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Sara Klee, Judith P Sinn, Aleah Holmes, Brian L Lehman, Teresa Krawczyk, Kari A Peter, Timothy W McNellis
Elongation factor P (EF-P) facilitates the translation of certain peptide motifs, including those with multiple proline residues. EF-P must be post-translationally modified for full functionality; in Enterobacteria this is accomplished by two enzymes, EpmA and EpmB, which catalyze the β-lysylation of EF-P at a conserved lysine position. Mutations to efp or its modifying enzymes produce pleiotropic phenotypes, including decreases in virulence, swimming motility, and extracellular polysaccharide production, as well as proteomic perturbations...
March 18, 2019: Journal of Bacteriology
Daoling Wang, Aiqin Sun
The fluorescence effect induced by Kβ photons is usually so small that it can be neglected. However, in the Fe-Mn system, omitting Kβ fluorescence correction will lead to the overestimation of the Mn content especially when Mn is the minor alloy element. In this study, the error in the Mn concentration induced by Kβ fluorescence was investigated by both Monte Carlo simulation, using the pyPENELOPE program, and systematic electron probe measurements on the Fe-0.53% Mn alloy standard by the aid of CalcZAF software...
March 14, 2019: Microscopy and Microanalysis
Julien M Allaz, Michael L Williams, Michael J Jercinovic, Karsten Goemann, John Donovan
Electron microprobe trace element analysis is a significant challenge. Due to the low net intensity of peak measurements, the accuracy and precision of such analyses relies critically on background measurements, and on the accuracy of any pertinent peak interference corrections. A linear regression between two points selected at appropriate background positions is a classical approach for electron probe microanalysis (EPMA). However, this approach neglects the accurate assessment of background curvature (exponential or polynomial), and the presence of background interferences, a hole in the background, or an absorption edge can dramatically affect the results if underestimated or ignored...
February 12, 2019: Microscopy and Microanalysis
Gaihua He, Yuping Duan, Lulu Song, Xuefeng Zhang
A facile and simple chemical route has been used to synthesize novel three-dimensional (3D) architectures of nickel-doped ε-MnO2 without the addition of any surfactant or organic template. Nickel salt is used directly as the reagent rather than as an additive to produce doped manganese dioxide, which is different from the overwhelming majority of previous synthetic methods for doped MnO2 for use as an electromagnetic wave absorption material. This method overcomes the shortcomings of the previously reported approaches of doping with a slight amount of metallic ion, which is sometimes hard to detect...
January 28, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
Kwangjae Park, Dasom Kim, Kyungju Kim, Seungchan Cho, Hansang Kwon
In this research, we successfully fabricate high-hardness and lightweight Al-Ti composites. Al-Ti composites powders with three compositions (Al-20, 50, and 80 vol.% Ti) are mixed using ball milling and subsequently subjected to spark plasma sintering (SPS). The microstructures and phases of the Al-Ti composites are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and field emission-electron probe microanalysis (FE-EPMA). These tests confirm the presence of several intermetallic compounds (ICs) (Al₃Ti, Al₅Ti₂, Al11 Ti₅) in the composites, and we are able to confirm that these ICs are produced by the reaction of Al and Ti during the SPS process...
January 21, 2019: Materials
Eleanor S Jennings, Jon Wade, Vera Laurenz, Sylvain Petitgirard
Metal-silicate partitioning studies performed in high-pressure, laser-heated diamond anvil cells (DAC) are commonly used to explore element distribution during planetary-scale core-mantle differentiation. The small run-products contain suitable areas for analysis commonly less than tens of microns in diameter and a few microns thick. Because high spatial resolution is required, quantitative chemical analyses of the quenched phases is usually performed by electron probe microanalysis (EPMA). Here, EPMA is being used at its spatial limits, and sample thickness and secondary fluorescence effects must be accounted for...
January 22, 2019: Microscopy and Microanalysis
Baoyu Geng, Rongfeng Zhou, Lu Li, Haiyang Lv, Yongkun Li, Dan Bai, Yehua Jiang
In this work, an electric current pulse (ECP) of 500A was applied on a hypereutectic high chromium cast iron (HHCCI) melt before it began to solidify, and the effect of ECP on primary carbides was investigated. The characteristics of the primary carbides were analyzed by X-ray diffraction (XRD), electron probe micro-analyzer (EPMA), transmission electron microscopy (TEM), micro hardness tester, and other techniques. The results showed that ECP not only refined the primary (Cr, Fe)₇C₃ carbides, but also decreased the average content of Cr in the primary carbides...
