Doppler Profiles Research Articles

Thermal Doppler Broadening of Spectral Emissions in Space and Astrophysical Plasmas

Abstract The paper develops analytical modeling of thermal Doppler broadening of spectral profiles for particle populations described by kappa distributions, in the absence or presence of potential fields. The kappa distribution provides a straightforward replacement for the Maxwell distribution, that is, a generalization for describing systems characterized by local correlations among their particles, commonly found in space and astrophysical plasmas. The corresponding Voigt profiles are derived by convoluting the thermal and natural/collisional Lorentzian profiles. The kappa velocity distributions are employed to derive the thermal Doppler and Voigt profiles, while the kappa phase-space distributions in the presence of potential fields that depend on the position vector, are used to derive their respective differential profiles. We focus on attractive power-law potentials (oscillation-type, gravitational-type, and angular potentials), and study the variations of the produced Voigt differential profiles in detail. The developed formulations and guidelines provide a useful and statistically well-grounded “toolbox” for future reference in data analyses, simulations, analytical modeling, and theories of spectroscopy and related subjects of space and astrophysical plasmas.

Effects of oral trazodone on echocardiographic and hemodynamic variables in healthy cats.

The purpose of this study was to evaluate the effects of oral trazodone on echocardiographic variables, heart rate (HR) and blood pressure (BP) in healthy cats. Client-owned domestic cats between 2 and 8 years of age were recruited. Cats were considered healthy based on physical examination, complete blood count, blood chemistry profile, urinalysis, total thyroxine concentration, non-invasive BP measurement by Doppler method and a screening transthoracic echocardiogram with simultaneous electrocardiogram. Echocardiographic variables assessed pre-trazodone and 90-120 mins post-trazodone (50 mg PO) included left ventricular internal diameter in systole and diastole, interventricular septal and left ventricular free-wall thickness in systole and diastole, left atrial size, left auricular function and left ventricular diastolic function assessed by spectral Doppler transmitral and pulmonary venous flow velocities, and tissue Doppler profiles. Mean echocardiographic and hemodynamic variables were calculated for pre- and post-trazodone examinations for each cat. Pre- and post-trazodone variables were analyzed with a paired t-test with significance set at P <0.05. Twelve healthy cats were evaluated. Trazodone was administered to all cats and a sedative effect was observed. There were no clinically significant differences in any echocardiographic variables post-trazodone administration. Systolic BP was significantly decreased after trazodone (P = 0.001) with no significant change in HR. Trazodone did not alter echocardiographic variables, in a clinically relevant manner, in this group of healthy cats. Trazodone may aid in obtaining transthoracic echocardiograms without affecting HR or echocardiographic variables but may significantly lower BP in healthy cats.

A Comprehensive Update on Stillbirth Prevention: from Preconception to Postpartum, Individuals to Public Health Administrations

Stillbirth is a devastating event for the pregnant woman, families, and care providers alike. No preventable stillbirths should be tolerated, no matter how low the incidence is. The rate of reducing stillbirth rate is less than satisfactory and warrants continued efforts. Indeed, massive researches from all specialties bloomed in recent years. Some interventions are with good evidence and feasible to be practiced, while others are preliminary but exciting to be investigated further. The purpose of this review is a comprehensive overview of the recent studies on stillbirth prevention. An emphasis is placed on novel ideas or areas to be improved on that might interest prospective readers. For pregnant women, optimized healthy lifestyle including body weight, blood sugar, and blood pressure control is warranted. Vigilance on fetal movement is important for detecting fetal distress. Sudden vigorous movement means no less than reduced movement and should prompt timely evaluations. Sleep in supine position compromises maternal vena cava and poses increased stillbirth risks; thus, mothers are advised to sleep on their left side. For health professionals, biomarkers are studied to detect early placental insufficiency. Doppler velocimetry, fetal cardiotocography, and biophysical profile are helpful in evaluating fetal well-being but require adequate training and careful interpretation. Timely iatrogenic delivery is effective in lowering perinatal deaths but should be balanced against newborn prematurity. Precision medicine, utilizing genetic studies, microarrays to analyze causes of death or fetal hypoxia severity in utero is promising in filling the knowledge gaps about stillbirth. Special effort should be allocated to bereavement services, follow-up clinics, and social support to minimize the psychological impact on stillbirths. Moreover, care bundles that set specific goals, algorithms, including stillbirth investigations and cause classifications should be implemented, followed by auditing and data analysis. In the long run, health promotion in women by empowerment through gender equality and access to medical resources should be strived for. Stillbirth prevention is a work undone but has received ongoing attention and massive research efforts. Individuals, healthcare providers, and policy makers alike should stay interested and up to date.

