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

Disc Clearing of Young Stellar Objects: Evidence for Fast Inside-out Dispersal

The time-scale over which and the modality by which young stellar objects (YSOs) disperse their circumstellar discs dramatically influences the eventual formation and evolution of planetary systems. By means of extensive radiative transfer (RT) modelling, we have developed a new set of diagnostic diagrams in the infrared colour-colour plane (K-[24] vs. K-[8]), to aid with the classification of the evolutionary stage of YSOs from photometric observations. Our diagrams allow the differentiation of sources with unevolved (primordial) discs from those evolving according to different clearing scenarios (e.g. homologous depletion vs. inside-out dispersal), as well as from sources that have already lost their disc. Classification of over 1500 sources in 15 nearby star-forming regions reveals that approximately 39 % of the sources lie in the primordial disc region, whereas between 31 % and 32 % disperse from the inside-out and up to 22 % of the sources have already lost their disc. Less than 2 % of the objects in our sample lie in the homogeneous draining regime. Time-scales for the transition phase are estimated to be typically a few 10^5 years independent of stellar mass. Therefore, regardless of spectral type, we conclude that currently available infrared photometric surveys point to fast (of order 10 % of the global disc lifetime) inside-out clearing as the preferred mode of disc dispersal.Comment: 31 pages, 21 figures, 6 tables, accepted for publication in MNRA

Sensitivity of ATLAS to FCNC single top quark production

The anomalous production of single top quarks via flavour-changing neutral currents (FCNCs), u(c)+g -> t, is studied using the ATLAS detector at the Large Hadron Collider. Detector simulation is done using the fast simulation package ATLFAST. A number of important systematic effects have been addressed. Based on a cut-based analysis, we shows that, with 10 fb-1, ATLAS can observe such top FCNC interactions with 5 sigma significance if the anomalous coupling strengths are k_ug/Lambda=k_cg/Lambda >= 0.0120 $^{+0.0014}_{-0.0012}$ (sys.) TeV-1, or equivalently Br(t->ug)+Br(t->cg) >= 2.64 $^{+0.63}_{-0.54}$ (sys.) x 10^{-4}$. In terms of production cross section, such a discovery requires at least 13.7 pb of anomalous single top quark production. With this level of sensitivity, ATLAS will be able to test some models of new physics

Prevalence of Campylobacterin chickens from different production systems

info:eu-repo/semantics/draf

Scalar and Spinor Particles in the Spacetime of a Domain Wall in String Theory

We consider scalar and spinor particles in the spacetime of a domain wall in the context of low energy effective string theories, such as the generalized scalar-tensor gravity theories. This class of theories allows for an arbitrary coupling of the wall and the (gravitational) scalar field. First, we derive the metric of a wall in the weak-field approximation and we show that it depends on the wall's surface energy density and on two post-Newtonian parameters. Then, we solve the Klein-Gordon and the Dirac equations in this spacetime. We obtain the spectrum of energy eigenvalues and the current density in the scalar and spinor cases, respectively. We show that these quantities, except in the case of the energy spectrum for a massless spinor particle, depend on the parameters that characterize the scalar-tensor domain wall.Comment: LATEX file, 21 pages, revised version to appear in Phys. Rev.

Mesofauna do solo em floresta secundária e em cultivos do cupuaçuzeiro e do guaranazeiro no município de Belém-Pará.

bitstream/item/59302/1/CPATU-ComTec77.pd

Caracterização físico-hídrica de latossolo amarelo da região de Capitão Poço, Pará.

bitstream/item/42255/1/Boletim-Pesquisa-133-CPATU.pd

Mesenteric panniculitis

A 68 years old male patient presented with recurrent abdominal pain and with a palpable mas

Linear Theory of Electron-Plasma Waves at Arbitrary Collisionality

The dynamics of electron-plasma waves are described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite-Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency, and eigenmode spectrum of electron-plasma waves are found as functions of the collision frequency and wavelength. A comparison is made between the collisionless Landau damping limit, the Lenard-Bernstein and Dougherty collision operators, and the electron-ion collision operator, finding large deviations in the damping rates and eigenmode spectra. A purely damped entropy mode, characteristic of a plasma where pitch-angle scattering effects are dominant with respect to collisionless effects, is shown to emerge numerically, and its dispersion relation is analytically derived. It is shown that such a mode is absent when simplified collision operators are used, and that like-particle collisions strongly influence the damping rate of the entropy mode.Comment: 23 pages, 10 figures, accepted for publication on Journal of Plasma Physic