bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial cell damage by the complement system of channel catfish, Ictalurus punctatus
Authors: Rosell-Davis Rosemarie , Jenkins Jill A. , Coons Lewis B. , Ourth Donald D.
Published: June 2020

The alternative complement pathway (ACP) provides the non-immune channel catfish with protection against many Gram-negative bacteria. The role of serum complement against Gram-negative bacteria is death of cells by insertion of the membrane attack complex (C5b-9) into the cell membrane. The assembly of the membrane attack complex is generated by the ACP and is activated by bacterial cell wall components. Pseudomonas fluorescens is a pathogen of channel catfish. In this study, bacteria were examined after incubation with catfish serum by scanning and transmission electron microscopy (SEM and TEM) for ultrastructural evidence of cell envelope damage by the complement system.

A percent bactericidal assay determined that catfish plasma was 99% bactericidal against a 24 h culture of P. fluorescens (ATCC 13525). Following a 1 h incubation at 30°C of bacterial dilutions with equal volumes of serum, heat-inactivated serum, zymosan-adsorbed serum, or saline, the bacterial cells were filtered onto 0.22 um nuclepore filters, fixed in glutaraldehyde, dehydrated in ethanol, critical point dried, sputter coated with 15 nm gold and imaged using a JEOL SEM.
Improved preservation of the otolithic membranes
Authors: Cohen G. M. , Grasso J. S. , Domeier M. L. , Mangonon P. T.
Published: June 2020

Any explanation of vestibular micromechanics must include the roles of the otolithic and cupular membranes. However, micromechanical models of vestibular function have been hampered by unresolved questions about the microarchitectures of these membranes and their connections to stereocilia and supporting cells. Otolithic membranes are notoriously difficult to preserve because of severe shrinkage and loss of soluble components. We have empirically developed fixation procedures that reduce shrinkage artifacts and more accurately depict the spatial relations between the otolithic membranes and the ciliary bundles and supporting cells.

We used White Leghorn chicks, ranging in age from newly hatched to one week. The inner ears were fixed for 3-24 h in 1.5-1.75% glutaraldehyde in 150 mM KCl, buffered with potassium phosphate, pH 7.3; when postfixed, it was for 30 min in 1% OsO4 alone or mixed with 1% K4Fe(CN)6. The otolithic organs (saccule, utricle, lagenar macula) were embedded in Araldite 502. Semithin sections (1 μ) were stained with toluidine blue.
Electron microscopic study of age-related changes in the spleen of the cat
Authors: Faroon O. M. , Henry R. W.
Published: June 2020

The spleen is involved in several immunological and physiological activities. The spleen serves as a “reservoir” of red blood cells, and their rapid release is correlated with the development of the capsule and the trabeculae. The spleen is a site of hematopoietic activity in the early stages of life. Investigations of age-related changes in megakaryocytopoiesis has been conducted on the rat spleen. Age-dependent changes which influence the microenvironment may lead to a decrease in the hematopoiesis and lymphocytic response. The decrease of immune response in aged animals has been investigated.

The decline of immunological activity in animals and humans, increases susceptibility to infectious disease and malignancy. Splenic structure and age-related changes has been studied in rats and other mammalian species. However, there is no information on the changes which occur with age in the spleen of the cat. Therefore, this preliminary study, using cats of varying ages (prenatal to adult), was done to prepare for a quantitative study.
Morphometric analysis of cellular interactions with the endothelium during the development of arterial lesions using Scanning Electron Microscopy and digital image analysis
Authors: Rosenfeld M.E. , Karboski C. , Prescott M.F. , Goodwin P. , Ross R.
Published: June 2020

Previous research documenting the chronology of the cellular interactions that occur on or below the surface of the endothelium during the initiation and progression of arterial lesions, primarily consisted of descriptive studies. The recent development of lower cost image analysis hardware and software has facilitated the collection of high resolution quantitative data from microscopic images. In this report we present preliminary quantitative data on the sequence of cellular interactions that occur on the endothelium during the initiation of atherosclerosis or vasculitis utilizing digital analysis of images obtained directly from the scanning electron microscope. Segments of both atherosclerotic and normal arteries were obtained from either diet-induced or endogenously (WHHL) hypercholesterolemic rabbits following 1-4 months duration of hypercholesterolemia and age matched control rabbits. Vasculitis was induced in rats following placement of an endotoxin soaked thread adjacent to the adventitial surface of arteries.
A SEM analysis of thin indium films for immunoassay applications
Authors: Wajer S. D. , Charles H. K.
Published: June 2020

