Circumferential Component Research Articles

Hydrodynamic parameters affecting flow-accelerated corrosion in elbows

Flow-accelerated corrosion (FAC) is a serious degradation mechanism affecting carbon-steel piping in the secondary coolant systems of nuclear power plants. Many researchers have investigated the correlation between wall thinning and hydrodynamic parameters; however, their relationship remains unclear. In this study, the hydrodynamic parameters influencing FAC in elbow sections were investigated for identifying the locations highly susceptible to FAC. Accelerated FAC tests and computational fluid dynamics (CFD) analyses were conducted on a specimen containing elbow sections. The results revealed that the side of the elbow pipe was the most susceptible to FAC because it experienced the most severe wall thinning. The velocity and vorticity vectors obtained from the CFD analysis were decomposed into axial, circumferential, and radial components within a cylindrical coordinate system to evaluate their effects. We found that all velocity and vorticity components contribute to the rate of wall thinning induced by FAC. Therefore, a combination of velocity and vorticity components should be used as hydrodynamic parameters to characterize FAC-induced wall thinning. Specifically, the circumferential velocity and axial vorticity were identified as dominant parameters influencing FAC in the elbows.

Transport enhancement in the laminar rotating disk boundary layer

Enhanced momentum and heat transport in a three-dimensional rotating disk boundary layer due to the consideration of a wavy disk surface is an already known fact in the literature. Such a transport enhancement is primarily associated with two fundamental attributes of the wavy disk: the increased surface area and the enhanced convection due to the surface undulations. However, there exists no further information about their individual role, mutual interaction, and individual share in enhancing the convective transport in the rotating disk boundary layer. This study aims to investigate these facts in detail by considering radially heterogeneous different wavy configurations on the disk surface. It is revealed that the said attributes contribute non-trivially to enhance the transport phenomena. Their impactful role is identified due to the strengths of circumferential and crossflow velocity components, the magnitude of flow swirl angle, and hence due to the coefficients of skin friction and their inter relationship. In this regard, a fundamental benchmark regarding the relative strength of the two coefficients of skin friction is identified from the flat disk case. Decisive observations regarding the impact of surface undulations and the increased surface area of the wavy disk on the enhanced convective transport are made with the aid of this benchmark. It is observed that the enhanced transport phenomena, especially the heat transfer, mainly depend upon the further dominance of the circumferential velocity component. In the situations of increased dominance of rotational flow Kw>Kf, the increased convection and surface area collectively contribute to enhance the thermal transport while in a reverse situation Kw<Kf the convection contributes adversely by even reducing the impact of the increased surface area. In the neutral situation where the dominance of rotational velocity is neither increased nor decreased (i.e., Kw≈Kf), any increase in the transport phenomena is wholly due to the increased surface area. Therefore, the presence of surface undulations or increase in surface area is not the only criterion for an optimum rise in the transport phenomena, rather the impact of surface undulations on the velocity profiles is important which is manipulated due to their positioning on the disk surface. It is observed that the presence of surface undulations in the central and intermediate regions on the disk surface causes to increase the gradients of the crossflow velocity while their presence in the near rim location causes to enhance the gradients of the circumferential velocity. Thus, the configurations that have higher undulations in the near rim region outperform the other configurations.

Sex differences in clinical profile, left ventricular remodeling and cardiovascular outcomes among diabetic patients with heart failure and reduced ejection fraction: a cardiac-MRI-based study

