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  1. Article: Elucidation of Reaction Mechanisms Far from Thermodynamic Equilibrium.

    Nagao, Raphael

    ChemistryOpen

    2015  Volume 5, Issue 2, Page(s) 164–167

    Abstract: Far from equilibrium: This thesis provides a deep mechanistic analysis of the electrooxidation of methanol when the system is kept far from the thermodynamic equilibrium. Under an oscillatory regime, interesting characteristics between the elementary ... ...

    Abstract Far from equilibrium: This thesis provides a deep mechanistic analysis of the electrooxidation of methanol when the system is kept far from the thermodynamic equilibrium. Under an oscillatory regime, interesting characteristics between the elementary reaction steps were observed. We were able to elucidate the effect of the intrinsic drift in a potential time-series responsible for spontaneous transition of temporal patterns and the carbon dioxide decoupling from direct and indirect pathways.
    Language English
    Publishing date 2015-12-20
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2655605-4
    ISSN 2191-1363
    ISSN 2191-1363
    DOI 10.1002/open.201500212
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Finding influential nodes in networks using pinning control: Centrality measures confirmed with electrochemical oscillators.

    Bomela, Walter / Sebek, Michael / Nagao, Raphael / Singhal, Bharat / Kiss, István Z / Li, Jr-Shin

    Chaos (Woodbury, N.Y.)

    2023  Volume 33, Issue 9

    Abstract: The spatiotemporal organization of networks of dynamical units can break down resulting in diseases (e.g., in the brain) or large-scale malfunctions (e.g., power grid blackouts). Re-establishment of function then requires identification of the optimal ... ...

    Abstract The spatiotemporal organization of networks of dynamical units can break down resulting in diseases (e.g., in the brain) or large-scale malfunctions (e.g., power grid blackouts). Re-establishment of function then requires identification of the optimal intervention site from which the network behavior is most efficiently re-stabilized. Here, we consider one such scenario with a network of units with oscillatory dynamics, which can be suppressed by sufficiently strong coupling and stabilizing a single unit, i.e., pinning control. We analyze the stability of the network with hyperbolas in the control gain vs coupling strength state space and identify the most influential node (MIN) as the node that requires the weakest coupling to stabilize the network in the limit of very strong control gain. A computationally efficient method, based on the Moore-Penrose pseudoinverse of the network Laplacian matrix, was found to be efficient in identifying the MIN. In addition, we have found that in some networks, the MIN relocates when the control gain is changed, and thus, different nodes are the most influential ones for weakly and strongly coupled networks. A control theoretic measure is proposed to identify networks with unique or relocating MINs. We have identified real-world networks with relocating MINs, such as social and power grid networks. The results were confirmed in experiments with networks of chemical reactions, where oscillations in the networks were effectively suppressed through the pinning of a single reaction site determined by the computational method.
    Language English
    Publishing date 2023-09-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1472677-4
    ISSN 1089-7682 ; 1054-1500
    ISSN (online) 1089-7682
    ISSN 1054-1500
    DOI 10.1063/5.0163899
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Desenvolvimento de software e interface para o controle por retroalimentação atrasada em sistemas eletroquímicos

    Eduardo Parma / Laura Menezes / Sidnei A. Baldin / Raphael Nagao

    Química Nova, Vol 44, Iss 6, Pp 755-

    2021  Volume 759

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2021-08-01T00:00:00Z
    Publisher Sociedade Brasileira de Química
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Padrões de Turing em sistemas químicos

    Raphael Nagao / Hamilton Varela

    Química Nova, Vol 39, Iss 4, Pp 474-

    2016  Volume 485

    Abstract: Spontaneous pattern formation in reaction-diffusion systems was theoretically proposed by Alan M. Turing in 1952. His breakthrough conceptions of chemical self-organization were able to explain how patterns emerge in nature and the symmetry breaking, ... ...

    Abstract Spontaneous pattern formation in reaction-diffusion systems was theoretically proposed by Alan M. Turing in 1952. His breakthrough conceptions of chemical self-organization were able to explain how patterns emerge in nature and the symmetry breaking, which are of utmost importance, for instance, in the context of origin of life. Along with the experimental observations in the Belousov-Zhabotinsky reaction and the development of the nonequilibrium thermodynamics by Prigogine and co-workers, Turing predictions are considered the foundation of the field of Nonlinear Chemical Dynamics. This review aims to describe the basis of Turing structures with their consequent scientific achievements and to provide future directions in the development of this field.
    Keywords Turing patterns ; self-organization ; nonlinear dynamics ; pattern formation ; oscillations ; Chemistry ; QD1-999
    Language English
    Publishing date 2016-05-01T00:00:00Z
    Publisher Sociedade Brasileira de Química
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Quasiperiodic behavior in the electrodeposition of Cu/Sn multilayers: extraction of activation energies and wavelet analysis.

