Segregation of Bismuth to Triple Junctions in Copper

Abstract: Quantitative X-ray microanalysis is used to obtain the elemental compositions of tissues and cells. Concentrations are calculated on the basis of volume (mmolL−1 of packed cells) and mass (mmolkg−1 dry weight). Elemental maps are obtained by using a computer to control the position of a beam in an electron microscope and to record the signals from the scanning transmission electron microscope (STEM) and energy dispersive X-ray spectrometer (EDS) X-ray detectors. These X-ray images provide better visualization of elemental distributions than ``spot'' mode analysis by analyzing thousands of spots sequentially. When concentrations are determined on the basis of volume, it is assumed that the section thickness created during cryosectioning, and shrinkage during freeze-drying of a frozen section, are uniform. These assumptions have been examined with a nucleated red blood cell model. Even distributions of cytoplasmic Fe and K, which we observed, can only occur if cryomicrotomy produces sections with smooth surfaces and uniform thickness. In addition, by using bone marrow cryosections we have found that the relative shrinkage between nucleated and non-nucleated cells is similar. Therefore, the assumptions made about volume calculations do appear to be reasonable under the conditions used in this study.

MSA and MAS Sustaining Members

Abstract: The theoretical interpretation of lattice resolution in high-angle annular dark-field images produced in a scanning transmission electron microscope (STEM) has been a subject of controversy. A first-order perturbation theoretical analysis is presented here, which shows that the contrast in the image arises from large-angle multiphonon, incoherent scattering, which is atomic number dependent. The lattice resolution is a consequence of coherently filling the objective aperture, and dynamical elastic diffraction preceding the large-angle multiphonon scattering is not a necessary requirement. Elastic scattering to the higher order Laue zone (HOLZ) is also shown to be negligible, compared with the incoherent scattering. Calculations from application of the theory are also presented. They show that lattice images formed using the high-angle annular dark-field detector are sensitive to atomic number and are relatively insensitive to defocus. Although high-angle annular dark-field lattice imaging appears to be simple, scattering into the high-angle detector can only be approximately described by an incoherent imaging model.

The presence of estrogen and progesterone receptors on human breast carcinomas correlates with both response to hormonal therapy and survival. Quantitation of receptor activity is typically performed by radioreceptor assay on fresh frozen tumor tissue obtained at the time of surgical resection. Estrogen and progesterone receptor reactivity can also be detected immunohistochemically on frozen sections of breast cancer and in appropriately fixed paraffin embedded tissues. Several studies have shown that semi-quantitative visual determination and quantitative image analysis assessment of estrogen and progesterone receptor immunoreactivity on fixed tissue sections is highly correlated with biochemical measurements of receptor in frozen samples. We recently developed a procedure for the simultaneous localization and quantitation of antigens in fixed tissue samples that does not involve antigen extraction, radioactive materials, or image analysis. In this procedure, which we term a “Midwestern assay”, fixed tissue sections are used with antigen-specific enzyme-linked antibodies to generate soluble reaction products which are spectrophotometrically quantitatable, as in an ELISA, and deposited reaction products which are microscopically localizable, as in enzyme-based immunohistochemistry.

Atomic Structure and Chemistry of Boundaries/Interfaces

Acknowledgments

Abstract: A human chromosome pq34 region-specific, microdissected library was constructed by using laser microdissection techniques. This library contains over 10,000 clones with an average insert size of 450 bp. It has greater coverage of the dissected chromosome region as compared with the needle-dissected chromosome 9q34 library. The laser microdissection technique provides more accurate chromosome targeting and easier operation than existing needle microdissection techniques. To simplify the procedure for chromosome microdissection and chromosome fragment collection, a trapping-cutting system was developed. This technique involves the use of two trapping beams which hold a single chromosome in suspension, and a third cutting beam, which dissects the immobilized chromosome. A collection chamber allowing for the fast collection of dissected chromosome fragments needs to be developed. However, DNA can be cloned from trapped chromosome fragments with an insert size comparable to that of both needle-cut and laser-cut chromosomes.

