bluuebunny/crossref_metadata_2025 huggingface dataset:
Monochromatic X-ray microscopy in the water window with a compact laser system
Authors: Kado M. , Richardson M. , Gabel K. , Jin F.
Published: June 2020

It is a dream of biologist to observe the intact structure of a biological specimen at high resolution without any artifacts. The development of high resolution x-ray microscopy is a new technique well suited to this purpose. The advantages of x-ray microscopy are seen to be: (i) the contrast can be provided by its components, thereby avoiding possible artifacts caused by the staining and fixation of specimens; (ii) x-ray microscopy is capable of observing thicker specimens (up to a few (μm)than electron microscopy with less damage; (iii) the actual location of the element can be visualizedwhen the proper x-ray wavelength is chosen. (iv) three-dimensional observation may be possible with asingle exposure of x rays. X-ray contact microscopy is presendy the most suitable method by which to evaluate these advantages.

It is generally accepted that the highest contrast in x-ray images of in-vitro biological specimens will be obtained with radiation have a wavelength in the so-called “water window”, (2.3-4.4 nm). Both laser plasmas and synchrotrons are bright source of radiation in this region.
Colloidal systems in soils
Authors: Thieme J. , Niemeyer J. , Guttman P.
Published: June 2020

In soil science the fraction of colloids in soils is understood as particles with diameters smaller than 2μm. Clay minerals, aquoxides of iron and manganese, humic substances, and other polymeric materials are found in this fraction. The spatial arrangement (microstructure) is controlled by the substantial structure of the colloids, by the chemical composition of the soil solution, and by thesoil biota. This microstructure determines among other things the diffusive mass flow within the soils and as a result the availability of substances for chemical and microbiological reactions. The turnover of nutrients, the adsorption of toxicants and the weathering of soil clay minerals are examples of these surface mediated reactions. Due to their high specific surface area, the soil colloids are the most reactive species in this respect. Under the chemical conditions in soils, these minerals are associated in larger aggregates. The accessibility of reactive sites for these reactions on the surface of the colloids is reduced by this aggregation. To determine the turnover rates of chemicals within these aggregates it is highly desirable to visualize directly these aggregation phenomena.
Bridging the resolution gap between x-ray crystallography and electron microscopy
Authors: Stewart P. L. , Fuller S. D. , Burnett R. M.
Published: June 2020

While x-ray crystallography provides atomic resolution structures of proteins and small viruses, electron microscopy can provide complementary structural information on larger assemblies. A significant computational challenge is faced in bridging the resolution gap between the two techniques. X-ray crystallographic data is collected in the range of 2-10 Å, while image reconstructions from electron micrographs are at a resolution of 25-35 Å. A further problem is that density derived from cryo-electron micrographs is distorted by the contrast transfer function of the microscope, whichaccentuates certain resolution bands.

A novel combination of electron microscopy and x-ray crystallography has revealed the various structural components forming the capsid of human type 2 adenovirus. An image reconstruction of the intact virus (Fig. 1), derived from cryo-electron micrographs, was deconvolved with an approximate contrast transfer function to mitigate microscope distortions (Fig. 2). A model capsid was calculated from 240 copies of the crystallographic structure of the major capsid protein and filtered to the correct resolution (Fig. 3).
3-D structure of single filaments from the acrosomal bundle of Limulus sperm by 400 kV cryoelectron microscopy: Scruin binds to homologous actin subdomains
Authors: Agris Jacob , Schmid Michael F. , Jakana Joanita , Matsudaira Paul , Chiu Wah
Published: June 2020

Scruin (102 kDa), an actin binding and bundling protein, is found in a 1:1 complex with actin in the acrosomal process of Limulus sperm. The protein sequence of scruin is unrelated to any known actin binding proteins but reveals a tandem pair of homologous domains (Way and Matsudaira, manuscript submitted). Sequence comparisons reveal homology in each domain with kelch, a gene in Drosophila that is important in nutrient transport into the oocyte and in the maintenance of a cellular structure called the ring canal, and with MIPP, a mouse placental protein of unknown function. Their similarity with scruin suggests a cytoskeletal function and they may form a new family of actin crosslinking proteins. The actin binding domains in this family of proteins have not been identified.

To understand the structural basis of actin crosslinking and bundling, we have been studying the acrosomal bundle by cryoelectron microscopy. The actin bundle of the Limulus acrosomal process is structurally unique because it can be considered as a single 3-dimensional crystal in space group PI, with 28 actin subunits and scruin molecules per unit cell.
A comparison of three cryotechniques (freeze-drying, cryosubstitution, cryosectioning) of specimen preparation for immunolabelling of bacterial antigens ofCoxiella burnetii
Authors: McCaul T. F. , Gould R. J.
Published: June 2020

Immuno-electron microscopy has allowed the selective localisation of molecules with high resolution and high specificity. Cryopreparatory methods have provided better retention of antigenicity suitable for precise immunolabelling together with optimal structural preservation of cellular components. Cryosubstitution and cryoultramicrotomy have widely been exploited for immunolabelling. Molecular Distillation Dryer (MDD), a form of freeze-drying technique, has recently been used for immunolabelling of Plasmodium falciparum stress proteins and nuclear ribonucleoprotein particles in cultured cells. In the present study, we report the comparison of all three cryotechniques in the immunolabelling of bacterial antigens ofCoxiella burnetii.

