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61.
Hélio A. Stefani Stanley N.S. Vasconcelos Frederico B. Souza Flávia Manarin Julio Zukerman-Schpector 《Tetrahedron letters》2013
A general and efficient reaction of indole with oxalyl chloride and nucleophiles providing indole-3-glyoxyl derivatives has been developed in mild conditions. In the same fashion, the other reaction involved the addition of organic azides leading to the synthesis of indole-3-glyoxyl-1,2,3-triazoles, which proceeds smoothly generating the products in moderate to high yields. 相似文献
62.
L.A. Trevisan T. Frederico L. Tomio 《The European Physical Journal C - Particles and Fields》1999,11(2):351-357
The strangeness content of the nucleon is determined from a statistical model using confined quark levels, and is shown to
have a good agreement with the corresponding values extracted from experimental data. The quark levels are generated in a
Dirac equation that uses a linear confining potential (scalar plus vector). With the requirement that the result for the Gottfried
sum rule violation, given by the New Muon Collaboration (NMC), is well reproduced, we also obtain the difference between the
structure functions of the proton and neutron, and the corresponding sea quark contributions.
Received: 15 March 1999 / Revised version: 15 April 1999 / Published online: 14 October 1999 相似文献
63.
F. F. Bellotti T. Frederico M. T. Yamashita D. V. Fedorov A. S. Jensen N. T. Zinner 《Few-Body Systems》2014,55(8-10):1025-1027
Universal properties of mass-imbalanced three-body systems in 2D are studied using zero-range interactions in momentum space. The dependence of the three-particle binding energy on the parameters (masses and two-body energies) is highly non-trivial even in the simplest case of two identical particles and a distinct one. This dependence is parametrized for ground and excited states in terms of supercircles functions in the most general case of three distinguishable particles. 相似文献
64.
A procedure for preconcentration and determination of lead in water is described. The method is based on the sorption of Pb(II) in a minicolumn packed with a functionalized sorbent and subsequent elution with acidic solution. The determination of lead content in the eluate was carried out using flame atomic absorption spectrometry. The sorbent was prepared by immobilization of the ligand 4-(5'-bromo-2'-thiazolylazo)orcinol on polystyrene-divinylbenzene through an azo spacer. Diazotization and coupling reactions were used for synthesis of the sorbent. Some variables affecting the preconcentration were optimized using a full factorial design. Under optimized conditions, the method presented a detection limit of 0.5 microg/L and enrichment factor of 36 for a sample volume of 25 mL. The accuracy of the method was tested by the determination of lead in a standard reference material (National Institute of Standards and Technology 1643d Fresh Water). The proposed procedure was applied to the determination of lead in samples of natural and drinking waters. 相似文献
65.
Luciano Farias de Novaes Lucas Oliveira Borges José Alberto Domingues Rodrigues Suzana Maria Ratusznei Marcelo Zaiat Eugenio Foresti 《Applied biochemistry and biotechnology》2010,162(3):885-899
Many lab-scale studies have been carried out regarding the effect of feed strategy on the performance of anaerobic sequencing
batch reactors (ASBR); however, more detailed pilot-scale studies should be performed to assess the real applicability of
this type of operation. Therefore, the objective of this work was to assess the effect of feed strategy or fill time in a
1-m3 mechanically stirred pilot-scale sequencing batch reactor, treating 0.65 m3 sanitary wastewater in 8-h cycles at ambient temperature. Two reactor configurations were used: one containing granular biomass
(denominated ASBR) and the other immobilized biomass on polyurethane foam as inert support (denominated anaerobic sequencing
batch biofilm reactor (AnSBBR)). The reactors were operated under five distinct feed strategies, namely: typical batch and
fed-batch for 25%, 50%, 75%, and 100% of the cycle length. Stirring frequency in the ASBR was 40 rpm with two flat-blade turbine
impellers and 80 rpm in the AnSBBR with two helix impellers. The results showed that both the ASBR and AnSBBR when operated
under typical batch, fed-batch for 50% and 75% of the cycle length, presented improved organic matter removal efficiencies,
without significant differences in performance, thus showing important operational flexibility. In addition, the reactors
presented operation stability under all conditions. 相似文献
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69.
L.A. Trevisan C. Mirez T. Frederico L. Tomio 《The European Physical Journal C - Particles and Fields》2008,56(2):221-229
Within a statistical model of linear confined quarks we obtain the flavor asymmetry and corresponding structure function of
the nucleon. The model parameters are fixed by the experimental available data. The temperature parameter is adjusted by the
Gottfried sum rule violation and the chemical potentials by the corresponding up (u) and down (d) quark normalizations in
the nucleon. The light antiquark and quark distributions in the proton, given by d̄/ū, d/u and d̄-ū, as well as the neutron
to proton ratio of the structure functions, extracted from the experimental data, are well fitted by the model. As the quark-confining
strengths should be flavor dependent, a mechanism is introduced in the model to adjust the corresponding distribution, in
order to improve the comparison obtained for the sea-quark asymmetries in the nucleon with the available experimental analysis.
PACS 11.30.Hv; 14.20.Dh; 12.39.Ki; 12.40.Ee; 11.55.Hx 相似文献
70.
We study the low-energy universality observed in three-body models through a scale-independent approach. From the already
estimated infinite number of three-body excited energy states, which happen in the limit when the energy of the subsystem
goes to zero, we are able to identify the lower energies of the helium trimers as possible examples of Thomas-Efimov states.
By considering this example, we illustrate the usefulness of a scaling function, which we have defined. The approach is applied
to bosonic systems of three identical particles, and also to the case where two kinds of particles are present.
Received June 30, 1999; revised July 27, 1999; accepted for publication August 29, 1999 相似文献