La renovación de la palabra en el bicentenario de la Argentina : los colores de la mirada lingüística

El libro reúne trabajos en los que se exponen resultados de investigaciones presentadas por investigadores de Argentina, Chile, Brasil, España, Italia y Alemania en el XII Congreso de la Sociedad Argentina de Lingüística (SAL), Bicentenario: la renovación de la palabra, realizado en Mendoza, Argentina, entre el 6 y el 9 de abril de 2010. Las temáticas abordadas en los 167 capítulos muestran las grandes líneas de investigación que se desarrollan fundamentalmente en nuestro país, pero también en los otros países mencionados arriba, y señalan además las áreas que recién se inician, con poca tradición en nuestro país y que deberían fomentarse. Los trabajos aquí publicados se enmarcan dentro de las siguientes disciplinas y/o campos de investigación: Fonología, Sintaxis, Semántica y Pragmática, Lingüística Cognitiva, Análisis del Discurso, Psicolingüística, Adquisición de la Lengua, Sociolingüística y Dialectología, Didáctica de la lengua, Lingüística Aplicada, Lingüística Computacional, Historia de la Lengua y la Lingüística, Lenguas Aborígenes, Filosofía del Lenguaje, Lexicología y Terminología

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Free energies underlying ion binding and transport in protein channels: Free energy perturbation simulations of ion binding and selectivity for valinomycin

As a step to increasing the reliability of the calculation of free energies underlying ion binding and transport in protein channels, free energy perturbation simulations have been performed for the binding of alkali-metal cations to the cyclic depsipeptide molecule, valinomycin, and compared with experimental measurements of binding by two-phase salt extraction equilibria. Valinomycin was chosen because it forms regular 1:1 ion complexes through its ester carbonyl ligands of crystallographically known three-dimensional structure in which the cation is sufficiently enfolded by the molecule that the overall size, shape, and charge distribution of the complex is virtually the same regardless of the species of cation bound (i.e. the complexes are 'isosteric'). The experimentally measured selectivities are sufficiently similar, in a wide variety of solvent environments, that the differences in free energies measured between the different ion-valinomycin complexes in a convenient solvent can be taken as equivalent to the differences in free energies in vacuo. This enables the adequacy of Warshel's MOLARIS force field for computing ion-specific differences in binding to be tested and provides an opportunity for refining the estimates for the appropriate values of partial charge and Lennard-Jones 6-12 parameters for an ester carbonyl group

Ion-selective properties of a small ionophore in methanol studied by free energy perturbation simulations

The ion-selective properties of the cyclic depsipeptide molecule valinomycin in methanol are studied by free energy perturbation molecular dynamics simulations. The dependence of the alkali cation selectivity on the dipole moment of the backbone carbonyl groups that ligate the ion is examined and found to behave in a systematic way. Since available force fields have not been parametrized for this type of ion-carbonyl interaction, the results are used to determine carbonyl partial charges that reproduce the observed selectivity quantitatively. The optimal dipole moment is somewhat higher than that normally used in molecular mechanics force fields and indicates that there is a significant polarization of the carbonyl groups by the field from the ion The simulations also suggest that the unloading of ions mainly would occur through the lactic acid face of the molecule since it does not provide as effective a shield against attack from the solvent as the more hydrophobic isohydroxyvaleri

Counting channels: a tutorial guide on ion channel fluctuation analysis

Ion channels open and close in a stochastic fashion, following the laws of probability. However, distinct from tossing a coin or a die, the probability of finding the channel closed or open is not a fixed number but can be modified (i.e., we can cheat) by some external stimulus, such as the voltage. Single-channel records can be obtained using the appropriate electrophysiological technique (e.g., patch clamp), and from these records the open probability and the channel conductance can be calculated. Gathering these parameters from a membrane containing many channels is not straightforward, as the macroscopic current I iNPo, where i is the single-channel current, N the number of channels, and Po the probability of finding the channel open, cannot be split into its individual components. In this tutorial, using the probabilistic nature of ion channels, we discuss in detail how i, N, and Po max (the maximum open probability) can be obtained using fluctuation (nonstationary noise) analysis (Sigworth FJ. G Gen Physiol 307: 97–129, 1980). We also analyze the sources of possible artifacts in the determination of i and N, such as channel rundown, inadequate filtering, and limited resolution of digital data acquisition by use of a simulation computer program (available at www.cecs.cl)

Free energy perturbation simulations of cation binding to valinomycin

Experimental values of the free energies of cation binding to the cyclic depsipeptide molecule, valinomycin, obtained from Pedersen-type salt extraction measurements, provide data against which it is possible to test the adequacy of the procedures and force fields of the molecular dynamics algorithms, MOLARIS and GROMOS. These data are then used to assess appropriate values for the partial charges of the ester carbonyl oxygen and carbon. Valinomycin was chosen because it has only one kind of ion-binding ligand and because the cation is sufficiently enfolded by the molecule in the ion-complexes that the overall size and shape of the complex is virtually the same regardless of the species of cation bound. For such an 'isosteric complex', the experimentally measured selectivities are sufficiently similar in a wide variety of solvent environments that the differences in free energies measured between the different ion-valinomycin complexes by two-phase salt extraction experiments into dic

Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8)

© 2014 by The American Society for Biochemistry and Molecular Biology, Inc. Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca2+-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening re