Solid-state Electrochemical Sensor Based on a Cross-linked Copper(II)-doped Copolymer and Carbon Nanotube Material for Selective and Sensitive Detection of Monohydrogen Phosphate

A novel solid-state electrochemical sensor based on a newly synthesized cross-linked copper(II) doped-copolymer and carbon nanotube material was developed for the direct determination of monohydrogen phosphate ions (HPO₄²⁻). The synthesized copolymers were characterized by FTIR, XPS, TG/DTG-DTA and SEM techniques. The sensor had a Nernstian slope:-30.7±0.4 mV/decade, linear concentrations range: 1.0×10⁻⁶ - 1.0×10⁻¹ M, detection limit: 6.5×10⁻⁷ M, response time: 4 s and life time: 17 weeks. The sensor displayed constant potentials in the pH range 7.0-9.5. The sensor was successfully used as an indicator electrode in potentiometric titration and the direct determination of HPO₄ ²⁻ in water samples.     

Coupled out of plane vibrations of spiral beams for micro-scale applications

An analytical method is proposed to calculate the natural frequencies and the corresponding mode shape functions of an Archimedean spiral beam. The deflection of the beam is due to both bending and torsion, which makes the problem coupled in nature. The governing partial differential equations and the boundary conditions are derived using Hamilton’s principle. Two factors make the vibrations of spirals different from oscillations of constant radius arcs. The first is the presence of terms with derivatives of the radius in the governing equations of spirals and the second is the fact that variations of radius of the beam causes the coefficients of the differential equations to be variable. It is demonstrated, using perturbation techniques that the derivative of the radius terms have negligible effect on structure’s dynamics. The spiral is then approximated with many merging constant-radius curved sections joined together to approximate the slow change of radius along the spiral. The equations of motion are formulated in non-dimensional form and the effect of all the key parameters on natural frequencies is presented. Non-dimensional curves are used to summarize the results for clarity. We also solve the governing equations using Rayleigh’s approximate method. The fundamental frequency results of the exact and Rayleigh’s method are in close agreement. This to some extent verifies the exact solutions. The results show that the vibration of spirals is mostly torsional which complicates using the spiral beam as a host for a sensor or energy harvesting device.     

Transient acoustic radiation from impacted beam-like structures

Transient acoustic radiation from transverse vibrations of beams and beam-like structures is obtained by modelling the structure as a series of contiguous dipoles. A time-dependent expression is developed for sound radiation from a dipole source by Fourier synthesis. Acoustic radiation from the beam is obtained by integrating the sound pressure from the differential dipole elements over the beam length. Time-dependent integration limits are used to account for the transient effects. An analogous discrete formulation is described for beams of arbitrary geometry and density. The radiation patterns of a uniform unbaffled beam are given for frequencies below and above the critical frequency. The results are applied to model the sound radiation from an impact-excited beam.     

Impacts of uniaxial elongation on the bandstructures of two-dimensional sonic crystals and associated applications

Influences of uniaxial elongation along the [11] direction of triangular and [10] direction of square sonic crystals under the constraint of conserved unit cell area are investigated by examining band structures and equi-frequency contours. Lowest-lying band gap of the triangular lattice observed at high filling fractions diminishes for negative elongation (compression), whereas another band gap develops at lower frequencies whose width reaches appreciable values for moderate elongation. The band gap of the square lattice, which appears at high filling fractions, is modified slightly with elongation. Frequency ranges of the bands, and thus the group velocities along the high-symmetry directions, vary with elongation which may be useful in applications like slow sound propagation. Elongation is observed to modify the equi-frequency contours significantly through reducing the lattice symmetry. The most prominent impact is the transformation of closed contours into open ones, whereas the rest are stretched either along or normal to the elongation axis of the 1st Brillouin Zone. This observation is utilized to implement wide-band all-angle self-collimation and superprism effect, which are demonstrated through Finite-Element computations.     

Three new dinuclear silver(I) complexes derived from pyrazolyl type ligands

Three NNN type ligands derived from 2,6-dichlorpyroidine, pyrazol and 3,5-dimethylpyrazole and their silver complexes were prepared in methanol media. The complex structures were characterized using IR spectroscopy, X-ray diffraction and elemental analysis. X-ray studies showed the complexes to be dimeric in structure. The two nitrogen atoms of the ligand coordinated the first Ag(I) ion whereas the second Ag(I) ion was coordinated by the third nitrogen donor. The nitrate structure was not ionic in a done of its oxygen atoms coordinated an Ag(I) ion. The Ag(I) ion was seen to be situated in a deformed tetrahedral coordination sphere. Thermogravimetric studies showed the complexes to decompose similar to explosive material. The decomposition temperature was observed to increase with increasing hydrogen atoms in the structure.     

