bluuebunny/crossref_metadata_2025 huggingface dataset:
A transmission electron microscope study of the complex annealing behaviour of amorphous layers due to ion implantation in silicon
Authors: Drosd R.
Published: June 2020

It is well known that very high dose ion implantation of Si results in an amorphous (α) layer. However, the annealing of this α layer with its complicated dependence on such variables as implant species, implantation dose and temperature, crystal orientation, and thermal history is not well understood. Many of the past studies have employed the ion chanelling technique to study the crystallization of the α layer. Although this technique gives useful information concerning the α layer thickness, it tells little about the type and density of defects present. Hence the electron microscope gives unique information of the detailed mechanism of crystallization of α Si layers.

One of the most striking features of the annealing behaviour is its dependence on the crystal orientation. Previous studies indicate the (111) orientation crystallizes much more slowly than the (100), leaving behind a high density of stacking faults and twins.
Anisotropic radiation damage of potassium tetracyano platinate (KCP)
Authors: Uyeda N. , Kirkland E. J. , Siegel B. M.
Published: June 2020

The direct observation of structural change by high resolution electron microscopy will be essential for the better understanding of the damage process and its mechanism. However, this approach still involves some difficulty in quantitative interpretation mostly being due to the quality of obtained images. Electron diffraction, using crystalline specimens, has been the method most frequently applied to obtain a comparison of radiation sensitivity of various materials on the quantitative base. If a series of single crystal patterns are obtained the fading rate of reflections during the damage process give good comparative measures. The electron diffraction patterns also render useful information concerning the structural changes in the crystal. In the present work, the radiation damage of potassium tetracyano-platinatewas dealt with on the basis two dimensional observation of fading rates of diffraction spots. KCP is known as an ionic crystal which possesses “one dimensional” electronic properties and it would be of great interest to know if radiation damage proceeds in a strongly asymmetric manner.
Radiation enhanced precipitation and dissolution of precipitates investigated by transmission electron microscopy
Authors: Kesternich W.
Published: June 2020

Ni-Cr-Fe alloys are the basis for a large family of super alloys and structural steels to be applied in fast breeder and fusion reactor components. A program has been started in Jülich to investigate the point defect kinetics and irradiation induced phase instabilities in pure Ni-Cr-Fe alloys. Fig. 1 shows the change of electrical resistivity as a function of annealing temperature of a homogenized unirradiated Ni75-Cr13-Fe alloy and of the same alloy after electron irradiation and after α-irradiation. The increase of the resistivity and its subsquent decrease is explained by clustering of atoms and subsequent precipitation.

Effects of clustering in the unirradiated and electron irradiated specimens cannot be detected by transmission electron microscopy. Aging at 500 and 600°C for 250 hours also does not reveal any microstructural changes by TEM. After °-irradiation, however, precipitates as well as dislocation loops show up as black spot or black-white contrast depending on the imaging conditions Fig. 2
Determination of the structural aspects of favored grain boundary reaction sites
Authors: Gronsky Ronald , Thomas Gareth
Published: June 2020

Of the techniques which have been employed in the study of grain boundary precipitation reactions, none have demonstrated sufficient resolution to directly reveal the structural characteristics of active nucleation sites. This information is vital since many existing interpretations of conventional TEM data are in conflict.The present paper describes an application of high resolution electron microscopy which distinguishes atomic level details in both the boundary and growth front regions of grain boundary precipitates, and indicates the structure and mechanisms responsible for enhanced reaction kinetics.

Experiments were performed on an Al-9.5 at.% Zn alloy aged for 30 mins, at 180°C to encourage heterogeneous nucleation at grain boundaries. Two examples of early stage grain boundary precipitates are shown in Fig. 1, both of which have been nucleated in the lower grain. It is seen that in (b) the precipitate is much more sharply faceted than in (a). Notably the orientation of the grain boundary plane is very near to that of the close-packed {111} matrix planes of the lower grain for precipitate (b), whereas the boundary is sharply inclined to {111} for precipitate (a).
Electron microscopy studies of grain boundary segregation in α Al2O3
Authors: Krivanek Ondrej L. , Harmer Martin , Geiss Roy
Published: June 2020

Solute segregation at grain boundaries is a common phenomenon in ceramic systems. Under certain circumstances it can lead to a reduction in the boundary migration rate by an impurity drag mechanism. This favours pore attachment to grain boundaries during the later stages of sintering and allows high densities to be achieved. To interpret the sintering data one needs to know the spatial distribution of the additives, and how the additives affect the defect structure of the material. Spatial distributions can be measured by Auger electron spectroscopy, but this technique cannot distinguish additives present as separate second phase from those in solid solution, and is restricted to materials that fracture intergranularly.

