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Microscopy and Microanalysis

Yue Li, Di Zhang, Ilker Capoglu, Karl A Hujsak, Dhwanil Damania, Lusik Cherkezyan, Eric Roth, Reiner Bleher, Jinsong S Wu, Hariharan Subramanian, Vinayak P Dravid, Vadim Backman
Essentially all biological processes are highly dependent on the nanoscale architecture of the cellular components where these processes take place. Statistical measures, such as the autocorrelation function (ACF) of the three-dimensional (3D) mass-density distribution, are widely used to characterize cellular nanostructure. However, conventional methods of reconstruction of the deterministic 3D mass-density distribution, from which these statistical measures can be calculated, have been inadequate for thick biological structures, such as whole cells, due to the conflict between the need for nanoscale resolution and its inverse relationship with thickness after conventional tomographic reconstruction...
April 18, 2017: Microscopy and Microanalysis
Takuya Nakashima, Hiroyuki Suhara, Hidekazu Murata, Hiroshi Shimoyama
High-quality color output from digital photocopiers and laser printers is in strong demand, motivating attempts to achieve fine dot reproducibility and stability. The resolution of a digital photocopier depends on the charge density distribution on the organic photoconductor surface; however, directly measuring the charge density distribution is impossible. In this study, we propose a new electron optical instrument that can rapidly measure the electrostatic latent image on an organic photoconductor surface, which is a dielectric surface, as well as a novel method to quantitatively estimate the charge density distribution on a dielectric surface by combining experimental data obtained from the apparatus via a computer simulation...
April 12, 2017: Microscopy and Microanalysis
Steven R Spurgeon, Yingge Du, Scott A Chambers
With the development of affordable aberration correctors, analytical scanning transmission electron microscopy (STEM) studies of complex interfaces can now be conducted at high spatial resolution at laboratories worldwide. Energy-dispersive X-ray spectroscopy (EDS) in particular has grown in popularity, as it enables elemental mapping over a wide range of ionization energies. However, the interpretation of atomically resolved data is greatly complicated by beam-sample interactions that are often overlooked by novice users...
April 5, 2017: Microscopy and Microanalysis
Sina Baier, Christian D Damsgaard, Michael Klumpp, Juliane Reinhardt, Thomas Sheppard, Zoltan Balogh, Takeshi Kasama, Federico Benzi, Jakob B Wagner, Wilhelm Schwieger, Christian G Schroer, Jan-Dierk Grunwaldt
When using bifunctional core@shell catalysts, the stability of both the shell and core-shell interface is crucial for catalytic applications. In the present study, we elucidate the stability of a CuO/ZnO/Al2O3@ZSM-5 core@shell material, used for one-stage synthesis of dimethyl ether from synthesis gas. The catalyst stability was studied in a hierarchical manner by complementary environmental transmission electron microscopy (ETEM), scanning electron microscopy (SEM) and in situ hard X-ray ptychography with a specially designed in situ cell...
April 5, 2017: Microscopy and Microanalysis
Yuncheng Du, Hector M Budman, Thomas A Duever
Accurate and fast quantitative analysis of living cells from fluorescence microscopy images is useful for evaluating experimental outcomes and cell culture protocols. An algorithm is developed in this work to automatically segment and distinguish apoptotic cells from normal cells. The algorithm involves three steps consisting of two segmentation steps and a classification step. The segmentation steps are: (i) a coarse segmentation, combining a range filter with a marching square method, is used as a prefiltering step to provide the approximate positions of cells within a two-dimensional matrix used to store cells' images and the count of the number of cells for a given image; and (ii) a fine segmentation step using the Active Contours Without Edges method is applied to the boundaries of cells identified in the coarse segmentation step...
April 3, 2017: Microscopy and Microanalysis
Ilka Sötje, Tamar Dishon, Frank Hoffmann, Sabine Holst
Statoliths are the only hard structures in the gelatinous bell of most scyphozoan medusae and investigations on these structures could promote investigations of the understudied population dynamics and phylogeny of jellyfish. We examined the statoliths of Aurelia aurita jellyfish of different ages by light microscopic and microtomographic measurements supplemented by scanning electron microscopy. The morphometric analyses confirmed that statolith numbers and sizes increase during jellyfish development and revealed that newly-formed statoliths had similar shapes that may change during statolith growth...
