Freeze-fracture techniques have contributed much to our understanding of membrane composition and macromolecular architecture. However, further substantive contributions from freeze fracture have seemed unlikely because: a) replicas typically fragmented, destroying histological orientation within samples; b) histochemical staining techniques were thought to be incompatible with bleach- or acid-cleaned freeze-fracture replicas; c) the limit of resolution was presumed to be 3-5 nm; and d) there were no methods for directing the fracture plane to specific components within a tissue. Recent developments in “grid-mapped freeze fracture” and freeze-fracture immunocytochemistry have addressed each of these limitations.

Using grid-mapped freeze fracture, samples are mapped in three dimensions using confocal microscopy before freeze-fracture (Fig. A), as well as after replication and stabilization in Lexan plastic on a gold “Finder” grid (Fig. B). After replica cleaning, areas of interest are correlated in confocal and TEM images —— for example, cilia of the ependymal layer of rat spinal cord (Fig. C).

The resolution of any microscope is usually taken as the benchmark of its quality. When thinking about the scanning electron microscope(SEM) a comparison of its resolution to the resolutions quot-ed for other comparable instruments such as the transmission EM or the scanning tunneling micro-scope has unfortunately led some users to the view that the SEM is only a second best choice. In fact the spatial resolution that can be anticipated for an optimized SEM is highly competitive with its peers making it clearly the microscopy of choice.

The resolution of the SEM depends on two classes of factors; those which are inherent to the use of electrons as an imaging tool, and those which relate to the performance of the instrumentation (and possibly of the operator) used to perform the microscopy. The use of electrons as the scanning probe, and the choice of secondary electrons as the usual imaging mode, potentially affects the achievable resolution in three ways.

The pituitary specific transcription factor Pit-1 is required for transcriptional activity of the prolactin (PRL) gene. The Pit-1 protein is a member of the POU homeodomain transcription factors that is expressed in several different anterior pituitary cell types, where it functions as an important determinant of pituitary-specific gene expression. The Pit-1 protein generally interacts with DNA elements in the PRL gene promoter as a dimer, and has been demonstrated to associate with other transcription factors. The objective of our research is to define the critical molecular events involved in transcriptional regulation of the PRL gene in living cells. Methods that allow monitoring of the intimate interactions between protein partners in living cells provide an unparalleled perspective on these biological processes. Using the jellyfish green fluorescent protein (GFP) as a tag, we applied the fluorescence resonance energy transfer (FRET) technique to visualize where and when the Pit-1 protein interacts in the living cell. FRET is a quantum mechanical effect that occurs between donor (D) and acceptor (A) fluorophores provided: (i) the emission energy of D is coincident with the energy required to excite A, and (ii) the distance that separating the two fluorophores is 10-100 Å. Mutant forms of GFP that fluoresce either green or blue (BFP) have excitation and emission spectra that are suitable for FRET imaging.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

In recent years, the magnetic force microscope (MFM) has been used not only for the evaluation of magnetic media but also for the measurement of magnetic characteristics of quantum dots as well as in various fields, because the MFM can visualize magnetic field on the sample surface with the high resolution. The MFM observation in ultra-high vacuum (UHV) requires to reduce the adsorption layer on the sample surface for high resolution observation. The slope detection mode using the variation of vibrating cantilever is basically unstable in UHV due to the increase in the Q factor of the cantilever. Accordingly it has been used for the MFM observation in air. On the other hand, the FM detection technique offers a very high sensitivity because of the high Q factor.

This repot describes the MFM technique to take a magnetic image steadily in UHV. We observed the surface of a magnetic material with MFM technique in UHV, and compared the slope detection technique, the phase detection technique using phase variation of cantilever vibration, and the FM detection technique.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Introduction: There is considerable interest in the use of three-dimensional porous scaffolds for tissue regeneration. The presence of an interconnected framework of pores with large surface area facilitates the formation of extracellular matrix and permits cellular ingrowth into implanted structures. For scaffolds to be useful for tissue regeneration, they must maintain good dimensional stability during the lifetime of the implant. While the initial scaffold architecture is often well characterized, a systematic study of the influence of incubation on the scaffold architecture is critical to ensure that the scaffolds retain their interconnected network of pores during their useful lifetime. Herein, we report on the evaluation of the architecture of polyarylate scaffolds and their stability under in vitro conditions using scanning electron microscopy (SEM).

The polymers used in this study were selected from a library of degradable polyarylates. This library is the first reported combinatorial library of biodegradable condensation polymers.

As a crystal gets smaller, diffraction spots stay visible for larger deviations from the Bragg condition. The upper limit of such deviations is connected to the threshold for getting lattice fringes in TEM images. This in turn allows one to quantify the probability of seeing cross lattice fringes along a certain zone axis. In this abstract we examine a simple semi-empirical model for the probability of detecting (001) zone cross-fringes of a spherical crystal of cubic lattice.

