Fringing field optimization of hemispherical deflector analyzers using BEM and FDM

In this paper we present numerical modeling results for fringing field optimization of hemispherical deflector analyzers (HDAs), simulated using boundary-element and finite-difference numerical methods. Optimization of the fringing field aberrations of HDAs is performed by using a biased optical axis and an optimized entry position offset (paracentric) from the center position used in conventional HDAs. The described optimization achieves first-order focusing thus also further improving the energy resolution of HDAs.     

Reactivity of mixed organozinc and mixed organocopper reagents: 11. Nickel‐catalyzed atom‐economic aryl–allyl coupling of mixed (n‐alkyl)(aryl)zincs

Group selectivity in the allylation of mixed (n‐butyl)(phenyl)zinc reagent can be controlled by changing reaction parameters. CuCN‐catalyzed allylation in tetrahydrofuran (THF)–hexamethylphosphoric triamide is n‐butyl selective and also γ‐selective in the presence of MgCl₂, whereas CuI‐catalyzed allylation in THF in the presence of n‐Bu₃P takes place with a n‐butyl transfer:phenyl transfer ratio of 23:77 and an α:γ transfer ratio of phenyl of 76:24. NiCl₂(Ph₃P)₂‐catalyzed allylation in the presence of LiCl is phenyl selective with an α:γ ratio of 65:35. The reaction of methyl‐ or n‐butyl(aryl)zinc reagents with an allylic electrophile in THF at room temperature in the presence of NiCl₂(Ph₃P)₂ catalyst and LiCl as an additive provides an atom‐economic alternative to aryl–allyl coupling using diarylzincs. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemical sensor based on a sepiolite clay nanoparticle-based electrochemical sensor for ascorbic acid detection in real-life samples

Ionics - A new electrode composed of sepiolite clay (SC) carbon paste (CP) was developed and used for the adsorptive stripping differential pulse voltammetric quantification of ascorbic acid (AA)....     

Operator time‐splitting techniques combined with quintic B‐spline collocation method for the generalized Rosenau–KdV equation

In this article, the generalized Rosenau–KdV equation is split into two subequations such that one is linear and the other is nonlinear. The resulting subequations with the prescribed initial and boundary conditions are numerically solved by the first order Lie–Trotter and the second‐order Strang time‐splitting techniques combined with the quintic B‐spline collocation by the help of the fourth order Runge–Kutta (RK‐4) method. To show the accuracy and reliability of the proposed techniques, two test problems having exact solutions are considered. The computed error norms L₂ and L_∞ with the conservative properties of the discrete mass Q(t) and energy E(t) are compared with those available in the literature. The convergence orders of both techniques have also been calculated. Moreover, the stability analyses of the numerical schemes are investigated.     

Stochastic Decomposition in M/M/∞ Queues with Markov Modulated Service Rates

Motivated by the need to study transportation systems in which incidents cause traffic to slow down, we consider an M/M/∞ queueing system subject to random interruptions of exponentially distributed durations. System breakdowns, where none of the servers work, as well as partial failures, where all servers work with lower efficiency, are investigated. In both cases, it is shown that the number of customers present in the system in equilibrium is the sum of two independent random variables. One of these is the number of customers present in an ordinary M/M/∞ queue without interruptions.     

Neuroactive Peptide Nanofibers for Regeneration of Spinal Cord after Injury

The highly complex nature of spinal cord injuries (SCIs) requires design of novel biomaterials that can stimulate cellular regeneration and functional recovery. Promising SCI treatments use biomaterial scaffolds, which provide bioactive cues to the cells in order to trigger neural regeneration in the spinal cord. In this work, the use of peptide nanofibers is demonstrated, presenting protein binding and cellular adhesion epitopes in a rat model of SCI. The self‐assembling peptide molecules are designed to form nanofibers, which display heparan sulfate mimetic and laminin mimetic epitopes to the cells in the spinal cord. These neuroactive nanofibers are found to support adhesion and viability of dorsal root ganglion neurons as well as neurite outgrowth in vitro and enhance tissue integrity after 6 weeks of injury in vivo. Treatment with the peptide nanofiber scaffolds also show significant behavioral improvement. These results demonstrate that it is possible to facilitate regeneration especially in the white matter of the spinal cord, which is usually damaged during the accidents using bioactive 3D nanostructures displaying high densities of laminin and heparan sulfate‐mimetic epitopes on their surfaces.     

