Doppler Velocity Research Articles

Parametric Survey of Nonaxisymmetric Accretion Disk Instabilities: Magnetorotational Instability to Super-Alfvénic Rotational Instability

Accretion disks are highly unstable to magnetic instabilities driven by shear flow, where classically, the axisymmetric, weak-field magnetorotational instability (MRI) has received much attention through local WKB approximations. In contrast, discrete nonaxisymmetric counterparts require a more involved analysis through a full global approach to deal with the influence of the nearby magnetohydrodynamic (MHD) continua. Recently, rigorous MHD spectroscopy identified a new type of ultralocalized, nonaxisymmetric instability in global disks with super-Alfvénic flow. These super-Alfvénic rotational instabilities (SARIs) fill vast unstable regions in the complex eigenfrequency plane with (near eigen)modes that corotate at the local Doppler velocity and are radially localized between Alfvénic resonances. Unlike discrete modes, they are utterly insensitive to the radial disk boundaries. In this work, we independently confirm the existence of these unprecedented modes using our novel spectral MHD code Legolas, reproducing and extending our earlier study with detailed eigenspectra and eigenfunctions. We calculate the growth rates of SARIs and MRI in a variety of disk equilibria, highlighting the impact of field strength and orientation, and find correspondence with analytical predictions for thin, weakly magnetized disks. We show that nonaxisymmetric modes can significantly extend instability regimes at high mode numbers, with maximal growth rates comparable to those of the MRI. Furthermore, we explicitly show a region filled with quasi-modes whose eigenfunctions are extremely localized in all directions. These modes must be ubiquitous in accretion disks, and play a role in local shearing box simulations. Finally, we revisit recent dispersion relations in the appendix, highlighting their relation to our global framework.

Source Region of the Solar Wind: Statistics of the Doppler Velocities at the Chromosphere

The solar wind has been extensively studied recently with in situ observations, and the understanding of its counterpart near the solar surface has also progressed significantly. With the spectroscopic observations from the Chinese Hα Solar Explorer (CHASE), the chromospheric Dopplergram of the full solar disk is first obtained almost simultaneously. By investigating the statistics of the Doppler velocities at the chromosphere, we find that the coronal hole (CH) regions are dominated by Doppler blueshifts, with a stronger net magnetic flux region corresponding to smaller blueshift velocity. In addition to the average blueshift, the probability density of the Doppler shift is not symmetrically distributed but shows an excess at the redshift side, while the reference region does not show such an asymmetry. The redshift asymmetry may provide a possible clue for the interchange reconnection that might happen just above the chromosphere. By sampling the regions at the network boundaries in the CHs, the probability density is slightly enhanced at the parts of both larger blueshifts and redshifts compared with the result for the whole CH region. As the reference region also shows such enhancement, the crucial area associated with the origin of solar wind is not identified efficiently by sampling the overall network boundaries as demonstrated here. The present study shows the first attempt at interpreting the origin of solar wind in the transient CHs based on the CHASE spectroscopic observations, and a combination of full-disk and high-resolution observations is helpful in the future for firmly understanding the source region of solar wind.

Global Coronal Plasma Diagnostics Based on Multislit Extreme-ultraviolet Spectroscopy

Full-disk spectroscopic observations of the solar corona are highly desired to forecast solar eruptions and their impact on planets and to uncover the origin of solar wind. In this paper, we introduce a new multislit design (five slits) to obtain extreme-ultraviolet (EUV) spectra simultaneously. The selected spectrometer wavelength range (184–197 Å) contains several bright EUV lines that can be used for spectral diagnostics. The multislit approach offers an unprecedented way to efficiently obtain the global spectral data but the ambiguity from different slits should be resolved. Using a numerical simulation of the global corona, we primarily concentrate on the optimization of the disambiguation process, with the objective of extracting decomposed spectral information of six primary lines. This subsequently facilitates a comprehensive series of plasma diagnostics, including density (Fe xii 195.12/186.89 Å), Doppler velocity (Fe xii 193.51 Å), line width (Fe xii 193.51 Å), and temperature diagnostics (Fe viii 185.21 Å, Fe x 184.54 Å, Fe xi 188.22 Å, and Fe xii 193.51 Å). We find a good agreement between the forward modeling parameters and the inverted results at the initial eruption stage of a coronal mass ejection, indicating the robustness of the decomposition method and its immense potential for global monitoring of the solar corona.

