Systematic Detection of Short‐Term Slow Slip Events in Southcentral Alaska

Slow slip events (SSEs) are important for the slip budget along a megathrust fault. Although the recurrence of weeks-long short-term SSEs (S-SSEs) in southcentral Alaska has been suggested, a large amount of noise prevented us from detecting discrete events. We applied a systematic detection method to Global Navigation Satellite System data and detected 31 S-SSEs during the 14-year analysis period. The events mainly occurred at a depth from 35 to 45 km at a down-dip extension of the 1964 Alaska earthquake, and the active clusters correlated with the region of the subducting Yakutat microplate. A large cumulative slip of S-SSEs indicated a significant contribution to stress transfer along the plate interface, and its source area spatially coincided with that of the long-term SSEs and the afterslip of the 1964 earthquake. Large and recurrent S-SSEs are key phenomena for understanding interplate slip kinematics in this region

EXAMINATION OF A METHOD FOR DETECTION OF WALKING HEEL STRIKE AND TOE-OFF OVER A WIDE RANGE OF SPEEDS

This study examines a simple method to accurately detect heel strike (HS) and toe off (TO) timing over a wide range of walking speeds. HS was the moment when the heel passed a threshold in the downward direction. TO was the moment when the fifth metatarsal passed the threshold in the upward direction. The accuracies of these measurements were evaluated by comparing the moment acquired using a force platform. The root mean square (RMS) errors were 6.10 ms for HS and 15.6 ms for TO. These errors were smaller than those of previous studies. Furthermore, walking speed did not affect the detection precision in this method. Therefore, the detection method proposed in this study can detect HS and TO timing with better accuracy over a wide range of walking speed than previous methods

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筑波大学修士(情報学)学位論文・平成31年3月25日授与(41264号

Earthquake Swarm Detection Along the Hikurangi Trench, New Zealand: Insights Into the Relationship Between Seismicity and Slow Slip Events

Earthquake swarms, which are anomalous increases in the seismicity rate without a distinguishable mainshock, often accompany transient aseismic processes, such as fluid migration and episodic aseismic slip along faults. Investigations of earthquake swarm activity can provide insights into the causal relationship between aseismic processes and seismicity. Slow slip events (SSEs) along the plate interface in the Hikurangi Trench, New Zealand, are often accompanied by intensive earthquake swarms. However, the detailed spatiotemporal distribution of these earthquake swarms is still unclear. Here, we use the epidemic-type aftershock-sequence (ETAS) model to detect earthquake swarms (M ≥ 3) and create a new earthquake swarm catalog (1997–2015) along the Hikurangi Trench. We compare the earthquake swarm catalog with Global Navigation Satellite System (GNSS) time series data, and existing SSE and tectonic tremor catalogs. Most of the detected (119) earthquake swarm sequences were intraplate events, and their epicenters were mainly concentrated along the east coast of the North Island, whereas many tectonic tremors were located inland. Twenty-five of the detected earthquake swarms occurred within 25 days before and after transient eastward GNSS displacements due to known or newly detected SSEs. We find that the earthquake swarms sometimes preceded the GNSS displacements by more than several days. SSE-induced stress loading is therefore not a plausible triggering mechanism for these pre-SSE earthquake swarms. We propose that high fluid pressure within the slab, which accumulated before the SSEs, may have caused intraplate fluid migration, which in turn triggered the pre-SSE earthquake swarms

A new device for the simultaneous recording of cerebral, cardiac, and muscular electrical activity in freely moving rodents

AbstractWe present a new technique for the simultaneous capture of bioelectrical time signals from the brain and peripheral organs of freely moving rodents. The recording system integrates all systemic signals into an electrical interface board that is mounted on an animal's head for an extended period. The interface board accommodates up to 48 channels, enabling us to analyze neuronal activity patterns in multiple brain regions by comparing a variety of physiological body states over weeks and months. This technique will advance the understanding of the neurophysiological correlate of mind–body associations in health and disease

Titanium as an Instant Adhesive for Biological Soft Tissue

A variety of polymer‐ and ceramic‐based soft‐tissue adhesives have been developed as alternatives to surgical sutures, yet several disadvantages regarding the mechanical properties, biocompatibility, and handling hinder their further application particularly when applied for immobilization of implantable devices. Here, it is reported that a biocompatible and tough metal, titanium (Ti), shows instant and remarkable adhesion properties after acid treatment, demonstrated by ex vivo shear adhesion tests with mouse dermal tissues. Importantly, in vivo experiments demonstrate that the acid‐treated Ti can easily and stably immobilize a device implanted in the mouse subcutaneous tissue. Collectively, the acid‐treated Ti is shown as a solid‐state instant adhesive material for biological soft tissues, which can have diverse applications including immobilization of body‐implantable devices

Analysis of bone regeneration based on the relationship between the orientations of collagen and apatite in mouse femur

In this study, we focused on the preferential orientation of the extracellular matrix (ECM) of bone, since ECM orientation has been shown to significantly affect the mechanical functions of bones. Bone analysis is in most cases based on the premise that the apatite crystallizes on the collagen template such that its c-axis is parallel with the running direction of the collagen fibril. Bone regeneration analysis has also been discussed assuming that the apatite c-axis orientation reflects collagen orientation. To understand the regeneration processes of both collagen and apatite individually, the preferential orientations of apatite and collagen in regenerated bone were simultaneously analyzed using a bone regeneration model of mouse femur with an 0.8-mm drill hole defect. The defects in mouse femur were filled with mineralized bone matrix, which shows an intact mineral density. However, the directions of orientation of the collagen and apatite deviate from the femur longitudinal axis in the regenerated bone. Moreover, electron diffraction analysis revealed that the apatite c-axis aligned along the extended axis of a collagen fibril both in regenerated and intact bones, indicating that the direction of the apatite c-axis is regulated by collagen fibril orientation even in the regenerated bone. In conclusion, the less-oriented apatite crystallite observed in the regenerated bone was shown to be formed due to the less-oriented collagen fibrils.Ozasa R., Nakatsu M., Moriguchi A., et al. Analysis of bone regeneration based on the relationship between the orientations of collagen and apatite in mouse femur. Materials Transactions 61, 381 (2020); https://doi.org/10.2320/matertrans.MT-M2019341