bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved structural preservation of high-pressure frozen cartilage
Authors: Studer Daniel , Wagner Jeannine , Hunziker Ernst B. 
Published: June 2020

Adult cartilage is a unique tissue in that it is avascular and lacks innervation. The chondrocytes are embedded in an extracellular matrix which in most cases occupies 60 to 90% of the tissue volume. The ultrastructure and composition of rat growth plate cartilage has been investigated (1). It was found that during conventional chemical fixation of me tissue (2), about 60% of the extracellular matrix proteoglycans were lost (3). This artefact can be prevented if proteoglycans are precipitated by cationic dyes (eg. ruthenium hexaamine trichloride) during fixation (4) which forms relatively large precipitates by rendering high resolution imaging impossible. High pressure frozen extracellular matrix revealed a fine meshwork which was attributed to proteoglycan distribution (5). A meshwork due to segregation during freezing was not seen in recent experiments where adaequately frozen cartilage was investigated.200μm thick sections of rat growth plate cartilage were excised in a bath of hexadecene (6). The sections were again processed under hexadecene, firstly punched (diameter 1.7mm) and then transferred to an aluminum sandwhich (corresponding in size to the sample).
Three-dimensional imaging and physiology of live neurons and glia: Confocal light and correlative high-voltage Electron Microscopy
Authors: Turner J.N. , Szarowski D.H. , Shain W. , Davis-Cox M. , Carpenter D.O. , Fejtl M. 
Published: June 2020

Correlating physiologic measures with three-dimensional (3D) imaging at the light and electron microscopic levels is a powerful combination of methods for studying the structure and function of biological systems. Neurobiology is an ideal field for the application of these methods because neurons and glia have complex and extensive 3D structure, and their physiology is under intense study. Neurons, such as those studied here from Aplysia, can be more than 100 μm in diameter, and glia undergo large scale 3D shape change as a function of a number of physiologic parameters. The ability to accurately quantitate the 3D structure, volume and surface area of live neurons and glia is important to our understanding of the complex function of these cells.Neurons were isolated from the major ganglia of juvenile Aplysia Californica and glia were obtained from long term cultures of LRM 55 cells or as primary isolates from rats. Cultures were exposed to Dil dissolved in DMSO with or without 20% Pluronic F-127 and added to the culture media. The imaging instrument was an Olympus IMT-2 and a Bio-Rad MRC-600.
Deferoxamine-induced ultrastructural lesions of nucleoli in MCF-7 carcinoma cell line
Authors: Wang Fen , Head Jonathan F. , Elliott Robert L. 
Published: June 2020

Deferoxamine(DFO), an iron chelator, has been demonstrated to inhibit the growth of a variety of human malignant cell lines. Evidence suggests that DFO exerts its primary effect by chelating ferric iron and inhibiting DNA and RNA synthesis.The effects of DFO on MCF-7 cells have been investigated. The IC50 and IC90 inhibitory concentrations of DFO on MCF-7 cells were 4.8 uM and 9.5 uM, respectively. This inhibition can be reversed by equimolar concentrations of iron and iron-loaded transferrin. Alterations in the ultrastructure of nucleoli of MCF-7 cells exposed to the DFO in the concentrations of 4.8uM and 9.5uM for 24 hours, 48 hours and 72 hours were studied by transmission electron microscopy. The cells were grown in 24 well plates in alpha-MEM supplemented with 10% FCS and incubated at 37°C. They were harvested with trypsin-EDTA, pelleted into Beem capsules and centrifuged. A standard specimen preparation procedure was employed for transmission electron microscopy.
Characterization of HF-treated Si(111) surfaces using REM, SEM, and XPS
Authors: Ma Y. , Lordi S. , Eades J. A. 
Published: June 2020

The imperfections on silicon wafers have become more and more crucial as the dimensions of integrated circuits are progressively reduced in the submicron range. The problems relating to the HF acid etching of Si surfaces have recently been studied using different techniques. It has been found that Si-H bonding is responsible for the passivation of HF-treated surfaces, and the roughness of the surfaces is related to the pH value of HF acid used for etching. The roughness of those surfaces was in most cases characterized indirectly by the width of the Si-H absorption peaks in IR spectra. Only in limited cases, were they studied by STM, a direct imaging technique.Here, we try to characterize the HF-treated Si(111) surfaces using direct imaging techniques, REM and SEM and a spectroscopy technique, XPS. The morphology of Si(111) surfaces HF-treated under different conditions was directly imaged in TEM, and SEM for comparison.
A cryo-SEM technique developed and applied to surfactant liposomes
Authors: Bhadriraju Kiran , Bellare Jayesh 
Published: June 2020

