Arch Wall Research Articles

Application Of Particle Image Velocimetry For The Anatomical Comparison Of Haemodynamics In Healthy And Treated Aortas.

The leading cause of mortality and morbidity globally is cardiovascular disease (CVD). CVD can present in the thoracic aorta as atherosclerosis, an aneurysm or a dissection, which can be related to certain fluid mechanics metrics. This study investigates the fluid flow profiles within a healthy and a branched endovascular graft-treated rigid phantom, manufactured from Sylgard 184, to determine the effect geometry has on the resulting fluid mechanics and the subsequent biological processes. Planar particle image velocimetry data was recorded to visualise steady flow conditions at Reynolds numbers 4500 (peak), 3400 (mean), and −225 (reverse). Evaluation of anatomical features affecting the flow fields, concluded that the tapering of the healthy thoracic aorta naturally aids in the prevention of low flow on the inner arch wall more effectively than the untapered graft-treated model. Focus on the aortic branches demonstrated the angle of the aortic branches in relation to the aortic arch, highly affects the regions of low and high blood flow present within each branch. However, due to the biological response (or lack of) associated with a cellular boundary and synthetic material, the haemodynamic changes in the aortic arch and branches have different challenges. Therefore, direct replication of a healthy geometry is not necessarily optimal for the design of an endovascular graft.

Combined Pubic Arch and Ischial Bone Resection for Metachronous and Frequent Local Recurrences of Rectal Cancer.

Complete surgical resection with negative margins remains the cornerstone for curative treatment of rectal cancer; however, local recurrence can pose a significant challenge. Herein, we aimed to introduce a novel surgical technique for combined resection of the pubic arch and ischial bone in the context of treating recurrent rectal cancer. We present a case of a patient with a fourth local recurrence of rectal cancer, with no evidence of distant metastasis. The tumor directly invaded the posterior wall of the pubic arch. To achieve complete tumor resection, an osteotomy was performed using a thread wire saw at the bilateral pubic rami and ischial bones. Intraoperative frozen section analysis (rapid tissue examination) was conducted on tissue samples from the lateral margins of the planned osteotomy line. Samples were negative for adenocarcinoma (cancerous cells). The combined resection of the pubic arch and ischial bone was successfully performed with negative margins for adenocarcinoma, as confirmed by frozen section analysis. Mastery of the surgical technique for combined resection of the pubic arch and ischial bone may be clinically significant for achieving complete resection in cases of multiple resections for locally recurrent rectal cancer.

Simulation of Elbow Erosion of Gas–Liquid–Solid Three-Phase Shale Gas Gathering Pipeline Based on CFD-DEM

Shale gas gathering pipelines often contain liquid water and solid sand in the early stage of production, which leads to the failure of pipeline components easily under the action of gas–liquid–solid three phases. A computational fluid dynamics (CFD) model based on the fluid volume method (VOF) and discrete element method (DEM) was established to study the flow law of gas–liquid–solid three-phase flow in the elbow of shale gas gathering pipeline and the erosion law of the inner surface of the elbow was studied by coupling the Oka erosion prediction model. By comparing the experimental results of erosion damage of the elbow, it is found that the model established can well predict the erosion characteristics and erosion amount under the action of three phases. Combined with the field pipeline parameters and operating conditions, the paper further simulates the elbow erosion behavior under relevant working conditions. The results show that the particles rotate clockwise from the outer wall of the pipe through the bottom of the pipe when passing through the elbow under the action of gas and water phases. When the gas velocity increases, the particles at the elbow mainly gather at the bottom of the elbow and the wall of the outer arch. When the water content increases gradually, the particles gathered on the outer arch wall of the elbow move along the outer arch wall of the elbow and face the inner arch surface gradually, and the erosion area is mainly concentrated on the outer arch wall of the elbow and the outlet horizontal pipe. Under the condition of the liquid phase, the movement characteristics of the water phase and particles in the elbow of the gas gathering pipeline and the erosion characteristics of the pipeline surface are obviously different from those under the condition of the gas–solid two-phase. The model and simulation results established in this paper provide a reference for the erosion damage protection of shale gas gathering pipeline elbow.

