Scanning electron microscopy (SEM) can produce striking three-dimensional images of biological cells and tissues with submicron resolution of surface morphology. Such cell surfaces are often complex blends of folds, extrusions, and pockets that may be necessary in the positioning of specific molecules within interaction range of each other. Thus, surface changes can have a spatial control over some molecular functions, and identification of select molecules at distinct morphological locations becomes critical to our understanding of total cell function.

Confocal microscopy is widely used in cell biology. Like other filter-based systems, traditional confocal microscopes are limited by the spectral bands established by each optical filter. As a result, emission spectra from labels and/or autofluorescence can be overlapped leading to spectral crosstalk and inability to quantify the amount of signal originating from each individual fluorescent species. The need for accurate quantification of in vivo cellular processes and in-depth knowledge of organelle development and microstructure led Monsanto to search for non-commercial microscopes that could achieve those goals. Through a cooperative research and development agreement (CRADA) established between Monsanto and Sandia Corporation in August 2006, we built a new 3D-hyperspectral confocal fluorescence imaging system, specifically designed to meet the analytical requirements of plant specimens.

For many years now, the combination of the modern S/TEM system (scanning/transmission electron microscope) with the X-ray energy dispersive spectrometer (XEDS) has resulted in Analytical Electron Microscopes (AEMs) able to deliver both high-resolution imaging and elemental composition maps in the same instrument. This ability to correlate local elemental composition with microstructure has greatly broadened the applications realm of the S/TEM instrument. The boundaries of performance for many of these applications are now determined by limits in XEDS system detection sensitivity. In this article, we describe an AEM with greatly enhanced detection sensitivity due to a number of innovations in the system architecture, including: a high-brightness Schottky FEG source, four detectors integrated deeply into the objective lens, windowless silicon drift detector technology with shutters, and high-speed electronics readout. This new system architecture provides many performance benefits, such as improved light element detection, better sample tilt response, faster mapping, and especially enhanced system detection sensitivity.

Feldspar is the name for a mineral group consisting of nearly 20 triclinic or monoclinic mineral species, of which only nine are well documented and widely distributed in the Earth's crust. Single members of the feldspar group belong to the so-called framework—or tectosilicates, where SiO4- and AlO4-tetrahedra share all their oxygen ions, resulting in an infinite three-dimensional network . Feldspar crystals include the major elements K, Na, Ca, Al, as well as Si and thus may be attributed to one of the following three endmembers: potassium-feldspar (K-feldspar) KAlSi3O8, albite NaAlSi3O8, or anorthite CaAl2Si2O8 (Table 1). Solid solutions occur between K-feldspar and albite, forming what is commonly known as alkali feldspar, and between albite and anorthite, forming plagioclase. The alkali feldspar group consists of orthoclase, microcline, sanidine, and anorthoclase, whereas the plagioclase group includes albite, oligoclase, andesine, labradorite, bytownite, and anorthite .

Atomic force microscopy (AFM) began as an art as well as a science, and in many ways it continues to be an art and a science. Despite the existence of new, better, faster, bigger (or smaller!) atomic force microscopes (AFMs), some of the of the fundamental challenges remain—probe tips, sample dirt, and moving beyond leading-edge results obtained with one biological system to obtain leading-edge results with a related system.

Neurons in the central nervous system (CNS) are extensively interconnected, and consequently almost half of the human brain is occupied by wiring in the form of the myelinated axons. Dysfunction and degeneration of these axons can result in profound and permanent disability. Axons are much more complex than simple wires, however. Signal propagation relies on elaborate ultrastructural specializations at the nodes of Ranvier, which are demarcated by gaps between myelin sheaths. As living extensions of neurons, axons also require constant replenishment of metabolites and organelles such as energy-generating mitochondria. Studies of pathogenesis of myelinated axons are often constrained by microscopic complexity that requires nanometer-scale resolution over substantial three-dimensional distances.

Wootz is the name given to a crucible steel prepared in India. Coze noted that the name “wootz” first appeared in printed form in a report by Pearson in 1795. However, the origin of the name itself is unclear though it was proposed by Yule and Burnell in the Hobson-Jobson Dictionary that the word “wootz” could come from “ukku” in the Kanadda language.

