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Microscopy and Microanalysis

Elliot Padgett, Robert Hovden, Jessica C DaSilva, Barnaby D A Levin, John L Grazul, Tobias Hanrath, David A Muller
Electron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a "missing wedge" of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking...
December 11, 2017: Microscopy and Microanalysis
Jun Young Cheong, Joon Ha Chang, Sung Joo Kim, Chanhoon Kim, Hyeon Kook Seo, Jae Won Shin, Jong Min Yuk, Jeong Yong Lee, Il-Doo Kim
We trace Sn nanoparticles (NPs) produced from SnO2 nanotubes (NTs) during lithiation initialized by high energy e-beam irradiation. The growth dynamics of Sn NPs is visualized in liquid electrolytes by graphene liquid cell transmission electron microscopy. The observation reveals that Sn NPs grow on the surface of SnO2 NTs via coalescence and the final shape of agglomerated NPs is governed by surface energy of the Sn NPs and the interfacial energy between Sn NPs and SnO2 NTs. Our result will likely benefit more rational material design of the ideal interface for facile ion insertion...
December 8, 2017: Microscopy and Microanalysis
Muhammad Burhan Khan, Humaira Nisar, Choon Aun Ng, Kim Ho Yeap, Koon Chun Lai
Image processing and analysis is an effective tool for monitoring and fault diagnosis of activated sludge (AS) wastewater treatment plants. The AS image comprise of flocs (microbial aggregates) and filamentous bacteria. In this paper, nine different approaches are proposed for image segmentation of phase-contrast microscopic (PCM) images of AS samples. The proposed strategies are assessed for their effectiveness from the perspective of microscopic artifacts associated with PCM. The first approach uses an algorithm that is based on the idea that different color space representation of images other than red-green-blue may have better contrast...
December 7, 2017: Microscopy and Microanalysis
Elena Ruggeri, Keith F DeLuca, Cesare Galli, Giovanna Lazzari, Jennifer G DeLuca, Joanne E Stokes, Elaine M Carnevale
Confocal microscopy was used to image stages of equine zygote development, at timed intervals, after intracytoplasmic sperm injection (ICSI) of oocytes that were matured in vivo or in vitro. After fixation for 4, 6, 8, 12, or 16 h after ICSI, zygotes were incubated with α/β tubulin antibodies and human anticentromere antibody (CREST/ACA), washed, incubated in secondary antibodies, conjugated to either Alexa 488 or Alexa 647, and incubated with 561-Phalloidin and Hoechst 33258. An Olympus IX81 spinning disk confocal microscope was used for imaging...
December 6, 2017: Microscopy and Microanalysis
Doaa M Mokhtar, Manal T Hussein, Ahmed H S Hassan
Endogenous melatonin is a hormone secreted by pineal gland; it has several roles in metabolism, reproduction, and remarkable antioxidant properties. Studies on the melatonin effect on the adrenal glands which are important endocrine organs, controlling essential physiological functions, are still deficient. In this study, we attempted to investigate the effect of exogenous melatonin treatment on the adrenal cortex and medulla using several approaches. Adrenal glands of 15 Soay ram were examined to detect the effect of melatonin treatment...
December 4, 2017: Microscopy and Microanalysis
Chonghong Zhang, Jiejie Lv, Fuchun Li, Xuelin Li
Calcite spherulites have been observed in many laboratory experiments with different bacteria, and spherulitic growth has received much interest in mineralogy research. However, the nucleation and growth mechanism, as well as geological significance of calcite spherulites in solution with bacteria is still unclear. Herein, spherulites composed of an amorphous core, a Mg-calcite body and an organic film were precipitated by the Curvibacter lanceolatus HJ-1 bacterial strain in a solution with a molar Mg/Ca ratio of 3...
December 4, 2017: Microscopy and Microanalysis
Timothy J Ruggles, Geoffrey F Bomarito, Andrew H Cannon, Jacob D Hochhalter
Digital image correlation (DIC) in a scanning electron microscope and high-angular resolution electron backscatter diffraction (HREBSD) provide valuable and complementary data concerning local deformation at the microscale. However, standard surface preparation techniques are mutually exclusive, which makes combining these techniques in situ impossible. This paper introduces a new method of applying surface patterning for DIC, namely a urethane microstamp, that provides a pattern with enough contrast for DIC at low accelerating voltages, but is virtually transparent at the higher voltages necessary for HREBSD and conventional EBSD analysis...
