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71.
Consider a labeled convex n-gon in the plane and a point x in general position in the interior. We associate with this a collection (x) of 3-element sets, namely those 3-element subsets of the vertices which contain x in their interior. We investigate the problem of characterizing those collections of subsets which can be represented in this matter. We give a complete characterization of this and a related problem.School of Mathematics, University of Minnesota, Minneapolis, MN 55455. This work was supported in part by NSF grant DMS-8700995.Department of Mathematics, University College London, Gower Street, London, WC1E 6BT, England. Work done while Hill Visiting Professor at the University of Minnesota. 相似文献
72.
Paul McGill 《Aequationes Mathematicae》1990,39(1):114-119
We solve the functional equation
相似文献
73.
Absolute OH· concentrations and relative H-atom and O-atom profiles have been measured in a laminar, co-flowing methane/air diffusion flame burning at atmospheric pressure. Laser absorption and laser-induced fluorescence methods were used to probe the A
2 X
2IIitransition in OH·. The maximum OH· concentration is found to be 1.8±0.2 ×1016 cm–3 (mole fraction =5.0×10–3) at a temperature of 2080 K, which is twice the value calculated assuming local total equilibrium but less than half that predicted from partial equilibrium (O2+H2 2OH·). Multiphoton ionization (2+1 process at 243 nm) has been used to detect H atoms, while laser-induced fluorescence at 845 nm excited by two-photon absorption at 226 nm was employed to observe O atoms. In both cases it was found that low photon intensities (2×108W/cm2) and a retroreflected beam, Doppler-free geometry was required in order to avoid the photolytic production of the species of interest. For all of the concentration profile data it is necessary to correct the raw signals for variations in collisional quenching. In the case of the multiphoton ionization measurements the variation in electron detection sensitivity as a function of flame position must be accounted for as well. Establishing absolute H-atom and O-atom concentrations is discussed in terms of partial equilibrium considerations and detailed flame structure calculations.Formerly the National Bureau of Standards 相似文献
74.
Paul McGill 《Probability Theory and Related Fields》1989,83(3):355-389
Summary We study how Brownian motion behaves under time change by a fluctuating additive functionalA
t
, in particular letting be the first passage time ofA
t
to zero we computeP
–x[B
dy] explicitly in certain cases. The calculation is not an easy one, our method uses the Désiré André relation for the overshoot of a Lévy process and depends on some elliptic function identities. This paper only considers the one boundary case whereA
t
is increasing (resp. decreasing) on the positive (resp. negative) half line. 相似文献
75.
Dudley Paul Johnson 《Journal of Theoretical Probability》1989,2(4):433-436
We show that under suitable conditions $$\begin{gathered} E_x f\left\{ {a + \int_0^t \beta \left[ {b + \int_0^s {\alpha \left( {X_r } \right)dr, c + s, X_s } } \right]ds, b + \int_0^t {\alpha \left( {X_s } \right)ds, c + t, X_t } } \right\} \hfill \\ = e^{tG} f\left[ {a, b, c, x} \right] \hfill \\ \end{gathered} $$ whereX t is a Brownian motion andG is the generator of a (C 0) contraction semigroupe tG. 相似文献
76.
S. Bamidele Sanni H. Behm Paul T. Beurskens E. Kayode Adesogan James I. Durodola 《Journal of chemical crystallography》1988,18(5):575-582
A new cytotoxic macrocyclic diterpenoid named Japodagrol, C20H28O4, has been isolated from the ornamental plantJatropha podagrica, family Euphorbiaceae, grown in Nigeria. The structure of the title compound, C20H28O4, was solved by X-ray analysis.M
r
=332.44, monoclinic space groupC2,a=23.285(4),b=6.5105(12),c=12.505(3) Å,=98.504(17),V=1874.8 Å3,Z=4,D
c
=1.178 Mg/m3. CuK radiation (graphite crystal monochromator, =1.54184 A), (CuK)=6.13 cm–1,F(000)=720,T=290 K. Final conventionalR factor=0.035,R
w
=0.038 for 3349 observed reflections. The structure was solved with the programDirdif. The 5-membered ring is closed to a half-chair form. The compound contains inter- and intramolecular hydrogen bonds. 相似文献
77.
In the absence of any trapping agent, stable neopentyl-Pd intermediates can terminate a catalytic cycle by undergoing a regioselective C-H activation, leading to various spiro or fused cyclopropane derivatives in a straightforward manner. If the neopentyl-Pd intermediate contains a heteroatom at a suitable position, C-H activation does not occur and stable palladacycles are isolated. 相似文献
78.
M. Jonathan Fray Paul Allen Paul R. Bradley Clare E. Challenger Michael Closier Tim J. Evans Mark L. Lewis John P. Mathias Carly L. Nichols Yvonne M. Po-Ba Hayley Snow Mark H. Stefaniak Hannah V. Vuong 《Tetrahedron》2006,62(29):6869-6875
The synthesis of ten substituted aminomethylene tetrahydro-isoquinolines is described, proceeding in eight steps from 5-hydroxyisoquinoline via reductive amination of N-Boc tetrahydro-isoquinoline 5-carboxaldehyde. Likewise, reductive amination was used to prepare four substituted dihydro-isoindoles from the corresponding aldehyde. The dihydro-isoindole ring system was conveniently accessed via a 2+2+2 cycloaddition reaction. 相似文献
79.
80.
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