Search Results (18)

Abdominal aortic aneurysm (AAA) is a critical condition with high rupture risk, and the maximum diameter alone is insufficient for prediction. Pulse wave velocity (PWV), a surrogate of aortic stiffness, can be estimated using 4D-Flow magnetic resonance imaging (MRI), but requires validation under dilated conditions. This in vitro study examined the relationship between PWV and stiffness by comparing healthy and aneurysmal compliant aortic models. Two latex phantoms were fabricated to represent normal and AAA geometries. A circulatory MRI-compatible system simulated physiological inlet flow, with flow rates measured across perpendicular planes using 4D- and 2D-Flow MRI. PWV was derived from transit times of the systolic upstroke and interplane distances. Complementary 1D numerical simulations and laboratory flowmeter measurements were performed. Although the wall elasticity and thickness were identical, PWV in the healthy model ranged from 6.2 to 7.7 m/s and in the aneurysmal model it ranged from 14.2 to 15 m/s. This increase was confirmed by temporal overlap of thoracic flow curves and reduced slope in the transit time–distance regression. Results were consistent across simulations, 2D-Flow, and flowmeter data. Findings highlight that indirect 4D-Flow assessment of thoracic stiffness in the presence of AAA must account for wave reflections introduced by dilation, which significantly alter PWV estimation. Full article

The monitoring of peripheral electrical bioimpedance (EBI) variations is a promising method that has the potential to replace invasive or burdensome techniques for cardiovascular measurements. Segmental or continuous recording of peripheral pulse waves can serve as a basis for calculating prognostic markers like pulse wave velocity (PWV) or include parameters such as pulse transit time (PTT) or pulse arrival time (PAT) for noninvasive blood pressure (BP) estimation, as well as potentially novel cardiovascular risk indicators. However, several technical, analytical, and interpretative aspects need to be resolved before the EBI method can be adopted in clinical practice. Our goal was to investigate and improve the application of EBI, executing its comparison with other cardiovascular assessment methods in patients hospitalized for coronary catheterization procedures. Methods: We analyzed data from 44 non-acute patients aged 45–74 years who were hospitalized for coronary catheterization at East Tallinn Central Hospital between 2020 and 2021. The radial EBI and electrocardiogram (ECG) were measured simultaneously with central and contralateral pressure curves. The Savitzky–Golay filter was used for signal smoothing. The Hankel matrix decomposer was applied for the extraction of cardiac waveforms from multi-component signals. After extracting the cardiac component, a period detection algorithm was applied to EBI and blood pressure curves. Results: Seven points of interest were detected on the pressure and EBI curves, and four with good representativeness were selected for further analysis. The Spearman correlation coefficient was low for all but the central and distal pressure curve systolic upstroke time points. A high positive correlation was found between PWV measured both invasively and with EBI. The median value of complimentary pulse wave velocity (CPWV), a parameter proposed in the paper, was significantly lower in patients with normal coronaries compared to patients with any stage of coronary disease. Conclusions: With regard to wearable devices, the EBI-derived PAT can serve as a substrate for PWV calculations and cardiovascular risk assessment, although these data require further confirmation. Full article

