bluuebunny/crossref_metadata_2025 huggingface dataset:
Some aspects of optimizing contrasts for the investigation of joint materials in the environmental scanning electron microscope
Authors: Schnarr Holger , Füting Manfred W.
Published: June 2010

In the environmental scanning electron microscope, material joints of different atomic mass and different electrical conducting properties can easily be observed simultaneously without coating the specimen. For such heterogeneous materials, the quality of the image can be optimized with respect to contrast and resolution if the contrast types as well as their significance to the composition of the image are known.
Use of the environmental scanning electron microscope for the observation of the swelling behaviour of cellulosic fibres
Authors: Jenkins L. M. , Donald A. M.
Published: June 2010

We have developed a method for observing transverse swelling of cellulosic fibres in the environmental scanning electron microscope (ESEM). The presence of liquid water in the ESEM specimen chamber allows the observation of in situ hydration without the need for coating, freezing, or drying of the sample. For reproducibility of the hydration and dehydration process, specialised mounting techniques are required and control of the conditions for condensation and evaporation of liquid water is necessary. The sensitivity of these cellulosic materials to the electron beam was investigated, showing that some damage mechanisms are enhanced by the continual presence of water vapour in the chamber. A discussion is presented of the effect of various experimental parameters on the extent and time of onset of the damage, and we outline steps to maximise the amount of useful experimental time for these fibres.
Environmental scanning electron microscopy of personal and household products
Authors: Hoyberg Karen
Published: June 2010

The ability to forego sample preparation and to make observations directly in the environmental scanning electron microscope has benefited both household and personal product research at Unilever Research. Product efficacy on biological materials such as microcomedones was easily ascertained. Skin biopsies were examined in a moist state with no sample preparation. Effects of relative humidity on detergents were visually determined by recreating the necessary conditions in the microscope. Effects of cooling rates on the morphology of softener sheet actives that remained on polyester fabric were characterized via dynamic experimentation.
Three‐dimensional studies of siC polytype transformations
Authors: Saparin G. V. , Obyden S. K. , Ivannikov P. V. , Shishkin E. B. , Mokhov E. N. , Roenkov A. D. , Hofmann D. H.
Published: June 2010

Scanning electron microscopy technique in colour cathodoluminescence mode is proposed for two‐dimensional (2‐D) and three‐dimensional (3‐D) studies of polytype structures of SiC epitaxial layers grown by the sublimation sandwich method. It allows us to perform layer‐by‐layer structure analysis of a polytype on depths up to 2.5 μm with high resolution. An effect of polytype instability under growth on singular substrate (0001) is revealed. It leads to the fact that the grown SiC layer represents the set of alternating sublayers of different polytypes such as 4H, 6H, and 3C. Some mechanisms of polytype syntaxy in SiC are discussed.
Double‐layer coating for field‐emission cryo‐scanning electron microscopy—present state and applications
Authors: Walther P. , Müller M.
Published: June 2010

Imaging of fast‐frozen samples is the most direct approach for electron microscopy of organic material. It prevents chemical fixation and drying artifacts. Frozen samples can be replicated and imaged in the transmission electron microscope (TEM), or they can be directly visualized in the cryo‐scanning electron microscope (cryo‐SEM). Double‐layer coating combines these two techniques and many of their advantages. With this method, the frozen bulk sample is coated similar to the TEM‐replica technique with, for example, a shadow of platinum (at an angle of 45°) and an additional layer of carbon. Then, the sample is cryo‐transferred to an SEM equipped with a cold stage and imaged with the material‐dependent backscattered electron signal that shows the platinum distribution. With this method, charging artifacts and the effects of beam damage are significantly reduced. Although currently the resolution of the replica technique cannot be surpassed, the method greatly facilitates the processing of brittle, rapidly frozen samples because no replica cleaning is necessary. This makes the method especially suitable for high‐pressure frozen samples.
Macromolecular substructure in nuclear pore complexes by in‐lens field‐emission scanning electron microscopy
Authors: Allen T. D. , Bennion G. R. , Rutherford S. A. , Reipert S. , Ramalho A. , Kiseleva E. , Goldberg M. W.
Published: June 2010

Scanning electron microscopy (SEM) has produced a wealth of novel images that have significantly complemented our perception of biological structure and function, derived initially from transmission electron microscopy (TEM) information. SEM is a surface imaging technology, and its impact at the subcellular level has been restricted by reduced resolution in comparison with TEM. Recently, SEM resolution has been considerably improved by the advent of high‐brightness sources used in field‐emission instruments (FEISEM) which have produced resolution of around 1 nm, virtually equivalent to TEM “working resolution.” Here we review our findings in the use of FEISEM in the imaging of nuclear envelopes and their associated structures, such as nuclear pore complexes, and the relationships of structure and function. FEISEM allows the structurally orientated cell biologist to visualise, directly and in three dimensions, subcellular structure and its modulation with a view to understanding its functional significance.
Atomic force microscopy as a tool for study of human hair
Authors: You H. , Yu L.
Published: June 2010

