bluuebunny/crossref_metadata_2025 huggingface dataset:
Monolayer Morphology and Collapse Induced by Lung Surfactant Protein: Observation Via Fluorescence and Atomic Force Microscopy
Authors: Lipp Michael M.
Published: June 2020

Understanding the role of lung surfactant specific proteins in lipid monolayers is essential for improved treatments for Respiratory Distress Syndrome, which is a leading cause of death in premature infants. Fluorescence (FM) and Atomic Force (AFM) microscopies reveal that the amino-terminal peptide of lung surfactant protein SP-B alters the behavior of palmitic acid (PA) monolayers, enhancing their in vivo performance. The combination of these techniques provides an excellent correlation between the protein-lipid interactions on the molecular level with the macroscopic properties of the monolayer.

SP-B protein incorporates into monolayers of PA, an important component of natural and synthetic lung surfactants monolayers. The effect of the protein on the monolayer is evidenced in the isotherm data shown in Fig 1, in which the area per PA molecule, compressibility, and surface pressure at collapse all increase as a function of increasing protein concentration. The protein accomplishes this by inhibiting the formation of ordered phases of PA. This is seen via FM as a transition from a homogeneous, dark ordered phase without protein (Fig 2a) to a network of a disordered, bright phase (the fluorescent lipid probes used in this study prefer to partition into disordered phases, making them appear as bright regions in FM images) that separates ordered phase domains at coexistence (Fig. 2b). The network is stabilized by the low line tension between the bright phase and other lipid phases as confirmed by the formation of extended linear domains of bright phase in a dark background, or “stripe” phases (Fig. 3a) under certain subphase conditions. Similar stripe phases also occur in single component fluorescein-labeled SP-B monolayers (Fig 3b), implying that the protein is responsible for the reduction in line tension. The formation of the fluid phase network is responsible for the increased collapse resistance of these mixed monolayers. The mechanism of collapse shifts from a heterogeneous process of nucleation and growth of large rigid crystalline collapse phases (Fig. 4a) to a more homogeneous process with nucleation and growth of smaller domains distributed uniformly across the film (Fig. 4b). This is due to the protein-induced network breaking up and isolating the domains of ordered phase, effectively lowering the probability of finding a heterogeneous nucleation site within each domain (analagous to the classic experiments of Turnbull on supercooled microemulsions of metallic liquids). The partitioning of the protein into the bright phase network was confirmed through the use of a dual-probe system. Fluorescein-labeled SP-B was added to a PA monolayer incorporating a fluorescent lipid analogue that emits at a higher wavelength. Upon imaging the same region of a monolayer at the different wavelengths (Fig. 5a and 5b), the protein is seen to be located in the bright phase network regions as expected.
Inhomogeneous Reaction between Epitaxial Al and Si(111) Revealed by Scanning Internal Photoemission Microscopy (IPEM)
Authors: Miyazaki S. , Okumura T. , Miura Y. , Hirose K.
Published: June 2020

Aluminum is one of the most important materials for the Si LSI metallization. An epitaxial growth of Al films on Si can be achieved since the lattice constant ratio between Al and Si is approximately given by 3 to 4. It is expected that epitaxial Al films are highly stable against thermal annealing. However, epitaxial-Al/Si contacts have sometimes shown a significant change in Schottky barrier height (SBH) and interface structure upon annealing. The objective of this paper is to clarify the relation between the SBH inhomogeneity and the thermally induced reaction between Al and Si through grain boundaries. The microscopic SBH distribution was measured by using scanning internal- photoemission microscopy (IPEM).

Epitaxial Al layers were deposited on n-Si(l11) by electron beam evaporation at substrate temperatures of 220°C and 250°C. In the as-deposited state, the Al film fabricated at 220°C consisted mainly of “type-A”- and partially of “type-”"-orientated interfaces (referred to as a mixed phase: MP-AS), while that deposited at 250°C consisted only of “type-B” (referred to as a single phase: SP-AS). The samples were annealed for 1 hour at temperatures between 450-550°C and then quenched.
Intranet Web System, a Simple Solution to Companywide Information-on-demand
Authors: Zhang Xiao
Published: June 2020

Intranet, a private corporate network that mirrors the internet Web structure, is the new internal communication technology being embraced by more than 50% of large US companies. Within the intranet, computers using Web-server software store and manage documents built on the Web’s hypertext markup language (HTML) format. This emerging technology allows disparate computer systems within companies to “speak” to one another using the Internet’s TCP/IP protocol. A “fire wall” allows internal users Internet access, but denies external intruders intranet access. As industrial microscopists, how can we take advantage of this new technology? This paper is a preliminary summary of our recent progress in building an intranet Web system among GE microscopy labs. Applications and future development are also discussed.