The highly infectiousC. burnetiiwas prefixed in 3% glutaraldehyde (66 mM cacodylate buffer, pH 6.8 ). The cells were then pre-embedded in 2% low-temperature agarose on Durapore hydrophilic membrane prior to cryofixation using a LifeCell CF100 metal-mirror system. A 1% glutaraldehyde in 100% methanol was used as a medium for cryosubstitution in a Reichert CS Auto Cryosubstitution apparatus.
Synaptic organization of the gustatory NST
Authors: Whitehead M. C.
Published: June 2020

A fundamental problem in taste research is to determine how gustatory signals are processed and disseminated in the mammalian central nervous system. An important first step toward understanding information processing is the identification of cell types in the nucleus of the solitary tract (NST) and their synaptic relationships with oral primary afferent terminals. Facial and glossopharyngeal (LIX) terminals in the hamster were labelled with HRP, examined with EM, and characterized as containing moderate concentrations of medium-sized round vesicles, and engaging in asymmetrical synaptic junctions. Ultrastructurally the endings resemble excitatory synapses in other brain regions.

Labelled facial afferent endings in the RC subdivision synapse almost exclusively with distal dendrites and dendritic spines of NST cells. Most synaptic relationships between the facial synapses and the dendrites are simple. However, 40% of facial endings engage in complex synaptic relationships within glomeruli containing unlabelled axon endings particularly ones termed "SP" endings. SP endings are densely packed with small, pleomorphic vesicles and synapse with both the facial endings and their postsynaptic dendrites by means of nearly symmetrical junctions.
Optical subsectioning and multiple focal-plane imaging in the standing-wave fluorescence microscope
Authors: Bailey Brent , Krishnamurthi Vijay , Lanni Frederick
Published: June 2020

Standing-wave fluorescence microscopy (SWFM) is a direct-imaging method through which very high axial resolution can be obtained in certain types of biological specimens. In the microscope, interference of light is used to produce a standing-wave field through the specimen, so that it is illuminated in a pattern of planar zones, rather than uniformly. Fluorescence is excited with spatial selectivity in proportion to the intensity pattern. In the instruments in use at present, two nearlycollimated s-polarized beams from a laser are directed into the specimen from opposite sides at mirrorimage angles with respect to the microscope axis (Figure). The alternating nodal and antinodal planes of the field are in this case parallel to the object focal plane, with a node spacing equal to λo/(2n cos θ), where θ is the beam angle, and n is the refractive index of the specimen. The minimum node spacing, λo/2n, is obtained when the beams are counterpropagating on-axis, and is typically 0.18 μm. In the simplest SWFM system, a mirror is placed behind the specimen such that an on-axis beam interferes with its reflection. In our dual-beam instrument, the laser output is split, and the beams directed into the specimen through a pair of opposed high-NA objectives. In both cases, the standing-wave field planes can be shifted axially through the specimen, by control of the phase of one of the beams. This can be done with high precision by use of a piezoelectric mirror drive. For SWFM to work well, it is necessary that the specimen be a weak phase object, i.e., that the refractive index heterogeneity be small.
Combined fluorescent and gold nucleic acid probes
Authors: Powell Richard D. , Hainfeld James F. , Churchill Mair E. A. , Belmont Andrew S.
Published: June 2020

Site-specific probes which incorporate both fluorophores and the 1.4 nm “Nanogold” gold particle have been prepared (Fig. 1). Specimens labeled with these probes may be imaged by fluorescence microscopy, then examined at higher resolution in the electron microscope without an additional gold-labeling step: this allows better specimen preservation and unprecedented correlation between the two sets of complementary data. In addition, the covalent gold attachment procedure allows the preparation of electron microscopy probes using small molecules, which cannot be coupled to colloidal gold.

Two types of probes have been prepared. In the first, the Nanogold particle was covalently attached, via peripheral primary amine groups, to Hoescht-33258, a fluorescent dye which is specific for AT-rich regions of double-stranded DNA. Excess Hoescht-33258 was removed by membrane separation. The resulting reagent was tested in Chinese hamster ovary cells: results are shown in Figs. 2 and 3. Specific staining of the nucleus was observed both by fluorescence microscopy and in the light microscope, using silver enhancement (Danscher's procedure) to visualize the gold-labeled regions.
The catalytic activity of adenosine monophosphate deaminase in murine thymus as revealed by Transmission Electron Microscopy
Authors: Bielat K. , Tritsch G.
Published: June 2020

AMP deaminase was visualized in a manner analogous to our previous approach with adenosine deaminase. The caloro-analog of AMP, i.e., 6 Chloropurine riboside 5′ monophosphate (CPRMP) (from Sigma) was shown to be a substrate of this enzyme which liberates Cl− which is precipitated with added Ag+, and, after exposure to light electron sense Ag° grains are deposited at loci of enzyme activity. The substrate at a concentration of 1.1 mM in 50 mM HEPES buffer, pH 7.2, in the presence of 150 mM K+ (as the acetate), 3mM ATP and 10μM pentostatin deoxycoformycin) was incubated with freshly excised tissue from a female C-57 BL/6 mouse. The substrate concentration is 1.4 times Km for rabbit muscle enzyme (Sigma), and K+ and ATP are allosteric activators of this Enzyme. Because many cells contain ecto 5′-nucleotidase activity, pentostatin was added to prevent manifestation of denosine deaminase activity of dechlorination of any nucleoside that might be formed. Any Cl− formed by adenosine deaminase would be precipitated with the added Ag+ and thus result in Ago deposits which would be indistinguishable from the Ago deposited by AMP deaminase.
HVEM tomography of the Golgi apparatus: A structural study of the trans-cisternae and trans-Golgi network
Authors: Ladinsky Mark S. , Kremer James R. , Furcinitti Paul S. , Howell Kathryn E. , McIntosh J.Richard
Published: June 2020

