bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Photon Excitation Microscopy in Cellular Biophysics
Authors: Piston David W.
Published: June 2020

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10 5 limits the average input power to less than 10 mW, only slightly greater than the power normally used in confocal microscopy.

Three properties TPEM give this method a tremendous advantage over conventional optical sectioning microscopies for the study of thick samples: 1) The excitation is limited to the focal volume because of the intensity-squared dependence of the two-photon absorption. This inherent localization provides three-dimensional resolution and eliminates background equivalent to an ideal confocal microscope without requiring a confocal spatial filter, whose absence enhances fluorescence collection efficiency. Confinement of excitation to the focal volume also minimizes photobleaching and photo damage - the ultimate limiting factors in fluorescence microscopy of living cells and tissues. 2) The two-photon technique allows imaging of UV fluorophores with conventional visible light optics in both the scanning and imaging systems, because both the red excitation light (~700 nm) and the blue fluorescence (>400 nm) are within the visible spectrum. 3) Red or infrared light is far less damaging to most living cells and tissues than bluer light because fewer biological molecules absorb at the higher wavelengths. Longer wavelength excitation also reduces scattering of the incident light by the specimen, thus allowing more of the input power to reach the focal plane. This relative transparency of biological specimens to 700 nm light permits deeper sectioning, since both absorbance and scattering are reduced.
Correlative Microscopy in Pathology
Authors: Howell D. N. , Miller S. E. , LeFurgey E.A. , Ingram P. , Shelburne J.D.
Published: June 2020

Microscopy has always provided important anatomical and structural information for biologists and clinicians. The amount of information available has increased exponentially as a result of recent advances in light microscopy, immunohistochemistry, in situ hybridization, electron microscopy, and microprobe analysis. These techniques provide important insights regarding the anatomic distribution, biochemistry, and physiology of a wide range of analytes, including ions and elements, genes and their products, molecular fragments, whole molecules, and macromolecular complexes such as ribosomes and viruses.

Proper interpretation of this vast array of new information requires a correlative approach with regard to both different types of data (e.g., biochemical and structural observations) and different levels of resolution (e.g., gross, light microscopic, and electron microscopic observations). This principle is of particular importance to the pathologist, whose ultimate goal is to apply studies of tissues and body fluids to the understanding of disease as it affects the whole organism. Correlative information is particularly important in the interpretation of ultrastructural studies, where high resolution is often obtained at the expense of context. Accordingly, our laboratories have always emphasized the importance of correlative microscopy. In the case of electron microprobe analysis, we have published different regimens that allow the precise correlation of the chemical data obtained with an x-ray spectrometer with structural data seen by transmitted light microscopy (1,2).
The Role of Hepatocytes as the Body’s “Glucostat” Correlation of Data from Studies Ranging from a (Analysis of Biochemical and Morphological Observations) to Z (Zipping Up cDNA Probes and mRNA)
Authors: Cardell E. L. , Gao J.K. , Giffin B.F. , Cardell R.R.
Published: June 2020

The maintenance and regulation of blood glucose levels is a vitally important liver function, among more than 500 metabolic functions ascribed to hepatocytes. Brain cells cannot function properly if blood glucose levels vary greatly from the normal range of 90-100 mg/100 ml; coma results from extremes of hypo- or hyper-glycemia, and death occurs when the status is not corrected. Because glucose is the primary energy source for brain cells, other cell types throughout the body utilize lipids and amino acids as energy sources in a “glucose-sparing” mechanism to reserve relatively low levels of blood glucose for use by the brain. Acting collectively as the body’s “glucostat,” hepatocytes convert glucose to insoluble glycogen by the process of glycogenesis when blood glucose levels are high (post-prandial, absorptive state), and convert glycogen, fats, and/or protein-derivatives to glucose when blood glucose levels are low (post-adsorptive, fasting state). Various other cell types in the body form glycogen and utilize it for their own energy needs, but only hepatocytes, certain kidney tubule cells, and enterocytes have glucose-6-phosphatase (G-6-Pase), the enzyme needed to convert glycogen back to glucose for release to the blood. Hepatocytes specialize and excel in this process called glycogenolysis; the G-6-Pase is found in the smooth endoplasmic reticulum that can be abundant in these cells and varies according to changes in the individual’s nutritional and physiological status. In addition, hepatocytes have the enzyme phosphoenylpyruvate carboxykinase (PEPCK) that allows gluconeogenesis, the conversion of amino acids ultimately to glucose when carbohydrate sources are not available.
Grain Boundary Dislocation Structure and Motion in an Aluminum Σ=3 Bicrystal
Authors: Medlin D. L. , Foiles S.M. , Carter C. Barry
Published: June 2020

A lattice dislocation may interact with a grain boundary leaving either a residual dislocation or a step or both. These products may then contribute to further deformation by themselves moving along the interfaces. For instance, Pond1 observed the dissociation of a perfect lattice dislocation in an aluminum Σ=3 (211) incoherent twin boundary by a reaction of the type:

