bluuebunny/crossref_metadata_2025 huggingface dataset:
TEM study of phosphorus-implanted pseudomorphic Si0.88Ge0.12 on Si(100)
Authors: David Theodore N. , Lie Donald Y.C , Song J. H. , Crozier Peter
Published: June 2020

SiGe is being extensively investigated for use in heterojunction bipolar-transistors (HBT) and high-speed integrated circuits. The material offers adjustable bandgaps, improved carrier mobilities over Si homostructures, and compatibility with Si-based integrated-circuit manufacturing. SiGe HBT performance can be improved by increasing the base-doping or by widening the base link-region by ion implantation. A problem that arises however is that implantation can enhance strain-relaxation of SiGe/Si.Furthermore, once misfit or threading dislocations result, the defects can give rise to recombination-generation in depletion regions of semiconductor devices. It is of relevance therefore to study the damage and anneal behavior of implanted SiGe layers. The present study investigates the microstructural behavior of phosphorus implanted pseudomorphic metastable Si0.88Ge0.12 films on silicon, exposed to various anneals.

Metastable pseudomorphic Si0.88Ge0.12 films were grown ~265 nm thick on a silicon wafer by molecular-beam epitaxy. Pieces of this wafer were then implanted at room temperature with 100 keV phosphorus ions to a dose of 1.5×1015 cm-2.
A precursor to the breakdown of homogeneous growth in low temperature MBE GaAs detected by ellipsometry
Authors: Walck S. D. , Eyink K. G. , Haas T. W. , Streetman B. G.
Published: June 2020

GaAs grown by MBE at low temperature (LT) in the range of 150-250°C forms a highly resistive film after it has been annealed. The high resistance of annealed LT-GaAs has been use to provide a semi-insulating layer lattice-matched to GaAs. For this reason, LT layers must have reproducible properties and must be of high crystalline quality for subsequent epitaxial layers. The as-grown LT-GaAs typically has 1-2% excess As which is responsible for an increase in the lattice constant of about 0.1 %. The thickness of the LT-GaAs layer is limited by the strain energy in the film which leads to the formation of pyramidal defects which is known as the critical thickness, hc. In-situ single wavelength ellipsometry has been used to precisely set a reference temperature for a given As beam equivalent pressure (BEP) which can be used to grow reproducible LT-GaAs layers. In the past, XTEM has been used to determine hc, however, in-situ ellipsometry can also be used to monitor the film’s optical properties during growth and can detect the different regions from breakdown of homogeneous growth through the film’s strain relaxation by the generation of the pyramidal defects to the formation of polycrystalline GaAs, if the growth is allowed to continue that far. An XTEM micrograph of such a film with the growth regions defined is shown in Fig. 1.
Absorption and scattering of ultraviolet radiation by titania pigment in bis-phenol-A polycarbonate
Authors: Hutchins Gudrun A. , Pickett James E.
Published: June 2020

The surface of bis-phenol-A polycarbonate oxidizes after prolonged exposure to sunlight. During the laboratory testing of stabilizers and coatings, the effect of sunlight is typically simulated by a xenon arc lamp, with maximum polycarbonate sensitivity between 300 and 340 nm. Titania pigment is a strong absorber of ultraviolet radiation and in its presence the affected surface layer will be thinner. The titania pigment utilized in polymer blends typically ranges from 100 nm to 350 nm in diameter.

Microtomed polycarbonate thin sections stain very well with ruthenium tetroxide vapor and the degree of staining is a sensitive indicator of the degree of oxidation or chemical reaction. Ruthenium tetroxide oxidizes the polymer surfaces of the thin section which results in the localized precipitation of ruthenium dioxide. In addition, the heavily oxidized surface polymer does not microtome evenly, resulting in a very fine craze pattern that is accentuated by the RuO4 stain.

With these techniques it was possible to demonstrate the absorption of ultraviolet radiation by titania particles by imaging the abrupt end of the heavily oxidized layer at the positions of individual pigment particles.
Microstructure of laser-irradiated, conducting Kapton polyimide
Authors: Callahan D. L. , Ball Z. , Phillips H. M. , Sauerbrey R.
Published: June 2020

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.

Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.
Preparation of cross section samples of ferrimagnetic iron garnet thin films for EM structural characterization
Authors: Simion B.M. , Ramesh R. , Thomas G.
Published: June 2020

Ferrimagnetic iron garnet thin film multilayered heterostructures were deposited by pulsed laser deposition on paramagnetic [111]-oriented single crystalline GdGa-garnet (GGG) substrates. Bismuth and rare-earth substituted iron garnet thin films are being presently considered as good potential candidates for the next generation of thermo-magneto-optical (TMO) permanent memories, due to their improved magneto-optical (MO) response to the green laser radiation. As reported previously, improved magnetic and MO properties were shown by multilayered Y3Fe5O12/Bi3Fe5O12 (YIG/BIG) and Y3Fe5O12/Eu1Bi2Fe5Ol2 (YIG/EBIG) heterostructures when compared to their single layer counterparts. The present study tries to elucidate the relationship between the films microstructure and their improved properties. Along with x-ray structural characterization, scanning electron microscopy for topographical characterization and analytical transmission electron microscopy for chemical and microstructural analysis are being used.

