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41.
Androić D Armstrong DS Arvieux J Bailey SL Beck DH Beise EJ Benesch J Benmokhtar F Bimbot L Birchall J Bosted P Breuer H Capuano CL Chao YC Coppens A Davis CA Ellis C Flores G Franklin G Furget C Gaskell D Gericke MT Grames J Guillard G Hansknecht J Horn T Jones MK King PM Korsch W Kox S Lee L Liu J Lung A Mammei J Martin JW McKeown RD Micherdzinska A Mihovilovic M Mkrtchyan H Muether M Page SA Papavassiliou V Pate SF Phillips SK Pillot P Pitt ML Poelker M Quinn B Ramsay WD Real JS Roche J 《Physical review letters》2012,108(12):122002
The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Δ)- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d(Δ)- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A(γ)-=-5.2 to +5.2 ppm. The measurement performed in this work leads to A(γ)-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V(ud)/V(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering. 相似文献
42.
Godden TM Quilter JH Ramsay AJ Wu Y Brereton P Boyle SJ Luxmoore IJ Puebla-Nunez J Fox AM Skolnick MS 《Physical review letters》2012,108(1):017402
We demonstrate coherent optical control of a single hole spin confined to an InAs/GaAs quantum dot. A superposition of hole-spin states is created by fast (10-100?ps) dissociation of a spin-polarized electron-hole pair. Full control of the hole spin is achieved by combining coherent rotations about two axes: Larmor precession of the hole spin about an external Voigt geometry magnetic field, and rotation about the optical axis due to the geometric phase shift induced by a picosecond laser pulse resonant with the hole-trion transition. 相似文献
43.
E. Beckmann Drugman Ramsay und W. Gabel 《Fresenius' Journal of Analytical Chemistry》1907,46(4):248-250
Ohne Zusammenfassung 相似文献
44.
Arlan Ramsay 《Israel Journal of Mathematics》1985,51(4):339-346
If a locally compact groupG acts on a Lebesgue probability space (X, λ), it is natural to consider these conditions: (a) each group element preserves the class of λ, and (b) the action function
is measurable. The latter is a weakening of the requirement that the action be Borel, providedX has a particular Borel structure as well as the σ-algebra of measurable sets. In this paper, we give an example showing that
such an action need not be Borel relative to the given Borel structure, and prove that there is always a conull invariant
subset and a new standard Borel structure on that subset for which the action is Borel. This is the meaning of the title.
Supported by a University of Colorado Faculty Fellowship. 相似文献
45.
C. Camy-Peyret J.-M. Flaud J.-Y. Mandin J.-P. Chevillard J. Brault D.A. Ramsay M. Vervloet J. Chauville 《Journal of Molecular Spectroscopy》1985,113(1):208-228
High-resolution spectra of water vapor have been recorded, with very good signal-to-noise ratios, between 16500 and 25250 cm?1 using visible Fourier transform spectroscopy. Precise line positions have been derived, and 1174 vibration-rotation transitions belonging to 23 different bands of H2O have been assigned, leading to the determination of 539 vibration-rotation energy levels and greatly extending our knowledge of the highly excited vibrational states of the water molecule. The measurement of 630 line intensities with accuracies varying from 5 to 35%, depending on the strength of the line, has been performed. 相似文献
46.
A data smoothing method is described where the roughness penalty depends on a parameter that must be estimated from the data.
Three levels of parameters are involved in this situation: Local parameters are the coefficients of the basis function expansion defining the smooth, global parameters define low-dimensional trend and the roughness penalty, and a complexity parameter controls the amount of roughness in the smooth. By defining local parameters as regularized functions of global
parameters, and global parameters in turn as functions of complexity parameter, we define a parameter cascade, and show that
the accompanying multi-criterion optimization problem leads to good estimates of all levels of parameters and their precisions.
The approach is illustrated with real and simulated data, and this application is a prototype for a wide range of problems
involving nuisance or local parameters. 相似文献
47.
48.
49.
L. Auvray A. Ayral L. Cot T. Dabadie C. Guizard J. Ramsay 《Journal of Sol-Gel Science and Technology》1994,2(1-3):205-209
The mechanisms of oxide gel formation in inverse micelle and lamellar surfactant systems have been investigated by Small Angle Neutron Scattering (SANS). In the first of these processes colloidal particles and gels are formed by the controlled hydrolysis and condensation of metal alkoxides in a reversed microemulsion system (water in oil), where the water is confined in the microemulsion core. With this route the rate of formation and structure of the oxide gel can be controlled by appropriate choice of the surfactant molecule (e.g. chain length) and the volume fraction of the micelles dispersed in the continuous organic phase. Investigations have been made with the system cyclohexane/water/C8E
x
, where C8E
x
is the non-ionic surfactant octylphenyl polyoxyethylene. The influence of the size and structure of the microemulsion has been studied by contrast variation (using deuterated solvents) before and during the reaction to form zirconia gels, and the mechanism of gelation is analysed in terms of percolation of fractal cluster aggregates. The structure of gels formed in surfactant/water lamellar phase systems, using surfactants with greater chain length, has also been investigated by SANS. The application of contrast variation to study such anisotropic bilayer systems, in which oriented gel films can be formed, is illustrated. 相似文献
50.
Li P Xu Z Liu H Wennefors CK Dobrikov MI Ludwig J Shaw BR 《Journal of the American Chemical Society》2005,127(48):16782-16783
This report describes a one-pot synthesis of alpha-P-borano-, alpha-P-thio-, and alpha-P-seleno-modified nucleoside diphosphate analogues that are otherwise difficult to obtain. The key step involves the intramolecular nucleophilic attack by an amino group in 5 to remove the gamma-phosphate. The absolute configurations of P-diastereomers were confirmed by analysis of their 1H NMR. Affinity studies revealed that the nucleoside boranodiphosphates are potentially useful in antiviral research. 相似文献