Introduction: Evidence for the diagnostic yield of noninvasive diagnostic assessment for the diagnosis of peripheral arterial disease (PAD) in diabetic foot syndrome (DFS) is poor. Pulse volume recordings (PVRs) at the forefoot level could be a valuable diagnostic tool in the presence of medial arterial calcification. Patients and methods: Patients with DFS who underwent invasive angiography between 01/2020 and 11/2024 and had corresponding PVRs performed within 30 days prior to the procedure were included. DFS was classified according to the Wagner–Armstrong classification. Clinical characteristics and hemodynamic parameters, including systolic ankle pressures and ankle–brachial index were recorded. PVRs were analyzed semiquantitatively by investigators blinded to the clinical information and quantitatively with determination of upstroke time (UST), upstroke ratio (USR), and maximum systolic amplitude (MSA). Angiographic PAD severity was graded according to the GLASS classification. Statistical analysis included univariate significance tests, 2 × 2 contingency tables, receiver–operator characteristic (ROC) analysis and determination of interobserver agreement. Results: In this study, 90 extremities of 70 patients were analyzed, 47 of whom had an ABI ≥ 1.3. Critical limb-threatening ischemia with non-pulsatile PVRs was evident in 6.7%. An abnormal PVR curve morphology (mildly or severely abnormal) yielded a sensitivity and specificity of 63.3% and 85.7% for detection of severe PAD (GLASS stages 2 and 3). Interobserver agreement of semiquantitative PVR rating was substantial (Cohen’s kappa 0.8) in 51 evaluated cases. For detection of any PAD (GLASS ≥ 1) or severe PAD (GLASS ≥ 2), we found the highest diagnostic accuracy for MSA (area under the curve [AUC] 0.89 and 0.82). With a cut-off value of 0.58 mmHg, MSA had a sensitivity of 91.4% and a specificity of 80.8% for detection of any PAD (GLASS ≥ 1). MSA with a cut-off of 0.27 mmHg had a sensitivity of 72.2% and a specificity of 77.1% for detection of severe PAD, whereas the sensitivity and specificity for detection of inframalleolar disease were 62.9% and 69.4%, respectively. Results were consistent in subgroup analyses. Conclusions: PVRs with extraction of quantitative features offer promising diagnostic yield for detection of PAD in the setting of DFS. MSA outperformed UST and USR but showed limited capability of detecting impaired inframalleolar outflow. Full article

The wing kinematics of birds plays a significant role in their excellent unsteady aerodynamic performance. However, most studies investigate the influence of different kinematic parameters of flapping wings on their aerodynamic performance based on simple harmonic motions, which neglect the aerodynamic effects of the real flapping motion. The purpose of this article was to study the effects of wing kinematics on aerodynamic performance for a pigeon-inspired flapping wing. In this article, the dynamic geometric shape of a flapping wing was reconstructed based on data of the pigeon wing profile. The 3D wingbeat kinematics of a flying pigeon was extracted from the motion trajectories of the wingtip and the wrist during cruise flight. Then, we used a hybrid RANS/LES method to study the effects of wing kinematics on the aerodynamic performance and flow patterns of the pigeon-inspired flapping wing. First, we investigated the effects of dynamic spanwise twisting on the lift and thrust performance of the flapping wing. Numerical results show that the twisting motion weakens the leading-edge vortex (LEV) on the upper surface of the wing during the downstroke by reducing the effective angle of attack, thereby significantly reducing the time-averaged lift and power consumption. Then, we further studied the effects of the 3D sweeping motion on the aerodynamic performance of the flapping wing. Backward sweeping reduces the wing area and weakens the LEV on the lower surface of the wing, which increases the lift and reduces the aerodynamic power consumption significantly during the upstroke, leading to a high lift efficiency. These conclusions are significant for improving the aerodynamic performance of bionic flapping-wing micro air vehicles. Full article

The polished rod dynamometer operates under alternating loads and large temperature differences for a long time, inevitably leading to zero drift and temperature drift issues. At the same time, conventional inversion of polished rod dynamometer cards fails to consider the impact of friction loads, resulting in inaccurate production and liquid level calculations from pump dynamometer cards. Based on the oil-filled environment in the sucker rod and tubing during the upstroke of the pumping unit, this paper proposes a rapid identification method for the four characteristic points of the polished rod dynamometer card to obtain a calculation method for friction loads at the velocity reversal points A and C. The gravity of the polished rod string in the liquid column serves as the benchmark for calibrating the polished rod dynamometer card. Combined with basic well data, a one-dimensional wave equation difference calculation method is used to solve for the pump dynamometer card. An approximation algorithm is employed to achieve rapid calibration of the polished rod dynamometer card and inversion of the pump dynamometer card. Calculation and engineering application results indicate that the accuracy of production and liquid level calculations obtained from the pump dynamometer card through online correction of the polished rod dynamometer card exceeds 90%, achieving the goal of engineering digitization applications. Full article

