INDEX relaxation times compared

A chromia-alumina catalyst may contain protons both as surface hydroxyl groups and as adsorbed water, and therefore it exhibits a proton NMR spectrum. Alumina itself has been extensively studied by proton NMR, but this experimental technique has not been widely applied to the chromia-alumina system. Until recently, the nearest approach to this application was by Selwood and his co-workers 165, 166) who found that the spin-lattice relaxation time of the protons in water was modified by contacting the water with a chromia-alumina catalyst. By comparing this effect with that of Cr + ions in aqueous solution, the authors obtained a rough index of the accessibility of the ohromia, which in effect could be regarded as an approximate measure of the number of surface chromium ions. Ibers et al. 167) studied the proton NMR of HCr02. 

Thus the birefringence of the liquid crystal is much more critical in the fluorescence polarization studies. Measurements of the order parameter of excited molecules are possible if the rotational relaxation time of the solute is small compared with the lifetime of the emitting state. The birefringence of the liquid crystal is also of critical importance if one wishes to determine the solvent order from the absorption polarization spectrum of the solvent in its nematic phase. The complications arise from the strong refractive index dispersion in the wavelength regions of the solvent absorption bands. Saupe and Maier [104] have treated this case. The same difficulties arise of course if the solute and the solvent absorption overlap. 

It is interesting to note that not only differences in refractive indexes, but also relaxation times, can be determined by the birefringence method [166]. The laser birefringence detection method is presented in Ref. [166]. Details of the necessary calculations and a comparison of the results obtained compared with rheological methods are also shown are shown in Ref. [166]. 

The model of Mead [23] includes only the terminal zone, and here the key difference from the models of Carrot and Guillet [51] and Leonardi et al. [52 ] is that the latter authors include the dependence of the terminal relaxation time on the molecular weight distribution. Leonardi et al [ 52 ] compare the predictions of their comprehensive model with those of Mead s model [23] and with experimental data. They conclude that Mead s approach is useftrl when the average molecular weight is high, i.e. when the and when the polydispersity index is... 

The relaxation of a local mode is characterized by the time-dependent anomalous correlations the rate of the relaxation is expressed through the non-stationary displacement correlation function. The non-linear integral equations for this function has been derived and solved numerically. In the physical meaning, the equation is the self-consistency condition of the time-dependent phonon subsystem. We found that the relaxation rate exhibits a critical behavior it is sharply increased near a specific (critical) value(s) of the interaction the corresponding dependence is characterized by the critical index k — 1, where k is the number of the created phonons. In the close vicinity of the critical point(s) the rate attains a very high value comparable to the frequency of phonons. 

The rotational temperature obtained from a linear relation in the Boltzmann plot of the rotational energy distribution is an index of the lifetime in the intermediate excited state and decreases with decreasing lifetime. The rotational temperature of CO desorbed from Pt(l 1 1) is very low as compared with that of NO desorption, i.e. the lifetime of the excited CO is supposed to be much shorter than that of NO. In the case of CO desorption from Pt(l 11), however, the lifetime is not obtained from the rotational energy distribution, since desorbed molecules are detected by the (2 + 1 )REMPI method in the experiment [ 12] and then the single rotational states are not resolved. On the other hand, the rotational temperature of NO desorbed from Pt(l 1 1)-Ge surface alloy is lower than that from Pt(l 1 1). Then, it is speculated that the lifetime of the excited CO on the alloy is shorter than that on Pt( 111) and the residence time of the excited CO on the alloy is too short to be desorbed. As a consequence, the excited CO molecules are recaptured in the relaxation without desorption. However, it has not been understood why the lifetime of the excited CO molecule (or the excited CO-Pt complex) on Pt( 1 1 1) is shorter than that of the excited NO molecule (complex) on Pt(l 11), and further on the Pt-Ge alloy as compared with Pt(l 1 1). 

In 113 patients undergoing general anesthesia, intravenous midazolam 15 mg slowed recovery of the twitch height after vecuronium and atracurium compared with diazepam. The recovery index was not altered (162). However, in another study in 20 patients, midazolam 0.3 mg/kg did not affect the duration of blockade, recovery time, intensity of fasciculations, or adequacy of relaxation for tracheal intubation produced by suxamethonium 1 mg/kg, nor the duration of blockade and adequacy of relaxation for tracheal intubation produced by pancuronium 0.025 mg/kg in incremental doses until 99% depression of muscle-twitch tension was obtained (161). Furthermore, in 60 patients undergoing maintenance anesthesia randomly assigned to one of six regimens (etomidate, fentanyl, midazolam, propofol, thiopental plus nitrous oxide, or isoflurane plus nitrous oxide), midazolam did not alter rocuronium dosage requirements (165). 

---