Atomic force microscopy (AFM) is a newly developed microscopic technique that offers high‐resolution power, less intrusive measurement, and requires little sample pretreatment for elucidating structures of biological materials in three dimensions and in their natural environment. In this study, AFM has been used not only as an imaging technique for examining human hair structure at high resolution, but also as a tool for quantitative assessment of the effect of treatment in 10 mM phosphate buffered saline of pHs 3.0, 7.0, and 11.0 and heating on human hair structure. It is observed that the hair cuticle is a sensitive indicator of external influences on hair structure, and that its height can be used as a parameter for quantitative assessment. The experimental results obtained show that the swelling of hair caused by the incubation in the buffer decreases with the increase of the pH values and that, depending on the duration of heating, the hair undergoes structural expansion and shrinkage. This study demonstrates that AFM can be used as a valuable alternative to conventional microscopic techniques for hair research.
Optically active centers in diamond as‐grown at temperatures 1200–1350°C
Authors: Ekimov E. A. , Klimin S. A. , Borovikov H. F. , Saparin G. V. , Obyden S. K. , Rulev G. B.
Published: June 2010

Diamonds were grown in the vicinity of the “diamond‐graphite” equilibrium state by the spontaneous crystallization method to study the creation of defects and crystalline imperfections. Crystals were synthesized in the graphite‐Ni‐Mn system. Raman and luminescence spectroscopy, electron microscopy, and optical absorption spectroscopy were used for diamond crystal inspection. Diamonds were classified into three groups: (1) black, nontransparent, curved, flat‐faced crystals; (2) dark or black semitransparent crystals of cubic habit with faceting of the cube vertices by (111) planes; (3) amber‐yellow crystals showing a cubic‐octahedral habit.

The yellow crystals revealed the infrared (IR) absorption spectra within the range of 800–4000 cm‐1 that are peculiar for diamonds of the 1a group. IR spectra displayed a number of additional absorption peaks for black semitransparent crystals. A marked peak at 2835 cm‐1 and a less pronounced peak at 2919 cm‐1 unambiguously demonstrate the presence of hydrogen. An intensive absorption in the range of 800–1100 cm‐1 with a maximum at 969 cm‐1 may be explained by both the presence of hydrogen and extended defects, taking into account the data arrived at by cathodoluminescence, emission spectra, and Raman spectroscopy. For the first time, the narrow peak at 1332 cm‐1, unknown for mined diamonds and observed in flame‐chemical vapor deposition (FL‐CVD) diamond films, was revealed in diamonds synthesized under high pressure.

The presence of peaks with maximum at 2919, 1252, and 1332 cm‐1 in the IR spectra of the black diamonds and FL‐CVD diamond films indicated a certain similarity in diamond formation for high‐ pressure and vapor deposition techniques and an important role of hydrogen in high‐pressure diamond growth. The source of hydrogen is probably graphite used in the synthesis. The increase in diamond synthesis temperature decreases the probability of hydrogen capture and provides a better crystal quality. Cathodoluminescence scanning electron microscopy demonstrated the spatial distribution of luminescence centers on different diamond crystal faces. Some crystal fragments emit A‐band (420–460 nm) and have well‐faceted faces that confirm their high perfection and quality that are close to natural diamonds.
A multiple technical approach to the study of apoptotic cell micronuclei
Authors: Columbaro M. , Gobbi P. , Renò F. , Luchetti F. , Santi S. , Valmori A. , Falcieri E.
Published: June 2010

Apoptotic micronuclei have been studied, in different cell types, from a morphologic and functional point of view. Conventional electron microscopy, in various staining conditions, selective cytochemistry for DNA, and freeze fracture for the analysis of chromatin fiber organization and size were performed. In situ TdT and Pol I immunofluorescent techniques were carried out to detect double‐ and single‐strand DNA breaking points by confocal laser scanning microscopy. Apoptotic cell ultrathin cryosections were also performed and were analysed by field emission in lens scanning electron microscopy. Double/single strand massively cleaved DNA was detected in micronuclei, with a highly supercoiled, uniformly packed, very dense arrangement.
Morphologic and temporal analysis of vascular smooth muscle cell apoptosis induced by c‐Myc and E1A
Authors: Allen R. Todd , Hunter William J. , Agrawal Devendra K.
Published: June 2010

Apoptosis is a physiologic form of cell death present in many disease conditions. When the balance of mitosis versus apoptosis is altered, tumor‐like growth or degeneration of tissues may ensue. This appears to occur in several diseases, including those of the cardiovascular system, where apoptosis plays a key role in atherosclerosis and restenosis following angioplasty. Since c‐myc is upregulated in the pathogenesis of these diseases, we chose to study the sequential morphologic features of programmed cell death in vascular smooth muscle cells induced by c‐myc and by the adenovirus early gene E1A. Morphology and timed events in apoptotic cell cultures were analyzed by scanning electron microscopy, transmission electron microscopy, and time‐lapse videomicroscopy. We observed that both c‐myc‐and E1A‐induced apoptosis (in serum‐free medium) resulted in numerous, tightly packed clusters of apoptotic blebs, as well as in one or two asymmetrically larger blebs. Transmission electron microscopy analysis revealed the larger blebs contained mostly nuclear chromatin, whereas the many smaller fragments often had little or no chromatin. Time‐lapse studies showed that apoptosis was induced at a slower rate in cells stably transfected with c‐myc versus those stably transfected with E1A. The early changes of apoptosis, including cell shrinkage and intense blebbing, occurred in under 5 min in both cells. Slight alterations such as cell size and further rounding occurred up to 8 h following the initial changes of apoptosis. Rather than being a part of the apoptotic response, release from the culture floor almost entirely resulted from movement of the culture flask. These studies provide a framework of timed morphologic events for future mechanistic investigation into the key aspects of myc‐and E1A‐induced apoptosis in vascular smooth muscle.
Elemental and molecular imaging of human hair using secondary ion mass spectrometry
Authors: Gillen Greg , Roberson Sonya , Ng Connie , Stranick Michael
Published: June 2010

