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排序方式: 共有77条查询结果,搜索用时 15 毫秒
1.
L. F. Brum Malta Marta Eloisa Medeiros 《Journal of Thermal Analysis and Calorimetry》2005,81(1):149-152
Summary This work reports the room-temperature stabilization of the Bi4V2-xFexIIO11-1.5x γ ‘ phase, a promising ionic conductive material that finds application in solid oxide fuel cell and oxygen sensor devices. The Fe(II) cation proved to be a better stabilizer than Fe(III), which was previously used, since a lower substitution degree of V5+ is needed for the former. Powder X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry were used in these experiments. 相似文献
2.
Cláudia A. Kodaira Ana Valéria S. Lourenço Maria Cláudia F.C. Felinto Eduardo M.R. Sanchez Francisco J.O. Rios Luiz Antonio O. Nunes Magnus Gidlund Oscar L. Malta Hermi F. Brito 《Journal of luminescence》2011,131(4):727-731
Neodymium based fluorescence presents several advantages in comparison to conventional rare earth or enzyme-substrate based fluorescence emitting sources (e.g.Tb, HRP) . Based on this fact we have herein explored a Nd-based fluoroimmunoassay. We efficiently detected the presence of an oxidized low-density lipoprotein (oxLDL) in human plasma a well-known marker for cardiovascular diseases, which causes around 30% of deaths worldwide. Conventional fluoroimmunoassay uses time-resolved luminescence techniques, with detection in the visible range, to eliminate the fluorescence background from the biological specimens. By using an immunoassay based on functionalized Y2O3:Nd3+ nanoparticles, where the excitation and emission processes in the Nd3+ ion occur in the near-infrared (NIR) region, we have succeeded in eliminating the interferences from the biological fluorescence background, avoiding the use of time-resolved techniques. This yields higher emission intensity from the Nd3+-nanolabels and efficient detection of anti-oxidized low-density lipoproteins (anti-oxLDL) by Y2O3:Nd3+-antibody-antigen conjugation, leading to a novel biolabeling method. 相似文献
3.
Patrícia Santiago de Oliveira Patricio Iaci Miranda Pereira Natália Cristina Ferreira da Silva Eliane Ayres Fabiano Vargas Pereira Rodrigo Lambert Oréfice 《European Polymer Journal》2013
Polyurethane waterborne synthesis was performed using a two-step method, commonly referred to as a prepolymer method. Nanocomposites based on waterborne polyurethane and cellulose nanocrystals were prepared by the prepolymer method by altering the mode and step in which the nanofillers were incorporated during the polyurethane formation. The morphology, structural, thermal, and mechanical properties of the resulting nanocomposite films were evaluated by Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and tensile tests. FTIR results indicated that the degree of interaction between the nanofillers and the WPU through hydrogen bonds could be controlled by the method of cellulose nanocrystal incorporation. Data obtained from SAXS experiments showed that the cellulose nanocrystals as well as the step of the reaction in which they are added influenced the morphology of the polyurethane. The reinforcing effect of CNCs on the nanocomposites depends on their morphology. 相似文献
4.
Fernando P. Carvalho João M. Oliveira M. Malta M. Eugénia Lemos 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):119-125
During the past century extensive uranium mining took place in Portugal for radium and uranium production. One such uranium mine was the Boco Mine, in operation during the 1960s and 70s. Mining waste and open pits were left uncovered since mine closure. During the nineties a quarry for sand extraction was operated in the same site and water from a local stream was extensively used in sand sieving. Downstream the mine area, agriculture soil is used for cattle grazing. Water from the stream, water wells, soil, pasture and sheep meat were now analyzed for radionuclides of uranium natural series. The U-series radionuclide 226Ra was generally the highest in concentrations especially in soil, pasture, and in internal organs of sheep. 226Ra concentrations were 1,093 ± 96 Bq/kg (dry weight, dw) in soil, 43 ± 3 Bq/kg (dw) in pasture, and 193 ± 84 mBq/kg (wet weight, ww) in muscle tissue of sheep. Other sheep internal organs displayed much higher 226Ra concentrations, such as the brain and kidneys with 1,850 ± 613 mBq/kg (ww) and 6,043 ± 6,023 mBq/kg (ww), respectively. Results of analyses of tissue samples from sheep grown in a comparison area were 2 to 16 times lower, depending on the organ. Absorbed radiation doses for internal organs were computed and may exceed 5.2 mGy/y in the case of kidneys, near three times higher than in animals from the reference area, but below the threshold for biological effects. Radionuclide transfer in the terrestrial food chain and radiation exposure of the human population is discussed. 相似文献
5.