BackgroundHeart failure with reduced ejection fraction (HFrEF) is associated with a high rate of mortality and morbidity. Evidence has shown that sex differences may be an important contributor to phenotypic heterogeneity in patients with HFrEF. Although diabetes mellitus (DM) frequently coexists with HFrEF and results in a worse prognosis, there remains a need to identify sex-related differences in the characteristics and outcomes of this population. In this study, we aimed to investigate the between-sex differences in clinical profile, left ventricular (LV) remodeling, and cardiovascular risk factors and outcomes in patients with HFrEF concomitant with DM.MethodsA total of 273 patients with HFrEF concomitant with DM who underwent cardiac MRI were included in this study. Clinical characteristics, LV remodeling as assessed by cardiac MRI, and cardiovascular risk factors and outcomes were compared between sexes.ResultsWomen were older, leaner and prone to have anemia and hypoproteinemia but less likely to have ischemic etiology. Cardiac MRI revealed that despite similar LVEFs between the sexes, there was more LV concentric remodeling, less impaired global systolic peak strain in longitudinal and circumferential components and a decreased likelihood of late gadolinium enhancement presence in women than in men. During a median follow-up time of 34.6 months, women exhibited better overall survival than men did (log-rank P = 0.042). Multivariable Cox proportional hazards analysis indicated different risk factors for predicting outcomes between sexes, with hypertension [hazard ratio (HR) = 2.05, 95% confidence interval (CI) 1.05 to 4.85, P = 0.041] and hypoproteinemia (HR = 2.27, 95% CI 1.06 to 4.37, P = 0.039) serving as independent determinants of outcomes in women, whereas ischemic etiology (HR = 1.96, 95% CI 1.11 to 3.48, P = 0.021) and atrial fibrillation (HR = 1.86, 95% CI 1.02 to 3.41, P = 0.044) served as independent determinants of outcomes in men.ConclusionsAmong patients with HFrEF concomitant with DM, women displayed different LV remodeling and risk factors and had better survival than men did. Sex-based phenotypic heterogeneity in patients with HFrEF in the context of DM should be addressed in clinical practice.

Flow and Performance Characterization of Rotating Detonation Combustor Integrated with Various Convergent Nozzles

In this study, convergent nozzles of various area ratios (ARs) are used downstream of an annular rotating detonation combustor (RDC) to increase the operating pressure and approach sonic conditions at the nozzle throat. Reactant methane and oxygen-enriched air (67% O2 and 33% N2 by volume) are supplied in counterflow arrangement from two separate plenums located at the base of the RDC annulus. Based on experimentation, a total mass flow rate of 0.32 kg/s was chosen to achieve stable, single-wave mode RDC operation for all test cases, allowing for one-to-one comparisons. The internal performance of the RDC was characterized by ion probes and pressure measurements (wall static and oscillating) in supply plenums and across different axial locations of the combustor. Particle image velocimetry (PIV) at 100 kHz was utilized to measure axial and circumferential velocity components within a two-dimensional region of interest located downstream of the converging nozzle exit. Results show higher internal performance of the RDC with increasing AR of the convergent nozzle. PIV measurement illustrated that the flow oscillation amplitudes decrease with an increasing AR of the converging nozzle. The exit flow contained significant nonuniformity and unsteadiness even with a converging nozzle of AR 2.0, indicating incomplete choking of the flow at the nozzle throat.

Static analysis of new lightweight racing wheel for Formula Society of Automotive Engineers (FSAE) race car for product innovation

A lightwheel has the potential to be widely used to enhance the safety of racing cars and improve car performance by providing an estimation of wheel width spokes quantity, and other constant variables. This study is, therefore, aimed at designing a new lightweight racing wheel. In this study, a Finite Element Model (FEA) was implemented to investigate the static analysis of the newly designed lightweight racing wheel. Since the lightweight wheel characteristics play an important role in the stability and control of the racing car under severe manoeuvres, the wheel mass, von Mises stress, deformation, and safety factor were determined. It was observed that the circumferential component is vital for estimating the lightweight design of racing car wheel design. Therefore, this parameter could be better assessed for future studies.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ВИХРЕВОГО ДВИЖЕНИЯ ДВУХФАЗНОГО ПОТОКА В ДЕЗИНТЕГРАТОРНОЙ МЕЛЬНИЦЕ

