scholarly journals Twist geometry of nanocelluloses probed by electron microdiffraction

2020 ◽  
Author(s):  
YU OGAWA
Keyword(s):  
Electron Microdiffraction

The effects of surface absorbed monolayer microdiffraction patterns

1988 ◽  
Vol 46 ◽  
pp. 680-681
Author(s):  
M. Pan ◽  
J.M. Cowley
Keyword(s):  
Surface Potential ◽  
Electron Probe ◽  
Potential Distribution ◽  
Crystal Surface ◽  
Normal Direction ◽  
Surface Image ◽  
Extended Surface ◽  
Gas Molecules ◽  
Surface Nature ◽  
Electron Microdiffraction

Electron microdiffraction patterns, obtained when a small electron probe with diameter of 10-15 Å is directed to run parallel to and outside a flat crystal surface, are sensitive to the surface nature of the crystals. Dynamical diffraction calculations have shown that most of the experimental observations for a flat (100) face of a MgO crystal, such as the streaking of the central spot in the surface normal direction and (100)-type forbidden reflections etc., could be explained satisfactorily by assuming a modified image potential field outside the crystal surface. However the origin of this extended surface potential remains uncertain. A theoretical analysis by Howie et al suggests that the surface image potential should have a form different from above-mentioned image potential and also be smaller by several orders of magnitude. Nevertheless the surface potential distribution may in practice be modified in various ways, such as by the adsorption of a monolayer of gas molecules.

Identification by Electron Microdiffraction of Intermetallic Phases in a Duplex Stainless Steel

1990 ◽  
Vol 48 (2) ◽  
pp. 494-495
Author(s):  
A. Redjaïmia ◽  
J.P. Morniroli ◽  
G. Metauer ◽  
M. Gantois
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Convergent Beam Electron Diffraction ◽  
Intermetallic Phases ◽  
Small Particles ◽  
Parallel Beam ◽  
Diffraction Patterns ◽  
Average Size ◽  
Convergent Beam ◽  
Electron Microdiffraction

2D and especially 3D symmetry information required to determine the crystal structure of four intermetallic phases present as small particles (average size in the range 100-500nm) in a Fe.22Cr.5Ni.3Mo.0.03C duplex stainless steel is not present in most Convergent Beam Electron Diffraction (CBED) patterns. Nevertheless it is possible to deduce many crystal features and to identify unambiguously these four phases by means of microdiffraction patterns obtained with a nearly parallel beam focused on a very small area (50-100nm).From examinations of the whole pattern reduced (RS) and full (FS) symmetries the 7 crystal systems and the 11 Laue classes are distinguished without ambiguity (1). By considering the shifts and the periodicity differences between the ZOLZ and FOLZ reflection nets on specific Zone Axis Patterns (ZAP) which depend on the crystal system, the centering type of the cell and the glide planes are simultaneously identified (2). This identification is easily done by comparisons with the corresponding simulated diffraction patterns.

Microdiffraction analysis of precipitate crystallography and morphology in Al alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 954-955
Author(s):  
B.C. Muddle ◽  
G.R. Hugo
Keyword(s):  
Point Group ◽  
Hexagonal Lattice ◽  
Intersection Point ◽  
Saed Pattern ◽  
Point Symmetry ◽  
Hexagonal Symmetry ◽  
Precipitate Crystal ◽  
The Matrix ◽  
The Subject ◽  
Electron Microdiffraction

Electron microdiffraction has been used to determine the crystallography of precipitation in Al-Cu-Mg-Ag and Al-Ge alloys for individual precipitates with dimensions down to 10 nm. The crystallography has been related to the morphology of the precipitates using an analysis based on the intersection point symmetry. This analysis requires that the precipitate form be consistent with the intersection point group, defined as those point symmetry elements common to precipitate and matrix crystals when the precipitate crystal is in its observed orientation relationship with the matrix.In Al-Cu-Mg-Ag alloys with high Cu:Mg ratios and containing trace amounts of silver, a phase designated Ω readily precipitates as thin, hexagonal-shaped plates on matrix {111}α planes. Examples of these precipitates are shown in Fig. 1. The structure of this phase has been the subject of some controversy. An SAED pattern, Fig. 2, recorded from matrix and precipitates parallel to a <11l>α axis is suggestive of hexagonal symmetry and a hexagonal lattice has been proposed on the basis of such patterns.

