Dynamical properties and chaos synchronization of a new chaotic complex nonlinear system

In this paper, we introduce a new chaotic complex nonlinear system and study its dynamical properties including invariance, dissipativity, equilibria and their stability, Lyapunov exponents, chaotic behavior, chaotic attractors, as well as necessary conditions for this system to generate chaos. Our system displays 2 and 4-scroll chaotic attractors for certain values of its parameters. Chaos synchronization of these attractors is studied via active control and explicit expressions are derived for the control functions which are used to achieve chaos synchronization. These expressions are tested numerically and excellent agreement is found. A Lyapunov function is derived to prove that the error system is asymptotically stable.     

Sterically Controlled Regiospecific Cyclization of Aldose-5-ethyl-1,2,4-triazino[5,6- b ]indol-3-ylhydrazones to Linearly Annelated 3-Polyhydroxyalkyl-10-ethyl-1,2,4-triazolo-[4′,3′:2,3]-1,2,4-triazino[5,6- b ]indoles

 Condensation of aldoses with 5-ethyl-3-hydrazino-1,2,4-triazino[5,6-b ]indole gave the corresponding aldose-5-ethyl-1,2,4-triazino[5,6-b ]indol-3-ylhydrazones which were acetylated to their poly-O-acetyl derivatives. The latter underwent sterically controlled regiospecific oxidative cyclization with bromine in acetic acid and sodium acetate to sterically favourable linearly annelated 3-polyacetoxyalkyl-10-ethyl-1,2,4-triazole[4′,3′:2,3]-1,2,4-triazino[5,6-b ]indoles rather than to their sterically unfavourable angularly annelated regioisomers. The regiospecific outcome of this heterocyclization is discussed in terms of electronic as well as steric factors, and the assigned structures have been corroborated on the basis of chemical as well as spectroscopic evidence. De-O-acetylation of the acetoxyindoles with ammonium hydroxide in methanol gave the title compounds. Representative members of the prepared compounds were tested for antimicrobial activity.     

Sterically Controlled Regiospecific Cyclization of Aldose-5-ethyl-1,2,4-triazino[5,6-b]indol-3-ylhydrazones to Linearly Annelated 3-Polyhydroxyalkyl-10-ethyl-1,2,4-triazolo-[4′,3′:2,3]-1,2,4-triazino[5,6-b]indoles

Summary.  Condensation of aldoses with 5-ethyl-3-hydrazino-1,2,4-triazino[5,6-b ]indole gave the corresponding aldose-5-ethyl-1,2,4-triazino[5,6-b ]indol-3-ylhydrazones which were acetylated to their poly-O-acetyl derivatives. The latter underwent sterically controlled regiospecific oxidative cyclization with bromine in acetic acid and sodium acetate to sterically favourable linearly annelated 3-polyacetoxyalkyl-10-ethyl-1,2,4-triazole[4′,3′:2,3]-1,2,4-triazino[5,6-b ]indoles rather than to their sterically unfavourable angularly annelated regioisomers. The regiospecific outcome of this heterocyclization is discussed in terms of electronic as well as steric factors, and the assigned structures have been corroborated on the basis of chemical as well as spectroscopic evidence. De-O-acetylation of the acetoxyindoles with ammonium hydroxide in methanol gave the title compounds. Representative members of the prepared compounds were tested for antimicrobial activity. Received November 3, 1999. Accepted December 13, 1999     

Adsorption,Thermodynamic, and Experimental Studies of Corrosion Inhibitor of Tin in 0.2 M Maleic Acid by Hydrogen Phosphate Ions (HPO42−)

The inhibition efficiency of H₂PO₄²⁻ ions against tin corrosion in 0.2 M maleic acid is studied using electrochemical methods, surface analytical methods, and thermodynamic analysis. The potentiodynamic polarization plots showed the presence of an active/passive transition state of the tin electrode. The EIS measurements confirmed that the inhibition efficiency of H₂PO₄²⁻ increased by increasing the concentration (η=81 % at C_inh=2.10⁻² M) and decreased by rising the temperature. The polarization tests demonstrated that the inhibitor performs as a cathodic-type. The adsorption of the inhibitor was spontaneous and followed the Langmuir adsorption isotherm. A model of the inhibition mechanism was suggested.     

