bluuebunny/crossref_metadata_2025 huggingface dataset:
HREM studies of structure, defects and phase transformation in zirconia and Mn stabilised zirconia
Authors: Sharma Renu
Published: June 2020

Zirconia is known to exist in three different structure types: monoclinic, tetragonal and cubic. Monoclinic is the room temperature form that transforms to tetragonal and finally to cubic at progressively higher temperatures. The monoclinic to tetragonal transformation is reversible, exhibits hysteresis and has been widely studied by thermal analysis, high temperature x-ray diffraction and electron diffraction. This transformation has an undesirable effect on some materials properties. The cubic form of zirconia has been stabilised with yttria, calcia, alumina and magnesia. The decomposition of zirconium carbonate and zirconium manganese carbonate to the respective oxides and their phase tranformation has been studied in situ by electron diffraction and high resolution electron microscopy (HREM) and the results are reported here.

The carbonates used in these studies were precipitated from their aqueous solution. Thin crystal fragment were dispersed on holey carbon grids using a suspension in ethanol. A JE0L 4000EX microscope, with double tilt goniometer and on-line Digital MicroVAX II image-analysis system, operating at 400KV, was used for HREM studies.
High-resolution work on zeolites
Authors: Alfredsson V.
Published: June 2020

Zeolites are aluminosilicates with very open frameworks . The structures are characterized by the presence of tunnels or large cavities. The Si and Al sit in the centre of oxygen tetrahedra which are linked together.

HREM work on zeolites has two big disadvantages. The greatest problem is the beam sensitivity of the crystals. After a short time in the electron beam they become amorphous. To improve the stability, the zeolites are made with as high Si/Al ratio as possible, the microscope is run with a very spread electron beam and at low magnification. A TV-camera with an image intensifier is used for focusing. Higher accelerating voltage has also proved to enhance the lifetime of the crystals in the beam. Secondly, an artefact caused by the shape of the contrast transfer function (CTF), gives false information to the images creating dark contrast in areas where there are no atoms. Two different solutions to this problem have been worked out. The first is to change the shape of the CTF by changing the focus and the second by removing the artifact effect caused by the CTF by means of image processing.
Radiation damage in rutile and perovskite
Authors: Buck E.C. , Jones I.P.
Published: June 2020

The radiation damage characteristics of some of the phases of SYNROC, notably rutile and the perovskites, barium titanate and calcium titanate have been investigated. The effects of electron irradiation on a number of simple oxides, such Al2O3 , ZnO and MgO are well documented. The effects are generally more complicated than those in metals, as there are two or more charged species usually of significantly differing masses. Electron irradiated oxides generally form pure edge interstitial loops and undergo a decrease in displacement energy (Ed ) with increasing temperature. The latter effect has been ascribed to the occurrence of two separate displacements, one for the anion and one for the cation, corresponding to the minimum and maximum in the temperature versus displacement voltage curves. Optical measurements have been used to distinguish anion from cation displacements.

Irradiation of rutile in the temperature range 200°C to 400°C with lMeV electrons caused the production of pure edge interstitial unfaulted dislocation loops of the type b=a<100> lying on {100}s planes (FIG. 1.).
Successive observation of hydration growth with cryo-SEM
Authors: Suzuki T. , Ogura K. , Ono A.
Published: June 2020

A cryo-scanning microscope enables us to observe specimens at a temperature as low as 140K. Thus a specimen containing much water can be observed in a frozen state, and morphological changes of specimens such as hydrates can be stopped, for observation at an adequate stage of reaction. The former feature is mainly used for biological specimens. We made an experiment to confirm the possibility of the good use of the latter feature for observation of the hydration process.

When water is added to cement or plaster, the hydrate is grown and its morphology is extremely changed after the reaction. The morphology of the materials before or after the reaction can be observed with a conventional SEM easily. But, morphological changes under reaction cannot be observed by the conventional method. Such an observation, especially successive observation of the same region, is considered to be quite interesting and important.
TEM observation of iron oxide pillars in montmorillonite
Authors: Mori H. , Murata Y. , Yoneyama H. , Fujita H.
Published: June 2020

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.

Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.
Austenite transformation products in quenched low-carbon HSLA steel
Authors: Varughese R. , Howell P. R.
Published: June 2020

The alloy design for the HSLA-100 plate steel aims at optimizing the strength and toughness through developing a refined ferritic microstructure while enhancing the weldability by lowering the carbon levels to 0.04 wt% or less. The austenite grain refining potential of microalloying additions of niobium is coupled with the hardenability effects of Mn, Ni, Cr and Mo to achieve a fine acicular microstructure through water quenching prior to age-hardening through copper precipitation. Wilson et. al, in developing CCT diagrams for these HSLA steels noted that the as-quenched microstructure in the 0.04 wt% carbon steel consisted of a mixture of martensite and bainite and their results indicated that a fully martensitic microstructure at slightly higher carbon levels contributed to enhanced toughness. In this paper, we present our results on the microstructural features found in an oil-quenched sample of the HSLA-100 steel.