The Golgi apparatus is a membranous organelle that plays central roles in the secretory processes of eukaryotic cells. The apparatus consists of multiple convoluted cisternae, some of which are connected to a tubulo-vesicular system known as the trans-Golgi network (TGN). The TGN is thought to be the primary site for sorting and targeting of lipids and proteins to other cellular locations. Only a few studies have addressed the 3-D structure of the Golgi apparatus, and fewer still have focused on the structure of the TGN.

We have employed high voltage electron microscopy (HVEM) and computer axial tomography to study the TGN in 3-D. For these experiments, the trans-most cisternae and TGN of normal rat kidney (NRK) cells were labeled by photoconversion of internalized BODIPY-ceramide. Cells were then postfixed and embedded in Epon-Araldite. Semithick (250nm) sections were cut, post-stained with uranyl acetate and lead citrate, and surface-labeled with 15nm colloidal gold to provide fiducial markers for image alignment. Sections were viewed at 18,300x in a JEM-1000 HVEM operating at 1MeV.
Optimizing immunohistochemical staining for the HGF receptor c-MET in formalin-fixed paraffin-embedded archival human tissue
Authors: Evans B.A. , Song K.C. , Strom S.C. , Zarnegar R. , Bahnson R. , Bisceglia M.H. , Michalopoulos G.K. , Becich M.J.
Published: June 2020

Frozen tissue immunohistochemistry is a useful technique employed in diagnostic and research investigations and is often used despite a loss of morphological detail. Formalin fixation yields much better tissue preservation, but may mask the antigen sites. We have optimized a technique that allows us to study the distribution of the HGF receptor, c-MET, in formalin fixed, paraffin embedded tissue using commercially available polyclonal antisera in which we unmasked antigens sites with protease digestion. The technique we use is detailed below.

Sections are incubated in the following:

1)

4 μm paraffin sections are deparaffinized and hydrated

2)

0.03% protease (Type XXIV: Sigma) for 2 min at RT

3)

0.5% H2O2in methanol for 30 min at RT

4)

Protein Blocking Agent (Lipshaw/Immunon) for 1 hr at RT

5)

1° antibody ( Santa Cruz Biotech, Santa Cruz, CA) for 2 hr at RT

a.)

c-MET (c-12) rabbit polyclonal IgG, 1:200 dilution in PBS

b.)

h-MET (c-28) rabbit polyclonal IgG, 1:100 dilution in PBS

c.)

m-MET (c-21) rabbit polyclonal IgG, 1:100 dilution in PBS
Observations on the ultrastructure of inguinal cryptorchid testis in children
Authors: Bane Hani I. , Abalkhail A. , Al-Bagdadi F. , Abu-Ghalyun Y.
Published: June 2020

Cryptorchidism is most frequently reported in horses, swine, and man. Neoplasia has been documented in the descended testes of unilateral cryptorchid testes in children. It has been reported that 10% of the testicular tumors in humans were associated with cryptorchidism. Most of the reported information did not specify the difference between inguinal and abdominal cryptorchid testes. Recently histological and ultrastructural morphological differences have been reported. The spermatoginia of many cryptorchid males bear a congenital lesion. It has been recommended that screening children for early detection of cancer, with undescended testis will reduce cancer. The purpose of this investigation is to characterize the ultrastructural changes of inguinal cryptorchid testes of children at different ages, treated at Princess Basmah teaching Hospital at Irbid, Jordan. It is anticipated that this study will provide information for timing decision for surgical correction. Children with cryptorchid testis between one and thirteen years old were presented to Princess Basmah teaching hospital.
Is the life cycle of Elysia chlorotica ended by disease?
Authors: Maugel T. K. , Pierce S.K.
Published: June 2020

All of the individuals in populations of E. chlorotica (Opisthobranchia, Ascoglossa) in the Cape Cod region disappear during June or early July. Specimens collected from the field at varying times throughout the Fall, Winter and Spring, and held in aquaria, all die coincident with the disappearance of the field populations. This pattern has been attributed to the “normal” life cycle, the result of massive metabolic costs associated with Spring reproduction, senescence and aging, although individuals of all size classes die together. We have discovered, as part of an EM study of the slugchloroplast symbiosis, that the late Spring-early Summer animals are infected with viruses. The viruses are evident in both the nucleus and cytoplasm of several cell types and budding viruses are often present within the cytoplasm. The viruses are of at least three morphologic types with size ranges of 80-90 nm, 40-50 nm, and 20-30 nm. The viral infection could be the result of generalized immune failure in the aging animals. However, the possibility also exists that the massive viral infection is responsible for the synchronous death of the population each year. Supported by NSF-IBN-9117248.
Intracellular interactions of Leishmania mexicana with a cell line from Toxorhynchites amboinensis (77M-248) larvae
Authors: Argüello Carlos
Published: June 2020

