Change in Abdominal Aortic Aneurysm Sac Diameter After Endovascular Repair: A Single-Center Experience From Taiwan

Purpose: The purpose of this study was to investigate the change in the diameter of infrarenal abdominal aortic aneurysm (AAA) sacs after endovascular aortic repair (EVAR) in Taiwanese patients and to depict its association with clinical outcomes. Materials and Methods: This retrospective cohort study was conducted on patients who underwent EVAR for infrarenal AAA between January 2011 and December 2016. All preoperative and follow-up computed tomography (CT) images were reviewed. Postoperative CT angiography was arranged after 1 month and annually thereafter. The maximal diameter on the axial plane and the maximal diameter perpendicular to the centerline on the coronal and sagittal planes were measured. The study examined post-EVAR sac diameter change over time and compared the differences in adverse events (AEs) among groups. Results: The survey included a total of 191 patients with a median follow-up duration of 2.5 (interquartile range: 1.1–2.9) years. Overall survival rates at 1, 2, and 5 years were 92%, 81%, and 76%, respectively. According to their last CT scans, the patients were categorized into 3 groups as follows: shrinkage, stationary, and enlargement, which comprised 58 (30.4%), 118 (61.8%), and 15 (7.9%) patients, respectively. Pre-EVAR characteristics and sac diameters were similar among the groups. Sac shrinkage was exclusively observed in the first 2 years, whereas sac enlargement developed at all follow-up periods. Patients with sac enlargement had higher incidence rates of endoleaks, complications, and reintervention than the other groups. Conclusion: Based on our observations, post-EVAR sac shrinkage only occurs in the first 2 years; however, post-EVAR sacs may enlarge at any point and even after 5 years. In our study, patients with sac enlargement had higher rates of adverse events and reintervention.

Estimation of stator and rotor forms distortions influence on operating parameters of a hydrogenerator

The field calculation was carried out using finite element method of the Ansys Maxwell software package and verification in the Matlab Simulink software. It should be noted that there are several regulatory documents that describe criteria for permissible distortion of the rotor shape, where the air gap between the stator and the rotor at diametrically opposite points should not differ from each other by more than ± 20% from the average value equal to their halfsum. In this work, a calculation was carried out covering this interval of diameter change; an analysis was carried out considering change in range of ± 35% of the air gap’s width’s value. Results of the research showed that a change in a value of the air gap up to 10% would make a significant contribution to magnitude of magnetic field induction, which increases the value of main losses in a core of magnetic circuit of the generator. Also, there is a significant decrease in voltage (from 25 to 50%) of a nominal voltage in nominal power mode, which requires increase in current in field magnetizing coil, leading to ohmic losses’ increase in rotor’s windings.

Experimental Analysis of Driver Visual Characteristics in Urban Tunnels

Through an urban tunnel-driving experiment, this paper studies the changing trend of drivers’ visual characteristics in tunnels. A Tobii Pro Glasses 2 wearable eye tracker was used to measure pupil diameter, scanning time, and fixation point distribution of the driver during driving. A two-step clustering algorithm and the data-fitting method were used to analyze the experimental data. The results show that the univariate clustering analysis of the pupil diameter change rate of drivers has poor discrimination because the pupil diameter change rate of drivers in the process of “dark adaptation” is larger, while the pupil diameter change rate of drivers in the process of “bright adaptation” is relatively smooth. The univariate and bivariate clustering results of drivers’ pupil diameters were all placed into three categories, with reasonable distribution and suitable differentiation. The clustering results accurately corresponded to different locations of the tunnel. The clustering method proposed in this paper can identify similar behaviors of drivers at different locations in the transition section at the tunnel entrance, the inner section, and the outer area of the tunnel. Through data-fitting of drivers’ visual characteristic parameters in different tunnels, it was found that a short tunnel, with a length of less than 1 km, has little influence on visual characteristics when the maximum pupil diameter is small, and the percentage of saccades is relatively low. An urban tunnel with a length between 1 and 2 km has a significant influence on visual characteristics. In this range, with the increase in tunnel length, the maximum pupil diameter increases significantly, and the percentage of saccades increases rapidly. When the tunnel length exceeds 2 km, the maximum pupil diameter does not continue to increase. The longer the urban tunnel, the more discrete the distribution of drivers’ gaze points. The research results should provide a scientific basis for the design of urban tunnel traffic safety facilities and traffic organization.

