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David Charles Pepper 《Macromolecular rapid communications》1996,17(3):157-161
Recently rediscovered evidence supports the conclusion that the bimodality of molarmass distributions in polystyrenes initiated by HCIO4 is not, as widely believed, the consequence of independent chain-growth by different propagating species, but originates from lack of uniformity in reagent concentrations during the earliest stage of the polymerization, where the time-scale of the growth and decay of the transient ionic population is short compared with that of mixing, in conventional preparative experiments. 相似文献
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S. Cin D. D. Arnone H. P. Hughes D. Whittaker M. Pepper D. A. Ritchie 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We show that the presence of InAs dots embedded in a host GaAs quantum well containing a two-dimensional electron gas dramatically modifies the cyclotron resonance (CR). Far-infrared CR measurements show two modes with different dispersions with applied magnetic field B. The lower-frequency mode, with a sub-linear dependence on B, is identified as a CR at low B, developing into a skipping orbit around the dot perimeters at higher B. This has not been previously observed for a system with randomly distributed scatterers. The higher-frequency mode is identified as a magnetoplasmon localised by the confining effect of the arrays of repulsive potentials due to the dots in the well. 相似文献
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D. C. Pepper 《Macromolecular Symposia》1992,60(1):267-277
The lecture reviews recent studies on vinyl and vinylidene compounds, chiefly alkyl cyanoacrylates. It emphasizes the kinetics, especially the distinctive SINT (slow-initiation-no-termination) pattern, and the composite mechanism of initiation by tertiary amines. The need for corroboration of interpretations, clarification of ambiguities and extensions is emphasized. 相似文献
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Total Synthesis Establishes the Biosynthetic Pathway to the Naphterpin and Marinone Natural Products
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Lauren A. M. Murray Dr. Shaun M. K. McKinnie Dr. Henry P. Pepper Reto Erni Dr. Zachary D. Miles Michelle C. Cruickshank Dr. Borja López‐Pérez Prof. Bradley S. Moore Dr. Jonathan H. George 《Angewandte Chemie (International ed. in English)》2018,57(34):11009-11014
The naphterpins and marinones are naphthoquinone meroterpenoids with an unusual aromatic oxidation pattern that is biosynthesized from 1,3,6,8‐tetrahydroxynaphthalene (THN). We propose that cryptic halogenation of THN derivatives by vanadium‐dependent chloroperoxidase (VCPO) enzymes is key to this biosynthetic pathway, despite the absence of chlorine in these natural products. This speculation inspired a total synthesis to mimic the naphterpin/marinone biosynthetic pathway. In validation of this biogenetic hypothesis, two VCPOs were discovered that interconvert several of the proposed biosynthetic intermediates. 相似文献