Abstract: Tissue Doppler imaging (TDI) mode of echocardiography plays a crucial role in diagnosing several cardiac conditions by recording the myocardial contraction velocities. To mitigate the need of experts for performing echocardiography, several studies have proposed the use of Seismocardiogram as an easier alternative to measure the cardiac timings. However, exact correlation with tissue Doppler measured cardiac velocities has not been explored. Moreover, most of the applications only use single channel contact accelerometers on the chest, thus limiting their utility. In this work, we propose the use of a novel airborne ultrasound based surface motion camera (SMC) for non-contact multichannel recording of cardiac induced surface velocities from the chest. Validation study was conducted on 30 healthy subjects with simultaneous recordings of single channel ECG along with the chest surface velocities followed by clinical Echocardiography. The SMC recorded surface velocity waveforms show correlation similarity of over 0.6 with Tissue Doppler velocity waves extracted from the echocardiographic images. Discrete time warping based distance analysis was also performed to quantify their morphological similarity. Quantitative parameters including the peak systolic velocity and amplitude ratio extracted from the chest recordings show a linear correlation (R² greater than 0.8) with that of the TDI values. Additionally, multichannel recording allows visualization of the velocity profiles on the chest and efficiently captures the spatial variations for left ventricular and septal sites. Hence, this new modality shows the potential to be a vital diagnostic technique for non-contact and robust monitoring of the cardio-mechanical functions.

Abstract: Oceanic domains form via the break-up of the continental lithosphere resulting from extensional tectonic processes that eventually create passive margins. Whether active rifting and subsequent volcanic break-up occur within the oceanic lithosphere remains ambiguous. New seismic reflection data from the southern Bay of Bengal, where multiple mantle plumes were active during the late Cretaceous, provide visual evidence for resolving this issue. The studied seismic profile reveals an ∼300-km-wide anomalous crustal domain characterized by basement highs, irregular Moho depth fluctuations, and a thick pile of well-organized upper crustal dipping reflections. These features resemble those of volcanic passive margins, i.e., stacked volcanoclastic layers, seaward-dipping reflectors, underplating and failed rifting centers. Here, we document a similar setting within an intraoceanic domain, which is consistent with the active rifting model, with an excess magma supply presumably associated with active mantle upwelling. The structures described in the present study require a multistage dynamic process during local impingement of the northward-drifting Indian oceanic lithosphere by mantle upwelling, with a transition from thermal doming, intense volcanic eruptions and magmatic underplating, to lithospheric extension and necking, and finally to an incipient but failed rift. The volcanism initiated at ∼84–85 Ma, and volcanics were emplaced on young oceanic lithosphere with an age of ∼7–8 Ma. The active mantle upwelling that promoted the intraoceanic rifting was likely driven by a weak or pulsed branch of the Kerguelen Plume, which is also involved in producing the Ninety-East Ridge. These findings help further understand the processes dominating lithospheric breakup and extend some concepts seaward from passive margins to the interior of the oceanic lithospheric domain.

Abstract: Detecting surface contamination on thin thermoformed polymer plates is a critical issue for various industrial applications. Lamb waves offer a promising solution, though their effectiveness is challenged by the strong attenuation and anisotropy of the polymer plates. This issue is addressed in the context of a calcium carbonate (CaCO3) layer deposited on a polypropylene (PP) plate. First, the viscoelastic properties of the PP material are determined using a genetic algorithm inversion of data measured with a scanning laser vibrometer. Second, using a bi-layer plate model, the elastic properties and thickness of the CaCO3 layer are estimated. Based on the model, the sensitivity analysis is performed, demonstrating considerable effectiveness of the A1 Lamb mode in detecting thin layers of CaCO3 compared to Lamb modes A0 and S0. Finally, a direct application of this work is illustrated through in-situ monitoring of CaCO3 contaminants using a straightforward inter-transducer measurement.