Normal Wave Research Articles

Tunable narrow transparency windows induced by the coupled quasi-guided modes in borophene plasmonic nanostructure

A grating-assisted triple-layer continuous borophene sheets structure is presented to investigate the phase-coupled plasmon-induced transparency (PIT) effect at the near-infrared communication band. In the proposed structure, the diffraction grating is utilized to couple the normal incident waves, which excites the quasi-guided mode in triple-layer continuous borophene sheets. Compared to the patterned structure, the requirement of complicated processing techniques and extra doping configurations for tuning carrier density can be avoided by using the continuous borophene sheet. Additionally, the narrower transparency windows are shown in the spectral responses via the phase coupling between two detuned quasi-guided modes with high quality factors. The transparency windows can be efficiently tuned by adjusting the carrier densities in borophene sheets or the separation distances between the borophene sheets. The analytical results based on temporal coupled mode theory and transfer matrix method are consistent with the numerical simulations via finite-difference time-domain calculations. The proposed scheme provides the promising design of a tunable PIT component that is compatible with optical communication technology.

Noninvasive Transcutaneous Auricular Vagal Nerve Stimulation Improves Gastric Slow Waves Impaired by Cold Stress in Healthy Subjects

Background/AimsStress is known to inhibit gastric motility. The aim of this study was to investigate the effects and autonomic mechanisms of transcutaneous auricular vagal nerve stimulation (taVNS) on cold stress (CS)–induced impairment in gastric motility that are relevant to the brain-gut interactions in healthy volunteers. Materials and MethodsHealthy volunteers (eight women; age 28.2 ± 1.8 years) were studied in four randomized sessions (control, CS, CS + taVNS, and CS + sham-electrical stimulation [sham-ES]). Each session was composed of 30 minutes in the fasting state and 30 minutes after a standard test meal. CS was induced during minutes 10 to 30 after the meal, whereas taVNS or sham-ES was performed during minutes 0 to 30 after the meal. The electrogastrogram and electrocardiogram were recorded for assessing gastric slow waves and autonomic functions, respectively. ResultsFirst, CS decreased the percentage of normal gastric slow waves (59.7% ± 9.8% vs 85.4% ± 4.5%, p < 0.001 vs control); this impairment was dramatically improved by taVNS (75.5% ± 6.3% vs 58.4% ± 12.5%, p < 0.001 vs sham-ES). Second, CS increased the symptom score (22.0 ± 12.1 vs 39.3 ± 11.5, p = 0.001 vs control); taVNS, but not sham-ES, reduced the symptom score (26.0 ± 12.2 vs 38.3 ± 21.6, p = 0.026 vs sham-ES). Third, CS decreased vagal activity assessed from the spectral analysis of heart rate variability (0.21 ± 0.10 vs 0.26 ± 0.11, p < 0.05 vs control) and increased the sympathovagal ratio (4.89 ± 1.94 vs 3.74 ± 1.32, p = 0.048 vs control); taVNS normalized CS–induced suppression in vagal activity (0.27 ± 0.13 vs 0.22 ± 0.10, p = 0.049 vs sham-ES; p > 0.05 vs control) and CS-induced increase in the sympathovagal ratio (3.28 ± 1.61 vs 4.28 ± 2.10, p = 0.042 vs sham-ES; p > 0.05 vs control). ConclusionThe noninvasive taVNS improves the CS-induced impairment in gastric pace-making activity, possibly by reversing the detrimental effect of CS on autonomic functions. taVNS may have a therapeutic potential for stress-induced gastric dysmotility.