Due to the brittleness of both films and substrates, conventional cross section sample preparation becomes extremely difficult. Samples under roughly 20 μm thickness break under the lowest load of the dimpler.
Advanced TEM sample preparation techniques for submicron Si devices
Authors: Basham P. B. , Tsai H. L.
Published: June 2020

The use of transmission electron microscopy (TEM) to support process development of advanced microelectronic devices is often challenged by a large amount of samples submitted from wafer fabrication areas and specific-spot analysis. Improving the TEM sample preparation techniques for a fast turnaround time is critical in order to provide a timely support for customers and improve the utilization of TEM. For the specific-area sample preparation, a technique which can be easily prepared with the least amount of effort is preferred. For these reasons, we have developed several techniques which have greatly facilitated the TEM sample preparation.

For specific-area analysis, the use of a copper grid with a small hole is found to be very useful. With this small-hole grid technique, TEM sample preparation can be proceeded by well-established conventional methods. The sample is first polished to the area of interest, which is then carefully positioned inside the hole. This polished side is placed against the grid by epoxy Fig. 1 is an optical image of a TEM cross-section after dimpling to light transmission.
Hydrogen-induced phase transformations in α2+B2 Ti-25Al-10Nb-3V-lMo titanium aluminide
Authors: Pierron X. , De Graef M. , Pollock T.M. , Thompson A.W.
Published: June 2020

Titanium aluminide alloys containing the DO19α2 (Ti3Al) phase, such as Ti-25Al-10Nb-3V-1Mo (at.%), are known to be sensitive to hydrogen. Such alloys could provide an alternative for conventional Ti alloys in a hydrogen-rich environment, and an understanding of the hydrogen embrittlement mechanisms acting in these materials is needed. Hydrides are known to form in conventional Ti alloys. Hence, a systematic study was undertaken to investigate the possibility of hydrogen-induced second phases in the Ti-25Al-10Nb-3V-1Mo alloy. We report here that internal hydrogen results in the precipitation of an orthorhombic OH phase in the α2 grains. The morphology and the orientations of the orthorhombic variants can be successfully described using group theory and the phenomenological theory of martensitic transformations.

The as-received material consisted of bars extruded in the (α2 + β) phase field at 1037°C, then oil quenched. A solutionizing treatment at 1085°C, followed by free cooling at 0.1°C/s to room temperature resulted in a microstructure containing primary α2 grains and α2 secondary laths in a B2 matrix.
Structural determination of L-phase with Aucu(I) ordered structure observed in a new maraging steel
Authors: Liu Ping
Published: June 2020

A new maraging stainless steel has recently been developed at Sandvik and is termed Sandvik 1RK91 (12Cr-9Ni-4Mo-2Cu-1Ti-0.3Al-0.2Si (wt%)). The anomalous tempering response after aging at 475°C, combined with high strength, ductility, corrosion resistance and a high resistance to overaging were attributed to the formation of a quasicrystalline phase. In addition to this an ordered phase designated L-phase precipitated during prolonged aging. The structure type of this phase was determined by electron diffraction combined with EDX analysis. The material was annealed in the temperature range 1050-1150°C with subsequent air cooling and then aged at 475°C for up to 100 hours. Thin foils and carbon replica were studied using a Jeol 2000 FX analytical transmission electron microscope (TEM/STEM) equipped with a Link AN 10000 EDX system operating at 200 kV.

The plate-like L-phase precipitated after prolonged aging at 475°C(100 h) as shown in Fig. 1(a). A typical EDX spectrum from L-phase is shown in Fig. 1(b).
A study of the dislocation core structure in high nitrogen austenitic stainless steel by weak beam EM
Authors: Zhou M. , Kelly T.F. , Flinn J.E.
Published: June 2020

The large strengthening effect of nitrogen interstitials and its strong influence on the dislocation distribution of Fe-Cr-Ni austenite have been rationalized by Owen et al. using a short-range-order-based model. However, the model cannot explain the high population of screw dislocations resulted from a small amount of plastic deformation. Grujicic suggested that nitrogen addition to Fe-Cr-Ni austenitic stainless steels causes spreading of the screw dislocation core into two or more non-parallel planes which results in low dislocation mobility. Higher stress and higher temperature are thus required to overcome the energy barrier for the movement of dislocations. The core structure of dislocations in nitrogen-containing stainless steels is of fundamental importance for understanding the strengthening mechanism of this material. The weak beam dark field imaging technique allows the direct observation of partial dislocations and stacking faults bonded by the partials. When the optimum imaging condition is satisfied, relatively intense, narrow images of less than 2 nm wide can be obtained.
AEM analysis of stress corrosion cracks
Authors: Lewis N. , Perry D. J. , Bunch M. L.
Published: June 2020