A Flexible Millimeter-Wave Radio Channel Emulator Design With Experimental Validations

A millimeter-wave (mm-wave) channel emulator (CE) is an essential tool for air-interface testing of the upcoming mm-wave communication systems. A flexible CE, which is capable of frequency setting from sub-6 GHz to mm-wave bands and flexible system bandwidth setting, is highly desirable. This is due to the fact that potential frequency bands and system bandwidths are undecided for mm-wave systems and it is likely that multibands with scalable system bandwidths will be supported. In this communication, a frequency-extension scheme based on frequency up-and-down conversion and a novel bandwidth enhancement scheme based on the band-combining principle are proposed to upgrade the existing sub-6 GHz CE to meet the requirements in the mm-wave CE design. The designed mm-wave CE is experimentally validated, where the measured Doppler and delay profiles agree well with the target ones. Moreover, the beamforming validation measurements showed that excellent gain and phase control of the mm-wave CE output ports can be realized.

Temperature and pressure dependence of the line shape at λ = 763 nm in oxygen concentration detection

Gas line shape is determined by the Voigt profile, which is the convolution of Lorentz and Doppler profiles. The calculation amount in the Voigt profile is much larger than that in the two other profiles, and an approximate Lorentz or Doppler profile is generally used in gas concentration detection via tunable laser absorption spectroscopy. The normalized peak ratio and error function are introduced to compare the approximating effect of the two profiles. The normalized peak ratio value is simulated for Doppler profile and Lorentz profiles over a variable temperature and pressure, respectively. The 10%, 5% and 2.5% error functions for pressure versus temperature are obtained for the two profiles. Oxygen at a wavelength of 760 nm is used to demonstrate the simulation results. The presented method of investigating line shapes can be applied to other gas spectrum lines.

Leveraging Audio Signals for Early Recognition of Inattentive Driving with Smartphones

Real-time driving behavior monitoring is a corner stone to improve driving safety. Most of the existing studies on driving behavior monitoring using smartphones only provide detection results after an abnormal driving behavior is finished, not sufficient for driver alerting and avoiding car accidents. In this paper, we leverage built-in audio devices on smartphones to realize early recognition of inattentive driving events including Fetching Forward , Picking up Drops , Turning Back , and Eating or Drinking . Through empirical studies of driving traces collected in real driving environments, we find that each type of inattentive driving event exhibits unique patterns on Doppler profiles of audio signals. This enables us to develop an E arly R ecognition system, ER , which can recognize inattentive driving events at an early stage and alert drivers timely. ER employs machine learning methods to first generate binary classifiers for every pair of inattentive driving events, and then develops a modified vote mechanism to form a multi-classifier for all four types of inattentive driving events, for atypical inattentive driving events along with other driving behaviors. It next turns the multi-classifier into a gradient model forest to achieve early recognition of inattentive driving. Through extensive experiments with eight volunteers driving for about two months, ER can achieve an average total accuracy of 94.80 percent for inattentive driving recognition and recognize over 80 percent inattentive driving events before the event is 50 percent finished.

