Mechanical properties of nerve roots and rami radiculares isolated from fresh pig spinal cords

No reports have described experiments designed to determine the strength characteristics of spinal nerve roots and rami radiculares for the purpose of explaining the complexity of symptoms of medullary cone lesions and cauda equina syndrome. In this study, to explain the pathogenesis of cauda equina syndrome, monoaxial tensile tests were performed to determine the strength characteristics of spinal nerve roots and rami radiculares, and analysis was conducted to evaluate the stress-strain relationship and strength characteristics. Using the same tensile test device, the nerve root and ramus radiculares isolated from the spinal cords of pigs were subjected to the tensile test and stress relaxation test at load strain rates of 0.1, 1, 10, and 100 s-1 under identical settings. The tensile strength of the nerve root was not rate dependent, while the ramus radiculares tensile strength tended to decrease as the strain rate increased. These findings provide important insights into cauda equina symptoms, radiculopathy, and clinical symptoms of the medullary cone.

First mushroom-shaped adhesive microstructure:A review

This letter reviews the adhesive and frictional properties of the first mushroom-shaped adhesive microstructure （MSAMS）, which has come a long way from inspiration by the attachment devices evolved in beetles to a large-scale industrial production. It was shown to have an that about twice higher pull-off force compared to a smooth control made from the same material measured on smooth substrates. Pull-off forces measured underwater are even higher than those in air. Moreover, it retained adhesive performance over thousands of attachment cycles and initial adhesive capability could be recovered by washing after being contaminated. In shearing, MSAMS exhibits reduced and stabilized friction in comparison with a smooth control, which demonstrated pronounced stick-slip motion, and shows zero pull-off force in a sheared state, allowing the adhesion to be switched on and off. The presence of a fluid in the contact zone showed adhesion enhancement on both smooth and rough substrates. All these features lead us to conclude that MSAMS may have practical potential in a variety of applications.

HOW DIFFERENT VARIABLES AFFECT THE ACCURACY OF HAND-TIMING

To analyze the process of hand-timing and the resulting data collected from the hand-timing computer system(HTCS),including the timing operator′s reaction times of starting and stopping the watch,the results from the timing,the simulated electronic timing,the major factor that affects the time-keeper′s accuracy of time-keeping were studied,i.e.the stability of the timekeeper′s reaction time,rather than the time-keeper′s reation time.The leading cause that inflicts error between the hand-time-keeping and the electrionic time-keeping consists in the pitfall that the time-keeper makes a wrong judgment in stopping the watch.The analytical results provide theoretic gist for the selection and training of time-keeping operators.

New simulation model for bone formation markers in osteoporosis patients treated with once-weekly teriparatide

Daily 20-mg and once-weekly 56.5-mg teriparatide（parathyroid hormone 1–34） treatment regimens increase bone mineral density（BMD） and prevent fractures, but changes in bone turnover markers differ between the two regimens. The aim of the present study was to explain changes in bone turnover markers using once-weekly teriparatide with a simulation model. Temporary increases in bone formation markers and subsequent decreases were observed during once-weekly teriparatide treatment for 72 weeks. These observations support the hypothesis that repeated weekly teriparatide administration stimulates bone remodeling, replacing old bone with new bone and leading to a reduction in the active remodeling surface. A simulation model was developed based on the iterative remodeling cycle that occurs on residual old bone. An increase in bone formation and a subsequent decrease were observed in the preliminary simulation. For each fitted time point, the predicted value was compared to the absolute values of the bone formation and resorption markers and lumbar BMD. The simulation model strongly matched actual changes in bone turnover markers and BMD. This simulation model indicates increased bone formation marker levels in the early stage and a subsequent decrease. It is therefore concluded that remodeling-based bone formation persisted during the entire treatment period with once-weekly teriparatide.

Biomechanical study of the atlantoaxial joint after artifi- cial atlanto-odontoid joint arthroplasty

Objective： To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint （AAOJ） arthroplasty by comparing with a conventional method. Methods： After anterior decompression, 24 human ca- daveric spinal specimens of C0-C3 were randomly divided into two groups： Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw （ATAS） fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation. Results： Compared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a sig- nificant decrease in the range of motion （ROM） and neu-tral zone （NZ） during flexion, extension and lateral bending （P〈0.05）; however, with regard to axial rotation, there was no significant difference in ROM and NZ （P〉0.05）. Com- pared with anterior decompression with ATAS fixation, an- terior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant differ- ence was found in ROM and NZ （P〉0.05）; however, as for axial rotation, there was a significant increase in ROM and NZ （P〈0.05）. Conclusion： The self-designed AAOJ has an excellent biomechanical performance, which can restore excellent in- stant stability and preserve the movement of the atlanto- axial joint.

Switchable shape memory polymer bio-inspired adhesive and its application for unmanned aerial vehicle landing

Controlled and switchable adhesion is commonly observed in biological systems.In recent years,many scholars have focused on making switchable bio-inspired adhesives.However,making a bio-inspired adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge.A Shape Memory Polymer Bio-inspired Adhesive(SMPBA)was successfully developed,well realizing high adhesion(about 337 kPa),relatively low preload(about90 kPa),high adhesion-to-preload ratio(about 3.74),high switching ratio(about 6.74),and easy detachment,which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect(SME).Furthermore,SMPBA exhibits adhesion strength of80–337 kPa on various surfaces(silicon,iron,and aluminum)with different roughness(Ra=0.021–10.280)because of the conformal contact,reflecting outstanding surface adaptability.The finite element analysis verifies the bending ability under different temperatures,while the adhesion model analyzes the influence of preload on contact area and adhesion.Furthermore,an Unmanned Aerial Vehicle(UAV)landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces.This study provides a novel switchable bio-inspired adhesive and UAV landing method.

The Role of Vanes in the Damping of Bird Feathers

Bird feathers sustain bending and vibrations during flight.Such unwanted vibrations could potentially cause noise and flight instabilities.Damping could alter the system response,resulting in improving quiet flight,stability,and controllability.Vanes of feathers are known to be indispensable for supporting the aerodynamic function of the wings.The relationship between the hierarchical structures of vanes and the mechanical properties of the feather has been previously studied.However,still little is known about their relationship with feathers’damping properties.Here,the role of vanes in feathers’damping properties was quantified.The vibrations of the feathers with vanes and the bare shaft without vanes after step deflections in the plane of the vanes and perpendicular to it were measured using high-speed video recording.The presence of several main natural vibration modes was observed in the feathers with vanes.After trimming vanes,more vibration modes were observed,the fundamental frequencies increased by 51-70%,and the damping ratio decreased by 38-60%.Therefore,we suggest that vanes largely increase feather damping properties.Damping mechanisms based on the morphology of feather vanes are discussed.The aerodynamic damping is connected with the planar vane surface,the structural damping is related to the interlocking between barbules and barbs,and the material damping is caused by the foamy medulla inside barbs.