Cicadas are heavy fliers well known for their life cycles and sound production; however, their flight capabilities have not been extensively investigated. Here, we show for the first time that cicadas appropriate backward flight for additional maneuverability. We studied this flight mode using computational fluid dynamics (CFD) simulations based on three-dimensional reconstructions of high-speed videos captured in a laboratory. Backward flight was characterized by steep body angles, high angles of attack, and high wing upstroke velocities. Wing motion occurred in an inclined stroke plane that was fixed relative to the body. Likewise, the directions of the half-stroke-averaged aerodynamic forces relative to the body (local frame) were constrained in a narrow range (<20°). Despite the drastic difference of approximately 90° in body posture between backward and forward flight in the global frame, the aerodynamic forces in both flight scenarios were maintained in a similar direction relative to the body. The forces relative to the body were also oriented in a similar direction when observed during climbs and turns, although the body orientation and motions were different. Hence, the steep posture appropriated during backward flight was primarily utilized for reorienting both the stroke plane and aerodynamic force in the global frame. A consequence of this reorientation was the reversal of aerodynamic functions of the half strokes in backward flight when compared to forward flight. The downstroke generated propulsive forces, while the upstroke generated vertical forces. For weight support, the upstroke, which typically generates lesser forces in forward flight, is aerodynamically active in backward flight. A leading-edge vortex (LEV) was observed on the forewings during both half strokes. The LEV’s effect, together with the high upstroke velocity, increased the upstroke’s force contribution from 10% of the net forces in forward flight to 50% in backward flight. The findings presented in this study have relevance to the design of micro-aerial vehicles (MAVs), as backward flight is an important characteristic for MAV maneuverability or for taking off from vertical surfaces. Full article

This study presents a model experiment method that can accurately reproduce the flapping motion of insect wings and measure related unsteady aerodynamic data in real time. This method is applied to investigate the aerodynamic characteristics of inclined hovering, which distinguishes it from normal hovering by having asymmetric wing rotation during the two half strokes. In the study of the aerodynamic influence of the downstroke rotational angle, it is found that the rotational angle affects lift generation by changing the angle between the wing surface and the horizontal plane in the mid-downstroke. When the wing is almost parallel to the horizontal plane in the mid-downstroke, the vortex structure can maintain structural integrity and a large magnitude, which is conducive to the generation of high lift. In the study of the aerodynamic effect of the upstroke rotational angle, the windward conversion mechanism is proposed to explain the influence of the upstroke rotational angle on the direction and magnitude of thrust. Obtaining the rotational angle that is most conducive to maintaining the flight state of hovering in the present study can provide guidance for the structural design and kinematic control of micro aerial vehicles. Full article

The Three-Piece Oil Control Ring (TPOCR) is becoming a viable option for heavy duty gas and hydrogen engines due to the low particle concentration in these engines. Although direct oil leakage from the gap is not likely to happen with the misalignment of the upper and lower rail gaps, there exist other less-apparent oil leaking mechanisms through the TPOCR. This work is targeted at understanding the oil leakage’s source and destination through the rail and liner interfaces across the whole cycle. The 2D Laser Induced Fluorescence technique was applied on an optical engine to study the oil transport behavior. Combined with a TPOCR model for dynamics and lubrication, the mechanisms that cause rail twist and oil scraping by the upper rail were analyzed. It was found that the symmetrical rail can scrape the oil up in the up-strokes. The scraped oil first accumulates in the clearance between the upper rail and groove, as well as at the upper corner of the rail Outer Diameter before being transferred to both the third land and liner when the piston changes direction at Top Dead Center. Rails with an asymmetrical profile can reduce or enhance these effects depending the orientation of the rails. This study provides findings that could help design the engine to better control Lubricate Oil Consumption and properly lubricate the Top Dead Center’s dry region at the same time. Full article

