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61.
An efficient rhodium(I)-catalyzed addition of arylboronic acids to (benzyl-/arylsulfonyl)acetonitrile is described. Novel β-sulfonylvinylamine products are formed in a stereoselective fashion (Z-alkene). Upon hydrolysis, useful β-keto sulfones are obtained with a broad scope of aryl and sulfonyl substituents. 相似文献
62.
Let brk(C4;Kn, n) be the smallest N such that if all edges of KN, N are colored by k + 1 colors, then there is a monochromatic C4 in one of the first k colors or a monochromatic Kn, n in the last color. It is shown that brk(C4;Kn, n) = Θ(n2/log2n) for k?3, and br2(C4;Kn, n)≥c(n n/log2n)2 for large n. The main part of the proof is an algorithm to bound the number of large Kn, n in quasi‐random graphs. © 2010 Wiley Periodicals, Inc. J Graph Theory 67: 47‐54, 2011 相似文献
63.
Lin YS Zheng JX Tsui YK Yen YP 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1552-1558
Three structurally simple thiourea derivatives 1-3 were prepared, and their chromogenic behaviors toward various anions were investigated in aqueous solution. Among them 1 showed good sensitivity and selectivity for cyanide ion and also can distinguish it from other anions by different color changes. Besides that, the receptor 1 has a sensitive detection limit (1.27 μM) for cyanide ion accordingly it can be used as a colorimetric sensor for the determination of cyanide ion. The use of the test strip of sensor 1 to detect cyanide ion was also reported. 相似文献
64.
V. Sametoglu V. Sauer Y. Y. Tsui 《Applied Physics A: Materials Science & Processing》2013,110(4):823-827
The resolution enhancement of laser-induced forward transfer (LIFT) is investigated through the pre-patterning of Cr on the donor substrate. 85 nm dots are first patterned on a microscope slide, and an 800 nm wavelength and 130 fs pulse laser with a beam waist of ~9 μm is used to transfer the Cr dots to an acceptor substrate. The threshold fluence is found to be ~0.15 the threshold fluence of a similar continuous film, which is thought to be due to the fact that no force is needed to tear away Cr from the film itself, unlike in a continuous film experiment. Since the volume of the material limits the transfer feature sizes instead of the laser parameters, as in a continuous film system, minimum transferable feature diameters are significantly lower compared to the continuous film case. Also, the transferred feature diameters are not dependent on the laser parameters, so the diameters are consistent across a wide range of fluences. The force per unit area generated by the laser at threshold fluence is estimated to be ~3 GPa, which is consistent with previous results in the literature. The simplified model that our pre-patterned Cr LIFT experiment represents would make it an ideal case for benchmarking molecular dynamics simulations of femtosecond laser ablation. 相似文献
65.
Timothy T. Ho Manisha Gupta Fatema Rezwana Chowdhury Zhijiang Chen Ying Yin Tsui 《Applied physics. B, Lasers and optics》2013,113(3):429-436
Here, we report the fabrication of diamond-like carbon (DLC) thin films using pulsed laser deposition (PLD). PLD is a well-established technique for deposition of high-quality DLC thin films. Carbon tape target was ablated using a KrF (248 nm, 25 ns, 20 Hz) excimer laser to deposit DLC films on soap-coated substrates. A laser fluence between 8.5 and 14 J/cm2 and a target to substrate distance of 10 cm was used. These films were then released from substrates to obtain freestanding DLC thin foils. Foil thicknesses from 20 to 200 nm were deposited using this technique to obtain freestanding targets of up to 1-inch square area. Typically, 100-nm-thick freestanding DLC films were characterized using different techniques such as AFM, XPS, and nano-indentation. AFM was used to obtain the film surface roughness of 9 nm rms of the released film. XPS was utilized to obtain 74 % sp2, 23 % sp3, and 3 % C–O bond components. Nano-indentation was used to characterize the film hardness of 10 GPa and Young’s modulus of 110 GPa. Damage threshold properties of the DLC foils were studied (1,064 nm, 6 ns) and found to be 7 × 1010 W/cm2 peak intensity for our best ultrathin DLC foils. 相似文献
66.
本文介绍一台采用双潘宁型多电荷重离子源的200kV重离子加速器,简述它在GaP光探测器的研制、聚合物材料和金属材料的离子注入改性等方面的研究与应用。 相似文献
67.