ROTracker: a novel MMW radar-based object tracking method for unmanned surface vehicle in offshore environments

Unmanned surface vehicles (USVs) offer significant value through their capability to undertake hazardous and time-consuming missions across water surfaces. Recently, as the application of USVs has been extended to nearshore waterways, object tracking is vital to the safe navigation of USVs in offshore scenes. However, existing tracking systems for USVs are mainly based on cameras or LiDAR sensors, which suffer from drawbacks such as lack of depth perception or high deployment costs. In contrast, millimeter-wave (MMW) radar offers advantages in terms of low cost and robustness in all weather and lighting conditions. In this work, to construct a robust and low-cost tracking system for USVs in complex offshore scenes, we propose a novel MMW radar-based object tracking method (ROTracker). The proposed ROTracker combines the physical properties of MMW radar with traditional tracking systems. Specifically, we introduce the radar Doppler velocity and a designed motion discriminator to improve the robustness of the tracking system toward low-speed targets. Moreover, we conducted real-world experiments to validate the efficacy of the proposed ROTracker. Compared to other baseline methods, ROTracker achieves excellent multiple object tracking accuracy in terms of 91.9% in our collected dataset. The experimental results demonstrated that the proposed ROTracker has significant application potential in both accuracy and efficiency for USVs, addressing the challenges posed by complex nearshore environments.

Chaff Cloud Integrated Communication and TT&C: An Integrated Solution for Single-Station Emergency Communications and TT&C in a Denied Environment

In response to potential denial environments such as canyons, gullies, islands, and cities where users are located, traditional Telemetry, Tracking, and Command (TT&C) systems can still maintain core requirements such as availability, reliability, and sustainability in the face of complex electromagnetic environments and non-line-of-sight environments that may cause service degradation or even failure. This paper presents a single-station emergency solution that integrates communication and TT&C (IC&T) functions based on radar chaff cloud technology. Firstly, a suitable selection of frequency bands and modulation methods is provided for the emergency IC&T system to ensure compatibility with existing communication and TT&C systems while catering to the future needs of IC&T. Subsequently, theoretical analyses are conducted on the communication link transmission loss, data transmission, code tracking accuracy, and anti-multipath model of the emergency IC&T system based on the chosen frequency band and modulation mode. This paper proposes a dual-way asynchronous precision ranging and time synchronization (DWAPR&TS) system employing dual one-way ranging (DOWR) measurement, a dual-way asynchronous incoherent Doppler velocity measurement (DWAIDVM) system, and a single baseline angle measurement system. Next, we analyze the physical characteristics of the radar chaff and establish a dynamic model of spherical chaff cloud clusters based on free diffusion. Additionally, we provide the optimal strategy for deploying chaff cloud. Finally, the emergency IC&T application based on the radar chaff cloud relay is simulated, and the results show that for severe interference, taking drones as an example, under a measurement baseline of 100 km, the emergency IC&T solution proposed in this paper can achieve an accuracy range of approximately 100 m, a velocity accuracy of 0.1 m/s, and an angle accuracy of 0.1°. In comparison with existing TT&C system solutions, the proposed system possesses unique and potential advantages that the others do not have. It can serve as an emergency IC&T reference solution in denial environments, offering significant value for both civilian and military applications.