Polarization insensitive dual band metamaterial with absorptance for 5G sub-6 GHz applications

A couple ring enclosed circular geometric resonator (CRECGR) based dual-band polarization insensitive metamaterial (MM) with high effective medium ratio (EMR), and excellent absorptance is proposed in this study, which can be utilized as a sensor and absorber in the 5G sub-6 GHz frequency range. A circular geometry-based unique patch has been introduced in the proposed unit cell to achieve high polarization insensitive properties with excellent absorption for the 5G sub-6 GHz spectrum. The distinctive feature of this proposed CRECGR unit cell is its simple and unique structure with a high EMR of 11.13, polarization insensitive up to 180°, and epsilon negative (ENG) properties, including a negative refractive index and near-zero permeability for 5G sub-6 GHz applications. Furthermore, this designed unit cell yields excellent absorption properties with high quality factor. The designed MM unit cell is fabricated on low loss Rogers RT5880 printed media with an electrical dimension of 0.089λ × 0.089λ × 0.017λ. The performance of the designed CRECGR metamaterial is determined using Computer Simulation Technology (CST), Advanced Design Software (ADS), and measurements. The CRECGR unit cell offers dual resonances at 3.37 GHz and 5.8 GHz, covering the 5G sub-6 GHz band with ENG, near-zero permeability and negative index. The polarization insensitive properties of the unit cell were also investigated for maximum angle of incidence, which confirmed the identical response. The simulated outcome is verified by experiment with excellent accordance. Moreover, the unit cell performance with a complete backplane is explored, noting a maximum absorption of 99.9% for all normal and oblique incidence waves, suitable for sensing and antenna systems. In addition, the suggested unit cell sensing performance is evaluated using the permittivity-based sensing model. The proposed MM outperforms recent related studies in terms of polarization insensitivity up to 180°, high insensitive absorptivity, high EMR, and sensing applications. These features prove that the proposed CRECGR metamaterial is perfect for 5G Applications.

Machine Learning Techniques Applied for Exploring Heart Disease and Classifying Stages through ECG Signal

Electrocardiogram (ECG) has given crucial data concerning various heart attack criterion of the human heart this examination can be the key goal of the research for the detection and prevention of cardiac circumstances frighten. The proposed method using machine learning techniques for classifying and analyzing ECG signal processing and this research mainly developed for early discovery of heart diseases and also the prediction of stages level. The dataset was utilized as a person ECG signal of Heart Database which was taken from the UCI repository of Machine learning dataset vault. In this paper, a simple algorithm is presented for to discover R-peaks automatically from a single lead digital ECG data. The proposed method detecting the time interval of the ECG signal from the R-peaks level next level with the double squared difference signal is used to localize the region of QRS which is the time interval between the binary data. this method consists of different stages of sorting from the raw data for reducing nosier signal, threshold a difference signal of ECG by analyzing the time interval of QRS, and finally a comparison of relative magnitude to detect the region of interval processing to analyze accuracy result. The proposed research novel machine learning techniques of the multi-module neural network system (MMNNS) is used to analyze the imbalance problem form the ECG signal classification if the wave was abnormal then the user of dataset patients will be affected by heart diseases. Using the time interval varies from the range of QRS then it analyzes the abnormal of ECG by MMNNS algorithm to define the classification result and finally analyze the stages. If the patients were presented an abnormal ECG signal compared with a normal ECG signal wave graph then they were affected by heart diseases if whether they patients were affected then finally classify the stages of heart diseases whether they are predictable/unpredictable stages. The examination result is completed among two strategies on the better accuracy premise and effective training time of the process.

Incident-Angle-Dependent Extraordinary Transmission of the Terahertz Bull’s-Eye Structure

The bull's-eye structure in the terahertz (THz) frequency region has ample applications owing to its ability to focus free-propagating waves into subwavelength apertures, resulting in enhanced transmission, that is, extraordinary transmission. However, its coupling properties have been primarily discussed in terms of the normal plane-wave incidence to the structure. In this study, we investigate the multiple resonances in extraordinary transmission with normal and oblique incident waves. The experiment using a widely tunable and high-power THz wave source revealed two types of resonances. The main resonance split depends on the incident angle, and the other corresponds to the side lobe of the main resonances. The results are explained by a simple analytical model using a finite number of scattering media. The analysis is supported by the full-wave simulation using the finite-element method, which agrees with the experimental results. The coupling mechanisms will be applicable to design devices, such as THz biosensing devices or THz antennas for rapid communication systems.

