bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiments with a scanning tunneling microscope (STM) mounted in a scanning electron microscope (SEM)
Authors: Wells Oliver C. , Welland Mark E. 
Published: June 2020

Scanning tunneling microscopes (STM) exist in two versions. In both of these, a pointed metal tip is scanned in close proximity to the specimen surface by means of three piezos. The distance of the tip from the sample is controlled by a feedback system to give a constant tunneling current between the tip and the sample. In the low-end STM, the system has a mechanical stability and a noise level to give a vertical resolution of between 0.1 nm and 1.0 nm. The atomic resolution STM can show individual atoms on the surface of the specimen.A low-end STM has been put into the specimen chamber of a scanning electron microscope (SEM). The first objective was to investigate technological problems such as surface profiling. The second objective was for exploratory studies. This second objective has already been achieved by showing that the STM can be used to study trapping sites in SiO2.
SbC15 intercalated graphite
Authors: Mittleman R. K. , Parker N. W. 
Published: June 2020

SbC15 intercalated graphite is one of the most widely studied of the graphite intercalated compounds. The reasons for this are that upon intercalation SbC15 undergoes the dissociation reaction:3SbC15 + 2e- ⇒ 2SbC16- + SbCl31consequently the physical properties of the compound are not merely a superposition of the parent material. SbC15-graphite compounds are also among the most stable of the graphite intercalants.
The formation of hydrogen phases on twin boundaries in Si
Authors: Vanderwalker D. M. 
Published: June 2020

When a Si crystal is placed in a hydrogen plasma, H ions diffuse into the crystal and passify dangling bonds at point defects, dislocations, and grain boundaries. The H passivation changes the electrical properties of silicon. The nucleation of H-Si solid second phases was not discussed before this experiment, although H-Si complexes were thought to form. This study is of the formation of H phases on twins in silicon.A Si sample, which was compressed along a <231> axis at 420°C and cooled under a high stress, was placed in a closed gas discharge tube between Pt electrodes. The pressure of the H gas was less than one torr. A hydrogen plasma was produced when 440 volts were applied at 180°C and maintained for 90 minutes.
Resolution vs specimen thickness comparison of 100kV, 200kV, and 1000kV electron microscopes using semithick sections
Authors: Cole R. W. , Marko M. 
Published: June 2020

We have found that micrographs of conventional epoxy sections up to 0.25 μm in thickness taken at either 200 kV or 1000 kV are of equally good quality, although at some thickness beyond 0.25 μm there is a rapid divergence in quality. We note that even lOOkV microscopes can be used with sections up to about 0.5 μm for prescreening grids to be viewed on higher voltage instruments.Although several papers have been published dealing with resolution at different specimen thicknesses and/or different accelerating voltages, we are not aware of data relating to the maximum useful specimen thickness for biological work at 200 kV. Only one paper involved biological specimens using acclerating voltages lower than 400 kV.
Characterization of magnetic microstructure at high spatial resolution
Authors: Scheinfein M.R. 
Published: June 2020

Advances in metal epitaxial growth techniques have produced renewed interest in magnetic materials through the unique properties of novel atomically engineered structures. Ultrathin layered and nanocrystalline, textured composites possess unique magnetic properties which are intimately connected to the physical microstructure on both the atomic and nanometer length scales. The length scales present in magnetic interactions span several orders of magnitude from the atomic length scales of the exchange interaction, to the mesoscopic length scales important in anti-ferromagnetic RKKY coupling between thin ferromagnetic films and small particles, to the macroscopic length scales determined by the long range magnetostatic interactions which are responsible for the formation of magnetic domains.Special characterization and computation techniques are required to analyze the micromagnetic and microstructural properties of these novel, low dimensional systems. In order to correlate the structure with the magnetic properties of any system, in-situ growth, structural, chemical and magnetic characterization is desirable.Most methods used for the observation of micromagnetic structure rely on a contrast mechanism derived from the magnetic fields present in ferromagnetic systems. We have implemented the conventional Fresnel, and less conventional Differential Phase Contrast modes of imaging magnetic microstructure in an HB5 STEM.
Ultrastructural effects of manganese in cultured heart cells
Authors: Winter Kerri 
Published: June 2020