The chemical composition (in weight percentage) of the 1 1/4" thick plate steel is given below.
TEM of the tempering reactions in 2.25 Cr 1Mo steel
Authors: Parameswaran P. , Vijayalakshmi M. , Raghunathan V.S.
Published: June 2020

The precipitation of carbides in the ferritic steels, has been the subject of several investigations. This paper discusses the precipitation of carbides in 2.25Cr-1Mo steels. The sequence of changes that occur in the morphology, structure and composition of carbides as a function of tempering temperatures and carbon content, 0.06%C(A) and 0.11%C(B) has been examined in detail.

The steels were austenitized at 1323K for 1h and quenched in flowing argon gas(AQ), followed by tempering in the range 823-1023K for varying durations of time. Structural and chemical information of carbides were obtained using electron diffraction and analytical microscopy respectively. The Cliff-Lorimer ratio method, incorporating theoretically calculated correction factors was employed in the analysis of spectra.

Following AQ, both steels exhibited a mixture of bainite and polygonal ferrite. Fig.1 shows the presence of coarse distribution of carbides in bainite and relatively carbide-free ferrite matrix in steel B. The repartitioning of carbon takes place during AQ and transforms carbon rich regions into bainite. The inset in Fig.1 is the SAD pattern obtained from the bainite, the analysis of which confirms that the precipitates are Fe3C.
Microstructural evolution of modified 9Cr-1Mo steel due to annealing and high-temperature fatigue
Authors: Jones Wendell B. , Hills C.R. , Polonis D.H.
Published: June 2020

The microstructural evolution of Modified 9Cr-lMo steel has been investigated for a variety of conditions, including normalizing, tempering and subsequent annealing. The alleged advantages of the modified alloy for high temperature service, when compared to the standard 9Cr-lMo composition, have been examined for high temperature fatigue conditions; the only difference between the two alloys is the presence of micro additions of V and Nb in the modified alloy.

Air cooling (normalizing) of Modified 9Cr-lMo from 1045°C results in the precipitation of fine (FeCr)3C particles within the martensite laths. Additional carbide precipitation and changes in the dislocation structure occur during the tempering of martensite at 700°C and 760°C after normalizing. The precipitation of M23C6 carbides occurs preferentially at lath interfaces and dislocations. The formation of Cr2C was detected during the first hour of tempering over the range 650-760°C, but was replaced by VC within one hour at 760°C. During prolonged annealing at 550°C-650°C, following tempering, the lath morphology remains relatively stable in the absence of simultaneously applied stresses; partitioning of the laths into subgrains and some carbide coarsening are beginning after 400 hr. annealing at 650°C (Fig. 1), but the lath morphology persists. The martensite lath stability is attributed primarily to the VC precipitates distributed along the lath interfaces (Fig. 2) and promotes improved performance of the Modified 9Cr-lMo alloy over the the standard alloy under static tensile and creep conditions.
Dislocation loops in single-crystal NiAl
Authors: Liu Yaping
Published: June 2020

In the conventional viewpoint, dislocation loops of vacancy type in single crystal NiAl can only exist in Al-rich compositions. Their configurations and their changes when deformation occurs, and their effects on the deformation have not been studied thoroughly.

In the present study, nickel-rich NiAl single crystals of 48.1∼48.6 at %A1 were annealed at 1315°C for 50 hours, then cooled at 200°C/hr to permit vacancy condensation. Single-crystal samples cut with an [001] axis then underwent high temperature (850°C) tensile and cyclic deformation. TEM specimens were cut from the undeformed, 0.3% tensile strain, ±0.5 cyclic and 30∼40% tensile deformation samples.

Two kinds of dislocations, edge and screw, were found in the undeformed NiAl. Edge dislocations consisted of concentric dislocation loops (Fig. 1) and spiral dislocations (dislocation A in Fig. 2). They lie on cubic planes and have cubic line orientations. Invisibility conditions of g.b=0 and g.b x u=0 show that they have <001> type Burgers vectors normal to the loop planes. The shift in image position on changing the sign of g was used to verify that the loops are vacancy in nature.
An atomic model for premartensitic tweed in Ni-Al as derived from HREM images
Authors: Schryvers D. , Tanner L.E.
Published: June 2020

The premartensitic microstructures observed in the quenched Ni1-XAlx (B2) phase have been examined at room temperature by HREM. Depending on the composition the material transforms martensitically to a close-packed 7R (5) stacking at Ms≈200 K (x=0.37) or to the 3R (L10) structure at Ms≈290 K (x=0.36). In CTEM images the premartensitic structure is revealed as the well known two-beam tweed contrast. In HREM phase contrast images a random fine-scale mosaic assembly of micromodulated domains is observed (fig. 1). Fig. 2 shows a single domain in which the intensity modulation can clearly be seen. From images taken under different conditions the following observations (among others) could be made: 1) the micromodulation has an averaged incommensurate wavelength of≈1.3 nm, 2) OD reproduces the <110>* diffuse streaks confirming the static nature and the correlation with the tweed image, 3) each domain exhibits a single modulation, 4) the intensity difference is of the order of 60-85%, 5) some images (e.g., fig. 2) reveal dots elongated perpendicular to the wave-vector, 6) in some cases a small average deviation (≈1%) from the cubic symmetry can be measured. These different characteristics could be explained by assuming, per domain, small transverse shuffle plus shear distortions of the {110}<> type and including a decrease in atom displacement from the center to the edge of each domain. The atomic model and one calculated image are presented in fig. 3.
Diffraction study on bainite of Cu-Al alloy
Authors: Liu Delu , Ko T.
Published: June 2020

