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排序方式: 共有172条查询结果,搜索用时 250 毫秒
51.
H. Ower Th.W. Elze J. Idzko K. Stelzer E. Grosse H. Emling P. Fuchs D. Schwalm H.J. Wollersheim N. Kaffrell N. Trautmann 《Nuclear Physics A》1982,388(2):421-444
Multiple Coulomb excitation of 232Th, 234U and 236U by 5.3 208Pb ions has been studied using γ-ray spectroscopy. Excitation of ground-band levels is observed up to spin Iπ = 26+ (tentatively 28 +) in 232Th and 234U and Iπ = 28+ (tentatively 30+)in 236U. High-spin levels of the Kπ = 0? octupole-vibrational bands are also observed in these nuclei. The measured transition energies between ground-band levels suggest that at several units of angular momentum are carried by single particles aligned with the rotation axis.This result can be understood in terms of a super band built on aligned two-quasiparticle configurations which crosses the ground-state rotational band at a rotational frequency of . The E2 transition-matrix elements deduced from the experimental γ-yields agree within their errors with the rigid-rotor predictions up to the highest spins observed.The experimental results are discussed using the concept of rotation alignment and are compared with predictions of the rotation-vibration model and the interacting-boson model. 相似文献
52.
J. Heintze G. Heinzelmann P. Igo-Kemenes R. Mundhenke H. Rieseberg V. Roberto B. Schürlein H. W. Siebert V. Soergel H. Stelzer K. -P. Streit A. H. Walenta 《Physics letters. [Part B]》1977,70(4):482-486
Partial branching ratios have been measured in six lepton momentum bins between 120 and 180 MeV/c. From these, six relations between the form factor slopes λ+ and λ0 have been derived. Using the world average value λ+ = 0.029 ± 0.003 and combining the six partial results on λ0, we obtain λ0 = 0.019 ± 0.010. This value is in agreement with the Callan-Treiman relation and other predictions. Together with recent K30 results, it supports the rule. The agreement of our result with the value of λ0 obtained from Kμ3 Dalitz-plot studies supports muon-electron universality. 相似文献
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55.
J. Heintze G. Heinzelmann P. Igo-Kemenes R. Mundhenke H. Rieseberg B. Schürlein H.W. Siebert V. Soergel H. Stelzer K.-P. Streit A.H. Walenta 《Nuclear Physics B》1979,149(3):365-380
The decay K+ → e+υγ has been investigated. For the structure-dependent part with positive γ-helicity (SD+) the branching ratio is obtained from 51 ± 3 events observed in the kinematical region Ee ? 235 MeV, Eγ > 48 MeV and θeγ > 140°. For the corresponding part with negative γ-helicity we obtain an upper limit Γ(SD?)/Γ(SD+) < 11 (90% CL) from the sample of electrons with energies 220 MeV ? Ee < 230 MeV and with no γ in the backward direction. This upper limit implies that the ratio of structure-dependent axial vector amplitudes lies outside the region .For the decay the limit 90% confidence level) was found. 相似文献
56.
PtCl(2) constitutes an efficient and practical catalyst for a set of different atom economical rearrangement reactions of enynes. This includes (i) a formal enyne metathesis reaction delivering 1,3-dienes, (ii) the formation of polycyclic vinylcyclopropane derivatives, and (iii) an unprecedented O-->C allyl shift reaction if unsaturated ethers are employed. Although these transformations produce significantly different structural motifs, they share a common mechanism comprising a cationic manifold triggered by the pi-complexation of Pt(II) onto the alkyne unit of the substrates. Strong experimental support for the proposed mechanism comes from deuterium-labeling studies, a careful analysis of the product distribution pattern, and the fact that in some cases PtCl(2) can be replaced by simple Lewis or Br?nsted acids as the catalysts. 相似文献
57.
Michael Tepper Othmar Stelzer Thomas Häusler William S. Sheldrick 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract Amino acids containing functionalized aromatic substituents are of considerable interest as building blocks for the syntheses and the design of new types of proteins and pharmacologically active compounds. In contrast to amino acids bearing phosphonated phenyl substituents [1], phosphinophenyl derivatives have been reported only very recently[2]. We have been able to synthesize phosphinophenyl amino acids of type 1 or 2 by nucleophilic phosphination [3] of the potassium salts of 2-and 4-fluoro-a-phenylglycine and-alanine with potassium phosphides Ph(R')PK in high yields. 相似文献
58.
Andrew M. Kelly Verena Kaltenhauser Inge Mühlbacher Karl Rametsteiner Harald Kren Christian Slugovc Franz Stelzer Frank Wiesbrock 《Macromolecular bioscience》2013,13(1):116-125
A set of poly(2‐oxazoline)‐derived (co‐)polymers was prepared by microwave‐assisted polymerizations and acid‐mediated hydrolysis and tested for antimicrobial activity in 50 × 50 × 2 mm PP compound plates containing 5 wt% of the polymers. Antimicrobial activity against gram‐negative E. coli and P. aeruginosa as well as C. albicans depended only on the degree of hydrolysis, while antimicrobial activity against gram‐positive S. aureus was only observed for hydrolyzed poly(2‐nonyl‐2‐oxazoline)s. The surface energies of the compound plates compared to pure PP were hardly altered, and the compounds can be considered as alternatives for PP. The presence of the biocide additives at the surface of the PP compound plates could be shown by combined ATR‐IR, zeta potential, and SEM‐EDX measurements. Antimicrobial activity was maintained during double incubation as well as for lowered amounts of the biocide additive of 1% in PP compound plates.
59.
R. J. Charity R. Freifelder A. Gobbi N. Herrmann K. D. Hildenbrand F. Rami H. Stelzer J. P. Wessels G. Casini P. R. Maurenzig A. Olmi A. A. Stefanini J. Galin D. Guerreau U. Jahnke A. Péghaire J. C. Adloff B. Bilwes R. Bilwes G. Rudolf M. Petrovici M. Gnirs D. Pelte 《Zeitschrift für Physik A Hadrons and Nuclei》1991,341(1):53-73
Events with 2, 3 and 4 heavy-fragments (A≧20) have been detected in the reactions100Mo+100Mo atE/A =18.7, 23.7 MeV and120Sn+120Sn atE/A=18.4 MeV. The experiments were performed with an array of 12 detectors which together covered a large fraction of the forward hemisphere and allowed a high detection efficiency for these events. Masses and energies of all fragments have been reconstructed by means of an improved version of the kinematic coincidence method. The probabilitiesP 3 andP 4 of producing 3- and 4-body events were found to depend mainly on the dissipated energy rather than on the bombarding energy, thus indicating that their origin lies more in the decay properties of the excited fragments than in the dynamics of the interaction. Emission of light particles from the composite system is shown to become more relevant with increasing bombarding energy and may explain the drop of theP 3 andP 4 curves at high energy losses. Small deviations of theP 3 andP 4 curves at 23.7A · MeV from those at lower bombarding energies were used to estimate the amount of a possible pre-equilibrium light particle emission as a function of impact parameter. 相似文献
60.