    Menezes, Laura / Parma, Eduardo / Machado, Eduardo G / Nagao, Raphael

    Physical chemistry chemical physics : PCCP

    2019  Volume 21, Issue 37, Page(s) 21057–21063

    Abstract: Living systems are one of the many examples in which self-organizing systems yield more intricate structures than those that can be achieved using a "step-by-step" approach. This phenomenon can be observed in electrochemical organic synthesis, ... ...

    Abstract Living systems are one of the many examples in which self-organizing systems yield more intricate structures than those that can be achieved using a "step-by-step" approach. This phenomenon can be observed in electrochemical organic synthesis, oscillating metal deposition and in chemical clocks. There is a plenitude of temporal instabilities during self-organization, from ordinary period-one oscillations, going through quasiperiodicity, to the onset of chaos. Here, we describe the emergence of quasiperiodic behavior during the oscillatory electro-deposition of Cu/Sn. The time-series were characterized using a continuous wavelet transform in order to extract the oscillation frequency of the process with changes in temperature, and to calculate the apparent activation energies. Two different energy ranges are presented, and these are attributed to an activation barrier (∼50 kJ mol
    Language English
    Publishing date 2019-09-17
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c9cp03605a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: The electrosynthesis of gold(I) complexes

    Carolina Galuppo / Jaqueline Alvarenga / Adriana C. Queiroz / Igor Messias / Raphael Nagao / Camilla Abbehausen

    Electrochemistry Communications, Vol 110, Iss , Pp - (2020)

    A clean, one-pot method

    2020  

    Abstract: Gold complexes are emerging as promising compounds in a range of applications. Synthetic methods for producing these complexes involve multiple steps, the use of reducing agents, inert atmosphere techniques and transmetallation reactions, resulting in ... ...

    Abstract Gold complexes are emerging as promising compounds in a range of applications. Synthetic methods for producing these complexes involve multiple steps, the use of reducing agents, inert atmosphere techniques and transmetallation reactions, resulting in contaminated products and low yields. Here we demonstrate, for the first time, a clean, one-pot electrosynthesis method which produces gold(I)-N-heterocyclic carbenes and gold(I)-bis-phosphine by the anodic corrosion of a polycrystalline gold electrode in a solution containing the ligands and the electrolyte. The electrochemical reactions require only electrons and, therefore, the production of the complexes starts from the zero-valent metal, avoiding contamination with other metals, as is the case in transmetallation reactions, or byproducts generated by the use of reducing agents. Keywords: Electrosynthesis, Gold(I) complexes, Organometallics
    Keywords Industrial electrochemistry ; TP250-261 ; Chemistry ; QD1-999
    Subject code 540
    Language English
    Publishing date 2020-01-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Multivariate statistical analysis of chemical and electrochemical oscillators for an accurate frequency selection.

    Kitagaki, Bianca T / Pinto, Maria R / Queiroz, Adriana C / Breitkreitz, Márcia C / Rossi, Federico / Nagao, Raphael

    Physical chemistry chemical physics : PCCP

    2019  Volume 21, Issue 30, Page(s) 16423–16434

    Abstract: The effect of experimental parameters on the frequency of chemical oscillators has been systematically studied since the first observations of clock reactions. The approach is mainly based on univariate changes in one specific parameter while others are ... ...

    Abstract The effect of experimental parameters on the frequency of chemical oscillators has been systematically studied since the first observations of clock reactions. The approach is mainly based on univariate changes in one specific parameter while others are kept constant. The frequency is then monitored and the effect of each parameter is discussed separately. This type of analysis, however, does not take into account the multiple interactions among the controllable parameters and the synergic responses on the oscillation frequency. We have carried out a multivariate statistical analysis of chemical (BZ-ferroin catalyzed reaction) and electrochemical (Cu/Cu
    Language English
    Publishing date 2019-05-30
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c9cp01998g
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Modulation of Turing Patterns in the CDIMA Reaction by Ultraviolet and Visible Light.

    Nagao, Raphael / de Miranda, Renan C C / Epstein, Irving R / Dolnik, Milos

    The journal of physical chemistry. A

    2019  Volume 123, Issue 5, Page(s) 992–998

    Abstract: We have carried out the first systematic study of the effects of ultraviolet light, both alone and in combination with visible white light, on Turing patterns in the chlorine dioxide-iodine-malonic acid (CDIMA) reaction. The ultraviolet light used has a ... ...