Doppler Profile Tracing Using MPCF on MU Radar and Sodar: Performance Analysis

Wind profilers (WPs) are ground-based pulsed Doppler radars operating in the UHF/very high frequency (VHF) bands. They use backscatter from clear-air turbulence as a tracer of background wind in the troposphere and up to mesosphere. Wind profiling systems range from large research radar systems to smaller operational units. In recent times, multiparameter cost function (MPCF) has emerged as a computationally efficient Doppler profile estimation method. It has been claimed that the MPCF method can be easily migrated to any vertically sounding clear-air wind profiling system that works in Doppler beam swinging mode. In order to investigate this claim, MPCF was applied to the following wind profiling systems: the middle and upper atmosphere (MU) radar, located at Shigaraki, Japan, which is an active phased array VHF radar system with 475 transceivers, and Doppler sodar, located at Pune, India, which uses acoustic frequency to obtain echoes in the planetary boundary layer. Both these systems are complementary in the sense that they cover ranges from ground to about 80 km. During the experimentation, the MPCF algorithm did not need any change of parameters except the matching of the data reading formats. The results of MPCF on the MU radar were validated with Radiosonde data. These results indicate that the MPCF works seamlessly on all types of WP systems irrespective of the carrier, range, and radar type.

Comparison Between Duplex Ultrasound and Multigate Quality Doppler Profile Software in the Assessment of Lower Limb Perforating Vein Direction

The aim was to assess more accurately the net flow of the lower limb perforating veins (PVs). This was an observational prospective study. Two hundred and twenty one limbs with chronic venous disease (C1-6EpAs,pPr) of 193 patients underwent a duplex ultrasound (DUS). All identified PVs were scanned also by means of quality Doppler profile (QDP) multigate analysis in order to determine their net inward and outward flow direction. A comparison between the traditional pulsed wave Doppler analysis and QDP was performed to detect potential discrepancy between the traditional definition of PV incompetence and a net outward flow. The DUS investigation identified 774PVs. Only 7.7% of the PVs showed an outward flow lasting more than 500ms. Among the PVs showing a longer than 500ms outward flow, QDP assessment revealed net outward flow in only 84% of the PVs along the thigh and in 28.6% along the lower leg. Among the PVs showing a shorter than 500ms outward flow, QDP assessment reported a net outward flow in 2.4% of the PVs along the thigh and in 47.3% of those along the lower leg. The sensitivity of an outward flow lasting more than 500ms in detecting an actual net outward flow was 13.9% (9-20.1%). The specificity of an outward flow lasting less than 500ms in detecting a net inward flow was 96.4% (93.2-98.3%). A lack of overlap exists between the finding of a PV outward flow lasting more than 500ms and the net outward flow of the same vessel. The traditional definition of PV incompetence is challenged by the reported data and further investigations are required to identify a gold standard assessment.

Geometry-Based Statistical Modeling of Non-WSSUS Mobile-to-Mobile Rayleigh Fading Channels

In this paper, we present a novel geometry-based statistical model for small-scale non-wide-sense stationary uncorrelated scattering (non-WSSUS) mobile-to-mobile (M2M) Rayleigh fading channels. The proposed model builds on the principles of plane wave propagation to capture the temporal evolution of the propagation delay and Doppler shift of the received multipath signal. This is different from existing non-WSSUS geometry-based statistical channel models, which are based on a spherical wave propagation approach, that in spite of being more realistic is more mathematically intricate. By considering an arbitrary geometrical configuration of the propagation area, we derive general expressions for the most important statistical quantities of nonstationary channels, such as the first-order probability density functions of the envelope and phase, the four-dimensional (4-D) time-frequency correlation function (TF-CF), local scattering function (LSF), and time-frequency-dependent delay and Doppler profiles. We also present an approximate closed-form expression of the channel's 4-D TF-CF for the particular case of the geometrical one-ring scattering model. The obtained results provide new theoretical insights into the correlation and spectral properties of non-WSSUS M2M Rayleigh fading channels.

Lorentz–Doppler profiles of hydrogen/deuterium lines for magnetic fusion: analytical solution for any angle of observation and any magnetic field strength

We extend the analytical results for the Lorentz–Doppler profiles of highly-excited hydrogen/deuterium spectral lines for the arbitrary strength of the magnetic field B, obtained in a paper by one of us, Oks (2015 J. Quant. Spectr. Rad. Transfer 156 24), for observations parallel or perpendicular with respect to B, to arbitrary angles of the observation ψ. We study the evolution of the effect of the suppression of the π-components (compared to the σ-components) as the angle of the observation ψ decreases from 90°, i.e., as ψ decreases from the value, at which this counterintuitive effect was discovered in the paper quoted above. We show that the suppression of the π-components (compared to the σ-components) occurs at the perpendicular or close to the perpendicular direction of observation (with respect to the magnetic field B), but disappears at lower values of the angle of the observation. Our results should be important, e.g., for spectroscopic diagnostics of edge plasmas of various magnetic fusion devices around the world. Another finding is that the width of the Lorentz–Doppler profiles is a non-monotonic function of the magnetic field for observations perpendicular to B, which is yet another counterintuitive result.

