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81.
Inmaculada Molina Pinilla Manuel Bueno Martínez Francisca Zamora Mata Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》1998,36(1):67-77
Two poly(ester amides) containing three methoxy groups stereoregularly attached to the main chain have been prepared by using naturally occurring L -arabinose and D -xylose as the starting materials. The polymers were prepared by the active ester polycondensation method and characterized by elemental analysis, IR, and 1H- and 13C-NMR spectroscopies. Both viscosimetry and GPC were used to estimate the molecular weights. The polymers are hydrophilic, one of them being water soluble, and exhibited moderate optical activity. Thermal and X-ray diffraction studies revealed that they are slightly crystalline and stable up to 250°C under nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 67–77, 1998 相似文献
82.
Jesus Bueno Manuel Melguizo M. Luisa Quijano John Nicolson Low 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):o363-o366
The supramolecular structures of the isomeric compounds 5,7‐dimethoxyimidazo[1,2‐c]pyrimidine, C8H9N3O2, (I), and 7‐methoxy‐1‐methylimidazo[1,2‐a]pyrimidin‐5(1H)‐one, C8H9N3O2, (II), are determined by weak C—H⃛N and C—H⃛O hydrogen bonds in (I), which generate alternating linked centrosymmetric R(8) and R(10) rings that form a ribbon running parallel to the c axis, and by C—H⃛O bonds in (II), which link the molecules into sheets comprising centrosymmetric R(10) and R(22) rings. 相似文献
83.
J.A. de Azcárraga A.J. Macfarlane A.J. Mountain J.C. Pérez Bueno 《Nuclear Physics B》1998,510(3):657-687
The forms of the invariant primitive tensors for the simple Lie algebras Al, Bl, Cl, and Dl are investigated. A new family of symmetric invariant tensors is introduced using the non-trivial cocycles for the Lie algebra cohomology. For the Al algebra it is explicitly shown that the generic forms of these tensors become zero except for the l primitive ones and that they give rise to the l primitive Casimir operators. Some recurrence and duality relations are given for the Lie algebra cocycles. Tables for the 3- and 5-cocycles for su(3) are su(4) are also provided. Finally, new relations involving the d and f su(n) tensors are given. 相似文献
84.
Hernan A. Orgueira Manuel Bueno Jose Luis Funes Juan A. Galbis Oscar Varela 《Journal of polymer science. Part A, Polymer chemistry》1998,36(15):2741-2748
Stereoregular, enantiomerically pure, chiral polyamides of the –AB– type, containing a natural (glycine) and a synthetic [(S)-5-amino-4-methoxypentanoic acid (AMP)] component have been prepared by the active ester polycondensation method. Thus, polyamide 7 was obtained by polycondensation of the conveniently activated H2NGly–AMPCO2R unit ( 6 ). In this reaction, 7 appeared accompanied by a considerable amount of cyclic (Gly–AMP)2 ( 8 ), which makes the isolation and purification of 7 difficult. The formation of cyclic byproducts could be avoided by preparing and polymerizing the oligoamide H2NGly–AMP–AMPCO2R ( 11 ), which has the terminal carboxyl group activated as the pentachlorophenyl ester. The resulting polyamide ( 12 ) was obtained in 85% yield and free of macrolactams, such as 8 . The new polyamides 7 and 12 were characterized by elemental analysis and infrared and 1H- and 13C-nuclear magnetic resonance spectroscopies. Thermal studies revealed that 12 is crystalline and yields films with spherulitic texture by slow evaporation of formic acid solutions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2741–2748, 1998 相似文献
85.
We characterize active redundancy through compensator transform and use the reverse rule of order 2 (RR2) property between compensator processes to investigate the problem of where to allocate a spare in a k-out-of-n:F system of dependent components through active redundancy. 相似文献
86.
This paper deals with the bilinear symmetrization problem associated with Sobolev inner products. Let 007B;Q
n
}
n=0
be the sequence of monic polynomials orthogonal with respect to a Sobolev inner product of order 1 when one of the measures is discrete and the other one is a nondiscrete positive Borel measure. Furthermore, assume that the supports of such measures are symmetric with respect to the origin so that the corresponding odd moments vanish. We consider the orthogonality properties of the sequences of monic polynomials 007B;P
n
}
n=0
and {R
n
}
n=0
such that Q
2n
(x)=P
n
(x
2), Q
2n+1(x)=xR
n
(x
2). Moreover, recurrence relations for {P
n
}
n=0
and {R
n
}
n=0
are obtained as well as explicit algebraic relations between them. 相似文献
87.
Bruno Alves Rocha Marina Rezende Rodrigues Paula Carolina Pires Bueno Ana Rita de Mello Costa-Machado Mirela Mara de Oliveira Lima Leite Vaz Andresa Piacezzi Nascimento Hernane Silva Barud Andresa Aparecida Berretta-Silva 《Journal of Thermal Analysis and Calorimetry》2012,108(1):87-94
The propolis produced in Southeastern Brazil is known as green propolis (BGP) because of its color and the most important
plant source is Baccharis dracunculifolia. Several authors reported biological activities such as antiulcer, anti-inflammator, antimutagenic, antifungal/antibacterial,
antileishmanial/antiplasmodial for the BGP. For this reason, BGP has been extensively employed in food and beverages, thus
helping improve health and preventing diseases. Some authors related that the biological activities of BGP are mostly due
to its high levels of prenylated ρ-coumaric acids derivatives, mainly artepillin C. The inclusion complex between Brazilian
green propolis (BGP) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was prepared and its characterization was investigated by
different analytical techniques (X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetry) and suggesting
that propolis was molecularly dispersed in the HP-β-CD matrix. The increasing solubility of chemical constituents was determined
using quantitation methods for total flavonoids and polyphenols. Furthermore, it was developed a method for the quantitation
and identification of the main compounds by high-performance liquid chromatography in order to evaluate the increasing water
solubility of each constituent in aqueous BGP extract (aromadendrin, isosakuranetin, and artepillin C). The antioxidant activity
was evaluated by chemical assay 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging. 相似文献
88.
89.
90.
Laura Tositti Enio Bueno Pereira Silvia Sandrini Davide Capra Ottavio Tubertini Maria Giovanna Bettoli 《International journal of environmental analytical chemistry》2013,93(5):259-274
This work reports the first results of atmospheric radon measurements performed at the Italian Antarctic station located at Terra Nova Bay (74.69°S; 164.12°E) during summer campaigns of 1995-96, 1996-97 and 1997-98. Mean222Rn concentrations was 0.51 - 0.43 Bq mm3 (median = 0.37 Bq mm3), and ranged from 0.01 to 2.74 Bq mm3 . On the average, these values were considered high, in comparison to results reported for other sites in Antarctica at equivalent latitudes. This could be explained by two causes: radon data for Terra Nova Bay were only for the summer period, when the ice-free area is at its maximum and thus the radon emission to the atmosphere; and by the larger ice-free area at Terra Nova Bay compared, for example, to measurements taken at another Antarctic site by the same technique (Ferraz station - 62°05'S; 058°23.5'W). The mean 222Rn to 220Rn activity ratio was 4.4 - 4.2, ranging between 0.1 and 45.3. The highest ratios indicated that some of observed surges of concentration of 222Rn could be attributed to not local sources. Lower radon concentrations were observed during katabatic wind events. The diurnal radon variation followed the general trend observed for continental areas located at lower latitudes. 相似文献