In alumina, the standard sintering additive is MgO, but TiO2 can be used where hardness of the sintered material is important. We have studied Al2O3 doped with 0.1 w/o TiO2. Thin foils were prepared by ion beam milling, and examined by 1) conventional electron microscopy to investigate the grain and pore structure of the material, 2) high resolution lattice imaging to test for the presence of intergranular phases at grain boundaries, and 3) X-ray microanalysis to probe the Ti concentration profile across grain boundaries and near pore surfaces.
Hardening effects of grain boundary defect structure
Authors: Venkatesh Eswarahalli S. , Murr L.E.
Published: June 2020

The grain boundary defect structure can be changed to advantage by appropriate mechanical and thermal treatments. Researchers continue to show interest in understanding the effects of boundary defect structure on the mechanical properties of polycrystalline metals and alloys. Grain boundary structural features such as boundary ledges have been considered as a means of strengthening in metals and alloys. Considering the various models of Hall-Petch analyses, the grain boundary strength, σg can be expressed as σg = 8αGb(l-υ)m(L/ℓ); where m is the grain boundary ledge density, L is the grain size, ℓ is the distance of dislocation source in the adjacent grain matrix from the boundary, and G, b, and υ have the usual meaning. In particular, the influence of grain boundary ledge density on the strength (hardness) of grain boundaries is considered in the present paper.

In the present investigation, pure (99.98%) nickel sheet mill (hot) rolled to 0.022 in. thick was used.
Investigation of boundary structure of copper phthalocyanine crystal grains in resolving crystallographic planes
Authors: Natsvlishvili G.I.
Published: June 2020

Deformed crystals of copper phtalocyanine have been investigated. The crystals were deformed in the process of grinding. Large angle grain boundaries with good resolution of dislocations and crystallographic planes (001) have been detected in the electron microscope JEM-100 C.

Fig1 shows the grain dislocation boundary with disorientation angles ≈ll.5°.Attention should be paid to the asymmetry of the boundary. The boundary for the left side grain is almost parallel to the plane (100), while the atomic planes of the right side grain break off at the boundary at a distance of ≈65 Å from each other. The measured Burgers vector (b=12.6 Å) and the distance between the dislocations in the wall correspond to the measured disorientation angle.

If the image of the region of ‘perfect’ lattice is projected from the same negative under the photographic enlarger on the printed photograph, it will be easy to see that the elastic fields of dislocation forming the boundary given in fig. 1 are also asymmetric.
A RMEED and SEM investigation of metal oxidation phenomena
Authors: Hembree G.G. , Cowley J.M. , Otooni M.A.
Published: June 2020

We have recently completed an in-situ study of the reaction of copper thin films at low oxygen pressures (10-5 torr) and relatively high temperatures (500-700°C).These conditions allow convenient observation over reasonably short reaction times in our UHV RMEED/SEM instrument(1).

Epitaxially grown (111) copper films of approximately 100nm thickness were prepared in a conventional HV system and placed in the UHV system as produced on their mica substrates. Epitaxy was confirmed by TED/TEM on pieces of the film which were stripped off the substrate and by the electron channeling patterns observed in the SEM. Initial treatment in the UHV system included annealing at 300°C for several hours and a final anneal at 500°C for one hour. In one case the film was sputter cleaned with a 700eV argon ion beam between the two annealing processes. Some oxide nuclei of various sizes were observed after this treatment.

After the initial cleaning pure copper reflection diffraction patterns as in Fig.1 were recorded up to the sixth order.
Strip domains in Nife single and multilayer thin films with inplane magnetization
Authors: Herd S.R. , Ahn K.Y.
Published: June 2020

In this paper we attempted to correlate the microstructure of single and multilayered NiFe (80/20) films with the magnetic domain structure as a function of coercivity Hc and film thickness below 700Å. The films were prepared by either E-beam evaporation or rf-sputtering onto carbon covered mica at RT. All films were coated with a protective layer on both top and bottom surfaces, as well as a spacer layer in the case of the multilayered films, of either SiO or SiO2.

The Hc was found to drop sharply with increasing thickness from >10 oe to 6 oe between 10Å and 30Å which could be attributed to the diminishing island structure. At 30Å well separated, 200-300Å sized islands contain many small grains of up to 30Å size. Island size then decreases while the grainsize increases with thickness until a residual void network is formed around indivudial grains of size comparable to the thickness.
Orthopyroxene to talc transformation
Authors: Boland J.N. , Eggleton R.A.
Published: June 2020

Mineralogical transformations that occur during the weathering of rocks are complex processes involving both physical and chemical changes. Although it may be difficult to relate the primary minerals to the secondary phases of the weathering process, there is evidence that certain transformations occur topotaxially. The clinopyroxene, hedenbergite, alters to montronite, an iron-rich montmorillonite mineral, topotaxially; the transformation has been modelled by a crystallographic shear of 1/2[101] on (100) of the pyroxene. This shear mechanism converts the chain silicate into a sheet structure. A similar process may be postulated for several other pyroxene alterations. The commonly observed orthopyroxene to talc transformation has been studied in detail using electron microscopy, electron microprobe, optical microscopy and x-ray diffraction.

