bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Boundary Segregation in NI-Base Alloys: an Integrated Approach using FIB, TEM and SIMS
Authors: McMahon G , Phaneuf M
Published: July 2020

Segregation of elements to the grain boundaries in Ni-base alloys can have a large effect on the mechanical and corrosion properties of these materials. The extent of segregation, whether it is equilibrium or non-equilibrium segregation, is dependent upon the thermo-mechanical treatments applied to the alloy. in order to determine if a particular thermo-mechanical process delivers the desired microstructure, a complete microstructural analysis including an examination of grain boundary segregation must be performed.

In the past, TEM has been used to identify the various phases and precipitates in these materials through the use of bright- and dark-field imaging, electron diffraction, and EDS. However, one of the elements that can play a large role in determining the properties of these alloys is boron. in this group of alloys, boron is generally present in bulk analyses in only a few tens of ppm, and as a result it is difficult to detect using the aforementioned techniques. More commonly, boron segregation to the grain boundaries is usually studied by means of Auger analysis, whereby the sample is charged with hydrogen in order to promote brittle intergranular fracture in-situ in the Auger microprobe. Boron can then be detected at the surface of the clean grain boundary fracture surfaces.
TEM Sample Preparation of Polymer Based Nanocomposites using Focused Ion Beam Technique
Authors: Miyagawa H , Chiou W-A , Daniel IM
Published: July 2020

Recently, several studies have been conducted to investigate the behavior of polymer based composites reinforced with clay particles, which can remarkably improve the properties of the polymers. Studies using transmission electron microscopy (TEM) are necessary to understand the role of clay minerals/particles in the reinforcing effect in the polymer based materials. TEM sample preparation of polymer/clay nanocomposites using conventional techniques has been difficult and tedious. Nevertheless, the focused ion beam (FIB) technique for preparing metal and ceramic samples provides another method for preparing polymer nanocomposite samples. This paper presents a new approach for preparing TEM specimens of the polymer nanocomposites using the FIB technique.

Two types of epoxy (Dow Chemical Company, DER 331) nanocomposite samples were investigated: one containing 7.5 wt.% organomontmorillonite clay (Southern Clay Products Inc., Cloisite 30B) and the other (carbon fiber reinforced plastics; CFRP) containing carbon fibers (Hexel Fibers, AS4) in addition to 5 wt. % clay. Details of preparing the epoxy based clay nanocomposites will be published elsewhere. Procedures for preparing TEM thin sections using FIB were based on techniques developed by Ramirez de Arellano et al.
Remote Control Scanning Electron Microscope with Web Operatoin Interface
Authors: Yamada Atsushi , Kobayashi Toshiharu , Negishi Tsutomu , Matsumoto Sunao , Handa Nobuo , Tsuchida Takayoshi , Sugano Naoki , Iwatsuki Masashi
Published: July 2020

Recently, SEM (Scanning Electron Microscope) and the other observation devices are coming to use a LAN (Local Area Network) to save the image in the database. We developed a remote control system in which SEM image and Control interface is indicated on the WEB Browser. in this system, SEM can be controlled by an external (client) PC installed in a general WEB Browser(Internet Explorer). Accordingly, operation interface can be indicated on the WEB browser.

A JSM-6700F is connected to a LAN, and so the microscope can be controlled by a client PC. Figure. 1 shows the block diagram of SEM remote control system. The JSM-6700F has two lines to the LAN for image transfer and communication with the SEM control. in order to transfer the image, the image size squeezes from 1280 × 1024-pixels (SEM image size) to 640 × 480-pixels for quick transfer. The image signal (640 × 480-pixels) is connected to the video server only, and then the image transfers to the client PC via LAN. The SEM control communicates with client PC for external command. On the other hand, the SEM control interface and the image are indicated on WEB Browser (Internet explorer) as shown Figure 2. The SEM control interface is composed of the SEM image area and the SEM control part. The SEM image indicates the 640×480-pixels live image. This pixel number was an image quality sufficient to adjust the focus. When a high quality image is necessary, the image of 1280 × 1024-pixels is saved on the the SEM(server) side by choosing the image save button.
Automated Very Low Magnification Imaging for TEM
Authors: Potter CS , Carragher B , Kriegman D , Pulokas J
Published: July 2020

A typical TEM specimen grid provides approximately a 2×2 mm area that is available for imaging. in order to identify and locate suitable targets on the grid the microscopist must usually inspect the grids at magnifications that allow for only a small area of the grid in the field of view at a time. Systematically searching the grid and mentally keeping track of relative locations presents a challenge for a microscopist especially as the image normally rotates as the magnification is changed. We present an automated technique that creates a very low magnification (VLM) image of the entire available imaging area on the grid. The VLM image can then be used as a reference map for searching the grid at high magnification.

