Stereo Scanning Electron Microscopy Research Articles

Nutlet micromorphology and its taxonomic and phylogenetic significance in Salvia (Lamiaceae)

Salvia (sage) is a species rich and medicinally important genus. Species-level identification is usually very difficult, particularly in closely related species. Here, we investigated nutlet micromorphological characteristics of 51 taxa belonging to S. subg. Salvia, S. subg. Sclarea and Salvia verticillata clade (S. subg. Heterosphace) by stereo binocular microscopy and scanning electron microscopy to show their taxonomic and phylogenetic value. The present study is the most comprehensive nutlet micromorphological study based on the number of taxa studied in the genus so far. The size of nutlets varies from 1.61 mm (S. verticillata subsp. verticillata) to 8.44 mm (S. albimaculata) in length, 1.02 mm (S. verticillata subsp. verticillata) to 4.20 mm (S. macrochlamys) in width. Nutlet length/width ratio ranges from 1.02 (S. bracteata and S. indica) to 3.06 (S. albimaculata). The basic shape of nutlets is elliptic, widely elliptic, circular, ovate or obovate. Five nutlet sculpturing patterns are present namely colliculate, reticulate, verrucate, rugose and foveate. The variation of surface sculpturing, nutlet shape, size, and exocarp cell shape provide useful diagnostic properties at species and subgenus level. However, nutlet micromorphological characters are of low phylogenetic value in studied Salvia species.

<p><strong>Mericarp morphology of the genus <em>Origanum</em> (Lamiaceae) and its taxonomic significance in Turkey</strong></p>

Origanum is a well-known genus that is widely distributed and comprises many hybrids and endemic species in Turkey. Some morphological and molecular studies in the literature have aimed to clarify infrageneric or sectional classification of the genus. However, studies regarding the shape, size, and color of mericarps of Origanum taxa remain limited. The mericarp micromorphology of 30 taxa, including 7 hybrids of the genus Origanum, were evaluated herein using both stereo microscopy and scanning electron microscopy (SEM) to determine some useful features for taxonomical classification of the genus. The shapes of mericarps are usually ellipsoid, rarely ellipsoid-oblong, obovoid, broadly obovoid, while the color of mericarps vary from shades of brown to reddish. A significant variation was observed in the surface ornamentation of mericarps, which was mainly useful at the sectional and species level. Also determined were 2 main types: I and II, and 5 subtypes: pusticulate, reticulate-ruminate, reticulate-foveate, ruminate, and foveate. The micromorphological characters of mericarps, in addition to their morphological features, will contribute taxonomically to the classification of the sections of the genus Origanum and separation of the species within the sections. In addition, these characters will be useful to understand the effect of hybridization on variations in the micromorphological characters. This was the first detailed study on the mericarp micromorphology of the genus Origanum and its taxonomic implications.

3D Stereo Reconstruction of SEM Images

In this work is proposed a new fully automated methodology using computer vision and dynamic programming to obtain a 3D reconstruction model of surfaces using scanning electron microscope (SEM) images based on stereovision. The horizontal stereo matching step is done with a robust and efficient algorithm based on semi-global matching. The cost function used in this study is very simple since the brightness and contrast change of corresponding pixels is negligible for the small tilt involved in stereo SEM. It is used a sum of absolute differences (SAD) over a variable pixel size window. Since it relies on dynamic programming, the matching algorithm uses an occlusion parameter which penalizes large depth discontinuities and, in practice, smooths the disparity map and the corresponding reconstructed surface. This step yields a disparity map, i.e. the differences between the horizontal coordinates of the matching points in the stereo images. The horizontal disparity map is finally converted into heights according to the SEM acquisition parameters: tilt angle, image magnification and pixel size. A validation test was first performed using as reference a microscopic grid with manufacturer specifications. Finally, with the 3D model are proposed some applications in materials science as roughness parameters estimation and wear measurements.

