bluuebunny/crossref_metadata_2025 huggingface dataset:
A Big Tripod Polisher; 16 Years of Imaging Surfaes
Authors: Marks LD
Published: July 2020

Electron Microscopy of surfaces has always been a topic for a few stubborn souls. In addition to the standard headaches of electron microscopes (maintenance, breakdown) one has to handle the additional complications of maintaining a clean enough vacuum to make the results mean anything. (Without vacuum control the structures observed may be due to the contaminants, and hence meaningless.) To complicate things further, in addition to conventional ex-situ sample preparation one has to clean and equilibriate the surface while still retaining thin enough regions for useful study. The final step is to work out which techniques provide surface information and learn how to exploit them. It is appropriate to look at some of the key elements that are needed.

Sample Handling: The key to success with surfaces is not really the microscopy, but instead the sample treatment. The first crucial element is control over the sputter cleaning process.(While simple heating would be less damaging, if one wants to look at something other than silicon sputter cleaning is a must.)
Diffraction Channeling and the Production of Secondary Excitation
Authors: Pennycook SJ
Published: July 2020

The pivotal role played by Archie Howie in the development of many areas of electron microscopy is universary acknowledged.Here I would like to highlight his contribution to the quantitative description of secondary excitations, which was an important influence on the development of Z-contrast imaging in zone-axis crystals. Secondary excitations are those such as x-ray emission which occur following a primary scattering event, in this case excitation of inner shell electrons. The first important concept to be realized by Archie was that dynamical diffraction and channeling are different manifestations of the same physical effect, namely, the multiple scattering of electrons within a crystal. Second was the realization that processes which are localized within the unit cell will show a dependence on diffraction conditions, such as incident beam orientation, and could therefore be described quantitatively using dynamical diffraction theory. Precisely the same theory was used to describe the orientation dependence of cathodoluminescence

The development of the STEM for high resolution imaging was of course due primarily to Crewe and coworkers, with an annular detector to allow efficient detection of elastic scattering over a wide angular range.
Investigating the Effect of As and Te Passivation on the MBE Growth of Cdte (111) On Si (111) Substrates
Authors: Xin Y , Rujirawat S , Brill G , Browning ND , Pennycook SJ , Sivananthan S , Sporken R
Published: July 2020

The epitaxial growth of CdTe on Si is currently being investigated as a means of generating an alternative substrate for the subsequent growth and processing of HgCdTe based infrared detecting devices. The most favorable orientation for the growth of high-quality HgCdTe is CdTe (111)B, which has been demonstrated to be grown on miscut Si (001) substrates with very high quality. However, twinning islands and multiple domains are present at the nucleation stage, which has a detrimental effect on the device properties.

An alternative approach, which has the potential to overcome the multiple domain problems in the nucleation stage, is to grow CdTe (111) B on Si (111) substrates. However, previous reports have shown that the direct growth of CdTe onto Si (111) results in an A-polarity for the films. In an attempt to overcome this limitation, passivation of the substrate surface has been investigated.
TEM Study of Short-Range-Order in Zirconolite Induced by High Temperature Ion Irradiation
Authors: Wang S X , Wang L M , Ewing R C
Published: July 2020

Zirconolite (CaZrTi207) is an important phase proposed for high level nuclear waste immobilization. Zirconolite was irradiated by 1 MeV Kr+ at various temperatures. At room temperature, zirconolite became amorphous after a dose of 7x1014 ions/cm2.1 Amorphization dose increased with temperature due to thermal annealing. The critical temperature, above which amorphization does not occur, was estimated to be 654 K. During the low temperature irradiation (<654 K), concurrent with amorphization, zirconolite transformed from a monoclinic structure to the cubic pyrochlore structure and then to the fluorite substructure. The structural change is due to the disordering between cations and between oxygen and oxygen vacancies.

After an irradiation at 673 K to a dose of 3.6x1015 ions/cm, the zirconolite samples remained crystalline. The diffraction pattern consists of strong maxima from the fluorite structure and diffuse maxima surrounding the Bragg positions of the pyrochlore superlattice (FIG. 1). Diffuse scattering patterns have been reported in other phases, and were generally attributed to the shortrange- order (SRO) domains.
Nanoscale Lead Inclusions in Silicon
Authors: Johnson E , Johansen A , Touboltsev VS , Sarholt L , Dahmen U
Published: July 2020

TEM analyses of Si implanted with immiscible elements have shown that the implanted species characteristically segregate to form nanoscale inclusions in the amorphous Si matrix. Subsequen annealing induced recrystallization was found to lead to simultaneous removal of nearly all of the implanted species, explained in terms of stress-induced trapping of the implanted atoms at the amc phous/crystalline interface as it progresses towards the surface.

The solubility of Pb in Si is negligible, and it has previously been shown-that elemental nanoscale inclusions can be formed in Si either by ion implantation at elevated temperature or by rapid solidi cation. In the present work single crystals of <110> Si have been implanted with 80 keV Pb+ k at 300K, 625K and 925K respectively. The implanted fluence was 8-1019 m−2 corresponding to an average concentration of about 3 at.%. Combined TEM and RBS/channeling analysis showed that implantations at 300 K and 625 K induced amorphization of the implanted layer with dense distributions of nanoscale lead inclusions embedded in the amorphous silicon matrix (fig. 1).
Relationship Between High-Strain-Rate Superplasticity and Interface Microstructure in Aluminum Alloy Composites
Authors: Koike J , Sickafus KE , Mitchell TE
Published: July 2020

The Al alloy composites reinforced with Si3N4 or SiC have been reported to exhibit superplasticity at high strain rate of faster than 1x10−2 s−1. It has been shown in many aluminum alloy composites that the optimum superplastic temperature coincides with an incipient melting temperature. The coincidence suggests a contribution of the liquid phase to the superplasticity mechanism. This paper shows a direct evidence of partial melting along matrix grain boundaries and matrix-reinforcement interfaces. Based on the obtained results, the role of the liquid phase in the high-strain-rate superplasticity is discussed.

