Nickel(II) complexes bearing pyrazolylpyridines: synthesis,structures and ethylene oligomerization reactions

Reactions of 2‐bromo‐6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine ( L1 ) and 2,6‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine ( L2 ) with NiCl₂ and NiBr₂ led to the formation of their respective metal complexes [NiCl₂(L1)] ( 1 ), [NiBr₂(L1)] ( 2 ) and [NiBr₂(L2)] ( 3 ) in moderate to high yields. The complexes were characterized using elemental analyses, mass spectrometry and single‐crystal X‐ray diffraction for 2 . The solid‐state structure of 2 confirmed the bidentate coordination mode of L1 and formation of a monometallic compound. Activation of the nickel(II) pre‐catalysts with methylaluminoxane afforded active catalysts in the ethylene oligomerization reaction to produce mainly butenes (84–86%). In contrast, activation of nickel(II) pre‐catalyst 2 with ethylaluminium dichloride resulted in partial Friedel–Crafts alkylation of the toluene solvent by the preformed oligomers. Complex structure, nature of co‐catalyst employed, type of solvent and reaction conditions influenced the catalytic behaviour of these pre‐catalysts. Copyright © 2015 John Wiley & Sons, Ltd.     

High-performance 850 nm vertical-cavity surface-emitting laser in Gigabit Ethernet network

High-performance oxide vertical-cavity surface-emitting (VCSEL) laser is fabricated, and its usefulness is demonstrated as a suitable transmitting light source at 850 nm operating wavelength for Gigabit Ethernet application. Utilization of barrier reduction layers reveals low-threshold current requirement for operation at high modulation bandwidth. The electrical and optical characteristics, measured from the fabricated VCSEL, are simulated for Gigabit Ethernet transmission. Data rates of 1.25 Gbps with a bit error rate of 10⁻¹¹ are achieved by the use of a specific multimode network simulator.     

Multi-Fractal Formalism for Quasi-Self-Similar Functions

The study of multi-fractal functions has proved important in several domains of physics. Some physical phenomena such as fully developed turbulence or diffusion limited aggregates seem to exhibit some sort of self-similarity. The validity of the multi-fractal formalism has been proved to be valid for self-similar functions. But, multi-fractals encountered in physics or image processing are not exactly self-similar. For this reason, we extend the validity of the multi-fractal formalism for a class of some non-self-similar functions. Our functions are written as the superposition of similar structures at different scales, reminiscent of some possible modelization of turbulence or cascade models. Their expressions look also like wavelet decompositions. For the computation of their spectrum of singularities, it is unknown how to construct Gibbs measures. However, it suffices to use measures constructed according the Frostman's method. Besides, we compute the box dimension of the graphs.     

Interacting dark energy with inhomogeneous equation of state

We have investigated the model of dark energy interacting with dark matter by choosing inhomogeneous equations of state for the dark energy and a nonlinear interaction term for the underlying interaction. The equations of state have dependencies either on the energy densities, the redshift, the Hubble parameter or the bulk viscosity. We have considered these possibilities and have derived the effective equations of state for the dark energy in each case.     

Mass renormalization and runaway solutions

Zeitschrift für Physik B Condensed Matter - The relationship between negative mechanical mass and runaway solutions is studied using the model of a charged spherical shell. The model yields...     

Synthesis of a cyclic peptide containing norlanthionine: effect of the thioether bridge on peptide conformation

Two diastereomeric analogues of ring C of nisin incorporating a novel norlanthionine residue have been synthesized via a triply orthogonal protecting group strategy. A full structural study was carried out by NMR, which elucidated the conformational properties of the two peptides and enabled the identity of each diastereoisomer to be proposed.     

Form factors,branching ratio and forward–backward asymmetry in B→K<Subscript>1</Subscript>ℓ<Superscript>+</Superscript>ℓ<Superscript>-</Superscript> decays

We study long-distance effects in the rare exclusive semileptonic decays B→K₁ℓ⁺ℓ^-, where K₁ is the axial vector meson. The form factors describing the meson transition amplitudes of the effective Hamiltonian are calculated using the Ward identities, which are then used to calculate the branching ratio and the forward–backward asymmetry in these decay modes. The zero of the forward–backward asymmetry is of special interest and provides us with a precision test of the standard model.     

Neural networks for Nyquist plots prediction in a nanocomposite polymer electrolyte (PEO–LiPF<Subscript>6</Subscript>–EC–CNT)

In this study, the Nyquist plots for nanocomposite polymer electrolyte system (polyethylene oxide (PEO)–lithium hexafluorophosphate (LiPF₆)–ethylene carbonate (EC)–carbon nanotube (CNT)), which was produced by using solution cast technique, were obtained using Bayesian neural network. First, to prepare the training and test set of the network, some results were experimental obtained and recorded. In the experiment, PEO, LiPF₆, EC, and CNT were mixed at various ratios. The effects of the chemical composition on the impedance spectra of polymer electrolyte system were investigated. In neural network training, different chemical composition and real impedance were used as inputs and imaginary impedance in the produced polymer electrolytes was used as outputs. After the training process, the test data were used to check system accuracy. As a result, the neural network was found successful for the prediction of imaginary impedance of nanocomposite polymer electrolyte system.