The absolute isotopic ratios of the hydrogen content of two reference water standards called ''SMOW"e and "SLAP* were measured to define an absolute isotopic scale. This isotopic scale can be used to normalize measurements of the natural isotopic variations in waters. The principle of the method used to define the zero of the scale is given. The absolute D/H ratios of SMOW and SLAP were measured by mass spectrometric comparison with calibration mixtures prepared in the laboratory. The following values are obtained: (g)sMow = 155.76f0.05 x lo-' @) = 89.02 0.05 x lo-' SLAP/SMOV= 428.50+0.10Samples of about 20 cc of the reference standards SMOW and SLAP are available from the International Atomic Energy Agency, on request.

The absolute isotopic ratios of the hydrogen content of two reference water standards called “SMOW”2 and “SLAP3 were measured to define an absolute isotopic scale. This isotopic scale can be used to normalize measurements of the natural isotopic variations in waters. The principle of the method used to define the zero of the scale is given. The absolute D/H ratios of SMOW and SLAP were measured by mass spectrometric comparison with calibration mixtures prepared in the laboratory. The following values are obtained: Samples of about 20 cc of the reference standards SMOW and SLAP are available from the International Atomic Energy Agency, on request.

The issue of the influence of wall vibrations on the behavior of wind instruments is still under debate. The mechanisms of vibroacoustic couplings involved in these vibrations are difficult to investigate, as fluid-structure interactions are weak. Among these vibroacoustic interactions, the present study is focused on the coupling between the internal acoustic field and the mechanical behavior of the duct. For this purpose, a simplified single reed instrument consisting of a brass tube connected to a clarinet mouthpiece has been studied. A theoretical model of coupling between the plane inner acoustic wave and mechanical modes is developed and suggests that in order to obtain measurable effects of wall vibrations, the geometrical parameters of the studied tube have to be unusual compared to that of real instruments. For a slightly oval-shaped and very thin brass tube, it is shown theoretically and experimentally that a coupling between the inner plane acoustic wave and ovalling mechanical modes occurs and results in disturbances of the input impedance, which can slightly affect the tone color of the sound produced. It is concluded that the reported effects are unlikely to occur in real instruments except for some organ pipes.

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