Oxytocin receptor expressing neurons utilize Piezo2 to mediate the baroreflex in female mice

Oxytocin is a neuropeptide in clinical trials for mental health disorders that is also reported to have beneficial effects on cardiovascular function. Arterial baroreceptors contribute to cardiovascular function by relaying information pertaining to perfusion pressure to the brain. Neurons that give rise to arterial baroreceptors reside in the nodose ganglion (NG). These neurons utilize Piezo2, a mechanosensitive ion channel, to convert pressure and stretch exerted on the vascular wall of the aortic arch into action potentials that are carried by the vagus nerve to the brain. Upon receiving this information, the brain initiates the baroreflex which adjusts cardiac output and vasculature resistance to maintain blood pressure at optimal levels. Interestingly, we have determined that a subpopulation of NG neurons express both the oxytocin receptor (Oxtr) and Piezo2. Here, we test the overall hypothesis that Piezo2 synthesized by Oxtr-expressing neurons mediate cardiovascular function in male and female mice. Mice that express Cre-recombinase at the Oxtr locus were bred to mice with LoxP sites flanking the Piezo2 gene. This resulted in offspring with the Piezo2 gene selectively deleted from cells that express the Oxtr gene (Oxtr Piezo2 KO) or littermates only harboring LoxP sites flanking the Piezo2 gene (controls). To validate the selective deletion of Piezo2 from neurons that express Oxtr, we used RNAscope in situ hybridization to label Oxtr and Piezo2 mRNAs within the NG. In control mice, we frequently observed NG neurons double-labeled for Oxtr and Piezo2 mRNAs. In contrast, colocalization of these mRNAs was not observed in NG neurons obtained from OxtrPiezo2 KO mice. Cardiovascular recordings were performed in anesthetized mice administered the vasoactive drug phenylephrine (PE; i.v.) to determine whether deletion of Piezo2 from Oxtr-expressing neurons affects blood pressure, heart rate, and the baroreflex. Baseline systolic blood pressure was lower in male OxtrPiezo2 KO mice compared to controls but resting heart rate was similar amongst the groups. Pressor and bradycardic responses to PE were not different between male OxtrPiezo2 KO mice and controls, suggesting that deletion of Piezo2 from Oxtr-expressing neurons has no effect on the baroreflex in male mice. Female OxtrPiezo2 KO mice had baseline systolic blood pressure and heart rate that were similar to controls. In females, delivery of PE similarly increased systolic blood pressure in OxtrPiezo2 KO mice and controls, but remarkably, the significant bradycardia that was observed in control mice was completely absent in female OxtrPiezo2 KO mice. Collectively, these results suggest that Piezo2 expression in neurons that synthesize Oxtr is necessary to evoke the baroreflex specifically in female mice. AHA 23POST1020034 to KE. NHLBI R01HL136595, R35HL150750, R01HL145028 and NCCIH R65AT012142 to ADK & EGK. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Influence of brine leakage on frozen wall development in offshore sand layer when active freezing: A numerical study

Brine leakage after freezing pipe fracture when active freezing will cause local structural defects or even failure of frozen wall. A water-heat-solute coupled model that includes a modified Michalowski model considering both temperature and salt concentration was proposed to simulate the freezing construction in offshore sand layer. It was verified by the artificial freezing model tests of saturated saline sand under seepage. The structural defects of frozen wall were observed at the boundary between straight and arch walls on the upstream. The range of the structural defect and the closing time of frozen wall both rise with larger pressure head. The brine leakage was then simulated to evaluate the effects of both pressure head and fracture range of freezing pipe on the structural defect of frozen wall. As indicated by the normalized unfrozen water content contour, there are obvious flaws in determining whether the frozen wall is closed only by the average temperature when brine leakage. A characteristic index, the area ratio of structural defect of frozen wall, was derived from the normalized unfrozen water content contour. The structural defect results from brine leakage when the pressure head is below 2.0 m, otherwise from both brine leakage and groundwater seepage. It is recommended that in addition to monitoring temperature during active freezing, additional moisture monitoring devices should be installed to prevent brine leakage hazards.

