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125.
Christopher J. Williamson 《Analytica chimica acta》1999,380(2-3):413-416
Matt surfaced versions of the Ceramic Colour Standards are produced by CERAM Research by means of an abrasion technique applied to the normally gloss surface. These are available as an alternative to the existing matt standards made from opal glass, pressed powder and ‘plastic'. The existing standards have good matt surfaces but generally have a comparatively short life due to the delicate nature of the surface. This causes problems in maintaining continuity of measurement. The Ceram Research matts also have a good matt surface which, being ceramic should be durable. This paper reports the results of a series of measurements made on selected standards, which show that the standards are durable. In addition it was found that it was possible to clean the standards, returning them close to their original colour values. 相似文献
126.
An adaptation of multiphoton ionization spectroscopy is presented in which a single vibrational—rotational level of an excited electronic state is pumped using a dye laser, and a second, independently tunable dye laser beam induces multiphoton ionization from this excited level. Several advantages of this technique are demonstrated using molecular iodine. 相似文献
127.
Craig Williamson John M. D. Storey William T. A. Harrison 《Journal of chemical crystallography》2006,36(4):277-282
The syntheses and structures of two N-substituted thio-imidazoles are reported. The geometrical parameters for both compounds, including essentially planar imidazole rings, are consistent with previous structural studies of related materials. The only possible non-van der Waals’ interactions influencing the molecular packing are weak C–H⋯π bonds. Crystal data: C12H14N2S (N-methyl-N′-2-phenylethyl-imidazol-2-thione), M
r = 218.31, monoclinic, P21/n, (No. 14), a = 6.8441(2) ?, b = 12.9960(4) ?, c = 13.4703(4) ?, β = 97.7729(16)°, V = 1187.12(6) ?3, Z = 4, R(F) = 0.039, wR(F
2) = 0.104. C19H20N2S (N,N′-bis((s)-1-phenylethyl)imidazol-2-thione), M
r = 308.43, orthorhombic, P212121 (No. 19), a = 10.4060(3) ?, b = 10.6712(3) ?, c = 14.8932(3) ?, V = 1653.81(7) ?3, Z = 4, R(F) = 0.038, wR(F
2) = 0.085. 相似文献
128.
Kenneth Hensley Kelly S. Williamson Michael L. Maidt S. Prasad Gabbita Paula Grammas Robert A. Floyd 《Journal of separation science》1999,22(8):429-437
For three decades, high performance liquid chromatography has proven itself to be a powerful, flexible, and inexpensive tool for basic and clinical research. Recent advances in our understanding of disease have prompted a demand for more sensitive and selective methods of routine bioanalysis, particularly with respect to the determination of oxidative metabolites and biomarkers of oxidative stress. Multidimensional detectors utilizing coulometric arrays offer a solution to these research needs. The challenge to the bioanalyst is now to creatively apply HPLC-ECD technology to promising research and clinical enterprises. 相似文献
129.
A.H. El-Astal I. Weaver G.W. Martin A. Al-Khateeb T.P. Williamson M.J. Lamb C.L.S. Lewis T. Morrow 《Applied Physics A: Materials Science & Processing》1999,69(7):S573-S576
A Langmuir probe was used as a diagnostic of the temporally evolving electron number densities within a low-temperature laser-ablated titanium plasma expanding in vacuum. Measurements were made following ablation by a KrF excimer laser (248 nm, F=30 ns) and a frequency-doubled Nd:YAG laser (532 nm, F=7.5 ns) for laser power densities between 85 MW cm-2 and 1130 MW cm-2 on target. Electron number density data were obtained from the saturation electron current region of the probe (I/V) characteristic. Peak electron number densities in the range 1.5᎒10 cm-3 to 1.5᎒13 cm-3 were measured, at a distance of 5 cm along the target normal, for the laser power range investigated. Above ablation threshold the temporally integrated electron flux increased linearly with incident power density for both ablation wavelengths. The ablation thresholds, in terms of peak power density within the laser spot on the target, were found to be 85ᆨ MW cm-2 for KrF ablation and 300ᇆ MW cm-2for 2P YAG ablation. 相似文献
130.
Gary E. Martin R. Thomas Williamson Peter G. Dormer Wolfgang Bermel 《Magnetic resonance in chemistry : MRC》2012,50(8):563-568
ADEQUATE experiments provide an alternative to the more commonly employed GHMBC experiment for the establishment of long‐range heteronuclear connectivities. The 1,1‐ADEQUATE experiment allows the unequivocal identification of both protonated and non‐protonated carbon resonances adjacent to a protonated carbon. The 1,n‐ADEQUATE experiment establishes correlations via an initial 1JCH heteronuclear transfer followed by an nJCC out‐and‐back transfer, most typically, via three carbon–carbon bonds. Hence, the 1,n‐ADEQUATE experiment allows the equivalent of 4JCH heteronuclear correlations to be probed when they are not observed in a GHMBC spectrum. Aside from the lower sensitivity of the 1,n‐ADEQUATE experiment relative to GHMBC experiments, the interpretation of the former is also complicated by the ‘leakage’ of 1JCC correlations into the spectrum that must be identified. A method for the inversion of 1JCC correlations to facilitate the interpretation of 1,n‐ADEQUATE spectra is presented that allows a single experiment to be performed to access 1JCC and nJCC correlation information. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献