bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission Electron Microscopy study of lead sulfide whiskers
Authors: Mansour S.A. , Scholz R. 
Published: June 2020

This paper describes a transmission electron microscopy (TEM) study of the structure and growth mechanism of lead sulfide (PbS) whiskers. PbS whiskers were grown inside the stainless steel nozzle of a kerosene burner. The nozzle had a 0.5 mm aperture, and was fitted with an Al-spiral coil to filter kerosene impurities. The burner was operated continuously for four weeks at a kerosene pressure of 2-3 bars and a flame temperature of about 350°C before the nozzle clogged. A thick black deposit of fine PbS whiskers was found inside the nozzle.TEM specimens were prepared by ultrasonically suspending the fine black powder in alcohol. The suspended particles were deposited on a perforated carbon film supported on a copper grid, and examined with a JEM-1200EX transmission electron microscope operated at 120kV accelerating voltage. A JEM-4000EX transmission electron microscope was used for high resolution electron microscopy.Fig. 1. shows an EM micrograph of typical PbS whiskers. Each appears to have a high-contrast core encapsulated in a lower contrast shell. The electron diffraction pattern of a single whisker protruding over a hole in the carbon film is shown in Fig. 2.
Atomic-level structure and composition at interfaces
Authors: Smith David J. 
Published: June 2020

The latest generation of high-resolution electron microscopes (HREMs) have structural resolution limits on the order of atomic dimensions, thereby opening up the possibilities for direct observation of atomic (re)arrangements at crystal defects and discontinuities such as interfaces. With recent advances in growth methods, novel types of optical, X-ray and electronic devices which are based upon nanometer-scale multilayers (MLS) have been developed. This short review considers the prospects and limitations of the HREM technique for elucidating the structure and composition of interfaces in these layered materials, including such details as the interface roughness, the extent of interpenetration (i.e. compositional gradients) and the coherent/incoherent nature of the interface. The complementary nature of information available from other TEM methods is also briefly discussed.The common (and essential) requirement for HREM characterization of layered structures is that they must be aligned with their interfaces(s) edge-on with respect to the incident beam direction. It is therefore useful if the multilayers are deposited onto a well-defined surface of a crystalline substrate,typically Si or GaAs, which can then provide a basis for orientation purposes. The development of routine methods for preparing cross-sectional MLS specimens, either by ion-milling or cleavage , has also done much to stimulate recent HREM observations.
Procedures for Point and Space Group Analysis
Authors: Tanaka M. 
Published: June 2020

Description of general procedures for point- and space-group determination by convergent-beam electron diffraction(CBED) soon appears in a special issue of J. Electron Microsc. Tech. The essence of them was already given in the flow charts in ref.2. We here demonstrate the procedures using an example of La2 CuO4 - 6, which is the end member of a 40K class superconductor La2-x Mx CuO4 - 6 (M = Ba, Sr and Ca). The CBED method has utilized to date only dynamical extinction(GM lines) appearing in zeroth-order Laue-zone(ZOLZ) reflections for the space-group determination. We emphasize that the use of GM lines appearing in higher-order Laue-zone(HOLZ) reflections makes it easy to determine crystal space-groups.The substance was already known to belong to the orthorhombic system with the lattice parameters of a=5.3548Å, b=5.4006Å and c=13.1592Å. Fig. 1(a) shows a CBED pattern taken at the [001] incidence, Fig.l(b) being the central part of Fig.l(a). The whole pattern has a symmetry 2mm. This indicates that the crystal has two mirror symmetries perpendicular to each other and that the point group is mmm or mm2.
Studies of magnetic structure of written bits using Lorentz microscopy
Authors: Nguyen T.A. , Alexopoulos P.S. , Lambert S.E. , Sanders I.L. , Hwang C. 
Published: June 2020