Mathematical models and the results of their numerical calculations play an important role at the modern level of automation of technological processes. The development of mathematical models to determine the design-technological or energy-power parameters of the operation of grinding equipment allows to obtain numerical information about the rational modes of its operation. In this study, numerical results were obtained from calculating a mathematical model of the vortex motion of a two-phase flow for the second stage of grinding depending on the physical and mechanical characteristics of the material being ground (ρp) and the current radius Rk of the grinding chamber of the unit. A method for numerically determining the speed characteristics of unit operating modes for materials with different physical and mechanical properties is presented. In the work, using the analysis of graphs of the sought functions of the mathematical model of the vortex motion of a two-phase flow, the velocity fields are presented in the form of diagrams of the radial, circumferential (tangential) and axial velocity components, which characterize the intensity of the flow dynamics inside the original design of the grinding chamber of the mill. In the process of mathematical modeling, it was established that the radial and circumferential (tangential) components of the two-phase flow velocities at current radii in the range Rk = 0.1–0.2 m reach their maximum values, both for solid particles of the crushed material and for the carrier phase – air. It has been determined that for the circumferential component of the velocity of a two-phase flow in a vortex at Rk = 0.3 m, its maximum is observed for both solid particles and the carrier phase – up = uo = 112.1 m/s.

Modal signal analysis of parabolic shell structures with flexoelectric sensors

The flexoelectric effect, garnering extensive attention in recent years, is an electro-mechanical coupled gradient effect that widely exists in dielectric materials and holds great potential for applications in structural sensing and actuation. The parabolic shell structure, characterized by line focusing, finds widespread use in key structural components such as solar trough collectors and communication antennas. Distributed sensing of the structural states of these parabolic shells is critical for vibration control, health monitoring, and shape control of precision structural systems. Therefore, flexoelectric sensing research based on parabolic shell structure has become an important topic. This study establishes a mathematical model for flexoelectric sensing in a parabolic shell with four-sided simply supported boundary conditions. The model is based on the direct flexoelectric effect, and thin shell assumption, and incorporates specific Lamé parameters and curvature radius. The electro-mechanical strain gradient/signal generation characteristics and distributed modal flexoelectric signals on the parabolic shell are investigated. The sensing signal under the open-circuit conditions is deduced, and the flexoelectric sensing signal and sensing characteristics of different modes are analyzed. The formulation of the flexoelectric neural sensing signal for the parabolic shell structure is provided and divided into two components: a circumferential bending component and a longitudinal bending component. In the case studies, the effects of design parameters such as flexoelectric sensor thickness, size, and aspect ratios are evaluated and compared. The analysis and results of this study offer a theoretical foundation and reference for refining the design parameters of the flexoelectric sensor and determining its optimal sensing position, and potentially paving the way for new applications of flexoelectric sensing technology.

Study on fracture characteristics and mechanisms of red sandstone under high-voltage pulse discharge

To investigate the influences of geometrical size and discharge voltage of the pulse discharge equipment on the fracture characteristics and mechanisms of sandstone under high-voltage pulses, a series of experiments was conducted using a high-voltage pulse discharge device on sandstone circular disc specimens of sandstone with a thickness of 10 mm. These experiments covered a range of disc diameters ranging from 50 mm to 142 mm and discharge voltages from 15 kV to 40 kV. Through these experiments, the fracture characteristics of sandstone at both macroscopic and microscopic levels were investigated. In the experiments, a quantitative analysis of surface fracture was undertaken based on fracture density and fractal damage. Additionally, using the principle of energy equivalence, numerical simulation methods were used to study the damage evolution process in sandstone. The research results indicate that the formation and distribution of fractures in the sandstone specimens are significantly affected by geometrical size and discharge voltage. By analyzing the interaction between stress waves and fracture propagation, combined with indoor experimental results, the fracture mechanism was revealed. The high temperature and shock wave generated by the plasma channel leads to the crushing zone near the electrode, while the circumferential tensile component of the stress wave can result in radial fractures, and the reflected tensile wave leads to circumferential and radial fractures near the boundary.

