Doppler Velocimetry Research Articles

Ca2+ signals in human umbilical endothelial cells derived from pregnancy with fetal growth restriction associated with hypertensive disorder.

Fetal growth restriction associated with hypertensive disorders of pregnancy (FGR-HDP) is a prevalent pathology with a higher risk of perinatal morbimortality. In this condition, placental insufficiency and endothelial dysfunction serve key roles. The present prospective cohort study monitored 11 patients with an FGR-HDP and 15 with full-term normotensive pregnancies and studied post-natal intracellular calcium concentration ([Ca2+]i) signals in human umbilical vein endothelial cells (HUVECs). Small fetuses with placental insufficiency were identified using fetal biometry with Doppler velocimetry. Mean gestational age and birth weight were 31.8±4.1 weeks and 1,260±646 g for FGR-HDP and 39.2±0.8 weeks and 3,320±336 g for normal births, respectively. Abnormal umbilical artery Doppler waveforms were found in 64% of neonates with FGR-HDP. A significant percentage (86%) of FGR newborns were admitted to the neonatal intensive care unit at Gustavo Fricke hospital, Viña del Mar, Chile, with one case of death after birth. [Ca2+]i signals were measured by microfluorimetry in Fluo-3-loaded HUVECs from primary cultures. Altered [Ca2+]i signals were observed in HUVECs from FGR-HDP, where the sustained phase of ATP-induced [Ca2+]i responses was significantly reduced compared with the normotensive group. Also, the [Ca2+]i signals induced with 10 mM Ca2+ after depletion of internal Ca2+ stores were significantly higher. The present study provides a better comprehension of the role of altered cytosolic Ca2+ dynamics in endothelial dysfunction and an in vitro model to assess novel therapeutic approaches for decreasing or preventing complications in FGR-HDP.

Non-Markovian Doppler Velocimetry of Optically Propelled Microparticles in Hollow-Core Photonic Crystal Fiber

Non-Markovian Doppler Velocimetry of Optically Propelled Microparticles in Hollow-Core Photonic Crystal Fiber

Numerical Analysis of Water–Sediment Flow Fields within the Intake Structure of Pumping Station under Different Hydraulic Conditions

The vortices, backflow, and siltation caused by sediment-laden flow are detrimental to the safe and efficient operation of pumping stations. To explore the effects of water–sediment two-phase flow on the velocity field, vorticity field, and sediment distribution within intake structures, field tests and numerical simulations were conducted in this study with consideration for the sediment concentration, flow rate, and start-up combination. We applied a non-contact laser scanner and ultrasonic Doppler velocimetry to obtain the field data and reverse modeling of the three-dimensional model of the intake structure under siltation. A multiphase flow model based on the Euler–Euler approach combined with the k-ε turbulence model was adopted for numerical simulation under 10 working conditions, and the reliability was verified with field data. The results indicate that sediment promotes the evolution of coaxial vortices into larger-scale spiral vortices along the water depth, and the process of sediment deposition is controlled by the range, intensity, and flow velocity of the backflow zone. Furthermore, the maximum volume fraction of the near-bottom sediment increased by 202.01% compared to the initial state. The increase in flow rate exacerbates the turbulence of the flow field. Although the increase in sediment concentration benefits the flow diffusion, it further promotes sediment deposition. This study provides a new idea for modeling complex surfaces and considers different operating conditions. It can serve as a scientific reference for the structural optimization and anti-siltation design of similar water-conservancy projects.

Technology and times scales in Photonic Doppler Velocimetry (PDV)

Photonic Doppler Velocimetry (PDV) is a fiber-based measurement amenable to a wide range of experimental conditions. Interference between two optical signals—one Doppler shifted and the other not—is the essential principle in these measurements. A confluence of commercial technologies, largely driven by the telecommunication industry, makes PDV particularly convenient at near-infrared wavelengths. This discussion considers how measurement time scales of interest relate to the design, operation, and analysis of a PDV measurement, starting from the steady state through nanosecond resolution. Benefits and outstanding challenges of PDV are summarized, with comparisons to related diagnostics.