UNRAVELING GENDER DISPARITIES AND PROGNOSTIC INSIGHTS IN MODERATE AORTIC STENOSIS: A RETROSPECTIVE STUDY

Abstract Aortic stenosis (AS) is the most prevalent valvular heart disease in developed countries, associated with reduced survival if severe AS remains untreated. Recent reports note unfavorable outcomes in moderate AS (mAS) patients, challenging optimal intervention timing. Variations in pathophysiology linked to sex differences, involving sex hormones, activation of the renin–angiotensin–aldosterone system, and dysregulation in collagen synthesis, have been observed. Yet, limited data exists on sex–specific differences in mAS outcomes. This single–center, retrospective study included 150 patients (median age 79±13 years, female sex 48%) diagnosed with mAS who underwent comprehensive echocardiography in IRCCS Fondazione Ca’ Granda Ospedale Maggiore Policlinico of Milan from July 2022 to October 2023. Clinical data, encompassing demographics details and therapy, were obtained via record reviews and phone interviews. Death verification relied on the ‘Sistema Informativo Socio–Sanitario Regione Lombardia’ database. Echocardiographic records were digitally stored and post–processed by four independent investigators using Medimatic ComPACS workstation. Men were significantly younger than women (75±10 vs 79±9.7 years, p= 0.016). They exhibited lower left ventricular (LV) ejection fraction, larger LV end–systolic volume and stroke volume compared to women (54±7 vs 59±10%; p=0.028. 55±36 vs 31±13 ml; p<0.001. 83±18 vs 75±18 ml; p=0.030). Men had significantly smaller aortic valve (AV) area index to body surface area (BSA) (0.6±0.09 vs 0.7±0.1 cmq/mq; p<0.001) and lower doppler velocity index (0.32±0.07 vs 0.38±0.11; p<0.001) than women. Coronary artery disease and smoking were more frequent in men (53.3 vs 46.7%; p=0,002. 52.6 vs 47.4%; p<0.001). In survival analysis, 15% of women and 30.8% of men experienced events, with male gender independently associated with the composite outcome (all–cause mortality and AV replacement) over a mean follow–up time of 200 ± 133 days, showing a median survival of 244±16 vs 255±15 days for females (p–value=0.025). In multivariable analysis including relevant clinical variables (hemoglobin and AV index to BSA), male sex remained independently associated with the composite outcome (hazard ratio 2,01; CI 1.0–4.17; p=0.05). Women diagnosed with mAS exhibited a lower incidence of AV replacement and all–cause mortality. These findings may suggest the existence of different clinical and echocardiographic phenotypes among patients with AS.

Mitigation method of acoustic doppler velocity measurement bias

A Doppler velocity log (DVL) is used to estimate ship’s velocity by processing seafloor echo. The velocity measurement bias (i.e., long term accuracy) is often regarded as an important technical specification to quantify the accuracy of DVL. The bias describes the accuracy of the instrument after averaging over a sufficiently long time, such that the velocity variance approaches zero. The goal of this paper is to obtain an effective method to mitigate the bias in velocity measurement based on analyzing the DVL seafloor echo characteristics. First, a DVL bottom echo model is constructed based on highlight model, which can focus on the statistical characteristics of the echo waveform information. Then the algorithm for retrieving the echo highlight information is presented. The parameters of the highlight model based on experimental data of DVL echo are analyzed. The intrinsic connection between the highlight model and the point-based scattering model is discussed. Finally, the method of velocity measurement to mitigate the bias according to the relationship between the statistical characteristics of the highlights and bias is put forward. Simulation results show that the proposed method significantly mitigates the bias.

Dynamic changes of hepatic vein Doppler velocities predict preload responsiveness in mechanically ventilated critically ill patients

BackgroundAssessment of dynamic parameters to guide fluid administration is one of the mainstays of current resuscitation strategies. Each test has its own limitations, but passive leg raising (PLR) has emerged as one of the most versatile preload responsiveness tests. However, it requires real-time cardiac output (CO) measurement either through advanced monitoring devices, which are not routinely available, or echocardiography, which is not always feasible. Analysis of the hepatic vein Doppler waveform change, a simpler ultrasound-based assessment, during a dynamic test such as PLR could be useful in predicting preload responsiveness. The objective of this study was to assess the diagnostic accuracy of hepatic vein Doppler S and D-wave velocities during PLR as a predictor of preload responsiveness.MethodsProspective observational study conducted in two medical–surgical ICUs in Chile. Patients in circulatory failure and connected to controlled mechanical ventilation were included from August to December 2023. A baseline ultrasound assessment of cardiac function was performed. Then, simultaneously, ultrasound measurements of hepatic vein Doppler S and D waves and cardiac output by continuous pulse contour analysis device were performed during a PLR maneuver.ResultsThirty-seven patients were analyzed. 63% of the patients were preload responsive defined by a 10% increase in CO after passive leg raising. A 20% increase in the maximum S wave velocity after PLR showed the best diagnostic accuracy with a sensitivity of 69.6% (49.1–84.4) and specificity of 92.8 (68.5–99.6) to detect preload responsiveness, with an area under curve of receiving operator characteristic (AUC–ROC) of 0.82 ± 0.07 (p = 0.001 vs. AUC–ROC of 0.5). D-wave velocities showed worse diagnostic accuracy.ConclusionsHepatic vein Doppler assessment emerges as a novel complementary technique with adequate predictive capacity to identify preload responsiveness in patients in mechanical ventilation and circulatory failure. This technique could become valuable in scenarios of basic hemodynamic monitoring and when echocardiography is not feasible. Future studies should confirm these results.

