bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-resolved high-resolution electron microscopy of structural stability in mgo clusters
Authors: Kizuka T. , Tanaka N.
Published: June 2020

Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science.

In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.

MgO and gold were subsequently deposited on sodium chloride (001) substrates. The specimens, single crystalline MgO films on which Au particles were dispersed were separated in distilled water and observed by using a 200-kV high-resolution electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder system.
Probing vacancies and structural distortions at individual defects in ceramics using EELS
Authors: Wallis D. J. , Browning N. D.
Published: June 2020

In electron energy loss spectroscopy (EELS), the near-edge region of a core-loss edge contains information on high-order atomic correlations. These correlations give details of the 3-D atomic structure which can be elucidated using multiple-scattering (MS) theory. MS calculations use real space clusters making them ideal for use in low-symmetry systems such as defects and interfaces. When coupled with the atomic spatial resolution capabilities of the scanning transmission electron microscope (STEM), there therefore exists the ability to obtain 3-D structural information from individual atomic scale structures. For ceramic materials where the structure-property relationships are dominated by defects and interfaces, this methodology can provide unique information on key issues such as like-ion repulsion and the presence of vacancies, impurities and structural distortion.

An example of the use of MS-theory is shown in fig 1, where an experimental oxygen K-edge from SrTiO3 is compared to full MS-calculations for successive shells (a shell consists of neighboring atoms, so that 1 shell includes only nearest neighbors, 2 shells includes first and second-nearest neighbors, and so on).
The structure and properties of misfit layer compounds
Authors: Curzon A. E.
Published: June 2020

The purpose of this article is to provide an introduction to the class of compounds known as misfit layer compounds.

An example of a misfit layer compound is (NdS)1.2NbS2 In the present study this material was made by heating appropriate amounts of sulphur powder, niobium powder and neodymium chips in an evacuated quartz tube at 850°C for 12 hours. A subsequent five day process involving transport and back transport at 1000°C in the presence of iodine as transport agent led to the formation of lustrous crystal platelets suitable for electron microscopy and electron diffraction studies. The orthorhombic material consists of alternate layers of NdS (two atoms thick) and layers of NbS2 (three atoms thick) each perpendicular to the c-axis. Fig. 1 shows a [100] view of the structure observed in recent studies. Though it differs from the structure reported in other work, both reported forms have features in common which are characteristic of all misfit layer compounds.
Can The Icosahedral Phase Be Modeled as a Crystal?
Authors: Bian Weimin , Zhu Yimei
Published: June 2020

We propose a crystal model that is in excellent agreement with the experimental electron diffraction patterns and high-resolution electron microscopy images of the icosahedral phase in Mn-Al and related systems. Structurally, the model has long-range translational order with a large unit-cell (Im3 space group) containing 10038 atoms, as well as orientational order characterized by symmetry close to the m35 point group which is commonly assigned for quasicrystals.

Fig.l(a)-(c) show, respectively, the SAD patterns of the so-called twofold, threefold, and fivefold axes observed in rapid quenched Al-14at%Mn. Simulation of the corresponding SAD patterns (Fig.l(d)-(h)) suggested that they did not result from a single zone-axis diffraction, but from several closely orientated zone axes. For example, Fig.1(f) was generated by the superposition of the [305], [508], and [8 0 13],…. axes (denoted as N-<305>); the rotation angles from the [001] axis to each axis are 30.96°, 32.01°, and 31.61 °, respectively. All are very close to 31.71 °, which is the angle between a twofold and a fivefold axis in the m35 point group. In a conventional electron diffraction experiment, if the [001] axis of the crystal is rotated 31.71° around the [010] axis, these three zone axes would simultaneously satisfy the Bragg conditions and cannot be separated. Such superposition in the projected diffraction pattern, especially when the unit-cell is large, can yield a pseudo-fivefold symmetry which is indistinguishable with a true fivefold symmetry in SAD.
Subcellular and multicelluar organization of calcium signaling in liver
Authors: Thomas A.P. , Robb-Gaspers L.D.
Published: June 2020

Cytosolic Ca2+ ([Ca2+]i) is a ubiquitous intracellular messenger in mammalian cells, and imaging studies of single living cells loaded with fluorescent Ca2+ indicators have demonstrated that the [Ca2+]i changes induced by extracellular agonists are often organized in complex temporal and spatial patterns. A number of hormones that regulate hepatic metabolism, including vasopressin and α1adrenergic agonists, bring about their effects through a rise in [Ca2+]i mediated by the Ca2+-mobilizing second messenger IP3. Imaging studies of isolated hepatocytes have demonstrated that the [Ca+]i responses during continuous exposure to these hormones consist of a series of discrete [Ca+]i spikes, the frequency of which is determined by the dose of agonist. By contrast, the amplitude and kinetics of the individual [Ca+]i spikes are not affected by changing the agonist dose. In addition to the temporal organization in the form of [Ca2+]i oscillations, the [Ca2+]i changes are also spatially organized into regenerative [Ca2+]i waves that propagate throughout the cytoplasm and nucleoplasm of the cell from a discrete plasma membrane locus. These oscillatory [Ca2+]i waves are generated by the complex interplay of [Ca2+]i and IP3 in regulating the gating properties of the IP3- receptor Ca2+ channel, which is located in the endoplasmic reticulum Ca2+ store.
Absence of temporal ordering of apoptotic features in heat-shock treated leukemia and lymphoma cell lines
Authors: Fairbain D. W. , Standing M.D. , O'Neill K.L.
Published: June 2020

Apoptosis is a genetically defined response to physiological stimuli that results in cellular suicide. Features common to apoptotic cells include chromatin condensation, oligonucleosomal DNA fragmentation, membrane blebbing, nuclear destruction, and late loss of ability to exclude vital dyes. These characteristics contrast markedly from pathological necrosis, in which membrane integrity loss is demonstrated early, and other features of apoptosis, which allow a non-inflammatory removal of dead and dying cells, are absent. Using heat shock-induced apoptosis as a model for examining stress response in cells, we undertook to categorize a variety of human leukemias and lymphomas with regard to their response to heat shock. We were also interested in determining whether a common temporal order was followed in cells dying by apoptosis. In addition, based on our previous results, we investigated whether increasing heat load resulted in increased apoptosis, with particular interest in relatively resistant cell lines, or whether the mode of death changed from apoptosis to necrosis.
Skeletal-muscle ultrastructural pathology in patients with sepsis and multiple organ failure syndrome (MOFS)
Authors: Márquez A. , Diaz N.L. , Finol H.J. , Correa M.E.
Published: June 2020

To date the most accepted definition of sepsis includes the suspicion of infection plus the systemic response to it (tachypnea, tachycardia and hypothermia or hyperthermia). This condition could lead to the so called multiple organ failure syndrome (MOFS) when there are evidences of flinctional compromise in two or more systems. Muscle weakness and wasting are common findings in those patients. The skeletal muscle histopathology in patients with those two conditions has been poorly studied. The only electron microscopic investigation we could find describes alterations in muscle fibers and endplates.In this work we describe the whole spectrum of changes found in skeletal muscle of patients suffering from sepsis and MOFS.

Five patients recluded in an Intensive Care Unit were selected, two had a diagnosis of sepsis, and three presented MOFS. Needle muscle biopsies from quadriceps femoris muscle were obtained. Tissue samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.
Electron microscopy study of skeletal muscle microvasculature in the paraneoplastic phenomenon
Authors: Tonino P. , Finol H.J. , Márquez A. , Müller B. , Correa M. , Sosa L.
Published: June 2020

In addition to signs and symptoms at sites of primary and metastatic disease, cancer can cause manifestations in remote sites that are not directly affected by any focus of disease. Such manifestations of malignancy are collectivelly known as paraneoplastic phenomenon. Muscular manifestations consist of slight to severe and usually proximal wasting and weakness. In our laboratory we described the ultrastructural pathology of skeletal muscle in the paraneoplastic phenomenon in patients with bronchogenic and cervix carcinoma. In these studies a brief report on capillary alterations was made. The present investigation was undertaken in order to extent the study on the microvasculature in the skeletal muscle paraneoplastic phenomenon.

Muscle biopsies were obtained in patients suffering from bronchogenic carcinoma (n= 10), gastric carcinoma (n= 7), cervix carcinoma (n= 1) and lymphoma (n= 4). Tissue samples were processed by routine transmission electron microscope techniques and observed in a Hitachi H-500 EM.
Application of a corrected LVSEM in Biology: Artefacts in imaging of uncoated biological material
Authors: Wepf R. , Haider M. , Kroug M. , Mills D. , Zach J.
Published: June 2020

In Biology high resolution SEM has become of special interest to study the surface representations of isolated macromolecular complexes as well as the organisation of such complexes and organelles in their natural context.

Apart from the probe size, surface imaging in the nm-scale is limited by the interaction volume of the primary electrons, which directly increases with increasing primary energy. On one hand at low voltages (200-1000eV) the interaction volume can be kept minimal, but a probe size of 1-2 nm can only be obtained by a correction of the spherical and chromatic aberrations (Zach, 1990; Haider et al., 1994). On the other hand, the probe size at high voltages is mainly limited by diffraction and spherical aberation but nevertheless a probe sizes <1 nm at 30keV can be routinely achieved (Nagatani et al., 1987). To overcome the resolution limitation by the large interaction volume in bulk samples, biological specimens are coated with a very thin (1-2 nm) metal film to localize the SE-signal at the surface of the specimen (Joy, 1990).
Environmental Scanning Electron Microscope (ESEM) Observation of Subsurface Charge Effects in Insulators: Implications for Electron Imaging and X-Ray Microanalysis
Authors: Griffin B.J. , Nockolds C.E.
Published: June 2020

The nature of subsurface charging in non-conductive samples has been investigated and modelled by a number of authors. Potential effects of subsurface charging include modification in electron range and interaction volume, variation in secondary electron yield, and reduction in incident electron beam energy and consequent modification to the emitted x-ray signal.