Leishmania is an intracellular parasite that lives in phagocytic vacuoles of macrophages . The promastigote form of the parasite is flagellated and interacts with macrophages through specific cell membrane receptors . Once inside phagocytic vacuoles, the parasite differentiates into the amastigote form which is small and aflagellated. Part of the life cycle of the parasite occurs in the lumen of the digestive tract of an insect, with a body temperature of 25-27 °C that promotes the preferential differentiation of the promastigote form. A cell line ( TRA-248 ) isolated from Toxorhynchites amboinensis has been adapted to grow at two different temperatures 24° and 34°C, and used in the study of dengue virus. This quality of TRA-248 cells is of relevance since they permit to analyze the behavior of leishmania in an insect cell at two distinct temperatures. In this study, TRA- 248 cells and promastigotes interacted in culture at 24° and 34°C, for 12, 24 and 48 hrs and determine if the parasites are phagocyted and able to differentiate into the amastigote form. Also, the activity of acid phosphatase was compared between TRA-248 cells and macrophages.
Ultrastructural morphology of Pneumocystis carinii exposed to (β-1-3 glucan synthase inhibitors LY 302146 and LY 307853
Authors: Goheen M. P. , Bartlett M.S. , Current W.L. , Shaw M.M. , Smith J.W.
Published: June 2020

Pneumocystis carinii (PC) is an extracellular pathogen which frequently causes pneumonia in immunocompromised patients and is a significant cause of morbidity and mortality in patients with acquired immunodeficiency syndrome (AIDS). Trimethoprim plus sulphamethoxazole and pentamidine are the most often prescribed treatments for PC induced pneumonia but these drugs often cause severe side-effects in individuals with AIDS and are less effective if relapse occurs. For these reasons the search for more effective compounds continues.

The cell walls of PC cysts are rich in glucosyl/mannosyl/and N-acetyl-D-glucosamine residues and are digested by treatment with Zymolyase a β-1-3 glucanase. Therefore, compounds which are inhibitors of β-1-3 glucan synthase may be effective against PC. Immunosupressed mice infected with PC have been treated sucessfully with compounds LY302146 and LY307853 sodium salt both of which are inhibitors of β-1-3 glucan synthase. To help delineate their mode of action, electron microscopic evaluation of samples of PC grown in cultures containing these compounds was undertaken.
A modified method of pre-embedding EM immunocytochemistry which improves specificity and simplifies the process for in vitro cells
Authors: Tao-Cheng J.-H. , Tanner V. A.
Published: June 2020

EM Immunocytochemistry (ICC) localizes specific antigens at the subcellular level. We present here a modified method to process in vitro cells for pre-embedding EM ICC. The first advantage of this method is that it uses multiwell plastic chamber slides for cell cultures, and offers (a) excellent light microscopic images for precise monitoring of the cells and ICC staining throughout the procedure, including the final embedded Epon block, (b) efficiency in EM processing, especially the ease of removing the slide from the Epon blocks after polymerization, and (c) convenience of carrying out many different experimental conditions such as fixative composition and antibody dilutions on the same multichamber slide. The second advantage of this method is the use of a 1.4 nm gold probe which is covalently bound to the secondary antibody, and gives (a) precise localization of the antigenic sites in the form of individual silver grains which do not obscure the underlying fine structure, and (b) higher sensitivity and specificity of the ICC staining because the covalent conjugation of the gold to the secondary antibody is very stable and is not easily displaced.
Structural analysis of the E. coli RUVB branch migration protein by EM and image analysis
Authors: Yu X. , Benson K. , Stasiak A. , Tsaneva I. , West S. , Egelman E. H.
Published: June 2020

We have been interested in the structure and function of proteins involved in genetic recombinaton. The ruv locus on the E. coli chromosome contains three genes (ruvA, ruvB and ruvC) that are important for genetic recombination and DNA repair. The ruvA and ruvB genes form part of the SOS response to DNA damage and encode the RuvA and RuvB proteins. Together, RuvA and RuvB promote the branch migration of Holliday junctions in a reaction that requires ATP hydrolysis. Each protein plays a defined role, with RuvA responsible for DNA binding (and, in particular, junction recognition), whereas the RuvB ATPase provides the motor for branch migration. Sequence analysis has identified RuvB as a member of a superfamily of helicases, and experimentally it has been shown that RuvB, in the presence of RuvA, acts as an ATP-dependent helicase.