Manganese (e.g. Mn2+, Mn gluconate, Mn-DPDP) has been used as a contrast reagent for magnetic resonance imaging of liver and myocardial perfusion. In addition, Mn has been used to block the voltage-dependent calcium channel, interfere with excitation-contraction coupling, and inhibit Na/Ca exchange. Although Mn has proved useful in both clinical and research settings, little information is available about its effects on cell structure. Therefore, we examined the effects of Mn on ultrastructure in a model system of cultured embryonic chicken heart cells.Free-floating cardiac myocyte aggregates were cultured from 11 day-old chick embryos. Aggregates were incubated with a HEPES/TRIS-buffered salt solution containing various concentrations of MnCl2 (0, 1, 20 mM) for 5 min at 37°C. Following incubation, buffer solution was removed, aggregates were chemically fixed in glutaraldehyde and processed for routine electron microscopic analysis. Parallel studies on confluent myocytes were conducted to assess the Mn uptake by atomic absorption spectroscopy.
Jet freezing of cells and tissues with and without cryoprotectants
Authors: Parthasarathy M.V. , Daugherty Carole , Müller T. 
Published: June 2020

For the past several years cryofixation/freeze-substitution techniques have become valuable alternatives to chemical fixation of biological specimens. The superiority of cryofixation in preserving labile cell structures has been documented in several studies. Commercially available jet freezers and the BAL-TEC HPM010 high pressure freezer have extended high quality cryofixation from monolayer cells to cells relatively deep inside tissues. High pressure freezing can theoretically freeze biological materials of 0.5 mm thickness without the use of cryoprotectants and propane jet freezing is reported to freeze biological samples up to 40 μm in thickness without cryoprotection. Although high pressure freezing is the obvious method of choice for freezing large biological samples, its high cost combined with its apparent inability to consistently preserve microfilaments in some plant cells has prompted us to explore the capability of jet freezing to yield well frozen samples with and without cryoprotectants.We used the commercially available jet freezer JFD 030 (BAL-TEC) to obtain our results. Tightly pelleted cells sandwiched between 0.1 mm thick copper specimen carriers normally froze well without any cryoprotectants, after propane jet freezing (Figs. 1-2).
High-pressure freezing improves quantitative and qualitative structural data in the actinomycete microsymbiont frankia
Authors: Howard Berg R. 
Published: June 2020

Symbiotic plant root nodules containing the nitrogen-fixing bacterium Frankia occur on a variety of woody shrubs and trees. Ever since the first micrographs of freeze substituted cells of Frankia in culture were published there has been impetus to see if freeze substitued nodule tissue will improve imaging of Frankia in vivo. High pressure freezing/freeze substitution (HPFS) accomplishes this.Frankia is an actinomycete that fixes N2 in a specialized multicellular, spherical structure termed the “symbiotic vesicle” that is surrounded by a multilamellate envelope (MLE) comprised of lipids. Early work based on MLE birefringence suggested the MLE was a O2 diffusion barrier, thereby protecting nitrogenase from O2- inactivation. Recently this has been challenged by freeze fracture data. Traditionally it has been assumed that the MLE is electrontranslucent because the lamina of the MLE are extracted by dehydration solvents, producing the “void space”--an extraction artifact hindering TEM analysis of MLE structure.En bloc staining with chromic acid stains the MLE, showing that the MLE is present after exposure to dehydration solvents and that the void space results from tissue shrinkage in the symbiotic vesicle (Figure 1).
The influence of confocal microscope design on imaging performance
Authors: Sheppard C J R 
Published: June 2020

The confocal microscope is now widely used in both biomedical and industrial applications for imaging, in three dimensions, objects with appreciable depth. There are now a range of different microscopes on the market, which have adopted a variety of different designs. The aim of this paper is to explore the effects on imaging performance of design parameters including the method of scanning, the type of detector, and the size and shape of the confocal aperture.It is becoming apparent that there is no such thing as an ideal confocal microscope: all systems have limitations and the best compromise depends on what the microscope is used for and how it is used. The most important compromise at present is between image quality and speed of scanning, which is particularly apparent when imaging with very weak signals. If great speed is not of importance, then the fundamental limitation for fluorescence imaging is the detection of sufficient numbers of photons before the fluorochrome bleaches.
Three-dimensional image reconstruction of fluorescence micrographs without knowing the point spread function
Authors: Holmes Timothy J. , Krishnamurthi Vijaykumar , Liu Yi-Hwa 
Published: June 2020

