Radiation chemistry of tris(acetylacetonato) cobalt(iii) in aqueous solutions

Abstract

On radiolysis tris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C₂H₂OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 10¹⁰, 2.3 × 10⁹ and 4.7 × 10⁹ M^?1sec^?1 respectively. Absorption spectra of the irradiated solutions indicate the formation of bis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co⁺⁺) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that G_eaq- ∽ _H ⁺ G_oH ∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs.     

Adsorption effects and NMR properties: Continuous chain approach

The NMR properties of nuclei linked to long linear polymer molecules are sensitive to the influence of hard walls. In this context, the residual energy of tensorial spin-spin interactions is calculated using a path integral approach. Several thermodynamic quantities of the polymer system (free energy, equation of state,...) are also expressed, taking chain stiffness effects and the presence of two repulsive walls into consideration.     

Differentiable conjugacy of the Poincaré type vector fields on

We prove that on , except for those germs of vector fields whose linear parts are conjugated to , any two Poincaré type vector fields are at least conjugated to each other provided their linear approximations have the same eigenvalues and the nonlinear parts are generic.

     

A 250?GHz, 50?W, CW Second Harmonic Gyrotron

A design concept of a 250 GHz, ≈ 50 W, CW, second harmonic gyrotron for spectroscopy will be presented in this paper. Mode competition, in particular with regard to competition with first harmonic modes, and mode selection procedures are carefully investigated by considering various candidate modes and the TE_6,2 and TE_6,3 modes are chosen as probable operating modes. Cold cavity and self-consistent calculations of power and efficiency are carried out to determine optimum parameters for these two modes. The results indicate that an output power of well over 50 W, CW can be achieved.     

Controlling optical responses through local dielectric resonance in nanometre metallic clusters

Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances \varepsilon₁ and \varepsilon₂. Through varying the difference admittance ratio \eta [ = (\varepsilon₂- \varepsilon ₀) / (\varepsilon₁- \varepsilon₀)], we find that their optical responses are determined by the local resonance. There is a blueshift of absorption peaks with the increase of \eta. Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances, we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-component composites \varepsilon_e= \varepsilon₀ \bigl(1 + \sum_n=1^{n_s} [(\gamma_n2+ \eta \gamma_n2)/({\varepsilon₀(s - s_n))]} \bigr), and the sum rule of cross sections: \sum_n=1^{n_s} {(\gamma_n2+ \eta \gamma_n2 ) = N_h1+ N_h2, where N_h1and N_h2 are the numbers of \varepsilon₁ and \varepsilon₂ bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.     

Electron paramagnetic resonance, optical and electrical properties of vanadyl doped alkali germanoborate glasses

Glasses with composition xGeO₂.(0.30−x)M₂O.0.70B₂O₃ (M=Li, K) containing 2.0 mol% of V₂O₅ have been prepared in the range 0.00≤x≤0.15 by normal melt quenching method. Electron paramagnetic resonance (EPR), optical transmission and absorption spectra and dc conductivity of these glasses have been studied. Spin Hamiltonian parameters (SHPs) of VO²⁺ ions, dipolar hyperfine coupling parameter, P, Fermi contact interaction parameter, K and molecular orbital coefficients (α² and γ²) have been calculated. In GeO₂·Li₂O·B₂O₃ glasses there is no change in the tetragonality of the V⁴⁺O₆ complex and the size of 3d_xy orbit also remains unchanged with increase in GeO₂ content. In GeO₂·K₂O·B₂O₃ glasses, there is an increase in the tetragonality of the V⁴⁺O₆ complex and the 3d_xy orbit expands with increase in GeO₂ content. Values of the theoretical optical basicity, Λ_th, have also been reported. Optical band gap decreases with increase in GeO₂ content. The dc conductivity of these glasses decreases and the activation energy increases with increase in GeO₂:M₂O ratio.     

Terfenol-D/PZT磁电复合材料的磁电相位移动研究

采用粘合法制备了叠层结构的块体Terfenol-D/PZT磁电复合材料,测量了不同频率下的磁电回线,采用新的极坐标下的方式做图.从极坐标下的磁电回线中可以看出,随直流磁场的变化,非谐振频率下的磁电相位发生了轻微移动,移动幅度随频率的增加而增加;而在谐振频率下,伴随着巨磁电效应,磁电相位发生了显著移动,移动幅度达到了近90°.与粉末Terfenol-D/环氧树脂/PZT磁电复合材料对比之后表明,非谐振频率下块体Terfenol-D/PZT的磁电相位移动主要由涡流引起;而谐振频率下大幅度相位移动则主要来源于Terfenol-D的磁致弹性变化.     

级联双稳Duffing系统的随机共振研究

研究了级联双稳Duffing系统的随机共振特性, 证明级联双稳Duffing系统变尺度系数、阻尼比和级数等参数的适当调节, 不仅可实现大参数信号的级联随机共振, 而且可优化单级双稳Duffing系统的随机共振特征, 即参数调节的级联双稳Duffing系统能实现比单级双稳Duffing系统更好的随机共振输出. 此外, 级联双稳Duffing系统对方波信号具有良好的滤波整形作用, 可用于实现含噪方波信号的波形恢复. 关键词： 级联双稳Duffing系统 随机共振 变尺度 参数调节