Scaffold-aided repair of articular cartilage studied by MRI

OBJECTIVE: The objective of the study was to evaluate the ability of the noninvasive magnetic resonance techniques to monitor the scaffold-aided process of articular cartilage repair. MATERIALS AND METHODS: Defects of 4 mm in diameter and 3 mm in depth were created in right knees of 30 adolescent white New Zealand rabbits. Fourteen rabbits were implanted with poly(lactide-co-glycolic acid) (PLGA) scaffold trimmed to match the size and the shape of the defect (PLGA+ group). No procedure was applied to the remaining 16 animals (PLGA- group). Animals were sacrificed sequentially at 4, 12, and 24 weeks after the surgery and magnetic resonance T (2)-weighted images (400 MHz) of the dissected bone plugs at eight different echo times were taken to derive T (2) relaxation time. The images and the T (2) time dependencies versus the tissue depth were statistically analyzed. Histological results of bone plugs were evaluated using semiquantitative histological scales. RESULTS: The results obtained for PLGA repair tissue were evaluated versus the PLGA- group and the healthy tissue harvested from the opposite knee (reference group), and compared with histological results (hematoxylin and eosin staining). The magnetic resonance images and T (2) relaxation time profiles taken 4 weeks after surgery for both the PLGA- and PLGA+ group did not reveal the tissue reconstruction. After 12 weeks of treatment T (2) time dependence indicates a slight reconstruction for PLGA+ group. The T (2) time dependence obtained for PLGA+ samples taken after 24 weeks of treatment resembled the one observed for the healthy cartilage, indicating tissue reconstruction in the form of fibrous cartilage. The tissue reconstruction was not observed for PLGA- samples. CONCLUSION: The study revealed correlation between magnetic resonance and histology data, indicating the potential value of using MRI and spatial variation of T (2) as the noninvasive tools to evaluate the process of articular cartilage repair. It also suggested, that the PLGA scaffold-aided treatment could help to restore the proper architecture of collagen fibrils.     

基于Petri网的港区综合能源系统优化调度建模研究

港区是交通行业重点耗能领域,如何提高能源利用效率、减少环境污染、实现综合能源管理是共同关注的话题.所以要进行综合能源的一体化设计,实现港区用能效率最优,提高能源基础设施利用率.在分析港区综合能源系统和负荷系统的基础上,采用多Agent系统和着色Petri网理论,建立港区综合能源系统优化调度模型,根据用电负荷合理分配综合...     

Melt electrospinning onto cylinders: effects of rotational velocity and collector diameter on morphology of tubular structures

Melt electrospinning writing is a direct‐writing additive manufacturing process that involves depositing a continuous, viscous and electrohydrodynamically stabilised molten jet onto a collector. Here, molten threads of medical‐grade polycaprolactone (PCL) are directed towards stationary/rotating cylindrical collectors (0–6600 rpm), including very slow revolutions well below the critical translation speed (approximately 600 mm min^?1) of the molten jet. In this slow‐rotation region, the speed of the jet is faster than the movement of the collector and buckled/coiled fibres are produced due to compressive viscoelastic forces. The results are porous PCL tubes with wall morphologies often associated with viscoelastic liquids impinging onto a surface. The curvature of the collector affects how the fibre is deposited, with preferential fibre deposition along the axis of the cylinder. When the collector rotation speed is increased to greater than the speed of the jet, then straight fibres are produced. Such tubular structures have applications in tissue engineering. © 2015 Society of Chemical Industry     

Quality analysis of hybrid adhesive-spot welded joints

In the paper, practical aspects of hybrid adhesive-welded joints are described. For the joints made of low-alloy car-body sheet steel HS340LA 1.2 mm thick at selected variable process parameters, a wide range of destructive and non-destructive tests was carried-out. The joints were made using three constructional adhesives, one of those dedicated for hybrid joints. For this adhesive, the most favourable hardening conditions were established. Quality analysis of hybrid joints was based on ultrasonic testing with use of an RSWA (Resistance Spot Weld Analyser) device, metallographic examinations, basic mechanical testing and tests at complex stress state, visual testing with a high-speed camera. Results were compared with adhesive bonding and spot welding. The whole research is summarized with conclusions drawn on the grounds of experimental and analytical results.     

Variational modelling of wave–structure interactions with an offshore wind-turbine mast

We consider the development of a mathematical model of water waves interacting with the mast of an offshore wind turbine. A variational approach is used for which the starting point is an action functional describing a dual system comprising a potential-flow fluid, a solid structure modelled with nonlinear elasticity, and the coupling between them. We develop a linearized model of the fluid–structure or wave–mast coupling, which is a linearization of the variational principle for the fully coupled nonlinear model. Our numerical results for the linear case indicate that our variational approach yields a stable numerical discretization of a fully coupled model of water waves and an elastic beam. The energy exchange between the subsystems is seen to be in balance, yielding a total energy that shows only small and bounded oscillations amplitude of which tends to zero with the second-order convergence as the timestep approaches zero. Similar second-order convergence is observed for spatial mesh refinement. The linearized model so far developed can be extended to a nonlinear regime.     

比托姆体育馆

项目所在地是波兰西南部上西里西亚地区。该地区是著名的煤矿开采中央区域。诸多相类似的地区当下都在进行空间和文化上的重塑。该体育馆设计是比托姆市此类复兴式建筑中唯一的一个体育项目,建筑师期许能够以此来重塑开采后被废弃的区域。     

Synthesis and characterization of the manganese cobaltite spinel prepared using two “soft chemical” methods

Using the coprecipitation method and EDTA gel processes, manganese cobaltite (Mn_1.5Co_1.5O₄) powders were successfully synthesized. The thermal decomposition behavior of the gel precursors, phase formation and morphology of the Mn_1.5Co_1.5O₄ powders were characterized by means of DTA/TGA and MS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Well-crystallized dual-phase manganese cobaltite spinel, containing both the cubic and tetragonal phases, was obtained at room temperature for both types of powders calcinated at 800 °C for 10 h in static air, without formation of any intermediate phase. SEM investigations show that the Mn_1.5Co_1.5O₄ powders prepared using two “soft chemical” methods were agglomerates composed of approximately micron-sized particles. The structure and morphology of the bulk samples, as well as their electrical conductivity, were investigated using XRD, SEM, and EIS, respectively. Mn_1.5Co_1.5O₄ spinels with different microstructure exhibited excellent electrical conductivity and structural stability. Major emphasis was placed on structural transformations of the spinel solid solutions with temperature and their effect on the electrical properties of these solutions.