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[en] The observed spectrum of five-minute solar oscillations enables an almost complete prediction of the power spectrum that has been attributed, up to now, to longer period oscillations
[fr]Le spectre des oscillations solaires observees dans la bande de 5mn permet de rendre compte a peu pres completement du spectre de puissance attribue jusqu'ici a des oscillations de periodes plus longues
[en] Despite theoretical predictions on the existence of solar gravity oscillations (g modes), their detection is still marginal. The main reasons are their frequencies, ν<0.2 mHz, and amplitudes of less than 10 cm/s. However, because these modes are extremely sensitive to the physical conditions in the very deep Sun, they can give detailed information on the physics of the core. Using a resonant scattering spectrophotometer the radial velocity was measured of the Sun at the KI 769.9 nm line with very high resolution and temporal stability. The observations carried out at Izana (Tenerife) continuously for the last three years were used to search for solar g modes. Analysis of the whole lot of data as one single time series provides a spectral resolution of 12 nHz, and a signal with amplitude above noise level, ∼1 cm/s. Several techniques are used in order to find the signature of g modes and calculate the parameters P0 and νr. Individual peaks, well above noise level, are identified and their frequencies are likely to correspond with g modes. (author). 4 figs., 13 refs
[en] We analyse the applicability of the two-flat-test calibration method across wide spatial frequency range based on its calculated accuracy. A number of simulations have been performed to determine the accuracy of the absolute calibration. The simulation results show that the two-flat-test calibration method is applicable to surfaces within the spatial frequency range from 1.67×10"−"1 to 1.67×10"−"3 mm"−"1
[en] Measurements of interference spectral density of the FEhU-85, FEhU-87, FEhU-140 photocurrent and dark current in the diode regime are conducted. It is shown that spectral densities of the FEhU-85, FEhU-87, FEhU-140 dark currents have the 1/f character. It is revealed that fluctuations of instant values of the FEhU-140 photocurrent and dark current at frequencies where flicker noise prevails, are far from Gaussian ones and within high frequency range they are Gaussian ones, but with dispersion differing from that for Poisson flux of photoelectrons
[en] We report the observations of a main-sequence star, HD 42618 (Teff = 5765 K, G3V) by the space telescope CoRoT. This is the closest star to the Sun ever observed by CoRoT in term of its fundamental parameters. Using a preliminary version of CoRoT light curves of HD 42618, p modes are detected around 3.2 mHz associated to l = 0, 1 and 2 modes with a large spacing of 142 μHz. Various methods are then used to derive the mass and radius of this star (scaling relations from solar values as well as comparison between theoretical and observationnal frequencies) giving values in the range of (0.80 − 1.02)Msun and (0.91 − 1.01)Rsun. A preliminary analysis of l = 0 and 1 modes allows us also to study the amount of penetrative convection at the base of the convective envelope.
[en] We present the results of a study of the major low-frequency sources of seismic activity at the Virgo site. These sources are of natural and human origin: oceanic microseism (below 1 Hz), local traffic and human activity on site (below 10 Hz). Using data collected during the commissioning of the central Virgo interferometer (CITF) we have measured the seismic coupling to the interferometer, demonstrating that seismic noise contributed to the CITF dark fringe noise only below approximately 2 Hz
[en] A computerized method for the measurement of the frequency response of nuclear reactors is described. The sinusoidal input signal is realized by computer control of the automatic controller. The upper frequency limit is given by the inertness of the control rod system. (author)
[en] A large solar pore with a granular light bridge was observed on October 15, 2008 with the IBIS spectrometer at the Dunn Solar Telescope and a 69-min long time series of spectral scans in the lines Ca II 854.2 nm and Fe I 617.3 nm was obtained. The intensity and Doppler signals in the Ca II line were separated. This line samples the middle chromosphere in the core and the middle photosphere in the wings. Although no indication of a penumbra is seen in the photosphere, an extended filamentary structure, both in intensity and Doppler signals, is observed in the Ca II line core. An analysis of morphological and dynamical properties of the structure shows a close similarity to a superpenumbra of a sunspot with developed penumbra. A special attention is paid to the light bridge, which is the brightest feature in the pore seen in the Ca II line centre and shows an enhanced power of chromospheric oscillations at 3–5 mHz. Although the acoustic power flux in the light bridge is five times higher than in the ''quiet'' chromosphere, it cannot explain the observed brightness.
[en] A simple reverse bending machine is described for tests in low cycle fatigue at elevated temperatures. The machine is easy to construct, simple to operate, and it is especially useful for detailed metallographic investigations in low cycle fatigue. The machine has been used for strain amplitudes up to +- 0.5% and frequencies of the order of 10-3--10-1 Hz. Some typical experimental results are described for high-purity aluminum tested in air at 300 0C