The intranet Web system is an inexpensive yet powerful alternative to other forms of internal communication. It can greatly improve communications, unlock hidden information, and transform an organization. The intranet microscopy Web system was built on the existing GE corporate-wide Ethernet link running Internet’s TCP/IP protocol (Fig. 1). Netscape Navigator was selected as the Web browser. Web’s HTML documentation was generated by using Microsoft® Internet Assistant software. Each microscopy lab has its own home page. The microscopy Web system is also an integrated part of GE Plastics analytical technology Web system.
The CM200 Feg-Twin Optimized for Cryo-Electron Microscopy
Authors: Lücken Uwe , Otten Max T.
Published: June 2020

The requirements for cryo-electron microscopy are: good vacuum, high resolution under low-dose conditions at low magnification, low drift with cooled cryo-transfer holders and, in some cases, fast spotscan imaging. For our cryo microscopes we have introduced special factory tests in which these specifications will be met.

In order to obtain high spatial frequencies at low magnification an appropriate specimen with a statistical distribution of small spacings and a fine-grained recording film is needed. We used amorphous tungsten on carbon as specimen and overexposed and underdeveloped Agfa Scienta film (Fig. 1). The laser diffractogram in Fig. 2 presents Thon rings out to 0.19 nm in a one-second exposure flood-beam image. The result of a similar experiment done with a cooled cryo-transfer holder is shown in Fig. 3. Flood-beam images of gold islands and carbon black on a thin carbon film were taken at 66 OOOx at liquid-nitrogen temperature with one second exposure under low-dose conditions. The laser diffractogram clearly shows Thon rings out to 0. 2 nm.
Development of High-Definition Image Processing System for a FE-SEM
Authors: Yamada M. , Yoshihara T. , Arima H. , Nimura Y. , Kobayashi T. , Nielsen C.
Published: June 2020

This paper presents the development of a new, fully digital image processing system for a field emission SEM (FE-SEM) which can eliminate fluctuations in the emission current. The system can display, in real time, images with 1280 × 1024 pixels on a viewing CRT, allowing direct observation of high definition SEM images on the FE-SEM.

In the past, even though image was acquired and recorded (photographed) with the resolution higher than 1,000 x 1,000 pixels, it was generally observed on the viewing CRT at the resolution of only about 500 x 500 pixels for real-time observation. This created a difference in image quality between the two CRT's. Using a CRT of the same pixel resolution for observation as on the recording CRT, the difference in image quality can be minimised, provided that the characteristics (speed and resolution) of the image processing and scan generator system are improved and optimised for digital processing.
Characterization of small inclusions: SEM vs TEM, or is it even worth considering Sem?
Authors: Blais Carl , L’Espérance Gilles , Baril Éric , Forget Clément
Published: June 2020

Inclusions of technological importance are often in the size range from 0.1 to 1 μm, These inclusions are generally too thick for EEL-spectrometry and require the use of EDS to characterize their chemical composition. Recent Monte Carlo simulations indicated that scanning electron microscopes (SEM’s) equiped with a field emission gun (FEG) might challenge transmission electron microscopes (TEM’s) for the charaterization of small inclusions, In the light of these results, we investigated the possibility of using a FEGSEM to characterize inclusions found in micro-alloyed steel welds used for arctic applications. The main setbacks of using EDS for such a task are due to the presence of small phases of unknown thicknesses, non-homogeneity of the X-ray generation volumes, variation in absorption along the path length of the X-rays, etc., Even though these problems are encoutered in both the SEM and the TEM, the relative ease of imaging the very small inclusions in TEM confers a definite advantage to this technique. Furthermore, TEM allows to obtain convergent-bearn electron diffraction patterns (CBED) which complement the chemical composition characterization, thereby allowing the unambiguous identification of the phases present (chemistry and crystal structure).
Microstructural characterization of Cu-Sn-Ni Solder in microelectronic packaging
Authors: Duh J. G. , Young C. C. , Cheng C. H.
Published: June 2020

Microelectronic packaging has experienced exciting growth in the past years, and solder joints plays important roles in the reliability of package system. Lead-tin (Pb-Sn) alloys are the most prominent solders for the interconnection and packaging of modern electionic components and devices. However, there are environmental concern on the toxicity of Pb. These concerns have inspired a great deal of research to study the feasibility of lead-free replacement alloys. It is known that the presence of intermetallic is often an indication of good wetting in solder joints. Nevertheless, excessive intermetallic growth may be detrimental to joint reliablity. The purpose of this study is to investigate the growth evolution between unleaded Cu-Sn-Ni alloys and metallized layer. These results will help to characterize the effect of aging on the microstructural and mechanical properties of solder / metallized layer / substrate systems.
Log-polynomial background subtraction in energy-filtered TEM
Authors: Evans N. D. , Bentley J.
Published: June 2020

An inverse power relation is widely used to model the background under inner shell ionization edges in both electron energy-loss spectrometry (EELS) and energy-filtered transmission electron microscopy (EFTEM). Proper background subtraction is necessary to obtain correct core-loss integrated intensities in EELS or elemental maps in EFTEM. However, the empirical inverse power relation often does not accurately model the background when losses at slightly lower energies interfere with the edge of interest, or in general, when energy losses are less than ∼200 eV. In such cases, the background of EELS spectra has been successfully fitted as a linear least-squares fit to a polynomial, usually a quadratic of the form: log(I) = A + BX + CX2, where I = intensity and X = log(energy loss). In the present study, this alternative background model, the “log-polynomial,” has been applied to pre-edge images for background subtraction from post-edge energy-filtered images.
ALCHEMI of B2-Ordered Fe50Al45Me5 alloys
Authors: Anderson Ian M.
Published: June 2020

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.

