Doppler Contribution Research Articles

Detecting relativistic Doppler by multi-tracing a single galaxy population

New data from ongoing galaxy surveys, such as the Euclid satellite and the Dark Energy Spectroscopic Instrument (DESI), are expected to unveil physics on the largest scales of our universe. Dramatically affected by cosmic variance, these scales are of interest to large-scale structure studies as they exhibit relevant corrections due to general relativity (GR) in the n-point statistics of cosmological random fields. We focus on the relativistic, sample-dependent Doppler contribution to the observed clustering of galaxies, whose detection will further confirm the validity of GR in cosmological regimes. Sample- and scale-dependent, the Doppler term is more likely to be detected via cross-correlation measurements, where it acts as an imaginary correction to the power spectrum of fluctuations in galaxy number counts. We present a method allowing us to exploit multi-tracer benefits from a single data set, by subdividing a galaxy population into two sub-samples, according to galaxies’ luminosity/magnitude. To overcome cosmic variance we rely on a multi-tracer approach, and to maximise the detectability of the relativistic Doppler contribution in the data, we optimise sample selection. As a result, we find the optimal split and forecast the relativistic Doppler detection significance for both a DESI-like Bright Galaxy Sample and a Euclid-like Hα galaxy population.

Patent Forame Ovale: Contribution of Transcranial Doppler in Patient Diagnosis

Patent Forame Ovale: Contribution of Transcranial Doppler in Patient Diagnosis

Wide-angle effects in multi-tracer power spectra with Doppler corrections

We examine the computation of wide-angle corrections to the galaxy power spectrum including redshift-space distortions and relativistic Doppler corrections, and also including multiple tracers with differing clustering, magnification and evolution biases. We show that the inclusion of the relativistic Doppler contribution, as well as radial derivative terms, are crucial for a consistent wide-angle expansion for large-scale surveys, both in the single and multi-tracer cases. We also give for the first time the wide-angle cross-power spectrum associated with the Doppler magnification-galaxy cross correlation, which has been shown to be a new way to test general relativity.In the full-sky power spectrum, the wide-angle expansion allows integrals over products of spherical Bessel functions to be computed analytically as distributional functions, which are then relatively simple to integrate over.We give for the first time a complete discussion and new derivation of the finite part of the divergent integrals of the form ∫0 ∞ drrnjℓ (kr) jℓ' (qr), which are necessary to compute the wide-angle corrections when a general window function is included. This facilitates a novel method for integrating a general analytic function against a pair of spherical Bessel functions.

A Modified NLCS Algorithm for High-Speed Bistatic Forward-Looking SAR Focusing with Spaceborne Illuminator

The coupling and spatial variation of range and azimuth parameters is the biggest challenge for bistatic forward-looking SAR (BFSAR) imaging. In contrast with the monostatic SAR and translational invariant bistatic SAR (TI-BSAR), the range cell migration (RCM), and Doppler parameters of high-speed bistatic forward-looking SAR (HS-BFSAR) have two-dimensional spatial variation characteristics, which makes it difficult to obtain SAR images with satisfactory global focusing. Firstly, based on the configuration of the spaceborne illuminator and high-speed forward-looking receiving platform, the accurate range-Doppler domain expression of the echo signal is derived in this paper. Secondly, using this analytical expression, a range nonlinear chirp scaling (NLCS) is proposed to equalize the RCM and equivalent range frequency modulation (FM) rate so that they can be uniformly processed in the two-dimensional frequency domain. Next, in the azimuth processing, the proposed method decomposes the Doppler contribution of the transmitter and receiver, respectively. Then, an azimuth NLCS is used to eliminate the spatial variation of the azimuth FM rate. Finally, a range-dependent azimuth filter is constructed to achieve azimuth compression. Simulation results validate the efficiency and effectiveness of the proposed algorithm.

Adjunct Methods for the Detection of Patent Foramen Ovale: The Contribution of Transcranial Doppler and the Valsalva Manoeuvre.