Echocardiography to predict left ventricular filling pressure for long-term paediatric heart transplant patients.

Left ventricular diastolic dysfunction is a recognised sequela following transplantation in paediatric heart transplant patients. Traditional echocardiographic indices do not correlate well with left ventricular filling pressure immediately after transplantation. This study aimed to assess whether these indices have any long-term correlation after transplantation in paediatric patients. A retrospective chart review of 41 patients who had a heart transplant before the age of 24 years was performed. The median time since the transplantation was 11 years. Data obtained from surveillance cardiac catheterisation and echocardiographic examination were reviewed. Traditional echocardiographic indices of diastolic function were compared with the pulmonary capillary wedge pressure and left ventricular end-diastolic pressure obtained from cardiac catheterisation. The median age at transplant was 12.1 years, and the median time since transplant was 11 years. Eighteen patients (43%) had a history of at least one rejection episode and 12 patients (29%) had a history of cardiac allograft vasculopathy. There was no correlation between mitral inflow E velocity, mitral E/A ratio, tissue Doppler velocities, mitral E/e' (mitral inflow E velocity to mitral annular velocity), and elevated pulmonary capillary wedge pressure or elevated left ventricular end-diastolic pressure. There was no correlation between mitral valve deceleration time or isovolumetric relaxation time with elevated pulmonary capillary wedge pressure or elevated left ventricular end-diastolic pressure. Our findings suggest that traditional echocardiographic indices of diastolic function do not correlate well with elevated invasive pulmonary capillary wedge pressure or elevated left ventricular end-diastolic pressure in paediatric heart transplant patients' long-term post-transplantation.

Dynamical and Microphysical Aspects of Two Distinct Precipitation Systems in the Himalayas With 206.5 MHz Radar and WRF Model

AbstractThe dynamical and microphysical aspects of two different precipitating systems have been investigated using the ARIES Stratosphere‐Troposphere Radar (ASTRad) facility and further substantiated by Weather Research Forecasting (WRF) model over Manora Peak. The first event (Case‐I) is associated with the southwest Indian summer monsoon that occurred on 4 August 2020, with a vertical extension of 10–12 km and leads to liquid phase precipitation. The second event (Case‐II) linked to the winter western disturbance occurred on 5 February 2021. This precipitating system was developed with a vertical extension of 6–7 km, resulting in both liquid and solid phase precipitation. Such distinct vertical extension of the systems is found to be associated with the thermodynamical conditions and prevailed large‐scale circulations. By analyzing the vertical structure of these systems using three Doppler moments estimated from the ASTRad (equivalent Reflectivity dBZe, Doppler velocity, and Spectral width), maximum dBZe (∼60 dB) is observed in Case‐II, while higher spectral width (>2 m s−1) is associated to Case‐I. The microphysical processes assessed by the WRF model pointed out that Case‐I involved snow accretion on supercooled droplets, leading to graupel and raindrop formation, while in Case–II, solid and liquid precipitation resulted from ice processes, including accretion or autoconversion. These findings highlight the significance of integrating radar and modeling data to understand the dynamical and microphysical evolution of precipitation under the influence of orography in the Himalayan region.