scholarly journals THE NATURE OF STORAGE IRON IN IDIOPATHIC HEMOCHROMATOSIS AND IN HEMOSIDEROSIS

1960 ◽  
Vol 112 (4) ◽  
pp. 551-570 ◽  
Author(s):  
Goetz W. Richter
Keyword(s):  
Electron Microscope ◽  
Iron Hydroxide ◽  
Aqueous Media ◽  
Thalassemia Major ◽  
Solubility Curve ◽  
Colloidal Iron ◽  
Wide Range ◽  
Nitrogen Concentrations ◽  
Idiopathic Hemochromatosis ◽  
Electron Microdiffraction

Using three different methods of cells fractionation, hemosiderin granules were isolated from tissues (liver and/or spleen) of three patients. The samples were obtained from a case of idiopathic hemochromatosis, a case of thalassemia major with secondary (transfusional?) hemosiderosis, and a case of transfusional hemosiderosis associated with an unclassified anemia. Iron, nitrogen, and protein content of the hemosiderin granules varied over a wide range. Electron microscopy of sectioned granules revealed aggregates of dense particles of different shapes, with diameters ranging from 10 A to about 75 A. In some of the granules dense particles corresponding to the iron hydroxide micelles of ferritin molecules were abundant. But many of the granules contained very few of these molecules. The presence of ferritin and apoferritin in the samples of hemosiderin granules was demonstrated by means of precipitin tests in agar-gel, using rabbit antiferritin sera with known antibody nitrogen concentrations. At least three antigenic components were detected in highly purified crystalline ferritin prepared from tissues of the three patients; the hemosiderin granules contained the same antigens, but probably in much smaller quantities. Both ferritin and apoferritin molecules were extracted from hemosiderin granules, and were demonstrated in the electron microscope after suitable preparation. The solubility curve of human ferritin in solutions of (NH4)2SO4 was investigated. The results indicate that substantial quantities of ferritin or apoferritin can be lost in saline, aqueous media during isolation of hemosiderin granules from cells. It was shown by means of electron microdiffraction on selected hemosiderin granules that the dense particles represent forms of partly hydrated α-Fe2O3. The conditions necessary for electron microdiffraction in an electron microscope precluded an exact determination of the state of hydration of the α-Fe2O3 or of its structural relation to (FeOOH) micelles of pure ferritin in its undenatured state. The findings were considered in the light of evidence on the structure and disposition of hemosiderin in situ in cells, and on the structure of ferritin. Differences between endogenous hemosiderin and hemosiderin derived from injections of colloidal iron compounds were pointed out. The evidence indicates that in hemochromatosis and in secondary hemosiderosis much of the inorganic storage iron in liver and spleen is derived from degraded ferritin. The findings suggest that an abnormal cellular metabolic pathway of ferritin is implicated in the pathogenesis of hemochromatosis and transfusional hemosiderosis.

Electron microdiffraction patterns of small metallic particles

1983 ◽  
Vol 47 (2) ◽  
pp. 169-176 ◽  
Author(s):  
A. Gómez ◽  
P. Schabes-retchkiman ◽  
M. José-Yacamán ◽  
T. Oca[ngrave]a
Keyword(s):  
Metallic Particles ◽  
Electron Microdiffraction

Microdiffraction from stacking faults and twin boundaries in F.c.c. crystals

1983 ◽  
Vol 16 (2) ◽  
pp. 171-175 ◽  
Author(s):  
J. Zhu ◽  
J. M. Cowley
Keyword(s):  
Stacking Faults ◽  
Theoretical Models ◽  
Antiphase Domain ◽  
Interference Effects ◽  
Twin Boundaries ◽  
Acta Cryst ◽  
General Relevance ◽  
Domain Boundaries ◽  
Good Agreement ◽  
Electron Microdiffraction

