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121.
A method is proposed for disentangling exponentials of operators that belong to finite-dimensional Lie algebras. A straightforward matrix representation is combined with a widely used parameter-differentiation method, giving rise to a simpler and more systematic procedure. The SU(1, 1), SU(2) and double photon algebras are explicitly considered as illustrative examples.Work partly supported by Fundación Antochas Project No. 1108911 and by the USA-Argentina Cooperative Research Project NSF INT-8802247 and CONICET No. 163/88. 相似文献
122.
Juli K. Dixon 《School science and mathematics》1997,97(7):352-358
The effects of a dynamic instructional environment (based on use of The Geometer's Sketchpad, N. Jackiw, 1991 , in a computer lab) and visualization on eighth-grade students' (N= 241) construction of the concepts of reflection and rotation were investigated. Also investigated were the effects of the environment on students' two- and three-dimensional visualization. After controlling for initial differences, it was concluded that students experiencing the dynamic environment significantly outperformed students experiencing a traditional environment on content measures of the concepts of reflection and rotation, as well as on measures of two-dimensional visualization. The students' environment did not significantly affect their three-dimensional visualization. 相似文献
123.
Iodine and the pincer complex [Pd(O,N,C-L)I], where L is the monoanionic ligand resulting from deprotonation of the acetyl group of the dimethylmonoketal of 2,6-diacetylpyridine, are in equilibrium at low temperatures with the palladium(IV) complex [Pd(O,N,C-L)I(3)], which can be isolated at -40 °C and characterized by (1)H NMR spectroscopy and X-ray diffraction studies, in spite of its great instability. When the same reaction is carried out at room temperature, a quantitative reductive elimination process occurs, giving L-I, which in the presence of water affords L'-I, resulting from hydrolysis of L-I. 相似文献
124.
Guoli Huang Xiaojie Qiu Juli Jiang Leyong Wang 《Journal of organometallic chemistry》2011,696(18):2949-2957
[Ni(L1)2](PF6)2 (3a, L1 = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)methyl)imidazolyl-idene), [Ni(L2)2(CH3CN)](PF6)2 (3b, L2 = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)-methyl)benzimidazolylidene), and [Hg(L1)2(CH3CN)2](PF6)2 (4) have been successfully prepared and fully characterized by NMR, ESI-MS spectroscopy, and X-ray diffraction analysis. The nickel complexes reveal a square-planar structure with two carbene ligands and benzimidazole groups at the cis configuration. The nickel complex 3b has been proved to be a highly efficient catalyst for Friedel-Crafts alkylation of indoles with β-nitrostyrenes at room temperature in moderate-to-excellent yields. The crystal packing structure of 4 shows that double-stranded 1D supramolecular chains are formed by inter-chain benzimidazole rings and pyridine rings face-to-face π-π stacking interactions. 相似文献
125.
Julián D. Osorio Juliana Giraldo Juan C. Hernández Alejandro Toro Juan P. Hernández-Ortiz 《Heat and Mass Transfer》2014,50(4):483-492
The diffusion–reaction of aluminum (Al) and oxygen (O), to form thermally grown oxide (TGO) layers in thermal barrier coatings (TBCs), is studied through an analytical model. A nonsymmetrical radial basis function approach is used to numerically solve the mass balance equations that predict the TGO growth. Correct boundary conditions for the Al and O reactions are laid out using scaling arguments. The Damköhler number shows that the O–Al reaction is several orders of magnitude faster than diffusion. In addition, a comparison between aluminum and oxygen diffusivities indicates that TGO growth is governed by aluminum diffusion. The results are compared with experimental measurements on air plasma spray-deposited TBCs treated at 1,373 K with exposure times ranging from 1 to 1700 hours. We found that, for several time decades, the thickness of the thermally grown layer has power law dependence of time with an exponent of ½, following the diffusion control mechanism. At later times, however, the presence of other oxides and additional kinetics modify the diffusive exponent. 相似文献
126.
Jianmin Jiao Wang Xie Yumei Li Prof. Dr. Chen Lin Prof. Dr. Juli Jiang Prof. Dr. Leyong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201933
Iodine capture is of great significance for disposal of the hazardous radioactive iodine. CTX[P(O)Ph] , one kind of censer-shaped macrocycle cyclotrixylohydroquinoylene ( CTX ) derivatives, was applied as an efficient iodine adsorbent. It showed satisfactory iodine adsorption capacity in vapor phase and could be reused without obvious adsorption capacity loss. Besides, the adsorbent could also uptake iodine in water. Fortunately, two iodine loading CTX[P(O)Ph] crystal structures were obtained under different conditions to explore the mechanism of iodine adsorption. This work provides a relatively rare example of iodine adsorption by macrocycle. It is promising that the results with crystal information might be meaningful for exploring and designing new kinds of iodine adsorbents. 相似文献
127.
Guoliang Zhu Hui Zeng Shuangbo Zhang Jana Juli Xiaoyun Pang Jan Hoffmann Yan Zhang Nina Morgner Yun Zhu Guohong Peng Hartmut Michel Fei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):351-359
Respiratory chain complexes convert energy by coupling electron flow to transmembrane proton translocation. Owing to a lack of atomic structures of cytochrome bc1 complex (Complex III) from thermophilic bacteria, little is known about the adaptations of this macromolecular machine to hyperthermophilic environments. In this study, we purified the cytochrome bc1 complex of Aquifex aeolicus, one of the most extreme thermophilic bacteria known, and determined its structure with and without an inhibitor at 3.3 Å resolution. Several residues unique for thermophilic bacteria were detected that provide additional stabilization for the structure. An extra transmembrane helix at the N-terminus of cyt. c1 was found to greatly enhance the interaction between cyt. b and cyt. c1, and to bind a phospholipid molecule to stabilize the complex in the membrane. These results provide the structural basis for the hyperstability of the cytochrome bc1 complex in an extreme thermal environment. 相似文献
128.
María del Carmen Grande Jorge Álvarez Juliá Carmen Raquel Barrero 《Physics and Chemistry of Liquids》2019,57(2):151-162
Density, sound velocity and refractive index of ethyl lactate + acetonitrile mixtures were measured at five temperatures from 283.15 to 323.15 K. Excess molar volumes, partial molar volumes, thermal expansion coefficients, isentropic compressibility and molar refraction values were calculated. It is concluded that deviations from ideality in this system should be assigned to the ability of the smaller acetonitrile molecules to occupy free volume space of ethyl lactate. 相似文献
129.
130.
We study numerically the mean access times for random walks on hybrid disordered structures formed by embedding scale-free
networks into regular lattices, considering different transition rates for steps across lattice bonds (F) and across network shortcuts (f). For fast shortcuts (f/F≫1) and low shortcut densities, traversal time data collapse onto a universal curve, while a crossover behavior that can be
related to the percolation threshold of the scale-free network component is identified at higher shortcut densities, in analogy
to similar observations reported recently in Newman-Watts small-world networks. Furthermore, we observe that random walk traversal
times are larger for networks with a higher degree of inhomogeneity in their shortcut distribution, and we discuss access
time distributions as functions of the initial and final node degrees. These findings are relevant, in particular, when considering
the optimization of existing information networks by the addition of a small number of fast shortcut connections. 相似文献