Cross-sectional analytical electron microscopy (AEM) was used to study stress corrosion cracking (SCC) cracks in pressurized water in an attempt to understand the mechanism of cracking. AEM is particularly well suited to study the crack tip, the crack sides and the corrosion product inside the crack. These analyses provide clues about the stress (i.e., plasticity), the environment (corrosion product) and material (precipitates/grain boundary composition) which are the key factors controlling SCC. In mis investigation SCC cracks were filled with epoxy, dimpled and ion-milled in argon until electron transparent. A cross-section of an SCC crack in Alloy 600 generated in deaerated water is shown in Figure 1. The crack is intergranular and generally propagates down grain boundaries without carbides as shown in Figure 1. The crack seen in Figure 2 is an exception and propagated down a grain boundary containing Cr7C3 carbides. Although dislocations are clearly observed in bom figures, no deformation is observed uniquely associated with the cracks and no voids have been observed ahead of the cracks.
Position-tagged spectrometry: a new approach for EDS spectrum imaging
Authors: Mott Richard B. , Waldman Charles G. , Batcheler Rosa , Friel John J.
Published: June 2020

Graphical display of the spatial distribution of elements in a specimen has been recognized as a powerful technique since the earliest days of electron-beam x-ray microanalysis. With recent advances in computing power and mass storage, it has become practical to save complete spectra at each pixel rather than simple window counts, providing great flexibility for analytical post-processing. The term "spectrum imaging" has been coined to describe such a data structure.

Hunt and Williams give a concise summary of the advantages of spectrum imaging, including the ability to map an element which was not known to be present when the data were acquired, and the ability to integrate spectra from image regions of arbitrary shape to improve statistical precision. Quantitative analysis may also be applied at each pixel to produce a concentration map, which is more informative than the raw or perhaps background-subtracted window counts usually displayed. Sensitive discrimination of phases is possible using various fitting techniques on the pixel spectra, matching them against each other or against standards.
Indirect measurements in micro-space with the EM
Authors: Newberry Sterling P.
Published: June 2020

At the 1958 meeting of our society, then known as EMSA, the author introduced the concept of microspace and suggested its use to provide adequate information storage space and the use of electron microscope techniques to provide storage and retrieval access. At this current meeting of MSA, he wishes to suggest an additional use of the power of the electron microscope.

The author has been contemplating this new use for some time and would have suggested it in the EMSA fiftieth year commemorative volume, but for page limitations. There is compelling reason to put forth this suggestion today because problems have arisen in the “Standard Model” of particle physics and funds are being greatly reduced just as we need higher energy machines to resolve these problems. Therefore, any techniques which complement or augment what we can accomplish during this austerity period with the machines at hand is worth exploring.
Automated measurement of size and visibility of small inclusions in HREM images
Authors: Paciornik S. , Xiao S.Q. , Hinderberger S. , Johnson E. , Dahmen U.
Published: June 2020

This work describes an automatic image analysis method for measuring the visibility and apparent size of inclusions in a matrix, imaged by HREM. The method is based on intensity changes between the matrix and inclusion regions of the image. It provides a quantitative way of describing changes that are generally interpreted only in a qualitative sense. It also allows for measurements in situations of very low visibility where visual estimates are nearly impossible. The method measures the mean squared intensity difference between lines of an image defined as

R = mean [(Im(x) - Im(x0))2]

Im(x) is a line, selected by the user, which is scanned across the image. Im(x0) is the first line of the scan, taken in a region away from the inclusion. For each position of Im(x), Im(x0) is subtracted pixel by pixel, and the average of all squared intensity differences, is obtained (R).

As the line is scanned across the image, R will oscillate with a period given by the lattice spacing along the scan direction.
Algorithms for automated montage synthesis of images from laser-scanning confocal microscopes
Authors: Becker D. E.
Published: June 2020

An efficient, robust, and widely-applicable technique is presented for computational synthesis of high-resolution, wide-area images of a specimen from a series of overlapping partial views. This technique can also be used to combine the results of various forms of image analysis, such as segmentation, automated cell counting, deblurring, and neuron tracing, to generate representations that are equivalent to processing the large wide-area image, rather than the individual partial views. This can be a first step towards quantitation of the higher-level tissue architecture. The computational approach overcomes mechanical limitations, such as hysterisis and backlash, of microscope stages. It also automates a procedure that is currently done manually. One application is the high-resolution visualization and/or quantitation of large batches of specimens that are much wider than the field of view of the microscope.

