Velocity Gradient Research Articles

Group cohesion and passive dynamics of a pair of inertial swimmers with three-dimensional hydrodynamic interactions.

When swimming animals form cohesive groups, they can reap several benefits. Our understanding of collective animal motion has traditionally been driven by models based on phenomenological behavioral rules, but more recent work has highlighted the critical importance of hydrodynamic interactions among a group of inertial swimmers. To study how hydrodynamic interactions affect group cohesion, we develop a three-dimensional, inviscid, far-field model of a swimmer. In a group of two model swimmers, we observe several dynamical phases, including following, divergence, collision, and cohesion. Our results illustrate when cohesive groups can passively form through hydrodynamic interactions alone, and when other action is needed to maintain cohesion. We find that misalignment between swimmers makes passive cohesion less likely; nevertheless, it is possible for a cohesive group to form through passive hydrodynamic interactions alone. We also find that the geometry of swimmers critically affects the group dynamics due to its role in how swimmers sample the velocity gradient of the flow.

Uncovering the structure and kinematics of the ionized core of M\,2-9 with ALMA

We present interferometric observations at 1 and 3\,mm with the Atacama Large Millimeter Array (ALMA) of the free-free continuum and millimeter(mm)-wavelength recombination line (mRRL) emission of the ionized core (within lsim 130\,au) of the young planetary nebula (PN) candidate M\,2-9. These inner regions are concealed in the vast majority of similar objects. A spectral index for the mm-to-centimeter(cm) continuum of sim 0.9 indicates predominantly free-free emission from an ionized wind, with a minor contribution from warm dust. The mm continuum emission in M\,2-9 reveals an elongated structure along the main symmetry axis of the large-scale bipolar nebula with a C-shaped curvature surrounded by a broad-waisted component. This structure is consistent with an ionized, bent jet and a perpendicular compact dusty disk. The presence of a compact equatorial disk (of radius sim 50\,au) is also supported by redshifted CO and absorption profiles observed from the base of the receding northern lobe against the compact background continuum. The redshift observed in the CO absorption profiles likely signifies gas infall movements from the disk toward a central source. The mRRLs exhibit velocity gradients along the axis, implying systematic expansion in the C-shaped bipolar outflow. The highest expansion velocities (sim 80\ are found in two diagonally opposed compact regions along the axis, referred to as the high-velocity spots or shells (HVSs), indicating either rapid wind acceleration or shocks at radial distances of sim 0 (sim 15-25\,au) from the center. A subtle velocity gradient perpendicular to the lobes is also found, suggesting rotation. Our ALMA observations detect increased brightness and broadness in the mRRLs compared to previously observed profiles, implying variations in wind kinematics and physical conditions on timescales of less than two years, which is in agreement with the extremely short kinematic ages (lsim 0.5-1\,yr) derived from observed velocity gradients in the compact ionized wind. Radiative transfer modeling indicates an average electron temperature of sim 15000\,K and reveals a nonuniform density structure within the ionized wind with electron densities ranging from to 10$^8$\ These results potentially reflect a complex bipolar structure resulting from the interaction of a tenuous companion-launched jet and the dense wind of the primary star.

Research on Hydraulic Characteristics of Water Leakage Phenomenon of Waterproof Hammer Air Valve in Water Supply Pressure Pipeline Based on Sustainable Utilization of Water Resources in Irrigation Areas

