Detection of stationnary bubbles by the measurement of the harmonic distortion of an ultrasonic wave.

M. Vacher, R. Goutte, F. Lakestani, M. Perdrix

Second Mediterranean Conference on Medical and Biological Engineering

BIOMED 80 - 15-19 September 1980 - Marseille France

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Nonlinear Behaviour of Micro-bubbles : Application to their Ultrasonic Detection.

M. Vacher, G. Gimenez, R. Goutte

Acustica, vol.54 (1984) p.274-283}

@article{MVACHER84,
author = "M. Vacher, G. Gimenez, R. Goutte",
title = "Nonlinear Behaviour of Micro-bubbles : Application to their Ultrasonic Detection",
journal = "Acustica",
volume = "54",
pages = "274-283",
year = 1984 }

publication dans une revue à comité de lecture

Summary. - A method allowing the detection and size measurement of steady bubbles included in biological tissues is described. Radial movement of a bubble driven by an ultrasonic wave is determined with the help of the Kirkwood-Bethe-Gilmore equation. Numerical investigations shows that the frequency spectrum of the pressure radiated bubble contains a second harmonic with a non-negligible amplitude only when the radius of the bubble is close to the resonant value. The feasibility of the steady-bubble detection method is demonstrated using a transducer which emits an ultrasonic wave of frequency f and a transducer which receives the pressure radiated from the bubble. A lock-in amplifier then extracts the frequency components 2f included in the signal produced by the receiving transducer. In the case of a driven wave with a frequency of 1.6 MHz and an amplitude of 1.45kPa, a 2nd harmonic with amplitude of 200 mPa is collected at a point of 3.3 cm distant from the bubble. In presence of a bubble distribution, a frequency scan allows measurement of the various sizes of bubbles.

Pentagonal phases as a transient state of the reversible icosahedral-rhombohedral transformation in Al-Fe-Cu.

Menguy N., Audier M., Guyot P., Vacher M.

Phil. Mag. B, 1993,vol.68, N°5, p.595-606}

publication dans une revue à comité de lecture

Abstract. - From a transmission electron microscopy study, a transient state of the icosahedral-to-rhombohedral transformation in Al-Fe-Cu has been characterized as being constituted of an alternate mixing of two pentagonal structures. These pentagonal phases have been identified from high-resolution electron microscopy and diffraction patterns. The linear phason fields relating their structure to the icosahedral phase have been fully determined. Such a transient state results from the transformation of a modulated icosahedral phase, itsel obtained from the icosahedral state and precedes the formation of the crystalline multidomain structure of the rhombohedral phase. The interpretation proposed for the formation of these pentagonal phases can be related to that given in a previous paper on the modulated icosahedral state, where the modulation whas found to result from the propagation of phason waves along fiveold directions of the six-dimensional hyperspace.

Etude des réseaux de lignes de flux magnétiques dans des mono-cristaux de Bi-2212 irradiés aux ions lourds.

Weiss F., Miramond C., Rouault A., Senateur J.P., Thomaso O., Audier M., Vacher M., Groult D., Hardy V., Provost J., Ruyter A., Simon C.

IIIème Journées d'Etudes des Supra-conducteurs à Haute Température Critique. Caen (France), 16-17 nov. 1993.

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Résumé. - Nous présentons les premiers résultats d'une étude sur l'influence des défauts vis-à-vis du piégeage des lignes de flux magnétiques dans des monocristaux de bi2Sr2Ca1Cu2Ox. Ces monocristaux, non irradiés ou irradiés sur l'accélérateur du GANIL avec des ions (Pb56+) d'énergie 6GeV ont été décorés dans l'etat supraconducteur selon la technique de Bitter. Les réseaux de lignes de flux magnétiques ont été caractérisés par microscopie électronique à balayage et avec un analyseur d'images. Les résultats montrent que les réseaux de lignes de flux magnétique sont fortement dépendants de la densite de défauts résultants de l'irradiation. Pour caractériser l'état de désordre, nous avons appliqué une méthode de calcul de termes d'énergie élastique des réseaux de lignes de flux magnétiques. Cette méthode ne peut être appliquées que si la transformée de Fourier des réseaux de vortex présente des reflexions discrètes.

Relationships between the quasicristalline and approximant phase in the Al-Pd-Mn system; an application of the linear phason strain field theory.

Audier M., Duneau M., Vacher M.

ICPM-94,Babha Atomic Research Center. Bombay (Inde). 9-11 Mars 1994.

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Abstract. - Al-Pd-Mn liquidus phase fields have been determined for icosahedral, diagonal and several periodic compounds which are approximant crystals of the quasicrystals. Structure analysis of these phases have been carried out by transmission electron microscopy. As defined from the linear phason strain theory, the different crystal approximants can be distinguished as belonging either to the icosahedral phase or to the decagonal phase. It is firstly shown that the bases vectors of approximants can be obtained by cutting linearly sheared hyperlattices which have, at least, three hyperdimensional lattice vectors into the physical space. Knowing the atomic structure of two approximants, it is afterward examined from which atomic surfaces these atomic structures can be generated. The independance of the symmetry of the approximant as a function of the cut origin in the hyperspace is discussed.

Réseaux de vortex dans BiSr2CaCu2Ox.

Weiss F, Miramond C., Thomas O., Rouault A., Senateur J.P., Audier M., Vacher M., Groult D., Hardy V., Provost J.,Ruyter A., Simon C.

J. Phys. III France, 1994, vol. 4, p.2225

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Abstract. - Results of the defect influence on the flux line lattice in Bi2Sr2Ca1Cu2Ox single crystals are presented. These crystals, non irradiated or irradiated at GANIL with heavy ions (Pb56+, 6GeV) have been decorated with Ni particles in the superconducting state using the Bitter technique. The defects involved are columnar defects. Resulting decorated flux line patterns have been characterized using scanning electron microscopy and computer image analysis. Disorder of the decorated flux line networks have been found to be strongly dependent on the defect density, which results from the irradiation. In order to characterize this disorder, a method for determining elastic energy terms in the deformation of flux line patterns has been investigated. This method can be applied if Fourier transforms of the decorated flx line patterns exhibit distinct reflections.

Study of the magnetic flux line patterns in HTSC-crystals by means of decoration technique and image analysis.

Wurster K., Weiss F., Rouault A., Audier M., Vacher M.

Physica C, 1994, p.235-240

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Abstract. - The flux line patterns in different HTSC-crystals have been analyzed. the various twin structures of an YBa2Cu3O7 crystal were identified in decoration images and the pinning potential was estimated. In Bi2Sr2Ca1Cu2O7 single-crystals vortex chains were observed in tilted magnetic field.

The Al-Pd-Pm decagonal phase and T, R, tau2-R approximants.

Audier M., Duneau M., Vacher M.

Colloque National sur les Quasi-cristaux, INSTN Saclay (France), 1-3 juin 1994.

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Shear transformation and oblique projection in internal space applied to the generation of atomic structural models for Al-Pd-Mn decagonal approximants.

Beraha L., Audier M., Duneau M., Vacher M.

Vth Int. Conf. of Quasicristals, Avignon (France), 22-26 mai 1995.

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Abstract. - TEM observations have been carried out on the Al-Pd-Mn decagonal phase and two of its approximant structures. The cell parameters of these structures can be interpreted as projections from a sum lattice Lambda (+) Lambdah, Lambdah corresponding to a mirror image of Lambda in the 6D hyperspace. A model of two interpenetrating incomplete Mackay clusters is proposed. The projection of these periodic structures on the {a,c} plane falls on the nodes of 2D approximants of the Penrose tiling.