Secondary ion mass spectrometry (SIMS) is used to image the spatial distribution of elemental and molecular species on the surface and in cross sections of doped human hair using a magnetic sector SIMS instrument operated as an ion microprobe. Analysis of electrically insulating, non‐planar hair samples requires one of two different methods of charge compensation to be used depending on the polarity of the sputtered secondary ions. For detection of positive secondary ions, the hair is imaged using a ∼0.5 μm diameter, 19.5 keV impact energy, O− microbeam with no auxiliary electron bombardment. For detection of negative secondary ions, a ∼ 0.2 μm diameter, 14.5 keV impact energy Cs+ microbeam is used in conjunction with normal incidence, low‐energy electron bombardment. Both of these methods allow submicrometer spatial resolution elemental and molecular secondary ion images to be obtained from hair samples without metallic coating of the sample surface prior to analysis. Several examples are presented that reflect potential application areas for these analytical methods.
Complete angular distribution of electrons backscattered from tilted multicomponent specimens
Authors: Berger D. , Niedrig H.
Published: June 2010

This paper reports on the possibilities of predicting the angular distribution of electron backscattering from multicomponent specimens by use of a mean atomic number which is derived from the atomic or mass concentrations of the elements. It is found that Büchner's model using a quadratic weighed average of the atomic numbers is suitable although it is only based on single scattering.
Microstructural changes in zein proteins during extrusion
Authors: Batterman‐Azcona Sheri J. , Lawton John W. , Hamaker Bruce R.
Published: June 2010

Changes in proteins during extrusion may influence the texture of ready‐to‐eat (RTE) corn‐based extruded foods. This study focused on microstructural changes and dispersal patterns of corn storage proteins, zeins, that occur during extrusion processing. Model systems were used that consisted of two types of corn protein: commercial zein and corn gluten meal (CGM), combined with corn starch. Commercial zein is not encased in protein bodies, whereas CGM is comprised of zeins encapsulated in protein bodies. Mixtures were extruded under conditions that resulted in different specific mechanical energy (SME). The microstructure of the resulting extrudates was analyzed using transmission electron microscopy (TEM) with immunogold labeling of the α‐zein storage protein. The micrographs showed that the greatest zein dispersal occurred in CGM/starch extrudates, especially under high SME conditions. The micrographs also showed that, at both mild and harsh extrusion conditions, commercial zein/starch extrudates contained large protein aggregates. Under mild extrusion conditions, protein bodies in the CGM/starch extrudates partially retained their spherical shapes, but during harsher processing, protein bodies were disrupted and dispersed zein appeared to form fibrils. Such protein fibrils may influence texture and/or quality of extruded corn‐based snacks and breakfast foods.
Nanoscale optical imaging of chromosomes with apertureless microscopy
Authors: Bridger P. M. , McGill T. C.
Published: June 2010

Near‐field optical structure of the centromere region of undyed polytene chromosomes has been observed using an apertureless near‐field optical microscope that detects the intensity of light scattered from an atomic force microscope tip under laser illumination. The centromere is of primary importance to the functioning of the chromosome in the cell during cell division. It is also particularly interesting for structural/optical studies since its DNA repeat sequences are highly conserved among organisms and it is possible that they play a part in the centromere self assembly (Clark and Wall 1996).
The effect of fast secondary electrons on X‐ray microanalysis in the scanning electron microscope
Authors: Gauvin Raynald , Hovington Pierre , Drouin Dominique
Published: June 2010

In this paper, the effect of fast secondary electrons (FSE), which result from inelastic scattering of incident electrons, on the characterization of materials in the scanning electron microscope are investigated with the aid of Monte Carlo simulations. The effect of FSE on x‐ray microanalysis of light elements is investigated. A full description of the Monte Carlo simulations of FSE in solids is given.
Image sharpness measurement in the scanning electron microscope—Part III
Authors: Zhang Nien Fan , Postek Michael T. , Larrabee Robert D. , Vladár András E. , Keery William J. , Jones Samuel N.
Published: June 2010

