Acceleration of Solvation Free Energy Calculation via Thermodynamic Integration Coupled with Gaussian Process Regression and Improved Gelman-Rubin Convergence Diagnostics

The determination of the solvation free energy of ions and molecules holds profound importance across a spectrum of applications spanning chemistry, biology, energy storage, and the environment. Molecular dynamics simulations are a powerful tool for computing this critical parameter. Nevertheless, the accurate and efficient calculation of solvation free energy becomes a formidable endeavor when dealing with complex systems characterized by potent Coulombic interactions and sluggish ion dynamics and, consequently, slow transition across various metastable states. In the present study, we expose limitations stemming from the conventional calculation of the statistical inefficiency g in the thermodynamic integration method, a factor that can hinder the determination of convergence of the solvation free energy and its associated uncertainty. Instead, we propose a robust scheme based on Gelman-Rubin convergence diagnostics. We leverage this improved estimation of uncertainties to introduce an innovative accelerated thermodynamic integration method based on Gaussian Process regression. This methodology is applied to the calculation of the solvation free energy of trivalent rare earth elements immersed in ionic liquids, a scenario where the aforementioned challenges render standard approaches ineffective. The proposed method proves effective in computing solvation free energy in situations where traditional thermodynamic integration methods fall short.Comment: Main text: 24 pages, 8 figures; Supporting information: 8 pages, 9 figures, 2 table

Estimativa de erosão do solo na região do Programa de Assentamento Dirigido do Distrito Federal

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, 2018.A erosão é um processo natural de degradação do solo que provoca a perda de nutrientes e o transporte de sedimentos. O avanço da expansão agrícola no Cerrado, substituindo áreas de vegetação nativa por pastagens e plantações acelera o processo natural de erosão dos solos. Para redução dos impactos da expansão agrícola é necessário o planejamento territorial, agrícola e ambiental, considerando de forma específica a análise da ocorrência ou não da erosão do solo. No presente estudo, foi estimado a erosão laminar no Projeto de Assentamento Dirigido do Distrito Federal ((PAD-DF) nos últimos anos, oferecendo subsídios para o planejamento territorial com a identificação de áreas críticas e fatores que mais influenciaram a perda de solo. Para estimar a erosão laminar, utilizou-se a Equação Universal de Perda de Solo (EUPS), adaptada para ambiente de Sistema de Informação Geográfica (SIG). A maior parte da área estudada (97,8%) no PAD-DF apresentou quantidade de perda de solos inferior a 15 t ha-1ano-1, considerado níveis toleráveis de erosão laminar. Os locais onde ocorreu maior taxa de erosão foram na agricultura irrigada. O tipo de uso da terra foi o fator que mais influenciou no aumento da quantidade de perda de solos, onde as áreas cobertas por vegetação natural apresentaram níveis inferiores de erosão. Portanto, as práticas de conservação e manejo adequado dos solos aliada à conservação dos remanescentes de vegetação nativa se apresentam como as principais alternativas para redução das taxas de erosão para a região

Bonding in Uranium(V) Hexafluoride Based on the Experimental Electron Density Distribution Measured at 20 K

International audienceThe electron density distribution of [PPh4][UF6] was obtained from high-resolution X-ray diffrac-tion data measured at 20 K. The electron density was mod-eled with an augmented Hansen-Coppens multipolar formalism. Topological analysis reveals that the U-F bond is of incipient covalent nature. Theoretical calculations add further support to the bonding description gleaned from the experimental model. The impact of the uranium anomalous dispersion terms on the refinement is also discussed

Effect of Intra-molecular Disorder and Inter-molecular Electronic Interactions on the Electronic Structure of Poly-p-Phenylene Vinylene (PPV)

We investigate the role of intra-molecular conformational disorder and inter-molecular electronic interactions on the electronic structure of disorder clusters of poly-p-phenylene vinylene (PPV) oligomers. Classical molecular dynamics is used to determine probable molecular geometries, and first-principle density functional theory (DFT) calculations are used to determine electronic structure. Intra-molecular and inter-molecular effects are disentangled by contrasting results for densely packed oligomer clusters with those for ensembles of isolated oligomers with the same intra-molecular geometries. We find that electron trap states are induced primarily by intra-molecular configuration disorder, while the hole trap states are generated primarily from inter-molecular electronic interactions.Comment: 4 pages, 4 figures. Compile with pdflate

Music classification by transductive learning using bipartite heterogeneous networks

The popularization of music distribution in electronic format has increased the amount of music with incomplete metadata. The incompleteness of data can hamper some important tasks, such as music and artist recommendation. In this scenario, transductive classification can be used to classify the whole dataset considering just few labeled instances. Usually transductive classification is performed through label propagation, in which data are represented as networks and the examples propagate their labels through\ud their connections. Similarity-based networks are usually applied to model data as network. However, this kind of representation requires the definition of parameters, which significantly affect the classification accuracy, and presentes a high cost due to the computation of similarities among all dataset instances. In contrast, bipartite heterogeneous networks have appeared as an alternative to similarity-based networks in text mining applications. In these networks, the words are connected to the documents which they occur. Thus, there is no parameter or additional costs to generate such networks. In this paper, we propose the use of the bipartite network representation to perform transductive classification of music, using a bag-of-frames approach to describe music signals. We demonstrate that the proposed approach outperforms other music classification approaches when few labeled instances are available.Sao Paulo Research Foundation (FAPESP) (grants 2011/12823-6, 2012/50714-7, 2013/26151-5, and 2014/08996-0

