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Microscopy and Microanalysis

Andreas Stoffers, Juri Barthel, Christian H Liebscher, Baptiste Gault, Oana Cojocaru-Mirédin, Christina Scheu, Dierk Raabe
In the course of a thorough investigation of the performance-structure-chemistry interdependency at silicon grain boundaries, we successfully developed a method to systematically correlate aberration-corrected scanning transmission electron microscopy and atom probe tomography. The correlative approach is conducted on individual APT and TEM specimens, with the option to perform both investigations on the same specimen in the future. In the present case of a Σ9 grain boundary, joint mapping of the atomistic details of the grain boundary topology, in conjunction with chemical decoration, enables a deeper understanding of the segregation of impurities observed at such grain boundaries...
February 20, 2017: Microscopy and Microanalysis
Chang-Min Kwak, Young-Tae Kim, Chan-Gyung Park, Jae-Bok Seol
Two challenges exist in laser-assisted atom probe tomography (APT). First, a drastic decline in mass-resolving power is caused, not only by laser-induced thermal effects on the APT tips of bulk oxide materials, but also the associated asymmetric evaporation behavior; second, the field evaporation mechanisms of bulk oxide tips under laser illumination are still unclear due to the complex relations between laser pulse and oxide materials. In this study, both phenomena were investigated by depositing Ni- and Co-capping layers onto the bulk LaAlO3 tips, and using stepwise APT analysis with transmission electron microscopy (TEM) observation of the tip shapes...
February 20, 2017: Microscopy and Microanalysis
Lu Zhao, Antoine Normand, Jonathan Houard, Ivan Blum, Fabien Delaroche, Olivier Latry, Blaise Ravelo, Francois Vurpillot
Atom probe has been developed for investigating materials at the atomic scale and in three dimensions by using either high-voltage (HV) pulses or laser pulses to trigger the field evaporation of surface atoms. In this paper, we propose an atom probe setup with pulsed evaporation achieved by simultaneous application of both methods. This provides a simple way to improve mass resolution without degrading the intrinsic spatial resolution of the instrument. The basic principle of this setup is the combination of both modes, but with a precise control of the delay (at a femtosecond timescale) between voltage and laser pulses...
February 8, 2017: Microscopy and Microanalysis
Ida G Fostad, Jon R Eidet, Neil S Lagali, Darlene A Dartt, Sten Ræder, Edvard B Messelt, Tor P Utheim
The purpose of this work was to determine whether the morphology of the oral mucosa epithelium (OME) of patients with xerostomia differ from patients without xerostomia. In total, 34 patients with dry eye disease (DED) with or without xerostomia were examined at The Norwegian Dry Eye Disease Clinic with in vivo confocal microscopy of the lower lip. In addition, age- and gender-matched healthy controls (HC) were included. DED patients with xerostomia had a higher superficial to deep backscatter ratio compared with DED patients without xerostomia (p=0...
February 6, 2017: Microscopy and Microanalysis
Saransh Singh, Marc De Graef
The dictionary-based approach to the indexing of diffraction patterns is applied to electron channeling patterns (ECPs). The main ingredients of the dictionary method are introduced, including the generalized forward projector (GFP), the relevant detector model, and a scheme to uniformly sample orientation space using the "cubochoric" representation. The GFP is used to compute an ECP "master" pattern. Derivative free optimization algorithms, including the Nelder-Mead simplex and the bound optimization by quadratic approximation are used to determine the correct detector parameters and to refine the orientation obtained from the dictionary approach...
February 6, 2017: Microscopy and Microanalysis
Jing Guo, Kyung-Tae Shin, Xiang-Shun Cui
Cyclin E1 (CCNE1) is a core component of cell cycle regulation that drives the transition into the S phase. CCNE1 plays critical roles in cell cycle, cell proliferation, and cellular functions. However, the function of CCNE1 in early embryonic development is limited. In the present study, the function and expression of Ccne1 in porcine early parthenotes were examined. Immunostaining experiments showed that CCNE1 localized in the nucleus, starting at the four-cell stage. Knockdown of Ccne1 by double-stranded RNA resulted in the failure of blastocyst formation and induced blastocyst apoptosis...
February 6, 2017: Microscopy and Microanalysis
Ty J Prosa, David J Larson
Approximately 30 years after the first use of focused ion beam (FIB) instruments to prepare atom probe tomography specimens, this technique has grown to be used by hundreds of researchers around the world. This past decade has seen tremendous advances in atom probe applications, enabled by the continued development of FIB-based specimen preparation methodologies. In this work, we provide a short review of the origin of the FIB method and the standard methods used today for lift-out and sharpening, using the annular milling method as applied to atom probe tomography specimens...
February 6, 2017: Microscopy and Microanalysis
Manuel Toledano, Raquel Osorio, Inmaculada Cabello, Estrella Osorio, Manuel Toledano-Osorio, Fátima S Aguilera
The aim of this study was to investigate if load cycling affects interfacial integrity of glass ionomer cements bonded to sound- or caries-affected dentin. A conventional glass ionomer, Ketac Bond, and a resin-modified glass ionomer (Vitrebond Plus), were applied to dentin. Half of the specimens were load cycled. The interfaces were submitted to dye-assisted confocal microscopy evaluation. The unloaded specimens of sound and carious dentin were deficiently hybridized when Ketac Bond was used. Ketac Bond samples showed an absorption layer and an adhesive layer that were scarcely affected by fluorescein penetration (nanoleakage), in sound dentin...