To investigate the causes of water leakage in the waterproof hammer air valve and its impact on sustainable water resource management, the DN100 waterproof hammer air valve was taken as the research object. By using the overset grid solution method of ANSYS Fluent 2021 R1 software, the flow field simulation of the waterproof hammer air valve was carried out. The transient action during the ascent phase of the key structural component floating ball, and the velocity and pressure distribution of the flow field inside the air valve are analyzed. The results showed that by giving different inlet flow velocities, the normal flow velocity range for the floating ball to float up was below 35 m/s and above 50 m/s. When the inlet flow velocity was between 35 m/s and 50 m/s, the growth rate of the pressure difference above and below the floating ball increased from 1.48% to 5.79% and then decreased to 0.4%. The floating ball would not be able to float up due to excessive outlet pressure above, which would cause the DN100 waterproof hammer air valve to leak water and fail to provide water hammer protection. When the inlet flow rate is 5 m/s, the velocity and pressure inside the valve body increase with time during the upward movement of the floating ball inside the waterproof hammer air valve and tend to stabilize at 400 ms. Through the generated pressure and velocity cloud maps, it can be observed that the location of maximum pressure is at the bottom of the buoy, directly below the floating ball, and at the narrow channels on both sides of the outflow domain. The location of the maximum velocity is at the small inlet of the bottom of the buoy. When the inlet speed of the valve is constant, a large amount of water flow is blocked by the floating ball, reducing the flow velocity and forming partial backflow below the floating ball, with an obvious vortex phenomenon. A small portion of the water flow passes through the air valve at a high velocity from both ends of the channel, and the water flow below the floating ball is in an extremely unstable state under the impact of high-speed water flow, resulting in a large gradient of water flow velocity passing through the valve. The research results not only help to improve the operational efficiency of water resource management systems but also reduce unnecessary water resource waste, thereby supporting the goal of sustainable water resource management.

Evaluating the mixed convection flow of Casson fluid from the semi-infinite vertical plate with radiation absorption effect

This study examines a steady laminar Casson fluid flow induced by a semi-infinite vertical plate under the impact of the Darcy-Forchheimer relation and thermal radiation. The features of mixed convection, cross-diffusion, radiation absorption, heat generation, chemical reactions and viscous dissipation are also considered to explain the transport phenomenon. The resultant system of equations, concerned with the problem under consideration, is transformed into a group of non-linear ordinary differential equations (ODEs) by means of similarity variables. The bvp4c method, an instrument popular for its numerical accomplishments, is utilized to solve this problem. The effect of flow parameters on heat transfer, concentration and velocity is evaluated via diagrams. To validate our code, we have compared the present outcomes to the prevenient literature, and stable consent has been detected. Moreover, the friction coefficient Cfx, Nusselt number Nux, and Sherwood number Shx are also computed to assess velocity gradient, efficiency of heat transfer and mass transfer process, respec-tively.

Predictive Value of NT-proBNP, FGF21, Galectin-3 and Copeptin in Advanced Heart Failure in Patients with Preserved and Mildly Reduced Ejection Fraction and Type 2 Diabetes Mellitus

Background and Objectives: Heart failure (HF) is one of the most common initial presentations of cardiovascular disease (CVD) in patients with type 2 diabetes mellitus (T2DM). There are different cardiac biomarkers related to the pathophysiological mechanisms of HF in T2DM. The current research aims to identify additional biomarkers that could improve the diagnosis and prognosis of HFpEF, which is currently assessed using NT pro-BNP levels. NT pro-BNP is a valuable tool for diagnosing heart failure but may not always correlate with clinical symptom severity or can present normal levels in certain cases, such as obesity. Biomarkers like FGF-21 and galectin-3 could provide greater insight into heart failure severity, especially in diabetic patients. The main objective of the current study is to assess the performance of NT-proBNP, FGF21, Galectin-3 and Copeptin to discriminate between advanced and mild HF. Materials and Methods: A total of 117 patients were enrolled in this study and divided into two groups: 67 patients in NYHA functional class I-II (mild HF) and 50 patients in NYHA III-IV (advanced HF). NT-pro BNP, FGF21, Galectin 3 and Copeptin serum levels were determined with the ELISA method. Receiver operating characteristic (ROC) analysis and binomial logistic regression analysis were used to measure the ability of the studied biomarkers to distinguish between advanced and mild HF patients. Results: In patients with T2DM with advanced HF, serum FGF21 level was significantly positively correlated with eGFR (ρ = 0.35, p = 0.0125) and triglycerides (ρ = 0.28, p = 0.0465) and significantly negatively correlated with serum levels of HDL cholesterol (ρ = −0.29, p = 0.0386) and with RV-RA gradient (ρ = −0.30, p = 0.0358). In patients with mild HF, serum FGF21 level was significantly negatively correlated with NT-proBNP levels (ρ = −0.37, p = 0.0022), E/e’ ratio (ρ = −0.29, p = 0.0182), TR velocity (ρ = −0.24, p = 0.0470) and RV-RA gradient (ρ = −0.24, p = 0.0472). FGF21 (AUC = 0.70, 95% CI: 0.60−0.79) and NT-proBNP (AUC = 0.73, 95% CI: 0.63–0.82) demonstrated significant predictive value to discriminate T2DM patients with advanced HF from those with mild HF. Elevated values for FGF21 (≥377.50 ng/mL) or NTproBNP (≥2379 pg/mL) were significantly associated with increased odds of advanced HF after adjusting for demographic and clinical covariates. Conclusions: NTpro-BNP and FGF21 have a similar ability to discriminate T2DM patients with advanced HF from those with mild HF. Univariable and multivariable logistic models showed that, FGF21 and NTproBNP were independent predictors for advanced HF in patients with preserved and mildly reduced ejection fraction and T2DM.

