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排序方式: 共有397条查询结果,搜索用时 78 毫秒
21.
Philippe Franck Beáta Dajka-Halász Katrien Monsieurs Bert U.W. Maes 《Tetrahedron》2008,64(26):6030-6037
Pd-catalyzed cyclodehydrohalogenation involving oxidative addition of aromatic C-Br or activated azaheteroaromatic C-Cl bonds and C(sp2)-H activation have been investigated at high reaction temperatures (180-200 °C). This allowed the fast (10-30 min) synthesis of a variety of azaheteroaromatic ring systems (dibenzo[f,h]phthalazine, dibenzo[f,h]cinnoline, benzofuro[2,3-d]pyridazine, 5H-pyridazino[4,5-b]indole, 7H-indolo[2,3-c]quinoline and 5H-δ-carboline) in moderate to good yields. 相似文献
22.
Gowravaram Sabitha C. Nagendra Reddy Peddabuddi Gopal J.S. Yadav 《Tetrahedron letters》2010,51(43):5736-5739
A convergent stereoselective total synthesis of (+)-anamarine via cross-metathesis (CM) protocol starting from 2-butyn-1,4-diol and vinyl lactone is reported. Other key features of the strategy include the use of Sharpless asymmetric epoxidation, Sharpless dihydroxylation, and Red-Al reduction. 相似文献
23.
Ruili Zhang Tomonori Maeda Sho Kusaka Kei-ichiro Murai 《Journal of solid state chemistry》2010,183(3):620-623
Host lattice Ba3Si5O13−δNδ oxonitridosilicates have been synthesized by the traditional solid state reaction method. The lattice structure is based on layers of vertex-linked SiO4 tetrahedrons and Ba2+ ions, where each Ba2+ ion is coordinated by eight oxygen atoms forming distorted square antiprisms. Under an excitation wavelength of 365 nm, Ba3Si5O13−δNδ:Eu2+ and Ba3Si5O13−δNδ:Eu2+,Ce3+ show broad emission bands from about 400-620 nm, with maxima at about 480 nm and half-peak width of around 130 nm. The emission intensity is strongly enhanced by co-doping Ce3+ ions into the Ba3Si5O13−δNδ:Eu2+ phosphor, which could be explained by energy transfer. The excitation band from the near UV to the blue light region confirms the possibility that Ba3Si5O13−δNδ:Eu2+, Ce3+ could be used as a phosphor for white LEDs. 相似文献
24.
采用sol-gel法制备了Y3+掺杂Ba0.90Sr0.08Ca0.02TiO3(BSCT)纳米粉体及细晶陶瓷。通过TG-DTG、XRD、SEM和TEM对样品结构及形貌进行了表征,并测试了陶瓷的介电性能。研究表明,Y3+掺杂BSCT纳米粉体主要为立方相BaTiO3,烧结后陶瓷晶粒尺寸在0.68~2.24μm可控,Y3+掺杂可以抑制陶瓷晶粒的生长,使陶瓷的tC向低温方向移动。随Y3+掺杂量的增大,陶瓷的介电温谱εr-t趋于平缓,当x(Y3+)为7.0%时,陶瓷的室温εr大幅度提高到9 176。 相似文献
25.
本文研究了生物组织的改进的δ-P1近似漫反射光学模型,推导了含有等效光源一阶矩的双点源近似空间分辨漫反射解Rδ-P1(ρ).研究表明,考虑等效光源一阶矩的光学模型,较好地描述了具有强的前向散射特性和较大吸收系数的生物组织散射特性;与漫射近似下的漫反射率RSDA(ρ)相比,新的光学模型能较好地描述光源附近的漫辐射强度分布,并且由于解析表达式中含有散射相函数的二阶参量γ,这对
关键词:
组织光学
1近似')" href="#">δ-P1近似
等效光源
微区漫反射 相似文献
26.
Oxygen nonstoichiometry (δ), total conductivity (σ) and thermoelectric power (S) of the LaFe0.7Ni0.3O3 − δ sample have been studied as functions of temperature and oxygen partial pressure. Based on the results of the direct reduction of the sample in hydrogen flow at 1100 °C the absolute oxygen content (3 − δ) has been found to vary from 2.999 to 2.974 in the range of 1273-1373 K and 10− 3-0.21 atm. The point defect equilibrium models have been proposed and fitted to the set of experimental data in the form of log p(O2) = f(δ)T dependences. The values of standard thermodynamic quantities of defect formation reactions have been assessed. The joint analysis of oxygen nonstoichiometry, total conductivity and thermoelectric power has been performed using a small-polaron approach. The values of partial conductivity, partial thermopower and mobilities of electronic charge carriers have been calculated. The p-type semiconducting behavior of LaFe0.7Ni0.3O3 − δ has been explained by the higher mobility values of electron holes than those of electrons in the whole range of thermodynamic parameters studied. 相似文献
27.
M. Ali HaiderAaron J. Capizzi Mitsuhiro MurayamaSteven McIntosh 《Solid State Ionics》2011,196(1):65-72
La0.6Sr0.4CoxFe1−xO3−δ (LSCF), La0.6Sr0.4Cu0.2Fe0.8O3−δ, Ba0.5Sr0.4Co0.8Fe0.2O3−δ and LaFeO3−δ nanoparticles were synthesized by a reverse micelle procedure. Controlling the size of the micelles through the water:oil phase ratio enabled synthesis of phase pure perovskite particles with average sizes from 14 nm to 50 nm. Small amounts of an impurity phase, likely cobalt oxide, were detected in the XRD spectrum of high cobalt content samples of LSCF (x = 0.8). La0.6Sr0.4Co0.2Fe0.8O3−δ nanoparticles were utilized to coat the surface of a dense thin-film La0.6Sr0.4Co0.2Fe0.8O3−δ solid oxide fuel cell cathode. The polarization resistance of the nanoparticle coated electrode, measured at open circuit in air at 973 K, was 20% lower than an equivalent un-coated electrode. 相似文献
28.
Bi2Sr2Ca1Cu2O8+δ (Bi-2212) films were grown on (1 0 0) oriented SrTiO3 (STO) substrate using sol-gel spin-coating method. The effects of heat treatment conditions and coating times on the phase formation and surface morphology were investigated using thermal analysis, optical microscope, X-ray diffraction, and scanning electronic microscopy. Mixed phases were formed from 820 to 840 °C, and Bi-2212 single phase was obtained at 830 °C for 3 h. c-axis epitaxial films with smooth surfaces were obtained by drying at 600 °C and coating for 5 times. 相似文献
29.
Toshiaki Kaminaka Miki Wadati 《Physics letters. A》2011,375(24):2460-2464
We study higher order solutions of Lieb-Liniger integral equation for a one-dimensional δ-function Bose gas. By use of the power series expansion method, the integral equation is solved and the correction terms which improve the Bogoliubov theory are calculated analytically in the weak coupling regime. Physical quantities such as the ground state energy and the chemical potential are represented by a dimensionless parameter γ=c/ρ, where c is the interaction strength and ρ is the number density of particles while the quasi-momentum distribution function is expressed in terms of a dimensionless parameter λ=c/K, where K is the cut-off momentum. 相似文献
30.