bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal effects of the electron beam and implications of surface damage in the analysis of bone tissue
Authors: Holmes Jennifer L. , Bachus Kent N. , Bloebaum Roy D.
Published: June 2010

Electron beam interactions with specimens in the scanning electron microscope (SEM) can lead to increased surface temperatures and damage. These changes may have significant consequences in the analysis of bone tissue. An investigation was performed to measure the surface temperature changes associated with the electron beam on a thermocouple with systematic variations in operating conditions. Probe currents, magnifications, and accelerating voltages were incrementally adjusted to measure the temperature changes and to make assessments for determining optimal operating conditions for the SEM in future analyses of bone tissue. Results from this study suggest that thermal effects were minimal at lower accelerating voltages (< 20 kV), lower probe currents (< 10 nA), and lower magnifications, but surface damage may still occur during the analysis of bone tissue.
Three‐dimensional reconstruction and motion analysis of living, crawling cells
Authors: Soll David R. , Voss Edward , Johnson Olof , Wessels Deborah
Published: June 2010

Cell behavior is three‐dimensional (3‐D), even when it takes place on a flat surface. Migrating cells form pseudopods on and off the substratum, and the cell body undergoes height changes associated with a 1 min behavior cycle. Inside the cell, the nucleus has a 3‐D migratory cycle, and vesicles move up and down in the z‐axis as a cell locomotes. For these reasons, the two‐dimensional (2‐D) analysis of cellular and subcellular behavior is, in many cases, inadequate. We have, therefore, developed 3‐D motion analysis systems that reconstruct the cell surface, nucleus, pseudopods, and vesicles of living, crawling cells in 3‐D at time intervals as short as 1 s, and compute more than 100 parameters of motility and dynamics morphology at 1‐s intervals. We are now in the process of developing a multimode reconstruction system that will allow us to reconstruct and analyze fluorescently tagged molecular complexes within the differential interference contrast‐imaged subcellular architecture of a crawling cell. These evolving technologies should find wide application for a host of biomedical problems.
Field‐emission scanning electron microscopy of the internal cellular organization of fungi
Authors: Müller Wally H. , van Aelst Adriaan C. , Humbel Bruno M. , van der Krift Theo P. , Boekhout Teun
Published: June 2010

Internal viewing of the cellular organization of hyphae by scanning electron microscopy is an alternative to observing sectioned fungal material with a transmission electron microscope. To study cytoplasmic organelles in the hyphal cells of fungi by SEM, colonies were chemically fixed with glutaraldehyde and osmium tetroxide and then immersed in dimethyl sulfoxide. Following this procedure, the colonies were frozen and fractured on a liquid nitrogen‐precooled metal block. Next, the fractured samples were macerated in diluted osmium tetroxide to remove the cytoplasmic matrix and subsequently dehydrated by freeze substitution in methanol. After critical point drying, mounting, and sputter coating, fractured cells of several basidiomycetes were imaged with field‐emission SEM. This procedure produced clear images of elongated and spherical mitochondria, the nucleus, intravacuolar structures, tubular‐ and plate‐like endoplasmic reticulum, and different types of septal pore caps. This method is a powerful approach for studying the intracellular ultrastructure of fungi by SEM.
Polymer‐based materials to be used as the active element in microsensors: A scanning force microscopy study
Authors: Porter Timothy L. , Eastman Michael P. , Pace Danielle L. , Bradley Michelle
Published: June 2010

Polymer‐based materials can be incorporated as the active sensing elements in chemiresistor devices. Most of these devices take advantage of the fact that certain polymers will swell when exposed to gaseous analytes. To measure this response, a conducting material such as carbon black is incorporated within the nonconducting polymer matrix. In response to analytes, polymer swelling results in a measurable change in the conductivity of the polymer/carbon composite material. Arrays of these sensors may be used in conjunction with pattern recognition techniques for purposes of analyte recognition and quantification. We have used the technique of scanning force microscopy (SFM) to investigate microstructural changes in carbon‐polymer composites formed from the polymers poly(isobutylene) (PIB), poly (vinyl alcohol) (PVA), and poly (ethylene‐vinyl acetate) (PEVA) when exposed to the analytes hexane, toluene, water, ethanol, and acetone. Using phase‐contrast imaging (PI), changes in the carbon nanoparticle distribution on the surface of the polymer matrix are measured as the polymers are exposed to the analytes in vapor phase. In some but not all cases, the changes were reversible (at the scale of the SFM measurements) upon removal of the analyte vapor. In this paper, we also describe a new type of microsensor based on piezoresistive microcantilever technology. With these new devices, polymeric volume changes accompanying exposure to analyte vapor are measured directly by a piezoresistive microcantilever in direct contact with the polymer. These devices may offer a number of advantages over standard chemire‐sistor‐based sensors.
Dynamic secondary electron contrast effects in liquid systems studied by environmental scanning electron microscopy
Authors: Stokes D. J. , Thiel B. L. , Donald A. M.
Published: June 2010

