Thermocapillary migrations of drops and bubbles

The transport phenomenon of drops or bubbles is a very important topic in fundamental hydrodynamics research and practical applications such as material processing and the chemical engineering. In microgravity environment, if drops or bubbles stay in a continuous phase with non-uniform temperature ¯eld, they will start to move as a result of the variance of the interface tension. This kind of movement is called the Marangoni migration. This review tries to sum up the main results in this ¯eld on theoretical analysis, numerical simulations and experiments. So far the theoretical analysis is still limited to the linear or weak nonlinear steady questions, while the current numerical simulations can already obtain the time- dependent process of the bubble/drop migration when the e®ect of heat convection is small. For strong heat convection problem, or when the Marangoni number is bigger than 100, no numerical result is in consistence with those of experiments so far. Some of the lastest numerical results are shown when heat convection is strong, and the main di®erence between strong and weak heat convection is analyzed. Finally, we also discuss the main unresolved problems in this ¯eld and some possible directions in the future.

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)(60)(PO)(40)(EO)(60) (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1x10(5) s(-1), the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1x10(5) s(-1), the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system.

Period-doubling bifurcations of the thermocapillary convection in a floating half zone

This study experimentally explored the fine structures of the successive period-doubling bifurcations of the time-dependent thermocapillary convection in a floating half zone of 10 cSt silicone oil with the diameter d (0)=3.00 mm and the aspect ratio A=l/d (0)=0.72 in terrestrial conditions. The onset of time-dependent thermocapillary convection predominated in this experimental configuration and its subsequent evolution were experimentally detected through the local temperature measurements. The experimental results revealed a sequence of period-doubling bifurcations of the time-dependent thermocapillary convection, similar in some way to one of the routes to chaos for buoyant natural convection. The critical frequencies and the corresponding fractal frequencies were extracted through the real-time analysis of the frequency spectra by Fast-Fourier-Transformation (FFT). The projections of the trajectory onto the reconstructed phase-space were also provided. Furthermore, the experimentally predicted Feigenbaum constants were quite close to the theoretical asymptotic value of 4.669 [Feigenbaum M J. Phys Lett A, 1979, 74: 375-378].

Dynamics of morphological changes for mitochondrial fission and fusion

Mitochondria experience continuous fusion and fission in a living cell, but their dynamics remains poorly quantified. Here a theoretical model was developed, upon a simplified population balance equation (PBE), to predict the morphological changes induced by mitochondrial fission and fusion. Assuming that both fission and fusion events are statistically independent, the survival probability of mitochondria staying in the fission or fusion state was formulated as an exponentially-decayed function with time, which depended on the time-dependent distribution of the mitochondrial volume and the fission and fusion rates. Parametric analysis was done for two typical volume distributions. One was Gamma distribution and the other was Gaussian distribution, derived from the measurements of volume distribution for individual mitochondria in a living cell and purified mitochondria in vitro. The predictions indicated that the survival probability strongly depended on morphological changes of individual mitochondria and was inversely correlated to the fission and fusion rates. This work provided a new insight into quantifying the mitochondrial dynamics via monitoring the evolution of the mitochondrial volume.

Effect of Nozzle Temperature on the Performance of a 1 kW H2-N2 Arcjet Thruster

A 1 kW-class arcjet thruster was ¯red in a vacuum chamber at a pressure of 18 Pa. A gas mixture of H2 : N2 = 2.8 : 1.5 in volume at a total °ow rate of 4.3 slm was used as the propellant with an input power ¯xed at 860 W. The time-dependent thrust, nozzle temperature and inlet pressure of the propellant were measured simultaneously. Results showed that with the increase in nozzle temperature the thrust decreased and various losses increased. The physical mechanisms involved in these effects are discussed.

Isolated sub-30-as pulse generation of an He+ ion by an intense few-cycle chirped laser and its high-order harmonic pulses

We present an efficient method to generate a ultrashort attosecond (as) pulse when a model He+ ion is exposed to the combination of an intense few-cycle chirped laser pulse and its 27th harmonics. By solving the time-dependent Schroumldinger equation, we found that high-order harmonic generation (HHG) from He+ ion is enhanced by seven orders of magnitude due to the presence of the harmonic pulse. After optimizing the chirp of the fundamental pulse, we show that the cut-off energy of the generated harmonics is extended effectively to I-p+25.5U(p). As a result, an isolated 26-as pulse with a bandwidth of 170.5 eV can be obtained directly from the supercontinuum around the cut-off of HHG. To better understand the physical origin of HHG enhancement and attosecond pulse emission, we perform semiclassical simulations and analyze the time-frequency characteristics of attosecond pulse.

Topological objects in the O(3) nonlinear sigma model

We study the topological defects in the nonlinear O(3) sigma model in terms of the decomposition of U(1) gauge potential. Time-dependent baby skyrmions are discussed in the (2 + 1)-dimensional spacetime with the CP1 field. Furthermore, we show that there are three kinds of topological defects-vortex lines, point defects and knot exist in the (3 + 1)-dimensional model, and their topological charges, locations and motions are determined by the phi-mapping topological current theory.

