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132 results on '"Leite, José R."'

1. The statistics of chaos in a bursting laser

Author

Barbosa, Wendson A. S., Rosero, Edison J., Tredicce, Jorge R., and Leite, Jose R. Rios

Subjects
Physics - Optics, Nonlinear Sciences - Chaotic Dynamics
Abstract

We demonstrate experimentally how semiconductor lasers subjected to double optical feedback change the statistics of their chaotic spiking dynamics from Gaussian to long-tail Power Law distributions associated to the emergency of bursting. These chaotic regimes, which are features of excitable complex systems, are quantified by the tail exponent $\alpha$ and appear by changing the ratio between the feedback times. Transitions to bursting occur in the neighbourhood of low order Farey fractions. The physics behind these transitions is related to the variation of threshold pump current in the compound system as obtained from a deterministic set of rate equations. Numerical integration also verifies the observed chaos transitions indicating the possibility of controlling the bursting chaotic statistics., Comment: 10 pages, 7 figures

Published
2019
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2. BR-bombesin: a novel bombesin-related peptide from the skin secretion of the Chaco tree frog (Boana raniceps) with physiological gastric effects

Author

de Sousa, Nayara Alves, Marani, Mariela M., Lopes, André Luís Fernandes, Silva, Emanuelle Morais, Barbosa, Eder Alves, Vasconcelos, Andreanne Gomes, Kuzniewski, Felipe T. B., Lustosa, Suellen Sousa, Gomes, Karina Pereira, Colugnati, Diego Basile, Rocha, Jefferson A., Santos, Lucianna Helene, Benquerer, Marcelo P., Quelemes, Patrick, Véras, Leiz, Moreira, Daniel C., Gadelha, Kalinne Kelly Lima, Magalhães, Pedro Jorge Caldas, Plácido, Alexandra, Eaton, Peter, Nicolau, Lucas, Medeiros, Jand Venes R., and Leite, José R. S. A.

Published
2022
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3. Deterministic chaos in an ytterbium-doped mode-locked fiber laser

Author

Mélo, Lucas B. A., Palacios, Guillermo F. R., Carelli, Pedro V., Acioli, Lúcio H., Leite, José R. Rios, and de Miranda, Marcio H. G.

Subjects
Physics - Optics, Nonlinear Sciences - Chaotic Dynamics
Abstract

We experimentally study the nonlinear dynamics of a femtosecond ytterbium doped mode-locked fiber laser. With the laser operating in the pulsed regime a route to chaos is presented, starting from stable mode-locking, period two, period four, chaos and period three regimes. Return maps and bifurcation diagrams were extracted from time series for each regime. The analysis of the time series with the laser operating in the quasi mode-locked regime presents deterministic chaos described by an unidimensional Rossler map. A positive Lyapunov exponent $\lambda = 0.14$ confirms the deterministic chaos of the system. We suggest an explanation about the observed map by relating gain saturation and intra-cavity loss.

Published
2018
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5. Occurrence and evolutionary conservation analysis of α‐helical cationic amphiphilic segments in the human proteome

Author

Costa, Igor S. D., primary, Junot, Tiago, additional, Silva, Fernanda L., additional, Felix, Wanessa, additional, Cardozo Fh, José L., additional, Pereira de Araujo, Antonio F., additional, Pais do Amaral, Constança, additional, Gonçalves, Sónia, additional, Santos, Nuno C., additional, Leite, José R. S. A., additional, Bloch Jr, Carlos, additional, and Brand, Guilherme D., additional

Published
2023
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6. Do entangled photons induce two-photon two-atom transitions more efficiently than other states of light ?

Author

Zheng, Zhan, Saldanha, Pablo L., Leite, Jose R. Rios, and Fabre, Claude

Subjects
Quantum Physics, Physics - Optics
Abstract

We study in this paper the efficiency of different two-photon states of light to induce the simultaneous excitation of two atoms of different kinds when the sum of the energies of the two photons matches the sum of the energies of the two atomic transitions, while no photons are resonant with each individual transition. We find that entangled two-photon states produced by an atomic cascade are indeed capable of enhancing by a large factor the simultaneous excitation probability as compared to uncorrelated photons, as predicted some years ago by Muthukrishnan et al, but that several non-entangled, separable, correlated states, produced either by an atomic cascade or parametric down conversion, or even appropriate combinations of coher- ent states, have comparable efficiencies. We show that the key ingredient for the increase of simultaneous excitation probability is the presence of strong frequency anti-correlation and not time correlation nor time-frequency entanglement.

