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排序方式: 共有133条查询结果,搜索用时 15 毫秒
51.
Optimisation of a gas chromatographic method for trace gaseous impurities in nitrogen trifluoride by column sequence reversal 总被引:1,自引:0,他引:1
Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low mg/L levels included dioxygen (O2), dinitrogen (N2), carbon dioxide (CO2), carbon monoxide (CO), sulfur hexafluoride (SF6), methane (CH4) and nitrous oxide (N2O). Carbon tetrafluoride (CF4) is also present in the product at levels of 20-400mg/L and had to be analysed as well. This paper compares the use of a custom-built dual-channel gas chromatograph utilising single column back flush switching on one channel for the determination of O2, N2, CH4 and CO with column sequence reversal on a second channel for the determination of CO2, N2O, SF6 and CF4 to a similar system using a combination of dual-column back flush and heart-cut configurations. Pulsed discharge helium ionisation detectors were used on both channels in both configurations. 相似文献
52.
Mark J. Harrison Adam P. Graebner Walter J. McNeil Douglas S. McGregor 《Journal of Crystal Growth》2006,290(2):597-601
A reliable method for depositing a layer of carbon on the inner walls of a fused silica ampoule is described and characterized. Carbon deposition rates were found to be 0.33 μm/h at mid-length and range from 0.26 to 0.55 μm/h at the ends of a 150 mm long ampoule. Deposition rate was found to vary along the length of the ampoule, but not along the radial perimeter. 相似文献
53.
Aihara H Alston-Garnjost M Avery RE Barker AR Bauer DA Bay A Belcinski R Bingham HH Bloom ED Buchanan CD Caldwell DO Chao HY Chun SB Clark AR Cowan GD Crane DA Dahl OI Daoudi M Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Erné FC Fairfield KH Fridman A Godfrey G Hauptman JM Ho C Hofmann W Kamae T Kenney RW Khacheryan S Kofler RR Lambert DJ Langeveld WG Layter JG Lin WT Linde FL Loken SC Lu A Lynch GR Lys JE Madaras RJ Magnuson BD Marsiske H Masek GE Mathis LG Maxfield SJ McNeil RR 《Physical review D: Particles and fields》1990,41(9):2667-2674
54.
Smith JR McNeil RR Breedon RE Kim GN Ko W Lander RL Maeshima K Malchow RL Rowe J Stuart D Imlay R Kirk P Lim J Metcalf W Myung SS Cheng CP Gu P Li J Li YK Ye MH Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG Abe K Fujii Y Higashi Y Kim SK Kurihara Y Maki A Nozaki T Omori T Sagawa H Sakai Y Sugimoto Y Takaiwa Y Terada S Walker R Kajino F Perticone D Poling R Thomas T Ishi Y Miyano K Miyata H 《Physical review D: Particles and fields》1990,42(3):949-951
55.
56.
Tomohiro Kubo Morgan S. Young Kendra D. Souther Matthew D. Hannigan Anne J. McNeil 《Journal of polymer science. Part A, Polymer chemistry》2021,59(3):268-273
The discovery of catalyst-transfer polymerization and its further developments have led to unprecedented control over the length and sequence of conjugated polymers. However, the methods themselves are technically challenging to perform due to the air- and moisture-sensitivities of the monomers and catalysts. Herein, we report a catalyst-transfer polymerization method that affords poly(3-hexylthiophene) in high yields without using an inert atmosphere. The synthesis capitalizes on a rapid Negishi cross-coupling using a moisture-tolerant organozinc monomer mediated by an air-stable Pd precatalyst. This simple method should make conjugated polymer synthesis more accessible to a broader range of researchers and may be generalizable to other monomer scaffolds. 相似文献
57.
58.
Santhosh Kumar K. S. Dr. Yugang Li Dr. Yves Gnanou Dr. Ulrich Baisch Dr. Yohan Champouret Dr. Rinaldo Poli Prof. Kiyoshi C. D. Robson W. Stephen McNeil Prof. 《化学:亚洲杂志》2009,4(8):1257-1265
Complexes Co[OC(Ph)CHC(Me)NAr]2 [Ar=Ph, 1 ; o,o′‐C6H3Me2 (Xyl), 2 ; p‐C6H4CF3, 3 ] are tested in the polymerization of vinyl acetate (VAc) initiated by V‐70 (0.8 equiv) at 30 °C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected Mn values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2 > 1 > 3 . Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V‐70/ 1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(β‐diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization. 相似文献
59.
L Zhou H Ishizaki M Spitzer KL Taylor ND Temperley SL Johnson P Brear P Gautier Z Zeng A Mitchell V Narayan EM McNeil DW Melton TK Smith M Tyers NJ Westwood EE Patton 《Chemistry & biology》2012,19(7):883-892
Highlights? Zebrafish provide a viable assay for the biological toxicity of 5-nitrofurans ? ALDH2 inhibitors prevent 5-nitrofuran toxicity in zebrafish and yeast ? Genetic dependence on ALDH2 for 5-nitrofuran toxicity in zebrafish and yeast systems ? 5-Nitrofurans bind to and are substrates of human ALDH2 相似文献
60.
A method is demonstrated that allows a planar wiggler high-gain Free-Electron-Laser (FEL) amplifier to lase so that the interaction with an odd harmonic of the radiation field dominates that of the fundamental. This harmonic lasing of the FEL is achieved by disrupting the electron interaction with the usually dominant fundamental while allowing that of a harmonic interaction to evolve unhindered. The disruption is achieved by a series of relative phase changes between the electrons and the ponderomotive potentials of both the fundamental and harmonic fields. Such phase changes are relatively easy to implement and some current FEL designs would require little or no structural modification to test the scheme. 相似文献