Effect of turbulent coflows on the dynamics of turbulent twin jets

The impact of turbulent coflows on the dynamics of turbulent twin round jets is investigated experimentally. Parallel twin jets, at three jet spacing values and two Reynolds number/jet-to-coflow velocity ratios, were released into turbulent coflows with two distinct levels of turbulence intensity. Velocity measurements were made using acoustic Doppler velocimetry. An increase in the coflow turbulence intensity leads to an earlier merging and combining of the jets and also accelerates the rate of decay with downstream distance of the mean centerline excess velocity of the jets. The mean velocity on the symmetry line, for different values of jet spacing, ratios of jet exit velocity to coflow mean velocity, and coflow turbulence intensity, is self-similar when scaled by the maximum mean velocity on the symmetry line and the corresponding streamwise distance. Moreover, as the turbulence level of the coflow intensifies, the turbulence intensity along the symmetry line of the jets increases. The longitudinal integral length scale on the symmetry line of the twin jets decreases as the coflow turbulence intensity increases. The energy spectra of the coflowing twin jets show that the turbulence in the coflow transfers the energy contained by the larger scales to the smaller scales at a greater rate than that which occurs for jets in a quiescent background. However, as the jet spacing increases, less energy is transferred to the smaller scales.

A clinical study on Doppler velocimetry of umbilical artery and middle cerebral artery in post-dated pregnancy in the prediction of fetal outcome

A clinical study on Doppler velocimetry of umbilical artery and middle cerebral artery in post-dated pregnancy in the prediction of fetal outcome

Effects of composition on the explosive properties of potassium chlorate and oils

Abstract Potassium chlorate has long been utilized as an excellent oxidizing agent in pyrotechnics and explosives. As mixtures of potassium chlorate and any type of combustible material can be explosive, there is a potential risk of misuse in homemade explosives. Unlike commercial explosives, homemade chlorate and oil mixtures do not have a constant composition, which limits their understanding. This study reports the effects of two types of oil (motor oil and cooking oil) and their ratios (ranging from 2.5% to 40.0% (w/w)) on the explosive properties of such mixtures. The impact sensitivity was highest at a motor oil ratio of 5%. The friction sensitivity increased with an increasing oil ratio, reaching a maximum at an oil ratio of around 22.5%, and was close to those of primary explosives. The motor oil mixtures exhibited higher sensitivity than the cooking oil mixtures at oil ratios of 25% or less. A 10% oil mixture, which was close to the ratio of oxygen balance equal to zero, detonated in weak confinement, such as a paper cylinder. The highest detonation velocities in a polypropylene tube were around 2300 and 2550 m/s at a 10% ratio of motor oil and cooking oil, respectively. The velocities of the metal case wall, measured by photonic Doppler velocimetry, reached about 1100 m/s near the end of acceleration. These results show that homemade chlorate and oil mixtures are capable of detonation and quite sensitive over a wide range of oil ratios, with sufficient power to cause damage in the vicinity.

Role of Cerebroplacental Ratio in Predicting Perinatal Outcome.

Objective Doppler velocimetry provides a sensitive, non-invasive, and safe method of surveillance of fetal hemodynamics and fetomaternal circulation. Cerebroplacental ratio (CPR) is an indicator of placental function and fetal maladaptation to placental insufficiency. Cerebroplacental ratio (CPR) is becoming a significant indicator of unfavorable pregnancy outcomes, which has implications for the assessment of fetal well-being. This study aimedto determine the cut-off value of the cerebroplacental ratio (CPR) in appropriate for gestational age (AGA) fetuses in high-risk mothers to predict adverse perinatal outcomes. We also compared the efficacy of CPR, umbilical artery pulsatility index (UmA PI), and middle cerebral artery pulsatility index (MCA PI) for predicting adverse perinatal outcomes. Design and setting This was a prospective observational study conducted at the Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. Methods A total of 100 women with singleton high-risk pregnancies were included in this prospective observational study. Obstetric ultrasound was performed at the time of recruitment, and fetal weight and CPR were noted. Based on fetal weight, patients were divided into AGA and fetal growth restriction (FGR) groups; CPR was measured; patients were followed up fortnightly; and outcomes were noted. Main outcome The effectiveness of CPR, UmA PI, and MCA PI for predicting poor perinatal outcomes and identifying the cut-off value of CPR in appropriate for gestational age (AGA) fetuses in high-risk mothers was assessed. Result The values of MCA PI, UmA PI, and CPR were statistically significant between AGA and FGR (p-value =.023, .002 and .0001), respectively. The cut-off value for CPR-detecting adverse outcomes in AGA was 1.49. It has sensitivity, specificity, positive predictive value, and negative predictive value of 67.5%, 68%, 71.69%, and 70.21%, respectively. Conclusion Cerebroplacental ratio (CPR) reflects both circulatory insufficiency of the placenta and adaptive changes of the middle cerebral artery, indicating an important non-invasive surveillance modality.

