Low Doppler Research Articles

Aortic valve calcium score to mean gradient ratio: a new frontier in aortic stenosis prognostication

Abstract Introduction Aortic stenosis (AS) presents diagnostic challenges, especially in patients with discordant low gradient AS (LGAS), i.e., small aortic valve area (AVA) and low Doppler mean gradient (MG). LGAS is associated with worse outcomes compared to concordant AS. Aortic valve calcium score (AVCS) is a measure of AS severity independent of flow and helps diagnose severe AS. It is unknown if the degree of discordance in AVCS and MG is of any clinical significance. A high AVCS/MG ratio may indicate impaired ventricular function and response to pressure overload despite preserved LVEF, potentially contributing to worse outcomes. Purpose This study aims to elucidate the prognostic significance of the AVCS/MG ratio in patients with severe AS and preserved left ventricular ejection fraction (LVEF) undergoing TAVR. We hypothesized a higher AVCS/MG ratio correlates with increased mortality. Methods Patients who underwent transcatheter aortic valve replacement (TAVR) from 2010 to 2020 for native valve severe AS with LVEF≥50% were identified from an institutional database. AVCS were obtained within 90 days of pre-TAVR echocardiography. Patients were divided into tertiles based on their AVCS/MG ratio. Primary outcome was overall mortality. Results The analysis included 1067 patients (mean age 79±9 years, 43% female); overall AVA was 0.80±0.14 cm², LVEF 63±6%, MG 46±12 mmHg, AVCS 2630±1528 AU, and AVCS/MG ratio 58±31. Patients stratified by AVCS/MG tertiles showed no difference in overall comorbidity index across tertiles (Figure 1). However, the group in the highest tertile was the oldest (80±8 vs 79±8 vs 77±9 years), predominantly male (87% vs 61% vs 24%), with the highest prevalent atrial fibrillation (44% vs 28% vs 25%) and stroke volume index <35 mL/m² (16% vs 11% vs 5%). 9-year survival was 15% vs 25% vs 36% (p<0.001, Figure 2). In multivariate analysis adjusted for age, sex, comorbidities, LVEF and AVA, AVCS/MG ratio was independently associated with increased risk of mortality (HR 1.005; 95% CI [1.001-1.008], p=0.005). Conclusion Higher AVCS/MG discordance is associated with increased risk of mortality following TAVR. Serial AVCS measurements during progressive AS may help identify patients at higher risk who may potentially benefit from earlier aortic valve intervention.

ThP8.7 - Giant Cell Arteries: Diagnostics

Abstract Aim Giant cell arteritis (GCA) poses a risk of severe ischaemic complications such as irreversible blindness which mandates early recognition of condition. We aimed to evaluate effectiveness of ultrasound doppler (USD) in diagnosing GCA compared to temporal artery biopsy (TAB) and American College of Rheumatology (ACR) score. Method This retrospective study included patients with suspected GCA who had consecutive TAB and USD examinations performed over a course of three years (2017-2022) which was correlated with ACR score. The data was also analysed to assess further management. Results There were 64 patients over this period who had both studies performed (22 were excluded as they did not have TAB) with 64% having an ACR score ≥3. Twenty males and forty-four females with a median age of 77 years (IQR 84-67). Overall, 81% patients had a negative USD result. Comparing USD results with TAB gold standard, there was sensitivity of 63% and specificity of 84%. Comparing USD results with ACR as gold standard, there was sensitivity of 20% and specificity of 83%. Forty percent patients with negative doppler result were continued on treatment mainly due to improvement of symptoms in response to steroids. Conclusion US Doppler has high diagnostic specificity and low sensitivity which makes it time-efficient, cost-effective and allows for the implementation of fast-track management pathway for majority patients. In certain circumstances, as cases of low clinical suspicion and positive doppler result, an additional test (TAB) would be required to confirm the diagnosis and cases where clinical suspicion is high with negative doppler, TAB should be considered.