The sample was Al-Mg (5052) alloy reinforced with 20vol% Si3,N4 particles, fabricated by a powder metallurgy process. The sample showed an excellent superplasticity under the conditions given in Table 1. Partial melting was confirmed to occur at 821 K by differentail scanning calorimetry. The microstructural changes during heating were observed in situ by TEM using a heating stage. The structure of interfaces and grain boundaries was observed by HREM. Chemical analysis was performed with EDS attached to VG-STEM.
Characterization of Nanoporous TiO2 Membranes Used as Electrodes for Injection Solar Cells
Authors: Su DS , Bloeck U , Meißner B , Willig F , Giersig M
Published: July 2020

High efficiency solar cells require large surface layers as acceptor [1], Nanoporous titanium dioxide film is an optimun choice for that purpose. For instance, porous titanium dioxide film of one micrometer thickness, prepared by colloidal chemistry, has a porous surface whose area is 100 times larger than the surface of a compact planar film. Obviously, accessibility to surface and crystal phase of the titanium dioxide are of prime importance. In this work, we characterize nanoporous titanium dioxide membranes on Si substrate by means of high-resolution transmission electron microscopy and electron diffraction.

Colloidal TiO2 sols were prepared by a wet chemical method [2]. The resulting colloidal TiO2 sol was autoclaved in a titanium autoclave for 12h at 230°C. A portion of the autoclaved sol was concentrated under vacuum at 30°C until a concentration of 20% TiO2 (by weight) was reached. 40% (by weight of Ti02) carbowax was added to this paste and stirred over night at room temperature.
Preparation of Silicon Oxide Nanostructures Using Anodic Alumina as Templates
Authors: Zhang Ming , Bando Y , Wada K , Kurashima K
Published: July 2020

There is currently an intensive effort to develop large-scale semiconductor nanowire or nanotube materials, such as Si and silicon oxide SiOx (l<x<2), with the uniform wide range of sizes up to 30nm, which would open us new opportunities in semiconductor and catalysis industries but is difficult to achieve at present. Up to our knowledge, the detailed study on macroscopic synthesis of aligned silicon oxide nanostructures with about 30nm diameter has not been carried on yet.

The ordered nanochannel-array anodic alumina were prepared via the anodization of aluminum textured pattern on the surface in a 3% oxalic acidic solution under the constant-voltage condition. It is about 6 μm and contains ordered cylindrical pores with the uniform diameter of 20-30nm and almost perpendicular to the film surface. The aligned silicon oxide nanostructures were prepared on this anodic alumina using a sol-gel method.

For sol aged at room temperature and dipped for lmin., nanowires are formed in a shorter period of aging time; while nanotubes are synthesized in a longer time (above 23 days).
Double Length-Scale Ordered Nanoporous Silica
Authors: Yin JS , Wang ZL
Published: July 2020

Ordered assembly of hollow structures of silica and carbon have drawn much attention recently because of their applications in low-loss dielectrics, catalysis, filtering and photonics. The structure is ordered on the length-scale of the template spheres and the pore sizes are in submicron to micron range. Alternatively, ordered porous silica with much smaller pore sizes in nanosize range (< 30 nm), produced deliberately by introducing surfactant, has also been processed, in which the porosity is created by co-polymers. In this research, a new silica nanostructure with double length-scale ordered porosities was processed, one being at the submicron scale of hollow spheres created by a template of polystyrene (PS), and the other at nano-scale created by self-assembled co-polymers.

Typical processing route includes three steps. Firstly, the ordered template of PS was created. The as-received PS with mean particle size of 203 nm was used as the raw material.
The Characterization and Phase Transformation in Iron Oxides
Authors: Liao KC
Published: July 2020

In the processing of sheet steel, slabs are normally heated in a reheat furnace in the temperature range of 1200° -1300° C, extracted, hot rolled on a hot strip mill (HSM) and further processed. Because of the high operating temperature and the availability of oxygen, the steel surface is usually severely oxidized. The furnace scale could be a few millimeters thick. Abnormally thick scale may not be easily removed by high-pressure water sprays at the HSM. Rolled-in scale can contribute to underpickling and potentially result in the generation of steel surface defects.

Furnace scale typically consists of three oxide layers, Fe2O3 (hematite) on the outside surface, Fe3O4 (magnetite) in the middle and FeO1+x (wustite) next to the steel substrate. An example is shown in Figure 1. The three oxide layers are identified by H (hematite), M (magnetite) and W (wustite). Furnace scale samples of low carbon steel have been analyzed via x-ray diffraction (XRD) and optical metallography in order to characterize the scale.
Enhancement of SEM/EDS Analysis Using FIB Sample Preparation
Authors: Vartuli CB , Stevie FA , Bindell JB , Shofner TL , Purcell BM
Published: July 2020

Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) has become less useful for semiconductor samples as feature dimensions decrease. It has become increasingly difficult to get sufficient signal from small features because of the large interaction volume of the primary beam. As the interaction volume is dependent on the accelerating energy of the primary electron beam, decreasing the accelerating voltage will decrease the interaction volume. This increases the percentage of signal from the feature of interest, but also lowers the number of peaks available for interpretation, reducing the sensitivity of the analysis. Several elements commonly used in the fabrication of semiconductors have overlapping peaks at lower energies, and the ability to distinguish between them is lost at low accelerating energies. It is possible to modify samples using Focused Ion Beam (FIB) to improve EDS resolution without decreasing the accelerating voltage.

