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91.
Alessandra Silveira Machado Ramon Silva Santos Amanda Goulart Rodrigues Leonardo Borghi Davi Ferreira de Oliveira Marcelino José dos Anjos Ricardo Tadeu Lopes 《X射线光谱测定》2019,48(5):543-552
Carbonate rocks play an important role in petroleum geology by acting as reservoir rocks, generators, and even hydrocarbon sealants, accounting for about half of the oil and gas reserves known in the world. The study of these carbonate rocks have become very important in the hydrocarbon exploration scene in Brazil because of they consist in analogous for reservoir rocks of the presalt interval. Thus, the objective of this research was to use X-ray microfluorescence (micro-XRF) and X-ray microtomography analysis, as complementary techniques, in order to characterize samples of carbonate rocks in respect to their structures, textures, mineralogy, and pores. The microtomographic analyses allowed the identification of the horizontal structures as parallel lamination, horizontal, and vertical fractures filled by calcite and biotic constituents (gastropods bioclasts). Different composition of minerals were also identified, as calcite, quartz, feldspars, iron sulfides, and oxides. The porosity (ranges <1 to17%), and the high-density elements could also be quantified, as well as their distribution in each sample. The micro-XRF analysis present a direct relationship with the distribution of minerals that compound carbonate rocks, highlighting some structures, as well as helping to identify trace and minor elements in the carbonates (Mn, Sr, and Mg). 相似文献
92.
93.
Synthesis and Structural Features of New Schiff Base Complexes of Mononuclear MnIV,Dinuclear CoIICoIII,and Tetranuclear CuII 下载免费PDF全文
Davi F. Back Gelson Manzoni de Oliveira Cibele Mensch Canabarro Bernardo Almeida Iglesias 《无机化学与普通化学杂志》2015,641(5):941-947
2‐(((2‐Hydroxy‐3‐methoxyphenyl)methylene)amino)‐2(hydroxymethyl)‐1,3‐propanediol (LH4, as abbreviation) reacts with MnCl2 · 4H2O, CoCl2 · 6H2O, and Cu(ClO4)2 · 6H2O to give the new complexes [Mn(LH2)2] ( 1 ), [Co2Cl(H2O)(LH2)2] · 4H2O ( 2 ), and [Cu4(LH2)4(H2O)4] ( 3 ). Complex 1 is formed by the assembly of two molecules of the ligand with one manganese(IV) ion. In the mixed‐valence cobalt complex 2 there is an asymmetry between the coordination spheres of cobalt(II) and cobalt(III). In the tetramer 3 four copper(II) ions attain a distorted tetrahedral configuration surrounded by four molecules of the ligand. 相似文献
94.
Evaluation of the Antioxidant Activity of Copper(II) Complexes containing Tris‐(hydroxymethyl)aminomethane (TRIS) Units 下载免费PDF全文
Cibele M. Canabarro Joice Ceolin Josiéli D. Siqueira Bernardo A. Iglesias Gelson Manzoni de Oliveira Davi F. Back Patrick T. Campos 《无机化学与普通化学杂志》2016,642(21):1192-1197
The structural analysis and the SOD‐like activity of CuII complexes [(Cu)(C16H18N3O5)]ClO4 ( 1 ) and [(Cu)4(C36H52N8O12)] ( 2 ) are described with ligands obtained from the condensation of picolinaldehyde and 2‐formylpyrrole with tris(hydroxymethyl)aminomethane (TRIS). Finally, complex 1 catalyzes the dismutation of superoxide efficiently with IC50 values in the range of 0.43 micromolar solution, evaluated through the inhibition of the photoreduction of nitro blue tetrazolium (NBT) (superoxide dismutase assay). 相似文献
95.
96.
lida Bonfada Gelson Manzoni de Oliveira Davi Fernando Back Ernesto Schulz Lang 《无机化学与普通化学杂志》2005,631(5):878-881
Chloridrate of pyridoxine (vitamin B6) reacts with UO2(NO3)2·6H2O in acetonitril containing triethylamine to give the complex salt [UO2(PN)2(H2O)]Cl2. The structure of the novel compound was analyzed by single crystal X‐ray diffraction affording the centrosymmetric triclinic space group . In [UO2(PN)2(H2O)]2+ two zwitterionic pyridoxine molecules complex the uranium atom in a planar manner with a water molecule achieving the coordination of a semi planar pentagon. The two uranyl oxo ligands set the axis of a distorted pentagonal bipyramide. The ability of vitamin B6 pyridoxine to react with UO22+ allowing the chelation of one uranium atom represents a very specific model of assimilation of uranium by living beings. It could also explain the serious damages caused by heavy or radioactive metals like uranium since their complexation “in vivo” by enzymatic systems like pyridoxal phosphate‐containing enzymes would lead to a modification of the prosthetic groups of the metalloenzymes with loss of their catalytic activities. 相似文献
97.
98.
Utilization of nondestructive techniques for analysis of the Martian meteorite NWA 6963 and its implications for astrobiology 下载免费PDF全文
Bruno L. do Nascimento‐Dias Davi F. de Oliveira Alessandra S. Machado Olga M.O. Araújo Ricardo T. Lopes Marcelino J. dos Anjos 《X射线光谱测定》2018,47(1):86-91
Martian meteorites are excellent study materials for understanding the present and past of Mars, as they are important historical astrophysical artifacts because they possess information about Martian geological evolution and physical and chemical characteristics. In our case, we analyzed the NWA 6963 Martian meteorite classified as basaltic shergottite because of its chemical structure. A computerized microtomography (μCT) study in the NWA 6963 Martian meteorite provided us with 2D and 3D images that were extremely useful for ascertaining the internal structure of the analyzed sample and gave us the opportunity to find a crumpled material with a very peculiar structural format. In addition, it was possible to observe through the μCT that this encrusted material also has a completely different density of the meteorite. Calcium, strontium, and potassium were detected qualitatively, among others through the technique of X‐ray fluorescence. 相似文献
99.
Large corporations fund their capital and operational expenses by issuing bonds with a variety of indexations, denominations, maturities and amortization schedules. We propose a multistage linear stochastic programming model that optimizes bond issuance by minimizing the mean funding cost while keeping leverage under control and insolvency risk at an acceptable level. The funding requirements are determined by a fixed investment schedule with uncertain cash flows. Candidate bonds are described in a detailed and realistic manner. A specific scenario tree structure guarantees computational tractability even for long horizon problems. Based on a simplified example, we present a sensitivity analysis of the first stage solution and the stochastic efficient frontier of the mean-risk trade-off. A realistic exercise stresses the importance of controlling leverage. Based on the proposed model, a financial planning tool has been implemented and deployed for Brazilian oil company Petrobras. 相似文献
100.
Toimil P Daviña R Sabín J Prieto G Sarmiento F 《Journal of colloid and interface science》2012,367(1):193-198
The influence of La(3+) on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La(3+) for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin-Landau-Verwey-Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La(3+) showed that these ions induce aggregation of liposomes at 25 °C and at 60 °C. At 25 °C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60 °C, when both bilayers have the same conformation. The experimental results also indicate that the c.a.c. is higher at 60 °C than at 25 °C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25 °C can be prevented by increasing the solution temperature for La(3+) concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids. 相似文献