A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.
EXELFS analysis of natural diamond and diamond films on si substrates
Authors: Moller A. Duarte , Araiza L. Cota , Borja M. Avalos
Published: June 2020

In this work, we report the EXELFS results obtained from a polycrystalline diamond film grown on smooth silicon substrates using the Hot Filament Chemical Vapor Deposition (HF-CVD) technique in a two-step deposition process published elsewhere. In order to evaluate the quality of the thin film obtained, these results were compared with results obtained from natural diamond. The diamond sample was prepared in cross-section by ion milling where the nominal size of diamond.

particles was about 1 μn. The EXELFS experiments were performed in a JEOL-2010 Transmission Electron Microscope with a GATAN-666 PEELS attachment. A primary energy of 200 KeV was used with an average acquisition time of 5 minutes. The extended fine structure (EFS) energy range was 300 eV. In order to obtain the local structure, the standard procedure developed for EXAFS was applied here. The natural diamond particles with a nominal size of 1 μn were taken from commercial powder.
EXELFS χ-data renormalization
Authors: Qian M. , Sarikaya M. , Stern E.A.
Published: June 2020

Extended Electron Energy Loss Fine Structure (EXELFS) spectroscopy is useful not only because it contains the same local atomic structure information as XAFS (X-ray Absorption Fine Structure), but also it has good low Z element sensitivity, up to nanoscale spatial resolution, and the capability of combining other high spatial resolution TEM measurements together with EXELFS. Until presently, due to poor quality of the EELS data, however, the EXELFS technique has not been developed to its full advantage. We have introduced various new methods to improve the data acquisition technique which includes removal of channel to channel gain variation and correction of dark-current background under real conditions; on-line aligning and accumulation, of virtually unlimited number of spectra while monitoring the thickness change (sample drift), radiation damage, electron beam energy drifts, and change in energy resolution during measurements. We have also developed a systematic data analysis procedure which utilizes the sophisticated UWXAFS data analysis software package after correction of the differences between EXELFS and XAFS data.
Effect of thickness variations on EELS spatial-difference profiles
Authors: Bruley J. , Williams D. B.
Published: June 2020

This paper concerns the influence of sample thickness on spatial-difference spectra, and seeks to identify if an interface dependent signal may be generated as an artifact of grain boundary grooving. The spatial-difference profiling technique may be used to identify variations in composition and electronic structure across interfaces at sub-nanometer length scales. The signal-to-background ratios and hence visibility of small changes to the near-edge structure and edge intensities are enhanced using this technique by removing intense energy dependent backgrounds. These backgrounds are assumed to be only slowly varying with respect to the electron probe position. A spatial-difference spectrum is generated from the difference between two spectra after suitable normalization or scaling. This scaling is achieved by either matching intensities of the background prior to a characteristic absorption edge (for compositional profiles) or by normalizing to some characteristic structure of the near-edge structure (for bonding profiles). The latter is performed typically after subtraction of a smooth power-law background modeled in the region immediately preceding the edge.
Radon transforms, alignment, and 3d-reconstruction from random projections
Authors: Radermacher Michael
Published: June 2020

Since their inception three-dimensional reconstruction techniques have been based on the theory of Radon transforms. Only much later have Radon transforms been recognized as powerful tools for image processing and pattern recognition. Techniques like the “common lines ” technique for finding the orientation of projections of highly symmetrical particles, which had been developed using Fourier transforms, can easily be translated into a technique that uses Radon transforms. In contrast to Fourier transforms Radon transforms have the advantage of being real valued which simplifies many interpolation steps. The central section theorem known for Fourier transforms also applies to Radon transforms. The two- or three-dimensional Fourier transform on a polar grid can be obtained from the two- or three-dimensional Radon transform by a one-dimensional (radial) Fourier transforms and vice versa. Fourier transforms obtained by a one-dimensional transformation of the Radon transform will be referred to a Fourier/Radon transforms.
The Synthetic Aperture Microscope
Authors: Franklin William R. , Turpin Terry M. , Lapides Jeffrey R. , Price Craig , Woodford Paul , Peachey Lee D.
Published: June 2020

It is well known that the resolution of a microscope depends critically on the aperture of its objective lens. Achieving wide apertures requires the lens to be extremely close to the sample being imaged, which is often inconvenient. We describe an optical microscope, currently in breadboard form, that achieves a large aperture, and thus high resolution, with a large (theoretically unlimited) working distance, based on the principles of synthetic aperture radar (SAR).
Use of digital microscopy in process control during the manufacture of rubber-modified thermoplastics
Authors: Dineen M. T.
Published: June 2020

The production of rubber modified thermoplastics can exceed rates of 30,000 pounds per hour. If a production plant needs to equilibrate or has an upset, that means operating costs and lost revenue. Results of transmission electron microscopy (TEM) can be used for process adjustments to minimize product loss. Conventional TEM, however, is not a rapid turnaround technique. The TEM process was examined, and it was determined that 50% of the time it took to complete a polymer sample was related to film processing, even when using automated equipment. By replacing the conventional film portion of the process with a commercially available system to digitally acquire the TEM image, a production plant can have the same TEM image in the control room within 1.5 hours of sampling.