The samples were prepared in an FIE 800 FIB and imaged in an Hitachi S-4700 SEM.
In-Situ Transformation of a Zinc Tem Lift-Out Specimen
Authors: Prenitzer BI , Collins S , Giannuzzi L A
Published: July 2020

The focused ion beam (FIB) lift out (LO) technique has been used to prepare transmission electron microscopy (TEM) specimens from individual Zn powder particles [1]. The Zn microstructure observed by TEM was compared to the Zn microstructure analyzed by traditional metallographic preparation techniques. It was concluded that the Ga focused ion milling produced no apparent microstructural damage to the Zn [1]. A low magnification TEM image of the FIB prepared Zn specimen obtained from a Philips EM430 operating at 300 KeV is shown in figure la.

The Zn FIB LO specimen was then processed in a plasma cleaner. After subjecting the Zn specimen to the plasma cleaning operation, the specimen was observed in a Philips EM400 operating at 120 KeV. The Zn specimen completely transformed during in situTEM observation at 120 KeV. The specimen was then subsequently observed in an EM430 to analyze the transformed Zn at 300 KeV.
Characterization of Thin Films on Oxide Using a Unique Tem Specimen Preparation Process
Authors: Lam Lawrence K , Ast Dieter G
Published: July 2020

Transmission Electron Microscopy technique is a powerful tool to examine microstructures. However, the specimen preparation process usually requires tedious and careful cutting and lapping. In this paper, we present a TEM specimen preparation process which is simple, requires about one hour, and allows specific areas of patterned films deposited on silicon dioxide to be examined. The sample consisted of three thin film layers deposited on a Corning 1737 glass substrate. The top layer was 1000 A thick, low temperature oxide; the middle layer, 1000 A thick; amorphous silicon; the bottom layer, 1000 A thick, low temperature oxide. The top oxide layer was patterned to contain a square array of 10 × l0um openings, with a 100 um center to center spacing. A thin nickel layer was the evaporated, and the specimen was heated to form nickel silicide in the 10 × 10 um areas where Ni and Si were in contact.
Synthesis of Electron Energy Loss Spectra and Application to Quantifying Detection Limits in Materials Science
Authors: Menon N K , Krivanek O L , Natusch M K H
Published: July 2020

Electron energy loss spectroscopy (EELS) is a powerful microanalytical tool that can be used to characterize the composition and other properties of a wide range of materials. The compositional information is retrievable from the pattern of edges displayed in the energy-loss spectrum [1]. Under favorable experimental conditions, concentrations below 1000 ppm of many different elements can be detected on a nanometer scale [2].

The minimum detectable mass (MDM) and the minimum detectable mass fraction (MDF) attainable in practice depend on many parameters (sample thickness, incident beam convergence / acceptance angles, primary energy, electron dose, probe size, detector efficiency, etc.), and there are no easy rules that can be used to predict them. For instance, a minority element that gives rise to an edge situated at an energy just lower than a major edge due to a principal constituent is much easier to detect than a minority element that gives rise to an edge just above the major edge.
Two-dimensional carrier profiling of advanced sub-micron silicon devices using Scanning Capacitance Microscopy
Authors: Konkar Atul A , Chen Wei , Noehring Kari
Published: July 2020

With the continuing push for reduction in the device dimensions into the deep sub-u,m dimensions, the critical need for physical and electrical characterization on this sub-μ,m scale is evident. The National Technology Roadmap has identified need for two-dimensional (2D) dopant/carrier profiling with a spatial resolution of 10 nm. Though current techniques used for dopant profiling such as secondary ion mass spectroscopy (SIMS) and spreading resistance profiling (SRP) have a high sensitivity, these offer good resolution only in the depth direction. The spatial resolution in the lateral direction in these techniques is limited to several tens or hundreds of microns. To acheieve the required lateral spatial resolution different scanning probe based techniques have been explored. One of the most promising of these class of techniques is scanning capacitance microscopy (SCM). In SCM a conductive atomic force microscope (AFM) probe tip is scanned across the surface and simultaneously an a.c. bias is applied between the tip and the sample.
Chemical Imaging With a Scanning Probe Microscope
Authors: Kossakovski Dmitri A , Baldeschwieler John D , Beauchamp J L
Published: July 2020

Scanning Probe Microscopy (SPM) is a superb tool for topographical analysis of samples. However, traditional varieties of SPM such as Atomic Force, Scanning Tunneling and Near-field Scanning Optical Microscopy have limited chemical contrast capability. Recently, several advanced techniques have been reported which provide chemical information in addition to topographical data. All these methods derive advantage from combinations of scanning probe methodologies and some other, chemically sensitive technique. Examples of such approaches are: Near-field Scanning Raman Imaging, Near-field Scanning Infrared Microscopy and mass spectrometric analysis with laser ablation through fiber probes.

