bluuebunny/crossref_metadata_2025 huggingface dataset:
The experimental determination of the surface ionization value φ(0) for Al-Kα radiation
Authors: Bastin G.F. , Dijkstra J.M. , Heijligers H.J.M.
Published: June 2020

The surface ionization value (φ(0)) plays a crucial role in matrix correction procedures, not only in bulk applications under extreme conditions (ultra-light element radiations) but certainly also in thin-film applications. By definition the (φ(0) value for the x-radiation of a particular element is the ratio between the x-ray intensity emitted by an infinitely thin film of that element on a substrate and the intensity emitted from the same unsupported film. In an earlier publication we described our work on setting up data bases of systematic thin-film measurements. In this work we deposited several elements (Al, Pd) in six different thicknesses (10 to 320 nm) onto a wide variety of polished substrates (Be up to Bi) and the x-ray intensities of the film elements were measured over a wide range in accelerating voltage (3 to 30 kV). In the same deposition runs the same films were deposited onto rock salt crystals.
Characterization of Mo/SiO2 interfacial reactions in metal halide arc tube by analytical TEM
Authors: Jeon S.J. , Sung C. , Chao Chung
Published: June 2020

The purpose of this study is to investigate the interfacial reactions between Mo foil and quartz in metal halide arc tubes. After welding to a tungsten cathode, the Mo foil was specially treated before Mo/SiO2 pinch seal operation. Mo foils in arc tubes show different performance in lamp depending on the type of the treatment. Mo/SiO2 interfacial reactions and amounts of Mo diffusion into the SiO2 were analyzed using TEM, SEM and EDS in order to understand the different properties of arc tubes.

Arc tubes were treated with one of the following conditions : (A)untreated, (B)dry hydrogen fired, (C)process “B” plus humidity exposure. Cross-sectional TEM and SEM samples in the longitudinal direction of the arc tube through the center of Mo foil were prepared. Two Mo/SiO2 interfacial areas, one near the end of the W cathode and the other the longitudinal center of the foil were compared each other.
A computer-generated three-dimensional view of the developing human biliary system
Authors: Vijayan V. , Tan CEL
Published: June 2020

With the advent of computers, microscopy has entered an exciting new era of computerised three dimensional (3D) reconstruction. Using serial sections, it is now possible to generate complex 3D images, that can be rotated at various angles to study the organ systems of interest. In this project, the first of its kind, we have used computer generated 3D reconstruction to study the developing human biliary system.

The human biliary system consists of the extra and intrahepatic components. The extrahepatic system develops from the embryonic hepatic diverticulum and is tubular from the start. The intrahepatic bile ducts arise from the Ductal Plate. The Ductal Plate comprises of sheets of biliary epithelium, with discontinuous luminal spaces, that appear within the mesenchyme along the portal vein branches. The Ductal Plate is remodelled into tubular definitive bile ducts by an orderly process of epithelial deletion and selection which occurs between 11-13 weeks of gestation
Morphological evolution of nanometer-sized BaTiO3particles
Authors: Chun C. M. , Navrotsky A. , Aksay I. A.
Published: June 2020

Highly pure, stoichiometric, nanometer-sized, and fairly monodispersed anhydrous crystalline BaTiO3particles are synthesized under hydrothermal conditions in a single process step without further heat treatment by reacting titanium isopropoxide [Ti(OC3H7)4] precursor in aqueous solutions of Ba(OH)2at 80°C. Traditional considerations of solution hydrolysis, solute condensation, and nucleation only partly explain the generation of the “raspberry-like” BaTiO3particles composed of 5∼10 nm primary crystalline particles. Consequently, the colloidal interaction of the precipitating particles and, therefore, controlled aggregation of freshly nucleated particles must be taken into account. Our TEM studies show aggregation growth of small subunits to form uniform, rounded polyhedral particles, suggesting colloidal stability may play a key role in controlling precipitate size and shape.

In order to investigate the evidence supporting the aggregation growth, Ti(OC3H7)4precursor (Aldrich) has been added to l.OM Ba(OH)2solution and hydrothermally reacted at 80°C in polyethylene bottles. Four molecules of water and two hydroxyl ions attach through their oxygen atoms to the titanium of Ti(OC3H7)4in a nucleophilic process.
Multi-mode light microscopy of microtubule assembly dynamics and chromosome movement in vivo and In vitro
Authors: D. Salmon E. , Waters J. C. , Waterman-Storer C.
Published: June 2020

We have developed a multi-mode digital imaging system which acquires images with a cooled CCD camera (Figure 1). A multiple band pass dichromatic mirror and robotically controlled filter wheels provide wavelength selection for epi-fluorescence. Shutters select illumination either by epi-fluorescence or by transmitted light for phase contrast or DIC. Many of our experiments involve investigations of spindle assembly dynamics and chromosome movements in live cells or unfixed reconstituted preparations in vitro in which photodamage and phototoxicity are major concerns. As a consequence, a major factor in the design was optical efficiency: achieving the highest image quality with the least number of illumination photons. This principle applies to both epi-fluorescence and transmitted light imaging modes. In living cells and extracts, microtubules are visualized using X-rhodamine labeled tubulin. Photoactivation of C2CF-fluorescein labeled tubulin is used to locally mark microtubules in studies of microtubule dynamics and translocation. Chromosomes are labeled with DAPI or Hoechst DNA intercalating dyes.
Quantitative elemental analysis of bacterial polyphosphate bodies using scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy
Authors: Goldberg J. , Gonzalez H. , Jensen T.E. , Corpe W.A.
Published: June 2020

The elemental composition of polyphosphate bodies (PPB's) has been determined qualitatively previously using energy dispersive x-ray spectrometers (EDX) and in bodies isolated from cells. In this present study we determine in several bacteria their quantitative elemental composition using EDX in conjunction with a STEM.