A Hitachi H-600 TEM Operated at 100 kV with a tungsten filament was retrofitted with a SEMICAPS™ image collection and processing workstation and a KODAK MEGAPLUS™ charged coupled device (CCD) camera (Fig. 1). Media Cybernetics Image-Pro Plus software was included, and connections to a Phaser II SDX printer and the network were made. Network printers and other PC and Mac software (e.g. NIH Image) were available. By using digital acquisition and processing, the time it takes to produce a hard copy of a digital image is greatly reduced compared to the time it takes to process film.
Critical issues in ceramic microstructures
Authors: Clarke D. R.
Published: June 2020

As the number and variety of ceramic materials have grown so rapidly in the last few decades, ranging from silicon nitride structural ceramics to the perovskite superconductors to the ferroelectric oxides to semiconducting sensors, the number of scientific and technical issues has also grown rapidly. Many of the basic questions relate to the role the microstructures play in determining the observed physical behavior but increasingly it is not the geometric properties of the microstructure that are of central concern but rather compositional variations and associated electrical characteristics. These require the continued development of microscopy techniques to complement the tremendous advances in microstructural understanding that have already been made possible by microscopy in the past.

Since the role of microscopy is such a broad one, only a few of the most generic problems in microstructure characterization will be described in this talk. The topics selected include the characterization of intergranular films in liquid-phase sintered ceramics, the charge distribution at interfaces and the associated space charge, the epitaxial growth of oxides on oxide substrates, and the use of fluorescence imaging to identify phases and non-destructively measure local strains.
Characterization of crystalline titanium dioxide synthesized at room temperature
Authors: Gopal Mani
Published: June 2020

A process has been developed to synthesize crystalline titanium dioxide powders from aqueous solutions at low temperatures (T<100°C) and atmospheric pressure. Processing at slow reaction rates causes the formation of the thermodynamically favored rutile phase. Faster reaction rates promote the formation of anatase, the statistically favored phase. Processing at intermediate rates causes a mixture to be formed (Fig. 1). This paper reports the TEM and SEM characterization of rutile, precipitated at 40°C.

Specimens for TEM were collected on holey carbon grids suspended vertically in the stirred solution. After removal, the grids were washed in isopropyl alcohol and dried under a heat lamp. For SEM analysis, a drop of the solution was placed on the specimen holder and dried. The top surface was then washed with isopropyl alcohol to remove any contamination and observed.

The bright field image (Fig. 2b) of the rutile precipitates shows them to have a nominal size of 50-100 ran. The sharpness of the (002) ring in the electron diffraction pattern (Fig. 2a) indicates the needles are elongated in the [002] direction. The corresponding dark-field image (Fig. 2c) shows that individual needles are comprised up of smaller particulates (HR-TEM shows them to be ∼3 nm in size). It is important to note that in each needle, all the particulates diffract together or they all do not, indicating a common orientational relationship.
Electron-Beam-induced transformations in zirconia-alumina nanolaminates: An In situ high-resolution Electron–Microscopy study
Authors: Schofield M.A. , Gajdardziska-Josifovska M. , Whig R. , Aita C.R.
Published: June 2020

Composite systems containing zirconia have been used extensively as transformation-toughening materials based on a stress induced martensitic transformation of the metastable tetragonal phase of zirconia to the monoclinic phase. Recently it has been shown that tetragonal zirconia can be stabilized in zirconia-alumina nanolaminates grown by reactive sputter deposition, when the zirconia layer is less than 6 nm thick. Cross-section high resolution transmission electron microscopy (HRTEM) of these nanolaminates revealed localized tetragonal-to-monoclinic transformation caused by sample preparation. In this study, quantitative HRTEM is used to analyze the zirconia nanocrystallite transformation in situ, by controlled exposure of the sample to the electron beam of the microscope.