Indium metal films have been used as host substrate materials for biological immunoassays. Indium film immunoassays involve the optical detection of specific antibody-antigen reactions using either transmitted or reflected white light. In the immunoassay process, drops of a purified antibody solution are placed on 5 to 25 nm thick indium films supported on a glass substrate (i.e., indium slide). After incubation, the antibody solution is washed off, leaving visible spots of reactive antibody. The slide is then coated with an unrelated protein which covers any non-antibody areas thus making the whole slide appear optically uniform. Placing the indium slide in an appropriate antigen solution will cause a visible response, since the antibody-antigen reaction complex will contain two layers of protein and will be darker than the surrounding background. In addition to the biological reaction sensitivities, the indium film immunoassay response is critically dependent on the bulk and surface properties of the indium film.
Chromosome banding in cultured cells transformed by polyoma virus
Authors: Mazzone H. M.
Published: June 2020

Chromosome banding procedures commonly employ treatment steps in order to visualize the bands. In various cases, band-positive regions of chromosomes are observed after the latter are exposed to, e.g., acids, bases, salts, heat, or enzymes. Recently, mouse chromosomes treated with the antibiotic actinomysin D and the dye acridine orange demonstrated high resolution G-banding patterns by light microscopy. However, occasionally, banding can be produced with little or no treatment of the chromosomes. The present report describes the presence of bands in chromosomes of cultured cells whereby no treatment steps, as noted above, were employed. It is interesting that the history of the cells included their transformation by polyoma virus.

Maintenance of virus-transformed Syrian hamster cell lines and their examination in the transmission electron microscope (TEM) was done in the Department of Biology of the Massachusetts Institute of Technology.
Plant Pathology Diagnosed by X-Ray Microanalysis
Authors: Resau J. H. , Howell N. , Chang S. H.
Published: June 2020

Spinach grown in Texas developed “yellow spotting” on the peripheral portions of the leaves. The exact cause of the discoloration could not be determined as there was no evidence of viral or parasitic infestation of the plants and biochemical characterization of the plants did not indicate any significant differences between the yellow and green leaf portions of the spinach. The present study was undertaken using electron microscopy (EM) to determine if a micro-nutrient deficiency was the cause for the discoloration.

Green leaf spinach was collected from the field and sent by express mail to the EM laboratory. The yellow and equivalent green portions of the leaves were isolated and dried in a Denton evaporator at 10-5Torr for 24 hrs. The leaf specimens were then examined using a JEOL 100 CX analytical microscope. TEM specimens were prepared according to the methods of Trump et al.
The effect of drying technique on the appearance of surface features in the Cryptophyceae
Authors: Gillott Marcelle A.
Published: June 2020

The Cryptophyceae is a class of unicellular flagellated algae which can be found in a variety of marine and freshwater habitats. One of the features which separates cryptomonads from other groups of algae is its complex cell covering, referred to as the periplast. Variation in periplast organization can also be used to distinguish among the cryptomonad genera. The periplast consists of an internal plate or plates which underlies the plasma membrane and may have external components as well. The periplast covers the whole cell except for the vestibulum (a subapical depression from which the flagella emerge) and the gullet or furrow. Since Lugol's fixation (recommend by Munawar and Bistricki, 1979) or glutaraldehyde fixation followed by critical point drying (recommended by Santore, 1977) can cause collapse and distortion of cell shape; Santore (1984) has questioned the validity of the furrow as a cell shape characteristic.
Prevalence of the pit and antipit in the genus Glycine
Authors: Yaklich R. W. , Vigil E. L. , Wergin W. P.
Published: June 2020

The legume seed coat is the site of sucrose unloading and the metabolism of imported ureides and synthesis of amino acids for the developing embryo. The cell types directly responsible for these functions in the seed coat are not known. We recently described a convex layer of tissue on the inside surface of the soybean (Glycine max L. Merr.) seed coat that was termed “antipit” because it was in direct opposition to the concave pit on the abaxial surface of the cotyledon. Cone cells of the antipit contained numerous hypertrophied Golgi apparatus and laminated rough endoplasmic reticulum common to actively secreting cells. The initial report by Dzikowski (1936) described the morphology of the pit and antipit in G. max and found these structures in only 68 of the 169 seed accessions examined.
The use of lanthanum to characterize cell wall permeability in relation to the freezing response of woody plants
Authors: Wisniewski M. , Schaffer K. , Hershberger W.
Published: June 2020

