricted to stationary vibrations, i.e., variations in pitch and amplitude cannot be handled. In order to investigate the dynamical range of PE-vibrations, knowledge about the temporal processes during substitute voice production is of crucial interest. Thus, time-dependent model parameters are suggested in order to quantify non-stationary PE-vibrations and drawing conclusions on the temporal characteristics of tissue stiffness, oscillating mass, pressure, and geometric distributions within the PE-segment. To adapt the numerical model to the PE-vibrations, an automatic, block-based optimization procedure is applied, comprising a combined global and local optimization approach. The suggested optimization procedure is validated with 75 synthetic data sets, simulating non-stationary oscillations of differently shaped PE-segments. The application to four high-speed recordings is shown and discussed. The correlation between model and PE-dynamics is
≥
97 %.
Journal Article
CP Studies and Non-Standard Higgs Physics
2006
There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders.