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91.
92.
F. J. Berry T. Birchall C. D. Gibbs C. Frampton C. Hallett 《Hyperfine Interactions》1988,41(1):459-462
The57Fe Mössbauer spectra recorded at 4.2K from the trirutile-type iron chromium tellurates of composition Fe2?xCrxTeO6, where x=0–2, show that the angle θ, which describes the perpendicular orientation of the magnetic moment to the basal plane of the Fe2TeO6 unit cell, is not changed by the incorporation of chromium until x exceeds 1.2 At this critical limit θ begins to rapidly cant to smaller values until, at compositions approaching Cr2TeO6, it approaches a parallel orientation to the basal plane. The125Te and129I Mössbauer spectra recorded from the compound FeCrTeO6 at 77 and 4.2K are consistent with the presence of a supertransferred magnetic hyperfine field at the tellurium nucleus ofca. 76 kG. 相似文献
93.
N K Gibbs N J Traynor B E Johnson J Ferguson 《Journal of photochemistry and photobiology. B, Biology》1992,13(3-4):275-288
Anecdotal reports suggest that the dihydropyridine calcium antagonist, nifedipine (NIF), may be phototoxic in human skin. We have studied NIF phototoxicity in vitro using UVA fluorescent tubes (Sylvania PUVA). NIF was phototoxic to Candida albicans and induced photohaemolysis both with NIF present during irradiation and with pre-irradiated drug. In V79 hamster fibroblasts, NIF (10 micrograms ml-1) was phototoxic MTT assay) 24 h after irradiation (0-112 kJ m-2); at 7.5 kJ m-2, about 70% of cells were damaged whilst at 37.5 kJ m-2, only about 45% of cells were damaged. A similar pattern was seen with pre-irradiated NIF. Absorption spectroscopy showed that the NIF absorption maximum (Amax approximately 340 nm) blue-shifted to 314 nm at low UVA doses (7.5 kJ m-2 or less) and red-shifted to 345 nm at higher doses (isosbestic point, 325 nm). Thin layer chromatography of irradiated NIF showed a single photoproduct (PP1; Amax approximately 314 nm) formed at 7.5 kJ m-2 or less which disappeared at higher UVA doses to give further photoproducts. PP1 was highly dark toxic to V79 cells (50% damage at about 5 micrograms ml-1) but PP1 pre-irradiated with UVA was non-toxic. Preliminary gas chromatography-mass spectroscopy studies suggest that PP1 is the nitroso derivative of NIF. These results indicate that NIF phototoxicity in vitro is partially mediated by initial formation of a toxic photoproduct (PP1) but, paradoxically, subsequent UVA irradiation may reduce phototoxicity. The NIF concentrations required to induce in vitro phototoxicity are much greater than therapeutic plasma levels. Unless there is skin accumulation of NIF or PP1, our in vitro results suggest that NIF may not be an important skin-photosensitizing agent in vivo. 相似文献
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J.W.-H. Leung A.S.-C. Cheung K.D. Gibbs L.C. O’Brien 《Journal of Molecular Spectroscopy》2006,238(1):42-48
Vibrational bands belonging to the [15.0] 2Δ5/2-A2Δ5/2, [15.0] 2Δ5/2-X2Π3/2, and [15.0] 2Π3/2-X2Π3/2 electronic transitions of NiCl have been observed in the 14 000-16 000 cm−1 region. The [15.0] 2Δ5/2 and [15.0] 2Π3/2 states are identified for the first time. The observed bands have been recorded at high spectral resolution using several techniques, which include intracavity laser spectroscopy (ILS), Fourier transform emission spectroscopy (FTS), and laser induced fluorescence (LIF) spectroscopy. For the ILS absorption spectra, NiCl molecules were produced in a nickel hollow cathode operated with a small amount of CCl4. For the FTS emission spectra, excited NiCl molecules were produced in a King-type carbon tube furnace loaded with NiCl2 and heated to 1600 °C. In the LIF work, NiCl molecules were produced by reacting laser-ablated nickel with PCl3 seeded in argon. Detailed analysis of rotational transition lines indicates that the observed [15.0] 2Δ5/2 and [15.0] 2Π3/2 states are only separated by 10 cm−1 and are interacting with each other. Molecular constants for these newly observed electronic states are reported. 相似文献
96.
The broadening of the125Te Mössbauer spectral absorption with decreasing temperature in compounds of the type Cr2?x Fe x Te x TeO6 (x=0.4, 0.8, 1.0, 1.5) is attributed to the presence of a supertransferred magnetic hyperfine field. The origin of the supertransferred magnetic hyperfine field, which is not observed in antiferromagnetically ordered Cr2TeO6 or Fe2TeO6, is associated with an imbalance in the magnetic exchange interaction at tellurium which results from the replacement of chromium by iron. 相似文献
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