Construyendo mejores sociedades: los grupos escolares y el proceso de inclusión-exclusión educativa

La escuela tiene el reto de ser el espacio donde se decide el rumbo de nuestras sociedades. En el empeño de sociedades más justas e inclusivas es preciso comprender el entramado socioeducativo y su impacto de forma más compleja, especialmente el grupo escolar como espacio de mediación. Para ello se propone, como alternativa teórica para el análisis de los procesos de inclusión-exclusión educativa, un marco conceptual que comprende las desigualdades desde la subjetividad social/grupal y coloca la mirada sobre la responsabilidad institucional. En este ensayo discutiremos sobre la responsabilidad de las instituciones escolares en las garantías para la inclusión, el papel del personal docente en el diseño de la actividad escolar y el funcionamiento de los grupos escolares desde su relación con el proceso de inclusión-exclusión educativa. Se presentan algunas características para entender la articulación de estas dimensiones y la forma en que cada una de ellas favorece o dificulta la inclusión. De este modo, se muestra que, junto a los elementos estructurales y políticas educativas, la subjetivación del proceso en la vida cotidiana de la escuela garantiza mayores o menores niveles de inclusión. El ensayo defiende la noción de grupo para trabajar con una perspectiva más social de la educación y sus ventajas en el proceso de formación. Muestra cómo, en el proceso de inclusión-exclusión educativa, influyen de forma articulada las decisiones y las estrategias institucionales que organizan y estructuran la vida de los grupos escolares, sentando las pautas para la experiencia escolar

Theoretical and methodological articulations between the processes of educational inclusion-exclusion, group cohesion and performance

El espacio escolar es poderoso en su capacidad de instituir contenidos subjetivos que reproduzcan o transformen el ordenamiento social. Por ello, la Psicología necesita contribuir a producir instituciones escolares transformadas y transformadoras. No obstante, padece separaciones entre sus disciplinas que limitan su accionar. El artículo presenta las premisas para una mirada transdiciplinar de la escuela. Se articula un modelo que propone un modo de diagnosticar y transformar la realidad de estas instituciones a partir de tres procesos: la cohesión grupal, la inclusiónexclusión educativa y el rendimiento. El modelo emplea como unidades de análisis la institución educativa y el grupo escolar como espacio psicológico condicionado, pero también transformador. Ello permite un análisis desde la multideterminación de los procesos de la relación subjetividad-grupalidad en la contextualidad social. Coloca la responsabilidad en las instituciones y se enfoca en procesos subjetivos en relación con elementos estructurales.O espaço escolar é poderoso em sua capacidade de instituir conteúdos subjetivos que reproduzem ou transformam a ordem social. Por esse motivo, a psicologia precisa contribuir para a produção de instituições escolares transformadas e transformadoras. No entanto, sofre separações entre suas disciplinas que limitam suas ações. O artigo apresenta as premissas para uma visão transdisciplinar da escola. Articula-se um modelo que propõe uma maneira de diagnosticar e transformar a realidade dessas instituições a partir de três processos: coesão grupal, inclusão-exclusão educacional e desempenho. O modelo utiliza a instituição educacional e o grupo escolar como unidades de análise como um espaço psicológico condicionado, mas também transformador. Isso permite uma análise a partir da multideterminação dos processos da relação subjetividade-grupo na contextualidade social. Coloca responsabilidade nas instituições e concentra-se em processos subjetivos em relação aos elementos estruturais.The school space is powerful in its ability to institute subjective contents that reproduce or transform the social order. For this reason, psychology needs to contribute to producing transformed and transformative school institutions. However, it suffers from separations between its disciplines that limit its actions. The article presents the premises for a transdisciplinary view of the school. A model is articulated that proposes a way of diagnosing and transforming the reality of these institutions from three processes: group cohesion, educational inclusion-exclusion and performance. The model uses the educational institution and the school group as units of analysis as a conditioned psychological space, but also transformative. This allows an analysis from the multidetermination of the processes of the subjectivity-group relationship in social contextuality. It places responsibility on institutions and focuses on subjective processes in relation to structural elements.Facultad de Psicologí

Music shapelets for fast cover song regognition

A cover song is a new performance or recording of a previously recorded music by an artist other than the original one. The automatic identification of cover songs is useful for a wide range of tasks, from fans looking for new versions of their favorite songs to organizations involved in licensing copyrighted songs. This is a difficult task given that a cover may differ from the original song in key, timbre, tempo, structure, arrangement and even language of the vocals. Cover song identification has attracted some attention recently. However, most of the state-of-the-art approaches are based on similarity search, which involves a large number of similarity computations to retrieve potential cover versions for a query recording. In this paper, we adapt the idea of time series shapelets for contentbased music retrieval. Our proposal adds a training phase that finds small excerpts of feature vectors that best describe each song. We demonstrate that we can use such small segments to identify cover songs with higher identification rates and more than one order of magnitude faster than methods that use features to describe the whole music.FAPESP (grants #2011/17698-5, #2013/26151-5, and 2015/07628-0)CNPq (grants 446330/2014-0 and 303083/2013-1