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1.
Using only basic tools from the theory of modular forms, the rational points of bounded height on the sphere are counted and shown to be uniformly distributed. The more difficult case of points with a given height is also treated. 相似文献
2.
The application of the simulated ab-initio molecular orbital (SAMO) method — a new non-empirical technique — to the band structure of polymers is reported. The method uses full ab-initio results on small molecules to construct for polymers molecular orbitals which simulate those obtained from full ab-initio treatments. Results are compared with those obtained from published ab-initio and semi-empirical calculations. 相似文献
3.
M. J. Apps M. J. M. Duke L. G. Stephens-Newsham 《Journal of Radioanalytical and Nuclear Chemistry》1988,123(1):133-147
A study has been carried out of the uptake of uranium and other radionuclides by plants growing on abandoned tailings from an uranium mining operation. Assay methods included instrumental neutron activation analysis, delayed neutron counting, fission track imaging, and counting of natural radioactivity. Care was taken to avoid contamination of the plant material and a number of methods are described to identify such contamination. All plants observed showed high uptake of radionuclides, compared to plants studied from naturally uraniferous and control areas. Graminoid (grass-like) plants showed significant uptake in the above-ground parts while woody plants showed exceedingly high uranium accumulation in the root portions. These results have significance in determination of the spread of radioactive material from such sites. 相似文献
4.
M. J. Apps M. J. M. Duke B. V. Turner 《Journal of Radioanalytical and Nuclear Chemistry》1987,110(1):245-252
Fission track analysis (FTA) has been used to investigate the biological uptake of uranium. Examination of fission track maps of black spruce twigs (from areas of uranium mineralization and mill tailings) shows uranium to be concentrated in the inner bark while decreasing in the outer bark of the twigs. Track clusters in the bark, too large to be uraniferous airborne particulate matter, are identified as being associated with resin canals in the twigs. The results of this work help clarify the mechanisms by which uranium is incorporated in black spruce twigs. The observation of decreasing uranium content with the increasing age of black spruce twigs by an earlier worker, can now be explained by the relative reduction in volume of the uranium enriched inner bark with age. 相似文献
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Round C. I. Williams C. D. Duke C. V. A. 《Journal of Thermal Analysis and Calorimetry》1998,54(3):901-911
Pure silica zeolite ZSM-5 has been synthesised in a slightly acidic aqueous fluoride medium which produces the protonated
form of the zeolite ZSM-5 [1]. Tetrahalometallate [2] species of cobalt and manganese have been synthesised and increasing
mole fractions incorporated into the zeolite synthesis gel. The products have been analysed and characterised using simultaneous
thermogravimetric-derivative thermogravimetric analysis (TG-DTG). The thermal decomposition, under nitrogen of the associated
tetraethylammonium (TEA+) and tetrapropylammonium (TPA+) cations occluded within the zeolite channels is indicative and characteristic of the incorporation of the heteroatoms into
the zeolitic framework. Analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF),
and Fourier transform infrared spectroscopy (FTIR) has confirmed the reliability of thermogravimetric (TG) and derived thermogravimetric
analysis (DTG) as a diagnostic tool.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
The ab initio Neglect of Differential Diatomic Overlap (N.D.D.O.) method of Roby is tested numerically for an extensive series of molecules. Agreement with the full ab initio molecular orbital method is poor. Total energies are more negative and dipole moments are overestimated. The failings of the N.D.D.O. method are accounted for using multipole-multipole expansions. 相似文献
9.
Douglas E. Moore Sarah Roberts-Thomson Dong Zhen Colin C. Duke 《Photochemistry and photobiology》1990,52(4):685-690
Irradiation with UVA light of the anti-inflammatory drug diclofenac [2-(2,6-dichloroanilino)phenylacetic acid] in aqueous buffer or methanol solution leads to sequential loss of both chlorine substituents and ring closure to carbazole-1-acetic acid as the major product. Minor products result from substitution by the solvent. The photosensitizing properties of diclofenac and its major photoproduct were tested with singlet oxygen substrates and in the free radical polymerization of acrylamide. Although the major carbazole product is a weakly phototoxic agent, able to generate singlet oxygen more efficiently than diclofenac, the free radical photodechlorination process is postulated as the probable initiation step of in vivo photosensitivity responses. 相似文献