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41.
Novel diacetylene macrocycles 1 and 2 bearing dibenzylphosphine oxide were synthesised via Eglinton acetylenic intramolecular coupling. The X-ray analysis of crystals of macrocycles 1 and 2 demonstrated that the better-aligned tubular supramolecular structure was formed in macrocycle 1 than in macrocycle 2, which provided the possibility of diacetylene topochemical polymerisation in solid state of macrocycle 1. UV–vis, Raman spectroscopy and X-ray analysis indicated that the crystals of macrocycle 1 could undergo topochemical diacetylene polymerisation only on their surface by light irradiation; differential scanning calorimetry, solid-state 13C NMR spectroscopy and solubility test demonstrated that the crystals of macrocycle 1 could undergo diacetylene topochemical polymerisation inside solid by heat. As expected, based on the topological analysis of crystal structure, the crystals of macrocycle 2 could not undergo diacetylene topochemical polymerisation either by light irradiation or heat. 相似文献
42.
The authors consider a family of finite-dimensional Lie superalgebras of O-type
over an algebraically closed field of characteristic p > 3. It is proved that the Lie superalgebras
of O-type are simple and the spanning sets are determined. Then the spanning
sets are employed to characterize the superderivation algebras of these Lie superalgebras.
Finally, the associative forms are discussed and a comparison is made between these Lie
superalgebras and other simple Lie superalgebras of Cartan type. 相似文献
43.
Molecular dynamics simulations have been performed to study the potential of mean force (PMF) between passivated gold nanoparticles (NPs) in supercritical CO(2) (scCO(2)). The nanoparticle model consists of a 140 atom gold nanocore and a surface self-assembled monolayer, in which two kinds of fluorinated alkanethiols were considered. The molecular origin of the thermodynamics interaction and the solvation effect has been comprehensively studied. The simulation results demonstrate that increasing the solvent density and ligand length can enhance the repulsive feature of the free energy between the passivated Au nanoparticles in scCO(2), which is in good agreement with previous experimental results. The interaction forces between the two passivated NPs have been decomposed to reveal various contributions to the free energy. It was revealed that the interaction between capping ligands and the interaction between the capping ligands and scCO(2) solvent molecules cooperatively determine the total PMF. A thermodynamic entropy-energy analysis for each PMF contribution was used to explain the density dependence of PMF in scCO(2) fluid. Our simulation study is expected to provide a novel microscopic understanding of the effect of scCO(2) solvent on the interaction between passivated Au nanoparticles, which is helpful to the dispersion and preparation of functional metal nanoparticles in supercritical fluids. 相似文献
44.
45.
This study compared one lesson across four U.S. “traditional” textbook series, two U.S. reform‐based textbook series, and one Chinese mathematics textbook series in teaching the connection between multiplication and division. The results showed the differences across U.S. and Chinese lessons in both the teaching and the practice parts of the lesson across three dimensions (i.e., problem schemata, response requirement, and algebra readiness). In particular, the Chinese lesson's penetrating analysis or explanation of the topic is reflected in its deliberately constructed examples and wide range of problems (pertaining to problem types and difficulty levels) present in the teaching and practice sections of the lesson. None of analyzed U.S. lessons are comparable with the Chinese lesson with respect to the breadth and depth in teaching the topic. A deliberate emphasis, both arithmetically and algebraically, on problem schema acquisition as found in the Chinese lesson represents a promotion of symbolic or higher order of conceptual understanding. The findings are discussed within the context of teaching big ideas through problem schemata acquisition and the importance of symbolic level of conceptual understanding. 相似文献
46.
All-atomic molecular dynamics simulations have been performed to study the interfacial structural and dynamical properties of passivated gold nanoparticles in supercritical carbon dioxide (scCO(2)). Simulations were conducted for a 55-atom gold nanocore with thiolated perfluoropolyether as the packing ligands. The effect of solvent density and surface coverage on the structural and dynamical properties of the self-assembly monolayer (SAM) has been discussed. The simulation results demonstrate that the interface between nanoparticle and scCO(2) solvent shows a depletion region due to the preclusion of SAM. The presence of scCO(2) solvent around the passivated Au nanoparticle can lead to an enhanced extension of the surface SAM. Under full coverage, the structure and conformation of SAM are insensitive to the density change of scCO(2) fluid. This simulation results clarify the microscopic solvation mechanism of passivated nanoparticles in supercritical fluid medium and is expected to be helpful in understanding the scCO(2)-based nanoparticle dispersion behavior. 相似文献
47.
A novel route for a preparation of eccentric Au-titania core-shell nanoparticles using gold nanoparticles (AuNPs) with block copolymer shells as a template is reported. AuNPs with poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) block copolymer shells are first prepared by UV irradiation of the solution of PVP-b-PEO/HAuCl(4) complexes. Then the sol-gel reaction of titanium tetra-isopropoxide (TTIP) selectively on the surfaces of AuNPs leads to Au-titania core-shell composite nanoparticles. The eccentric Au-titania core-shell nanoparticles are obtained from the Au-titania core-shell composite nanoparticles by removal of organic interlayer by UV treatment. Photocatalytic activities of the resulting eccentric core-shell nanoparticles are investigated in terms of the degradation of methylene blue (MB). The results show that the eccentric core-shell structures endow the catalyst with greatly enhanced photocatalytic activity. 相似文献
48.
Let F be the underlying base field of characteristic p > 3 and denote by Γō the even part of the finite-dimensional Lie superalgebra Γ.We give the generator sets of the Lie algebra Γō.Using certain properties of the canonical tori of Γō,we describe explicitly the derivation algebra of Γō. 相似文献
49.
50.
通过在 N-甲基吡咯烷酮(NMP)有机溶剂中锌电极与 CuI之间的置换反应,在锌电极上原位构建了一层致密且疏水的铜金属保护层(Cu@Zn)。铜金属保护层能有效地隔离锌电极与电解液的接触,减少锌电极-电解液界面的析氢和腐蚀等副反应。同时,铜金属保护层还具有较好的亲锌性,更小的界面电阻,更低的成核能垒,有利于锌离子均匀沉积,从而有效抑制了锌枝晶的生成。Cu@Zn对称电池实现了超过 1 700 h(1 mA·cm-2)和 1 330 h(3 mA·cm-2)的循环寿命。采用商用 MnO2与之匹配得到的Cu@Zn||MnO2全电池不仅在1 A·g-1下具有168.5 mAh·g-1的可逆比容量,还可稳定循环2 000次以上 相似文献