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Abstract: The atomic-scale structure of tilt grain boundaries has been studied by high-resolution electron microscopy (HREM) in several ceramics and metals such as NiO, yttria stabilized zirconia, Au, and Al. It is found that when grain boundaries are formed between two crystals a considerable variety of modes of relaxations, i.e., the rearrangements of atoms in and near the grain boundary core are possible, depending on grain boundary geometry and the interatomic interactions. The atomic relaxations within and near the grain boundary core often include relaxations that involve the formation of stacking faults in low-stacking-fault energy fcc materials. Grain boundary dissociations are also observed for several grain boundary geometries. Computer simulations of grain boundary structures in metals have in general been able to reproduce the relaxation features at least on a qualitative level. In contrast, ceramic grain boundaries typically are more complex and not always tractable by simple computer relaxation procedures, since the formation of point defects and partial occupancy of atomic columns may be involved in the relaxation processes. It is found that when a boundary is not allowed to relax to its lowest energy state due to geometrical constraints, a multitude of grain boundary core structures can exist. Such conditions are expected to be characteristic for nanocrystalline materials. Because of its close connection to grain boundary properties, quantification of the volume expansion by HREM techniques is an important goal of grain boundary research. Image simulations of grain boundaries suggest that for most materials of interest the 3-fold astigmatism must be corrected to better than 100 nm to achieve the desired accuracies.

Abstract: This investigation presents the interaction of dislocations and semicoherent precipitates (Ω phase) in an Al-Cu-Mg-Ag alloy. The study shows that the semicoherent precipitate is cut by dislocations during deformation. Conventional transmission electron microscopy (TEM) and high resolution TEM (HRTEM) observations demonstrate that shearing of precipitates by dislocations occurs by multiple cutting in the precipitate. The step height caused by cutting on the Ω precipitate is only several atomic layers of the Ω phase. The Ω phase is strengthened after shearing by dislocations. A strengthening mechanism is proposed on the basis of this observation. The strengthening mechanism is not only applicable to the Ω precipitate in Al-Cu-Mg-Ag alloys but also to the other semicoherent precipitates in other alloys.

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Abstract: Since 1972 the author and colleagues at Ford Motor Company have been publishing results of materials analyses which were obtained using ambient temperature or cryomicrotomy as one of the sample preparation techniques. Generally two types of sectioning, thin and ultrathin, were pursued for light-optical and electron-optical microscopy, respectively. These papers include the study of the following materials, which have been separated into nine classes: polymer composites, polymer blends, reverse osmosis membranes, carbon fibers, elastomers, automotive exhaust catalysts, aluminum surface coatings, aluminum alloy automotive wheels, and rapidly solidified aluminum alloys. This review is not intended to reiterate the conclusions of these prior publications but will provide the reader with an insight into the many ways microtomy can be used for materials studies.

Structure and Bonding at NiFATAL ERROR -- Missing abstract.ndash;ZrO2 (Cubic) Interfaces Formed by the Reduction of a NiOFATAL ERROR -- Missing abstract.ndash;ZrO2 (Cubic) Composite

Poly-[(trans-1,2-diaminocyclohexane) platinumj-carboxyamylose (“poly-plat”), 5-sulfosalicylato-trans -(1,2-diaminocyclohexane) platinum (SSP), and 4-hydroxy-∝-sulfonylphenylacetato (trans 1,2-diaminocyclohexane) platinum (II) (SAP) are second generation analogs of cisplatin (CDDP) with higher efficacy and potency than cisplatin. This is particularly true of “poly-plat” which contains 1/5 the platinum of CDDP. In order to understand the mechanism of action of these compounds, isolated murine peritoneal macrophages in culture medium were treated with “poly-plat”, SSP, or SAP (5 μg/ml) for 2 h. Drug containing medium was then replaced with fresh medium and the cells were allowed to incubate at 37° C (5% CO2) for 24 h. Supernatants were collected at 0.5, 1, 2, and 24 h post-treatment for immunocytochemical analysis. Confocal microscopy studies demonstrated an increase in the number of lysosomes in the treated macrophages, but only “poly-plat” and SSP treated macrophages were stimulated to form cytoplasmic extensions at 2 h and 24 h.

