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排序方式: 共有173条查询结果,搜索用时 229 毫秒
91.
Daniel Botelho da Silva Abdelouahid Samadi María do Carmo Carreiras 《Tetrahedron letters》2010,51(48):6278-6281
An unexpected, but simple method for the efficient synthesis of new 2.2′-azopyridine dyes, such as (E)-diethyl 6,6′-(diazene-1,2-diyl)bis(5-cyano-2-methyl-4-phenylnicotinates) (2, 4, 6, 8, 10, and 12), based on the treatment of ethyl 6-amino-5-cyano-2-methyl-4-arylnicotinates (1, 3, 5, 7, 9, and 11) with NBS/benzoyl peroxide, is described. The X-ray diffraction analysis and the UV-vis absorption spectra of dye 2 are reported and discussed. 相似文献
92.
Luiz C. L. Botelho 《International Journal of Theoretical Physics》2009,48(9):2715-2729
We present a simple proof that self-avoiding fermionic strings solutions solve formally (in a Quantum Mechanical Framework)
the QCD(U(N
c
)) Loop Wave Equation written in terms of random loops. 相似文献
93.
Adcox K Adler SS Ajitanand NN Akiba Y Alexander J Aphecetche L Arai Y Aronson SH Averbeck R Awes TC Barish KN Barnes PD Barrette J Bassalleck B Bathe S Baublis V Bazilevsky A Belikov S Bellaiche FG Belyaev ST Bennett MJ Berdnikov Y Botelho S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy J Butsyk S Carey TA Chand P Chang J Chang WC Chavez LL Chernichenko S Chi CY Chiba J Chiu M Choudhury RK Christ T Chujo T Chung MS Chung P Cianciolo V Cole BA D'Enterria DG 《Physical review letters》2002,89(8):082301
Data from Au + Au interactions at sqrt[s(NN)]=130 GeV, obtained with the PHENIX detector at the Relativistic Heavy-Ion Collider, are used to investigate local net charge fluctuations among particles produced near midrapidity. According to recent suggestions, such fluctuations may carry information from the quark-gluon plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays. 相似文献
94.
Adcox K Adler SS Ajitanand NN Akiba Y Alexander J Aphecetche L Arai Y Aronson SH Averbeck R Awes TC Barish KN Barnes PD Barrette J Bassalleck B Bathe S Baublis V Bazilevsky A Belikov S Bellaiche FG Belyaev ST Bennett MJ Berdnikov Y Botelho S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy J Butsyk S Carey TA Chand P Chang J Chang WC Chavez LL Chernichenko S Chi CY Chiba J Chiu M Choudhury RK Christ T Chujo T Chung MS Chung P Cianciolo V Cole BA D'Enterria DG 《Physical review letters》2002,88(24):242301
Identified pi(+/-), K(+/-), p, and (-)p transverse momentum spectra at midrapidity in sqrt[s(NN)] = 130 GeV Au+Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. Within errors, all midrapidity particle yields per participant are found to be increasing with the number of participating nucleons. There is an indication that K(+/-), p, and (-)p yields per participant increase faster than the pi(+/-) yields. In central collisions at high transverse momenta (p(T) > or =2 GeV/c), (-)p and p yields are comparable to the pi(+/-) yields. 相似文献
95.
Adcox K Adler SS Ajitanand NN Akiba Y Alexander J Aphecetche L Arai Y Aronson SH Averbeck R Awes TC Barish KN Barnes PD Barrette J Bassalleck B Bathe S Baublis V Bazilevsky A Belikov S Bellaiche FG Belyaev ST Bennett MJ Berdnikov Y Botelho S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy J Butsyk S Carey TA Chand P Chang J Chang WC Chavez LL Chernichenko S Chi CY Chiba J Chiu M Choudhury RK Christ T Chujo T Chung MS Chung P Cianciolo V Cole BA D'Enterria DG 《Physical review letters》2002,88(19):192302
Two-pion correlations in square root[s(NN)] = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at square root[s(NN)] = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R(out)/R(side)) is consistent with unity and independent of k(T). 相似文献
96.