Mechanical characterization and torsional buckling of pediatric cardiovascular materials

In complex cardiovascular surgical reconstructions, conduit materials that avoid possible large-scale structural deformations should be considered. A fundamental mode of mechanical complication is torsional buckling which occurs at the anastomosis site due to the mechanical instability, leading surgical conduit/patch surface deformation. The objective of this study is to investigate the torsional buckling behavior of commonly used materials and to develop a practical method for estimating the critical buckling rotation angle under physiological intramural vessel pressures. For this task, mechanical tests of four clinically approved materials, expanded polytetrafluoroethylene (ePTFE), Dacron, porcine and bovine pericardia, commonly used in pediatric cardiovascular surgeries, are conducted (n = 6). Torsional buckling initiation tests with n = 4 for the baseline case (L = 7.5 cm) and n = 3 for the validation of ePTFE (L = 15 cm) and Dacron (L = 15 cm and L = 25 cm) for each are also conducted at low venous pressures. A practical predictive formulation for the buckling potential is proposed using experimental observations and available theory. The relationship between the critical buckling rotation angle and the lumen pressure is determined by balancing the circumferential component of the compressive principal stress with the shear stress generated by the modified critical buckling torque, where the modified critical buckling torque depends linearly on the lumen pressure. While the proposed technique successfully predicted the critical rotation angle values lying within two standard deviations of the mean in the baseline case for all four materials at all lumen pressures, it could reliably predict the critical buckling rotation angles for ePTFE and Dacron samples of length 15 cm with maximum relative errors of 31% and 38%, respectively, in the validation phase. However, the validation of the performance of the technique demonstrated lower accuracy for Dacron samples of length 25 cm at higher pressure levels of 12 mmHg and 15 mmHg. Applicable to all surgical materials, this formulation enables surgeons to assess the torsional buckling potential of vascular conduits noninvasively. Bovine pericardium has been found to exhibit the highest stability, while Dacron (the lowest) and porcine pericardium have been identified as the least stable with the (unitless) torsional buckling resistance constants, 43,800, 12,300 and 14,000, respectively. There was no significant difference between ePTFE and Dacron, and between porcine and bovine pericardia. However, both porcine and bovine pericardia were found to be statistically different from ePTFE and Dacron individually (p < 0.0001). ePTFE exhibited highly nonlinear behavior across the entire strain range [0, 0.1] (or 10% elongation). The significant differences among the surgical materials reported here require special care in conduit construction and anastomosis design.

The Echocardiographic Evaluation of the Right Heart: Current and Future Advances.

To discuss physiologic and methodologic advances in the echocardiographic assessment of right heart (RH) function, including the emergence of artificial intelligence (AI) and point-of-care ultrasound. Recent studies have highlighted the prognostic value of right ventricular (RV) longitudinal strain, RV end-systolic dimensions, and right atrial (RA) size and function in pulmonary hypertension and heart failure. While RA pressure is a central marker of right heart diastolic function, the recent emphasis on venous excess imaging (VExUS) has provided granularity to the systemic consequences of RH failure. Several methodological advances are also changing the landscape of RH imaging including post-processing 3D software to delineate the non-longitudinal (radial, anteroposterior, and circumferential) components of RV function, as well as AI segmentation- and non-segmentation-based quantification. Together with recent guidelines and advances in AI technology, the field is shifting from specific RV functional metrics to integrated RH disease-specific phenotypes. A modern echocardiographic evaluation of RH function should focus on the entire cardiopulmonary venous unit-from the venous to the pulmonary arterial system. Together, a multi-parametric approach, guided by physiology and AI algorithms, will help define novel integrated RH profiles for improved disease detection and monitoring.

Minimal model for the dependence of stresses in the wall of a cerebral vessel on the parameters of a smooth muscle cell

A minimal mathematical model of the wall of a small arterial vessel is described. This model is created based on the published results of experiments performed on rat cerebral vessels. It is assumed that the active stress has only a circumferential component and depends on the circumferential stretch, calcium concentration in the cytoplasm, and the membrane potential of smooth muscle cells. The presented model for a small artery can qualitatively reproduce the results of more sophisticated models for other vessels under normal physiological conditions. Unlike a similar model, that accounts for only one cellular parameter, the addition of membrane potential as one of the main parameters was crucial to reveal a qualitative change in the dependency of circumferential stress on stretch and the radial coordinate with an alteration in vascular tone. At fixed values of membrane potential and calcium concentration in the phase of a development of vascular tone, stress decreases as it approaches the outer wall of the vessel and increases as stretch increases, and after it is formed, the direction of changes in the circumferential stress reverses.