The process has been studied in an interaction zone that develops between unaltered orthopyroxene and talc layers formed along grain boundaries and within cracks. The growth of the interaction zone occurs by the migration of the interface into the unaltered orthopyroxene-Fig. 1.
Transmission electron microscopy of magnetic minerals
Authors: Smith P.P.K.
Published: June 2020

The study of palaeomagnetism has had a great impact on the earth sciences, providing the first conclusive proof that continental drift has occurred. Although it is generally accepted that the primary magnetisation of basic igneous rocks is a thermal remanent magnetisation (TRM) carried by opaque iron-titanium oxide minerals, particularly those of the magnetite-ulvospinel series, there is still some doubt as to the exact magnetic state of the grains responsible for this palaeomagnetic TRM. The great stability of the TRM in many igneous rocks suggests a population of non-interacting particles, each consisting of a single magnetic domain, but it has been argued that the grain size of magnetic minerals in rocks is much greater than the critical size for this behaviour. For magnetite this critical size is about 0. 05 μm for equidimensional particles, rising to about 1 μm for elongated grains with an axial ratio of 10 : 1 (Evans, 1972). Thus single-domain particles would not be detected by conventional (optical) petrographic techniques.
Characterization of polymeric materials by TEM
Authors: Russell R.R.
Published: June 2020

Structural characterization of the expanding cavalcade of engineering polymers is now as important to the materials application engineer as to the basic researcher. Direct transmission electron microscopy (TEM) is the primary method for delineation and evaluation of microstructures in many polymer blends and composites and thus plays a major role in characterization studies.

Only TEM clearly resolves structural components, such as phases and fillers in many polymeric materials. This technique can also reveal the effects of strain (crazing, shearing or phase deformation) in polymer microstructures. Thus, by utilizing TEM, bulk structural documentation (Figure 1) as well as the results of laboratory testing (Figure 2) or manufacturing processes can be studied.

Basic to successful direct TEM structural characterization of any material are reliable sample preparation techniques capable of producing thin samples which retain the true features of the bulk material.Ultramicrotomy is used extensively for producing such thin samples from polymers.
Determination of the phase structure of polymerblends by electron microscopy
Authors: Kaemof Dr. G.
Published: June 2020

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.

The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).

The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.

The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.
Analytical TEM of the discontinuous reaction in Cu-Be-Co alloys
Authors: Williams D.B.
Published: June 2020

The discontinuous reaction in commercial Cu-1.87%Be,-0.257%Co alloys has been observed in a TEM/STEM. Microdiffraction has been used to determine precipitate/ matrix orientation relationships and high resolution X-ray microanalysis has enabled the effect of the Co on the discontinuous and continuous precipitation reactions to be studied.

Discs of Cu-Be, solution treated at 800°C for 1 hour were water quenched and aged for varying times between 175°C and 340°C. Thin foils were prepared by jetelectropolishing with a solution of 30% HNO3 in methanol at -50°C and 25 volts. All foils exhibited the discontinuous reaction which occurs at grain boundaries only and consists of alternate lamellae of the α Cu-Be solid solution and the metastable intermediate γ' (CuBe) phase which grow at the expense of homogeneous matrix γ'. A typical STEM micrograph of the reaction is shown in fig. 1. The γ' precipitates, initially ascribed erroneously to the presence of a G.P. zone solves, were later identified as a B2 superlattice structure with a=0.27nm, although evidence for superlattice spots has been disputed.
STEM microanalysis of precipitates in a nickel-base superalloy
Authors: Craven A.J. , Menzies R.G. , Bricknell R.H.
Published: June 2020

In a powder compacted nickel-base superalloy used in high temperature applications, a group of metal carbides (MC) 200-600nm in diameter were observed. Many of these precipitates contained an inner particle (20-60nm in diameter) which will be referred to as the nucleus. In addition to the commercial interest in such a metallurgical system, the identification of the two types of particles provides an interesting problem in microanalysis. Currently two analytical techniques are available on the VG Microscopes HB5, scanning transmission electron microscopes (STEM); energy dispersive X-ray analysis (EDX) and transmission electron energy loss spectroscopy (TEELS).