Structure of bainite in Cu-Al and Cu-Zn-Al alloys has been reported as 3R, 9R or 18R long period stacking structure (LPS) by X-ray and electron diffraction studies. In the present work, a Cu-25.5 (at)% Al alloy sample was heated at 900°C for 2 h then isothermally held at 450°C for 60 s before quenching into iced brine. FIG.1 shows a TEM bright field image of bainite plates (marked B) grown from grain boundary. The parent phase ( with DO3 structure ) has transformed to martensite (marked M ) during cooling from 450° C to 0°C. Both bainite and martensite plates have dense striations inside.

Careful diffraction study on a JEOL 2000FX TEM with accelerating voltage 200 KV revealed (FIG.2) that the diffraction patterns contai_ning the same zone axis [001] ( hexagonal index ) or [111]c ( cubic index ) are from a bainite plate with obtuse V-shape. They are indexed as [010], [140], [130], [120], [230], [340] and [110] zone pattern for hexagonal system respectively.
A new alloy phase produced in the co-deposited Bi-Mn films in a composition range 50-30 at% Mn
Authors: Yamada Takashi , Yoshida Kentaroh
Published: June 2020

Only one alloy phase, MnBi, is described to exist in the equilibrium phase diagram of Bi-Mn system. However, other alloy phase than MnBi were successfully prepared by the present authors by making use of vacuum deposition techniques. One of them is a metastable Mn3Bi, which forms in co-deposited films whose composition are in a range, 85 to 65 at% Mn. The authors are now investigating the films in a neighboring composition range, 50 to 30 at% Mn.

The films in the as-deposited state, which are prepared by the co-deposition and has a composition in this range, show halos and Debye-Sherrer rings in diffraction patterns. The rings can be indexed as those of Bi type lattice even though as much as 50 to 30 at% Mn must be included in the film. No crystal grains of Mn nor of any other alloy phases were detected in the micrograph. When the films was warmed up ty irradiating with an intense electron beam in an microscope, new crystals were observed to appear and grow. Figure 1 is a bright-field image showing this change in the film of 37.9 at% Mn. The intense beam was focused at the central part of the figure and black areas at this place are the crystals produced by this heating. Small grains surrounded by the black areas are the Bi type crystals which are going to suffer from the change. Other part of the figure than this central region, including these small grains, still show diffuse halos and the Bi type Debye-Sherrer rings. Black areas eating these unreacted regions are single crystalline for the most cases. Two of diffraction patterns taken from these black areas are shown in Figs. 2 and 3.
Interface state and bonding effect of clay mineral-organic polymer composite material
Authors: Chenghuang Xu , Kaiyi Chen
Published: June 2020

The urgent need of new types of materials accelerates the research and development of polymeric composite material, among them the ones composed of organic polymer and inorganic polymeric particles are very spectacular.

Clay mineral particles are inorganic nonmetallic particles of layered structure. As a rich and cheap resource, clay mineral has found wide applications in polymeric composite material industry, but its frequent use is no more than a filler. For heighten its use value, it is imperative to make full use of its structural property by trying various pretreatments. To this end, kaolin , the strengthening agent of rubber, is chosen as the object and SEM-EDS analysis are chosen as the means of our study. Our study centers on: a) the influence of activation and modification on the structure and surface state of kaolin particles; b) the interface state of modified kaolin and rubber and their bonding effect.
Observations on a fibrous form of silicon carbide
Authors: Otero Diaz L.C. , Landa Canovas A.R. , Hansen S. , Hyde B.G.
Published: June 2020

During a phase and structure analysis of the ytterbium sulphide system we observed, in addition to various ytterbium sulphides , some fibrous crystals ≃10-100 μm long, ≃0.5 μm diameter, e.g. Fig.10. In the optical microscope they were seen to be crystalline, white and transparent. In the electron microscope planar defects were seen in parts of them; usually normal to the fibre axis, and often closely aggregated into groups, e.g. Figs. 1a and 2a, which were taken with JE0L 2000 FX and 4000 EX microscopes.

The fibre morphology was unexpected, and ytterbium sulphides (with the exception of Yb2S3, which is yellow)are black and metallic in appearance. Futhermore the electron diffraction patterns from the fibres did not correspond to any knownor possible YbS phase/ structure.