We report an investigation into a dynamic contrast phenomenon in water‐oil emulsions imaged in the environmental scanning electron microscope. Secondary electron contrast between oil and water phases is shown to change with scan rate, even inverting in extreme cases. This effect is attributed to the fact that charge carriers in liquids have intermediate mobilities compared with those in metallic conductors and solid insulators. Thus, increasing the electron energy flux density (via slower scan rates) results in the temporary accumulation of excess charge, which in turn gives rise to increased secondary electron emission. Excess charge dissipates between frames, however, such that classical charging of the specimen is not observed. The oils used here have conductivities lower than that of water, making them more susceptible to the effect. However, the material within the primary electron interaction volume is a conductive medium. We demonstrate that charging effects are not seen in regions of the oil where the interaction volume is in contact with the more conductive continuous water phase. Secondary electron emission from these regions therefore approximates to the intrinsic yield.
The swelling behavior and wet morphology of water‐absorbable polymer materials
Authors: Xia Feng , Chen Fen , Hu Yuxian , Wang Ximei , Lin Shaokun
Published: June 2010

In this research work, a low‐temperature examination method for scanning electron microscopy (SEM) is introduced. A water‐absorbable polymer material, the sulfonated polyethylene (SPE) ion‐exchange hollow fiber membrane, was used for the experiments. With this low‐temperature technique, the wet morphology of the water‐absorbable sulfonated polyethylene hollow fiber membrane was revealed. The results obtained from this investigation offer some important information to explain the behavior of the SPE hollow fiber membranes when they are applied in pervaporation separation of water/ organic solvent mixtures, such as water/ethylene glycol, water/ethanol, and so forth.
Natural color scanning electron microscopy based on the frequency characteristics of the human visual system
Authors: Oho Eisaku , Watanabe Masashi
Published: June 2010

The principles of image formation in natural color scanning electron microscopy (NC‐SEM) are discussed in detail. This method is based on the frequency characteristic of the human visual system. It is shown that the Mach effect and masking effect are important in the characteristics. The former, which can enhance structural details, is visually similar to the edge effect in secondary electron (SE) images, and the latter is required for proper representation of very degraded color information obtained from a light microscope. When using these effects suitably, an NC‐SEM image with the resolution equivalent to that of an SEM image can be acquired, though it is composed of an SEM image and a special video microscopy (VM) image with a resolution much lower than the SEM image of the identical view. The NC‐SEM is more effective than the SEM in observation, interpretation, and analysis of various samples with important color information.
Fundamental problems of imaging subsurface structures in the backscattered electron mode in scanning electron microscopy
Authors: Rau E. I. , Reimer L.
Published: June 2010

In‐depth imaging of subsurface structures in scanning electron microscopy (SEM) is usually obtained by detecting backscattered electrons (BSE). For a layer‐by‐layer imaging in BSE microtomography, it is preferable to use an energy filtering of BSE. A simple approach is used to estimate the contrast by using backscattering coefficients of bulk materials and the maximum escape depths of the BSE. The contrast obtained by BSE energy filtering is about twice that of the standard BSE method by varying the acceleration voltage. The contrast decreases with increasing information depth. The information depth is about four times smaller than the electron range. The transmission of the spectrometer influences the minimum current of the order of 10−8 A that is needed to get a contrast of 1%, for example.
Application of the low‐loss scanning electron microscope image to integrated circuit technology. Part 1– applications to accurate dimension measurements
Authors: Postek Michael T. , Vladár András E. , Wells Oliver C. , Lowney Jerry L.
Published: June 2010

Scanning electron microscopes (SEMs) are the most extensively used tools for dimensional metrology and defect inspection for integrated circuit technologies with 180 nm and smaller features. Currently, almost all SEMs are designed to collect as many secondary and backscattered electrons as possible. These signals are mainly secondary electrons (SE1, SE2, and SE3) detected with various detection schemes. To facilitate the electron collection, very strong electric and magnetic fields are applied not just in the path of the primary electron beam but to the emerging electrons as well. These new systems provide strong signals, thus better signal‐to‐noise ratio, and thus resulting in higher throughput than older ones. On the other hand, the use of secondary electrons means that measurement results are much more prone to the detrimental effects of electron beam interactions, sample charging, and sample contamination than measurements with higher‐energy backscattered electrons. The use of backscattered electrons, especially low‐loss electrons (LLE), can provide better surface sensitivity, edge accuracy, and repeatability, possibly at the expense of measurement speed. This two‐part study investigates the benefits and drawbacks of low‐loss electron imaging to edge characterization for dimensional metrology and enhancement of fine surface features done through filtration or separation of the generated LLE signal and the use of energy‐dependent signals. Part 1 reviews and illustrates the potential for accurate dimensional measurements at low accelerating voltage by LLE, and Part 2 will concentrate on the enhancement of surface features in chemical‐mechanically planarized specimens with the use of a novel LLE detector.
Light collection efficiency and light transport in backscattered electron scintillator detectors in scanning electron microscopy
Authors: Filippov M. N. , Rau E. I. , Sennov R. A. , Boyde A. , Howell R. G. T.
Published: June 2010