In this contribution we report the development of a new method in this family of chemically sensitive scanning probe techniques: Laser Induced Breakdown Spectroscopy with Shear Force Microscopy, LIBS-SFM. Traditional LIBS experiments involve focusing a pulsed laser beam onto the sample and observing optical emission from the plasma formed in the ablation area. The emissions are mostly in the UV/visible range, and the signal is due to electronic transitions in excited atoms and ions in the plasma plume. The spectra are analyzed to identify chemical elements. The spatial resolution of LIBS is limited by the wavelength and beam quality of the laser used for ablation. The experiments may be conducted in vacuum, controlled atmosphere, or ambient air.
The Effect of Thin Water Films on Force Microscopy Measurements
Authors: Sedin D , Rowlen K
Published: July 2020

The atomic force microscope (AFM) is a powerful tool for probing surface topography, in addition to chemical and mechanical properties of surfaces. To investigate the chemical properties of a sample, force measurements are made between the AFM's “molecular finger,” or probe, and the sample. Force measurements can be made in many environmental conditions, which makes the AFM a versatile technique. However, in ambient conditions most samples are covered by a thin layer of water. When the AFM probe comes into contact with the thin water layer, a capillary bridge forms between the AFM probe and sample. Because of this water layer, it is believed that in ambient conditions a non-surface specific capillary force dominates the adhesive force between the AFM probe and sample. The non-surface specific capillary force should obscure any information about the surface. Currently, we are studying to what extent the capillary forces are non-surface specific and what influence this has on pull-off-force measurements.
Effect of surface oxide characteristics on Scanning Capacitance Microscopy Imaging
Authors: Konkar Atul A , Chen Wei , Noehring Kari
Published: July 2020

Scanning capacitance microscopy (SCM) is currently one of the most promising tools for twodimensional carrier profiling. This technique, based upon atomic force microscope (AFM) operated in the contact mode, uses a conductive probe which is scanned over the semiconductor surface. The conductive probe, oxide on the surface of the semiconductor, and the semiconductor substrate form a metal-oxide-semiconductor (MOS) structure. An a.c. bias is applied to the tip and the capacitance of the MOS structure is monitored. The a.c. bias changes the depletion of carriers in the semiconductor and thus the total capacitance of the structure. The maximum capacitance of the MOS structure is obtained when the semiconductor is in accumulation and the total capacitance of the structure is the capacitance of the semiconductor surface oxide. The minimum capacitance is obtained when the semiconductor region under the tip is in inversion. Since SCM the output signal is proportional to the differential capacitance, to get a high signal we need to maximize the difference between the maximum and minimum in the total MOS capacitance.
Direct Magnetic Excitation of Cantilevers for Dynamic Force Microscocopy in Liquids
Authors: Lindsay SM
Published: July 2020

The mechanical Q-factor of an AFM cantilever immersed in fluid is reduced to a small value (ca. 3) owing to viscous damping. Thus, a large driving force is needed to excite the cantilever into bending motion in fluid. There are two common methods for exciting cantilevers for dynamic force microscopy in fluids, illustrated in Figure 1. Fig. la illustrates acoustic excitation in which a piezoelectric transducer displaces the base of the cantilever, causing bending motion of the cantilever when the driving frequency is near to a bending resonance of the cantilever. Fig. lb shows magnetic excitation. In magnetic excitation, a magnetic field is used to cause bending of a magnetic cantilever either through magnetostriction or MXB forces.

Acoustic excitation has the highest amplitude at mechanical resonances of the cantilever housing, with the result that the response is dominated by these sharp features,Fig. 2a. In contrast, the response to magnetic excitation is intrinsic to the cantilever, Fig. 2b. Thus, magnetic excitation permits the cantilever to be driven over a wide range of frequencies. This is important for calibration of the amplitude and for experiments involving time and concentration dependence in tip-sample interactions, e.g., anti-body recognition imaging.
Single Protein Mechanics Studied with Afm Techniques
Authors: Carrion-Vazquez M , Oberhauser AF , Fowler SB , Marszalek PE , Clarke J , Fernandez JM
Published: July 2020

The Atomic Force Microscope is a simple instrument capable of imaging single macromolecules with submolecular resolution and measure the forces required to unfold a single protein domain (Fig. 1).

The AFM method of unfolding a tandem modular protein generates a characteristic sawtooth pattern in the force-extension curves (Fig. 2). The measured spaces between the peaks are thought to correspond to the increase in contour length (ΔΔLC) of the protein caused by the unfolding of one of its modules. In order to demonstrate the validity of this model and measure the sensitivity of the AFM we have designed an experiment where we have inserted a cluster of 5 Gly into the loop joining the F and G b-strands of the I27 module of the I band from human cardiac titin. This loop is clearly within the folded structure of the module and hence, if our predictions are correct, unfolding of the I27-5Gly module should reveal an expanded ΔLC. We expect to measure an increase in the contour length increment of ΔΔLC = 5 ✗ 0.38 nm =1.9 nm.
Structural and Organizational Studies of Soluble Tar-Chewchea Complexes by Electron Microscopy and Image Analysis
Authors: Francis Noreen R , Shaikh Tanvir R , Levit Mikhail N , Melanson Linda A , Stock Jeffrey B , DeRosier David J
Published: July 2020

The transmembrane receptor for aspartate, Tar, in Escherichia coliand Salmonellais representative of a large class of receptors that generates chemotaxis responses by regulating the activity of an associated histidine kinase, CheA. Tar is composed of an Nterminal extracellular ligand-binding domain linked through a transmembrane sequence to a C-terminal signaling domain in the cytoplasm. The isolated cytoplasmic domain of Tar fused to a leucine zipper sequence forms soluble ternary complexes with CheA and an adapter protein, CheW. The isolated complex is biochemically active, has a molecular weight of 1,400,000 Daltons, and includes approximately 28 receptor signaling domains for 2 CheA dimers.

