Matching effect

Keywords Coarse-graining, Force-matching, Effective fragment potential method, Molecular... 

Scheme 13.16. Matched effect in the asymmetric allyltitanation results in a high diastereofacial selectivity.

A study on the combined use of a chiral substrate obtained by alcoholysis of a 4-benzylidene-5(4//)-oxazolone with a chiral alcohol coupled with hydrogenation using a chiral catalyst has also been described. This work shows that the matching effect of double asymmetric induction in hydrogenation can be modulated by a solvent effect. 

Trial and error calculation to match effective firing densities ... 

It should be noted that when the reaction is conducted with a chiral aldehyde and a chiral y-substituted allyltins, a matching effect when both partners impose a convergent selectivity, or a mismatching effect when the facial selectivity is divergent, may happen . Such a stereoconvergent effect was used in the synthesis of the antitumour agent azinomycin (equation 4). 

Wang, Z. Hirschi, J. S. Singleton, D. A. Recrossing and dynamic matching effects on selectivity in a Diels-Alder reaction, Angew. Chem. Int. Ed. 2009,45,9156-9159. 

As demonstrated by Hartmann and Hahn (1962), energy-matched conditions can be created with the help of rf irradiation that generates matched effective fields (see Section IV). Although Hartmann and Hahn focused on applications in the solid state in their seminal paper, they also reported the first heteronuclear polarization-transfer experiments in the liquid state that were based on matched rf fields. A detailed analysis of heteronuclear Hartmann-Hahn transfer between scalar coupled spins was given by Muller and Ernst (1979) and by Chingas et al. (1981). Homonuclear Hartmann-Hahn transfer in liquids was first demonstrated by Braunschweiler and Ernst (1983). However, Hartmann-Hahn-type polarization-transfer experiments only found widespread application when robust multiple-pulse sequences for homonuclear and heteronuclear Hartmann-Hahn experiments became available (Bax and Davis, 1985b Shaka et al., 1988 Glaser and Drobny, 1990 Brown and Sanctuary, 1991 Ernst et al., 1991 Kadkhodaei et al., 1991) also see Sections X and XI). 

Here the generic term Hartmann-Hahn experiment is used for polarization- or coherence-transfer experiments that are based on the Hartmann-Hahn principle (see Section II), that is, on matched effective fields that are created by a rf irradiation scheme. These experiments may be classified according to the following practical and theoretical aspects (see Fig. 6) that are related to properties of samples, spin systems, coherent magnetization transfer, effective Hamiltonians, multiple-pulse sequences, and incoherent magnetization transfer ... 

As stated in the introduction of this section, we use Hartmann-Hahn experiment as the generic term for transfer experiments that are based on the Hartmann-Hahn principle, that is, on matched effective fields. Because two vanishing effective fields are also matched, Hartmann-Hahn sequences need not have finite effective fields. Examples of Hartmann-Hahn sequences without effective spin-lock fields are MLEV-16 (Levitt et al, 1982), WALTZ-16 (Shaka et al., 1983b) and DIPSI-2 (Shaka et al., 1988). Note that the term Hartmann-Hahn sequence has also sometimes been used in the literature in a more restricted sense for experiments with matched but nonvanishing effective spin-lock fields (see, for example, Chandrakumar and Subramanian, 1985, and Griesinger and Ernst, 1988). 

With vf = 10 kHz, these sequences create only a small effective field that is on the order of a few hertz in the offset range between 11.5 kHz (MLEV-16) and between 9 kHz (DIPSI-2), respectively. Spins in this range of offsets have approximately matched effective fields Iv Kv,) and efficient Hartmann-Hahn transfer is possible,... 

GIO. Goeken, N. E., Thompson, J. S., and Cony, R. J. A 2-year trial of prospective HIA-DR matching. Effects on renal allograft survival and rate of transplantation. Transplantation 32, 522-527 (1981). 

Another matching effect can occur when molecular motion, for example, rotation of a methyl group, simultaneously modulates the hyperfine coupling constants and the chemical reactivity, the result being a violation of magnetic equivalence of the nuclei of the group. This phenomenon, which... 

The concept that index matching could enhance the optical penetration depth of the whole blood is proved in both in vitro experiments and theoretical studies [91-93], It should be accounted for that blood optical clearing is defined not only by refractive index matching effect, but also by changes of red blood cells size and their aggregation ability when chemicals are added. 

S. Takagi, T. Shimada, M. Eguchi, T. Yui, H. Yoshida, D. A. Tryk, H. Inoue, High-density adsorption of cationic porphyrins on clay layer siufaces without aggregation the size-matching effect, Langmuir, 18, 2265-2272 (2002). 

At the third location, Argonaut thin-fuel foils or thin depleted uranium oxide-aluminum foils of the Argonaut composition are jacketed by fuel sections. The thickness t is made equal to that of the fuel element again in an effort to match effective resonance integrals. Foils can also be placed on the outside of the fuel sections to check interior versus exterior activation. 

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