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41.
P. Barahona O. Pea A.B. Antunes C. Campos G. Pecchi Y. Moreno C. Moure V. Gil 《Journal of magnetism and magnetic materials》2008,320(14):e61-e64
Partial substitution of manganese by cobalt in rare-earth perovskites REMnO3 leads to unusual magnetic phenomena because of the simultaneous presence of Mn3+, Mn4+, Co2+ and Co3+ species. The magnetic nature of the RE cation plays a fundamental role in the magnetic properties. We present herein two specific families: for RE=La the magnetic behavior of the |Co+Mn| network is observed, while for Gd its strong magnetic moment interacts with the transition metals, leading to a spin reversal state. Magnetic interactions are maximized at x=0.50, as if two regimes exist: for x<0.5 Co substitutes Mn in the REMnO3 manganite, and for x>0.5 Mn substitutes Co in the RECoO3 cobaltite. 相似文献
42.
Paulo Antunes 《Letters in Mathematical Physics》2008,86(1):33-45
We define Poisson quasi-Nijenhuis structures with background on Lie algebroids and we prove that any generalized complex structure
on a Courant algebroid which is the double of a Lie algebroid has an associated Poisson quasi-Nijenhuis structure with background.
We prove that any Lie algebroid with a Poisson quasi-Nijenhuis structure with background constitutes, with its dual, a quasi-Lie
bialgebroid. We also prove that any pair (π,ω) of a Poisson bivector and a 2-form induces a Poisson quasi-Nijenhuis structure with background and we observe that particular
cases correspond to already known compatibilities between π and ω.
This paper was presented as a poster in the conference “Poisson 2008”, EPFL, Lausanne, in July 2008. 相似文献
43.
44.
Pereira AA Martins GF Antunes PA Conrrado R Pasquini D Job AE Curvelo AA Ferreira M Riul A Constantino CJ 《Langmuir : the ACS journal of surfaces and colloids》2007,23(12):6652-6659
Four lignin samples were extracted from sugar cane bagasse using four different alcohols (methanol, ethanol, n-propanol, and 1-butanol) via the organosolv-CO2 supercritical pulping process. Langmuir films were characterized by surface pressure vs mean molecular area (Pi-A) isotherms to exploit information at the molecular level carrying out stability tests, cycles of compression/expansion (hysteresis), subphase temperature variations, and metallic ions dissolved into the water subphase at different concentrations. Briefly, it was observed that these lignins are relatively stable on the water surface when compared to those obtained via different extraction processes. Besides, the Pi-A isotherms are shifted to smaller molecular areas at higher subphase temperatures and to larger molecular areas when the metallic ions are dissolved into the subphase. The results are related to the formation of stable aggregates (domains) onto the water subphase by these lignins, as shown in the Pi-A isotherms. It was found as well that the most stable lignin monolayer onto the water subphase is that extracted with 1-butanol. Homogeneous Langmuir-Blodgett (LB) films of this lignin could be produced as confirmed by UV-vis absorption spectroscopy and the cumulative transfer parameter. In addition, FTIR analysis showed that this lignin LB film is structured in a way that the phenyl groups are organized preferentially parallel to the substrate surface. Further, these LB films were deposited onto gold interdigitated electrodes and ITO and applied in studies involving the detection of Cd+2 ions in aqueous solutions at low concentration levels through impedance spectroscopy and electrochemical measurements. FTIR spectroscopy was carried out before and after soaking the thin films into Cd+2 aqueous solutions, revealing a possible physical interaction between the lignin phenyl groups and the heavy metal ions. The importance of using nanostructured systems is demonstrated as well by comparing both LB and cast films. 相似文献
45.
Luís Antônio Dantas Silva Fernanda Vieira Teixeira Raphael Caixeta Serpa Najla Locatelli Esteves Rayane Ramos dos Santos Eliana Martins Lima Marcílio Sérgio Soares da Cunha-Filho Adriano Antunes de Souza Araújo Stephânia Fleury Taveira Ricardo Neves Marreto 《Journal of Thermal Analysis and Calorimetry》2016,123(3):2337-2344
46.
