Site multiplicity

The presence in the NQR spectrum of more resonances than there are equivalent nuclei in the guest molecule is incontrovertible evidence that there is more than one distinct inclusion site. Several examples of this are shown in Table 2. 

H G Equivalent Resonance Ref. Guest Ratio Nuclei Frequencies  

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The adverse reactions associated with the menotropins include ovarian enlargement, hemoperitoneum (blood in the peritoneal cavity), abdominal discomfort, and febrile reactions. Urofollitropin administration may result in mild to moderate ovarian enlargement, abdominal discomfort, nausea, vomiting, breast tenderness, and irritation at the injection site Multiple births and birth defects have been reported with the use of both menotropins and urofollitropin. 

Site-binding constants have been determined for only a limited range of simple oxides with only one type of surface site. Multiple-surface site minerals occurring in the deep-well environment such as silicates, aluminosilicates, and complex oxides (such as manganese oxide) will require much more complex TLMs. 

Catechol-O-methyltransferase (COMT) is widely distributed throughout the animal and plant kingdom and is primarily associated with the cytosolic fraction of rat liver, skin, kidney, glandular tissue, heart, and brain. In humans, a membrane-bound COMT also has been characterized which is encoded by the same gene as the cytosolic COMT, but with a different transcription start site. Multiple polymorphic forms of COMT may be expressed within a species. COMT catalyzes the transfer of a methyl group from SAM to one of the phenolic groups of a catechol in the presence of Mg2+ ions. With only a few exceptions, all of the methyl acceptor substrates of COMT require the catechol moiety. 

The [2Fe 2S], [3Fe S], and [4Fe S] clusters that are found in simple Fe S proteins are also constituents of respiratory and photosynthetic electron transport chains. Multicluster Fe S enzymes such as hydrogenase, formate dehydrogenase, NADH dehydrogenase, and succinate dehydrogenase feed electrons into respiratory chains, while others such as nitrate reductase, fhmarate reductase, DMSO reductase, and HDR catalyze the terminal step in anaerobic electron transport chains that utihze nitrate, fumarate, DMSO, and the CoB S S CoM heterodisulfide as the respiratory oxidant. All comprise membrane anchor polypeptide(s) and soluble subunits on the membrane surface that mediate electron transfer to or from Mo cofactor (Moco), NiFe, Fe-S cluster or flavin active sites. Multiple Fe-S clusters define electron transport pathways between the active site and the electron donor or... 

Active centers single site multiple sites... 

Among the first applications of DAS and DOR were O studies of crystalline silicates, in which spectacular gains in resolution of up to two orders of magnitude were obtained (Chmelka et al. 1989, Mueller et al. 1991, Mueller et al. 1992). In the case of wollastonite, nine sites were resolved, in agreement with the site multiplicity expected from the crystal structure (Figure 6.4). The use of field-dependent data to deduce isotropic information from changes in the isotropic position has now been supplemented by MQ MAS NMR. In the second dimension of the 2D DAS and MQ data sets... 

The last column in Table 7.2 contains site occupancies by all atoms in the format required by LHPM-Rietica. The occupancy of each site ( ) is given as a product of the population parameter (g) and site multiplicity (m) divided by the multiplicity of the general site position (A ) ... 

Fractional population factors in GSAS are treated as g s (see Eq. 7.8), while site multiplicities are automatically accounted for and cannot be changed. Site populations, however, can be refined when needed. For example, a population factor g = 0.75 for an A atom in a site with multiplicity 4 means that 75% of the site is occupied and that there are 3 A atoms in the unit cell. Obviously, the fractional population factor cannot be greater than unity or less than zero. When the refined value is out of the range 0 < g < 1, this usually points to the incorrect assignments of atom types or incorrectly located atom(s). 

The site multiplicity and the site symmetry are both given in parenthesis. 

Although the studies of phase transitions by NQR methods stay an active field that draw important results, they are not considered in this review article, the reader can refer to the reviews of K.B. Dillon223 in the book series Spectroscopic Properties of Inorganic and Organometallic Compounds. We only give an example below of the utility of NQR to solve ambiguous NMR site multiplicities. 

This graph shows the effects the way they really are. Note, however, that as the variables increase, the number of interaction terms skyrockets, eating valuable degrees of freedom. Perhaps, a better way to perform this study would be to separate the anatomical sites, because their results are not compared directly anyway, and use a separate statistical analysis for each. However, by the use of dummy variables, the evaluation can be made aU at once. There is also a strong argument to do the study as it is, because the testing is performed on the same unit—a patient—just at different anatomical sites. Multiple analysis of variance could also be used where multiple dependent variables would be employed, but many readers would have trouble... 

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