Comparison of Xe single bubble sonoluminescence in water and sulfuric acid

Using the equations of fluid mechanics with proper boundary conditions and taking account of the gas properties, we can numerically simulate the process of single bubble sonoluminescence, in which electron-neutral atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation, and the radiative attachment of electrons to atoms and molecules contribute to the light emission. The calculation can quantitatively or qualitatively interpret the experimental results. We find that the accumulated heat energy inside the compressed gas bubble is mostly consumed by the chemical reaction, therefore, the maximum degree of ionization inside Xe bubble in water is much lower than that in sulfuric acid, of which the vapour pressure is very low. In addition, in sulfuric acid much larger pa and R0 are allowed which makes the bubbles in it much brighter than that in water.     

硫酸中多气泡声致发光光谱

非线性声波方程与气泡脉动方程联立, 可以描述声空化云中的声场以及任何一个气泡的脉动过程,为数值计算空化场问题提供了理论框架.计算的声压分布变化可以用来计算单气泡动力学,了解任何位置处气泡发光过程以及气泡内气体温度和压强变化等. 对浓硫酸中氙气泡空化云的计算定性符合实验观测, 只有钠原子线谱的计算结果相比实验观测有些出入.     

Finite-amplitude vibration of a bubble in water

The numerical results obtained by Rayleigh-Plesset （R-P） equation failed to agree with the experimental Mie scattering data of a bubble in water without inappropriately increasing the shear viscosity and decreasing the surface tension coefficient. In this paper, a new equation proposed by the present authors （Qian and Xiao） is solved. Numerical solutions obtained by using the symbolic computation program from both the R-P equation and the Qian-Xiao （Q-X） equation clearly demonstrate that Q-X equation yields best results matching the experimental data （in expansion phase）. The numerical solutions of R-P equation also demonstrate the oscillation of a bubble in water depends strongly upon the surface tension and the shear viscosity coefficients as well as the amplitude of driving pressure, so that the uniqueness of the numerical solutions may be suspected if they are varied arbitrarily in order to fit the experimental data. If the bubble＇s vibration accompanies an energy loss such as the light radiation during the contract phase, the mechanism of the energy loss has to be taken into account. We suggest that by use of the bubble＇s vibration to investigate the state equations of aqueous solutions seem to be possible. We also believe that if one uses this equation instead of R-P equation to deal with the relevant problems such as the ＇phase diagrams for sonoluminescing bubbles＇, etc., some different results may be expected.     

An efficient deprotection of oximes to carbonyls catalyzed by silica sulfuric acid in water under ultrasound irradiation

Deprotection of oximes to the corresponding carbonyl compounds in silica sulfuric acid/surfactant/paraformaldehyde system can be carried out in excellent yields at 50 °C in water under ultrasound irradiation.     

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.     

Investigation of a mutual interaction force at different pressure amplitudes in sulfuric acid

This paper investigates the secondary Bjerknes force for two oscillating bubbles in various pressure amplitudes in a concentration of 95% sulfuric acid.The equilibrium radii of the bubbles are assumed to be smaller than 10 μm at a frequency of 37 kHz in various strong driving acoustical fields around 2.0 bars (1 bar=10 5 Pa).The secondary Bjerknes force is investigated in uncoupled and coupled states between the bubbles,with regard to the quasi-adiabatic model for the bubble interior.It finds that the value of the secondary Bjerknes force depends on the driven pressure of sulfuric acid and its amount would be increased by liquid pressure amplitude enhancement.The results show that the repulsion area of the interaction force would be increased by increasing the driven pressure because of nonlinear oscillation of bubbles.     

Sonoluminescence and sonochemical reactions in cavitation fields. A review

Contemporary ideas on the nature of cavitation are reviewed in this paper. The general theories of sonoluminescence and sonochemical reactions, the origin, stability and splitting of cavitation bubbles, the dynamics of cavitation field evolution, the peculiarities of cavitation effects at low intensity and low-frequency acoustic oscillations, the sonoluminescence quenching effect and some questions on the energetics of cavitation fields are discussed. The electrical theory of the splitting of cavitation bubbles may, as shown in the paper, become an alternative to the thermal theories of cavitation in the future.     

Concomitance in single bubble sonoluminescence of period doubling in emission and shape distortion

We report the first direct observation for a single stable sonoluminescing bubble of a shape instability. Furthermore we show that stable saturation of the shape distortion caused by the instability for a certain range of parameters is experimentally possible and furthermore is directly linked to the curious phenomenon of flash by flash period doubling of the sonoluminescent emission as the afterbounce instability causing the shape distortion is always period doubled whenever the emission is & vice versa.     