Furthermore, the a/3[111] dislocation was observed to dissociate into two partial grain boundary dislocations (GBD), with Burgers vectors of approximately 2a/9[111] and a/9[111], separating structurally degenerate regions of opposite rigid body displacement.
Grain-Boundary Characteristics in Austenitic Steel
Authors: Caul M.D. , Randle V.
Published: June 2020

Grain boundaries are an active area of research interest due to their effect on material property and structure relationships. In order to discuss material properties with regard to grain boundaries it is necessary to know the boundary type. The optimum technique for performing this task is Electron Backscatter Diflfraction (EBSD) in concert with the Scanning Electron Microscope (SEM). By collecting texture measurements in the form of individual orientations from grains it is possible to obtain misorientation measurements from grain boundaries. These measurements are three of the five degrees of freedom necessary to geometrically describe a grain boundary. The other two can be obtained by a serial sectioning technique.

Grain boundaries in austenitic steel specimens, isothermally aged at either 700°C or 800°C, have been evaluated with the aim of relating boundary geometry to Cr2N precipitate formation. Samples were analysed using SEM and EBSD in order to obtain orientation measurements of individual grains to misorientations at grain boundaries and to Cr2N precipitates. These precipitates are detrimental to room temperature properties of high nitrogen stainless steels, so a reduction in their formation at grain boundaries would be advantageous. The steel is therefore an ideal candidate material for relating boundaries to material properties. The 700°C isothermally aged sample induces precipitate formation at grain boundaries whereas precipitation by cellular decomposition of austenite occurs in the 800 CC sample. The 700°C sample was used to categorise boundary types using the CSL model and relate this to Cr2N formation. The 800°C sample was used to examine the effect of aging temperature on boundary inclination. Therefore all five degrees of freedom in grain boundary geometry were obtained.
On the Relationship Between Grain-Boundary Character Distribution and Intergranular Corrosion
Authors: Lehockey E.M. , Palumbo G. , Lin P. , Brennenstuhl A.
Published: June 2020

Intergranular corrosion can under severe conditions lead to “grain-dropping” which results in significant material loss. It has been demonstrated that grain boundaries described by low-Σ CSL misorientations are more resistant to corrosion, cracking (SCC), and sliding (creep) than “general” boundaries, and that the frequency of these “special” boundaries can be enhanced offering the possibility of producing materials with improved bulk corrosion and creep properties. This contribution presents a model for predicting the effect of “special” boundaries on the extent of gross wastage from grain-dropping.

For any grain to be ejected from the matrix, all of its bounding interfaces must be fully compromised. Assuming “special” grain boundaries are immune to corrosion and considering a material containing hexagonal prism grains with a diameter and length, d, it can be shown that the probability, X, of observing grain-dropping at a depth, L, through the material thickness is related to the “special” boundary fraction, Fsp, by:
A Simple and Inexpensive Route to Remote Electron Microscopy
Authors: Völkl E. , Allard L.F. , Nolan T.A. , Hill D. , Lehmann M.
Published: June 2020

Due to the availability of fast computer networks such as Ethernet, FDDI and ATM, the idea of Telemicroscopy, including running electron microscopes from remote locations has gained momentum. Fan, Ellisman, Zaluzec and Parvin, have discussed aspects of systems which support such capabilities. In each of these reports the authors describe new stand-alone software packages that are required to run their systems. In order to make remote microscopy more universally available, we have chosen to expand de facto standard commercial software to provide for computerized microscope control and remote control.

All of the major instruments in our user facility have been converted to digital operation and the darkroom has been abandoned completely. It is a logical extension of digital imaging to provide for computer control of the instrument operation, since the instrument parameters can be adjusted using feedback from analysis of the digital image. Digital image recording and display typically uses commercial software such as DigitalMicrograph© (which controls e.g. the CCD camera on the HF-2000). This program
provides the four capabilities necessary to implement instrument control. It allows camera control,provides image processing tools, incorporates a scripting language and also allows C-code to be implemented.
Webscope.TEM: A Modular System for Distributed TEM
Authors: Kisseberth N.J. , Potter C.S. , Brauer G.E. , Lindquist J.A. , Jatko M.K. , Carragher B.
Published: June 2020

We will describe our implementation of a system for controlling and acquiring images from a transmission electron microscope (TEM) over a distributed network. Over the past few years several groups have begun to develop systems for remote microscopy and there are now a number of prototypes and working examples that demonstrate the feasibility of this goal. The system we are developing is part of a larger project which we refer to as the World Wide Laboratory (WWL). This is a collaborative effort between the Beckman Institute, the Biomedical Magnetic Resonance Laboratory, and the National Center for Supercomputing Applications at the University of Illinois. The goal of the WWL project is to provide a set of specifications for developing instrument control servers and image processing tools which can be accessed over the Internet through a variety of user interfaces. We are currently developing servers and control applications for TEM, a magnetic resonance imaging system, a scanning tunneling microscope and a laser scanning confocal microscope.
Electron Microscopy and Educational Outreach on the World Wide Web
Authors: Gardner John S. , Rice Judy , Fogt Bill , Erickson Kali , Harrison Russell
Published: June 2020