December 22, 2018: Materials
Shaoying Li, Xiaojun Xi, Yiwa Luo, Mingtao Mao, Xiao Shi, Jing Guo, Hanjie Guo
In this paper, the precipitation of carbide and wear loss of high-carbon 8 mass% Cr tool steel at two tempering conditions (i.e., 773⁻803 K and 823⁻853 K) were studied by INCA Steel, EPMA-1720H, XRD, and ML-10 tester. The results show that the particles of test steels include the carbides (Cr₇C₃ and Cr23 C₆) and carbides nucleated on Al₂O₃. When carbides are of the same size, the number of carbides in test steel at a tempering temperature of 773⁻803 K is greater than that at a tempering temperature of 823⁻853 K, especially when the size of carbides is less than 5 μm...
December 7, 2018: Materials
Ben Buse, Jon Wade, Xavier Llovet, Stuart Kearns, John J Donovan
Secondary fluorescence (SF), typically a minor error in routine electron probe microanalysis (EPMA), may not be negligible when performing high precision trace element analyses in multiphase samples. Other factors, notably wavelength dispersive spectrometer defocusing, may introduce analytical artifacts. To explore these issues, we measured EPMA transects across two material couples chosen for their high fluorescence yield. We measured transects away from the fluorescent phase, and at various orientations with respect to the spectrometer focal line...
December 3, 2018: Microscopy and Microanalysis
Fenghou Xie, Chongyun Shao, Meng Wang, Qinling Zhou, Fengguang Lou, Wenbin Xu, Chunlei Yu, Suya Feng, Lili Hu
Yb3+ /Al3+ co-doped silica fibers (YDFs) with almost identical core glass compositions were prepared using the sol-gel and modified chemical vapor deposition (MCVD) methods. The photodarkening (PD) and laser performance before and after the PD process were tested under 974 nm pumping. The doping homogeneity of Yb3+ ions and clusters of Yb3+ ions in preform slices of these two fibers were investigated via optical absorption spectroscopy, photoluminescence emission spectra, electron probe microanalysis (EPMA), and low-temperature (4 K) electron paramagnetic resonance (EPR)...
October 29, 2018: Optics Express
Soroush Modabberi
Muteh Gold Deposit is the biggest active gold district in Iran consisting of two mines, Senjedeh and Chah-Khatoun, and seven mineral occurrences. Senjedeh has been mined about 20 years ago and was recently closed because of the depletion of the reserves. Chah-Khatoun went into operation few years ago. During the previous decades, more than 22 Mt of low-grade wastes has been produced from both mines. The wastes are assumed to be a possible source of gold, especially with recent increase in the world gold prices...
November 19, 2018: Environmental Monitoring and Assessment
Paula López-Arce, Fernando Garrido, Javier García-Guinea, Andreas Voegelin, Jörg Göttlicher, Jose Miguel Nieto
Samples of an open-air pyrite roasting heap from the 19th century in the Riotinto mine area (SW Spain) and surrounding sediments and soil along a seasonal surface runoff channel were analyzed to study thallium (Tl) phase transformations during historical roasting of Tl-bearing arsenian pyrite, secondary weathering processes, Tl dispersion and current environmental pollution. Results from Electron Probe Microanalyses (EPMA) indicate an even distribution of Tl in pyrite grains of an ore sample (22 mg kg-1 total Tl), suggesting that Tl is incorporated in the pyrite structure rather than in discrete Tl-sulfide microparticles...
January 15, 2019: Science of the Total Environment
Weimin Bai, Guanglong Xu, Mingyue Tan, Zhijie Yang, Lijun Zeng, Di Wu, Libin Liu, Ligang Zhang
β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand and manipulate the phase transformation and microstructure evolution during homogenization and precipitation. In this work, diffusion couple technique was employed to investigate the diffusion behaviors in bcc Ti-Mo-Zr alloys...
