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The Fourier transform infrared spectrum of monoisotopic SF 5 Cl has been recorded in the 650- to 960-cm region at a temperature of 203 K, a pressure of 0.2 mbar, and an instrumental bandwidth of 0.002 cm. The ν 1 /ν 8 dyad near 900 cm has been analyzed with an effective Hamiltonian developed up to the fourth order and the help of a recently developed set of programs called C 4 v TDS ( C 4 v Top Data System, http://www.u-bourgogne.fr/LPUB/C4VTDS.html ); 1346 transitions for ν 1 , 351 transitions for ν 8 , and 406 ground state combination differences have been assigned and fitted. A global fit has been obtained with an rms of 0.00082 cm for the ν 1 ( a 1 ) band, of 0.0011 cm for the ν 8 ( e ) band, and of 0.00064 cm for the ground state.

The Fourier transform infrared spectrum of monoisotopic SF535Cl has been recorded in the 650- to 960-cm−1region at a temperature of 203 K, a pressure of 0.2 mbar, and an instrumental bandwidth of 0.002 cm−1. The ν1/ν8dyad near 900 cm−1has been analyzed with an effective Hamiltonian developed up to the fourth order and the help of a recently developed set of programs called C4vTDS (C4vTop Data System, http://www.u-bourgogne.fr/LPUB/C4VTDS.html); 1346 transitions for ν1, 351 transitions for ν8, and 406 ground state combination differences have been assigned and fitted. A global fit has been obtained with an rms of 0.00082 cm−1for the ν1(a1) band, of 0.0011 cm−1for the ν8(e) band, and of 0.00064 cm−1for the ground state.

We present a development of the Hamiltonian, dipole moment, and polarizability operators of XY5Z(C4v) molecules using a tensorial formalism derived from the one developed previously in Dijon for XY6molecules. These operators are involved in the calculation of the energies and intensities of rovibrational transitions and are essential for spectrum simulations. Expressions for the matrix elements are derived for all these operators.

A tensorial formalism adapted to the case of XY5Zsymmetric tops has been developed as an extension of the usual one for the octahedral molecules. We use the O(3) ⊃ Oh⊃ C4vgroup chain. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are also deduced in the C4vgroup itself.

Lung pressure-volume hysteresis of cat lungs has been found by Hildebrandt (J. Appl. Physiol. 28, 365–372, 1970) to be 20–50% larger than predicted from stress adaptation data on the basis of a viscoelastic model. We have reinvestigated this phenomenon in isolated rat lungs with a different approach, in which the approximation inherent to using a model is avoided Lung transfer function was derived from the digitally-computed Laplace transform of the pressure decay following a step volume change and used to predict lung pressure-flow relationship in the frequency domain. The latter was expressed in terms of lung effective resistance (Rlc) and effective elastance (Elc), and compared to the observed values (Rl and El) in the frequency range 0.01–0.5 Hz. The measurements were made in 5 lungs at a transpulmonary pressure (Pl) of 0.5 kPa and in 5 others at a Pl of 0.8 kPa. Rl was found to be 23–41% larger than Rlc at Pl=0.5 and 29–51% larger at Pl=0.8. El did not differ significantly from Elc at Pl=0.5 but was 14–28% larger at Pl=0.8. These results are in good agreement with previous findings. The differences between Rl and Rlc are proportional to the reciprocal of frequency and, thus, correspond to a rate-independent dissipation. They are consistent with a yield stress of 3–6 Pa.

Abstract: The mechanical impedance of the respiratory system Zrs is usually measured by forced excitation while the patient breathes spontaneously. Pressure and flow signals due to breathing contaminate the excitation signals, leading to a poor signal-to-noise ratio (SNR) and thus to errors in impedance estimation, especially at low frequencies (up to 8 Hz). To enhance SNR in the recorded signals we designed an infinite impulse response digital filter for the frequent case in which the excitation is pseudorandom. The algorithm is based on narrowband second-order bandpass elements centred at the excitation frequencies. The performance of the filter was assessed in a simulation study by superposing forced excitation signals (2–32 Hz) from a reference model and the signals of breathing recorded from 16 subjects. When compared with a conventional high-pass filtering, the devised filtering resulted in an increase in SNR which was almost constant over the whole frequency band: 6·30±0·98 dB (mean±SD). This improvement in SNR was reflected in an increase in the number of subjects for which the corresponding coherence y2 attained a value greater than the conventional threshold of acceptability (y2=0·95). At the lowest frequency (2 Hz) only two (12·5 per cent) simulated subjects had y2≥0·95 with the conventional high-pass filtering. By contrast, when using the devised comb filter the number of subjects with y2≥0·95 increased up to 13 (81 per cent). The results obtained suggest that this filter may be useful to improve SNR and thus Zrs estimation.