For over five years, Utah Valley area high school students have been invited to the Brigham Young University Microscopy Lab to conduct individual and group research projects. This outreach program provides each student with concrete, “hands-on” experience in the field of microscopy and an application of the scientific principles learned in the high school classroom. The program utilizes the expertise of university faculty, lab personnel, undergraduate research assistants, corporate professionals and public school teachers as well as microscopy facilities and equipment (Fig. 1). These elements combine in an effort to mold confident and experienced young professionals. The outreach program has produced students who have published, won contests, earned scholarships and found employment opportunities within the field. However, the program has only been able to serve a limited number of students who want to participate. With the aid of developing technology and the distributed learning model, the influence of electron microscopy can be spread more effectively.

The study of microscopy including several related subjects is now more accessible through the creation of a World Wide Web site at Brigham Young University (BYU). Users can select from a variety of menus including a Library, Teaching Center, Learning Center, and Explore Your Mini- Worlds. Student research images have been collected and downloaded through the use of computerized imaging and microscopy (Fig. 2).
The CM120-Biofilter: Digital Imaging of Unstained Specimen, a Comparison of Zero-Loss and Unfiltered Images
Authors: Lücken Uwe , Frank de Jong A. , Busing Wim M. , Rees Jeremy , Nadarzinski Klaus , Kundmann Mike K.
Published: June 2020

A new system for energy-filtered electron microscopy (EFTEM) has been developed, adapted for the study of life science specimens. Attention has been given to integration, ease of use and the typical problems encountered while investigating unstained and cryo-specimens. Low-dose, cryo-capabilities and a high contrast objective lens have been combined with an imaging energy filter, digital image recording with phosphorus scintillator and advanced image processing capabilities. The CM120-BioFilter is an integration of the CM 120-BioTWIN with the Gatan post-column imaging filter GIF100. The BioTWIN objective lens (Cs=6.2 mm, f=5.9 mm) is optimized for high-contrast imaging. The GIF100 is a computer-controlled, second- order corrected energy filter with a cooled multiscan CCD for digital image recording. Improvement of the contrast can be achieved if inelastically scattered electrons are removed. A comparison of zero-loss filtered and unfiltered images from unstained specimens is presented.

The contrast of thick, unstained specimens is limited by the high amount of inelastic scattering. Images from thick sections of unstained spleen tissue shown in Fig. 1 are compared by means of mean and standard deviation of multiscan CCD data.
Development of a Computer-Controlled 120kV High-Performance Tem
Authors: Kobayashi H. , Nagaoki I. , Nakazawa E. , Kamino T.
Published: June 2020

A new computer controlled 120kV high performance TEM has been developed(Fig. 1). The image formation system of the microscope enables us to observe high resolution, wide field,and high contrast without replacing the objective lens pole-piece. The objective lens is designed for high- contrast (HC) and high-resolution(HR) modes, and consists of a double gap and two coils. A schematic drawing of the objective lens and the strength of the magnetic field of the lens is described in Fig.2. When the objective lens is used in HC mode, upper and lower coils are operated at a lens current of same polarity to form the long focal length. The focal length(fo), spherical aberration coefficient(Cs) and chromatic aberration coefficient (Cc) in HC mode at 100kV are 6.5, 3.4 and 3.1mm, respectively. Magnification range at HC mode is × 700 to × 200,000. The viewing area with an objective aperture of a diameter of 10μm is 160mm in diameter. In HR mode, the polarity of lower coil current is reversed to form a shorter focal length for high resolution image observation. The fo, Cs and Cc of the objective lens in HR mode at lOOkV are 3.1, 2.8 and 2.3mm, respectively. The highest magnification in HR mode is × 600,000.
Detective Quantum Efficiency of 25μm Pixel Imaging Plate
Authors: Taniyama A. , Shindo D. , Oikawa T. , Kersker M.
Published: June 2020

The 25μm pixel Imaging Plate (IP) is expected to apply to high-resolution transmission electron microscopy (HRTEM) because of its higher spatial resolution than the 50μm pixel IP. It seems that the 25μm pixel IP, which has wide dynamic range and good linearity, is effective for HRTEM with low exposure to reduce electron radiation damage. In order to apply the IP to the HRTEM appropriately, it is necessary to understand the detective efficiency of the IP. In this paper, signal to noise (S/N) ratio and detective quantum efficiency (DQE) of the 25μm pixel IP at accelerating voltages of 100, 200 and 1250kV are presented and a suitable amount of electron exposure for HRTEM is discussed.