Understanding the fundamental size limits of magnetic bits for high density information storage requires detailed knowledge of the magnetic structure of the written bits. Bit definition, fringing fields and magnetic structures at and between transition zones are important information for the design of future magnetic media. Using Lorentz microscopy, we have investigated these parameters in Co-alloy thin films as a function of recording density (200, 600 and 1000 fc/mm) on discrete tracks of widths from 0.6 to 10 μm.The magnetic media consist of a Co-alloy and an underlayer prepared by sputtering onto a sputter-cleaned Si disk. The magnetic parameters for the magnetic layer are: coercive field Hc = 950 Oe, remanent magnetization Mr = 533 emu/cm3 and media thickness d = 400 Å. The discrete tracks were formed on the surface of the disk by sputter-etching through a photoresist mask to remove media between the tracks. This permits the recording characteristics of tracks as narrow as 0.6 μm to be investigated using heads of conventional width.
In situ experimentation: Seeing is believing
Authors: Butler E. Paul 
Published: June 2020

The advent of the high voltage electron microscope (HVEM) in the early 1970's initiated a period of intense interest and growth in dynamic in situ experimentation. The two factors responsible for this change were:– increased volume in the pole-piece gap– increased penetration of thicker samplesIncreased volume freed up space for the stage designer to construct complex yet robust and reliable stages capable of heating/cooling, deformation and environmental control. His task was made easier in side entry stage configurations, which simplified the job of supplying services to and from the specimen holder and provided one ready made axis of tilt along the rod itself. Increased penetration made it possible to observe the true course of many reactions for the first time, overcoming the effects of high surface/volume ratio which so often resulted in a distortion of reaction events in very thin specimens.
Application of the imaging plate to quantitative analysis of electron-diffraction and high-resolution electron microscopy
Authors: Hiraga K. , Shindo D. , Hirabayashi M. , Oikawa T. , Mori N. , Kersker M. 
Published: June 2020

The “Imaging Plate” (IP) has three superior characteristics, i.e., high sensitivity to the electron beam, and a wide dynamic range and good linearity for electron dose compared with conventional EM films. The use of the IP is expected to lead to quantitative analysis of electron microscopy. The purpose of the present work is to examine the possibility of application of the IP to the quantitative analysis of electron diffraction and high-resolution electron microscopy.By using the TEM-IP System developed by Oikawa et al., which is published in this conference, electron diffraction patterns and high-resolution electron micrographs taken on the IP with an effective size of 102 х 77 mm2 were convertedinto digital data of 2048 х 1536 pixels with 4096 gray levels. Observations of electron diffraction patterns and high-resolution electron micrographs were made with a 200 kV (JEM-2000FX) and a 400 kV (JEM-4000EX) electron microscope, respectively.
A new technique utilizing Scanning Electron Microscopy at low temperature and voltage to analyze native-state reservoir rocks
Authors: Stuart C. J. , Liang L.-C. , Toney J. B. 
Published: June 2020

A new analytical technique has been developed to allow direct imaging of native-state petroleum reservoir rocks by the use of the scanning electron microscope (SEM) in a low voltage mode combined with a solid-state cryo-system device. The SEM investigation of native-state reservoir rock samples is important since it enables direct visualization of: (1) the spatial distributions of the fluids in the pore system; (2) clay minerals in their natural hydrated states; (3) the native mineralogy; (4) combined effects on the reservoir's wettability and permeability. The technique uses low voltage SEM to image the uncoated surface of the wet sample at a high vacuum and applies the cryostage to control the vapor pressure of the fluid phase while imaging. A differentially pumped environmental chamber is not required with this approach.This technique utilizes a solid-state thermoelectric cooler device (TED) to achieve the required sample cooling. The TED operates on the Peltier principle permitting the surface of the TED to reach a temperature as low as 110 degrees centigrade below its reference temperature. A sample stage is refitted with a TED substage which is water-cooled. The water-cooling of the substage coupled with the TED allows a precise control of the sample temperature. The sample is fixed to the substage so that it is in direct thermal contact with the TED. The TED is then biased (by the use of DC currents) to provide the effective cooling necessary to minimize vaporization of the interstitial fluids in the sample. The sample and stage temperatures are constantly monitored by means of two microtype-K thermocouple devices. With this approach, no liquid nitrogen is needed for this technique.
Direct lattice imaging of domain boundaries in N-paraffin binary eutectics formed from the vapor phase
Authors: Zhang W.P. , Dorset D.L. 
Published: June 2020