Published
2013

7. An excitable electronic circuit as a sensory neuron model

Author

Medeiros, Bruno N. S., Minces, Victor, Mindlin, Gabriel B., Copelli, Mauro, and Leite, José R. Rios

Subjects
Physics - Biological Physics, Quantitative Biology - Neurons and Cognition
Abstract

An electronic circuit device, inspired on the FitzHugh-Nagumo model of neuronal excitability, was constructed and shown to operate with characteristics compatible with those of biological sensory neurons. The nonlinear dynamical model of the electronics quantitatively reproduces the experimental observations on the circuit, including the Hopf bifurcation at the onset of tonic spiking. Moreover, we have implemented an analog noise generator as a source to study the variability of the spike trains. When the circuit is in the excitable regime, coherence resonance is observed. At sufficiently low noise intensity the spike trains have Poisson statistics, as in many biological neurons. The transfer function of the stochastic spike trains has a dynamic range of 6 dB, close to experimental values for real olfactory receptor neurons., Comment: 10 pages, 6 figures

Published
2011
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8. Occurrence and evolutionary conservation analysis of α‐helical cationic amphiphilic segments in the human proteome.

Author

Costa, Igor S. D., Junot, Tiago, Silva, Fernanda L., Felix, Wanessa, Cardozo Fh, José L., Pereira de Araujo, Antonio F., Pais do Amaral, Constança, Gonçalves, Sónia, Santos, Nuno C., Leite, José R. S. A., Bloch, Carlos, and Brand, Guilherme D.

Abstract

The existence of encrypted fragments with antimicrobial activity in human proteins has been thoroughly demonstrated in the literature. Recently, algorithms for the large‐scale identification of these segments in whole proteomes were developed, and the pervasiveness of this phenomenon was stated. These algorithms typically mine encrypted cationic and amphiphilic segments of proteins, which, when synthesized as individual polypeptide sequences, exert antimicrobial activity by membrane disruption. In the present report, the human reference proteome was submitted to the software kamal for the uncovering of protein segments that correspond to putative intragenic antimicrobial peptides (IAPs). The assessment of the identity of these segments, frequency, functional classes of parent proteins, structural relevance, and evolutionary conservation of amino acid residues within their corresponding proteins was conducted in silico. Additionally, the antimicrobial and anticancer activity of six selected synthetic peptides was evaluated. Our results indicate that cationic and amphiphilic segments can be found in 2% of all human proteins, but are more common in transmembrane and peripheral membrane proteins. These segments are surface‐exposed basic patches whose amino acid residues present similar conservation scores to other residues with similar solvent accessibility. Moreover, the antimicrobial and anticancer activity of the synthetic putative IAP sequences was irrespective to whether these are associated to membranes in the cellular setting. Our study discusses these findings in light of the current understanding of encrypted peptide sequences, offering some insights into the relevance of these segments to the organism in the context of their harboring proteins or as separate polypeptide sequences. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Somuncurins: Bioactive Peptides from the Skin of the Endangered Endemic Patagonian Frog Pleurodema somuncurense

Author

Cancelarich, Natalia L., primary, Wilke, Natalia, additional, Fanani, Marı́a L., additional, Moreira, Daniel C., additional, Pérez, Luis O., additional, Alves Barbosa, Eder, additional, Plácido, Alexandra, additional, Socodato, Renato, additional, Portugal, Camila C., additional, Relvas, João B., additional, de la Torre, Beatriz G., additional, Albericio, Fernando, additional, Basso, Néstor G., additional, Leite, José R., additional, and Marani, Mariela M., additional

Published
2020
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20. Epiisopilosine alkaloid has activity against Schistosoma mansoni in mice without acute toxicity

