Powder x-ray diffraction studies, of the

Powder X-Ray Diffraction Studies of the Polyoxocation Selenate Salts... 

Powder X-ray diffraction studies of USbOs, USb30io and Sb204 as a function of calcination time and temperature allowed investigation of the mechanism of formation of the phases, USbOs and USbsOio- Accordingly, USbOs, which was formed at about 675 °C, was considered to be the precursor of the USbsOio phase [43]. At this temperature Sb20s was also initially present and since it was not stable it reacted with USbOs to produce USb30io. The USbsOio phase increased in concentration as the temperature was increased. At 980 °C the USbsOio phase was decomposed to re-form USbOs. 

Nnhn H, Rossbach J (2000) LINAC-based short wavelength FELs The challenges to be overcome to produce the nltimate X-ray source-the X-ray laser. Synchrot Radial News 13 18-32 OTfare D, Evans ISO, Francis R, Price S, O Brien S (1998a) The use of in situ powder diffraction in the study of intercalation and hydrothermal reaction kinetics. Mater Sci Forum 278 367-378 OHare D, Evans ISO, Francis RJ, Halasyamani PS, Norby P, Hanson J (1998b) Time-resolved, in situ X-ray diffraction studies of the hydrothermal syntheses of microporous materials. Microporous Mesoporous Mat 21 253-262... 

Harris. M.D.M. Cameson. I. Thomas, J.M. Powder x-ray diffraction studies of a loiv-temperature phase transition in the n-hexadecane/urea inclusion compound. 3. Chem. Soc.. Faraday Trans. 1990. 86. 3135. 

Recently three-dimensional metal complex hosts have been developed from the two-dimensional Hofmann type host lattices, M(NH3)2Ni(CN)4, by replacing the ammonia groups by bidentate ligands, with the aim of enlarging the range of guest molecules which can be accommodated in the host lattices [1-5]. In a previous study Mathey et al. reported the preparation of the Ni(4,4 -bipyridyl)Ni(CN)4 host lattice and its benzene, xylene, naphthalene and anthracene clathrates [5]. We have extended this study and prepared M(4,4 -bipyridyl)Ni(CN)4-2G (M = Ni or Cd G = dioxane, toluene, aniline or iV,AT-dimethylaniline) clathrates for the first time. In this study an IR spectroscopic study of the M(4,4 -bipy)Ni(CN)4 -MG compounds (where M = Ni or Cd, G = dioxane, benzene, toluene, aniline or iV,AT-dimethylaniline, n=0-2) (abbreviated henceforth as M-Ni-bipy-G) are reported. Additional information is obtained from the laser-Raman spectrum of the Cd-Ni-bipy complex. We also recorded the powder X-ray diffraction patterns of the M-Ni-bipy complexes. 

X-ray diffraction consists of the measurement of the coherent scattering of x-rays (phenomenon 4 above). X-ray diffraction is used to determine the identity of crystalline phases in a multiphase powder sample and the atomic and molecular stmctures of single crystals. It can also be used to determine stmctural details of polymers, fibers, thin films, and amorphous soflds and to study stress, texture, and particle size. 

Trialkyl- and triarylarsine sulfides have been prepared by several different methods. The reaction of sulfur with a tertiary arsine, with or without a solvent, gives the sulfides in almost quantitative yields. Another method involves the reaction of hydrogen sulfide with a tertiary arsine oxide, hydroxyhahde, or dihaloarsorane. X-ray diffraction studies of triphenylarsine sulfide [3937-40-4], C gH AsS, show the arsenic to be tetrahedral the arsenic—sulfur bond is a tme double bond (137). Triphenylarsine sulfide and trimethylarsine sulfide [38859-90-4], C H AsS, form a number of coordination compounds with salts of transition elements (138,139). Both trialkyl- and triarylarsine selenides have been reported. The trialkyl compounds have been prepared by refluxing trialkylarsines with selenium powder (140). The preparation of triphenylarsine selenide [65374-39-2], C gH AsSe, from dichlorotriphenylarsorane and hydrogen selenide has been reported (141), but other workers could not dupHcate this work (140). 

In 1983, Buelens et al. conducted studies using Linde-manufactured 0.05 pm gamma alumina powder [30]. This work using a RDE resulted in incorporation levels of 0.035 and 0.0175 wt%, i.e. no significant incorporation. Work published in 1987 by the same group resulted in codeposition of 1.45, 0.55 and 0.30 wt% [37]. Comparison of this latter work to the work from 1983 shows codeposition increased by more than an order of magnitude. While the absolute amounts may be questionable in accuracy, the relative increase is significant. Neither of the RDE studies [30, 37] involved x-ray diffraction verification of the Linde powders, presumably since Chen et al. [31] had published such verification. 

The /3-polymorphic form of anhydrous carbamazepine is official in the USP [3], The USP stipulates that, The X-ray diffraction pattern conforms to that of USP Carbamazepine Reference Standard, similarly determined. No limits have been set in the USP for the other polymorphs of anhydrous carbamazepine. Although several polymorphic forms of anhydrous carbamazepine have been reported, only the a- and /3-forms have been extensively studied and characterized [49]. A comparison of the powder x-ray diffraction patterns of these two forms revealed that the 10.1 A line (peak at 8.80° 26) was unique to a-carbamazepine, and so this line was used for the analysis (Fig. 5). It was possible to detect a-carbamazepine in a mixture where the weight fraction of a-carbamazepine was 0.02 at a signal-to-noise ratio of 2. Much greater sensitivity of this technique has been achieved in other systems. While studying the polymorphism of l,2-dihydro-6-neopentyl-2-oxonicotinic acid, Chao and Vail [50] used x-ray diffractometry to quantify form I in mixtures of forms I and II. They estimated that form I levels as low as 0.5% w/w can be determined by this technique. Similarly the a-inosine content in a mixture consisting of a- and /3-inosine was achieved with a detection limit of 0.4% w/w for a-inosine [51]. 

Nalidixic acid is another example of BCS class II drug, with oral bioavailability limited by poor solubility and slow dissolution (40). Compared to drug powder alone, the solid dispersion of nalidixic acid with P-cyclodextrin or PYP or sodium starch glycolate had much faster dissolution. X-ray diffraction studies revealed the formation of amorphous areas and less degree of crystallinity in the solid dispersion of nalidixic acid with excipients. 

In surfactant solutions, these molecules tend to remain in the hydrophobic domains. Interaction between the dyes and the polar head groups of the surfactants prevents aggregation of these dyes in the a-ZrP galleries. Surfactant-dye and matrix-dye interactions align the chromophores with the charge centers closer to the a-ZrP surface, and the hydrophobic ends are buried in the surfactant hydrocarbon chains. The binding of the dyes to the surfactant-a-ZrP matrix is confirmed from powder x-ray diffraction studies as well as from centrifugation studies [69],... 

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