A preliminary study on the effect of breathing on heart rate and blood pressure variability in patients with chronic diseases with abnormal sleep breathing

ObjectiveTo analyze the relationship between heart rate and blood pressure variability and respiration in patients with chronic respiratory disorders during night sleep.Methods16 patients with chronic diseases with abnormal sleep and respiration were included. Polysomnography was used to analyze the R‐R interval of nasal airflow electrocardiogram in normal stable breathing period and wave breathing period (OB) during nighttime sleep, and the variation of blood pressure based on finger‐tip photoelectric volume pulse wave (PPG) and pulse wave conduction time (PTT).The ResultsThe ratio of the number of respiratory cycles to the number of heart rate variability cycles (B‐n / HRV‐n) was (1.00 ± 0.04), to the number of systolic blood pressure (SBP) variability cycles (B‐n / SBPV‐n) was (1.02 ± 0.10), and diastolic blood pressure (DBP) variability cycles (B‐n / DBPV‐B‐n) was (1.00 ± 0.11), The ratio of respiratory cycle number to heart rate variability cycle number (OB‐n / OB‐HRV‐n) during OB was (1.22 ± 0.18). The ratio of respiratory cycle number to systolic blood pressure variation cycle number (OB‐n / OB‐SBPV‐n) was (1.19 ± 0.22), and DBP(OB‐n / OB‐DBPV‐n) was (1.15 ± 0.15), both of which were higher than those in normal stable breathing period (P &lt; 0.01). During the normal and stable breathing period, the average amplitude of heart rate variability (HRV‐B‐M) of each respiratory cycle rhythm was (2.64 ± 1.59) bpm, the average amplitude of systolic blood pressure variability (SBPV‐B‐M) of each respiratory cycle rhythm was (2.83 ± 1.22) mmhg, and diastolic blood pressure variability (DBPV‐B‐M) was (2.40 ± 0.86) mmhg, which were slightly higher than those of the normal people, but there was no significant difference compared with the normal people and hypertensive patients without sleep apnea. The mean amplitude of heart rate variability (OB‐HRV‐B‐M) at each respiratory cycle rhythm in OB period was (3.56 ± 1.57) bpm, the mean amplitude of heart rate variability (OB‐HRV‐OB‐M) at each OB period was (13.75 ± 4.25) bpm, The average amplitude of diastolic blood pressure variability (OB‐DBPV‐B‐M) was (2.82 ± 1.95) mmhg, which was higher than that in normal stable respiratory period. The difference between OB‐SBPV‐B‐M and normal stable respiratory systolic blood pressure variability (SBPV‐B‐M) was significant. The variation range of systolic blood pressure (OB‐SBPV‐OB‐M) in each OB cycle was (16.83 ± 9.29) mmhg, which was much larger than that of OB‐SBPV‐B‐M and SBPV‐B‐M (P &lt; 0.01).ConclusionThe variations of blood pressure and heart rate in patients with chronic respiratory disorders during normal and stable breathing at night are similar to those in normal people and hypertensive patients without sleep respiratory disorders in the same period in our laboratory, The variation amplitude of heart rate and blood pressure in wavy breathing period was greater than that in normal and stable breathing period .confirming that the variation of heart rate and blood pressure was respiratory origin.

Multi-level inverter with novel carrier pulse width modulation technique for high voltage applications

&lt;span&gt;The present work deals with multilevel inverters (MLI) with modified carrier pulse width modulation technique and its application, especially in solar-based applications due to its modularity in structure and suitability for medium or high-power applications. Several multilevel inverters are introduced for various applications. One of the drawbacks of these inverters is high total harmonic distortion (THD) value in the output which impacts the power quality. The main objective of this work is to improve the power quality, thereby increasing the life and performance of the overall system at the consumer side. The most popular and compact cascaded multilevel DC-link inverter (CMDCLI) is considered for study and employed for 11-level operation. In general, sinusoidal pulse width modulation (SPWM) technique is used for control of inverter. However, the present work proposes a modified carrier-based hybrid pulse width modulation (HPWM) technique and has been tested with CMLDCLI. This novel technique compares the THD performance results with normal carrier wave considering R-L load. The results are analyzed in MATLAB environment and are validated with experimental results.&lt;/span&gt;

