Synchronized Anti-Phase and In-Phase Oscillations of Intracellular Calcium Ions in Two Coupled Hepatocytes System

We study the dynamic behaviour of two intracellufar calcium oscillators that are coupled through gap junctions both to Ca^2＋ and inositol（1,4,5）-trisphosphate （IP3）. It is found that synchronized anti-phase and in-phase oscillations of cytoplasmic cadcium coexist in parameters space. Especially, synchronized anti-phase oscillations only occur near the onset of a Hopf bifurcation point when the velocity of IP3 synthesis is increased. In addition, two kinds of coupling effects, i.e., the diffusions of Ca^2＋ and IP3 among cells on synchronous behaviour, are considered. We fnd that small coupling of Ca^2＋ and large coupling of IP3 facilitate the emergence of synchronized anti-phase oscillations. However, the result is contrary for the synchronized in-phase case. Our findings may provide a qualitative understanding about the mechanism of synchronous behaviour of intercellular calcium signalling.     

Dynamics Analysis and Transition Mechanism of Bursting Calcium Oscillations in Non-Excitable Cells

A one-pool model with Ca^2＋-activated inositol-trisphosphate-concentration degradation is considered. For complex bursting Ca^2＋ oscillation, point-cycle bursting of subHopf-subHopf type is found to be in the intermediate state from quasi-periodic bursting to point-point bursting of subHopf-subHopf type. The fast-slow burster analysis is used to study the transition mechanisms among simple periodic oscillation, quasi-periodic bursting, point-point and point-cycle burstings. The dynamics analysis of different oscillations provides better insight into the generation and transition mechanisms of complex intra- and inter-cellular Ca^2＋ signalling.     

Synchronization,stickiness effects and intermittent oscillations in coupled nonlinear stochastic networks

Long distance reactive and diffusive coupling is introduced in a spatially extended nonlinear stochastic network of interacting particles. The network serves as a substrate for Lotka-Volterra dynamics with 3rd order nonlinearities. If the network includes only local nearest neighbour interactions, the system organizes into a number of local asynchronous oscillators. It is shown that (a) Introduction of all-to-all coupling in the network leads the system into global, center-type, conservative oscillations as dictated by the mean-field dynamics. (b) Introduction of reactive coupling to the network leads the system to intermittent oscillations where the trajectories stick for short times in bounded regions of space, with subsequent jumps between different bounded regions. (c) Introduction of diffusive coupling to the system does not alter the dynamics for small values of the diffusive coupling p_diff, while after a critical value p_diff ^c the system synchronizes into a limit cycle with specific frequency, deviating non-trivially from the mean-field center-type behaviour. The frequency of the limit cycle oscillations depends on the reaction rates and on the diffusion coupling. The amplitude σ of the limit cycle depends on the control parameter p_diff.     

Atomic Diffusion in Cu/Si （111） and Cu/SiO2/Si （111） Systems by Neutral Cluster Beam Deposition

The Cu films are deposited on two kinds of p-type Si （111） substrates by ionized duster beam （ICB） technique. The interface reaction and atomic diffusion of Cu/Si （111） and Cu/SiO2/Si （111） systems are studied at different annealing temperatures by x-ray diffraction （XRD） and Rutherford backscattering spectrometry （RBS）. Some significant results are obtained： For the Cu/Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs when annealed at 230℃. The diffusion coefficients of the samples annealed at 230℃ and 500℃ are 8.5 ×10^-15 cm^2.s^-1 and 3.0 ×10^-14 cm^2.s^-1, respectively. The formation of the copper-silicide phase is observed by XRD, and its intensity becomes stronger with the increase of annealing temperature. For the Cu/SiO2//Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs and copper silicides are formed when annealed at 450℃. The diffusion coefficients of Cu in Si are calculated to be 6.0 ×10^-16 cm^2.s^-1 at 450℃, due to the fact that the existence of the SiO2 layer suppresses the interdiffusion of Cu and Si.     

