Stripping voltammetric analysis of dicofol on graphene-modified glassy carbon electrode

Ionics - This study is related to the development of a highly sensitive and selective electrode for the electroanalysis of dicofol (DCF) by the modification of a glassy carbon electrode (GCE) with...     

An inhibition type amperometric biosensor based on tyrosinase enzyme for fluoride determination

In this study, a new biosensor based on the inhibition of tyrosinase for the determination of fluoride is described. To construct the biosensor tyrosinase was immobilized by using gelatine and cross-linking agent glutaraldehyde on a Clark type dissolved oxygen (DO) probe covered with a teflon membrane which is sensitive for oxygen. The phosphate buffer (50 mM, pH 7.0) at 30 °C were established as providing the optimum working conditions. The method is based on the measurement of the decreasing of dissolved oxygen level of the interval surface that related to fluoride concentration added into reaction medium in the presence of catechol. Inhibitor effect of fluoride results in decrease in dissolved oxygen concentration. The biosensor response depends linearly on fluoride concentration between 1.0 and 20 μM with a response time of 3 min.In the characterization studies of the biosensor some parameters such as reproducibility, substrate specificity and storage stability were carried out. From the experiments, the average value (x), Standard deviation (S.D) and coefficient of variation (C.V %) were found as 10.5 μM, ± 0.57 μM, 5.43%, respectively for 10 μM fluoride standard.     

A location–allocation heuristic for the capacitated multi-facility Weber problem with probabilistic customer locations

The capacitated multi-facility Weber problem is concerned with locating m facilities in the Euclidean plane, and allocating their capacities to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a non-convex optimization problem and difficult to solve. In this work, we focus on a probabilistic extension and consider the situation where the customer locations are randomly distributed according to a bivariate distribution. We first present a mathematical programming formulation, which is even more difficult than its deterministic version. We then propose an alternate location–allocation local search heuristic generalizing the ideas used originally for the deterministic problem. In its original form, the applicability of the heuristic depends on the calculation of the expected distances between the facilities and customers, which can be done for only very few distance and probability density function combinations. We therefore propose approximation methods which make the method applicable for any distance function and bivariate location distribution.     

Injectivity relative to closed submodules

Let R be a ring. An R-module X is called c-injective if, for every closed submodule L of every R-module M, every homomorphism from L to X lifts to M. It is proved that if R is a Dedekind domain then an R-module X is c-injective if and only if X is isomorphic to a direct product of homogeneous semisimple R-modules and injective R-modules. It is also proved that a commutative Noetherian domain R is Dedekind if and only if every simple R-module is c-injective.     

Investigation of isospin forbidden 0+ → 0+ Fermi beta decays with Pyatov method

In the present work, the matrix elements, isospin impurities and log ft values of the isospin forbidden 0⁺ → 0⁺ beta decays have been investigated. The calculated results have been compared with available experimental and another theoretical data. The isotopic invariance of the Hamiltonian has been restored by Pyatov method. Within the quasi-particle random phase approximation (QRPA), the computations have been performed both in presence and absence of the pairing interactions.     

Temperature dependent energy relaxation time in AlGaN/AlN/GaN heterostructures

The two-dimensional (2D) electron energy relaxation in Al_0.25Ga_0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (T_e) of hot electrons was obtained from the lattice temperature (T_L) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range T_e > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al_0.25Ga_0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures.     

Synthesis and proton conductivity studies of azole functional organic electrolytes

As an attempt to produce azole functional proton conductors, organic electrolytes with triazole and tetrazole functional groups were synthesized via substitution reaction of 1,3,5-benzenetricarbonyl trichloride with aminotriazole and aminotetrazole. The samples were doped with triflic acid with molar ratios of 0.25 and 0.50. FTIR, nuclear magnetic resonance (NMR), and elemental analysis were used to characterize the resulting materials. Thermogravimetric analysis showed that the samples are thermally stable up to 150?°C. The effect of acid doping on proton conductivity was investigated with impedance spectrometer. Both pure samples and the doped ones revealed high proton conductivity. In anhydrous conditions (TMA)-TriTA_0.50 and TMA-TetTA_0.50 have proton conductivities of 1.8 and 19?mS/cm at 150?°C, respectively. Solid-state NMR studies revealed that there are three different types of hydrogen-bonded acidic proton in the systems. Moreover, these different types of acidic protons present at different ratio in triazole and tetrazole systems.     

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb–As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3 As in Na3As, Cu3 P and Li3Bi structures, and Rb5 As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan’s equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young’s modulus, the shear modulus, Poisson’s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

The structure of N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine

The N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine, C₁₄H₁₁N₃Cl₂, M _r = 292.17, crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 10.707(2), b = 9.615(2), c = 25.944(6) Å. The benzimidazole ring system is planar and makes a dihedral angle of 77.8(1)° with the phenyl ring. The structure is stabilized by an N–H···N hydrogen bond.     

On the spectral norms of Cauchy–Toeplitz and Cauchy–Hankel matrices

In this study, we have found upper and lower bounds for the spectral norm of Cauchy–Toeplitz and Cauchy–Hankel matrices in the forms T_n=[1/(a+(i−j)b)]ⁿ_i,j=1, H_n=[1/(a+(i+j)b)]ⁿ_i,j=1.