Cardiovascular disease in central bearded dragons (Pogona vitticeps): 54 cases (2007-2022).

To describe the clinical features, histopathologic lesions, and outcome of cardiovascular disease in central bearded dragons. 54 bearded dragons. Retrospective evaluation of captive bearded dragons with antemortem imaging or postmortem diagnosis of cardiovascular disease from 2007 to 2022 from 6 hospitals. The total prevalence of cardiovascular disease was 3.3% (54/1,655). Physical examination findings were available in 46 cases with change in mentation being the most common finding (n = 28/46 [60.9%]), followed by dehydration (17/46 [37%]), palpable coelomic mass (13/46 [28.3%]), dyspnea (10/46 [21.7%]), and sunken eyes (10/46 [21.7%)]. Doppler auscultation revealed an arrhythmia in 5/34 (14.7%) animals. Diagnostic imaging was only performed on 21 animals, and 10 (47.6%) had cardiovascular abnormalities described. In total, 84 cardiovascular diagnoses were found in 54 animals. The most common diagnosis was myocarditis (n = 14) followed by aneurysms (11), pericardial effusion (9), atherosclerosis (7), epicarditis (7), and myocardial degeneration/necrosis (7). Overall, 62 causes of death were identified in 52 cases, with cardiovascular disease being the most common (n = 18/52 [34.5%]). Only 3/54 animals were diagnosed with congestive heart failure. Animals with aneurysms were more likely to die to due cardiovascular disease compared to other types of cardiovascular diagnoses (OR, 43.75; 95% CI, 4.88 to 392.65; P < .001). Diagnosis of cardiovascular disease in bearded dragons is challenging given the inconsistent clinical presentation; however, it should remain a differential in animals with nonspecific signs of illness. Antemortem diagnostics are recommended in suspected cases, including diagnostic imaging. Of the cardiovascular diseases described, aneurysms most often contributed to clinical demise.

Frequency-shifted photonic Doppler velocimetry (PDV) for measuring deceleration of projectiles in soils

Frequency-shifted photonic Doppler velocimetry (PDV) for measuring deceleration of projectiles in soils

Characterization of ejecta in shock experiments with multiple light scattering

Upon impact, the free surface of a solid metal may eject a cloud of fast and fine particles. Photon Doppler Velocimetry (PDV) is one of the optical diagnostics used to characterize these ejecta. Although the technique provides a direct way to estimate the particle velocities in the single scattering regime, it has been shown that multiple scattering cannot be neglected in real ejecta. Here, we derive a model for PDV measurements starting from the first principles of wave scattering. We establish rigorously the relationship between the specific intensity and the measured signal, as well as the Radiative Transport Equation (RTE) that describes the evolution of the specific intensity upon scattering and absorption in dynamic ejecta, including the effects of inelastic scattering and inhomogeneities in the optical properties. We also establish rigorously the connection between the Monte Carlo scheme used for numerical simulations and the solution to the RTE. Using numerical simulations, we demonstrate the crucial contribution of multiple scattering to PDV spectrograms as well as the effect of statistical inhomogeneities in particle size distribution. These results could substantially impact the analysis of ejecta by PDV.

Upconversion Photonic Doppler Velocimetry Based on Stimulated Brillouin Scattering

Optical up-conversion photonic Doppler velocimetry (PDV) based on stimulated Brillouin Scattering (SBS) with an all-fiber link structure is proposed in this article. Because SBS limits the laser power transmitted by a fiber over long distances, the probe does not have enough outgoing light to reach the measured surface and cannot receive the signal light. Traditionally, SBS is avoided, but it is a phase-conjugated light and shifts down relative to the source light, so it can be used as a reference light in the laser interference structure to achieve up-conversion heterodyne velocimetry. Compared with general homodyne velocimetry (DPS), SBS-PDV naturally upconverts and has more interference fringes and higher resolution at low-speed measurement. In the gas multiple reflection impact compression experiment, the velocity measurement results of SBS-PDV and dual-laser heterodyne Velocimetry (DLHV) are basically consistent, and the accuracy is better than 0.8%. Due to its coaxial heterodyne optical path, this kind of photonic Doppler velocimetry is suitable for low-velocity and long-distance practical applications in the field of shock wave physics.

