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The monochromatic and geometrically anisotropic acoustic field generated by 400 and 120 nm diameter copper nanowires simply dropped on a 10 μm silicon membrane is investigated in transmission using three-dimensional time-resolved femtosecond pump-probe experiments. Two pump-probe time-resolved experiments are carried out at the same time on both sides of the silicon substrate. In reflection, the first radial breathing mode of the nanowire is excited and detected. In transmission, the longitudinal and shear waves are observed. The longitudinal signal is followed by a monochromatic component associated with the relaxation of the nanowire's first radial breathing mode. Finite difference time domain (FDTD) simulations are performed and accurately reproduce the diffracted field. A shape anisotropy resulting from the large aspect ratio of the nanowire is detected in the acoustic field. The orientation of the underlying nanowires is thus acoustically deduced.
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http://dx.doi.org/10.1021/acs.nanolett.6b03260 | DOI Listing |
IEEE Trans Med Imaging
September 2025
In ultrasound imaging, propagation of an acoustic wavefront through heterogeneous media causes phase aberrations that degrade the coherence of the reflected wavefront, leading to reduced image resolution and contrast. Adaptive imaging techniques attempt to correct this phase aberration and restore coherence, leading to improved focusing of the image. We propose an autofocusing paradigm for aberration correction in ultrasound imaging by fitting an acoustic velocity field to pressure measurements, via optimization of the common midpoint phase error (CMPE), using a straight-ray wave propagation model for beamforming in diffusely scattering media.
View Article and Find Full Text PDFJ Acoust Soc Am
September 2025
Department of Physics, University of Louisiana at Lafayette, Lafayette, Louisiana 70503, USA.
A method is presented for determining the significant parameters, maximum wind speed and radius of maximum wind speed, of the surface winds associated with a hurricane. The method is based on Bayesian inversion, using Markov chain Monte Carlo sampling. Underwater acoustic measurements are used to estimate parameters in the axisymmetric Holland model for hurricane surface winds.
View Article and Find Full Text PDFIEEE Trans Biomed Eng
September 2025
Objective: Transcranial ultrasound (US) stimulation (TUS) has emerged as a promising technique for minimally invasive, localized, deep brain stimulation. However, indirect auditory effects during neuromodulation require careful consideration, particularly in experiments with rodents. One method to prevent auditory responses involves applying tapered envelopes to US bursts.
View Article and Find Full Text PDFJ Voice
September 2025
Bielefeld University, P.O. Box 10 01 31, Bielefeld D-33501, Germany. Electronic address:
To this day, the assessment of human voices remains a challenge due to (i) inconsistencies in subjective ratings and (ii) the lack of objective measurements for the perceptual impressions of voice characteristics. This can lead to significant consequences in applied fields such as speech therapy, where the assessment of voices is crucial for a successful treatment. In this paper, we address the explanation of voice and its characteristics from two different angles: In a first study, 22 speech therapists in training assessed a set of 20 non-pathological voices regarding 20 voice characteristics before and after receiving an expert explanation.
View Article and Find Full Text PDFMagn Reson Med
September 2025
A.I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
Since its introduction more than 30 years ago, the blood oxygenation level-dependent (BOLD) contrast remains the most widely used method for functional MRI (fMRI) in humans and animal models. The BOLD contrast is typically acquired with echo planar imaging (EPI) to obtain sensitization of the signal during the echo time (TE) to dynamic changes in deoxyhemoglobin content, while achieving high spatiotemporal resolution and full brain coverage. However, EPI-based fMRI also faces multiple shortcomings, including sensitivity to body motion, susceptibility-related signal dropouts, interference with multimodal sensors, and loud acoustic noise.
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