6-alkoxy-3,4-dihydro-2h-pyrans from substituted α,β-unsaturated esters

Cycloaddition reactions of substituted α,β-unsaturated esters with various electronich olefins lead to 6-alkoxy-3,4-dihydro-2H-pyrans.     

A hybrid metaheuritic technique developed for hourly load forecasting

Electricity load forecasting has become one of the most functioning tools in energy efficiency and load management and utility companies which has been made very complex due to deregulation. Due to the importance of providing a secure and economic electricty for the consumers, having a reliable and robust enough forecast engine in short‐term load management is very needful. Fuzzy inference system is one of primal branches of Artificial Intelligence techniques which has been widely used for different applications of decision making in complex systems. This paper aims to develop a Fuzzy inference system as a main forecast engine for Short term Load Forecasting (STLF) of a city in Iran. However, the optimization of this platform for this special case remains a basic problem. Hence, to address this issue, the Radial Movement Optimization (RMO) technique is proposed to optimize the whole Fuzzy platform. To support this idea, the accuracy of the proposed model is analyzed using MAPE index and an average error of 1.38% is obtained for the forecast load demand which represents the reliability of the proposed method. Finally, results achieved by this method, demonstrate that an adaptive two‐stage hybrid system consisting of Fuzzy & RMO can be an accurate and robust enough choice for STLF problems. © 2016 Wiley Periodicals, Inc. Complexity 21: 521–532, 2016     

Alkyl chain length effect on construction of copper(II) complexes with tridentate Schiff base ligand and DNA interaction

Two tridentate Schiff base ligands were synthesized by condensation of equimolar amounts of benzoylacetone and 2-amino-1-ethanol or 3-amino-1-propanol, H₂L¹ and H₂L², respectively. The reaction of the Schiff base ligands with Cu(CH₃COO)₂ in methanol leads to (CuL¹)₄, 1 and (CuL²)₂, 2. In the tetranuclear cubane species, the tridentate H₂L has both a chelating and a bridging mode, after double deprotonation of the enolic OH groups. The copper(II) centers are five-coordinate with a NO₄ donor set from the ligands. The coordination geometry around each copper ion is essentially square pyramidal with one nitrogen and two oxygens from one ligand and two oxygens of adjacent ligands from the next unit of the cubane. In dinuclear 2, H₂L² has chelating and bridging modes after double deprotonation of the enolic OH groups. The dianionic form of the Schiff base coordinates forming a six-membered chelate ring with Cu(II). Two such monomeric CuL² entities are eventually linked through the alkoxo bridges to produce dinuclear 2. The absorption spectra strongly suggest that 2 interacts with CT-DNA. Both 1 and 2 appear to be more efficient than the parent compound in DNA cleavage.     

Reversible Melting of Semi-crystalline Polymers Frequency dependence of the reversible melting enthalpy

Modulated DSC (MDSC) has been used to study the heat flow during melting and crystallisation of some semi-crystalline polymers i.e. different grades of polyethylene (LDPE, LLDPE and HDPE), and polypropylene (PP). The heat capacities measured by MDSC are compared with the hypothetical complex heat capacities of Schawe and it is shown that numerically they are equivalent; nevertheless, the concept of the complex heat capacity is problematic on a thermodynamic basis. A reversing heat flow (proportional to the experimental heat capacity of the material) was present at all conditions used for the study. In the melting zone of the polymers it depends on the modulation frequency and on the amplitude. Higher amplitude and frequency of modulation reduce the ratio of the reversing heat flow to the total heat flow, the latter is nearly independent on these parameters. The reversible component of the melting enthalpy of polymers depends on the modulation frequency, the modulation amplitude and the type of the polymer. It increases by increasing the branching in polyethylene. The existence of the reversible heat flow during the crystallisation and melting is contrary to the current hypotheses and theories of polymer crystallisation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies of laser-induced cavitation and tissue ablation in saline using a fibre-delivered pulsed HF laser