When analysing thinned foils there is the problem of interference from a layer of matrix on the precipitate or from the outer precipitate surrounding the nucleus. Even if the foil is thinned to the extent that layering effects are removed EDX still suffers two drawbacks; (i) Inadequate collimation leads to system peaks following general specimen illumination; (ii) X-rays and electrons leaving the area analysed generate characteristic peaks from adjacent regions.
Micro Auger analysis using a field emission source
Authors: Bovey P.E. , Wardell I.R.M. , Williams P.M.
Published: June 2020

The use of a high brightness field emission source holds clear promise in the area of micro Auger analysis of surfaces. The high current density and small probe diameter obtainable from the field emitter (30 n A into 300Ǻ, for example) offer the possibility of recording Auger spectra from areas less than 300Ǻ, as previously demonstrated . Furthermore, the ultra high vacuum technology necessary for a reliable field emission source, is wholly compatible with the type of vacuum experimental vessel customary in surface analysis applications.

We describe here results obtained with an HB50A Auger Microprobe in which an environmental cell, introduced on a bellows movement into the experimental vessel, permits heating to 800°C in an atmosphere of 0.1 torr of gas. The sample under study was pure polycrystalline iron.

This was reacted with methane at 750°C in situ for 12 hours. The carbon resulting from cracked methane, dissolved in the iron to such an extent that, on cooling to 600˚C, precipitation occured. Figure 1 shows an SEM image of a characteristic precipitate, recorded with the sample held at 600˚C at a magnification of 2,000 X.
A quantitative approach to inner shell losses
Authors: Leapman R.D. , Rez P. , Mayers D.F.
Published: June 2020

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.

The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as
Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy
Authors: Zaluzec N. J.
Published: June 2020

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.

The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation
The symmetry of dynamical microdiffraction patterns from dislocation cores
Authors: Spence J.C.H.
Published: June 2020

Within useful approximations, the point group symmetry of a zero layer dynamical electron diffraction pattern is the same as that of the crystal potential projected in the beam direction. It is not necessarily centrosymmetric, as in the X-ray case. This result can be used to determine the point symmetry of crystal defects from microdiffraction (CBED) patterns. The CBED pattern from perfectly crystalline specimens is sensitive to the probe position (STEM scan coordinate) and to the focus setting and aberrations of the objective lens only in regions where the diffraction discs overlap. This region is detected for STEM lattice imaging. For CBED patterns formed with the probe situated over a defect the entire pattern is sensitive to lens focussing and probe position. These patterns may therefore be used to determine both the symmetry of the defect structure by the methods of Goodman and the absolute location of centers of symmetry in the structure.
Plastic deformation of θ ' in Al-4%Cu alloy
Authors: Bhat Shrikant P.
Published: June 2020

deformation behavior of Al-Cu alloys aged to contain θ ' has been the subject of many investigations (e.g., Ref. 1-5). Since θ ' is strong and hard, dislocations bypass θ ' plates (Orowan mechanism) at low strains. However, at high strains the partially coherent θ ' plates are probably sheared, although the mechanism is complex, depending on the form of deformation. Particularly, the cyclic straining of the bulk alloy is known to produce gross bends and twists of θ '. However, no detailed investigation of the deformation of θ ' has yet been reported; moreover, Calabrese and Laird interpreted the deformation of θ ' as largely being elastic.

During an investigation of high temperature cyclic deformation, the detailed electron-microscopic observation revealed that, under reversed straining conditions, θ ' particles are severely distorted--bent and twisted depending on the local matrix constraint. A typical electronmicrograph, showing the twist is shown in Fig. 1. In order to establish whether the deformation is elastic or plastic, a sample from a specimen cycled at room temperature was heated inside the microscope and the results are presented in a series of micrographs (Fig. 2a-e).
Application of an analytical electron microscope to surface deformation and wear research
Authors: Carpenter R.W.
Published: June 2020

A primary objective of surface deformation and wear research is the correlation between surface deformation and wear made under different loading and environmental conditions with the near-surface deformation substructure in the material. The multiple imaging modes of an analytical electron microscope, TEM/STEM and SEM, together with single surface thinning methods should permit direct examination of both the external worn surface and immediately underlying deformation substructure in one instrument.This method eliminates the inconvenience of using two instruments to characterize surface and subsurface regions and the problem of disregistry between areas examined in two instruments. This paper presents first results using the method to examine stylus tracks on aluminum.

Annealed, flat 3-mm-dia disks of commercial purity (1100 grade) A1 were electropolished to a flat specular surface on one side and then put in a ruling device for surface deformation. Straight wear tracks were ruled on the polished surface using a smooth hemispherically shaped stylus having a 2.5μm radius.
Observation of initial cracking in hydrogen-charged pure iron
Authors: Takeyama T. , Takahashi H.
Published: June 2020

It is considered that hydrogen atoms in iron dissolve interstitially in the matrix, segregate at some lattice defects, are absorbed at the interface of foreign atoms or inclusion, and/or precipitate as a gas phase. This precipitation of gaseous hydrogen in iron causes the formation of void, microcrack and blister, which affects the mechanical properties of the iron. Fracture due to hydrogen embrittlement may be caused by a crack initiation and growth, and propagation. It is obvious that this fracture depends on the diffusion of hydrogen atoms through the iron. However, the mechanism of hydrogen embrittlement cracking has not been fully explained.