In woody plants, tissues displaying freeze tolerance respond to low temperature by the rapid loss of cellular water to extracellular ice whereas tissues exhibiting freeze avoidance exhibit deep supercooling in which case cellular water is isolated from the dehydrative and nucleating effects of extracellular ice. Biophysical data on cells that exhibit deep supercooling has led some authors to speculate that the structure and size of pores in cell walls would play an integral role in imparting a barrier to water movement and spread of ice. Distribution of the apoplastic tracer, lanthanum nitrate, was examined in stem tissues of several species of woody plants using a transmission electron microscope (TEM) in order to acquire data on general permeability of cell walls in species that deep supercool (P. persica, C. florida, B. lenta) vs. those that exhibit extracellular freezing (S. babylonica, B. papyrifera).
Double-tilting specimen holder cooled by liquid helium for JEM-4000EX
Authors: Hashimoto H. , Yokota Y. , Hashimoto M. , Sukedai E. , Endoh H. , Shimizu R. , Etoh T. , Harada Y. , Aoki Y.
Published: June 2020

For the study of phase transformation and structure change of crystals at low temperature in atomic scale, flowing liquid He specimen cooling holder has been constructed. It was aimed to achieve the low temperature without giving any effects to the resolution and analytical function of JEM-4000EX such as X-ray detection system and goniometer functions. The pole piece of electron lens used in this experiment has the following functions, i.e. Cs=2.88mm Cc=2.69mm f=3.55mm and the resolution is 0.34nm. The present specimen stage can be tilted ±20 degrees to X- and Y-directions inside of this pole piece. In connection of double tilt mechanism and protection of heat loss, double layered bellows are fabricated at the entrance of driving mechanism. At this point every vibrations from outside of the microscope such as from pumping out system of introduced liquid helium (the pipe A in Fig. 1) would be extinguished. This mechanism is fabricated in the vacuum box (marked by B in Fig.1).
Liquid crystalline order of biopolymers in cuticles and bones
Authors: GIRAUD-GUILLE Marie-Madeleine
Published: June 2020

The two major polymers of animal skeletal structures are chitin, a polysaccharide associated with proteins in arthropod cuticles, and collagen the main protein of bone. Electron microscopic studies, with the use of a goniometric stage, have shown that in biological tissues, the three-dimentional arrangement of these biopolymers often follow liquid crystalline geometries. Moreover highly concentrated solutions of purified collagen molecules spontaneously form close assemblies known as cholesteric phases. These results suggest that the determinism of supramolecular order in many extracellular matrices could well correspond to liquid crystalline assembly principles.

The crab cuticle first allowed to establish an analogy between the fibrous chitin-protein network and the arrangement of molecules in cholesteric liquid crystals. The demonstration was obtained by tilting, in the electronic microscope, sections showing a typical pattern consisting of series of nested arcs (Fig.1). The suppression, or even better the inversion of arcs, validates the cholesteric model where the fibrillar directions, all parallel to the epidermis, rotate continuously from one plane to the next when moving outwards (LIVOLANT et al, 1978).
A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre
Authors: Liu Jun , Gunnison Katie E. , Sarikaya Mehmet , Aksay Ilhan A.
Published: June 2020

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.
Cryo-TEM of micelles and lyotropic liquid crystals in non-aqueous solvents
Authors: Lin Zuchen
Published: June 2020

Surfactant molecules can form spherical micelles in water above the critical micellization concentration. At still higher concentrations, they can form thread-like micelles and liquid crystals. Cryo-transmission electron microscopy of these microstructures in water is now used successfully for studying aqueous biological and synthetic systems. The controlled environment vitrification system (CEVS) makes it possible to prepare samples accurately. Further, The on-grid processing makes specimens possible from evolving systems halted in mid-process.

Despite all the successes with aqueous systems, imaging of microstructures formed in non-aqueous solvents has not been reported. The main difficulties are radiation damage, thermal drift of the specimen, and low contrast. As small a spot size and as well spread a beam as possible are needed for low magnification searching. During the image recording, the minimum dose and lowest magnification possible are desired in order to avoid the thermal drift and radiation damage while maintaining an adequate signal-to-noise ratio.
Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation
Authors: Williams Shawn , Zhang Xiaodong , Lamm Susan , Van’t Hof Jack
Published: June 2020

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.
Epithelial cell morphology on titanium implant surfaces
Authors: Laffoon John E. , Keller J.C. , Zaharias R.
Published: June 2020

Previous work has indicated that the in vitro attachment and morphology of epithelial cells derived from oral mucosa are affected by substrate morphology. These findings have importance for dental implants in order to maintain an intact permucosal seal for the prevention of peri-implant disease similar in etiology to periodontitis. Since current dental implants have a variety of surface compositions ana morphologies, a more complete understanding of this tissue/implant interface is required.

