Thin-film transducers for the detection and imaging of Brillouin oscillations in transmission on cultured cells

Mechanical imaging and characterisation of biological cells has been a subject of interest for the last twenty years. Ultrasonic imaging based on the scanning acoustic microscope (SAM) and mechanical probing have been extensively reported. Large acoustic attenuation at high frequencies and the use of conventional piezo-electric transducers limit the operational frequency of a SAM. This limitation results in lower resolution compared to an optical microscope. Direct mechanical probing in the form of applied stress by contacting probes causes stress to cells and exhibits poor depth resolution. More recently, laser ultrasound has been reported to detect ultrasound in the GHz range via Brillouin oscillations on biological cells. This technique offers a promising new high resolution acoustic cell imaging technique. In this work, we propose, design and apply a thin-film based opto-acoustic transducer for the detection in transmission of Brillouin oscillations on cells. The transducer is used to generate acoustic waves, protect the cells from laser radiation and enhance signal-to-noise ratio (SNR). Experimental traces are presented in water films as well as images of the Brillouin frequency of phantom and fixed 3T3 fibroblast cells

CHARGE DENSITY WAVES IN THE LAYERED TRANSITION METAL DICHALCOGENIDES

Les dichalcogénides de métaux de transition de groupe Va présentent une surface de Fermi reliable aux instabilités structurales. Dans des corps tels que IT-TaS2, ces effets apparaissent clairement dans les propriétés électromagnétiques qui sont anormales. Le but de l'article est de présenter des preuves expérimentales, en particulier par la diffraction des électrons et les rayons X, pour l'adoption d'un état fondamental CDW couple a une distorsion périodique de réseau. Nous montrons comment cet état fondamental peut être perturbé en intercalant des métaux alcalins ou des terres rares.The metallic layered transition metal dichalcogenides of group Va exhibit Fermi surface linked structural instabilities. In materials such as IT-TaS2, these effects readily manifest themselves in the electromagnetic properties, hitherto regarded as anomalous. The primary aim of the present paper is to present the diffraction evidence from electron and X ray observations, for the adoption of a charge density wave ground state coupled to a periodic lattice distortion, and to show how this ground state may be perturbed by alkali metal and rare earth intercalation

Acoustic Emission Measurements during Cyclic Fatigue of Welded A533B Plates Containing Defects

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Studies of laser-generated ultrasonic waveforms at different orientations

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Acoustic emission measurements using point-contact transducers

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