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The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm,
Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of 137Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the
photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other
measured values. 相似文献
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Behforouz M Haddad J Cai W Arnold MB Mohammadi F Sousa AC Horn MA 《The Journal of organic chemistry》1996,61(19):6552-6555
The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield. 相似文献
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A.R. de L. Musgrove B.J. Allen J.W. Boldeman D.M.H. Chan R.L. Macklin 《Nuclear Physics A》1976,259(3):365-377
The neutron capture cross section of 40Ca has been measured with ≈ 0.2 % energy resolution below En = 300 keV. Resonance parameters have been extracted for many new p- and d-wave resonances. Gamma-ray spectra were also measured following capture in one doublet and two resolved resonances below 50 keV. Strong feeding of low-lying p-wave levels was observed in all cases. Calculations showed that valence transitions were inadequate to account for the observed dominance of these transitions and a further mechanism is required. The average resonance parameters obtained from the data are as follows: 〈D〉 = 37 + 4keV, 104S1 = 0.16 ± 0.05, 104S2 = 2.0 ± 0.7. The average radiative widths and standard deviations of their distributions were found to be strongly l-dependent as follows: 〈Γγ〉s = 1.5 ± 0.9 eV, 〈Γγ〉p = 0.36 ± 0.09 eV and 〈Γγ〉d = 0.7 ± 0.4 eV. 相似文献
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The structure of 3,3-bis(chloromercury)-2,4-pentanedione is reported. The space group indicated is C2/c with unit cell dimensions: a = 15.048(2), b = 10.921(6), c = 16.080(4) Å, and β = 134.74(1)°. Three-dimensional absorption-corrected diffractometer data were used in the refinement of the structure to a conventional R(F) value of 0.079. Anisotropic temperature factors were used for Hg and Cl atoms while C and O atoms were refined isotropically. Both Hg atoms are bound to the γ-carbon of acetylacetone. Solid state Raman and infrared spectra are reported. Lowering of the C=O stretching frequency is discussed in terms of the crystal structure. 相似文献
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Time-of-flight powder neutron diffraction data have been used to refine the crystal structure of the ordered, distorted perovskite Sr2YRuO6. Yttrium and ruthenium are octahedrally coordinated in this material with average MO bond lengths of 2.202 and 1.955 Å, respectively. Constant wavelength neutron diffraction data show that Sr2YRuO6 is a Type I antiferromagnet at 4.2 K with an ordered magnetic moment of 1.85 μB per Ru5+ ion. The Néel temperature of Sr2YRuO6 was determined to be 26 K. The data suggest that the 4d3 electrons in this material are localized rather than itinerant. 相似文献