Discs of titanium, representing implant surfaces, were polished through 600 grit SiC papers or were polished thru lμm diamond paste to prepare grooved or smooth specimens respectively for SEM studies. For complimentary TEM studies of cell/substrate interfaces, standard tissue culture plastic was polished with 600 grit paper or was left intact prior to the application of a thin sputtercoated layer of titanium. All specimens were sterilized by exposure to UV light prior to the in vitro studies. Gingival and/or buccal epithelial cells derived from adult rat oral mucosa were maintained in FAD culture media supplemented with 10% fetal bovine serum.
SEM and Field Mmission study of silicon field emitter array
Authors: Liu Jiang , Hren John J.
Published: June 2020

Arrays of nanometer-scale field emitters have recently become attractive candidates for device applications where high frequency and high current are desirable attributes. High emission current can be obtained from densely packed Spindt-type emitter arrays with very low extraction voltage. Concern with the optimum geometrical shape of each emitter and the fraction of active emitters, makes a combined study of field emission and scanning electron microscopy especially useful.

Several geometrical structures, as well as several materials, have been used to fabricate the field emitter arrays. The present study concentrates on silicon-base emitters fabricated at the Microelectronics Center of North Carolina (MCNC). Each emitter has a pyramidal structure, fabricated by anisotropic chemical etching of highly doped (ND = 1017 cm−3) n-type silicon. Figure 1 shows a SEM micrograph of a typical Si field emitter with a radius of curvature less than 30 nm. The field required for electron emission, about 3 × 107 V/cm, is created by a relatively low voltage applied to the extraction gate, a metal film less than one micron distant and deposited over a dielectric layer of silicon oxide (Figures 2 and 3).
UHV-STM studies of silicon nano-pyramid growth on silicon surface at high temperature
Authors: Sato T. , Kitamura S. , Sueyoshl T. , Iwatukl M. , Nielsen C.
Published: June 2020

Recently, the growth process and relaxation process of crystalline structures were studied by observing a SI nano-pyramid which was built on a Si surface with a UHV-STM. A UHV-STM (JEOL JSTM-4000×V) was used for studying a heated specimen, and the specimen was kept at high temperature during observation. In this study, the nano-fabrication technique utilizing the electromigration effect between the STM tip and the specimen was applied. We observed Si atoms migrated towords the tip on a high temperature Si surface.

Clean surfaces of Si(lll)7×7 and Si(001)2×l were prepared In the UHV-STM at a temperature of approximately 600 °C. A Si nano-pyramid was built on the Si surface at a tunneling current of l0nA and a specimen bias voltage of approximately 0V in both polarities. During the formation of the pyramid, Images could not be observed because the tip was stopped on the sample. After the formation was completed, the pyramid Image was observed with the same tip. After Imaging was started again, the relaxation process of the pyramid started due to thermal effect.
Characterization of photosystem II with the atomic-force microscope
Authors: Marr Kathleen M. , Lyon Mary K.
Published: June 2020

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.
Ratio imaging of intracellular ion concentration
Authors: Bolsover Stephen R.
Published: June 2020

The field of intracellular ion concentration measurement expanded greatly in the 1980's due primarily to the development by Roger Tsien of ratiometric fluorescence dyes. These dyes have many applications, and in particular they make possible to image ion concentrations: to produce maps of the ion concentration within living cells. Ion imagers comprise a fluorescence microscope, an imaging light detector such as a video camera, and a computer system to process the fluorescence signal and display the map of ion concentration.

Ion imaging can be used for two distinct purposes. In the first, the imager looks at a field of cells, measuring the mean ion concentration in each cell of the many in the field of view. One can then, for instance, challenge the cells with an agonist and examine the response of each individual cell. Ion imagers are notnecessaryfor this sort of experiment: one can instead use a system that measures the mean ion concentration in a just one cell at any one time. However, they are very much more convenient.
Voltage dependence of the electron diffraction amplitudes in the ab initio analysis of copper perchlorophthalocyanine
Authors: Tivol W.F. , Turner J.N. , Dorset D.L.
Published: June 2020

Copper perchlorophthalocyanine has become a model compound for exploring the application of electron microscopic and diffraction methods in high resolution molecular structure research. Because of the scattering contrast between the Cu and Cl heavy atoms and the lighter C and N atoms, it was not possible to determine the structure with electron diffraction data obtained at 100 kV a number of years ago. Dynamical scattering all but obscures the detail in the diffraction data due to the unit cell Fourier transform. Studies at 500 kV had also determined that the electron microscopic images were influenced by dynamic scattering. Since our HVEM can be operated from 100 kV to 1.2 MV in 100 kV steps, we are studying the influence of accelerating voltage on our ability to determine atomic-level molecular structure.