Photopolymerization-Induced Two-Beam Coupling and Light-Induced Scattering in Polymethyl Methacrylate

Light amplification due to two-beam coupling is realized in doped polymethyl methacrylate （PMMA） glasses. A coupling gain as large as 14 cm^-1 is obtained. The dynamic behaviour of absorption and light-induced scattering due to the process of photopolymerization are also studied. The results show that the amplification and its dynamic process enable possible applications of PMMA in optical devices.     

Numerical Simulations of Calcium Ions Spiral Wave in Single Cardiac Myocyte

The calcium ions （Ca^2＋） spark is an elementary Ca^2＋ release event in cardiac myocytes. It is believed to buildup cell-wide Ca^2＋ signals, such as Ca^2＋ transient and Ca^2＋ wave, through a Ca^2＋-induced Ca^2＋ release （CICR） mechanism. Here the excitability of the Ca^2＋ wave in a single cardiac myoeyte is simulated by employing the fire-diffuse-fire model. By modulating the dynamic parameters of Ca^2＋ release and re-uptake channels, we find three Ca^2＋ signaling states in a single cardiac myoeyte： no wave, plane wave, and spiral wave. The period of a spiral wave is variable in the different regimes. This study indicates that the spiral wave or the excitability of the system can be controlled through micro-modulation in a living excitable medium.     

Cs^＋-K^＋ Exchange in Z-Cut KTiOPO4 Crystal Covered with Chromium Masking Layer

Cs^＋-K^＋ ion exchanges are performed on z-cut KTiOPO4 crystals with chromium coating covered. The temperature of ion exchange is 430℃, and the time range from 15min to 30min. The dark mode spectra of the samples are measured by the prism coupling method. The channel structures on the samples are observed by a microscope and the near field pattern of the channel waveguides are measured by the end-fire coupling method. The refractive index of the samples increases and the increments at surface are modulated due to the existence of Cr film. In the region covered by Cr film, the refractive index of the samples at the surface increases dramatically in a shallow layer. The results of energy dispersive x-ray spectra indicate that in the region covered with Cr film, Cr ions participate in the ion exchange process, and enhance the refractive index. The results may provide a possibility that achieves index enhancement and Cr doping synchronically.     

Electronic Curves Crossing in Methyl Iodide by Spin--Orbit Ab Initio Calculation

An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized effective curves of low-lying states, including spin-orbit coupling and relativistic effects, are calculated. The spin-orbit electronic curve crossing between ^3Qo＋ and ^1Q1, and the shadow minimum in potential energy curve of ^3Qo＋ at large internuclear distance are found in both sets of the curves according to the present calcu- lations. The crossing position is in the range of Re-1 = 0.2370 3：0.0001 nm. Comparisons with other reports are presented.     

Characteristics of a Cataphoresis He-Ca+ Recombination Laser

A cataphoretic input of calcium vapour into the active volume of pulsed He-Ca^＋ laser is designed and made. The recombination laser at 373.3 nm and the R-M transition laser at 854.6 nm are achieved experimentally with modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The dependences of work parameters such as the pulse frequency, the power supply voltage and the helium pressure on laser output characteristics at 373.3nm line are measured and discussed. The maximum laser output power of 136mW and the specific power of 5.9 m W/cm^3 are obtained, respectively.     

Semi-passivity and synchronization of diffusively coupled neuronal oscillators

We discuss synchronization in networks of neuronal oscillators which are interconnected via diffusive coupling, i.e. linearly coupled via gap junctions. In particular, we present sufficient conditions for synchronization in these networks using the theory of semi-passive and passive systems. We show that the conductance based neuronal models of Hodgkin-Huxley, Morris-Lecar, and the popular reduced models of FitzHugh-Nagumo and Hindmarsh-Rose all satisfy a semi-passivity property, i.e. that is the state trajectories of such a model remain oscillatory but bounded provided that the supplied (electrical) energy is bounded. As a result, for a wide range of coupling configurations, networks of these oscillators are guaranteed to possess ultimately bounded solutions. Moreover, we demonstrate that when the coupling is strong enough the oscillators become synchronized. Our theoretical conclusions are confirmed by computer simulations with coupled Hindmarsh-Rose and Morris-Lecar oscillators. Finally we discuss possible “instabilities” in networks of oscillators induced by the diffusive coupling.     