EDSxanalysis (with a LINK AN 10000, JE0L 2000 FX microscope) revealed the presence of Si in the fibres, but not heavier elements.
Characterization of defects in tabular silver halide grains
Authors: Goessens C. , Schryvers D. , Van Landuyt J. , Verbeeck A. , De Keyzer R.
Published: June 2020

Silver halide grains (AgX, X=Cl,Br,I) are commonly recognized as important entities in photographic applications. Depending on the preparation specifications one can grow cubic, octahedral, tabular a.o. morphologies, each with its own physical and chemical characteristics. In the present study crystallographic defects introduced by the mixing of 5-20% iodide in a growing AgBr tabular grain are investigated. X-ray diffractometry reveals the existence of a homogeneous Ag(Br1-xIx) region, expected to be formed around the AgBr kernel. In fig. 1 a two-beam BF image, taken at T≈100 K to diminish radiation damage, of a triangular tabular grain is presented, clearly showing defect contrast fringes along four of the six directions; the remaining two sides show similar contrast under relevant diffraction conditions. The width of the central defect free region corresponds with the pure AgBr kernel grown before the mixing with I. The thickness of a given grain lies between 0.15 and 0.3 μm: as indicated in fig. 2 triangular (resp. hexagonal) grains exhibit an uneven (resp. even) number of twin interfaces (i.e., between + and - twin variants) parallel with the (111) surfaces. The thickness of the grains and the existence of the twin variants was confirmed from CTEM images of perpendicular cuts.
Microstructural characterization of Ca2SiO4 particles in a CaZrO3 and a MgO matrix
Authors: Kim Y. J. , Mast E. , Hou T. I. , Kriven W. M.
Published: June 2020

Dicalcium silicate (abbreviated C2S) has five polymorphs at atmospheric pressure. The monoclinic (β) to orthorhombic (γ) transformation is accompanied by a 12 % volume increase on cooling and a 4.6° unit cell shape change. These analogies to ZrO2 make C2S a potential transformation toughener. Recently C2S particles have been successfully mixed with a calcium zirconate (abbreviated CZ) phase to form a composite ceramic with a microstructure similar to ZTA.

The two composites were prepared in different ways. For the C2S/CZ composite, C2S powder was prepared by the Pechini method with starting materials of Ca(NO3)2 and colloidal silica. 10 vol % C2S was mixed with CZ and sintered at 1600°C for 2 hours. For the C2S/MgO composite, C2S powder was formed by reaction of SiO2.xH2O and CaCO3 at 1450°C. Solutions containing 15 vol % C2S were mixed with solutions of fine magnesia containing an acrylic resin. The suspension was dried and sintered at 1600°C for 3.5 hours. Microstructures of both composites were examined by SEM and TEM.
Microstructural study of the effects of potassium vapour on carbonised materials
Authors: Garrick L.S. , Fryer J.R. , Baird T.
Published: June 2020

Metallurgical coke in the blast furnace provides a permeable matrix through which reducing gases may ascend and molten materials descend. A lack of permeability will inevitably lead to a poor gas distribution and result in a reduction of the furnace output and efficiency.

A decrease in the permeability of the carbonaceous coke matrix arises when changes induced by the blast furnace environment occur in the properties of the material and effect the matrix voidage by causing a reduction of coke strength. A major influence of change within the blast furnace is the presence of recirculating alkali, particularly potassium, which is known to induce considerable microstructural changes (enhanced localised ordering), within the metallurgical coke. These microstructural changes lead to structural weakening as a consequence of a variety of factors:-
A new type of liquid crystalline structure- The chiral smectic E phase of a comb-shaped polymer
Authors: Li L. S. , Stupp S. I.
Published: June 2020

The polymer investigated here is a comb-shaped macromolecule containing long chiral teeth. The highly dipolar -CN group is part of the stereogenic center located in an aliphatic spacer between aryl units. This center occurs with a high degree of configurational order, thus yielding a chiral molecule of high enantiomeric purity. The chemical structure of the polymer is shown below, Thin films of this polymer were prepared using a solution casting technique and examined in a Philips 420 electron microscope.Fig. 1 shows a selected area electron diffraction pattern of the film, indicating that reflections are distributed with hexagonal symmetry. However this pattern cannot be indexed by hexagonal unit cell parameters but only orthorhombic ones having the values, a=8.24Å, b=5.34Å, γ=90° . The observed d-spacings and their indices are listed in Table 1. Based on Table 1 it is obvious that the lattice of the polymer is orthorhombic and the c axis (the side-chain axis ) is perpendicular to the film.
Observation of the Sulphur Atoms in Cu2S Using HREM
Authors: Yu Y.D. , Guan R. , Kuo K.H. , Hashimoto H.
Published: June 2020

We have indicated that the lighter atoms such as oxygen in Cu2O can be observed at the specimen with optimal thicknesses based on the dynamic effect of electron diffraction(1). This rule in principle should hold good for the imaging of other lighter atoms such as sulphur atom in Cu2S. However, this point of view needs further experimentally confirm because up to now only oxygen atoms have been observed in Cu2O and a series of new suboxides of copper and nickel (2). In addition, the sulphur atom is much heavier than oxygen one though is still lighter than copper atom. In the present report we provide such a confirmation.