Author

Guimarães, Maria A., primary, de Oliveira, Rosimeire N., additional, de Almeida, Rebeca L., additional, Mafud, Ana C., additional, Sarkis, Ana L. V., additional, Ganassin, Rayane, additional, da Silva, Marcos P., additional, Roquini, Daniel B., additional, Veras, Leiz M., additional, Sawada, Tânia C. H., additional, Ropke, Cristina D., additional, Muehlmann, Luis A., additional, Joanitti, Graziella A., additional, Kuckelhaus, Selma A. S., additional, Allegretti, Silmara M., additional, Mascarenhas, Yvonne P., additional, de Moraes, Josué, additional, and Leite, José R. S. A., additional

Published
2018
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21. HPLC‐DAD, ESI–MS/MS, and NMR of Lycopene Isolated From P. guajava L. and Its Biotechnological Applications

Author

Amorim, Adriany G. N., primary, Souza, Jessica M. T., additional, Santos, Raimunda C., additional, Gullón, Beatriz, additional, Oliveira, Ana, additional, Santos, Luiz F. A., additional, Virgino, Adamor L. E., additional, Mafud, Ana C., additional, Petrilli, Helena M., additional, Mascarenhas, Yvonne P., additional, Delerue‐Matos, Cristina, additional, Pintado, Manuela E., additional, and Leite, José R. S. A., additional

Published
2018
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22. Electronic structure of complex defects in silicon

Author

Leite, José R., Assali, Lucy V. C., Gomes, Vivili M. S., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Ferenczi, G., editor, and Beleznay, F., editor

Published
1988
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23. Topical protection of mice laryngeal mucosa using the natural product cashew gum

Author

Figueiredo, Aline A., primary, Santana, Ana P. M., additional, Nicolau, Lucas A. D., additional, Batista‐Lima, Francisco J., additional, Wong, Deysi V. T., additional, Lucetti, Larisse T., additional, Batista, Gabriela L. P., additional, Caminha, Natália A., additional, Medeiros, Jand V. R., additional, Silva, Durcilene A., additional, Leite, José R. S. A., additional, Santos, Armênio A., additional, Soares, Pedro M. G., additional, Sifrim, Daniel, additional, and Souza, Marcellus H. L. P., additional

Published
2017
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27. Topical protection of mice laryngeal mucosa using the natural product cashew gum.

Author

Figueiredo, Aline A., Santana, Ana P. M., Nicolau, Lucas A. D., Batista‐Lima, Francisco J., Wong, Deysi V. T., Lucetti, Larisse T., Batista, Gabriela L. P., Caminha, Natália A., Medeiros, Jand V. R., Silva, Durcilene A., Leite, José R. S. A., Santos, Armênio A., Soares, Pedro M. G., Sifrim, Daniel, Souza, Marcellus H. L. P., and Batista-Lima, Francisco J

Abstract

Objectives/hypothesis: Evaluate the effect of in vitro exposure of mice laryngeal mucosa to solutions that simulated human gastric juice and to assess the topical protective effect of cashew gum on mice laryngeal mucosal integrity in vitro.Study Design: Animal study.Methods: Murine (Swiss) laryngeal samples were mounted in Ussing chambers. The luminal side of biopsies was exposed to solutions of different acidity with or without pepsin and/or taurodeoxycholic acid (TDC). Transepithelial electrical resistance (TER) was continuously recorded. The topical protective effect of cashew gum solution was evaluated by precoating the biopsies before the exposure with a solution at pH 5 containing 5 mM TDC. Changes in TER and mucosal permeability to fluorescein were measured.Results: Exposure of laryngeal mucosa to acidic solutions containing pepsin and TDC provoked a pH-dependent drop in TER with the maximal effect at pH 1, but still present at pH 5 (weakly acidic). The exposure of the laryngeal mucosa to a solution of pH 5 with TDC, but not with pepsin, produced a dose-dependent decrease in TER. Precoating the mucosa with cashew gum prevented the reduction of TER and increased transepithelial permeability by exposure to a solution at pH5 containing TDC.Conclusions: Weakly acidic solutions containing bile acids can produce impairment of laryngeal epithelial barrier, which may be protected by topical treatment with cashew gum.Level Of Evidence: NA. Laryngoscope, 128:1157-1162, 2018. [ABSTRACT FROM AUTHOR]

Published
2018
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28. HPLC‐DAD, ESI–MS/MS, and NMR of Lycopene Isolated From <italic>P. guajava</italic> L. and Its Biotechnological Applications.