A Platform for Free-Weight Exercise Monitoring with Passive Tags

Regular free-weight exercise helps to strengthen natural movements and stabilize muscles that are important to strength, balance, and posture of human beings. Prior works have exploited wearable sensors or RF signal changes for activity sensing, recognition, and counting, etc.. However, none of them have incorporated three key factors necessary for a practical free-weight exercise monitoring system: recognizing free-weight activities on site, assessing their qualities, and providing useful feedbacks to the bodybuilder promptly. Our FEMO system provides an integrated free-weight exercise monitoring service that incorporates all the essential functionalities mentioned above. FEMO achieves this by attaching passive RFID tags on the dumbbells and leveraging the Doppler shift profile of the reflected backscatter signals for on-site free-weight activity recognition and assessment. The rationale behind FEMO is 1) since each free-weight activity owns unique arm motions, the corresponding Doppler shift profile should be distinguishable to each other. 2) Doppler profile of each activity has a strong spatial-temporal correlation that implicitly reflects the quality of the activity. We implement FEMO with COTS RFID devices and conduct a two-week experiment. The preliminary result from 15 volunteers demonstrates that FEMO can be applied to a variety of free-weight activities, and provide valuable feedbacks for activity alignment.

P29.03: Assessment of fetal myocardial performance index in routine follow‐up of twin pregnancy: feasibility study

To demonstrate the feasibility of fetal left-ventricular myocardial performance index (LV-MPI) assessment in routine follow-up of twin pregnancy. Qualitative assessment of LV-MPI measures was performed prospectively by two gynecologist-obstetrician operators on mono and dichorionic twin pregnancies managed between March and July 2016 in a single tertiary referral fetal medicine unit. Each measure was retrospectively scored by 2 pediatric cardiologists using a 10-points scale based on 7 parameters. Only measures with a score ≥8/10 were validated. The LV-MPI value, the time to perform the measure and the nature of technical problems faced during the measure were also reported. Twin–twin transfusion syndrome (TTTS) pregnancies were excluded. Sixty-two measures of LV-MPI were performed on 64 fetuses from 32 consecutive twin pregnancies between 16 and 35 WG. Two (3%) measures could not be performed due to technical difficulties and 2 measures performed at 33 WG on fetuses from the same pregnancy were not validated due to an unsatisfying Doppler profile despite a correct anatomical position. All validated measures were performed in less than 5 minutes with a median LV-MPI value of 0.43 (range 0.23-0.78). The most frequently reported technical problem by operators was to obtain the proper anatomical position. LV-MPI assessment is properly and quickly achieved by trained operators without major technical problems during the follow-up of twin pregnancies. Recently published data suggest that echocardiographic findings including LV-MPI in the recipient fetus may provide substantial predictive information to assess cardiovascular and therefore global morbidity and mortality during TTTS. The present study warrants further routine evaluation of LV-MPI in TTTS severity staging.

Sub-Doppler two-photon absorption induced by the combination of a single-mode laser and a frequency comb

The two-photon transition $5S-5P-5D$ in rubidium vapor is investigated by detecting the fluorescence from the $6P_{3/2}$ state when the atomic system is excited by the combined action of a cw diode laser and a train of ultrashort pulses. The cw-laser plays a role as a velocity-selective filter and allows for a spectroscopy over a large spectral range including the $5D_{3/2}$ and $5D_{5/2}$ states. For a counterpropagating beam configuration, the response of each atomic velocity group is well characterized within the Doppler profile, and the excited hyperfine levels are clearly resolved. The contribution of the optical pumping to the direct two-photon process is also revealed. The results are well described in a frequency domain picture by considering the interaction of each velocity group with the cw laser and the modes of the frequency comb.