March 27, 2017: Microscopy and Microanalysis
Francois Vurpillot, Frédéric Danoix, Matthieu Gilbert, Sebastian Koelling, Michal Dagan, David N Seidman
This article reviews recent advances utilizing field-ion microscopy (FIM) to extract atomic-scale three-dimensional images of materials. This capability is not new, as the first atomic-scale reconstructions of features utilizing FIM were demonstrated decades ago. The rise of atom probe tomography, and the application of this latter technique in place of FIM has unfortunately severely limited further FIM development. Currently, the ubiquitous availability of extensive computing power makes it possible to treat and reconstruct FIM data digitally and this development allows the image sequences obtained utilizing FIM to be extremely valuable for many material science and engineering applications...
March 24, 2017: Microscopy and Microanalysis
Nicolas Rolland, François Vurpillot, Sébastien Duguay, Baishakhi Mazumder, James S Speck, Didier Blavette
Accuracy of atom probe tomography measurements is strongly degraded by the presence of phases that have different evaporation fields. In particular, when there are perpendicular interfaces to the tip axis in the specimen, layers thicknesses are systematically biased and the resolution is degraded near the interfaces. Based on an analytical model of field evaporated emitter end-form, a new algorithm dedicated to the 3D reconstruction of multilayered samples was developed. Simulations of field evaporation of bilayer were performed to evaluate the effectiveness of the new algorithm...
March 22, 2017: Microscopy and Microanalysis
Brian Langelier, Hugo P Van Landeghem, Gianluigi A Botton, Hatem S Zurob
Improved understanding of the interactions between solutes and the austenite/ferrite interface can benefit modeling of ferrite growth during austenite decomposition, as the transformation kinetic is significantly affected by solutes that influence interface mobility. Solute-interface interactions dominate solute segregation at the interface in binary systems, but in multi-component alloys, solute-solute interactions may also affect segregation. In this study, interface segregation in Fe-Mn-N is examined and compared with Fe-Mn-C, to reveal the extent to which C affects the segregation of Mn...
March 21, 2017: Microscopy and Microanalysis
Qin Shen, Hao Chen, Wenqing Liu
The microstructural evolution of precipitation in two model alloys, Fe-NiAl and Fe-NiAl-Cu, was investigated during aging at 500°C for different times using atom probe tomography (APT). The APT results reveal that the addition of Cu effectively increases the number density of NiAl precipitates. This is attributed to Cu promoting the nucleation of NiAl particles by increasing the chemical driving force and decreasing the interfacial energy. The NiAl precipitates of the Fe-NiAl-Cu alloy grow and coarsen at a slower rate than that of the Fe-NiAl alloy, mainly due to the slower diffusion rate of the Cu atoms...
March 21, 2017: Microscopy and Microanalysis
Kristina Lindgren, Krystyna Stiller, Pål Efsing, Mattias Thuvander
Radiation induced clustering affects the mechanical properties, that is the ductile to brittle transition temperature (DBTT), of reactor pressure vessel (RPV) steel of nuclear power plants. The combination of low Cu and high Ni used in some RPV welds is known to further enhance the DBTT shift during long time operation. In this study, RPV weld samples containing 0.04 at% Cu and 1.6 at% Ni were irradiated to 2.0 and 6.4×1023 n/m2 in the Halden test reactor. Atom probe tomography (APT) was applied to study clustering of Ni, Mn, Si, and Cu...
March 21, 2017: Microscopy and Microanalysis
Samuel D Keyes, Neil J Gostling, Jessica H Cheung, Tiina Roose, Ian Sinclair, Alan Marchant
The use of in vivo X-ray microcomputed tomography (μCT) to study plant root systems has become routine, but is often hampered by poor contrast between roots, soil, soil water, and soil organic matter. In clinical radiology, imaging of poorly contrasting regions is frequently aided by the use of radio-opaque contrast media. In this study, we present evidence for the utility of iodinated contrast media (ICM) in the study of plant root systems using μCT. Different dilutions of an ionic and nonionic ICM (Gastrografin 370 and Niopam 300) were perfused into the aerial vasculature of juvenile pea plants via a leaf flap (Pisum sativum)...
March 21, 2017: Microscopy and Microanalysis
Michal Dagan, Baptiste Gault, George D W Smith, Paul A J Bagot, Michael P Moody
An automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes individual atoms on the specimen's surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM's potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms...
