排序方式: 共有37条查询结果,搜索用时 15 毫秒
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A new, highly efficient synthesis of chiral β2,3-disubstituted-β-amino acid derivatives has been developed, based on an allylation procedure employing allene and a catalytic Pd/In bimetallic process. 相似文献
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Joseph W. McCaffrey Dimitrios A. Papaconstantopoulos 《Solid State Communications》1974,14(11):1055-1058
The K X-ray absorption spectrum of calcium has been calculated using the results of a self-consistent energy band calculation by the augmented plane wave method. The computed spectrum is in good agreement with experiment. 相似文献
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Robert R. McCaffrey Paras N. Prasad Mark Fornalik Robert Baier 《Journal of Polymer Science.Polymer Physics》1985,23(8):1523-1532
Coherent this films of poly[bis(p-toluene sulfonate) diacetylene] were successfully formed by modified Langmuir–Blodgett techniques using two methods: (i) Photopolymerization of the monomer film at the gas/liquid interface and then transfer to a solid substrate, and (ii) transfer of the monomer film to the solid substrate and subsequent photopolymerization on the substrate itself. The films thus obtained were characterized by traditional force–area isotherms while on pure water subphases. Segments were transferred at either 1 or 10 dyn/cm surface pressure, in different stages of photopolymerization, to glass or germanium substrates. The films on the substrate were characterized by the methods of multiple attenuated-internal-reflection infrared spectroscopy, ellipsometry, contact-potential measurement, and laser Raman spectroscopy. Our results show that the films are multimolecular and about 100 Å thick. Of special interest were the observation of significant anisotropy of oriented dipoles and the ability to obtain excellent spectral data for these very thin oriented films. Raman spectroscopic features are similar to those observed for the bulk polymer, even in the low-frequency region. Polarized Raman spectroscopy confirmed the presence of local anisotropy in these films. 相似文献
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2-(MeR1CCR2)-and 2-(CH2CR1CH2CH2)-pyridine (R1,R2 = H or Me) undergo 1,2-double-bond shifts and 2-(CH2CHCH2CH2CH2)-pyridine undergoes a 1,3-double-bond shift on displacement of norbornadiene from [M(CO)4norb] (M = Cr, Mo or W) to give complexes of the type [M(CO)4LL'] (LL' = 2-(allyl)or 2-(substituted allyl)-pyridine), which do not exhibit conformational isomerism involving the plane of the coordinated olefin. 相似文献
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Ronald Grigg Shaun McCaffrey Visuvanathar Sridharan Colin W.G. Fishwick Colin Kilner Stewart Korn Kevin Bailey John Blacker 《Tetrahedron》2006,62(52):12159-12171
An efficient synthesis of both R- and S-enantiomers of 2-arylallyl-α-amino acids via a diastereoselective Pd/In mediated catalytic allylation of chiral N-sulfinyl-α-imino esters is described. The potential for further enhancement of molecular complexity and creating contiguous chiral centres by interfacing these processes with catalytic cyclisation–anion capture methodology is demonstrated. 相似文献
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A.S. Sachrajda Y. Feng R.P. Taylor R. Newbury P.T. Coleridge J.P. McCaffrey 《Superlattices and Microstructures》1996,20(4):651-656
We have fabricated a device which can be transformed from a Corbino to a two terminal Hall bar geometry by the activation of a single electrostatic gate. The behaviour in the Hall bar mode is both quantitatively and qualitatively in disagreement with predictions of the Landauer–Buttiker formula. The origin of the disagreement relates to the ‘ideal contact’ assumption implicit in the Landauer–Buttiker formula which breaks down under the novel conditions of this experiment. 相似文献
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The synthesis and study of metallic nanoparticles are of continued and significant interest, with applications in materials science, catalysis, and medicine. The properties of metallic nanoparticles depend strongly on their particle size, shape, and interparticle distances. It is therefore desirable for the synthesis of metallic nanoparticles to be controlled for specific shapes and sizes. The rapid development in this research area has attracted intense interest from researchers with diverse expertise, and numerous methods towards the synthesis of monodisperse nanoparticles have been reported. In this Focus Review, we provide an overview of recent progress in the development of the template synthesis of metallic nanoparticles using closed‐shell structures, including biological molecules/assemblies and cage molecules. 相似文献
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Main chain polymeric radicals from several acrylic polymers, produced by laser flash photolysis at 248 nm in liquid solution, have been studied using direct detection time-resolved electron paramagnetic resonance (TREPR) spectroscopy at 9.5 GHz. Highly isotactic poly(methyl methacrylate) (i-PMMA) shows a sharp, well-resolved spectrum at about 95 degrees C. Using synthetic methodology to disrupt the tacticity of i-PMMA, we observed different fast-motion hyperfine coupling constants for the main chain radicals. By raising the temperature of observation, we returned the coupling constants to the same value as those in the highly isotactic sample. This result is related qualitatively to the degree of stiffness of the polymer chains as a function of tacticity. The concept is tested further by comparison to two other acrylic polymers with bulky side chains: poly(fluorooctyl methacrylate) (PFOMA) and poly(adamantyl methacrylate) (PAMA), whose main chain radicals show significant line broadening even at 110 degrees C. Solvent effects on both spectral appearance (the alternating line-width effect) and kinetic decays (attributed to T1 relaxation) are also presented and discussed in terms of main chain conformational motion. 相似文献
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