Ovarian artery Doppler velocimetry effects after myoinositol and lipoic acid therapy in PCOs patients

Background: Polycistic ovary syndrome (PCOs) is one of the most common endocrine and metabolic disorders in premenopausal women. This is the second part of an extended report regarding the significant effects of the therapy based on an Alfa Lipoic Acid (ALA)/Myoinositol (Myo) combined drug on adnexal parameters, as assessed by ultrasound technique. Methods: A prospective cohort trial. Data regarded thirty four italian nulliparous women considered for the study, control cases were chosen from an initial group of sixty-nine healthy women group paired by age and nulliparous status. Patients underwent a Myoinositol plus ALA regimen twice a day in a continued fashion in a twenty four months period. Ultrasound examinations were coincident with the fifth day of menstrual period and were set as follows: Time 0 (first evaluation), Time 12 (after twelve months) and finally Time 24 (after 24 months). Results: The mean age was 31.4 years old. Results regarding any significant change in the endometrial width, number of follicles, and the ovarian volumes within the time of the trial, showed no significant changes in the intervals considered. Conversely, the parameters dealing with color Doppler velocimetry waves of the ovarian arteries showed a significant decreasing trend, considering the first values and after 12 and 24 months. Conclusions: Considering a consistent and significant decrease in ovarian arteries resistance, we may hypothesize that Inositol plus ALA therapy may block the vascular effects of hyperadrogenism, maybe playing a role in the anti oxidant and anti inflammatory pathways

Using double pulse laser ablation in air to enhance the strength of laser-driven shocks

In the process of multi-pulse laser ablation, inter-pulse delay time, Δt, is known to be an important parameter for maximizing ablation efficiency as well as impulse imparted to the target. In this work, using photon Doppler velocimetry, we show that for single pairs of colinear pulses (1064 nm, 8 ns, ∼ 60 J cm-2 per pulse) in air, the peak free surface velocity of the back surface of an aluminum target (125 µm thick) is increased, by a factor of nearly 3, when Δt = 10 microseconds, compared with both pulses arriving simultaneously (Δt = 0). Fast imaging of the ablation process suggests this enhancement is due to rarefaction of the contiguous air in the passage of the leading shock produced by ablation, which then in turn allows a larger fraction of the energy of the second pulse to reach the target surface. This interpretation is strengthened by additional experiments in which the two pulses do not overlap on the target surface, but the shock strength is nevertheless enhanced. Given a fixed energy budget this work suggests a prescription for maximizing laser-driven shock strength by judicious choice of inter-pulse delay.

Numerical modeling of interaction of turbulent flow with trash screen in open channels

Trash screens are widely employed at the entrance of hydraulic structures, water intakes, and pumping stations to trap flowing debris that could exasperate downstream troubles. The characteristics of the vertical trash screen flow are measured using a Three-Dimensional Acoustic Doppler Velocimetry instrument for different flow conditions. The governing equations of the flow are numerically solved using k–ω SST, k–ϵ STD, k–ϵ RNG, and Reynolds Stress Model (RSM) and Large Eddy Simulations (LES). ANSYS-Fluent is used for these numerical simulations. The free surface of the vertical trash screen flow is computed by the volume of fluid method. The Grid Convergence Index is used to analyze the impact of the chosen grid structure on the numerical results. Experimental measurements of the velocity field and free surface profiles are compared with the numerical results of 3D simulations for validation. This study aims to identify the behavior of flow through screens in more detail through experimental and numerical simulations. The computed flow profiles considering all five cases agree well with the measured profile, whereas streamwise velocity in most portions of the flow, the k-ω SST outperforms the other models, and the RSM turbulence model is the second most effective.

Vortex motion in vaneless space and runner passage of pump-turbine in S-shaped region

This study examines the S-characteristic, a key factor affecting the safe grid connection and operation of pumped-storage units, and its significant impact on the safety of pumped-storage power stations. We conducted numerical simulations and model experiments to investigate vortex motion characteristics in the vaneless space and runner passage of pump-turbines operating within the S-shaped region, along with an analysis of pressure pulsation characteristics. The accuracy of these simulations was validated through laser Doppler velocimetry experiments, and particle image velocimetry experiments were used to capture vortex motion in the vaneless space. We observed that vortices generated on the guide vane side follow the flow direction, blocking the guide vane passage, while those generated by runner blades move in the opposite direction. Employing an entropy production theory and the Liutex method, we investigated vortex distribution and hydraulic loss in the S-shaped region. The results show that reduced flow rates lead to significant vortices in the vaneless space and guide vane area, which become main contributors to energy loss in this region. These vortices, along with those in the runner passage, mainly arise from flow separation on blade and guide vane surfaces due to suboptimal inflow conditions. The study also identifies pressure fluctuations in the vaneless space, induced by a rotating stall, as the most significant pressure pulsation phenomenon, which significantly impacts the performance of the unit in both upstream and downstream directions.

