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61.
D.K. Brice 《Physics letters. A》1978,66(1):53-56
Spin rotation experiments with implanted μ+ projectiles are a convenient method for extending studies of the isotope effect for hydrogen diffusion in metals to very light mass. In the present letter information is presented which allows a determination of the mean free path for vacancy production by μ+ particles slowing down in C (graphite), Al, V, Fe, Ni, Cu, Nd, Pd, and Ta targets. Also given is the excess distance traveled by the μ+ after its energy is reduced below the threshold necessary for vacancy production in these materials. 相似文献
62.
Crane SG Brice SJ Goldschmidt A Guckert R Hime A Kitten JJ Vieira DJ Zhao X 《Physical review letters》2001,86(14):2967-2970
Laser cooling and atomic trapping techniques have been employed to confine polarized 82Rb atoms ( T1/2 = 75 s) in a magnetic time-orbiting-potential (TOP) trap. We have observed the parity-violating correlation between the emitted positron momentum and the parent nuclear spin as a continuous function of angle and positron energy for this pure Gamow-Teller (GT) transition. These proof-of-principle measurements demonstrate the utility of exploring fundamental symmetries in a TOP trap and the steps required to improve sensitivity in the search for physics beyond the standard model. 相似文献
63.
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
64.
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
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Let G = (V, E) be a graph with vertex set V and edge set E. Given non negative integers r, s and t, an [r, s, t]-coloring of a graph G is a proper total coloring where the neighboring elements of G (vertices and edges) receive colors with a certain difference r between colors of adjacent vertices, a difference s between colors of adjacent edges and a difference t between colors of a vertex and an incident edge. Thus [r, s, t]-colorings generalize the classical colorings of graphs and can have applications in different fields like scheduling, channel assignment problem, etc. The [r, s, t]-chromatic number χ r,s,t (G) of G is the minimum k such that G admits an [r, s, t]-coloring. In our paper we propose several bounds for the [r, s, t]-chromatic number of the cartesian and direct products of some graphs. 相似文献
68.
69.
Dr. Michael L. Singleton Geert Pirotte Dr. Brice Kauffmann Dr. Yann Ferrand Dr. Ivan Huc 《Angewandte Chemie (International ed. in English)》2014,53(48):13140-13144
The postsynthetic modulation of capsules based on helical aromatic oligoamide foldamers would be a powerful approach for controlling their receptor properties without altering the initial monomer sequences. With the goal of developing a method to increase the size of a cavity within a helix, a single‐helical foldamer capsule was synthesized with a wide‐diameter central segment that was designed to intercalate with a second shorter helical strand. Despite the formation of stable double‐helical homodimers (Kdim>107 M ?1) by the shorter strand, when it was mixed with the single‐helical capsule sequence, a cross‐hybridized double helix was formed with Ka>105 M ?1. This strategy makes it possible to direct the formation of double‐helical heterodimers. On the basis of solution‐ and solid‐state structural data, this intercalation resulted in an increase in the central‐cavity size to give a new interior volume of approximately 150 Å3. 相似文献
70.
Tuning the Guest‐Binding Ability of a Helically Folded Capsule by In Situ Modification of the Aromatic Oligoamide Backbone
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Dr. Guillaume Lautrette Dr. Christophe Aube Dr. Yann Ferrand Dr. Muriel Pipelier Dr. Virginie Blot Dr. Christine Thobie Dr. Brice Kauffmann Prof. Didier Dubreuil Dr. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1547-1553
Starting from a previously described aromatic oligoamide helically folded capsule that binds tartaric acid with high affinity and diastereoselectivity, we demonstrate the feasibility of the direct in situ modification of the helix backbone, which results in a conformational change that reduces its affinity for guests by two orders of magnitude. Specifically, ring contraction of the central pyridazine unit into a pyrrole in the full helical sequence was investigated by using electrochemical and chemical processes. The sequence containing the pyrrole was synthesized independently in a convergent manner to ascertain its structure. The conformation of the pyrrolic folded capsule was elucidated in the solid state by X‐ray crystallography and in solution by using 1H and 13C NMR spectroscopy. Solution studies revealed an unanticipated solvent‐dependent equilibrium between the anti–anti and syn–syn conformations of the pyrrole ring with respect to its two adjacent pyridine units. Titrations of the pyrrole‐containing sequence monitored by 1H NMR spectroscopy confirmed the expected drop in affinity for tartaric acid and malic acid that arises from the conformation change in the backbone that follows the replacement of the pyridazine by a pyrrole. The reduction of the pyridazine to a pyrrole was characterized by cyclic voltammetry both on the entire sequence and on a shorter precursor. The lower cathodic potential of the precursor made its preparative‐scale electroreduction possible. Direct in situ modification of the pyridazine within the entire capsule sequence was achieved chemically by using zinc in acetic acid. 相似文献