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The content of rare earth elements was analysed in USGS-standard rocks BCR-1 and G-2 and in lunar fines samples from Apollo-12 using activation analysis techniques. 相似文献
64.
Hanspeter Kraft 《Mathematische Annalen》1971,193(1):49-56
Ohne Zusammenfassung 相似文献
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Hans Fritz Paul Hug Hanspeter Sauter Tammo Winkler Enno Logemann 《Magnetic resonance in chemistry : MRC》1977,9(2):108-112
Carbon-13 n.m.r. spectra of formic, acetic, propionic and butyric acid amides with N,N-di-n-alkyl substituents have been completely assigned with the aid of extensive double resonance experiments. The data obtained were used to study long range steric effects on chemical and solvent shifts. 相似文献
67.
Schenker R Weihe H Andres H Basler R Chaboussant G Michelsen K Aebersold M Büttner H Güdel HU 《Inorganic chemistry》2002,41(16):4266-4274
The properties of the spin state manifold of the tetranuclear cluster Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O (bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine) are investigated by combining magnetic susceptibility and magnetization measurements with an inelastic neutron scattering (INS) study on an undeuterated sample of Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O. The temperature dependence of the magnetic susceptibility indicates an S = (1)/(2) ground state, which requires antiferromagnetic interactions both between Cr(3+) and Ni(2+) ions and among the Cr(3+) ions. INS reveals potential single-ion anisotropies to be negligibly small and enables an accurate determination of the exchange parameters. The best fit to the experimental energy level diagram is obtained by an isotropic spin Hamiltonian H = J(CrNi)(S(1)().S(4)() + S(2)().S(4)() + S(3)().S(4)()) + J(CrCr)(S(1)().S(2)() + S(1)().S(3)() + S(2)().S(3)()) with J(CrNi) = 1.47 cm(-)(1) and J(CrCr) = 1.25 cm(-)(1). With this model, the experimental intensities of the observed INS transitions as well as the temperature dependence of the magnetic data are reproduced. The resulting overall antiferromagnetic exchange is rationalized in terms of orbital exchange pathways and compared to the situation in oxalato-bridged clusters. 相似文献
68.
Various laterally fluoro-substituted benzonitriles have been prepared containing a trans-4-(n-alkyl)cyclohexane ring linked to the 4-position of the benzonitriles either through a methyleneoxy (? CH2O–) or an ethylene (? CH2CH2-) bridge. The bridging group links the benzonitrile and cyclohexane rings either directly or through an additional 1,4-bonded cyclohexane or benzene ring. The synthesis and liquid-crystal transition temperatures of these new compounds are described. In several cases the nematic-isotropic transition temperatures of F-substituted benzonitriles are found to be higher than those of the non-laterally substituted analogues. 相似文献
69.
Diquaternary salts of 2,4-di-(4-pyridyl)-1,3,5-triazines have been prepared. The salts can be regarded as reversible one electron transfer systems with redox potentials (E0) of about ?0·44 V in the pH range 7·0–8·5. 2,4-Bis-(4-methyl-4-pyridinio)-1,3,5-triazinediium dihalides are effective post-emergent herbicides at application rates of 4–6 kg/hectare. 相似文献
70.
Carotenoid Glycosyl Esters Synthesis of β-D -Glucosyl 8′-Apo-β-carotene-8′-oate and β-D -Glucosyl Vitamin-A-oate (β-D -Glucosyl Retionate) β-D -glucosyl 8′-apo-β-carotene-8′-oate (III) and β-D -glucosyl vitamin-A-oate (VI) were regio- and stereoselectively synthesized in high yields from the N-acylimidazoles I and IV, respectively, or from the N-acyltriazoles II and V, respectively, and unprotected β-D -glucose, according to the method described for the synthesis of di(β-D -glucosyl) 8,8′-diapo-carotene-8,8′-dioate [1]. It seems that this method can generally be applied for the synthesis of β-D -glucosyl esters of polyene carboxylic acids. 相似文献