P421 INTRA–CARDIAC AND ALL LAYERS CARDIAC INVOLVEMENT BY SQUAMOUS NON–SMALL CELL LUNG CANCER

Abstract A 73 year–old man was referred by his general practitioner to our ambulatory for worsening dyspnea. He also reported substantial weight loss (almost 20 kg during the last three months), new onset dysphonia and dry cough. The patient’s medical history also included a former tobacco addiction, arterial hypertension and dyslipidemia. There was not history of cardiomiopathy. Electrocardiogram, showed: sinus rhythm, 60/min with inferior and anterior–lateral abnormality of repolarization. No laboratory exams were available at the first visit. An echocardiogram was performed, showing: marked septal hypertrophy (IVSd= 23 mm), septal hypokinesia, with an ejection fraction at lower limits of normality (EF= 54%), neither systolic anterior motion of the mitral valve. Minimal pericardial effusion was seen. We required a CT scan of the chest, that showed a large (5x8x11cm) mass in the left upper lobe with ipsilateral mediastinal lymphadenopathy. The mass directly extended into the mediastinum with infiltration of pericardial leaflet, left atrium and the left wall of the aortic arch. A hypodense formation of approximately 4 cm in the interventricular septum in the apical portion was reported. PET–CT with FDG was performed, which documented hypercaptation of the radioactive tracer at the level of the above–mentioned lesions. The patient underwent fine–needle aspiration biopsy of the lung mass and the histological examination led to the diagnosis of squamous cell carcinoma of the lung. Systemic treatment with carboplatin plus placlitaxel and pembrolizumab was subsequently started. A cardiac CMR was performed, which documented an area of 30x17x31 mm located at the septal (mid–apical portion), apex and parapical portion of the free wall of the right ventricle with transmural extension. At this area, extensive late gadolinium enanchement (LGE) at marginal level with a central non–capillary core and hyperintense in T2 sequences (compatible with central necrotic lesion). The pericardium also showed LGE and a mild pericardial effusion (maximum 8 mm); left atrium involvement, seen on CT, was not documented . After he completed the third cycle of CHT, at 5 months from the diagnosis, the echocardiogram showed a substantial disappearance of the mass infiltrating the interventricular septum without evidence of pericardial effusion. The ecg was substantially unchanged. The patient stopped carboplatin and paclitaxel after 3 cycles and kept maintenance pembrolizumab still ongoing.

Shaking table tests of large cross-sectional multi-crack tunnel linings

To study the dynamic response law of large-section cracked lining structures under seismic waves, comparative tests of large-scale shaker tunnel models of non-destructive lining structure (model 1), a crack in the vault of the lining structure (model 2), and two parallel cracks in the vault of the lining structure (model 3) were carried out by applying 0.1-1.0 g progressively increasing the peak acceleration of the input waves. This paper visually showed the distribution of cracks in three groups of the lining structures. In addition, the acceleration response of the lining and surrounding rock, dynamic soil pressure, the dynamic strain on the inner and outer surfaces of the lining, and dynamic internal force variation were obtained, and the seismic performance of three groups of lining structures was discussed. The results showed that the seismic weak positions of model 1 were the arch shoulder and the arch foot, the seismic weak positions of model 2 were the arch shoulder, the arch foot, the initial damage area, and the inverted arch, and the seismic weak positions of model 3 were the positions of the arch foot, the cracks of the vault, the inverted arch, and the arch wall. The soil pressure values at the vault of three groups of models were model 2 > model 1 > model 3 in turn. The surrounding rock amplified the input seismic waves. With the gradual increase of the peak acceleration, the seismic energy was gradually consumed due to plastic damage to the lining structure or the loosening and destruction of the overlying soil, resulting in the acceleration amplification coefficient value of the surrounding rock in the upper part of the lining structure showing a changing trend of first increasing and then decreasing. When the peak acceleration was 0.2 g, the crack propagation phenomenon occurs in the initial crack position of model 2 and model 3. When the peak acceleration was 0.4 g, the cracking phenomenon occurs at the right arch foot of model 1. The above phenomenon confirmed the conclusion that cracks can weaken the seismic performance of the structure. When the peak acceleration was 0.8 g, the peak values of the amplification coefficient of the lining at the inverted arch and near the filled soil surface were about 1.2 and 1.6 respectively. The research results can provide a reference for the seismic performance evaluation of cracked tunnels.

