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排序方式: 共有668条查询结果,搜索用时 46 毫秒
111.
F. Kuchler E. Babcock M. Burghoff T. Chupp S. Degenkolb I. Fan P. Fierlinger F. Gong E. Kraegeloh W. Kilian S. Knappe-Grüneberg T. Lins M. Marino J. Meinel B. Niessen N. Sachdeva Z. Salhi A. Schnabel F. Seifert J. Singh S. Stuiber L. Trahms J. Voigt 《Hyperfine Interactions》2016,237(1):95
Permanent electric dipole moments (EDMs) arise due to the breaking of time-reversal or, equivalently, CP-symmetry. Although EDM searches have so far only set upper limits, which are many orders of magnitude larger than Standard Model (SM) predictions, the motivation for more sensitive searches is stronger than ever. A new effort at FRM-II incorporating 129Xe and 3He as a co-magnetometer can potentially improve the current limit. The noble gas mixture of 129Xe and 3He is simultanously polarized by spin-exchange optical pumping and then transferred into a high-performance magnetically shielded room. Inside, both species can freely precess in the presence of applied magnetic and electric fields. The precession signals are detected by LTc SQUID sensors. In EDM cells with silicon electrodes we observed spin lifetimes in excess of 2500 s without and with high-voltage applied. This meets one requirement to achieve our goal of improving the EDM limit on 129Xe by several orders of magnitude. 相似文献
112.
Biologically interesting fluoren-9-one and xanthen-9-one derivatives have been prepared by a novel aryl to imidoyl palladium migration, followed by intramolecular arylation. The fluoren-9-one synthesis appears to involve both a palladium migration mechanism and a C-H activation process proceeding through an unprecedented organopalladium(IV) hydride intermediate. The results from deuterium labeling experiments are consistent with the proposed dual mechanism. 相似文献
113.
Campo MA Zhang H Yao T Ibdah A McCulla RD Huang Q Zhao J Jenks WS Larock RC 《Journal of the American Chemical Society》2007,129(19):6298-6307
A novel 1,4-palladium migration between the o- and o'-positions of biaryls has been observed in organopalladium intermediates derived from o-halobiaryls. The organopalladium intermediates generated by this migration have been trapped either by a Heck reaction employing ethyl acrylate or by Suzuki cross-coupling using arylboronic acids. This palladium migration can be activated or deactivated by choosing the appropriate reaction conditions. Chemical and computational evidence supports the presence of an equilibrium that correlates with the C-H acidity of the available arene positions. 相似文献
114.
Here we report a simple and fast method for wine fingerprinting based on direct matrix-assisted laser desorption/ionization
(MALDI) mass spectrometry analysis of different red wine samples, useful for batch-to-batch analysis and for the detection
of key compounds even in trace amounts which may vary from vintage to vintage, and from one treatment to another one. A series
of 20 samples from different wines were subjected to MALDI mass spectrometry. We found that 2,5-dihydroxybenzoic acid is far superior with respect to all the matrices tested To the best of our knowledge this is the
first application of an effective wine profiling not limited to detection of anthocyanins. More than 80 molecular species
were detected. Moreover, qualitative and quantitative differences were observed, owing to the nature and relative abundance
of different chemical compounds among the wines. 相似文献
115.
Weak and strong convergence theorems for strict pseudo-contractions in Hilbert spaces 总被引:1,自引:0,他引:1
Giuseppe Marino 《Journal of Mathematical Analysis and Applications》2007,329(1):336-346
Let C be a closed convex subset of a real Hilbert space H and assume that T is a κ-strict pseudo-contraction on C with a fixed point, for some 0?κ<1. Given an initial guess x0∈C and given also a real sequence {αn} in (0,1). The Mann's algorithm generates a sequence {xn} by the formula: xn+1=αnxn+(1−αn)Txn, n?0. It is proved that if the control sequence {αn} is chosen so that κ<αn<1 and , then {xn} converges weakly to a fixed point of T. However this convergence is in general not strong. We then modify Mann's algorithm by applying projections onto suitably constructed closed convex sets to get an algorithm which generates a strong convergent sequence. This result extends a recent result of Nakajo and Takahashi [K. Nakajo, W. Takahashi, Strong convergence theorems for nonexpansive mappings and nonexpansive semigroups, J. Math. Anal. Appl. 279 (2003) 372-379] from nonexpansive mappings to strict pseudo-contractions. 相似文献
116.
A Cecinato F Marino P Di Filippo L Lepore M Possanzini 《Journal of chromatography. A》1999,846(1-2):255-264
The distribution ratios of n-alkanes, polynuclear aromatic hydrocarbons (PAHs) and nitrated PAH components between fine and coarse fractions of soot has been investigated in downtown Rome through three field campaigns carried out at different times of the year. The preferential accumulation of almost all species investigated onto fine particles has been observed in all field experiments performed. Moreover, nitrated PAHs had varied distributions, according to the origin of their occurrence in the atmosphere; in fact, congeners of photochemical origin accumulated more in fine particles than those released by primary sources. 相似文献
117.
A numerical experiment was carried out on the gas flow field between two eccentric cylinders, one of which is rotating. Attention was paid to the presence of separated recirculating regions from the continuum to the rarefied regimes. The direct simulations were performed by means of a Monte Carlo (DSMC) method and bi‐polar co‐ordinates were adopted. The calculations were relative to isothermal walls at the same temperature. Streamlines and velocity profiles were evaluated as functions of the Knudsen number, of the Mach number and of the geometric parameters. The gas considered was argon. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
118.
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120.
Antonio De Nino Angelo Liguori Loredana Maiuolo Tiziana Marino Antonio Procopio Giovanni Sindona 《Journal of the American Society for Mass Spectrometry》1997,8(12):1257-1261
The anions (I–III) obtained from O-methyl 5′-O-(5′-deoxythymidine) 3′-O-(2′,3′-dideoxyuridine) phosphate by the competitive removal of the 3-N-H protons of the nucleobases and of the methyl group from the phosphotriester bond, assume in the gas phase stable conformations as a function of their charge site. The mass-analyzed ion kinetic energy (MIKE) spectra of I and III show that the regioselective backbone cleavage of the internucleotidic linkage is controlled by the 2′-H proton transfer to the nucleobase within the 5′-end nucleoside. Similar pathways are taken by species II when the nucleobase is eliminated as neutral from the 5′-end nucleoside. 相似文献