The crystallites of Cu2S shown in Fig.l were obtained by sulfurizing at 300°C of the copper thin film which was sealed in a glass tube with mg sulphur left on the tube wall in a vacuum of about 10-2 Pa. The energy dispersive spectrocscopy analysis indicated that they are the sulfides and the electron diffraction analysis indicated they have anti-fluorite structure.
New form of Transmission Cross Coefficient for High-Resolution Imaging
Authors: Ishizuka Kazuo
Published: June 2020

It is well known that taking into account spacial and temporal coherency of illumination as well as the wave aberration is important to interpret an image of a high-resolution electron microscope (HREM). This occues, because coherency of incident electrons restricts transmission of image information. Due to its large spherical and chromatic aberrations, the electron microscope requires higher coherency than the optical microscope. On an application of HREM for a strong scattering object, we have to estimate the contribution of the interference between the diffracted waves on an image formation. The contribution of each pair of diffracted waves may be properly represented by the transmission cross coefficients (TCC) between these waves. In this report, we will show an improved form of the TCC including second order derivatives, and compare it with the first order TCC.

In the electron microscope the specimen is illuminated by quasi monochromatic electrons having a small range of illumination directions. Thus, the image intensity for each energy and each incident direction should be summed to give an intensity to be observed. However, this is a time consuming process, if the ranges of incident energy and/or illumination direction are large. To avoid this difficulty, we can use the TCC by assuming that a transmission function of the specimen does not depend on the incident beam direction. This is not always true, because dynamical scattering is important owing to strong interactions of electrons with the specimen. However, in the case of HREM, both the specimen thickness and the illumination angle should be small. Therefore we may neglect the dependency of the transmission function on the incident beam direction.
Structure of PhoE Porin as Determined by Electron Crystallography
Authors: Jap Bing K.
Published: June 2020

PhoE porin is a member of a family of pore forming proteins that are found in the outer membrane o Gram-negative bacteria. In E. coli , there are a variety of porins, such as OmpF, OmpC and PhoE. These porins have been shown to have no specific binding site for substrate although PhoE porin has been demonstrated to have some selectivity for anions and phosphate-containing compounds. Porins font general diffusion channels allowing small molecules, such as nutrients and waste products, of less that about 600 daltons, to diffuse freely across the membrane. In addition, porins also act as receptors for various bacterial phages. The closing and opening of the porin channels have been shown, at least, in vitro , to be voltage-gated.

We have purified PhoE porin and reconstituted the purified protein with lipid, forming two-dimensional crystalline patches. The crystalline patches diffract to resolution better than 3.0Å. We have collected diffraction patterns of PhoE porin embedded in trehalose at various tilt angles up to about 60 degrees. The diffraction patterns were combined to form a complete 3-D diffraction data set. The diffraction data show that there are two orientations of B-strands, one with the strand axis normal to the membrane plane and the other with the axis tilted about 35 degrees from the membrane normal. This is consistent with projectior map of PhoE porin at 3.5Å resolution which shows that a significant fraction of the 6-sheet strands an oriented with the strand axis almost normal to the membrane plane.
Cryo-Electron Microscopy and Correlation Averaging of Frozen-Hydrated, Polymorphic 2D Crystals of the Mitochondrial Outer Membrane Channel
Authors: Guo Xiao-Wei
Published: June 2020

Voltage-dependent, anion-selective channels (VDAC) are formed in the mitochondrial outer membrane (mitOM) by a 30-kDa polypeptide. These channels form ordered 2D arrays when mitOMs from Neurospora crassa are treated with soluble phospholipase A2. We obtain low-dose electron microscopic images of unstained specimens of VDAC crystals preserved in vitreous ice, using a Philips EM420 equipped with a Gatan cryo-transfer stage. We then use correlation analysis to compute average projections of the channel crystals. The procedure involves Fourier-filtration of a region within a crystal field to obtain a preliminary average that is subsequently cross-correlated with the entire crystal. Subregions are windowed from the crystal image at coordinates of peaks in the cross-correlation function (CCF, see Figures 1 and 2) and summed to form averages (Figure 3).

The VDAC channel forms several different types of crystalline arrays in mitOMs. The polymorph first observed during phospholipase treatment is a parallelogram array (a=13 run, b=11.5 run, θ==109°) containing 6 water-filled pores per unit cell. Figure 1 shows the CCF of a sub-field of such an “oblique” array used to compute the correlation average of Figure 3A. With increased phospholipase treatment, other polymorphs are observed, often co-existing within the same crystal. For example, two distinct (but closely related) types of lattices occur in the field corresponding to the CCF of Figure 2: a “contracted” version of the parallelogram lattice (a=13 run, b=10 run, θ=99°), and a near-rectangular lattice (a=8.5 run, b=5 nm). The pattern of maxima in this CCF suggests that a third, near-hexagonal lattice (a=4.5 nm) may also be present. The correlation averages of Figures 3B-D were computed from polycrystalline fields, using peak coordinates in regions of CCFs corresponding to each of the three lattice types.
Three-Dimensional Structure of Cobalt-Tetrammine-ATP Induced Membrane Crystals of Na,K-ATPase
Authors: Skriver Elisabeth , Hebert Hans , Kavéus Urban , Maunsbach Arvid B.
Published: June 2020

2-D membrane crystals of renal Na,K-ATPase have been induced to obtain structural information about the sodium pump. Crystalline arrays of the p21 and the p1 type formed during incubation in media containing vanadate and magnesium have been analyzed by image processing and the 3-D structures determined. We report here a new 3-D structure reconstructed from membrane crystal with p4 symmetry that were formed during incubation with cobalt-tetrammine-ATP (Co(NH3)4ATP) which is an MgATP analogue complex that binds to the enzyme and stabilizes it in an E2conformational state.