Substantial Global Radial Variations of Basalt Content Near the 660‐km Discontinuity

AbstractMid‐ocean ridges generate basalt and harzburgite, which are introduced into the mantle through subduction as a mechanical mixture, contributing to both lateral and radial compositional heterogeneity. The possible accumulation of basalt in the mantle transition zone has been examined, but details of the mantle composition below the 660‐km discontinuity (hereafter d660) remain poorly constrained. In this study, we utilize the subtle waveform details of S660S, the underside shear‐wave reflection off the d660, to interpret the seismic velocity, density, and compositional structure near, and particularly below, the d660. We identify a significant difference in S660S waveform shape in subduction zones compared to other regions. The inversion results reveal globally enriched basalt at the d660, with a notably higher content in subduction zones, consistent with the smaller impedance jump and S660S peak amplitude. The basalt fraction decreases significantly to less than 10% near 800‐km depth, forming a global harzburgite‐enriched layer and resulting in a steep seismic velocity gradient just below the d660, in agreement with 1D global reference models. The striking compositional radial variations near the d660 verify geodynamic predictions and challenge the applicability of homogeneous radial compositional models in the mantle. These variations may also affect the viscosity profile and, consequently, the dynamics at the boundary between the upper and lower mantle.

High-performance near-substrate heat sink with Tesla-like rotor-wing microchannel for chiplet cooling application

Microchannel heat sink provides a viable solution for enhancing thermal management in high-power chiplets. However, in consideration of cooling efficiency, low pressure drop, cost-effectiveness and reliability, it’s challenging to create an effective heat sink for a million-watt chip. Inspired by Tesla structure, this study introduces a Tesla-like rotor-wing microchannel (TRWM) to boost cooling performance. Due to the features of main channels, branch channels, and micro-islands in TRWM design, fluid in microchannel is effectively mixed and stirred with varied flow patterns, high temperature gradients and significant velocity gradients, which enhances the cooling capacity through precise fluid dynamics adjustment. Three different TRWMs are designed and compared by simulations. And the simulated results show that TRWM of 135° model achieves a maximum heat flux of 1514 W cm−2 @0.1 cm2 under a 60 K temperature rise, improving cooling efficiency by 19.4 % over the traditional channel design with 1221 W cm−2 @0.1 cm2. And then, the TRWM is fabricated using Ultraviolet Lithgraphie Galvanoformung Abformung (UV-LIGA) and bonding processes. Ultimately, the fabricated 135° TRWM sample demonstrated a heat dissipation capacity of up to 1446 W cm-2 @0.1 cm2 with a temperature increase of 60 K, which corresponds well with the simulated results. Moreover, the discrepancy between the actual and simulated values is less than 6.3 % under the same conditions. This performance provides a practical design solution for chiplet cooling and highlights the potential of bioinspired microfluidics.