VLM images were obtained at a nominal magnification of 57x using a Philips CM200 TEM equipped with a Gatan CCD camera. The VLM image of the entire 2 mm specimen grid can be created using a mosaic of 49 images, each 512×512 pixels in size. The sampling distance between the images in the 7×7 array is 300μm and the pixel size is 680nm. The images are then automatically tiled and re-sampled to form a final VLM matrix of 4K×4K with a pixel size of 730nm. The resampling factors for the tiling operation include the scale and the relative angle between the camera and goniometer axes. These factors are determined automatically from a calibration process that characterizes the goniometer.
Application of a SQL Database for Automated Image Acquisition and Analysis for CRYOEM
Authors: Fellmann D , Carragher B , Potter CS , Pulokas J
Published: July 2020

We have been developing a software system, called Leginon, for the control and acquisition of images from a transmission electron microscope. This software allows for the automatic acquisition of images under low dose conditions from a specimen embedded in vitreous ice. Thousands of images are collected during each session at the microscope. These images are collected at various magnifications and under a variety of conditions. For example, images are collected of the entire grid, individual grid squares, individual holes within the square, and several high magnification images are acquired for one to several targets within each hole (figure 1). in addition, for each identified hole an image is acquired at the low dose focus position. Power spectra are also calculated for each of the high magnification images as well as for the focus images. For managing these images we are using a relational database management system. We have also developed a bench of tools to store, access, and display the data as well as tools for extracting information from the database.

A database is a structured collection of data in which the information is classified by categories. Each category is then stored in a table and these tables are linked together by defined relations. Data may be combined from several tables on request. We have been using MySQL as our relational database management system. This allows us both to manage the images and to refer each image to its real context. in other words, through the database, we can keep track of information related to the microscope settings (e.g. defocus, electron dose, magnification, goniometer coordinates etc.), the type of image, and overall information about the specimen and the experiment.
Quantitating Calcium in Biological Specimens by Direct Fittingof X-ray Spectra
Authors: Ho R , Jia Z , Somlyo AP , Shao Z
Published: July 2020

Electron probe microanalysis has been a useful method for biological research for some years. Its advantages include the low background of x-ray spectra and range to include characteristic peaks of most biological elements. The traditional method of analyzing biological X-ray spectra filtering both the experimental and reference spectra with a top-hat filter, before performing a linear least squares fit, to remove the slowly varying background. We show that, as expected, this procedure introduces an additional error in the quantitation results, and reduces the sensitivity and precision of this method. Our experience with quantitating trace elements with EELS shows that direct fit of unfiltered spectra yields the highest sensitivity, when the data contain only statistical errors. Biological specimens usually contain high K and low Ca, and in X-ray spectra the K Kβ peak is overlapped with the Ca Kα peak. A small error in extracting the K signal will dramatically affect the quantitation of Ca. We demonstrate here the application of a direct fitting procedure, which focuses on the Ca and K region of the X-ray spectra (2800 ∼ 4900 eV), and yields smaller fitting uncertainties compared to the traditional filtered fit method in trace Ca quantitation.
Parallel Confocal Microscope using Vertical-Cavity Surface Emitting Laser Array
Authors: Fujita Motonobu , Naruse Makoto , Ishikawa Masatoshi
Published: July 2020

Here we show a confocal microscope system where a vertical-cavity surface-emitting laser (VCSEL) array is introduced for the parallel probing beams.

A VCSEL array is a semiconductor laser device that emits circular beams vertically to the surface of the chip, which can directly be used as confocal laser microscope applications. The VCSEL device itself can be the parallel beam source of the confocal laser system, whereas in conventional Nipkow disc-based system, several lenses are required to form probing beams. Figure 1 shows the basic structure of VCSEL-based confocal microscope systems. Since there is typically no correlation between individual channels of VCSEL, there are no interferences among dense parallel beam arrays. Additionally, in the case of Nipkow disc system, the signal to noise ratio of the detected light is another problem: some of the light from the source laser reflects at the surface of the disc, which eventually could be detected by the sensor as noise. in the proposed system no such problem occurs as shown in Fig. 2(a). in addition, “all” optical beam from VCSEL is used as probing beam whereas most of the power is lost at the disc as compared in Fig. 2(b). in addition, pixel parallel illumination control is also achievable by controlling each channel of the VCSEL so that the dynamic range of the detected signal is maximized.
The Use of Multidimensional Microscopy in the Characterization of Retinal Vascular Development in a Murine Model
Authors: Summers Robert G , Aguilar Edith , Leonard Marilyn , Friedlander Martin
Published: July 2020

The murine retinal vasculature develops in its entirety following birth through the process of angiogenesis. This developing system provides an extremely accessible model for investigation of angiogenic mechanisms in general and as they pertain to vascular diseases of the eye (e.g. diabetic retinopathy and macular degeneration). The model is particularly relevant clinically because the developmental events of retinal vascularization are nearly identical in mice and humans, although primate vessels develop in utero during the final trimester of pregnancy and are thus less accessible for experimental study. The model is also excellent for the testing of anti-angiogenic agents as potential treatments for vascular diseases. in this report we outline the use of confocal optical microscopy and multiphoton microscopy in the 3-dimensional characterization of retinal vascular development in the mouse.