Membrane-bound Na,K-ATPase purified from renal outer medulla was incubated in 0.5 mM Co(NH3)4ATP and 0.5 mM CoCl2for one hour at 37°C and then at 4°C for 28 days. Tilt series of crystalline membrane fragment negatively stained with 1% uranyl acetate were recorded in a Jeol 100CX electron microscope at angels from −60° to +60° with increments of 6°. Electron micrographs of the tilt series were digitized into 512 × 512 pixel squares using a EIKONIX 1412 scanner and image processing performed with the "EM" program system.
Design of the VG HB603 300kV Field-Emission STEM
Authors: von Harrach H.S. , Colling J.A. , Keyse R. , Morphew J.
Published: June 2020

A new generation of UHV field-emission STEMs operating at up to 300 kV has been designed by VG Microscopes. The design philosophy of these instruments has been to improve further the analytical performance achieved by 100 kV cold field-emission STEMs, such as the VG HB501 series.

There are three types of instrument with a common basic design:

HB603: an analytical STEM with optimised X-ray microanalysis (0.3srad collection angle per detector) and parallel/serial electron energy-loss facilities;

HB603U: a high-resolution STEM with optimised high-angle dark-field detection and < 0.13 nm resolution;

HB603S: a full UHV STEM with Auger analyser and specimen preparation facilities at 3 × 10-10 mbar pressure throughout the instrument.
A New Illumination System for an Analytical Transmission Electron Microscope Using a Condensor Objective Lens
Authors: Benner Gerd , Bihr Johannes , Prinz Manfred
Published: June 2020

The most suitable objective lens for an analytical transmission electron microscope (TEM) is the single-field condensor objective lens developed by Riecke/Ruska [1]. This lens permits both high-resolution TEM operation and the generation of small electron probes needed for the analytical, microditfraction and scanning transmission electron microscope (STEM) modes. The symmetrical position of the specimen allows maximum specimen tilting and an optimum detector arrangement (EDX, SE, BSE). For this type of lens in TEM illumination mode an auxiliary lens has to be used or the excitation of the objective lens must be changed. This paper describes an automated illumination system which realizes the Koehler illumination [2] and does not require an auxiliary lens.

An illumination system for use in an analytical TEM must meet the following requirements:
Computer-Assisted Microscope Alignment
Authors: Marks L.D.
Published: June 2020

Full alignment of a high resolution electron microscope, including alignment of the beam tilt, is a very difficult process. Whereas astigmatism correction is relatively straightforward, correcting the beam tilt is by no means so simple and there is a strong interaction between astigmatism and tilt so that it is possible to apparently correct the two at one defocus. To overcome this problem, the method of applying a ± tilt oscillation to the beam has been introduced previously, the principle being to adjust the texture of an amorphous carbon film image so that it is symmetric with respect to the tilt oscillations. This procedure works, but in practice is not easy to use and there are additional experimental problems in terms of loss of intensity due to insufficiently corrected beam shift/tilt purity.

As an extension of this process, and as a general extension of astigmatism correction as well, we have developed a procedure for providing a computer generated optical diffraction pattern to compliment the standard TV image. One critical problem was providing optical diffraction patterns at a sufficiently rapid speed to make the process experimentally viable; one optical diffraction pattern every 5 seconds for example is too slow. The numerical procedure can be broken down into a number of different steps:
Yag Single Crystals for Scintillators of Stem
Authors: Hibino M. , Irie K. , Autrata R. , schauer P.
Published: June 2020

Although powdered phosphor screens are usually used for scintillators of STEM, it has been found that the phosphor screen of appropriate thickness should be used depending on the accelerating voltage, in order to keep high detective quantum efficiency. 1 It has been also found that the variation in sensitivity, due to granularity of phosphor screens, makes the measurement of fine electron probe difficult and that the sensitivity reduces with electron irradiation specially at high voltages.

In order to find out a preferable scintillator for STEM, single crystals of YAG (yttrium aluminum garnet), which are used for detecting secondary and backscattered electrons in SEM were investigated and compared with powdered phosphor screens, at the accelerating voltages of 100kV and 1 MV. A conventional electron detection system, consisting of scintillator, light guide and PMT (Hamamatsu Photonics R268) was used for measurements. Scintillators used are YAG single crystals of 1.0 to 3.2mm thicknesses (with surfaces matted for good interface to the light guide) and of 0.8mm thickness (with polished surface), and powdered P-46 phosphor screens of 0.07mm and 1.0mm thicknesses for 100kV and 1MV, respectively. Surfaces on electron-incidence side of all scintillators are coated with reflecting layers.
S/N Ratio Characteristics of the Imaging Plate System for A TEM
Authors: Oikawa T. , Mori N. , Osuna T. , Ohnishi M. , Kawasaki M.
Published: June 2020

The fundamental characteristics of the Imaging Plate System for a TEM (TEM-IP System) have already been ascertained and the system has began to be put to practical use in various fields of transmission electron microscopy. When considering the practicability of any image recording device, the “image quality” is an important factor.

