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901.
Natalia Cabrera-Lobera Noelia Velasco Roberto Sanz Manuel A. Fernández-Rodríguez 《Tetrahedron》2019,75(31):4071-4080
A practical and environmentally benign Brønsted acid?catalyzed protocol for the preparation of all-carbon tetrasubstituted allenes, consisting in the direct SN? addition of tri- or dimethoxy arenes or allyltrimethylsilane to tertiary propargylic alcohols, has been developed. In addition, a straightforward synthesis of densely substituted 2H-chromenes by metal-free tandem allenylation/heterocyclization reaction of methoxyphenols and tertiary alkynols is presented. 相似文献
902.
J. Vijande F. Fernández A. Valcarce 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):722-724
We present a theoretical framework that accounts for the new DJ and DsJ mesons measured in the open-charm sector. These resonances are properly described if considered as a mixture of conventional
P-wave quark-antiquark states and four-quark components. The narrowest states are basically P-wave quark-antiquark mesons, while the dominantly four-quark states are shifted above the corresponding two-meson threshold.
We study the electromagnetic decay widths as basic tools to scrutiny their nature. 相似文献
903.
D. Fernández-Fraile A. Gómez Nicola 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):848-850
We present recent results on the calculation of transport coefficients for a pion gas at zero chemical potential in Chiral
Perturbation Theory (ChPT) using the Linear Response Theory (LRT). More precisely, we show the behavior of DC conductivity
and shear viscosity at low temperatures. To compute transport coefficients, the standard power counting of ChPT has to be
modified. The effects derived from imposing unitarity are also analyzed. As physical applications in relativistic heavy-ion
collisions, we show the relation of the DC conductivity to soft-photon production and phenomenological effects related to
a non-zero shear viscosity. In addition, our values for the shear viscosity to entropy ratio satisfy the KSS bound. 相似文献
904.
S. González de la Hoz L. March E. Ros J. Sánchez G. Amorós F. Fassi A. Fernández M. Kaci A. Lamas J. Salt 《The European Physical Journal C - Particles and Fields》2008,54(4):691-697
In the ATLAS computing model the tiered hierarchy ranged from the Tier-0 (CERN) down to desktops or workstations (Tier-3).
The focus on defining the roles of each tiered component has evolved with the initial emphasis on the Tier-0 and Tier-1 definition
and roles. The various LHC (Large Hadron Collider) projects, including ATLAS, then evolved the tiered hierarchy to include
Tier-2’s (Regional centers) as part of their projects. Tier-3 centres, on the other hand, have been defined as whatever an
institution could construct to support their Physics goals using institutional and otherwise leveraged resources and therefore
have not been considered to be part of the official ATLAS computing resources. However, Tier-3 centres are going to exist
and will have implications on how the computing model should support ATLAS physicists. Tier-3 users will want to access LHC
data and simulations and will want to enable their resources to support their analysis and simulation work. This document
will define how IFIC (Instituto de Física Corpuscular de Valencia), after discussing with the ATLAS Tier-3 task force, should
interact with the ATLAS computing model, detail the conditions under which Tier-3 centres can expect some level of support
and set reasonable expectations for the scope and support of ATLAS Tier-3 sites. 相似文献
905.
López-Cortina S Basiulis DI Marsi KL Muñoz-Hernández MA Ordoñez M Fernández-Zertuche M 《The Journal of organic chemistry》2005,70(19):7473-7478
[reaction: see text] The synthesis of pure cis- and trans-3-methoxy-2,2,6-trimethyl-3-phenyl-1,3-oxaphosphorinanium tetrafluoroborate salts 3a and 3b, respectively, molecules designed to evaluate the effect of oxygen on the steric course of base-induced nucleophilic displacement of the methoxy group at phosphorus, was accomplished. It was found that these isomeric salts react with aqueous sodium hydroxide to produce the corresponding phosphine oxides 7a and 7b with complete retention of configuration at phosphorus. 相似文献
906.
[reaction: see text] Two separate strategies have been developed for the preparation of highly substituted pyridines from 1,2,4-triazines via the inverse-electron-demand Diels-Alder reaction: a microwave-promoted, solvent-free procedure and a tethered imine-enamine (TIE) approach. Both routes avoid the need for a discrete aromatization step and offer significant advantages over the classical methods, giving a wide variety of tri-, tetra-, and penta-substituted pyridines in high, optimized yields. 相似文献
907.
908.
Fay JP Guaita MS Danelón JL Chifflet S Wawrzkiewicz M Fernández HM Ross DA 《Journal of AOAC International》2005,88(4):995-997
The objective of this work was to compare the traditional Van Soest's procedure to analyze neutral detergent fibers (NDF) and acid detergent fibers (ADF) using filtering crucibles (VS) with a semiautomatic method which uses filter bags in an ANKOM Technology Corp. instrument (ANK). Nine ruminant feeds widely used in the temperate region of Argentina were analyzed: soybean meal expeller, alfalfa, pasture silage, ryegrass, corn silage, weeping lovegrass, tall wheatgrass, guinea grass, and barley grass. Four runs were done for each technique and feed. The comparison of ADF and NDF means by the means test for paired samples showed no significant differences between techniques (alpha = 0.01). The variability among runs was greater with the VS method than the ANK, both for NDF, standard deviation (SD) = 0.71 vs 0.39, and for ADF, SD = 0.83 vs 0.56, but the differences were not significant. The linear regressions were VS = 1.43 + 0.95 ANK; R2 = 0.99, and VS = 0.53 + 0.98 ANK; R2 = 0.99 for NDF and ADF, respectively, which indicated a strong linear relationship among the results of both procedures. It was concluded that the ANK procedure gave results comparable to those of the VS method when ruminant feeds from the temperate region of Argentina were analyzed. 相似文献
909.
Fernández I Gómez GR Alfonso I Iglesias MJ Ortiz FL 《Chemical communications (Cambridge, England)》2005,(43):5408-5410
The first examples of configurationally stable N-benzyl-N-phosphinoyl carbanions are described. Their applications to the synthesis of homochiral gamma-aminophosphinic acids and esters via highly enantioselective dearomatising reactions are shown. 相似文献
910.
Escribano R Fernández D Sloan JJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(8):1759-1766
The application of wavelet filtering and analysis in spectroscopy is discussed in relation to the analysis of complex atmospheric spectra, where contributions from condensed phase particles and gas phase molecules are present in the form of broad-band features and narrow lines, respectively. The broad-band contribution can be extracted as the 'smooth signal' component of the wavelet transform, with a large reduction in the size of the corresponding data files. This procedure is applied to an investigation of the H2SO4 aerosol content of a series of atmospheric spectra measured in the ATMOS missions. The sulfate content of the smooth signal is analysed by means of correlation techniques, using a set of laboratory reference spectra of varying sulfuric acid concentration and temperature. Correlation density maps and correlation curves are used to select the most appropriate spectral zones for sulfate analysis and to assess the sulfate aerosol content in the atmosphere subsequent to the eruption of the Mount Pinatubo volcano. 相似文献