Experimentally, scintillator detectors used in scanning electron microscopy (SEM) to record backscattered electrons (BSE) show a noticeable difference in detection efficiency in different parts of their active zones due to light losses transport in the optical part of the detector. A model is proposed that calculates the local efficiency of the active parts of scintillator detectors of arbitrary shapes. The results of these calculations for various designs are presented.
Quality measures in applications of image restoration
Authors: Kriete Andres , Naim Maria , Schäfer Lutz
Published: June 2010

We describe a new method for the estimation of image quality in image restoration applications. We demonstrate this technique on a simulated data set of fluorescent beads, in comparison with restoration by three different deconvolution methods. Both the number of iterations and a regularisation factor are varied to enforce changes in the resulting image quality. First, the data sets are directly compared by an accuracy measure. These values serve to validate the image quality descriptor, which is developed on the basis of optical information theory. This most general measure takes into account the spectral energies and the noise, weighted in a logarithmic fashion. It is demonstrated that this method is particularly helpful as a user‐oriented method to control the output of iterative image restorations and to eliminate the guesswork in choosing a suitable number of iterations.
Application of the low‐loss scanning electron microscope image to integrated circuit technology. Part II— chemically‐mechanically planarized samples
Authors: Wells Oliver C. , McGlashan‐Powell Maurice , Vladár András E. , Postek Michael T.
Published: June 2010

Chemical‐mechanical planarization (CMP) is a process that gives a flat surface on a silicon wafer by removing material from above a chosen level. This flat surface must then be reviewed (typically using a laser) and inspected for scratches and other topographic defects. This inspection has been done using both the atomic force microscope (AFM) and the scanning electron microscope (SEM), each of which has its own advantages and disadvantages. In this study, the low‐loss electron (LLE) method in the SEM was applied to CMP samples at close to a right angle to the beam. The LLEs show shallower topographic defects more clearly than it is possible with the secondary electron (SE) imaging method. These images were then calibrated and compared with those obtained using the AFM, showing the value of both methods. It is believed that the next step is to examine such samples at a right angle to the beam in the SEM using the magnetically filtered LLE imaging method.
Rapid diagnosis of fungal infection of intravascular catheters in newborns by scanning electron microscopy
Authors: Sbarbati Andrea , Fanos Vassilios , Bernardi Paolo , Tatò Luciano
Published: June 2010

Intravascular catheters carry a significant risk of becoming colonized with bacteria and fungi and are important risk factors of septicemia in premature neonates. The study was undertaken to evaluate whether scanning electron microscopy (SEM) examination of removed catheters can be useful in early diagnosis of plastic infection by Candida, providing information useful for initiation of an eventual therapy. The evolution of in the 28 catheters (umbilical or central) implanted in 24 newborns for prematurity was studied by SEM and transmission electron microscopy (TEM). In 4 of 24 patients, SEM examination revealed the presence of Candida in form of yeast or hyphae. In one of these patients, TEM confirmed the presence of organisms. In each case, hemoculture and culture of the catheter itself confirmed the diagnosis. The study demonstrates that SEM can identify fungi in the biomaterials covering the catheter surface in a few hours, allowing an early diagnosis of plastic infection.
Measurement technique for the incident electron current in secondary electron detectors and its application in scanning electron microscopes
Authors: Agemura Toshihide , Fukuhara Satoru , Todokoro Hideo
Published: June 2010

A measurement technique for incident electron current in secondary electron (SE) detectors, especially the Everhart‐Thornley (ET) detector, based on signal‐to‐noise ratio (SNR), which uses the histogram of a digital scanning electron microscope (SEM) image, is described. In this technique, primary electrons are directly incident on the ET detector. This technique for measuring the correlation between incident electron current and SNR is applicable to the other SE detectors. This correlation was applied to estimate the efficiency of the ET detector itself, to evaluate SEM image quality, and to measure the geometric SE collection efficiency and the SE yield. It was found that the geometric SE collection efficiency at each of the upper and lower detectors of a Hitachi S‐4500 SEM was greater than 0.78 at all working distances.
A quantitative cryo‐scanning X‐ray microanalysis protocol for the examination of the eye
Authors: Wadley Robert , Junghans Barbara , Dickson Mel , Liang Helena
Published: June 2010

