Transmission electron microscopy of chondrule minerals in the Allende meteorite: constraints on the thermal and deformational history of granular olivine-pyroxene chondrules

1995 ◽  
Vol 43 (3-4) ◽  
pp. 469-483 ◽  
Author(s):  
Wolfgang Friedrich Müller ◽  
Stephan Weinbruch ◽  
Rudolf Walter ◽  
Gerhild Müller-Beneke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Deformational History ◽  
Transmission Electron ◽  
History Of

Enamel Crystal Shape: History of an Idea

1987 ◽  
Vol 1 (2) ◽  
pp. 322-329 ◽  
Author(s):  
H. Warshawsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Unit Cell ◽  
Cross Sectional ◽  
Transmission Electron ◽  
History Of ◽  
Sectional Shape ◽  
Imaging Plane

The purpose of this paper is to review evidence which casts doubt on the interpretation universally applied to hexagonal images seen in sectioned enamel. The evidence is based on two possible models to explain the hexagonal profiles seen in mammalian enamel with transmission electron microscopy. The "hexagonal ribbon" model proposes that hexagonal profiles are true cross-sections of elongated hexagonal ribbons. The "rectangular ribbon" model proposes that hexagonal profiles are caused by three-dimensional segments that are parallelepipeds contained in the Epon section. Since shadow projections of such rectangular segments give angles that are inconsistent with the hexagonal unit cell, a model based on ribbons with rhomboidal cut ends and angles of 60 and 120° is proposed. The "rhomboidal ribbon" model projects shadows with angles that are predicted by the unit cell. It is suggested that segments of such crystallites in section project as opaque hexagons on the imaging plane in routine transmission electron microscopy. Morphological observations on crystallites in sections - together with predictions from the hexagonal, rectangular, and rhomboidal ribbon models - indicate that crystallites in rat incisor enamel are flat ribbons with rhomboidal cross-sectional shape. Hexagonal images in electron micrographs of thin-sectioned enamel can result from rhomboidal-ended, parallelepiped-shaped segments of these crystallites projected and viewed as two-dimensional shadows.

scholarly journals Infection With a Novel Rickettsiella Species in Emperor Scorpions (Pandinus imperator)

2020 ◽  
Vol 57 (6) ◽  
pp. 858-870
Author(s):  
Sushan Han ◽  
Aníbal G. Armién ◽  
Janet E. Hill ◽  
Champika Fernando ◽  
Dan S. Bradway ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rapid Progression ◽  
Protein Coding ◽  
Hematopoietic Organ ◽  
Transmission Electron ◽  
History Of ◽  
Gross Lesions ◽  
Membrane Bound ◽  
Methenamine Silver

Rickettsiella infection was diagnosed in 4 adult emperor scorpions ( Pandinus imperator) from 2 different collections over a 3-year period. One case had a 2-day history of weakness, failure to lift the tail, or respond to stimulation, with rapid progression to death. The other 3 cases were found dead. There were no gross lesions, but histologically the hemolymphatic vasculature and sinuses, presumed hematopoietic organ, heart, midgut and midgut diverticula, nerves, and skeletal muscle were infiltrated with phagocytic and granular hemocytes with necrosis. Phagocytic hemocytes contained abundant intracellular microorganisms that were Fite’s acid-fast-positive, Macchiavello-positive, variably gram-positive or gram-negative, and Grocott’s methenamine silver-negative. By transmission electron microscopy, hemocytes contained numerous phagocytic vacuoles with small dense bacterial forms (mean 0.603 × 0.163 μm) interspersed with large bacterial forms (mean 1.265 × 0.505 μm) and few intermediary forms with electron-dense nucleoids and membrane-bound crystalline arrays (average 4.72 μm). Transmission electron microscopy findings were consistent with bacteria of the family Coxiellaceae. Based on sequencing the 16S ribosomal RNA gene, the identity was confirmed as Rickettsiella, and phylogenetic analysis of protein-coding genes gidA, rspA, and sucB genes suggested the emperor scorpion pathogen as a new species. This study identifies a novel Rickettsiella causing infection in emperor scorpions and characterizes the unique pathological findings of this disease. We suggest this organism be provisionally named Rickettsiella scorpionisepticum.

