scholarly journals REDUCTION OF HEATING ARTIFACTS IN THIN SECTIONS EXAMINED IN THE ELECTRON MICROSCOPE

1957 ◽  
Vol 3 (6) ◽  
pp. 1017-1022 ◽  
Author(s):  
Michael L. Watson
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
High Melting ◽  
High Melting Point ◽  
Tissue Mass ◽  
Thin Sections ◽  
Tissue Sections ◽  
Reduce Surface Tension ◽  
Substrate Film ◽  
General Appearance

Certain phenomena affecting contrast obtained from tissue sections with the electron microscope have been investigated and a technique is described for reducing destruction by the electron beam of fine details in sections. It has been concluded that loss of embedding material is slightly higher at exposed surfaces of sections than it is at surfaces covered by substrate film. Covering of both surfaces of sections with thin films of formvar, collodion, or carbon materially improves the general appearance, reduces distortion, and sometimes reduces loss of tissue mass from the section as result of exposure to the electron beam. This improvement is considered to result from the relatively high melting-point of the covering films which serve to eliminate or reduce surface-tension or other forces operating in methacrylate softened by the electron beam.

Quantitation in thin Sections Within the Electron Microscope

1976 ◽  
Vol 34 ◽  
pp. 336-337
Author(s):  
J. Edie
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Electron Scattering ◽  
Volume Density ◽  
Thin Sections ◽  
Faraday Cage ◽  
Local Mass ◽  
Physical Measurements ◽  
Mass Volume ◽  
Varying Mass

In TEM image formation, the observed contrast variations within thin sections result from differential electron scattering within microregions of varying mass thickness. It is possible to utilize these electron scattering properties to obtain objective information regarding various specimen parameters (1, 2, 3).A pragmatic, empirical approach is described which enables a microscopist to perform physical measurements of thickness of thin sections and estimates of local mass, volume, density and, possibly, molecular configurations within thin sections directly in the microscope. A Faraday cage monitors the transmitted electron beam and permits measurements of electron beam intensities.

Optimizing Spatial Resolution for X-ray Microanalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 694-695
Author(s):  
Eric Lifshin ◽  
Raynald Gauvin ◽  
Di Wu
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Spatial Resolution ◽  
Maximum Diameter ◽  
Thin Sections ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Limiting Value ◽  
Made In

In Castaing’s classic Ph.D. dissertation he described how the limiting value of x-ray spatial resolution for x-ray microanalysis, of about 1 μm, was not imposed by the diameter of the electron beam, but by the size of the region excited inside the specimen. Fifty years later this limit still applies to the majority of measurement made in EMAs and SEMs, even though there is often a need to analyze much finer structures. When high resolution chemical analysis is required, it is generally necessary to prepare thin sections and examine them in an analytical electron microscope where the maximum diameter of the excited volume may be as small as a few nanometers. Since it is not always possible or practical, it is important to determine just what is the best spatial resolution attainable for the examination of polished or “as received” samples with an EMA or SEM and how to achieve it experimentally.

scholarly journals IDENTIFICATION OF GLYCOGEN IN ELECTRON MICROGRAPHS OF THIN TISSUE SECTIONS

1960 ◽  
Vol 8 (3) ◽  
pp. 575-589 ◽  
Author(s):  
Jean Paul Revel ◽  
Leonard Napolitano ◽  
Don W. Fawcett
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Animal Species ◽  
Short Exposure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Microscopic Appearance ◽  
Tissue Sections ◽  
Lead Hydroxide ◽  
Electron Microscopic Appearance

The electron microscopic appearance of glycogen has been studied in the organs of several animal species. Glycogen almost always appears as roughly circular granules from 150 to 400 A in diameter. The intrinsic electron density of glycogen varies from tissue to tissue; however, treatment with lead hydroxide as described by Watson deeply stains the granules. Glycogen pellets were isolated from some of the tissues studied by centrifugation. Such pellets were shown to be glycogen by chemical and histochemical criteria. When thin sections of the pellet are examined under the electron microscope they can be seen to consist of densely packed granules similar to those found in the intact tissues. Such pellets are also stained for electron microscopy by short exposure to lead hydroxide.