Analysis of elements present in fluids contained in small, poorly accessible sections of biological tissue is challenging. The choroid of the eye, which is a vascular tissue approximately 100 μm thick, surrounds the retina for the purposes of nutrient supply and metabolite removal, and which in the chick shows dramatic volumetric change in response to visual experiences. Because fluid homeostasis is critical to good vision, a complete understanding of the ionic changes driving large shifts in ocular fluids is required. However, the structure of the choroid and retina make extraction of pure fluids for analysis extremely difficult. Elemental x‐ray analysis on a transverse chorioretinal specimen was performed after rapid freezing of a whole chick eye in liquid nitrogen, and mechanically fracturing the frozen globe. Using a Polaron Cryotrans System on a Cambridge S‐360 scanning electron microscope and a Kevex Quantum detector, spectra were obtained for blood vessels, lymphatic vessels and vitreous that were readily visible at 265x. Analysis was performed on a frozen control solution of the elements found in the vessels. The elements and their concentrations found in blood vessels by x‐ray analysis compared well with those from whole blood as established by conventional means. The analysis for lymph yielded results compatible with expectations; no other published data for small lymphatics enable a direct comparison. In conclusion, x‐ray analysis can be used to acquire information that is otherwise unobtainable from tissue in situ. The same bulk‐frozen elemental microanalysis protocol would have application to other organs and tissues when access to the site would destroy the integrity of the tissue under investigation.
Human chromatid ultrastructure: New observations with scanning and transmission electron microscopy
Authors: Jenkins Edmund C. , Wen G. Y. , Jenkins Edmund C. , Genovese Marilyn , Brown W. Ted
Published: June 2010

Two new observations have been made on human chromatid/chromosome ultrastructure using both scanning and transmission electron microscopy (SEM, TEM). A bipartite, apparently half‐chromatid‐like structure was observed in whole human chromosomes studied with SEM and in longitudinally sectioned chromosomes analyzed with TEM. In addition, we also observed a zipper‐like configuration as the parallel sister chromatids separated likely due to the supercoiled structure of the chromosome and chromatid. It is possible that either or both of these new observations resulted from our (improved) method of preparing the chromosomes for SEM and TEM.
Evaluation of Demineralized Dentin Contraction by Stereo Measurements Using Environmental and Conventional Scanning Electron Microscopy
Authors: Dusevich V. M. , Eick J. D.
Published: June 2010

Numerous investigations of etched human dentin are performed using scanning electron microscopy (SEM). Usually specimens are fractured and cross sections of etched layers with underlying unaffected dentin are observed. Results from this study showed that the edge of the etched layer contracted and became curved after fracture of wet specimens and that tensile stresses were developed in this layer by acid etching. The degree of contraction was determined utilizing profiles of the specimen edges obtained with the help of stereo measurements. Fixation in glutaraldehyde decreased the contraction in wet specimens prepared for environmental scanning electron microscopy (ESEM). Fixation also decreased shrinkage of the demineralized layer due to gradual desiccation in the ESEM during observation. For conventional SEM, the contraction was minimized if specimens of etched and fixed dentin were fractured in the dry condition after dehydration.
Computer modeling of three‐dimensional reconstruction algorithm of cathodoluminescence material properties, analysis of errors, and optimization of variable parameters
Authors: Ivannikov P. V. , Dronov S. V. , Saparin G. V. , Obyden S. K.
Published: June 2010

Three‐dimensional (3‐D) reconstruction of cathodoluminescence (CL) properties of materials (Saparin et al.1997) is a new nondestructive technique that measures quantum yield information of subsurface layers as a set of two‐dimensional image sections. This technique is able to synthesize a 3‐D image without destroying the sample. The basis for this technique is the fact that the electrons in scanning electron microscopy penetrate the sample at different depths with a variation of accelerating voltage. The detected CL emission integrates the information from the full volume occupied by the charge carriers. Estimating the errors that occur during the reconstruction process is complex since these errors are caused by necessary approximations, noise, and the imperfection of the 3‐D reconstruction algorithm that is employed. An analysis of the factors that affect the accuracy of the technique has been made. The estimation of systematic errors and the optimization of variable parameters were calculated by computer modeling.
Second‐harmonic generation from biological tissues: Effect of excitation wavelength
Authors: Deng Xiaoyuan , Williams Elizabeth D. , Thompson Erik W. , Gu X. Gan Min
Published: June 2010

We report on the measurement of second‐harmonic signals from hyperplastic parenchyma and stroma in malignant human prostate tissue under femtosecond pulsed illumination in the wavelength range from 730 to 870 nm. In particular, the relationship of the second‐harmonic generation to the excitation wavelength is measured. The result in these two regions behaves considerably differently and thus provides a possible indicator for identifying tissue components and malignancy.
Dinosaur eggshell study using scanning electron microscopy
Authors: Jackson Frankie D. , Schweitzer Mary H. , Schmitt James G.
Published: June 2010

Visualization and analysis of structural features in fossil dinosaur eggs by scanning electron microscopy augment information from traditional petrographic light microscopy. Comparison of characteristics in fossil and modern eggshells allows inferences to be made regarding dinosaur reproductive biology, physiology, and evolutionary relationships. Assessment of diagenetic alteration of primary eggshell calcite structure that occurs during fossilization provides important information necessary for taxonomic identification and paleoenvironmental interpretations.
Lattice‐Like Array Particles on Xenopus oocyte Plasma Membrane
Authors: Lau Joan M. , Xingyou Hong , Yu Lei
Published: June 2010