입사각 안정성을 갖는 밀리미터파 대역 주파수 선택적 레이돔 설계

In this study, a frequency-selective radome in the millimeter-wave band with excellent incident-angle stability is designed. The hybrid structure comprising the designed radome combines a multilayered composite material, which has a rectangular loop-type FSS (frequency selective surface) structure with frequency-selective transmission characteristics in the millimeter-wave band. It has a low transmission loss of ≤1 dB in the pass band and a high blocking characteristic of ≥10 dB in the X-band for polarization TE (transverse electric). Additionally, the TM (transverse magnetic) modes and incidence angles ranged from 0° to 50°. To confirm the design performance, a hybrid composite structure is fabricated and the transmission characteristics in the millimeter-wave band and X-band are measured using free-space measurement. The results confirm that the normal incident wave has a passband center frequency and stopband center frequency of 0.62 and 13.45 dB, respectively.

Middle Devonian brachiopod-hosted sclerobiont assemblage from the northern shelf of Gondwana (Mader Basin, Morocco): Diversity, colonization patterns and relation to coeval palaeocommunities

Middle Devonian (Eifelian/Givetian transition) brachiopod-hosted sclerobiont assemblage from Gondwana (Morocco, eastern Anti-Atlas, Mader Basin) has been studied for the first time. The analysis of hundreds of brachiopod shells revealed at least 26 sclerobiont taxa, making the studied palaeoecommunity one of the most diverse Middle Devonian sclerobiont assemblage reported to date. The palaeocommunity is dominated by encrusting organisms, in particular bryozoans, foraminifers, ascodictyids and microconchids, whereas bioeroders are represented by Clionolithes and Oichnus ichnospecies. As supported by microfacies, fossil preservation and the presence of encrusting Rothpletzella algae, the sclerobionts developed in a calm, euphotic, offshore marine environment situated below normal wave base. Prevalence of articulated shells without signs of either extensive mineral staining, or taphonomic alteration resulting from hydrodynamic processes, as well as preservation of some delicate encrusters ( Vinella , Rothpletzella ), indicate that the palaeocommunity did not undergo extensive time-averaging. The hosts were colonized syn vivo , as evidenced by the epibiont growth near the commissure margin, the presence of shell malformations and even embedded auloporid corals and cornulitid tubeworms. Competition for space among sclerobionts was apparently limited, as suggested by the very low number of overgrowth interactions, indicating that the shelly substrate available for colonization was abundant. The presence of the same dominant groups of sclerobionts on different host taxa indicates a lack of species-selectivity by these colonizing sclerobionts. It also suggests that the sclerobiont species pool in the environment was generally similar throughout the deposition of the sampled rock interval. As testified by the host brachiopod and bryozoan species, the sclerobiont assemblage from this locality of northern Gondwana had strong affinities with those from the southern margin of Laurussia, most likely reflecting strong connectivity between these regions provided by the South Equatorial – North Gondwana current system during the late Eifelian Kačák transgressive episode. • Diverse sclerobionts colonizing Middle Devonian brachiopods from Morocco are reported. • The assemblage is dominated by bryozoans, foraminifers, ascodictyids and microconchids. • The sclerobionts developed in a calm, euphotic, offshore environment below normal wave base. • The sclerobionts had strong affinities with assemblages inhabiting southern margin of Laurussia. • Their dispersion was enhanced during the late Eifelian Kačák transgressive episode.

