Objective: To investigate the degree of stenosis of the internal carotid artery required for continuous blood flow in an interposition vein bypass to the middle cerebral artery. Methods: Computational fluid dynamics techniques were used to investigate a case of common carotid to middle cerebral artery brain bypass with varying degrees of internal carotid artery stenosis. Blood flow patterns across the patient-specific brain bypass were evaluated. Results: Simulation found that for cross section stenosis of less than 60%, no flow occurred in the bypass graft. Further narrowing of the internal carotid artery increased flow linearly within the bypass graft. There was significant energy loss and pressure gradient difference between the proximal and distal anastomosis sites of the bypass.
Conclusion: Computational fluid dynamics helps us to quantify the flow distribution, wall shear stress and pressure gradient in brain bypass surgery. The angle of the distal anastomosis had no effect on hemodynamic indices, allowing this consideration to be ignored in modeling. This modeling technique is useful to estimate the required degree of stenosis in the artery that is to be occluded to ensure sustained flow in the bypass. This will be of importance where there is staged surgery with a time interval between the bypass and the definitive internal carotid artery occlusion.
This review discussed the origin, manufacturing process, chemical composition, factors affecting quality and health benefits of matcha (Camellia sinensis), and the application of chemometrics and multi-omics in the science of matcha. The discussion primarily distinguishes between matcha and regular green tea with processing and compositional factors, and demonstrates beneficial health effects of consuming matcha. Preferred Reporting Items for Systematic Reviews and Meta-Analyses was adopted to search for relevant information in this review. Boolean operators were incorporated to explore related sources in various databases. Notably, climate, cultivar, maturity of tea leaves, grinding process and brewing temperature impact on the overall quality of matcha. Besides, sufficient shading prior to harvesting significantly increases the contents of theanine and chlorophyll in the tea leaves. Furthermore, the ground whole tea leaf powder delivers matcha with the greatest benefits to the consumers. The health promoting benefits of matcha are mainly contributed by its micro-nutrients and the antioxidative phytochemicals, specifically epigallocatechin-gallate, theanine and caffeine. Collectively, the chemical composition of matcha affected its quality and health benefits significantly. To this end, more studies are required to elucidate the biological mechanisms of these compounds for human health. Chemometrics and multi-omics technologies are useful to fill up the research gaps identified in this review.