Electroanalytical detection of pindolol: comparison of unmodified and reduced graphene oxide modified screen-printed graphite electrodes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Surface characterization and osteoblast-like cells culture on collagen modified PLDLA scaffolds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of furanic aldehydes in sugarcane bagasse by high-performance liquid chromatography with pulsed amperometric detection using a modified electrode with nickel nanoparticles

A glassy carbon electrode chemically modified with nickel nanoparticles coupled with reversed-phase chromatography with pulsed amperometric detection was used for the quantitative analysis of furanic aldehydes in a real sample of sugarcane bagasse hydrolysate. Chromatographic separation was carried out in isocratic conditions (acetonitrile/water, 1:9) with a flow rate of 1.0 mL/min, a detection potential of -50 mV vs. Pd, and the process was completed within 4 min. The analytical curves presented limits of detection of 4.0 × 10(-7) mol/L and 4.3 × 10(-7) mol/L, limits of quantification of 1.3 × 10(-6) and 1.4 × 10(-6) mol/L, amperometric sensitivities of 2.2 × 10(6) nA mol/L and 2.7 × 10(6) nA mol/L for furfural and 5-hydroxymethylfurfural, respectively. The values obtained in this sample by the standard addition method were 1.54 ± 0.02 g/kg for 5-hydroxymethylfurfural and 11.5 ± 0.2 g/kg for furfural. The results demonstrate that this new proposed method can be used for the quick detection of furanic aldehydes without the interference of other electroactive species, besides having other remarkable merits that include excellent peak resolution, analytical repeatability, sensitivity, and accuracy.

In vitro reduction of Streptococcus mutans biofilm on silver nanoparticle-modified resin composite

Introduction: Currently, new methods to reduce biofilm formation on biomaterials are very studied, for example the use of silver nanoparticles, which were bactericidal. However, there are few studies investigating the benefits of these particles in dental restorative materials. Objective: This study aimed to compare in vitro the Streptococcus mutans biofilm formation on conventional light-cured composite resin with that on experimental light-cured composite resin, modified with silver nanoparticles. Material and methods: Discs were produced with either conventional resin (control group) and resin modified with different concentrations of silver nanoparticles, 0.1%, 0.3% and 0.6 % wt. (groups 1, 2 and 3, respectively). The samples were incubated in bacterial suspension (S. mutans) enriched with 20% sucrose to promote biofilm growth on the surfaces. Incubation times were 1, 4 and 7 days. After each period, adherent biofilms were disaggregated by ultrasound. Then, the numbers of viable cells recovered from the biofilms were counted through the serial dilution method. A morphological analysis of biofilm was also performed by Scanning Electron Microscopy. The data were subjected to Anova and Tukey’s test (α = 0.05). Results: The number of viable cells was statistically lower in groups 2 and 3 than in group 1 and control group, after the three incubation periods, without statistical difference between groups 2 and 3. The number of viable cells was statistically lower in group 1 than in control group, after 4 and 7 days of incubation. Conclusion: Resins modified with silver presented reduction of S. mutans biofilm on their surfaces, according to the conditions of this study.

Photocatalytic decomposition of rhodamine-b using scandium and silver-modified TiO2 powders

Semiconductor-mediated photocatalytic oxidation is an interesting method for water decontamination and a specially modified TiO2 is said to be a promising material. This study verified that the synthesis of 1wt%Ag modified-Sc0.01Ti0.99O1.995 powder samples prepared by Polymeric Precursor Method is capable of forming a mixture of anatase-rutile phase with high photocatalytic performance. This kind of material is found to have a lower bandgap compared to the TiO2-anatase commercial powders, which can be associated to an innovative hybrid modification. The simultaneous insertion of scandium in order to generate a p-type semiconductor and a metallic silver nanophase acting as an electron trapper demonstrated being capable of enhancing the degradation of rhodamine B compared to the commercial TiO2. In spite of the different thermal treatments or phase amounts, the hybrid modified powder samples showed higher photocatalytic activity than the commercial ones.