Applicability of characterization techniques on fine scale surfaces

In this study, several surface topographies typical for dental implants were evaluated by different measurement techniques. The samples were prepared by machine turning, wet chemical etching and electrochemical polishing of titanium discs. The measurement techniques included an atomic force microscope (AFM), coherence scanning interferometer (CSI) and a 3D stereo scanning electron microscope (SEM). The aim was to demonstrate and discuss similarities and differences in the results provided by these techniques when analyzing submicron surface topographies. The estimated surface roughness parameters were not directly comparable since the techniques had different surface spatial wavelength band limits. However, the comparison was made possible by applying a 2D power spectral density (PSD) function. Furthermore, to simplify the comparison, all measurements were characterized using the ISO 25178 standard parameters. Additionally, a Fourier transform was applied to calculate the instrument transfer function in order to investigate the behavior of CSI at different wavelength ranges. The study showed that 3D stereo SEM results agreed well with AFM measurements for the studied surfaces. Analyzed surface parameter values were in general higher when measured by CSI in comparison to both AFM and 3D stereo SEM results. In addition, the PSD analysis showed a higher power spectrum density in the lower frequency range 10−2–10−1 µm−1 for the CSI compared with the other techniques.

Comparative evaluation of topographical data of dental implant surfaces applying optical interferometry and scanning electron microscopy

ObjectiveComparability of topographical data of implant surfaces in literature is low and their clinical relevance often equivocal. The aim of this study was to investigate the ability of scanning electron microscopy and optical interferometry to assess statistically similar 3-dimensional roughness parameter results and to evaluate these data based on predefined criteria regarded relevant for a favorable biological response. MethodsFour different commercial dental screw-type implants (NanoTite Certain Prevail, TiUnite Brånemark Mk III, XiVE S Plus and SLA Standard Plus) were analyzed by stereo scanning electron microscopy and white light interferometry. Surface height, spatial and hybrid roughness parameters (Sa, Sz, Ssk, Sku, Sal, Str, Sdr) were assessed from raw and filtered data (Gaussian 50μm and 5μm cut-off-filters), respectively. Data were statistically compared by one-way ANOVA and Tukey–Kramer post-hoc test. For a clinically relevant interpretation, a categorizing evaluation approach was used based on predefined threshold criteria for each roughness parameter. ResultsThe two methods exhibited predominantly statistical differences. Dependent on roughness parameters and filter settings, both methods showed variations in rankings of the implant surfaces and differed in their ability to discriminate the different topographies. Overall, the analyses revealed scale-dependent roughness data. Compared to the pure statistical approach, the categorizing evaluation resulted in much more similarities between the two methods. SignificanceThis study suggests to reconsider current approaches for the topographical evaluation of implant surfaces and to further seek after proper experimental settings. Furthermore, the specific role of different roughness parameters for the bioresponse has to be studied in detail in order to better define clinically relevant, scale-dependent and parameter-specific thresholds and ranges.

SD-SEM: sparse-dense correspondence for 3D reconstruction of microscopic samples

Scanning electron microscopy (SEM) imaging has been a principal component of many studies in biomedical, mechanical, and materials sciences since its emergence. Despite the high resolution of captured images, they remain two-dimensional (2D). In this work, a novel framework using sparse-dense correspondence is introduced and investigated for 3D reconstruction of stereo SEM images. SEM micrographs from microscopic samples are captured by tilting the specimen stage by a known angle. The pair of SEM micrographs is then rectified using sparse scale invariant feature transform (SIFT) features/descriptors and a contrario RANSAC for matching outlier removal to ensure a gross horizontal displacement between corresponding points. This is followed by dense correspondence estimation using dense SIFT descriptors and employing a factor graph representation of the energy minimization functional and loopy belief propagation (LBP) as means of optimization. Given the pixel-by-pixel correspondence and the tilt angle of the specimen stage during the acquisition of micrographs, depth can be recovered. Extensive tests reveal the strength of the proposed method for high-quality reconstruction of microscopic samples.