Bacteria were grown as previously described or were collected from natural sources. Portions of each sample were air dried on formvar coated grids. Separate samples were fixed and embedded in Epon. For x-ray analysis cells of interest were first located using the TEM mode. The microscope was then switched to the STEM mode. Analysis of cell components was carried out in the spot mode (75 kV) of the STEM. The spot diameter at 100,000x is approximately 20nm. The objective lens current was adjusted so a total x-ray count of 600 to 1,000 cps was attained for the 100 sec. count time. Spectra were collected on a PGT IMIX (EDX). The data was analyzed using a bulk sample analysis program (ZAF method) in standardless mode (w/w). Latex spheres of known density (1.05 g per cu cent) and volume were analyzed to obtain a standard (mass/weight).
Multiple-fracturing and viewing of the same frozen sample at different depths using a low temperature FESEM
Authors: Parthasarathy M.V. , Daugherty C.
Published: June 2020

The versatility of Low Temperature Field Emission SEM (LTFESEM) for viewing frozen-hydrated biological specimens, and the high resolutions that can be obtained with such instruments have been well documented. Studies done with LTFESEM have been usually limited to the viewing of small organisms, organs, cells, and organelles, or viewing such specimens after fracturing them.

We use a Hitachi 4500 FESEM equipped with a recently developed BAL-TEC SCE 020 cryopreparation/transfer device for our LTFESEM studies. The SCE 020 is similar in design to the older SCU 020 except that instead of having a dedicated stage, the SCE 020 has a detachable cold stage that mounts on to the FESEM stage when needed. Since the SCE 020 has a precisely controlled lock manipulator for transferring the specimen table from the cryopreparation chamber to the cold stage in the FESEM, and also has a motor driven microtome for precise control of specimen fracture, we have explored the feasibility of using the LTFESEM for multiple-fracture studies of the same sample.
“Leaky vacuum” SEM for materials scientists
Authors: Horsewell A. , Appel C.C. , Bilde-Sørensen J.B.
Published: June 2020

‘Leaky vacuum’ SEM is carried out at Risø using the Electroscan™ E-3 Environmental SEM and the low vacuum JEOL 5310 LVSEM. In our laboratory, a wide variety of materials problems has led us to develop several novel ‘leaky vacuum’ SEM methods which will be described here; a) in-situ fracture mechanics experiments, b) utilization of charge contrast to characterize local conductivity of insulators, c) removal of beam skirting error in energy dispersive X-ray analysis.

In-situ fracture-mechanics experiments

Crack tip processes in non-conducting materials such as ceramics and polymer composites cannot be observed in the conventional SEM because the vacuum deposited conductive coatings peel away around the edges of the growing cracks. Charge prevention is readily achieved in die ESEM through ionization of the 5-10 torr atmosphere around the specimen surface. Not only is the large specimen chamber convenient for special rigs, but the poor vacuum means low demands on the rig construction with respect to out-gassing of lubricants, strain gauges and electrical monitors.
An overview of functional magnetic-resonance imaging
Authors: Hu Xiaoping , Le Tuong , Kim Seong-Gi , Ugurbil Kamil
Published: June 2020

In the past few years, one of the most significant developments in magnetic resonance imaging (MRI) is the use of MR imaging to non-invasively map human cortical function without the use of exogenous contrast agents . Since its introduction in 1992, functional magnetic resonance imaging (fMRI) has emerged as a powerful tool for studying neuronal function and generated an enormous amount of interest among neuroscientists, NMR scientists, and clinicians. The purpose of this paper is to outline the principle of fMRI and the associated technical issues and illustrate the utility of fMRI with representative applications.

The basis of fMRI is the blood oxygenation level dependent (BOLD) contrast which is derived from the fact that deoxyhemoglobin is paramagnetic and changes in the local concentration of deoxyhemoglobin within the brain lead to alterations in the magnetic resonance signal. Neuronal activation within the cerebral cortex causes an increase in blood flow without a commensurate increase in oxygen extraction.
Structure of III-V oxides
Authors: Liliental-Weber Z. , Li M. , Li G. S. , Chang-Hasnain C. , Weber E.R.
Published: June 2020

The lack of high-quality native oxides on the III-V compounds has hindered the development of III-V integrated circuits and optoelectronic technology. Recently it was shown that stable oxides can be formed in the III-V compounds rich in Al, such as AlxGa1-x As similarly as it was done in Si technology by the reaction of AlxGa1-x As with H2O vapor (in N2 carrier gas) at elevated temperatures (∼400−450°C). The high quality of these oxides was attributed to the formation of stable AlO(OH) and Al2O3 compounds. However, this conclusion was not definitive, since several Al rich compounds were proposed as well. In addition, it was never clarified whether the excess As created in this process has any role in the stabilization of these oxides, in reducing leakage current or in impurity diffusion. Moreover there is concern as to the quality of the oxide/GaAs interfaces created by lateral oxidation of an intermediate AlGaAs layer.
Structural Investigation of B+ Ion Implantation Induced Amorphization in Polycrystalline Ni Thin Films
Authors: Liu P.C. , Zaluzec N.J. , Okamoto P.R. , Meshii M.
Published: June 2020

High fluence metalloid ion implantation have been shown to induce amorphous phase formation in transition metals systems1,2 In this study Electron Energy Loss Spectroscopy (EELS) and Energy Filtered Selective Area Electron Diffraction (EFSAED) techniques have been employed along with conventional TEM to characterize the structural and electronic changes resulting from B+ ion implantation into polycrystalline Ni thin films.