    Abstract We have carried out the first systematic study of the effects of ultraviolet light, both alone and in combination with visible white light, on Turing patterns in the chlorine dioxide-iodine-malonic acid (CDIMA) reaction. The ultraviolet light used has a sharp peak at 368 nm and can perturb the system selectively. It primarily decomposes chlorine dioxide in a zeroth-order reaction, and when it is used to illuminate Turing patterns, shrunken spots are formed with an imperfect hexagonal arrangement. The ultraviolet light competes directly with the visible white light via the photoreaction with dissolved chlorine dioxide, which prevents the total suppression of patterns at intermediate intensities of white light. These results suggest that specific wavelengths of light in the ultraviolet spectrum selectively modify the chemistry behind the pattern formation and can be utilized to generate novel self-organized structures under forcing conditions. We propose a modified Lengyel-Epstein model to incorporate the effect of ultraviolet illumination and obtain good qualitative agreement between simulations and experiments. These results support the idea that chlorine dioxide photoreaction is a key step in modulating CDIMA patterns under ultraviolet illumination.
    Language English
    Publishing date 2019-01-30
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5215
    ISSN (online) 1520-5215
    DOI 10.1021/acs.jpca.8b10819
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Tuning Electrochemical Bistability by Surface Area Blocking in the Cathodic Deposition of Copper

    Júlia Rospendowiski / Maria R. Pinto / Cristian Hessel / Elton Sitta / Raphael Nagao

    ACS Omega, Vol 3, Iss 10, Pp 13636-

    2018  Volume 13646

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2018-10-01T00:00:00Z
    Publisher American Chemical Society
    Document type Article ; Online
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  10. Article: Influence of the Ligands in Cu(II) Complexes on the Oscillatory Electrodeposition of Cu/Cu₂O

    Pinto, Maria R / Pereira, Guilherme B / Queiroz, Adriana C / Nagao, Raphael

    Journal of physical chemistry. 2020 May 14, v. 124, no. 23

    2020  

    Abstract: Oscillatory electrodeposition reactions have been utilized to create nanostructured materials under the microscale and nanoscale. This alternative method of synthesis, when compared to the traditional step-by-step synthesis procedure, takes advantage of ... ...

    Abstract Oscillatory electrodeposition reactions have been utilized to create nanostructured materials under the microscale and nanoscale. This alternative method of synthesis, when compared to the traditional step-by-step synthesis procedure, takes advantage of the self-organizing processes that do not require any external control or template-based support, resulting in materials with higher complexity in terms of structure and composition. Nanolayers made of Cu and semiconductor composites, such as Cu/Cu₂O, can be finely tuned by controlling ordinary period-one oscillations in the cathodic deposition. As the reaction media is alkaline, a complexing agent is commonly added in the solution to prevent the precipitation of the copper ions as hydroxides. Lactate and tartrate molecules are two α-hydroxy carboxylate organic ligands extensively used for this aim. Although some studies have shown the electrochemical synthesis of Cu/Cu₂O nanolayers, no grounded discussion about the influence of the chemical nature of the ligands on the oscillatory reaction has been investigated so far. Here, we provide a well-detailed and rigorous study of the effect of both ligands in the electrodeposition of Cu/Cu₂O under galvanostatic control, accurately mapping differences in the oscillation period and amplitude. On the basis of recent advances on the understanding of the copper complex structures, we attributed a distorted tetrahedral structure with four monodentate lactate ligands linked to the Cu²⁺ central ion ([Cu(Lac)₄]²–) and a distorted square-planar coordination of the tartrate’s deprotonated alkoxide groups, forming a chelate ([Cu(TartH–₂)₂]⁶–), as the species that have a buffering effect on the oscillatory mechanism and, consequently, can control the extension of the oscillation period and amplitude. In this matter, the tartrate complex should have a higher buffering capacity to prolong the period and decrease the amplitude. More importantly, we unequivocally show that a surface blocking effect due to the adsorption reactions cannot be neglected in the mechanism description. The adsorption of the tartrate anions and its complexes has, also as an outcome, period enlargement and amplitude shrinkage, as compared to that of the lactate. Hence, both mechanisms seem to operate in the adjustment of the dynamic characteristics of the oscillatory electrodeposition of Cu/Cu₂O.
    Keywords adsorption ; electroplating ; electrosynthesis ; lactic acid ; ligands ; semiconductors ; shrinkage
    Language English
    Dates of publication 2020-0514
    Size p. 12559-12568.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.0c02959
    Database NAL-Catalogue (AGRICOLA)

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