Clinical Characteristics and Computed Tomography Findings in Adult Patients With an Aberrant Right Subclavian Artery: A Single-Center Retrospective Cohort Study.

We sought to determine the prevalence and possible features associated with symptoms in adult patients diagnosed with an aberrant right subclavian artery (ARSA). In this single-center retrospective study, 386 adult patients were diagnosed with ARSA on chest CT scans performed between June 2016 and April 2021. Patients were grouped by the presence of symptoms, which included dysphagia, shortness of breath, cough, and upper airway wheezing. Four cardiothoracic radiologists reviewed the chest CT scans to assess features of ARSA. Agreement and multivariable logistic regression analyses were performed to determine interobserver variability and features associated with the presence of symptoms, respectively. The prevalence of ARSA was 1.02% and 81.3% of patients were asymptomatic. Shortness of breath (74.6%) was the most common symptom. Interobserver agreement was acceptable with most variables having an interclass correlation coefficient or κ >0.80. A patient's height > 158 cm (OR: 2.50, P = 0.03), cross-sectional area > 60 mm 2 of ARSA at the level of the esophagus (OR: 2.39, P = 0.046), and angle >108 degrees formed with the aortic arch (OR: 1.99, P = 0.03) were associated with the presence of symptoms on multivariable logistic regression. A distance increase per 1 mm between ARSA and trachea (OR: 0.85, P = 0.02) was associated with decreased odds of symptoms. Aberrant right subclavian artery is an incidental finding in most adult patients. The cross-sectional area at the level of the esophagus, angle formed with the medial wall of the aortic arch, distance between the ARSA and the trachea, and a patient's height were features associated with the presence of symptoms.

Application of the 5F JL4 Catheter in Bronchial Artery Embolization With the Opening in the Inferior Wall of the Aortic Arch.

We investigated the efficacy and safety of bronchial artery embolization (BAE) using a 5F JL4 catheter in patients with hemoptysis and a bronchial artery opening in the inferior wall of the aortic arch. This was a single-center retrospective study. Seventeen patients underwent BAE using 5F JL4. We then evaluated technical success (TS), clinical success (CS), incidence of complications, and hemoptysis recurrence rate (RR). The TS rate of microcatheter superselective catheterization and CS rate after surgery were 100%, and the incidence of severe complications and postoperative RR were 17.6%. Bronchial artery embolization for hemoptysis with a BA opening in the inferior wall of the aortic arch using the 5F JL4 catheter could be a safe method. The short- and medium-term results were excellent.

An unusual occurrence of penetrating aortic arch injury by a ball-point pen: a case report and review of the literature

BackgroundAortic arch injuries account for about 8% of thoracic aortic injuries. Penetrating zone I neck injuries account for 18% of vascular injuries in the neck and have great potential to traverse to involve thoracic vascular structures as well. The hard and soft signs of vascular injury facilitate triage of patients on an individual basis. We present a case of a ball-point pen traversing through zone I of the neck and causing penetrating aortic arch injury with minimal mediastinal haemorrhage.Case presentationWe present a polytrauma patient who was admitted with traumatic brain injury and a ball-point pen lodged above the sternal notch in zone I of the neck following a road traffic accident. He underwent mediastinal exploration via a median sternotomy. The ball-point pen was found penetrating the anterior wall of the aortic arch and resting in its lumen. The ball-point pen was successfully explanted and primary repair of the penetrating aortic arch injury was done. He had an uneventful recovery without any added secondary neurological complications.ConclusionPenetrating aortic arch injuries are rare compared to injuries of the ascending aorta and descending aorta. They require a high index of suspicion, rapid investigation and urgent intervention in view of their high associated fatality. The ball-point pen in this case assumed the shape of a plug which acted as a seal at the site of injury preventing catastrophic exsanguination.