Tailor-Designed Models for the Turbulent Velocity Gradient through Normalizing Flow.

Small-scale turbulence can be comprehensively described in terms of velocity gradients, which makes them an appealing starting point for low-dimensional modeling. Typical models consist of stochastic equations based on closures for nonlocal pressure and viscous contributions. The fidelity of the resulting models depends on the accuracy of the underlying modeling assumptions. Here, we discuss an alternative data-driven approach leveraging machine learning to derive a velocity gradient model which captures its statistics by construction. We use a normalizing flow to learn the velocity gradient probability density function (PDF) from direct numerical simulation (DNS) of incompressible turbulence. Then, by using the equation for the single-time PDF of the velocity gradient, we construct a deterministic, yet chaotic, dynamical system featuring the learned steady-state PDF by design. Finally, utilizing gauge terms for the velocity gradient single-time statistics, we optimize the time correlations as obtained from our model against the DNS data. As a result, the model time realizations resemble the time series from DNS statistically closely.

Effect of wall contact angle on the conjugate heat transfer for flow boiling processes in rectangular microchannels

Microchannel boiling heat transfer offers a promising solution to address extreme high heat flux in miniaturized and high-density integrated electronic devices. In this work, we performed numerical studies to elucidate the complex flow boiling process in a square microchannel using the open-source platform OpenFOAM. The governing equations of the two-phase flow was solved based on the finite volume framework, and the surface tension together with phase change models were incorporated to study the wettability and conjugate heat transfer in the microchannel. First, the stability of the liquid film shows that smaller contact angles lead to thicker and stable liquid films near the solid wall, while larger contact angles result in thinner and fragile films. Second, the heat transfer, represented by the dimensionless parameter Nu, shows that smaller contact angles result in higher and more uniform distribution of Nu. The velocity gradient causes the Nu to be higher for the sidewalls than for the bottom wall. The contact angle also affects the peak value of Nu. Small contact angles result in large solid wall temperature gradients and more efficient heat transfer. Finally, the simulation results show that smaller thermal conductivity of the solid results in larger temperature gradient in the flow direction, implying that the conjugate heat transfer is less efficient. Overall, the present numerical findings provide useful guidance for efficient thermal management in electronic devices.

Link between permanent shear-banding and local concentration fluctuations in suspensions of compressible microgels

We uncover the occurrence of shear banding in dense suspensions of compressible microgels. Velocimetry measurements evidence the presence of permanent but unsteady shear-banding for sufficiently small Peclet numbers, with the formation of a central plug-like flow. Small-angle neutron scattering experiments under shear link the observed banding phenomenon to structural variations along the velocity gradient, providing a connection between the arrested band and the increase in structural correlations associated with changes in the local packing fraction. This provides unique evidence of a shear–concentration coupling mechanism in jammed suspensions of compressible particles.

A public grid of radiative transfer simulations for Lyα and metal lines in idealised galactic outflows

The vast majority of star-forming galaxies are surrounded by large reservoirs of gas ejected from the interstellar medium. Ultraviolet absorption and emission lines represent powerful diagnostics to constrain the cool phase of these outflows, through resonant transitions of hydrogen and metal ions. The interpretation of these observations is often remarkably difficult as it requires detailed modelling of the propagation of the continuum and emission lines in the gas. To this aim, we present a large public grid of ≈20 000 simulated spectra that includes H I Lyα and five metal transitions associated with Mg II, C II, Si II, and Fe II which is accessible online. The spectra have been computed with the RASCAS Monte Carlo radiative transfer code for 5760 idealised spherically symmetric configurations surrounding a central point source emission, and characterised by their column density, Doppler parameter, dust opacity, wind velocity, as well as various density and velocity gradients. Designed to predict and interpret Lyα and metal line profiles, our grid exhibits a wide diversity of resonant absorption and emission features, as well as fluorescent lines. We illustrate how it can help better constrain the wind properties by performing a joint modelling of observed Lyα, C II, and Si II spectra. Using CLOUDY simulations and virial scaling relations, we also show that Lyα is expected to be a faithful tracer of the gas at T ≈ 104 − 105 K, even if the medium is highly ionised. While C II is found to probe the same range of temperatures as Lyα, other metal lines merely trace cooler phases (T ≈ 104 K). As their gas opacity strongly depends on gas temperature, incident radiation field, metallicity and dust depletion, we caution that optically thin metal lines do not necessarily originate from low H I column densities and may not accurately probe Lyman continuum leakage.