We recorded electron diffraction patterns from crystals epitaxially oriented on KCl and tilted 26.5° relative to the beam in order to align the c-axis of the unit cell along the beam direction.
A novel approach to the identification of microcrystals with electrons
Authors: Le Page Y.
Published: June 2020

Measurement of conventional-cell data requires observations along several specific zone axes in most cases. On the contrary, as shown in and outlined below, primitive-cell data can be extracted ab-initio, without trial-and-error, from single CBED patterns exposed along any zone axis, and displaying at least ZOLZ and first-order Laue-zone (FOLZ) spots.

The CRYSTDAT database, which is up-to-date and accessible on-line, contains over 180,000 entries, each with cell data, chemistry and reference to published work for a compound. It can be searched for primitive cell data and partial chemistry. In combination with the previous remark, this shows that crystallites can be identified from single CBED patterns, and from partial chemical information obtained on them by Energy-Dispersive X-ray spectroscopy.

CBED patterns are analyzed as follows. Two-dimensional (xP.vP) cartesian coordinates are measured for centers of all diffraction spots on the CBED film from an arbitrary origin. To each Bragg spot P on the film corresponds a scaied reciprocal vector FS with projections on the three axes:
Space group determination by CBED: G-M lines and holz interactions
Authors: Dravid Vinayak P.
Published: June 2020

Symmetry determination remains as a powerful and fascinating application of CBED techniques. As pointed out by Gjønnes & Moodie and later developed by Steeds & Vincent, the appearance of lines of missing intensity (G-M lines) in certain kinematically forbidden reflections in CBED patterns can be analyzed to obtain information about the presence and type of translational symmetry elements in the crystal space group, such as screw axis and glide planes. However, the microscopist must be aware of numerous pitfalls in analyzing G-M lines as they can be confused with other diffuse scattering (2-D diffraction) present in most CBED patterns. Furthermore, unambiguous determination of exact translational symmetry elements and their orientation requires careful choice of zone axis, voltage and analysis of indices of the forbidden reflections. When done properly, such experiments reveal the exact location and type of translational symmetry elements, e.g. whether the glide plane is a, b, c, n or d type.
The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis
Authors: Cockayne David , McKenzie David
Published: June 2020

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.

Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.
Application of analytical electron microscopy to studies of equilibrium and non-equilibrium segregation in materials
Authors: Kenik Edward A
Published: June 2020

Segregation of solute atoms to grain boundaries, dislocations, and other extended defects can occur under thermal equilibrium or non-equilibrium conditions, such as quenching, irradiation, or precipitation. Generally, equilibrium segregation is narrow (near monolayer coverage at planar defects), whereas non-equilibrium segregation exhibits profiles of larger spatial extent, associated with diffusion of point defects or solute atoms. Analytical electron microscopy provides tools both to measure the segregation and to characterize the defect at which the segregation occurs. This is especially true of instruments that can achieve fine (<2 nm width), high current probes and as such, provide high spatial resolution analysis and characterization capability. Analysis was performed in a Philips EM400T/FEG operated in the scanning transmission mode with a probe diameter of <2 nm (FWTM). The instrument is equipped with EDAX 9100/70 energy dispersive X-ray spectrometry (EDXS) and Gatan 666 parallel detection electron energy loss spectrometry (PEELS) systems. A double-tilt, liquid-nitrogen-cooled specimen holder was employed for microanalysis in order to minimize contamination under the focussed spot.
Progress in electron energy loss spectroscopy of Cu-ZSM-5 zeolite
Authors: Liu D. R.
Published: June 2020

The copper containing zeolite Cu-ZSM-5 recently has attracted worldwide attention due to its ability to decompose nitrogen oxides (NOx) , an undesirable constituent of vehicle exhaust. Faced with the problem of NOx control in lean burn engines designed to improve fuel economy, this zeolite is thought to hold the promise of more efficient catalytic converters for NOx. An effort was therefore made to characterize this material with a JEOL-2000FXII analytical electron microscope.