Electron microscopy of the complexes indicates well-defined bundles, presumably composed of numerous receptor filaments surrounding a core of CheA dimers and CheW. CheA also interacts with CheY, the response regulator of the bacterial flagellar motor. Immunoelectron microscopy has provided a general picture of the domain organization of the complexes.
2-Photon Excitation Laser Scanning Microscopy for High Resolution Imaging In Scattering Biological Tissues: Applications to Neuroscience
Authors: Svoboda K , Burbach BJ , Lendvai B , Mainen ZF , Maravall M , Nimchinsky E , O’Brien P , Sabatini B , Stern E
Published: July 2020

Optical microscopy has been at the center of biological research, and neuroscience in particular, for a long time. For example, over one hundred years ago advances in microscopical techniques directly led to the discovery that neurons are in fact cells (the so-called ‘neuron doctrine’), and subsequently to the description of the high-resolution structure of the nervous system. More recently, the development of fluorescent indicators of cellular function, including Ca2+, Na+, and pH indicators, has made it possible to image not only the structure of neurons but also aspects of their function. The most important of these has been the measurement of intracellular free calcium concentration, [Ca2+]. Calcium is an important messenger molecule because it couples electrical excitation to biochemical signaling cascades. In addition, in neurons [Ca2+] is also a good indicator of local electrical excitation and thus [Ca2+] imaging allows the measurement of cellular excitability in subcellular compartments that are inaccessible to other methods.
Biological Applications of Chromophores With Large Two-Photon Cross Sections
Authors: Dickinson ME , McCord-Maughon D , Staub K , Levin MD , Parker T , Fraser SE , Marder SR
Published: July 2020

One current limitation of two-photon technology is the lack of optimized fluorochromes for Two-Photon Laser Scanning Microscopy (TPLSM). Recently, Albota et al. (1998) have reported the design and synthesis of a number of bis(styryl)benzene derivatives that have large fluorescence quantum yields and greater two-photon absoption cross sections than any of fluorochromes that are currently used for TPLSM. As a first step in understanding how such molecules could be used in biological experiments, we have tagged a donor-πdonor molecule with biotin. We have successfully used this dye to detect quail nuclei in 2- 4 day old fixed embryos that have been reacted with QCPN, a quail specific monoclonal antibody. We have observed that this molecule gives a very intense signal, among the most intense signals we have been able to measure in our immunoassay. In particular, the brightness was about a factor of four higher than Rhodamine B-labelled streptavidin (containing 3.3 moles of dye per streptavidin tetramer).
Multi-Dimensional Microscopic Analysis of Sea Urchin Development
Authors: Summers R , Martins G , Morrill J
Published: July 2020

Several modalities of microscopic analysis have been employed in the investigation of development in the embryos of the sea urchins Strongylocentrotus purpuratusand Lytechinus  variegatus. These include scanning electron microscopy, confocal optical microscopy and multiphoton laser scanning microscopy. These techniques all provide information on embryonic morphogenesis in three-dimensions and may be of use in the analysis of other developing organisms.

Scanning Electron Microscopy. Scanning electron microscopy bridges the gap between light and transmission electron microscopy. Operation in the secondary electron image mode with stereo-pair images combines great depth of field in focus from 10-50,000x with true 3D images of topographical features from whole embryos to macromolecules. The SEM's backscatter electron imaging mode allows one to see and map spatial geographies of colloidal gold labeled probes (e.g. antibodies, lectins) that bind to exposed surfaces of embryos, cells and extracellular matrices.
Contributions of Microscopy to the Diagnosis and Investigation of Aids-Associated Renal Disease
Authors: Howell D N , Szczech L A
Published: July 2020

Microscopy has had a major role in the analysis of renal disorders associated with human immunodeficiency virus (HIV) infection, both as a diagnostic method and as a means of studying pathogenic mechanisms. In the diagnostic realm, microscopic analysis of renal tissue obtained at biopsy and autopsy is a mainstay for the detection of a wide range of glomerular, vascular, and tubulointerstitial diseases. As an investigative tool, microscopy has made an important, albeit somewhat controversial, contribution to our understanding of the pathogenesis of at least one HIV-associated renal lesion.

A variety of ultrastructural alterations have been documented in association with HIV infection. These include tubuloreticular inclusions (most commonly seen in vascular endothelial cells and mononuclear leukocytes)(Fig. la), cylindrical confronting cisternae (typically found in mononuclear leukocytes) (Fig. lb), and nuclear abnormalities such as nuclear bodies and granular change (most often in tubulointerstitial cells) (Fig. lc).
N-Formyl Peptide Receptors Display an Asymmetric Distribution In Migrating Human Neutrophils
Authors: Loitto Vesa-Matti , Rasmusson Birgitta , Magnusson Karl-Eric
Published: July 2020

A debated and yet unanswered question, in regard to polarization and directed movement of phagocytic cells, concerns the distribution of chemoattractant receptors during cell locomotion1. We have therefore studied the instantaneous distribution of N-formyl-peptide receptors on living neutrophils. Using a fluorescent N-formyl-peptide receptor antagonist, tert-butyloxycarbonyl-Phe(D)-Leu-Phe(D)-Leu-Phe-OH (Boc-FLFLF), and a fluorescent receptor agonist, formyl-Nle-Leu-Phe-Nle-Tyr-Lys (fnLLFnLYK), the localization of the chemoattractant receptors could be followed during random migratio2. Neutrophils were adhered to plasma-coated coverslips. A Nomarski differential interference contrast (DIC)- image was taken, and rapidly followed by a fluorescence-image captured with a water-cooled, slow-scan CCD-camera. Then a second DIC-image was directly recorded to reveal the direction of cell movement.