Sex Dependent Exacerbation of Salt Sensitive Hypertension and Cardiac Dysfunction Is Associated With Upregulation of miRNA Targeting ADAM17 and ACE2 in the Brain

Background: The DOCA-salt model has been widely used to study salt-sensitive hypertension and we previously reported that it is associated with ADAM17-mediated ACE2 shedding in the central nervous system. However, previously reported data are mainly from male mice, and it is unclear whether female mice exhibit the same phenotypes. Objective: We aimed to compare sex specific development of salt sensitive hypertension and cardiac dysfunction and investigate miRNA regulation associated with these changes. Methods: C57 mice (male and females, n = 8 -15) underwent uninephrectomy and telemetry implantation (DSI Inc.) for blood pressure (BP) conscious recording. After baseline recording, a DOCA pellet (50 mg, 21 days, Innovative Research of America) was implanted subcutaneously and drinking water was replaced by 1% NaCl solution to induce salt sensitive hypertension. Cerebral Spinal fluid (CSF) was collected at baseline and after 3 weeks of DOCA-salt treatment for exosome miRNA sequencing (Creative Biolab). In another set of mice, cardiac function was assessed by echocardiography (Visualsonics Vevo F2) and invasive left ventricular hemodynamics (Transonic). Mortality from each group was analyzed as well. Results: Baseline BP was not different between male and female mice. Following DOCA-salt treatment for 3 weeks, BP was increased in both sexes, with higher systolic BP observed in males compared to females (active phase: 173.0 ± 19.6 vs. 154.2 ± 19.1 mmHg, p<0.05). Although ejection fraction was not changed in either male or female mice, mitral peak early diastolic filling velocity and tissue doppler showed that E/E’ was increased in both sexes compared to baselines (Male: 33.4 ± 4 vs. 26.6 ± 1.9; Female: 30.3 ± 5.0 vs. 26.4 ± 4), with a greater increase in males (25.3% vs. 14.4%). In addition, hemodynamics revealed increased left ventricular end-diastolic pressure (11.1 ± 1.9 vs. 4.5 ± 0.5 mmHg, p<0.01) and relaxation time constant Tau (6.7 ± 1.0 vs. 4.9 ± 0.5 msec, p<0.01) in DOCA-salt treated males compared to non-treated controls, with no changes shown in female mice. These data suggest worsened cardiac diastolic function in males compared to females following DOCA-salt treatment. Moreover, a 20% mortality was observed in males while no death occured in females, confirming a more severe phenotype in males. Furthermore, miRNAseq analysis of CSF exosomes showed several upregulated miRNA in males but not in females following DOCA-salt treatment. Notably, miR206 associated with increased ADAM17 activity was increased by 8-fold in males but only 3-fold n females. Conclusion: DOCA-salt treatment promotes exacerbated hypertension, impaired cardiac function and mortality in a sex dependent manner, associated with upregulation of key miRNA targeting the brain renin-angiotensin system. The changes of ADAM17 and ACE2 targeted exosome miRNAs in the central nervous system might contribute to the sex difference in the cardiovascular dysfunction phenotypes in this model. This work was supported in part by a research grant from the National Institutes of Health (HL163588). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Statistical Investigation of Wave Propagation in the Quiet-Sun Using IRIS Spectroscopic Observations

In this analysis, we use spectroscopic observations of the quiet Sun made by the IRIS instrument and investigate wave propagation. We analyze various spectral lines formed in different atmospheric layers, such as the photosphere, chromosphere, and transition region. We examine the Doppler velocity time series at various locations in the quiet Sun to determine the dominant oscillation periods. Our results executing statistical analysis resemble those of the classical physical scenario, indicating that the photosphere is mainly characterized by the dominant 5 minute period, while the chromosphere is primarily associated with the 3 minute oscillation period. In the transition region, we observe a variety of oscillation periods, with dominant periods of 3, 8, and 12 minutes. We estimate the cutoff frequency by deducing the phase difference between two Doppler velocity time series obtained from spectral line pairs in different atmospheric layers formed at different temperatures. This reveals a significant correlation between 3 minute periods in the transition region and photospheric oscillations, suggesting that these oscillations in the transition region might propagate from the photosphere. Additionally, we analyze the phase difference between chromospheric oscillations and photospheric oscillations, demonstrating that only the 3 minute oscillations propagate upward. Based on the statistical analyses, we suggest the presence of magnetoacoustic waves in the solar atmosphere, some of which are propagating from the lower solar atmosphere upward, while some others are propagating downward. The transition region carries both long-period oscillations generated in situ and some photospheric oscillations that are also able to reach there from below.

Doppler-derived pulmonary pulse transit time measurements in chronic obstructive pulmonary disease: Reproducibility and cardiopulmonary function.

