Crystal ordered

This is achieved by coupling the system to a suitably defined order parameter that is sensitive to the crystal order (the stacking sequence of 111 planes in this case), and doing umbrella sampling with this quantity. The result of the simulation is the free energy difference between both candidate structures—and the winner is fed... 

The transitions of the coil-globule type were considered not only in the usual space, but also in the space of monomeric units orientation, where such transition is equivalent to the nematic liquid crystal ordering [60,61]. Such an approach using the formalism developed by I.M. Lifshitz has led to the creation of the theory of liquid crystal ordering in the solutions of semi-flexible macromolecules [62,63]. 

After a given time (before crystals are visible), the coverslips are transferred over reservoirs containing lower precipitant concentrations that would normally yield clear drops (Fig. 3.4). As in dilution, the time of transfer is selected by reference to the time which it took to see the first crystals in the initial screens. The transfer lasts 1-2 seconds. This technique has produced significant improvement in crystal order of a number of proteins (e.g. Saridakis and Chayen, 2000,2003 Krengel et al., 2006). 

Iron oxides in soils have in common that they are of extremely small crystal size and/or low crystal order. This, in combination with their low concentration (only tens g kg in most soils) explains why soil iron oxides have escaped identification for a long time in spite of their obvious existence as seen from the soil colour. In the past, therefore, Fe oxides in surface environments have been considered to be amorphous to X-rays and often called limonite , which mineralogically, is an obsolete term. Furthermore, in order to identify the clay minerals in soils properly, Fe oxides are usually removed before X-ray diffraction methods are applied (Alexander et al., 1939 Mehra Jackson, 1960). 

The single hydrogen of the trianion was found to occupy only one of the two octahedral sites rather than being randomly disordered in the crystalline state in both octahedral sites, with an occupancy factor of 0.5 for each position. This observed crystal ordering of the polar C v trianions, which are identically oriented... 

The review continues with case studies of the surface reactivities of a few representative crystalline oxides and chlorides (as single crystals, ordered films, or dispersed materials) with simple probe molecules. The systems are essentially those indicated in topic 1. 

In these computations, it was assumed, following Flakus [104, 109], that there is some breaking of the IR selection rule (introduced via the q° parameter), which is increasing when the crystal order is increased, that is, when the temperature is lowered. 

The degree of crystal ordering is defined by the order parameter ... 

Internal Structure of Silk and Linen. Triangular-shaped silk filaments (called brins and composed of the protein fibroin) are embedded in a second protein (sericin) to form the bave unit. Microscopic examination of fabrics woven with the silk bave unit and subsequently cleaned of sericin reveals paired brin filaments. Fibroin contains 16 amino acids, and more than 80 of the polymer is composed of glycine, alanine, and serine only (6). Their small side groups allow chains of these amino acids to pack together closely to form the crystalline portions of the fiber. The bulkier amino acids, such as tyrosine, disrupt crystal order and produce the amorphous areas of the internal structure of the fiber. 

Of course the modulus of a block copolymer with ordered spherical microdomains is much lower than that of a crystalline solid. Near the disordering transition, the potential energy holding each domain or atom in place is of order ksT, and the modulus is roughly vksT, where v is the number of domains or atoms. This gives an elastic modulus 10 -10 dyn/cm for typical block copolymers with spherical domains, as opposed to 10 -10 dyn/cm for atomic crystals. Ordered spherical diblock copolymers are therefore soft solids. They deflect under an imposed shear stress, but do not flow continuously unless that stress exceeds a critical value, the yield stress (Watanabe and Kotaka 1984). 

The preferred type of ordering in the JT crystal depends upon the interaction between the centers that has the form (2) where, in general, k is the phonon wave vector and the branch of the phonon mode. The crystal ordering occurs correspondingly to the wave vector k for which the Fourier transform of the interaction constant is a maximum. It leads to the occupation by the electrons of the certain preferred components of the electron degenerate term at different crystal sites and correspondingly to the preferred orientation of local JT distortions. 

Annealing (near TCon) Chemical Crystal Ordering... 

For the synthesis of side chain liquid crystal polyphosphazenes, the most important examples in Figure 2 are the alkoxy- and aryloxy-polymers. Mesophase behavior has been noted with simple side chains, such as trifluoroethoxy and aryloxy side chains (9). This mesophase behavior is not conventional liquid crystal order, but polymers which exist in a conformationally disordered state (10). 

The resolution of a crystal, how far it diffracts into reciprocal space, is a good measure of crystal order. It tells us immediately to what limit of precision we can expect to structurally characterize the molecules that make up the crystal. This is highly variable between protein crystals, and often between different crystal forms of the same macromolecule. Consider the diffraction patterns in Figure 6.23. 

Other secondary factors that could influence the enthalpy-relaxation process are substantial subsidiary modes of motion and structure-forming capability. Enthalpy-relaxation rates for blsphenol-A polycarbonate (PC), which has substantial mcdn-chcdn motion in the glassy states (8.10-17), and for poly(ethylene terephthalate) (PET), which in addition to having subsidiary modes of motion has significant crystal-ordering tendency (8,9)> were studied in detail, and the results are reported here. 

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