Automated Identification and Classification of Stereochemistry: Chirality and Double Bond Stereoisomerism

Stereoisomers have the same molecular formula and the same atom connectivity and their existence can be related to the presence of different three-dimensional arrangements. Stereoisomerism is of great importance in many different fields since the molecular properties and biological effects of the stereoisomers are often significantly different. Most drugs for example, are often composed of a single stereoisomer of a compound, and while one of them may have therapeutic effects on the body, another may be toxic. A challenging task is the automatic detection of stereoisomers using line input specifications such as SMILES or InChI since it requires information about group theory (to distinguish stereoisomers using mathematical information about its symmetry), topology and geometry of the molecule. There are several software packages that include modules to handle stereochemistry, especially the ones to name a chemical structure and/or view, edit and generate chemical structure diagrams. However, there is a lack of software capable of automatically analyzing a molecule represented as a graph and generate a classification of the type of isomerism present in a given atom or bond. Considering the importance of stereoisomerism when comparing chemical structures, this report describes a computer program for analyzing and processing steric information contained in a chemical structure represented as a molecular graph and providing as output a binary classification of the isomer type based on the recommended conventions. Due to the complexity of the underlying issue, specification of stereochemical information is currently limited to explicit stereochemistry and to the two most common types of stereochemistry caused by asymmetry around carbon atoms: chiral atom and double bond. A Webtool to automatically identify and classify stereochemistry is available at http://nams.lasige.di.fc.ul.pt/tools.ph

Classical integrability of chiral QCD2QCD_{2} and classical curves

In this letter, classical chiral $QCD_{2}$ is studied in the lightcone gauge $A_{-}=0$. The once integrated equation of motion for the current is shown to be of the Lax form, which demonstrates an infinite number of conserved quantities. Specializing to gauge group SU(2), we show that solutions to the classical equations of motion can be identified with a very large class of curves. We demonstrate this correspondence explicitly for two solutions. The classical fermionic fields associated with these currents are then obtained.Comment: Final version to appear in Mod. Phys. Lett. A. A reference and two footnotes added. 6 pages revte

Cosmological solutions in generalized hybrid metric-Palatini gravity

We construct exact solutions representing a Friedmann-Lema\^itre-Robsertson-Walker (FLRW) universe in a generalized hybrid metric-Palatini theory. By writing the gravitational action in a scalar-tensor representation, the new solutions are obtained by either making an ansatz on the scale factor or on the effective potential. Among other relevant results, we show that it is possible to obtain exponentially expanding solutions for flat universes even when the cosmology is not purely vacuum. We then derive the classes of actions for the original theory which generate these solutions.Comment: 14 pages, 17 figure

Converging Perturbative Solutions of the Schroedinger Equation for a Two-Level System with a Hamiltonian Depending Periodically on Time

We study the Schroedinger equation of a class of two-level systems under the action of a periodic time-dependent external field in the situation where the energy difference 2epsilon between the free energy levels is sufficiently small with respect to the strength of the external interaction. Under suitable conditions we show that this equation has a solution in terms of converging power series expansions in epsilon. In contrast to other expansion methods, like in the Dyson expansion, the method we present is not plagued by the presence of ``secular terms''. Due to this feature we were able to prove absolute and uniform convergence of the Fourier series involved in the computation of the wave functions and to prove absolute convergence of the epsilon-expansions leading to the ``secular frequency'' and to the coefficients of the Fourier expansion of the wave function

Analysis of the influence of the líbero in different phases of game in volleyball