Chirlene Nascimento Botelho Daniele Pavão e Pavão Flávio Santos Damos Rita de Cássia Silva Luz 《Electroanalysis》2021,33(8):1936-1944
The present work describes the development of a photoelectrochemical sensor based on titanium dioxide, cadmium telluride quantum dots and the tris (2,2′-bipyridyl) ruthenium(II) chloride complex for detection of Isoniazid (INH). The Ru(bpy)32+/CdTe-QDs/TiO2/FTO photoelectrochemical platform was characterized by scanning electrochemical microscopy, electrochemical impedance spectroscopy and amperometry. The photoelectrochemical sensor presented two linear ranges for INH concentrations ranging from 0.5 to 150 μmol L−1 and 150 to 1270 μmol L−1, with a theoretical detection limit of 0.02 μmol L−1. The sensor was successfully applied for the determination of INH in drugs samples used in the treatment of tuberculosis. 相似文献
97.
Botelho do Rego AM Ferraria AM El Beghdadi J Debontridder F Brogueira P Naaman R Rei Vilar M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(19):8765-8773
The adsorption of phenylphosphonic acid (PPA) on GaAs (100) surfaces from solutions in acetonitrile/water mixtures was studied using Fourier transform infrared spectroscopy in attenuated total reflection in multiple internal reflections (ATR/MIR), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), and atomic force microscopy (AFM). ATR/MIR in situ showed that the accumulation of PPA molecules near the GaAs surface increased with the water concentration in the solution. For water contents lower than 4%, ATR/MIR and XPS results are consistent with the formation of a low-density monolayer. A mechanism is proposed for H2O percentages lower than 4% involving the creation of interfacial bonds through a Br?nsted acid-base reaction, which involves the surface hydroxyl groups most probably bound to Ga. It was found that the morphology of the final layer depended strongly on the water concentration in the adsorbing solution. For water concentrations equal to or higher than 5%, the amount of adsorbed molecules drastically increased and was accompanied by modifications in the infrared spectral region corresponding to P-O and P=O. This sudden change indicates a deprotonation of the acid. XPS studies revealed the presence of extra oxygen atoms as well as gallium species in the layer, leading to the conclusion that phosphonate and hydrogenophosphonate ions are present in the PPA layer intercalated with H3O+ and Ga3+ ions. This mechanism enables the formation of layers approximately 10 times thicker than those obtained with lower H2O percentages. HREELS indicated that the surface is composed of regions covered by PPA layers and uncovered regions, but the uncovered regions disappeared for water contents equal to or higher than 5%. XPS results are interpreted using a model consisting of a monolayer partially covering the surface and a thick layer. This model is consistent with AFM images revealing roughness on the order of 7 nm for the thick layer and 0.2-0.5 nm for the thin layer. Sonication proves to be an effective method for reducing layer thickness. 相似文献
98.
99.
Both pressurized solvent extraction (PSE) and reflux extraction in various solvents were used to select the most efficient system for the determination of the quantity of perfluorooctanoic acid (PFOA) present in polytetrafluoroethylene polymers. After evaporating the solvent, PFOA was determined using liquid chromatography tandem mass spectrometry. Ethanol, water and methanol gave comparable results and were shown to be good solvents for this extraction. Acetonitrile was a reasonable solvent using the reflux extraction method, but not with PSE. Chloroform resulted in poor recovery for both extraction methods. PSE proved to be the more efficient extraction method. 相似文献
100.
The determination of chromium, copper, manganese, nickel and vanadium in carbonaceous samples by slurry introduction graphite
furnace atomic absorption spectrometry and after microwave assisted digestion are compared. Parameters such as atomization
and pyrolysis temperatures, and surfactant concentration as well as the homogenization procedure were optimized. The slurries
were prepared by mixing adequate amounts of the pulverized samples with 0.05% Triton X-100, sonicating for, at least, 40 seconds
during the preparation to separate aggregates and for 20 seconds immediately before being autosampled. It was not necessary
to use modifiers and calibration against aqueous standards was possible for all the elements. Coke, graphite and certified
coal samples were analyzed, and no significant difference was observed using both procedures. Good agreement between found
and certified values was obtained.
Received January 24, 2000. Revision September 26, 2000. 相似文献