Numerical solutions of the Kawahara type equations using radial basis functions

This study is carried out to investigate the numerical solutions of the Kawahara, KdV‐Kawahara, and the modified Kawahara equations by using the meshless method based on collocation with radial basis functions. Results of the meshless method with different radial basis functions are presented for the travelling wave solution of the Kawahara type equations. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 28: 542–553, 2012     

Preconcentration and selective extraction of chromium species in water samples using amino modified mesoporous silica

Speciation and separation of chromium (VI) and chromium (III) from aqueous solutions were investigated using amino-propyl functionalised mesoporous silica (AP-MCM-41) as an adsorbent. The as-synthesised adsorbent was produced following a simple synthesis method at room temperature prior to template removal using microwave digestion. The maximum adsorption capacity at 111.1mg/g was calculated according to the Langmuir isotherm model, suggesting a 1:1 monolayer adsorption mechanism. Moreover, AP is a simple chelate, yet it can extract Cr (VI) exclusively from solutions containing other mixed metal ions simply by tuning the solution pH. Recovery of Cr (VI) from loaded sorbents is equally easy to perform with 100% extraction efficiencies allowing reuse of the sorbent and recovery of Cr (VI) from aqueous solutions containing a complex mixture of ions. The material would find use in environmental remediation applications, as a selective adsorbent of Cr (VI) or even as a solid-phase extraction stationary phase to remove and pre-concentrate Cr (VI) from aqueous solutions; this study demonstrates enrichment factors of 100 although higher levels are also possible.     

Enhancing electrochromic properties of conducting polymers via copolymerization: Copolymer of 1‐(4‐fluorophenyl)‐2,5‐di(thiophen‐2‐yl)‐1H‐pyrrole with 3,4‐ethylene dioxythiophene

A copolymer of 1‐(4‐fluorophenyl)‐2,5‐di(thiophen‐2‐yl)‐1H‐pyrrole (FPTP) with 3,4‐ethylene dioxythiophene (EDOT) was electrochemically synthesized and characterized. While poly(FPTP) (P(FPTP)) has only two colors in its oxidized and neutral states (blue and yellow), its copolymer with EDOT has five different colors (purple, red, light gray, green, and blue). Electrochromic devices based on P(FPTP‐co‐EDOT) and poly(3,4‐ethylenedioxythiophene) (PEDOT) were constructed and characterized. The oxidized state of the device shows blue color whereas it shows purple for the reduced state. At several potentials the device has good transparency with green and gray colors. Maximum contrast (Δ%T) and switching time of the device were measured as 23% and 1.1 s at 555 nm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4496–4503, 2007     

Synthesis and characterization of a new soluble conducting polymer and its electrochromic device

A mixture of isomers 2,5-di(4-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole, 2-(4-methyl-thiophen-2-yl)-5-(3-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole and 2,5-di(3-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole (Me-SNS(NO₂)) were synthesized. Resulting monomers were polymerized chemically, producing soluble polymers in common organic solvents. The average molecular weight has been determined by gel permeation chromatography (GPC) as Mn=5.6×10³ for the chemically synthesized polymer. The monomers were also electrochemically polymerized in the presence of LiClO₄, NaClO₄ (1:1) as the supporting electrolyte in acetonitrile solvent. Resulting polymers were characterized via CV, FTIR, NMR, SEM and UV–Vis spectroscopy. Spectroelectrochemistry analysis of polymer revealed Π–Π^* transition below 300 nm, with an electronic band gap of 2.18 ev. Switching ability of the polymer was evaluated by kinetic study measuring percent transmittance (%T) at the maximum contrast point, indicating that poly(Me-SNS(NO₂)) is a suitable material for electrochromic devices.     

Effects of a magnetic field on chaos for low Prandtl number convection in porous media

The effects of a magnetic field on the route to chaos in a fluid-saturated porous layer were investigated based on the approach of dynamical systems. A low dimensional Lorenz-like model was obtained using Galerkin truncated approximation. The presence of a magnetic field helped delay the convective motion. The transition from steady convection to chaos via a Hopf bifurcation produced a limit cycle which may be associated with a homoclinic explosion at a slightly subcritical value of the Rayleigh number.     