DQE is expressed as the comparative noise level (σi2/σo2) measured by the ratio of the mean-square fluctuation of incident electrons (σi2) to that of output signal (σo2). In this experiment, the distribution of the incident electrons was assumed to be Poisson statistics.
Quantitative particle analysis: fact or fiction
Authors: Small J.A. , Armstrong J.T.
Published: June 2020

In conventional microprobe analysis, the samples and standards have a controlled geometry, i.e. flat polished, and infinitely large with respect to the electron beam interaction volume. As a result, the measured x-ray intensities for the analyzed elements vary in a predictable manner with composition and the various elemental concentrations can be calculated from a choice of several analytical algorithms. Unlike conventional analysis, the quantitative analysis of particles with the electron probe presents a very difficult analytical challenge. Most particles are irregularly shaped and do not have controlled geometries. In addition, depending on their size, they may not be “infinitely” thick with respect to the electron beam. Because of the random sizes and shapes, the emitted x-ray intensity from particles may be greater than or less than the intensities from a flat conventional sample of the same composition. A diagram from Armstrong of the interaction between an electron beam and a particle is shown in Fig. 1 and illustrates the “particle” effects that make quantitative particle analysis so difficult.
Automated fine-particle analysis using scanning electron microscopy
Authors: O’Keefe Catherine A. , Watne Tina M.
Published: June 2020

Owing to analytical advances, submicron particles as small as 0.1 μm can be characterized for chemical composition, size, and shape using scanning electron microscopy (SEM). Once these characteristics are determined, the individual particles can be grouped into categories that provide size, shape, and chemical/mineral distributions of the fine particle fraction.

An important application of submicron particle analysis is in solving ash-related problems in coal combustion and gasification systems. The Energy & Environmental Research Center (EERC) at the University of North Dakota is involved in an international consortium formed by the Electric Power Research Institute (EPRI), with U.S. Department of Energy Morgantown Energy Technology Center support, to study ash-related problems associated with the cleaning of hot gases in advanced energy systems. Before the gases are sent through a gas turbine to produce electricity, the particulates are removed with ceramic filters. Filters designed to trap the ash have a tendency to become plugged with ash, eventually causing operational problems. The focus of the project is to characterize the ashes from several filter systems to determine the mechanisms by which difficult-to-clean ash is formed and how it blinds hot-gas filters.
Analysis of completed commercial semiconductors using EPMA
Authors: Packwood R. , Phaneuf M.W. , Weatherall V. , Bassignana I.
Published: June 2020

The development of specialized analytical instruments such as the SIMS, XPS, ISS etc., all with truly incredible abilities in certain areas, has given rise to the notion that electron probe microanalysis (EPMA) is an old fashioned and rather inadequate technique, and one that is of little or no use in such high technology fields as the semiconductor industry. Whilst it is true that the microprobe does not possess parts-per-billion sensitivity (ppb) or monolayer depth resolution it is also true that many times these extremes of performance are not essential and that a few tens of parts-per-million (ppm) and a few tens of nanometers depth resolution is all that is required. In fact, the microprobe may well be the second choice method for a wide range of analytical problems and even the method of choice for a few.

The literature is replete with remarks that suggest the writer is confusing an SEM-EDXS combination with an instrument such as the Cameca SX-50. Even where this confusion does not exist, the literature discusses microprobe detection limits that are seldom stated to be as low as 100 ppm, whereas there are numerous element combinations for which 10-20 ppm is routinely attainable.
Identification of phases in corium held at high temperature in a tungsten crucible by SEM, EPMA, and EBSD
Authors: Schneider B. , Bouchet C. , Perodeaud P. , Dugne O. , Maurizi A. , Valin F. , Guíneau C. , Bordier G
Published: June 2020

Heat treatments of U − Zr − O mixtures of different oxygen contents (ranging from 1 to 35 at. %) and of a constant U/Zr ratio (U/Zr = 1.35 which is characteristic of the inner part of a pressurized-water reactor) were performed in order to study the high temperature behavior of corium. The selected U-Zr-O mixtures were put in a tungsten crucible and heated to 2050°C. The specimens were thereafter analyzed by Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA) and Electron BackScattering Diffraction (EBSD).

SEM surface analysis showed a complex system (Fig. 1). Four different phases were characterized. The uranium-rich matrix (noted P1) gave no diffraction pattern by EBSD. The average composition of the sharp grains (P2) located near the tungsten crucible surface was 66 at. % of W and 34 at. % of Zr. The diffraction pattern of this phase was accurately indexed with the fee structure parameters of W2Zr (Fig. 2).
Characterization of phases in an as-cast Mo-B-Si alloy by WDS EPMA
Authors: Nunes C. A. , Fournelle J.H. , Perepezko J.H.
Published: June 2020

EPMA experiments have been carried out to support an extensive study involving phase equilibria, solidification pathways and diffusion in Mo-rich Mo-B-Si alloys. In this work we have characterized the phases present in an as-cast 60Mo-30B-10Si (at%) alloy by WDS EPMA in order to provide further information to understand some anomalous backscattered electron images of this alloy.