In this study, the S/N ratio of the TEM-IP System, one of the evaluation factors for the “image quality” of the system is estimated.

Signal measurement was carried out under two readout conditions high resolution mode (HR-Mode) and high sensitivity mode (HS-Mode), which are available in the IP-reader of the PIXsysTEM. In order to distinguish between instrumental noise (system noise) and noninstrumental noise (quantum noise), the S/N ratio was measured as a function of the electron dose, and the dose was widely varied in the dynamic range of the system.
Towards Composition Determination in Compound Semiconductors by High-Angle Annular Dark-Field Imaging
Authors: Martin J L , Chapman J N , Nicholson W A P , Stanley C R , Kean A H
Published: June 2020

An analytical technique with high spatial resolution is required to investigate the composition of thin layers in compound semiconductor multilayer specimens. The techniques currently in use in TEM can broadly be divided into those in which element-specific signals are collected (e.g. EDX) and those in which compositional information is inferred from the variation in the position or magnitude of some contrast feature in the image (e.g. the displacement of thickness fringes in a wedge-shaped sample ). In this paper we report on the determination of the atomic fraction of Al, denoted x, in the Alx Ga1-x As/GaAs

system by analysis of high-angle annular dark field (HADF) images. The principal advantage of using an imaging technique is that the required information is contained in the variation of a signal proportional to an elastic scattering or a thermal-diffuse scattering cross-section rather than one related to an inner shell excitation. As the former are generally a few orders of magnitude larger than the latter it is possible to obtain an image from a wide area of specimen in the time that is required to collect an adequate EDX spectrum from a single position. Thus accumulation of the required information is much more rapid. Instances where it is desirable to perform a quantitative assay over a wide area include specimens in which there are graded interfaces where the atomic fraction varies continuously (e.g. to obtain specific light-guiding properties) or specimens which are deposited at elevated temperatures where Ga desorption can lead to significant variations from the expected composition. In both circumstances it is useful to make measurements at several locations in planes perpendicular to the growth direction. This is possible using techniques where cross-sectional specimens are employed but not where the presence of a wedge is essential.
Nanoseconds Double-Frame and Streak Transmission Electron Microscopy
Authors: Bostanjoglo Oleg , Kornitzky Jochen
Published: June 2020

Material processing and synthesis is increasingly done by lasers. In order to apply this modern tool effectively, the laser-induced physical processes must be well known. As transmission electron microscopy is a powerful method to study the structure of the treated material, it seemed worthwhile to extend this technique for fast phase transitions, as are triggered by laser radiation. High-speed TEM may be realized either by pulsing the detector /l/ or the illuminating electron beam. The latter technique is more convenient and is described here.

Fig. 1 shows a high-speed TEM designed for taking either double frame images (exposure/ repetition times ≿ 10 ns/≿ 50 ns) or streak images of transitions induced by a laser in the thin film specimen. It consists of a modified commercial TEM, an attached Q-switched (FWHM 50 ns), frequency-doubled (532 nm) Nd:YAG laser for treating the specimen, and electronics for electron beam pulsing and image storage. The TEM is equipped with focusing/deflecting optics for the laser radiation, an electron beam pulser generating either the exposure times for double frame pictures or the streak, and an image shifter. The image detector is a proximity focusing double stage MicroChannel Plate (MCP)/scintillator assembly. A CCD camera transfers the image to a PC-backed digitizing and frame grabbing card. The components are synchronized by a specially designed logic unit /2/.
New Feasible Concepts of Aberration Correction for Realizing High-Resolution Electron Microscopes
Authors: Rose H.
Published: June 2020

The imaging performance of the light optical lens systems has reached such a degree of perfection that nowadays numerical apertures of about 1 can be utilized. Compared to this state of development the objective lenses of electron microscopes are rather poor allowing at most usable apertures somewhat smaller than 10-2 . This severe shortcoming is due to the unavoidable axial chromatic and spherical aberration of rotationally symmetric electron lenses employed so far in all electron microscopes.

The resolution of such electron microscopes can only be improved by increasing the accelerating voltage which shortens the electron wave length. Unfortunately, this procedure is rather ineffective because the achievable gain in resolution is only proportional to λ1/4 for a fixed magnetic field strength determined by the magnetic saturation of the pole pieces. Moreover, increasing the acceleration voltage results in deleterious knock-on processes and in extreme difficulties to stabilize the high voltage. Last not least the cost increase exponentially with voltage.
Electron Holography Improving Transmission Electron Microscopy
Authors: Lichte Hannes
Published: June 2020

Generally, the electron object wave o(r) is modulated both in amplitude and phase. In the image plane of an ideal imaging system we would expect to find an image wave b(r) that is modulated in exactly the same way, i. e. b(r) =o(r). If, however, there are aberrations, the image wave instead reads as b(r) =o(r) * FT(WTF) i. e. the convolution of the object wave with the Fourier transform of the wave transfer function WTF . Taking into account chromatic aberration, illumination divergence and the wave aberration of the objective lens, one finds WTF(R) = Echrom(R)Ediv(R).exp(iX(R)) . The envelope functions Echrom(R) and Ediv(R) damp the image wave, whereas the effect of the wave aberration X(R) is to disorder amplitude and phase according to real and imaginary part of exp(iX(R)) , as is schematically sketched in fig. 1.

