Regularity and identification of Generalized Multifractional Gaussian Processes

International audienceIn this article a class of multifractal processes is introduced, called Generalized Multifractional Gaussian Process (GMGP). For such multifractional models, the Hurst exponent on the celebrated Fractional Brownian Motion is replaced by a function, called the multifractional function, which may be irregular. The main aim of thi paper is to show how to identify irregular multifractional functions in the setting of GMGP. Examples of discontinuous multiractional functions are also given

Les mouvements de capitaux dans les sociétés au Maroc (1912-1955). Leurs aspects géographiques

Ayache Albert. Les mouvements de capitaux dans les sociétés au Maroc (1912-1955). Leurs aspects géographiques. In: Bulletin de l'Association de géographes français, N°275, 35e année,1958. pp. 17-27

Évolution récente de l'industrie minière au Maroc

Ayache Albert. Évolution récente de l'industrie minière au Maroc. In: L'information géographique, volume 24, n°5, 1960. pp. 215-217

Les grèves de juin 1936 au Maroc

Ayache Albert. Les grèves de juin 1936 au Maroc. In: Annales. Economies, sociétés, civilisations. 12ᵉ année, N. 3, 1957. pp. 418-429

Harmonic response from microscopic antibubbles

International audienceAn antibubble is a gas bubble containing a liquid droplet core. Both the droplet and the gas bubble are typically surrounded by stabilising shells. Owing to electrostatic forces exerted by these shells, core droplets of micrometer diameter do not readily coalesce with the surrounding liquid medium. Owing to the incompressibility of the liquid droplet core, antibubbles will oscillate asymmetrically, i.e., the radial excursion amplitude of the surface is greater during expansion than during contraction, when subjected to diagnostic ultrasound. Consequently, the harmonic content of the ultrasound signal radiated from antibubbles must be higher than that from identical bubbles without a liquid core. Whether the harmonic signal component generated by physical antibubbles is higher than the harmonic component of identical bubbles without a core has been studied here. We subjected prefabricated antibubbles and identical bubbles without core droplets to 1-MHz ultrasound and to a commercial ultrasound system, and recorded the spectra with a broadband transducer oriented perpendicularly to the transmitter. Normalised by the acoustic response from the medium, the antibubble signal shows stronger higher harmonics than the reference signal, and negligible fundamental response. In conclusion, antibubbles are suitable candidates for harmonic imaging. The generation of higher harmonics without fundamental has been attributed to asymmetric antibubble expansion

声学泡、反泡泡和细胞

International audienc

Acoustic hydrophobic particles

National audienc

Asymmetric oscillations of endoskeletal antibubbles

International audienceAntibubbles have been under investigation as potential vehicles in ultrasound-guided drug delivery. It is assumed that antibubbles can expand unhampered, but cannot contract beyond the size of their inner core. In this study, this hypothesis was tested on endoskeletal antibubbles and reference bubbles. These were subjected to 3-cycle pulses of 1-MHz ultrasound, whilst being recorded with a high-speed camera operating at 10 million frames per second. At low acoustic amplitudes (200 kPa), antibubbles and bubbles oscillated symmetrically. At high acoustic amplitudes (1.00 MPa), antibubbles and bubbles oscillated asymmetrically, but antibubbles significantly more so than bubbles. Furthermore, fragmentation and core release were observed at these amplitudes. This finding may have implications for ultrasound-guided drug delivery using antibubbles

Géographie du Maroc, par Fernand Joly,... Albert Ayache,... Jean Fardel,... Léon Suech,...

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