The alloy was produced by arc-melting pure Mo, B and Si under argon. The EPMA analysis was carried out in a CAMECA SX-50 EPMA on a polished and flat surface of the material. In order to avoid additional absorption of the B-Kex radiation the sample was not coated.

The analysis of boron in the presence of Mo presents serious interference between the Mo My line and the B-Koc line (Figure 1).
ALCHEMI of NbCr2/V C15-structured laves phase
Authors: Kotula P.G. , Anderson I.M. , Chu F. , Mitchell T.E. , Bentley J.
Published: June 2020

Laves-phase intermetallics are of potential interest for use as high temperature structural materials, of which NbCr2-based C15-structured Laves phases are particularly attractive. Vanadium-alloyed NbCr2 Laves phases have been studied. The defect mechanism of a ternary Laves phase is crucial to understanding its physical metallurgy and deformation behavior. It is suggested based on the Nb-Cr-V phase diagram and first-principles total energy and electronic structure calculations for NbCr2 that V should occupy the B sites in C15-structured AB2. In this paper, ALCHEMI is employed to examine this assumption for one composition of a V-alloyed NbCr2 Cl5 Laves phase.

A Nb-Cr-V alloy of composition Nb33Cr42V25 was prepared by arc-melting followed by annealing at 1400°C for 120 h. Specimens were prepared for microanalysis by cutting 3 mm discs followed by dimpling and ion milling. Energy-dispersive X-ray (EDX) spectra were acquired with a Philips CM30 operating at 300 kV and equipped with a Kevex Quantum detector. Fourteen spectra were collected near <014> over a range of {400} excitations between symmetry and beyond {12 0 0}.
Analytical Electron Microscopy of nanometer-size precipitates in al alloys with a 200-kV field-emission TEM
Authors: Howe J. M. , Ringer S. P. , Muddle B. C. , Polmear I. J.
Published: June 2020

Certain trace elements are known to have a pronounced effect on the nucleation kinetics of metastable phases in Al alloys. This provides many opportunities for alloy design. Understanding the role of trace elements in the precipitation process is difficult because they are typically present at levels of less than 0.1 at.% and involve early stages of clustering or segregation to precipitates. This paper presents recent results from the application of a 200 kV thermal field-emission gun (FEG) transmission electron microscope (TEM) to study trace element additions and the early stages of precipitation in Al alloys, using the case of an experimental alloy designated ALMAGEM as an example.

An Al-2.41Cu-0.34Mg-0.lSi-0.04Ge alloy was cast into a book mold, homogenized, solution treated at 525°C, water quenched and aged for 12.5 h at 170°C to peak hardness. Disks 3 mm in diameter were electropolished in a HNOs/methanol solution and examined at 200 kV in a JEOL 2010F FEG TEM with a high-tilt (±30°) pole piece.
Color image analysis in optical microscopy
Authors: Laroche Sylvain
Published: June 2020

Most of the applications in microscopic image analysis are still solved by a heuristic method that focuses on the specificity of each problem. This is particularly true for applications involving color images. Because of this, the design of robust algorithms has remained time consuming and is usually performed by an image analysis expert with many years of experience. How then can the knowledge of the expert be transferred to the less specialized microscopist? How can the specificity of a typical application be related to general color image analysis tools?

Only a general approach can work towards decreasing the heuristic aspect of the design phase and help the common user perform image analysis without the assistance of an expert. To illustrate such an approach, two typical applications, one in material science, and the other in the biomedical field are presented:
Practical considerations and applications of digital imaging in a core microscopy facility
Authors: Price R.L.
Published: June 2020

The Integrated Microscopic Analysis Facility (IMAF) at the University of South Carolina School of Medicine is a core
research and imaging facility that provides service for the faculty, staff and students of the medical school and associated hospitals. The IMAF currently houses one scanning and two transmission electron microscopes, a confocal scanning laser microscope, and several image processing computers and programs. While not yet totally converted to digital technology, we have been successful in introducing digital imaging to several areas of our imaging capabilities during the last few years. The purpose of this abstract and subsequent presentation is to present some practical considerations and problems we have encountered in the conversion of the IMAF to digital imaging microscopy, and to present brief results from some projects which were not possible before the introduction of digital imaging to the facility.

There is little doubt that in the past few years one of the major advances for those of us who work in the areas of light and electron microscopy has been the development of digital imaging technology.
Performance evaluation of a second generation metaphase finder for chromosome-based radiation dosimetry.
Authors: Pollitt D. , McLean J. , Johnson F. , Rivest J-F. , Gibbons D.
Published: June 2020

To be useful, a metaphase chromosome finder must be able to quickly identify chromosome spreads, rank them in terms of analysability and relocate them for visual examination at high magnification. In addition, the system should use state-of-the-art technology which is commercially available at competitive prices. The metaphase finder described here uses an 8-bit CCD camera (640 × 480 pixel resolution) and an Olympus BX-50 microscope with a × 20 apochromat objective. The camera composite video signal is connected to an image processing card (Matrox “COMET” card) for a final image resolution of 2.4 × 2.4 μm (5.8 μm2) per pixel for a 100 × 80 μm field of view. The microscope stage movements and focusing are under software control (illumination and filter selection are manual). Miniature motors (MicroMo 1616 series) and reduction gearboxes were retrofitted to a standard Olympus microscope stage and to the fine focus control shaft.
Spiral carbon tubes grown by a mixed-valent oxide-catalytic carbonization process
Authors: Wang L. , Kang Z. C.
Published: June 2020