We describe studies of the interaction of 400 ns duration, fibre delivered, multiline (2.6–3.0 m) HF-laser pulses with cornea and retina samples in saline. In this wavelength region water exhibits strong absorption (beam penetration depth 1.6 m) and laser heating leads to the creation of a hot, high pressure, vapour cavity (laser-induced cavitation) at the fibre tip. The dynamics of vapour cavity growth have been investigated experimentally using the laser shadowgraph technique and theoretically by employing an equivalent spherical cavity model for an incompressible liquid. Measurements of ablation rates and transient acoustic pressures for cornea ablation in saline, together with scanning electron microscope evaluation of irradiated samples are used to assess the damage range and mechanisms for this mid-IR laser in a strongly absorbing fluid.     

Use of reversible denaturation for adsorptive immobilization of urease

Urease was chosen as a model multimeric protein to investigate the utility of reversible denaturation for immobilization to a hydrophobic support. Of the various procedures investigated, acidic denaturation provided the highest degree of immobilization and enzymatic activity with lowering of K _m (apparent). Exposure of hydrophobic clusters in the protein molecule induced by the acidic pH environment was confirmed by fluorescence studies using 8-anilino-1-naphtalene-sulfonate as a hydrophobic-reporter probe. The catalytic potential of the enzyme at low pH values was dramatically improved with significant heat and pH stability enhancement on immobilization. Furthermore, the immobilized preparation was used successfully in continuous catalytic transformations. Based on the results presented in this article and a recent report involving a relatively more simple monomeric protein, it is suggested that reversible denaturation may be of general utility for immobilization of proteins, which are not normally adsorbed on hydrophobic supports.     

Geometry, charge distribution, and surface speciation of phosphate on goethite

The surface speciation of phosphate has been evaluated with surface complexation modeling using an interfacial charge distribution (CD) approach based on ion adsorption and ordering of interfacial water. In the CD model, the charge of adsorbed ions is distributed over two electrostatic potentials in the double-layer profile. The CD is related to the structure of the surface complex. A new approach is followed in which the CD values of the various surface complexes have been calculated theoretically from the geometries of the surface complexes. Molecular orbital calculations based on density functional theory (MO/DFT) have been used to optimize the structure of a series of hydrated surface complexes of phosphate. These theoretical CD values are corrected for dipole orientation effects. Data analysis of the PO4 adsorption, applying the independently derived CD coefficients, resolves the presence of two dominant surface species. A nonprotonated bidentate (B) complex is dominant over a broad range of pH values at low loading (< or =1.5 micromol/m(2)). For low pH and high loading, a strong contribution of a singly protonated monodentate (MH or MH-Na) complex is found, which differs from earlier interpretations. For the conditions studied, the doubly protonated bidentate (BH2) and monodentate (MH2) surface complexes and the nonprotonated monodentate (M) complex are not significant contributors. These findings are discussed qualitatively and quantitatively in relation to published experimental in-situ CIR-FTIR data and theoretical MO/DFT-IR information. The relative variation in the peak intensities as a function of pH and loading approximately agrees with the surface speciation calculated with the CD model. The model correctly predicts the proton co-adsorption of phosphate binding on goethite and the shift of the IEP at low phosphate loading (< or =1.5 micromol/m(2)). At higher loading, it deviates.     

2‐(1H‐Benzotriazole‐1‐yl)‐1,1,3,3‐Tetramethyluronium Tetrafluoro Borate (TBTU) as an Efficient Coupling Reagent for the Esterification of Carboxylic acids with Alcohols and Phenols at Room Temperature

Esterification of carboxylic acids with alcohols and phenols by using 2‐(1H‐benzotriazole‐1‐yl)‐1,1,3,3‐tetramethyluronium tetrafluoroborate (TBTU) in the presence of triethylamine as a base proceeded smoothly under mild conditions to afford the corresponding esters in good to high yields in acetonitrile at room temperature.     

A wide potential window aqueous supercapacitor based on LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>–rGO nanocomposite

Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn₂O₄/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm²) is 268.75 F/g (258 mF/cm²), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li₂SO₄ electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.