During an unconnected experimental series on large surface area, polished mineral samples unusual images were observed following spot x-ray analysis. On these specimens, a bright circle centred on the analysis point was observed at low magnification in the secondary electron image. Around diis bright circle was a concentric dark zone with diffuse edges. This effect was noted to be time variant, with the scanned area progressively increasing in brightness until the contrast with the circle was lost. Curiously however the perimeter of the circle was defined at this stage by a narrow 'dark' ring. This serendipitous observation has led to the observation and definition of subsurface charging in insulators, albeit at a preliminary stage.
Biological applications of ESEM: Examination of fully hydrated samples
Authors: Gilpin C.J.
Published: June 2020

The environmental scanning electron microscope (ESEM) utilises a secondary electron detector capable of operating at pressures in the range of 1 ~ 20 Torr (130 ~ 2700 Pascals). By use of differential pumping apertures the electron gun and column can be maintained at "normal" vacuum levels of 10-5 Torr. A pressure of 10-2 Torr exists within the secondary electron detector separated from the specimen chamber by another differential pumping aperture. The specimen chamber pressure is produced by admitting a gas to the chamber under operator control. The gas can be any ionisable gas. Water vapour is a commonly used chamber gas. By controlling chamber gas pressure and sample temperature, by means of a Peltier effect stage, condensation and evaporation can be produced. The ability to maintain samples in a fully hydrated state in this way singles out the Electroscan ® ESEM as a unique instrument. ESEM presents an opportunity to examine biological samples with their natural water content present.
Tip-sample force interaction and surface local hardness in STM and AFM imaging
Authors: Whangbo M.-H. , Bengel H. , Magonov S. N.
Published: June 2020

STM and AFM images of various layered inorganic compounds, organic conducting salts and polymers were examined to assess the role of the tip-sample force interaction in scanning probe microscopy. To a first approximation, the AFM image of a sample surface is described by the total electron density plot ρ(r0), and the STM image by the partial electron density plot, ρ(r0, ef). In these calculations, the structures of the surface layers are taken from the bulk crystal structures, so that a surface deformation induced by the tip force is neglected.

During the scanning in STM and AFM measurements, a sample surface often undergoes a geometry relaxation due to the tip-sample force interactions. As depicted in Fig. 1a, the macroscopic deformation of a sample surface caused by the tip force is explained in terms of classical theories in which the interacting solids are treated as materials with uniform density distributions. For a surface with several different chemical environments, the extent of the surface atom depression is determined by the local hardness.
Correlation of film stress and the mechanical response of Au thin films
Authors: Jarausch K.F. , Houston J.E. , Russell P.E.
Published: June 2020

The investigation of the mechanical properties of nanostructured materials is critical to the continuing development of thin film technology. For example, the semiconductor industry must understand how stress and strain effect the electronic properties of superlattices and cause the delamination of metal interconnect films. A variety of nano-indentation techniques have been developed as tools to investigate the mechanical behavior of thin films. In a previous study the interfacial force microscope (IFM) was used to survey the mechanical response of 200nm thick Au films deposited on various substrates under various deposition conditions. By combining the methods of contact mechanics and classic indentation techniques, quantitative investigations of the effective elastic modulus and the maximum shear-stress at the plastic threshold were tabulated. The results indicated a large variation in these parameters for the various film/substrates, while the values were consistent over a single film/substrate. The observed variation could be explained by several factors: differences in the films morphology, adhesion to the substrate, or residual stress.
Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy
Authors: Kinney H. , Occelli M.L. , Gould S.A.C.
Published: June 2020

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.

We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.
Novel labeling methods for em analysis of ultrathin cryosections
Authors: Robinson John M. , Takizawa Toshihiro
Published: June 2020

Ultrathin cryosections are the most favorable material for localization of intracellular antigens with particulate probes (e.g., colloidal gold) in post-embedding immunocytochemistry. Cryosections are prepared under the most benign conditions as compared to embedding samples in various kinds of plastic media. Typically, higher labeling efficiencies can be achieved with ultrathin frozen sections than with plastic sections.

We have utilized human neutrophils, the most abundant type of leukocyte, as a model system to explore labeling procedures for ultrathin cryosections. These labeling procedures can serve as alternative or complementary approaches to the traditional colloidal gold label. Neutrophils are characterized by the presence of numerous granules in their cytoplasm. For many years, the model for neutrophil structure has held that there are two granule types in these cells, the socalled azurophilic and specific granules. We have described an additional cytoplasmic compartment with unusual properties in neutrophils. This compartment is characterized by the presence of the enzyme alkaline phosphatase (Fig. 1).
An improved method for preparation and stereo imaging of negative-stained phospholipid vesicles by field-emission STEM
Authors: Apkarian Robert P. , Lee Stephen , Menger Fredric M.
Published: June 2020

The method of application of negative stains and the subsequent chemical interaction with various types of phospholipids affect vesicle morphology. Temperature, pH, stain concentration, and the method by which the vesicle solution is applied to the grid necessitates a systematic study. We have developed a method for spray mounting and uranyl acetate (UA) staining of extruded vesicles composed of dilauroylphosphatidylcholine (DLPC, 95%) and dimyristoylphosphatidylcholine (DMPC, 5%) from which we could acquire quality stereo images with high resolution field emission STEM.