Shock Environment Assessment of Underground Arch–Wall Structures Subjected to Ground Shock

Shock Environment Assessment of Underground Arch–Wall Structures Subjected to Ground Shock

Arch Height Effect and Optimal Section Selection of Strata Behavior of Straight Wall Arch Roadway Under Mining Condition

Arch Height Effect and Optimal Section Selection of Strata Behavior of Straight Wall Arch Roadway Under Mining Condition

The Importance of TEE Examination in Patients with Pseudoaneurysm of Arch of Aorta Post-TEVAR Procedure

AbstractA 57-year-old male patient presented to the emergency department with acute onset severe and tearing pain in the back. He was a chronic smoker and was a known hypertensive. He was admitted in view of type B aortic dissection with entry tear distal to left subclavian artery (LSCA) and underwent thoracic endovascular aortic repair (TEVAR) procedure for the same. Two stents (34–30–200mm size, Ankura, Lifetech, Nanshan District, Shenzhen, China) were placed overlapping each other to cover the dissection flap starting from distal end of left common carotid artery to proximal part of celiac artery. Post-stenting, patient developed recurrent episodes of melena, abdominal distension, and fever that were managed conservatively. Two months later, a routine follow-up computed tomographic aortic angiography revealed a focal contrast filled outpouching (2.1*1.9cm) extending from the proximal part of endovascular stent with surrounding thrombosis from anterior wall of the aortic arch. On inspecting the arch vessels, an ostial occlusion of LSCA was also discovered. Routine blood investigations were all within normal limits. Two-dimensional echocardiography showed a normal biventricular function with concentric left ventricular hypertrophy. All valves were normal.

A canine model of aortic arch aneurysm created with autologous pericardium

BackgroundTo establish a canine model of aortic arch aneurysm that is suitable for research on new devices and techniques applied to the aortic arch. Materials and methodsFifteen mongrel dogs underwent surgery. The autologous pericardial patch was sewn on the aortotomy site in the anterior wall of the aortic arch. The animals were followed up for 3 months postoperatively. Computed tomography angiography was used to visualize and measure the aneurysm model. Hematoxylin and eosin staining was used to observe the histological characteristics of the aneurysm model. Changes in aneurysm diameter over time were analyzed using analysis of variance. ResultsOne dog died of hemorrhage during surgery. Fourteen dogs survived the surgical procedure. Two of them died on the first postoperative day because of ruptures at the suturing margin. The diameter of the aneurysm model was twice as large as that of the aortic arch. There was no significant change in the maximum diameter of the aneurysm model during the follow-up period. ConclusionsWe established a controllable and stable aortic arch aneurysm model created with an autologous pericardium patch. The aneurysm model can be used to research endoleaks after thoracic endovascular aortic repair and new endovascular techniques can be applied to the aortic arch.

Endocrine Disruptor Bisphenol a Affects the Neurochemical Profile of Nerve Fibers in the Aortic Arch Wall in the Domestic Pig.

Bisphenol A (BPA) is a synthetic compound utilized in industry for the production of various plastics. BPA penetrates into the environment and adversely affects living organisms. Therefore, the influence of various BPA dosages on the neurochemical characteristics of nerve fibers located in the aortic branch wall was investigated in this study utilizing a double immunofluorescence method. It was found that BPA in concentration of 0.5 mg/kg body weight/day causes a clear increase in the density of nerves within aortic branch walls immunoreactive to cocaine- and amphetamine-regulated transcript (CART), calcitonin gene-related peptide (CGRP), neuronal isoform of nitric oxide synthase (nNOS), pituitary adenylate cyclase-activating peptide (PACAP), and vasoactive intestinal polypeptide (VIP). Nerves containing galanin (GAL) and/or somatostatin (SOM) did not change when BPA was introduced into the system. Changes noted after administration of BPA at a dose of 0.05 mg/kg body weight/day were less visible and concerned fibers immunoreactive to CART, CGRP, and/or PACAP. The obtained results show that BPA affects the neurochemical coding of nerves in the aortic branch wall. These fluctuations may be the first signs of the influence of this substance on blood vessels and may also be at the root of the disturbances in the cardiovascular system.

