Syntheses, characterization and solid state thermal studies of N-propyl-1,2-diaminoethane (L) and N-isopropyl-1,2-diaminoethane (L′) complexes of nickel(II) nitrite: X-ray single crystal structure of trans-[NiL2(NO2)2]

Linkage isomers trans-bis(N-propyl-1,2-diaminoethane)dinitronickel(II) (brown, 1), trans-bis(N-isopropyl-1,2-diaminoethane)dinitritonickel(II) (blue-violet, 2a) and trans-bis(N-isopropyl-1,2-diaminoethane)dinitronickel(II) (brown, 2b) have been synthesized from solution and X-ray single crystal structure analysis of complex (1) has been performed. Simultaneous TG-DTA analyses reveal that complex (1) exhibits two successive phase transitions before to undergo decomposition (initial temperature of decomposition, Ti = 215 °C). The first one is reversible (82–98 °C; ΔH = 1.75 kJ mol⁻¹ for heating and 93–77 °C; ΔH = −1.65 kJ mol⁻¹ for cooling) and the second one is irreversible endothermic (135–150 °C kJ mol⁻¹; ΔH = 1.80 kJ mol⁻¹) phase transition. No visual color changes are observed in any of the two transitions. The causes related to the first phase transition remain unexplored. However, on the basis of IR spectral studies the second phase transition is supposed to be due to conformational changes of the diamine chelate rings. On the other hand, complexes (2a) and (2b) undergo decomposition without showing any phase transition [Ti = 185 and 195 °C for (2a) and (2b), respectively].     

Electrodeposition of polyaniline, poly(2-iodoaniline), and poly(aniline-co-2-iodoaniline) on steel surfaces and corrosion protection of steel

Polyaniline (PANi), poly(2-iodoaniline) (PIANi), and poly(aniline-co-2-iodoaniline) (co-PIANi) were synthesized using cyclic voltammetry in acetonitrile solution containing tetrabuthylammonium perchlorate (TBAP) and perchloric acid (HClO₄) on 304-stainless steel electrodes. Adherent and black polymer films were obtained on the electrodes. The structure and properties of these polymer films were characterized by FTIR and UV-vis spectroscopy and electrochemical method. The corrosion performance of PANi, PIANi, and co-PIANi coated electrodes were investigated in 0.5 M hydrochloric acid (HCl) solutions by potentiodynamic polarization technique, open circuit potential-time curves and electrochemical impedance spectroscopy, EIS. It was found that the PANi film could provide much better protection than PIANi, and co-PIANi and PANi films have barrier property as well as acting as passivator. On the other hand PIANi and co-PIANi films are acting as barrier coatings which were related with the prevention of cathodic reaction taking place at metal\electrolyte interface. EIS measurement shows that every coating gives protection efficiency of greater than 75% after 48 h of immersion time in corrosive test solution.     

High-frequency properties of thin amorphous ribbons

Magnetic energy losses have been investigated in Co-based near-zero-magnetostriction amorphous ribbons from DC to 10 MHz. Attention has been devoted to the properties of field-annealed ribbons thinned down to 5.8 μm and their behavior at high frequencies. A rationale is provided for the frequency dependence of the magnetic losses over the investigated many-decade range through analysis of the loss components. Ribbons annealed under transverse field benefit by limited irreversible domain wall activity and correspondingly reduced hysteresis and excess losses. Based on the near-linear response of the material and the permeability–energy loss relationship, the separate contributions of domain wall displacements and rotations to the magnetization process and the related dissipation effects are singled out at all frequencies. Very thin amorphous ribbons are shown to display lower loss and higher permeability (i.e. higher Snoek's product) than Mn–Zn ferrites at all frequencies.     

Quadrupole relaxation enhancement and polarisation transfer in DMSO solution of [Bi(NO3)3(H2O)3]*18-crown-6 in solid state

ABSTRACT

¹H spin-lattice relaxation studies have been performed for pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 in powder and its solution in dimethyl sulfoxide (DMSO). The experiments have been carried out in the frequency range of 10?kHz–30?MHz and the temperature range of 240–277?K; at 277?K the solution is already frozen. The ¹H relaxation of pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 has been interpreted in terms of three dynamical processes. Quadrupole Relaxation Enhancement effects have been observed in the frozen DMSO solution of [Bi(NO₃)₃(H₂O)₃]*18-crown-6. The specific mechanisms of the ¹H spin-lattice relaxation enhancement have been discussed distinguishing between effects caused by time independent (residual) and fluctuating ¹H-²⁰⁹Bi dipole-dipole interactions.     

Microstructure and optical properties of nanocrystalline ZnO and ZnO:(Li or Al) thin films

Zinc oxide thin films (ZnO, ZnO:Li, ZnO:Al) were deposited on glass substrates by a sol-gel technique. Zinc acetate, lithium acetate, and aluminum chloride were used as metal ion sources in the precursor solutions. XRD analysis revealed that Li doped and undoped ZnO films formed single phase zincite structure in contrast to Al:ZnO films which did not fully crystallize at the annealing temperature of 550 °C. Crystallized films had a grain size under 50 nm and showed c-axis grain orientation. All films had a very smooth surface with RMS surface roughness values between 0.23 and 0.35 nm. Surface roughness and optical band tail values increased by Al doping. Compared to undoped ZnO films, Li doping slightly increased the optical band gap of the films.     

Symmetries and Motions in NUT-Taub Spinning Space

We review the geodesic motion of pseudo-classical spinning particles in curved space. We describe the generalized Killing equations for spinning spaces and express the constants of motion. We apply the formalism to solve for the motion of a pseudo-classical Dirac fermion in NUT-Taub spinning space and analyze the motion on a cone and on a plane.     

A study of the level properties of 57Co from the (τ, d) reaction on 56Fe

The ⁵⁶Fe(τ, d)⁵⁷Co reaction has been studied at E_τ = 18 MeV using the Tandem Van de Graaff accelerator and the multichannel magnetic spectrograph of the Nuclear Physics Laboratory, Oxford, Angular distributions have been measured for most of the levels up to E_x ≈ 7.8 MeV and are analysed in terms of the DWBA theory of direct reactions. The l_p values and the transition strengths compared with available theories.     

RLT-POS: Reformulation-Linearization Technique-based optimization software for solving polynomial programming problems

In this paper, we introduce a Reformulation-Linearization Technique-based open-source optimization software for solving polynomial programming problems (RLT-POS). We present algorithms and mechanisms that form the backbone of RLT-POS, including constraint filtering techniques, reduced RLT representations, and semidefinite cuts. When implemented individually, each model enhancement has been shown in previous papers to significantly improve the performance of the standard RLT procedure. However, the coordination between different model enhancement techniques becomes critical for an improved overall performance since special structures in the original formulation that work in favor of a particular technique might be lost after implementing some other model enhancement. More specifically, we discuss the coordination between (1) constraint elimination via filtering techniques and reduced RLT representations, and (2) semidefinite cuts for sparse problems. We present computational results using instances from the literature as well as randomly generated problems to demonstrate the improvement over a standard RLT implementation and to compare the performances of the software packages BARON, COUENNE, and SparsePOP with RLT-POS.