The protozoan parasite Toxoplasma gondii is representative of a large group of parasites within the phylum Apicomplexa, which share a highly unusual motility system that is crucial for locomotion and active host cell invasion. Despite the importance of motility in the pathology of these unicellular organisms, the motor mechanisms for locomotion remain uncertain, largely because only limited data exist about composition and organization of the cytoskeleton. By using cytoskeleton stabilizing protocols on membrane-extracted parasites and novel imaging with high-resolution low-voltage field emission scanning electron microscopy (LVFESEM), we were able to visualize for the first time a network of actin-sized filaments just below the cell membrane. A complex cytoskeletal network remained after removing the actin-sized fibers with cytochalasin D, revealing longitudinally arranged, subpellicular microtubules and intermediate-sized fibers of 10 nm, which, in stereo images, are seen both above and below the microtubules. These approaches open new possibilities to characterize more fully the largely unexplored and unconventional cytoskeletal motility complex in apicomplexan parasites.

We developed a novel electron-diffraction technique by focusing a small probe above (or below) the sample in an electron microscope to measure charge density and lattice displacement in technologically important materials. The method features the simultaneous acquisition of shadow images within many Bragg reflections, resulting in parallel recording of dark-field images (PARODI). Because it couples diffraction with images, it is thus suitable for studying crystals as well as their defects. We used this technique to accurately locate the charge-carrying holes in superconducting crystals, and to determine displacement vectors across planar faults by comparing the experiments with calculations, and by using fitting and error analyses. Examples are given for complex YBa2Cu3O7 and Bi2Sr2CaCu2O8+δ oxides and the newly discovered MgB2 superconductor.

Biological macromolecules embedded in vitreous ice are known to suffer from charging while being imaged in an electron transmission cryomicroscope. We developed an electron beam coater that deposits conductive films onto the surface of frozen-hydrated specimens. The conductive films help to dissipate charge during electron irradiation of poorly conductive ice-embedded biological samples. We observed significant reduction in charging of ice-embedded catalase crystals suspended over holes in a holey carbon film after coating them with a 30-Å-thick layer of an amorphous alloy, Ti88Si12. Images of the crystals after coating showed diffraction spots of up to 3 Å resolution.

The same Bragg reflection in TiO2 from 12 different (CBED) patterns (from different crystals, orientations, and thicknesses) are analyzed quantitatively to evaluate the consistency of the quantitative CBED method for bond-charge mapping. The standard deviation in the resulting distribution of derived X-ray structure factors is found to be an order of magnitude smaller than that in conventional X-ray work, and the standard error (0.026% for FX(110)) is slightly better than obtained by the X-ray Pendellösung method applied to silicon. This is sufficiently accurate to distinguish between atomic, covalent, and ionic models of bonding. We describe the importance of extracting experimental parameters from CCD camera characterization, and of surface oxidation and crystal shape. The current experiments show that the QCBED method is now a robust and powerful tool for low-order structure factor measurement, which does not suffer from the large extinction (multiple scattering) errors that occur in inorganic X-ray crystallography, and may be applied to nanocrystals. Our results will be used to understand the role of d-electrons in the chemical bonding of TiO2.

The Microscopy Society of America, the Microbeam Analysis Society, the International Metallographic Society and the Congress of InterAmerican Societies of Electron Microscopy invite you to Microscopy and Microanalysis 2003, which is also the VII InterAmerican Congress on Electron Microscopy/VII Congreso InterAmericano de Microscopía Electrónica.

The city of San Antonio with its location, history, and culture is an ideal host for this Pan American meeting. The Convention Center and three of the participating hotels are located downtown on the amazing River Walk. Many restaurants and shops are clustered around the River Walk as is La Villita, an arts village and a National Register Historical District. A few blocks from the River Walk is Market Square, which is a center of the Mexican culture featuring patio restaurants, a farmers market, and El Mercado, the largest Mexican marketplace outside of Mexico. You will find that downtown San Antonio is a very convenient, interesting, and unique venue for our meeting. For transportation information, maps, visitor's guides, and much more, see http://www.sanantoniovisit.com/.

One of the most interesting aspects of this book is the frequency at which the contributing authors are found in the references at the end of not one, but usually several chapters: this is by no means a mistake. Editors Hacker and Gu have assembled a wealth of expertise from well-known individuals in the fields of autometallography, immunogold-silver staining and molecular morphology. Composed of 16 chapters with a total of 32 contributing authors, the material is presented in a very well organized and coherent format.

This issue of Microscopy and Microanalysis contains selected papers from the fifth Regional Workshop of the European Microbeam Analysis Society (EMAS) on Electron Probe Microanalysis—Practical Aspects that took place May 22–25, 2002 at Szczyrk, Poland. The meeting was organized by the Polish National Branch of EMAS in collaboration with the Silesian University of Technology (Faculty of Materials Engineering and Metallurgy) and the Polish Academy of Science (Institute of Metallurgy and Materials Science).

The changes of the work function (Φ) and the secondary electron emission (SEE) of oxygen covered polycrystalline tungsten occurring after ion sputtering and heat treatments have been investigated. The chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS), and the electron emission properties by work function spectroscopy (WFS). We observed in what manner the chemical changes of the surface are reflected in the work function and SEE. The simultaneous change of Φ and SEE in the case of oxygen covered tungsten have been pointed out and a direct relationship between them can be supposed.

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Of all the long-lived particles available as probes of condensed matter, and of all the signals available on a modern electron microscope, electron nanodiffraction patterns provide the strongest signal from the smallest volume. The technique is therefore perfectly suited to nanostructural investigations in inorganic chemistry and materials science. The Vacuum Generators HB501S, an ultrahigh vacuum (UHV) variant of the HB501 scanning transmission electron microscope (STEM), with side-entry double-tilt stage, specimen preparation and analysis chamber, three postspecimen lenses, and cold field-emission tip with integral magnetic gun lens, has therefore been modified to optimize nanodiffraction and quantitative convergent beam electron diffraction (QCBED) performance. A one-micrometer grain-size phosphor screen lying on a fiber-optic faceplate atop the instrument is fiber-optically coupled to a 2048 × 2048 charge-coupled device (CCD), 16-bit camera. This arrangement promises to provide much greater sensitivity, larger dynamic range, and a better modulation transfer function (MTF) than conventional single crystal scintillator (YAG) CCD systems, with noticeable absence of cross talk between pixels. The design of the nanodiffraction detector system is discussed, the gain of the detector is measured, the spherical aberration constant of the objective lens is measured by the Ronchigram method, and preliminary results from the modified instrument are shown.

Recent evidence supports the notion that biological functions of extracellular matrix (ECM) are highly correlated to not only its composition but also its structure. This article integrates confocal microscopy imaging and image-processing techniques to analyze the microstructural properties of ECM. This report describes a two- and three-dimensional fiber middle-line tracing algorithm that may be used to quantify collagen fibril organization. We utilized computer simulation and statistical analysis to validate the developed algorithm. These algorithms were applied to confocal images of collagen gels made with reconstituted bovine collagen type I, to demonstrate the computation of orientations of individual fibers.

A new Monte Carlo method has been developed for simulating backscattered electron spectra, and this was applied for determining the surface excitation parameter (SEP). The simulation is based on direct tracking of electron trajectories in the solid, taking into account elastic and inelastic events. The elastic scattering cross sections are taken from literature, while inelastic cross section data are obtained by a fitting procedure. After some iterations, the program produces electron spectra fitting well to the experimental ones. Si and Ge electron spectra were simulated and SEP values were calculated. The SEP values are compared to other ones from literature.

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