Modern Physics Letters B

Experimentally observed aggregates in under-saturated aqueous solutions are analyzed. Aggregates studied include: 0.5 to 6 micrometer-sized domains composed of solvated strong electrolyte ions, organic- or bio-molecules; clusters of up to 280 water molecules.

Hitherto, the customary electrostatic (ES) theories could not explain the formation of these large aggregates. Recently, it was shown that quantum electrodynamic (QED) interactions might affect the structure of solutions. Our analysis indicates that these interactions cause the observed aggregations.

We found the observed aggregate characteristics conform to those of QED coherent domains. For example, QED predicts that dilution, e.g. from 2 M to 1 M, causes an increase of several hundred percent in the size of domains composed of solvated coherently oscillating molecules or ions. For solutions of DNA or NaCl, the measured cluster size as a function of concentration is available in the literature. We found it to be in agreement with the QED predictions.

By making use of ϕ-mapping topological current theory and the decomposition of gauge potential theory, we investigate the skyrmion excitations of spin Hall effect induced by optical fields in neutral atomic system. It is shown that the topological structures of these skyrmions are characterized by ϕ-mapping topological numbers: Hopf indices and Brouwer degrees. Based on the bifurcation theory of ϕ-mapping theory, it is found that the skyrmions can be generated or annihilated at the limit point and they encounter, split or merge at the bifurcation point.

Currently, synchronizability of networks is mainly studied in terms of the eigen ratio of the coupling matrix, which is a pure property of network topology. In this work, we clarify that although the eigen ratio is relevant to the possible range of coupling strength for achieving synchronization, it cannot fully determine the latter. The magnitude of the eigenvalues also plays a decisive role. We emphasize that synchronizability of networks is inherently related to the local dynamics on networks. It is not appropriate to discuss synchronizability of networks without considering the specific dynamics on them. For three typical types of local dynamics, we discuss the implication of synchronizability of networks.

By introducing a stress potential function, we transform the plane elasticity equations of two-dimensional quasicrystals of point group 10, to a partial differential equation. And then we use the complex variable function method for classical elasticity theory to that of the quasicrystals. As an example, a decagonal quasicrystal in which there is an arc is subjected to a uniform pressure p in the elliptic notch of the decagonal quasicrystal is considered. With the help of conformal mapping, we obtain the exact solution for the elliptic notch problem of quasicrystals. The work indicates that the stress potential and complex variable function methods are very useful for solving the complicated boundary value problems of higher order partial differential equations which originate from quasicrystal elasticity.

An analytical expression for the equation of state and thermo-physical quantities of exponential-6 (exp-6) fluid are derived based on the Ross variational perturbation theory. The developed formalism is applied to N₂ fluid. Comparisons of theory and simulations for exp-6 potential fluid are presented. The agreement of numerical results of pressure and internal energy with Monte Carlo (MC) simulations show that the theoretical model is satisfactory except where a few points from metastable ones appeared in literature. The expression has been applied to fluid nitrogen and the fitting to experimental data of fluid N₂ is surprisingly good. The predictions of pressure in the range of high temperature and high density are satisfactory. It has also been found that the analytic equation of state for exp-6 potential fluid based on RDF proposed by Sun et al. is better in a wide range of pressures and temperatures than that derived from PY expression. Comparisons show that a potential dependence on temperature and density (or volume) may be necessary for the understanding of interaction between N₂ molecules. The equation of state can also be extended to application of important real gases such as H₂, O₂, CH₄, CO and CO₂.

By introducing the entangled state representation and following Feynman's assumption that "electron pairs are bosons … A bound pair acts as a Bose particle", we construct a Hamiltonian operator for the Josephson transmission line (JTL) detector, then we use the Heisenberg equation of motion to derive the modified Josephson equation. Based on the modified Josephson equation, the measurement dynamics of JTL detector is investigated, which will be helpful for us to analyze the quantum measurement of JTL detector.

In this paper, control of the uncertain multi-scroll critical chaotic system is studied. According to variable structure control theory, we design the sliding mode controller of the uncertain multi-scroll critical chaotic system, which contains sector nonlinearity and dead zone inputs. For an arbitrarily given equilibrium point of the uncertain multi-scroll chaotic system, we achieve global stabilization for the equilibrium points. Particularly, a class of proportional integral (PI) switching surface is introduced for determining the convergence rate. Furthermore, the proposed control scheme can be extended to complex multi-scroll networks. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control scheme.

The effects of electrical parameters including applied voltages, duty cycles, and frequencies, on the structures of titania film by micro arc oxidation (MAO) technology were studied. Micro arc oxidation was conducted for Ti with pulsed dc power supply. The voltage was controlled at various constant applied voltages (200, 230, 270 V) with various pulse frequencies (dc, 20, 30, 40, 50 kHz) for 3 minutes, and the pulse current was measured with time. There seems to be a minimum absolute duty period (26 μs) in order to allow oxide thickness to grow, because with a duty period lower than 26 μs, the oxide may stop growing. In other words, with less than 26 μs, it is hard for Ti ions to diffuse through the oxide film to grow to a certain thickness.

The effect of the surface on edge dislocation glide in the crystal with point defects both on the surface and in the bulk is studied theoretically. It is shown that the drag force of dislocation can be reduced by the image forces to several orders of magnitude in nanoscale region.

Within the 1D Hubbard model, linear closed chains with various numbers of sites are considered in particle–particle self-consistent random phase approximation (SCRPA) for the T-matrix. Encouraging results with a minimal numerical effort are obtained, confirming earlier results with this theory for other models. SCRPA solves the two-site problem exactly. It therefore contains the two electrons and high density Fermi gas limits correctly.

The formation of GdBa₂Cu₃O_7-δ(Gd123) from metal oxalate precursor with average grain size less than 40 nm using the coprecipitation method is reported. The coprecipitated powders were heated at 900°C for 12 hours, pelletized and then sintered at 920°C for 15, 20 and 25 hours, respectively. All samples showed a dominant Gd123 phase with the orthorhombic structure. The amount of impurity phase Gd₂BaCuO₅(Gd211) can be controlled by varying the sintering time. This work shows that nano-sized oxalate powders produced via coprecipitation method can be an effective technique to synthesize high quality GdBa₂Cu₃O_7-δ samples where the amount of (Gd211) can be controlled by varying the sintering duration. The percentage of Gd211 impurity decreased with increase in sintering time. This result is useful in utilizing the Gd211 phase as pinning center in enhancing the transport properties.