The irradiation conditions used in this study to induce the zirconia transformation are summarized in Table 1. The mildest irradiation condition corresponds to normal imaging illumination used in this study to obtain high resolution images. Under these normal illumination conditions, the first condenser lens (CI) is used to form a 0.1 μm sized probe which is over focused on the sample by the second condenser lens (C2).
Short-range order of oxygen vacancies in stabilized cubic ZrO2
Authors: Dai Z.-R. , Wang Z.L.
Published: June 2020

Diffuse scattering of stabilized cubic zirconia is an interesting subject for many years because it is correlated to the local atomic arrangements that deviate from the average structure, thus, it is responsible for many important physical properties of the material, such as electric conductivity and structural stability. Much research work was performed using X-ray and neutron diffraction. As limited by the nature of these techniques, however, large size crystals are required to perform the experiments, thus, the results are a statistical average over a larger volume containing defects, interfaces and dislocations. In this paper, electron diffraction is used to characterize the diffuse scattering of submicron size cubic ZrO2 partially stabilized with MgO and Y2O3. Kinematical electron diffraction theory is applied to calculate the diffuse scattering patterns and the Cowley‘s short-range order (SRO) parameters. Discussion relating to short-range correlation between oxygen and vacancy, vacancy and vacancy is given.
membrane traffic: Microtubule motor cycles and kinectin
Authors: Sheetz Michael P.
Published: June 2020

Although membrane traffic can occur in the absence of microtubules, the rapid metabolism of many eucaryotic cells requires that vesicular organelles are actively transported. Microtubule-dependent transport is particularly robust in actively growing cells and the volume of membrane transported increases dramatically in going from static to growth conditions. Both inward and outward movement are regulated simultaneously implying coordinate activation of both motors or a transport cycle. Relatively large complexes of the microtubule motors and associated proteins are responsible for powering the movements (reviewed in Vallee and Sheetz, 1996). Of the many motors that have been described, kinesin and cytoplasmic dynein are the most abundant and have been the focus of these studies. Included in the microtubule motor complexes are motor receptors and activating factors. A membranous motor receptor, kinectin, was identified on the basis of its interaction with kinesin (Toyoshima et al., 1992). An antibody to kinectin blocks both kinesin binding to organelles and kinesin-dependent motility of those organelles (Kumar et al., 1995).
Adrenal gland ultrastructural pathology in plasmodium berghei parasitized mice
Authors: Pulido-Méndez M. , Finol H.J. , Rodríguez-Acosta A. , Márquez A. , Aguilar I. , Girón M.E. , González N. , García-Tamayo J.
Published: June 2020

The use of animal models is widely accepted in malaria research. Plasmodium berghei has been extensively studied because it produces a mortal malaria in rodents. Electron microscopic studies on brain and liver pathology have been performed in this infection. In a previous ultrastructural work we reported the capillary alterations observed in adrenal cortex in P. berghei infected mice. In this work we describe the cell and capillary changes we found in adrenal cortex and medulla in this infection.

Male mice weighing 18-22 g were inoculated intraperitoneally with P. berghei infected erythrocytes. At the ninth day animals were sacrificed when parasitemia ranged between 80-90%. Adrenal gland samples were processed by routine techniques and observed in a Hitachi H-500 transmission electron microscope.
Direct whole mount electron microscopic demonstration of inhibition of fibrinogen-gold binding by antagonists of the platelet glycoprotein IIb-IIIa Receptor
Authors: Mattson J. C. , Khurana S. , Farrah D. M. , Hatfield H. K.
Published: June 2020

Glycoprotein IIb-IIIa (GPIIb-IIIa) is an externally exposed membrane complex on platelets which serves as an activation-dependent receptor for fibrinogen, fibronectin, von Willebrand factor and vitronectin. These ligands share an RGD sequence which binds to a specific site on GPIIIa. In addition, fibrinogen has a gamma chain dodecapeptide sequence that also interacts with GPIIb. Binding of fibrinogen to GPIIb-IIIa is directly responsible for cross-bridging adjacent platelets leading to platelet aggregate formation. In the search for pharmacologic anti-thrombotic agents, there has been considerable interest in drugs that inhibit platelet function, aspirin being the classic example. Recent efforts have been directed to the development of agents that target GPIIb-IIIa. Several synthetic peptides and peptidomimetic agents have been developed to compete with the RGD binding site on GPIIb-IIIa. Monoclonal antibodies directed against sites at or near the fibrinogen binding domains on GPIIb-IIIa have also been of considerable interest. The chimerised Fab fragment of the monoclonal antibody 7E3 (ReoPro, Centocor) has been approved by the US FDA to reduce the thrombotic complications of high risk angioplasty.
Oxidative injury and endothelial cell dysfunction in diabetic retinopathy: A combined cytochemical and immunocytochemical study
Authors: Ellis E. Ann , Grant Maria B. , Murray Frederick T. , Wachowski Martha B.
Published: June 2020

Endothelial cell dysfunction has been implicated in a number of microvascular complications of diabetes. Microvascular changes in diabetic retinopathy present initially as leaky vessels in the neural retina which lead to deterioration of vision. Oxidative injury as a result of free radical production has been suggested as a mechanism of endothelial cell dysfunction caused by hyperglycemia.

