Molecular Dynamic Study for Chiral Discrimination of a -Phenylethylamine by Modified Cyclodextrin in Gas Chromatography

A molecular dynamic method in conjunction with a statistic test has been utilized to model chiral recognition of a -phenylethylamine on heptakis (2,6-di-O-butyl-3-O-butyryl)-b -cyclodextrin in gas chromatography. The modelling data correlated with the chromatographic elution order, and indicated that the preferred site of a -phenylethylamine is the interior of cavity.     

Improving histogram-based image contrast enhancement using gray-level information histogram with application to X-ray images

Many applications of histogram-based techniques for the purposes of image enhancement are well known. However, these techniques often fail to produce satisfactory results for a broad variety of low-contrast images (e.g., X-ray images). In this paper, we propose a new form of histogram for image contrast enhancement. The input image is first divided into several equal-sized regions according to the intensities of gradients, their corresponding statistical values of gray levels are then modified respectively, and finally the processed histogram for the whole image is obtained by the summation of all the weighted values of regions. The fundamental characteristic of this new form of histogram is that the amplitudes of its components can objectively reflect the contribution of the gray levels to the representation of image information. Accordingly, this new histogram is called gray-level information histogram. The performance of many histogram-based enhancement techniques might be improved dramatically using the proposed histogram. Testing on the X-ray images validates the effectiveness of the new histogram.     

Synthesis, Structure and Thermal Behavior of a New Coordination Polymer Based on Mixed Pyrazine-2-carboxylate and Oxalate Ligands

Abstract  

A new 4d–4f coordination polymer, [AgGd(pyzc)₂(ox)·H₂O)] (1) [pyzc = Pyrazine-2-carboxylate, ox = oxalate] has been successfully synthesized under hydrothermal conditions and structurally determined by single-crystal X-ray diffraction, and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis and power X-ray diffraction. Single-crystal X-ray analysis reveals that it crystallizes in the monoclinic space group P2 ₁ /c with a = 10.0746(1) ?, b = 18.642(1) ?, c = 8.0525(2) ?, β = 112.470(1)°, Mr = 617.34, Z = 4, V = 1505.6(2) ?³, μ = 5.732, F(000) = 1164. The Gd(III) ion is nine-coordinated by two O-donors and two N-donors of two different chelating pyzc ligands, four O-donors of two different chelating oxalate ligands, and one O-donor of another carboxylate group of one pyzc ligand. The compound represents a 3D microporous polymeric network constructed by gadolinium–oxalate chains and Ag-pyzc subunits.     

Solutions of a second-order Hamiltonian system with periodic boundary conditions

By using the least action principle and the saddle point theorem, some existence theorems are obtained, viz. the existence of solutions to a second-order Hamiltonian system with periodic boundary conditions in the cases when the gradient of the nonlinearity is bounded sublinearly and linearly respectively.     

Ultrafast optical switching in Kerr nonlinear photonic crystals

Nonlinear photonic crystals made from polystyrene materials that have Kerr nonlinearity can exhibit ultrafast optical switching when the samples are pumped by ultrashort optical pulses with high intensity due to the change of the refractive index of polystyrene and subsequent shift of the band gap edge or defect state resonant frequency. Polystyrene has a large Kerr nonlinear susceptibility and almost instantaneous response to pump light, making it suitable for the realization of ultrafast optical switching with a response time as short as a few femtoseconds. In this paper, we review our experimental progress on the continual improvement of all-optical switching speed in two-dimensional and three-dimensional polystyrene nonlinear photonic crystals in the past years. Several relevant issues are discussed and analyzed, including different mechanisms for all-optical switching, preparation of nonlinear photonic crystal samples by means of microfabrication and self-assembly techniques, characterization of optical switching performance by means of femtosecond pump-probe technique, and different ways to lower the pump power of optical switching to facilitate practical applications in optical information processing. Finally, a brief summary and a perspective of future work are provided.     

Hemi[hexa­aqua­magnesium(II)] (μ‐2,6‐bis{[bis­(carboxyl­ato­methyl)­amino]­methyl}‐4‐chloro­phenolato)­bis­[di­aqua­magnesium(II)] decahydrate

The crystal structure of the title compound, [Mg(H₂O)₆]_0.5[Mg₂(C₁₆H₁₄ClN₂O₉)(H₂O)₄]·10H₂O, shows that this bi­nuclear complex consists of two Mg centres in distorted octahedral geometry, joined by an oxo bridge which is a derivative of the deprotoned hydroxy group of the phenolate in the ligand mol­ecule. In the anion, the coordination sphere of each Mg^II ion is completed by two carboxyl­ates, a tertiary N atom and two water mol­ecules. The inner coordination spheres for the Mg^II ions are very similar, both in ligand sets and in geometry. Each unit of the binuclear complex has one negative charge neutralized by a neighbouring hydrated cation, [Mg(H₂O)₆]²⁺, in which the Mg atom lies on an inversion centre. In each cell, there are 34 water mol­ecules and most of them participate in the formation of hydrogen bonds, which contribute greatly to the stability of the whole structure.     

Entropy in Subordination and Filtering

We propose a stochastic model of transmitting random information at random time. In this model, the signal is observed as a random sampling according to an increasing stable stochastic process. Thus we are given a subordinate stochastic process which is a typical irreversible process. As the characteristic of this phenomea we observe the loss of entropy.     

Laser-jamming analysis of combined fiber lasers to imaging CCD

To complete a successful laser jamming to imaging charge coupled device (CCD) based on combined fiber lasers, the interactions between CCD and combined fiber lasers were analyzed in detail. The saturation and crosstalk thresholds of CCD were achieved, which are lower than 10 mW/cm². Through theoretical analysis and numerical simulations, the thermal processes under single pulse, multi-pulses and continuous laser irradiations were developed. The simulation results have proved the possibility of hard damage caused by multi-pulses and continuous laser irradiations. The combined fiber lasers is suitable to deploy optical saturation jamming at present. The further applications of combined fiber lasers need a more powerful laser source and a more accurate tracking and pointing system.     

A stage-structured predator–prey model with disturbing pulse and time delays

In this article we propose a stage-structured predator–prey model with disturbing pulse and time delays and obtain the sufficient conditions for the global attractivity of predator-eradiation periodic solution and permanence of the system. We also show that time delay, pulse catching rate and the period of pulsing can affect the dynamics of the system.