Author

Amorim, Adriany G. N., Souza, Jessica M. T., Santos, Raimunda C., Gullón, Beatriz, Oliveira, Ana, Santos, Luiz F. A., Virgino, Adamor L. E., Mafud, Ana C., Petrilli, Helena M., Mascarenhas, Yvonne P., Delerue‐Matos, Cristina, Pintado, Manuela E., and Leite, José R. S. A.

Subjects
LYCOPENE, ANTIOXIDANTS, GUAVA, CAROTENOIDS, HIGH performance liquid chromatography
Abstract

Psidium guajava L. have been reported to be a rich source of antioxidant compounds. Its carotenoids have been highlighted by their high antioxidant capacity, which offers several benefits for human health. In this sense, lycopene isomers need to be identified. In this work, the comprehensive chemical characterization, by HPLC‐DAD, MS/MS, and NMR, of lycopene isolated from P. guajava L., antioxidant and antimicrobial activity of lycopene extracts and isolated lycopene are evaluated. The FTIR results reported a structure with Z configuration, confirmed by UV‐Vis, with λmax = 448, 473, and 505 nm for 5‐Z lycopene. Furthermore, MS/MS positive ionization shows one fragment m/z 309 [M‐227]+, relatively abundant for isolated lycopene. Experimental and Theoretical NMR studies revealed that guava may contain 5‐Z lycopene because of the similarity found among the peaks. Lycopene extracts presented higher antioxidant activity than isolated lycopene, from both P. guajava L. and tomato, when measured by ABTS and ORAC (r2 = 0.9995 and r2 = 0.9992, respectively). In addition, lycopene extract shows antibacterial efficacy against E. coli, S. aureus, and L. innocua, presenting MBC values of 20 mg mL−1. These results suggest that lycopene extract have potential applicability for food, cosmetics, and pharmaceutical industry. Practical Applications: Lycopene from P. guajava L. is characterized by HPLC‐DAD, MS, NMR, FTIR, and X‐Ray, presented antioxidant capacity by ORAC and antibacterial efficacy against food pathogens. Lycopene is isolated from P. guajava L., and lycopene extracts produced are characterized by HPLC‐DAD and ESI‐MS/MS. Lycopene isolated from P. guajava L. following the process may be 5‐Z isomer of lycopene. [ABSTRACT FROM AUTHOR]

Published
2018
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31. Rogue waves in optically injected lasers: Origin, predictability, and suppression

Author

Ministerio de Ciencia e Innovación (España), Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco, Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), European Office of Aerospace Research and Development, Generalitat de Catalunya, Institución Catalana de Investigación y Estudios Avanzados, Zamora-Munt, J., Garbin, Bruno, Barland, Stéphane, Giudici, Massimo, Rios Leite, José R., Masoller, Cristina, Tredicce, Jorge R., Ministerio de Ciencia e Innovación (España), Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco, Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), European Office of Aerospace Research and Development, Generalitat de Catalunya, Institución Catalana de Investigación y Estudios Avanzados, Zamora-Munt, J., Garbin, Bruno, Barland, Stéphane, Giudici, Massimo, Rios Leite, José R., Masoller, Cristina, and Tredicce, Jorge R.

Abstract

Rogue waves are devastating extreme events that occur in many natural systems, and a lot of work has focused on predicting and understanding their origin. In optically injected semiconductor lasers rogue waves are rare ultra-high pulses that sporadically occur in the laser chaotic output intensity. Here we show that these optical rogue waves can be predicted with long anticipation time, that they are generated by a crisis-like process, and that noise can be employed to either enhance or suppress their probability of occurrence. By providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can contribute to improve the performance of injected lasers and can also enable new experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been observed. © 2013 American Physical Society.

