Green-pumped high-power optical parametric oscillator based on periodically poled MgO-doped stoichiometric LiTaO3

A high-power 532 nm-pumped multikilohertz nanosecond optical parametric oscillator using a periodically poled 1.0 mol.% MgO-doped stoichiometric lithium tantalate crystal that could be operated from room temperature to 200 degrees C without damage is reported. A broad continuous tuning range from 855 to 1410 nm was achieved within a single domain period. Efficient operation of high peak power and watt level average power with a power conversion of 62.5% was measured. These results show that a high-resolution high average power visible tunable source can be realized.     

Influence of an electrostatic potential at the metal/electrolyte interface on the electron binding energy of adsorbates as probed by X-ray photoelectron spectroscopy

We present a study of the influence of an electrostatic potential across the Au(1 1 1)/4,4′-dithiodipyridine (PySSPy)-SAM/0.01 M NaOH interface on the electron binding energies of the N 1s and S 2p orbitals of the adsorbate, as probed by X-ray photoelectron spectroscopy (XPS). The observed systematic binding energy shift for N(1s) with electrode potential of −0.9 eV/V has been assigned to a so-called electrochemical shift, i.e., an apparent shift of the binding energy due to the potential drop in the electric double layer. No systematical shift was observed for the S(2p) core level of the thiol with electrode potential. The results are contrasted by measurements in 0.1 M H₂SO₄, where no electrochemical shift was found for the protonated nitrogen.     

Additional symmetries and Bäcklund transformations for the dispersionless Harry Dym hierarchy

We give a dispersionless Toda-like extension to the dispersionless Harry Dym (dDym) hierarchy. The extended dDym (EdDym) hierarchy has a dressing formulation, and its underlying solution structure can be investigated through the twistor construction. We show that additional symmetries of the solution space generate Backlund transformations of the EdDym hierarchy. We present some examples of constructing new solutions of the (2+1)-dimensional dDym and EdDym equations via Bäcklund transformations.     

Formation of single-electron-transistors using self-assembly of nanoparticle chains

We present a single-step template-free self-assembly method for constructing 1D-chains and 1D-networks of Au-nanoparticles. The chains are formed by simply increasing the ion concentration of nanoparticle solution so that the attractive van der waals force prevails over the repulsive Coulomb interaction. A combination of this method and the previously developed charge trapping technique allows us to place the 1D-chains/networks at designed locations. Further, the nanoparticle structures are stable enough to withstand the subsequent e-beam lithographic processes for formation of nanoparticle-based electronics such as a single electron transistor. Prominent Coulomb oscillation was observed at temperatures as high as 120 K.     

正磷酸硅晶相形成温度与配酸比的研究

4,4-二甲基二氧六环-1,3(DMDO)催化制异戊二烯P₂O₅-SiO₂(0.6)催化剂,高温长时间活化能形成Si₃(PO₄)₄,有良好的选择性.前文^[1]配酸比在0～2都可形成Si₃(PO₄)₄,0.8和1.2的选择率虽然不变,但DMDO转化率却明显下降,同时发现颗粒间粘接.     

Numerical study of turbulent trailing-edge flows with base cavity effects using URANS

Turbulent flows over lifting surfaces exhibiting trailing-edge vortex shedding often cause adverse and complex phenomena, such as self-induced vibration and noise. In this paper, a numerical study on flow past a blunt-edged two-dimensional NACA 0015 section and the same section with various base cavity shapes and sizes at high Reynolds numbers has been performed using the unsteady Reynolds-averaged Navier–Stokes (URANS) approach with the realisable κ–ε turbulence model. The equations are solved using the control volume method of second-order accuracy in both spatial and time domains. The assessment of the application of URANS for periodic trailing-edge flow has shown that reasonable agreement is achieved for both the time-averaged and fluctuating parameters of interest, although some differences exist in the prediction of the near-wake streamwise velocity fluctuation magnitudes. The predicted Strouhal numbers of flows past the squared-off blunt configuration with varying degrees of bluntness agree well with published experimental measurements. It is found that the intensity of the vortex strengths at the trailing-edge is amplified when the degree of bluntness is increased, leading to an increase in the mean square pressure fluctuations. The numerical prediction shows that the presence of the base cavity at the trailing-edge does not change the inherent Strouhal number of the 2D section examined. However, it does have an apparent effect on the wake structure, local pressure fluctuations and the lift force fluctuations. It is observed that the size of the cavity has more influence on the periodic trailing-edge flow than its shape does.     