The aim of the present work was to investigate the microcrack and microvoid generated by the precipitation of hydrogen charged by cathodic method.

Pure iron was cold-rolled to a sheet of 0.5mm thickness. After cutting, specimens were annealed at 700°C for one hour in a vacuum of 10-5torr. The grain size was l0̴20 μm. The specimens were charged with hydrogen by applying cathodic potentials in electrolytic cells containing O.1N-H2SO4 with the addition of 250 mg/ℓsodium arsenite to act as a recombination poison.
Freeze-fracturing and replication at -260 C
Authors: Gross H. , Müller T. , Wildhaber I. , Winkler H. , Moor H.
Published: June 2020

In order to quantify the information contained in metal replicas we chose periodic test specimen. The so-called HPI-layer (a sheet-like protein monolayer) of the bacterium Deinococcus radiodurans was examined by freeze-drying (“surfaces“) and the paracrystalline regions of the plasmalemma of baker's yeast were studied by means of freeze-fracturing (“fracture faces“). 2-D periodic structures allow the application of digital image processing (Fourier filtration, correlation averaging, analysis of the granularity) which greatly facilitate assessment of methodological processes.

After freeze-drying and Pt/C- and Ta/W-shadowing we achieved image averaged details at the molecular level on both surfaces of the HPI-layer (Figs. 1-5). Unidirectional shadowing (Figs. 1-3) gives information about the surface properties (mainly in the third dimension) whereas rotary shadowing (Figs. 4,5) provides information about the lateral arrangement and the symmetry of the lattice subunits. When the specimen is thin and a relatively large proportion of its surface is accessible to the evaporated material, as in the case of the HPI-layer, a 3-D model can be produced easily by combining the shadowing data obtained on both surfaces (Fig. 7).
A simple procedure for obtaining clean sections for TEM
Authors: Chien K. , Van de Velde R. , Heusser R.
Published: June 2020

After ultrathin sections are cut, contamination can result not only from the staining and rinsing solutions but also from improper handling technique. A new procedure is described which is simple to perform and enables one to obtain cleaner sections for EM examination.

Commercially available instruments and materials (Ted Pella, Inc.) are used for this procedure: A Pelco Vacuum Device (fig. 1) is connected by flexible plastic tubing to an adaptor which can accept various sized metal needles. The vacuum can be finger-tip controlled at the aperture within the adaptor. Cohen-Pelco Tabbed Grids are used for section support. A flat, silicone rubber grid holder is used for staining and rinsing of several grids at one time.
Bronchial stereocilia in the immotile cilia syndrome: A case report
Authors: Price George , Cerezo Lizardo
Published: June 2020

Ultrastructural defects of ciliary structure have been known to cause recurrent sino-respiratory infection concurrent with Kartagener's syndrome. (1,2,3) These defects are also known to cause infertility in both males and females. (4) Overall, the defects are defined as the Immotile, or Dyskinetic Cilia Syndrome (DCS). Several ultrastructural findings have been described, including decreased number of cilia, multidirection orientation, fused and compound cilia, membrane blebs, excess matrix in the axoneme, missing outer tubular doublets, translocated doublets, defective radial spokes and dynein arms. A rare but noteworthy ultrastructural finding in DCS is the predominance of microvilli-like structures on the luminal surface of the respiratory epithelium. (5,6) These permanent surface modifications of the apical respiratory epithelium no longer resemble cilia but reflect the ultrastructure of stereocilia, similar to that found in the epidydimal epithelium. Like microvilli, stereocilia are devoid of microtubular ultrastructure in comparison with true cilia.
Laboratory administration: An overview
Authors: Spurlock Ben O.
Published: June 2020

Numerous articles have been published on the design, operation and maintenance of an electron microscopy facility. This discussion will be directed toward identifying some of the administrative situations unique to a diagnostic laboratory and to offer suggestions for addressing these matters should they arise. It may be well, at this time, to remember that the critical difference between a diagnostic facility and most other laboratories is not that the specimens we study are from human beings but that the results of our efforts become a part of that patient's permanent legal medical records. In view of the number of laboratories in which the responsible electron microscopist is not a Pathologist, I will focus this talk on laboratory inspection for licensure and discuss some possible legal considerations. As I am neither a physician nor an attorney, the following remarks are not intended to represent a medical/legal opinion but to reflect my own personal experiences as Director of a diagnostic electron microscopy facility at the Medical College of Georgia and its affiliated institutions.
The application of electron microscopy to diagnosis in gynecologic neoplasms and tumor-like conditions
Authors: Roth Lawrence M.
Published: June 2020

