Cyclotron resonance and effective mass renormalizations in Sr2RuO4

Using a microwave cavity perturbation technique, we have succeeded in observing cyclotron resonances in the layered Perovskite superconductor Sr₂RuO₄. Three cyclotron masses are deduced, corresponding to m_cγ=9.7m_e, m_cβ=5.8m_e and m_c=4.3 m_e. A comparison between these values and the effective masses deduced from other techniques provides us with a unique means of gauging the role of Coulomb correlations in the title compound.     

Dipolar interactions and origin of spin ice in ising pyrochlore magnets

Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the nearest-neighbor "spin ice" model. We discuss the dipolar energy scale present in both these materials and discuss how spin-ice behavior can occur despite the presence of long-range dipolar interactions. We present results of numerical simulations and a mean field analysis of Ising pyrochlore systems. Based on our quantitative theory, we suggest that the spin-ice behavior in these systems is due to long-range dipolar interactions, and that the nearest-neighbor exchange in Dy2Ti2O7 is antiferromagnetic.     

The estimation of leucine aminopeptidase produced by molting nematodes with labeled leucinamide as substrate

Leucine aminopeptidase activity was measured using l-[U-¹⁴C]leucinamide as substrate. The leucine freed by hydrolysis was separated by high voltage electrophoresis and estimated in a scintillation counter. The method was especially useful for studying the production of LAP during the molting of infective juveniles of the nematodes, H. contortus, because activity could be measured without purifying or concentrating the enzyme.     

Librational anharmonicity in solid α-N2

The effects of librational anharmonicity in solid α-N₂ are studied. Anharmonic frequencies are obtained using a boson representation for torsional motion. Two-libron and (one stretch + one libron) processes observed via Raman spectroscopy are discussed. Cubic libron-phonon interactions are shown to account for anomalies in the widths of the optical phonons as observed in infrared absorption.     

Quantum oscillation of Hall resistance in the extreme quantum limit of an organic conductor (TMTSF)2ClO4

We report resistance and magnetic torque experiments under a high magnetic field up to 45 T in a three dimensional quantum Hall (QH) system (TMTSF)(2)ClO(4), where TMTSF = tetramethyltetraselenafulvalene. The Hall resistance shows huge oscillations accompanied with sign reversal after the final QH state, where the Landau level filling factor is unity, is removed above 26 T. The magnetic torque also oscillates with the field. The results suggest that a novel quantum state, where the character of the carriers periodically changes with the field, is stabilized in the extreme quantum limit.     

Photoproduction of the omega meson on the proton at large momentum transfer

The differential cross section, dsigma/dt, for omega meson exclusive photoproduction on the proton above the resonance region (2.6相似文献   

Diels-Alder reactions of 5-vinyl-1-acyl-2-aryl-2,3-dihydro-4-pyridones: regio- and stereoselective synthesis of octahydroquinolines

[reaction: see text] Readily available 5-vinyldihydropyridones 2 undergo Diels-Alder cyclization with various dienophiles to afford novel octahdroquinolines. The process is highly stereoselective and provides heterocyclic products containing synthetically useful functionality.