Thomas Combriat (University of Oslo): "Cells on the move - Tickling biology with ultrasonic waves"
"Ultrasonic waves are commonly used in hospitals for non-invasive diagnostics: all of us have probably be probed by this technique even before being even born. Even though low intensity ultrasounds are usually considered as being completely safe, and high intensities to have some effects on tissues by physicians, the exact interplay between ultrasounds and biological materials is still debated. The exact phenomenon(s) is of special interest in the context of mechanotransduction in biology: genes expression of cells can be affected by mechanical stimuli such as, for instance, acoustic waves. This could provide a new tool for understanding biological systems, but also for patient treatment completing or replacing drug based medicine.
In this talk I will present our trials to tackle this problem from a physicist point of view: using stroboscopic fast imaging and digital image correlation (DIC), the mechanical impact of ultrasounds on living tissues can be investigated in vitro. This can provide information both on the mechanics of the studied system but also its response to a well defined stimulation."
Andreas Grøvan Aspaas (University of Oslo): "What causes transient deformations in the Åknes landslide, Norway?"
"Slow creeping landslides move at rates of millimeters to several meters per year. They can cause extensive damage to infrastructure and pose a major threat to human lives if failing catastrophically. Landslides can progressively weaken over time by rock mass damage processes that may occur by constant slow creep or sudden transient slips. Eventually, damage can lead to strain localization along the basal shear plane and catastrophic failure of the landslide. When observed, transient slip events, also called creep bursts, may induce short-term loading and hence can control landslide stability. These creep bursts correspond to short periods that can last several days where the displacement of a landslide accelerates and then decelerates. Here, we compiled and analyzed extensive multiphysics data series of the Åknes landslide, Norway. This landslide is moving at a slow rate of 6 cm per year, and could generate a large tsunami wave in a fjord if it would rupture catastrophically. Based on time series of an array of eight seismometers, five extensometers, seven borehole inclinometers and piezometer strings, and ten continuous GPS stations, sampled with time resolutions down to 5 minutes over several years, we detected creep bursts in this landslide. These events interact with a distinct creep trend related to seasonal variations of rainfall and snowmelt. We analyze the creep bursts in regards to micro earthquake activity and water pressure levels, to study their origin."
You will find the complete schedule for Njord Seminar Series spring '22 here.
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