Artificial
ligaments prepared from polyethylene terephthalate (PET)
are widely accepted for clinical anterior cruciate ligament (ACL)
reconstruction to recover the native function of knee joints. However,
due to the chemical inertness and hydrophobicity of PET, improving
its bioactivity and promoting graft–bone integration are still
great challenges. Inspired by the natural biomineralization process
on the surface of a historical stone, in this study, a bioactive organic/inorganic
composite coating that is composed of poly(allylamine hydrochloride)
and chondroitin sulfate with magnesium silicate (MgSiO3) doping is developed for surface modification of PET (MSPC-PET).
This composite coating promotes adhesion and proliferation of bone
marrow mesenchymal stem cells (BMSCs) and its bioactive inorganic
components (MgSiO3) could induce osteogenic differentiation
of BMSCs. Furthermore, an in vivo experiment indicated that this composite
coating might afford superior graft–bone integration between
MSPC-PET and the host bone tunnel, and fibrous scar tissue formation
was also inhibited. More importantly, a biomechanical analysis proved
that there was a strong integration between the MSPC-PET graft and
the bone tunnel, which will improve biomechanical properties for the
restoration of ACL function. This study shows that this bioactive
composite coating-modified PET graft for the ACL reconstruction can
effectively achieve good integration of ACL artificial grafts and
bone tunnels and prevent surgical failure.
The interaction between a permanent magnet (PM) assumed as a magnetic dipole and a flat high-temperature superconductor (HTS) is calculated by the advanced frozen-image model. When the dipole vertically moves above the semi-infinite HTS, the general analytical expression of vertical force and that of torque are obtained for an arbitrary angle between the magnetization direction of the PM and the c axis of the HTS. The variations of the force and torque are analyzed for angle and vertical movements in both zero-field cooling (ZFC) condition and field cooling (FC) condition. It is found that the maximum vertical repulsive or attractive force has the positive or negative cosine relation with the angle. However, the maximum torque has the positive or negative sine relation. From the viewpoint of the rotational equilibrium, the orientation of the magnetic dipole with zero angle is deemed to be an unstable equilibrium point in ZFC, but the same orientation is considered as a stable equilibrium point in FC. In addition, both of the variation cycles of the maximum force and torque with the angle are π.
Tectonic regime change refers to the process in which the two periods of tectonic movement changes and produce corresponding tectonic regime change surfaces (unconformity surfaces) and other geological responses in the process of basin development and evolution. The change of tectonic movement is the root cause of tectonic regime change. Tectonic regime changes produce different geological responses, which can be used as the signs to identify tectonic regime changes. In order to study the characteristics of tectonic regime changes of Chepaizi Uplift in Junggar Basin and the control on oil and gas migration and accumulation, four stages of tectonic regime changes were identified by using the techniques of the rock acoustic emission (AE) technology, tectonic subsidence analysis, and tectonic stratigraphic sequence analysis, which occurred at the end of Early Permian, the end of Late Triassic, the end of Jurassic, and the end of Paleogene, respectively. The main stratigraphic product of tectonic regime change is the unconformity structure. The unconformity structure has obvious stratification, including the bottom conglomerate layer, the weathered clay layer, and the semiweathered rock layer, and plays an important role in controlling oil and gas migration and accumulation. The weathered clay layer and the hydrolysis layer have a sealing and shielding effect on oil and gas; the leaching layer can become the effective reservoir; at the same time, the leaching layer can provide a channel for the lateral transportation of oil and gas.
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