Polycrystalline Ni thin films of thickness ~500Å have been prepared by evaporating pure Ni (99.99%) onto commercial Bioden R.F.A. acetyl cellulose films in a vacuum of 5 × 106 Torr at room temperature. The TEM samples are obtained by dissolving the underlying acetyl cellulose layer using acetone wetting from below the TEM grids. The resulting films exhibit a continuous, non-textured fee polycrystalline rings pattern with an average grain size of 17 ± 4 nm.Ion implantation was performed in an implantation chamber using 50 keV B+ ions directed at normal incidence to the Ni TEM samples. The sample configuration consists of a -500 Å Ni energy degrader films on the 100 mesh Cu grids situated in front of the polycrystalline Ni thin films on the 300 mesh Cu grids. Such configuration maintains optimum efficiency of B+ ion implantation while producing a more homogeneous profile. After a total incident dose of 4.22x1017 ions/cm2, the implanted polycrystalline Ni thin films was transferred to the Philips EM420 electron microscope equipped with a Gatan (M-607) serial EELS detector for structural characterization.
TEM microscopical examination of the magnetic domain boundaries in a super Duplex austenitic-ferritic stainless steel
Authors: Fourlaris G. , Gladman T. , Maylin M. , Lane R. , Papadimitriou G. D.
Published: June 2020

It is well known that, due to the good corrosion resistance certain grades of stainless steels have significant applications in marine environments. For the development of certain large naval structures, in addition to the good corrosion resistance, other requirements are imposed such as high strength and toughness coupled with suitable magnetic characteristics.

It has been demonstrated in an earlier publication that significant improvements in the coercivity, maximum induction and remanence values can be achieved, by using a 2205 type Duplex austenitic -ferritic stainless steel (DSS) instead of the low alloy medium carbon steels currently being used. These improvements are achieved in the as received 2205 material, and after small amounts of cold rolling have been applied, to increase the strength. In addition, the modification of the duplex austenitic-ferritic microstructure, via a heat treatment route, results in a finer austenite ‘island’ dispersion in a ferritic matrix and provides an attractive option for further modification of the magnetic characteristics of the material.
Educating Congress on the importance of investigator-initiated biomedical research: Role of individual investigators and professional societies
Authors: Brinkley B. R.
Published: June 2020

Although American biomedical science relies heavily on the Federal Government for research funding, individual scientists have traditionally shunned politics and public policy. In years past, scientists were not encouraged to mingle with politicians, most of whom viewed scientists as fuzzballs and eggheads with whom they had little in common. Scientists generally believed that government and society valued their services and would always provide substantial support for research and training. Today, biomedical research funding requires a keen knowledge of the U. S. Congress and the political process. Indeed, our professional survival and that of our students and trainees requires active involvement in Washington politics. We can no longer defer the task of justifying our role in society to institutions or blue ribbon panels of elite science experts. Democratic decision-making at its best is process-oriented, time-consuming, and bottom-up, not top-down. Through its proactive policies involving networking, congressional testimony, education and targeted funding goals, the Public Policy Committee of the American Society for Cell Biology has provided a model strategy for member-oriented commitment to science and public policy.
Merging of electron-diffraction intensities acquired with a slow-scan CCD camera of crotoxin complex crystals to 3.5Å resolution
Authors: Brink Jaap , Chiu Wah
Published: June 2020

Crotoxin complex is the principal neurotoxin of the South American rattlesnake, Crotalus durissus terrificus and has a molecular weight of 24 kDa. The protein is a heterodimer with subunit A assigneda chaperone function. Subunit B carries the lethal activity, which is exerted on both sides ofthe neuro-muscular junction, and which is thought to involve binding to the acetylcholine receptor. Insight in crotoxin complex’ mode of action can be gained from a 3 Å resolution structure obtained by electron crystallography. This abstract communicates our progress in merging the electron diffraction amplitudes into a 3-dimensional (3D) intensity data set close to completion. Since the thickness of crotoxin complex crystals varies from one crystal to the other, we chose to collect tilt series of electron diffraction patterns after determining their thickness. Furthermore, by making use of the symmetry present in these tilt data, intensities collected only from similar crystals will be merged.

