Of poor crystals

Plastic clays composed largely of poorly crystallized kaolinite but having small amounts of iUite, and at times montmorillonite, are widely used ia bonding mol ding sands, especially ia the United States. 

The double bond in bicyclopropylidene (144) is shorter than in 142 and in ethene. Bond distances (A) from XD (-40 °C) have large uncertainties because of poor crystal quality,... 

Arsenic Oxidation States. A solution sample was taken 257 hr after initiation of the 300°C basalt + arsenic-doped deionized water experiment (Run D2-8, Table II). The data from arsenic oxidation state AAS analysis of the initial As(V)-doped water (0-hr sample) and of the 257-hr solution sample are given in Table HI. All detectable arsenic was in the +3 oxidation state [As(V) <15pg/L] in the 257-hr sample. Standard additions of AsGD) and As(V) to the 257-hr sample were quantitatively recovered. To desorb arsenic from particulates in this sample, an aliquot of the solution was treated with 5% hydrofluoric acid. The higher As(III) content of the treated 257-hr sample aliquot (110 vs. 61pg/L, Table HI) demonstrates that sorption occurred. Scanning transmission electron microscopic (STEM) analysis of the particulates indicated the presence of poorly crystallized high-iron illite . 

Replacement of the soft PMe2 donor group by hard NR2 or OR groups ensured the isolation of thermally stable and sublimable derivatives (Sect. 6.3). However, high volatility and solubility went at the expense of poor crystallization behavior. At least their monomeric constitution could be not excluded from their mass spectra (Fig. 15) [120]. 

M 1832). The microscopic appearance of the five samples cut with lactose revealed the presence of poorly crystallized lactose monohydrate. The X-ray diffraction patterns of all the cut samples were similar. Table III shows the ratios of the impurities present in each of the exhibits. Even though many of the exhibits had been cut, a constant relationship of the relative concentrations of the by-products was found, except with the last sample (M 1833). From these results, we concluded that the heroin in one of the exhibits (M 1832) in the Michigan case did correspond with those found in Texas. We also concluded that all exhibits of the Texas case came from a common source, and,finally, that two sources of heroin existed in the Michigan case. 

It was stated that weakly crystallized tobermorite was synthesized in a mixture of calcium hydroxide and silica gel. The reaction is most efficient at the reagent ratio CaO Si02=5/6 and water-to-solid ratio 4 1. At short activation time, the formation of poor crystallized calcium silicates of B type with tobermorite-like structure was observed, Mechanochemically obtained tobermorite is stable till 800°C. Above this temperature, it... 

Even if the problems of poor crystal intergrowth due to local exhaustion of reactants in the autoclave and synthesis of zeolite material in the bulk of the solution were solved, an important problem remains, related to the fact that several batch synthesis cycles (with their associated heating and cooling processes) are often required to achieve a zeolite membrane of good quality. Thus, a synthesis procedure in which reactants are continuously supplied to the synthesis vessel while this is maintained at a constant temperature would clearly be desirable not only for performance but also for the feasibility of the scale-up. This type of approaches has already been tested for inner MFI and NaA zeolite membranes [33-35], and the results obtained indicate that the formation of concomitant phases and the amount of crystals forming in the liquid phase are greatly reduced. Similarly, the continuous seeding of tubular supports by cross-flow filtration of aqueous suspensions [36-37] has been carried out for zeolite NaA membrane preparation. 

Sciences de TUnivers. His research interests focus on environmental mineralogy and biogeochemistry of metal contaminants and trace elements using X-ray structural techniques. In the mid-80s, he initiated a new research program on the structure and surface reactivity of poorly crystallized Fe oxides. In the early 90s, this program was extended to Mn oxides, and specifically to minerals of the bimessite family. In the mid-90s, he pioneered the application of synchrotron techniques to determination of the speciation of heavy metals in natural systems. In the last two years, he was a key developer of an X-ray microprobe at the Advanced Light Source of the Lawrence Berkeley National Laboratory dedicated to the study of complex environmental materials. He is also co-lead PI of the French Absorption spectroscopy beamline in Material and Environmental sciences (FAME) at the European Synchrotron Radiation Facility (ESRF) in Grenoble. 

At temperatures higher than about 80 °C, the oxyhydroxides become thermodynamically more stable than the trihydroxides (54) and thus tend to form. Poorly crystallized solids designated as pseudoboehmite form at lower temperatures, whereas weU-crystaUized boehmite forms at higher temperatures or after longer aging. The typical conditions for the formation of poorly crystallized, gelatinous pseudoboehmite are pH values of about... 

The speciation and structure of Fe-Si systems have also been examined between pH 3 and 10 at n > 3 and Si/Fe = 0 to 4 [80-82]. Based upon XRD results, the phases that are formed are generally amorphous with only small amounts of poorly crystallized akaganeite detected at pH 3. 

Commercially available fibers with a composition close to that of mullite (3Ab03-2Si02 or 71.80 wt.% AI2O3 and 28.20 wt.% SiO ) consist of poorly crystallized mullite or a mixture of transition... 

Fig. 3.4 RT Mossbauer spectra of poorly crystallized goethite fitted with two doublets (a) and a relatively well crystallized goethite (b) with corresponding hyperfine field distribution (c)...

Fig. 3.16 Evolution of the 80 K spectra of poorly crystallized Al-substituted maghemite, 7-Fe2-xAlx03 with increasing A1 content (after da Costa et al. [126])...

Finally, we have obtained spectra of / -trialanine of varying crystal quality. By comparing the spectrum from an annealed sample (originally of poor crystal quality) with the spectrum of another poor quality sample exposed to vacuum to remove any trace water, it was shown that line broadening and some spectral line shifts can be attributed to crystal defects rather than the presence of water. Overall, we have shown the extreme sensitivity of THz spectra to intermolecular interactions including variations in the level of hydration, hydrophobic interactions between solvent and peptide and the presence of crystal defects. 

The C-S-H phase is the main binding agent in portland cement pastes. The exact structure of C-S-H is not easily determined. Considering the several possibilities by which the atoms and ions are bonded to each other in this phase, a model may be constructed. Figure 6 shows a number of possible ways in which siloxane groups, water molecules, and calcium ions may contribute to bonds across surfaces or in the interlayer position of poorly crystallized C-S-H material.1 1 In this structure, vacant comers of silica tetrahedra will be associated with cations, such as Ca". ... 

Murthy NS, Minor H. Analysis of poorly crystallized polymers using resolution enhanced X-ray diffraction scans. Polymer 1995 36 2499-2504. 

---