Variability of Shoreline Water Levels on an Atoll in the Maldives

AbstractMany atolls in tropical oceans are under the threat of sea‐level rise. Mitigation planning requires reliable estimates of increasing wave runup in response to sea‐level rise and changes in wave climate. However, shoreline dynamics on reef‐lined coasts, particularly the effect of low‐frequency waves, are not yet fully understood. Herein, we present a field study on the southernmost atoll of the Maldives to clarify the variability of shoreline water levels driven by waves and tides. The atoll is located just south of the equator and has a moderate wave climate; it is occasionally impacted by long‐distance swells from the South Indian Ocean. Wave evolution on a reef‐lined coast was observed in situ for a period of seven months. The shallow water depth tightly constrains reef‐flat waves under normal wave conditions; however, this constraint is broken under extreme conditions by low‐frequency waves generated from long‐period swells. Particularly, very low‐frequency waves (&lt;0.005 Hz) are amplified via wave resonance over the reef platform and significantly contribute to shoreline motions. Our observation of shoreline motions confirmed that, under energetic conditions, extreme wave run‐ups are characterized by swell run‐ups riding on crests of low‐frequency waves. A combined approach of observations and analytical modeling revealed the long‐term variability of shoreline water levels, highlighting the stochastic nature of extreme water levels influenced by a joint probability of far‐field swells and high tides. Our results suggested that extreme shoreline water levels would increase at a significantly higher rate than sea‐level rise in the future.

Quasi-Optical Theory of Relativistic Cherenkov Oscillators and Amplifiers with Oversized Electrodynamic Structures

Using the quasi-optical approach, we investigate wave propagation along the periodically corrugated surfaces and their interaction with rectilinear relativistic electron beams (REBs). At the periodical structure, the field can be expanded into a series of spatial harmonics, which, in the case of shallow corrugations, represent paraxial wavebeams with mutual coupling described within the method of effective surface magnetic currents. We present the dispersion equation for the normal waves. Two limit cases can be recognized: in the first one, the frequency is far from the Bragg resonance and the wave propagation can be described within the impedance approximation with the field presented as a sum of the fundamental slow wave and its spatial harmonics. In the interaction with a rectilinear REB, this corresponds to the convective instability of particles’ synchronism with the fundamental (0th) or higher spatial harmonics (TWT regime), or the absolute instability in the case of synchronism with the −1st harmonic of the backward wave (BWO regime). In the latter case, at the frequencies close to the Bragg resonance, the field is presented as two antiparallel quasi-optical wavebeams, leading to the absolute instability used in the surface-wave oscillators operating in the π-mode regime. Based on the developed theory, we determine the main characteristics of relativistic Cherenkov amplifiers and oscillators with oversized electrodynamical systems. We demonstrate the prospects for the practical implementation of relativistic surface-wave devices in submillimeter wavebands.

A 3D boundary element method for analysing the hydrodynamic performance of a land-fixed oscillating water column device

In this work, the theoretical hydrodynamic performance of an onshore Oscillating Water Column (OWC) device, subjected to normal wave incidence, is investigated. Based on linear surface-wave theory, the full solution of the boundary value problem (BVP) is obtained by using a three-dimensional (3D) boundary element method (BEM) with nine-noded quadrilateral elements. The method of subdomains is used to solve the BVP by applying the BEM separately to each of its regions, and the continuity of velocity potential and flux are used to match the problem. The capture width, hydrodynamical coefficients and free surface elevations are analysed for different OWC geometric parameters of the chamber. Numerical results for the hydrodynamic performance were found to be in good agreement with cases reported elsewhere. The findings show that the chamber configuration and the linearized air compressibility have a significant impact on the capture width bandwidth, the resonant frequency and the free surface elevation within the chamber.

Aharonov–Bohm (AB) flux and thermomagnetic properties of Hellmann plus screened Kratzer potential as applied to diatomic molecules using Nikiforov–Uvarov-Functional-Analysis (NUFA) method

In this work, we study an approximate bound state solution of a 2D Schrodinger equation under the influence of external magnetic and Aharonov–Bohm (AB) fields with Hellmann plus screened Kratzer potential (HPSKP) using the Nikiforov–Uvarov-functional- analysis method (NUFA). We obtained the normalised wave function expressed in terms of the Jacobi polynomial. The energy spectra were also obtained in closed form and used to study the energy levels of hydrogen and chromium hydride molecules. The partition function was evaluated using Poisson’s summation approach while other thermomagnetic properties such as free energy, mean energy, entropy, heat capacity, magnetisation, magnetic susceptibility, persistent current at zero and finite temperatures were evaluated analytically.

