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Microscopy and Microanalysis

Jingxu Zheng, Zhongyuan Luo, Lida Tan, Bin Chen
In the present study, nano-sized cuboid-shaped particles in Mg-Nd-Y are studied by means of Cs-corrected atomic-scale high-angle annular dark-field scanning transmission electron microscopy. The structure of the cuboid-shaped phase is identified to be yttrium (major component) and neodymium atoms in face-centered cubic arrangement without the participation of Mg. The lattice parameter a=5.15 Å. During isothermal aging at 225°C, Mg3(Nd,Y) precipitates adhere to surface (100) planes of the cuboid-shaped particles with the orientation relationship: $[100]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[100]_{{{\rm Cuboid}}} $ and $[310]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[012]_{{{\rm Cuboid}}} $ ...
November 30, 2016: Microscopy and Microanalysis
Dingrong Yi, Linghua Kong, Ranjith K Kankala, Zi Wang
There is an unmet need for researchers in life sciences and clinical pathology to obtain untainted target cells with very high accuracy, which are suitable for subsequent genome and protein analysis. In this paper, an electrostatic capture laser microdissection technology (ECM) is proposed and explained. Following microscopic identification and separation of target cells from the surrounding tissues using laser cutting, the ECM uses electrostatic forces to capture target cells. Validation experiments indicate that ECM can capture a wide assortment of contamination-free homogeneous samples, ranging from very tiny pieces of a few micrometers in diameter to large pieces with a surface area of over 40,000 µm2...
November 28, 2016: Microscopy and Microanalysis
Vladimir P Oleshko, Andrew A Herzing, Christopher L Soles, Jared J Griebel, Woo J Chung, Adam G Simmonds, Jeffrey Pyun
Poly[sulfur-random-(1,3-diisopropenylbenzene)] copolymers synthesized via inverse vulcanization represent an emerging class of electrochemically active polymers recently used in cathodes for Li-S batteries, capable of realizing enhanced capacity retention (1,005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. The composite cathodes are organized in complex hierarchical three-dimensional (3D) architectures, which contain several components and are challenging to understand and characterize using any single technique...
November 24, 2016: Microscopy and Microanalysis
Michael Marko, Chyongere Hsieh, Eric Leith, David Mastronarde, Sohei Motoki
Phase plate (PP) imaging has proven to be valuable in transmission cryo electron microscopy of unstained, native-state biological specimens. Many PP types have been described, however until the recent implementation of the "hole-free" phase plate (HFPP), imaging has been challenging. We found the HFPP to be simple to construct and to set up in the transmission electron microscopy, but care in implementing automated data collection is needed. Performance may be variable, both initially and over time, thus it is important to monitor and evaluate image quality by observing the power spectrum...
November 24, 2016: Microscopy and Microanalysis
Michael J Zachman, Emily Asenath-Smith, Lara A Estroff, Lena F Kourkoutis
Scanning transmission electron microscopy (STEM) allows atomic scale characterization of solid-solid interfaces, but has seen limited applications to solid-liquid interfaces due to the volatility of liquids in the microscope vacuum. Although cryo-electron microscopy is routinely used to characterize hydrated samples stabilized by rapid freezing, sample thinning is required to access the internal interfaces of thicker specimens. Here, we adapt cryo-focused ion beam (FIB) "lift-out," a technique recently developed for biological specimens, to prepare intact internal solid-liquid interfaces for high-resolution structural and chemical analysis by cryo-STEM...
November 21, 2016: Microscopy and Microanalysis
Maria J Pereira, Joao S Amaral, Nuno J O Silva, Vitor S Amaral
Determining and acting on thermo-physical properties at the nanoscale is essential for understanding/managing heat distribution in micro/nanostructured materials and miniaturized devices. Adequate thermal nano-characterization techniques are required to address thermal issues compromising device performance. Scanning thermal microscopy (SThM) is a probing and acting technique based on atomic force microscopy using a nano-probe designed to act as a thermometer and resistive heater, achieving high spatial resolution...
November 21, 2016: Microscopy and Microanalysis
Maria Teresa Freire, António Santos Silva, Maria do Rosário Veiga, Jorge de Brito, Frank Schlütter
In this paper the characterization of a gypsum plaster sample from the end of the 19th century simulating imperial red porphyry using a multi-analytical approach is presented and discussed. The results of X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TGA-DTA), physical and mechanical properties are summarized. In order to have further insight into the microstructure, polarized light microscopy (PLM), scanning electron microscopy coupled with energy dispersive X-ray spectrometer (SEM-EDS), and micro Raman spectroscopy analyzes were also made...