Dr. Nataliia S. Kariaka Dr. Victor A. Trush Dr. Viktoriya V. Dyakonenko Dr. Svitlana V. Shishkina Dr. Sergii S. Smola Dr. Nataliia V. Rusakova Dr. Tetiana Y. Sliva Dr. Paula Gawryszewska Dr. Albano N. Carneiro Neto Prof. Dr. Oscar L. Malta Prof. Dr. Vladimir M. Amirkhanov 《Chemphyschem》2022,23(14):e202200129
New lanthanide dimethyl-N-benzoylamidophosphate (HL) based tetrakis-complexes NEt4[LnL4] (Ln3+=La, Nd, Sm, Eu, Gd, Tb, Dy) are reported. The complexes are characterized by means of NMR, IR, absorption, and luminescent spectroscopy as well as by elemental, X-Ray, and thermal gravimetric analyses. The phenyl groups of the four ligands of the complex anion are directed towards one side, while the methoxy groups are directed in the opposite side, which makes the complexes under consideration structurally similar to calixarenes. The effect of changing the alkali metal counterion to the organic cation NEt4+ on the structure and properties of the tetrakis-complex [LnL4]- is analyzed. The complexes exhibit bright characteristic for respective lanthanides luminescence. Rather high intensity of the band of 5D0→7F4 transition, observed in the luminescence spectrum of NEt4[EuL4], is discussed based on theoretical calculations. 相似文献
6.
7.
We present a magnetic study of vanadium oxide nanotubes (VOx-NTs) with polyaniline (PAni). Transmission electron microscopy (TEM) shows the tubular shape and the multi-wall structure of the nanotubes. The static magnetic susceptibility measured at different magnetic fields shows a Curie behavior, while the magnetization versus magnetic field presents a non-linear dependence at low temperatures. Both experiments can be explained by the presence of paramagnetic ions with S = 1/2. Using Electron Paramagnetic Resonance technique, we identified as V4+(3d1) the paramagnetic ions present in the nanostructures. All the experimental results can be explained by a fraction between 14% and 18% of V4+ with respect to the total V atoms in the system. 相似文献
8.
Aires da Conceição Silva Lucia C.S. Aguiar Andréa Luzia F. de Souza Luiz Fernando Brum Malta 《Tetrahedron letters》2010,51(30):3883-6491
In this work, we present ligand-free Suzuki cross-coupling reactions in PEG 300 under thermal conditions at 55 °C with good yields of conversion; better results were obtained with low reaction time. In 1 hour, 1-iodo-4-nitrobenzene and phenylboronic acid reached 98% of the yield and 9700 of TON. Better results were obtained with Pd(0) sources. The reaction system was recycled up to three times with good activity. 相似文献
9.
Neyva M. L. Romeiro Rigoberto G. S. Castro Sandra M. C. Malta Luiz Landau 《Transport in Porous Media》2007,70(1):1-10
We study a one-dimensional multi-species system of dispersive-advective contaminant transport equations coupled by nonlinear
biological (kinetic reactions) and physical (adsorption) processes. To deal with the nonlinearities and the coupling, and
to avoid additional computational costs, we propose a linearization technique based on first-order Taylor’s series expansions.
A stabilized finite element in space, combined with an Euler implicit finite difference discretization in time, is used to
approximate the dispersive-advective transport problem. Three computational tests are performed with different boundary conditions,
retardation factors and kinetic parameters for a nonlinear reactive multi-species transport model. The proposed methodology
is shown to be accurate and decrease computational costs in the numerical implementation of nonlinear reactive transport problems. 相似文献
10.
Malta L. F. B. Cafffarena V. R. Medeiros M. E. Ogasawara T. 《Journal of Thermal Analysis and Calorimetry》2004,75(3):901-910
Doped ceria was studied in the last 20 years as a solid electrolyte capable of replacing stabilized zirconia in fuel cells.
Nevertheless, one of the problems concerned with the application of this material is the joint presence of the Ce(III) and
Ce(IV) in the ceria sublattice, mainly under low partial pressure of oxygen. TG and DTA measurements were performed in order
to verify non-stoichiometric character for cerias hydrothermally treated under reflux and in autoclave. X-ray powder diffraction
was used to observe long-range structural evolution varying time and temperature of reaction and the type of hydrothermal
synthesis. Finally, scanning electron microscopy (SEM) gave the temperature influence for powder morphology. Those techniques
pointed out that: i) reaction temperature is not important for converting Ce3+ to Ce4+; ii) testing the reaction time parameter, it is observed quite complete oxidation for the 2-12 h range; and iii) the type of
hydrothermal synthesis parameter influences the crystallinity and non-stoichiometric character of products.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献