Topological objects in two-gap superconductor

We discuss the non-Abelian topological objects, in particular the non-Abrikosov vortex and the magnetic knot made of the twisted non-Abrikosov vortex, in two-gap superconductor. We show that there are two types of non-Abrikosov vortex in Ginzburg-Landau theory of two-gap superconductor, the D-type which has no concentration of the condensate at the core and the N-type which has a non-trivial profile of the condensate at the core, under a wide class of realistic interaction potential. We prove that these non-Abrikosov vortices can have either integral or fractional magnetic flux, depending on the interaction potential. We show that they are described by the non-Abelian topology pi(2)(S-2) and pi(1)(S-1), in addition to the well-known Abelian topology pi(1)(S-1). Furthermore, we discuss the possibility to construct a stable magnetic knot in two-gap superconductor by twisting the non-Abrikosov vortex and connecting two periodic ends together, whose knot topology pi(3)(S-2) is described by the Chern-Simon index of the electromagnetic potential. We argue that similar topological objects may exist in multi-gap or multi-layer superconductors and multi-component Bose-Einstein condensates and superfluids, and discuss how these topological objects can be constructed in MgB2, Sr2RuO4, He-3, and liquid metallic hydrogen.

Optical absorption spectra of Na-5, Na-6 and Na-7 clusters: a theoretical study

In the frame of time-dependent density functional theory, the: dynamical polarizabilities of Na-5, Na-6 and Na-7 clusters are calculated using a time-dependent local density approximation. By using Fourier transformation, the optical absorption spectra of Na-5, Na-6 and Na-7 clusters are obtained from their dynamical polarizabilities. It is shown that experimentally measured optical absorption spectra of Na-5, Na-6 and Na-7 clusters are reproduced in our calculations. Furthermore, the calculations of Na-6 and Na-7 clusters are in good agreement with the results of configuration interaction method. Compared with the three-dimensional structure of Na-6, the calculated optical absorption spectra of Na-6 with the two-dimensional structure are more close to the experimental data.

High-order harmonic generation and multi-photon ionization of Na-2 in laser fields

In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na-2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.

Particle transfer and fusion cross-section for super-heavy nuclei in dinuclear system

Within the dinuclear system (DNS) conception, instead of solving the Fokker-Planck equation (FPE) analytically, the master equation is solved numerically to calculate the fusion probability of super-heavy nuclei, so that the harmonic oscillator approximation to the potential energy of the DNS is avoided. The relative motion concerning the energy, the angular momentum and the fragment deformation relaxations is explicitly treated to couple with the diffusion process. The nucleon transition probabilities, which are derived microscopically, are related with the energy dissipation of the relative motion. Thus they are time dependent. Comparing with the analytical solution of FPE at the equilibrium, our time-dependent results preserve more dynamical effects. The calculated evaporation residue cross-sections for one-neutron emission channel of Pb-based reactions are basically in agreement with the known experimental data within one order of magnitude.

多分量对偶超导理论和口袋模型；Multi-component Dual Superconductor Theory and Bag Model

基于联络新参数化方案研究了多分量对偶超导模型。给出了多分量Ginzburg-Landau模型中的自对偶解,并研究了磁通量子数趋于无穷大时的墙涡旋解,以及与口袋模型之间的联系。

The single vortex in the FFLO state

In this Letter, we study the generalized Ginzburg-Landau (GL) functional near the tricritical temperature, and obtain the vortex solution of the FFLO state. Furthermore, we investigate the structure of the vortex and find that the vortices shrink when the Zeeman effect is weaken or temperature is lowered. (C) 2010 Elsevier B.V. All rights reserved.

Production of Superheavy Nuclei in Massive fusion reactions

A master equation is constructed to treat the nucleon transfer process in heavy ion fusion reactions to form superheavy nucleus. The relative motion concerning the energy, the angular momentum and the fragment deformation relaxations is explicitly treated to couple with the diffusion process. The nucleon transition probabilities, which are derived microscopically, are thus time dependent. The calculated evaporation residue cross-sections for both cold and hot fusion are in good agreement with the known experimental data.

Nonadiabatic photodissociation dynamics

The photodissociation dynamics of the triatomic (or pseudo-triatomic) system in the nonadiabatic multiple electronic states is investigated by employing a time-dependent quantum wavepacket method, while the time propagation of the wave packet is carried out using the split-operator scheme. As a numerical example, the photodissociation dynamics of CH,l in three electronic states (1)Q(1)(A'), (1)Q(1)(A"), and (3)Q(0+) is studied and CH3I is treated as a pseudotriatomic model. The absorption spectra and product vibrational state distributions are calculated and compared with previous theoretical work. (C) 2004 Wiley Periodicals, Inc.