Syntheses and Structures of Zinc Bis(phosphinimino)methanide Complexes

Reactions of bis(phosphinimino)methanes H₂C(PPh₂NR)₂ [R = SiMe₃ (L¹H), Ph (L²H), 2,6‐iPr₂‐C₆H₃ (DIPP) (L³H)] with ZnR₂ (R = Me, Et) yielded the corresponding bis(phosphinimino)methanide zinc complexes LZnMe [L² ( 1 ), L³ ( 2 )] and LZnEt [L¹ ( 3 ), L² ( 4 ), and L³ ( 5 )]. Complexes 1 – 5 were characterized by heteronuclear NMR (¹H, ¹³C, ³¹P) and IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction.     

Investigation of energetic materials prepared by reactions of diamines with picryl chloride

Five compounds containing picryl group(s) were synthesized from reactions of hydrazine, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane and 1,7-diaminoheptane with picryl chloride under hydrothermal conditions in methanol. Hydrazine reaction yielded N-2,4,6-trinitrophenylhydrazine which has a single picryl group, whereas the other reactants formed symmetric products with both amine groups connected to picryl groups. These compounds are N,N′-di-2,4,6-trinitrophenyl-1,2-diaminoethane, bis-N,N′-di-2,4,6-trinitrophenyl-1,3-diaminopropane, bis-N,N′-di-2,4,6-trinitrophenyl-1,4-diaminobutane and bis-N,N′-di-2,4,6-trinitrophenyl-1,7-diaminoheptane. Molecular structures of two of these compounds, N-2,4,6-trinitrophenylhydrazine and bis-N,N′-di-2,4,6-trinitrophenyl-1,3-diaminopropane, were revealed by XRD methods. All compounds were investigated by TG and DSC methods. The thermal behaviour of N-2,4,6-trinitrophenylhydrazine was explosive, undergoing a strong explosion in a very short temperature interval, 180–185 °C. In cases of the other compounds, it was found out that the carbon chain between two picryl groups reduced the explosion enthalpy. In addition, the theoretical formation enthalpy of N-2,4,6-trinitrophenylhydrazine was calculated by running CBS-4 M energy calculations under Gaussian 09 software package. From the calculated value, reaction enthalpy values for the possible explosion pathways were investigated in accordance with the experiment. The path with reaction enthalpy closest to the experimental value was proposed as the explosion mechanism.     

Preparation and Application of a Hydrochar-Based Palladium Nanocatalyst for the Reduction of Nitroarenes

In the present study, a novel heterogeneous catalyst was successfully fabricated through the decoration of palladium nanoparticles on the surface of designed Fe₃O₄-coffee waste composite (Pd-Fe₃O₄-CWH) for the catalytic reduction of nitroarenes. Various characterization techniques such as XRD, FE-SEM and EDS were used to establish its nano-sized chemical structure. It was determined that Pd-Fe₃O₄-CWH is a useful nanocatalyst, which can efficiently reduce various nitroarenes, including 4-nitrobenzoic acid (4-NBA), 4-nitroaniline (4-NA), 4-nitro-o-phenylenediamine (4-NPD), 2-nitroaniline (2-NA) and 3-nitroanisole (3-NAS), using NaBH₄ in aqueous media and ambient conditions. Catalytic reactions were monitored with the help of high-performance liquid chromatography. Additionally, Pd-Fe₃O₄-CWH was proved to be a reusable catalyst by maintaining its catalytic activity through six successive runs. Moreover, the nanocatalyst displayed a superior catalytic performance compared to other catalysts by providing a shorter reaction time to complete the reduction in nitroarenes.