Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst

Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant.     

Polybenzimidazole‐decorated carbon nanotube: A high‐performance proton conductor

Interaction between negatively charged Nafion^® and a positively charged polybenzimidazole‐decorated carbon nanotube leads to the formation of an ionic complex with high charge density for proton conduction, which can lead to an improvement in transport properties. Here we investigate the high‐temperature and low‐humidity proton conductivity of this nanocomposite membrane as a potential membrane for fuel cell applications.

     

Charge-transfer complexes of 4-nitrocatechol with some amino alcohols

Charge-transfer (CT) complexes formed from the reactions of 4-nitropyrocatechol (4-nCat) as an electron acceptor with four amino alcohols: 2-aminoethanol, 1-amino-2-propanol, 4-aminobutanol and N-(2-hydroxyethyl)-1,3-diaminopropane (NHEDAP) as electron donors, have been studied spectrophotometrically in H₂O and H₂O/EtOH at 20, 25, 30, 35 and 40 °C. The calculated values of the oscillator strength and transition moment confirm the formation of CT-complexes. The thermodynamic and spectroscopic parameters were also evaluated for the formation of CT-complexes. The equilibrium constants ranged from 9.00 to 2.20 l mol^?1 (M^?1). These interactions are exothermic and have relatively large standard enthalpy and entropy changes (ΔH values ranged from ?15.58 to ?3.10 kJ mol^?1; ΔS ranged from 26.81 to ?3.25 J K^?1 mol^?1). The solid CT-complexes have been synthesized and characterized by IR, NMR, mass spectrometry and thermal analysis. The photometric titration curves and other spectrometric data for the reactions indicated that the data obtained refer to the formation of 1:1 charge-transfer complex of [(4-nCat) (NHEDAP)] and 1:2 charge-transfer complexes of other amino alcohols [(4-nCat) (amino alcohol)₂]. The effect of alkali and alkaline earth metals on increasing the equilibrium constant of the CT-complexation was also investigated.     

WDM and DWDM optical filter based on 2D photonic crystal Thue–Morse structure

This paper describes elaboration of two dimensional photonic crystal structures based on Thue–Morse sequence. Our results establish that the optical properties of these aperiodic multilayer systems can be tailored by adjusting either the radius of some cells of the proposed structure or defect characteristics. We introduce a resonant cavity in the proposed structure to select desirable wavelengths for filtering. Bandwidth of selected wavelengths are about 1 nm and suitable for communication applications. Also, our simulations show that efficiency of the proposed structure is enough. The total footprint of proposed filter is 331.24 μm², therefore it is suitable to be integrated in all optical chips.     

A new multi-objective stochastic model for a forward/reverse logistic network design with responsiveness and quality level

Logistic network design has an important and strategic platform in an efficient and effective supply chain management, and usually involves multiple and conflicting goals, such as cost/profit, resource balance, customer responsiveness, quality, and the like. Besides, due to the implementation of government legislation, environmental concern, social responsibility and customer awareness, companies have been forced by customers not only to supply environmentally amicable products but also to be responsible for the returned products. Hence, this paper presents a stochastic multi-objective model for forward/reverse logistic network design under a uncertain environment including three echelons in forward direction (i.e., suppliers, plants, and distribution centers) and two echelons in backward direction (i.e., collection centers and disposal centers). We demonstrate a method to evaluate the systematic supply chain configuration maximizing the profit, customer responsiveness, and quality as objectives of the logistic network. The set of Pareto optimal solutions is obtained and also financial risk relevant to them is computed in order to show the tradeoff between objectives. The results give important insight for fostering the decision making process.     

First principles study on spin and orbital magnetism in CuFeSb and CuCoSb alloys with C1b structure

In this work the effect of spin–orbit coupling and orbital polarization (OP) corrections on the spin and orbital magnetism of two half-Heusler alloys (CuFeSb and CuCoSb) is investigated by means of local spin density calculations. It is demonstrated that OP corrections predict large orbital moments for Fe and Co individual atoms in the considered compounds. It is found that the Heusler alloys with C1_b structure are potential candidates to show large orbital magnetism.     

Some results on the strength of relaxations of multilinear functions

We study approaches for obtaining convex relaxations of global optimization problems containing multilinear functions. Specifically, we compare the concave and convex envelopes of these functions with the relaxations that are obtained with a standard relaxation approach, due to McCormick. The standard approach reformulates the problem to contain only bilinear terms and then relaxes each term independently. We show that for a multilinear function having a single product term, this approach yields the convex and concave envelopes if the bounds on all variables are symmetric around zero. We then review and extend some results on conditions when the concave envelope of a multilinear function can be written as a sum of concave envelopes of its individual terms. Finally, for bilinear functions we prove that the difference between the concave upper bounding and convex lower bounding functions obtained from the McCormick relaxation approach is always within a constant of the difference between the concave and convex envelopes. These results, along with numerical examples we provide, give insight into how to construct strong relaxations of multilinear functions.     

Teaching European mathematics in the Ottoman Empire during the eighteenth and nineteenth centuries: between admiration and rejection

The purpose of this study is to examine the modernizing process in the teaching of mathematics in three countries that were part of the Ottoman Empire, namely Turkey, Egypt and Tunisia, during the eighteenth and nineteenth centuries. In each case, a permanent state of war and continued European pressures made the need of reforms of military structures a vital necessity for the preservation of the state. Some of the military reforms proposed, although they met with rejection and resulted in revolts and in the dismissal of most of their initiators, did sow wholesome seeds into the educational system which would be transformed first in Muhammad Ali??s Egypt, then in Mahm??d II??s Turkey and finally in Khayr al-D??n??s Tunisia who introduced important and comprehensive reforms under which the teaching of modern mathematics played a non-negligible part. The second part outlines the transformations of the educational institutions and their role in the introduction of the new imported Western mathematics. Finally, we detail the type of mathematics taught into the newly founded military and engineering schools and insist on the efforts made by the Egyptians for translating into Arabic French textbooks.     

The first report of [2+2] ketene–imine cycloaddition reactions (Staudinger) on carbon nanotubes

Several new carbon nanotube-functionalized β-lactams have been synthesized from chiral imines derived from β-d-glucopyranosylamine and a ketene from carbon nanotube-based oxyacetic acid via a [2+2] cycloaddition reaction. The cycloadducts were characterized by thermogravimetric analysis, Raman spectrometry, IR, and N₂ adsorption processes.     

Convergence of distributed optimal control problems governed by elliptic variational inequalities

First, let u _g be the unique solution of an elliptic variational inequality with source term g. We establish, in the general case, the error estimate between $u_{3}(\mu)=\mu u_{g_{1}}+ (1-\mu)u_{g_{2}}$ and $u_{4}(\mu)=u_{\mu g_{1}+ (1-\mu) g_{2}}$ for ????[0,1]. Secondly, we consider a family of distributed optimal control problems governed by elliptic variational inequalities over the internal energy g for each positive heat transfer coefficient h given on a part of the boundary of the domain. For a given cost functional and using some monotony property between u ₃(??) and u ₄(??) given in Mignot (J.?Funct. Anal. 22:130?C185, 1976), we prove the strong convergence of the optimal controls and states associated to this family of distributed optimal control problems governed by elliptic variational inequalities to a limit Dirichlet distributed optimal control problem, governed also by an elliptic variational inequality, when the parameter h goes to infinity. We obtain this convergence without using the adjoint state problem (or the Mignot??s conical differentiability) which is a great advantage with respect to the proof given in Gariboldi and Tarzia (Appl. Math. Optim. 47:213?C230, 2003), for optimal control problems governed by elliptic variational equalities.