Study of the Long-Lasting Daytime Field-Aligned Irregularities in the Low-Latitude F-Region on 13 June 2022

The unusual daytime F-region Field-Aligned Irregularities (FAIs) were observed by the HCOPAR and the satellites at low latitudes on 13 June 2022. These irregularities survived from night-time to the following afternoon at 15:00 LT. During daytime, they appeared as fossil structures with low Doppler velocities and narrow spectral widths. These characteristics indicated that they drifted along the magnetic field lines without apparent zonal velocity to low latitudes. Combining the observations of the ICON satellite and the Hainan Digisonde, we derived the movement trails of these daytime irregularities. We attributed their generation to the rapid ascent of the F-layer due to the fluctuation of IMF Bz during the quiet geomagnetic conditions. Subsequently, the influence of the substorm on the low-latitude ionosphere was investigated and simulated. The substorm caused the intense Joule heating that enhanced the southward neutral winds, carrying the neutral compositional disturbances to low latitudes and resulting in a negative storm effect in Southeast Asia. The negative storm formed a low-density circumstance and slowed the dissipation of the daytime FAIs. These results may provide new insights into the generation of post-midnight irregularities and their relationship with daytime fossil structures.

Postnatal Genetic and Neurodevelopmental Assessment in Infants Born at Term With Severely Low Birth Weight of Non-placental Origin

ABSTRACT Small for gestational age (SGA) newborns are generally defined as those with a birth weight below the 10th percentile. Fetuses diagnosed with fetal growth restriction (FGR) are usually evaluated to determine if there is a pathological cause and thus a higher risk for adverse outcomes due to being small. Often when this diagnosis is made early in the third trimester, chromosomal microarray analysis is recommended to detect genetic disease. This study was designed to determine the frequency of monogenic disorders in term infants with severely low birth weight but normal Doppler results, as well as to estimate the frequency of neurodevelopmental impairment when a genetic etiology was ruled out. Inclusion criteria for this study were singleton pregnancy; term delivery; birth weight more than 2.5 SDs below the mean; normal Doppler studies of the umbilical artery, fetal middle cerebral artery, cerebroplacental ratio, and uterine artery; no maternal hypertensive disease; and no prenatal fetal structural or identified genetic anomalies or fetal infection. Exclusion criteria included incomplete data. Exome sequencing was completed using saliva sampling and blood sampling, and standard neurodevelopmental assessment techniques were used for children 2 to 3.5 and 6 to 8 years old. Children aged between 3.5 and 6 years were not included because of lack of standardized neurodevelopmental testing. A total of 63 families were contacted, and 7 (11%) reported that a genetic disorder had been diagnosed after birth. In addition, 18 individuals without a known genetic disorder who met all the criteria underwent exome sequencing and neurodevelopmental testing. Of the 7 who reported a postnatally diagnosed genetic syndrome, 5 were Mendelian monogenetic and 2 were epigenetic, including Cockayne syndrome; short stature, microcephaly, and endocrine dysfunction syndrome; Renpenning syndrome; Noonan syndrome; Russell-Silver syndrome; and Prader-Willi syndrome. Median birth weight among the children with genetic disorders was not different from children without. Exome sequencing was normal in the 18 children who were tested and who had not been previously diagnosed with a genetic syndrome. None of the children showed less than average neurodevelopment on overall assessment in the lower age group. In the higher age group, 2 children were classified as having low IQ, with one borderline and one extremely low, with low scores in all other domains as well. In addition, 6 individuals showed a low score in at least 1 of the 5 domains, with the largest deviations showing in the domains of verbal comprehension and working memory. Clinicians should be aware of the potential outcomes of FGR even when other complications are not present. Counseling about genetic analysis prenatally or within a short postnatal timeframe could save a lot of time and effort in evaluating children later. In addition, children should be carefully assessed in later childhood for neurodevelopmental differences that are treatable or that may require different resources. Future research should focus on further homogenizing the population to get more accurate results, as well as dealing with potential biases in this study.