钾扩散耦合引起的心脏中螺旋波的变化

在某些情况下, 心肌细胞外的钾离子浓度是变化的, 钾离子的横向扩散会导致细胞外钾离子的聚集和产生钾扩散耦合, 用考虑钾扩散耦合的Luo-Rudy相I心脏模型研究了钾扩散耦合对螺旋波动力学的影响. 数值模拟结果表明: 当钾扩散耦合比较强时, 钾扩散耦合使细胞外钾离子浓度先升高, 然后做规则振荡, 导致螺旋波做无规则漫游; 观察到螺旋波的波臂宽度和频率随钾扩散耦合的强度增大而减小, 这样, 当钾扩散耦合足够强时, 钾扩散耦合可以消除螺旋波和时空混沌. 关键词： 钾扩散耦合 螺旋波 时空混沌     

Fine-Structure Splittings of Nitrogen Isoelectronic Sequence： Competitions among Spin-Orbit Interactions, Breit Interactions and Electron Correlations

Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration interaction method with quantum-electrodynamics corrections performed by the GRASP code, we calculate the fine-structure energy levels of the ground-state configuration （1s^22s^22p^3） of the nitrogen isoelectronic sequence, according to the L-S coupling scheme with atomic number Z up to 22. Based on the calculated results, we elucidate the mechanism of the orderings of fine-structure energy levels of 2^ D3/2,5/2 and 2^P1/2,3/2 respectively, i.e. for 2^D3/2,5/2 orderings, the competition between the spin-orbit interactions and the Breit interactions; for 2^P1/2,3/2 orderings, the electron correlations, especially the electron correlations owing to the 2p^5 configuration interactions.     

Bursting Ca2+ Oscillations and Synchronization in Coupled Cells

A mathematical model proposed by Grubelnk et al. [Biophys. Chem. 94 （2001） 59] is employed to study the physiological role of mitochondria and the cytosolic proteins in generating complex Ca^2＋ oscillations, lntracellulax bursting calcium oscillations of point-point, point-cycle and two-folded limit cycle types are observed and explanations are given based on the fast/slow dynamical analysis, especially for point-cycle and two-folded limit cycle types, which have not been reported before. Furthermore, synchronization of coupled bursters of Ca^2＋ oscillations via gap junctions and the effect of bursting types on synchronization of coupled cells are studied. It is argued that bursting oscillations of point-point type may be superior to achieve synchronization than that of point cycle type.     

The one-dimensional Lennard-Jones system: collective fluctuations and breakdown of hydrodynamics

The dynamical correlations of a model consisting of particles constrained on the line and interacting with a nearest-neighbour Lennard-Jones potential are computed by molecular-dynamics simulations. A drastic qualitative change of the spectral shape, from a phonon-like to a diffusive form, is observed upon reducing the particle density even ad moderate temperatures. The latter scenario is due to the spontaneous fragmentation of the crystal-like structure into an ensemble of “clusters" colliding among themselves. In both cases, the spectral linewidths do not follow the usual q² behaviour for small wavenumbers q, thus signalling a breakdown of linearized hydrodynamics. This anomaly is traced back by the presence of correlations due to the reduced dimensionality.     

