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981.
982.
983.
Summary Methods for the determination of Th in the range of low concentrations are compiled and discussed. Application of spectrophotometry and voltammetry is investigated. Spectrophotometry is applicable down to concentrations of the order of 0.1 g/l as long as the ratio U:Th is low. Voltammetric determination of Th is not possible in the presence of Al. 相似文献
984.
H. Hora H. Haseroth T. Henkelmann C. E. Hill G. Korschinek R. Matulioniene C. S. Taylor 《Czechoslovak Journal of Physics》1992,42(9):927-938
The need for highly charged heavy ions from projected particle accelerators has recently led to a re-evaluation of the complex processes of ion production in laser generated plasmas. Possible mechanisms for the production of intense beams of high charge state ions are investigated as is the experimental evidence for these mechanisms. The hypothesis that 20 keV ions are driven by hot electrons is not supported by experimental work to date. This work, on the other hand, suggests that 30ps pulsation is the basic mechanism for the acceleration of tantalum ions up to charge state 8+ whose energy increases linearly with charge state up to 24keV. For long pulses and charge states between 8+ and 18+, it appears that there is a secondary mechanism of electron impact ionisation by plasma electrons of approximately 200 eV in the plasma in front of the target, resulting in ions whose energy of around 24 keV is independent of charge state. 相似文献
985.
986.
987.
Thron JL Allison WW Alner GJ Ambats I Ayres DS Balka LJ Barr GD Barrett WL Benjamin D Border PM Brooks CB Cobb JH Cockerill DJ Courant H Dawson JW Demuth DM Edwards VW Ewen B Fields TH Garcia-Garcia C Giles RH Giller GL Goodman MC Gray RN Heilig SJ Hill N Hoftiezer JH Jankowski DJ Johns K Kafka T Kasahara SM Kochocki J Leeson W Litchfield PJ Longley NP Lopez FV Lowe MJ Mann WA Marshak ML May EN Maxam D McMaster L Milburn RH Miller WH Minor CP Napier A Oliver WP Pearce GF Perkins DH Peterson EA 《Physical review D: Particles and fields》1992,46(11):4846-4851
988.
J.S. Cowpe J.S. Astin R.D. Pilkington A.E. Hill 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1335-1342
Response Surface Methodology (RSM) was employed to optimize LIBS analysis of single crystal silicon at atmospheric pressure and under vacuum conditions (pressure 10− 6 mbar). Multivariate analysis software (StatGraphics 5.1) was used to design and analyze several multi-level, full factorial RSM experiments. A Quality Factor (QF) was conceived as the response parameter for the experiments, representing the quality of the LIBS spectrum captured for a given hardware configuration. The QF enabled the hardware configuration to be adjusted so that a best compromise between resolution, signal intensity and signal noise could be achieved. The effect on the QF of simultaneously adjusting spectrometer gain, gate delay, gate width, lens position and spectrometer slit width was investigated, and the conditions yielding the best QF determined. 相似文献
989.
Helene Z. Hill George J. Hill Krystyna Cieszka Michael Azure Indu Chowdhary Robert M. Sayre 《Photochemistry and photobiology》1995,61(5):479-483
A diffusible multitherapy resistance factor (MTRF) is produced by Cloudman S91 melanoma cells in vitro. The MTRF decreases sensitivity of the target cell line, S91/amel, to γ-irradiation, UVC (200–280nm) and mitomycin C (MMC). In the present study, we demonstrate that MTRF also increases the survival of S91/amel after exposure to actinomycin D (AMD) and vinblastine (VBL). The MTRF is thus effective when target cells have been exposed to five genotoxic agents that act by different mechanisms. It does not alter the response to the same five agents of the S91/13 producer cells, which are presumably saturated with the factor. The factor has no effect on the survival of S91/amel cells that have been exposed to lethal doses of near monochromatic UVB (280–320nm) or UVA (320–400nm) or to polychromatic FS20 lamps. The lack of effectiveness of MTRF after cells have been exposed to near (300–400nm) UV radiation indicates that in this wavelength range, S91 melanoma cells are killed by mechanisms that are different from the lethal effects of the five genotoxic agents (γ-irradiation, UVC, MMC, AMD and VBL) to which the target cells demonstrate a response. 相似文献
990.
Udit AK Belliston-Bittner W Glazer EC Nguyen YH Gillan JM Hill MG Marletta MA Goodin DB Gray HB 《Journal of the American Chemical Society》2005,127(32):11212-11213
We report direct electrochemistry of the iNOS heme domain in a DDAB film on the surface of a basal plane graphite electrode. Cyclic voltammetry reveals FeIII/II and FeII/I couples at -191 and -1049 mV (vs Ag/AgCl). Imidazole and carbon monoxide in solution shift the FeIII/II potential by +20 and +62 mV, while the addition of dioxygen results in large catalytic waves at the onset of FeIII reduction. Voltammetry at higher scan rates (with pH variations) reveals that the FeIII/II cathodic peak can be resolved into two components, which are attributable to FeIII/II couples of five- and six-coordinate hemes. Digital simulation of our experimental data implicates water dissociation from the heme as a gating mechanism for ET in iNOS. 相似文献