Suitable crystals of glucose-embedded crotoxin complex were searched for in the defocussed diffraction mode with the goniometer tilted to 55° of higher in a JEOL4000 electron cryo-microscopc operated at 400 kV with the crystals kept at -120°C in a Gatan 626 cryo-holder. The crystal thickness was measured using the local contrast of the crystal relative to the supporting film from search-mode images acquired using a 1024 x 1024 slow-scan CCD camera (model 679, Gatan Inc.).
400-kV electron imaging of ice-embedded fascin-actin bundle
Authors: Jakana Joanita , Edwards Robert , Bryan Joseph , Schmid Michael F. , Chiu Wah
Published: June 2020

Fascin is a 55 kDa actin filament bundling protein first isolated from sea urchin egg actin gels by Kane. These gels consist of actin-fascin bundles cross linked by spectrin. Purified actin and fascin produce bundles when mixed in vitro, with an actin-fascin stoichiometry of 4.6 to 1 at saturation. Cloning of sea urchin fascin cDNA revealed homology to an uncharacterized Drosophila protein called singed. The singed phenotype, misshapen bristles and female sterility, canbe explained by a lack of actin bundles and Cant el al has shown recently that the singed gene product can bundle actin. Mammalian fascins have now been cloned from humans and mice. Murinefascin is highly expressed in brain; immunofluorescence reveals fascin localized to filopodia extending from the leading edge of hippocampal neuron growth cones.

A soluble, active recombinant mouse fascin has been produced as a fusion protein with E. coli thioredoxin. When mixed with F-actin this fusion protein produces bundles with an actin-fascin ratio of approximately 4.1:1. The bundle was frozen in a thin layer of vitreous ice and examined at 400 kV in the JEOL 4000 electron microscope under low dose condition with a procedure previously described.
Charging phenomena observed on biological specimens in a 400-kV electron cryo-microscope
Authors: Brink Jaap , Sherman Michael , Berriman John , Chiu Wah
Published: June 2020

There is an ever present need in electron microscopy of biological specimens to improve the quality of the recorded data to approach the atomic resolution capability of the modem instruments. The method adopted which has yielded the only significant advance in this direction is to directly phase theelectron diffraction amplitudes of 2-dimensional crystals using the Fourier transforms of high resolution images. Cryo methods have improved the preservation and stability of the specimen to the relatively high electron dose irradiation which is required for imaging compared to electron diffraction. In the cases, however, where the actual power of the structure factors was compared with those that were transferred by the microscope’s imaging system, a large attenuation was measured. Spot-scan imaging has been shown to improve the image quality by reducing the beam-induced movement. Charging of the specimen appears to cause similar deleterious effects on image resolution, but it requires different methods aimed at resolution improvement. Proteins are insulators and because of secondary electron loss they will become positively charged during irradiation. Defocused diffraction brightfield imagescan display the charged nature of an irradiated specimen as an apparent increase in mass. A comparison wasmade of the degree of charging and discharging between using 100 and 400 keV electrons on streptavidin crystals in glucose and catalase crystals in amorphous ice. We show that when the region of the irradiated sample includes part of the supporting carbon film, the charge build-up is prevented.
Ultrastructural aspects of olfactory signal transduction and its development
Authors: Menco Bert Ph. M.
Published: June 2020

Vertebrate olfactory receptor cells are specialized neurons that have numerous long tapering cilia. The distal parts of these cilia line the interface between the external odorous environment and the luminal surface of the olfactory epithelium. The length and number of these cilia results in a large surface area that presumably increases the chance that an odor molecule will meet a receptor cell. Advanced methods of cryoprepration and immuno-gold labeling were particularly useful to preserve the delicate ultrastructural and immunocytochemical features of olfactory cilia required for localization of molecules involved in olfactory signal-transduction. We subjected olfactory tissues to freeze-substitution in acetone (unfixed tissues) or methanol (fixed tissues) followed by low temperature embedding in Lowicryl K11M for that purpose. Tissue sections were immunoreacted with several antibodies against proteins that are presumably important in olfactory signal-transduction.
New frontiers in multispectral chemical imaging
Authors: Schaeberle Michael D. , Treado Patrick J.
Published: June 2020

Recent advancements in visible and near-infrared multichannel detectors as well as the availability of novel imaging quality tunable filters make multispectral chemical imaging microscopy viable for routine materials characterization. Our research involves the development and application of chemical imaging methods that are rapid, non-invasive, and intuitive. The methods require limited sample preparation, and can be performed at high spectral and spatial resolution.The chemical imaging techniques employ Raman scattering, fluorescence emission or infrared absorption spectroscopies in combination with optical microscopy. In general, the methods provide qualitative and quantitative information about the composition and distribution of constituents within a wide host of materials, including biological tissues, polymers, and semiconductors.

Silicon charge-coupled device (CCD) detectors are widely utilized for image detection in visible microscopy. Currently underutilized, but providing significant capabilities for chemical imaging based on infrared vibrational absorption are focal plane array (FPA) detectors providing sensitivity in the near-infrared and mid infrared. These include cameras constructed from indium antimonide (InSb), platinum silicide (PtSi), indium gallium arsenide (InGaAs) and mercury cadmium telluride (MCT).
Use of FIM-1 to study the role of protein kinase C in T-cell polarization
Authors: Poenie Martin , Legler Christine , Morgan Tom , Chen Chii-Shiarng , Lee Jong Ran
Published: June 2020

Protein kinase C (PKC) plays an important role in many activities associated with cell movement and secretion. For example, when cytotoxic T lymphocytes are deplete of PKC by prolonged exposure to phorbol ester, they exhibit a large increase in [Ca2+]iupon contact with an antigenic target but they are unable to kill. In these cells, polarization events such as translocation of talin, the microtubule organizing center, and secretory granules to the vicinity of target cell contact site are blocked. This suggests that PKC could play a fundamental role in regulating directional movements of proteins and cytoplasmic organelles within the cell. If so, we would expect that translocation and activation of PKC would also be localized, perhaps due to the localized formation of diacylglycerol at the target contact site. As a means to investigate this hypothesis, we studied the PKC-dependent association between talin and the membrane integrin, LFA-1 in CTL-target conjugates. Prior to CTL-target binding, talin is distributed diffusely throughout the cytoplasm whereas LFA-1 is evenly distributed over the cell surface.
Immunocytochemical localization of lactase in the brush border, Golgi complex and endocytotic granules of pig jejunal enterocytes
Authors: Heath Julian P. , Harrell Rhonda G. , Kömüves László G.
Published: June 2020

