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排序方式: 共有433条查询结果,搜索用时 15 毫秒
71.
Gustavo Von Poelhsitz André Luiz Bogado Márcio Peres de Araujo Heloisa S. Selistre-de-Araújo Javier Ellena Eduardo E. Castellano Alzir Azevedo Batista 《Polyhedron》2007
The reaction of RuCl3NO · 2H2O with stoichiometric amount of dppf, 1,1′-bis(diphenylphosphino)ferrocene, afforded the new neutral nitrosyl complex fac-[RuCl3(NO)(dppf)] which was characterized by spectroscopical, electrochemical and X-ray crystallography techniques as well as elemental analysis. The νNO band in the IR spectrum is at 1860 cm−1 (CH2Cl2 solution) and in the cyclic voltammogram an irreversible wave was observed at −1.35 V, both are characteristics of a nitrosonium (NO+) character for the coordinated NO. Additionally, preliminary in vitro antitumor activity against the MDA-MB-231 breast tumor cell line was carried out for the new complex. The initial results indicated an important activity for fac-[RuCl3(NO)(dppf)] (IC50 = 10 ± 3 μM ). The complex has a higher cytotoxicity than the precursor complex RuCl3NO · 2H2O, the free dppf ligand as well as the reference metallodrug cisplatin. 相似文献
72.
73.
Determination of pyrimethanil and kresoxim-methyl in soils by headspace solid-phase microextraction and gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
Navalón A Prieto A Araujo L Vílchez JL 《Analytical and bioanalytical chemistry》2004,379(7-8):1100-1105
A method using headspace solid-phase microextraction (HS-SPME) then gas chromatography–mass spectrometry with selected ion monitoring (GC–MS, SIM) has been developed for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in soil and humic materials. Both fungicides were extracted on to a fused-silica fibre coated with 85 m polyacrylate (PA). Response-surface methodology was used to optimise the experimental conditions. For soil samples the linear dynamic range of application was 0.004–1.000 g g–1 for pyrimethanil and 0.013–1.000 g g–1 for kresoxim-methyl. The detection limits were 0.001 g g–1 and 0.004 g g–1 for pyrimethanil and kresoxim-methyl, respectively. HP-SPME–GC–MS analysis was highly reproducible—relative standard deviations (RSD) were between 6.7 and 12.2%. The method was validated by analysis of spiked matrix samples and used to investigate the presence of pyrimethanil and kresoxim-methyl above the detection limits in soil and humic materials. 相似文献
74.
María S. Di Nezio Marcelo F. Pistonesi Wallace D. Fragoso Mrcio J.C. Pontes Hctor C. Goicoechea Mrio C.U. Araujo e Beatriz S. Fernndez Band 《Microchemical Journal》2007,85(2):194-200
This paper proposes an analytical method to determine directly and simultaneously five phenolic compounds (4-nitrophenol, 2-nitrophenol, phenol, 2,4,6-trichlorophenol and 4-chlorophenol) in sea water (Ria de Bahía Blanca, Argentine). The advantages of this method is that only requires spectrophotometric measurements (separation steps and derivatization reagents are avoided) and chemometric modelling (PLS and MLR–SPA).The statistical comparison between PLS — a well established multivariate method — and MLR–SPA — a recently presented chemometric modelling — demonstrated better analytical performance for the later one. This fact is indicative of the potentiality of MLR–SPA for solving complex analytical problems. 相似文献
75.
Araujo M. Lucia G. C. Giordano Roberto C. Hokka Carlos O. 《Applied biochemistry and biotechnology》1998,(1):493-504
Cells ofCephalosporium acretnonium ATCC 48272 immobilized in calcium alginate beads were utilized for cephalosporin C production and the results were compared
with those obtained with free cells. The experiments were performed with synthetic medium containing glucose and sucrose as
carbon and energy sources. Experimental effectiveness factor values were obtained at various cell and dissolved-oxygen concentrations,
considering Monod kinetics for the respiration rate, and were compared with the values calculated with zero-order kinetics
in spherical bioparticle. The results showed that the assumption of oxygen limitation by diffusion in the bioparticle was
correct, and that cephalosporin C production with immobilized cells is perfectly viable, although a slightly lower rate than
that obtained in the free cell process was observed. 相似文献
76.