Beneficial Effects of Self-Motion for the Continuous Phase Analysis of Ac-Coupled Doppler Radars

This paper analyzes the beneficial effects on phase detection arising from the motion of an ac-coupled Doppler radar. Indeed, although the presence of an ac coupling stage suppresses the dc offset after the receiver RF output, due to the coupling capacitor, a high-pass behavior is introduced; the presence of a high-pass behavior leads to signal distortion, particularly for low Doppler frequencies, which are typical in many biomedical or industrial applications. Since the target displacement is usually extracted from the phase history, this effect might, in turn, worsen the overall accuracy of the system. Moreover, if the target alternates stationary and moving time intervals, the phase detection step becomes challenging. Indeed, during the stationary time, the output of the RF front-end shows only noise fluctuations that, in turn, result in uncorrelated phases which might be confused with the real target displacement. This negative effect might be avoided by keeping the radar continuously moving, thus exploiting what is usually considered a state that is negative and worthy of attention. In this contribution, this effect is addressed from a different perspective, and ad hoc experimental case studies are shown to demonstrate the effectiveness of the proposed system. This task has been accomplished through theoretical analysis and related experimental activity.

Subpixel segmentation of borehole fractures from low resolution Doppler ultrasound images using machine learning

Ultrasonic imaging is utilized in oil and gas, and geothermal boreholes using various logging tools. The imaging resolution of these tools is physically limited by the point spread function (PSF) of the imaging system. It is of interest to be able to accurately resolve features that are blurred out due to the PSF limit. This work evaluates a convolutional neural network (CNN), adapted from medical ultrasound imaging, to obtain subpixel estimates of fracture shape and area in boreholes from ultrasonic power Doppler images. The CNN was trained using a dataset generated using simplified ultrasonic simulations, ignoring effects due to fluid dynamics. The performance of the CNN model was tested on experimental scans obtained using a laboratory setup using a water based drilling mud. The CNN was able to estimate the fracture areas with a significantly lower mean absolute error of 5.0±3.9mm2, compared to 22.9±1.7mm2 using the conventional thresholding method. The CNN also enabled the estimation of fracture shape and area using a single frame of the power Doppler image, compared to about 30 frames required for the thresholding method, facilitating a possible increase in scanning speed of the logging tool. Although, the CNN in this work is applied on power Doppler images from borehole fractures, the model can be easily adapted for similar other applications, such as ultrasonic pulse-echo imaging of boreholes, cement bond evaluation, perforation evaluation in production logging, etc.

Subcarrier modulation based phase-coded coherent lidar.

This paper presents a lean subcarrier modulation-based phase-coded coherent lidar system with a non-quadrature receiver and sampling ratio lower than the Nyquist sampling ratio. Specifically, by utilizing the drawbacks of low Doppler tolerance in encoding signals, phase information can be obtained after pulse compression, and the mirror frequency introduced by real sampling can be negligible. Validation experiments based on inverse synthetic aperture lidar are performed, with the corresponding imaging results having a resolution superior to 4cm, demonstrating our system's efficiency in phase acquisition that is free from frequency aliasing.

Verification of Gaia Data Release 3 Single-lined Spectroscopic Binary Solutions With Three Transiting Low-mass Secondaries

While secondary mass inferences based on single-lined spectroscopic binary (SB1) solutions are subject to degeneracies, this degeneracy can be lifted through the observations of eclipses. We combine the subset of Gaia Data Release 3 SB1 solutions consistent with brown dwarf-mass secondaries with the Transiting Exoplanet Survey Satellite (TESS) Object of Interest (TOI) list to identify three candidate transiting brown dwarf systems. Ground-based precision radial velocity follow-up observations confirm that TOI-2533.01 is a transiting brown dwarf with orbiting TYC 2010-124-1 and that TOI-5427.01 is a transiting very low-mass star with orbiting UCAC4 515-012898. We validate TOI-1712.01 as a very low-mass star with transiting the primary in the hierarchical triple system BD+45 1593. Even after accounting for third light, TOI-1712.01 has a radius nearly a factor of 2 larger than predicted for isolated stars with similar properties. We propose that the intense instellation experienced by TOI-1712.01 diminishes the temperature gradient near its surface, suppresses convection, and leads to its inflated radius. Our analyses verify Gaia DR3 SB1 solutions in the low Doppler semiamplitude limit, thereby providing the foundation for future joint analyses of Gaia radial velocities and Kepler, K2, TESS, and PLAnetary Transits and Oscillations light curves for the characterization of transiting massive brown dwarfs and very low-mass stars.