When purified RuvB protein was incubated (in the presence of the ATP analog, ATP-γ-S) with covalently closed, relaxed dsDNA, double-ringed structures were observed on the DNA in the electron microscope (Fig. 1). The DNA must be passing through the center of these rings, since the rings are always aligned along a common axis.
Image restoration of thick biological specimens using a through focus series as applied to electron tomography
Authors: Han Karen F. , Sedat John W. , Agard David A.
Published: June 2020

The main focus of our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the reconstruction of an object by combining multiple projection views of the object at different tilt angles. It is thus imperative to obtain an accurate representation of the projected object mass density to reconstruct the object correctly in three dimensions. Due to the effects of electron-specimen interactions and microscope lens aberrations, image intensities are not always related to the projected mass density in a simple fashion. We are using a variety of techniques to interpret collected images. In previous work, we have analyzed image formation for thick (0.3-0.7um) biological specimens by electron energy loss spectroscopy and imaging, as well as Ewald sphere construction analysis. In this work, we have modified existing techniques to restore images with only three focus levels using the exit surface wave reconstruction as a reference for comparison.
Comparison of hydathodes and stomata in Ficus formosana maxim
Authors: Chen C. C. , Chen Y. R.
Published: June 2020

Two major ways of water discharge from plant leaves are vapour transpiration and liquid guttation through stomata and hydathodes, resptectively. However, besides pure water, guttation fluid contains various salts, sugars and other organic substances which cause injury to plants through their accumulation on leaf surface. Functionally, hydathodes not only play an important role on water excretion but also on retrieval of minerals and their structures are different from those of stomata, even though both have same phylogenic origin. In the present study, the distribution, strcuture, and cytology of hydathodes and stomata of Fisuc formosana Maxim were reported.

Leaf blades of fully expanded leaf were cut with a razor blade into small cubes in fixation buffer containing 2.5% glutaraldehyde. These were transfered to fresh fixation buffer for 2 h, postfixed in 1% osmium tetraoxide for 4 h, dehydrated through an ethanol series, and then infiltrated and embedded in Spurr's resin. Sections in golden color were collected on grids, doubly stained with uranyl acetate and lead citrate, and observed with a Hitachi H-600 transmission electron microscope (TEM).
The use of fractal analysis to describe in vitro drug effects: Effect of lovastatin on CaCo-2 cell differentiation
Authors: Maleeff Beverly E. , Hart Timothy K. , Klinkner Anne M. , Waites C. Robbie , Bugelski Peter J. , Kerns William D.
Published: June 2020

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoAR) have been shown to inhibit cell growth and to affect cell differentiation in a variety of in vitro systems. The human colon carcinoma cell line CaCo-2, when grown on permeable membranes, undergoes high order differentiation into a well-organized monolayer of columnar enterocytes. However, in the presence of the HMG CoAR inhibitor lovastatin, these cells fail to differentiate, lose contact inhibition and overgrow the culture support. Changes in cell differentiation can be described by measurements of mean cell height (MCH) or mean monolayer height (MMH), and are illustrated with representative micrographs. In this study, we have applied fractal geometry in addition to traditional morphometry to quantitatively describe the effect of lovastatin on CaCo-2 cell differentiation in vitro.

CaCo-2 cells were plated at sub-confluency (∽ 60,000 cells/cm2) on collagen-coated Transwell™ permeable polycarbonate membrane supports (Costar Corp., Cambridge, MA) in culture dishes and allowed to attach for at least 24 hours.
Microscopic investigations of novel intracellular bodies of a Nocardia SP
Authors: Stites J. L.
Published: June 2020

A Nocardia sp.was found during an initial transmission electron microscopic (TEM) examination to have unusual intracellular bodies (ICB's) which do not appear to have been described previously in the literature. Most intracellular structures within bacteria have been classified as storage granules, a product of membrane invagination (i.e. mesosomes), or vacuoles. In bacteria there are no known intracellular membrane-bound organelles, and all internal membranes are invaginations of the unit membrane. Several microscopic-level examinations of the Nocardia sp. ICB's were initiated in order to determine their overall structure, classification, and internal constitution.

Different TEM staining procedures were performed to determine possible molecular components of the ICB. In all of the staining protocols the ICB's showed a lack of electron density similar to the cell wall. Because the ICB's showed no affinity to any stain, it appeared they do not have strong positive charge (phosphotungstic acid), are not protein rich (en bloc uranyl acetate), lack glycogen and are not phosphate or sulphur rich (lead citrate), nor do they contain lipids or ribonucleic acids (osmium tetroxide).
X-ray analysis of materials: Avoiding the pits and other practical hints
Authors: Sandborg Alan
Published: June 2020

Introduction:

EDS analysis of samples in a SEM or TEM is usually portrayed as a very simple process; just image your specimen, turn on the x-ray analyzer and all will be revealed about the chemistry of your sample. Unfortunately, that approach can be very misleading at best, and disastrous at worst. The analyst should get used to preparing himself for EDS x-ray analysis just like he or she does for any other process. A set of preparation steps should be followed until they become an unconscious method to be used before accepting the information coming from the EDS x-ray spectrum. After proper basic preparation, interpretation of the results and the selection of operating parameters is still very important due to the detailed nature of the specimen.

Preparation:

The most basic need is for the EDS system to be calibrated. This can be a difficult or simple task depending on the age of the system. Next, the basic geometry of the beam, sample and EDS detector needs to be considered. Before starting to analyze a specimen, the operator has probably put a good deal of effort into obtaining an optimum image. But the optimum parameters for imaging and x-ray analysis are rarely the same.
Interpretation of HRTEM images by image simulation: An introduction to theory and practice
Authors: O’Keefe Michael A.
Published: June 2020