The term blind deconvolution refers to the deconvolution, or deblurring, of a signal (optical, sound, or other) without explicit knowledge of the point spread function (PSF). The PSF is, instead, reconstructed concurrently with the deblurred signal from the collected, noisy data. Blind deconvolution methodologies have been under study for general signal processing applications, such as in restoring phonographs, as early as 1968. Ayers and Dainty have performed pioneering blind deconvolution research for deblurring 2D images, which has been applied to astronomy. Inspired by this earlier blind deconvolution research, we have taken a new approach which is based on maximum likelihood estimation (MLE). Our approach is extended from previous research in applying MLE to positron-emission tomography (PET). A novelty of our research is in the application of MLE and blind deconvolution to 2D and 3D fluorescence microscopy.The fundamental advantage of the MLE approach over some of the other blind deconvolution approaches is that it is a mathematical optimization approach, wherein the likelihood functional of the collected image data, the fluorescence probe concentration and the PSF is maximized.
Three-Dimensional reconstruction of the synaptonemal complex from pachytene maize meiocytes using Electron Microscopy tomography
Authors: Fung Jennifer C. , Scalettar Bethe A. , Agard David A. , Sedat John W. 
Published: June 2020

The synaptonemal complex (SC) is a structure involved in the synapsis of homologous chromosomes during the prophase I stage of meiosis. Although the exact function of the complex is unknown, it has been suggested that one possible role might be to promote recombination by ensuring close synapsis of the homologous chromosomes. In addition, it is thought that the SC may also be required to convert the resulting recombination events into functional chiasmata to provide for proper chromosome segregation at the end of the first stage of meiosis.The SC structure itself is highly conserved across a variety of species. The organization of the SC is tripartite consisting of lateral, central and transverse elements. Two-dimensional cytological observations have been made to characterize the general features of these SC components. The lateral elements are 300 - 500 Å wide proteinaceous structures which flank the synapsed regions of the chromosome bivalent. Between the two lateral elements is a central region containing the central element commonly characterized as a less dense amorphous structure.
Polymorphism of fiber cell junctions in mammalian lens
Authors: Costello M. Joseph , Al-Ghoul Kristin J. , Oliver Timothy N. , Lane C. Wesley , Wodnicka Magdalena , Wodnicki Pawel 
Published: June 2020

Previous studies of junctional specializations between bovine lens fiber cells have indicated that pentalamellar profiles in isolated membranes correspond to gap junctions (GJs), undulating square array junctions (SAJs) and thin symmetric junctions (TSJs). We show here that this same junctional diversity occurs in the intact tissue and that the differences in thickness and staining patterns can be documented by density profiles from thin-section TEM images of in vivo and isolated membranes.Fresh bovine lenses were mounted on edge and vibratome sectioned parallel the optic axis. Sections near the center were fixed (paraformaldehyde, glutaraldehyde, and tannic acid) for thin-section analysis or were dissected on a glass slide to select a group of fiber cells within a narrow region, such as the deep cortex about 2 mm from the lens surface. Membranes were isolated from this small fraction of cells using a new procedure, essentially, suspending in buffer, washing 30 min in 4M urea and pelleting at low speed in an AirFuge (Beckman).
Processing of high-resolution images of irradiated ceramics
Authors: Lewis M.E. , Qin L.C. , Sreeram A.N. , Hobbs L.W. 
Published: June 2020