The female reproductive tract may be the site of a wide variety of benign and malignant tumors, as well as non-neoplastic tumor-like conditions, most of which can be diagnosed by light microscopic examination including special stains and more recently immunoperoxidase techniques. Nevertheless there are situations where ultrastructural examination can contribute substantially to an accurate and specific diagnosis. It is my opinion that electron microscopy can be of greatest benefit and is most cost effective when applied in conjunction with other methodologies. Thus, I have developed an approach which has proved useful for me and may have benefit for others. In cases where it is deemed of potential value, glutaraldehyde-fixed material is obtained at the time of frozen section or otherwise at operation. Coordination with the gynecologic oncologist is required in the latter situation. This material is processed and blocked and is available if a future need arises.
Comparative analysis of crystalline lens gap junctions
Authors: Kuszak J.R. , Shek Y.H. , Carney K.C. , Rae J.L.
Published: June 2020

In freeze-etch replicas, gap junctions are identifiable on PF faces as raised plaques of membrane with aggregated hexameric transmembrane proteins. On EF faces, gap junctions are seen as imprinted membrane plaques that have pits corresponding to the connexons of the gap junction from the previously conjoined cell. By these criteria, several investigators have demonstrated that gap junctions are more numerous between fiber cells of the crystalline lens than between cells of any other organ. A review of this literature suggests that there is considerable species variation in the percent of fiber cell membrane specialized as gap junction in crystalline lenses. In electrophysiological studies, cells are considered to be electrotonically coupled to one another if an intracellular potential change can be elicited at essentially all locations when current is applied at a single intracellular location. Electrotonic coupling is presumed to be mediated by gap junctions.
Undecagold labelling of glutamine synthetase from E. coli
Authors: Lipka J.J. , Hainfeld J.F. , Wall J.S.
Published: June 2020

Glutamine synthetase (GS) from E. coli consists of 12 identical 50 kD subunits arranged in a double hexagon with one six-fold axis of rotational symmetry and six two-fold axes. The divalent cations Mn2+ or Co2+ induce the formation of linear face-to-face aggregates of individual GS molecules, resulting in the formation of long linear arrays, GSn. This aggregation is retarded and eventually reversed to the native form (GS) as the salt concentration increases. We have used an undecagold (11-Au) cluster ion, ((p-H2NCH2C6H4)3) - P)7Au113+, which induces similar aggregation of native GS, resulting in a wide distribution of ordered linear arrays of GSn (where n=2-10, or more). These aggregates show the highly electron dense labels located exclusively at the face-to-face interaction surface. Specimens of the GS aggregates have been studied with the Brookhaven STEM and molecular weight values have been determined with the Brookhaven STEM mass measurement computer system.
Nucleoprotein: DNA hybridization as a preparative method to isolate specific eukaryotic genes as chromatin
Authors: Workman J.L. , Langmore J.P.
Published: June 2020

Determining the structure and protein composition of chromatin in different states of genetic activity is critical for understanding eukaryotic gene expression. Very little is known about the dependence of chromatin structure upon the sequence or transcriptional activity of the DNA, except in the 2 cases in which particular genes can be isolated from the remainder of the chromatin. In the first case, active ribosomal RNA genes have been shown by EM to contain structurally altered nucleosomes. EM has also shown that SV40 minichromosomes possess a DNA sequence that is devoid of nucleosomes. Clearly, EM is capable of resolving sequence and activity specific features of chromatin, but is limited by the number of genes that have been purified.

We have adapted methods of nucleic acid enzymology and hybridization in order to isolate specific genes as intact chromatin. Our methods are DNA sequence specific and thus are generally applicable to isolating a chosen gene at different points in development, differentiation and growth.
Electron microscopy of myosin molecules
Authors: Craig Roger
Published: June 2020

Myosin is the major contractile protein of muscle, where it exists as a filamentous polymer (about 1.6μm long and 15nm in diameter) containing several hundred myosin molecules. The myosin filaments overlap with filaments of actin (the other main protein of muscle) and contraction is brought about by a sliding of these two filament types past each other. The sliding force is generated by a portion of each myosin molecule (the myosin crossbridge) which projects from the surface of the filament and attaches cyclically to actin in a manner which “rows” the filaments past each other. The energy for rowing comes from the hydrolysis of ATP by the myosin crossbridges, a process that is activated by their interaction with actin. Myosin also occurs in many nonmuscle cells where, together with actin, it generates a variety of motile activities (e.g. cell division) by a mechanism that is probably similar to the sliding mechanism occurring in muscle.
Systematic evaluation of microangiopathy in diabetic Chinese hamsters: I. Morphometric analysis of minimal glomerular basement membrane thickness in 19-23 month old Chinese hamsters
Authors: Diani A.R. , Sawada G.A. , Peterson T. , Wyse B.M. , Blanks M.C. , Vidmar T.J. , Gerritsen G.C.
Published: June 2020