High-resolution transmission electron microscope (HRTEM) image simulation was conceived in 1970 in response to a referee's questioning of the interpretation of images of a niobium oxide. Two years later a suite of HRTEM image simulation programs had been established and shown to accurately reproduce experimental HRTEM images when imaging parameters were accurately known. These first simulated images proved that the original interpretation of the niobium oxide images was indeed correct. Once these programs were available, it was possible to explore HRTEM imaging parameters including specimen ionicity, validity of the projection approximation, and the resolution-limiting effects of incident-beam convergence. Over the twenty years since then, the range of uses of HRTEM simulation has continued to expand, as has the number of programs available. World-wide distribution of the SHRLI (simulated high-resolution lattice image) code inspired some researchers to produce new or modified simulation programs and others to compare the results produced by these programs (fig.1).
Recent morphological surprises in diblock copolymer systems
Authors: Disko M. M. , Behal S. K. , Liang K. S. , Roe R. J. , Jeon K. J.
Published: June 2020

Diblock copolymers form ordered interfacial surfaces that range from lamellae, to cylinders, to the ordered bicontinuous double diamond (OBDD) structure, and spheres on a cubic lattice as the size of one component is increased. Flexible control of these materials presents an opportunity for structural materials, adhesives and selective separations. Mixtures of diblock copolymers with homopolymers exhibit similar structures due to changes in the interfacial curvature that accompany "swelling" the like-component of the diblock with homopolymer. Ordering behavior in systems of this type depends on the elastic properties and molecular weights (MW's) of the polymers, annealing temperature and annealing time. We have examined the changes in morphology of a styrene-butadiene (SB) diblock copolymer mixed with homopolymer polystyrene (hS). Sample made by casting from toluene solution, annealing at 130°C for 2-10 days, staining B-rich regions with OsO4, and microtoming thin-sections at -90°C. The SB MW was 49 800 g/mol with an S-block MW of 25 500 g/mol, and 24 400 g/mol for the B-block. Two hS components were used, having MW's of 26 000 g/mol (h26) and 19 300 g/mol (h19). We refer to the samples by the hS molecular weight and total polystyrene volume fraction, e.g. h26/0.67.
Managing digital images with SEM viewer™
Authors: Denault Lauraine , de la Parra Robin , von Roesgen Claude
Published: June 2020

In 1992 Millipore's Corporate SEM Lab made the transition from conventional analog recording of images to digital acquisition and archival. Commonly requested images could be easily and reliably retrieved, without significant loss of image quality or resolution.

In theory, digital images could be sent over a network to desktop PC's for review, (rather than producing hard copy of all images). Using established wide area network system, the scope of incorporating digital images significantly broadened. A significant barrier appeared in that the images were acquired using two different hardware/software packages, by two different SEMs (ISI DS130-C and ElectroScan ESEM). Although both generate TIFF images the "flavors" are somewhat different. The TIFF formats were incompatible because the tags used for magnification, micron bar, and descriptor line data were different. As a result, only the image itself generated from one program could be read by the other program, as with all available TIFF readers. Our dilemma was how to enable a single program to recognize and display all necessary information i.e., magnification, descriptor line, and the micron bar with the image.
Attachment of oral bacteria to titanium surfaces: An SEM study
Authors: Laffoon J. E. , Anderson R. L. , Keller J. C. , Wu-Yuan C. D.
Published: June 2020

Titanium (Ti) dental implants have been used widely for many years. Long term implant failures are related, in part, to the development of peri-implantitis frequently associated with bacteria. Bacterial adherence and colonization have been considered a key factor in the pathogenesis of many biomaterial based infections. Without the initial attachment of oral bacteria to Ti-implant surfaces, subsequent polymicrobial accumulation and colonization leading to peri-implant disease cannot occur. The overall goal of this study is to examine the implant-oral bacterial interfaces and gain a greater understanding of their attachment characteristics and mechanisms. Since the detailed cell surface ultrastructure involved in attachment is only discernible at the electron microscopy level, the study is complicated by the technical problem of obtaining titanium implant and attached bacterial cells in the same ultra-thin sections. In this study, a technique was developed to facilitate the study of Ti implant-bacteria interface.

Discs of polymerized Spurr’s resin (12 mm x 5 mm) were formed to a thickness of approximately 3 mm using an EM block holder (Fig. 1). Titanium was then deposited by vacuum deposition to a film thickness of 300Å (Fig. 2).
The concerted use of SEM, TEM, and SCM for examination of resin-dentin interfaces
Authors: Van Meerbeek B. , Conn L. J. , Duke E. S.
Published: June 2020

Restoration of decayed teeth with tooth-colored materials that can be bonded to tooth tissue has been a highly desirable property in restorative dentistry for many years. Advantages of such an adhesive restorative technique over conventional techniques using non-adhesive metal-based restoratives include improved restoration retention with minimal sacrifice of sound tooth tissue for retention purposes, superior adaptation and sealing of the restoration margins in prevention of caries recurrence, improved stress distribution across the tooth-restoration interface throughout the whole tooth, and even reinforcement of weakened tooth structures. The dental adhesive technology is rapidly changing. An efficient resin bond to enamel has already long been achieved. Its bonding mechanism has been fully elucidated and has proven to be a durable and reliable clinical treatment. However, bonding to dentin represents a greater challenge. After the failures of a dentin acid-etch technique in imitation of the enamel phosphoric-acid-etch technique and a bonding procedure based on chemical adhesion, modern dentin adhesives are currently believed to bond to dentin by a micromechanical hybridization process. This process is developed by an initial demineralization of the dentin surface layer with acid etchants exposing a collagen fibril arrangement with interfibrillar microporosities that subsequently become impregnated by low-viscosity monomers. Although the development of such a hybridization process has well been documented in the literature, questions remain with respect to parameters of-primary importance to adhesive efficacy.
A new computer-powered TEM with unique imaging capabilities
Authors: Benner G. , Frey J. , Rosβ-Meβemer M. , Probst W.
Published: June 2020

