The Field-Dependent Magnetization of d5–d7 Metal β−Diketonate Complexes and Their Macromolecular Polymers

A vibrating sample magnetometer (VSM) has been used to study the field-dependent magnetization, M(H), of the d⁵?d⁷ metal acetates [M(OAc)₂.nH₂O], metal β?diketonate complexes [M(tba)₂(H₂O)₂] and the macromolecular polymers [M(tba)₂(4,4-bipy)]_n (where, M = Mn(II), Fe(II), and Co(II), OAc = O₂CCH₃, tba = deprotonated 3-benzoyl-1.1.1-trifluoroacetone, and 4,4-bipy = 4,4′-bipyridine). The magnetic field strength (H) was applied in the range of 0?10⁴ O_e at ambient temperature (ca. 23°C). The experimental results showed that the d⁵?d⁷ metal acetate, complexes and polymers exhibit low paramagnetic properties excepting [Fe(tba)₂(4,4-bipy)]_n polymer, which had negative magnetization M(emu/g) showing diamagnetic properties in the range 0?10⁴ O_e. The magnetization was almost equal to zero without an applied magnetic field (H(O_e)) for each d⁵?d⁷ metal acetate, complex, and polymer. The linear M(H) curve had a magnetic saturation for iron and manganese acetate species at the magnetic field strengths of 3.1 × 10³ and 4.7 × 10³ Oe, respectively. The external magnetic field reached 9.0 × 10³ O_e without any saturation magnetization for the cobalt compounds. The coordination effect of 3-benzoyl-1.1.1-trifluoroacetone (H-tba) and 4,4′-bipyridine (4,4′-bipy) ligands on the field-dependent magnetization M(H) and paramagnetic behavior of d⁵?d⁷ metal atoms is discussed. The field-dependent magnetization M(H) curves of metal β?diketonate complexes and the polymers including d⁵?d⁷ metal acetates showed a weak field octahedral geometry.     

A continuous vibration theory for rotors with an open edge crack

In this paper a new continuous model for flexural vibration of rotors with an open edge crack has been developed. The cracked rotor is considered in the rotating coordinate system attached to it. Therefore, the rotor bending can be decomposed in two perpendicular directions. Two quasi-linear displacement fields are assumed for these two directions and the strain and stress fields are calculated in each direction. Then the final displacement and stress fields are obtained by composing the displacement and stress fields in the two directions. The governing equation of motion for the rotor has been obtained using the Hamilton principle and solved using a modified Galerkin method. The free vibration has been analyzed and the critical speeds have been calculated. Results are compared with the finite element results and an excellent agreement is observed.     

Switchable single- and dual-wavelength erbium-doped fiber laser assisted by four-wave mixing with wide and continuous tunability

A widely tunable and stable erbium-doped fiber laser based on four-wave mixing effect in a highly nonlinear fiber is proposed and experimentally demonstrated. By adjusting reflected power from a dual-selective element, the ring laser is switchable between single- and dual-wavelength operations. The tuning range of the single laser is 22.78 nm, from 1,542.07 to 1,564.85 nm, while the wavelength spacing of the dual-wavelength can be continuously tuned from 0.52 to 22.78 nm. The laser is stable with output peak power fluctuation of <1 dB in 30-min interval.     

Chemical composition and antimicrobial activity of the essential oil of Anthemis altissima L. var. altissima

The essential oil obtained from the flowering parts of Anthemis altissima L. var. altissima was analysed by gas chromatography and gas chromatography mass spectroscopy. In this study, 34 compounds representing 98.76% of the essential oil were identified. The main components were α-terpineol (26.42%), β-pinene (9.23%), cis-chrysanthenyl acetate (6.30%), globulol (5.36%), n-tricosane (4.41%), terpinen-4-ol (4.08%) and 1,8 cineole (3.84%). Antibacterial activities of the essential oil and its two major components (α-terpineol and β-pinene) were determined using microdilution method against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) bacteria. The essential oil showed a broad-spectrum antibacterial activity (MICs ranged from 3.13 to 6.25?μL?mL(-1)). It was found that α-terpineol with minimum inhibitory concentration (MIC) values of the range 0.87-1.56?μL?mL(-1) was a more potent antibacterial agent than β-pinene with MIC values of the range 1.56-6.25?μL?mL(-1). All of them, the essential oil, β-pinene and α-terpineol, were more effective against Gram-positive bacteria than Gram-negative ones.     