March 20, 2017: Microscopy and Microanalysis
Masoud Rashidi, Hans-Olof Andrén, Fang Liu
In creep resistant Z-phase strengthened 12% Cr steels, MX (M=Nb, Ta, or V, and X=C and/or N) to Z-phase (CrMN, M=Ta, Nb, or V) transformation plays an important role in achieving a fine distribution of Z-phase precipitates for creep strengthening. Atom probe tomography was employed to investigate the phase transformation in a Nb-based Z-phase strengthened trial steel. Using iso-concentration surfaces with different concentration values, and subtracting the matrix contribution enabled us to reveal the core-shell structure of the transient precipitates between MX and Z-phase...
March 20, 2017: Microscopy and Microanalysis
Torben Boll, Kinga A Unocic, Bruce A Pint, Krystyna Stiller
This study applies atom probe tomography (APT) to analyze the oxide scales formed on model NiAlCr alloys doped with Hf, Y, Ti, and B. Due to its ability to measure small amounts of alloying elements in the oxide matrix and its ability to quantify segregation, the technique offers a possibility for detailed studies of the dopant's fate during high-temperature oxidation. Three model NiAlCr alloys with different additions of Hf, Y, Ti, and B were prepared and oxidized in O2 at 1,100°C for 100 h. All specimens showed an outer region consisting of different spinel oxides with relatively small grains and the protective Al2O3-oxide layer below...
March 20, 2017: Microscopy and Microanalysis
Kezhi Ren, Xiaohua Tan, Heyun Li, Hui Xu, Ke Han
We study the effects of Dy, Nb, and Ga additions on the microstructure and magnetic properties of Nd2Fe14B/α-Fe nanocomposites. Dy, Nb, and Ga additions inhibit the growth of the soft magnetic α-Fe phase. Dy and Nb additions are able to refine the microstructure, whereas Ga addition plays only a minor role in prohibiting crystal growth. The magnetic properties are sensitive to Dy, Nb, and Ga additions. The Dy-containing alloy enhances the intrinsic coercivity of 872 kA/m because Dy partially replaces Nd, forming (Nd, Dy)2Fe14B...
March 20, 2017: Microscopy and Microanalysis
Andrey Denisyuk, Tomáš Hrnčíř, Jozef Vincenc Oboňa, Sharang, Martin Petrenec, Jan Michalička
We report on the mitigation of curtaining artifacts during transmission electron microscopy (TEM) lamella preparation by means of a modified ion beam milling approach, which involves altering the incident angle of the Ga ions by rocking of the sample on a special stage. We applied this technique to TEM sample preparation of a state-of-the-art integrated circuit based on a 14-nm technology node. Site-specific lamellae with a thickness <15 nm were prepared by top-down Ga focused ion beam polishing through upper metal contacts...
March 20, 2017: Microscopy and Microanalysis
Zemin Wang, Xulei Fang, Hui Li, Wenqing Liu
The formation of copper-rich precipitates of 17-4 precipitate hardened stainless steel has been investigated, after tempering at 350-570°C for 4 h, by atom probe tomography (APT). The results reveal that the clusters, enriched only with Cu, were observed after tempering at 420°C. Segregation of Ni, Mn to the Cu-rich clusters took place at 450°C, contributing to the increased hardening. After tempering at 510°C, Ni and Mn were rejected from Cu-rich precipitates and accumulated at the precipitate/matrix interfaces...
March 16, 2017: Microscopy and Microanalysis
Andrew J London, Daniel Haley, Michael P Moody
Due to the intrinsic evaporation properties of the material studied, insufficient mass-resolving power and lack of knowledge of the kinetic energy of incident ions, peaks in the atom probe mass-to-charge spectrum can overlap and result in incorrect composition measurements. Contributions to these peak overlaps can be deconvoluted globally, by simply examining adjacent peaks combined with knowledge of natural isotopic abundances. However, this strategy does not account for the fact that the relative contributions to this convoluted signal can often vary significantly in different regions of the analysis volume; e...
March 16, 2017: Microscopy and Microanalysis
Lizhe Qin, Lanying Lin, Feng Fu, Mizi Fan
Emulsion polymer isocyanate (EPI) and urea-formaldehyde (UF) were selected as typical resin systems to investigate the microstructure of wood-adhesive interphases by fluorescence microscopy (FM) and confocal laser scanning microscopy (CLSM). Further, a quantitative micromechanical analysis of the interphases was conducted using nanoindentation. The FM results showed that the UF resin could penetrate the wood to a greater extent than the EPI resin, and that the average penetration depth for these two resin systems was higher in the case of latewood...
March 15, 2017: Microscopy and Microanalysis
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