1. Introduction

A modern electron microscope designed for routine operation must provide user-friendly operation and a high degree of automation without compromising its imaging performance. Adequate computerization of the system is the way to achieve this goal. Up to now even the most advanced computer controlled microscopes can set important parameters like the magnification, the image brightness or the image orientation only in discrete steps. In the new Zeiss EM 906 continuous adjustment of these parameters has been realised for the first time by means of realtime computer interpolation of the lens excitations between the discrete lens current combinations corresponding to the discrete parameter settings.

2. Computer architecture of the microscope

The computer network comprises a DOS-compatible system (host) computer, four subsystems controlled by separate microprocessor and a flexible data and program memory. The integrated system computer controls the electron optics while the gun, the goniometer, the camera and the vacuum system are controlled and monitored by autonomous microprocessor systems, which are connected to the host computer for data transfer via interrupt-controlled parallel interfaces.
The EM208: A new microscope for life science
Authors: Busing Wim M. , de Jong Marc J. C. , Otten Max T.
Published: June 2020

Over the past decades the transmission electron microscope (TEM) has undergone a large number of improvements and extensions: in life science new scientific breakthroughs have been made for example by using cryo-techniques on high-resolution TEMs. These breakthroughs were made possible by improvements in vacuum quality, resolution, cryo-holder stability, etc. There are, however, many institutions where the improvements and extensions of the current generation of TEMs are never used, because they are not necessary in the type of investigations for which these microscopes are used. As a consequence, the microscopes are more (and sometimes even too) expensive to buy and run. They are also unnecessarily complicated, increasing the cost of running these instruments through the extra skill required from the operators. In essence, the microscopes have changed, but the work for which they are used hasremained (nearly) the same. A good example can be found in the pathology departments of many hospitals, where the TEM work involves routine investigations of biopsies and capital investment and running costs are under great pressure. Philips Electron Optics has therefore developed and built a new TEM, the EM208, which completes the current range of TEMs supplied.
{10}<110> edge dislocations in YSZ films grown on (100)MgO by PLD
Authors: Heffelfinger Jason R. , Carter C. Barry
Published: June 2020

Yttria-stabilized zirconia (YSZ) is currently used in a variety of applications including oxygen sensors, fuel cells, coatings for semiconductor lasers, and buffer layers for high-temperature superconducting films. Thin films of YSZ have been grown by metal-organic chemical vapor deposition, electrochemical vapor deposition, pulse-laser deposition (PLD), electron-beam evaporation, and sputtering. In this investigation, PLD was used to grow thin films of YSZ on (100) MgO substrates. This system proves to be an interesting example of relationships between interfaces and extrinsic dislocations in thin films of YSZ.

In this experiment, a freshly cleaved (100) MgO substrate surface was prepared for deposition by cleaving a lmm-thick slice from a single-crystal MgO cube. The YSZ target material which contained 10mol% yttria was prepared from powders and sintered to 85% of theoretical density. The laser system used for the depositions was a Lambda Physik 210i excimer laser operating with KrF (λ=248nm, 1Hz repetition rate, average energy per pulse of 100mJ).
TEM studies of modified lead zirconate titanate ceramics
Authors: Viehland Dwight. , Xu Z. , Dai X. H.
Published: June 2020

The microstructural, structural, dielectric, and polarization properties of antiferroelectric PZST and PLZT ceramics have been studied as a function of Sn and La-contents, respectively. These materials are of interests for applications as antiferroelectric-ferroelectric phase switching actuators, however their transformational characteristics are currently unknown. In these systems, various ferroelectric and antiferroelectric phases have been reported over a narrow compositional range. These include: antiferroelectric orthorhombic, antiferroelectric tetragonal, rhombohedral ferroelectric, multi-cell cubic paraelectric, and single-cell cubic paraelectric. Dielectric anomalies are not observed at the ferroelectric to antiferroelectric or antiferroelectric to multicell cubic transformations. The maximum dielectric constant is found near the temperature of the formation of the multicell cubic state, which is ˜30°C above the transformation into the antiferroelectric tetragonal state. No macroscopic symmetry changes are observed near the temperature of the dielectric maximum.

The compositional systems investigated in this study were (Pb1-xLax)(Zr1-yTiy)O3 (PLZT x/(1-y)/y) and Pb(0.98)Nb0.02[(Zr1-x,Snx)1-yTiy]1-zO3 (PZST x/y/2). The compositions chosen for study were PLZT 0/95/, 1/95/5, 2/95/5, 3/95/5 and 5/95, and PZST 45/0/2, 45/3/2, 45/6/2, and 45/9/2.
Epitaxial ferroelectric thin films
Authors: Ghonge S. G. , Goo E. , Ramesh R. , Haakenaasen R. , Fork D. K.
Published: June 2020

Microstructure of epitaxial ferroelectric/conductive oxide heterostructures on LaAIO3(LAO) and Si substrates have been studied by conventional and high resolution transmission electron microscopy. The epitaxial films have a wide range of potential applications in areas such as non-volatile memory devices, electro-optic devices and pyroelectric detectors. For applications such as electro-optic devices the films must be single crystal and for applications such as nonvolatile memory devices and pyroelectric devices single crystal films will enhance the performance of the devices. The ferroelectric films studied are Pb(Zr0.2Ti0.8)O3(PLZT), PbTiO3(PT), BiTiO3(BT) and Pb0.9La0.1(Zr0.2Ti0.8)0.975O3(PLZT).