Using fnLLFnLYK we observed that the distribution of N-formyl-peptide receptors was clearly heterogeneous as shown in figure. Fluorescence was concentrated mainly at the rear and front of elongated locomoting cells, leaving the cell body almost non-fluorescent.
Clofoctol-Induced Ultrastructural Changes In Staphylococcus Aureus
Authors: Maleeff Beverly E , Pearson Stewart C , Payne David J , Hart Timothy K
Published: July 2020

Clofoctol [2-(2,4-dichlorobenzyl)-4-(tetramethyl-l,l,3,3-butyl) phenol] is a synthetic antibacterial compound with activity against both Gram-positive1 and Gram-negative2 microorganisms. Although the specific mechanism of Clofoctol action has not been fully elucidated, it is reported to alter the permeability of the cytoplasmic membrane in Bacillus subtilis, and is used clinically to treat upper respiratory tract infections in humans. Staphylococcus aureus is a major human Grampositive pathogen that causes a variety of human diseases ranging from localized skin suppuration and food poisoning to life threatening presentations such as septicemia and endocarditis. Several clinical isolates of S. aureus have recently been identified that are resistant to all currently available antibacterial therapies. Consequently, the identification of new antimicrobial targets in this organism is of paramount importance. The purpose of this study was to investigate the in vitro effects of Clofoctol on S. aureus.

Ultrastructural examination of S. aureus revealed a population of actively dividing cells.
Fatal Encephalitis In Young Children, Taiwan, 1998
Authors: Goldsmith Cynthia S , Shieh Wun-Ju , Pallansch Mark A , Ksiazek Thomas G , Hsueh Chuen , Jung Shih-Ming , Kuo Tseng-Tong , Chen Yi-Ping , Zaki Sherif R
Published: July 2020

During April-July 1998, an increase in fatal cases of neurologic disease in young children occurred in Taiwan, with at least 55 fatalities reported. Concurrently, an outbreak of hand, foot, and mouth disease (HFMD) was also occurring. In fatal cases, the acute illness was characterized by fever, or rash, or mouth ulcers, followed by a rapid cardiopulmonary failure; death frequently occurred within 24 hours of hospitalization. Approximately three-fourths of the fatalities were in children less than 3 years of age. We report here the findings from autopsy specimens from two of the fatal cases of encephalomyelitis.

In Case 1, a 9-year-old female, H&E sections of central neurologic system (CNS) tissue showed perivascular infiltrate, areas of inflammation, necrosis, and neuronal degeneration. Immunohistochemical (IHC) staining was positive when using a monoclonal antibody for enterovirus 71 (EV71), a picornavirus associated with HFMD.
Comparison of the Effect of the Carbamate Herbicides, Barban and Chlorpropham, on Mrc-5 and Hela Cells
Authors: Tate J E , Palisano J R
Published: July 2020

Barban and chlorpropham are common carbamate herbicides that disrupt mitosis by destabilizing plant microtubules. Tubulins, protein subunits of microtubules, in plant and animal cells are highly conserved through evolution. Plant and animal cells have been shown to possess similar microtubule structural proteins, microtubule binding proteins, and organizational proteins. These similarities suggest that herbicides targeting plant microtubules might also affect animal microtubules. Previous tubulin immunofluorescence microscopic studies of HeLa cells, a human cervical cancer cell line, have shown that barban is strongly cytoskeletotoxic and chlorpropham is weakly cytoskeletotoxic. Both barban and chlorpropham have been shown to disrupt mitosis and disorganize spindle apparatus formation in numerous types of mammalian cancer cells.

This investigation was undertaken to examine the effect of barban and chlorpropham on MRC-5 cells, a normal human fibroblast cell line, as well as on HeLa cells. A monoclonal antibody to α-tubulin, a microtubule specific protein, was used to probe the formation of spindle apparatuses in dividing cells.
Morphological Correlates of the Protection Afforded By Varma Mixture In Rat Cornea Exposed to Half Mustard (Cees).
Authors: Petrali JP , Henein M , Ali AH , Devamanoharan PS , Hamilton TA , Varma SD
Published: July 2020

Whole body exposure to the chemical warfare agent, mustard gas, bis-(2-chloroethyl) sulfide, or its laboratory model compound, half mustard, 2-chloroethyl ethyl sulfide (CEES), induces cutaneous, respiratory and ocular impairments. Of these, ocular damage causes the most immediate incapacitation with initial symptoms evident within minutes. This incapacitation is a result of irritation and edema of eyelids, conjunctiva and especially cornea. Development of corneal epithelial lesions and edema leads to deterioration of corneal transmissive and refractive properties with untoward effects on visual acuity. Heretofore, there has been no specific pretreatment, or antidotal therapy for mustard gas-induced ocular impairment. In the present study, we describe morphological correlates of the apparent attenuation of such damage by a mixture compound developed by Varma et al. Varma mixture (VM) consists of compounds known to provide bio-energetic support, prevent oxidative stress, modulate membrane permeability and support tissue metabolism. The mustard agent used in this study was CEES.
Demonstrating Angiogenesis In a Human Testicular Malignant Tumor Using the Scid-Maus Model. Intravital Video Microscopy and Scanning Electron Microscopy of Vascular Corrosion Casts
Authors: Aharinejad S , Schlag M , Abri H , Fink M , Nourani F , Nedwed S , Schlatter P
Published: July 2020

