Electrocatalytic oxidation of methanol onto platinum particles decorated nanostructured poly (1,5-diaminonaphthalene) film

In this work, platinum particles decorated nanostructured poly (1,5-diaminonaphthalene) modified glassy carbon electrode (Pt/Nano-PDAN/MGCE) is prepared. The composite catalysts are characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical methods. The electrochemical methanol oxidation reaction is studied at the surface of this modified electrode. At same Pt loading, the Pt/Nano-PDAN/MGCE can act as higher efficient catalyst for methanol oxidation than that Pt/MGCE. Then, the influence of some parameters such as potential scan rates, switching potential, and methanol concentration on its oxidation as well as long-term stability of the modified electrode have studied by electrochemical methods. Also, ability of the modified electrode toward electrocatalytic oxidation of formaldehyde as an intermediate in methanol oxidation has been investigated.     

Decaaquabis(μ3‐4‐hydroxypyridine‐2,6‐dicarboxylato)bis(4‐hydroxypyridine‐2,6‐dicarboxylato)tetramanganese(II) 3.34‐hydrate: a new three‐dimensional open metal–organic framework based on a tetranuclear MnII complex of chelidamic acid and undecameric stitching water clusters

4‐Hydroxypyridine‐2,6‐dicarboxylic acid (chelidamic acid, cdaH₃) reacts with MnCl₂·2H₂O in the presence of 2‐amino‐4‐methylpyrimidine in water to afford the tetranuclear title complex, [Mn₄(C₈H₃NO₅)₄(H₂O)₁₀]·3.34H₂O, built through carboxylate bridging. The tetranuclear complex sits on a centre of inversion at (, , ). In the crystal, discrete undecameric (H₂O)_10.34 water clusters (involving both coordinated and uncoordinated water molecules, with one site of an uncoordinated water molecule not fully occupied) assemble these tetranuclear Mn^II complex units via an intricate array of hydrogen bonding into an overall three‐dimensional network. The degree of structuring of the (H₂O)_10.34 supramolecular association of water molecules observed in the present compound, imposed by its environment and vice versa, will be discussed in comparison to that observed for the (H₂O)₁₄ supramolecular clusters in the case of the dinuclear complex [Mn₂(cdaH)₂(H₂O)₄]·4H₂O [Ghosh et al. (2005). Inorg. Chem. 44 , 3856–3862].     

Copper Supported on the SiO2 Nanoparticle in Click Chemistry: An Alternative Catalytic System for Regioselective and One‐Pot Synthesis of 1,2,3‐Triazoles and β‐Hydroxytriazoles

In this work, readily prepared copper supported on the SiO₂ nanoparticles has been found to effectively catalyze the 1,3‐dipolar cycloaddition of a variety of azides, alkynes, epoxides and sodium azide, furnishing the corresponding 1,2,3‐triazoles and β‐hydroxytriazoles. Click reaction proceeds in short reaction times and under mild reaction conditions, and the resulting products are obtained in good yields at ambient temperature.     

A Model-Based Approach and Analysis for Multi-Period Networks

The aim of this contribution is to address a general class of network problems, very common in process systems engineering, where spoilage on arcs and storage in nodes are inevitable as time changes. Having a set of capacities, so-called horizon capacity which limits the total flow passing arcs over all periods, the min-cost flow problem in the discrete-time model with time-varying network parameters is investigated. While assuming a possibility of storage or and spoilage, we propose some approaches employing polyhedrals to obtain optimal solutions for a pre-specified planning horizon. Our methods describe some reformulations based on polyhedrals that lead to LP problems comprising a set of sparse subproblems with exceptional structures. Considering the sparsity and repeating structure of the polyhedrals, algorithmic approaches based on decomposition techniques of block-angular and block-staircase cases are proposed to handle the global problem aiming to reduce the computational resources required.     