Fine powder samples of Cu-ZSM-5 and H-ZSM-5 were acquired from a vendor and analyzed in a comparative study. The AEM specimens were made either by placing a droplet of a fine powder suspension on a carbon coated grid, or by microtoming a resin embedded block of the zeolite and collecting thin sections on a grid. Fig. 1 is a high resolution micrograph taken in the channel direction (the b-axis) of the zeolite crystalline structure along with the diffraction pattern from the same area (Fig. 2). Both Cu-ZSM-5 and H-ZSM-5 samples showed the same structure images in all lattice orientations. These results are consistent with the published x-ray diffraction data on the ZSM-5 zeolite lattice structure.
Imaging small particles with secondary electrons
Authors: Liu J. , Spinnler G. E. , Ron A. E.
Published: June 2020

High resolution secondary electron microscopy (HRSEM) in dedicated scanning transmission electron microscopy (STEM) instruments has proved very useful for characterizing supported catalysts. In order to understand the contrast mechanisms of HRSEM images of small particles, clean samples and UHV environments are needed since the emission of secondary electrons (SEs) can be significantly influenced by contamination on the particle surface. In this paper we report results on imaging small metal particles by HRSEM in a UHV STEM instrument. In addition, we show that with computer assistance digitized HRSEM images of small metal particles can be used to estimate the average inelastic mean free path and the mean escape depth of the collected SEs.

The Vacuum Generators UHV STEM HB-501S, codenamed MIDAS (a Microscope for Imaging, Diffraction and Analysis of Surfaces), was used for these experiments. Detailed descriptions of the MIDAS system have been published previously. The collection efficiency of SEs approaches 100% through the use of magnetic ‘parallelizers’ situated inside the objective pole pieces.
Magnification Errors in the SEM
Authors: Geller Joseph D.
Published: June 2020

Test and inspection instrumentation requirements are becoming more stringent, as evidenced by the International Standards Organization ISO-9001 certification. To qualify for certification it will be mandatory to calibrate and maintain calibration on laboratory instrumentation. The semiconductor industry also requires accuracies in the sub-micrometer range. However, “the SEM does not always tell the truth”. This work addresses magnification accuracy.

Magnification accuracy in the scanning electron microscope (SEM) is affected by the instruments design, manufacture, calibration, and its operating environment. In order to check and calibrate the instrument a standard is required. The only currently available NIST (National Institute of Standards and Technology) magnification standard for the SEM (SRM-484) measures in one dimension and only at higher (> 1000X) magnifications. Recognizing that microscopy is by nature two-dimensional we need to calibrate SEMs in both the X & Y dimensions. A suitable standard has been developed which is usable at least over the normal range of SEM accelerating voltages (200eV and higher) and magnifications (10X to 50,000X).
Application of the Sterecon System for the Determination of Area, Volume, and Linear Distance of Cell Surface Topography of Secondary and Backscatter Electron Stereoscopic Images in Low-Voltage Field Emission SEM
Authors: Erlandsen Stanley L. , Wells Carol L. , Olmsted Stephen B. , Leith ArDean , Marko Michael
Published: June 2020

Extraction of quantitative information on surface topography in SEM can.be accomplished with, stereoscopic visual parallaxes. This method has received little attention in the last decade and to our knowledge has not been applied to high resolution secondary or backscatter electron images from field emission SEM. The STERECON system was developed for 3-D reconstruction of cells from stereo images obtained by high voltage EM. The present study describes the application of STERECON to quantitative determination of volume, surface area, and linear distance of topographical features in high resolution SEM.

Trophozoites of the free-living protozoan, Hexamita inflata, and two bacterial species (Proteus mirabilus and Enterococcus faecalis) were fixed in 2.5-3.0% glutaraldehyde, dehydrated in ethanol, critical point dried in CO2, and coated with about 1 nm of platinum before examination at low kV (<4.0) in a Hitachi S-900 field emission SEM equipped with secondary (Se) and backscatter (YAG scintillator) detectors and photographed on Polaroid type 52 film using a stereo tilt of 8°.
SEM studies of fracture phenomena and wall structure in micrometeoroid impact craters in spacecraft metals
Authors: Murr L. E. , Niou C-S. , Rivas J. M. , Quinones S. , Advani A. H.
Published: June 2020

There has been a considerable effort over nearly a decade to examine the size frequencies, compositions, and origins of particles producing impact craters in a variety of materials surfaces on the Solar Maximum Mission spacecraft, retrieved communications satellites (such as Palapa-B2), and more recently the LDEF (Long Duration Exposure Facility) spacecraft. Three regimes of particles have emerged: natural cosmic dust or interplanetary dust particles (IDP's), man-made orbital debris (including paint or other spacecraft component or coating chips having compositions different from the impacted materials); and orbital debris, often spacecraft debris or secondary (ejecta) debris, having the same composition as the impacted material. However more than 50% of all LDEF impacts into metallic targets did not yield sufficient projectile residue to permit analysis using EDS techniques in electron beam instruments (SEM or STEM in particular).

