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Amorphous selenium

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https://www.readbyqxmd.com/read/28781183/selenium-speciation-in-phosphate-mine-soils-and-evaluation-of-a-sequential-extraction-procedure-using-xafs
#1
Jessica E Favorito, Todd P Luxton, Matthew J Eick, Paul R Grossl
Selenium is a trace element found in western US soils, where ingestion of Se-accumulating plants has resulted in livestock fatalities. Therefore, a reliable understanding of Se speciation and bioavailability is critical for effective mitigation. Sequential extraction procedures (SEP) are often employed to examine Se phases and speciation in contaminated soils but may be limited by experimental conditions. We examined the validity of a SEP using X-ray absorption spectroscopy (XAS) for both whole and a sequence of extracted soils...
October 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28743927/solid-state-77-se-nmr-of-organoselenium-compounds-through-cross-polarization-magic-angle-spinning-cpmas-method
#2
Duo Wei, Mengting Han, Lei Yu
Characterization of selenium states by (77)Se NMR is quite important to provide vital information for mechanism studies in organoselenium-catalyzed reactions. With the development of heterogeneous polymer-supported organoselenium catalysts, the solid state (77)Se NMR comes to the spotlight. It is necessary to figure out an advanced protocol that provides good quality spectra within limited time because solid state (77)Se NMR measurements are always time consuming due to the long relaxation time and the relatively low sensitivity...
July 25, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28649806/structure-of-amorphous-selenium-by-2d-77-se-nmr-spectroscopy-an-end-to-the-dilemma-of-chain-versus-ring
#3
Maxwell Marple, Jackson Badger, Ivan Hung, Zhehong Gan, Kirill Kovnir, Sabyasachi Sen
Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking to date. The primary controversy regarding the structure of amorphous Se relates to the relative fraction of Se atoms residing in ∞1Se chains versus in Se8 rings. Herein we present the results of a two-dimensional solid-state (77) Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that 1) the Se8 rings and the ∞1Se chains are characterized by their unique (77) Se NMR signatures and 2) the structure of amorphous Se consists exclusively of ∞1Se chains...
June 25, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28543761/experimental-characterization-of-a-direct-conversion-amorphous-selenium-detector-with-thicker-conversion-layer-for-dual-energy-contrast-enhanced-breast-imaging
#4
David A Scaduto, Olivier Tousignant, Wei Zhao
PURPOSE: Dual-energy contrast-enhanced imaging is being investigated as a tool to identify and localize angiogenesis in the breast, a possible indicator of malignant tumors. This imaging technique requires that x-ray images are acquired at energies above the k-shell binding energy of an appropriate radiocontrast agent. Iodinated contrast agents are commonly used for vascular imaging, and require x-ray energies greater than 33 keV. Conventional direct conversion amorphous selenium (a-Se) flat-panel imagers for digital mammography show suboptimal absorption efficiencies at these higher energies...
August 2017: Medical Physics
https://www.readbyqxmd.com/read/28497903/semiconducting-nanowire-based-optoelectronic-fibers
#5
Wei Yan, Yunpeng Qu, Tapajyoti Das Gupta, Arouna Darga, Dang Tùng Nguyên, Alexis Gérald Page, Mariana Rossi, Michele Ceriotti, Fabien Sorin
The recent ability to integrate semiconductor-based optoelectronic functionalities within thin fibers is opening intriguing opportunities for flexible electronics and advanced textiles. The scalable integration of high-quality semiconducting devices within functional fibers however remains a challenge. It is difficult with current strategies to combine high light absorption, good microstructure and efficient electrical contact. The growth of semiconducting nanowires is a great tool to control crystal orientation and ensure a combination of light absorption and charge extraction for efficient photodetection...
May 12, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28477001/bacteriogenic-synthesis-of-selenium-nanoparticles-by-escherichia-coli-atcc-35218-and-its-structural-characterisation
#6
Aruna Jyothi Kora, Lori Rastogi
A biosynthetic method for the production of selenium nanoparticles under ambient temperature and pressure from sodium selenite was developed using Gram-negative bacterial strain Escherichia coli ATCC 35218. Bacteriogenic nanoparticles were methodologically characterized employing UV-vis, XRD, Raman spectroscopy, SEM, TEM, DLS and FTIR techniques. Generation of nanoparticles was visualized from the appearance of red colour in the selenite supplemented culture medium and broad absorption bands in the UV-vis. Biofabricated nanoparticles were spherical, polydisperse, ranged from 100-183 nm and the average particle size was about 155 nm...
March 2017: IET Nanobiotechnology
https://www.readbyqxmd.com/read/28274870/construction-of-a-cordyceps-sinensis-exopolysaccharide-conjugated-selenium-nanoparticles-and-enhancement-of-their-antioxidant-activities
#7
Yidong Xiao, Qilin Huang, Zhaomin Zheng, Han Guan, Shiyu Liu
A Cordyceps sinensis exopolysaccharide (EPS)-conjugated selenium nanoparticles (SeNPs) were successfully constructed through the reduction of SeO3(2-). The EPS-SeNPs were characterized in terms of formation, morphology, size, Se distribution and phase by UV-vis, FT-IR, transmission electron microscopy (TEM), dynamic light scattering (DLS), energy dispersive X-ray (EDX) and wide angle X-ray diffraction (WAXD) measurements. Results revealed that the SeNPs conjugated to EPS were amorphous and could be well dispersed at a size range of 80-125nm...