Immunohistochemistry (IHC) has provided major insights about the classification of brain tumors by identifying cellular markers of phenotype, and about tumor growth potential with nuclear markers of proliferation. Newer in situ hybridization shows promise in tumor classification and prognostication.

Fig. 1 shows the sensitive and reliable avidin-biotin conjugate (ABC) method of localizing glial fibrillary acidic protein (GFAP). GFAP is the most specific marker of gliomas, tumors of brain cells, available today. The ABC method can be used to find any antigen for which a primary antibody is available. A molecular bridge then links this primary antibody bound to tissue with a label that can be seen, a substrate of the horseradish peroxidase (HRP) enzyme like diaminobenzidine (DAB) that produces a brown, insoluble reaction product at the site of the antigen. IHC for GFAP has revealed that brain tumors previously thought to be sarcomas are actually malignant gliomas (Fig. 2).

Abstract: The magnetic behavior of lithographically defined thin film elements of permalloy imaged by Lorentz microscopy is described. Elements of thickness <100 nm, with in-plane dimensions in the micron and sub-micron range and of varying shape, have been subjected to in situ fields using an electron microscope that has been optimized for magnetic imaging. The information provided from the imaging modes has identified the details of the magnetization reversal mechanisms in the elements during the course of a hysteresis cycle. In particular, domain wall clusters which form at the edges of the elements are observed prior to switching of the magnetization. Results are described from elements with near single and multidomain structures with different geometry.

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Abstract: The compositional profile of a narrow layer of InAsxPl−x in InP has been determined using energy-filtered Fresnel contrast analysis, high-resolution electron microscopy (HREM), and high-angle annular dark-field (HAADF) imaging. The consistency of the results obtained using the three techniques is discussed, and conclusions are drawn both about the validity of interpreting the magnitude of Fresnel contrast data quantitatively and about the degree to which high-angle annular dark-field images of such materials are affected by inelastic scattering and strain.

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Analysis of Experimental Error in High Resolution Electron Micrographs

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The human immunodeficiency virus (HIV-1) is dependent upon the synthesis of TAT for efficient transcriptional activation and replication. Following translocation to the nucleus TAT interacts with a cis-acting TAT-responsive element located between nucleotides +1 and +42 within the HIV-1 long terminal repeat. This region contains an RNA stem loop structure TAR which interacts with TAT and cellular proteins to increase transcription 1000 fold We have transfected human T-lymphocytes with an expression vector containing the HIV-1 LTR driving the synthesis of TAT-72. A stable cell line was generated by selection with G418. Cells were grown on round glass coverslips coated with a solution of fibronectin overnight (at 37 °C). In addition to light microscopy (LM) observations, cells on coverslips were fixed with a 3.5% glutaraldehyde buffered solution (0.1 M Na cacodylate) for 5 min at room temperature and gently centrifliged in a microfuge (400 rpm, 3min) to obtain a cellular pellet.

Large cell (T - cell) lymphoma is a malignant neoplasm derived from activated lymphoid cells, involving lymph nodes, spleen, subcutaneous lesions. Ultrastructural examination facilitates the determination of this particular type of lymphoma, specifically by the presence of lytic granules in the cytoplasm containing proteins involved in the target cell destruction. One of these, expressed specifically is TIA-1, a cytotoxic granule-associated protein with RNA binding domains initially identified using a monoclonal antibody reactive with a 15KD protein present in the granules of cytotoxic lymphocytes.

Tissue from seven cases of large cell lymphoma from the archives of our department were fixed for electron microscopy studies with a mixture of4% paraformaldehyde and 1% glutaraldehyde in 0.1M sodium cacodylate buffer and embedded either in Poly/Bed 812 with osmium tetroxide postfixation, or in LR White without osmication. For immunogold labelling, ultrathin sections placed on Nickel grids were incubated with a murine monoclonal TIA-1 antibody (1:50) (Coulter Co) overnight at 4°C.