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2. Abelian Chern-Simons vortices in the presence of magnetic impurities

Author

Bazeia, Dionisio, Campos, João G. F., and Mohammadi, Azadeh

Subjects
High Energy Physics - Theory, Nonlinear Sciences - Pattern Formation and Solitons
Abstract

This work deals with Abelian Chern-Simons vortices interacting with magnetic impurities. We compute static solutions with winding numbers zero and one. Then, we develop a numerical algorithm to simulate their collisions. Collisions between a vortex with winding number two and a magnetic impurity are also performed. All scattering results are interpreted in terms of the moduli space approximation and compared with the Abelian Maxwell-Higgs model.

Published
2024
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4. Medindo o crescimento proveniente do enfrentamento de situações adversas: a influência da centralidade da memória autobiográfica = Measuring growth through adversity: the influence of the autobiographical memory centrality = Midiendo el crecimiento proveniente del enfrentamiento de situaciones adversas: influencia de la centralidad de la memoria autobiográfica

Author

Campos, João Oliveira Cavalcante

Subjects
memória autobiográfica, memória - fisiologia, vida, psicologia, Psychology, BF1-990
Abstract

O crescimento pós-traumático (CPT) refere-se à mudança positiva em algum aspecto da experiência humana como resultado do enfrentamento de situações adversas. O presente trabalho investigou se as evidências de validade externa do Inventário de Crescimento PósTraumático (PTGI) são mais consistentes quando se compara os resultados de um subgrupo que pontuou alto na Escala de Centralidade de Eventos (ECE) com os de um subgrupo que pontuou baixo. A ECE avalia em que medida o evento de referência contribuiu na formação da identidade dos indivíduos. Participaram do estudo 317 indivíduos que passaram por situações adversas variadas. As correlações entre CPT e suporte social, sentido de vida, satisfação com a vida, religiosidade e desajuste psicológico apresentaram maior magnitude e coerência no subgrupo pontuou alto na ECE. Os resultados fortalecem a concepção de que apenas eventos que levam a uma reavaliação das crenças centrais dos indivíduos devem ser incluídos nos estudos de CPT

Published
2019

5. Collisions between kinks with long-range tails: a simple and efficient method

Author

Campos, João G. F. and Mohammadi, Azadeh

Subjects
High Energy Physics - Theory, Nonlinear Sciences - Pattern Formation and Solitons
Abstract

We construct initial configurations for the scattering between kinks with long-range tails. For this purpose, we exploit kink solutions in the presence of Bogomol'nyi-Prasad-Sommerfield (BPS)-preserving impurities. This approach offers a highly efficient method and effortless implementation with a negligible computational cost. Our algorithm has a much smaller complexity than the usual minimization method, becoming more than a hundred times faster in some scenarios. Consequently, conducting kink-antikink simulations becomes remarkably straightforward.

Published
2023
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6. Kink scattering in the presence of geometric constrictions

Author

Campos, João G. F., Simas, Fabiano C., and Bazeia, D.

Subjects
High Energy Physics - Theory
Abstract

We investigate kink-antikink collisions in a model characterized by two scalar fields in the presence of geometric constrictions. The model includes an auxiliary function that modifies the kinematics associated with one of the two fields. An important fact is that one of the fields can be solved independently, being responsible for changing the internal structure of the second one. We performed several collisions and observed the presence of resonance windows for small values of the parameters. Furthermore, we have been able to show the alternation between the appearance of oscillating pulses, as well as the annihilation and formation of kink-antikink pairs when the geometric constriction is more pronounced. The study of kink dynamics in models with geometric constrictions is connected with issues of interest such as domain wall formation and magnetization at the manometric scale., Comment: 30 pages, 17 figures, final version to be published in JHEP

Published
2023
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7. Kink-antikink collisions in the $\phi^8$ model: short-range to long-range journey

Author

Bazeia, Dionisio, Campos, João G. F., and Mohammadi, Azadeh

Subjects
High Energy Physics - Theory, Nonlinear Sciences - Pattern Formation and Solitons
Abstract

We studied kink-antikink collisions in (1+1)-dimensional spacetime for all $Z_2$ symmetric $\phi^8$ models with four degenerate minima. Such a polynomial model has only one free parameter, allowing us to conduct an exhaustive analysis. We performed detailed simulations in all three sectors of the model. We observed resonance windows from both localized and delocalized modes, as well as a sector change with the formation of additional kink-antikink pairs. Furthermore, we were able to show how collisions are modified when two quadratic minima merge into a quartic one, causing the kinks to acquire a long-range character. We demonstrated that when the tail not facing the opposing kink is long-range, incoming kinks and antikinks decay directly into radiation, as suggested in \cite{campos2021interaction}, by forming a large number of small kink-antikink pairs. Finally, we briefly discussed whether our analysis could be generalized to other polynomial models.

Published
2023
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29. Interfacial capacitance in lithium disilicate glass: Experimental factors and charge carrier density.