The NADPH oxidase complex catalyzes the formation of superoxide (O2·−); hydrogen peroxide (H2O2) is formed by dismutaion of O2·−. Cytochemical localization of the free radical derived oxidant, H2O2, was done by the cerium NADPH/NADH oxidase method in eyes of obese, noninsulin dependent diabetic BBZ/Wor rats with diabetes of five and ten months duration. Age matched, nondiabetic controls were eyes from BB/WorDRrats. Endothelial cell dysfunction, indicated by leaky vessels, was documented by colloidal gold immunocytochemical localization of extravasated endogenous serum albumin on sections of retina in which H2O2had been localized.
Localization of endothelial nitric oxide synthase in the normal and failing human atrial myocardium
Authors: Wei Chi-Ming , Bracamonte Margarita , Jiang Shi-Wen , Daly Richard C. , McGregor Christopher G.A. , Zhang Shaobo , Young Charles Y. F.
Published: June 2020

Nitric oxide (NO) is a potent endothelium-derived relaxing factor which also may modulate cardiomyocyte inotropism and growth via increasing cGMP. While endothelial nitric oxide synthase (eNOS) isoforms have been detected in non-human mammalian tissues, expression and localization of eNOS in the normal and failing human myocardium are poorly defined. Therefore, the present study was designed to investigate eNOS in human cardiac tissues in the presence and absence of congestive heart failure (CHF).

Normal and failing atrial tissue were obtained from six cardiac donors and six end-stage heart failure patients undergoing primary cardiac transplantation. ENOS protein expression and localization was investigated utilizing Western blot analysis and immunohistochemical staining with the polyclonal rabbit antibody to eNOS (Transduction Laboratories, Lexington, Kentucky).
FT-IR microspectroscopic mapping of diseased brain tissue
Authors: Wetzel D. L. , Choo L-'P , Mantsch H. H. , Jackson M. , LeVine S. M.
Published: June 2020

Multiple frozen sections of brain tissue representing three diseased cases and two normal cases were prepared for examination by microtoming and thaw mounting on barium fluoride optical windows (2mm × 13mm). Chosen from the microtomed sections were those from each of the diseased brains that included both a lesion site typical of that disease and surrounding tissue to allow contrast in functional group mapping between the adjacent tissue in the microscopic field. Among sections prepared from one specimen frozen to the microtome specimen holder one or more were used for staining to support the visual selection process. Remaining sections mounted on barium fluoride windows were tested for infrared optical transmission by scanning the spectra at selected sites of interest. The range of infrared absorbance and the sample scattering characteristics affected the quality of individual spectra. With visible light microscopy it was necessary to verify consistency of focus throughout the part selected for potential mapping since with the programmed moving stage experiment spectra are collected from all points at the same distance of the objective from the stage once focussing has been set.
Interaction of internalized, viable listeria monocytogenes with MHC class II molecules and low pH compartments
Authors: Iadarola Linda , Webster Paul
Published: June 2020

Listeria monocytogenes, an aerobic, non-sporulating, gram-positive bacillus, is a contaminant of the food we eat and is capable of surviving in the cytoplasm of infected cells. Ingestion of contaminated foods by susceptible individuals (newborn, elderly and immuno-compromised) can result in severe systemic disease resulting from opportunistic infections. There is a high case fatality rate in immunocompromised individuals.

During the course of infection, L. monocytogenes invades cells by adhering to the cell membrane from where the bacteria are internalized into membrane bound phagosomes. Disruption of the phagosome membrane allows the bacteria to gain access to the cell cytoplasm where they grow and multiply. In the cytoplasm, actin polymerization on the bacteria surface cause them to move in the cell and form long cytoplasmic protrusions at the cell surface. The protrusions, with a bacterium at the tip, are taken up by adjacent, uninfected cells which then become infected.
High-Resolution sem and Clostridial Attachment
Authors: Panessa-Warren B. , Tortora G.T. , Warren J.
Published: June 2020

Since the mid 1960’s when the TEM was a new and primary tool for elucidating the classification of the various strains of microorganisms, investigators around the world have been reporting morphological surface aberrations (such as hairs, ribbons, tubular appendages and feather-like structures) of the clostridial endospore that facilitate and verify the classification of these organisms. Yolton Pope, Samsonoff and others were unable to discern the function, of these appendages and stated that the “functional role of spore appendages remains obscure”.

Today, there is still no information on the functional role, if any, of these “appendages” and “hairs”. For the past few years we have been examining the endospores from two clostridial species that are pathogenic in man and higher mammals,C.sporogenesATCC3584, andC.difficileATCC 9689and43594. These organisms cause wound infections, pseudomembranous colitis, and nosocomial diarrhea. Our previous work strongly suggested that the outer envelope of these spores, the exosporium, had a “morphological plasticity” that allowed the spores to attach to a surface that supported bacterial growth5,6. With current advances in high resolution SEM using LaB6 and field emission sources, it is now possible to study these extremely small and complex spore appendages at all stages of germination with spacial orientation capabilities not possible when the original studies were done. Over the past 2 yrs, the advances in software technology and improved SEM resolution and image enhancement capabilities, make it possible to work with fields of intact spores still attached to a nutritive surface and examine the exosporium and membrane contacts with the nutrient surface at resolution and magnifications formerly reserved for TEM. This investigation combines attachment studies using agar substrates (Trypticase Soy agar + 5% glucose, and Blood CDC agar) and human cells (lung fibroblasts and colon cells), with high resolution imaging of intact spores on their nutritive substrate (agar and human cell)to determine the ultrastructural changes that accomplish clostridial colonization. Studies were also done to determine if attachment was altered as a result of exposure to cation substitution, cation chelation, or colchicine treatment.
A survey of detector options for the “leaky-vacuum” SEM
Authors: McKernan Stuart , Mansfield John F.
Published: June 2020

