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771.
William Alan Bertsche G. B. Andresen M. D. Ashkezari M. Baquero-Ruiz P. D. Bowe P. T. Carpenter E. Butler C. L. Cesar S. F. Chapman M. Charlton S. Eriksson J. Fajans T. Friesen M. C. Fujiwara D. R. Gill A. Gutierrez J. S. Hangst W. N. Hardy R. S. Hayano M. E. Hayden A. J. Humphries J. L. Hurt R. Hydomako S. Jonsell L. Kurchaninov N. Madsen S. Menary P. Nolan K. Olchanski A. Olin A. Povilus P. Pusa F. Robicheaux E. Sarid D. M. Silveira C. So J. W. Storey R. I. Thompson D. P. van der Werf J. S. Wurtele Y. Yamazaki 《Hyperfine Interactions》2012,212(1-3):61-67
In efforts to trap antihydrogen, a key problem is the vast disparity between the neutral trap energy scale ( $\sim\!50\,\upmu\mathrm{eV}$ ), and the energy scales associated with plasma confinement and space charge (~1 eV). In order to merge charged particle species for direct recombination, the larger energy scale must be overcome in a manner that minimizes the initial antihydrogen kinetic energy. This issue motivated the development of a novel injection technique utilizing the inherent nonlinear nature of particle oscillations in our traps. We demonstrated controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm or tenuous plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. The nature of this injection overcomes some of the difficulties associated with matching the energies of the charged species used to produce antihydrogen. 相似文献
772.
An FP Bai JZ Balantekin AB Band HR Beavis D Beriguete W Bishai M Blyth S Boddy K Brown RL Cai B Cao GF Cao J Carr R Chan WT Chang JF Chang Y Chasman C Chen HS Chen HY Chen SJ Chen SM Chen XC Chen XH Chen XS Chen Y Chen YX Cherwinka JJ Chu MC Cummings JP Deng ZY Ding YY Diwan MV Dong L Draeger E Du XF Dwyer DA Edwards WR Ely SR Fang SD Fu JY Fu ZW Ge LQ Ghazikhanian V Gill RL Goett J Gonchar M Gong GH Gong H Gornushkin YA Greenler LS Gu WQ Guan MY Guo XH Hackenburg RW Hahn RL Hans S He M He Q 《Physical review letters》2012,108(17):171803
The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle θ(13) with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GWth-day live-time exposure in 55 days, 10,416 (80,376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R=0.940±0.011(stat.)±0.004(syst.). A rate-only analysis finds sin(2)2θ(13)=0.092±0.016(stat.)±0.005(syst.) in a three-neutrino framework. 相似文献
773.
774.
Duxi Zhang L. A. Gill R. G. Cooks 《Journal of the American Society for Mass Spectrometry》1998,9(11):1146-1157
Primary and secondary amines, when examined in atmospheric pressure chemical ionization, electrospray ionization, or chemical ionization, display protonated imines in their mass spectra. These products arise formally by nucleophilic substitution at the α-carbon with loss of both ammonia and molecular hydrogen. Collision-induced dissociation (CID) is used to characterize the product ions by comparison with authentic protonated imines. Gas-phase ion/molecule reactions of protonated amines with neutral amines also yield products that correspond to protonated imines (deamination and dehydrogenation), as well as providing simple deamination products. The reaction mechanism was investigated further by reacting the deamination product, the alkyl cation, with a neutral amine. The observed dehydrogenation of the nascent protonated secondary amine indicates that the reaction sequence is loss of ammonia followed by dehydrogenation even though the isolated protonated secondary amines did not undergo dehydrogenation upon CID. Formation of the deamination products in the protonated amine/amine reaction is competitive with proton-bound dimer formation. The proton-bound dimers do not yield deamination products under CID conditions in the ion trap or in experiments performed using a pentaquadrupole instrument. This demonstrates that the geometry of the proton-bound dimer, in which the α-carbons of the alkylamines are well separated [C a -N-H-N-C a ], is an unsuitable entry point on the potential energy hypersurface for formation of the imine [C a -N-C a ]. Isolation of the proton-bound dimers in the quadrupole ion trap is achieved with low efficiency and this characteristic can be used to distinguish them from their covalently bound isomers. 相似文献
775.
