The effect of solution temperature on crystallite size and magnetic properties of Zn substituted Co ferrite nanoparticles

In this work zinc substituted cobalt ferrite nanoparticles (Co_0.5Zn_0.5Fe₂O₄) have been synthesized by the coprecipitation method, using stable ferric, zinc and cobalt salts with sodium hydroxide, at different solution temperatures, from room temperature to 363 K. The cobalt-zinc ferrite crystalline phase, the particle size and the morphology of the resulting nanoparticles were studied by X-ray diffraction and transmission electron microscopy. The average crystallite size of each sample was calculated from the broadening of the most intense peak (3 1 1), using Scherrer's formula and the results show crystallite sizes increased from 6 to 8 nm by increasing the solution temperature from room temperature to 363 K respectively. Room temperature VSM measurements show that the prepared nanoparticles have superparamagnetic behavior and did not saturate at maximum field of 800 kA/m. The variation of AC-susceptibility of the samples with respect to temperature was measured and it was found that the blocking temperature increased from 198 to 270 K by increasing the solution temperature from room temperature to 363 K respectively. FTIR spectra of the samples have been analyzed in the frequency range 400-4000 cm⁻¹, which also confirms the results of XRD.     

A unique circular path of moving single bubble sonoluminescence in water

Based on a quasi-adiabatic model,the parameters of the bubble interior for a moving single bubble sonoluminescence (m-SBSL) in water are calculated.By using a complete form of the hydrodynamic force,a unique circular path for the m-SBSL in water is obtained.The effect of the ambient pressure variation on the bubble trajectory is also investigated.It is concluded that as the ambient pressure increases,the bubble moves along a circular path with a larger radius and all bubble parameters,such as gas pressure,interior temperature and light intensity,increase.A comparison is made between the parameters of the moving bubble in water and those in N-methylformamide.With fluid viscosity increasing,the circular path changes into an elliptic form and the light intensity increases.     

A Pseudospectral Method for Fractional Optimal Control Problems

In this article, a direct pseudospectral method based on Lagrange interpolating functions with fractional power terms is used to solve the fractional optimal control problem. As most applied fractional problems have solutions in terms of the fractional power, using appropriate characteristic nodal-based functions with suitable power leads to a more accurate pseudospectral approximation of the solution. The Lagrange interpolating functions and their fractional derivatives belong to the Müntz space; such functions are employed to show that a relationship exists between the Karush–Kukn–Tucker conditions associated with nonlinear programming and the first optimal necessary conditions. Furthermore, the convergence of the method is investigated. The obtained numerical results are an indication of the behavior of the algorithm.     

Solvent‐Dependent Enantiodivergence in the Chlorocyclization of Unsaturated Carbamates

A remarkable solvent‐controlled enantiodivergence is seen in the hydroquinidine 1,4‐phthalazinediyl diether ((DHQD)₂PHAL)‐catalyzed chlorocyclization of unsaturated carbamates. Eyring plot analyses of this previously unreported reaction are used to probe and compare the R‐ and S‐selective pathways. In the CHCl₃/hexanes solvent system, the pro‐R process shows a surprising increase in selectivity with increasing temperature. These studies point to a strongly solvent‐dependent entropy–enthalpy balance between the pro‐R and pro‐S pathways.     

Simulation of nonlinear fractional dynamics arising in the modeling of cognitive decision making using a new fractional neural network

By the rapid growth of available data, providing data-driven solutions for nonlinear (fractional) dynamical systems becomes more important than before. In this paper, a new fractional neural network model that uses fractional order of Jacobi functions as its activation functions for one of the hidden layers is proposed to approximate the solution of fractional differential equations and fractional partial differential equations arising from mathematical modeling of cognitive-decision-making processes and several other scientific subjects. This neural network uses roots of Jacobi polynomials as the training dataset, and the Levenberg-Marquardt algorithm is chosen as the optimizer. The linear and nonlinear fractional dynamics are considered as test examples showing the effectiveness and applicability of the proposed neural network. The numerical results are compared with the obtained results of some other networks and numerical approaches such as meshless methods. Numerical experiments are presented confirming that the proposed model is accurate, fast, and feasible.     

Estimation of homogeneous rate constants of reaction of electrochemically generated ortho‐benzoquinones with 1,3‐indandione

Electrochemical oxidation of some catechol derivatives has been studied in the presence of 1,3‐indandione as nucleophile in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate the participation of electrochemically produced o‐benzoquinones in the Michael reaction with 1,3‐indandione to form the corresponding new catechol derivatives. On the basis of the EC mechanism, the observed homogeneous rate constants (k_obs) of reaction of produced o‐benzoquinones with 3‐indandione were estimated by comparing the experimental cyclic voltammograms with the digitally simulated results. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 605–613, 2007     

Results on Varextropy Measure of Random Variables

In 2015, Lad, Sanfilippo and Agrò proposed an alternative measure of uncertainty dual to the entropy known as extropy. This paper provides some results on a dispersion measure of extropy of random variables which is called varextropy and studies several properties of this concept. Especially, the varextropy measure of residual and past lifetimes, order statistics, record values and proportional hazard rate models are discussed. Moreover, the conditional varextropy is considered and some properties of this measure are studied. Finally, a new stochastic comparison method, named varextropy ordering, is introduced and some of its properties are presented.     

Three-component synthesis and antibacterial evaluation of some novel 1,2-dihydroisoquinoline derivatives

Isoquinoline reacts with dialkyl acetylenedicarboxylates in the presence of kojic acid or8-hydroxyquinoline to generate 1,2-dihydroisoquinoline derivatives. The simplicity, mild reaction conditions and high yields of products make it an interesting process compared to other approaches. The compounds have been analyzed for antibacterial activity against Gram negative and Gram positive bacteria. The results indicated that 1,2-dihydroisoquinolines derived from kojic acid are effective against all of the studied bacteria especially against Bacillus subtilis, while the products obtained from8-hydroxyquinoline are active only against Gram positive bacteria.     

133Cs NMR Study of Cs+ Ion Complexes with?Aza-18-crown-6, Diaza-18-crown-6 and?Dibenzyldiaza-18-crown-6 in Binary Acetonitrile?CNitromethane Mixtures

Cesium-133 nuclear magnetic resonance spectroscopy was used as a sensitive probe to investigate the stoichiometry and stability of Cs⁺ ion complexes with aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6) and dibenzylediaza-18-crown-6 (DBzDA18C6) in different binary acetonitrile?Cnitromethane mixtures. In all cases, the exchange between free and complexed cesium ion was fast on the NMR time scale and only a single population average resonance was observed. The ¹³³Cs chemical shift?Cmole ratio data indicated that the cesium ion forms 1:1 cation?Cligand complexes with the investigated aza-crowns in all acetonitrile?Cnitromethane mixtures. The formation constants of the resulting complexes were evaluated from computer fitting of the chemical shift?Cmole ratio data. The stability of the resulting 1:1 complexes with Cs⁺ were found to vary in the order A18C6 > DBzDA18C6 > DA18C6. In all cases, there is the inverse relationship between the complex stability constants and the amount of acetonitrile in the mixed solvent.