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排序方式: 共有238条查询结果,搜索用时 15 毫秒
101.
Catalysis by transition metal ions in oxidation reactions with hydrogen peroxide and alkyl hydroperoxides is a leading topic in the pursuit of more sustainable and selective processes, to obtain compounds with high added value. The most recent achievements concerning the synthesis and characterization, as well as the key aspects of reactivity, of V(V) and Mo(VI) peroxo complexes have been collected here. 相似文献
102.
van Kalkeren HA Leenders SH Hommersom CR Rutjes FP van Delft FL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(40):11290-11295
Several important reactions in organic chemistry thrive on stoichiometric formation of phosphine oxides from phosphines. To avoid the resulting burden of waste and purification, cyclic phosphine oxides were evaluated for new catalytic reactions based on in situ regeneration. First, the ease of silane-mediated reduction of a range of cyclic phosphine oxides was explored. In addition, the compatibility of silanes with electrophilic halogen donors was determined for application in a catalytic Appel reaction based on in situ reduction of dibenzophosphole oxide. Under optimized conditions, alcohols were effectively converted to bromides or chlorides, thereby showing the relevance of new catalyst development and paving the way for broader application of organophosphorus catalysis by in situ reduction protocols. 相似文献
103.
Floris FM 《The Journal of chemical physics》2012,136(11):116102
104.
Arnaldi R Averbeck R Banicz K Castor J Chaurand B Cicalò C Colla A Cortese P Damjanovic S David A De Falco A Devaux A Drees A Ducroux L En'yo H Fargeix J Ferretti A Floris M Förster A Force P Guettet N Guichard A Gulkanian H Heuser JM Keil M Kluberg L Lourenço C Lozano J Manso F Masoni A Martins P Neves A Ohnishi H Oppedisano C Parracho P Pillot P Puddu G Radermacher E Ramalhete P Rosinsky P Scomparin E Seixas J Serci S Shahoyan R Sonderegger P Specht HJ Tieulent R Usai G Veenhof R 《Physical review letters》2006,96(16):162302
We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate. 相似文献
105.
R. Arnaldi K. Banicz K. Borer J. Castor B. Chaurand W. Chen C. Cicalò A. Colla P. Cortese S. Damjanovic A. David A. de Falco A. Devaux L. Ducroux H. En’yo J. Fargeix A. Ferretti M. Floris A. F?rster P. Force N. Guettet A. Guichard H. Gulkanian J. M. Heuser M. Keil L. Kluberg Z. Li C. Louren?o J. Lozano F. Manso P. Martins A. Masoni A. Neves H. Ohnishi C. Oppedisano P. Parracho P. Pillot T. Poghosyan G. Puddu E. Radermacher P. Ramalhete P. Rosinsky E. Scomparin J. Seixas S. Serci R. Shahoyan P. Sonderegger H. J. Specht R. Tieulent G. Usai R. Veenhof H. K. W?hri 《The European Physical Journal C - Particles and Fields》2009,61(4):711-720
The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158 A GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The mass spectrum for M<1 GeV is consistent with a dominant contribution from π
+
π
−→ρ→μ
+
μ
− annihilation. The associated ρ spectral function shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs.
The slope parameter T
eff associated with the transverse momentum spectra rises with mass up to the ρ, followed by a sudden decline above. The rise for M<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for M>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source
in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated
empirical evidence, including also a Planck-like shape of the mass spectra at low p
T
and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude
with first results on ω in-medium effects. 相似文献
106.
Cudazzo P Profeta G Sanna A Floris A Continenza A Massidda S Gross EK 《Physical review letters》2008,100(25):257001
We present a first-principles study of the electron-phonon interaction and the prediction of the superconducting critical temperature in molecular metallic hydrogen. Our study is able to single out the features which drive the system towards superconductivity: mainly, a rich and complex Fermi surface and strongly coupled phonon modes driving the intra- or intermolecular charge transfer. We demonstrate that in this simple system, a very high superconducting critical temperature can be reached via electron-phonon and Coulomb electron-electron interactions. 相似文献
107.
van Lingen HL Zhuang W Hansen T Rutjes FP Jørgensen KA 《Organic & biomolecular chemistry》2003,1(11):1953-1958
A novel tandem reaction involving an oxa-Michael addition, followed by a Friedel-Crafts alkylation has been developed. This catalytic tandem reaction, which provides facile and efficient access to optically active functionalised chromanes, proceeds under the influence of bisoxazoline-based catalysts to give diastereomerically pure products in enantioselectivities up to 81% and excellent yields. The optimisation studies, the scope of the reaction, and a model that on the basis of PM3 calculations predicts the outcome of the reaction will be detailed. 相似文献
108.
Beltrame P Cadoni E Floris C Gelli G Lai A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(12):2693-2697
The 2-, 3- and 4-amino-pyridine and their protonated forms, obtained by reaction with pyridinium chloride, were investigated by 15N NMR spectroscopy. Exhaustive evidence has been found that the protonation occurs mainly on the annular nitrogen. Protonation of 4-aminopyridine by dehydrohalogenation of 1,1,2,2-tetrachloroethane (TCE) was also studied by 13C NMR spectroscopy, which indicated that the protonation occurs via the formation of adducts. 相似文献
109.
110.
On the nature of turbulence 总被引:10,自引:0,他引:10
A mechanism for the generation of turbulence and related phenomena in dissipative systems is proposed.The research was supported by the Netherlands Organisation for the Advancement of Pure Research (Z.W.O.). 相似文献