We employed confocal microscopy to characterize the events of vascular development from postnatal days 0-56 (P0-P56). During this time the retinas are transformed from simple, thin bilaminar structures to more complex, functional, adult sensory organs. Retinal morphogenesis continues until P42. Retinas were dissected from eyes and vessels stained with collagen type-IV antibody (1) or Bandeiraea simplicifolia (Griffonia) lectin-dye conjugate (2) to outline the blood vessels. All patent vessels were stained by both techniques.
Enhancement of Reflection-Enhanced Backscatter Confocal Microscopy
Authors: Keith C H , Witek R
Published: July 2020

Tremendous advances have been made in the last twenty years in extending the usefulness of the light microscope in visualizing living biological specimens, and it is now possible to visualize most thin tissues in an unstained state at – or near – the limit of optical resolution. in general, however, these techniques have been used successfully on biological specimens in the transmitted light mode; unstained biological specimens generally do not have sufficient albedo or sufficient difference in refractive index from their surroundings to be efficiently visualized in epi-illumination. A number of applications, including studies of the growth of bacteria on metallic substrates, and studies of the studies of the formation of interfaces between living neurons and silicon chips, would benefit from being able to resolve living, unstained biological specimens growing on opaque substrates

We found that by imaging biological specimens on a reflective substrate in the reflection mode of the confocal microscope, we could get images that resemble transmission mode differential interference contrast images.
Angiotensin II Induces Translocation of Protein Kinase C α and ε in Neonatal Rat Cardiac Myocytes
Authors: Bullard Tara A , Goldsmith Edie , Price Robert L
Published: July 2020

Angiotensin II (Ang II) plays an important role in heart development and has been shown to stimulate the formation of premyofibrils and differentiation of cardiac myocytes. Ang II signaling occurs through two types of receptors, the AT1 and AT2 receptors, both of which appear to play a role in the development of the myocardium. Through the use of specific Ang II receptor blockers it as been shown that blocking the AT1 receptor with Losartan (Merck) inhibits the formation of premyofibrils and sarcomere formation and that blocking the AT2 receptor with PD123,319 (Parke-Davis) inhibits the formation of trabeculae in the developing heart.

In a number of cases it has been shown that signal transduction mechanisms operate through different growth factor receptors and elicit specific responses within a cell type. Protein kinase C (PKC) is a family of closely related signal transduction enzymes that phosphorylate proteins on serine or threonine residues.
Evaluation of Confocal Microscopy System Performance: Applications for Imaging Morphology and Death in Embryos and Rerpoductive Tissue/Organs
Authors: Zucker R M , Price OT
Published: July 2020

The confocal laser-scanning microscope (CLSM) has enormous potential in many biological fields. It is remarkable that procedures to test the performance of these machines are not done routinely by most investigators and thus many of the machines in operation are working at levels of sub optimal performance. When these machines are checked, it is usually a subjective assessment of performance accomplished by primarily evaluating the system using a specific test slide provided by each user’s laboratory. We have devised test methods on the Leica TCS-SP and TCS-4D systems to ensure that these machines were working properly and delivering their correct performance. Tests were derived or perfected that measure field illumination, lens clarity, laser power, laser stability, dichroic functionality, spectral registration, axial resolution, overall machine stability, and system noise. It is anticipated this type of data will help to set performance standards for confocal microscopes and eliminate the current subjectivity in evaluating the CLSM. These tests will also serve as a guide for other investigators to insure that their machines are working correctly and providing data that is accurate and having the necessary resolution, sensitivity and precision.
Non-linear Spectral Microscopy-Multi-Photon Fl, SHG and THG
Authors: Cheng Ping-chin , Sun Chi-Kuang , Kao Fu-Jen , Lin Bai-Ling
Published: July 2020

The non-linear nature of multi-photon fluorescence (FL) excitation, SHG and THG restricts the signal detecting volume to the vicinity of the focal point. As a result, the technology has intrinsic optical sectioning capability. The use of multi-photon fluorescence excitation also allows micro-fluorometry at high spatial resolution. Figure 1 shows a conventional optical micrograph of maize protoplasts, the time lapse fluorescence spectral change from a single chloroplast is shown in FIG 2. Under high intensity illumination, biological specimen not only emits fluorescence, but also generates harmonic emissions. in addition to the Ti-sapphire laser commonly used in multiphoton microscopy, the use of ultra-fast Cr-fosterite laser made simultaneous detecting two- and three-photon fluorescence, SHG and THG possible. in addition to the fluorescence signals generated by multi-photon excitation process, non-linear phenomena such as harmonic generation can also provide useful information about the structure and optical properties of a specimen (Kao et al., 2000). Simultaneous recording the spectral response in an image (x-y-λ) can provide insight about the nature of the signal.
What Can Epitope Specific Antibodies Tell us About the Organization of Caveolin in Cells?
Authors: Robinson JM
Published: July 2020

There are three members of the caveolin (CAV) gene family that give rise to four polypeptides. These polypeptides are CAV-1α, CAV-1β, CAV-2, and CAV-3. The CAV-1β isoform is a truncated form of CAV-1α that lacks 31 amino acids at the N-terminus of the molecule. The CAV- 1β molecule arises through an alternative splicing mechanism.

