Kinetics and mechanism of the reduction of colloidal MnO2 by glycyl-leucine in the absence and presence of surfactants

The kinetics of the reduction of water-soluble colloidal manganese dioxide by glycyl-leucine (Gly-Leu) has been investigated in the presence of perchloric acid both in aqueous as well as micellar media at 35 °C. The study was carried out as functions of [MnO₂], [Gly-Leu] and [HClO₄]. The first-order-rate is observed with respect to [MnO₂], whereas fractional-order-rates are determined in both [Gly-Leu] and [HClO₄]. Addition of sodium pyrophosphate and sodium fluoride enhanced the rate of the reaction. Further, the use of surfactant micelles is highlighted as, in favourable cases, the micelles help the redox reactions by bringing the reactants into a close proximity due to hydrogen bonding. While the ionic surfactants SDS and CTAB have not shown any effect on the reaction rate, the nonionic surfactant TX-100 has catalytic effect which is explained in terms of the mathematical model proposed by Tuncay et al. (1999). The Arrhenius and Eyring equations are valid for the reaction over the range of temperatures used and different activation parameters (E_a, ΔH^#, ΔS^# and ΔG^#) have been evaluated. Kinetic studies show that the redox reaction between MnO₂ and Gly-Leu proceeds through a mechanism combining one- and two-electron pathways: Mn(IV) → Mn(III) → Mn(II) and Mn(IV) → Mn(II). On the basis of the observed results, a possible mechanism has been proposed and discussed.     

A novel mixed valent Cu(II)-Cu(I) 2D framework made of a hydrazone and μ-SCN bridged metallacyclic loops cross-linked by μ(3)-SCN chains

A mixed valent copper complex [Cu(II)Cu(I)(L)(μ-SCN)(μ(3)-SCN)](n) (LH = N'-((pyridin-2-yl)methylene)acetohydrazide) has been synthesized and characterized. It is a unique example of a 2D mixed valent Cu(II)-Cu(I) interlinked molecular assembly with a very unusual bridging property of the hydrazone ligand. An extraordinary in situ partial Cu(II)→ Cu(I) reduction is observed in this system at room temperature.     

Calderón type formula in Quantum calculus

In this paper, a Calderón type reproducing formula involving finite q$q$-measures is considered in Quantum calculus.     

Pre-amp EDFA ASE noise minimization for optical receiver transmission performance optimization

Amplified spontaneous emission (ASE) noise mitigation from the pre-amp erbium-doped fiber amplifier (EDFA) to the photon detector (PD) in optical receivers can be reduced by optimizing the EDFA at the optical receiver level to achieve optimal optical receiver transmission performance.     

Resource allocation for performance improvement

In this paper the problem of allocating resources among Decision Making Units is considered. This study covers the case in which several homogeneous units are operating under the supervision of a central unit. The resource allocation is carried out by the DM (central unit) in such a way that the overall performance of the system is improved. Performance is defined by means of a convex combination of the ratio of the efficiencies before and after the resource allocation. It is assumed that each unit is allowed to modify its resources within the current production possibility set. A novel model is proposed which aims at achieving the best performance of the system. The method is capable of dealing with some additional constraints, imposed by the DM. The model is illustrated by a simple numerical example and a real application.     

Efficiency analysis to incorporate interval-scale data

We develop an approach to efficiency analysis to enable us to incorporate interval-scale data in addition to ratio-scale data. Our approach introduces a measure of inefficiency and identifies efficient units as is done in Data Envelopment Analysis. The basic idea in our approach is to find the “best” hyperplane separating the units that are better and worse than each unit. “Best” is defined in such a way that the number of not-better units is maximal. The efficiency measure is defined as a proportion of not-better units to all units. The results are invariant under a strictly increasing linear re-scaling of any input- or output-variables. Thus zeroes or negative values do not cause problems for the analysis. The approach is used to analyze the data of the research evaluation exercise recently carried out at the University of Joensuu, Finland.     

Invariance of a Shift-Invariant Space

A shift-invariant space is a space of functions that is invariant under integer translations. Such spaces are often used as models for spaces of signals and images in mathematical and engineering applications. This paper characterizes those shift-invariant subspaces S that are also invariant under additional (non-integer) translations. For the case of finitely generated spaces, these spaces are characterized in terms of the generators of the space. As a consequence, it is shown that principal shift-invariant spaces with a compactly supported generator cannot be invariant under any non-integer translations.     

Réaction du n-bromosuccinimide sur les aryl-2 dioxolannes-1,3 d'eroulement de la réaction

Reaction of NBS with 1,3-dioxolanes fused to a bicyclo[2.2.1] skeleton involves two intermediates, the dioxolanylium ion and the 2-succinimido-1,3-dioxolane. Evidence is presented that the unusual stability of the former ionic species is due to the steric hindrance towards endo attack by bromide ion, thus leading to the succinimido compound which by action of hydrobromic acid formed insitu, yields the former ionic species which finally gives the dioxolane ring-opening products. Some factors influencing the efficiency of the NBS reaction with hindered dioxolanes are pointed out.     

The c-alkylation of nitroalkame anions by l-substituted-2-t-butyl-4-phenyl- and -2,4-diphenyl-5,6-dihydrobenzo(ulbarh]quinolinium cations

- The N-substituents are transferred from the title cations to the C-atom of nitroalkane anions in high yield at 25-80°C in DMSO solution. The title cations are readily available from the appropriate pyrylium cations and primary amines of types RCH₂,NH₂, and RR'CHNH₂, allowing a general 2-step method for the preparation of higher nitro- alkanes. Spectral properties of a variety of nitroalkanes are discussed.