Deoxyribonucleic acid (DNA) has been considered as a possibility for molecular electronics. Because DNA is able to recognize other molecules—other strands of DNA—and because it binds together with similar DNA strands in a very unique way, scientists have suggested the possibility of using DNA as an electronic circuit without having to build in any other circuitry. The DNA would bind with other similar DNA strands that it recognizes and then use the connecting properties of the DNA to create a self-assembled biological wire for electrical conduction. Until recently, uncertainty existed about whether DNA could conduct at all, and if it could, how well it could conduct. Scientific speculations ranged from DNA being a superconductor to a complete insulator. Recent research, however, by Dr. Sidney R. Cohen in collaboration with Dr. Ron Naaman and Dr. Claude Nogues of the Weizmann Institute of Science, Scanned Probe Microscopy Unit, in Rehovot, Israel, aided by the enabling technologies of ultra-high-resolution microscopy and negative-stiffness vibration isolation, has shed new light on the electrical transport properties of DNA, focusing on the capacity of single molecules of DNA to transport current along individual strands.

When it comes to mineral synthesis, there is a lot we can learn from nature. Although we can synthesize a range of materials in the laboratory, the experimental conditions are often constrained to particular ranges of temperature, pH, etc. Biological systems, on the other hand, seem to be able to produce individual minerals and complex composite mineral structures under a variety of conditions, many of which are far from those applied to create their synthetic counterparts. Understanding how nature does this could provide a means to produce novel biomimetic materials with potential applications in a diverse range of fields from medicine to materials engineering.

Polymers play an essential role in modern materials science. Because of the wide variety of mechanical and chemical properties of polymers, they are used in nearly every industry. Knowledge about their physical and chemical properties on the nanometer scale is often required. However, some details about the phase-separation process in polymers are difficult to study with conventional characterization techniques because these methods cannot chemically differentiate phases with good spatial resolution without damage, staining, or preferential solvent washing.

Steve Chapman's “An Old Man's Saga” in the May 2009 issue of Microscopy Today about the various methods he has used for determining when saturation is achieved in the common self-biased electron gun prompts me to share with Microscopy Today's readers my experience in lecturing to my students about the characteristics of this remarkable device.

One of the capabilities of electron microscopes is to obtain diffraction patterns, which can be analyzed to give information about the structure of the specimen. This brief review discusses some of the technical considerations in using electron diffraction patterns for structural analysis. The technique of selected-area electron diffraction uses diffraction obtained from a limited region of the specimen.

The study of pollen is important in paleoecology, paleontology, archeology, and forensics. The outer shell of a pollen grain bears characteristic features that help in determining the species or genus of origin. To view the pollen grain from several angles in a light microscope, the sample is usually mounted in glycerol and rolled on the microscopic slide by pushing the coverslip. For teaching, training, and also for establishing databases of pollen images, it is desirable to obtain three-dimensional datasets that allow rotation and viewing from any angle and reslicing in the computer.

Digital images carry a great deal of information, but they should not stand alone. They need to be accompanied by experimental variables, equipment used, personnel involved, image-processing operations performed, and site information. It is essential to maintain a link between pixel data and experimental conditions associated with the picture.

A liposome is a spherical particle formed by a lipid bilayer enclosing an aqueous compartment at its center. These particles can be comprised of a variety of lipids, particularly phospholipids. They have been long considered as potential delivery devices in the medical and pharmaceutical industries because of their ability to encapsulate different compounds as the lipids form into liposomes. The biocompatibility of many liposomes has been widely studied, and this has led to the development of a number of drug formulations. The ability of liposomes to be stored in the body and to be taken up by cells makes them ideal for drug delivery.

Nano- and micro-patterned substrates have become a powerful tool in cell biology in recent years. Although great progress has been made in applying these substrates to cell populations or single cells, visualization of cells in direct contact with nanostructured interfaces remains a challenge. A central question that needs to be addressed by imaging is the number of biomolecules in contact with a single cell.

Element-selective imaging and analysis at atomic resolution have become possible by the recent advancements in TEM and STEM. However, the spatial resolution in images of soft materials can be limited by electron beam damage and/or contamination. This contamination is a carbonaceous layer deposited on the specimen surface as a result of electron bombardment. Beam-induced specimen contamination is caused by polymerization of hydrocarbons that are present in a TEM specimen chamber. The electron beam reacts with stray hydrocarbons in the beam's path to create hydrocarbon ions, which then condense and form carbon-rich polymerized film on the area being irradiated. Figure 1a shows contamination spots created on a carbon thin foil by illuminating a beam with an intensity of 5.6 × 104 el/nm·s at an accelerating voltage of 200 kV. The thickness of the contamination spots can be estimated by electron energy-loss spectroscopy (EELS). With increase in the irradiation period, the intensity of the zero-loss peak decreases, but the overall intensities in the energy-loss regions of the spectrum increase (Figure 1b). The thickness (D) can be estimated using the equation, D = Λ·ln(It/I0), where Λ is the total mean free path for inelastic scattering, and It and I0 are the integral intensities of the overall spectrum and the zero-loss peak, respectively. Using this equation, the thickness of the contamination was found to be about 600 nm with a 10-minute irradiation.