The vesicles were prepared by 19 passes through a low pressure extruder containing a 0.1 μm polycarbonate membrane filter. After extrusion, 0.5 ml of vesicle solution was diluted with 3.5 ml of 0.1 μm filtered water and vortexed. The concentration of diluted phospholipid was 1.35 mM. The vesicle solution and 2 % UA stain in Milli-Q purified deionized water were mixed at room temperature 1:1 v/v. The UA solution was first prepared at 2X the desired concentration (4%) and sonicated into aqueous solution for at least 15 min. Before mixing with the vesicle solution, the UA was diluted to the desired 2% concentration and run through a 0.1 ¼m filter.
Low-temperature low-voltage scanning electron microscopy (LTL VSEM) of uncoated frozen biological materials: A simple alternative
Authors: Ahlstrand G. G.
Published: June 2020

Introduction.

Scanning Electron Microscopy (SEM) of biological materials, e.g. plants, fungi, insects, bacteria, host-pathogen interactions, and food systems, requires sample stabilization. Conventional strategies of chemical fixation (e.g. buffered glutaraldehyde, paraformaldehyde, osmium tetroxide), dehydration (ethanol or acetone series), critical point drying (CPD) and metal coating (Au/Pd) in a sputter coater or vacuum evaporator are often by applied. However, delicate biological materials may not withstand the stress of conventional preparation and acquire artifact such as collapse or shrinkage of cells or loss of soluble components (Fig la). Sophisticated devices and techniques are available which quick-freeze (<1.0 s), metal coat and transfer specimens under vacuum into the SEM. Herein I describe a simple, inexpensive alternative in which fresh biologicals are frozen slowly (< 1.5 min.) on an SEM cold stage, imaged directly without metal coating (Fig lb) at low SEM acceleration voltage (kV), and defrosted if needed with nitrogen gas (N2).
Energy filtering TEM of transfected DNA
Authors: Maleckl Marek
Published: June 2020

Energy filtering transmission electron microscopy (EFTEM) relies upon spatial separation of imaging electrons based upon their energy within an energy loss spectrum (Ottensmeyer 1986). In particular, EFTEM allows contrast enhancement in the zero loss mode and element mapping with electron spectroscopic imaging.These capabilities find a new application in studies of transgenesis in which constructs, probes, and antibodies are marked with organometallic clusters. Since the basic routes of intracellular trafficking of the transfected DNA have become recognized along with the crucial role played by nuclear pores as the selection gates (Malecki et al., 1995, Malecki and Skowron 1995),the current research is pursued by means of ultramicroscopy.

Two strategies were developed for ultrastructural imaging of the transfected plasmid DNA with EFTEM. In both strategies, the transfected cells were cryo-immobilized, embedded in Lowlcryl K4M, and sectioned;plasmid constructs, transfection complexes containing nuclear localization signals, and transfection procedures were described previously (Malecki 1995).In the first strategy, the plasmid DNA was covalently conjugated to Nanogold (Nanoprobes) prior to transfections.
Nature of caveolae in the endothelial cells of toad urinary bladders
Authors: Mia A.J. , Ford J. , Oakford L.X. , Yorio T.
Published: June 2020

Intact toad urinary hemibladder sacs have been in use for many years as a membrane model for experimental studies of transepithelial aqueous transfer under osmotic gradient. The toad bladder tissue is composed of several cell types. Recently, we reported the presence of a large concentration of caveolae in the granular epithelial cells of toad urinary bladders. Caveolae are microstructures which arise by invagination of the plasma membrane on the cytoplasmic side of the cell. Currently, we report the presence of caveolae in endothelial cells of toad urinary bladder.

Urinary hemibladder sacs were excised from doubly-pithed toads, Bufo marinus, fixed using 1% glutaraldehyde in PIPES, postfixed in 1% osmium tetroxide, dehydrated and embedded in epon blocks. Ultrathin sections were exposed to uranyl acetate and lead citrate for transmission electron microscopy. In some cases, the bladder sacs were tied up at the ends of glass tubes and equilibrated in aerated Ringer's solution for 30 min prior to experimental procedures.
Modulation of tubular microstructural self-assembly in galactosylceramides: Influence of N-linked fatty acyl chains
Authors: Kulkarni Vitthal S. , Brown Rhoderick E.
Published: June 2020

Our recent studies have indicated that aqueous dispersions of galactosylceramides (GalCers) containing nervonoyl [24:1Δ15(CiS)] acyl chains, which constitute the major unsaturated acyl moieties in bovine brain GalCer, form tubular bilayers. In an effort to define the structural parameters that modulate tubule formation, we synthesized a series.of GalCers having successively shortercismonounsaturated acyl chains than the tubule-forming 24:1 GalCer and investigated the resulting microstructural self-assemblies by freeze fracture and deep etch electron microscopy.

