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81.
Chaos around the separatrices of resonant chains during the reconnection process in Tokamaks with non-monotonic profiles is analysed. To characterize the extension of chaos in the system, we estimate the convergence of the chaotic lines by computing the winding number profiles in the neighborhood of the separatrices. Some simulations were performed and we have detected, for these non-twist mappings, a reduction of chaos during the reconnection process. A theoretical interpretation based on the overlapping of resonance pictures is proposed in order to explain the decrease of chaos. These results may contribute to interpret the recently observed improvement in reversal magnetic shear in Tokamaks. 相似文献
82.
Ivana M. A. Diniz Giovanna R. Souto Iuri D. P. Freitas José Alcides A. de Arruda Janine M. da Silva Tarcília A. Silva Ricardo A. Mesquita 《Photochemistry and photobiology》2020,96(1):182-190
Cisplatin plays a central role in cancer chemotherapy, but resistance to this drug remains a major obstacle in treatment. Drawbacks related to cisplatin failure may be associated with cell energy metabolism. This study investigated whether photobiomodulation (PBM) can potentiate the effects of cisplatin on keratinocytes (HaCat) and cancer cells (SCC25 and HN12). Cells were treated with laser (GaAlAs; 660 nm; 60 mW; 0.33 J; 2.14 W cm−2; 11.7 J cm−2 and 6 s) and cisplatin (7.8 μg mL−1) to evaluate cell viability, Ki-67, VEGF, TGF-β1, EGF expression and ROS production. Observations were validated in the SCC25 cell lineage, where the type of cell death (necrosis/apoptosis) and the amount of ATP were assessed. Cell lineages showed increased sensitivity to cisplatin associated with PBM (Cis-PBM). Ki-67 was augmented in all cell lineages treated with Cis-PBM when compared to cisplatin alone (Cis). Cis or Cis-PBM significantly decreased VEGF expression in cancer cells, while no changes were seen in the expression of TGF-β1 or EGF compared to control. ROS levels were similar in the Cis and Cis-PBM groups. Cells treated with Cis-PBM died by apoptosis, leading to greater consumption of ATP. These observations suggest that PBM may potentiate the effects of cisplatin, leading to increased drug cytotoxicity and enhanced cell death. 相似文献
83.
Elisangela Muncinelli Caldas Eliana Weber de Menezes Tânia Mara Pizzolato Silvio Luis Pereira Dias Tania Maria Haas Costa Leliz Ticona Arenas Edilson Valmir Benvenutti 《Journal of Sol-Gel Science and Technology》2014,72(2):282-289
A mesoporous silica-based hybrid material composed of silica xerogel modified with an ionic silsesquioxane, which contains the 1,4-diazoniabicyclo[2.2.2]octane chloride group, was obtained. The silsesquioxane film is highly dispersed on the surface. This hybrid material was utilized to develop a carbon paste electrode (CPE) for determination of methyl parathion. Transmission FTIR, elemental analysis and N2 adsorption–desorption isotherms were used for characterization of the material. The electrochemical behavior of methyl parathion was evaluated by cyclic voltammetry and differential pulse voltammetry. It was observed a linear response to methyl parathion in the concentration range from 1.25 × 10?7 to 2.56 × 10?6 mol L?1 by employing the carbon paste electrode, in Britton–Robinson buffer solution (pH 6). The achieved detection limit (3 SD of the blank divided by the slope of calibration curve) was 0.013 µmol L?1 and sensitivity was 6.3 µA µmol L?1. This result shows the potentiality of this electrode for application as electrochemical sensor for methyl parathion. 相似文献
84.
Recently some furanonaphthoquinones were isolated from Tabebuia species2,3,4. The structures la, lb2, and li4 were assigned to three of these compounds (those of la and lb being later confirmed by synthesis3,5,6). However, for the three other isolated compounds the spectroscopic data did not permit a decision to be made between the 2,3,4 - - - 4 isomeric pairs of structure lc and Id, le and lf 3, and lg and lh 4. Compounds la, lb, and le (or If), were tested in the KB cell culture assay and shown to be more active cytotoxic agents than lapachol2,3, the probable biogenetic precursor of all of them. 相似文献
85.
The dynamics of a negative gain suppression factor laser diode subjectedto injection current modulation is similar to that of a damped nonlinearoscillator under periodic forcing. Quasi-periodicity, frequency lockingand chaos may be present, depending on the values of the forcingparameters. We have found, for some parameter values, type-Iintermittent behavior and crisis-induced intermittency. Scaling lawswere obtained for the duration of the laminar phase and the chaos-chaosswitchings, respectively. The scale exponents are very close to thoseexpected for one-dimensional unimodal maps. 相似文献
86.
We present in this work an exact renormalization group (RG) treatment of a one-dimensional p-wave superconductor. The model proposed by Kitaev consists of a chain of spinless fermions with a p-wave gap. It is a paradigmatic model of great actual interest since it presents a weak pairing superconducting phase that has Majorana fermions at the ends of the chain. Those are predicted to be useful for quantum computation. The RG allows to obtain the phase diagram of the model and to study the quantum phase transition from the weak to the strong pairing phase. It yields the attractors of these phases and the critical exponents of the weak to strong pairing transition. We show that the weak pairing phase of the model is governed by a chaotic attractor being non-trivial from both its topological and RG properties. In the strong pairing phase the RG flow is towards a conventional strong coupling fixed point. Finally, we propose an alternative way for obtaining p-wave superconductivity in a one-dimensional system without spin–orbit interaction. 相似文献
87.
Marco A. Garms Marco T.C. Andrade Iberê L. Caldas 《Chaos, solitons, and fractals》2009,39(5):2169-2178
We present a computational procedure to control an experimental chaotic system by applying the occasional proportional feedback (OPF) method. The method implementation uses the fuzzy theory to relate the variable correction to the necessary adjustment in the control parameter. As an application we control the chaotic attractors of the Chua circuit. We present the developed circuits and algorithms to implement this control in real time. To simplify the used procedure, we use a low resolution analog to digital converter compensated for a lowpass filter that facilitates similar applications to control other systems. 相似文献
88.
Joao Guilherme Caldas Steinstraesser Rodrigo Cienfuegos Jose Daniel Galaz Mor Antoine Rousseau 《Journal of Applied Analysis & Computation》2018,8(3):859-872
We propose a Schwarz-based domain decomposition method for solving a dispersion equation consisting on the linearized KdV equation without the advective term, using simple interface operators based on the exact transparent boundary conditions for this equation. An optimization process is performed for obtaining the approximation that provides the method with the fastest convergence to the solution of the monodomain problem. 相似文献
89.
Juan A. Jaén Alcides Mu?óz Jaime Justavino Cecilio Hernández 《Hyperfine Interactions》2009,192(1-3):51-59
The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mössbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite α-FeOOH and lepidocrocite γ-FeOOH are early corrosion products. Maghemite γ-Fe2O3 and magnetite Fe3O4 have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite β-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite α-Fe2O3 in one sample. 相似文献
90.