Dynamic Behavior of Spicules Inferred from Perpendicular Velocity Components

Abstract Understanding the dynamic behavior of spicules, e.g., in terms of magnetohydrodynamic (MHD) wave mode(s), is key to unveiling their role in energy and mass transfer from the photosphere to corona. The transverse, torsional, and field-aligned motions of spicules have previously been observed in imaging spectroscopy and analyzed separately for embedded wave-mode identification. Similarities in the Doppler signatures of spicular structures for both kink and torsional Alfvén wave modes have led to the misinterpretation of the dominant wave mode in these structures and is a subject of debate. Here, we aim to combine line- of-sight (LOS) and plane-of-sky (POS) velocity components using the high spatial/temporal resolution Hα imaging-spectroscopy data from the CRisp Imaging SpectroPolarimeter based at the Swedish Solar Telescope to achieve better insight into the underlying nature of these motions as a whole. The resultant three-dimensional velocity vectors and the other derived quantities (e.g., magnetic pressure perturbations) are used to identify the MHD wave mode(s) responsible for the observed spicule motion. We find a number of independent examples where the bulk transverse motion of the spicule is dominant either in the POS or along the LOS. It is shown that the counterstreaming action of the displaced external plasma due to spicular bulk transverse motion has a similar Doppler profile to that of the m = 0 torsional Alfvén wave when this motion is predominantly perpendicular to the LOS. Furthermore, the inferred magnetic pressure perturbations support the kink wave interpretation of observed spicular bulk transverse motion rather than any purely incompressible MHD wave mode, e.g., the m = 0 torsional Alfvén wave.

Line shapes in turbulent plasmas

The fluctuations and oscillations observed in turbulent plasmas may affect the line shapes emitted by atoms and ions. We investigate several plasma conditions for which a spectroscopic signature of plasma turbulence can be observed. Starting from the simple model of microturbulence for Doppler profile, we examine how information on turbulent fluctuations is obtained in astrophysics and magnetic fusion plasmas. We recall the potential of a formalism which expresses the measured line shape in function of the probability density function of the fluctuating plasma parameters. New calculations of hydrogen dipole autocorrelation functions and line shapes are presented for plasmas affected by strong Langmuir turbulence and nonlinear wave collapse. We propose a model using a sequence of envelope solitons for the electric field created by the wave packets and felt by the emitters, and show that the line shape may be dominated by the effect of strong Langmuir turbulence.

Estimation of Doppler Profile Using Multiparameter Cost Function Method

Wind profilers (WPs) are a special category of ground-based radar instruments used to obtain 3-D profile of wind velocity along the altitude in atmosphere. They transmit radio wave pulses in very high frequency (VHF) or ultrahigh frequency (UHF) bands in vertical and near-vertical directions. The Doppler frequency shift and the time of flight of the echo signals from each beam are measured. These data are analyzed to get the radial velocities of atmospheric targets at all the ranges. The data must be processed from at least three noncoplanar beam directions together to estimate 3-D wind profile. The signal-to-noise ratio is very low for the higher range target echoes. Also, echoes are often contaminated by nonatmospheric signals like clutter, radio frequency interference, and so on. Determining accurate wind profile, especially at higher heights, becomes a challenging task due to these factors. This paper presents a novel algorithm for the estimation of radial velocity profile by processing the set of Doppler power spectra of all range bins. The algorithm identifies prospective atmospheric echoes components. Then it forms velocity profile trails connecting five range bins. The program rejects the profile trails that show velocity change higher than a predefined limit. The remaining trails are evaluated using a specially designed multiparameter cost function (MPCF). The trails with maximum cost are selected and then connected to construct the complete Doppler profile or the radial velocity profile. The key innovation in this method is an improvised function that is created by weighted addition of two terms. The first term is proportional to the signal power, and the second term is a nonlinear function of differential wind shear. This algorithm has been tried on multiple sets of the Indian mesosphere–stratosphere–troposphere radar data and the lower atmospheric WP radar data. The performance of this method is compared with other methods, namely, the adaptive moment estimation method and fuzzy logic approach. It has been observed that the new method shows excellent consistency in extracting the Doppler profile from the power spectral data. This method requires at least 30% lesser computations compared with other methods. The results of the MPCF method showed a very good match with the data obtained from concurrently operated Global Positioning System sonde, an independent wind profiling method. This paper also shows the results on the performance improvement using power spectra from the symmetrical beams. This algorithm shows a great promise as a tool for automatic Doppler profile tracing.