A patent foramen ovale (PFO) is present in 25% of the population. In some patients, especially those without traditional stroke risk factors and with no immediately apparent cause, a cryptogenic stroke may be caused by an embolus passing through the PFO to the systemic circulation. The identification, or indeed exclusion, of a PFO is sought in these patients, most commonly using contrast-enhanced transthoracic or transoesophageal echocardiography. Another method for detecting a PFO is transcranial Doppler, which allows the detection of PFO possibly without the need for an echo laboratory, and with arguably improved sensitivity. This review will focus on transcranial Doppler detection of PFO, with a brief summary of echocardiographic techniques and the use of ultrasound contrast agents, and the role of provocations to increase diagnostic accuracy, specifically the Valsalva manoeuvre. We discuss the phases alongside the direct and indirect signs of an adequate Valsalva manoeuvre.

Multi-wavelength spectroscopic probes: biases from neglecting light-cone effects

Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. In a companion paper, we applied a Fisher analysis to forecast the expected precision on f NL and the detectability of the lensing magnification and Doppler contributions to the power spectrum. Here we assess the bias on the best-fit values of f NL and other parameters, from neglecting these light-cone effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), both individually and combined together. We conclude that lensing magnification at higher redshifts must be included in the modelling of spectroscopic surveys. If lensing is neglected in the analysis, this produces a bias of more than 1σ — not only on f NL, but also on the standard cosmological parameters.

An integrated approach based on advanced CTG parameters and Doppler measurements for late growth restriction management

BackgroundThe clinical diagnosis of late Fetal Growth Restriction (FGR) involves the integration of Doppler ultrasound data and Fetal Heart Rate (FHR) monitoring through computer assisted computerized cardiotocography (cCTG). The aim of the study was to evaluate the diagnostic power of combined Doppler and cCTG parameters by contrasting late FGR –and healthy controls.MethodsThe study was conducted from January 2018 to May 2020. Only pregnant women who had the last Doppler measurement obtained within 1 week before delivery and cCTG performed within 24 h before delivery were included in the study. Two hundred forty-nine pregnant women fulfilling the inclusion criteria were enrolled in the study; 95 were confirmed as late FGR and 154 were included in the control group.ResultsAmong the extracted cCTG parameters, Delta Index, Short Term Variability (STV), Long Term Variability (LTV), Acceleration and Deceleration Phase Rectified Slope (APRS, DPRS) values were lower in the late FGR participants compared to the control group. In the FGR cohort, Delta, STV, APRS, and DPRS were found different when stratifying by MCA_PI (MCA_PI <5th centile or > 5th centile). STV and DPRS were the only parameters to be found different when stratifying by (UA_PI >95th centile or UA_PI <95th centile). Additionally, we measured the predictive power of cCTG parameters toward the identification of associated Doppler measures using figures of merit extracted from ROC curves.The AUC of ROC curves were accurate for STV (0,70), Delta (0,68), APRS (0,65) and DPRS (0,71) when UA_PI values were > 95th centile while, the accuracy attributable to the prediction of MCA_PI was 0.76, 0.77, 0.73, and 0.76 for STV, Delta, APRS, and DPRS, respectively.An association of UA_PI>95th centile and MCA_PI<5th centile with higher risk for NICU admission, was observed, while CPR < 5th centile resulted not associated with any perinatal outcome. Values of STV, Delta, APRS, DPRS were significantly lower for FGR neonates admitted to NICU, compared with the uncomplicated FGR cohort.ConclusionsThe results of this study show the contribution of advanced cCTG parameters and fetal Doppler to the identification of late FGR and the association of those parameters with the risk for NICU admission.Trial registrationRetrospectively registered.

VP17.19: The use of three vessels and trachea view in second trimester ultrasound for the diagnosis of cardiac malformations

To determine the use of three vessels and trachea (3VT) view in fetal second trimester cardiac scanning for the diagnosis of cardiac malformations. We analysed all the second trimester ultrasounds in a terciary referring centre during 5 years (N: 10092). We performed a retrospective study of 66 women diagnosed of fetal cardiac malformations in this ultrasound scan (0.71%). The 3VT view is an ultrasound transverse plane in the upper mediastinum. The abnormalities detected were confirmed postnatally by a pediatric cardiologist, echocardiography or autopsy. 52 of the 66 fetuses (78.79%) showed an abnormal 3VT view. We classified the lesions according to the most evident abnormal ultrasound finding. Abnormal vessel size was found in 40.38%. Abnormal colour Doppler pattern with turbulent flow or reverse flow was found in five fetuses with outflow tract stenosis. Abnormal vessel alignment and arrangement was found in 3 fetuses. Abnormal vessel number was found in 7 fetus (3 fetus with two vessels instead of three and 4 fetus with four vessels instead of three). Abnormal location of vessels in relation to the trachea was found in 39.39%. This ultrasound view is very reliable in the diagnosis of an important group of critical heart defects involving the outflow tracts and the aortic arch. The three vessels and trachea view, with the contribution of colour Doppler, is a good and easy method for screening heart defects. VP17.19: Table 1.

