Crystalline moderators, heavy

C. Heavy crystalline moderators. For crystalline materials, the dynamics of the atomic motions is well represented in terms of the quantized, simple-harmonic vibrations of the lattice. These excitations are commonly known as phonons, and are of considerable interest to the solid-state physicist. Since the materials of interest as reactor moderators will occur in polycrystalline form, the use of the incoherent approximation to determine the cross... 

The results for beryllium will be qualitatively similar to those for graphite, but the effects of crystalline binding will be somewhat smaller, since the average frequency of the lattice vibrations in beryllium is somewhat lower than in graphite. A brief, qualitative summary of the effects of binding on the spectra for heavy crystalline moderators can be given as follows ... 

Complexes of DMAC and many inorganic haHdes have been reported (20). These complexes are of iaterest because they catalyze a number of organic reactions. Complexes of DMAC and such heavy metal salts as NiBr2 exert a greater catalytic activity than the simple salts (21). The crystalline complex of SO and dimethylacetamide has been suggested for moderating the reaction conditions ia sulfation of leuco vat dyestuffs (22). 

A series of double compounds of arsenious oxide and the iodides of bivalent light and heavy metals has been described.6 The compounds are obtained in crystalline form by saturating hot moderately concentrated solutions of the iodides with arsenious oxide and allowing to cool. The following have been prepared ... 

Figure 2 (top) Equilibrium phase diagram at 25°C for liquid paraffin. Tween-80, and Span-80. Liquid crystalline areas indicated for changing water concentrations 15% w/w water (lamellar phase) 20% w/w (lamellar phase) O 25% w/w (lamellar phase) 30% w/w (hexagonal phase) 35% w/w (hexagonal phase), (bottom) The effect of composition on the ease of emulsion formation for liquid paraffin. Tween-80. and Span-80 systems. The area enclosed between the heavy broken line has "good" spontaneity and the light broken line "moderate" spontaneity. The remainder is "poor". (From Ref. 9.)... 

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