An alternative method to measure the on-axis difference-frequency sound in a parametric loudspeaker without using an acoustic filter

The self-demodulation characteristic of finite-amplitude ultrasonic sound waves can be applied with parametric loudspeaker to reproduce audible sound with highly directivity. But measuring the difference-frequency sound is still a problem due to the spurious sound generated as a result of nonlinearity caused by the product of the primary waves at the receiving system. In this paper, based on the phase-cancellation method and the Gaussian beam expansion technique, an alternative method is proposed to measure the on-axis difference-frequency sound accurately without using any traditional acoustic filter, where the spurious sound can be greatly reduced or even eliminated. The proposed method is more suitable for the case where the piston source in the parametric loudspeaker comprises multiple small piezoelectric transducers (PZTs) and each transducer element in the array may have different frequency response. The validity of the proposed method is confirmed both by simulations and experiments.     

Thermodynamic Nonequilibrium Features in Binary Diffusion

Diffusion is a ubiquitous physical phenomenon where thermodynamic nonequilibrium effects(TNEs) are outstanding issues. In this work, we employ the discrete Boltzmann method to investigate the TNEs in the dynamic process of binary diffusion. The main features of the distribution function in velocity space are recovered and discussed.It is found that, with the decreasing gradients of macroscopic quantities(such as density, concentration, velocity, etc.),both the local and global TNEs decrease with the time but increase with the relaxation time in a power law, respectively.     

Quantum Secure Communication by Using GHZ State in High-Dimensional Hilbert Space

We propose a quantum superdense coding secure communication scheme by using GHZ state. This scheme combines the ideas of quantum superdense coding and sequence transmission. Its distinct advantage is high source capacity. In addition, in checking eavesdropping, we need not to destroy quantum entanglement.     

A rapid method for isolation of human hemoglobin benzo[a]pyrene diol epoxide derived adducts using high performance liquid chromatography

A method is described to isolate rapidly human hemoglobin-benzo[a]pyrene diol epoxide adducts. A combination of 300 A pore size C4 reversed phase HPLC to effect separation of adducted protein from native protein, and mu-bore C18 reversed phase HPLC to isolate and partially characterize proteolytic peptide adducts (by UV), was used.     

The roles of benzoic acid and water on the Michael reactions of pentanal and nitrostyrene catalyzed by diarylprolinol silyl ether

The roles of benzoic acid and water on the Michael reaction of pentanal and nitrostyrene catalyzed by diarylprolinol silyl ether are revealed by density functional theory calculations. The calculations demonstrate that the benzoic acid is ready to attack the catalysts and form a hydrogen bond between the hydrogen atom of the COOH of benzoic acid and one of the N atoms of the catalyst. The complex formed from pentanal, catalyst and benzoic acid attacks nitroalkene and forms transition states. Finally, the transition states hydrolyze and the products are formed. The calculations demonstrate that the stereoselectivity is dominated by the steric hindrance of the 2-substituent groups, and the benzoic acid can increase the reaction rate evidently by decreasing the activation energies; however, H(3)O(+) or strong acid may prevent the formation of the transition states between enamines and nitroalkenes. The employed solvent can decrease the activation energies and promote the proton transfer from benzoic acid onto the catalyst 2. The calculated enantiomeric excess values are in good agreement with the experimental results. These calculations also reveal that the role of benzoic acid is dependent on the sophisticated structures of the catalysts and provide a valuable index for the structural design of new catalysts and selection of additives or co-catalysts.     