The impact of relativistic effects on the 3D Quasar-Lyman-α cross-correlation

We study the impact of relativistic effects in the 3-dimensional cross-correlation between Lyman-α forest and quasars. Apart from the relativistic effects, which are dominated by the Doppler contribution, several systematic effects are also included in our analysis (intervening metals, unidentified high column density systems, transverse proximity effect and effect of the UV fluctuations). We compute the signal-to-noise ratio for the Baryonic Oscillation Spectroscopic Survey (BOSS), the extended Baryonic Oscillation Spectroscopic Survey (eBOSS) and the Dark Energy Spectroscopic Instrument (DESI) surveys, showing that DESI will be able to detect the Doppler contribution in a Large Scale Structure (LSS) survey for the first time, with a S/N >7 for rmin > 10 Mpc/h, where rmin denotes the minimum comoving separation between sources. We demonstrate that several physical parameters, introduced to provide a full modelling of the cross-correlation function, are affected by the Doppler contribution. By using a Fisher matrix approach, we establish that if the Doppler contribution is neglected in the data analysis, the derived parameters will be shifted by a non-negligible amount for the upcoming surveys.

Indication for Doppler evaluation in the management of intrauterine growth restriction of vascular origin in Sub-Saharan Africa

Objective: To assess the contribution of Doppler in foetal monitoring and decision-making during delivery in case of in-utero vascular growth retardation.&#x0D; Design: We conducted a retrospective cohort study from January 2015 to December 2017 in the Gynaecology and Obstetrics Department of the Yopougon University Hospital (Abidjan, Ivory Coast). It included 130 patients who gave birth in a setting of pre-eclampsia with intrauterine growth restriction (IUGR) from 28 weeks of amenorrhoea.&#x0D; Results: The average age of patients was 31years. Nulliparous (33% of our patients) and pauciparous (41% of our patients) women were the group most affected. The mean gestational age at the first Doppler examination was 32 weeks of amenorrhoea. Doppler abnormalities were 65% in uterine Doppler and 90% in umbilical Doppler. The meancerebrovascular ratio was reversed in 90% of the cases. Perinatal mortality was 22.3% (n = 29) with 21 foetal death in utero and 8 neonatal deaths. The time interval between absent end-diastolic or reverse flow velocity and in-utero foetal death was 3.8 days.&#x0D; Conclusion: Foetal and umbilical Doppler ultrasound greatly modified the management of intrauterine growth retardation related to hypertension.

Indication for Doppler evaluation in the management of intrauterine growth restriction of vascular origin in Sub-Saharan Africa

Objective: To assess the contribution of Doppler in foetal monitoring and decision-making during delivery in case of in-utero vascular growth retardation.&#x0D; Design: We conducted a retrospective cohort study from January 2015 to December 2017 in the Gynaecology and Obstetrics Department of the Yopougon University Hospital (Abidjan, Ivory Coast). It included 130 patients who gave birth in a setting of pre-eclampsia with intrauterine growth restriction (IUGR) from 28 weeks of amenorrhoea.&#x0D; Results: The average age of patients was 31years. Nulliparous (33% of our patients) and pauciparous (41% of our patients) women were the group most affected. The mean gestational age at the first Doppler examination was 32 weeks of amenorrhoea. Doppler abnormalities were 65% in uterine Doppler and 90% in umbilical Doppler. The meancerebrovascular ratio was reversed in 90% of the cases. Perinatal mortality was 22.3% (n = 29) with 21 foetal death in utero and 8 neonatal deaths. The time interval between absent end-diastolic or reverse flow velocity and in-utero foetal death was 3.8 days.&#x0D; Conclusion: Foetal and umbilical Doppler ultrasound greatly modified the management of intrauterine growth retardation related to hypertension.