Aortic knob width is associated with non-dipping blood pressure pattern

Background: Aortic knob width (AKW) is the measurement of the radiographic configuration composed of the foreshortened aortic arch and a part of the descending aorta. We investigated the relationship between the nondipper pattern and AKW. Material and methods: All patients’ office blood pressure measurements and 24-hour ambulatory blood pressure readings were recorded. A blood pressure drop of less than 10% was defined as non-dipping. The patients were grouped into Group 1; dipper pattern (37 patients; 22F, and mean age 49.2 ± 11.7 yrs) and Group 2; non-dipper pattern (64 patients; 37F, and mean age 53.7 ± 13.1 yrs). On posteroanterior chest radiography, the widest point of the aortic knob was measured along the straight imaginary line from the lateral edge of the trachea to the left lateral wall of the aortic arch. Results: AKW was significantly higher in Group 2 compared to group 1 (36.7 ± 5.7 vs. 30.7 ± 4.5 mm, p < 0.001). The mean daytime and night-time systolic blood pressures, the mean night-time diastolic blood pressure levels, 24-hour mean blood pressure and mean pulse pressures were higher; percentage of nocturnal drops was significantly lower in Group 2 compared to Group 1. AKW was determined to be the parameter that was mostly related to the non-dipper pattern. A ROC analysis revealed that the area under the curve values for AKW values of non-dippers were 0.796 (95% CI: 0.707–0.884, p < 0.001). Conclusion: AKW is significantly higher in non-dipper individuals compared to dippers. AKW values above 32.6 mm on the chest radiograph may be associated with non-dipper pattern especially in hypertensive individuals.

Negatively-charged Liposome Nanoparticles Can Prevent Dyslipidemia and Atherosclerosis Progression in the Rabbit Model.

Negatively charged nanoliposomes have a strong attraction towards plasma lipoprotein particles and can thereby regulate lipid metabolism. Here, the impact of such nanoliposomes on dyslipidaemia and progression of atherosclerosis was investigated in a rabbit model. Two sets of negatively-charged nanoliposome formulations including [Hydrogenated Soy Phosphatidylcholine (HSPC)/1,2-distearoyl-sn-glycero-3- phosphoglycerol (DSPG)] and [1,2- Dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC)/1,2-Dimyristoyl-sn-glycero-3-phosphorylcholine (DMPG)/Cholesterol] were evaluated. Rabbits fed a high-cholesterol diet were randomly divided into 3 groups (n=5/group) intravenously administrated with HSPC/DSPG formulation (DSPG group; 100 mmol/kg), DMPC/DMPG formulation (DMPG group; 100 mmol/kg), or the normal saline (control group; 0.9% NaCl) over a 4-week period. The atherosclerotic lesions of the aortic arch wall were studied using haematoxylin and eosin staining. Both DSPG and DMPG nanoliposome formulations showed a nano-sized range in diameter with a negatively-charged surface and a polydispersity index of <0.1. After 4 weeks administration, the nanoliposome formulations decreased triglycerides (-62±3% [DSPG group] and -58±2% [DMPG group]), total cholesterol (-58±9% [DSPG group] and -37±5% [DMPG group]), and lowdensity lipoprotein cholesterol (-64±6% [DSPG group] and -53±10% [DMPG group]) levels, and increased high-density lipoprotein cholesterol (+67±28% [DSPG group] and +35±19% [DMPG group]) levels compared with the controls. The nanoliposomes showed a significant decrease in the severity of atherosclerotic lesions: mean values of the intima to media ratio in DMPG (0.96±0.1 fold) and DSPG (0.54±0.02 fold) groups were found to be significantly lower than that in the control (1.2±0.2 fold) group (p<0.05). Anionic nanoliposomes containing [HSPC/DSPG] and [DMPC/DMPG] correct dyslipidaemia and inhibit the progression of atherosclerosis.