Mathematical morphology as an image processing and analysis tools is both a science and an art. The theory of mathematical morphology is rooted in topology, where a set-theoretic framework is the basis of binary morphology. Gray-scale morphology is an extension into the space of functions. This rigorous formulation has provided powerful transformations, operating directly on the information content of an image. However, it is up to the investigator’s creativity to devise the appropriate criteria for each problem at hand.The main focus of the present study is the analysis of image contrast and the relationship with the underlying structure of the material. Image processing and analysis methods based on mathematical morphology were applied to high resolution micrographs of irradiated ceramics: electronirradiated tridymite and ion-irradiated lead pyrophosphate single crystal.The interesting feature of these images is the presence of periodic, aperiodic and partially ordered structures, Fig.s la and 2a.
Standard formats for the exchange and storage of image data
Authors: Egerton R.F. , Bright D.S. , Davilla S.D. , Ingram P. , Kirkland E.J. , Kundmann M. , Lyman C.E. , Rez P. , Steele E. , Zaluzec N.J. 
Published: June 2020

In microscopy, there is an increasing need for images to be recorded electronically and stored digitally on disk or tape. This image data can be shared by mailing these magnetic media or by electronic transmission along telephone lines (e.g. modem transfer) or special networks, such as Bitnet and Internet. In each case, the format in which the image is stored or transmitted must be known to the recipient in order to correctly recover all the information. Because there are many image formats to choose from, it would undoubtedly save misunderstanding and frustration if a group of individuals with similar interests and needs could agree upon a common format. The MSA Standards Committee has surveyed several formats which could be of particular interest to microscopists, with a view to making a recommendation to our community.Our chief concern has been compatibility with existing software, combined with an adequate representation of the data, compactness of data storage (on disk) and reasonable rate of data transfer.
Determining chromatin structure by computer-aided image analysis
Authors: Olesen James B. , Heckman Carol A. 
Published: June 2020

In the present research, we address the problem of how chromatin fibers are ordered in band and interband regions along the length of a Drosophila polytene chromosome. Our approach employs image processing as a preliminary step to amplify the image contrast. Then, computerized pattern recognition methods are used to study how the chromatin is arranged.Polytene chromosomes were isolated from salivary glands and squashed on glass microscope slides. The slides were immersed in liquid nitrogen and the coverslips were removed with a razor blade. Small droplets of a polymer developed in our laboratory called HACH (a mixture of 2- hydroxyhexanedial, carbohydrazide and hydrazine) were then placed over individual chromosome spreads and the slides were left at 26°C overnight to allow for HACH polymerization. HACHembedded samples were removed from the slides, mounted on resin blocks, trimmed and thinsectioned at a thickness of approximately 100 nm. Sections were floated onto formvar-coated gold grids and viewed with a Zeiss 10C transmission electron microscope operated at 80kV.
Visualization of the anionic sites in the cell wall of apple fruit using a cationic colloidal gold probe
Authors: Roy Stéphane , Conway William S. , Watada Alley E. , Pooley Christopher D. , Wergin William P. 
Published: June 2020

The ripening of fleshy fruits involves a softening process that consists of biochemical changes in the cell wall and leads to cell separation. Calcium is an important constituent of the cell wall and plays roles in maintaining the firmness of fruit and in reducing postharvest decay. The modification of cell wall strength is believed to be influenced by calcium that interacts with acidic pectic polymers to form crossbridges. This study examined how the frequency and distribution of anionic binding sites in the cell walls of apple fruit were influenced by calcium infiltration.Mature “Golden Delicious” apple fruits were pressure infiltrated with either H2O or a 4% solution of CaCl2and the pericarp was sampled and processed according to standard procedures. Cationic poly-Llysine colloidal gold complex was used in a one-step procedure to visualize anionic sitesin muro. Observations were performed with light microscopy, following silver intensification, and with transmission electron microscopy.
Electron microscopy of the changes in the sperm head curvature of the palm squirrel (Funambulus Penanti)
Authors: Bawa S. R. , Bawa R. , Bains H. K. 
Published: June 2020