Growth of malignant tumors relies on development of new vessels from the existing vessels, a process called angiogenesis. Little is known about the pattern of chronic vascular growth in the human germ cell testicular cancer. To shed light on this topic, we injected human CRL-2073 testicular cancer cells or saline (sham treated mice) into the testes of SCID-mice and studied the growth of the tumor's vasculature using intravital video microscopy (IVM) on days 7, 14, 21, 28 and 37 after injection. On each day, 4 mice were studied. To better identify microvessels, fluorescein isothiocyanate-dextran (FITC) was injected i.v. prior to IVM. After IVM, one testis was cast with Mercox and studied in a scanning electron microscope (SEM), the other was used for histology. IVM images were transferred to the computer and analyzed using the Lucia morphometry software.
Examination of Large Unilamellar Vesicles (Luvs) Using Cryo-hrsem and Cryo-Stem
Authors: Caran K L , Apkarian R P , Menger F M
Published: July 2020

Vesicles derive their structure from the aqueous environment surrounding and within them. It follows that traditional EM specimen preparation techniques of fixation, dehydration and drying can induce a variety of morphological changes to the membranes. Vitrification of aqueous suspensions of vesicles provides a means for observation of these structures in their fully hydrated unfixed state. Common cryogenic techniques for the visualization of these and other colloidal particles include cryo-TEM of vitrified thin films and freeze-fracture TEM (FF-TEM) of platinum replicas. We report the use of cryo-high resolution SEM (cryo- HRSEM) and cryo-STEM for the study of the morphology of membrane features of synthetic extruded vesicles.

LUVs were prepared by the extrusion method. Dried lipid films of l-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) were hydrated with 0.5 mL of Milli-Q water and stirred for 10 minutes to make suspensions (10 mM in lipids) which were extruded 19 times through a polycarbonate filter with 100 nm pores.
Quantitating Pressure-Induced Optic Nerve Injury In A Rat Model Of Glaucoma.
Authors: Johnson EC , Cepurna WO , Morrison JC
Published: July 2020

Elevated intraocular pressure (IOP) is the most widely recognized risk factor for glaucoma and the target of nearly all current glaucoma therapy. The goal of our laboratory is to understand mechanism by which elevated IOP results in axonal degeneration in the optic nerve.

In order to study the effects of IOP level on the optic nerve, we have developed a number of methods to modulate IOP in the rat. We sclerose the aqueous humor outflow pathways to elevate IOP for a period of weeks to produce focal optic nerve lesions. This method reproduces many of the pathological characteristics of human glaucoma. A modification of this method uses constant light (CL) housing to stabilize the normally wide circadian IOP oscillations, simplifying the correlation of IOP history with lesion size. However, the CL-stabilized IOP in untreated, fellow eyes is above the normal light phase IOP of 20 mm Hg and close to the normal dark, phase value of 30 mm Hg.
Recent Advances In Microscopy Of The Ear
Authors: Trune DR
Published: July 2020

Historically microscopy of the ear has been difficult because it is entirely encased in bone. This not only impeded fixation, embedding, and sectioning of the ear for histology and immunohistochemistry, but also made experimental microscopic observation of the living ear virtually impossible. Numerous recent advancements in microscopy have improved our ability to observe the delicate cellular structures of the ear, as well as utilize high magnification microscopy on living tissue for experimental and physiological studies.

Traditional immunohistochemistry at both the light and electron microscopic levels is now facilitated by better antigen preservation through improvements in decalcification, more permeable plastics, and thousands of commercially produced antibodies. Individual cell surface receptors now can be identified, as well as their upregulation by circulating steroids, drugs, antibodies, and enzymes. Cochlear tissues also can be completely dissociated and the electrophysiology of individual living hair cells recorded with microelectrodes while under microscopic observation.
Surface Morphological Changes Of Hela Cells Exposed To Tamoxifen And Taxol
Authors: Majumdar SK , Valdellon J
Published: July 2020

Tamoxifen and taxol are two promising chemotherapeutic agents currently used in cancer treatment, but each has its own unique mechanism of action. Tamoxifen, known to inhibit the activity of estrogen on malignant mammary gland cells, was recently approved by the FDA for the treatment of breast cancer. Taxol, extracted from the Pacific Yew tree, Taxus brevifolia, is an antimitotic agent that binds specifically to the β-subunit, promoting the assembly and stabilization of tubulin polymers. Studies have shown that tamoxifen and taxol induce cytostatic and cytotoxic effects leading to the death of several cancer cell types in vitro.In this research, the surface ultrastructural effects of both tamoxifen and taxol were investigated in human cervical cancer cells (HeLa).