Effects of image charges, interfacial charge discreteness, and surface roughness on the zeta potential of spherical electric double layers

We investigate the effects of image charges, interfacial charge discreteness, and surface roughness on spherical electric double layer structures in electrolyte solutions with divalent counterions in the setting of the primitive model. By using Monte Carlo simulations and the image charge method, the zeta potential profile and the integrated charge distribution function are computed for varying surface charge strengths and salt concentrations. Systematic comparisons were carried out between three distinct models for interfacial charges: (1) SURF1 with uniform surface charges, (2) SURF2 with discrete point charges on the interface, and (3) SURF3 with discrete interfacial charges and finite excluded volume. By comparing the integrated charge distribution function and the zeta potential profile, we argue that the potential at the distance of one ion diameter from the macroion surface is a suitable location to define the zeta potential. In SURF2 model, we find that image charge effects strongly enhance charge inversion for monovalent interfacial charges, and strongly suppress charge inversion for multivalent interfacial charges. For SURF3, the image charge effect becomes much smaller. Finally, with image charges in action, we find that excluded volumes (in SURF3) suppress charge inversion for monovalent interfacial charges and enhance charge inversion for multivalent interfacial charges. Overall, our results demonstrate that all these aspects, i.e., image charges, interfacial charge discreteness, their excluding volumes, have significant impacts on zeta potentials of electric double layers.     

Rare earth element (REE) in surface mangrove sediment by instrumental neutron activation analysis

A study is carried out on the concentrations of rare earth element (REE) elements present in surface mangrove sediments from 10 locations throughout west coast Malaysia. In carrying out the analysis, the best and most convenient method being the instrumental neutron activation analysis (INAA). Samples were obtained, dried, crushed to powdery form and samples prepared for INAA. All the samples for analysis were weighted approximately 150 mg for short irradiation and 200 mg for long irradiation time. As calibration and quality control procedures, blank samples, standard reference material SL-1 were then irradiated with thermal neutron flux of 4 × 10¹² cm^?2 s^?1 at the MINT TRIGA Mark II research reactor which operated at 750 kW by using a pneumatic transport facility. The REE elements of surface sediment samples in this study are Dy, Sm, Eu,Yb, Lu, Tb, La and Ce. It was found that the level of concentrations of all the REE elements varies in the range (0.35–117.4 mg/kg). The geochemical behavior of REEs in surface sediments and normalized pattern (chondrite and shale) has been studied. The degree of sediments contaminations were computed using an enrichment factor. The results showed that the enrichment factor varied in the range (0.75–6.75).     

Direct N−H Activation to Generate Nitrogen Radical for Arylamine Synthesis via Quantum Dots Photocatalysis

Represented herein is the first example of N-radical generation direct from N−H bond activation under mild and redox-neutral conditions. The in situ generated N-radical intercepts a reduced heteroarylnitrile/aryl halide for C−N bond formation under visible-light irradiation of quantum dots (QDs). A series of aryl and alkylamines with heteroarylnitriles/aryl halides exhibit high efficiency, site-selectivity and good functional-group tolerance. Moreover, consecutive C−C and C−N bond formation using benzylamines as substrates is also achieved, producing N-aryl-1,2-diamines with H₂ evolution. The redox-neutral conditions, broad substrate scope, and efficiency of N-radical formation are advantageous for organic synthesis.     

石墨烯/铁氰化钴复合膜修饰玻碳电极同时测定对苯二酚、邻苯二酚和间苯二酚

采用滴涂法和电沉积法制备了石墨烯/铁氰化钴复合膜修饰玻碳电极. 用扫描电镜对该纳米复合膜进行了表征.用循环伏安法研究了对苯二酚(HQ)、邻苯二酚(CT)和间苯二酚(RS)在修饰电极上的电化学行为. 实验结果表明, 相对于裸玻碳电极和石墨烯修饰电极, HQ, CT 和RS 在石墨烯/铁氰化钴修饰电极上的氧化峰电流显著提高. 利用差分脉冲伏安法测定, HQ, CT 和RS 分别在1.0×10^－6～1.5×10^－4 mol/L, 1.0×10^－6～2.0×10^－4 mol/L 和3.5×10^－6～2.5×10^－4 mol/L浓度范围内与氧化峰电流呈良好的线性关系, 相关系数分别为0.991, 0.993 和0.992. 信噪比为3 时, HQ, CT 和RS 检出限分别为2.0×10^－7, 2.1×10^－7 和3.5×10^－7 mol/L. 将该方法用于水样分析, 回收率为95.6%～106.1%.