Doppler-derived pulmonary pulse transit time (pPTT) is an auspicious hemodynamic marker in chronic pulmonary diseases. The aim is to compare four distinct pPTT measurements and its relation to right cardiac and pulmonary function. Prospectively, 25 chronic obstructive pulmonary disease (COPD) patients (four patients excluded) and 32 healthy subjects underwent repeated distinct pPTT measurements, standard echocardiography, and pulmonary function testing on the same day. pPTT was defined as the interval from the R or Q-wave in the electrocardiogram to the corresponding pulse wave Doppler peak late systolic (S) 2 or diastolic (D) pulmonary vein flow velocity (pPTT R-S, Q-S, R-D, Q-D). Reproducibility was assessed using Bland-Altman analysis, coefficient of variation (COV), intraclass correlation coefficient (ICC), and power calculations. Associations with right ventricular RV tissue and pulse wave Doppler velocities (RV E', RV S', RV A', RV E, RV A, RV E/E', RV E/A), TAPSE, right ventricular fractional area change, left ventricular systolic and diastolic function (LV ejection fraction, E, A, E/A, E/E', septal E', lateral E'), LA diameters, as well as forced expiratory volume in 1 s, forced vital capacity (FVC) predicted (%), and in liters were analyzed. There was no significant difference and no bias between pPTT measures (p range:.1-.9). COV was in COPD 1.2%-2.3%, in healthy subjects 1.0%-3.1%. ICC ranged from.92 (COPD) to.96 (healthy subjects). In COPD significant correlations were found for pPTT R-S, Q-S and R-D with RV E`, (all>ρ:.49,<p=.0364), pPTT R-S, Q-S with RV E/E` (both>ρ:.49,<p=.0291), pPTT Q-S with RV S´ (ρ:.58, p=.0134), RV A (ρ:.59, p=.0339) and heart rate>ρ: -.39,<p=.0297). pPTT R-S, R-D showed significant correlations with FVC predicted (%) (ρ:.48 p=.0224) and FVC (l) (ρ:.47 p=.0347). All pPTT measures exhibited high reproducibility. In COPD patients pPTT measures correlate with diastolic right ventricular function. Defining Q as starting point seems clinically advantageous considering electromechanical desynchrony in patients with conduction disorders.

Assessment of Polar Ionospheric Observations by VIPIR/Dynasonde at Jang Bogo Station, Antarctica: 2. Ionospheric Ion Drift Velocity

AbstractSince the installation at the Antarctic Jang Bogo Station (JBS) in 2017, Korea Polar Research Institute (KOPRI) has been operating the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) equipped with Dynasonde analysis (JVD). The two‐dimensional ion velocity is one of the key ionospheric parameters obtained from the JVD. The ionospheric ion velocities are compared with simultaneous, but independent, measurements of the Doppler velocity obtained from SuperDARN East radar at Dome C. The JVD ion velocity vector is projected to the line‐of‐sight direction of the SuperDARN observation over the JBS to be directly compared with each other. The result of comparison shows a reasonable agreement with the correlation coefficient of 0.72. The linear regression coefficient of about 0.5 represents that the JVD ion velocity is generally smaller than the SuperDARN observations by the regression coefficient, which may result from the different height ranges of the measurements. It is also found that the correlation coefficient increases with increasing magnetic activity (Kp), which suggests that the small‐scale ionospheric density irregularities tend to move with large‐scale plasma motion that is driven by enhanced plasma convection with increasing Kp.

Sparus Docking Station: A current aware docking station system for a non‐holonomic AUV

AbstractThis paper presents the design and development of a funnel‐shaped Sparus Docking Station intended for the non‐holonomic torpedo‐shaped Sparus II Autonomous Underwater Vehicle. The Sparus Docking Station is equipped with sensors and batteries, allowing for a stand‐alone long‐term deployment of the vehicle. An inverted Ultra Short Base‐Line system is used to locate the Docking Station as well as to provide long‐term drift‐less vehicle navigation. The Sparus Docking Station is able to observe the ocean currents using a Doppler Velocity Log, being motorized to allow its self‐alignment with the current. Moreover, a docking algorithm accounting for the current is used to guide the robot during the docking maneuver. The paper reports consecutive successful experimental results of the docking maneuver in sea trials in two different countries.