November 21, 2016: Microscopy and Microanalysis
Amin Golpour, Martin Pšenička, Hamid Niksirat
Calcium regulates many intracellular events such as growth and differentiation during different stages of gamete development. The aim of this study was to localize and quantify the intracellular distribution of calcium during different developmental stages of spermatogenesis in sterlet, Acipenser ruthenus, using a combined oxalate-pyroantimonate technique. The distribution of calcium was described in spermatogonium, spermatocyte, spermatid, and spermatozoon stages. In the spermatogonium and spermatocyte, calcium deposits were mainly localized in the nucleus and cytoplasm...
November 21, 2016: Microscopy and Microanalysis
Igor Pantic, Dejan Nesic, Milos Basailovic, Mila Cetkovic, Sanja Mazic, Jelena Suzic-Lazic, Martin Popevic
Despite previous research efforts in the fields of histology and cell physiology, the relationship between chromatin structural organization and nuclear shape remains unclear. The aim of this research was to test the existence and strength of correlations between mathematical parameters of chromatin microarchitecture and roundness of the nuclear envelope. On a sample of 240 nuclei of adrenal zona fasciculata cells stained using the DNA-specific Feulgen method, we quantified fractal parameters such as fractal dimension and lacunarity, as well as textural parameters such as angular second moment (ASM), entropy, inverse difference moment, contrast, and variance...
November 8, 2016: Microscopy and Microanalysis
Noureddine Hadji
When the value of the dispersion coefficient is "greatly different from 0.5," as is the case for "free-electron" materials such as sodium (Na), the approximate expression for the volume plasmon critical wave vector (PCV) used by Hadji stops being valid and a different, more precise, expression must be used. Here a more accurate PCV formula is used to get a more accurate expression for plasmon scattering cross-section per atom (PSCA) species. This PSCA is then employed to calculate some physical quantities for several "free-electron" materials and together with the techniques from the quoted paper to determine values for physical quantities from amorphous silicon (a-Si) experimental data...
November 8, 2016: Microscopy and Microanalysis
Xiang Li Zhong, Sibylle Schilling, Nestor J Zaluzec, M Grace Burke
In recent years, an increasing number of studies utilizing in situ liquid and/or gaseous cell scanning/transmission electron microscopy (S/TEM) have been reported. Because of the difficulty in the preparation of suitable specimens, these environmental S/TEM studies have been generally limited to studies of nanoscale structured materials such as nanoparticles, nanowires, or sputtered thin films. In this paper, we present two methodologies which have been developed to facilitate the preparation of electron-transparent samples from conventional bulk metals and alloys for in situ liquid/gaseous cell S/TEM experiments...
November 7, 2016: Microscopy and Microanalysis
Ruo-Xi Zhang, Shui-Yuan Yang
In electron probe microanalysis where materials are coated with a thin conductive carbon coat before analysis, the X-ray intensity detected from a specimen may be affected to various degrees by the thickness of the carbon coating. Differences in the carbon film thickness between specimens and standards may lead to errors in analytical results, particular for lower energy X-rays. In this study, we demonstrate that the location and the distance of the specimen relative to the carbon tip in the coating chamber can affect the thickness of the carbon film produced on the specimen surface during carbon coating...
November 4, 2016: Microscopy and Microanalysis
Cristina Herrera, Nicholas J Mantis, Richard Cole
Retrograde transport is a process in which proteins are trafficked from the plasma membrane and endosomes to biosynthetic and secretory organelles, namely the Golgi apparatus and endoplasmic reticulum (ER). A number of plant and bacterial toxins, including cholera toxin and ricin toxin, exploit retrograde transport to gain entry into host cells, although the specifics of this process have remained difficult to probe by laser scanning confocal microscopy (LSCM). Here we demonstrate the use of super-resolution and live-cell imaging [stimulated emission depletion (STED)] to visualize exogenously applied ricin toxin within the ER...