scholarly journals An Electron Microscope Study of Myelin Figures

1959 ◽  
Vol 5 (3) ◽  
pp. 491-500 ◽  
Author(s):  
Walther Stoeckenius
Keyword(s):  
Molecular Structure ◽  
Electron Microscope ◽  
Fatty Acid ◽  
Human Brain ◽  
Electron Microscope Study ◽  
Striking Similarity ◽  
Fixed Tissue ◽  
Thin Sections ◽  
Tissue Sections ◽  
Myelin Figures

In the electron microscope, thin sections of OsO4-fixed myelin figures from the phospholipide fraction of human brain show a pattern of parallel dark lines with a repeating period of about 40 A. It is shown that the dark lines probably represent the reaction product of OsO4 with double bonds in the fatty acid chains, thereby marking the central portion of one bimolecular lamella. The addition of globin results in dense lines 25 to 50 A wide that cover the surface of the myelin figures. When such a figure consists of only two bimolecular leaflets of lipide covered with globin, the structure shows striking similarity to the image of cell membranes in fixed tissue sections. A hypothetical schema is given of the molecular structure of the figure, and the distribution of OsO4 in it.

Low Au Content Ohmic Contacts to n-GaAs Incorporating Sputtered Tungsten Oxide

1992 ◽  
Vol 260 ◽  
Author(s):  
Naftali Lustig ◽  
R. G. Schad ◽  
A. Fleischman
Keyword(s):  
Electron Beam ◽  
Melting Point ◽  
Contact Resistance ◽  
Gaas Substrate ◽  
Ohmic Contacts ◽  
High Melting ◽  
Low Oxygen ◽  
High Melting Point ◽  
Depth Profiles ◽  
Ohmic Contact Formation

ABSTRACTElectron-beam (e-beam) evaporated low Au content NiGe(Au)W ohmic contacts with a contact resistance (Rc) as low as 0.15 Ω-mra have been reported. Due to the high melting point of W it is desirable to deposit this layer by means other than e-beam evaporation. However, the use of nearly oxygen-free sputtered W, yields contact resistances in excess of 0.7 Ω-mm. By replacing the sputtered W by a reactively sputtered metallic W oxide, containing ∼25 at. % oxygen, the low contact resistance (Rc < 0.15 Ω-mm) is restored. Contacts employing a reactively sputtered W nitride in place of W oxide also yield high Rc's (∼0.75 Ω-mm). Auger depth profiles of the reacted contacts show a significant outdiffusion of Ga from the GaAs substrate in the presence the oxygenated W but not in the low oxygen and the W nitride contacts. These results and the fact that our previously reported e-beam evaporated W contacts also contain ∼25 at. % oxygen, suggest an oxygen assisted ohmic contact formation mechanism.

The crystalline modifications and the morphology and structure of J-1 polymer spherulites

1989 ◽  
Vol 47 ◽  
pp. 360-361
Author(s):  
L. S. Li ◽  
P. H. Geil
Keyword(s):  
Thin Films ◽  
Electron Microscope ◽  
Melting Point ◽  
Chain Structure ◽  
High Melting ◽  
High Melting Point ◽  
Intermolecular Hydrogen Bonds ◽  
Morphology And Structure ◽  
Electron Microscopes ◽  
Image Position

The J-1 polymer (Poly(bis 4, 4' dicyclohexylmethane)n-dodecanediamide) (E. I. du Pont)has a well defined chain structure in which cyclohexyl groups and intermolecular hydrogen bonds make the chains rigid. This results in a high melting point for this polymer in the range of 290°C. However, there is also some flexibility in the chains of this polymer due to the -(CH2)10- segments and -(CH2)- groups between every two cyclohexyl groups along the chains. The combination of rigidity and flexibility in the J-1 polymer would lead to a variety of morphologies. In order to varify this we have studied the morphology and structure of the J-1 polymer crystallized from solution.Thin films of J-1 polymer with single crystals and six different kinds of spherulites were prepared by evaporation of solvent from am-cresol solution of J-1 polymer at temperatures of 160°-210°C. The thin films were examined in both polarizing and electron microscopes. A Philips 430 electron microscope was used at 200, 250 or 300 kV accelerating voltages.

