排序方式: 共有28条查询结果,搜索用时 31 毫秒
1.
Oxidation of a variety of compounds, including methionine (Met), using a complex formed between dirhodium(II) acetate and the lacunary form of phosphotungstic acid as the catalyst is effective over a wide range of conditions, including pH 2–10. Thus, amperometric detection at a composite in which this complex is immobilized in a sol–gel material does not place restrictions on selection of conditions for separations by reverse-phase HPLC. A demonstration of this point is shown by a study of Met, Met–Phe, Phe–Met, Met–Met, and Gly–Met–Gly (Phe, phenylalanine; Gly, glycine). Using a 0.05 M phosphate buffer at pH 6.7, a C18 column, and a flow rate of 1 ml min−1, capacity factors for Met, Gly–Met–Gly, Met–Met, and Phe–Met were 1.4, 2.1, 5.6, and 34, respectively. Phe–Met and Met–Phe co-eluted. 相似文献
2.
Iodice M Cusanno F Acha A Ambrozewicz P Aniol KA Baturin P Bertin PY Benaoum H Blomqvist KI Boeglin WU Breuer H Brindza P Bydzovský P Camsonne A Chang CC Chen JP Choi S Chudakov EA Cisbani E Colilli S Coman L Craver BJ De Cataldo G de Jager CW De Leo R Deur AP Ferdi C Feuerbach RJ Folts E Fratoni R Frullani S Garibaldi F Gayou O Giulani F Gomez J Gricia M Hansen JO Hayes D Higinbotham DW Holmstrom TK Hyde CE Ibrahim HF Jiang X Kaufman LJ Kino K Kross B Lagamba L LeRose JJ Lindgren RA 《Physical review letters》2007,99(5):052501
An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak. 相似文献
3.
Qian X Allada K Dutta C Huang J Katich J Wang Y Zhang Y Aniol K Annand JR Averett T Benmokhtar F Bertozzi W Bradshaw PC Bosted P Camsonne A Canan M Cates GD Chen C Chen JP Chen W Chirapatpimol K Chudakov E Cisbani E Cornejo JC Cusanno F Dalton MM Deconinck W de Jager CW De Leo R Deng X Deur A Ding H Dolph PA Dutta D El Fassi L Frullani S Gao H Garibaldi F Gaskell D Gilad S Gilman R Glamazdin O Golge S Guo L Hamilton D Hansen O Higinbotham DW Holmstrom T Huang M Ibrahim HF Iodice M Jiang X Jin G 《Physical review letters》2011,107(7):072003
We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations. 相似文献
4.
J. Glister G. Ron B.W. Lee R. Gilman A.J. Sarty S. Strauch D.W. Higinbotham E. Piasetzky K. Allada W. Armstrong J. Arrington H. Arenhövel A. Beck F. Benmokhtar B.L. Berman W. Boeglin E. Brash A. Camsonne J. Calarco J.P. Chen S. Choi E. Chudakov L. Coman B. Craver F. Cusanno J. Dumas C. Dutta R. Feuerbach A. Freyberger S. Frullani F. Garibaldi J.-O. Hansen T. Holmstrom C.E. Hyde H. Ibrahim Y. Ilieva C.W. de Jager X. Jiang M.K. Jones Hyekoo Kang A. Kelleher E. Khrosinkova E. Kuchina G. Kumbartzki J.J. LeRose R. Lindgren P. Markowitz S. May-Tal Beck E. McCullough D. Meekins 《Physics letters. [Part B]》2011
5.
Shneor R Monaghan P Subedi R Anderson BD Aniol K Annand J Arrington J Benaoum H Benmokhtar F Bertin P Bertozzi W Boeglin W Chen JP Choi S Chudakov E Cisbani E Craver B de Jager CW Feuerbach RJ Frullani S Garibaldi F Gayou O Gilad S Gilman R Glamazdin O Gomez J Hansen JO Higinbotham DW Holmstrom T Ibrahim H Igarashi R Jans E Jiang X Jiang Y Kaufman L Kelleher A Kolarkar A Kuchina E Kumbartzki G LeRose JJ Lindgren R Liyanage N Margaziotis DJ Markowitz P Marrone S Mazouz M Meekins D Michaels R 《Physical review letters》2007,99(7):072501
We investigated simultaneously the 12C(e,e'p) and 12C(e,e'pp) reactions at Q2=2 (GeV/c)2, xB=1.2, and in an (e, e'p) missing-momentum range from 300 to 600 MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5+/-2)% of the 12C(e,e'p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e'p) missing-momentum vector, an experimental signature of correlations. 相似文献
6.