Numerical simulation of heat and mass transient behavior during WAAM overlapping deposition with external deflection magnetic field

During the magnetic controlling wire arc additive manufacturing (WAAM) process, the external magnetic field directly influences the arc shape and the molten pool flow, which can further affect the morphology of the deposition layer and the overlapping flatness. This study introduced an external deflection magnetic field (EDM) with longitudinal and deposition direction components into the WAAM process. A numerical simulation model of the coupling of the arc and the molten pool was established on the basis of a weak coupling method. The numerical simulation model was utilized to investigate the effect of the EDM field on the heat and mass transfer behaviors in the WAAM overlapping deposition process. The results showed that the EDM field generated an additional electromagnetic force in the welding arc and molten pool with circumferential and single-side lateral components. The additional electromagnetic force drove the arc plasma to the rear of the molten pool and the side of the solidified weld bead simultaneously, which resulted in more heat and electromagnetic force concentrated on the gap of the overlapping beads. An asymmetric circumferential rotating vortex appeared in the molten pool, which drove the melted metal to fill the gap of the overlapping beads and improved the overlapping flatness.

Experimental and numerical study of flow structure in a model of distal anastomosis of femoral artery

Physical and numerical simulation of the steady blood flow was carried out focusing on the distal end-to-side anastomosis of a graft to the femoral artery. The angle between the graft and the artery was 60°. Two Reynolds numbers were considered that corresponded to the physiological range when estimated using the average (Re = 240) and maximum (Re = 1640) blood flow through the human femoral artery over a single cardiac cycle. The experiment included flow visualization and measurements of instantaneous vector fields of velocity using an optical SIV (Smoke Image Velocimetry) technique. Direct numerical simulation (DNS) was employed for numerical study. The distribution of blood flows through the branches of the main artery was 80 % in the antegrade and 20 % in the retrograde direction. Main patterns in the distribution of velocity and its root-mean-square fluctuations in both branches of the main artery were revealed. Flow separation regions were observed in the branching area. Additionally, secondary flows (Prandtl’s vortices of the first kind) were revealed. The flow in the branching area was still laminar Re = 240, while the signs of transition to turbulence were documented within separation regions at Re = 1640. Distributions of streamwise and circumferential components of skin friction vector were estimated. In some regions of flow, these components were shown to be comparable in size. The location of regions was revealed in which the friction magnitude in the considered flow regimes was lower than the one in an unimpaired artery (developed laminar flow in a circular pipe) at appropriate Reynolds numbers.

Does speckle tracking transthorasic echocardiography show subtle changes in left ventricular function in patient with heart failure with reduced ejection fraction treated by Sacubitril-Valsartan