Dynamics, Evolution, and Facies Preservation of a Microtidal Chenier Plain, Joal-Fadiouth (Senegal, West Africa)

Youm, C.I.; Morales, J.A.; Doumbouya, M.F.; Garcia-Villalba, E.; Sow, I.S., and Sow, E., 2023. Dynamics, evolution, and facies preservation of a microtidal chenier plain, Joal-Fadiouth (Senegal, West Africa). Journal of Coastal Research, 39(2), 257–265. Charlotte (North Carolina), ISSN 0749-0208. Cheniers are coarse sediment ridges formed above finer sediments deposited on a tidal flat, the origin and development of which have traditionally been attributed to storm waves. Joal-Fadiouth is a microtidal system located on the southern coast of Senegal (West Africa). This system presents a succession of sandy and shelly ridges displaying a facies architecture consistent with a chenier plain facies model. This study combines aerial orthophotographs and sediment cores to interpret the sedimentary dynamics and facies of the chenier plain under analysis. The genesis of the last active chenier is related to the arrival of sand from the frontal ebb-tidal delta. Breaching processes occurred in the ebb delta, inducing the abandonment of the frontal lobe by the ebb-tidal currents. Fair-weather waves rework the sand from the frontal lobe, causing a migration of the sand in a manner similar to the formation of a typical nearshore swash bar. In Joal-Fadiouth, these bars soar and migrate over a tidal flat through the action of normal waves during spring high tides. Relict cheniers present shelly gravel sediments coarser than those observed in active cheniers. Thus, the final stage of stabilization of cheniers was attributed to the action of more energetic storm waves. The cheniers that accumulate during the action of ordinary and continuous processes tend not to persist, and only the coarsest cheniers formed during high-energy events finally remain in the sedimentary record. In addition to discussing the preservation of active coastal forms, this work is of regional interest, given that so far there has been only one work on cheniers in West Africa since 1989.

The 1:20 scaled hydraulic model test and field experiment of barge-type floating offshore wind turbine system

Objective of this study is to develop a barge-type floating offshore wind turbine (FOWT) in order to face extreme environmental conditions in western Taiwan offshore water area. The prototype of FOWT considered here consists of (1) NERL 5 MW wind turbine, (2) a single steel column with a hub height of 90 m above sea level, (3) a square barge-type floating platform equipped with a damping pool and heave plate to improve the stability of the floating foundation, (4) catenary mooring system using anchor chain, and installation at a water depth of 70 m in the western Taiwan offshore water area.In order to verify the feasibility of the concept, a 1/20 scale model of the FOWT prototype was used by conducting hydraulic model tests in the large flume (300m × 5m× 5m) at Tainan Hydraulics Laboratory (THL), National Cheng Kung University (NCKU) and field experiments at the Anping Harbor. Hydraulic model tests include (1) regular wave test, with normal wave period from 5.7sec to 8.9sec, and long wave period from 9 s to 14sec. (2) irregular wave test, including normal sea condition, northeast monsoon sea condition, ten-year return period typhoon wave condition, and 50-year return period typhoon wave condition. Moreover, investigation of wind speed, wind direction, wave height, dynamic motion of FOWT, mooring tension, and rotor speed were conducted in the field experiment.After examining the motion of the barge-type offshore floating wind turbine, it was found that the pitch and the roll motions could satisfy the DNV standard. The tension of the mooring line did not exceed the minimum breaking load (MBL), which indicating the good stability of the barge-type FOWT proposed by this study.