EDIG-CHANGES

Context. The kinematic information of the extraplanar diffuse ionized gas (eDIG) around galaxies provides clues to the origin of the gas. Aims. The eDIG-CHANGES project studies the physical and kinematic properties of the eDIG around the CHANG-ES sample of nearby edge-on disk galaxies. Methods. We use a novel multi-slit narrow-band spectroscopy technique to obtain the spatial distribution of the spectral properties of the ionized gas around NGC 891, which is often regarded as an analogue of the Milky Way. We developed specific data reduction procedures for the multi-slit narrow-band spectroscopy data taken with the MDM 2.4 m telescope. The data presented in this paper cover the Hα and [N II]λλ6548, 6583 Å emission lines. Results. The eDIG traced by the Hα and [N II] lines shows an obvious asymmetric morphology, being brighter in the northeastern part of the galactic disk and extending a few kiloparsecs above and below the disk. Global variations in the [N II]/Hα line ratio suggest additional heating mechanisms for the eDIG at large heights beyond photoionization. We also construct position-velocity (PV) diagrams of the eDIG based on our optical multi-slit spectroscopy data and compare them to similar PV diagrams constructed with the H I data. The dynamics of the two gas phases are generally consistent with each other. Modelling the rotation curves at different heights from the galactic mid-plane suggests a vertical negative gradient in turnover radius and maximum rotation velocity, with magnitudes of approximately 3 kpc kpc−1 and 22 − 25 km s−1 kpc−1, respectively. Conclusions. Our measured vertical gradients of the rotation curve parameters suggest significant differential rotation of the ionized gas in the halo, often referred to as the lagging eDIG. Systematic study of the lagging eDIG, using the multi-slit narrow-band spectroscopy technique developed in our eDIG-CHANGES project, will help us to better understand the dynamics of the ionized gas in the halo.

Using contrasts in horizontal P-wave reflectivity to map the base of the continental lithosphere: Results for the central and eastern U.S.

Vertical-incidence seismic reflection profiles generated from global phases for 16 earthquakes recorded by stations of the Transportable Array (TA) show distinctive patterns of P-wave reflectivity in the uppermost mantle beneath the central and eastern United States. The overall distribution of reflections identified objectively using the sign test statistic applied to bootstrapped stacks is consistent with a westward increase in depth of the lithosphere-asthenosphere boundary (LAB) from roughly 110 to 250 km that is marked within the lower lithosphere by piecewise continuous segments of elevated horizontal P-wave reflectivity. For some profiles, the onsets of zones of increased reflectivity closely match depths corresponding to the maximum negative S-wave velocity gradients found by surface-wave tomography, suggesting that P-wave reflectivity can be used to help characterize properties of the lower lithosphere. We suggest that the vertical change in horizontal reflectivity straddles the lithosphere-asthenosphere transition, encompassing a broad zone of layering caused by increased strain in the lower lithosphere as well as drag-induced flow in the asthenosphere. Some of the lines also show waveforms that fall within the depth range of arrivals identified as midlithospheric discontinuities (MLDs) in overlapping Sp receiver-function profiles. The reflection waveforms observed in the TA lines are mostly multicyclic with a mix of polarities indicating a layered transition, consistent with previous observations and model studies that show the breakup of single Sp waveforms into a series of less prominent, shorter-period P-wave reflections as the dominant frequency of incident energy is increased.