Fully automated or semi‐automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. Testing and proving that the instrument is performing at a satisfactory level of sharpness is an important aspect of quality control. The application of Fourier analysis techniques to the analysis of SEM images is a useful methodology for sharpness measurement. In this paper, a statistical measure known as the multivariate kurtosis is proposed as an additional useful measure of the sharpness of SEM images. Kurtosis is designed to be a measure of the degree of departure of a probability distribution. For selected SEM images, the two‐dimensional spatial Fourier transforms were computed. Then the bivariate kurtosis of this Fourier transform was calculated as though it were a probability distribution. Kurtosis has the distinct advantage that it is a parametric (i.e., a dimensionless) measure and is sensitive to the presence of the high spatial frequencies necessary for acceptable levels of image sharpness. The applications of this method to SEM metrology will be discussed.
A scanning and transmission electron microscopy study of the parabronchial unit in quail (Coturnix coturnix) and town pigeons (Columba livia)
Authors: Klika E. , Scheuermann D. W. , de Groodt‐Lasseel M. H. A. , Bazantova I. , Switka A.
Published: June 2010

A combined scanning electron (SEM) and transmission electron microscopy (TEM) investigation was undertaken to gain insight into the complex structural pattern of the atrial compartment and the gas exchange tissue of parabronchial units in quail and town pigeons. The aim was also to depict the changes taking place in the parabronchial unit in the late prehatching and early posthatching periods in quail. The standard SEM and TEM investigation was carried out in 13 mature quail and 8 town pigeons. The developmental study involved embryonic quail (Days 15, 16, 17), newly hatched quail, quail 24 h after hatching, and quail aged 2, 10, 19, and 25 days (3 individuals per group). The luminal relief of the parabronchus is formed by anastomosing interatrial septa delineating the atrial pits, which are thinner and shallower in pigeons. The atrial bottom opens in mature individuals into 3–6 infundibula. The extracellular material represented by trilaminar substance, which does not appear until hatching, veils the surface relief of the parabronchial epithelium, which is consequently hardly accessible to three‐dimensional visualization. Only in town pigeons with fewer discontinuous layers of extracellular material was it possible to visualize the surface of the atrial epithelium, that is, of the granular and squamous atrial cells. The SEM analysis has convincingly shown the intricate spatial organization of atria, infundibula, and air and blood capillaries of the gas exchange tissue. The retinacula, that is, parallelly arranged processes of squamous respiratory cells bridging the air‐capillary lumina, were evidenced by SEM and TEM. The complex structure of the avian parabronchus has been successfully demonstrated in the present SEM and TEM study.
Scanning probe microscopy studies of cereal seed storage protein structures
Authors: Tatham Arthur S. , Thomson Neil H. , McMaster Terence J. , Humphris Andrew D. L. , Miles Mervyn J. , Shewry Peter R.
Published: June 2010

Scanning probe microscopes (SPMs) share a number of common features which give the techniques advantages over conventional light and electron microscopy. First, high resolution, up to the atomic level, is possible in certain cases, and second, they are nondestructive, requiring no staining or coating and the images can be obtained in the hydrated state or under water. Scanning probe microscopes, particularly scanning tunnelling microscopes (STM) and atomic force microscopes (AFM), have been used to study food‐related systems, ranging from relatively large structures such as starch granules to the organisation of secondary structures in proteins and the interaction of proteins. The seed storage proteins (gluten) of wheat are responsible for the viscous and elastic properties of wheat doughs that allow them to be used for a wide range of different food products. Using AFM and STM, images of individual and groups of proteins have been obtained in both the dry and hydrated states. The ability to work in liquid environments allows the conformation of proteins to be determined under conditions approaching “native.” The AFM and STM have been used to image both gliadins and glutenins and to study their aggregative behaviour in relation to gluten and dough systems.
Dynamic confocal scanning laser microscopy methods for studying milk protein gelation and cheese melting
Authors: Auty M. A. E. , Fenelon M. A. , Guinee T. P. , Mullins C. , Mulvihill D. M.
Published: June 2010

Dynamic confocal scanning laser microscopy (CSLM) methods were developed to enable observation of milk protein gelation and cheese melting. Protein aggregation and the formation of gel networks in renneted full‐fat and low‐fat milks and glucono‐δ‐lactone (GDL)‐acidified skim milks were observed by CSLM and observations correlated with increases in shear modulus (G′) and dynamic viscosity (η*) as determined by dynamic amplitude oscillatory rheology. Confocal scanning laser microscopy observation of low‐fat and full‐fat cheeses showed changes in fat distribution and an increase in staining intensity during cheese melting.
Microstructure of whole milk powder and of insolubles detected by powder functional testing
Authors: McKenna A. B. , Lloyd R. J. , Munro P. A. , Singh H.
Published: June 2010

The functional properties of whole milk powder (performance during reconstitution in water and coffee) are routinely measured to determine powder quality. An examination of the microstructure of milk powder and of the insoluble material collected after applying a series of functional tests provided insight into why the insoluble material formed during reconstitution.

