[en] A new type of density soliton, which we call open-quotes dipole density soliton,close-quote close-quote is discovered in data from the Freja satellite. Like the dip or hump density solitons that were recently discovered in the Freja data [D.-J. Wu, G.-L. Huang, and D.-Y. Wang, Phys. Plasmas 3, 2879 (1996)], the dipole density solitons are also associated with strong electric spikes (∼ a few 100 mV/m) and have a spatial scale length of a few 100 m. This indicates that the three types of density solitons (dip, hump, and dipole) probably have the same physical nature. In this paper, a two-dimensional solitary kinetic Alfvacute en wave (SKAW) model with a dipole vortex structure is proposed to account for the three kinds of density solitons (dip, hump, and dipole), in which the differences in their appearances can naturally be attributed to differences in the positions and directions at which the satellite crosses dipole vortex structures. Some features of this two-dimensional SKAW model are discussed, and the results are compared to the one-dimensional cases. copyright 1997 American Institute of Physics

[en] A new type of density soliton, a dipole density soliton, as well as single dip and hump density solitons, were discovered in recent satellite observations of space plasmas. Moreover, these three kinds of density solitons are all associated with similar local electromagnetic fluctuations with Alfvacute en characteristics and have the similar spatial scale comparable with the electron inertial length. This indicates that they originate from the same physical mechanism. We propose that the solitary plasma dipole vortex model can consistently account for these three kinds of density solitons, with the differences in their appearances attributed to the differences in the positions and directions at which the satellite crosses the solitary dipole vortex. copyright 1996 The American Physical Society

[en] The γ-radiation effect of polypropylene was investigated in the presence of three kinds of p-tert-butylcalix[n]arene (n=4, 6, 8) in air at ambient temperature. The influence of radiation dose and store time upon the mechanical properties of the irradiated PP sheets were measured. The results showed that the radiation stabilization was reduced with the increase of the ring size of calixarenes. Based on the mass spectra and the analysis of post-irradiated product, the mechanism of radiation degradation of p-tert-butylcalix[4]arene has been proposed. (author)

[en] Picosecond voltage pulses were generated in YBCO microstriplines by irradiation with a picosecond laser. An autocorrelation method was proposed and applied to measure the temporal decay of these ultrafast voltage pulses. It was also ascertained that these pulses were generated in the superconducting state. Using a 40 ps laser, voltage pulses with fast components < 40 ps were obtained. This fast decay was dependent on the bias current. There were also significant thermal components in these pulses. Methods of generating even shorter pulses are discussed

No abstract available

[en] The surface stress effects on bending behavior of nanowires have recently attracted a lot of attention. In this letter, the incremental deformation theory is first applied to study the surface stress effects upon the bending behavior of the nanowires. Different from other linear continuum approaches, the local geometrical nonlinearity of the Lagrangian strain is considered, therefore, the contribution of the surface stresses is naturally derived by applying the Hamilton's principle, and influence of the surface stresses along all surfaces of the nanowires is captured. It is first shown that the surface stresses along all surfaces have contribution not only on the effective Young's modulus of the nanowires but also on the loading term in the governing equation. The predictions of the effective Young's modulus and the resonance shift of the nanowires from the current method are compared with those from the experimental measurement and other existing approaches. The difference with other models is discussed. Finally, based on the current theory, the resonant shift predictions by using both the modified Euler-Bernoulli beam and the modified Timoshenko beam theories of the nanowires are investigated and compared. It is noticed that the higher vibration modes are less sensitive to the surface stresses than the lower vibration modes.

[en] Europium (Eu³⁺) doped YBa₃B₉O₁₈ were synthesized by conventional solid state solidification methods. (Y_1-xEu_x)Ba₃B₉O₁₈ formed solid solutions in the range of x=0-1.0. The luminescence property measurements upon excitation in ultraviolet-visible range show well-known Eu³⁺ excitation and emission. The charge transfer excitation band of Eu³⁺ dominates the excitation spectra. The emission spectrum of Eu³⁺ ions consists mainly of several groups of lines in the 550-720 nm region, due to the transitions from the ⁵D₀ level to the levels ⁷F_J (J=0, 1, 2, 3, 4) of Eu³⁺ ions. The dependence of luminescence intensity on Eu³⁺ concentration shows no concentration quenching for fully concentrated EuBa₃B₉O₁₈. Eu³⁺ doped YBa₃B₉O₁₈ are promising phosphors for applications in displays and optical devices.

[en] In this Letter, both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. Through the numerical simulation, a new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. Experiments were conducted to validate the numerical design. In the experiment, piezoelectric transducers were used to generate and receive guided wave signals. The results show that the numerical predictions are in very good agreement with the experimental measurements. Specifically, the connection between the local resonance in the thin plate and its wave attenuation mechanism was discussed. -- Highlights: → Both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. → A new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. → Experiments were conducted to validate the numerical design. → The connection between the local resonance in the thin plate and its wave attenuation mechanism was investigated.

[en] La_0.7Ca_0.3MnO₃ thin films grown on SrTiO₃ (100) substrates by off-axis sputtering technique exhibit a fully strained film when the thickness of films is thinner than 25 nm. Transport and magnetic properties of the films for the magnetic field applied parallel to the surface of the films were consistent and could be easily explained by the domain-rotation model. However, these properties were not consistent when the field applied perpendicular to the substrate. The critical field for which peak resistivity was observed in the magnetoresistance measurement, H _c'(-perpendicular ) ∼ 79,500 A m^-1, one order of magnitude higher than the coercive field, H _c perpendicular ∼ 7950 A m^-1. The peak width of the in-plane X-ray diffraction peak (200) of the films as measured by a five-axis X-ray diffractometer showed an exponential decrease to the thickness of films. This broadening cannot be explained by the strain effect alone. We found that nanostructures, such as the ferromagnetic phase segregation in the paramagnetic matrix or the columnar structure in films that introduced excess domain walls, could be responsible for the inconsistency between H _c' perpendicular and H _c perpendicular