The Accuracy and Reliability of Automated Oscillometric Measurement of Ankle-Brachial Index in the Diagnosis of Peripheral Artery Disease

Comparing the accuracy and reliability of ankle-brachial index (ABI) measured by an oscillometric device with the Doppler method in peripheral arterial disease (PAD). 122 patients admitted to the department of interventional radiology with PAD were studied. ABI was measured with the 2 methods in random order. After excluding the inconclusive results, Doppler ABIs were compared with the oscillometric ABIs in each limb, the reliability was evaluated by intraclass correlation coefficient (ICC), and the accuracy and consistency were assessed by receiver operating characteristic curves and Bland-Altman method. In 122 patients (244 legs), 27 legs got inconclusive oscillometric results, 4 legs got inconclusive oscillometric and inconclusive dorsalis pedis artery Doppler results, 2 legs had oscillometric cuff pressure intolerance. Using Doppler ABI <0.9 as a diagnostic threshold, compared with the high Doppler ABI, oscillometric method had a sensitivity of 57.81%, a specificity of 95.18%, the ICC was 0.626 (95% confidence interval [CI]: 0.536-0.701), Bland-Altman method showed 11/211 (5.21%) difference points outside the 95% limits of agreement. Compared with the low Doppler ABI, oscillometric method had a sensitivity of 50.66%, a specificity of 98.31%, the ICC was 0.541(95% CI: 0.483-0.630), Bland-Altman method showed 11/211 (5.21%) difference points outside the 95% limits of agreement. Using 1.00 as the diagnostic threshold and considering error oscillometric results as abnormal ABIs, the sensitivity improved to 88.05% with high Doppler ABI and 81.42% with the low. The accuracy and reliability of oscillometric ABI in patients with PAD is unsatisfied, which makes it not suitable as an alternative method in clinic disease assessment. Using 1.0 as the ABI oscillometric threshold for PAD diagnosis can improve the diagnostic value.

High-Resolution Wideband Waveform Design for Sonar Based on Multi-Parameter Modulation

The design of transmitting waveforms is an effective way to improve the detection performance of sonar systems. For the problem of high-range sidelobe when designing reverberation-resistant waveforms, this paper proposes a high-resolution wideband composite waveform design with reverberation suppression performance and a waveform parameter improvement method. Firstly, we propose a novel wideband waveform, which utilizes linear frequency modulation (LFM) as the fundamental pulse, referred to as multi-parameter coded modulation LFM pulse (MPCM-LFM). Additionally, we deduce the wideband ambiguity function for waveform design. Then, we deduce the constraint relations of the waveform parameters for different sub-band overlaps, and according to the mathematical expressions of the obtained range ambiguity function, we analyze in detail the effects of the waveform parameters on the range ambiguity function under different constraints. Secondly, on the basis of the analysis, we also propose a hopping carrier frequency constraint rule to optimize the spectral performance, and the range sidelobe is restrained effectively in significant measure by this parameter improvement method. Finally, we analyze the computer simulation results. It is obvious that our proposed waveform parameter improvement method leads to good results. The proposed improved MPCM-LFM signal shows a “near-thumbtack” ambiguity function, whose sidelobe suppression performance is superior to other classical waveforms in the desired region, and it can realize high-precision parameter estimation. In addition, the proposed improved MPCM-LFM signal possesses good performance in detecting stationary and low Doppler targets in the background of reverberation.

Research on Acquisition Performance of FFT Algorithm for Low-Frequency Spread-Spectrum Signals Using Acoustic Sensors

An essential precondition for the effective use of low-frequency spread-spectrum acoustic signals is their synchronous acquisition. Due to the low bit rate that low-frequency spread-spectrum signals have, the length of the spreading spectrum code and the number of intra-chip carriers need to be precisely designed to balance the acquisition performance and the bit rate in low-frequency spread-spectrum signals. Furthermore, the selection of the acquisition method and sampling frequency depends on the specific application and system requirements, which will directly affect the processing speed and accuracy. Firstly, this study uses a cyclical stepping search combined with a fixed threshold and maximum correlation discriminant method to improve the FFT acquisition algorithm with a low Doppler frequency. Secondly, the effects of the spreading spectrum code parameters and sampling frequency on the acquisition performance are also investigated through simulation and experiments with acoustic sensors. The results show that both lengthening the spreading spectrum code and increasing the number of intra-chip carriers can greatly improve the acquisition performance. Increasing the sampling frequency can improve the ranging accuracy but has a very limited improvement effect on the acquisition performance.

