SOME SUBGROUPS OF THE EXTENDED HECKE GROUPS (λ_q)

The authors consider the extended Hecke groups H(λq) generated by T(z) = -1 / z, S(z) = -1/(z + λq,) and R(z) = 1 / z with A, = 2 cos(π/q) for q≥3 an integer. In this paper, the even subgroup He(λq), the second commutator subgroup H (λq) and the principal congruence subgroups Hp(λq) of the extended Hecke groups H(λq) are studied. Also, relations between them are given.     

Effects of processing parameters on the mechanical properties of polypropylene random copolymer

The mechanical properties of polypropylene random copolymer (PP-R) with different processing parameters were studied. Special attention is devoted to the investigation of the influence of masterbatch addition on the variation in the mechanical properties of injection moulded PP-R. Tensile, instrumented Charpy impact, Shore D hardness, differential scanning calorimeter (DSC) and Vicat softening temperature (VST) tests were conducted on the test samples containing different colour masterbatches varying from 0.5 to 10 wt%. The observed changes in the mechanical behaviour are explained by the type and level of masterbatch content. The natural UV weathering performance of the PP-R material was studied from the masterbatch type point of view. The effect of processing parameters on material performance was studied on samples which were directly obtained from extruded pipes and on injection moulded samples.

Finally, the effects of storage time on the polymer properties were investigated.     

Synthesis of Chiral Calix[4]arene Derivative and Evaluation of its Recognition Properties

The article describes the synthesis and extraction properties of a new chiral calix[4]arene Schiff base ligand 5, which has been synthesized from 5,17-diformyl-25,27-bis-(4-nitrobenzyloxy)-26,28-dihidroxycalix[4]arene (4) by treatment with (S)-(-)-1-phenylethylamine. In this synthesis, it was thought to explore the role of chiral, as well as Schiff base sites in the recognition of targeted species ions (such as dichromate anions) as well as neutral/chiral molecules. At low pH, the ligand 5 is more effective for transferring the dichromate anions from an aqueous into a dichloromethane layer; may be due to the protonation of nitrogen atoms.

The extraction properties of ligand 5 towards the some selected α -amino acid methylesters are also reported. However, the ligand 5 did not display any selectivity towards the selected α-amino acid methylesters.     

Furo- and thieno-fused 1,3-diazepine-4,6-diones

We report the first preparation of furo- and thieno-fused 1,3-diazepine-4,6-dione derivatives starting from ethyl 2-(2-methoxy-2-oxoethyl)-3-furancarboxylate and -thiophencarboxylate. The ester functionalities connected to the hetero-ring were converted regiospecifically into the desired amides. The ester groups attached to the methylene unit were converted into isocyanates via Curtius rearrangement. The ring-closure reaction was performed in the presence of lithium bis(trimethylsilyl)amide at room temperature to give furo- and thieno-fused diazepinone derivatives.     

Synthesis and Properties of Thiophene and Dithiin Functionalized Tetrathiafulvalenes

Abstract

Syntheses of two analogues of tetrathiafulvalene (TTF), fused to 1,4-dithiin and thiophene rings, substituted with thiophene moieties, have been illustrated. The syntheses were accomplished through the reaction of a 1,8-diketone with phosphorus pentasulfide or Lawesson's reagent in boiling dry toluene. Conversion of the thioketones to their the oxo forms with mercury (II) acetate, was followed by self-coupling in freshly distilled boiling triethyl phosphite. Attempts for their electro-polymerizations through the thiophene groups at the peripherals were unsuccessful. Computational chemistry studies revealed that the thiophene groups did not exhibit enough spin densities to perform polymerization.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Dendrimer Templated Synthesis of Carbon Nanotube Supported PdAu Catalyst and its Application as Hydrogen Peroxide Sensor

