Reaction-Diffusion Equations with Polynomial Drifts Driven by Fractional Brownian Motions

A reaction-diffusion equation on [0, 1] ^d with the heat conductivity κ > 0, a polynomial drift term and an additive noise, fractional in time with H > 1/2, and colored in space, is considered. We have shown the existence, uniqueness and uniform boundedness of solution with respect to κ. Also we show that if κ tends to infinity, then the corresponding solutions of the equation converge to a process satisfying a stochastic ordinary differential equation.     

Analysis of dextromethorphan and pseudoephedrine in human plasma and urine samples using hollow fiber-based liquid–liquid–liquid microextraction and corona discharge ion mobility spectrometry

We report on the use of hollow fiber liquid-liquid-liquid microextraction (HF-LLLME) followed by corona discharge ion mobility spectrometry for the determination of dextromethorphan and pseudoephedrine in urine and plasma samples. The effects of pH of the donor phase, stirring rate, ionic strength and extraction time on HF-LLLME were optimized. Under the optimized conditions, the linear range of the calibration curves for dextromethorphan in plasma and urine, respectively, are from 1.5 to 150 and from 1 to 100 ng mL^?1. The ranges for pseudoephedrine, in turn, are from 30 to 300 and from 20 to 200 ng mL^?1. Correlation coefficients are better than 0.9903. The limits of detection are 0.6 and 0.3 ng mL^?1 for dextromethorphan, and 8.6 and 4.2 ng mL^?1 for pseudoephedrine in plasma and urine samples, respectively. The relative standard deviations range from 6 to 8%.

Comparison of volatile constituents, and antioxidant and antibacterial activities of the essential oils of Thymus caucasicus, T. kotschyanus and T. vulgaris

A comparison of the chemical composition, and antioxidant and antibacterial activities of the essential oils obtained from the aerial parts of Thymus caucasicus, T. kotschyanus, and T vulgaris was carried out. The oils, obtained by hydrodistillation, were analyzed by GC and GC/MS. Twenty, 29 and 22 compounds representing 94.8%, 96.6% and 98.2% of the essential oils of T. caucasicus, T. kotschyanus and T. vulgaris, respectively, have been identified. The oil of T. caucasicus was characterized by 1,8-cineol (21.5%), thymol (12.6%), beta-fenchyl alcohol (8.7%), nerolidol (7.8%), terpinolene (7.2%), alpha-pinene (7.0%) and myrcene (6.8%). In the oil of T. kotschyanus, carvacrol (24.4%), beta-caryophyllene (14.5%), gamma-terpinene (12.4%), alpha-phellandrene (10.8%), p-cymene (9.8%) and thymol (6.8%) were the predominant compounds, whereas the main components of T. vulgaris oil were thymol (43.8%), p-cymene (15.2%), germacrene-D (11.7%), terpinolene (3.4%), carvacrol (3.2%), beta-caryophyllene (2.8%) and alpha-thujene (2.2%). In all three plants oil, hydrocarbon monoterpenes predominated over sesquiterpenes. Antioxidant activities were assessed by determining IC50 values in the DPPH radical scavenging assay. Antibacterial activity was determined by measuring minimum inhibitory concentration (MIC) using the broth dilution method. The essential oils of T. caucasicus, T. kotschyanus and T. vulgaris showed free radical scavenging and antibacterial activity.     

Diorganotin(IV) complexes of biologically potent 4(3H)-quinazolinone derived Schiff bases: synthesis, spectroscopic characterization, DNA interaction studies and antimicrobial activity

Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and characterized by elemental analyses, IR, (1)H NMR, MS and thermal studies. The Schiff bases are obtained by the condensation of 3-amino-2-methyl-4(3H)-quinazolinone with different substituted aldehydes. The elemental analysis data suggest the stoichiometry to be 1:1 ratio formation. Infrared spectral data agreed with the coordination to the central metal ion through imine nitrogen, lactam oxygen and deprotonated phenolic oxygen atoms. All the synthesized compounds have been evaluated for antimicrobial activity against selected species of microorganisms. In addition, DNA binding/cleavage capacity of the compounds was analyzed by absorption spectroscopy, viscosity measurements and gel electrophoresis methods.     

