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991.
The coupled-channels method for the treatment of the continuum is used to study the negative parity excited states of the 4He nucleus in the Tamm-Damcoff approximation. It is shown that the splittings within the SU(4) supermultiplet are well reproduced in this calculation when the spin-dependent forces responsible for the removal of the degeneracy are taken appropriately into account. The location of the T = 0, 1? resonance and the admixture of spurious c.m. excitation in the intrinsic excitation are discussed. In addition to interpreting the observed spectrum, the available experimental data for the particle channels are well described by the theory. 相似文献
992.
Some salient features, such as self-absorption and selective excitation of elements, of microwave excited thorium iodide and other electrodeless discharge lamps are discussed. The importance of these features for classification and analysis of spectra and possibly for spectrochemical analysis is indicated. The use of the electrodeless lamp as a source for the excitation of molecular spectra is pointed out. 相似文献
993.
Vijay M. Rao Donald G. Mitchell Robert M. Steiner Matthew D. Rifkin D.Lawrence Burk Jr. David Levy Samir K. Ballas 《Magnetic resonance imaging》1988,6(6):661-667
Since considerable expansion of hematopoietic marrow occurs in patients with sickle cell anemia (SCA), magnetic resonance images of 20 hips in 10 patients with known homozygous SCA were reviewed to determine a) if low signal hematopoietic marrow extended into the femoral capital epiphysis and b) if the MR characteristics of avascular necrosis (AVN) differed depending on the type of epiphyseal marrow. Our results revealed variable epiphyseal marrow type; mixed (fatty and hematopoietic) marrow (42%), fatty marrow (32%), hematopoietic marrow (16%) and hemosiderotic marrow (10%). AVN occurred irrespective of the underlying marrow. Segmental areas of low signal intensity in variable shapes (ring, band, crescent or large homogeneous area) was the most consistent MR manifestation of AVN in SCA. A low signal intensity peripheral rim surrounding a central zone, isointense with epiphyseal marrow on T1 and T2 weighted images, was most frequently observed similar to that described in patients without hemoglobinopathy. The notable difference, however, was of segmental areas within the same femoral head that demonstrated variable central zone signal on T2 weighted images. Further, while an increase in hip joint fluid is commonly seen with both early and advanced AVN in patients without hemoglobinopathy; it was increased in only one hip in patients with SCA. The observed differences in MR characteristics may be due to different pathophysiology of AVN in patients with SCA. 相似文献
994.
995.
Y. K. Rao B. V. Acharya B. Rangamannar 《Journal of Radioanalytical and Nuclear Chemistry》1985,94(6):363-372
Specific surface area of antimony oxide samples, one commercial and the other prepared from antimony trichloride have been measured by heterogeneous isotope exchange, gas adsorption, airpermeability and microscopic methods. Specific surface areas obtained by these four methods for the two samples were compared and the observed differences are explained. 相似文献
996.
997.
In 1965, Chowla and Walum conjectured that, holds for each ε > 0 and x → ∞, where integers a ≥ 0 and k ≥ 1 are given and Pk is the periodic Bernoulli function of order k. Recently, the authors established this conjecture in case k ≥ 2 and with ε = 0 while if , with a log factor. In this paper, it is proven that the conjecture, in case , k = 2, is true “on average”. 相似文献
998.
High resolution H1 and F19 nuclear magnetic resonance spectra of 1-fluoro, 2, 4-dinitrobenzene were obtained and analyzed to determine all the parameters involved. As the spectrum of one of the protons is well separated from that of the other two, the secular equation has been solved in the first approximation. The analysis gives the following spin-spin coupling constants: J0 HH = 8.7 ± 0.3 cps., Jm HH = 2.9 ± 0.2 cps., Jp HH = 0.6 ± 0.3 cps., J0 HH = 10.4 ± 0.2 cps., and the two meta H-F coupling constants were found to be considerably different being 6.5 ± 0.3 cps. and 3.8 ± 0.3 cps. It has been found that theortho andmeta H-F coupling constants have the same sign as theortho andpara H-H coupling constants. 相似文献
999.
1000.