Since the inception of the “Leaky-Vacuum” SEM (known by various manufacturers as environmental-, wet-, variable-pressure-, high-pressure- SEM) samples may be imaged with environmental conditions which are radically different from those in traditional SEMs. The presence of a (relatively) high pressure in the sample chamber affects the ability of the microscope to form a small, well defined electron probe on the surface of the sample, thereby affecting the ultimate resolution of the microscope. The environment also affect the operation of most SEM detectors. In this contribution the operation of different SEM detectors will be surveyed, and their performance in the "Leaky-Vacuum" SEM environment will be examined.

The most common detector in the SEM, the Everhart-Thornley (E-T) secondary electron (SE) detector, suffers most strongly from the effect of the residual chamber gas at high pressures. SEs emitted from the sample are low in energy and frequently collide with the residual chamber gas. This causes an electron cascade which ultimately overloads the E-T detector.
Environmental microscopy of capillary stress-induced strain behavior in ambient-pressure aerogels
Authors: Rao Sudeep M. , Samuel Joshua , Prakash Sai S. , Brinker C. Jeffrey
Published: June 2020

Ambient pressure silica aerogel thin films have recently been prepared by exploiting reversible drying shrinkage caused by derivatization of the internal gel surface. Aerogels have porosities of upto 99.9% and due to the small size of the pores (few nanometers), large capillary stresses are produced in gels that are partially saturated with a wetting liquid. As a result of these capillary stresses, the flexible silica network undergoes strain which has been observed using environmental microscopy. This technique allows variation of the equilibrium vapor pressure and temperature, and a simultaneous monitoring of the deformation of the unconstrained film thickness. We have observed >600% deformation during the pore-filling and pore-emptying cycles. In this presentation, we discuss the unique stress-strain behavior of these films.

Ref.: Sai S. Prakash, C. Jeffrey Brinker, Alan J. Hurd & Sudeep M. Rao, "Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage", Nature. Vol. 374, 30 March, 1995, 439-443.
Poly(3-alkylthiophene) membranes for gas separation
Authors: Musselman I. H. , Washmon L. , Varadarajan D. , Tielsch B. J. , Fulghum J. E.
Published: June 2020

The separation of gases is a commercial process conducted primarily via cryogenic distillation. An alternative method involves the use of solvent cast polymer membranes. Unlike distillation, membrane processes are energy efficient, easy to scale-up, and require only electrical energy in their operation. Current membrane separation applications include oxygen or nitrogen enrichment of air, the separation of carbon dioxide from natural gases, and the recovery of hydrogen from refinery and purge streams. In our laboratory, gas separation membranes are being developed based on conducting, soluble and processable polymers such as poly(3-n-alkylthiophene)s. The chemistry of these membranes is being altered by changing the R group (e.g. octyl, dodecyl), the oxidation state, and by incorporating zeolites and molecular sieves to facilitate gas transport. An important aspect of this project concerns establishing the relationship(s) between the structure of poly(3-alkylthiophene) membranes and their bulk properties, specifically permeabilities and selectivities for various gases. It is anticipated that this understanding will help to elucidate the mechanism by which gas separation occurs in these membranes.
Atomic force microscopy studies of microstructure and properties of self-assembled monolayers
Authors: Richards J. F. , Troughton E. B. , Dennis R. A. , Russell P. E.
Published: June 2020

Self-assembled monolayers are unique structures and have received considerable attention from microscopists seeking to image the predicted molecular level structure. More recently, practical engineering applications of SAMs have been proposed in areas ranging from corrosion barriers to adhesion promoters to lithographic resists. While some of the applications of interest, most notably the lithographic resists, can be developed on substrates close to the ideal; such as single crystal Si wafers or thin epitaxial films; many others will require the coating of very non-ideal surfaces. These may range from materials such as Al or ferrous based metals to engineering polymeric materials. In this study we have taken a two-pronged approach to develop reliable systematic atomic force microscopy (AFM) techniques for the determination of both microstructure and properties of SAMs on various substrates of interest.

We have chosen to investigate n-alkanethiols (SH-(CH2)n-1-CH3) on single crystal gold as our reference system for technique development.
Quantitative Scanned Probe Microscopy
Authors: Russ J.C. , Scott P. J.
Published: June 2020

The great advantage of the atomic force microscope and related technologies (tunneling current, near field optical, tips that oscillate vertically or laterally, etc.) has been simplicity of design. Vertical deflection of a reference tip on a cantilevered probe is detected by light scattering and used to shift the sample in the z direction to restore tip position. The output is generally in the form of surface images rather than measurements with high dimensional accuracy. Atomic scale resolution is achievable but lower magnification imaging is more difficult.