Abstract Introduction Pathophysiology of HF involves a maladaptive response during which the (RAAS) is activated. RAAS activation leads to VC, HT, increased aldosterone levels, increased sympathetic tone, and eventually, cardiac remodeling, all of which are detrimental to the progression of the disease. By blocking these maladaptive elements, ACEIs or ARBs play a major role in reducing morbidity and mortality due to HF, Simultaneously, the NP system is also activated, hence the elevated BNP and NT-pro BNP seen in HF exacerbations. This is a Compensatory mechanism that leads to VD, natriuresis and diuresis, lowers BP, lowers sympathetic tone, and reduces aldosterone levels. The NP system works antagonistically to the RAAS and has favorable effects on the pathogenesis of HF NP are broken down by an enzyme called neprilysin and blocking of its action by neprilysin inhibitor prevent the breakdown of NP leading to prolonged duration of the favorable effects of these peptides. Sacubitril/valsartan is a first-in-class medicine that contains a neprilysin (NEP) inhibitor (sacubitril) and (Ang-II) receptor blocker (valsartan). STE is a sensitive tool for assessing ventricular function, even subclinical myocardial alterations that traditional imaging techniques are not able to detect. Sub endocardial function is powered mostly by longitudinal contraction, it is impaired earlier than circumferential or radial component's. Therefore, Longitudinal function is in most cases the best early marker of LV dysfunction. Objective The aim of our study is to retrospectively detect if the patients treated by sacubitril/valsartan showed no improvement in LVEF assessed by TTE, is the same patient will shows improvement in LVEF assessed by 2D STE? Methods Our study will include 200 patients with HFrEF. All participants were subjected to the following: History taking, Physical examination, Serial 12-lead ECG, 2D echo to assess: -LVEDD, LVESD and LVEF%, LVEDVI (ml/m2), LVESVI (ml/m2), (LAVI) ml/m2, E/e′ ratio. 2D STE was done before and after 6 months of sacubitril/valsartan. Results Age 48 ± 9 years, 63% females, 9 (4.5%) were in NYHA FC I, 120 (60%) NYHA FC II, 64 (32%) of patients were in NYHA FC III &amp; 7 (3.5%) were in FC IV. improved to NYHA FC I, 82 (41%) NYHA FC II 118 (59%), LVEDV, LVESV, LVEF, E/e′ were 139.3 ± 7.3, 89.7 ± 4.7, 34.9 ± 2.8, 11.2 ± 2.7, that all improved to 139.1 ± 10.5, 89.0 ± 4.4, 35.6 ± 2.6, 9.1 ± 2.3. 82 (41%) patient showed improvement in LVEF either by traditional TTE or STE, 118 (59%) patients showed no improvement of EF by traditional TTE, of them 74 (37%) patients was improved detected by STE while 44 (22%) patients showed no improvement in EF neither by TTE nor by STE. Conclusion STE is more accurate diagnostic tool for detecting early improvment in LVEF that not detected by traditional TTE in patient with HFREF treated by scubitril/valsartan. Additional Content An author video to accompany this abstract is available on https://academic.oup.com/eurheartjsupp. Please click on the arrow next to ‘More Content’ and then click on ‘Author videos’.

Cross-Diffusion and Higher-Order Chemical Reaction Effects on Hydromagnetic Copper–Water Nanofluid Flow Over a Rotating Cone in a Porous Medium

Spin coating of engineering components with advanced functional nanomaterials which respond to magnetic fields is growing. Motivated by exploring the fluid dynamics of such processes, a mathematical model is developed for chemically reactive Cu–H2O magnetohydrodynamic (MHD) nanofluid swirl coating flow on a revolving vertical electrically insulated cone adjacent to a porous medium under a radial static magnetic field. Heat and mass transfer is included and Dufour and Soret cross-diffusion effects are also incorporated in the model. Thermal and solutal buoyancy forces are additionally included. To simulate chemical reaction of the diffusing species encountered in manufacturing processes, a higher-order chemical reaction formulation is also featured. Via suitable scaling transformations, the governing nonlinear coupled partial differential conservation equations and associated boundary conditions are reformulated as a nonlinear ordinary differential boundary value problem. MATLAB-based shooting quadrature with a Runge–Kutta method is deployed to solve the emerging system. Concentration, temperature and velocity variations for various nondimensional flow parameters have been visualized and analyzed. In addition, key wall characteristics, i.e., radial and circumferential skin friction, Nusselt number and Sherwood number, have also been computed. Validation with earlier studies is also included. The simulations indicate that when compared to a lower-order chemical reaction, a higher-order chemical reaction allows a greater rate of heat and mass transfer at the cone surface. Increasing Dufour (diffuso-thermal) and Soret numbers generally reduces radial and circumferential skin friction and also Nusselt number, whereas it elevates the Sherwood number. Both skin friction components are also suppressed with increasing Richardson number. Strong deceleration in the tangential and circumferential velocity components is induced with greater magnetic field.