Josepha Yohanna de Jesus Eliane Santos de Carvalho Dantas Mairim Russo Serafini Paula dos Passos Menezes Juliana Cordeiro Cardoso Ricardo Luiz Cavalcanti Albuquerque-Jr Jivaldo do Rosário Matos Juliana Ferreira de Oliveira Irwin Rose Alencar de Menezes Francilene Amaral da Silva Adriano Antunes de Souza Araújo 《Journal of Thermal Analysis and Calorimetry》2016,123(3):2003-2012
47.
48.
Rodrigo O.M.A. de Souza Lilian M.C. Matos Ingrid C.R. Costa Selma G.F. Leite O.A.C. Antunes 《Tetrahedron letters》2009,50(17):2017-1605
The present Letter details our findings on the lipase-catalyzed Michael reactions between primary or secondary amines and acrylonitrile. Several lipases were evaluated, and good results were obtained leading to the formation of Michael adducts in shorter reaction times than the uncatalyzed reactions. 相似文献
49.
Antunes R Rendell L Gordon J 《The Journal of the Acoustical Society of America》2010,127(5):3239-3247
Sperm whale clicks are characterized by a multi-pulsed structure. The time lag between consecutive pulses, i.e., the inter-pulse interval (IPI), is related to the size of the sound production organ such that its measurement provides a means to acoustically estimate the size of individual whales. Due to off-axis effects the identification of pulses is, however, not always straightforward, and automatic measurement methods provide not only more objective estimation, but may also facilitate IPI estimation in cases where single click measurements are ambiguous. In particular, averaging measurements over a time series of clicks from the same whale could enhance the discrimination of time invariant pulses. The authors developed two automatic methods of automatic IPI measurement based on waveform and autocorrelation averaging and compared their accuracy and consistency with other previously used methods. Manual measurement by an experienced operator provided the most self-consistent estimates. The autocorrelation averaging technique had the best overall performance of the automated methods achieving a very similar performance to manual measurement. On some recordings cepstrum averaging methods converged when autocorrelation did not. Therefore, applying both of these automated methods and choosing the best of the two are recommended. 相似文献
50.
Eder do Couto TavaresMarcelo Ribeiro Leite Oliveira Jan JanczakCamila Grossi Vieira Leandro de Carvalho AlvesRodrigo Antunes Castro Lígia Maria Mendonça VieiraRenata Hernandez Lindemann Genivaldo Júlio PerpétuoLeila Léa Yuan Visconte Mayura Marques Magalhães Rubinger 《Polyhedron》2012,31(1):494-501
Four zinc(II)-bis(trithiocarbimato) complexes with the general formula A2[Zn(RSO2NCS3)2] [A = Ph4P+: R = CH3 (1), 4-CH3C6H4 (2); A = Bu4N+: R = CH3 (3), 4-CH3C6H4 (4)] were obtained by the reaction of sulfur with the correspondent zinc(II)-bis(dithiocarbimato) complexes. Additionally, the compound (Ph4P)2[(CH3SO2NCS2)2S)] (5) was prepared from the potassium methylsulfonildithiocarbimate by oxidation with iodine. The compounds were characterized by elemental analyses and IR, 1H NMR and 13C NMR spectroscopies. The compounds 4 and 5 were also characterized by X-ray diffraction techniques. The compound 4 crystallizes in the centrosymmetric space group C2/c of the monoclinic system. The Zn(II) is in a distorted tetrahedral environment (ZnS4) in compound 4, and differ from the coordination mode observed in compound 1, which involves one sulfur and one nitrogen atom of each trithiocarbimate ligand. Compound 5 is the first example of a compound containing a bis(N-alkylsulfonyldithiocarbimate)-sulfide dianion and crystallises in the non-centrosymmetric space group P41212 of the tetragonal system. 相似文献