• Geomechanics and Engineering
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• v.29 no.3
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• pp.291-300
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• 2022

Tunnel boring machines combined with the earth pressure balanced shield method (EPB shield TBMs) have been adopted in urban areas as they allow excavation of tunnels with limited ground deformation through continuous and repetitive excavation and support. Nevertheless, the expansion of TBM construction requires much more minor and exquisitely controlled surface settlement to prevent economic loss. Several parametric studies controlling the tunnel's geometry, ground properties, and TBM operational factors assuming ordinary conditions for EPB shield TBM excavation have been conducted, but the impact of excessive excavation on the induced settlement has not been adequately studied. This study conducted a numerical evaluation of surface settlement induced by the ground loss from face imbalance, excessive excavation, and tail void grouting. The numerical model was constructed using FLAC3D and validated by comparing its result with the field data from literature. Then, parametric studies were conducted by controlling the ground stiffness, face pressure, tail void grouting pressure, and additional volume of muck discharge. As a result, the contribution of these operational factors to the surface settlement appeared differently depending on the ground stiffness. Except for the ground stiffness as the dominant factor, the order of variation of surface settlement was investigated, and the volume of additional muck discharge was found to be the largest, followed by the face pressure and tail void grouting pressure. The results from this study are expected to contribute to the development of settlement prediction models and understanding the surface settlement behavior induced by TBM excavation.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.356-363
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• 2010

Background: Connexin 43-mediated gap junctional communication plays an important role in atherosclerosis. Numerous studies have demonstrated a correlation between mitral valve annular calcification and atherosclerotic disease. However, the relevance of connexin 43 to mitral valve disease remains unclear. We hypothesized that the mechanism contributing to mitral valve disease is associated with alterations in cell-to-cell communication mediated by changes in Connexin 43 expression. Material and Method: Twenty male New Zealand rabbits were divided into two groups: animals in group 1 (n=10) were fed a normal chow diet, whilst those in group 2 (n=10) received a diet containing 1% cholesterol for 12 weeks. After sacrificing the animals, the mitral valves were excised and analyzed with immunohistochemical staining and Real-time Reverse Transcriptase polymerase chain reaction (real time RT-PCR). Result: Myofibroblasts and macrophages were found concentrated within the endothelial layer on the ventricular side of the leaflet in the cholesterol diet group. Immunohistochemial staining showed elevated expression of connexin43 in the cholesterol diet group. Real-time RT-PCR revealed increased connexin43 mRNA levels in mitral valves from hypercholesterolemic animals. Conclusion: Our finding that connexin43 expression is increased in mitral valves of hypercholesterolemic rabbits suggests that alterations in cell-to-cell communication via connexin43 containing gap junctions play a role in the development of mitral valve disease in hypercholesterolemia.

• Journal of Cardiovascular Imaging
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• v.31 no.1
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• pp.18-23
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• 2023

BACKGROUND: Three-dimensional (3D) transesophageal echocardiogram (TEE) is the gold standard for the diagnosis of degenerative mitral regurgitation (dMR) and preoperative planning for transcatheter mitral valve repair (TMVr). TEE is an invasive modality requiring anesthesia and esophageal intubation. The severe acute respiratory syndrome coronavirus 2 pandemic has limited the number of elective invasive procedures. Multi-detector computed tomographic angiography (MDCT) provides high-resolution images and 3D reconstructions to assess complex mitral anatomy. We hypothesized that MDCT would reveal similar information to TEE relevant to TMVr, thus deferring the need for a preoperative TEE in certain situations like during a pandemic. METHODS: We retrospectively analyzed data on patients who underwent or were evaluated for TMVr for dMR with preoperative MDCT and TEE between 2017 and 2019. Two TEE and 2 MDCT readers, blinded to patient outcome, analyzed: leaflet pathology (flail, degenerative, mixed), leaflet location, mitral valve area (MVA), flail width/gap, anterior-posterior (AP) and commissural diameters, posterior leaflet length, leaflet thickness, presence of mitral valve cleft and degree of mitral annular calcification (MAC). RESULTS: A total of 22 (out of 87) patients had preoperative MDCT. MDCT correctly identified the leaflet pathology in 77% (17/22), flail leaflet in 91% (10/11), MAC degree in 91% (10/11) and the dysfunctional leaflet location in 95% (21/22) of patients. There were no differences in the measurements for MVA, flail width, commissural or AP diameter, posterior leaflet length, and leaflet thickness. MDCT overestimated the measurements of flail gap. CONCLUSIONS: For preoperative TMVr planning, MDCT provided similar measurements to TEE in our study.