Plasma membrane from Xenopus laevis oocytes has been used as a model system to study membrane structure and particle components, including native and exogenously expressed proteins. Previous studies by electron microscopy (EM) and atomic force microscopy (AFM) compared intramembrane particles (IMPs) on uninjected oocyte membranes to oocytes expressing proteins of interest. These studies observed randomly distributed IMPs on the surface of the oocyte plasma membrane. In this paper, we introduce a novel technique to isolate oocyte membranes by bursting the oocyte and depositing its membrane on a flat mica substrate. The flat surface membrane preparation allows high‐resolution AFM images to be obtained, revealing a novel structure of densely packed particles. These particles exhibit a regular, repeating pattern of a lattice‐like array with orderly packing and are thus termed “lattice‐like array particles” (LAPs). The LAPs are orderly yet imperfectly packed, are located in depressed pools, occur with a low frequency on the oocyte membrane surface, and have not previously been seen using other isolation and imaging methods. Histogram analysis of the center‐to‐center distance between LAPs suggest their size to be about 44 nm in diameter, considerably larger than other reported size estimates of IMPs. These results indicate that LAPs represent a novel membrane particle organization, which merits further study.
Irregular snow crystals: Structural features as revealed by low temperature scanning electron microscopy
Authors: Wergin William P. , Erbe Eric F. , Rango Albert , Foster James , Pooley Christopher
Published: June 2010

For nearly 50 years, investigators using light microscopy have vaguely alluded to a unique type of snow crystal that has become known as an irregular snow crystal. However, the limited resolution and depth‐of‐field of the light microscope has prevented investigators from characterizing these crystals. In this study, a field‐emission scanning electron microscope, equipped with a cold stage, was used to document the structural features, physical associations, and atmospheric metamorphosis of irregular snow crystals. The crystals appear as irregular hexagons, measuring 60 to 90 mm across, when viewed from the aaxis. Their length (c‐axis) rarely exceeds the diameter. The irregular crystals are occasionally found as secondary particles on other larger forms of snow crystals; however, they most frequently occur in aggregates consisting of more than 100 irregular crystals. In the aggregates, the irregular crystals have their axes oriented parallel to one another and, collectively, tend to form columnar structures. Occasionally, these columnar structures exhibit rounded faces along one side, suggesting atmospheric metamorphoses during formation and descent. In extreme cases of metamorphoses, the aggregates would be difficult to distinguish from graupel. Frost, consisting of irregular crystals, has also been encountered, suggesting that atmospheric conditions that favor their growth can also occur terrestrially.
Characterization of atmospheric particles by electron probe X‐ray microanalysis
Authors: Alföldy Bálint , Török Szabina , Trincavelli Jorge , Castellano Gustavo
Published: June 2010

Microchemical glass standards were used to validate a quantitation method based on peak‐to‐background (P/B) ratios from electron probe x‐ray microanalysis spectra. This standardless method was applied to the determination of concentrations of individual particles from Mα or Lα lines, as well as from Kα lines. The algorithm was tested on particulate glass samples for diameters ranging from 1 to 20 μm. The determined concentrations did not depend on particle size. The certified values for elements were well matched, except for Na, which may migrate under electron bombardment. Finally, classification of qualitative results obtained for aerosol particles was completed by the P/B quantitative method.
Evaluation of fan‐pattern spray nozzle wear using scanning electron microscopy
Authors: Krause C. R. , Reichard D. L. , Zhu H. , Brazee R. D. , Fox R. D. , Ozkan H. E.
Published: June 2010

Worn nozzles on spray equipment severely affect the efficiency of crop management systems while causing unnecessary pesticide contamination of non target areas. Scanning electron microscopy (SEM) that has been applied for direct measurement of pesticide deposition, was used to observe worn and unused brass and stainless steel fan‐pattern spray nozzles. Wear and other changes were observed in both nozzle materials. Scanning electron microscopy can provide nozzle manufacturers with greater insight and needed information on nozzle mechanics to improve performance. More reliable delivery of pesticide spray should enhance integrated pest and disease management and crop protection for growers.
Correction for piezoelectric creep in scanning probe microscopy images using polynomial mapping
Authors: Trawick Matthew L. , Megens Mischa , Angelescu Dan E. , Harrison Christopher , Vega Daniel A. , Chaikin Paul M. , Register Richard A. , Adamson Douglas H.
Published: June 2010

