Sagnac Effect in the Kerr-Newman and Reissner-Nordstrom Fields

By means of a formal analogy with the Aharonov-Bohm effect, the Sagnac time delay and the corresponding Sagnac phase shift in the Kerr-Newman and Reissner-Nordstrfm spacetimes are discussed. We find that the effect depends on the properties of the source of the gravitational field. The contributions made by the electric charge of the gravitational source can be employed to weaken it in the Kerr-Newman spacetime, even if a phase shift and a time delay still appear. This is due to the properties of the rotating source of the gravitational field.     

Second- and third-harmonic generations for a nondilute suspension of coated particles with radial dielectric anisotropy

We derive expressions for the effective nonlinear susceptibility tensors for both the second harmonic generation (SHG) and induced third harmonic generation (THG) of nonlinear composite materials, in which nondilute coated particles with radial dielectric anisotropy are randomly embedded in the linear host. Two types of coated particles are considered. The first is that the core possesses a second order nonlinear susceptibility and the shell is linear and radially anisotropic, while the second is that the core is linear with radial anisotropy and the shell has a second order nonlinear susceptibility. We observe greatly enhanced SHG and THG susceptibilities at several surface plasmon resonant frequencies. For the second model, due to the coating material being metallic, there exists two fundamental resonant frequencies ω_c1 and ω_c2, whose difference ω_c2-ω_c1 is strongly dependent on the interfacial parameter and the radial dielectric anisotropy. Furthermore, in both systems, the adjustment of the dielectric anisotropy results in larger enhancement of both SHG and induced THG susceptibilities at surface plasmon resonant frequencies than the corresponding isotropic systems. Therefore, both the core-shell structure and the dielectric anisotropy play important roles in determining the nonlinear enhancement and the surface resonant frequencies.     

Convection-Dominated Accretion Flows with Radiative Cooling

By numerically solving the set of basic equations describing black hole accretion flows with low accretion rates, we show that although the dynamical structure of these flows is essentially unaffected by radiative processes in comparison with the case in which the radiation is not considered, the radiative cooling can be more important than the advective cooling in the flow＇s convection-dominated zone, and this result may have implications to distinguish observationally convection-dominated accretion flows from advection-dominated accretion flows.     

Piezoelectric and bonding properties of a cement-based composite for dental application

A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed.     

Flexible ceramic–polymer composite films with temperature-insensitive and tunable dielectric permittivity

BaTiO₃–polymer composite layers have been produced by the spin-on technique (thickness 3–10 μm). The dielectric permittivity of the layers at room temperature can be tuned from 2.8 to approximately 33 by varying the ceramic filling from 0 to 60% by volume. The dielectric properties of the films are almost insensitive to temperature variations in the range 20–180 °C. Free-standing composite layers with ceramic content ≤50% are flexible without noticeable change of permittivity after repeated mechanical bending. Received: 22 November 2001 / Accepted: 24 November 2001 / Published online: 23 January 2002     

Geodesics of Spherical Dilaton Spacetimes

The properties of spherical dilaton black hole spacetimes are investigated through a study of their geodesics. The closed and non-closed orbits of test particles are analysed using the effective potential and phase-plane method. The stability and types of orbits are determined in terms of the energy and angular momentum of the test particles. The conditions of the existence of circular orbits for a spherical dilaton spacetime with an arbitrary dilaton coupling constant α are obtained. The properties of the orbits and in particular the position of the innermost stable circular orbit are compared to those of the Reissner-Nordstrom spacetime. The circumferential radius of innermost stable circular orbit and the corresponding angular momentum of the test particles increase for α≠ 0.     

Synchronization in complex networks by time-varying couplings

Synchronization in networks of complex topologies using couplings of time-varying strength is numerically investigated. The time-dependencies of coupling strengths are coupled to the dynamics of the nodes in a way to enhance synchronization. By time-varying couplings, oscillators are found to take quite a short time to reach synchronization state when the couplings are relatively strong. Even when a nearly regular networks of large-size with few shortcuts is difficult to be synchronized by fixed couplings, the time-varying couplings can easily enhance the emergence of synchronization.     

Effective permittivity of materials containing graded ellipsoidal inclusions

We prove a generic theorem stating the equivalence between a graded dielectric ellipsoid (with gradation along a family of internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach to homogenize dispersions of ellipsoidal graded particles.     

Design of a novel bioreactor and application in vascular tissue engineering

Endothelial cells (ECs) detachment under high shear stress at the early period of transplantation resulted in thrombosis and occlusion. To solve this problem, we developed a novel bioreactor. The bioreactor mimicked the formation of pulsatile flow in physiological conditions. Human umbilical vein ECs were seeded onto the lumen of living tissue conduits grown within dog peritoneal cavity. The shear stress generated by the bioreactor was increased step by step from 1.5 ± 0.8 dyn/cm² to 5.3 ± 2.4 dyn/cm², and was applied to ECs after static culture for 2 days. The results showed that completely confluent monolayer ECs were elongated, and were oriented parallel to the flow direction. The bioreactor could provide good environment for formation of endothelium. Stepwise increase shear stress could strengthen cell-cell and cell-extracellular matrix. The flow conditions of the bioreactor play a key role to determine the quality of the ECs lining.