Microangiopathy has been recognized as a critical complication which afflicts the human diabetic population and magnifies the risk for permanent injury and/or mortality. One of the major manifestations of diabetic microvascular disease in man appears to be capillary basement membrane thickening (CBMT) which has been termed the “hallmark of diabetic microangiopathy”. CBMT of diabetic patients seems to be a product of vascular injury imposed by the interaction of metabolic derangement, environmental factors and genetics (1). Although the degree of thickening varies with age, duration of diabetes, severity of metabolic impairment and location in the body, capillary basement membranes from the kidney, skeletal muscle and heart are usually expanded in diabetic man. However, due to the sparsity of systematic studies and inherent problems with human experimentation, the pathogenesis of CBMT remains controversial. In an attempt to achieve a better understanding of the etiology and progression of CBMT, diabetic animal models have recently been the focal point of intensive research (2).
Arterial lesions in dopamine-infused rats
Authors: Bugelski P. J. , Walsh Vockley C. , Sowinski J. , Arena E. , Morgan D. G.
Published: June 2020

Dopamine is administered by intravenous infusion to maintain renal blood flow in patients with shock and congestive heart failure. This effect is probably due to dopamine receptors present in the renal vasculature. Dopamine also has agonist activity at α-adrenergic receptors which can evoke vasoconstriction. Alpha-adrenergic agonists produce medial necrosis in various arterial beds of the rat, including those in which dopamine exerts a vasodilator effect. To determine the effects on these arteries, we administered dopamine to rats by intravenous infusion and examined their gastric and renal arteries by transmission and scanning electron microscopy. Sprague Dawley rats were infused via tail vein with 20 μg/kg/min of dopamine HCl. For transmission EM (TEM), rats infused with dopamine for 1, 4 or 24 hours were perfused with 1% phosphate-buffered glutaraldehyde, post-fixed in 1% OsO4, stained en bloc with uranyl magnesium acetate, dehydrated and embedded in epoxy.
Discrimination of monomer from multimer DNA disk-shaped toruses by freezeetch TEM
Authors: Ruben George C. , Marx Kenneth A.
Published: June 2020

In vitro collapse of DNA by trivalent cations like spermidine produces torus (donut) shaped DNA structures thought to have a DNA organization similar to certain double stranded DNA bacteriophage and viruses. This has prompted our studies of these structures using freeze-etch low Pt-C metal (9Å) replica TEM. With a variety of DNAs the TEM and biochemical data support a circumferential DNA winding model for hydrated DNA torus organization. Since toruses are almost invariably oriented nearly horizontal to the ice surface one of the most accessible parameters of a torus population is annulus (ring) thickness. We have tabulated this parameter for populations of both nicked, circular (Fig. 1: n=63) and linear (n=40: data not shown) ϕX-174 DNA toruses. In both cases, as can be noted in Fig. 1, there appears to be a compact grouping of toruses possessing smaller dimensions separated from a dispersed population possessing considerably larger dimensions.
High-voltage electron microscopy of insect capsule viruses
Authors: Mazzone H.M. , Wray G.
Published: June 2020

The High-Voltage Electron Microscope (HVEM) affords the researcher an opportunity to study insect virus inclusion bodies, intact, without resorting to physical thin-sectioning or chemical degradation procedures. In this manner polyhedral inclusion bodies, isolated from insects infected with nuclopolyhedrosis viruses (NPVs) were observed with the HVEM, and the numerous viruses lying internally, clearly delineated.

In the present report we used the HVEM to study, in whole mount, another type of insect virus inclusion body, that from the capsule (granulosis) viruses of two hosts, the fall webworm, Hyphantria cunea (Drury) and the yellow wollybear, Diacrisia virginica (Fabricius). The insect capsule viruses, like the NPVs, are characterized by a crystalline protein matrix which occludes enveloped, rod-shaped virus particles. Whereas the inclusion bodies of NPVs contain a number of virus particles in each inclusion body, those of the capsule viruses contain, generally, only one virus particle in each capsule or granule.
Morphometric SEM study of the effects of ACTH on endothelial fenestrae in the rat adrenal cortex
Authors: Curtis J. , Schwartz K. S. , Apkarian R. P.
Published: June 2020

A scanning electron microscope (SEM) study was made of the effect of adrenocorticotropic hormone (ACTH) on the size and numbers of fenestrae/unit area in the capillary endothelium of the zona fasciculata (ZF) of the rat adrenal. The stimulatory effect of ACTH on cholesterol uptake via high density lipoproteins in the rat and evidence for the secretion of glucocorticoids by exocytosis of lipid droplets described by Rhodin suggest that endothelial change may accompany these transport phenomena.