The upper limit for the deviation of crystal orientation from the exact Bragg condition, without losing cross fringes down a given zone, is expressed as the maximum half-angle θ1 between the zone and the electron beam. The solid angle σ subtended by a cone with this half-angle is proportional to the probability px that a randomly-oriented crystal will show the cross-fringes associated with that zone. A schematic, illustrating the principle used to calculate the probability of seeing cross-fringes, is given in Figure 1.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

Most scanning electron microscopy is performed at low magnification; applications utilising the large depth of field nature of the SEM image rather than the high resolution aspect. Some environmental SEMs have a particular limitation in that the field of view is restricted by a pressure limiting aperture (PLA) at the beam entry point of the specimen chamber. With the original ElectroScan design, the E-3 model ESEM utilised a 500 urn aperture which gave a very limited field of view (∼550um diameter at a 10mm working distance [WD]). An increase of aperture size to ∼lmm provided an improved but still unsatisfactory field of view. The simplest option to increase the field of view in an ESEM was noted to be a movement of the pressure and field, limiting aperture back towards the scan coils1. This approach increased the field of view to ∼2mm, at a 10mm WD. A commercial low magnification device extended this concept and indicated the attainment of conventional fields of view.

We report here a specific type of edge strength anisotropy observed in field emission scanning electron microscope (FESEM) images. The images show weaker edge gradients in the scanning direction and hence these edges frequently go undetected. Direct application of edge detection algorithms to images with nondistinct edges, such as powder particles, show strong bias to edges perpendicular to the scanning direction. Edge orientation polarograms obtained from these images always show strong fictitious particle orientation in the scanning direction. In this work, we discuss an edge-sharpening algorithm that corrects for this bias and results in relatively more accurate and consistent edge orientation information.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Development of high-density longitudinal magnetic recording media (used for computer hard disks) with good noise performance and high thermal stability requires optimization of both alloy composition and processing methods. In CoCr(PtTa) thin films, intergranular Cr segregation is responsible for decoupling the magnetic exchange between the small ferromagnetic grains. The corresponding Cr depletion within the grains affects the “bulk” magnetic anisotropy. However, the nanoscale structural and chemical details that are needed for modeling and for guiding material development are not well understood. Energy-filtered transmission electron microscopy (EFTEM) has been used to characterize a series of CoCrTa/Cr, CoCrPt/Cr, and CoCrPtTa/Cr media sputtered under various processing conditions, in order to understand their structure-property-processing relationships.

Processing typical for hard-disk media was used: 30 or 60-nm films of a Cr underlayer followed by a Co alloy were d.c. magnetron sputtered onto a NiP-plated Al substrate pre-heated to 250°C.

Accurate descriptions of dispersed metals are of central importance in optimizing the activity, selec-tivity and stability of a diverse set of catalysts and chemistries. Improved methods for quantifying metal dispersion, alloying and support interactions help form mechanistic understandings of catalyst function at the atomic scale. In this paper we discuss ideal capabilities of a transmission electron microscope for catalysis, and give an update on the use of a next-generation field-emission TEM/STEM for structural and analytical studies of supported metal catalysts.

Characterizing nanometer-sized metal particles requires high performance imaging, high sensitivity analysis, and minimal disruption of the physical state of the particles. No single microscope combines all key performance factors with ease of use. Schottky field-emitter instruments provide high current-density probes with excellent stage stability (nm drifts in > 10 min. observed), < 0.7 eV energy reso-lution for EELS, and a turbo-pumped vacuum system for minimal carbon contamination while using nanometer probes and nanoamps of current. Scanning TEM performance is also key.

Message from the President.

MSA calendar of events.

Council members.

MSA appointed officers.

MSA sustaining members.

MSA awards.

Application of an appropriate ceramic surface coating to mechanical components such as bearings and gears can provide longer life and increased performance reliability. Metal-containing hydrocarbon (Me-C:H) coatings possess high hardness, together with low friction and low wear rate. They have also been suggested to adhere better to metallic substrates. This combination of attractive mechanical/tribological properties makes Me-C:H coatings potentially useful for surface modification of a wide range of mechanical components.

Using the technique of inductively coupled plasma (ICP) assisted vapor deposition[1], we have synthesized Ti-containing hydrocarbon (Ti-C:H) coatings with a wide range of Ti compositions[2]. Coating mechanical properties such as modulus and hardness have been measured by the technique of nanoindentation and correlated to Ti and hydrogen compositions[2,3].

We have performed detailed microstructural examination of Ti-C:H coatings by transmission electron microscopy (TEM), Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, and X-ray Absorption Near Edge Structure (XANES) spectroscopy.

A variety of porous materials are used in a number of tissue-engineering applications such as cell transplantation and drug delivery. They provide a temporary scaffolding for a large cell mass, however they must have a fully interconnected pore structure. One such material is sodium alginate, a naturally derived polysaccharide which is isolated from seaweed. Sodium alginate can de dissolved in water to form a highly viscous solution that can be cross-linked in the presence of divalent cations (e.g., Ca2+) to form what is known a as hydrogels. We have developed a method for the fabrication of porous beads of sodium alginate and have attempted to measure the pore size, density and distribution in the beads. Characterization of the pore size and distribution is necessary to determine if the material is appropriate to promote cellular in-growth. The characterization procedures have been limited to conventional scanning electron microscopy (SEM) and mercury intrusion porosimetry. There has been some concern as to the potential introduction of artifacts (spatial distortion) during dehydration and sample preparation during these characterizations.