Unusual Intranuclear Structures in Chick Sympathetic Neurons

1967 ◽  
Vol 25 ◽  
pp. 188-189
Author(s):  
E. B. Masurovsky ◽  
H. H. Benitez ◽  
M. R. Murray
Keyword(s):  
Electron Microscope ◽  
Sympathetic Neurons ◽  
Uranyl Acetate ◽  
Sympathetic Ganglia ◽  
Lead Citrate ◽  
Thin Sections ◽  
Cns Neurons ◽  
Mammalian Cns

Recent light- and electron microscope studies concerned with the effects of D2O on the development of chick sympathetic ganglia in long-term, organized culture revealed the presence of rod-like fibrillar formations, and associated granulofibrillar bodies, in the nuclei of control and deuterated neurons. Similar fibrillar formations have been reported in the nuclei of certain mammalian CNS neurons; however, related granulofibrillar bodies have not been previously described. Both kinds of intranuclear structures are observed in cultures fixed either in veronal acetate-buffered 2%OsO4 (pH 7. 4), or in 3.5% glutaraldehyde followed by post-osmication. Thin sections from such Epon-embedded cultures were stained with ethanolic uranyl acetate and basic lead citrate for viewing in the electron microscope.

Fine Structure of Interdental Cells in the Mouse Cochlea

1970 ◽  
Vol 28 ◽  
pp. 140-141
Author(s):  
Roberta M. Bruck
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Young Adult ◽  
Uranyl Acetate ◽  
Ground Substance ◽  
Tectorial Membrane ◽  
Lead Citrate ◽  
Unusual Structure ◽  
Thin Sections ◽  
Collagenous Fibers

An unusual structure in the cochlea is the spiral limbus; this periosteal tissue consists of stellate fibroblasts and collagenous fibers embedded in a translucent ground substance. The collagenous fibers are arranged in vertical columns (the auditory teeth of Haschke). Between the auditory teeth are interdental furrows in which the interdental cells are situated. These epithelial cells supposedly secrete the tectorial membrane.The fine structure of interdental cells in the rat was reported by Iurato (1962). Since the mouse appears to be different, a description of the fine structure of mouse interdental cells' is presented. Young adult C57BL/6J mice were perfused intervascularly with 1% paraformaldehyde/ 1.25% glutaraldehyde in .1M phosphate buffer (pH7.2-7.4). Intact cochlea were decalcified in .1M EDTA by the method of Baird (1967), postosmicated, dehydrated, and embedded in Araldite. Thin sections stained with uranyl acetate and lead citrate were examined in a Phillips EM-200 electron microscope.

Residual Gas Reaction in the Electron Microscope: II The Design of a Gas-Control Chamber for Quantitative Observations

1969 ◽  
Vol 27 ◽  
pp. 82-83
Author(s):  
Chester J. Calbick ◽  
Richard E. Hartman
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Local Environment ◽  
Chamber Pressure ◽  
Objective Lens ◽  
Ion Pump ◽  
Quantitative Studies ◽  
Precise Knowledge ◽  
Differential Pumping ◽  
And Control

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

SEM Examination of a Used Diamond Knife

1971 ◽  
Vol 29 ◽  
pp. 452-453
Author(s):  
J. Temple Black
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
High Magnification ◽  
Metallic Materials ◽  
Wide Spread ◽  
Thin Sections ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Scanning Electron ◽  
Diamond Knife

Since its introduction by Fernandez-Moran, the diamond knife has gained wide spread usage as a common material for cutting of thin sections of biological and metallic materials into thin films for examination in the transmission electron microscope. With the development of high voltage E.M. and scanning transmission E.M., microtomy applications will become increasingly important in the preparation of specimens. For those who can afford it, the diamond knife will thus continue to be an important tool to accomplish this effort until a cheaper but equally strong and sharp tool is found to replace the diamond, glass not withstanding.In Figs. 1 thru 3, a first attempt was made to examine the edge of a used (β=45°) diamond knife by means of the scanning electron microscope. Because diamond is conductive, first examination was tried without any coating of the diamond. However, the contamination at the edge caused severe charging during imaging. Next, a thin layer of carbon was deposited but charging was still extensive at high magnification - high voltage settings. Finally, the knife was given a light coating of gold-palladium which eliminated the charging and allowed high magnification micrographs to be made with reasonable resolution.

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