Molybdenum(VI) imido complexes: formation of [Mo(NPh)(S2CNR2)3]X and [Mo(NPh)(S2CNR2)2(μ-MoO4)]2 (R?=?Me, Et) from the reaction of [MoO2(S2CNR2)2] and PhNCO under aerobic conditions

Abstract  

Products from the thermolysis of PhNCO and [MoO₂(S₂CNR₂)₂] (R = Me, Et) are highly dependent upon the reaction conditions. When carried out in air, the major products are cations, [Mo(NPh)(S₂CNR₂)₃]⁺, as shown by a crystal structure of [Mo(NPh)(S₂CNEt₂)₃]₂[Mo₆O₁₉]. Under rigorously anaerobic conditions, reaction of two equivalents of PhNCO with [MoO₂(S₂CNR₂)₂] affords [Mo(NPh)₂(S₂CNR₂)₂] as the major product. However, chloroform solutions of the bis(imido) complexes hydrolyze in air to afford [Mo(NPh)(S₂CNR₂)₂(μ-MoO₄)]₂, in which molybdate groups bridge between molybdenum(VI) imido-bis(dithiocarbamate) centers. These results are placed in context of our earlier studies of these reactions that lead to the formation of oxo-disulfide [MoS₂(NPh)(S₂CNR₂)₂] and dimeric molybdenum(V) [MoO(μ-NPh)(S₂CNR₂)]₂ complexes, thus allowing a full picture of these transformations to be established.     

The (Lp, Lq) bilinear Hardy-Littlewood function for the tail

Let (X, B, μ, T) be a measure preserving dynamical system on a finite measure space. Consider the maximal function

Ionic conductivity studies of chitosan-based polymer electrolytes doped with adipic acid

Chitosan acetate–adipic acid film polymer electrolytes have been prepared by the solution cast technique. The highest conductivity is 1.4 × 10⁻⁹ S cm⁻¹ for 35 wt.% of adipic acid at room temperature. The sample with highest conductivity has the lowest activation energy. Calculations using the Rice and Roth model provide number of mobile ions, η. The conductivity is dependent on the diffusion coefficient and mobility.     

Sequential injection chromatography against HPLC and CE: Application to separation and quantification of amoxicillin and clavulanic acid

Sequential injection chromatography (SIC) has been recently proposed as an alternative separation technique. SIC has the advantages of inexpensiveness, rapid operation procedure, small dimension, short stabilization time, friendly maintenance process and less reagent consumption. In contrast, SIC has had suffered from some limitations. In the current study, a higher pressure resistant selection valve with additional ports than that available in commercially SIC systems was installed. This development allows achieving solution propulsion without showing leakage and linking more standard/sample solutions. In addition, a new method for the separation and quantification of amoxicillin and clavulanic acid in pharmaceutical formulations has been optimized and validated. A comparative study on the efficiency of the SIC method with previous HPLC and CE methods was conducted as well. Besides the benefits of the instrumentation of SIC, the proposed method has shown some advantages over previous HPLC and CE methods with respect to reagent consumption and sample frequency. Other such analytical characters of the SIC method as resolution, peak symmetry, number of theoretical plates, linearity range, accuracy, precision and limits of detection and quantification, recorded comparable results with those obtained from previous HPLC and CE methods.     

Developing new method for quantifying pindolol by sequential injection analysis

An inexpensive, rapid, safe and green method for pindolol assay in medicines was developed using sequential injection analysis (SIA) technique. The method was based on the oxidation of pindolol by dichromate in sulfuric acid media. A chromogenic form of pindolol was spectrophotometrically detected at 640 nm. The 3³ full-factorial design approach was applied to optimize acid concentration, pindolol volume and reaction time. The automation of SIA and the optimization process offered satisfactorily selectivity to the method. The recovery of pindolol in the presence of clopamide as a companion drug, besides excipients usually found in tablet formulation, was in the range of 96.5–98.4%. The automation also provided good repeatability, with a relative standard deviation value of 2.2% for seven replicates. Additionally, the miniaturization of SIA rendered the method reagent-saving (the total consumed reagent volumes was 120 μL) and environ-mentally-friendly (the total waste volume was 1320 μL). Furthermore, both the automation and miniaturization offered a rapid procedure (the sample frequency was 22 samples/h). On the other hand, the chemometric optimization improved the detectability of the method with the limits of detection and quantification of 0.57 and 1.9 μg/mL, respectively.     