November 2, 2016: Microscopy and Microanalysis
Victor Volkov, Carole C Perry
The article explores the theory of infrared-visible sum frequency generation microscopy of phospholipid envelopes with dimensions larger than the wavelength of the nonlinear emission. The main part of the study concerns derivation and accounting for the contributions of effective nonlinear responses specific to sites on the surfaces of a bilayer envelope and their dependence on polarization condition and experimental geometry. The nonlinear responses of sites are mapped onto the image plane according to their emission directions and the numerical aperture of a sampling microscope objective...
October 27, 2016: Microscopy and Microanalysis
Xavier Llovet, Philippe T Pinard, Erkki Heikinheimo, Seppo Louhenkilpi, Silvia Richter
We report electron probe microanalysis measurements on nickel silicides, Ni5Si2, Ni2Si, Ni3Si2, and NiSi, which were done in order to investigate anomalies that affect the analysis of such materials by using the Ni L3-M4,5 line (Lα). Possible sources of systematic discrepancies between experimental data and theoretical predictions of Ni L3-M4,5 k-ratios are examined, and special attention is paid to dependence of the Ni L3-M4,5 k-ratios on mass-attenuation coefficients and partial fluorescence yields. Self-absorption X-ray spectra and empirical mass-attenuation coefficients were obtained for the considered materials from X-ray emission spectra and relative X-ray intensity measurements, respectively...
October 26, 2016: Microscopy and Microanalysis
Palena A Pinto, Guillaume Colas, Tobin Filleter, Grace M De Souza
Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) is a ceramic material used in indirect dental restorations. However, phase transformation at body temperature may compromise the material's mechanical properties, affecting the clinical performance of the restoration. The effect of mastication on 3Y-TZP aging has not been investigated. 3Y-TZP specimens (IPS E-max ZirCAD and Z5) were aged in three different modes (n=13): no aging (control), hydrothermal aging (HA), or chewing simulation (CS). Mechanical properties and surface topography were analyzed...
October 26, 2016: Microscopy and Microanalysis
Mathias Procop, Vasile-Dan Hodoroaba, Ralf Terborg, Dirk Berger
A method is proposed to determine the effective detector area for energy-dispersive X-ray spectrometers (EDS). Nowadays, detectors are available for a wide range of nominal areas ranging from 10 up to 150 mm2. However, it remains in most cases unknown whether this nominal area coincides with the "net active sensor area" that should be given according to the related standard ISO 15632, or with any other area of the detector device. Moreover, the specific geometry of EDS installation may further reduce a given detector area...
October 25, 2016: Microscopy and Microanalysis
Shiladitya Chatterjee, George H Major, Barry M Lunt, Massoud Kaykhaii, Matthew R Linford
Resist lithography is an important microfabrication technique in the electronics industry. In this, patterns are transferred by irradiation onto a photosensitive polymer. SU-8 has emerged as a favorite photoresist for High Aspect Ratio (HAR) lithography, showing high chemical and mechanical stability and biocompatibility. Unfortunately, its poor adhesion to substrates is a drawback, with possible solutions being the use of low-viscosity SU-8, surface modification with a low molecular weight adsorbate like hexamethyldisilazane (HMDS), or a commercial adhesion promotion reagent...
October 17, 2016: Microscopy and Microanalysis
David R Diercks, Brian P Gorman, Johannes J L Mulders
Six precursors were evaluated for use as in situ electron beam-induced deposition capping layers in the preparation of atom probe tomography specimens with a focus on near-surface features where some of the deposition is retained at the specimen apex. Specimens were prepared by deposition of each precursor onto silicon posts and shaped into sub-70-nm radii needles using a focused ion beam. The utility of the depositions was assessed using several criteria including composition and uniformity, evaporation behavior and evaporation fields, and depth of Ga+ ion penetration...
October 17, 2016: Microscopy and Microanalysis
Ben Buse, Stuart Kearns, Charles Clapham, Donovan Hawley
A prototype Peltier thermoelectric cooling unit has been constructed to cool a cold finger on an electron microprobe. The Peltier unit was tested at 15 and 96 W, achieving cold finger temperatures of -10 and -27°C, respectively. The Peltier unit did not adversely affect the analytical stability of the instrument. Heat conduction between the Peltier unit mounted outside the vacuum and the cold finger was found to be very efficient. Under Peltier cooling, the vacuum improvement associated with water vapor deposition was not achieved; this has the advantage of avoiding severe degradation of the vacuum observed when warming up a cold finger from liquid nitrogen (LN2) temperatures...
October 5, 2016: Microscopy and Microanalysis
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