Signal fine structure

The cis content in all these polymers can be readily determined from either their or H NMR spectra. The H NMR spectrum of polynorbomene gives well-resolved olefinic proton signals (multiplets) at 5.35 ppm (i) and 5.21 ppm (c), also a-proton signals (fine structure unresolved) at 2.8 ppm (c) and 2.45 ppm (r) (Larroche 1982). The C NMR spectra give, in addition, information on the proportions of double-bond dyads and triads, and hence on the distribution of cis and trans double bonds. There are two main questions to be answered (i) what... 

The X-ray instrumentation requires a commercial small angle X-ray camera, a standard fine structure X-ray generator and a sample manipulator if scanning is requested. The essential signal is the relative difference between the refraction level Ir and the absorption level Ia. Both levels are measured simultaneously by two scintillation detectors. At fixed angles of deflection this signal depends solely on the inner surface density factor C and thickness d of the sample [2] ... 

Figure 8.40 The k ySk) extended X-ray absorption fine structure (EXAFS) signal, Fourier transformed and then retransformed after application of the filter window indicated, in (a) osmium metal and (b) a 1% osmium catalyst supported on silica. (Reproduced, with permission, Ifom Winnick, FI. and Doniach, S. (Eds), Synchrotron Radiation Research, p. 413, Plenum, New York, 1980)...

If, for example, four signals are found in regions appropriate for benzene ring protons S =6-9, four protons on the basis of the height of the integrals), then the sample may be a disubstituted benzene (Fig. 2.6). The most effective approach is to analyse a multiplet with a clear fine structure... 

A poor digital resolution will result in loss of some of the fine structure of an NMR signal. To increase the digital resolution, we need either to maintain the same number of data points but reduce the spectral width or, alternatively, to maintain the spectral width but increase the number of data points. Which method would you prefer for achieving a better signal-to-noise ratio ... 

Analytical electron microscopy (AEM) can use several signals from the specimen to analyze volumes of catalyst material about a thousand times smaller than conventional techniques. X-ray emission spectroscopy (XES) is the most quantitative mode of chemical analyse in the AEM and is now also useful as a high resolution elemental mapping technique. Electron energy loss spectroscopy (EELS) vftiile not as well developed for quantitative analysis gives additional chemical information in the fine structure of the elemental absorption edges. EELS avoids the problem of spurious x-rays generated from areas of the spectrum remote from the analysis area. 

EXELFS (the extended energy-loss fine structure) carries information about the bonding and co-ordination of the atoms contributing to the edge. However, the signal needs to be strong before statistically reliable information can be obtained. 

Chemical bonding information is also obtained when the Auger transition involves valence levels, as with the KVV Auger transitions of carbon and oxygen. As Fig. 3.24 shows, the fine structure of the C KVV signal can be used as a fingerprint of the state of the carbon, but is difficult to interpret further. 

Swanson, P.C. (2002) Fine structure and activity of discrete RAG-HMG complexes on V(D)J recombination signals. Mol. Cell. Biol. 22, 1340-1351. 

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