Target detection approach for DRM‐based passive bistatic radar

This study discussed the problem of target detection for digital radio mondiale (DRM)-based passive bistatic radar (PBR). In the surveillance signal, the power of zero Doppler contribution (ZDC) is stronger than the echoes of weak targets. These targets can hardly be shown in the range-Doppler map of classical cross-ambiguity function (CAF). The clutter should be removed before using CAF-matched correlator. The authors utilised Doppler channel detector (CHAD) to solve the above problem for DRM-based PBR in this study. It can unify the ZDC rejection and the target detection in one process. Compared to CAF detector, the CHAD had a lower random pedestal for low Doppler frequency shifts. The results of experiment data proved the effectiveness of the CHAD for DRM-based PBR.

Study of Doppler broadening Compton scattering and cross section determination for the elements Fe, Zn, Ag, Au and Hg

To assess the contribution of Doppler broadening and examine theCompton profile, the Compton energy absorption cross sections aremeasured and calculated using formulas based on a relativisticimpulse approximation. The Compton energy-absorption crosssections are evaluated for different elements (Fe, Zn, Ag, Au and Hg)and for a photon energy range (1 - 100 keV). With using these crosssections,the Compton component of the mass–energy absorptioncoefficient was derived, where the electron momentum prior to thescattering event caused a Doppler broadening of the Compton line.Also, the momentum resolution function was evaluated in terms ofincident and scattered photon energy and scattering angle. The resultsof cross sections for the coherent and incoherent processes arecompared with theoretical values and reported values of otherresearchers. The present results are in agreement with the theoreticalvalues.

Perturbed redshifts from N -body simulations

In order to keep pace with the increasing data quality of astronomical surveys the observed source redshift has to be modeled beyond the well-known Doppler contribution. In this article I want to examine the gauge issue that is often glossed over when one assigns a perturbed redshift to simulated data generated with a Newtonian $N$-body code. A careful analysis reveals the presence of a correction term that has so far been neglected. It is roughly proportional to the observed length scale divided by the Hubble scale and therefore suppressed inside the horizon. However, on gigaparsec scales it can be comparable to the gravitational redshift and hence amounts to an important relativistic effect.

Backward-emitted sub-Doppler fluorescence from an optically thick atomic vapor

Literature mentions only incidentally a sub-Doppler contribution in the excitation spectrum of the backward fluorescence of a dense vapor. This contribution is here investigated on Cs vapor, both on the first resonance line (894 nm) and on the weaker second resonance line (459 nm). We show that in a strongly absorbing medium, the quenching of excited atoms moving towards a window irradiated under near normal incidence reduces the fluorescence on the red side of the excitation spectrum. Atoms moving slowly towards the window produce a sub- Doppler velocity-selective contribution, whose visibility is here improved by applying a frequency-modulation technique. This sub-Doppler feature, induced by a surface quenching combined with a short absorption length for the incident irradiation, exhibits close analogies with the narrow spectra appearing with thin vapor cells. We also show that a normal incidence irradiation is essential for the sub-Doppler feature to be observed, while it should be independent of the detection geometry

EP16.17: Contribution of uterine artery Doppler in the prediction of uteroplacental insufficiency

A prospective descriptive study was conducted in Department “A” of gynecology and obstetrics in the maternity centre of Tunis. We followed 50 patients, with previous pregnancy complications correlated to placental insufficiency. Patients were randomised in two groups. The first group received Aspirin. The second one received Aspirin + Enoxaparin. For each patient, uterine artery Doppler was performed in the first, second then third trimesters. We evaluated the presence of uterine artery notch. Adverse pregnancy outcomes were notified and correlated to the sonographic results. Iatrogenic events were recorded. A first trimester bilateral uterine artery notch was found in 36% of the patients. A second trimester bilateral notch was found in 18% of the cases. 20% of patients had a unilateral notch in the second trimester. 6 % (n=3) of included patients had severe pregnancy outcome (2 cases of fetal death and 1 severe pre-eclampsia) These 3 patients had persistent bilateral uterine Artery Doppler notch. Mild complications were found in 7% of cases (mild pre-eclampsia). Severe adverse pregnancy outcomes seem to be correlated to the persistence of uterine Artery Doppler Notch after the first trimester despite the use of Aspirin and enoxaparin. Uterine artery Doppler screening could be a non invasive method to predict uteroplacental insufficiency in high risk populations. Persistent bilateral uterine artery notch could predict late severe adverse pregnancy outcome. Its association with maternal characteristics study and biochemical markers could better its predictive value.

