On the efficient and reliable numerical solution of rate-and-state friction problems

We present a mathematically consistent numerical algorithm for the simulation of earthquake rupture with rate-and-state friction. Its main features are adaptive time-stepping, a priori mesh-adaptation, and a novel algebraic solution algorithm involving multigrid and a fixed point iteration for the rate-and-state decoupling. The algorithm is applied to a laboratory scale subduction zone which allows us to compare our simulations with experimental results. Using physical parameters from the experiment, we find a good fit of recurrence time of slip events as well as their rupture width and peak slip. Preliminary computations in 3D confirm efficiency and robustness of our algorithm

Three-dimensional Quasi-Static Displacement of Human Middle-ear Ossicles under Static Pressure Loads: Measurement Using a Stereo Camera System

The time delay and/or malfunctioning of the Eustachian tube may cause pressure differences across the tympanic membrane, resulting in quasi-static movements of the middle-ear ossicles. While quasi-static displacements of the human middle-ear ossicles have been measured one- or two-dimensionally in previous studies, this study presents an approach to trace three-dimensional movements of the human middle-ear ossicles under static pressure loads in the ear canal (EC). The three-dimensional quasi-static movements of the middle-ear ossicles were measured using a custom-made stereo camera system. Two cameras were assembled with a relative angle of 7 degrees and then mounted onto a robot arm. Red fluorescent beads of a 106-125 µm diameter were placed on the middle-ear ossicles, and quasi-static position changes of the fluorescent beads under static pressure loads were traced by the stereo camera system. All the position changes of the ossicles were registered to the anatomical intrinsic frame based on the stapes footplate, which was obtained from µ-CT imaging. Under negative ear-canal pressures, a rotational movement around the anterior-posterior axis was dominant for the malleus-incus complex, with small relative movements between the two ossicles. The stapes showed translation toward the lateral direction and rotation around the long axis of the stapes footplate. Under positive EC pressures, relative motion between the malleus and the incus at the IMJ became larger, reducing movements of the incus and stapes considerably and thus performing a protection function for the inner-ear structures. Three-dimensional tracing of the middle-ear ossicular chain provides a better understanding of the protection function of the human middle ear under static pressured loads as immediate responses without time delay. Keywords ambient pressure variation micro-computed tomography imaging middle-ear ossicles protection function quasi-static displacement static pressure static pressure loads stereo camera system three-dimensional displacemen

Three examples concerning the interaction of dry friction and oscillations

We discuss recent work concerning the interaction of dry friction, which is a rate independent effect, and temporal oscillations. First, we consider the temporal averaging of highly oscillatory friction coefficients. Here the effective dry friction is obtained as an infimal convolution. Second, we show that simple models with state-dependent friction may induce a Hopf bifurcation, where constant shear rates give rise to periodic behavior where sticking phases alternate with sliding motion. The essential feature here is the dependence of the friction coefficient on the internal state, which has an internal relaxation time. Finally, we present a simple model for rocking toy animal where walking is made possible by a periodic motion of the body that unloads the legs to be moved

Researching retired ex-servicemen: reflections on ethnographic encounters

The opportunities and challenges that younger, female, civilian researchers can encounter when undertaking ethnographic research with predominantly male military veterans are relatively underexplored sociologically. This is despite a growing literature on reflexivity in military studies over the past decade. To address this gap, we draw on symbolic interactionist insights to examine the reflective account of a British, female researcher in her mid-20s, who conducted qualitative research with 20 ‘older’ (aged 60+) retired servicemen from the Royal British Legion, a United Kingdom charity providing support for military veterans and their families. The study explored ex-servicemen’s embodied experiences of physical activity. The findings presented here cohere around four salient themes identified in the ethnographic reflections: (1) researcher positionality as a young, female, civilian researcher in a traditionally masculine militarised world; (2) managing distressing topics and interactional discomfort; (3) maintaining an ‘ethic of care’; and (4) dilemmas regarding representational issues and ex-servicemen’s embodied experiences

Cerebral blood flow velocity progressively decreases with increasing levels of verticalization in healthy adults. A cross-sectional study with an observational design

BackgroundAutoregulation of the cerebral vasculature keeps brain perfusion stable over a range of systemic mean arterial pressures to ensure brain functioning, e.g., in different body positions. Verticalization, i.e., transfer from lying (0°) to upright (70°), which causes systemic blood pressure drop, would otherwise dramatically lower cerebral perfusion pressure inducing fainting. Understanding cerebral autoregulation is therefore a prerequisite to safe mobilization of patients in therapy.AimWe measured the impact of verticalization on cerebral blood flow velocity (CBFV) and systemic blood pressure (BP), heart rate (HR) and oxygen saturation in healthy individuals.MethodsWe measured CBFV in the middle cerebral artery (MCA) of the dominant hemisphere in 20 subjects using continuous transcranial doppler ultrasound (TCD). Subjects were verticalized at 0°, −5°, 15°, 30°, 45° and 70° for 3–5 min each, using a standardized Sara Combilizer chair. In addition, blood pressure, heart rate and oxygen saturation were continuously monitored.ResultsWe show that CBFV progressively decreases in the MCA with increasing degrees of verticalization. Systolic and diastolic BP, as well as HR, show a compensatory increase during verticalization.ConclusionIn healthy adults CBFV changes rapidly with changing levels of verticalization. The changes in the circulatory parameters are similar to results regarding classic orthostasis.RegistrationClinicalTrials.gov, identifier: NCT04573114

Vergleichende morphologische und histologische untersuchungen am geruchsorgan der knochenfische

1. Untersucht wurden 18 Knochenfischarten aus 13 Familien.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47539/1/435_2004_Article_BF00429940.pd

The Five Aspects Meal Model, FAMM : From Michelin Guide to public meal sector

Doktorsavhandling Cecilia Magnusson Sporr