There have been very few attempts to investigate the microstructural and microchemical nature of the micrometeoroid crater walls, especially in the context of the integrity of the wall in relation to the target metal, and the propensity for cracking and crack nucleation within the crater wall.
High-angle annular dark-field stem imaging: more than just z-contrast!
Authors: Perovic D.D.
Published: June 2020

Following the development of dedicated scanning-transmission electron microscopy (STEM), significant advances have been made in atomic number (Z)-contrast imaging using a high-angle annular detector (HAAD). With the exclusion of coherent (ie. Bragg) scattering, the HAAD allows for truly incoherent imaging with high compositional sensitivity approaching the simple Z2-dependence of unscreened Rutherford scattering. However, recent experimental studies have indicated that HAADF-STEM imaging is not always straightforward. For example, Fig. 1 shows a digitally acquired HAADF-STEM image of a (B,As)-doped Si multilayer. The B-doped (˜ 0.7 at.%B) layers appear significantly brighter than the adjacent Si matrix in contradiction with a simple Z-contrast argument. It was found that an increase in incoherent scattering from the B-doped regions results due to the presence of atomic displacements of the surrounding Si atoms which effectively behave as “frozen-in” static phonons. Accordingly, the B-doped layers quasi-elastically scatter electrons to relatively high angles giving rise to enhanced contrast in HAADF.
Nickel L2,3 core energy loss studies in NiSi2
Authors: Wong Kaikee , Silcox John
Published: June 2020

The L2 and L3 edges in EELS spectra of 3d transition metals arise primarily from dipole excitation of the 2p1/2 and 2p3/2 electrons to unfilled 3d states. Since the initial states have narrow energy widths, the L2,3 edges reflect the conduction band density of states (DOS) with d character. By comparing the Ni L2,3 edges in NiSi2 to those in pure Ni, the bonding between Ni and Si can be studied.

Experiments were carried out in an UHV HB501A STEM operating at 100 keV with a serial EELS spectrometer. The spot size and the current were estimated to be 5 Å and 0.1 nA respectively. Both the convergence and the detector angles were about 11 mrad. The spectra were recorded in steps of 0.25 eV for Ni and 0.5 eV for NiSi2. Long dwell times were necessary to achieve high signal to noise ratio in the core loss spectra and typically 5 sec per energy step was used.
Characterization of TiSi2/TiN thin films on Si by HREM
Authors: Sharma Renu
Published: June 2020

Titanium Nitride is commonly used as a diffusion barrier layer in Al-Si contacts. There are different techniques employed to deposit TiN layers on silicon, out of them thermally grown and reactively sputtered are most common. Reactive sputtering is a one step process and is favoured for manufacturing. The orientation of TiN thin films controls the orientation of Al films deposited. As sputtered films has random orientation hence the overlying Al films is randomly oriented as well. In order to achieve higher electromagnetic resistance, Al films should be well oriented. Thermally grown TiN thin films are highly oriented but their thickness is limited to about 20nm. We have used HREM and micro-analytical techniques to analyze the thickness, structure and compositions of various layers formed during thermal growth of TiN layers deposited under different conditions.

Thermally grown Ti films on Si <100> wafers of varying thicknesses were deposited and annealed in NH3 atmosphere at different temperatures and times. Second layer of titanium was deposited and processed on some of the samples (double process) in order to increase the thickness of TiN layer.
Electron microscopy studies of PZT ferroelectric film capacitor structures
Authors: Kaushik V. , Maniar P. , Olowolafe J. , Jones R. , Campbell A. , Hance R. , Mogab C.J.
Published: June 2020

Lead zirconium titanate films (Pb (Zr,Ti) O3 or PZT) are being considered for potential application as dielectric films in memory technology due to their high dielectric constants. PZT is a ferroelectric material which shows spontaneous polarizability, reversible under applied electric fields. We report herein some results of TEM studies on thin film capacitor structures containing PZT films with platinum-titanium electrodes.

The wafers had a stacked structure consisting of PZT/Pt/Ti/SiO2/Si substrate as shown in Figure 1. Platinum acts as electrode material and titanium is used to overcome the problem of platinum adhesion to the oxide layer. The PZT (0/20/80) films were deposited using a sol-gel method and the structure was annealed at 650°C and 800°C for 30 min in an oxygen ambient. XTEM imaging was done at 200KV with the electron beam parallel to <110> zone axis of silicon.