Study of ferroelastic behavior and microstructure in polycrystalline LaCoO3 using Transmission Electron Microscopy

2009 ◽  
Vol 3 (1) ◽  
Author(s):  
S. Kell ◽  
M. Tanase ◽  
R.F. Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Defect Density ◽  
Atomic Scale ◽  
Tem Analysis ◽  
Perovskite Type Oxide ◽  
Transmission Electron ◽  
History Of ◽  
Perovskite Type

LaCoO3 is a ferroelastic perovskite-type oxide. It has been shown to undergo creep at room temperature. LaCoO3 responds to stress by changing its domain structure, resulting in formation of spontaneous strain. The microstructure of a sample of polycrystalline LaCoO3 with history of stress was investigated using Transmission Electron Microscopy (TEM). It was compared to an unstrained sample to determine what changes are produced. TEM analysis has shown an increase in defect density as well as the appearance of atomic scale ordering. The causes of the observed ordering and their relation to ferroelastic behavior are explored.

scholarly journals An unusual case of bullae and scars

2019 ◽  
Vol 6 (1) ◽  
pp. 125
Author(s):  
Tanvi P. Vaidya ◽  
Ramesh M. Bhat ◽  
Sukumar Dandekeri
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Epidermolysis Bullosa ◽  
Unusual Case ◽  
The Body ◽  
Male Child ◽  
Clinical Impression ◽  
Nail Dystrophy ◽  
Transmission Electron ◽  
History Of

<p align="center">The term epidermolysis bullosa (EB) encompasses a group of inherited mechano-bullous disorders, clinically characterized by blisters over skin and mucosae following minor frictional trauma. The diagnosis is predominantly clinical, but further classification is carried out by defining the histological level of the split. Histopathology tends to be ambiguous, as it was in this case. Our case is of a twelve-year-old male child who came with complaints of recurrent painful fluid filled lesions all over the body since 10 days of birth, aggravated by trauma, with exacerbations in the summer, and with a history of similar lesions in the mother and maternal uncle. On examination, there were multiple flaccid bullae, crusted erosions, scars and milia over trauma prone sites, such as the elbows, back, knees, shins and knuckles, with nail dystrophy and pitting of the teeth. The clinical impression as well as histopathology suggested a dominant dystrophic or a junctional EB, but immunofluorescence antigen mapping revealed it to be a case of EB simplex. We must thus bear in mind that histopathology is not definitive in EB, and immunofluorescence antigen mapping or transmission electron microscopy is imperative to correctly diagnose it.</p>

Techniques for Transmission Electron Microscopy of Fiber-Matrix Interfaces in Aluminum Alloy-Boron Composites by Ion Erosio

1971 ◽  
Vol 29 ◽  
pp. 204-205
Author(s):  
G. G. Shaw
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Alloy ◽  
Electron Beam ◽  
Pure Aluminum ◽  
Ion Milling ◽  
Transmission Electron ◽  
Fiber Matrix ◽  
Ion Erosion ◽  
Row Of Fibers

The morphology and composition of the fiber-matrix interface can best be studied by transmission electron microscopy and electron diffraction. For some composites satisfactory samples can be prepared by electropolishing. For others such as aluminum alloy-boron composites ion erosion is necessary.When one wishes to examine a specimen with the electron beam perpendicular to the fiber, preparation is as follows: A 1/8 in. disk is cut from the sample with a cylindrical tool by spark machining. Thin slices, 5 mils thick, containing one row of fibers, are then, spark-machined from the disk. After spark machining, the slice is carefully polished with diamond paste until the row of fibers is exposed on each side, as shown in Figure 1.In the case where examination is desired with the electron beam parallel to the fiber, preparation is as follows: Experimental composites are usually 50 mils or less in thickness so an auxiliary holder is necessary during ion milling and for easy transfer to the electron microscope. This holder is pure aluminum sheet, 3 mils thick.

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