Defect engineering modified graphite carbon nitride (g-C3N4) has been widely used in various photocatalytic systems due to the enhanced catalytic activity by multiple defect sites (such as vacancies or functional...

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Roller pumps are commonly used in circulatory assist devices to deliver blood, but the inherent high mechanical stresses (especially wall shear stress) may cause considerable damage to cells. Conventional experimental approaches to evaluate and reduce device-induced cell damage require considerable effort and resources. In this work, we describe the use of a new computational fluid dynamics method to more effectively study roller pump systems. A generalized parametric model for the fluid field in a typical roller pump system is presented first, and analytical formulations of the moving boundary are then derived. Based on the model and formulations, the dynamic geometry and mesh of the fluid field can be updated automatically according to the time-dependent roller positions. The described method successfully simulated the pulsing flow generated by the pump, offering a convenient way to visualize the inherent flow pattern and to assess shear-induced cell damage. Moreover, the highly reconfigurable model and the semiautomated simulation process extend the usefulness of the presented method to a wider range of applications. Comparison studies were conducted, and valuable indications about the detailed effects of structural parameters and operational conditions on the produced wall shear stress were obtained. Given the good consistency between the simulated results and the existing experimental data, the presented method displays promising potential to more effectively guide the development of improved roller pump systems which produce less mechanical damage to cells.

The key to image-guided surgery (IGS) technology is to find the transformation relationship between preoperative 3D images and intraoperative 2D images, namely, 2D/3D image registration. A feature-based 2D/3D medical image registration algorithm is investigated in this study. We use a two-dimensional weighted spatial histogram of gradient directions to extract statistical features, overcome the algorithm’s limitations, and expand the applicable scenarios under the premise of ensuring accuracy. The proposed algorithm was tested on CT and synthetic X-ray images, and compared with existing algorithms. The results show that the proposed algorithm can improve accuracy and efficiency, and reduce the initial value’s sensitivity.

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