Effect of heat treatment on impact resistance of AU5GT and AS7G06 aluminum alloys

Impact strength is one of the major mechanical properties that a material should possess in order to absorb sudden changes in the load intensity. The objective of current study is to compare the impact strength of two material (AU5GT and AS7G06), which are used in different structural applications. Almost no work is available which compares the impact strength of selected grade alloys along with different heat treatment cycles. Specimens are heat treated first as per designed cycles, later impact testing is performed. Charpy impact test is conducted in accordance with ASTM E23-12 standard method on three samples with and without heat treatment for each cycle. Solutionizing on samples is done at constant time and temperature to achieve homogenization. Later, aging is conducted at different temperatures ranging from 100-200°C (different intervals) at constant time to find the effect of precipitation hardness that actually increases the strength. Sample hardness is determined using Vickers micro hardness testing machine for each heat treatment cycle. Charpy test results provided the impact energy that is used to determine the strength before fracture. Heat treated samples have showed increase in impact strength for AS7G06 aluminum alloy while AU5GT shows very little change. This is because of growing the precipitation with respect to temperature, which resulted in more hard regions across grains. Hardness also shows an increasing relationship, as expected. Fracture surfaces are analyzed on stereo microscopy and Scanning electron microscopy (SEM) to find the final mode of fracture, that is brittle, ductile or transitional (combination of both brittle and ductile).

Crack initiation and propagation paths in small diameter FSW 6082-T6 aluminium tubes under fatigue loading

This paper reports results of fatigue tests of friction stir welded (FSW) aluminium tubes. Relatively small 38 mm diameter tubes were used and hence an automated FSW process using a retracting tool was designed for this project, as the wall thickness of the aluminium tube was similar to the diameter of the FSW tool. This is a more complex joint geometry to weld than the more usual larger diameter tube reported in the literature. S-N fatigue testing was performed using load ratios of R = 0.1 and R = -1. Crack path analysis was performed using both low magnification stereo microscopy and scanning electron microscopy, in order to identify crack initiation sites and to determine the direction of crack propagation. Work is still in progress to follow the crack path through the various microstructural zones associated with the weld. A simple statistical analysis was used to characterize the most typical crack initiation site. This work forms part of a wider project directed at determining multiaxial fatigue design rules for small diameter 6082-T6 aluminium tubes that could be of use in the ground vehicle industry.

Combined ion micro probe and SEM analysis of strongly non uniform deposits in fusion devices

Conventional ion beam analysis (IBA) of deposited layers from fusion devices may have insufficient accuracy due to strongly uneven appearance of the layers. Surface roughness and spatial variation of the matrix composition make interpretation of broad beam spectra complex and non obvious. We discuss complications of applied IBA arising for fusion-relevant surfaces and demonstrate how quantification can be improved by employing micro IBA methods. The analysis is bound to pre-defined regions on the sample surface and can be extended by employing beams of several types, scanning electron microscopy (SEM) and stereo SEM techniques.

3-D reconstruction of ash vesicularity: Insights into the origin of ash-rich explosive eruptions

Explosive volcanic eruptions are characterized by highly variable degrees of magma fragmentation, even during a single eruptive event. The increasing amount of fine pyroclasts is often uncritically related to explosive magma–water interaction (i.e., hydromagmatic fragmentation). Here we report examination of two examples of major explosive eruptions from the Quaternary Vulsini Volcanic District (central Italy), in which the fine-grained nature of deposits, even in near-vent settings, indicates negligible effect of transport and implies the eruption of highly fragmented magmas. SEM morphoscopy of the juvenile products rules out extensive ash production due to hydromagmatic fragmentation. We apply a recently developed Stereo-Scanning Electron Microscopy (SSEM) technique (Proussevitch et al., 2011) to determine vesicularity features (e.g., bubble size distribution and bubble number density; hereafter BSD and BND, respectively) of ash particles. SSEM analysis provides new insights into magma vesiculation history and fragmentation mechanism leading to major ash-rich eruptions. We conclude that extensive ash production was related to essentially magmatic processes involving high degrees of decompression in shallow magma reservoirs.

