排序方式: 共有73条查询结果,搜索用时 31 毫秒
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Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
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EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
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A. M. Sirunyan A. R. Tumasyan V. A. Khachatryan A. G. Petrosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2016,51(4):299-306
The procedure of identification of tagging jets in the Higgs boson production process with a following decay of the Higgs boson to τ-leptons (VBF H→τ?τ+) at the endcup region of the upgraded CMS detector at large amount (140) of additionally imposed pp-interactions is given. The efficiency and purity of tagging jets selection at the CMS endcup region are estimated. 相似文献
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We propose a picture of Wigner function scars as a sequence of concentric rings along a two-dimensional surface inside a periodic orbit. This is verified for a two-dimensional plane that contains a classical hyperbolic orbit of a Hamiltonian system with 2 degrees of freedom. The stationary wave functions are the familiar mixture of scarred and random waves, but the spectral average of the Wigner functions in part of the plane is nearly that of a harmonic oscillator and individual states are also remarkably regular. These results are interpreted in terms of the semiclassical picture of chords and centers. 相似文献
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Sun R Colin E Ajitanand NN Alexander JM Barton MA DeYoung PA Drake KL Elmaani A Gelderloos CJ Gualtieri EE Guinet D Hannuschke S Jaasma JA Kowalski L Lacey RA Lauret J Norbeck E Pak R Peaslee GF Stern M Stone NT Sundbeck SD Vander Molen AM Westfall GD Yang LB Yee J 《Physical review letters》2000,84(1):43-46
For central collisions of (17-115)A MeV 40Ar+Cu, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1-2 GeV. For such high deposition energies, statistical multifragmentation models predict much more extensive nuclear disassembly than is observed. 相似文献
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Fujiwara M Akimune H van Den Berg AM Cribier M Daito I Ejiri H Fujimura H Fujita Y Goodman CD Hara K Harakeh MN Ihara F Ishikawa T Janecke J Kawabata T Raghavan RS Schwarz K Tanaka M Yamanaka T Yosoi M Zegers RG 《Physical review letters》2000,85(21):4442-4445
Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos. 相似文献
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Khachatryan V Sirunyan AM Tumasyan A Adam W Bergauer T Dragicevic M Erö J Fabjan C Friedl M Frühwirth R Ghete VM Hammer J Hänsel S Hartl C Hoch M Hörmann N Hrubec J Jeitler M Kasieczka G Kiesenhofer W Krammer M Liko D Mikulec I Pernicka M Rohringer H Schöfbeck R Strauss J Taurok A Teischinger F Wagner P Waltenberger W Walzel G Widl E Wulz CE Mossolov V Shumeiko N Suarez Gonzalez J Benucci L Cerny K De Wolf EA Janssen X Maes T Mucibello L Ochesanu S Roland B Rougny R Selvaggi M Van Haevermaet H 《Physical review letters》2011,106(11):112001
Measurements of the total and differential cross sections dσ/dp(T)(B) and dσ/dy(B) for B(+) mesons produced in pp collisions at sqrt[s]=7 TeV are presented. The data correspond to an integrated luminosity of 5.8 pb(-1) collected by the CMS experiment operating at the LHC. The exclusive decay B(+)→J/ψK(+), with J/ψ→μ(+)μ(-), is used to detect B(+) mesons and to measure the production cross section as a function of p(T)(B) and y(B). The total cross section for p(T)(B)>5 GeV and |y(B)|<2.4 is measured to be 28.1±2.4±2.0±3.1 μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement. 相似文献
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Chatrchyan S Khachatryan V Sirunyan AM Tumasyan A Adam W Bergauer T Dragicevic M Erö J Fabjan C Friedl M Frühwirth R Ghete VM Hammer J Hänsel S Hoch M Hörmann N Hrubec J Jeitler M Kiesenhofer W Krammer M Liko D Mikulec I Pernicka M Rohringer H Schöfbeck R Strauss J Taurok A Teischinger F Wagner P Waltenberger W Walzel G Widl E Wulz CE Mossolov V Shumeiko N Suarez Gonzalez J Bansal S Benucci L De Wolf EA Janssen X Maes J Maes T Mucibello L Ochesanu S Roland B Rougny R Selvaggi M Van Haevermaet H 《Physical review letters》2011,107(9):091802
Electroweak production of the top quark is measured for the first time in pp collisions at √=7 TeV, using a data set collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb?1. With an event selection optimized for t-channel production, two complementary analyses are performed. The first one exploits the special angular properties of the signal, together with background estimates from the data. The second approach uses a multivariate analysis technique to probe the compatibility with signal topology expected from electroweak top-quark production. The combined measurement of the cross section is 83.6±29.8(stat+syst)±3.3(lumi) pb, consistent with the standard model expectation. 相似文献