The automated montage synthesis begins by computing a concise set of landmark points for each partial view. The type of landmarks used can vary greatly depending on the images of interest. In many cases, image analysis performed on each data set can provide useful landmarks. Even when no such “natural” landmarks are available, image processing can often provide useful landmarks.
The development of an electronic microscopy journal on the world wide web
Authors: Mansfield John F.
Published: June 2020

Developments in digital camera technology and digital data acquisition have allowed many of us to record most, if not all of our data entirely electronically. We are able to present this data at conferences and meetings direct from the desktop of a small personal computer. Why should we not think of publishing the data in the same manner? Indeed the assembly of the traditional scientific manuscript; printing out the text according to the journals strict format and printing and annotating the micrographs may really be thought of as a backward step. Frequently images, spectra and diffraction patterns appear much better on the screen of the computer than when they are printed out on paper. While this may be simply a limitation of developments in the printing technology lagging behind those in the display technology, why wait for the printing technology to catch up? We should publish electronically.

Since it’s inception in 1989, The World Wide Web (typically shortened to the WWW or just The Web) has proved to be a tremendously popular system for the publication and dissemination of an incredibly broad spectrum of information.
Specimen preparation: the Achilles Heel of Microscopy
Authors: Kestel B.
Published: June 2020

As the variety of microscopy techniques to reveal new information increases, the difficulty of preparing suitable specimens for examination has also grown. Some microscopy requires very uniform thickness, smooth surfaces, and minimal preparation induced damage or contamination. The variety of materials studied, their different physical properties, and the number of techniques available makes this process more troublesome than some project planners realize. New employees of an organization are often given this task, but their inexperience may compound the problem. A worker's success in this process may be increased by experience with tedious hobbies, teamwork events, or the need to record pertinent details of processes.

A starting point for optical microscopy, mechanical dimpling before ion milling, and the making of thin slices or wedges is mechanical polishing. The relatively new tripod polishing technique is based on controlled mechanical polishing using very fine abrasives. Examples of modified equipment and simple fixtures which make surface polishing easier, faster, and of high quality with reduced labor will be shown.
Measuring intermolecular forces using thermal noise in an Atomic Force Microscope
Authors: Cleveland J.P. , Schaeffer T. , Hansma P.K.
Published: June 2020

Understanding intermolecular forces in liquids at distances below a few nanometers is extremely important in many fields because forces on this length scale determine properties such as chemical bonding, wetting, and specific molecular recognition. However, it is difficult to measure forces over these length scales and perhaps even more difficult to understand them theoretically. The problem stems from the fact that it is hard to make simplifying approximations on these length scales. For example, continuum models usually break down because the finite size of the solvent molecules (typically several angstroms) can not be ignored. Molecular dynamics must often be used to study these systems, limiting the accessible time scales to, at most, many nanoseconds with current computing power.

Atomic force microscopy (AFM) is a relatively new technique that is proving useful in the measurement of forces at these small length scales. Probably the oldest and most direct way to measure a force is through the deflection of a spring, and in many ways, the AFM is simply a much smaller version of more familiar spring based instruments that measure force such as a weight scale.
3-D reconstruction of paracrystalliné biological specimens by tomography
Authors: Taylor K. A. , Winkler H.
Published: June 2020

The calculation of 3-D images of paracrystalline objects is often done using methods appropriate to 2-D crystals. However, this method leads to a loss of information about the structural variations within the paracrystal. Structural variations are often referred to as noise but may represent important features. In our own work with 3-D imaging of sectioned insect flight muscle (IFM) structural variations represent the adjustment in crossbridge form imposed by the filament lattice. In order to complement our averaged 3-D images obtained by 2-D crystal methods, we have experimented with performing essentially the same procedures using all the data, both sampled and continuous, to generate the 3-D image. While the method embodies no new principles, the combination of protocols appears to be unique.

The procedure uses the following steps: (1) A uniaxis tilt series ranging to ±75° is recorded. The increment between tilt angles decreases as tilt angle increases and ranges from ˜8° at low angles to ˜2° at high tilts.
The structure and function of the nuclear lamins
Authors: Goldman R.D. , Goldman A. , Khuon S. , Montag-Lowy M. , Moir R. , Spann T.
Published: June 2020

The nuclear lamins are the Type V intermediate filament proteins comprising the nuclear lamina. The lamina is located subjacent to the nucleoplasmic face of the nuclear envelope where it interfaces with chromatin. The lamins are major karyoskeletal proteins which are thought to play important roles in the formation and maintenance of nuclear shape and architecture, as well as in the supramolecular organization of chromatin. The lamins have long been thought to be stable polymeric constituents of the interphase nuclear matrix, due to their insolubility in solutions containing detergents and high salt concentrations. During mitosis, however, the nuclear lamins depolymerize during nuclear envelope breakdown. Subsequently, the lamins repolymerize around the decondensing chromosomes as the nuclear envelope reassembles at the end of mitosis. Although there is a significant amount known about the properties and potential functions of the lamins during mitosis, surprisingly little is known about their properties during interphase. In light of this, we have undertaken experiments which are aimed at determining the properties of the lamins in interphase cells.
Tubulin structure at intermediate resolution
Authors: Downing K. H. , Wolf S. G. , Nogales E.
Published: June 2020

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.

Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.
X-ray microanalysis of mineralized deposits in a variety of pathological conditions in the brain
Authors: Ackerley C. A. , Becker L. E.
Published: June 2020

Although a small degree of mineralization can be a common occurrence without associated pathological symptoms, certain diseases of the brain do however exhibit distinct increases in mineralization with characteristic distributions l>2. In this study, tissues from a number of these disorders were prepared for x-ray microanalysis in several ways. Where possible, material was slam frozen on a liquid nitrogen cooled polished copper block, cryosections prepared and freeze dried in the scanning transmission electron microscope (STEM) using a cold stage prior to analysis by energy dispersive x-ray spectrometry (EDS). In addition, samples were freeze substituted for several days, embedded in LR white and cut on dry knives before analysis. Where only formalin fixed paraffin embedded materials were available, .5μ.m sections were cut and mounted on carbon planchets. The specimens were then deparaffinized with xylene and viewed with the backscatter electron detector (BEI) in the scanning electron microscope (SEM) and analyzed by EDS.
How does lysozyme affect Escherichia coli: questions arising from impact frozen and freeze-substitutet bacteria
Authors: Gabrieli A. , Wild P. , Schraner E.M. , Pellegrini A. , von Fellenberg R.
Published: June 2020

Since the discovery by Fleming in 1922 that lysozyme has the ability to lyse Grampositive bacteria but not Gram-negative bacteria the assumption was established that lysozyme per se cannot affect Gram-negative bacteria. One basis of this assumption is that lysozyme is an enzyme with muramidase activity acting on the peptidoglycan. In E. coli, the peptoglycan layer is protected by the outer membrane, and, thus lysozyme has no access to it unless the outer membrane is destroyed, e.g. by EDTA or complement1. Accidentally, Pellegrini et al. found that lysozyme kills but does not lyse E. coli. Electron microscopy of bacteria fixed with aldehydes revealed that affected E. coli were often enlarged, the cytoplasm destroyed to various extend, but the cell membranes seem to remain intact (Fig. 1).

Chemical fixation is proved to induce dramatic changes in bacterial structure. Thus we immobilized bacteria after exposure to lysozyme at 37°C for 15 min by impact freezing on a liquid nitrogen cooled copper block.
Compliance mapping of cells using force-distance (F/S) curve imaging with the AFM
Authors: Marchese-Ragona S. P. , Wörtge M.
Published: June 2020

The Atomic Force Microscope is an extremely sensitive force measuring instrument which routinely measures the force exerted on the AFM tip by the sample, with a routine force resolution in the pico Newton range. By plotting the distance that the z-piezo is extended vs. cantilever deflection (force), one can produce what is traditionally known as a force distance (F/S) curve. Analysis of the F/S curve allows one to extract information on micro elasticity and plasticity of cell surfaces as well as the magnitude of any tip-sample binding that may occur. To increase the utility of the F/S curve for cell biological studies an to overcome the lateral distortion experienced by soft material in the scan direction we have developed a technique that images by performing a F/S curve for every pixel of the image. For a 200 × 200 pixel image, 40,000 F/S curves are generated with 25 data points in each F/S curve. The data obtained by this type of imaging can be conveniently analyzed in the following four ways:
Bismuth hematoxylin staining of nucleic acids
Authors: Smith A.A.
Published: June 2020

Hematoxylin is readily oxidized to the blue pigment hematein. Hematein can complex with a wide variety of metal salts or mordants to form mordant dyes. These dyes stain various components of animal tissues. The component stained depends on the metal in the mordant dye.

Alum hematoxylin uses trivalent aluminum ion as a mordant. At extreme dilution, requiring long staining times, alum hematoxylin is a specific stain for nucleic acids. As usually used, alum hematoxylin stains nucleoproteins, staining them nearly as well after the removal of the nucleic acids as before.

Bismuth shows a high affinity for nucleic acids. Although all common bismuth salts are insoluble in water, sodium bismuthate reacts with an aqueous solution of hematoxylin to produce hematein and trivalent bismuth ions. The bismuth ions complex with the hematein to form a water-soluble “bismuth hematoxylin.” HEPES (N-[2-hydroxyethyl]piperazine- N'-2-ethanesulfonic acid), 8 mg/ml of solution, greatly increases the amount of bismuth hematoxylin formed. Glycerol, 1/8 v/v, improves the stability of the complex.
Different carbohydrate substrates affect cell wall adhesion in candida albicans
Authors: Browning Sara L. , Crang Richard F. E. , Burns Aaron D. , Vossbrinck Charles R.
Published: June 2020

Candida albicans is an imperfect dimorphic yeast which is an opportunistic human pathogen that can cause diseases ranging from superficial to life-threatening systemic infections. Its ability to infect, however, depends upon its ability to adhere to host cells. A previous study has shown that adhesion of certain strains of C. albicans is made possible through a major cell wall antigen of approximately 49 kDa. This protein is also found to be associated with a carbohydrate (believed to be mannose), resulting in a glycoprotein. Growing the yeast in different carbon substrates has demonstrated differences in host cell adhesion.