Twelve rats received two Dexamethasone (DEX) ip injections (25 μg DEX/100 g body wt.), the first at 8 PM and the second at 8 AM the next day, to inhibit the release of endogenous ACTH by the anterior pituitary. The animals were then divided into two groups. Six animals received only saline vehicle and six rats received ACTH (100 ng/100 g body wt.).
Scanning electron microscope observation of the endings of the odontoblast process in human and animal dentin
Authors: Chernecky R. , Smith D.C.
Published: June 2020

Recent SEM studies have demonstrated that the odontoblast process occupies the dentinal tubules of fully formed dentin, up to the dentinal-enamel junction (Maniatopoulos and Smith, 1982, 1983; Yamada et al, 1983). There is however, still debate on how the processes end at the dentinal-enamel or dentinal-cementum junction. It was the purpose of this study to investigate the endings of the odontoblast process in these areas.

Materials and Methods:

Freshly extracted human and rat teeth were a) split mechanically by the use of a mallet and a chisel, b) decalcified in 18% E.D. T.A. for 6 hr, c) washed in PBS for 1 hr, d) digested with bacterial collagenase for 2 hr at 37°C, e) fixed in 2% glutaraldehyde with 0.1M cacodylate buffer for 12 hr, f) post-fixed in 1% osmium, g) dehydrated in a graded series of aqueous alcohol. All solutions had 0.1M sucrose added to maintain almost near physiological osmolarity, ph was 7.4. Then specimens were routinely processed for scanning electron microscopy (ISI-60).

Results:

Odontoblast processes were observed in the inner, middle and outer part of dentin, up to the dentin-enamel or dentino-cementum junction, in all specimens examined. These observations verify the findings of previous workers in the field. At the area of mantle dentin the odontoblast processes were observed to be divided, giving two or more terminal branches (schematically shown in fig 1-3). In this area the processes were observed to end forming spherical structures (fig 1-9). These spherical endings of the odontoblast processes were observed after the total removal of the enamel and part of the mantle dentin through demoralization. These structures were observed on the surface of the dentin in close relation to the openings of the dentinal tubules (fig 4,5,8 and 9) and presenting a true continuation to the odontoblast processes (fig 6,7). In some specimens (fig 5,6) spheres were collapsed probably due to specimen dehydration following fracture and SEM preparation, whereas in other specimens they appeared intact (fig 8,9). Some endings (fig 8,9) showed smaller spherical projections on the main sphere body. The spherical endings of the odontoblast processes were observed in both crown and root mantle dentin.

Conclusions:

The results suggest that i) the odontoblast processes occupy the full length of fully developed dentin in both human and rat teeth, up to the dentino-enamel or dentino-cementum junction, ii) The odontoblast processes end in the mantle dentin in the form of spherical structures.

Acknowledgement:

The authors are grateful to Dr. M. Sigal for the initial preparation of the specimens.
Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine
Authors: Faroon O. , Al-Bagdadi F. , Snider T. G. , Titkemeyer C.
Published: June 2020

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.

The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.
Neurosecretory pathways to an insect flight motor nerve identified by light and electron cobalt chloride microscopy
Authors: Wasserman Arthur J.
Published: June 2020

Motor nerve innervation of muscle may do more than simply initiate contraction. There is the long-term trophic relationship between nerve and muscle and the shorter modulatory actions of biogenic amines and peptides. These substances could come from the motor axon itself, an auxilary neurosecretory (NS) axon that accompanies the motor nerve or the general circulation by diffuse release from a storage organ. This study establishes the presence of NS axons in the motor nerve IINlb to the dorsal longitudinal (flight) muscle (DLM) of the hawkmoth,Manduca sexta. The sources of NS material are identified by light and electron cobalt chloride microscopy (LECCM).
Heavy-metal compartmentalization by algal cells
Authors: Jensen T.E. , Rachlin J.W. , Baxter M. , Warkentine B. , Jani V.
Published: June 2020

A key question in biology is to understand how cells exposed to heavy metals mitigate the metal's toxic effects. In an attempt to answer this question we have been investigating the effects of heavy metals on cells, especially the possible compartmentalization or sequestering mechanism they may have which would reduce the toxic effect.

A variety of cyanobacteria (Cyanophyceae) and eukaryotic algae (Chlorophyceae and Bacillarophyceae) were studied to determine if metal binding takes place and if so if the metal is compartmentalized in the cells. Metals used in the study included Ba, Cd, Co, Ca, Hg, Mg, Mn, Ni, Pb, Sr and Zn. Cells were exposed to different concentrations of the metal for varying time periods and then air dried onto formvar coated nylon grids. Cells were located using the STEM mode (dark field setting but with a bright field image) of a JOEL U-3 SEM. The SEM was operated at 25 KV and 4X10-10 A beam current.