Freeze-fracture replication TEM and Cryo-TEM are developed techniques for studying surfactant dispersions. Application of freeze-fracture cryo-SEM with direct imaging to such systems has the advantages of observing a greater range of particle sizes, large depth of field implying larger tilts together with rotation, and freeze-etching/freeze drying the sample while imaging it. A procedure for cryo-SEM of liquid colloids, which uses a simple sample preparation setup, and its results for liposomal dispersions, are described here.Samples are plunge-frozen by a freezing device (Fig.l) made from a standard desoldering tool (Fig.2) used as a plunging unit. Fracture plates (Fig.3) are made from 0.1 mm thin copper sheet made adhesive to the liquid by 400 mesh TEM grids that are bent over the two edges of the plates and stuck on the non-sample side with a rubber adhesive. The sample is sandwiched between a pair of fracture plates (Fig.3) and plunged into liquid Freon-22 kept at its freezing point (-160°C) in an electrically heated cup (Fig.l) cooled by a liquid liquid nitrogen bath.
High-resolution gold labeling
Authors: Hainfeld James F. , Furuya Frederic R. , Carbone Kyra , Simon Martha , Lin Beth , Braig Kerstin , Horwich Arthur L. , Safer Daniel , Blechschmidt Bernd , Sprinzl Mathias , Ofengand James , Boublik Milas 
Published: June 2020

A recently developed 1.4 nm gold cluster has been found to be useful in labeling macromolecular sites to 1-3 nm resolution. The gold compound is organically derivatized to contain a monofunctional arm for covalent linking to biomolecules. This may be used to mark a specific site on a structure, or to first label a component and then reassemble a multicomponent macromolecular complex. Two examples are given here: the chaperonin groEL and ribosomes.Chaperonins are essential oligomeric complexes that mediate nascent polypeptide chain folding to produce active proteins. The E. coli chaperonin, groEL, has two stacked rings with a central hole ∽6 nm in diameter. The protein dihydrofolate reductase (DHFR) is a small protein that has been used in chain folding experiments, and serves as a model substrate for groEL. By labeling the DHFR with gold, its position with respect to the groEL complex can be followed. In particular, it was sought to determine if DHFR refolds on the external surface of the groEL complex, or whether it interacts in the central cavity.
Microscopic study of male Morpho rhetenor wing scales
Authors: Bingham L. , Bingham I. , Tanner J. , Driscoll C. , Geary S. , Hollingshead J. , Hansen B. , Gardner J. S. 
Published: June 2020

The morphology of pigmented ventral scales and non-pigmented iridescent dorsal scales of Morpho rhetenor wings were compared using scanning electron microscopy and light microscopy. Sections of wing and individual scales were mounted at various angles on stubs for SEM evaluation. Some scales were embedded in Spurr’s resin and sectioned for LM and SEM.Pigmented scales are ornamented by ridges parallel to the axis of the scale (Fig. 1). They are approximately 1.5 μm apart with holes through the membrane between ridges. The non-pigmented iridescent scales similarly contain a series of parallel ridges, but with several layers of lamellae (Fig. 2). The distance between these ridges is only approximately 0.7 μm (Fig. 3). Much smaller and more frequent holes can be observed between these ridges (compare Figs. 1 and 3). The overlapping layers of lamellae form stacks of thin films, which resemble a “Christmas tree” structure. The space between the overlapping lamellae is 0.05 μm and there appear to be holes through the midrib between lamellar stacks (Fig. 4).
The effect of torbafylline on capillary morphology in primate skeletal muscle after ischemic reperfusion injury
Authors: Gregory Michael A , Mars Maurice 
Published: June 2020