Tunnel Behaviour Caused by Basement Excavation in Clay

Many researchers have investigated the effect of basement excavation on tunnel deformation. However, the influence of consolidation on the interaction of basement-tunnel-soil is rarely considered or systematically studied in clay. In this study, three-dimensional coupled-consolidation finite element analyses were conducted to investigate the effect of consolidation on the tunnel response to excavation. An advanced nonlinear constitutive model was adopted, and numerical parametric investigations were conducted to study the effect of the excavation depth, tunnel stiffness, soil permeability coefficient, and consolidation time on the tunnel response. The results revealed that the basement excavation led to stress release, which caused tunnel heave. Owing to the dissipation of excess negative pore water pressure, the tunnel heave further increased to become approximately twice as large compared with that observed when the foundation pit excavation had just been completed. As the consolidation time increased, the longitudinal tunnel heave and tunnel diameter change caused by the foundation pit excavation gradually increased, but the growth rate was slower down. When the consolidation time changed from 50 days to 150 days, the maximum tunnel heave at the crown and the maximum tunnel diameter change increased by 1.18 and 1.48 times, respectively. The soil’s permeability coefficient did not have a significant effect on the tunnel heave at the crown nor on the tunnel diameter change. The results obtained by this study are expected to be useful as an engineering reference for the analysis of soil structure problems in clay.

Imaging surveillance after open aortic repair: a feasibility study of three-dimensional growth mapping

OBJECTIVES Confident growth assessment during imaging follow-up is often limited by substantial variability of diameter measurements and the fact that growth does not always occur at standard measurement locations. There is a need for imaging-based techniques to more accurately assess growth. In this study, we investigated the feasibility of a three-dimensional aortic growth assessment technique to quantify aortic growth in patients following open aortic repair. METHODS Three-dimensional aortic growth was measured using vascular deformation mapping (VDM), a technique which quantifies the localized rate of volumetric growth at the aortic wall, expressed in units of Jacobian (J) per year. We included 16 patients and analysed 6 aortic segments per patient (96 total segments). Growth was assessed by 3 metrics: clinically reported diameters, Jacobian determinant and targeted diameter re-measurements. RESULTS VDM was able to clearly depict the presence or absence of localized aortic growth and allows for an assessment of the distribution of growth and its relation to anatomic landmarks (e.g. anastomoses, branch arteries). Targeted diameter change showed a stronger and significant correlation with J (r = 0.20, P = 0.047) compared to clinical diameter change (r = 0.15, P = 0.141). Among 20/96 (21%) segments with growth identified by VDM, growth was confirmed by clinical measurements in 7 and targeted re-measurements in 11. Agreement of growth assessments between VDM and diameter measurements was slightly higher for targeted re-measurements (kappa = 0.38) compared to clinical measurements (kappa = 0.25). CONCLUSIONS Aortic growth is often uncertain and underappreciated when assessed via standard diameter measurements. Three-dimensional growth assessment with VDM offers a more comprehensive assessment of growth, allows for targeted diameter measurements and could be an additional tool to determine which post-surgical patients at high and low risk for future complications.

Diameter change in completely remodelled proximal descending aorta after acute type I dissection repair: implications for estimating the pre-dissection size