The microstructures (transmission electron microscopy and confocal microscopy) of four commercial whole milk powder samples and of the insoluble material produced during functional testing were assessed. The microstructure of the whole milk powder could be related to features observed in the microstructure of some of the insolubles collected after powder functional testing. It is likely that heating conditions throughout the powder manufacturing process resulted in the denaturation of β‐lactoglobulin and its interaction with other proteins and fat globule membrane components, thus influencing the solubility of the milk powder. The application of shear during processing resulted in the greatest change to powder solubility in this study. Increasing homogenisation pressure during processing resulted in fat globule size reduction, adsorption of casein micelles to the fat globule membrane, and the formation of clusters of fat globules caused by the sharing of adsorbed casein micelles. The presence of large numbers of these clusters in the milk powder increased the formation of insoluble material during powder reconstitution in water and coffee.
The effect of freezing method and frozen storage conditions on the microstructure of wild blueberries as observed by cold‐stage scanning electron microscopy
Authors: Allan‐Wojtas P. , Goff H. D. , Stark R. , Carbyn S.
Published: June 2010

Microstructural information about fresh fruit is difficult to obtain using standard electron microscopy methods. Frozen fruit presents additional temperature‐related challenges. However, the food industry would benefit from data that show structure/function relationships in fruit and changes that occur during freezing and frozen storage.

The feasibility of using cold stage scanning electron microscopy (cryo‐SEM) to describe and define the structure/function relationships of quality attributes of frozen wild blueberries was tested. Cryo‐SEM was used to evaluate the structure of wild blueberries that had been frozen using three different methods, stored at three different temperatures, and held in frozen storage for 5 months. Micro‐structural data were then compared with quality measures, which included changes in percentage drip, damaged berries, and anthocyanin leakage, to explore relationships between structural changes and observed quality changes.

Cryo‐SEM results indicated that microstructural changes observed in frozen blueberry samples are characteristic of their temperature history. Quality measurements and microstructural data are in agreement that improvement of frozen blueberry quality resulted from faster freezing rates and lower temperatures of storage than are used presently in standard production methods. This study indicates that cryo‐SEM can be a valuable tool in assessing frozen blueberry quality and developing optimal conditions for freezing wild blueberries.
Treatment of anionic emulsion systems using chitosan, polyacrylamide, and aluminum sulfate
Authors: Pinotti A. , Bevilacqua A. , Zaritzky N.
Published: June 2010

The presence of emulsified oil in waste water of the edible fats industry can interfere with many tertiary or advanced waste water treatments such as adsorption, filtration, and various membrane techniques, and can cause severe problems in the step of biological treatment. The objective of the present work was to compare the performance of three destabilizers: chitosan, polyacrylamide, and aluminum sulfate to flocculate an O/W emulsion formulated with different emulsifiers (sodium dodecyl sulfate and sodium tetradecyl sulfate). Experiments were performed on a model system constituted by sunflower oil/ water emulsions. Methods used were turbidimetry, colloidal titration, and microscopic observation. Results showed that the increase of surfactant chain length increases the destabilizer dose necessary to produce desta‐bilization and reaching zero charge. In chitosan and polyacrylamide treatments, redispersion was observed for both sodium dodecyl sulfate and sodium tetradecyl sulfate emulsions. In the case of treatment with aluminum sulfate, turbidity values remained nearly constant, showing that redispersion does not take place in this case.
Influence of topography and specimen preparation on backscattered electron images of bone
Authors: Vajda Eric G. , Humphrey Scott , Skedros John G. , Bloebaum Roy D.
Published: June 2010

Backscattered electron (BSE) images of bone exhibit graylevel contrast between adjacent lamellae. Mathematical models suggest that interlamellar contrast in BSE images is an artifact due to topographic irregularities. However, little experimental evidence has been published to support these models, and it is not clear whether submicron topographical features will alter BSE graylevels. The goal of this study was to determine the effects of topography on BSE image mean graylevels and graylevel histogram widths using conventional specimen preparation techniques. White‐light interferometry and quantitative BSE imaging were used to investigate the relationship between the BSE signal and specimen roughness. Backscattered electron image graylevel histogram widths correlated highly with surface roughness in rough preparations of homogeneous materials. The relationship between BSE histogram width and surface roughness was specimen dependent. Specimen topography coincided with the lamellar patterns within the bone tissue. Diamond micromilling reduced average surface roughness when compared with manual polishing techniques but did not significantly affect BSE graylevel histogram width. The study suggests that topography is a confounding factor in quantitative BSE analysis of bone. However, there is little quantitative difference between low‐to‐moderate magnification BSE images of bone specimens prepared by conventional polishing or diamond micromilling.
Some theoretical considerations on X‐ray microanalysis in the environmental or variable pressure scanning electron microscope
Authors: Gauvin Raynald
Published: June 2010

This paper presents a new correction procedure for quantitative x‐ray microanalysis in the environmental or variable pressure scanning electron microscope (SEM). This method is based on a plot of the measured intensity as a function of the fraction of nonscattered beam intensity, fp. The theory predicts that the plot should be linear and the corrected intensity is given for fp = 1. The advantage is that such a plot is valid for any measured pressures, which is not the case with the usual pressure correction methods. To use this method, a simple equation is derived to compute fp. Other variations of this correction procedure are also presented. Comparison with measurements performed by Mansfield (1999) show the great consistency of this method.
The interaction of biological molecules with clay minerals: A scanning force microscopy study
Authors: Porter T. L. , Eastman M. P. , Whitehorse R. , Bain E. , Manygoats K.
Published: June 2010