Caveolae are specialized plasma membrane microdomains that are expressed at high levels in some cell types (e.g., endothelium, adipocytes, fibroblasts). These specialized regions of the plasma membrane have a characteristic omega-shaped appearance with diameters ranging from 40-90 run. They are distinct from clathrin-coated pits since they lack the characteristic coated appearance in electron microscopy. Caveolae were among the first structures to be discovered by biological electron microscopy. However, biochemical characterization of these structures did not begin in earnest until a marker protein was identified. The initial marker was the 22-kDa protein known as caveolin.
Internalisation of CD46, Membrane Cofactor Protein, As Determinee By Light, Cofocal, and Electron Microscopy
Authors: Ellis Sarah , Crimeen Blessing , Farrelly Caroline , Russell Sarah
Published: July 2020

Human CD46 (membrane cofactor protein) is expressed on all nucleated human cells and is a cellsurface regulator of activated complement as well as a receptor for both the measles and herpes 6 viruses. CD46 is also expressed in particularly high levels on some tumor cell lines. Complement leads to the recognition of foreign material, targeting it for removal and immune cytolysis. The primary role of CD46 is to bind to one of the complement components, C3b, thereby protecting host cells from autologous complement attack. in addition to its role as a complement regulatory factor, CD46 acts as a measles virus (MV) receptor. Despite the development and use of an effective MV vaccine, at least one million deaths occur each year. MV infection leads to downregulation of cell surface CD46 and immunosupression. MV (and probably also C3b) is internalized shortly after complex formation with CD46, yet, despite much work in this area, precisely how MV enters cells is largely unclear.
A New Pre-Embedding Immunogold Method That Permits to Obtain a Very High Signal with a Very Good Ultrastucture
Authors: Grondin G , Bcaudoin AR
Published: July 2020

The ultimate goal of the immunocytochemistry is to get the best signal with the lowest background while preserving ultrastructure. Unfortunaly too often the experimentator faces a compromise between density of the signal and ultrastructure preservation (1). with the advent of hight resolution confocal light microscopy, two photon imaging and other new technologies there is a need to provide the best immunocytochemical complementary results with the high resolution of the electron microscope. But often for exemple the high level of labelling observed by immunofluorescence microscopy is not matched by immunocytochemistry (2). One approach to obtain comparable levels of labelling is to use comparable protocols. We propose here such a new immunogold method. to illustrate our point we used a very convenient biological material, the adherent cells grown on 35 mm plastic culture dishes. The following procedure was applied : Confluent endothelial cells were fixed in situ for 3 hours with the following freshly prepared and filtered solution : 1 % 1-lysine, 4% paraformaldehyde, 0.04% glutaraldehyde, 0.25% sodium metaperiodate in 0.04M sodium cacodylate buffer, pH 7.4.
In Situ Characterization of Dynamic Changes in the Microstructure and Chemistry of Catalysts
Authors: Crozier PA
Published: July 2020

Controlled atmosphere electron microscopy (CAEM) is a form of in situ microscopy in which the sample is exposed to a reactive gas during observation. This instrument essentially combines the nano-structural characterization features of a TEM with a microreactor and is ideal for studying gas/solid reactions in catalysts. Such in situ techniques can provide a link between surface studies performed under UHV conditions and catalytic reactions run in high-pressure reactors. with correctly designed experiments, CAEM is a powerful technique for correlating dynamic changes in microstructure with catalysis and can be used to provide insights on the location of active sites and mechanisms for catalysis. Baker and colleagues have worked for over thirty years on different heterogeneous catalysts using in situ electron microscopy (see [1] for example). Gai has also published many studies on the application of CAEM to oxide catalysts [2].

The technique usually relies on detecting a change in the heterogeneous catalyst during a catalytic reaction.
The Influence of Surface Termination and Domain Structure on the Photochemical Reactivity of SrTiO3 and BaTiO3
Authors: Giocondi Jennifer L , Rohrer Gregory S
Published: July 2020

The crystallographic orientation and atomic termination layer of oxide catalysts are known to influence their reactivity. The objective of this work was to measure how the relative photochemical reactivities of two ternary titanates vary with surface orientation and composition. The surface structure property relationships derived from these observations can be used to define optimized photocatalyst microstructures.

To measure the relative reactivity of surfaces with different orientations, crystallites (∽ 20 μm in diameter) in a polycrystalline ceramic were examined individually. First, polycrystalline specimens of BaTiO3 and SrTiO3 were synthesized using conventional ceramic processing. Surfaces for analysis were prepared by polishing and thermal etching in air. The surface orientations of selected grains in the sample were then determined from backscattered electron diffraction patterns recorded in a scanning electron microscope. to make a local measurement of the photochemical activity of each grain, we used a well established probe reaction (the reduction of aqueous Ag+ to Ag0) that deposits metallic silver on the surface as a reaction product.
Automated Imaging of Combinatorial Chemistry Synthesis Arrays in a Large Chamber Low Vacuum SEM
Authors: Schumacher Elaine F , Wendelbo Rune
Published: July 2020

In combinatorial chemistry, miniaturization and automation are used to carry out many experiments in a simultaneous array, as opposed to doing single experiments in sequence. This high throughput approach is widely used in the drug industry, and is now finding application in the development of novel materials for catalysis. Successful implementation of combinatorial methodology to speed discovery and commercialization of new materials requires that these techniques be applied to every step of the experimental process, from combination of reagents for synthesis through characterization and performance testing.

