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Wu X.,NRC Institute for Microstructural Sciences | Robertson M.D.,Acadia University | Kawasaki M.,JEOL United States | Baribeau J.-M.,NRC Institute for Microstructural Sciences
Ultramicroscopy | Year: 2012

The effects of specimen tilt and probe convergence angle on annular dark field (ADF) image contrast of Si 0.8Ge 0.2 heteroepitaxial strained layers on (100) Si were investigated in a 200kV scanning transmission electron microscope (STEM) for a TEM specimen thickness of 195nm. With 0.5 degrees of specimen tilt away from the exact 〈011〉 zone-axis orientation, the signal-to-noise level of atomic columns was significantly reduced for both Si 0.8Ge 0.2 and Si in high resolution ADF-STEM lattice images. When the specimen was tilted 0.5 degrees around the 〈011〉 axis, or the STEM probe convergence semiangle was reduced from 14.3 to 3.6mrad, the ADF-STEM image intensity profiles across the Si 0.8Ge 0.2 and Si layers changed significantly as compared to those obtained at the exact 〈011〉 zone axis orientation, and no longer reflected the composition changes occurring across the layer structure. Multislice image simulation results revealed that the misfit strain between the Si 0.8Ge 0.2 and Si layers, and strain relaxation near the surface of the TEM specimen, were responsible for the observed changes in image intensity. © 2012. Source

Taber B.,Agilent Technologies | Zens A.,JEOL United States
Journal of Magnetic Resonance | Year: 2015

We report in this paper an analysis of double-tuned 1H/2H circuits that are capacitively or inductively matched to 50 Ω ports. In this analysis we use a novel new parameter called the circuit fill factor (CFF). It provides a means of characterizing the performance degradation associated with additional inductors in the circuit in addition to circuit losses. This parameter allows for quick and insightful analysis of multiple tuned circuits for efficiency. It is also shown that magnetically coupled double-tuned circuits are less prone to unwanted spurious resonances due to their general symmetry which eliminates multiple ground paths in the circuit. ©2015 Elsavier inc.All right reserved. Source

Fraser D.,Lourdes University | Deroo C.S.,Detroit Institute of Arts | Cody R.B.,JEOL United States | Armitage R.A.,Eastern Michigan University
Analyst | Year: 2013

Prior to exhibiting an African Komo mask from the collections of the Detroit Institute of Arts, a multianalytical approach was undertaken to characterize the flaking encrusted coating on the surface of the mask. Preliminary XRF and FTIR examination of the coating on the Komo mask revealed the presence of significant quantities of iron and protein, possibly indicating the presence of blood. Raman spectroscopy showed evidence for the porphyrin structure of haem as well. To confirm that blood was indeed present in the coating, we developed a novel method for identifying the haem moiety from blood by use of in situ methylation and direct analysis in real time mass spectrometry (DART-MS). Following a denaturing step with formic acid, the resulting solution was combined with an excess of phenyltrimethylammonium hydroxide to promote desorption, applied to a melting point tube, and placed into the direct analysis in real time ion source gas stream at 550 °C. The permethylated haem ion (m/z 644.208) from myoglobin, haemoglobin, fresh blood, and blood aged in the laboratory for 10 years was readily observed above the background. By the described DART-TOF-MS method, permethylated haem was positively identified in the mask coating, confirming the presence of blood. This method has obvious utility in forensic science beyond that for identifying blood incorporated in cultural heritage materials. © 2013 The Royal Society of Chemistry. Source

Shimma S.,National Cancer Center | Miki S.,MSI Inc | Cody R.B.,JEOL United States | Toyoda M.,Osaka University
Comprehensive Analytical Chemistry | Year: 2013

We have proposed the novel analytical concept of "precision on-site mass spectrometry," especially in the environmental studies arena. The high-quality analytical data produced using these novel miniaturized mass spectrometers provide reliable results only previously available with large research grade instrumentation. In order to realize this concept, we developed an ultra-high mass resolution miniaturized time-of-flight mass spectrometer henceforth referred to as "infiTOF." The high-resolution capability of infiTOF is due to its theoretical infinite flight path contained within a single closed flight orbit. Mass resolutions above 10,000 are easily achievable employing this portable system, making it comparable to magnetic sector mass spectrometers and large research grade TOF instruments. Taking into account this resolution capability, we thought it would be advantageous to conduct polychlorinated biphenyls (PCBs) analysis using fast gas chromatography/high-resolution mass spectrometry utilizing this system. In this chapter, the application of PCBs analyses using infiTOF is thoroughly described. In addition, the concept of on-site mass spectrometry, an overview of recent miniaturized mass spectrometers, and the performance evaluation of infiTOF are included. © 2013 Elsevier B.V. Source

Voorhees K.J.,Colorado School of Mines | Jensen K.R.,Colorado School of Mines | McAlpin C.R.,Colorado School of Mines | Rees J.C.,Centers for Disease Control | And 3 more authors.
Journal of Mass Spectrometry | Year: 2013

Bacterial fatty acid profiling is a well-established technique for bacterial identification. Ten bacteria were analyzed using both positive- and negative-ion modes with a modified matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) approach using CaO as a matrix replacement (metal oxide laser ionization MS (MOLI MS)). The results show that reproducible lipid cleavage similar to thermal in situ tetramethyl ammonium hydroxide saponification/derivatization had occurred. Principal component analysis showed that replicates from each organism grouped in a unique space. Cross validation (CV) of spectra from both ionization modes resulted in greater than 94% validation of the data. When CV results were compared for the two ionization modes, negative-ion data produced a superior outcome. MOLI MS provides clinicians a rapid, reproducible and cost-effective bacterial diagnostic tool. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd. Source

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