Entry distribution, fission barrier, and formation mechanism of 254102No

The entry distribution in angular momentum and excitation energy for the formation of 254No has been measured after the 208Pb(48Ca,2n) reaction at 215 and 219 MeV. This nucleus is populated up to spin 22Planck's over 2pi and excitation energy greater, similar6 MeV above the yrast line, with the half-maximum points of the energy distributions at approximately 5 MeV for spins between 12Planck's over 2pi and 22Planck's over 2pi. This suggests that the fission barrier is greater, similar5 MeV and that the shell-correction energy persists to high spin.     

Phonon screening in high-temperature superconductors

In good conductors optical phonons are usually screened, and therefore not observed. However, sharp features due to infrared-active modes in the copper-oxygen planes are observed in the optical conductivity of Pr1.85Ce0.15CuO4 and YBa2Cu3O6.95. Oscillator strengths indicate that the screening of these modes is poor or totally absent. These materials are compared with eta-Mo4O11, in which lattice modes appear suddenly below the charge-density wave transition. It is proposed that poor screening in the cuprates originates from fluctuating charge inhomogeneities in the copper-oxygen planes.     

A model for the shell current in a reversed field pinch

A model for the shell current in a reversed field pinch which includes the current induced by the motion of the plasma is discussed. This model gives a good approximation to the magnitude and time dependence of a shell current measured experimentally     

Pharmazeutische Pr?parate

Ohne Zusammenfassung     

Fusion reactions with the one-neutron halo nucleus (15)C

The structure of (15)C, with an s(1/2) neutron weakly bound to a closed-neutron shell nucleus (14)C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction (15)C+(232)Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring (14)C+(232)Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for (15)C, while the cross sections for (14)C match the trends measured for (12,13)C.     

Lowest breathing mode of bosonic helium clusters

We analyze various microscopic calculations of vibrational frequencies for ⁴He_N clusters, N = 3-728. The lowest breathing frequency with total angular momentum J = 0 varies smoothly as a function of N, with a maximum around N = 50-120. Received 11 July 2001     

Spectrum and dynamics of the BCS-BEC crossover from a few-body perspective

The spectrum of two spin-up and two spin-down fermions in a trap is calculated using a correlated Gaussian basis throughout the range of the BCS-BEC crossover. These accurate calculations provide a few-body solution to the crossover problem. This solution is used to study the time evolution of the system as the scattering length is changed, mimicking experiments with Fermi gases near Fano-Feshbach resonances. The structure of avoiding crossings in the spectrum allow us to understand the dynamics of the system as a sequence of Landau-Zener transitions. Finally, we propose a ramping scheme to study atom-molecule coherence.     

Stress amplification and plastic flow for spheroidal shells: Applications to myopia

Amplification of effective stress and plastic strain rates after yielding are derived for the anisotropic stress fields of the prolate and oblate spheroidal shells as models of the myopic and hyperopic eyes. Dimensionless closed-form results are presented for arbitrary axis ratio with both constant shell thickness and variable shell thickness, using the constant scleral mass assumption. The results show that the myopic and hyperopic eyes are susceptible to failure by plastic yielding at the equator and pole, respectively, for high intraocular pressures. Experimental data from the equatorial zone of rabbit sclera shows scleral yielding and plastic flow for intraocular pressures greater than 32 mm Hg. Practical applications include glaucoma and pathological myopia.