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Lin Xilei M. Speziali E. Orvini 《Journal of Radioanalytical and Nuclear Chemistry》1992,157(2):265-272
A pre-irradiation separation procedure, for gallium determination in biological and environmental materials by neutron activation analysis (NAA) is reported. The proposed method, based on ion-exchange chromatography, allows to eliminate the radiation risk, while taking the advantages of high sensitivity of NAA. The single comparator method is employed for gallium quantitative evaluation. Since no standard reference materials with certified gallium contents were available, the reliability of the proposed method was extensively investigated by various approaches. Four biological and one environmental standard reference materials, with gallium contents ranging from 54 g/g-3 ng/g, have been analyzed. 相似文献
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Fajardo M. Pérez Alcázar G. A. Moreira A. M. Speziali N. L. 《Hyperfine Interactions》2004,158(1-4):395-400
The local environment of implanted 111Ag (t
1/2 = 7.45 d) in single-crystalline [0001] ZnO was evaluated by means of the perturbed angular correlation (PAC) technique. Following
the 60 keV low dose (1 × 1013 cm−2) 111Ag implantation, the PAC measurements were performed for the as-implanted state and following 30 min air annealing steps,
at temperatures ranging from 200 to 1050°C. The results revealed that 42% of the probes are located at defect-free SZn sites (ν
Q ∼ 32 MHz, η = 0) in the as-implanted state and that this fraction did not significantly change with annealing. Moreover, a progressive
lattice recovery in the near vicinity of the probes was observed. Different EFGs assigned to point defects were furthermore
measured and a general modification of their parameters occurred after 600°C. The 900°C annealing induced the loss of 30%
of the 111Ag atoms, 7% of which were located in regions of high defects concentration. 相似文献
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Anayive Pérez-Rebolledo Nivaldo L. Speziali Eduardo E. Castellano Heloisa Beraldo 《Journal of organometallic chemistry》2006,691(18):3919-3930
Reaction of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH, HL1) and its N(4)-methyl (H2Bz4Me, HL2) and N(4)-phenyl (H2Bz4Ph, HL3) derivatives with SnCl4 and diphenyltin dichloride (Ph2SnCl2) gave [Sn(L1)Cl3] (1), [Sn(L1)PhCl2] (2), [Sn(L2)Cl3] (3), (4) [Sn(L3)PhCl2] (5) and [Sn(L3)Ph2Cl] (6). Infrared and 1H, 13C and 119Sn NMR spectra of 1-3, 5 and 6 are compatible with the presence of an anionic ligand attached to the metal through the Npy-N-S chelating system and formation of hexacoordinated tin complexes. The crystal structures of 1-3, 5 and 6 show that the geometry around the metal is a distorted octahedron formed by the thiosemicarbazone and either chlorides or chlorides and phenyl groups. The crystal structure of 4 reveals the presence of and trans [Ph2SnCl4]2−. 相似文献
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Three environmental matrices proposed as Certified Reference Materials, issued by the EU Standards, Measurement and Testing Programme (SMTP) formerly Bureau Communautaire de Reference (BCR) have been characterized for their trace element contents.The materials are: BCR 277 R Estuarine Sediment, BCR 280 R Lake Sediment and BCR 320 R Channel Sediment.Several trace elements, including As, Co, Cr, Fe, Mn, Ni, Sb, Sc, Th, U and Zn have been determined by our laboratory using Instrumental Neutron Activation Analysis (INAA). Our contributed values are being considered for the final certification. 相似文献
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Marcelo R. L. Oliveira José E. J. C. Graúdo Nivaldo L. Speziali Vito M. De Bellis 《Structural chemistry》1999,10(1):41-45
Potassium N-4-methylphenylsulfonyldithiocarbimate, K2(4-CH3C6H4SO2N=CS2), reacted with nickel(II) chloride hexahydrate and tetrabutylammonium bromide to form the bis(N-4-methylphenylsulfonyldithiocarbimate)nickelate(II) tetrabutylammonium salt (Bu4N)2[Ni(4-CH3C6H4S2C=NSO2)2]. The elemental analyses, IR and UV-Vis data obtained were consistent with the formation of a
diamagnetic planar complex. The 1H NMR and the 13C NMR spectra showed the expected signals for the dithiocarbimate moiety and the tetrabutylammonium cation. The single-crystal structure analysis showed that this substance crystallizes in the triclinic
space group with a = 10.474(3) Å, b = 10.767(3) Å, c = 13.657(3) Å and = 81.54(2)°, = 80.44(2)°, = 67.63(2)°, V = 1398.5(8) Å3, and Z = 2. The nickel atom is coordinated to four sulfur atoms. 相似文献
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In the study of trace elements in the different human brain areas, a critical evaluation of the values available in the literature is of great importance in attempting to establish reliable baseline levels, i.e., Reference Values (RVs) for toxicological assessment studies.This paper reviews the published values of minor and trace elements in the pituitary gland (hypophysis) of “normal” humans.Eighteen published papers are taken into account, 15 of which refer to the entire gland, whereas in three of them, only the adenohypophysis is considered.It turns out that essential elements such as Cu, Fe, Se and Zn were more frequently determined, whereas As, Br, Ca, Co, Cr, Cs, K, Mg, Mn, Ni and Rb were seldom investigated.Mercury was determined by several authors because of the concern caused by Hg release from dental amalgam fillings.Most values were obtained by Neutron Activation Analysis (NAA), which appears to have played a pioneer role in this field.Literature data on trace element levels in pituitary gland are at present insufficient to establish RVs; rather, they can be considered only as indicative values.Future investigations based on large populations of control subjects, with standardization of the preanalytical factors and the use of fit-for-purpose Standard or Certified Reference Materials (SRMs, CRMs) should therefore be envisaged. 相似文献
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E. Galvão da Silva A. Abras N. L. Speziali A. O. R. Sette Câmara 《Applied Physics A: Materials Science & Processing》1980,22(4):389-392
Mössbauer spectroscopy has been used to study nine natural chromite samples from deposits throughout Brazil and one sample from Philippine. It was possible to identify three different groups of chromite spinels, depending on the iron distribution over tetrahedral and octahedral sites. Using the Mössbauer Fe3+/Fe2+ ratio, chemical analysis and x-ray data a chemical formula was proposed for each group. 相似文献