October 8, 2018: Materials
R Böttcher, H T Langhammer, S Kücker, C Eisenschmidt, S G Ebbinghaus
Electron paramagnetic resonance (EPR) investigations of BaTiO3   +  0.04 BaO  +  x/2 Fe2 O3 (0.007  ⩽  x  ⩽  0.05) ceramics and BaTi0.98 Fe0.02 O3 single crystals were performed to study the incorporation of Fe ions in the hexagonal 6H-BaTiO3 lattice and their defect properties. The samples were characterized by x-ray diffraction and wavelength-dispersive x-ray electron probe microanalysis. EPR spectra were recorded both in X- and Q-bands at room temperature. Angle-dependent single crystal EPR investigations and simulations of the ceramic powder EPR spectra revealed three different centers, which can be attributed to Fe3+ ions incorporated on crystallographically different Ti sites...
October 24, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Zhuguo Li, Mariko Nagashima, Ko Ikeda
Long-term immobilization ratios of strontium (Sr2+ ) and cesium (Cs⁺) in paper sludge ash-based geopolymer (PS-GP) were investigated in one year. PS-GP paste specimens were prepared in the conditions of 20 °C and 100% R.H., using two kinds of paper sludge ash (PS-ash). Two kinds of alkaline solution were used in the PS-GP as activator. One was prepared by diluting aqueous Na-disilicate (water glass) with seawater. Another was a mixture of this solution and caustic soda of 10 M concentration. When seawater was mixed into the alkaline solution, unstable fixations of Sr2+ and Cs⁺ were greatly improved, resulting stable and high immobilization ratios at any age up to one year, no matter what kind of PS-ash and alkaline solution were used...
August 24, 2018: Materials
J M Xiang, G B Mi, S J Qu, X Huang, Z Chen, A H Feng, J Shen, D L Chen
The high-temperature structural applications of Ti2 AlNb-based alloys, such as in jet engines and gas turbines, inevitably require oxidation resistance. The objective of this study is to seek fundamental insight into the oxidation behavior of a Ti2 AlNb-based alloy via detailed microstructural characterization of oxide scale and scale/substrate interface after oxidation at 800 °C using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM)...
August 24, 2018: Scientific Reports
S E Challinger, I D Baikie, G Flannigan, S Halls, K Laing, L Daly, N Nic Daeid
Most traditional techniques to recover latent fingermarks from metallic surfaces do not consider the metal surface properties and instead focus on the fingermark chemistry. The scanning Kelvin probe (SKP) technique is a non-contact, non-destructive method, used under ambient conditions, which can be utilised to recover latent prints from metallic surfaces and does not require any enhancement techniques or prevent subsequent forensic analysis. Where a fingermark ridge contacted the metal, the contact potential difference (CPD) contrast between the background surface and the fingermark contact area was 10-50mV...
October 2018: Forensic Science International
Svetlana Shkolyar, Jack D Farmer
Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through the study of Miocene-Pliocene evaporites of the Verde Formation (central Arizona). We assessed the effects of diagenesis on BPP, integrating outcrop-scale observations with six lab analyses: thin-section petrography, X-ray diffraction, Raman spectroscopy, total organic carbon (TOC), electron probe microanalysis (EPMA), and visible to near-infrared (VNIR) reflectance spectroscopy...
November 2018: Astrobiology
Shenghui Guo, Xiaolei Ye, Liang Wang, Sivasankar Koppala, Li Yang, Tu Hu, Jiyun Gao, Ming Hou, Longtao Hu
Microwave pressureless sintering (MPS) method is successfully applied in the fabrication of Cu based metallic matrix for diamond tools. The main purpose of this work is to obtain better mechanical properties when the metal binder of the diamond tools was prepared by the MPS method. The orthogonal experimental method is adopted to design the sintering process parameters. The optimized experimental conditions are suggested as 880 °C of sintering temperature, 375 MPa of cold pressure, and 35 min of withholding time...
August 16, 2018: Materials
Franck Tessier
Nitrogen (and also oxygen) determination has become an important parameter to characterize (oxy)nitride materials for many properties and applications. Analyzing such anions with accuracy is still a challenge for some materials. However, to date, a large panel of methodologies is available to answer this issue with relevant results, even for thin films. Carrier gas hot extraction techniques and electron probe microanalysis with wavelength dispersive spectroscopy (EPMA-WDS) look attractive to analyze bulk materials and thin films, respectively...
August 1, 2018: Materials
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