Ahmed Z Allada K Aniol KA Armstrong DS Arrington J Baturin P Bellini V Benesch J Beminiwattha R Benmokhtar F Canan M Camsonne A Cates GD Chen JP Chudakov E Cisbani E Dalton MM de Jager CW De Leo R Deconinck W Decowski P Deng X Deur A Dutta C Franklin GB Friend M Frullani S Garibaldi F Giusa A Glamazdin A Golge S Grimm K Hansen O Higinbotham DW Holmes R Holmstrom T Huang J Huang M Hyde CE Jen CM Jin G Jones D Kang H King P Kowalski S Kumar KS Lee JH LeRose JJ Liyanage N Long E McNulty D 《Physical review letters》2012,108(10):102001
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV2 and beam energy E(b) = 3.48 GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors. 相似文献
7.
Aniol KA Armstrong DS Averett T Benaoum H Bertin PY Burtin E Cahoon J Cates GD Chang CC Chao YC Chen JP Choi S Chudakov E Craver B Cusanno F Decowski P Deepa D Ferdi C Feuerbach RJ Finn JM Frullani S Fuoti K Garibaldi F Gilman R Glamazdin A Gorbenko V Grames JM Hansknecht J Higinbotham DW Holmes R Holmstrom T Humensky TB Ibrahim H de Jager CW Jiang X Kaufman LJ Kelleher A Kolarkar A Kowalski S Kumar KS Lambert D LaViolette P LeRose J Lhuillier D Liyanage N Margaziotis DJ Mazouz M McCormick K 《Physical review letters》2006,96(2):022003
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero. 相似文献
8.
An electrocatalytic amperometric detector for the ion chromatographic determination of CN− is described. A conducting composite that is based on a graphite-loaded sol–gel material comprises the working electrode. The composite is doped with a RuII metallodendrimer which is demonstrated to promote the electrochemical oxidation of CN− at potentials positive of 0.5 V vs. Ag/AgCl. In 6 mM NaOH, 0.05 M NaCl flowed at 1.0 ml min−1, a 5-point calibration curve with the following linear least squares parameters is obtained over the range, 1.0–30 M CN−: slope, 24.2±0.1 nA M−1; intercept, −6±2 nA; and r, 0.9997. The detection limit, 0.7 μM CN−, compares favorably to that obtained by amperometry at a silver electrode, 0.5 μM CN−, under comparable experimental conditions. A 60-min preconcentration by Donnan dialysis increases the sensitivity by a factor of 23.6. 相似文献
9.
Rajaram D Burnstein RA Chakravorty A Chan A Chen YC Choong WS Clark K Dukes EC Durandet C Felix J Gidal G Gu P Gustafson HR Ho C Holmstrom T Huang M James C Jenkins CM Kaplan DM Lederman LM Leros N Longo MJ Lopez F Lu LC Luebke W Luk KB Nelson KS Park HK Perroud JP Rubin HA Teng PK Volk J White CG White SL Zyla P 《Physical review letters》2005,94(18):181801
A sensitive search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-) has been performed using a sample of approximately 10(9) Xi(-) hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Xi(-)-->pmu(-)mu(-))<4.0x10(-8) at 90% confidence, improving on the best previous limit by 4 orders of magnitude. 相似文献
10.
It was found that oxygen chemisorption on ZnO surfaces is accelerated by as much as three orders of magnitude after illumination in the presence of CO + O2. This accelerated chemisorption is characterized by electron transfer and thermal activation as is oxygen chemisorption on “real” ZnO surfaces. The observed behavior is attributed to the formation of surface complexes (involving carbon, oxygen and Zn ions) which enhance oxygen chemisorption. These complexes are stable at room temperature and render the surface inert to further CO-interaction. 相似文献