Arrays of catalyst precursors and molecular sieves synthesized by combinatorial methods must be rapidly screened for particle size distribution and morphology. Optimization of these characteristics is crucial for successful manufacture of formed products such as beads or extrudates on a commercial scale, and has traditionally been done by manual examination of dispersed powder samples in an SEM
Alloy Compositions in Model Bimetallic Catalysts
Authors: Tsen S-CY , Crozier P A , Liua J
Published: July 2020

For supported bimetallic catalysts it is important to know if the metal components are present in the form of ordered alloys or metal mixtures. For metals with similar crystal structure, Vegard's law predicts a simple relationship between alloy composition and lattice dimensions [1]. It is therefore possible to use high-resolution electron microscopy (HREM) to provide both structural and compositional information. in nanometer sized particles, accurate determination of the lattice spacing from fringes in an HREM image is difficult because of errors due to signal-to-noise, particle tilt and edge effects [2,3]. However, statistical distributions of fringe spacing can be used to determine the lattice spacing of particle ensembles to within 1.5% when measurements are carried out on at least 100 particles [2]. We extend this technique with model AuPd bimetallic catalysts and show that Vegard's law applies to nanometer-sized particles.

Model bimetallic catalysts were prepared by sputtering metal from AuPd alloy targets and/or a Pd target onto thin amorphous carbon substrates.
Characterization of Nanometer-Sized Metal Clusters
Authors: Bradley Steven A
Published: July 2020

Characterization of nanometer-sized particles dispersed onto a porous support is critical for understanding performance of heterogenous catalysts. The electron microscope offers a unique capability for measuring the cluster size and chemistry of these nanometer-sized metal clusters. Cluster size and size distribution can be readily determined by using high angle annular darkfield or z-contrast microscopy. However, as catalysts become more complex with additional components that modify the metal activity, determination of the chemistry of individual clusters could be interesting. Conducting such studies is not straightforward and some of the problems associated with making such measurements will be discussed using model catalysts and a VG HB 601UX dedicated STEM.

Problems associated with this type of measurement can include the instability of the small metal particle under the intense, focused electron beam as well as spurious signals from the area surrounding the region of interest.
Quantitative Characterization of Particle Shape of FCC Catalysts by Image Analysis
Authors: Li Zhengmin , Xu Xingzhong , Yang Jinghe , Xu Xiuling , Yu Weijun , Yue Xiuying
Published: July 2020

In the fluidized catalytic cracking (FCC) unit of oil refinery, the attrition resistance of FCC catalysts is affected by particle shape. Although some sophisticated methods, such as Fractal dimension and Fourier analysis, have been introduced to particle shape analysis, most of them are used to assess the shape of individual particle. It is difficult to be used as a means of powder quality control in the course of application and production of FCC catalysts. So three shape factors, i.e. Short/long ratio (S), Roundness (R) and Concavity (C), are applied to characterize them in three different aspects.

A small quantity of FCC catalyst powders were spread on a glass slide M and a thin layer of glue was spread on another glass slide N, then all the particles on slide M were sprinkled on slide N by vibrating manually up and down, in the meantime moving back and forth more than 10 times.
Energy-Filtered Imaging of Colloidal Cobalt Metal Particles
Authors: Disko MM , Popplewell J , Grady KO’ , Hutchings J
Published: July 2020

Supported transition metal particles are often used as heterogeneous catalysts. Elemental mapping with energy-filtered transmission electron microscopy (EFTEM) offers distinct advantages over conventional TEM and x-ray analysis for these systems. Thickness maps, metal identification, support identification, and direct imaging of oxide layers all represent key new information made possible with EFTEM. Energy-filtered transmission electron microscopy with an omega filter has been used to show Ni, Cu and Cr distributions in an alumina-supported catalyst. in this paper we look at analogous cobalt particles from a colloidal suspension supported on a carbon film.

Energy-filtered TEM maps were obtained using a Gatan Image Filter at 200 kV integrated with an FEI CM200FEG microscope. The colloidal cobalt particles have a nominal diameter of 10 nm, providing an excellent model system when supported on thin amorphous carbon supports. Figures 1 - 3 show cobalt L23, oxygen K and elastic micrographs of partially oxidized cobalt particles (native oxide present after drying).
Direct Observation of Changes of the Metal-Substrate Interface Chemistry in Supported Heterogeneous Catalysts
Authors: Klie RF , Browning ND , Disko MM
Published: July 2020

The heterogeneous catalytic system Pt/SiO2 is widely used in “three-way” catalysts, because of its highly selective catalytic reduction of NO by hydrocarbons at low operating temperatures. Although used effectively for more than a decade, in recent years it has become clear that the core phenomena of heterogeneous catalysis can occur at interfaces. in the work presented here, we seek to better understand the role of the atomic and electronic structure of interfaces in making particular reactions facile and moderating the stability and selectivity of a catalytic system.