咖啡酸与乳蛋白结合的光谱特性及结合物抗氧化活性变化

利用紫外光谱和荧光光谱技术评价了咖啡酸与乳蛋白(α-酪蛋白、β-酪蛋白、κ-酪蛋白、α-乳白蛋白、β-乳球蛋白)两者结合的结合常数、结合作用力、结合距离以及能量转移效率,通过二苯代苦味酰基(DPPH)自由基清除率和铁离子还原能力(FRAP)对两者结合导致的抗氧化活性变化进行了测定。结果表明咖啡酸会使乳蛋白发生内源性荧光猝灭。吉布斯自由能变ΔG<0,表明反应是自发进行的。其中咖啡酸与α-酪蛋白之间以静电引力结合(ΔH<0,ΔS>0),与β-酪蛋白、α-乳白蛋白的结合作用力为氢键(ΔH<0,ΔS<0),与κ-酪蛋白、β-乳球蛋白是以疏水作用力结合(ΔH>0,ΔS>0)。两者结合距离r0<7nm,符合非辐射能量转移条件,证明咖啡酸对乳蛋白的荧光猝灭是由于生成不发光的配合物而引起的静态猝灭。此外,两者结合导致咖啡酸的抗氧化能力受到不同程度的抑制。     

Luminescence and Energy Transfer in Frozen Solutions of Uranyl Sulfate in Selective Excitation

Luminescence spectra of vitrified solutions of uranyl sulfate in a concentrated sulfuric acid are investigated in the range 4.2–80 K in selective laser excitation. It is shown that the luminescence spectra are a superposition of two components — the component that is related to the resonance excitation of uranyl complexes and the component that is caused by the luminescence of uranyl complexes sensitized by the transfer of electron-excitation energy from the resonance-excited centers. The nonselective character is established for the spectral migration of electron-excitation energy with participation of the bending vibrations of the uranyl complex that ensure direct vibrational transitions between neighboring electronic energy levels. The temperature evolution of the luminescence spectra can be described within the framework of the model of configuration coordinates with allowance for only the linear terms of vibronic interaction.     

Kinetic regularities of the interaction between styrene and formaldehyde catalyzed by sulfuric acid

The spectrophotometric method was used to study the kinetics of the interaction of styrene with formaldehyde in 10–40 wt % H₂SO₄ aqueous solutions at 25°C. The reaction of formation of the unsaturated alcohol was established to be reversible. The reaction was for the first time demonstrated to be of the first order with respect to monomeric formaldehyde (CH₂O). A mechanism of the reaction was proposed.     

Comparison between the 3D numerical simulation and experiment of the bubble near different boundaries

Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element method is applied to simulate the evolution of the bubble. Elastic-plasticity of structure being taken into account, the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dynamics near different boundaries. Supported by the National Natural Science Foundation of China (Grant No. 50779007), the National Science Foundation for Young Scientists of China (Grant No. 50809018), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070217074), the Defense Advanced Research Program of Science and Technology of Ship Industry (Grant No. 07J1.1.6), and Harbin Engineering University Foundation (Grant No. HEUFT07069)     

Spectral signs of reaction between dihydric phenols and boric acid

We have studied the vibrational spectra and thermal curves (DTA, DTG, and TG) for the products of reaction between total shale phenols and boric acid, and also the polymer matrix of a gas-filled alkyl resorcinol polymer modified by mixtures of boric acid and aluminum oxide. Based on analysis of the IR absorption spectra, we show that the reason for the change in the physicochemical properties of the foam polymer is complex formation between the polymer and the additive. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 260–263, March–April, 2006.     

An alternative method to remove PEO-PPO-PEO template in organic-inorganic mesoporous nanocomposites by sulfuric acid extraction

Sulfuric acid is used as an extraction agent to remove PEO-PPO-PEO templates in the organic-inorganic mesoporous nanocomposites from the triconstituent co-assembly which includes the low-polymerized phenolic resins, TEOS and triblock copolymer F127. The XRD and TEM results show well ordered mesostructure after extraction with sulfuric acid. As followed from the N₂ sorption isotherms the extracted composites possess high surface areas (332-367 m²/g), large pore volumes (0.66-0.78 cm³/g), and large pore sizes (about 10.7 nm). The FT-IR analysis reveals almost complete elimination of triblock copolymer F127, and the maintenance of organic groups. This method shows potentials in removing templates from nanocomposites containing functional moieties.     