The present study was designed to test the hypothesis that the selectivity of blocking the late Na⁺ current (I_NaL) over the peak Na⁺ current (I_NaP) is related to the fast offset kinetics of the Na⁺ channel inhibitor. Therefore, the effects of 1 µM GS967 (I_NaL inhibitor), 20 µM mexiletine (I/B antiarrhythmic) and 10 µM quinidine (I/A antiarrhythmic) on I_NaL and I_NaP were compared in canine ventricular myocardium. I_NaP was estimated as the maximum velocity of action potential upstroke (V⁺_max). Equal amounts of I_NaL were dissected by the applied drug concentrations under APVC conditions. The inhibition of I_NaL by mexiletine and quinidine was comparable under a conventional voltage clamp, while both were smaller than the inhibitory effect of GS967. Under steady-state conditions, the V⁺_max block at the physiological cycle length of 700 ms was 2.3% for GS967, 11.4% for mexiletine and 26.2% for quinidine. The respective offset time constants were 110 ± 6 ms, 456 ± 284 ms and 7.2 ± 0.9 s. These results reveal an inverse relationship between the offset time constant and the selectivity of I_NaL over I_NaP inhibition without any influence of the onset rate constant. It is concluded that the selective inhibition of I_NaL over I_NaP is related to the fast offset kinetics of the Na⁺ channel inhibitor. Full article

The unsteady RANS equations for a two-dimensional hydrofoil were solved using ANSYS Fluent to model and simulate the hydrofoil at a constant Reynolds number, Re, of 2 × 10⁵ and a fixed reduced frequency, f*, of 0.14. The simulations were performed by varying parameters, such as the number of deflectors N, tilt angle of the deflectors β, and vertical spacing of the deflectors J* = J/c, to determine the effect of the upstream deflector’s position on the hydrofoil’s performance. The results demonstrated that the deflector was effective at redirecting the separated flow away from the edges, which was then amplified downstream before colliding with the leading edge of the oscillating hydrofoil to increase power extraction. The performance of the oscillating hydrofoil was highly reliant on all three studied parameters. The hydrofoil with two deflectors (N = 2) displayed marginally superior power extraction capability compared to the hydrofoil with a single deflector (N = 1). Furthermore, the hydrofoil with the rightward inclined deflector at a low tilt angle (−5° ≥ β ≥ −10°) exhibited relatively better power extraction performance than the others. The best deflector design increased the hydrofoil’s cycle-averaged power coefficient by approximately 32% compared to a hydrofoil without a deflector. The vortex structures revealed that the flow evolution and power extraction performance were dependent on the size, robustness, and growth rate of the leading edge vortex (LEV) as well as the timing of LEV separation. The power extraction efficiency of an oscillating hydrofoil increased in the mid downstroke and upstroke due to the formation of a more robust LEV when the hydrofoil–deflector interaction was advantageous, but it dropped in the wing reversal due to the early separation of the LEV when the hydrofoil–deflector interaction was counterproductive. Full article

Na_v1.5 is the main voltage-gated sodium channel found in cardiac muscle, where it facilitates the fast influx of Na⁺ ions across the cell membrane, resulting in the fast depolarization phase—phase 0 of the cardiac action potential. As a result, it plays a major role in determining the amplitude and the upstroke velocity of the cardiac impulse. Quantitively, cardiac sodium channel activates in less than a millisecond to trigger the cardiac action potential and inactivates within 2–3 ms to facilitate repolarization and return to the resting state in preparation for firing the next action potential. Missense mutations in the gene that encodes Na_v1.5 (SCN5A), change these time constants which leads to a wide spectrum of cardiac diseases ranging from long QT syndrome type 3 (LQT3) to sudden cardiac death. In this mini-review I will focus on the missense mutations in the inactivation gate of Na_v1.5 that results in arrhythmia, attempting to correlate the location of the missense mutation to their specific phenotype. Full article

