On the complex factorization of the Lucas sequence

In this paper, firstly we present a connection between determinants of tridiagonal matrices and the Lucas sequence. Secondly, we obtain the complex factorization of Lucas sequence by considering how the Lucas sequence can be connected to Chebyshev polynomials by determinants of a sequence of matrices.     

On the influence of boundary conditions on the modal properties of a base frame

Supports of turbomachineries can be designed as base frames, which are constructions of steel-plates. One of the most important design requirements of the turbomachinery system is to avoid of natural frequencies in the operating speed range. Thus, a rotor dynamics analysis (see e.g. [1]), which is usually carried out using transfer matrix methods or finite element methods has to take the dynamic stiffness of the base frame into account. However, there are several problems to identify this complex and frequency dependent parameter, for example the localization of excitation or measurement responses and the difficulty of the support of base frames, e.g jack screws. In this article the support of a test base frames is analyzed by modal analysis experimentally. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electroanalysis of Caffeic Acid in Red Wine and Investigation of Thermodynamic Parameters Using an Ag Nanoparticles Modified Poly(Thiophene) Film Glassy Carbon Electrode

A silver nanoparticle decorated poly(thiophene) modified glassy carbon electrode (GCE) was prepared for determination of caffeic acid. The Ag/PTh/GCE surface was characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) spectroscopy. The modified electrode has shown higher electrocatalytic activity towards the oxidation of caffeic acid. The peak current of was found linear in the concentration range from 1.00×10^?8 to 4.83×10^?6 M with a detection limit of 5.3×10^?9 M (S/N=3). The modified electrode was used for determination of CA concentration in red wine samples. The thermodynamic constants, entropy change (ΔS), enthalpy change (ΔH) and Gibbs free energy change (ΔG) were calculated as ?166.34 J/(mol K), ?154.24 kJ/mol and ?104.75 kJ/mol at 25 °C, respectively.     

A New and Convenient Synthesis of Amino‐phthalimide (1H‐Isoindole‐1,3(2H)‐dione) Derivatives and Their Photoluminescent Properties

A new and convenient synthesis for amino‐phthalimide (1H‐isoindole‐1,3(2H)‐dione) derivatives has been developed starting from an α,β‐unsaturated ketone. The ketones were reacted with amines to give aromatic amine products. This is the first time that substituted amine groups have been incorporated in aromatic rings. The mechanism of the product formation is rationalized by the 1,2‐addition of amines to ketones. All aromatic compounds exhibited high fluorescence properties at the blue‐green region.     

Feasibility of tetracycline,a common antibiotic,as chelating agent for spectrophotometric determination of UO2 2+ after cloud point extraction

A cloud point extraction (CPE) procedure was presented for the preconcentration of UO₂ ²⁺ ion in different water samples. Tetracycline (TC) is the second most widely used antibiotics in the world and is used as chelating agent. To the best of our knowledge, this is the first work that an antibiotic is used as a chelating agent for CPE of UO₂ ²⁺. Besides, the use of TC as complexing agent provides excellent chelating features. TC molecule has large numbers of functional groups (adjacent hydroxyl oxygen atoms and cyclohexanone oxygen atoms, amide groups) which can form stable complex with UO₂ ²⁺. After complexation with TC, UO₂ ²⁺ ions were quantitatively recovered in Triton X-100 after cooling in the ice bath. 3.0 mL of acetate buffer was added to the surfactant-rich phase prior to its analysis by UV–Vis spectrophotometer. The influence of analytical parameters including pH, buffer volume, TC, Triton X-100 concentrations, bath temperature, incubation time were optimized. The effect of the matrix ions on the recovery of UO₂ ²⁺ ions was investigated. The limit of detection was 0.0746 μg mL^?1 along with enrichment factor of 14.3 with a R.S.D. of 3.6 %. The proposed procedure was applied to the analysis of various environmental water samples. On the other hand, the electronic distribution of TC molecule is investigated with their frontier molecular orbital density distributions.     

Intercalation of graphite and hexagonal boron nitride by lithium

Although graphite and hexagonal form of BN (h-BN) are isoelectronic and have very similar lattice structures, it has been very difficult to intercalate h-BN while there are hundreds of intercalation compounds of graphite. We have done a comparative first principles investigation of lithium intercalation of graphite and hexagonal boron nitride to provide clues for the difficulty of h-BN intercalation. In particular lattice structure, cohesive energy, formation enthalpy, charge transfer and electronic structure of both intercalation compounds are calculated in the density functional theory framework with local density approximation to the exchange-correlation energy. The calculated formation enthalpy of the considered forms of Li intercalated h-BN is found to be positive which rules out h-BN intercalation without externally supplied energy. Also, the Li(BN)₃ form of Li-intercalated h-BN is found to have a large electronic density of states at the Fermi level and an interlayer state that crosses Fermi level at the zone center; these properties make it an interesting material to investigate the role of interlayer states in the superconductivity of alkali intercalated layered structures. The most pronounced change in the charge distribution of the intercalated compounds is found to be charge transfer from the planar σ states to the π states.     