Sonographic Evaluation of Doppler Parameters Within the Central Retinal Artery: A Cohort Study

Objective: The objective of this study was to assess the Doppler parameters, associated within the central retinal artery (CRA), based on a cohort of Nigerian participants. Materials and Methods: A total of 66 participants were recruited and consented at a medical clinic in Calabar, Nigeria, and presented from August 2019 to December 2023. The diagnostic data points recorded on this cohort were their fasting blood glucose (FBG) (mmol/L), CRA peak systolic velocity (PSV), CRA end-diastolic velocity (EDV), the resistive index (RI), and pulsatility index (PI). The data analysis was completed to provide descriptive information, as well as correlations. The statistical significance was set at P &lt; .05. Results: In this cohort, the women demonstrated a higher PSV and EDV, based on the vascular flow within the right CRA (Rt. PSV [20.8 ± 6.0 SD] and Rt. EDV [5.8 ±2.1 SD]), as well as the left CRA (Lt. PSV [20. 6 ± 4.4 SD] and Lt. EDV [6.2 ± 2.0 SD]). This was compared to the men’s data taken on the vascular flow within the right CRA (Rt. PSV [19.6 ± 5.3 SD] and Rt. EDV [5.2 ± 1.8 SD]), as well as their left CRA (Lt. PSV [19.2± 4.7 SD] and Lt. EDV [5.3 ± 1.3 SD]). The participants’ FBG levels did not correlate with their respective Doppler parameters. The Doppler parameters, based on the flow within the right CRA, showed moderate to weak positive correlations compared with the left CRA. The PSV recorded in the right CRA was varied across the specific participant age groups of 17 to 25 and 26 to 34 years. Conclusion: Potential sex and age-related variations in the Doppler velocities, recorded within the CRA, were specific to this cohort, and the sample size may have compromised the overall study’s statistical power. A replication of this research is needed, and data from a larger cohort of participants are needed.

Autonomous underwater vehicle link alignment control in unknown environments using reinforcement learning

AbstractHigh‐speed underwater wireless optical communication holds immense promise in ocean monitoring and surveys, providing crucial support for the real‐time sharing of observational data collected by autonomous underwater vehicles (AUVs). However, due to inaccurate target information and external interference in unknown environments, link alignment is challenging and needs to be addressed. In response to these challenges, we propose a reinforcement learning‐based alignment method to control the AUV to establish an optical link and maintain alignment. Our alignment control system utilizes a combination of sensors, including a depth sensor, Doppler velocity log (DVL), gyroscope, ultra‐short baseline device, and acoustic modem. These sensors are used in conjunction with a particle filter to observe the environment and estimate the AUV's state accurately. The soft actor‐critic algorithm is used to train a reinforcement learning‐based controller in a simulated environment to reduce pointing errors and energy consumption in alignment. After experimental validation in simulation, we deployed the controller on an actual AUV called Tri‐TON. In experiments at sea, Tri‐TON maintained the link and angular pointing errors within 1 m and , respectively. Experimental results demonstrate that the proposed alignment control method can establish underwater optical communication between AUV fleets, thus improving the efficiency of marine surveys.

Long-Term Coherent Integration Algorithm for High-Speed Target Detection.

Long-term coherent integration (CI) can effectively improve the radar detection capability for high-speed targets. However, the range walk (RW) effect caused by high-speed motion significantly degrades the detection performance. To improve detection performance, this study proposes an improved algorithm based on the modified Radon inverse Fourier transform (denoted as IMRIFT). The proposed algorithm uses parameter searching for velocity estimation, designs a compensation function based on the relationship between velocity and distance walk and Doppler ambiguity terms, and performs CI based on the compensated signal. IMRIFT can achieve RW correction, avoid the blind-speed sidelobe (BSSL) effect caused by velocity mismatch, and improve detection performance, while ensuring low computational complexity. In addition, considering the relationship between energy concentration regions and bandwidth in the 2D frequency domain, a fast method based on IMIRFT is proposed, which can balance computational cost and detection capacity. Finally, a series of comparative experiments are conducted to demonstrate the effectiveness of the proposed algorithm and the fast method.

