ObjectivesThis study investigated the stage-specific and location-specific deposition and characteristics of minerals in human osteoarthritis (OA) cartilages via multiple nano-analytical technologies.MethodsNormal and OA cartilages were serially sectioned for micro-CT, scanning electron microscopy with energy dispersive X-ray spectroscopy, micro-Raman spectroscopy, focused ion beam scanning electron microscopy, high-resolution electron energy loss spectrometry with transmission electron microscopy, nanoindentation and atomic force microscopy to analyse the structural, compositional and mechanical properties of cartilage in OA progression.ResultsWe found that OA progressed by both top-down calcification at the joint surface and bottom-up calcification at the osteochondral interface. The top-down calcification process started with spherical mineral particle formation in the joint surface during early-stage OA (OA-E), followed by fibre formation and densely packed material transformation deep into the cartilage during advanced-stage OA (OA-A). The bottom-up calcification in OA-E started when an excessive layer of calcified tissue formed above the original calcified cartilage, exhibiting a calcified sandwich structure. Over time, the original and upper layers of calcified cartilage fused, which thickened the calcified cartilage region and disrupted the cartilage structure. During OA-E, the calcified cartilage was hypermineralised, containing stiffer carbonated hydroxyapatite (HAp). During OA-A, it was hypomineralised and contained softer HAp. This discrepancy may be attributed to matrix vesicle nucleation during OA-E and carbonate cores during OA-A.ConclusionsThis work refines our current understanding of the mechanism underlying OA progression and provides the foothold for potential therapeutic targeting strategies once the location-specific cartilage calcification features in OA are established.
Passive upper limb exoskeletons are often designed to relieve muscle fatigue of manufacturing workers. Existing exoskeletons often provide partial assistance, and their assistive torque is only affected by elastic elements and mechanisms, which, however, are not sufficient because of the changing load of the shoulder joint due to the motion of the elbow and the weight of various tools. To improve the assistive effect without affecting the free movement of the arm, a passive exoskeletal vest has been designed. This exoskeleton has two operating states which can be switched using a unique ratchet bar mechanism. The upper arm can be locked at any vertical position when engaged. The assistive torque is determined by the load. The arm also can move freely without any resistance when separated. Seven subjects participated in the evaluation experiment, who performed static tasks, precision tasks, and dynamic tasks. The experimental data demonstrate that (1) the exoskeleton can effectively reduce the activation level of related muscles at a variety of tasks. (2) The accuracy and stability of the arm during heavy work are not affected. (3) The exoskeleton has a minimal restriction on the range of motion of the arm. (4) the comfort and portability achieved a high score of 8 (1-10) from subjective measures. The experimental results further revealed that the designed exoskeletal vest could effectively relieve the shoulder burden, where it does not impede or restrain the arm's movements.
Security is one of the key issues in communications, but it has not attracted much attention in the field of underwater wireless optical communication (UWOC). This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing (OFDM) modulation, based on the three-layer chaotic encryption and chaotic discrete Fourier transform (DFT) precoding. The three-layer chaotic encryption processes are bit stream diffusion, in-phase/quadrature encryption, and time-frequency scrambling. With multi-fold data encryption, the scheme can create a keyspace of 9.7 × 10 179 , effectively resisting brute force attacks and chosen-plaintext attacks. A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.
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