GalCers having W-linked erucic [22:1Δ13(CiS)], eicosenoic [20:Δ11(CiS)], or oleic [18:Δ9(CiS)] acyl chains were synthesized and purified as previously reported for 24:1 GalCer. Dispersions were prepared by hydrating dry lipid at >90°C with phosphate buffer (pH 6.6) followed by vigorous vortexing and three freeze-thaw cycles. Samples were cryo-fixed from room temperature (22°C) by plunging into liquid propane cooled by liquid nitrogen, were fractured in a Balzers 300 freeze fracture apparatus at -120°C, and were etched for 6 min. at -100°C.
The influence of surface roughening and Si{111} facets on low temperature Si homoepitaxy
Authors: Karpenko O.P , Yalisove S.M.
Published: June 2020

Recent research in the area of low temperature (T<450°C) epitaxial growth of semiconductors has revealed a number of interesting phenomena which are not yet fully understood. One suchphenomena is the crystalline to amorphous phase transition which occurs during low temperature Si homoepitaxy. For low temperature Si homoepitaxy, crystalline growdi is limited by a critical epitaxial thickness (hepi), beyond which Si grows as an amorphous phase. It has been established that hepi follows an Arrhenius relation with temperature, is preceded by an increase in surface roughness,and is affected by the presence of impurities and the substrate surface orientation. Although the formation of amorphous Si is not fully understood, several models have been proposed to explain this phenomenon. One of these models suggests that Si amorphization is associated with surface roughening andthe formation of Si{111} facets at the growth surface. According to this model, hepi shoulddecreaseasthe density of Si{111} microfacets on the starting increases.
Time-resolved high-resolution electron microscopy of structural transformation in nanocrystalline ZnO films
Authors: Kizuka T. , Tanaka N.
Published: June 2020

Mechanical properties of polycrystalline materials become anomalous when the grain size and grain boundary length decrease to nanometer scale. For example, ductility and toughness increase significantly in nanometer-grained ceramics (nanocrystalline ceramics). Ductility increases due to appearance of fine-grained-superplastic deformation. Grain boundary migration and interface migration are fundamental processes of the superplastic deformation. Structural transformation of fine grains is a factor which limits the toughness in polycrystalline ceramics because the transformation relaxes internal strain. The behavior of grain boundaries and interfaces, such as diffusion bonding and Czochralski-type crystal growth at ambient temperature, can be analyzed by a time-resolved high-resolution electron microscopy (TRHREM) developed by Kizuka et al.,

In the present study, grain boundary migration and successive transformation of crystal structure in nanocrystalline ZnO were investigated by TRHREM.

Zinc oxide was vacuum-deposited on air-cleaved (001) surfaces of sodium chloride at 200°C. TRHREM was carried out at room temperature using a 200-kV electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder.
Dynamic Observation of a Surface Reconstruction of Au-Deposited Si Particle
Authors: Kamino T. , Yaguchi T. , Tomita M. , Saka H.
Published: June 2020

Metal deposition is one of the most effective methods to reconstruct the surface structure of Si, and a number of studies using electron microscopes have been carried out. Endo et al. have studied Au-deposited Si(111) surface by ultra-high vacuum(UHV) scanning electron microscope(SEM), and obtained SEM images of 7 × 7 and 5 × 2-Au structure at 600°C. Ozawa et al. have observed Audeposited Si(111) surface by UHV-transmission electron microscope(TEM) and observed the formation of 5 × 2-Au structure at 700°C. Marks et al. have studied the structure of Au-deposited Si(lll) surface to reconstruct electronic potential on the surface.

Recently, we developed a direct heating type- specimen heating holder consists of two heating elements, for use with a conventional analytical TEM, and applied to an in-situ study of the surface reconstruction of Au-deposited Si at high temperature. A schematic drawing of the heating holder is shown in Fig. 1. Tungsten wire with a diameter of 25εm was used as the heating elements. The upper heating element was used for metal deposition, in this case Au, and lower one for the heating of substrate material, in this case Si. The microscope used in the study is a H-9000NAR analytical TEM operated at 300kV. The spherical and chromatic aberration coefficients of the objective lens were 0.69 and 1.4mm, respectively, and the TEM image resolution was 0.175nm
Characterization of reactive phase formation in sputter-deposited Ni/Al multilayer thin films using TEM
Authors: Lucadamo G. , Barmak K. , Michaelsen C.
Published: June 2020

The subject of reactive phase formation in multilayer thin films of varying periodicity has stimulated much research over the past few years. Recent studies have sought to understand the reactions that occur during the annealing of Ni/Al multilayers. Dark field imaging from transmission electron microscopy (TEM) studies in conjunction with in situ x-ray diffraction measurements, and calorimetry experiments (isothermal and constant heating rate), have yielded new insights into the sequence of phases that occur during annealing and the evolution of their microstructure.