Piezo devices used for x-y and z axis control have a limited range of motion and are noisy, nonlinear and subject to creep. Piezo displacement is not simply a function of voltage, or of the time integral of current, but depends upon many factors including rate and distance of motion, and internal resistance and capacitance in the device. It is possible in principle to calibrate such a system using a reference grid standard, but even this is highly dependent on scanning speed (different in the x, y, z directions) and will not provide quantitative z information.
Scanning probe microscopy of polymers in the field emission SEM
Authors: Brostin J.
Published: June 2020

The field emission SEM (FESEM) is well suited for imaging polymer and other non-conductive surfaces. High resolution SEM images can be obtained without the application of a conductive coating when operated at low accelerating voltages. Compositional imaging in the backscattered electron mode is facilitated at low voltages by the incorporation of a microchannel plate (MCP) detector. The MCP equipped FESEM has been shown to be phenomenally sensitive to very small differences in average atomic number. Compositional contrasts are achieved in polymer and other low-Z composites that differ only in oxygen content. Those systems that completely lack intrinsic contrast can be differentially stained with ruthenium tetroxide vapors.

These capabilities make the FESEM an ideal platform for locating phases and/or subtle features for scanning probe microscopy (SPM). Transparent, thin coatings or very fine, heterogeneously dispersed structures that cannot be readily located or observed with conventional light optics can generally be seen in the FESEM.
Rapid microwave processing of skeletal muscle for TEM
Authors: Smith S.A. , Martella A.
Published: June 2020

Rapid tissue processing for transmission electron microscopy is a desired goal in a clinical EM laboratory. Reducing the time from tissue submission to examination in the electron microscope shortens turnaround time for diagnosis. Microwave enhanced tissue processing will accomplish these goals.

Microwave technology reduces the time for tissue fixation and processing and may improve overall results. Fixation times can be reduced from minutes to seconds and resin polymerization from hours to minutes. Dehydration and infiltration steps can also be reduced, so that microwave rapid tissue processing can yield ultrathin sections from unfixed tissue in three hours.

Three microwave protocols to process skeletal muscle biopsies are compared to standard processing. The protocols test the efficacy of microwave fixation, dehydration, and resin infiltration and polymerization. Protocol #1 uses microwave enhanced 4:1 formaldehyde/glutaraldehyde primary fixation followed by routine processing for remaining steps. Protocol #2 uses microwave primary fixation and 2% OsO4 post-fixation followed by routine processing. Protocol #3 uses microwave enhanced processing for entire procedure. Protocol #4 uses the standard processing technique.
The Basis for Fibrinogen Cedar Rapids (γ R275C) Fibrin Network Structure
Authors: DiOrio J.P. , Mosesson M. W. , Siebenlist K. R. , Olson J.D. , Hainfeld J. F. , Wall J. S.
Published: June 2020

Fibrinogen ‘Cedar Rapids’ is a heterozygous dysfibrinogenemia characterized by delayed and abnormal fibrin polymerization. The specific molecular defect (γ R275C) is relatively common, but in only one case, fibrinogen Tokyo II, has the ultrastructural basis for defective clot formation been determined. This report reflects similar structural studies on Cedar Rapids fibrinogen and fibrin. Crosslinked fibrinogen molecules and fibrils, were prepared at 1 mg/ml in the presence of factor XIIIa (100 u/ml). When γ chains had become ˜10 to 20% crosslinked to γ dimers, samples were diluted with Hepes buffered saline, pH 7, to a fibrinogen concentration of 5 to 10 μg/ml. Three μl was then injected into 3 μl buffer on a carbon-coated EM grid, the specimen allowed to attach for one minute, fluid-exchanged several times with 150 mM NH4 acetate solution, frozen in liquid nitrogen, freeze-dried, and imaged at the Brookhaven STEM facility using a 40 kv probe focused at 0.25 nm. Fibrin for scanning EM (SEM) was formed directly on carbon-formvar coated gold grids. Clots that had formed overnight were fixed with 2.5% glutaraldehyde in 0.1 M Hepes, pH 7 buffer containing 0.2% tannic acid, washed with buffer, dehydrated, CO2 critical point dried, coated with 7.5 nm platinum, and imaged in a JOEL Field Emission SEM operated at 5 kV.
Cosmetology treatments on human hair: An SEM study
Authors: Bowling D.F.
Published: June 2020

High school cosmetology students study the methods and effects of various human hair treatments, including permanents, straightening, conditioning, coloring and cutting. Although they are provided with textbook examples of overtreatment and numerous hair disorders and diseases, a view of an individual hair at the high resolution offered by an SEM provides convincing evidence of the hair‘s altered structure. Magnifications up to 2000X provide dramatic differences in perspective. A good quality classroom optical microscope can be very informative at lower resolutions.

Students in a cosmetology class are initially split into two groups. One group is taught basic controls on the SEM (focus, magnification, brightness, contrast, specimen X, Y, and Z axis movements). A healthy, untreated piece of hair is initially examined on the SEM The second group cements a piece of their own hair on a stub. The samples are dryed quickly using heat or vacuum while the groups trade places and activities.