At present, CNT supported catalysts were prepared by two different methods as NaBH₄ reduction and dendrimer templated NaBH₄ reduction method to observe the effect of preparation method on the sensitivity and activity of H₂O₂ reduction. Then, CNT supported Pd_xAu_y bimetallic nanocatalysts having various atomic ratio were synthesized via novel dendrimer templated NaBH₄ reduction method. The resulting materials were characterized employing XRD and TEM. Crystallite size of 10 %Pd_0.7Au_0.3/CNT_dendrimer was obtained from XRD 17.1 nm and mean particle size obtained from TEM is about 15 nm. Moreover, the electrochemical behavior of these catalysts was characterized by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Pd_xAu_y bimetallic nanocatalysts have excellent electrocatalytic properties and great potential for applications in electrochemical detection. The sensitivity and the limit of detection values for the prepared sensor with monometallic 10 % Pd/CNT_dendrimer catalysts are 219.78 μA mM^?1cm^?2 and 2.6 μM, respectively. However, the sensor constructed with 10 %Pd_0.7Au_0.3/CNT_dendrimer modified electrode has a very high sensitivity of 316.89 μA mM^?1 cm^?2 with a quick response time of 2 s and a wide linear range of 0.001–19.0 mM. In addition, the interference experiment indicated that the 10 % Pd_0.7Au_0.3/CNT_dendrimer nanoparticles have good selectivity toward H₂O₂.     

Oxygen assisted laser cutting mechanism—a laminar boundary layer approach including the combustion process

The present study examines the combined effects of chemical reactions taking place between a gas jet and molten metal, the cooling effect of the jet and the evaporation of metal, during a CO₂ laser cutting process. A laminar boundary layer approach was used to develop a theoretical model for the oxygen gas jet laser cutting mechanism. An experiment was carried out to monitor the keyhole formation using a video recorder and detect the light emitted from the entrance and exist surfaces of the workpiece using a fibre-optic probe during the cutting process. The experimental study was extended to employ two different workpiece materials (stainless steel and mild steel) at two thicknesses, and varying oxygen assisting gas pressures. It is found that the theoretical model developed in the present study is valid for a cutting speed of about 30 mm s⁻¹ and all jet velocities up to sonic, since the effect of shock is excluded in the model.     

Modeling Ergodic, Measure Preserving Actionson Shifts of Finite Type

 In this paper we show that shifts of finite type satisfying a strong topological mixing property are universal models for ergodic measure preserving dynamical systems.     

Role of electrolyte pH on structural and magnetic properties of Co–Fe films

Co–Fe films were electrodeposited on polycrystalline Titanium substrates from the electrolytes with different pH levels. X-ray diffraction (XRD) was used to study the crystal structure of the films. The XRD patterns showed that the films grown at the pH levels of 3.70 and 3.30 have a mixed phase consisting of face-centred cubic (fcc) and body-centred cubic, while those grown at pH=2.90 have only fcc structure. It was observed that the film composition, by energy dispersive x-ray spectroscopy, contain around 88 at% Co and 12 at% Fe for all films investigated in this study. Morphological observations indicated that all films have grainy structure with the slight change of grain size depending on the electrolyte pH. Magnetoresistance measurements, made at room temperature, showed that all films exhibited anisotropic magnetoresistance, which is affected by the electrolyte pH. From the magnetic measurements made by vibrating sample magnetometer, the saturation magnetization increases as the electrolyte pH decreases. Furthermore, all films have in-plane easy-axis direction of magnetization.     

In situ electrochemical solid-phase extraction of anions and cations using polypyrrole and overoxidized sulfonated polypyrrole

A new method for the extraction of both anions and cations is proposed using electro-synthesized polypyrrole (PPy) and overoxidized sulfonated polypyrrole film (OSPPy). In situ anion (chloride, nitrate, sulfate) and cation (calcium, magnesium) uptake and release were examined under controlled potential conditions for prospective applications in electrochemically controlled solid-phase extraction (EC-SPE). The PPy film was used as an anode (anion-exchanger) and OSPPy film was used as a cathode (cation-exchanger) material and reverse order of the electrodes were investigated in EC-SPE. This new cell arrangement containing two ion exchanger polymer electrodes was developed to provide in situ removal of both anions and cations from aqueous solution. Simple preparation of the film coatings on a platinum plate was possible using a constant potential method. Applied positive and negative potentials facilitated the in situ extraction and desorption of ions, respectively. Both anions and cations were desorbed into sample aliquot and were determined by ion chromatography (IC). The method was validated using a standard reference material and tested for the determination of the ions in real water samples.