December 4, 2017: Microscopy and Microanalysis
Susumu Imashuku, Koichiro Ono, Kazuaki Wagatsuma
The potential of the application of an X-ray excited optical luminescence (XEOL) analyzer and portable analyzers, composed of a cathodoluminescence (CL) spectrometer and electron probe microanalyzer (EPMA), to the on-line and on-site analysis of nonmetallic inclusions in steel is investigated as the first step leading to their practical use. MgAl2O4 spinel and Al2O3 particles were identified by capturing the luminescence as a result of irradiating X-rays in air on a model sample containing MgAl2O4 spinel and Al2O3 particles in the size range from 20 to 50 μm...
November 27, 2017: Microscopy and Microanalysis
Dana Fialová, Radim Skoupý, Eva Drozdová, Aleš Paták, Jakub Piňos, Lukáš Šín, Radoslav Beňuš, Bohuslav Klíma
The great potential of scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) is in detection of unusual chemical elements included in ancient human dental calculus to verify hypotheses about life and burial habits of historic populations and individuals. Elemental spectra were performed from archeological samples of three chosen individuals from different time periods. The unusual presence of magnesium, aluminum, and silicon in the first sample could confirm the hypothesis of high degree of dental abrasion caused by particles from grinding stones in flour...
November 20, 2017: Microscopy and Microanalysis
Toby Sanders, Ilke Arslan
Electron tomography has become an essential tool for three-dimensional (3D) characterization of nanomaterials. In recent years, advances have been made in specimen preparation and mounting, acquisition geometries, and reconstruction algorithms. All of these components work together to optimize the resolution and clarity of an electron tomogram. However, one important component of the data-processing has received less attention: the 2D tilt series alignment. This is challenging for a number of reasons, namely because the nature of the data sets and the need to be coherently aligned over the full range of angles...
November 16, 2017: Microscopy and Microanalysis
Guillaume Wille, Jennifer Hellal, Patrick Ollivier, Annie Richard, Agnes Burel, Louis Jolly, Marc Crampon, Caroline Michel
Understanding biofilm interactions with surrounding substratum and pollutants/particles can benefit from the application of existing microscopy tools. Using the example of biofilm interactions with zero-valent iron nanoparticles (nZVI), this study aims to apply various approaches in biofilm preparation and labeling for fluorescent or electron microscopy and energy dispersive X-ray spectrometry (EDS) microanalysis for accurate observations. According to the targeted microscopy method, biofilms were sampled as flocs or attached biofilm, submitted to labeling using 4',6-diamidino-2-phenylindol, lectins PNA and ConA coupled to fluorescent dye or gold nanoparticles, and prepared for observation (fixation, cross-section, freezing, ultramicrotomy)...
November 16, 2017: Microscopy and Microanalysis
Dai Tang, Mauro E Ferreira, Petrus C Pistorius
Automated inclusion microanalysis in steel samples by computer-based scanning electron microscopy provides rapid quantitative information on micro-inclusion distribution, composition, size distribution, morphology, and concentration. Performing the analysis at a lower accelerating voltage (10 kV), rather than the generally used 20 kV, improves analysis accuracy and may improve spatial resolution, but at the cost of a smaller backscattered electron signal and potentially smaller rate of generation of characteristic X-rays...
November 10, 2017: Microscopy and Microanalysis
Enrico Di Russo, Ivan Blum, Jonathan Houard, Gérald Da Costa, Didier Blavette, Lorenzo Rigutti
The composition of GaAs measured by laser-assisted atom probe tomography may be inaccurate depending on the experimental conditions. In this work, we assess the role of the DC field and the impinging laser energy on such compositional bias. The DC field is found to have a major influence, while the laser energy has a weaker one within the range of parameters explored. The atomic fraction of Ga may vary from 0.55 at low-field conditions to 0.35 at high field. These results have been interpreted in terms of preferential evaporation of Ga at high field...