A dynamic linearized wall model for turbulent flow simulation: towards grid convergence in wall-modeled simulations

This paper addresses the common issue of (no-)grid convergence in wall-modeled numerical simulations and proposes a dynamic linearization technique applied to the Spalart-Allmaras wall model to achieve a proper behavior on fine grids and low-friction areas. A theoretical analysis of the numerical error committed on the shear stress balance close to the walls is performed. It shows that the error is due to the inappropriate imposition of too steep wall-normal velocity gradients that cannot be properly accounted for on the typical grids used for wall-modeled simulations. Based on this error quantification, a dedicated wall model linearization technique is proposed, following the approach developed by Tamaki, Harada and Imamura in 2017. In the proposed modified linearization method, the linearization distance is modified and adjusted dynamically. This is done according to the theoretical shear stress error estimate, in order to keep the numerical error below a user-defined threshold. The method is applied to well-referenced test cases of increasing complexity from the Turbulence Modeling Resource. Overall, the proposed wall model clearly exhibits appropriate grid convergence properties and is also able to predict accurately non-equilibrium boundary layers and flow separation using proper grid refinement.

Unsteady Secondary Flow Structure at a Large River Confluence

AbstractRiver confluences, which are characterized by complex hydrodynamics, are key nodes for flood control and environmental protection. Two field surveys were carried out at the confluence of the Yangtze River and Poyang Lake to investigate the transient character of flow structures, which are often assumed steady. Repeat‐transect acoustic Doppler current profile measurements were processed and analyzed, adopting a new method to separate mean flow from turbulence and measurement error based on physics‐informed generalized Tikhonov regularization. The two field surveys were characterized by two distinct mixing interface modes: A so‐called Kelvin–Helmholtz (KH) mode, and a wake mode. In KH mode, large‐scale flow fluctuations were observed. These flow fluctuations exert a substantial influence on the alternation of secondary flows by changing the water surface pressure gradient, affecting the intensity of secondary flows rather than their spatial structure. We infer that temperature‐induced stratification is the main cause of this. In the wake mode, multiple vortices in the wake region at the confluence apex also produced flow fluctuations, directly related to the primary velocity gradient. We argue that even for constant incoming flows, secondary flow at river confluences can exhibit channel‐scale unsteadiness related to migration of the turbulent mixing interface. Our findings highlight the crucial role of density effects in regulating secondary flow unsteadiness, which is essential for understanding contaminant and sediment dispersal in river systems.

Stability Assessment of Weirs Reinforced with Sheet Piles

Extreme weather events induced by climate change are increasing across the world. In particular, floods resulting from unpredictable heavy rains cause significant damage to property and human life. In Korea, river and underwater structure management is performed continuously in accordance with strict regulations. However, to prepare for unprecedented downpours, the structures of river reservoirs must be reinforced and their stability must be evaluated. This study focuses on the stability evaluation of piping, which represents the main cause of weir collapse. To this end, sheet piles are applied to weirs to evaluate the effects of changes in their length and location on their seepage discharge, seepage velocity, and maximum hydraulic gradient. Additionally, piping stability evaluation of weirs is conducted using sheet piles by evaluating the critical velocity. The results derived in this study are expected to be highly beneficial for reinforcing weirs currently in operation as well as for the design, construction, and operation of future underwater structures.

Quantifying the Expanding and Cooling Effects into the Double Adiabatic Evolution of the Solar Wind Through the Expanding Box Model