We investigate model supported platinum catalysts by atomic resolution Z-contrast imaging and EELS using a 200 kV STEM/TEM JEOL2010F with a post column GIF. The combination of these techniques allows us to obtain direct images of the metal particle and its interface with the supporting SiO2, and to correlate that with the modulation of the Si L-edge fine structure.
High Angle Annular Dark Field (HAADF) STEM Tomography of Nanostructured Catalysts
Authors: Weyland M , Midgley PA , Thomas JM
Published: July 2020

Progress in the design of catalysts based on nanoparticles supported within a mesoporous silica framework requires structural analysis at high spatial resolution. While bulk analysis by X-ray diffraction and EXAFS can give the structure of active sites they are unable to determine their relative positions and local physical structure. Some success has been achieved using a combination of STEM ADF imaging and EDX mapping to elucidate such structures but these results are limited to giving 2D projections of 3D arrangements. The need exists therefore to analyse specimens in full 3D. A suitable approach is electron tomography where the 3D structure is reconstructed from a tilt series of 2D projections. in conventional electron tomography a tilt series is acquired using bright field (BF) TEM. However the large beam current means such an approach generally cannot be used on specimens based on a mesoporous silica framework as beam damage can develop rapidly.
Surface Structures of Catalytic Oxides
Authors: Erdman N , Pless JD , Poeppelmeier KR , Marks LD
Published: July 2020

Transition metal oxides have been studied extensively over the last few decades, due to their electro optical and catalytic properties.The overall properties of these oxides and the heterostructures that can be built on them depend upon the surface structure, composition and morphology. However, the available information on the surface structures of transition metal oxides is scarce and often contradictory. Knowledge of the atomic structure of the catalytically active surfaces and of the adsorbed reactants and intermediates under in-situ reaction conditions is crucial for an understanding of catalytic oxidation at the molecular level, and will subsequently create possibilities for faster development of new catalysts, improve their performance on industrial level, and lower the costs associated with processing. The objective of the current work is to develop and apply the available experimental (UHV chambers, UHV-HREM, catalytic treatment chamber) and computational techniques (Direct Methods analysis and multislice simulations of electron diffraction data) to improve understanding of catalytic phenomena under various environmental conditions.
Truly Quantitative EELS Imaging - Let’s Not Settle For Just Pretty Pictures Anymore
Authors: Hunt John A
Published: July 2020

The term “quantitative“ means many things to many people. in imaging its value is often discounted to mean only that a more intense region can be said to have more of what is being measured than a less intense region. Others may be more stringent and require an approximately linear relationship between the measured property and image intensity. (This is most often the case in EFTEM and spectrum imaging) Some specimens contain internal references (such as elements with a known stoichiometric relationship) that are sufficient to get to a true concentration calibration for an image. However, in EELS imaging this still doesn’t allow us to get an understanding of our errors and rarely is it helpful in determining detection or quantification limits.

A competent high-school chemistry or physics student could tell us that a quantitative measurement includes both a measured value and an estimate of its error.
’A Priori’ synthesis of electron energy-loss spectra for detection limit quantification
Authors: Menon N K , Krivanek O L , Hunt J A
Published: July 2020

A software package has been developed that synthesizes entire energy-loss spectra for an arbitrary distribution of impurities embedded in an arbitrary matrix, for user specified sample parameters and acquisition conditions. The simulation of a complete spectrum facilitates the estimation of quantities such as the Minimum Detectable Mass (MDM) or the Minimum Detectable Number of atoms (MDN). This is addressed with particular attention to optimising the acquisition conditions to maximize the detectability and also to estimating the error in a typical EELS quantification. It is envisaged that this approach will have wide-ranging implications for the role of EELS in quantitative microanalysis.

Electron Energy Loss Spectroscopy (EELS) is widely recognized as a microanalytical tool capable of characterizing the elemental composition of materials with nm-level resolution and sensitivity approaching single atoms. Extracting quantitative information from EEL spectra is complicated by the fact that both the cross-sections and the pre-edge background used for inner-shell analysis vary widely.
Results from a New Fast, High Sensitivity, Eels Spectrometer
Authors: Trevor C , Harmon R , Brink H , Hunt J
Published: July 2020

Last year we discussed the performance of a new parallel EELS spectrometer, the ENFINA™. The spectrometer optics have been considerably improved over past designs and the detector changed from a photodiode to a charge coupled device that was designed specifically for spectroscopy. in this work we present application examples that demonstrate some of the capabilities of the ENFINA™.