Nano-sized manganese oxide: a proposed catalyst for water oxidation in the reaction of some manganese complexes and cerium(iv) ammonium nitrate

According to UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy, nano-sized manganese oxides are proposed as active catalysts for water oxidation in the reaction of some manganese complexes and cerium(iv) ammonium nitrate.     

Metal-free aromatic hydrogenation: aniline to cyclohexyl-amine derivatives

Hydrogenation of the N-bound phenyl rings of amines, imines, and aziridine is achieved in the presence of H(2) and B(C(6)F(5))(3), affording the corresponding N-cyclohexylammonium hydridoborate salts.     

Nano-sized layered aluminium or zinc-manganese oxides as efficient water oxidizing catalysts

Nano-sized layered aluminium or zinc-manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed.     

Preparation of chemically deposited thin films of CdS/PbS solar cell

The present paper reports the preparation of a solar cell which has a cross-sectional scheme: ITO/CdS/PbS, containing a commercially transparent conductive ITO; chemically deposited n-type CdS (340 nm) and absorbed layer of p-type PbS (1400 nm). The structural and optical properties of the constituent films are presented. X-ray diffraction showed that all of the thin films are polycrystalline. Using scanning electron microscopy, the present study revealed that the films have uniform surface morphology over the substrate. The solar cell was characterized by determining the open circuit voltage, short-circuit current density, and J–V under 40 mW/cm² solar radiation. The efficiency of the solar cells was 1.35%, which is much higher (0.041, 0.5 and 0.1–0.4%) and slightly smaller (1.65%) than some solar cells reported in the literature.     

The effect of number of baffles on the improvement efficiency of primary sedimentation tanks

In this study, the effect of different numbers of baffles is investigated using computational simulation. Laboratory measurements using different numbers of constant height baffles in a rectangular primary sedimentation tank are conducted. The velocity fields measured by an Acoustic Doppler Velocimeter (ADV) are used to verify the results of the computational model. The effects of the number of baffles arrangement on the hydraulic performance of primary settling tanks are studied by using two different ways: the parameters of flow pattern and the Flow Through Curves (FTCs) method. The results of both the experimental and computational investigations indicate that increasing the number of baffles in suitable positions provides minimum volume of the recirculation region, dissipates the kinetic energy, creates a uniform flow field in the tank and finally the hydraulic efficiency of the sedimentation tank will be improved.     

Chaos control and generalized projective synchronization of heavy symmetric chaotic gyroscope systems via Gaussian radial basis adaptive variable structure control

This paper proposes the chaos control and the generalized projective synchronization methods for heavy symmetric gyroscope systems via Gaussian radial basis adaptive variable structure control. Because of the nonlinear terms of the gyroscope system, the system exhibits chaotic motions. Occasionally, the extreme sensitivity to initial states in a system operating in chaotic mode can be very destructive to the system because of unpredictable behavior. In order to improve the performance of a dynamic system or avoid the chaotic phenomena, it is necessary to control a chaotic system with a periodic motion beneficial for working with a particular condition. As chaotic signals are usually broadband and noise like, synchronized chaotic systems can be used as cipher generators for secure communication. This paper presents chaos synchronization of two identical chaotic motions of symmetric gyroscopes. In this paper, the switching surfaces are adopted to ensure the stability of the error dynamics in variable structure control. Using the neural variable structure control technique, control laws are established which guarantees the chaos control and the generalized projective synchronization of unknown gyroscope systems. In the neural variable structure control, Gaussian radial basis functions are utilized to on-line estimate the system dynamic functions. Also, the adaptation laws of the on-line estimator are derived in the sense of Lyapunov function. Thus, the unknown gyro systems can be guaranteed to be asymptotically stable. Also, the proposed method can achieve the control objectives. Numerical simulations are presented to verify the proposed control and synchronization methods. Finally, the effectiveness of the proposed methods is discussed.