In the past few years, we have been studying the crystal structures of binary paraffin solids in the continuum of states from the stable solid solution through the eutectoid to the fully fractionated eutectic. While electron diffraction data have been very useful to detect microstructures, direct lattice images are needed to depict domain separation.As an example of an eutectic, C30H62/C40H82 thin films were prepared epitaxially on the (100) cleavage face of KCl substrates kept at room temperature under a vacuum of 10−5 torr using the method described by Ueda and Ashida and in our study of palmitone. The specimens were annealed at 40°C for 2 hours. To enhance the phase contrast of lattice images, no carbon films were evaporated onto the organic crystals. After solvating the KCl substrate in pure water, the thin films were collected on holey-carbon coated copper grids for high-resolution study. The thin crystals were examined with a JEOL JEM-100CX electron microscope at 100 kV, and lattice images were taken on Kodak DEF-5 X-ray films at a direct magnification of 19,000X. A minimum dose system was used to reduce the radiation damage during observation.
Film thickness measurement by a cross-sectional SEM
Authors: Nagatani T. , Suzuki T. , Yamada M. , Nakagawa M. 
Published: June 2020

It is well known that metal films evaporated or sputtered in vacuum are not continuous at a thickness of less than several ten nanometers, but show fine particle distributions or have island granularities as thickness increases. Morphorogy of deposited thin films have been one of the major investigation areas in nucleation, crystal growth, crystal surface studies and so on. There is a room for discussions concerning physical properties such as non-ohmic conductivities of the thin metal films in relation to morphorogy.However, almost all micrographs obtained by electron microscopes, both TEMs and SEMs, showing such thin metal films are two dimensional, that is, there is not much information how deposited films are growing on the substrate. Owing to the recent development of a high resolution SEM having a probe size of smaller than 1nm by a combination of highly excited condenser-objective lens and a field emission electron source, three dimensional information for the thin film can be provided as shown in Fig. 1. These specimens are Pt sputter-coated on Si wafers at room temperature with a so-called “magnetron” sputter coater, and then fractured for crosssection study by the HRSEM.
Fast imaging method for native liposomes: cryo Electron Microscopy for use in research and quality monitoring
Authors: Roeding J. F. 
Published: June 2020

Because of their high affinity to biological membranes liposomes are used in cosmetics and pharmaceuticals. Encapsulated active agents can be transported through biological barriers into cells. Apart from chemical properties, the physical characteristics of liposomes determine their ability of penetration and resorption: Vesicle size, lamellarity (number of membranes) and homogeneity are criterias for the quality of liposome-formulations and usually can be measured with laser-light-scattering combined with e.g. NMR-spectroscopy. Classification of liposomes in type (lamellarity) and size or differentiation of liposomes from other particles e.g. oil-droplets or crystals however requires imaging of the liposomes in their native state. Cryofixation and subsequent cryo-electron-microscopy enable to recognize the form and the structure of liposomes. In view of the low mass of the liposome shell, contrast in a conventional transmission electron micoscope is too weak for rapid, reliable recording of these structures. Imaging in an energy filtered transmission electron microscope (EFEM), however, provides optimum contrast and hence a basis for the correct assessment of the liposome structure including measurement and classification.Using a special pair of tweezers, take a hydrophilic perforated film (Triafol) and mount it in the injector. Using a pipette, apply 5μl of liposome suspension on this film so that a clear drop is visible. The excess liquid is removed by placing a piece of paper on the film for about 2 seconds. After this, the injector is immediately shot into the cryogen (ethane liquid). Removed from the cryogen and loaded in the specimen holder the specimen can be tranferred to the cryo EM and observed at minimum electron dose on the TV monitor using the image intensifier camera.
A Cryo-transfer facility for the VG HB501 STEM
Authors: Nicholls A.W. , Bovey P.E. 
Published: June 2020