Structural Characterizations of Bi2Sr2CaCu2O8FATAL ERROR -- Missing abstract.plus;FATAL ERROR -- Missing abstract.dgr; Twist Boundaries Using Advanced Transmission Electron Microscopy

Abstract: A novel method for the synthesis of polypeptides using polystyrene/divinylbenzene copolymers as solid supports has drawn the attention of medicinal, pharmaceutical, and agricultural chemists because of its utility in combinatorial chemistry and parallel synthesis. In this method, arrays of solid-phase organic synthesis experiments are conducted simultaneously thereby enabling the preparation of large numbers of novel compounds over a short time period. The analysis of organic compounds attached to polymer supports presents unique challenges to chemists. This study presents some results of the application of energy-dispersive X-ray spectrometry (EDS) in the environmental scanning electron microscope (ESEM) to this problem. EDS in the ESEM has the advantages of minimal sample size, speed, and simplicity because the analyses are performed without special specimen preparation. The progress of a two-step synthetic transformation was followed using EDS-ESEM by the presence of a sulfur peak in the first synthetic step and by a bromine peak in the second step. The synthetic products were also evaluated by infrared spectroscopy and by elemental analysis (ion chromatography). The agreement of the qualitative analysis among all three techniques was good. Analysis by EDS-ESEM not only complements current analytical techniques in solid phase synthesis; it also provides insight into the details of the synthetic transformation.

Abstract: This work reports the distribution of a large, representative sample population of grain boundary plane crystallography in pure, annealed copper by use of an improved experimental procedure. The new methodology reduces the laboriousness and improves the accuracy of data collection, and so is described in detail. Analysis of the results concentrates on the Σ3 boundaries, and shows that three-quarters of these were tilt boundaries on the 011 zone. Of these tilt boundaries, nearly half were coherent twins, i.e., on 111/111 planes, or near coherent twins on 23,17,17/775 planes. The high population of the second group is thought to be due to oxygen take-up during annealing. The data in general showed a trend for lower energy Σ3s to occur more frequently. The results were interpreted in terms of boundary energies, local equilibration, and comparisons with previous work in copper and other systems.

Abstract: Films of Fe3O4 were prepared by sputter deposition onto MgO substrates of both 〈100〉 and 〈110〉 orientations. The films used in this study were mainly 50 nm thick. X-ray diffraction, Mössbauer spectroscopy, and other techniques revealed that the films were stoichiometric single crystals. Electron microscopy showed that the films were essentially dislocation free. Despite this high degree of perfection, the magnetic properties of the films were inconsistent with bulk single crystal properties. For example, the magnetization of the films did not saturate in fields as large as 7 Tesla, while bulk single crystals saturate by 0.1 Tesla.

Abstract: Transient liquid phase (TLP) bonding is a joining process in which a liquid-forming interlayer is placed between the substrates to be joined. At the bonding temperature, the interlayer initially liquates. Subsequently, interdiffusion between the liquid interlayer and the adjacent substrates results in a change in the overall composition of the joint, such that isothermal resolidification of the joint takes place. Standard models of the TLP process assume the sequential occurrence of discrete dissolution, isothermal solidification, and homogenization processes. This study uses edge-on transmission electron microscopy investigations to challenge the general applicability of such standard models to the TLP bonding of a variety of systems involving the B2 type intermetallic compound NiAl as a substrate material. This article considers the formation of boride phases apparently at the bonding temperature in NiAl/Ni-Si-B/Ni bonds. The precipitation of repeating sequences of phases in NiAl/Cu/Ni joints and the reliquation of the NiTi substrate in NiAl/Cu/NiTi bonds after the completion of isothermal solidification are examined.

Program Committee

Abstract: We have explored freeze-substitution combined with low-temperature embedding in rat taste buds for postembedding immunocytochemistry. A major difference in taste bud cells that were rapidly frozen without prior chemical fixation and those that were fixed and cryoprotected before freezing was that electron-dense core granules were virtually absent. The antibodies used in these initial studies were directed against calcitonin gene-related peptide (CGRP), a peptide commonly found in nociceptive neurons; the α-subunits of two G-proteins involved in bitter and sweet taste transduction; and choline acetyl transferase (ChAT), an enzyme involved in the synthesis of acetylcholine. Anti-CGRP immunolabeled a subpopulation of unmyelinated perigemmal neurons; anti-Gqα labeled a larger subpopulation of these neurons and the microvilli of cells that were most likely from Type II vallate taste buds. α-Gustducin was found in cytoplasm of Type II and/or III cells and probably in microvilli of Type I cells of vallate taste buds. The best labeling results were obtained with anti-ChAT, which stained microvilli and lateral membranes of some Type II vallate taste bud cells, and the cytoplasm of some other Type II and/or III vallate cells. In addition, anti-ChAT labeled electron-opaque materials inside taste bud pores of vallate papillae, but, under the same conditions, not granules of Type I cells or most of the vesicles in von Ebner's glands. These data suggest that we can not assume a priori that the contents of the electron-dense core granules of Type I cells, or even of those of von Ebner's glands, contain the precursors of the taste bud pore–dense substances.

