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211.
Fa-Nian Shi Filipe A. Almeida Paz Penka I. Girginova Luís Mafra Vítor S. Amaral Joo Rocha Anna Makal Krzysztof Wozniak Jacek Klinowski Tito Trindade 《Journal of Molecular Structure》2005,754(1-3):51-60
Two new compounds containing multidentate chelating organic residues of N-(phophonomethyl)iminodiacetic acid (H4pmida), [M(pyr)(H2O)4][M2(Hpmida)2(pyr)(H2O)2]·2(H2O) (where pyr=pyrazine and M=Co2+ or Ni2+ for I and II, respectively) have been synthesised and structurally characterised by single-crystal and powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermal analysis and solid-state 31P MAS NMR. The compounds contain discrete binuclear anionic [M2(Hpmida)2(pyr)(H2O)2]2− units in which one pyrazine ligand bridges two M2+ cations which are completely trapped inside three five-membered chelate rings formed by the Hpmida3− ligands. These moieties close pack in the ac plane via a series of strong and highly directional O–HO hydrogen bonds leading to the formation of anionic layers. One-dimensional cationic coordination polymers are placed in-between and strongly hydrogen-bonded to these layers. The magnetic properties of these two materials are also reported. 相似文献
212.
E. F. S. Vieira A. R Cestari S. F. Zawadzki S. M. Rocha 《Journal of Thermal Analysis and Calorimetry》2004,75(2):501-506
Thermogravimetry (TG) was used to provide some new information on some polybutadiene-based polyurethanes. The results showed
two main mass decomposition stages, from 230 to 564°C. The first mass loss stages were used to quantify the hard segments
of the polymers. The results correlated well with the ASTM methodology. In addition, two 23 factorial design studies were applied to evaluate the importance of some selected factors on the TG results of the polyurethanes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
213.
A. K. Ávila T. O. Araujo R. M. H. Borges P. R. G. Couto M. F. G. Rosias O. G. F. Rocha D. S. Vaitsman V. Dias 《Accreditation and quality assurance》2005,10(6):277-282
Todays and tomorrows globalized world requires the acceptance of each others capabilities, competence and metrological traceability of measurements to the International System of Units and thus mutual acceptance of quantitative results. Therefore, mutually and publicly recognized standards and certificates are needed at national and international levels. An important step to attain this ambitious goal is to intensify regional metrological collaboration. The exercises of interlaboratorial comparisons are important as part of a system to guaranty the quality of analysis. To estimate the sources of uncertainty associated with the determination of toxic trace element concentrations in rice and to perform an interlaboratorial comparison, a sample containing cadmium, copper, lead and zinc was distributed to four Brazilian laboratories. The laboratories used atomic emission spectroscopy, graphite furnace atomic absorption spectroscopy and flame atomic absorption spectroscopy. The evaluation of the results provided by the laboratories was made by statistical and graphical methods comparing the results of each laboratory to the certified value. 相似文献
214.
Maria?Jo?o?RochaEmail author Eduardo?Rocha Albina?D?Resende Alexandre?Lobo-da-Cunha 《BMC biochemistry》2003,4(1):2
Background
This study was aimed primarily at testing in the liver of brown trout (Salmo trutta ) spectrophotometric methods previously used to measure the activities of catalase and hydrogen peroxide producing oxidases in mammals. To evaluate the influence of temperature on the activities of those peroxisomal enzymes was the second objective. A third goal of this work was the study of enzyme distribution in crude cell fractions of brown trout liver. 相似文献215.
Teresa M.V.D. Pinho e Melo Maria I.L. Soares António M.d’A. Rocha Gonsalves 《Tetrahedron letters》2006,47(5):791-794
Diazafulvenium methides generated from the solution pyrolysis of pyrazolo[1,5-c][1,3]thiazole-2,2-dioxides participate in [8π+2π] cycloadditions giving pyrazolo[1,5-a]pyridine derivatives. 1-Methyl-diazafulvenium, generated under flash vacuum pyrolysis reaction conditions, undergoes an intramolecular sigmatropic [1,8]H shift giving 1-vinyl-1H-pyrazoles. 相似文献
216.
217.
Jos Antnio Paixo Manuela Ramos Silva Ana Matos Beja Abílio J. F. N. Sobral Susana H. Lopes A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o721-o723
In the title compound, C15H17NO2, the ethoxycarbonyl group is anti with respect to the pyrrole N atom. The angle between the planes of the phenyl and pyrrole rings is 48.26 (9)°. The molecules are joined into dimeric units by a strong hydrogen bonds between pyrrole N—H groups and carbonyl O atoms. The geometry of the isolated molecule was studied by ab initio quantum mechanical calculations, employing both molecular orbital Hartree–Fock (MO–HF) and density functional theory (DFT) methods. The minimum energy was achieved for a conformation where the angle between the planes of the phenyl and pyrrole rings is larger, and that between the ethoxycarbonyl and pyrrole planes is smaller than in the solid‐state molecule. 相似文献
218.
219.