Short correlation time, temperature

The signal transients for 9A = —60° and for other concentrations were also measured (data not shown). For the neat liquid CH3I no temperature dependence of T2 was found within experimental accuracy and a short correlation time, rc < 300 fs. 

These motions are complex and do no not allow to find a simple correlation between the temperature and the short correlation time. Calculating the value of the rotational correlation time of the fluorophore itself Of from equation 5.27... 

For water at room temperature Tc is around 3 ps. This is a very short correlation time and in such cases the relaxation time is given by... 

The conventional, and very convenient, index to describe the random motion associated with thermal processes is the correlation time, r. This index measures the time scale over which noticeable motion occurs. In the limit of fast motion, i.e., short correlation times, such as occur in normal motionally averaged liquids, the well known theory of Bloembergen, Purcell and Pound (BPP) allows calculation of the correlation time when a minimum is observed in a plot of relaxation time (inverse) temperature. However, the motions relevant to the region of a glass-to-rubber transition are definitely not of the fast or motionally averaged variety, so that BPP-type theories are not applicable. Recently, Lee and Tang developed an analytical theory for the slow orientational dynamic behavior of anisotropic ESR hyperfine and fine-structure centers. The theory holds for slow correlation times and is therefore applicable to the onset of polymer chain motions. Lee s theory was generalized to enable calculation of slow motion orientational correlation times from resolved NMR quadrupole spectra, as reported by Lee and Shet and it has now been expressed in terms of resolved NMR chemical shift anisotropy. It is this latter formulation of Lee s theory that shall be used to analyze our experimental results in what follows. The results of the theory are summarized below for the case of axially symmetric chemical shift anisotropy. 

Huan et al. [41] measured the behavior of a small fluidized bed consisting of 45-80 mustard seeds in a small-bore vertical magnet. The small sample size allowed short pulses, and spatial distribution of collision correlation times and granular temperature were measured directly and compared with the hydrodynamic theory of Garzo and Dufty [42], This paper [41] contains an excellent survey of previous experiments on fluidized beds. 

There has been considerable interest in using fluorescence anisotropy to detect multiple environments in membranes as with fluorescence lifetimes (see above). For example, if a fluorophore is located in two environments with long and short lifetimes, then the fluorescence anisotropy decay process at longer times after excitation will be dominated by the long-lived fluorescent species. This occurs with parinaric acids, and this situation has been explored for a number of theoretical cases. 60 A similar situation has been found for DPH in two-phase lipid systems by collecting anisotropy decay-associated spectra at early and late times after excitation. 61 Evidence was found for more than one rotational environment in vesicles of a single lipid of it is at the phase transition temperature. It is important to identify systems showing associated anisotropy decays with more than one correlation time, each of... 

The following, well-acceptable assumptions are applied in the presented models of automobile exhaust gas converters Ideal gas behavior and constant pressure are considered (system open to ambient atmosphere, very low pressure drop). Relatively low concentration of key reactants enables to approximate diffusion processes by the Fick s law and to assume negligible change in the number of moles caused by the reactions. Axial dispersion and heat conduction effects in the flowing gas can be neglected due to short residence times ( 0.1 s). The description of heat and mass transfer between bulk of flowing gas and catalytic washcoat is approximated by distributed transfer coefficients, calculated from suitable correlations (cf. Section III.C). All physical properties of gas (cp, p, p, X, Z>k) and solid phase heat capacity are evaluated in dependence on temperature. Effective heat conductivity, density and heat capacity are used for the entire solid phase, which consists of catalytic washcoat layer and monolith substrate (wall). 

The low concentration of mercury in the bottom ash results from one or a combination of the following short retention time in the gas stream, the smaller surface area, and/or the higher temperatures at which it is removed from the system. The mercury concentrations in the filter particulates collected during the isokinetic sampling did not show any direct correlation with the ash studies because the mercury collected on the heated filter was partially revolatilized during sampling and collected in the remaining portions of the train. 

Product characterization from liquefaction has not been extensive. Phi 1p and Russell (95) have examined products by Py-GCMS from metal halide catalyzed hydrogenation of a vitrinite, alginite, and inertinite, each from a different source. They were able to correlate Py-GCMS results with reaction temperature. King, et al. (96) examined the short contact time liquefaction of macerals separated by DGC from a single hvB bituminous coal. They found correlations between density and reactivity and composition of the products. 

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