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21.
H. Kurreck S. Aguirre H. Dieks J. Gtschmann J. v. Gersdorff H. Newman H. Schubert M. Speck T. Stabingis J. Sobek P. Tian A. Wiehe 《Radiation Physics and Chemistry》1995,45(6):853-865
Porphyrin quinones (P-Qs), covalently linked via different aliphatic bridges, have been synthesized and studies in their (porphyrin) cationic and (semiquinone) anionic radical states by EPR, ENDOR and TRIPLE resonance techniques. Electron transfer (ET) from the porphyrin donor to the quinone acceptor could be observed by time-resolved picosecond fluorescence spectroscopy (singlet ET) and by time-resolved EPR spectroscopy (triplet ET) in isotropic fluid solution and in anisotropic media (liquid crystals and reversed micelles). Steady-state in situ photoexcitation of P-Qs in CTAB cationic reversed micelles yielded the corresponding semiquinone radical anions. In TRITON X-100 reversed micelles both the radical cation of the porphyrin and the radical anion of the semiquinone could be detected, which occured in complete emission. In covalently linked porphyrin flavins ET from the photoexcited porphyrin fragment to the flavin and, in addition, energy transfer from the photoexcited flavin to the porphyrin could be observed. 相似文献
22.
M.J. Boylan J. Bellerby Josephine Newman A.R. Manning 《Journal of organometallic chemistry》1973,47(2):C33-C35
Whereas Co2(CO)8 and RNC (R= Me, Et, and Cy) react to give mixtures of [(RNC)5Co] [Co(CO)4] and the covalent, carbonyl-bridged [(RNC)mCo2(CO)8?m] derivatives (m = 1–3), [(π-dienyl)Fe(CO)2]2 give only [(π-dienyl)2Fe2(CO)4?n(CNR)n] complexes (dienyl = C5H5, MeC5H4 and C9H7; n = 1–2) that exist in solution as mixtures of cis- and trans-CO- and RNC-bridged tautomers with the μ-RNC species decreasing in importance as the bulk of R increases. 相似文献
23.
Charles M. Newman 《Constructive Approximation》1991,7(1):389-399
LetV(t) be the even function on (–, ) which is related to the Riemann xi-function by (x/2)=4
–
exp(ixt–V(t))dt. In a proof of certain moment inequalities which are necessary for the validity of the Riemann Hypothesis, it was previously shown thatV'(t)/t is increasing on (0, ). We prove a stronger property which is related to the GHS inequality of statistical mechanics, namely thatV' is convex on [0, ). The possible relevance of the convexity ofV' to the Riemann Hypothesis is discussed.Communicated by Richard Varga. 相似文献
24.
David J. Barsky Geoffrey R. Grimmett Charles M. Newman 《Probability Theory and Related Fields》1991,90(1):111-148
Renormalization arguments are developed and applied to independent nearest-neighbor percolation on various subsets of
d
,d2, yielding:
Corollaries of these results include uniqueness of the infinite cluster for such 's and sufficiency of the following for proving continuity of the full-space phase transition: showing that percolation in the full-space at densityp implies percolation in the half-space at thesame density. 相似文献
| Equality of the critical densities,p c (), for a half-space, quarter-space, etc., and (ford>2) equality with the limit of slab critical densities. |
| Continuity of the phase transition for the half-space, quarter-space, etc.; i.e., vanishing of the percolation probability, (p), atp=p c (). |
25.
Sibilant groove place and width were initially examined during [s] [s] in isolation and in CV and VC syllables. The [s] was found to be produced through a 6- to 8-mm-wide groove near the front of the alveolar ridge by one talker and near the back of the ridge by the other. [s] was produced through a 10- to 12-mm groove behind the posterior border of the alveolar ridge by both. In the second experiment three subjects used visual articulatory feedback to vary sibilant groove width and place systematically. One subject was able to do this with comparatively few retrials; one had difficulty with certain targeted grooves; one had difficulty with many targeted grooves. The noises generated were replayed to 14 listeners who labeled them as "s," "probably s," "probably sh," or "sh." They usually heard the sound as [s] when the grooves were narrow and near the front of the alveolar process, [s] when the groove was wider and behind the alveolar process. Noise through grooves that matched natural speech places and widths usually produced higher listener recognition scores. Exceptions were found when the subjects had unusual difficulty in achieving stipulated groove widths and places. 相似文献
26.
27.
28.
R. P. A. C. Newman 《General Relativity and Gravitation》1981,13(3):257-282
Results are established concerning perturbations of each empty Robertson-Walker space-time (M, g) with a nonvanishing cosmological constant. The perturbed space-times have the general form (
) with
an extension ofM, and
lying in an open neighborhood of g in a type ofW
m
topology. These results indicate that large classes of such perturbations give rise to space-times which suffer from one of two types of incompleteness. 相似文献
29.
C. M. Newman 《Communications in Mathematical Physics》1981,79(1):133-140
The renormalized, dimensionless 4-point coupling constant of scalar one dimensional field theories is maximized uniquely by the critical point theories (obtainable as the scaling limit of 4 models). The renormalized coupling constant of certain scalar one dimensional lattice field theories is maximized uniquely (for fixed correlation length) by the corresponding spin-1/2 model.Alfred P. Sloan Research Fellow, on leave from Indiana University. Research supported in part by NSF Grant MCS 77-20683 and by the U.S.-Israel Binational Science Foundation 相似文献
30.
C.G. Newman B.N. Diel D.P. Paquin M.A. Ring 《Journal of organometallic chemistry》1977,137(3):281-286
Methylation of SiH4, MeSiH3, Si2H6, GeH4 and B2H6, but not of PH3 or AsH3, was observed during reaction (230–324°C) with GaMe3. The products from the SiH4 and Si2H6 reactions were MeSiH3, Me2SiH2 and Me3SiH. The GeH4-derived products were similar, with Me4Ge also being formed. The only methylated products from B2H6 was BMe3. The silane reactions were surface-catalyzed (presumably by surface hydroxyl groups), while those of GeH4 and B2H6 may have occurred via gas-phase free radical processes. 相似文献