Tectonic stress in the structures of the Northern Priokhotie (Magadan region) according to geological data

Tectonic fracturing of the Mesozoic and Cenozoic structures was studied in the Northern Priokhotie (Magadan region). The cataclastic analysis method and the statistical method of fracture density analysis were used to reconstruct their state of stress. It is revealed that the folded structures of the Arman’-Viliga synclinorium are subjected to horizontal shearing; the axis of maximum compression is sublatitudinal (azimuth 67°, angle 12°); extension is submeridional (azimuth 161°, angle 19°). In the Uda-Murgal volcanic arc, horizontal extension with shear takes place; the compression axis is directed to NW (azimuth 259°, angle 29°), and the extension axis to NE (azimuth 152°, angle 26°). In the Okhotsk-Chukotka volcanogenic belt, volcanic structures are in the field of varying tectonic stresses, from predominant horizontal extension to horizontal shear. The Cenozoic intermontane depressions of the Miocene – Pliocene ages are subjected to horizontal shear; the compression axis is directed to NE (azimuth 214°, angle 29°), and the extension axis to NW (azimuth 121°, angle 4°). The results of the comparative analysis of the stress states in the above-mentioned areas reliably show that the diversity of the stress state types is statistically related to the structural positions of the studies sites. Such diversity cannot be explained by an influence of active faults, or by any consecutive superposition of deformations at different stages, despite the fact that the deformations have complicated the observed pattern of the stress states. We conclude that each subsequent geodynamic stage only introduced additional elements into the previous structure, but did not completely transform it.

SDR (Seaward Dipping Reflectors) types in the water area of the Mendeleev Rise, Arctic Ocean

<p>The Mendeleev Rise is represented by an asymmetric uplifted crustal block with strongly rugged by half-graben and horst structures. High-amplitude reflectors similar to SDR (Seaward Dipping Reflectors) were found in half-grabens. Similar structures were found in the Toll and Podvodnikov basins.</p><p>The top of the SDR complex is usually relatively well defined and corresponds to the rift-post-drift boundary with an age of about 100 Ma. Small, sharp conical build-ups with a chaotic internal structure are often observed at the top of the SDR – probably submarine volcanoes. There may have been two stages of volcanism. The bottom of the SDR complex corresponds to the top of the acoustic basement (about 125 Ma). The thickness of one wedge is about 1, 5 - 3 sec. The length of distinct wedges in the Mendeleev Rise’s area is about 25-50 km, in the Podvodnikov basin’s area – 50-100 km.</p><p>Several types of SDR have been identified. The first type is identified within the Toll basin and the Mendeleev Rise. This is the most classic type.  Wedges of this type are characterized by greater thickness, but less length. Wedges are strongly curved. Several distinct wedges stand out. Distinct wedges overlap each other towards the stretch center and start from one point. SDR have longer wedges and slightly less thickness in the Podvodnikov basin’s area. The SDR complex is highly spaced apart. Wedges are less curved. Distinct wedges are located in separate half-grabens and have no common starting point. The reflectors cool down and become brighter in the central part of the Podvodnikov basin, near the axial horst. Both complexes are characterized by probable existence volcanic edifices in the top.</p><p>We traced the distribution and direction of SDRs, the bottom of the grabens, the position of probable volcanic edifices and made a map. There is symmetry and logic in the distribution of SDR. In the Toll basin, reflectors fall into each other – from the Mendeleev Rise and from the Chukotka plateau – and meet at a structure reminded of an interrupted rift. The rift is parallel to the Mendeleev Rise and the Chukotka Plateau. We can see at on Magnetic Anomalies Map. This probably corresponds to the central axis of extension of the Toll basin. Oppositely directed SDRs from the Mendeleev Rise and the Lomonosov Ridge meet near a raised block in the Podvodnikov basin. Nature of raised block is not fully understood. We call it axial horst. This uplift is subparallel to the Mendeleev Rise. This is probably associated with the central extension axis for the Podvodnikov basin.</p><p>Mendeleev Rise, Podvodnikov and Toll basins were formed approximately at the same time according to the seismic correlation.</p><p>This study was supported by RFBR grant (18-05-70011).</p>

Correction: McGrath, T., et al. An Auto-Calibrating Knee Flexion-Extension Axis Estimator using Principal Component Analysis with Inertial Sensors. Sensors 2018, 18(6), 1882

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Evaluating the Ergonomic Benefit of a Wrist Brace on Wrist Posture, Muscle Activity, Rotational Stiffness, and Peak Shovel-Ground Impact Force During a Simulated Tree-Planting Task

Background Tree planters are at a high risk for wrist injury due to awkward postures and high wrist loads experienced during each planting cycle, specifically at shovel-ground impact. Wrist joint stiffness provides a measure that integrates postural and loading information. Objective The purpose of this study was to evaluate wrist joint stiffness requirements at the instant of shovel-ground impact during tree planting and determine if a wrist brace could alter muscular contributions to wrist joint stiffness. Method Planters simulated tree planting with and without wearing a brace on their planting arm. Surface electromyography (sEMG) from six forearm muscles and wrist kinematics were collected and used to calculate muscular contributions to joint rotational stiffness about the wrist. Results Wrist joint stiffness increased with brace use, an unanticipated and negative consequence of wearing a brace. As a potential benefit, planters achieved a more neutrally oriented wrist angle about the flexion/extension axis, although a less neutral wrist angle about the ulnar/radial axis was observed. Muscle activity did not change between conditions. Conclusion The joint stiffness analysis, combining kinematic and sEMG information in a biologically relevant manner, revealed clear limitations with the interface between the brace grip and shovel handle that jeopardized the prophylactic benefits of the current brace design. This limitation was not as evident when considering kinematics and sEMG data independently. Application A neuromechanical model (joint rotational stiffness) enhanced our ability to evaluate the brace design relative to kinematic and sEMG parameter-based metrics alone.