Solving the multiobjective environmental/economic dispatch problem using weighted sum and ε-constraint strategies and a predictor-corrector primal-dual interior point method

This paper proposes a technique for solving the multiobjective environmental/economic dispatch problem using the weighted sum and ε-constraint strategies, which transform the problem into a set of single-objective problems. In the first strategy, the objective function is a weighted sum of the environmental and economic objective functions. The second strategy considers one of the objective functions: in this case, the environmental function, as a problem constraint, bounded above by a constant. A specific predictor-corrector primal-dual interior point method which uses the modified log barrier is proposed for solving the set of single-objective problems generated by such strategies. The purpose of the modified barrier approach is to solve the problem with relaxation of its original feasible region, enabling the method to be initialized with unfeasible points. The tests involving the proposed solution technique indicate i) the efficiency of the proposed method with respect to the initialization with unfeasible points, and ii) its ability to find a set of efficient solutions for the multiobjective environmental/economic dispatch problem.

An Alternative Method for the Simultaneous Determination of Copper and Lead for Quality Control of Sugar Cane Spirit using a Nanotube-Based Sensor

The development of an electroanalytical method for simultaneous determination of copper and lead ions in sugar cane spirit (cachaca) using carbon paste electrode modified with ascorbic acid and carbon nanotubes (CPE-AaCNT) is described. Squarewave voltammetry (SWV) with anodic stripping was employed, and this technique was optimized with respect to the following parameters: frequency (50 Hz), amplitude (100 mV) and scan increment (9 mV). The analytical curves were linear in the range from 0.0900 to 7.00 mg L-1 for lead and copper. The limits of detection were 48.5 and 23.9 mu g L-1 for lead and copper, respectively. The developed method was applied to the simultaneous determination of copper and lead in five commercial samples of sugar cane spirit. The results were in good agreement with those obtained by F AAS/GF AAS (flame atomic absorption spectrometry/graphite furnace atomic absorption spectrometry) and showed that CPE-AaCNT can be successfully employed in the simultaneous determination of these metals in real sugar cane spirit samples.

Optimal reactive power flow via the modified barrier Lagrangian function approach

A new approach called the Modified Barrier Lagrangian Function (MBLF) to solve the Optimal Reactive Power Flow problem is presented. In this approach, the inequality constraints are treated by the Modified Barrier Function (MBF) method, which has a finite convergence property: i.e. the optimal solution in the MBF method can actually be in the bound of the feasible set. Hence, the inequality constraints can be precisely equal to zero. Another property of the MBF method is that the barrier parameter does not need to be driven to zero to attain the solution. Therefore, the conditioning of the involved Hessian matrix is greatly enhanced. In order to show this, a comparative analysis of the numeric conditioning of the Hessian matrix of the MBLF approach, by the decomposition in singular values, is carried out. The feasibility of the proposed approach is also demonstrated with comparative tests to Interior Point Method (IPM) using various IEEE test systems and two networks derived from Brazilian generation/transmission system. The results show that the MBLF method is computationally more attractive than the IPM in terms of speed, number of iterations and numerical conditioning. (C) 2011 Elsevier B.V. All rights reserved.