Models of the iron-only hydrogenase: Reactions of [Fe2(CO)6(μ-pdt)] with small bite-angle diphosphines yielding bridge and chelate diphosphine complexes [Fe2(CO)4(diphosphine)(μ-pdt)]

Reactions of [Fe₂(CO)₆(μ-pdt)] (1) (pdt = SCH₂CH₂CH₂S) and small bite-angle diphosphines have been studied. A range of products can be formed being dependent upon the nature of the diphosphine and reaction conditions. With bis(diphenylphosphino)methane (dppm), thermolysis in toluene leads to the formation of a mixture of bridge and chelate isomers [Fe₂(CO)₄(μ-dppm)(μ-pdt)] (2) and [Fe₂(CO)₄(κ²-dppm)(μ-pdt)] (3), respectively. Both have been crystallographically characterised, 3 being a rare example of a chelating dppm ligand in a first row binuclear system. At room temperature in MeCN with added Me₃NO · 2H₂O, the monodentate complex [Fe₂(CO)₅(κ¹-dppm)(μ-pdt)] (4) is initially formed. Warming 4 to 100 °C leads the slow conversion to 2, while oxidation (on alumina) gives [Fe₂(CO)₅(κ¹-dppmO)(μ-pdt)] (5). With bis(dicyclohexylphosphino)methane (dcpm), heating in toluene cleanly affords [Fe₂(CO)₄(μ-dcpm)(μ-pdt)] (6). With Me₃NO · 2H₂O in MeCN the reaction is not clean as the phosphine is oxidised but monodentate [Fe₂(CO)₅(κ¹-dcpm)(μ-pdt)] (7) can be seen spectroscopically. With 1,2-bis(diphenylphosphino)benzene (dppb) and cis-1,2-bis(diphenylphosphino)ethene (dppv) the chelate complexes [Fe₂(CO)₄(κ²-dppb)(μ-pdt)] (8) and [Fe₂(CO)₄(κ²-dppv)(μ-pdt)] (9), respectively are the final products under all conditions, although a small amount of [Fe₂(CO)₅(κ²-dppvO)(μ-pdt)] (10) was also isolated. Protonation of 2 with HBF₄ affords a cation with poor stability while with the more basic diiron centre in 6 readily forms the stable bridging-hydride complex [(μ-H)Fe₂(CO)₄(μ-dcpm)(μ-pdt)][BF₄] (11) which has been crystallographically characterised.     

Remotely pumped hybrid double-pass L-band optical amplifier utilizing chirped fiber Bragg

This paper reported an investigation of remotely pumped double pass L-band amplifier with dispersion compensation technique. The proposed design used chirped fiber Bragg grating (CFBG) to reflect the amplified signal back into the active medium, compensate the effect of fiber dispersion and block the recycled forward amplified spontaneous emission (ASE) and the residual 1480 nm pump power. The characterization of the design was done experimentally. The gain is 37.5 dB and noise figure is 4 dB with best BER of 10⁻⁵² is achieved when the EDF is placed 150 km away from the transmitter and 48 km before the receiver terminal.     

Proteome profile of zebrafish caudal fin based on one-dimensional gel electrophoresis LCMS/MS and two-dimensional gel electrophoresis MALDI MS/MS analysis

Zebrafish (Danio rerio) is the widely used vertebrate model animal for understanding the complexity of development and disease process. Zebrafish has been also extensively used in understanding the mechanism of regeneration for its extensive capability of regenerating fins and other tissues. We have analyzed the proteome profile of zebrafish caudal fin in its native state based on one-dimensional gel electrophoresis LCMS/MS and two-dimensional gel electrophoresis MS/MS analyses. A total of 417 proteins were identified as zebrafish fin tissue specific, which includes 397 proteins identified based on one-dimensional gel electrophoresis LCMS/MS analysis and 101 proteins identified based on two-dimensional gel electrophoresis MALDI MS/MS. The proteins mapped to the zebrafish fin tissue were shown to be involved in various biological activities related to development, apoptosis, signaling and metabolic process. Focal adhesion, regulation of actin cytoskeleton, cancer-related pathways, mitogen-activated protein kinase signaling, antigen processing and presentation, and proteasome are some of the important pathways associated with the identified proteome data set of the zebrafish fin.     

N-halamine biocidal coatings via a layer-by-layer assembly technique

Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.