Exponentially growing cells were treated with 5, 10, 15, and 20 μg/ml of tamoxifen and 1 μg/ml of taxol (LC50) for 24, 48, 72, and 96 hours. For scanning electron microscopy (SEM), the cells were grown on coverslips, fixed in 2% glutaraldehyde followed by 1% osmium tetroxide.
Dynamics Of Mitochondria In ρ° Human Cells Repopulated With Exogenous Mtdna Observed By Transmission Electron Microscopy
Authors: Lu Yun , King Michael P
Published: July 2020

Mitochondrial DNA (mtDNA) mutations have been found associated with several neuromuscular diseases. In order to address further mechanisms of pathogenesis of the specific mtDNA mutations in responsible for these diseases, the ρ° human cell culture system has been established and has been widely used in recent years (4)'(5). This system is based upon the repopulating of human cells, which are completely depleted of mtDNA (termed ρ° cells), with exogenous mitochondria containing the mtDNA of interest. Molecular genetic and biochemical analysis showed that transformants can be obtained with various mitochondrial donors and the respiratory competence can be restored. In this study, the ultrastructural and immunocytochemical variations of mitochondria in human cell lines cultured in this system observed by transmission electron microscopy are reported.

Cell cultures for wild-type 143B, ρ206, and transmitochondrial cell lines have been described previously. Cells were trypsinized and collected from individual culture plates, and then were fixed with 3% paraformaldehyde and 0.04% glutaradehyde in 0.1 M phosphate-buffered saline (PBS) with 4% sucrose (pH 7.6) at RT.
Ultrastructure Of Conidium And Disjunctor Development In The Plant Pathogenic Fungus Monilinia Vaccinii-Corymbosi
Authors: Mims C W , Richardson E A
Published: July 2020

Monilinia vaccinii-corymbosi is the cause of mummy berry disease of commercial blueberries (Vaccinium spp.) grown in the United States and Canada (1). Ovaries of blueberry flowers are infected by the conidia (asexual spores) of this pathogen. However, despite their importance in disease initiation, little is known of the ultrastructural features of these conidia. The only ultrastructural data on these spores has come from the work of Batra (2) who used scanning electron microscopy to describe the morphology of the so-called “disjunctors” which connect adjacent conidia of M. vaccinii-corymbosi. The presence or absence of disjunctors is an important taxonomic character in the genus Monilinia (1) but little is known of their development and exact nature. The objective of this study was, therefore, to elucidate details of conidium and disjunctor development in M. vaccinii-corymbosi.
Investigation Of Dna Organization In Spermatozoa Using High Resolution Scanning Electron Microscopy
Authors: Klaus Angela V , Steven Ward W
Published: July 2020

The average somatic nucleus is only 10 microns in diameter, yet contains 2 meters of DNA coiled within its volume. This compaction must be accomplished in such a way so that the DNA remains accessible to the machinery of transcription, replication and repair. Sperm nuclei also have compacted DNA; however, structurally and functionally the arrangement of DNA in sperm is vastly different from that of somatic DNA. Somatic DNA is initially compacted by coiling around histone octamers, while sperm DNA is bound to elongate, highly basic proteins called protamines. Protamines bind the major groove of the double helix and allow adjacent DNA strands to come in close contact by neutralizing the negative charge of the sugar-phosphate backbone. Figure 1 illustrates the two most widely accepted models of DNA compaction in both somatic and sperm nuclei.

The arrangement of DNA within sperm nuclei is difficult to study because it is so highly compressed.
Light Microscopy, Confocal Laser Scanning Microscopy And Scanning And Transmission Electron Microscopy Of Cerebellar Golgi Cells.
Authors: Castejόn O , Sims P
Published: July 2020

The cerebellar cortex of albino mice, hamsters, teleost fishes, primates and human have been examined by correlative microscopy to study the Golgi cell soma, dendritic processes, axonal plexus and synaptic connections in the granular and molecular layers. For light microscopy (LM) toluidinc blue stained-plastic embedded scmithin sections and Golgi light microscopy preparations were used. For confocal laser scanning microscopy (CLSM) of hamster cerebellum the FM4-64 fluorescent stain was used as intracellular tracer (1). Conventional and high resolution scanning electron microscopy (SEM) of teleost fishes, primates and human were coated with gold-palladium and chromium (2). I Transmission electron microscopy (TEM). either by ullrathin sections or frccze-clching replicas, were examined to characterize synaptic connections in the granular and molecular layers. The Golgi cells appeared in the granular layer as polygonal, stellate, round or fusiform microncurons. 10-25 μm in maximal dimension, surrounded by the granule cell groups. Golgi light microscopy.
Incorporation Of Membrane Proteins Into Lipid Bilayers For Scanning Transmission Electron Microscopy And Single Particle Reconstruction
Authors: McAlduff DE , Heng YM , Ottensmeyer FP
Published: July 2020

The experimental approaches available to study the structure of most membrane proteins are limited. X-ray crystallography or electron crystallography rely on the availability or creation of 3D or 2D crystals to obtain high resolution structural information of membrane proteins. Single particleimaging of detergent solubilized protein is also possible, but removes the protein from its native environment. Torecreate suchan environment, we have developed a method which permits membrane proteins to be visualized in a lipid bilayer support.

A copper grid overlaid with a holey plastic film is vertically submerged into a lipid monolayer (Fig.l). This action creates planar lipid bilayers spanning 1 to 10 μm holes of the plastic film. These synthetic membranes have a thickness of approximately 40 Å, comparable to literature values for various cell membranes and are reasonably stable under a defocused beam in a transmission electron microscope (TEM)(Fig.2). Proteoliposomes with appropriate proteins in their membrane are added to the still-wet fresh lipid bilayers such that the liposomes fuse with the planar membrane (Fig.3).