Robust synchronization of a class of uncertain chaotic systems based on quadratic optimal theory and adaptive strategy

This paper presents a chaos synchronization method for a class of uncertain chaotic systems using the combination of an optimal control theory and an adaptive strategy. A quadratic optimal regulator and an adaptive control are used to represent the controller's structure. The asymptotic stability of the corresponding error dynamical system is guaranteed through Lyapunov stability analysis. The proposed controller is employed in two uncertain chaotic Lu systems, and their promising performances are illustrated.     

Syntheses and characterization of Sr(OH)2 and SrCO3 nanostructures by ultrasonic method

The Sr(OH)₂ and SrCO₃ nanostructures were synthesized by reaction of strontium(II) acetate and sodium hydroxide or tetramethylammonium hydroxide (TMAH) via ultrasonic method. Reaction conditions, such as the concentration of the Sr²⁺ ion, aging time, power of the ultrasonic device and alkali salts show important roles in the size, morphology and growth process of the final products. The pure crystalline SrCO₃ were obtained by heating of product at 400 °C. The Sr(OH)₂ and SrCO₃ nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal gravimetric (TG), differential thermal analyses (DTA) and the infrared spectroscopy (IR).     

Ultrasound-induced membrane lipid peroxidation and cell damage of Escherichia coli in the presence of non-woven TiO2 fabrics

A non-woven titanium dioxide (TiO₂) fabric was applied to disinfection by ultrasound (US) irradiation, and the disinfection efficiency and lipid peroxidation of Escherichia coli (E. coli) cell membrane were evaluated to investigate the killing process. The addition of non-woven TiO₂ fabric enhanced hydroxyl (OH) radical generation and disinfection efficiency. Judging from the disinfection experiments using glutathione or t-butanol as a radical scavenger, the OH radical played a major role in cell killing in sonodynamic disinfection with non-woven TiO₂ fabric. Moreover, to understand the detailed killing process, damage to cell membrane was also evaluated using a diphenyl-1-pyrenylphosphine (DPPP) fluorescent probe, which detects the membrane’s lipid peroxidation. The addition of non-woven TiO₂ fabric aggravated this peroxidation. This aggravation was caused by the OH radical according to an assay using a radical scavenger. From these results, it was concluded that non-woven TiO₂ fabric as a sonocatalyst promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced a major disorder in the E. coli cell membrane under US irradiation.     

Microwave-enhanced palladium-catalyzed cross-coupling reactions of potassium vinyltrifluoroborates and allyl acetates: a new route to 1,4-pentadienes

[reaction: see text] A novel and straightforward microwave synthesis of 1,4-pentadienes has been developed involving the cross-coupling of potassium vinyltrifluoroborates and allyl acetates in the presence of a palladium catalyst.     

Speciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents

A method based on ion chromatography (IC) and inductively coupled plasma MS (ICP-MS) was developed for the speciation of arsenic in water and soil extracts. An anion-exchange column (G3154A/101) was used to separate As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) with excellent resolution. Various ammonium salts, including NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4HCO3, were examined as eluents to reduce matrix interference from chloride and to solve clogging problems. The best arsenic speciation was obtained within 9 min with excellent resolution and without interference from high chloride concentrations using an eluent containing 7.5 mM (NH4)2HPO4 at pH 7.9. The detection limits for the target arsenic species ranged from 0.1 to 0.4 microg/L with direct injection of sample without matrix elimination. The proposed method was effectively demonstrated by determining arsenic species in contaminated waters and soils of Bangladesh.     

Theoretical study of dihydrogen bonds between (XH)2, X = Li, Na, BeH, and MgH, and weak hydrogen bond donors (HCN, HNC, and HCCH)

The dihydrogen-bonded (DHB) complexes formed by (XH)2, with X = Li, Na, BeH, and MgH, with one, two, and four protonic molecules (HCN, HNC, and HCCH) have been studied. These complexes have been compared to those of the XH monomers with the same hydrogen bond donor molecules. The energetic results have been rationalized based on the electrostatic potential of the isolated hydridic systems. The electron density properties have been analyzed within the AIM methodology, both at the bond critical points and the integrated values at the atomic basins. Exponential relationships between several properties calculated at the bond critical points (rho,nabla2rho, lambdai, G, and V) and variation of integrated properties (energy, charge, and volume) vs the DHB distance have been obtained.     

Structural and spectroscopic properties of trans-difluoro(1,4,8,12-tetraazacyclopentadecane)chromium(III) perchlorate hydrate

The structure of [CrF(2)([15]aneN(4))]ClO(4).H(2)O ([15]aneN(4)=1,4,8,12-tetraazacyclopentadecane) has been determined by a single-crystal X-ray diffraction study at 173 K. The complex crystallizes in the space group P1- of the triclinic system with two mononuclear formula units in a cell of dimensions a=9.6117(7) A, b=10.2882(7) A, c=11.0001(7) A and alpha=99.7570(10) degrees, beta=105.6080(10) degrees and gamma=113.7130(10) degrees. The complex cation unit has its central Cr atom in an octahedral coordination with four nitrogen atoms and two fluorine atoms in a trans position. Three six-membered and one five-membered chelate rings of the [15]aneN(4) ligand are in a chair-twist(skew)-chair-gauche conformation sequence. The gauche five-membered ring is disordered with the twist six-membered ring opposite. The four H atoms in the chiral N atoms have the trans-II (CTCg) type configuration. The mean Cr-N and Cr-F bonds are 2.095(2) and 1.8752(13) A, respectively. The IR and visible spectral properties are consistent with the result of X-ray crystallography. The resolved band maxima of the electronic d-d spectrum are fitted with secular determinant for quartet state energy of d(3) configuration in tetragonal field including configurational but neglecting spin-orbit coupling. It is confirmed that the fluoride has strong sigma- and pi-donor properties toward the chromium(III) ion and the nitrogen atoms of the [15]aneN(4) ligand also have a strong sigma-donor character.     

Intertrimer and intratrimer metallophilic and excimeric bonding in the ground and phosphorescent States of trinuclear coinage metal pyrazolates: a computational study

The interactions present in cyclic trinuclear coinage metal pyrazolates were studied computationally. Cuprophilic interaction was found to bind the singlet ground state of the dimer of trimers [[Cu(Pz)](3)](2), overcoming electrostatic repulsion. The large variation in intertrimer separations found in the literature for coinage metal pyrazolates is consistent with the relatively weak metallophilic interaction. The emissive triplet excited-state geometry of [[M(Pz)](3)](2) is predicted by density functional calculations to show major geometric distortion caused by Jahn-Teller instability and excimeric M-M bonding. Large calculated Stokes' shifts, which are also observed for experimental models, are consistent with significant excited-state distortions for these materials. The major finding derived from the present study is that the intertrimer M...M contraction in the emissive T(1) state is much more than the intratrimer contraction in all [[M(Pz)](3)](2) models, giving rise to a lower T(1) --> S(0) phosphorescence energy in these models than in analogous monomer-of-trimer models. The observations made here point to a great potential for rationally tuning the emission properties of trinuclear coinage metal complexes through choice of the metal and ligands.