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31.
Harold M. Bell Deborah B. Bowles Fred Senese 《Magnetic resonance in chemistry : MRC》1981,16(4):285-289
The use of additive parameters for the prediction of NMR chemical shifts is widely practised. However, no correlations are available for highly deshielded methine protons. In this work, methine chemical shifts have been studied using both multiple linear regression analysis and Simplex function minimization in an effort to determine under what limiting circumstances the additivity of shift parameters can be expected to apply. As expected, it was not possible to explain satisfactorily all methine shifts with a single set of substituent parameters. However, if only the deshielded cases were considered (H—CXYZ, where at least two of the three groups X, Y, and Z are electron-withdrawing), a much better set of parameters could be determined. Using a data set of 440 of these deshielded methine shifts, involving 31 different substituents, a standard error of estimate of 0.20 ppm is found for protons spread between 3.0 and 7.5 ppm. 相似文献
32.
The energy functional for the Skyrme density-dependent force is used to calculate the interaction potential between two 16O nuclei. A two-centre harmonic oscillator potential is employed to construct the density and kinetic energy density of the ground state of the combined system and of the separated nuclei. The antisymmetrization effects are investigated. The relative motion of the nuclei is taken approximately into account and the energy dependence of the potential derived from the Skyrme force is presented. 相似文献
33.
Ahmad QR Allen RC Andersen TC D Anglin J Barton JC Beier EW Bercovitch M Bigu J Biller SD Black RA Blevis I Boardman RJ Boger J Bonvin E Boulay MG Bowler MG Bowles TJ Brice SJ Browne MC Bullard TV Bühler G Cameron J Chan YD Chen HH Chen M Chen X Cleveland BT Clifford ET Cowan JH Cowen DF Cox GA Dai X Dalnoki-Veress F Davidson WF Doe PJ Doucas G Dragowsky MR Duba CA Duncan FA Dunford M Dunmore JA Earle ED Elliott SR Evans HC Ewan GT Farine J Fergani H Ferraris AP Ford RJ Formaggio JA Fowler MM 《Physical review letters》2002,89(1):011301
Observations of neutral-current nu interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the nu(e) component of the 8B solar flux is phis(e) = 1.76(+0.05)(-0.05)(stat)(+0.09)(-0.09)(syst) x 10(6) cm(-2) s(-1) for a kinetic energy threshold of 5 MeV. The non-nu(e) component is phi(mu)(tau) = 3.41(+0.45)(-0.45)(stat)(+0.48)(-0.45)(syst) x 10(6) cm(-2) s(-1), 5.3sigma greater than zero, providing strong evidence for solar nu(e) flavor transformation. The total flux measured with the NC reaction is phi(NC) = 5.09(+0.44)(-0.43)(stat)(+0.46)(-0.43)(syst) x 10(6) cm(-2) s(-1), consistent with solar models. 相似文献
34.
35.
The paper outlines the results of an investigation to characterize the response of P75/934 graphite/epoxy tubes with a stacking
sequence of [15/0/±10/0/−15]
s
under pure torsion and combined axial/torsion loading. The experimentally observed nonlinear response and path-dependent
failure are discussed in terms of material nonlinearities at the ply level and first-ply failure loads with the help of an
analytical model.
Paper was presented at the 1989 SEM Spring Conference on Experimental Mechanics held in Cambridge, MA on May 28–June 1. 相似文献
36.