We have used the technique of scanning force microscopy (SFM) to investigate the reaction of both amino acids and activated nucleotides in the presence of the clay mineral Cu(II)‐exchanged hectorite. Using simulated prebiotic heating and wetting cycles, we have shown that the clay mineral acts to adsorb, concentrate, and subsequently catalyze the polymerization of these biological monomers into short peptides and oligonucleotides. The presence of the Cu(II) cations within the clay intergallery regions, and at surface step edges and cracks, is crucial for the observed reactions to occur. Clay minerals such as hectorite may have thus played an important role in the evolution of biologically viable molecules on the prebiotic earth.
Nanodissection and noncontact imaging of plasmid DNA with an atomic force microscope
Authors: Geisler Bernd , Noll Frank , Hampp Norbert
Published: June 2010

In this paper we report that a combination of noncontact and contact atomic force microscopy is a convenient and reliable method for imaging and dissecting single plasmid deoxyribonucleic acid (DNA) strands on mica at ambient conditions without leaving feedback and without damage to the scanning tips. The width and thickness measured at different points of the DNA strands agree with literature data and are the same before and after dissection.
Microcratering within the lunar regolith — a theory and observation
Authors: Hammond Ernest C. , Berry F. Denise , Mitchell Franchezka , Barron Daniel , Cohen Samuel H.
Published: June 2010

Since the Apollo 11 mission to the moon, there has been substantial analysis of the lunar rocks and soil grains, utilizing more recent advances in electron probe technologies. It is the objective of this research to revisit the theories concerning the microcratering within the lunar regolith. Recent theories have included the idea that the microcratering phenomenon was caused by meteoric impacting onto the lunar surface during early lunar history. Other theories have suggested that the microcratering was a result of secondary ejector associated with micrometeoric and meteoric impact. This research team suggests that microcratering may have been associated with primordial dust during and before the formation of our solar system.
The remote electron beam‐induced current analysis of grain boundaries in semiconducting and semi‐insulating materials
Authors: Holt D. B.
Published: June 2010

When no charge collecting p‐n junction or Schottky barrier is present in the specimen, but two contacts are applied, conductive mode scanning electron microscope (SEM) observations known as remote electron beam‐induced current (REBIC) can be made. It was described as “remote” EBIC because the contacts to the specimen can lie at macroscopic distances from the beam impact point. In recent years, REBIC has been found to be useful not only for studies of grain boundaries in semiconducting silicon and germanium, but also in semi‐insulating materials such as the wider bandgap II‐VI compounds and electroceramic materials like varistor ZnO and positive temperature coefficient resistor (PTCR) BaTiO3. The principles of this method are outlined. Accounts are given of the five forms of charge collection and resistive contrast that appear at grain boundaries (GBs) in REBIC micrographs. These are (1) terraced contrast due to high resistivity boundary layers, (2) peak and trough (PAT) contrast due to charge on the boundary, (3) reversible contrast seen only under external voltage bias due to the beta‐conductive effect in a low conductivity boundary layer, (4) dark contrast due to enhanced recombination, and (5) bright contrast apparently due to reduced recombination. For comparison, the results of the extensive EBIC studies of GBs in Si and Ge are first outlined and then the results of recent REBIC grain boundary studies in both semiconducting and semi‐insulating materials are reviewed.
Use of low‐temperature field emission scanning electron microscopy to examine mites
Authors: Wergin William P. , Ochoa Ronald , Erbe Eric F. , Craemer Charnie , Raina Ashok K.
Published: June 2010

Partly because mites are microscopic in size and fragile in nature, acarologists estimate that less than five percent of extant species have been taxonomically described. Recently, data from conventional scanning electron microscopy (SEM) have been used to facilitate the descriptions and complement the information that has been historically obtained with the light microscope. However, the conventional preparation techniques associated with SEM frequently prevent or compromise the results. This study evaluated the use of low‐temperature field emission SEM to image mites and their hosts. Results indicated that a modified cryofixation procedure, which was associated with this technique, retained the mites at their living/feeding sites in natural behavioral positions. Furthermore, the turgor of the specimens, even eggs and soft‐bodied species, was also maintained. The structure and orientation of delicate structures such as setae, which would be subjected to mechanical damage during conventional chemical fixation, dehydration, and drying, were also preserved after cryofixation. Field emission SEM, which provided useful magnification beyond that attainable with a conventional SEM, also enabled resolution of ultrastructural features, such as tenent hairs on the empodium and pores on the dorsal surface that had not previously been observed. These advantages indicate that the low‐temperature field emission SEM can provide important structural data that can be used to study the anatomy, morphology, and bioecology of mites.
A dynamical bragg equation for high‐order laue zone reflections
Authors: Chen S.‐J. , Howitt D. G. , Harker A. B.
Published: June 2010