In this paper we report on reactive phase formation in sputter-deposited lNi:3Al multilayer thin films with a periodicity A (the combined thickness of an aluminum and nickel layer) from 2.5 to 320 nm. A cross-sectional TEM micrograph of an as-deposited film with a periodicity of 10 nm is shown in figure 1. This image shows diffraction contrast from the Ni grains and occasionally from the Al grains in their respective layers.
New specimen holders for low-angle ion milling of TEM specimens
Authors: Alani R. , Swann P.R.
Published: June 2020

The important role of milling angle in the preparation of ion milled TEM specimens can not be over emphasized. While higher milling angles produce more rapid milling of specimen surface, ion milling at glancing angles of about 5° or less has become increasingly popular because it produces higher quality specimens and fewer artifacts, especially specimens composed of materials which are difficult to mill. Specimens milled at higher angles are of lower quality and include surface roughness, limited thin areas and differential thinning rates for different constituents in specimen; low angle ion milling overcomes many of these problems.

A major requirement for low angle ion milling is a specimen holder with an appropriate line of sight capability. That is, the specimen holder must permit one or more ion beams to be directed against the specimen at angles down to 0°. The “single post specimen holder” is an example of a specimen holder providing low angle ion milling capability.
Industrial applications of TOF-SIMS imaging
Authors: Pachuta Steven J.
Published: June 2020

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has in recent years become a useful tool for surface analysis in industrial laboratories. All elements and isotopes, as well as many molecular entities, can be detected by SIMS, with most of the signal coming from the outer 10 - 20 Å of the surface. The initial penetration of TOF-SIMS into industry was as an improvement over existing quadrupole instruments, with higher mass range, mass resolution, and sensitivity. The coupling of TOF-SIMS with high brightness liquid metal ion sources greatly expanded the applicability of the technique, making chemical imaging of the outermost monolayers of a surface a routine experiment.

Several examples will be presented of TOF-SIMS imaging applied to real-world materials encountered in an industrial analytical laboratory. All results were obtained from a PHI-Evans TFS series instrument equipped with an FEI two-lens 69Ga+ liquid metal ion gun (LMIG). When operated at 25 keV beam energy, a primary ion beam diameter of 2500 Å in continuous mode, and 1-2 μm in pulsed mode, can routinely be obtained.
Interfacial reactions in metal matrix composites revealed by imaging SIMS
Authors: Levi-Setti R. , Chabala J.M. , Wolbach W. , Soni K.K.
Published: June 2020

Secondary ion mass spectrometry (SIMS), often in its non-imaging manifestation, is a powerful analytical technique that has found numerous applications in the semiconductor, geochemistry and organic chemistry industries. Given its strengths, which often complement those of traditional electron-probe-based analyses, it is surprising that SIMS has not found a larger clientele among Researchers studying engineered and biological materials. To illustrate the power of high-spatial-resolution SIMS for the investigation of advanced materials, we summarize a series of experiments examining the microstructure and microchemistry of alloys reinforced with ceramic fibers. The goals of this presentation are twofold: first, to notify the scientific community about the capabilities of imaging SIMS; and second, to elevate (hopefully) the study of metal-matrix composites via SIMS from an important but obscure engineering pursuit to a thriving profession. The principal advantages of the SIMS technique for this study are i) polished, bulk samples can be analyzed (i.e. thinning is not required); ii) the distribution of most elements and isotopes can be measured with submicrometer resolution; iii) the signal-to-noise is very good (essentially no background).
The merger of microscopy and advanced computing: A new frontier for the 21st century
Authors: Ellisman Mark H. , Soto Gabriel E. , Martone Maryann E.
Published: June 2020

Establishing and maintaining state-of-the-art national resources such as HVEM, IVEM and supercomputing centers involves considerable initial cost and continued support of staff with special skills and knowledge. The increased availability of high performance computing and communications offers scientists the potential for effective remote interactive use of such centralized, specialized, and expensive facilities. Anticipating improvements in computing and communications infrastructure, a collaborative computational environment, or “Collaboratory for Microscopic Digital Anatomy” (CMDA), is being developed that will provide a researcher at a remote site distributed interaction with unique instrumentation for the acquisition and manipulation of biological images. The prototype outlined in figure 1 was developed at the San Diego Microscopy and Imaging Resource. The CDMA integrates remote interactive acquisition and analysis of 2- and 3-dimensional electron microscopic data from state-of-the-art digital image acquisition systems such as a computer-controled IVEM. A software system has been developed that provides interactive control of image acquisition from the IVEM from a remote laboratory (and eventually any laboratory on the Internet). Sophisticated software tools for image analysis, visualization, and data management of these digital images are also under development. The system design will provide transparent distribution of tasks that require extensive computation to high performance computers accessible on the network. These tasks include the derivation of 3-dimensional structure using electron microscope tomography, automatic feature extraction for serial section reconstructions as well as manipulation and exploration of 3-dimensional biological datasets.
Evolutionary conservation of ‘Basket’ structure in nuclear pore complexes, and their possible role in mRNA export
Authors: Allen T. D. , Goldberg M. W. , Pelling C. , Solovei I.
Published: June 2020

