Coupled electronic and morphologic changes in graphene oxide upon electrochemical reduction

Peer reviewedPostprin

Behavioral alarm treatment for nocturnal enuresis

PURPOSES: To investigate the efficacy of alarm treatment in a sample of Brazilian children and adolescents with nocturnal enuresis and relate treatment success to age and type of clinical support. MATERIALS AND METHODS: During 32 weeks, 84 children and adolescents received alarm treatment together with weekly psychological support sessions for individual families or groups of 5 to 10 families. RESULTS: 71% of the participants achieved success, defined as 14 consecutive dry nights. The result was similar for children and adolescents and for individual or group support. The time until success was shorter for participants missing fewer support sessions. CONCLUSIONS: Alarm treatment was effective for the present sample, regardless of age or type of support. Missing a higher number of support sessions, which may reflect low motivation for treatment, increased the risk of failure.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Nacional de Desenvolvimento Científico e Tecnológic

Quench dynamics of the Kondo effect: transport across an impurity coupled to interacting wires

We study the real-time dynamics of the Kondo effect after a quantum quench in which a magnetic impurity is coupled to two metallic Hubbard chains. Using an effective field theory approach, we find that for noninteracting electrons the charge current across the impurity is given by a scaling function that involves the Kondo time. In the interacting case, we show that the Kondo time decreases with the strength of the repulsive interaction and the time dependence of the current reveals signatures of the Kondo effect in a Luttinger liquid. In addition, we verify that the relaxation of the impurity magnetization does not exhibit universal scaling behavior in the perturbative regime below the Kondo time. Our results highlight the role of nonequilibrium dynamics as a valuable tool in the study of quantum impurities in interacting systems

Exchange-spring behavior in bimagnetic CoFe2O4/CoFe2 nanocomposite

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 and ferrimagnetic oxide/ferromagnetic metal CoFe2O4/CoFe2 nanocomposites. The latter compound is a good system to study hard ferrimagnet/soft ferromagnet exchange coupling. Two steps were used to synthesize the bimagnetic CoFe2O4/CoFe2 nanocomposites: (i) first preparation of CoFe2O4 nanoparticles using the a simple hydrothermal method and (ii) second reduction reaction of cobalt ferrite nanoparticles using activated charcoal in inert atmosphere and high temperature. The phase structures, particle sizes, morphology, and magnetic properties of CoFe2O4 nanoparticles have been investigated by X-Ray diffraction (XRD), Mossbauer spectroscopy (MS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) with applied field up to 3.0 kOe at room temperature and 50K. The mean diameter of CoFe2O4 particles is about 16 nm. Mossbauer spectra reveal two sites for Fe3+. One site is related to Fe in an octahedral coordination and the other one to the Fe3+ in a tetrahedral coordination, as expected for a spinel crystal structure of CoFe2O4. TEM measurements of nanocomposite show the formation of a thin shell of CoFe2 on the cobalt ferrite and indicate that the nanoparticles increase to about 100 nm. The magnetization of nanocomposite showed hysteresis loop that is characteristic of the exchange spring systems. A maximum energy product (BH)max of 1.22 MGOe was achieved at room temperature for CoFe2O4/CoFe2 nanocomposites, which is about 115% higher than the value obtained for CoFe2O4 precursor. The exchange-spring interaction and the enhancement of product (BH)max in nanocomposite CoFe2O4/CoFe2 have been discussed.Comment: 9 pages, 10 figure

Fast batch injection analysis system for on-site determination of ethanol in gasohol and fuel ethanol

AbstractA simple, accurate and fast (180injectionsh−1) batch injection analysis (BIA) system with multiple-pulse amperometric detection has been developed for selective determination of ethanol in gasohol and fuel ethanol. A sample aliquot (100μL) was directly injected onto a gold electrode immersed in 0.5molL−1 NaOH solution (unique reagent). The proposed BIA method requires minimal sample manipulation and can be easily used for on-site analysis. The results obtained with the BIA method were compared to those obtained by gas-chromatography and similar results were obtained (at 95% of confidence level)

Simultaneous determination of ethanol and methanol in fuel ethanol using cyclic voltammetry

AbstractA new and simple strategy for the simultaneous determination of ethanol and methanol in fuel ethanol using cyclic voltammetry at a gold electrode is reported. A fuel ethanol aliquot was added into an electrochemical cell containing 0.5molL−1 NaOH and 0.1% (v/v) of methanol as the electrolyte and both analytes were determined using cyclic voltammetry. Ethanol was selectively detected at +0.19V and both compounds were detected at +1.20V. Current subtraction (using a correction factor) could be used for the selective determination of methanol. The limits of detection were estimated to be 0.028% and 0.045% (v/v) for ethanol and methanol, respectively. The proposed method presented similar results to those obtained by gas chromatography at a 95% confidence level

Health-promoting effects of Thymus herba-barona, Thymus pseudolanuginosus, and Thymus caespititius decoctions

Thymus herba-barona, Thymus pseudolanuginosus, and Thymus caespititius decoctions were screened for their phenolic constituents, along with their potential antioxidant, anti-inflammatory, and antibacterial activities. The total phenolic compounds in the extracts of the three plants ranged from 236.0 ± 26.6 mgGAE/g (T. caespititus) to 293.0 ± 30.5 mgGAE/g of extract (T. pseudolanuginosus), being particularly rich in caffeic acid derivatives, namely rosmarinic acid and its structural isomers, as well as flavones, such as luteolin-O-glucuronide. The T. pseudolanuginosus extract presented the best DPPH radical scavenging ability (EC 50 = 10.9 ± 0.7 µg/mL), a high reducing power (EC 50 = 32.2 ± 8.2 µg/mL), and effectively inhibited the oxidation of β-carotene (EC 50 = 2.4 ± 0.2 µg/mL). The extracts also showed NO· scavenging activity close to that of ascorbic acid, and thus might be useful as anti-inflammatory agents. In addition, they exhibited antibacterial activity against gram-negative and gram-positive bacteria. Staphylococcus aureus strains were the most sensitive bacteria to thyme extracts, with minimum inhibitory concentration and minimum bactericidal concentration values in the range of 0.6–3.5 mg/mL. Overall, this work is an important contribution for the phytochemical characterization and the potential antioxidant, anti-inflammatory, and antimicrobial activities of these three Thymus species, which have been poorly explored.The authors acknowledge to the Foundation for Science and Technology (FCT), the European Union, the National Strategic Reference Framework (QREN), the European Regional Development Fund (FEDER), and Operational Programme Competitiveness Factors (COMPETE), for funding the Organic Chemistry Research Unit (QOPNA) (project PEst-C/QUI/UI0062/2013; FCOMP-01-0124-FEDER-037296).info:eu-repo/semantics/publishedVersio

Synchronization time in a hyperbolic dynamical system with long-range interactions

We show that the threshold of complete synchronization in a lattice of coupled non-smooth chaotic maps is determined by linear stability along the directions transversal to the synchronization subspace. We examine carefully the sychronization time and show that a inadequate observation of the system evolution leads to wrong results. We present both careful numerical experiments and a rigorous mathematical explanation confirming this fact, allowing for a generalization involving hyperbolic coupled map lattices.Comment: 22 pages (preprint format), 4 figures - accepted for publication in Physica A (June 28, 2010