Research on the Detection Method of Tunnel Surface Flatness Based on Point Cloud Data

The curved surface of the tunnel is symmetrical. The curved surface of the tunnel can be roughly divided into the left and right arch walls along the direction of the central axis of the tunnel. The symmetry of the tunnel needs to be analyzed when the flatness inspection of the tunnel engineering is carried out. The flatness of the initial support of the tunnel project is an important indicator of the quality inspection and acceptance of the tunnel project. The three-dimensional laser scanner (3DLS) can be used to detect its rapidity effectively. According to the points obtained by the scanner, the surface fitting method based on B-spline interpolation and the SG bar initial support value processing method are used to optimize the tunnel surface to obtain the initial degree calculation reference. Based on the method, a calculation system for the initial flatness of the tunnel based on 3DLS technology is established. At the same time, the calculation method of the overall field of view distance and the development of small blocks is proposed. Through its application and comparison with traditional methods, the analysis shows that the three-dimensional laser scanning technology is feasible in the detection of the initial branch of the tunnel, and achieves a high degree of accuracy requirements.

Abstract 12817: Experimental Analysis of Bicuspid Aortic Valve Hemodynamics: Effect of Mild Aortic Dilatation on Systolic Flow Characteristics

Introduction: Aortic diameter is a determinant index in deciding surgical intervention for aortic aneurysm with bicuspid aortic valve (BAV). However, the treatment of a mildly dilated ascending aorta remains controversial. We experimentally investigated influence of mild dilatation of the ascending aorta on BAV-related hemodynamics in 3 BAV morphologies. Methods: An MRI-compatible pulsatile flow circulation system incorporating an aortic valve model and aortic arch model was developed. Tricuspid aortic valve (TAV) and 3 asymmetric BAV models including RL-, RN-, and LN-BAV were constructed by suturing bovine pericardium as cusps to aorta. The aortic arch models with the ascending diameters of 30 mm (non-dilatation) and 40 mm (mildly dilatation) were compared. Streamlines and the circulations (m 2 /s) of peak systolic flow in non- and mildly dilated ascending aorta were assessed using 4D-flow MRI in each BAV morphology (Fig). Results: Streamlines showed eccentric aortic valvular outflow jets impinging on the outer curvature of the ascending aorta, proximal arch, and left-anterior supra-valvular aortic wall in RL-, RN-, and LN-BAV, respectively. Regardless of the non-dilated or mildly dilated aorta, the circulations of peak systolic flow were larger in the BAVs than the TAV model (non-dilated aorta, TAV 0.005; RL- 0.016; RN- 0.026; LN-BAV 0.011 m 2 /s, mildly dilated aorta, TAV 0.009; RL- 0.017; RN- 0.028; LN-BAV 0.025 m 2 /s). Right-handed rotation was observed in RL- and RN-BAV, whereas LN-BAV presented left-handed rotation. In LN-BAV, the circulation markedly increased in the mildly dilated ascending aorta. Conclusions: Asymmetric BAV morphology was associated with highly eccentric aortic valvular outflow jet that directly impinged on the aortic wall, and the large circulation of peak systolic flow. The dilatation of the ascending aorta, even mild dilatation, might induce further increase in the circulation of systolic flow, especially in LN-BAV morphology.

Influence of Lining Design Parameters on the Greenhouse Gas Emissions of Chinese Highway Tunnel Construction

To realize low-carbon design for tunnel construction, the authors explored the relationship between tunnel design and greenhouse gas (GHG) emissions. This study proposed typical design models of Chinese highway tunnels based on the lining design specifications and engineering design cases. The research modified the GHG emission calculation method based on the standard quota system. The marginal GHG emissions caused by a change of design parameters of tunnel lining were determined. The results show that the emissions from shotcrete, concrete arch wall, system bolts, and steel frames are sensitive to the change of design parameters, while steel mesh is not. As the design thickness increases, the emissions of the concrete arch wall, inverted arch, and shotcrete increase approximately linearly. The emission distributions of system bolts and steel frames under different spacing are given. Under the same longitudinal spacing condition, the emission ratio of I18 and I16 steel frames is 1.197, and that of I16 and I14 steel frames is 1.316. By defining the marginal emissions caused by the change of design parameters, this study carried out basic work for highway tunnel low-carbon designs. The research is of strategic significance for achieving energy conservation and emission reduction in the tunnel industry.