Dust flow analysis by low coherence Doppler lidar

Visualization of dust flow and wind dynamics near the ground surface are essential for understanding the mixing and interaction between geosphere and atmosphere near the surface. Knowing the temporal dust flow is beneficial in dealing with air pollution and health issues. Dust flows near the ground surface are difficult to monitor because of their small temporal and spatial scale. In this study, we propose a low-coherence Doppler lidar (LCDL) for measuring dust flow near the ground with high temporal and spatial resolutions of 5 ms and 1 m, respectively. We demonstrate the performance of LCDL in laboratory experiments using flour and calcium carbonate particles released into the wind tunnel. LCDL experiment results show a good agreement with anemometer measurement in wind speeds ranging from 0 to 5 m/s. The LCDL technique can reveal dust’s speed distribution, which is affected by mass and particle size. As a result, different speed distribution profiles can be used to determine dust type. The simulation results of dust flow coincide well with the experimental results.

도플러 저해상도 레이다의 탐지성능 향상을 위한 속도 기반 하이브리드 도플러 처리 기법

본 논문에서는 SIR을 높이기 위하여 속도 기반 하이브리드 도플러 처리 기법을 제안하였다. 본 논문에서 제안하는 기법은 Moving target indicator(MTI)와 Finite impulse response(FIR) 2가지 필터를 속도 구간별로 사용하는 기법이다. 제안한 알고리즘에서는 속도 경계 값을 사용 하는데, 이 값을 결정하는 2가지 파라미터를 몬테카를로 시뮬레이션을 통하여 찾았다. 첫 번째는 모호 속도이며 속도 경계 값과 선형관계인 것을 알아내었다. 두 번째는, FIR 필터의 클러터 표준편차 이며, 속도 경계 값과 로그관계에 있다는 것을 알아내었다. 탐지확률은 Signal to interference ratio(SIR)이 클수록 높아지므로, SIR을 높이면 탐지성능이 향상된다. 제안된 알고리즘은 시뮬레이션을 통하여 검증되었다.

Measurement of microwave electric field based on electromagnetically induced transparency by using cold Rydberg atoms

Microwave electric fields are measured by using cold Rydberg atoms. We obtain spindle-shaped cold atomic clouds in a magneto-optical trap and then pump the cold atoms to quantum state 5S&lt;sub&gt;1/2&lt;/sub&gt;, &lt;i&gt;F&lt;/i&gt; = 2, &lt;i&gt;m&lt;/i&gt;&lt;sub&gt;F&lt;/sub&gt; = 2 by using an optical-pump laser. We obtain the Rydberg electromagnetic induction transparency (EIT) spectrum peak with narrow linewidth by the low temperature and small residual Doppler broadening. The results show that the typical EIT linewidth with 16 μK cold atoms is about 460 kHz which is 15 times narrower than that of 7 MHz obtained in the thermal vapor cell. The microwave electric field amplitude is measured by Autler-Townes splitting (EIT-AT splitting) in the cold atoms at frequencies of 9.2, 14.2 and 22.1 GHz, receptively. The results show that there is a good linear relationship between the EIT-AT splitting interval and the microwave electric field amplitude. The lower limit of the microwave electric field amplitude that can be measured in the linear region can reach as low as 222 μV/cm, which is about 22 times larger than the lower limit in the traditional thermal vapor cell about of 5 mV/cm. The improvement of the lower limit by EIT-AT splitting method is roughly proportional to the narrowing EIT line width by cold atom samples. This demonstrates that benefiting from the smaller residual Doppler effect and the narrower EIT linewidth in cold atoms, the cold atom system is more advantageous in the experimental measuring of the weak microwave electric field amplitude by using the EIT-AT splitting method. This is of great benefit to the absolute calibration of very weak microwave electric fields. Furthermore, the lower limit of the microwave electric field amplitude that can be measured is smaller than 1 μV/cm by using the change of transmittance of the prober laser at the EIT resonance, and the corresponding sensitivity can reach 1 μV·cm&lt;sup&gt;–1&lt;/sup&gt;·Hz&lt;sup&gt;–1/2&lt;/sup&gt;. These results demonstrate the advantages of cold atomic sample in microwave electric field measurement and its absolute calibration.

