Susceptibility difference

To obtain the susceptibility difference AK we make the following calculation. For naphthalene and higher aromatic hydrocarbons the average C —C distance7 is 1.41A, corresponding to AA= — 38.0X.10-6 for a six-electron hexagon. In general we write for AK the expression... 

Consider a porous medium with magnetic susceptibility difference Ax between the confining solid and the permeating fluid (Figure 3.7.1). Magnetic field gradients will develop in the pore space. The spatial distribution of this internal magnetic... 

Fig. 15. Comparison of a water suppressed muscle spectrum and a spectrum from yellow bone marrow containing almost pure fat (triglycerides). Measurement parameters STEAM sequence, TE=10 ms, TM=15 ms, TR = 2 s, 40 acq., VOI (11 X 11 X 20) mm. (a) Spectrum from TA muscle recorded after careful positioning of the VOI, avoiding inclusion of macroscopic fatty septa allows separation of extramyocellular (EMCL, broken lines) and intramyocellular lipid signals (IMCL, dotted lines) based on susceptibility differences. For this reason characteristic signals from fatty acids occur double. Signals of creatine (methyl, Crs, and methylene, Cr2) show triplet and doublet structure, respectively, due to dipolar coupling effects. Further signals of TMA (including carnitine and choline compartments), Taurine (Tau), esters, unsaturated fatty acids (-HC=CH-), and residual water are indicated, (b) Spectrum from yellow fatty bone marrow of the tibia with identical measuring parameters, but different amplitude scale.

Because of the differential impact of escolar- or oilfish-related problems around the world, and also variation in individual susceptibility, different governments continue to promulgate only modest regulation on both fish. Only three countries, Japan, South Korea, and Italy, completely ban the trading and import of the two fish, while other countries only issue special guidelines or warnings toward them (Table 1.2). It therefore remains that the majority of countries do not have any regulations for the two fish. 

When solubility dictates use of different deuteriated solvents for reference and measured samples, the chemical shift (5corr measured against the external reference and corrected for susceptibility difference must be also corrected for the difference in the chemical shifts of the lock signals, A. With a deuterium lock this difference is just the difference in 2H NMR chemical shifts of the two deuteriated solvents, which equals the difference in XH shifts of their pro tic isotopomers (equation 4) ... 

Here neglect magnetic-susceptibility differences they can be restored with no trouble.)... 

Atherosclerosis susceptibility differences among progenitors of recombinant inbred strains of mice were described by Paigen et al. (1990). 

EXAMPLE 16.2 What is the magnetic field gradient created by a 1-ppm magnetic susceptibility difference across a capillary wall of thickness 1 pm in a 1,5-T imager ... 

An alternative method for referencing Li shifts in organolithium compounds has recently been proposed by Jackman et al. [45]. It takes advantage of the multiple frequency probes and radio frequency systems of modem spectrometers and is independent of volume susceptibility difference and the nature of the lock substance. The spectrometer has to be calibrated with, for example, a 0.3 M solution of LiCl in [D]methanol containing 5% TMS. The methanol C signal (secondary reference) is then referenced to the primary standard (TMS) which yields... 

Lutz WK. 2001. Susceptibility differences in chemical carcinogenesis linearize the dose-response relationship threshold doses can be defined only for individuals. Mutat. Res. 482 71-76... 

Advantage was taken of the different field geometries in the 22.5 and 50.3 MHz instruments to correct for magnetic susceptibility differences between samples. The 50.3 MHz instrument used a superconducting magnet with the magnetic field parallel to the sample axis. The 22.5 MHz instrument used an electromagnet whose field was perpendicular to the sample axis. When the same sample was run on both instruments, true chemical shifts, unaffected by susceptibility differences, could be obtained (16). The relationship is... 

Pollutants have opposing effects on epithelia obtained from different donors [116], which reflects a population heterogeneity and susceptibility differences among donors. To account for such variability, it is necessary to test toxicants on epithelia obtained from multiple donors. 

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