El objetivo del estudio fue analizar la participación y la influencia del jugador líbero en la fase de ataque y en la fase de defensa en voleibol masculino de alto nivel. La muestra de estudio estuvo compuesta por 1101 acciones de juego de recepción y defensa, de los cuatro equipos masculinos mejor clasificados en los JJOO de Pekin 2008. Las variables consideradas en el estudio fueron: clasificación del equipo, jugador receptor/defensa, zona de recepción/defensa, eficacia de recepción/defensa, eficacia de la colocación, zona de ataque/contraataque, tiempo de ataque/contraataque, eficacia de ataque/contraataque. La medida de dichas variables se realizó mediante la observación sistemática, indirecta y externa. Se recurrió a la estadística descriptiva y, posteriormente, se utilizaron técnicas de estadística inferencial, basada en tablas de contingencia, valores de Chi-cuadrado y V de Cramer. Los resultados mostraron que, en la fase de defensa, hubo asociaciones significativas entre: el jugador que defiende y la zona de defensa, predominando la defensa del líbero en zona 5; el jugador que defiende y la eficacia de la defensa, siendo mejorada por parte del líbero; el jugador que defiende y la zona de contraataque, incrementándose los ataques por zona 6 cuando defiende el líberoThe aim of the study was to analyse the libero’s participation and their influence in the attack and defence phases in men's elite volleyball. The sample of this study was composed by 1101 pass and defence game actions of the four highest-placed teams in the 2008 Beijing Olympic Games. The study’s variables include team classification, receiving/defending player, pass/defence zone, pass/defence effectiveness, setting effectiveness, attack/counterattack zone, attack/counterattack time, and attack/counterattack effectiveness. These variables were measured by both indirect and external systematic observation. A descriptive statistical study was used, followed by inferential statistical techniques based on contingency tables, Chi-square tests, and Cramer's V values. The results revealed that there were significant associations during the defensive stage of the game between the defending player and the defensive phase, the libero’s defence predominating in zone 5; the defending player and defence efficiency, which is improved by the libero; the defending player and counterattack, as attacks increased in zone 6 when the libero was defendin

Computational Simulation of an Agricultural Robotic Rover for Weed Control and Fallen Fruit Collection—Algorithms for Image Detection and Recognition and Systems Control, Regulation, and Command

The continuous rise in the world’s population has increased the need for food, resulting in a rise of agricultural holdings to ensure the supply of these goods directly to the populations and indirectly to all processing industries in the food business. This situation has led agriculture to reinvent itself and introduce new technics and tools to ensure tighter control of the crops and increase yields in food production. However, the lack of labor coupled with the evolution of weeds resistant to herbicides created a crisis in agricultural food production. However, with the growing evolution in electronics, automation, and robotics, new paths are emerging to solve these problems. A robotic rover was designed to optimize the tasks of weed control and collection of fallen fruits of an orchard. In weed control, a localized spraying system is proposed, therefore reducing the amount of applied herbicides. With fruit collection, it is possible to direct fallen fruits for animal feeding and possible to reduce microbial activity on the next campaign crops, therefore avoiding damage. This study proposes the simulation of this robotic rover on robotic simulation software. It also proposes the replication of a similar environment of an orchard to generate an algorithm that controls the rover on the tasks of localized spraying and fallen fruit collection. Creating and testing these algorithms by using a robotic simulator speed up and ease the evaluation of different scenarios and hypotheses, with the added benefit of being able to test two tasks simultaneously. This method also allows greater freedom and creativity because there are no concerns about hardware damage. It should also be noted that development costs are very low.info:eu-repo/semantics/publishedVersio

Non supersymmetric strong coupling background from the large N quantum mechanics of two matrices coupled via a Yang-Mills interaction

We derive the planar large N non-supersymmetric background of the quantum mechanical hamiltonian of two hermitean matrices coupled via a Yang-Mills interaction, in terms of the density of eigenvalues of one of the matrices. This background satisfies an implicit non linear integral equation, with a perturbative small coupling expansion and a solvable large coupling solution, which is obtained. The energy of system and the expectation value of several correlators are obtained in this strong coupling limit. They are free of infrared divergences.Comment: Latex, 13 page

A Dain Inequality with charge

We prove an upper bound for angular-momentum and charge in terms of the mass for electro-vacuum asymptotically flat axisymmetric initial data sets with simply connected orbit space