Bulk magnetic susceptibility

Separation of EMCL and IMCL in proton muscle spectra is possible due to the different geometrical arrangement of these lipid compartments resulting in different bulk magnetic susceptibility (BMS). EMCL are nestled in long fatty septa along the muscle fibre bundles or fasciae, and can thus be described in a simplified way as coaxial cylinders. IMCL are located in a roughly spherical... 

Observe atoms not directly bonded to metal magnetization transferred at a distance Observe at normal biological temperatures Determine bulk magnetic susceptibility... 

The first 10 powder diffraction lines for each phase are given in Table 1. Bulk magnetic susceptibility measurements (77-300°K) show that both platinum disulfide and platinum ditelluride are diamagnetic, with susceptibilities of -31(2) and -12(1) emu/mole respectively, as expected for low-spin d6 octahedral ions. Platinum disulfide shows semiconducting behavior between 77 and 300°K, with an activation energy of 0.10(1) eV, whereas platinum ditelluride is metallic. 

Table 66 Bulk Magnetic Susceptibilities and Effective Magnetic Moments of Agn Complexes at —298 K...

The T2 relaxation times of 50 /rsec and 40 msec given in the preceding discussion correspond to line half-widths of 6.4 kHz and 8 Hz, respectively. Whipple et al. (265) concluded that the line widths of several hundred Hz which are obtained in practice must be due to bulk magnetic susceptibility effects. This type of line broadening is removable by MAS (273) and they were the first to obtain high resolution spectra with linewidths similar to those expected from the T2 values. 

Solvent effects on nuclear magnetic resonance (NMR) spectra have been studied extensively, and they are described mainly in terms of the observed chemical shifts, 8, corrected for the solvent bulk magnetic susceptibility (Table 3.5). The shifts depend on the nucleus studied and the compound of which it is a constituent, and some nuclei/compounds show particularly large shifts. These can then be employed as probes for certain properties of the solvents. Examples are the chemical shifts of 31P in triethylphosphine oxide, the 13C shifts in the 2-or 3-positions, relative to the 4-position in pyridine N-oxide, and the 13C shifts in N-dimethyl or N-diethyl-benzamide, for the carbonyl carbon relative to those in positions 2 (or 6), 3 (or 5) and 4 in the aromatic ring (Chapter 4) (Marcus 1993). These shifts are particularly sensitive to the hydrogen bond donation abilities a (Lewis acidity) of the solvents. In all cases there is, again, a trade off between non-specific dipole-dipole and dipole-induced dipole effects and those ascribable to specific electron pair donation of the solvent to the solute or vice versa to form solvates. 

An external reference is a compound placed in a separate container from the sample. For liquid samples, an external reference compound is often placed as a neat (undiluted) liquid either in a small sealed capillary tube inside the sample tube or in the thin annulus formed by two precision coaxial tubes. In either case, the usual rapid sample rotation (Section 3.2) makes the reference signal appear as a sharp line superimposed on the spectrum of the sample. An external reference is advantageous in eliminating the possibility of intermolecular interactions or chemical reaction with the sample. Also, there are no problems with solubility of the reference in the sample solution. There is, however, a serious difficulty raised by the difference in bulk magnetic susceptibility between sample and reference. 

The experimental methods used to study Fen spin crossovers include measurement of bulk magnetic susceptibility, vibrational spectroscopy (because M—L bond strengths differ appreciably between the HS and LS states), crystallography, and Mossbauer spectroscopy. 

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