Storm-Time Strong Field-Aligned Ion Upflow in Region of the SED Plume

We report the observations from the GPS TEC and DMSP F-13 satellites showing that very strong upward field-aligned （FA） ion velocity and flux in the outer region of the storm-enhanced density （SED） occurred in the event of the geomagnetic storm on 29-31 May 2003. By a method of coordinate transformation, upward FA ion velocities in excess of 25Orals are obtained from the observations of the DMSP F-13 satellite. Further, an FA ion flux is estimated to be about 4.5 x 1013 ions/m2 s in the dusk sector. The estimated FA ion velocity and flux provide a powerful direct proof to support the scenario that there is a strong coupling of particles between the ionosphere and plasmasphere in the region of the SED plume. In the process, FA ion flux transports from the ionosphere to the plasmasphere in the region of the SED plume. Therefore, the plume of SED in the ionosphere provides an important source to the enhanced density of O^＋ in the storm-time plasmasphere.     

First-Principles Study on Magnetic Properties of V-Doped ZnO Nanotubes

Electronic and magnetic properties of V-doped ZnO nanotubes in which one of Zn^2＋ ions is substituted by V^2＋ ions are studied by the first-principles calculations of plane wave ultra-soft pseudo-potential technology based on the spin-density function theory. The computational results reveal that spontaneous magnetization in Vdoped （9,0） ZnO nanotubes can be induced without p-type or n-type doping treatment, and the ferromagnetism is isotropic and independent of the chirality and diameter of the nanotubes. It is found that V-doped ZnO nanotubes have large magnetic moments and are ferromagnetic half-metal materials. Moreover, the ferromagnetic coupling among V atoms is generated by O 2p electron spins and V 3d electron spins localized at the exchanging interactions between magnetic transitional metal （TM） impurities. The appearance of ferromagnetism in V-doped ZnO nanotubes gives some reference to fabrication of a transparent ferromagnet which may have a great impact on industrial applications in magneto-optical devices.     

Structural, electronic and magnetic properties of Cr-doped (ZnTe)12 clusters

We have studied the energetics and magnetism in Cr-doped (ZnTe)₁₂ clusters by first principles density functional calculations. Total energy calculations suggest that it is energetically most favourable for Cr atoms to substitute at Zn sites. Both ferromagnetic and anti-ferromagnetic coupling between the Cr atoms exist depending on the Cr-Cr distance in the clusters. The magnetic exchange coupling between Cr atoms is short-ranged.     

Surface Diffuseness Anomaly in 16O+208Pb Quasi-elastic Scattering at Backward Angle

The quasi-elastic scattering excitation function of the doubly magic ^16O＋^208 Pb system at a backward angle is measured at sub-barrier energies with high precision. The diffuseness parameters extracted from both the singlechannel and the coupled-channels calculations give almost the same value a = 0.76 ± 0.04 fro. The results show that the coupling effect is negligible for the spherical system. The obtained value is smaller than the extracted value from the fusion excitation function, but larger than the value of a -- 0.63 fm, which is from the systematic analysis of elastic scattering data.     

Characteristics of Cladding-Pumped Short Er3+/Yb3+ Codoped Single Mode Phosphate Glass Fibre

We experimentally investigate the laser characteristics of a series of short pieces of newly-developed Er³⁺/Yb³⁺ codoped single mode phosphate glass fibres via the cladding pump of a 976nm multimode laser diode. A stablecontinuous-wave single transverse mode laser with over 85mW at 1553nm is generated from a 5.5-cm-long active fibre. Single mode laser output power per unit length is up to 15mW/cm. Moreover, the slope efficiency is 11.8% when the pump power is below 940mW and the 3dB linewidth is 0.06nm at the maximum pump power. The numerical simulation results show that the laser emission slope efficiency can exceed 20% by means of increasing the coupling efficiency of the pump to the fibre core further.     

Cosmological Models with Time Dependent G and Λ Coupling Scalars

A cosmological model in which the universe has its critical density and gravitational constants generalized as coupling scalars in Einstein's theory is considered. A general method of solving the field equations is given. An exact solution for matter distribution in cosmological models satisfying G=G₀(R/R₀)ⁿ is presented. Corresponding physical interpretations of the cosmological solutions are also discussed.