C. albicans (strain SC-5314) from the Bristol Myers Squibb Culture Collection (Wallingford, CT) was grown separately in media of several carbon substrates: sucrose, fructose, glucose, and mannose, at 37°C for 24 hr. Each group of cells were washed in phosphate-buffered saline and suspended in freshly isolated human buccal cells for 1 hr. During that time, counts were made every 10 min to determine an average number of adhered yeast cells/buccal cell based on counts of 100 buccal cells. Representative scanning electron micrographs were taken (Fig. 1).
Renal handling of native and glycated albumins by the normal mouse
Authors: Londoño I. , Bendayan M.
Published: June 2020

One of the major pathophysiological sequela of long-term hyperglycemia is the increased glycation of proteins. The glycation reaction consists in the covalent attachment of glucose molecules to amino groups in proteins forming a stable product, the Amadori adduct. Albeit further transformations can occur, Amadori adducts constitute the predominant form of circulating glycated proteins in normal and diabetic subjects, and seem to be directly involved in the pathogenesis of diabetic nephropathy.

In an attempt to determine the role of glycated proteins in glomerular hyperfiltration and proteinuria characteristics of diabetic nephropathy, we have evaluated the renal handling of glycated albumins by the normal mouse, at two levels: the glomerular filtration and the tubular epithelial reabsorption. Bovine serum albumin (BSA) was glycated in vitro within conditions allowing for the formation of Amadori products. Both native and glycated albumins were tagged to haptens and intravenously injected in mice. Upon 10 and 30 min of circulation, the renal cortex was fixed and processed for immunocytochemical labeling which combined anti-hapten antibodies and protein A-gold complexes.
Evaluation of the emerging coleorhiza and radicle of Bromus tectorum using SEM and light microscopy
Authors: Christensen Maren , Gardner John S. , Allen Phil S.
Published: June 2020

The coleorhiza is a nonvascular sheath that encloses the embryonic radicle in Gramineae, and is generally the first tissue to emerge during germination. Coleorhiza cells develop extensions similar to root hairs, which are difficult to study quantitatively in situ because they are extremely sensitive to desiccation and breakage. Protective, absorptive and adhesive roles have been postulated for this tissue, but have received limited attention, This study used scanning electron microscopy (SEM) and light microscopy (LM) to characterize the coleorhiza and radicle during germination of Bromus tectorum, a species that often emerges from the soil surface in semiarid habitats.

Caryopses (seeds) were imbibed at various water potentials over solutions of polyethylene glycol (PEG) or in soil until coleorhizae had emerged. For SEM, seeds imbibed over PEG were frozen in liquid freon and then freeze dried, Seeds imbibed in soil were frozen in liquid nitrogen and then freeze dried. For LM, seeds imbibed over PEG were subjected to freeze substitution in dry acetone with 1% OSO4 at -80°C for 19 days.
Effects of Thaxatomin A on the fine structure of potato tubers
Authors: Stein B. D. , King R. R. , Hammerschmidt R.
Published: June 2020

Streptomyces scabies and S. acidiscabies cause common scab in potato plants. At the start of infection a brown lesion develops ahead of the actual site of infection on tubers. This observation led to the isolation of the toxin thaxtornin A from infected potato tubers. Application of the toxin to tubers replicates many of the symptoms seen in infected tubers. Potato mini-tubers were cultured by the methods of C. H. Lawrence (personal communication) where nodal segments of stolons from sprouted tubers were placed in White's media with 8% sucrose and 0.4% agar. Thaxtornin A, 20M1 at 10-5M, was applied to the surface of the mini-tubers. Samples, 24 hours later, were fixed in 2.7% glutaraldehyde in 0.1M Na cacodylate buffer, pH 7.0, and postfixed in 1% OsO4. Part of the samples were dehydrated by an ethanol series, critical point dried, placed on aluminum stubs, gold coated, viewed and photographed by SEM. The remainder of the samples were dehydrated in a graded acetone series, infiltrated in epoxy resin (as formulated by John Heckman, 5.0g VCD, 7.4g Quetol 651, 26g NSA, and 0.4g DMAE).
The use of Griffonia simplicifolia lectin, GSA-I-B-4, to determine the extent of neovascularity in murine neoplasms
Authors: Bucana C. D. , Reynolds D. , Dunner K. , Radinsky R. , Fidler I. J.
Published: June 2020

Angiogenesis plays a critical role in many physiological and pathological processes and is measured by a vascularity index derived from quantification of newly formed blood vessels. Although the identification of human endothelial cells can be accomplished by binding of antibodies against Factor VIII or binding of Ulex europeaus I agglutinin (UEA-I), in murine tissues these markers produce poor results. Since the lectin (GSA-I-B4) from the seeds of Griffonia simplicifolia which binds to -D-galactose, has been shown to bind preferentially to murine endothelial and some epithelial cells,' we determined if binding of this lectin will identify mouse endothelial cells within and around tumors growing in different organs of the mouse such as lung, kidney, bladder, and subcutaneous space.