Figure 2 shows the PZT and Pt layers only, since the structure had a tendency to peel off at the Ti-Pt interface during TEM sample preparation.
Insitu TEM observation of epitaxial CoSi2 formation on (100) silicon
Authors: Smith P.L. , Hsia S.L. , Tan T.Y. , McGuire G.E
Published: June 2020

Self-aligned titanium and cobalt silicide layers on silicon (Salicides) have been used as low resistivity metal contacts for advanced CMOS devices. However, the scaling of devices to smaller dimensions places increasing requirements on Salicide properties. Controlling junction consumption, interface roughness, lateral growth, thermal stability and resistivity during silicide formation limit the use of these materials. Epitaxial silicides offer significant advantages over polycrystalline films because of their thermal stability and low resistivity. Epitaxial Ti and Co disilicides have been grown on (111)Si by MBE. Recently, growth of epitaxial Co disilicide on (001)Si has been reported using bimetallic layers of Co and Ti as source materials. Planar CoSi2/Si interfaces with defect free grains have been produced. Uniform low resitivity films are produced using standard processing conditions. The process involves sequential deposition of Ti and Co on (001 )Si. Titanium is a reactive metal which acts as a getter for the residual native oxide on the Si surface and as a reaction barrier between Co and Si at low temperatures.
Column-by-column compositional imaging by z-contrast STEM
Authors: Pennycook S. J. , Jesson D. E. , Chisholm M. F.
Published: June 2020

The use of a high-angle detector in STEM imparts incoherent characteristics to the image while simultaneously introducing a strong compositional sensitivity through the ∼Z2dependence of the highangle scattering cross sections. The destruction of coherence is achieved in two ways. Firstly, the wide angular range of the detector averages interference fringes in thetransverseplane, even if predominantly coherent scattering is detected, resulting in improved resolution and a lack of contrast reversals. Coherence along the beam direction largely remains so that with increasing thickness the intensity increases initially as t2, becoming oscillatory as the Ewald sphere intersects only subsidiary maxima of the crystal shape factor (see Fig. 1). Coherence along a column can effectively be broken by ensuring that the detector is dominated by diffuse scattering, which at large angles is dominated by multiphonon scattering (the simultaneous emission and/or absorption of several phonons in a single scattering event).
Automated EPXMA of individual environmental particles
Authors: Van Grieken R. , Artaxo P. , Xhoffer C.
Published: June 2020

In studies on environmental particles, microbeam analysis techniques are still invoked very seldom. This is rather surprising in view of the importance that particles have in the environment. To study particulate samples by individual particle analysis requires the measurements of a large population set in order to obtain statistically meaningful data. At the University of Antwerp, a JEOL Superprobe JXA - 733 is automated with a system for the automated particle recognition and characterization (PRC). An electron beam is raster-scanned over a preset sample area by means of a digital beam control. A particle is detected when the electron backscattered signal of the closed particle contour points exceeds a preset threshold value. An X-ray spectrum can be accumulated while performing cross scans over the particle. Thus the PRC program is set up in three sequential steps: localizing, sizing and chemical characterization, after which the beam scans for the next particle.
Time-of-flight secondary ion mass spectrometry of bulk polymers using patterned silver overlayers to enhance the molecular microanalysis of trace additives
Authors: Mawn M. P. , Linton R. W. , Benninghoven A.
Published: June 2020

When coupled to a time-of-flight (TOF) mass analyzer which provides a high transmission, quasi-simultaneous detection of secondary ions, and theoretically unlimited mass range, secondary ion mass spectrometry (SIMS) is well suited for submonolayer molecular analysis of solid surfaces. Additionally, molecular ion images may be obtained by using a focused primary ion beam rastered on the sample surface to provide lateral distributions of chemical species.

TOF-SIMS has been shown effective at characterizing low level polymer additives such as UV absorbers, thermal stabilizers, anti-oxidants, and slip agents in polymer extracts deposited on roughened Ag substrates. Additionally, in-situ analysis of linear low density polyethylene (LLDPE) samples using TOF-SIMS has provided information on surface segregation and surface oxidation. The polymer extract analysis has the advantage of both preconcentrating the polymer additives, as well as providing enhanced ion yields through Ag canonization. However, the in-situ analysis is also a valuable approach since it alleviates the time consuming extraction procedure and provides information on additive surface segregation and oxidation.
Characterization of frozen hydrated biological specimens by low-loss EELS
Authors: Sun Songquan , Leapman Richard D.
Published: June 2020

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.

We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.