A Modified Technique of Rat Tail Suspension for Longer Periods of Observation

FALCAI MJ, LOUZADA MJQ, DE PAULA FJA, OKUBO R, VOLPON JB. A modified technique of rat tail suspension for longer periods of observation. Aviat Space Environ Med 2012; 83:1176-80. Background: Rat tail suspension is an accepted method to create experimental osteopenia. However, suspension periods longer than 3 wk may cause tail skin sloughing or rat slippage. The hypothesis was that a traction system with skeletal anchorage through one tail vertebra would prolong the suspension time without significant complications. Methods: There were 80 young adult female Wistar rats that were submitted to one of the following interventions: skeletal tail suspension (N = 20), skin tail suspension (N = 20), no intervention (N = 20), and a baseline control (N = 20). All animals were followed up either for 3 (N = 10) or 6 (N = 10) wk. Animals were assessed for clinical signs of stress and tolerance to suspension. The femur evaluation was in terms of mineral density content, mechanical resistance, and histomorphometry. Results/Discussion: All animals reached the 3-wk end point. However, for the 6-wk period, seven animals suspended by the skin traction method were discarded (70%) because of signs of stress and skin sloughing. In contrast, there was one loss in the skeletal suspension group (10%). All suspended animals developed similar osteopenia at 3 wk characterized by decreased bone mineral content, weakened bone resistance, and loss of femoral mass. At 6 wk, all suspended animals had similar osteopenic parameters, but they were not statistically different from those of the rats in the 3-wk groups. Therefore, suspension longer than 3 wk did not increase the bone deterioration in the femur.

Modified CUPRAC spectrophotometric quantification of total polyphenol content in beer samples using Cu(II)/neocuproine complexes

Cu(II)/neocuproine (2,9-dimethyl-1,10-phenanthroline) complexes were utilized for spectrophotometric determination of total polyphenol content in beers. This procedure is based on the reduction of Cu(II) by polyphenols in hydroethanolic medium (pH 7.0) in the presence of neocuproine, yielding Cu(I)/complexes with maximum absorption at 454 nm. The sensitivity of the proposed method was compared with the AOAC method using tannic and gallic acid as standards. The average apparent molar absorptivity, in L cm(-1) mol(-1), of tannic acid (3.50 +/- 0.20) x 10(5) and gallic acid (5.12 +/- 0.21) x 10(4), was twice as high for the proposed method. A lower limit of detection (LOD) (2.9 x 10(-1) mg L-1) was found when tannic acid was used in the proposed method. Additionally, less interference from the most common additives in beers was noticed. Total content of polyphenols was analyzed in 17 Brazilian samples. Results ranged from 35.5 to 556 mg L-1 of tannic acid, with higher values for recovery rates (45.4-118%, mean 85.0%) than for gallic acid. Although tannic acid is a mixture of polygalloyl glucoses, the total polyphenol content found in the samples suggests that tannic acid should be used as a standard. This is the first attempt to use this particular copper complex to quantify total polyphenol content in beer samples. (C) 2012 Elsevier Inc. All rights reserved.

Carbon nanotubes modified with antimony nanoparticles: A novel material for electrochemical sensing

In this study, a novel material for the electrochemical determination of bisphenol A using a nanocomposite based on multi-walled carbon nanotubes modified with antimony nanoparticles has been investigated. The morphology, structure, and electrochemical performance of the nanocomposite electrodes were characterised by field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, and cyclic voltammetry. A scan rate study and electrochemical impedance spectroscopy showed that the bisphenol A oxidation product is adsorbed on nanocomposite electrode surface. Differential pulse voltammetry in phosphate buffer solution at pH 6, allowed the development of a method to determine bisphenol A levels in the range of 0.5-5.0 mu mol L-1, with a detection limit of 5.24 nmol L-1 (1.19 mu g L-1). (C) 2012 Elsevier Ltd. All rights reserved.

Development of an enzymeless electroanalytical method for the indirect detection of creatinine in urine samples

The aim of this study is to develop a new enzymeless electroanalytical method for the indirect quantification of creatinine from urine sample. This method is based on the electrochemical monitoring of picrate anion reduction at a glassy carbon electrode in an alkaline medium before and after it has reacted with creatinine (Jaffe's reaction). By using the differential pulse voltammetry technique under the optimum experimental conditions (step potential, amplitude potential, reaction time, and temperature), a linear analytical curve was obtained for concentrations of creatinine ranging from 1 to 80 mu mol L-1, with a detection limit of 380 nmol L-1. This proposed method was used to measure creatinine in human urine without the interference of most common organic species normally present in biological fluids (e.g., uric acid, ascorbic acid, glucose, and phosphocreatinine). The results obtained using urine samples were highly similar to the results obtained using the reference spectrophotometric method (at a 95% confidence level). (C) 2012 Elsevier B.V. All rights reserved.

