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101.
102.
V. E. Lyubovitskij A. Faessler Th. Gutsche M. A. Ivanov J. G. Krner 《Progress in Particle and Nuclear Physics》2003,50(2):329-339
We present a summary of results for exclusive decays of single and double heavy-flavored baryons in the relativistic three-quark model. 相似文献
103.
Henk D.L Hollmann János Körner Simon Litsyn 《Journal of Combinatorial Theory, Series A》1997,80(2):388-393
We show that if the collection of all binary vectors of lengthnis partitioned intokspheres, then eitherk2 orkn+2. Moreover, such partitions withk=n+2 are essentially unique. 相似文献
104.
S. V. Trukhanov I. O. Troyanchuk D. D. Khalyavin I. M. Fita H. Szymczak K. Bärner 《Journal of Experimental and Theoretical Physics》2002,94(2):329-335
Investigations are performed of the crystal structure and magnetic and electromagnetic properties of single crystals (0.23 ≤x≤0.34) and polycrystals (0 ≤x ≤0.50) of an Nd1?x BaxMnO3?δ system of solid solutions. It is found that, for samples prepared in the air, the maximal Curie temperature (T C ) does not exceed 150 K, while, in the case of polycrystalline samples in the concentration range of 0.34 ≤x ≤0.50, prepared in a reducing medium (a gaseous mixture of argon and carbon monoxide), T C increases to 320 K. As a result of the reducing medium effect on the compositions, the type of the magnetic phase transition to the paramagnetic state changes from the first to second order. The electrical resistivity of reduced polycrystalline samples (0.34≤x ≤0.50) decreases in magnitude and correlates with the behavior of magnetization. Both series of samples, prepared both in the air and in a reducing medium, exhibit a transition from the metal to dielectric state at a temperature below T C . The temperature and field dependences of magnetization for the stoichiometric polycrystalline com-position of Nd0.50Ba0.50MnO3 are measured under conditions of hydrostatic pressure. It is demonstrated that the hydrostatic pressure induces in Nd0.50Ba0.50MnO3 the transition from the antiferromagnetic to ferromagnetic state. Based on the measurement results, hypothetical magnetic phase diagrams are constructed for the system of solid solutions being treated, depending on the concentration of barium and the method of preparation. It is found that no T TC increase is observed in single crystals (0.23≤x≤0.34) such as is observed in polycrystals. It is assumed that the abrupt increase in T C of polycrystalline samples prepared in a reducing medium is a result of the emergence of extended defects and microstresses in the crystal lattice. 相似文献
105.
106.
107.
Gerhard Brner 《Physik in unserer Zeit》2006,37(6):264-265
108.
The photooxidation of sanguinarine, coralyne and berberine was studied in oxygenated alkaline methanol solutions. Rose bengal as photosensitizer significantly accelerates the process, indicating the importance of singlet molecular oxygen in the reaction mechanism. The quantum yield of sensitized oxidation was found to increase significantly with pH and reaches 0.4 for berberine at pH 13.8. The direct oxidation of alkaloids is less efficient, the quantum yield does not exceed 0.01 even in oxygen-saturated solutions. The photoinduced electron ejection does not play a role in the oxidation. The uncharged pseudobase forms, which are present in alkaline medium, are oxidized much more easily than the alkaloid cations. 相似文献
109.
Börner J Vieira Idos S Pawlis A Döring A Kuckling D Herres-Pawlis S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4507-4512
Zinc bis(chelate) guanidine complexes promote living lactide polymerization at elevated temperatures. By means of kinetic and spectroscopic analyses the mechanism has been elucidated for these special initiators that make use of neutral N-donor ligands. The neutral guanidine function initiates the polymerization by a nucleophilic ring-opening attack on the lactide molecule. DFT calculations on the first ring-opening step show that the guanidine is able to act as a nucleophile. Three transition states were located for ligand rearrangement, nucleophilic attack, and ring-opening. The second ring-opening step was modeled as a representation for the chain growth because here, the lactate alcoholate opens the second lactide molecule via two transition states (nucleophilic attack and ring-opening). Additionally, the resulting reaction profile proceeds overall exothermically, which is the driving force for the reaction. The experimental and calculated data are in good agreement and the presented mechanism explains why the polymerization proceeds without co-initiators. 相似文献
110.
Rahn T Bendrath F Hein M Baumann W Jiao H Börner A Villinger A Langer P 《Organic & biomolecular chemistry》2011,9(14):5172-5184
Bis-cyclopropanated 1,3,5-tricarbonyl compounds were prepared by a sequence of Claisen condensations and cyclopropanations. The optimization of the conditions proved to be very important to suppress retro-Claisen reactions. The conformation of these molecules was studied by experimental and computational methods. The syn/syn;syn/syn conformation is present for all derivatives. It is exclusively present in the case of the derivative containing a phenyl group located at the terminal carbon atom. In most cases, equilibria with other conformers are found. 相似文献