We describe a method for using polynomial mapping to correct scanning probe microscope images for distortion due to piezoelectric creep. Because such distortion varies from image to image, this method can be used when the actual locations of some features within an image are known absolutely, or in a series of images in which the actual locations of some features are known not to vary. While the general case of polynomial mapping of degree N requires the determination of 2(N+1)2 matrix elements by regression, we find that by understanding the mechanism by which piezoelectric creep distorts scanning probe microscope images, we can fix most of these coefficients at 0 or 1 a priori, leaving only 2(N+1) coefficients to be determined by regression. We describe our implementation of this strategy using the Interactive Data Language (IDL) programming language, and demonstrate our technique on a series of atomic force microscopy (AFM) images of diblock copolymer microdomains. Using our simplified scheme, we are able to reduce the effects of distortion in an AFM image from 5% of the scan width to a single pixel, using only five reference points.
Scanning Electron Microscopy Analysis of Corrosion Degradation on Tinplate Substrates
Authors: Zumelzu E. , Cabezas C. , Vera A.
Published: June 2010

The degradation of electrolytic tinplate used in food containers was analysed and evaluated, using scanning electron microscopy and electrochemical measurements of microcorrosion and ion dissolution by atomic absorption to prevent food contamination caused by metal traces and to increase the durability of such tinplates.
Rime and graupel: Description and characterization as revealed by low‐temperature scanning electron microscopy
Authors: Rango Albert , Foster James , Josberger Edward G. , Erbe Eric F. , Wergin William P. , Pooley Christopher
Published: June 2010

Snow crystals, which form by vapor deposition, occasionally come in contact with supercooled cloud droplets during their formation and descent. When this occurs, the droplets adhere and freeze to the snow crystals in a process known as accretion. During the early stages of accretion, discrete snow crystals exhibiting frozen cloud droplets are referred to as rime. If this process continues, the snow crystal may become completely engulfed in frozen cloud droplets. The resulting particle is known as graupel. Light microscopic investigations have studied rime and graupel for nearly 100 years. However, the limiting resolution and depth of field associated with the light microscope have prevented detailed descriptions of the microscopic cloud droplets and the three‐dimensional topography of the rime and graupel particles. This study uses low‐temperature scanning electron microscopy to characterize the frozen precipitates that are commonly known as rime and graupel. Rime, consisting of frozen cloud droplets, is observed on all types of snow crystals including needles, columns, plates, and dendrites. The droplets, which vary in size from 10 to 100 μm, frequently accumulate along one face of a single snow crystal, but are found more randomly distributed on aggregations consisting of two or more snow crystals (snowflakes). The early stages of riming are characterized by the presence of frozen cloud droplets that appear as a layer of flattened hemispheres on the surface of the snow crystal. As this process continues, the cloud droplets appear more sinuous and elongate as they contact and freeze to the rimed crystals. The advanced stages of this process result in graupel, a particle 1 to 3 mm across, composed of hundreds of frozen cloud droplets interspersed with considerable air spaces; the original snow crystal is no longer discernible. This study increases our knowledge about the process and characteristics of riming and suggests that the initial appearance of the flattened hemispheres may result from impact of the leading face of the snow crystal with cloud droplets. The elongated and sinuous configurations of frozen cloud droplets that are encountered on the more advanced stages suggest that aerodynamic forces propel cloud droplets to the trailing face of the descending crystal where they make contact and freeze.
Tools and Procedures for Quantitative Microbeam Isotope Ratio Imaging by Secondary Ion Mass Spectrometry
Authors: Gillen Greg , Bright David
Published: June 2010

In this work we demonstrate the use of secondary ion mass spectrometry (SIMS) combined with the Lispix image processing program (Bright 1995) to generate quantitative isotope ratio images from a test sample of a calcium‐aluminum rich inclusion from the Allende meteorite that is known to contain discrete mineral grains with perturbed Mg isotopic ratios. Using 19.5 keV impact O‐ primary ion bombardment and detection of positive secondary ions, microbeam imaging SIMS has allowed us to identify, from the isotope ratio images, enrichments in the 26Mg/24Mg isotope ratio of approximately 5‐15% in selected mineral grains. Using custom image processing software, each isotopic ratio image is corrected on an individual pixel basis for a number of factors including detector dead‐time, mass bias effects, and isobaric interferences. We have developed procedures for correlating the isotopic images with polarized optical microscopy so that targeted mineral grains could be identified for further SIMS analysis. Finally, additional image processing tools have been developed to allow for pixel‐by‐pixel evaluation of the influence of detector dead‐time and count rate errors on the isotopic ratio images and for correlation of the isotopic images with elemental distribution maps.
MgATP‐induced conformational changes in a single myosin molecule observed by atomic force microscopy: Periodicity of substructures in myosin rods
Authors: Taniguchi Mieko , Suzuki Shigehito , Yamane Takashi , Matsumoto Osamu , Okuda Ayumu , Taga Tooru , Nishino Yasunobu
Published: June 2010