The modified Hodge test is a useful tool for ruling out klebsiella pneumoniae carbapenemase

OBJECTIVE: Enterobacteriaceae bacteria harboring Klebsiella pneumoniae carbapenemase are a serious worldwide threat. The molecular identification of these pathogens is not routine in Brazilian hospitals, and a rapid phenotypic screening test is desirable. This study aims to evaluate the modified Hodge test as a phenotypic screening test for Klebsiella pneumoniae carbapenemase. METHOD: From April 2009 to July 2011, all Enterobacteriaceae bacteria that were not susceptible to ertapenem according to Vitek2 analysis were analyzed with the modified Hodge test. All positive isolates and a random subset of negative isolates were also assayed for the presence of blaKPC. Isolates that were positive in modified Hodge tests were sub-classified as true-positives (E. coli touched the ertapenem disk) or inconclusive (distortion of the inhibition zone of E. coli, but growth did not reach the ertapenem disk). Negative results were defined as samples with no distortion of the inhibition zone around the ertapenem disk. RESULTS: Among the 1521 isolates of Enterobacteriaceae bacteria that were not susceptible to ertapenem, 30% were positive for blaKPC, and 35% were positive according to the modified Hodge test (81% specificity). Under the proposed sub-classification, true positives showed a 98% agreement with the blaKPC results. The negative predictive value of the modified Hodge test for detection was 100%. KPC producers showed high antimicrobial resistance rates, but 90% and 77% of these isolates were susceptible to aminoglycoside and tigecycline, respectively. CONCLUSION: Standardizing the modified Hodge test interpretation may improve the specificity of KPC detection. In this study, negative test results ruled out 100% of the isolates harboring Klebsiella pneumoniae carbapenemase-2. The test may therefore be regarded as a good epidemiological tool.

The boundedness of penalty parameters in an augmented Lagrangian method with constrained subproblems

Augmented Lagrangian methods are effective tools for solving large-scale nonlinear programming problems. At each outer iteration, a minimization subproblem with simple constraints, whose objective function depends on updated Lagrange multipliers and penalty parameters, is approximately solved. When the penalty parameter becomes very large, solving the subproblem becomes difficult; therefore, the effectiveness of this approach is associated with the boundedness of the penalty parameters. In this paper, it is proved that under more natural assumptions than the ones employed until now, penalty parameters are bounded. For proving the new boundedness result, the original algorithm has been slightly modified. Numerical consequences of the modifications are discussed and computational experiments are presented.

beta-ZnMoO4 microcrystals synthesized by the surfactant-assisted hydrothermal method: Growth process and photoluminescence properties

In this communication, we investigate the effect of different surfactants: cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP-K40) on the growth process of zinc molybdate (beta-ZnMoO4) microcrystals synthesized under hydrothermal conditions at 140 degrees C for 8 h. These microcrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) measurements. XRD patterns proved that these crystals are monophasic and present a wolframite-type monoclinic structure. FE-SEM images revealed that the surfactants modified the crystal shapes, suggesting the occurrence of distinct crystal growth processes. The CTAB cationic surfactant promotes the hindrance of small nuclei that leads to the formation of rectangle-like crystals, SDS anionic surfactant induces a growth of irregular hexagons with several porous due to considerable size effect of counter-ions on the crystal facets, PVP-K40 non-ionic surfactant allows a reduction in size and thickness of plate-like crystals, while without surfactants have the formation of irregular plate-like crystals. Finally, the PL properties of beta-ZnMoO4 microcrystals were explained by means of different shape/size, surface defects and order-disorder into lattice. (C) 2011 Elsevier B.V. All rights reserved.