One of the fundamental problems in space physics is the expansion dynamics of the solar wind, strongly correlated with collective plasma reactions, such as wave instabilities that tend to relax kinetic anisotropies. The expansion is in general described through the double adiabatic or Chew–Goldberger–Low (CGL) theory, which sets the main ideas and plasma expansion’s major role in describing plasma cooling/heating dynamics. Here, using the expanding box model (EBM) we revisit the CGL description including plasma expansion. Our primary objective is to isolate the expanding effects into the conservation of the double adiabatic invariants, a key aspect of the CGL theory. Following the same approximations and assumptions as in EBM and CGL theory, we developed a CGL-like description in which the expansion modifies the conservation of the double adiabatic invariants. Our results show that the double adiabatic equations are no longer conserved if plasma cooling is introduced through the EBM, with explicit dependence on expanding parameters, magnetic field profiles, and velocity gradients. Solving the equations for different magnetic field and density profiles (obtained self-consistently through the equations), we compute the evolution of temperature anisotropy and plasma beta, which deviates from CGL predictions and empirical observations. This deviation is attributed to the plasma cooling effect induced by the expansion of the plasma. The results suggest that heating mechanisms even play a major role in counteracting plasma cooling during expansion.

Aortic valve tissue quantification in bicuspid aortic valve stenosis

Abstract Background The relative contribution of calcific versus noncalcific aortic valve tissue volume to aortic stenosis (AS) in bicuspid aortic valve (BAV) is unclear. Purpose We aimed to assess the association of aortic valve tissue volume quantified by contrast-enhanced CT with echocardiographic AS severity, and diagnostic implication of noncalcific tissue volume for severe AS. Methods We retrospectively identified 234 patients with BAV who had echocardiographic AS severity and contrast-enhanced CT evaluation within six months and left ventricular ejection ≥50%, including 150 severe AS (aortic valve area≤1 cm2 or indexed valve area≤0.6cm2/m2 plus mean grdient≥40mmHg or peak velocity≥4 m/s), 84 nonsevere AS (61 with at least mild AS: peak veloicty≥2.0 m/s plus mean gradient ≥10mmHg, and 23 with normal aortic valve function). Contrast-enhanced CT aortic valve calcific volume and noncalcific (fibrosis) volume were quantified using patient-specific Hounsfield unit thresholds (Figure). Noncontrast CT aortic valve calcium score (AVCscore) was quantified by the Agaston method. CT measurements were indexed to echocardiographic aortic valve annulus area and square-root transformed for the analysis. Results Of 234 patients, the mean age was 64±11 years, and 64% were men. There were positive correlations of indexed calcific volume, noncalcific volume, and inverse correlations of percentages of noncalcific volume (noncalcific volume divided by the sum of calcific and noncalcific volume) with peak velocity and mean gradient (|r|=0.30 to 0.68). Among 150 patients with severe AS, 28 had an AVCscore below the severe AVC threshold (1200 AU in women and 2000 AU in men) while exhibited a higher percentage of noncalcific volume compared to 122 patients with severe AVCscore (67±15% vs. 39±15%, p<0.001). After excluding 122 patients with severe AS and severe AVCscore, the indexed noncalcific volume was associated with severe AS (β±S.E: 0.18±0.07, p=0.005) with an area under the curve of 0.71; in contrast, AVCscore was not (p=0.55). Conclusion Both calcific and noncalcific aortic valve tissue volume contribute to AS severity in patients with BAV. Notably, noncalcific tissue volume is a key factor in determining severe AS in patients without severe AVCscore, suggesting its potential diagnostic value.Figure

Impact of systolic coronary flow reversal in patients with aortic stenosis: assessment with transthoracic echocardiography