STEM spectrum imaging requires a spectrometer of high speed and sensitivity if useful data is to be collected in a short period of time. The ENFINA™ spectrometer achieves both of these through a radically improved point spread function, increased sensitivity, and fast detector readout. Useful spectrum images can be acquired in a few minutes. Figure 1 shows a dark-field STEM image of a typical semiconductor. A spectrum image containing 190 x 150 spectra was acquired from within the marked area.
Insight Into the Properties of Functional Materials with Energy Filtered and Analytical TEM
Authors: Botton GA
Published: July 2020

Energy filtered (EF) imaging and energy loss fine structure analysis have now become routine tools to characterize very complex microstructures at high spatial resolution. When combined with energy dispersive x-ray spectroscopy microanalysis in a field emission gun transmission electron microscope (TEM) and with samples prepared by a large array of techniques such as FIB or microtoming, these analytical techniques can tackle real-life and more fundamental problems in materials science. This paper presents some examples of this work that highlight the complementarity of information obtained either from EF imaging, near-edge structures and EDS microanalysis. These examples are taken from work in the development of battery materials for automotive applications and in the study of ultrathin magnetic layers. Other examples of high spatial resolution energy loss fine structure at interfaces of high-K dielectric-Si in interface are shown in elsewhere in these proceedings.
Three Dimensional Energy Filtered Transmission Electron Microscopy (3D-EFTEM)
Authors: Weyland M , Midgley PA
Published: July 2020

Energy filtered transmission electron microscopy (EFTEM) has been developed in recent years to be a highly flexible tool for spatially resolved microanalysis. The basic technique has been extended to allow fully quantitative mapping of single elements, or a large range of elements using an image-spectroscopy approach. All these techniques are still limited by the nature of the TEM as a structure projector; any elemental map is only a 2D projection of what is in reality a 3D structure. A fully 3D approach to EFTEM analysis would offer additional insights into many materials problems and make possible meaningful analysis of certain systems for the first time. Three-dimensional electron microscopy (electron tomography) offers one path for the reconstruction of 3D structures from 2D projections. Although this has been well developed for solving the structure of biological macromolecules and viruses its use in the physical sciences is quite new.
Analysis of the Defect Chemistry at Gd-Doped Ceria Grain Boundaries
Authors: Ito Y , Lei Y , Browning ND , Mazanec TJ
Published: July 2020

Gd3+ doped Ce oxides are very promising candidates as electrolytes for solid oxide fuel cells operating at ∼ 500 °C. For their successful commercial implementation, a full understanding of the defect chemistry in the bulk and at grain boundaries is essential. in particular, the contribution of the grain boundaries to the total ionic conductivity through such effects as the segregation of impurities, dopants and vacancies is of crucial importance. Here the effect of the atomic structure on the local electronic properties, i.e. oxygen coordination and cation valence at grain boundaries of the fluorite structured Gd0.2Ce0.8O2-x ceramic electrolyte is investigated by a combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the JEOL 201 OF STEM (operating at 200keV, and aligned for a probe size ∼ 0.2 nm).

Preliminary O K- and Ce M45-edges were acquired from points in the grains (A and B) and grain boundary shown in Figure 1.
Bifurcation Patterns and Branching Exponents in Branchial Vessels in Tadpoles of Xenopus laevis Daudin during Metamorphosis-3D-Measurements from Microvascular Corrosion Casts
Authors: Minnich B , Bartel H , Karch R , Schreiner W , Lametschwandtner A
Published: July 2020

Introduction

Fluid transport systems of organisms [1] in general and the blood vascular system in particular are considered to be optimally designed. From Murray's laws [2] it is concluded that an arterial bifurcation where the diameter of the parent vessel (d0) relates to the larger (d1) and the smaller daughter vessel (d2) according to d0  3 = d1  3 + d2  3 is optimal. Interestingly, existing data predominantly refer to arterial branchings of the fully developed circulatory system of mammals. to the best of our knowledge there are no data available on arterial bifurcations and venous mergings in an initially growing but then regressing tubular system of blood vessels as it is found in the gill filter apparatus of the anuran tadpole where the highly complex three-dimensional vascular network totally disappears at the end of metamorphosis.
The Ultrastructure of the Connective Tissue Matrix is Significantly Improved Using Cryo-Fixation At High Pressure
Authors: Keene D , Tufa S
Published: July 2020

The investigation of connective tissue ultrastructure has historically relied on chemical fixation to stabilize micro architecture. These fixatives are not effective in retaining many matrix molecules, including proteoglycans, and allow precipitation of many other components in subsequent processing steps. The result is a preponderance of open space between matrix components. Cells shrink considerably and a precipitation of molecules in highly concentrated regions leads to artifacts including the lamina lucida and lamina densa of basement membranes. Cryo-fixation at high pressure followed by freeze substitution seeks to immobilize tissue components within vitreous (non-crystalline) ice, which is later substituted with acetone at temperatures below the recrystalization temperature of water. Formation of large ice crystals during any part of the preparation protocol significantly distorts structure and can be recognized in the compound microscope. Recognition of smaller freezing artifacts, including microcrystalline ice, is imperative for interpretation of resulting images.
Recent Advances in Microwave-Assisted Specimen Processing for in-Situ Hybridization
Authors: Sanders Mark A , Gartner David M
Published: July 2020