Morphometric studies have shown that experimental drug Torbafylline (T) alters the response of skeletal myofibres to ischemic reperfusion injury (IRI). An ultrastructural study has been instituted to determine if and/or how T may “protect” the muscle from IRI. This report outlines the effect that 3 hours of tourniquet mediated ischemia and up to 24 hours of reperfusion has on the capillaries of primate skeletal muscle, with and without prior administration of T.Sixteen adult vervet monkeys (8 control - 8 experimental) were studied under general anesthesia. In each case, a hindlimb was exsanguinated using an Esmarch bandage. To induce lower limb ischemia, a pneumatic tourniquet was applied to the thigh at 100mm Hg above systolic pressure for 3 hours. In 4 control animals, open muscle biopsies were taken from the tibilais anterior before tourniquet application (BTA), just prior to tourniquet deflation, and after 3 and 6 hours of reperfusion. In the remaining 4 animals, biopsies were taken BTA and after 12, 18 and 24 hours of reperfusion.
Scanning electron microscopy evaluation of heat cured composite resin after surface preparation to enhance bond strength
Authors: Imamura Glen M. , Reinhardt John W. , Perdigao Jorge 
Published: June 2020

Tooth shaded composite resin is frequently used as a direct restorative material in the oral cavity. However, during setting it undergoes a volumetric shrinkage which can result in leakage around margins of the restoration. Indirect techniques avoid intraoral shrinkage by fabricating and curing the composite at elevated temperatures outside of the mouth. Higher curing temperatures also improve physical properties in vitro. The completed restoration is then cemented into the prepared cavity with a low viscosity composite resin cement. This study evaluated the effect of varied surface preparation and chemical conditioning on the bond strength of two different indirect heat cured composite resins to a composite resin luting cement.Well and disk specimens of a microfilled resin (Concept, Williams), groups 1-7, and a minifilled hybrid resin (Herculite-XRV-Lab, Kerr), groups 8-14, were fabricated and cured at 250° C and 85 psi pressure. Each resin set was randomly divided into 7 groups of 10 specimens.
Secondary ion mass spectroscopy in the biological and materials sciences
Authors: Linton Richard W. 
Published: June 2020

Secondary ion mass spectrometry (SIMS) is based upon energetic ion bombardment of surfaces resulting in in the emission of sputtered particles, including both atomic and molecular ions. The use of mass spectrometric detection provides a highly versatile and sensitive tool for surface and thin film chemical analysis. In recent years, the scope of the technique has broadened to include a variety of analysis modes including:1.Elemental Depth Profiling (dynamic SIMS),2.Laterally Resolved Imaging (ion microprobe or ion microscope analysis),3.Image Depth Profiling (combination of modes 1 and 2 providing 3-D images),4.Molecular Monolayer Analysis (static SIMS),5.Sputtered Neutral Mass Spectrometry (post-ionization).Much of the early work in dynamic SIMS centered on the development of depth profiling and imaging techniques, with an emphasis on applications to electronic materials. SIMS has made extensive contributions to semiconductor materials science since the 1960's, including the development of new devices and processes, and in failure analysis.
Contact and non-contact atomic-force microscopy of type I collagen
Authors: Chernoff Ellen A.G. , Chernoff Donald A. , Kjoller Kevin 
Published: June 2020

Introduction. Type I collagen was examined using two types of atomic force microscopes (AFM) in a continuing effort to refine the process of obtaining molecular information from biological materials using scanning probe microscopy. Operating in air, a contact mode (Nanoscope II) and a non-contact mode AFM (Nanoscope III) were used to image collagen fibrils polymerized from pepsin-extracted type I bovine skin collagen adsorbed onto mica substrates. AFM is a practical method for high resolution examination of extracellular matrix material without the time consuming preparative techniques required for electron microscopy.Methods. For fibrillar collagen samples, Vitrogen 100 (Collagen Corporation, Palo Alto, CA) was prepared according to a modification of the procedure provided by Collagen Corp. for neutralized isotonic collagen gels. Monomeric collagen samples were prepared by diluting the vitrogen in 0.012M HCl.Images captured with the Nanoscope II AFM (Digital Instruments, Santa Barbara, CA) used a “J” scanner (horizontal range of 120 um).
Finding noise-related artifacts in scanned-probe microscope images
Authors: Siriwardane H. , Fraundorf P. , Fei L , James W.J. , Newkirk J. , Pringle O.A. 
Published: June 2020