Proton conducting composite membranes based on poly(1-vinyl-1,2,4-triazole) and nitrilotri (methyl triphosphonic acid)

Polymer electrolyte composite membranes based on poly(1-vinyl-1,2,4-triazole) (PVTRI) and nitrilotri(methyl triphosphonic acid) (TPA) were investigated. PVTRI was produced by free radical polymerization of 1-vinyl-1,2,4-triazole. The polymer PVTRI was doped with TPA at various molar ratios x=0.125, x=0.25, and x=0.5. The proton transfer from TPA to the triazole rings was proved with Fourier-transform infrared spectroscopy (FT-IR). Thermogravimetry (TG) analysis showed that the samples are thermally stable up to approximately 250 °C. DSC results illustrated the homogeneity of the materials as well as the softening effect of the dopant. Cyclic voltammetry results illustrated that the electrochemical stability domain of the dopant extends over 1.5 V. The maximum proton conductivity has been measured for PVTRITPA-0.25 as 8.5×10⁻⁴ S cm⁻¹ at 150 °C.     

Design,Synthesis, and Biological Evaluation of Pyridazinones Containing the (2-Fluorophenyl) Piperazine Moiety as Selective MAO-B Inhibitors

Twelve pyridazinones (T1–T12) containing the (2-fluorophenyl) piperazine moiety were designed, synthesized, and evaluated for monoamine oxidase (MAO) -A and -B inhibitory activities. T6 was found to be the most potent MAO-B inhibitor with an IC₅₀ value of 0.013 µM, followed by T3 (IC₅₀ = 0.039 µM). Inhibitory potency for MAO-B was more enhanced by meta bromo substitution (T6) than by para bromo substitution (T7). For para substitution, inhibitory potencies for MAO-B were as follows: -Cl (T3) > -N(CH₃)₂ (T12) > -OCH₃ (T9) > Br (T7) > F (T5) > -CH₃ (T11) > -H (T1). T6 and T3 efficiently inhibited MAO-A with IC₅₀ values of 1.57 and 4.19 µM and had the highest selectivity indices (SIs) for MAO-B (120.8 and 107.4, respectively). T3 and T6 were found to be reversible and competitive inhibitors of MAO-B with K_i values of 0.014 and 0.0071, respectively. Moreover, T6 was less toxic to healthy fibroblast cells (L929) than T3. Molecular docking simulations with MAO binding sites returned higher docking scores for T6 and T3 with MAO-B than with MAO-A. These results suggest that T3 and T6 are selective, reversible, and competitive inhibitors of MAO-B and should be considered lead candidates for the treatment of neurodegenerative disorders like Alzheimer’s disease.     

Effects of Heavy Iodine Atoms and π-Expanded Conjugation on Charge Transfer Dynamics in Carboxylic Acid BODIPY Derivatives as Triplet Photosensitizers

Borondipyrromethene (BODIPY) chromophores are composed of a functional-COOH group at meso position with or without a biphenyl ring, and their compounds with heavy iodine atoms at −2, −6 positions of the BODIPY indacene core were synthesized. The photophysical properties of the compounds were studied with steady-state absorption and fluorescence measurements. It was observed that the absorption band is significantly red-shifted, and fluorescence signals are quenched in the presence of iodine atoms. In addition to that, it was indicated that the biphenyl ring does not affect the spectral shifting in the absorption as well as fluorescence spectra. In an attempt to investigate the effect of π-expanded biphenyl moieties and heavy iodine atoms on charge transfer dynamics, femtosecond transient absorption spectroscopy measurements were carried out in the environment of the tetrahydrofuran (THF) solution. Based on the performed ultrafast pump-probe spectroscopy, BODIPY compounds with iodine atoms lead to intersystem crossing (ISC) and ISC rates were determined as 150 ps and 180 ps for iodine BODIPY compounds with and without π-expanded biphenyl moieties, respectively. According to the theoretical results, the charge transfer in the investigated compounds mostly appears to be intrinsic local excitations, corresponding to high photoluminescence efficiency. These experimental findings are useful for the design and study of the fundamental photochemistry of organic triplet photosensitizers.     

Effect of hexagonal boron nitride on poly(vinyl phosphonic acid) composite polymer electrolytes for fuel cells

In this work, hexagonal boron nitride nanoparticles were used as inorganic fillers, which increase the mechanical and thermal stabilities as well as the proton conductivity of the proton conducting composite membranes prepared by blending of poly(vinyl phosphonic acid) and hexagonal boron nitride. Thermo gravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to 200°C. Scanning electron microscopy analysis indicated the homogeneous distribution of boron nitride nanoparticles in the polymer matrix. The crystallinity of the membranes was characterized by using X-ray Diffraction. X-ray patterns support semi-crystalline nature of the composite materials.