Estimation of initial conditions and parameters of a chaotic evolution process from a short time series

Tracing back to the initial state of a time-evolutionary process using a segment of historical time series may lead to many meaningful applications. In this paper, we present an estimation method that can detect the initial conditions, unobserved time-varying states and parameters of a dynamical (chaotic) system using a short scalar time series that may be contaminated by noise. The technique based on the Newton-Raphson method and the least-squares algorithm is tolerant to large mismatch between the initial guess and actual values. The feasibility and robustness of this method are illustrated via the numerical examples based on the Lorenz system and Rossler system corrupted with Gaussian noise.     

A New Highly Selective Fluorescent Silver Probe

We have synthesized 3,3,7,7-tetra[N-ethyl-N-benzyl(acetamide)-2-oxymethyl]-5- oxanonane (EBAOO) and its terbium complex. The crystal structures of the complex were determined: [Tb(EBAOO)](2)[Tb(NO(3))(5)](3).H(2)O, Orthorhombic, a=40.722 (6) A, b=18.418 (3) A, c=20.496 (3) A. In the structure, the rare earth ion satisfies nine coordination. The geometry of the nine-coordinate polyhedron is discussed in terms of the dihedral angle and the mean plane. The luminescence of the complex is noticeably enhanced upon complexation with Ag(+), which is due to the suppression of photoinduced electron transfer (PET) process. Therefore, the terbium complex can be used as a selective fluorescent silver probe.     

Switching from bonding to nonbonding: temperature-dependent metal coordination in a zinc(II) sulfadiazine complex

The metal coordination in the mononuclear complex diamminebis(sulfadiazine)zinc shows a unique temperature dependence: High-resolution diffraction data prove that the coordination is almost tetrahedral at 100 K, whereas a fifth longer interaction becomes relevant at 200 K. The change in the geometry is fully reversible and is also reflected in the charge density of the compound.     

Qualitative Analysis of Crossing Limit Cycles in Discontinuous Liénard-Type Differential Systems

In this paper, we investigate qualitative properties of crossing limit cycles for a class of discontinuous nonlinear Liénard-type differential systems with two zones separated by a straight line. Firstly, by applying left and right Poincaré mappings we provide two criteria on the existence, uniqueness and stability of a crossing limit cycle. Secondly, by geometric analysis we estimate the position of the unique limit cycle. Several lemmas are given to obtain an explicit upper bound for the amplitude of the limit cycle. Finally, a predatorprey model with nonmonotonic functional response is studied, and Matlab simulations are presented to show the agreement between theoretical results and numerical analysis.     

气体密度对瑞利散射法测量团簇尺寸影响的初步分析

 瑞利散射法被广泛地应用于测量团簇尺寸,通常视散射信号的强弱只正比于团簇的大小。从理论推导得到瑞利散射信号并不仅仅是团簇尺寸的函数,而与团簇尺寸、气体密度和结合率均有关系,认为采用瑞利散射法测量团簇尺寸应考虑气体密度对测量结果的影响。并用该分析方法研究了氩团簇沿喷嘴轴线的尺寸分布情况：团簇尺寸沿喷嘴轴线并不是单纯的单调变化,而是在某个位置达到最大值,并且这个位置与背景压强等因素有关。     

Structure of hexakis(imidazole)nickel(II) disalicylate, [Ni(Im)6](Sal)2

The crystal and molecular structures of [Ni(Im)₆](Sal)₂ (Im = imidazole, Sal = salicylate) have been determined by X-ray crystallography. It crystallizes in the triclinic system, space group P1¯, with lattice parameters a = 8.3125(2), b = 8.7168(1), c = 12.3262(3) Å, = 90.341(1), = 96.33(1), = 101.544(1)°, and Z = 1. The crystal structure of the title compound is built up of discrete monomeric molecules of [Ni(Im)₆](Sal)₂. The nickel(II) ions have an octahedral geometry with the NiN₆ chromophore. In the solid state, the title compound forms a network through N—H···O hydrogen bonds, the intermolecular hydrogen bonds connect the Ni(Im)²⁺ ₆ moieties and salicylate molecules.     

Structure of bis(O,O′-diisopropyldithiophosphato-S,S′) (1,10-phenanthroline-N1,N10)zinc(II) complex, [Zn(phen)(S2P(OiPr)2)2]

The crystal and molecular structure of [Zn(phen)(S₂P(OiPr)₂)₂] (Phen = 1,10-phenanthroline) has been determined by X-ray crystallography. It crystallizes in the Monoclinic system, space group C2/c, with lattice parameters a = 19.315(4), b = 10.438(2), c = 16.567(3)Å, = 102.89 (3)°, and Z = 4. The complex has C₂ symmetry. The coordination geometry of each Zn atom, by two S atoms from two (O,O-diisopropyldithiophosphato) anions and by two N atoms from phenanthroline ligand, is that of a slightly distorted tetrahedron [Zn—S 2.2914(8)Å Zn—N 2.111(2)Å]. The Zn···S distances to the noncoordinated S atoms are long: 3.5276 Å, which are indicated that there are much weaker interactions between them.     

Theoretical understanding mechanisms and stereoselectivities of [2+2] cycloaddition of ketenes with ketimines catalyzed by bifunctional N-heterocyclic carbene

Structural Chemistry - Reaction mechanism of NHC-catalyzed asymmetric [2+2] cycloaddition reaction between ketenes and isatin-derived ketimines for the formation of spirocyclic...     

Correlation between composition and hydrogen storage behaviors of the Li2NH-MgNH combination system

Hydrogen storage performances of a Li(2)NH-xMgNH combination system (x = 0, 0.5, 1 and 2) are investigated for the first time. It is found that the hydrogenated samples with MgNH exhibit a significant reduction in the dehydrogenation temperatures. Mechanistic investigations reveal that there is a strong dependence of the hydrogen storage reaction process on the molar ratio between MgNH and Li(2)NH. As a consequence, tuning of thermodynamics is achieved for hydrogen storage in the Li(2)NH-xMgNH system by changing the reaction routes, which is ascertained to be the primary reason for the reduction in the operating temperature for hydrogen desorption. Specifically, it is found that under 105 atm hydrogen (140-280 °C) 5.6 wt% hydrogen is reversibly stored in the Li(2)NH-0.5MgNH combination system, which is greater than in the well-investigated Mg(NH(2))(2)-2LiH system.     

Anisotropic dewetting polydimethylsiloxane surface fabricated using ultrashort laser pulses

Anisotropic dewetting polydimethylsiloxane(PDMS) surfaces, which consist of groove-like micro/nanostructures(so-called hierarchical structures), are fabricated using an ultrashort pulsed laser. The contact angles(CAs) are measured parallel to the microgrooves, which are always larger than those measured perpendicular to the microgrooves, exhibiting a superhydrophobic anisotropy of approximately 4° on these fabricated PDMS surfaces at optimized parameters. These pulsed-laser irradiated surfaces exhibit enhanced hydrophobicity with CAs that increase from 116° to 156° while preserving the anisotropic dewetting. Additionally, the wettability of the surfaces with different morphologies is investigated. The temporal evolution of the wettability of the pulsed-laser irradiated PDMS surface is also observed within the first few hours after pulsed laser irradiation.