Examination of ultrathin sections of the spermatozoa recovered from the epididymis of the Indian palm squirrel (Funambulus penanti) indicates that the sperm head undergoes changes in its curvature during epididymal transit.Testis and epididymis of an adult male squirrel were dissected and small pieces of tissue fixed in 2.0% glutaraldehyde in 0.1 M phosphate buffer and post-fixed in osmium tetroxide. After dehydration in graded acetone the material was embedded in Araldite. Ultrathin sections were cut on a Reichert Jung Ultracut, picked-up on copper grids, stained with Reynold’s lead citrate-uranyl acetate and examined with a JEOL 1200 EX transmission electron microscope.Ultrathin sections of the caput epididymal spermatozoa reveal that their plasma membrane is adherent to the underlying acrosome (Figure 1). When these spermatozoa reach the corpus epididymis the plasma membrane surrounding the head becomes ruffled (Figure 2). The lifting-up of the plasma membrane around the head is restricted to the posterior bend of the acrosome.
Ultrastructural change of the cell membranes on myocardium following treatment with H2O2
Authors: Oguro Tatsuo , Aihara Kaoru , Aida Kuniharu , Asano Goro , Ashraf Muhammad 
Published: June 2020

It has been suggested that hydrogen peroxide (H2O2) is indirectly associated with postischemicreperfusion injury of the heart. Previously, we reported that the heart was not damaged when perfused with exogenously generated superoxide anions. However, H2O2 which is a dismutation product of superoxide anion severely affected the heart structure and function, and the combined effects of H2O on membrane lipid and proteins result in the formation of membranous bleb.In this study, we evaluated the ultrastructural changes of the cell membranes in isolated rat hearts and cultured myocytes following treatment with exogenous H2O2. In the isolated hearts, 300μM H2O2 was perfused for 15 min and in the isolated cultured myocytes an equal amount of H2O2 was added to the culture medium for 30 min. This dosage of H2O2 was found to be injurious to the heart in our previous study. In the isolated cultured myocytes, 300μM H2O2 was added to the medium for 30 min.
Adrenal and vagus modulation of cisplatin-induced gastric emptying and ulceration
Authors: Aggarwal Surinder K. 
Published: June 2020

Cisplatin is a most valuable broad spectrum antineoplastic drug available for the treatment of testicular and ovarian cancers. It has several severe toxic side effects of which gastrointestinal and nephrotoxicity are the major dose limiting. It also induces hypocalcemia and Hypomagnesemia that have been demonstrated to effect the secretory activity of the neurohypophysis and the parathyroid glands. In rats cisplatin treatment causes stomach bloating and ulceration that can be ablated by daily injections of calcium just before the treatment and during the treatment or using vagotomy. Adrenalectomy has also been shown to prevent ulceration. Present study is an effort to determine the effect of cisplatin on morphological and cytochemical changes in the neuromuscular interactions of the stomach smooth muscle and the adrenal glands before and after vagotomy.Male Wistar rats [Crl:(WI)BR] weighing 200-300 g were given intraperitoneal injection of 9 mg/kg in 0.85% saline. Alternate group of animals received in addition daily injections of calcium (1 ml of 1.3% calcium chloride).
SEM comparison between dentin surfaces etched with acid agents and dentin surfaces irradiated with laser
Authors: Silberman Jaime , Vargas Marcos , Denehy Gerald 
Published: June 2020

Preliminary research has indicated that laser etching may create a roughened dentin surface similar to that produced by enamel acid etching. Localized melting and recrystallization produce fungiform projections on dentinal surfaces. Consequently, this surface may present potential for bonding composite resin restorations. The purpose of this investigation was to compare using SEM and dentin topography that results from both acid etching and laser treatment, and also make comparisons between the effectiveness of various laser exposure parameters. In addition, a shear bond strength pilot study was done to corroborate the SEM results.Forty-two molars were collected and randomly divided into six groups. Dentin surfaces were prepared by horizontal section through the middle third of the teeth crown and finished with 600-grit paper. Five of the groups were laser treated with LX-20 CO2 surgical laser. The dentin treatments of each group were as follows: Group #1: Dentin etched with 10% Maleic Acid, Group #2: Dentin irradiated with CO2 laser at 2W mode 5, Group #3: Dentin etched with 10% Maleic acid and 3W mode 5 and then etched with 10% Maleic acid, Group #5: Dentin irradiated at 3W mode 7, Group #6: Dentin irradiated at 3W mode 9.