硫氰酸铵-十二烷基二甲基苄基氯化铵-水体系浮选分离汞(Ⅱ)

研究了硫氰酸铵-十二烷基二甲基苄基氯化铵-水体系浮选分离汞(Ⅱ)的行为及其常见金属离子的分离条件。控制pH=5.0,当0.01mol/L硫氰酸铵溶液和0.01mol/L十二烷基二甲基苄基氯化铵(DDBAC)溶液的用量分别为0.30、0.50mL时,体系中形成的不溶于水的三元缔合物(DDBAC)2[Hg(SCN)4]可浮于水相上层形成界面清晰的液-固两相,分相过程中,Hg2+被定量浮选,而Zn2+,Cd2+,Mn2+,Ni2+,Co2+,Fe2+等离子在此条件下不被浮选,实现了Hg2+的定量分离。该方法对合成水样中微量Hg2+进行定量浮选分离测定,浮选率为96.0%—108.8%。     

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium-Catalyzed Cycloisomerization of 3-Acyloxy-4-ene-1,9-diynes to Bicyclo[5.3.0]decatrienes

Rholling in the bicycles: A rhodium(I)-catalyzed cycloisomerization for the synthesis of bicyclic compounds containing a cycloheptatriene ring from linear alkenynes (see scheme; cod=1,5-cyclooctadiene) is proposed to proceed through 1,2-acyloxy migration, 6?π electrocyclization, migratory insertion, and reductive elimination. The overall process can be viewed as a novel intramolecular [5+2] cycloaddition with concomitant 1,2-acyloxy migration.     

A luminol-based micro-flow-injection electrochemiluminescent system to determine reactive oxygen species

A flow injection analysis (FIA) system with electrochemiluminescent (ECL) detection has been established. Based on a specially designed flow-through ECL cell with a very simple structure, the system possesses rapid response and high sensitivity. With luminol as the ECL reagent, the response of hydrogen peroxide (H₂O₂) was investigated on the developed FIA-ECL system. After optimizing the experimental conditions, such as the electric parameters, the buffer condition and the flow rate, it was demonstrated that the developed FIA-ECL system works well for quantified assays. Compared with reported works, the present results indicate that the developed FIA-ECL system has the lowest limit of detection (S/N = 3) of 3.0 × 10⁻⁹ mol/L for H₂O₂, which is equal to the level of chemiluminescence (CL). The developed system was successfully used to monitor the yield of reactive oxygen species (ROSs) in water vapour during the work of an ultrasonic humidifier with H₂O₂ as index. And the amount of ROSs in some other real samples, including tap water, drinking water and river water was detected with recoveries from 92.0% to 106%.     

Pd/PR3-catalyzed cross-coupling of aromatic carboxylic acids with electron-deficient polyfluoroarenes via combination of decarboxylation with sp2 C-H cleavage

By using Pd(TFA)(2)/PCy(3) as a catalyst, a broad range of aromatic carboxylic acids, including heteroaromatic carboxylic acids, efficiently underwent decarboxylative coupling with an array of polyfluoroarenes in the presence of stoichiometric amount of silver salts to generate biaryls. Silver salts were adjusted to the reactivity of aromatic carboxylic acids to efficiently suppress the protodecarboxylation and therefore improve decarboxylative cross-couplings. It was established that the palladium complex containing the PCy(3) ligand was capable of catalyzing the decarboxylation of electron-rich aromatic carboxylic acids, and silver salts promoted the decarboxylation of both electron-rich and -deficient ones. To explain the two different decarboxylation processes, two possible reaction pathways are proposed, which were further supported by the facts that the stoichiometric arylpalladium complex can directly arylate pentafluorobenzene in the presence of PCy(3) and the arylpalladium complex can catalyze the decarboxylative coupling of 2,4-dimethoxybenzoic acid with pentafluorobenzene. The kinetic isotope effect of 4.0 clearly showed that the C-H bond cleavage of polyfluoroarenes is involved in the rate-determining step.