The clinical value of maternal and fetal Doppler parameters in low-risk postdates pregnancies – a prospective study

Objective: The objective of this study is to determine the clinical significance of maternal and fetal ultrasound Doppler flow indices in postdates pregnancies.Methods: This prospective study comprised 120 low-risk pregnant women beyond 40 weeks of gestation. All participants underwent Doppler assessment including of fetal middle cerebral artery (MCA), umbilical, and uterine arteries. Perinatal outcomes were recorded and evaluated for possible associations with Doppler flow values. Adverse perinatal outcomes were defined as umbilical cord arterial pH <7.1, Apgar score <7 at 5 min, neonatal admission to a neonatal intensive care unit, and emergency cesarean section due to abnormal intrapartum cardiotocogramResults: Adverse perinatal outcome rate was 17.5% (n = 21). Doppler indices of umbilical artery, MCA, uterine artery and the cerebroplacental ratio (CPR) did not differ significantly between pregnant women with and without adverse perinatal outcomes. Neonatal birth weight was found to correlate negatively with umbilical artery Doppler indices, including the peak systolic to end diastolic ratio (p = .04), the resistance index (p = .02), and the pulsatility index (p = .01). Doppler values of the uterine artery, MCA and CPR did not correlate with neonatal birth weight.Conclusions: The contribution of maternal and fetal ultrasound Doppler to the prediction of adverse perinatal outcomes in low-risk postdates pregnancies is low. Hence, performing routine Doppler examination as part of postdates pregnancy assessments is unlikely to yield significant clinical benefit.

A general relativistic signature in the galaxy bispectrum: the local effects of observing on the lightcone

Next-generation galaxy surveys will increasingly rely on the galaxy bispectrum to improve cosmological constraints, especially on primordial non-Gaussianity. A key theoretical requirement that remains to be developed is the analysis of general relativistic effects on the bispectrum, which arise from observing galaxies on the past lightcone, as well as from relativistic corrections to the dynamics. As an initial step towards a fully relativistic analysis of the galaxy bispectrum, we compute for the first time the local relativistic lightcone effects on the bispectrum, which come from Doppler and gravitational potential contributions. For the galaxy bispectrum, the problem is much more complex than for the power spectrum, since we need the lightcone corrections at second order. Mode-coupling contributions at second order mean that relativistic corrections can be non-negligible at smaller scales than in the case of the power spectrum. In a primordial Gaussian universe, we show that the local lightcone projection effects for squeezed shapes at z ∼ 1 mean that the bispectrum can differ from the Newtonian prediction by ≳ 10% when the short modes are k ≲ (50 Mpc)−1. These relativistic projection effects, if ignored in the analysis of observations, could be mistaken for primordial non-Gaussianity. For upcoming surveys which probe equality scales and beyond, all relativistic lightcone effects and relativistic dynamical corrections should be included for an accurate measurement of primordial non-Gaussianity.

A Unifying Approach for Disturbance Cancellation and Target Detection in Passive Radar Using OFDM

—This paper addresses the problem of mobile target detection in multipath scenarios with a passive radar using DVB-T transmitters of opportunity. For such emissions, it has been shown the interest in implementing mismatched correlators, reducing both the zero Doppler contribution (ZDC) masking effects and the false alarm rate. A very efficient mismatched reference signal is obtained with the reciprocal filter (or inverse filter) which consist in a modulus frequential equalization of the transmitted signal. We propose here to revisit the reciprocal filter based correlator and to reinterpret it as a so-called Doppler channel detector (CHAD). This new interpretation allows a direct rejection of the ZDC, unifying in one and the same step the main disturbance mitigation and the detector construction. We provide a statistical theoretical study of the performance and a comparison with the matched correlator i.e. the classical cross-ambiguity function (CAF). We demonstrate that CHAD has a random pedestal (a clutter floor level) significantly lower than that of the classical CAF for low Doppler frequency shifts. Numerical experiments on simulated and real data as well validate the mathematical derivations. Index Terms—Passive bistatic radar (PBR), passive covert radar (PCR), passive coherent location (PCL), digital video broadcasting-terrestrial (DVB-T), orthogonal frequency division multiplexing (OFDM), cross-ambiguity function (CAF), mismatched filter, reciprocal filter, clutter.

EP11.01: Contribution of colour Doppler according to the type of malformation

EP11.01: Contribution of colour Doppler according to the type of malformation