Synthesis of carbon tubes is vitally important in carbon research and applications. In this paper, spiral carbon tubes are grown by a mixed-valent oxide-catalytic carbonization (MVOCC) process. The carbon tubes are highly twisted and have many growth induced nodes. (Fig. 1). The product has high purity and no catalyst particle is found in the product. With the presence of inter-lock structure, the mechanical properties of the material made using the spiral carbon tubes could be significantly improved. The inner tube is not completely hollow but interconnected by graphitic layers. The surfaces of the tubes have many open graphitic edges, thus, a high chemical activity of the tubes is expected. Figure 2 shows a low-magnification TEM image at the initiation side of a carbon tube, where a spiral node is formed. The non-uniform contrast across the node region reflects the spiral geometry at the node.
In-situ and ex-situ AFM imaging of μN load indents on silicate glass/alumina interfaces
Authors: Zagrebelny A. V. , Lilleodden E. T. , Nelson J. C. , Ramamurthy S. , Carter C. B.
Published: June 2020

Contact which only involves a small volume of material is becoming increasingly important to many industries including micromachines, microelectronics, and magnetic recording. The ability to characterize surface roughening on the micro- and nanoscopic scale is invaluable in understanding microplasticity due to indentation, scratches, wear, fatigue and epitactic mismatch. It has been demonstrated that AFM studies are appropriate for developing a mechanistic approach to μN load indentation analysis since they allow deformation volumes and residual depths to be measured and characterized directly and unambiguously.

In the present study, interfaces between silicate glass and single-crystal α-Al2O3 have been studied using AFM and nanoindentation. The interfaces between the glass and the crystalline grains were prepared by growing films of anorthite (CaAl2Si2O8) composition with thickness ranging 100-200 nm on single-crystal sapphire substrates of {1120} (A-plane) and {1102} (R-plane) crystallographic orientations by pulsed-laser deposition (PLD). Some specimens were subjected to heat treatments in a conventional box furnace causing films to dewet the substrates. Fig. 1 shows schematically the morphology of the dewetted film which has resulted in the formation of distinctive islands, 0.5-2 μm in size. Both types of specimens were tested with two different micro/nanomechanical testers.
Time-resolved high-resolution electron microscopy of grain migration process in MgO films
Authors: Kizuka T. , Iijima M. , Tanaka N.
Published: June 2020

High-resolution electron microscopy (HREM) has been employed intensively to analyze the atomic structures of grain boundaries and interfaces having two dimensional structures inside polycrystalline and composite materials. Furthermore time-resolved HREM (TRHREM) is required to analyze the behavior of grain boundaries and interfaces at atomic scale. The grain boundary migration, which is a typical grain boundary behavior, is a fundamental process relating to structural stability of polycrystalline materials. The mechanism of the migration has been still unknown.

In the present study, the variation of atomic arrangement at the grain boundary migration of a MgO [001]Σ5 boundary was analyzed by TRHREM.

Magnesium oxide polycrystalline films were prepared by vacuum-deposition on air-cleaved (001) surfaces of sodium chloride at 300°C. TRHREM was carried out at room temperature using a 200-kV electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder. The spatial resolution of the system was 0.2 nm at 200 kV and the time resolution was 1/60 s. Electron beam density was 30 A/cm2.
Atomic structure of internal Cu/Al2O3 interfaces
Authors: Dehm G. , Scheu C. , Rühle M.
Published: June 2020

Metal/Ceramic compounds show a wide range of applications, ranging from electronic packaging to bio-medical implants. A detailed knowledge of the bimaterial interface is therefore necessary in order to understand the compound properties and their dependence on microstructure and atomic configuration. In this study, thin overlayers of Cu on (0001) α-Al2O3 were grown by molecular beam epitaxy. The films possess a fixed (111)cu<110>cu ‖ (0001)s[1010]s (index S: Al2O3) orientation relationship to the substrate. High resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscoppy (EELS) were applied to obtain information about the interface structure and the bonding mechanism of the interface at an atomic level. The HRTEM studies were performed on the Jeol JEM ARM 1250, an atomic resolution microscope operated at 1250 kV3. The bonding mechanism between Cu and Al2O3 can be determined by an analysis of the energy-loss near-edge structure (ELNES) of the internal interfaces. Those investigations were carried out in a VG HB501 dedicated scanning transmission electron microscope equipped with a parallel EELS (Gatan 666PEELS).
SIMS direct ion imaging in the mineralogical sciences
Authors: McMahon G. , Cabri L. J.
Published: June 2020

The use of secondary ion mass spectrometry (SIMS) has enjoyed increasing popularity in the mineralogical sciences owing to its high sensitivity to all elements in the periodic table with detection limits in the parts per million to parts per billion regime, coupled with the ability to display maps of elemental distribution at these detection levels with a spatial resolution of 1 μm. A description of the technique and its application to a wide variety of mineralogical problems has recently been reviewed.

