RESUMO

The correct evaluation of ligand binding free energies by computational methods is still a very challenging active area of research. The most employed methods for these calculations can be roughly classified into four groups: (i) the fastest and less accurate methods, such as molecular docking, designed to sample a large number of molecules and rapidly rank them according to the potential binding energy; (ii) the second class of methods use a thermodynamic ensemble, typically generated by molecular dynamics, to analyze the endpoints of the thermodynamic cycle for binding and extract differences, in the so-called 'end-point' methods; (iii) the third class of methods is based on the Zwanzig relationship and computes the free energy difference after a chemical change of the system (alchemical methods); and (iv) methods based on biased simulations, such as metadynamics, for example. These methods require increased computational power and as expected, result in increased accuracy for the determination of the strength of binding. Here, we describe an intermediate approach, based on the Monte Carlo Recursion (MCR) method first developed by Harold Scheraga. In this method, the system is sampled at increasing effective temperatures, and the free energy of the system is assessed from a series of terms W(b,T), computed from Monte Carlo (MC) averages at each iteration. We show the application of the MCR for ligand binding with datasets of guest-hosts systems (N = 75) and we observed that a good correlation is obtained between experimental data and the binding energies computed with MCR. We also compared the experimental data with an end-point calculation from equilibrium Monte Carlo calculations that allowed us to conclude that the lower-energy (lower-temperature) terms in the calculation are the most relevant to the estimation of the binding energies, resulting in similar correlations between MCR and MC data and the experimental values. On the other hand, the MCR method provides a reasonable view of the binding energy funnel, with possible connections with the ligand binding kinetics, as well. The codes developed for this analysis are publicly available on GitHub as a part of the LiBELa/MCLiBELa project (https://github.com/alessandronascimento/LiBELa).

RESUMO

Resumen Introducción: El secuestro político es una práctica de presión sobre el Estado que se vuelve recurrente en Colombia por parte de grupos armados ilegales, particularmente por las FARC. Objetivo: Elaborar el perfil del guerrillero que volvería a la legalidad de cara al posible éxito el proceso de paz entre el gobierno colombiano y las Farc. Materiales y métodos: Es una investigación exploratoria descriptiva que se apoya en el análisis de contenido, a partir de la lectura de siete libros cuyos autores fueron víctimas del secuestro político por parte de las Farc. Resultados: El guerrillero llega casi siempre muy joven a las Farc, por hambre, miedo, necesidad o convicción; se inserta en una organización de estructura rígida y vertical, en cuya ideología es adoctrinado fácilmente, porque al provenir casi siempre de sectores pobres, le cala ese discurso. Se adapta fácilmente-casi siempre a la selva-, pero desarrolla insensibilidad frente a la vida ajena, incluso de los animales. Los jefes son autoritarios, caprichosos y con alta injerencia en decisiones cotidianas de guerrilleros y secuestrados. Conclusiones: El guerrillero raso que regresaría a la legalidad es joven, con nivel académico bajo o medio, pero alto nivel de adoctrinamiento; muy recursivo en la vida cotidiana; acostumbrado a obedecer y con la lógica de apoyar sus decisiones en las armas.

Abstract Introduction: This paper stems from an investigation to characterize the political kidnapping by the FARC in Colombia. Objective: To develop the profile of the guerrilla who would succeed the legality if the peace process between the Colombian government and the FARC. Materials and methods: It is a descriptive exploratory research based on content analysis, from the reading of seven books whose authors were victims of political kidnapping by the FARC. Results: The guerrilla reaches almost always very young squad, hunger, fear, need or belief; it is inserted in a rigid and vertical organization structure, whose ideology is easily indoctrinated, because almost always come poor, will cove that speech. It fits almost always easy to the jungle, but develops insensitivity to people's lives, even animals. The bosses are authoritarian, whimsical and high interference in everyday decisions of guerrillas and hostages. Conclusions: The guerrilla fighter would return to legality she is young, with low or average academic level, but high level of indoctrination; very resourceful in everyday life; used to obey and logic to support their decisions on arms.

Resumo Introdução: O sequestro político é una prática de presão sob o Estado que torna-se recorrente na Colômbia por grupos armados ilegais, particularmente pela FARC. Objetivo: Construir o perfil do guerrilheiro que retornaria à legalidade ao possível sucesso no processo de paz entre o governo colombiano e a Farc. Materiais e métodos: É uma pesquisa exploratoria descritiva que apoia-se no análise de contido, a partir da leitura de sete livros cujos autores foram vítimas do sequestro político por parte da Farc. Resultados: O guerrilheiro chega quase sempre muito joven à Farc, pela fome, medo, necessidade ou convição; inserta-se numa organização de estrutura rígida e vertical, cuja ideologia é adoutrinada fácilmente, porque ao vir quase sempre de setores pobres, identifica-se com esse discurso. Adapta-se fácilmente -quase sempre à floresta-, mas desenvolve insensibilidade frente à vida alheia, inclusive dos animais. Os chefes são autoritários, caprichosos e com alta injerência em decisições cotidianas de guerrilheiros e sequestrados. Conclusões: O guerrilheiro caso que regresasse à legalidade é joven, com nível acadêmico baixo ou médio, mas alto nível de adoutrinamento; muito recursivo na vida cotidiana; acostumado ao obedecer e com a lógica de apoiar as suas decisões nas armas.

RESUMO

We consider a family of homogeneous nonlinear dispersive equations with two arbitrary parameters. Conservation laws are established from the point symmetries and imply that the whole family admits square integrable solutions. Recursion operators are found for two members of the family investigated. For one of them, a Lax pair is also obtained, proving its complete integrability. From the Lax pair, we construct a Miura-type transformation relating the original equation to the Korteweg-de Vries (KdV) equation. This transformation, on the other hand, enables us to obtain solutions of the equation from the kernel of a Schrödinger operator with potential parametrized by the solutions of the KdV equation. In particular, this allows us to exhibit a kink solution to the completely integrable equation from the 1-soliton solution of the KdV equation. Finally, peakon-type solutions are also found for a certain choice of the parameters, although for this particular case the equation is reduced to a homogeneous second-order nonlinear evolution equation.