Neutron scattering studies dependence

On the basis of the SANS results, a molecular mechanism has been recently proposed for the toughness enhancement of DN gels [34]. This mechanism rationalizes the changes in molecular structure of the DN gel constituents observed via in-situ neutron scattering measurements, the composition dependence of the solution viscosity, and the thermodynamic interaction parameters of PAMPS and PAAm molecules obtained previously from neutron scattering studies. More specifically, this proposed mechanism provides an explanation for the observed periodic compositional fluctuations in the micrometer range induced by large strain deformation. 

A neutron-scattering study of the alloy Gej gTe 825 the amorphous and liquid states has shown that a change in co-ordination number from 2.43 to 3.25 takes place on melting. In the liquid state the observed co-ordination number can be fitted by assuming four-fold co-ordination of Ge and threefold co-ordination of Te, whilst in the amorphous state four-fold co-ordination of Ge and two-fold co-ordination of Te is assumed. The dependence of the structure of thin films of (SnTe)i (PbSe)a, and (SnTe)j (PbTe)a on the phase composition (0 < x < 1) and on the conditions of preparation has been reported. Thermochemical data have been obtained for alloys of tellurium with tin and lead over the whole reinge of concentrations. 

Fig. 8 A slight modification of the structure can lead to completely different properties, as is illustrated by methyl-substituted his-urea compound 14 that, in contrast to gelator 13. forms a typically weak gel. The oscillatory rheology experiment shows the weak gels characteristic frequency dependency of G and G" (right), and small-angle neutron scattering studies revealed that the molecular wires are only two molecules thick, as depicted in the tentative model in the middle. (Reproduced from Ref [38].)...

In most cases, it appears possible to interpret the critical behavior of microemulsion mixtures as a liquid/gas-like critical point [113-116]. Several light- and neutron-scattering studies on oil-rich ternary and quaternary microemulsions have clearly demonstrated that the structure of these media can be described as a solution of interacting water-in-oil droplets. As first shown by Calje et al. [117], the droplets may behave essentially as hard spheres. However, in many systems an attractive contribution to the interactions exists. It has been established that the strength of attractions between W/0 micelles is strongly dependent on the micellar size and on the chain lengths of both the alcohol and oil molecules. In particular, attractions have been found to increase when the micellar radius increases or the alcohol chain length decreases and the molecular volume of the oil increases [114, 115, 118-120]. 

S. Cinelli, M. Freda, G. Onori, A. Paciaroni, A. Santucci, Hydration-dependent internal dynamics of macromolecules A neutron scattering study, J. Mol. Liq. 117 (2005) 99-105. 

In this paper we report a neutron scattering study performed on a model membrane system incorporated with various amount of cholesterol. The experimental data gives detailed insight into the phospholipid-cholesterol phase diagram, and shows how the observations depends on the thermal history of the sample. The data show also, however, that much more structural studies must be performed in order to get a complete understanding of the effect of cholesterol on membrane structures. 

Also known for some time is a phase transition at low temperature (111K), observed in studies with various methods (NQR, elasticity measurement by ultrasound, Raman spectrometry) 112 temperature-dependent neutron diffraction showed the phase transition to be caused by an antiphase rotation of adjacent anions around the threefold axis ([111] in the cubic cell) and to lower the symmetry from cubic to rhombohedral (Ric). As shown by inelastic neutron scattering, this phase transition is driven by a low-frequency rotatory soft mode (0.288 THz 9.61 cm / 298 K) 113 a more recent NQR study revealed a small hysteresis and hence first-order character of this transition.114 This rhombohedral structure is adopted by Rb2Hg(CN)4 already at room temperature (rav(Hg—C) 218.6, rav(C—N) 114.0 pm for two independent cyano groups), and the analogous phase transition to the cubic structure occurs at 398 K.115... 

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