지상레이다의 PT-파형 수신신호와 항공기 추적정보를 이용한 항공기 도플러 프로파일 추출

지상레이다의 PT-파형 수신신호와 항공기 추적정보를 이용한 항공기 도플러 프로파일 추출

Target Extraction and Imaging of Maritime Targets in the Sea Clutter Spectrum Using Sparse Separation

Detection and imaging of endoclutter maritime targets is a difficult problem, because the signal return of the target and the clutter overlap in both Doppler frequency and time. Consequently, traditional Doppler filtering is severely limited in terms of extracting the target signature for further processing. This letter proposes a new sparsity-based Doppler filtering and extraction paradigm for maritime radar where the different backscattered signals are separated in the endoclutter region based on their Doppler bandwidths rather than their Doppler frequencies. The novelty of this letter is successful extraction of the target profiles in the endoclutter region using the application of morphological component analysis with time-frequency transforms. Illustrative results of the proposed approach for boat Doppler profile extraction and inverse synthetic aperture image formation outperform traditional range-Doppler processing in endoclutter. The method represents a new paradigm for target detection and imaging in sea clutter.

Helicity-induced shapes of resonant four-wave mixing responses from photofragments

Doppler profiles of the Degenerate Resonant Four-Wave Mixing (DFWM) spectral responses from rapidly recoiling products of photodecomposition by plane-polarized radiation are theoretically studied. Emphasis is placed on the shapes produced by rotational helicity when orientations of the angular momenta and the recoil velocities of nascent particles are correlated. Illustrations are provided for cases when a decay of resonating states tangibly affects the helicity-induced DFWM profiles.

The effect of intraumbilical fetal nutrition via a subcutaneously implanted port system on amino acid concentration by severe IUGR human fetuses.

To determine if intrauterine intraumbilical supplementation with amino acids (AA) and glucose can improve neonatal outcome of severe growth restricted human fetuses (IUGR). Prospective pilot study of intrauterine treatment of severe IUGR fetuses [n=14, 27 weeks of gestation (range 23-31)] with cerebroplacental ratio <1, with long-term intraumbilical AA and glucose supplementation (10% of feto-placental blood volume/day) using a perinatal port system alone (n=5) or combined with hyperbaric oxygenation (n=1, HBO) vs. control group (n=8). The duration of continuous intraumbilical AA/glucose supplementation was 11 (6-13) days. Daily intravascular fetal nutrition significantly prolonged the brain sparing to delivery interval by 24 (14-33) days vs. 5.6 (2-12) days in controls. Fetal nutrition reduced blood flow resistance in the placental circulation but did not affect the Doppler profile of cerebral arteries. Higher weight gain of 113.5 (36-539) g was observed following supplementation compared to 33.3 (8-98) g in the control group (P<0.05). In spite of this, fetuses below 28 weeks of gestation did not sufficiently benefit from infused commercial AA. We found a reduced fetal plasma concentration of the essential AA histidine, threonine, lysine and arginine, and non-essential AA taurine, in severe IUGR fetuses in both groups. Long-term supplementation with a commercial AA formula led to a slight, but not significant, reduction of histidine, threonine, lysine, arginine, asparagine and glutamine. However, the concentration of tryptophan and glutamic acid slightly increased. HBO can be combined with AA supplementation via a port system. In one case, the port system was also successfully used for fetal blood transfusion. Intravascular treatment of IUGR with fetal nutrition can prolong pregnancy with severe placental insufficiency and brain sparing for many weeks. However, rather than normalizing AA concentrations, an enhanced AA imbalance was observed in IUGR fetuses following supplementation. These deviations in AA concentrations prevent the recommendation for use of commercial AA solutions for prenatal treatment of extreme preterm IUGR fetuses.