Flow investigation of two-stand ultrasonic flow meters in a wide dynamic range by numerical and experimental methods

The enhancement of two-stand ultrasonic flow meters relies upon obtaining a precise understanding and prediction of their complex flow physics throughout their entire dynamic range of operation. This study provides a comprehensive numerical and experimental investigation of the flow physics of a typical two-stand ultrasonic flow meter by industry standards. Predictions based on computational fluid dynamics simulations are employed to obtain numerical results, which are validated through experiments based on laser Doppler velocimetry and static pressure drop. Results indicate that no qualitative changes occur beyond an inflow Reynolds number of 104 in terms of coherent structures and flow dynamics. Analysis of the static pressure distribution across cross-sections reveals that the stands are the most influential areas contributing to pressure drop. In cases with turbulent inflow, there is a noticeable recovery of static pressure following significant pressure gradients across the stands, while such recovery is absent in scenarios with laminar inflow. Both numerical and experimental approaches yield excellent agreement in outcomes, accurately estimating the axial velocity within the flow meter’s measurement volume and the pressure drop across it, with deviations within experimental uncertainty ranges of 2 standard deviations. The developed numerical methodology demonstrates its potential to accurately evaluate complex internal-flow systems with similar flow features and Reynolds number ranges. The flow dynamics for a wide dynamic range of operation in two-stand ultrasonic flow meters are shown in detail in both laminar and turbulent flow regimes, displaying rolling vortices, detached flow, and recirculation zones.

Characteristics of Step-Shaped Laser-Driven Flyers on Fiber End Face Based on a Ti/Al Ablation Layer.

Laser-driven flyers (LDF), which can launch the flyer on the interaction of a laser pulse with a thin film of metal, have been widely used in many fields, such as ignition, space scrap metal science, and dynamic high-pressure physics. However, at present, further development of LDF is being hindered by the high reflectivity of the ablation layer and low energy utilization efficiency of LDF on the fiber end face. Herein, improved LDFs were designed and fabricated by mask plate and magnetron sputtering. Improved LDF incorporates a Ti/Al composite film as the ablation layer, while the flyer layer features a smaller diameter round platform design. Reflectivity of samples under static and dynamic conditions and driving characteristics of samples were tested using an optical isolator and photonic doppler velocimetry system. The velocity of the improved LDFs reaches 1.7 km/s with a peak acceleration of 8.7 × 1010 m/s2. LDF with a Ti/Al composite film as the ablation layer demonstrates a static absorption rate of 59%, which gradually increases to 65% under laser irradiation. This absorption rate is notably higher compared with the static absorption rate (20%) and the peak absorption rate under laser irradiation (40%) of an Al layer. Consequently, there is a substantial improvement of about 35% in the flyer velocity. In contrast to the plane-shaped LDF, the velocity profile of the flyer and impact crater morphology suggest that the step-shaped LDF offers a 15% improvement in velocity and a 50% increase in acceleration, with better flyer integrity observed.

Flume Experiments for Flow around Debris Accumulation at a Bridge

We conducted flume experiments to study the flow behavior around a debris accumulation at a two-pier bridge. An Acoustic Doppler Velocimetry was utilized to measure velocity in cases with and without debris. We examined the impact of this accumulation on the velocity field and bed shear stress to better understand the flow and sediment transport mechanisms near the debris buildup at the bridge. Debris clusters were found to cause strong downward flows behind the bridge piers and to create turbulent shear layers emanating from the debris base. These flow patterns caused an increase in bed shear stress behind the piers by up to 40%. Downstream of the bridge, the debris-induced bed shear stress increase persisted for a distance equivalent to four times the spacing between the piers.

651 Lung size and doppler velocimetry after serial amnioinfusions in fetuses with renal agenesis/dysplastic kidneys

651 Lung size and doppler velocimetry after serial amnioinfusions in fetuses with renal agenesis/dysplastic kidneys