Atherosclerosis is an important cause of cardiovascular disease. The wall shear stress (WSS) is one of the key factors of plaque formation and dislodgement. Currently, WSS estimation is based on the measurement of the blood velocity gradient. However, due to the lack of flow field measurements in carotid stenosis vessels, the two distribution forms (parabolic and non-parabolic) commonly considered in numerical simulations could cause WSS estimates to differ by more than 40%, which could seriously affect the accuracy of mechanical analysis. This study applied three-dimensional (3D) printing technology to create an experimental model of real-structure carotid arteries. Microparticle image velocimetry was adopted to comprehensively measure blood velocity field data at the stenosis location, providing experimental validation of numerical simulation (Fluent; finite volume method) results. Then, the flow field was simulated at a normal human heart rate (45–120 beats per minute). The radial sectional velocity exhibited a plateau-like distribution with a similar velocity in the central region (more than 65% of the total channel width). This study provides an accurate understanding of the WSS at the carotid stenosis location and proposes a reliable method for the study of flow fields under various blood flow conditions.

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In petroleum production, microbial investigations are essential for microbial-induced corrosion (MIC) control and enhanced oil recovery (EOR) processes. It is suggested that microorganisms can attach to the inner wall of pipes as biofilms, which are more stable and could cause more serious corrosion than planktonic microorganisms in the water phase. At present, research on the biofilms during oil production is mainly focused on the surface pipelines, while few reports have directly investigated biofilms in vertical deep wells. Therefore, in this study, wellbore biofilms were sampled during well workover from several well-tube segments corresponding to different original depths (approximately 0, 840, and 1330 m). The injected water was sampled as well. The results of the 16S rRNA gene library sequencing showed that the biofilms and water-phase communities were distinct (dissimilarity of 0.56–0.64), although they shared 64 OTUs. At the phylum level, the relative abundance of Proteobacteria was 74.65% in the water phase and only 7.86–27.41% in the biofilms. The dominant phylum, Firmicutes, was 6.03–41.21% in the three biofilms, while only 1.16% in the water phase. With increasing depth, the biofilm communities became more diverse (Shannon index of 3.43–4.21), more anaerobic, and more thermophilic possibly due to the depleting oxygen and increasing temperature in samples from the deeper well. For instance, the relative abundance of anaerobes (archaea and strict anaerobic bacteria) in biofilms increased from 18.32 to 40.53%. Thermophilic bacteria (such as Kosmotoga) increased from 6.65 to 15.82%. Among methanogens, hydrogenotrophic genera (such as Methanobacterium and Methanolinea) increased from 3.66 to 9.68%. This study revealed the structural differences between water-phase and biofilm communities in the well, and the depth-dependent distribution of the biofilm communities. These results improved the understanding of microbial ecology in wellbores, which will benefit microbial activity control measures applied in oil production processes, including MIC and oil recovery.

Atherosclerotic stenosis of the carotid artery may lead to cerebral infarction, stroke and other serious consequences, and it is usually treated clinically with carotid endarterectomy. By comparing the pre- and postoperative flow fields, it can be shown that the operation improves hemodynamic parameters such as the velocity, wall shear stress and wall pressure of the local flow field of the carotid artery. However, previous studies have rarely considered the difference between postoperative and healthy carotid flow fields, and thus the cause of any postoperative restenosis may remain hidden. Therefore, this study constructed preoperative, postoperative and (hypothetically) healthy carotid artery models based on the real vascular structure data of a patient and applied numerical simulations verified by physical models to compare hemodynamic parameters such as flow rate, flow state, and wall shear. The results showed that after the operation, the maximum carotid blood flow velocity decreased from 2.8 m/s to 1.02 m/s, the maximum wall shear stress decreased from 190 Pa to approximately 75 Pa, the wall pressure of the carotid inlet recovered from 3000 Pa to 400 Pa, and the vortex in the distal ICA disappeared. In addition, this study also found a vortex and low-level wall shear stress of approximately 5 Pa remained in the carotid bifurcation after the operation, which also lacked spiral flow, unlike the healthy model. Therefore, due to the morphological differences between the postoperative and healthy carotid artery, adverse hemodynamic factors and a potential risk of postoperative restenosis will remain after the procedure.