Atrial Shunt Device Effects on Cardiac Structure and Function in Heart Failure With Preserved Ejection Fraction

Although the results of A Study to Evaluate the Corvia Medical Inc IASD System II to Reduce Elevated Left Atrial Pressure in Patients with Heart Failure (REDUCE LAP-HF II) trial were neutral overall, atrial shunt therapy demonstrated potential efficacy in responders (no latent pulmonary vascular disease and no cardiac rhythm management device). Post hoc analyses were conducted to evaluate the effect of shunt vs sham stratified by responder status. To evaluate the effect of atrial shunt vs sham control on cardiac structure/function in the overall study and stratified by responder status. This was a sham-controlled randomized clinical trial of an atrial shunt device in heart failure with preserved ejection fraction (HFpEF)/HF with mildly reduced EF (HFmrEF). Trial participants with evaluable echocardiography scans were recruited from 89 international medical centers. Data were analyzed from April 2023 to January 2024. Atrial shunt device or sham control. Changes in echocardiographic measures from baseline to 1, 6, 12, and 24 months after index procedure. The modified intention-to-treat analysis of the REDUCE LAP-HF II trial included 621 randomized patients (median [IQR] age, 72.0 [66.0-77.0] years; 382 female [61.5%]; shunt arm, 309 [49.8%]; sham control arm, 312 [50.2%]). Through 24 months, 212 of 217 patients (98%) in the shunt arm with evaluable echocardiograms had patent shunts. In the overall trial population, the shunt reduced left ventricular (LV) end-diastolic volume (mean difference, -5.65 mL; P <.001), left atrial (LA) minimal volume (mean difference, -2.8 mL; P =.01), and improved LV systolic tissue Doppler velocity (mean difference, 0.69 cm/s; P <.001) and LA emptying fraction (mean difference, 1.88 percentage units; P =.02) compared with sham. Shunt treatment also increased right ventricular (RV; mean difference, 9.58 mL; P <.001) and right atrial (RA; mean difference, 9.71 mL; P <.001) volumes but had no effect on RV systolic function, pulmonary artery pressure, or RA pressure compared with sham. In the shunt arm, responders had smaller increases in RV end-diastolic volume (mean difference, 5.71 mL vs 15.18 mL; interaction P =.01), RV end-systolic volume (mean difference, 1.58 mL vs 7.89 mL; interaction P =.002), and RV/LV ratio (mean difference, 0.07 vs 0.20; interaction P <.001) and larger increases in transmitral A wave velocity (mean difference, 5.08 cm/s vs -1.97 cm/s; interaction P =.02) compared with nonresponders randomized to the shunt, suggesting greater ability to accommodate shunted blood through the pulmonary circulation enabling LA unloading. In this post hoc analysis of the REDUCE LAP-HF II trial, over 2 years of follow-up, atrial shunting led to reverse remodeling of left-sided chambers and increases in volume of right-sided chambers consistent with the shunt flow but no change in RV systolic function compared with sham. Changes in cardiac structure/function were more favorable in responders compared with nonresponders treated with the shunt, supporting the previously identified responder group hypothesis and mechanism, although further evaluation with longer follow-up is needed. ClinicalTrials.gov Identifier: NCT03088033.

Recent advances in multimodal imaging in tetralogy of fallot and double outlet right ventricle.

In the ever-evolving field of medical imaging, this review highlights significant advancements in preoperative and postoperative imaging for Tetralogy of Fallot (TOF) and double outlet right ventricle (DORV) over the past 18 months. This review showcases innovations in echocardiography such as 3D speckle tracking echocardiography (3DSTE) for assessing right ventricle-pulmonary artery coupling (RVPAC) and Doppler velocity reconstruction (DoVeR) for intracardiac flow fields evaluation. Furthermore, advances in assessment of cardiovascular anatomy using computed tomography (CT) improve the integration of imaging in ablation procedures. Additionally, the inclusion of cardiac magnetic resonance (CMR) parameters as risk score predictors for morbidity, and mortality and for timing of pulmonary valve replacement (PVR) indicates its significance in clinical management. The utilization of 4D flow techniques for postoperative hemodynamic assessment promises new insights into pressure mapping. Lastly, emerging technologies such as 3D printing and 3D virtual reality are expected to improve image quality and surgical confidence in preoperative planning. Developments in multimodality imaging in TOF and DORV are poised to shape the future of clinical practice in this field.