The nuclear pore complex (NPC) is a macromolecular complex which provides transport through the nuclear envelope. Each NPC has a diameter of around 120 nms, and extends outwards into the cytoplasm by some 20 nms via eight cytoplasmic filaments of granular substructure. On the nucleoplasmic face, NPC ‘cages’ or ‘baskets’ project some 60 nms into the nuclear interior where they terminate in an inner basket ring that supports a further structure, the nuclear envelope lattice (NEL), a network of filaments. Both the NEL and NPC baskets have been visualised to date only in amphibian germinal vesicle nuclear envelopes. All current models of NPC structure are based on data from amphibian oocytes, mainly due to the convenience of isolating clean and well preserved nuclear envelopes. It is important therefore to determine how widely these structures are conserved in other groups throughout the animal kingdom, as a basis for the overall evolutionary conservation of NPC structure.
Three-Dimensional reconstruction of the synaptonemal complex from high-pressure frozen maize meiocytes using IVEM Tomography
Authors: Fung Jennifer C. , Agard David A. , Sedat John W.
Published: June 2020

The synaptonemal complex (SC) is a key macromolecular assembly formed during meiosis of most eukaryotes. It has a crucial role in maintaining synapsis between homologous chromosomes and in ensuring proper segregation of the homologs through the establishment of functional chiasmata. Recently, biochemical and genetic efforts have begun to identify some of the protein components of the SC. As these efforts progress, a more detailed analysis of SC structure will also be needed to incorporate these new components into the overall organization of the SC.

Early efforts into the analysis of SC structure have established that its general architecture is conserved throughout many organisms. The basic features found in every SC are the two lateral elements and the central element, both which run longitudinally between the homologs during the pachytene stage of prophase I. Transverse elements which run perpendicular to the homolog axis through the central region are also often found. Although the general features of the SC are conserved, the internal architecture of these components can differ.
Androgen-induced plasticity at a “vocal” neuromuscular synapse
Authors: Kelley Darcy B. , Tobias Martha L. , Ellisman Mark
Published: June 2020

Brain and muscle are sexually differentiated tissues in which masculinization is controlled by the secretion of androgens from the testes. Sensitivity to androgen is conferred by the expression of an intracellular protein, the androgen receptor. A central problem of sexual differentiation is thus to understand the cellular and molecular basis of androgen action. We do not understand how hormone occupancy of a receptor translates into an alteration in the developmental program of the target cell. Our studies on sexual differentiation of brain and muscle in Xenopus laevis are designed to explore the molecular basis of androgen induced sexual differentiation by examining how this hormone controls the masculinization of brain and muscle targets.

Our approach to this problem has focused on a highly androgen sensitive, sexually dimorphic neuromuscular system: laryngeal muscles and motor neurons of the clawed frog, Xenopus laevis. We have been studying sex differences at a synapse, the laryngeal neuromuscular junction, which mediates sexually dimorphic vocal behavior in Xenopus laevis frogs.
Cisplatin-induced changes in the gastric smooth muscle and its calcium modulation
Authors: Aggarwal S. K.
Published: June 2020

Cisplatin (cis-Dichlorodiammineplatinum II; CDDP) a potent broad spectrum anti-cancer drug produces severe toxic side effects including kidney damage, nausea and vomiting, loss of hearing, peripheral neuropathy, hypomagnesemia and hypocalcemia. Our studies using rat as the model system show that these toxicities are related to calcium homeostasis and can be controlled through the exogenous administration of calcium before CDDP treatment.

Cytochemical and ultrastructural studies in Wistar rats [Crl:(WI)BR] show that CDDP in its hydrolyzed state under low chloride ion concentrations, within the cell, causes uncoupling of oxidative phosphorylation, calcium efflux from the mitochondria, inhibits ATP synthesis, lowers membrane-associated calcium and various membrane transport enzymes. It also induces an increase in the number of lysosomes. CDDP causes a drop in the blood calcium levels with a corresponding increase in the dark cells of the parathyroid gland. In rats CDDP causes hypercontraction of the uterine smooth muscle and an undue distension of the stomach through the noncontractility of its smooth muscle thus inhibiting gastric motility, leading to the development of ulcers.
Mapping the density and mineral phase of calcium in bone at the interface with biomaterials using scanning x-ray microscopy
Authors: Buckley C. J. , Downes S. , Khaleque N. , Bellamy S. J. , Zhang X.
Published: June 2020