Published
2013

32. Rogue waves in optically injected lasers: origin, predictability, and suppression

Author

Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Zamora Munt, Jordi, Garbin, Bruno, Barland, Stéphane, Giudici, Massimo, Rios Leite, José R., Masoller Alonso, Cristina, Tredicce, Jorge R., Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Zamora Munt, Jordi, Garbin, Bruno, Barland, Stéphane, Giudici, Massimo, Rios Leite, José R., Masoller Alonso, Cristina, and Tredicce, Jorge R.

Abstract

Rogue waves are devastating extreme events that occur in many natural systems, and a lot of work has focused on predicting and understanding their origin. In optically injected semiconductor lasers rogue waves are rare ultra-high pulses that sporadically occur in the laser chaotic output intensity. Here we show that these optical rogue waves can be predicted with long anticipation time, that they are generated by a crisis-like process, and that noise can be employed to either enhance or suppress their probability of occurrence. By providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can contribute to improve the performance of injected lasers and can also enable new experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been observed., Peer Reviewed, Postprint (published version)

Published
2013

33. Deterministic optical rogue waves

Author

Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Bonatto, Cristian, Feyereisen, Michael, Barland, Stéphane, Giudici, Massimo, Masoller Alonso, Cristina, Rios Leite, José R., Tredicce, Jorge R., Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Bonatto, Cristian, Feyereisen, Michael, Barland, Stéphane, Giudici, Massimo, Masoller Alonso, Cristina, Rios Leite, José R., and Tredicce, Jorge R.

Abstract

Experimental observations of rare giant pulses or rogue waves were done in the output intensity of an optically injected semiconductor laser. The long-tailed probability distribution function of the pulse amplitude displays clear non-Gaussian features that confirm the rogue wave character of the intensity pulsations. Simulations of a simple rate equation model show good qualitative agreement with the experiments and provide a framework for understanding the observed extreme amplitude events as the result of a deterministic nonlinear process., Peer Reviewed, Postprint (published version)

Published
2011

35. Synchronization Properties of Bidirectionally Coupled Semiconductor Lasers Under Asymmetric Operating Conditions

Author

Martínez Ávila, Jhon Fredy, Vicente, Raúl, Rios Leite, José R., Mirasso, Claudio R., Martínez Ávila, Jhon Fredy, Vicente, Raúl, Rios Leite, José R., and Mirasso, Claudio R.

Abstract

We study, both experimentally and numerically, a system of two coupled semiconductor lasers in an asymmetric configuration. A laser subject to optical feedback is bidirectionally coupled to a free running laser. While maintaining the coupling strength, we change the feedback rate and observe a transition from highly correlated low-frequency fluctuations to episodic synchronization between dropouts and jump-ups. Our results resemble those obtained recently in a unidirectionally coupled system [Buldú et al., Phys. Rev. Lett. 96, 024102 2006].

Published
2007

38. Deterministic Optical Rogue Waves

Author

Bonatto, Cristian, primary, Feyereisen, Michael, additional, Barland, Stéphane, additional, Giudici, Massimo, additional, Masoller, Cristina, additional, Leite, José R. Rios, additional, and Tredicce, Jorge R., additional

Published
2011
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44. Delayed coupling of logistic maps

Author

Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Masoller Alonso, Cristina, Cavalcante, Hugo, Rios Leite, José R., Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Masoller Alonso, Cristina, Cavalcante, Hugo, and Rios Leite, José R.

Abstract

We study the synchronization of logistic maps in a one-way coupling configuration. The master system is coupled to the slave system with a delay n1, and the slave is a delayed logistic map with a delay n2. We show that when the slave system has no delay (n2=0), perfectly synchronized solutions exist for strong enough coupling. In these solutions the slave variable y is retarded with respect to the master variable x with a retardation equal to the delay of the coupling [y(i+n1)=x(i)]. When n2¿0, a regime of generalized synchronization is observed, where y(i+n1) is synchronized with x(i), but not completely, since the master and the slave systems obey different maps. We introduced a similarity function as an indicator of the degree of synchronization and, using a noisy master source, distinguished synchronization from noise-induced correlations., Peer Reviewed, Postprint (published version)

Published
2001

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