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91.
Steven J. Shirbin Steven C. Zammit Sebastian M. Marcuccio Spencer J. Williams 《Tetrahedron letters》2010,51(22):2971-1759
Aryl imidazylates are effective electrophilic partners in copper-free palladium-catalyzed Hiyama and Sonogashira cross-coupling reactions. The Sonogashira cross-coupling of estron-3-yl imidazylate afforded the corresponding phenylacetylene derivative in excellent yield. 相似文献
92.
Spencer Bloch Hélène Esnault Dirk Kreimer 《Communications in Mathematical Physics》2006,267(1):181-225
The appearance of multiple zeta values in anomalous dimensions and β-functions of renormalizable quantum field theories has given evidence towards a motivic interpretation of these renormalization group functions. In this paper we start to hunt the motive, restricting our attention to a subclass of graphs in four dimensional scalar field theory which give scheme independent contributions to the above functions. 相似文献
93.
Moreland L.D. Schamiloglu E. Lemke W. Korovin S.D. Rostov V.V. Roitman A.M. Hendricks K.J. Spencer T.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(5):554-565
The Sinus-6, a high-power relativistic repetitively-pulsed electron beam accelerator, is used to drive various slow wave structures in a BWO configuration in vacuum. Peak output power of about 550 MW at 9.45 GHz was radiated in an 8-ns pulse. We describe experiments which study the relative efficiencies of microwave generation from a two-stage nonuniform amplitude slow wave structure and its variations without an initial stage. Experimental results are compared with 2.5 D particle-in-cell computer simulations. Our results suggest that prebunching the electron beam in the initial section of the nonuniform BWO results in increased microwave generation efficiency, Furthermore, simulations reveal that, in addition to the backward propagating surface harmonic of the TM01 mode, backward and forward propagating volume harmonics with phase velocity twice that of the surface harmonic play an important role in high-power microwave generation and radiation 相似文献
94.
We find the asymptotic number of connected graphs with k vertices and k−1+l edges when k,l approach infinity, re-proving a result of Bender, Canfield and McKay. We use the probabilistic method, analyzing breadth-first search on the random graph G(k,p) for an appropriate edge probability p. Central is the analysis of a random walk with fixed beginning and end which is tilted to the left. 相似文献
95.
96.
J. N. Spencer Travis F. Ganunis Abrahim I. Zafar Shaym Puppala James L. Ealy Larry J. Fenton Sunita Gupta C. H. Yoder J. E. Mihalick 《Journal of solution chemistry》1992,21(9):1005-1012
Equilibrium constants and enthalpies of hydrogen-bond formation of mcresol to various cyclic (crown) and acyclic polyethers have been determined in benzene solvent. Equilibrium constants indicated no evidence for an operative macrocyclic effect; the relationship between the increasing size of the equilibrium constant and the number of ether oxygens was rationalized with a simple statistical thermodynamic model. Enthalpies of interactions ranged between –19 and –23 kJ-mol–1. In agreement with PCILO calculations, enthalpies of interaction were essentially independent of the number of oxygen atoms in the ether; no significant difference in enthalpies of interaction between cyclic and acyclic ethers was found. 相似文献
97.
98.
Efficient algorithms for finding minimum spanning trees in undirected and directed graphs 总被引:5,自引:0,他引:5
Recently, Fredman and Tarjan invented a new, especially efficient form of heap (priority queue). Their data structure, theFibonacci heap (or F-heap) supports arbitrary deletion inO(logn) amortized time and other heap operations inO(1) amortized time. In this paper we use F-heaps to obtain fast algorithms for finding minimum spanning trees in undirected
and directed graphs. For an undirected graph containingn vertices andm edges, our minimum spanning tree algorithm runs inO(m logβ (m, n)) time, improved fromO(mβ(m, n)) time, whereβ(m, n)=min {i|log(i)
n ≦m/n}. Our minimum spanning tree algorithm for directed graphs runs inO(n logn + m) time, improved fromO(n log n +m log log log(m/n+2)
n). Both algorithms can be extended to allow a degree constraint at one vertex.
Research supported in part by National Science Foundation Grant MCS-8302648.
Research supported in part by National Science Foundation Grant MCS-8303139.
Research supported in part by National Science Foundation Grant MCS-8300984 and a United States Army Research Office Program
Fellowship, DAAG29-83-GO020. 相似文献
99.
S. A. Dodds T. L. Estle G. A. Gist Qiuan Zhu S. L. Rudaz D. P. Spencer E. J. Ansaldo J. H. Brewer D. R. Noakes R. Keitel 《Hyperfine Interactions》1986,32(1-4):869-872
Magnetic resonance of a spin system which is acted upon by a large near-resonance oscillating magnetic field transverse to
a static field has been studied experimentally and theoretically for many years. The technique of DEMUR (Double Electron Muon
Resonance) has many advantages for such studies. This paper will describe the results of an experiment to study the precession
of the muonium triplet near magnetic resonance using DEMUR. 相似文献
100.