Studies on the Structure of Flowers and Inflorescences of Cornelian Cherry (Cornus mas L.)

This study reports on the arrangement of flower buds and structure of floral organs of cornelian cherry (Cornus mas L.) cultivars local to Turkey. The local cultivars were investigated under stereo microscope, light microscope, and scanning electron microscope (SEM). The results indicate that each node has two oppositely positioned buds on 1-year-old shoot. Inflorescences resembled the umbel structure that enclosed four (two sets of oppositely oriented) bud scales. The mean flower number varied between 16.3 and 19.9 per cluster among the cultivars. The flowers resembled the hermaphrodite type and one flower was found to have four rudimentary sepals, four petals, four stamens, and one pistil. The stamens were noted to be arranged around the base of the ovary. Each normal anther was observed to have two pollen-producing theca, and each theca was found to have two locules. The number of pollen grains per anther varied between 1380 and 4240 among the genotypes. The pistil was noted to have a deeply hollowed papillate stigmatic surface, and the central part of the style had conducting tissue. The ovarium part of the pistil was found to be surrounded by the nectary tissue, inferior type, and had two atropous ovules. The fruit resembled single-seeded, stone fruit type. This study is the first detailed study on the flower morphology and inflorescences of the cornelian cherry cultivars in Turkey.

TiB2 Ceramic Tool Turning 45# Steel Experimental Study

By using ordinary lathe, carried out cutting experimental study with cylindrical turning 45# steel on TiB2 ceramic cutting tool. By using Stereo Microscopy and Scanning Electron Microscopy, recorded cutting tool surface’s friction and wear conditions. The results showed that higher cutting speed could made surface roughness decrease and surface quality better; TiB2 ceramic cutting tool’s wear mechanism was abrasive wear, aoxidation wear; wear of blade tip and main flank face were more serious.

Microscopical studies of nephtyid chaetae (Annelida: Polychaeta: Nephtyidae) from Northern Europe and Arctic

The chaetal structure of some species of Nephtyidae from the North Polar Ocean has been studied using both stereo compound light microscopy (LM) and scanning electron microscopy (SEM): Aglaophamus malmgreni, A. rubellus, Micronephthys hartmannschroederae, M. minuta, M. neotena, Nephtys assimilis, N. caeca, N. ciliata, N. cirrosa, N. hombergii, N. hystricis, N. kersivalensis, N. longosetosa, N. paradoxa, N. pente and N. rickettsi. All nephtyid chaetae are simple; noto- and neurochaetae are similar. There are four main chaetal types: capillary, barred, chaetae with spines and lyrate (the latter are absent in investigated species). Chaetae that appear smooth under LM usually have at least some small sporadically scattered spines under SEM, but truly smooth chaetae also exist. All barred chaetae are preacicular. Chaetae with spines, and capillary chaetae, are mainly postacicular. The basal regions of chaetae with spines are smooth, and spines appear in sporadically scattered arrangements, gradually becoming more dense but still in irregular rows. In the most ornate cases (spinose chaetae), the spines gradually join together basally, at first in irregular, then regular, rows and form ‘combs’. The number of spines in such combs can increase from 3–4 up to 20–25 along the chaetae. In old chaetae, the combs can become detached as a whole unit. The chaetal morphology is most developed in the middle of a spinose chaeta, and thereafter the pattern and form of the spines changes in reverse order (combs, irregular combs, sporadic spines) terminating in smooth tips. Spinose chaetae of different species and genera can differ in the number of spines forming the combs, the distance between combs and size of the spines. Some species have ‘combs’ with single spines (so-called serrate chaetae). Other species have no distinct combs at all. Geniculate chaetae are a form of serrate chaetae.

