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991.
A flaw of fundamental nature in foundations and pratical applications of efficient seismic prospecting is discussed. The authors
invite the geophysical community to organize a broad discussion in the seismic literature devoted to basic problems of seismic
prospecting and its applications.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 225, 1997, pp. 240–262.
Translated by N. S. Zabavnikova and T. N. Surkova 相似文献
992.
MnAs0.88P0.12 has been studied by powder neutron diffraction in external magnetic fields up to 15.2 kOe and temperatures down to 4.2 K. MnAs0.88P0.12 takes the MnP type atomic arrangement and exists in para-, ferro- and different (essentially) helimagnetic states. The observation of a double 000± satellite at 4.2 K < T 70 K adds further evidence to the chain of arguments for distinction between the helimagnetic states H'a (4.2 K < T < TS,1 ≈ 70 K) and Ha (TS,2 ≈ 180 K < T < TN = (243 ± 5) K). External magnetic fields at 4.2 K < T < 70 K evoke a new magnetic state, which is also characterized by a satellite doublet, and is tentatively designated H'a,fan. 相似文献
993.
994.
995.
K. Skarsvåg 《Nuclear Physics A》1975,253(2):274-288
The gross time distribution of γ-rays from spontaneous fission of 252Cf has been measured in the time range 10?14?10?10 s after fission for γ-ray energies greater than 0.15 MeV. The measurements have been made by a new method based upon the solid angle aberration. From the measured correlation between half-lives and γ-ray transition energies it is concluded that the transitions are predominantly E2, single-particle transitions at high energies, and mostly vibrational and rotational transitions at lower energies. Some contribution of E1 transitions and M1-E2 mixtures cannot be excluded, however. It was found that about 30% ofthe γ-rays emitted within 12 ns with energies greater than 0.10 MeV, have half-lives shorter than 1 ps and about 52 % half-lives between 1 and 100 ps. The relative yield of γ -rays and γ-ray energy in the time range 10?14 to 1.2 × 10?7 s ater fission is given. 相似文献
996.
Development of an X-ray fluorescence spectrometric method for the analysis of atmospheric aerosol samples 总被引:1,自引:0,他引:1
A simple, rapid method was developed for the analysis of aerosol samples by X-ray fluorescence spectrometry. Aerosol measurements were made using various sample supports (Whatman and Teflon filters, Prolene® foil). The calibration procedure was carried out by dripping 500 μl of a gradually diluted multi-elemental standard solution (CertiPUR® 11355) onto the top of the sample supports, which were then dried at ambient temperature. Thirteen elements, namely Na, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr and Pb were calibrated and quantified. The optimal measurement parameters (excitation conditions, measuring times for each element) were determined on the basis of blank values and the amplitude of the signals. The filters were covered with Ta or Re plates to ensure infinite thickness for the penetration depth of the primary X-ray beam. It was also demonstrated that these plates served as a secondary target. The accuracy, precision and detection limits (0.01–0.18 mg/kg) were calculated. All the analytical parameters were better when Teflon filters and Prolene® foil were used than in the case of Whatman quartz fibre filters. 相似文献
997.
H. Weissbuch E. Botezatu M. Grądinaru 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(2):385-391
A method for the simultaneous determination of the uranium and thorium content in various types of natural waters, has been
worked out. The method is based on the separation of uranium from thorium, and their subsequent purification on strong basic
anion exchange resin. An increased chemcial yield, precision and selectivity result in this manner. The assay of uranium and
thorium is performed spectrophotometrically in the form of their Arsenazo III complex. Under the studied conditions, the spectrophotometric
method can be used instead of the fluorimetric method, without the difficulties of the latter.
相似文献
998.
999.
The enzymatic synthesis of three isotopomers of l-DOPA labeled with deuterium and tritium at α carbon atom was elaborated. These compounds were converted into [(1S)-2H]–, [(1S)-
3H]–, and doubly labeled [(1S)-2H/3H]-dopamines using enzyme tyrosine decarboxylase. Doubly labeled (1R) isotopologue, i.e., [(1R)-2H/3H]-dopamine, was afforded by enzymatic decarboxylation of authentic l-DOPA carried out in deuteriated and tritiated incubation medium. 相似文献
1000.