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21.
If p is an arbitrary parabolic subsuperalgebra of g = gl(m + n), p(m), a character formula for the generic finite-dimensional irreducible g-module, such that p is the stabilizer of its lowest weight space, is announced. Furthermore, an estimate for the character of any finite-dimensional irreducible g-module in terms of its highest weight with respect to a distinguished Borel subsuperalgebra is presented (inequality (4)) and a sufficient condition for this to be an equality is found. In this way, two generalizations of the Kac character formula for typical modules are obtained: a formula concerning an arbitrary Borel subsuperalgebra ((1)) and a more effective formula ((3)) for the special case of a distinguished Borel subsuperalgebra. The complete proofs will appear in [14].Partially supported by Contract 911/11.04.88 with the Bulgarian Ministry of Culture, Science, and Education. 相似文献
22.
G. N. Dorofeenko Yu. P. Andreichikov É. A. Zvezdina V. A. Bren' G. E. Trukhan V. V. Derbenev A. N. Popova 《Chemistry of Heterocyclic Compounds》1974,10(10):1177-1181
The pyridinium ring as a substituent in aniline is an electron acceptor, the effect of which is comparable to the effect of NO2 and N(CH3)2 groups. Correlation of the reactivities with the basicities of the amino groups is not observed in the investigated reactions of N-(aminophenyl)pyridinium perchlorates with some electrophilic reagents, inasmuch as steric factors apparently play a greater role. 相似文献
23.
The total synthesis of a didemnin B analogue containing a conformationally constrained replacement for the isostatine moiety is reported. Synthetic highlights include an improved preparation of 2-hydroxy-3-cyclohexenecarboxylic acid and a new strategy for accessing the macrocycle. 相似文献
24.
B. L. Tumanskii A. A. Kadyrov O. A. Popova L. T. Lantseva N. N. Bubnov S. P. Solodovnikov K. N. Makarov 《Russian Chemical Bulletin》1991,40(5):903-907
The EPR method was used to study the structure of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes. The capacity for spin adducts to split off hydrogen atoms is determined by the degree of steric screening of the free radical center. The preparative photochemical reaction of hydrosilanes and dialkyl phosphites with perfluoro-4-methylpent-2-ene leads to regiospecific hydrosilylation and hydrophosphorylation products with yields up to 80%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1018–1023, May, 1991. 相似文献
25.
26.
[formula: see text] Tamandarin A (1), a newly isolated natural product similar in structure to didemnin B (2), was shown to be somewhat more active in vitro than 2 against pancreatic carcinoma with an ED50 value 1.5 to 2 ng/mL. We report here the first total synthesis of 1. The key steps include a practical stereoselective synthesis of the Hiv-isostatine unit, high-yielding linear precursor formation, a successful macrocyclization, and coupling of the macrocycle with the side chain to afford tamandarin A (1). 相似文献
27.
I. Pelant M. N. Popova J. Hála M. AmbroŽ V. Lhotská K. Vacek 《Czechoslovak Journal of Physics》1987,37(10):1183-1197
Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg2Cl2 crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric points, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either at, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg2Cl2 is proposed regarding Hg2Cl2 crystal as a linear chain of molecules.The authors express thanks to Dr. . Barta for supplying the Hg2Cl2 crystals, Dr. Z. Bryknar for critical comments and Dr. B. Velický for stimulating discussion. We thank also Dr. V. Kohlová for assistance during measurement. 相似文献
28.
Spectrophotometric investigation of the reaction of eriochrome cyanin RC and magnesium and aluminium
The reaction of magnesium or aluminium ions with Eriochrome Cyanin RC in alkaline medium leads to formation of a complex of type ML. The molar absorptivities of the complexes are 1.90 +/- 0.14 x 10(3)1. mole(-1).cm(-1) at 570 nm for the magnesium complex and 3.87 +/- 0.04 x 10(4) at 555 nm for the aluminium complex. The conditional stability constants of the complexes were determined at various pH values, and hence the overall formation constants, which were found to be log beta(111) = 8.65 +/- 0.06 for MgOHL, log beta(121) = 22.29 +/- 0.05 for AlH(2)L, log beta(111) = 18.25 +/- 0.14 for AlHL, and log beta(101) = 13.66 +/- 0.01 for AlL. 相似文献
29.
Z. Popova R. Dimitrova Chr Dimitrova G. Wendt 《Reaction Kinetics and Catalysis Letters》1989,39(1):27-32
Temperature programmed reduction (TPR) has been used to study the redox behavior of Ni(II) ions in nickel sodium mordenite (NiNaM) and decationated nickel mordenite (NiHM). The TPR profiles suggest that Ni(II) ions occupy nonequivalent sites with different cooridination states in the mordenite. The reducibility of Ni(II) depends strongly on the zeolite acidity.
() NiII NiNaM NiHM. . .相似文献
30.
TPD data indicate that N2O is desorbed from Ru and -Al2O3 without decomposition in one step and from Ru/Al2O3 in two steps with simultaneous decomposition to nitrogen and oxygen.
, N2O Ru -Al2O3 , Ru/Al2O3— .相似文献