The drawback of SIMS is the rather complicated nature of quantification schemes necessitated by sample matrix effects, which refer to differences in the sensitivity for a given element in samples of different composition. These differences result from changes in the ionization efficiency and sputtering yield (sample matrix specific) as well as changes in secondary ion transmission and ion collection efficiencies (instrument specific). Therefore, the use of matrix-matched standards of known concentration is required to establish a calibration factor known as the relative sensitivity factor (RSF) which can be used to convert the experimentally measured secondary ion intensity into concentration values. Furthermore, the effect of changes in ion intensity caused by variations in primary beam current or analysis at different sample positions is removed by normalization to an ion species which represents the matrix material.
Distinguishing between YBa2Cu3O7-x and Y2BaCuO5 in melt-processed YBa2Cu3O7-x
Authors: Riches J.D. , Barry J.C. , McGinn P.J.
Published: June 2020

Much of the work in high temperature superconducting ceramics in the last few years has been aimed at improving the critical current density (Jc). By melt-texturing samples it is possible to achieve a significant increase in the Jc of bulk YBa2Cu3O7-x (Y123). It has been known for some time that additions of Y2Ba2CuO5 (Y211) in the Y123 superconductor can improve the Jc. However, for the maximum improvement the Y211 particles must be very fine and well distributed throughout the sample. Thus it is clearly of considerable interest to be able to examine a bulk sample and be able to easily distinguish between the Y123 and Y211 particles. By a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) it is possible to study grain size, inclusion size and dislocation structure in the same sample.
Light – microscopic analysis of the physical properties of cytoplasm in living cells
Authors: Hori Masatoshi , Jones Jeffrey D. , Janson Lee , Ragsdale Keith , Luby-Phelps Katherine
Published: June 2020

We have used a variety of optical techniques to explore the intracellular constraints on diffusion, cytoplasmic compartmentalization and biomechanics of living tissue culture cells. Fluorescence ratio imaging measurements of solvent viscosity in single cells indicate that the solvent viscosity of cytoplasm does not differ detectably from bulk water. Nevertheless, data obtained by fluorescence recovery after photobleaching (FRAP) of inert tracer molecules suggest that macromolecular crowding and molecular sieving retard the long-range translational diffusion of protein-sized molecules from 4 to 50-fold relative to their diffusion in dilute aqueous solution.

Transient binding interactions with intracellular components may additionally retard the diffusion of proteins. Recent FRAP studies of fluorescent analogs of calmodulin suggest that as little as 5% of this protein is freely diffusing, even in unstimulated cells where intracellular [Ca2+] is below the threshold for activation of calmodulin binding to calcium-dependent targetsin vitro. Preliminary data show that binding is mitigated or abolished by charge reversal mutations in the central helix of calmodulin or by a point mutation in calcium binding loop 4 that greatly reduces the affinity of calmodulin for Ca2+.
Real-Time Confocal Imaging of Calcium Changes Upon Exocytosis in Paramecium
Authors: Levin Sergei , Satir Birgit H.
Published: June 2020

Exocytosis in the unicellular eukaryote Paramecium occurs rapidly upon stimulation with the biological secretagogue lysozyme (100 μM) in a Ca2+-dependent manner. Prior to stimulation each cell contains several thousand dense core secretory vesicles (trichocysts) docked beneath the cell membrane which can be induced to fuse with the plasma membrane either globally or locally. Fusion of the vesicle is followed by secretion and expansion of the trichocyst content from a 4 μm protein crystalline array to a 40 μm spear-like protein structure that are visible in the light microscope. The exocytosis microdomain of the cell membrane has been well characterized in earlier freeze fracture studies. The specific site of exocytosis was shown to consist of a rosette (fusion rosette) of 9 to 11 intramembrane particles surrounded by two outer rings of smaller sized particles. It is below these fusion rosettes that each of the secretory vesicles is docked and primed to release upon stimulation. In the absence of assembled fusion rosette normal release of trichocysts is blocked, as demonstrated with rosette defective mutants1. The fusion rosette has been postulated to function as calcium gates involved in exocytosis3. Paramecium has three known distinct Ca2+ channels: 1) the ciliary voltage-gated channel, 2) the hyper-polarization-activated channel, and 3) the anterior mechanosensory channel. Recently, we have described experiments indicating the presence of a fourth type of Ca2+ channel, a specific receptor operated Ca2+ conductance associated with lysozyme stimulated exocytosis. In this study we have visualized local (temporal and spatial) calcium fluxes associated with discrete exocytic events, using real time confocal microscopy (Nikon, RCM 8000) and calcium imaging with Indo-1 dual emission dye.
Effect of pH and inhibitors on beta-amyloid fibril assembly
Authors: Maleeff Beverly E. , Hart Timothy K. , Wood Stephen J. , Wetzel Ronald
Published: June 2020