Scanned probe microscope images often contain structure which does not belong to the actual specimen. Some of this structure arises in time-domain instabilities of the microscope and its environment, some of it arises with imperfect attempts of the feedback loop to hold force or current constant, and some of it reflects tip (as opposed to specimen) structure. We illustrate here: (i) artifacts of the first kind, i.e. those which are independent of tip shape and which exist in the slow-scan limit, (ii) the way in which low-pass filtering can give such artifacts three-dimensional character, and (iii) tests involving Fourier phases and amplitudes in scanned probe images which can signal the presence of such artifacts.The first and best test for artifacts related to time-domain instability is simply to locate precisely the same feature in two micrographs, if possible taken with different scan speeds (e.g. at different magnfications). If the feature remains unchanged in structure and size, then it is unlikely to be a purely time domain artifact.
Hard-copy imaging options
Authors: Polizzotto Leonard 
Published: June 2020

Photographic film has played a central role in the recording of microscope images since the invention of photography in the 1830s. Photography rapidly creates an accurate record of the microscopic specimen and avoids the subjectivity that was inherent in written and artistic descriptions of visual observations. Both instant and conventional films offer high resolution, the ability to record a large tonal gradation, and a stable media for long-term data storage.
Newer techniques, such as thermal, ink jet, and laser prints, have grown in popularity because they offer ease-of-use or lower per-image cost. Despite recent improvements, none of these techniques offer the resolution or stability of a photograph. In general, people have been forced to sacrifice quality and permanence in order to achieve the lower per-image cost and ease-of-use promised by alternative recording systems.Photographic hard copy has traditionally served as both the communication and storage medium. The introduction of digital storage methods has made these functions more distinct.
Determination of structure factors of copper by convergent beam electron diffraction
Authors: Mansfield John , Saunders Martin , Burgess George , Bird David , Zaluzec Nestor 
Published: June 2020

There has been considerable recent interest in the determination of structure factors from convergent-beam electron diffraction (CBED) patterns and the ultimate goal is the ability to retrieve the crystal structure of an unknown crystal by inversion of a CBED pattern. There are a number of different methods that have been used to extract structure factor information. The zone-axis pattern fitting technique of Bird and Saunders has recently been used to obtain structure factors for silicon that compare well with those obtained by X-ray methods. This work extends the techniques to f.c.c. metals, specifically copper.CBED patterns were recorded from [110] zone axes of electropolished foils of pure copper (99.999% purity) in the Philips EM420T at Argonne National Laboratory. The patterns were energy-filtered by scanning the whole pattern across the entrance aperture of a Gatan #607 serial energy loss spectrometer and collecting the zero loss intensity only (energy window ∼5eV).
Observation of a supported metal catalyst in an ultra-high-resolution field-emission SEM
Authors: Liu J. , Spinnler G. E. 
Published: June 2020

Zeolites loaded with noble-metal particles are interesting catalytic systems. The relative positions of small metal particles on and within the support structure may have significant consequences for catalytic activity. Small metal particles dispersed on model and commercial catalyst supports have been observed by using secondary and Auger electrons in a UHV STEM. In this paper we further report preliminary results of observing a metal/zeolite catalyst in a commercial high-resolution field-emission SEM and investigate the contrast variations of SEM images with the change of incident beam energies.Metal-loaded zeolite samples were ground to fine powders and were dispersed onto a thin holey carbon film coated on a copper grid. The samples were directly observed without being coated with conducting materials. Such coating would obscure fine-scale surface details and make imaging of small metal particles impossible. The experiments were performed in a field-emission Hitachi S-5000 SEM, operating from 0.5 to 30 kV.
Characterization of Al/GaAs Schottky barriers with thin Si interfacial layers
Authors: Bench M.W. , Miller T.J. , Nathan M.I. , Carter C.B. 
Published: June 2020

It has been shown in previous reports that barrier height variations can be achieved in GaAs Schottky diodes grown using molecular beam epitaxy by utilizing a thin epitaxial Si layer (a few monolayers) between the GaAs and the Al contact. The effective barrier height was found to be dependent on the thickness and growth conditions of the Si layer. However, there has remained a question as to the exact nature of the interfacial Si layer. In the present investigation, samples with different Si layer thicknesses (no Si, 6 Å Si, and 20 Å Si, as determined in situ during growth using reflection high energy electron diffraction (RHEED)) were characterized using transmission electron microscopy (TEM) to determine the nature of the Si layers. In the present study, it was also found that the presence of the interfacial Si layers affected the growth orientation and morphology of the Al layers.The layer structures investigated were grown using molecular beam epitaxy in a system described elsewhere.
Lorentz Electron Microscopy of cobalt borides in a platinum cobalt matrix
Authors: Qiu N. , Wittig J.E. 
Published: June 2020