The accuracy of pulse oximeters in measuring transient changes in oxygen saturation (SaO2) may be affected by the oximeter time response. The aim of this study was to assess the effect of modifying the pulse oximeter averaging time (T) on the measurement of SaO2 in patients with the sleep apnea-hypopnea syndrome (SAHS). Twelve patients with severe SAHS were studied during a nap with conventional oximeters: Ohmeda 3740 and Criticare 501. We compared the readings of each patient's oxygen desaturation measured simultaneously with two identical pulse oximeters. One oximeter was the control (T = 3 seconds), and in the other T was set from 3 seconds to 21 seconds. No significant differences in SaO2 were found when both oximeters were set to the same T (3 seconds). In contrast, increasing T to 12 seconds and 21 seconds in one of the oximeters resulted in considerable and significant differences in the measured SaO2: oxygen desaturation was underestimated by up to 60% when compared with the control. The misestimation of SaO2 induced by settings of T which are within the range selectable in conventional oximeters may be of epidemiological significance when pulse oximetry is used as a complementary diagnostic tool to classify sleep events in SAHS.

The low resolution absorption spectroscopy of the first five excited electronic states of IrF6has made possible some new assignments for the vibronic transitions of this molecule, and the determination of new vibronic parameter values. They are more accurate than those found in the literature. In this aim, we introduce a simplified tensorial formulation for the linear Jahn–Teller terms in a fourfold degenerate electronic state of anXY6-type molecule, which allows easier computation of matrix elements and avoids the use of perturbation theory. Methods for IrF6synthesis (using a dynamical flow system) and purification are also presented.

The SiH2D2asymmetric top has nine vibrational modes, five of them forming a pentad strongly perturbed by Coriolis interactions. High-levelab initiocalculations of SiH2D2have been performed which yield numerous spectroscopic parameters related to the harmonic and anharmonic force fields. The bending pentad comprising ν4(A1), ν7(B1), ν5(A2), ν9(B2), and ν3(A1) has been studied by high-resolution Fourier transform spectroscopy; the region 600–1050 cm−1has been investigated with a resolution of ca. 4 × 10−3cm−1. Raman BOXCARS spectroscopy has been used for the infrared inactive ν5band. The Raman apparatus function was 0.0054 cm−1. Assignments of about 4000 transitions including all bands have been made, mostly employing ground state combination differences techniques, and a global fit has been performed. The fundamentals ν4(681.624 cm−1), ν7(742.640 cm−1), ν5(842.381 cm−1), ν9(859.750 cm−1), and ν3(942.741 cm−1) are strongly coupled by A-, B-, and C-type Coriolis interactions, andab initiopredictions of these interaction parameters were used to set up a network of interactions that was refined by the experimental data. The global standard deviation for the entire body of data is 7.1 × 10−4cm−1. Satisfactory synthetic spectra which are very sensitive to relative signs of dipole moment derivatives and Coriolis interaction constants were obtained with the guidance ofab initiocalculations. Finally, fair to good agreement of experimental andab initiocalculated molecular parameters was obtained. For the first time, a complete analysis of the pentad of SiH2D2in the 10–16 μm region has been carried out. A full set of rovibrational parameters is given for these five interacting levels, including first and second order Coriolis interaction constants.

Abstract: An optical method for measuring the frequency response of pressure transducers is described. The method allows the calculation of the varying pressure of ate pressure. Displacement is measured by a photodetector position sensor with the aid of a laser beam reflected on a mirror attached to the loudspeaker diaphragm. The method is based on the short time response of the optical system and it presents some advantages with regard to the usual dynamic calibration using a microphone reference: (a) it has a good response at low frequencies; (b) it is unaffected by environmental conditions; and (c) the system can easily be recalibrated.