Brendon D. Gill Harvey E. Indyk Merilyn Manley-Harris 《Analytical and bioanalytical chemistry》2013,405(15):5311-5319
A method for the simultaneous analysis of nucleosides and nucleotides in infant formula using reversed-phase liquid chromatography–tandem mass spectrometry is described. This approach is advantageous for compliance testing of infant formula over other LC-MS methods in which only nucleotides or nucleosides are measured. Following sample dissolution, protein was removed by centrifugal ultrafiltration. Chromatographic analyses were performed using a C18 stationary phase and gradient elution of an ammonium acetate/bicarbonate buffer, mass spectrometric detection and quantitation by a stable isotope-labelled internal standard technique. A single laboratory validation was performed, with spike recoveries of 80.1–112.9 % and repeatability relative standard deviations of 1.9–7.2 %. Accuracy as bias was demonstrated against reference values for NIST1849a certified reference material. The method has been validated for the analysis of bovine milk-based, soy-based, caprine milk-based and hydrolysed milk protein-based infant formulae. Figure
LC-MS/MS MRM chromatogram of mixed nucleoside and nucleotide standard 相似文献
776.
Synthesis and Antimicrobial Screening of Some Novel 2‐(5‐(4‐(1H‐Benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐4,5‐dihydro‐1H‐pyrazol‐3‐yl)phenols Incorporated by Triazole Moiety 下载免费PDF全文
Mohammad U. Shaikh Ganesh R. Jadhav Rajesh P. Kale Asha V. Chate Deepak R. Nagargoje Charansingh H. Gill 《Journal of heterocyclic chemistry》2014,51(2):513-517
A novel series of 2‐(5‐(4‐(1H‐benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐4,5‐dihydro‐1H‐pyrazol‐3‐yl)phenols derivative has been synthesized from (E)‐3‐(4‐(1H‐benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐1‐(2‐hydroxyphenyl)prop‐2‐en‐1‐ones in ethanol and hydrazine hydrate under reflux condition. The synthesized compounds were screened for antibacterial activity against Gram‐positive bacteria viz Staphylococcus aureus and Bacillus subtilis and Gram‐negative bacteria viz Escherichia coli and Salmonella typhi, respectively. Some of the tested compounds showed significant antimicrobial activity. IR, 1H NMR, mass spectral data, and elemental analysis elucidated the structures of all the newly synthesized compounds. 相似文献
777.
Khandebharad Amol U. Sarda Swapnil R. Gill Charansingh H. Soni Mahesh G. Agrawal Brijmohan R. 《Research on Chemical Intermediates》2016,42(6):5779-5787
Research on Chemical Intermediates - An environmentally benign novel strategy is developed for the synthesis of tetrahydrobenzo[b]pyrans by using thiamine mononitrate as a green catalyst, with the... 相似文献
778.
Solution NMR spin-relaxation experiments were used to compare mus-ms dynamics in RNase A in the apo form and as complexed to the substrate-mimic, pTppAp. The crystal structure of the RNase A/pTppAp complex was determined and demonstrates that this ligand binds at the active site and utilizes established substrate binding sites in its interaction with RNase A. Relaxation-compensated CPMG experiments identify flexible residues in and around the active site in both the apo and pTppAp-bound enzyme. Quantitative analysis of the NMR spin-relaxation dispersion curves show that the time scale of motion in RNase A is unchanged when pTppAp binds and is similar to the time scale for the rate-determining step of the catalytic reaction. Temperature-dependent measurements provide an activation barrier for motion of 5.2 +/- 1.0 kcal/mol and 4.5 +/- 1.2 kcal/mol for the apo and pTppAp forms of RNase A, respectively. These data indicate very similar motion exists in the free and bound enzyme. Additionally, chemical shift data suggests that the magnitude of motion is also similar for these two forms and that it is likely that apo enzyme interconverts to a structure that resembles a ligand-bound form. Likewise, it appears that the bound conformation samples the apo enzyme form even when ligand is present. Taken together the data imply that RNase A is in a preexisting dynamic equilibrium between two conformations that represent the open and closed enzyme forms. These data suggest that ligand binding stabilizes the bound conformer but does not induce it. 相似文献
779.
In Tae Kim Sang Woo Lee Tae Hyoung Kwak Jung Youl Lee Hyang Suk Park So Young Kim Chang Min Lee Hoi Eun Jung Jun‐Gill Kang Tack‐Jin Kim Hee‐Jung Kang ChangMoon Park Ronald L. Elsenbaumer 《Macromolecular rapid communications》2002,23(9):551-554
Oxidative coupling reaction of 1‐hexyl–3,4‐dimethylpyrrole affords a conjugated conducting poly(1‐hexyl‐3,4‐dimethyl‐2,5‐pyrrolylene) (PHDP), which is completely soluble in common organic solvents. The luminescence of PHDP is comparable to that of poly(N‐vinylcarbazole) (PVK), which has been widely used in electroluminescence devices. The quantum efficiency of PHDP is 2.5 times higher than that of PVK. A rationalization is presented relating the conductivity of PHDP to its polymer structure. 相似文献
780.