Optimal deep-space heliocentric transfers with an electric sail and an electric thruster

An electric solar wind sail is a propellantless propulsive system that generates thrust by exploiting the electrostatic interaction between solar wind ions and one or more charged tethers. Assuming a realistic near-term design in which the sail is composed of a limited number of tethers, the propulsive acceleration provided to the spacecraft is small. Moreover, according to a recent thrust model, the propulsive acceleration vector is constrained to lie in a cone centered on the outward radial direction with half-angle equal to about 20 degrees, resulting in a small circumferential component of the propulsive acceleration. In order to overcome these issues, a possible strategy consists in combining the electric sail with an electric thruster that provides a low thrust steerable around the circumferential direction. The effectiveness of such a combination is thoroughly analyzed in this work for deep-space heliocentric transfers. Transfer trajectories are obtained as outputs of a multi-objective optimization procedure, in which a suitable linear function of the flight time and the propellant consumption is minimized, considering different relative weights of the two competing requirements. Two exemplary case studies, consisting of Earth-Mars and Earth-Venus ephemeris-free circle-to-circle transfers, are presented to show the effectiveness of the proposed arrangement.

A Method for Correcting Endoscopic Images to Measure the Size of Defects on the Inner Surface of a Hole

A method is proposed for correcting endoscopic images to enable the measurement of inner surface defects in holes. The distortion is decomposed into circumferential and axial components based on imaging principles, and geometric constraints are added to simplify the correction model parameters to a central coordinate and nonlinear parameter, improving accuracy at the edge of endoscopic images. Experimental results demonstrate good universality with an average error rate of 5.35% in defect measurements, making it applicable for automatic and intelligent detection of hole parts and pipelines.

Fluid dynamics by 4D flow CMR in Marfan and Loeys-Dietz patients before and after valve sparing aortic root replacement

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III (Spain), Sociedad Española de Cardiología Introduction Patients with Marfan or Loeys-Dietz syndrome present abnormal aortic flow patterns in the arch and the proximal descending aorta that may contribute to aortic dilation (1,2). Valve sparing aortic root replacement, which is effective in reducing the risk of aortic dissection in case of severe dilation, may also normalize flow patterns beyond the replaced aorta and potentially slow its progressive aortic dilation. Purpose To assess aortic flow dynamics in these patients with Marfan or Loeys-Dietz by 4D flow cardiovascular magnetic resonance (CMR) before and after valve sparing aortic root replacement (David surgery), and to compare the results with those of healthy volunteers (HV). Methods Patients with Marfan or Loeys-Dietz syndrome underwent two non-contrast enhanced 4D flow CMR, one before and another after undergoing David surgery. Healthy volunteers matched for age, sex and BSA were also included for comparison. Maximum velocity, in-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) and wall shear stress (WSS) magnitude and its axial and circumferential components were obtained at 24 planes covering the thoracic aorta from the sinotubular junction to the descending aorta at the diaphragmatic level (3–5). Results Sixteen patients and 21 healthy volunteers were included. Demographic and clinical data is presented in Table. The mean time between the CMR prior and posterior to surgery was 15 months. Compared to HV, patients with CTD before intervention presented lower maximum velocity at the proximal ascending aorta (Figure 1A), lower IRF and circumferential WSS at the arch and the proximal descending aorta (Figure 1B and F), lower magnitude and axial WSS at the proximal ascending and descending aorta (Figure 1E and D), and increased SFRR at the proximal descending aorta (Figure 1C). The intervention completely restored maximum velocity and partially-restored physiological helical flow and circumferential WSS, but barely improved axial WSS and SFRR. Conclusion Valve sparing aortic root replacement in patients with Marfan or Loeys-Dietz syndrome partially restore to physiological level both in-plane rotational flow and circumferential wall shear stress in the descending aorta.