Tumors were excised, fixed in 10% formalin and processed for histology. The original procedure was modified to include a microwave antigen retrieval procedure which appears to enhance the signal better than trypsin treatment of the deparaffinized sections (Fig. 1 and 2).
Proliferating cells in the vertebrate small intestine: an immunohistocheniical study
Authors: Kömüves Làszló G.
Published: June 2020

In the small intestinal mucosa of healthy adult mammals proliferating cell are confined to the crypts of Lieberkiihn. Earlier radioautographic studies identified proliferative cells in the small intestine of several non-mammalian vertebrates. However, it is still not clear whether cell renewal is confined to proliferative compartment within the small intestinal mucosa in non-mammalian vertebrates. In the present study proliferative cells were identified using an immunological marker of cell proliferation, the proliferating cell nuclear antigen (PCNA) in the small intestine of several non-mammalian vertebrate species, including birds (zebrafinch, Poephila guttata), reptiles (green anole, Anolis carolinensis), amphibia (axolotl, Ambystoma mexicanum), and fishes (goldfish, Carassius auratus).

Segments of the small intestine were fixed in 4% formaldehyde in 0.86 M phosphate buffer, pH=7.2 and embedded in paraffin. Deparaffinized and rehydrated sections were microwaved in citrate buffer. The immunohistochemical detection method used in this study based on the capillary action principle, as developed by Brigati.
Low temperature SEM comparisons of adjacent freeze-fractured and freeze-etched areas on frozen, hydrated samples
Authors: Wergin William P. , Erbe Eric F. , Yaklich Robert W.
Published: June 2020

Most biological samples contain 70-95% water, consequently cryofixation and freeze-fracturing result in relatively smooth surfaces that exhibit few structural details. Freeze-etching, a technique that solved this problem, was initially developed for TEM observations of virus particles by Steere nearly 40 years ago. The technique, which sublimes water-ice from the surface of a fractured sample, produces surface topography that corresponds to the structural components on the freeze-etched face. This technique was further enhanced by recovering the complementary halves of a fractured sample, etching one of the surfaces and then comparing the complementary replicas from the freeze-fractured and freeze-etched faces. Recently, similar techniques were used on frozen, hydrated samples to examine complementary halves of freeze-fractured, freeze-etched specimens by low temperature SEM. Imaging complementary images of frozen, hydrated specimens in the SEM was faster than imaging complementary replicas in the TEM, however the procedure required specialized holders and was technically demanding.

To simplify comparisons of freeze-fracture, freeze-etch images, samples were frozen, fractured and etched in the prechamber of an Oxford CT 1500 HF Cryotrans system that was attached to a Hitachi S-4100 FESEM.
High-resolution electron microscopy of beam-sensitive specimens: Results with paraffin
Authors: Zemlin F. , Reuber E. , Beckmann E. , Dorset D.
Published: June 2020

Many of the most interesting specimens are so severely damaged during the electron microscopical imaging that no useful image emerges from the electron noise. One method of reducing this radiation damage is to cool the specimen, and if this helps it seems reasonable to cool it down as far as possible. This goal is reached most straightforwardly by using the Siemens helium-cooled superconducting objective lens designed by I. Dietrich and co-workers.
Effects of illumination spot size on high-resolution image contrast for radiation-sensitive specimens
Authors: Downing Kenneth H.
Published: June 2020

Electron diffraction patterns of a number of different protein crystals extend to well beyond 0.4 nm. However, until quite recently, no images of these crystals had been obtained which showed such high resolution. The recent introduction of monolayer crystals of paraffin, which diffract at 0.4 nm several thousand times as strongly as typical protein crystals, has made it possible to obtain such high-resolution images almost routinely, and has allowed the study of the causes for the previous lack of success. It has been found that the images of paraffin crystals fall far short of images which could be obtained under ideal circumstances. Not only do the images only rarely show the pseudo-hexagonal symmetry of the crystals, but quantitative analysis of lattice images has shown that under normal conditions the image contrast is typically only about 3-4% of that which is theoretically possible, based on the strength of electron diffraction spots.
Methodology for determining the three-dimensional crystal structure of myosin Sl from electron microscopy of orthogonal thin sections
Authors: Baker T. S. , Winkelmann D. A.
Published: June 2020

Detailed knowledge of the structure of myosin is essential for understanding the mechanism of muscle contraction. The discovery of conditions for crystallizing the head of myosin (Sl = subfragment 1) has led to systematic studies of the SI structure by x-ray crystallography and electron microscopy. We describe the method used to determine the structure of the myosin Sl molecule by electron microscopy (Fig. 3). This method involved independently reconstructing the three-dimensional density of several thin sections obtained from oriented crystals and then combining these reconstructions to produce a final, averaged density map of a single unit cell.
Stain contamination and embedding in electron microscopy
Authors: Mollenhauer Hilton H.
Published: June 2020

