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Results of additional analyses on female age, litter size, and elevation

Magnetic resonance elastography (MRE) serves as an important diagnostic tool. It represents one of numerous approaches to monitor tissue stiffness. The most fundamental challenges that MRE face are posed by two linking factors: Constructing a mechanical device that induces tissue motion to the depth of interest and meaningfully resolving said movement in the complex magnetic resonance imaging (MRI) signal. This work aims to address these challenges by improving the quantification of tissue stiffness through the development of a new actuation system for MRE. Firstly, a 3D printed pneumatic turbine vibrator was developed to induce sinusoidal mechanical waves. It used an eccentrically rotating mass generating a centrifugal force in the turbine. Contrary to conventionally used acoustic pressure drivers, the pneumatic turbine was capable of producing wave amplitudes in the range of appropriate shear waves in human tissue - especially at higher frequencies due to the centrifugal force increasing quadratically in relation to the rotational frequency. A technical assessment showed that the turbine generated vibrations in the range of 30 Hz to 150 Hz. The extent of artifacts caused by the materials brought into the field of view was restricted to the proximity of the actuator. It did not affect image quality in the region of interest. The turbine was MR-safe and an in-house certification according to §3 MPG was conducted, which enabled in-house clinical in vivo studies. The actuation system was additionally extended to a dual turbine actuator in order to investigate if the attenuation of shear waves could be further compensated by using two wave sources. Secondly, a motion encoding sequence was developed to meaningfully encode the tissue motion in the MRI signal. It was a spin-echo echo-planar-imaging sequence (SE-EPI) and contained a motion encoding gradient (MEG) adjustable for actuation frequencies ranging from 40 Hz to 120 Hz. To accurately reconstruct the wave velocities, i.e tissue elasticity, a trigger was implemented that synchronized the motion encoding sequence to the mechanical waves. Thirdly, the actuator system was evaluated regarding its performance for MRE image acquisition in a clinical MRI scanner. Silicone-based tissue elasticity mimicking phantoms were developed as test objects with known elasticity. Their shear moduli were in the range of 1.47 kPa to 7.29 kPa, which corresponds to the range of human soft tissue elasticities. A prostate phantom and an anthropomorphic abdominal phantom were manufactured. MR images were acquired with the SE-EPI sequence and were sufficient in terms of signal to noise ration (liver: SNR = 71.5) and contrast to noise ratio (liver: CNR = 16.5). The phantoms may also be used for multi-modal imaging; besides MRI, computed tomography (liver: 106+/-6 HU) and ultrasound imaging by adding scatter particles is feasible. The actuator did not interfere with the imaging procedure and could be integrated into existing clinic equipment. Three actuation set-ups were evaluated: a single, a large surface and a dual source actuation. For each, the strength of the MEG was varied from 5 mT/m to 20 mT/m for actuation frequencies ranging from 50 Hz to 80 Hz. The dual source actuation demonstrated a more uniform penetration of a larger volume of interest, especially in the peripheral region of the abdominal phantom. The obtained elasticity maps showed elasticity values (liver: 1.12+/-0.16 kPa, filling material: 4.37+/-0.52 kPa) in accordance to the results obtained by rheometric testing of the silicone samples. Additionally, an in vivo MRE examination was conducted, which served as a proof-of-principle for the successful implementation of the first developed MRE actuator system in our clinic. For both liver and prostate MRE, the actuator was well tolerated by the volunteer. Since the developed actuation technique is non-invasive, its incorporation into routine MRI protocols will facilitate patient acceptance, while its short additional set-up time will also increase clinical acceptance. MRE is a unique technique for the identification of various pathologies and the quantification of the shear modulus has the potential to become a further independent parameter for MRI diagnostics in a variety of clinical applications.

Die Autorin greift in ihrem Beitrag den Aspekt der Reproduktion männlicher Herrschaft in pädagogischen Institutionen auf. Unter dem Titel „Man(n) wird da so hineingelobt“ – Ko-Konstruktion von Männlichkeit und Aufstieg ins Schulleitungsamt an Grundschulen nimmt die Autorin die Beobachtung zum Ausgangspunkt, dass auch in diesem frauendominierten Feld die Wahrscheinlichkeit einer Übernahme von Leitungsfunktionen für männliche Lehrkräfte nach wie vor größer ist als für weibliche. Sie zeigt auf, wie in der pädagogischen Institution Schule die ‚Eignung‘ von Personen für eine bestimmte Funktion durch spezifische Geschlechterkonstruktionen hergestellt wird. Auf der Basis von Interviews und Beobachtungen bei Qualifikationsmaßnahmen für an Leitungspositionen interessierten Lehrkräften wird rekonstruiert, wie die Beteiligten von einer mangelnden Passung zwischen Männlichkeit und dem Aufgabenfeld einer Grundschullehrkraft und gleichzeitig von einer Eignung der Männer für Leitungsaufgaben ausgehen. Beides mündet in konkrete Formen der Aufstiegsermutigung für männliche Lehrkräfte, die ihre weiblichen Kolleginnen nicht erfahren, sodass es auf der Basis zugeschriebener Eignung bei der unhinterfragten Verknüpfung von Männlichkeit und institutionalisierten Einflussmöglichkeiten bleibt. (DIPF/Orig.)

The spatiotemporal dynamics of human activity requires a better understanding of the ecological effects on wildlife. This thesis focuses on the behavioural response of a harvested species, moose (Alces alces), to dynamic human activities e.g. hunting and recreation, and to static influences like roads, using experimental and descriptive approaches. Potentially lethal (hunting) and non-lethal (hiking, snowmobiling) activities provoked short-lived increases in moose movement activity and caused spatial displacement. The data suggests a uniform response towards unexpected disturbance and that moose are sensitive to human proximity. Hunting clearly provoked the strongest response. Moose approached by a hunting dog commonly fled, suggesting adjustments in anti-predator behaviour towards a non-native predator. This may lead to predator facilitation where wolves and human predation co-exist, because the moose’s behavioural response towards one predator possibly increases the predation risk by the other. Unexpectedly, hiking and motor-driven (snowmobiling) recreational activity caused a comparable change in moose behaviour. The short-lived response towards dynamic human activities indicates a rather minor impact on moose total energy budget from a single disturbance. Moose seldom crossed roads, but did increasingly so during migration. Road-crossing sites were aggregated, suggesting well established travel routes and corridors for migratory moose. Moose did not cross roads more often during hunting season. In general, moose little utilized habitats in proximity to roads. Moose-vehicle collisions did not occur where and when moose most commonly cross roads. My results suggest a higher risk to human safety during times of poor visibility and close to urban areas, but not necessarily in the vicinity of forests. For wildlife subject to intensive harvest and sensitive to human proximity, I emphasize the need to include animal behavioural, landscape ecological, political as well as socio-economical aspects for future research concerning human-wildlife interactions. I also recommend future research to combine wildlife movement data from active tracking sensors such as GPS-collars together with collision data to improve conclusions about wildlife movement corridors and traffic risk zones.