Orthogonal packing of enantiomerically pure helical silver coordination networks

The combination of the chiral tecton based on the (R)-6,6'-dibromo-1,1'-binaphthyl moiety bearing two isonicotinoyl groups with AgX (X = BF4-, CF3SO3-, PF6-) leads to the formation of enantiomerically pure helical strands with orthogonal packing in the rare space group I2(1)3.     

A Relation Between Closure Operators on a Small Category and Its Category of Presheaves

In this paper we show that each factorization structure on a small category , satisfying certain conditions, yields a presheaf on and a morphism of presheaves . We then give connections, and set up one to one correspondences, between subclasses of the following classes: (a) closure operators on (b) subobjects of (c) morphisms from to (d) weak Lawvere–Tierney topologies (e) weak Grothendieck topologies (f) closure operators on .     

Closed-form solution for free vibration of piezoelectric coupled annular plates using Levinson plate theory

Free vibration analysis of annular moderately thick plates integrated with piezoelectric layers is investigated in this study for different combinations of soft simply supported, hard simply supported and clamped boundary conditions at the inner and outer edges of the annular plate on the basis of the Levinson plate theory (LPT). The distribution of electric potential along the thickness direction in the piezoelectric layer is assumed as a sinusoidal function so that the Maxwell static electricity equation is approximately satisfied. The differential equations of motion are solved analytically for various boundary conditions of the plate. In this study the closed-form solution for characteristic equations, displacement components of the plate and electric potential are derived for the first time in the literature. To demonstrate the accuracy of the present solution, comparison studies is first carried out with the available data in the literature and then natural frequencies of the piezoelectric coupled annular plate are presented for different thickness-radius ratios, inner-outer radius ratios, thickness of piezoelectric, material of piezoelectric and boundary conditions. Present analytical model provides design reference for piezoelectric material application, such as sensors, actuators and ultrasonic motors.     

Study of reaction between activated acetylenes and N,N′‐diethyl‐2‐thiobarbituric acid in the presence of isocyanides or triphenylphosphine

In a series of separate experiments reaction between N,N′‐diethyl‐2‐thiobarbituric acid and acetylenic diesters in the presence of isocyanides or triphenylphosphine led to highly functionalized 4H‐pyrano[2,3‐d]thiopyrimidine or 1,4‐di‐ionic organophosphorus derivatives. The ¹H NMR spectra of diethyl‐7‐(2,6‐dimethylphenylamino)‐4‐oxo‐2‐thio‐ 1,3‐diethyl‐4H‐pyrano[2,3‐d]pyrimidine‐5,6‐dicarboxylate showed dynamic NMR effect that was attributed to restricted rotation around the aryl‐nitrogen single bond. Activation free energy (ΔG^≠) for this process is about 54.85 ± 2 kJ mol⁻¹. Betaines as 1,4‐diionic organophosphorus compounds in this reaction are possessed of two vicinal stereogenic centers and exist in the solution as a mixture of two diastereoisomers. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:228–235, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20601     

Nanocomposite Silica Aerogel Activated Carbon: Preparation,Characterization and Application to Remove Lead(II) from Aqueous Solutions

Anovel nanocomposite adsorbent, Silica aerogel activated carbon (SA‐AC) has been prepared for the purpose of removing lead ions from aqueous solution in batch process. The nanocomposite was characterized by Fourier transform infrared spectra (FTIR) and scanning electron microscope (SEM). In the present investigation, Pb(II) adsorption experiments on nanocomposite were conducted on aqueous solution at different initial Pb(II) concentration, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Optimum pH for the adsorption was found to be 6 with corresponding adsorbent dosage level of 0.5 g and 60 °C temperature. The equilibriumwas achieved within 30 min of contact time. It is remarkable that using the developed nanocomposite absorbent, more than 90% of Pb(II) can be removed under desirable experimental conditions. The efficiency of the ions adsorption was determined using atomic absorption spectroscopy. Langmuir and Freundlich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data was given by the Freundlich isotherm equation. Desorption experiments by elution of the adsorbent with nitric acid show that the nanocomposite could be reused without significant losses of its initial properties.