A recently developed cryotransfer facility has been successfully used to transfer both hydrated and dehydrated sections from a cryo-microtome to the column of the HB501 STEM with no significant warming or ice formation during transfer. This new accessory enables X-ray and energy loss analytical work to be carried out on frozen biological sections at much higher spatial resolution than is possible with conventional TEM systems.The construction and operation of the cryotransfer stage are summarized schematically in Figs. 1 and 2. Fig. 1 shows the central region of the HB501 optical column containing the objective lens (1), the post-specimen dc ana ac scan coil assembly (2), the annular dark field detector (3), the diffraction screen (4) and the airlock (5) through which room temperature specimens are normally loaded into the top-entry stage. A special stage base (6) is used which incorporates a liquid nitrogen-cooled block into which specimens are loaded by means of a side-entry manipulator (10). This manipulator is mounted on a support bracket (7) and enters the column through an isolation valve (8). Movement is achieved by a mechanism (not shown) mounted on the outer end of the bracket (7) and vacuum sealed by a bellows (11). The manipulator is liquid nitrogen-cooled by cooling pipes passing axially through the bellows. Loading and unloading of specimens is via an entry lock (9) which can be vented to dry nitrogen. A liquid nitrogen cooled, shrouded transfer rod (not shown) is used to transport specimens from the cryo-microtome to the entry lock.
Lattice resolution in natural polymers
Authors: Revol J.-F. 
Published: June 2020

Recent developments in low-dose electron microscopy have led to reports of crystal lattice fringes in natural polymers extremely sensitive to damage by electron irradiation. In one of these studies, lattice images of (β-chitin from the diatom Thalassiosira-fluviatilis were obtained and subsequent computer processing produced the molecular projection of this biopolymer crystal along its b-axis at 0.35 nm resolution. Similar direct structural studies have not been done yet on the α-chitin which is far the most abundant polymorphic form found in nature. The present work reports the direct imaging of crystallite lattice fringes of α-chitin microfibrils from lobster tendon, with a preliminary analysis of the results in terms of crystallite size and perfection.A typical preparation of α-chitin microfibrils is shown in Figure 1. The image, recorded by diffraction contrast, shows bundles of long microfibrils as well as smaller elements less aggregated and of different length. These smaller elements, composed of shorter crystallites, are the result of the combined action of the acid hydrolysis and of the ultrasound treatment which broke down the originally long microfibrils. When aggregated into larger ribbons, the width of the microfibrils cannot be detrmined due to overlapping, but when viewed individually, the microfibrils exhibit a lateral size of about 10 to 14 nm (see arrows).
Dynamics of microtubules in higher plant mitosis: Functional kinetochore fiber in Haemanthus endosperm
Authors: Bajer A. S. , Molé-Bajer J. 
Published: June 2020

The majority of conceptual interpretations of the molecular mechanism of chromosome transport is based on the centriolar spindle. The prevailing interpretations have been modified and altered frequently and, in spite of considerable progress recently, the molecular mechanism remains elusive. The reasons for this slow progress are multiple. We believe that, underestimated and trivial as it seems, one of the major problems is the emphasis on the centriolar spindle where the presence of the aster obstructs the organization of the spindle pole and clouds the essential problem of the anchorage of the kinetochore fiber. Therefore, we have concentrated deliberately on higher plant endosperm of Haemanthus, which has the largest and clearest acentriolar mitotic spindles known. A large number of dividing cells on each preparation (averaging about 500 with a maximum of about 1800), combined with natural variation and experimental lowering of the available tubulin, have allowed us to characterize division in cells, which we believe have the threshold number of microtubules required for a functional spindle. Our conclusions on how mitosis works are very different from any current interpretation.Endosperm cells of Haemanthus katherinae Bak. were used as material. Microtubule distribution was analyzed in immunogold stained cells fixed about 45 minutes after preparation. Therefore all cells damaged during and shortly after preparation were excluded because they do not immuno-stain. Over 95% of the remaining cells complete mitosis. Cells with average microtubule numbers (see Figs in ) were compared with cells containing very low numbers of microtubules, occasionally found in controls (Figs. 1-4) and after experimental depletion. Microtubule depletion occurs in about 30% of the cells after routine growing of plants 10°C - 12°C for 10-14 days and is retained for 2-3 days at room temperatures (21°C - 24°C). Observations are based on several hundreds of cells, comprising multiple examples of transitions between various degrees of microtubule depletion.
Does cellulose II occur in nature?
Authors: Roberts E.M. , Saxena I.M. , Brown R.M. 
Published: June 2020