June 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28131038/microbial-selenium-sulfide-reduction-for-selenium-recovery-from-wastewater
#8
S P W Hageman, R D van der Weijden, A J M Stams, P van Cappellen, C J N Buisman
Microbial reduction of selenium sulfide (SeS2) is a key step in a new treatment process to recover selenium from selenate and selenite streams. In this process, selenate is first reduced to selenite, and subsequently selenite is reduced by sulfide and precipitates from the solution as SeS2. The latter is bio-reduced to elemental selenium and sulfide. Two anaerobic granular sludges (Eerbeek and Emmtec) were tested for their efficiency to reduce commercial crystalline SeS2. Emmtec sludge had the highest reducing capacity with commercial SeS2 and was therefore also used for the bioreduction of laboratory synthesized amorphous SeS2...
May 5, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28047248/tu-fg-209-01-a-model-of-noise-anisotropy-in-amorphous-selenium-digital-detectors
#9
R Acciavatti, A Maidment
PURPOSE: One of the main advantages of amorphous selenium (a-Se) photoconductors is high spatial resolution. It has also been shown that the noise power spectra (NPS) is effectively white (frequency-independent) at various angles of x-ray incidence. One limitation of previous studies on NPS is that the effect of digitization has not been modeled. This work demonstrates that the NPS becomes colored (frequency-dependent) once digitization is taken into account. METHODS: A mammography system is modeled by tracing rays between the focal spot and the detector...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046344/mo-ab-bra-07-low-dose-imaging-with-avalanche-amorphous-selenium-flat-panel-imager
#10
J Scheuermann, A Howansky, A Goldan, S Leveille, O Tousignant, K Tanioka, W Zhao
PURPOSE: We present the first active matrix flat panel imager (AMFPI) capable of producing x-ray quantum noise limited images at low doses by overcoming the electronic noise through signal amplification by photoconductive avalanche gain (gav). The indirect detector fabricated uses an optical sensing layer of amorphous selenium (a-Se) known as High-Gain Avalanche Rushing Photoconductor (HARP). The detector design is called Scintillator HARP (SHARP)-AMFPI. This is the first image sensor to utilize solid-state HARP technology...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28044397/selenium-iv-vi-reduction-and-tolerance-by-fungi-in-an-oxic-environment
#11
C E Rosenfeld, J A Kenyon, B R James, C M Santelli
Microbial processes are known to mediate selenium (Se) oxidation-reduction reactions, strongly influencing Se speciation, bioavailability, and transport throughout the environment. While these processes have commonly been studied in anaerobic bacteria, the role that aerobic fungi play in Se redox reactions could be important for Se-rich soil systems, dominated by microbial activity. We quantified fungal growth, aerobic Se(IV, VI) reduction, and Se immobilization and volatilization in the presence of six, metal-tolerant Ascomycete fungi...
May 2017: Geobiology
https://www.readbyqxmd.com/read/27939658/solution-and-surface-chemistry-of-the-se-iv-fe-0-reactions-effect-of-initial-solution-ph
#12
Xuefen Xia, Lan Ling, Wei-Xian Zhang
Aspects of solution and solid-phase reactions between selenite (Se(IV)) and nanoscale zero-valent iron (nZVI) were investigated. Experimental results on the effects of initial solution pH, formation and evolution of nZVI corrosion products, and speciation of selenium in nZVI were presented. In general, the rate of Se(IV) removal decreases with increasing initial pH. The observed rate constants of Se(IV) removal decreased from 0.3530 to 0.0364 min(-1) as pH increased from 4.0 to 10.0. Composition and morphology of nZVI corrosion products and selenium species were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS)...
February 2017: Chemosphere
https://www.readbyqxmd.com/read/27895876/assessment-of-mean-glandular-dose-in-mammography-system-with-different-anode-filter-combinations-using-mcnp-code
#13
Lida Gholamkar, Ali Asghar Mowlavi, Mahdi Sadeghi, Mitra Athari
BACKGROUND: X-ray mammography is one of the general methods for early detection of breast cancer. Since glandular tissue in the breast is sensitive to radiation and it increases the risk of cancer, the given dose to the patient is very important in mammography. OBJECTIVES: The aim of this study was to determine the average absorbed dose of X-ray radiation in the glandular tissue of the breast during mammography examinations as well as investigating factors that influence the mean glandular dose (MGD)...