We have used immunofluorescence light microscopy (IFLM) and immunogold electron microscopy (IEM) to study the distribution of lactase phlorizin hydrolase, a developmentally regulated brush border enzyme, in the enterocytes of suckling neonatal piglets. Tissues were collected from the jejunum and fixed in 4% paraformaldehyde. Cryosections were incubated in mouse monoclonal anti-pig lactase antibody (PBB 3/7/3/2, from Dr. A. Quaroni, Cornell Univ.) followed by either FITC- or 10 nm gold-conjugated anti-mouse IgG. IFLM and IEM images were digitally acquired from video and processed.

Jejunal villus enterocytes of non-suckled piglets possess an apical endocytic complex and a sub-nuclear Golgi complex (Fig. 1). In the jejunal crypts, differentiating enterocytes possess an immature brush border and a supra-nuclear Golgi complex (Fig. 2). In suckled animals, absorption of colostral proteins by villus enterocytes results in the formation of dense apical and basal granules (Fig. 3); crypt cells do not accumulate granules. Many of the granules are juxtaposed to the Golgi complex (Fig. 4).
Demonstration of ultra-high-resolution soft x-ray tomography using a scanning transmission x-ray microscope
Authors: Haddad W. S. , McNulty I. , Trebes J. E. , Anderson E. H. , Yang L. , Brase J. M.
Published: June 2020

X-ray microscopy has been an active area of research for many years, but it is now beginning to emerge as a viable imaging tool for microbiologists and materials scientists. Several groups have developed x-ray microscopes of various types using synchrotron sources laser plasma sources, and x-ray lasers. The most productive systems have been the scanning transmission x-ray microscopes (STXM). Near diffraction limited performance can be achieved with such instruments. There are however no x-ray optics having sufficiently high numerical aperture (NA) to achieve resolution in depth that is comparable with the transverse resolution. Currently the best x-ray zone plates have a NA < 0.1 for radiation in the water window. The ratio of depth resolution to transverse resolution ∂l\∂t ≈ 2/NA > 20 for present state-of-the-art zone plates.

In order to improve the depth resolution, it is necessary to effectively increase the NA of the imaging system. This can be done by recording several views of the object over a large angular range. If each of the views is taken with low NA optics such that the longitudinal extent of the object is less than the depth resolution of the imaging system, then each view will be a 2-D projection of the object.
Mild detergent treatment of thin carbon substrate films
Authors: Simon Martha N. , Lin Beth Y. , Wall Joseph S.
Published: June 2020

The preparation of biological specimens for the STEM by the wet film technique and subsequent freeze-drying, has been shown to preserve biological structures reasonably well and give good mass measurements on them. However, the thin (2-3 nm) carbon substrate film, prepared by ultra-high vacuum evaporation onto a freshly cleaved crystal of rock salt, is never perfect for the attachment of fragile biological structures. The film is floated on a dish of clean water and grids covered with holey film are placed face down on the floating thin carbon film. The grids are picked up from above one at a time such that the carbon film retains a droplet of water. This water is exchanged by washing and wicking and the specimen is injected into the drop followed by further washing and wicking. After the final wash, the grid is blotted between two pieces of filter paper (retaining solution less than 1 μm thick), plunged into liquid nitrogen slush, and freeze-dried under vacuum overnight.
Microscopic study of Forcipomyia whitcombe ovary
Authors: Ba-Omar Taher A. , Devera David
Published: June 2020

We have been investigating the structure of the Forcipomyia whitcombe (Diplera: Ceratopogonidae) ovary. The F. Whitcombe are biting midges which are one of the newly discovered species of Diptera: Ceratopogonidae found in Oman. They are found in bushland and grassland of the mountain of Dhofar (southern part of the Sultanate of Oman); Jabal Oara and Jabal Qamar. These midges are associated with the monsoon which hits that part of Oman during the summer months (end of June - mid September).

Specimens were collecled using nets and fix directly in 70% alcohol. Some specimens were processed for light microscopy (LM) using routine histological technique and stained with H&E. Others were processed for scanning electron microscopy (SEM); dehydrated in acetone, dried in a critical point dryer (CPD). They were then cut into halves in which the lower half was coaled with gold and then examined with Jeol SEM.

The body of the insect measures about 1.3 mm in length. The study showed that this insect possesses paired ovaries. Next to the ovaries there is the spermatheca (sperm storage). Each ovary contains several ovarioles polytrophic type. Each ovariole possesses several eggs which are enclosed in a layer of follicular cells (supporting and nourishing cells).
Ultra-high resolution SEMI-in-lens type FE-SEM, JSM-6320F, with strong magnetic-field lens with built-in secondary-electron detector
Authors: Miyokawa T. , Kazumori H. , Nakagawa S. , Nielsen C.
Published: June 2020

We have developed a strongly excited objective lens with a built-in secondary electron detector to provide ultra-high resolution images with high quality at low to medium accelerating voltages. The JSM-6320F is a scanning electron microscope (FE-SEM) equipped with this lens and an incident beam divergence angle control lens (ACL).

