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951.
Karin Gutkowski Eleonora Freire Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(3):m77-m80
The title complex, {[Pr4(C2H3O2)10(C2O4)(H2O)2]·2H2O}n, was synthesized under hydrothermal conditions from praseodymium acetate and the ionic liquid 1‐butyl‐3‐methylimidazolium chloride via an in situ oxalate‐ligand synthesis. The compound is a two‐dimensional polymer and in the structure presents tightly bound planes parallel to (100), which are in turn linked into a three‐dimensional network by hydrogen bonds involving both coordinated and solvent water molecules. The oxalate anion lies across an inversion centre and acts as a bridge between pairs of Pr atoms within a tetranuclear segment of the polymer. 相似文献
952.
Black condensates (BC) are wastes of the insulation corkboard industry that contain several valuable chemicals, including friedelin, a terpene exhibiting biological activity. Herein, we report a straightforward procedure to extract friedelin from BC. Using this procedure, we were able to extract friedelin with yields between 0.4% and 2.9% and to further purify it obtaining purities from 77.0% to 99.3% (HPLC). The initial BC (2 batches), extracted raw product and purified friedelin were analyzed using FTIR. The extraction yields and purities were found to be directly related to the intensity of the carbonyl vibration at 1713 cm(-1) in the FTIR spectrum of the used BC batch. Therefore, these spectra can be used to screen and select BC batches suitable for friedelin extraction. 相似文献
953.
Ana María Atria Gino Corsini Natalia Herrera Maria Teresa Garland Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(5):m169-m172
The two isomorphous title compounds, [M(C5H7N6)2(C9H6O4)2(H2O)2]·4H2O or M2+(Hdap+)2(hpt2−)2(H2O)2·4H2O {where dap is 2,6‐diaminopurine, H2hpt is homophthalic acid [2‐(2‐carboxyphenyl)acetic acid] and M is NiII or CoII}, consist of neutral M2+(Hdap+)2(hpt2−)2(H2O)2 monomers, where the MII cation lies on an inversion centre and its MN2O4 octahedral environment is defined by one N atom (from Hdap+), two O atoms (from one hpt2− dianion and one water molecule) and their inversion images. The structures are unusual in that the Hdap+ cation occurs in an uncommon protonated state (as 2,6‐diamino‐7H‐purin‐1‐ium) and both ligands bind in an unprecedented monodentate fashion. The existence of a large number of donors and acceptors for hydrogen bonding, together with π–π interactions, leads to a rather complex three‐dimensional structure. 相似文献
954.
Ricardo Saraiva de Camargo Gilberto de Miranda Jr. Ricardo P.M. Ferreira 《Operations Research Letters》2011,39(5):329-337
An efficient procedure that concurrently generates Outer-Approximation and Benders cuts is devised to tackle the single allocation hub location problem under congestion, an MINLP. The proposed method is able to optimally solve large instances (up to 200 nodes) in reasonable time. The combination of both cuts is an algorithmic novelty. 相似文献
955.
Ricardo Riaza 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(1):213-223
The presence of nonlinearities in the capacitance and the inductance in van der Pol type electrical circuits defines a linearly implicit (or quasilinear) counterpart of the classical Liénard systems. When the reactances remain positive, the existence of a unique attracting periodic solution follows, with minor modifications, as in the classical setting. Novel results are obtained when the values of reactances may vanish at certain points of the state space; these points yield singularities of the model, and the existence of an attracting periodic solution can be characterized in terms of the behavior of certain smooth solutions crossing the singular manifold through so-called I-singularities. 相似文献
956.
Mario Esteban Muñoz Sergio Ricardo Batlouni Irene Bastos Franceschini Vicentini Carlos Alberto Vicentini 《Micron (Oxford, England : 1993)》2011,42(8):892-897
The present study examined the testicular structure and the seminal pathway in freshwater fish Leporinus macrocephalus (Garavello and Britski, 1988). Twenty-five specimens of this species were studied. Testicular structure was analyzed using light and transmission electron microscopy. The testicular main ducts were examined by means of conventional histology, corrosion–cast technique and scanning electron microscopy. Additional techniques were applied for polysaccharides histochemistry and immunohistochemistry for androgen receptor. The testicular parenchyma was classified as the anastomosing tubular testis type with spermatogonia occurring along the lengths of the seminiferous tubules. The seminiferous tubules emptied directly into the testicular main ducts. The wall of the testicular main ducts in L. macrocephalus consisted of three layers: epithelium, connective tissue and peritoneum. The epithelium changed from simple cuboidal to pseudostratified. The histochemical analysis revealed the presence of granules PAS positive in the epithelial cells. The immunoreactivity to androgen receptor was noted in the testicular main ducts through all cytoplasmic areas of epithelial cells. 相似文献
957.
