Conclusions from problem resolution

A partial resolution of the influence of vibrations on the properties of water was put forward by Wallqvist and Teleman. In this work it was shown that some earlier simulations were susceptible to an imbalance of translational, rotational, and vibrational temperatures. Thus the enhancements of the diffusion coefficient initially attributed to intramolecular motion were caused in fact by an enhanced translational temperature. In this case the simulation exhibited an average correct temperature, but with enhanced translation temperature and very cold vibrations. Because the time for the temperature mixing was on the order of 200 ps, these simulations were not properly equilibrated. Later a velocity resampling scheme was used to overcome these problems, and results were found to be in agreement with the assessment of Barrat and McDonald. The general conclusion from the work by Wallqvist and Tele-man is that flexibility actually slows molecular motion, because of an artificial enhancement of the monomer dipole moment, but has little effect on the intermolecular structural properties. 

Analysis schemes developed for identifying clay minerals in the TEM based on EDS spectra (e.g., Murdoch et al.100) are inappropriate for colloidal samples dispersed on polycarbonate filters due to complications associated with the various sample-beam-substrate interactions that differ dramatically from that of ideal samples or standards with smooth polished surfaces.94 96 101 102 Correction procedures that account for the influence of particle size and morphology on x-ray spectra have been widely available for some time,101102 but these techniques have not been applied to the analysis of environmental particulates. To overcome the limitation of quantitative elemental analysis, some research groups have compared the x-ray spectra for sample colloids to the spectra for various minerals of similar size and composition under the same instrumental and sample preparation conditions to calibrate instrumental response.7 24 93 Noting the resolution problems associated with SEM analysis of submicron colloids, several research groups have chosen TEM as the primary discrete particle analysis technique,21 52 103 104 or have combined TEM analysis techniques, such as electron diffraction and x-ray microanalysis, to confirm conclusions drawn from SEM surveys.7,93 105... 

In conclusion, then, it may be stated that a correlation between P430 and FeS-A/FeS-B in photosystem I still lacks definitive, kinetic evidence. As mentioned earlier, the inherent difficulty for this problem lies in the lack of optical spectral specificity on the one hand and the limitation of time resolution and temperature in the EPR technique on the other. The necessary but not yet sufficient evidence derived from absorption spectra, the correlation found from somewhat unrefined kinetic studies, plus the finding of an analogous iron-sulfur protein and its correlation with the newly measured C-P430 in green sulfur bacteria, all make a correlation between the two species reasonable. Furthermore, as discussed in detail in Section IV.C. of Chapter 29, the recent kinetic-spectrophotometric measurements ofVassiliev et a/. and the more... 

Walsh investigated the possibility of using a continuum as a source for atomic absorption spectroscopy and came to the conclusion that it was not a desirable source. He noted that a resolution of over 500,000 would be required and that the intensity of a very narrow segment of a continuum would be extremely low. He therefore advocated the use of the hollow cathode source. Reference to Figure 10-1 will serve as a reminder concerning the problem of measuring the decrease in signal intensity caused by line absorption from a continuum. 

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