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive heart condition which causes fibro-fatty myocardial scarring, ventricular arrhythmias, and sudden cardiac death. Most cases of ARVC can be linked to pathogenic mutations in the cardiac desmosome, but the pathophysiology is not well understood, particularly in early phases when arrhythmias can develop prior to structural changes. Here, we created a novel human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model of ARVC from a patient with a c.2358delA variant in desmoglein-2 (DSG2). These DSG2-mutant (DSG2^Mut) hiPSC-CMs were compared against two wildtype hiPSC-CM lines via immunostaining, RT-qPCR, Western blot, RNA-Seq, cytokine expression and optical mapping. Mutant cells expressed reduced DSG2 mRNA and had altered localization of desmoglein-2 protein alongside thinner, more disorganized myofibrils. No major changes in other desmosomal proteins were noted. There was increased pro-inflammatory cytokine expression that may be linked to canonical and non-canonical NFκB signaling. Action potentials in DSG2^Mut CMs were shorter with increased upstroke heterogeneity, while time-to-peak calcium and calcium decay rate were reduced. These were accompanied by changes in ion channel and calcium handling gene expression. Lastly, suppressing DSG2 in control lines via siRNA allowed partial recapitulation of electrical anomalies noted in DSG2^Mut cells. In conclusion, the aberrant cytoskeletal organization, cytokine expression, and electrophysiology found DSG2^Mut hiPSC-CMs could underlie early mechanisms of disease manifestation in ARVC patients. Full article

The nature, occurrence, morphological basis and functions of insect wing deformation in flight are reviewed. The importance of relief in supporting the wing is stressed, and three types are recognized, namely corrugation, an M-shaped section and camber, all of which need to be overcome if wings are to bend usefully in the morphological upstroke. How this is achieved, and how bending, torsion and change in profile are mechanically interrelated, are explored by means of simple physical models which reflect situations that are visible in high speed photographs and films. The shapes of lines of transverse flexion are shown to reflect the timing and roles of bending, and their orientation is shown to determine the extent of the torsional component of the deformation process. Some configurations prove to allow two stable conditions, others to be monostable. The possibility of active remote control of wing rigidity by the thoracic musculature is considered, but the extent of this remains uncertain. Full article

Elsholtzia ciliata essential oil (E. ciliata) has been developed in Lithuania and internationally patented as exerting antiarrhythmic properties. Here we demonstrate the pharmacological effects of this herbal preparation on cardiac electrical activity. We used cardiac surface ECG and a combination of microelectrode and optical mapping techniques to track the action potentials (APs) in the Langendorff-perfused rabbit heart model during atrial/endo-/epi-cardial pacing. Activation time, conduction velocity and AP duration (APD) maps were constructed. E. ciliata increased the QRS duration and shortened QT interval of ECG at concentrations of 0.01–0.1 μL/mL, whereas 0.3 μL/mL (0.03%) concentration resulted in marked strengthening of changes. In addition, the E. ciliata in a concentration dependent manner reduced the AP upstroke dV/dt_max and AP amplitude as well as APD. A marked attenuation of the AP dV/dt_max and a slowing spread of electrical signals suggest the impaired functioning of Na⁺-channels, and the effect was use-dependent. Importantly, all these changes were at least partially reversible. Our results indicate that E. ciliata modulates cardiac electrical activity preferentially inhibiting Na⁺ conductance, which may contribute to its effects as a natural antiarrhythmic medicine. Full article

Upstroke time (UT), measured from the foot-to-peak peripheral pulse wave, is a merged parameter used to assess arterial stiffness and target vascular injuries. In this study, we aimed to investigate UT for the prediction of cardiovascular and all-cause mortality in patients with chronic kidney disease (CKD). This longitudinal study enrolled 472 patients with CKD. Blood pressure, brachial pulse wave velocity (baPWV), and UT were automatically measured by a Colin VP-1000 instrument. During a median follow-up of 91 months, 73 cardiovascular and 183 all-cause mortality instances were recorded. Multivariable Cox analyses indicated that UT was significantly associated with cardiovascular mortality (hazard ratio (HR) = 1.010, p = 0.007) and all-cause mortality (HR = 1.009, p < 0.001). The addition of UT into the clinical models including traditional risk factors and baPWV further increased the value in predicting cardiovascular and all-cause mortality (both p < 0.001). In the Kaplan–Meier analyses, UT ≥ 180 ms could predict cardiovascular and all-cause mortality (both log-rank p < 0.001). Our study found that UT was a useful parameter in predicting cardiovascular and all-cause mortality in CKD patients. Additional consideration of the UT might provide an extra benefit in predicting cardiovascular and all-cause mortality beyond the traditional risk factors and baPWV. Full article