Inhibitive action of indole-5-carboxylic acid towards corrosion of mild steel in deaerated 0.5 M sulfuric acid solutions

Inhibition of mild steel corrosion in deaerated 0.5 M sulfuric acid solutions containing various concentrations of indole-5-carboxylic acid is studied in the temperature range from 25 to 55 °C using weight-loss, potentiodynamic and spectrophotometric tests. The adsorptive behaviour of inhibitor is also investigated using electrochemical impedance spectroscopy measurements. The indole-5-carboxylic acid is found to shift the corrosion potentials towards more noble values. This shift indicates that the addition of inhibitor mainly affects the anodic process, raising the anodic overpotential more than that of the cathodic, i.e. the indole-5-carboxylic acid behaves as mixed-type inhibitor. Because the cathodic Tafel slopes for hydrogen reduction (b_c) are affected, the inhibitor probably affects the hydrogen reduction mechanism. The activation energy values (E_a) indicate that the indole-5-carboxylic acid increases the activation energy of the corrosion reaction. The adsorption behaviour of indole-5-carboxylic acid follows Langmuir's isotherm. Both the low values of and its decrease with temperature suggest physical adsorption. Double layer capacitance-potential curves indicate considerable adsorption of the inhibitor in the potential range (−400 to −800 mV/_SCE).     

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 0.5 M sulfuric acid

The corrosion inhibition of 1-(2-pyridylazo)-2-naphthol (PAR) on the corrosion of cold rolled steel in 0.5 M sulfuric acid (H₂SO₄) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that together with chloride ion, PAR is an effective corrosion inhibitor for steel corrosion in sulfuric acid. It was found that for steel corrosion inhibition in the presence of single PAR in sulfuric acid the Temkin adsorption isotherm may be used to explain the adsorption phenomenon. For the mixture of PAR and NaCl used as corrosion inhibitor, however, the Langmuir adsorption isotherm can be used to satisfactorily elucidate the adsorption of mixture of PAR and NaCl. Potentiodynamic polarization studies showed that single PAR mainly acts as a cathodic inhibitor for the corrosion of steel in 0.5 M sulfuric acid. The mixture of PAR and chloride ion, however, acts as a mixed type inhibitor that mainly inhibits cathodic reaction of the steel corrosion in sulfuric acid. By means of electrochemical polarization tests, a desorption potential at ca. −370 mV was observed for the adsorption of mixture of PAR and chloride ion, when potential reaches this value, adsorbed inhibitor molecule heavily departs from the steel surface. For the mixture of PAR and chloride ion, thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C, the kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The most suitable range of inhibitor concentration was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and PAR was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.     

Reconstruction on Au(0 0 1) vicinal surfaces in UHV and in sulfuric acid solution

Using scanning tunneling microscopy we have studied the reconstruction on Au(1 1 n) surfaces in ultra-high vacuum and in electrolyte. Similar to the well-known (5 × 20) quasi-“hex” reconstruction on Au(0 0 1), the reconstruction consists of parallel reconstruction lines along the steps indicative of a higher atom density in the first Au layer. In contrast to nominally flat Au(0 0 1) where the reconstruction period is 1.44 nm, we find considerably larger reconstruction periods (1.8−1.96 nm) on incidentally flatter regions of nominal Au(1 1 9), Au(1 1 11), and Au(1 1 17) surfaces. The enlarged reconstruction period is attributed to the stress field on stepped surfaces. In agreement with previous studies we find a reconstruction free zone at the step edges.     

UV-Raman study and theoretical analogue of picolinic acid in aqueous solution

High quality Raman spectrum of picolinic acid aqueous solution with ultraviolet (UV) excitation of 325 nm was obtained in this article. The state of picolinic acid in aqueous solution has been investigated over a wide range of solution pH values. The distinct changes of UV-Raman spectra accompanied with the pH variations indicate the changes of molecule structure. The calculations based on density functional theory were used to analyze the states of picolinic acid in aqueous solution. By comparing the experimental frequencies with the calculated ones, it can be concluded that when pH value varies from high to low, the picolinic acid tends to change from the anion form to the zwitterion that have the intermolecular hydrogen COOH?N bond.     

熔拉和腐蚀单模阶跃光纤的模场分析

考虑到包层厚度和包层外介质的影响 ,在单模光纤的高斯近似理论基础上 ,导出了单模阶跃光纤模场半径方程 ,并就光纤在传感等领域应用中常见的熔拉和腐蚀处理两种情况 ,进行了相应的数值计算 ,给出了近似解析解。引入特性转换点 ,对模场特性作了分析。