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61.
Matthew L. Read Andreas Krapp Pedro O. Miranda Lise-Lotte Gundersen 《Tetrahedron》2012,68(7):1869-1885
Arenes and heteroarenes carrying a halogen and an amino- or hydroxy group have been converted to allylamino- or allyloxy-furyl-(hetero)arenes. These compounds underwent IMDAF reactions to give complex fused polycyclic heterocycles. The reactivity of the substrates was highly dependent on the detailed substitution pattern, however cyclizations occurred with high stereoselectivity in most cases. Experimental findings regarding reactivity and stereoselectivity were supported by calculations. 相似文献
62.
Cristina Stere Mihaela‐Corina Iovu Horia Iovu Adrian Boborodea Dan Sorin Vasilescu Simon James Read 《先进技术聚合物》2001,12(5):300-305
The polymerization of ?‐caprolactone initiated by two catalyst systems was studied: (1) carbazole‐potassium in the presence of 18‐crown‐6 ether and (2) NdCl3/TBP/TIBA (neodymiumtrichloride/tri‐n‐butyl‐phosphate/triisobutylaluminium) at the molar ratio 1/3/1. For both initiator systems conversion/time plots were determined and the polymers were characterized by IR, GPC and by 1H‐ and 13C?NMR spectroscopy. Polyesters with the highest molecular weight (M n?44 000 g/mol) were obtained for the polymerizations initiated by the carbazole‐potassium/18‐crown‐6 ether system. The features of the polymerization initiated by the carbazole‐potassium/18‐crown‐6 ether system are discussed on the basis of a simple scheme. The nature of this polymerization is non‐living. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
63.
Advani R. Hogge J.P. Kreischer K.E. Pedrozzi M. Read M.E. Sirigiri J.R. Temkin R.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(6):943-950
We report experimental results on a megawatt power level, 140-GHz coaxial gyrotron oscillator. The gyrotron has an inverted magnetron injection gun (IMIG) designed for operation at up to 95 kV and 88 A. The IMIG has an inner grounded anode which extends from the center of the gun down through the entire length of the tube including the cavity and collector. The IMIG was tested at up to 105 kV and 93 A in 3 μs pulses, achieving an electron beam power of 10 MW. The output power from the coaxial gyrotron cavity was transported to an internal mode converter and a single mirror that coupled the power out transversely from the tube axis. A maximum output power of up to 1 MW was obtained in the TE27,11 mode at 142 GHz at an efficiency of 16%, about one half of the design efficiency. The reduced efficiency was attributed to nonuniformity of the cathode emission and the sensitivity to the relative alignment of the electron gun, coaxial insert, and cavity. The cathode emission over the azimuthal angle was measured for two cathodes and was shown to be nonuniform due to both temperature and emitter work function nonuniformity. The gyrotron was also tested in two alternate configurations: 1) with the internal mode converter removed (axial output), and 2) with both the internal converter and the coaxial insert removed (empty cavity). In operation in the empty cavity configuration, which is equivalent to a conventional gyrotron oscillator, output power of up to 0.9 MW was observed 相似文献
64.
The genome sequence of the rice blast fungus Magnaporthe grisea 总被引:8,自引:0,他引:8
Dean RA Talbot NJ Ebbole DJ Farman ML Mitchell TK Orbach MJ Thon M Kulkarni R Xu JR Pan H Read ND Lee YH Carbone I Brown D Oh YY Donofrio N Jeong JS Soanes DM Djonovic S Kolomiets E Rehmeyer C Li W Harding M Kim S Lebrun MH Bohnert H Coughlan S Butler J Calvo S Ma LJ Nicol R Purcell S Nusbaum C Galagan JE Birren BW 《Nature》2005,434(7036):980-986
Magnaporthe grisea is the most destructive pathogen of rice worldwide and the principal model organism for elucidating the molecular basis of fungal disease of plants. Here, we report the draft sequence of the M. grisea genome. Analysis of the gene set provides an insight into the adaptations required by a fungus to cause disease. The genome encodes a large and diverse set of secreted proteins, including those defined by unusual carbohydrate-binding domains. This fungus also possesses an expanded family of G-protein-coupled receptors, several new virulence-associated genes and large suites of enzymes involved in secondary metabolism. Consistent with a role in fungal pathogenesis, the expression of several of these genes is upregulated during the early stages of infection-related development. The M. grisea genome has been subject to invasion and proliferation of active transposable elements, reflecting the clonal nature of this fungus imposed by widespread rice cultivation. 相似文献
65.
A Solution to the Invariant Subspace Problem on the Space l1 总被引:2,自引:0,他引:2
In this paper, which is a sequel to our earlier paper [1], weslightly modify the methods used in [1] to produce a continuouslinear operator on l1 with no nontrivial closed invariant subspace. 相似文献
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69.
Methods for the analysis of thiodiglycol sulphoxide, a metabolite of sulphur mustard, in urine using gas chromatography-mass spectrometry. 总被引:1,自引:0,他引:1
Two methods have been developed for the analysis of thiodiglycol sulphoxide, a metabolite of sulphur mustard, in urine. The first method recovers thiodiglycol sulphoxide from urine by extraction from a solid absorbent tube and clean up on Florisil. In the second method thiodiglycol sulphoxide is reduced to thiodiglycol with acidic titanium trichloride prior to extraction. This method detects thiodiglycol, thiodiglycol sulphoxide, and their acid-labile esters, as the single analyte thiodiglycol. In both cases the recovered analytes were converted to the bis(pentafluorobenzoyl) derivative of thiodiglycol and detected by gas chromatography-mass spectrometry using negative ion chemical ionisation. The limits of detection were 1 ng per 0.5-ml sample of urine. Urine from five normal human subjects showed low background levels of thiodiglycol sulphoxide in the range 2-8 ng/ml. However, a sixth subject was found to be excreting levels of thiodiglycol sulphoxide as high as 36 ng/ml. The first method has been used in toxicokinetic studies of sulphur mustard and the second method is intended to be used for the retrospective confirmation of mustard poisoning in casualties of chemical warfare. 相似文献
70.
A highly enantio- and diastereoselective intramolecular Stetter reaction has been developed. Subjection of alpha,alpha-disubstituted Michael acceptors to an asymmetric intramolecular Stetter reaction results in a highly enantioselective conjugate addition and a diastereoselective proton transfer. Available evidence suggests the diastereoselective protonation occurs via intramolecular delivery to the sterically more hindered face of the enolate. The scope of the trisubstituted Michael acceptors has been examined and found to be broad with respect to the size of the alpha-substituent and nature of the Michael acceptor. Aliphatic and aromatic aldehydes were examined and found to afford the desired product in good overall yield with high enantio- and diastereoselectivity. 相似文献