November 10, 2017: Microscopy and Microanalysis
Anatoly K Khitrin, Jonathan C Petruccelli, Michael A Model
The formation of a bright-field microscopic image of a transparent phase object is described in terms of elementary geometrical optics. Our approach is based on the premise that the image replicates the intensity distribution (real or virtual) at the front focal plane of the objective. The task is therefore reduced to finding the change in intensity at the focal plane caused by the object. This can be done by ray tracing complemented with the requirement of energy conservation. Despite major simplifications involved in such an analysis, it reproduces some results from the paraxial wave theory...
November 6, 2017: Microscopy and Microanalysis
Etienne Brodu, Emmanuel Bouzy
Transmission Kikuchi diffraction is an emerging technique aimed at producing orientation maps of the structure of materials with a nanometric lateral resolution. This study investigates experimentally the depth resolution of the on-axis configuration, via a twinned silicon bi-crystal sample specifically designed and fabricated. The measured depth resolution varies from 30 to 65 nm in the range 10-30 keV, with a close to linear dependence with incident energy and no dependence with the total sample thickness...
December 2017: Microscopy and Microanalysis
Ádám István Hegyi, Péter Dusán Ispánovity, Michal Knapek, Dániel Tüzes, Kristián Máthis, František Chmelík, Zoltán Dankházi, Gábor Varga, István Groma
Plastic deformation of micron-scale crystalline materials differs considerably from bulk samples as it is characterized by stochastic strain bursts. To obtain a detailed picture of the intermittent deformation phenomena, numerous micron-sized specimens must be fabricated and tested. An improved focused ion beam fabrication method is proposed to prepare non-tapered micropillars with excellent control over their shape. Moreover, the fabrication time is less compared with other methods. The in situ compression device developed in our laboratory allows high-accuracy sample positioning and force/displacement measurements with high data sampling rates...
October 17, 2017: Microscopy and Microanalysis
Daniel Hadraba, Jiri Janacek, Eva Filova, Frantisek Lopot, Rik Paesen, Ondrej Fanta, Anneliese Jarman, Alois Necas, Marcel Ameloot, Karel Jelen
Fibrillar collagen in tendons and its natural development in rabbits are discussed in this paper. Achilles tendons from newborn (~7 days) to elderly (~38 months) rabbits were monitored in intact (n tendons=24) and microtome sectioned (n tendons=11) states with label-free second harmonic generation microscopy. After sectioning, the collagen fiber pattern was irregular for the younger animals and remained oriented parallel to the load axis of the tendon for the older animals. In contrast, the collagen fiber pattern in the intact samples followed the load axis for all the age groups...
October 2017: Microscopy and Microanalysis
Igor Pantic, Jovana Paunovic, Danijela Vucevic, Tatjana Radosavljevic, Stefan Dugalic, Anita Petkovic, Sanja Radojevic-Skodric, Senka Pantic
Although there are numerous recent works focusing on fractal properties of DNA and chromatin, many issues regarding changes in chromatin fractality during physiological aging remain unclear. In this study, we present results indicating that in mice, there is an age-related reduction of chromatin fractal complexity in a population of spleen follicular cells (SFCs). Spleen tissue was obtained from 16 mice and fixated in Carnoy solution. The youngest animal was newborn, and each animal was exactly 1 month older than the previous...
October 2017: Microscopy and Microanalysis
Kevin P Bohannon, Ronald W Holz, Daniel Axelrod
The refractive index in the interior of single cells affects the evanescent field depth in quantitative studies using total internal reflection (TIR) fluorescence, but often that index is not well known. We here present method to measure and spatially map the absolute index of refraction in a microscopic sample, by imaging a collimated light beam reflected from the substrate/buffer/cell interference at variable angles of incidence. Above the TIR critical angle (which is a strong function of refractive index), the reflection is 100%, but in the immediate sub-critical angle zone, the reflection intensity is a very strong ascending function of incidence angle...
October 2017: Microscopy and Microanalysis
Vipin N Tondare, John S Villarrubia, András E Vlada R
Three-dimensional (3D) reconstruction of a sample surface from scanning electron microscope (SEM) images taken at two perspectives has been known for decades. Nowadays, there exist several commercially available stereophotogrammetry software packages. For testing these software packages, in this study we used Monte Carlo simulated SEM images of virtual samples. A virtual sample is a model in a computer, and its true dimensions are known exactly, which is impossible for real SEM samples due to measurement uncertainty...
October 2017: Microscopy and Microanalysis
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