The objective lens is so strongly excited as to have peak axial Magnetic flux density near the specimen surface (Fig. 1). Since the speciien is located below the objective lens, a large speciien can be accomodated. The working distance (WD) with respect to the accelerating voltage is limited due to the magnetic saturation of the lens (Fig.2). The aberrations of this lens are much smaller than those of a conventional one. The spherical aberration coefficient (Cs) is approximately 1/20 and the chromatic aberration coefficient (Cc) is 1/10. for accelerating voltages below 5kV. At the medium range of accelerating voltages (5∼15kV). Cs is 1/10 and Cc is 1/7. Typical values are Cs-1.lmm. Cc=l. 5mm at WD=2mm. and Cs=3.lmm. Cc=2.9 mm at WD=5mm. This makes the lens ideal for taking ultra-high resolution images at low to medium accelerating voltages.
Automatic alignment of stereo images
Authors: Haselgrove John , Fodor Lou , Peachey Lee
Published: June 2020

Stereoscopic pairs of electron microscope images are used for quantitative 3D information. A prerequisite for the measurement is to position the two images correctly relative to each other and with the stereo rotation axis of each image aligned vertically for viewing. Although this alignment procedure is relatively straightforward to perform using prints of the images, it is not straightforwardto do once the images have been digitized directly from the microscope. We have developed an algorithm for determining the parameters needed for orienting digitized images. Four parameters are needed: The displacements Δx and Δy by which one of the images must be translated to be superimposed on the other, and the angles Θ1 and Θr by which the left and right images must be rotated to bring the stereo-rotation axis vertical.

The microscopist first uses an interactive routine to identify the coordinates xl(i),yl(i) and xr(i),yr(i) of a number (N) of fiducial points which can easily be recognized on each image.
Cryo imaging using an energy-filtering TEM (EFTEM): Optimum use of phase-contrast transfer function (PCTF)
Authors: Probst W. , Zellmann E. , Benner G. , Weimer E.
Published: June 2020

Lack of contrast is one of the numerous problems arising from imaging of vitrified biological macromolecules in a TEM. This is due to the similar density of biological material and of vitreous ice and to the high background of inelastic scattering in the ice which is about four times that of carbon.Consequently in a CTEM images have to be recorded 1-3 μm underfocus to maximise phase contrast which in the same sense decreases the reliability of density information.

Elastic filtering using an (EFTEM) allows closer to focus imaging still achieving considerable contrast. For 3D reconstruction of molecular densities the largest source of error is likely to arise from contributions of the PCTF. Thus, such images have to be corrected for the PCTF, which is much morereliably done for elastically filtered images close to focus.

Thin vitreous ice films containing the virus particles were prepared on holey carbon grids and examined with cryo EM procedures. Images of frozen-hydrated cucumber mosaic virus (CCMV) particles ( Ø of roughly 25 nm) were recorded in Elastic Brightfield mode using the Zeiss EM 912 OMEGA with integrated imaging spectrometer and Koehler Illumination. Magnification was 50.000x, HT 120 kV, energy width 7 eV, total dose 800 electrons /nm2.
Advances in backscattered-electron Kikuchi patterns for crystallographic phase identification
Authors: Michael J. R. , Goehner R. P.
Published: June 2020

The development of a charged coupled device (CCD)-based detector for the acquisition of high quality backscattered electron Kikuchi patterns (BEKP) has allowed crystallographic phase identification studies to be conducted in the scanning electron microscope (SEM). High quality BEKPs suitable for analysis have been obtained from a wide variety of materials. Phase identification through a combination of BEKP and energy dispersive x-ray spectrometry (EDS) has been performed with relatively little specimen preparation compared to electron diffraction in the transmission electron microscope. This paper will discuss the measurement of the depth resolution of the BEKPs. Crystallographic phase identification through a combination of BEKP and energy dispersive x-ray spectrometry is demonstrated by the identification of a Laves phase in an Fe-Ni-Cr-Nb alloy. The CCD-based detector has been described in detail previously and will not be discussed here. The thickness of the surface region that gives rise to the BEKP has been reported to be quite thin, thus requiring care in surface preparation.
Grown-in defects in CVD α-Si3N4
Authors: Zhou D. S. , Mitchell T. E.
Published: June 2020

Silicon nitride has been extensively studied due to its promising mechanical properties at high temperature. There are three ways to form bulk materials, namely, reaction-sintering, hot isothermal pressing, and chemical vapor deposition (CVD), among which only CVD method can produce large single crystal regions enabling determination of some fundamental physical and mechanical properties.