Relationships between biventricular myocardial function and oxygen uptake during exercise in healthy adolescent male athletes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): UK Research and Innovation Medical Research Council Doctoral Training Programme Grant Work supported as part of a research partnership between the University of Bristol and Canon Medical Systems UK that determines the independence of the research from either parties. Background Biventricular cardiac function improves with increasing work-rate during exercise in healthy elite athletes, but how it relates to concomitantly measured oxygen uptake (VO2) is not well known. Assessing cardiac determinants of cardiorespiratory fitness through multimodal evaluations may lead to improvements in clinical stress testing protocols and better understanding of exercise physiology. Purpose The aim of this study was to investigate whether left and right ventricular (LV and RV) systolic function measured by speckle tracking echocardiography (STE) at submaximal exercise (moderate and high intensity domains) is associated with concomitantly measured VO2 in healthy adolescent male athletes. Methods Elite male football players &amp;lt;16 years-old underwent cardiopulmonary exercise testing with concomitant STE at 50 W steps. Exercise intensity domains were defined based on the gas exchange threshold (GET). LV and RV free wall (FW) peak systolic longitudinal strain (Sl), strain rate (SRl) and LV average (12 mid and basal segments) circumferential strain (Sc) and strain rate (SRc) were measured. Cardiac function relation to peak VO2 was evaluated using linear regression, and its relationships to VO2 within each exercise intensity domain using repeated measures mixed linear models, before and after adjusting for heart rate (HR). Results A total of n=94 athletes were included (mean age 14.7 ± 1 years). Mean peak VO2 and work-rate were 43 ± 7 mL·min-1·kg-1 and 215 ± 40 W, respectively. Relationships between cardiac function and VO2, by exercise intensity domain are shown in Figure 1 with all regression coefficients shown in Table 1. Only LV Sl at high intensity was correlated to peak VO2 (p = 0.04). Within exercise intensity domains higher LV Sl (Figure 1A) and SRl (Figure 1B) were associated with higher concomitantly measured VO2 at both moderate and high intensity. Higher SRc (Figure 1C) and RV FW SRl (Figure 1F) were associated with higher VO2 only at moderate intensity. LV Sc (Figure 1C) and RV FW Sl (Figure 1E) were not associated with concomitant VO2 during exercise at moderate or high intensity. Only LV Sl and SRl at moderate and high intensity remained significantly associated to concomitantly measured VO2 after further adjusting by HR (Table 1). Conclusions In healthy adolescent athletes, only LV longitudinal strain and strain rate measured at moderate and high intensity were associated with VO2 independent of HR response. There were differences in myocardial response to exercise both between the two ventricles, and between the longitudinal and circumferential components of LV function. These require further research, both in healthy and disease groups, especially in RV pathology, where components of myocardial function could play different roles in limiting exercise capacity.

Mechanism study on the effect of self-circulating casing treatment with different circumferential coverage ratios on the axial compressor stability

To reveal the mechanisms underlying the effect of self-circulating casing treatment with different circumferential coverage ratios on the stability of the axial compressor, a three-dimensional unsteady numerical was hereby conducted on Rotor 35. The circumferential coverage ratios of self-circulating casing of 20%, 40%, 60%, and 80% were designed, respectively. The calculated results point out that all the schemes effectively expand the stable working range of the compressor and that the expansion effect is positively correlated with the circumferential coverage ratio. The self-circulating casing with an 80% circumferential coverage ratio exhibits the highest stall margin improvement at 14.83%. The internal flow field analysis shows that the underlying mechanism for the compressor stability increasing with the increase in the circumferential coverage ratio is that after the flows with a higher circumferential speed component enter the self-circulating casing suction port, sufficient circumferential space is required to complete the transformation in the flow direction, so that the flows can smoothly enter the self-circulating casing and subsequent development can be carried out. The larger circumferential size of the self-circulating casing creates favorable conditions for more airflows to enter the self-circulating casing. With the increase in the circumferential coverage ratio, the suction effect of self-circulating casing on low-speed fluid at the blade tip and the bleeding mass flow rate is larger, and a better compressor expansion effect is thereby achieved.