A Facile One‐pot Synthesis and Anticancer Evaluation of Interesting Pyrazole and Pyrimidinthione via Heterocyclic Interconversion

Design and synthesis of new pyrazole, pyrimidinthione, and triazepinthione derivatives via heterocyclic ring opening of azacoumarin were promoted with grinding and ultrasonic reaction conditions. Efficient solventless one‐pot synthesis can be well progressed to afford the good yield of new heterocyclic products that were characterized by IR, ¹H‐NMR, MS, and microanalytical data. Anticancer evaluation for the synthesized compounds exhibited moderate to good cytotoxicity such as pyrazole derivatives 5 , 9 , and 14 that displayed best cytotoxic activities with IC₅₀ 8.16 ± 1.1, 7.02 ± 0.6, and 5.12 ± 0.41 μg/mL and 9.28 ± 0.7, 6.45 ± 0.9, and 5.85 ± 0.26 μg/mL for MCF‐7 and WI cells, respectively. Pyrimidine derivatives 6 , 11 , and 15 exhibited strong cytotoxicity with IC₅₀ 8.9 ± 0.62, 7.16 ± 0.5, and 7.72 ± 0.41 μg/mL against MCF‐7.     

Preparation of capped silver nanoparticles using sunlight and cationic surfactants and their biological activity

Silver nanoparticles were prepared in situ using sunlight and cationic surfactants. Silver nano-particles were confirmed using UV–vis spectrophotometry, transmission electron microscopy(TEM), electron diffraction, dynamic light scattering(DLS) and FTIR. Increasing the hydrophobic chain length of surfactants increase the amount of silver nano-particles formed in addition to increasing their stability.The results showed formed, uniform, well arranged hexagonal and spherical shapes. The prepared silver nanoparticles exhibit enhanced biological activity against Gram-positive, Gram-negative bacteria and sulfate reducing bacteria(SRB).     

Metformin Containing Nickel (II) Complexes: Synthesis,Structural Characterization,Binding and Kinetic Interactions with BSA,Antibacterial and in-vitro Cytotoxicity Studies

In quest of antimicrobial and anticancer agents, metformin containing Ni (II) complexes, [Ni (Met)₂]Cl·OH ( 1 ) and [Ni (Met)(IDA)] ( 2 ) {Met: metformin, IDA: iminodiacetic acid} were synthesized and X-ray structure of 1 is four-coordinate square planar geometry. Bovine serum albumin (BSA) interaction and binding studies to Met, IDA and their Ni (II) complexes were investigated and showed a strong interaction. A static quenching process was proposed at low concentrations of compounds whereas, combined quenching process was observed for 1 and 2 at higher concentrations. Kinetic stability, affinity and association constants of compounds-BSA were studied using stopped-flow technique and a mechanism was proposed: a fast and reversible step of BSA binding including complex formation and dissociation was proposed; for the second step, a reversible reaction was observed for 1 and 2 whereas, an irreversible reaction with Met and IDA was observed indicating that coordination with nickel ions change the interaction mechanism. Additionally, the antibacterial investigation against both Gram-positive and Gram-negative bacteria showed that all compounds exhibited significant activities. They also show cytotoxicity against HepG2 human liver cancer cell but the half maximal inhibitory concentration (IC50) values obtained for the cell lines were higher in comparison with cisplatin. Although Met-BSA and IDA-BSA are kinetically more stable than that of 1 -BSA and 2 -BSA, 1 -BSA and 2 -BSA showed better antibacterial and cytotoxic activities which is in agreement with the binding constants.     

Numerical investigation on nano boundary layer equation with Navier boundary condition

In this paper, by applying rational Legendre collocation technique and relaxation method, the classical laminar boundary layer equations with the nonlinear Navier boundary conditions are investigated. The features of the flow characteristics for different values of n are discussed. Numerical approaches are used to find solutions for the cases n > 1 / 2 corresponding to the flow past a wedge and n = 1 / 2 corresponding to the flow in a convergent channel. During the comparison, the effectivity and stability of the applied methods are demonstrated. The effects of the varying slip length, index parameter, components of velocity, and tangential stress are analyzed. Copyright © 2012 John Wiley & Sons, Ltd.     

A new capillary zone electrophoresis method for the analysis of Ginkgo biloba extracts and Ginkgo biloba pharmaceutical products

Ginkgo biloba, traditional Chinese medicine is now generally accepted. Separation and determination of active components in G. biloba is important for the product quality control. Therefore, the development of an effective and reliable separation method is important. In this work, a new capillary electrophoretic (CZE) method for separation of the G. biloba leaf extracts components was developed and optimized by the use of experimental design and artificial neural network (ANN). Under best separation conditions, in gamma-CD-modified buffer, the separation was reached within 10 min (36 mM borate BGE, pH 9.2, 1 mM gamma-CD), while the hydrodynamic mode for sample injection (2 s) and UV detection at 270 nm were applied. The method developed was validated and applied for analysis of various extracts and G. biloba products.     

Reverse Osmosis Membranes for Seawater Desalination State-of-the-Art

Abstract

The field of membrane technology has developed very rapidly during the last three decades. In this study, the major technical and commercial developments that took place in the field of reverse osmosis membranes as applied to seawater desalination are investigated. A brief historical review for each membrane type is also presented.