The presence of cobalt borides significantly increases the intrinsic coercivity (Hic) of a Pt-Co alloy. Whereas the maximum Hic for a binary Pt-Co alloy is less than 5 kOe, a ternary Pt42Co45B13 (at%) alloy exhibits intrinsic coercivity as large as 15.2 kOe. The optimum microstructure for the maximum Hic consists of a dispersion of cobalt boride precipitates having the orthorhombic Co3B structure in an Ll0 Pt-Co matrix. Lorentz electron microscopy of the magnetic structure of these cobalt borides has been used to elucidate their strong influence on the magnetic properties of this alloy. Magnetic domain wall thickness measurements assist with modeling of the magnetic hardening mechanism.Processing the Pt42Co45B13 (at%) material utilized an initial rapid solidification step followed by annealing at 800°C. Samples for Lorentz electron microscopy were prepared by dimple grinding and ion milling to electron transparency. The Lorentz imaging employed the standard Fresnel contrast method by operating a Philips CM20T at 200 kV in the low magnification (LM) mode.
TEM of electron-beam induced crystallization of an amorphous AuFe.03/Si Spin-Glass Multilayer
Authors: Howell D.A. , Hoines L. , Crimp M.A. , Bass J. , Heckman J.W. 
Published: June 2020

The use of thin film multilayers for the study of physical phenomena (e.g. spin-glass dc magnetic susceptibility, giant magnetoresistance, and x-ray reflectivity) has grown recently as the technology for their preparation has improved. The multilayers in this study were produced for an investigation of finite-size effects in a AuFe.03 spin-glass.We prepared the samples by dc sputtering of a AuFe.03, alloy and a Si target in an UHV system. The specimen in this investigation had 67 bilayers of 3 nm spin-glass layers alternating with 7 nm amorphous silicon (a-Si) layers on a (001) single-crystal silicon substrate for a total film thickness of 670 nm. Ultrathin cross-sections were prepared by cleaning the thin-film surface in Freon TF and gluing this surface to a clean ground-glass slide with epoxy. We removed the thin-film from its silicon substrate by peeling the substrate from the film which remained on the glass slide.
A cross-sectional TEM study of ion-sputtered hydroxyapatite on silicon
Authors: Raghunathan K.V. , Griffin R.D. , Rigney E.D. , Janowski G.M. , Petrik G. 
Published: June 2020

Recent improvements in biomaterials have led to the development of coatings such as hydroxyapatite (HA), a calcium phosphate phase. One of the main reasons for the interest in HA as a coating material for titanium bone implants is that it is component of bone and teeth and would be expected to be biocompatible.HA can be deposited by ion beam sputtering, which produces a thin, adherent coating which is initially amorphous. Studies of HA sputter deposited onto titanium have shown that the bond strength increases if the samples are heated-treated under vacuum and decreases if heat-treated in air (Figure 1). The present study will characterize the microstructural evolution of HA which was deposited on a model substrate, Si, after heat treatment.Coatings of HA were ion beam sputter deposited onto single crystal [001] silicon wafers. The HA-coated silicon wafers were heat treated in air or vacuum at either 500 or 600°C for one hour.
A comparison of Schottky emission and cold field-emission cathodes
Authors: Swanson L.W. , Rathkey D.S. 
Published: June 2020

We compare Schottky Emission (SE) and Cold Field Emission (CFE) cathodes with respect to emission characteristics and environmental factors. The CFE cathodes most commonly used are W<310> and a slightly oxidized W<100> used at room temperature. The SE cathode most commonly used is a ZrO coated W<100> emitter which has a localized work function of 2.8 ±0.2 eV on the <100> plane.In terms of emission mechanism, SE and CFE represent two extremes of a continuous change in surface electric field strength F and temperature T of a pointed cathode. The primary difference between a SE and CFE cathode is F, T, and energy distribution as shown in Fig. 1. TheSE cathode emission distribution contains mostly non-tunneling electrons terminated on the low energy side by the work function barrier. In contrast, the CFE emission distribution is defined by tunneling electrons terminated on the high energy side near the Fermi level of the metal.