Generation of hyperchaos from the Chen–Lee system via sinusoidal perturbation

A system with more than one positive Lyapunov exponent can be classified as a hyperchaotic system. In this study, a sinusoidal perturbation was designed for generating hyperchaos from the Chen–Lee chaotic system. The hyperchaos was identified by the existence of two positive Lyapunov exponents and bifurcation diagrams. The system is hyperchaotic in several different regions of the parameters c, ε, and ω. It was found that this method not only can enhance or suppress chaotic behavior, but also induces chaos in non-chaotic parameter ranges. In addition, two interesting dynamical behaviors, Hopf bifurcation and intermittency, were also found in this study.     

Thermo-optical study of UV cured polyether urethane diacrylate films with dispersed octadecanol

Thermally reversible light scattering (TRLS) films are prepared from ultraviolet (UV) curing of polyether urethane diacrylate (PEUDA) with dispersed low molecular weight 1-octadecanol (OD). Depending on the temperature, the OD domains are crystalline or amorphous and this produce opaque or transparent films in a reversible way. Stable optically transparent and light scattering states are obtained after 100 successive heating–cooling cycles. Moreover, morphologies of the OD domains could be varied significantly with the cure temperature and this led to notable discrepancy in optical properties. By using an UV-mask and curing in two steps at different temperatures, complex patterns could be recorded in the film that were encoded at high temperatures (60 °C) and revealed at low temperatures (i.e., at room temperature), which makes the film a candidate for thermo-optical recording medium.     

Electrodeposition behavior of Mg with Zn from acidic sulfate solutions

Electrodeposition of Mg with Zn in acidic sulfate solutions with polyethylene glycol and octadecyl dimethyl benzyl ammonium chloride as additives was investigated by scanning electron microscopy, X-ray diffraction, and potentiodynamic polarization techniques. The results show that these two compounds act in a synergetic way to suppress Zn deposition markedly and facilitate Mg reduction. Zn–0.46%Mg coatings are produced under high cathodic current densities, which have lower corrosion potentials than Zn coatings and hydrogen evolution in neutral chloride solutions. Magnesium hydroxide may cause current oscillations at high cathodic polarizations in plating solutions without zinc salts due to its formation and peel-off. An “induced co-deposition” mechanism is proposed for Zn–Mg alloy electrodeposition.     

An ab initio simulation of the UV/Visible spectra of substituted chalcones

The electronic absorption spectra of 29 phenyl-ring substituted chalcones have been investigated with the time-dependent density functional theory (TD-DFT) and polarizable continuum TD-DFT (PCM-TD-DFT). It turns out that the hybrid PBE1PBE functional with the 6-31G basis set provide reliable λ_max when the solvent effects are included in the model. Comparisons with experimental values lead to a mean absolute error of 12 nm (0.136 eV). Moreover, the observed substituent effects are reproduced by calculation qualitatively. The λ_max of substituted chalcone in phenyl ring A is less sensitive to substitution than that in ring B. The linear correlation of Hammett’s substituent constants (σ_P) with LUMO energies is better with respect to HOMO energies. The calculation reveals that the maximum absorption band mainly results from the π→π* transition from HOMO to LUMO. The analysis of the electron density plots of frontier molecular orbitals show that most transitions should be of valence excitation nature.      

Crystal growth and morphology of hindered phenol AO-60

Crystal growth of a hindered phenol compound, tetrakis [methylene-3-(3-5-ditert-butyl-4-hydroxy phenyl) propionyloxy] methane (trade name AO-60), was successfully recorded by optical microscopy (OM) equipped with a hot stage. The morphology of AO-60 crystals, grown at 100 °C from amorphous state, appeared in the form of tetragonal-sloped step growth. Further study using scanning electron microscopy (SEM) and atomic force microscopy (AFM) experimentally demonstrated that AO-60 crystals had a hopper-like morphology, which had occurred rarely in the condition of organic compound crystals but predominantly rather to inorganic compound crystals in the reported literatures. The morphological features observed on the crystal surfaces suggested step growth and hopper growth mechanism. Besides, a raising around the edge of the AO-60 hopper crystal was also experimentally characterized for the first time.     

Optimizing the quadruple-potential waveform for the pulsed amperometric detection of neomycin

Determination of neomycin is important for quality control of the pharmaceutical preparation. A quadruple-potential waveform used for pulsed amperometric detection of neomycin was investigated. The waveform cleans the electrode by application of a potential more negative than the potential limit to avoid the formation of gold oxide during applying positive potential to clean gold electrode, thus decreasing the dissolution resulting recession of the gold working electrode within gold oxide formation/reduction cycles in the triple-potential waveform. Waveform parameters were optimized to maximize the signal-to-noise ratio (S/N). The detection limit of neomycin B is lower than 0.01 microg/ml. The linearity of framycetin (plotted as peak area of neomycin B) ranges from 0.05 to 100 microg/ml with correlation coefficient 0.9998. R.S.D. (n = 60) of the peak area of neomycin B is lower than 2%. The quadruple-potential waveform shows low detection limits and long-term reproducibility.     

Fast resistive reconnection regime in the nonlinear evolution of double tearing modes

Phases of nonlinear double tearing modes are studied numerically. The first two phases lead to the formation and growth of magnetic islands and are followed by a fast reconnection phase to complete the process, driven by a process of neighboring magnetic separatrices merging and magnetic islands coupling. The fast growth can be understood as a result of the island interaction equivalent to a steadily inward flux boundary driven. Resistivity dependences for various phases are studied and shown by scaling analysis for the first time. It is found that after an early Sweet-Parker phase with a eta(1/2)-scale, a slow nonlinear phase in a Rutherford regime with a eta(1)-scale is followed by the fast reconnection phase with a eta(1/5)-scale.     

二维小波变换在粮虫图像处理中的应用

提出了用小波变换检测储粮害虫图像边缘的方法,这种方法通过对二维小波变换图像局部极大值的检测得到图像的边缘信息.计算表明,将二维小波变换应用于储粮害虫的图像去噪和边缘检测,不仅可以保留图像的边缘特征,视觉效果好,还可以得到较清晰的粮虫特征图像,为粮虫图像特征提取打下了良好的基础.     

Bacterial carbon processing by generalist species in the coastal ocean

The assimilation and mineralization of dissolved organic carbon (DOC) by marine bacterioplankton is a major process in the ocean carbon cycle. However, little information exists on the specific metabolic functions of participating bacteria and on whether individual taxa specialize on particular components of the marine DOC pool. Here we use experimental metagenomics to show that coastal communities are populated by taxa capable of metabolizing a wide variety of organic carbon compounds. Genomic DNA captured from bacterial community subsets metabolizing a single model component of the DOC pool (either dimethylsulphoniopropionate or vanillate) showed substantial overlap in gene composition as well as a diversity of carbon-processing capabilities beyond the selected phenotypes. Our direct measure of niche breadth for bacterial functional assemblages indicates that, in accordance with ecological theory, heterogeneity in the composition and supply of organic carbon to coastal oceans may favour generalist bacteria. In the important interplay between microbial community structure and biogeochemical cycling, coastal heterotrophic communities may be controlled less by transient changes in the carbon reservoir that they process and more by factors such as trophic interactions and physical conditions.