Abstract Background In patients with aortic stenosis (AS), increased systolic wall stress due to increased afterload reduces systolic coronary flow, often leading to systolic coronary flow reversal (SFR) in epicardial coronary arteries. Purpose We used transthoracic echocardiography (TTE) to evaluate severity of AS, left ventricular function, and coronary flow, and investigated echocardiographic indicators associated with SFR. Methods We prospectively evaluated consecutively presenting patients who visited our valvular heart disease outpatient clinic or were admitted to our hospital for investigation of AS (July 2023 to February 2024). Based on ESC guidelines, severity of AS and the left ventricular function were assessed with TTE. At the same time, TTE was used to measure distal left anterior descending coronary artery flow. SFR was defined as the presence of a reversal coronary flow component in systole. Based on the presence or absence of SFR in coronary flow measurements, patients were classified into SFR+ or SFR− groups. The inclusion criteria were AS of moderate or greater severity, and the exclusion criteria were known coronary stenosis and the inability to assess coronary flow. Results Enrolled 28 patients were classified into SFR+ (7 patients) and SFR − (21 patients) groups. Comparing baseline characteristics between the SFR+ and SFR− groups, although there were no significant differences in left ventricular indicators such as left ventricular mass index, left ventricular ejection fraction, stroke volume index, and E/e’ between the two groups, left ventricular global longitudinal strain was significantly lower in the SFR+ group (12.0±3.1%, 14.9±3.0%, p=0.026) (Table 1). Regarding indexes of AS assessment, aortic valve peak velocity and aortic valve mean pressure gradient values were significantly higher in the SFR+ group than in the SFR − group ([475±68 cm/s, 379±55 cm/s, p<0.001] and [56.2±16.5 mm Hg, 34.8±10.5 mm Hg, p<0.001], respectively) (Table 1). Representative cases show Figure 1. Conclusion The presence of SFR in patients with AS assessed using TTE may be a simple echocardiographic index that may be associated with potential decline in left ventricular function and progression of AS.

Reverse cardiac remodeling induced by endovascular treatment of coarctation of the aorta

Abstract Background Previously, we have showed the 3-year clinical safety and efficacy of balloon expandable versus self-expandable stents in native coarctation of the aorta (CoA) in a randomized clinical trial (RCT). Very few prospective studies have addressed the changes of echocardiographic parameters in mid to long-term follow up of CoA patients treated endovascularly. Purpose We aimed to demonstrate the improvement of echocardiographic parameters among patients undergoing coarctoplasty with stent based on core laboratory-confirmed baseline and 3-year follow up transthoracic echocardiographic (TTE) images. Methods In the index RCT, adult patients with de novo native CoA were randomized into two groups based on stent types. All randomized patients received the 3-year structural follow-up including aortic CT angiography and TTE. The current prospective cohort substudy, included all patients with available baseline and three-year core laboratory TTEs. Results Of 92 patients initially randomized, 71 participated in the 3-year structural follow up. No baseline core lab images were available in 39 patients, and thus, 32 patients (a median age of 32 (24.8 – 37.5) years, (14 women [43.8%]) were included in this subgroup study. One out of the 32 patients presented with recoarctation which was successfully treated before the 3-year evaluation. Peak systolic gradient and end-systolic velocity of the coarctation stenting site were 17.38 ± 6.55 mmHg and 0.93 ± 0.24 m/s respectively in the 3-year follow-up. Septal E’ and lateral E’ velocities were improved significantly (8.6 ± 1.73 cm/s to 9.35 ± 2 cm/s, P = 0.02 and 12.74 ± 2.96 cm/s to 13.92 ± 2.44 cm/s, P = 0.03, respectively). In addition, septal E/E’ ratio (10.84 ± 2.83 to 9.21 ± 3.17, P = 0.02) and lateral E/E’ ratio (7.39 ± 2.24 to 6.29 ± 1.97, P = 0.02) showed significant improvement. Significant reduction in LV mass [160 (130–203) g to 142 (IQR= 121–172) g, P = 0.001], and septal and posterior LV thicknesses were also demonstrated (0.9 (0.8–1.0) cm to 0.81 (0.77–0.93) cm, P = 0.004) and 0.92 ± 0.14 cm to 0.85 ±0.09 cm, P = 0.01, respectively). Twelve (37.5%) patients had baseline LVH which was normalized in 9 (75%). Lastly, 12 (41.3%) of our population had diastolic dysfunction at baseline study which significantly decreased to 4 (13.7%) in the three-year follow-up evaluation. Conclusion In the present core laboratory-based study, coarctoplasty with stent has favorable effects on diastolic function and LV hypertrophy during midterm follow-up in adult population with de novo native aortic coarctation treated with stent.