Many factors (e.g., resolution of microscope, type of tissue, and preparation of sample) affect electron microscopical images and alter the amount of information that can be retrieved from a specimen. Of interest in this report are those factors associated with the evaluation of epoxy embedded tissues. In this context, informational retrieval is dependant, in part, on the ability to “see” sample detail (e.g., contrast) and, in part, on tue quality of sample preservation. Two aspects of this problem will be discussed: 1) epoxy resins and their effect on image contrast, information retrieval, and sample preservation; and 2) the interaction between some stains commonly used for enhancing contrast and information retrieval.
Breakthroughs and breakdowns: the portrayal of biological macromolecules in computer-processed images of negatively stained specimens
Authors: Steven Alasdair C.
Published: June 2020

Negative staining - the contrast enhancement technique of applying solutions of heavy metal salts to macromolecular particles whose structures are ultimately inferred from the distribution of electron-opaque material that envelopes them - was introduced almost thirty years ago. Since then, the technique has undergone many modifications and refinements, but remains perhaps the most widely used method of preparing isolated biological macromolecules for electron microscopic observation. The advent of image processing, with its potentialities for noise reduction and three-dimensional reconstruction, greatly expanded the scope of negative staining electron microscopy for quantitative reproducible structural analyses. Here we survey the development of this combined methodology and consider its capabilities and limitations as currently practised.
Electron image conversion
Authors: Herrmann K.-H.
Published: June 2020

Electronic image converters are installed in conventional transmission electron microscopes (CTEM) for several reasons depending on the field of application:

1. Their real-time response permits immediate observation and evaluation of the image as required for both high precision adjustment of microscopes for atomic resolution in material science and minimum exposure technique in biology.

2. Used as a fast interface to the computer, an electronic image converter allows on-line image processing for both automatic adjustment and low-dose techniques.
Application of electron spectroscopic imaging to frozen hydrated specimens
Authors: Murray John M.
Published: June 2020

Techniques and equipment for examination of biological specimens by TEM in the frozen hydrated state are rapidly improving. A major advantage of these methods is the capability of examining delicate cellular components in their native state. This advantage can be realized only by taking care to avoid artefacts of sample preparation that have confused interpretation of EM images in the past. Thus it is preferred to examine the frozen hydrated samples without fixation or staining. In this case, the contrast in the image depends entirely on the difference in electron density between water and the constituents of the sample, generally protein, carbohydrate, nucleic acids, and to a lesser degree, lipid. These electron density differences are quite small, and the image contrast is correspondingly low.
NMR imaging and spectroscopy of tissue at high resolution: problems and prospects
Authors: Matwiyoff Nicholas A.
Published: June 2020

When the nuclei of atoms like hydrogen (1H), carbon (13C), phosphorus (31P), and sodium (23Na) are subjected to a static magnetic field, they can be induced to emit electromagnetic radiation. This phenomenon, called nuclear magnetic resonance (NMR), was first demonstrated experimentally by the research groups of Bloch and Purcell in 1946. Because the spectrum of the radiation emitted depends on the type of nucleus and its chemical environment, NMR spectroscopy was rapidly exploited by chemists and has become a major tool for the investigation of molecular structure and the analysis of complex mixtures. More recently the NMR response of living systems subjected to known gradients of a static magnetic field has been exploited in medicine to construct images of the concentration and environment of hydrogen (protons) in the water and fat of soft tissues in the body.
Correlation averaging of two-dimensional crystals: basic strategy and refinements
Authors: Baumeister W. , Rachel R. , Guckenberger R. , Hegerl R.
Published: June 2020

Introduction

Correlation averaging (CAV) is meanwhile an established technique in image processing of two-dimensional crystals /1,2/. The basic idea is to detect the real positions of unit cells in a crystalline array by means of correlation functions and to average them by real space superposition of the aligned motifs. The signal-to-noise ratio improves in proportion to the number of motifs included in the average. Unlike filtering in the Fourier domain, CAV corrects for lateral displacements of the unit cells; thus it avoids the loss of resolution entailed by these distortions in the conventional approach. Here we report on some variants of the method, aimed at retrieving a maximum of information from images with very low signal-to-noise ratios (low dose microscopy of unstained or lightly stained specimens) while keeping the procedure economical.
RecA-DNA complexes: What we can learn about structure and dynamics from disordered filaments using computed image analysis
Authors: Egelman E.H.
Published: June 2020

The recA protein (38,000MW) of E. coli forms helical polymers which are able, in an ATP-dependent reaction, to mediate the entire genetic recombination process, including the search for homology, homologous pairing, and strand transfer. We have been using computed image analysis of electron micrographs of different recA complexes in an effort to understand the function of this protein in recombination. These filaments typically show poor helical order. We have studied the systematic deviations from helical order (the disorder) present in static images of recA complexes as a means of understanding the dynamics of recA filaments in solution.