Evaluation of Inertial Measurement Units for Short Time Motion Tracking

The goal of the present paper is to investigate inertial measurement systems for the ability to reconstruct the short time rigid body motion of objects, e.g. clumps in snow avalanches. While strapdown inertial navigation is well established, special algorithms are needed for the accurate motion reconstruction for short time motion with partially known boundary conditions. Furthermore, low cost inertial sensors are available with the ability to log translational accelerations and angular velocities as well as magnetic flux densities, which need to be extended with respect to GPS, time synchronization, and power management functionalities. In this paper, a newly developed system to measure the motion inside snow avalanches with redundant sensors, which have significantly higher measurement ranges than systems published in the past, is presented. In addition, an algorithm for motion reconstruction from measured translational accelerations, angular velocities and magnetic flux densities is derived. Furthermore, an optimization by eliminating terminal translational velocities is presented. The developed system is tested and its function is confirmed by reproducible measurement data from two experiments on skis, whereas these experiments differ in the magnitude of rotations. The presented motion reconstruction algorithm was used to evaluate the measurement data and thus the newly developed measurement system.

Transient Attitude Motion of TNS-0#2 Nanosatellite during Atmosphere Re-Entry

Attitude motion reconstruction of the Technological NanoSatellite TNS-0 #2 during the last month of its mission is presented in the paper. The satellite was designed to test the performance of the data transmission via the Globalstar communication system. This system successfully provided telemetry (even during its atmosphere re-entry) up to an altitude of 156 km. Satellite attitude data for this phase is analyzed in the paper. The nominal satellite attitude represents its passive stabilization along a geomagnetic field induction vector. The satellite was equipped with a permanent magnet and hysteresis dampers. The permanent magnet axis tracked the local geomagnetic field direction with an accuracy of about 15 degrees for almost two years of the mission. Rapid altitude decay during the last month of operation resulted in the transition from the magnetic stabilization to the aerodynamic stabilization of the satellite. The details of the initial tumbling motion after the launch, magnetic stabilization, transition phase prior to the aerodynamic stabilization, and subsequent satellite motion in the aerodynamic stabilization mode are presented.

Coupling chromatin structure and dynamics by live super-resolution imaging

Chromatin conformation regulates gene expression and thus, constant remodeling of chromatin structure is essential to guarantee proper cell function. To gain insight into the spatiotemporal organization of the genome, we use high-density photoactivated localization microscopy and deep learning to obtain temporally resolved super-resolution images of chromatin in living cells. In combination with high-resolution dense motion reconstruction, we find elongated ~45- to 90-nm-wide chromatin “blobs.” A computational chromatin model suggests that these blobs are dynamically associating chromatin fragments in close physical and genomic proximity and adopt topologically associated domain–like interactions in the time-average limit. Experimentally, we found that chromatin exhibits a spatiotemporal correlation over ~4 μm in space and tens of seconds in time, while chromatin dynamics are correlated over ~6 μm and last 40 s. Notably, chromatin structure and dynamics are closely related, which may constitute a mechanism to grant access to regions with high local chromatin concentration.