Numerical Study on the Vortex States of High-T c Superconductors with Point Defects: Novel Phases in the Vortex Liquid Region

Phase diagram of high-T _c vortex states in with point defects is investigated by large-scale Monte Carlo simulations. We find that the first-order boundary between the vortex slush and vortex liquid phases terminates at a critical point, and that there is a step of the specific heat above the critical point as reported experimentally. As the system size increases, this step becomes sharper but smaller, and is associated with a crossover rather than a thermodynamic phase transition.     

Anisotropic Superconducting Properties of MgB2 and Related Compounds

Anisotropic superconducting properties of inter-metallic compounds MgB₂, Y₂PdGe₃, and CaAlSi with AlB₂ structure are studied by detailed angular dependent transport measurements. MgB₂ and CaAlSi shows appreciable anisotropy of the upper critical field, H _c2, with mass anisotropy parameter =3 and 2, respectively, while Y₂PdGe₃ is almost isotropic. In-plane anisotropy of H _c2 in these hexagonal superconductors is very small, consistent with the prediction based on GL theory.     

Pesticide adsorption by granular activated carbon adsorbers. 1. Effect of natural organic matter preloading on removal rates and model simplification

The adsorptive removal of periodic spikes of the trace synthetic organic chemicals (SOCs) simazine and asulam from water containing natural organic matter (NOM) was studied in pilot-scale granular activated carbon (GAC) adsorbers over a period of nearly 3 years. The SOC removal percentage obtained at any preloading time and bed depth was independent of the liquid-phase SOC concentration, and equations derived from the ideal adsorbed solution theory and a pore surface diffusion model validated this observation. The pseudo-steady-state SOC removal rate, (dC/dz), at each preloading time and bed depth was therefore first order with respectto the liquid-phase SOC concentration, C. Furthermore, the removal modulus, k, in the resulting SOC removal rate expression was a reflection of the solid-phase concentration of the NOM fraction that interfered with the adsorption of SOCs. Analysis of the removal modulus values indicated that the mass transfer zone of the NOM fraction competing with asulamtraveled more rapidlythrough the GAC adsorber than that competing with simazine. Given the similar molecular sizes of the targeted SOCs, this result was primarily explained by differences in SOC adsorbabilities, where the more weakly adsorbing asulam was less capable of displacing preloaded NOM. Consequently, the NOM fraction competing with asulam constituted a larger percentage of the total NOM than that competing with simazine.     

Total sputtering yields of solids under MeV-energy Si ion bombardment

Total sputtering yields have been measured for SiO₂ and Cu targets bombarded with Si ions at an incident energy between 500 keV and 5.0 MeV using a quartz crystal microbalance technique. In order to measure total yields accurately, we have developed a beam modulation technique to avoid the effect of thermal drift. In the MeV energy range, an ion penetrates through thin SiO₂ and Cu targets and is implanted into a quartz crystal. Therefore, the thickness of these layers deposited on quartz crystals was carefully controlled to avoid damage of quartz crystal by incident ions. As a result, total sputtering yields of SiO₂ increased with incident Si ion energy, while those of the Cu target decreased. The total yields of the SiO₂ target were represented well by a power low of the electronic stopping power.     

Basic study on filtering using the frequency characteristics of reflected waves from underground radar

The waves reflected from objects were extracted and basic studies were conducted on the frequency characteristics of these reflected waves with aim of improving the signal/noise ratio of underground radar images. Aerial tests conducted on steel pipes and steel plates showed that the respective hyperbolic curve signals have different characteristics. Using this principle to filter the signals from buried pipes made it possible to extract only the buried pipe signals.The efficiency to distinguish individual object in underground radar images can be improving by using this filter effectively.     

Computational dynamics approach to the effect of damping on stability of a cantilevered column subjected to a follower force

The paper discusses on the basis of computational approach the effect of small damping on the theoretical flutter bounds of a cantilevered column subjected to a follower force. A cantilevered viscoelastic column having a tip mass is considered. The impulse responses of the column are studied by the mode superposition method to observe the growth rate of the motion. It is established that the growth rate of the motion of the nonconservative column with a larger but small size of damping is greater than that with the smaller. It is demonstrated that the gap between the flutter predictions made by considering and neglecting damping can be bridged by assuming the practical concept of stability, the stability in a finite time interval.     

Platelet activating factor induced respiratory mucosal damage

Human sinus mucosal specimens from eight normal individuals were exposed to platelet activating factor (PAF) at concentrations ranging from 10⁻⁶ M to 10⁻¹¹ M in a humidified CO₂ chamber at 37°C. The mucosal surface of the specimens was recorded on video tapes and magnified 2,500 times on a 19-inch television (TV) monitor. Ciliary activity of each ciliated cell was photoelectrically measured on the TV monitor in real time. PAF induced mucosal damage which resulted in a coarse profile including ciliostasis and exfoliation of epithelial cells. The length of the incubation period in which the initial coarse profile occurred on the mucosal surface inversely correlated with the concentration of exposed PAF ranging from 10⁻⁶ M to 10⁻¹⁰ M with r=−0.712 (p<2×10⁻⁴). Both the control medium and 10⁻⁸ M lysoPAF showed no effect on ciliary activity or mucosal surface alteration even after 24 hr of exposure. Significant ciliary inhibition was noted after 6 hr of exposure to PAF at concentrations of 10⁻⁸ M and 10⁻¹⁰ M (p<0.05). After 10 hr of exposure, significant ciliary inhibition (p<0.01) was noted at all concentrations. Inhibition occurred in a time- and dose-dependent manner. The length of the incubation period in which initial ciliostatis occurred and the level of PAF concentration showed an inverse correlation with r=−0.918 (p<10⁻⁶). These results indicate that PAF is cytotoxic to human respiratory mucosa. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.