Analysis of embankment underlain by elastic half-space: 2.5D model with paralongitudinal approximations to the half-space

This article presents a set of close approximations to model an elastic half-space supporting an embankment, which are evaluated in the context of phase velocity spectra, i.e. in terms of the normal wave propagation modes of the embankment-half-space system. The ultimate, intended target of these approximations is in the modeling of vertically-acting loads that may travel over the embankment with some prescribed, constant longitudinal speed. The proposed approximations are analogous to the well-known paraxial approximations that closely mimic a half-space terminating at a plane boundary, but differ from these in that the approximations herein aim at properly modeling not the waves with near normal incidence to the half-space, but waves which propagate at shallow, grazing angles along the longitudinal direction of load motion. Thus, these can be referred to as paralongitudinal approximations. The resulting expressions allow for a very effective simulation of the system at hand for loads moving with subcritical speed and solved in the context of a 2.5D solution method. Such 2.5D formulation considers a continuous model in the longitudinal direction and a discrete model in transverse planes.

Detection of a diastolic heart sound in children and young adults using high-frame-rate echocardiography

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Colin"s Kids, Inc. PO Box 93 Hopewell, NJ 08525 Introduction The auscultatory finding of a fourth heart sound (S4) is clinically associated with a pathologic decrease in left ventricular compliance, but may be seen in healthy children by phonocardiography. High-frame-rate difference imaging (HFRDI) has demonstrated several propagating myocardial phenomena in the left ventricular (LV) lateral wall throughout the cardiac cycle, including during diastole. We hypothesize that these visualized wave phenomena correlate with physiologic and pathologic heart sounds. Purpose Using HFRDI, we sought to define the characteristics of a LV lateral wall late diastolic wave in healthy children and young adults. Methods HFRDI was obtained from the apical 4-chamber view with synchronized electrocardiogram (ECG) on the T5 system (Phased Array Research Scanner) acquiring images for this study between 587 and 1174 frames per second (depending on participant imaging characteristics). In addition, tissue Doppler images were acquired with synchronized ECG and phonocardiography (PCG) on a commercial ultrasound machine (Figure 1). Timing events were measured from the QRS onset on the ECG tracing. An S4 wave correlate was defined by meeting the following criteria: 1) occurring after the P wave on ECG; 2) at or after the onset of a’ on TDI; 3) occurring during the PCG S4; and 4) occurring prior to the S1 wave complex. The timing of the S4 wave in HFRDI was measured from the onset of QRS to the first appearance of the wave, and the wave velocity was calculated by measuring the length of the lateral wall and counting temporally calibrated image frames while the wave was visible. Results Nine healthy volunteers completed the imaging protocol with a median age of 20 years (range 6 – 22 years). A single, distinct late diastolic HFRDI wave was seen in all participants propagating from apex to base of the lateral LV free wall. This wave met the defined criteria to be a visual correlate of S4 in all participants. Measurements of correlated events are presented in Table 1. S4 propagating velocity was 2.96 ± 1.8 m/sec and occurred 25 ± 18 msec prior to the QRS onset. There is a strong positive correlation between age and S4 velocity [r(7) = 0.76, p = 0.019]. Conclusion The S4 heart sound can be reliably visualized by high frame rate imaging and has similar characteristics in healthy children and young adults. Further definition of normal and abnormal S4 wave characteristics may lead to a novel tool in defining LV diastolic function. Abstract Table 1 Abstract Figure 1

Design of a low-RCS circularly polarized metasurface array using characteristic mode analysis

In this paper, a novel design strategy for a circularly polarized metasurface antenna array that integrates low scattering and well-behaved radiation is proposed. Firstly, based on the Jerusalem cross-shaped patch, a metasurface element with 180° reflection phase difference under orthogonal normal incident waves is designed. The characteristic mode theory is utilized to analyze the metasurface element mode to excite the linear polarization radiation. Then, the metasurface antenna elements are arranged orthogonally in a 2×2 subarray and fed with a 90° phase difference, which achieves high port isolation, better circular polarization radiation and low scattering performance. Finally, the 4×4 array is fabricated and measured, and the good agreement between simulation and measurement verifies the effectiveness of the design method.

