Effects of electron correlation in x-ray diffraction and an electron diffraction study of XeF<sub>6</sub>

SummaryA detailed electron and X-ray diffraction study of a suite of nephelines from a wide range of paragenetic environments indicates that, in all cases studied, additional weak maxima of scattered intensity are present. Similar intensity maxima have previously been observed and described in an isolated case by Sahama. Thermal treatment at temperatures as low as 200° C causes these maxima to become noticeably diffuse, implying a structural transformation.

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Shell regeneration in Helix pomatia

Canadian Journal of Zoology ◽

10.1139/z69-011 ◽

1969 ◽

Vol 47 (1) ◽

pp. 51-53 ◽

Cited By ~ 21

Author(s):

A. S. M. Saleuddin ◽

Karl M. Wilbur

Keyword(s):

Electron Microscopy ◽

Electron Diffraction ◽

Diffraction Study ◽

Helix Pomatia ◽

Electron Diffraction Study ◽

X Ray Diffraction ◽

X Ray ◽

Polarizing Microscope ◽

Injured Area ◽

Shell Regeneration

The early stages of the shell regeneration in Helix pomatia have been studied by electron microscopy. Within 1 hour after the removal of a piece of shell, minute crystals of CaCO3 appear in the injured area. Electron diffraction study showed these crystals to be aragonite. Calcite crystals were also present at later stages of regeneration (after 3 hours) as shown by polarizing microscope and X-ray diffraction. Vaterite was found in 1 of 12 cases. Spherulites were observed in regeneration at the shell edge but not elsewhere.

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Electron Diffraction of Wet Retina Rod Disc Membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100073453 ◽

1973 ◽

Vol 31 ◽

pp. 602-603

Author(s):

S. W. Hui ◽

V. R. Matricardi ◽

D. F. Parsons

Keyword(s):

Electron Diffraction ◽

Diffraction Study ◽

Electron Diffraction Study ◽

Natural State ◽

Rod Outer Segments ◽

X Ray Diffraction ◽

X Ray ◽

Steel Research ◽

The U.S ◽

Made In

Electron diffraction is extremely useful in studying membrane preparations in microscopic quantities. Although certain biological membranes, especially those occured in natural lemella form, have been subject to X-ray diffraction studies, so far no electron diffraction study of wet membranes had been reported, apart from a preliminary attempt made in this laboratory.! The reasons had been: 1) The inability to keep the specimen in its natural state during observation, and 2) The naturally occured lemella of membranes such as nerve myelin, retina rod and chloroplast are usually too thick for the electron beam to penetrate.We report here our preliminary results on an electron diffraction study of the disc membranes of whole wet retina rod outer segments, using the 1 Mev electron microscope at the U.S. Steel Research Center at Monroeville, Pa., with a hydration stage built by this laboratory for that microscope.

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Electron diffraction study of the validity of the Th6 space group for solid carbon dioxide

Canadian Journal of Physics ◽

10.1139/p70-355 ◽

1970 ◽

Vol 48 (23) ◽

pp. 2852-2856 ◽

Cited By ~ 2

Author(s):

A. E. Curzon

Keyword(s):

Carbon Dioxide ◽

Electron Diffraction ◽

Diffraction Study ◽

Reasonable Agreement ◽

Electron Diffraction Study ◽

Solid Carbon ◽

X Ray Diffraction ◽

Solid Carbon Dioxide ◽

X Ray ◽

Diffraction Patterns

Electron diffraction patterns obtained with 65 kV electrons (wavelength = 0.0466 Å) from polycrystalline carbon dioxide at about 77 °K are in reasonable agreement with the patterns to be expected from a lattice having the accepted Th6 symmetry of solid carbon dioxide. The calculated and observed intensities of the rings agree, provided the parameter u which measures the separation of adjacent carbon and oxygen atoms is taken to be larger than u = 0.1083 which was obtained from earlier X-ray work. Agreement between experiment and theory is obtained for u such that 0.1083 < u < 0.1250 but further work is required if u is to be determined precisely.Detailed consideration is given to those rings for which H = √17 and H = √18, where H = √(h2 + k2 + l2). In the present experiments the observed intensities of these rings agree with the calculated intensities but similar agreement was not found in earlier X-ray diffraction work.

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