Cellulose, a carbohydrate polymer of :ß-D-glucose, occurs in several different crystalline forms called allomorphs. “Cellulose II” is by far the most abundant allomorph found in nature, but a few organisms have been suggested to synthesize another crystalline form called “cellulose II” (summarized in). Some of these reports are now considered uncertain due to the presence of clay contaminants or because extractions requiring high concentrations of alkali can convert cellulose I to cellulose II. Because identification of organisms that synthesize native cellulose II could help further understanding of how cellulose crystallization occurs, we have reexamined several of the organisms suggested to produce this allomorph. Care was taken to minimize the atrifacts mentioned above. Included in this study were the algae HalicystisandEnteromorpha, and the slime mold Dictyostelium.In the course of our studies, we have also found that certain mutants of the bacterium Acetobacter xylinum synthesize cellulose II instead of the cellulose I allomorph produced by the wild type.Bacterial cellulose was purified from mutants of Acetobacter xylinum as previously described. After extraction in organic solvents, cellulose was purified from Halicystis (UTEX strain 1260) by brief treatment with 15-20% HCl at 100°C and extraction with 1N NaOH and 0.25M NaBH4 (2 x 30 minutes, 100°C). The ultrastructure of these samples were examined by negative staining with uranyl acetate. Cellulose from Enteromorpha (UTEX strain 739) was purified as described above or extracted by soaking overnight in 24% KOH at room temperature. X-ray diffraction powder patterns were recorded with a Debye-Scherrer camera and Cu k-alpha radiation. The crystalline form of cellulose from stalks of Dictyostelium discoidium was studied by electron diffraction. Individual stalks were harvested and cleaned in dilute HCl. Electron diffraction patterns produced at 120 kV were recorded on Kodak 35 mm Tri-X film.
Digital video and laser microscopic studies of developmental events in living neurons and nervous systems
Authors: Smith S. , Forscher P. , Cooper M. , Waxman A. 
Published: June 2020

Motility and structural change are extremely important aspects of nervous system development. We are working to refine digital video and laser confocal light microscopic methods for visualization of neuronal motility both in situ and in vitro. Our efforts are oriented especially toward the collection of digitally-enhanced time-lapse movies, for which purpose we especially favor the use of the optical memory disc video recorder. It is our feeling that such dynamic observations are yielding insights not obtainable from examination of fixed specimens. Work to be discussed includes video microscopic studies of the basic motility mechanisms of neuronal growth cones in vitro and laser confocal observations of mammalian CNS growth cone motility and cell proliferation and migration events in slices of embryonic rat cortex.As cell markers for the laser confocal studies, we have used a variety of fluorescent compunds including the lipid stain Dil(C18-3) and the Ca indicator Fluo-3. The latter compound is of special interest in revealing the cytosolic calcium transients associated with various forms of cell signalling as well as making cell structure and motility visible. We have found the use of slow-scan, single-sweep laser image acquisition especially valuable in the collection images from living, moving cells, as this mode circumvents the blurring of moving specimen details associated with the prolonged integration times of low-light-level video data acquisition and multi-sweep averaging in laser scanning systems.