OBJECTIVES Pre-dissection diameter of the proximal descending thoracic aorta (p-DTA), if available, would be the reference for determining the size of the stent graft or elephant trunk. Acute type B dissection is known to increase p-DTA diameter by 23% (Rylski factor). This study aimed to investigate the accuracy of estimating post-remodelling diameter of the p-DTA based on the Rylski factor and other post-dissection morphological parameters in acute type I dissection, based on the assumption that the post-remodelling diameter is similar to the pre-dissection diameter. METHODS In 60 patients with acute type I dissection showing complete remodelling of the p-DTA false lumen after surgical repair, preoperative and post-remodelling computed tomography scans were reviewed. Parameters, including maximal true lumen diameter (TLDmax) and aortic area-derived diameter divided by the Rylski factor (AoDRylski), were measured at the p-DTA. RESULTS After complete remodelling, p-DTA diameter decreased by 4.1 mm (P < 0.001). The equivalent to the Rylski factor was 15%. Both TLDmax and AoDRylski frequently showed ≥2 mm discrepancy from post-remodelling aortic diameter (36.7% and 48.3%, respectively, P = 0.30). When 2 parameters coincided within 2 mm, two-third of their estimations were accurate. AoDRylski was more accurate than TLDmax in patients with a large extent of circumferential dissection, and vice versa with less circumferential dissection (P = 0.027). CONCLUSIONS Prediction of post-remodelling aortic diameter relying on a single morphologic parameter carries a substantial risk of overestimation and underestimation. Evaluation based on the extent of circumferential dissection together with the 2 parameters may provide a more reliable estimation.

Effect of Diameter, Length, and Chirality on the Properties of Silicon Nanotubes

The mechanical properties of nanostructures are a researcher's favorite topics. In the meantime, the mechanical and physical properties of the two dimensional structures and the nanotubes have attracted greater attention due to their wide application. Si (Si) nanotubes are structures consisting of Si atoms that are aligned as honeycombs (hexagonal). This structure has created some special properties in Si nanotubes. In this paper, Young’s modulus values and stress strain diagrams of Si nanotubes are investigated using molecular dynamics method and the Tersoff potential. Then, the changes effect of size and dimension was investigated for a closer look. For this purpose, the effect of nanotube diameter, length, and chirality shift from zigzag to armchair were studied. The results showed that the fracture stress of nanotube decreased with increasing the length of Si nanotube. It was also shown that the armchair structure was stronger than the zigzag. The effect of diameter change on the mechanical properties was also investigated and it was observed that no specific order could be found between the diameter changes with the Si nanotube strength. The results were in good agreement with other studies.

Bending Capacity of Concrete-Encased Underground Electrical Duct Banks under Monotonic Loading: An Experimental Study

The bending capacity of concrete-encased underground electrical duct banks has been the subject of considerable investigation using the load-structure method; however, the role of high-density polyethylene (HDPE) conduits and the thresholds of electrical duct banks has not been fully scrutinized. This study examines the bending behaviors of electrical duct banks subjected to monotonic vertical loading in a soil box using an advanced monitoring device to measure the conduit diameter change. An analysis of the experiment shows the effective role of HDPE conduits in improving the bending capacity of electrical duct banks. The results suggest 5% and 7.5% as the deformation rate thresholds with respect to the ultimate states of serviceability and bearing capacity, respectively. The threshold of the longitudinal curvature radius is determined to be 18000 m. Finally, the evolution trends of the stress and deformation rates of HDPE conduits are recommended for the monitoring indexes and control standards of electrical duct banks.

Efficacy and Safety Profile of Montgomery T-Tube Implantation in Patients with Tracheal Stenosis

Background. Tracheal stenosis is able to lead to airway obstruction. Objective. To evaluate the efficacy and safety profile of Montgomery T-tube implantation in patients with tracheal stenosis. Methods. Fifty-two patients with tracheal stenosis diagnosed between 2016 and 2019 were included in this retrospective cohort study. The patients were divided into observation group (n = 25 cases) and control group (n = 27). The therapeutic effect, arterial blood gas analysis, arterial oxygen partial pressure (PaO2), arterial carbon dioxide partial pressure (PaCO2), shortness of breath score, airway diameter change, dyspnea score, quality of life, and safety were compared between the two groups before and after treatment. Results. The therapeutic effect of the observation group gained better results than that of the control group (84.00% vs. 62.96%). One week after operation, the pH value, SaO2, PaCO2, shortness of breath score, airway diameter change, dyspnea score, life quality, and incidence of postoperative complications in the observation group exerted better results as compared to the control group. Conclusion. The implantation of Montgomery T-tube has effective function in terms of improving the symptoms of dyspnea and the life quality of patients with safety profile in patients harboring tracheal stenosis.