Co-localization of proteins and nucleic acid sequences by in situ hybridization and immunohistochemistry is frequently difficult as the procedure necessary to detect the target structure of one technique may negatively affect the target of the other. Structural impairments may also limit the application of the two techniques. to overcome these problems we developed a method to perform in situ hybridization and immunohistochemistry on Chromosome spreads, intact cells and semi-thin sections of methyl methacrylate-embedded tissue. Microwavestimulated antigen retrieval, signal amplification by catalyzed reporter deposition, and fluorescent dyes were used for all techniques, yielding high sensitivity and excellent morphological preservation compared to conventional processing techniques. Co-localization of in situ hybridization and immunohistochemistry probes with high morphological resolution was achieved using computerized image reconstruction. The latter may allow for the co-localization of multiple antigens and a specific DNA sequence at the same tissue level.
Use Tungsten Shadowing to Study Biological Macromolecules
Authors: Ryazantsev Sergey N
Published: July 2020

Shadowing is widely used for biological macromolecules and their complexes structure determination. It has been shown that tungsten shadowing produces fine granularity and good structural detail resolution. We have developed a working prototype of an electron beam evaporator (“electron gun“) based on the principle described by V. Vasiliev. The electron gun has characteristics that allow us to deposit high quality films of carbon or even pure tungsten. in addition we have constructed a prototype sample handling apparatus for freeze drying and shadowing. The prototype allows tilting of +/- 90° in 2° increments, rotation (if desired) at 6 rpm, controlled heating at a rate of 1-2° per min, and cooling using a liquid nitrogen trap attached to the device. The system is vacuumed by 480 1/sec maglev turbomolecular pump with scroll pump at the first stage. It produces oil-free vacuum in 2-5*10-7 torr range, which we believe, is sufficient for good quality shadowing.
EELS Studies of ZnO and ZnO:In Films Deposited By Spray Pyrolysis
Authors: Paraguay D. F , Miki-Yoshida M , Espinosa-Magaña F
Published: July 2020

Zinc oxide based coatings are of much interest in science and technology due to their interesting applications, such as in gas sensor devices, transparent electrodes, piezoelectric devices, varistor,surface acoustic-wave devices,etc. Thin films of ZnO also have some advantages over indium tin oxide (ITO) and tin oxide, which are usually used as transparent conductors, the former are chemically stable to a hydrogen plasma such as that used in the elaboration of solar cells. Many techniques have been employed to produce zinc oxide based coatings e.g. radio frequency magnetron, spray pyrolysis, sputtering, chemical vapor deposition, sol gel, pulsed laser deposition, etc. Among these techniques, the spray pyrolysis has proved to be a simple, reproducible, and inexpensive method, particularly useful for large area applications.

The main features of the spray pyrolytic system are fully described elsewhere. We have used a spray system attached onto mobile stage that provides a sweeping movement to the spray nozzle.
TEM Studies of Disorder-Order Transition in the Acid-Catalyzed Growth of Mesoscopic Silica Thin Films
Authors: Yao N , Ku A Y , Saville D A , Aksay I A
Published: July 2020

Mesoscopic silica is synthesized by using a self-assembling organic species to direct the structure of an inorganic matrix. It has attracted much interest because of its potential for use in a wide variety of catalysis, separations and nanotechnology applications. The commercial success of this material depends on the ability to simultaneously tailor the channel size and organization. A more complete understanding of the mechanism by which the material forms should lead to improved control over the structure. Small angle X-ray diffraction studies have shown that there is an “induction period” which precedes the observation of well-packed channels in films grown at the air-water interface. However, scattering data alone are unable to establish how the development of order might occur. Direct observation of the evolution is necessary to determine the mechanism by which well-packed, nanometer-sized channels form.

Continuous mesoporous silica thin films were grown at the air-water interface.
Microanalysis of AFM Tips Coated with Cerium Oxide
Authors: Gilliss Shelley R , Fairer Jeffrey K , Ravishankar N , Schwabel Mark G , Barry Carter C
Published: July 2020

Cerium oxide is widely used for chemomechanical polishing (CMP) of silicate glasses. Uses include finishing of optical elements and planarizing dielectrics in the semiconductor industry. This study is designed to investigate the fundamentals of the cerium oxide/silica CMP process by measuring the interaction force between silicate glasses and cerium oxide. Surface forces involved in the polishing of glass by a cerium oxide abrasive can be studied in a controlled manner by measuring sample-tip interactions between a glass substrate and a cerium oxide tip in an atomic force microscope (AFM). Commercially available AFM tips have been coated with thin, uniform films of cerium oxide. By using a square pyramid tip as a template for the shape of the cerium oxide film, challenges related to irregular or blunt tip shape can be overcome. However, complete characterization of structure, shape and chemical composition is required before useful information can be obtained using the AFM.