A new 3D method of measuring bubble size distributions from vesicle fragments preserved on surfaces of volcanic ash particles

We have developed a novel method of measuring bubble size distributions from their remains expressed on the surfaces of volcanic ash particles. The morphology of the ash fragments retains a record of bubble size at the time of fragmentation in the curvature of the convex surfaces on the ash fragments. This curvature can be measured using stereo scanning electron microscopy (SSEM), and morphology can be represented using a digital elevation model (DEM) of ash particle surfaces. Due to the vagaries of the sensitivity of SSEM imagery to surface roughness, a three-point fit technique produces more robust results for curvature than a least-squares approach for curve-fitting of ellipsoids of revolution to ash surfaces. The method allows measurement of vesicles within a size range from one to over a million cubic microns. The inferred bubble size distributions so obtained can potentially provide valuable insights regarding magma dynamics and vesiculation that lead to the explosive eruptions that produce ash. An error analysis of the methodology indicates reasonably accurate reconstruction of bubble geometries and bubble size distributions (BSD). Accuracy is constrained primarily by the size of ash particles themselves since the mode of the BSD should be at least a standard deviation smaller than the dominant dimensions of the particles for robust results.

3D-measurement with the stereo scanning electron microscope on sub-micrometer structures

In this paper the photometric or the so called “shape from shading” method is presented. In comparison to existing methods the efficiency of the detector system was considered and the requirements of the cosine Lambert’s law for the angle distribution of the emitted electrons are suppressed. This new method was experimentally verified by measuring a steel sphere, a holographic grating and a hologram.

Advances in lasers and optical micro-nano-systems

Lasers represent a well consolidated technology: nevertheless, research in this field remains very active and productive, in both basic and applied directions. At the moment significant attention is given to those sources that bring together high power and compactness. Such high power lasers find important applications for material treatments and such applications are presented by Ehsani et al and Saiedeh Saghafi et al, in the treatment of dielectric thin films (Alteration of optical and morphological properties of polycarbonate illuminated by visible/IR laser beams) or of biological tissues like pistachio seeds (Investigating the effects of laser beams (532 and 660 nm) in annihilation of pistachio mould fungus using spectrophotometry analysis). In particular the latter paper show how laser sources can find very important applications in new domains, preserving goods and food without the need for preservatives or pesticides by simply sterilizing them using light. Optical Micro and Nano Systems presents a new domain for exploration. In this framework this special issue is very attractive, because it assembles papers reporting new results in three directions: new techniques for monitoring integrated micro- and nano-systems, new integrated systems and novel high performance metamaterial configurations. Integrated micro-components can be monitored and controlled using reflectance measurements as presented by Piombini et al (Toward the reflectance measurement of micro components). Speckle formation during laser beam reflection can also be a very sophisticated tool for detecting ultra-precise displacements, as presented by Filter et al (High resolution displacement detection with speckles : accuracy limits in linear displacement speckle metrology). Three dimensional integrated optical structures is indeed a big challenge and a peculiarity of photonics, they can be formed through traditional holography or using more sophisticated and novel technologies. Thus, special manipulation of the writing-reading optical beam can push holography toward storages at higher data densities, as presented by Norihiko Ishii et al (Wavefront compensation method using novel index in holographic data storage). Along a similar direction Furlan et al describe a very innovative technique for producing optical traps using novel Devil micro-lenses (Volumetric multiple optical traps produced by Devil’s lenses). Vynnyk et al presented an interesting application of electron microscopy for monitoring sub-micrometric structures in 3D configurations (3D-measurement with the stereo scanning electron microscope on sub-micrometer structure). Finally, S. Rao et al present two interesting papers on integrated structures compatible with silicon technology: one describes the realisation of low-loss waveguides using amorphous silicon, a relatively novel material with many applications in very different domains (Low-loss amorphous silicon waveguides grown by PECVD on indium tin oxide), and one on the realisation of a electrically drivable device with affective compatibility with CMOS technology (Electro-optical modulating multistack device based on the CMOS-compatible technology of amorphous silicon). We hope that this special issue of the Journal of the European Optical Society will reflect the interest of the European Scientific Community toward these fundamental and applied topics and will demonstrate to readers some of the actual directions of research. We express our full appreciation to the authors that participated to this initiative which acts only as a primer for the vast amount of work now being undertaken in laser physics and applications in micro- and nano-systems. We would like to give a special thank to the paper reviewers for their important role in the paper selection process and all the journal staff for their very professional support, dedication and energy, which made this special issue feasible.

