Synthesis, spectral characterization and in vitro microbiological evaluation of novel glyoxal, biacetyl and benzil bis-hydrazone macrocyclic Schiff bases and their Co(II), Ni(II) and Cu(II) complexes

A series of binuclear Co(II), Ni(II) and Cu(II) complexes were synthesized by the template condensation of glyoxal, biacetyl or benzil bis-hydrazide, 2,6-diformyl-4-methylphenol and Co(II), Ni(II) or Cu(II) chloride in a 2:2:2 M ratio in ethanol. These 22-membered macrocyclic complexes were characterized by elemental analyses, magnetic, molar conductance, spectral, thermal and fluorescence studies. Elemental analyses suggest the complexes have a 2:1 stoichiometry of the type [M₂LX₂]·nH₂O and [Ni₂LX₂2H₂O]·nH₂O (where M = Co(II) and Cu(II); L = H₂L¹, H₂L² and H₂L³; X = Cl; n = 2). From the spectroscopic and magnetic studies, it has been concluded that the Co(II) and Cu(II) complexes display a five coordinated square pyramidal geometry and the Ni(II) complexes have a six coordinated octahedral geometry. The Schiff bases and their metal complexes have also been screened for their antibacterial and antifungal activities by the MIC method.     

Phytochemical investigation and antifeedant activity of Premna latifolia leaves

The essential oil of Premna latifolia Roxb. was obtained by hydrodistillation of fresh leaves of the plant having an oil yield of 0.05%, both non-polar and essential oil were analysed by GC and GC-MS. Hexane fraction of the leaves of P. latifolia was transesterified and analysed by GC and GC-MS, 40 non-polar components were identified comprising 89.3%. The most abundant fatty acid constituents were hexadecanoic acid (25.04%), 8,11,14-docosatrienoic acid (13.62%), octadecanoic acid (6.82%), 9,12-octadecadienoic acid (4.19%) and 29 components were investigated in the essential oil which comprises 78.1%. The most abundant oil constituents were 1-octen-3-ol (35.69%), terpendiol II (7.19%), δ-guaiene (7.49%) 2-undecanone (4.80%) and α-pinene (3.27%). Different extracts were also tested against polyphagous crop pest Spodoptera litura for antifeedant activity. Essential oil showed maximum growth reduction of 56.83% followed by chloroform extract of 43.93%.     

A fluidic-muscle driven force-controlled parallel platform for physical simulation of virtual spatial force-displacement laws

Described in this paper is a six-legged Stewart-Gough parallel platform driven by a relatively new type of fluidic muscles. The advantage of the platform is that it is virtually free of stick-slip effects. Thus, the device is well-suited for fine-tuned force control and for physical simulation of virtual force-displacement laws. The legs of the platform are of type RRPS and are equipped with a coaxial coil spring and a fluidic muscle providing push and pull forces. Each leg is equipped with a force sensor, a pressure sensor, and a magnetostrictive position encoder. The control for the platform consists of six control loops for the six operated actuators with model-based force control comprising individual gas models as well as the rubber nonlinearities for each leg. The control law also includes the gas flow in the proportional directional control valve in 3/3-way function. The present paper describes the basic architecture of the platform, the dynamic models, as well as testbed results for the existing fluidic-muscle parallel platform DynaHex. It is shown that the presented control scheme leads to a stable force control of the platform for quasi-static motion. As an application, the device will be employed in fields of biomechanics, as well as in general environments requiring physical simulation.     

Thermotropic copolyesters. III. Synthesis and characterization of liquid crystal copolyesters containing the bicyclo[2.2.2]octane ring system

A number of thermotropic copolyesters which contain the bicylo[2.2.2]octane ring system have been synthesized. Because of the stiffening effect of the bicyclo[2.2.2]octane group on the chain, the sebacoyl spacer was used to obtain meltable compositions.     

The polarography of oximes: II. 1,2-Acenaphthaquinone monoxime

Polarography of 1,2-acenaphthaquinone monoxime has been carried out in buffers (pH 3.5–13.0) of constant ionic strength 0.5 M and 40% alcohol $\text{v}\text{v}$ at 25 ± 0.5 °C. The oxime group underwent diffusion-controlled reduction (4e) over the whole pH range. The number of electrons involved in the reduction was found by coulometric method as well as by incorporating the values of diffusion coefficients, obtained by using a McBain-Dawson cell, into the Ilkovi? equation. Koutecky's method has been used to compute the kinetic parameters (αn_aand ?log K_f.h) for the reduction of the oxime group and a reduction mechanism is proposed.     

Alcoholate complexes of chromium(III) chloride

Summary A number of alcoholate complexes of chromium chloride with the general formula, CrCl₃ · xROII (R = Me, Et, i-Pr, n-Bu and n-Ilexyl; x = 3 and 4) have been synthesized by the reactions of CrCl₃ · 3 TIIF with an excess of the appropriate alcohols under reflux. Physicochemical studies such as i.r., visible reflectance, electron spin resonance spectra and thermogravimetric measurements, in addition to elemental analyses, throw light on the structure of these complexes.     

Quantum theory of the cyclotron resonance lineshape for a two-dimensional electron-phonon system

Mössbauer spectra of ¹³³Cs implanted in diamond show the growth of an amorphous layer with increasing ion dose. The annealing of this layer after heat treatment has also been observed.     

Arc plasma synthesized LaB<Subscript>6</Subscript> nanocrystallite film on various substrates as a field emitter

Lanthanum hexaboride (LaB₆) nanocrystallites/nanowires have been successfully synthesized using gas phase condensation in arc plasma. Our results show that the LaB₆ nanowires have ~20 nm diameter and length of several micrometers. The as-synthesized LaB₆ nanocrystallites and nanowires are crystalline in nature. Field emission studies were carried out on as synthesized LaB₆ nano-powder deposited on W and Re tips and foils, and also on Si foil substrates under ultra high vacuum. The Fowler–Nordheim plots obtained from the current–voltage characteristics are found to be linear in accordance with the quantum mechanical tunneling phenomenon. High value of field enhancement factor (8177) is observed for LaB₆ on Re substrate, indicating that the electron emission is from the nanometric features of the LaB₆. Our results show that the arc plasma synthesized LaB₆ nanocrystalline film exhibits good emission stability as emitter without severe deviations from the initial set value and also a strong ability to withstand the ion bombardment, which is useful for low operation voltage vacuum micro/nano electronic devices.     

Low threshold field electron emission from solvothermally synthesized WO2.72 nanowires

Field emission studies of WO_2.72 nanowires synthesized by a solvothermal method have been performed in the planar diode configuration under ultra high vacuum conditions. Fowler–Nordheim plots obtained from the current-voltage characteristics follow the quantum mechanical tunneling process and a current density of ∼8.3×10⁶ μA/cm² can be drawn at an applied electric field of 2 V/μm. The field enhancement factor is 33025, while the turn-on field is only 1.4 V/μm. The emission current-time plot recorded at the pre-set value of emission current of 1 μA over a period of more than 3 h exhibits an initial increase and a subsequent stabilization of the emission current. The results reveal that the WO_2.72 nanowire emitters synthesized by the solvothermal method are promising cathode materials for practical applications.