Since in ordinary electron microscopy only the amplitude of the image wave can be recorded by the intensity of the image, the wave aberration has to be chosen such that the object component of interest (phase or amplitude) is directed into the image amplitude. Using an aberration free objective lens, for X=0 one sees the object amplitude, for X= π/2 (“Zernike phase contrast”) the object phase. For a real objective lens, however, the wave aberration is given by X(R) = 2π (.25 Csλ3R4 + 0.5ΔzλR2), Cs meaning the coefficient of spherical aberration and Δz defocusing. Consequently, the transfer functions sin X(R) and cos(X(R)) strongly depend on R such that amplitude and phase of the image wave represent only fragments of the object which, fortunately, supplement each other. However, recording only the amplitude gives rise to the fundamental problems, restricting resolution and interpretability of ordinary electron images:
Holographic Interference Electron Microscopy by Numerical Reconstruction Method
Authors: Ohshita Akinori , Minamide Hiroshi , Saito Yahachi , Tomita Hiroshi
Published: June 2020

Holographic interference electron microscopy has recently been put to practical use with a field-emission electron microscope. In this microscopy, the optical image reconstruction method are usually used, but many practical difficulties such as optical adjustment are always accompanied. On the other hand, the numerical image reconstruction method has many advantages. In this paper, therefore, holographic interference electron microscopy are tried by using a numerically reconstructed image.

In the first step, an off-axis Fresnel electron hologram (Fig.1) was formed in a 100 kV thermionic-emission electron microscope equipped with an electron biprism. MgO smoke particles were used as a specimen. A reconstructed image is given by the convolution of amplitude transmittance of an electron hologram with propagation function from a hologram plane to an image reconstruction plane. In the second step for the numerical reconstruction, the hologram was enlarged and printed on a photographic paper.
CRYO-Electron Microscopy of Reovirus Intermediate Subviral Particles
Authors: Wang Guoji , Dryden Kelly A. , Coombsf Kevin M. , Furlongt Deirdre B. , Timothy Baker S.
Published: June 2020

Reovirus, the type member of the Reoviridae family, contains a segmented dsRNA genome, a multi-shell protein capsid structure, and transcriptase activity. The virus has been extensively characterized biochemically and genetically, although details of the structural organization of the RNA and protein components are not completely established. Reovirus contains eight structural proteins, three in the outer capsid (σ1, σ3, μ1C) and five associated with the core capsid (σ2, λl, λ2, λ3, μ2) . A number of morphogenetically related viral products including mature virions, cores and intermediate subviral particles (ISVP) exist naturally in the host cell. ISVPs are similar to virions, but lack σ3, and the cell recognition protein, σl extends radially outward from the viral surface by ∽40 nm. We have initialized a study of the structure of unstained, frozen-hydrated ISVPs using cryo-electron microscopy and three-dimensional image reconstruction techniques.

ISVP samples were generated by digesting purified reovirus with α-chymotrypsin for 20 minutes.Aliquots of 4μl were applied to freshly-prepared, perforated carbon films, blotted with filter paper and rapidly plunged into liquid ethane. The sample was maintained at∽-170°C and images were recorded in a Philips EM420 microscope at ∽1 μm underfocus and at a nominal magnification of 30,000 × with an electron dose <1000e-/nm2.
Three-Dimensional Structure of Cloned T3 Connector Protein at 1.6nm Resolution
Authors: Carrascosa José L. , Valpuesta José M. , Fujisawa Hisao
Published: June 2020

The head to tail connector of bacteriophages plays a fundamental role in the assembly of viral heads and DNA packaging. In spite of the absence of sequence homology, the structure of connectors from different viruses (T4, Ø29, T3, P22, etc) share common morphological features, that are most clearly revealed in their three-dimensional structure. We have studied the three-dimensional reconstruction of the connector protein from phage T3 (gp 8) from tilted view of two dimensional crystals obtained from this protein after cloning and purification.

DNA sequences including gene 8 from phage T3 were cloned, into Bam Hl-Eco Rl sites down stream of lambda promotor PL, in the expression vector pNT45 under the control of cI857. E R204 (pNT89) cells were incubated at 42°C for 2h, harvested and resuspended in 20 mM Tris HC1 (pH 7.4), 7mM 2 mercaptoethanol, ImM EDTA. The cells were lysed by freezing and thawing in the presence of lysozyme (lmg/ml) and ligthly sonicated. The low speed supernatant was precipitated by ammonium sulfate (60% saturated) and dissolved in the original buffer to be subjected to gel nitration through Sepharose 6B, followed by phosphocellulose colum (Pll) and DEAE cellulose colum (DE52). Purified gp8 appeared at 0.3M NaCl and formed crystals when its concentration increased above 1.5 mg/ml.