Synthesis,crystal structure,spectroscopy, thermal properties and carbonic anhydrase activities of new metal(II) complexes with mefenamic acid and picoline derivatives

The mononuclear six metal(II) complexes ([Co(mef)₂(3-pic)₂(CH₃OH)₂] (1), [Ni(mef)₂(3-pic)₂(CH₃OH)₂] (2), [Cu(mef)₂(3-pic)₂] (3), [Co(mef)₂(4-pic)₂] (4), [Ni(mef)₂(4-pic)₂] (5), and [Cu(mef)₂(4-pic)₂] (6) with mefenamic acid and picoline ligands were synthesized, characterized, and their carbonic anhydrase inhibitory activities were evaluated. The six complexes were characterized by elemental analysis, FT-IR spectroscopy, and thermal analyses. The crystal structures of 1, 3, and 6 were determined by X-ray crystallography. The complexes have octahedral geometry. In 1, the mefenamato ligand behaved as monodentate whereas in 3 and 6, the mefenamato ligand acted as a bidentate ligand. Complexes 3 and 6 consist of the mefenamate and 4-picoline ligands. In 1, unlike the other complexes, methanol acted as a ligand and was involved in the coordination. Carbonic anhydrase I and II isoenzymes were purified from human erythrocytes. The in vitro effects of mefenamic acid, 3-picoline, 4-picoline, and the six metal(II) complexes on these isoenzymes were evaluated.     

Two New 2-Benzoylbenzoate Metal Complexes with Bapen: Synthesis,Spectroscopic and Crystal Structures

Abstract  

Coordination compounds of compositions [Ni(bba)₂(bapen)] (1) and [Cu(bba)₂(bapen)]0.5H₂O (2), where bba = 2-benzoylbenzoate, bapen = N,N′-bis(3-aminopropyl)ethylenediamine, have been prepared. The crystal and molecular structure of (1) and (2) were determined by X-ray analysis. Nickel and copper atoms are six-coordinated by four N atoms of amine and O donor atoms of 2-benzoylbenzoate anions, whereas 0.5 water molecule is situated outside the coordination sphere in (2). The calculated ∆(OCO) values are consistent with presence of monodentate carboxylate. Thermal analysis show that the mass losses of 1 in the temperature ranges 240–343 °C correspond to the decomposition of bba ligands, while the mass losses of 2 in the temperature ranges 105–125 °C correspond to the decomposition of crystal lattice water molecule.     

A comparative study of Artificial Bee Colony algorithm

Artificial Bee Colony (ABC) algorithm is one of the most recently introduced swarm-based algorithms. ABC simulates the intelligent foraging behaviour of a honeybee swarm. In this work, ABC is used for optimizing a large set of numerical test functions and the results produced by ABC algorithm are compared with the results obtained by genetic algorithm, particle swarm optimization algorithm, differential evolution algorithm and evolution strategies. Results show that the performance of the ABC is better than or similar to those of other population-based algorithms with the advantage of employing fewer control parameters.     

Khayyam with Cabri: experiences of pre-service mathematics teachers with Khayyam's solution of cubic equations in dynamic geometry environment

The study reported in this article deals with the observed actionsof Turkish pre-service mathematics teachers in dynamic geometryenvironment (DGE) as they were learning Khayyam's method forsolving cubic equations formed as x³ + ax = b. Having learnedthe method, modelled it in DGE and verified the correctnessof the solution, students generated their own methods for solvingdifferent types of cubic equations such as x³ + ax² = b andx³ + a = bx in the light of Khayyam's method. With the presentedteaching experiment, students realized that Khayyam's mathematicsis different from theirs. We consider that this gave them anopportunity to have an insight about the cultural and socialaspects of mathematics. In addition, the teaching experimentshowed that dynamic geometry software is an excellent tool fordoing mathematics because of their dynamic nature and accurateconstructions. And, it can be easily concluded that the historyof mathematics is useful resource for enriching mathematicslearning environment.