Grande CA Araujo JD Cavenati S Firpo N Basaldella E Rodrigues AE 《Langmuir : the ACS journal of surfaces and colloids》2004,20(13):5291-5297
New adsorbents were prepared and tested for the separation of propane-propylene mixtures by adsorption. The ordered mesoporous material SBA-15 was used as the starting material for silver-ion deposition for pi-complexation with propylene. Two different loadings of silver were evaluated. Adsorption equilibrium and kinetic measurements of propane and propylene in the matrix (pure SBA-15) and the silver-modified adsorbents were performed at 323, 343, and 373 K. In this temperature range, the selectivity of propylene in one of the materials (Ag/SBA-15 = 0.5) is in the range 13-22 because the amount of propane adsorbed is very small, 0.095 mmol/g of propane versus 1.12 mmol/g of propylene at 100 kPa and 343 K. The diffusivity of both hydrocarbons is not seriously affected by the introduction of silver into the mesoporous structure. 相似文献
77.
Araujo E Rodríguez-Malave AJ González AM Rojas OJ Peñaloza N Bullón J Lara MA Dmitrieva N 《Applied biochemistry and biotechnology》2002,97(2):91-103
In this work, the effect of Fento’s reagent on the degradation of residual Kraft black liquor was investigated. The effect
of Fenton’s reagent on the black liquor degradation was dependent on the concentration of H2O2. At low concentrations (5 and 15 mM) of H2O2, Fenton’s reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium
pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H2O2, Fenton’s reagent induced an extensive degradation of lignin (95–100%) and discoloration of the black liquor. In the presence
of traces of iron, the addition of H2O2 alone induced mainly lignin fragmentation. In conclusion, Fenton’s reagent and H2O2 alone can degrade residual Kraft black liquor under acidic conditions at room temperature. 相似文献
78.
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
79.
Caruline de S. C. Machado Rafael E. Klumpp Victor H. Ayusso Uyime Donatus Mariana X. Milagre João V. de S. Araujo Glauson A. F. Machado I. Costa 《Surface and interface analysis : SIA》2019,51(12):1231-1239
In this work, the effect of eight types of surface treatments on the corrosion resistance of friction stir welded samples of an AA2198-T8 Al-Cu-Li alloy were tested and compared in an attempt to find suitable alternatives to toxic and carcinogenic hexavalent chromium treatments. All the samples were anodized and subjected to different post-anodizing treatments. The post-anodizing treatments were (1) hydrothermal treatment in Ce (NO3)3 6H2O solution; (2) hydrothermal treatment in Ce (NO3)3 6H2O solution with H2O2; (3) hydrothermal treatment in boiling water; (4) hexavalent chromium conversion coating; and (5) immersion in BTSE (bis-1,2-(triethoxysilyl) ethane. The corrosion resistance of the treated samples was evaluated by immersion tests in sodium chloride solution (0.1 mol L−1 NaCl) and electrochemical impedance spectroscopy (EIS) of the friction stir weldment. The results showed that among the alternative treatments, the Ce-containing solutions presented the best corrosion resistance, especially when used without peroxide. 相似文献
80.
Marieta L.C. Passos Paula C.A.G. Pinto João L.M. Santos M. Lúcia M.F.S. Saraiva André R.T.S. Araujo 《Analytica chimica acta》2015
Nanoparticles (NPs) exhibit a number of distinctive and entrancing properties that explain their ever increasing application in analytical chemistry, mainly as chemosensors, signaling tags, catalysts, analytical signal enhancers, reactive species generators, analyte recognition and scavenging/separation entities. 相似文献