Jason J. Benkoski Steven E. Bowles Ronald L. Jones Jack F. Douglas Jeffrey Pyun Alamgir Karim 《Journal of Polymer Science.Polymer Physics》2008,46(20):2267-2277
The self‐assembly of dispersed polymer‐coated ferromagnetic nanoparticles into micron‐sized one‐dimensional mesostructures at a liquid–liquid interface was reported. When polystyrene‐coated Co nanoparticles (19 nm) are driven to an oil/water interface under zero‐field conditions, long (≈ 5 μm) chain‐like assemblies spontaneously form because of dipolar associations between the ferromagnetic nanoparticles. Direct imaging of the magnetic assembly process was achieved using a recently developed platform consisting of a biphasic oil/water system in which the oil phase was flash‐cured within 1 s upon ultraviolet light exposure. The nanoparticle assemblies embedded in the crosslinked phase were then imaged using atomic force microscopy. The effects of time, temperature, and colloid concentration on the self‐assembly process of dipolar nanoparticles were then investigated. Variation of either assembly time t or temperature T was found to be an interchangeable effect in the 1D organization process. Because of the dependence of chain length on the assembly conditions, we observed striking similarities between 1D nanoparticle self‐assembly and polymerization of small molecule monomers. This is the first in‐depth study of the parameters affecting the self‐assembly of dispersed, dipolar nanoparticles into extended mesostructures in the absence of a magnetic field. © 2008 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys 46: 2267–2277, 2008 相似文献
37.
A. P. Serebrov V. A. Mityukhlyaev A. A. Zakharov T. Bowles G. Greene J. Sromicki 《JETP Letters》1997,66(12):802-808
A new type of source of ultracold neutrons (UCNs) is proposed. The source operates on the basis of a pulsed spallation source.
Solid deuterium makes it possible to obtain UCN density 104 neutrons/cm3 as a result of high gain at low temperatures and the possibility of withstanding high pulsed heat loads as a result of the
high specific heat of solid deuterium.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 765–770 (25 December 1997) 相似文献
38.
We numerically approximate, on the real line, solutions to a large class of parabolic partial differential equations which are “gradient flows” of some energy functionals with respect to the L p -Wasserstein metrics for all p>1. Our method relies on variational principles involving the optimal transport problem with general strictly convex cost functions. 相似文献
39.
Ahmad QR Allen RC Andersen TC Anglin JD Barton JC Beier EW Bercovitch M Bigu J Biller SD Black RA Blevis I Boardman RJ Boger J Bonvin E Boulay MG Bowler MG Bowles TJ Brice SJ Browne MC Bullard TV Bühler G Cameron J Chan YD Chen HH Chen M Chen X Cleveland BT Clifford ET Cowan JH Cowen DF Cox GA Dai X Dalnoki-Veress F Davidson WF Doe PJ Doucas G Dragowsky MR Duba CA Duncan FA Dunford M Dunmore JA Earle ED Elliott SR Evans HC Ewan GT Farine J Fergani H Ferraris AP Ford RJ Formaggio JA Fowler MM 《Physical review letters》2002,89(1):011302
The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8B spectrum, the night minus day rate is 14.0%+/-6.3%(+1.5%)(-1.4%) of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the nu(e) asymmetry is found to be 7.0%+/-4.9%(+1.3%)(-1.2%). A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution. 相似文献
40.
J. N. Abdurashitov V. N. Gavrin S. V. Girin V. V. Gorbachev T. V. Ibragimova A. V. Kalikhov N. G. Khairnasov T. V. Knodel I. N. Mirmov A. A. Shikhin E. P. Veretenkin V. M. Vermul V. E. Yants G. T. Zatsepin T. J. Bowles W. A. Teasdale D. L. Wark J. S. Nico M. L. Cherry B. T. Cleveland R. Davis Jr. K. Lande P. S. Wildenhain S. R. Elliott J. F. Wilkerson 《Physics of Atomic Nuclei》2000,63(6):943-950
The solar-neutrino-capture rate measured by the Russian-American Gallium Experiment on metallic gallium during the period from January 1990 to December 1997 is (67.2 ?7.0?3.0 +7.2+3.5 ) SNU, where the uncertainties are statistical and systematic, respectively. This result represents a 7σ depression in the neutrino flux in relation to the predicted standard-solar-model rates. The experimental procedures used and data analysis are presented. 相似文献