Orthopaedic surgery often involves the insertion of a prosthetic implant. For successful and rapid healing, it is important for the prosthesis to make a close and well integrated bond with the bone tissue. To assist this integration, a number of “biomaterials” are on trial as components in the prosthetic implants. Much work is in progress to determine the phase, composition and density of bone mineral at the bone/biomaterial interface. It is expected that the results of this work can be used to develop synthetic calcium phosphates which can be incorporated in prosthetic implants. The composition of bone and biomaterials has been investigated using techniques such as x-ray diffraction, Infra-red, NMR and EXAFS on homogenized samples. However, these studies do not determine the spatial distribution of the bone mineral, its density, localized mineral phase or cellular integration with biomaterials. Electron microscopy with electron probe microanalysis, light and Infra-red microscopy can indicate the presence of mineral in relation to the tissue morphology, but do not give a spatial measure of the density or chemical phase of the mineral at the sub micron level.
Mapping DNA and protein in biological samples using the scanning transmission x-ray microscope
Authors: Zhang X. , Balhorn R. , Jacobsen C. , Kirz J. , Williams S.
Published: June 2020

The Scanning Transmission soft X-ray Microscope (STXM) at the XIA beamline at the National Synchrotron Light Source, Brookhaven National Laboratory, has achieved 50 nm Rayleigh resolution and has been used to image wet biological samples using the natural absorption differences between carbon and water in the water window (between carbon and oxygen K-absorption edges). The step-like jumps in the absorption of soft x-rays by materials as a function of energy have been used for elemental mapping. Examination of these absorption "edges" with high energy resolution resolves fine absorption structures. These fine structures are strongly affected by the atom's local environment, such that they carry detailed information about the atom's chemical state. We have used this chemical sensitivity to distinguish between materials which have similar elemental composition but are chemically different. Images with 50 nm resolution and spectra from a spot size less than (0.2 (μm)2 can be acquired routinely.

Figure 1 shows the x-ray absorption fine structure spectra at the carbon absorption edge from DNA and bovine serum albumin (BSA, a typical protein) taken using the STXM.
Scanning luminescence x-ray microscopy: Progress toward selective staining using microspheres
Authors: Jacobsen C. , Fu J. , Mayer S. , Wang Y. , Williams S.
Published: June 2020

In scanning luminescence x-ray microscopy (SLXM), a high resolution x-ray probe is used to excite visible light emission (see Figs. 1 and 2). The technique has been developed with a goal of localizing dye-tagged biochemically active sites and structures at 50 nm resolution in thick, hydrated biological specimens. Following our initial efforts, Moronne et al. have begun to develop probes based on biotinylated terbium; we report here our progress towards using microspheres for tagging.

Our initial experiments with microspheres were based on commercially-available carboxyl latex spheres which emitted ~ 5 visible light photons per x-ray absorbed, and which showed good resistance to bleaching under x-ray irradiation. Other work (such as that by Guo et al.) has shown that such spheres can be used for a variety of specific labelling applications. Our first efforts have been aimed at labelling ƒ actin in Chinese hamster ovarian (CHO) cells. By using a detergent/fixative protocol to load spheres into cells with permeabilized membranes and preserved morphology, we have succeeded in using commercial dye-loaded, spreptavidin-coated 0.03μm polystyrene spheres linked to biotin phalloidon to label f actin (see Fig. 3).
Computing cell tractions from particle displacements on silicone rubber substrata
Authors: Oliver Tim , Ishihara Akira , Jacobsen Ken , Dembo Micah
Published: June 2020

In order to better understand the distribution of cell traction forces generated by rapidly locomoting cells, we have applied a mathematical analysis to our modified silicone rubber traction assay, based on the plane stress Green’s function of linear elasticity. To achieve this, we made crosslinked silicone rubber films into which we incorporated many more latex beads than previously possible (Figs. 1 and 6), using a modified airbrush. These films could be deformed by fish keratocytes, were virtually drift-free, and showed better than a 90% elastic recovery to micromanipulation (data not shown). Video images of cells locomoting on these films were recorded. From a pair of images representing the undisturbed and stressed states of the film, we recorded the cell’s outline and the associated displacements of bead centroids using Image-1 (Fig. 1). Next, using our own software, a mesh of quadrilaterals was plotted (Fig. 2) to represent the cell outline and to superimpose on the outline a traction density distribution. The net displacement of each bead in the film was calculated from centroid data and displayed with the mesh outline (Fig. 3).
A new family of fluorescent calcium indicators designed to resist leakage or for measuring calcium near membranes
Authors: Poenie Martin , Minta Akwasi , Vorndran Charles
Published: June 2020

The use of fura-2 as an intracellular calcium indicator is complicated by problems of rapid dye leakage and intracellular compartmentalization which is due to a probenecid sensitive anion transporter. In addition there is increasing evidence for localized microdomains of high calcium signals which may not be faithfully reported by fura-2.

We have developed a new family of fura-2 analogs aimed at addressing some of these problems. These new indicators are based on a modified bapta which can be readily derivatized to produce fura-2 analogs with a variety of new properties. The modifications do not affect the chromophore and have little impact on the spectral and metal binding properties of the indicator. One of these new derivatives known as FPE3 is a zwitterionic analog of fura-2 that can be loaded into cells as an acetoxymethyl ester and whose retention in cells is much improved. The improved retention of FPE3 is important for both cuvettebased measurements of cell suspensions and for calcium imaging.