.α-Si3N4 is trigonal, P31c, with lattice parameters a=0.782 nm and c=0.559 nm. Crystals were grown by Praxair Coating Technology. The CVD process was performed with HSiCl3, NH3 and H2 gases reacted at 1500°C and at a pressure of 0.5 torr. Generally, there are two types of crystals, one with the hexagonal prismatic needle pointing in the [0001] direction; the other with a needle growth direction of [100], For the present study, the [100] crystals were used. Grown-in defects in the polycrystal regions were investigated using polarized light microscopy and transmission electron microscopy (TEM). TEM specimens were prepared bv standard techniques through cutting, grinding, dimpling and ion milling. A Philips CM30 TEM was used operating at 300 kV.
A new route for the interpretationof reconstructed wavefunctions in HRTEM
Authors: Op de Beeck M. , Van Dyck D. , Coene W.
Published: June 2020

During the last years the renewed interest in focus variation wavefunction reconstruction algorithms has lead to a spectacular improvement of the obtainable resolution in FEG-HRTEM. Unfortunately, it was found that only for thin specimens the reconstructed wavefunction is directly interpretable in terms of the projected atomic potential. Hence there is a need for a direct structure reconstruction algorithm, starting from the reconstructed electron wavefunction. Here we propose a new channelling method in real space that only relies on the very basic concepts of dynamical diffraction in zone axis orientation, and which is very suitable to reveal the correspondence between the wavefunction and the column structure. In this way, a parametrised analytical expression can be obtained so as to reconstruct the projected structure of the object, requiring minimal prior knowledge.

In order to develop a sensible structure reconstruction method, a good understanding of the multiple dynamical diffraction process is required.
The structure of zeolite LZ-277
Authors: Bateman C. A. , Kirchner R. M.
Published: June 2020

LZ-277 is a new aluminosilicate molecular sieve. It has an x-ray diffraction (XRD) pattern nearly identical to zeolite phi but with a much smaller pore size. Whether LZ-277 and phi-like materials are intergrowths or a physical mixture of phases has been a matter of debate. The ability to determine the structure of complex zeolites has been enhanced by HREM and, more recently, by the ability to simulate XRD patterns of faulted materials. In this study, the structure of zeolite LZ-277 is reported and confirmed by simulating the XRD pattern of this highly faulted material.

The low magnification micrograph shows the faulted and intergrown disc morphology typical of this material (Figure 1). The faulting is most typically twinning on (001), and is shown in the [010] diffraction pattern (Figure 2). The pattern is indexed on an a = 1.38 nm, c = 1.50 nm unit cell and both lattice parameters and systematic absences are consistent with chabazite in space group Rm.
Detection of internal Pt clusters in zeolite FAU using serial sectioning with diamond-knife ultramicrotomy and HRTEM
Authors: Bovin J.-O. , Alfredsson V. , Karlsson G. , Blum Z. , Terasaki O.
Published: June 2020

Zeolite Y or X (FAU) has a very open framework structure with 13 Å diameter cages. Small metal clusters fit well in such cages. In catalytic research it is essential to localize the metal clusters; are they in the zeolite cavities or on the zeolite surface? In this study we will describe a method, using high resolution transmission electron microscopy (HRTEM) imaging of ultrathin sections, that give evidence that platinum is located within the zeolite. It will be shown that clusters preferably aggregate in the larger cages of the frequently occurring {111}-twin planes (TP).
Zeolite NaY (Si/Al=2.8) crystals were ion exchanged with Pt(NH3)4 Cl2 according to standard literature procedures. After ion exchange the specimen was oxidized in O2 at 383 K for three hours and finally reduced in H2 at 298 K for two hours.

The zeolite crystals were embedded in epoxy resin (Spurr) for preparation of ultrathin sections. The composition of the resin was 15.0 g vinylcyclohexene dioxide (ERL 4206), 6.0 g polypropylene glycol diglycidyl ether (DER 736), 39.0 g nonenyl succinic anhydride (NSA), and 0.3 g dimethylamino ethanol (S-l).
Structure of sputter-deposited amorphous Pd-Si alloy studied by High Resolution Electron Microscopy
Authors: Hirotsu Yoshihiko , Anazawa Kazunori , Nagakura Sigemaro
Published: June 2020

Recent structural studies of amorphous alloys by precise X-ray and neutron diffraction, Mossbauer spectroscopy and NMR have shown an atomic ordering developing beyond the first neighbor atomic distance, which is called a medium range ordering (MRO) of atoms in amorphous alloys. Lattice fringe images extending in a range of 1 to 2 nm have been observed in amorphous alloys by high resolution electron microscopy(HREM), indicating a possible formation of the MRO structures. In our HREM study of amorphous Pd77.5Cu6Si16.5 alloy ribbons, MRO domains with α-Pd-like structure were observed under the most appropriate underfocus condition. For more detailed understanding of MRO structure, it is necessary to calculate HREM images for possible MRO models and compare them with observed ones. In this study, we calculated HREM images for an amorphous Pd80Si20 with (1) a dense random packing(DRP) structure, (2) a FCC MRO structure( a FCC cluster embedded in the DRP structure) and (3) an icosahedral MRO structure( an icosahedral cluster embedded in the DRP structure).
HREM characterization of lanthana-supported rhodium catalysts
Authors: Bernal S. , Botana F.J. , Calvino J.J. , Cifredo G. , García R. , Molina S. , Rodríguez-Izquierdo J.M.
Published: June 2020

Metals supported on rare earth sesquioxides present a non- conventional behavior. Ordinary H2 and-or CO chemisorption techniques cannot be straightforwardly used to characterize this group of catalysts. The assessement to the data of metallic dispersions and the establishment of the occurrence and extent of metal-support interaction phenomena are determinant in order to interpret the properties of these catalysts in hydrogenation reactions. In this work HREM is proposed as a powerfull technique for the study of lanthana supported rhodium catalysts. Such catalysts would be considered as representative of a series of metals supported on rare earth sesquioxides.
Plan-view TEM of planar interfaces
Authors: Dravid V.P. , Notis M.R. , Lyman C.E. , Revcolevschi A.
Published: June 2020