Progressive Enlargement of Filtrations and Backward Stochastic Differential Equations with Jumps

This work deals with backward stochastic differential equations (BSDEs for short) with random marked jumps, and their applications to default risk. We show that these BSDEs are linked with Brownian BSDEs through the decomposition of processes with respect to the progressive enlargement of filtrations. We prove that the equations have solutions if the associated Brownian BSDEs have solutions. We also provide a uniqueness theorem for BSDEs with jumps by giving a comparison theorem based on the comparison for Brownian BSDEs. We give in particular some results for quadratic BSDEs. As applications, we study the pricing and the hedging of a European option in a market with a single jump, and the utility maximization problem in an incomplete market with a finite number of jumps.     

Development of a stability-indicating capillary electrophoresis method for norfloxacin and its inactive decarboxylated degradant

A simple, accurate, precise, rapid and sensitive stability-indicating capillary electrophoresis (CE) method was optimized and validated for the simultaneous determination of norfloxacin and its inactive decarboxylated degradant in pharmaceuticals. The univariant method was used to optimize electrophoretic factors including injection time, separation voltage and column temperature. Electrolyte concentration and pH were optimized using the factorial design and response surface methods. The optimum conditions obtained were: 10 mmol l^− 1 phosphate at pH 2.5, hydrodynamic injection time of 8 s at pressure 0.5 p.s.i., separation voltage 25 kV and column temperature 25 °C. The separation was carried out into a fused-silica capillary column (31.2 cm length × 50 μm i.d.) with detection at 301 and 285 nm for the intact drug and the degradant, respectively using a diode array detector. For both analytes, the method enjoys wide dynamic range (1-50 μg ml^− 1) with good detectability (limits of detection 0.11 μg ml^− 1). In addition, acceptable accuracy (recovery > 95%); and good repeatability and intermediate precision (RSD < 3.5%) were obtained.     

Tunable silver-shell dielectric core nano-beads array for thin-film solar cell application

The absorbance spectra of thin-film solar cells (TFSCs) can be enhanced by constructing the tunable periodic Ag-shell nano-bead (PASNB) arrays in the active material. In this paper, we investigated a plasmonic thin-film solar cell (TFSC) which composed of the arrays of PASNB deposited onto a crystalline silicon layer. By performing three-dimensional finite element method, we demonstrate that near field coupling among the PASNB arrays results in SPR modes with enhanced absorbance and field intensity. The proposed structure can significantly enhance the plasmonic activity in a wide range of incident light and enlarge working wavelength of absorbance in the range of near-UV, visible and near-infrared. We show that the sensitivity of the PASNB arrays reveals a linear relationship with the thickness of Ag-shell nano-bead (ASNB) for both the anti-bonding and bonding modes in the absorbance spectra. The broadband of absorbance spectra could be expanded as a wide range by varying the thickness of ASNB while the particle size is kept constant. Simulation results suggest this alternative scheme to the design and improvements on plasmonic enhanced TFSCs can be extended to other nanophotonic applications.     

Molecular imprinted polymer for β-carotene for application in palm oil mill effluent treatment

Palm oil mill effluent (POME) is one of the most significant pollutant in the form of wastewater. It could have negative effects on the environment include the emission of biogas and water pollution which comes from discharging the brownish tick POME to the water bodies if not properly managed. Discharge of dark brownish colored of POME directly into water bodies may affect the aquatic life as it will reduce sunlight penetration and suppress the photosynthetic activity. A molecularly imprinted polymer (MIP) for removal of β-carotene from POME has been aimed to develope in this study. The preparation of β-carotene imprinted and non-imprinted polymer (NIP) involves polymerization of β-carotene (or without it) with β-cyclodextrin (β-CD), 9-vinylcarbazole (9VC), tolylene diisocyanate (TDI) and N,N-dimethylformamide (DMF) as the monomer, co-monomer, cross-linker and solvent (porogen), respectively. Analysis from FTIR showed that MIP and NIP have similar characteristic peak with different peaks intensity, indicating the similarity in the backbone structure of polymerization. TGA result displayed high thermal stability with final decomposition at 320 °C for MIP-β-CD-9VC as compared to NIP-β-CD-9VC. The pH study shows that sorption of β-carotene increased with decreasing the pH of POME and the maximum sorption capacities achieved at pH 2 were 10 μg/g and 7 μg/g for MIP-β-CD-9VC and NIP-β-CD-9VC, respectively. The maximum sorption achieved by using 500 mg of MIP as the sorption of β-carotene increased with increasing the dosage of MIP. Kinetic model evaluation has been applied on this prepared materials. The sorption equilibrium data was well described by Freundlich model. The results indicated that the sorption of β-carotene on MIP follows a pseudo–second–order kinetic.