Author

Zallocco, Vinicius Martins, Campos, João Vitor, and Rodrigues, Ana Candida Martins

Subjects
*GOLD electrodes, *SPACE charge, *SOLID electrolytes, *IONIC crystals, *CHARGE carriers
Abstract

The formation of an electric double‐layer (EDL) is an important phenomenon for many research areas, including energy storage technology. Although EDL is well‐known in electrochemistry, most of the studies involve the characterization of liquid electrolyte/electrode interfaces, and only a limited number of studies in solid‐solid contacts, such as solid electrolyte/electrode interface are available. This paper employed electrochemical impedance spectroscopy (EIS) to systematically investigate the influence of experimental factors in the interfacial capacitance arising from the electrode polarization in a lithium disilicate glass/gold electrode interface. It analyzed the influence of a.c. input voltage amplitude, samples' roughness (mechanical and chemomechanical polishing) and thickness, range of applied frequency and temperature, and the number of impedance cycles. In short, it was found that an input voltage range of 15–60 mV is indicated to minimize potential electrochemical processes during electrode polarization, where the data is reproducible from the second measurement cycle onward. Smoother surfaces closely approximated ideal electrode spike behavior, with surface treatment exhibiting influence on interfacial capacitance values. Moreover, as expected, we observed an increase in relative permittivity values with increasing thickness, accompanied by decreased capacitance values. Finally, by employing optimal experimental conditions and analyzing the inflection frequency (finflection${{f}_{inflection}}$) of the ε′$\varepsilon ^{\prime}$ versus log(f$f$) curve, we determined that the ratio between effective charge carriers (ne${{n}_e}$) and the total number of charge carriers (nt${{n}_t}$) nent$\frac{{{{n}_e}}}{{{{n}_t}}}$ falls within the range of 5–12% between 130°C and 280°C. [ABSTRACT FROM AUTHOR]

Published
2025
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45. Mitochondrial genome variants associated with amyotrophic lateral sclerosis and their haplogroup distribution.

Author

Briones, Marcelo R. S., Campos, João H., Ferreira, Renata C., Schneper, Lisa, Santos, Ilda M., Antoneli, Fernando M., and Broach, James R.

Abstract

Introduction/Aims: Amyotrophic lateral sclerosis (ALS) may be familial or sporadic, and twin studies have revealed that even sporadic forms have a significant genetic component. Variants in 55 nuclear genes have been associated with ALS and although mitochondrial dysfunction is observed in ALS, variants in mitochondrial genomes (mitogenomes) have not yet been tested for association with ALS. The aim of this study was to determine whether mitogenome variants are associated with ALS. Methods: We conducted a genome‐wide association study (GWAS) in mitogenomes of 1965 ALS patients and 2547 controls. Results: We identified 51 mitogenome variants with p values <10−7, of which 13 had odds ratios (ORs) >1, in genes RNR1, ND1, CO1, CO3, ND5, ND6, and CYB, while 38 variants had OR <1 in genes RNR1, RNA2, ND1, ND2, CO2, ATP8, ATP6, CO3, ND3, ND4, ND5, ND6, and CYB. The frequencies of haplogroups H, U, and L, the most frequent in our ALS data set, were the same in different onset sites (bulbar, limb, spinal, and axial). Also, intra‐haplogroup GWAS revealed unique ALS‐associated variants in haplogroups L and U. Discussion: Our study shows that mitogenome single nucleotide variants (SNVs) are associated with ALS and suggests that these SNVs could be included in routine genetic testing for ALS and that mitochondrial replacement therapy has the potential to serve as a basis for ALS treatment. [ABSTRACT FROM AUTHOR]

Published
2024
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46. Visualisation of Random Forest classification.

Author

Maçãs, Catarina, Campos, João R, Lourenço, Nuno, and Machado, Penousal

Subjects
MACHINE learning, RANDOM forest algorithms, DECISION trees, VISUAL analytics, TELEPHONE calls
Abstract

Decision Trees (DTs) stand out as a prevalent choice among supervised Machine Learning algorithms. These algorithms form binary structures, effectively dividing data into smaller segments based on distinct rules. Consequently, DTs serve as a learning mechanism to identify optimal rules for the separation and classification of all elements within a dataset. Due to their resemblance to rule-based decisions, DTs are easy to interpret. Additionally, their minimal need for data pre-processing and versatility in handling various data types make DTs highly practical and user-friendly across diverse domains. Nevertheless, when confronted with extensive datasets or ensembles involving multiple trees, such as Random Forests, its analysis can become challenging. To facilitate the examination and validation of these models, we have developed a visual tool that incorporates a range of visualisations providing both an overview and detailed insights into a set of DTs. Our tool is designed to offer diverse perspectives on the same data, enabling a deeper understanding of the decision-making process. This article outlines our design approach, introduces various visualisation models, and details the iterative validation process. We validate our methodology through a telecommunications use case, specifically employing the visual tool to decipher how a DT-based model determines the optimal communication channel (i.e. phone call, email, SMS) for a telecommunication operator to use when contacting a client. [ABSTRACT FROM AUTHOR]

Published
2024
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