INSIGHTS FROM FOSSIL FISH TAPHONOMY INTO THE DEPOSITIONAL ENVIRONMENT OF THE LOWER MILWAUKEE FORMATION (BERTHELET MEMBER, LATEST MIDDLE DEVONIAN)

ABSTRACT The fossiliferous, argillaceous dolostone of the latest Middle Devonian (Givetian) Milwaukee Formation contains abundant disarticulated fish skeletal elements. This study refines depositional environment reconstruction of the Milwaukee Formation through taphonomic analysis of this fish assemblage. Robust skeletal elements of placoderm grinding teeth, fin spines, and armored plating dominate the assemblage. Specimens display variation in taphonomic attributes including color, luster, corrasion (chemical corrosion and/or physical abrasion), presence of pyrite and phosphate permineralization, and epibionts. Rare occurrences of teeth belonging to osteichthyan fish are also taphonomically variable. Associated invertebrates are diverse and include abundant cephalopod internal molds and pyritized brachiopods often randomly oriented in shell hashes. In sum, these observations suggest deposition on a marine shelf between normal and storm wave base. During low-energy background periods, fish plates exposed on the seafloor would undergo initial disarticulation, epibiont attachment, and color- and luster-altering corrasion and phosphatization. Buried skeletal elements were ‘protected' from epibiont attachment and corrasion, but occasional low oxygen conditions in the substrate led to early diagenetic pyrite permineralization. Periodic high-energy storm events were responsible for complete disarticulation as well as reworking and reexposure of buried skeletal elements (and burial of others), resulting in a time-averaged assemblage with a wide range of taphonomic attributes. Robust placoderm skeletal elements were best suited to survive fossilization in this setting and therefore the placoderm-dominated fossil assemblage appears to be an artifact of taphonomic processes and energy of the depositional environment.

Transcutaneous Electrical Acustimulation Ameliorates Motion Sickness Induced by Rotary Chair in Healthy Subjects: A Prospective Randomized Crossover Study

ObjectivesMotion sickness (MS) is a common physiological response to real or virtual motion. The purpose of this study was to investigate the effects of transcutaneous electrical acustimulation (TEA) on MS and the underlying mechanisms in healthy subjects. Materials and MethodsA total of 50 healthy participants were recruited and randomly assigned into two groups to complete two separate sessions in a crossover study. A Coriolis rotary chair was used as a model to provoke severe MS. The total tolerable rotation time and Graybiel scoring scale were recorded. Gastric slow waves were detected by electrogastrogram. The autonomic nervous function, including the vagal activity, was evaluated by the analysis of heart rate variability derived from the electrocardiogram recording. The serum levels of arginine vasopressin (AVP) and norepinephrine (NE) were examined. ResultsOf note, 22 participants in TEA and only 11 participants in the sham-TEA session completed the entire five-rotation MS stimuli (p = 0.019). TEA significantly prolonged the total tolerable rotation time of MS stimuli (220.4 ± 11.59 vs 173.6 ± 12.3 seconds, p < 0.001) and lowered MS symptom scores (12.56 ± 2.03 vs 22.06 ± 3.0, p < 0.001). TEA improved the percentage of normal gastric slow waves, compared with sham-TEA (56.0 ± 2.1% vs 51.6 ± 2.0%, p = 0.033). TEA also significantly enhanced vagal activity compared with sham-TEA (0.41 ± 0.02 vs 0.31 ± 0.02, p < 0.001). In addition, the increased serum levels of AVP and NE on MS stimulation were markedly suppressed by TEA treatment, compared with sham-TEA (AVP, 56.791 ± 4.057 vs 79.312 ± 10.036 ng/mL, p = 0.033; NE, 0.388 ± 0.037 vs 0.501 ± 0.055 ng/mL, p = 0.021). ConclusionsNeedleless TEA is a potent therapeutic approach for severe MS, as it increases participants' tolerance and ameliorates MS symptoms, which may be attributed to the integrative effects of TEA on autonomic functions and neuroendocrine balance.