February 2, 2017: Microscopy and Microanalysis
Frédéric De Geuser, Baptiste Gault
There are two main projections used to transform, and reconstruct, field ion micrographs or atom probe tomography data into atomic coordinates at the specimen surface and, subsequently, in three dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison with the more widely used and well-established point projection (or pseudo-stereographic projection), which underpins data reconstruction in most software packages currently in use across the community...
February 2, 2017: Microscopy and Microanalysis
Emmanuel Denimal, Ambroise Marin, Stéphane Guyot, Ludovic Journaux, Paul Molin
We present a computational method for pseudo-circular object detection and quantitative characterization in digital images, using the gradient accumulation matrix as a basic tool. This Gradient Accumulation Transform (GAT) was first introduced in 1992 by Kierkegaard and recently used by Kaytanli & Valentine. In the present article, we modify the approach by using the phase coding studied by Cicconet, and by adding a "local contributor list" (LCL) as well as a "used contributor matrix" (UCM), which allow for accurate peak detection and exploitation...
February 1, 2017: Microscopy and Microanalysis
Stephanie Besztejan, Sercan Keskin, Stephanie Manz, Günther Kassier, Robert Bücker, Deybith Venegas-Rojas, Hoc K Trieu, Andrea Rentmeister, R J Dwayne Miller
We present liquid-cell transmission electron microscopy (liquid-cell TEM) imaging of fixed and non-fixed prostate cancer cells (PC3 and LNCaP) with high resolution in a custom developed silicon nitride liquid cell. Fixed PC3 cells were imaged for 90-120 min without any discernable damage. High contrast on the cellular structures was obtained even at low electron doses (~2.5 e-/nm2 per image). The images show distinct structures of cell compartments (nuclei and nucleoli) and cell boundaries without any further sample embedding, dehydration, or staining...
January 31, 2017: Microscopy and Microanalysis
Stella Pedrazzini, Andrew J London, Baptiste Gault, David Saxey, Susannah Speller, Chris R M Grovenor, Mohsen Danaie, Michael P Moody, Philip D Edmondson, Paul A J Bagot
The functional properties of the high-temperature superconductor Y1Ba2Cu3O7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y7.7Ba15.3Cu23O54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques...
January 31, 2017: Microscopy and Microanalysis
Björn Pfeiffer, Johannes Maier, Jonas Arlt, Carsten Nowak
Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe...
January 30, 2017: Microscopy and Microanalysis
Alexandre La Fontaine, Sandra Piazolo, Patrick Trimby, Limei Yang, Julie M Cairney
The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole...
January 30, 2017: Microscopy and Microanalysis
Jonathan M Hyde, Gérald DaCosta, Constantinos Hatzoglou, Hannah Weekes, Bertrand Radiguet, Paul D Styman, Francois Vurpillot, Cristelle Pareige, Auriane Etienne, Giovanni Bonny, Nicolas Castin, Lorenzo Malerba, Philippe Pareige
Irradiation of reactor pressure vessel (RPV) steels causes the formation of nanoscale microstructural features (termed radiation damage), which affect the mechanical properties of the vessel. A key tool for characterizing these nanoscale features is atom probe tomography (APT), due to its high spatial resolution and the ability to identify different chemical species in three dimensions. Microstructural observations using APT can underpin development of a mechanistic understanding of defect formation. However, with atom probe analyses there are currently multiple methods for analyzing the data...
January 30, 2017: Microscopy and Microanalysis
Daniel Haley, Paul A J Bagot, Michael P Moody
In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium...
January 30, 2017: Microscopy and Microanalysis
Gayle V Wall, Daria A Rutkowska, Eshchar Mizrachi, Henk Huismans, Vida van Staden
The bulk of the major core protein VP7 in African horse sickness virus (AHSV) self-assembles into flat, hexagonal crystalline particles in a process appearing unrelated to viral replication. Why this unique characteristic of AHSV VP7 is genetically conserved, and whether VP7 aggregation and particle formation have an effect on cellular biology or the viral life cycle, is unknown. Here we investigated how different small peptide and enhanced green fluorescent protein (eGFP) insertions into the VP7 top domain affected VP7 localization, aggregation, and particle formation...
January 23, 2017: Microscopy and Microanalysis
Zirong Peng, Pyuck-Pa Choi, Baptiste Gault, Dierk Raabe
Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition...
January 17, 2017: Microscopy and Microanalysis
Johannes Mielke, Pavla Dohányosová, Philipp Müller, Silvia López-Vidal, Vasile-Dan Hodoroaba
The potential of electrospray deposition, for the controlled preparation of particles for imaging in electron microscopes, is evaluated on various materials: from mono-modal suspensions of spherical particles to multimodal suspensions and to real-world industrial materials. It is shown that agglomeration is reduced substantially on the sample carrier, compared with conventional sample preparation techniques. For the first time, it is possible to assess the number concentration of a tri-modal polystyrene suspension by electron microscopy, due to the high deposition efficiency of the electrospray...
January 9, 2017: Microscopy and Microanalysis
Osamu Nishikawa, Masahiro Taniguchi
In 1994, a new type of atom probe instrument, named the scanning atom probe (SAP), was proposed. The unique feature of the SAP is the introduction of a small extraction electrode, which scans over a specimen surface and confines the high field, required for field evaporation of surface atoms in a small space, between the specimen and the electrode. Thus, the SAP does not require a sharp specimen tip. This indicates that the SAP can mass analyze the specimens which are difficult to form in a sharp tip, such as organic materials and biomolecules...
December 22, 2016: Microscopy and Microanalysis
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