A fully automated algorithm for heart rate detection in post-dive precordial Doppler ultrasound

Background: Doppler ultrasound is used currently in decompression research for the evaluation of venous gas emboli (VGE). Estimation of heart rate from post-dive Doppler ultrasound recordings can provide a tool for the evaluation of physiological changes from decompression stress, as well as aid in the development of automated VGE detection algorithms that relate VGE presence to cardiac activity. Method: An algorithm based on short-term autocorrelation was developed in MATLAB to estimate the heart rate in post-dive precordial Doppler ultrasound. The algorithm was evaluated on 21 previously acquired and labeled precordial recordings spanning Kisman-Masurel (KM) codes of 111–444 (KM I–IV) with manually derived instantaneous heart rates. Results: A window size of at least two seconds was necessary for robust and accurate instantaneous heart rate estimation with a mean error of 1.56 ± 7.10 bpm. Larger window sizes improved the algorithm performance, at the cost of beat-to-beat heart rate estimates. We also found that our algorithm provides good results for low KM grade Doppler recordings with and without flexion, and high KM grades without flexion. High KM grades observed after movement produced the greatest mean absolute error of 6.12 ± 8.40 bpm. Conclusion: We have developed a fully automated algorithm for the estimation of heart rate in post-dive precordial Doppler ultrasound recordings.

Neonatal heart rate monitoring at birth with hands-free foetal doppler

There is a need for improved measurement and documentation of the neonatal heart rate immediately after birth, which currently relies on auscultation with a stethoscope. Measurement of the heart rate is a medical requirement within the first minute after birth in all babies. Heart rate at birth is the only reliable indicator of the health of the neonate which does not establish breathing immediately. In sick neonates pulse oximetry is usually available but does not provide an output for the first minute even in healthy neonates. Although the ECG is considered the gold standard, it may provide a false measurement due to pulseless electrical activity of the myocardium. Neonatal ECG technology is not routinely available at birth, however prior to birth the fetal heart rate is routinely obtained and documented by a low cost doppler ultrasound. Recently the fetal doppler has been shown to be effective immediately after birth on the neonatal chest (Hutchon 2022) but requires constant attention by the carer, and may interfere with measures to provide positive pressure ventilation or other resuscitation measures. A fetal doppler ultrasound device has been extended to provide a hands free sensor which is secured on the neonatal chest by the surface tension of the transducer gel. The system also works well through polythene and provides a safe and effective neonatal heart rate monitor inside a sterile polythene bag for use at caesarean birth. The design features are presented and preliminary data showing the precordial doppler provides a heart rate closely equivalent to the heart rate from the gold standard ECG.

Method of increasing the range resolution of radio pulse sensors of short-range radar systems

The description of a new method for increasing the resolution of radio pulse sensors (RPS) designed for short- range radar systems (SRRS) for detecting and measuring motion parameters of location objects is presented. The essence of the method is that the controlled area of space with the targets located in it is periodically irradiated with probing radio pulses, and during their radiation, radio pulses reflected from the targets are simultaneously received and divided into two quadrature channels. Next, they are mixed with probing radio pulses, and the time-overlapping parts of these radio pulses are converted into the region of low Doppler frequencies in the form of two quadrature video pulses. Then, the quadrature video pulses received in these channels are sampled by amplitude, stored at multiple points in time and digitally processed according to the proposed algorithm. The method is implemented in the RPS made on the basis of a horn-lens antenna, a Doppler receiving and transmitting module with quadrature outputs of converted signals, a synchronization and pulse generation unit, as well as a digital signal processing unit. The RPS can be used in onboard (for example, automotive) SRRS designed to detect moving targets, measure the distance to them, as well as determine the speed and direction of movement. The results of experimental studies have been obtained on the example of the 8-mm autodyne RPS made on the basis of the oscillator on a planar Gann-diode.