Gouré E Thiabaud G Carboni M Gon N Dubourdeaux P Garcia-Serres R Clémancey M Oddou JL Robin AY Jacquamet L Dubois L Blondin G Latour JM 《Inorganic chemistry》2011,50(14):6408-6410
The coupling of electron and proton transfers is currently under intense scrutiny. This Communication reports a new kind of proton-coupled electron transfer within a homodinuclear first-row transition-metal complex. The triply-bridged complex [Fe(III)(μ-OPh)(μ(2)-mpdp)Fe(II)(NH(2)Bn)] (1; mpdp(2-) = m-phenylenedipropionate) bearing a terminal aminobenzyl ligand can be reversibly deprotonated to the anilinate complex 2 whose core [Fe(II)(μ-OPh)(μ(2)-mpdp)Fe(III)(NHBn)] features an inversion of the iron valences. This observation is supported by a combination of UV-visible, (1)H NMR, and M?ssbauer spectroscopic studies. 相似文献
958.
Torres-Pardo A Jiménez R González-Calbet JM García-González E 《Inorganic chemistry》2011,50(23):12091-12098
An exhaustive temperature dependent structural and dielectric study of the tetragonal tungsten bronze-type Sr(2)NaNb(5)O(15) (SNN) compound has been performed in the 300-100 K temperature range, by combining X-ray, neutron diffraction, and transmission electron microscopy with dielectric measurements, in order to clarify the structural effects responsible for the observed low temperature dielectric properties. Interestingly, a relevant second anomaly in the dielectric constant, in addition to the ferroelectric (FE) to paraelectric (PE) transition at T(C) = 518 K is found at T ≈ 240 K, revealing a relaxor-like behavior of the material at low temperature. This phenomenon has been previously observed in FE perovskite-type phases and referred to as the re-entrant phenomenon. However, FE polarization tends to vanish below this low temperature dielectric anomaly and this fact is not expected for a classical relaxor-ferroelectric phase. Although there is no structural transition from RT to 100 K, there is a change in the elastic properties of the material in the considered temperature range and the intense anomaly at ~240 K could be associated to a smeared-out phase transition to a frustrated FE/ferroelastic (FEL) low temperature state in correlation with subtle structural effects. 相似文献
959.
Cerón-Camacho R Hernández S Le Lagadec R Ryabov AD 《Chemical communications (Cambridge, England)》2011,47(10):2823-2825
Electrochemical studies of [Os(C-N)(x)(N-N)(3-x)](m+) (1) consisting of known Os(II) species with x = 0 (a) and 1 (b) and crystallographically characterized new Os(III) bis- and tris-metalacycles with x = 2 (c) and 3 (d) (N-N = 2,2'-bipyridine, (-)C-N = 2-phenylpyridinato) revealed a Nernstian behavior in MeCN. A stepwise replacement of neutral N-N ligands by three anionic C-N donors covers a 2 V potential range from -1 to +1 V vs. Ag/AgCl for the Os(III)/Os(II) feature. 相似文献
960.
Velichka Kontozova-Deutsch Felix Deutsch Ricardo H.M. Godoi René Van Grieken Karolien De Wael 《Microchemical Journal》2011,99(2):508-513
Levels of urban gaseous and particulate pollutants were investigated in the Cathedral of Cologne, Germany in the framework of the EU-project “VIDRIO”. The purpose of this study was to evaluate the influence of a protective double glazing system on the preservation of ancient stained glass windows by sampling at protected and unprotected windows (indoors, in the interspace and outdoor of the Cathedral). The interspace between the ancient stained glass window and the protective glazing is flushed in the Cathedral by indoor air, hence isolating the historic glass from the outdoor air and exposing it to indoor air on both sides of the glass panels. Concentrations of aggressive gaseous pollutants such as NO2, SO2, O3 and CO2 as well as elemental concentrations of bulk particles and relative abundances of single particles were surveyed at all sampling locations. Elemental concentrations in bulk particulate matter were found to be significantly lower inside the Cathedral in comparison to the outdoor air. This result is advantageous for the stained glass windows. Single particle analysis of the samples from Cologne showed also soil dust and organic particles as well as sulphates and nitrates, from which the latter two compounds are dangerous for the stained glass windows. On the base of the obtained results, it can be concluded that the protective glazing system in the Cathedral of Cologne can be considered as predominantly advantageous from both the gases' point of view (except for NO2-candles burning) and from the particles' point of view. 相似文献