Electron microdiffraction patterns have been obtained from regions of diameter about 15 Å in thin crystals of stainless steel containing twin boundaries and stacking faults. The diffraction spots show splittings which are characteristic of the type of defect present as a result of interference effects in the coherent convergent electron beam. The observations of spot splitting are in good agreement with calculations based on simple theoretical models. In conjunction with previous work on antiphase domain boundaries [Zhu & Cowley (1982). Acta Cryst. A38, 718–724] these results suggest that the observation of spot splitting is of general relevance for the study of all planar faults in thin crystals.

Nanoscopic unequivocal analysis of twinned crystal structures with tetragonal or orthogonal unit cells by electron microdiffraction

1999 ◽  
Vol 32 (3) ◽  
pp. 397-403 ◽  
Author(s):  
M. Leicht ◽  
T. Remmele ◽  
D. Stenkamp ◽  
H. P. Strunk
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Transmission Electron ◽  
Unit Cells ◽  
Convergent Beam ◽  
Chalcogenide Compound ◽  
Habit Planes ◽  
Twinned Crystal Structure ◽  
Electron Microdiffraction

In this study, a particular type of nanoscopic twinned crystal structure which can occur in any tetragonal or orthogonal crystal structure with a ratio of lattice parameters c/a=c/b=2 is presented. This type of twinning is characterized by twin components whosecaxes are oriented perpendicular to one another, by twin-habit planes parallel to {102} planes, and by a superstructure along the twin boundaries which is described by orthogonal unit cells with lattice parameters 2a, 2a,a. Furthermore, the suitability of electron microdiffraction, a diffraction technique of transmission electron microscopy (TEM) with a moderately convergent beam, for the analysis of such twinned crystal structures is demonstrated. For this demonstration, electron microdiffraction is applied to the chalcogenide compound Cu2In3Se5, which indeed exhibits the proposed twinned crystal structure.

Real-space dynamical simulation for electron microdiffraction effects

1999 ◽  
Vol 80 (2) ◽  
pp. 99-107 ◽  
Author(s):  
K Du ◽  
Y.M Wang ◽  
H.Q Ye ◽  
H.Y Pan
Keyword(s):  
Real Space ◽  
Dynamical Simulation ◽  
Electron Microdiffraction

scholarly journals Synthesis and Characterization of Hybrid Core-Shell Fe3O4/SiO2 Nanoparticles for Biomedical Applications

Acta Naturae ◽  
2017 ◽  
Vol 9 (4) ◽  
pp. 58-65
Author(s):  
I. V. Zelepukin ◽  
V. O. Shipunova ◽  
A. B. Mirkasymov ◽  
P. I. Nikitin ◽  
M. P. Nikitin ◽  
...  
Keyword(s):  
Biomedical Applications ◽  
High Sensitivity ◽  
Sio2 Nanoparticles ◽  
Quantitative Information ◽  
Eukaryotic Cell ◽  
Polymer Shell ◽  
Transmission Electron ◽  
Shell Forming ◽  
Electron Microdiffraction

The creation of markers that provide both visual and quantitative information is of considerable importance for the mapping of tissue macrophages and other cells. We synthesized magnetic and magneto-fluorescent nanomarkers for the labeling of cells which can be detected with high sensitivity by the magnetic particle quantification (MPQ) technique. For stabilization under physiological conditions, the markers were coated with a dense silica shell. In this case, the size and zeta-potential of nanoparticles were controlled by a modified Stober reaction. Also, we developed a novel facile two-step synthesis of carboxylic acid-functionalized magnetic SiO2 nanoparticles, with a carboxyl polymer shell forming on the nanoparticles before the initiation of the Stober reaction. We extensively characterized the nanomarkers by transmission electron microscopy, electron microdiffraction, and dynamic and electrophoretic light scattering. We also studied the nanoparticle cellular uptake by various eukaryotic cell lines.

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