Abstract 12100: Catastrophic Large Post-Stemi Inferoseptum Ventricular Septal Rupture With Left-to-Right Shunt and an Inferoseptum Pulsatile Pseudoaneurysm

Case Presentation: 49-year-old male without known cardiovascular history presented with three days of atypical chest discomfort. 12-lead EKG revealed ST-segment elevations in II-III-aVF and depression in V1 suggestive of an acute infero-posterior MI (A), Troponin T at 6.85 ng/mL. Following administration of DAPT and heparinization, emergent coronary angiography proved a dominant RCA with proximal 60% and middle 100% occlusion (B), 80% focal stenosis at mid-LAD and 70% focal stenosis at prox-LCx (C). PCI with intra-aortic balloon pump support was performed, with two DES deployed in the RCA, use of a trans-venous pacemaker was required for complete AV block, and two defibrillations required for ventricular fibrillation. Following further hemodynamic compromise unexplained by his hemodynamic parameters, TEE was performed, demonstrating a large mid/distal infero-septum ventricular septal defect with left to right shunt (D, E and F), as well as a basal/mid infero-septum large pseudo-aneurysm (PSA) cavity (contained rupture) (G: low velocity Doppler flow from LV to PSA cavity, H and I show intact septum). The patient continued to decompensate requiring escalation to temporary mechanical circulatory support with VA-ECMO. Heart transplantation was initially considered, family decided to withdraw care due to multi-organ failure and poor prognosis Discussion: Due to widespread availability of primary percutaneous coronary intervention with early reperfusion, mechanical complications post MI are less common in current days. Following transmural MI, persistent hypotension and cardiogenic shock should alert for complications such as VSD or PSA. While VSD may be amenable to percutaneous or surgical closure, PSA is associated with very high mortality even if surgery is attempted. Given the presence of both a VSD and PSA, mechanical support with VA-ECMO allowed us to support the patient for several days as a bridge to decision regarding heart transplantation

Ice Aggregation in Low‐Level Mixed‐Phase Clouds at a High Arctic Site: Enhanced by Dendritic Growth and Absent Close to the Melting Level

AbstractLow‐level mixed‐phase clouds (MPCs) occur extensively in the Arctic, and are known to play a key role for the energy budget. While their characteristic structure is nowadays well understood, the significance of different precipitation‐formation processes, such as aggregation and riming, is still unclear. Using a 3‐year data set of vertically pointing W‐band cloud radar and K‐band Micro Rain Radar (MRR) observations from Ny‐Ålesund, Svalbard, we statistically assess the relevance of aggregation in Arctic low‐level MPCs. Combining radar observations with thermodynamic profiling, we find that larger snowflakes (mass median diameter larger than 1 mm) are predominantly produced in low‐level MPCs whose mixed‐phase layer is at temperatures between −15 and −10°C. This coincides with the temperature regime known for favoring aggregation due to growth and subsequent mechanical entanglement of dendritic crystals. Doppler velocity information confirms that these signatures are likely due to enhanced ice particle growth by aggregation. Signatures indicative of enhanced aggregation are however not distributed uniformly across the cloud deck, and only observed in limited regions, suggesting a link with dynamical effects. Low Doppler velocity values further indicate that significant riming of large particles is unlikely at temperatures colder than −5°C. Surprisingly, we find no evidence of enhanced aggregation at temperatures warmer than −5°C, as is typically observed in deeper cloud systems. Possible reasons are discussed, likely connected to the ice habits that form at temperatures warmer than −10°C, increased riming, and lack of particle populations characterized by broader size distributions precipitating from higher altitudes.

Underwater acoustic communication based on chirp spread spectrum with cyclic shifted PN sequences

In this presentation, we propose a new underwater acoustic communication technique that combines a binary PN (Pseudo Noise) sequence to which cyclic shift is applied and a CSS (Chirp Spread Spectrum) method that is robust against low Doppler shift. PN sequences are known to have sharp autocorrelation function and cyclic properties. In the case of the previous CSS method, 1-bit per symbol was mapped according to the sign of the slope in the time-frequency domain of the chirp signal, but the proposed method maps 2-bit per symbol according to the cyclic shift direction of PN sequence and the slope of the chirp. As a result, the transmission data rate is doubled. For example, “00” symbol is expressed as an up-chirp and right cyclic shifted PN sequence, and “11” symbol can be expressed as a down-chirp and left cyclic shifted PN sequence. This combination can have excellent autocorrelation properties and Doppler shift immunity. The performance of the proposed method will be compared with that of the previous method by presenting the results of the sea trial. [Work supported by the Agency for Defense Development, South Korea, Grant No. UD200002DD.]