Experiments crystals

One now wonders whether these two phenomena are to be observed also for the whole two-dimensional surface of a crystal non-locking of the crystal surface in spite of lattice periodicity, and divergence of the fluctuation-induced thickening of the interface (or crystal surface), and in consequence the absence of facets. The last seems to contradict experience crystals almost by definition have their charm simply due to the beautifully shining facets which has made them jewelry objects since ancient times. 

H. IwasakiandF. Iwasaki, Morphological variations of quartz crystals as deduced from computer experiments,/. Crystal Growth, 151,1995, 348-58... 

A subsequent paper (05TA1969) reported the preparation of four pyrrolo fused TBs, 34a, 34b, 35a and 35b from 33a,b (no chiral induction was observed) (see reaction of 30, 31a,b and 32). The absolute configuration of 34a, [a]o = -193, was determined by X-ray crystallography. A CIAT experiment (crystallization-induced asymmetric transformation) allows the transformation of the crude mixture of 34b and 35b into pure 35b (Scheme 7). The thiophene derivative WADPIB (03AX(E)o745) (see VI.A) also belongs to this section. 

Fig. 8. The thermal conductivity of HMX as a function of temperature. Symbols this work (liquid phase) solid bold line experiment (crystal phase) solid thin line semi-empirical form used in some combustion models. The dashed line is an extrapolation of the experimental data for HMX crystal into liquid region.

Pesticides are subject to considerable loss by evaporation when they are thinly spread over large areas of crop exposed to moving air. In this situation they are subject also to biochemical, photochemical, and solution losses which make it difficult to assess directly evaporation under field conditions. The rate of evaporation of water is easily determined and has been the subject of much experiment. The relationship of loss of pesticide to loss of water from the same surface can be verified by laboratory experiments. Crystallization and solution in leaf substances exert some effect also. When the pesticide is distributed in the soil, evaporation of water can accelerate that of the water-soluble pesticide the mechanism lies in capillary flow of solution and not in the evaporation process itself. 

SYNTHESIS OF LEAD IODIDE CRYSTALS. In the three shuttle experiments, crystals grew symmetrically over the entire membrane, and a few crystals also grew out In the chamber away from the membrane as shown In Figure 2. Some crystals were dislodged from the membrane during reentry or during removal of the solutions, but many remained attached. On the other hand, with the apparatus lying horizontally in... 

The important point is that the determination of the crystallization conditions for various polymorphic forms need not be a completely random process. The combination of keen thoughtful observation with consideration of all the available crystal structures and thermodynamic information can provide extremely useful guidelines, if not for success, then at the very least for further experiments. Crystallization is almost never a sure-fire procedure, especially when one is trying to selectively produce a particular polymorph, and one that has proven consistently or suddenly elusive. 

A shattering experience. Crystals of phosphorylase a grown in the presence of glucose shatter when a substrate such as glucose 1-phosphate is added. Why ... 

The experiments crystallized plagioclase in the composition range Ango-An4o, which covers most terrestrial magmatic plagioclases. In the case of lanthanides, Bindeman et al. (1998) find a positive correlation between RT In and Xad-For lanthanum the relationship is... 

Virtually all of the products that have been manufactured by Chirotech have used recrystallization at some point of the process to remove the catalyst (see Section 2.2). This not only removes the catalyst, but also generally raises the enantiomeric excess and enhances the product purity. It should be noted that at S/C 5000 for a substrate such as the candoxatril precursor 11 the catalyst would only contribute 0.006% (60 ppm) rhodium impurity if all of it were retained in the product. Current regulations stipulate that the rhodium content needs to be less than 5 ppm in the final product [25], but in our experience crystallization is a highly effective method to provide final products that are within specification for rhodium content. 

Identification of such eflFects is made difficult, however, by the complexity of a crystallization experiment. Crystallization typically occurs from a molecularly inhomogeneous, aqueous gel, prepared by combination of a silica and an alumina source together with varying amounts of hydroxide ion. Since the product obtained is often nucleation-controlled, variables in an experiment can include not only the silica source (gel, sol, sodium silicate) and the alumina source (sodium aluminate, aluminum sulfate) but also the detailed mixing and crystallizing procedures (temperatures, aging, stirring rate, etc.). 

Fig. 23.10. iPS, quenched to the glassy state and then crystallized at various temperatures (Left) Variation of during a subsequent heating, obtained by SAXS experiments. Crystallization line and melting line. (Right) DSC thermograms of samples, measured after isothermal crystallization processes with a heating rate of 0.5 K min [9.20]... 

The parameters defining the repulsion and dispersion non-bonded interactions for 4-aminobenzoic acid in the second paper were modified to use those of Williams, with a specific modification of the Williams carboxylic proton-pyridine nitrogen repulsion potential for the 4-aminobenzoic acid-2,2 -bipyridine co-crystal. Calculations now predicted that the P polymorph of 4-aminobenzoie aeid was 1.3 kcal moP more stable than the a polymorph, which was in much better accord with experiment. Crystal structure searching was performed for eo-crystals and for the single component crystals using Crystal Predictor.The search algorithm successfully found the experimental structures for the single component systems considered. 

Key words Phane syntheses, a//-homocalixaienes, atf-homocalixpyridines, host tailoring, large functionalized cavities, host properties, liquid-liquid-extraction experiments, crystal structures. 

In initial experiments crystallization into a chiral space group — the first requirement — was ensured by the incorporation of a chiral handle on the monomer. As a result, enantiomerically pure monomer starting material gave homochiral crystals, i.e., all crystals were right-handed or left-handed but not a mixture. Asymmetric synthesis was demonstrated for a monomer 13 in which Rj was the -CH2CH3 and R2 was either or (-)-(R) ec-butyl. When polycrystalline samples of either the... 

As the elongation takes about 10 ms in this experiment, crystallization of the NOCs finishes during elongation for (L). On the other hand, the spherulites crystallize slowly after elongation ceases. 

Table 9.2. Deviation of experiment crystallization kinetic theories for...

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