A dynamically corrected Bragg equation for high‐order Laue zone (HOLZ) reflections is derived directly from the Bloch wave formalism instead of the geometric argument used to deduce the kinematical Bragg condition. It differs from the kinematical Bragg equation by replacing the plane wave vector in the kinematical equation with the Bloch wave vectors. This dynamical equation reduces to the kinematical equation when the crystal potential is zero. It also demonstrates the occurrence of dynamical shifts for the HOLZ reflections but their absence for the zero‐order Laue zone (ZOLZ) reflections in the symmetrical Laue case.
Lengths measurements in microvascular corrosion castings: Two‐dimensional versus three‐dimensional morphometry
Authors: Minnich Bernd , Lametschwandtner Alois
Published: June 2010

In the present study we compared measurements of vessel lengths from (a) single‐digital scanning electron microscope (SEM) images of microvascular corrosion casts (VCCs) of gill filters of tadpoles of Xenopus laevis Daudin by two‐dimensional (2‐D) morphometry (Optimas 6.5, Optimas Corp., Bothell, Wash., USA; planar measurements) and (b) digital stereopairs by three‐dimensional (3‐D) morphometry (3D‐Morphometry, Minnich and Muska OEG, Salzburg). Depending on the spatial orientation of the vessels measured, we found a maximum difference of 58.84% (100 [3‐D]‐41.16 [2‐D]) in vessel lengths by 3‐D morphometry versus 2‐D morphometry, which, in multiple (segmental) lengths measurements or when determining space angles, might be even higher. Based on results we consider 3‐D morphometry of VCCs to be the method of choice for lengths measurements.
The reduction of the beam gas interactions in the variable pressure scanning electron microscope with the use of helium gas
Authors: Adamiak B. , Mathieu C.
Published: June 2010

This paper presents experimental observations on electron scattering by gases (helium and air) in the specimen chamber of a variable pressure scanning electron microscope. It shows an important reduction of the beam scattering with the use of helium gas, and the consequences for the x‐ray microanalysis are discussed.
Surface investigations on HgBr2 single crystals by using confocal scanning laser microscopy
Authors: Stanciu George A. , Polychroniadis E. K.
Published: June 2010

A confocal scanning laser microscope operating at 514 and 488 nm has been used to obtain two‐dimensional (2‐D) images of the mercuric bromide (HgBr2) crystal surface by photoluminescence, reflection, and transmission phenomena. Our measurements indicate that regions showing a strong photoluminescence may appear on the surface. By processing the 2‐D images, we obtained the three‐dimensional images, which offer a better possibility for the investigation. The analysis of spectral lines may be correlated with the presence of the Hg impurities.
Three‐dimensional morphology of cerebellar climbing fibers. A study by means of confocal laser scanning microscopy and scanning electron microscopy
Authors: Castejon Orlando J. , Sims P.
Published: June 2010

The intracortical pathway of cerebellar climbing fibers have been traced by means of scanning electron microscpy (SEM) and confocal laser scanning microscopy (CLSM) to study the degree of lateral collateralization of these fibers in the granular Purkinje cell and molecular layers. Samples of teleost fish were processed for conventional and freeze‐fracture SEM. Samples of hamster cerebellum were examined by means of CLSM using FM4–64 as an intracellular stain. High resolution in lens SEM of primate cerebellar cortex was carried out using chromium coating. At scanning electron and confocal laser microscopy levels, the climbing fibers appeared at the white matter and granular layer as fine fibers with a typical arborescence or crossing‐over branching pattern, whereas the mossy fibers exhibited a characteristic dichotomous bifurcation. At the granular layer, the parent climbing fibers and their tendrils collaterals appeared to be surrounding granule and Golgi cells. At the interface between granule and Purkinje cell layers, the climbing fibers were observed giving off three types of collateral processes: those remaining in the granular layer, others approaching the Purkinje cell bodies, and a third type ascending directly to the molecular layer. At this layer, retrograde collaterals were seen descending to the granular layer. By field emission high‐resolution SEM of primate cerebellar cortex, the climbing fiber terminal collaterals were appreciated ending by means of round synaptic knobs upon the spines of secondary and tertiary Purkinje cell dendrites.
Three‐dimensional microscopy data exploration by interactive volume visualization
Authors: Fang Shiaofen , Dai Yi , Myers Frederick , Tuceryan Mihran , Dunn Kenneth
Published: June 2010

This paper presents a new volume visualization approach for three‐dimensional (3‐D) interactive microscopy data exploration. Because of their unique image characteristics, 3‐D microscopy data are often not able to be visualized effectively by conventional volume visualization techniques. In our approach, microscopy visualization is carried out in an interactive data exploration environment, based on a combination of interactive volume rendering techniques and image‐based transfer function design methods. Interactive volume rendering is achieved by using two‐dimensional (2‐D) texture mapping in a Shear‐Warp volume rendering algorithm. Image processing techniques are employed and integrated into the rendering pipeline for the definition and searching of appropriate transfer functions that best reflect the user's visualization intentions. These techniques have been implemented successfully in a prototype visualization system on low‐end and middle‐range SGI desktop workstations. Since only 2‐D texture mapping is required, the system can also be easily ported to PC platforms.
Semiconductor devices “from inside”
Authors: Mil'shtein S.
Published: June 2010

