Shift functions, signed

Fig. 4. NMR shifts of Pt (a) and -Cu (b) in copper-platinum alloys as a function of composition. Both shifts change sign (with respect to the usual shift standards), and zero shift does not mean that the samples are not metallic.

Inhibition of AChE leads to a net accumulation of synaptic ACh levels, with persistent activation of cholinergic receptors on poslsynaptic cells. Under normal conditions, this shift to enhanced cholinergic receptor activation leads to functional signs and symptoms of cholinergic... 

In many cases arithmetic operations must be performed on signed values. These values may be stored as bit patterns in an array, in which case the signed shift functions Sla and Sra can be employed. Additionally, tool vendors will often provide an extension to the std Joglc 1164 package that con-... 

A calibration of the popular B3LYP and BP86 density functionals for the prediction of Fe isomer shifts from DFT calculations [16], using a large number of complexes with a wide range of iron oxidation states and a span of about 2 mm s for the isomer shifts, yielded a value for the calibration constant a = —0.3666 mm s a.u. (see Chap. 5). Note the negative sign, which indicates that a positive isomer shift of a certain compound relative to a reference material reveals a lower electron density at the nuclei in that compound as compared to nuclei in the reference material. 

Fig. 4.6 Chromatographic separation factors for various uranium isotopes vs. 238U as a function of mass at 433 K. s = ln[(238U/1U)iv,aq/(238U/1U)vi,resin]- The field shift (FS) and vibrational (BM) contributions are of opposite sign. Triangles = calculated vibrational (Bigeleisen-Mayer) contribution, diamonds = calculated FS contribution, circles = measured effects, open squares = calculated effects. Note that agreement between calculation and experiment is quantitative. The correlation lines are drawn through even/even data points only (Data from Bigeleisen, J., J. Am. Chem. Soc., 118, 3676 (1996))...

The problem of the sign of AR/R for the divalent tin compounds was investigated by Lees and Flinn (16). In the relationship between the quadrupole splitting and chemical shift for the stannous compounds, two distinct correlations became apparent—compounds with a linear covalent bond, and compounds with a predominantly planar bond. Furthermore, there exists a linear relationship between the number of 5 p electrons and the chemical shift and hence the total 5 electron density. Using free tin ion wave functions in a self-consistent field calculation, they showed that the direct eflEect of adding 5 electrons is considerably... 

There is no clear correlation between the chemical shift or the ir absorption frequency and the length and linearity of the hydrogen bonds in the protonated diamines. The most reliable test for the nature of the potential function appears to be the sign of the isotope effect on the chemical shift of the hydrogen-bonded proton. 

This normalization implies that a population parameter equal to 1 corresponds to a population of one electron for the spherically symmetric function d00. The nonspherical functions (/ > 0) represent a shift of density between regions of opposite sign. They have both positive and negative lobes which integrate to equal but opposite numbers of electrons. For these functions, the normalization expression... 

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