Comment on Weymouth's “X-Ray Diffraction Analysis of Prehistoric Pottery”

1974 ◽  
Vol 39 (4Part1) ◽  
pp. 619-620 ◽  
Author(s):  
Prudence M. Rice
Keyword(s):  
Diffraction Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Prehistoric Pottery ◽  
Diffraction Peaks

AbstractWeymouth's X-ray diffraction analysis of prehistoric pottery necessitates a reevaluation of what diffraction peaks and "groupings" of peaks mean culturally. Specifically, archaeologists need to clarify what they mean by "temper" and what "temper" means behaviorally. X-ray diffraction will not screen out naturally occurring inclusions in the clay from those added by potters; consequently, X-ray data based on mineral ratios cannot necessarily be interpreted culturally as "temper" added by potters.

scholarly journals An Expeditious Total Synthesis of 5′-Deoxy-toyocamycin and 5′-Deoxysangivamycin

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 737 ◽  
Author(s):  
Xiangyou Dong ◽  
Jie Tang ◽  
Chen Hu ◽  
Jiang Bai ◽  
Haixin Ding ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Diffraction Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Benzoyl Group

In present paper, an expeditious total synthesis of naturally occurring 5′-deoxytoyocamycin and 5′-deoxysangivamycin was accomplished. Because of the introduction of a benzoyl group at N-6 of 4-amino-5-cyano-6-bromo-pyrrolo[2,3-d]pyrimidine, a Vorbrüggen glycosylation with 1,2,3-tri-O-acetyl-5-deoxy-β-D-ribofuranose afforded a completely regioselective N-9 glycosylation product, which is unambiguously confirmed by X-ray diffraction analysis. All of the involved intermediates were well characterized by various spectra.

X-ray diffraction analysis of stacking and twin faults in f.c.c. metals: a revision and allowance for texture and non-uniform fault probabilities

2000 ◽  
Vol 33 (2) ◽  
pp. 296-306 ◽  
Author(s):  
L. Velterop ◽  
R. Delhez ◽  
Th. H. de Keijser ◽  
E. J. Mittemeijer ◽  
D. Reefman
Keyword(s):  
Diffraction Analysis ◽  
Line Profile ◽  
Intensity Distribution ◽  
Original Description ◽  
Powder Pattern ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Line Profile ◽  
Crystallite Sizes ◽  
Diffraction Peaks

A revision is presented of the original description by Warren [X-ray Diffraction, (1969), pp. 275–298. Massachusetts: Addison-Wesley] of the intensity distribution of powder-pattern reflections from f.c.c. metal samples containing stacking and twin faults. The assumptions (in many cases unrealistic) that fault probabilities need to be very small and equal for all fault planes and that the crystallites in the sample have to be randomly oriented have been removed. To elucidate the theory, a number of examples are given, showing how stacking and twin faults change the shape and position of diffraction peaks. It is seen that significant errors may arise from Warren's assumptions, especially in the peak maximum shift. Furthermore, it is explained how to describe powder-pattern reflections from textured specimens and specimens with non-uniform fault probabilities. Finally, it is discussed how stacking- and twin-fault probabilities (and crystallite sizes) can be determined from diffraction line-profile measurements.

Powder diffraction analysis of an interstratified marcasite/pyrite structure

1995 ◽  
Vol 10 (3) ◽  
pp. 198-203 ◽  
Author(s):  
Neil E. Johnson ◽  
Sidney S. Pollack ◽  
Elizabeth A. Frommell ◽  
Patricia A. Eldredge
Keyword(s):  
Catalytic Activity ◽  
Stacking Faults ◽  
Catalyst Precursor ◽  
X Ray Diffraction ◽  
Aromatic Rings ◽  
X Ray ◽  
Naturally Occurring ◽  
Benzylic Carbon ◽  
Diffraction Peaks ◽  
Diffraction Patterns

A synthetic catalyst precursor formed by sulfiding ferrihydrite (Fe3+O(OH)) in the presence of a hydrogen donor produces X-ray diffraction patterns resembling a mixture of both naturally occurring FeS2 polymorphs marcasite and pyrite. The diffraction peaks display a differential broadening, however, wherein only those peaks coincident to both marcasite and pyrite are strong and sharp, a feature that cannot be accounted for by a simple physical mixture. The broadening is analogous to that found in hexagonal cobalt, where occasional stacking faults produce interstratification of the hexagonal and cubic close-packed forms, resulting in strongly coherent diffraction only along the stacking direction. The crystal structures of marcasite and pyrite are virtually identical if viewed perpendicular to the (101) and (001) planes, respectively. Calculation of diffraction patterns based upon models of interstratifying marcasite and pyrite layers along these planes demonstrates that a sequence with marcasite-to-pyrite and pyrite-to-marcasite stacking fault probabilities of 0.22 provides a good fit to the experimental pattern. This interstratified material is a precursor to a species that shows catalytic activity for cleaving C-C bonds between aromatic rings and benzylic carbon atoms at low (<350 °C) temperatures.

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

1993 ◽  
Vol 58 (12) ◽  
pp. 2924-2935 ◽  
Author(s):  
Jane H. Jones ◽  
Bohumil Štíbr ◽  
John D. Kennedy ◽  
Mark Thornton-Pett
Keyword(s):  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
High Yield ◽  
Monoclinic Space Group ◽  
The Novel ◽  
X Ray Diffraction ◽  
Metal Centre ◽  
X Ray ◽  
Yield Formation ◽  
Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

Bis(μ-carboxylato)dienerhodium(I) Complexes - Synthesis, Characterization and Catalytic Activity

2008 ◽  
Vol 73 (8-9) ◽  
pp. 1205-1221 ◽  
Author(s):  
Jiří Zedník ◽  
Jan Sedláček ◽  
Jan Svoboda ◽  
Jiří Vohlídal ◽  
Dmitrij Bondarev ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Diffraction Analysis ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
X Ray

Dinuclear rhodium(I) η2:η2-cycloocta-1,5-diene (series a) and η2:η2-norborna-2,5-diene (series b) complexes with μ-RCOO- ligands, where R is linear C21H43 (complexes 1a, 1b), CH2CMe3 (2a, 2b), 1-adamantyl (3a, 3b) and benzyl (4a, 4b), have been prepared and characterized by spectroscopic methods. Structures of complexes 2b, 3a and 4a were determined by X-ray diffraction analysis. Complexes prepared show low to moderate catalytic activity in polymerization of phenylacetylene in THF giving high-cis-transoid polymers, but they show only oligomerization activity in dichloromethane.

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