Operation of any semiconductor device can be presented by unique configuration of the electrical field (potential) and charge (doping) distribution within the device. More specifically, the status of operation is described by the quasi‐Fermi energy (QFE) profile across the device. Visualization of the dynamic operation of the device and quantitative measurements of the QFE profile is provided by differential voltage contrast (DVC), which is a modification of the secondary electron imaging in a scanning electron microscope (SEM). The DVC consists of storing two images of a tested semiconductor device. Exposed to the electron beam is a cross section, for example, of a field effect transistor (FET). The first image, covering the entire inside of the FET from source to drain, is taken when the device is not biased. The second image of the same area is taken when the transistor is biased. The secondary electron signal is enhanced or retarded by actual distribution of a potential across the tested device. Subtraction pixel by pixel of the two carefully aligned images removes morphologic contrast from the screen, takes away surface features and contamination of the sample, and reveals the contribution of the electrical field to the changes of contrast. The calibration procedure allows measurement of the potential distribution with a precision of 0.05 V. The first derivative of a potential profile provides for distribution of the electrical field and the second derivative gives the doping profile across the tested device. A variety of semiconductor devices such as p‐n junctions, Zener diodes, MOSFET's, MESFET's, solar cells and optical detectors, quantum well lasers, etc., were tested. Videotaping of the tested devices allows us to observe the changes in the electrical field and charge distribution as the device operates in a wide range of electrical or optical signals.
Ultrastructure and reproduction behaviour of single CHO‐K1 cells exposed to near infrared femtosecond laser pulses
Authors: Oehring H. , Riemann I. , Fischer P. , Halbhuber K.‐J. , König K.
Published: June 2010

In the present work, the authors investigated ultrastructural changes as well as the reproduction behaviour of preselected single CHO‐K1 cells exposed to 170 femtosecond laser pulses at different power output levels in comparison with cells outside the illumination volume. The ultrashort laser pulses were provided by an 80 MHz Ti:sapphire laser at 780 nm. The cells were scanned ten times with a scan rate of 1/16 s−1. Single CHO‐K1 cells exposed to low mean power of 2 mW revealed no significant changes in ultrastructure after laser exposure. In some cases, changes of mitochondria with slight disordering of cristae were found. Cytoplasm was filled with vesicles that seemed to be released from Golgi stacks. Cells irradiated with higher powers demonstrated more dramatic changes in ultrastructure. A considerable number of swollen mitochondria in conjunction with loss of cristae was observed. The main event of mitochondrial changes was the formation of electron dense bodies in the mitochondrial matrix. In addition, lumen of endoplasmatic reticulum was enlarged. Highest applied mean laser power of 12.5 mW lead to complete destruction of mitochondria and their transformation to electron dense structures containing membrane material. Compared with cell targets irradiated with 2 mW mean power, the release of vesicles from Golgi stacks seemed to be rather moderate. Cells localised outside the laser beam revealed no ultrastructural changes. Low mean laser power at 2 mW was unable to impair the reproduction behaviour of CHO‐K1 cells. At higher laser power output levels, CHO‐K1 cells started to delay cell division. At 12.5 mW, no cell division occurred. The obtained results may be helpful in recommending parameters for safe femtosecond laser microscopy of living specimens.
Inexpensive, high‐quality optical relay for use in confocal scanning beam imaging
Authors: Ribes A. C. , Damaskinos S. , Dixon A. E.
Published: June 2010

An inexpensive, high optical‐quality relay lens made up of two eyepieces arranged in an afocal assembly for use in confocal scanning laser imaging is described. In the past we have used relays, within our confocal microscopes, made up of achromats with long focal lengths (≥10 cm), which take up large optical tracks and suffer from significant amounts of astigmatism and curvature of field. We quantify aberrations associated with achromat and eyepiece relays using CODE V optical design and analysis software. The eyepiece relay is found to be more compact, better corrected, and not significantly more expensive than its achromat counterpart. In addition to being used to interconnect two scanning mirrors optically as well as scanning mirrors with microscope objectives, it can form part of the optics in a confocal scanning laser MACROscope®‐Micro‐scope system (Biomedical Photometrics, Inc., Waterloo, Ontario, Canada). Due to design constraints, the MACRO‐scope®‐Microscope system cannot incorporate a conventional wide‐field microscope into its structure such as is done in most commercial confocal microscopes. The eyepiece relay is used as a stand‐alone, compact optical link between the scanning mirrors and the microscope objective. This consequently makes the MACROscope®‐Microscope system more compact and easier to commercialize.
The effects of space charge on contrast in images obtained using the environmental scanning electron microscope
Authors: Toth M. , Phillips M. R.
Published: June 2010

We present experimental evidence for the existence of a space charge in the environmental scanning electron microscope. Space charge formation is attributed to differences in the mobilities of negative and positive charge carriers in the imaging gas. A model is proposed for the behavior of space charge during image acquisition. The effects of space charge on images acquired using the gaseous secondary electron detector, ion current, and backscattered electron signals are interpreted using the proposed model.