Convergent Beam Electron Diffraction and Transmission Electron Microscopy Study of Interfacial Defects in Gallium Nitride Homoepitaxial Films

Abstract: The traditional methods for studying polymer microstructure in the transmission electron microscope largely hinge on the use of differential heavy-element staining to induce amplitude contrast. However, adequate staining agents are not available for all polymer systems. Furthermore, nonlinearities in the distribution of stain, particularly at interfaces, degrade the achievable resolution. Spatially resolved electron energy loss spectroscopy (EELS), on the other hand, provides a new opportunity to study polymer microstructure by providing rich spectroscopic features and high spatial resolution. Translating this opportunity into practice is underpinned by three main factors: (1) the availability of spectral fingerprints distinguishing various polymers; (2) the limits of achievable resolution; and (3) the ultimate constraints imposed by electron irradiation. This study discusses these issues and demonstrates the use of spatially resolved EELS with examples from hydrocarbon homopolymer and homopolymer blends of polyphenylene sulfide (PPS) and polyethylene terephthalate (PET), nylon 6/high-density polyethylene (HDPE) and polystyrene/polyethylene (PS/PE).

We have described previously the presence of IL2R on human carcinoma (CA) cell lines (squamous cell carcinoma of the head and neck, gastric carcinoma, renal cell carcinoma) and tumors in situ (1,2,). These carcinomas expressed IL2Rβ and γ (intermediate affinity IL2R) and I-labeled IL2 was found to bind to these receptors. Scatchard analyses showed that 13,500 IL2Rβ/cell and about 300 IL2Rα were present on the surface of PCI-1, a SCCHN cell line. The mRNA and proteins for IL2Rβ and γ were consistently detectable in tumor cell lines and fresh tumor tissues. Binding of recombinant IL2 to IL2R resulted in a partial but significant inhibition of tumor cell growth, decreased expression of class I MHC antigens and ICAM-1 on tumor cells and their increased sensitivity to growth-modulating cytokines IFN-γ, TNF-α or TGFβ. These effects were IL2-dose dependent, and were optimal at doses >10nM. Anti-IL2Rβ Abs reversed IL2-induced growth inhibition, an indication that exogenous IL2 delivered a negative growth signal to CAs via the β chain of IL2R.

Abstract: Atomistic simulations were performed for the {222}MgO/Cu interface by local density functional theory (LDFT) methods, within the plane-wave-pseudopotential representation, and by (classical) molecular dynamics and statics. The electronic spectra obtained with LDFT calculations showed a localized interface state within the bulk MgO gap, approximately 1 eV above the MgO valence band edge. LDFT adhesive energy calculations, as a function of interface spacing and translations parallel to the interface, were employed to devise an interatomic potential suitable for large-scale atomistic simulation. The interface structure, which was obtained with molecular dynamics (and statics) calculations based on the resultant potential, exhibited a misfit dislocation network with trigonal symmetry, and no standoff dislocations.

Abstract: Because of their chemical properties, bacterial capsules tend to collapse during dehydration before electron microscopy. The purpose of this study is thus to evaluate the use of monoclonal antibodies (mAbs) against capsular material to stabilize and visualize bacterial capsule. Two important porcine pathogens with a known ultrastructure, namely, Actinobacillus pleuropneumoniae and Streptococcus suis, were used. Our data indicate that mAbs, either immunoglobulin G (IgG) or IgM, preferably from ascite fluids, can be used to stabilize bacterial capsular material in preparation for electron microscopy. However, because of their low antibody titer, the use of mAbs from culture supernatants is not recommended.