Transmission electron microscopy (TEM), incorporating imaging, diffraction and spectrometry has contributed significantly to the understanding of the structure of crystalline interfaces. Traditionally, planar interfaces are investigated using cross-sectional views (electron beam parallel to the interface) of the specimen. However, plan-view TEM (PVTEM) has recently emerged as a viable and supplementary technique to cross-sectional TEM (XTEM). PVTEM enjoys certain definite advantages over XTEM. One important consideration is that the interface in a PV specimen is buried (sandwiched between two crystals) and is expected to be free of artefacts induced by specimen preparation procedures. Moreover, many multilayer electronic materials are amenable to PVTEM because they can be easily backthinned to electron transparency with virtually no damage to the internal interfaces. PV specimens clearly contain much larger interface area than XTEM specimens, which may be of great significance when statistics are considered. Apart from these considerations PVTEM studies can also offer specific information about the interface not always possible in XTEM. In this brief communication we report some of our results on imaging, diffraction and spectrometry of interfaces obtained by viewing the interfaces in the PV mode.
An HRTEM study of grain boundaries in long-chain Te crystals
Authors: Isshiki Toshiyuki , Michiyuki Toshiya , Saijo Hiroshi , Shiojiri Makoto
Published: June 2020

A Te crystal is an aggregate of spiral chains arranged about the c-axis of the hexagonal cell, and hence exhibits the growth and morphology characteristic of the long chain molecules. This paper describes the structure of grain boundaries induced during the crystal growth. Te films of a thckness of t=18 nm, vacuum deposited onto glass substrates at 120”C, were observed with a JEM 200-CX electron microscope (Cs=1.2 mm).

Fig. 1a shows an HRTEM image of a grain boundary along with edge dislocations in a Te crystal. The projection of Te chains is schematically shown in Fig. 1b. Figs. 1c and 1d show enlarged images of the area enclosed by a rectangle in Fig. 1a, taken at Δf=15 and 85 nm. Each side of the boundary is either R-(p3121) or L-(p3221) crystal having the α-axis approximately parallel to the incident electron beam. Thus, there are eight possible orientations between the two grains, as shown in Table 1.
Spatial resolution measurements of electron backscatter diffraction patterns (EBSPs) in the scanning electron microscope
Authors: Hjelen Jarle , Nes Erik
Published: June 2020

In the EBSP method the stationary electron beam hits a highly tilted bulk specimen in the SEM. The backscattered Bragg diffracted electrons form the Kikuchi line pattern on a phosphor screen. Since the first EBSP experiments were carried out in 1973, this technique has been further developed to determine crystal orientations in connection with texture development in aluminium. Using the EBSP method to calculate local lattice curvatures in heavily deformed aluminium, the spatial resolution has to be better than the selected area channeling pattern (SACP) method.

The EBSP resolution (d) was measured by moving the electron beam digitally across grain boundaries in an aluminium sample. The resolution was defined to be the overlapping distance between two diffraction patterns.
Defect fine Structures as observed by in situ experiments
Authors: Saka H.
Published: June 2020

An in-situ experiment in an electron microscope is now a well established and useful technique in materials science. In this review recent contributions of in-situ experiments, especially of straining and heating experiments, to materials science will be high-lighted.The earlier works have been reviewed by Saka and Imura.

It is believed that an external stress gives rise to an anistropy in the rate at which point defects are absorbed by edge dislocations; this mechanism is considered to explain the irradiation creep. A combined in situ tensile/irradiation experiment in a HVEM has been carried out to study effects of applied stress on the growth of dislocation loops. Fig. 1 shows typical microstructures of Ag irradiated at 403K for 10 min with 1MV electrons in the absence (a), and in the presence of an external stress of 5.5 kg/mm2 (b). Frank loops of interstial type, formed by electron irradiation, grew more rapidly in the direction of the external tensile stress than in the others. These results show that an external tensile stress has a profound effect on climb rates of Frank loops of interstitial type. However, detailed analysis of the results indicates that there is a considerable discrepancy between experiment and theory.
Arrangement of molecules at lattice defect in an organic crystal
Authors: Maeda Takashi , Isoda Seiji , Kobayashi Takashi
Published: June 2020

Many important properties of organic crystals are known to be controlled by a small amount of impurities and lattice imperfections. We have reported the molecular arrangements at defects in some metal complxes which are composed of elements such as N,O and metal in addition to C and H. The lattice energy or defect energy calculation of these materials could not be carried out with sufficient accuracy, because of the existence of such hetero atoms. In this paper we show defect structures found in epitaxial films of a simple hydrocarbon, quarterylene(Fig.1), which contains no hetero atoms and their structure was partly studied. Quarterylene purified by sublimation in a stream of nitorogen gas was deposited on a cleaved (001) surface of several kinds of alkali-halides in a vacuum of 5x10-5 Pa. The substrates cleaved in air were preheated for two hours in the vacuum and were colled at a desined temperature. The film thickness was controlled to be about lOnm.

At the substrate temperatures lower than 170°C, the quarterylene film is composed of long fibrous crystals, whose long axes are parallel to two perpendicular directions in the substrate surfaces. At higher temperatures than 170°C, planar continuous crystals grow together with some fibrous ones as shown in Fig.2.