J. J. Lin W. Y. Lin R. F. Tsui 《Physica C: Superconductivity and its Applications》1993,210(3-4):455-462
We have measured the resistivities of Al2O3-Bi2Sr1.8Ca1.2Cu2Oy and MgO-Bi2Sr1.8Ca1.2Cu2Oy composites with the nominal Bi2Sr1.8Ca1.2Cu2Oy volume fraction, 2212, ranging from 0.15 to 1.00. For the Al2O3-Bi2Sr1.8Ca1.2Cu 2Oy composites, we find for the samples with 2212≥0.6 that the superconducting transition temperature, Tc, is not disturbed by the addition of Al2O3. For 2212<0.3, no zero-resistivity state is observed. For the MgO-Bi2Sr1.8Ca1.2Cu2Oy composites, Tc is barely disturbed for the samples with ρ2212≥0.7. No superconducting state is observed for the samples with ρ2212<0.35. The variation of (300 K) with ρ2212 indicates a three-dimensional percolating Bi-Sr-Ca-Cu-O matrix occurring at ρ2212≈0.19 and ≈0.15 in Al2O3-Bi2Sr1.8Ca1.2 Cu2Oy and MgO-Bi2Sr1.8Ca1.2Cu2Oy, respectively. Both resistivity and magnetization measurements suggest that the reactions of Bi2Sr1.8Ca1.2Cu2Oy with MgO are weaker than with Al2O3. 相似文献
68.
Jianzhong Zhang Yusheng Zhao Jiang Qian Paulo A. Rigg Carl W. Greeff Yunpeng Yang Yanbin Wang 《Journal of Physics and Chemistry of Solids》2005,66(7):1213-1219
The phase diagram of zirconium metal has been studied using synchrotron X-ray diffraction and time-of-flight neutron scattering at temperatures and pressures up to 1273 K and 17 GPa. The equilibrium phase boundary of the α-ω transition has a dT/dP slope of 473 K/GPa, and the extrapolated transition pressure at ambient temperature is located at 3.4 GPa. For the ω-β transition, the phase boundary has a negative dT/dP slope of 15.5 K/GPa between 6.4 and 15.3 GPa, which is substantially smaller than a previously reported value of −39±5 K/GPa in the pressure range of 32-35 GPa. This difference indicates a significant curvature of the phase boundary between 15.3 and 35 GPa. The α-ω-β triple point was estimated to be at 4.9 GPa and 953 K, which is comparable to previous results obtained from a differential thermal analysis. Except for the three known crystalline forms, the β phase of zirconium metal was found to possess an extraordinary glass forming ability at pressures between 6.4 and 8.6 GPa. This transformation leads to a limited stability field for the β phase in the pressure range of 6-16 GPa and to complications of high-temperature portion of phase diagram for zirconium metal. 相似文献
69.
The structural and magnetic phase diagrams of Coa(1−x)MnaxGeb epitaxial films near the composition of Heusler alloy Co2MnGe have been studied using combinatorial molecular beam epitaxy techniques. Epitaxial growth on Ge (1 1 1) has been stabilized over nearly the entire composition range of the ternary system. Epitaxial constraints play an important role for the small number of observed structural phases. The variety of high-temperature magnetic properties, and the structural and chemical compatibilities with group IV elements make the ternary system promising for the science and applications of spintronics. 相似文献
70.
Yeng-Yung Tsui 《国际流体数值方法杂志》1991,13(2):167-199
This paper is concerned with a number of upstream-weighted second- and third-order difference schemes. Also considered are the conventional upwind and central difference schemes for comparison. It commences with a general difference equation which unifies all the given first-, second- and third-order schemes. The various schemes are evaluated through the use of the general equation. The unboundedness and accuracy of the solutions by the difference schemes are assessed via various analyses: examination of the coefficients of the difference equation, Taylor series truncation error analysis, study of the upstream connection to numerical diffusion, single-cell analysis. Finally, the difference schemes are tested on one- and two-dimensional model problems. It is shown that the high-order schemes suffer less from the problem of numerical diffusion than the first-order upwind difference scheme. However, unboundedness cannot be avoided in the solutions by these schemes. Among them the linear upwind difference scheme presents the best compromise between numerical diffusion and solution unboundedness. 相似文献