Electrical contact to ferroelectric films is commonly made with metals such as Pt. Metals generally have a large difference in work function compared to the work function of the ferroelectric oxides. This results in a Schottky barrier at the interface and the interfacial space charge is believed to responsible for domain pinning and degradation in the ferroelectric properties resulting in phenomenon such as fatigue.
High-Resolution Electron Microscopy of condensed clusters in a potassium barium oxomolybdate
Authors: Ramlau R. , Schimek G. L. , McCarley R. E. , Simon A.
Published: June 2020

The recently synthesized compound K0.19Ba3.81Mo22O34 is a representative of the ternary and quaternary reduced molybdenum oxides in which clusters built from molybdenum octahedra are arranged in layers of composition AxByMo4n+2O6n+4. The number of trans-edgesharing molybdenum octahedra in the cluster is represented by n. The general concept of cluster condensation is formulated and discussed elsewhere. For K0.19Ba3.81Mo22O34, n is equal to 5. A ternary representative, likewise with n = 5, is In6Mo22O34.

By x-ray structure analysis, K0.19Ba3.81Mo22O34 proved to crystallize in space group P21/a with parameters a = 0.9908(2) nm, b = 0.9353(2) nm, c = 1.5951(3) nm, and β = 98.78(2)°. The potassium atoms were found to reside on the same sites as the barium atoms with an almost statistical distribution.

We studied K0.19Ba3.81Mo22O34 by high-resolution electron microscopy (HREM). Small fragments of a crystal were investigated using a Philips CM30/ST microscope operating at 300 kV (point resolution 0.19 nm). At appropriate orientations of the crystal fragments, HREM images reveal domains of two ordered polytypes: a monoclinic and an orthorhombic one (Figs. 1 and 2).
Analysis of reacted nuclear-waste glass using electron beams
Authors: Buck E. C. , Dietz N. L. , Bates J. K.
Published: June 2020

When waste glass reacts with water, secondary phases may form, which will effect the distribution of radionuclides formally contained within the glass. In order to determine the long term behavior of waste glass, the secondary phases formed need to be identified. Analytical electron microscopy (AEM) is being used to characterize the secondary phases. Glasses have been reacted in test vessels at different surface areas to leachate volumes (S/V) and for periods in excess of 700 days. Increasing the S/V permits one to accelerate the reaction. Samples of the reacted waste forms are embedded in epoxy and thin sectioned by ultramicrotomy for observation in the transmission electron microscopy (TEM). Examinations were performed in a JEOL 2000FXII TEM operated at 200 kV. This abstract describes two types of glass tests, a high level waste sludge based glass and a low level waste glassy slag. Many hundreds of glass tests have been performed and examined by TEM to determine layer thickness, morphology of the leach layer, and identification of secondary phases.
Investigations using wide-angle electron diffraction on pair ordering mechanisms in FeTb alloys by thermal annealing
Authors: Tewes M. , Zweck J. , Hoffmann H.
Published: June 2020

In our recent work we have shown that electron diffraction is a suitable and precise method to observe short range ordering in various amorphous FeTb alloys by calculating pair distribution functions (PDFs) from these data by means of a fourier inversion. A PDF g(r) is an autocorrelation function of the specimen’s density fluctuations: g(r) = 4πr(ϱ(r) - ϱo) with ϱ(r): autocorrelation of the local density in a distance r, and ϱo macroscopic density of the specimen. The spatial resolution that can be achieved is better than 0.02 nm, and the fine structure of the first coordination shell of the short range order has been described quantitatively with an isotropic structure model. The deviation between calculated and measured PDFs has been about 2%.

However, the origin of the uniaxial perpendicular anisotropy in rare earth / transition metal amorphous alloys like FeTb is in general attributed to small anisotropic concentration fluctuations on an atomic scale as introduced in pair ordering, band orientation or stress induced anisotropy models.
Analysis of vacuum- and beam-sensitive pharmaceutical compounds in the EM
Authors: Neilly J. P. , Zaluzec N. J. , Meyer G. A. , Miller M. F.
Published: June 2020

When very small amounts of a chemical compound are available for analysis or the compound is impure, analytical electron microscopy may be the method of choice for studying its physical and chemical characteristics. Before a compound is analyzed in the transmission electron microscope (TEM) it is desirable to assess its behavior in die high vacuum and ionizing radiation of the microscope. In this paper we describe a systematic approach for determining the response of a pharmaceutical compound to the effects of high vacuum and ionizing electron radiation as well as techniques used to stabilize the material in the microscope.

Vacuum stability of a hydrated compound was evaluated through weighing experiments to determine if the water of hydration was removed. Known amounts of the compound were placed in the specimen chamber of a Philips 501 SEM for periods of 0.25, 0.5, 1, 2, 5 and 17 hours. The powders were then removed, reweighed and changes in weight were recorded.