A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions

The theory on the ultrasonic absorption of electrolyte solutions we have proposed previously [T. Yamaguchi et al., J. Chem. Phys. 126, 144505 (2007)] is extended to calculate the frequency-dependent electric conductivity of the solution. The ionic contribution of the dielectric relaxation spectrum is obtained at the same time. The theory is able to handle the contributions of both the ion-pair dynamics and the relaxation of ionic atmosphere, as is the case of ultrasonic absorption. The effect of the barrier height between the contact and solvent-separated ion pairs is investigated in detail. It is clarified that the competition between the dissociation and reorientational relaxation rates of the contact ion pair is an important factor for the ion pair to be regarded as the ion pair in terms of ionic conductivity.     

Theoretical study on the sound absorption of electrolytic solutions. II. Assignments of relaxations

The theory on the ultrasonic absorption spectrum of electrolytic solutions recently proposed by us is applied to the model system that resembles to the aqueous solution of MgSO4. The charges on ions are reduced to +/-1.5e in order to obtain the equilibrium structure by the integral equation theory. The theory reproduces the existence of two relaxations around 100 kHz and 1 GHz. The physical origin of the relaxation is analyzed based on the theoretical expression. The slower relaxation is shown to originate in the formation of contact ion pair, in harmony with the conventional assignment. The amplitude of this relaxation agrees with the experimental one fairly well. The absorption cross section is a weakly increasing function of the concentration of the salt in theory, whereas it depends little on the concentration in experiment, which is ascribed to the weaker association of the pair in the theory. The deviation from the Debye relaxation is found for the faster process, and the concentration dependence is small. The analysis shows that this relaxation stems from the coupling between the pressure and the long-range concentration fluctuation, and the concentration independence and the non-Debye relaxation are explained based on the theoretical analysis. In particular, the theory demonstrates that this process has the t(-3/2) tail in the time domain, which is confirmed by numerical calculation. The deviation of the theoretical relaxation amplitude from the experimental one is elucidated in terms of the theoretical expression of the coefficient.     

Effect of sonication on nitroxide-controlled free radical polymerization of styrene

Effect of sonication on the autopolymerization of styrene in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy as the mediating radical was investigated at 110-135 degrees C. The thermal polymerization under sonication proceeded in the manner of a "living" radical polymerization to afford well-defined polystyrene. The sonication was found to decrease the induction period and increase the polymerization rate.     

Numerical simulation of liquid velocity distribution in a sonochemical reactor

Ultrasonically induced flow is an important phenomenon observed in a sonochemical reactor. It controls the mass transport of sonochemical reaction and enhances the reaction performance. In the present paper, the liquid velocity distribution of ultrasonically induced flow in the sonochemical reactor with a transducer at frequency of 490 kHz has been numerically simulated. From the comparison of simulation results and experimental data, the ultrasonic absorption coefficient in the sonochemical reactor has been evaluated. To simulate the liquid velocity near the liquid surface above the transducer, which is the main sonochemical reaction area, it is necessary to include the acoustic fountain shape into the computational domain. The simulation results indicate that the liquid velocity increases with acoustic power. The variation of liquid height also influences the behavior of liquid velocity distribution and the mean velocity above the transducer centre becomes a maximum when the liquid height is 0.4 m. The liquid velocity decreases with increasing the transducer plate radius at the same ultrasonic power.     

A standard method to calibrate sonochemical efficiency of an individual reaction system

Fricke reaction, KI oxidation and decomposition of porphyrin derivatives by use of seven types of sonochemical apparatus in four different laboratories were examined in the range of frequency of 19.5 kHz to 1.2 MHz. The ultrasonic energy dissipated into an apparatus was determined also by calorimetry. Sonochemical efficiency of Fricke reaction and KI oxidation was defined as the number of reacted molecule per unit ultrasonic energy. The sonochemical efficiency is independent of experimental conditions such as the shape of sample cell and irradiation instruments, but depends on the ultrasonic frequency. We propose the KI oxidation dosimetry using 0.1 moldm(-3) KI solution as a standard method to calibrate the sonochemical efficiency of an individual reaction system.     

Broadband WET: a novel technique for quantitative characterization of minor components in foods

NMR analysis of foods frequently suffers from a problem of dynamic range, which limits the detection of minor components due to the huge signals of water and major components such as sugars. In the present study, we propose a new method named as ‘broadband WET’. This pulse scheme was applied to persimmon fruit juice for saturating the resonances of water and sugars, which covered a broad bandwidth. In comparison with the conventional solvent suppression methods such as WET and DPFGSE‐WATERGATE, it was shown that broadband WET provided highly selective suppression of resonances covering an extensive bandwidth and quantitative signals of minor components without distortion. The proposed method is suitable to detect quantitative signals of the minor components with a high sensitivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Optic phonons in mixed crystal of CuClCuBr

Optic phonons in CuClCuBr mixed crystals have been studied by means of Raman scattering and infrared absorption measurements. It is concluded that this system belongs to the two-mode type. The observed behaviour of the phonon mode is accounted for by the modified random-element-isodisplacement model fairly well. In connection with this interpretation, the origin of the double peak in the pure CuCl is discussed.     

Ferrocene-containing polymers. XIII. Polymeric compounds possessing carboxyphenyl side groups

As an extension of earlier work on the condensation of ferrocene with aldehydes, the polycondensation of ferrocene with p- and o-carboxybenzaldehyde is described. While, in the former case, regular polycondensation occurs giving rise to a polymer composed of ferrocenylene and 4-carboxybenzal units, a deviation from this route is observed in the o-carboxybenzaldehyde case, where a polymer containing both carboxybenzal and 3,3-phthalide bridging units between the ferrocenylene groups is formed instead. This unexpected behavior can be accounted for by a hydride abstraction mechanism. In support of the polymer structure proposed, 3-ferrocenylphthalide and 3,3-diferrocenylphthalide are isolated as intermediates or by-products. In both polymer series, number-average molecular weights up to 3000 (unsubfractionated) are measured. The polymers are soluble in a number of organic solvents and can be cured with epoxides.