October 2016: Iranian Journal of Radiology: a Quarterly Journal Published By the Iranian Radiological Society
https://www.readbyqxmd.com/read/27866614/in-vivo-synthesis-of-nano-selenium-by-tetrahymena-thermophila-sb210
#14
Yin-Hua Cui, Ling-Li Li, Nan-Qing Zhou, Jing-Hua Liu, Qing Huang, Hui-Juan Wang, Jie Tian, Han-Qing Yu
Nano-selenium has a great potential to be used in chemical, biological, medical and environmental fields. Biological methods for nano-selenium synthesis have attracted wide interests, because they can be operated at ambient temperature and pressure without complicated equipments. In this work, a protozoa, Tetrahymena thermophila (T. thermophila) SB210, was used to in vivo synthesize nano-selenium. The biosynthesized nano-selenium was characterized using transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy...
December 2016: Enzyme and Microbial Technology
https://www.readbyqxmd.com/read/27632529/second-harmonic-generation-from-an-individual-amorphous-selenium-nanosphere
#15
C R Ma, J H Yan, Y M Wei, G W Yang
Among the numerous nonlinear optics effects, second harmonic generation (SHG) is always a hotspot and it is extensively used for optical frequency conversion, biomedical imaging, etc. However, SHG is forbidden in a medium with inversion symmetry under the electric-dipole approximation. Here, we demonstrated SHG from a single amorphous selenium (a-Se) nanosphere under near-infrared femtosecond pulse excitation. It was found that SH spectra are tunable with the size of a-Se nanospheres and the SHG efficiency of a single a-Se sphere with a diameter over 300 nm is estimated at 10(-8)...
October 21, 2016: Nanotechnology
https://www.readbyqxmd.com/read/27584907/correlative-light-and-electron-microscopy-using-quantum-dot-nanoparticles
#16
Murray C Killingsworth, Yuri V Bobryshev
A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using widefield fluorescence light microscopy and transmission electron microscopy (TEM). To demonstrate the protocol we have immunolabeled ultrathin epoxy sections of human somatostatinoma tumor using a primary antibody to somatostatin, followed by a biotinylated secondary antibody and visualization with streptavidin conjugated 585 nm cadmium-selenium (CdSe) quantum dots (QDs)...
August 7, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27564846/electrochemistry-of-selenium-with-sodium-and-lithium-kinetics-and-reaction-mechanism
#17
Qianqian Li, Heguang Liu, Zhenpeng Yao, Jipeng Cheng, Tiehu Li, Yuan Li, Chris Wolverton, Jinsong Wu, Vinayak P Dravid
There are economic and environmental advantages by replacing Li with Na in energy storage. However, sluggishness in the charge/discharge reaction and low capacity are among the major obstacles to development of high-power sodium-ion batteries. Among the electrode materials recently developed for sodium-ion batteries, selenium shows considerable promise because of its high capacity and good cycling ability. Herein, we have investigated the mechanism and kinetics of both sodiation and lithiation reactions with selenium nanotubes, using in situ transmission electron microscopy...
September 27, 2016: ACS Nano
https://www.readbyqxmd.com/read/27514819/mitochondria-mediated-protein-regulation-mechanism-of-polymorphs-dependent-inhibition-of-nanoselenium-on-cancer-cells
#18
Ge Wang, Yuming Guo, Gai Yang, Lin Yang, Xiaoming Ma, Kui Wang, Lin Zhu, Jiaojiao Sun, Xiaobing Wang, Hua Zhang
The present study was (i) to prepare two types of selenium nanoparticles, namely an amorphous form of selenium quantum dots (A-SeQDs) and a crystalline form of selenium quantum dots (C-SeQDs); and (ii) to investigate the nano-bio interactions of A-SeQDs and C-SeQDs in MCF-7, HepG2, HeLa, NIH/3T3, L929 cells and BRL-3A cells. It was found that A-SeQDs could induce the mitochondria-mediated apoptosis, necrosis and death of cells, while C-SeQDs had much weaker effects. This polymorphs-dependent anti-proliferative activity of nano-selenium was scarcely reported...
2016: Scientific Reports
https://www.readbyqxmd.com/read/27472329/substrate-and-passivation-techniques-for-flexible-amorphous-silicon-based-x-ray-detectors
#19
Michael A Marrs, Gregory B Raupp
Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium...
2016: Sensors
https://www.readbyqxmd.com/read/27353373/biomimetic-synthesis-of-selenium-nanoparticles-by-pseudomonas-aeruginosa-atcc-27853-an-approach-for-conversion-of-selenite
#20
Aruna Jyothi Kora, Lori Rastogi
A facile and green method for the reduction of selenite was developed using a Gram-negative bacterial strain Pseudomonas aeruginosa, under aerobic conditions. During the process of bacterial conversion, the elemental selenium nanoparticles were produced. These nanoparticles were systematically characterized using various analytical techniques including UV-visible spectroscopy, XRD, Raman spectroscopy, SEM, DLS, TEM and FTIR spectroscopy techniques. The generation of selenium nanoparticles was confirmed from the appearance of red colour in the culture broth and broad absorption peaks in the UV-vis...
October 1, 2016: Journal of Environmental Management
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