Correlated fragments

B. Liu and A. D. McLean, ]. Chem. Phys., 91, 2348 (1989). The Interacting Correlated Fragments Model for Weak Interactions, Basis Set Superposition Error, and the Helium Dimer Potential. 

BLEVE models arc a blend of empirical correlations (for size, duration, and radiant fraction) and more fundamental relationships (for view factor and transmissivity). Baker et al. (1983) have undertaken a dimensional analysis for diameter and duration which approximates a cube root correlation. Fragmentation correlations are empirical. 

Several methods have been developed for establishing correlations between IR vibrational bands and substructure fragments. Counterpropagation neural networks were used to make predictions of the full spectra from RDF codes of the molecules. 

Thiazole disulfides absorb at 235 and 258 nm (320-322) and characteristic infrared bands are reported in Ref. 320. The activities of 2-cyclo-hexyldithiomethylthiazoles as vulcanization accelerators have been correlated with their mass-spectral fragmentation patterns (322). 

Electron ionization occurs when an electron beam crosses an ion source (box) and interacts with sample molecules that have been vaporized into the source. Where the electrons and sample molecules interact, ions are formed, representing intact sample molecular ions and also fragments produced from them. These molecular and fragment ions compose the mass spectrum, which is a correlation of ion mass and its abundance. El spectra of tens of thousands of substances have been recorded and form the basis of spectral libraries, available either in book form or stored in computer memory banks. 

There are correlations between mass spectral fragmentations and thermal and photochemical fragmentations and rearrangements see Sections 4.02.1.2.1 and 4.02.1.2.2. 

Fig. 41. Empirical correlation between 0-0 distance, barrier height and hydrogen-atom transfer distance in OH-O fragment.

The benzene rings A and B derived from the H NMR spectrum can be completed using Table 41.1. The way in which the enol ether is bonded is indicated by the correlation signal of the proton at Sh = 8.48. The structural fragment C results. Incorporating the C atom resonating at 5c = 123.3, which has not been accommodated in ring A or B and which is two bonds Jch) removed from the enol ether proton. 

The position of the second CC double bond in the structural fragment E follows finally from the correlation of the C signals at 5c = 37.8 and 49.8 with the //signals at 3h = 4.47 and 4.65. Note that trans protons generate larger cross-sectional areas than cis protons as a result of larger scalar couplings. 

At this stage of the interpretation, the CH correlations across two or tliree bonds CH COLOC plot) provide more detailed information. The H shifts given in the CH COLOC diagram, showing correlation maxima with the C atoms at a distance of two to tliree bonds from a particular proton, lead to the recognition of eight additional structural fragments B-I (Table 50.2). 

At the end of this section, let us return briefly to the spectra shown in Fig. 3. Notice the structure in the mass spectrum of QoCa, between the completion of the first metal layer at 32 and the second at 104. This structure is identical in the fragmentation mass spectra of fullerenes covered with Ca and with Sr. It is reminiscent of the subshell structure of pure Ca clusters. The subshells could be correlated with the formation of stable islands during the growth of the individual shells[10,l 1]. The sublayer structure we observe here may also give some clue to the building process of these layers. However, the data is presently insufficient to allow stable islands to be identified with certainty. 

The total number of fragments is a function of vessel size and periiaps other parameters. Holden (1985) gives a correlation based on 7 incidents as equation 9.1-35. where F is the number of fragments and V is the vessel volume in m for the range 700 to 2,500 m. ... 

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