No abstract available

[en] A new approximate method to calculate the space-time acoustic wave motion generated by an impulsive point source in a horizontally layered configuration is presented. The configuration consists of a stack op fluid layers between two acoustic half-spaces where the source and the receiver are located in the upper half-space. A distorted-wave Born approximation is introduced; the important feature of the present method is the assumption of the presence of a background medium with vertical varying root-mean-square acoustic wave speed. A closed-form expression for the scattered field in space and time as a function of the contract parameters is arrived at. The result is in close agreement with synthetic seismograms calculated in a rigorous way. In the inverse scheme the wave speed and mass density can be reconstructed within a single trace. Results of the inversion scheme applied to synthetic data have been shown. (author)

[en] Local onset of boiling in any pressure water cooling systems, as a PWR for instance, can mean a possible dangerous mismatch between the produced heat and the cooling capabilities. Its consequences can lead to serious accidental conditions and a reliable technique to detect such a phenomenon is therefore of particular need. Most techniques used up to now rely basically on local measurements and assume therefore usually the previous knowledge of the actual hot or boiling spot. The method proposed here based on externally located accelerometers appears to be sensitive to the global behaviour of the mechanical structure and is therefore not particularly bound to any exact localization of the sensors. The vibrations produced in the mechanical structure of the heated assembly are measured by accelerometers placed on the external surfaces that are easily accessible. The onset of the boiling, the growth and condensation of the bubbles on the heated wall, induces a resonance in the structure and an excitation at its particular eigen frequencies. Distinctive peaks are clearly observed in the spectral density function calculated from the accelerometer signal as soon as bubbles are produced. The technique is shown to be very sensitive even at the earliest phase of boiling and quite independent on sensor position. A complete hydrodynamic analysis of the experimental channels have been performed in order to assess the validity of the method both in steady conditions and during rapid power transients

[en] The South Pole Acoustic Test Setup (SPATS) has been installed to measure the acoustic properties of the Antarctic ice sheet around the South Pole. It comprises acoustic sensors and transmitters that have been frozen in the upper 500 m of four IceCube drill holes to study the feasibility of acoustic neutrino detection in ice. One of the critical design parameters of an acoustic neutrino detector will be the noise level which determines the lower energy threshold for a given detector configuration. In this talk first results on the absolute level obtained with two years of SPATS data are presented and uncertainties due to the environmental conditions and the challenging in-situ calibration of sensors are discussed.

[en] We review the status of the Lake Baikal Neutrino Experiment. The Neutrino Telescope NT200 has been operating since 1998 and has been upgraded to the 10 Mton detector NT200+ in 2005. We present selected astroparticle physics results from long-term operation of NT200. Also discussed are activities towards acoustic detection of UHE-energy neutrinos, and results of associated science activities. Preparation towards a km3-scale (Gigaton volume) detector in Lake Baikal is currently a central activity. As an important milestone, a km3-prototype string, based on completely new technology, has been installed and is operating together with NT200+ since April, 2008.

[en] Aim: To evaluate the association between liver stiffness measured by acoustic radiation force impulse (ARFI) elastometry and the outcome of antiviral treatment in patients with chronic viral hepatitis B and C. Materials and methods: Thirty-eight patients with chronic viral hepatitis B (n = 16) or hepatitis C (n = 22) underwent liver biopsy and ARFI elastometry of the right hepatic lobe. A follow-up assessment using ARFI was performed a mean of 2.3 years after the baseline evaluation. The patients with favourable outcome were classified in group S and those receiving no treatment, showing no response to treatment, or experiencing a relapse were classified in group N. Results: The 38 patients had an initial mean ARFI value of 1.56 ± 0.62 m/s as compared with 1.54 ± 0.64 m/s in the follow-up evaluation. Group S showed a significant decline in ARFI values (1.55 ± 0.60 m/s versus 1.34 ± 0.47 m/s; p < 0.05) and included 16 (64%) patients with lower shear wave velocities at follow-up. In group N, liver stiffness values showed a slight but not significant increase (1.57 ± 0.70 m/s versus 1.93 ± 0.77 m/s). Conclusion: Changes in liver stiffness during antiviral therapy can be assessed by ARFI reflecting response or no response. ARFI elastometry is an additional, useful tool for the follow-up assessment of treatment outcome in patients with chronic viral hepatitis B or C infection

[en] The history of the meaning of ''martensitic transformation'' over the past forty years is briefly reviewed, and an area of common agreement is identified centered on the concepts of ''cooperative atomic motion'' and ''shape change''. A search is made for the minimum elements required in a definition that will be simple, compact, precise and easily tested. It is argued that cooperative atomic motion implies acoustic emission, and that this could provide an important operational element in the definition. A distillation of past definitions, with this new ingredient added yields, as a proposed irreducible definition: A martensitic transformation involves a cooperative motion of a set of atoms across an interface causing a shape change and sound. (orig.)

[en] Updates from the second phase of the Study of Acoustic Ultra-high energy Neutrino Detection (SAUND) experiment are presented. The data accumulated since July 2006 are discussed. Signal processing techniques intended to isolate neutrino-induced acoustic signals are also reported.

[en] The development of a reliable detection technique for the onset of boiling has been further pursued. Besides the already studied tube geometry, a more realistic annular set up has been used where a fuel pin model, electrically heated, is placed. Using accelerometers on the pin, on the structure and on specific instrumentation cables the onset of boiling was clearly monitored by the emergence of a typical resonance frequency. The influence of pressure and heat power was analysed in detail. Furthermore, a glass model has been constructed in order to better correlate the observed measurement with the boiling parameters, as bubble radius, frequency and collapse mode

[en] LIDEC-XL allows the detection of water through a metallic wall of large thickness - up to 110 mm - such as a steam generator. The device delivers an alarm to the control room. (author). 1 fig