Studies on the Preparation and Gas Sensing Properties of SnO<sub>2</sub> Nanostructures at Room Temperature

The SnO2 nanostructures have been synthesized by carbon-assisted growth at 800 oC for 3 hours. Using high pure tin powder as the source materials. The synthesized products were investigated by stereo microscope, X-rays diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns show that the prepared products are tetragonal-structures with the lattice constant a = 0.4718 nm and c = 0.3187 nm. SEM images indicate that SnO2 nanowires are about tens of micrometers in length, 80-100 nm in width. The diameter of SnO2 nanoparticles vary from 10 nm to 100 nm. The synthesized products are high sensitivity and fast response time to ethanol gas at room temperature.

Synthesis and Characterization of Nanostructured Materials Prepared from SiO<sub>2 </sub>and GeO<sub>2</sub> Mixture by Carbon Assisted Method

Nanostructured materials were synthesized by thermal evaporation process using silicon dioxide and carbon from coconut shell charcoal or graphite mixed with GeO2 by the ratio of 5:1:1 at temperature 1200 oC in one atmosphere of nitrogen for 3 hours. The nanostructured materials were characterized by the stereo microscope (image analyzer) and scanning electron microscope. The diameters of nanowires vary from 10 nm to 50 nm and length of several 10 micrometers. Length of nanorods was around 15 micrometers and diameters vary from 10 nm to 100 nm.

Stereo imaging and cytocompatibility of a model dental implant surface formed by direct laser fabrication

Direct laser fabrication (DLF) allows solids with complex geometry to be produced by sintering metal powder particles in a focused laser beam. In this study, 10 Ti6Al4V alloy model dental root implants were obtained by DLF, and surface characterization was carried out using stereo scanning electron microscopy to produce 3D reconstructions. The surfaces were extremely irregular, with approximately 100 microm deep, narrow intercommunicating crevices, shallow depressions and deep, rounded pits of widely variable shape and size, showing ample scope for interlocking with the host bone. Roughness parameters were as follows: R(t), 360.8 microm; R(z), 358.4 microm; R(a), 67.4 microm; and R(q), 78.0 microm. Disc specimens produced by DLF with an identically prepared surface were used for biocompatibility studies with rat calvarial osteoblasts: After 9 days, cells had attached and spread on the DLF surface, spanning across the crevices, and voids. Cell density was similar to that on a commercial rough microtextured surface but lower than on commercial smooth machined and smooth-textured grit-blasted, acid-etched surfaces. Human fibrin clot extension on the DLF surface was slightly improved by inorganic acid etching to increase the microroughness. With further refinements, DLF could be an economical means of manufacturing implants from titanium alloys.

Ultrastructural basement membrane topography of the bladder epithelium.

The basement membrane underlies epithelium and separates it from deeper tissues. Recent studies suggest that nanoscale topography of the surface of basement membrane may modulate adhesion, migration, proliferation and differentiation of overlying epithelium. This study was performed to elucidate nanoscale topographic features of basement membrane of the bladder. Bladder tissues were obtained from three adult female rhesus macaques. A process was developed to remove the epithelium while preserving the underlying basement membrane, and tissues were evaluated by immunohistochemistry and scanning electron microscopy (SEM). Detailed measurements were made of stereo SEM images to quantitatively define topographic features. Measurements made from multiple SEM images of bladder basement membrane provided the following values for topographic features: mean feature height, 178+/-57 nm; mean fiber diameters, 52+/-28 nm; mean pore diameter, 82+/-49 nm; and mean interpore distance (center to center), 127+/-54 nm. These dimensions are similar to those reported previously for basement membranes of other species and anatomical locations. This information provides a rational basis for design of nanostructured biomaterials to produce composite grafts for repair or replacement of segments of the urinary tract.