This paper discusses the conformational changes in a single myosin molecule directly observed using atomic force microscopy (AFM). The myosin molecules were pretreated in rigor solutions without MgATP or in relaxed solutions with various concentrations of MgATP. The images of these molecules were obtained using a tapping mode AFM. The results indicate that the orientation of the myosin's heads and tail strongly depend on the MgATP concentration. Without using MgATP, almost all of the myosin molecules are in the extended form; however, when MgATP is used, the molecules bend according to the level of MgATP concentration. The mean‐square end‐to‐end distance of the myosin molecules is significantly shorter with p[MgATP] = 4 than with p[MgATP] = 6. The rod region did not show the same level of intensity along their length in the extended form. The rods exhibited clusters of discontinuity, which were identified as substructures. The size of these substructures change at intervals that are multiples of 14.3‐14.5 nm, which reflects the periodicity of the α;‐helical coiled coils. The substructure clusters also correspond to the myosin cross‐bridge spacing in muscles (14.3 or 43 nm). These results suggest that the myosin's head bends in conjunction with the bending or tilting in the helical substructures. Conformational changes of the myosin molecule induced by MgATP seem to mimic the molecular motions in a muscle's force generation process.
Software acceleration techniques for the simulation of scanning electron microscope images
Authors: Seeger Adam , Fretzagias Charalampos , Taylor Russell
Published: June 2010

A scanning electron microscope (SEM) simulator was developed based on the models used in the MONSEL software. This simulator extends earlier work by introducing an object‐oriented framework and adding optimization methods based on precomputation of electron trajectories. Several optimizations enable speedup by factors of 5–100 on a single processor over unoptimized simulations without introducing additional approximations. The speedup for a particular surface depends on the selfsimilarity of the surface at the scale of the electron penetration depth. We further accelerate by parallelizing the calculations for a total speedup of about 100‐2000 on 30 processors. The goal of this work was to create a system capable of simulating a quantitatively accurate SEM image of a relatively unconstrained surface. Results of this work include simulation software, optimization algorithms, performance measurements with various optimizations, and examples of simulated images.
A microcantilever‐based pathogen detector
Authors: Weeks B. L. , Camarero J. , Noy A. , Miller A. E. , De Yoreo J. J. , Stanker L.
Published: June 2010

The ability to detect small amounts of materials, especially bacterial organisms, is important for medical diagnostics and national security issues. Engineered micromechanical systems provide one approach for constructing multifunctional, highly sensitive, real‐time, immunospecific biological detectors. We present qualitative detection of specific Salmonella enterica strains using a functionalized silicon nitride microcantilever. Detection is achieved due to a change in the surface stress on the cantilever surface in situ upon binding of a small number of bacteria. Scanning electron micrographs indicate that less than 25 adsorbed bacteria are required for detection.
Electron backscatter diffraction characterization of inlaid cu lines for interconnect applications
Authors: Field D. P. , Muppidi T. , Sanchez J. E.
Published: June 2010

Automated electron backscatter diffraction (EBSD) techniques have been used to characterize the microstructures of thin films for the past decade or so. The recent change in strategy from an aluminum‐based interconnect structure in integrated circuits to one based on copper has necessitated the development of new fabrication procedures. Along with new processes, complete characterization of the microstructures is imperative for improving manufacturability of the Cu interconnect lines and in‐service reliability. Electron backscatter diffraction has been adopted as an important characterization tool in this effort. Cu microstructures vary dramatically as a function of processing conditions, including electroplating bath chemistry, sublayer material, stacking sequence of sublayers, annealing conditions, and line widths and depths. Crystallographic textures and grain size and grain boundary character distributions, all of which may influence manufacturability and reliability of interconnect lines, are ideally characterized using EBSD. The present discussion presents some results showing structural dependence upon processing parameters. In addition, the authors identify an in‐plane orientation preference in inlaid Cu lines {111} normal to the line surface and 〈110〉 aligned with the line direction. This relationship tends to strengthen as the line width decreases.
New application of variable‐pressure/environmental microscopy to semiconductor inspection and metrology
Authors: Postek Michael T. , Vladár András E.
Published: June 2010

Variable‐pressure/environmental scanning electron microscopy has been used for successful investigation binary and phase‐shifting chromium on quartz optical photomasks. This methodology was also applied to patterned 193 nm photoresist structures. The application of this methodology to semiconductor metrology is new because of the recent availability of variable‐pressure scanning electron microscopy (SEM) instrumentation equipped with high‐resolution, high‐signal, thermally assisted field emission technology in conjunction with large chamber and sample transfer capabilities. The variable‐pressure SEM methodology employs a gaseous environment around the sample to help diminish the charge build‐up that occurs under irradiation with the electron beam. Although very desirable for the charge reduction in many biological, pharmaceutical, and food applications, this methodology has not been employed for semiconductor photomask or wafer metrology until now. This is a new application of this technology to this area, and it shows great promise in inspection, imaging, and metrology in a charge‐free operational mode. For accurate metrology, variable‐pressure SEM methodology also affords a path that minimizes, if not eliminates, the need for charge modeling. This paper presents some of the early results in the variable‐pressure SEM metrology of photomask and photoresist structures.
Mathematical modeling of human secondary osteons
Authors: Ascenzi Maria‐Grazia , Kabo J. Michael , Andreuzzi Marta
Published: June 2010