Fluorescence “turn-on” chemosensor for the selective detection of zinc ion based on Schiff-base derivative

N,N′-phenylenebis(salicylideaminato) (L) has been used to detect trace amounts of zinc ion in acetonitrile–water solution by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to zinc ions in MeCN/H₂O (1:1, v/v) solution. The fluorescence enhancement of L is attributed to the 1:1 complex formation between L and Zn(II), which has been utilized as the basis for selective detection of Zn(II). The linear response range for Zn(II) covers a concentration range of 1.6 × 10^?7 to 1.0 × 10^?5 mol/L, and the detection limit is 1.5 × 10^?7 mol/L. The fluorescent probe exhibits high selectivity over other common metal ions, and the proposed fluorescent sensor was applied to determine zinc in water samples and waste water.     

Ultrasound promoted one-pot synthesis of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds in aqueous media: A complementary ‘green chemistry’ tool to organic synthesis

A green and simple approach to assembling of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds via three-component reaction of kojic acid, malononitrile, and aromatic aldehydes in aqueous media under ultrasound irradiation is described. The combinatorial synthesis was achieved for this methodology with applying ultrasound irradiation while making use of water as green solvent. In comparison to conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst are prominent features of this green procedure.     

The dynamics of two coupled Van der Pol oscillators with attractive and repulsive coupling

We consider a variant of two coupled Van der Pol oscillators with both attractive and repulsive mean-field interactions. In the presence of attractive coupling, the system is in the complete synchrony, while repulsive coupling shows anti-synchronization state leading to suppression of oscillations with increasing interaction strength. The coupled system with both attractive and repulsive interactions shows competitive tendencies of being complete synchronization and anti-synchronization resulting in the stabilization of the fixed point. We have also studied the effect of the damping coefficient of the VdP oscillator on the nature of the transition from oscillatory to a steady-state. These oscillators stabilize to unstable equilibrium point or coupling dependent inhomogeneous steady state via second or first-order transitions respectively depending upon the damping coefficient and coupling strength. These transitions are analyzed in the parameter plane by analytical and numerical studies of the two coupled Van der Pol oscillators.     

Optimal TiO2–Graphene Oxide Nanocomposite for Photocatalytic Activity under Sunlight Condition: Synthesis,Characterization, and Kinetics

TiO₂–graphene oxide nanocomposites have been fabricated by the sol–gel technique for degradation of a typical cationic dye solution. The prepared photocatalysts were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric‐differential analyses, Brunauer–Emmett–Teller surface area measurement, and scanning and transmission electron microscopy. In addition, the photocatalytic activities of samples were evaluated by degradation of methylene blue aqueous solution under the sunlight irradiation. The change in color of solution was evaluated by the UV–vis spectroscopy, and the maximum photocatalytic decoloration (94%) was achieved within 60 min, which exceeded that of pure anatase under the same conditions. The results show that the nanocomposite containing 9.0 wt% of graphene oxide has the superior photocatalytic performance to either single‐phase anatase or other composites containing different amounts of graphene oxide. The experimental degradation data obtained from the batch tests were analyzed by a modified kinetic model, which predicted the performance with higher regression coefficients and lower relative errors. The distribution of TiO₂ nanoparticles (<20 nm) on graphene oxide sheets is proposed to be the efficient factor in the homogeneous degradation of dye which can concomitantly improve the photocatalytic activity.     

The Evolution of the Concept of Controllability

This paper traces the evolution of the central concept of controllability of state space systems introduced by Kalman to its behavioural generalisation byWillems, and beyond to distributed behaviours. It turns out that controllability in this new formalism is identical to the notion of a potential in physics or of exactness in mathematics.