Isovector solitons and Maxwell's equations

We present an isovector Lagrangian, which admits stable, nonsingular soliton solutions in three space dimensions. The spherical solution and its total energy are obtained via a variational procedure. An antisymmetric, second-rank tensor is defined in terms of the isovector field and its derivatives. This tensor satisfies Maxwell's equations. The corresponding current is identically conserved and the total charge is topologically quantized.     

Dynamics of solitons in inhomogeneous Josephson junctions

We examine the dynamics of sine-Gordon solitons in an inhomogeneous Josephson junction. Two types of inhomogeneity are worked out: (1) varying refractive index or dielectric constant, and (2) varying parameters in the nonlinear term. Simplified analytical explanations are also presented for the numerical results.     

Phosphorylated PEG (PPEG) as a new support for generation of nano‐Pd(0): application to the Heck–Mizoroki and Suzuki–Miyaura coupling reactions

Polyethylene glycols (PEGs) with different molecular weights (M_w = 200, 400, 1000) were phosphorylated to their bis‐diphenyl phosphinite derivatives as stable solids which are melted in the range 140–160°C. These phosphorylated PEGs were used as ligands and reducing agents to generate nano‐Pd(0) catalysts in 2.5–8.3 nm. The nano‐Pd(0) particles supported on phosphorylated PEG₂₀₀ were applied for the efficient Heck–Mizoroki carbon–carbon coupling reactions of ArX (X = Cl, Br, I) at 80–100°C under solvent‐free conditions and for the Suzuki–Miyaura coupling reaction in ethanol at 70°C. The catalyst was recycled easily and reused for several runs. Copyright © 2013 John Wiley & Sons, Ltd.     

Batch and continuous fixed-bed column biosorption of thorium(IV) from aqueous solutions: equilibrium and dynamic modeling

Biosorption of thorium(IV) from aqueous solution by Cystoseira indica alga was investigated in batch and fixed-bed column experiments. In the batch study the effects of pH and initial concentration were investigated. The optimum pH for Th(IV) biosorption was found to be 3.5. The experimental isotherms obtained at different pH conditions were analyzed using three two-parameter models and three three-parameter models. Among the two-parameter models the Langmuir model and among the three-parameter models the Redlich–Peterson model vividly described the equilibrium data. The results showed that C. indica alga is a homogeneous biosorbent and Th(IV) biosorption is a favorable and physical process. The maximum biosorption capacity from the Langmuir model was 151.3, 195.7 and 120.6 mg/g at pH 2.5, 3.5 and 4.5, respectively. The continuous isotherm obtained from the column data was modeled by the Langmuir model and the maximum biosorption capacity was 283.8 mg/g. The experimental data were fitted by the use of an analytical and a numerical model, namely Clark and mass transfer models. The results showed that the mass transfer model adequately described the experimental data. Sensitivity analysis revealed that the value of k _in has more effect than the axial dispersion coefficient (D _z) on the shape of breakthrough curve.     

New polypyrrole–carbon nanotubes–silicon dioxide solid‐phase microextraction fiber for the preconcentration and determination of benzene,toluene, ethylbenzene,and o‐xylene using gas liquid chromatography

For the first time, a polypyrrole–carbon nanotubes–silicon dioxide composite film coated on a steel wire was prepared by an electrochemical method. Scanning electron microscopy images showed that this composite film was even and porous. The prepared fiber was used as an absorbent for the headspace solid‐phase microextraction of benzene, toluene, ethylbenzene, and o‐xylene, followed by gas chromatographic analysis. This method presented an excellent performance, which was much better than that of a polypyrrole–carbon nanotube fiber. It was found that under the optimized conditions, the linear ranges were 0.01–200 ng/mL with correlation coefficients >0.9953, the detection limits were 0.005–0.020 ng/mL, the relative standard deviations were 3.9–6.4% for five successive measurements with a single fiber, and the reproducibility was 5.5–8.5% (n = 3). Finally, the developed method was successfully applied to real water samples, and the relative recoveries obtained for the spiked water samples were from 91.0 to 106.7%.     

The Influence of Ripeness on the Phenolic Content,Antioxidant and Antimicrobial Activities of Pumpkins (Cucurbita moschata Duchesne)

Cucurbita moschata Duchesne (Cucurbitaceae) is a plant food highly appreciated for the content of nutrients and bioactive compounds, including polyphenols and carotenoids, which contribute to its antioxidant and antimicrobial capacities. The purpose of this study was to identify phenolic acids and flavonoids of Cucurbita moschata Duchesne using high-performance liquid chromatography–diode array detection–electrospray ionization tandem mass spectrometry (HPLC–DAD–ESI-MS) at different ripening stages (young, mature, ripened) and determine its antioxidant and antimicrobial activities. According to the results, phenolic acids and flavonoids were dependent on the maturity stage. The mature fruits contain the highest total phenolic and flavonoids contents (97.4 mg GAE. 100 g⁻¹ and 28.6 mg QE. 100 g⁻¹).A total of 33 compounds were identified. Syringic acid was the most abundant compound (37%), followed by cinnamic acid (12%) and protocatechuic acid (11%). Polyphenol extract of the mature fruits showed the highest antioxidant activity when measured by DPPH (0.065 μmol TE/g) and ABTS (0.074 μmol TE/g) assays. In the antimicrobial assay, the second stage of ripening had the highest antibacterial activity. Staphylococcus aureus was the most sensitive strain with an inhibition zone of 12 mm and a MIC of 0.75 mg L⁻¹. The lowest inhibition zone was obtained with Salmonella typhimurium (5 mm), and the MIC value was 10 mg L⁻¹.     

Synthesis,spectroscopic characterization,crystal structures,and theoretical studies of (<Emphasis Type="Italic">E</Emphasis>)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone and (<Emphasis Type="Italic">E</Emphasis>)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone

Two thiosemicarbazones, (E)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone (24-MBTSC (1)) and (E)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone (25-MBTSC (2)), derived from 2,4-dimethoxybenzaldehyde and 2,5-dimethoxybenzaldehyde, respectively, with thiosemicarbazide have been synthesized and their structures were characterized by elemental analyses, FT-IR, ¹H NMR spectroscopy, and X-ray single-crystal diffraction analysis. Molecular orbital calculations have been carried out for 1 and 2 by using an ab initio method (HF) and also density functional method (B3LYP) at 6-31G basis set. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, with a = 8.1342(5) Å, b = 18.1406(10) Å, c = 8.2847(6) Å, β = 109.7258(17)°, V = 1150.75(12) Å³, and Z = 4, whereas compound 2 crystallizes in the orthorhombic system, space group Pbca, with a = 11.0868(6) Å, b = 13.1332(6) Å, c = 15.9006(8) Å, V = 2315.2(2) Å³, and Z = 8. The compounds 1 and 2 displays a trans-configuration about the C=N double bond.