This investigation explores the structural dimensions and patterns within single secondary osteons, with consideration of their biological variation. New data from images obtained previously of osteons observed through linearly polarized light, electron microscopy, and micro‐x‐ray, combined with recent findings on lamellae by circularly polarized light, confocal microscopy, synchrotron x‐ray diffraction, and micro‐x‐ray, provide the basis for novel computerized models of single osteons and single lamellae. The novelty of such models is the concurrent representation of (1) collagen‐hydroxyapatite orientation, (2) relative hydroxyapatite percentage, (3) distributions of osteocytes' lacunae and canaliculae, and (4) biological variations in dimensions of the relevant structures. The mathematical software Maple realizes the computerized models. While the parts of the models are constructed on a personal computer, the voluminous data associated with the representation of lacunar and canalicular distributions require a supercomputer for assembly of the models and final analysis. The programming used to define the models affords the option to randomize the dimensional specifications of osteons, lamellae, lacunae, and canaliculae within the experimentally observed numeric ranges and distributions. Through this option, the program can operate so that each run of the file produces a unique random model within the observed biological variations. The program can also be run to implement specific dimensional requirements. The modeling has applications in the microstructural study of fracture propagation and remodeling, as well as in the simulation of mechanical testing. The approach taken here is of wide application and could be of value in other areas of microscopy such as scanning electron microscopy, microcomputerized tomography scan, and magnetic resonance imaging on cancellous bone structures.
Effect of shot noise and secondary emission noise in scanning electron microscope images
Authors: Sim K. S. , Thong J. T. L. , Phang J. C. H.
Published: June 2010

The effect of shot noise and emission noise due to materials that have different emission properties was simulated. Local variations in emission properties affect the overall signal‐to‐noise ratio (SNR) value of the scanning electron microscope image. In the case in which emission noise is assumed to be absent, the image SNRs for silicon and gold on a black background are identical. This is because only shot noise in the primary beam affects the SNRs, irrespective of the assumed noiseless secondary electron emission or backscattered electron emission processes. The addition of secondary emission noise degrades the SNR. Materials with higher secondary electron yield and backscattering electron yield give rise to higher SNR. For images formed from two types of material, the contrast of the image is lower. The reduction in image signal reduces the overall image SNR. As expected, large differences in δ or η give rise to higher SNR images.
Contributions of scanning electron microscopy to the assessment of the effectiveness of stone conservation treatments
Authors: de Buergo M. Alvarez , Fort R. , Gomez‐Heras M.
Published: June 2010

The efficiency of 16 products (with consolidating and/or water‐repellency effects) applied to granites and limestones have been assessed by means of scanning electron microscopy (SEM). The technique offers the possibility of observing the porous system of the stone, the products' filming capacity, the penetration depth of the products into the stone, their distribution on the porous system, and their conservation degree through time. Scanning electron microscopy has to be considered as complementary to some other tests and techniques to assess the efficiency of conservation treatments, such as stone‐water contact angle, water vapour permeability, and global colour variations, among others. The conclusion reached is that the SEM technique defines some of the parameters, properties, and characteristics that highly control the efficiency of the treatments. This work confirms the SEM technique, particularly using backscattering electrons, as a very useful and complementary tool to assess the efficiency of the conservation treatments applied to stone materials for restoration purposes.
Research on double‐probe, double‐ and triple‐tip effects during atomic force microscopy scanning
Authors: Chen Yong , Cai Jiye , Liu Meili , Zeng Gucheng , Feng Qian , Chen Zhengwei
Published: June 2010

Information obtained by atomic force microscopy (AFM) depends strongly on the kind of probe or tip used; therefore, probe and tip effects have to be taken into account when verifying or interpreting the data acquired. In many papers, double‐tip effects have been mentioned while other research was done; however, there are only a few special reports on double‐ or triple‐tip effects, especially double‐probe effects. In our paper, metaphase chromosomes of Chinese hamster ovary (CHO) cells, aggregates of pectin molecules, membrane surface of mouse embryonic stem cells, and R‐phycoerythrin‐conjugated immunoglobulin G complexes were imaged by AFM with high‐quality probes, double‐probe cantilever, and doubletip and triple‐tip probes, respectively, in order to determine double‐probe, double‐tip, and triple‐tip effects during AFM scanning. We found that the double‐probe, double‐tip, and triple‐tip effects share the same principle, and that these effects correlate with distance and height differences between probes of double‐probe cantilever or tips of double‐tip or multiple‐tip probes. Since many other factors influence double‐probe or double‐tip effects, more in‐depth studies must be undertaken. However, this initial research will make all users of AFM techniques aware of double‐probe and double‐tip or triple‐tip effects during AFM scanning and aid in verifying or interpreting the data acquired.