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.
Hepatocyte ultrastructural alterations in perimetastatic areas
Authors: Finol H. J. , Correa M. E. , Sosa L.A. , Márquez A. , Díaz N.L.
Published: June 2020

In classical oncological literature two mechanisms for tissue aggression in patients with cancer have been described. The first is the progressive invasion, infiltration and destruction of tissues surrounding primary malignant tumor or their metastases; the other includes alterations produced in remote sites that are not directly affected by any focus of disease, the so called paraneoplastic phenomenon. The non-invaded tissue which surrounds a primary malignant tumor or its metastases has been usually considered a normal tissue . In this work we describe the ultrastructural changes observed in hepatocytes located next to metastases from diverse malignant tumors.

Hepatic biopsies were obtained surgically in patients with different malignant tumors which metatastized in liver. Biopsies included tumor mass, the zone of macroscopic contact between the tumor and the surrounding tissue, and the tissue adjacent to the tumor but outside the macroscopic area of infiltration. The patients (n = 5), 36–75 years old, presented different tumors including rhabdomyosarcoma, leiomyosarcoma, pancreas carcinoma, biliar duct carcinoma and colon carcinoma. Tissue samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.
Spermatic multinucleation in infertile agriculture workers exposed to carbofuranyl pesticide
Authors: Gallegos de L. G. , Arizpe S. M.M. , Alvarado C. L.E. , Ramirez B. E.
Published: June 2020

It is known that the exposure to gonadotoxic agents cause male infertility in agricutural workers. Pesticides provoke a detrimental effect on the spermatogenesis characterized by low count of sprematozoa, as well as sperm motility and morphology alterations. Simultaneosly an increase in FSH seric levels is present.

The semen analysis was proposed in 1975 to detect sperm quality and function alteration induced by chemical agents. There are many morphologic anomalies related to the noxious action of some gonadotoxic agents, ie. head deformities, microcephalia, tail defects, etc.

We detected in our laboratory a pair of cases of infertile patients, that presented high levels of teratozoospermia with a high percentage of multinucleated spermatozoa and spermatids, and referred exposure to Carbofuranyl (Furadan 300). Since this agent has not been classified as gonadotoxic, we tried to show it's posible causal relationship with spermatic multinucleation phenomenon observed and the fertility of these patients.
Movement of spotted fever rickettsiae through tick host cells in vitro
Authors: Munderloh U. G. , Hayes S. F. , Cummings J. , Kurtti T. J.
Published: June 2020

Spotted fever group (SFG) rickettsiae are obligate intracellular prokaryotes that include tick-borne pathogens of animals and man as well as organisms that live in symbiotic association with their tick hosts. A striking feature of the behavior of pathogenic rickettsiae in the vertebrate is their ability to quickly disseminate between cells from the original site of entry shortly after infection, and before severe lesions are detected. Similarly, ticks become systemically infected with SFG rickettsiae, indicating that an efficient mechanism of dispersal also exists in the vector. This is accomplished despite the fact that rickettsiae are not motile.

Kadurugamuwa et al. (1991) have used light and electron microscopy to show that Shigella flexneri utilize host cytoskeletal components to travel through cytoplasmic extensions and penetrate into neighboring cells. Using mammalian cells cultured in vitro, Heinzen et al. (1993) have demonstrated that SFG rickettsiae cause host cell actin polymerization at one rickettsial pole causing them to be propelled through the cytoplasm, and to transfer rapidly from cell to cell.
Progress in high-resolution CRYO-SEM imaging of viral particles
Authors: Chen Ya , Letchworth Geoffrey , White John
Published: June 2020

Low-temperature high-resolution scanning electron microscopy (cryo-HRSEM) has been successfully utilized to image biological macromolecular complexes at nanometer resolution. Recently, imaging of individual viral particles such as reovirus using cryo-HRSEM or simian virus (SIV) using HRSEM, HV-STEM and AFM have been reported. Although conventional electron microscopy (e.g., negative staining, replica, embedding and section), or cryo-TEM technique are widely used in studying of the architectures of viral particles, scanning electron microscopy presents two major advantages. First, secondary electron signal of SEM represents mostly surface topographic features. The topographic details of a biological assembly can be viewed directly and will not be obscured by signals from the opposite surface or from internal structures. Second, SEM may produce high contrast and signal-to-noise ratio images. As a result of this important feature, it is capable of visualizing not only individual virus particles, but also asymmetric or flexible structures. The 2-3 nm resolution obtained using high resolution cryo-SEM made it possible to provide useful surface structural information of macromolecule complexes within cells and tissues. In this study, cryo-HRSEM is utilized to visualize the distribution of glycoproteins of a herpesvirus.